Head-up display systems and transport aircraft

Abstract

Provided are a head-up display system and a transport equipped therewith, the head-up display system comprising: a windshield glass having a selective reflection layer; and a projector including laser light sources of three colors of blue light, green light, and red light for forming a projection image on the windshield glass. The selective reflection layer includes selective reflection central wavelengths λB, λG, and λR at a light incidence angle of 60°, 400 nm ≤ λB < 500 nm, 500 nm ≤ λG < 600 nm, 600 nm ≤ λR ≤ 700 nm, and all of XB / XG, XB / XR, and XG / XR fall within the range of 0.80-1.20.　In the above description, XB = RB×LB, XG = RG×LG, and XR = RR×LR.　RB, RG, and RR denote natural light reflectances at λB, λG, and λR, and LB, LG, and LR denote the luminances of blue, green, and red laser light emitted from the projector.

Description

[Technical Field]

[0001] This invention relates to a head-up display system and a transport aircraft. [Background technology]

[0002] Currently, there are known head-up displays or head-up display systems that project images onto the windshield glass of vehicles, providing drivers with various information such as maps, driving speed, and vehicle status. In a head-up display system, a virtual image containing the various information described above is projected onto the windshield glass and observed by the driver. The virtual image is positioned in front of the windshield, outside the vehicle. Typically, the virtual image is positioned more than 1000 mm in front of the windshield, and is located outside the windshield. This allows the driver to obtain the various information described above without significantly shifting their gaze while looking at the outside world in front of them. Therefore, it is expected that using a head-up display system will enable safer driving by allowing drivers to obtain various information.

[0003] In head-up display systems, a technique is known to use a curved vehicle windshield made of laminated glass with a wedge-shaped cross-section to reduce the double image caused by the reflection of projected light from both the front and back surfaces of the windshield glass. Furthermore, research is being conducted on techniques to reduce reflected light from the glass surface to near zero by using the Brewster angle so that P-polarized light is incident on the glass surface. For example, Patent Document 1 describes a windshield glass that includes a λ / 2 phase difference layer and four or more cholesteric liquid crystal reflective layers, each having a different center wavelength for selective reflection. According to Patent Document 1, by including a cholesteric liquid crystal layer having a center wavelength for selective reflection between 350 nm and 490 nm as one of the cholesteric liquid crystal reflective layers, it is possible to provide a windshield glass that appears transparent when viewed perpendicular to the windshield glass, and whose aesthetic appearance is not impaired even in ambient light. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-81296 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] In head-up displays incorporating a P-polarized reflective film into the windshield glass, in addition to legal regulations requiring a transmittance of 70% or more, it is also required that the display image appears transparent (white light appears white) from various angles, considering the clarity and aesthetic appeal of the displayed image. To achieve this, it is conceivable to use a laser with a narrow emission wavelength bandwidth as the light source for the imager, and to use a selective reflective layer with a narrow full width at half maximum and high reflectivity as the reflective layer of the P-polarized reflective film, as described in the embodiment of Patent Document 1. By using such an imager light source and selective reflective layer in combination, it is thought that the imager light can be reflected efficiently, and the brightness of the image (clarity of the displayed image) can be increased while maintaining high transmittance. However, after further investigation by the inventors, it has been found that with the windshield glass described in Patent Document 1, if the reflectivity is set to make the exterior color transparent, there is a problem in that the color of the displayed image (hereinafter referred to as "image color") becomes red.

[0006] The present invention provides a head-up display including a laser light source for forming a projection image and a windshield glass, a head-up display system with a neutral image color tone, and a transport vehicle equipped with this head-up display. The object is to solve this problem.

Means for Solving the Problem

[0007] As a result of intensive studies in view of the above problems, the inventors of the present invention have found that the above problems can be solved by controlling the balance between the reflectivities of blue light, green light, and red light of the selective reflection layer in the windshield glass and the emission intensities (luminances) of the three-color laser lights of blue light, green light, and red light in the laser light source so as to satisfy specific regulations, and thus have arrived at the present invention.

[0008] That is, the problems of the present invention have been solved by the following means. 〔1〕 A head-up display system having a windshield glass with a selective reflection layer and a projector including a laser light source for forming a projection image on this windshield glass, where the selective reflection layer includes three wavelengths of λ B , λ G and λ R as the selective reflection center wavelengths at an incident angle of light of 60°, 400 nm ≤ λ B < 500 nm 500 nm ≤ λ G < 600 nm 600 nm ≤ λ R ≤ 700 nm the laser light source emits three-color laser lights of blue light, green light, and red light, A head-up display system that satisfies all of the following regulations (a) to (c). Regulation (a) 0.80 ≤ X B / X G ≤ 1.20 Regulation (b) 0.80 ≤ X B / X R ≤ 1.20 Regulation (c) 0.80 ≤ XG / X R ≤1.20 In the above provisions, X B =R B ×L B X G =R G ×L G X R =R R ×L R That is the case. R B The λ of the selected reflection layer is B This shows the natural light reflectance at R G The λ of the selected reflection layer is G This shows the natural light reflectance at R R The λ of the selected reflection layer is R This shows the natural light reflectance at L. B L indicates the brightness of the blue laser light emitted from the above projector, G L indicates the brightness of the green laser light emitted from the above projector, R This indicates the brightness of the red laser light emitted from the above projector. [2] A head-up display system as described in [1] that satisfies all of the following requirements (a1) to (c1). Regulation (a1) 0.90 ≤ X B / X G ≤1.10 Regulation (b1) 0.90≦X B / X R ≤1.10 Regulation (c1) 0.90≦X G / X R ≤1.10 In the above provisions, X B , X G and X R The above X B , X G and X R It is synonymous with [the above]. [3] The above-mentioned natural light reflectance R of the selected reflective layer B , R G and R R However, R B >RG ≥R R A head-up display system according to [1] or [2] that satisfies the relationship. [4] The above-mentioned natural light reflectance R of the selected reflective layer B and R G However, R B / R G A head-up display system described in any one of [1] to [3] that satisfies the relationship ≥ 1.10. [5] The selective reflection center wavelength λ at an incident angle of light of 60° includes the above-mentioned selective reflection layer. B , λ G and λ R The full width at half maximum is 100 nm or less for all of them, and the above natural light reflectance R B , R G and R R A head-up display system described in any one of [1] to [4], wherein all of the above are 25% or more. [6] The head-up display system according to any one of [1] to [5], wherein the windshield glass includes at least one polarization conversion layer. [7] The head-up display system according to any one of [1] to [6], wherein the above-mentioned selective reflective layer is made of cholesteric liquid crystal. [8] The head-up display system according to any one of [1] to [5], wherein the above-mentioned selective reflective layer is formed by laminating an optically anisotropic layer and an optically isotropic layer. [9] A transport aircraft equipped with a head-up display system as described in any one of [1] to [8]. [Effects of the Invention]

[0009] The head-up display system of the present invention can project an image with neutral color tones. Therefore, in a transport vehicle equipped with the head-up display of the present invention, the head-up display can project an image with neutral color tones. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram illustrating an example of the head-up display system of the present invention. [Figure 2] This is a schematic diagram showing one example of the configuration of a windshield glass having a linearly polarized reflective film containing a cholesteric liquid crystal layer, used in the head-up display system of the present invention. [Figure 3] This is a schematic cross-sectional view showing one example of the configuration of a windshield glass having a linearly polarizing reflective film made of a dielectric multilayer film, used in the head-up display system of the present invention. [Figure 4] Figure 3 is a schematic diagram showing the relationship between the refractive index of a linearly polarizing reflective film when the windshield glass is viewed from the front. [Figure 5] This is a schematic diagram showing the arrangement of the windshield glass, liquid crystal panel, and luminance meter when evaluating the image color of the head-up display in the embodiment. [Figure 6] This is the natural light reflection spectrum of windshield glass No. 101, fabricated in the example, at an incident light angle of 5°. [Figure 7] This is the natural light reflection spectrum of windshield glass No. 101, fabricated in the example, at an incident light angle of 60°. [Modes for carrying out the invention]

[0011] In this invention, "~" is used to mean that the numerical values ​​written before and after it are included as the lower and upper limits. For example, when ε1 is between the numerical values ​​α1 and β1, the range of ε1 is the range that includes the numerical values ​​α1 and β1, and in mathematical notation, this is α1 ≤ ε1 ≤ β1. In this invention, the terms "angle" expressed as a specific numerical value such as 60°, and "parallel" and "perpendicular," unless otherwise specified, include an error range generally accepted in the technical field of this invention. For example, this means being within a range of less than ±10° from the exact angle, and the error from the exact angle is preferably 7° or less, and more preferably 5° or less.

[0012] In this invention, when we refer to "sense" in relation to circularly polarized light, we mean whether it is right-handed or left-handed circularly polarized. The sense of circularly polarized light is defined as follows: when light is viewed as if it were traveling towards the viewer, right-handed circular polarization occurs when the tip of the electric field vector rotates clockwise as time increases, and left-handed circular polarization occurs when it rotates counterclockwise.

[0013] In this invention, the term "sense" is sometimes used to refer to the twisting direction of the helix of a cholesteric liquid crystal. When the twisting direction (sense) of the helix of a cholesteric liquid crystal is to the right, it reflects right-circularly polarized light and transmits left-circularly polarized light. When the sense is to the left, it reflects left-circularly polarized light and transmits right-circularly polarized light.

[0014] In this invention, when the term "light" is used, unless otherwise specified, it refers to visible light and natural light (unpolarized). Visible light is electromagnetic radiation with wavelengths visible to the human eye, specifically light in the wavelength range of 380 to 780 nm. Invisible light is light with wavelengths less than 380 nm or greater than 780 nm. Furthermore, although not limited to these, visible light is defined as follows: light in the 420-490 nm wavelength range is blue light (B light), light in the 495-570 nm wavelength range is green light (G light), and light in the 620-750 nm wavelength range is red light (R light). In addition, although not limited to these, infrared light refers to the non-visible light range with wavelengths between 780 nm and 2000 nm.

[0015] In this invention, "visible light transmittance" refers to the visible light transmittance of a light source A as defined in JIS (Japanese Industrial Standards) R 3212:2015 (Test Methods for Automotive Safety Glass). Specifically, it is the transmittance obtained by measuring the transmittance at each wavelength in the range of 380 to 780 nm using a spectrophotometer with a light source A, and then multiplying the transmittance at each wavelength by a weighting coefficient obtained from the wavelength distribution and wavelength spacing of the CIE (International Commission on Illumination) standard relative luminous efficiency adapted to light, and taking a weighted average. Furthermore, when simply referring to "reflected light" or "transmitted light," it is used to include scattered light and diffracted light.

[0016] In this invention, p-polarization refers to polarization that vibrates in a direction parallel to the plane of incidence of light. The plane of incidence refers to a plane perpendicular to the reflective surface (such as the surface of a windshield glass) that contains both the incident and reflected light rays. In p-polarization, the plane of vibration of the electric field vector is parallel to the plane of incidence.

[0017] In this invention, the front phase difference is a value measured using an AxoScan manufactured by Axometrics. Unless otherwise specified, the measurement wavelength is 550 nm. The front phase difference can also be measured using a KOBRA21ADH or WR (manufactured by Oji Instruments Co., Ltd.) by incident light of a wavelength within the visible light range in the direction normal to the film. When selecting the measurement wavelength, the wavelength selective filter can be manually replaced, or the measured value can be converted using a program or the like.

[0018] In this invention, the birefringence (Δn) of the liquid crystal compound is a value measured according to the method described on page 214 of "Liquid Crystals: Fundamentals (edited by Mitsuji Okano and Shunsuke Kobayashi)". Specifically, Δn at 60°C can be determined by injecting the liquid crystal compound into a wedge-shaped cell, irradiating it with light of a wavelength of 550 nm, and measuring the refraction angle of the transmitted light.

[0019] In this invention, optical isotropy in the "optical isotropic layer" means that it does not exhibit birefringence. On the other hand, optical anisotropy in the "optical anisotropic layer" means that it exhibits birefringence, and in the optical anisotropic layer, as described later, the refractive index n in the slow axis direction in the plane e1and the refractive index n in the direction perpendicular to this slow phase axis direction in the plane (the phase-advancing phase axis direction in the plane) o2 That is, n e1 >n o2 They are in a relationship.

[0020] In this invention, "projection image" refers to an image based on the projection of light from the projector used. In the head-up display system (HUD system) of this invention, the projection image is perceived by the observer as a virtual image that appears to float in front of the smooth surface of the windshield glass. In this invention, "image (screen image)" means an image displayed on the projector's drawing device or an image drawn on an intermediate image screen or the like by the drawing device. Unlike a virtual image, an image is a real image. The images and projected images may be monochrome, multi-colored (two or more colors), or full-color.

[0021] Furthermore, in this invention, the term "liquid crystal compound" is used to include compounds that no longer exhibit liquid crystal properties due to curing reactions or the like.

[0022] The HUD system of the present invention is typically used when mounted on vehicles such as automobiles and trains, aircraft, and transport vehicles such as ships.

[0023] The head-up display system (hereinafter referred to as the HUD system) of the present invention will be described in detail below based on preferred embodiments illustrated in the attached drawings. Note that the dimensions and scale of parts in the drawings may differ from those of the actual parts for the sake of explanation. Also, the drawings may be schematic in order to facilitate understanding.

[0024] <<Head-Up Display System (HUD System)>> The HUD system of the present invention is a HUD system having a windshield glass with a selective reflection layer and a projector including a laser light source for forming a projection image on the windshield glass. As described later, in the HUD system of the present invention, the selective reflection layer has the following λ as the selective reflection center wavelength at an incident angle of light of 60°. B , λ G and λ R including three wavelengths of 400 nm ≤ λ B < 500 nm 500 nm ≤ λ G < 600 nm 600 nm ≤ λ R ≤ 700 nm The laser light source emits three-color laser lights of blue light, green light, and red light, which is a HUD system that satisfies all of the following regulations (a) to (c). Regulation (a) 0.80 ≤ X B / X G ≤ 1.20 Regulation (b) 0.80 ≤ X B / X R ≤ 1.20 Regulation (c) 0.80 ≤ X G / X R ≤ 1.20 In the above regulations, X B = R B × L B and X G = R G × L G and X R = R R × L R is. R B represents the natural light reflectance of the selective reflection layer at λ B , R G represents the natural light reflectance of the selective reflection layer at λ G , R R represents the natural light reflectance of the selective reflection layer at λ R . Also, L B represents the luminance of the blue laser light in the light emitted from the projector, L GL indicates the brightness of the green laser light emitted from the above projector, R This indicates the brightness of the red laser light emitted from the above projector.

[0025] The HUD system of the present invention has a selective reflective layer with a selective reflection center wavelength in a specific wavelength range. By controlling the product of the natural light reflectance at these selective reflection center wavelengths and the luminance of the laser light emitted from the projector so that all of the above conditions (a) to (c) are met, the balance of light intensity in the visible light range of the light reflected from the windshield glass can be adjusted, and the image color can be made neutral. In other words, when a white image is projected, a white image without any color tint can be projected. Furthermore, the laser light emitted from the projector passes through a medium (usually air) before entering the selective reflective layer of the windshield glass. This passage through the medium affects the brightness L of each color laser light. B , L G and L R It is thought that it will hardly be modulated.

[0026] Figure 1 shows an example of the HUD system of the present invention. The HUD system 20 of the present invention, shown in Figure 1, comprises a windshield glass 24 and a projector 22.

[0027] In the HUD system 20 illustrated in Figure 1, the projector 22 emits p-polarized light, and the reflective film 10 in the windshield glass 24 reflects the p-polarized light to display an image.

[0028] When the windshield glass 24A includes a linearly polarized reflective film 10A as shown in Figure 2, the linearly polarized reflective film 10A first converts the p-polarized projected light incident from the second glass plate 28 side into circularly polarized light via a polarization conversion layer 14. Next, the selective reflective layer 11 (cholesteric liquid crystal layer 12) selectively reflects this circularly polarized light and re-incidentates it to the polarization conversion layer 14. Furthermore, the polarization conversion layer 14 converts the circularly polarized light into p-polarized light. As a result, the linearly polarized reflective film 10A reflects the incident p-polarized projected light while maintaining its p-polarized state. Therefore, the polarization conversion layer 14 is configured to convert the incident p-polarized light into circularly polarized light in the direction of rotation reflected by the selective reflection layer 11 (cholesteric liquid crystal layer 12), according to the sense of circularly polarized light that the selective reflection layer 11 (cholesteric liquid crystal layer 12) selectively reflects. That is, if the selective reflection layer 11 selectively reflects right-handed circularly polarized light, the polarization conversion layer 14 is configured to convert the incident p-polarized light into right-handed circularly polarized light. Conversely, if the selective reflection layer 11 selectively reflects left-handed circularly polarized light, the polarization conversion layer 14 is configured to convert the incident p-polarized light into left-handed circularly polarized light.

[0029] When the windshield glass 24 includes a linearly polarized reflective film 10B as shown in Figure 3, the linearly polarized reflective film 10B selectively reflects the p-polarized projected light incident from the second glass plate 28 side while retaining its p-polarization.

[0030] In the HUD system 20, it is preferable that the projector 22 projects p-polarized light onto the second glass plate 28 of the windshield glass 24. By using p-polarized light projected by the projector 22 onto the windshield glass 24, reflection of the projected light by the first glass plate 30 and the second glass plate 28 of the windshield glass 24 can be significantly reduced, thereby suppressing problems such as the observation of double images. Preferably, the projector 22 projects p-polarized light onto the windshield glass 24 at a Brewster angle. This eliminates reflection of the projected light from the first glass plate 30 and the second glass plate 28, enabling the display of a clearer image.

[0031] <Windshield glass> In Figure 1, the windshield glass 24 is a windshield glass having a first glass plate 30, a reflective film 10 including a selective reflective layer, and a second glass plate 28 in that order.

[0032] Windshield glass refers to the windows and windshields of vehicles such as cars and trains, airplanes, ships, motorcycles, and amusement rides. Windshield glass is preferably used as the front windshield and windshield located in the direction of travel of the vehicle.

[0033] The windshield glass 24A shown in Figure 2 comprises, in this order, a second glass plate 28, an interlayer 36, a linearly polarizing reflective film 10A, a heat seal layer 38, and a first glass plate 30. In Figure 2, the linear polarizing reflective film 10A is arranged such that the polarization conversion layer 14 is on the second glass plate 28 side and the phase difference layer 16 (transparent substrate 18) is on the first glass plate 30 side. The windshield glass 24B shown in Figure 3 comprises, in this order, a second glass plate 28, an interlayer 36, a linearly polarizing reflective film 10B, another interlayer 36, and a first glass plate 30.

[0034] When the above-mentioned windshield glass is used in a vehicle, curved glass is often used for the second glass plate 28 and the first glass plate 30. In that case, if the second glass plate 28 is on the inside of the vehicle and the first glass plate 30 is on the outside of the vehicle, the second glass plate 28 is positioned with its convex side facing the first glass plate 30, and the first glass plate 30 is positioned with its concave side facing the second glass plate 28.

[0035] When the second glass plate 28 and the first glass plate 30 are curved glass, in the example shown in Figure 2, the polarization conversion layer 14 and the selective reflection layer 11 are arranged in that order from the convex side of the second glass plate 28 toward the first glass plate 30. The phase difference layer 16 is also arranged between the selective reflection layer 11 and the first glass plate 30.

[0036] From a legal regulatory standpoint, the visible light transmittance of the windshield glass is preferably 70% or higher, more preferably over 70%, even more preferably 75% or higher, and particularly preferably 80% or higher. The above-mentioned visible light transmittance is preferably satisfied at any position on the windshield glass, and is particularly preferably satisfied at the position where the reflective film is present. As described later, the reflective film can increase the visible light transmittance, and the above-mentioned visible light transmittance can be satisfied regardless of which type of glass commonly used for windshield glass is used.

[0037] Figures 6 and 7 show examples of natural light reflection spectra of windshield glass. These examples are for windshield glass No. 101 in the embodiment, with the angle of incidence of light set to 5° or 60°, respectively. As shown in Figures 6 and 7, the reflective film containing the selective reflective layer used in the present invention retains a reflection peak originating from the selective reflective layer even when sandwiched between thick glass.

[0038] There are no restrictions on the shape of the windshield glass; it is determined appropriately depending on the object in which the windshield glass is installed. The windshield glass may be, for example, flat, or it may have a three-dimensional shape with curved surfaces such as concave or convex. For windshield glass molded for applicable vehicles, the sides that are normally facing upwards, the observer side, the driver side, and the viewer side (such as the inside of the vehicle) can be specified.

[0039] In the case of windshield glass, the reflective film only needs to be provided on the projected image display area (projected image reflective area) of the windshield glass. Furthermore, in the case of windshield glass, the reflective film may be provided between the glass panes of the laminated glass windshield, or it may be provided on the outer surface of the glass pane of the windshield glass.

[0040] When a reflective film including a selective reflective layer used in the present invention is provided on the outer surface of a windshield glass plate, the reflective film may be provided inside the vehicle (on the incident side of the projected image) or on the outside, but it is preferable that it be provided inside. Furthermore, the reflective film containing the selective reflective layer used in the present invention has lower scratch resistance compared to a glass plate. Therefore, when the windshield glass has a laminated glass structure, it is more preferable to place the reflective film between the two glass sheets that make up the laminated glass in order to protect the reflective film.

[0041] As described above, a reflective film is a component that displays a projected image by reflecting the projected image. Therefore, the reflective film should be placed in a position where the projected image projected from a projector or the like can be displayed in a visible manner. In other words, the reflective film including the selective reflective layer used in the present invention functions as a combiner in a HUD system. In a HUD system, a combiner is an optical component that can display an image projected from a projector in a visible manner, and when the combiner is observed from the incident surface side of the projected image, it can simultaneously observe information on the opposite side of the incident surface of the projected light, such as a landscape. In other words, the combiner functions as an optical path combiner that displays the ambient light and the light of the projected image in superimposed form.

[0042] The reflective film may be provided over the entire surface of the windshield glass, or it may be provided on a part of the surface of the windshield glass, but it is preferable that it is provided on a part. When a reflective film is provided on a part of the windshield glass, the reflective film may be provided at any position on the windshield glass. However, when used as a HUD system, it is preferably provided so that a virtual image is shown at a position easily visible to an observer such as a driver. For example, the position where the reflective film is provided on the windshield glass may be determined from the relationship between the position of the driver's seat in a vehicle equipped with a HUD system and the position where the projector is installed. The reflective film may be planar without a curved surface or may have a curved surface. Further, the reflective film may have a concave or convex shape as a whole and may be configured to enlarge or reduce a projected image for display.

[0043] [1] Reflective film The reflective film 10, as a selective reflection layer, has, as the selective reflection center wavelengths at an incident angle of light of 60°, the λ B , λ G and λ R including three wavelengths, and is not particularly limited as long as it includes a selective reflection layer that can satisfy all of the following prescribed (a) to (c) with respect to each color laser light in the laser light source.

[0044] 〔Selective reflection layer〕 The windshield glass used in the HUD system of the present invention has the following selective reflection layer. That is, the above selective reflection layer has, as the selective reflection center wavelengths at an incident angle of light of 60°, the following λ B , λ G and λ R including three wavelengths, 400 nm ≤ λ B < 500 nm 500 nm ≤ λ G < 600 nm 600 nm ≤ λ R ≤ 700 nm The following prescribed (a) to (c) are all satisfied with respect to the three-color laser lights of blue light, green light, and red light emitted from the projector used in the HUD system of the present invention. Prescribed (a) 0.80 ≤ XB / X G ≤1.20 Regulation (b) 0.80≦X B / X R ≤1.20 Regulation (c) 0.80≦X G / X R ≤1.20 In the above provisions, X B =R B ×L B X G =R G ×L G X R =R R ×L R That is the case. R B The λ of the selected reflection layer is B This shows the natural light reflectance at R G The λ of the selected reflection layer is the λ of the above selected reflection layer. G This shows the natural light reflectance at R R The λ of the selected reflection layer is R This shows the natural light reflectance at L. B L indicates the brightness of the blue laser light emitted from the above projector, G L indicates the brightness of the green laser light emitted from the above projector, R This indicates the brightness of the red laser light emitted from the above projector. Note that the above natural light reflectance R B , R G and R R The unit of measurement, and the brightness L of each color laser light emitted from the above projector. B , L G and L R The unit is X as specified in regulations (a) to (c). B , X G and X R It is sufficient if the ratio of two of these is correctly determined and unified. From here on, the above natural light reflectance R B , R G and R R The unit is %, and the brightness L of each color laser light emitted from the above projector is B , LG and L R The unit is cd / m 2 It will be described as follows.

[0045] In the present invention, the selective reflection center wavelength of the selective reflection layer and the full width at half maximum of the reflection peak having this selective reflection center wavelength are determined as follows. As detailed in the embodiments described later, when the reflection spectrum is measured at a desired (e.g., 60°) angle of incident light relative to the normal direction of the selective reflection layer using a spectrophotometer (JASCO Corporation, V-670), a maximum reflectance peak is observed in the selective reflection band. Of the two wavelengths that result in the midpoint (average) reflectance between the maximum reflectance of this peak and the minimum reflectance at the tail of the maximum peak, the value of the shorter wavelength is λ. l (nm), the wavelength value on the longer wavelength side is λ h If (nm), the selective reflection center wavelength λ and its half-width Δλ can be expressed by the following equations. λ=(λ l +λ h ) / 2 Δλ=(λ h -λ l ) As described above, the selective reflection center wavelength obtained is approximately the same as the wavelength at the centroid of the reflection peak of the circularly polarized reflection spectrum measured at a desired angle of incident light relative to the normal direction of the selective reflection layer, when the selective reflection layer is made of cholesteric liquid crystal. Furthermore, in the present invention, the natural light reflectance at the selective reflection center wavelength of the selective reflection layer is also determined by the method described in the examples below. The reflection spectrum of the selective reflective layer was measured in the state of the windshield glass including the selective reflective layer, as described in the examples below.

[0046] In this invention, the brightness L of the blue laser light emitted from the projector B The brightness L of the green laser light emitted from the projector G , and the brightness L of the red laser light emitted from the projector. RThese terms all refer to the brightness of the blue laser light, the brightness of the green laser light, and the brightness of the red laser light, respectively, in the light emitted from the projector. For example, if the projector's drawing device does not have a laser brightness modulation means, the brightness of each color laser light in the laser light source is the brightness L of the laser light emitted from the projector. B , L G and L R On the other hand, if the projector's drawing device is equipped with a laser brightness modulation means such as an external modulator, the brightness of each color laser light after the brightness of the laser light in the laser light source has been modulated by the laser brightness modulation means will be the same as the brightness of the laser light in the light emitted from the projector L. B , L G and L R This is the result. Below, L B , L G and L R Simply the brightness L of the laser light B , L G and L R It is also called by this name. The brightness L of the blue, green, and red laser light mentioned above B , L G and L R This is the natural light reflectance R of the selective reflective layer. B , R G and R R The above provisions (a) to (c) will be adjusted as appropriate between them. The brightness L of the laser light mentioned above B , L G and L R In bright environments such as daytime, it has high brightness (for example, 10,000 cd / m²). 2 (To a certain extent), and in dark environments such as at night, low brightness (for example, 3 cd / m²) 2 You can adjust the setting appropriately according to the environment, such as to the degree of 1-30,000 cd / m². 2 Preferably, 2 to 20,000 cd / m² 2 This is preferable. In this invention, the brightness L of the above-mentioned laser light B , L G and LR This value is measured using a luminance meter (for example, a luminance meter BM-5A (product name) manufactured by Topcon Corporation) to determine the output light of each laser emitted from the projector.

[0047] The selected reflection center wavelength λ at an incident angle of 60° of light, as described above. B , λ G and λ R This is appropriately adjusted in relation to the wavelength of the laser light source used to satisfy all of the above requirements (a) to (c). Furthermore, in relation to commonly used blue, green, and red laser light, λ B The wavelength is preferably in the range of 430 to 470 nm, and more preferably in the range of 440 to 460 nm, λ G The wavelength is preferably in the range of 500 to 550 nm, and more preferably in the range of 510 to 540 nm, λ R The wavelength is preferably in the range of 600 to 650 nm, and more preferably in the range of 610 to 640 nm.

[0048] From the viewpoint of making the image color tone more neutral and improving it, the above provisions (a) to (c) are preferably the following provisions (a1) to (c1). Regulation (a1) 0.90 ≤ X B / X G ≤1.10 Regulation (b1) 0.90≦X B / X R ≤1.10 Regulation (c1) 0.90≦X G / X R ≤1.10 In the above provisions, X B , X G and X R The above X B , X G and X R It is synonymous with [the above]. Furthermore, X in the above provisions (a1) to (c1) B / X G , X B / X R , and, XG / X R The upper limit is preferably 1.05 or less, more preferably 1.03 or less, and even more preferably 1.00 or less.

[0049] The above-mentioned natural light reflectance R of the selected reflective layer B , R G and R R From the perspective of making the reflected color at an incident angle of 60° closer to white and further improving transparency, R B >R G ≥R R It is preferable that the relationship is satisfied. Furthermore, the above-mentioned natural light reflectance R of the selected reflective layer B and R G From the perspective of making the reflected color at an incident angle of 5° closer to white and improving transparency, R B / R G It is preferable that the relationship ≥ 1.10 is satisfied. Note, R B / R G There is no particular upper limit to R, but 1.30 or less is practical. G / R R While there are no particular restrictions, a range of 0.90 to 1.10 is practical, and 1.00 to 1.10 is preferable.

[0050] As mentioned above, in-vehicle head-up display systems require transparency that exceeds legal requirements and a transparent appearance from various angles for aesthetic reasons. To maintain the legally mandated 70% or higher transparency and make the appearance as close to transparent (white) as possible, conventional methods involved reducing reflectivity. However, reducing reflectivity too much reduces the brightness of the displayed image (projected image), resulting in poor visibility.

[0051] In this invention, since a laser light source with a narrow emission wavelength band is used, the selective reflection layer includes a selective reflection center wavelength λ at an incident angle of light of 60°, which allows for efficient reflection of imager light and high transmittance while maintaining high image brightness (sharpness of the displayed image). B , λ G and λR The full width at half maximum of each is 100 nm or less, and the above natural light reflectance R B , R G and R R It is preferable that each of these amounts is 25% or more. In a windshield glass in which a reflective film having a selective reflective layer is sandwiched between green glass, with the full width at half maximum of the selective reflection center wavelength set to 100 nm or less and a natural light reflectance of 25% or more, the natural light transmittance can be set to 70% or more (80% or more with clear glass sandwiching).

[0052] From the perspective of improving the reflective color while increasing transmittance, the λ of the selective reflective layer B Natural light reflectance R B , λ G Natural light reflectance R G and λ R Natural light reflectance R R In both cases, 25-60% is preferred, and 30-50% is more preferred. As shown in Figure 6 as an example, the natural light reflectance of the selective reflective layer used in the present invention at an incident light angle of 5° can all be kept below 50%.

[0053] From the perspective of improving the reflected color while increasing transmittance, the selective reflection center wavelength λ at an incident angle of light of 60° is considered. B The full width at half maximum is preferably 10 to 100 nm, and more preferably 15 to 40 nm. Similarly, from the viewpoint of improving the reflected color while increasing transmittance, the selective reflection center wavelength λ at an incident angle of light of 60° is considered. G The full width at half maximum is preferably 10 to 100 nm, and more preferably 15 to 55 nm. Similarly, from the viewpoint of improving the reflected color while increasing transmittance, the selective reflection center wavelength λ at an incident angle of light of 60° is considered. R The full width at half maximum is preferably 10 to 100 nm, and more preferably 15 to 55 nm.

[0054] Furthermore, if the selective reflection layer has a layer (for example, the cholesteric liquid crystal UV layer described later) whose selective reflection center wavelength at an incident angle of 60° of light is between 300 nm and 400 nm, then the selective reflection center wavelength of this layer at an incident angle of 60° of light is λ UV The wavelength is preferably 330-395 nm, and more preferably 350-390 nm. Also, the λ of the selective reflection layer UV Natural light reflectance R UV The selective reflection center wavelength λ at an incident angle of light of 60° UV The full width at half maximum is preferably 10 to 100 nm, and more preferably 15 to 40 nm.

[0055] Examples of reflective films including the selective reflective layer described above include a linearly polarized reflective film including a cholesteric liquid crystal layer having the function of reflecting circularly polarized light, and a linearly polarized reflective film including a selective reflective layer (hereinafter also referred to as a "dielectric multilayer film") having the function of reflecting linearly polarized light, which is formed by laminating an optically anisotropic layer and an optically isotropic layer. The linearly polarized reflective films will be described below, based on the linearly polarized reflective film 10A in the windshield glass 24A shown in Figure 2, and the linearly polarized reflective film 10B in the windshield glass 24B shown in Figure 3. The cholesteric liquid crystal layer and dielectric multilayer film will be described separately in the descriptions of each linearly polarized reflective film.

[0056] [1-1] Linear polarized reflective film containing a cholesteric liquid crystal layer Figure 2 is a schematic diagram showing an example of a windshield glass 24 used in the present invention, and the linearly polarized reflective film 10A contained in this windshield glass 24 has a polarization conversion layer 14, a selective reflective layer 11, a phase difference layer 16, and a transparent substrate 18 in this order.

[0057] The selective reflection layer 11 includes three cholesteric liquid crystal layers (12R, 12G, 12B). The three cholesteric liquid crystal layers have different selective reflection center wavelengths at an incident angle of 60° of light, and each has a selective reflection center wavelength λ at an incident angle of 60° of light, as described later. B A cholesteric liquid crystal layer 12B having the following characteristics, and the selective reflection center wavelength λ at an incident angle of light of 60° (described later). G A cholesteric liquid crystal layer 12G having the following, and the selective reflection center wavelength λ at an incident angle of light of 60° (described later). R This corresponds to the cholesteric liquid crystal layer 12R having the following properties. In the illustrated example, the cholesteric liquid crystal layer 12R, cholesteric liquid crystal layer 12G, and cholesteric liquid crystal layer 12B are present in this order. In the illustrated example, each cholesteric liquid crystal layer is in direct contact with any of the other cholesteric liquid crystal layers.

[0058] Although not shown in Figure 2, it is also preferable from the viewpoint of suppressing reflected color to include, in addition to the three cholesteric liquid crystal layers (12R, 12G, 12B) described above, a cholesteric liquid crystal layer having a selective reflection center wavelength of 300 nm or more and less than 400 nm at an incident angle of light of 60° (hereinafter referred to as the cholesteric liquid crystal layer UV). By providing a cholesteric liquid crystal UV layer, when the windshield glass is configured to include the cholesteric liquid crystal layer and phase difference layer described later, the color (especially yellowish) observed when the windshield glass is viewed under ambient light can be suppressed.

[0059] As is well known, a cholesteric liquid crystal layer is a layer in which a liquid crystal compound is fixed in the orientation of a helical structure of the cholesteric liquid crystal phase. It reflects light at a selective reflection center wavelength corresponding to the pitch of the helical structure and transmits light in other wavelength ranges. Furthermore, a cholesteric liquid crystal layer exhibits selective reflectivity for either left- or right-handed circularly polarized light at specific wavelengths.

[0060] In a selective reflective layer having a cholesteric liquid crystal layer, the reflected wavelength and reflectivity can be adjusted by the selective reflection center wavelength and thickness (number of helical pitches) of the cholesteric liquid crystal layer.

[0061] Here, as shown in Figure 2, it is preferable that each cholesteric liquid crystal layer is in direct contact with any other cholesteric liquid crystal layer. For example, in the example shown in Figure 2, the selective reflection center wavelength λ at an incident angle of light of 60° R A cholesteric liquid crystal layer 12R having a selective reflection center wavelength λ at an incident angle of light of 60° G The cholesteric liquid crystal layer 12G having the following properties is in contact with each other, and the selective reflection center wavelength λ at an incident angle of light of 60° is also present. G A cholesteric liquid crystal layer 12G having a selective reflection center wavelength λ at an incident angle of light of 60° B A cholesteric liquid crystal layer 12B having the above properties is in contact with each other.

[0062] When cholesteric liquid crystal layers are spaced apart, the interlayer thickness increases, making it difficult to obtain the interference effect of light reflected by each cholesteric liquid crystal layer. In contrast, by configuring the cholesteric liquid crystal layers to be in contact with each other, the wavelength bandwidth can be narrowed by the interference effect of light reflected by each cholesteric liquid crystal layer. In particular, when the thickness of each cholesteric liquid crystal layer is thinner than the wavelength of light (visible light 380nm to 780nm), the interference effect becomes even more pronounced.

[0063] In this invention, the cholesteric liquid crystal layers are not limited to being in direct contact with each other, but may be laminated via an adhesive layer or the like.

[0064] Here, each cholesteric liquid crystal layer has the aforementioned λ as its selective reflection center wavelength at an incident angle of light of 60°. B , λ G and λ RIt is sufficient if the cholesteric liquid crystal layer has at least one selective reflection center wavelength among the three wavelengths, but it is also acceptable if at least one layer of the cholesteric liquid crystal layer has two or more selective reflection center wavelengths. A cholesteric liquid crystal layer having two or more selective reflection center wavelengths is achieved by a helical structure in which the helical pitch changes in the thickness direction.

[0065] Furthermore, although the illustrated example shows the selective reflection layer 11 having three cholesteric liquid crystal layers with different selective reflection center wavelengths, it is not limited to this configuration. The selective reflection layer 11 may have one cholesteric liquid crystal layer, or it may have two or four or more cholesteric liquid crystal layers.

[0066] From the viewpoint of exhibiting high transmittance while showing sufficient natural light reflectance due to the selective reflective layer 11, the total thickness of the selective reflective layer 11 is preferably 0.5 to 30 μm, and more preferably 1 to 15 μm.

[0067] Here, it is preferable that the reflective film reflects linearly polarized light. When the reflective film is incorporated into the windshield glass and used as a combiner for a head-up display, it is preferable that the projected image light is p-polarized, i.e., linearly polarized, in order to suppress reflection on the surface of the windshield glass. In a linearly polarized reflective film as shown in Figure 2, the selective reflective layer, which consists of a cholesteric liquid crystal layer, reflects circularly polarized light. Therefore, in a linearly polarized reflective film, it is preferable to have a layer that converts linearly polarized light incident on the reflective film into circularly polarized light. Examples of layers that convert the polarization state of light include a polarization conversion layer and a phase difference layer.

[0068] The polarization conversion layer exhibits optical rotation and birefringence with respect to visible light, and converts the polarization state of incident light. In this invention, the polarization conversion layer consists of a layer of birefringent material, such as a liquid crystal compound, oriented with a twist of 360° or less. A phase difference layer alters the state of incident polarization by introducing a phase difference (optical path difference) between two orthogonal polarization components. In this invention, the phase difference layer is a layer in which birefringent materials such as liquid crystal compounds are arranged in the same direction, and does not possess optical activity.

[0069] The above-mentioned reflective film can be configured such that the light-entering side of the selective reflective layer has a polarization conversion layer or a phase difference layer, thereby converting the linearly polarized light incident on the reflective film into circularly polarized light, the selective reflective layer reflecting the circularly polarized light, and the polarization conversion layer or phase difference layer converting the reflected circularly polarized light back into linearly polarized light before emission.

[0070] In the example of the windshield glass shown in Figure 2, the reflective film 10 has a polarization conversion layer 14 on one side of the selective reflective layer 11 and a phase difference layer 16 on the other side, with the polarization conversion layer 14 on the side of the second glass plate 28 which is the inside of the vehicle, and the phase difference layer 16 on the side of the first glass plate 30 which is the outside of the vehicle.

[0071] In this case, the polarization conversion layer 14 has the function of converting the projected p-polarized light (linearly polarized light) into circularly polarized light that is reflected by the cholesteric liquid crystal layer of the selective reflection layer 11. On the other hand, the phase difference layer 16 has an optical compensation function for light incident from the outside of the windshield glass. For example, when s-polarized light incident from the outside of the windshield glass passes through the polarization conversion layer 14, its polarization state changes, and a p-polarized component becomes mixed in. Since polarized sunglasses cut out s-polarized light, this p-polarized component passes through the polarized sunglasses. As a result, the function of polarized sunglasses in cutting out glare from reflected light, which is mainly composed of s-polarized light, is impaired, causing problems that interfere with driving. In contrast, by having a configuration with a phase difference layer 16 and providing optical compensation with the phase difference layer 16, the suitability of polarized sunglasses can be improved.

[0072] In the example shown in Figure 2, the reflective film 10 is configured such that the polarization conversion layer 14 is on the side of the second glass plate 28 facing the interior of the vehicle, and the phase difference layer 16 is on the side of the first glass plate 30 facing the exterior of the vehicle. However, the configuration is not limited to this. The reflective film 10 may also be configured such that the polarization conversion layer 14 is on the side of the first glass plate 30 facing the exterior of the vehicle, and the phase difference layer 16 is on the side of the second glass plate 28 facing the interior of the vehicle.

[0073] In this case, the phase difference layer 16 has the function of converting the projected p-polarized light (linearly polarized light) into circularly polarized light that is reflected by the cholesteric liquid crystal layer of the selective reflection layer 11. On the other hand, the polarization conversion layer 14 has an optical compensation function for light incident from the outside of the windshield glass, and by performing optical compensation with the polarization conversion layer 14, the suitability for polarized sunglasses can be improved.

[0074] Furthermore, the reflective film may have a polarization conversion layer on both sides of the selective reflective layer 11, or it may have a phase difference layer on both sides. In this case, the polarization conversion layer or phase difference layer placed on the inside of the vehicle should be configured to have the function of converting the projected p-polarized light (linearly polarized light) into circularly polarized light that is reflected by the cholesteric liquid crystal layer of the selective reflection layer 11. On the other hand, the polarization conversion layer or phase difference layer located on the outside of the vehicle may be configured to have an optical compensation function for light incident from the outside of the windshield glass. The polarization conversion layer and phase difference layer will be described in detail later.

[0075] The following describes in detail the cholesteric liquid crystal layer, polarization conversion layer, phase difference layer, and transparent substrate, which are components of the linearly polarized reflective film including the cholesteric liquid crystal layer described above.

[0076] [Cholesteric liquid crystal layer] The cholesteric liquid crystal layer has the aforementioned λ as its selective reflection center wavelength at an incident light angle of 60°. B , λ G and λ RThe cholesteric liquid crystal layer is not particularly limited as long as it contains the three wavelengths and satisfies all of the above-mentioned requirements (a) to (c) in relation to each color laser light from the laser light source. In the present invention, the cholesteric liquid crystal layer refers to a layer in which a cholesteric liquid crystal phase is fixed. A cholesteric liquid crystal layer is a layer in which the orientation of the liquid crystal compound in the cholesteric liquid crystal phase is maintained. Typically, a cholesteric liquid crystal layer is formed by polymerizing and curing a polymerizable liquid crystal compound in the orientation of the cholesteric liquid crystal phase by ultraviolet irradiation and heating, thereby forming a non-fluid layer that simultaneously changes in orientation to a state that does not change due to external fields or external forces. In addition, it is sufficient that the optical properties of the cholesteric liquid crystal phase are maintained within the layer, and the liquid crystal compound in the layer does not need to exhibit liquid crystalline properties anymore. For example, a polymerizable liquid crystal compound may have its molecular weight increased by the curing reaction and may no longer have liquid crystalline properties.

[0077] Cholesteric liquid crystal phases are known to exhibit selective circular polarization reflection, which selectively reflects circularly polarized light of either right-circularly polarized or left-circularly polarized light, while transmitting circularly polarized light of the other sense. Many films formed from compositions containing polymerizable liquid crystal compounds have been conventionally known as films containing a layer on which a cholesteric liquid crystal phase exhibiting selective circular polarization reflectivity is fixed, and prior art can be referenced for the cholesteric liquid crystal layer.

[0078] The center wavelength λ of selective reflection in a cholesteric liquid crystal layer at an incident light angle of 5° depends on the pitch P (=period of the helix) of the helical structure (helical orientation structure) in the cholesteric liquid crystal phase, and follows the relationship n = n × P with respect to the average refractive index of the cholesteric liquid crystal layer. As can be seen from this equation, the center wavelength of selective reflection can be adjusted by adjusting the n value and / or the P value. The pitch P of a helical structure (one helical pitch) is, in other words, the length in the helical axis direction for one turn of the helix, that is, the length in the helical axis direction for a 360° rotation of the director (long axis direction in the case of a rod-shaped liquid crystal) of the liquid crystal compound constituting the cholesteric liquid crystal phase. The helical axis direction of a typical cholesteric liquid crystal layer coincides with the thickness direction of the cholesteric liquid crystal layer.

[0079] In the aforementioned head-up display system, by using it so that light is incident on the windshield glass at an oblique angle, the reflectivity on the surface of the glass plate on the side where the projected light is incident can be reduced. At this time, light also incident obliquely on the cholesteric liquid crystal layer constituting the selective reflective layer 11 of the reflective film 10. For example, light incident on the reflective film 10 at an angle of 45° to 70° relative to the normal in air with a refractive index of 1 will pass through the cholesteric liquid crystal layer with a refractive index of approximately 1.61 at an angle of approximately 26° to 36°. In this case, the reflected wavelength shifts to the shorter wavelength side. In a cholesteric liquid crystal layer where the selective reflection center wavelength for light with an incident angle of 5° is wavelength λ, when the light ray passes through the cholesteric liquid crystal layer at an angle θ² with respect to the normal direction of the cholesteric liquid crystal layer (the direction of the helical axis of the cholesteric liquid crystal layer), the selective reflection center wavelength λd is expressed by the following equation. λd = λ × cosθ²

[0080] Therefore, for example, a cholesteric liquid crystal layer having a central wavelength λ of selective reflection in the range of 650 to 780 nm can reflect projected light in the range of 520 to 695 nm when θ2 is 26° to 36°. Because this wavelength range is a wavelength range with high visual sensitivity, it contributes significantly to the brightness of the projected image, resulting in the achievement of a high-brightness projected image.

[0081] The helical pitch of the cholesteric liquid crystal phase depends on the type of chiral agent used with the polymerizable liquid crystal compound and its concentration; therefore, the desired pitch can be obtained by adjusting these factors. For methods of measuring the helical sense and pitch, the methods described in "Introduction to Liquid Crystal Chemistry Experiments" edited by the Japanese Liquid Crystal Society, Sigma Publishing, 2007, p. 46, and "Liquid Crystal Handbook" edited by the Liquid Crystal Handbook Editorial Committee, Maruzen, p. 196, can be used.

[0082] Each cholesteric liquid crystal layer used is one in which the helical sense is either right-handed or left-handed. The sense of circularly polarized light reflected by the cholesteric liquid crystal layer (the direction of rotation of the circularly polarized light) coincides with the helical sense. When there are multiple cholesteric liquid crystal layers with different selective reflection center wavelengths, the helical senses of each cholesteric liquid crystal layer may all be the same, or they may include different ones. However, it is preferable that the multiple cholesteric liquid crystal layers all have the same helical sense.

[0083] Furthermore, if the reflective film 10 has multiple cholesteric liquid crystal layers as the selective reflective layer 11, it is preferable not to include cholesteric liquid crystal layers with different helical senses as cholesteric liquid crystal layers that exhibit selective reflection in the same or overlapping wavelength ranges. This is to avoid the transmittance in a specific wavelength range decreasing to, for example, less than 50%.

[0084] The half-width Δλ (nm) of the selective reflection band exhibiting selective reflection depends on the birefringence Δn of the liquid crystal compound and the pitch P described above, following the relationship Δλ = Δn × P. Therefore, the width of the selective reflection band can be controlled by adjusting Δn. Δn can be adjusted by changing the type or mixing ratio of the polymerizable liquid crystal compound, or by controlling the temperature during orientation fixation. To form a single type of cholesteric liquid crystal layer with the same central wavelength for selective reflection, multiple cholesteric liquid crystal layers with the same pitch P and the same helical sense may be stacked. By stacking cholesteric liquid crystal layers with the same pitch P and the same helical sense, circular polarization selectivity can be increased at a specific wavelength.

[0085] When stacking multiple cholesteric liquid crystal layers in the selective reflective layer 11, the separately prepared cholesteric liquid crystal layers may be stacked using an adhesive or the like, or a liquid crystal composition containing a polymerizable liquid crystal compound or the like may be directly applied to the surface of the cholesteric liquid crystal layer formed by the method described later, and the orientation and fixing steps may be repeated, the latter being preferred. This is because forming the next cholesteric liquid crystal layer directly on the surface of the previously formed cholesteric liquid crystal layer causes the orientation of the liquid crystal molecules on the air interface side of the previously formed cholesteric liquid crystal layer to match the orientation of the liquid crystal molecules on the underside of the cholesteric liquid crystal layer formed on top of it, resulting in good polarization characteristics of the cholesteric liquid crystal layer laminate. Furthermore, interference irregularities that may arise from thickness variations in the adhesive layer are not observed.

[0086] The thickness of the cholesteric liquid crystal layer is preferably 0.2 to 10 μm, more preferably 0.3 to 8 μm, and even more preferably 0.4 to 5 μm.

[0087] (Method for fabricating a cholesteric liquid crystal layer) The following describes the materials and methods for fabricating the cholesteric liquid crystal layer. Materials used to form the cholesteric liquid crystal layer described above include liquid crystal compositions containing polymerizable liquid crystal compounds and chiral agents (optically active compounds). If necessary, the above-mentioned liquid crystal composition, which has been mixed with a surfactant and a polymerization initiator and dissolved in a solvent, can be applied to a support, an alignment layer, or a lower cholesteric liquid crystal layer. After cholesteric alignment maturation, the liquid crystal composition can be fixed by curing to form the cholesteric liquid crystal layer.

[0088] (Polymerizable liquid crystal compound) The polymerizable liquid crystal compound may be a rod-shaped liquid crystal compound or a disc-shaped liquid crystal compound, but a rod-shaped liquid crystal compound is preferred. Examples of rod-shaped polymerizable liquid crystal compounds that form a cholesteric liquid crystal layer include rod-shaped nematic liquid crystal compounds. Preferred rod-shaped nematic liquid crystal compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyanosubstituted phenylpyrimidines, alkoxysubstituted phenylpyrimidines, phenyldioxanes, trans, and alkenylcyclohexylbenzonitriles. Not only low molecular weight liquid crystal compounds but also high molecular weight liquid crystal compounds can be used.

[0089] Polymerizable liquid crystal compounds are obtained by introducing polymerizable groups into liquid crystal compounds. Examples of polymerizable groups include unsaturated polymerizable groups, epoxy groups, and aziridinyl groups, with unsaturated polymerizable groups being preferred and ethylenically unsaturated polymerizable groups being particularly preferred. Polymerizable groups can be introduced into the molecules of liquid crystal compounds by various methods. The number of polymerizable groups in a polymerizable liquid crystal compound is preferably 1 to 6 per molecule, more preferably 1 to 3. Examples of polymerizable liquid crystal compounds include compounds described in Makromol. Chem., Vol. 190, p. 2255 (1989), Advanced Materials, Vol. 5, p. 107 (1993), U.S. Patent No. 4,683,327, U.S. Patent No. 5,622,648, U.S. Patent No. 5,770,107, WO95 / 22586, WO95 / 24455, WO97 / 00600, WO98 / 23580, WO98 / 52905, Japanese Patent Publication No. 1-272551, Japanese Patent Publication No. 6-016616, Japanese Patent Publication No. 7-110469, Japanese Patent Publication No. 11-080081, and Japanese Patent Publication No. 2001-328973, etc. Two or more polymerizable liquid crystal compounds may be used in combination. Using two or more polymerizable liquid crystal compounds in combination can lower the orientation temperature.

[0090] Furthermore, the amount of polymerizable liquid crystal compound added to the liquid crystal composition is preferably 80 to 99.9% by mass, more preferably 85 to 99.5% by mass, and even more preferably 90 to 99% by mass, relative to the solid content mass (mass excluding solvent) of the liquid crystal composition.

[0091] To improve visible light transmittance, the cholesteric liquid crystal layer may have a low Δn. Low-Δn cholesteric liquid crystal layers can be formed using low-Δn polymerizable liquid crystal compounds. The following describes low-Δn polymerizable liquid crystal compounds in detail.

[0092] (Low Δn polymerizable liquid crystal compound) A cholesteric liquid crystal phase can be formed using a low-Δn polymerizable liquid crystal compound, and a film on which this phase is fixed can be obtained to acquire a narrow-band selective reflective layer. Examples of low-Δn polymerizable liquid crystal compounds include those described in WO2015 / 115390, WO2015 / 147243, WO2016 / 035873, Japanese Patent Publication No. 2015-163596, and Japanese Patent Publication No. 2016-053149. For liquid crystal compositions that provide a selective reflective layer with a small half-width, see also the description in WO2016 / 047648.

[0093] The liquid crystal compound is also preferably a polymerizable compound represented by the following formula (I) as described in WO2016 / 047648.

[0094] [ka]

[0095] In formula (I), A represents a phenylene group which may have a substituent or a trans-1,4-cyclohexylene group which may have a substituent, L represents a single bond, -CH2O-, -OCH2-, -(CH2)2OC(=O)-, -C(=O)O(CH2)2-, -C(=O)O-, -OC(=O)-, -OC(=O)O-, -CH=CH-C(=O)O- or -OC(=O)-CH=CH-, m represents an integer from 3 to 12, and Sp 1 and Sp 2Each of these independently represents a single bond, a linear or branched alkylene group having 1 to 20 carbon atoms, or a linear or branched alkylene group having 1 to 20 carbon atoms in which one or more -CH2- are replaced by a group selected from -O-, -S-, -NH-, -N(CH3)-, -C(=O)-, -OC(=O)-, and -C(=O)O-, Q 1 and Q 2 Each of these independently represents either a hydrogen atom or a polymerizable group represented by one of the following formulas Q-1 to Q-5. 1 and Q 2 At least one of the following groups is a polymerizable group. In the following formula, * indicates a bonding site.

[0096] [ka]

[0097] In formula (I), the phenylene group is preferably a 1,4-phenylene group. When we say that the phenylene group and the trans-1,4-cyclohexylene group "may have substituents," the substituents are not particularly limited and include, for example, alkyl groups, cycloalkyl groups, alkoxy groups, alkoxycarbonyl groups, amide groups, amino groups, and halogen atoms, as well as groups formed by combining two or more of the above substituents. An example of a substituent is the -C(=O)-X group described later. 3 -Sp 3 -Q 3 Examples of substituents are shown. When the phenylene group and the trans-1,4-cyclohexylene group have substituents, they may have 1 to 4 substituents. When there are two or more substituents, the two or more substituents may be the same or different from each other.

[0098] Alkyl groups may be linear or branched. The number of carbon atoms in an alkyl group is preferably 1 to 30, more preferably 1 to 10, and even more preferably 1 to 6. Examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, 1,1-dimethylpropyl, n-hexyl, and isohexyl groups, as well as linear or branched heptyl, octyl, nonyl, decyl, undecyl, and dodecyl groups. The above description of alkyl groups also applies to alkoxy groups and alkoxycarbonyl groups containing alkyl groups. Specific examples of alkylene groups include divalent groups obtained by removing one arbitrary hydrogen atom from each of the above-mentioned examples of alkyl groups. Examples of halogen atoms include fluorine, chlorine, bromine, and iodine.

[0099] The number of carbon atoms in the cycloalkyl group is preferably 3 to 20, more preferably 5 or more, more preferably 10 or less, even more preferably 8 or less, and particularly preferably 6 or less. Examples of cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups.

[0100] The substituents that the phenylene group and the trans-1,4-cyclohexylene group may have include alkyl groups, alkoxy groups, or -C(=O)-X 3 -Sp 3 -Q 3 This is preferable. Here, X 3 These are single bonds, -O-, -S-, or -N(Sp 4 -Q 4 )- indicates, or Q 3 and Sp 3 This shows the nitrogen atom that forms a ring structure with it. 3 and Sp 4Each of these independently represents a single bond, a linear or branched alkylene group having 1 to 20 carbon atoms, or a linear or branched alkylene group having 1 to 20 carbon atoms in which one or more -CH2- groups are replaced by groups selected from -O-, -S-, -NH-, -N(CH3)-, -C(=O)-, -OC(=O)-, and -C(=O)O-.

[0101] Q 3 and Q 4 Each of these independently represents a hydrogen atom, a cycloalkyl group, a group in which one or more -CH2- groups in a cycloalkyl group are replaced by groups selected from -O-, -S-, -NH-, -N(CH3)-, -C(=O)-, -OC(=O)-, and -C(=O)O-, or a polymerizable group represented by any of formulas Q-1 to Q-5.

[0102] In a cycloalkyl group, one or more -CH2- groups are replaced with groups selected from -O-, -S-, -NH-, -N(CH3)-, -C(=O)-, -OC(=O)-, and -C(=O)O-. Specific examples include tetrahydrofuranyl group, pyrrolidinyl group, imidazolidinyl group, pyrazolidinyl group, piperidyl group, piperazinyl group, and morphonyl group. The substitution position is not particularly limited. Of these, the tetrahydrofuranyl group is preferred, and the 2-tetrahydrofuranyl group is particularly preferred.

[0103] In equation (I), L represents a single bond, -CH2O-, -OCH2-, -(CH2)2OC(=O)-, -C(=O)O(CH2)2-, -C(=O)O-, -OC(=O)-, -OC(=O)O-, -CH=CH-C(=O)O-, or -OC(=O)-CH=CH-. It is preferable that L be -C(=O)O- or -OC(=O)-. The m-1 Ls may be identical or different from each other.

[0104] Sp 1 and Sp 2Each of these independently represents a single bond, a linear or branched alkylene group having 1 to 20 carbon atoms, or a linear or branched alkylene group having 1 to 20 carbon atoms in which one or more -CH2- groups are replaced by groups selected from -O-, -S-, -NH-, -N(CH3)-, -C(=O)-, -OC(=O)-, and -C(=O)O-. Sp 1 and Sp 2 Preferably, each of these groups is independently -OC(=O)-, -C(=O)O-, -O-, or a linear alkylene group having 1 to 10 carbon atoms, or a linking group composed of two or more of these groups. Examples of linking groups composed of -OC(=O)-, -C(=O)O-, -O-, or two or more linear alkylene groups having 1 to 10 carbon atoms include linear alkylene groups having 1 to 10 carbon atoms, each having a linking group selected from -O-, -OC(=O)-, and -C(=O)O- bonded to both ends (i.e., a linear alkylene group having 1 to 10 carbon atoms with -O-, -OC(=O)-, or -C(=O)O- bonded to both ends). Sp 1 and Sp 2 Q is one of the ends of a straight-chain alkylene group having 1 to 10 carbon atoms. 1 Or Q 2 It is more preferable that the group has -O- bonded to one end and -O-, -OC(=O)-, or -C(=O)O- bonded to the other end.

[0105] Q 1 and Q 2 Each of these independently represents either a hydrogen atom or a polymerizable group represented by one of the above formulas Q-1 to Q-5. However, Q 1 and Q 2 At least one of them exhibits a polymerizable group, and it is preferable that both are polymerizable groups. The polymerizable group is preferably an acryloyl group (formula Q-1) or a methacryloyl group (formula Q-2).

[0106] In formula (I), m represents an integer of 3 to 12. m is preferably an integer of 3 to 9, more preferably an integer of 3 to 7, and even more preferably an integer of 3 to 5.

[0107] The polymerizable compound represented by formula (I) preferably contains at least one phenylene group which may have a substituent and at least one trans-1,4-cyclohexylene group which may have a substituent as A. The polymerizable compound represented by formula (I) preferably contains 1 to 4 trans-1,4-cyclohexylene groups which may have a substituent as A, and more preferably contains 1 to 3. Further, the polymerizable compound represented by formula (I) preferably contains one or more phenylene groups which may have a substituent as A, and more preferably contains 1 to 4.

[0108] In formula (I), when the number obtained by dividing the number of trans-1,4-cyclohexylene groups represented by A by m is mc, 0.1 < mc < 0.9 is preferred, 0.3 < mc < 0.8 is more preferred, and 0.5 < mc < 0.7 is even more preferred. It is also preferred that the liquid crystal composition contains a polymerizable compound represented by formula (I) with 0.1 < mc < 0.3 together with a polymerizable compound represented by formula (I) with 0.5 < mc < 0.7.

[0109] Specific examples of the polymerizable compound represented by formula (I) include, in addition to the compounds described in paragraphs 0051 to 0058 of WO2016 / 047648, the compounds described in JP-A-2013-112631, JP-A-2010-070543, Patent No. 47255,16, WO2015 / 115390, WO2015 / 147243, WO2016 / 035873, JP-A-2015-163596, and JP-A-2016-053149.

[0110] The liquid crystal composition for forming a cholesteric liquid crystal layer with a low Δn may contain a polymerizable liquid crystal compound other than the polymerizable compound represented by the above formula (I) (hereinafter referred to as other polymerizable liquid crystal compounds). Other polymerizable liquid crystal compounds include those compounds other than the polymerizable liquid crystal compound represented by formula (I) above, which are listed as examples of polymerizable liquid crystal compounds mentioned above. In a liquid crystal composition that forms a cholesteric liquid crystal layer with a low Δn, the proportion of the polymerizable compound represented by formula (I) above to the total amount of polymerizable liquid crystal compounds is preferably 30 to 100% by mass, more preferably 50 to 100% by mass, and even more preferably 70 to 100% by mass.

[0111] (Chiral agents: optically active compounds) Chiral agents have the function of inducing a helical structure in the cholesteric liquid crystal phase. Since different chiral compounds induce different helical senses or helical pitches, they should be selected according to the purpose. There are no particular restrictions on the chiral agent, and commonly used compounds can be used. Examples of chiral agents include compounds described in the Liquid Crystal Device Handbook (Chapter 3, Section 4-3, Chiral Agents for TN and STN, p. 199, edited by the 142nd Committee of the Japan Society for the Promotion of Science, 1989), Japanese Patent Publication Nos. 2003-287623, 2002-302487, 2002-080478, 2002-080851, 2010-181852, and 2014-034581, among others.

[0112] Chiral agents generally contain an asymmetric carbon atom, but axially asymmetric or planar asymmetric compounds that do not contain an asymmetric carbon atom can also be used as chiral agents. Examples of axially asymmetric or planar asymmetric compounds include binaphthyl, helicene, paracyclophane, and their derivatives. The chiral agent may have polymerizable groups. When both the chiral agent and the liquid crystal compound have polymerizable groups, a polymerization reaction between the polymerizable chiral agent and the polymerizable liquid crystal compound can form a polymer having repeating units derived from the polymerizable liquid crystal compound and repeating units derived from the chiral agent. In this embodiment, it is preferable that the polymerizable groups of the polymerizable chiral agent are of the same type as the polymerizable groups of the polymerizable liquid crystal compound. Therefore, the polymerizable groups of the chiral agent are preferably unsaturated polymerizable groups, epoxy groups, or aziridinyl groups, more preferably unsaturated polymerizable groups, and even more preferably ethylenically unsaturated polymerizable groups. Furthermore, the chiral agent may be a liquid crystal compound.

[0113] As chiral agents, isosorbide derivatives, isomannide derivatives, and binaphthyl derivatives can be preferably used. As isosorbide derivatives, commercially available products such as LC756 (trade name) manufactured by BASF may be used. In the liquid crystal composition, the chiral agent content is preferably 0.01 to 200 mol%, and more preferably 1 to 30 mol%, of the polymerizable liquid crystal compound.

[0114] Furthermore, as mentioned above, the cholesteric liquid crystal layer of the selective reflective layer of the linearly polarized reflective film may have two or more selective reflection center wavelengths. A cholesteric liquid crystal layer having two or more selective reflection center wavelengths is achieved by changing the pitch of the helical structure in the thickness direction. A cholesteric liquid crystal layer in which the pitch of the helical structure changes in the thickness direction can be fabricated by changing the amount of light irradiation in the thickness direction when forming the cholesteric liquid crystal layer using a chiral agent whose helical twisting power (HTP) changes upon light irradiation.

[0115] Chiral agents whose HTP changes upon light irradiation include those that undergo reverse isomerization, dimerization, and isomerization and dimerization upon light irradiation. When the chiral agent has a photo-isomerizable group, the photo-isomerizable group is preferably an isomerization site of a compound exhibiting photochromic properties, an azo group, an azoxy group, or a cinnamoyl group. As specific compounds, the compounds described in JP-A No. 2002-080478, JP-A No. 2002-080851, JP-A No. 2002-179668, JP-A No. 2002-179669, JP-A No. 2002-179670, JP-A No. 2002-179681, JP-A No. 2002-179682, JP-A No. 2002-338575, JP-A No. 2002-338668, JP-A No. 2003-313189, and JP-A No. 2003-313292, etc. can be used.

[0116] (Polymerization initiator) The liquid crystal composition preferably contains a polymerization initiator. In the mode of advancing the polymerization reaction by ultraviolet irradiation, the polymerization initiator to be used is preferably a photo-polymerization initiator capable of initiating the polymerization reaction by ultraviolet irradiation. Examples of photoinitiators include α-carbonyl compounds (described in the specifications of U.S. Patent Nos. 2,367,661 and 2,367,670), acyloin ether compounds (described in the specification of U.S. Patent No. 2,448,828), α-hydrocarbon-substituted aromatic acyloin compounds (described in the specification of U.S. Patent No. 2,722,512), polynuclear quinone compounds (described in the specifications of U.S. Patent Nos. 3,046,127 and 2,951,758), a combination of a triarylimidazole dimer and p-aminophenyl ketone (described in the specification of U.S. Patent No. 3,549,367), acridine and phenazine compounds (described in JP-A-60-105667 and the specification of U.S. Patent No. 4,239,850), acylphosphine oxide compounds (described in JP-B-63-040799, JP-B-5-029234, JP-A-10-095788, JP-A-10-029997, JP-A-2001-233842, JP-A-2000-080068, JP-A-2006-342166, JP-A-2013-114249, JP-A-2014-137466, Patent No. 4,223,071, JP-A-2010-262028, and JP-T-2014-500852), oxime compounds (described in JP-A-2000-066385 and Patent No. 4,454,067), and oxadiazole compounds (described in the specification of U.S. Patent No. 4,212,970), etc. For example, the descriptions in paragraphs 0500 to 0547 of JP-A-2012-208494 can also be taken into consideration.

[0117] As the polymerization initiator, it is also preferable to use an acylphosphine oxide compound or an oxime compound. As an acylphosphine oxide compound, for example, IRGACURE 810 (trade name, compound name: bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide) manufactured by BASF Japan Ltd. can be used. As an oxime compound, commercially available products such as IRGACURE OXE01 (trade name, manufactured by BASF), IRGACURE OXE02 (trade name, manufactured by BASF), TR-PBG-304 (trade name, manufactured by Changzhou Strong Electronic New Materials Co., Ltd.), ADEKA Arclus NCI-930 (trade name, manufactured by ADEKA), and ADEKA Arclus NCI-831 (trade name, manufactured by ADEKA) can be used. A single polymerization initiator may be used, or two or more may be used in combination. The content of the photopolymerization initiator in the liquid crystal composition is preferably 0.1 to 20% by mass, and more preferably 0.5 to 5% by mass, relative to the content of the polymerizable liquid crystal compound.

[0118] (Crosslinking agent) The liquid crystal composition may optionally contain a crosslinking agent to improve the film strength and durability after curing. Suitable crosslinking agents include those that cure with ultraviolet light, heat, or moisture. There are no particular restrictions on the crosslinking agent, and it can be appropriately selected according to the purpose. Examples of crosslinking agents include polyfunctional acrylate compounds such as trimethylolpropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate; epoxy compounds such as glycidyl(meth)acrylate and ethylene glycol diglycidyl ether; aziridine compounds such as 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate] and 4,4-bis(ethyleneiminocarbonylamino)diphenylmethane; isocyanate compounds such as hexamethylene diisocyanate and biuret-type isocyanate; polyoxazoline compounds having an oxazoline group in the side chain; and alkoxysilane compounds such as vinyltrimethoxysilane and N-(2-aminoethyl)3-aminopropyltrimethoxysilane. In addition, a commonly used catalyst can be used depending on the reactivity of the crosslinking agent, which can improve productivity in addition to improving film strength and durability. These may be used individually or in combination of two or more. The crosslinking agent content in the liquid crystal composition is preferably 3 to 20% by mass, and more preferably 5 to 15% by mass, relative to the solid content mass (mass excluding solvent) of the liquid crystal composition. By setting the crosslinking agent content to 3% by mass or more, the effect of improving crosslink density can be obtained, and by setting the crosslinking agent content to 20% by mass or less, a decrease in the stability of the cholesteric liquid crystal layer can be prevented. Note that "(meth)acrylate" is used to mean "either acrylate or methacrylate, or both."

[0119] (Orientation control agent) An orientation control agent may be added to the liquid crystal composition to contribute to the stable or rapid formation of a planar-oriented cholesteric liquid crystal layer. Examples of orientation control agents include fluorine (meth)acrylate polymers described in paragraphs

[0018] to

[0043] of Japanese Patent Application Publication No. 2007-272185, compounds represented by formulas (I) to (IV) described in paragraphs

[0031] to

[0034] of Japanese Patent Application Publication No. 2012-203237, and compounds described in Japanese Patent Application Publication No. 2013-113913. Furthermore, one type of orientation control agent may be used alone, or two or more types may be used in combination.

[0120] The amount of orientation control agent added to the liquid crystal composition is preferably 0.01 to 10% by mass, more preferably 0.01 to 5% by mass, and particularly preferably 0.02 to 1% by mass, relative to the total mass of the polymerizable liquid crystal compound.

[0121] (Other additives) Furthermore, the liquid crystal composition may contain at least one additive selected from various sources, such as surfactants for adjusting the surface tension and uniformity of the coating film, and polymerizable monomers. Additionally, polymerization inhibitors, antioxidants, ultraviolet absorbers, light stabilizers, colorants, and metal oxide fine particles may be added to the liquid crystal composition as needed, within limits that do not degrade optical performance.

[0122] A cholesteric liquid crystal layer can be formed by dissolving a liquid crystal composition, which consists of a polymerizable liquid crystal compound, a polymerization initiator, and optionally added chiral agents, surfactants, etc., in a solvent, onto a transparent substrate, a phase difference layer, an alignment layer, or a previously prepared cholesteric liquid crystal layer, drying it to obtain a coating film, and then irradiating this coating film with active light to polymerize the cholesteric liquid crystal composition, thereby forming a cholesteric liquid crystal layer with fixed cholesteric regularity. Furthermore, a laminated film consisting of multiple cholesteric liquid crystal layers can be formed by repeatedly performing the above-described manufacturing process for the cholesteric liquid crystal layer.

[0123] (solvent) There are no particular restrictions on the solvent used in preparing the liquid crystal composition, and it can be appropriately selected depending on the purpose, but organic solvents are preferably used. There are no particular restrictions on the organic solvent, and it can be appropriately selected depending on the purpose. Examples include ketones, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, and ethers. These may be used individually or in combination of two or more. Among these, ketones are particularly preferred when considering the environmental impact.

[0124] (Coating, orientation, polymerization) There are no particular restrictions on the method of coating the liquid crystal composition onto the transparent substrate, alignment layer, underlying cholesteric liquid crystal layer, etc., and a suitable method can be selected depending on the purpose. Examples of coating methods include wire bar coating, curtain coating, extrusion coating, direct gravure coating, reverse gravure coating, die coating, spin coating, dip coating, spray coating, and slide coating. Alternatively, the liquid crystal composition can be applied to a support separately and then transferred. The liquid crystal molecules are oriented by heating the coated liquid crystal composition. The heating temperature is preferably 200°C or lower, and more preferably 130°C or lower. This orientation treatment yields an optical thin film in which the polymerizable liquid crystal compound is twisted and oriented so that it has a helical axis substantially perpendicular to the film surface.

[0125] The liquid crystal composition can be cured by further polymerizing the oriented liquid crystal compound. Polymerization can be carried out by thermal polymerization or photopolymerization using light irradiation, but photopolymerization is preferred. For light irradiation, ultraviolet light is preferred. The irradiation energy is 20 mJ / cm². 2 ~50J / cm 2 Preferably, 100-1,500 mJ / cm² 2 This is preferable. To promote the photopolymerization reaction, light irradiation may be carried out under heating conditions or in a nitrogen atmosphere. The irradiation ultraviolet wavelength is preferably 350 to 430 nm. From the viewpoint of stability, a higher polymerization reaction rate is preferable, specifically, 70% or more is preferred, and 80% or more is more preferred. The polymerization reaction rate can be determined by measuring the consumption rate of polymerizable functional groups in the infrared absorption spectrum.

[0126] [Polarization conversion layer] The polarization conversion layer 14 is a layer in which the helical orientation structure of the liquid crystal compound is fixed, and it is preferable that the number of pitches x of the helical orientation structure and the thickness y of the polarization conversion layer (in μm) satisfy all of the following relational expressions (a) to (c). 0.1≦x≦1.0 ··· Formula (a) 0.5≦y≦3.0 ··· Formula (b) 3000≦(1560×y) / x≦50000 ··· Formula (c) Note that one pitch in the helical structure of a liquid crystal compound corresponds to one turn of the helix. In other words, a pitch of 1 is defined as a state where the director (the long axis direction in the case of a rod-shaped liquid crystal) of a spirally oriented liquid crystal compound is rotated 360°.

[0127] If the polarization conversion layer has a helical structure of a liquid crystal compound, it will exhibit optical rotation and birefringence with respect to visible light, which has a wavelength shorter than the reflection peak wavelength in the infrared region. Therefore, polarization in the visible region can be controlled. By setting the pitch number x of the helical orientation structure of the polarization conversion layer and the film thickness y of the polarization conversion layer within the above range, it is possible to impart a function of optical compensation for visible light by the polarization conversion layer, or a function of converting linearly polarized light (p-polarized light) incident on the reflective film into circularly polarized light.

[0128] The polarization conversion layer exhibits optical activity and birefringence with respect to visible light because the liquid crystal compound has a helical structure that satisfies relational equations (a) to (c). In particular, by setting the pitch P of the helical structure of the polarization conversion layer to a length corresponding to the pitch P of the cholesteric liquid crystal layer, whose selective reflection center wavelength is in the long-wavelength infrared region, high optical activity and birefringence are exhibited with respect to short-wavelength visible light.

[0129] The relational expression (a) is “0.1 ≦ x ≦ 1.0”. If the pitch number x of the helical structure is less than 0.1, inconveniences such as insufficient optical rotation and birefringence will occur. Also, when the pitch number x of the helical structure exceeds 1.0, inconveniences such as excessive optical rotation and birefringence and inability to obtain the desired elliptical polarization will occur.

[0130] The relational expression (b) is “0.5 ≦ y ≦ 3.0”. If the thickness y of the polarization conversion layer is less than 0.5 μm, the film thickness is too thin, and inconveniences such as insufficient optical rotation and birefringence will occur. When the thickness y of the polarization conversion layer exceeds 3.0 μm, inconveniences such as excessive optical rotation and birefringence, inability to obtain the desired circular polarization, and easy occurrence of orientation defects, which are not preferable for manufacturing, will occur.

[0131] The relational expression (c) is “3000 ≦ (1560 × y) / x ≦ 50000”. If “(1560 × y) / x” is less than 3000, inconveniences such as excessive optical rotation and inability to obtain the desired polarization will occur. When “(1560 × y) / x” exceeds 50000, inconveniences such as insufficient optical rotation and inability to obtain the desired polarization will occur.

[0132] [[ID=2,6]]In the present invention, the pitch number x of the helical structure of the polarization conversion layer is more preferably 0.1 to 0.8, and the film thickness y is more preferably 0.6 μm to 2.6 μm. Also, “(1560 × y) / x” is more preferably 5000 to 13000.

[0133] That is, for the polarization conversion layer, it is preferable that the pitch P of the helical structure is long and the pitch number x is small. Specifically, it is preferable that the polarization conversion layer has a helical pitch P equivalent to that of a cholesteric liquid crystal layer whose selective reflection center wavelength is in the long-wavelength infrared region, and a small number of pitches x. More specifically, it is preferable that the polarization conversion layer has a helical pitch P equivalent to that of a cholesteric liquid crystal layer whose selective reflection center wavelength is 3000 to 10000 nm, and a small number of pitches x. Such a polarization conversion layer exhibits the optical rotation and birefringence properties for visible light more favorably because the selective reflection center wavelength corresponding to the pitch P is much longer than that of visible light.

[0134] Such polarization conversion layers can be formed in essentially the same way as conventional cholesteric liquid crystal layers. However, when forming the polarization conversion layer, it is necessary to adjust the liquid crystal compound used, the chiral agent used, the amount of chiral agent added, and the film thickness so that the number of pitches x of the helical structure in the polarization conversion layer and the film thickness y [μm] satisfy all of the relationships (a) to (c).

[0135] <Layer with fixed helical orientation structure (helical structure) of liquid crystal compound> A layer in which the helical orientation structure (helical structure) of a liquid crystal compound is fixed is a so-called cholesteric liquid crystal layer, meaning a layer in which the cholesteric liquid crystal phase is fixed. A cholesteric liquid crystal layer is a layer in which the orientation of the liquid crystal compound in the cholesteric liquid crystal phase is maintained. Typically, a cholesteric liquid crystal layer is formed by polymerizing and curing a polymerizable liquid crystal compound in the orientation of the cholesteric liquid crystal phase by ultraviolet irradiation and heating, thereby forming a non-fluid layer that simultaneously changes in orientation to a state that does not change due to external fields or external forces. In addition, it is sufficient that the optical properties of the cholesteric liquid crystal phase are maintained within the layer, and the liquid crystal compound in the layer does not need to exhibit liquid crystalline properties anymore. For example, a polymerizable liquid crystal compound may have its molecular weight increased by the curing reaction and may no longer have liquid crystalline properties.

[0136] As mentioned above, the center wavelength λ of selective reflection by the cholesteric liquid crystal layer depends on the pitch P (=period of the helix) of the helical structure (helical orientation structure) in the cholesteric liquid crystal phase, and follows the relationship between the average refractive index n of the cholesteric liquid crystal layer and λ = n × P. As can be seen from this equation, the center wavelength of selective reflection can be adjusted by adjusting the n value and / or the P value.

[0137] The helical pitch of the cholesteric liquid crystal phase depends on the type of chiral agent used with the polymerizable liquid crystal compound and its concentration; therefore, the desired pitch can be obtained by adjusting these factors. As mentioned above, the cholesteric liquid crystal layer used as a polarization conversion layer has its helical pitch adjusted so that the selective reflection center wavelength is in the long-wavelength infrared region. The method for forming the cholesteric liquid crystal layer as a polarization conversion layer is basically the same as the method for forming the cholesteric liquid crystal layer described above.

[0138] [Retardation layer] A phase difference layer alters the state of incident polarization by introducing a phase difference (optical path difference) between two orthogonal polarization components.

[0139] If the phase difference layer is located on the outside of the vehicle and is optically compensated for, the frontal phase difference of the phase difference layer should be such that it can be optically compensated for. In this case, the phase difference layer preferably has a front retardation of 50 nm to 160 nm at a wavelength of 550 nm. Furthermore, when a windshield glass having a reflective film is mounted on a vehicle, it is preferable that the angle of the lagging axis is 10° to 50° or -50° to -10°, with the direction corresponding to the vertically upward direction of the surface of the second glass plate being defined as 0°.

[0140] Furthermore, if the phase difference layer converts linearly polarized light to circularly polarized light, the front phase difference of the phase difference layer is preferably configured to give λ / 4, or it may be configured to give 3λ / 4 as the front phase difference. Also, the angle of the slow axis should be arranged so as to be in the direction that converts the incident linearly polarized light to circularly polarized light.

[0141] In this case, the phase difference layer preferably has a front phase difference in the range of 100 to 450 nm at a wavelength of 550 nm, and more preferably in the range of 120 to 200 nm or 300 to 400 nm. Furthermore, the direction of the slow axis of the phase difference layer is preferably determined according to the incident direction of the projected light for displaying the projected image when the reflective film 10 is used in a head-up display system, and the sense of the helix of the cholesteric liquid crystal layer constituting the selective reflective layer.

[0142] The phase difference layer is not particularly limited and can be appropriately selected depending on the purpose. Examples of phase difference layers include stretched polycarbonate film, stretched norbornene-based polymer film, transparent film containing and oriented inorganic particles having birefringence such as strontium carbonate, thin film in which an inorganic dielectric is obliquely deposited on a support, film in which polymerizable liquid crystal compounds are uniaxially oriented and fixed in orientation, and film in which liquid crystal compounds are uniaxially oriented and fixed in orientation.

[0143] In particular, a film in which a polymerizable liquid crystal compound is uniaxially oriented and its orientation fixed is a suitable example of a phase difference layer. Such a phase difference layer can be formed, for example, by applying a liquid crystal composition containing a polymerizable liquid crystal compound to a transparent substrate, a temporary support, or the surface of an alignment layer, forming the polymerizable liquid crystal compound in the liquid crystal composition in a nematic orientation in a liquid crystal state, and then fixing it by curing. In this case, the formation of the phase difference layer can be carried out in the same manner as the formation of the cholesteric liquid crystal layer described above, except that a chiral agent is not added to the liquid crystal composition. However, when nematic orientation is performed after coating the liquid crystal composition, the heating temperature is preferably 50 to 120°C, and more preferably 60 to 100°C.

[0144] The phase difference layer may be a layer obtained by applying a composition containing a polymer liquid crystal compound to the surface of a transparent substrate, temporary support, or orientation layer, forming a nematic orientation in a liquid crystal state, and then fixing this orientation by cooling.

[0145] There are no restrictions on the thickness of the phase difference layer, but it is preferably 0.2 to 300 μm, more preferably 0.5 to 150 μm, and even more preferably 1.0 to 80 μm. The thickness of the phase difference layer formed from the liquid crystal composition is not particularly limited, but it is preferably 0.2 to 10 μm, more preferably 0.5 to 5.0 μm, and even more preferably 0.7 to 2.0 μm.

[0146] The phase difference layer has a slow phase axis set at an angle α, for example, with respect to an axis in any direction of the phase difference layer. The direction of the slow phase axis can be set, for example, by rubbing the alignment film that forms the layer below the phase difference layer.

[0147] The linearly polarized reflective film described above may have layers other than the selective reflective layer, polarization conversion layer, and phase difference layer described above. For example, the linearly polarized reflective film may have a transparent substrate, an adhesive layer, etc. For example, in the example shown in Figure 2, the linearly polarized reflective film 10A has a transparent substrate 18 positioned on the opposite side of the phase difference layer 16 from the selective reflective layer 11. The transparent substrate 18 supports the phase difference layer 16, the selective reflective layer 11 (cholesteric liquid crystal layer), and the polarization conversion layer 14. The transparent substrate 18 may also be used as a support when forming the phase difference layer 16, the selective reflective layer 11 (cholesteric liquid crystal layer), and the polarization conversion layer 14.

[0148] The above-mentioned linear polarizing reflective film may be in the form of a thin film or sheet, etc. Before being used in the windshield glass, the above-mentioned linear polarizing reflective film may be in the form of a roll of thin film, etc.

[0149] It is preferable that both the transparent substrate (support) and the adhesive layer are transparent in the visible light region. Furthermore, it is preferable that both the transparent substrate and the adhesive layer have low birefringence. Low birefringence means that in the wavelength range in which the selective reflective layer contained in the windshield glass used in the present invention exhibits reflection, the front phase difference is 10 nm or less. It is preferable that this front phase difference is 5 nm or less. Moreover, it is preferable that both the support and the adhesive layer have a small difference in refractive index from the average refractive index (in-plane average refractive index) of the selective reflective layer.

[0150] [Transparent base material] The transparent substrate can also be used as a substrate when forming a selective reflective layer. The transparent substrate used for forming the selective reflective layer may be a temporary support that is peeled off after the selective reflective layer is formed. Therefore, the finished reflective film and windshield glass do not necessarily contain the transparent substrate. If the finished reflective film or windshield glass contains the transparent substrate, rather than being peeled off as a temporary support, it is preferable that the transparent substrate is transparent in the visible light region.

[0151] There are no restrictions on the material of the transparent substrate. Examples of transparent substrates include plastic films such as polyethylene terephthalate (PET) and other polyesters, polycarbonates, acrylic resins, epoxy resins, polyurethanes, polyamides, polyolefins, cellulose derivatives, and silicones. In addition to the plastic films mentioned above, glass may also be used as a temporary support.

[0152] The thickness of the transparent substrate can be approximately 5.0 to 1000 μm, preferably 10 to 250 μm, and more preferably 15 to 90 μm.

[0153] In this case, as shown in the example in Figure 2, when the transparent substrate 18 is placed on the side of the first glass plate 30, i.e., on the outside of the vehicle, it is preferable that the transparent substrate 18 contains an ultraviolet absorber. By including an ultraviolet absorber in the transparent substrate 18, the degradation of the reflective film (selective reflective layer) due to ultraviolet light can be suppressed.

[0154] [1-2] Linear polarized reflective film containing dielectric multilayer film Figure 3 is a schematic diagram showing an example of a windshield glass used in the present invention. The linearly polarized reflective film 10B contained in this windshield glass 24B consists of a selective reflective layer (dielectric multilayer film) in which optically anisotropic layers (13Ra, 13Ga, 13Ba) and optically isotropic layers (13Rb, 13Gb, 13Ba) are alternately laminated. In the illustrated example, the linearly polarized reflective film 10B has a first laminated portion 13R in which optically anisotropic layer 13Ra and optically isotropic layer 13Rb are alternately laminated, a second laminated portion 13G in which optically anisotropic layer 13Ga and optically isotropic layer 13Gb are alternately laminated, and a third laminated portion 13B in which optically anisotropic layer 13Ba and optically isotropic layer 13Bb are alternately laminated. The above dielectric multilayer film has the following λ as its selective reflection center wavelength at an incident angle of light of 60°: B , λ G and λ R The dielectric multilayer film is not particularly limited as long as it contains the three wavelengths and satisfies all of the above-mentioned requirements (a) to (c) in relation to each color laser light from the laser light source.

[0155] The first laminated section 13R, the second laminated section 13G, and the third laminated section 13B have different thicknesses for the optically anisotropic layer and the optically isotropic layer. Furthermore, the number of layers, refractive index, etc., may also differ.

[0156] Furthermore, in the above linearly polarized reflective film, the refractive index n in the slow axis direction of the optical anisotropy layer e1 The refractive index n of the optically isotropic layer o2 exceeding (i.e., n e1 >n o2 ), refractive index n in the direction perpendicular to the slow axis of the optical anisotropy layer o1 The refractive index n of the optically isotropic layer o2 It is essentially the same as this. Multiple optically anisotropic layers are stacked so that their respective slow axes are parallel. Therefore, as shown in Figure 4, in one direction (up and down in Figure 4), the refractive index (n e1 ) is a layer with a high refractive index (n o2This results in a stacked state with layers having a low refractive index. On the other hand, in the direction perpendicular to this direction (left-right direction in Figure 4), layers with the same refractive index are stacked. When placing the linear polarizing reflective film 10B on the HUD system 20 shown in Figure 1, it is positioned so that the axis P of the linear polarizing reflective film 10B shown in Figure 4 coincides with the vertical direction Y of the windshield glass 24.

[0157] A film in which layers with low refractive index (low refractive index layers) and high refractive index (high refractive index layers) are alternately laminated is known to reflect light of specific wavelengths due to structural interference between numerous low and high refractive index layers. Therefore, the linearly polarized reflective film 10B shown in Figures 3 and 4 reflects linearly polarized light in the vertical direction and transmits linearly polarized light in the horizontal direction in Figure 4.

[0158] Here, the dielectric multilayer film used in the HUD system of the present invention has the selected reflection center wavelength at an incident angle of light of 60° as the aforementioned λ. B , λ G and λ R It includes these three wavelengths and satisfies all of the aforementioned requirements (a) to (c) in relation to each color laser light in the laser light source.

[0159] In dielectric multilayer films, the selective reflection center wavelength and reflectivity can be adjusted by the refractive index difference between the low-refractive-index layer and the high-refractive-index layer, thickness, number of layers, etc. In the example shown in Figure 3, the first layer 13R mainly controls the selective reflection center wavelength λ at an incident angle of 60° of light. R This achieves a reflection having the following properties, and the second stacked portion 13G provides the aforementioned selective reflection center wavelength λ at an incident angle of 60° of light. G This achieves a reflection having the following properties, and the third stacked portion 13B provides the aforementioned selective reflection center wavelength λ at an incident angle of 60° of light. B It achieves a reflection that possesses this property.

[0160] In the dielectric multilayer film described above, the reflection peak having the selective reflection center wavelength determined by the method described above is defined as a peak with a maximum value that is 2% or more greater than the difference from the adjacent minimum value, and with a full width at half maximum of 10 to 200 nm.

[0161] As mentioned above, the selective reflection center wavelength and reflectance in a dielectric multilayer film can be adjusted by the refractive index difference between the low-refractive-index layer and the high-refractive-index layer, the thickness, and the number of layers. Specifically, the selective reflection center wavelength can be adjusted by setting the thickness d of the low-refractive-index layer and the high-refractive-index layer to d = λ / (4 × n), based on the wavelength λ and refractive index n of the reflected light. Furthermore, the reflectance increases with the number of layers of the low-refractive-index and high-refractive-index layers, so the reflectance can be adjusted by adjusting the number of layers. In addition, the full width at half maximum of the reflection peak having this selective reflection center wavelength can be adjusted by the refractive index difference between the low-refractive-index layer and the high-refractive-index layer.

[0162] Here, the full width at half maximum (FWHM) of a reflection peak having a selected center wavelength depends on the difference between the refractive index in the slow axis direction of the optical anisotropic layer and the refractive index of the optical isotropic layer, with the FWHM increasing as the difference in refractive index increases. Furthermore, if reflection peaks with low reflectivity are at nearby wavelengths, interference occurs, causing the reflection peaks to become too strong or too weak. From the viewpoint of improving the brightness of the displayed image while increasing transmittance by appropriately adjusting the FWHM of reflection peaks having a selected center wavelength, and from the viewpoint of reducing the effects of interference with adjacent reflection peaks, the difference between the refractive index in the slow axis direction of the optical anisotropic layer and the refractive index of the optical isotropic layer is preferably 0.03 to 0.20, more preferably 0.05 to 0.14, and even more preferably 0.05 to 0.10.

[0163] Furthermore, the dielectric multilayer film has a selective reflection center wavelength at an incident angle of light of 60°, as described above (λ). B A light-reflecting layer having the aforementioned λ G A light-reflecting layer having the aforementioned λ R It consists of light-reflecting layers having such layers, and it is preferable that these light-reflecting layers are in contact with each other. For example, in the example shown in Figure 3, the selective reflection center wavelength λ at an incident angle of light of 60°R A first laminated portion 13R having a selected reflection center wavelength λ at an incident angle of light of 60° G The second laminated portion 13G, which has the following characteristics, is in contact with each other, and the selective reflection center wavelength λ at an incident angle of light of 60° G The second laminated portion 13G has a selective reflection center wavelength λ at an incident angle of light of 60°. B The third laminated portion 13B, which has the same properties, is in contact with each other. The first laminated portion 13R, the second laminated portion 13G, and the third laminated portion 13B are light-reflecting layers that constitute a dielectric multilayer film (selective reflective layer) used in the HUD system of the present invention.

[0164] Although not shown in Figure 3, it is also preferable from the viewpoint of suppressing reflected color to include, in addition to the three laminated sections 13R, 13G, and 13B, a selective reflection layer (hereinafter referred to as the UV light reflection layer) formed by laminating an optically anisotropic layer and an optically isotropic layer, having a selective reflection center wavelength of 300 nm or more and less than 400 nm at an incident angle of light of 60°. By providing a UV light-reflecting layer, when the windshield glass is configured to include the aforementioned cholesteric liquid crystal layer and phase difference layer, the color (especially yellowish) observed when the windshield glass is viewed under ambient light can be suppressed.

[0165] If the optical reflective layers, each having a selective reflection center wavelength at an incident angle of 60° of light, are spaced apart, the interlayer thickness increases, making it difficult to obtain the interference effect of the light reflected by each optical reflective layer. In contrast, by configuring the optical reflective layers to be in contact with each other, the full width at half maximum of the reflection peaks with each selective reflection center wavelength can be narrowed by the interference effect of the light reflected by each optical reflective layer.

[0166] The linear polarizing reflective film described above may be in the form of a thin film or sheet. Before being used in windshield glass, the linear polarizing reflective film may be in the form of a roll of thin film.

[0167] For example, materials and methods for fabricating dielectric multilayer films can be those described in Japanese Patent Publication No. 9-506837. Specifically, dielectric multilayer films can be formed using a wide variety of materials by processing under conditions selected to obtain the refractive index relationship. Generally, it is necessary that the first material has a different refractive index from the second material in a selected direction. This difference in refractive index can be achieved by various methods, including stretching, extrusion, or coating during or after film formation. Furthermore, it is preferable that the two materials have similar rheological properties (e.g., melt viscosity) so that they can be extruded simultaneously.

[0168] Materials particularly suitable for use in dielectric multilayer films include PEN (polyethylene naphthalate) and PET (polyethylene terephthalate) as materials for the optically anisotropic layer, and (isotropically adjusted) PEN, PET, and PMMA (polymethyl methacrylate resin) as materials for the optically isotropic layer.

[0169] As described above, the linearly polarized reflective film (dielectric multilayer film) used in the HUD system of the present invention has the selected reflection center wavelength at an incident angle of light of 60° as the aforementioned λ B , λ G and λ R To achieve a configuration having three wavelengths, it is preferable to have three laminated sections with different thicknesses for the optically anisotropic layer and the optically isotropic layer. In the present invention, the three laminated sections can be formed by stretching, extrusion molding, etc. as described above, and then the laminated sections can be bonded together to produce a linearly polarized reflective film (dielectric multilayer film). Alternatively, the thickness before processing can be adjusted so that three laminated sections of different thicknesses are formed, and the three laminated sections can be integrally formed by stretching, extrusion molding, etc.

[0170] The thickness of the dielectric multilayer film is preferably 2.0 to 50 μm, and more preferably 8.0 to 30 μm.

[0171] A linearly polarized reflective film containing a dielectric multilayer has a selective reflective layer (dielectric multilayer) formed by laminating an optically anisotropic layer and an optically isotropic layer. In addition to the dielectric multilayer, the linearly polarized reflective film may also include a phase difference layer, a polarization conversion layer, a support, and an adhesive layer.

[0172] The phase difference layer, polarization conversion layer, support (transparent substrate), and adhesive layer used in the above-mentioned linearly polarized reflective film can be described in the same way as the phase difference layer, polarization conversion layer, transparent substrate (support), and adhesive layer used in the linearly polarized reflective film including the cholesteric liquid crystal layer described above.

[0173] Below, we will describe, in order, the components of the windshield glass other than the reflective film mentioned above: the glass plate (laminated glass), the intermediate layer, and the heat-seal layer (adhesive layer).

[0174] [2] Laminated glass The windshield glass may have a laminated glass structure. The windshield glass used in the HUD system of the present invention is preferably laminated glass, and preferably has the above-mentioned reflective film between the first glass plate and the second glass plate. The windshield glass may be configured such that a reflective film is placed between a first glass plate and a second glass plate. However, it is preferable that the windshield glass is configured such that an interlayer (interlayer sheet) is provided between the first glass plate and the reflective film, and between the reflective film and the second glass plate. In the windshield glass, as an example, the second glass plate is positioned on the side opposite to the viewing side of the HUD system (outside the vehicle), and the first glass plate is positioned on the viewing side (inside the vehicle). In the windshield glass used in the HUD system of the present invention, the designations "first" and "second" in the first and second glass plates have no technical significance and are merely provided for convenience to distinguish between the two glass plates. Therefore, the second glass plate may be on the inside of the vehicle and the first glass plate on the outside. For the first and second glass plates, etc., glass plates commonly used for windshield glass can be used. For example, glass plates with a visible light transmittance of 80% or less, such as 73% and 76%, such as heat-shielding green glass, may be used. Even when using glass plates with low visible light transmittance in this way, by using the reflective film described above, it is possible to produce windshield glass that has a visible light transmittance of 70% or more even at the position of the reflective film.

[0175] There are no particular restrictions on the thickness of the glass plate, but it should be approximately 0.5 to 5.0 mm, preferably 1.0 to 3.0 mm, and more preferably 2.0 to 2.3 mm. The material or thickness of the first glass plate and the second glass plate may be the same or different.

[0176] Windshield glass having a laminated glass structure can be manufactured by the conventional method for producing laminated glass. Generally, laminated glass can be manufactured by sandwiching an interlayer film between two glass plates, repeating heat treatment and pressure treatment (such as treatment using rubber rollers) several times, and finally performing heat treatment under pressure using an autoclave or the like.

[0177] A windshield glass having a laminated glass structure with a reflective film and an interlayer may, for example, be manufactured by first forming a reflective film on the surface of a glass plate and then using the laminated glass manufacturing method described above, or it may be manufactured using the laminated glass manufacturing method described above, with the interlayer containing the reflective film described above being used. When forming a reflective film on the surface of a glass plate, the glass plate on which the reflective film is attached may be either a first glass plate or a second glass plate. In this case, the reflective film may be bonded to the glass plate, for example, with an adhesive (heat-seal layer).

[0178] [3] interlayer The interlayer 36 prevents the glass from penetrating the vehicle and shattering in the event of an accident. In the example shown in Figure 2, the linear polarizing reflective film 10A is bonded to the second glass plate 28; in the example shown in Figure 1, the reflective film 10 is bonded to the second glass plate 28; and in the example shown in Figure 3, the linear polarizing reflective film 10B is bonded to both the second glass plate 28 and the first glass plate 30.

[0179] Any interlayer commonly used as an interlayer (interlayer sheet) in laminated glass can be used as the interlayer (interlayer sheet). For example, a resin film containing a resin selected from polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer, and chlorine-containing resin can be used. The above-mentioned resin is preferably the main component of the interlayer. The main component refers to a component that accounts for 50% or more by mass of the interlayer.

[0180] Of the resins mentioned above, at least one of polyvinyl butyral and ethylene-vinyl acetate copolymer is preferred, with polyvinyl butyral being more preferred. The resin is preferably a synthetic resin. Polyvinyl butyral can be obtained by acetalizing polyvinyl alcohol with butyraldehyde. The preferred lower limit of the degree of acetalization of the above-mentioned polyvinyl butyral is 40% or more, the preferred upper limit is 85% or less, the more preferred lower limit is 60% or more, and the more preferred upper limit is 75% or less.

[0181] Polyvinyl alcohol is typically obtained by saponifying polyvinyl acetate, and polyvinyl alcohol with a saponification degree of 80-99.8 mol% is commonly used. Furthermore, the preferred lower limit for the degree of polymerization of the polyvinyl alcohol is 200 or higher, and the preferred upper limit is 3000 or lower. When the degree of polymerization of the polyvinyl alcohol is 200 or higher, the puncture resistance of the resulting laminated glass is less likely to decrease, and when it is 3000 or lower, the moldability of the resin film is good, and the rigidity of the resin film does not become too high, resulting in good processability. A more preferred lower limit is 500 or higher, and a more preferred upper limit is 2000 or lower.

[0182] Furthermore, there are no restrictions on the thickness of the interlayer 36; the thickness can be set according to the forming material, etc., in the same way as the interlayer of a commonly used windshield glass.

[0183] In Figure 1, the windshield glass 24 has a heat-seal layer 38 between the reflective film 10 and the first glass plate 30, and the reflective film 10 and the second glass plate 28 are bonded together with an interlayer 36, but this is not a limitation. In other words, a configuration in which a heat-seal layer is provided between the reflective film 10 and the second glass plate 28, and an interlayer is provided between the reflective film 10 and the first glass plate 30 is also acceptable. Alternatively, the windshield glass 24 may have no interlayer 36, and a heat seal layer 38 may be used for bonding the reflective film 10 to the second glass plate 28, and for bonding the reflective film 10 to the first glass plate 30.

[0184] (Interlayer including reflective film) An interlayer for laminated glass containing a reflective film can be formed by laminating the reflective film to the surface of the aforementioned interlayer. Alternatively, the reflective film can be formed by sandwiching it between two of the aforementioned interlayers. The two interlayers may be the same or different, but it is preferable that they be the same. For bonding the reflective film and the interlayer, a standard bonding method can be used, and lamination is preferred. The lamination process is preferably carried out under certain heating and pressurizing conditions to prevent the laminate (reflective film) and the interlayer from delaminating after processing. To ensure stable lamination, the surface temperature of the interlayer on the bonding side is preferably 50-130°C, and more preferably 70-100°C. Pressurization is preferable during lamination. There are no restrictions on the pressurization conditions, but 2.0 kg / cm² is preferable. 2 Preferably less than 196 kPa, and between 0.5 and 1.8 kg / cm³. 2 (49-176 kPa) is more preferable, and 0.5-1.5 kg / cm³ 2 (49-147 kPa) is even more preferable.

[0185] Furthermore, if the reflective film has a support (transparent substrate), the support may be peeled off simultaneously with lamination, immediately after lamination, or immediately before lamination. In other words, the reflective film attached to the interlayer obtained after lamination does not need to have a support. One example of a method for manufacturing an interlayer containing a reflective film is: (1) A first step of laminating a reflective film onto the surface of a first interlayer to obtain a first laminate, and (2) A second step of laminating a second interlayer to the side of the reflective film in the first laminate that is opposite to the side to which the first interlayer is laminated. For example, in the first step, the reflective film and the first interlayer are bonded together without the support and the first interlayer facing each other. Then, the support is peeled off the reflective film. Furthermore, in the second step, the second interlayer is bonded to the surface from which the support was peeled off. This makes it possible to manufacture an interlayer containing a reflective film that does not have a support. In addition, by using this interlayer containing a reflective film, laminated glass in which the reflective film does not have a support can be easily manufactured. To ensure stable and damage-free peeling of the support, the temperature of the support when peeling it from the reflective film is preferably 40°C or higher, and more preferably 40-60°C.

[0186] [4] Heat seal layer (adhesive layer) The heat-seal layer (adhesive layer) 38 is, for example, a layer made of a coating-type adhesive. In the example shown in Figure 2, the linearly polarized reflective film 10A is attached to the first glass plate 30 by the heat-seal layer 38. In the windshield glass used in the present invention, instead of the heat-seal layer 38, the linearly polarized reflective film 10A may be attached to the first glass plate 30 by an interlayer. Also, if the linearly polarized reflective film 10A is smaller than the interlayer 36 that attaches the second glass plate 28 to the linearly polarized reflective film 10A, the linearly polarized reflective film 10A may be attached to the first glass plate 30 by the interlayer 36.

[0187] There are no restrictions on the heat seal layer 38; any commonly used coating-type adhesive can be used as long as it can ensure the transparency required for the windshield glass 24 and adhere the reflective film 10 to the glass with the necessary adhesive strength. The heat seal layer 38 may be the same as the interlayer 36, such as PVB. In addition, adhesives such as acrylate-based adhesives can be used for the heat seal layer 38, as described below.

[0188] The heat-seal layer 38 may be formed from an adhesive. Adhesives can be classified into hot-melt type, thermosetting type, photocuring type, reaction-curing type, and pressure-sensitive adhesive type that does not require curing, from the perspective of curing method. Furthermore, regardless of the type of adhesive, compounds selected from acrylate-based, urethane-based, urethane-acrylate-based, epoxy-based, epoxy-acrylate-based, polyolefin-based, modified olefin-based, polypropylene-based, ethylene vinyl alcohol-based, vinyl chloride-based, chloroprene rubber-based, cyanoacrylate-based, polyamide-based, polyimide-based, polystyrene-based, and polyvinyl butyral-based materials can be used as the material. From the viewpoint of workability and productivity, a photocuring type is preferred as the curing method, and from the viewpoint of optical transparency and heat resistance, it is preferable to use a compound selected from acrylate-based, urethane acrylate-based, and epoxy acrylate-based materials.

[0189] The heat-seal layer 38 may be formed using a highly transparent adhesive transfer tape (OCA tape). As the highly transparent adhesive transfer tape, commercially available products for image display devices, especially commercially available products for the surface of the image display part of an image display device, may be used. Examples of commercially available products include adhesive sheets manufactured by Panac Co., Ltd. (product name: PD-S1, etc.) and adhesive sheets of the MHM (product name) series manufactured by Nichiei Kako Co., Ltd.

[0190] There are no restrictions on the thickness of the heat seal layer 38. Therefore, depending on the material used to form the heat seal layer 38, a thickness that provides sufficient adhesion can be set as appropriate. In this case, if the heat seal layer 38 is too thick, it may not be possible to adhere the reflective film 10 to the second glass plate 28 or the first glass plate 30 while maintaining sufficient flatness. Considering this point, the thickness of the heat seal layer 38 is preferably 0.1 to 800 μm, and more preferably 0.5 to 400 μm.

[0191] <Projector> A "projector" is a "device that projects light or an image," and includes a "device that projects a drawn image," and emits projection light carrying the image to be displayed. In the HUD system of the present invention, the projector includes a laser light source that emits three colors of laser light: blue light, green light, and red light, and is not particularly limited as long as it satisfies all of the above-mentioned provisions (a) to (c) with respect to the aforementioned selective reflective layer, but it is preferable that it emits p-polarized projection light. In a HUD system, the projector should be positioned so that projected light (preferably p-polarized projected light) carrying the image to be displayed is incident on the reflective film in the windshield glass at an oblique angle.

[0192] In a HUD system, the projector preferably includes a drawing device and reflects an image (real image) drawn on a small intermediate image screen as a virtual image using a combiner. Any projector that can emit p-polarized light can be used in a standard projector used in a HUD system. Furthermore, it is preferable that the projector has a variable virtual image formation distance, i.e., a variable virtual image formation position.

[0193] Methods for changing the image formation distance of a virtual image in a projector include, for example, moving the image generation surface (screen) (see Japanese Patent Publication No. 2017-21302), switching between multiple optical paths with different optical path lengths (see WO2015 / 190157), changing the optical path length by inserting and / or moving a mirror, changing the focal length by using a lens assembly as an imaging lens, moving the projector 22, switching between multiple projectors with different virtual image formation distances, and using a variable focus lens (see WO2010 / 116912).

[0194] The projector may be one that can continuously change the image formation distance of the virtual image, or one that can switch the image formation distance of the virtual image at two or three or more points. Here, it is preferable that at least two of the virtual images projected by the projector have different image formation distances of 1 meter or more. Therefore, if the projector is capable of continuously changing the image formation distance of the virtual images, it is preferable that the image formation distance of the virtual images can be changed by 1 meter or more. Using such a projector is preferable because it can suitably handle situations where the driver's line of sight differs greatly, such as when driving at normal speeds on ordinary roads and when driving at high speeds on expressways.

[0195] (Drawing device) The drawing device may be a device that displays an image itself, or it may be a device that emits light capable of drawing an image. In a drawing device, the light from a light source should be adjusted by a drawing method such as an optical modulator, laser luminance modulation means, or optical deflection means for drawing. A drawing device means a device that includes a light source and further includes an optical modulator, laser luminance modulation means, or optical deflection means for drawing, depending on the drawing method.

[0196] (light source) The light source used in the HUD system of the present invention is a laser light source that emits three colors of laser light: blue light, green light, and red light. There are no particular limitations as long as it can satisfy all of the above-mentioned requirements (a) to (c) in relation to the aforementioned selective reflective layer. Commonly used laser light sources used in projectors, drawing devices, and displays can be used, and semiconductor lasers are preferably used. For example, when using a semiconductor laser as a laser light source, the peak wavelength of the blue laser light is typically 450±10nm, the peak wavelength of the green laser light is typically 518±7nm, and the peak wavelength of the red laser light is typically 638±5nm. The peak wavelength of the blue laser light emission wavelength and the selective reflection center wavelength λ in the aforementioned selective reflection layer. B The absolute value of the difference is usually 10 nm or less, and preferably 5 nm or less. Similarly, the peak wavelength of the green laser light emission wavelength and the selective reflection center wavelength λ in the aforementioned selective reflection layer G The absolute value of the difference is usually 7 nm or less, preferably 4 nm or less, and is the difference between the peak wavelength of the emission wavelength of the red laser light and the selective reflection center wavelength λ in the aforementioned selective reflection layer. R The absolute value of the difference is usually 5 nm or less, and preferably 3 nm or less.

[0197] (Drawing method) The drawing method can be selected according to the laser light source emitting the three colors of laser light mentioned above: blue light, green light, and red light. Examples include a scanning method that utilizes a laser.

[0198] The scanning method involves scanning a light ray across a screen and creating an image using the afterimage of the eye. For example, see the descriptions in Japanese Patent Publication No. 7-270711 and Japanese Patent Publication No. 2013-228674. In the scanning method using a laser, it is sufficient that luminance-modulated laser light of each color, such as red, green, and blue light, is combined into a single light ray using a multiplexing optical system or a focusing lens, and that the light ray is scanned by a light deflection means and drawn on an intermediate image screen, which will be described later. In the scanning method, for example, the brightness modulation of red, green, and blue laser light may be performed directly as a change in the intensity of the light source, or it may be performed by an external modulator. Examples of optical deflection means include galvanometer mirrors, a combination of galvanometer mirrors and polygon mirrors, and MEMS (Micro Electro Mechanical Systems), of which MEMS is preferred. Examples of scanning methods include random scanning and raster scanning, of which raster scanning is preferred. In raster scanning, the laser light can be driven, for example, at the resonant frequency in the horizontal direction and with a sawtooth wave in the vertical direction. Since the scanning method does not require a projection lens, it is easy to miniaturize the device. In particular, the raster scan method is common, in which a light source module with blue, green, and red laser light sources illuminates a two-axis MEMS mirror with RGB light, and the MEMS mirror is driven at high speed to draw an image on an intermediate image screen with the reflected RGB light.

[0199] The light emitted from the drawing device may be linearly polarized or natural light (unpolarized). In a drawing device using a laser light source, the emitted light is essentially linearly polarized. In a drawing device where the emitted light is linearly polarized and the emitted light contains light of multiple wavelengths (colors), it is preferable that the polarization direction (transmission axis direction) of the light of multiple wavelengths is the same. It is known that some commercially available drawing devices have non-uniform polarization directions in the wavelength ranges of red, green, and blue light (see Japanese Patent Publication No. 2000-221449). Specifically, there are known examples where the polarization direction of green light is perpendicular to the polarization directions of red light and blue light. As mentioned above, in the HUD system of the present invention, it is preferable that the projected light emitted by the projector is p-polarized.

[0200] (Intermediate image screen) As described above, the drawing device may use an intermediate image screen. The "intermediate image screen" is a screen on which an image is drawn. That is, when the light emitted from the drawing device is not yet visible as an image, the drawing device uses this light to form a visible image on the intermediate image screen. The image drawn on the intermediate image screen may be projected onto the combiner by light passing through the intermediate image screen, or it may be projected onto the combiner after being reflected from the intermediate image screen.

[0201] Examples of intermediate image screens include scattering films, microlens arrays, and screens for rear projection. When using plastic materials as intermediate image screens, if the intermediate image screen has birefringence, the polarization plane and light intensity of the polarized light incident on the intermediate image screen are disturbed, which can easily cause color unevenness in the combiner (reflective film). However, this problem of color unevenness can be reduced by using a phase difference film with a predetermined phase difference. As an intermediate image screen, one that has the function of spreading and transmitting incident light rays is preferable, because it enables magnified display of the projected image. Examples of such intermediate image screens include screens composed of a microlens array. Microarray lenses used in HUD systems are described, for example, in Japanese Patent Publication No. 2012-226303, Japanese Patent Publication No. 2010-145745, and Japanese Patent Publication No. 2007-523369. The projector may include a reflector or the like that adjusts the optical path of the projected light formed by the drawing device.

[0202] For HUD systems using windshield glass as a reflective film, refer to Japanese Patent Publication No. 2-141720, Japanese Patent Publication No. 10-96874, Japanese Patent Publication No. 2003-98470, U.S. Patent No. 5013134, and Japanese Patent Publication No. 2006-512622, etc.

[0203] [Projection light (incident light)] It is preferable that the incident light be incident at an oblique angle of 45° to 70° with respect to the normal of the reflective film. The Brewster angle at the interface between glass with a refractive index of about 1.51 and air with a refractive index of 1 is about 56°. By incidenting p-polarized light within the above-mentioned angle range, less reflected light from the surface of the viewing-side windshield glass is directed to the selective reflective layer of incident light for projected image display, enabling image display with minimal double image effects. The angle mentioned above is preferably 50° to 65°. In this case, the configuration should allow observation of the projected image on the incident side of the projected light at an angle of 45° to 70°, preferably 50° to 65°, with respect to the normal of the selective reflective layer, on the opposite side from the incident light.

[0204] The incident light may enter the windshield glass from any direction, such as above, below, left, or right, and should be determined in accordance with the viewing direction. For example, a configuration in which the light enters from below at the oblique angle described above is preferred. Furthermore, it is preferable that the reflective film on the windshield glass is positioned to reflect incident p-polarized light.

[0205] As described above, the projected light used for displaying projected images in the HUD system of the present invention is preferably p-polarized light that vibrates in a direction parallel to the incident plane. If the projector's emitted light is not linearly polarized, it may be p-polarized by providing a linearly polarizing film (polarizer) on the projector's emitted light side, or it may be p-polarized in the optical path from the projector to the windshield glass by a conventional method using a linearly polarizing film or the like. In this case, the component that p-polarizes the non-linearly polarized projected light is also considered to constitute the projector in the HUD system of the present invention. As described above, for projectors where the polarization direction of the emitted light is not uniform in the wavelength ranges of red, green, and blue light, it is preferable to selectively adjust the polarization direction to allow the light to be incident as p-polarized light in the wavelength ranges of all colors.

[0206] As mentioned above, the HUD system (projector) may be a projection system that allows for variable virtual image positioning. By allowing for variable virtual image positioning, the driver can view the virtual image more comfortably and conveniently. The virtual image formation position is the position from which the vehicle driver can see the virtual image, for example, a position at least 1000 mm away from the driver, beyond the windshield glass.

[0207] In Figure 1, the vertical direction Y of the windshield glass 24 corresponds to the vertical direction of the vehicle or other object on which the windshield glass 24 is installed, with the ground side being the bottom and the opposite side being the top. Note that when the windshield glass 24 is installed on a vehicle or other object, it may be installed at an angle for structural or design reasons. In this case, the vertical direction Y will be along the surface of the windshield glass 24. The surface is the outer side of the vehicle.

[0208] The present invention is basically configured as described above. Although the HUD system and its components, such as the windshield glass, have been described in detail above, the present invention is not limited to the embodiments described above, and various improvements or modifications may be made without departing from the spirit of the present invention. [Examples]

[0209] The present invention will be described in more detail below based on examples. The materials, amounts used, proportions, processing content, and processing procedures shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the specific examples shown below. In the following examples, "parts" and "%" used to express composition refer to mass unless otherwise specified. Room temperature is assumed to be 25°C.

[0210] <Preparation of coating solution> (1) Coating solution for forming a cholesteric liquid crystal layer The following components were mixed in the composition ratios shown below to prepare each narrow-band cholesteric liquid crystal layer forming solution for each cholesteric liquid crystal layer (UV1, B1, G1, R1) whose selective reflection center wavelength is the desired wavelength shown in Table 1 below. ------------------------------------------------------------------ Coating solution for forming a narrow-band cholesteric liquid crystal layer ------------------------------------------------------------------ ·Rod-shaped liquid crystal compound 101 55 parts by mass ·Rod-shaped liquid crystal compound 102 30 parts by mass ·Rod-shaped liquid crystal compound 201 13 parts by mass ·Rod-shaped liquid crystal compound 202 2 parts by mass • Polymerization initiator IRGACURE OXE01 (product name, manufactured by BASF) 1.0 parts by mass • Orientation control agent 1 (fluorine-based horizontal orientation agent 1) 0.01 parts by mass • Orientation control agent 3 (fluorine-based horizontal orientation agent 3) 0.01 parts by mass • Right-rotating chiral agent Paliocolor LC756 (product name, BASF) (Manufactured by the company) Adjusted to match the target's selected reflection center wavelength. • Solvent (methyl ethyl ketone): Amount sufficient to achieve a solute concentration of 20% by mass. ------------------------------------------------------------------

[0211] Rod-shaped liquid crystal compound 101: [ka]

[0212] Rod-shaped liquid crystal compound 102: [ka]

[0213] Rod-shaped liquid crystal compounds 201 and 202: [ka]

[0214] Orientation control agent 1: [ka]

[0215] Orientation control agent 3: [ka]

[0216] (Reflective properties of the cholesteric liquid crystal layer) Using the cholesteric liquid crystal layer forming solutions prepared above, single-layer cholesteric liquid crystal layers (layers cured by polymerization reaction) with a thickness of approximately 3 μm were fabricated on a temporary support in the same manner as the fabrication of cholesteric liquid crystal layers described later. All fabricated cholesteric liquid crystal layers were confirmed to be right-circularly polarized reflective layers, and the selective reflection center wavelength (center wavelength) and the full width at half maximum of the reflection peak were confirmed to be the wavelengths shown in Table 1 below. Note that the selective reflection center wavelength and the full width at half maximum of the reflection peak listed in Table 1 are values ​​measured by the reflection spectrum measurement of the selective reflection layer described later in [Evaluation α].

[0217] [Table 1]

[0218] (2) Coating solution for forming a phase difference layer The following components were mixed in the composition ratio shown below to prepare a coating solution for forming a phase difference layer. ·Mixture 1 100 parts by mass • Fluorine-based horizontal orientation agent 1 (orientation control agent 1) 0.05 parts by mass • Fluorine-based horizontal orientation agent 2 (orientation control agent 2) 0.01 parts by mass • Polymerization initiator IRGACURE OXE01 (product name, manufactured by BASF) 1.0 parts by mass • Solvent (methyl ethyl ketone): Amount sufficient to achieve a solute concentration of 20% by mass.

[0219] (3) Coating solution for forming a polarizing layer The following components were mixed in the composition ratio shown below to prepare a coating solution for forming a polarizing layer. ·Mixture 1 100 parts by mass • Fluorine-based horizontal orientation agent 1 (orientation control agent 1) 0.05 parts by mass • Fluorine-based horizontal orientation agent 2 (orientation control agent 2) 0.02 parts by mass • Right-rotating chiral agent Paliocolor LC756 (trade name, BASF) (manufactured by) 0.26 parts by mass • Polymerization initiator IRGACURE OXE01 (product name, manufactured by BASF) 1.0 parts by mass • Solvent (methyl ethyl ketone): Amount sufficient to achieve a solute concentration of 20% by mass.

[0220] Mixture 1: [ka]

[0221] Orientation control agent 2: [ka]

[0222] (Polarization characteristics of the polarization conversion layer) The selective reflection center wavelength λ of the polarization conversion layer obtained from the polarization conversion layer forming coating solution prepared above was 10,000 nm at an incident angle of light of 5°. The selective reflection center wavelength λ at an incident angle of 5° of light was measured by FTIR (Fourier Transform Infrared Spectroscopy, PerkinElmer, product name: Spectrum Two) after fabricating a single layer of cholesteric liquid crystal with a thickness of approximately 3 μm on a temporary support using the polarization conversion layer forming coating solution prepared above. Furthermore, in a cholesteric liquid crystal layer, the thickness d of the helical structure is expressed as "pitch P of the helical structure × number of pitches". As mentioned above, the pitch P of the helical structure refers to the thickness of the layer when the helically oriented liquid crystal compound rotates 360°. Also, in a cholesteric liquid crystal layer, the selective reflection center wavelength λ at an incident angle of light of 5° coincides with "pitch P of the helical structure × average refractive index n in the plane" (λ = P × n). Therefore, the pitch P of the helical structure becomes "selective reflection center wavelength λ at an incident angle of light of 5° / average refractive index n in the plane" (P = λ / n).

[0223] [Example 1] Fabrication of windshield glass <1-1> Fabrication of a selective reflective layer consisting of a cholesteric liquid crystal layer (1) Preparation of saponified cellulose acylate film In the preparation of the cellulose acylate film described in Example 20 of International Publication No. 2014 / 112575, a cellulose acylate film with a thickness of 40 μm was prepared in the same manner as described in the International Publication No. 2014 / 112575, except that instead of 2 parts by mass of the ultraviolet absorber described in paragraph

[0277] of International Publication No. 2014 / 112575, a core layer cellulose acylate dope was used, which consisted of 3 parts by mass of the ultraviolet absorber UV-531 (trade name) manufactured by Teisei Chemicals Co., Ltd., per 100 parts by mass of cellulose acetate (excluding ester oligomer A). The prepared cellulose acylate film was passed through a dielectric heating roll at a temperature of 60°C to raise the film surface temperature to 40°C. Then, an alkaline solution with the composition shown below was applied to one side of the film using a bar coater at a rate of 14 mL / m². 2 The mixture was applied in this manner and then left under a steam-type far-infrared heater (manufactured by Noritake Co., Ltd.) heated to 110°C for 10 seconds. Next, using the same bar coater, add 3 mL / m² of pure water. 2 It was applied in this manner. Next, the cellulose acylate film (transparent support) was prepared by repeating the process of washing with a fountain coater and draining with an air knife three times, followed by drying in a 70°C drying zone for 5 seconds. The in-plane phase difference of a saponified cellulose acylate film was measured using AxoScan (Axometrics, trade name) and was found to be 1 nm.

[0224] ------------------------------------------------------------------ Composition of alkaline solution ------------------------------------------------------------------ • Potassium hydroxide 4.7 parts by mass ·Water 15.7 parts by mass Isopropanol 64.8 parts by mass • Surfactants (C 16 H 33 O(CH2CH2O) 10 H) 1.0 parts by mass • Propylene glycol 14.9 parts by mass ------------------------------------------------------------------

[0225] (2) Formation of the orientation film Apply an orientation film-forming coating solution with the composition shown below to the saponified surface of a saponified cellulose acylate film (transparent support) using a wire bar coater at a rate of 24 mL / m². 2 The material was applied in this manner and dried with 100°C hot air for 120 seconds to form an oriented film.

[0226] ------------------------------------------------------------------ Composition of coating solution for aligning film formation ------------------------------------------------------------------ • 28 parts by mass of the modified polyvinyl alcohol shown below • Citrate ester (product name: AS3, manufactured by Sankyo Chemical Co., Ltd.) 1.2 parts by mass • Photoinitiator (Product name: Irgacure 2959, manufactured by BASF) 0.84 parts by mass Glutaraldehyde 2.8 parts by mass ·Water 699 parts by mass • Methanol 226 parts by mass ------------------------------------------------------------------

[0227] Modified polyvinyl alcohol: [ka]

[0228] (3) Fabrication of a laminate of a phase difference layer, a selective reflection layer, and a polarization conversion layer (3-1) Fabrication of the phase difference layer A cellulose acylate film with an orientation film formed on it was used as a support (transparent substrate). The orientation film surface of the support was subjected to rubbing in a direction rotated 45° clockwise from the long side of the support. Specifically, a rayon cloth was used, and the procedure was performed under the following conditions: pressure: 0.1 kgf (0.98 N), rotation speed: 1000 rpm (revolutions per minute), conveying speed: 10 m / min, and number of cycles: 1 round trip.

[0229] The phase difference layer forming solution prepared above was applied to the rubbed surface of the orientation film on the support using a wire bar, and then dried. Next, place it on a hot plate at 50°C and, in an environment with an oxygen concentration of 1000 ppm or less, use a Fusion UV Systems electrodeless lamp "D-bulb" (60 mW / cm²). 2 The liquid crystal phase was fixed by irradiating it with ultraviolet light for 6 seconds. This resulted in obtaining a phase difference layer whose thickness was adjusted to achieve the desired front phase difference, i.e., the desired retardation. The retardation of the fabricated phase difference layer was measured using AxoScan (Axometrics, product name) and found to be 126 nm.

[0230] (3-2) Fabrication of selective reflective layer The cholesteric liquid crystal layer (UV1) forming solution prepared above was applied to the surface of the obtained phase difference layer using a wire bar at room temperature so that the film thickness after drying was as shown in Table 3 below, thereby obtaining a coated layer. The coated layer was dried at room temperature for 30 seconds, then heated in an 85°C atmosphere for 2 minutes. Afterwards, it was heated in an environment with an oxygen concentration of 1000 ppm or less at 60°C using a Fusion D valve (60 mW / cm²). 2 The cholesteric liquid crystal phase was fixed by irradiating it with ultraviolet light at 60% output for 6 to 12 seconds using a lamp, and a cholesteric liquid crystal layer UV1 with the film thickness described in Table 3 below was obtained. Next, cholesteric liquid crystal layer B1, cholesteric liquid crystal layer G1, and cholesteric liquid crystal layer R1 were laminated on the surface of the obtained cholesteric liquid crystal layer UV1 in the order shown in Table 3 below, to obtain a laminate in which four cholesteric liquid crystal layers are laminated on top of the phase difference layer. Each of the cholesteric liquid crystal layers B1, G1, and R1 was fabricated one layer at a time, in the same manner as when fabricating the cholesteric liquid crystal layer UV1, except that the coating solution for forming the corresponding cholesteric liquid crystal layers (B1, G1, and R1) was used instead of the coating solution for forming the cholesteric liquid crystal layer (UV1). In addition, the selective reflective layer of No. 106 was fabricated in the same manner as before, except that the cholesteric liquid crystal layer UV1 was omitted and the cholesteric liquid crystal layer B1 was laminated on the surface of the phase difference layer.

[0231] (3-3) Fabrication of the polarization conversion layer Next, the polarization conversion layer-forming coating solution prepared above was applied to the outermost surface of the cholesteric liquid crystal layer of the obtained laminate to a thickness of 1.7 μm to form a polarization conversion layer (twisted layer). The polarization conversion layer was formed in the same manner as in the preparation of the cholesteric liquid crystal layer described above, except that the polarization conversion layer-forming coating solution was used instead of the cholesteric liquid crystal layer-forming coating solution. The resulting polarization conversion layer was a twisted layer with a selective reflection center wavelength λ10000nm and a pitch of 0.265. In this way, a laminate (also referred to as a "reflective film") was fabricated by stacking a phase difference layer, a selective reflection layer, and a polarization conversion layer in that order on a support (transparent substrate).

[0232] <1-2> Fabrication of a selective reflective layer (dielectric multilayer film) made of linearly polarized reflective film Based on the method described in Japanese Patent Publication No. 9-506837, a selective reflective layer consisting of a linearly polarized reflective film was prepared as follows.

[0233] 2,6-Polyethylene naphthalate (PEN) and a copolyester (coPEN) consisting of 70 mol% naphthalate and 30 mol% terephthalate were synthesized in a standard polyester resin synthesis kettle using ethylene glycol as the diol. The obtained single-layer films of PEN and coPEN were extruded, stretched at approximately 150°C with a stretch ratio of 5:1, and heat-treated at approximately 230°C for 30 seconds. As a result of this stretching and heat treatment, the refractive index of the PEN film was approximately 1.86 along the slow axis (orientation axis), and the refractive index along the transverse axis was 1.64. It was confirmed that the coPEN film was isotropic and had a refractive index of approximately 1.64.

[0234] Next, by adjusting the stretching ratio, the refractive index of the PEN film with respect to the slow axis became approximately 1.71, and the refractive index with respect to the transverse axis became 1.64. It was confirmed that the coPEN film is isotropic and has a refractive index of approximately 1.64. In other words, the difference Δn between the refractive index of the optically anisotropic layer, the PEN film, in the direction of the slow axis, and the refractive index of the optically isotropic layer, the coPEN film, is 0.07.

[0235] Next, a linearly polarized reflective film (also referred to as a "reflective film") was fabricated by stretching and heat-treating a laminate obtained by simultaneously extruding PEN and coPEN. The thickness of this linearly polarized reflective film is approximately 28 μm, and it has the following layers in this order: linearly polarized reflective layer UV2, which has 44 alternating layers each of PEN and coPEN with the thickness shown in column UV2 of Table 2 below; linearly polarized reflective layer B2, which has 44 alternating layers each of PEN and coPEN with the thickness shown in column B2 of Table 2 below; linearly polarized reflective layer G2, which has 39 alternating layers each of PEN and coPEN with the thickness shown in column G2 below; and linearly polarized reflective layer R2, which has 38 alternating layers each of PEN and coPEN with the thickness shown in column R2 below. Specifically, using an 88-slot supply block equipped with a standard extrusion die, under the same conditions as described in Example 1 of Japanese Patent Publication No. 9-506837, pre-stretched laminates corresponding to the UV2 layer, B2 layer, G2 layer, and R2 layer shown in Table 2 below were prepared. Then, the laminates formed by stacking all of these were uniaxially stretched at approximately 150°C with a stretch ratio of 5:1, and the stretched laminates were heat-treated in an air oven at approximately 230°C for 30 seconds to produce a linearly polarized reflective film. For example, for the unstretched laminates corresponding to the UV2 layer in Table 2 below, extrusion molding was performed at 295°C under conditions of approximately 7.9 pounds / hour for PEN and 7.6 pounds / hour for coPEN, so that the thickness would be an optical quarter wavelength of 445 nm. The unstretched laminates corresponding to the B2, G2, and R2 layers were extruded based on the same approach. Note that the selective reflection center wavelength and the full width at half maximum of the reflection peak listed in Table 2 are values ​​measured by the reflection spectrum measurement of the selective reflection layer described later in [Evaluation α].

[0236] [Table 2]

[0237] <2-1> Fabrication of windshield glass having a selective reflective layer made of a cholesteric liquid crystal layer Using the laminate prepared above, in which a support (transparent substrate), a phase difference layer, a selective reflection layer, and a polarization conversion layer are stacked in that order, a laminate was prepared in which a second glass plate, an interlayer, a polarization conversion layer, a selective reflection layer (cholesteric liquid crystal layer), a phase difference layer, a support (transparent substrate), a heat seal layer, and a first glass plate are stacked in that order. In the above-mentioned laminate, the heat-seal layer was formed by applying a heat-seal layer forming solution to the support (transparent substrate) side of the selective reflective layer, which consists of a cholesteric liquid crystal layer, using a wire bar, drying it, and then heating it at 50°C for 1 minute to form a heat-seal layer with a thickness of 1 μm. The resulting laminate was held at 90°C and 10kPa (0.1 atm) for one hour, and then heated in an autoclave (manufactured by Kurihara Seisakusho) at 115°C and 1.3MPa (13 atm) for 20 minutes to remove air bubbles, thereby obtaining windshield glass Nos. 101-104, 106, and c11.

[0238] <2-2> Fabrication of windshield glass having a selective reflective layer made of linearly polarized reflective film Using the linearly polarized reflective film prepared above, a laminate was fabricated in which a second glass plate, an interlayer, a selective reflective layer (dielectric multilayer film), an interlayer, and the first glass plate were stacked in this order. The obtained laminate was held at 90°C and 10kPa (0.1 atm) for one hour, and then heated in an autoclave (manufactured by Kurihara Seisakusho) at 115°C and 1.3MPa (13 atm) for 20 minutes to remove air bubbles and obtain windshield glass No. 105. Furthermore, the linearly polarized reflective film was laminated such that the linearly polarized reflective layer UV2 was on the first glass plate side and the linearly polarized reflective layer R2 was on the second glass plate side.

[0239] The windshield glass described above was used by cutting each layer to the same shape as the first and second glass plates described above. The glass plate, interlayer, and heat-sealing layer forming solution used in the production of the above-mentioned windshield glass are as follows: For the first and second glass plates, we used glass plates measuring 120mm in length x 100mm in width and 2mm in thickness (manufactured by Central Glass Co., Ltd., FL2, visible light transmittance 90%). Furthermore, a 0.38mm thick PVB (polyvinyl butyral) film manufactured by Sekisui Chemical Co., Ltd. was used as an interlayer. Furthermore, to prepare the heat seal layer, a coating solution for forming a heat seal layer was used, which was prepared by mixing the following components in the composition ratio shown below. (Coating liquid for forming a heat seal layer) • PVB sheet pieces (manufactured by Sekisui Chemical Co., Ltd., Esrec Film) 5.0 parts by mass • Methanol 90.25 parts by mass • Butanol 4.75 parts by mass

[0240] Table 3 below summarizes the configuration of the selective reflective layer in each windshield glass. The selective reflective layer in No. c11 was prepared in the same manner as in the preparation of the selective reflective layer in No. 103, except that the coating solutions for forming each cholesteric liquid crystal layer (UV, B, G, and R) listed in Table 2 of Japanese Patent Application Publication No. 2018-81296 were used instead. The optical properties of each cholesteric liquid crystal layer (UV3, B3, G3, and R3) in No. c11 are the same as the optical properties of each reflective layer (UV, B, G, and R) described in Table 3 of Japanese Patent Publication No. 2018-81296. Furthermore, in the measurement of the reflection spectrum of the selective reflection layer described later in [Evaluation α], the full width at half maximum of the reflection peaks with each selective reflection center wavelength in the selective reflection layer No. c11, measured with the incident light angle set to 60°, was 30 nm for cholesteric liquid crystal layer UV3, 35 nm for cholesteric liquid crystal layer B3, 45 nm for cholesteric liquid crystal layer G3, and 47 nm for cholesteric liquid crystal layer R3.

[0241] [Table 3]

[0242] [Example 2] Design of a head-up display Head-up displays No. 201-206 and c21, which are equipped with the windshield glass Nos. 101-106 and c11 fabricated as described above and a projector including a laser light source for forming projected images, were designed such that the second glass plate side of each windshield glass is the side into which the light from the laser light source enters. Head-up display systems No. 201 to 206 are the head-up display systems of the present invention, and head-up display system No. c21 is a comparative head-up display system. Furthermore, the reflective characteristics of the selective reflective layer in each windshield glass, the output power of each laser light source, and the relationship between the reflectance of the selective reflective layer and the brightness of the laser light in each head-up display system, as well as the evaluation results of image color and reflected color, are summarized in Table 4 below.

[0243] [Evaluation α] Measurement of the reflectance spectrum of the selective reflector layer Of the fabricated windshield glass panels, a black PET (polyethylene terephthalate) film (light absorber) was laminated to the back surface of the first glass panel. Using a spectrophotometer (JASCO Corporation, V-670), P-polarized or S-polarized light was incident from a desired angle relative to the normal direction of the windshield glass surface through the second glass plate of the windshield glass, and the reflection spectra of P-polarized and S-polarized light in the wavelength band of 300 to 800 nm were measured. The average value (average reflection spectrum) of the measured P-polarized and S-polarized reflection spectra was calculated. The graph shown in Figure 6 is the reflection spectrum measured when light was incident at an angle of 5° relative to the normal direction of the surface of windshield glass No. 101, and the graph shown in Figure 7 is the reflection spectrum measured when light was incident at an angle of 60° relative to the normal direction of the surface of windshield glass No. 101. In this invention, the selective reflection center wavelength (60°), reflectance (60°), and full width at half maximum (60°) refer to values ​​calculated based on the reflection spectrum measured when light is incident at an angle of 60° with respect to the normal direction of the windshield glass surface, while the selective reflection center wavelength (5°) refers to a value calculated based on the reflection spectrum measured when light is incident at an angle of 5° with respect to the normal direction of the windshield glass surface.

[0244] Furthermore, the average of the reflectance when P-polarized light is incident and the reflectance when S-polarized light is incident is equivalent to the reflectance when unpolarized light (natural light) is incident. In other words, the average of the reflectance spectra for P-polarized light and S-polarized light is equivalent to the reflectance spectrum when natural light is incident.

[0245] From the average values ​​of the calculated P-polarized and S-polarized reflection spectra, the selective reflection center wavelength λ and its full width at half maximum Δλ for the wavelength bands of 400 nm to less than 500 nm, 500 nm to less than 600 nm, and 600 nm to 700 nm were calculated using the method described above, based on the maximum value of the natural light reflectance and the two wavelengths that represent the reflectance midway between the maximum and minimum values ​​of the natural light reflectance. Furthermore, the reflectance at each selective reflection center wavelength λ was defined as the reflectance value at the selective reflection center wavelength λ in the average value of the calculated P-polarized and S-polarized reflection spectra.

[0246] [Evaluation 1] Evaluation of reflective color Natural light was incident on the first glass plate from a direction 5° to the normal direction of the first glass plate, and the reflectance spectrum was measured using a spectrophotometer (JASCO Corporation, V-670) from the normal direction of the first glass plate (observation position 5 in Figure 5). In accordance with JIS (Japanese Industrial Standards) R3106, the reflectance was calculated by multiplying the reflectance by a coefficient corresponding to the luminous efficiency and the emission spectrum of the D65 light source at wavelengths of 380 to 780 nm in 10 nm increments, and the reflected color a* and b* were calculated from these spectra. Furthermore, the same calculation was performed when the angle of incidence of natural light was changed to a direction of 60° with respect to the normal direction of the first glass plate. The reflected color was evaluated according to the evaluation criteria below. In this test, an evaluation of "AA to B" indicates that the reflected color is sufficiently suppressed and is desirable. In Table 4 below, the evaluations listed in the 5° and 60° columns for reflected color correspond to the evaluation when natural light is incident from a direction of 5° or 60° to the normal direction of the first glass plate, respectively. - Evaluation Criteria (Reflective Color) - AA: |a*|≦3 and |b*|≦3, so it appears white when white is projected onto it. A: |a*| ≤ 5 and |b*| ≤ 5 (excluding those that fall under AA above), and when white is projected, it appears almost white. B: |a*|≦7 and |b*|≦7 (excluding those that fall under AA or A above), and when white is projected, it appears to have a very slight tint.

[0247] [Evaluation 2] Evaluation of image color The output power of each color of the projector's laser light source was adjusted to the values ​​shown in Table 4 below, and a white image was projected from the projector at a 60° angle to the normal direction of the second glass plate. The color of the image was measured using a Topcon BM-5A colorimeter (product name) and evaluated according to the evaluation criteria below. More specifically, the image color was evaluated using the setup shown in Figure 5. The fabricated windshield glass 1 was tilted with its long side horizontal and its short side vertical, so that the second glass plate side was facing downwards. An image was projected onto the second glass plate from a projector 2 placed on the second glass plate side, and the color of the projected image was measured using a colorimeter 3. Projector 2 consisted of an RGB light source module with blue, green, and red laser light sources and a MEMS mirror. The distance between Projector 2 and the windshield glass 1 was 500 mm. For evaluation, p-polarization, i.e., linear polarization where the electric vector oscillation plane is parallel to the plane of the paper in Figure 5, was used. In this exam, a score of "AA to B" is considered a passing level. - Evaluation Criteria (Image Color Tone) - AA:|a*|≦3 and |b*|≦3, so the image appears white. A: |a*| ≤ 5 and |b*| ≤ 5 (excluding those that fall under AA above), and the image appears almost white. B: |a*| ≤ 7 and |b*| ≤ 7 (excluding those that fall under AA or A above), and the image appears slightly colored. C:|a*|≦9 and |b*|≦9 (excluding those that fall under any of AA, A, or B above), and the image appears color-tinted.

[0248] [Evaluation β] Measurement of laser light brightness The brightness L of each color laser light under the output power conditions of the laser light source for the above [Evaluation 2] evaluation of image color. B , L G and L R The following measurements were taken: L B The brightness of Projector 2 was measured using a Topcon BM-5A colorimeter (product name) when the output power of the blue laser light source was set to 49mW. G and L R Similarly, the luminance for the green and red laser light sources under the output power conditions listed in Table 4 was measured using a Topcon BM-5A colorimeter (product name). The brightness L of the laser light emitted from the projector 2, measured in this manner, is measured. B , L G and L R And the reflectance R of the selective reflective layer B , R G and R R From the product of, X B , X G and X R Calculate the ratio of these values, X B / X G , X B / X R , X G / X R The result was calculated.

[0249] [Evaluation 3] Evaluation of visible light transmittance Natural light was incident on the first glass plate from a direction 0° to the normal direction of the first glass plate, and the transmittance spectrum was measured from the normal direction of the second glass plate using a spectrophotometer (JASCO Corporation, V-670). In accordance with JIS R3106, the transmittance was calculated by multiplying the transmittance by a coefficient corresponding to the luminous sensitivity and the emission spectrum of light source A at wavelengths of 10 nm increments from 380 to 780 nm. In the head-up display systems No. 201 to 206 of the present invention, the windshield glasses No. 101 to 106 all have a transmittance of 80% or more. Even when laminated glass is formed using green glass instead of the first and second glass plates, the transmittance remains well above 70%.

[0250] [Table 4]

[0251] (Notes in the table) The selective reflection wavelength (60°) refers to the selective reflection center wavelength (60°), and its unit is nm. The unit of reflectance (60°) is %, and the unit of laser light source power is mW. PB, PG, and PR refer to the output power of the blue laser light, the output power of the green laser light, and the output power of the red laser light, respectively. RB / RG represents the ratio of reflectances, indicating the ratio of the value to the left of the " / " to the value to the right of the " / ". XB / XG in the table corresponds to X in specification (a). B / X G In the table, XB / XR is specified in (b) X B / X R In the table, XG / XR refers to X in the definition (c) G / X R These correspond to each other.

[0252] From the results in Table 4, the following can be seen. In comparative head-up display system No. c21, where the selective reflective layer in the windshield glass and the laser light source for forming the projected image did not meet the specifications (a) to (c), the projected image appeared color-shifted (image color evaluation "C") and was inferior. In contrast, the head-up display systems No. 201 to 206 of the present invention, which satisfy requirements (a) to (c), projected images that were almost colorless and close to neutral (image color evaluation "A" to "B"), exhibiting excellent image color. Furthermore, the head-up display systems No. 201 to 206 of the present invention exhibited high transparency, at or above the same level as the comparative head-up display system No. c21, in terms of the reflected color from their appearance.

[0253] Although we have described the present invention along with its embodiments, we do not intend to limit our invention in any detail of the description unless specifically designated, and we believe that it should be interpreted broadly without contradicting the spirit and scope of the invention as set forth in the appended claims.

[0254] This application claims priority based on Japanese Patent Application No. 2021-162101, filed in Japan on 30 September 2021, the contents of which are incorporated herein by reference as part of this specification. [Explanation of Symbols]

[0255] 1. Windshield glass 2 Projectors 3. Colorimeter 5. Observation position 10 Reflective film 10A Linear Polarizing Reflective Film 10B Linear Polarizing Reflective Film 11 Selective Reflection Layer 12 Cholesteric liquid crystal layer 12R Selective reflection center wavelength λ at an incident angle of light of 60° R Cholesteric liquid crystal layer having 12G Selective reflection center wavelength λ at an incident angle of light of 60° G Cholesteric liquid crystal layer having 12B Selective reflection center wavelength λ at an incident angle of light of 60° B Cholesteric liquid crystal layer having 13R Selective reflection center wavelength λ at an incident angle of light of 60° R First laminate having 13G Selective reflection center wavelength λ at an incident angle of light of 60° G Second laminate having 13B Selective reflection center wavelength λ at an incident angle of light of 60° B Third laminate having 13Ra, 13Ga, 13Ba optically anisotropic layer 13Rb, 13Gb, 13Bb optically isotropic layer 14 Polarization conversion layer 16 Retardation layer 18 Transparent base material 20. Head-Up Display System (HUD System) 22 Projectors 24, 24A, 24B Windshield Glass 28. Second glass plate 30 First glass plate 36 Interlayer 38 Adhesive layer (heat seal layer) D Driver n e1 Refractive index in the slow axis direction of the optically anisotropic layer n o1 Refractive index in the direction perpendicular to the slow axis of the optical anisotropy layer n o2 Refractive index of an optically isotropic layer Y vertical direction

Claims

1. A head-up display system comprising a windshield glass having a selective reflective layer and a projector including a laser light source for forming an image on the windshield glass, The selective reflection layer has the following λ as its selective reflection center wavelength at an incident angle of light of 60°. Ｂ , λ Ｇ and λ Ｒ It includes these three wavelengths, 400nm≦λ Ｂ <500nm 500nm≦λ Ｇ <600nm 600nm≦λ Ｒ ≦700nm The aforementioned laser light source emits three colors of laser light: blue light, green light, and red light. A head-up display system that satisfies all of the following requirements (a) to (c). The regulation (a) is 0.80 ≤ X Ｂ / X Ｇ ≤1.20 Provision (b) 0.80 ≤ X Ｂ / X Ｒ ≤1.20 Regulation (c) 0.80 ≤ X Ｇ / X Ｒ ≤1.20 In the above provisions, X Ｂ = R Ｂ ×L Ｂ X Ｇ = R Ｇ ×L Ｇ X Ｒ = R Ｒ ×L Ｒ That is the case. R Ｂ The λ of the selective reflection layer is Ｂ This shows the natural light reflectance at R Ｇ The λ of the selective reflection layer is Ｇ This shows the natural light reflectance at R Ｒ The λ of the selective reflection layer is Ｒ This shows the natural light reflectance at L. Ｂ L indicates the brightness of the blue laser light emitted from the projector, Ｇ L indicates the brightness of the green laser light emitted from the projector, Ｒ This indicates the brightness of the red laser light emitted from the projector.

2. A head-up display system according to claim 1, satisfying all of the following requirements (a1) to (c1). Specify (a1) 0.90≦X Ｂ / X Ｇ ≤1.10 Specify (b1) 0.90≦X Ｂ / X Ｒ ≤1.10 Regulation (c1) 0.90≦X Ｇ / X Ｒ ≤1.10 In the above provisions, X Ｂ , X Ｇ and X Ｒ The above X Ｂ , X Ｇ and X Ｒ It is synonymous with [the above].

3. The natural light reflectance R of the selected reflective layer Ｂ , R Ｇ and R Ｒ However, R Ｂ > R Ｇ ≥ R Ｒ A head-up display system according to claim 1 or 2 that satisfies the relationship.

4. The natural light reflectance R of the selected reflective layer Ｂ and R Ｇ However, R Ｂ / R Ｇ A head-up display system according to claim 1 or 2 that satisfies the relationship ≥ 1.

10.

5. The selective reflection center wavelength λ at an incident angle of light of 60°, which is included in the selective reflection layer. Ｂ , λ Ｇ and λ Ｒ The full width at half maximum of each is 100 nm or less, and the natural light reflectance R of the selective reflective layer Ｂ , R Ｇ and R Ｒ The head-up display system according to claim 1 or 2, wherein each of these is 25% or more.

6. The selective reflection layer includes the selective reflection center wavelengths λB, λG, and λR at an incident angle of light of 60°, and the full width at half maximum of each wavelength is 100 nm or less. The head-up display system according to claim 2, wherein the natural light reflectances R B, RG and RR of the selective reflective layer are all 25% or more, and the relationships R B > RG ≥ RR and R B / RG ≥ 1.10 are satisfied.

7. The head-up display system according to claim 1 or 2, wherein the windshield glass includes at least one polarization conversion layer.

8. The head-up display system according to claim 1 or 2, wherein the selective reflective layer is made of cholesteric liquid crystal.

9. The head-up display system according to claim 1 or 2, wherein the selective reflective layer is formed by laminating an optically anisotropic layer and an optically isotropic layer.

10. A transport aircraft equipped with the head-up display system according to claim 1 or 2.

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