Head-up display system and optical functional layer for head-up display

Abstract

A head-up display system is provided with a video display unit (2) that emits display light that represents a display video, and a functional glass (4) that projects the video projected by the video display unit (2). The functional glass (4) contains an optical functional layer having reverse wavelength dispersivity, the arrangement angle (alpha) of the functional glass (4) is 20-70 DEG, and a reflected image is visually confirmed in the range of the viewing angle of Brewster angle (beta-(90 DEG-angle alpha) + / -15 DEG with respect to the functional glass (4).

Description

Technical Field

[0001] The present invention relates to a head-up display system and an optical functional layer applied to the head-up display. Background Art

[0002] As a method of displaying information to the driver in a car, airplane, etc., a navigation system, a head-up display (hereinafter also referred to as "HUD"), etc. HUD is a system that projects an image projected by an image projection device such as a liquid crystal display (hereinafter also referred to as "LCD") onto, for example, a car windshield.

[0003] The light emitted from the image display unit is reflected by the reflector, further reflected by the windshield, and reaches the observer. The observer sees the image projected on the windshield, but the image appears to be located farther away from the windshield. In this method, the driver can obtain various information while looking at the front of the windshield without moving his eyes, so it is safer than the previous car navigation that requires moving the eyes.

[0004] In the HUD system, the display information is projected and overlapped with the actual scenery seen through the windshield. However, the display light is reflected from two surfaces of the windshield, the indoor side and the outdoor side, so the reflected image becomes a double image, making it difficult to see the display information.

[0005] In response to this problem, it is known that a phase difference element that can change the polarization direction by 90° is used in a windshield for automobiles, thereby improving the problem of reflected images becoming double images. For example, Patent Document 1 discloses that when S-polarized display light is incident on a windshield for automobiles equipped with a film-shaped optical rotator at a Brewster angle, a portion of the S-polarized light is reflected on the surface of the windshield on the inside of the vehicle, and the S-polarized light passing through the surface is converted into P-polarized light by the optical rotator, and further all the P-polarized light is emitted to the outside of the vehicle on the surface of the windshield on the outside of the vehicle, thereby preventing double images.

[0006] In addition, as another method for suppressing double images, the following technology is known, in which a light reflecting film made of a cholesterol liquid crystal layer for reflecting circularly polarized light is sandwiched between two 1 / 4 wavelength plates to form a light control film, and P polarized light is incident using the light control film (Patent Document 2). In this technology, the incident linearly polarized light is converted into circularly polarized light by the 1 / 4 wavelength plate, and the converted circularly polarized light is reflected by the light reflecting film made of the cholesterol liquid crystal layer, thereby allowing the observer to visually confirm it.

[0007] [Prior art literature]

[0008] [Patent Document]

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 6-40271

[0010] Patent Document 2: International Publication No. 2016 / 056617 Summary of the invention

[0011] [Problems to be solved by the invention]

[0012] However, in the automobile windshield described in Patent Document 1, the conversion between S polarization and P polarization cannot be performed very efficiently, and there is a risk of double images due to the S polarization that cannot be emitted to the outside of the vehicle and returns. In addition, in the technology described in Patent Document 2, it is still hoped that the P polarization incident on the 1 / 4 wavelength plate on the inside of the vehicle is converted into circular polarization as efficiently as possible, and it is hoped that the circular polarization incident on the 1 / 4 wavelength plate on the outside of the vehicle is converted into P polarization more efficiently through the cholesterol liquid crystal layer.

[0013] Therefore, an object of the present invention is to provide a head-up display system and an optical functional layer for a head-up display which are excellent in the effect of suppressing the occurrence of double images.

[0014] [Methods to solve the problem]

[0015] A head-up display according to an embodiment of the present invention includes an image display unit that emits display light representing a display image, and functional glass that projects the image projected by the image display unit.

[0016] The functional glass includes an optical functional layer showing reverse wavelength dispersion.

[0017] The configuration angle α of the functional glass is not less than 20° and not more than 70°.

[0018] Furthermore, with respect to the aforementioned functional glass, a reflected image is visually confirmed within a viewing angle range of Brewster angle β-(90°-angle α)±15°.

[0019] The optical functional layer for a head-up display system according to the embodiment of the present invention is provided in the head-up display system.

[0020] [Effects of the Invention]

[0021] According to the present invention, a head-up display system and an optical functional layer for a head-up display having an excellent effect of suppressing the occurrence of double images can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 1 is a schematic diagram showing an embodiment of a head-up display system according to the present invention.

[0023] Figure 2 Schematic diagram showing another embodiment of the head-up display system of the present invention.

[0024] Figure 3This is a schematic side cross-sectional view showing one embodiment of the optical functional layer for a head-up display of the present invention.

[0025] Figure 4 Is presented containing Figure 3 This is a schematic side cross-sectional view of one embodiment of an optical laminate including an optical functional layer.

[0026] Figure 5 Is presented containing Figure 4 This is a schematic side cross-sectional view of one embodiment of the functional glass of the optical laminate. DETAILED DESCRIPTION

[0027] The following describes the embodiments of the present invention with reference to the accompanying drawings. In addition, the following embodiments are only examples of several representative embodiments of the present invention, and various changes can be implemented within the scope of the present invention. In addition, the term "for head-up display" may be omitted and only described as optical functional layer, optical laminate, functional glass. In addition, the terms "(meth)acryl", "(meth)acrylate" and the like represent "acryl" or "methacryl", "acrylate" or "methacrylate", respectively. In addition, "head-up display" may be described as HUD, and the film used for the phase difference layer may be described as phase difference film.

[0028] [Heads-up display]

[0029] The head-up display of the present invention comprises an image display unit that emits display light representing a display image, and a functional glass that projects the image projected by the image display unit. In addition, the functional glass contains an optical functional layer that represents reverse wavelength dispersion, and the configuration angle α of the functional glass is greater than 20° and less than 70°. In addition, relative to the functional glass, a reflected image is visually confirmed within the range of a viewing angle of Brewster angle β-(90°-angle α)±15°. As described above, the functional glass contains an optical functional layer that represents reverse wavelength dispersion, and the functional glass is used and configured in a manner that a reflected image is visually confirmed at a specific viewing angle, thereby effectively suppressing the generation of double images. In particular, in the head-up display of the present invention, when the functional glass is used as a windshield of a vehicle, the most preferred viewing angle is used at each angle of the various windshields, and the generation of double images can be effectively suppressed in various types of vehicles, and visual confirmation personnel can use the head-up display system without pressure in a wide range of viewing angles.

[0030] Figure 1 An embodiment of the HUD system of the present invention is presented in a schematic diagram. Figure 1The HUD system shown in the figure includes an image display unit (display) 2 for display light representing a display image, a reflector 3 for reflecting the display light emitted from the image display unit 2, and a functional glass 4 for projecting the image projected by the image display unit 2. The display light emitted from the image display unit 2 is reflected by the reflector 3, and the reflected display light is projected onto the functional glass 4 functioning as a windshield, thereby allowing the image projected via the light path 5 to reach the observer 1, and the virtual image of the display image 6 can be visually confirmed. Figure 1 In the HUD system shown, the display light emitted by the image display unit 2 is incident on the functional glass 4 via the reflector 3, but the image display unit 2 may directly be incident on the functional glass 4. In addition, the image display unit 2 may emit display light representing the display image and reflect it on the reflector 3, and the reflected light may pass through a polarizing plate before reaching the functional glass 4, thereby adjusting the display light emitted by the image display unit 2 and irradiating the functional glass 4 with the desired polarized light.

[0031] In existing head-up display systems that project desired images onto the windshield, the incident angle of the projection light containing the display image relative to the windshield is generally about 60° to 70°, and the viewing angle for visually confirming the reflected image is usually set to an angle of about 5° downward from the driver's horizontal line of sight. In the HUD system of the present invention, the configuration angle α of the functional glass is 20° to 70°, and the reflected image is visually confirmed within the viewing angle range of Brewster angle β-(90°-angle α) ±15° relative to the functional glass. Here, the configuration angle α of the functional glass is the inclination angle of the functional glass relative to the support body on which the functional glass is provided. Figure 1 In the HUD system shown, the angle α is the angle between the functional glass 4 and the dotted line connected thereto. When the functional glass 4 is a windshield of a vehicle, the angle α is the angle at which the windshield is tilted toward the inside of the vehicle. In addition, the Brewster angle β refers to the incident angle when the reflectivity of the p-polarized light is zero when the display light is incident on the surface of the functional glass. Figure 1 In the HUD system shown, the incident angle of the display light relative to the vertical axis of the functional glass 4 shown by the dotted line is the angle β at which the reflectivity of the p-polarized light becomes zero. In the HUD system of the present invention, the light is incident from air with a refractive index of 1 to glass with a refractive index of about 1.5, so the Brewster angle β is about 56°.

[0032] In the HUD system of the present invention, when the configuration angle α of the functional glass is 20° or more and 70° or less, a reflected image is visually confirmed within the range of the viewing angle of Brewster angle β-(90°-angle α)±15° relative to the functional glass, but the viewing angle may be at least one of the value calculated by Brewster angle β-(90°-angle α) or the value calculated by Brewster angle β-(90°-angle α)±15°. For example, when the configuration angle α of the functional glass is 50°, the viewing angle may be at least one of 16° of the value calculated by 56°-(90°-50°), 31° of the value calculated by ±15°, and 1°.

[0033] The configuration angle α of functional glass is preferably 25° or more and 70° or less. Angle α is configured within this range, thereby improving the range in which the generation of double images can be suppressed. In addition, with respect to functional glass, it is more preferred to visually confirm the reflected image within the range of the viewing angle of Brewster angle β-(90°-angle α) ±10°. The range in which the generation of double images can be suppressed can be improved by making the viewing angle within this range. In addition, the viewing angle can also be at least one of the values ​​calculated with Brewster angle β-(90°-angle α) or the values ​​calculated with Brewster angle β-(90°-angle α) ±10°.

[0034] <Image Display Unit>

[0035] The display light emitted by the image display unit is preferably S-polarized light or P-polarized light. The image display unit is not particularly limited as long as it can emit the desired P-polarized light or S-polarized light before reaching the final functional glass, and examples thereof include a liquid crystal display device (LCD), an organic EL display (OLED), etc. When the image display unit is a liquid crystal display device, the emitted light is usually linearly polarized light, so it can be used directly. On the other hand, when the image display unit is an organic EL display, for example Figure 2 As shown, the image display unit 2 can be composed of a light source 2A and a polarizing plate 2B that can emit P polarized light or S polarized light. In addition, when the HUD system is used in an automobile, for example, a polarizing plate, a 1 / 2 wavelength plate and other optical components can be arranged at the light emission outlet of the instrument panel, and the liquid crystal display device and the organic EL display can be adjusted in a manner that the image display unit can emit P polarized light or S polarized light. In addition, the light source used in the image display unit is not particularly limited, and a laser light source, an LED light source, etc. can be used. In addition, the central reflection wavelength of the phase difference element constituting the optical functional layer is set in a manner corresponding to the luminous spectrum of the above-mentioned light source, thereby more effectively making the displayed image clearer.

[0036] <Reflector>

[0037] The HUD system of the present invention may optionally include a reflector. The reflector is not particularly limited as long as it can reflect the display light from the image display unit toward the functional glass, and may be composed of, for example, a plane mirror, a concave mirror, etc. When a concave mirror is used as the reflector, the concave mirror can amplify the display light from the display at a specific magnification.

[0038] [Optical functional layer]

[0039] In the HUD system of the present invention, the optical functional layer included in the functional glass preferably includes at least one retardation layer, and more preferably includes two retardation layers. Figure 3 1 shows one embodiment of an optical functional layer (optical functional layer for HUD) included in the functional glass for a HUD system of the present invention. The optical functional layer 10 includes two retardation layers 101 stacked together and a bonding layer 102 bonding the retardation layers 101 to each other. Figure 3 In the embodiment, the bonding layer 102 and the two phase difference layers 101 are respectively disposed adjacent to each other, that is, the two phase difference layers 101 are respectively stacked on both sides of the bonding layer 102. When the bonding layer 102 and the phase difference layer 101 are stacked, the phase difference layer 101 is preferably disposed on the outer side of the optical functional layer 10, that is, on the side not in contact with the bonding layer 102, on the supporting substrate described later.

[0040] The phase difference value of the phase difference layer is preferably greater than 200nm and less than 350nm, and more preferably greater than 220nm and less than 300nm. When the optical functional layer contains multiple phase difference layers, the phase difference values ​​of each phase difference layer can be the same or different, but the optical functional layer is more preferably provided with two phase difference layers with different phase difference values.

[0041] <Phase difference layer>

[0042] The phase difference layer contained in the optical functional layer refers to a layer having the function of converting the polarization axis of the incident light, and examples thereof include (A-1) a 1 / 2 wavelength plate, (A-2) a 1 / 4 wavelength plate, (A-3) a laminate of a 1 / 2 wavelength plate and a circularly polarized light reflecting layer, (A-4) a laminate of a 1 / 4 wavelength plate and a circularly polarized light reflecting layer, and (A-5) other layers having any phase difference. The phase difference layer contains at least one of the above-mentioned (A-1) to (A-5). When the optical functional layer contains two phase difference layers, each phase difference layer can use any of the above-mentioned (A-1) to (A-5) or a combination of any of the above-mentioned (A-1) to (A-5), and each phase difference layer can be different or the same. When the optical functional layer contains multiple phase difference layers, the phase difference layers are preferably all (A-1) 1 / 2 wavelength plates, and more preferably, the optical functional layer contains two phase difference layers and each phase difference layer is a 1 / 2 wavelength plate. Furthermore, two or more retardation layers may function as a half-wavelength plate as a whole. For example, an optical functional layer that combines (A-1) to (A-5) and functions as a half-wavelength plate as a whole may be used.

[0043] <1 / 2 Wavelength Plate>

[0044] When a 1 / 2 wavelength plate is used as the phase difference layer, the 1 / 2 wavelength plate is a phase difference element having the function of converting P polarization into S polarization or converting S polarization into P polarization, that is, having the function of converting the polarization axis. For example, the phase difference film composed of polycarbonate or cycloolefin polymer can be uniaxially stretched in a manner that the phase difference becomes 1 / 2 of the wavelength, or the horizontally aligned polymerizable liquid crystal is aligned in a thickness that the phase difference becomes 1 / 2 of the wavelength, thereby obtaining it. Generally speaking, a 1 / 2 wavelength plate using a horizontally aligned polymerizable liquid crystal is composed of a polymerizable liquid crystal layer and a supporting substrate, the polymerizable liquid crystal layer being a layer having the function of converting the polarization axis, and the supporting substrate is coated with a coating liquid that forms the polymerizable liquid crystal layer. The polymerizable liquid crystal layer can also be transferred to other substrates (such as an intermediate film or a glass plate) for use. When the 1 / 2 wavelength plate contains more than two phase difference layers, it is more preferred to have one supporting substrate relative to each phase difference layer. From the perspective of the alignment of the liquid crystal, the upper limit of the thickness of the 1 / 2 wavelength plate is preferably less than 10 μm, and more preferably less than 5 μm. On the other hand, from the perspective of the polymerization of the liquid crystal, the lower limit of the thickness of the 1 / 2 wavelength plate is preferably greater than 0.3 μm, and more preferably greater than 0.5 μm. When the incident light is incident from a position inclined relative to the main surface of the 1 / 2 wavelength plate, there is a situation where the phase difference changes due to the incident angle of the light. At this time, in order to more closely match the phase difference, for example, a phase difference element that adjusts the refractive index of the phase difference element can be used, thereby suppressing the phase difference change accompanying the incident angle. For example, when the refractive index in the slow axis direction within the plane of the phase difference element is nx, the refractive index in the direction orthogonal to nx within 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 in a manner of greater than 0.3 and less than 1.0, and more preferably greater than 0.5 and less than 0.8.

[0045] Nz=(nx-nz) / (nx-ny) (1)

[0046] When the 1 / 2 wavelength plate contains a polymerizable liquid crystal layer, the liquid crystal composition constituting the polymerizable liquid crystal layer is coated on a supporting substrate. When the 1 / 2 wavelength plate is used for HUD, in order to maintain the visual confirmation of the displayed image, the supporting substrate is preferably transparent in the visible light region, specifically, the average transmittance of visible light with a wavelength of 380 nm to 780 nm is 50% or more, preferably 70% or more, and more preferably 85% or more. In addition, the supporting substrate may be colored or uncolored, but it is more preferably less colored. In addition, the refractive index of the supporting substrate is more preferably 1.2 to 2.0, and more preferably 1.4 to 1.8. The thickness of the supporting substrate can be appropriately selected according to the application, preferably 5 μm to 1000 μm, more preferably 10 μm to 250 μm, and particularly preferably 15 μm to 150 μm.

[0047] The supporting substrate may be a single layer or a laminate of two or more layers. Examples of the supporting substrate include triacetyl cellulose (TAC), acrylic acid, polycarbonate, polyvinyl chloride, polyolefin, and polyethylene terephthalate (PET). Among these, triacetyl cellulose (TAC), polyolefin, and acrylic acid, which have less birefringence, are more preferred, and the phase difference value Re in the in-plane direction is more preferably less than 15 nm, and more preferably less than 10 nm. In addition, the phase difference value Rth in the thickness direction is more preferably less than 60 nm, and more preferably less than 10 nm.

[0048] Next, a method for making a 1 / 2 wavelength plate using a nematic liquid crystal monomer having a polymerizable group is described. This method, for example, dissolves a nematic liquid crystal monomer having a polymerizable group in a solvent, and then adds a photopolymerization initiator. The solvent is not particularly limited as long as it can dissolve the liquid crystal monomer used, and examples thereof include cyclopentanone, toluene, methyl ethyl ketone, methyl isobutyl ketone, etc., and cyclopentanone and toluene are more preferred. Thereafter, the solution is applied to a plastic substrate such as a PET film or a TAC film used as a supporting substrate in a manner that is as uniform as possible in thickness, and the solvent is removed by heating while being placed for a fixed time at a temperature condition that can form and align liquid crystals on the supporting substrate. At this time, before coating the surface of the plastic film, a rubbing treatment in the desired alignment direction may be performed, or an optical alignment material (hereinafter referred to as "alignment film coating liquid") that can exert optical alignment by irradiating polarized light may be formed on the surface of the plastic film substrate and irradiated with polarized light, etc., thereby making the alignment of the liquid crystal more uniform. The slow axis of the 1 / 2 wavelength plate can be controlled at the desired angle and the haze value of the 1 / 2 wavelength plate can be reduced. Then, while maintaining the alignment, the nematic liquid crystal monomer is irradiated with ultraviolet light from a high-pressure mercury lamp to fix the alignment of the liquid crystal, thereby obtaining a 1 / 2 wavelength plate with the desired slow axis.

[0049] The main function of the half-wavelength plate is to convert the S-polarized light or P-polarized light that passes through the surface without being reflected into P-polarized light or S-polarized light. This can reduce the reflection from the supporting substrate arranged on the outside and suppress double images.

[0050] Figure 1 , 2 In the HUD system shown, when the phase difference layer included in the functional glass 4 is a 1 / 2 wavelength plate, if the incident light to the functional glass 4 is S polarized light, part of the light incident on the functional glass 4 at the Brewster angle β will be directly reflected on the surface of the functional glass 4 and visually recognized by the observer 1. On the other hand, the incident light passing through the functional glass 4 will be converted into P polarized light by the 1 / 2 wavelength plate inside. Thereafter, when the light is emitted from the functional glass 4 to the air, it becomes the Brewster angle again at the interface with the air, so the reflection of the P polarized light is suppressed, and it is difficult to produce a double image. On the other hand, when the incident light to the functional glass 4 is P polarized light, the P polarized light is incident on the functional glass 4 at the Brewster angle β, thereby suppressing the reflection on the glass surface, and it is difficult to produce a double image. On the other hand, the incident light passing through the functional glass 4 is converted into S polarized light by the 1 / 2 wavelength plate inside. Thereafter, when the light is emitted from the functional glass 4 to the air, the light is reflected at the interface with the air and visually recognized by the observer 1. As described above, regardless of the type of polarized light incident on the functional glass 4, by using the HUD of the present invention, the occurrence of double images can be suppressed, and a head-up display with excellent visual recognition can be provided.

[0051] <1 / 4 Wavelength Plate>

[0052] A quarter wavelength plate can also be used as the phase difference layer. A quarter wavelength plate is a phase difference element that has the function of converting circular polarization into linear polarization. For example, a phase difference film composed of polycarbonate or cycloolefin polymer can be uniaxially stretched in a manner that the phase difference becomes 1 / 4 of the wavelength, or a horizontally aligned polymerizable liquid crystal can be aligned in a thickness that the phase difference becomes 1 / 4 of the wavelength. In addition, similar to the half wavelength plate, the quarter wavelength plate preferably contains a polymerizable liquid crystal layer. At this time, the quarter wavelength plate is composed of a polymerizable liquid crystal layer and a supporting substrate, and the polymerizable liquid crystal layer serves as a layer that has the function of converting the polarization axis, and the supporting substrate is coated with a coating liquid that forms the polymerizable liquid crystal layer. The polymerizable liquid crystal layer and the supporting substrate can use the same materials as the nematic liquid crystal monomer and the supporting substrate used in the above-mentioned half wavelength plate.

[0053] When the phase difference deviation caused by wavelength dispersion is large, a phase difference element called a broadband quarter-wave plate may be used for the quarter-wave plate. A broadband quarter-wave plate refers to a phase difference element that can reduce the wavelength dependence of the phase difference. For example, a half-wave plate and a quarter-wave plate with the same wavelength dispersion are stacked in such a way that the angle between their slow axes is 60°, and a polycarbonate phase difference element that reduces the wavelength dependence of the phase difference (made by Teijin: PUREACEWR-S). In addition, when the display light is obliquely incident with respect to the quarter-wave plate, such as a HUD, the phase difference may change depending on the incident angle of the light, depending on the phase difference element. At this time, as a method of more closely matching the phase difference, for example, a phase difference element that adjusts the refractive index of the phase difference element may be used, thereby suppressing the phase difference change associated with the incident angle. As this example, when the refractive index in the slow axis direction within the plane of the phase difference element is nx, the refractive index in the direction orthogonal to nx within 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 above formula (1) is preferably controlled in a manner of being greater than 0.3 and less than 1.0, and more preferably greater than 0.5 and less than 0.8. From the perspective of the orientation of the liquid crystal, the upper limit value of the thickness of the 1 / 4 wavelength plate is more preferably less than 10 μm, and more preferably less than 5 μm. On the other hand, the lower limit value of the thickness of the 1 / 4 wavelength plate is more preferably greater than 0.3 μm, and more preferably greater than 0.5 μm.

[0054] The 1 / 2 wavelength plate or 1 / 4 wavelength plate used as the phase difference layer is preferably a polymerizable liquid crystal layer containing a polymerizable liquid crystal compound. A polymerizable liquid crystal compound refers to a nematic liquid crystal monomer having a polymerizable group in the molecule and exhibiting liquid crystal properties within a temperature range or a concentration range. Examples of polymerizable groups include (meth)acryloyl, vinyl, chalcone, cinnamoyl and epoxy groups. In addition, in order to make the polymerizable liquid crystal exhibit liquid crystal properties, it is more preferred to have a mesogen group in the molecule. The mesogen group refers to, for example, a biphenyl group, a terphenyl group, a (poly)phenyl benzoate group, a (poly)ether group, a benzylideneaniline group, or an acenaphthenequinoline group. Rod-shaped or plate-shaped substituents such as pyroline, or disc-shaped substituents such as biphenyl, phthalocyanine, or azacrown, that is, groups with the ability to induce liquid crystal phase behavior. Liquid crystal compounds with rod-shaped or plate-shaped substituents are publicly known in the art as rod-shaped liquid crystals. The nematic liquid crystal monomers with polymerizable groups can include polymerizable liquid crystals such as those described in Japanese Patent Publication No. 2003-315556 and Japanese Patent Publication No. 2004-29824, PALIOCOLOR series (manufactured by BASF) and RMM series (manufactured by Merck). These nematic liquid crystal monomers with polymerizable groups can be used alone or in a mixed majority.

[0055] In addition, a polymerizable compound without liquid crystal properties that can react with a nematic liquid crystal monomer having a polymerizable group may also be added. Examples of such compounds include ultraviolet curable resins. Examples of ultraviolet curable resins include dipentaerythritol hexa(meth)acrylate, a reaction product of dipentaerythritol penta(meth)acrylate and 1,6-hexamethylene diisocyanate, a reaction product of a triisocyanate having an isocyanuric ring and pentaerythritol tri(meth)acrylate, a reaction product of pentaerythritol tri(meth)acrylate and isophorone diisocyanate, dipentaerythritol penta(meth)acrylate, dipentaerythritol tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate. ester, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, tri(acryloxyethyl) isocyanurate, tri(methacryloxyethyl) isocyanurate, reaction product of glycerol triglycidyl ether and (meth)acrylic acid, caprolactone-modified tri(acryloxyethyl) isocyanurate, reaction product of trimethylolpropane triglycidyl ether and (meth)acrylic acid, triglyceride di(meth)acrylate, reaction product of propylene glycol diglycidyl ether and (meth)acrylic acid di(meth)acrylate, polypropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, reaction product of 1,6-hexanediol diglycidyl ether and (meth)acrylic acid, 1,6-hexanediol di(meth)acrylate, glycerol di(meth)acrylate, reaction product of ethylene glycol diglycidyl ether and (meth)acrylic acid, reaction product of diethylene glycol diglycidyl ether and (meth)acrylic acid ) acrylic acid reaction product, bis(acryloyloxyethyl) hydroxyethyl isocyanurate, bis(methacryloyloxyethyl) hydroxyethyl isocyanurate, reaction product of bisphenol A diglycidyl ether and (meth) acrylic acid, tetrahydrofurfuryl (meth)acrylate, caprolactone-modified tetrahydrofurfuryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, polypropylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, phenoxyhydroxypropyl (meth)acrylate, acryl In some embodiments, the present invention relates to methoxy-polyethylene glycol (meth)acrylate, methoxy-tetraethylene glycol (meth)acrylate, methoxy-triethylene glycol (meth)acrylate, methoxy-ethylene glycol (meth)acrylate, methoxy-ethyl (meth)acrylate, glycidyl (meth)acrylate, glyceryl (meth)acrylate, ethyl carbitol (meth)acrylate, 2-ethoxyethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, 2-cyanoethyl (meth)acrylate, a reaction product of butyl glycidyl ether and (meth)acrylic acid, butoxy-triethylene glycol (meth)acrylate, and butanediol mono(meth)acrylate, etc. These can be used alone or in combination. These UV-curable resins without liquid crystal properties need to be added to such an extent that the composition containing the nematic liquid crystal monomer does not lose its liquid crystal properties, and preferably, the amount is 0.1 to 20 parts by mass, and more preferably, 1.0 to 10 parts by mass, relative to 100 parts by mass of the nematic liquid crystal monomer having a polymerizable group.

[0056] When the nematic liquid crystal monomer having a polymerizable group and the polymerizable compound having no liquid crystal properties are ultraviolet curable, a photopolymerization initiator is added to cure the composition containing them by ultraviolet rays. Examples of the photopolymerization initiator include 2-methyl-1-[4-(methylthio)phenyl]-2-N- 1-(4-dodecylphenyl)-2-hydroxy-2-methylpropane-1-one ("DAROCUR 953" manufactured by Merck), 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one ("DAROCUR 1116" manufactured by Merck), 2-hydroxy-2-methyl-1-phenylpropane-1-one ("Omnirad 2959" manufactured by IGM Resins BV), 1-(4-dodecylphenyl)-2-hydroxy-2-methylpropane-1-one ("DAROCUR 1116" manufactured by Merck), 1-(4-isopropylphenyl)-2-hydroxy-2-methyl ...1116" manufactured by Merck), 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one ("Omnirad 1116" manufactured by IGM Resins BV), 1-(4-dodecylphenyl)-2-hydroxy-2-methylpropane-1-one ("Omnirad 1116" manufactured by IGM Resins BV), 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one ("Omnirad 1116" manufactured by IGM Resins BV), 1-(4-dodecylphenyl)-2-hydroxy-2-methylpropane-1-one (" 1173”) and acetophenone compounds such as diethoxyacetophenone; benzoin compounds such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether and 2,2-dimethoxy-2-phenylacetophenone (“IRGACURE 651” manufactured by BASF); diphenyl ketone compounds such as benzoylbenzoic acid, benzoylbenzoic acid methyl ester, 4-phenyldiphenyl ketone, hydroxydiphenyl ketone, 4-benzoyl-4'-methyldiphenyl sulfide, 3,3'-dimethyl-4-methoxydiphenyl ketone (“KAYACURE MBP” manufactured by Nippon Kayaku Co., Ltd.); and thioxanthone, 2-chlorothioxanthone (“KAYACURE CTX” manufactured by Nippon Kayaku Co., Ltd.), 2-methylthioxanthone, 2,4-dimethylthioxanthone (“KAYACURE Thioxanthone compounds such as 2,4-dichlorothioxanthone ("KAYACURE CTX" manufactured by Nippon Kayaku Co., Ltd.), 2,4-diethylthioxanthone ("KAYACURE DETX" manufactured by Nippon Kayaku Co., Ltd.), and 2,4-diisopropylthioxanthone ("KAYACURE DITX" manufactured by Nippon Kayaku Co., Ltd.) are also included. More preferred photopolymerization initiators include Irgacure OXE01, Irgacure OXE02, Irgacure OXE03, and Irgacure OXE04 (all manufactured by BASF), Omnirad TPO H, Omnirad 1300, Omnirad 184, Omnirad 369, Omnirad 379, Omnirad 819, Omnirad 127, Omnirad 907, and Omnirad 1173 (all manufactured by IGM Resins BV), and more preferred are Omnirad TPO H, Irgacure OXE01, Irgacure OXE02, Omnirad 1300, and Omnirad 907.These photopolymerization initiators may be used alone or in combination of a plurality of types in any proportion.

[0057] When a phenyl ketone compound or a thioxanthone compound is used as the photopolymerization initiator, an auxiliary agent may be used in combination to promote the photopolymerization reaction. Examples of the auxiliary agent include amine compounds such as triethanolamine, methyldiethanolamine, triisopropanolamine, n-butylamine, N-methyldiethanolamine, diethylaminoethyl methacrylate, Michelle's ketone, 4,4'-diethylaminobenzophenone, ethyl 4-dimethylaminobenzoate, (n-butoxy)ethyl 4-dimethylaminobenzoate, and isopentyl 4-dimethylaminobenzoate.

[0058] The amount of the photopolymerization initiator and the auxiliary agent added is preferably within a range that does not affect the liquid crystallinity of the composition, and the amount is preferably 0.5 to 10 parts by mass, more preferably 2 to 8 parts by mass, relative to 100 parts by mass of the ultraviolet-curable compound in the composition. In addition, the auxiliary agent is preferably contained in a range of 0.5 to 2 times the amount of the photopolymerization initiator.

[0059] When the phase difference layer uses a laminate of a 1 / 2 wavelength plate and a circularly polarized light reflecting layer, or a laminate of a 1 / 4 wavelength plate and a circularly polarized light reflecting layer, the 1 / 2 wavelength plate and the 1 / 4 wavelength plate are as described above, respectively, and the circularly polarized light reflecting layer is preferably a cholesteric liquid crystal layer using cholesteric liquid crystal, for example. From the viewpoint of the orientation of the cholesteric liquid crystal, the upper limit of the thickness of the circularly polarized light reflecting layer is preferably 10 μm or less, and more preferably 5 μm or less. On the other hand, from the viewpoint of the polymerization of the cholesteric liquid crystal, the lower limit of the thickness of the circularly polarized light reflecting layer is preferably 0.3 μm or more, and more preferably 0.5 μm or more.

[0060] <Next layer>

[0061] When the phase difference layers are adhered to each other via an adhesive layer, the adhesive used as the adhesive layer may include acrylic or rubber adhesives (pressure sensitive adhesives), and acrylic adhesives that are easy to adjust adhesion, holding power, etc. are more preferred. The adhesive may include ultraviolet curing resin compositions, thermosetting resin compositions, and mixtures thereof. In the case of an ultraviolet curing resin composition, the composition mixed with a plurality of monomers having an acryl group or an epoxy group is irradiated with ultraviolet light in the presence of a photopolymerization initiator to cure it, thereby bonding the optical functional layers. In the case of a thermosetting resin composition, the composition mixed with a plurality of monomers having an epoxy group is heated in the presence of an acid catalyst to cure it, thereby bonding the optical functional layers. In addition, a composition composed of a multi-monomer or polymer having an amino group, a carboxyl group, or a hydroxyl group is heated and cured in the presence of a compound having an isocyanate group or melamine, thereby bonding the optical functional layers.

[0062] In the HUD system of the present invention, the optical functional layer contained in the functional glass correctly performs polarization conversion in a wide wavelength range in the visible light region, so it exhibits reverse wavelength dispersion. Generally speaking, polymers show normal dispersion in which the absolute value of birefringence increases on the short wavelength side, but if it is a liquid crystal compound in which the birefringence increases on the long wavelength side by controlling the value of birefringence Δn of each wavelength of visible light, reverse wavelength dispersion can be obtained. In addition, in accordance with the wavelength dispersion characteristics of the liquid crystal compound, the appropriate phase difference value and slow axis of multiple phase difference layers are combined to form a stack of phase difference layers, thereby also obtaining reverse wavelength dispersion. As a combination of the multiple phase difference layers, even when a half-wave plate is stacked as a phase difference layer, the angle θ between the polarization axis of the S-polarized light or P-polarized light incident at a position inclined by 45° or more and 65° or less from the vertical axis and the slow axis of the half-wave plate is appropriately controlled for the slow axis angle of each phase difference layer, thereby enabling the half-wave plate to exhibit good polarization axis conversion performance over a wide wavelength range. As a result, the generation of double images can be suppressed over a wide viewing angle, and the displayed image can be visually confirmed more clearly. At this time, from the perspective of the controllability of the slow axis of the half-wave plate and the production cost, the layer having the function of converting the polarization axis is preferably a half-wave plate containing a polymerizable liquid crystal layer.

[0063] The polarization axis conversion performance as an indicator of reverse wavelength dispersion is preferably a higher polarization conversion rate in the wavelength range of 380 to 780 nm in the visible light region. For example, the conversion rate of S-polarized light or P-polarized light incident at a position inclined 56° from an axis perpendicular to the surface of the functional glass containing the optical functional layer, that is, the conversion rate of S-polarized light or P-polarized light incident on the surface of the functional glass at the Brewster angle is preferably 80% or more at wavelengths of 450nm and 710nm, and 95% or more at a wavelength of 580nm. It is more preferred that the conversion rate of S-polarized light or P-polarized light is 90% or more at wavelengths of 450nm and 710nm, and 97% or more at a wavelength of 580nm.

[0064] When the optical functional layer contains two phase difference layers, the optical functional layer as a whole preferably exhibits reverse wavelength dispersion. The phase difference value, slow axis angle pattern, and combination of reverse wavelength dispersion that exhibits good polarization conversion properties over a wide band obtained by using two phase difference layers are preferably that each phase difference layer is a 1 / 2 wavelength plate and has a phase difference value of 200 nm or more and 350 nm or less.

[0065] The combination of the slow axis angles of the two phase difference layers is preferably (i) the slow axis angle of one phase difference layer is greater than +15° and greater than +35°, and the slow axis angle of the other phase difference layer is greater than -80° and less than -60°, or (ii) the slow axis angle of one phase difference layer is greater than -35° and less than -15°, and the slow axis angle of the other phase difference layer is greater than +60° and less than +80°. More specifically, it is more preferred that the slow axis angle of one phase difference layer is a positive value, and the slow axis angle of the other phase difference layer is a negative value, and it is more preferred that the sum of the absolute values ​​of the slow axis angles of each phase difference layer is within the range of 90°±20.

[0066] Furthermore, the combination of the slow axis angle and the phase difference value in the two phase difference layers is preferably such that the phase difference value of the first phase difference layer having a larger absolute value of the slow axis angle is larger than the phase difference value of the second phase difference layer having a smaller absolute value of the slow axis angle.

[0067] When the optical laminate contains two phase difference layers, each phase difference layer contains the above phase difference value, slow axis angle pattern and / or combination, thereby when the incident angle of light on the functional glass surface is inclined at 56°, that is, when the light is incident at the Brewster angle, the polarization conversion in the visible light wavelength region can be improved. In addition, in the HUD system of the present invention, the display light emitted from the image display unit is incident from the phase difference layer side with a larger phase difference value in the two phase difference layers, thereby expanding the range in which the generation of double images can be suppressed.

[0068] In the HUD system of the present invention, when the Brewster angle of the S-polarized light or P-polarized light incident on the functional glass is β, the incident angle of the light emitted from the image display unit incident on the functional glass as the display medium is preferably in the range of β-10° to β+10°, and more preferably in the range of β-5° to β+5°. In addition, the incident angle refers to the angle between the axis perpendicular to the surface of the display medium (functional glass) and the light incident on the surface of the display medium (hereinafter referred to as "incident angle X").

[0069] In one embodiment of the HUD system of the present invention, the phase difference layer included in the optical functional layer uses a 1 / 2 wavelength plate, the windshield as the display medium is a functional glass, and when the display light emitted from the image display unit is S polarized light, the S polarized light emitted from the image display unit is incident through the reflector 3 in the range of β-10° to β+10°, that is, incident at an angle near the Brewster angle β relative to the axis perpendicular to the functional glass surface, preferably incident at an incident angle of the Brewster angle β, thereby suppressing the reflection of the P polarized light converted by the functional glass on the outer glass plate of the vehicle, and suppressing the generation of double images. That is, if the incident angle of the S polarized light does not reach β-10° or exceeds β+10°, the incident angle of the S polarized light will deviate from the angle near the Brewster angle, so the reflection of the P polarized light converted by the 1 / 2 wavelength plate will increase, and there is a situation where double images are generated.

[0070] In one embodiment of the HUD system of the present invention, when the optical functional layer includes two or more retardation layers, it is preferred that light enters from the side where the retardation layer with the highest refractive index is disposed. Although the reason is not clear, it can be confirmed that the viewing angle when S-polarized light is incident on the functional glass is improved.

[0071] In addition, in other embodiments of the HUD system of the present invention, a laminate of two 1 / 4 wavelength plates is sandwiched between one or more circularly polarized reflective layers (cholesterol-like liquid crystal layers) as an optical functional layer system, and the windshield as a display medium is a functional glass, and when the display light emitted from the image display unit is P polarized light, the generation of double images can be suppressed in the same way. Generally, the reflected light from the road surface is S polarized light, so polarized sunglasses are designed to absorb S polarized light. Therefore, in the previous HUD system using S polarized light, the visual confirmation of the displayed image of the HUD through the polarized sunglasses will be extremely reduced. On the other hand, if the HUD system using P polarized light reaches the observer, the generation of double images can be suppressed, and the visual confirmation of the displayed image can also be improved when wearing polarized sunglasses. In addition, when the circularly polarized light reflecting layer is a cholesterol liquid crystal layer, the circularly polarized light passing through the circularly polarized light reflecting layer is converted into the original P polarized light by passing through the second 1 / 4 wavelength plate, and the slow axis of the second 1 / 4 wavelength plate is set in a positional relationship orthogonal to the slow axis of the first 1 / 4 wavelength plate. The converted P polarized light is also incident at an angle close to the Brewster angle with respect to the vehicle outer side glass surface outside the second 1 / 4 wavelength plate. Therefore, the reflection of the P polarized light on the vehicle outer side glass surface outside the second 1 / 4 wavelength plate can also be greatly reduced, and as a result, the generation of double images can be greatly improved.

[0072] In the HUD system of the present invention, for example, when an optical functional layer including a 1 / 2 wavelength plate is provided as a phase difference layer, in order to efficiently perform polarization conversion (for example, converting P polarization into S polarization, or converting S polarization into P polarization), it is preferred to control the angle θ between the polarization axis of S polarization or P polarization incident from a position inclined 45° to 65° from the axis perpendicular to the functional glass surface and the slow axis of the optical functional layer to be 35° to 47°. By making the incident angle of S polarization or P polarization incident on the functional glass in the range of 45° to 65°, when P polarization is incident on the functional glass, the reflectivity of the functional glass surface can be suppressed to less than 2% in theory. The P polarization passing through is converted into S polarization by the 1 / 2 wavelength plate, and the converted S polarization is reflected at the interface between the functional glass and the air on the opposite side of the incident side. The reflected S polarization is converted into P polarization again by the 1 / 2 wavelength plate, and the P polarization reaches the observer. In addition, when S-polarized light is incident on the functional glass, the S-polarized light is reflected on the surface of the functional glass, and the S-polarized light reaches the observer. A portion of the S-polarized light that passes through is converted into P-polarized light by the 1 / 2 wavelength plate, and the converted P-polarized light passes through the functional glass on the opposite side of the incident side or the interface between the functional glass and the air under reflection. As described above, the incident angle X of the S-polarized light or P-polarized light incident on the functional glass is controlled, thereby suppressing the generation of double images. In addition, when the angle θ is less than 35° or exceeds 47°, the polarization axis conversion performance of converting the P-polarized light incident on the functional glass into the S-polarized light or converting the S-polarized light into the P-polarized light is low, resulting in the risk of generating double images. By appropriately controlling the angle θ, the 1 / 2 wavelength plate can present good polarization axis conversion performance, resulting in a clearer visual confirmation of the displayed image.

[0073] When the optical functional layer contains a 1 / 2 wavelength plate as a phase difference layer, in order to properly control the polarization axis conversion performance, the angle θ is preferably a value calculated by the following formulas (2) and (3). The technical significance of the following formulas (2) and (3) is explained here. When S-polarized light or P-polarized light incident on the functional glass passes through a 1 / 2 wavelength plate having a medium with a refractive index different from that of air, the incident angle X incident on the 1 / 2 wavelength plate will change. Here, the incident angle X of the S-polarized light or P-polarized light relative to the functional glass is α, the actual incident angle X incident on the 1 / 2 wavelength plate, that is, the refractive angle of the 1 / 2 wavelength plate is B, and the refractive index of air is n A , the refractive index of the 1 / 2 wavelength plate is n B According to Snell's law, sinA / sinB=n B / n AIf the formula is simplified to an equation for finding B, formula (3) can be derived. On the other hand, when the polarization axis of the S polarized light incident on the functional glass is the x-axis, the polarization axis of the P polarized light is the y-axis, and the phase difference value when the angle between the y-axis and the slow axis of the 1 / 2 wavelength plate is θ is Re, through vector analysis, the y-axis is expressed as Re·cosθ and the x-axis is expressed as Re·sinθ. Here, it is known that the polarization axis conversion performance of the 1 / 2 wavelength plate will be the maximum when the incident light is at 45° relative to the slow axis of the 1 / 2 wavelength plate, so in theory, the angle θ between the polarization axis of the S polarized light or the polarization axis of the P polarized light and the slow axis of the optical functional layer is preferably 45°. However, as mentioned above, even if the angle between the polarization axis of the S polarized light or the polarization axis of the P polarized light incident on the functional glass and the slow axis of the 1 / 2 wavelength plate is θ, the actual angle incident on the 1 / 2 polarizing plate is B. Therefore, regarding the y-axis of Re·cosθ (theoretical y-axis), if the y-axis when the x-axis is tilted toward the center at an angle B (the actual y-axis) is obtained, then Re·cosθ / actual y-axis=sin(90°-B) holds, and the actual y-axis is expressed as Re·cosθcosB. As mentioned above, the angle between the slow axis of the 1 / 2 wavelength plate and the polarization axis of the S polarized light or the polarization axis of the P polarized light is preferably 45°. In order to make the angle between the polarization axis of the S polarized light or the P polarized light incident on the functional glass and the slow axis of the 1 / 2 wavelength plate 45°, the x-axis (Re·sinθ) needs to be equal to the actual y-axis (Re·cosθcosβ), so Re·sinθ=Re·cosθcosβ is obtained. This formula is simplified, and formula (2) is derived based on it. As described above, by controlling the angle θ in close relation to the angle B actually incident on the half-wavelength polarizer based on the values ​​calculated by the following equations (2) and (3), the polarization axis conversion performance of the half-wavelength plate can be utilized to the maximum extent.

[0074] tanθ=cos B (2)

[0075]

[0076] θ: The angle between the slow axis of the 1 / 2 wavelength plate and the polarization axis of S-polarized light or P-polarized light incident at any incident angle A on the functional glass

[0077] A: The incident angle of S-polarized light or P-polarized light relative to the functional glass.

[0078] n A :The refractive index of air.

[0079] n B :Refractive index of 1 / 2 wavelength plate

[0080] The range of the angle θ is preferably controlled within the range of ±5° of the angle θ value, and more preferably within the range of ±3°. If the angle θ is outside the range of ±5° of the angle that satisfies the value calculated by the above formulas (2) and (3), the polarization conversion efficiency exhibited by the 1 / 2 wavelength plate will become lower. By controlling the range of the angle θ according to the value calculated by the above formulas (2) and (3), the decrease in the polarization conversion efficiency of the 1 / 2 wavelength plate can be suppressed.

[0081] Substitute the refractive index of the 1 / 2 wavelength plate into formula (3), and use the refractive index in the slow axis direction of the 1 / 2 wavelength plate as nx, the refractive index in the direction orthogonal to the slow axis direction for obtaining nx in the plane of the 1 / 2 wavelength plate as ny, and the refractive index in the thickness direction of the 1 / 2 wavelength plate as nz, and use the average value of the sum as the average refractive index. In addition, when using a commercially available 1 / 2 wavelength plate, the average refractive index can use the value recorded in the catalog, etc. In addition, when using the above-mentioned polymerizable liquid crystal as the material of the 1 / 2 wavelength plate, if the original normal refractive index no and abnormal refractive index ne of the liquid crystal are used, the average refractive index is expressed as (nx+ny+nz) / 3=(no+no+ne) / 3. If a specific example of θ calculated by formulas (2) and (3) is presented, for example, when the refractive index of air is 1.00, a 1 / 2 wavelength plate with a refractive index of 1.55 is used, and the incident angle X of S-polarized light or P-polarized light is 45°, according to formulas (2) and (3), the value of θ is 42°, so the range of θ is more preferably 37° to 47°, and more preferably 39° to 45°. When the incident angle X of S-polarized light or P-polarized light is 50°, according to formulas (2) and (3), the value of θ is 41°, so the range of θ is more preferably 36° to 46°, and more preferably 38° to 44°. In addition, when the incident angle X of S-polarized light or P-polarized light is 56° or 60°, according to formulas (2) and (3), the value of θ is 40°, so the range of θ is more preferably 35° to 45°, and more preferably 37° to 43°. When the incident angle X of S-polarized light or P-polarized light is 65°, the θ value is 39° according to equations (2) and (3), so the range of θ is preferably 34° to 44°, and more preferably 36° to 42°.

[0082] <Interlayer>

[0083] The functional glass may further contain an intermediate film. That is, an optical laminate (optical laminate for HUD) in which an optical functional layer is further laminated with an intermediate film may be used. The intermediate film is preferably a resin film of a thermoplastic resin, and more preferably a film of polyvinyl butyral. The intermediate film may be one sheet or multiple sheets, and is preferably an optical laminate having a structure in which an optical functional layer is sandwiched by two intermediate films. In addition, the optical laminate may also use two different optical functional layers. At this time, the two optical functional layers are preferably the same in that the difference in the slow axis angles in the same plane is the same.

[0084] Figure 4 1 shows an embodiment of an optical laminate (optical laminate for HUD) included in the functional glass of the HUD system of the present invention. The optical laminate 20 has a structure in which an optical functional layer 10 is sandwiched between two intermediate films 201. The optical functional layer 10 corresponds to, for example, Figure 3 The optical layered body 20 can be produced by laminating the intermediate film 201 and the optical layer 10 .

[0085] The interlayer can use a thermoplastic resin, and it is more preferred to use a generally used automotive interlayer. The automotive interlayer can be, for example, polyvinyl butyral resin (PVB), polyvinyl alcohol resin (PVA), ethylene / vinyl acetate copolymer resin (EVA), or cycloolefin polymer (COP). Interlayers made of these resins are more versatile as interlayers for laminated glass, so they are more preferred. In addition, the thickness of the interlayer is not particularly limited as long as it is within the range that does not affect the reflection of the display light when the optical laminate is applied to the HUD system, and can be appropriately designed according to the application.

[0086] Ultraviolet absorbers, antioxidants, antistatic agents, heat stabilizers, colorants, adhesive regulators, etc. can be appropriately added to the interlayer film. In particular, the interlayer film dispersed with infrared absorbing microparticles is more important when making high-performance heat-shielding laminated glass. The infrared absorbing microparticles are microparticles of conductive materials such as metals such as Sn, Ti, Zn, Fe, Al, Co, Ce, Cs, In, Ni, Ag, Cu, Pt, Mn, Ta, W, V, and Mo, oxides of the metals, nitrides of the metals, or composites containing at least two of these. In addition, Sn, Sb, F, etc. can be mixed into these materials. In particular, tin-doped indium oxide (ITO), antimony-doped tin oxide (ATO), and fluorine-doped tin oxide, which are transparent in the visible light range, are more preferred when used as architectural and automotive windows that require transparency. The particle size of the infrared absorbing microparticles dispersed in the interlayer film is preferably 0.2 μm or less. If the particle size of the microparticles is less than 0.2 μm, light scattering in the visible light region can be suppressed and infrared rays can be absorbed, radio wave permeability and transparency can be ensured without generating haze, and physical properties such as adhesion, transparency, and durability equivalent to those of an unadded interlayer can be maintained, and laminated glass processing can be performed in general laminated glass production line operations. In addition, when PVB is used as an interlayer, in order to keep the moisture content of the interlayer at the most preferred level, the lamination process is performed in a constant temperature and humidity room. In addition, the interlayer can be partially colored, with a layer having a sound insulation function sandwiched therebetween, or with a slope in thickness (wedge-shaped) to reduce the generation of double images (ghosting phenomenon) in the HUD, etc.

[0087] The lamination method of the intermediate film and the optical functional layer is not particularly limited, and an example thereof is a method of laminating the intermediate film and the optical functional layer by simultaneously pressing the intermediate film and the optical functional layer with a nip roller. When laminating, if the nip roller can be heated, the intermediate film and the optical functional layer can be pressed while being heated. In addition, if the adhesion between the intermediate film and the optical functional film is poor, the intermediate film and the optical functional film can be laminarized after surface treatment such as corona treatment or plasma treatment.

[0088] The intermediate film can be directly laminated on one or both sides of the optical functional layer in a state dissolved in a solvent. When using polyvinyl butyral resin (PVB), the lower limit of the butyralization degree is preferably 40 mol%, more preferably 55 mol%, and particularly preferably 60 mol%. On the other hand, the upper limit of the butyralization degree is more preferably 85 mol%, more preferably 80 mol%, and particularly preferably 75 mol%. In addition, the butyralization degree can be measured by infrared absorption spectroscopy (IR), for example, FT-IR can be used for measurement.

[0089] The lower limit of the hydroxyl content of the polyvinyl butyral resin is preferably 15 mol%, and the upper limit is preferably 35 mol%. If the hydroxyl content is less than 15 mol%, when the interlayer film and the glass plate described later are bonded to produce laminated glass, the adhesion between the interlayer film and the glass plate will be reduced, or the penetration resistance of the laminated glass will be reduced. On the other hand, if the hydroxyl content exceeds 35 mol%, the interlayer film will become hard.

[0090] Polyvinyl butyral resin can be prepared by acetalizing polyvinyl alcohol with aldehyde. Polyvinyl alcohol is usually obtained by saponifying polyvinyl acetate, and polyvinyl alcohol having a saponification degree of 80 mol% or more and 99.8 mol% or less is generally used. In addition, the upper limit of the degree of polymerization of polyvinyl alcohol is more preferably 4000, more preferably 3000, and particularly preferably 2500. If the degree of polymerization exceeds 4000, it is difficult to form an intermediate film.

[0091] [glass plate]

[0092] The functional glass contains a glass plate. That is, the functional glass used in the HUD of the present invention (functional glass for HUD) is a laminate of the optical functional layer or optical laminate and the glass plate. The glass plate may be one or more, but it is more preferably a functional glass having a structure in which the optical functional layer or optical laminate is sandwiched between two glass plates. The functional glass is suitable for use as a display medium in a HUD system.

[0093] When the functional glass is produced using the optical functional layer or optical laminate, for example, the optical functional layer or optical laminate is arranged between two glass plates and pressed together at high temperature and high pressure, thereby obtaining a functional glass having the optical functional layer or optical laminate arranged in a laminated glass. Figure 5 One embodiment of the functional glass used in the HUD system of the present invention is shown. Figure 5The functional glass 30 shown has a structure in which an optical laminate 20 is sandwiched between two glass plates 301. The optical laminate 20 is, for example, equivalent to Figure 4 In the optical laminate shown, the optical functional layer 10 is sandwiched between two intermediate films 201. Figure 5 As shown, when the glass plates 301 are laminated on the optical laminate 20 , the intermediate film 201 also functions as a pressure-sensitive adhesive or bonding agent for maintaining the adhesion between the two glass plates 301 and the optical laminate 20 .

[0094] Functional glass can be produced, for example, by laminating the above-mentioned optical functional layer or optical laminate to a glass plate. As an example of a method for laminating an optical functional layer or an optical laminate to a glass plate, an adhesive or a bonding agent can be applied to one or both sides of the optical functional layer or the optical laminate, and then the glass plate is laminated to obtain the functional glass. The adhesive or bonding agent is not particularly limited, but it is preferably a material with excellent adhesion when it is peeled off later, for example, a silicone adhesive, an acrylic adhesive, etc. are more preferably used.

[0095] The glass plate is not particularly limited as long as it has a transparency that allows the forward scenery to be fully visually confirmed even when the functional glass used in the HUD system of the present invention is used as a windshield. In addition, the refractive index of the glass plate is preferably greater than 1.2 and less than 2.0, more preferably greater than 1.4 and less than 1.8, and particularly preferably about 1.5. In addition, the thickness, shape, etc. of the glass plate are not particularly limited as long as they are within the range that does not affect the reflection of the display light, and can be appropriately designed according to the application. In addition, a high-reflection film composed of a multilayer film and a metal thin film layer with a heat-shielding function can be provided on the reflective surface of these glass plates. These films can increase the reflectivity of incident polarized light, but when the functional glass is used as a windshield for an automobile, for example, it is more preferred to adjust the reflectivity in such a way that the visible light transmittance of the functional glass becomes 70% or more.

[0096] An example of a method for making functional glass using an optical functional layer or an optical laminate is specifically described. First, two glass plates are prepared. When using laminated glass for a windshield of a car, soda-lime glass made by a float process is used. The glass can be transparent or colored green, and there is no particular restriction. The thickness of these glass plates is usually about 2 mmt, but in response to the demand for lighter glass in recent years, glass plates slightly thinner than 2 mmt can also be used. Cut the glass plate into a specific shape and chamfer the edge of the glass, then wash it. When a black frame or dot printing is required, it is printed on the glass plate. When it is necessary to form a curved surface shape like a windshield, the glass plate is heated to above 650°C, and then shaped by mold pressing or bending by its own weight so that the two sheets have the same surface shape, and then the glass is cooled. If the cooling rate is too fast at this time, stress distribution will be generated in the glass plate, and tempered glass will be formed, so it should be cooled slowly. One of the glass plates prepared as described above is placed horizontally, an optical functional layer or an optical laminate is overlapped thereon, and another glass plate is further placed. Next, the optical functional layer and the intermediate film protruding from the edge of the glass plate are cut and removed with a cutting machine. Thereafter, the glass plates, optical functional layers or optical laminates stacked in a sandwich shape are heated to 80°C to 100°C while degassing the air present therebetween, and preliminary bonding is performed. There are two methods for degassing the air: a bag method in which the laminate of the glass plate / optical functional layer or optical laminate / glass plate is wrapped with a rubber bag made of heat-resistant rubber or the like and degassed, and a ring method in which only the end of the glass plate is covered and sealed with a rubber ring. Either method can be used. After the preliminary bonding is completed, the laminate of the glass plate / optical functional layer or optical laminate / glass plate taken out of the rubber bag, or the laminate with the rubber ring removed, is placed in an autoclave and heated at 10 to 15 kg / cm 2 The functional glass of the present invention having a laminated structure of glass plate / optical functional layer or optical laminate / glass plate is taken out from the autoclave after being cooled to below 50°C and then depressurized.

[0097] The functional glass obtained in this way can be used as windshields for various automobiles such as ordinary automobiles, small automobiles, light automobiles, large special automobiles, and small special automobiles, and can also be used as side glass, rear windshield, and skylight glass. In addition, it can also be used as windows for railway vehicles, ships, and airplanes, and can also be used as building materials and industrial window materials. Depending on the form of use, it can be used by stacking or bonding with components having UV blocking or dimming functions.

[0098] According to the above embodiments, the present invention relates to the following [1] to

[13] .

[0099] [1] A head-up display system comprising an image display unit for emitting display light for presenting a display image, and functional glass for projecting the image projected by the image display unit,

[0100] The functional glass comprises an optical functional layer exhibiting reverse wavelength dispersion.

[0101] The configuration angle α of the functional glass is not less than 20° and not more than 70°.

[0102] Furthermore, with respect to the aforementioned functional glass, a reflected image is visually confirmed within a viewing angle range of Brewster angle β-(90°-angle α)±15°.

[0103] [2] The head-up display system according to [1] above, wherein the configuration angle α of the functional glass is not less than 25° and not more than 70°,

[0104] With respect to the functional glass, a reflected image is visually confirmed within a viewing angle range of Brewster angle β-(90°-angle α)±10°.

[0105] [3] The head-up display system described in [1] or [2] above, wherein the optical functional layer includes at least one phase difference layer.

[0106] [4] The head-up display system according to [3] above, wherein the optical functional layer includes two phase difference layers, and the optical functional layer as a whole exhibits reverse wavelength dispersion.

[0107] [5] The head-up display system as described in [3] or [4] above, wherein the retardation layer has a retardation value of not less than 200 nm and not more than 350 nm.

[0108] [6] The head-up display system as described in any one of [3] to [5] above, wherein the optical functional layer includes two phase difference layers,

[0109] (i) one phase difference layer has a slow axis angle of +15° or more and +35° or more, and the other phase difference layer has a slow axis angle of -80° or more and -60° or less; or

[0110] (ii) The slow axis angle of one phase difference layer is not less than -35° and not more than -15°, and the slow axis angle of another phase difference layer is not less than +60° and not more than +80°.

[0111] [7] A head-up display system as described in any one of [3] to [6] above, wherein the optical functional layer contains two phase difference layers, and among the two phase difference layers, the phase difference value of one phase difference layer having a larger absolute value of the slow axis angle is larger than the phase difference value of the other phase difference layer having a smaller absolute value of the slow axis angle.

[0112] [8] A head-up display system as described in any one of [3] to [7] above, wherein the optical functional layer includes two phase difference layers, each phase difference layer being a half-wavelength plate.

[0113] [9] A head-up display system as described in any one of [3] to [8] above, wherein the optical functional layer includes two phase difference layers, and the display light emitted by the image display unit is incident from the phase difference layer side having a larger phase difference value among the two phase difference layers.

[0114]

[10] The head-up display system according to any one of [1] to [9] above, wherein the functional glass further includes an interlayer film.

[0115]

[11] The head-up display system as described in any one of [1] to

[10] above, wherein the functional glass includes a glass plate.

[0116]

[12] A head-up display system as described in any one of [1] to

[11] above, wherein the display light emitted by the image display unit is S-polarized light or P-polarized light.

[0117]

[13] An optical functional layer for a head-up display system, provided in the head-up display system as described in any one of [1] to

[12] above.

[0118] (Example)

[0119] The present invention is described in detail below by way of examples. In the examples, "parts" are parts by mass. In addition, the present invention is not limited to the following examples within the scope of the present invention. In addition, unless otherwise specified, the room temperature is within the range of 20°C ± 5°C.

[0120] [Example 1]

[0121] <Adjustment of coating liquid (liquid crystal composition)>

[0122] A coating solution A having the composition shown in Table 1 was prepared.

[0123] [Table 1]

[0124] Material(type) Material name (manufacturer name) Prescription quantity (servings) Polymerized Liquid Crystal LC242 (BASF) 25 Photopolymerization initiator Omnirad 907 (IGM Resins BV) 1 Solvents Toluene 74

[0125] <Production of Optical Functional Layer>

[0126] Two half-wave plates were prepared using the prepared coating solution A in the following order. The supporting substrate was a TAC film (TacBright "P960": thickness 60 μm) rubbed by the method described in Example 1 of Japanese Patent Application Publication No. 2002-90743. In addition, the rubbing angles were set so that the angle between the long direction of the film and the slow axis of the half-wave plate (hereinafter referred to as "slow axis angle") was -70° and 26°, respectively.

[0127] (i) The coating liquid A was applied on the rubbed surface of the TAC film at room temperature using a wire bar so that the thickness of the half-wavelength plate obtained after drying would be about 2 μm.

[0128] (ii) The obtained coating film was heated at 50°C for 2 minutes to remove the solvent and form a liquid crystal phase. Next, the liquid crystal phase was fixed by UV irradiation with a high-pressure mercury lamp (manufactured by HARISON TOSHIBA LIGHTING Co., Ltd.) at an output of 120W for 5 to 10 seconds, and a polymerizable liquid crystal layer was stacked on the TAC film to produce a 1 / 2 wavelength plate. The phase difference value of the 1 / 2 wavelength plate was measured with an automatic birefringence meter ("KOBRA-21ADH" manufactured by Oji Measurement Co., Ltd.), and two types of 1 / 2 wavelength plates were obtained, with a phase difference value of 293nm (slow axis angle -70°) at 546nm for R1 and 230nm (slow axis angle 26°) for R2.

[0129] (iii) For the half-wave plates R1 and R2 prepared in (i) to (ii) above, an acrylic adhesive ("SK-Dyne 906" manufactured by Soken Chemical Co., Ltd.) is used to laminate the polymerizable liquid crystal layer sides thereof so that the long directions of the half-wave plates are aligned, thereby preparing an optical functional layer.

[0130] The average transmission rate of the visible light wavelength region in the front direction (incident angle 56°) of each obtained 1 / 2 wavelength plate was about 79%, and the polarization conversion rate was 96.8% at a wavelength of 450nm, 99% at 580nm, and 92.5% at 710nm. The polarization conversion rate was measured by using the "UV-3600 Ultraviolet / Visible / Near Infrared Spectrophotometer" manufactured by Shimadzu Corporation, by arranging the polarizing plates in parallel and installing the optical laminate between them at an incident angle of 56°, and the transmission rate was obtained by subtracting the transmission rate at each wavelength from 100.

[0131] <Production of Optical Laminated Body>

[0132] A transparent polyvinyl butyral interlayer (thickness: 0.38 mm) containing 2-ethyl triethylene glycol dihexanoate as a plasticizer was prepared. The prepared interlayer was cut into the same size as the optical functional layer of the laminated 1 / 2 wavelength plate R1 and 1 / 2 wavelength plate R2, and the optical functional layer was arranged between the two polyvinyl butyral interlayers, and then pressed and bonded by a laminator to prepare an optical laminate.

[0133] <Production of functional glass>

[0134] An optical laminate is placed between two glass plates of the same size and thickness as the optical laminate to be produced, and then pressurized and heated to obtain functional glass. Specifically, the optical laminate and the transparent glass plate are first stacked on a transparent glass plate in sequence. The laminate is wrapped in a rubber bag and degassed in an autoclave heated to 90°C for 10 minutes to perform pre-bonding. After cooling to room temperature, the laminate is taken out of the rubber bag and again heated in an autoclave at 135°C and 12kg / cm 2 The functional glass with good appearance was prepared by heating and pressing under high pressure for 30 minutes. The average pass rate of the obtained functional glass in the visible light wavelength region in the front direction (incident angle 56°) was about 72%, and the polarization conversion rate was 96.8% at a wavelength of 450nm, 99% at 580nm, and 92.5% at 710nm. The polarization conversion rate was measured by using the "UV / visible / near infrared spectrophotometer UV-3600" made by Shimadzu Corporation, by arranging the polarizing plates in parallel, installing the functional glass in between at an incident angle of 56°, and measuring the pass rate, which is the value of subtracting the pass rate at each wavelength from 100.

[0135] <Production of Head-Up Display and Evaluation of Displayed Images>

[0136] by Figure 1A head-up display is produced in the configuration shown. A liquid crystal display panel capable of emitting S-polarized light relative to the functional glass 4 is provided as the image display unit 2 and the reflector 3, and the functional glass 4 uses the functional glass produced as described above. The functional glass 4 is arranged in a dark room in such a manner that the arrangement angle α of the functional glass 4 becomes 34°, and the S-polarized light emitted from the image display unit 2 is adjusted in such a manner that the incident angle X of the S-polarized light is incident at the Brewster angle β (about 56°) relative to the functional glass 4, and the reflected image is visually confirmed at the Brewster angle β (56°)-(90°-34°)±10°=0°±10° relative to the functional glass 4, that is, at viewing angles of 0°, 10°, and -10°, respectively. Here, when the viewing angle is a positive value, it becomes a depression angle, and when it is a negative value, it becomes an elevation angle. When the glass plate on the side of the 1 / 2 wavelength plate R1 with a phase difference value of 293nm is arranged on the side of the image display unit 2 and an image is projected, the image can be projected and displayed brightly and clearly. At this time, the visual from the viewpoint of observing the display image is offset in the up-down direction (vertical direction) and the left-right direction (horizontal direction), and the range in which the display image can be clearly projected is recorded as the viewing angle. If the double image is suppressed within the range of 10° in the up-down direction and 30° in the left-right direction, the range in which the double image can be suppressed is very wide, and it is evaluated as excellent "0". If the double image is suppressed within the range of 6° in the up-down direction and 30° in the left-right direction, the range in which the double image is suppressed is wide, and it is evaluated as good "△". If the double image cannot be suppressed within the range of the above-mentioned viewing angle, the suppression effect of the double image is insufficient, and it is evaluated as "×". The results are shown in Table 2.

[0137] [Example 2]

[0138] The functional glass was set so that the angle α was 29° and the reflected image was visually confirmed. The viewing angle of the shooting was (56°)-(90°-29°)±10°=-5°±10°, that is, -5°, 5°, and -15°. The optical functional layer, optical laminate, and functional glass were prepared in the same manner as in Example 1. The obtained functional glass was used to evaluate the displayed image in the same manner. The results are shown in Table 2.

[0139] [Example 3]

[0140] The functional glass was set so that the angle α was 39° and the reflected image was visually confirmed. The viewing angle of the image was (56°)-(90°-39°)±10°=5°±10°, that is, 5°, 15°, and -5°. The optical functional layer, the optical laminate, and the functional glass were prepared in the same manner as in Example 1. The obtained functional glass was used to evaluate the displayed image in the same manner. The results are shown in Table 2.

[0141] [Example 4]

[0142] The functional glass was set so that the angle α was 25° and the reflected image was visually confirmed. The viewing angles of the images were (56°)-(90°-25°)=-9°, -9°+15°, that is, -9°, 6°. The optical functional layer, the optical laminate and the functional glass were prepared in the same manner as in Example 1. The obtained functional glass was used to evaluate the displayed image in the same manner. The results are shown in Table 2.

[0143] [Example 5]

[0144] The functional glass was set so that the angle α was 70° and the reflected image was visually confirmed. The viewing angle of the image was (56°)-(90°-70°)=36°. The optical functional layer, the optical laminate and the functional glass were prepared in the same manner as in Example 1. The obtained functional glass was used to evaluate the displayed image in the same manner. The results are shown in Table 2.

[0145] [Example 6]

[0146] The functional glass was set so that the angle α was 34° and the reflected image was visually confirmed. The viewing angle of the image was (56°)-(90°-34°)±15°=15°, -15°. The optical functional layer, optical laminate and functional glass were prepared in the same manner as in Example 1. The obtained functional glass was used to evaluate the displayed image in the same manner. The results are shown in Table 2.

[0147] [Example 7]

[0148] The functional glass was set so that the angle α was 20° and the reflected image was visually confirmed. The viewing angles of the images were (56°)-(90°-20°)=-14°, -14°+15°, that is, -14°, 1°. The optical functional layer, the optical laminate and the functional glass were prepared in the same manner as in Example 1. The obtained functional glass was used to evaluate the displayed image in the same manner. The results are shown in Table 2.

[0149] [Example 8]

[0150] The functional glass was set so that the angle α was 44° and the reflected image was visually confirmed. The viewing angle of the image was (56°)-(90°-44°)=10°-10°, that is, 0°. The optical functional layer, the optical laminate and the functional glass were prepared in the same manner as in Example 1. The obtained functional glass was used to evaluate the displayed image in the same manner. The results are shown in Table 2.

[0151] [Example 9]

[0152] The functional glass was set so that the angle α was 50° and the reflected image was visually confirmed. The viewing angle of the image was (56°)-(90°-50°)=16°-15°, that is, 1°. The optical functional layer, optical laminate and functional glass were prepared in the same manner as in Example 1. The obtained functional glass was used to evaluate the displayed image in the same manner. The results are shown in Table 2.

[0153] [Comparative Example 1]

[0154] The functional glass was set so that the angle α was 75° and the reflected image was visually confirmed. The viewing angle of the image was (56°)-(90°-75°)=41°. The optical functional layer, the optical laminate and the functional glass were prepared in the same manner as in Example 1. The obtained functional glass was used to evaluate the displayed image in the same manner. The results are shown in Table 2.

[0155] [Example 10] to [Example 15], [Comparative Example 2] to [Comparative Example 6]

[0156] The optical functional layer was prepared by combining two kinds of 1 / 2 wavelength plates R1 and 1 / 2 wavelength plates R2 having the slow axis angles and phase difference values ​​shown in Table 2. The optical functional layer, optical laminate and functional glass were prepared in the same manner as in Example 1. The polarization conversion rate and displayed image were measured and evaluated in the same manner using the obtained functional glass. The results are shown in Table 2.

[0157] [Table 2]

[0158]

[0159] From the results in Table 2, it can be seen from the comparison between Examples 1 to 9 and Comparative Example 1 that when the functional glass having an optical functional layer that exhibits reverse wavelength dispersion as a whole is arranged in a manner that the angle α is within the range of 25 to 70°, the range in which the generation of double images can be suppressed is relatively wide, and a HUD system with good visual confirmation can be provided. In addition, by comparing Examples 10 to 15 with Comparative Examples 2 to 6, it can be confirmed that the functional glass contains an optical functional layer that exhibits reverse wavelength dispersion as a whole in combination of the phase difference value and the slow axis angle of two phase difference layers (1 / 2 wavelength plate R1, 1 / 2 wavelength plate R2), and by using this functional glass, the range in which the generation of double images can be suppressed is relatively wide, and a HUD system with good visual confirmation can be provided.

[0160] (Industrial Applicability)

[0161] The head-up display system of the present invention can effectively suppress the occurrence of double images, so the most preferred viewing angle is applied to various windshield angles, thereby effectively suppressing the occurrence of double images in various types of vehicles. As a result, visual confirmation personnel can use the head-up display system without pressure in a wide range of viewing angles.

[0162] Description of Reference Numerals

[0163] 1 Observer

[0164] 2 Image display unit

[0165] 2A Light Source

[0166] 2B polarizing plate

[0167] 3 Reflector

[0168] 4 Functional glass

[0169] 5 light paths

[0170] 6 Display image

[0171] 10 Optical functional layer

[0172] 101 Phase Difference Layer

[0173] 102 Adhesive layer

[0174] 20 Optical laminate

[0175] 201 Intermediate film

[0176] 30 Functional glass

[0177] 301 glass plate.

Claims

1. A head-up display system comprising an image display unit for emitting display light representing a display image, and functional glass for projecting an image projected by the image display unit, The functional glass includes an optical functional layer showing reverse wavelength dispersion. The configuration angle α of the functional glass is not less than 20° and not more than 70°. Furthermore, with respect to the aforementioned functional glass, a reflected image is visually confirmed within a viewing angle range of Brewster angle β-(90°-angle α)±15°.

2. The head-up display system according to claim 1, wherein: The configuration angle α of the functional glass is not less than 25° and not more than 70°. With respect to the functional glass, a reflected image is visually confirmed within a viewing angle range of Brewster angle β-(90°-angle α)±10°.

3. The head-up display system according to claim 1 or 2, wherein: The optical functional layer includes at least one retardation layer.

4. The head-up display system according to claim 3, wherein: The optical function layer includes two phase difference layers, and the optical function layer as a whole exhibits reverse wavelength dispersion.

5. The head-up display system according to claim 3, wherein: The retardation layer has a retardation value of not less than 200 nm and not more than 350 nm.

6. The head-up display system according to claim 3, wherein: The optical functional layer comprises two phase difference layers. (i) one phase difference layer has a slow axis angle of +15° or more and +35° or more, and the other phase difference layer has a slow axis angle of -80° or more and -60° or less; or (ii) The slow axis angle of one phase difference layer is not less than -35° and not more than -15°, and the slow axis angle of another phase difference layer is not less than +60° and not more than +80°.

7. The head-up display system according to claim 3, wherein: The optical function layer includes two retardation layers, wherein the retardation value of the first retardation layer having a larger absolute value of the slow axis angle is larger than the retardation value of the second retardation layer having a smaller absolute value of the slow axis angle.

8. The head-up display system according to claim 3, wherein: The optical functional layer includes two phase difference layers, and each phase difference layer is a 1 / 2 wavelength plate.

9. The head-up display system according to claim 3, wherein: The optical functional layer includes two retardation layers, and the display light emitted from the image display unit is incident from the retardation layer side having a larger retardation value among the two retardation layers.

10. The head-up display system according to claim 1 or 2, wherein: The functional glass further includes an interlayer film.

11. The head-up display system according to claim 1 or 2, wherein: The functional glass includes a glass plate.

12. The head-up display system according to claim 1 or 2, wherein: The display light emitted by the aforementioned image display unit is S-polarized light or P-polarized light. 13 . An optical functional layer for a head-up display system, arranged in the head-up display system according to claim 1 or 2.

Images