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WO2024195716A1 - Film réfléchissant, verre de pare-brise et système d'affichage tête haute - Google Patents

Film réfléchissant, verre de pare-brise et système d'affichage tête haute Download PDF

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Publication number
WO2024195716A1
WO2024195716A1 PCT/JP2024/010195 JP2024010195W WO2024195716A1 WO 2024195716 A1 WO2024195716 A1 WO 2024195716A1 JP 2024010195 W JP2024010195 W JP 2024010195W WO 2024195716 A1 WO2024195716 A1 WO 2024195716A1
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WIPO (PCT)
Prior art keywords
liquid crystal
less
layer
reflective film
light
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/JP2024/010195
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English (en)
Japanese (ja)
Inventor
昭裕 安西
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Fujifilm Corp
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Fujifilm Corp
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Application filed by Fujifilm Corp filed Critical Fujifilm Corp
Priority to JP2025508388A priority Critical patent/JPWO2024195716A1/ja
Publication of WO2024195716A1 publication Critical patent/WO2024195716A1/fr
Anticipated expiration legal-status Critical
Pending legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60J—WINDOWS, WINDSCREENS, NON-FIXED ROOFS, DOORS, OR SIMILAR DEVICES FOR VEHICLES; REMOVABLE EXTERNAL PROTECTIVE COVERINGS SPECIALLY ADAPTED FOR VEHICLES
    • B60J1/00—Windows; Windscreens; Accessories therefor
    • B60J1/02—Windows; Windscreens; Accessories therefor arranged at the vehicle front, e.g. structure of the glazing, mounting of the glazing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60K—ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES
    • B60K35/00—Instruments specially adapted for vehicles; Arrangement of instruments in or on vehicles
    • B60K35/20—Output arrangements, i.e. from vehicle to user, associated with vehicle functions or specially adapted therefor
    • B60K35/21—Output arrangements, i.e. from vehicle to user, associated with vehicle functions or specially adapted therefor using visual output, e.g. blinking lights or matrix displays
    • B60K35/23—Head-up displays [HUD]
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/01—Head-up displays
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/20—Filters
    • G02B5/26—Reflecting filters
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements

Definitions

  • 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.
  • a virtual image including 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 ahead, without having to move his or her line of sight significantly. Therefore, when using a head-up display system, it is expected that a driver can drive more safely while obtaining various pieces of information.
  • 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.
  • legal transmittance 70% or more and to bring the appearance color closer to transparency, it has been considered to lower the reflectance in the past.
  • the reflectance is lowered too much, the brightness of the displayed image (projected image) decreases, resulting in poor visibility.
  • Patent Document 2 proposes a reflective film with good brightness, external color, and transmittance, but there is a demand to further improve the visibility of red displays that indicate alerts in image content, in other words, to expand the color gamut of the image display.
  • the objective of the present invention is to provide a reflective film, windshield glass, and head-up display system that have high visible light transmittance, a wide color gamut of reflected light, high brightness of the displayed image, and good transparency of the appearance color.
  • the present invention solves this problem by making the reflectance steeper in a specific wavelength range, and increasing the reflectance while maintaining the transmittance. Specifically, this is achieved by the following means.
  • Requirement (ii) In the wavelength range of 660 nm or more and less than 720 nm, the maximum value of natural light reflectance is 10% or more and less than 30%, the natural light reflectance has a maximum value, and the half-value width of the reflectance at the maximum value is 10 nm or more and less than 80 nm.
  • Requirement (iii) In the wavelength range of 760 nm or more and less than 900 nm, the maximum value of natural light reflectance is 10% or more and less than 35%, the natural light reflectance has a maximum value, and the half-value width of the reflectance around the maximum value is 10 nm or more.
  • the natural light reflectance has a maximum value in the wavelength range of 380 nm or more and less than 480 nm, and the maximum value of the natural light reflectance is 10% or more and less than 25%.
  • the natural light reflectance has a maximum value in the wavelength range of 510 nm or more and less than 540 nm, and the maximum value of the natural light reflectance is 10% or more and less than 20%.
  • the polarization conversion layer is formed by fixing a helical orientation structure of a liquid crystal compound,
  • the reflective film according to [6] in which the pitch number x of the helical orientation structure in the polarization conversion layer and the film thickness y ( ⁇ m) 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...
  • a windshield glass comprising a first glass plate, the reflective film according to [1] or [2], and a second glass plate, in this order.
  • the first glass plate and the second glass plate are curved glass plates, The windshield glass according to [8], further comprising a reflective film and a second glass plate provided on the convex side of the first glass plate.
  • 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.
  • the reflective film has a transparent substrate, The windshield glass according to [8], wherein the transparent substrate is disposed on the second glass plate side.
  • the windshield glass according to [11], wherein the transparent substrate contains an ultraviolet absorbing agent.
  • a curved glass in which the first glass plate is disposed on the inside of a vehicle [16] The windshield glass according to [8], wherein a reflective film is provided on the concave side of the first glass plate.
  • the projector emits p-polarized projection image light.
  • the present invention provides a reflective film, windshield glass, and head-up display system that have high visible light transmittance, a wide color gamut of reflected light, high brightness of the displayed image, and good transparency of the appearance color.
  • FIG. 2 is a schematic diagram showing an example of the reflective film of the present invention.
  • 1 is a graph showing the relationship between wavelength and natural light reflectance in Example 1 of the present invention and Comparative Example 1.
  • FIG. 1 is a schematic diagram showing an example of a windshield glass having a reflective film of the present invention.
  • FIG. 1 is a schematic diagram showing an example of a head-up display having a reflective film of the present invention.
  • 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.
  • angle 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.
  • 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. In addition, although not limited thereto, 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.
  • B blue
  • G green
  • R red
  • the “visible light transmittance” is the A-light source visible light transmittance defined in JIS (Japanese Industrial Standards) R 3212:2015 (Testing method for automotive safety glass). That is, the transmittance is determined by measuring the transmittance at each wavelength in the range of 380 to 780 nm using an A-light source with a spectrophotometer, 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.
  • CIE Commission Internationale de Illumination
  • P-polarized light refers to 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 surface of a windshield glass) and includes the incident and reflected light rays.
  • the vibration plane of the electric field vector is parallel to the plane of incidence.
  • the front phase difference is a value measured using an AxoScan manufactured by Axometrics. Unless otherwise specified, the measurement wavelength is 550 nm.
  • the front phase difference can also be measured using a 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.
  • 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 having two or more colors, or full-color images.
  • the reflective film of the present invention has a selective reflection layer, and the selective reflection layer satisfies all of the following requirements (i) to (iii).
  • Requirement (i) In the wavelength range of 560 nm or more and less than 610 nm, the maximum value of natural light reflectance is 10% or more and less than 25%, the natural light reflectance has a maximum value, and the half-value width of the reflectance at the maximum value is 10 nm or more and less than 80 nm.
  • Requirement (ii) In the wavelength range of 660 nm or more and less than 720 nm, the maximum value of natural light reflectance is 10% or more and less than 30%, the natural light reflectance has a maximum value, and the half-value width of the reflectance at the maximum value is 10 nm or more and less than 80 nm.
  • Requirement (iii) In the wavelength range of 760 nm or more and less than 900 nm, the maximum value of natural light reflectance is 10% or more and less than 35%, the natural light reflectance has a maximum value, and the half-value width of the reflectance around the maximum value is 10 nm or more.
  • FIG. 1 is a schematic diagram showing an example of a 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.
  • 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.
  • 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.
  • each cholesteric liquid crystal layer is in direct contact with any of the other cholesteric liquid crystal layers.
  • the cholesteric liquid crystal layers are composed of three types of layers, red, green, and blue, but they may be of other colors having different selected central wavelengths, and the number of cholesteric liquid crystal layers may be three or more, or three or less.
  • a cholesteric liquid crystal layer is a layer in which liquid crystal compounds are fixed in a helical oriented state of the cholesteric liquid crystal phase, and it reflects light with a selective reflection center wavelength that corresponds to the pitch of the helical structure, and transmits light in other wavelength ranges.
  • cholesteric liquid crystal layers exhibit selective reflectivity for either left-handed or right-handed circularly polarized light at specific wavelengths.
  • the selective reflection layer satisfies all of the following requirements (i) to (iii).
  • Requirement (i) In the wavelength range of 560 nm or more and less than 610 nm, the maximum value of natural light reflectance is 10% or more and less than 25%, the natural light reflectance has a maximum value, and the half-value width of the reflectance at the maximum value is 10 nm or more and less than 80 nm.
  • Requirement (ii) In the wavelength range of 660 nm or more and less than 720 nm, the maximum value of natural light reflectance is 10% or more and less than 30%, the natural light reflectance has a maximum value, and the half-value width of the reflectance at the maximum value is 10 nm or more and less than 80 nm.
  • Requirement (iii) In the wavelength range of 760 nm or more and less than 900 nm, the maximum value of natural light reflectance is 10% or more and less than 35%, the natural light reflectance has a maximum value, and the half-value width of the reflectance around the maximum value is 10 nm or more.
  • the reflected wavelength and reflectance can be adjusted by the selective reflection center wavelength and thickness (helical pitch number) of the cholesteric liquid crystal layer.
  • Figure 2 shows an example of a natural light reflection spectrum that satisfies the above requirements (i) to (iii).
  • the graph shown by the solid line in Figure 2 is an example of a natural light reflection spectrum for the reflective film of Example 1, which will be described later.
  • the spectrum shown by the solid line in Figure 2 has a maximum natural light reflectance (maximum value) at a wavelength of about 590 nm in the wavelength range of 560 nm or more and less than 610 nm, and this value is approximately 18%, which is in the range of 10% to 25%.
  • the half-width of the spectrum with a peak at a wavelength of 590 nm is 51 nm, which is in the range of 10 to 80 nm. Therefore, the spectrum shown by the solid line in Figure 2 satisfies requirement (i).
  • the spectrum shown by the solid line in Figure 2 has a maximum natural light reflectance (maximum value) at a wavelength of about 690 nm in the wavelength range of 660 nm or more and less than 720 nm, and this value is about 28%, which is in the range of 10% to 30%.
  • the half-width of the spectrum with a peak at a wavelength of 590 nm is 35 nm, which is in the range of 10 to 80 nm. Therefore, the spectrum shown by the solid line in Figure 2 satisfies requirement (ii).
  • the spectrum shown by the solid line in Figure 2 has a maximum natural light reflectance (maximum value) at a wavelength of about 795 nm in the wavelength range of 760 nm or more and less than 900 nm, and this value is about 27%, which is in the range of 10% to 35%.
  • the half-width of the spectrum with a peak at a wavelength of 795 nm is 42 nm, which is in the range of 10 to 80 nm. Therefore, the spectrum shown by the solid line in Figure 2 satisfies requirement (iii).
  • in-vehicle head-up display systems are required to have a transmittance that meets or exceeds legal regulations, and an external color that is transparent when viewed from various angles from the standpoint of design.
  • legal transmittance 70% or more and bring the external color closer to transparency (white)
  • the conventional approach has been to lower the reflectance.
  • lowering the reflectance too much reduces the brightness of the displayed image (projected image), resulting in poor visibility.
  • the reflective film of the present invention can improve the transparency of the appearance color by setting the maximum natural light reflectance at wavelengths of 560 nm or more and less than 610 nm to a range of 10% to 25%.
  • the reflectance at around 550 nm of luminosity is important. Therefore, the transmittance can be ensured by setting the maximum natural light reflectance at wavelengths of 560 nm or more and less than 610 nm to 25% or less.
  • the reflective film of the present invention has a maximum natural light reflectance at wavelengths of 660 nm or more and less than 720 nm of 10% to 30%, and can improve the brightness of the displayed image.
  • the color of the image becomes blue to green only when the reflection is at wavelengths of 560 nm or more and less than 610 nm, and when the reflection is at wavelengths of 660 nm or more and less than 720 nm.
  • the reflective film of the present invention has a maximum natural light reflectance of 10% to 35% at wavelengths of 760 nm or more and less than 900 nm, thereby improving the transparency of the color when viewed from an oblique direction (incident angle of 65°) and widening the display color gamut of reflected light, thereby making the image color closer to the original image.
  • wavelength bands with low reflectance are formed in each of the wavelength bands of 560 nm or more and less than 610 nm and 660 nm or more and less than 720 nm, thereby improving the transmittance.
  • reducing the half-width in the wavelength region of 660 nm or more and less than 720 nm it is possible to increase the intensity of the reflectance while maintaining the transmittance, thereby improving the brightness of the displayed image.
  • the maximum natural light reflectance at 560 nm or more and less than 610 nm is preferably 11% to 24%, and more preferably 12% to 23%.
  • the maximum natural light reflectance in the range of 660 nm or more and less than 720 nm is preferably 16% to 29%, and more preferably 19% to 29%.
  • the maximum natural light reflectance in the range of 760 nm or more and less than 900 nm is preferably 15% to 34%, and more preferably 18% to 33%.
  • the half-width of the reflection peak is determined as follows. In each wavelength band, the peak at which the reflectance is greatest is taken as the maximum value, and the minimum values of reflectance on the short wavelength side and long wavelength side close to the maximum reflectance peak are found, the lower of which is taken as the minimum value. The average of the maximum and minimum values is found, and the wavelength band width at which the reflectance is equal to or greater than this average value is taken as the half-value width.
  • the spectrum shown by the solid line in Figure 2 has a maximum peak of natural light reflectance near 590 nm in the wavelength range of 560 nm or more and less than 610 nm, with a value of approximately 18%. Furthermore, among the minimum values close to this peak, the minimum value on the long wavelength side (near 640 nm) is lower at approximately 12%. The average value of the maximum and minimum values is 15%, and the wavelength bandwidth (half-width) where the reflectance at the maximum peak is 15% or more is approximately 51 nm.
  • the spectrum shown by the solid line in Figure 2 has a maximum peak of natural light reflectance near 690 nm in the wavelength range of 660 nm or more and less than 720 nm, with a value of approximately 28%. Furthermore, of the minimum values close to this peak, the minimum value on the long wavelength side (near 745 nm) is lower, at approximately 9%. The average value of the maximum and minimum values is 18.5%, and the wavelength bandwidth (half-width) where the reflectance at the maximum peak is 18.5% or more is approximately 35 nm.
  • the spectrum shown by the solid line in Figure 2 has a maximum peak of natural light reflectance near 795 nm in the wavelength range of 760 nm or more and less than 900 nm, with a value of approximately 27%. Furthermore, of the minimum values close to this peak, the minimum value on the short wavelength side (near 745 nm) is lower, at approximately 9%. The average value of the maximum and minimum values is 18%, and the wavelength bandwidth (half-width) where the reflectance at the maximum peak is 18% or more is approximately 42 nm.
  • the difference between the reflection peak and the minimum reflectance value on the shorter wavelength side of the reflection peak and the difference between the reflection peak and the minimum reflectance value on the longer wavelength side of the reflection peak is preferably 3% or more, more preferably 4% or more, and even more preferably 5% or more.
  • the spectrum shown by the solid line in Figure 2 has a reflection peak near a wavelength of 590 nm in the wavelength range of 560 nm or more and less than 610 nm, with a value of approximately 18%, and the minimum value on the short wavelength side of this reflection peak is approximately 14.5% at 560 nm, and the minimum value on the long wavelength side is approximately 16% at 610 nm. Therefore, the difference in reflectance between the reflection peak and the minimum value is 3.5% and 2%, respectively.
  • the spectrum shown by the solid line in Figure 2 has a reflection peak near a wavelength of 690 nm in the wavelength range of 660 nm or more and less than 720 nm, with a value of approximately 28%.
  • the minimum value on the short wavelength side of this reflection peak is approximately 16% at 660 nm, and the minimum value on the long wavelength side is approximately 11.5% at 720 nm. Therefore, the difference in reflectance between the reflection peak and the minimum value is 12% and 16.5%, respectively.
  • the spectrum shown by the solid line in Figure 2 has a reflection peak near a wavelength of 795 nm in the wavelength range of 760 nm or more and less than 900 nm, with a value of approximately 27%.
  • the minimum value on the short wavelength side of this reflection peak is approximately 10.5% at 760 nm, and the minimum value on the long wavelength side is approximately 16% near 835 nm. Therefore, the difference in reflectance between the reflection peak and the minimum value is 6.5% and 11%, respectively.
  • the spectrum shown by the solid line in Figure 2 is an example in which the maximum value (peak) in each wavelength range coincides with the maximum value, but this is not limiting, and the maximum value (peak) may be different, but it is preferable that the maximum value (peak) coincides with the maximum value.
  • the maximum value of natural light reflectance in the wavelength range of 660 nm or more and less than 720 nm, and the maximum value of natural light reflectance in the wavelength range of 760 nm or more and less than 900 nm are higher than the maximum value of natural light reflectance in the wavelength range of 560 nm or more and less than 610 nm.
  • the maximum value of the natural light reflectance in the wavelength range of 760 nm or more and less than 900 nm is close to the maximum value of the natural light reflectance in the wavelength range of 560 nm or more and less than 610 nm. This makes it possible to improve the luminance of a displayed image while maintaining a high visible light transmittance, and also to improve the transparency of the color of the displayed image.
  • the selective reflection layer can further improve the color tone of the appearance if it satisfies the following requirement (iv) and/or requirement (v). Therefore, when the color tone of the appearance is improved within the range where the transmittance is satisfied, the requirement is appropriately reflected in the layer structure.
  • Requirement (iv) The natural light reflectance has a maximum value in the wavelength range of 380 nm or more and less than 480 nm, and the maximum value of the natural light reflectance is 10% or more and less than 25%.
  • Requirement (v) The natural light reflectance has a maximum value in the wavelength range of 510 nm or more and less than 540 nm, and the maximum value of the natural light reflectance is 10% or more and less than 20%.
  • the selective reflection layer has two or more cholesteric liquid crystal layers with different selective reflection center wavelengths. It is also preferable that each cholesteric liquid crystal layer is in direct contact with any other cholesteric liquid crystal layer.
  • cholesteric liquid crystal layer 12R having a selective reflection center wavelength in the red wavelength region and cholesteric liquid crystal layer 12G having a selective reflection center wavelength in the green wavelength region are in contact with each other, and cholesteric liquid crystal layer 12G having a selective reflection center wavelength in the green wavelength region and cholesteric liquid crystal layer 12B having a selective reflection center wavelength in the blue wavelength region are in contact with each other.
  • the thickness between the layers becomes thicker, making it difficult to obtain the effect of interference of the light reflected by each cholesteric liquid crystal layer.
  • the wavelength band width can be narrowed by the effect of interference of the light reflected by each cholesteric liquid crystal layer.
  • 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 pronounced.
  • the cholesteric liquid crystal layers are not limited to being in direct contact with each other, but may be stacked via an adhesive layer or the like.
  • each cholesteric liquid crystal layer may have at least one selective reflection center wavelength, but at least one of the cholesteric liquid crystal layers may have two or more selective reflection center wavelengths.
  • a cholesteric liquid crystal layer having two or more selective reflection center wavelengths is achieved by a helical structure in which the helical pitch changes in the thickness direction.
  • the reflective film of the present invention preferably reflects linearly polarized light.
  • 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.
  • 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.
  • the polarization conversion layer exhibits optical rotation and birefringence for visible light, and converts the polarization state of incident light.
  • 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.
  • 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.
  • 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 .
  • the polarization conversion layer 14 has the function of optically compensating for light (s-polarized light) entering from the outside of the windshield glass (outside the vehicle), and optical compensation by the polarization conversion layer 14 can improve suitability for polarized sunglasses.
  • the reflective film of the present invention may have a polarization conversion layer on both sides of the selective reflection layer 11, or may have a retardation layer on both sides.
  • 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 that is reflected by the cholesteric liquid crystal layer of the selective reflection layer 11.
  • 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.
  • Windshield glass refers to the window glass and windshield glass of vehicles such as cars and trains, airplanes, ships, motorcycles, and playground equipment. Windshield glass is preferably used as the windshield and windshield glass located forward in the direction of travel of the vehicle.
  • FIG. 3 shows an example of a windshield glass.
  • the windshield glass 24 shown in FIG. 3 includes a first glass plate 28, an intermediate film 36, a reflective film 10, a heat seal layer 38, and a second glass plate 30, in this order.
  • 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.
  • the example shown in FIG. 3 has the polarization conversion layer 14 and the selective reflection layer 11 arranged in this order from the convex side of the first glass plate 28.
  • the retardation layer 16 is arranged between the selective reflection layer 11 and the second glass plate 30.
  • 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.
  • 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.
  • the windshield glass may be, for example, flat, or may be a three-dimensional shape with a curved surface such as a concave or convex surface.
  • the direction that is normally up during use, and the side that is visible, such as the observer side, the driver's side, and the inside of the vehicle can be specified.
  • the reflective film of the present invention 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, i.e., on the concave side of the first glass plate.
  • 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.
  • 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).
  • 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.
  • the selective reflection layer has a cholesteric liquid crystal layer and provides reflection that satisfies the above-mentioned requirements (i) to (iii).
  • 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.
  • the polymerizable liquid crystal compound may be polymerized by a curing reaction and no longer have liquid crystallinity.
  • the selective reflection central wavelength can be adjusted by adjusting the n value and/or the P value.
  • the pitch P of the helical structure (one helix pitch) is, in other words, the length in the helical axis direction corresponding to one turn of the helix, i.e., the length in the helical axis direction along which the director (the long axis direction in the case of rod-shaped liquid crystals) of the liquid crystal compound constituting the cholesteric liquid crystal phase rotates 360°.
  • the helical axis direction of a normal cholesteric liquid crystal layer coincides with the thickness direction of the cholesteric liquid crystal layer.
  • the selective reflection central wavelength and half width of the cholesteric liquid crystal layer can be determined, for example, as follows.
  • V-670 a spectrophotometer
  • a peak of reduced transmittance is observed in the selective reflection band. If the value of the shorter wavelength side of the two wavelengths that have an intermediate (average) transmittance between the minimum transmittance of this peak and the transmittance before the decrease is ⁇ l (nm) and the value of the longer wavelength side is ⁇ h (nm), the selective reflection central wavelength ⁇ and half width ⁇ can be expressed by the following formula.
  • 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.
  • 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.
  • the light is also obliquely incident on the cholesteric liquid crystal layer constituting the selective reflection layer 11 of the reflective film 10.
  • 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°.
  • the reflected wavelength is shifted to the short wavelength side.
  • a cholesteric liquid crystal layer having a selective reflection central wavelength of wavelength ⁇ when a light ray passes through the cholesteric liquid crystal layer at an angle of ⁇ 2 with respect to the normal direction of the cholesteric liquid crystal layer (the helical axis direction of the cholesteric liquid crystal layer), the selective reflection central wavelength is defined as wavelength ⁇ d.
  • a cholesteric liquid crystal layer having a central wavelength of selective reflection in the range of 660 to 720 nm can reflect projected light in the range of 535 to 647 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.
  • 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 using 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.
  • 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.
  • 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.
  • 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 exhibit selective reflection in the same or overlapping wavelength ranges do not include cholesteric liquid crystal layers with different helical senses. This is to avoid the transmittance in a specific wavelength range decreasing to, for example, less than 50%.
  • ⁇ n can be adjusted by adjusting the type or mixing ratio of the polymerizable liquid crystal compound, or by controlling the temperature during alignment fixing.
  • a plurality of cholesteric liquid crystal layers having the same pitch P and the same helical sense may be laminated. By laminating cholesteric liquid crystal layers having the same pitch P and the same helical sense, it is possible to increase the circular polarization selectivity at a specific wavelength.
  • a cholesteric liquid crystal layer prepared separately may be stacked using an adhesive or the like, or a liquid crystal composition containing a polymerizable liquid crystal compound or the like may be directly applied to the surface of a previous cholesteric liquid crystal layer formed by the method described below, and the alignment and fixation steps may be repeated, the latter being preferred.
  • 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.
  • the thickness of the cholesteric liquid crystal layer is preferably 0.5 to 10 ⁇ m, more preferably 1.0 to 8.0 ⁇ m, and even more preferably 1.5 to 6.0 ⁇ m.
  • 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.
  • the polymerizable liquid crystal compound may be a rod-shaped liquid crystal compound or a discotic liquid crystal compound, but is preferably a rod-shaped liquid crystal compound.
  • rod-shaped polymerizable liquid crystal compounds that form a cholesteric liquid crystal layer include rod-shaped nematic liquid crystal compounds.
  • rod-shaped nematic liquid crystal compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, and benzoic acid esters.
  • liquid crystal compounds include cyclohexane carboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes, and alkenylcyclohexylbenzonitriles.
  • a polymer liquid crystal compound can be used.
  • a polymerizable liquid crystal compound can be obtained by introducing a polymerizable group into a liquid crystal compound.
  • the polymerizable group include an unsaturated polymerizable group, an epoxy group, and an aziridinyl group, with an unsaturated polymerizable group being preferred, and an ethylenically unsaturated polymerizable group being particularly preferred.
  • 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 in one molecule is preferably 1 to 6, more preferably 1 to 3.
  • the polymerizable liquid crystal compound include compounds described in Makromol. Chem., Vol. 190, p. 2255 (1989), Advanced Materials Vol.
  • the amount of the polymerizable liquid crystal compound added to the liquid crystal composition is preferably 80 to 99.9% by mass, more preferably 85 to 99.5% by mass, and particularly preferably 90 to 99% by mass, based on the solid content mass of the liquid crystal composition (mass excluding the solvent).
  • the cholesteric liquid crystal layer may have a low ⁇ n.
  • a low ⁇ n cholesteric liquid crystal layer can be formed using a low ⁇ n polymerizable liquid crystal compound.
  • the low ⁇ n polymerizable liquid crystal compound is described in detail below.
  • a cholesteric liquid crystal phase is formed by using a low ⁇ n polymerizable liquid crystal compound, and this is fixed into a film, thereby obtaining a narrow-band selective reflection layer.
  • low ⁇ n polymerizable liquid crystal compounds are:
  • the liquid crystal composition that can provide a selective reflection layer having a small half-width include the compounds described in WO2015/115390, WO2015/147243, WO2016/035873, JP2015-163596A, and JP2016-053149A. Please also refer to the description in WO2016/047648.
  • liquid crystal compound is a polymerizable compound represented by the following formula (I) described in WO2016/047648.
  • A represents a phenylene group which may have a substituent or a trans-1,4-cyclohexylene group which may have a substituent
  • m represents an integer from 3 to 12;
  • Sp 1 and Sp 2 each independently represent a single bond, a linear or branched alkylene group having 1 to 20 carbon atoms, or a linear or branched alkylene group having 1 to 20 carbon atoms in which one or more -CH 2 - are -O-, -S-,
  • the phenylene group is preferably a 1,4-phenylene group.
  • the substituent is not particularly limited, and examples thereof include a substituent selected from the group consisting of an alkyl group, a cycloalkyl group, an alkoxy group, an alkyl ether group, an amide group, an amino group, a halogen atom, and a group formed by combining two or more of the above-mentioned substituents.
  • the phenylene group and the trans-1,4-cyclohexylene group may have 1 to 4 substituents.
  • the two or more substituents may be the same or different from each other.
  • 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.
  • alkyl group also applies to alkoxy groups containing an alkyl group.
  • Specific examples of the alkylene group include divalent groups obtained by removing any one hydrogen atom from each of the above alkyl group examples.
  • Examples of halogen atoms include fluorine, chlorine, bromine, and iodine atoms.
  • the number of carbon atoms in the cycloalkyl group is preferably 3 to 20, more preferably 5 or more, and preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less.
  • Examples of cycloalkyl groups include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl groups.
  • X 3 represents a single bond, -O-, -S-, or -N(Sp 4 -Q 4 )-, or a nitrogen atom forming a ring structure together with Q 3 and Sp 3.
  • cycloalkyl groups in which one or more -CH 2 - are replaced by -O-, -S-, -NH-, -N(CH 3 )-, -C( ⁇ O)-, -OC( ⁇ O)-, or -C( ⁇ O)O- include tetrahydrofuranyl, pyrrolidinyl, imidazolidinyl, pyrazolidinyl, piperidyl, piperazinyl, and morpholinyl groups.
  • the substitution position is not particularly limited. Of these, tetrahydrofuranyl is preferred, and 2-tetrahydrofuranyl is particularly preferred.
  • the m-1 Ls may be the same or different.
  • Sp 1 and Sp 2 each independently represent a linking group selected from the group consisting of a single bond, a linear or branched alkylene group having 1 to 20 carbon atoms, and a linear or branched alkylene group having 1 to 20 carbon atoms in which one or more -CH 2 - groups are replaced with -O-, -S-, -NH-, -N(CH 3 )-, -C( ⁇ O)-, -OC( ⁇ O)-, or -C( ⁇ O)O-.
  • Q1 and Q2 each independently represent a hydrogen atom or a polymerizable group selected from the group consisting of groups represented by the above formulas Q-1 to Q- 5 , provided that either Q1 or Q2 represents a polymerizable group.
  • the polymerizable group is preferably an acryloyl group (formula Q-1) or a methacryloyl group (formula Q-2).
  • the polymerizable compound represented by formula (I) preferably contains, as A, at least one phenylene group which may have a substituent and at least one trans-1,4-cyclohexylene group which may have a substituent.
  • the polymerizable compound represented by formula (I) preferably contains, as A, 1 to 4 trans-1,4-cyclohexylene groups which may have a substituent, more preferably 1 to 3, and even more preferably 2 or 3.
  • the polymerizable compound represented by formula (I) preferably contains, as A, at least one phenylene group which may have a substituent, more preferably 1 to 4, even more preferably 1 to 3, and especially preferably 2 or 3.
  • the liquid crystal composition contains a polymerizable compound represented by formula (I) where 0.1 ⁇ mc ⁇ 0.3 in addition to a polymerizable compound represented by formula (I) where 0.5 ⁇ mc ⁇ 0.7.
  • polymerizable compound represented by formula (I) include the compounds described in paragraphs 0051 to 0058 of WO2016/047648, as well as the compounds described in JP2013-112631A, JP2010-070543A, Japanese Patent No. 4725516, WO2015/115390, WO2015/147243, WO2016/035873, JP2015-163596A, and JP2016-053149A.
  • the chiral agent has the function of inducing a helical structure in the cholesteric liquid crystal phase. Since the sense or pitch of the helical structure induced by the chiral compound varies depending on the compound, the chiral compound may be selected according to the purpose.
  • the chiral agent is not particularly limited, and known compounds can be used. Examples of the chiral agent include compounds described in Liquid Crystal Device Handbook (Chapter 3, Section 4-3, Chiral Agents for TN and STN, p. 199, edited by the 142nd Committee of the Japan Society for the Promotion of Science, 1989), JP-A Nos. 2003-287623, 2002-302487, 2002-080478, 2002-080851, 2010-181852, and 2014-034581.
  • 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.
  • 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.
  • 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.
  • isosorbide derivatives As the chiral agent, isosorbide derivatives, isomannide derivatives, binaphthyl derivatives, etc. can be preferably used.
  • isosorbide derivative a commercially available product such as LC756 manufactured by BASF Corporation 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.
  • 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.
  • 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 examples of the compound 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.
  • the liquid crystal composition preferably contains a polymerization initiator.
  • the polymerization initiator used is preferably a photopolymerization initiator capable of initiating the polymerization reaction by irradiation with ultraviolet light.
  • the photopolymerization initiator include ⁇ -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), ⁇ -hydrocarbon-substituted aromatic acyloin compounds (described in U.S. Pat. No.
  • Oxide compounds JP-B-63-040799, JP-B-5-029234, JP-A-10-095788, JP-A-10-029997, JP-A-2001-233842, JP-A-2000-080068, JP-A-2006-342166, JP-A-2013-114249, JP-A-2014
  • Examples of such compounds include compounds described in JP-137466, JP 4223071, JP 2010-262028 A, and JP-T-2014-500852 A), oxime compounds (described in JP 2000-066385 A and JP 4454067 A), and oxadiazole compounds (described in U.S. Pat. No. 4,212,970).
  • the description in paragraphs 0500 to 0547 of JP 2012-208494 A can also be taken into consideration.
  • acylphosphine oxide compound As the polymerization initiator, it is also preferable to use an acylphosphine oxide compound or an oxime compound.
  • acylphosphine oxide compound for example, a commercially available product IRGACURE 810 (compound name: bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide) manufactured by BASF Japan Co., Ltd. can be used.
  • 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 from 0.1 to 20% by mass, more preferably from 0.5 to 5% by mass, based on the content of the polymerizable liquid crystal compound.
  • the liquid crystal composition may contain a crosslinking agent in order to improve the film strength and durability after curing.
  • a 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 depending on the purpose.
  • crosslinking agent examples 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.
  • polyfunctional acrylate compounds such as trimethylolpropane tri(meth)acrylate and penta
  • a known catalyst can be used depending on 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, and 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.
  • (meth)acrylate is used to mean "either one or both of acrylate and methacrylate.”
  • 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.
  • the alignment control agent include fluorine (meth)acrylate-based 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.
  • the amount of the alignment control agent added to the liquid crystal composition is preferably 0.01 to 10% by mass, more preferably 0.01 to 5% by mass, and particularly preferably 0.02 to 1% by mass, based on the total mass of the polymerizable liquid crystal compound.
  • 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.
  • 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.
  • the cholesteric liquid crystal layer can be prepared 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 repeatedly carrying out the above-mentioned manufacturing process for the cholesteric liquid crystal layer.
  • 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.
  • 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 provides 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.
  • 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 preferably 20 mJ/ cm2 to 50 J/ cm2 , and more preferably 100 to 1,500 mJ/ cm2 .
  • 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.
  • the polymerization reaction rate is preferably high, 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 spectroscopy.
  • 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: ⁇ m) 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. That is, one pitch is defined as a state in which the director of the helically aligned liquid crystal compound (the long axis direction in the case of a rod-shaped liquid crystal) rotates 360°.
  • the polarization conversion layer When the polarization conversion layer has a helical structure of liquid crystal compounds, it exhibits optical rotation and birefringence for visible light, which has a shorter wavelength than the reflection peak wavelength in the infrared range. This allows for control of polarization in the visible range.
  • 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 provide the polarization conversion layer with the function of optically compensating for visible light, or the function of converting linearly polarized light (p-polarized light) incident on the reflective film into circularly polarized light.
  • 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).
  • the pitch P of the helical structure of the polarization conversion layer is set to a length that corresponds to the pitch P of the cholesteric liquid crystal layer, whose selective reflection center wavelength is in the long infrared wavelength range, the polarization conversion layer exhibits high optical rotation and birefringence for short-wavelength visible light.
  • the relational expression (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 inability to obtain sufficient optical rotation and birefringence. 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.
  • the relationship (b) is "0.5 ⁇ y ⁇ 3.0". If the thickness y of the polarization conversion layer is less than 0.5 ⁇ m, 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 ⁇ m, 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, and other inconveniences will arise.
  • 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 is insufficient, causing inconvenience such as the inability to obtain the desired polarized light.
  • the pitch number x of the spiral structure of the polarization conversion layer is more preferably 0.1 to 0.8, and the film thickness y is more preferably 0.6 ⁇ m to 2.6 ⁇ m.
  • "(1560 ⁇ y)/x" is more preferably 5000 to 13000.
  • 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 the wavelength of visible light, and therefore the polarization conversion layer more suitably exhibits the optical rotation property and birefringence for visible light described above.
  • Such a polarization conversion layer can basically be formed in the same way as a known cholesteric liquid crystal layer. However, when forming the polarization conversion layer, it is necessary to adjust the liquid crystal compound used, the chiral agent used, the amount of chiral agent added, the film thickness, etc. so that the pitch number x of the helical structure and the film thickness y [ ⁇ m] in the polarization conversion layer satisfy all of the relational expressions (a) to (c).
  • a layer in which the helical orientation structure (helical structure) of a liquid crystal compound is fixed is a so-called cholesteric liquid crystal layer, which means a layer in which a cholesteric liquid crystal phase is fixed.
  • the cholesteric liquid crystal layer as a polarization conversion layer has a pitch of the helical orientation structure of 1 or less as shown in the relational formula (a), it does not substantially exhibit reflectivity for light of a selective reflection wavelength.
  • the cholesteric liquid crystal layer as the polarization conversion 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 and 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.
  • the polymerizable liquid crystal compound may be polymerized by a curing reaction and no longer have liquid crystallinity.
  • the selective reflection central wavelength can be adjusted by adjusting the n value and/or the P value.
  • 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.
  • the retardation layer changes the state of incident polarized light by imparting a phase difference (optical path difference) to two orthogonal polarized light components.
  • the front retardation of the retardation layer may be set to a retardation that provides optical compensation.
  • the retardation layer preferably has a front retardation of 50 nm to 160 nm at a wavelength of 550 nm.
  • the angle of the slow axis is preferably 10° to 50° or ⁇ 50° to ⁇ 10°.
  • the retardation layer when the retardation layer is disposed on the inside of the vehicle and converts linearly polarized light into circularly polarized light, it is preferable that the retardation layer is configured to give a front retardation of ⁇ /4, and may be configured to give a front retardation of 3 ⁇ /4.
  • the angle of the slow axis may be arranged so as to be oriented in such a way that the incident linearly polarized light is converted into circularly polarized light.
  • the retardation layer preferably has a front retardation in the range of 100 to 450 nm at a wavelength of 550 nm, more preferably 120 to 200 nm or 300 to 400 nm.
  • 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 that constitutes the selective reflection layer.
  • retardation layer there are no particular limitations on the retardation layer, and it can be appropriately selected depending on the purpose.
  • retardation layers include stretched polycarbonate films, stretched norbornene-based polymer films, transparent films containing and oriented inorganic particles with birefringence such as strontium carbonate, thin films formed by obliquely depositing inorganic dielectrics onto a support, films in which polymerizable liquid crystal compounds are uniaxially oriented and oriented, and films in which liquid crystal compounds are uniaxially oriented and oriented.
  • a film in which a polymerizable liquid crystal compound is uniaxially aligned and fixed is a suitable example of a retardation layer.
  • 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.
  • the retardation layer can be formed in the same manner as in the formation of the cholesteric liquid crystal layer described above, except that no chiral agent is added to the liquid crystal composition.
  • 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.
  • 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 the liquid crystal state, and then cooling to fix the alignment.
  • the thickness of the retardation layer is not limited, but is preferably 0.2 to 300 ⁇ m, more preferably 0.5 to 150 ⁇ m, and even more preferably 1.0 to 80 ⁇ m.
  • the thickness of the retardation layer formed from the liquid crystal composition is not particularly limited, but is preferably 0.2 to 10 ⁇ m, more preferably 0.5 to 5.0 ⁇ m, and even more preferably 0.7 to 2.0 ⁇ m.
  • the retardation layer has a slow axis that is tilted, for example, at an angle ⁇ with respect to an axis of any direction of the retardation layer.
  • the direction of the slow axis can be set, for example, by rubbing the alignment film that is the layer below the retardation layer.
  • the reflective film of the present invention may have layers other than the selective reflection layer, the polarization conversion layer, and the retardation layer.
  • the reflective film may have a transparent substrate, an adhesive layer, and the like.
  • 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.
  • the reflective film may be in the form of a thin film or sheet. Before being used on the windshield glass, the reflective film may be in the form of a roll or the like as a thin film.
  • the transparent substrate and the adhesive layer are all transparent in the visible light region.
  • 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.
  • the difference in refractive index between the support and the adhesive layer and the average refractive index (in-plane average refractive index) of the selective reflection layer is small.
  • 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.
  • transparent substrates include polyesters such as polyethylene terephthalate (PET), polycarbonate, acrylic resins, epoxy resins, polyurethanes, polyamides, polyolefins, cellulose derivatives, and plastic films such as silicone.
  • PET polyethylene terephthalate
  • acrylic resins acrylic resins
  • epoxy resins epoxy resins
  • polyurethanes polyamides
  • polyolefins polyolefins
  • cellulose derivatives cellulose derivatives
  • plastic films such as silicone.
  • glass may also be used as the temporary support.
  • the thickness of the transparent substrate should be approximately 5.0 to 1000 ⁇ m, preferably 10 to 250 ⁇ m, and more preferably 15 to 90 ⁇ m.
  • the transparent substrate 18 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.
  • the transparent substrate 18 contains an ultraviolet absorbing agent, deterioration of the reflective film (selective reflective layer) due to ultraviolet rays can be suppressed.
  • the windshield glass may have a laminated glass configuration.
  • the windshield glass of the present invention is preferably a laminated glass having 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 configuration in which the reflective film is directly disposed between the first glass plate and the second glass plate, but it is preferable that the windshield glass has an intermediate film (intermediate film sheet) disposed at least between the first glass plate and the reflective film and between the reflective film and the second glass plate.
  • the second glass plate is disposed on the opposite side (the vehicle exterior side) to the viewing side of the image in the HUD
  • the first glass plate is disposed on the viewing side (the vehicle interior side).
  • 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, may be used. Even when such glass plates having a low visible light transmittance are 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.
  • the thickness of the glass plate is not particularly limited, but is preferably about 0.5 to 5.0 mm, more preferably 1.0 to 3.0 mm, and even more preferably 2.0 to 2.3 mm.
  • the material or thickness of the first glass plate and the second glass plate may be the same or different.
  • a windshield glass having a laminated glass structure can be produced by using a known method for producing laminated glass.
  • the laminated glass can be produced by sandwiching an interlayer film for laminated glass between two glass sheets, repeatedly subjecting the interlayer film to heat treatment and pressure treatment (e.g., treatment using a rubber roller) several times, and finally subjecting the interlayer film to heat treatment under pressure using an autoclave or the like.
  • 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.
  • the reflective film is formed on the surface of a glass plate, the glass plate on which the reflective film is provided may be 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).
  • 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 Figure 3, it bonds the reflective film 10 and the first glass plate 28 together.
  • interlayer film sheet any known interlayer film used as an interlayer film (interlayer) in laminated glass can be used.
  • a resin film containing a resin selected from the group consisting of polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer, and chlorine-containing resins can be used.
  • the above-mentioned resin is preferably the main component of the interlayer film. Note that the main component refers to a component that accounts for 50% or more by mass of the interlayer film.
  • 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 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%.
  • Polyvinyl alcohol is usually obtained by saponifying polyvinyl acetate, and polyvinyl alcohol having a saponification degree of 80 to 99.8 mol % is generally used.
  • the preferred lower limit of the degree of polymerization of the polyvinyl alcohol is 200, and the preferred upper limit is 3000.
  • the degree of polymerization 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 formability of the resin film is good, and the rigidity of the resin film is not too high, so that the processability is good.
  • the more preferred lower limit is 500, and the more preferred upper limit is 2000.
  • the thickness of the intermediate film 36 there is no limit to the thickness of the intermediate film 36, and the thickness can be set according to the material it is made of, similar to the intermediate film of known windshield glass.
  • the windshield glass 24 has a heat seal layer 38 provided between the reflective film 10 and the second glass plate 30, and the reflective film 10 and the first glass plate 28 attached 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.
  • the windshield glass 24 may be configured without the intermediate film 36, and a heat seal layer 38 may be used to adhere the reflective film 10 to the first glass plate 28 and to adhere the reflective film 10 to the second glass plate 30.
  • 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.
  • 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.
  • a known lamination method can be used for bonding the reflective film and the interlayer, 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 interlayer do not peel off after processing.
  • 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 limitations on the pressure conditions, but a pressure of less than 2.0 kg/cm 2 (less than 196 kPa) is preferable, 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 even more preferable.
  • the reflective film 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 a surface of the reflective film in the first laminate opposite to the surface to which the first interlayer film is laminated.
  • 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.
  • a second interlayer film is laminated to the surface from which the support has been peeled off.
  • the heat seal layer (adhesive layer) 38 is, for example, a layer made of a coating type adhesive.
  • the reflective film 10 is attached to the second glass plate 30 by the heat seal layer 38.
  • the reflective film 10 may be attached to the second glass plate 30 by an intermediate film instead of the heat seal layer 38.
  • the reflective film 10 may be attached to the second glass plate 30 by the intermediate film 36.
  • the heat seal layer 38 there are no limitations to the heat seal layer 38, and any known adhesive made of various types of coating type adhesive 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 the same as the intermediate film 36, such as PVB.
  • an acrylate adhesive or the like can be used for the heat seal layer 38.
  • the heat seal layer 38 may be formed from an adhesive.
  • 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.
  • 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.
  • a photocuring type is preferable as the curing method, and from the viewpoints of optical transparency and heat resistance, it is preferable to use an acrylate-based, urethane acrylate-based, epoxy acrylate-based, or other material.
  • the heat seal layer 38 may be formed using a highly transparent adhesive transfer tape (OCA tape).
  • OCA 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 MHM series adhesive sheets manufactured by Nichiei Kako Co., Ltd.
  • the thickness of the heat seal layer 38 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.
  • the thickness of the heat seal layer 38 is preferably 0.1 to 800 ⁇ m, and more preferably 0.5 to 400 ⁇ m.
  • the head-up display system of the present invention comprises: The above-mentioned windshield glass, A head-up display system having a projector that irradiates a projection image light onto a first glass plate side of the windshield glass.
  • FIG. 4 shows an example of a head-up display system according to the present invention.
  • 4 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 similar configuration to the windshield glass 24 shown in FIG.
  • the projector 22 emits p-polarized projection light
  • the reflective film 10 reflects the p-polarized light to display an image.
  • the polarization conversion layer 14 first converts the incident p-polarized projection light into circularly polarized light.
  • 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.
  • the reflective film 10 reflects the incident p-polarized projection light while keeping it as p-polarized light.
  • the polarization conversion layer 14 is set to convert the incident p-polarized light into the circularly polarized light of the rotation direction reflected by the selective reflection layer 11 according to 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.
  • the projector 22 preferably irradiates p-polarized projection light onto the windshield glass 24 (second glass plate 30).
  • the projector 22 projects p-polarized light onto the windshield at the Brewster angle, thereby eliminating reflection of the light on the second glass plate 30 and the first glass plate 28, allowing for a clearer image to be displayed.
  • a "projector” is a “device that projects light or an image” and includes a “device that projects a drawn image” and emits projection light that carries an image to be displayed.
  • the projector preferably emits p-polarized projection light.
  • 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.
  • 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.
  • the projector any known projector used in a HUD can be used as long as it can emit p-polarized projection light.
  • the projector is one in which the imaging distance of the virtual image, i.e., the imaging position of the virtual image, is variable.
  • Methods for changing the imaging distance of a virtual image in a projector include, for example, moving the image generation surface (screen) (see JP 2017-21302 A), switching between multiple optical paths with different optical path lengths (see WO 2015/190157 A), changing the optical path length by inserting and/or moving a mirror, changing the focal length by using a lens assembly as an imaging lens, moving the projector 22, switching between multiple projectors with different virtual image imaging distances, and using a variable focus lens (see WO 2010/116912 A).
  • 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.
  • 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.
  • 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.
  • 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.
  • LEDs light-emitting diodes
  • OLEDs organic light-emitting diodes
  • discharge tubes laser light sources
  • LEDs and discharge tubes are preferred because they are suitable as light sources for drawing devices that emit linearly polarized light
  • LEDs are particularly preferred because LEDs have emission wavelengths that are not continuous 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.
  • 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 (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.
  • the DLP method is a display system using a DMD (Digital Micromirror Device), in which micromirrors are arranged in the number of pixels to draw an image, and light is emitted from a projection lens.
  • DMD Digital Micromirror Device
  • the scanning method is a method in which a light beam is scanned on a screen and an afterimage of the eye is utilized to form an image, and for example, the descriptions in JP-A-7-270711 and JP-A-2013-228674 can be referred to.
  • the luminance-modulated laser beams of each color for example, red light, green light, and blue light
  • the beam is scanned by an optical deflection means to be drawn on an intermediate image screen described later.
  • the luminance modulation of each color of laser light may be performed directly as a change in the intensity of the light source, or may be performed by an external modulator.
  • 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.
  • the scanning method include a random scan method and a raster scan method, and it is preferable to use 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.
  • the scanning method does not require a projection lens, so it is easy to miniaturize the device.
  • the light emitted from the imaging device may be linearly polarized or natural (unpolarized) light.
  • Drawing devices using an LCD or LCOS drawing method and drawing devices using a laser light source essentially emit linearly polarized light.
  • the polarization direction (transmission axis direction) of the light of the multiple wavelengths is the same. It is known that some commercially available drawing devices have non-uniform polarization directions in the wavelength ranges of red, green, and blue light of the emitted light (see JP 2000-221449 A).
  • the projection light emitted by the projector is preferably p-polarized light.
  • 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.
  • intermediate image screens include a scattering film, a microlens array, and a screen for rear projection, etc.
  • 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. This is because it allows for an 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 Translation of PCT International 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.
  • the windshield glass is particularly useful for HUDs that are used in combination with projectors that use light sources such as lasers, LEDs, and OLEDs (organic light-emitting diodes), whose emission wavelengths are not continuous in the visible light range. 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 to project displays such as LCDs (liquid crystal displays) that use polarized display light.
  • LCDs liquid crystal displays
  • the incident light is preferably incident at an oblique angle of 45° to 70° with respect to the normal line of 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
  • the reflected light from the surface of the windshield glass on the viewing side is small with respect to the selective reflection layer of the incident light for projected image display, and It is possible to display images with minimal overlapping effects. It is also preferable that the angle is 50° to 65°.
  • the projected image is observed on the side where the projection light is incident, on the opposite side to the incident light (opposite azimuth direction) with respect to the normal to the selective reflection layer.
  • Any configuration may be used as long as the laser beam can be emitted at an angle of 45° to 70°, preferably 50° to 65°, on the laser beam side.
  • 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 light is incident from below at an oblique incident angle as described above when in use.
  • the reflective film on the windshield glass is preferably arranged to reflect incident p-polarised light.
  • 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.
  • the light emitted from the projector 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.
  • 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.
  • the polarization direction of the emitted light is not uniform across the wavelength ranges of red, green, and blue light
  • the HUD 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 viewed by the driver of the vehicle, and is typically a position beyond the windshield glass, 1000 mm or more away from the driver.
  • 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 placed, and is defined as the ground side being the bottom side and the opposite side being the top side.
  • 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.
  • the present invention is basically configured as described above.
  • the reflective film, windshield glass, and head-up display system (HUD) of the present invention have been described in detail above, but the present invention is not limited to the above-described embodiment, and various improvements and modifications may of course be made without departing from the spirit of the present invention.
  • Coating solution for forming cholesteric liquid crystal layer (Coating solution for forming cholesteric liquid crystal layer)
  • coating solutions for forming cholesteric liquid crystal layers B2, R2, IR2
  • Table 1 the following components were mixed to prepare coating solutions for forming cholesteric liquid crystal layers having the following compositions.
  • Each cholesteric liquid crystal layer-forming coating solution was prepared by adjusting the formulation amount of the right-handed chiral dopant LC756 in the above-mentioned coating solution composition.
  • a single cholesteric liquid crystal layer having a thickness of 3 ⁇ m 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.
  • all 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.
  • Rod-shaped liquid crystal compound 101 55 parts by weight Rod-shaped liquid crystal compound 102: 30 parts by weight Rod-shaped liquid crystal compound 201: 13 parts by weight Rod-shaped liquid crystal compound 202: 2 parts by weight Polymerization initiator IRGACURE OXE01 (manufactured by BASF) 1.0 part by weight of alignment control agent 1 0.01 part by weight of alignment control agent 3 (fluorine-based horizontal alignment agent 3) 0.01 part by weight of right-handed chiral agent LC756 (manufactured by BASF) Adjusted to match the target selective reflection central wavelength - Solvent (methyl ethyl ketone) Amount to make the solute concentration 20% by mass ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  • Rod-shaped liquid crystal compound 201 Rod-shaped liquid crystal compound 202
  • 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.
  • a single cholesteric liquid crystal layer having a thickness of 3 ⁇ m 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.
  • all 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.
  • 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 ⁇ was obtained.
  • the selective reflection central wavelength ⁇ was determined by measuring a single cholesteric liquid crystal layer having a thickness of 3 ⁇ m on a temporary support using FTIR (Spectrum Two, manufactured by PerkinElmer).
  • the film thickness d of the helical structure can be expressed as "pitch P of the helical structure x pitch number".
  • the pitch P of the helical structure is the length of one pitch in the helical structure, and one pitch is the rotation of the helically oriented liquid crystal compound by 360°.
  • 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 ⁇ (central wavelength ⁇ ) of the polarization conversion layer targeted for the prepared coating solution for forming the polarization conversion layer.
  • an alkaline solution having the composition shown below was applied to one side of the film with a coating amount of 14 mL/ m2 using a bar coater, and the film was allowed to remain under a steam type far-infrared heater (manufactured by Noritake Co., Ltd.) heated to 110° C. for 10 seconds.
  • 3 mL/m 2 of pure water was applied using the same bar coater.
  • 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 with an AxoScan and found to be 1 nm.
  • 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.
  • the film was placed on a hot plate at 50° C. and irradiated with ultraviolet light for 6 seconds using 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, thereby fixing the liquid crystal phase.
  • a retardation layer was obtained whose thickness was adjusted to obtain the desired front retardation, i.e., the desired retardation.
  • the retardation of the produced retardation layer was measured by AxoScan and found to be 126 nm (Example 1).
  • the cholesteric liquid crystal layer forming coating solution (Y1) 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 1.2 ⁇ m, 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. Thereafter, in an environment with an oxygen concentration of 1000 ppm or less, the coating layer was irradiated with ultraviolet light at an output of 60% for 6 to 12 seconds using a D bulb (90 mW/cm lamp) manufactured by Fusion Co., Ltd. at 60° C.
  • a cholesteric liquid crystal layer Y1 having a thickness of 1.2 ⁇ m was repeated using the cholesteric liquid crystal layer forming coating liquid (R1) on the surface of the obtained cholesteric liquid crystal layer Y1 to form a cholesteric liquid crystal layer R1 having a thickness of 2.2 ⁇ m.
  • the same process was repeated using the cholesteric liquid crystal layer forming coating liquid (IR1) on the surface of the obtained cholesteric liquid crystal layer R1 to form a cholesteric liquid crystal layer IR1 having a thickness of 2.5 ⁇ m.
  • the same process was repeated using the cholesteric liquid crystal layer forming coating liquid (B1) on the surface of the obtained cholesteric liquid crystal layer IR1 to form a cholesteric liquid crystal layer B1 having a thickness of 0.7 ⁇ m.
  • 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 1.3 ⁇ m.
  • 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, thereby forming a polarization conversion layer and producing a reflective film.
  • the polarization conversion layer was formed in the same manner as in the formation of the above-mentioned cholesteric liquid crystal layer.
  • Examples 2 to 4, Comparative Example 1 A reflective film was prepared in the same manner as in Example 1, except that the structure of the cholesteric liquid crystal layer of the selective reflection layer was changed to the layer structure shown in Table 3 below, and each layer had the polarization conversion layer and retardation layer shown in Table 2.
  • the dotted line in the graph of FIG. 2 is the reflection spectrum of the reflective film of Comparative Example 1.
  • 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 rear surface of the glass plate.
  • a spectrophotometer V-670, manufactured by JASCO Corporation
  • P-polarized light and S-polarized light were incident from a direction of 5° to the normal direction of the reflective film surface, and the reflection spectrum was measured from 400 nm to 1000 nm.
  • the average value (average reflection spectrum) of the measured reflection spectra of P-polarized light and S-polarized light was calculated.
  • the average value of the reflectance when P-polarized light is incident and the reflectance when S-polarized light is incident is synonymous with the reflectance when unpolarized light (natural light) is incident.
  • the average value of the reflectance spectrum of P-polarized light and the reflectance spectrum of S-polarized light is synonymous with the reflectance spectrum when natural light is incident.
  • the reflective film of the embodiment has a higher reflectance at specific wavelengths than the reflective film of the comparative example, and therefore can increase the brightness of the displayed image.
  • the reflective film of the present invention has reflection peaks in each of the three wavelength ranges of 560 nm or more and less than 610 nm, 660 nm or more and less than 720 nm, and 760 nm or more and less than 900 nm, and therefore the displayed color gamut of the reflected light is wider than that of comparative example 1.
  • a windshield glass having each of the reflective films prepared above was produced as follows.
  • a first glass plate (manufactured by Central Glass Co., Ltd., FL2, visible light transmittance 90%) having a size of 120 mm length x 100 mm width and a thickness of 2 mm was prepared.
  • a PVB film having 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.
  • the coating liquid for forming a heat seal layer was applied to a reflective film (transparent substrate) using a wire bar, and then the coating liquid was dried and heated at 50° C. for 1 minute to obtain a heat seal layer having a thickness of 1 ⁇ m.
  • the reflective film, first glass plate, second glass plate, intermediate film, and heat seal layer were laminated to the configuration shown in Table 5 below, and the 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, and a windshield glass was obtained.
  • Visible light transmittance evaluation criteria A: 82% or more; B: 80% or more but less than 82%; C: Less than 80%
  • 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.
  • Evaluation criteria for P-polarized light reflectance A: 30% or more; B: 25% to less than 30%; C: Less than 25%
  • the examples of the present invention can be seen to provide good results in terms of P-polarized light reflectance (brightness of the displayed image) and reflected color while maintaining a high visible light transmittance compared to the comparative examples.
  • Comparative Example 1 did not satisfy requirements (i) to (iii) and had a low P-polarized light reflectance.
  • HUDs in-vehicle head-up display systems

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Optics & Photonics (AREA)
  • Mechanical Engineering (AREA)
  • Theoretical Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Transportation (AREA)
  • Optical Filters (AREA)

Abstract

L'invention concerne : un film réfléchissant qui a une transmittance de lumière visible élevée, une large plage de couleurs d'affichage pour une lumière réfléchie, une luminance élevée d'images d'affichage, et une bonne transparence de couleur d'aspect ; un verre de pare-brise ; et un système d'affichage tête haute. Le film réfléchissant a une couche réfléchissante sélective. La couche réfléchissante sélective satisfait à toutes les exigences (i) à (iii). Exigence (i) : Dans la plage de longueurs d'onde supérieure ou égale à 560 nm mais inférieure à 610 nm, la valeur maximale de la réflectance de lumière naturelle n'est pas inférieure à 10% mais inférieure à 25%, et la largeur totale à mi-hauteur du pic de la réflectance de lumière naturelle n'est pas inférieure à 10 nm mais inférieure à 80 nm. Exigence (ii) : Dans la plage de longueurs d'onde supérieure ou égale à 660 nm mais inférieure à 720 nm, la valeur maximale de la réflectance de lumière naturelle n'est pas inférieure à 10% mais inférieure à 30%, et la largeur totale à mi-hauteur du pic de la réflectance de lumière naturelle n'est pas inférieure à 10 nm mais inférieure à 80 nm. Exigence (iii) : Dans la plage de longueurs d'onde supérieure ou égale à 760 nm mais inférieure à 900 nm, la valeur maximale de la réflectance de lumière naturelle n'est pas inférieure à 10% mais inférieure à 35%, et la largeur totale à mi-hauteur du pic de la réflectance de lumière naturelle n'est pas inférieure à 10 nm.
PCT/JP2024/010195 2023-03-20 2024-03-15 Film réfléchissant, verre de pare-brise et système d'affichage tête haute Pending WO2024195716A1 (fr)

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Citations (8)

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JP2009514037A (ja) * 2005-10-31 2009-04-02 スリーエム イノベイティブ プロパティズ カンパニー 高コントラスト用途のための光学要素
WO2016133187A1 (fr) * 2015-02-20 2016-08-25 富士フイルム株式会社 Verre de pare-brise, et dispositif d'affichage tête haute
WO2017131174A1 (fr) * 2016-01-29 2017-08-03 日立マクセル株式会社 Élément de protection thermique/d'isolation thermique transparent ayant une fonction d'écran transparent
WO2018012469A1 (fr) * 2016-07-15 2018-01-18 富士フイルム株式会社 Membrane de réflexion sélective en longueur d'onde, film optique, procédé de fabrication d'une membrane de réflexion sélective en longueur d'onde, et dispositif d'affichage d'image
JP2019038707A (ja) * 2017-08-22 2019-03-14 富士フイルム株式会社 合わせガラスの製造方法
WO2019146423A1 (fr) * 2018-01-25 2019-08-01 富士フイルム株式会社 Élément d'affichage d'image projetée, vitre de pare-brise, et système d'affichage tête haute
WO2020080355A1 (fr) * 2018-10-17 2020-04-23 富士フイルム株式会社 Élément d'affichage d'image à projection, vitre de pare-brise, et système d'affichage tête haute
WO2022075184A1 (fr) * 2020-10-09 2022-04-14 富士フイルム株式会社 Film réfléchissant, verre de pare-brise et système d'affichage tête haute

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2009514037A (ja) * 2005-10-31 2009-04-02 スリーエム イノベイティブ プロパティズ カンパニー 高コントラスト用途のための光学要素
WO2016133187A1 (fr) * 2015-02-20 2016-08-25 富士フイルム株式会社 Verre de pare-brise, et dispositif d'affichage tête haute
WO2017131174A1 (fr) * 2016-01-29 2017-08-03 日立マクセル株式会社 Élément de protection thermique/d'isolation thermique transparent ayant une fonction d'écran transparent
WO2018012469A1 (fr) * 2016-07-15 2018-01-18 富士フイルム株式会社 Membrane de réflexion sélective en longueur d'onde, film optique, procédé de fabrication d'une membrane de réflexion sélective en longueur d'onde, et dispositif d'affichage d'image
JP2019038707A (ja) * 2017-08-22 2019-03-14 富士フイルム株式会社 合わせガラスの製造方法
WO2019146423A1 (fr) * 2018-01-25 2019-08-01 富士フイルム株式会社 Élément d'affichage d'image projetée, vitre de pare-brise, et système d'affichage tête haute
WO2020080355A1 (fr) * 2018-10-17 2020-04-23 富士フイルム株式会社 Élément d'affichage d'image à projection, vitre de pare-brise, et système d'affichage tête haute
WO2022075184A1 (fr) * 2020-10-09 2022-04-14 富士フイルム株式会社 Film réfléchissant, verre de pare-brise et système d'affichage tête haute

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