JP2018105920A - Electro-optic device - Google Patents

Abstract

An excellent white state is realized in an apparatus using an electrochromic material.
A first substrate 11 having a first electrode 15 on one side, a second substrate 12 having a second electrode 16 on one side and disposed opposite to the first substrate, and an electrodeposition material. And includes an electrolyte layer disposed between the first electrode and the second electrode, and the first electrode has an uneven shape on one side in contact with the electrolyte layer, and the surface roughness Ra of the uneven shape In this electro-optical device, the value of Ra / RSm, which is the ratio of the average length RSm, is 0.018 or more.
[Selection] Figure 3

Description

  The present invention relates to an electro-optical device configured using an electrochromic material.

  WO 2012/118188 pamphlet (Patent Document 1) includes a pair of substrates, a pair of electrodes formed on opposite surfaces of the pair of substrates, one of which is a transparent electrode having nano-order unevenness, and a pair of A dimming element having an electrolyte, an electrochromic material containing silver, and an electrolyte layer containing a mediator is disclosed. In this light control element, when a voltage is applied between a pair of electrodes, the silver ions in the electrochromic material are reduced and deposited as silver in one electrode to form a film, and when the voltage is released, the deposited silver is It dissolves again as silver ions. In this case, if silver is formed on a smooth electrode, the appearance is a mirror surface, and if silver is formed on a particle-modified electrode, the appearance is dark (black state) due to irregular reflection of light. . For this reason, if one of the pair of electrodes is smooth and the other is a particle-modified electrode, the mirror state and the dark state can be switched depending on the polarity of the voltage. Further, when the voltage is released, the space between the substrates is in a transparent state (a state in which light is transmitted).

  Since the above-described dimming element is in a specular state, a dark state, or a transparent state as an externally obtained state, for example, a screen for displaying an image projected by a projector using the dimming element is provided. When trying to configure, the mirror state is used. However, when the mirror surface state is used, strong reflection occurs only in the direction in which the incident angle and the reflection angle of the light constituting the image are equal, so that there is a disadvantage that the viewing angle becomes narrow. For this reason, it is desired to realize a good white state.

International Publication No. 2012/118188 Pamphlet

  A specific aspect of the present invention is to provide a technique capable of realizing a good white state in an apparatus using an electrochromic material.

  An electro-optical device according to one aspect of the present invention includes (a) a first substrate having a first electrode on one surface side, and (b) a second electrode on one surface side, and is disposed to face the first substrate. A second substrate; and (c) an electrodeposition material containing an electrolyte layer disposed between the first electrode and the second electrode, and (d) the first electrode comprising the electrolyte The electro-optical device has a concavo-convex shape on one side in contact with the layer, and a value of Ra / RSm, which is a ratio between the surface roughness Ra and the average length RSm, of the concavo-convex shape is 0.018 or more.

  According to the above configuration, it is possible to realize a good white state due to scattering of incident light in an apparatus using an electrochromic material.

FIG. 1 is a schematic cross-sectional view illustrating a configuration of an electro-optical device according to an embodiment. FIG. 2 is a schematic cross-sectional view for explaining the configuration of the first electrode in detail. FIG. 3 is a schematic cross-sectional view for explaining the operation principle of the electro-optical device. FIG. 4 is a diagram illustrating an observation image of the surface treatment state of each sample of the electro-optical device according to the example. FIG. 5 is a diagram illustrating screen characteristics of the electro-optical device according to the example. FIG. 6 is a diagram illustrating a relationship between relative reflection luminance and surface roughness of the electro-optical device according to the example. FIG. 7 is a diagram illustrating the relationship between the relative reflection luminance of the electro-optical device according to the example and Ra / RSm (ratio of Ra and RSm). FIG. 8 is a diagram showing the relationship between the size of the surface irregularities and the scattering efficiency.

  FIG. 1 is a schematic cross-sectional view illustrating a configuration of an electro-optical device according to an embodiment. The electro-optical device shown in FIG. 1 is used, for example, as a screen for displaying an image projected by a projector, and includes a first substrate 11, a second substrate 12, an electrolyte layer 13, a sealing material 14, and a driving device 20. It is comprised including. The first substrate 11 and the second substrate 12 are arranged with their one side facing each other.

  The first substrate 11 is a hard substrate (for example, a glass substrate) having translucency, for example. On the one surface side of the first substrate 11, a first electrode 15 having a fine uneven shape is provided over almost the entire surface. Similarly, the 2nd board | substrate 12 is a hard board | substrate (for example, glass substrate) which has translucency, for example. On the one surface side of the second substrate 12, a flat second electrode 16 is provided over almost the entire surface.

  The electrolyte layer 13 is configured by using an electrolytic solution containing an electrodeposition material, and is disposed between each surface of the first substrate 11 and the second substrate 12. Specifically, the electrolytic solution constituting the electrolyte layer 13 includes an electrochromic material, a mediator, a supporting electrolyte, a solvent, a gelling polymer, and the like.

As an example of the material constituting the electrolyte layer 13, 350 mM of AgBr can be used for the electrochromic material, 30 mM of CuCl ₂ can be used for the mediator, 700 mM of LiBr can be used for the supporting electrolyte, and triglyme can be used for the solvent.

  Note that the silver compound is not limited to the above, and silver chloride, silver oxide, silver bromide, silver iodide, silver nitrate, or the like can be used. The concentration of the silver compound is preferably, for example, 5 mM or more and 500 mM or less, but is not limited thereto.

The supporting electrolyte is not particularly limited as long as it promotes the redox reaction or the like of the coloring material. For example, lithium salt (LiCl, LiBr, LiI, LiBF ₄ , LiClO ₄ etc.), potassium salt (KCl, KBr, KI etc.) ), Sodium salts (NaCl, NaBr, NaI, etc.) can be preferably used. The concentration of the supporting electrolyte is preferably 10 mM or more and 1 M or less, but is not limited thereto.

  The solvent is not particularly limited as long as it can stably hold the coloring material and the like, and the refractive index n is close to or similar to the constituent materials of the first substrate 11 and the second substrate 12. It is desirable that the refractive indexes be approximately the same, in order to enhance transparency by preventing reflection at the interface as much as possible when the electro-optical device is in a transparent state. For example, if each substrate is made of alkali-free glass having a refractive index of 1.52, if the refractive index difference between the solvent and the glass is ± 0.15, the interface reflection can be reduced to 1% or less, and the refractive index difference is ± If it is 0.10, interface reflection can be made 0.5% or less. As such a solvent, a polar solvent such as propylene carbonate, an organic solvent having no polarity, an ionic liquid, an ion conductive polymer, a polymer electrolyte, and the like can be used. Specifically, triglyme (n = 1.432), propylene carbonate (n = 1.419), dimethyl sulfoxide (n = 1.479), N, N-dimethylformamide (n = 1.431), tetrahydrofuran ( n = 1.409), γ-butyrolactone (n = 1.436), and the like can be used.

  The sealing material 14 is provided between each surface side of the first substrate 11 and the second substrate 12 so as to surround a region where the substrates overlap each other, and seals the electrolyte layer 13. As the sealing material 14, for example, a UV curable sealing material, a UV / thermosetting sealing material, or a thermosetting sealing material can be used.

  In the present embodiment, a gap material (for example, 50 μm in diameter) is added to the sealing material 14, and the gap distance (cell thickness) between the first substrate 11 and the second substrate 12 is secured by this gap material. In addition, when using the thing of a large area as the 1st board | substrate 11 and the 2nd board | substrate 12, in order to reduce the nonuniformity of cell thickness, it is preferable to disperse | distribute a gap material in a substrate surface.

  The driving device 20 is connected to the first electrode 15 and the second electrode 16 and supplies a driving voltage to the electrolyte layer 13 through these.

  FIG. 2 is a schematic cross-sectional view for explaining the configuration of the first electrode in detail. Several configurations are conceivable for the configuration of the first electrode 15. The first electrode 15 in the embodiment shown in FIG. 2A includes a conductive film 22 provided along the surface shape of a large number of minute recesses 21 formed on one surface side of the first substrate 11. Yes. As illustrated, the conductive film 22 is provided along the surface shape of the recess 21, and has an uneven shape including a large number of recesses 24 on one surface side of the first substrate 11. The first electrode 15 in the embodiment shown in FIG. 2B has a conductive film 23 provided on one surface side of the first substrate 11, and the conductive film 23 is formed from a large number of fine recesses 24 on the one surface side. It has an uneven shape. According to any of these aspects, the first electrode 15 having a fine uneven shape can be obtained.

  FIG. 2C is a schematic cross-sectional view for explaining in detail the uneven shape of the first electrode. The unevenness on the surface of the conductive film 22 (or 23) of the first electrode 15 can be defined by, for example, the depth L and the width W of the recess 24 as illustrated. The depth L of the recess 24 is, for example, about 400 nm, and the width W of the recess 24 is, for example, several μm. Although a hemispherical shape as shown in the figure is considered as the shape model of the concave portion 24, it is considered that the shape is actually a random shape close to a hemispherical shape, and the depth and width thereof are not constant but may vary within a certain range. .

  FIG. 3 is a schematic cross-sectional view for explaining the operation principle of the electro-optical device. FIG. 3A shows the operating principle when realizing the white state. By applying a DC voltage between the first electrode 15 and the second electrode 16 so that the first electrode 15 side is at a relatively low potential, metal nuclei are generated and grown, and as shown in FIG. A metal film 30 is deposited on the recess 24 of one electrode 15. The metal film 30 deposited here is a dense film formed so as to follow a minute concavo-convex shape including each concave portion 24 as shown in the figure. If the uneven shape at this time is equal to or larger than the wavelength size of visible light, the incident light is scattered, so that the appearance is white.

  FIG. 3B shows an operation principle when realizing the mirror state. By applying a DC voltage between the first electrode 15 and the second electrode 16 so that the second electrode 16 side is at a relatively low potential, metal nuclei are generated and grown. A flat metal film 30 is deposited on the surface of the two electrodes 16. Since the incident light on the flat metal film at this time is regularly reflected, the appearance is a mirror surface. In addition, in a state where no voltage is applied between the first electrode 15 and the second electrode 16 (a state where no voltage is applied), the metal film is not deposited, so that the appearance is transparent.

  That is, according to the state of voltage application between the first electrode 15 and the second electrode 16, the electro-optical device according to the present embodiment has a white state (light scattering state), a specular state (light reflection state), and an appearance. Each state of a transparent state (light transmission state) can be obtained.

  Next, a method for manufacturing the electro-optical device of this embodiment will be described. Here, it is preferable for the case where the first electrode 15 is configured including the conductive film 22 provided in a large number of minute recesses 21 on one surface side of the first substrate 11 (see FIG. 2A). An example of the manufacturing method will be described.

  By subjecting one surface of a transparent substrate such as an alkali-free glass substrate to blasting, for example, a fine uneven shape is formed on the one surface side of the transparent substrate. Thereby, the 1st board | substrate 11 which has a fine uneven | corrugated shape on the one surface side is obtained. At this time, the roughness of the uneven shape of the first substrate 11 can be controlled by appropriately setting various conditions for the blast treatment. When blasting is used, the conditions include the particle size of the projection material (abrasive grains), the material of the projection material, the projection pressure, the projection angle, the substrate distance during processing, the processing time, and the like. Note that a wet etching process or the like may be used instead of the blasting process. Various conditions for the wet etching treatment include chemical composition, concentration, treatment time, and the like.

  Next, a conductive film is formed on the surface of the first substrate 11 having an uneven shape. For example, a transparent conductive film (ITO film) made of ITO (indium tin oxide) is formed by sputtering. Thereby, the 1st electrode 15 comprised by the electrically conductive film 22 provided in many fine recessed parts 21 provided in the one surface side of the 1st board | substrate 11 is obtained. The sheet resistance of the ITO film as the conductive film 22 is, for example, about 5Ω / sq., And the film thickness is several hundred nm.

  In addition, another transparent substrate such as an alkali-free glass substrate is prepared, and a conductive film is formed on one surface thereof. For example, an ITO film is formed by sputtering. Thereby, the 2nd board | substrate 12 which has the 2nd electrode 16 on the one surface side is obtained. The sheet resistance of the ITO film as the conductive film is, for example, about 5Ω / sq., And the film thickness is several hundred nm.

Note that the transparent conductive film is not particularly limited as long as light transmittance in the visible light region is high. For example, a ZnO film, a Ga ₂ O ₅ film, a graphene film, or the like can be used. Moreover, there is no limitation in particular also about the formation method of a transparent conductive film, For example, various methods, such as a vacuum evaporation method, an ion plating method, a spin coating method, are considered.

  Next, a sealing material to which a gap material is added is applied to one substrate, for example, one surface side of the first substrate 11. As the sealing material, for example, various types such as an ultraviolet curing type, a thermosetting type, a mixed type of ultraviolet curing and thermosetting can be used.

Further, a gap material is dispersed on the one surface side of the other second substrate 12. Although it is preferable from experience that the application rate at this time is 1 to 3 / mm ² , it is not limited thereto. In addition, it may replace with a gap material and may perform gap control by forming protrusions, such as a rib, on a board | substrate. In this case, the aspect ratio of the protrusion is preferably as high as possible.

  Next, an electrolytic solution containing an electrodeposition material is sealed between the first substrate 11 and the second substrate 12. This step can be performed, for example, by a one-drop filling method (ODF method). Specifically, after the electrolytic solution is dropped into a region surrounded by the sealing material on the one surface side of the first substrate 11, the one surface of the first substrate 11 and the one surface of the second substrate 12 are faced to each other, and both are attached. Match. Then, the sealing material is cured by applying ultraviolet rays and / or heat. Thereby, the sealing material 14 and the electrolyte layer 13 whose periphery is sealed thereby are obtained. Note that after the first substrate 11 and the second substrate 12 are bonded together, an electrolytic solution may be injected between them by a vacuum injection method, or other methods may be used.

  As described above, the electro-optical device of this embodiment can be manufactured. Even when the first electrode 15 is configured by providing a large number of fine recesses 24 on one surface of the conductive film 23 provided on one surface side of the first substrate 11 (see FIG. 2B), Except for the step of obtaining one electrode 15, the same manufacturing method as described above can be used. As for the step of obtaining the first electrode 15, for example, the conductive film 23 is formed on one surface of the first substrate 11 by an appropriate film forming method such as sputtering, and the one surface of the conductive film 23 is blasted or etched. A large number of recesses 24 may be formed by processing according to the above.

(Example)
As an example of the electro-optical device, several samples were manufactured.
The thickness of the electrolyte layer 13 of each sample was 50 μm. As an electrolyte, a solvent was triglyme, 350 mM of AgBr was added as an electrochromic material, 700 mM of LiBr was added as a supporting electrolyte, and 30 mM of CuCl ₂ was added as a mediator. As the first electrode 15 and the second electrode 16, ITO films having a sheet resistance of 5Ω / sq. Were used.

  About the uneven | corrugated shape of the surface of the 1st electrode 15, surface conditions, specifically average roughness (arithmetic average roughness) Ra, average length RSm, and average depth Rc are changed as follows by changing blast conditions. Different samples were prepared. The average roughness (arithmetic average roughness) Ra, the average length RSm, and the average depth Rc here correspond to those defined by the JIS standard (JIS B 0601: 2001).

Sample 1: Ra = 0.12 μm, RSm = 20.0 μm, Rc = 0.43 μm
Sample 2: Ra = 0.49 μm, RSm = 18.5 μm, Rc = 1.77 μm
Sample 3: Ra = 0.54 μm, RSm = 25.2 μm, Rc = 1.93 μm

  FIG. 4 is a diagram illustrating an observation image of the surface treatment state of each sample of the electro-optical device according to the example. Specifically, FIG. 4A is an observation image of the sample 1 and FIG. 4B is an observation image of the sample 2. Note that the observation image of sample 3 is omitted. As shown in the figure, the sample 1 has a surface roughness Ra of 0.12 μm, and the diameter of each recess 24 formed on the surface is approximately 2 to 5 μm. Sample 2 has a surface roughness Ra of 0.49 μm, and the diameter of each recess 24 formed on the surface is approximately 3 to 7 μm.

  Next, the viewing angle characteristics of each sample will be described. In general, the characteristics of the viewing angle of the screen are evaluated by the angle dependency of the reflected luminance at each angle with respect to the reflected luminance at an angle of 5 ° with respect to the normal direction of the substrate surface of the object to be measured. The range in which the image projected on the screen can be viewed is called the viewing range angle, which is the angle at which the relative reflection brightness is ½. For use as a screen, the viewing field angle is preferably 60 ° or more. For each sample, the reflection luminance at each angle was measured every 5 ° in the range of 5 ° to 60 °.

  FIG. 5 is a diagram illustrating screen characteristics of the electro-optical device according to the example. In sample 1, the viewing range angle is about 10 °, but in samples 2 and 3, the viewing range angle is at least 60 ° or more, indicating that the screen has sufficient screen characteristics. The surface roughness Ra of each of the samples 2 and 3 is 0.25 μm or more. In general, it is said that when Ra is ½ or more of the wavelength, scattering is intensified, and it can be seen that a result consistent with this is obtained.

  FIG. 6 is a diagram illustrating a relationship between relative reflection luminance and surface roughness of the electro-optical device according to the example. When the surface roughness Ra is larger than 0.4 μm, the viewing range angle tends to increase, but the relative reflection luminance at 60 ° with respect to the surface roughness Ra does not necessarily increase monotonously. This is considered to be related to the density of the surface irregularities of the first electrode 15. The surface irregularities exist at intervals of the average length RSm, but when RSm increases with respect to Ra, the density of the surface irregularities decreases and scattering decreases.

  FIG. 7 is a diagram illustrating the relationship between the relative reflection luminance of the electro-optical device according to the example and Ra / RSm (ratio of Ra and RSm). As shown in the figure, it can be seen that the relative reflection luminance at 60 ° increases as Ra / RSm increases. According to the approximate curve obtained based on each plot, it is understood that the value of Ra / RSm should be at least 0.018 or more in order to set the relative reflection luminance at 60 ° to 0.5 or more.

  FIG. 8 is a diagram showing the relationship between the size of the surface irregularities and the scattering efficiency. Scattering due to unevenness on the surface has different scattering efficiency depending on the unevenness height. When the surface unevenness of the first electrode 15 made of a silver film is approximated by a sphere, the scattering efficiency for one uneven portion of each size is as illustrated. The scattering cross section was determined by Mie scattering theory, and the scattering efficiency was determined by the ratio of the scattering cross section and the projected cross section of one concavo-convex portion. The scattering efficiency was 1 when the scattering cross section was larger than the projected cross section. From FIG. 8, the scattering efficiency is about 0.5 in the visible light region when the size of the surface irregularities is 10 μm. That is, 50% is a regular reflection component, which is a reflection characteristic close to specular reflection. Therefore, it can be seen that the average depth Rc of the surface irregularities needs to be smaller than this, and should be 10 μm or less. In general, when the size of the surface irregularities becomes 1/10 or less of the wavelength of incident light, scattering does not occur. The average depths Rc of the samples 2 and 3 having a viewing range angle of 60 ° or more are 1.77 μm and 1.93 μm, respectively, which are in good agreement with the surface unevenness size with high scattering efficiency obtained by calculation.

  According to the embodiments and examples as described above, it is possible to realize a good white state due to scattering of incident light in an electro-optical device using an electrochromic material.

  In addition, this invention is not limited to the content of embodiment mentioned above, In the range of the summary of this invention, it can change and implement variously. For example, in the above description, the screen is cited as an example of a suitable application of the electro-optical device according to the present invention, but the application is not limited to this.

DESCRIPTION OF SYMBOLS 11: 1st board | substrate 12: 2nd board | substrate 13: Electrolyte layer 14: Sealing material 15: 1st electrode 16: 2nd electrode 20: Drive device 21, 24: Recessed part 22, 23: Conductive film 30: Metal film

Claims (5)

A first substrate having a first electrode on one side;
A second substrate having a second electrode on one side and disposed opposite to the first substrate;
An electrolyte layer containing an electrodeposition material and disposed between the first electrode and the second electrode;
Including
The first electrode has a concavo-convex shape on one side in contact with the electrolyte layer, and a value of Ra / RSm, which is a ratio of the surface roughness Ra to the average length RSm, is 0.018 or more. is there,
Electro-optic device. The surface roughness Ra of the concavo-convex shape is ½ or more of visible light wavelength,
The electro-optical device according to claim 1. The surface roughness Ra of the irregular shape is larger than 0.4 μm,
The electro-optical device according to claim 1. An average depth Rc of the uneven shape is 10 μm or less.
The electro-optical device according to claim 1. The refractive index of each of the first substrate and the second substrate is 1.42 or more and 1.55 or less,
The difference between the refractive index of the solvent contained in the electrolyte layer and the refractive index of each of the first substrate and the second substrate is within ± 0.15,
The electro-optical device according to claim 1.