Head-up display system

Abstract

To provide a heads-up display (HUD) system in which coloring on a windshield is difficult to see even when wearing sunglasses, the HUD system having an image projector that projects an image and a resin film on which the image from the image projector is projected, the HUD system characterized in that, among light rays that constitute the image from the image projector, the intensity of a p-polarized light component is 51% or more of the intensity of all light components, and the resin film is configured so that the maximum value of the absolute value of a* and the maximum value of the absolute value of b* obtained by the following measurement method satisfy the following equations (1) and (2) with the incident plane relative to the horizontal plane being within 90 ± 10°. Maximum value of absolute value of a* ≤ 30 (1) Maximum value of absolute value of b* ≤ 30 (2).

Description

TECHNICAL FIELD

[0001] The present application relates to a head-up display system. BACKGROUND

[0002] A head-up display (HUD) system is a display system that projects information in the field of view of an occupant of a transport device such as a vehicle, for example, to improve the safety and comfort of driving by displaying travel route information, caution information, building information, and the like that match the scenery in front of the occupant. As for the mechanism thereof, the simplest way is to project an image obliquely from a projection portion of a windshield of the transport device from an image projector and to reflect it, thereby causing the reflected image to enter the field of view of the occupant.

[0003] As such an example, Patent Literature 1 discloses a head-up display that assembles a reflection polarizer that reflects only polarized light irradiated from an image projector in a projection member. However, the reflection performance of the head-up display of this structure varies depending on the reflection axis of the reflection polarizer, and thus in the case of projecting an image to a wide range of the projection portion of the windshield, the brightness of the display image sometimes produces a spot (unevenness). In addition, since a linearly polarized light component that is 90° different from the polarization direction of the image from the image projector among external light is transmitted, the visibility of either the display image or the external light is significantly reduced for an occupant wearing polarized sunglasses inside the vehicle.

[0004] In addition, as a means for suppressing the spot (unevenness) of the brightness of a wide-range display image and ensuring the visibility of the display image and the external light when wearing polarized sunglasses, for example, Patent Literature 2 discloses a head-up display system that has a reflection polarizer, a windshield, and an image projector, the windshield being layered with a wavelength plate on the observer side with respect to the reflection polarizer. The mechanism of the head-up display system that combines the reflection polarizer and the wavelength plate is to make the light projected from the image projector circularly or elliptically polarized light by the wavelength plate, and to reflect the light of the image by the reflection polarizer, and thus it is not limited to the direction of the reflection axis of the reflection polarizer, and it is possible to reflect a wide-range display image with uniform brightness. On the other hand, as for the external light, it is circularly or elliptically polarized light by being transmitted through the reflection polarizer and the wavelength plate, and even if the observer wears polarized sunglasses, it is possible to transmit the external light and thus to visually recognize it.

[0005] PRIOR ART DOCUMENTS

[0006] Patent Literature 1: Japanese Patent Application Laid-Open No. 2006-512622

[0007] Patent Literature 2: Japanese Patent Application Laid-Open No. 2019-113631 SUMMARY

[0008] Problem to be solved by the Invention

[0009] The head-up display system disclosed in Patent Literature 2 can maintain uniform reflection performance even in a case where the projection portion of the windshield projects an image over a wide range, and can visually recognize external light. However, when a passenger wearing polarized sunglasses visually recognizes external light that has been circularly polarized and elliptically polarized, there is a possibility that a color like a rainbow will be seen on the windshield, and there is a problem that the passenger's field of view will deteriorate.

[0010] Therefore, the present application has been achieved in order to solve the above problem, and an object thereof is to provide a head-up display system that can maintain uniform reflection performance even in a case where an image is projected over a wide range of a windshield like this, and that is difficult to see coloring on the windshield even when polarized sunglasses are worn.

[0011] Means for solving the problem

[0012] The present application for solving the above problem is composed of the following technical means. That is, a head-up display system that has an image projector that projects an image, and a resin film on which an image from the image projector is projected,

[0013] The head-up display system is characterized in that,

[0014] In light rays that constitute an image from the image projector, the intensity of p-polarized light components is 51% or more of the intensity of all light components with respect to an incident plane when the resin film is a reflecting plane,

[0015] The resin film is configured so that the maximum value of the absolute value of a* and the maximum value of the absolute value of b* obtained by the following measurement method satisfy the following equations (1) and (2), and the incident plane with respect to the horizontal plane becomes within 90 ± 10°.

[0016] Maximum value of absolute value of a* ≤ 30 (1)

[0017] Maximum value of absolute value of b* ≤ 30 (2)

[0018] <Measurement Method>

[0019] On a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd., an attached angle variable unit and a polarizer manufactured by Glan-Taylor Co. were installed, and polarized light that becomes s-polarized light with respect to an incident plane when a resin film is a reflecting plane was irradiated at an incident angle of 40°, 60°, and 80°, and further, light that has transmitted the resin film was transmitted through a polarizer with the s-polarized light as an absorption axis, and the transmittance in the range of wavelengths of 400 to 1600 nm was measured at each incident angle. Here, a slit was set to 2 nm (visible light) / automatic control (infrared light), a gain was set to 2, and a scanning speed was set to 600 nm / minute. Using the obtained transmittance spectrum, a spectral distribution of a D65 light source, and an isochromatic function of XYZ system, the absolute value of a* at each incident angle and the maximum value thereof and the absolute value of b* and the maximum value thereof were calculated.

[0020] The same measurement was performed by rotating the resin film with the point at which light reaches the film as the center, and an incident plane that satisfies the above-described formula (1) and formula (2) could be investigated.

[0021] Effects of the Invention

[0022] According to the present application, a head-up display system that can maintain uniform reflection performance even in the case of projecting an image over a wide range of a windshield, and that is difficult to see coloring on the windshield even when polarized sunglasses are worn can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is a schematic diagram for explaining a method of measuring transmittance in the first measurement method.

[0024] Figure 2 is one example of a graph that shows the transmittance T(θ, λ) (%) at an incident angle θ and the average value C(θ) (%) of the T(θ, λ) in the range of wavelengths of 450 nm to 750 nm. DETAILED DESCRIPTION

[0025] Hereinafter, a head-up display system of the present application will be specifically described. The present application is not limited to the embodiments including the following examples for explanation, and various modifications within a range that can achieve the object of the present application and that do not depart from the gist of the present application are of course included in the scope of the present application. In addition, the head-up display system is sometimes described as a HUD hereinafter.

[0026] The HUD system of the present application is characterized by having an image projector that projects an image and a resin film on which the image from the image projector is projected. In addition, it is important that, in the light rays that constitute the image projected from the image projector, the intensity of the p-polarized light component is 51% or more of the intensity of the entire light ray component with respect to the incident plane when the resin film is the reflecting plane. Here, p-polarized light indicates an electromagnetic wave in which the electric field component is parallel to the incident plane (linearly polarized light that vibrates parallel to the incident plane), and s-polarized light indicates an electromagnetic wave in which the electric field component is perpendicular to the incident plane (linearly polarized light that vibrates perpendicular to the incident plane). It is important that the light rays that constitute the image projected from the image projector contain a large amount of the p-polarized light component in terms of suppressing multiple images, which are images in which the display image appears to be multiple due to the deviation in the path of the light rays that are reflected on the respective surfaces of the front and back sides of the projection portion (information display portion) of the windshield of the transport equipment.

[0027] In the case where the light rays that constitute the image projected from the image projector contain s-polarized light, multiple images are seen due to reflection on the front and back surfaces of the components that constitute the information display portion, but in the case where the p-polarized light is incident at an incident angle near the Brewster angle, reflection hardly occurs on the front and back surfaces of the information display portion. In addition, by containing a large amount of p-polarized light in the light rays that constitute the image projected from the image projector, the decrease in the brightness of the display image can be suppressed even when polarized sunglasses are worn. Polarized sunglasses are designed to block the s-polarized light component in order to suppress the reflection of the s-polarized light component on the ground, which occupies the majority of the ground surface, or the glare of the windshield when the ground surface or the water surface is the reflecting surface, and to ensure a clear field of view. Thus, by causing the light rays that constitute the image projected from the image projector to contain a large amount of p-polarized light, which is 90° different from the direction of the polarization, the brightness of the display image can be maintained even when polarized sunglasses are worn. From these viewpoints, it is preferable that the proportion of the p-polarized light component in the light rays projected from the image projector be as high as possible, more preferably 90% or more, and further preferably 99% or more. In addition, according to the above reasons, there is no particular limitation on the upper limit of the proportion of the p-polarized light component in the light emitted from the projection light source, and it is virtually 100%.

[0028] It is important that the resin film be disposed in such a manner that the maximum value of the absolute value of a* and the maximum value of the absolute value of b* obtained by the following measurement method satisfy the following equations (1) and (2) with the incident plane becoming 90° ± 10° or less with respect to the horizontal plane.

[0029] Maximum value of absolute value of a* ≤ 30 (1)

[0030] Maximum value of absolute value of b* ≤ 30 (2)

[0031] <Measurement Method> (This measurement method is sometimes referred to as "first measurement method")

[0032] On a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd., an attached angle variable unit and a polarizer manufactured by Glan-Taylor Co. were installed, and polarized light that became s-polarized light with respect to an incident plane when a resin film was a reflecting plane was irradiated at an incident angle of 40°, 60°, and 80°, and further, light that had transmitted the resin film was transmitted through a polarizer with the s-polarized light as an absorption axis, and the transmittance in the range of wavelengths of 400 to 1600 nm was measured at each incident angle. Here, a slit was set to 2 nm (visible light) / automatic control (infrared light), the gain was set to 2, and the scanning speed was set to 600 nm / minute. Using the obtained transmittance spectrum, the spectral distribution of a D65 light source, and the isochromatic function of XYZ system, the absolute value of a* at each incident angle and the maximum value thereof and the absolute value of b* and the maximum value thereof were calculated.

[0033] The same measurement was performed by rotating the resin film with the point at which light reached the film as the center, and an incident plane that satisfied the above-described formula (1) and formula (2) could be investigated.

[0034] Further, the s-polarized light of the above-described measurement method is not HUD projection light of p-polarized light emitted from the light source, and as described later, is light that is supposed to enter from the outside scenery. In addition, the incident angle refers to the angle that the normal line of the surface of the resin film makes with the light that is incident to the resin film.

[0035] Figure 1 is a diagram for explaining the measurement of the transmittance by the above-described first measurement method. First, polarized light that became s-polarized light with respect to an incident plane when a resin film 1 was a reflecting plane was irradiated at an incident angle θ (incident light i), and transmitted light t1 was obtained. Next, the transmittance (T(θ, λ)) of transmitted light t2 that was obtained by the detector 3 at each wavelength λ, which was transmitted through the polarizer 2 at an incident angle of 0°, was obtained. In addition, the resin film 1 and the polarizer 2 were arranged in such a manner that it can be said that a manner in which the outside scenery is visually recognized while wearing general polarized sunglasses was modeled. This is because, as described above, the s-polarized light component accounts for the majority when light from the outside scenery is reflected by the ground surface or the water surface, and polarized sunglasses are designed to block this s-polarized light component in order to secure a clear field of view.

[0036] In addition, the chromaticity a* and b* represent chromaticity obtained using the transmittance T(0, λ) of each wavelength λ obtained at the incident angle θ, the spectral distribution of the D65 light source, and the isochromatic function of the XYZ system. In this chromaticity, the more positive the a* becomes, the stronger the red color becomes, and the more negative the a* becomes, the stronger the green color becomes. In addition, the more positive the b* becomes, the stronger the yellow color becomes, and the more negative the b* becomes, the stronger the blue color becomes. In the case where the chromaticity a* and b* are both 0, achromatic color is obtained.

[0037] The absolute values of a* and b* at the incident angles θ = 40°, 60°, and 80° are calculated, and the maximum values among them are found. By making the maximum values of the absolute values of the chromaticity a* and the absolute values of the chromaticity b* at these incident angles both 30 or less, the coloring of the windshield is not easily observed when polarized sunglasses are worn. The preferred values of these maximum values are both 22 or less, more preferably both 20 or less, and particularly preferably both 10 or less. If these maximum values are both 10 or less, the coloring of the windshield is not observed when polarized sunglasses are worn, and a transparent and good field of view can be provided.

[0038] In the HUD system of the present application, it is important to calculate the absolute values of a* and b* at the incident angles θ = 40°, 60°, and 80° so that the maximum values of both are 30 or less, and to arrange the incident surface so that it becomes within 90 ± 10° from the horizontal plane. By doing so, in the case where the incident surface is 90° from the horizontal plane, even if the driver wearing polarized sunglasses views the scenery outside, the coloring is not observed. Furthermore, in the case where the incident surface is within 90 ± 10° from the horizontal plane, even if the driver wearing polarized sunglasses changes the posture or tilts the head, the coloring of the windshield is not easily observed. In addition, as a method of calculating the absolute values of a* and b* at the incident angles θ = 40°, 60°, and 80° and investigating the incident surface that satisfies the maximum values of both being 30 or less, the same measurement can be determined by rotating the resin film with the point at which the light ray reaches the film as the center.

[0039] As a method of reducing the absolute values of a* and b* at the incident angle θ, the following method can be employed: using a laminated film in which at least two resin layers having different optical properties are laminated as the resin film, using a material having birefringence in at least one of the thermoplastic resins that is a main component of each layer constituting the laminated film, performing uniaxial stretching or biaxial stretching in which the stretch ratio in an arbitrary direction is increased, and arranging the direction in which the stretch ratio is high in a direction perpendicular to the aforementioned incident plane. Here, with respect to the direction of biaxial stretching, the direction in which the stretch ratio is high is referred to as the high-ratio direction, and the direction in which the stretch ratio is low is referred to as the low-ratio direction. As a method of further reducing the absolute values of a* and b* at the incident angle θ, the absolute values of a* and b* can be further reduced by further increasing the stretch ratio in the high-ratio direction, or further reducing the stretch ratio in the low-ratio direction, and increasing the difference in the stretch ratio between the high-ratio direction and the low-ratio direction. More specifically, it is preferable that the difference in the stretch ratio between the high-ratio stretching direction and the low-ratio stretching direction be 0.5 times or more, more preferably 0.8 times or more, and further more preferably 1.0 times or more. In addition, the range of the incident angle of 40° to 80° herein is an angle corresponding to the setting angle of the windshield of a general HUD system, and light irradiated at the incident angle of 40° to 80° transmits through the windshield, and thus if coloring is not observed on the windshield when wearing polarized sunglasses, the HUD system can be mounted on a variety of windshields. In addition, the high-ratio direction of the resin film is investigated by measuring the orientation axis of the resin film by the measurement method (1) described later.

[0040] In the HUD system of the present application, from the viewpoint of reducing coloring observed on the windshield, when the transmittance at the incident angle θ, the wavelength λ nm obtained by the first measurement method is set as T(θ, λ) (%), the average value of T(θ, λ) in the range of 450 nm to 750 nm of the wavelength is set as C(θ) (%), and the number of λ satisfying T(θ, λ) = C(θ) is set as N(θ), it is preferable that the minimum value among N(40), N(60), and N(80) be 4 or more.

[0041] Figure 2 One example of a graph showing the transmittance T(θ, λ) and the average value C(θ) of T(θ, λ) in the range of 450 nm to 750 nm of the wavelength is shown. N(θ) corresponds to the number of wavelengths in which the wavelength band higher than C(θ) and the wavelength band lower than C(θ) are continuously divided in T(θ, λ). In Figure 2In the example of the graph of the transmittance T(0, λ) of the windshield glass, N(0) = 2, there is a wavelength band in which T(0, λ) is higher than C(0) in the range of wavelengths from 450 nm to 750 nm. Therefore, the passenger wearing the polarized sunglasses can strongly observe the color of the light in this wavelength band. Here, as N(0) increases, the number of wavelength bands in which T(0, λ) is higher than C(0) increases, and the color formed by the color mixture of the light in the wavelength band is more likely to be observed. However, if N(0) is 4 or more, the color of the light in the wavelength band in which T(0, λ) is higher than C(0) increases, and the color observed becomes achromatic, and the passenger wearing the polarized sunglasses is less likely to observe the coloring of the windshield glass. In view of the above, it is more preferable that N(0) be 5 or more, and it is further preferable that N(0) be 6 or more. On the other hand, although there is no upper limit to N(0), it is preferable that N(0) be 8 or less from the viewpoint of realizability.

[0042] The range of the incident angle of 40° to 80° described herein is an angle that assumes the setting angle of the windshield glass of a general HUD system. If the minimum value among N(40), N(60), and N(80) is 4 or more, the HUD system can be mounted on a variety of windshield glasses. As a method of increasing N(0), the following methods or the like can be employed: a method of using a resin having birefringence in at least one of the two resin layers of the laminated structure of the resin film, performing uniaxial stretching or biaxial stretching with an increased difference in stretching magnification, and a method of arranging a direction with a high stretching magnification (in the case of uniaxial stretching, a stretching direction) in a direction perpendicular to the incident angle of the projection light source. In the case of biaxial stretching, it is preferable that the difference in magnification between the high-magnification stretching direction and the low-magnification stretching direction be 0.5 times or more, more preferably 0.8 times or more, and further preferably 1 time or more.

[0043] The HUD system of the present application preferably satisfies the relationship N(40) ≤ N(60) ≤ N(80) with respect to N(40), N(60), and N(80). When this relationship is satisfied, the coloring of the windshield glass is less likely to be observed when wearing polarized sunglasses. As a means for satisfying the relationship N(40) ≤ N(60) ≤ N(80), the same methods as those for increasing N(0) can be employed. On the other hand, when the relationship N(40) ≤ N(60) ≤ N(80) is not satisfied, the values of N(40), N(60), and N(80) are each smaller than when the relationship is satisfied, and the coloring is observed depending on the incident angle.

[0044] As for the resin film, when the reflectance (%) of light rays that become p-polarized light when incident on an incident plane with respect to the resin film surface as a reflecting plane at an incident angle of 20°, 40°, and 70°, respectively, is set as Rp20, Rp40, and Rp70, it is preferable that the relationship Rp20≤Rp40

[0045] In the HUD system of the present application, as for the resin film, when the reflectance (%) of light rays that become p-polarized light when incident on an incident plane with respect to the resin film surface as a reflecting plane at an incident angle of 20°, 40°, and 70°, respectively, is set as Rp20, Rp40, and Rp70, it is preferable that the relationship Rp20≤Rp40

[0046] In the HUD system of the present application, as for the resin film, when the reflectance (%) of light rays that become p-polarized light when incident on an incident plane with respect to the resin film surface as a reflecting plane at an incident angle of 20°, 40°, and 70°, respectively, is set as Rp20, Rp40, and Rp70, it is preferable that the relationship Rp20≤Rp40

[0047] The average reflectance of 10% or more means that even in the case of projecting an image over a wide range of the windshield of a transport device using the HUD system of the present application, a certain level of reflection performance can be maintained within the projected image range, and a display image with high luminance and few light spots can be displayed. On the other hand, in the case where the average reflectance is less than 10%, in the case of projecting an image over a wide range of the windshield, a spot of luminance that affects the degree of visual recognition can sometimes occur on a part of the display image within the projected range. For example, the head-up display described in Patent Document 1 is provided with a reflection polarizer, and if the reflection axis direction of the reflection polarizer is not made to coincide with the incident plane direction of the projection, the oblique reflectance of the incident light decreases. Therefore, in the case of projecting an image over a wide range of the windshield of the head-up display described in Patent Document 1, at a certain position within the projected range, the incident angle of the projection light source and the reflection axis of the reflection polarizer do not coincide, and the visual recognition of the display image can deteriorate. Furthermore, from the viewpoint of the azimuth angle dependence of the reflection axis of the reflection polarizer, a limitation occurs at the position of the image projector provided.

[0048] From the above viewpoint, the average reflectance is more preferably 30% or more, further preferably 50% or more, and particularly preferably 60% or more. In addition, the higher the average reflectance, the higher the luminance of the display image obtained when an image is projected over a wide range of the windshield, and on the other hand, since the visual recognition of external information via the windshield also deteriorates, the upper limit value is 90%. Furthermore, the average reflectance when p-polarized light is irradiated at an incident angle of 60° with respect to the surface of the resin film, and the surface of the film is rotated in-plane in a range of 0 to 90° with the irradiation point as the center can be measured by a spectrophotometer provided with an angle variable unit and a polarizer, and for example, can be measured by a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd.

[0049] The measurement of the average reflectance when a light ray that becomes p-polarized light with respect to the incident plane when the surface of the resin film is used as a reflection surface is irradiated at an incident angle of 60°, and the surface of the film is rotated in-plane in a range of 0 to 90° with the irradiation point as the center can be performed in the following order. First, p-polarized light is irradiated at an incident angle of 60° with respect to the resin film in which the orientation axis is arranged parallel to the incident plane, the reflectance spectrum in a wavelength range of 400 to 1600 nm is measured, and the average value of the reflectance in a wavelength range of 450 to 650 nm is found from the obtained reflectance spectrum. Then, the resin film is rotated in-plane to the right at an interval (increment) of 5° with the orientation axis of the resin film as the reference, the same measurement is performed, and this operation is repeated until the total rotation angle reaches 90°. The average values of the reflectance obtained at each angle thus obtained are added and averaged, and the average reflectance (%) when the resin film is rotated in-plane in a range of 0 to 90° with the orientation axis of the resin film as the reference is obtained.

[0050] As a method of making the average reflectance when a resin film surface is made the reflecting surface, and the light ray which is p-polarized light with respect to the incident surface is made to be incident at an angle of 60°, and the film surface is made to rotate in-plane in a range of 0 to 90° from the irradiation point as the center, 10% or more or the above preferable range, for example, a method of making the resin component constituting the resin film the preferable component, a method of making the structure of the resin film the preferable laminated structure, a method of making the stretching method, the stretching speed, the stretching ratio, the stretching temperature, and the like stretching conditions the preferable range when the resin film is manufactured through a stretching process, and a method of taking the resin film from the predetermined width range of the manufactured roll-shaped film can be cited.

[0051] More specifically, as the constitution of the resin film, it is preferable that two kinds of polyester resin layers whose main components are different are alternately laminated, and it is particularly preferable that one of the two kinds of polyester resins is crystalline polyester, and the other is non-crystalline polyester. As the stretching method, simultaneous biaxial stretching is more preferable than sequential biaxial stretching, and from the viewpoint of productivity, in the case of adopting sequential biaxial stretching, it is preferable to slow down the stretching speed in the length direction within a range in which the flatness is not deteriorated, and it is preferable to adjust the stretching ratio in the width direction to be higher than that in the length direction and not to become excessively high. The stretching temperature is preferably in a range of the glass transition temperature of the polyester resin whose glass transition temperature is high among the main components of each layer to the glass transition temperature of the resin + 100°C. In addition, when heat treatment is performed after stretching, it is preferable to perform additional stretching in the width direction in the first half of the heat treatment, or to perform relaxation treatment in the second half of the heat treatment.

[0052] The resin film provided in the HUD system of the present application is preferably mainly composed of a polyester resin. Here, the polyester resin refers to a condensate synthesized by dehydration condensation of a dicarboxylic acid and a diol to form an ester bond. "Mainly composed of a polyester resin" means that the polyester resin is contained in the resin film at more than 50% by mass and 100% by mass or less. The polyester resin constituting the resin film is not particularly limited as long as the effect of the present application is not impaired, and it is preferable that the main component is a polyester obtained by polymerization of a monomer mainly composed of an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid and a diol. Further, "mainly composed of an aromatic dicarboxylic acid or an aliphatic dicarboxylic acid" means that, when the total dicarboxylic acid unit constituting the polyester resin is taken as 100 mol%, 80 mol% or more and 100 mol% or less of the aromatic dicarboxylic acid unit or the aliphatic dicarboxylic acid unit is contained.

[0053] As the aromatic dicarboxylic acid, for example, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 4,4'-diphenyl dicarboxylic acid, 4,4'-diphenyl ether dicarboxylic acid, 4,4'-diphenyl sulfone dicarboxylic acid, and the like can be given. As the aliphatic dicarboxylic acid, for example, adipic acid, suberic acid, sebacic acid, dimer acid, dodecanedioic acid, cyclohexane dicarboxylic acid, and ester derivatives thereof, and the like can be given. Among them, terephthalic acid, isophthalic acid, and 2,6-naphthalene dicarboxylic acid are particularly preferable. These acid components can be used singly or in combination of two or more.

[0054] In addition, as the diol component, for example, ethylene glycol, p-xyleneglycol, 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, isosorbide, spiro glycol, bisphenyloxyethanol fluorene (BPEF), and the like can be given. Among them, ethylene glycol, polyalkylene glycol, and p-xyleneglycol are particularly preferable. These diol components can be used singly or in combination of two or more.

[0055] The resin film provided in the HUD system of the present application is preferably formed by alternately laminating two kinds of polyester resin layers different in the main component from the above-described polyester resin. It is particularly preferable that one of the two kinds of polyester resin is crystalline polyester and the other is non-crystalline polyester. The non-crystalline resin herein means a resin having a crystalline melting heat ΔHm of 5 J / g or less in the differential scanning calorimetry chart obtained by heating the resin from 25°C to 300°C at a temperature increasing rate of 20°C / min (1st run), holding it at that state for 5 minutes, then cooling it to a temperature below 25°C at a rate of 30°C / min, and again heating it from room temperature to 300°C at a temperature increasing rate of 20°C / min (2nd run), and the crystalline melting heat ΔHm is calculated from the peak area of the melting peak. The non-crystalline polyester is preferably composed of three or more copolymer components, and more preferably contains a polycyclic aromatic compound such as naphthalene or anthracene and a polyalkylene glycol having a number average molecular weight of 200 or more as the copolymer component.

[0056] The resin film of the HUD system of the present application can be manufactured, for example, by the following method. First, two kinds of thermoplastic resins are prepared in the form of particles or the like. The particles are dried in hot air or under vacuum as needed, and then supplied to different extruders. In the extruders, the thermoplastic resins are heated and melted at a temperature above the melting point, and the extrusion amount is homogenized by a gear pump or the like, and the resins are extruded, and foreign matter or modified resins or the like are removed by a filter or the like. Next, the two kinds of thermoplastic resins are sent through different flow paths into a multi-layer lamination device, and are alternately laminated. As the multi-layer lamination device, a manifold die, a feeding block, a static mixer or the like can be used, and a feeding block having 50 or more fine slits is particularly preferable. If such a feeding block is used, the device does not become extremely large, and foreign matter due to thermal deterioration is less, and high-precision lamination can be performed even if the number of layers is extremely large. In addition, the lamination precision in the width direction is also significantly improved compared to the prior art. In addition, in such a device, the thickness of each layer can be adjusted by the shape (length, width) of the slits, and therefore arbitrary layer thicknesses can also be easily achieved.

[0057] Next, the laminated molten resin is molded into a sheet shape using a mold, and is extruded onto a cooling body such as a casting drum to be cooled and solidified, and a cast film (a cast sheet) is obtained. At this time, an electrode in the form of a wire, a tape, a needle or a blade or the like is preferably used, and the molten resin sheet is brought into close contact with the cooling body such as a casting drum by electrostatic force to be rapidly cooled and solidified.

[0058] The cast film (the cast sheet) thus obtained is preferably subjected to biaxial stretching. Here, biaxial stretching refers to stretching in the length direction and the width direction, the length direction refers to the direction of travel of the film, and the width direction refers to the direction orthogonal to the length direction in the surface of the film. The stretching can be performed by sequentially stretching in the two directions (sequential biaxial stretching), or by simultaneously stretching in the two directions (simultaneous biaxial stretching). In addition, further re-stretching can be performed in the length direction and / or the width direction.

[0059] In the case of simultaneous biaxial stretching, in order to improve the visual recognition of the HUD system, the stretching speed is preferably 5 to 80% per second, and more preferably 10 to 50% per second. Generally, simultaneous biaxial stretching is performed using a tenter frame that holds both ends of the film with clips while conveying, and the stretching ratio is preferably 2 to 5 times in both the length direction and the width direction. The stretching temperature is preferably the glass transition temperature of the resin having a higher glass transition temperature among the polyester resins that are the main components of the layers of the cast film (the cast sheet) constituting the stretching, to the glass transition temperature of the resin + 100°C.

[0060] The biaxially stretched film is preferably heat-treated in a tenter at a temperature of from +100°C of the above-mentioned stretching temperature to +150°C of the above-mentioned stretching temperature. At this time, relaxation treatment is preferably performed at a relaxation rate of from 0.01 to 2% per second in the length direction and the width direction. The relaxation ratio with respect to the film width immediately before the relaxation is preferably from 0.90 to 0.99. Then, after the thus obtained resin film is uniformly and slowly cooled to room temperature, the edge portions of both ends held by the clips of the tenter are cut off and wound up.

[0061] In the case of sequential biaxial stretching, in order to improve the visual recognition of the HUD system, the stretching speed in the length direction is preferably from 50 to 300% per second, and more preferably from 70 to 150% per second. Generally, the stretching in the length direction is performed by the difference in the circumferential speed of the rolls, and the stretching ratio is preferably from 1.5 to 5. The stretching temperature is preferably from the average glass transition temperature of the two resins constituting the stretched cast film (flow-cast film) to the average glass transition temperature + 100°C. Subsequently, the uniaxially stretched film obtained by the stretching in the length direction is stretched in the width direction at a stretching speed of from 5 to 40% per second, and more preferably from 8 to 30% per second. Generally, the stretching in the width direction is performed using a tenter while transporting the film with both ends held by clips, and the stretching ratio is preferably from 1.5 to 6.5.

[0062] In order to produce the resin film used in the HUD system in which the tinting of the windshield glass is suppressed when polarized sunglasses are worn according to the present application, the difference in the stretching ratio in the length direction and the width direction of the film is preferably set to 0.5 or more. More preferably, the difference in the ratio is 0.8 or more, and further preferably 1.0 or more. In the case where the difference in the ratio is less than 0.5, depending on the angle of the light incident to the surface of the resin film, the tinting sometimes occurs when the projection portion provided with the resin film is visually recognized while polarized sunglasses are worn. In addition, if the stretching ratio in the low-ratio direction is less than 1.5, the mechanical strength in the low-ratio direction becomes low, and therefore the stretching ratio in the low-ratio direction is preferably at least 1.5 or more, and more preferably 2.0 or more. The stretching temperature is preferably from the glass transition temperature of the two resins constituting the uniaxially stretched film to be stretched to the glass transition temperature + 100°C.

[0063] The biaxially stretched film is preferably heat-treated at a temperature of the width direction stretching temperature + 100°C to the width direction stretching temperature + 150°C in the tenter. At this time, it is preferable to perform additional stretching in the width direction at a stretching speed of 5 to 20% / sec in the first half of the heat treatment, and to perform relaxation treatment in the width direction at a relaxation speed of 0.01 to 1% / sec in the second half of the heat treatment. The additional stretching ratio in the width direction is preferably 1.05 to 1.20 times, and the relaxation ratio is preferably 0.90 to 0.99 times with respect to the film width immediately before the relaxation. Then, after uniformly and slowly cooling the thus obtained resin film to room temperature, the edge portions of both ends held by the clips of the tenter are cut off and wound up. In this way, a resin film suitable for the HUD system of the present application can be obtained.

[0064] In the HUD system of the present application, with respect to the resin film, the average transmittance in the wavelength range of 450 to 650 nm when a light ray that becomes p-polarized light with respect to a certain incident plane is perpendicularly incident on the resin film, and the average transmittance in the wavelength range of 450 to 650 nm when a light ray that becomes s-polarized light with respect to the incident plane is perpendicularly incident on the resin film are preferably each 80% or more.

[0065] By making the transmittances of p-polarized light and s-polarized light in the wavelength range of 450 to 650 nm each 80% or more, in the case where the HUD system of the present application is incorporated in a part of the windshield of a transport equipment, the information of outside light such as scenery can be clearly visually recognized. From the above viewpoint, the transmittances are more preferably 85% or more. If the transmittances are 85% or more, the information of outside light can be more clearly visually recognized due to the improvement of transparency.

[0066] In order to obtain such a resin film, for example, a method in which the components of the resin constituting the resin film are the preferable components, a method in which the structure of the resin film is a preferable laminated structure, a method in which the stretching method, the stretching speed, the stretching ratio, the stretching temperature, and the like are controlled within a preferable range when the resin film is manufactured through a stretching process, and the like can be mentioned. More specifically, as the constituent components of the resin film, it is preferable to contain a non-crystalline substance. In the case where the sequential biaxial stretching is employed as the stretching method, it is preferable to reduce the stretching speed or the stretching ratio within a range in which the planarity is not deteriorated. The stretching temperature is higher than the average glass transition temperature of the two kinds of resins used, and the higher the better within a range in which the film transportability or the planarity of the film is not hindered.

[0067] The resin film used in the HUD system of the present application preferably has a change in average transmittance at wavelengths of 450 to 650 nm of 10% or less when the resin film is treated for 250 hours at 100°C. Here, the "change in average transmittance at wavelengths of 450 to 650 nm when treated for 250 hours at 100°C" refers to the difference between the average value of the transmittance at wavelengths of 450 to 650 nm when p-polarized light is incident at an angle of 70° to the surface of the resin film with the resin film as the reflecting surface, and the average value of the transmittance at wavelengths of 450 to 650 nm when p-polarized light is incident at an angle of 70° to the same surface of the same resin film after the resin film has been left in an atmosphere at 100°C for 250 hours.

[0068] A change in average transmittance of 10% or less means that the change in optical properties of the resin film caused by heat is suppressed to a low level. By using such a resin film in a HUD system, the decrease in display performance of the HUD system can be mitigated even when used for a long period of time. From the above viewpoint, the change in average transmittance is more preferably 5.0% or less, and further preferably 2.0% or less. Furthermore, the smaller the change in average transmittance, the better, and thus there is no lower limit, but from the viewpoint of feasibility, the lower limit is 0.1%.

[0069] As a method for achieving a change in average transmittance at wavelengths of 450 to 650 nm of 10% or less or in the above preferable range when the resin film is treated for 250 hours at 100°C, there is a method in which at least one of the thermoplastic resins that constitute the resin film is a polyester resin containing an aromatic dicarboxylic acid unit, an aromatic diol unit, and an alkylene glycol unit having a number average molecular weight of 200 or more. Of all the diol units that constitute the polyester resin, it is more preferable to contain 10 mol% or more and 40 mol% or less of a p-xylylenediol unit, and further preferable to contain 25 mol% or more and 40 mol% or less. In addition, it is also preferable to contain a BPEF unit instead of a p-xylylenediol unit, and the BPEF unit at this time is preferably 5 mol% or more and 10 mol% or less. Thus, while maintaining the high display performance of the HUD system, the stability of the resin film under a high-temperature environment is improved, so the decrease in display performance can be mitigated even when used for a long period of time.

[0070] In the HUD system of the present application, the internal haze of the resin film after being treated at 150°C for 2 hours is preferably 1% or less. By making the internal haze of the resin film after being treated at 150°C for 2 hours 1% or less, the workability to the HUD when the resin film is installed on the windshield of the transport equipment by heat processing treatment is improved, and the light resistance is improved. From the above viewpoint, the internal haze after being treated at 150°C for 2 hours is more preferably 0.5% or less. The lower the internal haze, the more excellent the transparency of the windshield, and thus there is no particular limitation on the lower limit, but from the viewpoint of feasibility, the lower limit is 0.1% or less.

[0071] As a method of making the internal haze of the resin film after being treated at 150°C for 2 hours 1% or less or within the above preferable range, the same method as that of making the change in the average transmittance at a wavelength of 450 to 650 nm when the resin film is treated at 100°C for 250 hours 10% or less or within the above preferable range can be given. From this viewpoint, it is particularly preferable that 25% or more and 40% or less of the p-xylylene glycol units be contained in all of the diol units constituting the polyester resin containing the aromatic dicarboxylic acid unit, the aromatic diol unit, and the alkylene glycol unit having a number average molecular weight of 200 or more.

[0072] The HUD system of the present application, from the viewpoint of improving the durability of the windshield, preferably has a structure in which a glass is laminated on one side of the resin film via an adhesive layer (this structure is sometimes referred to as "structure A"). In addition, the HUD system of the present application, on the basis of structure A, can further have a support member other than a glass. As such a support member, for example, a resin can be given, and polyethylene terephthalate, polycarbonate, acrylic, polyvinyl chloride, polyethylene, polypropylene, polymethyl pentene and a copolymer thereof, acrylonitrile-butadiene-styrene copolymer, and the like can be given. In addition, as the adhesive layer, a vinyl acetate resin system, a vinyl chloride-vinyl acetate copolymer system, an ethylene-vinyl acetate copolymer system, polyvinyl alcohol, polyvinyl butyral, polyvinyl acetal, polyvinyl ether, a nitrile rubber system, a styrene-butadiene rubber system, a natural rubber system, a chloroprene rubber system, a polyamide system, an epoxy resin system, a polyurethane system, an acrylic resin system, a cellulose system, polyvinyl chloride, polyacrylate, polyisobutylene, and the like can be given.

[0073] In addition, an adhesion modifier, a plasticizer, a heat stabilizer, an antioxidant, a UV absorber, an antistatic agent, a lubricant, a colorant, a crosslinking agent, and the like can be added to the adhesive layer. As the form of the adhesive layer before processing, a liquid, a gel, a block, a powder, a film, and the like can be given. As the curing method of the adhesive layer, solvent evaporation, moisture curing, heat curing, curing agent mixing, anaerobic curing, UV curing, hot melt cooling, pressure-sensitive, and the like can be given. As the lamination method, laminated molding, injection molding, and the like can be given, and the information display member is produced by heating, pressurizing, and using the above-described curing method of the adhesive layer. In addition, a hard coat layer, a wear-resistant layer, a scratch-resistant layer, an anti-reflection layer (hereinafter sometimes referred to as "AR layer"), a color correction layer, a UV absorbing layer, a light stabilizing layer (HALS), a heat ray absorbing layer, a printing layer, a gas barrier layer, an adhesive layer, a transparent electrode layer, and the like functional layers can be provided on the surface of the projection image display member.

[0074] In the case where the HUD system of the present application has the structure A, it is preferable to arrange the image projector on the side of the resin film which does not contact the adhesive layer. In addition, in order to suppress the generation of the multiple images, it is preferable to provide the AR layer on the side of the resin film which does not laminate the glass. Here, the AR layer refers to a layer having a lower refractive index than the surface of the resin film, and reduces the reflectance by the interference effect of light. As the formation method of the AR layer, there are wet methods such as roll coating, gravure coating, spin coating, and spray, and dry methods such as vacuum evaporation, sputtering, and CVD, and any of these methods can be used, and from the viewpoint of productivity, the wet method is more preferable.

[0075] In order to improve the durability of the windshield and obtain a significant multiple image suppression effect, the HUD system of the present application preferably has a structure in which the glass is laminated via the adhesive layer on both sides of the resin film (this structure is sometimes referred to as "structure B"). In addition, the HUD system of the present application, based on the structure B, can further have a support member other than the glass. As such a support member, a resin can be given, and polyethylene terephthalate, polycarbonate, acrylic, polyvinyl chloride, polyethylene, polypropylene, polymethylpentene and copolymers thereof, acrylonitrile-butadiene-styrene copolymer, and the like can be given. As the adhesive layer, a vinyl acetate resin-based, a vinyl chloride-vinyl acetate copolymer-based, an ethylene-vinyl acetate copolymer-based, a polyvinyl alcohol, a polyvinyl butyral, a polyvinyl acetal, a polyvinyl ether, a nitrile rubber-based, a styrene-butadiene rubber-based, a natural rubber-based, a chloroprene rubber-based, a polyamide-based, an epoxy resin-based, a polyurethane-based, an acrylic resin-based, a cellulose-based, polyvinyl chloride, polyacrylate, polyisobutylene, and the like can be given.

[0076] In addition, an adhesion adjusting agent, a plasticizer, a heat stabilizer, an antioxidant, an ultraviolet absorber, an antistatic agent, a lubricant, a colorant, a crosslinking agent, or the like can be added to the adhesive layer. As the form of the adhesive layer before processing, a liquid, a gel, a block, a powder, a film, or the like can be given. As the adhesive, an ethylene-based adhesive having high followability to the shape of the glass and excellent processability is more preferable. A polyvinyl acetal-based adhesive having a small difference in refractive index from the glass and excellent adhesion is more preferable, and a polyvinyl butyl acetal resin is particularly preferable. In order to impart heat shielding properties to the windshield, these adhesives can also contain an infrared absorber. As the infrared absorber, in addition to heat shielding particles, phthalocyanine compounds, naphthalocyanine compounds, anthracene cyanine compounds, and the like can be given. The heat shielding particles can be lanthanide series particles, antimony series particles, indium series particles, tin series particles, tungsten oxide series particles, and the like.

[0077] In the HUD system of the present application, when either of Structure A or Structure B is employed, the thickness of the glass used in these structures is preferably in the range of 0.5 mm to 6.0 mm from the viewpoint of balancing the lightness and the high strength of the windshield. The thickness of the glass is more preferably in the range of 1.0 mm to 5.0 mm from the above viewpoint.

[0078] In the HUD system of the present application, when Structure A is employed, the thickness of the adhesive layer is preferably in the range of 2 μm to 500 μm from the viewpoint of improving the durability of the windshield. In the HUD system of the present application, when Structure B is employed, the thickness of the adhesive layer is preferably in the range of 30 μm to 800 μm in order to improve the durability of the windshield and to obtain good processability.

[0079] In the HUD system of the present application, when either of Structure A or Structure B is employed, in order to improve the adhesion strength of the lamination interface when these structures are produced, surface treatment such as corona treatment, plasma treatment, primer treatment, or the like is preferably performed on the surface of the resin film or the glass. The HUD system of the present application can have a hard coat layer for protecting the surface on the outermost surface of the laminate including the resin film. In addition, the hard coat layer can also function as an AR layer.

[0080] In the HUD system of the present application, when Structure B is employed, when the two adhesive layers of the resin film are denoted as C1 and C2, respectively, it is preferable that the visible and infrared light transmittance T1 of C1 and the visible and infrared light transmittance T2 of C2 satisfy T2≠T1. Here, the visible and infrared light transmittance indicates the average transmittance of wavelengths of 400 to 1600 nm. In the case of T2≠T1, it is preferable in terms of the fact that a more highly precise HUD display image can be obtained by projecting the HUD display image from the adhesive layer C2 side and the fact that the heat of the infrared light can be suppressed from being stored in the projection light source.

[0081] In the HUD system of the present application, when either of Structure A or Structure B is employed, the proportion of the p-polarized light component contained in the transmitted light when a light ray that is p-polarized light with respect to the incident plane at the time when the resin film is used as a reflecting surface is incident at an incident angle of 60° is preferably 80% or more. By making the proportion of the p-polarized light component in the transmitted light 80% or more, the p-polarized light that is incident is converted to s-polarized light in the process of transmitting the resin film, the s-polarized light that is converted is reflected at the interface between the member constituting the information display portion and the atmosphere and is visually recognized by the occupant, and multiple images can be suppressed. From the above viewpoint, the proportion of the p-polarized light component in the transmitted light is more preferably 85% or more, and further preferably 90% or more.

[0082] As a method of making the proportion of the p-polarized light component in the transmitted light within the preferable range, for example, the composition of the resin constituting the resin film can be made the preferable composition, or the structure of the resin film can be made the preferable laminated structure, or when the resin film is manufactured by a stretching process, the stretching method, the stretching speed, the stretching ratio, the stretching temperature, and the like can be set to the preferable range, or the resin film can be taken from the predetermined width range of the manufactured roll-shaped film. More specifically, as the constitution of the resin film, it is preferable that two kinds of polyester resin layers having different main components are alternately laminated, and it is particularly preferable that one of the two kinds of polyester resins is crystalline polyester and the other is non-crystalline polyester. As the stretching method, simultaneous biaxial stretching is more preferable than sequential biaxial stretching, and from the viewpoint of productivity, when sequential biaxial stretching is employed, it is preferable that the stretching speed in the length direction is slowed down within a range in which the planarity is not deteriorated, and it is preferable that the stretching ratio in the width direction is adjusted to be higher than the stretching ratio in the length direction and not to be excessively high. The stretching temperature is higher than the average glass transition temperature of the two kinds of resins used, and the higher the temperature within a range in which the film transportability or the planarity of the film is not hindered is preferable. In addition, when heat treatment is performed after stretching, it is preferable that additional stretching in the width direction is performed in the first half of the heat treatment, or relaxation treatment is performed in the second half of the heat treatment. As the width range of the film, the closer to the center in the width direction is preferable.

[0083] The HUD system of the present application is mounted on a transportation device, a building, an electronic billboard, or the like and is used. The transportation device refers to a moving means that is driven by an occupant, such as an airplane, a ship, an automobile, a railway, or the like, the HUD system of the present application is assembled on a windshield of the transportation device, and for example, if it is an automobile, it is assembled on a front windshield or the like and displays information required by the occupant on the information display portion. At this time, the positional relationship between the projection light source and the windshield is adjusted in such a manner that the image projected from the projection light source is reflected at the information display portion and reaches the field of view of the occupant and is used. From the viewpoint of saving the size of the HUD system and improving the visual recognition, it is preferable that the incident angle of the projection is within the range of 40 to 75°, and more preferably 50 to 70°.

[0084] The following describes the resin film of the present application. The resin film of the present application is a resin film having an incident surface satisfying the following formulas (1) and (2) with respect to the maximum value of the absolute value of a* and the maximum value of the absolute value of b* obtained by the following measurement method. By mounting the resin film of the present application on a HUD system, coloring is not easily observed on the windshield even when polarized sunglasses are worn. The method for obtaining the film of the present application is as described above.

[0085] Maximum value of the absolute value of a* ≤ 30 (1)

[0086] Maximum value of the absolute value of b* ≤ 30 (2)

[0087] <Measurement method>

[0088] On a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd., an attached angle variable unit and a polarizer manufactured by Glan-Taylor Co. were mounted, and a polarized light that becomes s-polarized light with respect to the incident surface when the resin film is a reflecting surface was irradiated at an incident angle of 40°, 60°, and 80°, and further the light that passed through the resin film was made to pass through a polarizer with the s-polarized light as an absorption axis, and the transmittance in the wavelength range of 400 to 1600 nm was measured at each incident angle. Here, the slit was set to 2 nm (visible light) / automatic control (infrared light), the gain was set to 2, and the scanning speed was set to 600 nm / minute. Using the obtained transmittance spectrum, the spectral distribution of D65 light source, and the isochromatic function of XYZ system, the absolute value of a* and its maximum value and the absolute value of b* and its maximum value at each incident angle were calculated.

[0089] Further, the same measurement was performed by rotating the resin film with the point at which the light reached the film as the center, and the incident surface satisfying the above formulas (1) and (2) could be investigated.

[0090] In addition, in the transmittance spectrum obtained by the measurement method, when the incident angle at the time of transmittance measurement is θ, in the transmittance spectrum measured at the incident angle θ, when the transmittance at the wavelength λ nm in the wavelength range of 450 nm to 750 nm is T(θ, λ) (%), the average value of the transmittance in this range is C(θ) (%), and the number of λs satisfying T(θ, λ) = C(θ) in this range is N(θ), it is preferable that the minimum value among N(40), N(60), and N(80) is 4 or more. In addition, it is preferable that the N(40), N(60), and N(80) satisfy the relationship of N(40) ≤ N(60) ≤ N(80). The means for obtaining the resin film in this form are as described above.

[0091] Further, with respect to the resin film, it is preferable that the average reflectance in a case where a light ray of p-polarized light with an incident angle of 60° is irradiated and the film surface is rotated in a range of 0 to 90° with the irradiation point as the center is 10% or more. The means for obtaining the resin film in this form is as described above.

[0092] The resin film of the present application preferably has a change in the average transmittance at a wavelength of 450 to 650 nm of 10% or less when treated at 100°C for 250 hours, and preferably has an internal haze of 1% or less after treatment at 150°C for 2 hours. The means for obtaining the resin film in this form is as described above.

[0093] Examples

[0094] Hereinafter, the HUD system of the present application will be described using examples. However, the HUD system of the present application is not limited to the following modes.

[0095] [Measurement method of physical properties and evaluation method of effects]

[0096] The evaluation method of physical properties and the evaluation method of effects are described below.

[0097] (1) Orientation axis

[0098] A phase difference measuring device (KOBRA-21ADH) manufactured by Oji Scientific Instruments Co., Ltd. was used. A film sample cut to 3.5 cm x 3.5 cm was set on the device, and the orientation axis orientation in the film surface at an incident angle of 0° was measured.

[0099] (2) a* value, b* value

[0100] An attached angle variable unit and a polarizer manufactured by Glan-Taylor Co., Ltd. were installed on a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd., a polarized light that becomes s-polarized light with respect to the incident plane when the surface of the measurement sample, i.e., the surface of the resin film, is the reflecting plane was irradiated at an incident angle of 40°, and further the light that passed through the resin film was made to pass through a polarizer with the s-polarized light as the absorption axis, and the transmittance in a wavelength range of 400 to 1600 nm was measured. As the measurement conditions, the slit was set to 2 nm (visible light) / automatic control (infrared light), the gain was set to 2, the scanning speed was set to 600 nm / minute, and the a* value and the b* value were calculated using the obtained transmittance, the spectral distribution of the D65 light source, and the isochromatic function of the XYZ system. The a* value and the b* value were calculated for each angle by the same operation as described above, except that the incident angle was set to 60° and 80°.

[0101] (3) N(θ)

[0102] On a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd., an attached angle variable unit and a polarizer manufactured by Glan-Taylor Co. were installed, and a polarized light whose incident plane becomes s-polarized light when the incident plane is a reflecting plane in the case of the surface of a resin film as a sample to be measured was irradiated at an incident angle of 40°, and further, light transmitted through the resin film was transmitted through a polarizer whose absorption axis is the s-polarized light, and the transmittance T(λ) in the wavelength range of λ = 450 to 1600 nm was measured. As the measurement conditions, the slit was set to 2 nm (visible light) / automatic control (infrared light), the gain was set to 2, the scanning speed was set to 600 nm / min, and a polarizer was installed in front of the detector, and only the s-polarized light component in the transmitted light was made incident to the detector. In the obtained transmittance, the average transmittance in the wavelength range of λ = 450 to 650 nm was set to C(40), and the number of intersection points of the transmittance spectrum in the wavelength range of λ = 450 to 650 nm and the straight line T(40, λ) = C(40) was set to N(40). The incident angle was set to 60° and 80°, and N(60) and N(80) were obtained by the same operation as described above.

[0103] (4) Average reflectance and transmittance

[0104] On a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd., an attached angle variable unit and a polarizer manufactured by Glan-Taylor Co. were installed, and light was incident to the surface of a resin film as a sample to be measured at an incident angle of 20°, 40°, and 70°, respectively, the reflectance in the wavelength range of 400 to 1600 nm with respect to light whose incident plane becomes p-polarized light when the surface of the film is a reflecting plane was found, and the incident angle was set to 0°, the transmittance in the wavelength range of 400 to 1600 nm with respect to light whose polarization axis is the same as that of the p-polarized light (for convenience, the term "p-polarized light" is used) and light whose polarization axis is orthogonal thereto (for convenience, the term "s-polarized light" is used) was measured, and the average reflectance and the average transmittance in the wavelength range of 450 to 650 nm were found, respectively. As the measurement conditions, the slit was set to 2 nm (visible light) / automatic control (infrared light), the gain was set to 2, and the scanning speed was set to 600 nm / min.

[0105] (5) Average reflectance in the case where the resin film is subjected to in-plane rotation

[0106] The average reflectance was found in the order of (a1) to (a4) described below.

[0107] (a1) In the same procedure and measurement conditions as in (4), the reflectance spectrum in the wavelength range of 400 to 1600 nm of p-polarized light at an incident angle of 60° was measured with respect to the surface of a resin film as a sample to be measured which was disposed in such a manner that the incident plane is parallel to the orientation axis.

[0108] (a2) From the reflectance spectrum obtained in said (al), the average value of the reflectance in the wavelength range of 450 to 650 nm is calculated.

[0109] (a3) While rotating the resin film in-plane by 5° to the right, said (al) and (a2) are repeated at each rotation angle, and the measurement is ended when the total rotation angle reaches 90°.

[0110] (a4) The average values of the reflectance obtained at each rotation angle in said (al) to (a3) are added and averaged, and the average reflectance (%) in the case of rotating the resin film in-plane is obtained.

[0111] (6) Change in the average transmittance in the wavelength range of 450 to 650 nm

[0112] The resin film is left in an atmosphere at 25°C for 250 hours, and light which becomes p-polarized light with respect to the incident plane when the film surface is the reflecting plane is made incident at an incident angle of 70°, and otherwise the average transmittance is obtained in the same manner as in the evaluation method (5). Next, the resin film is left in an atmosphere at 100°C for 250 hours, and with respect to the same measurement site on the film surface as in the measurement of the average transmittance after left in an atmosphere at 25°C for 250 hours, light which becomes p-polarized light with respect to the incident plane when the film surface is the reflecting plane is made incident at an incident angle of 70° in the same manner as in the evaluation method (4), and the average transmittance is obtained. From these values, the difference between them is obtained, and this is taken as the change in the average transmittance in the wavelength range of 450 to 650 nm.

[0113] (7) Internal haze after treatment at 150°C for 2 hours

[0114] The resin film is left in an atmosphere at 150°C for 2 hours, and then is put in a liquid measurement quartz cell, is filled with flowing paraffin, and is measured using a haze meter (HGM-2DP) manufactured by Suga Test Instruments Co., Ltd., whereby the internal haze is measured with the film surface haze removed. The measurement position is changed at random, and this measurement is repeated 10 times, and the average value is taken as the internal haze value of the film.

[0115] (8) Proportion of p-polarized light component in transmitted light

[0116] This is obtained in the order of the following (bl) to (b3).

[0117] (b1) On a spectrophotometer (U-4100 Spectrophotometer) manufactured by Hitachi, Ltd., an attached angle variable unit and a polarizer manufactured by Glan-Taylor Co. were installed, and polarized light with an incident angle of 60° with respect to the incident plane when the surface of the sample, i.e., the resin film, was a reflecting plane was made to be p-polarized light, and a transmission spectrum in the wavelength range of 450 to 1600 nm was measured. As the measurement conditions, a slit was set to 2 nm (visible light) / automatic control (infrared light), a gain was set to 2, a scanning speed was set to 600 nm / minute, a polarizer was installed in front of the detector, and only the p-polarized light component in the transmitted light was made to be incident to the detector. From the obtained transmission spectrum, the average value of the transmittance in the wavelength range of 450 to 650 nm was calculated as the p-polarized light component amount Tpp in the transmitted light.

[0118] (b2) The light incident to the detector was made to be an s-polarized light component, the same experiment as in (c1) was performed, and the s-polarized light component amount Tps in the transmitted light was calculated.

[0119] (b3) The proportion (%) of the p-polarized light component was calculated from the following Formula 1.

[0120] Proportion (%) of the p-polarized light component in the transmitted light = Tpp / (Tpp + Tps) x 100 Formula 1

[0121] (9) Information display property

[0122] As the image projector, a display (SP-133CM) manufactured by Dreammaker Co. was used, a polarizer was installed, and an image was projected on the resin film or the laminate (information display portion) shown in the examples and comparative examples using light rays which became p-polarized light or s-polarized light when the resin film or the laminate was a reflecting plane with an incident angle of 60°, and the sharpness of the displayed image and the presence or absence of brightness spots (unevenness) were evaluated visually. The evaluation criteria were as follows.

[0123] : The displayed image projected on the information display portion was clear and had no brightness spots, and there was no problem in use.

[0124] : The displayed image projected on the information display portion had a little brightness spots, but the sharpness was high, and there was no problem in use.

[0125] : The displayed image projected on the information display portion was poor in sharpness, or had strong brightness spots, and there was a problem in use.

[0126] (10) Visual recognition property of coloring

[0127] The resin film or laminate obtained in each of the examples and comparative examples was inclined at 60° with respect to the vertical direction in the open air, and the visual recognition of coloring at that time was evaluated by observing it horizontally from a position 300 mm apart from the center of the resin film or laminate while wearing polarized sunglasses. The evaluation criteria are described below.

[0128] ◎: Almost no coloring was observed.

[0129] O: Slight coloring was observed, but there was no problem in use.

[0130] X: Strong coloring was observed.

[0131] [Resin used to obtain resin film]

[0132] To obtain the resin film used in each of the examples and comparative examples, the resins shown in Table 1 were used. In addition, Resin 1 is a crystalline resin, and Resins 2 to 10 are non-crystalline resins. In addition, "mol%" is the proportion in which the total amount of each of the dicarboxylic acid unit and the diol unit is set to 100 mol%.

[0133] Table 1

[0134]

[0135] [Resin film]

[0136] Resin film A, Q:

[0137] As the thermoplastic resin A, polyethylene terephthalate having an IV of 0.65 (Resin 1) was used. In addition, as the thermoplastic resin B, a copolymer of polyethylene naphthalate (polyethylene naphthalate copolymerized with 2,6-naphthalene dicarboxylic acid component at 80 mol% of the total acid components, isophthalic acid component at 20 mol% of the total acid components, and polyethylene glycol having a molecular weight of 400 at 4 mol% of the total glycol components, IV = 0.65) (Resin 2) was used. The prepared thermoplastic resin A and thermoplastic resin B were respectively fed to two single-screw extruders and melted at a temperature of 290°C. Subsequently, the thermoplastic resin A and thermoplastic resin B were respectively passed through five FSS-type vane disc filters, and then, while being metered by a gear pump, the thermoplastic resin A and thermoplastic resin B were merged by a stacking device having 801 slits so as to have a weight ratio of 1, to obtain a molten resin laminate in which the thermoplastic resin A was alternately stacked as the outermost layer in the thickness direction for 801 layers. Then, the molten resin laminate was discharged from a nozzle, cooled and solidified by a casting drum having a temperature of 25°C to obtain a cast film (flow cast film). The obtained cast film (flow cast film) was heated by a roller set set to a temperature of 60°C, and then, in the film length direction, stretched to 3.0 times by a roller set set to a temperature of 85°C at a stretching speed of 50% / sec, and then, temporarily cooled. The uniaxially stretched film thus obtained was introduced into a tenter, preheated by hot air at a temperature of 90°C, and then, stretched to 4.0 times in the film width direction at a stretching speed of 5% / sec at a temperature of 95°C. The stretched film was heat-treated by hot air at a temperature of 215°C in the tenter, and then, relaxed by 1% in the width direction under the same temperature conditions, and then, cooled to room temperature. Then, both end edge portions in the width direction were equally cut off, to obtain a roll of a resin film having a thickness of 75 μm and a width of 400 mm. A resin film A having a thickness of 75 μm was taken from the center position in the film width direction at 100 mm x 100 mm. In addition, a resin film Q having a thickness of 75 μm was also taken from the end portion in the width direction of the roll at 100 mm x 100 mm.

[0138] Resin films B to P:

[0139] Resin films B to P were obtained in the same manner as resin film A except that the number of layers, the resins of the respective layers, the stretching ratio, and the thickness were as shown in Table 2. In addition, the thickness was adjusted by adjusting the rotation speed of the casting drum. Furthermore, in resin film F and resin film G, the same resin was supplied to the two single-screw extruders to produce the films.

[0140] Table 2-1

[0141]

[0142] Table 2-2

[0143]

[0144] (Example 1)

[0145] A HUD system was produced, which had a projection light source that projects a light ray that becomes p-polarized light with respect to an incident plane when the resin film A is a reflecting surface, and the resin film A, and was configured so that the high-magnification stretching direction of the resin film A became a direction perpendicular to the incident plane of the light from the light source. The evaluation results are shown in Table 3.

[0146] (Example 2)

[0147] A glass plate having a thickness of 2 mm was attached to one side of the resin film A via an acrylic-based adhesive to obtain a laminate having the following structure. A projection light source that generates and radiates p-polarized light, and a HUD system configured so that the high-magnification stretching direction of the resin film A contained in the obtained laminate became a direction perpendicular to the incident plane were produced. The evaluation results are shown in Table 3.

[0148] Structure: resin film / adhesive layer (thickness 10 μm) / glass (thickness 2 mm).

[0149] (Example 3)

[0150] A glass plate having a thickness of 2 mm was attached to both sides of the resin film A via a polyvinyl butyral resin A (adhesive layer) that does not have heat insulation properties to obtain a laminate having the following structure. A projection light source that generates and radiates p-polarized light, and a HUD system configured so that the high-magnification stretching direction of the resin film A contained in the obtained laminate became a direction perpendicular to the incident plane were produced. The evaluation results are shown in Table 3.

[0151] Structure: glass (thickness 2 mm) / adhesive layer (thickness 350 μm) / resin film / adhesive layer (thickness 350 μm) / glass (thickness 2 mm).

[0152] (Examples 4 to 16, 21, Comparative Examples 1 to 3)

[0153] A HUD system was produced in the same manner as in Example 2 except for the resin film, the projection light source, and the relationship (perpendicular / parallel) of the high-magnification stretching direction to the incident plane as shown in Table 3. The evaluation results are shown in Table 3.

[0154] (Example 17)

[0155] A magnesium fluoride film was provided as an AR layer by a sputtering method with respect to the side of the resin film of the laminate of Example 2 on which no glass was laminated, to obtain a laminate having the following structure. A HUD system was produced which had the obtained laminate and a projection light source which generates and radiates p-polarized light. The evaluation results are shown in Table 3. Further, in the evaluation of the effect, the light source was placed on the side of the AR layer having the following structure.

[0156] Structure: AR layer (thickness 0.1 μm) / resin film (thickness 75 μm) / adhesive layer (thickness 10 μm) / glass (thickness 2 mm)

[0157] (Example 18)

[0158] A glass plate having a thickness of 2 mm was attached to both sides of the resin film A via a polyvinyl butyral resin B (adhesive layer) having heat insulation properties, the polyvinyl butyral resin B containing 0.035% by weight of cesium-doped tungsten oxide particles and 0.14% by weight of tin-doped indium oxide particles, to obtain a laminate having the following structure. A HUD system was produced which had the obtained laminate and a projection light source which generates and radiates p-polarized light. The evaluation results are shown in Table 3.

[0159] Structure: glass (thickness 2 mm) / adhesive layer (thickness 350 μm) / resin film (thickness 75 μm) / adhesive layer (thickness 350 μm) / glass (thickness 2 mm).

[0160] (Example 19)

[0161] A glass plate having a thickness of 2 mm was attached to one side of the resin film A via the polyvinyl butyral resin A (adhesive layer) of Example 3 and to the other side via the polyvinyl butyral resin B (adhesive layer) of Example 18, to obtain a laminate having the following structure. A HUD system was produced which had the obtained laminate and a projection light source which generates and radiates p-polarized light. The evaluation results are shown in Table 3. Further, in the evaluation of the effect, the light source was placed on the side of the glass which was in contact with the polyvinyl butyral A side.

[0162] Structure: glass (thickness 2 mm) / adhesive layer (thickness 350 μm) / resin film (thickness 75 μm) / adhesive layer (thickness 350 μm) / glass (thickness 2 mm).

[0163]

[0164]

[0165] Further, "maximum value of a* (θ), b* (θ)" in Table 3 means the maximum value among |a* (40)|, |a* (60)|, |a* (80)|, |b* (40)|, |b* (60)|, |b* (80)|.

[0166] Industrial applicability

[0167] According to the present application, it is possible to provide a head-up display system which can maintain uniform reflection performance even in the case of a wide projection of an image on a windshield, and which is not easily observed in interference color even when a polarizing sunglass is worn. The head-up display system of the present application, since it has the above-described characteristics, can be applied to a transport equipment or a building such as an airplane, a ship, an automobile, a railway, or an electronic billboard.

[0168] Explanation of reference numerals

[0169] 1: Resin film

[0170] 2: Polarizer

[0171] 3: Detector

[0172] i: Incident light (s-polarized light)

[0173] t1: Transmitted light (after passing through the projection section)

[0174] t2: Transmitted light (after passing through the projection section and the polarizer)

[0175] θ: Angle of incidence

[0176] T(θ, λ): Transmittance at wavelength λ nm when s-polarized light is irradiated at an angle of incidence θ° from a light source, passing through the resin film and the polarizer

[0177] C(θ): Average value of T(θ, λ) in the range of wavelengths 450 nm to 750 nm

Claims

1. A head-up display system provided with an image projector that projects an image and a resin film on which the image from the image projector is projected, the head-up display system being characterized in that the image projector projects light rays of which, among light rays constituting the image from the image projector, the intensity of p-polarized light component is 51% or more of the intensity of the entire light ray component with respect to an incident plane when the resin film is taken as a reflecting plane, the resin film is configured so that the maximum value of the absolute value of a* and the maximum value of the absolute value of b* obtained by the following measurement method satisfy the following equations (1) and (2) with the incident plane becoming in the range of 80° to 100° with respect to the horizontal plane, the maximum value of the absolute value of a* ≤ 30 (1) the maximum value of the absolute value of b* ≤ 30 (2) the measurement method is such that, on a spectrophotometer U-4100Spectrophotometer manufactured by Hitachi, Ltd., an attached angle-variable unit and a polarizer manufactured by Glan-Taylor Co. are installed, polarized light that becomes s-polarized light with respect to the incident plane when the resin film is taken as a reflecting plane is irradiated at incident angles of 40°, 60°, and 80°, further, light that has passed through the resin film is made to pass through the polarizer with the s-polarized light as an absorption axis, the transmittance in the range of wavelengths of 400 to 1600 nm is measured at each incident angle, in this case, the slit is set to 2 nm in the case of visible light and to automatic control in the case of infrared light, the gain is set to 2, the scanning speed is set to 600 nm / minute, using the obtained transmittance spectrum, the spectral distribution of D65 light source, and the isochromatic function of XYZ system, the absolute value of a* and its maximum value and the absolute value of b* and its maximum value at each incident angle are calculated, the same measurement is performed by rotating the resin film with the point at which the light ray reaches the film as the center, and the incident plane that satisfies the above equations (1) and (2) can be investigated, with respect to the resin film, the average reflectance in the case where light rays that become p-polarized light with respect to the incident plane when the resin film surface is taken as a reflecting plane are irradiated at an incident angle of 60° and the film surface is rotated in-plane in the range of 0 to 90° with the irradiation point as the center is 10% or more.

2. The head-up display system according to claim 1, in the transmittance spectrum obtained by the measurement method, when the incident angle at which the transmittance measurement is performed is set to θ, in the transmittance spectrum measured at the incident angle θ, when the transmittance at a wavelength λ nm in the range of wavelengths of 450 nm to 750 nm is set to T(θ, λ) with the unit of %, the average value of the transmittance in the range is set to C(θ) with the unit of %, and the number of λs that satisfy T(θ, λ) = C(θ) in the range is set to N(θ), the minimum value among N(40), N(60), and N(80) is 4 or more.

3. The head-up display system according to claim 2, the N(40), N(60), and N(80) satisfy the relationship of N(40) ≤ N(60) ≤ N(80).

4. The head-up display system according to any one of claims 1 to 3, Regarding the resin film, the reflectivity of light rays that are p-polarized relative to the incident surface when the resin film surface is the reflecting surface is incident at incident angles of 20°, 40° and 70° respectively is set as Rp20, Rp40 and Rp70, respectively, and the unit is % when the relationship Rp20≤Rp40<Rp70 is satisfied.

5. The head-up display system according to any one of claims 1 to 3, characterized in that, Regarding the resin film, the average transmittance in the wavelength range of 450 to 650 nm when p-polarized light is incident perpendicularly to the resin film with respect to a certain incident surface, and the average transmittance in the wavelength range of 450 to 650 nm when s-polarized light is incident perpendicularly to the resin film with respect to the incident surface, are both 80% or more.

6. The head-up display system according to any one of claims 1 to 3, The resin film is a film in which the change in average transmittance at wavelengths of 450–650 nm is less than 10% when treated at 100°C for 250 hours.

7. The head-up display system according to any one of claims 1 to 3, The resin film is a film with an internal haze of less than 1% after being treated at 150°C for 2 hours.

8. The head-up display system according to any one of claims 1 to 3, The structure (structure A) has a glass plate laminated on one side of the resin film via an adhesive layer.

9. The head-up display system according to any one of claims 1 to 3, The structure has a glass plate laminated on both sides of the resin film via an adhesive layer (structure B).

10. The head-up display system according to claim 8, characterized in that, An anti-reflective layer is provided on the surface of the resin film on the side without the laminated glass plates.

11. The head-up display system according to claim 9, characterized in that, At least one of the glass plates has an anti-reflective layer on the surface of the side not facing the adhesive layer.

12. The head-up display system according to claim 9, characterized in that, When the adhesive layers on both sides of the resin film are respectively set as C1 and C2, the visible and infrared light transmittance T1 of C1 and the visible and infrared light transmittance T2 of C2 satisfy T2≠T1.

13. The head-up display system according to any one of claims 1 to 3, characterized in that, The proportion of p-polarized light component in the transmitted light when the resin film is irradiated with p-polarized light at an incident angle of 60° is 80% or more.

14. A transportation device, characterized in that, The device is equipped with a head-up display system as described in any one of claims 1 to 13.

15. A resin film having at least one incident surface where the maximum value of the absolute value of a* and the maximum value of the absolute value of b*, determined by the following measurement method, satisfy the following equations (1) and (2). The maximum absolute value of a* is ≤30 (1) The maximum absolute value of b* is ≤30 (2) The measurement method was as follows: an attached angle variable unit and a polarizer made by Glan-Taylor were installed on a spectrophotometer U-4100 made by Hitachi, Ltd., polarized light whose incident plane was s-polarized light when the incident plane of the light to the resin film was a reflecting surface was irradiated at an incident angle of 40°, 60°, and 80°, and further the light transmitted through the resin film was transmitted through a polarizer whose absorption axis was the s-polarized light, the transmittance in the wavelength range of 400 to 1600 nm was measured at each incident angle, in this case, the slit was set to 2 nm in the case of visible light and to automatic control in the case of infrared light, the gain was set to 2, the scanning speed was set to 600 nm / min, the obtained transmittance spectrum, the spectral distribution of D65 light source, and the isochromatic function of XYZ system were used to calculate the absolute value of a* and its maximum value and the absolute value of b* and its maximum value at each incident angle, The same measurement was performed by rotating the resin film with the point at which the light reached the film as the center, and the incident plane satisfying the above formula (1) and formula (2) could be investigated, Regarding the resin film, the average reflectance when the light whose incident plane was p-polarized light when the surface of the resin film was a reflecting surface was irradiated at an incident angle of 60° and the film surface was rotated in the range of 0 to 90° with the irradiation point as the center was 10% or more.

16. The resin film according to claim 15, In the transmittance spectrum obtained by the measurement method, the incident angle at the time of the transmittance measurement was set to θ, in the transmittance spectrum measured at the incident angle θ, the transmittance at a wavelength λ nm in the range of 450 nm to 750 nm was set to T(θ, λ) with the unit of %, the average value of the transmittance in the range was set to C(θ) with the unit of %, and when the number of λs satisfying T(θ, λ) = C(θ) in the range was set to N(θ), the minimum value among N(40), N(60), and N(80) was 4 or more.

17. The resin film according to claim 16, The N(40), N(60), and N(80) satisfied the relationship of N(40) ≤ N(60) ≤ N(80).

18. The resin film according to any one of claims 15 to 17, The resin film had a change amount of the average transmittance at a wavelength of 450 to 650 nm when treated at 100°C for 250 hours of 10% or less.

19. The resin film according to any one of claims 15 to 17, The resin film had an internal haze of 1% or less after treatment at 150°C for 2 hours.

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