Reflection combiner for head-up display device and head-up display device

Abstract

This reflection combiner for a head-up display comprises a substrate (a), a reflection layer (b), and a translucent layer (C) having a thickness of 0.005-0.7 mm. The reflection ratios at 4 kinds of wavelengths of 400, 500, 600, 660 nm are 10-55 %. Preferably, the transmittance is equal to or less than 10 % in the entire range of wavelengths λ=390–660 nm.

Description

Technical Field

[0001] The present invention relates to a combiner which is an optical display member used in an in-vehicle head-up display (HUD) device or the like, and a head-up display device including the combiner.

[0002] A head-up display is a display device (display) that projects information by superimposing it so as to blend into the front scenery within the field of view of a person in the driver's seat, and projects an image onto the windshield or combiner of an automobile. The present invention relates to a reflective combiner that is not of the type that penetrates the front scenery.

Background Art

[0003] In an in-vehicle head-up display device using a combiner, a display image from a display including a light source is projected onto the combiner through a necessary optical system, and the display image is reflected by the combiner toward the position of the eyes of an occupant (driver), thereby forming an image of the display image in front of the vehicle with respect to the combiner (Patent Documents 1 and 2). The display image is a display of the traveling speed, engine speed, various warning lamps, navigation function, and the like.

[0004] Since the combiners of Patent Documents 1 and 2 are almost transparent, an occupant visually recognizes an image that is a superposition of an image of the scenery in front of the vehicle visible through the combiner and a display image optically reflected from the combiner.

[0005] As described in Patent Document 2, in the case of a transparent plate-shaped combiner, light is reflected on both the front surface and the back surface of the combiner, so that the display image appears as a "double image". As a result, the visibility and display quality of the display deteriorate. This "double image" becomes more prominent as the thickness of the plate of the plate-shaped combiner increases.

[0006] In Patent Documents 1 and 2, in order to suppress double imaging, an antireflection treatment is applied to the surface of the combiner. However, applying such an antireflection treatment increases the cost.

[0007] Patent Document 3 describes a combiner using an opaque black plate or a translucent black smoke plate as shown in FIG. 5.

[0008] A combiner using a black plate or a black smoke plate has high display brightness and clear image contours. Also, since the brightness of the background is low for a combiner using a black plate or a black smoke plate, the brightness difference (contrast) with the background becomes large, so the display is easy to see regardless of the brightness outside the vehicle and the condition of external light.

[0009] Moreover, by using an opaque black plate or a translucent black smoke plate as the combiner, reflection on the back side of the combiner can be suppressed, and the double image (double imaging) caused by the deviation and overlap of reflection on the front side and the back side of the transparent combiner can be made less noticeable.

[0010] As a result, measures such as applying a surface treatment to prevent double imaging (double imaging) to the combiner become unnecessary, and the cost can be reduced accordingly.

[0011] Also, while a general combiner has an antireflection film such as an expensive half mirror or a multilayer dielectric applied to its reflective surface to increase the surface reflectance to about 30% - 60%, the combiner of Patent Document 3 keeps the surface reflectance low (for example, about 7%) without applying an antireflection film or the like.

[0012] In the case of a transparent combiner, in order to compensate for the brightness difference (contrast) between the display image and the background and ensure visibility, it is necessary to perform surface treatment such as an expensive enhanced reflection film on the reflecting surface of the combiner to increase the surface reflectivity of the combiner. However, in the case of a combiner using a black plate or a black smoky plate, sufficient visibility can be ensured due to the brightness difference, so it is possible to eliminate the need to perform surface treatment such as an expensive enhanced reflection film on the reflecting surface of the combiner.

[0013] By omitting the enhanced reflection film, the costs of the combiner and the head-up display device are suppressed.

[0014] [Technical problems of conventional combiners] The above conventional combiner had the following technical problems.

[0015] <Increase in light quantity of light source> The display of a head-up display device using a combiner using a black plate or a black smoky plate as described in Patent Document 3 has the advantage that sufficient visibility can be ensured because the brightness difference (contrast) is large. However, for this purpose, it is necessary to make the light of the display or the light source sufficiently bright.

[0016] However, when the light of this display or light source is brightened, the power consumption of the light source increases, the temperature of the head-up display device rises, and there is a risk of adversely affecting the optical components and electronic components of the device.

[0017] <Necessity of improving reflectivity> In order to ensure visibility while suppressing the brightness of the display or light source to an extent that allows these power and heat generation problems, it is required to increase the reflectivity of a combiner using a black plate or a black smoky plate.

[0018] <Necessity of increasing refractive index> The optical reflectance of a black plate or a black smoke plate depends on the refractive index of the plate material when no surface treatment such as forming a reflective layer including an antireflection film is applied to the surface of the plate. To increase the reflectance, it is necessary to increase the refractive index.

[0019] Generally, a combiner is formed of glass, resin, or a composite material thereof. The refractive index n of a general resin is 1.35 to 1.65, not exceeding 1.7. Similarly, the refractive index n of glass is 1.45 to 1.95, not exceeding 2.0. For example, the refractive index of a PC (polycarbonate) resin is about 1.58, and the surface reflectance is about 5%.

[0020] Patent Document 3 describes that "the surface reflectance is kept low without applying an antireflection film or the like". The reflectance of this combiner is disclosed as about 7% as an example. The refractive index when the reflectance is about 7% is about 1.7.

[0021] Incidentally, assuming that the refractive index of the plate is n and the refractive index of the air in contact with the surface where light is incident is 1, the reflectance R can be obtained from the following formula. R ={(1 - n) / (1 + n)} 2

[0022] For example, when the refractive index is 2.0, the reflectance is about 0.11 (11%), when it is 2.6, it is about 0.20 (20%), and when it is 3.0, it is about 0.25 (25%).

[0023] In the case of a polycarbonate (PC) plate that is colorless and transparent with a thickness of several mm or less, reflection occurs on both the front and back surfaces, so the measured reflectance is about 10%. When the PC plate is translucent, the reflectance is in the range of about 5 to 10% depending on its transparency.

[0024] To obtain a reflectance of 10% or more, a plate for a combiner with a refractive index of 2.0 or more is required, which is impossible with general resins and extremely limited even with glass. Even if it can be selected, it becomes a special material and is costly.

[0025] Furthermore, achieving a reflectance of 20% or more or 25% or more is almost impossible without surface treatment such as forming a reflective layer including an antireflection film.

[0026] <Regarding incident angle and polarization dependence> The above relationship between reflectance and refractive index is an example in the case of a low incident angle and unpolarized light (random light). Strictly speaking, the reflectance depends not only on the refractive index but also on the incident angle, polarization (S-polarized light, P-polarized light), and further on the wavelength.

[0027] When increasing the incident angle in unpolarized light (random light), qualitatively, although the reflectance increases with the increase in the incident angle when the incident angle is above a certain value, arranging the combiner so that the incident angle exceeds 45° or even 60° may be unrealistic in terms of the structure of a head-up display device.

[0028] Compared with unpolarized light (random light), in the case of S-polarized light (although the reflectance at normal incidence with an incident angle of 0° is the same as that of unpolarized light), the increase in reflectance with the increase in the incident angle is remarkable.

[0029] However, not only is it difficult to arrange the combiner in the head-up display device due to the high incident angle, but also if the driver wears polarized sunglasses (polarized sunglasses cut only the S-polarized light of sunlight reflected from the bonnet, for example) while driving, almost no light (display image) from the combiner will be visible.

[0030] When the polarization is P-polarized light, (although the reflectance at normal incidence with an incident angle of 0° is the same as that of unpolarized light), the reflectance decreases with the increase in the incident angle, becomes zero reflection at a certain angle (Brewster angle), and further increases with the increase in the incident angle. Therefore, the arrangement of the combiner due to the incident angle is extremely limited and not practical.

[0031] This Brewster angle θ is related to the refractive index n by the relationship tanθ = n. For example, the refractive index of PC (polycarbonate resin) is approximately 1.58, and its Brewster angle is approximately 58°.

[0032] That is, in the case of P-polarized light, when the incident angle is in the range from 0° to 58°, the reflectance decreases as the incident angle increases and becomes zero at approximately 58°. Therefore, in this range, the smaller the incident angle, the higher the reflectance. However, when compared under the same incident angle conditions, the reflectance of P-polarized light is always lower than that of unpolarized light.

[0033] As described above, even if the incident angle and polarization (S-polarized light, P-polarized light) are adjusted and selected, if surface treatment such as forming a reflective layer including an antireflection film is not performed on a combiner using a black plate or a black smoky plate, it is difficult to select a plate material with a refractive index of 2.0 or more. Therefore, there is a problem that it is difficult to achieve a reflectance of 10% or more, and it is impossible to achieve 20% or 25% or more.

[0034] Therefore, it is necessary to sufficiently brighten the light of the light source in the head-up display device, and power consumption and heat generation become problems.

[0035] If a general reflective mirror that appears silver is used to increase the reflectance, light from outside the vehicle will also be reflected, making the display image difficult to see. Therefore, a combiner capable of adjusting the reflectance within a certain range, such as 10 - 55%, is required.

Prior Art Documents

Patent Documents

[0036]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0037] An object of the present invention is to provide a combiner for a head-up display device capable of adjusting the reflectance within a predetermined range, and a head-up display device including the combiner.

Means for Solving the Problems

[0038] In order to solve the above problems, the gist of the present invention is as follows.

[0039] [1] A substrate (a), a reflective layer (b), and a translucent layer (c) having a thickness of 0.005 to 0.7 mm having, a reflectance of 10 to 55% at four wavelengths of 400, 500, 600, and 660 nm, a reflective combiner for a head-up display device.

[0040] [2] The reflective combiner for a head-up display device according to [1], having a transmittance of 10% or less in the entire range of wavelength λ = 390 to 660 nm.

[0041] [3] The reflective combiner for a head-up display device according to any one of [1] or [2], wherein the reflective layer (b) is an aluminum or aluminum alloy layer.

[0042] [4] The reflective combiner for a head-up display device according to any one of [1] to [3], having a pencil hardness of F or more on the projection display surface.

[0043] [5] A head-up display device including the reflective combiner for a head-up display device according to any one of [1] to [3].

Effects of the Invention

[0044] In a combiner using a black plate or a black smoke plate as described in Patent Document 3, light is reflected on the front surface of the plate. In contrast, in the combiner of the present invention, after light (incident light) passes through the translucent layer (c) and is reflected by the reflective layer (b), it passes through the translucent layer (c) again to become reflected light.

[0045] Therefore, by adjusting the concentration of a coloring additive such as a black pigment contained in the translucent layer (c) and the thickness of the translucent layer, the transmittance of the translucent layer (c) can be adjusted. Further, thereby, it becomes possible to adjust the reflectance of the combiner.

[0046] According to the combiner of the present invention, since the reflectance can be adjusted between 10% and 55%, a display image with high brightness and clear contours is displayed. Further, sufficient visibility can be ensured by the brightness difference (contrast) with the background having low brightness by the combiner. In addition, since it is not necessary to increase the light amount of the display or the light source, it is possible to suppress power consumption and heat generation.

[0047] Note that a few percent (either 10% to 55%) weaker reflectance due to the main reflected light from the surface of the reflective layer (b) is superimposed with a slight reflected light having a reflectance of about a few percent due to the surface of the translucent layer (c), and there is a possibility that a double image (double reflection) occurs due to the deviation and overlap of the reflections. However, since the difference in their reflectances is large and the thickness of the translucent layer (c) is set to 0.7 mm or less, the deviation of the image can be suppressed to about 1 mm or less at an incident angle of 45°, for example, so that the double image (double reflection) can be made inconspicuous. Further, by making the thickness of the translucent layer (c) sufficiently thin, it is possible to make the double image (double reflection) hardly visible.

Brief Description of the Drawings

[0048]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

MODE FOR CARRYING OUT THE INVENTION

[0049] The first aspect of the present invention is a reflective combiner for a head-up display device, which has a base material (a), a reflective layer (b), and a translucent layer (c) with a thickness of 0.005 to 0.7 mm, and a reflectance at four wavelengths of 400, 500, 600, and 660 nm is 10 to 55%.

[0050] The second aspect of the present invention is the reflective combiner for a head-up display device according to the first aspect, having a transmittance of 10% or less in the entire range of wavelengths λ = 390 to 660 nm.

[0051] The third aspect of the present invention is the reflective combiner for a head-up display device according to the first or second aspect, having a transmittance of 0.1% or less in the entire range of wavelengths λ = 390 to 660 nm.

[0052] The fourth aspect of the present invention is the reflective combiner for a head-up display device according to any one of the first to third aspects, wherein the reflective layer (b) is an aluminum or aluminum alloy layer.

[0053] The fifth aspect of the present invention is the reflective combiner for a head-up display device according to any one of the first to fourth aspects, having a pencil hardness of F or more on the projection display surface.

[0054] The sixth aspect of the present invention is a reflective combiner for a head-up display device according to any one of the first to fifth aspects, wherein the base material (a) is made of resin.

[0055] The seventh aspect of the present invention is a reflective combiner for a head-up display device according to any one of the first to sixth aspects, wherein the base material (a) is made of a thermoplastic resin.

[0056] The eighth aspect of the present invention is a reflective combiner for a head-up display device according to any one of the first to seventh aspects, wherein the thickness of the base material (a) is 0.5 to 10 mm.

[0057] The ninth aspect of the present invention is a reflective combiner for a head-up display device according to any one of the first to eighth aspects, wherein the thickness of the reflective layer (b) is 50 to 300 nm.

[0058] The tenth aspect of the present invention is a reflective combiner for a head-up display device according to any one of the first to ninth aspects, wherein the semi-transparent tank (c) is a smoke coat, a smoke resin sheet, or a smoke resin film.

[0059] The eleventh aspect of the present invention is a reflective combiner for a head-up display device according to the tenth aspect, wherein the thickness of the smoke coat is 5 to 40 μm.

[0060] The twelfth aspect of the present invention is a reflective combiner for a head-up display device according to the tenth aspect, wherein the thickness of the smoke resin sheet or the smoke resin film is 10 to 700 μm.

[0061] The thirteenth aspect of the present invention is a head-up display device including a reflective combiner for a head-up display device according to any one of the first to twelfth aspects.

[0062] <Summary description of this embodiment> A configuration example of the combiner in this embodiment is shown in FIG. 1. Also, configuration examples of a head-up display device using the combiner of the present invention, taking FIG. 1 as an example, are shown in FIGS. 2, 3, and 4.

[0063] In this embodiment, as shown in FIGS. 2, 3, and 4, it is assumed that a combiner is used as part of a head-up display device mounted on a vehicle.

[0064] In the example shown in FIG. 2, a head-up display unit 1, which is part of the head-up display device, is arranged near the dashboard 5 of the vehicle. Inside the head-up display unit 1, at least a display 2 is provided. By reflecting the image displayed on the display 2 on the combiner 3, the image can be visually recognized by the occupant (driver). In order to reflect and display the image, the occupant (driver) can see it as a virtual image far away by the distance between the display 2 and the combiner 3. An airbag device 6 is installed on the steering wheel 4.

[0065] In the example shown in FIG. 3, the head-up display device is arranged at a position where the occupant (driver) can visually recognize the combiner from above the steering wheel 4, and a hood 7 is provided on the upper part of the combiner for countermeasures against external light.

[0066] In the example shown in FIG. 4, the head-up display device is arranged at a position where the driver can visually recognize the combiner from inside the steering wheel.

[0067] <Configuration> As shown in FIG. 1, the combiner of the present invention has at least a base material (a), a reflective layer (b), and a translucent layer (c) with a thickness of 0.005 to 0.7 mm. In addition to the base material (a), the reflective layer (b), and the translucent layer (c), it may include one or more of an adhesive layer, a hard coat layer, an antireflection layer, a weather-resistant layer, a colorless transparent layer (transparent layer), etc.

[0068] <Material of the base material (a)> Examples of the base material include resin, glass, metal, and ceramic, with resin being preferred. The resin base material can be molded into any shape and size by injection molding using a mold. Also, since the density is lower compared to the case of using glass or metal, the weight of the device can be reduced.

[0069] Resins are roughly classified into thermosetting resins and thermoplastic resins, with thermoplastic resins being desirable because they can be molded at low cost. Representative thermoplastic resins include polycarbonate (PC), polymethyl methacrylate (PMMA, acrylic), acrylonitrile-butadiene-styrene (ABS), polystyrene (PS), polypropylene (PP), cycloolefin polymer (COP), and cycloolefin copolymer (COC).

[0070] Other thermoplastic resins include polyethylene, polyacetal, polybutylene terephthalate, polyethylene terephthalate (PET), polyethylene naphthalate, various polyamides, polyphenylene ether, modified polyphenylene ether, polyphenylene sulfide, polyether ether ketone, polyether ketone, polyphenylene sulfide ketone, polyphenylene sulfide sulfone, polyether nitrile, aromatic polyester, liquid crystal polyester, polyarylate, polysulfone, polyether sulfone, polyetherimide (PEI), polyamideimide, polyimide, polyaminobismaleimide, polymethylpentene, fluororesins (polytetrafluoroethylene, tetrafluoroethylene / hexafluoropropylene / perfluoroalkoxy vinyl ether copolymer, tetrafluoroethylene / ethylene copolymer, polyvinylidene fluoride, tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, etc.), but are not limited thereto.

[0071] These thermoplastic resins can be used alone or in combination of two or more.

[0072] Examples of the mixture include blends of polybutylene terephthalate and polyethylene terephthalate, blends of polyphenylene ether and polyamide, blends of polyphenylene ether and polybutylene terephthalate, and the like.

[0073] The polycarbonate (PC) is not limited to a general aromatic polycarbonate mainly composed of bisphenol A. For example, aromatic polycarbonates, aliphatic polycarbonates, and aromatic aliphatic polycarbonates mainly composed of other raw materials can also be used. For example, as the diol component, polycarbonates mainly composed of ether diols such as isosorbide are also included.

[0074] In particular, PC, PMMA, ABS, PS, and PP are desirable in that they can be molded at low cost.

[0075] In addition, it is desirable to use PMMA and high-hardness PC with a pencil hardness of F or higher, as the scratch resistance of the combiner surface is improved.

[0076] When heat resistance is required, it is desirable to use heat-resistant ABS, polyarylate, PEI, COP, COC, etc.

[0077] <Thickness of the substrate (a)> The thickness of the substrate (a) is generally 0.5 to 10 mm.

[0078] When the thickness is thin, it is excellent in terms of weight reduction, but if it is too thin, the shape may not be stable due to insufficient rigidity, and the displayed image may be distorted. When the thickness is thick, it is excellent in terms of shape stability, but not only does the weight increase, but also the material cost of the substrate (a) becomes high.

[0079] <Shape of the substrate (a)> In the present invention, the portion of the substrate (a) to be projection-displayed is generally in the shape of a flat plate. Although it is desirable to be in the shape of a flat plate for projection display, it may be curved within a range that does not affect the projection display from the viewpoints of design and designability.

[0080] <Reflective layer (b)> The reflective layer (b) only needs to be able to optically reflect visible light, and its composition is not particularly limited. Further, the reflective layer (b) may be a laminate of films having different compositions.

[0081] <Material of the reflective layer (b)> Generally, metals are cited as the material of the reflective layer (b). The reflective layer may be an optical thin film formed by laminating dielectric films, but using a metal is more preferable in terms of simplicity of manufacturing method or design and is also industrially and cost-effective.

[0082] Examples of the metal include aluminum (Al), iron (Fe), cobalt (Co), chromium (Cr), nickel (Ni), copper (Cu), tin (Sn), indium (In), silver (Ag), platinum (Pt), gold (Au), and alloys containing one or more of these.

[0083] Among these, Al or its alloy, and Ag or its alloy are suitable because they have high reflectivity in the visible light wavelength range and can increase the reflectivity of the combiner. Al or its alloy is particularly preferable because it has relatively little wavelength dependence of reflectivity in the visible light wavelength range, and the appearance color of the combiner reflective surface can be easily adjusted by the translucent layer (c) due to the small difference in reflectivity at specific wavelengths. Al or its alloy is less expensive than Ag or Ag alloy.

[0084] <Method for forming the reflective layer (b)> Examples of the method for forming the reflective layer (b) include vacuum evaporation, vacuum sputtering film formation, plating, mirror printing, coating (painting), etc.

[0085] The method for forming the reflective layer (b) may also be a method of bonding a film-like metal to be the reflective layer (b) to the base material (a) and the translucent layer (c), or a method of laminating by applying and coating the translucent layer (c) on the metal film.

[0086] For the printing ink used for mirror printing to form the reflective layer (b), silver printing ink or the like in which metal powders such as aluminum powder and silver powder are blended and dispersed in synthetic resins such as acrylic resin, urethane resin, and polyester resin can be used.

[0087] As a printing method for such printing ink, printing methods such as screen printing, offset printing, gravure printing, and flexographic printing are used, and among them, screen printing is preferable.

[0088] The reflective layer (b) may be formed on the base material (a), and when the translucent layer (c) is a film or a sheet, the reflective layer (b) may be formed on the surfaces thereof.

[0089] The formation of the reflective layer (b) is desirable in that vacuum evaporation or vacuum sputtering film formation can form a homogeneous and smooth reflective surface.

[0090] In particular, it is desirable that the reflective layer (b) is a metal film. In the case of a metal film, in the design of the film structure before film formation, using a metal film rather than an oxide multilayer film is more desirable because the structure is simpler, the film formation material cost can be suppressed, and the film formation time can be shortened.

[0091] When using a metal with a high reflectivity, the reflectivity of the combiner of the present invention becomes high, and conversely, when using a metal with a low reflectivity, the reflectivity becomes low. Therefore, it is desirable to select a metal or its alloy used for the reflective layer whose reflectivity can be 50% or more.

[0092] Furthermore, in sputtering film formation, when the discharge power per unit area of the target is 25 W / cm 2 or more, particularly 40 W / cm 2 or more, the film formation rate can be 10 nm / s or more, particularly 15 nm / s or more, which is desirable in that film formation can be performed in a short time.

[0093] <Thickness of the reflective layer (b)> When vacuum evaporation or vacuum sputtering film formation is used as the method for forming the reflective layer (b), the thickness (film thickness) of the reflective layer (b) is appropriately set according to the required characteristics, but is preferably 50 to 300 nm, particularly preferably 90 to 150 nm.

[0094] When the film thickness is thin, the adhesion to the adjacent substrate (a) and the adhesion to the translucent layer (c) are excellent. However, if the film thickness is too thin, incident light may pass through the reflective layer and the reflected light may be insufficient. When the film thickness is thick, the stability of the reflectance with respect to incident light is excellent. However, if the film thickness is too thick, not only the manufacturing time and cost increase, but also the adhesion may be inferior. Therefore, it is desirable to select an appropriate thickness for the reflective layer (b) that is neither too thick nor too thin.

[0095] When forming the reflective layer (b), in order to improve the adhesion, a method of forming an underlayer in advance before vacuum film formation, a method of performing plasma treatment, or a method of performing both may be adopted. Among them, the method of performing plasma treatment in a vacuum immediately before vacuum film formation of the reflective layer (b) is desirable in that the process can be carried out in the same vacuum.

[0096] When the reflective layer (b) is formed by plating or mirror printing, or when a film-like metal (metal film) is used as the reflective layer, it is generally difficult to achieve a thickness of 1 μm or less that can be formed by the above-mentioned vacuum film formation, so the thickness is generally 1 μm or more.

[0097] <Surface roughness Ra of the reflective layer (b)> In order to make the display image clear, the surface roughness Ra of the reflective layer is desirably 100 nm or less, more desirably 10 nm or less. Also, when the reflective layer (b) is formed on the substrate (a) or the translucent layer (c) by vacuum film formation, it is desirable to make the surface roughness Ra of the surface of the substrate (a) or the translucent layer (c) on which the film is formed 100 nm or less, particularly 10 nm or less.

[0098] <Transmittance of the combiner> Due to the presence of the reflective layer (b), the combiner of the present invention is opaque with a transmittance of preferably 10% or less, particularly preferably 0.1% or less, in the wavelength range of λ = 390 to 660 nm.

[0099] <semi-transparent layer (c)> In the present invention, the semi-transparent layer (c) is composed of a smoke coat (coating) using a coating resin, or a smoke resin sheet or a smoke resin film.

[0100] 《Semi-transparent layer (c) composed of a smoke coat (coating) using a coating resin》 In one aspect of the present invention, the semi-transparent layer (c) is composed of a smoke coat formed using a coating resin. ·Coating method Examples of the coating method for the coating resin material include known coating methods such as spin coating method, dipping coating method, spraying method, slide coating method, bar coating method, roll coating method, gravure coating method, inkjet method, silk screen method, die coating method, flow coating method, cast transfer method, etc.

[0101] Among them, from the viewpoints of adjusting the thickness of the coating layer and coating unevenness, it is preferable to adopt the spraying method, inkjet method, gravure coating method, or silk screen method. For example, it is preferable to spray and apply the coating resin material using a robot arm spray or the like.

[0102] For example, the thickness of the coating layer can be adjusted by any one adjustment or a combination of two or more adjustments among the adjustment of the coating amount, the adjustment of the number of coating times, the adjustment of the distance from the object to be coated, the coating pattern, and the adjustment of the moving speed of the discharge port during coating.

[0103] More specifically, for example, if a robot arm spray is computer-controlled, as an operator, by inputting the coating amount and the number of coating times (number of coating layers) at each part according to the shape and size of the panel substrate to be coated into the computer, the thickness of the coating layer can be adjusted to a desired thickness.

[0104] · Coating resin material The coating resin material is not particularly limited, but a resin material used as a hard coat material is preferred.

[0105] Examples of the coating resin material include ultraviolet (UV) curable resin materials, solvent drying curable resin materials, thermosetting resin materials, etc. However, other coating materials can be used as appropriate.

[0106] Examples of the ultraviolet curable resin material include resin materials containing a photopolymerizable compound, that is, a compound having one or more photopolymerizable functional groups.

[0107] In addition, examples of the light used for irradiating when polymerizing the photopolymerizable compound include visible light, and ionizing radiation such as ultraviolet rays, X-rays, electron beams, α-rays, β-rays, and γ-rays.

[0108] Examples of the above photopolymerizable compound include a photopolymerizable monomer, a photopolymerizable oligomer, or a photopolymerizable polymer having a polymerizable unsaturated bond such as an acryloyl group or a methacryloyl group, a thiol group, an epoxy group, or an ethylenic double bond such as an allyl group in the molecule.

[0109] For example, a photopolymerizable monomer can be used in combination with a photopolymerizable oligomer or a photopolymerizable polymer.

[0110] Examples of the photopolymerizable monomer include polyfunctional monomers having two or more (i.e., bifunctional or more) photopolymerizable functional groups.

[0111] For example, diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tripropylene glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,6 - hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, tripentaerythritol octa(meth)acrylate, tetrapentaerythritol deca(meth)acrylate, isocyanuric acid tri(meth)acrylate, isocyanuric acid di(meth)acrylate, polyester tri(meth)acrylate, polyester di(meth)acrylate, bisphenol di(meth)acrylate, diglycerin tetra(meth)acrylate, adamantyl di(meth)acrylate, isobornyl di(meth)acrylate, dicyclopentane di(meth)acrylate, tricyclodecane di(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, and those modified with PO (propylene oxide), EO (ethylene oxide), etc. are included.

[0112] As the photopolymerizable oligomer, a polyfunctional oligomer having two or more functional groups is preferable.

[0113] For example, polyether (meth)acrylate, polyol (meth)acrylate, melamine (meth)acrylate, isocyanate (meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate, urethane (meth)acrylate, polyester - urethane (meth)acrylate, etc. are included.

[0114] As the photopolymerizable polymer, polyurethane (meth)acrylate, polyisocyanate (meth)acrylate, polyester - urethane (meth)acrylate, polyepoxy (meth)acrylate, etc. are included.

[0115] As the ultraviolet-curable resin material, it may be a resin material that contains a photoinitiator, and the photoinitiator absorbs ultraviolet rays, is excited and activated to cause a polymerization reaction, thereby causing a curing reaction of the ultraviolet-curable resin.

[0116] Examples of the photoinitiator include benzyl, benzophenone and its derivatives, thioxanthones, benzyldimethylketals, α-hydroxyalkylphenones, α-hydroxyacetophenones, hydroxyketones, aminoalkylphenones, acylphosphine oxides, and the like.

[0117] Among them, α-hydroxyalkylphenones are preferable because they hardly cause yellowing during curing and a transparent cured product can be obtained. Also, aminoalkylphenones are preferable because they have very high reactivity and a cured product with excellent hardness can be obtained.

[0118] The above photoinitiator can be used alone or in combination of two or more.

[0119] The addition amount of the photoinitiator is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the curable resin.

[0120] In the case of the ultraviolet-curable resin material, for example, the resin material is applied to the surface to be coated, then heated to dry the resin material to evaporate the solvent, and then the resin material is irradiated with light such as ultraviolet rays to polymerize (crosslink) the photopolymerizable compound, thereby curing the coating layer. However, it is not limited to this method.

[0121] The solvent-drying curable resin material may be any resin material that can form a film by simply drying the solvent added to adjust the solid content during coating, such as a thermoplastic resin.

[0122] In addition, examples of the thermosetting resin material include those containing a thermosetting resin such as a polyurethane resin, an epoxy resin, a phenolic resin, a urea resin, a diallyl phthalate resin, a melamine resin, a guanamine resin, an unsaturated polyester resin, an amino alkyd resin, a melamine-urea co-condensation resin, a silicone resin, and a polysiloxane resin.

[0123] In addition to the thermosetting resin, the thermosetting resin material may contain, as necessary, a curing agent such as a crosslinking agent and a polymerization initiator, a polymerization accelerator, a solvent, a viscosity modifier, an extender pigment, and the like.

[0124] As the curing agent, isocyanate, organic sulfonic acid, etc. are usually used for polyester resins and polyurethane resins, amine is used for epoxy resins, and peroxides such as methyl ethyl ketone peroxide and radical initiators such as azobisisobutyl ester are often used for unsaturated polyester resins.

[0125] Among the above, from the viewpoint of scratch resistance, a coat resin material having a pencil hardness of H or more when coated on a polycarbonate substrate is preferable.

[0126] In addition, the wettability (JIS K6768) of the coat resin material is preferably 22.6 dyn or less, and the viscosity (JIS K5600 2-2 flow cup method) of the coat resin material is preferably 7.5 seconds to 10.0 seconds.

[0127] From such a viewpoint, acrylic resins and urethane resins are particularly preferable as the base resin of the coat resin material. Among them, acrylic resins are particularly preferable from the viewpoint of surface hardness.

[0128] The above coat resin material may contain, as necessary, various additives such as conventionally known dispersants, surfactants, antistatic agents, silane coupling agents, thickeners, anti-coloring agents, coloring agents (pigments, dyes), defoamers, leveling agents, flame retardants, ultraviolet absorbers, adhesion imparting agents, polymerization inhibitors, antioxidants, surface modifiers, lubricants, antioxidants, and impact resistance modifiers.

[0129] From the viewpoint of adjusting the degree and speed of curing, it is desirable to use an ultraviolet curable resin.

[0130] · Method of making translucent (smoky) A smoky coat can be achieved by using a coat material in which a coloring additive is added to the coat resin. The coloring additive is preferably a black pigment. In the visible light wavelength range, since the wavelength dependence of the transmittance is small, the wavelength dependence of the reflectance when used as a combiner can also be reduced. When the wavelength dependence of the combiner reflectance can be suppressed, the color reproducibility of the display image from the display also improves. Examples of the black pigment include carbon black (specifically, lamp black, vegetable black, furnace black, channel black, thermal black, acetylene black, charcoal black, etc.), graphite (black lead), iron trioxide (black iron oxide), composite oxides of iron and manganese (Fe-Mn-based black), composite oxides of iron, manganese and copper (Fe-Mn-Cu-based black), composite oxides of cobalt, iron and chromium (Co-Fe-Cr-based black), composite oxides of copper and chromium (Cu-Cr-based black), composite oxides of copper, chromium and manganese (Cu-Cr-Mn-based black), composite oxides of cobalt, iron and manganese (Co-Fe-Mn-based black), lower-order titanium oxide (titanium black), aniline black, etc. Among them, composite oxides of iron and manganese, such as manganese ferrite in which part of the iron element of black iron oxide is substituted, are desirable, but not limited thereto.

[0131] By adjusting the black pigment concentration and the thickness of the translucent layer, the transmittance of the translucent layer (c) can be adjusted. From the transmittance of this translucent layer (c) and the reflectance of the reflective layer (b), the reflectance of the combiner (composed of the base material (a), the reflective layer (b) and the translucent layer (c)) is determined.

[0132] · Thickness of the translucent layer (c) made of the coat resin material The thickness of the translucent layer (c) made of the coat resin material is preferably 5 to 40 μm, more preferably 10 to 30 μm, and particularly preferably 15 to 25 μm.

[0133] If the thickness of the translucent layer (c) is excessively thin, uneven film thickness called "citrus peel (also referred to as orange peel or orange peel)" and uneven appearance are likely to occur, which may not be preferable. In addition, if the thickness of this translucent layer (c) is excessively thin, not only is it difficult to adjust to a predetermined thickness, but uneven thickness is also likely to occur. As a result, it may affect the transmittance of the translucent layer (c) and the reflectance value of the combiner.

[0134] Conversely, if the thickness of the translucent layer (c) is excessively thick, not only does it take time and cost in manufacturing, but it also tends to cause poor curing or insufficient curing of the coating resin. In addition, there is a risk that the translucent layer (c) is likely to peel off from the reflective layer (b), or the translucent layer (c) is likely to peel off from the base material (a) together with the reflective layer (b).

[0135] 《Translucent layer (c) made of a smoke resin sheet or a smoke resin film》 In another form of the present invention, the translucent layer (c) is made of a smoke resin sheet or a smoke resin film.

[0136] The thickness of this sheet or film needs to be 700 μm or less. This is because if it is thicker, double imaging will occur in the projected reflection image. The lower limit of the thickness of the sheet or film is not particularly limited, but generally it is 10 μm or more.

[0137] Examples of the resin of the sheet or film include, but are not limited to, PC, PMMA, and PET.

[0138] Regarding the difference between a resin sheet and a resin film, although they may be used appropriately depending on their thickness, there is no definite standard. According to the JIS (Japanese Industrial Standards) packaging terminology standard, a sheet is defined as having a thickness of 250 μm or more, and a film is defined as having a thickness of less than 250 μm. However, as a convention when using the terms sheet or film, it is not uncommon to use other values such as 200 μm as the boundary. When using a sheet or a film as the translucent layer (c) in the present invention, it is not limited to either.

[0139] When the translucent layer (c) is a sheet or a film, the reflective layer (b) can also be formed on this sheet or film.

[0140] <Reflectance> The reflectance of the combiner of the present invention will be described below.

[0141] The reflectance of the projection display area in the combiner of the present invention is preferably 10 - 55%, particularly preferably 25 - 45% at wavelengths λ = 400, 500, 600, 660 nm. If the reflectance is too low, the projection display will appear dark. Although it is possible to increase the light output of the light source to brighten the projected display image, this will increase the power consumption and at the same time cause the temperature of the light source to rise, which is not preferable.

[0142] If the reflectance is too high, while the projection display will become brighter, there is a possibility of reflection during the off / on state due to external light or the like, which is not preferable.

[0143] In the present invention, it is desirable that the ratio "R(400nm) / R(660nm)" of the reflectance "R(400nm)" at wavelength λ = 400 nm and the reflectance "R(660nm)" at wavelength λ = 660 nm is 0.5 - 2.0. This is because if this ratio is too small, the projected display image will have a yellow or red tint and the warm color will be strong, and if it is too large, the projected display image will have a blue or purple tint and the cool color will be strong.

[0144] <Transmittance> In the combiner of the present invention, the transmittance of the projection display area is preferably 10% or less, more preferably 1% or less, and particularly preferably 0.1% or less in the entire wavelength range of λ = 390 to 660 nm. Since the transmittance of the combiner is low, it is possible to prevent an adverse effect on the display by light from the back side of the display surface of the combiner.

[0145] <Pencil hardness (on the projection display surface)> From the viewpoint of scratch resistance, it is preferable that the pencil hardness of the projection display area in the combiner of the present invention is F or more.

[0146] Although not limited in the present invention, as described above, in order to improve scratch resistance, it is preferable to select a material in which the base material (a) has a pencil hardness of F or more.

[0147] Further, as the material of the translucent layer (c), it is particularly preferable that it is a resin material used as a hard coat material.

[0148] A hard coat layer may be provided separately from the translucent layer (c).

[0149] <Manufacturing method of the combiner> As an example of the manufacturing method of the combiner of the present invention, the following manufacturing methods A to E can be mentioned, but the manufacturing method is not limited to these.

[0150] Manufacturing method A: A reflective layer (b) is formed by vacuum deposition, for example, sputtering deposition, on a substrate (a), and a translucent layer (c) is coated thereon (Examples 1 to 4 apply).

[0151] Manufacturing method B: A reflective layer (b) is formed by vacuum deposition, for example, sputtering deposition, on a smoke resin sheet (or film) serving as the translucent layer (c), and the deposition surface is attached to a substrate (a) using, for example, an adhesive layer (Example 5 and Comparative Examples 4 to 8 apply).

[0152] Manufacturing Method C: Prepare a film for in-mold molding in which a plurality of layers including at least a translucent layer (c) and a reflective layer (b) are laminated in advance, and integrate it with the substrate (a) by in-mold molding.

[0153] Manufacturing Method D: Form a reflective layer (b) on a colorless transparent sheet (film), coat a translucent layer (c) on the surface of the colorless transparent sheet (film) opposite to the surface on which the reflective layer (b) is formed, and attach the reflective layer (b) to the substrate (a) using, for example, an adhesive layer. Note that the formation order of the reflective layer (b) and the translucent layer (c) may be reversed.

[0154] Manufacturing Method E: Mirror-print a reflective layer (b) on the substrate (a), and coat a translucent layer (c) thereon.

Examples

[0155] Examples are shown below to explain the present invention more specifically. However, the present invention is not limited to these, and various applications are possible without departing from the technical idea of the present invention.

[0156] <Measurement and Evaluation Methods> The measurement and evaluation methods performed on the examples and comparative examples are as follows.

[0157] <Reflectance> Using a spectrophotometer (Konica Minolta Japan Inc., model number: CM-2600d), the measured value by the SCI method including regular reflected light was measured as the reflectance.

[0158] This measuring instrument measures the wavelength range of λ = 360 to 740 nm at wavelength intervals of 10 nm.

[0159] <Brightness in Image Quality (Sensory Evaluation)> Under indoor (fluorescent lamp) conditions of 400 Lux, a white-filled circle with a diameter of 20 mm (white circle) was displayed on the display screen of a notebook computer with a black background, and a combiner sample was placed on the keyboard of the notebook computer to be incident on the combiner sample at an incident angle of 45°. The image reflected onto the combiner sample in the 45° reflection angle direction was visually observed, and the brightness of the white circle was subjectively evaluated. A*: Considerably bright A: Good B: Slightly dark but within the acceptable level C: Dark

[0160] <Reflections in image quality (subjective evaluation)> Under indoor (fluorescent lamp) conditions of 400 Lux, the same optical arrangement as for the subjective evaluation of brightness was used. However, nothing was displayed on the display screen of the notebook computer. Instead, a black resin plate with surface roughness (a non-mirror black plate) that assumed a pseudo-black background was placed in contact with the screen, and the degree of reflections was subjectively evaluated when visually observing the pseudo-black background reflected on the combiner sample. ◎: No visible reflections, good ○: Almost no visible reflections, good △: Slight visible reflections but within the acceptable level ×: Some visible reflections

[0161] <Double reflections in image quality (subjective evaluation) (20 pt)> Similar to the brightness evaluation, a notebook computer was used to display a large number of "=" (equal sign) and "-" (minus sign) in white characters on a black background. Similarly, it was incident at 45°, and it was subjectively evaluated whether double reflections occurred in the reflected image when visually observed.

[0162] In the MS Gothic font at 20 pt (point), the line width of "=" and "-" is approximately 1 / 2 mm (= 0.5 mm), and the distance from the top to the bottom of the white character "=" is approximately 2 mm. ○: No double reflections, good △: Slight blurring of the image like double reflections is visible but within the acceptable level △(Yuzu skin): Slight blurring of the image is visible due to the slight "yuzu skin" on the surface of the smoke hard coat layer, but it is at an acceptable level. ×: Double reflection is not allowed. ××: Double reflection is more clearly visible and not allowed. ×××: Double reflection is even more clearly visible and not allowed.

[0163] <Double reflection in image quality (sensory evaluation) (10pt)> Similar to the brightness evaluation, a notebook computer was used to display a large number of "=(equal sign)" and "-(minus sign)" in white characters on a black background, and the light was incident at 45° in the same way. Whether the reflected image was visually double-reflected was evaluated by sensory evaluation according to the same evaluation criteria as above.

[0164] In MS Gothic font 10pt, the line width of "=" and "-" is about 1 / 4 mm (=0.25 mm), and the distance from the top to the bottom of the white character "=" is about 1 mm.

[0165] <Pencil hardness (on the projection display surface)> It was carried out according to the following standards.

[0166] Japanese Industrial Standard JIS K5600-5-4:1999 (ISO / DIS 15184:1996)

[0167] <Transmittance (for the characteristic evaluation of the semi-transparent layer (c))> Due to some differences in the applicable measurement methods depending on the formation method and thickness of the semi-transparent layer (c), it will be explained individually below, but they are essentially similar.

[0168] 《In the case of the semi-transparent layer (c) which is a smoke coat (coating) using a coating resin》 Under the same conditions as the coating conditions on the reflective layer (b), the transmittance of a plate obtained by applying a smoke coat to a 1-mm thick colorless transparent PC plate was measured using a laser beam with a wavelength of λ = 660 nm and a photometer (photodiode).

[0169] That is, the transmittance in a state where the smoke coat layer corresponding to the semi-transparent layer (c) overlaps with the colorless transparent PC plate was measured.

[0170] Since the thickness of this smoke coat layer is as thin as about 5 to 40 μm, it is practically difficult to measure the transmittance of only this layer. Therefore, the method of measuring in combination with the colorless transparent PC substrate as described above is adopted.

[0171] Under the same conditions as when this transmittance is high, the reflectance of the plate smoke-coated on the reflective layer (b) becomes high. Conversely, under the same conditions as when this transmittance is low, the reflectance of the plate smoke-coated on the reflective layer (b) becomes low.

[0172] Incidentally, the transmittance of this 1-mm-thick colorless transparent PC plate at a wavelength λ = 660 nm is 90%.

[0173] Even if the transmittance of only this smoke coat layer corresponding to the translucent layer (c) cannot be measured, there is no problem in forming the translucent layer (c) by this smoke coat on the reflective layer (b).

[0174] This is because after smoke-coating the colorless transparent PC plate, the transmittance of this plate is measured, the reflectance of the plate smoke-coated on the reflective layer (b) formed under the same conditions is measured, and the correlation can be found in advance.

[0175] 《When using a smoke sheet as the translucent layer (c)》 When using a smoke sheet or plate as the translucent layer (c), since the thickness is 0.5 mm or more in the corresponding examples and comparative examples, the transmittance was directly measured with a laser beam of wavelength λ = 660 nm and a light quantity meter (photodiode).

[0176] The measured transmittance values at a wavelength λ = 500 nm measured using a spectrophotometer are also shown in Table 1 or 2.

[0177] When a reflective layer (b) is formed on this highly transmissive smoke sheet, the reflectance of the light incident from the smoke sheet corresponding to the semi-transparent layer (c) increases. Conversely, when the same reflective layer (b) is formed on a smoke sheet with a low transmittance, the reflectance of the light incident from the smoke sheet corresponding to the semi-transparent layer (c) decreases.

[0178] <Transmittance (for characteristic evaluation of the reflective combiner)> The transmittance of the combiner was measured at 1 nm intervals in the wavelength range of λ = 390 to 660 nm using a spectrophotometer, and the maximum transmittance was described in Table 1 or 2.

[0179] <Thickness of the semi-transparent layer (c)> Depending on the formation means and thickness of the semi-transparent layer (c), the following measurement methods were adopted.

[0180] 《In the case of the semi-transparent layer (c) which is a smoke coat (coating) using a coating resin》 For thickness evaluation, a glass plate was placed on the reflective layer (b) or on a 1 mm thick colorless transparent PC plate used for transmittance measurement, and after masking a part with tape, it was smoke-coated under the same conditions. Then, the glass plate was taken out, and the step and height difference between the smoke-coated part and the non-coated part by masking on the glass plate were measured using a constant-pressure thickness gauge (resolution 0.001 mm = 1 μm).

[0181] If the resolution can be measured with a high resolution of about 0.001 mm or more, it may be measured by a micrometer, a contact three-dimensional shape measuring machine, a non-contact three-dimensional measuring machine, a contact step gauge, a contact surface roughness meter, a laser microscope, etc.

[0182] As the glass plate, a cover glass generally commercially available for optical microscope observation was used. In addition, a commercially available slide glass or a silicon substrate for semiconductors cut to an appropriate size may be used.

[0183] In the smoke coating process, it is essential to use a plate that does not melt or deform and to have an adhesion to the smoke coating that does not interfere with thickness measurement.

[0184] 《When using a smoke sheet as the translucent layer (c)》 Before forming the reflective layer (b) on the smoke sheet, the thickness of the smoke sheet alone was measured with a vernier caliper (resolution 0.01 mm). Measurement may also be performed using a constant-pressure thickness measuring instrument, a micrometer, or the like.

[0185] <Other measurement methods for the thickness of the translucent layer (c)> To evaluate the thickness of the translucent layer (c), cross-sectional observation may be performed together with the reflective layer (b) or the base material (a).

[0186] The observation method is appropriately selected according to the required magnification and the like. For example, there are an optical microscope, a polarizing microscope, a laser microscope, a scanning electron microscope (SEM), a transmission electron microscope (TEM), and the like.

[0187] [Example 1] As the base material (a), a 1-mm-thick black opaque PC board was prepared, and aluminum was sputter-deposited thereon after plasma treatment to form the reflective layer (b). On this reflective layer (b), a smoke hard coat was applied with a thickness of 10 μm (= 0.010 mm) as the translucent layer (c).

[0188] The smoke hard coat is a coat having both an optical smoke function and a hard coat function with scratch resistance.

[0189] The measurement and evaluation results of the reflectance, image quality, and pencil hardness of the obtained plate are shown in Table 1. Before applying the smoke hard coat, the thickness evaluation of the smoke hard coat was performed in advance, and the transmittance when the smoke hard coat was applied to a colorless transparent PC board was measured.

[0190] [Example 2] The same procedure as in Example 1 was carried out, except that the thickness of the smoke hard coat of the translucent layer (c) was set to 20 μm (= 0.020 mm). The measurement and evaluation results are shown in Table 1.

[0191] [Example 3] The same procedure as in Examples 1 and 2 was carried out, except that the type of the coat resin material forming the translucent layer (c) and the thickness of the translucent layer (c) were changed to 15 μm. The measurement and evaluation results are shown in Table 1.

[0192] [Example 4] The same procedure as in Example 3 was carried out, except that the thickness of the translucent layer (c) was changed to 10 μm. The measurement and evaluation results are shown in Table 1.

[0193] [Example 5] A 0.5 mm thick smoke PC sheet (sheet) (transmittance at a wavelength λ = 660 nm: 57%) was prepared as the translucent layer (c), and aluminum was sputter-deposited thereon after plasma treatment to form a reflective layer (b). Then, the surface on the side of the reflective layer (b) was attached to a 1 mm thick black opaque PC sheet prepared as the base material (a). The measurement and evaluation results are shown in Table 1.

[0194] [Comparative Example 1] The same measurement and evaluation were carried out on a 1 mm thick black smoke PC sheet (transmittance at a wavelength λ = 660 nm: 46%). The results are shown in Table 2.

[0195] [Comparative Example 2] The same measurement and evaluation were carried out on a 1 mm thick black smoke PC sheet (transmittance at a wavelength λ = 660 nm: 19%). The results are shown in Table 2.

[0196] [Comparative Example 3] The same measurement and evaluation were carried out on a 1 mm thick black opaque PC sheet (which does not transmit any visible light). The results are shown in Table 2.

[0197] [Comparative Example 4] The same procedure as in Example 5 was carried out, except that the black smoke PC sheet of Comparative Example 1 was used as the translucent layer (c). The measurement and evaluation results are shown in Table 2.

[0198] [Comparative Example 5] The same procedure as in Example 5 was carried out except that the black smoke PC board of Comparative Example 2 was used as the translucent layer (c). The measurement and evaluation results are shown in Table 2.

[0199] [Comparative Example 6] The same procedure as in Example 5 was carried out except that a 1 mm thick black smoke high-hardness PC board (transmittance of 75% at a wavelength λ = 660 nm) was used as the translucent layer (c). The measurement and evaluation results are shown in Table 2.

[0200] [Comparative Example 7] The same procedure as in Example 5 was carried out except that a 2 mm thick black smoke high-hardness PC board (transmittance of 64% at a wavelength λ = 660 nm) was used as the translucent layer (c). The measurement and evaluation results are shown in Table 2.

[0201] [Comparative Example 8] The same procedure as in Example 5 was carried out except that a 3 mm thick black smoke high-hardness PC board (transmittance of 54% at a wavelength λ = 660 nm) was used as the translucent layer (c). The measurement and evaluation results are shown in Table 2.

[0202] [Comparative Example 9] The same procedure as in Example 2 was carried out except that the type of the coating resin material for forming the translucent layer (c) was changed to a different one from that in Examples 1 to 4. The measurement and evaluation results are shown in Table 2.

[0203]

Table 1

[0204]

Table 2

[0205] [Discussion] From Tables 1 and 2, the following is clear.

[0206] In Comparative Examples 1 to 3 and 5, double reflection is acceptable and good, but the brightness is insufficiently low. This is because the reflectance is low.

[0207] In Comparative Examples 4 and 6 to 8, the brightness is acceptable and good, but double reflection occurs. This is because the thickness of the translucent layer (c) is 1 mm or more, resulting in a deviation in the reflected light from the front and back surfaces of the black smoke sheet.

[0208] In Comparative Example 9, both double reflection and brightness are acceptable and good, but reflection can be seen. This is because the reflectance is too high.

[0209] In contrast, according to the present invention, by having a reflective layer (b) and a translucent layer (c) with a thickness of 0.7 mm or less, a combiner that can satisfy the brightness and avoid double reflection as in Examples 1 to 5 can be manufactured.

[0210] Although the present invention has been described in detail using specific embodiments, it is obvious to those skilled in the art that various changes can be made without departing from the intention and scope of the present invention. This application is based on Japanese Patent Application No. 2021-202695 filed on December 14, 2021, the entire contents of which are incorporated herein by reference.

Explanation of Reference Numerals

[0211] 1 Head-up display unit 2 Display 3 Combiner 4 Steering 5 Dashboard 6 Airbag device 7 Hood (a) Substrate (b) Reflective layer (c) Translucent layer (d) Adhesive layer

Claims

1. A base material (a), a reflective layer (b), and a translucent layer (c) having a thickness of 0.005 to 0.7 mm are provided, the base material (a), the reflective layer (b), and the translucent layer (c) are provided in this order, and the reflectance at four wavelengths of 400, 500, 600, and 660 nm of the light incident from the translucent layer (c) is 10 to 55%, a reflective combiner for a head-up display device.

2. The reflective combiner for a head-up display device according to Claim 1, having a transmittance of 10% or less in the entire range of wavelengths λ = 390 to 660 nm.

3. The reflective combiner for a head-up display device according to Claim 1 or 2, wherein the reflective layer (b) is an aluminum or aluminum alloy layer.

4. The reflective combiner for a head-up display device according to Claim 1 or 2, having a pencil hardness of F or more on the projection display surface.

5. A head-up display device including the reflective combiner for a head-up display device according to Claim 1 or 2.

Images