JP2004279680A - Display element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device by using a material which can transit from a metal reflection state to a transmission state and vice versa. <P>SOLUTION: The display device contains a plurality of pixels. Each of the plurality of pixels is equipped with: a first layer 1 containing a first material of which the optical characteristics changes in accordance with the concentration of a specified element; and a second layer containing a second material which can occlude the specified element. The second material is provided with a second layer 2 which can release or absorb the specified element upon voltage application and a pair of electrodes 3a and 3b to apply voltage to the second layer. The device is constructed so that the reflectance of the first layer 1 changes corresponding to the voltage. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a display device capable of controlling light reflectance and transmittance.
[0002]
[Prior art]
A phenomenon has been reported in which a metal thin film such as yttrium (Y) or lanthanum (La) combines with hydrogen to change to a hydride that can transmit visible light (Patent Document 1, Non-Patent Document 1). Since this phenomenon is reversible, it is possible to change the thin film between the metallic luster state and the transparent state by adjusting the hydrogen pressure in the atmosphere.
[0003]
If the optical characteristics of the thin film can be changed to switch between a state showing metallic luster and a transparent state, a light control mirror capable of freely adjusting the reflectance / transmittance of light can be realized. If the light control mirror is used, for example, as a window glass of a building or an automobile, sunlight can be blocked (reflected) or transmitted as necessary.
[0004]
Such a light control mirror has, for example, a structure in which a palladium layer is formed on an yttrium thin film. Palladium has a function of preventing surface oxidation of the yttrium thin film and a function of efficiently converting hydrogen molecules in the atmosphere to hydrogen atoms and supplying the same to yttrium. When yttrium chemically bonds to a hydrogen atom, YH ₂ Or YH ₃ Is formed. YH ₂ Is a metal, but YH ₃ Is a semiconductor and is transparent because its forbidden bandwidth is larger than the energy of visible light.
[0005]
Further, even at room temperature, YH ₂ ⇔YH ₃ Changes quickly (about several seconds), and it is possible to switch between a reflective (metallic luster) state and a transparent state according to the hydrogen content in the atmosphere.
[0006]
As another material capable of making the transition from metallic luster to transparent, for example, Mg ₂ Non-Patent Document 2 discloses a Ni thin film.
[0007]
[Patent Document 1]
U.S. Pat. No. 5,635,729
[Non-patent document 1]
Hubert, et al., Nature, (UK), March 1996, Volume 380, p. 231-234
[Non-patent document 2]
The Japan Society of Applied Physics 2001 Spring 31-a-ZS-14
[0008]
[Problems to be solved by the invention]
According to the above prior art, in order to change the optical state of a thin film, it is necessary to hydrogenate a material capable of transitioning from a metallic luster to a transparent material contained in the thin film by exposing the thin film to a hydrogen atmosphere. It is. Specifically, it is necessary to control the amount of hydrogen (hydrogen partial pressure) in the atmosphere gas in contact with the thin film. Since such control of the amount of hydrogen is performed on the entire surface of the thin film, the optical state of the entire thin film changes.
[0009]
For this reason, the above-mentioned prior art is premised on application to an application that changes the optical state of the entire thin film, such as a light control mirror, and is not proposed to be applied to a display device. For application to a display device, it is necessary to partition the thin film into a plurality of pixels and control the optical state for each pixel. However, it is difficult to control the amount of hydrogen in the atmospheric gas for each pixel, which is not practical.
[0010]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a display element using a material that can transition between a metal reflection state and a transmission state.
[0011]
[Means for Solving the Problems]
The display element of the present invention is a display element including a plurality of pixels, wherein each of the plurality of pixels includes a first layer including a first material whose optical characteristics change according to a concentration of a specific element; A second layer including a second material that may contain a specific element, wherein the second material emits or absorbs the specific element when a voltage is applied, and the second layer applies the voltage to the second layer. It is characterized by comprising a pair of electrodes for application, wherein the light reflectance of the first layer changes in response to the voltage, thereby achieving the object.
[0012]
In a preferred embodiment, the first material may transition between a light reflection state and a light transmission state according to the concentration of the specific element.
[0013]
In a preferred embodiment, when the first material is in a light reflecting state, the first layer diffusely reflects light.
[0014]
In a preferred embodiment, the first material is a particle.
[0015]
In a preferred embodiment, at least one of an upper surface and a lower surface of the first layer has irregularities.
[0016]
In a preferred embodiment, the first layer further includes colored particles, and the first material is adsorbed on the colored particles.
[0017]
In a preferred embodiment, the first layer transitions between a state in which light is diffusely reflected and a state in which light is transmitted, and the second layer has a light-transmitting property. And a light absorbing layer that absorbs light transmitted through the second layer.
[0018]
In a preferred embodiment, the first layer transitions between a state in which light is diffusely reflected and a state in which light is transmitted, the second layer has visible light absorption, and the second layer has Are arranged on the side opposite to the light incident surface of the first layer.
[0019]
The second layer may be disposed on the light incident side of the first layer and function as a color filter.
[0020]
The specific element may be hydrogen, and the second layer may include a hydrogen storage material.
[0021]
It is preferable that the second material emits or absorbs the specific element by transferring electrons.
[0022]
The first layer may have conductivity and function as one of the pair of electrodes.
[0023]
The display element of the present invention may be a reflective display element.
[0024]
The display element of the present invention can further have a backlight.
[0025]
The first layer may transition between a state in which light is mirror-reflected and a state in which light is transmitted, and may further include a backlight.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
First, the light control principle used for display in the display element of the present invention will be described.
[0027]
FIGS. 1A to 1C are schematic cross-sectional views illustrating the dimming principle of the display device of the present invention. The display element of the present invention has a plurality of pixels, and each pixel has a laminated structure of a light control layer M1 and a conversion layer M2. Display is performed by changing the light reflectance of the light control layer M1 for each pixel.
[0028]
The light control layer M1 shown in FIG. 1A includes a light control material whose optical characteristics change according to the concentration of a specific element. Preferred examples of the light modulating material include Y, La, and Mg described above. ₂ The light control layer 1 is a thin film of such a light control material, for example. Y, La, Mg ₂ Materials such as Ni alloys transition between a metal-semiconductor (or insulator) state depending on the hydrogen concentration.
[0029]
The conversion layer M2 includes a material (hereinafter, referred to as a “conversion material”) that can contain a specific element such as hydrogen. The conversion material emits or absorbs the specific element (for example, hydrogen) in response to an external stimulus such as injection of charge (electrons or holes) or light irradiation.
[0030]
Both the dimming layer M1 and the conversion layer M2 shown in FIG. 1A have an ability to absorb / release hydrogen, and are capable of moving charges (electrons or holes) and ions. It has conductivity.
[0031]
Hereinafter, the mechanism by which hydrogen ions move from the conversion layer M2 to the light control layer M1 or from the light control layer M1 to the conversion layer M2 by charge injection / release will be described. The feature of this mechanism is that ions of a specific element (hydrogen) that changes the optical characteristics of the light control layer M1 are moved not by an electrochemical reaction but by a charge transfer.
[0032]
FIG. 2A shows an initial state of the light control layer M1 and the conversion layer M2 included in the structure of FIG. In this initial state, an equilibrium state is formed between the light control layer M1 that does not substantially store hydrogen and the conversion layer M2 that stores hydrogen in advance. Since there is no sufficient concentration of hydrogen in the light control layer M1, the light control layer M1 is in a metal state and has a metallic luster.
[0033]
Next, as shown in FIG. 2B, a negative potential is applied to the light control layer M1 and a positive potential is applied to the conversion layer M2. At this time, electrons are injected into the light control layer M1 from a negative electrode (not shown), and the light control layer M1 is in an electron-rich state. On the other hand, holes are injected into the conversion layer M2 (electrons are extracted). The holes injected into the conversion layer M2 move inside the conversion layer M2 toward the light control layer M1. If holes are further continuously injected into the conversion layer M2 in such a hole movement process, the conversion layer M2 becomes a hole-rich state. Thus, the conversion layer M2 is in a state where hydrogen ions are easily released, while the light control layer M1 receives and retains hydrogen ions from the conversion layer M2.
[0034]
For this reason, the equilibrium state of hydrogen established between the light control layer M1 and the conversion layer M2 is broken, and the light control layer M1 is more likely to hold hydrogen, and the hydrogen ions released from the conversion layer M2 Moves to the light control layer M1. Thus, a new equilibrium state is formed as shown in FIG. In this state, the hydrogen transferred to the light control layer M1 and the light control material are combined, and the light control layer M1 becomes transparent.
[0035]
Describing the above reaction, M1 + M2 (H) → M1 (H) + M2. Here, M1 (H) and M2 (H) indicate a state where hydrogen is held in the light control layer M1 and a state where hydrogen is held in the conversion layer M2, respectively.
[0036]
As is clear from the above description, only the transfer of hydrogen ions is performed between the light control layer M1 and the conversion layer M2, and no reaction involving other ions occurs. When the polarity of the applied voltage is reversed in the state shown in FIG. 2C, the reaction proceeds in the opposite direction, and the state returns to the original equilibrium state shown in FIG. 2A.
[0037]
Instead of the structure shown in FIG. 1A, a laminated structure including the light control layer M1 and the conversion layer M2 shown in FIG. 1B may be provided. The light modulating layer M1 in FIG. 1B includes particles m1 of a light modulating material whose optical characteristics change according to the concentration of a specific element (hereinafter, may be referred to as “light modulating particles”). Preferred examples of the light modulating material include Y, La, and Mg described above. ₂ It is a Ni alloy. The light control layer M1 contains, for example, a binder resin, and the light control particles m1 are dispersed in the binder resin. The light control layer M1 also includes an electrolytic material (such as a conductive polymer) for transporting hydrogen ions or hydrogen from the conversion layer M2. The conversion layer M2 is substantially the same as the conversion layer M2 described with reference to FIG.
[0038]
When the structure shown in FIG. 1B is used, in the initial state of the light control layer M1 and the conversion layer M2 (FIG. 2A), there is no sufficient concentration of hydrogen in the light control layer M1. Each of the light control particles m1 dispersed in the light control layer M1 is in a metal state and mirror-reflects light. As described above, each of the light control particles m1 reflects light incident on the light control layer M1 in a random direction, and thus the light control layer M1 as a whole diffusely reflects light. Thereby, white reflected light is obtained. When the hydrogen ions move to the light control layer M1 and a new equilibrium state is formed (FIG. 2C), the hydrogen transferred to the light control layer M1 and the light control particles m1 combine to form each light control particle. m1 becomes transparent.
[0039]
Alternatively, a laminated structure including the light control layer M1 and the conversion layer M2 shown in FIG. 1C can be used. The light control layer M1 in FIG. 1C further includes colored particles m2 such as black particles, and the light control layer M1 in FIG. Is different from The conversion layer M2 in FIG. 1C is substantially the same as the conversion layer M2 described with reference to FIG.
[0040]
When the structure shown in FIG. 1B is used, in the initial state (FIG. 2A), similarly to the structure of FIG. 1B, each light modulating particle m1 adsorbed on the colored particles m2 is in a metal state. Mirrors the light. As described above, each of the light control particles m1 reflects light incident on the light control layer M1 in a random direction, and thus the light control layer M1 as a whole diffusely reflects light. Thereby, white reflected light is obtained. When the hydrogen ions move to the light control layer M1 and a new equilibrium state is formed (FIG. 2C), the hydrogen transferred to the light control layer M1 and the light control particles m1 combine to form each light control particle. m1 becomes transparent. As a result, the light control layer M1 shows the color of the colored particles m2, for example, black. As described above, since the light control layer M1 transitions between the diffuse reflection state and the colored state (also referred to as an absorption state), in this structure, the conversion layer M2 does not need to be transparent.
[0041]
In the present invention, a mechanism in which hydrogen ions move between the light control layer M1 and the conversion layer M2 by charge injection as shown in FIGS. 2A to 2C is used. It is not limited to. The display element of the present invention can also use a mechanism in which hydrogen ions move between the conversion layer M2 and the light control layer M1 by, for example, an electrochemical reaction. In this case, a solid electrolyte layer may be further provided between the light control layer M1 and the conversion layer M2, or the binder resin contained in the light control layer M1 of FIG. May be used. Alternatively, the display element of the present invention may not include the conversion layer M2. In this case, the light control layer M1 may further include a conversion material, and hydrogen ions may be moved between the light control particles m1 and the conversion material inside the light control layer M1.
[0042]
Regardless of which mechanism is used, the concentration of hydrogen ions in the light control layer M1 changes according to the voltage applied to the conversion material. It changes as shown in (c).
[0043]
Note that among the above, it is preferable to use a mechanism for moving hydrogen ions by injection of electric charge. In the case where hydrogen is driven by changing the equilibrium state of hydrogen by transferring charges (electrons or holes), it is not necessary to involve other ions other than hydrogen ions in the reaction. For this reason, there is an advantage that the response speed is higher than in the case where a mechanism based on an electrochemical reaction involving a plurality of types of ions is used. In addition, since no electrochemical reaction occurs, the possibility that hydrogen gas is generated on the positive electrode side is low, and stable operation as an electronic element can be achieved.
[0044]
Thus, the display element of the present invention can change the hydrogen content of the light control layer M1 by applying a voltage to the conversion layer M2 containing the conversion material. Therefore, the display device of the present invention is more practical than the dimming device of the prior art, which needs to control the partial pressure of hydrogen in the atmosphere. Further, in the related art, since the control of the hydrogen partial pressure is performed on the entire surface of the light control layer M1, the optical characteristics of the light control layer M1 change over the entire surface of the light control layer M1. On the other hand, in the present invention, since the above mechanism is used, the optical characteristics can be changed for each pixel by controlling the applied voltage for each pixel of the light control layer M1.
[0045]
Hereinafter, embodiments of the present invention will be described.
[0046]
(Embodiment 1)
First, an embodiment of a display element according to the present invention will be described with reference to the drawings. FIG. 3 is a schematic cross-sectional view of one pixel in the display element of the present embodiment, and FIG. 4 is a plan view of the display element of the present embodiment. Here, a reflection type full-color display element will be described as an example, but the present invention is not limited to this. For example, a black-and-white display element or a projection display element may be used.
[0047]
The display element of the present embodiment has a light absorption layer 5, an electrode 3b, a conversion layer 2, a light control layer 1, an electrode 3a, and a color filter 6, which are sequentially stacked on a substrate 1. As shown in FIG. 4, the electrode 3b has a plurality of patterns extending in parallel, and the electrode 3a has a plurality of patterns extending in a direction perpendicular to the electrode 3b. An appropriate voltage can be applied to the pair of electrodes 3a and 3b, but it is also possible to simply short-circuit the electrodes 3a and 3b as appropriate. The color filter 6 has a plurality of patterns extending substantially parallel to the electrode 3a. Of these patterns, typically, three patterns of R (red), G (green), and B (blue) are formed for each pixel.
[0048]
The order of laminating the conversion layer 2 and the light control layer 1 on the substrate 4 is not limited to the illustrated one. The conversion layer 2 is arranged on the side close to the substrate 4 and the light control layer 1 is formed thereon. May be. If the substrate 4 is a transparent substrate such as a glass substrate, the light absorbing layer 5 may be provided on the back surface of the substrate 4. When the light absorbing layer 5 has conductivity, the light absorbing layer 5 may be provided anywhere between the electrode 3a and the electrode 3b. Alternatively, the light absorbing layer 5 having conductivity can be used integrally with the electrode 3b or instead of the electrode 3b.
[0049]
The light control layer 1 in the present embodiment includes a light control material (e.g., yttrium) whose optical characteristics change according to the hydrogen concentration. In the present embodiment, the light control layer 1 is a film (for example, an yttrium film) formed using a light control material as shown in FIG. The light control layer 1 may be a single layer or may have a multilayer structure.
[0050]
Conversion layer 2 contains a conversion material that can contain hydrogen. This conversion material exchanges electrons with the electrode 3a to form hydrogen ions (H ⁺ ) Can be released / absorbed.
[0051]
In the illustrated example, a voltage can be applied to the conversion layer 2 of an arbitrary pixel by the electrodes 3a and 3b formed in a matrix. In a certain pixel, when a positive potential is applied to the electrode 3a and a negative potential is applied to the electrode 3b, hydrogen ions are released from the conversion material of the conversion layer 2 containing a sufficient amount of hydrogen in advance. The released hydrogen ions move in the electric field formed in the stacked structure, reach the light control layer 1, and are doped into the light control material. The mechanism of such hydrogen release and transfer is as described above. The light modulating material in the light modulating layer 1 combines with hydrogen to form a hydrogen metal compound. As a result, the light modulating material that was initially in a metallic state changes to a semiconductor or an insulator that transmits visible light.
[0052]
FIG. 5A shows a change in the state of the light control layer 1 and the conversion layer 2 as described above. When the light control material of the light control layer 1 is in a metal state, light incident on the display element is reflected by the light control layer 1 and passes through the color filter 6. Therefore, the light transmitted through the color filter 6 is visually recognized. When the light modulating material is a semiconductor or an insulator, the light modulating layer 1 becomes transparent, so that light incident on the display element passes through the light modulating layer 1 and is absorbed by the light absorbing layer 5. Therefore, black is visually recognized.
[0053]
Next, a method for manufacturing the display element of the present embodiment will be described.
[0054]
First, the substrate 4 is prepared. The substrate 4 only needs to be able to support the laminated structure formed on the substrate 4, and a glass substrate, a plastic substrate, a metal substrate, or the like can be used. Substrate 4 need not be transparent.
[0055]
The light absorption layer 5 is formed on the substrate 1. The light absorbing layer 5 may be a layer that absorbs light in the entire visible light region (black) or a layer that absorbs a part of light in the visible light region (other colors). The light absorbing layer 5 is formed by applying a black resin containing a carbon black-based black material on the substrate 1 by a spin coating method, for example.
[0056]
Thereafter, an electrode is formed on the light absorption layer 5. For example, a film with a thickness of 150 nm is formed by a sputtering method using ITO (Indium Tin Oxide). This film is patterned into a plurality of patterns having a width of 100 μm (corresponding to the width of the pixel). These patterns are substantially parallel to each other, and the interval between adjacent patterns is 10 μm.
[0057]
The transparent conversion layer 2 is formed on the electrode 3b. The conversion material contained in the conversion layer 2 can store and hold hydrogen atoms or ions in a steady state, and changes the hydrogen storage amount (retention amount) according to an external stimulus. Materials that can store such hydrogen include LaNi. ₅ , MnNi ₅ , CaNi ₅ ・ TiMn _1.5 , ZrMn1.5, ZrMn ₂ , TiNi, TiFe, Mg ₂ An alloy such as Ni can be used. Further, carbon nanotubes (CNT) or NiOOH can also be used. When NiOOH is used, hydrogen is transferred between the conversion layer 2 and the light control layer 1 by utilizing an electrochemical mechanism. It is preferable to provide an electrolyte layer between them.
[0058]
Conversion layer 2 may include an electrically conductive material in addition to the hydrogen storage material. When an electrically conductive material is included in the conversion layer 2, exchange of hydrogen ions with the light control layer 1 can be performed quickly. As the electrically conductive material, a material capable of conducting ions, such as a liquid or solid electrolyte, a conductive polymer that conducts electric charges (electrons or holes), or a charge transfer complex can be used. The conversion layer 2 may further include a binder material such as a binder resin, if necessary, in addition to the hydrogen storage material and the electrically conductive material.
[0059]
The charges injected from the electrodes 3a and 3b exchange charges in the light control layer 1 and the conversion layer 2, respectively. Since the charge injected from one electrode may move to the other electrode as it is, a layer having a role of a separator such as an ion exchange membrane (separate) is provided between the light control layer 1 and the conversion layer 2. Layer). The separate layer is desirably formed using a material to which ions can move in the layer but to which electric charge is unlikely to move. Such a material is, for example, an ion exchanger, a porous insulator, an ion conductive polymer material, or the like. When the separator layer is provided, the charge injected from one electrode is suppressed from penetrating to the other electrode. Therefore, in the light control layer 1 and the conversion layer 2, the ratio of the charge used for exchanging with the hydrogen ions in the injected electric charge is increased, so that the exchanging can be performed efficiently.
[0060]
In the present embodiment, the conversion layer 2 is formed as follows. Ultra fine particles of Ni alloy which is AB5 type Mm hydrogen storage alloy (dispersion center radius 10 nm), conductive polymer material P1 (material capable of transporting both electron and hole charges), and refractive index of acrylic resin as binder resin Used is a blend of glass and glass. By preparing a solution in which these materials are dissolved in a solvent and applying the solution by a spin coating method or a printing method, the conversion layer 2 having a thickness of, for example, 500 nm can be formed. The formation of such a conversion layer 2 may be performed using an inkjet method or other thin film deposition techniques.
[0061]
Next, the light control layer 1 is formed by a vapor deposition method, a sputtering method, or the like. The light control layer 1 is, for example, a 50 nm-thick yttrium film.
[0062]
Thereafter, the electrodes 3a and the color filters 6 are sequentially formed. The electrode 3a is transparent. The electrode 3a can be formed using ITO by a method similar to the method of forming the electrode 3b. However, the pattern of the electrode 3a is formed so as to extend in a direction substantially perpendicular to the direction in which the pattern of the electrode 3b extends, as shown in FIG. The width of the pattern and the interval between adjacent patterns are, for example, 100 μm and 10 μm, respectively. The color filter 6 is formed by a known method such as a printing method using a known material, for example. As shown in FIG. 4, the color filter 6 has a plurality of patterns having the same width as the width of the pattern of the electrode 3b, for example. Thus, a display element is obtained.
[0063]
By applying a voltage to the electrodes 3a and 3b of the display element, charges and ions are exchanged inside the conversion layer 2, and as a result, hydrogen is transferred between the conversion layer 2 and the light control layer 1 by the mechanism described above. Can cause movement. For this reason, for example, when a voltage as shown in FIG. 1 is applied using the light control layer 1 in which the hydrogen is not doped in the initial state and the conversion layer 2 in which hydrogen is stored in advance, hydrogen ions are supplied from the positive electrode side to the negative electrode. Then, the light control layer 1 is doped. That is, a hydrogen release reaction proceeds on the positive electrode side, and a bonding reaction between hydrogen and a metal proceeds on the negative electrode side, thereby forming a hydrogen metal compound. On the other hand, when a voltage in the opposite direction is applied, hydrogen moves in the opposite direction. Therefore, by changing the polarity of the applied voltage, the optical state of the light control layer 1 is reversibly switched between metallic luster and transparent. Can be switched.
[0064]
Considering only the movement of hydrogen stored in the conversion layer 2, the electrodes 3a and 3b may be short-circuited outside the laminated structure. Such a short circuit is a phenomenon similar to the discharge in the secondary battery, and can return the internal state of the laminated structure to the initial state.
[0065]
Since the conversion layer 2 and the light control layer 1 have the ability to retain hydrogen, when no voltage is applied (when an external circuit is open), no movement of hydrogen occurs and the optical control of the light control layer 1 is performed. (The memory function of the light control layer). For this reason, if a material having excellent hydrogen retention ability is selected, the dimming state can be maintained for a long time without consuming power.
[0066]
Contrary to the above example, a light control layer 1 doped with hydrogen in advance and a conversion layer 2 in which hydrogen is not stored may be used. In that case, by applying a positive potential to the light control layer 1 and a negative potential to the conversion layer 2, hydrogen is transferred from the light control layer 1 to the conversion layer 2, whereby the optical control of the light control material in the light control layer 1 is performed. The target state may be changed.
[0067]
In the present embodiment, since the light reflectance / light transmittance of the light control material can be controlled by the doping amount of hydrogen, the light control is performed by adjusting the voltage applied to the electrodes and the application time (duty ratio, etc.). The light reflectance / light transmittance of the layer 1 can be controlled. If the memory property based on the hydrogen retention ability is used, it is easy to maintain an appropriate light reflectance / light transmittance.
[0068]
When appropriately controlling the storage / release of such hydrogen, attention must be paid to the hydrogen equilibrium pressure-composition isotherm (hereinafter, referred to as "PTC characteristic curve"). As shown in FIG. 4, the PTC characteristic curve shows the relationship between the hydrogen storage amount and the hydrogen equilibrium pressure. In the graph of FIG. 6, the horizontal axis represents the hydrogen storage amount, and the vertical axis represents the hydrogen parallel pressure.
[0069]
In a portion where the PTC characteristic curve is substantially parallel to the horizontal axis (hereinafter referred to as a “plateau region”), the hydrogen storage pressure can be changed under a certain equilibrium pressure, so that the hydrogen equilibrium pressure is kept constant. In this state, the absorption / release of hydrogen can be performed reversibly. For this reason, the display element of the present embodiment performs the switching operation in the plateau region of the PTC characteristic curve.
[0070]
It is desirable that the conversion layer 2 and the light control layer 1 show substantially the same PTC characteristics. More specifically, as shown in FIG. 4, the ranges of the “hydrogen storage amount” in the plateau region in the PTC characteristic curves of the conversion layer 2 and the light control layer 1 overlap, and the level of the “hydrogen equilibrium pressure” is almost equal. Desirably equal. By showing the same hydrogen equilibrium pressure, the transfer of hydrogen between the light control layer 1 and the conversion layer 2 can be performed smoothly. If the hydrogen equilibrium pressure difference between the light control layer 1 and the conversion layer 2 becomes large, it becomes impossible to exchange hydrogen between the two layers even if hydrogen absorption and desorption occur in each layer. Because.
[0071]
The hydrogen storage amount range (width) of the plateau region of the PTC characteristic curve in the conversion layer 2 has a size including the hydrogen storage amount range (width) of the plateau region of the PTC characteristic curve in the light control layer 1. Is more preferable. In the display element of the present embodiment, since the light transmittance of the light control layer 1 is controlled by the hydrogen doping amount of the light control layer 1, the range of the change in the hydrogen storage amount in the conversion layer 2 is changed to the state change of the light control layer 1. If the required amount of change in the hydrogen doping amount is smaller than the required range, the optical state of the light control layer 1 cannot be sufficiently changed.
[0072]
FIG. 3 is referred to again. When the conversion layer 2 is transparent, the display element shown in FIG. 3 can perform switching between the metal reflection state and the transparent state. In order to form a state with high transparency, it is necessary to form not only the substrate 4 and the electrodes 3a and 3b, but also the conversion layer 2 from a material having a high transmittance (no absorption) in the entire visible light range. However, a conversion material such as a hydrogen storage material is often a metal or a colored material, and it is difficult to form a highly transparent conversion layer 2 from such a conversion material layer. Therefore, it is preferable to form the conversion layer 2 by mixing fine particles of the conversion material with a transparent material. Specifically, nanoparticles having a particle size equal to or smaller than the wavelength of light can be formed from the conversion material, and the nanoparticles can be bound with a binder resin having excellent transparency. The conversion layer 2 thus produced not only can exhibit both transparency and hydrogen storage capacity, but also has a surface area increased by converting the conversion material into nanoparticles, so that hydrogen absorption and desorption can be achieved. Efficiency is also expected to increase. It is preferable that the efficiency of hydrogen absorption and desorption by the conversion material be increased because the response speed of the dimming operation is improved. As the conversion material in an ultrafine particle state, a carbon-based material (CNT, fullerene, or the like), a potassium-graphite intercalation compound, or the like can also be used.
[0073]
It is preferable that the light control layer 1 diffusely reflect incident light in a metal reflection state. When the light control layer 1 diffusely reflects light, the display element displays white well.
[0074]
In order for the light control layer 1 to diffusely reflect light in the metal reflection state, for example, fine projections and / or recesses may be present on the surface of the light control layer 1 (FIG. 5B), The light control layer 1 may include light control particles as shown in FIG. 1B (FIG. 5C).
[0075]
First, the light modulating layer 1 having fine convex portions and / or concave portions on the surface will be described in detail.
[0076]
The light modulating layer 1 having fine projections and / or depressions on the surface can be formed, for example, as follows. As shown in FIG. 5B, an electrode 3a, a conversion layer 2, a dimming layer 1, and an electrode 3b are laminated in this order on a substrate 4 having a convex portion. The light control layer 1 is, for example, an yttrium film. Thereby, fine projections can be formed on the surface of the light control layer 1. If there are fine projections on the surface of the light control layer 1, when the light control layer 1 is in a metal reflection state, the reflected light is scattered and recognized as white, so that the surface of the light control layer 1 Appears white. On the other hand, when the light control layer 1 is in a transparent state, the light is absorbed by the conversion layer 2 and thus looks like black or another color.
[0077]
In the example shown in FIG. 5B, since the surface of the substrate has fine projections, the entire flatness of the conversion layer 2 and the light control layer 1 has a shape reflecting the unevenness of the substrate. I have. In other words, not only the top surface (the surface on the light reflection side) but also the bottom surface of the light control layer 1 has a shape reflecting the irregularities of the base. However, since the conversion layer 2 serving as the base does not need to have a concavo-convex structure, the substrate surface and the conversion layer 2 are formed flat, and fine concave portions and / or You may make it form a convex part.
[0078]
As described above, if the metal film such as the yttrium film is flat, the light is mirror-reflected. However, by providing unevenness on the surface of the metal film, the light control layer 1 diffusely reflects the light. Thus, a display element capable of displaying white can be provided. Such a display element is not limited to the color display element having the configuration shown in FIG. 3, and may be a black and white display element without the color filter 6. When applied to a black-and-white display element, white display can be performed more favorably, which is advantageous.
[0079]
Next, the light control layer 1 including the light control particles will be described in detail.
[0080]
FIG. 5C shows the light control layer 1 and the conversion layer 2 including the light control particles. In the light control layer 1 shown in FIG. 5C, fine particles 11 (for example, yttrium, lanthanum, hereinafter referred to as “light control fine particles”) formed using a light control material whose optical characteristics change according to the hydrogen concentration are included. Dispersed in binder resin. The average particle size of the light control fine particles 11 included in the light control layer 1 is, for example, 1 μm. As the binder resin, for example, an acrylic resin having a refractive index substantially equal to that of glass is used. The light control layer 1 further includes an electrically conductive material for exchanging hydrogen ions and charges between the light control fine particles 11 and the conversion layer 2. As the electrically conductive material, a material capable of conducting ions, such as a liquid or solid electrolyte, a conductive polymer (for example, P2) that conducts electric charges (electrons or holes), or a charge transfer complex can be used. .
[0081]
The light control layer 1 including the light control particles is formed, for example, as follows. The light control fine particles 11 are dispersed in a binder resin solution, and a coating solution in which an electrically conductive material is further dissolved is prepared. The coating solution can be formed by applying the coating solution on the conversion layer 2 by, for example, a spin coating method. The thickness of the light control layer 1 is, for example, about 3 μm. The light modulating layer 1 may be formed by using an ink jet method or another thin film deposition technique. The preferred thickness of the light control layer 1 is 1.5 μm or more and 50 μm or less. If it is less than 1.5 μm, the light control layer 1 having a high reflectance cannot be obtained, or the particle size of the light control fine particles 11 used for the light control layer 1 is limited. On the other hand, if it exceeds 50 μm, the conductivity of the light control layer 1 may be reduced.
[0082]
When the light control fine particles 11 are dispersed in the light control layer 1, as described with reference to FIG. 1B, when each light control fine particle 11 is in the metal state, each light control fine particle 11 is in the light control layer. Since light incident on the light control layer 1 is reflected in random directions, the light control layer 1 as a whole can diffusely reflect light.
[0083]
In addition to the light control layer 1 being diffusely reflected, the following advantages can be obtained by forming the light control material into particles. The surface area of the light modulating material can be increased as compared with the case where a thin film made of the light modulating material is used as the light modulating layer 1. Therefore, the efficiency of the reaction between the light modulating material and hydrogen is improved, and higher-speed switching is possible. Further, since the surface area of the light control material is increased, the state of the light control material included in the light control layer 1 can be controlled more reliably. As a result, the difference in reflectance between the diffuse reflection state and the transparent state of the light control layer can be increased.
[0084]
In order for the light control fine particles 11 to reflect light, it is desirable that each light control fine particle 11 has a particle size larger than the wavelength of visible light. Therefore, the particle size of the light control fine particles 11 is preferably 400 nm or more. It is more preferably at least 800 nm. When the thickness is 800 nm or more, transmission of visible light through the light control fine particles 11 can be more reliably prevented, so that the light reflectance of the light control layer 1 can be increased. On the other hand, the particle size of the light control particles m1 is preferably smaller than the thickness of the light control layer 1. If the particle diameter is larger than the thickness of the light control layer 1, the advantage of forming the light control material into particles as described above cannot be obtained. More preferably, the particle size of the light control fine particles 11 is 30 μm or less. When the particle size is 30 μm or less, the reaction efficiency between the light modulating material and hydrogen can be sufficiently increased, and the light incident on the light modulating layer can be surely diffusely reflected. More preferably, the particle size is 3 μm or less. When the particle size of the light control material is, for example, 1 μm, it is preferable that the thickness of the light control layer 1 be about 3 μm.
[0085]
In the display element of the present embodiment, a film of the conductive polymer P1 is disposed between the light control layer 1 and the conversion layer 2 to exchange charges and ions between the light control layer 1 and the conversion layer 2. Is preferred. A layer formed using an electrolyte material may be provided in addition to the charge transfer polymer film. Alternatively, a layer containing a polymer material having charge transfer properties and an electrolyte material may be provided. When a layer containing an electrolyte material (electrolyte membrane) is provided, the movement of hydrogen ions is likely to occur via the electrolyte membrane, so that the characteristics can be improved. Since the conductive polymer P1 is doped with ions for imparting conductivity, the conductive polymer P1 also has a function as an electrolyte membrane. When the light control layer 1 containing light control particles is used as described above, the binder resin of the light control layer 1 can also function as the polymer film or the electrolyte film.
[0086]
In the illustrated example, each of the conversion layer 2 and the light control layer 1 is a single layer, but the conversion layer 2 and / or the light control layer 1 may have a multilayer structure as necessary. Further, when the two conversion layers 2 are arranged so as to sandwich the light control layer 1, hydrogen is absorbed and released on the upper surface and the lower surface of the light control layer 1, so that the switching speed of the display element can be increased.
[0087]
Further, the display element shown in FIG. 3 has a simple matrix structure, but may be an active matrix drive display element having an active element for each pixel. Further, the display device shown in FIG. 3 is a color display device having the color filter 6, but may be a monochrome display device. The black-and-white display element has a configuration basically similar to the configuration shown in FIG. 3, but differs in that it does not have the color filter 6.
[0088]
The display element of the present embodiment can display very bright (high luminance) white as compared with a conventional liquid crystal display element. Further, the contrast ratio can be increased. The reason will be described below.
[0089]
The liquid crystal display device includes a deflecting plate in order to visualize a change in alignment of the liquid crystal molecules caused by applying a voltage. Therefore, of the light incident on the liquid crystal element, the proportion of light used for display is at most 50%. Therefore, there is a problem that white is particularly dark and the display is hard to be visually recognized. On the other hand, the display element of the present embodiment does not require a polarizing plate. Therefore, since the light reflected by the metal (or diffusely reflected by the metal) in the light control layer 1 is directly viewed through the color filter 6, bright white can be displayed. On the other hand, when the light control layer 1 is in the light transmitting state, the color of the light absorbing layer 5 is directly seen, so that a very high-quality black table can be obtained. As a result, the display contrast ratio can be increased.
[0090]
Since the display element of this embodiment has a memory property, the information once written is retained even when the power is turned off. Therefore, since a voltage needs to be applied only when rewriting is necessary, power consumption can be reduced.
[0091]
Further, the display element of the present embodiment can be manufactured only by sequentially laminating each layer on the substrate. Accordingly, there is no step of bonding two substrates and injecting a liquid crystal material between them, as in a liquid crystal display element, so that the manufacturing process is simple. Further, since the display element of the present embodiment does not have a liquid crystal layer, it can be thinner and lighter than the liquid crystal display element.
[0092]
The display element of the present embodiment can be applied to various display devices. For example, since the display element of this embodiment has high memory properties, it can be applied to electronic paper, an electronic book, and the like.
[0093]
(Embodiment 2)
Hereinafter, a second embodiment of the display device according to the present invention will be described with reference to FIG. As shown in FIG. 7, the display element of the present embodiment has a point that the conversion layer 2 has a function as a light absorption layer, and thus does not have a light absorption layer between the substrate 4 and the electrode 3b. However, this is different from the display element of the first embodiment.
[0094]
The display element of the present embodiment includes a conversion layer 2 that absorbs visible light. Such a conversion layer 2 can be formed, for example, from black CNT. When the conversion layer 2 is colored, or when the conversion layer 2 is transparent and a pigment or a colored resin is mixed therein, the state between the metal diffuse reflection state and the colored state is changed. Switching becomes possible.
[0095]
The light-absorbing conversion layer 2 is made of a potassium-graphite intercalation compound that functions as a hydrogen storage material and a conductive polymer material P1 (a material that can transport both electrons and holes) and an acrylic resin that functions as a binder resin. (Blend resin). Since the blended resin can be made into a solution, the conversion layer 2 can be formed by spin coating. The thickness of the conversion layer 2 can be set to, for example, about 500 nm. When the conversion layer 2 cannot absorb light sufficiently, a black resin may be further added to the conversion layer 2.
[0096]
The light control layer 1 is, for example, the same as the light control layer 1 used in the first embodiment. That is, an yttrium film having a thickness of about 50 nm may be used, or a film having particles of a light control material such as yttrium particles may be used. Further, the surface may have minute concave portions and / or convex portions.
[0097]
In order to exchange charges and ions between the light control layer 1 and the conversion layer 2, it is preferable to arrange a film of the conductive polymer P1 between the light control layer 1 and the conversion layer 2. A layer formed using an electrolyte material may be provided in addition to the charge transfer polymer film. Alternatively, a layer containing a polymer material having charge transfer properties and an electrolyte material may be provided. When a layer containing an electrolyte material (electrolyte membrane) is provided, hydrogen ions move through the electrolyte membrane, so that characteristics can be improved. Since the conductive polymer P1 is doped with ions for imparting conductivity, the conductive polymer P1 also has a function as an electrolyte membrane. In the case of the light control layer 1 containing particles of the light control material, the binder resin can also function as the polymer film or the electrolyte film.
[0098]
The electrode 3a is a transparent electrode as in the first embodiment, but the electrode 3b and the substrate 4 need not be transparent.
[0099]
When a voltage is applied to the electrodes 3a and 3b so that the conversion layer 2 is on the positive electrode side and the dimming layer 1 is on the negative electrode side with respect to the display element of the present embodiment, as shown in FIGS. Then, the light incident surface side of the display element changes from a metal (diffuse) reflection state to a black (light absorption) state.
[0100]
When the light modulating layer 1 is a film made of a light modulating material, as shown in FIG. 8A, the light incident surface side of the display element, which showed metal reflection in the initial state, is gradually applied by applying a voltage. It changes to a black (light absorbing) state. This is because the black conversion layer 2 is visually recognized as the light control layer 1 becomes transparent.
[0101]
As shown in FIGS. 8A and 8B, the light modulating layer 1 preferably diffuses and reflects light in a metal reflection state. As shown in FIG. 8 (b), if there are minute projections on the surface of the light control layer 1, the light incident surface side of the display element, which showed metal diffuse reflection in the initial state, is gradually applied by applying a voltage. It changes to a black (light absorbing) state. Further, as shown in FIG. 8C, when the light control layer 1 includes particles of the light control material (light control fine particles), the light incident surface side of the display element, which showed the metal diffuse reflection in the initial state, has , And gradually changes to a black (light absorbing) state by application of a voltage. This is because as the light control fine particles included in the light control layer 1 become transparent, the black conversion layer 2 becomes visible.
[0102]
8A to 8C, this state is maintained even when the power is turned off. Further, when the electrodes 3a and 3b are short-circuited or a voltage whose polarity is inverted is applied to the electrodes 3a and 3b, the light incident side surface of the display element changes so as to show metallic (diffused) luster. .
[0103]
A display element including the light control layer 1 that diffuses and reflects light in a metal reflection state as shown in FIGS. 8B and 8C can display bright and good white. Such a display element may be a black and white display element. FIG. 9 is a cross-sectional view showing the monochrome display element of the present embodiment. As shown in FIG. 9, the black-and-white display element has a basic configuration similar to that shown in FIG. 7, but differs in that it does not have a color filter 6.
[0104]
According to the present embodiment, there is no need to separately provide a light absorbing layer, so that the manufacturing process can be further simplified. In the display element of the first embodiment, light incident on the display element passes through the light control layer 1, the conversion layer 2, and the electrode 3 layer and is absorbed by the light absorption layer 5 in a light absorbing state. On the other hand, in the display element of the present embodiment, the light incident on the display element passes through only the light control layer 1 and is absorbed by the conversion layer 2 in the light absorbing state, so that the reflection generated at the interface of the layers and the like. Light is also reduced, and the quality of black display can be improved. Therefore, the contrast ratio of the display increases.
[0105]
(Embodiment 3)
Next, a third embodiment of the display element according to the present invention will be described with reference to FIG. The display element of the present embodiment has the same configuration as the display element of the first embodiment, but differs in the following points. In the first embodiment, the color filter 6 is provided on the electrode 3a. However, in the present embodiment, the conversion layer 2 has a color filter function, and it is not necessary to provide the color filter on the electrode 3a.
[0106]
In the configuration shown in FIG. 10, the light control layer 1 is provided on the side close to the substrate 4 and the conversion layer 2 is formed thereon, but the conversion layer 2 is arranged on the side close to the substrate 4 and The light control layer 1 may be formed. If the substrate 4 is a transparent substrate such as a glass substrate, the light absorbing layer 5 may be provided on the back surface of the substrate 4.
[0107]
The conversion layer 2 that can function as a color filter is formed, for example, as follows. Each of the RGB color pigments is mixed with the same material as the material used for the transparent conversion layer 1 of the first embodiment to prepare each of the RGB dispersion solutions. These dispersion solutions are applied on the light control layer 1 by an inkjet method so as to correspond to the pattern of the pixels. Thereby, the conversion layer 2 is formed. The coating method may be another known printing method such as a screen printing method or a roll printing method, in addition to the inkjet method.
[0108]
The display element of the present embodiment has the same display characteristics as the first embodiment. According to the present embodiment, there is no need to separately provide a color filter, so that the manufacturing process can be simplified.
[0109]
(Embodiment 4)
Next, a fourth embodiment of the display element according to the present invention will be described with reference to FIG. As described below, the light control layer 1 in the display element of this embodiment is different from the light control layer 1 in the display elements of the other embodiments described above. Other configurations are the same as in the first embodiment. The display element of the present embodiment does not have the light absorbing layer 5 as in the display element shown in FIG. 3 or the metal diffusion without using the light absorbing conversion layer 2 as in the display element shown in FIG. It is possible to switch between a reflective (white) state and a light absorbing (black or colored) state.
[0110]
FIG. 12 is a cross-sectional view showing the light control layer 1 and the conversion layer 2 in the display element of the present embodiment. As shown in FIG. 12, the light control layer 1 includes light control fine particles (such as yttrium fine particles) 11 similar to the light control fine particles included in the light control layer 1 of FIG. 5C. The light modulating fine particles 11 are adsorbed on the colored particles 10 such as, for example, carbon black particles. In order to surely adsorb the light control fine particles 11 to the surface of the color particles 10, it is preferable that the particle size of the light control particles 11 is smaller than the particle size of the color particles 10. The preferred particle size of the light control fine particles is the same as the preferred particle size described with reference to FIG.
[0111]
Such a light control layer 1 can be formed, for example, as follows. By mixing black particles having a particle size of 5 μm and light control particles having a smaller particle size (for example, 1 μm) in a binder resin solution, the light control particles are adsorbed so as to cover the surface of the black particles. . After the conductive polymer material P2 is further blended into the obtained solution, it is applied on the electrode 3b by a spin coating method. The thickness of the obtained light control layer 1 is, for example, 10 μm. Since the black particles are dispersed, the thickness of the light control layer 1 is larger than the thickness of the light control layer 1 of other embodiments. However, since both the carbon black fine particles and the light control fine particles show high conductivity, the entire light control layer 1 has sufficient conductivity.
[0112]
When a voltage is applied to the electrodes 3a and 3b so that the conversion layer 2 is on the positive electrode side and the dimming layer 1 is on the negative electrode side with respect to the display element of this embodiment, as shown in FIG. The light incident surface side of the display element that has shown reflection gradually changes to a black state. This is because the black particles become visible as the light modulating fine particles adsorbed on the black particles become transparent. This state is maintained even when the power is turned off. When the electrodes 3a and 3b are short-circuited or a voltage whose polarity is inverted is applied to the electrodes 3a and 3b, the light incident side surface of the display element changes so as to show a metal diffuse gloss.
[0113]
In the present embodiment, since the conversion layer 2 does not need to be transparent or black, there is much room for selection of a material used for the conversion layer 2. The electrode 3b does not need to be transparent, and may be a metal electrode.
[0114]
The display element of the present embodiment has the same display characteristics as the display element of the first embodiment.
[0115]
According to the display element of the present embodiment, when the light control fine particles included in the light control layer 1 are in a metal reflection state, the reflected light is scattered and recognized as white, so that the surface of the light control layer 1 becomes white. appear. On the other hand, when the light control fine particles are in a transparent state, light is absorbed by colored particles such as black particles, so that the surface of the light control layer 1 looks black or another color. Thus, the light control layer 1 itself transitions between the metal diffusion state and the light absorption (coloring) state. Therefore, in this embodiment, it is not necessary to separately provide a layer having a light absorbing property such as a light absorbing layer, so that the manufacturing process can be simplified.
[0116]
(Embodiment 5)
A fifth embodiment of the display element according to the present invention will be described with reference to FIG.
[0117]
The display element of this embodiment has the same configuration as that of the fourth embodiment, but differs in that the conversion layer 2 has a function of a color filter as shown in FIG.
[0118]
The light control layer 1 is the same as the light control layer 1 in the fourth embodiment. That is, the light control fine particles are included, and the light control fine particles are adsorbed to the black particles. The light control layer 1 can be formed by the same method as the method of forming the light control layer 1 in the fourth embodiment.
[0119]
The conversion layer 2 having a color filter function is, for example, the same as the conversion layer 2 in the third embodiment. The conversion layer 2 can be formed on the light control layer 1 by a method similar to the method of forming the conversion layer 2 in the third embodiment.
[0120]
According to this embodiment, since the light modulating layer 1 has a light absorbing property, it is not necessary to separately provide a layer having a light absorbing property such as a light absorbing layer, and the conversion layer 2 also functions as a color filter. Therefore, since it is not necessary to separately provide a color filter, the manufacturing process can be greatly simplified. Further, as compared with the display element of the first embodiment, the number of layers through which incident light and reflected light pass is reduced, so that light absorption in a white state and reflection of light in a black state are reduced. Is improved.
[0121]
(Embodiment 6)
With reference to FIG. 14, a sixth embodiment of the display device according to the present invention will be described.
[0122]
The display element of this embodiment has the same configuration as that of the fourth embodiment, except that a backlight 8 is provided on the back surface of the substrate 4 as shown in FIG. The display element of the present embodiment can switch between the transmissive display element and the reflective display element by turning on / off the backlight 8.
[0123]
The conversion layer 2 is transparent, for example, the same as the conversion layer 2 in the first embodiment. The conversion layer 2 can be formed on the electrode 3b by the same method as the method for forming the conversion layer 2 in the first embodiment.
[0124]
The light control layer 1 in the display element of the present embodiment is the same as the light control layer 1 in the fourth embodiment. That is, the light control fine particles are included, and the light control fine particles are adsorbed to the black particles. The light control layer 1 can be formed on the conversion layer 2 by the same method as the method of forming the light control layer 1 in the fourth embodiment.
[0125]
The stacking order of the conversion layer 2 and the light control layer 1 on the substrate 4 is not limited to the illustrated one, and the light control layer 1 may be disposed on the side closer to the substrate 4 and the conversion layer 2 may be formed thereon. . In this case, the conversion layer 2 may have a function of a color filter. Such a conversion layer 2 is, for example, the same as the conversion layer 2 in the fifth embodiment. Such a configuration is advantageous because the color filter 6 can be eliminated.
[0126]
In the present embodiment, the electrodes 3a, 3b and the substrate 4 are transparent. For example, the electrodes 3a and 3b are ITO electrodes, and the substrate 4 is a glass substrate.
[0127]
The backlight 8 may be a known backlight used for a liquid crystal display device or the like.
[0128]
The display element of the present embodiment can be used as a reflective display element when there is external light. That is, when sufficient light is incident from above the substrate 4, display by reflected light can be performed as in the fourth embodiment. On the other hand, when there is little external light and it is difficult to use the device as a reflective display device, the backlight 8 is turned on, so that the device can be used as a transmissive display device. Light incident on the light control layer 1 from the backlight 8 is absorbed by the light control layer 1 if the light control layer 1 of the pixel is in a light absorbing (black) state, so that the pixel displays black. When the light control layer 1 of the pixel changes to the metal diffuse reflection state, light incident on the light control layer 1 from the backlight 8 is scattered by the light control fine particles of the light control layer 1. The scattered light can be extracted from above the substrate 4. Therefore, the pixel displays white.
[0129]
As described above, according to the present embodiment, it can be used as either a transmissive display element or a reflective display element depending on the environment of external light, so that a display element with good visibility in a multi-scene can be realized.
[0130]
(Embodiment 7)
Referring to FIGS. 15A and 15B, a seventh embodiment of the display device according to the present invention will be described. The display element of this embodiment has the same configuration as that of the sixth embodiment, but differs in the following points. In the sixth embodiment, a film including light control particles adsorbed on colored particles is used as the light control layer 1, but in the present embodiment, a film of a light control material is used as the light control layer 1. The display element of the present embodiment can switch between the transmissive display element and the reflective display element by turning on / off the backlight 8.
[0131]
The light control layer 1 in the display element shown in FIGS. 15A and 15B may be any as long as it reflects light in a mirror in a metal reflection state. For example, a metal film such as an yttrium film as shown in FIG. This metal film is typically substantially flat.
[0132]
When there is external light, the display element of this embodiment can be used as a reflective display element as shown in FIG. That is, when sufficient light is incident from above the substrate 4, display by reflected light can be performed as in the sixth embodiment. If the light control layer 1 of the pixel is in a state of transmitting light, the incident light passes through the light control layer 1 and other layers and is absorbed by the turned-off backlight 8 on the back surface of the transparent substrate 4. Therefore, the pixel displays black. If the light control layer 1 of the pixel is in a state of reflecting light, the incident light is reflected by the light control layer 1, so that the pixel displays white. On the other hand, when there is little external light and it is difficult to use the device as a reflective display device, the backlight 8 is turned on, so that the device can be used as a transmissive display device as shown in FIG. Light incident on the light control layer 1 from the backlight 8 is reflected by the light control layer 1 and returned to the backlight 8 if the light control layer 1 of the pixel is in a mirror reflection state. Therefore, the pixel displays black. When the light control layer 1 of the pixel changes to a state of transmitting light, light incident on the light control layer 1 from the backlight 8 can be directly extracted from above the substrate 4. Therefore, the display of the pixel becomes white.
[0133]
In the present embodiment, as described above, the states of the light control layer 1 of the pixel to be displayed and the non-display pixel are different between the case where the light control layer 1 is used as a reflective display element and the case where the light control layer 1 is used as a transmissive display element. Therefore, it is preferable to invert the state of the light control layer 1 of each pixel with the switching between the reflective display element and the transmissive display element.
[0134]
Note that the order of lamination of the conversion layer 2 and the light control layer 1 with respect to the substrate may be reversed from that in the illustrated example.
[0135]
As described above, according to the present embodiment, it can be used as either a transmissive display element or a reflective display element depending on the environment of external light, so that a display element with good visibility in a multi-scene can be realized.
[0136]
(Embodiment 8)
A seventh embodiment of the display device according to the present invention will be described with reference to FIG. The display element of the present embodiment differs from the display elements of the other embodiments in that the light modulating layer 1 itself also serves as one of the electrodes, as shown in FIG.
[0137]
When the light control layer 1 is a metal film such as an yttrium film, the light control layer 1 can function as an electrode. Even if the light control layer 1 is a film containing particles of the light control material (light control fine particles), the light control layer 1 is used as an electrode if the binder resin of the light control layer 1 contains a conductive material. be able to. When the light control layer 1 is arranged on the substrate 4 side of the conversion layer 2, the light control layer 1 can function as the electrode 3b. Further, as shown in FIG. 13, when the light control layer 1 is disposed on the conversion layer 2, the light control layer 1 can function as the electrode 3a.
[0138]
In order for the light control layer 1 to function as an electrode, it is necessary to pattern a film formed from the light control material. As the light control material, the same material as the light control material used in the first embodiment can be used. In the present embodiment, the light control layer 1 is formed as follows. First, a metal film is formed on the conversion layer 2 by a sputtering method or the like. This metal film is patterned by a mask evaporation patterning, a wet / dry patterning process, or the like. Thereby, the light control layer 1 is obtained. The light control layer 1 has sufficient conductivity to function as an electrode.
[0139]
Alternatively, the light control layer 1 including light control fine particles may be formed. In this case, a solution containing necessary materials such as a binder resin, light control fine particles, and a conductive material was prepared, and the solution was patterned on the conversion layer 2 by using a known printing method. The light control layer 1 can be formed.
[0140]
In the present embodiment, a conversion layer 2 having the same light absorption as the conversion layer 2 in the second embodiment is used. Instead, a transparent conversion layer 2 similar to the conversion layer 2 in the first embodiment may be used. In that case, the light absorption layer 5 may be arranged somewhere between the light control layer 1 and the substrate 4.
[0141]
The display element of the present embodiment is not limited to the display element having the configuration shown in FIG. In addition, the light control layer 1 may function as one of the electrodes in the display element according to the other embodiments described above. For example, in the transmissive display element shown in FIG. 14, the light control layer 1 can function as an electrode without providing the electrode 3a (FIG. 17).
[0142]
According to the present embodiment, since the light control layer 1 also functions as an electrode, the number of manufacturing steps of the display element can be reduced.
[0143]
【The invention's effect】
According to the present invention, it is possible to provide a display element using a material that can transition between a metal reflection state and a transmission state. Since the display element of the present invention does not have a polarizing plate unlike a liquid crystal display element, it is possible to display with high brightness and a high contrast ratio.
[0144]
The display element of the present invention can be applied to various types of display devices of active matrix drive or simple matrix drive (including full-color and monochrome display devices). Further, the display element of the present invention can be applied to any of a reflection type, a transmission type, and a projection type display device. In particular, the use of the display element of the present invention is advantageous because a display device which can function as both a reflective display device and a transmissive display device can be formed. Further, since the display element of the present invention has high memory properties, it can be applied to electronic books and electronic paper.
[Brief description of the drawings]
FIGS. 1A to 1C are cross-sectional views schematically showing the light control principle of a display device according to the present invention.
FIG. 2 is a diagram illustrating the operation principle of the display element of the present invention.
FIG. 3 is a sectional view showing a first embodiment of a display element according to the present invention.
FIG. 4 is a plan view showing a first embodiment of a display element according to the present invention.
FIGS. 5A to 5C are cross-sectional views showing a light control layer and a conversion layer in the first embodiment of the display element according to the present invention.
FIG. 6 is a graph showing a hydrogen equilibrium pressure-composition isotherm (PTC characteristic curve) of the light control layer and the variable layer.
FIG. 7 is a sectional view showing a second embodiment of the display element according to the present invention.
FIGS. 8A to 8C are cross-sectional views showing a dimming layer and a conversion layer in a display device according to a second embodiment of the present invention.
FIG. 9 is a sectional view showing a second embodiment of the display element according to the present invention.
FIG. 10 is a sectional view showing a third embodiment of the display element according to the present invention.
FIG. 11 is a sectional view showing a fourth embodiment of the display element according to the present invention.
FIG. 12 is a sectional view showing a light control layer and a conversion layer in a fourth embodiment of the display element according to the present invention.
FIG. 13 is a sectional view showing a fifth embodiment of the display element according to the present invention.
FIG. 14 is a sectional view showing a sixth embodiment of the display element according to the present invention.
FIGS. 15A and 15B are cross-sectional views showing a seventh embodiment of the display element according to the present invention.
FIG. 16 is a sectional view showing an eighth embodiment of the display element according to the present invention.
FIG. 17 is a sectional view showing an eighth embodiment of the display element according to the present invention.
[Explanation of symbols]
M1 light control layer
M2 conversion layer
m1 light control fine particles
m2 colored particles
1 Light control layer
2 Conversion layer
3a Upper electrode
3b Lower electrode
4 Substrate
5 Absorption layer
6 Color filters
8 Backlight
10 Colored particles
11 Light control fine particles

Claims (15)

A display element including a plurality of pixels, wherein each of the plurality of pixels is
A first layer including a first material whose optical characteristics change according to the concentration of the specific element;
A second layer containing a second material that may contain the specific element, wherein the second material emits or absorbs the specific element when a voltage is applied;
A pair of electrodes for applying the voltage to the second layer,
A display element, wherein a light reflectance of the first layer changes in response to the voltage. The display element according to claim 1, wherein the first material can transition between a light reflection state and a light transmission state according to the concentration of the specific element. The display element according to claim 2, wherein the first layer diffusely reflects light when the first material is in a light reflecting state. The display device according to claim 3, wherein the first material is a particle. The display device according to claim 3, wherein at least one of an upper surface and a lower surface of the first layer has irregularities. The display element according to claim 4, wherein the first layer further includes colored particles, and the first material is adsorbed on the colored particles. The first layer transitions between a state in which light is diffusely reflected and a state in which light is transmitted, and the second layer has light transmittance,
The display device according to claim 3, further comprising a light absorption layer that absorbs light transmitted through the first layer and the second layer. The first layer transitions between a state in which light is diffusely reflected and a state in which light is transmitted, and the second layer has visible light absorption,
The display element according to claim 3, wherein the second layer is disposed on a side of the first layer opposite to a light incident surface. The display element according to claim 1, wherein the second layer is disposed on a light incident side of the first layer and functions as a color filter. The display element according to claim 1, wherein the specific element is hydrogen, and the second layer includes a hydrogen storage material. The display element according to claim 1, wherein the second material emits or absorbs the specific element by exchanging electrons. The display element according to claim 1, wherein the first layer has conductivity, and functions as one of the pair of electrodes. 13. The display device according to claim 1, which is a reflective display device. The display device according to claim 6, further comprising a backlight. The display element according to claim 1, wherein the first layer transitions between a state in which light is mirror-reflected and a state in which light is transmitted, and further includes a backlight.

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