Indication device

Abstract

This display device comprises: a transparent display having a front surface on which an image to be presented to observers is displayed and a rear surface located on the side opposite from the front surface, the rear surface being where the image passes through and is visually recognized; a dimmer sheet having a dimming layer obtained by dispersing a liquid crystal compound in a transparent polymer layer, the dimmer sheet being switchable between a transparent state and an opaque state; and a control unit for controlling the transparent state and opaque state of the dimmer sheet. The distance between the rear surface of the transparent display and a first surface of the dimmer sheet that faces the rear surface is 5 mm or greater in terms of air length.

Description

[Technical Field]

[0001] The present disclosure relates to a display device. [Background Art]

[0002] A transparent display makes the entire screen transparent when no image is displayed, and displays an image with the background of the transparent display transmitted when displaying an image. Since the color of the background of a transparent display may make an image difficult to view, the transmissive display, which is the transparent display described in Patent Document 1, corrects the color of the displayed image according to the color of the background. [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2019-144508 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] When viewed from the back surface located on the opposite side of the front surface on which an image is displayed, an image that is horizontally reversed with respect to the image displayed on the front surface transmits through a common transparent display, so that the image is visible to an observer. Therefore, when a transparent display is caused to function as a window or a partition, an observer who can visually recognize the transparent display from the back side can visually recognize the image of the transparent display from the back side. Accordingly, there is a demand for a display device that allows a user to switch between a state of displaying an image by transmitting the background and a state in which the image is difficult to visually recognize from the back side. [Means for Solving the Problem]

[0005] A display device for solving the above problems comprises a transparent display having a front surface on which an image presented to the observer is displayed and a back surface located on the opposite side of the front surface through which the image is visible, and a dimmable sheet having a dimmable layer in which a liquid crystal compound is dispersed in a transparent polymer layer, and which can switch between a transparent state and an opaque state, wherein the distance between the back surface of the transparent display and the first surface of the dimmable sheet facing the back surface is 5 mm or more in terms of air equivalent length.

[0006] The dimmable sheet, in which liquid crystals are dispersed in a transparent polymer layer, achieves opacity through clouding caused by narrow-angle scattering. Therefore, when the transparent display and the dimmable sheet are in close contact, the image from the transparent display is visible through the back of the dimmable sheet. With the above configuration, the distance between the back of the transparent display and the first surface of the dimmable sheet is 5 mm or more in terms of air equivalent length. This allows the light emitted from the back of the transparent display to be scattered between the transparent display and the dimmable sheet to the extent that the image viewed from the back becomes blurred. Thus, by switching between a first display state that shows the image with the background transparent and a second display state that blurs the image viewed from the back, it is possible to display images that take advantage of the transparency of the transparent display while maintaining image confidentiality and protecting privacy as needed.

[0007] In the above-described display device, the distance between the back surface of the transparent display and the first surface of the dimming sheet may be 50 mm or less in terms of air equivalent length. According to the above configuration, since the distance between the back of the transparent display and the first surface of the dimming sheet is 50 mm or less in terms of air equivalent length, the display device can have high transparency when the dimming sheet is transparent.

[0008] In the above-described display device, an air layer may be located between the back surface of the transparent display and the first surface of the dimming sheet. According to the above configuration, an air layer is located between the transparent display and the dimming sheet, which allows for a lighter display device.

[0009] In the above-described display device, a transparent substrate may be positioned between the back surface of the transparent display and the first surface of the dimming sheet. According to the above configuration, a transparent substrate supporting the transparent display and the dimming sheet is positioned between the transparent display and the dimming sheet, thereby increasing the strength of the display device.

[0010] In the above-described display device, a translucent mirror having a reflective surface may be included between the back surface of the transparent display and the first surface of the dimming sheet. According to the above configuration, when the dimming sheet is made transparent, the transparency of the display device can be maintained while making the image viewed from the back blurry. In addition, by reflecting a portion of the light incident from the back of the display device with the reflective surface, the image displayed on the display device and viewed from the front can be made sharper.

[0011] In the above-described display device, the transparent substrate located between the back surface of the transparent display and the first surface of the dimming sheet may be colored. According to the above configuration, when the dimming sheet is made transparent, the transparency of the display device can be maintained while the image viewed from the back can be made blurred. In addition, since a portion of the light incident from the back can be absorbed by the colored transparent substrate, the image viewed from the front can be made sharp.

[0012] In the above-described display device, the dimming sheet comprises a dimming layer, a pair of transparent electrode layers sandwiching the dimming layer, and a pair of transparent support layers sandwiching the dimming layer and the pair of transparent electrode layers. The dimming layer includes a transparent polymer layer that partitions a plurality of voids, and the liquid crystal compound and dichroic dye located within the voids. The orientation of the liquid crystal compound and the dichroic dye may be controlled according to the potential difference between the pair of transparent electrode layers.

[0013] According to the above configuration, since the dimming layer contains a dichroic dye whose orientation is controlled together with the liquid crystal compound, the opacity of the image when the display device is viewed from the back can be improved when the dimming sheet is opaque. In addition, the clarity of the image when the display device is viewed from the back can be improved.

[0014] The system may further include a transparent support substrate that supports a second surface of the dimming sheet located opposite to the first surface. With the above configuration, the second surface of the dimming sheet is supported by a transparent support substrate, which makes it possible to increase the mechanical strength of the display device.

[0015] In the above-described display device, the haze of the dimming sheet in the opaque state may be 85% or more. In the above-described display device, the clarity of the dimming sheet in the opaque state may be 60% or less.

[0016] In the above-described display device, the total light transmittance of the dimming sheet in the opaque state is 20% or less. According to the above configurations, the effectiveness of increasing image blurring can be enhanced by ensuring that the distance between the transparent display and the dimming sheet is 5 mm or more in terms of air.

[0017] In the above-described display device, the total light transmittance of the dimming sheet in its transparent state may be 40% or more. According to the above configuration, when the dimming sheet is transparent, the effectiveness of the display device in maintaining high transparency can be enhanced. [Effects of the Invention]

[0018] According to this disclosure, in a display device using a transparent display, it is possible to switch between a state in which an image is displayed by making the background transparent and a state in which the image viewed from the back is obscured, thereby ensuring the confidentiality of images and protecting privacy. [Brief explanation of the drawing]

[0019] [Figure 1] FIG. 1 is a schematic front view of the display device according to the first embodiment. [Figure 2] FIG. 2 is a cross-sectional view of the display device according to the embodiment. [Figure 3] FIG. 3 is a cross-sectional view of a normal-type light control sheet that constitutes the display device of the embodiment. [Figure 4] FIG. 4 is a cross-sectional view of a reverse-type light control sheet that constitutes the display device of the embodiment. [Figure 5] FIG. 5 is a cross-sectional view of a display device according to a second embodiment. [Figure 6] FIG. 6 is a cross-sectional view showing a part of a light control sheet according to a third embodiment. [Figure 7] FIG. 7 is a cross-sectional view of a display device according to a fourth embodiment. [Figure 8] FIG. 8 is a cross-sectional view of a display device according to a fifth embodiment. [Figure 9] FIG. 9 is a cross-sectional view of a display device according to a sixth embodiment. [Figure 10] FIG. 10 is a plan view showing a light control sheet included in a display device according to a seventh embodiment. [Figure 11] FIG. 11 is an operation diagram for explaining the operation of the embodiment. [Figure 12] FIG. 12 is an operation diagram for explaining the operation of the embodiment. [Figure 13] FIG. 13 is an operation diagram for explaining the operation of the embodiment. [Figure 14] FIG. 14 is an operation diagram for explaining the operation of the embodiment. [Figure 15] FIG. 15 is an operation diagram for explaining the operation of the embodiment. [Figure 16] FIG. 16 is an operation diagram for explaining the operation of the embodiment. [Figure 17] FIG. 17 is an operation diagram for explaining the operation of the embodiment. [Figure 18]Figure 18 is a diagram showing the device configuration of the dimming sheet and detection sheet included in the display device of the eighth embodiment. [Figure 19] Figure 19 is a table showing the evaluation results of the display devices for the test example and comparative example. [Figure 20] Figure 20 is a table showing the evaluation results of the display devices for the test example and comparative example. [Figure 21] Figure 21 is a table showing the evaluation results of the display devices for the test example and comparative example. [Modes for carrying out the invention]

[0020] (First Embodiment) A first embodiment of the display device will be described with reference to Figures 1 to 4. As shown in Figure 1, the display device 1 comprises a transparent display 2, a dimming sheet 3, and a control device 40. The transparent display 2 is a transparent display and includes a front surface 2A that displays an image 30 to be presented to the observer, and a back surface 2B located opposite to the front surface 2A. When the transparent display 2 is viewed from the front surface 2A, the background of the transparent display 2 is seen through the transparent display 2. The transparent display 2 is, for example, a self-emissive organic light-emitting diode (OLED) display. The dimming sheet 3 includes a first surface 3A facing the back surface 2B of the transparent display 2, and a second surface 3B located opposite to the first surface 3A. The front surface 2A of the transparent display 2 is the front surface 1A of the display device 1, and the second surface 3B of the dimming sheet 3 is the back surface 1B of the display device 1.

[0021] The dimming sheet 3 is positioned such that a space 6 is provided between it and the back surface 2B. The distance between the back surface 2B of the transparent display 2 and the first surface 3A of the dimming sheet 3 is 5 mm or more in terms of air. The dimming sheet 3 is either a normal type or a reverse type. A normal type dimming sheet 3 transitions from an opaque state to a transparent state when a voltage is applied, and returns from the transparent state to an opaque state when the voltage is removed. A reverse type dimming sheet 3 transitions from a transparent state to an opaque state when a voltage is applied, and returns from the opaque state to a transparent state when the voltage is removed. The normal type and the reverse type are similar in that they both include two transparent electrode layers and a dimming layer.

[0022] The transparent display 2 and the dimming sheet 3 are connected to a control device 40. The control device 40 switches between a non-display state (where the image 30 is not displayed) and a display state (where the image 30 is displayed) by controlling the voltage applied to the transparent display 2. The control device 40 also switches the dimming sheet 3 between an opaque state and a transparent state by controlling the drive voltage applied to the dimming sheet 3. The control device 40 may also be connected to an input operation device 50. The input operation device 50 is a device that receives user operations and switches between the non-display state and the display state of the transparent display 2, and between the transparent state and the opaque state of the dimming sheet 3. That is, the input operation device 50 receives user operations to switch the transparent display 2 between the non-display state and the display state. The input operation device 50 also receives user operations to switch the dimming sheet 3 between a transparent state and an opaque state.

[0023] The opacity of the dimming sheet 3 can be expressed by the haze specified in JIS K 7136:2000 "Plastics - Method for determining haze of transparent materials". Haze can be expressed as the percentage of transmitted light that is deviated by 2.5° or more from the incident light among the transmitted light passing through the test piece. When the dimming sheet 3 is made opaque, the haze may be 85% or more, and preferably 95% or more.

[0024] Furthermore, the total light transmittance when the dimming sheet 3 is opaque is 20% or less. The total light transmittance is a value measured using a method compliant with JIS K 7361-1:1997 "Plastics - Test method for total light transmittance of transparent materials - Part 1 Single beam method". It is even more preferable that the total light transmittance when the dimming sheet 3 is opaque is 10% or less. Furthermore, the total light transmittance when the dimming sheet 3 is transparent is 40% or more. It is even more preferable that the total light transmittance when the dimming sheet 3 is transparent is 50% or more. By having a total light transmittance of 40% or more when the dimming sheet 3 is transparent, it is possible to enhance the effectiveness of the display device 1 maintaining high transparency when the dimming sheet 3 is transparent.

[0025] The clarity of the opaque light-adjusting sheet 3 is 60% or less. Here, clarity is the degree to which the image of an object seen through the light-adjusting sheet 3 is clearly and without distortion, and can be expressed by the following formula (1). Clarity is also an index for evaluating whether the outline of the object seen through the light-adjusting sheet 3 is clearly visible or not.

[0026] 100 × {(LC - LR) / (LC + LR)} …(1) Light intensity LC is the amount of light that travels in a straight line along the optical axis of parallel light among the light transmitted through the dimming sheet 3. Light intensity LR is the amount of narrow-angle scattered light whose angle with respect to the optical axis of parallel light is within ±2.5°. If the dimming sheet 3 is of the reverse type, an AC voltage is applied between the pair of transparent electrode layers, and the state in which the haze of the dimming sheet 3 is saturated is set to opaque.

[0027] When the dimming sheet 3 is opaque, the haze, clarity, and total light transmittance of the dimming sheet 3 satisfy the above-mentioned ranges, thereby increasing the effectiveness of enhancing image blurring when the distance between the transparent display 2 and the dimming sheet 3 is 5 mm or more in air equivalent.

[0028] Figure 2 shows the cross-sectional structure of the display device 1. A space 6 is provided between the back surface 2B of the transparent display 2 and the first surface 3A of the dimming sheet 3. When the dimming sheet 3 is in close contact with the back surface 2B of the transparent display 2, even if the dimming sheet 3 is opaque, the proportion of light emitted from the transparent display 2 that passes through the dimming sheet 3 increases. As a result, the image displayed on the transparent display 2 is seen by an observer 101 facing the back surface 1B of the display device 1, and is therefore visible to the observer 101. This tendency is particularly pronounced when the light incident on the dimming sheet 3 is narrow-angle scattered.

[0029] Therefore, the display device 1 has a space 6 between the back surface 2B of the transparent display 2 and the first surface 3A of the dimming sheet 3 where light emitted from the back surface 2B of the transparent display 2 is scattered. Space 6 is an air layer, and light incident on space 6 is scattered within space 6. As a result, when the image 30 displayed on the transparent display 2 is viewed from the back, the image 30 becomes blurry.

[0030] The width W1 of space 6 is 5 mm or more. In other words, the relative distance between the transparent display 2 and the dimming sheet 3 is 5 mm or more. That is, the distance between the transparent display 2 and the dimming sheet 3 is 5 mm or more in terms of the air equivalent length LA. The air equivalent length LA is calculated by the following formula.

[0031] LA = T + T × (1 - 1 / n) In the above formula, T is the thickness of the medium located between the back surface 2B of the transparent display 2 and the first surface 3A of the dimming sheet 3, and n is the refractive index of the medium located between the back surface 2B of the transparent display 2 and the first surface 3A of the dimming sheet 3. In this embodiment, air is located between the back surface 2B of the transparent display 2 and the first surface 3A of the dimming sheet 3. Since the refractive index n of air is 1, in this embodiment, the distance between the back surface 2B of the transparent display 2 and the first surface 3A of the dimming sheet 3 is equal to the air equivalent length LA.

[0032] Furthermore, if the space 6 is filled with only one medium, the thickness T is equal to the distance between the back surface 2B of the transparent display 2 and the first surface 3A of the dimming sheet 3. In contrast, if the space 6 is filled with, for example, two mediums, the air equivalent length LA is the sum of the air equivalent length calculated by the above formula for the first medium and the air equivalent length calculated by the above formula for the second medium. For example, if an air layer and a substrate layer are located between the back surface 2B of the transparent display 2 and the first surface 3A of the dimming sheet 3, the sum of the thickness of the air layer and the air equivalent length at the thickness of the substrate layer is the air equivalent length at the distance between the back surface 2B and the first surface 3A.

[0033] By setting the width W1 to 5mm or more, the image viewed from the back 1B can be made blurred when the dimming sheet 3 is in an opaque state. If the lower limit of the width W1 is 10mm or more, the image viewed from the back 1B can be made even more blurred when the dimming sheet 3 is in an opaque state, thereby improving the opacity of the image 30. The width W1 of space 6 is 50mm or less. If the width W1 exceeds 50mm, the transparency of the display device 1 will decrease when the dimming sheet 3 is in a transparent state. In other words, by setting the width W1 to 50mm or less, the decrease in the transparency of the display device 1 when the dimming sheet 3 is in a transparent state is suppressed. To put it another way, by setting the width W1 to 50mm or less, the increase in the haze of the display device 1 when the dimming sheet 3 is in a transparent state is suppressed.

[0034] In order to increase the blurriness of the image viewed from the back surface 1B when the dimming sheet 3 is opaque, and to increase the transparency of the display device 1 when the dimming sheet 3 is transparent, the distance between the transparent display 2 and the dimming sheet 3 is preferably 5 mm or more and 20 mm or less, and more preferably 5 mm or more and 10 mm or less.

[0035] The cross-sectional structure of the dimming sheet 3 will be described with reference to Figures 3 and 4. Note that the thickness ratios of each layer shown in the cross-sectional view of the dimming sheet 3 are shown for illustrative purposes only. Therefore, the thickness ratios of each layer of the dimming sheet 3 are not limited to those shown in Figures 3 and 4.

[0036] Figure 3 shows the cross-sectional structure of a normal type dimming sheet 3C. The dimming sheet 3C has a dimming layer 11, a first transparent electrode layer 12A, a second transparent electrode layer 12B, a first transparent support layer 13A, and a second transparent support layer 13B. The dimming layer 11 is sandwiched between the first transparent electrode layer 12A and the second transparent electrode layer 12B.

[0037] The dimming sheet 3C is provided with a first connection region 15A and a second connection region 15B. In addition to the first connection region 15A and the second connection region 15B, the dimming sheet 3C also includes a dimming region 20. The first connection region 15A is a region within the dimming sheet 3C that does not include the dimming layer 11, the second transparent electrode layer 12B, and the second transparent support layer 13B. The first transparent electrode layer 12A is exposed in the first connection region 15A. The first terminal portion 6A is connected to the first transparent electrode layer 12A that is exposed in the first connection region 15A.

[0038] The second connection region 15B is a region within the dimming sheet 3C that does not contain the dimming layer 11, the first transparent electrode layer 12A, and the first transparent support layer 13A. The second transparent electrode layer 12B is exposed in the second connection region 15B. The second terminal portion 6B is connected to the second transparent electrode layer 12B that is exposed in the second connection region 15B.

[0039] The dimming region 20 is the portion of the dimming sheet 3C excluding the first connection region 15A and the second connection region 15B. In other words, the dimming region 20 is the portion of the dimming sheet 3C that includes the dimming layer 11.

[0040] Terminals 6A and 6B are electrically connected to the control device 40 via wirings 40A and 40B. The first terminal 6A is connected to the control device 40 via wiring 40A, and the second terminal 6B is connected to the control device 40 via wiring 40B. The control device 40 applies an AC voltage to the dimming region 20. The control device 40 generates a drive voltage signal to change the light transmittance, specifically the diffuse transmittance, and applies it to the first terminal 6A and the second terminal 6B. In this way, the control device 40 controls the potential difference between the first transparent electrode layer 12A and the second transparent electrode layer 12B in the dimming region 20. The second transparent electrode layer 12B is controlled, for example, to ground potential.

[0041] The light-adjusting layer 11 is a layer in which a liquid crystal compound is dispersed in a transparent polymer. The light-adjusting layer 11 includes a transparent polymer layer which is a resin composition, a liquid crystal composition, and a spacer (not shown). The transparent polymer layer is a cured product of a photopolymerizable compound. The photopolymerizable compound may be an ultraviolet-curable compound or an electron-beam-curable compound. The photopolymerizable compound is compatible with the liquid crystal composition. The transparent polymer layer partitions voids within the light-adjusting layer 11. The liquid crystal composition contains a liquid crystal compound and fills the voids in the transparent polymer layer. There may be two or more different sizes of voids. That is, multiple voids may include voids of a first size and voids of a second size different from the first size. The shape of the voids may be spherical, ellipsoidal, or irregular. When it is necessary to improve the controllability of the dimensions in the voids, the photopolymerizable compound is preferably an ultraviolet-curable compound. The spacer is interposed between the first transparent electrode layer 12A and the second transparent electrode layer 12B, thereby making the height of the photochromic layer 11, i.e., the thickness of the photochromic layer 11, uniform.

[0042] The liquid crystal composition can be held in one of the following forms: polymer network type, polymer dispersion type, or capsule type. The polymer network type has a transparent polymer network with a three-dimensional mesh structure, and holds the liquid crystal composition in the interconnected voids of the network. The polymer network is an example of a transparent polymer layer. The polymer dispersion type has numerous isolated voids within a transparent polymer layer, and holds the liquid crystal composition in the voids dispersed in the polymer layer. The capsule type holds a liquid crystal composition in a capsule shape within a transparent polymer layer. The thickness of the light-adjusting layer 11 may be 0.5 μm or more and 460 μm or less. In particular, the thickness of the light-adjusting layer 11 is preferably 1 μm or more and 100 μm or less, and more preferably 3 μm or more and 50 μm or less.

[0043] Each of the first transparent electrode layer 12A and the second transparent electrode layer 12B is conductive and transparent to visible light. Known materials can be used for the first transparent electrode layer 12A and the second transparent electrode layer 12B. Examples of materials for forming the first transparent electrode layer 12A and the second transparent electrode layer 12B include indium tin oxide, fluorine-doped tin oxide, tin oxide, zinc oxide, carbon nanotubes, and poly(3,4-ethylenedioxythiophene). The thickness of the first transparent electrode layer 12A and the second transparent electrode layer 12B is, for example, 5 nm to 500 nm, respectively.

[0044] Each of the first transparent support layer 13A and the second transparent support layer 13B is a substrate that is transparent to light in the visible region. Known materials can be used for the first transparent support layer 13A and the second transparent support layer 13B. An example of a material for forming the first transparent support layer 13A and the second transparent support layer 13B is a synthetic resin or an inorganic compound. Examples of synthetic resins include polyester, polyacrylate, polycarbonate, and polyolefin. Examples of polyester include polyethylene terephthalate and polyethylene naphthalate. Examples of polyacrylate include polymethyl methacrylate. Examples of inorganic compounds include silicon dioxide, silicon oxynitride, and silicon nitride. The thickness of the first transparent support layer 13A and the second transparent support layer 13B is, for example, 20 μm to 500 μm, respectively.

[0045] Each of the first terminal section 6A and the second terminal section 6B comprises, for example, a conductive adhesive layer and a wiring board. The conductive adhesive layer is formed from, for example, an anisotropic conductive film (ACF), anisotropic conductive paste (ACP), isotropic conductive film (ICF), isotropic conductive paste (ICP), etc. The wiring board is, for example, a flexible printed circuit board (FPC). Alternatively, each of the first terminal section 6A and the second terminal section 6B may have a structure in which a conductive material such as a conductive tape and wiring 40A, 40B are joined by soldering or the like.

[0046] The dimming layer 11 changes the orientation of the liquid crystal compound in response to the voltage change occurring between the first transparent electrode layer 12A and the second transparent electrode layer 12B. The change in orientation of the liquid crystal compound alters the degree of scattering, absorption, and transmission of visible light entering the dimming layer 11. Specifically, when no voltage signal is applied to the first transparent electrode layer 12A and the second transparent electrode layer 12B, the orientation of the liquid crystal compound in the longitudinal direction is irregular. As a result, the degree of scattering of light incident on the dimming layer 11 increases, causing the dimming region 20 to appear opaque and cloudy. On the other hand, when a voltage signal is applied and a potential difference of a predetermined value or more is generated between the first transparent electrode layer 12A and the second transparent electrode layer 12B, the liquid crystal compound is oriented, and the longitudinal direction of the liquid crystal compound becomes aligned with the electric field direction between the first transparent electrode layer 12A and the second transparent electrode layer 12B. That is, the longitudinal direction of the liquid crystal compound becomes approximately perpendicular to the plane in which the first transparent electrode layer 12A and the second transparent electrode layer 12B extend. As a result, light can more easily pass through the dimming layer 11, so the dimming region 20 becomes transparent.

[0047] Figure 4 shows the cross-sectional structure of the reverse-type dimming sheet 3D. The reverse-type dimming sheet 3D differs from the normal-type dimming sheet 3C in that it includes a first alignment layer 14A between the dimming layer 11 and the first transparent electrode layer 12A, and a second alignment layer 14B between the dimming layer 11 and the second transparent electrode layer 12B. The liquid crystal composition contained in the dimming layer 11 includes a negative-type liquid crystal compound having a negative dielectric constant.

[0048] When the driving voltage applied to the first transparent electrode layer 12A and the second transparent electrode layer 12B is released, the liquid crystal compound receives an orientation restricting force from the first alignment layer 14A and the second alignment layer 14B, causing the long axis of the liquid crystal compound to align with the stacking direction in the dimming sheet 3D. That is, it is approximately perpendicular to the plane over which the first alignment layer 14A and the second alignment layer 14B of the liquid crystal compound extend. As a result, the dimming sheet 3D suppresses scattering at the dimming layer 11 across the entire visible light spectrum, thereby becoming transparent.

[0049] When a driving voltage is applied, the liquid crystal compound is subjected to an orientation-restricting force by the electric field. The long axis direction of the liquid crystal compound begins to move in a direction perpendicular to the direction of the electric field. At this time, the long axis direction of the liquid crystal compound is constrained by the intermolecular interactions and the size of the voids in the liquid crystal composition, but it is oriented so as to scatter the light incident on the dimming sheet 3. As a result, the dimming sheet 3D experiences scattering in the dimming layer 11 across the entire visible light spectrum, thereby becoming opaque.

[0050] Next, the operation of the display device 1 will be explained with reference to Figure 2. Here, the operation of the display device 1 will be explained when the dimming sheet 3 is of the reverse type. The display device 1 switches between a non-display state in which the image 30 is not displayed and a display state in which the image 30 is displayed. The display device 1 has a first non-display state in which the dimming sheet 3 is transparent and a second non-display state in which the dimming sheet 3 is opaque. The display device 1 also has a first display state in which the image is transmitted through the back surface 1B and a second display state in which the visibility of the image 30 from the back surface 1B is reduced. In other words, the display device 1 has four modes.

[0051] (First hidden state) The following describes the non-display state. In the first non-display state, the control device 40 does not apply a drive voltage to the transparent display 2 to display the image 30, thereby turning off the transparent display 2, and also does not apply a drive voltage to the dimming sheet 3, thereby making the dimming sheet 3 transparent. In this first non-display state, the power consumption of the display device 1 is the lowest among the four modes. At this time, an observer 100 facing the front 1A of the display device 1 can see objects such as people located behind the back 1B. Similarly, an observer 101 facing the back 1B can see objects such as the observer 100 facing the front 1A. In the first non-display state, the transparency of the display device 1 is increased, thereby reducing the feeling of confinement in the space in which the display device 1 is installed. In other words, according to the first non-display state of the display device 1, the display device 1 can function as a highly transparent window or partition.

[0052] (Second hidden state) In the second non-display state, the control device 40 does not apply a drive voltage to the transparent display 2 to display the image 30, thereby turning off the transparent display 2, and applies a drive voltage to the dimming sheet 3, thereby making the dimming sheet 3 opaque. In the second non-display state, when the dimming sheet 3 is opaque, objects such as observer 101 located behind the back 1B are less visible to observer 100 facing the front 1A of the display device 1 than when the display device 1 is in the first non-display state. Also, objects such as observer 100 facing the front 1A are less visible to observer 101 facing the back 1B than when the display device 1 is in the first non-display state. In the second non-display state, even when the image 30 is not displayed, the confidentiality of the space partitioned by the display device 1 and the protection of privacy can be enhanced.

[0053] (First display state) In the first display state, the control device 40 applies a drive voltage to the transparent display 2, thereby displaying the image 30 on the transparent display 2, and does not apply a drive voltage to the dimming sheet 3, thereby making the dimming sheet 3 transparent. For information that does not require privacy protection, it is also possible to intentionally allow objects located behind the display to pass through. In the first display state, an observer 100 facing the front 1A of the display device 1 can view the image 30 superimposed on the background. An observer 101 facing the back 1B of the display device 1 views the image 30 displayed on the transparent display 2 in a reversed state compared to the image 30 viewed from the front 1A. In the first display state, the display device 1 displays the image 30 while increasing its transparency, thereby reducing the feeling of confinement in the space in which the display device 1 is installed. In other words, in the first display state of the display device 1, the display device 1 can function as a highly transparent window or partition.

[0054] (Second display state) In the second display state, the control device 40 applies a drive voltage to the transparent display 2, thereby displaying the image 30 on the transparent display 2, and also applies a drive voltage to the dimming sheet 3, thereby making the dimming sheet 3 opaque. When the drive voltage is applied, the dimming sheet 3 becomes cloudy, resulting in an opaque state. An observer 100 facing the front 1A of the display device 1 can see the image 30 displayed on the transparent display 2. An observer 101 facing the back 1B of the display device 1 can only see the image 30 with reduced visibility, or cannot see the image 30 at all. In this way, the confidentiality of the displayed image 30 is maintained, thereby protecting privacy. In addition, because the opaque dimming sheet 3 reduces the amount of incident light entering the transparent display from the back 1B of the display device 1, the observer 100 facing the front 1A can see a clear image 30.

[0055] Furthermore, in the first and second display states, the space 6 reduces the amount of light incident on the transparent display 2 via the dimming sheet 3, thereby improving the clarity of the image 30 as seen from the front 1A.

[0056] Thus, since the display device 1 can switch between each hidden state and each displayed state according to the usage situation, it is particularly effective when used in windows and partitions of buildings, windows of moving objects such as automobiles, etc.

[0057] As described above, the first embodiment of the display device provides the following advantages. (1-1) Since the distance between the back surface 2B of the transparent display 2 and the first surface 3A of the dimming sheet 3 is 5 mm or more in terms of air equivalent length, the light emitted from the back surface 2B of the transparent display 2 can be scattered between the transparent display 2 and the dimming sheet 3 to such an extent that the image 30 observed from the back surface 1B becomes blurred. Furthermore, by making it possible to switch between a first display state in which the image 30 is displayed by allowing the background to pass through, and a second display state in which the image 30 as seen from the back surface 1B becomes blurred, it is possible to display the image 30 while taking advantage of the transparency of the transparent display 2, and to maintain the confidentiality of the image 30 and protect privacy as needed.

[0058] (1-2) Since the distance between the back surface 2B of the transparent display 2 and the first surface 3A of the dimming sheet 3 is 50 mm or less in terms of air equivalent length, the display device 1 can maintain high transparency in the first non-display state and the first display state in which the dimming sheet 3 is transparent.

[0059] (1-3) Because an air layer, or space 6, is located between the transparent display 2 and the dimming sheet 3, the display device 1 can be made lighter. (1-4) Since the haze of the opaque dimming sheet 3 is 95% or more, the image 30 viewed from the back 1B of the display device 1 can be made blurred in the second display state.

[0060] (1-5) Since the clarity of the dimming sheet 3, which is opaque, is 60% or less, the image 30 viewed from the back 1B of the display device 1 can be made blurred in the second display state. (1-6) Since the total light transmittance of the opaque dimming sheet 3 is 20% or less, the image 30 viewed from the back 1B of the display device 1 can be made blurred in the second display state.

[0061] (1-7) Since the total light transmittance of the dimming sheet 3 in its transparent state is 40% or more, the display device 1 can maintain high transparency in the non-display state where the dimming sheet 3 is transparent and the image 30 is not displayed, and in the first display state where the image is transmitted from the back surface 1B.

[0062] (Second Embodiment) A second embodiment of the display device will be described with reference to Figure 5. The display device 1 of the second embodiment includes a transparent adhesive layer 4 and a transparent support substrate 5 in addition to the configuration of the display device 1 of the first embodiment. The transparent adhesive layer 4 is provided on the second surface 3B of the dimming sheet 3, thereby bonding the transparent support substrate 5 to the dimming sheet 3. The transparent adhesive layer 4 may have at least one property of ultraviolet scattering, ultraviolet absorption, infrared scattering, infrared absorption, and sound insulation.

[0063] The transparent support substrate 5 has a first surface 5A that is bonded to the transparent adhesive layer 4, and a second surface 5B located on the opposite side of the first surface 5A. The transparent support substrate 5 supports the dimming sheet 3 via the transparent adhesive layer 4. The transparent support substrate 5 supports the second surface 3B of the dimming sheet 3. The second surface 5B of the transparent support substrate 5 is the back surface 1B of the display device 1. The transparent support substrate 5 may be a single-layer structure or a multi-layer structure. The transparent support substrate 5 may have at least one of the following properties: ultraviolet scattering, ultraviolet absorption, infrared scattering, infrared absorption, scratch resistance, humidity penetration resistance, and anti-reflection.

[0064] As described above, according to the second embodiment, in addition to the effects described in (1-1) to (1-7) of the first embodiment, the following effects can be obtained. (2-1) The display device 1 is equipped with a transparent support substrate 5 that supports the dimming sheet 3, thereby increasing the mechanical strength of the display device 1.

[0065] (Third embodiment) A third embodiment of the display device 1 will be described with reference to Figure 6. In the third embodiment, the dimming sheet 3 includes a dimming layer 11 containing a dichroic dye.

[0066] Figure 6 shows a part of the reverse-type dimming sheet 3, specifically a cross-section of the PDLC (Polymer Dispersed Liquid Crystal) type dimming layer 11 and alignment layers 14A and 14B. Note that the dimming sheet 3 may also be of a normal type. Furthermore, the liquid crystal composition retention type in the dimming layer 11 may be a PNLC (Polymer Network Liquid Crystal) type, in which liquid crystal compounds are dispersed within a network-like polymer layer.

[0067] The light-adjusting layer 11 includes a transparent polymer layer 11P, a liquid crystal composition 11LC, and a spacer SP. The transparent polymer layer 11P is a cured product of a photopolymerizable compound. The photopolymerizable compound may be an ultraviolet-curable compound or an electron-beam-curable compound. The photopolymerizable compound is compatible with the liquid crystal composition 11LC.

[0068] The transparent polymer layer 11P partitions the voids 11D within the light-adjusting layer 11. The transparent polymer layer 11P has multiple voids 11D. When it is necessary to improve the controllability of the dimensions of the voids 11D, the photopolymerizable compound is preferably an ultraviolet-curable compound. An example of an ultraviolet-curable compound is one that contains polymerizable unsaturated bonds at the ends of its molecular structure. Alternatively, an ultraviolet-curable compound contains polymerizable unsaturated bonds in addition to the ends of its molecular structure. The photopolymerizable compound is one polymerizable compound or a combination of two or more polymerizable compounds. The liquid crystal composition 11LC fills the voids 11D of the transparent polymer layer 11P.

[0069] The liquid crystal composition 11LC contains a liquid crystal compound LCM and a dichroic dye DP. The liquid crystal composition 11LC may further contain viscosity reducers, defoamers, antioxidants, weather stabilizers, and solvents. Examples of weather stabilizers include ultraviolet absorbers and light stabilizers.

[0070] The retention type of the liquid crystal composition 11LC by the transparent polymer layer 11P may be the polymer dispersion (PDLC) type or polymer network (PNLC) type described above, or it may be a capsule type. The retention type of the liquid crystal composition 11LC is one of the group consisting of PDCL type, PNCL type, and capsule type.

[0071] The transparent polymer layer 11P of the PNLC-type light-adjusting layer 11 has a plurality of voids 11D partitioned by a three-dimensional network. The liquid crystal composition 11LC is located within the interconnected voids 11D of the network. The transparent polymer layer 11P of the capsule-type light-adjusting layer 11 has dispersed capsule-shaped voids 11D, and the liquid crystal composition 11LC is located within the voids 11D. There are two or more different sizes of voids 11D. That is, the plurality of voids 11D may include voids 11D having a first size and voids 11D having a second size different from the first size. The shape of the voids 11D is spherical, ellipsoidal, or irregular.

[0072] A liquid crystal compound (LCM) is at least one selected from the group consisting of Schiff bases, azos, azoxys, biphenyls, terphenyls, benzoic acid esters, trans, pyrimidines, pyridazines, cyclohexanecarboxylic acid esters, phenylcyclohexanes, biphenylcyclohexanes, dicyanobenzenes, naphthalenes, and dioxanes. A liquid crystal compound (LCM) is either a single liquid crystal compound or a combination of two or more liquid crystal compounds.

[0073] The dichroic dye DP has an elongated molecular shape, and its absorbance in the visible region along the molecular long axis is greater than its absorbance along the molecular short axis. In this embodiment, the dichroic dye DP exhibits a black or near-black color when its molecular long axis intersects the direction of incident light at a predetermined angle. In other words, the dichroic dye DP exhibits a black or near-black color when it is oriented such that at least its molecular long axis is substantially perpendicular to the normal direction of the contact surface between the light-adjusting layer 11 and the alignment layer 14A and the alignment layer 14B. The dichroic dye DP is driven by a guest-host type with a liquid crystal compound LCM as the host, thereby exhibiting color. Note that the dichroic dye DP may exhibit a color other than black.

[0074] The dichroic dye DP is at least one selected from the group consisting of polyiodine, azo compounds, anthraquinone compounds, naphthoquinone compounds, azomethine compounds, tetrazine compounds, quinophthalone compounds, merocyanine compounds, perylene compounds, and dioxazine compounds. The dichroic dye DP is one dye or a combination of two or more dyes. When it is necessary to increase lightfastness and the dichroic ratio, the dichroic dye is at least one selected from the group consisting of azo compounds and anthraquinone compounds, and is more preferably an azo compound.

[0075] The content of the dichroic dye DP is preferably 0.5% by weight or more and 10% by weight or less, and more preferably 1% by weight or more and 5% by weight or less, relative to the total weight of the light-adjusting layer 11. When the content of the dichroic dye DP is 0.5% by weight or more, the image viewed from the back surface 1B of the display device 1 can be made blurry when the light-adjusting sheet 3 is in an opaque state. When the content of the dichroic dye DP is 1% by weight or more, the image viewed from the back surface 1B of the display device 1 can be made even more blurry when the light-adjusting sheet 3 is in an opaque state.

[0076] The spacer SP is dispersed throughout the transparent polymer layer 11P. The spacer SP determines the thickness of the photochromic layer 11 around the spacer SP and makes the thickness of the photochromic layer 11 uniform. The spacer SP may be a bead spacer or a photospacer formed by exposure and development of a photoresist. The spacer SP is translucent and may be colorless and transparent or colored and transparent. Preferably, the color exhibited by a colored and transparent spacer SP is the same as the color exhibited by the dichroic dye DP.

[0077] The control device 40 applies a driving voltage to the first transparent electrode layer 12A and the second transparent electrode layer 12B, thereby controlling the orientation of the liquid crystal compound LCM and the dichroic dye DP according to the potential difference between the first transparent electrode layer 12A and the second transparent electrode layer 12B. The driving voltage is a voltage used to change the orientation state of the liquid crystal compound LCM and the dichroic dye DP.

[0078] When the driving voltage is released, the liquid crystal compound (LCM) is subjected to an orientation restricting force, causing the long axis direction of the liquid crystal compound (LCM) and the dichroic dye (DP) to be approximately parallel to the normal direction of the alignment layers 14A and 14B. As a result, the transmittance of diffused light through the dimming sheet 3 becomes higher than in the opaque state, and therefore the haze becomes lower than in the opaque state. In addition, the color of the dimming sheet 3 becomes colorless or nearly colorless.

[0079] When a driving voltage is applied, the long axis directions of the liquid crystal compound LCM and dichroic dye DP follow the electric field in such a way that the light incident on the dimming sheet 3 is scattered, causing the dimming sheet 3 to become opaque. Among the dichroic dyes DP, those whose smaller angle between the long axis direction and the normal direction of the alignment layers 14A and 14B is close to 90° exhibit a black color. Because a space 6 exists between the transparent display 2 and the dimming sheet 3, and because the opaque dimming sheet 3 exhibits a black color, the image viewed from the back surface 1B of the display device 1 can be made blurred.

[0080] As explained above, according to the third embodiment, in addition to the effects described in (1-1) to (1-7) of the first embodiment, the following effects can be obtained. (3-1) The dimming layer 11 contains a liquid crystal compound LCM and a dichroic dye DP, and is driven in a guest-host manner. Therefore, in the reverse-type dimming sheet 3, when a driving voltage is applied between the first transparent electrode layer 12A and the second transparent electrode layer 12B, it becomes a colored opaque state, thereby improving the opacity of the image when the display device 1 is viewed from the back surface 1B. In addition, when the dimming layer 11 contains a black dichroic dye DP, the dichroic dye DP absorbs the visible light incident from the back surface 1B of the display device 1, so that the observer 100 can see a clear image on the front surface 1A of the display device 1.

[0081] (Fourth Embodiment) A fourth embodiment of the display device will be described with reference to Figure 7. The display device 1 includes a transparent substrate 7 located between the transparent display 2 and the dimming sheet 3. In other words, the transparent substrate 7 is located in the space 6 between the transparent display 2 and the dimming sheet 3.

[0082] When the entire volume of space 6 is filled with transparent substrate 7, the thickness of the transparent substrate 7 is 5 mm or more in terms of air equivalent length. In other words, it is a value calculated by converting the thickness of the transparent substrate 7 to air equivalent length. As mentioned above, the air equivalent length LA of the transparent substrate 7 can be calculated based on the thickness of the transparent substrate 7 and the refractive index of the transparent substrate 7. The refractive index of the transparent substrate 7 is greater than the refractive index of air, which is 1. Therefore, the air equivalent length LA of the transparent substrate 7 is greater than the thickness of the transparent substrate 7.

[0083] The transparent substrate 7 comprises a first surface 7A and a second surface 7B which is the surface opposite to the first surface. The first surface 7A supports the back surface 2B of the transparent display 2, and the second surface 7B supports the first surface 3A of the dimming sheet 3. An adhesive layer may be provided between the transparent display 2 and the transparent substrate 7, and between the transparent substrate 7 and the dimming sheet 3, at least one of these. That is, the adhesive layer may be located only between the transparent display 2 and the transparent substrate 7, and between the transparent substrate 7 and the dimming sheet 3, or it may be located in both. Alternatively, the transparent display 2 and the transparent substrate 7 may be in contact without an adhesive layer, and the transparent substrate 7 and the dimming sheet 3 may be in contact without an adhesive layer. Alternatively, the transparent substrate 7 may occupy only a part of the space 6. That is, an air layer and the transparent substrate 7 may be located between the transparent display 2 and the dimming sheet 3. In this case, the transparent substrate 7 may be in contact with the transparent display 2, or in contact with the dimming sheet 3, or it may be separated from both the transparent display 2 and the dimming sheet 3.

[0084] The material used to form the transparent substrate 7 may be, for example, a resin material such as acrylic, polycarbonate (PC), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyimide (PI), or glass. The acrylic may be, for example, PMMA. The transparent substrate 7 may have a single-layer structure made of one material, or it may have a laminated structure having multiple layers made of different materials. That is, if the transparent substrate 7 has a laminated structure, it may include a first layer formed from a first material and a second layer formed from a second material different from the first material. The transparent substrate 7 may be colorless and transparent, or it may be colored and transparent.

[0085] The refractive index of the transparent substrate 7 may be greater than that of the transparent display 2. The refractive index of the transparent display 2 is the refractive index of the material constituting the outermost layer of the transparent display 2. Alternatively, the refractive index of the transparent substrate 7 may be less than or equal to that of the transparent display 2.

[0086] As explained above, according to the fourth embodiment, in addition to the effects described in (1-1) to (1-7) of the first embodiment, the following effects can be obtained. (4-1) Since the transparent substrate 7 that supports the transparent display 2 and the dimming sheet 3 is located between the transparent display 2 and the dimming sheet 3, the strength of the display device 1 can be increased.

[0087] (Fifth embodiment) A fifth embodiment of the display device will be described with reference to Figure 8. The display device 1 of this embodiment includes a translucent mirror 8 instead of the transparent substrate 7 of the fourth embodiment. The translucent mirror 8 is located between the transparent display 2 and the dimming sheet 3. A transparent adhesive layer 8C is located between the translucent mirror 8 and the transparent display 2, and between the translucent mirror 8 and the dimming sheet 3. The transparent adhesive layer 8C is made of a transparent adhesive. The first transparent adhesive layer 8C bonds the translucent mirror 8 to the transparent display 2, and the second transparent adhesive layer 8C bonds the translucent mirror 8 to the dimming sheet 3. Note that if each layer can be supported without adhesive, the transparent adhesive layer 8C may be omitted. That is, if it is possible to bond the translucent mirror 8 to the transparent display without using adhesive, the first transparent adhesive layer 8C may be omitted. Also, if it is possible to bond the translucent mirror 8 to the dimming sheet 3 without using adhesive, the second transparent adhesive layer 8C may be omitted.

[0088] The translucent mirror 8 is configured to reflect a portion of the visible light and transmit the rest. In the translucent mirror 8, a metal film 8B having a predetermined thickness is laminated on a transparent substrate 8A. The transparent substrate 8A can be the same substrate as the transparent substrate 7 of the fourth embodiment. At least one of aluminum, silver, and gold can be used as the material for forming the metal film 8B. The reflective surface 8D of the translucent mirror 8 on which the metal film 8B is provided may face the dimming sheet 3 via a transparent adhesive layer 8C. That is, the translucent mirror 8 has a reflective surface 8D. The reflective surface 8D is the surface of the transparent substrate 8A on which the metal film 8B is located. Alternatively, the reflective surface 8D may face the transparent display 2 via a transparent adhesive layer 8C. The translucent mirror 8 comprises a transparent substrate and a metal film, and the metal film may be attached to the transparent substrate.

[0089] When a translucent mirror 8 is interposed between the transparent display 2 and the dimming sheet 3, a portion of the light emitted from the back surface 2B of the transparent display 2 is reflected by the reflective surface 8D of the translucent mirror 8. In addition, a portion of the light incident through the dimming sheet 3 is also reflected. As a result, not only is the transmission of the image displayed on the transparent display 2 suppressed, but the incidence of light from the back surface of the transparent display 2 is also suppressed, making the image viewed from the front surface 1A of the display device 1 clearer.

[0090] As described above, according to the fifth embodiment, in addition to the effects described in (1-1) to (1-7) of the first embodiment and (4-1) of the fourth embodiment, the following effects can be obtained.

[0091] (5-1) Because the translucent mirror 8 is positioned between the transparent display 2 and the dimming sheet 3, when the dimming sheet 3 is made transparent, the transparency of the display device 1 is maintained while the image viewed from the back 1B can be made blurred. In addition, by reflecting a portion of the light incident from the back 1B of the display device 1 with the reflective surface 8D, the image 30 displayed on the display device 1 and viewed from the front 1A can be made clearer.

[0092] (Sixth Embodiment) Referring to Figure 9, a sixth embodiment of the display device will be described. In this embodiment, the display device 1 includes a colored transparent substrate 9 instead of the transparent substrate 7 of the fourth embodiment. The colored transparent substrate 9 is located between the transparent display 2 and the dimming sheet 3.

[0093] The colored transparent substrate 9 may be a substrate to which a dye has been added to glass or transparent resin. Alternatively, the colored transparent substrate 9 may be a substrate to which a colored film has been laminated to a transparent substrate. For example, the colored transparent substrate 9 is smoked glass. The colored transparent substrate 9 may face the transparent display 2 and the dimming sheet 3 via a transparent adhesive layer 9A. That is, the colored transparent substrate 9 may be attached to the transparent display 2 by a first transparent adhesive layer 9A and attached to the dimming sheet 3 by a second transparent adhesive layer 9A. Alternatively, the transparent adhesive layer 9A may be omitted.

[0094] The colored transparent substrate 9 absorbs a portion of the light incident from the back surface 1B of the display device 1. The colored transparent substrate 9 can make the image viewed from the back surface 1B blurred while maintaining the transparency of the display device 1. In addition, the colored transparent substrate 9 suppresses the incident light from the back surface 2B of the transparent display 2, thereby making the image displayed on the transparent display 2 clearer when viewed from the front surface 1A of the display device 1.

[0095] As described above, according to the sixth embodiment, in addition to the effects described in (1-1) to (1-7) of the first embodiment and (4-1) of the fourth embodiment, the following effects can be obtained.

[0096] (6-1) Because the colored transparent substrate 9 is positioned between the transparent display 2 and the dimming sheet 3, when the dimming sheet 3 is made transparent, the transparency of the display device 1 can be maintained while making the image 30 viewed from the back 1B blurry. In addition, because a portion of the light incident from the back 1B can be absorbed by the colored transparent substrate 9, the image 30 viewed from the front 1A can be made sharp.

[0097] (Seventh Embodiment) A seventh embodiment of the display device will be described with reference to Figures 10 to 17. The display device of this embodiment can be combined with the configurations of the display devices of the first to sixth embodiments described above.

[0098] (composition) Figure 10 shows the structure of the dimming sheet 3 as viewed from a viewpoint opposite the first transparent electrode layer 12A of the dimming sheet 3. For the sake of explanation, the first transparent support layer 13A of the dimming sheet 3 is omitted from the illustration in Figure 10.

[0099] As shown in Figure 10, the first transparent electrode layer 12A is divided into a plurality of electrode portions 12A1. Each electrode portion 12A1 is insulated from adjacent electrode portions 12A1. The boundary between electrode portions 12A1 may be a break, or it may be a region where the material constituting the first transparent electrode layer 12A has been modified and has lost conductivity. One first terminal portion 6A1 is connected to each electrode portion 12A1.

[0100] In contrast, the second transparent electrode layer 12B is a single layer. In other words, the second transparent electrode layer 12B is not divided. In the thickness direction of the dimming sheet 3, the second transparent electrode layer 12B faces all the electrode portions 12A1. One second terminal portion 6B is connected to the second transparent electrode layer 12B. Preferably, the second terminal portion 6B has a length that extends substantially over the entire length of the second transparent electrode layer 12B in the direction in which the electrode portions 12A1 are aligned. The second transparent electrode layer 12B may also have the same number of electrode portions as the first transparent electrode layer 12A, and each electrode portion may be insulated from adjacent electrode portions. In this case, each electrode portion of the second transparent electrode layer 12B faces the electrode portion 12A1 of the first transparent electrode layer 12A. In addition, one second terminal portion may be connected to each electrode portion of the second transparent electrode layer 12B.

[0101] The dimming area 20 of the dimming sheet 3 is divided into multiple dimming sections 20A. The number of dimming sections 20A is the same as the number of electrode sections 12A1 of the first transparent electrode layer 12A. Each dimming section 20A contains one of the multiple electrode sections 12A1. In the dimming sheet 3, each electrode section 12A1 is insulated from adjacent electrode sections 12A1, and one first terminal section 6A1 is connected to each electrode section 12A1. Therefore, each of the multiple dimming sections 20A can switch between transparent and opaque states independently of the other dimming sections 20A.

[0102] In this embodiment, multiple electrode sections 12A1 are connected to a control device 40, which in turn connects them to a single power supply. Alternatively, each electrode section 12A1 may be individually connected to a separate power supply. When multiple electrode sections 12A1 are connected to a single power supply, the dimming sheet 3 may include a voltage distribution section 12C, as shown in Figure 10. The voltage distribution section 12C includes one or more capacitors 12C1, and each capacitor 12C1 is connected in series to one of the electrode sections 12A1. In the example shown in Figure 10, each electrode section 12A1 is connected in series to one capacitor 12C1, but only some of the electrode sections 12A1 in the multiple electrode sections 12A1 may be connected to the capacitor 12C1.

[0103] The multiple capacitors 12C1 may include a capacitor 12C1 having a first capacitance value and a capacitor 12C1 having a second capacitance value different from the first capacitance value. In the multiple capacitors 12C1, the capacitance value of one capacitor 12C1 may be different from the capacitance values ​​of all the other capacitors 12C1. By providing a voltage distribution unit 12C in the dimming sheet 3, it is possible to change the magnitude of the drive voltage applied to each electrode unit 12A1 according to the magnitude of the capacitance value of the capacitor 12C1 connected to that electrode unit 12A1. Note that the dimming sheet 3 does not necessarily have to include a voltage distribution unit 12C.

[0104] The control device 40 may be configured to control the driving of the dimming unit 20A in accordance with the driving of the transparent display 2. The control device 40 may also be configured to generate a driving signal for the dimming sheet 3 corresponding to the display data each time the display data for displaying the image 30 on the transparent display 2 is switched, and to output the driving signal to the dimming sheet 3.

[0105] For example, the control device 40 may associate the driving of the dimming sheet 3 with each image frame for displaying the image 30 of the transparent display 2. That is, the control device 40 may associate the switching of image frames with the switching of the driving of the dimming sheet 3. In this case, the control device 40 may store the image frames and the driving sequences of the dimming sheet 3 in advance and associate the image frames with the driving sequences. Alternatively, the control device 40 may control the driving of each dimming unit 20A when the image frame is displayed, based on the image frame. Alternatively, the control device 40 may control the driving of each dimming unit 20A based on signals input from the input operation device 50 while the image 30 of the transparent display 2 is being displayed.

[0106] The control device 40 can control the display device 1 to one of the following three control modes when displaying the image 30. The first mode is a state in which the image 30 displayed by the transparent display 2 is visible from both the front 1A and the back 1B of the display device 1. The first mode corresponds to the first display state described above. The second mode is a state in which the image 30 displayed by the transparent display 2 is visible from the front 1A of the display device 1, but the image 30 is not visible from the back 1B of the display device 1. In the second mode, the transparent display 2 displays the image 30 in such a way that it cannot be seen from the back 1B of the display device 1, while the dimming sheet 3 is transparent. The third mode is similar to the second mode in which the image 30 displayed by the transparent display 2 is visible from the front 1A of the display device 1, but the image 30 is not visible from the back 1B of the display device 1. In the third mode, the image 30 is not visible from the back 1B of the display device 1 because the dimming sheet 3 is opaque. Therefore, if the dimming sheet 3 is transparent, the transparent display 2 may display an image 30 such that the image 30 can be seen from the back 1B of the display device 1. The third mode corresponds to the second display state described above. In the third mode, only some of the dimming units 20A included in the dimming sheet 3 may be opaque.

[0107] (action) The operation of the display device 1 will be explained with reference to Figures 11 to 17. Figures 11 to 15 are diagrams illustrating the operation of the display device 1 when observer 101 observes the display device 1 from the back surface 1B of the display device 1. Figures 16 and 17 are diagrams illustrating the operation of the display device 1 when observer 100 observes the display device 1 from the front surface 1A of the display device 1.

[0108] Figure 11 shows the image 30 transmitted through the back surface 1B of the display device 1, which is the second surface 3B of the dimming sheet 3, when the entire dimming sheet 3 is transparent. As shown in Figure 11, Image 30 contains four people. While it is possible to display the first person 30P1 and the second person 30P2, who are located in the center of Image 30, it may be required, from a privacy perspective, to display Image 30 in a way that makes it impossible to identify the third person 30P3 and the fourth person 30P4, who are located at the edges of Image 30.

[0109] In this case, as shown in Figure 12, among the multiple dimming units 20A, the dimming unit 20A that overlaps with the third person 30P3 in image 30 in the thickness direction of the display device 1, and the dimming unit 20A that overlaps with the fourth person 30P4 in image 30 in the thickness direction of the display device 1 are made opaque. This makes it possible to conceal the third person 30P3 and the fourth person 30P4 included in image 30 from the observer 101 who is observing image 30 from the back surface 1B of the display device 1. On the other hand, among the multiple dimming units 20A, the dimming unit 20A that overlaps with the first person 30P1 and the second person 30P2 in image 30 in the thickness direction of the display device 1 are transparent, so the observer 101 can see the first person 30P1 and the second person 30P2 included in image 30.

[0110] Thus, with the display device 1, it is possible to change the image visible to the observer 101 so that only a portion of the image 30 is not visible from the back surface 1B of the display device 1, without changing the image frames that make up the image 30 displayed on the transparent display 2.

[0111] Furthermore, for example, if the size of the image frame is small relative to the size of the transparent display 2, it is preferable that among the multiple dimming units 20A, the dimming units 20A that overlap with the portion of the transparent display 2 outside the portion where the image 30 is displayed, in the thickness direction of the display device 1, are opaque. This makes it more difficult for the observer 101 to focus on the portion outside the image 30 compared to when the portion of the transparent display 2 outside the image 30 is black.

[0112] Figures 13 to 15 illustrate the operation of the display device 1 when it is positioned between the exhibit and the observer 101. The display device 1 is, for example, part of a show window in a commercial facility. Alternatively, the display device 1 is positioned in a commercial facility so that it is visible from the show window.

[0113] As shown in Figure 13, a passenger car CR, an example of an exhibit, is located on the opposite side of the display device 1 from the observer 101. The exhibit could be, for example, clothing, home appliances, toys, or food products. The transparent display 2 displays image 30 in a position that does not overlap with the passenger car CR in the thickness direction of the display device 1. In this state, since the entire dimming sheet 3 is transparent, the entire passenger car CR and the entire image 30 are visible to the observer 101.

[0114] As shown in Figure 14, for example, the display device 1 can be driven such that only one of the multiple dimming units 20A is transparent, while the other dimming units 20A are opaque. As a result, the observer 101 can only see a part of the passenger car CR and cannot see the entire image 30.

[0115] Furthermore, as shown in Figure 15, for example, among the multiple dimming units 20A, the first dimming unit 20A may be transparent at the first timing, while the second dimming unit 20A may be transparent at a second timing different from the first timing, and the other dimming units 20A may be opaque. At the second timing, the observer 101 can see a part of the passenger car CR that is different from the part that the observer 101 saw at the first timing. Also, at the second timing, the observer 101 can see a part of the image 30.

[0116] In this way, by allowing observer 101, who is located outside the commercial facility, to see only a part of the exhibit, it is possible to stimulate the observer 101's desire to grasp the entire exhibit, thereby guiding the observer 101 from outside the commercial facility into the commercial facility.

[0117] The display device 1 may be used as described below. Specifically, the display device 1 may be installed in a window of a restaurant, such as a fast-food restaurant, where the inside of the restaurant can be seen from outside. In this case, the dimming sheet 3 of the display device 1 faces outside the restaurant, and the transparent display 2 faces inside the restaurant. The dimming sheet 3 being opaque prevents the inside of the restaurant from being seen from outside. On the other hand, the transparent display 2 can display images 30 that the restaurant wishes to offer to customers inside the restaurant.

[0118] Figures 16 and 17 illustrate the operation of the display device 1 when an item is placed on the opposite side from the observer 100. As shown in Figure 16, the display device 1 is installed, for example, in a room. On the opposite side of the display device 1 from the observer 100, there are parts of a desk TB and a chair CH, which are examples of items. When the dimming sheet 3 is transparent and the transparent display 2 is displaying image 30, parts of the desk TB and chair CH are visible through the display device 1. Therefore, the observer 100 sees an image in which parts of the desk TB and chair CH overlap with image 30. Consequently, the observer 100 has difficulty seeing image 30.

[0119] As shown in Figure 17, of the dimming sections 20A of the dimming sheet 3, the dimming section 20A that overlaps with the image 30 in the thickness direction of the display device 1 is opaque. As a result, a portion of the desk TB and a portion of the chair CH do not easily transmit light through the opaque dimming section 20A, so the observer 100 can see the image 30 where a portion of the desk TB and a portion of the chair CH do not overlap.

[0120] As described above, according to the seventh embodiment of the display device, the following effects can be obtained. (7-1) Depending on the usage status of the display device 1, it is possible to make only a portion of the multiple dimming units 20A transparent, or to change the dimming unit 20A that is transparent from the first dimming unit 20A to the second dimming unit 20A.

[0121] (Example of change) The display device 1 may include two or more dimming sheets 3. When the display device 1 includes two or more dimming sheets 3, the two or more dimming sheets 3 are arranged so that each dimming sheet 3 faces an area of ​​the transparent display 2 that does not face any other dimming sheets 3. This makes it possible to independently change the state of each dimming sheet 3 transmitted through the transparent display 2 in the thickness direction of the display device 1, between the portion of the transparent display 2 that overlaps with the first dimming sheet 3 and the portion that overlaps with the second dimming sheet 3. When the display device 1 includes two or more dimming sheets 3, all dimming sheets 3 may be connected to a single power supply, or each dimming sheet 3 may be connected to an individual power supply.

[0122] The diffuse transmittance of each dimming unit 20A is not limited to just two types: high diffuse transmittance and low diffuse transmittance. It is also possible to have three or more types, including an intermediate diffuse transmittance between high and low diffuse transmittance. In other words, the display device 1 may be configured to change the gradation of each dimming unit 20A in three or more gradations. In this case, the contrast between the image 30 displayed on the transparent display 2 and the state exhibited by the dimming sheet 3 can be adjusted by the diffuse transmittance of the dimming sheet 3 according to the diffuse transmittance of the dimming unit 20A.

[0123] (Eighth embodiment) An eighth embodiment of the display device will be described with reference to Figure 18. (composition) As shown in Figure 18, the display device 1 can include a detection sheet 60 in addition to the transparent display 2 and dimming sheet 3 described above. In the display device 1, the detection sheet 60 is positioned between the transparent display 2 and the dimming sheet 3 in the thickness direction of the display device 1. In this embodiment, with the detection sheet 60 positioned between the transparent display 2 and the dimming sheet 3, the distance between them should be 5 mm or more in terms of air.

[0124] The detection sheet 60 and the dimming sheet 3 are light-transmitting, allowing visible light to pass through. The detection sheet 60 and the dimming sheet 3 are approximately the same size. The detection sheet 60 is superimposed on the dimming sheet 3 so that its outer edge and the outer edge of the dimming sheet 3 are approximately aligned. The detection sheet 60 and the dimming sheet 3 are constructed as a single integrated structure. Note that the statement that the detection sheet 60 and the dimming sheet 3 are approximately the same size includes not only having the same size but also, for example, any size difference between the two sheets resulting from trimming of the edge of at least one sheet.

[0125] The detection sheet 60 comprises multiple detection units 60B, 60C, 60D, 60E, 60F, 60G, 60H, and 60I. Each detection unit 60B to 60I is located in a separate area within the detection sheet 60. In these separate areas, no part of one area overlaps with another, and no entire area overlaps with another. Each detection unit 60B to 60I is configured to detect changes in capacitance across almost the entire area it occupies. Each detection unit 60B to 60I employs either a surface type with a single conductive layer or a projection type with two opposing conductive layers. The detection units 60B to 60I employ may be a single type or two types. Each detection unit 60B to 60I has a rectangular shape extending in the horizontal direction. Each detection unit 60B to 60I does not overlap with one another and is arranged in a regular vertical direction perpendicular to the horizontal direction, with a certain interval between them. Hereinafter, the regular arrangement of each detection unit 60B to 60I will be referred to as the second sequence.

[0126] The dimming sheet 3 is equipped with multiple dimming units 20B, 20C, 20D, 20E, 20F, 20G, 20H, and 20I. The multiple dimming units 20B to 20I are set within a single dimming area 20. Each dimming unit 20B to 20I is configured to change the light transmittance of the diffused light in its own way. Each dimming unit 20B to 20I employs either a normal type or a reverse type. The method employed by all dimming units 20B to 20I may be a single type or two or more different types. Each dimming unit 20B to 20I has a rectangular shape extending horizontally. Each dimming unit 20B to 20I has a regular arrangement in the vertical direction, without overlapping each other and with a certain interval between them. Hereinafter, the regular arrangement of each dimming unit 20B to 20I will be referred to as the first arrangement. The regularity of the first sequence is the same as the regularity of the second sequence.

[0127] Furthermore, each dimming unit 20B to 20I faces a different detection unit 60B to 60I than the other dimming units 20B to 20I face. For example, dimming unit 20B faces detection unit 60B, and dimming unit 20C faces detection unit 60C. Also, dimming unit 20H faces detection unit 60H, and dimming unit 20I faces detection unit 60I.

[0128] Furthermore, "the regularity of the Mth sequence is the same as the regularity of the Nth sequence" means at least one of the following: 1) the arrangement direction of the elements arranged according to the Mth sequence (hereinafter, this element is defined as element M in this disclosure) is the same as the arrangement direction of the elements arranged according to the Nth sequence (hereinafter, this element is defined as element N in this disclosure); 2) the relationship between the relative sizes of elements M with respect to the arrangement order of elements M is the same as the relationship between the relative sizes of elements N with respect to the arrangement order of elements N; and 3) the relationship between the relative positions of elements M with respect to the arrangement order of elements M is the same as the relationship between the relative positions of elements N with respect to the arrangement order of elements N.

[0129] The control device 40 includes an input position determination unit 41, a change position identification unit 42, and a drive unit 43. These input position determination unit 41, change position identification unit 42, and drive unit 43 are examples of dimming processing units. The dimming processing unit is not limited to one that includes a central processing unit and memory and processes all of the various processes described later using software. For example, the dimming processing unit may include dedicated hardware (application-specific integrated circuit: ASIC) that performs at least some of the various processes. In other words, the dimming processing unit can be configured as a circuit including 1) one or more dedicated hardware circuits such as ASICs, 2) one or more processors (microcomputers) that operate according to a computer program (software), or 3) a combination thereof.

[0130] The detection result from the detection sheet 60 is input to the input position determination unit 41 as a detection signal SiA. Based on the detection signal SiA, the input position determination unit 41 determines whether each detection unit 60B to 60I has detected a change in capacitance. The input position determination unit 41 outputs the result of its determination.

[0131] For example, when a user taps the detection unit 60B via the transparent display 2, a detection signal SiA is input to the input position determination unit 41, indicating that a change in capacitance is detected in the detection unit 60B, and no change in capacitance is detected in the other detection units 60C to 60I. The input position determination unit 41 outputs a determination result indicating that the detection unit 60B is the target of the input, and the other detection units 60C to 60I are not the target of the input.

[0132] The result of the determination by the input position determination unit 41 is input to the change position identification unit 42 as determination data DA. The change position identification unit 42 associates one unique dimming unit 20B to 20I with each detection unit 60B to 60I according to the arrangement of each detection unit 60B to 60I. That is, the change position identification unit 42 associates one unique dimming unit 20B to 20I with each detection unit 60B to 60I, in order from top to bottom in the vertical direction, according to the arrangement of the eight detection units 60B to 60I. For example, the change position identification unit 42 associates dimming unit 20B with detection unit 60B and dimming unit 20C with detection unit 60C. Also, the change position identification unit 42 associates dimming unit 20H with detection unit 60H and dimming unit 20I with detection unit 60I.

[0133] The change position identification unit 42, based on the determination data DA, treats one of the dimming units 20B to 20I that is associated with the input target as the output target, and identifies that output target as the output destination of the change signal SiD. The change position identification unit 42 then outputs the result of its identification. For example, determination data DA indicating that the detection unit 60B is the input target and the other detection units 60C to 60I are not input targets is input to the change position identification unit 42. In this case, the change position identification unit 42, based on the determination data DA, treats the dimming unit 20B associated with the detection unit 60B as the output target, and identifies that dimming unit 20B as the output destination of the change signal SiD. The change position identification unit 42 then outputs as the result of its identification that the output destination of the change signal SiD is the dimming unit 20B.

[0134] The result of the change position identification unit 42 is input to the drive unit 43 as specific data DB. The drive unit 43 generates a change signal SiD based on the specific data DB. The change signal SiD is a drive signal for changing the current light transmittance of each dimming unit 20B to 20I. For example, when the drive unit 43 expresses the light transmittance of each dimming unit 20B to 20I in two levels, high and low, the drive unit 43 generates a change signal SiD to invert the current light transmittance. The drive unit 43 outputs the change signal SiD to the output target based on the specific data DB. For example, specific data DB indicating that dimming unit 20B is the output target is input to the drive unit 43. In this case, the drive unit 43 outputs the change signal SiD to dimming unit 20B based on the specific data DB.

[0135] (action) According to the display device 1 of this embodiment, for example, when each dimming unit 20B to 20I is in a transparent state, if the user taps the detection unit 60B, a change in capacitance is detected in the detection unit 60B, and no change in capacitance is detected in the other detection units 60C to 60I. As a result, a change signal SiD is output to the dimming unit 20B, causing the dimming unit 20B to change from a transparent state to an opaque state.

[0136] For example, when each dimming unit 20B to 20H is in a transparent state, if the user taps the detection unit 60D, a change in capacitance is detected in the detection unit 60D, while no change in capacitance is detected in the other detection units 60B, 60C, 60E to 60I. As a result, a change signal SiD is output to the dimming unit 20D, and the dimming unit 20D changes from a transparent state to an opaque state.

[0137] According to the display device 1, the user can switch between a transparent state and an opaque state in a portion of the dimming area 20 by tapping the detection sheet 60 of the display device 1. Therefore, for example, in order to prevent the image 30 displayed on the transparent display 2 from being visible from the back 1B of the display device 1, the user can switch at least a portion of the dimming area 20 from a transparent state to an opaque state by tapping the detection sheet 60. This prevents the image 30 displayed on the transparent display 2 from being visible from the back 1B of the display device 1.

[0138] For example, if the image 30 displayed on the transparent display 2 overlaps with the image of an object that is transparent to the back surface 1B of the display device 1, making the image 30 difficult to see, the user can tap the detection sheet 60 to switch at least a portion of the dimming area 20 from transparent to opaque. This reduces the overlap between the image 30 displayed on the transparent display 2 and the image of the object, making the image 30 easier for the user to see.

[0139] In all of the above cases, the user is viewing the image 30 displayed on the front surface 1A of the display device 1. As described above, according to the eighth embodiment of the display device, the following effects can be obtained.

[0140] (8-1) By tapping the detection sheet 60, the user can switch between a transparent state and an opaque state in at least a part of the dimming area 20, so that the user can decide whether or not the image 30 displayed on the transparent display 2 is transparent to the back surface 1B.

[0141] (Example of change) The diffuse transmittance of each dimming unit 20B to 20I is not limited to just two types: high diffuse transmittance and low diffuse transmittance. It is also possible to have three or more types, including an intermediate diffuse transmittance between high and low diffuse transmittance. In other words, the display device 1 may be configured to change the gradation of each dimming unit 20B to 20I in three or more gradations. In this case, the storage unit of the change position identification unit 42 can also store each input pattern in association with a change signal SiD for obtaining different light transmittances. The change position identification unit 42 then outputs the change signal SiD associated with the matched input pattern to the output target through the drive unit 43.

[0142] [Example Test] The test examples of the display device will be described in detail with reference to Figures 19 to 21. Note that these test examples are not intended to limit the present invention.

[0143] [Test Example 1] A sample of a normal type dimmable sheet was fabricated. In the dimmable sheet, when no driving voltage is applied and it is opaque, the haze is 98% and the clarity is 40%. Furthermore, the dimmable sheet has the same configuration as the normal type dimmable sheet 3 in the first embodiment.

[0144] To verify the clarity of the image when viewed from the back of the display device, a tablet was used instead of a transparent display (product name: Thinkpad tablet®, screen size: 12 inches, aspect ratio 4:3, 2160 x 1440 pixels, Lenovo Group). The opaque sample described above was placed facing the surface of the tablet's display. The distance, or gap, between the display surface and the first surface of the sample facing the display was set to 5 mm. In other words, the distance between the display surface and the first surface of the sample was set to 5 mm in terms of air equivalent length. This resulted in the display device of Test Example 1.

[0145] [Test Example 2] Except for setting the distance between the display surface and the first surface of the sample to 6 mm in Test Example 2, the configuration of the display device in Test Example 2 was the same as in Test Example 1.

[0146] [Test Example 3] Except for setting the distance between the display surface and the first surface of the sample to 8 mm in Test Example 3, the configuration of the display device in Test Example 3 was the same as in Test Example 1.

[0147] [Test Example 4] Except for setting the distance between the display surface and the first surface of the sample to 10 mm in Test Example 4, the configuration of the display device in Test Example 4 was the same as in Test Example 1.

[0148] [Test Example 5] Except for setting the distance between the display surface and the first surface of the sample to 15 mm in Test Example 5, the configuration of the display device in Test Example 5 was the same as in Test Example 1.

[0149] [Test Example 6] Except for setting the distance between the display surface and the first surface of the sample to 16 mm in Test Example 6, the configuration of the display device in Test Example 6 was the same as in Test Example 1.

[0150] [Comparative Example 1] Comparative Example 1 was a display device in which no dimming sheet was provided facing the surface of the display in Test Example 1.

[0151] [Comparative Example 2] Except for the fact that in Comparative Example 2 the surface of the display and the first surface of the sample were brought into close contact, thereby setting the distance between the surface of the display and the first surface of the sample to 0 mm, the configuration of the display device in Comparative Example 2 was the same as that in Test Example 1.

[0152] [Comparative Example 3] Except for setting the distance between the display surface and the first surface of the sample to 4 mm in Comparative Example 3, the configuration of the display device in Comparative Example 3 was the same as in Test Example 1.

[0153] [evaluation] With the dimming sheet set to opaque, images were displayed on the screen in the following patterns. Specifically, fonts ranging from 8pt to 48pt, photographs of people, and photographs of flowers were displayed. On a 12-inch screen, i.e., a screen with a height of 18.3cm and a width of 24.4cm, 8pt characters were 1.66mm in height and width on the screen, 22pt characters were 4.5mm in height and width, and 48pt characters were 10.0mm in height and width. The display methods for text and photographs were set to the following patterns 1 to 3.

[0154] Pattern 1: Display black text in sizes from 8pt to 22pt on a white background. Pattern 2: White text in sizes 8pt to 22pt is displayed on a black background. Pattern 3: Display black text (26pt-48pt size) and a photograph on a white background. Pattern 4: Display white text (26pt to 48pt size) and a photo on a black background.

[0155] [Evaluation Results] Figures 19 to 21 show the evaluation results. For each test example and comparative example display device, samples where the pattern displayed on the screen appeared unclear to the naked eye, thereby ensuring image confidentiality and privacy protection, were evaluated as "○". Samples where the pattern appeared particularly unclear, resulting in high image confidentiality and privacy protection, were evaluated as "◎". Furthermore, for each test example and comparative example display device, samples where the pattern appeared clear, thus failing to ensure image confidentiality and privacy protection, were evaluated as "×". In addition, for each test example and comparative example display device, samples where the image was difficult to distinguish, with clarity between "○" and "×", were evaluated as "△".

[0156] Figure 19 is a table evaluating the degree of blurriness when images of patterns 1 and 2 were displayed on a screen. When the evaluators visually inspected the display devices, most characters were identifiable on the display device of Comparative Example 1. On the display device of Comparative Example 2, 10pt characters were either unreadable or somewhat difficult to read, and while simple characters such as "い" could be identified among 12pt characters, complex kanji characters could not be identified. On the display device of Comparative Example 3, most characters were identifiable, but simple characters such as "い" in 22pt could be identified. For this reason, Comparative Examples 1 to 3 were evaluated as "×" in terms of image confidentiality and protection of privacy. On the other hand, in Test Examples 1 to 3, all characters were identifiable. For this reason, Test Examples 1 to 3 were evaluated as "○". Although not shown in Figure 19, Test Examples 4 to 6 also had blurriness, so they were evaluated as "○".

[0157] Figures 20 and 21 are tables evaluating the degree of blurriness when images of patterns 3 and 4 were displayed on a display. Figure 20 is a table evaluating the degree of blurriness when images of patterns 3 and 4 were displayed on the displays of the display devices of Comparative Examples 1-3 and Test Example 1. In Comparative Examples 1 and 2, most characters and photographs could be identified. In Comparative Example 3, 26pt characters could not be identified, but characters of 36pt or larger could be identified. In addition, in Comparative Examples 1-3, the outlines of fine details in photographs, such as the outlines of flower petals, could be identified. For this reason, Comparative Examples 1 and 2 were evaluated as "×", and Comparative Example 3, which was more difficult to identify characters and photographs than Comparative Examples 1 and 2, was evaluated as "△".

[0158] In Test Example 1, characters and photographs appeared more blurred than in Comparative Example 3. Specifically, in Test Example 1, characters of 26 pt or smaller could not be identified. Also, in Test Example 1, the visibility of 36 Pt characters differed depending on the character type. That is, characters such as "a", "e", and "o" could barely be identified but appeared blurred; characters "A", "B", and "C" were difficult to identify; and the characters meaning "recognition" could not be identified. Furthermore, in Test Example 1, the fine contours in the photograph could not be identified. For this reason, Test Example 1 was evaluated as "○".

[0159] FIG. 12 is a table evaluating the blurriness when images of patterns 3 and 4 are displayed on the displays of the display devices of Test Examples 2 to 6. In Test Example 2, substantially the same image as in Test Example 1 was visually recognized, but since characters and photographs appeared more blurred than in Test Example 1, identification of characters was difficult. For this reason, Test Example 2 was evaluated as "○". In Test Example 3, characters of 36 pt or smaller could not be identified, and most 48 Pt characters could not be identified. Also, in Test Example 3, fine contours in the photograph could not be identified. For this reason, Test Example 3 was evaluated as "○". For Test Examples 4 to 6, none of the characters could be identified, and the overall contours of the objects shown in the photograph were unclear. For this reason, Test Examples 4 to 6 were evaluated as "◎".

[0160] As described above, according to the evaluation results for the display devices of each Test Example and each Comparative Example, it was confirmed that when the distance between the surface of the display and the first surface of the light control sheet is 5 mm or more in terms of air conversion, an image displayed through the light control sheet in the opaque state is unclear.

Description of Reference Signs

[0161] 1…Display device 1A, 2A…Front surface 1B, 2B…Back surface 2…Transparent display 3…Light control sheet 3A…First surface 3A…Second surface 5…Transparent supporting base material 6…Space 7… Transparent substrate 8… Semi-transparent mirror 11…Dimming Layer 11D…gap 11P…Transparent Polymer Layer 12A…First transparent electrode layer 12B…Second transparent electrode layer 13A…First Transparent Support Layer 13B…Second Transparent Support Layer LCM…Liquid Crystal Compound DP…dichroic pigment

Claims

1. A transparent display having a front side on which an image presented to the observer is displayed, and a back side located opposite to the front side, through which the image is visible to another observer located on the opposite side of the observer, A light-adjusting sheet having a light-adjusting layer in which a liquid crystal compound is dispersed within a transparent polymer layer, and capable of switching between a transparent state and an opaque state, A translucent mirror having a reflective surface is included between the back surface of the transparent display and the first surface of the dimming sheet. The distance between the back surface of the transparent display and the first surface of the dimming sheet facing the back surface is 5 mm or more in terms of air equivalent length. The haze of the opaque dimming sheet is 85% or more. The clarity of the opaque light-adjusting sheet is 60% or less. Display device.

2. The aforementioned dimming sheet is The aforementioned dimming layer, A pair of transparent electrode layers sandwiching the light-adjusting layer, The photochromic layer and a pair of transparent support layers sandwiching the pair of transparent electrode layers, Equipped with, The light-adjusting layer comprises a transparent polymer layer that partitions a plurality of voids, and the liquid crystal compound and dichroic dye located within the voids. The orientation of the liquid crystal compound and the dichroic dye is controlled according to the potential difference between the pair of transparent electrode layers. The display device according to claim 1.

3. The light-adjusting sheet further comprises a transparent support substrate that supports the second surface located opposite to the first surface of the light-adjusting sheet. The display device according to claim 1.

4. The total light transmittance of the opaque dimming sheet is 20% or less. The display device according to claim 1.

5. The total light transmittance of the transparent light-adjusting sheet is 40% or more. The display device according to claim 1.

Images