Image display system and head-up display system

Abstract

To provide an image display system with no limit of eyewear, capable of realizing a view of a clear display image within a prescribed range, while securing an anti-glare effect against incident light from an outside in an entire visual field, and to provide a head-up display system using the same.SOLUTION: An image display system includes: an optical laminate (1) including an optical layer configured to convert a polarization direction of incident light by 90°, and at least one transparent resin base material; display image projection means (101) configured to emit s-polarized light to the optical laminate (1); a polarization control part (10B) configured to convert a polarization direction of incident light by 90°; and a polarization film (10A) configured to block the s-polarized light. The s-polarized light reflected at the optical laminate (1) enters the polarization film via the polarization control part (10B). The polarization control part (10B) is arranged on a dashboard inside a motor vehicle, and the polarization film (10A) is included in eyewear.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image display system that can ensure an anti-glare effect against external incident light while enabling clear visibility of a displayed image, and a head-up display system including the same. [Background technology]

[0002] Navigation systems and head-up display (hereinafter also referred to as "HUD") systems are used as methods for displaying information to drivers of automobiles, aircraft, etc. HUD is a system that projects an image projected from an image projection means such as a liquid crystal display (hereinafter also referred to as "LCD") onto, for example, the windshield of an automobile.

[0003] The light emitted from the image display means is reflected by a reflector and then by the windshield before reaching the viewer. The viewer sees the image projected onto the windshield, but the image appears to be located further away than the windshield. This method allows the driver to obtain various information while gazing fixedly at the road ahead through the windshield, with almost no movement of the eyes, making it safer than conventional car navigation systems that require the driver to shift their gaze.

[0004] Because HUDs project information superimposed on the view actually seen through the windshield, it is desirable for them to display a bright, easy-to-read image without obstructing the field of view. To achieve this, the device must be transparent enough to allow a clear view of the road ahead, and reflective enough to allow the image displayed by the HUD to be seen clearly. However, because the display light is reflected by both the inside and outside surfaces of the windshield, the reflected image becomes a double image, making it difficult to see the displayed information.

[0005] It is known that the problem of double images due to reflected light can be solved by using an optical rotator capable of changing the polarization direction by 90° in an automobile windshield. For example, Patent Document 1 discloses that when S-polarized display light is incident on an automobile windshield equipped with a film-like optical rotator inside at Brewster's angle, a portion of the S-polarized light is reflected by the surface of the windshield on the inside of the vehicle, the S-polarized light that passes through the surface is converted to P-polarized light by the optical rotator, and all of the P-polarized light is emitted outside the vehicle by the surface of the windshield on the outside of the vehicle, thereby preventing the occurrence of double images. Patent Document 1 also discloses that when P-polarized display light is incident on an automobile windshield at Brewster's angle, the P-polarized light is not reflected by the surface of the windshield on the inside of the vehicle, but the P-polarized light that passes through the surface is converted to S-polarized light by the optical rotator, and almost all of the S-polarized light is reflected by the surface of the windshield on the outside of the vehicle, and the S-polarized light is again converted to P-polarized light by the optical rotator, thereby preventing the occurrence of double images.

[0006] Sunglasses are sometimes used to reduce glare caused by light reflected from road surfaces, etc. Generally, light reflected from road surfaces tends to be polarized, so the use of polarized sunglasses is effective against this reflected light. However, polarized sunglasses are generally configured to cut out S-polarized light components due to their anti-glare function. Therefore, when a viewer wears polarized sunglasses, if the main component of display light is S-polarized, the brightness of the display light (display luminance) will be significantly reduced when the display light passes through the polarized sunglasses. Therefore, the way a virtual image appears will change significantly depending on whether the viewer is wearing polarized sunglasses, which may cause discomfort to the viewer.

[0007] Patent Document 2 discloses that when functional glass including a light control film in which a cholesteric liquid crystal layer is sandwiched between two quarter-wave plates is used as a windshield for an automobile, high visibility can be achieved even when wearing polarized sunglasses. Specifically, the document discloses that P-polarized display light is incident on such functional glass at the Brewster angle, the transmitted light is converted to circularly polarized light by a quarter-wave plate on the inside of the vehicle, and the circularly polarized light is further reflected by a cholesteric liquid crystal layer. Meanwhile, the transmitted light not reflected by the cholesteric liquid crystal layer is converted back to P-polarized light by a quarter-wave plate on the outside of the vehicle and emitted outside the vehicle, thereby preventing the occurrence of double images. However, this method requires conversion from P-polarized light to circularly polarized light, and depending on the conversion efficiency, the brightness may not be sufficient. Therefore, clearer visibility of the displayed image is required.

[0008] Patent Document 3 discloses that a head-up display device projects an image using light from a light source containing both S-polarized and P-polarized components, and uses polarized sunglasses that adjust the blocking axis at which incident light is blocked according to the retardation value of a phase difference plate placed on the windshield. However, with this method, unless the blocking axis is strictly controlled, it is difficult to obtain a sufficient anti-glare effect, and there is also the concern of double images.

[0009] Meanwhile, while inorganic glass is typically used for automobile windshields, in recent years there has been a demand for resin-based windshields in light of fuel efficiency through weight reduction, the ability to be integrated with surrounding components, and design. When resin-based windshields are used, it is expected that a single transparent resin substrate will be the main component, rather than a laminated glass structure with an interlayer film. Even in this case, improvements are required to address ghosting, as well as reduced brightness due to the influence of conversion efficiency, and further improvements are required to save energy. Patent Document 4 discloses that in an image display system in which S-polarized light is reflected by a display medium to view a display image, an optical laminate having an optical layer that converts the polarization direction of incident light by 90° is used as the display medium, and a polarization control unit having a predetermined polarization control function is provided in eyewear or an automobile visor, thereby suppressing the occurrence of double images and blocking external light such as reflected light from the road surface from reaching the viewer, thereby achieving sufficient anti-glare effects and the visibility of clear display images. However, there are concerns that the type of eyewear that can be used is limited and that the effect cannot be obtained outside the area covered by the visor. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 6-40271 [Patent Document 2] International Publication No. 2016 / 056617 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-225236 [Patent Document 4] Patent No. 6972423 Summary of the Invention [Problem to be solved by the invention]

[0011] The present invention provides an image display system that is not restricted by eyewear, that ensures anti-glare effects against external incident light throughout the entire field of view, and that enables clear visibility of displayed images within a specified range, and a head-up display system using the same. [Means for solving the problem]

[0012] As a result of intensive research into solving the above problems, the inventors have discovered that in an image display system in which S-polarized light is reflected by a display medium to allow the user to view a displayed image, by using as the display medium an optical laminate having an optical layer that converts the polarization direction of incident light by 90°, and by further providing a polarization control unit with a predetermined polarization control function, it is possible to suppress the occurrence of double images while blocking external light, such as reflected light from the road surface, from reaching the viewer, thereby achieving a sufficient anti-glare effect and allowing the user to view a clear displayed image, and have completed the present invention.

[0013] That is, the present invention relates to the following [1] to [9]. [1] (A) (a-1) an optical layer that changes the polarization direction of incident light by 90°, and (a-2) an optical laminate including at least one transparent resin substrate; (B) a display image projection means for emitting S-polarized light to the optical laminate; (C) (c-1) a polarization control unit that changes the polarization direction of incident light by 90°; and (c-2) a polarizing film that blocks S-polarized light, An image display system in which S-polarized light reflected by the optical laminate is incident on the polarizing film via the polarization control unit, The image display system includes the polarization control unit disposed on a dashboard in a vehicle, and the polarizing film provided on eyewear. [2] The image display system according to [1], wherein the optical layer is a half-wave plate. [3] The image display system according to [1] or [2], wherein the optical laminate further comprises (a-3) at least one glass plate. [4] The image display system according to any one of [1] to [3], wherein the optical layer has a thickness of 20 μm or less. [5] An image display system according to any one of [1] to [4], wherein the height range from the lower end to the upper end of the optical layer is a, and the height range from the lower end of the polarization control unit arranged on the dashboard to the upper end of the polarization control unit is b, and the height range of b includes a. [6] The image display system according to any one of [1] to [5], wherein the polarization control section is a half-wave plate. [7] The image display system according to any one of [1] to [6], wherein the polarization control section and the polarizing film are arranged in this order from the outside with respect to the viewer. [8] The image display system according to any one of [1] to [7], wherein the polarization control section has a substrate and an antireflection layer on the outermost surface. [9] The image display system according to any one of [1] to [8], wherein the optical layer is positioned such that the angle between the polarization axis of S-polarized light incident at an angle at Brewster's angle and the slow axis of the optical layer is within a range of 45°±3°. [9] A head-up display system including the image display system according to any one of [1] to [8]. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide an image display system and a head-up display system using the same that are not restricted by the use of ordinary eyewear, that ensure an anti-glare effect against external incident light throughout the entire field of view, and that enable clear visibility of displayed images within a specified range. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram illustrating an embodiment of an optical laminate included in an image display system of the present invention. [Figure 2] FIG. 2 is a schematic diagram illustrating an embodiment of a polarization control unit and a polarizing film included in the image display system of the present invention. [Figure 3]1 is a schematic diagram illustrating a first embodiment of a head-up display system including an image display system of the present invention. [Figure 4] 4 is a schematic diagram illustrating a path of light when reflected light from a road surface enters an optical laminate in a range having an optical layer in the head-up display system of FIG. 3. FIG. [Figure 5] 4 is a schematic diagram illustrating a path of light when reflected light from a road surface enters an area of ​​the optical laminate that does not have an optical layer in the head-up display system of FIG. 3. FIG. [Figure 6] FIG. 2 is a diagram illustrating an example of a layer configuration in a polarization control unit. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments according to the present invention will be described with reference to the drawings. Note that the following embodiments merely exemplify some representative embodiments of the present invention, and various modifications can be made within the scope of the present invention. Furthermore, the drawings schematically show width, size, thickness, shape, etc. compared to the actual embodiment for clarity of explanation, but this is merely an example. Furthermore, the drawings appropriately omit portions that are not necessary for explaining the effects of the present invention, but such omissions do not limit the scope of the present invention.

[0017] The image display system of the present invention includes: (A) (a-1) an optical layer that changes the polarization direction of incident light by 90° and (a-2) an optical laminate including at least one transparent resin substrate; (B) a display image projection means that emits S-polarized light onto the optical laminate; (C) (c-1) a polarization control unit that changes the polarization direction of incident light by 90°; and (c-2) a polarizing film that blocks S-polarized light. S-polarized light reflected by the optical laminate enters the polarization control unit, where it is converted to P-polarized light and passes through the polarizing film that blocks S-polarized light, allowing the viewer to view the image displayed on the optical laminate. Therefore, the viewer views a virtual image reflected on the viewer's side of the optical laminate. Meanwhile, S-polarized light that passes through the optical laminate is converted to P-polarized light by the optical layer, and the P-polarized light passes outside the optical laminate. As a result, the occurrence of double images can be significantly reduced. Furthermore, external light, such as light reflected from the road surface, incident from the outside of the optical laminate (the side opposite the observation side) contains a large amount of S-polarized light, which is converted to P-polarized light by the optical layer. However, this is reconverted to S-polarized light by the polarization control unit and blocked by the polarizing film that blocks S-polarized light, preventing the reflected light from reaching the viewer. Furthermore, S-polarized light is incident in areas that do not have the optical layer, but because the polarization control unit is not located in the path of this light, the transmitted light remains S-polarized and is blocked by the polarizing film that blocks S-polarized light. Therefore, reflected light is prevented from reaching the viewer. As a result, sufficient anti-glare effect and clear visibility of displayed images can be achieved.

[0018] Here, the observer side of the optical laminate refers to one surface of the optical laminate closer to the observer (viewer), i.e., the side where S-polarized light (hereinafter also referred to as "display light") from the display image projection means reaches, and the outside of the optical laminate refers to the other surface of the optical laminate farther from the observer (viewer), i.e., the side where S-polarized light from the display image projection means does not reach but where light from outside reaches. Furthermore, the outside, relative to the observer (viewer) described below, refers to the side where polarized light from the optical laminate enters the polarization control unit.

[0019] (A) Optical laminate The optical laminate used in the image display system of the present invention includes an optical layer and at least one transparent resin substrate. The optical laminate may further include at least one glass plate. FIG. 1 shows one embodiment of the optical laminate included in the image display system of the present invention. The optical laminate 1 includes an optical layer 2 and transparent resin substrates 3 disposed on both sides of the optical layer 2, with glass plates 4 further provided on both sides of the transparent resin substrate 3. The optical laminate 1 can be produced, for example, by providing each transparent resin substrate 3 on both sides of the optical layer 2, sandwiching them between the glass plates 4, and compressing them at high temperature and high pressure.

[0020] (a-1) Optical layer The optical layer has the function of changing the polarization direction of incident light by 90°, i.e., converting P-polarized light into S-polarized light or S-polarized light into P-polarized light. Examples of optical layers having such a function include a polarization rotator, such as a single half-wave plate whose retardation value is half the desired wavelength, and a laminate of multiple retardation plates, such as a laminate of two quarter-wave plates. Of these, the optical layer is preferably a half-wave plate.

[0021] (1 / 2 wavelength plate) A half-wave plate is a retardation element that converts P-polarized light into S-polarized light or S-polarized light into P-polarized light, i.e., converts the polarization axis. It can be obtained, for example, by uniaxially stretching a film made of polycarbonate or cycloolefin polymer so that the retardation is half the wavelength, or by orienting a horizontally oriented polymerizable liquid crystal to a thickness that results in a retardation of half the wavelength. Generally, a half-wave plate using a horizontally oriented polymerizable liquid crystal comprises a polymerizable liquid crystal layer that converts the polarization axis and a support substrate on which a coating liquid forming the polymerizable liquid crystal layer is applied. The upper limit of the thickness of such a polymerizable liquid crystal layer is preferably 10 μm or less, more preferably 5 μm or less, from the viewpoint of the alignment of the liquid crystal. Meanwhile, the lower limit of the thickness of the half-wave plate is preferably 0.3 μm or more, more preferably 0.5 μm or more, from the viewpoint of the polymerizability of the liquid crystal. When light is incident obliquely on the surface of the half-wave plate, the retardation may change depending on the angle of incidence of the light. In such a case, in order to more precisely match the phase difference, for example, by using a phase difference element whose refractive index is adjusted, it is possible to suppress the change in phase difference due to the incident angle. For example, when the refractive index in the slow axis direction in the plane of the phase difference element is nx, the refractive index in the direction perpendicular to nx in the plane of the phase difference element is ny, and the refractive index in the thickness direction of the phase difference element is nz, the coefficient Nz shown in the following formula (1) is preferably controlled to be 0.3 or more and 1.0 or less, more preferably 0.5 or more and 0.8 or less.

[0022] (Number 1) Nz=(nx-nz) / (nx-ny) (1)

[0023] In image display devices using such half-wave plates, in order to efficiently convert S-polarized light to P-polarized light, it is preferable to control the angle θ between the polarization axis of S-polarized light incident from a position tilted 45° to 65° from the axis perpendicular to the surface of the optical laminate and the slow axis of the half-wave plate to 35° to 47°. By setting the incident angle of S-polarized light incident on the half-wave plate to 45° to 65°, the reflectance of P-polarized light can theoretically be reduced to 2% or less, thereby suppressing the occurrence of double images. That is, the incident S-polarized light is reflected from the surface of the optical laminate, and this S-polarized light reaches the viewer. The transmitted S-polarized light is converted to P-polarized light by the half-wave plate, and the converted P-polarized light passes through without being reflected at the interface between the incident side and the air of the optical laminate on the opposite side. In this way, the occurrence of double images can be suppressed by controlling the incident angle of S-polarized light incident on the optical laminate. Furthermore, if the angle θ is less than 35° or greater than 47°, the polarization axis conversion performance for converting S-polarized light incident on the optical laminate to P-polarized light is low, resulting in a dark image on the display and potentially impairing the anti-glare effect of eyewear. Therefore, by appropriately controlling this angle θ, the half-wave plate exhibits good polarization axis conversion performance, resulting in a clearer, more visible image.

[0024] When the half-wave plate includes a polymerizable liquid crystal layer, the liquid crystal composition constituting the polymerizable liquid crystal layer is coated on a supporting substrate. When the half-wave plate is used in a HUD, such a supporting substrate is preferably transparent in the visible light range to maintain the visibility of the displayed image. Specifically, the visible light transmittance for wavelengths of 380 nm to 780 nm is preferably 50% or more, more preferably 70% or more, and even more preferably 85% or more. The supporting substrate may be colored, but is preferably uncolored or lightly colored. Furthermore, the refractive index of the supporting substrate is preferably 1.2 to 2.0, more preferably 1.4 to 1.8. The thickness of the supporting substrate may be selected appropriately depending on the application, and is preferably 5 μm to 1000 μm, more preferably 10 μm to 250 μm, and particularly preferably 15 μm to 150 μm.

[0025] The support substrate may be a single layer or a laminate of two or more layers. Examples of materials for the support substrate include triacetyl cellulose (TAC), acrylic, polycarbonate, polyvinyl chloride, polyolefin, and polyethylene terephthalate (PET). Among these, triacetyl cellulose (TAC), polyolefin, and acrylic, which have low birefringence, are preferred.

[0026] Next, a method for producing a half-wave plate using the nematic liquid crystal monomer having a polymerizable group will be described. For example, a nematic liquid crystal monomer having a polymerizable group is dissolved in a solvent, followed by the addition of a photopolymerization initiator. The solvent is not particularly limited as long as it can dissolve the liquid crystal monomer used. Examples include cyclopentanone, toluene, methyl ethyl ketone, and methyl isobutyl ketone, with cyclopentanone and toluene being preferred. The solution is then applied to a plastic substrate, such as a PET film or TAC film, used as a support substrate, to a uniform thickness. The solution is then heated to remove the solvent, and left for a certain period of time under temperature conditions that allow the liquid crystal to align on the support substrate. Before application, the surface of the plastic substrate can be subjected to a rubbing treatment in the desired orientation direction, or to an orientation treatment such as forming a film of a photoalignment material that exhibits photoalignment upon polarized light irradiation on the surface of the plastic substrate and then irradiating it with polarized light, thereby achieving more uniform liquid crystal alignment. This allows the slow axis of the half-wave plate to be controlled to a desired angle and reducing the haze value of the half-wave plate. Next, while maintaining this orientation, the nematic liquid crystal monomer is irradiated with ultraviolet light from a high-pressure mercury lamp or the like to fix the orientation of the liquid crystal, thereby obtaining a half-wave plate with the desired slow axis.

[0027] The primary role of a half-wave plate used as an optical layer is to convert S-polarized light that is transmitted without being reflected from the surface into P-polarized light. This reduces reflection from the transparent substrate placed outside the optical laminate and prevents double images. It also converts external light, such as light reflected from the road surface, into P-polarized light. While there are no particular limitations on the wavelength dispersion of a half-wave plate, it is preferable that it be suitable for head-up display applications. In particular, it is desirable for the half-wave plate to have reverse wavelength dispersion to accurately convert polarization over a wide wavelength range in the visible light region. Generally, polymers exhibit normal dispersion, in which the absolute value of birefringence increases toward shorter wavelengths. However, liquid crystal compounds that increase birefringence toward longer wavelengths by controlling the birefringence Δn value for each wavelength of visible light are preferred because they can achieve reverse wavelength dispersion. Furthermore, reverse wavelength dispersion can also be achieved by stacking multiple retardation plates with appropriate retardation values ​​corresponding to the wavelength dispersion characteristics of the liquid crystal compound in an appropriate combination of slow axes. When multiple retardation plates are stacked, the total thickness is preferably 20 μm or less, and more preferably 15 μm or less. In order to efficiently convert S-polarized light into P-polarized light, it is preferable that the half-wave plate serving as an optical layer is positioned such that the angle between the polarization axis of the S-polarized light incident at an angle at Brewster's angle and the slow axis of the half-wave plate is within a range of 45°±3°, more preferably within a range of 45°±2°, and even more preferably within a range of 45°±1°.

[0028] (a-2) Transparent resin base material The optical laminate has at least one transparent resin substrate, preferably two transparent resin substrates. In this case, it is preferable that the optical layer is sandwiched between the two transparent resin substrates. The two transparent resin substrates may be the same or different. There are no particular restrictions on the transparent resin substrate, but it is preferable that it is suitable for head-up display applications. In this case, there are certain restrictions on the visible light transmittance and haze value. For example, the visible light transmittance is preferably 70% or more, more preferably 75% or more, even more preferably 80% or more, particularly preferably 85% or more, and most preferably 90% or more. The haze value is preferably 2% or less, more preferably 1% or less, and even more preferably 0.5% or less. It is also preferable that the transparent resin substrate does not have optical anisotropy.

[0029] The thickness of the transparent resin substrate is preferably 0.005 mm or more and 1 mm or less. The upper limit of the thickness of the transparent resin substrate is more preferably 0.9 mm. Furthermore, the lower limit of the thickness of the transparent resin substrate is more preferably 0.01 mm. Examples of transparent resin substrates include cyclic polyolefins, polyethersulfones, polyarylates, polyethylene terephthalates, polycarbonate resins, acrylic resins such as polymethyl methacrylate, ABS (acrylonitrile-butadiene-styrene) resins, polyphenylene ether resins, and the like. Of these, polycarbonate resins, polymethyl methacrylate resins, and polyvinyl butyral are preferred. The transparent resin substrate may be a single type or a laminate of two or more layers.

[0030] In particular, polycarbonate resins are preferred because they have excellent transparency, high impact absorption, improved safety in the event of a collision, and excellent impact resistance, making them less likely to break in a minor collision. Polycarbonate resins, acrylic resins, cyclic polyolefin resins, polyphenylene ether resins, etc. can be blended with thermoplastic resins other than the main component resin to form resin compositions, as long as the properties of the present invention are not impaired. When the optical laminate further comprises glass plates (described later) and the optical laminate layer is supported or sandwiched between the glass plates, the transparent resin substrate is preferably polyvinyl butyral. The case where a glass plate (a-3) is placed on one side of the optical laminate is referred to as supported, and the case where a glass plate is placed on both sides is referred to as sandwiched.

[0031] (a-3) Glass plate The optical laminate layer may further include a glass plate, or may be used as functional glass supported or sandwiched between the glass plates. The glass plate is not particularly limited as long as it has sufficient transparency to allow the forward view to be sufficiently visible, even when the functional glass is used as a windshield. The refractive index of the glass plate is preferably 1.2 or more and 2.0 or less, more preferably 1.4 or more and 1.8 or less. The thickness, shape, etc. of the glass plate are also not particularly limited as long as they do not affect the reflection of display light, and can be appropriately designed depending on the application. These glass plates may also be provided on the reflective surface with a multilayered reflection-enhancing film, a thin metal film that also functions as a heat shield, or the like. These films can improve the reflectance of incident polarized light, but when the functional glass is used as an automobile windshield, it is preferable to adjust the reflectance so that the visible light transmittance of the functional glass is 70% or more. The glass plate also includes curved glass, such as that used in windshields.

[0032] Preferred methods for bonding an optical laminate layer to a glass plate include, for example, using a thermoplastic resin as a transparent resin substrate, sandwiching the optical layer between two sheets of thermoplastic resin, sandwiching the layer between two sheets of glass, and then compressing the layer at high temperature and high pressure. Alternatively, a thermoplastic resin is used, and the optical layer is peeled and transferred from the support substrate to the glass, and then sandwiched between two sheets of glass via a sheet of thermoplastic resin, and then compressing the layer at high temperature and high pressure. Peeling off the support substrate allows the optical layer to be made thinner. The thickness of the optical layer is preferably 20 μm or less, and more preferably 15 μm or less. The area where the optical layer is bonded to the glass is preferably adjusted to the display area of ​​the image in the head-up display. A thin optical layer makes the edge of the optical layer less visible when the optical layer is bonded to a portion of the glass, thereby preventing the appearance quality of the glass from being impaired. For example, if the image of the head-up display is to be displayed within the lower half of the glass, the area where the optical layer is bonded is preferably within the lower half of the glass. In this case, the thermoplastic resin is preferably, for example, polyvinyl butyral resin (PVB), polyvinyl alcohol resin (PVA), or ethylene-vinyl acetate copolymer resin (EVA), with PVB being more preferred. The thickness and hardness of the two transparent resin substrates are not particularly limited as long as they do not affect the reflection of display light, and functions such as UV protection, heat insulation, sound insulation, and light control can be appropriately designed depending on the application. Furthermore, the thickness and hardness of the two transparent resin substrates may be the same or different, but are preferably different.

[0033] The functional glass thus obtained can be used as windshields, side windows, rear windows, and roof glass for standard-sized automobiles, compact automobiles, and light automobiles, as well as large and small special-purpose automobiles. Furthermore, the functional glass can also be used as windows for railway vehicles, ships, and aircraft, and as window materials for building and industrial use. The functional glass can be used by laminating or bonding it with a member having at least one of UV-cutting, heat-shielding, sound-shielding, and light-adjusting functions.

[0034] (B) Display image projection means In the image display system of the present invention, the display image projection means used in the image display system includes a display image projection means for emitting S-polarized light. The display image projection means emits S-polarized display light so that the angle of incidence with respect to the surface of the optical laminate is near the Brewster angle. Here, an angle near the Brewster angle means that, when the Brewster angle of S-polarized light with respect to the surface of the optical laminate is α, the angle of incidence of S-polarized light incident on the optical laminate is in the range of α-10° to α+10°. When S-polarized light from the display image projection means enters the optical laminate at an angle near the Brewster angle, most of the S-polarized light is reflected and reaches the viewer, allowing the viewer to view a virtual image. On the other hand, S-polarized light that is not reflected by the surface of the optical laminate and passes through the optical laminate is converted to P-polarized light by the optical layer, and the converted P-polarized light passes through the optical laminate. As a result, reflection from outside the optical laminate is prevented, and the occurrence of double images can be suppressed. Note that as long as the light reaching the display image projection means is S-polarized, the light emitted from the display image projection means may be P-polarized. In this case, since it is necessary to convert the emitted P-polarized light into S-polarized light, it is preferable to provide, for example, a half-wave plate before the P-polarized light reaches the optical laminate.The image displayed on the head-up display is preferably within the lower half of the windshield, so that the driver can obtain various information while gazing at the front of the windshield with almost no movement of their eyes.

[0035] (c-1) Polarization control section The image display system of the present invention includes a polarization control unit. The polarization control unit preferably includes a retardation film that converts the polarization direction of incident light by 90°, i.e., converts S-polarized light to P-polarized light or P-polarized light to S-polarized light. An example of such a retardation film is a half-wave plate. Furthermore, the polarization control unit preferably includes a substrate to stabilize the shape of the polarization control unit.

[0036] To maintain the visibility of the displayed image, such a substrate is preferably transparent in the visible light region. Specifically, the visible light transmittance at wavelengths of 380 nm to 780 nm is 50% or more, preferably 70% or more, and more preferably 85% or more. The substrate may be colored, but is preferably uncolored or lightly colored. Furthermore, the refractive index of the substrate is preferably 1.2 to 2.0, more preferably 1.4 to 1.8. The substrate preferably has no or a small phase difference, such as glass. A small phase difference of the substrate can prevent the substrate from impairing its function of changing the polarization direction of incident light by 90°. The substrate may have a flat or curved shape. The thickness of the substrate may be selected appropriately depending on the application, and is preferably 1 mm to 10 mm, more preferably 2 mm to 8 mm, and particularly preferably 2.5 mm to 6 mm.

[0037] The substrate may be a single layer or a laminate of two or more layers. Examples of substrate materials include glass, triacetyl cellulose (TAC), acrylic, polycarbonate, polyvinyl chloride, polyolefin, and polyethylene terephthalate (PET). Among these, glass, triacetyl cellulose (TAC), polyolefin, and acrylic, which have low birefringence, are preferred.

[0038] The polarization control unit preferably has an antireflection layer on its outermost surface. The method for providing the antireflection layer is not particularly limited, but for example, an antireflection function can be imparted by laminating an AR (AntiReflection) / LR (Low Reflection) film, an AG (AntiGlare) film, or a moth-eye film, which are films having an antireflection layer, to the polarization control unit. The antireflection on the outermost surface can suppress surface reflection and glare of external light even when external light hits the polarization control unit, allowing a clear displayed image to be viewed. In AR / LR films, the materials are designed so that the light reflected from the surface of the anti-reflection layer and the light that passes through the anti-reflection layer and reflects at the interface between the anti-reflection layer and the base film substrate are of equal amplitude and opposite phase. This causes the two lights to interfere and cancel each other out, weakening the reflected light and preventing it from reaching the eye. AG film is an optical laminate in which a hard coat layer containing particles is applied to the surface of the base film substrate to create a textured surface. The textured surface diffuses incident light, reducing the glare of external light. In addition, moth-eye type anti-reflection films have protrusions smaller than the wavelength of visible light (380-780 nm) molded into the resin on the film, which almost completely prevents light reflection, similar to a moth's eye. The antireflection layer is preferably provided on at least the outermost surface on the viewer side, and more preferably on both the front and back surfaces. When provided on both the front and back surfaces, the antireflection layers may be the same or different.

[0039] The retardation film, substrate, and antireflection layer in the polarization control section are preferably bonded together via an adhesive layer. The types of adhesive layers between the layers may be the same or different, but are preferably selected depending on the surface characteristics of each layer. An example of the layer configuration is, as shown in Figure 6, an antireflection layer, an adhesive layer, an adhesive layer, a half-wave plate, a substrate, an adhesive layer, and an antireflection layer in this order from the viewer side. Examples of adhesives used in the adhesive layer include acrylic and rubber-based adhesives, with acrylic adhesives being preferred because their adhesive properties and holding power can be easily adjusted. Examples of adhesives used in the adhesive layer include ultraviolet-curable resin compositions, thermosetting resin compositions, and mixtures thereof. In the case of ultraviolet-curable resins, a composition containing a mixture of multiple monomers having acryloyl or epoxy groups can be cured and bonded by irradiating it with ultraviolet light in the presence of a photopolymerization initiator. In the case of thermosetting resin compositions, a composition containing a mixture of multiple monomers having epoxy groups can be cured and bonded by heating in the presence of an acid catalyst. Alternatively, a composition containing multiple monomers or polymers having amino, carboxyl, or hydroxyl groups can be cured and bonded by heating in the presence of a compound having an isocyanate or melamine group.

[0040] (c-2) Polarizing film The image display system of the present invention includes a polarizing film. The polarizing film preferably blocks S-polarized light. Examples of polarizing films that block S-polarized light include polarizing films whose absorption axis is parallel to the polarization axis of light reflected from the road surface, i.e., the S-polarized light incident on the polarizing film.

[0041] FIG. 2 is a schematic diagram showing one embodiment of a polarization control unit and a polarizing film included in the image display system of the present invention. In FIG. 2, polarization control unit 10B is disposed outside polarizing film 10A relative to the viewer. Therefore, the polarization direction of the incident polarized light is converted by 90° by polarization control unit 10B. If the converted polarized light is S-polarized light, the S-polarized light is blocked by polarizing film 10A. If the converted polarized light is P-polarized light, the P-polarized light passes through polarizing film 10A and reaches the viewer. As shown in FIG. 2, polarization control unit 10B and polarizing film 10A are disposed at a distance from each other. As will be described in detail below, an example of a case in which polarization control unit 10B and polarizing film 10A are disposed at a distance from each other is when the polarization control unit 10B is disposed on a dashboard and eyewear equipped with polarizing film 10A is used.

[0042] This paper describes a method for viewing a display image by wearing eyewear equipped with a polarizing film through a half-wave plate installed on the dashboard of a vehicle. In this method, the half-wave plate is installed on the light-incident side of typical polarized sunglasses, where the absorption axis of the polarizing filter is parallel to the polarization axis of the S-polarized light incident on the polarizing filter. To efficiently convert S-polarized light to P-polarized light or P-polarized light to S-polarized light, it is preferable to control the angle θ between the polarization axis of the linearly polarized light and the slow axis of the half-wave plate to between 35° and 47°. If the angle θ is less than 35° or greater than 47°, the polarization axis conversion performance for converting S-polarized light incident on the half-wave plate to P-polarized light is poor, resulting in a darker image on the display and potentially compromising the anti-glare effect of the eyewear. Therefore, by appropriately controlling this angle θ, the half-wave plate exhibits good polarization axis conversion performance, resulting in a clearer view of the displayed image. Furthermore, there are no particular restrictions on the wavelength dispersion of the half-wave plate as long as it is suitable for eyewear applications, but it is desirable for it to have reverse wavelength dispersion in order to accurately convert polarization over a wide wavelength range in the visible light region.

[0043] The arrangement of the optical layer and polarization control unit will now be described. The height range a from the lower end to the upper end of the optical layer refers to the vertical height range from the lower end to the upper end of the optical layer, as shown in Figure 3. The height range b from the lower end to the upper end of the polarization control unit located on the dashboard refers to the vertical height range from the lower end to the upper end of the polarization control unit located on the dashboard, as shown in Figure 3. In this case, it is preferable that the height range b from the lower end to the upper end of the polarization control unit located on the dashboard includes the height range a from the lower end to the upper end of the optical layer. With this configuration, S-polarized light entering the optical laminate from outside the height range a is converted to P-polarized light by the optical layer in the optical laminate and then converted to S-polarized light by the polarization control unit. Furthermore, S-polarized light entering the optical laminate from outside the height range a passes through the area of ​​the optical laminate that does not have the optical layer, thereby maintaining its S-polarized light. Therefore, in either case, the (c-2) polarizing film can block S-polarized light entering from outside the optical laminate. The absolute value of height range a is preferably 0.5 to 1 times the absolute value of height range b, more preferably 0.7 to 1 times, and even more preferably 0.9 to 1. By providing a wide overlap between height range a and height range b in this way, P-polarized light that is converted by the optical layers in the optical laminate out of S-polarized light incident from outside the optical laminate can be efficiently converted into S-polarized light by the polarization control unit. Furthermore, in the height range from the bottom to the top of the glass, i.e., the vertical height range from the bottom to the top of the glass, the height range a from the bottom to the top of the optical layer is preferably within the range of the lower side of the height range from the bottom to the top of the glass, 50% or less, more preferably 40% or less. By providing the optical layer in this way, necessary information can be displayed without affecting the forward visibility. In addition, a clear display image can be viewed within a necessary and sufficient range while ensuring an anti-glare effect against external incident light in the field of view of both the part where the upper optical layer of the optical laminate is not bonded and the part where the lower optical layer of the optical laminate is bonded.

[0044] First Embodiment FIG. 3 is a schematic diagram illustrating a first embodiment of a head-up display system including an image display system according to the present invention. As shown in FIG. 3, the HUD system (image display system) 100 of this embodiment includes a display image projection means 101 that emits S-polarized light as display light representing a display image within the lower half of an optical laminate, an optical laminate 1 onto which the S-polarized light emitted from the display image projection means 101 is incident, a polarization control unit 10B that changes the polarization direction of the incident light by 90°, and a polarizing film 10A that blocks the S-polarized light. In FIG. 3, the polarization control unit 10B and the polarizing film 10A are separately arranged, and the polarization control unit 10B is located on the dashboard of the automobile, outside the polarizing film 10A relative to the observer, i.e., in accordance with the incident range on the side onto which polarized light from the optical laminate 1 is incident. The polarization control unit 10B is also arranged so that polarized light is incident on the polarizing film 10A via the polarization control unit 10B. Furthermore, the polarization control unit 10B and the polarizing film 10A are arranged so that, when the height range from the lower end to the upper end of the optical layer is a and the height range from the lower end of the polarization control unit located on the dashboard to the upper end of the polarization control unit is b, a is included in the height range of b. As shown in FIG. 6, the polarization control unit 10B has a half-wave plate attached to a support substrate, and antireflection layers on both the front and back sides of the half-wave plate. The S-polarized light emitted from the display image projection means 101 is reflected by the reflecting mirror 102, and the reflected display light reaches the optical laminate 1. As shown in Fig. 1, the optical laminate 1 has an optical layer 2 in the lower half, transparent resin substrates 3 on both sides thereof, and glass plates 4 on both outer sides thereof.

[0045] In a HUD system configured as described above, S-polarized incident light 201 emitted from display image projection means 101 is incident on optical laminate 1 at an incident angle near Brewster's angle. Incident light 201 is reflected at the interface between the viewer-side surface of optical laminate 1 and air, generating reflected light 202. Because reflected light 202 is S-polarized, it is converted to P-polarized light by polarization control unit 10B. Even if polarizing film 10A, which blocks S-polarized light, is used for reflected light 202 that has been converted to P-polarized light, the P-polarized light is transmitted as is. Therefore, the transmitted reflected light 202 is visually recognized by the viewer as a display image.

[0046] Furthermore, incident light 201 that is not reflected as reflected light 202 and enters the optical laminate 1 propagates through the optical laminate 1 and is converted to P-polarized light by the optical layer 2. The incident light 201 converted to P-polarized light propagates at the interface between the air and the glass plate 4 arranged on the outside of the optical laminate 1 at approximately the Brewster angle. Therefore, reflection at the interface is suppressed, and the incident light 201 converted to P-polarized light passes through the optical laminate 1 as transmitted light 203.

[0047] On the other hand, FIG. 4 shows the path of light when light reflected from the road surface enters the optical laminate in the HUD system (image display system) 100 of FIG. 3. Because the light reflected from the road surface contains a large amount of S-polarized light, S-polarized light 204 enters from the outside of the optical laminate 1. The incident S-polarized light propagates through the optical laminate 1 and is converted to P-polarized light by the optical layer 2 in the area where the optical layer 2 is located. The incident light 204 converted to P-polarized light further propagates through the optical laminate 1 and passes through the optical laminate 1. Since the transmitted light 204 is P-polarized, it is converted to S-polarized light by the retardation film 10B. The transmitted light 204 converted to S-polarized light is blocked by the polarizing film 10A, which blocks S-polarized light. This prevents reflected light from the outside (outside the vehicle) from reaching the viewer. 5 shows the path of light in the HUD system (image display system) 100 of FIG. 3 when reflected light from the road surface enters the optical laminate in an area that does not have the optical layer 2. In the area that does not have the optical layer 2, S-polarized light that enters from outside the optical laminate 1 passes through as S-polarized light. Because the polarization control unit 10B is not arranged in the path of light in the area that does not have the optical layer 2, the transmitted light 204 is blocked by the polarizing film 10A, which blocks S-polarized light. This prevents reflected light from outside (outside the vehicle) from reaching the viewer. [Industrial Applicability]

[0048] The image display system of the present invention allows a head-up display that uses S-polarized light to view a displayed image without discomfort even when wearing eyewear equipped with a polarizing film that blocks S-polarized light, while also ensuring sufficient anti-glare effect against external light. Therefore, a clear displayed image can be viewed while ensuring anti-glare effect against external incident light. Such an image display system is useful for application to a head-up display system. Furthermore, the layer structure of the optical laminate is not complex, which can also contribute to simplifying the manufacturing process. [Explanation of symbols]

[0049] 1: Optical laminate 2: Optical layer 3, 3': Transparent resin base material 4: Glass plate 5, 5': Anti-reflection layer 6:1 / 2 wave plate 7: Circuit board 8, 8', 8'': Adhesive layer 10A: Polarizing film 10B: Polarization control unit 100: Head-up display system, image display system 101:Display image projection means 102:Reflector 201: Incident light 202:Reflected light 203,204: Transmitted light

Claims

1. (A) an optical laminate including (a-1) an optical layer that changes the polarization direction of incident light by 90°, and (a-2) at least one transparent resin substrate; (B) a display image projection means for emitting S-polarized light to the optical laminate; (C) (c-1) a polarization control unit that changes the polarization direction of incident light by 90°; and (c-2) a polarizing film that blocks S-polarized light, An image display system in which S-polarized light reflected by the optical laminate is incident on the polarizing film via the polarization control unit, The image display system includes the polarization control unit disposed on a dashboard in a vehicle, and the polarizing film provided on eyewear.

2. The image display system of claim 1 , wherein the optical layer is a half-wave plate.

3. 3. The image display system according to claim 1, wherein the optical laminate further comprises (a-3) at least one glass plate.

4. 3. The image display system according to claim 1, wherein the optical layer has a thickness of 20 [mu]m or less.

5. 3. The image display system of claim 1, wherein the height range from the lower end to the upper end of the optical layer is a, and the height range from the lower end of the polarization control unit arranged on the dashboard to the upper end of the polarization control unit is b, and the height range of b includes a.

6. 3. The image display system according to claim 1, wherein the polarization control section is a half-wave plate.

7. 3. The image display system according to claim 1, wherein the polarization control section and the polarizing film are arranged in this order from the outside with respect to the viewer.

8. 3. The image display system according to claim 1, wherein the polarization control section has a substrate and an anti-reflection layer on the outermost surface.

9. 3. The image display system according to claim 1, wherein the optical layer is positioned such that the angle between the polarization axis of S-polarized light incident at an angle at Brewster's angle and the slow axis of the optical layer is within the range of 45°±3°.

10. A head-up display system comprising the image display system according to claim 1 or 2.

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