Combiner and head-up display system

Abstract

The present invention addresses the problem of providing a combiner that, when applied in a head-up display system for a vehicle in which p-polarized light is used as projection light, achieves a bright projected image and suppresses dashboard reflection. The present invention also addresses the problem of providing a head-up display system.　A combiner according to the present invention comprises an antireflection layer, a base material, and a reflection layer in this order, wherein conditions (A) to (D) are satisfied.

Description

Combiner, head-up display system

[0001] The present invention relates to a combiner and a head-up display system.

[0002] In recent years, various types of head-up displays (hereinafter also referred to as "HUDs") have been widely applied in daily life, and in particular, head-up displays that display information by superimposing an image on an environmental image are often used in vehicles, aircraft, etc. Taking a vehicular head-up display as an example, optical information emitted from an information projection means such as a portable information terminal is projected onto the windshield or combiner of the automobile, and the information is displayed superimposed on the foreground. The combiner typically uses a member with a reflective function.

[0003] Incidentally, Patent Document 1 discloses a substrate with a semi-transparent mirror, which includes, in this order, a glass substrate, an undercoat film (e.g., a silicon oxide film) having a predetermined film thickness, and a semi-transparent reflective film (e.g., Al or an Al alloy) as a member with a reflective function.

[0004] Japanese Patent Application Laid-Open No. 2003-029010

[0005] The inventors fabricated the semi-transparent mirror-equipped substrate described in Patent Document 1, applied it to a combiner for a vehicle head-up display system that uses P-polarized light as projection light, and examined its functionality. As a result, they found that a phenomenon (hereinafter also referred to as "dashboard reflection") occurred in which reflected light from ambient light on the dashboard (for example, sunlight or interior vehicle lights such as LED lights) was superimposed on the image projected on the combiner (hereinafter also referred to as "projected image" or "HUD image"), making it difficult to see the projected image of the combiner. In addition, it is also desirable for the projected image of the combiner to have appropriate brightness and excellent visibility as basic characteristics.

[0006] In view of the above circumstances, an object of the present invention is to provide a combiner that, when used as a combiner for a head-up display system for a vehicle that uses P-polarized light as projection light, produces a bright projected image and suppresses dashboard reflections. Another object of the present invention is to provide a head-up display system.

[0007] The present inventors have found that the above-mentioned problems can be solved by the following configuration. [1] A combiner having an antireflection layer, a substrate, and a reflective layer in this order, which satisfies all of the following requirements (A) to (D): (A) The P-polarized reflectance when P-polarized light is incident on the combiner from the antireflection layer side at an incident angle of 45° is 20.0% or more. (B) The ratio of the P-polarized reflectance when P-polarized light is incident on the combiner from the antireflection layer side at an incident angle of 45° to the S-polarized reflectance when S-polarized light is incident on the combiner from the antireflection layer side at an incident angle of 45° is 1.20 or more. (C) The distance between the antireflection layer and the reflective layer in the thickness direction of the combiner is 30 μm or more. (D) The unpolarized reflectance when unpolarized light is incident on the combiner from the antireflection layer side at an incident angle of 45° is 20.0% or less. [2] The combiner according to [1] satisfies the following requirements (B1) and (C1): (B1) The ratio of the P-polarized reflectance when P-polarized light is incident on the combiner from the antireflection layer side at an incident angle of 45° to the S-polarized reflectance when S-polarized light is incident on the combiner from the antireflection layer side at an incident angle of 45° is 1.50 or more; (C1) The distance between the antireflection layer and the reflective layer in the thickness direction of the combiner is 1 mm or more; [3] The combiner according to [1] or [2] satisfies any of the following requirements (E) to (H): (E) The reflective layer has a dielectric multilayer film and a metal layer disposed in the dielectric multilayer film, the metal layer containing aluminum or silver; (F) The reflective layer is a dielectric multilayer film, and further has a retardation layer between the antireflection layer and the reflective layer, the in-plane retardation of the retardation layer at a wavelength of 550 nm is 200 to 350 nm. (G) The reflective layer is a cholesteric liquid crystal layer, and a retardation layer is further provided between the antireflection layer and the reflective layer. (H) The reflective layer is a linearly polarized light reflective layer including an optically isotropic layer and an optically anisotropic layer. [4] The combiner according to any one of [1] to [3], wherein the substrate is glass. [5] The combiner according to any one of [1] to [4], further comprising a light-shielding member on the side of the reflective layer opposite to the substrate side.[6] A head-up display system having the combiner according to any one of [1] to [5] and a projector that irradiates projection light onto the combiner. [7] The head-up display system according to [6], wherein the projector emits P-polarized light as the projection light. [8] The head-up display system according to [6] or [7], which is for use in a vehicle.

[0008] According to the present invention, when applied as a combiner in a head-up display system for a vehicle that uses P-polarized light as projection light, it is possible to provide a combiner that projects a bright image and suppresses dashboard reflections. Also, according to the present invention, it is possible to provide a head-up display system.

[0009] 12A is a schematic diagram showing a conventional head-up display system as viewed from the side; FIG. 12B is a schematic diagram showing a head-up display system of the present invention as viewed from the side; FIG. 12C is a schematic diagram showing an example of an embodiment of a combiner of the present invention; FIG. 12D is a schematic diagram showing an example of an embodiment of a combiner of the present invention; FIG. 12E is a schematic diagram showing an example of an embodiment of a combiner of the present invention; FIG. 12F is a schematic diagram showing an example of an embodiment of a combiner of the present invention; FIG. 12G is a schematic diagram showing an example of an embodiment of a combiner of the present invention; FIG. 12H is a schematic diagram showing an example of an embodiment of a combiner of the present invention;

[0010] The present invention will be described in detail below. Note that the figures described below are illustrative for explaining the present invention, and the present invention is not limited to the figures shown below. Note that in the following, the "to" symbol indicating a numerical range includes the values ​​written on both sides. For example, when ε1 is between numerical value α1 and numerical value β1, the range of ε1 includes numerical values ​​α1 and β1, and expressed in mathematical notation, α1≦ε1≦β1.

[0011] Unless otherwise specified, the term "light" refers to visible light and natural light (unpolarized). Visible light is electromagnetic light with wavelengths visible to the human eye, typically light in the wavelength range of 380 to 780 nm. Invisible light is light in the wavelength range less than 380 nm or greater than 780 nm. Furthermore, although not limited thereto, visible light in the wavelength range of 420 to 490 nm is blue (B) light, light in the wavelength range of 495 to 570 nm is green (G) light, and light in the wavelength range of 620 to 750 nm is red (R) light. Furthermore, in this specification, the arithmetic mean value of the reflectance when P-polarized light is incident (P-polarized reflectance) and the reflectance when S-polarized light is incident (P-polarized reflectance) is treated as synonymous with the reflectance when unpolarized light (natural light) is incident (unpolarized reflectance).

[0012] In this specification, the slow axis is defined at 550 nm unless otherwise specified.

[0013] In this specification, Re(λ) and Rth(λ) represent the in-plane retardation and the thickness direction retardation, respectively, at a wavelength λ. Unless otherwise specified, the wavelength λ is 550 nm. In this specification, Re(λ) and Rth(λ) are values ​​measured at a wavelength λ using an AxoScan OPMF-1 (manufactured by Optoscience). Specifically, by inputting the average refractive index ((nx + ny + nz) / 3) and the film thickness (d (μm)) into the AxoScan OPMF-1, the following slow axis direction (°) is calculated: Re(λ) = R0(λ) Rth(λ) = ((nx + ny) / 2 - nz) × d. Although R0(λ) is displayed as a numerical value calculated by the AxoScan OPMF-1, it means Re(λ).

[0014] In this specification, the angular relationship (e.g., "perpendicular," "parallel," etc.) is intended to include the range of error acceptable in the technical field to which the present invention pertains. Specifically, this means that the angle is within a range of less than ±10° from the exact angle, and the error from the exact angle is preferably within a range of ±5° or less, and more preferably within a range of ±3° or less.

[0015] In this specification, unless otherwise specified, the thickness (film thickness) of a layer is the average thickness measured using an optical microscope or a scanning electron microscope (SEM) for a thickness of 0.5 μm or more, and the average thickness is the average thickness measured using a transmission electron microscope (TEM) for a thickness of less than 0.5 μm. The average thickness is obtained by preparing a slice of the object to be measured using an ultramicrotome, measuring the thickness at any five points, and calculating the arithmetic average of the thicknesses.

[0016] [Combiner, Head-Up Display System] The combiner of the present invention has an antireflection layer, a substrate, and a reflective layer in this order, and satisfies all of the following requirements (A) to (D): (A) The P-polarized reflectance (hereinafter also referred to as "P-polarized reflectance (45°)") when P-polarized light is incident on the combiner from the antireflection layer side at an incident angle of 45° is 20.0% or more. (B) The ratio of the P-polarized reflectance (P-polarized reflectance (45°)) when P-polarized light is incident on the combiner from the antireflection layer side at an incident angle of 45° to the S-polarized reflectance (hereinafter also referred to as "S-polarized reflectance (45°)") when S-polarized light is incident on the combiner from the antireflection layer side at an incident angle of 45° (P-polarized reflectance (45°) / S-polarized reflectance (45°); hereinafter also referred to as "P-polarized / S-polarized ratio") is 1.20 or more. (C) The distance between the antireflection layer and the reflective layer in the thickness direction of the combiner is 30 μm or more. (D) The unpolarized reflectance (hereinafter also referred to as "unpolarized reflectance (45°)") when unpolarized light is incident on the combiner from the antireflection layer side at an incident angle of 45° is 20.0% or less.

[0017] The combiner of the present invention preferably further satisfies the following requirements (B1) and (C1): (B1) The P-polarized light / S-polarized light ratio is 1.50 or more, and (C1) The distance between the antireflection layer and the reflective layer in the thickness direction of the combiner is 1 mm or more.

[0018] In the above-mentioned requirement (A), the upper limit of the P-polarized light reflectance (45°) is preferably 40.0% or less, and more preferably 35.0% or less. In the above-mentioned requirements (B) and (B1), the upper limit of the P-polarized light / S-polarized light ratio is preferably 80.0 or less, and more preferably 40.0 or less. In the above-mentioned requirements (C) and (C1), the upper limit of the distance in the thickness direction of the combiner between the antireflection layer and the reflective layer is preferably 10 mm or less, and more preferably 5 mm or less, from the viewpoints of superior manufacturability and less likelihood of double images (ghosts) occurring at the interface.

[0019] In this specification, the P-polarized light reflectance (45°), the S-polarized light reflectance (45°), and the unpolarized light reflectance (45°) are each measured by the following procedures.

[0020] <P-Polarized Reflectance (45°)> P-polarized light is incident on the combiner at a polar angle of 45° relative to the normal direction of the combiner, and the reflection spectrum (wavelength range: 380 to 780 nm) of the specularly reflected light reflected by the combiner is measured using a spectrophotometer. Note that the light is incident toward the anti-reflection layer side of the combiner. The light source for the P-polarized light incident on the combiner is a light source capable of emitting light in the wavelength range of 380 to 780 nm. For example, a halogen lamp may be used as the light source, and a polarizer may be placed between the combiner and the halogen lamp to emit P-polarized light. Next, based on JIS R3106 2019, the P-polarized reflectance (45°) is calculated by multiplying the reflectance value based on the reflection spectrum obtained above by a weighting factor obtained from the CIE daylight D65 spectral distribution and the CIE photopic standard relative luminosity factor, and then calculating the weighted average. The weighting coefficients used are those shown in JIS R3106 2019 and corresponding to wavelengths in 10 nm increments in the wavelength range of 380 to 780 nm.

[0021] <S-polarized light reflectance (45°)> The procedure for measuring S-polarized light reflectance (45°) is the same as the procedure for measuring P-polarized light reflectance (45°) described above, except that the P-polarized light incident on the combiner is changed to S-polarized light.

[0022] <Unpolarized Reflectance (45°)> The unpolarized reflectance (45°) is determined as the arithmetic mean of the P-polarized reflectance (45°) and the S-polarized reflectance (45°) measured by the above-described measurement procedure.

[0023] One of the features of the present invention is the use of an anti-reflection layer. First, a problem with a head-up display system including a combiner without an anti-reflection layer will be described with reference to FIG. 1 . FIG. 1 is a schematic diagram of a head-up display system 100 viewed from the side. The head-up display system 100 includes a projector 112 that emits projection light (P-polarized light) and a combiner 114 that is positioned so that the projection light emitted from the projector 112 is incident at an incident angle of 45°. The combiner 114 includes a substrate 116 and a reflective layer 118, and the projection light is incident from the reflective layer 118 side. In the head-up display system 100 illustrated in FIG. 1 , the projection light emitted from the projector 112 is reflected by the combiner 114 and observed by an observer OB, as indicated by the solid line. When the combiner 114 is mounted on a vehicle, as shown by the dotted line, ambient light (e.g., sunlight or interior vehicle lighting such as LED lights) reflected from the dashboard 120 is reflected by the reflective layer 118 of the combiner 114, and this reflected light is superimposed on the image projected on the combiner 114 (dashboard reflection), which can be observed by the observer OB. The light reflected from the dashboard 120 as observed by the observer OB typically contains a large amount of S-polarized light. Furthermore, when the semi-transparent mirrored substrate described as a conventional technique is used as the combiner 114, the semi-transparent mirrored substrate has a high unpolarized reflectivity, and therefore, when projection light emitted from the projector 112 enters the combiner 114 at an incident angle of 45°, it is reflected with high reflectivity, resulting in excellent brightness of the projected image. However, the ambient light reflected from the dashboard 120 is also reflected with high reflectivity by the combiner 114, resulting in the problem of dashboard reflection.

[0024] In response to the above problem, the combiner of the present invention has an anti-reflection layer, a substrate, and a reflective layer arranged in this order, and further has a configuration that satisfies all of the above-mentioned (A) to (D). When applied as a combiner for a head-up display system for a vehicle that uses P-polarized light as projection light, the projected image is bright and dashboard reflection can be suppressed.

[0025] An example of a head-up display system according to the present invention will be described below.

[0026] [First Embodiment] Figure 2 shows a head-up display system according to a first embodiment. Figure 2 is a schematic side view of a head-up display system 10. The head-up display system 10 includes a projector 12 that emits projection light (P-polarized light) and a combiner 14 that is positioned so that the projection light emitted from the projector 12 is incident at an angle of 45°. The combiner 14 includes a reflective layer 16, a substrate 18, an anti-reflection layer 20 that is positioned 30 μm or more away from the reflective layer 16 in the thickness direction of the combiner, and a light-shielding layer (light-shielding member) 22 that is positioned on the side of the reflective layer 16 opposite the substrate 18. The projection light is incident on the combiner 14 from the anti-reflection layer 20 side. The combiner 14 also has a P-polarized light reflectivity (at 45°) of 20.0% or more, a P-polarized light / S-polarized light ratio of 1.20 or more, and an unpolarized light reflectivity (at 45°) of 20.0% or less. Although the combiner 14 includes a light-shielding layer 22, the light-shielding layer 22 is an optional component and does not necessarily have to be disposed on the combiner.

[0027] 3 is a schematic diagram illustrating the layer configuration of the reflective layer 16 of the combiner 14. The reflective layer 16 includes a dielectric multilayer film 30 and a metal layer 32 containing aluminum or silver disposed within the dielectric multilayer film 30. Specifically, the reflective layer 16 includes, from the substrate 18 side, a first dielectric layer 30A, a second dielectric layer 30B, the metal layer 32 containing aluminum or silver, a third dielectric layer 30C, and a fourth dielectric layer 30D.

[0028] Typically, the refractive index of a metal layer is expressed as a complex refractive index n-ik (k is the extinction coefficient), which includes an imaginary part. As a result, the reflection is also a complex number, and the phase of the reflection at the interface between the dielectric layer and the metal layer is shifted from 0° or 180°. Furthermore, aluminum and silver have an extremely low refractive index, n<1, compared to typical dielectric layers. By utilizing this characteristic, a metal layer is sandwiched between dielectric layers and the phase is controlled by the film thickness and refractive index of each layer, P-polarized light reflection can be made higher than S-polarized light reflection for obliquely incident light. Based on the above characteristics, the reflective layer 16 is configured such that a metal layer is sandwiched between dielectric layers. By utilizing the phase shift of the reflection at the interface between the dielectric layer and the metal layer and controlling the phase by the film thickness and refractive index of each layer, the reflective layer 16 exhibits a characteristic in which the P-polarized light reflectance (45°) is higher than the S-polarized light reflectance (45°).

[0029] In the head-up display system 10 illustrated in FIG. 2 , as shown by the solid line, projection light emitted from the projector 12 is reflected by the combiner 14 and observed by the observer OB. The combiner 14 includes an anti-reflection layer 20 and a mechanism that causes the light reflected by the reflective layer 16 to have a higher P-polarized reflectance (45°) than the S-polarized reflectance (45°). Therefore, as shown by the dotted line, the reflection of ambient light from the dashboard 120 is easily suppressed, while exhibiting a high P-polarized reflectance (45°). In other words, because the P-polarized reflectance (45°) of the combiner 14 is 20.0% or higher (satisfies requirement (A)), the image projected on the combiner 14 is observed by the observer OB as a bright image with excellent visibility. On the other hand, because the P-polarized light / S-polarized light ratio of the combiner 14 is 1.20 or more (satisfying requirement (B)), even if ambient light reflected from the dashboard 120 enters the combiner 14, the observer OB is unlikely to observe dashboard reflections. Also, because the unpolarized reflectance (45°) of the combiner 14 is 20.0% or less (satisfying requirement (D)), even if ambient light reflected from the dashboard 120 enters the combiner 14, the observer OB is unlikely to observe dashboard reflections. Note that if the distance between the reflective layer 16 and the antireflection layer 20 is less than 30 μm in the thickness direction of the combiner 14, optical interference occurs between the reflective layer 16 and the antireflection layer 20, making it difficult to satisfy the above-mentioned requirements (A) and (B).

[0030] Each component of the head-up display system 10 will be described in detail below.

[0031] <Projector> The configuration of the projector 12 is not particularly limited as long as it can emit projection light to be emitted to the combiner 14, and any known projector can be used.

[0032] The projection light emitted by the projector 12 is preferably P-polarized light. The projector 12 may have a polarizer therein in order to emit P-polarized projection light.

[0033] Examples of the projector 12 include an LCOS (Liquid Crystal on Silicon) projector, a laser projector, and a liquid crystal projector (liquid crystal display device).

[0034] <Anti-reflection layer> The anti-reflection layer 20 is not particularly limited as long as it is a layer that has the function of reducing reflectance, but it is preferably a layer with a low S-polarized light reflectance (45°). Examples of the anti-reflection layer 20 include an anti-reflection layer with a multilayer structure in which layers with a relatively low refractive index (low refractive index layers) and layers with a relatively high refractive index (high refractive index layers) are alternately stacked.

[0035] The antireflection layer 20 may have a structure including at least one low refractive index layer and at least one high refractive index layer, for example, a two-layer structure of low refractive index layer / high refractive index layer, a three-layer structure of low refractive index layer / high refractive index layer / low refractive index layer, or a structure including at least two low refractive index layers and at least two high refractive index layers, and high refractive index layers and low refractive index layers stacked alternately. The antireflection layer 20 preferably has a structure in which 2 to 6 layers are stacked in total. The film thickness of the antireflection layer 20 is preferably, for example, 50 to 300 nm. The refractive index of the low refractive index layer is preferably, for example, 1.20 to 1.70. Examples of materials constituting the low refractive index layer include silicon oxide (SiO ２ ), aluminum oxide (Al ２ O ３ ), and magnesium fluoride (MgF ２ The refractive index of the high refractive index layer is preferably, for example, 1.80 to 2.60. Examples of materials constituting the high refractive index layer include niobium oxide (Nb ２ O ５ ), titanium oxide (TiO ２ ), zirconium oxide (ZrO ２ ), silicon nitride (SiN), tantalum oxide (Ta ２ O ５ ), tungsten oxide (WO ３ ), cerium oxide (CeO ２), zinc oxide (ZnO), and indium tin oxide (ITO). The anti-reflection layer 20 can be adjusted to reduce the S-polarized light reflectance (45°) by adjusting the film thickness and refractive index of each layer.

[0036] <Substrate> The substrate 18 is a member that supports the antireflection layer and the reflective layer. The material of the substrate 18 is not particularly limited, and examples thereof include resin and glass, with glass (glass substrate) being preferred. When the substrate 18 is a resin substrate, examples of the substrate include plastic films such as polyesters such as polyethylene terephthalate (PET), polycarbonates, acrylic resins, epoxy resins, polyurethanes, polyamides, polyolefins, cellulose derivatives, and silicones.

[0037] The thickness of the substrate 18 is preferably 30 to 5000 μm, more preferably 35 to 4500 μm, and even more preferably 40 to 4000 μm.

[0038] <Reflective Layer> As described above, the reflective layer 16 has a laminated structure in which a metal layer is sandwiched between dielectric layers, and by utilizing the phase shift of reflection at the interface between the dielectric layer and the metal layer and by controlling the phase by the film thickness and refractive index of each layer, the reflective layer 16 exhibits a characteristic in which the P-polarized light reflectance (45°) is higher than the S-polarized light reflectance (45°).

[0039] (Metal Layer) The lower the refractive index of the metal layer 32, the higher the P-polarized light reflectance (45°). Therefore, the refractive index of the metal layer 32 at a wavelength of 550 nm is preferably 1.0 or less, more preferably 0.5 or less, and even more preferably 0.3 or less. The lower limit of the refractive index of the metal layer 32 at a wavelength of 550 nm is often 0.03 or more. Furthermore, the metal layer 32 is preferably a metal or a metal alloy. The metal layer 32 preferably contains aluminum or silver, and is preferably an aluminum or silver element or alloy, in order to facilitate setting the refractive index within the above-mentioned range. The thickness of the metal layer 32 is preferably 1 to 30 nm, more preferably 3 to 18 nm, in order to further increase the P-polarized light reflectance (45°) and the P-polarized light / S-polarized light ratio.

[0040] (Dielectric Multilayer Film) The first dielectric layer 30A, the second dielectric layer 30B, the third dielectric layer 30C, and the fourth dielectric layer 30D constituting the dielectric multilayer film 30 are made of, for example, ZnSnMgOx, ZnSnOx, ZnO, SnO, which can be formed by vapor phase film formation such as magnetron sputtering. ２ , SiN, TiO ２ , Si ３ N ４ , Mg ２ F, SiO ２ , and AlN films are preferred.

[0041] The first dielectric layer 30A, the second dielectric layer 30B, the third dielectric layer 30C, and the fourth dielectric layer 30D can increase the P-polarized light reflectivity (45°) and the P-polarized light / S-polarized light ratio. Therefore, it is preferable that the material and film thickness of each dielectric layer be set so that the first dielectric layer 30A and the second dielectric layer 30B, which are arranged on the light incident side of the metal layer 32, function as anti-reflection layers for the metal layer 32, and the third dielectric layer 30C and the fourth dielectric layer 30D, which are arranged on the opposite side of the metal layer 32 from the light incident side, function as reflection-enhancing layers for the metal layer 32.

[0042] The second dielectric layer 30B and the second dielectric layer 30C disposed adjacent to the metal layer 32 are preferably SiN films from the viewpoint of preventing the metal layer 32 from being oxidized by exposure to oxygen plasma. ２ Preferably it is a membrane.

[0043] The thickness of each of the first dielectric layer 30A, the second dielectric layer 30B, the third dielectric layer 30C, and the fourth dielectric layer 30D is preferably, for example, 1 to 300 nm. More specifically, the thickness of the first dielectric layer 30A is preferably 25 to 65 nm, the thickness of the second dielectric layer 30B is preferably 40 to 80 nm, the thickness of the third dielectric layer 30C is preferably 5 to 45 nm, and the thickness of the fourth dielectric layer 30D is preferably 17 to 57 nm.

[0044] Although the reflective layer 16 has a four-layer dielectric multilayer film 30, the number of layers is not limited to four, and may be two or more. The upper limit is preferably eight layers.

[0045] <Light-shielding layer> The light-shielding layer 22 is an optional component. Providing the light-shielding layer 22 in the combiner 14 further improves the visibility of the projected image reflected by the combiner 14. An example of the light-shielding layer 22 is a layer formed by dispersing a black agent (such as a black pigment or black dye) in a binder. The visible light transmittance of the light-shielding layer 22 is preferably 30% or less, more preferably 10% or less, and even more preferably 1% or less.

[0046] A commercially available product can be used as the light-shielding layer. A commercially available product that can be used includes a laminate of a light-shielding layer and a temporary support. An example of a commercially available product is a commercially available color correction film sold as black PET (Kukkiri Miel 125 μm, manufactured by Tomoegawa Corporation). The thickness of the light-shielding layer is preferably 1 to 200 μm, and more preferably 10 to 100 μm.

[0047] In the combiner 14, the distance between the anti-reflection layer 20 and the reflective layer 16 in the thickness direction of the combiner 14 is 30 μm or more, preferably 1 mm or more, more preferably 1.5 mm or more, and even more preferably 2.0 mm or more, in order to suppress optical interference between the reflective layer 16 and the anti-reflection layer 20 and easily satisfy the above-mentioned requirements (A) and (B). The upper limit is preferably 5.0 mm or less, more preferably 4.0 mm or less. When the combiner 14 is configured to include only the substrate 12 between the anti-reflection layer 20 and the reflective layer 16, the distance between the anti-reflection layer 20 and the reflective layer 16 in the thickness direction of the combiner 14 corresponds to the thickness of the substrate 12. For example, when another layer, such as an adhesive layer, is further interposed between the anti-reflection layer 20 and the reflective layer 16, the sum of the thickness of the other layer, such as the adhesive layer, and the thickness of the substrate 12 corresponds to the distance between the anti-reflection layer 20 and the reflective layer 16 in the thickness direction of the combiner 14.

[0048] Second Embodiment Next, a head-up display system according to a second embodiment will be described. The configuration of the head-up display system according to the second embodiment is similar to that of the head-up display system according to the first embodiment, except that a combiner 44 is used instead of the combiner 14. The combiner 44 will be described below with reference to FIG. 4. The combiner 44 shown in FIG. 4 includes, in this order, an anti-reflection layer 20, a first substrate 40, a second substrate 42, a λ / 2 plate 48 serving as a retardation layer, a dielectric multilayer film 46 serving as a reflective layer, and a light-shielding layer 22. Projection light emitted from the projector 12 is incident on the anti-reflection layer 20 side. Furthermore, the distance between the anti-reflection layer 20 and the dielectric multilayer film 46 in the thickness direction of the combiner 44 is 30 μm or more. The λ / 2 plate 48 corresponds to a retardation layer, and has an in-plane retardation of 200 to 350 nm at a wavelength of 550 nm. The combiner 44 has a P-polarized light reflectance (45°) of 20.0% or more, a P-polarized light / S-polarized light ratio of 1.20 or more, and an unpolarized light reflectance (45°) of 20.0% or less. The combiner 44 includes a light-shielding layer 22 and a second substrate 42, but the light-shielding layer 22 and the second substrate 42 are optional components and do not necessarily need to be disposed in the combiner.

[0049] The λ / 2 plate 48, which is a retardation layer, has an in-plane slow axis. When the projection light emitted from the projector 12 is incident on the combiner 44 from the anti-reflection layer 20 side, as shown in Figure 5, it is preferable that the projection light (P-polarized) is incident from a direction at a polar angle of 45° with respect to the normal direction of the combiner 44 (arrow in the figure) at an azimuth angle of 45° with respect to the in-plane slow axis of the λ / 2 plate 48, which is a retardation layer (note that Figure 5 shows, as an example, an aspect in which the projection light (P-polarized) is incident from a direction at a polar angle of 45° with respect to the normal direction of the combiner 44 at an azimuth angle of 45° with respect to the in-plane slow axis of the λ / 2 plate 48). The above-mentioned P-polarized light reflectance (45°) in this embodiment is a value obtained when P-polarized light is incident on the combiner 44 from a polar angle of 45° (arrow in the figure) with respect to the normal direction of the combiner 44 at an azimuth angle of 45° with respect to the in-plane slow axis of the λ / 2 plate 48, which is a retardation layer. The above-mentioned S-polarized light reflectance (45°) in this embodiment is a value obtained when S-polarized light is incident on the combiner 44 from a polar angle of 45° (arrow in the figure) with respect to the normal direction of the combiner 44 at an azimuth angle of 45° with respect to the in-plane slow axis of the λ / 2 plate 48, which is a retardation layer, similar to the above-mentioned P-polarized light reflectance (45°).

[0050] When P-polarized light (projection light) emitted from the projector 12 enters the combiner 44 from the anti-reflection layer 20 side at an incident angle of 45°, it passes through the λ / 2 plate 48 to become S-polarized light, and is then incident on and reflected by the dielectric multilayer film 46. The light reflected by the dielectric multilayer film 46 passes through the λ / 2 plate 48 again to become P-polarized light, which is observed by the eye of the observer OB. Here, the dielectric multilayer film 46 itself has a characteristic in which the S-polarized light reflectance when S-polarized light is incident at an incident angle of 45° is higher than the P-polarized light reflectance when P-polarized light is incident at an incident angle of 45°. In other words, the combiner 44 converts P-polarized light incident from the anti-reflection layer 20 side at an incident angle of 45° into S-polarized light using the λ / 2 plate 48, highly reflects it using the dielectric multilayer film 46, and then converts this S-polarized light back into P-polarized light, thereby achieving a higher P-polarized light reflectance when P-polarized light is incident at an incident angle of 45° than the S-polarized light reflectance when S-polarized light is incident at an incident angle of 45°.

[0051] The following describes in detail each component of the combiner 44. The anti-reflection layer 20 and the light-shielding layer 22 have the same configuration as the anti-reflection layer 20 and the light-shielding layer 22 in the combiner 14.

[0052] <Retardation Layer> A known λ / 2 plate can be used as the λ / 2 plate 48, which is the retardation layer. Here, the "λ / 2 plate" refers to a plate having a λ / 2 function. Examples of the λ / 2 plate 48 include a stretched polycarbonate film, a stretched norbornene-based polymer film, a transparent film containing and oriented inorganic particles having birefringence such as strontium carbonate, a thin film formed by obliquely depositing an inorganic dielectric on a support, a film in which a polymerizable liquid crystal compound is uniaxially oriented and fixed in orientation, and a film in which a liquid crystal compound is uniaxially oriented and fixed in orientation.

[0053] Among these, a film in which a polymerizable liquid crystal compound is uniaxially aligned and fixed is a suitable example of the λ / 2 plate 48. Such a λ / 2 plate 48 can be formed, for example, by applying a liquid crystal composition containing a polymerizable liquid crystal compound onto an alignment film of a substrate on which an alignment film has been formed, and then forming the polymerizable liquid crystal compound in the liquid crystal composition into a nematic alignment in a liquid crystal state, followed by fixing the alignment film by curing. The λ / 2 plate 48 may be used together with the substrate on which the alignment film has been formed as a component of the combiner 44, or the λ / 2 plate 48 alone may be used as a component of the combiner 44.

[0054] The in-plane retardation of the λ / 2 plate 48 at a wavelength of 550 nm is 200 to 350 nm, preferably 230 to 320 nm, and more preferably 250 to 300 nm. There are no limitations on the thickness of the λ / 2 plate 48, 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. There are no particular limitations on the thickness of the λ / 2 plate 48 formed from a liquid crystal composition, 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.

[0055] The position of the in-plane slow axis of the λ / 2 plate 48 can be arranged so as to be oriented to convert incident P-polarized light into S-polarized light. Specifically, the λ / 2 plate 48 is preferably arranged so that P-polarized light is incident from a direction at a polar angle of 45° with respect to the normal direction of the combiner 44, at an azimuth angle of 45° clockwise or 45° counterclockwise with respect to the direction of the in-plane slow axis of the λ / 2 plate 48 when viewed from the side where the projection light is incident. The direction of the in-plane slow axis of the λ / 2 plate 48 can be set, for example, by rubbing the alignment film of the λ / 2 plate 48.

[0056] <First Substrate> The first substrate 40 is a member that supports the anti-reflection layer. The material of the first substrate 40 is not particularly limited, and examples thereof include resin and glass, with glass being particularly preferred. When the first substrate 40 is a resin substrate, examples of the substrate include plastic films such as polyesters such as polyethylene terephthalate (PET), polycarbonates, acrylic resins, epoxy resins, polyurethanes, polyamides, polyolefins, cellulose derivatives, and silicones.

[0057] The thickness of the first substrate 40 is preferably 30 to 5000 μm, more preferably 35 to 4500 μm, and even more preferably 40 to 4000 μm.

[0058] <Second Substrate> The second substrate 42 is a member that supports the λ / 2 plate 48. The second substrate 42 is an optional member. An alignment film may be formed on the surface of the second substrate 42. The material of the second substrate 42 is not particularly limited, and examples thereof include resin and glass. When the second substrate 42 is a resin, examples thereof include plastic films such as cellulose derivatives, polyesters such as polyethylene terephthalate (PET), polycarbonates, acrylic resins, epoxy resins, polyurethanes, polyamides, polyolefins, cellulose derivatives, and silicones. The thickness of the second substrate 42 is preferably 30 to 200 μm, more preferably 35 to 150 μm, and even more preferably 40 to 100 μm.

[0059] In the combiner 44, the distance between the antireflection layer 20 and the reflective layer 46 in the thickness direction of the combiner 44 is 30 μm or more, preferably 1 mm or more, more preferably 1.5 mm or more, and even more preferably 2.0 mm or more, in order to suppress optical interference between the reflective layer 46 and the antireflection layer 20 and make it easier to satisfy the above-mentioned requirements (A) and (B). The upper limit is preferably 5.0 mm or less, more preferably 4.0 mm or less. When the combiner 44 is configured to include only three layers between the antireflection layer 20 and the reflective layer 46, namely, the first substrate 40, the second substrate 42, and the λ / 2 plate 48, which is a retardation layer, the distance between the antireflection layer 20 and the reflective layer 16 in the thickness direction of the combiner 44 corresponds to the sum of the thicknesses of the above three layers. If another layer, such as an adhesive layer, is further interposed between the anti-reflection layer 20 and the reflective layer 16, the sum of the thickness of this other layer, such as an adhesive layer, and the thickness of the above three layers corresponds to the distance in the thickness direction of the combiner 44 between the anti-reflection layer 20 and the reflective layer 46.

[0060] <Modifications> In the combiner 44, the λ / 2 plate 48 is disposed adjacent to the dielectric multilayer film 46, but the position of the λ / 2 plate 48 is not particularly limited as long as it is between the antireflection layer 20 and the dielectric multilayer film 46. That is, examples of modifications of the combiner 44 of the second embodiment include a configuration having the antireflection layer 20, the λ / 2 plate 48, the second substrate 42, the first substrate 40, the dielectric multilayer film 46, and the light-shielding layer 22 in this order as shown in Fig. 6, and a configuration having the antireflection layer 20, the second substrate 42, the λ / 2 plate 48, the first substrate 40, the dielectric multilayer film 46, and the light-shielding layer 22 in this order as shown in Fig. 7. Furthermore, as described above, the second substrate 42, which is a support layer for the λ / 2 plate 48, is an optional component and may not be included in the combiner 44.

[0061] Third Embodiment Next, a head-up display system according to a third embodiment will be described. The configuration of the head-up display system according to the third embodiment is the same as that of the head-up display system according to the first embodiment, except that a combiner 54 is used instead of the combiner 14. The combiner 54 will be described below with reference to FIG. 8. The combiner 54 shown in FIG. 8 includes, in this order, an antireflection layer 20, a first substrate 50, a second substrate 52, a λ / 4 plate 58 serving as a retardation layer, a cholesteric liquid crystal layer 56 serving as a reflective layer, and a light-blocking layer 22. Projection light emitted from the projector 12 is incident on the antireflection layer 20 side. In addition, the distance between the antireflection layer 20 and the cholesteric liquid crystal layer 56 in the thickness direction of the combiner 54 is 30 μm or more. The combiner 54 also has a P-polarized light reflectance (45°) of 20.0% or more, a P-polarized light / S-polarized light ratio of 1.20 or more, and an unpolarized light reflectance (45°) of 20.0% or less.

[0062] Although the combiner 54 includes the light-shielding layer 22 and the second substrate 52, the light-shielding layer 22 and the second substrate 52 are optional components and may not be disposed in the combiner.

[0063] The λ / 4 plate 58, which is a retardation layer, has an in-plane slow axis. When the projection light emitted from the projector 12 is incident on the combiner 54 from the anti-reflection layer 20 side, as shown in Figure 9, it is preferable that the projection light (P-polarized) is incident from a direction at a polar angle of 45° with respect to the normal direction of the combiner 54 (arrow in the figure) at an azimuth angle of 45° clockwise or 45° counterclockwise with respect to the in-plane slow axis of the λ / 4 plate 58, which is a retardation layer, when viewed from the side where the projection light is incident (note that Figure 9 shows, as an example, an aspect in which the projection light (P-polarized) is incident from a direction at a polar angle of 45° with respect to the normal direction of the combiner 54 at an azimuth angle of 45° with respect to the in-plane slow axis of the λ / 4 plate 58). The above-described P-polarized light reflectance (45°) in this embodiment is a value obtained when P-polarized light is incident on the combiner 54 from a polar angle direction of 45° with respect to the normal direction of the combiner 54 (arrow in the figure), at an azimuth angle of 45° clockwise or 45° counterclockwise with respect to the in-plane slow axis of the λ / 4 plate 58, which is a retardation layer, when viewed from the side where the projection light is incident. Whether the azimuth angle with respect to the in-plane slow axis of the λ / 4 plate 58, when viewed from the side where the projection light is incident, is 45° clockwise or 45° counterclockwise, is determined according to the helical sense of the cholesteric liquid crystal layer 56, which is a reflective layer.

[0064] Furthermore, in this embodiment, the above-mentioned S-polarized light reflectance (45°), like the above-mentioned P-polarized light reflectance (45°), is a value obtained when S-polarized light is incident on the combiner 54 from a direction at a polar angle of 45° relative to the normal direction of the combiner 54 (arrow in the figure), at an azimuth angle that forms an angle of 45° clockwise or 45° counterclockwise with respect to the in-plane slow axis of the λ / 4 plate 58, which is the retardation layer, when viewed from the side where the projection light is incident.

[0065] When P-polarized light (projection light) emitted from the projector 12 enters the combiner 54 from the anti-reflection layer 20 side at an incident angle of 45°, it passes through the λ / 4 plate 58 to become circularly polarized light, and then enters and is reflected by the cholesteric liquid crystal layer 56. The light reflected by the cholesteric liquid crystal layer 56 passes through the λ / 4 plate 58 again to become P-polarized light, which is observed by the eye of the observer OB. The combiner 54 has a characteristic in which the P-polarized light reflectance when P-polarized light is incident at an incident angle of 45° is higher than the S-polarized light reflectance when S-polarized light is incident at an incident angle of 45°.

[0066] Each component of the combiner 54 will be described in detail below. The anti-reflection layer 20 and the light-shielding layer 22 have the same configuration as the anti-reflection layer 20 and the light-shielding layer 22 in the combiner 14. The first substrate 50 has the same configuration as the first substrate 40 in the combiner 44.

[0067] <Retardation Layer> A known λ / 4 plate can be used for the λ / 4 plate 58, which is the retardation layer. Here, the "λ / 4 plate" refers to a plate having a λ / 4 function, specifically a plate having the function of converting linearly polarized light of a specific wavelength into circularly polarized light (or circularly polarized light into linearly polarized light). Examples of the λ / 4 plate 58 include an A plate and a twist layer, which will be described later. (A Plate) In this specification, the A plate is defined as follows. There are two types of A plates: a positive A plate (positive A plate) and a negative A plate (negative A plate). When the refractive index in the in-plane slow axis direction (the direction in which the in-plane refractive index is maximum) of the film is nx, the refractive index in the direction perpendicular to the in-plane slow axis is ny, and the refractive index in the thickness direction is nz, the positive A plate satisfies the relationship shown in formula (A1), and the negative A plate satisfies the relationship shown in formula (A2). Note that the positive A plate has a positive Rth value, while the negative A plate has a negative Rth value. Formula (A1): nx>ny≒nz Formula (A2): ny<nx≒nz Note that the above "≒" encompasses not only the case where the two are completely identical, but also the case where the two are substantially identical. This "substantially identical" includes, for example, the case where (ny-nz)×d (where d is the film thickness) is −10 to 10 nm, preferably −5 to 5 nm, which is included in "ny≒nz," and the case where (nx-nz)×d is −10 to 10 nm, preferably −5 to 5 nm, which is also included in "nx≒nz."

[0068] In the case of a positive A plate, in consideration of its function as a λ / 4 plate, Re(550) is preferably 100 to 180 nm, more preferably 120 to 160 nm, even more preferably 130 to 150 nm, and particularly preferably 130 to 145 nm.

[0069] The thickness of the λ / 4 plate 58 is not particularly limited, but 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 λ / 4 plate 58 formed from a liquid crystal composition is not particularly limited, but 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.

[0070] Examples of the λ / 4 plate 58 include a stretched polycarbonate film, a stretched norbornene-based polymer film, a transparent film containing and oriented inorganic particles having birefringence such as strontium carbonate, a thin film formed by obliquely depositing an inorganic dielectric on a support, a film in which a polymerizable liquid crystal compound is uniaxially oriented and fixed in orientation, and a film in which a liquid crystal compound is uniaxially oriented and fixed in orientation.

[0071] Among these, a film in which a polymerizable liquid crystal compound is uniaxially aligned and fixed is a suitable example of the λ / 4 plate 58. Such a λ / 4 plate 58 can be formed, for example, by applying a liquid crystal composition containing a polymerizable liquid crystal compound onto an alignment film of a substrate on which an alignment film has been formed, and then forming the polymerizable liquid crystal compound in the liquid crystal composition into a nematic alignment in a liquid crystal state, followed by fixing the alignment film by curing. The λ / 4 plate 58 may be used together with a substrate on which an alignment film has been formed as a component of the combiner 54, or the λ / 4 plate 58 alone may be used as a component of the combiner 54.

[0072] The position of the in-plane slow axis of the λ / 4 plate 58 can be positioned so that it converts incident P-polarized light (linearly polarized light) into circularly polarized light. The direction of the in-plane slow axis of the λ / 4 plate 58 can be positioned so that it converts light into the swirling direction reflected by the cholesteric liquid crystal layer 56, which is the reflective layer (i.e., so that it corresponds to the helical sense of the cholesteric liquid crystal layer 56, which is the reflective layer). Specifically, the λ / 4 plate 58 is preferably positioned so that P-polarized light is incident from a polar angle of 45° relative to the normal direction of the combiner 54, at an azimuth angle of 45° clockwise or 45° counterclockwise relative to the direction of the in-plane slow axis of the λ / 4 plate 58 when viewed from the side where the projection light is incident. The direction of the in-plane slow axis of the λ / 4 plate 58 can be set, for example, by rubbing the alignment film of the λ / 4 plate 58.

[0073] (Twist Layer) The twist layer is a layer (hereinafter also referred to as a "polarization conversion layer") in which a helical orientation structure of a liquid crystal compound is fixed, the helical orientation structure being twisted and aligned along a helical axis extending along the thickness direction. Furthermore, when the pitch number of the helical orientation structure is x and the film thickness of the twist layer (polarization conversion layer) is y (μm), the layer preferably satisfies the relationships of formulas (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 of the helical structure of the liquid crystal compound corresponds to one turn of the helix of the liquid crystal compound. In other words, a pitch number of 1 is defined as a state in which the director (the long axis direction in the case of rod-shaped liquid crystals) of the helically aligned liquid crystal compound rotates 360°.

[0074] The pitch number x of the helical structure of the twisted layer is more preferably 0.1 to 0.8, and the film thickness y is more preferably 0.6 to 2.6 μm. Furthermore, "(1560×y) / x" is more preferably 5000 to 13000. The twisted layer can be formed essentially in the same manner as known cholesteric liquid crystal layers. The liquid crystal compound in the twisted layer is fixed and may no longer exhibit liquid crystallinity. For example, when a twisted layer is formed using a polymerizable liquid crystal compound, the liquid crystal compound may be polymerized by a curing reaction and may no longer exhibit liquid crystallinity.

[0075] <Cholesteric Liquid Crystal Layer> The cholesteric liquid crystal layer refers to a layer in which a cholesteric liquid crystal phase is fixed. The cholesteric liquid crystal layer may be any layer in which the orientation of a liquid crystal compound in a cholesteric liquid crystal phase is maintained. The cholesteric liquid crystal layer is typically a layer in which a polymerizable liquid crystal compound is oriented in a cholesteric liquid crystal phase, and then polymerized and cured by ultraviolet irradiation, heating, or the like to form a layer with no fluidity, and at the same time, changed to a state in which the orientation does not change due to an external field or external force. Note that, in the cholesteric liquid crystal layer, it is sufficient that the optical properties of the cholesteric liquid crystal phase are maintained in the layer, and the liquid crystal compound in the layer may no longer exhibit liquid crystallinity. For example, the polymerizable liquid crystal compound may be polymerized by a curing reaction and no longer have liquid crystallinity.

[0076] The cholesteric liquid crystal layer used has a helical sense of either right or left. The sense of circularly polarized light (the direction of rotation of the circularly polarized light) reflected by the cholesteric liquid crystal layer corresponds to the helical sense. Cholesteric liquid crystal phases are known to selectively reflect circularly polarized light of either right-handed or left-handed sense, while transmitting circularly polarized light of the other sense. Numerous films formed from compositions containing polymerizable liquid crystal compounds have been known as films containing a layer fixed with a cholesteric liquid crystal phase that exhibits circularly polarized light selective reflectivity, and reference can be made to these prior art for information on cholesteric liquid crystal layers.

[0077] The central wavelength λ of selective reflection by a cholesteric liquid crystal layer (selective reflection central wavelength) depends on the pitch P (= helical period) of the helical structure (helical orientation structure) in the cholesteric liquid crystal phase, and follows the relationship λ = n × P with the average refractive index n of the cholesteric liquid crystal layer. As can be seen from this formula, the selective reflection central wavelength can be adjusted by adjusting the n value and / or the P value. The pitch P of the helical structure (one helix pitch) is, in other words, the length in the helical axis direction corresponding to one turn of the helix, i.e., the length in the helical axis direction along which the director (the long axis direction in the case of rod-shaped liquid crystals) of the liquid crystal compound constituting the cholesteric liquid crystal phase rotates 360°. The helical axis direction of a typical cholesteric liquid crystal layer coincides with the thickness direction of the cholesteric liquid crystal layer.

[0078] The selective reflection central wavelength and half-width of the cholesteric liquid crystal layer can be determined, for example, as follows. When the reflection spectrum of the cholesteric liquid crystal layer is measured from the normal direction using a spectrophotometer (V-670, manufactured by JASCO Corporation), a peak of reduced transmittance is observed in the selective reflection band. Of the two wavelengths at which the transmittance is intermediate (average) between the minimum transmittance of this peak and the transmittance before the decrease, the value of the wavelength on the shorter wavelength side is taken as λ l (nm), and the wavelength on the long wavelength side is λ h (nm), the selective reflection central wavelength λ and the half-width Δλ can be expressed by the following formula: λ=(λ l +λ h ) / 2Δλ = (λh -λ l The selective reflection central wavelength obtained as described above substantially coincides with the wavelength at the center of gravity of the reflection peak of the circularly polarized light reflection spectrum measured from the normal direction of the cholesteric liquid crystal layer.

[0079] In a cholesteric liquid crystal layer having a selective reflection center wavelength of wavelength λ, the selective reflection center wavelength when a light ray passes through the layer at an angle of θ2 with respect to the normal direction of the cholesteric liquid crystal layer (the helical axis direction of the cholesteric liquid crystal layer) is defined as wavelength λ. d Then, the wavelength λ d is expressed by the following formula: λ d =λ×cos θ2 Therefore, for example, when θ2 is between 26° and 36°, a cholesteric liquid crystal layer having a selective reflection center wavelength in the range of 650 to 780 nm can reflect projected light in the range of 520 to 695 nm.

[0080] The helical pitch of the cholesteric liquid crystal phase depends on the type and concentration of the chiral agent used together with the polymerizable liquid crystal compound, and the desired pitch can be obtained by adjusting these factors. The helical sense and pitch can be measured using 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" (Liquid Crystal Handbook Editorial Committee, Maruzen, p. 196).

[0081] The thickness of the cholesteric liquid crystal layer is preferably from 0.1 to 5.0 μm, more preferably from 0.15 to 4.0 μm, and even more preferably from 0.2 to 3.0 μm.

[0082] <Second Substrate> The second substrate 52 is a member that supports the λ / 4 plate 58. The second substrate 52 is an optional member. An alignment film may be formed on the surface of the second substrate 52. The material of the second substrate 52 is not particularly limited, and examples thereof include resin and glass. When the second substrate 52 is a resin, examples thereof include plastic films such as cellulose derivatives, polyesters such as polyethylene terephthalate (PET), polycarbonates, acrylic resins, epoxy resins, polyurethanes, polyamides, polyolefins, cellulose derivatives, and silicones. The thickness of the second substrate 52 is preferably 30 to 200 μm, more preferably 35 to 150 μm, and even more preferably 40 to 100 μm.

[0083] In the combiner 54, the distance between the antireflection layer 20 and the reflective layer 56 in the thickness direction of the combiner 54 is 30 μm or more, preferably 1 mm or more, more preferably 1.5 mm or more, and even more preferably 2.0 mm or more, in order to suppress optical interference between the reflective layer 56 and the antireflection layer 20 and make it easier to satisfy the above-mentioned requirements (A) and (B). The upper limit is preferably 5.0 mm or less, more preferably 4.0 mm or less. When the combiner 54 is configured to include only three layers between the antireflection layer 20 and the reflective layer 56, namely, the first substrate 50, the second substrate 52, and the λ / 4 plate 58 serving as a retardation layer, the distance between the antireflection layer 20 and the reflective layer 56 in the thickness direction of the combiner 54 corresponds to the sum of the thicknesses of the three layers. If another layer, such as an adhesive layer, is further interposed between the anti-reflection layer 20 and the reflective layer 56, the sum of the thickness of this other layer, such as an adhesive layer, and the thickness of the above three layers corresponds to the distance in the thickness direction of the combiner 54 between the anti-reflection layer 20 and the reflective layer 56.

[0084] <Modifications> In the combiner 54 described above, the λ / 4 plate 58 is disposed adjacent to the cholesteric liquid crystal layer 56, but the position of the λ / 4 plate 58 is not particularly limited as long as it is between the antireflection layer 20 and the cholesteric liquid crystal layer 56. That is, a modification of the combiner 54 of the third embodiment may be, for example, a configuration having the antireflection layer 20, the second substrate 52, the λ / 4 plate 58, the cholesteric liquid crystal layer 56, the first substrate 50, and the light-blocking layer 22 in this order, as shown in FIG.

[0085] Fourth Embodiment Next, a head-up display system according to a fourth embodiment will be described. The configuration of the head-up display system according to the fourth embodiment is similar to that of the head-up display system according to the first embodiment, except that a combiner 64 is used instead of the combiner 14. The combiner 64 will be described below with reference to FIG. 11 . The combiner 64 shown in FIG. 11 includes an anti-reflection layer 20, a substrate 68, a linearly polarized reflective layer 66 as a reflective layer, and a light-blocking layer 22, in this order. Projection light emitted from the projector 12 is incident on the anti-reflection layer 20 side. The distance between the anti-reflection layer 20 and the linearly polarized reflective layer 66 in the thickness direction of the combiner 64 is 30 μm or more. The combiner 64 has a P-polarized light reflectivity (45°) of 20.0% or more, a P-polarized light / S-polarized light ratio of 1.20 or more, and an unpolarized light reflectivity (45°) of 20.0% or less. It should be noted that although the combiner 64 includes a light-shielding layer 22, the light-shielding layer 22 is an optional component and does not necessarily have to be disposed on the combiner.

[0086] As will be described later, the linearly polarized light reflective layer 66 has a reflection axis (in-plane slow axis) that can reflect linearly polarized light. When projection light emitted from the projector 12 is incident on the combiner 64 from the anti-reflection layer 20 side, it is preferable that the projection light (P-polarized light) is incident from a direction at a polar angle of 45° with respect to the normal direction of the combiner 64, at an azimuth angle parallel to the in-plane slow axis of the linearly polarized light reflective layer 66. Note that the above-mentioned P-polarized light reflectance (45°) in this embodiment is a value when P-polarized light is incident on the combiner 64 from a direction at a polar angle of 45° with respect to the normal direction of the combiner 64, at an azimuth angle parallel to the in-plane slow axis of the linearly polarized light reflective layer 66. In this embodiment, the above-mentioned S-polarized light reflectivity (45°), like the above-mentioned P-polarized light reflectivity (45°), is the value obtained when S-polarized light is incident on the combiner 64 from a polar angle of 45° relative to the normal direction of the combiner 64, at an azimuth angle parallel to the reflection axis of the linearly polarized light reflective layer 66.

[0087] The following describes in detail each component of the combiner 64. The anti-reflection layer 20, the substrate 68, and the light-shielding layer 22 have the same configuration as the anti-reflection layer 20, the substrate 18, and the light-shielding layer 22 in the combiner 14.

[0088] <Reflective Layer (Linearly Polarized Reflective Layer)> Fig. 12A is a schematic diagram showing an example of the linearly polarized reflective layer 66. Fig. 12B is a schematic diagram showing the linearly polarized reflective layer 66 as viewed from the normal direction. As shown in Fig. 12A, the linearly polarized reflective layer 66 is formed by alternately laminating optically anisotropic layers 66a and isotropic layers 66b. In the linearly polarized reflective layer 66, the refractive index n ｅ１ is the refractive index n of the isotropic layer 66b ｏ２ and the refractive index n ｏ１ is the refractive index n of the isotropic layer 66b ｏ２ The optically anisotropic layers 66a are laminated so that their in-plane slow axes are parallel to each other. Therefore, as shown in FIG. 12B, in one direction (the vertical direction in FIG. 12B), the refractive index (n ｅ１ ) and a layer with a high refractive index (n ｏ２On the other hand, in the direction perpendicular to this direction (the left-right direction in FIG. 12B ), layers with the same refractive index are stacked.

[0089] It is known that a film in which layers with low refractive indexes (low refractive index layers) and layers with high refractive indexes (high refractive index layers) are alternately laminated reflects light of a specific wavelength due to structural interference between the many low refractive index layers and the high refractive index layers. Therefore, the linearly polarized light reflective layer 66 shown in Figures 12A and 12B reflects linearly polarized light in the in-plane slow axis direction of the optically anisotropic layer 66a (the up-down direction in Figure 12B) and transmits linearly polarized light in the left-right direction.

[0090] That is, the linearly polarized reflective layer 66 is a layer that selectively reflects linearly polarized light in a specific wavelength range. The linearly polarized reflective layer 66 preferably exhibits selective reflection in a portion of the visible light wavelength range. The linearly polarized reflective layer 66 may, for example, reflect light for displaying a projected image. The combiner 64 may be configured to have multiple linearly polarized reflective layers 66 corresponding to each wavelength range. The linearly polarized reflective layer 66 can transmit linearly polarized light that is not reflected. Therefore, by having the linearly polarized reflective layer 66, the combiner 64 can transmit a portion of light even in the wavelength range in which the linearly polarized reflective layer 66 exhibits reflection.

[0091] In a linearly polarized light reflective layer in which low-refractive index layers and high-refractive index layers are stacked, the reflected wavelength and reflectance can be adjusted by the difference in refractive index between the low-refractive index layers and the high-refractive index layers, the thickness, the number of layers, etc. Specifically, the wavelength λ of reflected light can be adjusted by setting the thickness d of the low-refractive index layers and the high-refractive index layers to d = λ / (4 x n) where λ is the wavelength of reflected light and n is the refractive index. Furthermore, since the reflectance increases with the number of low-refractive index layers and high-refractive index layers stacked, the reflectance can be adjusted by adjusting the number of layers stacked. Furthermore, the width of the reflection band can be adjusted by the difference in refractive index between the low-refractive index layers and the high-refractive index layers.

[0092] Materials and methods for preparing the linearly polarized light reflective layer can be those described, for example, in JP-A-9-506837. Specifically, a wide variety of materials can be used to form the linearly polarized light reflective layer when processed under conditions selected to achieve a refractive index relationship. Generally, it is necessary for the first material to have a refractive index different from that of the second material in a selected direction. This refractive index difference can be achieved by various methods, including stretching, extrusion, or coating during or after film formation. Furthermore, it is preferable for the two materials to have similar rheological properties (e.g., melt viscosity) so that they can be co-extruded.

[0093] A commercially available product can be used as the linearly polarized reflective layer. A commercially available product that is a laminate of a reflective polarizing plate and a temporary support can be used. Examples of commercially available products include commercially available optical films sold under the names DBEF (registered trademark) (manufactured by 3M) and APF (Advanced Polarizing Film (manufactured by 3M)). The thickness of the linearly polarized reflective layer is preferably 2.0 to 50 μm, more preferably 8.0 to 30 μm. The number of laminations of optically anisotropic layers and isotropic layers in the linearly polarized reflective layer may be appropriately determined depending on the required reflectance, etc., but is preferably 10 to 200 layers.

[0094] In the combiner 64, the distance between the antireflection layer 20 and the linearly polarized reflective layer 66 in the thickness direction of the combiner 64 is 30 μm or more, preferably 1 mm or more, more preferably 1.5 mm or more, and even more preferably 2.0 mm or more, in order to suppress optical interference between the linearly polarized reflective layer 66 and the antireflection layer 20 and facilitate satisfying the above-mentioned requirements (A) and (B). The upper limit is preferably 5.0 mm or less, more preferably 4.0 mm or less. When the combiner 64 is configured to include only a substrate 18 between the antireflection layer 20 and the linearly polarized reflective layer 66, the distance between the antireflection layer 20 and the linearly polarized reflective layer 66 in the thickness direction of the combiner 64 corresponds to the total thickness of the substrate 18. When another layer, such as an adhesive layer, is further interposed between the antireflection layer 20 and the reflective layer 66, the total thickness of the other layer, such as an adhesive layer, and the thickness of the substrate 18 corresponds to the distance between the antireflection layer 20 and the reflective layer 66 in the thickness direction of the combiner 64.

[0095] <Uses> The head-up display system of the present invention can be used in a variety of applications, including, for example, an in-vehicle head-up display system.

[0096] The present invention will be described in more detail below with reference to the following examples. The materials, amounts used, ratios, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the following examples.

[0097] [Example 1] [Preparation of Laminate 1A] Laminate 1A was prepared by forming an inorganic multilayer film (anti-reflection layer) on the surface of a glass substrate (200 mm long x 1000 mm wide, 2 mm thick) using magnetron sputtering. Laminate 1A had the following structure. The values ​​in parentheses indicate the film thickness. Glass substrate / Al ２ O ３ (80nm) / SiN(80nm) / SiO ２ (100 nm)

[0098] [Preparation of Laminate 1B] <Saponification of Cellulose Acylate Film> A cellulose acylate film (TAC film) having a thickness of 40 μm, a width of 1000 mm and a length of 200 mm was prepared using the same preparation method as in Example 20 of WO 2014 / 112575. UV-531 manufactured by Teisei Kako Co., Ltd. was added to this TAC film as an ultraviolet absorber. The amount added was 3 phr (per hundred resin). The prepared TAC film was passed through a dielectric heating roll at a temperature of 60°C, and the film surface temperature was raised to 40°C. Thereafter, an alkaline solution having the composition shown below was applied to one side of the film using a bar coater in an amount of 14 mL / m ２ The coating was then allowed to stand for 10 seconds under a steam-type far-infrared heater (manufactured by Noritake Co., Ltd.) heated to 110°C. Next, pure water was applied at a rate of 3 mL / m using the same bar coater. ２ The film was then washed with water using a fountain coater and then drained with an air knife three times, and then allowed to stay in a drying zone at 70°C for 5 seconds to dry, producing a saponified TAC film. The in-plane retardation of the saponified TAC film was measured with an AxoScan and found to be 1 nm.

[0099] Composition of alkaline solution: Potassium hydroxide 4.7 parts by mass; Water 15.7 parts by mass; Isopropanol 64.8 parts by mass; Surfactant (C 16 H 33 O(CHCHO) 10 H) 1.0 part by mass Propylene glycol 14.9 parts by mass

[0100] <Formation of Alignment Film> A coating solution for forming an alignment film having the composition shown below was applied to the saponified surface of the saponified TAC film at a rate of 24 mL / m using a wire bar coater.２ The coating was then dried with hot air at 100°C for 120 seconds.

[0101] ------------------------------------------------------------------ Composition of coating liquid for forming alignment film -------------------------------------------------- Modified polyvinyl alcohol shown below: 28 parts by mass Citrate ester (AS3, manufactured by Sankyo Chemical Co., Ltd.) 1.2 parts by mass Photoinitiator (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 ------------------------------------------------------------------

[0102] (Modified Polyvinyl Alcohol) In the following chemical formula, the numerical value attached to each repeating unit indicates the content by mass relative to all repeating units.

[0103] <Formation of Retardation Layer> A TAC film on which an alignment film was formed (hereinafter also referred to as "TAC film with alignment film") was used as a support (transparent support). One side of the support was subjected to a rubbing treatment (rayon cloth, pressure: 0.1 kgf (0.98 N), rotation speed: 1000 rpm (revolutions per minute), conveying speed: 10 m / min, number of times: 1 round trip) in a direction rotated 45° clockwise with respect to the long side direction of the support. The following retardation layer forming coating solution was applied to the rubbed surface of the alignment film on the support using a wire bar, and then dried. Next, the film was placed on a hot plate at 50°C, and heated in an environment with an oxygen concentration of 1000 ppm or less using an electrodeless lamp "D bulb" (60 mW / cm) manufactured by Fusion UV Systems. ２) for 6 seconds to fix the liquid crystal phase. This resulted in a retardation layer whose thickness was adjusted to achieve the desired front retardation, i.e., the desired in-plane retardation. The in-plane retardation of the prepared retardation layer at a wavelength of 550 nm was measured using an AxoScan and found to be 276 nm. The film thickness was 1.73 μm.

[0104] ------------------------------------------------ Composition of coating liquid for forming retardation layer ------------------------------------------------ Mixture 1 below: 100 parts by mass Fluorine-based horizontal alignment agent 1 (alignment control agent 1) below: 0.05 parts by mass Fluorine-based horizontal alignment agent 2 (alignment control agent 2) below: 0.01 parts by mass Polymerization initiator IRGACURE OXE01 (manufactured by BASF) 1.0 part by mass Solvent (methyl ethyl ketone) Amount to make the solute concentration 20% by mass ------------------------------------------------

[0105]

[0106]

[0107]

[0108] <Formation of Reflective Layer> Next, an inorganic multilayer film (reflective layer) was formed on the surface of the formed retardation layer using magnetron sputtering to prepare a laminate 1B. The inorganic multilayer film of the laminate 1B has the following configuration in order from the retardation layer side. The numbers in parentheses indicate the film thickness. (Retardation layer side) SiO ２ (53nm) / SiN (120nm) / SiO ２ (140nm) / SiN(20nm) / SiO ２ (150nm) / SiN (25nm)

[0109] [Preparation of Combiner 1] The glass substrate side of the prepared laminate 1A and the TAC film side of the laminate 1B were bonded via an adhesive layer (OCA). The adhesive layer had a thickness of 10 μm. Next, a 200 mm long x 1000 mm wide black PET sheet (manufactured by Tomoegawa Corporation, Kakukiri Miel 125 μm) was bonded to the surface of the reflective layer side of the obtained bonded body to prepare Combiner 1.

[0110] [Example 2] An inorganic multilayer film (anti-reflection layer) was formed on the surface of a glass substrate (200 mm long x 1000 mm wide, 2 mm thick) using magnetron sputtering to prepare a laminate 2A. The laminate 2A had the following structure. The values ​​in parentheses indicate the film thickness. Glass substrate / Al ２ O ３ (80nm) / SiN(80nm) / SiO ２ (100 nm)

[0111] Next, an inorganic multilayer film (reflective layer) was formed on the surface of the prepared laminate 2A facing the glass substrate by magnetron sputtering to prepare laminate 2B. The inorganic multilayer film (reflective layer) of laminate 2B has the following structure, in order from the glass substrate side. The numbers in parentheses indicate film thickness. (Glass substrate side) SiO ２ (45nm) / SiN(60nm) / Al(5nm) / SiN(25nm) / SiO ２ (37 nm)

[0112] [Preparation of Combiner 2] A 200 mm long x 1000 mm wide black PET (Kukkiri Miel 125 μm, manufactured by Tomoegawa Corporation) was attached to the surface of the reflective layer side of the prepared laminate 2B to prepare a combiner 2.

[0113] [Example 3] [Preparation of Laminate 3A] Laminate 3A was prepared by forming an inorganic multilayer film (anti-reflection layer) on the surface of a glass substrate (200 mm long x 1000 mm wide, 2 mm thick) using magnetron sputtering. Laminate 3A had the following structure. The values ​​in parentheses indicate the film thickness. Glass substrate / Al ２ O ３ (80nm) / SiN(80nm) / SiO ２ (100 nm)

[0114] [Preparation of Laminate 3B] <Preparation of Cholesteric Liquid Crystal Layer-Forming Coating Liquids B1, G1, R1, and IR1> Cholesteric liquid crystal layer-forming coating liquids were prepared to form the cholesteric liquid crystal layers (B1, G1, R1, and IR1) exhibiting the selective reflection center wavelengths described in the latter part of this document. Specifically, each cholesteric liquid crystal layer-forming coating liquid was prepared by mixing the components shown below and adjusting the formulation amount of the right-handed chiral dopant LC756 to match the target selective reflection wavelength. The selective reflection center wavelength of the cholesteric liquid crystal layer B1 was 450 nm, the selective reflection center wavelength of the cholesteric liquid crystal layer G1 was 590 nm, the selective reflection center wavelength of the cholesteric liquid crystal layer R1 was 790 nm, and the selective reflection center wavelength of the cholesteric liquid crystal layer IR1 was 860 nm. The reflection spectra of the selective reflection layers were measured using a spectrophotometer (V-670, manufactured by JASCO Corporation). ------------------------------------------------ Coating solutions B1, G1, R1, IR1 for forming cholesteric liquid crystal layer ---------------------------------------------------------------- Mixture 1 above: 100 parts by mass Fluorine-based horizontal alignment agent 1 (alignment control agent 1) above: 0.05 parts by mass Fluorine-based horizontal alignment agent 2 (alignment control agent 2) above: 0.02 parts by mass Right-handed chiral agent LC756 (manufactured by BASF) adjusted to match the target reflection wavelength Polymerization initiator IRGACURE OXE01 (manufactured by BASF) 1.0 part by mass Solvent (methyl ethyl ketone) amount to make the solute concentration 20% by mass ------------------------------------------------

[0115] <Preparation of TAC Film with Alignment Layer> A TAC film with an alignment layer was prepared by the same manufacturing procedure as that for the laminate 1B shown in Example 1.

[0116] <Preparation of Retardation Layer> A TAC film with an alignment film was used as a support (transparent substrate). One side of the support was subjected to rubbing treatment (rayon cloth, pressure: 0.1 kgf (0.98 N), rotation speed: 1000 rpm (revolutions per minute), conveying speed: 10 m / min, number of strokes: 1 round trip) in a direction rotated 45° clockwise from the long side direction of the support.

[0117] The retardation layer-forming coating liquid was applied to the rubbed surface of the alignment film on the support using a wire bar, and then dried. The retardation layer-forming coating liquid was the same as the retardation layer-forming coating liquid used in producing the laminate 1B shown in Example 1. Next, the film was placed on a hot plate at 50°C, and heated with an electrodeless lamp "D bulb" (60 mW / cm) manufactured by Fusion UV Systems in an environment with an oxygen concentration of 1000 ppm or less. ２ ) for 6 seconds to fix the liquid crystal phase. This resulted in a retardation layer whose thickness was adjusted to achieve the desired front retardation, i.e., the desired in-plane retardation. The in-plane retardation of the prepared retardation layer was measured with an AxoScan and found to be 138 nm. The film thickness was 0.86 μm.

[0118] <Preparation of Cholesteric Liquid Crystal Layer> The cholesteric liquid crystal layer-forming coating solution (B1) was applied to the surface of the obtained retardation layer using a wire bar at room temperature so that the dry film thickness after drying was 280 nm, thereby obtaining a coating layer. The coating layer was dried at room temperature for 30 seconds and then heated in an 85°C atmosphere for 2 minutes. Subsequently, in an environment with an oxygen concentration of 1000 ppm or less, ultraviolet light was irradiated at 60% output for 6 to 12 seconds using a Fusion D bulb (90 mW / cm lamp) at 60°C to fix the cholesteric liquid crystal phase, thereby obtaining a cholesteric liquid crystal layer B1 with a thickness of 280 nm. Next, the same process was repeated using the cholesteric liquid crystal layer-forming coating solution (G1) on the surface of the obtained cholesteric liquid crystal layer B1, thereby forming a cholesteric liquid crystal layer G1 with a thickness of 240 nm. Next, the same process was repeated using the cholesteric liquid crystal layer forming coating liquid (R1) on the surface of the obtained cholesteric liquid crystal layer G1 to form a cholesteric liquid crystal layer R1 having a thickness of 440 nm. Next, the same process was repeated using the cholesteric liquid crystal layer forming coating liquid (IR1) on the surface of the obtained cholesteric liquid crystal layer R1 to form a cholesteric liquid crystal layer IR1 having a thickness of 240 nm.

[0119] In this way, a selective reflection layer including four cholesteric liquid crystal layers was formed on the retardation layer, thereby producing a laminate 3B.

[0120] [Preparation of Combiner 3] The glass substrate side of the prepared laminate 3A and the TAC film side of the laminate 3B were bonded via an adhesive layer (OCA). The adhesive layer had a thickness of 10 μm. Next, a black PET sheet (125 μm thick, manufactured by Tomoegawa Corporation) measuring 200 mm in length and 1000 mm in width was bonded to the surface of the reflective layer (cholesteric liquid crystal layer) of the obtained bonded structure to prepare Combiner 3.

[0121] [Example 4] [Preparation of Laminate 4A] Laminate 1A was prepared by depositing an inorganic multilayer film (anti-reflection layer) on the surface of a glass substrate (200 mm long x 1000 mm wide, 2 mm thick) using magnetron sputtering. Laminate 4A had the following structure. The values ​​in parentheses indicate the film thickness. Glass substrate / Al ２ O３ (80nm) / SiN(80nm) / SiO ２ (100 nm)

[0122] [Preparation of Linearly Polarized Reflective Film] A linearly polarized reflective film was prepared as follows, based on the method described in JP-A-9-506837. 2,6-polyethylene naphthalate (PEN) and a 70% naphthalate / 30% terephthalate copolyester (coPEN) were synthesized in a standard polyester resin synthesis vessel using ethylene glycol as the diol. Monolayer films of PEN and coPEN were extruded and stretched at approximately 150°C with the longitudinal and transverse stretch ratios adjusted, and then heat-treated at approximately 230°C for 30 seconds. The refractive index of the PEN film along its in-plane slow axis (orientation axis) was confirmed to be approximately 1.74, the refractive index along the transverse axis was 1.64, and the refractive index of the coPEN film was confirmed to be approximately 1.64. That is, the difference Δn between the refractive index of the optically anisotropic layer along the in-plane slow axis and the refractive index of the isotropic layer was 0.10. Next, PEN and coPEN were co-extruded using a 25-slot feed block equipped with a standard extrusion die under conditions that satisfied the above-mentioned Δn relationship, thereby forming seven alternating layers of PEN and coPEN, each having a thickness shown in (1) of Table 1 below. The same procedure was then repeated to form PEN and coPEN layers, each having a thickness shown in (2) to (6) of Table 1, in the order shown in Table 1, in the number of layers shown in Table 1, thereby producing a laminate having a total of 92 layers. The stretched laminate was then heat-treated in an air oven at approximately 230°C for 30 seconds to produce a linearly polarized reflective film. The reflection spectrum of this linearly polarized reflective film was measured using a spectrophotometer (V-670, manufactured by JASCO Corporation), and a reflection spectrum with reflectance peaks at 470 nm, 500 nm, 550 nm, 600 nm, 650 nm, and 720 nm was obtained.

[0123]

[0124] [Preparation of Combiner 4] The glass substrate side of the prepared laminate 4A was bonded to a linearly polarized reflective film via an adhesive layer (OCA). The thickness of the adhesive layer was 10 μm. Next, a 200 mm long x 1000 mm wide black PET sheet (manufactured by Tomoegawa Corporation, Kakukiri Miel 125 μm) was bonded to the surface of the reflective layer (linearly polarized reflective layer) side of the obtained laminate, to prepare Combiner 4. The in-plane slow axis (reflection axis) of the linearly polarized reflective film was parallel to the vertical direction of the glass substrate of the laminate 4A.

[0125] [Example 5] [Preparation of Laminate 5A] Laminate 5A was prepared by forming an inorganic multilayer film (anti-reflection layer) on the TAC film side surface of Laminate 3B prepared in Example 3 using magnetron sputtering. Laminate 5A had the following structure. The values ​​in parentheses indicate the film thickness. Laminate 3B / Al ２ O ３ (80nm) / SiN(80nm) / SiO ２ (100 nm)

[0126] [Preparation of Combiner 5] The cholesteric liquid crystal layer (reflective layer) side of the prepared laminate 5A was bonded to a glass substrate (200 mm long x 1000 mm wide, 2 mm thick) via an adhesive layer (OCA). The adhesive layer had a thickness of 10 μm. Next, a 200 mm long x 1000 mm wide black PET sheet (manufactured by Tomoegawa Corporation, Kakukiri Miel 125 μm) was bonded to the glass substrate side of the obtained laminate to prepare Combiner 5.

[0127] Comparative Example 1 An inorganic multilayer film (reflective layer) was formed on the surface of a polycarbonate substrate (200 mm long x 1000 mm wide, 2 mm thick) by magnetron sputtering to prepare a laminate R1. The laminate R1 had the following structure. The values ​​in parentheses indicate the film thickness. SiO ２ (30nm) / TiO ２ (55nm) / SiO ２ (70 nm) / polycarbonate substrate

[0128] [Preparation of Combiner R1] A 200 mm long x 1000 mm wide black PET (manufactured by Tomoegawa Corporation, Kakuri Miel 125 μm) was laminated to the surface of the polycarbonate substrate side of the prepared laminate R1 to prepare a combiner R1.

[0129] Comparative Example 2 An inorganic multilayer film (reflective layer) was formed on the surface of a polycarbonate substrate (200 mm long x 1000 mm wide, 2 mm thick) by magnetron sputtering to prepare a laminate R2. The laminate R2 had the following structure. The values ​​in parentheses indicate the film thickness. SiO ２ (25nm) / Al(8nm) / SiO ２ (8 nm) / Polycarbonate substrate

[0130] [Preparation of Combiner R2] A 200 mm long x 1000 mm wide black PET (Kukkiri Miel 125 μm, manufactured by Tomoegawa Corporation) was laminated to the surface of the polycarbonate substrate side of the prepared laminate R2 to prepare Combiner R2.

[0131] [Various Measurements and Evaluations] [Measurement of P-Polarized Reflectance] P-polarized light was incident on the combiner at a polar angle of 45° relative to the normal direction of the combiner, and the reflection spectrum (wavelength range: 380 to 780 nm) of the specularly reflected light reflected by the combiner was measured using a spectrophotometer. The measurement method was specifically as follows. First, as shown in FIG. 13, which is a schematic side view of the combiner, a light source 72 emitting projection light (P-polarized light) and a combiner 74 were positioned so that the incident angle θ1 of the projection light from the light source 72 with respect to the combiner was 45° and the reflection angle θ2 was 45°. The combiner 74 was positioned so that its long side (lateral direction) was parallel to the horizontal direction. The light source 72 was a halogen lamp, and a polarizer (not shown) was placed between the combiner 74 and the halogen lamp to emit P-polarized light. Next, the projection light from the light source 72 was incident on the combiner 74 so that the incident plane of the projection light from the light source 72 (the incident plane corresponds to the plane including the normal vector of the combiner 74 and the wave vector of the incident light) was parallel to the short side direction (vertical direction) of the combiner 74, and the reflectance spectrum of the reflected light (specularly reflected light) of the projection light from the light source 72 at the combiner 74 was measured using a spectrophotometer (V-670, manufactured by JASCO Corporation) 76. At this time, the short side direction (vertical direction) of the combiner 74 was parallel to the vibration direction of the P-polarized light incident on the spectrophotometer 76 (in other words, the short side direction (vertical direction) of the combiner 74 was parallel to the vibration plane of the P-polarized light incident on the spectrophotometer 76). Note that the light incident side of the combiner 74 is on the side opposite to the light-shielding layer. Next, the P-polarized reflectance (45°) was determined by multiplying the reflectance value based on the reflection spectrum obtained above by a weighting factor obtained from the CIE daylight D65 spectral distribution and the CIE photopic standard relative luminosity factor, and then calculating the weighted average, in accordance with JIS R3106 2019. Note that the weighting factors used were those shown in JIS R3106 2019 and indicated in 10 nm increments in the wavelength range of 380 to 780 nm.

[0132] [Measurement of S-polarized light reflectance] The S-polarized light reflectance at an incident angle of 45° on the combiner (S-polarized light reflectance (45°)) was determined in the same manner as in the measurement of the P-polarized light reflectance described above, except that P-polarized light was changed to S-polarized light.

[0133] [Calculation of P-polarized light / S-polarized light ratio] From the obtained values ​​of P-polarized light reflectance (45°) and S-polarized light reflectance (45°), the ratio of P-polarized light reflectance (45°) to S-polarized light reflectance (45°) (P-polarized light reflectance (45°) / S-polarized light reflectance (45°)) was calculated.

[0134] [Calculation of Unpolarized Reflectance] The arithmetic mean value of the obtained P-polarized reflectance and S-polarized reflectance was calculated as the unpolarized reflectance (unpolarized reflectance (45°)).

[0135] Table 2 below shows the main configurations and measurement results of each combiner of the above-mentioned examples and comparative examples.

[0136]

[0137] [Evaluation] Each of the produced combiners was evaluated in various ways (image brightness, dashboard reflection, scratch resistance). The results are shown in Table 3.

[0138] [Image Brightness] As shown in FIG. 14 , which is a schematic side view of the combiner, an iPad® 82, functioning as a light source, was positioned below the combiner 84 so that the incident angle θ1 of the projected light from the iPad® 82 relative to the combiner 84 was 45° and the reflection angle θ2 was 45°. The combiner 84 was positioned so that its long side (lateral direction) was parallel to the horizontal. Note that the polarized light emitted from the iPad® 82 was circularly polarized light, and a λ / 4 film (not shown) was sandwiched between the iPad® 82 and the combiner 84 to appropriately convert the polarized light incident on the combiner 84 to P-polarized light. The anti-reflection layer side of the combiner 84 was the light incident side. Next, white text on a black background was displayed on the iPad® 82, and the observed HUD image (projected image) was evaluated according to the following criteria. When projected light (P-polarized) is incident on the combiner 84 from the iPad (registered trademark) 82, the incident plane (the incident plane corresponds to the plane containing the normal vector of the combiner 84 and the wave vector of the incident light) is set parallel to the short side direction (vertical direction) of the combiner 84. "A": Bright, and characters are easy to see. "B": Slightly dim, but characters are visible (acceptable level). "C": Dark, and characters are difficult to see.

[0139] [Dashboard Reflection] As shown in FIG. 15 , a side view of the combiner, an iPad® 82 functioning as a light source was placed below the combiner 84 so that the incident angle θ1 of the projected light from the iPad® 82 with respect to the combiner 84 was 45° and the reflection angle θ2 was 45°. The combiner 84 was placed so that its long side (lateral direction) was parallel to the horizontal. Note that the polarized light emitted from the iPad® 82 was circularly polarized light, and a λ / 4 film (not shown) was sandwiched between the iPad® 82 and the combiner 84 to appropriately convert the polarized light incident on the combiner 84 to P-polarized light. Next, a dashboard was cut out from a Toyota Lexus, and the cut-out dashboard 86 was placed on the iPad® 82 as shown in FIG. 15 . Next, white text was displayed on a black background on the iPad (registered trademark) 82, and an LED light was shone on the dashboard 86 to evaluate the annoyance of ambient light (reflected light from the LED) reflected in the observed HUD image. The anti-reflection layer side of the combiner 84 was the light incident side. When projected light (P-polarized light) was incident from the iPad (registered trademark) 82 to the combiner 84, the incident surface (the incident surface corresponds to the surface containing the normal vector of the combiner 84 and the wave vector of the incident light) was set parallel to the short side direction (vertical direction) of the combiner 84. "A": Dashboard reflection (reflection of ambient light) was barely noticeable. "B": Dashboard reflection was slightly visible, but at an acceptable level. "C": The dashboard was strongly reflected and was an annoyance.

[0140] [Scratch Resistance] The ease of scratching when the surface of each combiner (the surface on the antireflection layer side) was touched with a hand was evaluated according to the following evaluation criteria.

[0141] "A": The surface of the combiner is not scratched when scratched with a fingernail. "B": The surface of the combiner is not scratched when touched with a finger, but is slightly scratched when scratched with a fingernail. "C": The surface of the combiner is barely scratched when touched with a finger, but is noticeably scratched when scratched with a fingernail.

[0142] Table 3 is shown below.

[0143]

[0144] From Tables 2 and 3, it is clear that in a vehicle head-up display system using the combiner of the embodiment, when P-polarized light is used as the projection light, the projected image is bright and dashboard reflection can be suppressed.

[0145] REFERENCE SIGNS LIST 10 Head-up display system 12 Projector 14, 44, 54, 64, 74, 84 Combiner 16 Reflective layer 18, 68 Substrate 20 Anti-reflection layer 22 Light-shielding layer OB Anti-reflection layer 86, 120 Dashboard 30 Dielectric multilayer film 30A First dielectric layer 30B Second dielectric layer 30C Third dielectric layer, 30D Fourth dielectric layer 32 Metal layer 40, 50 First substrate 42, 52 Second substrate 48 λ / 2 plate (retardation layer) 46 Dielectric multilayer film (reflecting layer) 58 λ / 4 plate (retardation layer) 56 Cholesteric liquid crystal layer (reflecting layer) 66 Linearly polarized light reflective layer (reflecting layer) 72, 82 Light source θ1 Incident angle θ2 Reflection angle 76 Spectrophotometer

Claims

1. A combiner having an antireflection layer, a substrate, and a reflective layer in this order, which satisfies all of the following requirements (A) to (D): (A) The P-polarized reflectance is 20.0% or greater when P-polarized light is incident on the combiner from the antireflection layer side at an incident angle of 45°. (B) The ratio of the P-polarized reflectance when P-polarized light is incident on the combiner from the antireflection layer side at an incident angle of 45° to the S-polarized reflectance when S-polarized light is incident on the combiner from the antireflection layer side at an incident angle of 45° is 1.20 or greater. (C) The distance between the antireflection layer and the reflective layer in the thickness direction of the combiner is 30 μm or greater. (D) The unpolarized reflectance is 20.0% or less when unpolarized light is incident on the combiner from the antireflection layer side at an incident angle of 45°.

2. The combiner according to claim 1, satisfying the following requirements (B1) and (C1): (B1) The ratio of the P-polarized reflectance when P-polarized light is incident on the combiner at an incident angle of 45° from the antireflection layer side to the S-polarized reflectance when S-polarized light is incident on the combiner at an incident angle of 45° from the antireflection layer side is 1.50 or more. (C1) The distance between the antireflection layer and the reflective layer in the thickness direction of the combiner is 1 mm or more.

3. The combiner according to claim 1 or 2, satisfying any one of the following requirements (E) to (H): (E) the reflective layer comprises a dielectric multilayer film and a metal layer disposed within the dielectric multilayer film, the metal layer containing aluminum or silver; (F) the reflective layer is a dielectric multilayer film, and further comprises a retardation layer between the antireflection layer and the reflective layer, the retardation layer having an in-plane retardation of 200 to 350 nm at a wavelength of 550 nm; (G) the reflective layer is a cholesteric liquid crystal layer, and further comprises a retardation layer between the antireflection layer and the reflective layer; (H) the reflective layer is a linearly polarized light reflective layer comprising an optically isotropic layer and an optically anisotropic layer.

4. The combiner of claim 1 or 2, wherein the substrate is glass.

5. The combiner according to claim 1 or 2, further comprising a light-shielding member on the side of the reflective layer opposite to the substrate side.

6. A head-up display system comprising the combiner according to claim 1 or 2 and a projector that irradiates projection light onto the combiner.

7. The head-up display system according to claim 6, wherein the projector emits P-polarized light as the projection light.

8. The head-up display system according to claim 6, which is for a vehicle.

Images