Transparent display system, laminated film, and laminated sheet

Abstract

A transparent display system according to the present invention comprises: a video projector (1) that, by emitting light, projects video from a video emission surface; and a projection image display member (3) having a video display surface onto which a video is projected by using light emitted from the video projector (1). When the center point of a surface of the projection image display member (3) is denoted as the C point and an intersection line formed by a horizontal plane passing through the C point and a contact surface of the projection image display member (3) crossing each other at the C point is denoted as the reference axis C, an angle θ1 formed at the C point by the reference axis C and the orientation axis of the surface of the projection image display member (3) is 0-30° or 85-90°. When the projection image display member (3) is tilted by being rotated about the reference axis C to make a P wave incident on the surface of the projection image display member (3) such that the angle formed at the C point by the traveling direction of the P wave and the normal line of the contact surface of the projection image display member (3) is 60° and the traveling direction of the P wave is perpendicular to the reference axis C, the average reflectance at a wavelength of 400-700 nm is 5-100% and the average transmittance of visible light perpendicularly incident on the surface of the projection image display member (3) at the C point is 50-100%.

Description

Transparent display system, laminated film, and laminated sheet

[0001] The present invention relates to a transparent display system that can clearly display images without partial degradation of display quality in the display area even when images are projected over a wide range and at a wide viewing angle, as well as to a laminate film and a laminate sheet that can be suitably used in this system.

[0002] In recent years, aerial projection technologies, such as head-up displays and head-mounted displays, have been actively developed. These technologies project images onto transparent materials such as glass or transparent resin materials, superimposing the images on the surrounding scenery. A typical display method used in aerial projection technologies is to project an image (light) onto a transparent material from an oblique angle, reflect the image, and deliver the reflected image to the viewer's field of view.

[0003] Light is a composite wave composed of two types of polarized light with different vibration directions, generally referred to as P waves (P-polarized light) and S waves (S-polarized light). P waves refer to polarized light that vibrates perpendicular to the plane of incidence of light, while S waves refer to polarized light that vibrates parallel to the plane of incidence of light. The reflectance of P waves incident on a transparent material decreases as the angle of incidence increases, reaching 0% at a certain angle of incidence called the Brewster angle and then increasing again. On the other hand, the reflectance of S waves tends to increase monotonically as the angle of incidence increases. For these reasons, when projecting an image onto a transparent material from an oblique angle, it is common to project the image using a light source that emits light containing an S-wave component in order to project the image regardless of the installation configuration of the projection material (Patent Document 1). However, when projecting an image onto a transparent material using a light source that emits light containing an S-wave component, the image is reflected at interfaces including the outermost surfaces on both sides of the transparent material, and the reflected images reach the viewer's field of view via separate optical paths, resulting in the problem of the image being perceived as a multiplexed image.

[0004] To solve the above problem, a new projection method has been investigated in which a screen member (such as a film) that can reflect P waves even when incident obliquely is inserted into or attached to a transparent member, so that the image is not reflected on the outermost surface of the transparent member, but rather the light from the image is reflected only at the screen member portion, thereby solving the problem of multiple image display (Patent Documents 2 to 5).

[0005] Patent Publication No. 2021-507868 Patent Publication No. 2023-512713 Patent Publication No. 2023-502234 International Publication No. 2019 / 198635 International Publication No. 2023 / 054117

[0006] However, as exemplified by Patent Documents 2 and 3, when a uniaxially stretched laminated film is used as a screen member, it is possible to show a certain level of reflection regardless of the angle of incidence of light when an image is projected at an angle parallel to the orientation axis direction, but when an image is projected at an angle different from the orientation axis direction, the reflectance of light decreases and there is a problem of reduced visibility, such as increased reflection of the peripheral areas on the projected image display member.

[0007] As exemplified by Patent Documents 4 and 5, when a laminate film sequentially biaxially stretched at a substantially uniform magnification in both the longitudinal and width directions is used as a screen component, it has the advantage of being able to increase reflectivity as the angle of incidence increases, regardless of the azimuth angle inclined relative to the normal direction of the film surface. However, with such a laminate film, the P-wave image from the image projector is converted into an image of a composite wave of P and S waves due to the high phase difference and high orientation angle in areas other than the center of the film width direction, which are caused by the sequential biaxial stretching film-forming method. Therefore, when such a laminate film is used as a screen component, the influence of surface reflection from the transparent component due to S-waves is added, resulting in the problem of partial overlapping images in wide-area image displays. In other words, conventional technology has the potential problem of poor display quality depending on the viewing position and direction of the image.

[0008] In order to solve the above problems, the present invention aims to provide a transparent display system that allows images to be clearly viewed without overlapping images regardless of the display position or viewing azimuth angle when images are projected over a wide area or when images are viewed at a wide viewing angle, and a laminate film that can be suitably used as a projected image display component for the transparent display system.

[0009] The transparent display system of the present invention, which solves the above problems, and the laminate film used in the display system have the following features.

[0010] The transparent display system of the present invention is a transparent display system including an image projector that irradiates light to project an image from an image exit surface, and a projection image display member on whose image display surface an image is projected by the light irradiated from the image projector, wherein when the center point of the surface of the projection image display member is defined as point C, and the intersection line formed by the tangent plane of the projection image display member at point C and a horizontal plane passing through point C is defined as reference axis C, an angle θ1 formed between the orientation axis at point C on the surface of the projection image display member and the reference axis C is 0° or more and 30° or less, or 85° or more. and when P waves are incident on the surface of the projection image display member by rotating it around the reference axis C so that the angle between the normal to the tangent surface of the projection image display member at point C and the direction of propagation of the P waves is 60° and the reference axis C and the direction of propagation of the P waves are perpendicular, the average reflectance at wavelengths of 400 nm to 700 nm is 5% or more and 100% or less, and the average transmittance of visible light perpendicularly incident on the surface of the projection image display member at point C is 50% or more and 100% or less.

[0011] Here, the horizontal plane means a horizontal plane when an observer (user) of the transparent display system stands upright in the vertical direction.

[0012] Furthermore, in the laminate film of the present invention, when the center point of the film surface is point CF, the midpoints between point CF and an end in the short side direction are point X1F and point X2F, the midpoint between point CF and an end in the long side direction is point Y1F and point Y2F, the long side direction is the reference axis, and the angle between the reference axis and the orientation axis at each point is the film orientation angle, the variation (maximum value-minimum value) of the film orientation angle at each of the points is 30° or less, the average transmittance of visible light incident perpendicularly to the film surface at point CF is 50% or more and 100% or less, and when P waves are incident on the film surface from a direction perpendicular to the orientation axis, the angle between the normal to the film surface at point CF and the normal in a plane including the orientation axis is 60°, the average reflectance at a wavelength of 400 to 700 nm is 5% or more and 100% or less.

[0013] The present invention provides a transparent display system that can clearly display images over a wide area without causing deterioration in visibility such as overlapping images or insufficient display brightness in the display area, even when the system is used as an image projection device with an augmented reality function to project images over a wide area and at a wide viewing angle onto, for example, the entire surface of an automobile windshield, and also provides a laminate film that can be suitably used in this transparent display system.

[0014] It is a schematic cross-sectional view for explaining an embodiment of the transparent display system of the present invention. It is a schematic cross-sectional view for explaining an example of a projection image display member of a bonding type that can be used in the transparent display system of the present invention. It is a schematic cross-sectional view for explaining an example of a projection image display member of an interpolation type that can be used in the transparent display system of the present invention. It is a schematic view for explaining point C of the projection image display member constituting the transparent display system according to an embodiment of the present invention. It is a schematic view for explaining point C of the projection image display member constituting the transparent display system according to another embodiment of the present invention. It is a schematic perspective view for explaining the reference axis C of the projection image display member constituting the transparent display system of the present invention. It is a schematic perspective view for explaining the reference axis C of the projection image display member constituting the transparent display system of FIG. 4A. It is a schematic perspective view for explaining the reference axis C of the projection image display member constituting the transparent display system of FIG. 4B. It is a schematic perspective view for explaining the angle θ1 formed by the reference axis C and the alignment axis of the projection image display member constituting the transparent display system of the present invention. It is a schematic view for explaining points X1, X2, Y1, and Y2 of the projection image display member constituting the transparent display system of the present invention. It is a schematic diagram for explaining the area A in the transparent display system of the present invention. It is a schematic diagram for explaining the area A in the transparent display system of the present invention. It is a schematic diagram for explaining a method of calculating the area A in the transparent display system of the present invention. It is a schematic cross-sectional view for explaining a multiple image generated when an interpolation type projection image display member is used in the transparent display system of the present invention. It is a schematic cross-sectional view for explaining another example of the interpolation type projection image display member that can be used in the transparent display system of the present invention. It is a schematic cross-sectional view for explaining a multiple image generated when a bonding type projection image display member is used in the transparent display system of the present invention. It is a schematic plan view for explaining points CF, X1F, X2F, Y1F, and Y2F of the laminated film of the present invention. It is a schematic characteristic diagram for explaining the relationship between the depth in the thickness direction and the contrast difference (gray level) in the cross-sectional observation image of the laminated film of the present invention having a unit in which layers are alternately laminated in an array of (AB)n (n is a natural number representing the number of repeating units).

[0015] The transparent display system of the present invention will be described in detail below. The transparent display system of the present invention is a transparent display system including an image projector that projects an image by irradiating light, and a projection image display member on which an image is projected by the light from the image projector, wherein when a center point of the surface of the projection image display member is defined as point C, and an intersection line formed by an intersection of a tangent plane of the projection image display member at point C and a horizontal plane passing through point C is defined as a reference axis C, an angle θ1 formed between an orientation axis of point C on the surface of the projection image display member and the reference axis C is 0° to 30° or 85° to 90°. and when P waves are incident on the surface of the projection image display member by rotating the projection image display member around the reference axis C so that the angle between the normal to the tangent surface of the projection image display member at point C and the direction of travel of the P waves is 60° and the reference axis C and the direction of travel of the P waves are perpendicular, the average reflectance at wavelengths of 400 nm to 700 nm is 5% or more and 100% or less, and the average transmittance of visible light perpendicularly incident on the surface of the projection image display member is 50% or more and 100% or less.

[0016] In the present invention, a transparent display system refers to a display system in which the projection image display member is transparent from the viewpoint of an observer, and an image displayed on the projection image display member by light emitted from an image projector can be simultaneously viewed as being superimposed on the scenery behind the projection image display member. In this case, "transparent" refers to an average transmittance of 30% or more and 100% in the visible light range (400 to 800 nm) incident from the rear through the projection portion when the projection image display member is positioned at an installation angle for actual use and the image projection portion is viewed from the observer's line of sight. When an image is projected over a wide area of ​​the projection image display member and used to be superimposed on the scenery, it is preferable that this transmittance condition be satisfied over the entire projection portion.

[0017] Whether a projection image display member is "transparent" is determined by analyzing the average transmittance in the visible light region (wavelength 400 to 800 nm) at normal incidence according to the transmission spectral spectrum measurement using a spectrophotometer described below. Specifically, the spectral transmittance spectrum is measured at five points: point C, the center of the projection image display member described below; point X1, which is the midpoint between point C and the upper end; point X2, which is the midpoint between point C and the lower end; point Y1, which is the midpoint between point C and the left end; and point Y2, which is the midpoint between point C and the right end. If the average transmittance in the visible light region at all five points is 30% or more and 100% or less, the projection image display member is determined to be "transparent."

[0018] A specific example of such a transparent display system is an image projection device as shown in Fig. 1. Fig. 1 is a schematic diagram illustrating one embodiment of the transparent display system of the present invention. In the transparent display system of Fig. 1, an image projector 1 irradiates a projection image display member 3 with light 2 (image light) that forms the basis of the image, thereby projecting an image onto the projection image display member 3. This allows an observer 5 of the transparent display system to visually recognize a scene 4 seen behind the projection image display member 3 superimposed on information constituted by the image light 2 from the image projector 1. Note that reference numeral 6 indicates the angle of incidence of the image light from the image projector to the projection image display member, and the dashed line indicates the normal to the projection image display member (or, if the projection image display member has a curved surface, the normal to the tangent surface at the irradiation point).

[0019] The transparent display system of this embodiment can be used, for example, as a head-up display for manned transportation, as a transparent screen for spatial presentation in amusement applications, or as electronic signage applications such as signage and show windows. Manned transportation refers to transportation means such as vehicles, trains, airplanes, and ships, which are either driven by a person or operated unmanned with passengers. In such manned transportation, the transparent display system can be used as a head-up display that allows the driver to simultaneously view the scenery from the vehicle window while superimposing speed displays, navigation information, and the like, or as a signage application in which passengers view information superimposed on the scenery from the vehicle window.

[0020] 1 has one image projector unit, but if it is desired to project multiple types of images (for example, navigation information and images of an instrument panel such as a speedometer), multiple image projectors may be provided. That is, one preferred embodiment of the transparent display system of the present invention is one in which at least two image projector units are arranged side by side. Examples of image projectors in the display system of the present invention are shown below, but multiple image projectors of the same type may be arranged in parallel, or different types of image projectors may be arranged side by side.

[0021] In the transparent display system of the present invention, the image projector refers to a device capable of emitting image light. The image projector constituting the transparent display system of the present invention is not particularly limited as long as it is capable of emitting image light. However, when emitting an image at a single focus, general image projectors such as liquid crystal projectors, RGB lasers, DLP (Digital Light Processing), LCOS (Liquid Crystal on Silicon), liquid crystal, organic electroluminescence (EL), micro LEDs, mini LEDs, and light-emitting devices equipped with these can be used. On the other hand, image projectors capable of multifocal display can also be used to simultaneously project displays at different focuses to reduce the viewer's eye movement. In this case, a mirror reflection type projector that combines a reflective mirror and a magnifying mirror separately from the light-emitting device inside the display body, or a light guide type projector that emits light from a light-emitting device to a light guide member and converts the emission angle and emission range of the light beam before projecting it can be used. These image projectors can be freely selected taking into consideration the installation position, installation space capacity, installation angle, image projection position on the projection image display member, brightness and color gamut of the image obtained, and viewing angle.

[0022] In the transparent display system of the present invention, it is preferable that light from the image projector directly enters the projection image display member. The image from the image projector of the present invention is preferably an image using P waves to reduce overlapping images and ensure clear display when wearing polarized sunglasses. To increase the proportion of P waves in the image light, a linearly polarizing material can be retrofitted to control the vibration direction of these polarized waves immediately after emission from the image projector. However, this reduces the amount of light emitted from the image projector. Therefore, to maintain the display brightness of the image, it is necessary to increase the light intensity of the image projector itself, which may cause the image projector itself to heat up, resulting in display defects or malfunction. Furthermore, avoiding such malfunctions may require complex thermal design for dissipating heat from the image projector. Therefore, in terms of durability of the transparent display system (especially the image projector), it is preferable that the light emitted from the image projector directly reaches the projection image display member.

[0023] Here, an image using P waves refers to an image projected onto a projection image display member by light whose intensity is greater than that of S waves being incident on the projection image display member. Furthermore, P waves refer to electromagnetic waves whose electric field component is parallel to the plane of incidence (in other words, linearly polarized light that oscillates parallel to the plane of incidence), while S waves refer to electromagnetic waves whose electric field component is perpendicular to the plane of incidence (in other words, linearly polarized light that oscillates perpendicular to the plane of incidence).

[0024] It is also expected that an observer using a transparent display system will view an image from a specific position. Therefore, in order to enable the observer to view an image projected over a wide area, it is also preferable to project the image using multiple image projectors so that the image light is delivered to the observer by specular reflection from a wide angle. One of the features of the transparent display system of the present invention is that by arranging multiple image projectors in this way, the image can be clearly viewed without overlapping images even over a wide range and a wide viewing angle. This system is preferably used when the image is viewed partially or entirely over a wide area of ​​the projected image display member at the observer's line of sight.

[0025] Specifically, in the case of a head-up display (hereinafter sometimes referred to as HUD) for an automobile, two or more image projectors can be arranged side by side on or inside the dashboard, and different images can be displayed in tandem or independently. This configuration allows the observer (in this case, the driver) to simultaneously view signage such as nearby vehicle approach indicators and hazard warnings, in addition to information typically displayed on the instrument panel, such as speed display navigation information. Furthermore, by projecting HUD displays with different focal points from multiple image projectors arranged side by side, it is possible to effectively superimpose information on the depth of the landscape behind the projected image display element, allowing for more visual recognition of the information. While multiple image projectors can be arranged side by side in any orientation, considering the space available for installing the image projectors and the change in incident angle depending on the installation position, it is preferable from a design perspective to arrange them side by side relative to the projected image display element as viewed by the observer.

[0026] In this case, the image projectors arranged side by side at each installation position have different optical axes before reaching the line of sight of a particular observer. It is preferable to individually adjust the light emission direction of each image projector so that light is emitted along these optical axes without changing its polarization state. One method for doing so is to provide a linear polarizing plate at the light emission portion of each image projector and adjust the transmission axis direction of the polarizing plate for each image projector so that light from the image projector is emitted along the optical axis. Furthermore, to ensure that multiple observers can view a wide range of images, it is more preferable to adjust the transmission axis direction so that it points to the midpoint of each optical path to each observer. Alternatively, it is possible to project images without changing the polarization characteristics not only in the front direction of the image projector but also in oblique directions by providing a three-dimensionally curved image emission surface of the image projector or by providing a special polarizing plate on the top surface of the image emission surface whose transmission axis direction continuously changes depending on the emission direction.

[0027] In the transparent display system of the present invention, the projection image display member refers to a transparent member that can receive light from an image projector to project an image and that allows the background to be seen. The configuration of the projection image display member that constitutes the transparent display system of the present invention is not particularly limited as long as it satisfies the above requirements. For example, a laminate ( FIG. 2 , lamination method) in which a transparent hard material 9 and a light-reflecting material 7 (corresponding to the laminate film of the present invention), such as the laminate film of the present invention described below, are laminated, or a laminate ( FIG. 3 , insertion method) in which the light-reflecting material 7 is inserted inside the transparent hard material 9 can be used.

[0028] Examples of transparent hard materials include glass and transparent resins, and it is preferable to use a material with a thickness of 1 mm or more to ensure support. While there is no particular upper limit on the thickness of the transparent hard material, a thickness of 10 mm or less is preferred because an excessively thick transparent hard material unnecessarily increases the weight of the entire projection image display component. Examples of glass that can be used as the transparent hard material include not only single-layer glass but also laminated glass and tempered glass used in automobile windshields, side windows, and rear windows, as well as plate glass, double-glazed glass, and vacuum glass used as building materials. Examples of transparent resins that can be used as the transparent hard material include polyethylene terephthalate, polycarbonate, acrylic, polyvinyl chloride, polyethylene, polypropylene, polymethylpentene and its copolymers, and acrylonitrile-butadiene-styrene copolymers. These transparent resins may be a single component or a mixture of multiple components.

[0029] The transparent hard material and the light-reflective material may be laminated directly together using a method such as water lamination. However, due to concerns about peeling during use, lamination via an adhesive layer 8 such as a pressure-sensitive adhesive or adhesive is also possible, as shown in Figures 2 and 3. Examples of pressure-sensitive adhesives and adhesives include vinyl acetate resins, vinyl chloride-vinyl acetate copolymers, ethylene-vinyl acetate copolymers, nitrile rubbers, styrene-butadiene rubbers, natural rubbers, chloroprene rubbers, polyamides, epoxy resins, polyurethanes, acrylic resins, and cellulose-based adhesives, as well as polyvinyl alcohol, polyvinyl butyral, polyvinyl acetal, polyvinyl ether, polyvinyl chloride, polyacrylic esters, and polyisobutylene. These pressure-sensitive adhesives and adhesives may be used alone or in combination. To impart functionality, viscosity regulators, plasticizers, heat stabilizers, antioxidants, UV absorbers, antistatic agents, lubricants, colorants, crosslinking agents, and the like may be added alone or in appropriate combinations.

[0030] These pressure-sensitive adhesives and adhesives may be in liquid, gel, block, powder, film, etc. before processing. Methods for solidifying pressure-sensitive adhesives and adhesives include solvent evaporation, moisture curing, heat curing, curing agent mixing, anaerobic curing, ultraviolet curing, thermal melting and cooling, and pressure-sensitive. Lamination methods include lamination molding, injection molding, vacuum molding, pressure-pressure molding, and combined vacuum and pressure-pressure molding. Projection image display components are produced by applying heat, pressure, and the above-mentioned pressure-sensitive adhesive or adhesive solidification methods.

[0031] The thickness of the adhesive layer is generally 0.38 to 0.76 mm from the viewpoint of improving puncture resistance. However, a thinner adhesive layer can be used to address appearance issues such as orange peel caused by the difference in shrinkage between the light-reflecting material and the adhesive layer when producing the projection image display member, or to superimpose a main image and a ghost image to reduce the visibility of multiple images due to secondary reflections (ghost images) during image projection, as described below. From this viewpoint, it is preferable to use an adhesive layer with a thickness of 75 μm or less, and more preferably 50 μm or less. If the adhesive layer is wrinkled during lamination before processing, this may result in poor appearance of the projection image display member after processing. Therefore, when using the above-mentioned preferred thin adhesive layer, it is preferable to process the projection image display member after it has been pre-laminated with the light-reflecting material.

[0032] The light-reflecting material constituting the projection image display member may also have a functional layer on at least one surface, such as a hard coat layer, an abrasion-resistant layer, an anti-scratch layer, an anti-reflection layer, a color correction layer (visible light absorbing layer, polarizing layer), an ultraviolet absorbing layer, a light stabilizing layer, a heat absorbing layer, a printing layer, a gas barrier layer, or an adhesive layer. These layers may be single-layered or multi-layered, and one layer may have multiple functions.

[0033] Furthermore, if necessary, a functional layer identical to or different from that provided on the light-reflecting material can be provided on at least one surface of the projection image display member. As described below, depending on the installation angle of the projection image display member, reflection of P waves from the image projector may occur on the outermost surface of the transparent hard material. Furthermore, depending on the orientation state and phase difference conditions of the laminated film, P waves emitted from the image projector may be converted into a mixed wave of P waves and S waves after passing through the light-reflecting material, resulting in reflection of S waves that should not be included in the image projector at the outermost surface of the transparent hard material, resulting in the generation of overlapping images. To resolve this problem, an anti-reflection layer may be provided on the outermost surface of the transparent hard material to suppress reflection. Furthermore, the outermost surface of the transparent hard material is often required to have wear resistance, and a functional layer that combines the functions of a hard coat layer, a wear-resistant layer, an anti-scratch layer, etc. with the anti-reflection layer may be provided.

[0034] From the viewpoint of image clarity, the transparent display system of the present invention requires that when the center point of the projection image display member is defined as point C and the intersection line formed by the tangent surface of the projection image display member at point C and the horizontal plane passing through point C is defined as reference axis C, the angle θ1 between the orientation axis of the projection image display member at point C and the reference axis C must be between 0° and 30°, or between 85° and 90°.

[0035] The method for determining point C and reference axis C will be specifically explained below with reference to the drawings. First, a case will be described in which a laminate film, which will be described later as a suitable P-wave reflecting material, is applied to the entire projection image display member. A quadrilateral material is often used for projection image display members. When the projection image display member is a planar quadrilateral (including cases where the projection image display member is not strictly a planar quadrilateral due to slight rounding of corners or slight protrusions or recesses on the sides, but can be viewed macroscopically as the same), the intersection of the diagonal lines is defined as point C (reference numeral 10) as shown in FIG. 4A. Furthermore, when the projection image display member is planar, the surface of the projection image display member 3 corresponds to the tangent plane at point C 10. Therefore, as shown in FIG. 5, the intersection line between the tangent plane of the projection image display member 3 and a horizontal plane passing through point C (in other words, a horizontal plane passing through point C, reference numeral 11) is the reference axis C (reference numeral 12). In the case of a material having a shape other than a quadrilateral or a curved four-sided material, the point corresponding to the center of gravity of the material is defined as point C 10. Furthermore, in such a case, as shown in Figure 6A, the intersection of the tangent plane 13 at point C and the horizontal plane 11 passing through point C becomes the reference axis C12.

[0036] Next, we will describe the case where a laminate film (light-reflecting material) that can be preferably used as a P-wave reflecting material is applied to a portion of the projection image display member. In this case, since the image is projected within the area of ​​the laminate film that reflects P-polarized light, as shown in Figure 4B, the laminate film attached to the projection image display member is surrounded by a rectangle of the minimum area, and the intersection of the diagonals of this rectangle is defined as center point C 10. In this embodiment, reference axis C 12 is defined as the intersection line between tangent surface 13 of the projection image display member at point C and horizontal plane 11 that passes through point C, as shown in Figure 6B.

[0037] In the transparent display system of the present invention, the angle θ1 between the alignment axis at point C and the reference axis C must be 0° or more and 30° or less, or 85° or more and 90° or less. The angle θ1 between the alignment axis at point C and the reference axis C corresponds to reference symbol 15 in FIG. 7. The direction of the alignment axis at point C (reference symbol 14 in FIG. 7) can be determined from the direction of the alignment angle obtained by the method described in measurement method (7) below. Specifically, the alignment axis is defined as a line passing through point C on the surface of the projection image display member and extending in the direction of the alignment angle (if the projection image display member is curved, the alignment axis is defined as a line passing through point C and extending in the direction of the alignment direction projected onto the tangent surface at point C). This method is usually used to measure samples in film or sheet form, but even in structures that combine a transparent hard material and a light-reflecting material (laminated film), the transparent hard material often does not have a phase difference or orientation angle in light of the manufacturing method of the material, and since the influence of the orientation axis of these materials can be ignored, the angle θ1 between the orientation axis at point C and the reference axis C can also be determined in the same way for projection image display members. Note that hereinafter, "the angle θ1 between the orientation axis at point C and the reference axis C" may be simply referred to as "the angle θ1 at point C," and as will be described later, if the measurement point is a point other than point C, the angle θ can be determined in the same way except that the measurement point is replaced.

[0038] The angle θ1 at point C being between 0° and 30°, or between 85° and 90°, is a necessary condition for the image light emitted from the image projector to be displayed clearly at point C on the projection image display member without showing overlapping images.

[0039] In the transparent display system of the present invention, in order to resolve the issue of overlapping images (ghost images) caused by secondary light reflections that occur on the surface of a transparent hard material, which are different from the main image projected onto the projection image display member, it is preferable to use image light whose main component is P waves, which vibrate perpendicularly to the display surface (or the tangent surface in the case of a curved surface) of the projection image display member. P waves have an angle (Brewster's angle) at which the reflectance of image light reflected on the surface of a transparent hard material can be considered 0%, thereby reducing the occurrence of overlapping images when projecting an image onto an inclined projection image display member. Here, "mainly P waves" refers to a P-wave component that accounts for 51% to 100% of the light emitted from the image projector, assuming that the sum of the P-wave and S-wave components is 100%. To ensure clearer images without overlapping images, it is preferable that the P-wave component of the light emitted from the image projector be high, more preferably 90% or more, and even more preferably 99% or more, with the theoretical upper limit being 100%. The amount of P-wave component in the light of the image emitted from the image projector can be increased by using a light-emitting device equipped with a light source with a high ratio of P-waves as the image projector, or by selecting a retardation plate or polarizing plate with better polarization performance that effectively extracts only polarized waves in a specific direction within the image projector.

[0040] The projection image display member constituting the transparent display system of the present invention typically contains multiple light-reflecting interfaces resulting from differences in refraction. For example, when the laminate illustrated in FIG. 2 is used as the projection image display member, there are at least two light-reflecting interfaces, including the interface between the light-reflecting material and air and the interface between the outermost surface opposite the light-reflecting material and air. By increasing the proportion of P-waves in the light emitted from the image projector, the reflectance at the latter interface can be brought as close to 0% at Brewster's angle as possible. As a result, a transparent display system is achieved in which P-waves are reflected only at the highly reflective light-reflecting material portion, enabling clear image display without overlapping images. Furthermore, when the laminate illustrated in FIG. 3, in which the light-reflecting material is inserted between transparent hard materials, is used as the projection image display member, there are at least three light-reflecting interfaces, including the surface of the light-reflecting material and the interfaces between the transparent hard material and air on the incident surface and its opposite surface. However, the reflection at the latter two interfaces can be brought as close to 0% as possible at Brewster's angle as possible. Therefore, a clearer image display can be achieved by reflecting P-waves only at the light-reflecting material portion. The multiple image display in each configuration will be described separately later.

[0041] However, the inventors discovered that even when a light source primarily composed of P waves is used as an image projector and a projection image display member is positioned at a Brewster angle where reflection from the outermost surface of a transparent hard material is not possible, undesirable secondary reflection occurs at the outermost surface of the transparent hard material opposite the image incident side after passing through the light-reflecting material, depending on the orientation angle and phase difference of the projection image display member. More specifically, they discovered that depending on the orientation angle and phase difference of the light-reflecting material (laminated film) used in the projection image display member, the P waves emitted from the image projector are converted into mixed waves with S waves, causing reflections derived from S waves at the outermost surface of the transparent hard material, resulting in the perception of overlapping images. In particular, when the vibration direction of the P waves from the image projector and the orientation axis direction of the projection image display member are not parallel or perpendicular, the conversion to a mixed wave of P waves and S waves tends to be stronger depending on the angle between the two. It was found that, in particular, when the angle between the two is 45°, the conversion efficiency is highest, increasing the amount of S-wave components and resulting in stronger overlapping images.

[0042] Such overlapping images caused by the conversion of P-waves and S-waves into a mixed wave can be eliminated by making the vibration direction of the P-waves emitted from the image projector and the orientation axis direction of the projection image display member closer to parallel or perpendicular. Specifically, there are two methods: adjusting the P-wave vibration direction of the image projector so that the vibration direction of the P-waves coincides with the orientation axis direction of the projection image display member, and designing a light-reflecting material so that the orientation axis direction of the projection image display member coincides with the P-wave vibration direction of the image projector.

[0043] However, in the former case, in order to control the vibration direction of the P waves of the image projector's light source, it is necessary to change the orientation of the retardation plate and polarizing plate, which are components that emit polarized light in the image projector, but the installation conditions of these components are crucial to the color gamut and brightness of the image projector, so design changes are not easy. Also, it is possible to align the P wave vibration direction of the image with the orientation axis direction of the projected image display member by installing the image projector body at an angle to align it with the orientation axis direction of the projected image display member, but depending on the installation space issues and the irradiation range of the light of the image, the distance from the image projector to the projected image display member varies depending on the projection location, which can cause problems with image visibility, such as the image appearing to be stretched diagonally or the brightness of the image changing in parts. Therefore, the preferred conditions for achieving a clear image display are to use an image projector in which the vibration direction of the P waves is parallel to the long or short side direction of the image output surface of the image projector, to design the image projector so that the long or short side of the output surface is parallel to the reference axis of the projected image display member, and to design the projection image display member so that its orientation axis direction is parallel to the vibration direction of the P waves from the image projector.

[0044] Furthermore, what is important here is that in the transparent display system of the present invention, the image display surface of the projection image display member is inclined relative to the image output surface of the image projector. Due to this inclination of the projection image display member, the P-wave vibration direction of the image as seen by the observer and the orientation axis direction of the projection image display member appear to differ from the orientation axis direction in the plane when the projection image display member is viewed from the vertical direction, which affects the polarization state, especially the polarization state after transmission through the laminate film, which causes secondary reflections.

[0045] Specifically, if the vibration direction of the P-waves from the image projector and the orientation axis direction of the projection image display member are completely parallel or perpendicular (the angle θ1 at point C is 0° or 90°), there is no effect. However, if the angle θ1 at point C is any other value, the orientation axis direction of the projection image display member appears closer to the horizontal plane as seen by the observer. That is, if the angle θ1 at point C is larger (greater than 45° but less than 90°), the orientation axis direction of the projection image display member at point C appears to the observer as the angle between the orientation axis of the projection image display member and the reference axis becomes smaller, resulting in a state close to 45°, which increases the risk of image overlap. On the other hand, if the angle θ1 at point C is smaller than 45° (greater than 0° but less than 45°), the angle between the orientation axis of the projection image display member and the reference axis becomes smaller, which reduces the apparent angle between the P-wave vibration direction of the image light and the orientation axis direction of the projection image display member, thereby reducing the risk of image overlap at point C.

[0046] In light of the above, it is necessary to design the angle θ1 at point C to be a large value close to 90°, or an angle that reduces the apparent angle between the P-wave vibration direction and the orientation axis direction of the projection image display member, taking into account the inclination of the projection image display member. In other words, it is necessary to set the angle θ1 at point C to be between 0° and 30°, or between 85° and 90°. To further reduce the risk of overlapping images, it is preferable to design the angle θ1 at point C to be closer to 0° or closer to 90°.

[0047] One method for making the angle θ1 at point C between 0° and 30°, or between 85° and 90°, is to determine the orientation axis direction of the projection image display member, and then bond the projection image display member to the projection image display member so that the orientation axis satisfies the range of the angle θ1 at point C.

[0048] As mentioned above, the orientation axis of the projection image display member is determined by the orientation of the light-reflecting material, which is one of the constituent materials. However, cutting the light-reflecting material in a specific direction so as to satisfy the range of the angle θ1 at point C and laminating it each time a projection image display member is produced significantly reduces the manufacturing efficiency of the projection image display member. Therefore, it is preferable to cut the laminate film used as the light-reflecting material parallel to the longitudinal or width direction of the product roll and simply laminate it with the end faces aligned so that the angle θ1 at point C falls within the preferred range. From this perspective, it is preferable that the orientation axis of the laminate film used as the light-reflecting material be between 0° and 30°, or between 85° and 90°.

[0049] In the transparent display system of the present invention, in order to achieve clear image display over a wide range and a wide viewing angle on the projection image display member without overlapping images, it is preferable that the above orientation angle conditions are met over the entire projection image display member. Specifically, as shown in FIG. 8 , when the midpoint between point C and the upper end is defined as point X1 (reference number 16), the midpoint between point C and the lower end is defined as point X2 (reference number 17), the midpoint between point C and the left end is defined as point Y1 (reference number 18), and the midpoint between point C and the right end is defined as point Y2 (reference number 19), and the intersections between the tangent plane at each of points X1, X2, Y1, and Y2 and the horizontal plane passing through each of these points are defined as reference axes X1, X2, Y1, and Y2, respectively, it is preferable that the angle θ formed between the orientation axis of the projection image display member at points C, X1, X2, Y1, and Y2 and the reference axes at each of these points (reference axis C, reference axis X1, reference axis X2, reference axis Y1, and reference axis Y2) is 0° or more and 30° or less, or 85° or more and 90° or less.

[0050] To set the angle θ at points C, X1, X2, Y1, and Y2 to 0° or more and 30° or less, or 85° or more and 90° or less, it is preferable to use, for example, a laminate film whose orientation axis is aligned over the entire surface as the light-reflecting material. To obtain such a laminate film, it is preferable to set the ratio of the stretching ratio in the longitudinal direction to the width direction when biaxially stretching is performed, the stretching speed in the width direction, and the stretching ratio when stretching in the heat treatment step to the preferred conditions described below.

[0051] Furthermore, from the viewpoint of suppressing the occurrence of overlapping images over a wide range of the projection image display member, it is preferable that the variation in the orientation angle at points C, X1, X2, Y1, and Y2, when the direction of the reference axis (reference axis C, reference axis X1, reference axis X2, reference axis Y1, and reference axis Y2) at each point is 0°, be small, specifically, be 20° or less. By adopting such a design, the angle between the P-wave vibration direction and the orientation angle of the projection image display member is within a certain range over a wider range of the projection image display member surface, resulting in a transparent display system in which overlapping images are less likely to be visible throughout the surface. From this viewpoint, it is preferable that the variation in the orientation angle be as small as possible, more preferably 15° or less, even more preferably 10° or less, and particularly preferably 5° or less. From this viewpoint, the smaller the variation in the orientation angle, the better, but from the viewpoint of feasibility, the lower limit is preferably 1°.

[0052] Such orientation angle conditions can be achieved, for example, by using a laminate film described below as a light-reflecting material constituting the projection image display member of the transparent display system of the present invention. In particular, it is effective to set the laminate film manufacturing conditions, such as the ratio of the longitudinal and widthwise stretching ratios when biaxially stretching is performed, the widthwise stretching speed, and the stretching ratio when stretching in the heat treatment step, to the preferred conditions described below. Furthermore, in terms of the configuration of the laminate film, it is effective to use an alternating laminate structure in which the outermost layers on both sides are the same layer, and the main component of the thermoplastic resin layer not located on the outermost surface is an amorphous thermoplastic resin. These methods can be used in combination as appropriate.

[0053] In the transparent display system of the present invention, when the projection image display member is tilted by rotating it around a reference axis C, and P waves are incident on the surface of the projection image display member so that the angle between the normal to the tangent surface of the projection image display member at point C and the direction of propagation of the P waves is 60° and the reference axis C and the direction of propagation of the P waves are perpendicular, it is important that the average reflectance at wavelengths of 400 nm to 700 nm is 5% or more and 100% or less. By adopting this configuration, even under conditions where the polarized P waves are not normally reflected (i.e., when the incident angle is Brewster's angle), the reflective effect of the light-reflecting material of the projection image display member can ensure sufficient visibility of the scenery while projecting the image. The higher the average reflectance, the more preferable it is in terms of clearly projecting the image from the image projector; the upper limit is theoretically 100% according to the reflection spectrum measurement method described below. On the other hand, a high average reflectance may reduce the visibility of the scenery behind the projection image display member; if this point is taken into consideration, it is also preferable to lower the upper limit of the average reflectance. Regarding "tilting the projection image display member by rotating it around the reference axis C," if the projection image display member cannot be rotated, the position of the image projector or the direction of light irradiation may be adjusted so that the angle between the normal to the tangent surface of the projection image display member at point C and the direction of propagation of the P-wave is 60° and the reference axis C and the direction of propagation of the P-wave are perpendicular.

[0054] Therefore, from the above viewpoints, the average reflectance is preferably 5% or more and 65% or less, more preferably 5% or more and 50% or less, and even more preferably 15% or more and 35% or less. Having an average reflectance of 35% or less also reduces reflections around the image projector, making the superimposition of the image and the scenery on the projection image display member clearer. Furthermore, the laminate film described below, which can be preferably used in the projection image display member of the present invention, usually has a low reflectance at small angles of incidence. Therefore, even if the average reflectance of the projection image display member reaches 50%, it can be suitably used in the transparent display system of the present invention.

[0055] The average reflectance can be calculated from the resulting reflectance spectrum data by measuring the reflectance at a predetermined incident angle with a sampling pitch of 1 nm using a known spectrophotometer according to the measurement method (5) described below. In the present invention, the condition can be determined to be met if the following condition is met: "When the projection image display member is tilted by rotating it around the reference axis C, and P waves are incident on the projection image display member so that the angle between the normal to the tangent surface of the projection image display member at point C and the direction of propagation of the P waves is 60° and the reference axis C is perpendicular to the direction of propagation of the P waves, the average reflectance at wavelengths of 400 nm to 700 nm is 5% or more and 100% or less." If the projection image display member has a curved surface, the "normal at point C to the image display surface" is treated as the "normal at point C to the tangent surface of the image display surface" (hereinafter, the same applies to indicators such as optical properties measured by irradiating light at a specific point on the projection image display member at a predetermined incident angle).

[0056] To achieve an average reflectance of 5% or more and 100% or less, or within the above-mentioned preferred range, it is preferable to use a laminate film, as described below, as the light-reflecting material constituting the projection image display member. In particular, it is effective to adjust the difference in refractive index (in-plane normal refractive index) between adjacent layers of two types of thermoplastic resin layers constituting the alternating laminate structure of the laminate film and the number of layers. More specifically, for the former, it is preferable to set the difference in in-plane normal refractive index to 0.15 or less. On the other hand, if the difference in in-plane normal refractive index is too large, the average transmittance of light with wavelengths of 400 to 700 nm incident perpendicularly to the laminate film surface decreases, reducing the visibility of the scenery. From the above perspective, the difference in in-plane refractive index is more preferably 0.12 or less, and even more preferably 0.08 or less. For the latter, the average reflectance can be increased by increasing the number of layers.

[0057] Furthermore, in the transparent display system of the present invention, the average transmittance of visible light incident perpendicularly to the surface of the projection image display member must be 50% or more and 100% or less. Visible light, as used herein, refers to light in a wavelength band of 400 nm or more and 800 nm or less. Such a high transmittance of visible light allows the projection image display member to have transparency similar to that of transparent glass or a transparent resin film, thereby improving visibility when viewing a landscape through the projection image display member from a direction perpendicular to the surface of the projection image display member. From the above perspectives, the average transmittance is preferably 70% or more, more preferably 80% or more, even more preferably 83% or more, and particularly preferably 89% or more. If the average transmittance is 89% or more, the viewer can view the background without noticing the presence of a light-reflecting member within the projection image display member. From the perspective of ease of implementation, the upper limit of the average transmittance is preferably 99%.

[0058] The average transmittance can be measured by measuring the transmittance of light having a wavelength of 400 to 800 nm at an incident angle of 0° in 1 nm increments using a spectrophotometer and calculating the average value according to the measurement method (4) described below. In the present invention, if the condition "the average transmittance of visible light incident perpendicularly to the surface of the projection image display member is 50% or more and 100% or less" is satisfied, it can be determined that the condition is satisfied.

[0059] One method for increasing the average transmittance is to use a laminated film, as described below, as a light-reflecting material. In particular, reducing the difference in refractive index (in-plane average refractive index) between adjacent layers of the two types of thermoplastic resin layers constituting the alternating laminate unit of the laminated film in a direction parallel to the film surface is effective for increasing the average transmittance. Specifically, the difference in the in-plane average refractive index is preferably 0.07 or less, more preferably 0.06 or less, even more preferably 0.03 or less, and particularly preferably 0.02 or less. From the above viewpoint, the lower the difference in the in-plane average refractive index, the better, with the theoretical lower limit being 0.

[0060] In the transparent display system of the present invention, it is preferable that the area A (nm·%) enclosed by the reflection spectrum at wavelengths of 400 to 700 nm when P waves are incident on the surface of the projection image display member from a direction in which the angle between the normal to the tangent surface at point C and the normal to the tangent surface is 60° in a plane including the orientation axis, and the reflection spectrum at wavelengths of 400 to 700 nm when P waves are incident on the surface of the image display surface from a direction in which the angle between the normal to the tangent surface at point C and the normal to the tangent surface is 60° in a plane including a straight line perpendicular to the orientation axis within the tangent surface, satisfies 1000≦A≦6000.

[0061] Here, when calculating the area A (nm·%), "a plane containing the normal to the tangent plane at point C and a line within the tangent plane perpendicular to the orientation axis" refers to a plane containing a line within the film plane that forms a right angle with the orientation axis, and "reflection spectrum" refers to a spectrum obtained with the horizontal axis as wavelength (nm) and the vertical axis as reflectance (%) (this also applies to the laminated film of the present invention described below). In the following, "the area enclosed by the reflection spectrum at wavelengths of 400 to 700 nm when P waves are incident on the surface of the projection image display member from a direction in which the angle between the normal to the tangent surface at point C and the normal to the tangent surface in a plane containing the orientation axis is 60°, and the reflection spectrum at wavelengths of 400 to 700 nm when P waves are incident on the surface of the image display surface from a direction in which the angle between the normal to the tangent surface at point C and the normal to the tangent surface in a plane containing a line perpendicular to the orientation axis in the tangent surface" is sometimes referred to as "the area enclosed by the two reflection spectra," and "A" is sometimes referred to as "area A" (these points also apply to the laminate film of the present invention described below, with point C replaced by point CF).

[0062] Among the components constituting the projection image display member of the present invention, light-reflecting materials (e.g., laminate films described below) that have the function of reflecting P waves incident from an oblique direction exhibit the property of transmitting almost all P waves incident in the perpendicular direction and increasing reflectivity as the incident angle becomes more oblique. This property is manifested by the difference in in-plane and perpendicular refractive indices occurring when the multiple thermoplastic resin layers constituting the laminate film undergo a stretching film-forming process, resulting in a difference in the in-plane and perpendicular refractive indices. In particular, laminate films that can be preferably used in the transparent display system of the present invention exhibit an alternating laminate structure of two types of thermoplastic resin layers, as described below, with one thermoplastic resin layer preferably being a crystalline thermoplastic resin layer and the other being a microcrystalline or amorphous thermoplastic resin layer. By reducing the difference in the in-plane refractive indices between the different thermoplastic resin layers constituting the laminate film, such laminate films can achieve excellent transmittance and almost no reflection of light upon perpendicular incidence. On the other hand, by increasing the difference in the perpendicular refractive indices between the two types of thermoplastic resin layers, light at large angles of incidence can be reflected.

[0063] In the case of crystalline stretched films, unless a special polymer (e.g., polystyrene) is used that exhibits negative birefringence and is oriented perpendicular to the orientation direction upon stretching, the refractive index generally tends to increase along the orientation axis due to the alignment of the resin's crystalline segments, while the refractive index decreases in the direction perpendicular to the in-plane orientation direction and in the thickness direction as a reaction. This means that the refractive index change varies depending on the vibration direction and incident angle of the irradiated P wave and the tilt direction of the projection image display member. Therefore, the difference between the in-plane refractive index in the vibration direction of the P wave corresponding to the polarized light irradiation surface and the refractive index in the thickness direction varies depending on the tilt direction from the normal to the tangent surface of the projection image display member. As a result, the wavelength of the interference reflection and the difference in the in-plane average refractive index of the two alternating polymer layers also vary slightly. As shown in Figure 9, depending on the tilt axis direction, a spectrum with high reflectivity is obtained when tilted toward the orientation axis with a particularly high refractive index, and a spectrum with low reflectivity is obtained when tilted perpendicular to the orientation axis direction, resulting in a shift in the wavelength of the interference-reflected light (spectral shift).

[0064] In the transparent display system of the present invention, the area A can be calculated and determined by the following method, which will be described in detail with reference to Figures 9 and 10. Note that the reference numerals 20 to 22 in Figures 9 and 10 respectively represent the reflection spectrum at wavelengths of 400 to 700 nm when P waves are incident on the projection image display member from a direction tilted by 60° from the normal to the tangent plane at point C toward the orientation axis, the reflection spectrum at wavelengths of 400 to 700 nm when tilted by 60° in a direction perpendicular to the orientation axis, and the area A.

[0065] First, with wavelength (nm) on the horizontal axis and reflectance (%) on the vertical axis, a reflection spectrum for wavelengths of 400 to 700 nm is plotted when P-waves are incident on the projection image display member from a direction where the angle between the normal to the tangent plane at point C and the normal to the tangent plane is 60° in a plane containing the orientation axis. The reflection spectrum for wavelengths of 400 to 700 nm is plotted in the same manner, except that the P-wave irradiation direction is a direction where the angle between the normal to the tangent plane at point C and the normal to the tangent plane is 60° in a plane containing a line perpendicular to the orientation axis within the tangent plane. Next, the region enclosed by the two reflection spectra is identified. If the entire region falls within the wavelength range of 400 to 700 nm, as in the example of Figure 9, the area of ​​the region is calculated and designated as Area A (nm / %). If the region does not fall within the wavelength range of 400 to 700 nm, as in the example of Figure 10, the area of ​​the portion of the region within the wavelength range of 400 to 700 nm is calculated and designated as Area A (nm / %). When specifying the area surrounded by the two reflection spectra, if there are multiple surrounded areas, the area of ​​the largest area within the wavelength range of 400 to 700 nm is used as the area A (nm·%). The areas of the surrounded areas are calculated using the trapezoidal method.

[0066] The calculation method of area A will be described below with reference to Fig. 11, which is a schematic diagram illustrating the calculation method of area A in the present invention. In Fig. 11, reference numeral 20 denotes the reflection spectrum (hereinafter sometimes referred to as reflection spectrum α) at ​​wavelengths of 400 to 700 nm when P waves are incident on the projection image display member from a direction tilted 60° from the normal to the tangent plane at point C toward the orientation axis. Reference numeral 21 denotes the reflection spectrum (hereinafter sometimes referred to as reflection spectrum β) at wavelengths of 400 to 700 nm when tilted 60° toward a direction perpendicular to the orientation axis. Reference numeral 23 denotes the area of ​​a partial region surrounded by two reflection spectra, wavelength n and wavelength n+1 (in other words, area A corresponding to a wavelength of 1 nm).

[0067] The region between the two reflection spectra is divided into wavelength intervals of 1 nm, and the reflectances on the short wavelength side (represented as n (nm) in FIG. 11) of the reflection spectrum α and the reflection spectrum β are respectively represented as R ｎ , R' ｎ , the reflectances on the long wavelength side (n+1 (nm) in FIG. 11) of the reflection spectrum α and the reflection spectrum β are R ｎ＋１ , R' ｎ＋１ The area of ​​the region sandwiched between both reflection spectra is calculated according to the integral formula of the following formula (1). In the following formula (1), a represents the wavelength at the short wavelength end of the region sandwiched between both reflection spectra, and b represents the wavelength at the long wavelength end of the region sandwiched between both reflection spectra (since area A is calculated in the wavelength range of 400 to 700 nm, the minimum value of a is 400 nm and the maximum value of b is 700 nm). When the region sandwiched between both reflection spectra falls within the wavelength range of 400 to 700 nm, the area of ​​the region sandwiched between both reflection spectra is area A. When the region sandwiched between both reflection spectra does not fall within the wavelength range of 400 to 700 nm, the area of ​​the portion of the region sandwiched between both reflection spectra with a wavelength of 400 to 700 nm is area A.

[0068]

[0069] An area A of 1,000 or more and 6,000 or less means that the difference between the orientation axis direction in the plane of the projection image display member and the orientation direction perpendicular to the orientation axis direction in the film plane is within a moderate range. Such a projection image display member reflects light more strongly when tilted parallel to the orientation axis direction. Therefore, by installing a video projector so that light (P waves) is irradiated from the orientation axis direction, both background visibility and image clarity can be achieved. Meanwhile, because the difference in orientation between the two perpendicular directions is moderately suppressed, there are also advantages in that the image is less likely to become dark even when viewed from an oblique angle and that reflections of the surrounding scenery can be reduced. In other words, such a projection image display member is a suitable material for transparent display systems that project images over a wide range and a wide viewing angle.

[0070] From the above viewpoint, the area A is preferably 1000 or more and 4500 or less, more preferably 2000 or more and 4500 or less. When producing a laminated film to be used as a light-reflecting material, if the film is stretched strongly in a specific direction by sequential biaxial stretching, it is preferable to stretch at a higher magnification in the width direction than in the longitudinal direction. This is because it is easier to control the in-plane orientation state of the film across the entire width direction of the film. The size of the area A varies depending particularly on the in-plane refractive index of layer A (the difference between the refractive index in the direction of the orientation axis and the refractive index in the direction perpendicular to the orientation axis in the film plane), but also on the difference in the in-plane refractive index of the two types of thermoplastic resin layers.

[0071] In order to control the area A within the above-mentioned preferred range, it is effective to use a laminate film having the following characteristics as the light-reflecting material in the projection image display member of the transparent display system of the present invention. In terms of controlling the area A within the above-mentioned preferred range, the laminate film as the light-reflecting material is preferably formed by alternately laminating 51 or more layers of two types of resin layers selected so that the difference in the in-plane average refractive index between the two types of alternatingly laminated thermoplastic resin layers is 0.040 or less (preferably less than 0.040) and the difference in the in-plane normal refractive index is 0.150 or less (preferably 0.120 or less). Furthermore, it is also preferable to set the stretching magnification ratio in the longitudinal direction to the width direction within the preferred range described below, and further apply all or part of the following stretching film-forming conditions as a method for producing a biaxially stretched film.

[0072] When producing a laminate film, it is necessary to achieve a more uniform orientation state across the width direction during the width direction stretching process. In typical biaxially stretched films, a bowing phenomenon occurs, resulting from the shrinkage force difference caused by the temperature difference between the preheating and heat treatment processes. As a result, the orientation state (refractive index state) of the resulting laminate film differs between the width direction center and the width direction edge. To mitigate this bowing phenomenon and improve the orientation uniformity across the width direction, it is necessary to suppress the shrinkage force in the longitudinal direction during stretching. For this purpose, it is preferable to apply a stepwise temperature gradient during the stretching process. By providing a temperature gradient during the stretching process, the effects of shrinkage in the longitudinal direction due to Poisson's ratio caused by width direction stretching and the effects of the thermal shrinkage force difference caused by the temperature difference between the preheating and heat treatment processes before and after the stretching process can be reduced, thereby improving the orientation uniformity across the width direction of the resulting film. In this case, the temperature gradient is set within a temperature range from the glass transition temperature to the crystallization temperature of the resin with the highest glass transition temperature in the laminated film, and it is preferable that there be two or more temperature gradients before reaching the heat treatment temperature.

[0073] However, simply reducing the shrinkage force in the stretching step may result in different orientations in the width direction due to the shrinkage force caused by the temperature difference before and after the heat treatment step. Therefore, as a method for reducing the shrinkage force after the stretching step and further improving the orientation uniformity in the width direction, it is also preferable to use a method of lowering the heat treatment temperature to reduce the shrinkage force toward the stretching step in the longitudinal direction, or a method of increasing the rigidity of the film by extending the intermediate region between the stretching step and the heat treatment step and providing a temporary constant temperature or low temperature region (a region satisfying stretching temperature + 30°C ≥ intermediate region temperature). Increasing the rigidity of the film can reduce the effect of shrinkage in the longitudinal direction due to Poisson's ratio caused by the recoil of stretching in the width direction, thereby further reducing the bowing phenomenon.

[0074] The former method of reducing the heat treatment temperature may result in insufficient crystallization due to heat setting, resulting in an increased thermal shrinkage rate at the expense of uniform retardation and orientation angle. Therefore, it is preferable to suppress the shrinkage force in the longitudinal direction and then microstretch the laminate film in the width direction during the heat treatment process to place it in a tensed state. By adopting such a method, shrinkage in the longitudinal direction due to the temperature difference between the cooling process after the heat treatment process and the cooling process can be induced, reducing the bowing in the width direction that remained before the heat treatment process, thereby resulting in more uniform orientation in the width direction of the laminate film. In this case, the microstretching ratio (heat treatment post-stretching ratio) is 3% or more and 18% or less, more preferably 5% or more and 10% or less. By setting the microstretching ratio within the above range, a favorable balance can be achieved between uniform orientation in the width direction and thermal shrinkage in the width direction at high temperatures. Therefore, when the resulting laminate film is used as a projection image display member, both image display performance and good appearance can be achieved.

[0075] In the transparent display system of the present invention, it is preferable that the in-plane retardation is 3,000 nm or more and 10,000 nm or less at points C, X1, X2, Y1, and Y2, and the coefficient of variation (standard deviation / average value) of the in-plane retardation at each point is 0.1 or less. By controlling the in-plane retardation at each point and its coefficient of variation within the above ranges, it is possible to suppress color unevenness that is visible when the film is used as a component of a projection image display member exhibiting orientation, even when an observer wears polarized sunglasses for the purpose of preventing glare.

[0076] In the transparent display system of the present invention, by setting the in-plane retardation to 3000 nm or more, the phase change of the polarized light wave becomes finer, making color unevenness less visible. The in-plane retardation of the projection image display member is mainly caused by the phase of the light-reflecting material that constitutes the projection image display member, and a value close to 10,000 nm indicates a large difference between the refractive index in the direction parallel to the alignment axis of the projection image display member and the refractive index in the direction perpendicular to the alignment axis on the surface of the projection image display member. By keeping the in-plane retardation to 10,000 nm or less, image display properties at wide viewing angles are improved, unlike when a uniaxially stretched film is used as the light-reflecting material. From the above perspective, the in-plane retardation is more preferably 3000 nm or more and 5,000 nm or less. From the same perspective, it is also preferable that the coefficient of variation of the in-plane retardation is small, more preferably 0.08 or less, even more preferably 0.05 or less, with the theoretical lower limit being 0. It is particularly preferable that these preferred ranges are satisfied simultaneously.

[0077] In order to set the in-plane retardation at each point of the projection image display member to 3,000 nm or more and 10,000 nm or less, or the above-mentioned preferred range, and to set the coefficient of variation of the in-plane retardation at each point to 0.1 or less, or the above-mentioned preferred range, it is preferable to use a laminate film (described later) that can be preferably used as a light-reflecting material. Among the preferred stretching conditions described later in the sequential biaxial stretching film formation of the laminate film, it is effective to set the stretching ratio within a preferred range, provide a temperature gradient in the stretching step in the width direction stretching, provide a temporary low-temperature region before the heat treatment step, and perform slight stretching in the heat treatment step.

[0078] In the transparent display system of the present invention, the image projector irradiates P waves, and the angle between the electric field oscillation direction of the P waves on the surface of the projection image display member and the orientation axis at point C of the projection image display member is preferably 65° to 90°. The electric field oscillation direction of the P waves refers to the wave amplitude direction different from the propagation direction of the P waves. The electric field oscillation direction of the P waves can be determined by rotating the absorption axis direction of the linear polarizer on a projection image display member arranged so that the incident angle is 60°, and by identifying the absorption axis direction in which the reflected image appears darkest. By setting the angle between the electric field oscillation direction of the P waves on the surface of the projection image display member and the orientation axis at point C of the projection image display member to be 65° or more, the average visible light reflectance of the P waves of the projection image display member is reduced. This slightly reduces the brightness of the image projected from the image projector, while reducing the reflection of the surrounding environment around the image projector on the projection image display member. While the image from the image projector can be made clearer by increasing the brightness of the light emitted by the image projector, it is difficult to reduce the reflection of the surrounding environment without reducing the reflective performance of the projection image display member. Therefore, this type of design is preferable for achieving a clear image display without reflection on the projection image display member. Of course, the best image display performance can be achieved by designing the angle between the electric field oscillation direction of the P-wave and the orientation axis at point C of the projection image display member closer to 90°. To achieve an angle between the electric field oscillation direction of the P-wave on the surface of the projection image display member and the orientation axis at point C of the projection image display member of 65° to 90°, the image projector and the projection image display member can be selected and positioned so that the angle between the orientation axis at point C (the method for determining this will be described later) and the electric field oscillation direction of the incident P-wave is within the above range.

[0079] In the transparent display system of the present invention, the projection image display member preferably has a configuration in which a transparent hard material and a light-reflecting material are laminated via an adhesive layer, and the light-reflecting material is located on the light incident surface of the projection image display member. Here, "the light-reflecting material is located on the light incident surface of the projection image display member" means that the light-reflecting material is located closer to the video projector than the transparent hard material. This embodiment corresponds to the lamination-type configuration in which the projection image display member has a light-reflecting material on the surface of a transparent support, as exemplified in FIG. 2. Another preferred embodiment of the transparent display system of the present invention is an embodiment in which the projection image display member has a configuration in which a transparent hard material and a light-reflecting material are laminated via an adhesive layer, and the light-reflecting material is located in the middle of the projection image display member. This embodiment corresponds to the insertion-type configuration in which the light-reflecting material is located inside a transparent support, as exemplified in FIG. 3.

[0080] Although both configurations have in common the fact that P waves from the image projector are reflected by a light-reflecting material, they differ in the state of occurrence of a secondary reflected image (ghost image) that occurs on the surface of the transparent hard material except for a specific incident angle condition called Brewster's angle, which does not cause reflection on the surface of the transparent hard material. The higher the intensity of this ghost image relative to the intensity of the main reflected image reflected by the light-reflecting material, the higher the risk that the viewer will see a multiple image.

[0081] When the projection image display member is of the interpolation type as shown in Figure 3, under incident angle conditions other than the Brewster angle, at least two types of ghost images are generated, as shown in Figure 12: a ghost image (reference numeral 24) generated on the outermost surface of the transparent hard material on the side where the image light is incident, and a ghost image (reference numeral 25) generated on the outermost surface opposite the side where the image light is incident. Considering that the amount of light after passing through the light-reflecting material is reduced due to reflection on the light-reflecting material, the former ghost image of the two types of ghost images is more clearly visible. In order to suppress the ghost image generated on the outermost surface on the side where the image light is incident, it is important to reduce the reflection of the P-wave incident from the image projector on the surface of the transparent hard material.

[0082] In general, it is difficult to suppress the reflection of P waves on the surface of a transparent hard material by any method other than installing a projection image display member so that the angle of incidence of light from the image projector is Brewster's angle. Therefore, in order to suppress ghost images that occur on the outermost surface on the side where the image is incident, it is necessary to provide a functional layer that makes the ghost image on the outermost surface of the transparent hard material less visible, to make the ghost image virtually invisible by superimposing the ghost image on the main image (reference numeral 26) projected by reflection on the light-reflecting material, or to change the positional relationship between the image projector and the projection image display member so that the angle of incidence approaches Brewster's angle so as to minimize the reflection of P waves.

[0083] One method for providing a functional layer to obscure ghost images on the outermost surface where the light from the first image is incident is to provide a curable resin layer exhibiting a low refractive index on the outermost surface of a transparent hard material. Such a curable resin layer preferably has a refractive index lower than that of the transparent hard material and as close to the refractive index of air (= 1) as possible. In this case, a binder layer may be inserted between the transparent hard material and the curable resin layer to improve adhesion between them, so that the curable resin layer can exhibit a long-term ghost image suppression effect. However, when a transparent display system is used, for example, in an automotive head-up display, the outermost surface of the projection image display member requires high scratch resistance. Therefore, it is technically difficult to design a curable resin layer that combines scratch resistance, hardness, and transparency.

[0084] A second method for superimposing the main image reflected by the light-reflecting material and the ghost image to make them virtually invisible is, for example, to thin the adhesive layer 1 on the image projector side of the adhesive layers 1 and 2 (reference numerals 27 and 28) that make up the projection image display member, as shown in Figure 13. This configuration brings the image reflected by the light-reflecting material and the ghost image reflected by the outermost surface of the transparent hard material closer together as viewed by the observer, making it less likely for the observer to perceive the ghost image as a multiple image, even if the ghost image is highly bright. However, such a projection image display member has poor impact resistance on the side with the thinner adhesive layer, which can be a problem in applications requiring extremely high impact resistance for the projection image display member, such as automotive head-up displays.

[0085] Considering the above, the most effective method for suppressing overlapping images when the projection image display member is configured using an interpolation method is to adjust the positional relationship between the image projector and the projection image display member so that the reflection of P waves is minimized, thereby bringing the angle of incidence close to the Brewster angle. From this perspective, when the projection image display member is configured using an interpolation method, in the transparent display system of the present invention, when the angle θ2 between the light emitted by the image projector and the normal to the tangent surface of the projection image display member is defined as θ2, it is preferable that θ2 be 45° or more and 65° or less, and more preferably 48° or more and 65° or less. θ2 corresponds to the angle of incidence of light from the image projector, and by positioning the image projector and the projection image display member so that this is within the above range, the presence of ghost images reflected on the surface can be minimized even when an image is projected widely over the entire surface of the projection image display member.

[0086] In this case, by increasing the reflectance of light from the light-reflecting material, the contrast ratio of the main image to the ghost image is further increased, making the ghost image less noticeable. Therefore, when P waves are incident on the image display surface of the projection image display member at an angle of θ2, the average reflectance at wavelengths of 400 to 700 nm is preferably 35% to 100%, more preferably 45% to 100%.

[0087] Furthermore, when an observer views a projection image display member positioned at an angle relative to the horizontal plane, the incident angle θ2 at which image light is delivered to the observer by specular reflection from the image projector varies depending on the area where the image is projected. This change in eye level is referred to as the eyepoint. For example, in the case of a head-up display in an automobile, when the image is projected downward from a position directly in front of the observer at seated height, the incident angle of the image light often changes by approximately 5°, and this 5° corresponds to the amount of change in angle based on the eyepoint. Since the transparent display system of the present invention is required to clearly display images without overlapping images over a wide area of ​​the projection image display member, the average reflectance at wavelengths of 400 to 700 nm when P waves are incident on the image display surface of the projection image display member from a direction of θ2 + 5° is preferably 35% to 100%, more preferably 45% to 100%. This preferred reflectance can be achieved by designing the resin composition of the laminate film (particularly a combination of polymer layers with a large difference in refractive index perpendicular to the plane), the number of layers, the layer thickness distribution, and the overall thickness of the laminate film so as to reflect the visible light wavelength band. Note that the average reflectance within the above range can be preferably adopted whether the projection image display member is an interpolation type or a bonding type.

[0088] On the other hand, when the projection image display member is a bonding type as shown in Figure 14, a light-reflecting material is laminated on the outermost surface of the projection image display member facing the image projector, so only the ghost image 25 generated on the outermost surface opposite the side where the image is incident is visible as a multiple image. In this case, the brightness of the ghost image depends on the amount of light transmitted through the light-reflecting material, so under incident angle conditions other than Brewster's angle, the ghost image can be reduced by adding a visible light absorber (described below) or by increasing the reflectivity of the light-reflecting material. Unlike interpolation-type projection image display members, bonding-type projection image display members can suppress multiple images depending on the design of the projection image display member, so the range of incident angles at which multiple images are visible tends to be wider for bonding-type projection image display members than for interpolation-type projection image display members.

[0089] Specifically, if the angle between the light emitted by the image projector and the normal to the tangent surface of the projection image display member is θ2, setting θ2 in the range of 35° to 70° can suppress overlapping images and make the main image clear. Of course, by bringing the incident angle closer to the Brewster angle, reflection from the transparent hard material is reduced and overlapping images become more visible, so θ2 is more preferably 45° to 65°, and more preferably 48° to 65°. Setting θ2 to 35° or more ensures sufficient reflection from the light-reflecting material and reduces the amount of P-wave components reflected by the surface of the transparent hard material, making overlapping images less visible. On the other hand, setting θ2 to 70° or less suppresses a sudden increase in the reflectivity of P-waves, maintaining a low contrast ratio of the ghost image to the main image, making overlapping images less visible. Since θ2 corresponds to the angle of incidence of light from the image projector, it can be adjusted by placing the image projector and the projected image display member at the above angle so that the light from the image projector reaches the position of the observer's eyes.

[0090] One method for reducing the visibility of overlapping images is to add a visible light absorber to the adhesive layer used when laminating the light-reflecting material that constitutes the projection image display member. That is, in the transparent display system of the present invention, particularly in the case of a lamination method, the adhesive layer preferably contains a visible light absorber. As the visible light absorber, dyes or pigments that can be dispersed in thermoplastic resins and that exhibit absorption properties in wavelengths of 400 to 800 nm can be used. Visible light absorbers can be used alone or in combination. For example, when a transparent display system is used as a head-up display in an automobile or the like, a heat absorber may be used to suppress an increase in the temperature inside the vehicle due to solar heat. Examples of heat absorbers that have an absorption spectrum in the visible light absorption band include cesium-doped tungsten trioxide (CWO)-based materials and indium tin oxide (ITO)-based materials.

[0091] Furthermore, since the transparent display system of the present invention displays images by irradiating the projection image display member with P waves, it is sufficient to absorb only P waves, and a dichroic dye can be selected as such a material. Adding such visible light absorbers at high concentrations can further reduce the amount of light involved in ghost images and improve the effects of overlapping images. On the other hand, excessive use of visible light absorbers can reduce the visible light transmittance of the projection image display member, potentially worsening the visibility of scenery through the projection image display member. Therefore, it is preferable to add a visible light absorber to the adhesive layer of the projection image display member constituting the transparent display system of the present invention at a concentration that does not impair the average transmittance of visible light incident perpendicularly to the projection image display member.

[0092] In the projection image display member constituting the transparent display system of the present invention, the orientation of the light-reflecting material may convert P waves from the image projector into a mixed wave of P waves and S waves via the light-reflecting material. Therefore, reducing the influence of S waves reflected at the outermost surface of the transparent hard material, regardless of the installation angle, is effective in reducing ghost images. For this reason, when adding a visible light absorber to the adhesive layer, it is preferable to select a dichroic dye, such as iodine, anthraquinone dye, azo dye, or thiazole dye, which has a light transmission axis and a light absorption axis and can absorb only specific polarized light, rather than a visible light absorber such as a dye or pigment that uniformly reduces transmittance regardless of polarization.

[0093] When the dichroic dye described above is used as a visible light absorber, the angle between the light transmission axis of the visible light absorber and the vibration direction of the P wave emitted from the image projector is preferably 0° or more and 5° or less. That is, when the transparent display system of the present invention has a projection image display member of the above embodiment, the adhesive layer containing the visible light absorber preferably has a light absorption axis and a light transmission axis that are perpendicular to each other, and the angle between the light transmission axis and the vibration direction of the polarized P wave emitted from the image projector is preferably 0° or more and 5° or less. By bringing the vibration direction of the P wave from the image projector closer to parallel with the light transmission axis direction of the visible light absorber, the S-wave polarized component contained in the light transmitted through the light reflecting material, which is due to the phase difference or orientation angle of the light reflecting material such as a laminate film that can be used in the transparent display system of the present invention, can be cut. As a result, the amount of light of a ghost image generated by reflection on the outermost surface on the back side of the projection image display member can be reduced, thereby minimizing the overlapping images seen by the viewer.

[0094] In addition to adding a visible light absorber to the adhesive layer, another effective method for reducing ghost images is to use green glass, which has the function of absorbing heat rays and visible light, as the glass material. In particular, in the case of the interpolation method, it is effective to use green glass as the glass placed outside the light-reflecting material as seen from the viewer. In both the interpolation method and the lamination method, it is possible to use green glass in combination with a visible light absorber in the adhesive layer. However, depending on the concentration of the visible light absorber added, this may impair the light transmittance when the projection image display member is viewed from the front. Therefore, optimization is required to satisfy the visible light transmittance of the projection image display member described above.

[0095] The laminated film of the present invention, which can be preferably used as a light-reflecting material for the transparent display system of the present invention, will be described below.

[0096] In the laminated film of the present invention, when the center point of the film surface is defined as point CF, the midpoints between point CF and an end in the short side direction are defined as points X1F and X2F, the midpoint between point CF and an end in the long side direction is defined as points Y1F and Y2F, the long side direction is defined as a reference axis, and the angle between the reference axis and the orientation axis at each point is defined as a film orientation angle, the variation in the film orientation angle (maximum value-minimum value) at each of the points is 30° or less, the average transmittance of visible light perpendicularly incident on the film surface at point CF is 50% or more and 100% or less, and when P waves are incident on the film surface from a direction perpendicular to the orientation axis, the angle between the normal to the film surface at point CF and the normal in a plane including the orientation axis is 60°, the average reflectance is 5% or more and 100% or less at a wavelength of 400 to 700 nm.

[0097] The laminate film of the present invention is typically manufactured by biaxially stretching the film, as described below, and then wound into a roll. It is then unwound to the required size and cut for use. It is often a planar quadrilateral before being installed in a transparent display system. In the case of such a planar quadrilateral, the intersection formed by connecting the opposite sides of the rectangle is defined as point CF (reference numeral 29) as shown in Figure 15 . Even if the shape is not strictly a planar quadrilateral due to rounded corners or slight protrusions or recesses on the sides, it can be macroscopically considered to be a planar quadrilateral without considering the rounded corners. Furthermore, a parallel line is drawn through point CF along the short side of the cut laminate film. Two points, designated by reference numerals 30 and 31, which are midpoints between the end of the laminate film and the center point CF, are defined as points X1F and X2F, respectively. Furthermore, a parallel line is drawn through the center point CF along the long side of the cut laminate film, and the two points designated by the reference numerals 32 and 33, which are the midpoints between the ends of the laminate film and the line, are defined as points Y1 and Y2, respectively. When the laminate film has a shape other than a planar quadrilateral, the center of gravity is defined as point CF.

[0098] Furthermore, when the laminated film of the present invention is in the form of a film roll (laminated film roll) wound around a core and is not cut to a specified size, the CF point and other points are determined using a laminated film cut into a rectangle whose length is the width direction length x length direction = film roll width x 2 / 3 times the film roll width.

[0099] The laminate film of the present invention must have a film orientation angle variation of 30° or less at the five points. When a laminate film having a film orientation angle variation of more than 30° at the five points (CF, X1F, X2F, Y1F, and Y2F) is used as a projection image display member, regardless of the lamination direction of the laminate film on the glass, even when an image is projected by irradiating P waves at an incident angle equal to the Brewster angle, the P waves are converted into P waves + S waves by the orientation axis, resulting in significant overlapping images. Furthermore, when a laminate film having an orientation angle variation of more than 30° is used as a projection image display member, when an image from a video projector is projected over a wide area, the degree of conversion of P waves from the video projector into P waves + S waves by the orientation axis varies depending on the specific position and viewing angle. As a result, overlapping images are partially visible. From the viewpoint of reducing such overlapping images, the variation in the film orientation angle at the five points of the projection image display member is preferably 20° or less, more preferably 10° or less, further preferably 5° or less, and particularly preferably 4° or less. From the above viewpoint, the smaller the variation in the film orientation angle, the better, and the theoretical lower limit is 0°.

[0100] In order to make the film orientation angle variation at the above five points 30° or less or within the above preferred range, it is necessary to adjust the film-forming conditions and select an appropriate thermoplastic resin constituting the alternating laminate unit. For example, as the manufacturing conditions of the laminate film, for example, the ratio of the stretching magnification in the longitudinal direction to the stretching in the width direction in biaxial stretching, the stretching speed in the width direction, and the microstretching magnification when stretching in the heat treatment step are set to the preferred conditions described below. In addition, with regard to the thermoplastic resin constituting the alternating laminate unit, it is effective to use a microcrystalline resin or an amorphous resin as the main component of the thermoplastic resin layer (B layer) on the side that does not constitute the outermost layer of the thermoplastic resin layers constituting the alternating laminate unit as the thermoplastic resin B.

[0101] The laminate film of the present invention preferably has a length in the long side direction of 1 m or more. The transparent display system of the present invention is preferably used in applications where images are projected over a wide area, such as automotive head-up displays and transparent screens. Generally, such applications require the ability to clearly display images over a wider area than conventional displays, and therefore large-area laminate films are used. Note that the length in the long side direction refers to the length of the longest side in the case of a shape having at least one side, and in the case of a shape without sides such as an ellipse or circle, it refers to the distance between two points on the periphery that are the greatest distance apart. To make the length of the long side direction of the laminate film 1 m or more, it is sufficient to cut it out from a laminate film roll to a size that satisfies the above requirements.

[0102] It is important that the laminate film of the present invention has an average transmittance of 50% or more and 100% or less for visible light incident perpendicularly to the film surface at point CF. Here, "an average transmittance of 50% or more and 100% or less for visible light incident perpendicularly to the film surface" specifically means that the average transmittance of light with wavelengths of 400 to 800 nm incident perpendicularly to the film surface is 50% or more and 100% or less. Due to this high average transmittance for light with wavelengths of 400 to 800 nm, the laminate film of the present invention has transparency similar to that of transparent glass or transparent resin films. In other words, such a laminate film provides good background visibility when observed through the laminate film from a direction perpendicular to the film surface. From the above perspectives, the average transmittance is preferably 60% or more, more preferably 75% or more, even more preferably 85% or more, and particularly preferably 86% or more. An average transmittance of 85% or more allows the viewer to view the background without noticing the presence of the laminate film. The upper limit of the average transmittance is theoretically 100%, and from the perspective of ease of realization, it is preferably 99%.

[0103] The average transmittance of visible light incident perpendicularly to the laminated film surface can be measured by measuring the transmittance of light with a wavelength of 400 to 800 nm at an incident angle of 0° using a spectrophotometer in 1 nm increments and calculating the average value.

[0104] As described above, it is important that the overall projection image display member constituting the transparent display system of the present invention has an average transmittance of 50% to 100% for visible light incident perpendicularly thereto. However, when obtaining the projection image display member, the aforementioned visible light absorber may be added to the adhesive layer to reduce the effect of overlapping images, or a heat absorber may be added to the transparent hard material or adhesive layer to suppress an increase in the temperature inside the vehicle due to solar radiation. Considering the reduced transparency of the projection image display member due to the reduced visible light transmittance caused by these additives, the laminate film is required to have higher transparency. Therefore, it is more preferable that the laminate film of the present invention has an average transmittance of 75% to 100% for visible light incident perpendicularly to the film surface.

[0105] A laminate film having an average transmittance of 50% to 100% for visible light incident perpendicularly to the film surface, or within the above-mentioned preferred range, can be obtained by reducing the average difference in refractive index (in-plane refractive index) between the two thermoplastic resin layers constituting the alternating laminate unit in a direction parallel to the film surface. If the average difference in in-plane refractive index between the two thermoplastic resin layers is 0.060 or less, the average transmittance can be easily increased to 50% or more. If the average difference in in-plane refractive index between the two thermoplastic resin layers is 0.030 or less (preferably 0.020 or less), the average transmittance can be increased to 75% or more. If the average difference in in-plane refractive index between the two thermoplastic resin layers is 0.010 or less, the average transmittance can be increased to 85% or more. The refractive index of the thermoplastic resin layer located at the outermost layer of the laminate film is primarily measured by the prism coupler measurement described below. However, if the refractive index of only that layer cannot be accurately measured due to thin layer thickness or other reasons, it may be calculated by the EELS measurement described below. On the other hand, the refractive index of the thermoplastic resin layer located inside the laminate film can be calculated by the EELS measurement. In order to increase the average transmittance, it is also effective to reduce the number of layers constituting the alternately laminated unit, and the number of layers may be reduced within a range in which a decrease in image projection performance is acceptable.

[0106] It is important that the laminate film of the present invention has an average reflectance of 5% or more and 100% or less at wavelengths of 400 to 700 nm when P waves are incident on the film surface from a direction perpendicular to the orientation axis and at an angle of 60° between the normal to the film surface at point CF and the orientation axis in a plane including the normal. The orientation axis of the laminate film can be determined using a retardation measurement device such as a KOBRA-WPR, and details of the determination method using this device will be described later. Note that if the laminate film is large and measurement of the laminate film alone is difficult, a sample centered on point CF can be cut out from the laminate film as needed.

[0107] When P-waves are incident from a direction perpendicular to the orientation axis and at an angle of 60° between the normal to the film surface at point CF and the plane containing the orientation axis, an average reflectance of 5% or more at wavelengths of 400 to 700 nm can be obtained when an image is projected onto a projection image display member incorporating the laminate film of the present invention. Furthermore, when such a laminate film is used as a projection image display member, a clear reflected image can be obtained even when the brightness of the light emitted by the image projector is kept low, which is also preferable in terms of the thermal design of the image projector. From the above perspective, the average reflectance is preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more. On the other hand, if the average reflectance is too high, when the film is used as a projection image display member, the surroundings of the image projector may be reflected on the projection image display member, reducing the visibility of the scenery. For this reason, the upper limit of the average reflectance is preferably 70%, more preferably 45%, and even more preferably 30%.

[0108] A method for achieving an average reflectance of 5% or more and 100% or less, or within the above-mentioned preferred range, can be, for example, by adjusting the difference in refractive index (plane normal refractive index) between the two thermoplastic resin layers constituting the alternating laminate unit of the laminate film and the number of layers. In the former case, it is preferable to set the difference in plane normal refractive index to 0.150 or less. On the other hand, if this difference is too large, the average difference in in-plane refractive index tends to increase in conjunction with the difference in plane normal refractive index in terms of raw material design, and at the CF point, the average transmittance of light with wavelengths of 400 to 700 nm incident perpendicularly to the film surface may fall below 75%. Therefore, the difference in plane normal refractive index is more preferably 0.120 or less, and even more preferably 0.080 or less. The average reflectance can also be increased by increasing the number of layers, as in the latter case. The average reflectance can be determined from P-wave reflectance data at each wavelength measured at 1 nm intervals at an incident angle of 60°. A detailed measurement method will be described later.

[0109] A preferred configuration of the laminate film of the present invention exhibiting the above-mentioned properties will be described below. The laminate film of the present invention preferably has a unit in which 51 or more layers of A layers each having a crystalline thermoplastic resin A as a main component and B layers each having a thermoplastic resin B as a main component different from the thermoplastic resin A are alternately laminated. Here, the term "main component" refers to a component that is contained in an amount of more than 50% by mass but not more than 100% by mass when all components constituting the thermoplastic resin layer are taken as 100% by mass.

[0110] In the laminate film of the present invention, the thermoplastic resin layers "have different main components" means that they do not meet the following conditions for being considered to have the same main components. The difference in main components of the thermoplastic resin layers can be identified by analyzing the composition and components of each layer. However, it can also be determined that the thermoplastic resin layers "have different main components" if they meet at least one of the following conditions (1) to (3): Condition (1) The glass transition temperatures or melting points are different in differential scanning calorimetry (DSC); Condition (2) The contrast of the dyed images when cross-sectionally observed by transmission electron microscopy (TEM) is different; and Condition (3) The dielectric constants (refractive indexes) of the thermoplastic resin layers obtained by electron energy loss spectroscopy (EELS) are different.

[0111] The term "main component is the same" for thermoplastic resin layers means that the repeating units of the chemical structure of the thermoplastic resin constituting each thermoplastic resin layer are 95 mol% or more and 100 mol% or less in common, or that when comparing the constituent components of each thermoplastic resin layer, more than 50 mass% and 100 mass% or less of the components are common.

[0112] For example, in the case of the former, polyethylene terephthalate has as its main structural unit a structural unit (ethylene terephthalate unit) in which ethylene glycol units and terephthalic acid units are bonded by an ester bond, but when some of the repeating units of the thermoplastic resin constituting the layer are different but 95 mol % or more are in common, such as a layer made of homopolyethylene terephthalate and a layer made of polyethylene terephthalate copolymerized with 4 mol % isophthalic acid, the main component of both is considered to be the same.Furthermore, in the case of the latter, when some of the components constituting the thermoplastic resin layer are different but the amount of the repeating units is 50 mass % or less, such as a layer made only of homopolyethylene terephthalate and a layer containing 90 mass % homopolyethylene terephthalate with the remaining 10 mass % being other components, the main component of both is also considered to be the same. The repeating unit structure of the specific composition / chemical structure of each thermoplastic resin layer can be determined by determining the layer thickness of each thermoplastic resin layer according to the method described below in the layer structure of measurement method (2), and then cutting and removing the thermoplastic resin layer, or by scraping the layer to expose the outermost layer, using infrared spectroscopy (FT-IR method or nano-IR method), gas chromatograph / mass spectrometer (GC-MS), nuclear magnetic resonance device (NMR), or the like.

[0113] Next, we will explain "Condition (1) different glass transition temperatures or melting points in differential scanning calorimetry (DSC)." If it is difficult to identify the main component by the above method after extracting each thermoplastic resin layer, the thermoplastic resin layers constituting the laminate film can be determined to have "different main components" by showing different melting points and / or glass transition points in differential scanning calorimetry (DSC). In the laminate film of the present invention, showing different melting points and different glass transition temperatures means that at least one of the melting points and glass transition points differs by 0.1°C or more, preferably 2.0°C or more (in other words, at least one of the melting points and glass transition points of the thermoplastic resin layers differs by 0.1°C or more, preferably 2.0°C or more).

[0114] The easiest example to interpret is, for example, when differential scanning calorimetry of a laminated film is performed, and two different glass transition points, crystallization temperatures (exothermic peaks), or melting points (endothermic peaks) are confirmed. On the other hand, in the measurement temperature range of 25 ° C. or higher and 300 ° C. or lower described in the section on differential scanning calorimetry (DSC) in the measurement method (1) described below, the thermoplastic resin layer may not exhibit a glass transition point or melting point. However, if one thermoplastic resin layer exhibits a glass transition point or melting point and the other thermoplastic resin layer does not, it cannot be calculated as a temperature difference, but it is interpreted as the main components being different. For example, if two glass transition points are observed but only one melting point is observed, it can be interpreted that one of the two thermoplastic resin layers is mainly composed of an amorphous thermoplastic resin that does not have a melting point. In another embodiment, if two melting points can be confirmed, but only one or less glass transition temperature or crystallization temperature can be confirmed within the above temperature range, it can be interpreted that the laminated film contains a layer containing a thermoplastic resin as a main component, whose glass transition temperature or crystallization temperature is in a low temperature region outside the temperature range. In the present invention, measurement by DSC can be performed according to the method of JIS-K-7122 (1987), and details will be described later.

[0115] Next, we will explain "Condition (2) The contrast of the image after dyeing is different when observed by cross-section transmission electron microscopy (TEM)." The above two methods require the corresponding thermoplastic resin layer to be separated from the laminate film for analysis, which can make layer separation and analysis difficult. Therefore, to improve convenience, if the layer interface can be recognized by the contrast difference in the cross-sectional image observed by transmission electron microscopy, and if it can be confirmed that the difference in the average brightness of two adjacent layers is greater than any of the standard deviations of brightness within each adjacent thermoplastic resin layer by the method described in the section on layer interface (contrast difference) in measurement method (3) below, the contrast of the image after dyeing is different, and it can be determined that the main components of the adjacent thermoplastic resin layers are "different."

[0116] This contrast difference arises due to differences in electron beam scattering, crystal diffraction, and other properties between thermoplastic resin layers. Therefore, when the main components of thermoplastic resin layers differ according to the aforementioned criteria, the crystallinity, electron density, and electron staining states typically differ. Therefore, when thermoplastic resin layers have different main components, each thermoplastic resin layer can be visually recognized as a layer structure with different contrast in a cross-sectional image of the laminate film. In a preferred embodiment of the laminate film of the present invention, a laminate film having units in which two types of thermoplastic resin layers with different main components are alternately laminated exhibits a constant brightness if the thermoplastic resin layers are the same. Therefore, when the horizontal axis represents depth in the thickness direction and the vertical axis represents brightness and contrast (gray level in a grayscale display) at each point, a graph showing repeated ups and downs between brightnesses at two points is obtained, as shown in Figure 16. In Figure 16, reference numerals 34 to 36 represent, respectively, a graph showing the relationship between depth in the thickness direction and contrast (gray level) in a laminate film having an AB regular arrangement, the thickness of Layer A, and the thickness of Layer B (however, in this embodiment, Layer A is the layer with a relatively high crystallinity). The AB regular arrangement refers to an arrangement in which two types of thermoplastic resin layers (layer A and layer B) are alternately laminated in the thickness direction.

[0117] Next, we will explain "Condition (3) that the dielectric constants (or refractive indexes) of the thermoplastic resin layers obtained by electron energy loss spectroscopy (EELS) are different." Furthermore, the laminate film of the present invention may also be determined to have "different main components" if the refractive index (or dielectric constant) of the thermoplastic resin layers is different in the film plane direction or in the direction perpendicular to the film plane. Whether the main components of the thermoplastic resin layers are different is determined from the dielectric constant and refractive index of each thermoplastic resin layer obtained by EELS measurement according to the method described in the measurement method (3) below. More specifically, this can be determined by the following procedure. First, the main orientation axis direction of the laminate film is identified using a known retardation measurement device (e.g., the KOBRA-WPR retardation measurement device manufactured by Oji Scientific Instruments Co., Ltd.), and a cross-sectional sample of the laminate film is obtained so as to include this direction and the thickness direction of the laminate film. Next, each thermoplastic resin layer in the cross-sectional sample is irradiated with an electron beam, and the dielectric constant is analyzed to read the dielectric constant at a loss energy of 2.5 eV. If the difference in the dielectric constants of the obtained thermoplastic resin layers is 0.01 or more, the main components of the thermoplastic resin layers are determined to be "different."

[0118] According to Maxwell's electromagnetic theory, for non-magnetic materials that absorb very little light, such as the thermoplastic resins (described below) that can be suitably used in the laminate film of the present invention, the dielectric constant is generally equal to the square of the refractive index. Therefore, differences in the dielectric constants of the thermoplastic resin layers can be interpreted as differences in the refractive index of the thermoplastic resin layers, and therefore it can be determined that the main components are different. The magnitude relationship of the dielectric constants of the thermoplastic resin layers coincides with the magnitude relationship of their refractive indices.

[0119] If the difference in dielectric constant between the thermoplastic resin layers cannot be analyzed using a cross-sectional sample, a position corresponding to each thermoplastic resin layer may be identified using a scanning transmission electron microscope (STEM) and the laminate film may be cut in a direction parallel to the surface to obtain a thin section sample. In this case, the dielectric constant of the thin section sample of each thermoplastic resin layer can be analyzed using EELS measurement, and the difference in the main components of the thermoplastic resin layers can be determined according to the above criteria.

[0120] The thermoplastic resin used in the laminated film of the present invention may be a linear polyolefin such as polyethylene, polypropylene, poly(4-methylpentene-1), or polyacetal; an alicyclic polyolefin which is a ring-opening metathesis polymer of norbornenes, an addition polymer, or an addition copolymer with other olefins; a biodegradable polymer such as polylactic acid or polybutyl succinate; a polyamide such as nylon 6, nylon 11, nylon 12, or nylon 66; a polyester such as polypropylene terephthalate, polyethylene terephthalate, polybutylene terephthalate, or polyethylene-2,6-naphthalate; Examples of resins that can be used include olefin, aramid, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl butyral, ethylene-vinyl acetate copolymer, polyacetal, polyglycolic acid, polycarbonate, polyethersulfone, polyetheretherketone, modified polyphenylene ether, polyphenylene sulfide, polyetherimide, polyimide, polyarylate, tetrafluoroethylene resin, trifluoroethylene resin, trifluorochloroethylene resin, tetrafluoroethylene-hexafluoropropylene copolymer, and polyvinylidene fluoride. Among these, polyester is particularly preferred from the viewpoints of strength, heat resistance, transparency, and versatility. These resins may be copolymers or mixtures of two or more resins.

[0121] Polyester refers to a resin having a molecular structure in which dicarboxylic acid units and diol units are linked by ester bonds. Preferred polyesters are those obtained by polymerization of monomers primarily composed of aromatic or aliphatic dicarboxylic acids and diols. Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, and 4,4'-diphenylsulfonedicarboxylic acid. Examples of aliphatic dicarboxylic acids include adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexanedicarboxylic acid, and their ester derivatives. Among these, terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid, which exhibit high refractive indices, are preferred. These acid components may be used alone or in combination of two or more kinds, and further, oxyacids such as hydroxybenzoic acid may be partially copolymerized.

[0122] Examples of diol components include ethylene glycol (polyethylene glycol), 1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, diethylene glycol, triethylene glycol, polyalkylene glycol, 2,2-bis(4-hydroxyethoxyphenyl)propane, isosorbate, and spiroglycol. Of these, ethylene glycol is preferred. These diol components may be used alone or in combination of two or more.

[0123] The thermoplastic resin that is the main component of Layer A and Layer B of the laminate film of the present invention is preferably selected from, for example, the above-mentioned polyesters, such as polyethylene terephthalate and polymers thereof, polyethylene naphthalate and copolymers thereof, polybutylene terephthalate and copolymers thereof, polybutylene naphthalate and copolymers thereof, polyhexamethylene terephthalate and copolymers thereof, polyhexamethylene naphthalate and copolymers thereof, and the like.

[0124] A preferred combination of thermoplastic resins serving as the main components of Layer A and Layer B of the laminate film of the present invention is one in which the two thermoplastic resins have the same basic skeleton. This configuration reduces the likelihood of delamination. The "basic skeleton" here refers to the most abundant repeating unit constituting the thermoplastic resin. Specifically, if the thermoplastic resin is polyethylene terephthalate, its basic skeleton is an ethylene terephthalate skeleton. For example, when polyethylene terephthalate is used as one of the thermoplastic resins, it is preferable that the thermoplastic resin contains the same basic skeleton as polyethylene terephthalate, from the viewpoint of easily achieving a highly accurate laminate structure. When thermoplastic resins having different optical properties contain the same basic skeleton, the lamination precision is improved and delamination at the lamination interface is also reduced.

[0125] In addition, various additives such as antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic fine particles, fillers, antistatic agents, and nucleating agents may be added to each thermoplastic resin layer, either alone or in combination to the extent that the properties of the layer are not deteriorated.

[0126] In the laminate film of the present invention, it is preferred that Layer A be primarily composed of a crystalline thermoplastic resin A, and Layer B be primarily composed of a thermoplastic resin B different from Thermoplastic Resin A. More preferably, Layer A be primarily composed of a crystalline thermoplastic resin A, and Layer B be primarily composed of an amorphous thermoplastic resin B. When the thermoplastic resin A, which is the primary component of the thermoplastic resin layer (Layer A) constituting the laminate film, is a crystalline resin, stretching unevenness due to the absence of stress during stretching in the biaxial stretching production method described below is less likely to occur, improving the uniformity of the physical properties of the resulting laminate film. Furthermore, since at least Layer A is primarily composed of a crystalline resin, it is possible to physically hold and co-stretch the other thermoplastic resin layer (Layer B) laminated at the same time.

[0127] The crystallinity of a thermoplastic resin can be determined by checking the presence or absence of a melting point (endothermic peak) using a differential scanning calorimetry (DSC) analyzer. In particular, in the laminate film of the present invention, a thermoplastic resin that exhibits a melting enthalpy of 10 J / g or more, which corresponds to the integration of the melting point endothermic peak with the baseline, is defined as a crystalline thermoplastic resin. Note that a thermoplastic resin is defined as being amorphous when it does not exhibit this melting enthalpy, and a thermoplastic resin that exhibits a melting enthalpy and exhibits a value of less than 10 J / g is defined as a microcrystalline thermoplastic resin.

[0128] In the laminate film of the present invention, it is preferable that a crystalline thermoplastic resin layer (Layer A in the above embodiment) is located on both sides as the outermost layer. By using a crystalline thermoplastic resin as the main component of the thermoplastic resin layer located on the outermost layer, the laminate film is less likely to stick to rolls, clips, etc. during the production process, and poor stretching, deterioration of the surface condition, and process contamination are less likely to occur.

[0129] The laminate film of the present invention preferably has a unit in which 51 or more A layers and 51 or more B layers are alternately laminated, more preferably 401 or more layers, and even more preferably 801 or more layers. A unit in which 51 or more A layers and 51 or more B layers are alternately laminated or in the above preferred number of layers (sometimes referred to as an alternating laminate unit) can be formed, for example, by alternately laminating a thermoplastic resin for A layer and a thermoplastic resin for B layer by the method shown below (the thermoplastic resins for A layer and B layer may be compositions containing other components). Note that "51 or more A layers and B layers are alternately laminated" means that A layers and B layers are alternately laminated, and the total number of layers is 51 or more.

[0130] First, each thermoplastic resin is prepared in the form of pellets or the like, dried in hot air or under vacuum as necessary, and then fed into separate extruders. The pellets are heated and melted in the extruder at a temperature above their melting point, and the resin is extruded at a uniform extrusion rate using a gear pump or the like. After that, foreign matter and modified resins are removed using a filter or the like. Next, the two molten thermoplastic resins are fed into a multi-layer lamination device through separate flow paths and laminated alternately.

[0131] Multi-manifold dies, feed blocks, static mixers, and the like can be used as multi-layer lamination devices. It is particularly preferable to use a feed block having 51 or more, preferably 401 or more, and more preferably 801 or more fine slits. The use of such a feed block prevents the device from becoming excessively large, reduces the amount of foreign matter caused by thermal degradation, and enables high-precision lamination even when the number of layers is extremely large. Furthermore, the lamination accuracy in the width direction is significantly improved compared to conventional technology. Furthermore, with such devices, the thickness of each layer can be adjusted by the shape (length, width) of the slits, and the number of layers can be adjusted by the number of slits, making it easy to achieve any desired layer thickness or number of layers. The number of slits corresponds to the total number of laminated films, and the number of layers can be easily increased by increasing the number of slits. However, to avoid increasing the size of the device, the upper limit of the number of slits is preferably 2001.

[0132] In addition, it is preferable that the layer thickness distribution of the laminated film is such that the optical thicknesses of adjacent layers A and B satisfy formula (2), where λ is the reflection wavelength, nA is the in-plane normal refractive index of layer A, dA is the thickness of layer A, nB is the in-plane normal refractive index of layer B, dB is the thickness of layer B, and k is the order (natural number).

[0133]

[0134] The layer thickness distribution is preferably one of the following: a constant layer thickness distribution from one side of the laminate film to the opposite side; a layer thickness distribution that monotonically increases or decreases from one side of the laminate film to the opposite side; a layer thickness distribution in which the layer thickness increases and then decreases from one side of the laminate film to the center of the film; a layer thickness distribution in which the layer thickness decreases and then increases from one side of the laminate film to the center of the film; or a combination of these distributions. The layer thickness distribution preferably changes continuously, such as linearly, geometrically, or with a difference progression, or in which approximately 10 to 50 layers have approximately the same layer thickness and the layer thickness changes stepwise. Adjusting the layer thickness distribution creates a distribution in the optical thickness of adjacent layer pairs, allowing the width of the reflection band to be controlled.

[0135] A protective layer having a thickness of 1% or more of the total thickness of the multilayer laminate film can be preferably provided on both surface layers of the laminate film, and the thickness of the protective layer is preferably 4% or more of the total thickness of the laminate film. Increasing the thickness of the protective layer leads to suppression of flow marks during film formation, improvement in the accuracy of the actual layer thickness of each layer relative to the design, suppression of deformation of thin layers in the multilayer laminate film during and after the lamination process with other films or molded articles, and pressure resistance.

[0136] The thickness of the laminate film of the present invention is not particularly limited, but is preferably, for example, 20 μm or more and 300 μm or less. When the thickness is 20 μm or more, the laminate film has a strong stiffness and can ensure handleability. When the thickness is 300 μm or less, the laminate film does not have an excessively strong stiffness, improving moldability and facilitating processing into projection image display components with complex shapes.

[0137] In addition, functional layers such as a primer layer, a hard coat layer, an abrasion-resistant layer, a scratch-resistant layer, an anti-reflection layer, a color correction layer, an ultraviolet absorbing layer, a light stabilizing layer, a heat absorbing layer, a printing layer, a gas barrier layer, and an adhesive layer may be formed on at least one surface of the laminate film. These layers may be single-layered or multi-layered, and one layer may have multiple functions. In addition, the laminate film may contain additives such as ultraviolet absorbers, light stabilizers (HALS), heat absorbing agents, nucleating agents, and plasticizers. These components can also be used in combination within a range that does not impair the effects of the present invention.

[0138] In the laminate film of the present invention, the difference between the in-plane refractive index of Layer A in the orientation axis direction and the in-plane refractive index of Layer A in the direction perpendicular to the orientation axis is preferably 0.01 or more. Here, "perpendicular to the orientation axis" refers to the direction perpendicular to the orientation axis within the film plane. The in-plane refractive index of Layer A is determined by the structure and crystallinity of the thermoplastic resin used, the manufacturing conditions of the laminate film, and the molecular orientation behavior due to the stretching conditions in particular. It is preferable to use a thermoplastic resin that exhibits a melting enthalpy peak in DSC measurement and exhibits crystallinity as the main component of Layer A. This configuration results in the alignment of crystalline components during the stretching process, creating an orientation axis for the thermoplastic resin layer. The orientation axis direction generally corresponds to the direction in which the laminate film is stretched more strongly during the manufacturing process, and the orientation of crystalline components in this direction increases the refractive index. Conversely, the refractive index decreases in the non-oriented direction. A difference of 0.01 or more between the in-plane refractive index of Layer A in the orientation axis direction and the in-plane refractive index of Layer A in the direction perpendicular to the orientation axis means that the crystalline components of the thermoplastic resin constituting the laminate film are strongly oriented in a certain direction to a certain extent. It is important that the laminate film of the present invention, when used over a wide area as a light-reflecting material in a transparent display system, enables images to be viewed over a wide range or a wide viewing angle without overlapping images. To this end, it is preferable that the crystalline components of the thermoplastic resin constituting the laminate film are oriented in a certain direction (orientation axis direction) to a certain extent, and that the orientation axis direction is aligned in a constant direction over the entire surface of the laminate film, i.e., the variation in orientation is small.

[0139] To achieve these conditions, it is preferable to use process conditions that strongly stretch the laminate film in a specific direction. Such stretching can increase the difference between the refractive index in the direction of the orientation axis and the refractive index in the direction perpendicular to the orientation axis. The difference between the in-plane refractive index of layer A in the direction of the orientation axis and the in-plane refractive index of layer A in the direction perpendicular to the orientation axis is preferably 0.020 or more, more preferably 0.030 or more, and even more preferably 0.040 or more. This in-plane refractive index difference can be achieved by designing the ratio of the stretching ratio in the longitudinal direction and the width direction of the laminate film, the stretching speed in the width direction, and the small stretching ratio in the heat treatment step to preferred conditions in the manufacturing method described below. The upper limit of this in-plane refractive index difference is preferably 0.250, more preferably 0.100, from the viewpoint of the feasibility of achieving a difference in the in-plane refractive index of the laminate film in the biaxial stretching film-forming process.

[0140] In the laminate film of the present invention, the area A (nm %) enclosed by the reflection spectrum at a wavelength of 400 to 700 nm when a P wave is incident on the film surface at point CF from a direction where the angle between the normal to the film surface at point CF and the normal to the orientation axis is 60°, and the reflection spectrum at a wavelength of 400 to 700 nm when a P wave is incident on the film surface from a direction where the angle between the normal to the film surface at point CF and the normal to the orientation axis is 60°, preferably satisfies 1000≦A≦6000. The method for calculating the area A in the laminate film of the present invention is the same as the calculation method described in the section on the area A in the projection image display member above, and can be calculated by measuring two reflection spectra and using Figures 9 to 11 and the above formula (1).

[0141] An area A of 1,000 or more and 6,000 or less means that the difference in orientation between the orientation axis direction of the laminate film and the direction perpendicular thereto is within a moderate range. Such a laminate film more strongly reflects light from the orientation axis direction. Therefore, when such a laminate film is used as a light-reflecting material for a projection image display member, by installing a video projector so that light (P waves) is irradiated from the orientation axis direction, both background visibility and image clarity can be achieved. On the other hand, because the difference in orientation between the two orthogonal directions is moderately suppressed, the laminate film of the present invention in this embodiment also has the advantage that the image is less likely to become dark even when viewed from an oblique field of view and that reflections of the surrounding scenery can be reduced. In other words, a projection image display member using such a laminate film is a suitable material for the light-reflecting material of a projection image display member constituting the transparent display system of the present invention, which projects images over a wide range and a wide viewing angle.

[0142] From the above viewpoints, the area A of the laminated film is preferably 1000 or more and 4500 or less, more preferably 1500 or more and 4500 or less, and even more preferably 2000 or more and 4500 or less. When producing a laminated film, if the film is strongly stretched in a specific direction by sequential biaxial stretching, it is preferable to stretch the film at a higher magnification in the width direction than in the longitudinal direction. This is because the in-plane orientation state of the film can be easily controlled across the entire width direction.

[0143] In order to control the area A of the laminated film within the above-mentioned preferred range, it is preferable to alternately laminate 51 or more layers of two types of thermoplastic resin layers selected so that the difference in in-plane refractive index between layer A and layer B is 0.040 or less (preferably less than 0.040) and the difference in perpendicular-plane refractive index is 0.150 or less (preferably 0.120 or less). Furthermore, since the refractive index difference is also affected by changes in molecular orientation due to adjustment of the stretching ratio in each direction, it is also preferable to set the stretching ratio ratio in the longitudinal direction and the width direction when performing biaxial stretching within the preferred range described below, and further to employ other means for setting the area A of the projection image display member to 1000 or more and 6000 or less as described above as a method for producing a biaxially stretched film.

[0144] When the laminate film of the present invention is used as a light-reflecting material for a projection image display member, it is preferably laminated to a transparent hard material via an adhesive layer. In such a laminate configuration, the laminate film is required to conform to the shape of the transparent hard material in order to prevent appearance defects associated with wrinkles and bubbles in the laminate film. Typically, lamination with a transparent hard material involves heating and pressure, which causes the laminate film to shrink. Therefore, in order to prevent wrinkles and the like, it is preferable for the laminate film to have a certain heat shrinkage rate. In particular, when the transparent hard material has an uneven curved surface, such as an automobile windshield, using a non-heat-shrinkable laminate film will prevent air from escaping during lamination, potentially leaving appearance defects such as wrinkles and bubbles.

[0145] Furthermore, when laminating a laminate film and a transparent hard material via an adhesive layer and molding them, the molding process, which involves heat and pressure, can cause uneven thickness of the adhesive layer and uneven thickness of the laminate film due to differences in thermal shrinkage stress between the adhesive layer and the laminate film. Such uneven distortion and uneven thickness can cause light scattering and diffuse reflection, resulting in poor appearance of the resulting projection image display component and distortion of the projected image. Meanwhile, the transparent hard material that serves as the support barely deforms during the heating and pressure process, so the shape of the adhesive layer is hardly relaxed by the transparent hard material. Because laminate films contain interfaces formed by different thermoplastic resin layers, in addition to light scattering and diffuse reflection at the film surface, additional scattering and reflection at the interface also occur, making unevenness more noticeable than with monolayer films. Therefore, if a laminate film that is less prone to unevenness could be used, the problem of poor appearance of projection image display components could be alleviated.

[0146] For example, when forming an interpolation-type projection image display member in which a laminate film is positioned between two transparent hard materials via an adhesive layer, it is common to first bond the laminate film and adhesive layer at a low temperature (pre-lamination process), and then bond the laminate to the support by applying pressure at a higher temperature (compression bonding process). The method of the pre-lamination process is not particularly limited, but it is common to sandwich the film between two adhesive layers and roll laminate at 90 to 100°C, which is slightly higher than the glass transition temperature of the thermoplastic resin that exhibits the highest glass transition temperature among the thermoplastic resins that make up the laminate film. The method of the compression bonding process is also not particularly limited, but it is common to sandwich the sheet after the pre-lamination process between transparent hard materials, and if the transparent hard material is glass, to bond the sheets in an autoclave (pressurized and heated bonding furnace) at 140 to 150°C for 20 to 30 minutes under a pressure of 12 to 14 kg / cm. ２ Generally, the pressure is applied under the following conditions.

[0147] In addition, when a laminate film is laminated with a transparent hard material and an adhesive layer to form a projection image display member by a lamination method, the laminate film is sandwiched in advance between two transparent hard materials or metal molds of the same shape, and the laminate film is pre-shaped to the shape of the transparent hard material to be laminated at the lamination processing temperature, and then a cover glass is laminated, and lamination is performed using roll lamination molding, a vacuum bag method, or a TOM (three-dimensional surface coating method) molding method, and finally an autoclave treatment is performed for degassing. In this case, too, a method can be used in which heating and pressure treatment is performed at the above-mentioned heat treatment temperature, and the adhesive layer is solidified and pressed onto the transparent hard material to form the bond.

[0148] During this process, the laminated film and adhesive layer become flexible and shrink during the pre-lamination, pre-shaping, and pressure-bonding processes, but if these flexibility and shrinkage behaviors differ significantly, bubbles, wrinkles, and in-plane color unevenness will occur. Therefore, it is required that the laminated film shrinks not only during the high-temperature molding process but also at lower temperatures such as the pre-lamination process, i.e., that the shrinkage initiation temperature be lower than the glass transition temperature.

[0149] To improve the appearance of the projected image display member after molding due to shrinkage during the high-temperature molding process, the laminate film of the present invention preferably has a 150°C heat shrinkage rate S1 in the direction of the orientation axis and a 150°C heat shrinkage rate S2 in the direction perpendicular to the orientation axis of 1.0% to 4.0%. Here, "the direction perpendicular to the orientation axis" refers to the direction perpendicular to the orientation axis within the film plane. When the heat shrinkage rates in both the orientation axis direction and the direction perpendicular to the orientation axis are 1.0% or more in a 150°C atmosphere, bubbles and wrinkles are less likely to occur, particularly during the pressure bonding process and the degassing process in an autoclave, whether using the insertion method or the lamination method. On the other hand, when the heat shrinkage rate in each of the above directions is 4.0% or less in a 150°C atmosphere, excessive flexibility of the laminate film can be reduced, thereby reducing the deterioration of productivity and handling during molding, the occurrence of color unevenness, and poor appearance.

[0150] Furthermore, the laminate film of the present invention preferably satisfies the relationship 0.7≦S1 / S2≦1.5. Satisfying the relationship 0.7≦S1 / S2≦1.5 means that the laminate film undergoes balanced thermal shrinkage in the orientation axis direction and the direction perpendicular to it. By adopting such an embodiment, the laminate film does not shrink too strongly in a specific direction, thereby suppressing the occurrence of streak-like irregular appearance defects on the transparent image display member after processing, thereby improving the image display properties and appearance of the projection image display member. From the above perspective, it is more preferable to satisfy 0.7≦S1 / S2≦1.4, and even more preferably 0.8≦S1 / S2≦1.2.

[0151] In order to achieve a heat shrinkage rate of 1.0% to 4.0% in both the orientation axis direction and the direction perpendicular to the orientation axis in a 150°C atmosphere, methods for adjusting the stretching temperature, stretching ratio, heat treatment temperature, and film take-up tension can be exemplified. More specifically, the heat shrinkage rate can be increased by increasing the film stretching ratio, lowering the stretching temperature to a temperature close to the glass transition temperature of the thermoplastic resin exhibiting the highest glass transition temperature among the thermoplastic resins constituting the laminate film, or lowering the heat treatment temperature after stretching in the width direction. Furthermore, the 150°C heat shrinkage rate can be increased by increasing the tension of the film between the transverse stretching and the winding process in the longitudinal direction and by performing slight stretching in the width direction in the intermediate cooling step of the heat treatment process. These methods can also be used in combination as appropriate.

[0152] More specifically, the areal stretching ratio is preferably 11.0 times or more and 18.0 times or less, and more preferably 12.0 times or more and 18.0 times or less. When the in-plane stretching ratio is 11.0 times or more, it becomes easy to set the heat shrinkage rate in each direction in an atmosphere of 150°C to 1.0% or more and 4.0% or less (preferably 1.5% or more and less than 4.0%). Furthermore, when the in-plane stretching ratio is 18.0 times or less, whitening during film formation due to excessive stretching and a decrease in productivity due to film breakage are suppressed. Note that the longitudinal direction refers to the direction in which the film runs during the production process (the winding direction in the case of a film roll), and the width direction refers to the direction perpendicular to the longitudinal direction within the film plane, and the in-plane stretching ratio refers to the value obtained by multiplying the stretching ratio in the longitudinal direction by the stretching ratio in the width direction.

[0153] To obtain a laminate film satisfying the relationship 0.7≦S1 / S2≦1.4, it is effective to adjust the thermal shrinkage behavior in the longitudinal and width directions by stretching the film under the above-mentioned stretching conditions, and then adjusting the tension of the film between the transverse stretching and the winding process, or by adjusting the relaxation rate in the cooling process in the width direction stretching process. In particular, the laminate film of the present invention is preferably stretched strongly in the width direction to achieve a uniform orientation angle, so the thermal shrinkage rate in the width direction tends to be higher than that in the longitudinal direction. Therefore, to obtain a laminate film satisfying the relationship 0.7≦S1 / S2≦1.4, it is effective to perform biaxial stretching in the longitudinal and width directions, and then perform relaxation in the cooling process after the width direction stretching process to reduce the thermal shrinkage rate in the width direction. It is preferable to adjust the relaxation rate so that the thermal shrinkage rate satisfies this relationship.

[0154] In order for the laminate film of the present invention to exhibit shrinkage behavior even at lower temperatures such as those in the pre-lamination process and to provide a good appearance for the transparent image display member after molding, it is preferable that the relationship 0.7 × (S100 + S150) / 2 ≦ S125 ≦ 1.3 × (S100 + S150) / 2 be satisfied, where S100, S125, and S150 are the average values ​​of the heat shrinkage in the direction of the orientation axis and the heat shrinkage in the direction perpendicular to the orientation axis at 100°C, 125°C, and 150°C, respectively, in constant-load measurements in thermomechanical analysis. Hereinafter, "0.7 × (S100 + S150) / 2 ≦ S125 ≦ 1.3 × (S100 + S150) / 2" may be referred to as the relationship X.

[0155] Conventional technologies were designed with shrinkage behavior only in mind at 150°C, which meant that the shrinkage behavior between components during low-temperature processing could not be controlled, resulting in appearance defects when processed into projection image display components. By exhibiting a linear increase in shrinkage from low temperatures, the laminate film follows the shrinkage of the transparent hard material to be laminated at all temperatures during processing into projection image display components. Therefore, using such a laminate film as a light-reflecting material for projection image display components can reduce appearance defects in the resulting projection image display components. When S125 is 0.7 × (S100 + S150) / 2 or greater, excessive flexibility of the laminate film is suppressed, improving productivity and ease of handling during molding. Furthermore, when S125 is 1.3 × (S100 + S150) / 2 or less, bubbles, wrinkles, and in-plane color unevenness are less likely to occur during processing, especially the pre-lamination process.

[0156] To obtain a laminated film exhibiting such heat shrinkage behavior, it is effective to perform slight stretching during the process of slowly cooling to room temperature after heat treatment following widthwise stretching, or to perform pseudo-slight stretching by increasing the tension (draw) during the winding process after slow cooling. Furthermore, it is preferable that the film temperature reaches a temperature at which the amount of shrinkage is desired to be increased when the film is released from the clips after widthwise stretching. To achieve such temperature conditions, it is also effective to control the heat treatment temperature and the cooling temperature after heat treatment within a suitable range. These methods can also be combined as needed.

[0157] The laminate film of the present invention can also be formed into a laminate sheet by laminating a curable resin layer on at least one side thereof. That is, the laminate sheet of the present invention has a curable resin layer on at least one side of the laminate film of the present invention. The method for laminating a curable resin layer on the laminate film of the present invention is not particularly limited, but for example, coating with a coating composition can be preferably used. The coating composition preferably contains a solvent, a binder component, a photopolymerization initiator, inorganic particles, other additives, etc., and by appropriately controlling the type, physical properties, and amount of each material, a layer having the desired function can be formed.

[0158] The type of solvent in the coating composition for forming the curable resin layer of the laminate sheet of the present invention is not particularly limited, but typically, a solvent having a boiling point of 250°C or less at normal pressure is preferred. Specific examples include water, alcohols, ketones, ethers, esters, hydrocarbons, amides, and fluorine-containing compounds. These may be used alone or in combination of two or more.

[0159] The binder component refers to a material that is soluble in a solvent and hardens the coating film by volatilization of the solvent and its own polymerization and crosslinking reaction, and the state after hardening is called a binder. The binder component in the coating composition for forming the curable resin layer of the laminated film of the present invention is not particularly limited, and may be one type or a mixture of two or more types. In addition, the binder component is preferably a material that can be polymerized by using a photopolymerization initiator that can be cleaved by active energy rays to harden the coating film.

[0160] Specifically, when ultraviolet (UV) rays are used as the active energy rays and a photopolymerization initiator is used in combination, preferred binder components include, for example, polyfunctional (meth)acrylate monomers, (meth)acrylate oligomers, alkoxysilanes having a (meth)acrylic group, alkoxysilane hydrolysates having a (meth)acrylic group, alkoxysilane oligomers having a (meth)acrylic group, acrylic polymers having a (meth)acrylic group, urethane polymers having a (meth)acrylic group, epoxy polymers having a (meth)acrylic group, and silicone polymers having a (meth)acrylic group.

[0161] Examples of polyfunctional (meth)acrylate components include polyfunctional acrylates having two or more (meth)acryloyloxy groups in one molecule and modified polymers thereof, and specific examples thereof include pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol triacrylate, hexanemethylene diisocyanate, and urethane acrylate. These monomers can be used alone or in combination of two or more.

[0162] The acrylic polymer having a (meth)acrylic group is preferably synthesized by a polymerization reaction of a polyfunctional acrylate monomer (e.g., polyol acrylate, polyester acrylate, urethane acrylate, epoxy acrylate). Also preferably used is a silicone polymer that is a co-hydrolyzate of a silane compound having a methacrylic group (e.g., tetraalkoxysilane, alkyltrialkoxysilane) and a silane coupling agent.

[0163] Various photopolymerization initiators can be used, including photoradical polymerization initiators, photoacid generators, and photobase generators, although those capable of initiating or accelerating polymerization, silanol condensation, crosslinking, etc. of the binder in the coating composition through radical polymerization reaction or the like are preferred.

[0164] The coating composition used to form the curable resin layer of the laminate sheet of the present invention may contain inorganic particles. The inorganic particles contained in the inorganic particle dispersion are not particularly limited, but are preferably at least one selected from the group consisting of metal elements, semi-metal elements, and their oxides, nitrides, borides, carbonates, and sulfates, and are more preferably oxide particles containing at least one element of Si, Na, K, Ca, Mg, Ga, Zr, Ti, Al, In, Sb, Sn, and Ce. Specifically, silica (SiO ２), zirconium oxide (ZrO ２ ), titanium oxide (TiO ２ ), aluminum oxide (Al ２ O ３ ), indium oxide (In ２ O ３ ), zinc oxide (ZnO), tin oxide (SnO ２ ), antimony oxide (Sb ２ O ３ ), and indium tin oxide, etc. can be preferably used. These inorganic particles may be used alone or in combination of two or more kinds.

[0165] From the viewpoint of achieving both improved processability and reduced wear damage in practical use, the laminate film of the present invention preferably has a crack initiation pressure of 100 GPa or more and 600 GPa or less in a microscratch test method conforming to JIS R-3255:1997. The microscratch test method described here is a method for quantifying hardness in which a stylus having a diameter of several to several tens of micrometers is brought into contact with the outermost surface of a test object, the load applied to the stylus is measured while increasing the load over time, and the point at which the load behavior changes suddenly when a scratch is made on the surface is taken as the crack initiation pressure (the detailed measurement method will be described later). The device for measuring the crack initiation pressure is not particularly limited as long as it is capable of measurement, but for example, a scratch tester (CSR5000 manufactured by Rhesca Co., Ltd.) or the like can be used.

[0166] When the crack initiation pressure of the curable resin layer in the laminate sheet of the present invention is 100 GPa or more and 600 GPa or more, the occurrence of scratches due to abrasion can be suppressed and processability can be improved. As described above, the smoothness of the outermost surface of the curable resin layer is important for improving abrasion resistance, but it is also important that the curable resin layer has a certain level of hardness or more. When the crack initiation pressure of the curable resin layer is 100 GPa or more, the curable resin layer has a certain level of hardness or more, thereby reducing the occurrence of scratches due to abrasion. From the above perspective, the crack initiation load of the curable resin layer is preferably 150 GPa or more. As described above, from the viewpoint of reducing scratches due to abrasion, the higher the crack initiation load of the curable resin layer, the more preferable it is. However, as described above, it is also necessary to consider the processability during heating, which is in a trade-off relationship. From the viewpoint of maintaining good processability during heating, the upper limit of the crack initiation load of the curable resin layer is preferably 600 GPa, more preferably 500 GPa. The crack generation load of the curable resin layer can be controlled by adjusting the concentration of inorganic particles that affect the hardness of the curable resin layer or by selecting the type of monomer (binder component) used to form the curable resin layer.

[0167] Another method for measuring the hardness of a curable resin layer is pencil hardness measurement. However, when the object to be measured is a multi-layer laminate, the adhesive layer or substrate, which has a lower hardness than the curable resin layer, is likely to be indented when the pencil lead is pressed against the object, causing scratches in the curable resin layer at a lower load. Therefore, there is also the problem that the measured value tends to be low. On the other hand, the microscratch test method can measure the hardness at the outermost surface of the curable resin layer, making it possible to more accurately measure the hardness of the curable resin layer itself.

[0168] It is also preferable that the curable resin layer does not cause appearance defects due to distortion at the interface with the curable resin layer caused by thermal shrinkage of the laminate film substrate during the heating step during glass processing. In other words, as described in section (20) below, it is preferable that cracks (scratches) do not occur even when a laminate film having a curable resin layer laminated on glass is attached and heated. In order to prevent cracks from occurring during heating, it is effective to use a type of base resin used in the thermosetting resin layer that has appropriate flexibility, or to use a laminate film substrate that has a balanced thermal shrinkage and does not exhibit thermal shrinkage behavior such as extreme shrinkage in one direction. The thermal shrinkage balance of the laminate film substrate can be adjusted by, for example, reducing the difference in stretching ratio between two orthogonal directions.

[0169] Next, a preferred method for producing a laminate film that can be suitably used in the transparent display system of the present invention will be described below, taking as an example a laminate film in which two types of thermoplastic resin layers (layers A and B) are alternately laminated. However, the laminate film of the present invention should not be construed as being limited to this example. Note that the preferred ranges of each condition vary depending on the types of thermoplastic resins A and B that are the main components of layers A and B, but the following example shows a case in which a thermoplastic resin having an ethylene terephthalate skeleton or an ethylene naphthalate skeleton as the basic skeleton is used as either thermoplastic resin A or B, such as polyethylene terephthalate or polyethylene naphthalate.

[0170] Thermoplastic resin A and thermoplastic resin B are prepared in the form of pellets or the like as polymers that form the main components of the thermoplastic resin layers that make up the alternating laminate unit of the laminate film. The pellets are dried in hot air or under vacuum as needed, and then fed into separate extruders. Each thermoplastic resin is heated and melted in the extruder at a temperature above its melting point, and the extrusion rate is made uniform using a gear pump or the like, and the resin is extruded. Any foreign matter or modified resin is removed through a filter or the like.

[0171] The molten thermoplastic resins are then fed into a multi-layer lamination device. Multi-manifold dies, feed blocks, static mixers, and the like can be used as multi-layer lamination devices. However, in order to efficiently obtain the multi-layer laminate structure of the present invention, it is preferable to use a feed block with fine slits. The use of such a feed block prevents the device from becoming excessively large, reduces the amount of foreign matter generated due to thermal degradation, and enables high-precision lamination even when the number of layers is extremely large. Furthermore, the lamination accuracy in the width direction is significantly improved compared to conventional technology. Furthermore, with this device, the thickness of each layer can be adjusted by the shape (length, width) of the slits, making it easy to achieve any desired layer thickness.

[0172] The resulting molten laminate is then molded into a sheet using a die and extruded onto a cooling body such as a casting drum, where it is cooled and solidified to obtain a cast sheet. In this process, it is preferable to use a wire-, tape-, needle-, or knife-shaped electrode to electrostatically press the molten sheet against a cooling body such as a casting drum, thereby rapidly solidifying the molten sheet. Other preferred methods include blowing air from a slit-, spot-, or planar-shaped device to press the molten sheet against a cooling body such as a casting drum, or pressing the molten sheet against a cooling body using a nip roll to rapidly solidify the molten sheet. The temperature of the casting drum is preferably set below the softening point of the resin used, preferably between 10°C and 70°C.

[0173] The resulting cast sheet is then preferably stretched uniaxially in the width direction or biaxially in the longitudinal and width directions. In the case of biaxial stretching, biaxial stretching may be performed sequentially or simultaneously. If necessary, further re-stretching may be performed in the longitudinal and / or width directions. Note that, although the case of biaxial stretching will be described below, stretching in the width direction can also be performed in the uniaxial stretching case by the following method.

[0174] First, the case of sequential biaxial stretching will be described. In the case of sequential biaxial stretching, it is preferable to stretch in the width direction after stretching in the longitudinal direction. Here, stretching in the longitudinal direction refers to the first axial stretching to impart longitudinal molecular orientation to the cast sheet, and is usually performed by the difference in peripheral speed of the rolls. Stretching in the longitudinal direction may be performed in one stage using a pair of rolls, or in multiple stages using multiple pairs of rolls. The stretching ratio is preferably 2.0 to 10 times, more preferably 2.5 to 7.0 times. Furthermore, the stretching temperature is preferably set within the range of the glass transition temperature of the thermoplastic resin with the highest glass transition temperature among the thermoplastic resins constituting the laminate film to the glass transition temperature + 100°C. Furthermore, in order to ensure that the reflection spectrum obtained when a P wave is incident from a direction tilted by 60° from the normal to the film surface toward the orientation axis and the reflection spectrum obtained when the P wave is incident from a direction tilted by 60° to a direction perpendicular to the orientation axis do not overlap and exhibit the target area A, the stretching ratio in the longitudinal direction is preferably 2.7 to 3.5 times, preferably 2.7 to 3.4 times, which is lower than the stretching ratio in the width direction described below.

[0175] The uniaxially stretched film thus obtained may be subjected to a surface treatment such as corona treatment, flame treatment, or plasma treatment as necessary, and then an easy-adhesion layer having functions such as easy slippage, easy adhesion, and antistatic properties may be provided by in-line coating. In the in-line coating step, the easy-adhesion layer may be applied to one side of the laminate film, or may be applied to both sides of the laminate film simultaneously or one side at a time.

[0176] Next, the uniaxially stretched film is stretched in the width direction. Stretching in the width direction refers to biaxial stretching to impart width-direction orientation to the sheet. This is typically performed using a tenter, with both ends of the sheet being held with clips while being conveyed. The stretching ratio is preferably 2.0 to 10 times, with 2.5 to 7.0 times being particularly preferred. The stretching temperature is preferably the glass transition temperature of the thermoplastic resin A or B, whichever has the higher glass transition temperature, to that glass transition temperature + 120°C. The stretching speed is preferably increased to enhance width-direction orientation, and the maximum stretching speed in the stretching step is preferably 8% / sec, more preferably 20% / sec or higher. Furthermore, to adjust the aforementioned area A within a preferred range, it is preferable to stretch the film in the longitudinal direction at the preferred ratio, followed by 3.5 to 6.0 times width-direction stretching. Strong stretching in the width direction allows for uniform reflection spectra, retardation, and orientation across a wide area of ​​the film surface.

[0177] The biaxially stretched laminated film is then subjected to a heat treatment in a tenter at a temperature above the stretching temperature and below the melting point, followed by uniform slow cooling to room temperature and winding up. To achieve a more uniform orientation of the laminated film, it is preferable to use temperature conditions with a gentle gradient for the stretching and heat treatment steps. The temperature gradient is preferably within a temperature range above the glass transition temperature of the thermoplastic resin with the highest glass transition temperature and below the crystallization temperature of the thermoplastic resin with the highest crystallization temperature in the laminated film, and preferably includes two or more temperature gradients before reaching the heat treatment temperature.

[0178] As a method for reducing the shrinkage force after the stretching process and further improving the orientation uniformity in the width direction, it is preferable to lower the heat treatment temperature to reduce the shrinkage force toward the stretching process in the longitudinal direction, or to extend the intermediate region between the stretching process and the heat treatment process, and to provide a temporary constant temperature or low temperature region (a region where the intermediate region temperature is equal to or greater than the stretching temperature + 30°C) to increase the rigidity of the film. In addition, it is also preferable to suppress the shrinkage force in the longitudinal direction and then slightly stretch the laminated film in the width direction in the heat treatment process to put it in a tensioned state. From the viewpoint of achieving both a balance of thermal shrinkage and orientation taking into account the processability into a projection image display member, the microstretching ratio is 3% to 18%, more preferably 5% to 10%.

[0179] Furthermore, if necessary, in order to achieve a low orientation angle and to impart thermal dimensional stability to the laminated film, a relaxation treatment may be performed in the longitudinal and / or width directions while slowly cooling the laminated film in the cooling step after the heat treatment step. Furthermore, in order to adjust the heat shrinkage rate at low temperatures, it is also preferable to perform slight stretching in the width direction in this slow cooling step in a section where the film temperature is equal to or higher than the temperature at which the heat shrinkage rate is to be adjusted. It is also preferable to perform pseudo-slight stretching by increasing the tension (draw) in the winding step after slow cooling. These methods may be combined as appropriate.

[0180] In order to improve the visibility of image display over a wide area, the laminate film of the present invention preferably has a ratio of the widthwise stretching ratio to the longitudinal stretching ratio (the ratio of the widthwise stretching ratio / the longitudinal stretching ratio and the longitudinal stretching ratio / the widthwise stretching ratio being greater than 1) of 1.15 to 3.00. When the stretching ratio is 1.15 or more, the difference between the in-plane refractive index in the orientation axis direction and the in-plane refractive index in the direction perpendicular to the orientation axis is sufficiently large, resulting in more uniform orientation in the width direction, making it difficult to visually recognize overlapping images when images are displayed over a wide area. When the stretching ratio is 3.00 or less, the orientation in a specific direction is not too strong, reducing problems such as reduced film formability, such as film tearing, and poor appearance during processing due to high thermal shrinkage in the stretching direction. A more preferred stretching ratio that can achieve both uniform orientation and processability is 1.30 to 2.00, and even more preferably 1.50 to 2.00. When the film is stretched in multiple stages, the stretching ratio is calculated based on the stretching ratio of the film finally obtained.

[0181] Next, simultaneous biaxial stretching will be described. In the case of simultaneous biaxial stretching, the obtained cast sheet may be subjected to a surface treatment such as corona treatment, flame treatment, or plasma treatment as necessary, and then provided with functions such as easy slip, easy adhesion, and antistatic properties by in-line coating. In the in-line coating process, the easy adhesion layer may be applied to one side of the laminated film, or may be applied to both sides of the cast sheet simultaneously or one side at a time.

[0182] The cast sheet is then introduced into a simultaneous biaxial tenter, where it is conveyed while holding both widthwise ends of the sheet with clips, and simultaneously and / or stepwise stretched in the longitudinal and width directions. Simultaneous biaxial stretching machines include pantograph, screw, drive motor, and linear motor types. Drive motor or linear motor types are preferred, as they allow for arbitrary change in stretching ratio and relaxation treatment at any location. The stretching ratio is preferably 6 to 50 times, more preferably 8 to 30 times, in terms of area stretching ratio. Furthermore, to strongly express orientation in a specific in-plane direction, it is preferable to set the stretching ratios in the longitudinal and width directions to different values. The stretching speed may be the same or different speeds in the longitudinal and width directions. The stretching temperature is preferably between the glass transition temperature of the thermoplastic resin with the highest glass transition temperature among the resins constituting the laminate film and that glass transition temperature + 120°C.

[0183] To impart flatness and dimensional stability to the simultaneously biaxially stretched sheet, it is preferable to subsequently subject the sheet to heat treatment in a tenter at a temperature equal to or higher than the stretching temperature but lower than the melting point of the thermoplastic resin with the highest melting point (observed as the peak-top temperature of the highest endothermic peak obtained by DSC measurement after film formation). During this heat treatment, it is preferable to instantaneously subject the sheet to a relaxation treatment in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone in order to suppress the distribution of the main orientation axis in the width direction. After this heat treatment, the sheet is uniformly and slowly cooled, cooled to room temperature, and wound up. If necessary, relaxation treatment may be performed in the longitudinal and / or width directions during the slow cooling from the heat treatment. The sheet is instantly relaxed in the longitudinal direction immediately before and / or immediately after entering the heat treatment zone. The stretch ratio and other conditions can be the same as those for the sequential biaxial stretching described above.

[0184] The laminated film obtained as described above is trimmed to the required width using a winding device and wound up in a roll to prevent wrinkles from forming. Note that, during winding, both ends of the sheet may be embossed to improve the roll appearance.

[0185] Next, a method for manufacturing a projection image display member constituting the transparent display system of the present invention will be described, although the method for manufacturing a projection image display member of the present invention should not be construed as being limited to this example.

[0186] The following is an example of a manufacturing method for an interpolation-type projection image display member when the above-mentioned laminate film is used as a light-reflecting material. The transparent hard material, adhesive layer, and laminate film used in the projection image display member are each prepared in the size required for lamination. If the transparent hard material has a curved surface, the adhesive layer and laminate film are cut to a size larger than the transparent hard material. These materials are laminated in the following order to create an interpolation-type laminate: transparent hard material / adhesive layer / laminating film / adhesive layer / transparent hard material. The interpolation-type laminate thus formed is generally prepared by laminating the laminate film and adhesive layer at a low temperature (pre-lamination process), and then laminating them to a support by applying pressure at a higher temperature (main pressure bonding process).

[0187] The pre-lamination process is not particularly limited, but typically involves sandwiching a laminate film between two adhesive layer films and roll-thermal laminating at a temperature 10 to 30°C higher than the glass transition temperature of the highest thermoplastic resin among the thermoplastic resins constituting the laminate film. However, if the adhesive layer is thin, wrinkles may occur depending on the shape of the transparent hard material, which may result in air bubbles, wrinkles, and other deterioration in the appearance of the final projection image display component. Therefore, the laminate film and adhesive layer can be pre-pressed by heat roll lamination. The heat-pressure bonding temperature can be adjusted appropriately depending on the material of the adhesive layer, but when a material primarily composed of polyvinyl butyrate is used for the adhesive layer, a temperature of 80°C or higher and 140°C or lower is preferably selected.

[0188] The method of the main pressure bonding step after the pre-lamination step is not particularly limited, but the laminated body of the inserting method is subjected to an autoclave (pressurized heating and bonding furnace) at 140 to 150°C for 20 to 30 minutes under a pressure of 12 to 14 kg / cm. ２ It is common to use a pressure bonding method.

[0189] Next, an example of a method for manufacturing an internally-attached projection image display member when the laminate film is used as a light-reflecting material is described below. If necessary, a curable resin layer and a pressure-sensitive adhesive / adhesive layer are provided on the outermost surface of the laminate film. The curable resin layer can be formed using the method described in the evaluation method below. The adhesive layer can be made of polyvinyl butyrate, polyurethane, or the like, or can be provided by applying an optical adhesive whose main component is acrylic resin or the like, or by laminating an optical adhesive sheet.

[0190] The laminated sheet thus obtained is sandwiched between two sheets of transparent hard material or metal molds of the same shape, and the laminated film is pre-shaped at the lamination processing temperature to the shape of the transparent hard material to be laminated, and then a cover glass is laminated and the lamination is performed by roll lamination molding, vacuum bag method, or TOM molding method, and finally autoclave treatment is performed for degassing. In this case, too, a method can be used in which heating and pressure treatment is performed at the heat treatment temperature described in the processing step of the insertion method, and the adhesive layer is solidified and pressed to the transparent hard material to achieve adhesion.

[0191] The transparent display system of the present invention can be constructed by arranging the projection image display element manufactured in this manner and a suitably selected image projector (display) as described above so that the image is incident on the projection image display element at a predetermined incident angle.

[0192] The present invention will be described below with reference to examples, but the present invention is not limited to the embodiments shown in these examples. The properties and effects were measured and evaluated by the following methods.

[0193] (Methods for Measuring Characteristics and Evaluating Effects) The methods for measuring characteristics and evaluating effects in the present invention are as follows.

[0194] (1) Differential Scanning Calorimetry (DSC) Measurements were performed using a differential scanning calorimeter EXSTAR DSC6220 manufactured by Hitachi High-Technologies Corporation. Measurements and temperature readings were performed in accordance with JIS-K-7122 (1987). Specifically, approximately 5 mg of sample was placed on an aluminum pan and heated from 25°C (room temperature) to 300°C at a rate of 10°C / min. At a temperature higher than the glass transition temperature Tg (°C) at the intersection of the baseline and the tangent at the inflection point of the step transition portion, a microcrystalline melting temperature exhibiting a small endothermic peak different from the melting point was read as the heat treatment temperature of the laminated film. Furthermore, after heating, the sample was rapidly cooled with liquid nitrogen, and when heated again under the same conditions, the melting enthalpy Tm (J / g) corresponding to the area of ​​the endothermic peak (melting point) observed at the highest temperature side was read.

[0195] (2) Layer Structure, etc. The layer structure, etc. of the laminate film was identified and measured by observing a sample sliced ​​using an ultramicrotome with a transmission electron microscope (TEM). Specifically, a transmission electron microscope JEM-1400 Plus (manufactured by JEOL Ltd.) was used to observe the cross section of the laminate film (thickness direction, i.e., cross section perpendicular to the film surface) at an acceleration voltage of 100 kV, and a cross-sectional image was obtained to measure the layer structure (number of layers, regular arrangement, layer thickness distribution) and the thickness of each layer. Note that, in order to obtain a large contrast difference between each layer during cross-sectional observation, an electron stain (RuO ４ A staining technique using, for example, a dyeing technique using a dye such as a dyeing dye (e.g., a dyeing dye with a dyeing agent) was used. In addition, depending on the thickness of each layer, observation was performed at a direct magnification of 40,000 times when the thin film layer thickness was less than 100 nm, at a direct magnification of 20,000 times when the thin film layer thickness was 100 nm or more but less than 500 nm, and at a direct magnification of 1,000 to 10,000 times when the thin film layer thickness was 500 nm or more, depending on the thickness. The thickness of each layer was analyzed using the method described in the layer interface (contrast difference) in section (3) below, and the number of stacked layers, the regular arrangement (layer structure), the layer thickness of each layer, and the layer thickness distribution were determined.

[0196] (3) Layer Interface (Contrast Difference) The cross-sectional image obtained in the transmission electron microscope observation in section (2) above was converted to a compressed image file (JPEG) format, and position-brightness data was obtained by line profiling along the thickness direction of the laminate film using ImagePro-10 manufactured by MediaCybernetics. Subsequently, a five-point moving average was performed on the profile obtained by plotting the relationship between position and brightness using spreadsheet software (Microsoft Excel (registered trademark) 2016). The five-point moving average was performed by averaging brightness at five consecutive measurement positions, shifting the position by one point at a time, and repeating the same calculation to obtain a position-brightness profile. In the obtained five-point moving average processed position-brightness profile, the positions surrounded by inflection points where the slope changes from positive to negative or from negative to positive were determined to be one layer. For each layer obtained by this method, position-brightness data was then obtained in the planar direction (direction perpendicular to the thickness direction) of the laminate film. After calculating the average and standard deviation of the brightness obtained for each layer, if the difference between the average brightness values ​​of two adjacent layers was greater than either of the standard deviations of the brightness values ​​of the adjacent thermoplastic resin layers, the two adjacent layers were determined to be different. In addition, the difference (distance) between the positions of the inflection points was calculated as the layer thickness of each layer.

[0197] (4) Transmission Spectrum Measurement (Normal Incidence, Average Visible Light Transmittance) A sample of the projection image display member or laminate film to be measured was cut out into a 7 cm square from a predetermined measurement position (point C for the projection image display member, point CF for the laminate film). A Hitachi, Ltd. spectrophotometer (U-4100 Spectrophotometer) was fitted with an attached angle-variable reflection unit and a Glan-Taylor polarizer, and the transmission spectrum was measured in the wavelength range of 395 nm to 805 nm under both P-wave and S-wave irradiation conditions. The P-wave and S-wave measurement results were averaged to obtain the target transmission spectrum. The scan speed and sampling pitch were set to 600 nm / min and 1 nm, respectively. The transmission spectrum data for the wavelength range of 395 nm to 805 nm was averaged over 10 consecutive points, and the average value for wavelengths of 400 nm to 800 nm was calculated to obtain the average visible light transmittance. Point C of the projection image display member was the center of gravity of the projection image display member, and point CF of the laminate film was the intersection of the diagonals (corresponding to the center of gravity) of a piece cut to the same size as that used to produce the projection image display member shown in (13) and (14) (the same applies below).

[0198] (5) Reflection Spectrum Measurement (P Wave, Average Reflectance from 400 to 700 nm) For the samples cut out at points C and CF in (4) above, a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd. was fitted with an attached variable-angle reflection unit and a Glan-Taylor polarizer, and the reflectance when irradiated with P waves in the wavelength range of 395 to 705 nm was measured at a scan speed of 600 nm / min and a sampling pitch of 1 nm. The obtained reflection spectrum data was averaged over 10 consecutive points to calculate the average reflectance of P waves in the wavelength range of 400 to 700 nm. The conditions for the incidence of light on the projection image display member were as follows (I) and (II), and the reference axis C was the intersection line between the tangent surface of the projection image display member and the horizontal plane passing through point C. Furthermore, in the laminated film, P waves were incident from a direction in which the angle between the normal to the film surface at point CF and the orientation axis (specified by the method described in (7) below) in a plane including the normal and the orientation axis was 60° and perpendicular to the orientation axis, and from a direction in which the angle between the normal to the film surface at point CF and the normal to the film surface in a plane including the normal to the orientation axis and a line perpendicular to the orientation axis was 60°.

[0199] <Conditions for Irradiating Light onto a Projection Image Display Member> (I) The projection image display member was tilted by rotating it around the reference axis C, and P-waves were incident on the projection image display member so that the angle between the normal to the tangent surface of the projection image display member at point C and the direction of travel of the P-waves was 60° and the reference axis C was perpendicular to the direction of travel of the P-waves. (II) P-waves were incident on the projection image display member from a direction such that the angle between the normal to the tangent surface of the projection image display member at point C and the normal to the tangent surface in a plane containing a line perpendicular to the orientation axis within the tangent surface was 60°. (III) P-waves were incident on the projection image display member from a direction tilted by θ2+5° from the normal to the tangent surface at point C toward the orientation axis.

[0200] (6) Calculation of Area A For the samples at points C and CF cut out in (4) above, a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd. was fitted with an attached angle-variable reflection unit and a Glan-Taylor polarizer, and the reflectance when irradiated with P waves in the wavelength range of 395 to 705 nm at a predetermined incident angle was measured when the sample was tilted in a direction where the angle between the normal to the film surface and the orientation axis was 60°, and when the angle between the normal to the film surface and the normal to the film surface was 60° in a plane containing the normal to the film surface and a line perpendicular to the orientation axis.The area of ​​the region enclosed by both reflection spectra was calculated using the trapezoidal method to be the area A (nm %). Note that when the sample was a projection image display member, the normal to the film surface was the tangent plane of the projection image display member at point C.

[0201] (7) Retardation and Orientation Angle A retardation measurement device (KOBRA-WPR) manufactured by Oji Scientific Instruments Co., Ltd. was used. Measurement samples of the laminate film or projection image display member were cut out from a predetermined location in a 10 cm square, and the samples were placed on a large-format sample setting table at the bottom of the device. The orientation angle from the angle 0° defined by this measurement device and the in-plane retardation at 587 nm at normal incidence were then analyzed for the placed samples. The orientation angle was measured from -90° to 90°, and the axis including the direction indicated by the orientation angle obtained by the measurement was defined as the orientation axis. The coefficient of variation of the phase difference was measured at five points: the center point C (point CF) of each sample, the midpoints between the center point and the end in the short side direction, point X1 (point X1F) and point X2 (point X2F), and the midpoints between the center point and the end in the long side direction, point Y1 (point Y1F) and point Y2 (point Y2F). The standard deviation of the five measurement results was then divided by the average value to calculate a percentage. The variation in the orientation angle was calculated by subtracting the smallest orientation angle from the largest orientation angle relative to the reference 0 ° among the orientation angles at the five specified points. In addition, when the orientation angles at the five points show variation across the axial direction corresponding to ±90 °, the smaller angle between the orientation axis direction showing the smallest positive numerical value and the orientation axis direction showing the largest negative numerical value was adopted. The orientation axis is defined as the linear direction obtained by extending the direction indicated by the orientation angle with respect to the measurement point and the opposite direction. The measurement points for the projection image display member are five points: C, X1, X2, Y1, and Y2, but for the laminate film, these should be read as CF, X1F, X2F, Y1F, and Y2F, respectively. In this measurement, the projection image display member is curved, but considering the area of ​​the projection image display member, the maximum depth of the recesses, and the sample size obtained in this measurement, the measurement sample is substantially flat, so it was evaluated as being flat.

[0202] (8) Heat Shrinkage Rate Five measurement samples measuring 150 mm long x 10 mm short were cut from the laminated film along the orientation axis from point CF. These samples were left standing in an atmosphere of 23 ° C and 60% relative humidity for 30 minutes, and marks were made at approximately 100 mm intervals in the center of the longitudinal direction of the sample under that atmosphere. Next, the exact distance between the marks was measured using a Nikon universal projector (Model V-16A), and this value was designated as A (mm). Next, each sample piece was heat-treated in a hot air oven at 100 ° C, 125 ° C, or 150 ° C in a tension-free state for 30 minutes. Then, after cooling and conditioning for 1 hour in an atmosphere of 23 ° C and 60% relative humidity, the distance between the marks was measured and designated as B (mm). The heat shrinkage rate of each sample was calculated using A and B from the obtained formula (3). For each temperature condition, the average values ​​of the five samples were taken as the final heat shrinkage rates S100 (%), S120 (%), and S150 (%), and an investigation was conducted to determine whether or not the relationship X "0.7 × (S100 + S150) / 2 ≦ S125 ≦ 1.3 × (S100 + S150) / 2" was satisfied.

[0203]

[0204] (9) Refractive Index Evaluation (Thermoplastic Resin Layer Located on the Outermost Surface of the Laminated Film) The in-plane refractive index of the thermoplastic resin layer located on the outermost surface of the laminated film was measured under the following measurement conditions using a "SPA-4000" manufactured by SAIRON TECHNOLOGY, INC. The average value of the refractive index in the orientation axis direction of the laminated film and the refractive index in the direction perpendicular to the orientation axis direction was defined as the in-plane average refractive index. The orientation axis direction was specified as the direction passing through the measurement point and indicated by the orientation angle obtained in advance by the method described in the above item (7), and the direction perpendicular to the orientation axis was defined as the direction perpendicular to the orientation axis direction in the film plane. Laser: wavelength 632.8 nm Prism: GGG prism

[0205] (10) Electron Energy Loss Spectroscopy (EELS) Measurement Before measurement, the orientation axis direction of the laminate film was identified by the method described in (7) above. A cross-sectional (thickness direction) cut sample of the measurement target was prepared along a direction parallel to the orientation axis direction by ultrathin sectioning using an ultramicrotome, and a planar cut sample of each layer was prepared so that the cut sample was approximately parallel to the layer direction of the laminate film. The dielectric constant of the prepared cross-sectional / planar cut samples was measured using an atomic resolution analytical electron microscope ARM200F manufactured by JEOL Ltd. Specifically, an HAADF-STEM (High Angle Annular Dark-Field Scanning Transmission Electron Microscopy) image was acquired at an acceleration voltage of 80 kV and a beam spot size of 0.2 mmφ. After that, multipoint analysis (60 x 60 pixels, 20 nm / pixel) was performed on the layer to be measured at 50 msec to obtain data on energy loss and electron beam intensity. The same operation was performed on three points for each of the same thermoplastic resin layers in the laminate film, and data with an improved S / N ratio was obtained. From the obtained spectrum, background correction due to elastic scattering and removal of the multiple scattering effect were performed, and then the dielectric function of each layer was calculated using the Kramers-Kronig transformation shown in equation (4). The integral range during the Kramers-Kronig transformation was 0 to 200 eV. Based on the dielectric function of formula (4), the real and imaginary parts of the dielectric constant were calculated from formulas (5) and (6), respectively, and then the dielectric constant was calculated from formula (7) which is the square root of the sum of the squares of these. Using the above method, the dielectric constant of each thermoplastic resin layer at a loss energy of 2.5 eV was calculated and compared. In formulas (4) to (7), Re is the real part, Im is the imaginary part, ε is the dielectric constant (average value), ε(ω) is the dielectric function, and ε １ is the real part of the permittivity, ε ２ denotes the imaginary part of the dielectric constant, and ω and ω' denote the angular frequencies.

[0206]

[0207]

[0208]

[0209]

[0210] According to Maxwell's electromagnetic theory, the dielectric constant of a non-magnetic material that absorbs little light, such as the thermoplastic resin suitable for forming the thermoplastic resin layer constituting the laminate film of the present invention, is generally equal to the square of the refractive index. Therefore, it is possible to roughly estimate the refractive index of the thermoplastic resin layer from the dielectric constant of the thermoplastic resin layer. The refractive index of the thermoplastic resin layer not positioned at the outermost layer of the laminate film was calculated by proportional calculation using the ratio of the in-plane / normal-to-plane refractive index of each layer obtained from the EELS measurement and the absolute value of the thermoplastic resin positioned at the outermost layer obtained in (9).

[0211] (11) Crack Initiation Pressure of Curable Resin Layer and Adhesive Layer This was performed using a micro-scratch test method in accordance with JIS R-3255:1997. Specifically, a 4 cm x 4 cm square sample was cut out from the laminated film and placed on the measurement stage of a scratch tester (CSR5000 manufactured by Rhesca Co.) with the curable resin layer or adhesive layer facing the stylus side, and a surface scratch test was performed under the following conditions: Stylus: Diamond stylus (stylus diameter 15 μm) Scratch speed: 10 μm / sec Excitation amplitude: 50 μm Excitation frequency: 45 Hz Touch detection level: 3.0 mN Load conditions: Monotonically increasing (+1.33 mN / sec) Initial load: 0 mN Maximum load: 100 mN Measurement time: 600 seconds Measurement environment: 25°C, relative humidity 65%

[0212] The load at which the vertical sensor acceleration value (unitless) exceeded 200 for the first time during the time-dependent change from the start of measurement was defined as the crack initiation load. If the acceleration did not exceed 200 during the second measurement, the crack initiation pressure was taken as 800 mN. The crack initiation pressure was calculated from the obtained crack initiation load and the stylus diameter according to equation (8).

[0213]

[0214] (12) Method for Forming a Curable Resin Layer The coating materials and particles listed in Table 2-1 were mixed in the mass ratios listed in Table 2-2 to obtain hard coat coating materials HC-1, HC-2, and HC-3. The hard coat coating materials were applied to a laminated film using a stainless steel coating wire bar #12 manufactured by RD Specialties, and the layer was left to stand in a high-temperature bath at 100°C to volatilize the solvent. Subsequently, the layer was exposed to a UV irradiation device (Eye Graphics ECS-401GX) with an integrated light intensity of 770 mJ / cm. ２ The laminated film was cured by irradiating it with UV light so that the hard coat layer had a thickness of 10 μm.

[0215] (13) Preparation of Projection Image Display Member (Interpolation Method) Two concave glass plates measuring 1000 mm long x 1500 mm wide x 2 mm thick with a maximum curvature depth of 50 mm were used, with the concave surfaces facing up, to obtain a glass laminate in the following order: glass plate / adhesive layer 2 / laminated film / adhesive layer 1 / glass plate. The obtained glass laminate was placed in a rubber vacuum bag and held at 60°C for 30 minutes while suctioning under reduced pressure, and then held at 100°C for 60 minutes to perform pre-bonding. The pre-bonded glass laminate was placed in an autoclave and treated at a high temperature and pressure of 140°C and 13 atmospheres for 30 minutes to obtain a laminated glass (interpolation method) projection image display member. The same glass plates were used as the outermost layers on both sides.

[0216] (14) Preparation of Projection Image Display Member (Lamination Method) Two concave glass plates, each measuring 1000 mm long x 1500 mm wide x 2 mm thick and with a maximum curvature depth of 50 mm, were laminated with the concave surfaces facing up in the order glass plate / adhesive layer 2 / glass plate. Subsequently, the preliminary pressure bonding and main pressure bonding steps described in (13) were carried out to form a laminated glass. Next, a laminate sheet having adhesive layer 1, a laminating film, and a curable resin layer laminated in this order was laminated on the outermost concave surface of the laminated glass, with the curable resin layer facing the surface. Furthermore, a tempered glass plate of the same shape having a release-treated film formed thereon was laminated on top of the laminated glass, with the release-treated surface facing the laminating film, to form a glass laminate. The glass laminate was again placed in a rubber vacuum bag, degassed for 10 minutes while suctioning under reduced pressure, and then held at 130°C for 5 minutes to perform preliminary pressure bonding. The pre-pressed glass laminate was then heated at 140°C and 13 atmospheres (1.3 x 10 ６The glass laminate after the completion of the final pressure bonding was then removed from the autoclave and allowed to cool, and the tempered glass plate was removed to obtain the desired projection image display member (lamination type).

[0217] (15) Evaluation of Front Visibility (Driver's Eyes) of Transparent Display System The manufactured projection image display member was propped up and fixed so that the angle with the horizontal plane was (90-θ2)°. A transparent display system was constructed by installing an "iPad" (registered trademark) 2 display (manufactured by Apple Inc.) parallel to the horizontal plane at the bottom of the display member, located 1 / 4 of the way to the right of the recess of the projection image display member, with the long dimension of the projection image display member parallel to the long dimension of the projection image display member. In this transparent display system, the image visibility was evaluated on an 8-point scale as follows when viewed from a position parallel to the short dimension of the iPad (registered trademark) 2 display (manufactured by Apple Inc.) from the center of the installation position, at the same horizontal height as the image, and from a distance of 1 m from the image display position. A rating of S was the best, with S, A, B, C, D, and E / F being ranked in order of good, and N1 and N2 being judged to be poor display. S: The image was clearly visible throughout the entire display area without any double images. A: The image appeared slightly blurred in part of the display range, but was clearly displayed over a wide area without double images. B: The image appeared blurred in part or the entire display range, but it was not noticeable unless you looked closely. C: The image appeared blurred in part or the entire display range, to the extent that you could notice the image without looking closely. D: Multiple images were visible across the entire display range, but the contrast ratio of the main image was high and the impact on visibility was small. E: The main image was difficult to see due to reflections, but the presence of the image was recognizable. F: The displayed image was distorted due to poor quality such as streaks in the projected image display component, but the display itself was recognizable. N1: There was one type of image, but the image was dark and difficult to see due to reflections or insufficient display brightness. N2: Multiple images were visible across part or the entire display range, and visibility was poor due to the high contrast.

[0218] (16) Evaluation of diagonal visibility (passenger seat line of sight) of transparent display system In the transparent display system installed in (15), the image visibility was evaluated using the same evaluation criteria as in (15) when the image was viewed from the front of the display element at a position 1 / 4 to the left of the recess of the projection image display element, at the same horizontal height as the image, and 1 m away from the image display position.

[0219] (17) Evaluation of scenery visibility In the transparent display system installed in (15), the visibility of the scenery seen behind the projection image display member was visually evaluated from the position described in (15) according to the following criteria. The evaluation results were ranked in order of S, A, B, and C, with N being judged as failing. S: The scenery through the projection image display member was clearly visible. A: The scenery through the projection image display member appeared slightly dark due to reflection, but this did not affect practicality. B: The visibility of the scenery through the projection image display member was worse than that of evaluation A due to strong reflection, but this had only a slight effect on practicality. C: Although there was no reflection, the visibility of the scenery through the projection image display member was worse than that of evaluation B, and was at a level sufficient for practical use. N: The visibility of the scenery through the projection image display member was dark enough to impair practical use.

[0220] (18) Rainbow Irregularity Evaluation The degree of coloring was evaluated when viewed horizontally outdoors on a clear day while wearing polarized sunglasses during the evaluation in (17). The evaluation criteria are as follows: A: Almost no coloring was visible. B: Very slight coloring was visible, but this was not a problem in practical use. C: Strong coloring was visible.

[0221] (19) Appearance Evaluation of Projection Image Display Members A reflected image of a straight-tube white fluorescent lamp was projected onto the projection image display member prepared in (14), and the linear side portions of the projected image of the fluorescent lamp were visually inspected to see if there was any distortion of the reflected image due to wavy patterns or steps (streaks). The degree of appearance was evaluated according to the following criteria: S: No distortion of the reflected image was observed on the surface of the projection image display member, and the appearance was good. A: Slight distortion of the reflected image due to wavy patterns was observed on the surface of the projection image display member, but no distortion of the reflected image due to steps (streaks) was observed, and the level was acceptable for practical use. B: When closely observing the surface of the projection image display member, slight distortion of the reflected image due to small steps (streaks) was observed, but the level was acceptable for practical use. C: Distortion of the reflected image due to at least one of wavy patterns and steps (streaks) was clearly observed on the surface of the projection image display member, and the appearance quality was poor.

[0222] (20) Abrasion Resistance Test of Hard Coat Layer A 9 cm x 9 cm laminated film was manually attached to a 10 cm square glass piece using a roller at room temperature with Tomoegawa Paper Co.'s optical adhesive TD-06A to obtain a small piece of projection image display member. A test cloth was pressed against the light incident surface of the projection image display member, and the piece was rubbed under the following rubbing conditions. The occurrence of scratches was observed after a specified number of reciprocating strokes, and the number of times at which one or more scratches occurred was determined. The minimum pass mark was no scratches after 1,000 strokes, and the more tests performed before scratches occurred, the better the abrasion resistance.

[0223] <Rubbing conditions> Test cloth: TT-STex (wool) manufactured by TRIBOTOUCH Movement distance: 20 mm Movement speed: 50 mm / sec Pressed area: 6.5 mm x 6.5 mm Stress: 74 kPa Observation of scratch occurrence: every 100 reciprocations up to 1000 reciprocations, every 1000 reciprocations from 1000 to 30000 reciprocations, and every 5000 reciprocations after 30000 reciprocations.

[0224] (21) Heat crack test of hard coat layer The projection image display member prepared in (20) was left standing at 150°C for 2 hours, and after cooling to room temperature, the appearance was inspected and the number of cracks in the outermost layer was counted. The evaluation criteria are as follows: A: 0 cracks B: 1 to 3 cracks C: 4 or more cracks

[0225] The thermoplastic resins, additives, and water-based coating material X used in the examples and comparative examples of the present invention are described below. The copolymerization component amount of the polyester resin described here represents the copolymerization amount relative to 100 mol% of the acid component and 100 mol% of the diol component.

[0226] <Thermoplastic resins> Resin 1: A crystalline homopolyethylene terephthalate resin exhibiting a glass transition temperature of 78°C, a melting point of 254°C, and a melting enthalpy of 40 J / g. Resin 2: A crystalline polyethylene naphthalate resin copolymerized with 5 mol% of polyethylene glycol having a molecular weight of 400, exhibiting a glass transition temperature of 97°C, a melting point of 254°C, and a melting enthalpy of 33 J / g. Resin 3: A microcrystalline polyethylene terephthalate resin copolymerized with 20 mol% of naphthalenedicarboxylic acid, exhibiting a glass transition temperature of 90°C, a melting point of 211°C, and a melting enthalpy of 1 J / g. Resin 4: An amorphous polyethylene naphthalate resin copolymerized with 30 mol% of an isophthalic acid component relative to the total acid components and 4 mol% of polyethylene glycol having a molecular weight of 400 relative to the total diol components, exhibiting a glass transition temperature of 80°C. Resin 5: A crystalline polyethylene terephthalate resin copolymerized with 27 mol% of cyclohexanedimethanol, exhibiting a glass transition temperature of 75°C. Resin 6: Amorphous polyethylene naphthalate resin with a glass transition temperature of 90°C, copolymerized with 35 mol% of isophthalic acid component relative to the total acid component and 2 mol% of polyethylene glycol with a molecular weight of 400 relative to the total diol component.

[0227] <Additive> Acrylic polymer with an epoxy value of 1.4 meq / g and an average molecular weight of 2900 g / mol

[0228] <Water-based Coating Agent X> To a mixture of polyester resin 1 (100 parts by mass), reactive compound 1 (30 parts by mass), and reactive compound 2 (30 parts by mass) shown below, 0.5 parts by mass of colloidal silica particles having a particle size of 100 nm was added per 100 parts by mass of binder resin, which is the mixture of the resin and compound, and the solids concentration was adjusted to 5 parts by mass with water as a solvent. After that, 0.03 parts by mass of a surfactant was added per 100 parts by mass of water in total, and mixed to prepare a coating composition.

[0229] Polyester resin 1: An aqueous dispersion of polyester resin having the following copolymerization composition was obtained by the following procedure. The following copolymerization components and 0.1 parts of potassium titanium oxalate as a catalyst were added to a reactor, and the temperature was raised to 200°C while stirring and mixing under normal pressure in a nitrogen atmosphere. Next, the reaction temperature was gradually raised to 250°C over 4 hours to terminate the transesterification reaction. 15 parts by mass of this polyester resin and 85 parts by mass of water were added to a dissolution tank and dispersed with stirring at a temperature of 80 to 95°C over 2 hours to obtain a 15% aqueous dispersion of polyester resin.

[0230] (Copolymerization composition) Dicarboxylic acid component: 2,6-dimethyl naphthalenedicarboxylate: 88 mol % Sodium dimethyl 5-sulfoisophthalate: 12 mol % Diol component: Compound in which 2 mol of ethylene oxide are added to 1 mol of bisphenol S: 86 mol % 1,3-propanediol: 14 mol %

[0231] Reactive compound 1: Carbodiimide aqueous crosslinking agent (Nisshinbo Chemical Inc., "Carbodilite" (registered trademark) V-04) Reactive compound 2: Oxazoline-containing polymer aqueous dispersion (Nippon Shokubai Co., Ltd., "Epocross" (registered trademark) WS-500)

[0232] <Adhesive Layers> Adhesive layer A: 50 μm thick resin layer made of polyvinyl butyrate Adhesive layer B: 760 μm thick resin layer made of polyvinyl butyrate Adhesive layer C: Composite layer in which a 35 μm thick iodine-oriented linear polarizing film is sandwiched between 25 μm thick acrylic optical adhesive layers TD-06 manufactured by Tomoegawa Corporation Adhesive layer D: 25 μm thick acrylic optical adhesive layer TD-06 manufactured by Tomoegawa Corporation

[0233] Example 1: Resin 1 and Resin 3 were used, respectively, as the thermoplastic resins constituting the thermoplastic resin layers, Layer A and Layer B. Each of the prepared thermoplastic resins was separately fed into two twin-screw extruders in pellet form, melted at 280°C, and kneaded. The kneading conditions were set so that the screw rotation speed relative to the discharge rate was 0.7. Next, after passing through seven FSS-type leaf disc filters, the mixture was metered with a gear pump and merged in a feed block with 801 slits and a temperature controlled at 280°C to form a molten laminate with 801 layers, having a regular arrangement of Layer A / Layer B in the thickness direction and both surface layers being Layer A. The molten laminate that passed through the feed block was then fed into a T-die and molded into a sheet. It was then quenched and solidified on a casting drum with a surface temperature maintained at 25°C while an electrostatic voltage of 8 kV was applied by a wire to obtain a laminated cast sheet. The obtained laminated cast sheet was heated with a group of rolls set at 90 ° C., and then stretched 3.1 times in the longitudinal direction (longitudinal stretching) while rapidly heating from both sides of the film with a radiation heater within a stretching section length of 100 mm, and then cooled once. Subsequently, both sides of the obtained laminated uniaxially stretched film were subjected to corona discharge treatment in air to set the wet tension of the substrate film to 55 mN / m, and then coated with water-based coating agent X, which serves as a slippery layer, using #4 Metabar (hereinafter, "coating" refers to the above content), forming a transparent, slippery, and easy-adhesion layer. Furthermore, this uniaxially laminated film was introduced into a tenter, preheated with hot air at 100 ° C., and then stretched 3.6 times in the width direction (transverse stretching) at a temperature of 110 ° C. with a maximum stretching speed of 9% / sec. Immediately after transverse stretching, the biaxially stretched film passed through an intermediate zone controlled at 150°C. The biaxially stretched film was then heat-set with hot air at 200°C, relaxed by 3% in the width direction in a cooling process at 100°C, then slowly cooled to room temperature and wound up to obtain a 1500mm wide laminated film roll. No additional stretching was performed during heat setting in the width direction stretching or during the process of slowly cooling to room temperature. The thickness of the laminated film thus obtained was 80 μm (thickness of both surface layers: 3 μm).The laminated film roll was then cut into a rectangular shape measuring 1,000 mm in the longitudinal direction and 1,500 mm in the width direction to obtain a laminated film sample. The evaluation results of the obtained laminated film are shown in Table 1.

[0234] Examples 2 to 15, Comparative Examples 1 to 3: Laminated film rolls were obtained in the same manner as in Example 1, except that the thermoplastic resins of each layer and the film-forming conditions (longitudinal stretch ratio, widthwise stretch ratio, maximum widthwise stretching speed, heat treatment temperature, heat treatment additional stretch ratio, cooling temperature, and cooling additional stretch ratio) were changed as shown in Table 1. The heat treatment additional stretch ratio was adjusted so that the distance between the clips before and after the room with the highest heat treatment temperature increased linearly at a predetermined rate within that room, and the cooling additional stretch ratio was adjusted so that the distance between the clips increased linearly at a predetermined rate within the room at the very beginning of the cooling process. Evaluation results for the obtained laminated film rolls and laminate films are shown in Table 1. The take-up speed of the casting drum was adjusted so that the laminated film thickness was 80 μm.

[0235] Example 16 The HC-1 coating agent described in Table 2-2 was applied to the outermost surface of one side of the laminate film prepared in Example 1 according to the method for forming a curable resin layer described in (12), and a laminate sheet was obtained in which a curable resin layer having a thickness of 10 μm was laminated. Furthermore, adhesive layer 1 was laminated on the surface opposite to the surface on which the curable resin layer was laminated, and the laminate sheet was obtained by heating to 75 ° C and thermocompression bonding. The results of crack tests on the curable resin layer and adhesive layer disposed on each surface of the laminate sheet are shown in Table 3. Furthermore, a projection image display member (lamination method) was prepared using the laminate according to the method described in (14), and a transparent display system was constructed according to the method described in (15). The evaluation results for each item of the projection image display member and the transparent display system are shown in Table 3.

[0236] Examples 17 to 39, Comparative Examples 4 to 7 Laminates, projection image display members, and transparent display systems were obtained in the same manner as in Example 16, except that the glass processing and display configuration items in Tables 3 and 4 were set as shown in Tables 3 and 4. The evaluation results are shown in Tables 3 and 4.

[0237] (Example 40) The HC-1 coating agent described in Table 2-2 was applied to the outermost surface of one side of the laminate film prepared in Example 6 by the method described in (12), and a 10 μm thick curable resin layer was laminated to obtain a laminate sheet. Furthermore, on the surface opposite to the surface on which the curable resin layer was laminated of the laminate sheet, a 25 μm thick acrylic optical adhesive layer TD-06 manufactured by Tomoegawa Corporation, a 35 μm thick iodine-oriented linear polarizing film (laminated so that the direction perpendicular to the orientation axis of the laminate film and the transmission axis direction of the polarizing film were parallel), and the 25 μm thick acrylic optical adhesive layer TD-06 (with a release film on one side) were laminated in this order to obtain a laminate sheet (in other words, a laminate sheet in which the adhesive layer C was formed on the opposite side of the curable resin layer). The results of a crack test of the acrylic optical adhesive layer after peeling off the curable resin layer and release film of the laminate sheet are shown in Table 4. Furthermore, while peeling off the release film from the laminated sheet, the laminated sheet was heated with a heat gun to heat shrink the laminated sheet and degas it while bonding it to the outermost surface of the laminated glass described in (14), thereby obtaining a projection image display member (bonding method), and a transparent display system was constructed according to the method described in (15). The evaluation results of the obtained projection image display member and transparent display system are shown in Table 4.

[0238] Example 41: The HC-1 coating agent described in Table 2-2 was applied to the outermost surface of one side of the laminate film prepared in Example 5 using the method described in (12), and a 10 μm thick curable resin layer was laminated to obtain a laminate sheet. Furthermore, adhesive layer D was attached to the surface opposite to the surface on which the curable resin layer was laminated to obtain a laminate sheet for partial lamination. The laminate sheet was cut to a size of 200 mm length x 300 mm width and attached to a laminated glass prepared using the method described in (14), with the center positioned 300 mm from the bottom and 300 mm from the right of the concave side. During lamination, a method was used in which water was sprayed onto the laminated glass and degassed along with the water. A projection image display member (lamination method) was obtained in this way, and a transparent display system was constructed according to the method described in (15). The evaluation results of the obtained projection image display member and transparent display system are shown in Table 4.

[0239] Examples 42 and 43 A laminated sheet, a projection image display member (lamination method), and a transparent display system were obtained in the same manner as in Example 41, except that the glass processing and display configuration items in Table 4 were changed as shown in Table 4. The evaluation results are shown in Table 4.

[0240] (Example 44) Using the laminate film produced in Example 2, a projection image display member (interpolation type) was produced by the method described in (13), and further a transparent display system was constructed according to the method described in (15). The evaluation results of the projection image display member and the transparent display system are shown in Table 5.

[0241] (Examples 45 to 55, Comparative Example 8) Projection image display members (interpolation type) and transparent display systems were obtained in the same manner as in Example 44, except that the glass processing and display configuration items in Table 5 were changed as shown in Table 5. The evaluation results are shown in Table 5.

[0242]

[0243]

[0244]

[0245]

[0246]

[0247]

[0248] In Table 1, "the average reflectance when P waves are incident at an angle of 60° from the normal to the orientation axis direction" and "the average reflectance when P waves are incident at an angle of 60° from the normal to the orientation axis direction" mean "the average reflectance when P waves are incident on the film surface from a direction that is perpendicular to the orientation axis and that forms an angle of 60° with the normal to the film surface in a plane including the normal to the film surface at point CF and the orientation axis and is perpendicular to the orientation axis," respectively, and "the average reflectance when P waves are incident on the film surface from a direction that forms an angle of 60° with the normal to the film surface in a plane including the normal to the film surface at point CF and a line perpendicular to the orientation axis." In Tables 3 to 5, "the angle θ with the reference axis C" means "the angle θ1 between the orientation axis at point C and the reference axis C," and "the phase difference variation at five points" means "the coefficient of variation of the in-plane phase difference at five points (standard deviation / average value)."

[0249] The transparent display system of the present invention can be used as an image projection device with an augmented reality function, for example, to project an image over a wide range and a wide viewing angle onto a transparent member such as glass, and can clearly display an image over a wide area without causing deterioration in visibility, such as overlapping images or insufficient display brightness, at certain viewing angles or display areas. Such characteristics can be particularly favorably exhibited in the laminate film of the present invention. This allows a specific observer to obtain a large amount of information superimposed on the landscape without having to move their viewpoint more than necessary, thereby reducing fatigue caused by viewing a blurred image for a long period of time. Furthermore, even when multiple observers view the projected image display member from various viewpoints, they can obtain information clearly regardless of the viewing direction. Transparent display systems and laminate films with such characteristics can be suitably used in head-up displays for automobiles and the like, as well as screens for manned transportation, amusement applications, and signage applications.

[0250] 1: Image projector 2: Image light 3: Projected image display member 4: Scenery 5: Observer 6: Incident angle of image light 7: Light-reflecting material (laminated film) 8: Adhesive layer 9: Transparent hard material 10: Point C 11: Horizontal plane passing through point C 12: Reference axis C 13: Tangent plane at point C 14: Orientation axis at point C 15: Angle θ1 between the orientation axis at point C and reference axis C 16: Point X1 of projected image display member 17: Point X2 of projected image display member 18: Point Y1 of projected image display member 19: Point Y2 of projected image display member 20: Reflection spectrum at wavelengths of 400 to 700 nm when P waves are incident on the surface of the projected image display member from a direction where the angle between the normal to the tangent plane at point C and the normal to the tangent plane in a plane including the orientation axis and the normal to the tangent plane is 60° 21: Reflection spectrum at a wavelength of 400 to 700 nm when P waves are incident on the surface of the image display screen from a direction where the angle between the normal to the tangent surface at point C and the normal to the tangent surface in a plane containing a straight line perpendicular to the orientation axis within the tangent surface is 60°. 22: Area A 23: Area of ​​a partial region surrounded by two reflection spectra, wavelength n, and wavelength n+1 24: Ghost image occurring on the outermost surface on the side where image light is incident 25: Ghost image occurring on the outermost surface opposite the side where image light is incident 26: Main image projected by reflection on light-reflecting material 27: Adhesive layer 1 28: Adhesive layer 2 29: Point CF 30: Point X1F 31: Point X2F 32: Point Y1F 33: Point Y2F 34: Spectrum showing the relationship between depth in the thickness direction of a laminated film having an AB regular arrangement and change in contrast (gray level) 35: Thickness of layer A 36: Thickness of layer B

Claims

1. A transparent display system comprising an image projector that irradiates light to project an image from an image exit surface, and a projection image display member on which an image is projected onto an image display surface by the light irradiated from the image projector, wherein when the center point of the surface of the projection image display member is defined as point C, and the intersection line formed by the tangent plane of the projection image display member at point C and the horizontal plane passing through point C is defined as reference axis C, the angle θ1 between the orientation axis at point C on the surface of the projection image display member and reference axis C is between 0° or more and 30° or less, or between 85° or more and 90° or less, A transparent display system in which, when the projection image display member is tilted by rotating it around the reference axis C and P waves are incident on the surface of the projection image display member so that the angle between the normal to the tangent surface of the projection image display member at point C and the direction of propagation of the P waves is 60° and the reference axis C and the direction of propagation of the P waves are perpendicular, the average reflectance at wavelengths of 400 nm to 700 nm is 5% or more and 100% or less, and the average transmittance of visible light perpendicularly incident on the surface of the projection image display member at point C is 50% or more and 100% or less.

2. The transparent display system of claim 1, wherein the area A (nm·%) enclosed by the reflection spectrum at wavelengths of 400 to 700 nm when P waves are incident on the surface of the projection image display member from a direction where the angle between the normal to the tangent surface at point C and the normal to the tangent surface in a plane including the orientation axis is 60°, and the area A (nm·%) enclosed by the reflection spectrum at wavelengths of 400 to 700 nm when P waves are incident on the surface of the image display surface from a direction where the angle between the normal to the tangent surface at point C and the normal to the tangent surface in a plane including a straight line perpendicular to the orientation axis within the tangent surface is 60° satisfies 1000≦A≦6000.

3. The transparent display system according to claim 1 or 2, wherein, on the surface of the projection image display member, the midpoint between point C and the upper end is defined as point X1, the midpoint between point C and the lower end is defined as point X2, the midpoint between point C and the left end is defined as point Y1, and the midpoint between point C and the right end is defined as point Y2, and the intersections of the tangent planes at point X1, point X2, point Y1, and point Y2 with the horizontal plane passing through each of the points are defined as reference axes X1, X2, Y1, and Y2, respectively, and the angle θ formed between the orientation axis at point C, point X1, point X2, point Y1, and point Y2 and the reference axis at each of the points (reference axis C, reference axis X1, reference axis X2, reference axis Y1, and reference axis Y2) is between 0° or more and 30° or less, or between 85° or more and 90° or less.

4. The transparent display system according to claim 3, wherein the variation (maximum value-minimum value) of the angle θ is 20° or less.

5. The transparent display system of claim 3 or 4, wherein in the projection image display member, the in-plane retardation at point C, point X1, point X2, point Y1, and point Y2 is 3000 nm or more and 10000 nm or less, and the coefficient of variation (standard deviation / average value) of the in-plane retardation at each point is 0.1 or less.

6. A transparent display system according to any one of claims 1 to 5, wherein the projection image display member has a structure in which a transparent hard material and a light-reflecting material are laminated via an adhesive layer, and the light-reflecting material is disposed inside the projection image display member or on the image display surface.

7. A transparent display system according to any one of claims 1 to 6, wherein the image projector irradiates P waves, and the angle between the electric field vibration direction of the P waves on the surface of the projection image display member and the orientation axis at point C is 65° to 90°.

8. The transparent display system of claim 7, wherein the adhesive layer comprises a visible light absorber.

9. A transparent display system according to claim 7 or 8, wherein the adhesive layer has a light absorption axis and a light transmission axis that are perpendicular to each other, and the angle between the direction of the light transmission axis and the electric field vibration direction of the P wave is between 0° and 5°.

10. A transparent display system according to any one of claims 1 to 9, wherein the image projector irradiates the light from a direction in which the angle θ2 with respect to the normal to the tangent surface is 35° or more and 70° or less.

11. The transparent display system of claim 10, wherein the angle θ2 is between 45° and 65°.

12. A transparent display system as described in claim 10 or 11, wherein when P waves are incident on the image display surface from a direction such that the angle between the normal to the tangent surface at point C and the normal to the tangent surface in a plane including the orientation axis is the angle θ2 + 5°, the average reflectance at wavelengths of 400 to 700 nm is 35% or more and 100% or less.

13. The transparent display system according to any one of claims 1 to 12, wherein light emitted from the image projector is directly incident on the image display surface.

14. The transparent display system according to any one of claims 1 to 13, wherein the image projector comprises at least two units arranged side by side.

15. A head-up display using the transparent display system according to any one of claims 1 to 14.

16. A manned transportation vehicle equipped with the transparent display system according to any one of claims 1 to 14.

17. A screen using the transparent display system according to any one of claims 1 to 14.

18. A laminated film in which, when the center point of the film surface is point CF, the midpoints between said point CF and the end in the short side direction are point X1F and point X2F, the midpoint between said point CF and the end in the long side direction are point Y1F and point Y2F, the long side direction is the reference axis, and the angle between said reference axis and the orientation axis at each point is the film orientation angle, the variation in the film orientation angle (maximum value - minimum value) at each of said points is 30° or less, and at said point CF, the average transmittance of visible light incident perpendicularly to the film surface is 50% or more and 100% or less, and when P waves are incident on said film surface from a direction perpendicular to the orientation axis, the angle between the normal to said film surface at said point CF and the normal in a plane containing said orientation axis is 60°, the average reflectance at a wavelength of 400 to 700 nm is 5% or more and 100% or less.

19. The laminate film according to claim 18, wherein the area A (nm·%) enclosed by the reflection spectrum at wavelengths of 400 to 700 nm when P waves are incident on the film surface at the CF point from a direction where the angle between the normal to the film surface at the CF point and the normal in a plane including the orientation axis is 60°, and the reflection spectrum at wavelengths of 400 to 700 nm when P waves are incident on the film surface at the CF point from a direction where the angle between the normal to the film surface at the CF point and the normal to the film surface in a plane including a line perpendicular to the orientation axis is 60° satisfies 1000≦A≦6000.

20. A laminated film as described in claim 18 or 19, in which the 150°C heat shrinkage rate S1 in the direction parallel to the orientation axis and the 150°C heat shrinkage rate S2 in the direction perpendicular to the orientation axis are both 1.0% or more and 4.0% or less, and satisfy 0.7≦S1 / S2≦1.

5.

21. A laminate film according to any one of claims 18 to 20, wherein, when the average values ​​of the amounts of heat shrinkage in the direction parallel to the orientation axis and the amount of heat shrinkage in the direction perpendicular to the orientation axis at 100°C, 125°C, and 150°C in constant load measurements by thermomechanical analysis are S100, S125, and S150, respectively, the relationship 0.7 x (S100 + S150) / 2 ≦ S125 ≦ 1.3 x (S100 + S150) / 2 is satisfied.

22. A laminate film according to any one of claims 18 to 21, having a unit in which 51 or more layers of A layers whose main component is crystalline thermoplastic resin A and B layers whose main component is thermoplastic resin B different from said thermoplastic resin A are alternately laminated, and the difference between the in-plane refractive index of said A layers in the direction parallel to said orientation axis and the in-plane refractive index of said A layers in the direction perpendicular to said orientation axis is 0.01 or more.

23. A laminated film according to any one of claims 18 to 22, used in a transparent display system comprising an image projector that irradiates light to project an image from an image exit surface, and a projection image display member that projects an image onto an image display surface using the light irradiated from the image projector.

24. The laminated film according to any one of claims 18 to 23, wherein the length in the long side direction is 1 m or more.

25. A laminate sheet comprising the laminate film according to any one of claims 18 to 24, and a curable resin layer disposed on at least one of the film surfaces.

26. The laminate sheet according to claim 25, wherein the pressure at which cracks occur in the curable resin layer is 100 GPa or more and 600 GPa or less, as determined by a microscratch test method in accordance with JIS R-3255:1997.

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