Reflective films, windshield glass and head-up display systems

Abstract

Provided are a head-up display system, windshield glass, and a reflection film having high visible light transmittance, enabling increase of brightness of a display image, and having good transparency of color tone of appearance. The present invention has a selective reflection layer having a cholesteric liquid crystal layer that is obtained by fixing a cholesteric liquid-crystalline phase. In each of a wavelength range of not less than 400 nm but less than 500 nm and a wavelength range of not less than 500 nm but less than 600 nm, the maximum value of natural light reflectance is 10-25%, a difference between the largest local maximum value and the smallest local minimum value is not less than 3%, and the total value of wavelength bands in a region having a value higher than the average value of the maximum value and the minimum value is 20-80 nm. In a wavelength range of 600-800 nm, the maximum value of natural light reflectance is 10-25%, and the total value of wavelength bands in a region having a value higher than the average value of the maximum value and the minimum value is not less than 120 nm.

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 known a head-up display or a head-up display system that projects an image onto the windshield glass of a vehicle or the like 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 or the like. The position of the virtual image is located outside the vehicle and forward of the windshield glass. The position of the virtual image is usually 1000 mm or more forward of the windshield glass and 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 in front of him / her, without having to move his / her line of sight significantly. Therefore, when using a head-up display system, it is expected that the driver will be able to drive more safely while obtaining various pieces of information.

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

[0004] Patent Document 1 describes a light-reflecting film that includes one or more light-reflecting layers selected from the following light-reflecting layers: light-reflecting layer PRL-1 having a central reflection wavelength of 400 nm or more and less than 500 nm and a reflectance of 5% or more and 25% or less to ordinary light at the central reflection wavelength; light-reflecting layer PRL-2 having a central reflection wavelength of 500 nm or more and less than 600 nm and a reflectance of 5% or more and 25% or less to ordinary light at the central reflection wavelength; and light-reflecting layer PRL-3 having a central reflection wavelength of 600 nm or more and less than 700 nm and a reflectance of 5% or more and 25% or less to ordinary light at the central reflection wavelength. The light-reflecting film includes at least two light-reflecting layers having different central reflection wavelengths that are stacked together, and all of the at least two light-reflecting layers that are stacked reflect polarized light in the same direction.

[0005] The light reflective film described in Patent Document 1 is incorporated into, for example, a windshield glass to form a head-up display system. The windshield glass (combiner) that constitutes the head-up display system is required to have a high visible light transmittance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2016 / 056617 Summary of the Invention [Problem to be solved by the invention]

[0007] Here, in-vehicle head-up display systems are required to have a transmittance that exceeds legal regulations and an external color that is transparent when viewed from various angles from the standpoint of design. In order to maintain the legal transmittance of 70% or more and make the appearance color closer to transparent, it has been considered to lower the reflectance. However, if the reflectance is lowered too much, the brightness of the displayed image (projected image) decreases, resulting in poor visibility.

[0008] An object of the present invention is to provide a reflective film that has high visible light transmittance, can increase the brightness of a displayed image, and has good transparency in appearance color, and a windshield glass and a head-up display system that use this reflective film. [Means for solving the problem]

[0009] [1] A selective reflection layer having a cholesteric liquid crystal layer formed by fixing a cholesteric liquid crystal phase, The selective reflection layer is a reflective film that satisfies all of the following requirements (i) to (iii): (i) In the wavelength range of 400 nm or more and less than 500 nm, the maximum value of natural light reflectance is 10% to 25%, the difference between the maximum and minimum values ​​of natural light reflectance is 3% or more, and the total value of the wavelength bandwidth of the area higher than the average value of the maximum and minimum values ​​of natural light reflectance is 20 nm to 80 nm. (ii) In the wavelength range of 500 nm or more and less than 600 nm, the maximum value of natural light reflectance is 10% to 25%, the difference between the maximum and minimum values ​​of natural light reflectance is 3% or more, and the total value of the wavelength bandwidth of the area higher than the average value of the maximum and minimum values ​​of natural light reflectance is 20 nm to 80 nm. (iii) In the wavelength range of 600 nm or more and 800 nm or less, the maximum value of the natural light reflectance is 10% to 25%, and the total value of the wavelength bandwidth of the region higher than the average value of the maximum and minimum values ​​of the natural light reflectance is 120 nm or more. [2] The selective reflection layer has two or more cholesteric liquid crystal layers with different selective reflection center wavelengths, The reflective film according to [1], wherein the cholesteric liquid crystal layers are in contact with each other. [3] The reflective film according to [1] or [2], wherein the selective reflection layer has a cholesteric liquid crystal layer having two or more selective reflection center wavelengths. [4] The reflective film according to any one of [1] to [3], wherein the selective reflection layer has a total thickness of 0.4 μm to 2.0 μm. [5] The reflective film according to any one of [1] to [4], which reflects linearly polarized light. [6] The reflective film according to any one of [1] to [5], which has a retardation layer, a selective reflection layer, and a polarization conversion layer in this order. [7] The polarization conversion layer is formed by fixing a helical orientation structure of a liquid crystal compound, The reflective film according to [6], wherein the pitch number x of the helical orientation structure in the polarization conversion layer and the film thickness y (μm) of the polarization conversion layer satisfy all of the following formulas (a) to (c): 0.1≦x≦1.0 ··· Formula (a) 0.5≦y≦3.0 ··· Formula (b) 3000≦(1560×y) / x≦50000 ··· Formula (c) [8] A windshield glass comprising a first glass plate, the reflective film according to any one of [1] to [7], and a second glass plate, in this order. [9] The first glass sheet and the second glass sheet are curved glass sheets, The windshield glass according to [8], wherein a reflective film and a second glass plate are provided on a convex side of the first glass plate.

[10] The reflective film has a polarization conversion layer, The windshield glass according to [9], wherein a polarization conversion layer and a selective reflection layer are disposed in this order from the convex surface side of the first glass plate.

[11] The reflective film has a retardation layer, a retardation layer is disposed between the selective reflection layer and the second glass plate; The windshield glass according to [9] or

[10] , wherein the retardation layer has a front retardation of 50 nm to 160 nm at a wavelength of 550 nm, and a slow axis angle of 10° to 50° or -50° to -10° when a direction corresponding to a vertical upward direction of a surface of the first glass plate when the windshield glass is mounted on a vehicle is defined as 0°.

[12] The reflective film has a transparent substrate; The windshield glass according to any one of [9] to

[11] , wherein the transparent substrate is disposed on the second glass plate side.

[13] The windshield glass according to

[12] , wherein the transparent substrate contains an ultraviolet absorbing agent.

[14] The windshield glass according to any one of [8] to

[13] , further comprising an intermediate film between the first glass plate and the reflective film.

[15] The windshield glass according to any one of [8] to

[14] , further comprising a heat seal layer between the reflective film and the second glass plate.

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

[15] , A head-up display system having a projector that irradiates a projected image light onto a first glass plate side of a windshield glass.

[17] The head-up display system of

[16] , wherein the projector emits p-polarized projection image light. Effect of the Invention

[0010] According to the present invention, it is possible to provide a reflective film, a windshield glass, and a head-up display system that have high visible light transmittance, can increase the brightness of a displayed image, and have good transparency of the appearance color. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a schematic diagram showing an example of the reflective film of the present invention. [Diagram 2] 1 is a graph showing the relationship between wavelength and transmittance. [Diagram 3] FIG. 1 is a schematic diagram showing an example of a windshield glass having a reflective film of the present invention. [Figure 4] 1 is a graph showing the relationship between wavelength and transmittance. [Diagram 5] FIG. 1 is a schematic diagram showing an example of a head-up display having a reflective film of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the reflective film, windshield glass, and head-up display system of the present invention will be described in detail 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, the range of values ​​indicated by "~" includes the values ​​written on both sides. For example, ε 1 is the number α 1 ~Number β 1 That is, ε 1 The range of is the number α 1 and the number β 1 This range includes α 1 ≦ε 1 ≦β 1 It is. Unless otherwise specified, angles such as "an angle expressed by a specific numerical value," "parallel," "perpendicular," and "orthogonal" include an error range generally accepted in the relevant technical field. In addition, the term "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.

[0013] Unless otherwise specified, the term "light" refers to visible light and natural light (non-polarized). Visible light is electromagnetic light with wavelengths visible to the human eye, and generally refers to light in the wavelength range of 380 to 780 nm. Invisible light is light in the wavelength range of less than 380 nm or more than 780 nm. Also, although not limited to this, among visible light, light in the wavelength region of 420 to 490 nm is blue (B) light, light in the wavelength region of 495 to 570 nm is green (G) light, and light in the wavelength region of 620 to 750 nm is red (R) light.

[0014] "Visible light transmittance" refers to the A-light source visible light transmittance defined in JIS (Japanese Industrial Standards) R 3212:2015 (Testing method for automotive safety glass). In other words, it is the transmittance calculated by measuring the transmittance at each wavelength in the range of 380 to 780 nm with a spectrophotometer using 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 Illumination) standard relative luminous efficiency for light adaptation to calculate a weighted average. When the terms "reflected light" or "transmitted light" are used simply, they are used to include scattered light and diffracted light.

[0015] P-polarized light is polarized light that vibrates in a direction parallel to the plane of incidence of the light. The plane of incidence is perpendicular to the reflecting surface (such as the windshield glass surface) and includes 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.

[0016] 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, etc.

[0017] "Projection image" means an image that is not the surrounding scenery such as the front or the like, but is based on the projection of light from the projector used. A projection image is observed by an observer as a virtual image that appears beyond the reflective film of 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. In contrast to a virtual image, an image is a real image. The images and projected pictures may be monochrome images, multi-color images with two or more colors, or full-color images.

[0018] [Reflective film] The reflective film of the present invention is a selective reflection layer having a cholesteric liquid crystal layer formed by fixing a cholesteric liquid crystal phase; The selective reflection layer is a reflection film that satisfies all of the following requirements (i) to (iii). (i) In the wavelength range of 400 nm or more and less than 500 nm, the maximum value of natural light reflectance is 10% to 25%, the difference between the maximum and minimum values ​​of natural light reflectance is 3% or more, and the total value of the wavelength bandwidth of the area higher than the average value of the maximum and minimum values ​​of natural light reflectance is 20 nm to 80 nm. (ii) In the wavelength range of 500 nm or more and less than 600 nm, the maximum value of natural light reflectance is 10% to 25%, the difference between the maximum and minimum values ​​of natural light reflectance is 3% or more, and the total value of the wavelength bandwidth of the area higher than the average value of the maximum and minimum values ​​of natural light reflectance is 20 nm to 80 nm. (iii) In the wavelength range of 600 nm or more and 800 nm or less, the maximum value of the natural light reflectance is 10% to 25%, and the total value of the wavelength bandwidth of the region higher than the average value of the maximum and minimum values ​​of the natural light reflectance is 120 nm or more.

[0019] Fig. 1 is a schematic diagram showing an example of the reflective film of the present invention. The reflective film 10 shown in Fig. 1 has a polarization conversion layer 14, a selective reflection layer 11, a retardation layer 16, and a transparent substrate 18 in this order.

[0020] The selective reflection layer 11 has three cholesteric liquid crystal layers (12R, 12G, 12B). The three cholesteric liquid crystal layers have different selective reflection center wavelengths. In the illustrated example, the selective reflection layer 11 has, in this order, a cholesteric liquid crystal layer 12R having a selective reflection center wavelength in the red wavelength region, a cholesteric liquid crystal layer 12G having a selective reflection center wavelength in the green wavelength region, and a cholesteric liquid crystal layer 12B having a selective reflection center wavelength in the blue wavelength region. In the illustrated example, each cholesteric liquid crystal layer is in direct contact with any of the other cholesteric liquid crystal layers.

[0021] As is well known, a cholesteric liquid crystal layer is a layer in which liquid crystal compounds are fixed in a helical orientation state of a cholesteric liquid crystal phase, and reflects light with a selective reflection center wavelength according to the pitch of the helical structure and transmits light in other wavelength ranges. In addition, the cholesteric liquid crystal layer exhibits selective reflectivity for either left-handed or right-handed circularly polarized light at a specific wavelength.

[0022] In the present invention, the selective reflection layer satisfies all of the following requirements (i) to (iii). (i) In the wavelength range of 400 nm or more and less than 500 nm, the maximum value of natural light reflectance is 10% to 25%, the difference between the maximum and minimum values ​​of natural light reflectance is 3% or more, and the total value of the wavelength bandwidth of the area higher than the average value of the maximum and minimum values ​​of natural light reflectance is 20 nm to 80 nm. (ii) In the wavelength range of 500 nm or more and less than 600 nm, the maximum value of natural light reflectance is 10% to 25%, the difference between the maximum and minimum values ​​of natural light reflectance is 3% or more, and the total value of the wavelength bandwidth of the area higher than the average value of the maximum and minimum values ​​of natural light reflectance is 20 nm to 80 nm. (iii) In the wavelength range of 600 nm or more and 800 nm or less, the maximum value of the natural light reflectance is 10% to 25%, and the total value of the wavelength bandwidth of the region higher than the average value of the maximum and minimum values ​​of the natural light reflectance is 120 nm or more.

[0023] In a selective reflection layer having a cholesteric liquid crystal layer, the reflected wavelength and reflectance can be adjusted by the selective reflection central wavelength, thickness (helical pitch number) of the cholesteric liquid crystal layer, etc. In the example shown in Fig. 1, reflection that satisfies requirement (i) is realized by cholesteric liquid crystal layer 12B that mainly reflects light in the blue wavelength region, reflection that satisfies requirement (ii) is realized by cholesteric liquid crystal layer 12G that reflects light in the green wavelength region, and reflection that satisfies requirement (iii) is realized by cholesteric liquid crystal layer 12R that reflects light in the red wavelength region.

[0024] An example of a natural light reflection spectrum satisfying the above requirements (i) to (iii) is shown in Fig. 2. The graph shown in Fig. 2 is an example of a natural light reflection spectrum in the reflective film of Example 1 which will be described later.

[0025] In the spectrum shown in the graph of FIG. 2, in the wavelength range of 400 nm or more and less than 500 nm, the natural light reflectance reaches a maximum value (maximum value) near a wavelength of 480 nm, and the value is about 14.5%, which is in the range of 10% to 25%. In addition, in the wavelength range of 400 nm or more and less than 500 nm, the natural light reflectance reaches a minimum value near a wavelength of 440 nm, and the value is about 9.5%. Therefore, the difference between the maximum and minimum values ​​of the natural light reflectance is about 5%, which is 3% or more. In addition, in the wavelength range of 400 nm or more and less than 500 nm, the natural light reflectance reaches a minimum value near a wavelength of 440 nm, and the value is about 9.5%. Therefore, the average value of the maximum and minimum values ​​of the natural light reflectance is 12%. The wavelength band widths in the region where the natural light reflectance is higher than 12% are approximately 415 nm to 430 nm and 445 nm to 490 nm, and the total wavelength band width is about 60 nm, which is in the range of 20 nm to 80 nm. Therefore, the spectrum shown in the graph of FIG. 2 satisfies requirement (i).

[0026] In the spectrum shown in the graph of FIG. 2, in the wavelength range of 500 nm or more and less than 600 nm, the natural light reflectance reaches a maximum value (maximum value) near the wavelength of 555 nm, and the value is about 15.5%, which is in the range of 10% to 25%. In addition, in the wavelength range of 500 nm or more and less than 600 nm, the natural light reflectance reaches a minimum value near the wavelength of 505 nm, and the value is about 9%. Therefore, the difference between the maximum value and the minimum value of the natural light reflectance is about 6.5%, which is 3% or more. In addition, in the wavelength range of 500 nm or more and less than 600 nm, the natural light reflectance reaches a minimum value near the wavelength of 505 nm, and the value is about 9%. Therefore, the average value of the maximum value and the minimum value of the natural light reflectance is 12.3%. The wavelength bandwidth of the region where the natural light reflectance is higher than this 12.3% is approximately 520 nm to 575 nm, and the total value of the wavelength bandwidth is about 55 nm, which is in the range of 20 nm to 80 nm. Therefore, the spectrum shown in the graph of FIG. 2 satisfies requirement (ii).

[0027] In the spectrum shown in the graph of FIG. 2, in the wavelength range of 600 nm or more and 800 nm or less, the natural light reflectance reaches a maximum value (maximum value) near a wavelength of 750 nm, and the value is about 18.3%, which is in the range of 10% to 25%. In addition, in the wavelength range of 600 nm or more and 800 nm or less, the natural light reflectance reaches a minimum value near a wavelength of 600 nm, and the value is about 11.3%. Therefore, the average value of the maximum and minimum values ​​of the natural light reflectance is 14.8%. The wavelength bandwidth of the region where the natural light reflectance is higher than this 14.8% is approximately 650 nm to 780 nm, and the total value of the wavelength bandwidth is about 130 nm, which is 120 nm or more. Therefore, the spectrum shown in the graph of FIG. 2 satisfies requirement (iii).

[0028] As mentioned above, in-vehicle head-up display systems are required to have a transmittance that exceeds legal regulations and an exterior color that is transparent when viewed from various angles from the viewpoint of design. In order to maintain the legal transmittance of 70% or more and to make the exterior color closer to transparent (white), it has been thought that the reflectance should be lowered. However, if the reflectance is lowered too much, the brightness of the displayed image (projected image) decreases, resulting in poor visibility.

[0029] In contrast, the reflective film of the present invention can improve the transparency of the color by making the maximum value of the natural light reflectance at wavelengths of 500 nm or more and less than 600 nm in the range of 10% to 25%. In order to ensure the legal front transmittance of 70%, the reflectance at around 550 nm of luminosity is important. Therefore, the transmittance can be ensured by making the maximum value of the natural light reflectance at wavelengths of 500 nm or more and less than 600 nm 25% or less. Next, in order to increase the brightness, the reflectance at around 550 nm in an oblique direction (incident angle 60°) needs to be high. The reflective film of the present invention can improve the front brightness of the displayed image and improve the transparency of the color when viewed from an oblique direction (incident angle 60°) by satisfying that the maximum value of the natural light reflectance at wavelengths of 600 nm or more and 800 nm or less is 10% to 25% and the width of the reflection band is 120 nm or more. In addition, the reflection color at the front becomes yellow to red only when the reflection at wavelengths of 500 nm or more and less than 600 nm is the reflection at wavelengths of 500 nm or more and less than 600 nm is the reflection at wavelengths of 500 nm or more and less than 600 nm. Therefore, the reflective film of the present invention can improve the transparency of the color when viewed from the front (incident angle 5°) by making the maximum value of the natural light reflectance 10% to 25% in the wavelength range of 400 nm or more and less than 500 nm. Furthermore, by making the difference between the maximum and minimum values ​​of the natural light reflectance 3% or more in each of the wavelength ranges of 400 nm or more and less than 500 nm and the wavelength range of 500 nm or more and less than 600 nm, and making the total value of the wavelength bandwidth of the region higher than the average value of the maximum and minimum values ​​of the natural light reflectance 20 nm to 80 nm, that is, the narrow band, a wavelength range with low reflectance is formed in each of the wavelength ranges of 400 nm or more and less than 500 nm and the wavelength range of 500 nm or more and less than 600 nm, and therefore the transmittance is improved.

[0030] These effects enable the natural light transmittance of a windshield glass with a reflective film sandwiched between green glass to be 70% or more (80% or more when clear glass is sandwiched). In addition, the reflectance of the light wavelength of the displayed image can be 25% or more, improving the brightness of the displayed image. In addition, the transparency of the color when viewed from various directions can be improved.

[0031] From the viewpoint of increasing the transmittance while improving the reflected color, the maximum natural light reflectance in the range of 400 nm or more and less than 500 nm is preferably 11% to 20%, and more preferably 12% to 20%. Similarly, from the viewpoint of increasing the transmittance while improving the reflected color, the maximum natural light reflectance in the range of 500 nm or more and less than 600 nm is preferably 11% to 20%, and more preferably 12% to 20%. From the viewpoint of improving the reflected color and increasing the brightness of a displayed image, the maximum natural light reflectance in the range of 600 nm to 800 nm is preferably 15% to 23%, and more preferably 16% to 23%.

[0032] From the viewpoint of improving the reflected color while increasing the transmittance, the difference between the maximum and minimum natural light reflectance values ​​at 400 nm or more and less than 500 nm is preferably 4% or more and 20% or less, and more preferably 4% or more and 12% or less. Similarly, from the viewpoint of improving the reflected color while increasing the transmittance, the difference between the maximum and minimum natural light reflectance values ​​at 500 nm or more and less than 600 nm is preferably 4% or more and 20% or less, and more preferably 4% or more and 12% or less.

[0033] From the viewpoint of improving the reflected color while increasing the transmittance, the wavelength bandwidth of the region in which the reflectance is higher than the average value of the maximum and minimum reflectance values ​​from 400 nm or more to less than 500 nm is preferably 30 nm or more and 78 nm or less, and more preferably 35 nm or more and 75 nm or less. Similarly, from the viewpoint of improving the reflected color while increasing the transmittance, the wavelength bandwidth of the region in which the reflectance is higher than the average value of the maximum and minimum reflectance values ​​from 500 nm or more to less than 600 nm is preferably 30 nm or more and 78 nm or less, and more preferably 35 nm or more and 75 nm or less. The narrower the wavelength band width from 400 nm to less than 500 nm and from 500 nm to less than 600 nm, the more advantageous it is for the transmittance, but since the wavelength band width from 600 nm to less than 800 nm is wide, if the wavelength band width from 400 nm to less than 500 nm and / or the wavelength band width from 500 nm to less than 600 nm is too narrow, the reflected color may deteriorate. From this point of view, it is preferable that the wavelength band width from 400 nm to less than 500 nm and the wavelength band width from 500 nm to less than 600 nm are within the above ranges. Furthermore, the wavelength band width between 500 nm and less than 600 nm has a greater effect on the transmittance.

[0034] From the viewpoint of improving the reflected color while improving the front brightness of the displayed image, it is preferable that 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 from 600 nm to 800 nm is 120 nm to 200 nm.

[0035] Here, as shown in Fig. 1, the selective reflection layer preferably has two or more cholesteric liquid crystal layers with different selective reflection central wavelengths. Also, each cholesteric liquid crystal layer is preferably in direct contact with any other cholesteric liquid crystal layer. For example, in the example shown in Fig. 1, a cholesteric liquid crystal layer 12R having a selective reflection central wavelength in the red wavelength region and a cholesteric liquid crystal layer 12G having a selective reflection central wavelength in the green wavelength region are in contact with each other, and a cholesteric liquid crystal layer 12G having a selective reflection central wavelength in the green wavelength region and a cholesteric liquid crystal layer 12B having a selective reflection central wavelength in the blue wavelength region are in contact with each other.

[0036] If the cholesteric liquid crystal layers are spaced apart, the thickness between the layers becomes thicker, making it difficult to obtain the effect of interference of light reflected by each cholesteric liquid crystal layer. In contrast, if the cholesteric liquid crystal layers are in contact with each other, the wavelength band width can be narrowed by the effect of interference of light reflected by each cholesteric liquid crystal layer. In particular, if the thickness of each cholesteric liquid crystal layer is thinner than the wavelength of light (visible light 380 nm to 780 nm), the effect of interference becomes more prominent.

[0037] In the present invention, when the selective reflection layer 11 has two or more cholesteric liquid crystal layers, the cholesteric liquid crystal layers are not limited to being in direct contact with each other, and may be laminated via an adhesive layer or the like.

[0038] Here, each cholesteric liquid crystal layer may have at least one selective reflection central wavelength, but at least one of the cholesteric liquid crystal layers may have two or more selective reflection central wavelengths. A cholesteric liquid crystal layer having two or more selective reflection central wavelengths is achieved by a helical structure in which the helical pitch changes in the thickness direction.

[0039] In the illustrated example, the selective reflection layer 11 has three cholesteric liquid crystal layers having different selective reflection center wavelengths, but this is not limited to this, and the selective reflection layer 11 may have one cholesteric liquid crystal layer, or two or four or more cholesteric liquid crystal layers.

[0040] The selective reflection layer 11 has a total thickness of preferably 0.4 μm to 2.0 μm, more preferably 0.6 μm to 1.8 μm, and even more preferably 0.8 μm to 1.4 μm. If the total thickness of the selective reflection layer 11 is too thin, the natural light reflectance of the selective reflection layer 11 may be too low, making it difficult to increase the brightness of the displayed image. On the other hand, if the total thickness of the selective reflection layer 11 is too thick, the transmittance may be reduced.

[0041] Here, the reflective film of the present invention preferably reflects linearly polarized light. When the reflective film is incorporated into a windshield glass to be used as a combiner for a head-up display, it is preferable that the projected image light is p-polarized light, i.e., linearly polarized light, in order to suppress reflection on the surface of the windshield glass. On the other hand, in the present invention, the selective reflection layer has a cholesteric liquid crystal layer and reflects circularly polarized light. Therefore, the reflective film of the present invention preferably has a layer that converts linearly polarized light incident on the reflective film into circularly polarized light. Examples of layers that convert the polarization state of light include a polarization conversion layer and a retardation layer.

[0042] The polarization conversion layer exhibits optical rotation and birefringence for visible light, and converts the polarization state of the incident light. In the present invention, the polarization conversion layer is made of a layer in which a birefringent material such as a liquid crystal compound is oriented with a twist of 360° or less. The retardation layer changes the state of the incident polarized light by applying a phase difference (optical path difference) to two orthogonal polarized light components. In the present invention, the retardation layer is a layer in which a material having birefringence, such as a liquid crystal compound, is arranged in the same direction, and does not have optical rotation.

[0043] By configuring the reflective film to have a polarization conversion layer or a phase difference layer on the side of the selective reflection layer where light is incident, linearly polarized light incident on the reflective film can be converted into circularly polarized light, the selective reflection layer can reflect the circularly polarized light, and the polarization conversion layer or phase difference layer can convert the reflected circularly polarized light into linearly polarized light before it exits.

[0044] 1, the reflective film 10 has a polarization conversion layer 14 on one surface side of the selective reflection layer 11, and a retardation layer 16 on the other surface side. When such a reflective film 10 is incorporated into a windshield glass, it is arranged so that the polarization conversion layer 14 faces the first glass plate 28 on the vehicle interior side, and the retardation layer 16 faces the second glass plate 30 on the vehicle exterior side, as shown in FIG. 3 described later.

[0045] In this case, the polarization conversion layer 14 has the function of converting the projected p-polarized light (linearly polarized light) into circularly polarized light that is reflected by the cholesteric liquid crystal layer of the selective reflection layer 11 . On the other hand, the retardation layer 16 has a function of optically compensating for light incident from outside the windshield glass. For example, the polarization state of s-polarized light incident from outside the windshield glass changes when passing through the polarization conversion layer 14, and p-polarized components are mixed in. Since polarized sunglasses cut s-polarized light, this p-polarized component passes through the polarized sunglasses. This impairs the function of polarized sunglasses to cut glare from reflected light, which is mainly composed of s-polarized light, and causes a problem of impeding driving. In response to this, a configuration having the retardation layer 16 and optical compensation with the retardation layer 16 can improve suitability for polarized sunglasses.

[0046] 3, the reflective film 10 is configured so that the polarization conversion layer 14 is on the first glass plate 28 side facing the vehicle interior side and the retardation layer 16 is on the second glass plate 30 side facing the vehicle exterior side, but the present invention is not limited to this. The reflective film 10 may be configured so that the polarization conversion layer 14 is on the second glass plate 30 side facing the vehicle exterior side and the retardation layer 16 is on the first glass plate 28 side facing the vehicle interior side.

[0047] In this case, the retardation layer 16 has a function of converting the p-polarized light (linearly polarized light) projected into circularly polarized light that is reflected by the cholesteric liquid crystal layer of the selective reflection layer 11 . On the other hand, the polarization conversion layer 14 has a function of optically compensating for light incident from the outside of the windshield glass, and optical compensation by the polarization conversion layer 14 can improve suitability for polarized sunglasses.

[0048] The reflective film of the present invention may have a configuration in which a polarization conversion layer is provided on both sides of the selective reflection layer 11, or a configuration in which a retardation layer is provided on both sides. In this case, the polarization conversion layer or retardation layer placed on the inside of the vehicle may be configured to have the function of converting the projected p-polarized light (linearly polarized light) into circularly polarized light reflected by the cholesteric liquid crystal layer of the selective reflection layer 11. On the other hand, the polarization conversion layer or the retardation layer arranged on the outer side of the vehicle may have a function of optically compensating for light entering from the outside of the windshield glass. The polarization conversion layer and the retardation layer will be described in detail later.

[0049] [Windshield glass] The windshield glass of the present invention is The windshield glass comprises a first glass plate, the above-mentioned reflective film, and a second glass plate, in this order.

[0050] The windshield glass refers to 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 a windshield or windshield glass located in front of the vehicle in the traveling direction.

[0051] Figure 3 shows an example of windshield glass. The windshield glass 24 shown in FIG. 3 includes a first glass plate 28, an interlayer 36, a reflective film 10, a heat seal layer 38, and a second glass plate 30, in this order. In Figure 3, the reflective film 10 has a configuration similar to that of the reflective film 10 shown in Figure 1, and is arranged so that the polarization conversion layer 14 is on the first glass plate 28 side and the retardation layer 16 (transparent substrate 18) is on the second glass plate 30 side.

[0052] When the windshield glass of the present invention is used in a vehicle, curved glass is often used as the first glass plate 28 and the second glass plate 30. In this case, if the first glass plate 28 is located on the inside of the vehicle and the second glass plate 30 is located on the outside of the vehicle, the first glass plate 28 is disposed with its convex side facing the second glass plate 30, and the second glass plate 30 is disposed with its concave side facing the first glass plate 28.

[0053] 3, when the first glass plate 28 and the second glass plate 30 are curved glasses, the polarization conversion layer 14 and the selective reflection layer 11 are disposed in this order from the convex side of the first glass plate 28. The retardation layer 16 is disposed between the selective reflection layer 11 and the second glass plate 30.

[0054] The visible light transmittance of the windshield glass is not limited, but a higher transmittance is preferable. The visible light transmittance of the windshield glass is preferably 70% or more, more preferably more than 70%, further preferably 75% or more, and particularly preferably 80% or more. The above-mentioned visible light transmittance is preferably satisfied at any position of 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, so that the above-mentioned visible light transmittance can be satisfied even when any glass commonly used for windshield glass is used.

[0055] As an example, Fig. 4 shows an example of the natural light reflection spectrum of a windshield glass in which a reflective film having the natural light reflection spectrum shown in the graph of Fig. 2 is sandwiched between two glass plates. This example is the windshield glass of Example 1. As shown in FIG. 4, it is clear that the reflective film of the present invention still has unevenness in the natural light reflection spectrum due to the reflective film even when sandwiched between thick glass plates.

[0056] The shape of the windshield glass is not limited, and is appropriately determined according to the object to which the windshield glass is to be placed. The windshield glass may be, for example, flat or may be a three-dimensional shape having a curved surface such as a concave or convex surface. In the windshield glass formed for the vehicle to which it is applied, the direction that is the top during normal use, the observer side, the driver side, and the viewing side such as the inside of the vehicle can be specified.

[0057] In the windshield glass, the reflective film may be provided in a projected image display area (projected image reflecting area) of the windshield glass. In addition, in the windshield glass, the reflective film may be provided between the glass sheets of the windshield glass having a laminated glass configuration, or may be provided on the outer surface of the glass sheet of the windshield glass.

[0058] When the reflective film of the present invention is provided on the outer surface of a glass plate of a windshield glass, the reflective film may be provided either inside (the side where the projected image is incident) or outside of a vehicle, etc., but it is preferable that the reflective film be provided inside. The reflective film of the present invention has a lower scratch resistance than a glass plate, and 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 constituting the laminated glass in order to protect the reflective film.

[0059] As described above, the reflective film is a member for reflecting a projected image to display the projected image. Therefore, the reflective film may be provided at 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 head-up display (hereinafter also referred to as HUD). In a HUD, the combiner means an optical member that can visibly display an image projected from a projector and can simultaneously observe information on the side opposite to the incident side of the projected light, such as a landscape, when observing the combiner from the incident side of the projected image. That is, the combiner functions as an optical path combiner that displays the light of the outside world and the light of the projected image by superimposing them together.

[0060] The reflective film may be provided on the entire surface of the windshield glass, or may be provided 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 the reflective film is provided on a part of the windshield glass, the reflective film may be provided anywhere on the windshield glass, but it is preferable that the reflective film is provided at a position where a virtual image is easily visible to an observer such as a driver when used as a HUD. For example, the position where the reflective film is provided 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 planar 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 enlarged or reduced when displayed.

[0061] Hereinafter, the components of the reflective film and windshield glass of the present invention will be described.

[0062] <Selective reflection layer> The selective reflection layer has a cholesteric liquid crystal layer and provides reflection that satisfies the above-mentioned requirements (i) to (iii).

[0063] [Cholesteric Liquid Crystal Layer] The cholesteric liquid crystal layer means a layer in which a cholesteric liquid crystal phase is fixed. The cholesteric liquid crystal layer may be a layer in which the orientation of the liquid crystal compound in the cholesteric liquid crystal phase is maintained. The cholesteric liquid crystal layer may be a layer in which the polymerizable liquid crystal compound is oriented in the cholesteric liquid crystal phase, polymerized and cured by ultraviolet irradiation, heating, etc., to form a layer with no fluidity, and at the same time, changed to a state in which the orientation form is not changed by 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 anymore. For example, the polymerizable liquid crystal compound may be polymerized by a curing reaction and no longer have liquid crystallinity.

[0064] It is known that a cholesteric liquid crystal phase exhibits selective reflection of circularly polarized light, that is, selectively reflecting circularly polarized light of one sense, either right-handed or left-handed, and transmitting circularly polarized light of the other sense. Many films formed from compositions containing polymerizable liquid crystal compounds have been known as films containing a layer in which a cholesteric liquid crystal phase exhibiting circularly polarized light selective reflectivity is fixed, and reference can be made to these conventional techniques for the cholesteric liquid crystal layer.

[0065] The central wavelength (selective reflection central wavelength) λ of selective reflection by a cholesteric liquid crystal layer depends on the pitch P (= helical period) of the helical structure (helical orientation structure) in the cholesteric liquid crystal phase, and follows the relationship between the average refractive index n of the cholesteric liquid crystal layer and λ = n × P. As can be seen from this formula, the selective reflection central wavelength can be adjusted by adjusting the n value and / or the P value. The pitch P of the helical structure (one helix pitch) is, in other words, the length in the helical axis direction of one turn of the helix, i.e., the length in the helical axis direction in which the director (the long axis direction in the case of rod-shaped liquid crystals) of the liquid crystal compound that constitutes the cholesteric liquid crystal phase rotates 360°. The helical axis direction of a normal cholesteric liquid crystal layer coincides with the thickness direction of the cholesteric liquid crystal layer.

[0066] The selective reflection central wavelength and half width of the cholesteric liquid crystal layer can be determined, for example, as follows. When the reflection spectrum of the cholesteric liquid crystal layer is measured from the normal direction using a spectrophotometer (JASCO Corporation, V-670), a peak of reduced transmittance is observed in the selective reflection band. The value of the shorter wavelength of the two wavelengths that have an intermediate (average) transmittance between the minimum transmittance of this peak and the transmittance before the decrease is defined as λ l (nm), and the value of the wavelength on the long wavelength side is λ h (nm), the selective reflection central wavelength λ and the half width Δλ can be expressed by the following formula. λ = (λ l +λ h ) / 2Δλ=(λ h -λ l ) The selective reflection central wavelength obtained as described above substantially coincides with the wavelength at the center of gravity of the reflection peak of the circularly polarized light reflection spectrum measured from the normal direction of the cholesteric liquid crystal layer.

[0067] In a head-up display system described later, the light is made to enter the windshield glass at an angle, so that the reflectance on the glass plate surface on the projected light entrance side can be reduced. At this time, the light is also obliquely incident on the cholesteric liquid crystal layer constituting the selective reflection layer 11 of the reflective film 10. For example, light incident at an angle of 45° to 70° with respect to the normal to the reflective film 10 in air with a refractive index of 1 passes through the cholesteric liquid crystal layer with a refractive index of about 1.61 at an angle of about 26° to 36°. In this case, the reflected wavelength is shifted to the short wavelength side. In a cholesteric liquid crystal layer with a selective reflection central wavelength of λ, the light beam is θ with respect to the normal direction of the cholesteric liquid crystal layer (the helical axis direction of the cholesteric liquid crystal layer). 2 The selective reflection center wavelength when passing through at an angle of wavelength λ d Then, the wavelength λ d is expressed by the following formula: λ d = λ × cosθ 2

[0068] Therefore, for example, θ 2 When the angle is 26° to 36°, a cholesteric liquid crystal layer having a central wavelength of selective reflection in the range of 650 to 780 nm can reflect projected light in the range of 520 to 695 nm. Such a wavelength range is a wavelength region with high luminosity, and therefore contributes greatly to the brightness of a projected image, resulting in a projected image with high brightness.

[0069] The helical pitch of the cholesteric liquid crystal phase depends on the type of chiral agent used together with the polymerizable liquid crystal compound and its concentration, so the desired pitch can be obtained by adjusting these. The helical sense and pitch can be measured by the methods described in "Introduction to Liquid Crystal Chemistry Experiments" edited by the Japanese Liquid Crystal Society, published by Sigma Publishing in 2007, p. 46, and "Liquid Crystal Handbook" edited by the Liquid Crystal Handbook Editorial Committee, published by Maruzen, p. 196.

[0070] Each cholesteric liquid crystal layer has a right-handed or left-handed sense of helix, and the sense of circularly polarized light reflected by the cholesteric liquid crystal layer (the direction of rotation of the circularly polarized light) corresponds to the sense of the helix. In the case of having a plurality of cholesteric liquid crystal layers with different selective reflection central wavelengths, the sense of the helix of each cholesteric liquid crystal layer may be the same or different. However, it is preferable that the sense of the helix of each of the plurality of cholesteric liquid crystal layers is the same.

[0071] In addition, when the reflective film 10 has multiple cholesteric liquid crystal layers as the selective reflection layer 11, it is preferable that the cholesteric liquid crystal layers that show selective reflection in the same or overlapping wavelength ranges do not include cholesteric liquid crystal layers with different helical senses, in order to avoid the transmittance in a specific wavelength range decreasing to, for example, less than 50%.

[0072] The half-width Δλ (nm) of the selective reflection band that exhibits selective reflection depends on the birefringence Δn of the liquid crystal compound and the above-mentioned 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 adjusting the type or mixing ratio of the polymerizable liquid crystal compound, or by controlling the temperature when the alignment is fixed. In order to form one type of cholesteric liquid crystal layer with the same central wavelength of selective reflection, multiple cholesteric liquid crystal layers with the same pitch P and the same helical sense may be laminated. By laminating cholesteric liquid crystal layers with the same pitch P and the same helical sense, it is possible to increase the circular polarization selectivity at a specific wavelength.

[0073] When laminating a plurality of cholesteric liquid crystal layers in the selective reflection layer 11, a cholesteric liquid crystal layer prepared separately may be laminated using an adhesive or the like, or a liquid crystal composition containing a polymerizable liquid crystal compound or the like may be directly applied to the surface of a cholesteric liquid crystal layer previously formed by the method described below, and the alignment and fixing steps may be repeated, the latter being preferred. By forming the next cholesteric liquid crystal layer directly on the surface of the previously formed cholesteric liquid crystal layer, the orientation of the liquid crystal molecules on the air interface side of the previously formed cholesteric liquid crystal layer coincides with the orientation of the liquid crystal molecules on the lower side of the cholesteric liquid crystal layer to be formed thereon, improving the polarization characteristics of the laminate of cholesteric liquid crystal layers. Also, interference unevenness that may be caused by uneven thickness of the adhesive layer is not observed.

[0074] The thickness of the cholesteric liquid crystal layer is preferably from 0.5 to 10 μm, more preferably from 1.0 to 8.0 μm, and further preferably from 1.5 to 6.0 μm.

[0075] (Method of producing a cholesteric liquid crystal layer) The materials and method for producing the cholesteric liquid crystal layer will be described below. Materials used to form the above-mentioned cholesteric liquid crystal layer include a liquid crystal composition containing a polymerizable liquid crystal compound and a chiral agent (optically active compound), etc. If necessary, the above-mentioned liquid crystal composition, which is further mixed with a surfactant and a polymerization initiator and dissolved in a solvent, can be applied to a support, an alignment layer, a cholesteric liquid crystal layer serving as a lower layer, etc., and after cholesteric alignment maturation, the liquid crystal composition is cured and fixed to form a cholesteric liquid crystal layer.

[0076] (Polymerizable liquid crystal compound) The polymerizable liquid crystal compound may be either a rod-shaped liquid crystal compound or a discotic liquid crystal compound, but is preferably a rod-shaped liquid crystal compound. Examples of rod-shaped polymerizable liquid crystal compounds that form cholesteric liquid crystal layers include rod-shaped nematic liquid crystal compounds.As rod-shaped nematic liquid crystal compounds, azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoates, cyclohexane carboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes, and alkenylcyclohexylbenzonitriles are preferably used.Not only low molecular weight liquid crystal compounds, but also high molecular weight liquid crystal compounds can be used.

[0077] The polymerizable liquid crystal compound is obtained by introducing a polymerizable group into a liquid crystal compound. Examples of the polymerizable group include an unsaturated polymerizable group, an epoxy group, and an aziridinyl group, and an unsaturated polymerizable group is preferable, and an ethylenically unsaturated polymerizable group is particularly preferable. The polymerizable group can be introduced into the molecule of the liquid crystal compound by various methods. The number of polymerizable groups that the polymerizable liquid crystal compound has is preferably 1 to 6, more preferably 1 to 3, in one molecule. Examples of the polymerizable liquid crystal compound include compounds described in Makromol.Chem., Vol. 190, p. 2255 (1989), Advanced Materials, Vol. 5, p. 107 (1993), U.S. Pat. No. 4,683,327, U.S. Pat. No. 5,622,648, U.S. Pat. No. 5,770,107, WO95 / 22586, WO95 / 24455, WO97 / 00600, WO98 / 23580, WO98 / 52905, JP-A-1-272551, JP-A-6-016616, JP-A-7-110469, JP-A-11-080081, and JP-A-2001-328973. Two or more polymerizable liquid crystal compounds may be used in combination. The alignment temperature can be lowered by using two or more kinds of polymerizable liquid crystal compounds in combination.

[0078] The amount of the polymerizable liquid crystal compound added in the liquid crystal composition is preferably 80 to 99.9 mass %, more preferably 85 to 99.5 mass %, and particularly preferably 90 to 99 mass %, based on the solid content mass (mass excluding the solvent) of the liquid crystal composition.

[0079] In order to improve the visible light transmittance, the cholesteric liquid crystal layer may have a low Δn. The low Δn cholesteric liquid crystal layer can be formed by using a low Δn polymerizable liquid crystal compound. The low Δn polymerizable liquid crystal compound will be specifically described below.

[0080] (Low Δn polymerizable liquid crystal compound) A cholesteric liquid crystal phase is formed using a low Δn polymerizable liquid crystal compound, and this is fixed into a film to obtain a narrow-band selective reflection layer. Examples of low Δn polymerizable liquid crystal compounds include compounds described in WO2015 / 115390, WO2015 / 147243, WO2016 / 035873, JP2015-163596A, and JP2016-053149A. For liquid crystal compositions that provide a selective reflection layer with a small half-width, the description in WO2016 / 047648 can also be referred to.

[0081] The liquid crystal compound is also preferably a polymerizable compound represented by the following formula (I) described in WO2016 / 047648.

[0082] [ka]

[0083] In formula (I), A represents an optionally substituted phenylene group or an optionally substituted trans-1,4-cyclohexylene group, L represents a single bond, -CH 2 O-, -OCH 2 -, -(CH 2 ) 2 OC(=O)-, -C(=O)O(CH 2 ) 2 represents a linking group selected from the group consisting of -, -C(=O)O-, -OC(=O)-, -OC(=O)O-, -CH=CH-C(=O)O-, and -OC(=O)-CH=CH-, m represents an integer of 3 to 12, Sp 1 and Sp 2each independently represents a single bond, a linear or branched alkylene group having 1 to 20 carbon atoms, and one or more -CH 2 - is -O-, -S-, -NH-, -N(CH 3 Q represents a linking group selected from the group consisting of groups substituted with -C(=O)-, -OC(=O)-, or -C(=O)O-; 1 and Q 2 each independently represents a hydrogen atom or a polymerizable group selected from the group consisting of groups represented by the following formulas Q-1 to Q-5, 1 and Q 2 represents a polymerizable group.

[0084] [ka]

[0085] In formula (I), the phenylene group is preferably a 1,4-phenylene group. The substituents for the phenylene group and the trans-1,4-cyclohexylene group "may have a substituent" are not particularly limited, and examples thereof include substituents selected from the group consisting of alkyl groups, cycloalkyl groups, alkoxy groups, alkyl ether groups, amide groups, amino groups, halogen atoms, and groups formed by combining two or more of the above-mentioned substituents. Examples of the substituents include -C(=O)-X, which will be described later. 3 -Sp 3 -Q 3 The phenylene group and the trans-1,4-cyclohexylene group may have 1 to 4 substituents. When the phenylene group and the trans-1,4-cyclohexylene group have two or more substituents, the two or more substituents may be the same or different.

[0086] The alkyl group may be either linear or branched. The number of carbon atoms in the alkyl group is preferably 1 to 30, more preferably 1 to 10, and even more preferably 1 to 6. Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, neopentyl, 1,1-dimethylpropyl, n-hexyl, isohexyl, linear or branched heptyl, octyl, nonyl, decyl, undecyl, or dodecyl. The above explanation of the alkyl group is also applicable to an alkoxy group containing an alkyl group. In addition, specific examples of the alkylene group include divalent groups obtained by removing any one hydrogen atom from each of the above-mentioned examples of the alkyl group. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

[0087] The number of carbon atoms in the cycloalkyl group is preferably 3 to 20, more preferably 5 or more, and is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less. Examples of the cycloalkyl group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group.

[0088] Substituents which the phenylene group and the trans-1,4-cyclohexylene group may have are particularly alkyl groups, alkoxy groups, -C(=O)-X 3 -Sp 3 -Q 3 Preferred are substituents selected from the group consisting of: 3 is a single bond, -O-, -S-, or -N(Sp 4 -Q 4 )- or Q 3 and Sp 3 This indicates a nitrogen atom forming a ring structure with Sp. 3 , Sp 4each independently represents a single bond, a linear or branched alkylene group having 1 to 20 carbon atoms, and one or more -CH 2 - is -O-, -S-, -NH-, -N(CH 3 )-, -C(=O)-, -OC(=O)-, or -C(=O)O-.

[0089] Q 3 and Q 4 each independently represents a hydrogen atom, a cycloalkyl group, or one or more -CH 2 - is -O-, -S-, -NH-, -N(CH 3 )-, -C(=O)-, -OC(=O)-, or -C(=O)O-, or any polymerizable group selected from the group consisting of groups represented by formulae Q-1 to Q-5.

[0090] One or more -CH groups in the cycloalkyl group 2 - is -O-, -S-, -NH-, -N(CH 3 Specific examples of the group substituted with -, -C(=O)-, -OC(=O)-, or -C(=O)O- include a tetrahydrofuranyl group, a pyrrolidinyl group, an imidazolidinyl group, a pyrazolidinyl group, a piperidyl group, a piperazinyl group, and a morpholinyl group. The substitution position is not particularly limited. Among these, a tetrahydrofuranyl group is preferred, and a 2-tetrahydrofuranyl group is particularly preferred.

[0091] In formula (I), L is a single bond, -CH 2 O-, -OCH 2- , -(CH 2 ) 2 OC(=O)-, -C(=O)O(CH 2 ) 2It represents a linking group selected from the group consisting of -, -C(=O)O-, -OC(=O)-, -OC(=O)O-, -CH=CH-C(=O)O-, and -OC(=O)-CH=CH-. L is preferably -C(=O)O- or -OC(=O)-. m-1 Ls may be the same or different from each other.

[0092] Sp 1 , Sp 2 each independently represents a single bond, a linear or branched alkylene group having 1 to 20 carbon atoms, and one or more -CH 2 - is -O-, -S-, -NH-, -N(CH 3 represents a linking group selected from the group consisting of groups substituted with -C(=O)-, -OC(=O)-, or -C(=O)O-. 1 and Sp 2 are preferably each independently a linear alkylene group having 1 to 10 carbon atoms bonded to both terminals with linking groups selected from the group consisting of -O-, -OC(=O)-, and -C(=O)O-, or a linking group composed of one or more groups selected from the group consisting of -OC(=O)-, -C(=O)O-, -O-, and linear alkylene groups having 1 to 10 carbon atoms, and are preferably linear alkylene groups having 1 to 10 carbon atoms bonded to -O- at both terminals.

[0093] Q 1 and Q 2 each independently represents a hydrogen atom or a polymerizable group selected from the group consisting of groups represented by the above formulas Q-1 to Q-5, 1 and Q 2 represents a polymerizable group. The polymerizable group is preferably an acryloyl group (formula Q-1) or a methacryloyl group (formula Q-2).

[0094] In formula (I), m represents an integer of 3 to 12. m is preferably an integer of 3 to 9, more preferably an integer of 3 to 7, and even more preferably an integer of 3 to 5.

[0095] The polymerizable compound represented by formula (I) preferably contains at least one phenylene group which may have a substituent and at least one trans-1,4-cyclohexylene group which may have a substituent as A. The polymerizable compound represented by formula (I) preferably contains 1 to 4 trans-1,4-cyclohexylene groups which may have a substituent as A, more preferably 1 to 3, and even more preferably 2 or 3. Further, the polymerizable compound represented by formula (I) preferably contains one or more phenylene groups which may have a substituent as A, more preferably 1 to 4, even more preferably 1 to 3, and particularly preferably 2 or 3.

[0096] In formula (I), when the number of trans-1,4-cyclohexylene groups represented by A is divided by m to obtain mc, 0.1 < mc < 0.9 is preferable, 0.3 < mc < 0.8 is more preferable, and 0.5 < mc < 0.7 is even more preferable. It is also preferable that the liquid crystal composition contains a polymerizable compound represented by formula (I) with 0.1 < mc < 0.3 together with a polymerizable compound represented by formula (I) with 0.5 < mc < 0.7.

[0097] Specific examples of the polymerizable compound represented by formula (I) include, in addition to the compounds described in paragraphs 0051 to 0058 of WO2016 / 047648, the compounds described in JP-A-2013-112631, JP-A-2010-070543, Patent No. 4725516, WO2015 / 115390, WO2015 / 147243, WO2016 / 035873, JP-A-2015-163596, and JP-A-2016-053149.

[0098] (Chiral agent: optically active compound) The chiral agent has a function of inducing a helical structure of a cholesteric liquid crystal phase. Since chiral compounds have different helix senses or helix pitches induced by the compounds, they may be selected according to the purpose. As the chiral agent, there is no particular limitation, and known compounds can be used.As examples of chiral agents, compounds described in Liquid Crystal Device Handbook (Chapter 3, Section 4-3, TN, STN Chiral Agents, p. 199, Japan Society for the Promotion of Science, 142nd Committee, ed., 1989), JP2003-287623, JP2002-302487, JP2002-080478, JP2002-080851, JP2010-181852, and JP2014-034581, etc. can be mentioned.

[0099] Although chiral agents generally contain an asymmetric carbon atom, axially asymmetric or planarly asymmetric compounds that do not contain an asymmetric carbon atom can also be used as chiral agents. Examples of axially asymmetric or planarly asymmetric compounds include binaphthyl, helicene, paracyclophane, and derivatives thereof. The chiral agent may have a polymerizable group. 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 of group as the polymerizable group of the polymerizable liquid crystal compound. Therefore, the polymerizable group of the chiral agent is also preferably an unsaturated polymerizable group, an epoxy group or an aziridinyl group, more preferably an unsaturated polymerizable group, and particularly preferably an ethylenically unsaturated polymerizable group. The chiral agent may also be a liquid crystal compound.

[0100] As the chiral agent, isosorbide derivatives, isomannide derivatives, binaphthyl derivatives, etc. can be preferably used. As the isosorbide derivative, a commercially available product such as LC756 manufactured by BASF may be used. The content of the chiral dopant in the liquid crystal composition is preferably 0.01 to 200 mol %, more preferably 1 to 30 mol %, of the amount of the polymerizable liquid crystal compound. The content of the chiral dopant in the liquid crystal composition refers to the concentration (mass %) of the chiral dopant relative to the total solid content in the composition.

[0101] As described above, the cholesteric liquid crystal layer of the selective reflection layer of the reflective film of the present invention may have two or more selective reflection central wavelengths. A cholesteric liquid crystal layer having two or more selective reflection central wavelengths is achieved by changing the pitch of the helical structure in the thickness direction. A cholesteric liquid crystal layer in which the pitch of the helical structure changes in the thickness direction can be produced by changing the amount of light irradiation in the thickness direction when forming a cholesteric liquid crystal layer using a chiral agent whose helical twisting power (HTP) changes when irradiated with light.

[0102] Chiral agents whose HTP changes upon irradiation with light include those that undergo back-isomerization, dimerization, or both isomerization and dimerization upon irradiation with light. When the chiral agent has a photoisomerizable group, the photoisomerizable group is preferably an isomerizable site of a compound exhibiting photochromic properties, an azo group, an azoxy group, or a cinnamoyl group. Specific compounds that can be used include those described in JP-A-2002-080478, JP-A-2002-080851, JP-A-2002-179668, JP-A-2002-179669, JP-A-2002-179670, JP-A-2002-179681, JP-A-2002-179682, JP-A-2002-338575, JP-A-2002-338668, JP-A-2003-313189, and JP-A-2003-313292.

[0103] (Polymerization initiator) The liquid crystal composition preferably contains a polymerization initiator. In an embodiment in which the polymerization reaction is caused to proceed by irradiation with ultraviolet light, the polymerization initiator used is preferably a photopolymerization initiator capable of initiating the polymerization reaction by irradiation with ultraviolet light. Examples of the photopolymerization initiator include α-carbonyl compounds (described in U.S. Pat. Nos. 2,367,661 and 2,367,670), acyloin ethers (described in U.S. Pat. No. 2,448,828), α-hydrocarbon-substituted aromatic acyloin compounds (described in U.S. Pat. No. 2,722,512), polynuclear quinone compounds (described in U.S. Pat. Nos. 3,046,127 and 2,951,758), combinations of triaryl imidazole dimers and p-aminophenyl ketones (described in U.S. Pat. No. 3,549,367), acridine and phenazine compounds (described in JP-A-60-105,667 and U.S. Pat. No. 4,239,850), acylphosphites, and the like. 10-029997, JP-A-2001-233842, JP-A-2000-080068, JP-A-2006-342166, JP-A-2013-114249, JP-A-2014 JP-137466A, JP 4223071A, JP 2010-262028A, JP 2014-500852A), oxime compounds (JP 2000-066385A, JP 4454067A), and oxadiazole compounds (US Pat. No. 4212970). For example, the description in paragraphs 0500 to 0547 of JP 2012-208494A may also be taken into consideration.

[0104] As the polymerization initiator, it is also preferable to use an acylphosphine oxide compound or an oxime compound. As the acylphosphine oxide compound, for example, a commercially available product IRGACURE810 (compound name: bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide) manufactured by BASF Japan Co., Ltd. can be used. As the oxime compound, commercially available products such as IRGACURE OXE01 (manufactured by BASF), IRGACURE OXE02 (manufactured by BASF), TR-PBG-304 (manufactured by Changzhou Strong Electronic New Materials Co., Ltd.), Adeka Arcles NCI-831, Adeka Arcles NCI-930 (manufactured by ADEKA), and Adeka Arcles NCI-831 (manufactured by ADEKA) can be used. The polymerization initiator may be used alone or in combination of two or more kinds. The content of the photopolymerization initiator in the liquid crystal composition is preferably 0.1 to 20% by mass, more preferably 0.5 to 5% by mass, based on the content of the polymerizable liquid crystal compound.

[0105] (Crosslinking agent) The liquid crystal composition may contain a crosslinking agent in order to improve the film strength and durability after curing. As the crosslinking agent, those which are cured by ultraviolet light, heat, moisture, etc. can be suitably used. The crosslinking agent is not particularly limited and can be appropriately selected according to the purpose. Examples of the crosslinking agent include polyfunctional acrylate compounds such as trimethylolpropane tri(meth)acrylate and pentaerythritol tri(meth)acrylate; epoxy compounds such as glycidyl (meth)acrylate and ethylene glycol diglycidyl ether; aziridine compounds such as 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate] and 4,4-bis(ethyleneiminocarbonylamino)diphenylmethane; isocyanate compounds such as hexamethylene diisocyanate and biuret type isocyanate; polyoxazoline compounds having an oxazoline group in the side chain; alkoxysilane compounds such as vinyltrimethoxysilane and N-(2-aminoethyl)3-aminopropyltrimethoxysilane. In addition, a known catalyst can be used according to the reactivity of the crosslinking agent, and in addition to improving the film strength and durability, productivity can be improved. These may be used alone or in combination of two or more. The content of the crosslinking agent is preferably 3 to 20% by mass, more preferably 5 to 15% by mass. By making the content of the crosslinking agent 3% by mass or more, the effect of improving the crosslinking density can be obtained, and by making the content of the crosslinking agent 20% by mass or less, the decrease in stability of the cholesteric liquid crystal layer can be prevented. In addition, "(meth)acrylate" is used to mean "either one or both of acrylate and methacrylate."

[0106] (Alignment control agent) An alignment control agent that contributes to stably or quickly forming a cholesteric liquid crystal layer with a planar alignment may be added to the liquid crystal composition. Examples of the alignment control agent include fluorine (meth)acrylate polymers described in paragraphs

[0018] to

[0043] of JP-A-2007-272185, compounds represented by formulas (I) to (IV) described in paragraphs

[0031] to

[0034] of JP-A-2012-203237, and compounds described in JP-A-2013-113913. The alignment control agent may be used alone or in combination of two or more kinds.

[0107] The amount of the alignment control agent added in the liquid crystal composition is preferably 0.01 to 10 mass %, more preferably 0.01 to 5 mass %, and particularly preferably 0.02 to 1 mass %, based on the total mass of the polymerizable liquid crystal compound.

[0108] (Other additives) In addition, the liquid crystal composition may contain at least one selected from various additives such as a surfactant for adjusting the surface tension of the coating film and making the thickness uniform, and a polymerizable monomer, etc. In addition, the liquid crystal composition may further contain a polymerization inhibitor, an antioxidant, an ultraviolet absorber, a light stabilizer, a coloring material, metal oxide fine particles, etc., as necessary, within a range that does not deteriorate the optical performance.

[0109] The cholesteric liquid crystal layer can be formed by applying a liquid crystal composition, in which a polymerizable liquid crystal compound and a polymerization initiator, and further, if necessary, a chiral agent, a surfactant, etc. are dissolved in a solvent, onto a transparent substrate, a retardation layer, an alignment layer, or a previously prepared cholesteric liquid crystal layer, etc., and drying the liquid crystal composition to obtain a coating film, which is then irradiated with active light rays to polymerize the cholesteric liquid crystal composition, thereby forming a cholesteric liquid crystal layer in which cholesteric regularity is fixed. A laminated film consisting of a plurality of cholesteric liquid crystal layers can be formed by repeating the above-mentioned manufacturing process for the cholesteric liquid crystal layer.

[0110] (solvent) The solvent used in the preparation of the liquid crystal composition is not particularly limited and can be appropriately selected depending on the purpose, but an organic solvent is preferably used. The organic solvent is not particularly limited and can be appropriately selected according to the purpose, and examples thereof include ketones, alkyl halides, amides, sulfoxides, heterocyclic compounds, hydrocarbons, esters, and ethers. These may be used alone or in combination of two or more. Among these, ketones are particularly preferred when considering the burden on the environment.

[0111] (coating, alignment, polymerization) The method of applying the liquid crystal composition to the transparent substrate, the alignment layer, the cholesteric liquid crystal layer as the lower layer, etc. is not particularly limited and can be appropriately selected according to the purpose. Examples of the application method include wire bar coating, curtain coating, extrusion coating, direct gravure coating, reverse gravure coating, die coating, spin coating, dip coating, spray coating, and slide coating. It can also be performed by transferring the liquid crystal composition that has been applied on a support separately. The applied liquid crystal composition is heated to align the liquid crystal molecules. The heating temperature is preferably 200° C. or less, and more preferably 130° C. or less. This alignment treatment produces an optical thin film in which the polymerizable liquid crystal compound is twisted and aligned so that the helical axis is substantially perpendicular to the film surface.

[0112] The aligned liquid crystal compound can be further polymerized to harden the liquid crystal composition. The polymerization may be either thermal polymerization or photopolymerization using light irradiation, but photopolymerization is preferred. The light irradiation is preferably performed using ultraviolet light. The irradiation energy is 20 mJ / cm. 2 ~50J / cm 2 is preferable, and 100 to 1,500 mJ / cm 2 is more preferred. In order to promote the photopolymerization reaction, light irradiation may be performed under heating conditions or in a nitrogen atmosphere. The wavelength of the ultraviolet light to be irradiated is preferably 350 to 430 nm. From the viewpoint of stability, the polymerization reaction rate is preferably higher, preferably 70% or more, and more preferably 80% or more. The polymerization reaction rate can be determined by measuring the consumption rate of the polymerizable functional group by infrared absorption spectrum.

[0113] <Polarization conversion layer> The polarization conversion layer 14 is a layer in which the helical orientation structure of a liquid crystal compound is fixed, and it is preferable that the pitch number x of the helical orientation structure and the film thickness y (unit: μm) of the polarization conversion layer satisfy all of the following relational expressions (a) to (c). 0.1≦x≦1.0 ··· Formula (a) 0.5≦y≦3.0 ··· Formula (b) 3000≦(1560×y) / x≦50000 ··· Formula (c) One pitch of the helical structure of a liquid crystal compound is one turn of the helix of the liquid crystal compound. In other words, one pitch is defined as the state in which the director of the helically aligned liquid crystal compound (the long axis direction in the case of rod-shaped liquid crystal) rotates 360°.

[0114] When the polarization conversion layer has a helical structure of a liquid crystal compound, it exhibits optical rotation and birefringence for visible light, which has a shorter wavelength than the reflection peak wavelength in the infrared range. Therefore, it is possible to control the polarization in the visible range. By setting the pitch number x of the helical orientation structure of the polarization conversion layer and the film thickness y of the polarization conversion layer within the above range, it is possible to impart the function of optically compensating for visible light with the polarization conversion layer, or the function of converting linearly polarized light (p-polarized light) incident on the reflective film into circularly polarized light.

[0115] The polarization conversion layer exhibits optical rotation and birefringence for visible light because the liquid crystal compound has a helical structure that satisfies the relational expressions (a) to (c). In particular, by setting the pitch P of the helical structure of the polarization conversion layer to a length corresponding to the pitch P of the cholesteric liquid crystal layer whose selective reflection central wavelength is in the long infrared range, the polarization conversion layer exhibits high optical rotation and birefringence for visible light with a short wavelength.

[0116] The relationship (a) is 0.1≦x≦1.0. If the pitch number x of the helical structure is less than 0.1, problems arise such as insufficient optical rotation and birefringence being obtained. Furthermore, if the pitch number x of the helical structure exceeds 1.0, the optical rotation and birefringence become excessive, causing inconveniences such as failure to obtain the desired elliptically polarized light.

[0117] The relationship (b) is "0.5≦y≦3.0". If the thickness y of the polarization conversion layer is less than 0.5 μm, the film thickness is too thin, causing inconveniences such as inability to obtain sufficient optical rotation and birefringence. If the thickness y of the polarization conversion layer exceeds 3.0 μm, the optical rotation and birefringence will be excessive, making it impossible to obtain the desired circularly polarized light, and poor orientation will easily occur, which is unfavorable for production, resulting in other inconveniences.

[0118] The relationship (c) is 3000≦(1560×y) / x≦50000. If "(1560 x y) / x" is less than 3000, the optical rotation is excessive, and there arises a problem that the desired polarization cannot be obtained. If "(1560 x y) / x" exceeds 50,000, the optical rotation will be insufficient, causing inconvenience such as the inability to obtain the desired polarization.

[0119] In the present invention, the pitch number x of the helical structure of the polarization conversion layer is more preferably 0.1 to 0.8, and the film thickness y is more preferably 0.6 μm to 2.6 μm. Moreover, “(1560×y) / x” is more preferably 5000 to 13000.

[0120] That is, it is preferable that the polarization conversion layer has a long pitch P of the helical structure and a small pitch number x. Specifically, it is preferable that the polarization conversion layer has a helical pitch P equivalent to the pitch P of a cholesteric liquid crystal layer having a selective reflection central wavelength in the long infrared wavelength range, and a small pitch number x. More specifically, it is preferable that the polarization conversion layer has a helical pitch P equivalent to the pitch P of a cholesteric liquid crystal layer having a selective reflection central wavelength of 3000 to 10000 nm, and a small pitch number x. In such a polarization conversion layer, the selective reflection central wavelength corresponding to the pitch P is much longer than visible light, and therefore the polarization conversion layer more suitably exhibits the optical rotation property and birefringence for visible light described above.

[0121] Such a polarization conversion layer can be basically formed in the same manner as a known cholesteric liquid crystal layer. However, when forming the polarization conversion layer, it is necessary to adjust the liquid crystal compound to be used, the chiral agent to be used, the amount of chiral agent to be added, the film thickness, etc. so that the pitch number x of the helical structure and the film thickness y [μm] in the polarization conversion layer satisfy all of the relational expressions (a) to (c).

[0122] <Layer in which the helical alignment structure (helical structure) of liquid crystal compounds is fixed> A layer in which a helical orientation structure (helical structure) of a liquid crystal compound is fixed is a so-called cholesteric liquid crystal layer, which means a layer in which a cholesteric liquid crystal phase is fixed. The cholesteric liquid crystal layer may be a layer in which the orientation of the liquid crystal compound in the cholesteric liquid crystal phase is maintained. The cholesteric liquid crystal layer may be a layer in which the polymerizable liquid crystal compound is oriented in the cholesteric liquid crystal phase, polymerized and cured by ultraviolet irradiation, heating, etc., to form a layer with no fluidity, and at the same time, changed to a state in which the orientation form is not changed by 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 anymore. For example, the polymerizable liquid crystal compound may be polymerized by a curing reaction and no longer have liquid crystallinity.

[0123] As mentioned above, the central wavelength of selective reflection by the cholesteric liquid crystal layer (selective reflection central wavelength) λ depends on the pitch P (= helical period) of the helical structure (helical orientation structure) in the cholesteric liquid crystal phase, and follows the relationship between the average refractive index n of the cholesteric liquid crystal layer and λ = n × P. As can be seen from this formula, the selective reflection central wavelength can be adjusted by adjusting the n value and / or the P value.

[0124] The helical pitch of the cholesteric liquid crystal phase depends on the type of chiral agent used together with the polymerizable liquid crystal compound and its concentration, and therefore a desired pitch can be obtained by adjusting these. As described above, the helical pitch of the cholesteric liquid crystal layer used as the polarization conversion layer is adjusted so that the selective reflection central wavelength is in the long wavelength infrared region. The method for forming the cholesteric liquid crystal layer as the polarization conversion layer is basically the same as the method for forming the cholesteric liquid crystal layer described above.

[0125] <Retardation layer> A retardation layer changes the state of incident polarized light by creating a phase difference (optical path difference) between two orthogonal polarized light components.

[0126] When the retardation layer is disposed on the outer side of the vehicle and provides optical compensation, the front retardation of the retardation layer may be set to a retardation that provides optical compensation. In this case, the retardation layer preferably has a front retardation of 50 nm to 160 nm at a wavelength of 550 nm. In addition, when the direction corresponding to the vertical upward direction of the surface of the first glass plate when the windshield glass having the reflective film is mounted on a vehicle is defined as 0°, it is preferable that the angle of the slow axis is 10° to 50° or -50° to -10°.

[0127] In addition, when the retardation layer converts linearly polarized light into circularly polarized light, the retardation layer is preferably configured to give a front retardation of λ / 4, and may be configured to give a front retardation of 3λ / 4. The angle of the slow axis may be arranged so as to change the incident linearly polarized light into circularly polarized light.

[0128] In this case, the retardation layer preferably has a front retardation at a wavelength of 550 nm in the range of 100 to 450 nm, more preferably in the range of 120 to 200 nm or 300 to 400 nm, for example. In addition, the direction of the slow axis of the retardation layer is preferably determined according to the incident direction of the projection light for projecting an image when the reflective film 10 is used in a head-up display system, and the sense of the helix of the cholesteric liquid crystal layer constituting the selective reflection layer.

[0129] There is no particular limitation on the retardation layer, and it can be appropriately selected according to purpose.For example, retardation layer can be stretched polycarbonate film, stretched norbornene-based polymer film, transparent film containing and oriented inorganic particles having birefringence such as strontium carbonate, thin film obtained by obliquely depositing inorganic dielectric on support, film that is uniaxially oriented and fixed in orientation of polymerizable liquid crystal compound, and film that is uniaxially oriented and fixed in orientation of liquid crystal compound.

[0130] Among them, a film in which a polymerizable liquid crystal compound is uniaxially aligned and fixed is a suitable example of a retardation layer. As an example, such a retardation layer can be formed by applying a liquid crystal composition containing a polymerizable liquid crystal compound to a transparent substrate, a temporary support, or the surface of an alignment layer, forming the polymerizable liquid crystal compound in the liquid crystal composition into a nematic alignment in a liquid crystal state, and then fixing the alignment by curing. In this case, the retardation layer can be formed in the same manner as the formation of the cholesteric liquid crystal layer described above, except that no chiral agent is added to the liquid crystal composition. However, the heating temperature during nematic alignment after coating of the liquid crystal composition is preferably 50 to 120°C, more preferably 60 to 100°C.

[0131] The retardation layer may be a layer obtained by applying a composition containing a polymer liquid crystal compound to the surface of a transparent substrate, a temporary support, an alignment layer, or the like, forming a nematic alignment in a liquid crystal state, and then fixing the alignment by cooling.

[0132] The thickness of the retardation layer is not particularly limited, but is preferably 0.2 to 300 μm, more preferably 0.5 to 150 μm, and even more preferably 1.0 to 80 μm. The thickness of the retardation layer formed from the liquid crystal composition is not particularly limited, but is preferably 0.2 to 10 μm, more preferably 0.5 to 5.0 μm, and even more preferably 0.7 to 2.0 μm.

[0133] The retardation layer has a slow axis inclined at an angle α with respect to an axis of the retardation layer in any direction. The direction of the slow axis can be set by, for example, rubbing the alignment film that is the lower layer of the retardation layer.

[0134] The reflective film of the present invention may have layers other than the selective reflection layer, the polarization conversion layer, and the retardation layer. For example, the reflective film may have a transparent substrate, an adhesive layer, and the like. 1, the reflective film 10 has a transparent substrate 18 disposed on the opposite side of the retardation layer 16 to the selective reflection layer 11. The transparent substrate 18 supports the retardation layer 16, the selective reflection layer 11 (cholesteric liquid crystal layer), and the polarization conversion layer 14. The transparent substrate 18 may be used as a support when forming the retardation layer 16, the selective reflection layer 11 (cholesteric liquid crystal layer), and the polarization conversion layer 14.

[0135] The reflective film may be in the form of a thin film, a sheet, etc. Before being used on a windshield glass, the reflective film may be in the form of a roll or the like as a thin film.

[0136] It is preferable that the transparent substrate and the adhesive layer are all transparent in the visible light region. In addition, it is preferable that the transparent substrate and the adhesive layer have 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 shows reflection. This front retardation is preferably 5 nm or less. Furthermore, it is preferable that the support and the adhesive layer have a small difference in refractive index from the average refractive index (in-plane average refractive index) of the selective reflection layer.

[0137] <Transparent base material> The transparent substrate can also be used as a substrate when forming a selective reflection layer. The transparent substrate used for forming the selective reflection layer can be a temporary support that is peeled off after forming the selective reflection layer. Therefore, the completed reflective film and windshield glass do not need to include a transparent substrate. Note that, when the completed reflective film or windshield glass includes a transparent substrate, rather than being peeled off as a temporary support, the transparent substrate is preferably transparent in the visible light region.

[0138] There is no limitation on the material of the transparent substrate. Examples of the transparent substrate include polyesters such as polyethylene terephthalate (PET), polycarbonates, acrylic resins, epoxy resins, polyurethanes, polyamides, polyolefins, cellulose derivatives, and plastic films such as silicone. In addition to the above-mentioned plastic films, glass may be used as the temporary support.

[0139] The thickness of the transparent substrate may be about 5.0 to 1000 μm, preferably 10 to 250 μm, and more preferably 15 to 90 μm.

[0140] Here, as in the example shown in FIG. 3, when the transparent substrate 18 is disposed on the second glass plate 30 side, that is, on the vehicle exterior side, the transparent substrate 18 preferably contains an ultraviolet absorbing agent. When the transparent substrate 18 contains an ultraviolet absorbing agent, deterioration of the reflective film (selective reflective layer) due to ultraviolet rays can be suppressed.

[0141] <Laminated glass> The windshield glass may have a laminated glass configuration. The windshield glass of the present invention is preferably laminated glass and has the above-mentioned reflective film of the present invention between a first glass plate and a second glass plate. The windshield glass may have a structure in which a reflective film is disposed between the first glass plate and the second glass plate. However, it is preferable that the windshield glass has a structure in which an intermediate film (interlayer film sheet) is provided at least either between the first glass plate and the reflective film or between the reflective film and the second glass plate. In the windshield glass, for example, the second glass plate is disposed on the opposite side (the vehicle exterior side) to the viewing side of the image in the HUD, and the first glass plate is disposed on the viewing side (the vehicle interior side). 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 the two glass plates. Therefore, the second glass plate may be disposed on the vehicle interior side, and the first glass plate may be disposed on the vehicle exterior side. The glass plates such as the first glass plate and the second glass plate can be glass plates generally used for windshield glass. For example, glass plates having a visible light transmittance of 80% or less, such as 73% or 76%, such as green glass with high heat insulation properties, can be used. Even when a glass plate with a low visible light transmittance is used, a windshield glass having a visible light transmittance of 70% or more even at the position of the reflective film can be produced by using the reflective film of the present invention.

[0142] The thickness of the glass plate is not particularly limited as long as it is about 0.5 to 5.0 mm, preferably 1.0 to 3.0 mm, and more preferably 2.0 to 2.3 mm. The first glass plate and the second glass plate may be made of the same material or have different thicknesses.

[0143] A windshield glass having a laminated glass structure can be produced by using a known method for producing laminated glass. In general, the laminated glass can be produced by sandwiching an interlayer film for laminated glass between two glass sheets, repeatedly subjecting the interlayer 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.

[0144] A windshield glass having a laminated glass configuration including a reflective film and an interlayer film may, for example, be produced by forming a reflective film on the surface of a glass plate and then using the above-mentioned method for producing laminated glass, or may be produced by using an interlayer film for laminated glass including the above-mentioned reflective film and using the above-mentioned method for producing laminated glass. 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 may be attached to the glass plate with, for example, an adhesive (heat seal layer).

[0145] (Interlayer) The intermediate film 36 prevents glass from penetrating and shattering into the vehicle interior in the event of an accident, and in the example shown in FIG. 3, it bonds the reflective film 10 and the first glass plate 28 together.

[0146] As the interlayer film (interlayer film sheet), any known interlayer film used as an interlayer film (interlayer) in laminated glass can be used. For example, a resin film containing a resin selected from the group consisting of polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer, and chlorine-containing resin can be used. The above-mentioned resin is preferably the main component of the interlayer film. The main component refers to a component that occupies 50% by mass or more of the interlayer film.

[0147] 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 preferred lower limit of the degree of acetalization of the above-mentioned polyvinyl butyral is 40%, the preferred upper limit is 85%, the more preferred lower limit is 60%, and the more preferred upper limit is 75%.

[0148] 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 preferable lower limit of the polymerization degree of the polyvinyl alcohol is 200, and the preferable upper limit is 3000. When the polymerization degree of the polyvinyl alcohol is 200 or more, the penetration resistance of the obtained laminated glass is not easily reduced, and when it is 3000 or less, the moldability of the resin film is good, and the rigidity of the resin film is not too high, and the processability is good. The more preferable lower limit is 500, and the more preferable upper limit is 2000.

[0149] There is also no limitation on the thickness of the intermediate film 36, and the thickness may be set according to the forming material, etc., in the same manner as the intermediate film of a known windshield glass.

[0150] In the windshield glass 24, a heat seal layer 38 is provided between the reflective film 10 and the second glass plate 30, and the reflective film 10 and the first glass plate 28 are bonded together with an intermediate film 36, but the present invention is not limited to this. That is, a heat seal layer may be provided between the reflective film 10 and the first glass plate 28, and an intermediate film may be provided between the reflective film 10 and the second glass plate 30. Alternatively, the windshield glass 24 may not have the intermediate film 36, and the reflective film 10 may be attached to the first glass plate 28 and the reflective film 10 to the second glass plate 30 using a heat seal layer 38.

[0151] (Interlayer including reflective film) The interlayer film for laminated glass containing a reflective film can be formed by laminating the 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. The reflective film and the intermediate film can be bonded to each other by a known bonding method, but it is preferable to use a lamination process. The lamination process is preferably carried out under conditions of heating and pressure to a certain degree so that the laminate and the intermediate film do not peel off after processing. To perform stable lamination, the surface temperature of the interlayer on the bonding side is preferably 50 to 130°C, and 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.

[0152] In addition, when the reflective film has a support (transparent substrate), the support may be peeled off simultaneously with lamination, immediately after lamination, or immediately before lamination. In other words, the reflective film attached to the interlayer film obtained after lamination may not have a support. An example of a method for producing 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 laminated together without the support and the first interlayer film facing each other. Then, the support is peeled off from the reflective film. Furthermore, in a second step, a second interlayer film is laminated to the surface from which the support has been peeled off. This makes it possible to manufacture an interlayer film containing a reflective film that does not have a support. In addition, by using this interlayer film containing a reflective film, a laminated glass in which the reflective film does not have a support can be easily produced. 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, and more preferably 40 to 60°C.

[0153] (Heat seal layer) The heat seal layer (adhesive layer) 38 is, for example, a layer made of a coating type adhesive. In the example shown in Fig. 3, the reflective film 10 is attached to the second glass plate 30 by the heat seal layer 38. In the windshield glass of the present invention, the reflective film 10 may be attached to the second glass plate 30 by an intermediate film instead of the heat seal layer 38. In addition, when the reflective film 10 is small compared to the intermediate film 36 that attaches the first glass plate 28 and the reflective film 10, the reflective film 10 may be attached to the second glass plate 30 by the intermediate film 36.

[0154] There are no limitations on the heat seal layer 38, and any known adhesive made of various types of coating type adhesives can be used as long as it can ensure the necessary transparency for the windshield glass 24 and can bond the reflective film 10 to the glass with the necessary adhesion. The heat seal layer 38 may be made of the same material as the intermediate film 36, such as PVB. Alternatively, the heat seal layer 38 may be made of an acrylate adhesive or the like.

[0155] The heat seal layer 38 may be formed from an adhesive. From the viewpoint of the curing method, adhesives are classified into hot melt type, heat curing type, light curing type, reaction curing type, and pressure sensitive adhesive type that does not require curing. In addition, for any type of adhesive, compounds such as acrylate, urethane, urethane acrylate, epoxy, epoxy acrylate, polyolefin, modified olefin, polypropylene, ethylene vinyl alcohol, vinyl chloride, chloroprene rubber, cyanoacrylate, polyamide, polyimide, polystyrene, and polyvinyl butyral can be used as the material. 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, epoxy acrylate-based, or other material.

[0156] The heat seal layer 38 may be formed using a highly transparent adhesive transfer tape (OCA tape). As the highly transparent adhesive transfer tape, a commercially available product for image display devices, particularly a commercially available product for the surface of the image display part of an image display device, may be used. Examples of commercially available products include adhesive sheets (PD-S1, etc.) manufactured by Panac Corporation and adhesive sheets of the MHM series manufactured by Nichiei Kako Co., Ltd.

[0157] There is also no limitation on the thickness of the heat seal layer 38. Therefore, the thickness may be appropriately set according to the material from which the heat seal layer 38 is formed so as to obtain a sufficient adhesive strength. Here, if the heat seal layer 38 is too thick, it may not be possible to maintain sufficient flatness and attach the reflective film 10 to the first glass plate 28 or the second glass plate 30. In consideration of this point, the thickness of the heat seal layer 38 is preferably 0.1 to 800 μm, and more preferably 0.5 to 400 μm.

[0158] Next, a head-up display (HUD) having the reflective film of the present invention will be described. The head-up display of the present invention is The above-mentioned windshield glass, A head-up display system having a projector that irradiates a projection image light onto the first glass plate side of the windshield glass.

[0159] FIG. 5 shows an example of a head-up display of the present invention. 5 includes a windshield glass 24 and a projector 22. The HUD 20 is used in a vehicle such as a passenger car. The windshield glass 24 has a configuration similar to that of the windshield glass 24 shown in FIG.

[0160] In the HUD 20 using the reflective film 10 of the present invention, the projector 22 emits p-polarized projection light, and the reflective film 10 reflects the p-polarized light to display an image. Specifically, in the reflective film 10, the polarization conversion layer 14 first converts the incident p-polarized projection light into circularly polarized light. Next, the selective reflection layer 11 (cholesteric liquid crystal layer) selectively reflects this circularly polarized light, causing it to re-enter the polarization conversion layer 14. The polarization conversion layer 14 further converts the circularly polarized light into p-polarized light. As a result, the reflective film 10 reflects the incident p-polarized projection light while keeping it as p-polarized light. Therefore, the polarization conversion layer 14 is set to convert the incident p-polarized light into circularly polarized light of the rotation direction reflected by the selective reflection layer 11, depending on the sense of the circularly polarized light selectively reflected by the selective reflection layer 11 (cholesteric liquid crystal layer). That is, when the selective reflection layer 11 selectively reflects right-handed circularly polarized light, the retardation layer is set to convert the incident p-polarized light into right-handed circularly polarized light. Conversely, when the selective reflection layer 11 selectively reflects left-handed circularly polarized light, the retardation layer is set to convert the incident p-polarized light into left-handed circularly polarized light.

[0161] In the HUD 20, the projector 22 preferably irradiates p-polarized projection light onto the windshield glass 24 (second glass plate 30). By making the projection light that the projector 22 irradiates onto the windshield glass 24 p-polarized, it is possible to significantly reduce reflection of the projection light by the second glass plate 30 and the first glass plate 28 of the windshield glass 24, thereby suppressing inconveniences such as the observation of double images. Preferably, the projector 22 projects p-polarized light onto the windshield at the Brewster angle, which eliminates reflection of the light on the second glass plate 30 and the first glass plate 28, allowing for a clearer image to be displayed.

[0162] <Projector> A "projector" is a "device that projects light or an image," and includes a "device that projects a drawn image," and is a device that emits projection light that carries an image to be displayed. In the HUD of the present invention, the projector preferably emits p-polarized projection light. In a HUD, the projector is merely required to be disposed so that p-polarized projection light carrying an image to be displayed can be incident at an oblique angle on the reflective film in the windshield glass.

[0163] 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 via a combiner. Any known projector used in a HUD can be used as the projector as long as it can emit p-polarized projection light. In addition, it is preferable that the projector is one in which the imaging distance of the virtual image, i.e., the imaging position of the virtual image, is variable.

[0164] Methods for changing the imaging distance of a virtual image in a projector include, for example, a method of moving the image generation surface (screen) (see JP 2017-21302 A), a method of switching between multiple optical paths with different optical path lengths (see WO 2015 / 190157 A), a method of changing the optical path length by inserting and / or moving a mirror, a method of changing the focal length by using a lens pair as an imaging lens, a method of moving the projector 22, a method of switching between multiple projectors with different virtual image imaging distances, and a method of using a variable focus lens (see WO 2010 / 116912 A).

[0165] The projector may be one in which the imaging distance of the virtual image can be changed continuously, or one in which the imaging distance of the virtual image can be switched 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 m or more. Therefore, if the projector is capable of continuously changing the imaging distance of the virtual image, it is preferable that the imaging distance of the virtual image can be changed by 1 m or more. By using such a projector, it is preferable that the distance of the driver's line of sight can be appropriately handled even when the driver is driving at a normal speed on an ordinary road and when the driver is driving at a high speed on an expressway.

[0166] (Drawing Device) The drawing device may be a device that itself displays an image, or it may be a light-emitting device that can draw an image. In the imaging device, it is sufficient that the light from the light source is adjusted by an imaging method such as an optical modulator, a laser intensity modulation means, or an optical deflection means for imaging. The imaging device means a device that includes a light source and further includes an optical modulator, a laser intensity modulation means, or an optical deflection means for imaging depending on the imaging method.

[0167] (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. Among 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 have non-continuous emission wavelengths in the visible light range, and are therefore suitable for combination with combiners that use cholesteric liquid crystal layers that exhibit selective reflection in specific wavelength ranges, as described below.

[0168] (Drawing method) The drawing method can be selected according to the light source to be used, and is not particularly limited. Examples of the drawing method include a fluorescent display tube, an LCD (Liquid Crystal Display) method using liquid crystal, an LCOS (Liquid Crystal on Silicon) method, a DLP (registered trademark) (Digital Light Processing) method, and a scanning method using a laser. The drawing method may be a method using a fluorescent display tube integrated with a light source. The LCD method is preferable as the drawing method.

[0169] 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 method 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.

[0170] The scanning method is a method of scanning a light beam on a screen and using the afterimage of the eye to create a contrast, and for example, the descriptions in JP-A-7-270711 and JP-A-2013-228674 can be referred to. In the scanning method using a laser, the luminance-modulated laser beams of each color, for example, red light, green light, and blue light, are bundled into one beam by a multiplexing optical system or a condenser lens, and the beam is scanned by an optical deflection means to be drawn on an intermediate image screen described later. In the scanning method, for example, the luminance modulation of each color of laser light, for example, red light, green light, and blue light, may be performed directly as a change in the intensity of the light source, or may be performed by an external modulator. Examples of the light 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 the scanning method include a random scan method and a raster scan method, and it is preferable to use the raster scan method. In the raster scan method, the laser light can be driven, for example, with a resonant frequency in the horizontal direction and a sawtooth wave in the vertical direction. Since the scanning method does not require a projection lens, it is easy to miniaturize the device.

[0171] The light emitted from the drawing device may be linearly polarized or natural light (unpolarized). In imaging devices using an LCD or LCOS imaging system and imaging devices using a laser light source, the emitted light is essentially linearly polarized. In the case of an imaging device that emits linearly polarized light and that includes light of multiple wavelengths (colors), it is preferable that the polarization direction (transmission axis direction) of the light of the multiple wavelengths is the same. It is known that some commercially available imaging devices have non-uniform polarization directions in the wavelength ranges of red, green, and blue light of the emitted light (see JP 2000-221449 A). Specifically, there is known an example in which the polarization direction of green light is perpendicular to the polarization direction of red light and the polarization direction of blue light. As described above, in the HUD of the present invention, the projection light emitted by the projector is preferably p-polarized light.

[0172] (Intermediate image screen) As mentioned above, the drawing device may use an intermediate image screen. An "intermediate image screen" is a screen on which an image is drawn. That is, the drawing device forms a visible image on the intermediate image screen using light emitted by the drawing device, such as when the light is not yet visible as an image. The image drawn 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 reflection from the intermediate image screen.

[0173] Examples of intermediate image screens include a scattering film, a microlens array, and 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), but the problem of color unevenness can be reduced by using a retardation film having a predetermined phase difference. The intermediate image screen is preferably one that has a function of expanding and transmitting incident light rays, because this allows for the enlarged display of the projected image. An example of such an intermediate image screen is a screen that is configured with a microlens array. Microarray lenses used in HUDs are described in, for example, Japanese Patent Application Laid-Open No. 2012-226303, Japanese Patent Application Laid-Open No. 2010-145745, and Japanese Patent Publication No. 2007-523369. The projector may include a reflector or the like that adjusts the optical path of the projected light formed by the drawing device.

[0174] 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. 5,013134, and JP-A-2006-512622.

[0175] The windshield glass is particularly useful for HUDs that are used in combination with projectors that use lasers, LEDs, OLEDs (organic light-emitting diodes), etc., whose light emission wavelengths are not continuous in the visible light range, as light sources. This is because the central wavelength of the selective reflection of the cholesteric liquid crystal layer can be adjusted to match each emission wavelength. It can also be used for projection of displays such as LCDs (liquid crystal displays) that use polarized display light.

[0176] [Projection light (incident light)] The incident light is preferably incident at an oblique incidence angle of 45° to 70° with respect to the normal to the reflective film. The Brewster angle of the interface between glass with a refractive index of about 1.51 and air with a refractive index of 1 is approximately 56°, and by making p-polarized light incident within the above-mentioned angle range, there is less reflected light from the surface of the windshield glass on the viewing side with respect to the selective reflection layer of the incident light for projected image display, making it possible to display images with little double image effect. It is also preferable that the above-mentioned angle is 50° to 65°. In this case, it is sufficient that the projected image can be observed on the side where the projection light is incident, 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.

[0177] The incident light may be incident from any direction, such as above, below, left, right, etc., on the windshield glass, and may be determined according to 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. Also, the reflective film on the windshield glass is preferably arranged to reflect incident p-polarised light.

[0178] 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. When the light emitted from the projector is not linearly polarized, it may be p-polarized by providing a linear polarizing film (polarizer) on the side of the light emitted from the projector, or it may be p-polarized 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 member that converts the projection light that is not linearly polarized into 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 light in the wavelength ranges of all colors to enter as p-polarized light.

[0179] As described above, the HUD (projector) may be a projection system that allows the virtual image formation position to be changed. By allowing the virtual image formation position to be changed, 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 beyond the windshield glass, 1000 mm or more away from the driver.

[0180] The up-down direction Y of the windshield glass 24 corresponds to the top-to-bottom direction of the vehicle on which the windshield glass 24 is disposed, and is defined as the ground side being the bottom side and the opposite side being the top side. When the windshield glass 24 is disposed on a vehicle, it may be disposed at an angle due to the structure or design, in which case the up-down direction Y is the direction along the surface 25 of the windshield glass 24. The surface 25 is the outer surface of the vehicle.

[0181] The present invention is basically configured as described above. Although the reflective film, windshield glass, and head-up display system (HUD) of the present invention have been described in detail above, the present invention is not limited to the above-mentioned embodiments, and various improvements or modifications may be made without departing from the spirit and scope of the present invention. EXAMPLES

[0182] The features of the present invention will be described in more detail below with reference to examples. The materials, reagents, amounts and ratios of substances, and operations shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the following examples.

[0183] <Preparation of coating solution> (Cholesteric liquid crystal layer forming coating solution) For the coating solutions for forming cholesteric liquid crystal layers (B1, B2, G1 to G5, R1 to R6, IR1 to IR3) having the desired selective reflection central wavelength as shown in Table 1 below, the following components were mixed to prepare coating solutions for forming cholesteric liquid crystal layers having the following compositions. ·Mixture 1 100 parts by mass Fluorine-based horizontal alignment agent 1 (alignment control agent 1) 0.05 parts by weight Fluorine-based horizontal alignment agent 2 (alignment control agent 2) 0.02 parts by weight Right-handed chiral agent LC756 (BASF) Adjusted 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

[0184] [ka]

[0185] [ka]

[0186] [ka]

[0187] Each cholesteric liquid crystal layer-forming coating solution was prepared by adjusting the amount of the right-handed chiral dopant LC756 in the coating solution composition described above. Using each cholesteric liquid crystal layer-forming coating solution, a single cholesteric liquid crystal layer having a thickness of 3 μm was formed on a temporary support in the same manner as in the production of a half mirror described below, and the reflection characteristics of visible light were confirmed. As a result, it was confirmed that all of the produced cholesteric liquid crystal layers were right-handed circularly polarized light reflective layers, and that the selective reflection central wavelengths (central wavelengths) were as shown in Table 1 below.

[0188] (Cholesteric liquid crystal layer forming coating solution 2) For the coating solutions for forming cholesteric liquid crystal layers that form each cholesteric liquid crystal layer (B3, G6, R7, IR4) having a selective reflection center wavelength that is the desired wavelength shown in Table 1 below, the following components were mixed to prepare coating solutions for forming narrow-band cholesteric liquid crystal layers having the following compositions.

[0189] ------------------------------------------------------------------ Coating solution for forming narrow band cholesteric liquid crystal layer ------------------------------------------------------------------ ·Rod-shaped liquid crystal compound 101 55 parts by mass ·Rod-shaped liquid crystal compound 102 30 parts by mass ·Rod-shaped liquid crystal compound 201 13 parts by mass ·Rod-shaped liquid crystal compound 202 2 parts by mass Polymerization initiator IRGACURE OXE01 (BASF) 1.0 parts by mass Alignment control agent 1 0.01 parts by weight Alignment control agent 3 (fluorine-based horizontal alignment agent 3) 0.01 parts by mass Right-handed chiral agent LC756 (BASF) Adjustment to the target selective reflection center wavelength Solvent (methyl ethyl ketone) - Amount that makes the solute concentration 20% by mass ------------------------------------------------------------------

[0190] Rod-shaped liquid crystal compound 101 [ka]

[0191] Rod-shaped liquid crystal compound 102 [ka]

[0192] Rod-shaped liquid crystal compound 201 Rod-shaped liquid crystal compound 202 [ka]

[0193] Orientation control agent 3 [ka]

[0194] Each cholesteric liquid crystal layer-forming coating liquid was prepared by adjusting the formulation amount of the right-handed chiral dopant LC756 in the above-mentioned narrow band cholesteric liquid crystal layer-forming composition. Using each cholesteric liquid crystal layer-forming coating solution, a single cholesteric liquid crystal layer having a thickness of 3 μm was formed on a temporary support in the same manner as in the production of a half mirror described below, and the reflection characteristics of visible light were confirmed. As a result, it was confirmed that all of the produced cholesteric liquid crystal layers were right-handed circularly polarized light reflective layers, and that the selective reflection central wavelengths (central wavelengths) were as shown in Table 1 below.

[0195] [Table 1]

[0196] (Cholesteric liquid crystal layer forming coating solution C1) Regarding the cholesteric liquid crystal layer forming coating solution C1 for forming a cholesteric liquid crystal layer C1 having a plurality of selective reflection center wavelengths, the following components were mixed to prepare the cholesteric liquid crystal layer forming coating solution C1 having the following composition. ·Mixture 1 100 parts by mass Fluorine-based horizontal alignment agent 1 (alignment control agent 1) 0.05 parts by weight Fluorine-based horizontal alignment agent 2 (alignment control agent 2) 0.02 parts by weight · Right-handed chiral agent LC756, tuned to the target wavelength · Right-handed isomerizing chiral agent 1 Adjusted to the target wavelength Polymerization initiator PM7957 1 part by weight Solvent (methyl ethyl ketone) - Amount that makes the solute concentration 20% by mass

[0197] Right-handed isomerizing chiral agent 1 [ka]

[0198] Polymerization initiator PM7957 [ka]

[0199] (Coating solution for forming retardation layer) The following components were mixed to prepare a coating solution 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 weight Fluorine-based horizontal alignment agent 2 (alignment control agent 2) 0.01 parts by weight Polymerization initiator IRGACURE OXE01 (BASF) 1.0 parts by mass Solvent (methyl ethyl ketone) - Amount that makes the solute concentration 20% by mass

[0200] (Polarization conversion layer forming coating solution) The following components were mixed to prepare a coating solution 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 weight Fluorine-based horizontal alignment agent 2 (alignment control agent 2) 0.02 parts by weight 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

[0201] The coating solution for forming the polarization conversion layer was prepared by adjusting the formulation amount of the right-handed chiral agent LC756 in the above-mentioned coating solution composition so that when a cholesteric liquid crystal layer was formed, the desired selective reflection central wavelength λ was obtained. The selective reflection central wavelength λ was determined by measuring a single cholesteric liquid crystal layer having a thickness of 3 μm on a temporary support with 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. Also, in a cholesteric liquid crystal layer, the selective reflection central 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 central wavelength λ / average in-plane refractive index n" (P = λ / n). For this reason, a coating solution for forming a polarization conversion layer was prepared so that the selective reflection central wavelength λ of the cholesteric liquid crystal layer would be the desired wavelength. In the formation of the polarization conversion layer described below, the coating solution for forming the polarization conversion layer was applied to a desired film thickness to form a polarization conversion layer, and the pitch number was determined. Table 2 shows combinations of the pitch number, film thickness, and selective reflection central wavelength λ (central wavelength λ) of the polarization conversion layer targeted for the prepared coating solution for forming the polarization conversion layer.

[0202] [Table 2]

[0203] [Example 1] <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 International Publication No. 2014 / 112575. UV-531 manufactured by Teisei Kako Co., Ltd. was added to the cellulose acylate film as an ultraviolet absorbing agent. The amount added was 3 phr (per hundred resin). The prepared cellulose acylate film was passed through a dielectric heating roll at a temperature of 60° C. to raise the film surface temperature to 40° C. Then, an alkaline solution 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 mixture was then allowed to remain under a steam type far-infrared heater (manufactured by Noritake Co., Limited) heated to 110° C. for 10 seconds. Next, using the same bar coater, pure water was applied at 3 mL / m 2 It was applied. Next, washing with water using a fountain coater and draining with an air knife were repeated three times, and then the film was allowed to stay in a drying zone at 70° C. for 5 seconds and dried to prepare 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.

[0204] ---------------------------------------------------------------------------------- Composition of the alkaline solution ---------------------------------------------------------------------------------- Potassium hydroxide 4.7 parts by weight ·Water 15.7 parts by mass 64.8 parts by weight of isopropanol Surfactant (C 16 H 33 O(CH 2 CH 2 O) 10 H) 1.0 parts by mass Propylene glycol 14.9 parts by weight ----------------------------------------------------------------------------------

[0205] <Formation of alignment film> On the saponified surface of the saponified cellulose acylate film (transparent support), a coating solution for forming an alignment layer having the composition shown below was applied at 24 mL / m using a wire bar coater. 2 The coating was then dried with hot air at 100°C for 120 seconds.

[0206] ---------------------------------------------------------------------------------- Composition of coating solution for forming alignment film ---------------------------------------------------------------------------------- 28 parts by weight of modified polyvinyl alcohol as shown below Citric acid ester (AS3, Sankyo Chemical Co., Ltd.) 1.2 parts by weight Photoinitiator (Irgacure 2959, manufactured by BASF) 0.84 parts by weight Glutaraldehyde 2.8 parts by weight ·Water 699 parts by mass Methanol 226 parts by weight ----------------------------------------------------------------------------------

[0207] (Modified polyvinyl alcohol) [ka]

[0208] <Preparation of reflective film> The cellulose acylate film having the alignment layer formed thereon was used as a support (transparent substrate). One side of the support 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 round trips: 1) in a direction rotated 45° clockwise from the long side of the support.

[0209] A coating solution for forming a retardation layer was applied to the rubbed surface of the alignment film on the support using a wire bar, and then dried. Next, the specimen was placed on a hot plate at 50°C and heated with an electrodeless lamp "D bulb" (60 mW / cm2) 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 1).

[0210] The cholesteric liquid crystal layer forming coating solution (B1) was applied to the surface of the obtained retardation layer at room temperature using a wire bar so that the thickness of the dried film after drying would be 0.3 μm, thereby obtaining a coating layer. The coating layer was dried at room temperature for 30 seconds, and then heated for 2 minutes in an atmosphere at 85° C. Then, in an environment with an oxygen concentration of 1000 ppm or less, it was irradiated with ultraviolet light at 60% output for 6 to 12 seconds using a Fusion D bulb (90 mW / cm lamp) at 60° C. to fix the cholesteric liquid crystal phase, thereby obtaining a cholesteric liquid crystal layer B1 with a thickness of 0.3 μm. Next, the same process was repeated using the cholesteric liquid crystal layer forming coating liquid (G1) on the surface of the obtained cholesteric liquid crystal layer B1 to form a cholesteric liquid crystal layer G1 having a thickness of 0.54 μm. Next, the same process was repeated using the cholesteric liquid crystal layer forming coating liquid (R1) to laminate a cholesteric liquid crystal layer R1 having a thickness of 0.36 μm on the surface of the obtained cholesteric liquid crystal layer G1.

[0211] In this way, a selective reflection layer having three cholesteric liquid crystal layers on the retardation layer was obtained. The reflection spectrum of the selective reflection layer was measured with a spectrophotometer (V-670, manufactured by JASCO Corporation), and a reflection spectrum satisfying requirements (i) to (iii) was obtained. The graph shown in FIG. 2 shows the reflection spectrum of the reflective film of Example 1.

[0212] Next, the coating solution for forming a polarization conversion layer shown in Table 2 was further applied to the surface of the obtained cholesteric liquid crystal layer to the target film thickness shown in Table 2 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.

[0213] [Examples 2 to 5, Comparative Examples 1 to 7] The reflective films were prepared in the same manner as in Example 1, except that the structure of the cholesteric liquid crystal layer in the light-reflecting layer was changed to the layer structure shown in Table 3 below, and each layer had the polarization conversion layer (or retardation layer) shown in Table 2.

[0214] In addition, in Example 3, the cholesteric liquid crystal layers G6, R7, and IR4 were formed on a PET film having a thickness of 100 μm, and then the PET film was peeled off and the cholesteric liquid crystal layer B3 formed on the retardation layer was laminated in order with OCA (MHM-UVC15, manufactured by Nichiei Kako Co., Ltd., thickness 15 μm) to form a selective reflection layer. In addition, in Comparative Examples 1 to 3 and 5, each cholesteric liquid crystal layer was formed on a PET film with a thickness of 100 μm, and then the PET film was peeled off and the resulting layer was laminated with OCA (MHM-UVC15, manufactured by Nichiei Kako Co., Ltd., thickness 15 μm) to form a selective reflection layer.

[0215] In addition, for Comparative Examples 1 to 3, a reflective film was prepared by attaching a quarter-wave plate (Teijin Pure Ace WR-S, retardation 126 nm) to both sides of the selective reflection layer so that the slow axis angles were 45° and −45°, respectively. In addition, for Comparative Examples 5 to 7, a polarization conversion layer was attached to one side of the selective reflection layer, and a ¼ wavelength plate (Teijin Limited: Pure Ace WR-S) was attached to the other side to prepare a reflective film.

[0216] [Table 3]

[0217] [Example 6] A reflective film was produced in the same manner as in Example 1, except that in forming the cholesteric liquid crystal layer, the above-mentioned cholesteric liquid crystal layer forming coating liquid C1 was used to form a cholesteric liquid crystal layer C1 having multiple selective reflection center wavelengths as follows.

[0218] In the same manner as in Example 1, the coating solution C1 for forming a cholesteric liquid crystal layer was applied to the surface of a retardation layer formed on a support (alignment film) at room temperature using a wire bar so that the thickness of the dried film after drying was 1.2 μm, thereby obtaining a coating layer.

[0219] At room temperature, in air, UV light of 365 nm is applied at 30 mJ / cm 2The sample was then irradiated with 365 nm UV light at 60 mJ / cm2 and heated at 85°C for 1 minute. 2 The sample was then irradiated with light and heated at 85°C for 1 minute. After that, the sample was irradiated with light using a Fusion D bulb (90 mW / cm) at 50°C in an environment with an oxygen concentration of 1000 ppm or less. 2 The laminate was irradiated with ultraviolet light from a lamp (not shown) at an output of 60% for 6 to 12 seconds to fix the cholesteric liquid crystal phase, thereby obtaining a cholesteric liquid crystal layer C1.

[0220] A polarization conversion layer was formed on the surface of the formed cholesteric liquid crystal layer C1 in the same manner as in Example 1 to prepare a reflective film.

[0221] <Reflection spectrum measurement> The prepared 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 (V-670, manufactured by JASCO Corporation), P-polarized and S-polarized light were incident from a direction of 5° to the normal direction of the reflective film surface, and the reflection spectrum from 400 nm to 1000 nm was measured. The average value (average reflection spectrum) of the measured reflection spectra of P-polarized light and S-polarized light was calculated.

[0222] 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 reflection spectrum of P-polarized light and the reflection spectrum of S-polarized light is synonymous with the reflection spectrum when natural light is incident.

[0223] From the calculated average reflectance spectrum of P-polarized light and S-polarized light, Calculate the maximum value of natural light reflectance in the wavelength band of 400 nm or more and less than 500 nm, the difference between the maximum and minimum values ​​of the natural light reflectance, and the wavelength band width; Calculate the maximum value of natural light reflectance in the wavelength band of 500 nm or more and less than 600 nm, the difference between the maximum and minimum values ​​of the natural light reflectance, and the wavelength band width; The maximum value of natural light reflectance in the wavelength band from 600nm to 800nm ​​and the wavelength band width were calculated.

[0224] The wavelength bandwidth in the wavelength band of 400 nm or more and less than 500 nm is the width of the region in which the reflectance is higher than the average value of the maximum and minimum reflectance values ​​in the wavelength band of 400 nm or more and less than 500 nm. The wavelength bandwidth in the wavelength band of 500 nm or more and less than 600 nm is the width of the region in which the reflectance is higher than the average value of the maximum and minimum reflectance values ​​in the wavelength band of 530 nm or more and less than 600 nm. Moreover, the wavelength band width of 600 nm or more and 800 nm or less is the width of a region in which the reflectance is higher than the average value of the maximum and minimum reflectance values ​​in the wavelength band from 600 nm to 800 nm. The measurement results are shown in Table 4.

[0225] [Table 4]

[0226] <Making windshield glass> A windshield glass having each of the reflective films prepared above was produced as follows.

[0227] As the first and second glass plates, a first glass plate (manufactured by Central Glass Co., Ltd., FL2, visible light transmittance 90%) having a size of 120 mm in length, 100 mm in width and 2 mm in thickness was prepared. In addition, a PVB film with a thickness of 0.38 mm manufactured by Sekisui Chemical Co., Ltd. was prepared as an intermediate film. The heat seal layer was formed as follows.

[0228] <Preparation of heat seal layer> (Coating solution for forming heat seal layer) The following components were mixed to prepare a coating solution for forming a heat seal layer. PVB sheet piece (S-LEC film, manufactured by Sekisui Chemical Co., Ltd.) 5.0 parts by weight Methanol 90.25 parts by weight Butanol 4.75 parts by mass

[0229] (Formation of heat seal layer) The heat seal layer forming coating liquid was applied to a reflective film (transparent substrate) 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.

[0230] In each of the examples and comparative examples, the reflective film, the first glass plate, the second glass plate, the intermediate film, and the heat seal layer were laminated to have the configuration shown in Table 5 below, and this laminate was held at 90°C and 10 kPa (0.1 atm) for one hour, and then heated in an autoclave (manufactured by Kurihara Seisakusho) at 115°C and 1.3 MPa (13 atm) for 20 minutes to remove air bubbles, thereby obtaining a windshield glass.

[0231] [Table 5]

[0232] [Evaluation of visible light transmittance] Natural light was applied from the second glass plate side at a direction of 0° to the normal direction of the second glass plate, and the transmittance spectrum was measured using a spectrophotometer (V-670, manufactured by JASCO Corporation). According to JIS R3106, the transmittance was calculated and evaluated by multiplying the transmittance by a coefficient corresponding to the visual sensitivity and the emission spectrum of the A light source at wavelengths of 380 to 780 nm in 10 nm increments. The transmittance was evaluated according to the following evaluation criteria.

[0233] Transmittance evaluation criteria A: 82% or more (When laminated glass is formed with green glass, the transmittance is well over 70%) B: 80% or more but less than 82% (When green glass is used to form laminated glass, the transmittance exceeds 70%. This satisfies legal regulations, but manufacturing robustness is low.) C: Less than 80% (When green glass is used to form laminated glass, the transmittance is less than 70%, which does not meet legal regulations)

[0234] [Evaluation of P-polarized light reflectance] P-polarized light was incident from the first glass plate side in a direction of 65° to the normal direction of the first glass plate, and the reflectance spectrum of the specularly reflected light (direction of 65° to the normal direction, on the opposite side to the incident direction in the incident plane) was measured with a spectrophotometer (V-670, manufactured by JASCO Corporation). At this time, the long side direction (vertical direction) of the reflective film was parallel to the transmission axis of the P-polarized light incident on the spectrophotometer. According to JIS R3106, the reflectance of the projected image was calculated by multiplying the reflectance by a coefficient corresponding to the visual sensitivity and the emission spectrum of the D65 light source at wavelengths of 380 to 780 nm in 10 nm increments, and the luminance was evaluated. The luminance was evaluated according to the following evaluation criteria.

[0235] Evaluation criteria for P-polarized reflectance A: 25% or more (Images are visible through the P-polarized reflection system of the HUD, and double images are less likely to be seen) B: 20% to less than 25% (Images can be seen through the P-polarized reflective system of the HUD, but double images are seen.) C: Less than 20% (The image is difficult to see clearly due to the P-polarized reflection system of the HUD, and double images are often seen.)

[0236] [Evaluation of reflected color] Using the same method as for the transmittance, the reflectance was measured at incident angles of 5° and 60° with natural light, and the reflected color tones a* and b* were calculated from the spectrum.

[0237] Evaluation criteria for reflected color ·AA: |a*|≦3 and |b*|≦3 (appears white when white is projected) A: |a*|≦5 and |b*|≦5 (excluding those that fall under AA) (Appears almost white when white is projected) B: |a*|≦7 and |b*|≦7 (excluding those that fall under AA or A) (When projecting white, the image appears slightly colored) C: |a*|≦9 and |b*|≦9 (excluding those that fall into AA, A, or B) (When projecting white, the image appears slightly colored) D: 9<|a*| or 9<|b*| (when white is projected, it appears to be a different color) The results are shown in Table 6.

[0238] [Table 6]

[0239] As shown in Table 6, it is clear that the examples of the present invention provide better results in terms of visible light transmittance, P-polarized light reflectance (brightness), and reflected color than the comparative examples. Comparative Example 1 did not satisfy the requirement (i) and had a uniformly high natural light reflectance, resulting in a low visible light transmittance. Comparative Example 2 did not satisfy requirements (i) to (iii). The difference between the maximum and minimum natural light reflectance values ​​in requirements (i) and (ii) was less than 3%, and the total wavelength bandwidth in requirement (iii) was less than 120 nm, resulting in low visible light transmittance and low P-polarized reflectance. Comparative Example 3 did not satisfy requirements (i) and (ii), and the difference between the maximum and minimum natural light reflectance values ​​in requirements (i) and (ii) was less than 3%, resulting in low P-polarized reflectance. Comparative Example 4 did not satisfy requirement (i), and in addition, the total value of the wavelength band width in requirement (iii) was less than 120 nm, resulting in poor reflected color at an incident angle of 5°. Comparative Example 5 did not satisfy the requirements (i) and (ii), resulting in poor reflected color at an incident angle of 5°. In Comparative Example 6, the reflectance in the requirement (i) was high, and the requirement (ii) was not satisfied, so that the visible light transmittance was low and the reflected color at an incident angle of 60° was poor. In Comparative Example 7, the total value of the wavelength band width in requirement (iii) was less than 120 nm, and therefore the reflection color at an incident angle of 5° was poor.

[0240] Comparing Example 1 and Example 3, it is evident that it is preferable for the cholesteric liquid crystal layer of the selective reflection layer to be in direct contact with the substrate. Comparing Example 1 with Examples 4 and 5, it is apparent that the total thickness of the selective reflection layer is preferably 2.0 μm or less. It is understood from Example 6 that the cholesteric liquid crystal layer may have a plurality of selective reflection center wavelengths. From the above results, the effects of the present invention are clear. [Industrial Applicability]

[0241] The present invention can be suitably used for in-vehicle head-up display systems (HUDs), etc. [Explanation of symbols]

[0242] 10 Reflective film 11 Selective reflection layer 12R, 12G, 12B Cholesteric Liquid Crystal Layer 14 Polarization conversion layer 16 Retardation layer 18 Transparent base material 20 Head-up Display System (HUD) 22 Projector 24 Windshield Glass 28 First Glass Pane 30 Second Glass Pane 36 Interlayer 38 Adhesive layer D. Driver Y vertical direction

Claims

1. a selective reflection layer having a cholesteric liquid crystal layer formed by fixing a cholesteric liquid crystal phase; The selective reflection layer of the reflective film satisfies all of the following requirements (i) to (iii): (i) In the wavelength range of 400 nm or more and less than 500 nm, the maximum value of the natural light reflectance is 10% to 25%, the difference between the maximum and minimum values ​​of the natural light reflectance is 3% or more, and the total value of the wavelength bandwidth of the region higher than the average value of the maximum and minimum values ​​of the natural light reflectance is 20 nm to 80 nm. (ii) In the wavelength range of 500 nm or more and less than 600 nm, the maximum value of the natural light reflectance is 10% to 25%, the difference between the maximum and minimum values ​​of the natural light reflectance is 3% or more, and the total value of the wavelength bandwidth of the region higher than the average value of the maximum and minimum values ​​of the natural light reflectance is 20 nm to 80 nm. (iii) In the wavelength range of 600 nm or more and 800 nm or less, the maximum value of the natural light reflectance is 10% to 25%, and the total value of the wavelength bandwidth of the region higher than the average value of the maximum and minimum values ​​of the natural light reflectance is 120 nm or more.

2. the selective reflection layer has two or more cholesteric liquid crystal layers each having a different selective reflection central wavelength, The reflective film of claim 1 , wherein the cholesteric liquid crystal layers are in contact with each other.

3. The reflective film according to claim 1 or 2, wherein the selective reflection layer comprises a cholesteric liquid crystal layer having two or more selective reflection center wavelengths.

4. The reflective film according to any one of claims 1 to 3, wherein the selective reflection layer has a total thickness of 0.4 µm to 2.0 µm.

5. The reflective film according to any one of claims 1 to 4, which reflects linearly polarized light.

6. The reflective film according to any one of claims 1 to 5, comprising a retardation layer, the selective reflection layer, and a polarization conversion layer in this order.

7. the polarization conversion layer is formed by fixing a helical orientation structure of a liquid crystal compound, 7. The reflective film according to claim 6, wherein the pitch number x of the helical orientation structure in the polarization conversion layer and the film thickness y (μm) of the polarization conversion layer satisfy all of the following formulas (a) to (c). 0.1≦x≦1.0... Formula (a) 0.5≦y≦3.0... Formula (b) 3000≦(1560×y) / x≦50000... Formula (c)

8. A windshield glass comprising a first glass plate, the reflective film according to any one of claims 1 to 7, and a second glass plate, in this order.

9. The first glass plate and the second glass plate are curved glass plates, The windshield glass according to claim 8 , wherein the reflective film and the second glass plate are provided on a convex surface side of the first glass plate.

10. The reflective film has a polarization conversion layer, 10. The windshield glass according to claim 9, wherein the polarization conversion layer and the selective reflection layer are disposed in this order from the convex surface side of the first glass plate.

11. The reflective film has a retardation layer, the retardation layer is disposed between the selective reflection layer and the second glass plate, The retardation layer has a front retardation of 50 nm to 160 nm at a wavelength of 550 nm, and a slow axis angle of 10° to 50° or −50° to −10° when a direction corresponding to a vertical upward direction of a surface of the first glass plate when the windshield glass is mounted on a vehicle is defined as 0°. The windshield glass according to claim 9 or 10.

12. The reflective film has a transparent substrate, The windshield glass according to any one of claims 9 to 11, wherein the transparent base material is disposed on the second glass plate side.

13. 13. The windshield glass of claim 12, wherein the transparent substrate comprises an ultraviolet light absorber.

14. The windshield glass according to any one of claims 8 to 13, further comprising an intermediate film between the first glass plate and the reflective film.

15. The windshield glass according to any one of claims 8 to 14, further comprising a heat seal layer between the reflective film and the second glass plate.

16. A windshield glass according to any one of claims 9 to 15, a projector that irradiates projection light onto the first glass plate side of the windshield glass.

17. The head-up display system of claim 16 , wherein the projector emits p-polarized projection light.

Images