Indication device

Abstract

A display device according to the present invention comprises an image display body, an ultraviolet light projection unit, and an image projection unit. The image display body is installed at a position where sunlight is incident from a surface on one side of the image display body, and the ultraviolet light projection unit and the image projection unit are provided on the other side of the image display body.　The image display body has, in order from the ultraviolet light projection unit, a display function layer, a light control layer, and an ultraviolet light blocking layer, the display function layer includes a light responsive orientation change-inducing material and changes between a transparent state and a cloudy screen state, the light control layer includes a photochromic material and changes between a transparent state and a colored state, and the colored state is regarded as a state in which a larger amount of light of wavelengths in a visible light range absorbed by the light responsive orientation change-inducing material is transmitted than light of wavelengths in other visible light ranges, thereby making it possible to provide the display device capable of complementing the hue of light of wavelengths absorbed by the light responsive orientation change-inducing material.

Description

Technical Field

[0001] The present invention relates to a display device, and more particularly, to a display device having an image display body whose optical state changes between a transparent state and a turbid screen state.

Background Art

[0002] There is known a display device having an image display body whose optical state changes between a transparent state and a turbid screen state, and an image light projection unit (projector) that projects visible light onto the image display body in the screen state to display an image.

[0003] Patent Document 1 discloses a display device that irradiates an image display body with ultraviolet light to increase the light scattering property of the image display body and change it to a turbid screen state, and irradiates visible light of a specific wavelength to return it to the transparent state. The display functional layer of the image display body contains liquid crystal molecules and a light-responsive alignment change-inducing material.

[0004] The light-responsive alignment change-inducing material changes from a trans form to a cis form by ultraviolet light, and the bent molecular structure of the cis form disturbs the alignment of the liquid crystal molecules to increase the light scattering property of the display functional layer. By changing from the cis form to the trans form by visible light of a specific color, the disordered liquid crystal molecules are oriented and aligned, and the display functional layer returns to the transparent state.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the image display body described in Patent Document 1, the photoresponsive orientation change-inducing material that changes its optical state absorbs light of a specific wavelength in the visible light range, so a portion of the light projected from the image projection unit onto the screen-like image display body is absorbed.

[0007] Therefore, the visible image displayed on the above image display device will appear as a visible image with the color of light at wavelengths absorbed by the above-mentioned photoresponsive orientation change-inducing material removed.

[0008] This invention has been made in view of the problems of the prior art, and its objective is to provide a display device that can complement the color of light of wavelengths absorbed by the above-mentioned photoresponsive orientation change-inducing material. [Means for solving the problem]

[0009] The inventors of the present invention have conducted extensive research to achieve the above objectives and have found that these objectives can be achieved by providing a light-tuning layer that selectively transmits light in the wavelength range absorbed by the photoresponsive orientation change-inducing material, thereby completing the present invention.

[0010] That is, the display device of the present invention comprises an image display body, an ultraviolet light projection unit, and an image projection unit. The image display unit is installed in a position where sunlight is incident on one side thereof, and the ultraviolet light projection unit and the image projection unit are provided on the other side of the image display unit. Furthermore, the image display unit has, in order from the side of the ultraviolet light emitting section, a display function layer, a dimming layer, and an ultraviolet light shielding layer. The above display functional layer contains a photoresponsive orientation change-inducing material and changes between a transparent state and a cloudy screen state. The above-mentioned light-adjusting layer contains a photochromic material and changes between a transparent state and a colored state. The above-described colored state is characterized in that the photoresponsive orientation change-inducing material transmits more light of visible light wavelengths that it absorbs than light of other visible light wavelengths. [Effects of the Invention]

[0011] According to the present invention, by providing a light-adjusting layer that selectively transmits light in the wavelength range absorbed by the photoresponsive orientation change-inducing material, it is possible to provide a display device that can complement the color of light at the wavelength absorbed by the photoresponsive orientation change-inducing material. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram showing an example of the display device of the present invention. [Figure 2] This graph shows the absorption spectrum of the photoresponsive orientation change-inducing material, the diffuse reflectance of the display functional layer in the screen state, and the transmittance of the dimming layer in the colored state of the display device of the example. [Modes for carrying out the invention]

[0013] The present invention's display device will be described in detail. The display device of the present invention comprises an image display body, an image projection unit that projects a visible image onto the image display body, and an ultraviolet light projection unit that controls the optical state of the image display body.

[0014] As shown in Figure 1, the image display unit is installed in a position where sunlight is incident on one side of it, and the ultraviolet light projection unit and the image projection unit are provided on the other side of this image display unit.

[0015] As shown in Figure 1, the image display unit has, in order from the side where the ultraviolet light projection unit and image projection unit are provided, a display function layer, a dimming layer, and an ultraviolet shielding layer, and these are supported by a transparent substrate. Although Figure 1 shows the case where there is one transparent substrate, it may also be sandwiched between two transparent substrates.

[0016] The above-mentioned display functional layer exhibits an optical change between a transparent state and a cloudy screen state, and contains liquid crystal molecules, a photoresponsive alignment change-inducing material, and a transparent resin between two vertically aligned films.

[0017] When the display functional layer is irradiated with ultraviolet light, the molecular structure of the photo-responsive alignment change inducing material changes, whereby the alignment state of the liquid crystal molecules changes, resulting in a refractive index difference between the liquid crystal molecules and the transparent resin, and entering a screen state where light is scattered. When visible light of a specific wavelength is used, the molecular structure of the photo-responsive alignment change inducing material returns to its original state and becomes transparent.

[0018] When the display functional layer is in the screen state, the photo-responsive alignment change inducing material absorbs not only ultraviolet light but also light of some wavelengths in the visible light region as described above. Therefore, among the visible light projected from the image projection unit to the image display body in the screen state, the visible light of a specific wavelength is absorbed by the display functional layer.

[0019] Therefore, the visible image displayed on the display functional layer in the screen state is visually recognized as an image lacking the color tone corresponding to the light of the specific wavelength absorbed by the photo-responsive alignment change inducing material.

[0020] The image display body of the present invention contains a photochromic material and has a light control layer that changes between a transparent state and a colored state. The colored state of this light control layer is a state in which light of a specific wavelength in the visible light region absorbed by the photo-responsive alignment change inducing material is transmitted more than light of wavelengths in other visible light regions.

[0021] As described above, the image display body is installed at a position where sunlight enters from one side surface. Since sunlight passes through the image display body from one side surface to the other side, the color of the light transmitted through the light control layer is added to the visible image lacking a specific color tone displayed on the display functional layer.

[0022] At this time, if the light control layer is in the colored state, the light of a specific wavelength transmitted through the light control layer is added to the visible image lacking a specific color tone displayed on the display functional layer, so that the color tone corresponding to the light of the specific wavelength absorbed by the photo-responsive alignment change inducing material can be complemented.

[0023] Generally, visible images are displayed using a combination of three colors of light: red (R), green (G), and blue (B). Visible images lacking a specific color occur when the peak wavelength of any of these colors falls within the wavelength range absorbed by the photoresponsive orientation change-inducing material, resulting in a decrease in the light intensity of only that light.

[0024] Therefore, the wavelength of light transmitted by the light-modulating layer and the wavelength of light absorbed by the photoresponsive orientation-change-inducing material do not necessarily have to match. The light-modulating layer only needs to selectively transmit light of wavelengths that include light of a color whose light intensity decreases due to absorption by the photoresponsive orientation-change-inducing material.

[0025] As the above-mentioned photochromic material, one that becomes colored when irradiated with ultraviolet light can be used, and as the above-mentioned photoresponsive orientation change-inducing material, one that undergoes cis-trans isomerization by absorbing ultraviolet or visible light can be used.

[0026] By using such photoresponsive orientation change-inducing materials and photochromic materials, the switching of the optical state of the display functional layer and the switching of the optical state of the light-adjusting layer can be performed by a single ultraviolet light projection unit, without the need for a new control unit to control the light-adjusting layer. Therefore, by correcting the output brightness of the image projection unit, as described later, power is not consumed to compensate for the color, thus saving energy.

[0027] Furthermore, Table 1 below shows combinations of photoresponsive orientation change-inducing materials and photochromic materials that can complement the visible light wavelengths absorbed by the display functional layer in the screen state by the colored light-adjusting layer.

[0028] [Table 1]

[0029] Furthermore, it is preferable that the image display body is equipped with a light intensity measuring unit on the side where sunlight enters it, rather than on the image display body itself, and that the dimming layer in the colored state and the display function layer in the screen state satisfy the following relationship (1). (R2 / R1)<(L1R2+L2T2) / (L1R1+L2T1)<(R1 / R2)...Equation (1) however, T1 is the average value (%) of the transmittance of light in the visible light range that is absorbed by the above-mentioned photoresponsive orientation change-inducing material, which transmits through the colored photochromic layer. T2 is the average value of the transmittance (%) of light in the visible light range that is not absorbed by the above-mentioned photoresponsive orientation change-inducing material, which transmits through the colored photochromic layer. R1 is the average value of the diffuse reflectance (%) of visible light wavelengths that are scattered in the display functional layer in the screen state and absorbed by the above-mentioned photoresponsive orientation change-inducing material. R2 is the average value of the diffuse reflectance (%) of visible light wavelengths that are scattered in the display functional layer in the screen state and are not absorbed by the above-mentioned photoresponsive orientation change inducing material. L1 is the output brightness of the projected light in the visible light range, which the image projection unit projects onto the display function layer in screen state. L2 represents the output luminance calculated from the above-mentioned illuminance of sunlight in the visible light range that passes through the colored photochromic layer.

[0030] The above values ​​of (R2 / R1) and (R1 / R2) can be adjusted by the concentration of the photoresponsive orientation change-inducing material, and the value of (L1R2+L2T2) / (L1R1+L2T1) can be adjusted by the output of the image projection unit, the concentration of the photoresponsive orientation change-inducing material, and the concentration of the photochromic material. The value of T2 can be converted from the illuminance of sunlight measured by the illuminance measurement unit.

[0031] According to the above, for light in the visible light range that is absorbed by the photoresponsive orientation change-inducing material, The components of reflected light and transmitted light, respectively L1R1 / 100, L2T1 / 100...Formula (1-1) It can be expressed as follows. Similarly, for light in the visible light range that is not absorbed by the photoresponsive orientation change-inducing material, the components of reflected light and transmitted light are respectively L1R2 / 100, L2T2 / 100...Formula (1-2) It can be expressed as follows. From these, the ratio of the color balance between light in the visible light range that is not absorbed by the photoresponsive orientation change-inducing material and light in the visible light range that is absorbed by the photoresponsive orientation change-inducing material is, when only the components of reflected light are considered, L1R2 / L1R1=R2 / R1...Formula (1-3) In contrast, when comparing the sum of the reflected light component and the transmitted light component, (L1R2+L2T2) / (L1R1+L2T1)...Equation (1-4) This is the result. Therefore, when the colored dimming layer and the screen-state display function layer satisfy the relationship in equation (1), even if the illuminance of sunlight incident on the image display body differs depending on the weather, etc., in the range of 10,000 to 120,000 lux, a balance is achieved between the color of specific wavelengths that are absorbed by the screen-state display function layer and removed from the visible image, and the color of specific wavelengths that are added to the visible image by sunlight transmitted through the colored dimming layer, making it possible to perceive white when looking at the screen-state display function layer. In particular, when (L1R2+L2T2) / (L1R1+L2T1)=1 holds, the balance between the visible light wavelengths absorbed by the photoresponsive orientation change inducing material and the visible light wavelengths not absorbed by the photoresponsive orientation change inducing material, which is visible when looking at the screen-state display function layer, is optimal and therefore particularly preferable.

[0032] In other words, when (R2 / R1) ≥ (L1R2+L2T2) / (L1R1+L2T1), the color compensation by the tinted dimming layer is insufficient, and an image lacking certain colors is visible. When (L1R2+L2T2) / (L1R1+L2T1) ≥ (R1 / R2), the tint of certain colors added by the tinted dimming layer is too strong, and an image with color cast is visible.

[0033] In this invention, using a colorimeter CM3600 (Konica Minolta, Inc.), the transmittance of light transmitted through the dimming layer in the colored state and the diffuse reflectance of light reflected and scattered by the display function layer in the screen state were measured at 10 nm intervals. The values ​​were added together, and the average value was obtained by dividing by the number of measurement points.

[0034] Furthermore, the wavelength range in which the molar extinction coefficient of the photoresponsive orientation change-inducing material is 0.5 or higher was defined as the visible light absorption wavelength range, and the wavelength range in which the molar extinction coefficient is less than 0.5 was defined as the visible light non-absorbent wavelength range.

[0035] The display device of the present invention can correct visible images that lack specific colors when sunlight cannot compensate for the lack of color, such as at night, by changing the balance of the output brightness of the visible light emitted from the image projection unit.

[0036] The output brightness of visible light projected by the image projection unit onto the image display surface in screen mode preferably satisfies the relationship shown in equation (2) below. 1 < (L3 / L4) < (R2 / R1) 2 ...Equation (2) However, L3 is the output brightness of light in the visible light range that is absorbed by the photoresponsive orientation change inducing material when the above image projection unit displays white. L4 is the output brightness of light in the visible light range that is not absorbed by the photoresponsive orientation change inducing material, which is emitted when the above image projection unit displays white. R1 is the average value of the diffuse reflectance of visible light wavelengths absorbed by the photoresponsive orientation change-inducing material, which scatters the display functional layer in the screen state. R2 represents the average value of the diffuse reflectance of visible light wavelengths that are scattered by the display functional layer in the screen state and are not absorbed by the above-mentioned photoresponsive orientation change-inducing material.

[0037] According to the above, for light of visible wavelengths absorbed by the photoresponsive orientation change-inducing material, the component of reflected light is L3R1 / 100...Formula (2-1) It can be expressed as follows. Similarly, for light in the visible light range that is not absorbed by the photoresponsive orientation change-inducing material, the component of the reflected light is L4R2 / 100...Formula (2-2) It can be expressed as follows. From these, the ratio of the color balance between light in the visible light range that is not absorbed by the photoresponsive orientation change-inducing material and light in the visible light range that is absorbed by the photoresponsive orientation change-inducing material is: L4R2 / L3R1...Formula (2-3) This is the result. Now, assuming that output brightness L3 and L4 are equal, i.e., L3 / L4=1, equation (2-3) becomes: R2 / R1...Equation (2-4) This is the result. Also, if L3 / L4=R2 / R1, then equation (2-3) becomes: R1R2 / R2R1=1...Equation (2-5) This is the result. Furthermore, L3 / L4=(R2 / R1) 2 In this case, equation (2-3) is, R1 2 R2 / R2 2 R1=R1 / R2...Formula (2-6) This is the result. Therefore, as described above, if the luminance ratio (L3 / L4) of the light projected by the image projection unit onto the display function layer satisfies the relationship in equation (2), the color of specific wavelengths that have been removed from the visible image due to absorption by the display function layer in the screen state can be corrected by the luminance ratio of the light projected from the image projection unit, thereby improving the color balance ratio. Of these, the case where L3 / L4 = R2 / R1 is particularly preferable because the color balance ratio becomes 1.

[0038] Therefore, when viewing the display function layer in screen state, it is possible to balance the colors so that white is visible, and by similarly correcting other colors besides white, it is possible to suppress the visibility of images with a loss of color in the aforementioned specific colors.

[0039] Whether or not color correction can be achieved using sunlight can be determined by installing a light intensity measuring unit and measuring the light intensity received by the image display unit. This light intensity measuring unit can be installed on the side of the image display unit that receives sunlight, and may be installed on the image display unit itself or at a location away from the image display unit.

[0040] Specifically, when the illuminance measured by the above-mentioned illuminance measuring unit is less than 100 lux, color correction by the dimming layer is not possible, so the image projection unit corrects the output brightness so that (L3 / L4) satisfies the above equation (2).

[0041] Furthermore, when the brightness is 100 lux or higher, color correction is possible using the dimming layer, and the image projection unit does not perform output brightness correction, so (L3 / L4) becomes 1.

[0042] As the liquid crystal molecules for the above-mentioned display functional layer, nematic liquid crystals can be used, which have a rigid mesogenic skeleton and flexible long-chain alkyl groups, and possess optical anisotropy and dielectric anisotropy. These nematic liquid crystals have the property that rod-shaped liquid crystal molecules associate with each other and arrange themselves in a nearly constant direction.

[0043] As the transparent resin mentioned above, a polymer of a photopolymerizable monomer or a resin having an aromatic ring that has high affinity with liquid crystals and does not undergo phase separation can be used. Examples of resins having an aromatic ring include polyethylene terephthalate and liquid crystalline resins having biphenyl groups.

[0044] Furthermore, the above-mentioned display functional layer may contain a non-photoresponsive chiral compound as needed. As the non-photoresponsive chiral compound, one having different optical activity from the above-mentioned photoresponsive orientation change-inducing material can be used.

[0045] By using the above-mentioned non-photoresponsive chiral compound in combination, the helical twisting power (HTP) cancels each other out, and the disorder of the liquid crystal molecule arrangement caused by the torsional force of the trans-isomer photoresponsive orientation change-inducing material can be further suppressed.

[0046] The above-mentioned ultraviolet light shielding layer is a transparent film containing an ultraviolet absorber and an ultraviolet light diffuse reflector. By providing the above-mentioned ultraviolet light shielding layer, ultraviolet light incident on the display function layer and dimming layer from the opposite side of the image projection area is shielded. This prevents the image display from becoming cloudy due to sunlight causing the display function layer to become a screen and the dimming layer to become colored.

[0047] As the above-mentioned ultraviolet absorber, conventionally known ultraviolet absorbers that absorb ultraviolet light with a wavelength of 400 nm or less, do not absorb visible light, and have low coloration can be used. Examples include besozophenone derivatives, salicylic acid ester derivatives, triazole derivatives, and acrylonitrile derivatives. Examples of ultraviolet light diffuse reflectors include titanium dioxide and zinc oxide.

[0048] Glass or resin can be used as the transparent substrate, and ITO film or similar materials can be used as the transparent electrode when an electric field is applied to the display function layer.

[0049] The image projection unit of the above-mentioned display device comprises a visible light source, a projection lens, and a control device that controls these, and projects a visible image onto an image display surface in a screen state to display a visible image. The illuminance of this image projection unit is preferably 5000 lux or higher.

[0050] The above-mentioned photoresponsive orientation change-inducing material returns to its original molecular structure when left under visible light or exposed to visible light. Therefore, by projecting visible light from the image projection unit onto the image display, the image display can be quickly restored to a transparent state.

[0051] Furthermore, the ultraviolet light projection unit, like the image projection unit, comprises an ultraviolet light source, a projection lens, and a control device for controlling these. It projects ultraviolet light onto the image display body, isomerizing the molecular structure of the photoresponsive orientation change-inducing material and changing the optical state of the image display body. As the ultraviolet light source mentioned above, a light source having a peak wavelength in the absorption band of a photoresponsive orientation change-inducing material can be used. The ultraviolet light projection unit may be controlled by the control device of the image projection unit.

[0052] The display device of the present invention can be used, for example, on the windshield of an automobile or a shop window, and can switch between a screen state that projects and displays a visible light image and a transparent state that allows the viewer to see through to the other side. [Examples]

[0053] The present invention will be described in detail below with reference to examples, but the present invention is not limited to the following examples.

[0054] [Example 1] A transparent substrate was obtained by depositing a transparent electrode (indium tin oxide: ITO film) over the entire surface of one side of a transparent glass, and then a vertically aligned film (polyimide) was deposited over the entire surface of the transparent electrode.

[0055] A mixture was prepared containing 86.5% by mass of nematic liquid crystal (Merck: E44), 5.1% by mass of a photoresponsive orientation change-inducing material (azobenzene) represented by the following structural formula (1), 2.9% by mass of a photononresponsive chiral compound represented by the following structural formula (2), 3.3% by mass of a polymerizable monomer represented by the following structural formula (3), and 1.7% by mass of a polymerizable monomer represented by the following structural formula (4) and 0.5% by mass of a polymerization initiator (IGM Resins BV: IRGAUCERE819).

[0056] [ka]

[0057] [ka]

[0058] [ka]

[0059] [ka]

[0060] Two transparent glass plates are placed side by side with the vertically aligned film facing inward, creating a gap of 10 μm. The above mixture is then injected between these transparent glass plates while being heated, at a wavelength of 420 nm and a power of 7 mW / cm². 2 The monomers in the solution were polymerized by irradiating them with light for 20 minutes to create a functional display layer.

[0061] A photochromic solution was prepared by mixing photochromic materials (DAE-001 and DAE0012, both manufactured by Yamada Chemical) with a PMMA solution (manufactured by Yamada Chemical) at a concentration of 1.8% by mass. This photochromic solution was then applied to a transparent glass with the above-mentioned display functional layer using the drop-cast method and dried to form a light-adjusting layer. Furthermore, an ultraviolet light-shielding film containing a besozophenone derivative was attached to create an image display body.

[0062] Figure 2 shows the absorption spectrum of the photoresponsive orientation change-inducing material represented by the above structural formula (1), the diffuse reflectance of the display functional layer in the screen state, and the transmittance of the light-adjusting layer in the colored state. Figure 2 shows that in the wavelength range where the photoresponsive orientation change-inducing material absorbs (400-550 nm), the diffuse reflectance of the display functional layer in the screen state decreases, indicating that the color corresponding to this wavelength range is lost. Furthermore, the colored dimming layer selectively transmits light with a wavelength of 420nm, and it can be seen that this light, when transmitted through the display function layer in the screen state, can compensate for any missing colors. [Explanation of Symbols]

[0063] 1. Image display unit 11 Display function layer 12 Dimming Layer 13 Ultraviolet light shielding layer 14 Transparent substrate 2 Image projection unit 3. Ultraviolet light projection unit 4. Illuminance Measurement Unit S Sun

Claims

1. It comprises an image display unit, an ultraviolet light projection unit, and an image projection unit. The above image display unit is installed in a position where sunlight enters from one side. A display device having the ultraviolet light projection unit and the image projection unit provided on the other side of the image display body, The above image display unit has, in order from the side of the ultraviolet light emitting section, a display function layer, a dimming layer, and an ultraviolet light shielding layer. The above display functional layer contains a photoresponsive orientation change-inducing material and changes between a transparent state and a cloudy screen state. The above-mentioned light-adjusting layer contains a photochromic material and changes between a transparent state and a colored state. A display device characterized in that the above-described colored state is one in which the photoresponsive orientation change-inducing material transmits more light of visible light wavelengths absorbed by the material than light of other visible light wavelengths.

2. By irradiating the image display unit with ultraviolet light from the ultraviolet light projection unit, The above display function layer enters screen mode. The display device according to claim 1, characterized in that the above-mentioned dimming layer becomes colored.

3. Furthermore, the image display unit is equipped with a light illuminance measuring unit that measures light illuminance on the side of the image display unit where sunlight enters the image display unit. The colored dimming layer and the screen display layer are The display device according to claim 1, characterized in that it satisfies the relationship of the following formula (1). (R ２ / R １ ) < (L １ R ２ + L ２ T ２ ) / (L １ R １ + L ２ T １ ) < (R １ / R ２ )... Equation (1) however, T １ This is the average value of the transmittance of light of visible light wavelengths absorbed by the above-mentioned photoresponsive orientation change-inducing material, which passes through the colored light-adjusting layer. T ２ This is the average value of the transmittance of light in the visible light range that is not absorbed by the above-mentioned photoresponsive orientation change-inducing material, which passes through the colored light-adjusting layer. R １ This is the average value of the diffuse reflectance of light of visible light wavelengths that are scattered in the display functional layer in the screen state and absorbed by the above-mentioned photoresponsive orientation change-inducing material. R ２ This is the average value of the diffuse reflectance of light in the visible light range that is scattered in the display functional layer in the screen state and is not absorbed by the above-mentioned photoresponsive orientation change inducing material. L １ The output brightness of the projected light in the visible light range, which the image projection unit projects onto the display function layer in screen state, L ２ This represents the output luminance calculated from the above illuminance of sunlight in the visible light range that passes through the colored light-adjusting layer.

4. When the illuminance measured by the above illuminance measuring unit is less than 100 lux, The display device according to claim 3, characterized in that the output brightness of visible light projected by the above-mentioned image projection unit onto an image display surface in a screen state satisfies the relationship of the following formula (2). 1 < (L) ３ / L ４ ) < (R) ２ / R １ ) ２ ・・・Form (2) However, L ３ This refers to the output brightness of light in the visible light range that is absorbed by the photoresponsive orientation change-inducing material when the above image projection unit displays white, L ４ This refers to the output brightness of light in the visible light range that is not absorbed by the photoresponsive orientation change-inducing material, which is emitted when the above image projection unit displays white. R １ This is the average value of the diffuse reflectance of light in the visible light range that is absorbed by the above-mentioned photoresponsive orientation change-inducing material, which scatters the display functional layer in the screen state. R ２ This represents the average value of the diffuse reflectance of visible light wavelengths that are scattered by the display functional layer in the screen state and are not absorbed by the above-mentioned photoresponsive orientation change-inducing material.

5. When the illuminance measured by the above illuminance measuring unit is 100 lux or more, The brightness output by the above image projection unit is (L ３ / L ４ The display device according to claim 4, characterized in that ) is 1.

Images