Reflective films, windshield glass, and head-up display systems

Abstract

Provided are: a reflective film that, when applied to a head-up display, is capable of image display and can handle various authentications such as facial authentication and luster authentication implemented by using various infrared light sources; windshield glass; and a head-up display system. The present invention has a visible light selective reflection layer and an infrared light selective reflection layer, wherein the visible light selective reflection layer has at least one reflection peak in the 380-850 nm range and has a natural light reflectance of 5-25% at the reflection peak, and the infrared light selective reflection layer satisfies requirement 1 or requirement 2. Requirement 1: Having at least two reflection peaks in the 900-1,200 nm range and having a natural light reflectance of at least 26% at the reflection peaks. Requirement 2: Having one reflection peak in the 900-1,200 nm range, having a natural light reflectance of at least 26% at the reflection peak, and having a wavelength bandwidth of 120-500 nm in a region having a higher reflectance than the average of the maximum and minimum values of reflectance.

Description

[Technical Field]

[0001] The present invention relates to a reflective film that can be used as a combiner in a head-up display system, and to a windshield glass and a head-up display system having the reflective film. [Background technology]

[0002] Currently, there is a head-up display (HUD) or head-up display system that projects an image onto the windshield of a vehicle to provide the driver with various information such as a map, driving speed, and vehicle status. In a head-up display system, a virtual image containing the above-mentioned various pieces of information is projected onto the windshield glass and is observed by the driver. The virtual image is formed at a position outside the vehicle, forward of the windshield glass. The virtual image is usually formed at a position 1000 mm or more forward of the windshield glass, closer to the outside world than the windshield glass. This allows the driver to obtain the above-mentioned various pieces of information while looking at the outside world ahead, without having to move their eyes significantly. Therefore, when using a head-up display system, it is expected that drivers will be able to drive more safely while obtaining various pieces of information.

[0003] A head-up display system can be constructed by placing a reflective film on the windshield glass. Various reflective films that can be used in head-up display systems have been proposed.

[0004] Patent Document 1 describes a windshield glass including a projection image display area, in which the projection image display area includes a circularly polarized light reflective layer and a λ / 2 retardation layer, the circularly polarized light reflective layer includes four or more cholesteric liquid crystal layers, one of which has a central wavelength of selective reflection between 350 nm and 490 nm, and the central wavelengths of selective reflection of the four or more cholesteric liquid crystal layers are different from one another. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-081296 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, it is conceivable that a head-up display system can increase the added value of the HUD function by detecting the driver's face or iris. Specifically, an infrared light emitting device irradiates infrared light onto the windshield glass, which reflects the infrared light on a reflective layer of the windshield glass, irradiating the driver's face or eyes with the infrared light. The reflected infrared light is then reflected by the reflective layer and received by an IR (infrared light) sensor, thereby displaying a HUD image to the driver and detecting the driver's face or iris.

[0007] If the driver's face or iris can be detected in this way, it will be possible to add functions such as changing the display location of the HUD image to follow the movement of the driver's eyes or face, issuing an alert or encouraging the driver to take a break if the driver is dozing off or looking away for a long time, and preventing the engine from starting if the face recognition has not been registered, which will help prevent theft.

[0008] Generally, iris recognition uses infrared light with a wavelength of 810 nm. On the other hand, face recognition uses infrared light with wavelengths of 850 nm or 940 nm. No reflective film that can be used for various types of recognition using infrared light of such different wavelengths has been considered.

[0009] An object of the present invention is to provide a reflective film that, when applied to a head-up display, is capable of displaying images and is also compatible with various types of authentication, such as facial authentication and iris authentication, which are performed using various infrared light sources, as well as a windshield glass and a head-up display system that use this reflective film. [Means for solving the problem]

[0010] [1] A visible light selective reflection layer; an infrared light selective reflection layer; the visible light selective reflection layer has at least one reflection peak in the range of 380 nm to 850 nm, and the natural light reflectance at the wavelength of the reflection peak is 5% to 25%; A reflective film, wherein the infrared light selective reflection layer satisfies requirement 1 or requirement 2. Requirement 1: It has two or more reflection peaks in the range of 900 nm to 1200 nm, and the natural light reflectance at the wavelength of each reflection peak is 26% or more. Requirement 2: It has one reflection peak in the range of 900nm to 1200nm, the natural light reflectance at the wavelength of the reflection peak is 26% or more, and the wavelength bandwidth of the region where the reflectance is higher than the average value of the maximum and minimum reflectance values ​​in the range of 900nm to 1200nm is 120nm to 500nm. [2] a visible light selective reflection layer; an infrared light selective reflection layer; the visible light selective reflection layer has at least one reflection peak in the range of 380 nm to 850 nm, and the natural light reflectance at the wavelength of the reflection peak is 5% to 25%; The reflective film according to [1], wherein the infrared light selective reflection layer satisfies requirement 3 or requirement 4. Requirement 3: It has two or more reflection peaks in the range of 900 nm to 1200 nm, and the natural light reflectance at the wavelength of each reflection peak is 26% to 60%. Requirement 4: It has one reflection peak in the range of 900nm to 1200nm, the natural light reflectance at the wavelength of the reflection peak is 26% to 60%, and the wavelength bandwidth of the region where the reflectance is higher than the average value of the maximum and minimum reflectance values ​​in the range of 900nm to 1200nm is 120nm to 500nm. [3] The reflective film according to [1], wherein the infrared light selective reflection layer has one reflection peak in the range of 900 nm to 1200 nm, the natural light reflectance at the wavelength of the reflection peak is 26% or more, and the wavelength bandwidth of the region in which the reflectance is higher than the average value of the maximum and minimum reflectance in the range of 900 nm to 1200 nm is 170 nm to 400 nm. [4] A reflective film according to any one of [1] to [3], wherein the infrared light selective reflection layer has one reflection peak in the range of 900 nm to 1200 nm, the natural light reflectance at the wavelength of the reflection peak is 26% to 60%, and the wavelength bandwidth of the region in which the reflectance is higher than the average value of the maximum and minimum reflectance in the range of 900 nm to 1200 nm is 170 nm to 400 nm. [5] The reflective film according to any one of [1] to [4], which reflects linearly polarized visible light and infrared light. [6] The visible light selective reflection layer and the infrared light selective reflection layer are each made of a cholesteric liquid crystal layer formed by fixing a cholesteric liquid crystal phase; The reflective film according to any one of [1] to [5], which has a retardation layer. [7] The reflective film according to any one of [1] to [5], wherein the visible light selective reflection layer and the infrared light selective reflection layer are a laminate of an optically anisotropic layer and an isotropic layer. [8] The visible light selective reflection layer is (i) having at least one first reflection peak with a central reflection wavelength of 430 nm or more and less than 500 nm; (ii) have at least one second reflection peak with a central reflection wavelength of 530 nm or more and less than 600 nm; (iii) A third reflection peak having a central reflection wavelength of 600 nm or more and 850 nm or less. The reflective film according to any one of [1] to [7], which satisfies at least two of the above. [9] A windshield glass having a heat seal layer and the reflective film according to any one of [1] to [8] between a first glass plate and a second glass plate.

[10] The first glass sheet and the second glass sheet are curved glass sheets; the second glass plate is disposed with its concave surface facing the first glass plate; [9] The windshield glass according to [9], wherein the second glass plate, the heat seal layer, and the reflective film are adjacent to each other in this order.

[11] The windshield glass according to [9] or

[10] , which has an intermediate film between the first glass sheet and the reflective film.

[12] The windshield glass according to any one of [9] to

[11] , wherein the first glass sheet is clear glass and the second glass sheet is green glass.

[13] A windshield glass according to any one of [9] to

[12] , A head-up display system having a projector that irradiates p-polarized projection image light onto a reflective film on a windshield glass. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a reflective film that, when applied to a head-up display, is capable of displaying images and is also compatible with various types of authentication, such as facial authentication and iris authentication, which are performed using various infrared light sources, as well as a windshield glass and a head-up display system that use this reflective film. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram conceptually illustrating an example of a reflective film of the present invention. [Figure 2] FIG. 2 is a diagram conceptually showing another example of the reflective film of the present invention. [Figure 3] FIG. 2 is a diagram conceptually illustrating an example of a visible light selective reflection layer and an infrared light selective reflection layer. [Figure 4] FIG. 1 is a schematic diagram showing an example of a head-up display equipped with a windshield glass having a reflective film of the present invention. [Figure 5] FIG. 1 is a diagram conceptually illustrating an example of a windshield glass having a reflective film of the present invention. [Figure 6] FIG. 6 is a diagram conceptually showing the layer structure of the windshield glass shown in FIG. 5. [Figure 7] FIG. 1 is a diagram conceptually illustrating an example of a windshield glass having a reflective film of the present invention. [Figure 8] FIG. 8 is a diagram conceptually showing the layer structure of the windshield glass shown in FIG. 7. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The reflective film, windshield glass, and head-up display system of the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings. It should be noted that the drawings described below are illustrative for explaining the present invention, and the present invention is not limited to the drawings shown below. In the following, "to" indicating a numerical range includes the numbers written on both sides. For example, if ε1 is a number α1 to a number β1, the range of ε1 includes the numbers α1 and β1, and expressed in mathematical notation as α1≦ε1≦β1. Unless otherwise specified, angles such as "angles expressed by specific numerical values," "parallel," "perpendicular," and "orthogonal" include a generally acceptable error range in the relevant technical field. Furthermore, "same" includes a generally acceptable margin of error in the relevant technical field, and "overall" and the like also include a generally acceptable margin of error in the relevant technical field.

[0014] 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 in the wavelength range of 380 to 780 nm. Invisible light is light with wavelengths below 380 nm or above 780 nm. Furthermore, although not limited to this, among visible light, light in the wavelength region of 420 nm to 490 nm is blue (B) light, light in the wavelength region of 495 nm to less than 570 nm is green (G) light, and light in the wavelength region of 620 nm to 750 nm is red (R) light.

[0015] "Visible light transmittance" refers to the visible light transmittance for an A-light source as defined in JIS (Japanese Industrial Standards) R 3212:2015 (Test Methods for Automotive Safety Glass). That is, the transmittance is calculated by measuring the transmittance at each wavelength in the range of 380 to 780 nm using a spectrophotometer with an A-light source, and multiplying the transmittance at each wavelength by a weighting coefficient obtained from the wavelength distribution and wavelength interval of the CIE (Commission Internationale de l'Eclairage) photopic standard relative luminosity factor, and then calculating the weighted average. When the terms "reflected light" or "transmitted light" are used simply, they are used to mean scattered light and diffracted light.

[0016] P-polarized light is polarized light that vibrates parallel to the plane of incidence. The plane of incidence is perpendicular to the reflecting surface (such as the windshield glass surface) and includes both the incident and reflected light rays. In p-polarized light, the vibration plane of the electric field vector is parallel to the plane of incidence.

[0017] The front retardation is a value measured using an AxoScan manufactured by Axometrics. Unless otherwise specified, the measurement wavelength is 550 nm. The front retardation can also be measured using a KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments) with light of a wavelength within the visible light wavelength range incident in the normal direction to the film. The measurement wavelength can be selected by manually changing the wavelength selection filter, or by converting the measured value using a program or other method.

[0018] "Projection image" means an image that is not a view of the surroundings, such as the front, but is based on the projection of light from the projector used. A projected image is perceived by an observer as a virtual image that appears to appear beyond the reflective film on the windshield glass. "Screen image" means an image displayed on a projector's rendering device or an image rendered by a rendering device onto an intermediate image screen or the like. An image is a real image, as opposed to a virtual image. The images and projected video may be monochrome images, multicolor images with two or more colors, or full-color images.

[0019] [Reflective film] The reflective film of the present invention is a visible light selective reflection layer; an infrared light selective reflection layer; the visible light selective reflection layer has at least one reflection peak in the range of 380 nm to 850 nm, and the natural light reflectance at the wavelength of the reflection peak is 5% to 25%; The reflective film has an infrared light selective reflection layer that satisfies requirement 1 or requirement 2. Requirement 1: It has two or more reflection peaks in the range of 900 nm to 1200 nm, and the natural light reflectance at the wavelength of each reflection peak is 26% or more. Requirement 2: It has one reflection peak in the range of 900nm to 1200nm, the natural light reflectance at the wavelength of the reflection peak is 26% or more, and the wavelength bandwidth of the region where the reflectance is higher than the average value of the maximum and minimum reflectance values ​​in the range of 900nm to 1200nm is 120nm to 500nm.

[0020] Fig. 1 is a conceptual diagram showing an example of the reflective film of the present invention. The reflective film 10a shown in Fig. 1 has a visible light selective reflection layer 12 and an infrared light selective reflection layer 14a laminated in the thickness direction.

[0021] A reflective film 10a having a visible light selective reflection layer 12 and an infrared light selective reflection layer 14a is incorporated into a windshield glass and used in a head-up display system. Specifically, a HUD having the reflective film of the present invention, like a conventional HUD, projects an image onto the windshield glass from a projector, and the image light is reflected by the reflective film of the windshield glass to display it to the driver. At the same time, an infrared light irradiator irradiates the windshield glass with infrared light, which is reflected by the reflective film of the windshield glass to irradiate the driver's face or eyes. The reflected infrared light is then reflected by a reflective layer and received by an IR (infrared light) sensor. This allows a HUD having the reflective film of the present invention to display a HUD image to the driver and detect the driver's face or iris.

[0022] <Visible light selective reflection layer> The visible light selective reflection layer 12 is a reflective layer that selectively reflects light in the wavelength range of 380 nm to 850 nm, i.e., mainly visible light, and transmits light in other wavelength ranges (infrared light), and has at least one reflection peak in the range of 380 nm to 850 nm, with a reflectance of 5% to 25% for natural light (unpolarized light) at the wavelength of the reflection peak. In the example shown in FIG. 1, the visible light selective reflection layer 12 has a configuration in which an R reflection layer 16R that selectively reflects red light, a G reflection layer 16G that selectively reflects green light, and a B reflection layer 16B that selectively reflects blue light are stacked in the thickness direction.

[0023] The R reflective layer 16R is a reflective layer that selectively reflects light in the red wavelength range and transmits light in other wavelength ranges. The R reflective layer 16R has at least one reflection peak in the red wavelength range. The natural light reflectance at the wavelength of the reflection peak of the R reflective layer 16R is 5% to 25%. The G reflective layer 16G is a reflective layer that selectively reflects light in the green wavelength range and transmits light in other wavelength ranges. The G reflective layer 16G has at least one reflection peak in the green wavelength range. The natural light reflectance at the wavelength of the reflection peak of the G reflective layer 16G is 5% to 25%. The B reflective layer 16B is a reflective layer that selectively reflects light in the blue wavelength range and transmits light in other wavelength ranges. The B reflective layer 16B has at least one reflection peak in the blue wavelength range. The natural light reflectance at the wavelength of the reflection peak of the B reflective layer 16B is 5% to 25%.

[0024] The visible light selective reflection layer 12 has the R reflection layer 16R, the G reflection layer 16G, and the B reflection layer 16B, and can be configured to have at least three reflection peaks in the range of 380 nm to 850 nm, with natural light reflectances of 5% to 25%. For example, if the R reflection layer 16R, the G reflection layer 16G, and the B reflection layer 16B each have one reflection peak, the visible light selective reflection layer 12 will have three reflection peaks in the range of 380 nm to 850 nm.

[0025] The reflective film 10a has a visible light selective reflection layer 12 with at least one reflection peak in the range of 380 nm to 850 nm, and when incorporated into a windshield glass and used in an in-vehicle head-up display system (HUD), it can reflect an image projected onto the windshield glass to the driver, etc., allowing the driver, etc. to view a virtual image of the projected image. Furthermore, the visible light selective reflection layer 12 has a natural light reflectance of 25% or less at all reflection peak wavelengths in the range of 380 nm to 850 nm, and therefore can maintain the transmittance required for an in-vehicle head-up display system.

[0026] The visible light selective reflection layer 12 (R reflection layer 16R, G reflection layer 16G, and B reflection layer 16B) that selectively reflects light of a specific wavelength is preferably a cholesteric liquid crystal layer formed by fixing a cholesteric liquid crystal phase, or a laminate (so-called dielectric multilayer film) in which multiple optically anisotropic layers and isotropic layers are alternately stacked. The cholesteric liquid crystal layer and the laminate in which multiple optically anisotropic layers and isotropic layers are alternately stacked will be described in detail later.

[0027] In the example shown in FIG. 1, the visible light selective reflection layer 12 has three reflection layers (R reflection layer 16R, G reflection layer 16G, and B reflection layer 16B) having reflection peaks of different wavelengths, but this is not limited to this, and the visible light selective reflection layer 12 may have one reflection layer, two reflection layers, or four or more reflection layers.

[0028] 1, the visible light selective reflection layer 12 has an R reflection layer 16R that reflects red light, a G reflection layer 16G that reflects green light, and a B reflection layer 16B that reflects blue light, but the configuration is not limited to this. For example, the visible light selective reflection layer 12 may have a reflection layer that selectively reflects visible light in a wavelength range other than red light, green light, and blue light. Alternatively, for example, the visible light selective reflection layer 12 may have two or more R reflection layers with different reflection peak wavelengths.

[0029] In the present invention, the visible light selective reflection layer preferably satisfies at least two of the following conditions (i) to (iii): (i) having at least one first reflection peak having a central reflection wavelength of 430 nm or more and less than 500 nm, (ii) having at least one second reflection peak having a central reflection wavelength of 530 nm or more and less than 600 nm, and (iii) having a third reflection peak having a central reflection wavelength of 600 nm or more and less than 850 nm.

[0030] For example, in the visible light selective reflection layer 12 of the reflective film 10a shown in Figure 1, the B reflective layer 16B satisfies (i), the G reflective layer 16G satisfies (ii), and the R reflective layer 16R satisfies (iii), thereby making it possible to obtain a visible light selective reflection layer that satisfies all of the above requirements (i) to (iii).

[0031] When the visible light selective reflection layer satisfies at least two of the above (i) to (iii), the reflective film can reflect and display a projected two-color image or a color image when used in a HUD.

[0032] In the present invention, a reflection peak is a peak having a maximum value whose difference from the adjacent minimum value is 2% or more and a half-value width of 10 to 200 nm.

[0033] <Infrared light selective reflection layer> The infrared light selective reflection layer is a reflection layer that selectively reflects infrared light and transmits light in other wavelength ranges (visible light), and satisfies the following requirement 1 or requirement 2. Requirement 1: The lens has two or more reflection peaks in the range of 900 nm to 1200 nm, and the natural light reflectance at each reflection peak wavelength is 26% or more. Requirement 2: The lens has one reflection peak in the range of 900nm to 1200nm, the natural light reflectance at the wavelength of the reflection peak is 26% or more, and the wavelength bandwidth of the region where the reflectance is higher than the average value of the maximum and minimum reflectance values ​​in the range of 900nm to 1200nm (hereinafter simply referred to as "wavelength bandwidth") is 120nm to 500nm.

[0034] The infrared light selective reflection layer is composed of at least one reflective layer that selectively reflects light in a predetermined wavelength range and transmits light in other wavelength ranges. The infrared light selective reflection layer is preferably composed of a cholesteric liquid crystal layer formed by fixing a cholesteric liquid crystal phase, or a laminate (so-called dielectric multilayer film) in which optically anisotropic layers and isotropic layers are alternately stacked.

[0035] For example, as in the example shown in FIG. 1, when the infrared light selective reflection layer 14a is made up of one reflection layer, by adjusting the selective reflection wavelength and wavelength bandwidth of the cholesteric liquid crystal layer or dielectric multilayer film that serves as the reflection layer, the infrared light selective reflection layer 14a can have one reflection peak in the range of 900 nm to 1200 nm and satisfy Requirement 2. Furthermore, for example, as in the reflective film 10b shown in FIG. 2, the infrared light selective reflection layer 14b may be configured to have a first reflective layer 18a and a second reflective layer 18b, and the first reflective layer 18a and the second reflective layer 18b may be configured to reflect the same selective reflection wavelength and polarized light that is orthogonal to each other (for example, the first reflective layer 18a may be a right-handed circularly polarized reflective layer, and the second reflective layer 18b may be a left-handed circularly polarized reflective layer). Here, the mutually orthogonal polarized light refers to polarized light located on the back side of the Poincaré sphere, such as the north pole and south pole of the Poincaré sphere. Specifically, the mutually orthogonal polarized light refers to, for example, right-handed and left-handed circularly polarized light in the case of circular polarization, and to linearly polarized light in the case of linear polarization, which are orthogonal to each other.

[0036] Furthermore, for example, as in the reflective film 10b shown in FIG. 2, the infrared light selective reflection layer 14b has a first reflective layer 18a and a second reflective layer 18b, and the selective reflection wavelength of the first reflective layer 18a is different from the selective reflection wavelength of the second reflective layer 18b. This allows the infrared light selective reflection layer 14b to have two or more reflection peaks in the range of 900 nm to 1200 nm and satisfy Requirement 1.

[0037] As mentioned above, it is conceivable that head-up display systems could increase the added value of HUD functions by detecting the driver's face or iris. For example, it is possible to change the display location of the HUD image by following the driver's line of sight or facial movements, to issue an alert or encourage the driver to take a break if the driver is dozing or looking away for a long time, or to prevent theft by preventing the engine from starting if facial recognition is not registered. Generally, iris recognition uses infrared light with a wavelength of 810 nm. On the other hand, face recognition uses infrared light with wavelengths of 850 nm or 940 nm. No reflective film that can be used for various types of recognition using infrared light of such different wavelengths has been considered.

[0038] In contrast, the reflective film of the present invention has an infrared light selective reflection layer that has two or more reflection peaks with a natural light reflectance of 26% or more in the range of 900 nm to 1200 nm, or has one reflection peak with a natural light reflectance of 26% or more and a wavelength bandwidth of 120 nm to 500 nm.The reflective film of the present invention can be suitably used for various authentication methods using infrared light of different wavelengths because the infrared light selective reflection layer has multiple reflection peaks in the infrared wavelength range or a reflection peak with a wide wavelength bandwidth.

[0039] In the HUD, light is irradiated so that it is incident on the main surface of the reflective film at a predetermined angle (for example, an incident angle of 60°). When light is incident on the infrared light selective reflection layer from an oblique direction, the wavelength reflected by the infrared light selective reflection layer is shifted to a shorter wavelength. Therefore, by having an infrared light selective reflection layer with a reflection peak in the range of 900 nm to 1200 nm, it is possible to suitably reflect infrared light with wavelengths of 810 nm, 850 nm, and 940 nm, which are used for various types of authentication.

[0040] From the viewpoint of enabling the infrared light selective reflection layer to suitably reflect infrared light used in various authentication methods, when the infrared light selective reflection layer has one reflection peak in the range of 900 nm to 1200 nm, the wavelength bandwidth is preferably 170 nm to 400 nm, and more preferably 210 nm to 400 nm. The natural light reflectance at the wavelength of the reflection peak is preferably 26% to 100%, more preferably 26% to 90%, even more preferably 26% to 80%, and particularly preferably 26% to 60%.

[0041] It is also preferable that the infrared light selective reflection layer satisfies the following requirement 3 or 4. Requirement 3: The lens has two or more reflection peaks in the range of 900 nm to 1200 nm, and the natural light reflectance at each reflection peak wavelength is 26% to 60%. Requirement 4: The material has one reflection peak in the range of 900nm to 1200nm, the natural light reflectance at the wavelength of the reflection peak is 26% to 60%, and the wavelength bandwidth of the region where the reflectance is higher than the average value of the maximum and minimum reflectance values ​​in the range of 900nm to 1200nm is 120nm to 500nm.

[0042] Here, in FIG. 1, the infrared light selective reflection layer 14a is made up of one reflection layer, and in FIG. 2, the infrared light selective reflection layer 14b is made up of two reflection layers, but this is not limited to this, and the infrared light selective reflection layer may be made up of three or more reflection layers with different selective reflection wavelengths.

[0043] Furthermore, when the infrared light selective reflection layer has one reflection peak in the range of 900 nm to 1200 nm and a wavelength bandwidth of 120 nm to 500 nm, the infrared light selective reflection layer may have one reflection layer with a wide reflection wavelength bandwidth, or may have a configuration in which multiple reflection layers with similar central reflection wavelengths are stacked so that the infrared light selective reflection layer has one reflection peak with a wide bandwidth.

[0044] Next, the configurations of the cholesteric liquid crystal layer and the dielectric multilayer film that form each of the reflective layers of the visible light selective reflection layer and each of the reflective layers of the infrared light selective reflection layer will be described.

[0045] <Cholesteric liquid crystal layer> In the present invention, the term "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. For example, the cholesteric liquid crystal layer is a layer obtained by polymerizing and curing a polymerizable liquid crystal compound by ultraviolet irradiation, heating, or the like after the compound has been oriented in a cholesteric liquid crystal phase. The cholesteric liquid crystal layer is preferably a layer that has no fluidity and has been changed to a state in which the orientation state does not change due to an external field or external force. 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 does not need to exhibit liquid crystallinity any more. For example, a polymerizable liquid crystal compound may be polymerized by a curing reaction and lose its liquid crystallinity.

[0046] Cholesteric liquid crystal phases are known to exhibit selective reflection at specific wavelengths. In a typical cholesteric liquid crystal phase, the central wavelength of selective reflection (selective reflection central wavelength) λ depends on the helical pitch P in the cholesteric liquid crystal phase and follows the relationship λ = n × P with the average refractive index n of the cholesteric liquid crystal phase. Therefore, the selective reflection central wavelength can be adjusted by adjusting this helical pitch. The longer the helical pitch, the longer the selective reflection central wavelength of the cholesteric liquid crystal phase. The helical pitch is one pitch (helical period) of the helical structure of the cholesteric liquid crystal phase, or in other words, one turn of the helix. In other words, the helical pitch is the length of the helical axis direction in which the director (the long axis direction in the case of a rod-shaped liquid crystal compound) of the liquid crystal compound constituting the cholesteric liquid crystal phase rotates 360°.

[0047] The helical pitch of the cholesteric liquid crystal phase depends on the type and concentration of the chiral dopant used together with the liquid crystal compound when forming the cholesteric liquid crystal layer. Therefore, by adjusting these factors, a desired helical pitch can be obtained. That is, when a cholesteric liquid crystal layer is used as the visible light selective reflection layer, the helical pitch of the cholesteric liquid crystal phase can be adjusted by adjusting the type and concentration of the chiral agent so that the selective reflection center wavelength of the cholesteric liquid crystal layer is in the range of 380 nm to 850 nm. Furthermore, when the visible light selective reflection layer has an R reflection layer, a G reflection layer, and a B reflection layer as in the example shown in Figure 1, the type and concentration of the chiral agent used when forming each reflection layer can be adjusted to adjust the helical pitch of the cholesteric liquid crystal phase so that the selective reflection center wavelength of each reflection layer is in the desired range.

[0048] Similarly, when a cholesteric liquid crystal layer is used as the reflective layer of the infrared light selective reflection layer, the helical pitch of the cholesteric liquid crystal phase can be adjusted by adjusting the type of chiral agent and the concentration of the chiral agent added so that the selective reflection center wavelength of the cholesteric liquid crystal layer is in the range of 900 nm to 1200 nm.

[0049] The adjustment of pitch is described in detail in Fujifilm Research Report No. 50 (2005), pp. 60-63. 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).

[0050] Cholesteric liquid crystal phases also exhibit selective reflection for either left- or right-handed circularly polarized light at specific wavelengths. Whether the reflected light is right-handed or left-handed circularly polarized depends on the twist direction (sense) of the helix of the cholesteric liquid crystal phase. When the twist direction of the helix of the cholesteric liquid crystal phase is right-handed, right-handed circularly polarized light is reflected, and when the twist direction of the helix is ​​left-handed, left-handed circularly polarized light is reflected. The direction of rotation of the cholesteric liquid crystal phase can be adjusted by the type of liquid crystal compound forming the cholesteric liquid crystal layer and / or the type of chiral agent added.

[0051] Furthermore, in a cholesteric liquid crystal layer, the half-width Δλ (nm) of the selective reflection band (circularly polarized light reflection band) exhibiting selective reflection depends on the Δn of the cholesteric liquid crystal phase and the helical pitch P, and follows the relationship Δλ = Δn × P. Therefore, the width of the selective reflection band can be controlled by adjusting Δn. Δn can be adjusted by the type and mixing ratio of the liquid crystal compounds forming the cholesteric liquid crystal layer, as well as the temperature at which the alignment is fixed. Therefore, the wavelength bandwidth can be adjusted by adjusting the half-width Δλ of the selective reflection band by adjusting the type and mixing ratio of the liquid crystal compounds, as well as the temperature at which the alignment is fixed.

[0052] Furthermore, when the wavelength bandwidth of the reflective layer is to be widened, the reflective layer may be configured to have two or more cholesteric liquid crystal layers with different selective reflection wavelengths. By configuring the reflective layer to have two or more cholesteric liquid crystal layers with different selective reflection wavelengths stacked together, the reflection band of the reflective layer can be widened.

[0053] (Method for forming a cholesteric liquid crystal layer) The method for forming the cholesteric liquid crystal layer is not particularly limited, and various known methods may be used for the formation. For example, the cholesteric liquid crystal layer can be formed by applying a liquid crystal composition, which is prepared by dissolving a liquid crystal compound, a chiral agent, a polymerization initiator, and, if necessary, a surfactant, etc., in a solvent, onto a support or onto an underlayer formed on the support, drying the liquid crystal composition to obtain a coating film, orienting the liquid crystal compound in the coating film, and irradiating the coating film with actinic rays to harden the liquid crystal composition.

[0054] Furthermore, when the visible light selective reflection layer and / or the infrared light selective reflection layer has a configuration having a plurality of reflection layers, a cholesteric liquid crystal layer that will become each reflection layer may be formed on a support, and then peeled from the support and laminated to form a visible light selective reflection layer and / or an infrared light selective reflection layer having a configuration in which a plurality of cholesteric liquid crystal layers (reflection layers) are stacked. Alternatively, a first cholesteric liquid crystal layer may be formed on a support, and then a subsequent cholesteric liquid crystal layer may be sequentially formed on the formed cholesteric liquid crystal layer to form a visible light selective reflection layer and / or an infrared light selective reflection layer having a configuration in which a plurality of cholesteric liquid crystal layers (reflection layers) are stacked.

[0055] (liquid crystal compound) The liquid crystal compound used to form the cholesteric liquid crystal layer is not limited, and various known rod-shaped and discotic liquid crystal compounds can be used. Polymerizable liquid crystal compounds are also preferred.

[0056] As liquid crystal compounds, see Makromol. Chem., Vol. 190, p. 2255 (1989), Advanced Materials 5, p. 107 (1993), U.S. Patent No. 4,683,327, U.S. Patent No. 5,622,648 and U.S. Patent No. 5,770,107, WO 1995 / 22586, WO 1995 / 24455, WO 1997 / 00600, WO 1998 / 23580, WO 1998 / 52905, WO 2016 / 194327 and WO 2016 / 052367, JP-A-1-272551, JP-A-6-16616, JP-A-7-110469 and JP-A-11-80081, and JP-A-2001-328973 and the like are exemplified. The liquid crystal composition may contain two or more types of liquid crystal compounds.

[0057] Furthermore, the content of the liquid crystal compound in the liquid crystal composition is not particularly limited, but is preferably 80 to 99.9 mass %, more preferably 84 to 99.5 mass %, and even more preferably 87 to 99 mass %, relative to the solid mass of the liquid crystal composition (mass excluding the solvent).

[0058] (Chiral agent) As the chiral agent, various known agents can be used. Chiral agents have the function of inducing a helical structure in the cholesteric liquid crystal phase. The sense of the helix or helical pitch induced varies depending on the chiral agent, so they should be selected according to the purpose. The force with which a chiral agent induces a helical structure in a cholesteric liquid crystal phase is called the helical twisting power (HTP). When the same concentration of chiral agent is used, the greater the HTP of the chiral agent, the smaller the helical pitch.

[0059] Examples of the chiral agent include compounds described in Liquid Crystal Device Handbook (Chapter 3, Section 4-3, Chiral Agents for TN and STN, page 199, edited by the 142nd Committee of the Japan Society for the Promotion of Science, 1989), and in JP-A Nos. 2003-287623, 2002-302487, 2002-80478, 2002-80851, 2010-181852, and 2014-034581. The chiral agent generally contains an asymmetric carbon atom, but an axially asymmetric compound or a planarly asymmetric compound that does not contain an asymmetric carbon atom can also be used as the chiral agent. Examples of the axially asymmetric compound or the planarly asymmetric compound include binaphthyl, helicene, paracyclophane, and derivatives thereof. The chiral agent may have a polymerizable group.

[0060] When both the chiral agent and the liquid crystal compound have a polymerizable group, a polymer having a repeating unit derived from the polymerizable liquid crystal compound and a repeating unit derived from the chiral agent can be formed by a polymerization reaction between the polymerizable chiral agent and the polymerizable liquid crystal compound. In this embodiment, the polymerizable group of the polymerizable chiral agent is preferably the same type as the polymerizable group of the polymerizable liquid crystal compound. The chiral agent may be a liquid crystal compound, or may be a chiral agent that undergoes back isomerization, dimerization, or both isomerization and dimerization upon irradiation with light, thereby changing its HTP.

[0061] The content of the chiral dopant in the liquid crystal composition is preferably 0.01 to 200 mol %, more preferably 1 to 30 mol %, based on the total molar amount of the liquid crystal compound.

[0062] (Other additives) The liquid crystal composition may further contain, as necessary, a polymerization initiator, a crosslinking agent, an alignment control agent, a surfactant, a polymerization inhibitor, an antioxidant, an ultraviolet absorber, a light stabilizer, a colorant, metal oxide fine particles, etc., within a range that does not impair optical performance. The liquid crystal composition may also contain a solvent.

[0063] When the reflective film has a configuration including a cholesteric liquid crystal layer, the reflective film may also include a polarization conversion layer, a support, an adhesive layer, and the like in addition to the cholesteric liquid crystal layer.

[0064] Here, when a cholesteric liquid crystal layer is used as the reflective layer of the visible light selective reflection layer and the infrared light selective reflection layer, the reflective film preferably further has a retardation layer. When the reflective film has a retardation layer and is incorporated into a windshield glass, the retardation layer is disposed on the incident side of the visible light selective reflection layer and the infrared light selective reflection layer, so that incident linearly polarized light is converted into circularly polarized light by the retardation layer, the converted circularly polarized light is reflected by the visible light selective reflection layer and the infrared light selective reflection layer, and the reflected circularly polarized light is converted back into linearly polarized light. In other words, by configuring the reflective film to have a retardation layer, it is possible to make it reflect linearly polarized light. As will be described later, the reflective film incorporated into the windshield glass preferably reflects p-polarized light in order to suppress unnecessary reflection on the surface of the windshield glass. Therefore, when a cholesteric liquid crystal layer is used as the reflective layer of the visible light selective reflection layer and the infrared light selective reflection layer, the reflective film preferably further has a retardation layer and is disposed so that the reflective film reflects p-polarized light.

[0065] <Dielectric multilayer film> In the present invention, the dielectric multilayer film has a structure in which optically anisotropic layers 20 and isotropic layers 22 are alternately laminated, as shown in FIG. Generally, a dielectric multilayer film has a structure in which layers with high refractive index and layers with low refractive index are alternately stacked, and is capable of reflecting or transmitting only light in a specific wavelength range. In contrast, the dielectric multilayer film of the present invention is configured by alternately stacking optically anisotropic layers 20 and isotropic layers 22, and by alternately stacking layers with high refractive index and layers with low refractive index only in one direction, it reflects linearly polarized light in this direction.

[0066] For example, in the dielectric multilayer film, the refractive index ne1 is the refractive index of the isotropic layer, n o2 The refractive index n in the direction perpendicular to the slow axis of the optically anisotropic layer is larger than o1 is the refractive index of the isotropic layer, n o2 The optically anisotropic layers are laminated so that their slow axes are parallel to each other. With this configuration, the refractive index (n e1 ) and a layer with a high refractive index (n o2 ) are stacked in a direction perpendicular to the first direction, while layers with the same refractive index are stacked in a direction perpendicular to the first direction.

[0067] It is known that a film in which layers with low refractive index (low refractive index layers) and layers with high refractive index (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 dielectric multilayer film reflects linearly polarized light in the slow axis direction of the optically anisotropic layer and transmits linearly polarized light perpendicular to this.

[0068] The wavelength and reflectance of a dielectric multilayer film 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 stacked 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 × n), where λ is the wavelength of reflected light and n is the refractive index. Furthermore, since the reflectance increases with the number of stacked low-refractive index layers and high-refractive index layers, the reflectance can be adjusted by adjusting the number of stacked layers. 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.

[0069] Therefore, when a dielectric multilayer film is used as the reflective layer of the visible light selective reflection layer, the refractive index difference between the low refractive index layer and the high refractive index layer, the thickness, the number of stacked layers, etc. may be adjusted so that the selective reflection central wavelength of the dielectric multilayer film is in the range of 380 nm to 850 nm. Furthermore, when the visible light selective reflection layer has an R reflective layer, a G reflective layer, and a B reflective layer as in the example shown in Fig. 1, the refractive index difference between the low refractive index layer and the high refractive index layer of the dielectric multilayer film as each reflective layer, the thickness, the number of stacked layers, etc. may be adjusted so that the selective reflection central wavelength of each reflective layer is in the desired range.

[0070] Similarly, when a dielectric multilayer film is used as the reflective layer of the infrared light selective reflection layer, the refractive index difference between the low refractive index layer and the high refractive index layer, thickness, stacked layers, etc. may be adjusted so that the selective reflection center wavelength of the dielectric multilayer film is in the range of 900 nm to 1200 nm.

[0071] Here, the bandwidth of the reflection peak in the dielectric multilayer film depends on the difference between the refractive index in the slow axis direction of the optically anisotropic layer and the refractive index of the isotropic layer, and the larger the refractive index difference, the larger the bandwidth. Therefore, by adjusting the difference between the refractive index in the slow axis direction of the optically anisotropic layer and the refractive index of the isotropic layer to adjust the bandwidth of the reflection peak in the dielectric multilayer film, the reflection bandwidth of the reflective layer can be adjusted (broadened).

[0072] Materials and methods for producing dielectric multilayer films can be those described, for example, in JP-A-9-506837. Specifically, a wide variety of materials can be used to form dielectric multilayer films 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 coextruded.

[0073] Particularly suitable materials for use as dielectric multilayer films include PEN (polyethylene naphthalate) and PET (polyethylene terephthalate) for optically anisotropic layers, and (isotropically adjusted) PEN, PET, and PMMA (polymethyl methacrylate resin) for isotropic layers.

[0074] As described above, the reflective film of the present invention has a configuration in which a plurality of dielectric multilayer films having different selective reflection wavelengths are laminated. In the present invention, the plurality of dielectric multilayer films are formed by the above-mentioned stretching, extrusion molding, etc., and then the dielectric multilayer films are bonded together to produce the reflective film. Alternatively, the thickness before processing may be adjusted so that a plurality of different dielectric multilayer films are formed, and the plurality of dielectric multilayer films may be integrally formed by stretching, extrusion molding, etc.

[0075] The thickness of the dielectric multilayer film is preferably in the range of 2.0 to 50 μm, and more preferably in the range of 8.0 to 30 μm.

[0076] When the reflective film has a dielectric multilayer film, the reflective film may also include a polarization conversion layer, a support, an adhesive layer, and the like in addition to the dielectric multilayer film.

[0077] (Support) The support can also be used as a substrate when forming a cholesteric liquid crystal layer or a dielectric multilayer film as a reflective layer. The support used to form the reflective layer may be a temporary support that is peeled off after the reflective layer is formed. Therefore, the completed reflective film and windshield glass do not need to include a support. Note that when the completed reflective film or windshield glass includes a support rather than being peeled off as a temporary support, it is preferable that the support be transparent in the visible light region and the infrared light region.

[0078] There are no limitations on the material of the support. Examples of the support include plastic films such as polyesters such as polyethylene terephthalate (PET), polycarbonates, acrylic resins, epoxy resins, polyurethanes, polyamides, polyolefins, cellulose derivatives, and silicones. In addition to the above-mentioned plastic films, glass may also be used as the temporary support.

[0079] The thickness of the support may be about 5.0 to 1000 μm, preferably 10 to 250 μm, and more preferably 15 to 90 μm.

[0080] The support preferably has low birefringence. Low birefringence means that the front retardation is 10 nm or less in the wavelength range in which the reflective film of the windshield glass of the present invention exhibits reflection. This front retardation is preferably 5 nm or less. Furthermore, the support preferably has a small difference in refractive index from the average refractive index (in-plane average refractive index) of the reflective layer.

[0081] A windshield glass having a reflective film of the present invention and a head-up display (HUD) will be described below.

[0082] [Windshield glass] The reflective film of the present invention can be used to provide a windshield glass having a projection image display function.

[0083] The term "windshield glass" refers to the window glass and windshield glass of vehicles such as cars and trains, airplanes, ships, motorcycles, and playground equipment. The windshield glass is preferably used as the windshield or windshield glass located in front of the vehicle in the traveling direction.

[0084] There is no limitation on the visible light transmittance of the windshield glass, but a higher transmittance is preferable. The visible light transmittance of the windshield glass is preferably 70% or more, more preferably more than 70%, even more preferably 75% or more, and particularly preferably 80% or more. The above-mentioned visible light transmittance is preferably satisfied at any position on the windshield glass, and particularly at the position where the reflective film is present. As described above, the reflective film of the present invention has a high visible light transmittance, and therefore can be configured to satisfy the above-mentioned visible light transmittance even when any of the glasses commonly used for windshield glass is used.

[0085] The shape of the windshield glass is not limited and is determined appropriately depending on the object to which the windshield glass is to be placed. The windshield glass may be, for example, flat or may have a three-dimensional shape with a curved surface such as a concave or convex surface. In the windshield glass shaped for the vehicle to be used, the direction that is the top during normal use and the viewing side such as the observer side, the driver side, and the interior side of the vehicle can be specified.

[0086] In the windshield glass, the reflective film may have a uniform thickness or may have a non-uniform thickness. For example, the reflective film may have a wedge-shaped cross section like the vehicle glass described in JP-A-2011-505330, and the thickness of the reflective film may be non-uniform, but it is preferable that the reflective film has a uniform thickness.

[0087] In the windshield glass, the reflective film may be provided in the projected image display area (projected image reflection area) of the windshield glass. A head-up display (hereinafter also referred to as HUD) using windshield glass can be constructed by providing the reflective film of the present invention on the outer surface of the glass plate of a windshield glass, or by providing it between the glass plates of a windshield glass having a laminated glass configuration as described below.

[0088] When the reflective film of the present invention is applied to the outer surface of the glass plate of a windshield glass, the reflective film may be applied either inside (on the incident side of the projected image) or outside the vehicle, but it is preferable that it be applied inside. The reflective film of the present invention has lower scratch resistance than a glass plate. Therefore, when the windshield glass has a laminated glass structure, it is more preferable to provide the reflective film between the two sheets of glass that make up the laminated glass in order to protect the reflective film.

[0089] As described above, the reflective film is a component for displaying a projected image by reflecting the projected image. Therefore, the reflective film may be provided in a position where the projected image projected by a projector or the like can be visibly displayed. That is, the reflective film of the present invention functions as a combiner for a HUD. In a HUD, a combiner refers to an optical component that can visibly display an image projected from a projector and also allows, when the combiner is observed from the incident side of the projected image, to simultaneously observe information on the side opposite to the incident side of the projected light, such as a landscape. That is, the combiner functions as an optical path combiner that superimposes and displays external light and light from the projected image.

[0090] Furthermore, in the present invention, the reflective film is a component that reflects infrared light used for face authentication and / or iris authentication to irradiate the driver's face with the infrared light and also reflects the infrared light reflected from the face or pupils to a sensor. Therefore, the reflective film may be provided in a position where it can reflect infrared light projected from an infrared light irradiating device or the like that irradiates infrared light toward the driver.

[0091] The reflective film may be provided on the entire surface of the windshield glass or on a part of the surface of the windshield glass, but it is preferable that the reflective film be provided on a part of the surface. When a reflective film is provided on a portion of the windshield glass, the reflective film may be provided anywhere on the windshield glass, but it is preferable that the reflective film be provided in a position that is easily visible to an observer such as a driver when the HUD is used. For example, the position of the reflective film on the windshield glass can be determined based on the relationship between the position of the driver's seat in a vehicle equipped with the HUD and the position where the projector is installed. The reflective film may be flat and not curved, or may have a curved surface. The reflective film may also have a concave or convex shape as a whole, so that the projected image is displayed enlarged or reduced.

[0092] <Laminated glass> The windshield glass may have a laminated glass configuration. The windshield glass of the present invention is a laminated glass having the above-described reflective film of the present invention between a first glass plate and a second glass plate. The windshield glass may have a configuration in which a reflective film is disposed between the first glass sheet and the second glass sheet, but it is preferable that the windshield glass has an interlayer film (interlayer film sheet) disposed between at least one of the first glass sheet and the reflective film and the reflective film and the second glass sheet. In the windshield glass, for example, the second glass plate is arranged on the opposite side (exterior side of the vehicle) from the viewing side of the image on the HUD, and the first glass plate is arranged on the viewing side (interior side of the vehicle). Note that in the windshield glass of the present invention, the terms "first" and "second" in the first and second glass plates have no technical meaning and are provided for convenience to distinguish between the two glass plates. Therefore, the second glass plate may be on the interior side of the vehicle, and the first glass plate may be on the exterior side of the vehicle. Glass plates commonly used for windshield glass can be used for the glass plates such as the first glass plate and the second glass plate. For example, glass plates with a visible light transmittance of 82% or less, such as 73% or 76%, such as green glass with high heat insulation properties may be used. Even when glass plates with such low visible light transmittance are used, by using the reflective film of the present invention, a windshield glass having a visible light transmittance of 70% or more even at the position of the reflective film can be produced.

[0093] The thickness of the glass plate is not particularly limited, but is preferably about 0.5 to 5.0 mm, more preferably 1.0 to 3.0 mm, and more preferably 2.0 to 2.3 mm. The first and second glass plates may be made of the same material or may have different thicknesses.

[0094] A windshield glass having a laminated glass structure can be produced by a known method for producing laminated glass. Generally, the laminated glass can be produced by sandwiching an interlayer film for laminated glass between two glass plates, repeatedly subjecting the interlayer film to heat treatment and pressure treatment (e.g., treatment using a rubber roller) several times, and finally subjecting the interlayer film to heat treatment under pressure using an autoclave or the like.

[0095] A windshield glass having a laminated glass configuration including a reflective film and an interlayer film may be produced, for example, by forming a reflective film on the surface of a glass plate and then using the above-described method for producing laminated glass, or may be produced by using the above-described method for producing laminated glass using an interlayer film for laminated glass including the above-described reflective film. When the reflective film is formed on the surface of a glass plate, the glass plate on which the reflective film is provided may be either the first glass plate or the second glass plate. In this case, the reflective film is attached to the glass plate with, for example, an adhesive.

[0096] (interlayer film) The interlayer film (interlayer film sheet) can be any known interlayer film used as an interlayer film (interlayer layer) in laminated glass. For example, a resin film containing a resin selected from the group consisting of polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer, and chlorine-containing resins can be used. The above-mentioned resin is preferably the main component of the interlayer film. Here, the term "main component" refers to a component that accounts for 50% by mass or more of the interlayer film.

[0097] Of the above resins, polyvinyl butyral and ethylene-vinyl acetate copolymer are preferred, and polyvinyl butyral is more preferred. The resin is preferably a synthetic resin. Polyvinyl butyral can be obtained by acetalizing polyvinyl alcohol with butyraldehyde. The lower limit of the degree of acetalization of the polyvinyl butyral is preferably 40%, the upper limit is preferably 85%, the more preferably 60%, and the more preferably 75%.

[0098] Polyvinyl alcohol is usually obtained by saponifying polyvinyl acetate, and polyvinyl alcohol with a saponification degree of 80 to 99.8 mol % is generally used. The preferred lower limit of the degree of polymerization of the polyvinyl alcohol is 200, and the preferred upper limit is 3000. When the degree of polymerization of the polyvinyl alcohol is 200 or more, the penetration resistance of the resulting laminated glass is less likely to decrease, and when it is 3000 or less, the formability of the resin film is good, and the rigidity of the resin film is not too high, resulting in good processability. The more preferred lower limit is 500, and the more preferred upper limit is 2000.

[0099] (Interlayer including reflective film) An interlayer film for laminated glass containing a reflective film can be formed by laminating a reflective film to the surface of the above-mentioned interlayer film. Alternatively, the reflective film can be sandwiched between two of the above-mentioned interlayer films. The two interlayer films may be the same or different, but are preferably the same. Although a known lamination method can be used to bond the reflective film and the interlayer film, it is preferable to use a lamination process, which is preferably carried out under conditions of heat and pressure to a certain extent so that the laminate and the interlayer film do not peel off after processing. To ensure stable lamination, the temperature of the surface of the interlayer to be bonded is preferably 50 to 130°C, more preferably 70 to 100°C. It is preferable to apply pressure during lamination. There are no restrictions on the pressure conditions, but a pressure of 2.0 kg / cm is recommended. 2 Less than 196 kPa is preferable, and 0.5 to 1.8 kg / cm 2 (49 to 176 kPa) is more preferable, and 0.5 to 1.5 kg / cm 2 (49 to 147 kPa) is more preferable.

[0100] In addition, when the reflective film has a support, the support may be peeled off simultaneously with lamination, immediately after lamination, or immediately before lamination. In other words, the reflective film attached to the interlayer film obtained after lamination may not have a support. An example of a method for manufacturing an interlayer including a reflective film is as follows: (1) a first step of laminating a reflective film onto a surface of a first interlayer film to obtain a first laminate; and (2) A second step of laminating a second interlayer film to the surface of the reflective film in the first laminate opposite to the surface to which the first interlayer film is laminated. For example, in a first step, a reflective film and a first interlayer film are bonded together without the support and the first interlayer film facing each other. Next, the support is peeled off from the reflective film. Furthermore, in a second step, a second interlayer film is bonded to the surface from which the support has been peeled off. This makes it possible to produce an interlayer film containing a reflective film without a support. Furthermore, by using this interlayer film containing a reflective film, it is possible to easily produce laminated glass in which the reflective film does not have a support. In order to stably peel off the support without damage, the temperature of the support when peeling it off from the reflective film is preferably 40°C or higher, more preferably 40 to 60°C.

[0101] [HUD (Head-Up Display System)] The windshield glass can be used as a component of the HUD, which preferably includes a projector.

[0102] <Projector> A "projector" is a "device that projects light or an image," and includes a "device that projects a drawn image," emitting projection light that carries the image to be displayed. In the present invention, the projector of the HUD preferably emits projection light that is p-polarized. In a HUD, the projector is simply positioned so that p-polarized projection light carrying the image to be displayed can be incident on the reflective film in the windshield glass at an oblique angle of incidence.

[0103] In the HUD, the projector preferably includes a drawing device, and reflects and displays an image (real image) drawn on a small intermediate image screen as a virtual image by a combiner. Any known projector used in HUDs can be used as the projector as long as it can emit p-polarized projection light. It is preferable that the projector be one in which the imaging distance of the virtual image, i.e., the imaging position of the virtual image, is variable.

[0104] Methods for changing the imaging distance of a virtual image in a projector include, for example, moving the image generation surface (screen) (see JP 2017-21302 A), switching between multiple optical paths with different optical path lengths (see WO 2015 / 190157 A), changing the optical path length by inserting and / or moving a mirror, changing the focal length by using a lens assembly as an imaging lens, moving the imager, switching between multiple projectors with different virtual image imaging distances, and using a variable focus lens (see WO 2010 / 116912 A).

[0105] The projector may be one that can continuously change the imaging distance of the virtual image, or one that can switch the imaging distance of the virtual image at two or more points. Here, it is preferable that at least two of the virtual images projected by the projector have different imaging distances of 1 meter or more. Therefore, if the projector is capable of continuously changing the imaging distance of the virtual images, it is preferable that the imaging distance of the virtual images be changeable by 1 meter or more. Use of such a projector is preferable in that it can be used effectively even when the driver's line of sight distance differs greatly, such as when driving at normal speeds on an ordinary road and when driving at high speeds on an expressway.

[0106] (drawing device) The drawing device may be a device that displays an image itself, or may be a device that emits light that can draw an image. In a drawing device, light from a light source may be adjusted by a drawing method such as a light modulator, a laser intensity modulation means, or a light deflection means for drawing. The drawing device refers to a device that includes a light source and further includes a light modulator, a laser intensity modulation means, or a light deflection means for drawing, etc., depending on the drawing method.

[0107] (light source) There are no limitations on the light source, and known light sources used in projectors, drawing devices, displays, etc., such as LEDs (light-emitting diodes), organic light-emitting diodes (OLEDs), discharge tubes, and laser light sources, can be used. Of these, LEDs and discharge tubes are preferred because they are suitable as light sources for drawing devices that emit linearly polarized light, and LEDs are particularly preferred. This is because LEDs emit light with non-continuous wavelengths in the visible light range, making them suitable for use with combiners that use cholesteric liquid crystal layers that selectively reflect light in specific wavelength ranges, as described below.

[0108] (Drawing method) The drawing method can be selected depending on the light source to be used, and is not particularly limited. Examples of drawing methods include fluorescent display tubes, LCD (Liquid Crystal Display) and LCOS (Liquid Crystal on Silicon) methods that use liquid crystal, DLP (Digital Light Processing) methods, and laser scanning methods. The drawing method may be a method that uses a fluorescent display tube integrated with a light source. The LCD method is preferred as the drawing method.

[0109] In the LCD and LCOS systems, the light of each color is modulated and combined by an optical modulator, and the light is emitted from a projection lens. The DLP system is a display system that uses a DMD (Digital Micromirror Device), in which micromirrors equal in number to the number of pixels are arranged to draw images, and light is emitted from a projection lens.

[0110] The scanning method is a method in which a light beam is scanned on a screen and an afterimage in the eye is used to create an image, and reference can be made to the descriptions in, for example, Japanese Patent Application Laid-Open Nos. 7-270711 and 2013-228674. In the scanning method using a laser, intensity-modulated laser light of each color, for example, red, green, and blue light, is combined into a single light beam by a combining optical system or a condenser lens, and the light beam is scanned by an optical deflection means to form an image on an intermediate image screen, which will be described later. In the scanning method, for example, the brightness modulation of each color of laser light (red, green, and blue) may be performed directly by changing the intensity of the light source, or may be performed using an external modulator. Examples of optical deflection means include a galvanometer mirror, a combination of a galvanometer mirror and a polygon mirror, and MEMS (Micro Electro Mechanical Systems), among which MEMS is preferred. Examples of scanning methods include a random scan method and a raster scan method, with the raster scan method being preferred. In the raster scan method, the laser light can be driven, for example, at a resonant frequency in the horizontal direction and a sawtooth wave in the vertical direction. The scanning method does not require a projection lens, making it easy to miniaturize the device.

[0111] The light emitted from the drawing device may be linearly polarized or natural light (unpolarized). Drawing devices using LCD or LCOS drawing methods and drawing devices using a laser light source essentially emit linearly polarized light. In the case of a drawing device that emits linearly polarized light and that includes light of multiple wavelengths (colors), it is preferable that the polarization directions (transmission axis directions) of the light of the multiple wavelengths are the same. It is known that some commercially available drawing devices emit light with non-uniform polarization directions in the red, green, and blue wavelength regions (see JP 2000-221449 A). Specifically, there is a known example in which the polarization direction of green light is perpendicular to the polarization directions of red light and blue light. As described above, in the HUD of the present invention, the projection light emitted by the projector is p-polarized light.

[0112] (intermediate image screen) As mentioned above, the rendering device may use an intermediate image screen. An "intermediate image screen" is a screen on which an image is rendered. That is, the rendering device forms a visible image on the intermediate image screen using light emitted from the rendering device, even when the light is not yet visible as an image. The image rendered on the intermediate image screen may be projected onto the combiner by light passing through the intermediate image screen, or may be projected onto the combiner by light reflecting off the intermediate image screen.

[0113] Examples of intermediate image screens include a scattering film, a microlens array, a screen for rear projection, etc. When a plastic material is used as the intermediate image screen, if the intermediate image screen has birefringence, the polarization plane and light intensity of the polarized light incident on the intermediate image screen are disturbed, and color unevenness and the like are likely to occur in the combiner (reflection film). However, by using a retardation film with a predetermined phase difference, the problem of color unevenness can be reduced. The intermediate image screen is preferably one that has the function of widening and transmitting incident light rays, because this allows for the magnified display of the projected image. An example of such an intermediate image screen is a screen configured with a microlens array. Microarray lenses used in HUDs are described in, for example, Japanese Patent Application Laid-Open Nos. 2012-226303, 2010-145745, and 2007-523369. The projector may include a reflector or the like that adjusts the optical path of the projected light formed by the drawing device.

[0114] For HUDs using windshield glass as a reflective film, reference can be made to JP-A-2-141720, JP-A-10-96874, JP-A-2003-98470, US Pat. No. 5,013,134, and JP-A-2006-512622.

[0115] The windshield glass is particularly useful for HUDs that are used in combination with projectors that use lasers, LEDs, OLEDs (organic light-emitting diodes), and other light sources whose emission wavelengths are not continuous in the visible light range. This is because the reflection peak wavelength of the visible light selective reflection layer can be adjusted to match each emission wavelength. The glass can also be used for projecting displays that use polarized display light, such as LCDs (liquid crystal displays).

[0116] <Projection light (incident light)> It is preferable that incident light be incident at an oblique angle of 45° to 70° with respect to the normal to the reflective film. The Brewster angle at the interface between glass, which has a refractive index of approximately 1.51, and air, which has a refractive index of 1, is approximately 56°, and by making p-polarized light incident within this angle range, there is little reflection of the incident light for projecting images from the surface of the windshield glass on the viewing side, making it possible to display images with little double images. The angle is preferably 50° to 65°. In this case, the configuration may be such that the projected image can be observed on the side of incidence of the projection light at an angle of 45° to 70°, preferably 50° to 65°, with respect to the normal to the selective reflection layer on the opposite side to the incident light.

[0117] The incident light may be incident from any direction, such as above, below, left, or right, on the windshield glass, and may be determined in accordance with the viewing direction. For example, it is preferable that the incident light is incident from below at an oblique incident angle as described above when in use. The reflective film on the windshield glass only needs to be arranged so as to reflect incident p-polarized light.

[0118] As described above, the projected light when projecting images in the HUD of the present invention is preferably p-polarized light that vibrates in a direction parallel to the plane of incidence. If the light emitted by the projector is not linearly polarized, it may be converted to p-polarized light by providing a linear polarizing film (polarizer) on the projector's output side, or it may be converted to p-polarized light by a known method using a linear polarizing film or the like in the optical path from the projector to the windshield glass. In this case, the component that converts non-linearly polarized projection light to p-polarized light is also considered to constitute the projector in the HUD of the present invention. As described above, for projectors in which the polarization direction of the emitted light is not uniform across the wavelength ranges of red, green, and blue light, it is preferable to wavelength-selectively adjust the polarization direction and allow the light to enter as p-polarized light across the wavelength ranges of all colors.

[0119] As mentioned above, the HUD (projector) may be a projection system that allows the virtual image position to be changed. By changing the virtual image position, the driver can view the virtual image more comfortably and conveniently. The virtual image formation position is a position where the virtual image can be seen by the driver of the vehicle, and is typically a position 1000 mm or more away from the driver, beyond the windshield glass. Here, if the glass is non-uniform (wedge-shaped) in the reflective film as described in the above-mentioned JP2011-505330A, it becomes necessary to change the angle of the wedge when the virtual image formation position is changed. Therefore, for example, as described in JP2017-15902A, it becomes necessary to partially change the angle of the wedge to change the projection position and thereby respond to the change in the virtual image formation position in a pseudo manner. However, in a HUD that uses the windshield glass of the present invention and p-polarized light as described above, the use of wedge-shaped glass is unnecessary, and the thickness of the glass can be made uniform in the reflective film, so it is possible to suitably adopt a projection system that allows the virtual image formation position to be changed as described above.

[0120] Next, the HUD and the windshield glass will be described in more detail with reference to FIGS. FIG. 4 is a schematic diagram showing an example of a head-up display having a reflective film according to an embodiment of the present invention, and FIG. 5 is a schematic diagram showing an example of a windshield glass having a reflective film according to an embodiment of the present invention. The HUD 50 includes a projector 52 and a windshield glass 30, and is used in a vehicle such as a passenger car. The components of the HUD 50 have been described above.

[0121] In the HUD 50, the windshield glass 30 has a first glass plate 32, a heat seal layer 36, a reflective film 10, an interlayer 38, and a second glass plate 34, as conceptually shown in FIG. The reflective film 10 is the reflective film 10 shown in Fig. 1 and has a visible light selective reflection layer and an infrared light selective reflection layer. In the HUD 50, the reflective film 10 is arranged so that the vertical direction of the windshield glass 30 is parallel to the polarization direction of the linearly polarized light reflected by the reflective film 10. In the windshield glass (HUD) of the present invention, the reflective film may have a support. The up-down direction of the windshield glass 30 corresponds to the top-to-bottom direction of the vehicle on which the windshield glass 30 is installed, and is defined as the ground side being the bottom side and the opposite side being the top side. When the windshield glass 30 is installed on a vehicle, it may be installed at an angle due to structural or design considerations. In this case, the up-down direction is the direction along the surface of the windshield glass 30. The surface refers to the outer surface of the vehicle.

[0122] The projector 52 is as described above. Any known projector used in a HUD can be used as the projector 52, as long as it can emit p-polarized projection light carrying the image to be displayed. Preferably, the projector 52 is one in which the imaging distance of the virtual image, i.e., the imaging position of the virtual image, is variable.

[0123] In the HUD 50, the projector 52 irradiates p-polarized light onto the windshield glass 30 (first glass plate 32). By irradiating the windshield glass 30 with p-polarized light, the reflection of the projected light by the first glass plate 32 and the second glass plate 34 of the windshield glass 30 is significantly reduced, thereby preventing problems such as double images from being observed. Preferably, the projector 52 projects p-polarized light onto the windshield at the Brewster angle, which eliminates reflection of the projected light on the first glass plate 32 and the second glass plate 34, allowing for a clearer image to be displayed.

[0124] The windshield glass 30 is a so-called laminated glass, and has a heat seal layer 36, a reflective film 10, and an interlayer 38 between a first glass plate 32 and a second glass plate 34. Projection light emitted by the projector 52 is incident on the surface of the first glass plate 32. The reflective film 10 reflects p-polarized light, and as described above, the direction of the linearly polarized light reflected by the reflective film is set so as to reflect p-polarized light.

[0125] In the example shown in Figure 5, the reflective film 10 is attached to the second glass plate 34 by an intermediate film 38 and to the first glass plate 32 by a heat seal layer 36, and is sandwiched between the first glass plate 32 and the second glass plate 34. In the present invention, the first glass plate 32 and the second glass plate 34 of the windshield glass 30 are preferably disposed essentially parallel to each other.

[0126] The first glass sheet 32 ​​and the second glass sheet 34 are both known glass sheets (glass sheets) used in windshields of vehicles, etc. Therefore, the forming material, thickness, shape, etc. may be the same as those of glass sheets used in known windshields. The first glass sheet 32 ​​and the second glass sheet 34 shown in Figure 5 are both flat, but are not limited to this and may have a partially curved surface or an entirely curved surface.

[0127] The interlayer 38 prevents glass from penetrating into the vehicle interior and shattering in the event of an accident, and also bonds the reflective film 10 to the second glass sheet 34. A known interlayer (interlayer) used in laminated glass windshields can be used for the interlayer 38. Examples of materials for forming the interlayer 38 include polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer, chlorine-containing resin, and polyurethane.

[0128] There is also no limitation on the thickness of the interlayer 38, and the thickness may be set according to the forming material, etc., in the same way as the interlayer of known windshield glass.

[0129] The heat seal layer 36 is a layer made of, for example, a coating-type adhesive. The reflective film 10 is attached to the first glass plate 32 by the heat seal layer 36. In the windshield glass of the present invention, the reflective film 10 may be attached to the first glass plate 32 by an interlayer film instead of the heat seal layer 36. Furthermore, when the reflective film 10 is small compared to the interlayer film 38 that attaches the reflective film 10 to the second glass plate 34, the reflective film 10 may be attached to the first glass plate 32 by the interlayer film 38.

[0130] There are no limitations on the heat seal layer 36, and any known adhesive made of various coating-type adhesives can be used as long as it can ensure the transparency required for the windshield glass 30 and can bond the reflective film 10 to the glass with the required adhesive strength. The heat seal layer 36 may be made of the same material as the intermediate film 38, such as PVB. Alternatively, the heat seal layer 36 may be made of an acrylate adhesive or the like. Furthermore, the heat seal layer 36 may be made of the same material as the adhesive layer described above, as described below.

[0131] The heat seal layer 36 may be formed from an adhesive. Adhesives are classified into hot melt, heat-curing, photo-curing, reactive-curing, and pressure-sensitive adhesives that do not require curing, depending on the curing method. Each type of adhesive can use compounds such as acrylates, urethanes, urethane acrylates, epoxies, epoxy acrylates, polyolefins, modified olefins, polypropylenes, ethylene vinyl alcohols, vinyl chlorides, chloroprene rubbers, cyanoacrylates, polyamides, polyimides, polystyrenes, and polyvinyl butyrals. From the viewpoints of workability and productivity, a photocuring type is preferred as the curing method, and from the viewpoints of optical transparency and heat resistance, it is preferred to use an acrylate-based, urethane acrylate-based, or epoxy acrylate-based material.

[0132] The heat seal layer 36 may be formed using a highly transparent adhesive transfer tape (OCA tape). The highly transparent adhesive transfer tape may be a commercially available product for image display devices, particularly a commercially available product for the surface of the image display unit of an image display device. Examples of commercially available products include adhesive sheets (such as PD-S1) manufactured by Panac Corporation and adhesive sheets from the MHM series manufactured by Nichiei Kako Co., Ltd.

[0133] There is no limitation on the thickness of the heat seal layer 36. Therefore, the thickness may be appropriately set depending on the material from which the heat seal layer 36 is formed, so that a sufficient adhesive strength can be obtained. Here, if the heat seal layer 36 is too thick, it may be impossible to maintain sufficient flatness and attach the reflective film 10 to the first glass plate 32 or the second glass plate 34. In consideration of this point, the thickness of the heat seal layer 36 is preferably 0.1 to 800 μm, and more preferably 0.5 to 400 μm.

[0134] 5, a heat seal layer 36 is provided between the reflective film 10 and the first glass plate 32, and the reflective film 10 and the second glass plate 34 are bonded together with an intermediate film 38, but the present invention is not limited to this. That is, as in the windshield glass 30b shown in FIG. 7, a configuration may be adopted in which a heat seal layer 36 is provided between the reflective film 10 and the second glass plate 34, and an intermediate film 38 is provided between the reflective film 10 and the first glass plate 32. Alternatively, the windshield glass 30 may be configured without an intermediate film 38, and a heat seal layer 36 may be used to bond the reflective film 10 to the first glass plate 32 and to bond the reflective film 10 to the second glass plate 34.

[0135] In the HUD 50, the windshield glass 30 has a reflective film 10 between a first glass plate 32 and a second glass plate 34, and the reflective film 10 is attached to the first glass plate 32 by a heat seal layer 36, and the reflective film 10 is attached to the second glass plate 34 by an intermediate film 38.

[0136] As shown in FIG. 4, in the HUD 50, an observer of the image, i.e., a driver D, sees an image I projected by the projector 52 and reflected by the windshield glass 30. v Observing the virtual image of. In a typical HUD, the image projected by the projector is reflected by the windshield glass, and the driver observes the reflected light. A typical windshield is made of laminated glass, with two panes of glass, one on the inside and one on the outside. Therefore, with a HUD, the driver may observe a double image due to the light reflected by the two panes of glass. To address this issue, in a typical HUD, the cross-sectional shape of the windshield (intermediate film) is wedge-shaped so that the reflections from the inner and outer glass overlap, preventing the appearance of double images. However, as mentioned above, with a wedge-shaped windshield, if the imaging distance of the virtual image is changed to accommodate the difference in the driver's line of sight between normal driving, where the line of sight is close, and high-speed driving, where the line of sight is farther away, the angle of the wedge in the windshield will no longer match, and the image observed by the driver will become a double image.

[0137] In contrast, in the HUD 50 having the reflective film of the present invention, the projector 52 projects p-polarized light, the windshield glass 30 has a reflective film 10 that reflects p-polarized light between the first glass plate 32 and the second glass plate 34, and the driver D observes the light reflected by the reflective film 10. In such a configuration, the reflection of the light projected by the projector 52 is basically dominated by the reflection by the reflective film 10, so that double images are basically unlikely to occur. Therefore, in a HUD 50 that uses the reflective film 10 of the present invention on the windshield glass 30, there is no need to make the cross-sectional shape of the windshield glass 30 (interlayer film 38) wedge-shaped, and therefore, even if the imaging distance of the virtual image is changed, no double images will occur.

[0138] As described above, the reflective film of the present invention is used in a HUD that displays an image and performs face authentication (face detection) using infrared light and / or iris authentication. The HUD 50 that performs face authentication (face detection) and / or iris authentication further includes, in addition to the configuration of the HUD 50 described above, a reflecting film 10 on the windshield glass 30, and a reflecting film 11 on the windshield glass 30. IR and the infrared light reflected by the face or pupil of the driver D. IR2 In the example shown in FIG. 4, the projector 52 receives infrared light I IR It also serves as an infrared light irradiation device that irradiates the

[0139] (Infrared light irradiation device) The infrared light irradiation device can be any suitable light source that irradiates infrared light of a predetermined wavelength. Specifically, the light source can be any known light source such as an LED (light-emitting diode), an organic light-emitting diode (OLED), an infrared laser, a VCSEL (vertical-cavity surface-emitting semiconductor laser), a glow bar, a xenon lamp, or a halogen lamp.

[0140] Furthermore, in the HUD 50, face detection using infrared light specifically identifies whether the face of the driver D is a registered face, detects the position and orientation of the face, and detects facial movement. Therefore, it is preferable for the infrared light emitting device to irradiate an area including the area where the face of the driver D is located with infrared light. That is, it is preferable to irradiate the infrared light in a planar manner. When using an infrared LED as a method for rendering such planar infrared light, a high-output, wide-angle, and planar-irradiating device (with a beam angle of approximately ±45°) may be used for face recognition. For iris recognition, a relatively narrow beam angle (with a beam angle of approximately ±10°) may be used to concentrate irradiation near the eyes. Other methods include, for example, a method using an infrared laser, in which a VCSEL (vertical-cavity surface-emitting semiconductor laser) is used as a light source and a micro-diffraction element converts the light into a dot beam for irradiation.

[0141] Furthermore, the HUD 50 may have an infrared light emitting device as a device separate from the projector that projects the image, or the projector described above may emit infrared light in addition to the projected image.

[0142] (IR sensor) The IR sensor 54 detects the infrared light I irradiated by the infrared light irradiator. IR The reflected light I is reflected by the face of the driver D. IR2 As described above, the IR sensor 54 emits planar infrared light to detect the face of the driver D in the HUD that performs face detection. Therefore, the IR sensor 54 is a two-dimensional sensor that can detect planar infrared light.

[0143] The IR sensor 54 may be a combination of a photoelectric conversion element such as a CCD sensor or a CMOS sensor and an infrared filter that transmits infrared light, or an infrared camera.

[0144] There are no particular limitations on the method of face detection (face authentication) and iris authentication using an infrared irradiator and an IR sensor in a HUD using the reflective film of the present invention, and various known methods can be used, such as those described in International Publication No. 2019 / 026925, JP 2019-005576 A, and JP 2018-045437 A.

[0145] When the windshield glass of the present invention is used in a vehicle, curved glass is often used as the first glass sheet 32 ​​and the second glass sheet 34. In this case, if the first glass sheet 32 ​​is located on the inside of the vehicle and the second glass sheet 34 is located on the outside of the vehicle, the first glass sheet 32 ​​is disposed with its convex side facing the second glass sheet 34, and the second glass sheet 34 is disposed with its concave side facing the first glass sheet 32.

[0146] Furthermore, when the reflective film 10 is bonded to the first glass plate 32 via a heat seal layer 36, as in the windshield glass 30 shown in Fig. 5, the reflective film 10 is preferably arranged so that the infrared light selective reflection layer 14 faces the second glass plate 34, as shown in Fig. 6. In the example shown in Fig. 6, the reflective film 10 has a support 24, a visible light selective reflection layer 12, and an infrared light selective reflection layer 14, and the windshield glass 30 has the first glass plate 32, the heat seal layer 36, the support 24, the visible light selective reflection layer 12, the infrared light selective reflection layer 14, an interlayer 38, and the second glass plate 34 arranged in this order.

[0147] On the other hand, when the reflective film 10 is bonded to the second glass plate 34 via a heat seal layer 36, as in the windshield glass 30b shown in Fig. 7, the reflective film 10 is preferably arranged so that the infrared light selective reflection layer 14 faces the first glass plate 32, as shown in Fig. 8. In the example shown in Fig. 8, the reflective film 10 has a support 24, a visible light selective reflection layer 12, and an infrared light selective reflection layer 14, and the windshield glass 30b has the first glass plate 32, an interlayer 38, the infrared light selective reflection layer 14, the visible light selective reflection layer 12, the support 24, the heat seal layer 36, and the second glass plate 34 arranged in this order.

[0148] From the viewpoint of increasing the brightness of the image displayed on the HUD, it is preferable that the windshield glass has a configuration in which the reflective film 10 is disposed inside the interlayer 38, as shown in Fig. 5. On the other hand, from the viewpoint of impact resistance, it is preferable that the windshield glass has a configuration in which the reflective film 10 is disposed outside the interlayer 38, as shown in Fig. 7.

[0149] In the windshield glass of the present invention, the first glass sheet is preferably clear glass and the second glass sheet is preferably green glass. Clear glass is glass with high infrared light transmittance (infrared light transmittance of about 80% to 92%). On the other hand, green glass is glass with low infrared light transmittance (infrared light transmittance of about 10% to 60%). Using clear glass with high infrared light transmittance as the first glass sheet on the inside of the vehicle allows for suitable infrared-based facial and iris recognition, while using green glass with low infrared light transmittance as the second glass sheet on the outside of the vehicle improves heat insulation.

[0150] Here, in the reflective film of the present invention, when the infrared light selective reflection layer is made of a cholesteric liquid crystal layer, the infrared light selective reflection layer functions as a polarization conversion layer that controls the polarization state of visible light.

[0151] The infrared light selective reflection layer functions as a polarization conversion layer, improving the HUD's suitability for polarized sunglasses and further suppressing double images, particularly when p-polarized light is incident to form a projected image.

[0152] The reason why the function of the polarization conversion layer can improve suitability for polarized sunglasses is that the polarization conversion layer has a helical structure of a cholesteric liquid crystal phase, and exhibits optical rotation and birefringence for visible light, which has a wavelength shorter than the reflection peak wavelength in the infrared range, and can therefore control polarization in the visible range. In particular, the polarization of s-polarized light incident from the outside of the windshield glass is significantly changed by the retardation layer, but the pitch and film thickness of the helical structure in the infrared light selective reflection layer can provide suitable optical compensation as a polarization conversion layer for visible light, improving suitability for polarized sunglasses.

[0153] The reason why the function of the polarization conversion layer can further suppress double images is thought to be that it can suppress double images caused by light of wavelengths that are not in the selective reflection band of the visible light selective reflection layer being polarization converted by the visible light selective reflection layer and reflected by the back surface of the windshield glass.

[0154] Most of the glare that enters a vehicle's windshield from outside, such as reflected light from puddles, the windshield of an oncoming vehicle, or the hood, is s-polarized. For this reason, polarized sunglasses are designed to block the s-polarized light.

[0155] Here, when non-reflected polarized light enters and passes through a reflective layer that selectively reflects specific circularly polarized light, such as a cholesteric liquid crystal layer, the polarization state changes. As mentioned above, the glare component that enters the windshield glass from the outside is s-polarized light. Therefore, s-polarized light that passes through a reflective layer that selectively reflects circularly polarized light corresponding to p-polarized light ideally becomes circularly polarized light with a rotation direction corresponding to s-polarized light. This circularly polarized light is then converted back into s-polarized light by a retardation layer. Therefore, the s-polarized glare component that enters the windshield glass from the outside can be blocked by using polarized sunglasses.

[0156] However, s-polarized light entering the windshield glass from the outside does not only include components that are incident on the windshield glass's reflective film from the normal direction, but also enters the windshield glass at various angles. Therefore, in a HUD that projects p-polarized light using a retardation layer and a reflective layer that reflects circularly polarized light, s-polarized light that enters from the outside and passes through the reflective layer becomes elliptically polarized light rather than circularly polarized light. When such elliptically polarized light passes through the retardation layer, the transmitted light contains not only s-polarized light but also p-polarized light. Polarized sunglasses cannot block p-polarized light, so it passes through them. Therefore, in the case of a HUD that projects p-polarized light, the ability of polarized sunglasses to cut out the glare of the reflected light, which is primarily s-polarized light, is impaired, causing driving problems.

[0157] In contrast, the reflective film of the present invention has an infrared light selective reflection layer that functions as a polarization conversion layer for visible light. As described above, the polarization conversion layer exhibits optical rotation and birefringence for visible light. Furthermore, the reflected light that causes glare from the outside is mainly s-polarized light. Therefore, the s-polarized light incident on the polarization conversion layer is converted into elliptically polarized light with a rotation direction corresponding to the s-polarized light due to the optical rotation and birefringence of the polarization conversion layer. The elliptically polarized light that has passed through the polarization conversion layer then enters the visible light selective reflection layer. Since the rotation direction of the elliptically polarized light converted from s-polarized light is not the component reflected by the visible light selective reflection layer, it passes through the visible light selective reflection layer and is converted into circularly polarized light with a rotation direction corresponding to the s-polarized light. This circularly polarized light then passes through the retardation layer, where it is converted into s-polarized light and passes through the windshield glass. That is, in the reflective film of the present invention, the infrared light selective reflection layer functions as a polarization conversion layer, so that s-polarized light that enters the windshield glass from the outside and causes glare is transmitted as s-polarized light, and can be blocked by polarized sunglasses. Therefore, the suitability for polarized sunglasses can be improved in HUDs that project p-polarized light.

[0158] Furthermore, the projected light may contain s-polarized components that are not p-polarized. These components pass through the visible light selective reflection layer and are reflected by the outer surface (back surface) of the windshield glass, causing double images. In contrast, in the reflective film of the present invention, the infrared light selective reflection layer functions as a polarization conversion layer, so the polarization conversion layer, which has optical rotation and birefringence, converts the s-polarized light component that passes through the visible light selective reflection layer into a p-polarized light component. As mentioned above, p-polarized light has very low reflectance when it is incident on glass at an angle. Therefore, even if s-polarized light components are mixed in the projected light, they are converted into p-polarized light, thereby suppressing the reflection of s-polarized light by the outer surface of the windshield glass. Therefore, the reflective film of the present invention can also reduce double images caused by light that passes through the visible light selective reflection layer and is reflected by the outer surface (back surface) of the windshield glass.

[0159] The present invention is basically configured as described above. Although the reflective film and windshield glass of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various improvements and modifications may be made without departing from the spirit and scope of the present invention.

[0160] For example, the reflective film of the present invention may have other layers in addition to the visible light selective reflection layer and the infrared light selective reflection layer. Specifically, it may have a support, a polarization conversion layer, an alignment film, a retardation layer, etc. The polarization conversion layer is described in International Publication No. 2020 / 080355, etc. In addition, for example, it may have a polarization conversion layer adjacent to the infrared light selective reflection layer, or a retardation layer adjacent via an alignment film. [Example]

[0161] The features of the present invention will be explained in more detail below with reference to examples. The materials, reagents, amounts and proportions of substances, and procedures 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 is not limited to the following examples.

[0162] [Examples 1 to 3, Comparative Example 1] <Preparation of Composition for Forming Cholesteric Liquid Crystal Layer> (Cholesteric liquid crystal layer forming composition B, G1~G3, R1~R4, IR1~IR8) Cholesteric liquid crystal layer-forming compositions B, which form a cholesteric liquid crystal layer having a selective reflection center wavelength of 450 nm; cholesteric liquid crystal layer-forming compositions G1 to G3, which form cholesteric liquid crystal layers having selective reflection center wavelengths of 540 nm, 550 nm, and 590 nm, respectively; cholesteric liquid crystal layer-forming compositions R1 to R4, which form cholesteric liquid crystal layers having selective reflection center wavelengths of 633 nm, 720 nm, 740 nm, and 780 nm, respectively; and cholesteric liquid crystal layer-forming compositions IR1 to IR8, which form cholesteric liquid crystal layers having selective reflection center wavelengths of 835 nm, 850 nm, 1000 nm, 1050 nm, 1100 nm, 1150 nm, 1200 nm, and 1300 nm, respectively. Cholesteric liquid crystal layer-forming compositions having the following compositions were prepared by mixing the following components. ·Mixture 1 100 parts by mass Fluorine-based horizontal alignment agent 1 (alignment control agent 1) 0.05 parts by mass Fluorine-based horizontal alignment agent 2 (alignment control agent 2) 0.02 parts by mass Right-handed chiral agent LC756 (BASF) Adjust to the target reflection wavelength Polymerization initiator IRGACURE OXE01 (BASF) 1.0 parts by mass Solvent (methyl ethyl ketone) - Amount that makes the solute concentration 20% by mass

[0163] [ka]

[0164] [ka]

[0165] [ka]

[0166] Using each composition for forming a cholesteric liquid crystal layer, a single layer of cholesteric liquid crystal layer with a thickness of 3 μm was prepared on a temporary support in the same manner as in the preparation of a visible light selective reflection layer described below, and the reflection properties of visible light and infrared light were confirmed. As a result, it was confirmed that all the prepared cholesteric liquid crystal layers were right-handed circularly polarized light reflective layers, and that the selective reflection central wavelength (central wavelength) was the desired wavelength.

[0167] <Preparation of visible light selective reflection layer> Using the prepared composition for forming a cholesteric liquid crystal layer, a cholesteric liquid crystal layer was formed as follows so that the visible light selective reflection layer of each Example and Comparative Example had the layer structure shown in Table 1, and a visible light selective reflection layer was produced.

[0168] As a temporary support, a polyethylene terephthalate film (Cosmoshine A4100, manufactured by Toyobo Co., Ltd.) having a thickness of 100 μm was prepared. One surface of the temporary 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 reciprocations: 1).

[0169] The composition for forming the first cholesteric liquid crystal layer was applied to the rubbed surface of the temporary support at room temperature using a wire bar so that the thickness of the dried film after drying would be the thickness listed in Table 1, thereby obtaining a coating layer. The coating layer was dried at room temperature for 30 seconds, and then heated in an atmosphere of 85°C for 2 minutes. Thereafter, the coating layer was heated at 60°C in an environment with an oxygen concentration of 1000 ppm or less using a D bulb (90 mW / cm) manufactured by Fusion. 2 The film was irradiated with ultraviolet light from a lamp (such as a 1000 W lamp) at an output of 60% for 6 to 12 seconds to fix the cholesteric liquid crystal phase, thereby obtaining a cholesteric liquid crystal layer. Next, when there were two or more cholesteric liquid crystal layers, the same process was repeated using a composition for forming a cholesteric liquid crystal layer on the surface of the obtained cholesteric liquid crystal layer to sequentially form layers of the composition for forming a cholesteric liquid crystal layer from the second layer onwards.

[0170] <Preparation of infrared selective reflection layer> Next, a cholesteric liquid crystal layer-forming composition IR was applied to the surface of the visible light selective reflection layer so as to have the layer structure shown in Table 2, thereby forming a cholesteric liquid crystal layer that would become an infrared light selective reflection layer. The cholesteric liquid crystal layer was formed in the same manner as in the formation of the cholesteric liquid crystal layer of the visible light selective reflection layer described above. In this way, a reflective film was produced.

[0171] [Examples 4 to 5, Comparative Examples 2 to 5] A retardation layer was formed on a temporary support as described below, and then a cholesteric liquid crystal layer serving as a visible light selective reflection layer and a cholesteric liquid crystal layer serving as an infrared light selective reflection layer were formed in this order on the retardation layer to produce a reflective film. The method for forming the cholesteric liquid crystal layer serving as a visible light selective reflection layer and the cholesteric liquid crystal layer serving as an infrared light selective reflection layer was the same as in Example 1. The layer structures of the examples and comparative examples are as shown in Tables 1 and 2.

[0172] (Coating liquid for forming retardation layer) The following components were mixed to prepare a coating liquid for forming a retardation layer having the following composition. ·Mixture 1 100 parts by mass Fluorine-based horizontal alignment agent 1 (alignment control agent 1) 0.05 parts by mass Fluorine-based horizontal alignment agent 2 (alignment control agent 2) 0.01 parts by mass Polymerization initiator IRGACURE OXE01 (BASF) 1.0 parts by mass Solvent (methyl ethyl ketone) - Amount that makes the solute concentration 20% by mass

[0173] The coating liquid for forming the retardation layer was applied to the rubbed surface of the temporary support using a wire bar, and then dried. Then, the specimen 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 having a desired front retardation, i.e., a thickness adjusted to provide a desired retardation. The retardation of the produced retardation layer was measured by AxoScan and found to be 126 nm (Example 4).

[0174] [Examples 6 to 9, Comparative Example 6] A reflective film was prepared by forming a retardation layer, a visible light selective reflection layer, and an infrared light selective reflection layer in the same manner as described above, except that a TAC (triacetylcellulose) film that had been saponified as described below to form an orientation film was used as a support instead of a temporary support. The layer structures of the examples and comparative examples are as shown in Tables 1 and 2.

[0175] <Saponification of cellulose acylate film> A cellulose acylate film having a thickness of 40 μm was prepared by the same preparation method as in Example 20 of WO 2014 / 112575. The prepared cellulose acylate film was passed through a dielectric heating roll at a temperature of 60° C. to raise the surface temperature of the film to 40° C. Then, 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 left to stand for 10 seconds under a steam-type far-infrared heater (manufactured by Noritake Co., Ltd.) heated to 110°C. Next, using the same bar coater, pure water was applied at 3 mL / m 2 It was applied. Next, the film was 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, thereby preparing a saponified cellulose acylate film. The in-plane retardation of the saponified cellulose acylate film was measured by AxoScan and found to be 1 nm.

[0176] ---------------------------------------------------------------------------------- Composition of alkaline solution ---------------------------------------------------------------------------------- Potassium hydroxide 4.7 parts by mass ·Water 15.7 parts by mass Isopropanol 64.8 parts by mass Surfactant (C16H33O(CH2CH2O)10H) 1.0 parts by mass Propylene glycol 14.9 parts by mass ----------------------------------------------------------------------------------

[0177] <Formation of alignment film> A coating solution for forming an alignment layer having the composition shown below was applied to the saponified surface of a saponified cellulose acylate film (transparent support) at a rate of 24 mL / m using a wire bar coater. 2 The coating was applied and dried with hot air at 100°C for 120 seconds.

[0178] ---------------------------------------------------------------------------------- Composition of coating solution for forming alignment film ---------------------------------------------------------------------------------- 28 parts by weight of the modified polyvinyl alcohol shown below Citric acid 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 ----------------------------------------------------------------------------------

[0179] (denatured polyvinyl alcohol) [ka]

[0180] The alignment layer formed on the cellulose acylate film was rubbed (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.

[0181] [Table 1]

[0182] [Table 2]

[0183] [Examples 10 to 12] <Production of reflective film> Based on the method described in JP-A-9-506837, a reflective film having a visible light selective reflection layer and an infrared light selective reflection layer made of a dielectric multilayer film was prepared as follows.

[0184] (Formation of infrared selective reflection layer)

[0185] 2,6-Polyethylene naphthalate (PEN) and a 70% naphthalate / 30% terephthalate copolyester (coPEN) were synthesized in a standard polyester resin synthesis reactor using ethylene glycol as the diol. Monolayer films of PEN and coPEN were extruded, stretched at approximately 150°C with a 5:1 draw ratio, and heat-treated at approximately 230°C for 30 seconds. The refractive index of the PEN film along the slow axis (orientation axis) was approximately 1.86, the refractive index along the transverse axis was 1.64, and the refractive index of the coPEN film was approximately 1.64.

[0186] Next, PEN and coPEN were co-extruded using a 25-slot feed block equipped with a standard extrusion die to form 32 layers of alternating PEN and coPEN with the thickness shown in (1) of Table 3. The same procedure was repeated to form 32 layers of alternating PEN and coPEN with the thickness shown in (2) of Table 3, producing a laminate of infrared light selective reflection layers consisting of a total of 64 layers.

[0187] [Table 3]

[0188] By adjusting the stretch ratio, the refractive index of the PEN film along the slow axis was found to be approximately 1.71, that along the transverse axis was found to be 1.64, and that of the coPEN film was found to be approximately 1.64. In other words, the difference Δn between the refractive index of the optically anisotropic layer along the slow axis and that of the isotropic layer was found to be 0.07.

[0189] (Formation of visible light selective reflection layer) Next, in Example 10, PEN and coPEN were co-extruded onto the infrared selective reflective layer using a 25-slot feed block equipped with a standard extrusion die to form a visible light selective reflective layer having 16 alternating layers of PEN and coPEN with a thickness shown in (1) of Table 4 below. In addition, in Examples 11 and 12, by repeating the same operation, 16 layers of PEN and coPEN having thicknesses shown in (2) to (6) of Table 4 were alternately formed on the infrared selective reflection layer, thereby forming a visible light selective reflection layer having a total of 96 layers stacked.

[0190] [Table 4]

[0191] The stretched laminate was then heat-treated in an air oven at approximately 230°C for 30 seconds to produce a reflective film consisting of an infrared selective reflection layer and a visible light selective reflection layer. The thickness of the produced reflective film was approximately 20 μm. The reflection spectrum of this reflective film was measured using a spectrophotometer (JASCO Corporation, V-670), and a reflection spectrum with reflectance peaks at reflection bands of 450 nm, 550 nm, 650 nm, 700 nm, 750 nm, 800 nm, and 1100 nm was obtained. The infrared selective reflection layer combined the reflections from the layers formed in the configurations (1) and (2) in Table 3, resulting in a single reflection peak at a wavelength of 1100 nm with a half-width of 220 nm. The reflection spectrum of the visible light selective reflection layer is shown in Table 5, and the reflection spectrum of the infrared light selective reflection layer is shown in Table 6.

[0192] [Table 5]

[0193] [Table 6]

[0194] <Making windshield glass> Windshield glasses having the above-prepared reflective films were prepared as follows.

[0195] As the second glass plate, a glass plate (green glass, visible light transmittance 81%, transmittance at 1100 m 40%) measuring 120 mm in length, 100 mm in width, and 2 mm in thickness was prepared. A 0.76 mm thick PVB film manufactured by Sekisui Chemical Co., Ltd., cut to the same size, was placed on top of this second glass plate as an interlayer. A sheet of reflective film cut to 110 mm long x 90 mm wide was placed on top of the interlayer, with the slow axis aligned vertically. The front and back of the reflective film were oriented to form the layer structure shown in Table 7. A first glass plate measuring 120 mm in length, 100 mm in width, and 2 mm in thickness was placed on the reflective film. In Examples 1 to 7, and 10 and Comparative Examples 1 to 6, the same green glass as the second glass plate was used as the first glass plate, while in Examples 8, 9, 11, and 12, clear glass (FL2, manufactured by Central Glass Co., Ltd., visible light transmittance 90%, transmittance at 1100 nm 84%) was used. This laminate was kept at 90°C and 10 kPa (0.1 atmospheres) for one hour, and then heated in an autoclave (manufactured by Kurihara Seisakusho) at 115°C and 1.3 MPa (13 atmospheres) for 20 minutes to remove air bubbles, yielding a windshield glass.

[0196] In Examples 7, 8, and 11 and Comparative Examples 3 to 5, the first glass plate and the second glass plate were interchanged, that is, the interlayer film was disposed on the first glass plate side. In addition, in Examples 1 to 5 and Comparative Examples 1 to 5, the reflective film was peeled off from the temporary support and placed on the interlayer film. In Example 11 and Comparative Examples 3 to 5, a heat seal layer formed as follows was disposed between the second glass plate and the reflective film. In Example 12, a heat seal layer formed as follows was disposed between the first glass plate and the reflective film. In addition, in Examples 6 to 9, a heat seal layer formed as follows was disposed between the support of the reflective film and the glass plate on the side where no interlayer was disposed.

[0197] <Preparation of heat seal layer> (Coating liquid for forming heat seal layer) The following components were mixed to prepare a coating liquid for forming a heat seal layer. PVB sheet piece (S-LEC film, manufactured by Sekisui Chemical Co., Ltd.) 5.0 parts by mass Methanol 90.25 parts by mass Butanol 4.75 parts by mass

[0198] (Formation of heat seal layer) The coating liquid for forming the heat seal layer was applied to the reflective film or, if a support was provided, to the support using a wire bar, and then dried and heat-treated at 50°C for 1 minute to obtain a heat seal layer having a thickness of 1 μm. The configuration of the windshield glass, the type of glass plate, and the position of the infrared light selective reflection layer of each of the Examples and Comparative Examples are shown in Table 7. Note that the position of the infrared light selective reflection layer in Table 7 indicates on which glass plate side the infrared light selective reflection layer is disposed relative to the visible light selective reflection layer.

[0199] [Table 7]

[0200] [Examples 13 to 20] In Examples 13 to 20, reflective films were prepared in which the infrared light selective reflection layer had a laminated structure of a right-handed cholesteric liquid crystal layer and a left-handed cholesteric liquid crystal layer. <Preparation of Composition for Forming Left-Rotating Cholesteric Liquid Crystal Layer> (Cholesteric liquid crystal layer forming composition IR9) Regarding the cholesteric liquid crystal layer forming composition IR9 which forms a left-handed cholesteric liquid crystal layer having a selective reflection center wavelength of 1200 nm, the following components were mixed to prepare a cholesteric liquid crystal layer forming composition having the following composition. ·Mixture 1 100 parts by mass Fluorine-based horizontal alignment agent 1 (alignment control agent 1) 0.05 parts by mass Fluorine-based horizontal alignment agent 2 (alignment control agent 2) 0.02 parts by mass Levorotatory chiral agent Compound 1 Adjust to the target reflection wavelength Polymerization initiator IRGACURE OXE01 (BASF) 1.0 parts by mass Solvent (methyl ethyl ketone) - Amount that makes the solute concentration 20% by mass

[0201] ·Compound 1 [ka]

[0202] Using each composition for forming a cholesteric liquid crystal layer, a single layer of cholesteric liquid crystal layer with a thickness of 3 μm was prepared on a temporary support in the same manner as in the preparation of a visible light selective reflection layer described below, and the reflection properties of visible light and infrared light were confirmed. As a result, it was confirmed that the prepared cholesteric liquid crystal layer was a left-handed circularly polarized light reflective layer, and that the selective reflection central wavelength (central wavelength) was the desired wavelength.

[0203] (Polarization conversion layer forming coating liquid) The following components were mixed to prepare a coating liquid for forming a polarization conversion layer having the following composition. ·Mixture 1 100 parts by mass Fluorine-based horizontal alignment agent 1 (alignment control agent 1) 0.05 parts by mass Fluorine-based horizontal alignment agent 2 (alignment control agent 2) 0.02 parts by mass Right-handed chiral agent LC756 (BASF) Adjust to the reflection wavelength that matches the target pitch number and film thickness Polymerization initiator IRGACURE OXE01 (BASF) 1.0 parts by mass Solvent (methyl ethyl ketone) - Amount that makes the solute concentration 20% by mass

[0204] The coating solution for forming the polarization conversion layer was prepared by adjusting the formulation amount of the right-handed chiral dopant LC756 in the coating solution for forming the polarization conversion layer described above so that when a cholesteric liquid crystal layer was formed, the desired selective reflection center wavelength λ was obtained. The selective reflection center wavelength λ was determined by measuring a single cholesteric liquid crystal layer with a thickness of 3 μm on a temporary support using FTIR (Spectrum Two, manufactured by PerkinElmer). The film thickness d of the helical structure can be expressed as "pitch P of the helical structure x pitch number." As mentioned above, the pitch P of the helical structure is the length of one pitch in the helical structure, and one pitch is the 360° rotation of the helically oriented liquid crystal compound. Furthermore, in a cholesteric liquid crystal layer, the selective reflection center wavelength λ is equal to "length of one pitch P x average in-plane refractive index n" (λ = P x n). Therefore, the pitch P is equal to "selective reflection center wavelength λ / average in-plane refractive index n" (P = λ / n). For this reason, a coating liquid for forming a polarization conversion layer was prepared so that the selective reflection center wavelength λ of the cholesteric liquid crystal layer would be the desired wavelength. In the formation of the polarization conversion layer described below, this coating liquid for forming a polarization conversion layer was applied to a desired film thickness to form a polarization conversion layer, and the pitch number was determined. Table 8 shows the combinations of the pitch number, film thickness, and selective reflection central wavelength λ (central wavelength λ) of the polarization conversion layer that are the targets of the prepared coating liquid for forming the polarization conversion layer.

[0205] <Preparation of visible light selective reflection layer and infrared light selective reflection layer> The support was a TAC (triacetyl cellulose) film with an alignment film formed thereon, and the same procedure as above was carried out. A retardation layer was formed on the TAC film in the same manner as above, and then a cholesteric liquid crystal layer was formed using the cholesteric liquid crystal layer-forming composition prepared above so that the visible light selective reflection layer and the infrared light selective reflection layer of each example had the layer configuration shown in Tables 9 and 10, thereby producing a visible light selective reflection layer and an infrared light selective reflection layer. In Examples 13 to 16, an infrared light selective reflection layer and a visible light selective reflection layer were formed in this order on the retardation layer, and in Examples 17 to 20, a visible light selective reflection layer and an infrared light selective reflection layer were formed in this order on the retardation layer.

[0206] Next, the coating liquid for forming the polarization conversion layer shown in Table 8 was further applied to the surface of the obtained cholesteric liquid crystal layer to the target film thickness shown in Table 8 to form a polarization conversion layer and produce a reflective film. The polarization conversion layer was formed in the same manner as the above-mentioned cholesteric liquid crystal layer. In this way, a reflective film was produced.

[0207] <Making windshield glass> Windshield glass having each of the reflective films prepared above was prepared in the same manner as described above. The configuration of the windshield glass, the type of glass plate, and the position of the infrared light selective reflection layer in each example are shown in Table 11. The position of the infrared light selective reflection layer in Table 11 indicates which side of the glass plate the infrared light selective reflection layer is disposed on relative to the visible light selective reflection layer.

[0208] [Table 8]

[0209] [Table 9]

[0210] [Table 10]

[0211] [Table 11]

[0212] The reflectance and wavelength bandwidth at each reflection peak in each example and comparative example were measured as follows. The prepared linearly polarized reflective film was attached to the front surface of a glass plate, and a black PET film (light absorber) was attached to the back surface of the glass plate. Using a spectrophotometer (JASCO Corporation, V-670), P-polarized and S-polarized light were incident on the surface of the linearly polarized reflective film at an angle of 5° to the normal direction, and the reflection spectra were measured from 400 nm to 1500 nm. The average value (average reflection spectrum) of the measured P-polarized and S-polarized reflection spectra was calculated.

[0213] The average value of the reflectance when P-polarized light and the reflectance when S-polarized light are incident is synonymous with the reflectance when unpolarized light (natural light) is incident. In other words, the average value of the reflectance spectrum of P-polarized light and the reflectance spectrum of S-polarized light is synonymous with the reflectance spectrum when natural light is incident.

[0214] From the calculated average reflectance spectra of P-polarized light and S-polarized light, The reflection peak (maximum value of the maximum value) in the wavelength band of 780 nm to 1500 nm was extracted as the reflection peak, and its reflectance and wavelength band width were calculated.

[0215] The wavelength bandwidth of the reflection peak is the width of the region where the reflectance is higher than the average value of the maximum and minimum values ​​of the reflectance in the wavelength band of 780 nm to 1500 nm.

[0216] [evaluation] The produced windshield glasses were evaluated as follows.

[0217] <Facial recognition responsiveness> Infrared light (wavelengths 810nm, 850nm, and 940nm, all natural light) was incident from the first glass plate side at a 65° angle to the normal to the glass surface using infrared LEDs of different wavelengths, and was shone onto the face of a person sitting in front of the windshield glass. The infrared light reflected from the person's face and reflected specularly from the first glass surface at a 65° angle to the normal to the glass was detected by an IR sensor attached to the infrared LED, and the information was sent to an image processor for face and iris recognition, which was evaluated according to the following criteria. A: Facial and iris recognition were performed satisfactorily. (Facial recognition: Recognition was possible over a sufficient area. Iris recognition: Recognition was possible regardless of the position of the face.) B: Some parts of the face and iris recognition were insufficient, but this did not pose a problem in practical use. (In the case of face recognition: There were some areas that could not be recognized, but recognition was possible for most of the area. In the case of iris recognition: Iris recognition was not possible in some positions, but this did not pose a problem in practical use.) ·C: Facial recognition and iris recognition were slightly insufficient, but there were no practical problems. (In the case of facial recognition: There were more unrecognizable areas than in B, but it was within the usable range in practice. In the case of iris recognition: There were more positions where iris recognition was impossible than in B, but it was within the usable range in practice.) ·D: Facial recognition and iris recognition were impossible.

[0218] <Reflected color tone> Natural light was incident from directions of 5°, 15°, 30°, 45°, and 60° with respect to the normal direction of the glass from the second glass surface side, and the reflection spectrum was measured with a spectrophotometer (V-670, manufactured by JASCO Corporation). The a* and b* values of the reflected color tone in the D65 light source were calculated from the spectrum and evaluated according to the following criteria.

[0219] Evaluation criteria for reflected color tone Evaluated based on the values of a* and b* that are the largest at angles of 5°, 15°, 30°, 45°, and 60°, ·A: |a*| ≤ 5 and |b*| ≤ 5: Transparent color when viewed from any angle ·B: |a*| ≤ 5 and |b*| ≤ 18 (excluding the range of A): Appears slightly yellow at any angle ·C: Other than those corresponding to A and B: Does not appear to have a transparent color tone

[0220] <p-polarized reflectance> p-polarized light was incident from a direction of 65° with respect to the normal direction of the glass from the first glass plate side, and the specular reflected light (in the incident plane, in the direction opposite to the incident direction with respect to the normal direction, at a direction of 65° with respect to the normal direction) was measured for the reflectance spectrum with a spectrophotometer (V-670, manufactured by JASCO Corporation). At this time, the long side direction of the reflective film was made parallel to the transmission axis of the incident p-polarized light of the spectrophotometer. According to JIS R3106, at wavelengths of every 10 nm from 380 to 780 nm, the projection image reflectance was calculated by multiplying the reflectance by the coefficient corresponding to the visual sensitivity and the emission spectrum of the D65 light source, and evaluated as luminance. The evaluation of luminance was carried out according to the following evaluation criteria.

[0221] Evaluation criteria for p-polarized reflectance A: 25% or more (The HUD's p-polarized reflective system allows images to be seen, making it difficult to see double images.) B: 20% to less than 25% (Images can be seen through the HUD's p-polarized reflective system, but double images are seen.) C: Less than 20% (The HUD's p-polarized reflective system makes it difficult to see images clearly, and double images are often visible.)

[0222] <Suitability for polarized sunglasses> S-polarized light was incident on the glass surface on the second glass plate side at an angle of 65° to the normal direction of the glass, and the transmittance spectrum of the p-polarized light transmitted from the first glass plate side of the windshield glass was measured using a spectrophotometer (V-670, manufactured by JASCO Corporation). At this time, a linear polarizer was placed in the light receiving section of the spectrophotometer so that the vertical direction of the windshield glass was parallel to the transmission axis of the p-polarized light entering the spectrophotometer. According to JIS R3106, the visible light transmittance was calculated by multiplying the coefficient corresponding to luminosity and the emission spectrum of the D65 light source at wavelengths of 380 to 780 nm in 10 nm increments, and the result was evaluated as suitability for polarized sunglasses. The suitability for polarized sunglasses was evaluated according to the following evaluation criteria.

[0223] Evaluation criteria for polarized sunglasses suitability A: Less than 3% B: 3% to less than 5% ·C: 5% or more

[0224] <Impact resistance> A similar windshield glass measuring 300mm x 300mm was fabricated and subjected to a drop ball test based on JIS 3212 R. A steel ball (227 g, 38 mm diameter) was dropped from a height of 9 m onto windshield glass cooled to -20°C, the amount of glass that fell was measured, and the drop was evaluated according to the following criteria. A: The amount of glass dropped is 10g or less B: The amount of glass falling is between 10g and 15g C: The amount of glass dropped is 15g or more The results are shown in Table 12.

[0225] [Table 12]

[0226] As shown in Table 12, it can be seen that the responsiveness of face recognition and iris recognition in the working example is better than that in the comparative example. In Comparative Examples 1, 2, and 5, the peak of the reflected wavelength was outside the range of 900 nm to 1200 nm, and the reflected wavelength bandwidth was narrow, so face recognition and iris recognition using infrared light were not possible. In Comparative Example 3, the reflectance of the infrared light selective reflection layer was less than 26%, so face recognition and iris recognition using infrared light were not possible. In Comparative Example 4, the peak of the reflected wavelength was outside the range of 900 nm to 1200 nm, so face recognition and iris recognition using infrared light were not possible. In Comparative Example 6, the reflection wavelength bandwidth of the peak of the reflected wavelength was narrow, so face recognition and iris recognition using infrared light were not possible.

[0227] Comparing Example 1 and Example 2, it is clear that the half-value width of the reflection peak of the infrared light selective reflection layer is preferably 170 nm or more. A comparison between Example 2 and Example 4 reveals that the presence of a retardation layer improves the p-polarized light reflectance and the suitability for polarized sunglasses. Comparing Example 4 and Example 5, it is clear that the reflected color is improved when the visible light selective reflection layer satisfies two of the above-mentioned (i) to (iii). Comparison of Example 5 with Examples 6 to 9, and comparison of Example 10 with Examples 11 and 12, shows that impact resistance is improved by having a heat seal layer. Furthermore, comparison of Examples 6 to 9, and comparison of Examples 11 and 12, shows that impact resistance is improved by having a heat seal layer on the second glass plate side. A comparison of Examples 6 to 9 and a comparison of Examples 10 to 12 shows that the responsiveness of face authentication is improved by using clear glass for the first glass plate.

[0228] The results of Examples 13 to 20 are shown in Table 13.

[0229] [Table 13]

[0230] As shown in Table 13, it can be seen that Examples 13 to 20, in which the infrared light selective reflection layer is a laminate of a right-handed cholesteric liquid crystal layer and a left-handed cholesteric liquid crystal layer, also have better response times for face recognition and iris recognition than the comparative example. From the above results, the effects of the present invention are clear. [Industrial Applicability]

[0231] The present invention can be suitably used in in-vehicle head-up display systems (HUDs), etc. [Explanation of symbols]

[0232] 10, 10a, 10b Reflective film 12 Visible light selective reflection layer 14a, 14b Infrared light selective reflection layer 16R R reflective layer 16G G reflective layer 16B B reflective layer 18a 1st reflective layer 18b 2nd reflective layer 20 Optically anisotropic layer 22 Isotropic layer 24 Base material 30 Windshield Glass 32 First Glass Pane 34 Second Glass Pane 36 Heat seal layer 38 Interlayer 50 Head-up display system (HUD) 52 Imager D. Driver I IR Infrared light I V visible light

Claims

1. a visible light selective reflection layer; an infrared light selective reflection layer; the visible light selective reflection layer has at least one reflection peak in the range of 380 nm to 850 nm, and the natural light reflectance at the wavelength of the reflection peak is 5% to 25%, A reflective film, wherein the infrared light selective reflection layer satisfies requirement 1. Requirement 1: It has two or more reflection peaks in the range of 900 nm to 1200 nm, and the natural light reflectance at the wavelength of each reflection peak is 26% or more.

2. a visible light selective reflection layer; an infrared light selective reflection layer; the visible light selective reflection layer has at least one reflection peak in the range of 380 nm to 850 nm, and the natural light reflectance at the wavelength of the reflection peak is 5% to 25%, The reflective film according to claim 1 , wherein the infrared light selective reflection layer satisfies requirement 3. Requirement 3: It has two or more reflection peaks in the range of 900 nm to 1200 nm, and the natural light reflectance at the wavelength of each reflection peak is 26% to 60%.

3. a visible light selective reflection layer; an infrared light selective reflection layer; the visible light selective reflection layer has at least one reflection peak in the range of 380 nm to 850 nm, and the natural light reflectance at the wavelength of the reflection peak is 5% to 25%, the visible light selective reflection layer and the infrared light selective reflection layer are laminates of an optically anisotropic layer and an isotropic layer, A reflective film, wherein the infrared light selective reflection layer satisfies requirement 1 or requirement 2. Requirement 1: It has two or more reflection peaks in the range of 900 nm to 1200 nm, and the natural light reflectance at the wavelength of each reflection peak is 26% or more. Requirement 2: It has one reflection peak in the range of 900 nm to 1200 nm, the natural light reflectance at the wavelength of the reflection peak is 26% or more, and the wavelength bandwidth of the region in which the reflectance is higher than the average value of the maximum and minimum reflectance values ​​in the range of 900 nm to 1200 nm is 120 nm to 500 nm.

4. The infrared light selective reflection layer has one reflection peak in the range of 900 nm to 1200 nm, the natural light reflectance at the wavelength of the reflection peak is 26% or more, and the wavelength bandwidth of the region in which the reflectance is higher than the average value of the maximum and minimum reflectance values ​​in the range of 900 nm to 1200 nm is 170 nm to 400 nm. The reflective film according to claim 3.

5. The infrared light selective reflection layer has one reflection peak in the range of 900 nm to 1200 nm, the natural light reflectance at the wavelength of the reflection peak is 26% to 60%, and the wavelength bandwidth of the region where the reflectance is higher than the average value of the maximum and minimum reflectance values ​​in the range of 900 nm to 1200 nm is 170 nm to 400 nm. The reflective film according to any one of claims 3 to 4.

6. The reflective film according to any one of claims 1 to 5, which reflects linearly polarized visible light and infrared light.

7. the visible light selective reflection layer and the infrared light selective reflection layer are each a cholesteric liquid crystal layer formed by fixing a cholesteric liquid crystal phase, The reflective film according to claim 1 , further comprising a retardation layer.

8. 7. The reflective film according to claim 1, wherein the visible light selective reflection layer and the infrared light selective reflection layer are a laminate of an optically anisotropic layer and an isotropic layer.

9. The visible light selective reflection layer is (i) having at least one first reflection peak having a central reflection wavelength of 430 nm or more and less than 500 nm; (ii) has at least one second reflection peak having a central reflection wavelength of 530 nm or more and less than 600 nm; (iii) A third reflection peak having a central reflection wavelength of 600 nm or more and 850 nm or less. The reflective film according to any one of claims 1 to 8, which satisfies at least two of the above.

10. The reflective film according to any one of claims 1 to 9, for performing authentication using infrared light.

11. A windshield glass comprising a first glass plate, a second glass plate, and a heat seal layer and the reflective film according to any one of claims 1 to 10 between the first glass plate and the second glass plate.

12. the first glass plate and the second glass plate are curved glass plates; the second glass plate is disposed with its concave surface facing the first glass plate; The windshield glass according to claim 11, wherein the second glass sheet, the heat seal layer, and the reflective film are adjacent in this order.

13. 13. The windshield glass according to claim 11, further comprising an intermediate film between the first glass sheet and the reflective film.

14. The windshield glass according to any one of claims 11 to 13, wherein the first glass sheet is clear glass and the second glass sheet is green glass.

15. The windshield glass according to any one of claims 11 to 14, a projector that irradiates p-polarized projection light onto the reflective film of the windshield glass.

16. 16. The head-up display system of claim 15, further comprising an infrared light sensor.

17. The head-up display system of claim 16, further comprising an infrared light emitting device.

Images