Display device

Abstract

This display device is provided with an image display body, an ultraviolet light projection unit, and an image projection unit, the image display body being provided at a position where sunlight enters from one surface thereof, and the ultraviolet light projection unit and the image projection unit being provided on the other side of the image display body. Furthermore, the image display body has, in order from the ultraviolet light projection unit side, a display function layer that includes a photoresponsive orientation change inducing material and that changes between a transparent state and a white turbid screen state, a light control layer that includes a photochromic material and that changes between a transparent state and a white turbid screen state, and an ultraviolet light shielding layer that shields ultraviolet light from the display function layer. The light-responsive orientation change-inducing material changes between a transparent state and a colored state in which more light of a wavelength in a visible light region absorbed by the light-responsive orientation change-inducing material is transmitted than other light of a wavelength in a visible light region, so that a display device can be provided. It can complement the hue of the light of the wavelength absorbed by the photoresponsive 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 restore it to a transparent state. The display function layer of the image display body contains liquid crystal molecules and a light-responsive orientation change inducing material.

[0004] The light-responsive orientation 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 arrangement of the liquid crystal molecules to increase the light scattering property of the display function layer. By visible light of a specific color, it changes from the cis form to the trans form, and the disordered liquid crystal molecules are oriented and arranged neatly, whereby the display function layer restores the transparent state.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-185511 Summary of the Invention

[0008] Technical Problem to be Solved by the Invention

[0009] However, in the image display body described in Patent Document 1, the light-responsive orientation change inducing material that changes its optical state absorbs light of a specific wavelength in the visible light region, so a part of the light projected from the image light projection unit onto the image display body in the screen state is absorbed.

[0010] Therefore, the visible image displayed on the image display body is visually recognized as a visible image lacking the hue of the light of the wavelength absorbed by the light-responsive orientation change inducing material.

[0011] The present invention has been completed in view of the problems of such prior art, and an object thereof is to provide a display device that can supplement the hue of the light of the wavelength absorbed by the light-responsive orientation change inducing material.

[0012] Technical Means for Solving the Problem

[0013] The inventors of the present invention repeatedly conducted in-depth research to achieve the above object, and as a result, found that the above object can be achieved by providing a light control layer that selectively transmits light in the wavelength region absorbed by the light-responsive orientation change-inducing material, thereby completing the present invention.

[0014] That is, the display device of the present invention includes an image display body, an ultraviolet light projection unit, and an image projection unit.

[0015] The image display body is disposed at a position where sunlight enters from one side surface thereof, and the ultraviolet light projection unit and the image projection unit are disposed on the other side of the image display body.

[0016] Moreover, the image display body sequentially includes a display function layer, a light control layer, and an ultraviolet light shielding layer from the side of the ultraviolet light projection unit.

[0017] The display function layer contains a light-responsive orientation change-inducing material and changes between a transparent state and a turbid screen state.

[0018] The light control layer contains a photochromic material and changes between a transparent state and a colored state.

[0019] The colored state is a state in which light having a wavelength in the visible light region absorbed by the light-responsive orientation change-inducing material is transmitted more than light having wavelengths in other visible light regions.

[0020] Advantages of the Invention

[0021] According to the present invention, since a light control layer that selectively transmits light in the wavelength region absorbed by the light-responsive orientation change-inducing material is provided, a display device can be provided that can supplement the hue of light having the wavelength absorbed by the light-responsive orientation change-inducing material. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram showing an example of the display device of the present invention.

[0023] Figure 2 is a diagram showing the absorption spectrum of the light-responsive orientation change-inducing material, the diffuse reflectance of the display function layer in the screen state, and the transmittance of the light control layer in the colored state of the display device of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0024] The display device of the present invention will be described in detail.

[0025] The display device of the present invention includes: 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.

[0026] Moreover, as​​Figure 1 As shown, the image display body is arranged at a position where sunlight enters from one side surface thereof, and the ultraviolet light projecting unit and the image projecting unit are arranged on the other side of the image display body.

[0027] As Figure 1 shown, the image display body sequentially has a display function layer, a light control layer, and an ultraviolet ray shielding layer from the side where the ultraviolet light projecting unit and the image projecting unit are arranged, and they are supported by a transparent substrate. It should be noted that Figure 1 illustrates a case where there is one transparent substrate, and it can also be clamped by two transparent substrates.

[0028] The optical state of the display function layer changes between a transparent state and a turbid screen state, and liquid crystal molecules, a light-responsive orientation change inducing material, and a transparent resin are contained between two vertical alignment films.

[0029] By irradiating ultraviolet light to this display function layer, the molecular structure of the light-responsive orientation change inducing material changes, whereby the orientation state of the liquid crystal molecules changes, and it becomes a screen state where a refractive index difference is generated between the liquid crystal molecules and the transparent resin to cause light scattering. By visible light of a specific wavelength, the molecular structure of the light-responsive orientation change inducing material is restored and becomes a transparent state.

[0030] When the display function layer is in the screen state, as described above, the light-responsive orientation change inducing material not only absorbs ultraviolet light but also absorbs light of a part of wavelengths in the visible light region. Therefore, specific wavelength visible light in the visible light projected from the image projecting unit to the image display body in the screen state is absorbed by the display function layer.

[0031] Therefore, the visible image displayed on the display function layer in the screen state is visually recognized as an image with a lack of hue corresponding to the color of the specific wavelength light absorbed by the light-responsive orientation change inducing material.

[0032] 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 where it transmits more light of a specific wavelength in the visible light region absorbed by the light-responsive orientation change inducing material than light of wavelengths in other visible light regions.

[0033] Moreover, as described above, the image display body is arranged at a position where sunlight enters from one side surface, and sunlight transmits through the image display body from one side surface of the image display body to the other side. Therefore, in the visible image with a lack of specific hue displayed by the display function layer, the color of the light transmitted through the light control layer is added.

[0034] At this time, if the dimming layer is in a colored state, light of a specific wavelength transmitted through the dimming layer is added to the visible image lacking a specific hue displayed by the display functional layer, so that the hue of the color corresponding to the light of the specific wavelength absorbed by the light-responsive orientation change inducing material can be supplemented.

[0035] Generally, a visible image is displayed by a combination of light of three colors: red (R), green (G), and blue (B). The visible image lacking a specific hue is generated because the peak wavelength of any one of the lights is within the wavelength region absorbed by the light-responsive orientation change inducing material, and only the light intensity of that light decreases.

[0036] Therefore, the wavelength of the light transmitted through the dimming layer does not necessarily need to be the same as the wavelength of the light absorbed by the light-responsive orientation change inducing material. The dimming layer only needs to selectively transmit light having a wavelength of light including the color whose light intensity decreases due to the absorption by the light-responsive orientation change inducing material.

[0037] As the photochromic material, a photochromic material that becomes colored by irradiating ultraviolet light can be used. In addition, as the light-responsive orientation change inducing material, a compound that absorbs ultraviolet light and visible light and causes cis-trans isomerization can be used.

[0038] If such a light-responsive orientation change inducing material and a photochromic material are used, there is no need to provide a new control unit for controlling the dimming layer, and the optical state of the display functional layer and the optical state of the dimming layer can be switched by one ultraviolet light projection unit.

[0039] Therefore, by correcting the output brightness of the image projection unit below, etc., power is not consumed for supplementing the hue, and energy saving can be achieved.

[0040] In addition, through the dimming layer in the colored state, the combination of the light-responsive orientation change inducing material and the photochromic material that can supplement the light having a wavelength in the visible light region absorbed by the display functional layer in the screen state is as shown in Table 1 below.

[0041] [Table 1]

[0042]

[0043] In addition, the display device of the present invention includes an illuminance measurement unit that measures the illuminance on the side where sunlight enters the image display body closer to the sunlight than the image display body, and the dimming layer in the colored state and the display functional layer in the screen state satisfy the relationship of the following formula (1).

[0044] (R2 / R1) < (L1R2 + L2T2) / (L1R1 + L2T1) < (R1 / R2) … Formula (1)

[0045] Among them, T1 represents the average value of the transmittance (%) of light with a wavelength in the visible light region absorbed by the light-responsive orientation change-inducing material in the light-transmitting colored state of the light-dimming layer.

[0046] T2 represents the average value of the transmittance (%) of light with a wavelength in the visible light region not absorbed by the light-responsive orientation change-inducing material in the light-transmitting colored state of the light-dimming layer.

[0047] R1 represents the average value of the diffuse reflectance (%) of light with a wavelength in the visible light region absorbed by the light-responsive orientation change-inducing material scattered by the display function layer in the screen state.

[0048] R2 represents the average value of the diffuse reflectance (%) of light with a wavelength in the visible light region not absorbed by the light-responsive orientation change-inducing material scattered by the display function layer in the screen state.

[0049] L1 represents the output brightness of the projected light with a wavelength in the visible light region projected by the image projection unit onto the display function layer in the screen state.

[0050] L2 represents the output brightness converted from the sunlight with a wavelength in the visible light region of the light-transmitting colored state of the light-dimming layer by the illuminance.

[0051] The values of (R2 / R1) and (R1 / R2) can be adjusted by the concentration of the light-responsive orientation change-inducing material. In addition, the value of (L1R2 + L2T2) / (L1R1 + L2T1) can be adjusted by the output of the image projection unit, the concentration of the light-responsive orientation change-inducing material, and the concentration of the photochromic material. It should be noted that the value of T2 can be converted according to the sunlight illuminance measured by the illuminance measurement unit.

[0052] As described above, for the light with a wavelength in the visible light region absorbed by the light-responsive orientation change-inducing material,

[0053] The components of the reflected light and the transmitted light can be respectively expressed as

[0054] L1R1 / 100, L2T1 / 100... Equation (1-1).

[0055] Similarly, for the light with a wavelength in the visible light region not absorbed by the light-responsive orientation change-inducing material,

[0056] The components of the reflected light and the transmitted light can be respectively expressed as

[0057] L1R2 / 100, L2T2 / 100... Equation (1-2).

[0058] Thus, regarding the ratio of the color balance between the light having a wavelength in the visible light region not absorbed by the light-responsive orientation change-induced material and the light having a wavelength in the visible light region absorbed by the light-responsive orientation change-induced material, in the case of only the reflected light components with respect to each other, it is

[0059] L1R2 / L1R1 = R2 / R1… Equation (1-3),

[0060] In contrast, in the case of the components obtained by summing the reflected light components and the transmitted light components with respect to each other, it is

[0061] (L1R2 + L2T2) / (L1R1 + L2T1)… Equation (1-4).

[0062] Therefore, by making the light-shielding layer in the colored state and the display function layer in the screen state satisfy the relationship of Equation (1), even if the illuminance of the sunlight incident on the image display body varies depending on the weather or the like, it is possible to achieve a balance between the hue of a specific wavelength missing from the visible image due to absorption by the display function layer in the screen state and the hue of a specific wavelength added to the visible image by the sunlight transmitted through the light-shielding layer in the colored state within the range of its illuminance being 10000 to 120000 (lux), and visually recognize it as white when viewing the display function layer in the screen state. Among them, when (L1R2 + L2T2) / (L1R1 + L2T1) = 1 holds, the balance between the light having a wavelength in the visible light region absorbed by the light-responsive orientation change-induced material and the light having a wavelength in the visible light region not absorbed by the light-responsive orientation change-induced material visually recognized when viewing the display function layer in the screen state is the best, and thus it is particularly preferred.

[0063] That is, in the case of (R2 / R1) ≥ (L1R2 + L2T2) / (L1R1 + L2T1), an image visually recognized as lacking the hue of a specific color due to insufficient supplementation of the hue based on the light-shielding layer in the colored state, and in the case of (L1R2 + L2T2) / (L1R1 + L2T1) ≥ (R1 / R2), the hue of a specific color added by the light-shielding layer in the colored state is too strong, and thus it is visually recognized as an image with color coverage.

[0064] In the present invention, using a color difference meter CM3600 (Konica Minolta Inc.), the transmittance of the light transmitted through the light-shielding layer in the colored state and the diffuse reflectance of the light reflected / scattered by the display function layer in the screen state are added for the values measured at 10 nm intervals, and then divided by the number of each measurement point to obtain the average value.

[0065] It should be noted that the wavelength region where the molar absorptivity of the light-responsive orientation change-induced material is 0.5 or more is defined as the visible light absorption wavelength region, and the wavelength region where the molar absorptivity is less than 0.5 is defined as the visible light non-absorption wavelength region.

[0066] The display device of the present invention can correct a visible image lacking a specific color tone by changing the balance of the output brightness of visible light projected from the image light projection unit when it is impossible to supplement the color tone based on sunlight at night or the like.

[0067] The output brightness of the visible light projected by the image light projection unit onto the image display body in the screen state preferably satisfies the relationship of the following formula (2).

[0068] 1 < (L3 / L4) < (R2 / R1) 2 …Formula (2)

[0069] Wherein, L3 represents the output brightness of the light having a wavelength in the visible light region absorbed by the light-responsive alignment change inducing material and projected when the image light projection unit displays white.

[0070] L4 represents the output brightness of the light having a wavelength in the visible light region not absorbed by the light-responsive alignment change inducing material and projected when the image light projection unit displays white.

[0071] R1 represents the average value of the diffuse reflectance of the light having a wavelength in the visible light region absorbed by the light-responsive alignment change inducing material and scattered by the display functional layer in the screen state.

[0072] R2 represents the average value of the diffuse reflectance of the light having a wavelength in the visible light region not absorbed by the light-responsive alignment change inducing material and scattered by the display functional layer in the screen state.

[0073] As described above, for the light having a wavelength in the visible light region absorbed by the light-responsive alignment change inducing material, the component of the reflected light can be expressed as

[0074] L3R1 / 100…Formula (2-1).

[0075] Similarly, for the light having a wavelength in the visible light region not absorbed by the light-responsive alignment change inducing material, the component of the reflected light can be expressed as

[0076] L4R2 / 100…Formula (2-2).

[0077] Therefore, the ratio of the color tone balance between the light having a wavelength in the visible light region not absorbed by the light-responsive alignment change inducing material and the light having a wavelength in the visible light region absorbed by the light-responsive alignment change inducing material is

[0078] L4R2 / L3R1…Formula (2-3).

[0079] At this time, assuming that the output brightnesses L3 and L4 are equal, that is, L3 / L4 = 1, formula (2-3) is

[0080] R2 / R1… Equation (2-4).

[0081] In addition, assuming that L3 / L4 = R2 / R1, Equation (2-3) is

[0082] R1R2 / R2R1 = 1… Equation (2-5).

[0083] In addition, when L3 / L4 = (R2 / R1) 2 Equation (2-3) is

[0084] R1 2 R2 / R2 2 R1 = R1 / R2… Equation (2-6).

[0085] Therefore, as described above, by making the brightness ratio (L3 / L4) of the light projected from the image light projection unit to the display function layer satisfy the relationship of Equation (2), the hue of a specific wavelength missing in the visible image caused by the absorption of the display function layer in the screen state can be corrected by the brightness ratio of the light projected from the image light projection unit, and the ratio of the hue balance can be improved. Among them, when L3 / L4 = R2 / R1, the ratio of the hue balance is 1, so it is particularly preferred.

[0086] Therefore, when viewing the display function layer in the screen state, the balance of hues can be achieved and visually recognized as white. By correcting other colors other than white in the same way, the image with the hue missing of the specific color visually recognized can be suppressed.

[0087] Regarding whether the hue based on sunlight can be supplemented, it can be known by setting an illuminance measurement unit and measuring the illuminance received by the image display body. The illuminance measurement unit can be set on the side closer to the sunlight incidence than the image display body, can be set on the image display body itself, or can be set at a position far from the image display body.

[0088] Specifically, when the illuminance measured by the illuminance measurement unit is less than 100 (lux), the hue based on the dimming layer cannot be supplemented, so the image light projection unit corrects the output brightness so that (L3 / L4) satisfies the above Equation (2).

[0089] In addition, when it is 100 (lux) or more, the hue based on the dimming layer can be supplemented, and the image light projection unit does not correct the output brightness, so (L3 / L4) is 1.

[0090] As the liquid crystal molecules of the display function layer, nematic liquid crystals having a rigid mesogenic skeleton and a flexible long-chain alkyl group, having optical anisotropy and dielectric anisotropy can be used. This nematic liquid crystal has the property that rod-shaped liquid crystal molecules associate with each other and are arranged with substantially a certain directionality.

[0091] As the transparent resin, a resin having an aromatic ring with high affinity for liquid crystal and not undergoing phase separation, a polymer of a photopolymerizable monomer can be used. As the resin having an aromatic ring, for example, polyethylene terephthalate, a liquid crystalline resin having a biphenyl group, etc. can be used.

[0092] In addition, the display functional layer may contain a non-photo-responsive chiral compound as needed. As the non-photo-responsive chiral compound, a compound having optical activity different from that of the photo-responsive orientation change inducing material can be used.

[0093] By using the non-photo-responsive chiral compound in combination, the helical twisting power (HTP) can be canceled out with each other, and the alignment disorder of liquid crystal molecules caused by the twisting force of the photo-responsive orientation change inducing material in the trans form can be suppressed.

[0094] The ultraviolet light shielding layer is a transparent film containing an ultraviolet absorber and an ultraviolet light diffusing agent. By providing the ultraviolet light shielding layer, the ultraviolet light incident on the display functional layer and the light control layer from the side opposite to the image light projection part is shielded. As a result, the display functional layer becomes a screen state due to sunlight, and the light control layer becomes a colored state, so that the image display body can be prevented from becoming cloudy.

[0095] As the ultraviolet absorber, a conventionally known ultraviolet absorber that absorbs ultraviolet light with a wavelength of 400 nm or less, does not absorb visible light, and has less coloring property can be used. For example, benzophenone derivatives, salicylate derivatives, triazole derivatives, acrylonitrile derivatives can be cited. In addition, as the ultraviolet light diffusing agent, titanium oxide, zinc oxide, etc. can be cited.

[0096] As the transparent substrate, glass, resin, etc. can be used. As the transparent electrode when applying an electric field to the display functional layer, an ITO film, etc. can be used.

[0097] The image light projection part of the display device has a visible light source, a projection lens, and a control device for controlling them, and projects a visible image onto the image display body in a screen state to display the visible image.

[0098] The illuminance of this image light projection part is preferably 5000 (lux) or more.

[0099] The molecular structure of the photo-responsive orientation change inducing material is restored to its original state by being placed in visible light or exposed to visible light. Therefore, by projecting visible light from the image light projection part onto the image display body, the image display body can be quickly restored to a transparent state.

[0100] In addition, similar to the image projection unit, the ultraviolet light projection unit includes an ultraviolet light source, a projection lens, and a control device for controlling them, and projects ultraviolet light onto the image display body, causing the molecular structure of the light-responsive orientation change-inducing material to isomerize and changing the optical state of the image display body.

[0101] As the light source of the ultraviolet light, a light source having a peak wavelength in the absorption band of the light-responsive orientation change-inducing material can be used. It should be noted that the ultraviolet light projection unit can be controlled by the control device of the image projection unit.

[0102] Regarding the display device of the present invention, for example, it can be used for the windshield or display window of an automobile, and can switch between a screen state where a visible light image can be projected and displayed and a transparent state where the opposite side can be visually recognized.

[0103] Examples

[0104] Hereinafter, the present invention will be described in detail by way of examples, and the present invention is not limited to the following examples.

[0105] [Example 1]

[0106] A transparent substrate having a transparent electrode (indium tin oxide: ITO film) formed over the entire surface of one side of a transparent glass was obtained, and a vertically aligned film (polyimide) was formed over the entire surface of the transparent electrode.

[0107] A mixed solution containing the following substances was prepared: 86.5% by mass of a nematic liquid crystal (manufactured by Merck & Co., Inc.: E44), 5.1% by mass of a light-responsive orientation change-inducing material (azobenzene) represented by the following structural formula (1), 2.9% by mass of a light-non-responsive chiral compound represented by the following structural formula (2), 3.3% by mass of a polymerizable monomer represented by the following structural formula (3), 1.7% by mass of a polymerizable monomer represented by the following structural formula (4), and 0.5% by mass of a polymerization initiator (manufactured by IGM Resins B.V.: IRGAUCERE819).

[0108] [Chemical Formula 1]

[0109]

[0110] [Chemical Formula 2]

[0111]

[0112] [Chemical Formula 3]

[0113]

[0114] [Chemical Formula 4]

[0115]

[0116] Arrange two transparent glasses such that the vertical alignment film is on the inner side and the gap is 10 μm. While heating the mixture, inject it between these transparent glasses, and irradiate light with a wavelength of 420 nm and a power density of 7 mW / cm 2 for 20 minutes to polymerize the monomers in the solution and fabricate the display functional layer.

[0117] Mix a photochromic material (DAE - 001 and DAE0012, both manufactured by Yamada Chemical) into a PMMA solution (manufactured by Yamada Chemical) at a concentration of 1.8 mass%. Coating the resulting photochromic solution onto the transparent glass on which the display functional layer is formed by the spin - coating method and drying it to fabricate the light - adjusting layer. Further, paste an ultraviolet - light - shielding film containing a benzophenone derivative to fabricate the image display body.

[0118] The absorption spectrum of the light - responsive orientation - change - inducing material represented by the 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 are as Figure 2 shown.

[0119] As Figure 2 can be seen, in the wavelength region (400 - 550 nm) where the light - responsive orientation - change - inducing material has absorption, the diffuse reflectance of the display functional layer in the screen state decreases, and the hue of the color corresponding to this wavelength region is missing.

[0120] In addition, it can be seen that the light - adjusting layer in the colored state can selectively transmit light with a wavelength of 420 nm. By transmitting this light through the display functional layer in the screen state, the missing hue can be supplemented.

[0121] Symbol Explanation

[0122] 1 Image display body

[0123] 11 Display functional layer

[0124] 12 Light - adjusting layer

[0125] 13 Ultraviolet - light - shielding layer

[0126] 14 Transparent substrate

[0127] 2 Image light - projecting part

[0128] 3 Ultraviolet - light - projecting part

[0129] 4 Illuminance measuring part

[0130] S Sun

Claims

1. A display device includes an image display body, an ultraviolet light projection unit, and an image projection unit. The image display body is disposed at a position where sunlight enters from one side surface thereof. The ultraviolet light projection unit and the image projection unit are disposed on the other side of the image display body. Among them, the image display body sequentially has a display function layer, a light control layer, and an ultraviolet light shielding layer from the side of the ultraviolet light projection unit. The display function layer contains a light-responsive orientation change inducing material and changes between a transparent state and a turbid screen state. The light control layer contains a photochromic material and changes between a transparent state and a colored state. The colored state is a state in which light having a wavelength in a visible light region absorbed by the light-responsive orientation change inducing material is transmitted more than light having wavelengths in other visible light regions.

2. The display device according to claim 1, wherein ultraviolet light is irradiated from the ultraviolet light projection unit to the image display body, the display function layer becomes a screen state, and the light control layer becomes a colored state.

3. The display device according to claim 1, further comprising: a light intensity measurement unit that measures the light intensity on the side where sunlight enters the image display body, closer to the sunlight than the image display body. The light control layer in the colored state and the display function layer in the screen state satisfy the following relationship of formula (1): (R2 / R1) < (L1R2 + L2T2) / (L1R1 + L2T1) < (R1 / R2) … formula (1) Among them, T1 represents the average value of the transmittance of light having a wavelength in the visible light region absorbed by the light-responsive orientation change inducing material, transmitted through the light control layer in the colored state. T2 represents the average value of the transmittance of light having a wavelength in the visible light region not absorbed by the light-responsive orientation change inducing material, transmitted through the light control layer in the colored state. R1 represents the average value of the diffuse reflectance of light having a wavelength in the visible light region absorbed by the light-responsive orientation change inducing material, scattered by the display function layer in the screen state. R2 represents the average value of the diffuse reflectance of light having a wavelength in the visible light region not absorbed by the light-responsive orientation change inducing material, scattered by the display function layer in the screen state. L1 represents the output luminance of the projection light having a wavelength in the visible light region, projected by the image projection unit onto the display function layer in the screen state. L2 represents the output luminance converted from the light intensity of sunlight having a wavelength in the visible light region, transmitted through the light control layer in the colored state.

4. The display device according to claim 3, wherein when the light intensity measured by the light intensity measurement unit is less than 100 (lux), the output luminance of the visible light projected by the image projection unit onto the image display body in the screen state satisfies the following relationship of formula (2): 1 < (L3 / L4) < (R2 / R1) 2 … Equation (2) wherein, L3 represents the output luminance of light having a wavelength in the visible light region absorbed by the light-responsive orientation change inducing material, projected when the image projection unit displays white. L4 represents the output luminance of light having a wavelength in the visible light region not absorbed by the light-responsive orientation change inducing material, projected when the image projection unit displays white. R1 represents the average value of the diffuse reflectance of light having a wavelength in the visible light region absorbed by the light-responsive orientation change-inducing material and scattered in the display function layer in the screen state. R2 represents the average value of the diffuse reflectance of light having a wavelength in the visible light region not absorbed by the light-responsive orientation change-inducing material and scattered in the display function layer in the screen state.

5. The display device according to claim 4, wherein when the illuminance measured by the illuminance measurement unit is 100 (lux) or more, L3 / L4 of the luminance output by the image projection unit is 1.

Images