JP7059654B2 - Display devices, mobiles, lighting devices and reflectors - Google Patents

Description

The present invention relates to a display device, a moving body having a display device, a lighting device, and a reflector.

Many moving objects such as cars, ships, railroad cars, and airplanes are equipped with display devices. Patent Document 1 discloses, for example, a head-up display as a display device mounted on a moving body. In the display device disclosed in Patent Document 1, the image forming device that emits image light is arranged at a position that is not directly visible, such as inside a dashboard. Then, the image light formed by the image forming apparatus is guided to a position visible to the driver by a guiding means such as a mirror.

JP-A-2015-155948

By the way, when performing full-color display, the image forming apparatus emits light in a plurality of wavelength ranges different from each other (for example, wavelength ranges of red (R), green (G), and blue (B), which are the three primary colors of light). The intensity of light emitted by a general light source used in an image forming apparatus is not uniform over the entire visible light range and varies depending on the wavelength range. For example, the intensity of light emitted by a blue light emitting diode, which is generally used as a light source, is strong in the blue (B) wavelength range and weak in the green (G) and red (R) wavelength ranges. An image forming apparatus using such a general light source cannot obtain a desired color display. Therefore, it is necessary to adjust the intensity of light in a plurality of wavelength ranges included in the image light formed by the image forming apparatus. Similar needs exist for luminaires.

The present invention has been made in consideration of the above points, and is an image forming device or a display device or a lighting device including a light source that emits light including light in a plurality of wavelength ranges having different intensities from each other. It is an object of the present invention to provide a display device or a lighting device capable of emitting light in a plurality of wavelength ranges by reducing or changing the intensity difference thereof. It is also an object of the present invention to provide a mobile body having such a display device. Alternatively, it is an object of the present invention to provide a reflector used in the above-mentioned display device or lighting device.

The display device according to the present invention is
An image forming device that emits image light and
A polarization selective reflection layer that reflects the image light and changes the optical path of the image light is provided.
The polarization selective reflection layer includes a first cholesteric liquid crystal structure layer having a first wavelength as a selective reflection center wavelength, and a second cholesteric liquid crystal structure layer having a second wavelength different from the first wavelength as a selective reflection center wavelength. Have and
The intensity of the light in the first wavelength region including the first wavelength included in the image light emitted from the image forming apparatus is the second wavelength region including the second wavelength included in the image light emitted from the image forming apparatus. Weaker than the light intensity of
The first cholesteric liquid crystal structure layer is located on the incident side of the image light emitted from the image forming apparatus toward the polarization selective reflection layer, rather than the second cholesteric liquid crystal structure layer.

In the display device according to the present invention
The polarization selective reflection layer further includes a third cholesteric liquid crystal structure layer having a third wavelength different from the first wavelength and the second wavelength as the selective reflection center wavelength.
The intensity of the light in the second wavelength region included in the image light emitted from the image forming apparatus is higher than the intensity of the light in the third wavelength region including the third wavelength contained in the image light emitted from the image forming apparatus. Also weak,
The second cholesteric liquid crystal structure layer may be located on the incident side of the image light emitted from the image forming apparatus toward the polarization selective reflection layer, rather than the third cholesteric liquid crystal structure layer.

Further, the display device according to the present invention may further include a 1/4 wavelength retardation layer arranged at a position on the optical path of the image light from the image forming device to the polarization selective reflection layer.

Further, the display device according to the present invention may further include a 1/4 wavelength retardation layer arranged at a position on the optical path of the image light reflected by the polarization selective reflection layer.

Further, the display device according to the present invention is arranged at a position on the optical path of the image light from the image forming apparatus to the polarization selective reflection layer and on the optical path of the image light reflected by the polarization selective reflection layer. A 1/4 wavelength retardation layer may be further provided.

In this case, the 1/4 wavelength retardation layer may be laminated on the polarization selective reflection layer.

Further, the display device according to the present invention may further include a polarizing element arranged on the optical path of the image light after being reflected by the polarization selective reflection layer and transmitted through the 1/4 wavelength retardation layer. ..

Further, in the display device according to the present invention, the image forming device may emit the image light composed of the light of one of the linearly polarized light components.

Further, in the display device according to the present invention, the image forming device may include a liquid crystal display device.

Further, in the display device according to the present invention, the polarization selective reflection layer includes a cholesteric liquid crystal structure layer that selectively reflects light of a right circular polarization component and a cholesteric liquid crystal structure layer that selectively reflects light of a left circular polarization component. You may go out.

In this case, the display device according to the present invention may further include a polarizing element arranged on the optical path of the image light after being reflected by the polarization selective reflection layer.

Further, in the display device according to the present invention, in the image forming apparatus, the light source, the digital micromirror device that changes the optical path of the light from the light source, and the light whose optical path is changed by the digital micromirror device are incident. It may include a screen and.

Further, in the display device according to the present invention, the image forming apparatus includes a laser light source that emits a laser beam, a scanning device that changes the optical path of the laser beam over time, and the laser whose optical path is adjusted by the scanning device. It may include a screen on which light is incident.

Alternatively, the display device according to the present invention is
An image forming device that emits image light and
A polarization selective reflection layer that reflects the image light and changes the optical path of the image light is provided.
The polarization selective reflection layer includes a first cholesteric liquid crystal structure layer having a first wavelength as a selective reflection center wavelength, and a second cholesteric liquid crystal structure layer having a second wavelength different from the first wavelength as a selective reflection center wavelength. Have and
Light in the first wavelength region including the first wavelength included in the image light emitted from the image forming apparatus and light in the second wavelength region including the second wavelength contained in the image light emitted from the image forming apparatus. The stacking order of the first cholesteric liquid crystal structure layer and the second cholesteric liquid crystal structure layer contained in the polarization selective reflection layer is determined so as to change the intensity difference.

Further, the moving body according to the present invention includes any of the above-mentioned display devices according to the present invention.

Alternatively, the display device according to the present invention is
An image forming device that emits image light and
A polarization selective reflection layer that reflects the image light and changes the optical path of the image light is provided.
The polarization selective reflection layer includes a first cholesteric liquid crystal structure layer having a first wavelength as a selective reflection center wavelength, and a second cholesteric liquid crystal structure layer having a second wavelength different from the first wavelength as a selective reflection center wavelength. Have and
The image light emitted from the image forming apparatus includes light in a first wavelength region including the first wavelength and light in a second wavelength region including the second wavelength.

In the display device according to the present invention, the polarization selective reflection layer is included in the polarization selective reflection layer based on the intensity of the light in the first wavelength region included in the image light and the intensity of the light in the second wavelength region contained in the image light. The stacking order of the first cholesteric liquid crystal structure layer and the second cholesteric liquid crystal structure layer may be determined.

Alternatively, the lighting device according to the present invention is
A light source that emits illumination light and
A polarization selective reflection layer that reflects the illumination light emitted from the light source and changes the optical path of the illumination light is provided.
The polarization selective reflection layer includes a first cholesteric liquid crystal structure layer having a first wavelength as a selective reflection center wavelength, and a second cholesteric liquid crystal structure layer having a second wavelength different from the first wavelength as a selective reflection center wavelength. Have and
The intensity of the light in the first wavelength region including the first wavelength included in the illumination light emitted from the light source is the intensity of the light in the second wavelength region including the second wavelength included in the illumination light emitted from the light source. Weaker than
The first cholesteric liquid crystal structure layer is located on the incident side of the illumination light emitted from the light source and directed toward the polarization selective reflection layer, rather than the second cholesteric liquid crystal structure layer.

Alternatively, the lighting device according to the present invention is
A light source that emits illumination light and
A polarization selective reflection layer that reflects the illumination light emitted from the light source and changes the optical path of the illumination light is provided.
The polarization selective reflection layer includes a first cholesteric liquid crystal structure layer having a first wavelength as a selective reflection center wavelength, and a second cholesteric liquid crystal structure layer having a second wavelength different from the first wavelength as a selective reflection center wavelength. Have and
The difference in intensity between the light in the first wavelength region including the first wavelength included in the illumination light emitted from the light source and the light in the second wavelength region including the second wavelength contained in the illumination light emitted from the light source is changed. As such, the stacking order of the first cholesteric liquid crystal structure layer and the second cholesteric liquid crystal structure layer included in the polarization selective reflection layer is determined.

Alternatively, the lighting device according to the present invention is
A light source that emits illumination light and
A polarization selective reflection layer that reflects the illumination light emitted from the light source and changes the optical path of the illumination light is provided.
The polarization selective reflection layer includes a first cholesteric liquid crystal structure layer having a first wavelength as a selective reflection center wavelength, and a second cholesteric liquid crystal structure layer having a second wavelength different from the first wavelength as a selective reflection center wavelength. Have and
The illumination light emitted from the light source includes light in a first wavelength region including the first wavelength and light in a second wavelength region including the second wavelength.

In the lighting apparatus according to the present invention, the polarization selective reflection layer is included in the polarization selective reflection layer based on the intensity of the light in the first wavelength region included in the illumination light and the intensity of the light in the second wavelength region included in the illumination light. The stacking order of the first cholesteric liquid crystal structure layer and the second cholesteric liquid crystal structure layer may be determined.

Further, the reflector according to the present invention is
The light having an incoming surface and reflecting the light in the first wavelength region including the first wavelength incident on the incoming surface and the light in the second wavelength region including the second wavelength different from the first wavelength are reflected. A reflector including a polarization selective reflection layer that changes the optical path of light in the first wavelength region and light in the second wavelength region.
The polarization selective reflection layer includes a first cholesteric liquid crystal structure layer having the first wavelength as the selective reflection center wavelength, and a second cholesteric liquid crystal structure layer having the second wavelength as the selective reflection center wavelength.
The stacking order of the first cholesteric liquid crystal structure layer and the second cholesteric liquid crystal structure layer included in the polarization selective reflection layer changes the intensity difference between the light in the first wavelength region and the light in the second wavelength region. Has been decided.

According to the present invention, an image forming device or a display device or a lighting device including a light source that emits light including light in a plurality of wavelength ranges having different intensities, and the light in the plurality of wavelength ranges is different in intensity. It is possible to provide a display device or a lighting device capable of emitting light by relaxing or modifying the above. It is also possible to provide a mobile body having such a display device. Alternatively, a reflector used in the above-mentioned display device or lighting device can be provided.

FIG. 1 is a diagram for explaining an embodiment of the present invention, and is a vertical sectional view schematically showing a moving body and a display device. FIG. 2 is a diagram showing a selective reflector and an image forming apparatus that may be included in the display device of FIG. FIG. 3A is a diagram showing an example of a laminated body composed of a plurality of cholesteric liquid crystal structural layers. FIG. 3B is a graph showing the reflection characteristics of the laminate shown in FIG. 3A. FIG. 4A is a graph showing the reflection characteristics of another laminate composed of a plurality of cholesteric liquid crystal structural layers laminated in a stacking order different from that of the laminate shown in FIG. 3A. FIG. 4B is a graph showing the reflection characteristics of yet another laminate composed of a plurality of cholesteric liquid crystal structural layers laminated in a stacking order different from that of the laminate shown in FIG. 3A. FIG. 5 is a vertical sectional view showing a modified example of the display device. FIG. 6 is a vertical sectional view showing another modification of the display device. FIG. 7 is a vertical sectional view showing still another modification of the display device. FIG. 8 is a diagram for explaining a modification of the image forming apparatus. FIG. 9 is a diagram for explaining another modification of the image forming apparatus. FIG. 10 is a vertical sectional view showing still another modification of the display device. FIG. 11 is a diagram showing a selective reflector that may be included in the display device of FIG. FIG. 12 is a vertical sectional view showing still another modification of the display device.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings attached to the present specification, the scale and the aspect ratios are appropriately changed and exaggerated from those of the actual product for the convenience of illustration and comprehension.

1 and 2 are diagrams for explaining one embodiment according to the present invention. Of these, FIG. 1 is a vertical sectional view showing the entire configuration of the display device together with a part of the moving body, and FIG. 2 is a vertical sectional view showing a main part of the display device.

As shown in FIG. 1, the moving body 1 has a moving body main body 2 and a display device 10 mounted on the moving body main body 2. As the moving body main body 2, a car, a ship, a railroad vehicle, an airplane, or the like can be exemplified. In the example shown in FIG. 1, the mobile body 2 is an automobile. In this example, the display device 10 is arranged in the dashboard 4 and projects an image on the windshield 3. The image light projected toward the windshield 3 is reflected by the windshield 3 so that it can be observed by the driver of the moving body main body 2. The driver so as to visually recognize the virtual image at a position in front of the windshield 3 by the distance corresponding to the optical path length of the image light Li from the image forming device 30 included in the display device 10 to the windshield 3. Become. That is, in the example shown in FIG. 1, the display device 10 is configured as a projection type display device, more specifically, a head-up display.

In the example shown in FIG. 1, the dashboard 4 is formed with an opening 4a. The image light Li from the display device 10 goes to the windshield 3 through the opening 4a. On the other hand, as shown in FIG. 1, the external light Lx, particularly sunlight, incident on the inside of the moving body main body 2 through the windshield 3 travels in the opposite direction in the optical path of the image light Li and is inside the display device 10. Incident to. The image forming apparatus 30 included in the display apparatus 10 includes optical films having particularly low heat resistance, and its function may be impaired by receiving external light Lx. In one embodiment described below, a device is made to effectively suppress the heating of the image forming apparatus 30 included in the display device 10. Hereinafter, the details of the display device 10 in the present embodiment will be described.

Not limited to automobiles, the moving body 1 is usually provided with a display device 10, and the driver or the operator of the moving body 1 is in a state of the moving body main body 2 via the display device 10. And the surroundings of the moving body 2 can be confirmed. The driver or operator of the mobile body 1 is usually located in an area partitioned by transparent glass or the like, and grasps the external situation through the transparent glass. Therefore, the display device 10 mounted on the mobile body 2 tends to be installed in an environment in which external light Lx, particularly sunlight, is easily received. The embodiment described below is not limited to the automobile, but is widely useful in the display device 10 generally mounted on the mobile body 1.

As shown in FIG. 1, the display device 10 guides the housing 20, the image forming device 30 arranged in the housing 20, and the image light formed by the image forming device 30 to the outside of the housing 20. It has a guiding means 55 and. Further, in the illustrated example, the image light Li from the image forming apparatus 30 is composed of the light of one of the linearly polarized light components. Corresponding to such an image forming apparatus 30, a 1/4 wavelength retardation layer 50 is provided between the image forming apparatus 30 and the guiding means 55. Hereinafter, each component will be described.

The housing 20 is made of resin or metal. As shown in FIG. 1, the housing 20 is formed with an opening 21 at a position facing the windshield 3. The opening 21 is provided with a transparent cover 25 having visible light transmission. As a specific example, the transparent cover 25 can be a transparent plate made of a polycarbonate resin or an acrylic resin. Further, the transparent cover 25 uses infrared rays (a concept including near infrared rays) within a range that does not impair the transmission of visible light, which is the image light of the image forming apparatus 30, for the purpose of suppressing the incident of infrared rays into the housing 20. It may function as a reflecting infrared reflecting film or an infrared absorbing film that absorbs infrared rays.

The image forming apparatus 30 is an apparatus for forming an image, and emits image light Li that forms an image. As shown in FIG. 2, a liquid crystal display device 31 can be used as the image forming device 30.

In the example shown in FIGS. 1 and 2, the image light Li is composed of visible light in a plurality of wavelength ranges. The image light Li includes visible light L1 in the first wavelength region including the first wavelength, visible light L2 in the second wavelength region including the second wavelength, and visible light L3 in the third wavelength region including the third wavelength. It is composed of. The first wavelength, the second wavelength, and the third wavelength are different from each other. When the image forming apparatus 30 realizes color display by light in the wavelength ranges of red (R), green (G), and blue (B), which are the three primary colors of light, the image light Li emitted from the image forming apparatus 30. Is composed of, for example, visible light having a wavelength range of 430 to 460 nm, visible light having a wavelength range of 540 to 570 nm, and visible light having a wavelength range of 580 to 620 nm.

The image forming apparatus 30 may realize color display by light in a wavelength range of four or more colors. In this case, the image light Li is composed of light in a wavelength range of four or more colors. When the image forming apparatus 30 realizes color display by light in the wavelength range of deep red (DR), red (R), green (G), pale blue (LB) and blue (B), the image forming apparatus 30 is realized. The image light Li emitted from is, for example, visible light having a wavelength range of 430 to 460 nm, visible light having a wavelength range of 490 nm to 520 nm, visible light having a wavelength range of 540 to 570 nm, and a wavelength range of 580 to 620 nm. It may be composed of visible light and visible light having a wavelength range of 640 to 680 nm.

The liquid crystal display device 31 includes a liquid crystal display panel 32 and a surface light source device 33 arranged on the back side of the liquid crystal display panel 32 and illuminating the liquid crystal display panel 32 in a plane shape from the back side. The surface light source device 33 may be configured by various types of backlights such as a direct type and an edge light type. The liquid crystal display panel 32 functions as a shutter that controls the transmission or blocking of light from the surface light source device 33 for each pixel, and can display an image on the display surface.

The illustrated liquid crystal display panel 32 has a lower polarizing plate 32a, a liquid crystal cell 32b, and an upper polarizing plate 32c in order from the side of the surface light source device 33. The lower polarizing plate 32a and the upper polarizing plate 32c are absorption-type polarizing elements, and decompose the incident light into two orthogonal polarizing components (P wave and S wave) in one direction (direction parallel to the transmission axis). ), And absorbs the linearly polarized light component (for example, S wave) that vibrates in the other direction (direction parallel to the absorption axis) orthogonal to the one direction. It has a function.

An electric field can be applied to the liquid crystal cell 32b for each region forming one pixel. Then, the orientation direction of the liquid crystal molecules in the liquid crystal cell 32b changes depending on the presence or absence of the electric field application. As an example, the polarization component in a specific direction transmitted through the lower polarizing plate 32a arranged on the incoming light side rotates its polarization direction by 90 ° when passing through the liquid crystal cell 32b to which no electric field is applied, while rotating the polarization direction by 90 °. The polarization direction is maintained as it passes through the liquid crystal cell 32b to which an electric field is applied. In this case, whether the polarizing component vibrating in a specific direction transmitted through the lower polarizing plate 32a further transmits the upper polarizing plate 32c arranged on the light emitting side of the lower polarizing plate 32a depending on the presence or absence of an electric field applied to the liquid crystal cell 32b. Alternatively, it can be controlled whether it is absorbed by the upper polarizing plate 32c and blocked.

In this way, the liquid crystal display panel 32 (liquid crystal display unit) can control the transmission or blocking of light from the surface light source device 33 for each pixel. The details of the liquid crystal display device 31 are described in various publicly known documents (for example, "Flat Panel Display Encyclopedia (supervised by Tatsuo Uchida and Hiraki Uchiike)" published by Kogyo Chosakai in 2001). The above detailed description will be omitted.

The image light Li emitted from the liquid crystal display device 31 is the light of one linearly polarized light component corresponding to the transmission axis of the upper polarizing plate 32c. Then, in the illustrated example, the image light Li emitted from the image forming apparatus 30 is incident on the 1/4 wavelength retardation layer 50. The 1/4 wavelength retardation layer 50 imparts a phase difference of 1/4 wavelength to the transmitted light. In the 1/4 wavelength retardation layer 50, the image light Li composed of the light of one linearly polarized light component is converted into a right circular polarization component or a left circular polarization component by passing through the 1/4 wavelength retardation layer 50. As such, the direction of the slow axis is determined. In the examples shown in FIGS. 1 and 2, the image light Li transmitted through the 1/4 wavelength retardation layer 50 is converted into a right circular polarization component. Note that, in FIGS. 1 and 2, the 1/4 wavelength retardation layer 50 is arranged apart from the image forming apparatus 30, but is not limited to this. The 1/4 wavelength retardation layer 50 may be fixed to the image forming apparatus 30. For example, the 1/4 wavelength retardation layer 50 may be laminated on the image forming surface of the image forming apparatus 30. Further, the 1/4 wavelength retardation layer 50 may be laminated on the outermost surface of the polarization selective reflection layer 70, which will be described later.

Next, the guiding means (optical path adjusting optical system) 55 will be described. The guiding means 55 guides the image light Li from the image forming apparatus 30 toward the windshield 3. That is, the guiding means 55 is a projection optical system (projection optical system) that projects the image light Li from the image forming apparatus 30 onto the front glass 3. The guiding means 55 has a selective reflector 60 and a reflecting means 80.

Of these, the selective reflector 60 is configured to selectively reflect the image light Li to adjust the optical path of the image light Li, while transmitting most of the unnecessary external light Lx incident on the display device 10. Has been done. That is, the selective reflector 60 is a member expected to have a function of separating the optical path of the image light Li and the optical path of unnecessary external light Lx. By providing the selective reflector 60, it is possible to effectively prevent the external light Lx from advancing to the image forming apparatus 30. On the other hand, the reflecting means 80 is not provided with a function of separating the image light Li and the external light Lx. The reflecting means 80 may be configured as, for example, a reflecting mirror. In particular, in the illustrated example, the reflecting means 80 is configured as a concave mirror 81. By using the concave mirror 81, it is possible to magnify and project the image formed by the image forming apparatus 30. However, the guiding means 55 is not limited to the illustrated example, and may include, for example, an optical element such as a prism in place of the reflecting means 80 or in addition to the reflecting means 80.

Hereinafter, the selective reflector 60 of the guiding means 55 will be described in more detail. As shown in FIG. 2, the selective reflection plate 60 has a base material 61 and a polarization selective reflection layer 70 laminated on the base material 61. The polarization selective reflection layer 70 has a property of selectively reflecting the image light Li to change the optical path of the image light. That is, the polarization selective reflection layer 70 distinguishes the image light Li from some other light and reflects the image light with a higher reflectance than any other light. In the illustrated example, the polarization selective reflection layer 70 reflects the image light Li with a reflectance higher than that of the external light Lx. Further, the polarization selective reflection layer 70 has a property of selectively transmitting external light Lx. That is, the polarization selective reflection layer 70 distinguishes the external light Lx from some other light, and transmits the external light Lx with a higher transmittance than any other light. In the illustrated example, the polarization selective reflection layer 70 transmits the external light Lx with a higher transmittance than the image light Li.

As a specific configuration, the polarization selective reflection layer 70 includes a plurality of cholesteric liquid crystal structure layers having a cholesteric liquid crystal structure. The cholesteric liquid crystal structure layer is composed of a liquid crystal composition exhibiting cholesteric regularity, and the director of the liquid crystal molecules is continuously rotated in the thickness direction of the layer as the physical molecular arrangement of the liquid crystal molecules in the cholesteric liquid crystal structure. It has a spiral structure. The cholesteric liquid crystal structure has a polarization separation characteristic that separates a unidirectional circular polarization component and a circular polarization component in the opposite direction based on the physical molecular arrangement of such liquid crystal molecules. .. That is, in the cholesteric liquid crystal structure, the unpolarized light incident along the spiral axis is separated into two polarized light (right-circular polarization and left-circular polarization), one of which is transmitted and the other of which is reflected. .. This phenomenon is known as circular dichroism, and when the spiral winding direction in the spiral structure of the liquid crystal molecule is appropriately selected, the circular polarization component having the same optical rotation direction as the spiral winding direction is selectively reflected.

The maximum optical rotation light scattering in this case occurs at the wavelength λ ₀ of the following equation (1).
λ ₀ = nav ・ p… (1)
Here, p is the spiral pitch length (the length per pitch of the molecular spiral of the liquid crystal molecule) in the spiral structure of the liquid crystal molecule, and nav is the average refractive index in the plane orthogonal to the spiral axis.

Further, the wavelength bandwidth Δλ of the reflected light at this time is expressed by the following equation (2). Here, Δn is a birefringence value.
△ λ ＝ △ n ・ p… (2)

That is, the cholesteric liquid crystal structure layer has wavelength selectivity in addition to circular polarization selectivity. Therefore, the light of one circular polarization component (for example, right circular polarization in the selective reflection wavelength range) belonging to the range of the wavelength band width Δλ centered on the selective reflection center wavelength λ ₀ is polarized selective reflection. It is selectively reflected by the layer 70 (reflected at a higher transmittance than the other light), and the other light is selectively transmitted by the polarization selective reflection layer 70 (right circular polarization within the selective reflection wavelength range). It is transmitted with a higher transmittance than the light of the component).

The polarization selective reflection layer 70 reflects light in a plurality of wavelength ranges included in the visible light range (for example, a wavelength range of 380 nm to 780 nm). That is, in the examples shown in FIGS. 1 and 2, as described above, the image light Li is composed of visible light in a plurality of wavelength ranges, and the polarization selective reflection layer 70 corresponds to the light in the plurality of wavelength ranges. It contains at least two or more cholesteric liquid crystal structural layers having different spiral pitch lengths discontinuously. In the example shown in FIGS. 1 and 2, the visible light Li emitted from the image forming apparatus 30 is composed of light L1 in the first wavelength region, light L2 in the second wavelength region, and light L3 in the third wavelength region. There is. Therefore, based on the case where the light is vertically incident on the polarization selective reflection layer 70, the light whose selective reflection center wavelength is in the first wavelength region, the second wavelength region, and the third wavelength region is selectively reflected. As described above, the spiral pitch length of the cholesteric liquid crystal structure is determined for the plurality of cholesteric liquid crystal structure layers included in the polarization selective reflection layer 70.

Specifically, when the image forming apparatus 30 realizes color display by light in the red (R), green (G), and blue (B) wavelength ranges, the light is perpendicular to the polarization selective reflection layer 70. It is included in the polarization selective reflection layer 70 so as to selectively reflect light having a selective reflection center wavelength in the range of 430 to 460 nm, 540 to 570 nm and 580 to 620 nm, based on the case of being incident on. For a plurality of cholesteric liquid crystal structure layers, the spiral pitch length of the cholesteric liquid crystal structure is determined. When the image forming apparatus 30 realizes color display by light in the dark red (DR), red (R), green (G), pale blue (LB), and blue (B) wavelength range, the polarization selective reflection layer 70 Selectively select light having a selective reflection center wavelength in the range of 430 to 460 nm, 490 nm to 520 nm, 540 to 570 nm, 580 to 620 nm, and 640 to 680 nm, based on the case where light is incident perpendicular to the light. The spiral pitch length of the cholesteric liquid crystal structure may be determined for a plurality of cholesteric liquid crystal structure layers included in the polarization selective reflection layer 70 so as to reflect light.

The cholesteric liquid crystal structure of the cholesteric liquid crystal structure layer has an optical characteristic that the selective reflection wavelength range is shifted to the short wavelength side (so-called "blue shift") when light is obliquely incident. Therefore, it is preferable to appropriately adjust the spiral pitch length of the cholesteric liquid crystal structure according to the incident angle of the image light Li incident on the selective reflector 60 from the image forming apparatus 30.

In the example shown in FIG. 2, the polarization selective reflection layer 70 has a first cholesteric liquid crystal structure layer 71 having a first wavelength as a selective reflection center wavelength and a second cholesteric liquid crystal structure having a second wavelength as a selective reflection center wavelength. It has a layer 72 and a third cholesteric liquid crystal structure layer 73 having a third wavelength as a selective reflection center wavelength. The first cholesteric liquid crystal structure layer 71 selectively reflects the light of the right circular polarization component in the first wavelength region. Further, the second cholesteric liquid crystal structure layer 72 selectively reflects the light of the right circular polarization component in the second wavelength region. Further, the third cholesteric liquid crystal structure layer 73 selectively reflects the light of the right circular polarization component in the third wavelength region.

The thickness of the cholesteric liquid crystal structure layers 71, 72, 73 shall be such that the light of the specific circularly polarized light component that is selectively reflected is reflected approximately 100% (the size is such that the reflectance is saturated). Is preferable. The reflectance of the cholesteric liquid crystal structure layer directly depends on the number of spiral pitches, but if the spiral pitch length is fixed, it indirectly depends on the thickness of the cholesteric liquid crystal structure layer. Specifically, since it is said that about 4 to 10 pitches are required to obtain 100% reflectance, a material for forming a cholesteric liquid crystal structure layer (for example, a liquid crystal composition exhibiting cholesteric regularity). Although it depends on the type of material and the selective reflection wavelength range, for example, if it is a layer of cholesteric liquid crystal structure layer that reflects light in any of the wavelength ranges of red (R), green (G) and blue (B). It preferably has a thickness of about 1 to 10 μm. On the other hand, the thicker the cholesteric liquid crystal structure layer, the better, and if it is too thick, it becomes difficult to control the orientation, unevenness occurs, and the degree of light absorption by the material itself is high. The above range is appropriate as it will be large.

As a specific example, the first cholesteric liquid crystal structure layer 71 reflects unpolarized light in the wavelength range of 600 nm or more and 700 nm or less with a reflectance of 30% or more, and the second cholesteric liquid crystal structure layer 72 reflects 450 nm or more and 550 nm or less. The unpolarized light in the wavelength range of 30% or more is reflected, and the third cholesteric liquid crystal structure layer 73 reflects the unpolarized light in the wavelength range of 300 nm or more and 400 nm or less with a reflectance of 30% or more. You may do so.

In the display device 10 described above, the polarization selective reflection layer 70 selectively reflects the image light Li and transmits light in a wavelength range different from the image light Li and light having a circular polarization component different from the image light Li. As a result, the external light Lx, particularly sunlight, incident on the inside of the moving body main body 2 through the front glass 3 travels in the opposite direction in the optical path of the image light Li, and an optical film having low heat resistance (for example, upper polarization). It is possible to reduce the possibility of incident light on the image forming apparatus 30 including the plate 32c). Specifically, most of the external light Lx traveling in the opposite direction in the optical path of the image light Li passes through the polarization selective reflection layer 70. Therefore, the external light Lx reflected by the polarization selective reflection layer 70 and incident on the image forming apparatus 30 is only a small amount. That is, according to the present embodiment, it is possible to effectively deal with a problem that the image forming apparatus 30 is damaged by heating due to external light irradiation.

Further, in Patent Document 1, the external light Lx is prevented from being incident on the image forming apparatus 30 by diffusing the external light Lx. However, when the external light Lx is diffused in the housing 20 of the display device 10, the contrast of the image is lowered. On the other hand, in the above-mentioned display device 10, the image forming apparatus 30 reduces the possibility that the external light Lx is incident on the image forming apparatus 30 without using the means for diffusing the external light Lx. Therefore, the problem of contrast reduction due to the diffusion of external light is avoided.

Further, as shown in the example shown in FIG. 2, the selective reflector 60 includes a base material 61, three cholesteric liquid crystal structure layers 71, 72, 73 laminated on the base material 61, and a base material. It may have an absorption layer 62 laminated on the side opposite to the cholesteric liquid crystal structure layers 71, 72, 73 of 61. The absorption layer 62 functions as a beam stopper, and the external light Lx can be recovered without being diffused in the housing 20. As a result, it is possible to extremely effectively prevent the contrast decrease due to the diffusion of external light. The absorption layer 62 is not particularly limited, and a member capable of absorbing visible light and infrared rays (concept including near infrared rays) can be used. Specifically, a black light-absorbing rubber material, an inorganic oxide (for example, black alumite-treated aluminum) and the like can be used. Further, in order to prevent the absorption layer from being heated, it is also effective to install the heat radiation fins in the absorption layer 62 or to provide a cooling means such as a blower fan.

By the way, as described above, the image light Li emitted from the image forming apparatus 30 is composed of visible light L1, L2, L3 in a plurality of wavelength ranges. The intensity of the light emitted by the general light source 33 used in the image forming apparatus 30 is not uniform over the entire visible light range, and varies depending on the wavelength range. For example, the intensity of light emitted by a blue light emitting diode, which is generally used as a light source 33, is the strongest in the blue (B) wavelength range, followed by the strongest in the green (G) wavelength range, and the strongest in the red (R) wavelength range. weak. Therefore, when a light source having a different light intensity for each wavelength range is used as the light source 33 of the image forming apparatus 30, it may not be possible to obtain a desired color display.

Also in the examples shown in FIGS. 1 and 2, the light L1 in the first wavelength region, the light L2 in the second wavelength region, and the light L3 in the third wavelength region contained in the image light Li emitted from the image forming apparatus 30 are Its strength is different. Specifically, the intensity of the light L1 in the first wavelength region is weaker than the intensity of the light L2 in the second wavelength region, and the intensity of the light L2 in the second wavelength region is weaker than the intensity of the light L3 in the third wavelength region. .. Here, the intensity of light in the present specification refers to the intensity measured by a spectral irradiance meter (for example, Lightning Passport ALP-01 of SenseTEC).

In consideration of such circumstances, the polarization selective reflection layer 70 according to the present embodiment is for adjusting the intensity difference of the light L1, L2, L3 in a plurality of wavelength ranges having different intensities from each other emitted from the image forming apparatus 30. Has been devised. In the illustrated example, a device is devised to alleviate the difference in intensity of the light L1, L2, L3 in a plurality of wavelength ranges having different intensities from each other emitted from the image forming apparatus 30. As a result, the display device 10 can obtain a display of a desired color. Hereinafter, the polarization selective reflection layer 70 of the present embodiment will be described in more detail with reference to FIGS. 2 to 4B.

First, in the display device 10 shown in FIG. 1, the image light Li from the image forming device 30 is incident on the polarization selective reflection layer 70 diagonally, that is, at an incident angle larger than 0 °. Here, the incident angle is an angle formed by the incident direction of the image light Li and the normal direction of the light incoming surface 70a of the polarization selective reflection layer 70. Here, according to the findings obtained by the present inventors, when the image light is obliquely incident on the laminated body formed by laminating a plurality of cholesteric liquid crystal structural layers, the image light is not reflected as desired. be. That is, in some of the cholesteric liquid crystal structure layers contained in the laminated body, the light in the wavelength range to be reflected by the layer may not be reflected as desired. In particular, it has been found that in the cholesteric liquid layer structure layer arranged at a place away from the incoming surface of the laminated body, the reflectance of light in the wavelength range to be reflected by the layer tends to decrease. It was also found that such a phenomenon becomes more remarkable as the incident angle of the image light is larger.

With reference to FIGS. 3A and 3B, the reflection characteristics of the laminated body obtained by laminating a plurality of cholesteric liquid crystal structural layers will be described.

FIG. 3A is a vertical sectional view of a laminated body in which a plurality of cholesteric liquid crystal structural layers are laminated. The laminate 170 shown in FIG. 3A has a 1/4 wavelength retardation layer 150, a cholesteric liquid crystal structure layer 171 having a selective reflection center wavelength at 550 nm, and a cholesteric liquid crystal having a selective reflection center wavelength at 650 nm, in this order from the incoming light side. A structural layer 172, a cholesteric liquid crystal structure layer 173 having a selective reflection center wavelength at 600 nm, a cholesteric liquid crystal structure layer 174 having a selective reflection center wavelength at 450 nm, and a cholesteric liquid crystal structure layer 175 having a selective reflection center wavelength at 500 nm. It has a glass base material 161 and.

FIG. 3B shows the reflection characteristics of the laminated body 170 shown in FIG. 3A. The reflection characteristics were measured by incident white light on the laminated body 170 at an incident angle of 30 ° and measuring the reflected light using V-670 manufactured by JASCO Corporation.

As can be seen from FIG. 3B, the reflectance of the laminated body 170 is different for each wavelength range. Specifically, the reflectance of the laminate 170 is approximately 93% in the wavelength range of 510 to 560 nm, approximately 87% in the wavelength range of 610 to 650 nm, and approximately 82% in the wavelength range of 570 to 610 nm. In the wavelength range of 430 to 460 nm, it is about 76%, and in the wavelength range of 470 to 500 nm, it is about 65%. This is because the cholesteric liquid crystal structure layers 171, 172 arranged at a position close to the light entry surface 170a of the laminated body 170 can reflect the light of the selective reflection center wavelength with a high reflectance, but the light entry surface. The cholesteric liquid crystal structural layer 173, 174, 175 arranged at a position away from 170a shows that the reflectance of light having the selective reflection center wavelength is low. Such a difference in reflectance depending on the wavelength range is considered to be due to the following reasons.

That is, the light obliquely incident on the cholesteric liquid crystal structure layer undergoes phase modulation when it passes through the layer, and its polarization state changes. Then, when light is obliquely incident on the laminated body in which a plurality of cholesteric liquid crystal structure layers are laminated, phase modulation is brought to the light each time it passes through the cholesteric liquid crystal structure layer, and the polarization state is also applied to the light. It changes by the amount of phase modulation that has been added. As a result, for example, the light incident on the laminate as the light of the right circular polarization component is the light of the right elliptical polarization component or the light of the right elliptical polarization component when incident on the cholesteric liquid crystal structure layer arranged at a position away from the incoming surface of the laminate. It is converted to light of a linearly polarized light component, and in some cases, light of a left circularly polarized light component. Here, the cholesteric liquid crystal structure layer contained in the laminated body is usually designed to reflect the light of a specific circularly polarized light component contained in the light incident on the laminated body. Therefore, if the polarization state of the light incident on the laminated body is changed as described above, the cholesteric liquid crystal structure layer contained in the laminated body cannot reflect the light incident on the layer as desired. As described above, in the cholesteric liquid crystal structure layer arranged at a position away from the light entering surface of the laminated body, light having a different polarization state from the light incident on the laminated body is incident, so that the light incident on the layer is desired. Can't reflect like. Therefore, the reflection characteristics of the laminated body including the plurality of cholesteric liquid crystal structural layers differ depending on the stacking order of the plurality of cholesteric liquid crystal structural layers.

In the polarization selective reflection layer 70 shown in FIG. 2, the stacking order of the plurality of cholesteric liquid crystal structure layers 71 to 73 can be determined by utilizing the reflection characteristics of the laminated body obtained by laminating the plurality of cholesteric liquid crystal structure layers as described above. It is determined that light L1, L2, and L3 in a plurality of wavelength ranges having different intensities emitted from an image forming apparatus are reflected by relaxing the difference in intensity. That is, as described above, the image light Li is composed of the light L1 in the first wavelength region, the light L2 in the second wavelength region, and the light L3 in the third wavelength region, and the light L1 in the first wavelength region. The intensity is weaker than the intensity of the light L2 in the second wavelength region, and the intensity of the light L2 in the second wavelength region is weaker than the intensity of the light L3 in the third wavelength region. In order to alleviate the difference in intensity and reflect such light L1, L2, L3 having different intensities, in the polarization selective reflection layer 70 shown in FIG. 2, the first cholesteric liquid crystal structure layer 71 and the second cholesteric liquid crystal structure layer 71 are reflected. The 72 and the third cholesteric liquid crystal structure layer 73 are arranged as follows. That is, the first cholesteric liquid crystal structure layer 71 is more emitted from the image forming apparatus 30 than the second cholesteric liquid crystal structure layer 72 and directed toward the polarization selective reflection layer 70 on the incident side (side of the incoming light surface 70a) of the image light Li. It is located in. Further, the second cholesteric liquid crystal structure layer 71 is more emitted from the image forming apparatus 30 than the third cholesteric liquid crystal structure layer 73 and directed toward the polarization selective reflection layer 70 on the incident side (side of the incoming light surface 70a) of the image light Li. It is located in. Here, the "incident side" with respect to the polarization selective reflection layer 70 is the side on which the image light Li emitted from the image forming apparatus 30 is incident.

By arranging the first cholesteric liquid crystal structure layer 71 and the second cholesteric liquid crystal structure layer 72 as described above, the reflectance of the light L1 in the first wavelength region in the first cholesteric liquid crystal structure layer 71 can be determined by the second cholesteric liquid crystal display. It can be made higher than the reflectance of the light L2 in the second wavelength region in the structural layer 72. As a result, the difference between the intensity of the light L1 in the first wavelength region incident on the first cholesteric liquid crystal structure layer 71 and the intensity of the light L2 in the second wavelength region incident on the second cholesteric liquid crystal structure layer 72 is larger than the difference. The difference between the intensity of the light L1 in the first wavelength region reflected by the first cholesteric liquid crystal structure layer 71 and the intensity of the light L2 in the second wavelength region reflected by the second cholesteric liquid crystal structure layer 72 can be reduced. .. Further, by arranging the second cholesteric liquid crystal structure layer 72 and the third cholesteric liquid crystal structure layer 73 as described above, the reflectance of the light L2 in the second wavelength region in the second cholesteric liquid crystal structure layer 72 is set to the third. It can be made higher than the reflectance of the light L3 in the third wavelength region in the cholesteric liquid crystal structure layer 73. As a result, the difference between the intensity of the light L2 in the second wavelength region incident on the second cholesteric liquid crystal structure layer 72 and the intensity of the light L3 in the third wavelength region incident on the third cholesteric liquid crystal structure layer 73 is larger than the difference. The difference between the intensity of the light L2 in the second wavelength region reflected by the second cholesteric liquid crystal structure layer 72 and the intensity of the light L3 in the third wavelength region reflected by the third cholesteric liquid crystal structure layer 73 can be reduced. ..

As described above, the stacking order of the cholesteric liquid crystal structure layers 71, 72, 73 included in the polarization selective reflection layer 70 is the light L1 in the first wavelength region, the light L2 in the second wavelength region, and the third wavelength in the image light Li. Since the determination is based on the intensity of the light L3 in the region, the difference in intensity of the light L1, L2, L3 in a plurality of wavelength regions can be alleviated. Further, preferably, the intensities of the light L1, L2, L3 in a plurality of wavelength ranges can be made uniform.

It is clearly shown in FIGS. 4A and 4B that the reflection characteristics of the laminated body change depending on the stacking order of the plurality of cholesteric liquid crystal structural layers. That is, FIGS. 4A and 4B have a 1/4 wavelength retardation layer 150, a plurality of cholesteric liquid crystal structure layers 171-175, and a glass substrate 161, similarly to the laminate 170 shown in FIG. 3A. It shows the reflection characteristics of the laminated body that the stacking order of the plurality of cholesteric liquid crystal structure layers 171 to 175 is different. The reflection characteristics of each laminate were measured by incident white light on the 1/4 wavelength retardation layer 150 of the laminate at an incident angle of 30 ° and measuring the reflected light using a spectrophotometer V-670 manufactured by Nippon Spectroscopy.

In the laminate shown in FIG. 4A, the 1/4 wavelength retardation layer 150, the cholesteric liquid crystal structure layer 171 having the selective reflection center wavelength at 550 nm, and the cholesteric liquid crystal having the selective reflection center wavelength at 600 nm are in this order from the incoming light side. A structural layer 173, a cholesteric liquid crystal structure layer 175 having a selective reflection center wavelength at 500 nm, a cholesteric liquid crystal structure layer 172 having a selective reflection center wavelength at 650 nm, and a cholesteric liquid crystal structure layer 174 having a selective reflection center wavelength at 450 nm. The glass substrate 161 and the glass substrate 161 are laminated in this order. The reflectance of this laminate is higher in the wavelength range of 560 to 600 nm and 470 to 500 nm as compared with the reflectance characteristics of the laminate 170 shown in FIG. 3B. This is because the cholesteric liquid crystal structure layer 173 having a selective reflection center wavelength at 600 nm and the cholesteric liquid crystal structure layer 175 having a selective reflection center wavelength at 500 nm are closer to the incoming light side (about 1/4 wavelength) than the laminated body 170. It is considered that this is because it is arranged near the phase difference layer 150 side).

On the other hand, in the laminate shown in FIG. 4B, the 1/4 wavelength retardation layer 150, the cholesteric liquid crystal structure layer 172 having the selective reflection center wavelength at 650 nm, and the selective reflection center wavelength at 600 nm are provided in this order from the incoming light side. Cholesteric liquid crystal structure layer 173, cholesteric liquid crystal structure layer 171 having a selective reflection center wavelength at 550 nm, cholesteric liquid crystal structure layer 175 having a selective reflection center wavelength at 500 nm, and cholesteric liquid crystal structure layer 174 having a selective reflection center wavelength at 450 nm. And the glass base material 161 are laminated in this order. The reflectance of this laminate is higher in the wavelength range of 560 to 650 nm as compared with the reflectance characteristics of the laminate 170 shown in FIG. 3B. This is because the cholesteric liquid crystal structure layer 172 having a selective reflection center wavelength at 650 nm and the cholesteric liquid crystal structure layer 173 having a selective reflection center wavelength at 600 nm are more on the incoming light side (about 1/4 wavelength) as compared with the laminated body 170. It is considered that this is because it is arranged near the phase difference layer 150 side).

As can be seen from FIGS. 4A and 4B, the characteristics of the reflected light reflected by the polarization selective reflection layer can be adjusted as desired by changing the stacking order of the plurality of cholesteric liquid crystal structural layers of the polarization selective reflection layer. can do. As shown in FIG. 4A, when the stacking order of the plurality of cholesteric liquid crystal structural layers of the polarization selective reflection layer is determined so that the intensity of the reflected light becomes the highest in the wavelength range of 550 nm to 560 nm, the standard ratio of the human eye is determined. It is possible to obtain reflected light that matches the visual sensitivity. As a result, it is possible to obtain a high-brightness and easy-to-see image on the display device. Alternatively, the power consumption of the display device can be suppressed.

In the display device 10 shown in FIG. 7, which will be described later, the laminate shown in FIGS. 4A and 4B is adopted as the polarization selective reflection layer 70 provided with the 1/4 wavelength retardation layer 52, and the display device 10 is provided. Of the image projected on the front glass 3 of the moving body main body 2, the brightness and tint of the white portion intended to be displayed in white are measured using a color luminance meter CS-100A manufactured by Konica Minolta. As a result, the following results were obtained. That is, when the laminate shown in FIG. 4A is adopted, the chromaticity coordinates in the CIE1931-XYZ color system are x = 0.349 and y = 0.401, and the luminance is 2,510 [cd / m ² ]. ]Met. Further, when the laminate shown in FIG. 4B is adopted, the chromaticity coordinates in the CIE1931-XYZ color system are x = 0.370 and y = 0.364, and the luminance is 2,220 [cd / m ² ]. ]Met. From the above results, when the stacking order of the plurality of cholesteric liquid crystal structure layers contained in the polarization selective reflection layer 70 is determined so that the intensity of the reflected light is the highest in the wavelength range near 550 nm, the y value of the chromaticity becomes high. It is understood that the greenness of the white part becomes stronger. It is also understood that in this case, the brightness is high. On the other hand, when the stacking order of the plurality of cholesteric liquid crystal structure layers included in the polarization selective reflection layer 70 is determined so that the intensity of the reflected light is highest in the wavelength range near 650 nm, the x value of the chromaticity becomes high and the white portion It is understood that the redness of the color becomes stronger. As described above, it was confirmed that the display chromaticity and the brightness can be changed by changing the stacking order of the plurality of cholesteric liquid crystal structure layers of the polarization selective reflection layer 70.

Next, the operation of the display device 10 having the above configuration will be described.

First, the image light Li including the light L1 in the first wavelength region, the light L2 in the second wavelength region, and the light L3 in the third wavelength region is emitted from the image forming apparatus 30. Of the light L1, L2, and L3 contained in the image light Li, the intensity of the light L1 in the first wavelength region is weaker than the intensity of the light L2 in the second wavelength region, and the intensity of the light L2 in the second wavelength region is the third. It is weaker than the intensity of light L3 in the wavelength range. The image forming device 30 is a liquid crystal display device 31. Therefore, the image light Li is composed of light having a linearly polarized light component corresponding to the direction of the transmission axis of the upper polarizing plate 32c of the liquid crystal display device 31. As shown in FIGS. 1 and 2, the image light Li emitted from the image forming apparatus 30 then passes through the 1/4 wavelength retardation layer 50. The 1/4 wavelength phase difference layer 50 brings about 1/4 wavelength phase modulation for the image light Li. As a result, the polarization state of the image light Li is converted from one linear polarization to one circular polarization, for example, right circular polarization.

The image light Li transmitted through the 1/4 wavelength retardation layer 50 is directed to the polarization selective reflection layer 70 of the selective reflector 60. As shown in FIG. 2, the polarization selective reflection layer 70 has a first cholesteric liquid crystal structure layer 71, a second cholesteric liquid crystal structure layer 72, and a third cholesteric liquid crystal structure layer 73. The cholesteric liquid crystal structure layer is a layer having a cholesteric liquid crystal structure, has wavelength selectivity and circular polarization selectivity, and can selectively reflect image light Li. The first cholesteric liquid crystal structure layer 71, the second cholesteric liquid crystal structure layer 72, and the third cholesteric liquid crystal structure layer 73 are light L1 and L2 contained in the image light Li emitted from the image forming apparatus 30 and directed toward the polarization selective reflection layer 70. , L3 are stacked in this order from the incident side of the image light Li according to the intensity.

Among the cholesteric liquid crystal structure layers 71, 72, 72, in the third cholesteric liquid crystal structure layer 73 arranged at the position farthest from the incident side described above, the most of the lights L1, L2, L3 contained in the image light Li. The right circular polarization component of the light L3 in the third wavelength region, which has strong intensity, is reflected. Further, in the second cholesteric liquid crystal structure layer 72 located on the incident side described above with respect to the third cholesteric liquid crystal structure layer 73, the right circular polarization of the light L2 in the second wavelength region, which has a weaker intensity than the light L3 in the third wavelength region. The component is reflected. The second cholesteric is more than the difference between the intensity of the light L2 in the second wavelength region incident on the second cholesteric liquid crystal structure layer 72 and the intensity of the light L3 in the third wavelength region incident on the third cholesteric liquid crystal structure layer 73. The difference between the intensity of the light L2 in the second wavelength region reflected by the liquid crystal structure layer 72 and the intensity of the light L3 in the third wavelength region reflected by the third cholesteric liquid crystal structure layer 73 is small. Further, in the first cholesteric liquid crystal structure layer 71 located on the incident side of the second cholesteric liquid crystal structure layer 72, the right circular polarization of the light L1 in the first wavelength region, which has a weaker intensity than the light L2 in the second wavelength region. The component is reflected. The first cholesteric is more than the difference between the intensity of the light L1 in the first wavelength region incident on the first cholesteric liquid crystal structure layer 71 and the intensity of the light L2 in the second wavelength region incident on the second cholesteric liquid crystal structure layer 72. The difference between the intensity of the light L1 in the first wavelength region reflected by the liquid crystal structure layer 71 and the intensity of the light L2 in the second wavelength region reflected by the second cholesteric liquid crystal structure layer 72 is small.

The image light Li reflected by the selective reflector 60 is then magnified and reflected by the reflecting means 80. The image light Li magnified and reflected by the reflecting means 80 passes through the transparent cover 25 and is emitted from the display device 10. The image light Li is then reflected by the windshield 3 and is observed by the driver or the operator who is the observer.

Further, in the illustrated example, the image light finally observed is composed of one of the circularly polarized light components. Therefore, the image can also be observed by an observer wearing polarized sunglasses.

In the above-described embodiment described above, the display device 10 includes an image forming device 30 that emits image light Li and a polarization selective reflection layer 70 that reflects image light Li to change the optical path of image light Li. And have. The polarization selective reflection layer 70 includes a first cholesteric liquid crystal structure layer 71 having a first wavelength as a selective reflection center wavelength, and a second cholesteric liquid crystal structure layer 72 having a second wavelength different from the first wavelength as a selective reflection center wavelength. ,have. Here, the intensity of the light L1 in the first wavelength region including the first wavelength included in the image light Li emitted from the image forming apparatus 30 includes the second wavelength included in the image light Li emitted from the image forming apparatus 30. It is weaker than the intensity of light L2 in the second wavelength region. The first cholesteric liquid crystal structure layer 71 is located on the incident side of the image light Li emitted from the image forming apparatus 30 toward the polarization selective reflection layer 70, rather than the second cholesteric liquid crystal structure layer 72.

Further, the polarization selective reflection layer 70 further has a third cholesteric liquid crystal structure layer 73 having a third wavelength different from the first wavelength and the second wavelength as the selective reflection center wavelength. Here, the intensity of the light L2 in the second wavelength region included in the image light Li emitted from the image forming apparatus 30 is the intensity of the third wavelength region including the third wavelength included in the image light Li emitted from the image forming apparatus 30. It is weaker than the intensity of light L3. The second cholesteric liquid crystal structure layer 72 is located on the incident side of the image light Li emitted from the image forming apparatus 30 and directed toward the polarization selective reflection layer 70, rather than the third cholesteric liquid crystal structure layer 73.

In such a polarization selective reflection layer 70 of the display device 10, a plurality of cholesteric liquid crystals are used based on the respective intensities of the lights L1, L2, and L3 in a plurality of wavelength ranges contained in the image light Li emitted from the image forming device 30. The stacking order of the structural layers 71, 72, 73 is determined. As a result, in the polarization selective reflection layer 70, the lights L1, L2, and L3 having different intensities contained in the image light Li can be reflected by relaxing the difference in intensity. That is, normally, in a reflective layer composed of a plurality of cholesteric liquid crystal structure layers, when light is obliquely incident, it is reflected in the cholesteric liquid crystal structure layer arranged at a position away from the incident side of the light. The reflectance of light in the wavelength range to be reduced decreases. Therefore, the first cholesteric liquid crystal structure layer 71 that reflects the light L1 in the first wavelength region, which is weaker than the light L2 in the second wavelength region, and the second cholesteric liquid crystal structure layer 72 that reflects the light L2 in the second wavelength region. By arranging the light L1 on the incident side of the image light Li, the reflectance of the light L1 in the first wavelength region in the first cholesteric liquid crystal structure layer 71 can be adjusted to the light L2 in the second wavelength region in the second cholesteric liquid crystal structure layer 72. Can be higher than the reflectivity of. As a result, it is possible to reduce the difference in intensity and reflect the light L1 in the first wavelength region and the light L2 in the second wavelength region, which have different intensities from each other. That is, the intensity of the light L1 in the first wavelength region incident on the first cholesteric liquid crystal structure layer 71 and the intensity of the light L2 in the second wavelength region incident on the second cholesteric liquid crystal structure layer 72 are larger than the difference. The difference between the intensity of the light L1 in the first wavelength region reflected by the 1-cholesteric liquid crystal structure layer 71 and the intensity of the light L2 in the second wavelength region reflected by the second cholesteric liquid crystal structure layer 72 can be reduced. Further, the second cholesteric liquid crystal structure layer 72 that reflects the light L2 in the second wavelength region, which is weaker than the light L3 in the third wavelength region, and the third cholesteric liquid crystal structure layer 73 that reflects the light L3 in the third wavelength region. By arranging the light L2 on the incident side of the image light Li, the reflectance of the light L2 in the second wavelength region in the second cholesteric liquid crystal structure layer 72 can be adjusted to the light L3 in the third wavelength region in the third cholesteric liquid crystal structure layer 73. Can be higher than the reflectivity of. As a result, it is possible to reduce the difference in intensity and reflect the light L2 in the second wavelength region and the light L3 in the third wavelength region, which have different intensities from each other. That is, the intensity of the light L2 in the second wavelength region incident on the second cholesteric liquid crystal structure layer 72 and the intensity of the light L3 in the third wavelength region incident on the third cholesteric liquid crystal structure layer 73 are larger than the difference. The difference between the intensity of the light L2 in the second wavelength region reflected by the two cholesteric liquid crystal structure layer 72 and the intensity of the light L3 in the third wavelength region reflected by the third cholesteric liquid crystal structure layer 73 can be reduced. As described above, the difference in intensity between the lights L1, L2, and L3 incident on the cholesteric liquid crystal structure layers 71, 72, and 73 can be alleviated, and it becomes easy to obtain a desired color display on the display device 10.

In addition, in the display device 10, the polarization selective reflection layer 70 reflects the image light Li, while transmitting light having a circular polarization component different from the image light Li and light in a wavelength range different from the image light Li. be able to. Since the cholesteric liquid crystal structure layer forming the polarization selective reflection layer 70 has wavelength selectivity, the optical path of the image light Li such as infrared rays (concept including near infrared rays) and visible light in a wavelength range different from that of the image light Li is reversed. Most of the external light Lx incident on the display device 10 is transmitted through the polarization selective reflection layer 70. As a result, it is possible to effectively prevent a large amount of external light Lx from being incident on the image forming apparatus 30. Then, it is possible to effectively prevent the image forming apparatus 30 from being heated by external light and causing damage.

Further, in the display device 10, unnecessary light incident on the display device 10 is deflected from the image forming device 30 by transmitting the polarization selective reflection layer 70 instead of the reflection. Therefore, it is possible to effectively prevent unnecessary light from being emitted from the display device 10 along an optical path similar to that of the image light Li. Then, it is possible to effectively avoid image deterioration due to a decrease in contrast caused by this unnecessary light. Further, most of the unnecessary light deflected from the image forming apparatus 30 can be recovered after passing through the polarization selective reflection layer 70. Thereby, deterioration of the image caused by the external light Lx incident on the display device 10 can be more effectively prevented.

Further, when the polarization selective reflection layer 70 is manufactured, a cholesteric liquid crystal structure layer having a selective reflection wavelength region in the wavelength region of the image light Li in the visible light wavelength region may be prepared. Even in the full-color display device 10, the wavelength range of the image light Li is limited. Therefore, the polarization selective reflection layer 70 does not need to include a large number of cholesteric liquid crystal structure layers, and typically, it is sufficient for the color display display device 10 to include three cholesteric liquid crystal structure layers having different selective reflection wavelength ranges. be. Therefore, it is possible to effectively prevent the polarization selective reflection layer from being multi-layered, complicated, and expensive.

Further, the image formed by the light of the circularly polarized component can be visually recognized even through polarized sunglasses. From the above, the display device 10 according to the present embodiment is suitable for the moving body 1 in which an environment in which external light is easily incident is provided.

Further, in the above-described embodiment, the display device 10 has a 1/4 wavelength retardation layer 50 arranged at a position on the optical path of the image light Li from the layer forming device 30 to the polarization selective reflection layer 70. I have more. When the image light Li emitted by the image forming apparatus 30 is light of one linear polarization component, typically, when the image forming apparatus 30 is a liquid crystal display device 31, a laser projector, or the like, the polarization selective reflection layer 70 is reached. The image light Li can be converted into light having a circularly polarized light component that is selectively reflected by the polarization selective reflection layer 70 by the 1/4 wavelength retardation layer 50 arranged on the optical path of the above. Therefore, it is possible to enjoy the above-mentioned excellent effects while appropriately selecting the image forming apparatus 30.

Further, in the above-described embodiment, the image forming apparatus 30 emits the image light Li composed of the light of one of the linearly polarized light components. The image light Li composed of the light of one linearly polarized light component can be converted into a circularly polarized light component by using the 1/4 wavelength retardation layer 50. Therefore, the image light Li emitted from the image forming apparatus 30 can be used with high utilization efficiency.

It is possible to make various changes to the above-described embodiment. Hereinafter, an example of modification will be described with reference to the drawings. In the following description and the drawings used in the following description, the same reference numerals as those used for the corresponding portions in the above-described embodiment are used for the portions that can be configured in the same manner as in the above-described embodiment, and duplicates thereof are used. The explanation to be done is omitted.

For example, in the example shown in FIG. 2, the absorption layer 62 may be laminated on the side opposite to the cholesteric liquid crystal structure layers 71, 72, 73 of the base material 61, and the external light Lx is housed 20 by the absorption layer 62. It has been stated that it can be recovered without spreading within, but it is not limited to this. As another example of the method for processing the external light Lx, in the example shown in FIG. 5, the external light Lx transmitted through the selective reflector 60 is induced separately from the guiding means 55 for inducing the image light Li. External light guiding means 63 for this purpose is provided. The external light guiding means 63 may have various elements for guiding light, such as a lens, a prism, a reflecting mirror, and the like. In the example shown in FIG. 5, the external light guiding means 63 is composed of a reflecting mirror that bends the optical path of the external light Lx. The external light guiding means 63 guides the external light Lx to the outside of the housing 20 through the discharge opening 22 provided in the housing 20. However, the present invention is not limited to this example, and the external light Lx may be guided to the heat radiation fins provided for cooling the image forming apparatus 30 or the cooling system installed in the moving body main body 2. In the example shown in FIG. 5, the discharge opening 22 is covered with a lid material 22a that transmits visible light. The lid material 22a is capable of transmitting external light Lx and prevents dust and the like from entering the housing 20.

Further, as shown in FIG. 6, the display device 10 further includes a 1/4 wavelength retardation layer 51 arranged at a position on the optical path of the image light reflected by the polarization selective reflection layer 70. May be good. According to the 1/4 wavelength retardation layer 51, the image light Li reflected by the polarization selective reflection layer 70 can be converted from the circularly polarized light component to the light of the linearly polarized light component. Various optical applications can be easily applied to the image light Li having a linearly polarized component.

Further, as shown in FIG. 6, the polarizing element 27 arranged on the optical path of the image light Li after the display device 10 is reflected by the polarization selective reflection layer 70 and transmitted through the 1/4 wavelength retardation layer 51 is further added. You may have it. The polarizing element 27 may be either an absorption type polarizing element 27a or a reflective type polarizing element 27b. In the example shown in FIG. 6, instead of the transparent cover 25 in the above-described embodiment, the absorption type polarizing element 27a or the reflection type polarizing element 27b is installed in the opening 21 of the housing 20. The absorption type polarizing element 27a decomposes the incident light into two orthogonal polarization components (P wave and S wave) and vibrates in one direction (direction parallel to the transmission axis) (for example, P wave). ), And has a function of absorbing a linearly polarized component (for example, an S wave) that vibrates in the other direction (direction parallel to the absorption axis) orthogonal to the one direction. Further, the reflective polarizing element 27b decomposes the incident light into two orthogonal polarization components (P wave and S wave) and vibrates in one direction (direction parallel to the transmission axis) (for example, a linear polarization component). It has a function of transmitting a P wave) and reflecting a linearly polarized light component (for example, an S wave) that vibrates in the other direction (direction parallel to the absorption axis) orthogonal to the one direction.

In the example shown in FIG. 6, the image light Li is converted from a circularly polarized light component to a linearly polarized light component by passing through the 1/4 wavelength retardation layer 51. If the absorption type polarizing element 27a or the reflection type polarizing element 27b is arranged so that the light of the linearly polarized light component forming the image light Li can be transmitted, the utilization efficiency of the image light Li does not decrease. Further, it was confirmed that the reflectance of the windshield 3 is higher when the image light Li is linearly polarized (for example, S wave) than when it is circularly polarized, and the image light Li can be effectively used. .. In this respect as well, it is effective to provide a 1/4 wavelength retardation layer on the optical path of the image light Li reflected by the polarization selective reflection layer 70.

On the other hand, in the example shown in FIG. 6, only half of the external light Lx can pass through the absorption type polarizing element 27a or the reflection type polarizing element 27b. Therefore, the amount of external light Lx incident on the housing 20 of the display device 10 can be significantly reduced while maintaining the utilization efficiency of the image light Li. This makes it possible to more effectively prevent the temperature rise of the image forming apparatus 30 and the contrast decrease of the image without affecting the brightness of the image.

As with the transparent cover 25 described above, an infrared reflecting film or an infrared absorbing film may be laminated on the polarizing element 27.

Further, as shown in FIG. 7, the display device 10 replaces the above-mentioned 1/4 wavelength retardation layer 50 on the optical path of the image light Li from the layer forming device 30 to the polarization selective reflection layer 70 and is polarized. A 1/4 wavelength retardation layer 52 arranged at a position on the optical path of the image light Li reflected by the selective reflection layer 70 may be further provided. According to this example, when the image light Li emitted by the image forming apparatus 30 is light of one linearly polarized light component, typically, when the image forming apparatus 30 is a liquid crystal display device 31, a laser projector, or the like. The image light Li is converted into the light of the circularly polarized light component that is selectively reflected by the polarization selective reflection layer 70 by the 1/4 wavelength retardation layer 52 arranged on the optical path up to the polarization selective reflection layer 70. be able to. Further, the image light Li reflected by the polarization selective reflection layer 70 can be reconverted into a linear polarization component by the same 1/4 wavelength retardation layer 52. As a result, the polarization state of the image light Li after the optical path is adjusted by the polarization selective reflection layer 70 can be converted into a linear polarization component. Various optical applications can be easily applied to the image light Li having a linearly polarized component.

In particular, in the example shown in FIG. 7, the 1/4 wavelength retardation layer 52 is laminated on the polarization selective reflection layer 70. According to such an arrangement of the 1/4 wavelength retardation layer 52, the image light Li is 1/4 when it is incident on the polarization selective reflection layer 70 and twice after being reflected by the polarization selective reflection layer 70. The wavelength retardation layer 52 can be more reliably transmitted. Since the 1/4 wavelength retardation layer 52 can be arranged close to the polarization selective reflection layer 70, the display device 10 can be miniaturized.

Similar to the example shown in FIG. 6, in the example shown in FIG. 7, the image after the display device 10 is reflected by the polarization selective reflection layer 70 and transmitted through the 1/4 wavelength retardation layer 52. Further, the polarizing element 27 (absorbent type polarizing element 27a or reflective type polarizing element 27b) arranged on the optical path of the light Li may be further provided. By installing the absorption type polarizing element 27a or the reflective type polarizing element 27b, as already described with reference to FIG. 6, the temperature of the image forming apparatus 30 and the temperature of the image are increased without affecting the brightness of the image. It is also possible to prevent the decrease in contrast more effectively.

Further, in the above-described embodiment, the liquid crystal display device 31 is exemplified as the image forming device 30 that emits the image light Li composed of one of the linearly polarized light components, but the present invention is not limited to this example. For example, as shown in FIG. 8, the laser projector 36 can be used as an image forming apparatus 30 that emits image light Li composed of one linearly polarized light component. The laser projector 36 shown in FIG. 8 includes a laser light source 37 that emits laser light, a scanning device 38 that changes the optical path of the laser light over time, and a screen on which laser light whose optical path is adjusted by the scanning device is incident. 39 and. The scanning device 38 adjusts the optical path of the laser beam so that the laser beam scans on the screen. An image is formed on the laser light source 37 by dividing the screen into pixel regions and controlling the emission and emission stop of the laser light from the laser light source 37 for each pixel region. By adjusting the polarization state of the laser light oscillated from the laser light source 37 to one linear polarization component, the laser projector 36 emits the image light Li composed of one linear polarization component from the scanning device 38. Can be done. The laser projector 36 shown in FIG. 8 is advantageous in that the utilization efficiency of the light source light is extremely high as compared with the liquid crystal display device.

Further, in the above-described embodiment, an example is shown in which the image forming apparatus 30 that emits the image light Li composed of one of the linearly polarized light components is used, but the present invention is not limited to this. It is also possible to use an image forming apparatus that emits unpolarized image light Li. When the unpolarized image light Li is incident on the polarization selective reflection layer 70, approximately half of the image light Li is reflected by the polarization selective reflection layer 70. That is, although the utilization efficiency of the image light Li is reduced, the above-mentioned effects such that the contrast reduction of the image due to the reflection of external light can be effectively prevented can be enjoyed. For example, in the laser projector 36 shown in FIG. 8, the laser light source 37 oscillates a laser beam whose polarization state is not adjusted, or the liquid crystal display device 31 shown in FIG. 2 or the laser shown in FIG. When the projector 36 includes a member having a strong diffusion function, unpolarized image light Li is emitted from the image forming apparatus 30.

Further, the image forming apparatus 41 using the digital micromirror device 44 as shown in FIG. 9 also emits unpolarized image light Li unless special means are used. The image forming apparatus 41 shown in FIG. 9 includes a light source 42 that emits unpolarized light, a prism 43, and a digital micromirror device 44. The light source 42 includes, for example, a light emitting diode, and irradiates the prism 43 with unpolarized planar light. The planar light passes through the prism 43 and is incident on the digital micromirror device 44. The digital micromirror device 44 is a MEMS element including a large number of micromirrors, and functions as a reflection type spatial light modulator. The digital micromirror device 44 forms an image by switching the reflection direction of the micromirror for each pixel. The image light Li formed by the digital micromirror device 44 is totally reflected by the prism 43 and heads toward the selective reflector 60 of the guiding means 55.

The image forming apparatus 41 shown in FIG. 9 is advantageous in that the utilization efficiency of the light source light is extremely high as compared with the liquid crystal display apparatus. Even if only about half of the image light Li can be reflected by the polarization selective reflection layer 70, the utilization efficiency of the light source light is high as a whole.

Further, in combination with the image forming apparatus 30 that emits unpolarized image light Li, it is possible to devise ways to improve the utilization efficiency of the light source light. In the example shown in FIG. 10, an image forming apparatus 30 that emits unpolarized image light Li is used, and the polarization selective reflection layer 70 has a cholesteric liquid crystal structure layer that selectively reflects light of a right circular polarization component and a left. It may include both a cholesteric liquid crystal structural layer that selectively reflects light of a circularly polarized component. According to such an example, the unpolarized image light Li in the selective reflection wavelength range of the cholesteric liquid crystal structure layer can be reflected by the polarization selective reflection layer 70 with high reflectance, and the utilization efficiency for the light source light. And the energy efficiency of the entire display device 10 can be significantly improved.

The cholesteric liquid crystal structure layer that selectively reflects the light of the right circular polarization component and the cholesteric liquid crystal structure layer that selectively reflects the light of the left circular polarization component have the winding directions of the spiral structure formed by the liquid crystal molecules opposite to each other. The cholesteric liquid crystal structure layer that selectively reflects the light of the right circularly polarized light component and the cholesteric liquid crystal structure layer that selectively reflects the light of the left circularly polarized light component have the same selective reflection center wavelength by making the pitch of the spiral structure the same. Will have. In the specific example shown in FIG. 11, the polarization selective reflection layer 70 has the first to sixth cholesteric liquid crystal structure layers 71 to 76. The first to third cholesteric liquid crystal structure layers 71, 72, 73 selectively reflect the light of the right circular polarization component, and the fourth to sixth cholesteric liquid crystal structure layers 74, 75, 76 are of the left circular polarization component. Selectively reflect light. The first cholesteric liquid crystal structure layer 71 and the fourth cholesteric liquid crystal structure layer 74 have the same selective reflection center wavelength, and selectively reflect light L1 in the first wavelength region. The second cholesteric liquid crystal structure layer 72 and the fifth cholesteric liquid crystal structure layer 75 have the same selective reflection center wavelength, and selectively reflect light L2 in the second wavelength region. The third cholesteric liquid crystal structure layer 73 and the sixth cholesteric liquid crystal structure layer 76 have the same selective reflection center wavelength, and selectively reflect light L3 in the third wavelength region.

Further, also in the example shown in FIG. 10, the display device 10 may further have a polarizing element 27 arranged on the optical path of the image light Li after being reflected by the polarization selective reflection layer 70. The polarizing element 27 may be either an absorption type polarizing element 27a or a reflective type polarizing element 27b. In the example shown in FIG. 12, instead of the transparent cover 25 in the display device 10 shown in FIG. 10, an absorption type polarizing element 27a or a reflection type polarizing element 27b is installed in the opening 21 of the housing 20. ..

In this example, the image light Li reduces the amount of light by about half when it passes through the polarizing element 27. However, as described above, since the energy efficiency of the image forming apparatus itself that emits the unpolarized image light Li is excellent, the energy efficiency of the display apparatus 10 as a whole is still at a high level. On the other hand, in the example shown in FIG. 12, only half of the external light Lx can pass through the polarizing element 27. Therefore, the amount of external light Lx incident on the housing 20 of the display device 10 can be significantly reduced. This makes it possible to more effectively prevent the temperature rise of the image forming apparatus 30 and the contrast decrease of the image.

Although some modifications to the above-described embodiments have been described above, it is naturally possible to apply a plurality of modifications in combination as appropriate.

Further, in the above-described embodiment and its modification, the polarization selective reflection layer 70 selectively reflects light in the visible light region and transmits other light (particularly infrared rays), as a so-called cold mirror, which shields heat. We have described examples used for this, but are not limited to this. For example, the polarization selective reflection layer 70 according to the present invention may be used as a so-called hot mirror that selectively transmits light in the visible light region and reflects other light (particularly infrared rays).

Further, in the above-described embodiment and its modification, the case where the polarization selective reflection layer 70 reflects the image light Li from the image forming apparatus 30 and the reflected image light Li is used for a desired display in the display device 10. Has been explained, but it is not limited to this. The display device 10 may use the light transmitted through the polarization selective reflection layer 70 for a desired display. Also in this case, the plurality of cholesteric liquid crystal structure layers 71, 72, 73 of the polarization selective reflection layer 70 are each of the light L1, L2, L3 in a plurality of wavelength ranges contained in the image light Li emitted from the image forming apparatus 30. By laminating based on the intensity, the difference in intensity can be alleviated when the light L1, L2, and L3 in a plurality of wavelength ranges having different intensities are transmitted in the polarization selective reflection layer 70. As a result, it is easy to obtain a desired color display on the display device 10.

Further, in the above-described embodiment and its modification, a case where the polarization selective reflection layer 70 alleviates (reduces) the difference in intensity when reflecting light L1, L2, L3 in a plurality of wavelength ranges will be described. I've done it, but it's not limited to this. The polarization selective reflection layer 70 may be any as long as it can change the intensity difference when reflecting light L1, L2, L3 in a plurality of wavelength ranges. That is, the stacking order of the plurality of cholesteric liquid crystal structure layers 71, 72, 73 included in the polarization selective reflection layer 70 is the light L1, L2, L3 in a plurality of wavelength ranges included in the image light Li emitted from the image forming apparatus 30. It suffices if it is decided to change the intensity difference of.

In addition, in the stacking order of the plurality of cholesteric liquid crystal structure layers 71, 72, 73 of the polarization selective reflection layer 70, the polarization selective reflection layer 70 reflects light L1, L2, L3 in a plurality of wavelength ranges and changes the intensity difference thereof. When doing so, it may be determined to increase the intensity difference between the light L1, L2, and L3 in a plurality of wavelength ranges. In this case, the display device 10 can obtain a display having a desired color (for example, redness, bluishness, greenness, etc.).

Alternatively, in the stacking order of the plurality of cholesteric liquid crystal structure layers 71, 72, 73 of the polarization selective reflection layer 70, the polarization selective reflection layer 70 reflects light L1, L2, L3 in a plurality of wavelength ranges to change the intensity difference thereof. At that time, it may be determined to change the magnitude relationship of the intensities of the light L1, L2, L3 in a plurality of wavelength ranges. For example, in the examples shown in FIGS. 1 and 2, in the polarization selective reflection layer 70, the intensity of the light L1 in the first wavelength region becomes stronger than the intensity of the light L2 in the second wavelength region and the light L3 in the third wavelength region. As such, the light L1, L2, L3 may be reflected. That is, the stacking order of the plurality of cholesteric liquid crystal structure layers 71, 72, 73 of the polarization selective reflection layer 70 may be determined in this way. Alternatively, in the example shown in FIGS. 1 and 2, in the polarization selective reflection layer 70, the intensity of the light L2 in the second wavelength region becomes stronger than the intensity of the light L1 in the first wavelength region and the light L3 in the third wavelength region. As such, the light L1, L2, L3 may be reflected. That is, the stacking order of the plurality of cholesteric liquid crystal structure layers 71, 72, 73 of the polarization selective reflection layer 70 may be determined in this way. In these cases as well, the display device 10 can obtain a display having a desired color (for example, redness, bluishness, greenness, etc.).

Further, in the above-described embodiment and its modification, the case where the polarization selective reflection layer 70 is used for the display device 10 has been described, but the present invention is not limited to this. For example, the polarization selective reflection layer 70 may be used in a lighting device. In this case, the polarization selective reflection layer 70 relaxes or changes the intensity difference when reflecting the light L1, L2, L3 in a plurality of wavelength ranges emitted from the light source (or the image forming apparatus) of the lighting device. It may provide reflected light of a desired color such as white light. With such a polarization selective reflection layer 70, it is easy to obtain illumination of a desired color.

The above-mentioned lighting device includes a light source that emits illumination light and a polarization selective reflection layer that reflects the illumination light emitted from the light source to change the optical path of the illumination light. The polarization selective reflection layer includes a first cholesteric liquid crystal structure layer having a first wavelength as a selective reflection center wavelength, and a second cholesteric liquid crystal structure layer having a second wavelength different from the first wavelength as a selective reflection center wavelength. have. Further, the illumination light emitted from the light source includes light in the first wavelength region including the first wavelength and light in the second wavelength region including the second wavelength.

In this case, the first cholesteric liquid crystal structure layer and the second cholesteric included in the polarization selective reflection layer are based on the intensity of the light in the first wavelength region included in the illumination light and the intensity of the light in the second wavelength region included in the illumination light. The stacking order of the liquid crystal structural layers may be determined.

For example, the intensity of the light in the first wavelength region including the first wavelength contained in the light emitted from the light source is weaker than the intensity of the light in the second wavelength region including the second wavelength contained in the light emitted from the light source. The first cholesteric liquid crystal structure layer is located on the incident side of the illumination light emitted from the light source and directed toward the polarization selective reflection layer, as compared with the second cholesteric liquid crystal structure layer.

In the polarization selective reflection layer of such a lighting device, the stacking order of the plurality of cholesteric liquid crystal structure layers is determined based on the intensity of each of the light in a plurality of wavelength ranges contained in the illumination light emitted from the light source. As a result, in the polarization selective reflection layer, light in a plurality of wavelength ranges having different intensities contained in the illumination light can be reflected by relaxing the difference in intensity. That is, the first cholesteric liquid crystal structure is more than the difference between the light intensity in the first wavelength region incident on the first cholesteric liquid crystal structure layer and the light intensity in the second wavelength region incident on the second cholesteric liquid crystal structure layer. The difference between the intensity of the light in the first wavelength region reflected by the layer and the intensity of the light in the second wavelength region reflected by the second cholesteric liquid crystal structure layer can be reduced.

Alternatively, the illuminating device includes a light source that emits illumination light and a polarization selective reflection layer that reflects the illumination light emitted from the light source to change the optical path of the illumination light. The polarization selective reflection layer includes a first cholesteric liquid crystal structure layer having a first wavelength as a selective reflection center wavelength and a second cholesteric liquid crystal structure layer having a second wavelength different from the first wavelength as a selective reflection center wavelength. are doing. Then, the intensity difference between the light in the first wavelength region including the first wavelength included in the light emitted from the light source and the light in the second wavelength region including the second wavelength contained in the light emitted from the light source is changed. The stacking order of the first cholesteric liquid crystal structure layer and the second cholesteric liquid crystal structure layer included in the polarization selective reflection layer is determined.

In this case, the stacking order of the plurality of cholesteric liquid crystal structure layers of the polarization selective reflection layer is such that when the polarization selective reflection layer reflects light in a plurality of wavelength ranges and changes the intensity difference thereof, the intensity of the light in a plurality of wavelength ranges is changed. It may be determined to increase the difference. Alternatively, the stacking order of the plurality of cholesteric liquid crystal structure layers of the polarization selective reflection layer is such that when the polarization selective reflection layer reflects light in a plurality of wavelength ranges and changes its intensity difference, the intensity of the light in a plurality of wavelength ranges is changed. It may be decided to change the magnitude relationship. In these cases, it is possible to obtain lighting having a desired color (for example, redness, bluishness, greenness, etc.).

Alternatively, the reflector 60 according to the above-described embodiment and its modification has a light input surface 70a, and the light L1 and the first wavelength in the first wavelength region including the first wavelength incident on the light input surface 70a. Is a reflecting plate 60 including a polarization selective reflection layer 70 that reflects light L2 in a second wavelength region containing a different second wavelength and changes the optical paths of light L1 in the first wavelength region and light L2 in the second wavelength region. be. The polarization selective reflection layer 70 includes a first cholesteric liquid crystal structure layer 71 having a first wavelength as a selective reflection center wavelength, and a second cholesteric liquid crystal structure layer 72 having a second wavelength as a selective reflection center wavelength. The stacking order of the first cholesteric liquid crystal structure layer 71 and the second cholesteric liquid crystal structure layer 72 included in the polarization selective reflection layer 70 from the light input surface 70a side is the light L1 in the first wavelength region and the second wavelength region. It is determined based on the intensity of light L2.

In this case, the stacking order of the first cholesteric liquid crystal structure layer and the second cholesteric liquid crystal structure layer included in the polarization selective reflection layer 70 from the light input surface 70a side is the light L1 and the second in the first wavelength region. It may be determined to change the intensity difference of the light L2 in the wavelength range.

In the display device 10 and the lighting device using such a reflector 60, the polarization selective reflection layer 70 of the reflector 60 can reflect light in a plurality of wavelength ranges to change the intensity difference. As a result, it is possible to obtain a display or illumination having a desired color (for example, redness, bluishness, greenness, etc.). The reflector 60 may be provided with a mark (figure, character, unevenness, etc.) indicating the light entering surface 70a.

Li Image light L1 Light in the first wavelength range L2 Light in the second wavelength range L3 Light in the third wavelength range Lx External light 1 Moving body 2 Moving body Main body 3 Front glass 4 Dashboard 4a Opening 10 Display device 20 Housing 21 Opening 22 Discharge opening 25 Transparent cover 30 Image forming device 31 Liquid crystal display device 32 Liquid crystal display panel 32a Lower polarizing plate 32b Liquid crystal cell 32c Upper polarizing plate 33 Surface light source device 36 Laser projector 37 Laser light source 38 Scanning device 39 Screen 41 Image forming device 42 Light source 43 Prism 44 Digital micromirror device 50 1/4 wavelength retardation layer 51 1/4 wavelength retardation layer 52 1/4 wavelength retardation layer 55 Induction means 60 Selective reflector 61 Base material 62 Absorption layer 70 Polarizer selective reflector 71 1st cholesteric liquid crystal structure layer 72 2nd cholesteric liquid crystal structure layer 73 3rd cholesteric liquid crystal structure layer 74 4th cholesteric liquid crystal structure layer 75 5th cholesteric liquid crystal structure layer 76 6th cholesteric liquid crystal structure layer 80 Reflecting means 81 concave mirror

Claims (14)

An image forming device that emits image light and
A polarization selective reflection layer that reflects the image light and changes the optical path of the image light,
A 1/4 wavelength retardation layer arranged at a position on the optical path of the image light from the image forming apparatus to the polarization selective reflection layer and on the optical path of the image light reflected by the polarization selective reflection layer. , Equipped with
The polarization selective reflection layer includes a first cholesteric liquid crystal structure layer having a first wavelength as a selective reflection center wavelength, and a second cholesteric liquid crystal structure layer having a second wavelength different from the first wavelength as a selective reflection center wavelength. Have and
The intensity of the light in the first wavelength region including the first wavelength included in the image light emitted from the image forming apparatus is the second wavelength region including the second wavelength included in the image light emitted from the image forming apparatus. Weaker than the light intensity of
The first cholesteric liquid crystal structure layer is a display device located on the incident side of the image light emitted from the image forming apparatus and directed toward the polarization selective reflection layer, rather than the second cholesteric liquid crystal structure layer. The display device according to claim 1 , wherein the 1/4 wavelength retardation layer is laminated on the polarization selective reflection layer. The display device according to claim 1 or 2 , further comprising a polarizing element arranged on the optical path of the image light after being reflected by the polarization selective reflection layer and transmitted through the 1/4 wavelength retardation layer. The display device according to any one of claims 1 to 3 , wherein the image forming apparatus emits the image light composed of the light of one of the linearly polarized light components. The display device according to any one of claims 1 to 4 , wherein the image forming device includes a liquid crystal display device. An image forming device that emits image light and
A polarization selective reflection layer that reflects the image light and changes the optical path of the image light,
It comprises a polarizing element arranged on the optical path of the image light after being reflected by the polarization selective reflection layer.
The polarization selective reflection layer includes a first cholesteric liquid crystal structure layer having a first wavelength as a selective reflection center wavelength, and a second cholesteric liquid crystal structure layer having a second wavelength different from the first wavelength as a selective reflection center wavelength. Have and
The intensity of the light in the first wavelength region including the first wavelength included in the image light emitted from the image forming apparatus is the second wavelength region including the second wavelength included in the image light emitted from the image forming apparatus. Weaker than the light intensity of
The first cholesteric liquid crystal structure layer is located on the incident side of the image light emitted from the image forming apparatus and directed toward the polarization selective reflection layer, rather than the second cholesteric liquid crystal structure layer.
The polarization selective reflection layer is a display device including a cholesteric liquid crystal structure layer that selectively reflects light of a right circular polarization component and a cholesteric liquid crystal structure layer that selectively reflects light of a left circular polarization component. 6. The image forming apparatus includes a light source, a digital micromirror device that changes the optical path of light from the light source, and a screen on which the light whose optical path is changed by the digital micromirror device is incident. The display device described in. The polarization selective reflection layer further includes a third cholesteric liquid crystal structure layer having a third wavelength different from the first wavelength and the second wavelength as the selective reflection center wavelength.
The intensity of the light in the second wavelength region included in the image light emitted from the image forming apparatus is higher than the intensity of the light in the third wavelength region including the third wavelength contained in the image light emitted from the image forming apparatus. Also weak,
The second cholesteric liquid crystal structure layer is located on the incident side of the image light emitted from the image forming apparatus toward the polarization selective reflection layer, rather than the third cholesteric liquid crystal structure layer. The display device according to any one of the items. The image forming apparatus includes a laser light source that emits a laser beam, a scanning device that changes the optical path of the laser beam over time, and a screen to which the laser beam whose optical path is adjusted by the scanning device is incident. , The display device according to any one of claims 1 to 4 and 6 . An image forming device that emits image light and
A polarization selective reflection layer that reflects the image light and changes the optical path of the image light,
A 1/4 wavelength retardation layer arranged at a position on the optical path of the image light from the image forming apparatus to the polarization selective reflection layer and on the optical path of the image light reflected by the polarization selective reflection layer. , Equipped with
The polarization selective reflection layer includes a first cholesteric liquid crystal structure layer having a first wavelength as a selective reflection center wavelength, and a second cholesteric liquid crystal structure layer having a second wavelength different from the first wavelength as a selective reflection center wavelength. Have and
Light in the first wavelength region including the first wavelength included in the image light emitted from the image forming apparatus and light in the second wavelength region including the second wavelength contained in the image light emitted from the image forming apparatus. A display device in which the stacking order of the first cholesteric liquid crystal structure layer and the second cholesteric liquid crystal structure layer included in the polarization selective reflection layer is determined so as to change the intensity difference. A mobile body comprising the display device according to any one of claims 1 to 10 . A light source that emits illumination light and
A polarization selective reflection layer that reflects the illumination light emitted from the light source and changes the optical path of the illumination light is provided.
The polarization selective reflection layer includes a first cholesteric liquid crystal structure layer having a first wavelength as a selective reflection center wavelength, and a second cholesteric liquid crystal structure layer having a second wavelength different from the first wavelength as a selective reflection center wavelength. Have and
The intensity of the light in the first wavelength region including the first wavelength included in the illumination light emitted from the light source is the intensity of the light in the second wavelength region including the second wavelength included in the illumination light emitted from the light source. Weaker than
The first cholesteric liquid crystal structure layer is a lighting device located on the incident side of the illumination light emitted from the light source and directed toward the polarization selective reflection layer, rather than the second cholesteric liquid crystal structure layer. A light source that emits illumination light and
A polarization selective reflection layer that reflects the illumination light emitted from the light source and changes the optical path of the illumination light is provided.
The polarization selective reflection layer includes a first cholesteric liquid crystal structure layer having a first wavelength as a selective reflection center wavelength, and a second cholesteric liquid crystal structure layer having a second wavelength different from the first wavelength as a selective reflection center wavelength. Have and
The difference in intensity between the light in the first wavelength region including the first wavelength included in the illumination light emitted from the light source and the light in the second wavelength region including the second wavelength contained in the illumination light emitted from the light source is changed. A lighting device in which the stacking order of the first cholesteric liquid crystal structure layer and the second cholesteric liquid crystal structure layer included in the polarization selective reflection layer is determined. The light having an incoming surface and reflecting the light in the first wavelength region including the first wavelength incident on the incoming surface and the light in the second wavelength region including the second wavelength different from the first wavelength are reflected. A reflector including a polarization selective reflection layer that changes the optical path of light in the first wavelength region and light in the second wavelength region.
The polarization selective reflection layer includes a first cholesteric liquid crystal structure layer having the first wavelength as the selective reflection center wavelength, and a second cholesteric liquid crystal structure layer having the second wavelength as the selective reflection center wavelength.
The stacking order of the first cholesteric liquid crystal structure layer and the second cholesteric liquid crystal structure layer included in the polarization selective reflection layer from the side of the incoming surface is the light in the first wavelength region and the second wavelength region. It has been decided to change the difference in light intensity,
A reflector in which a 1/4 wavelength retardation layer is laminated on the side of the light input surface of the polarization selective reflection layer .

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