Head-up display system

Abstract

The present invention relates to an optical functional film for a head-up display, which has two or more slow axis zones with different slow axis angles in the same plane, and the maximum slow axis angle difference is more than 5° and less than 30°.

Description

Technical Field

[0001] The present invention relates to an optical functional film, an optical laminate, and a functional glass suitable for use in a head-up display, for example, and a head-up display using the same. Background Art

[0002] As a method of displaying information to drivers of cars, airplanes, etc., navigation systems, head-up displays (hereinafter also referred to as "HUD"), etc. are used. HUD is a system that projects images projected by an image projection device such as a liquid crystal display (hereinafter also referred to as "LCD") onto, for example, the windshield of a car.

[0003] The light emitted from the image display device is reflected by the reflector and further reflected by the windshield before reaching the observer. The observer sees the image projected on the windshield, but the image appears to be located farther away from the windshield. In this method, the driver can obtain various information while looking ahead at the windshield without moving his or her eyes, which is safer than conventional car navigation that requires moving the eyes.

[0004] In the HUD system, the display information is projected overlapping with the actual scenery seen through the windshield, but the display light is reflected from two surfaces of the windshield, the indoor side and the outdoor side, so the reflected image becomes a double image, making it difficult to see the display information.

[0005] With regard to this problem, it is known that a phase difference element that can change the polarization direction by 90° is used in a windshield for automobiles, thereby improving the problem of reflected images becoming double images. For example, Patent Document 1 discloses that when S-polarized display light is incident on a windshield for automobiles having a film-shaped optical rotator inside at a Brewster angle, a portion of the S-polarized light is reflected on the surface of the windshield inside the vehicle, and the S-polarized light that penetrates the surface is converted into P-polarized light by the optical rotator, and further all the P-polarized light is emitted to the outside of the vehicle on the surface of the windshield outside the vehicle, thereby preventing double images. However, in such a windshield for automobiles, if the conversion between S-polarized light and P-polarized light cannot be performed very efficiently, double images will be generated due to the S-polarized light that is not emitted to the outside of the vehicle but returns.

[0006] In addition, as for other methods of suppressing double images, there is a known technique in which a circularly polarized light reflecting film made using a cholesterol liquid crystal layer is sandwiched between two 1 / 4 wavelength plates to form a light control film, and the light control film is used to allow P polarized light to be incident (Patent Document 2). In this technique, incident linear polarized light is converted into circular polarized light by passing through the 1 / 4 wavelength plate, and the converted circular polarized light is reflected by the light reflecting film made using the cholesterol liquid crystal layer, thereby allowing the observer to observe. However, even with this technique, it is still desired that the P polarized light incident on the 1 / 4 wavelength plate on the inside of the vehicle is converted into circular polarized light as efficiently as possible, and it is desired that the circular polarized light incident on the 1 / 4 wavelength plate on the outside of the vehicle through the cholesterol liquid crystal layer is converted into P polarized light more efficiently.

[0007] [Prior art literature]

[0008] [Patent Document]

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 6-40271

[0010] Patent document 2: Japanese Patent No. 5973109. Summary of the invention

[0011] [Problems to be solved by the invention]

[0012] An object of the present invention is to provide an optical functional film for a head-up display, an optical laminate, a functional glass, and a head-up display system using the same, which have excellent polarization conversion efficiency.

[0013] [Methods to solve the problem]

[0014] The present inventors have conducted intensive studies to solve the above-mentioned problems and have found that by using an optical functional film for a head-up display having a plurality of slow axes in the same plane and the slow axis angles of the plurality of slow axes being different within a certain range, the polarization conversion efficiency can be improved, and when the optical functional film is used for a head-up display, the generation of double images can be suppressed over a wide range, thereby completing the present invention.

[0015] That is, the present invention relates to the following 1) to 8). 1)

[0017] An optical functional film for a head-up display has two or more slow axis zones with different slow axis angles in the same plane, and the maximum slow axis angle difference is more than 5° and less than 30°. 2)

[0019] The optical functional film as described in 1) above, wherein the maximum slow axis angle difference is 10° or more and 25° or less. 3)

[0021] An optical laminate for a head-up display comprises the optical functional film according to 1) or 2) above and an interlayer film. 4)

[0023] A functional glass for a head-up display comprises the optical functional film described in 1) or 2) above or the optical laminate described in 3) above, and a glass plate. 5)

[0025] A head-up display system comprises the optical functional film described in 1) or 2), the optical layered body described in 3), or the functional glass described in 4). 6)

[0027] A head-up display system as described in 5) above, wherein an angle formed by a slow axis at an incident angle of 90° where light emitted from a display image projection device is perpendicularly incident on the optical functional film, and a slow axis at an incident angle of 80° where the light is incident from a position where the axis perpendicular to the surface of the optical functional film is inclined 10° in a horizontal direction, is greater than 5° and less than 20°. 7)

[0029] A head-up display system as described in 5) or 6) above, wherein an angle formed by a slow axis having an incident angle of 90° where light emitted from a display image projection device is perpendicularly incident on the optical functional film, and a slow axis having an incident angle of 70° where the light is incident from a position inclined 20° in a horizontal direction from an axis perpendicular to the surface of the optical functional film, is greater than 10° and less than 30°. 8)

[0031] The head-up display system as described in any one of 5) to 7) above comprises the functional glass, and the incident angle of the light emitted from the display image projection device incident on the functional glass is in the range of α-10° to α+10° relative to the Brewster angle α.

[0032] [Effects of the invention]

[0033] According to the present invention, an optical functional film, an optical laminate, a functional glass, and a head-up display system using the same which are excellent in polarization conversion efficiency and suitable for use in a head-up display can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a front view showing one embodiment of the optical functional film of the present invention.

[0035] Figure 2 This is a front view showing one embodiment of the optical functional film of the present invention.

[0036] Figure 3This is a side cross-sectional view showing one embodiment of the optical layered body of the present invention.

[0037] Figure 4 This is a side cross-sectional view showing one embodiment of the functional glass of the present invention.

[0038] Figure 5 It is a schematic diagram showing an embodiment of the head-up display system of the present invention.

[0039] Figure 6 This is a schematic diagram showing an overview of how light emitted from a display projection device is incident on the functional glass of the present invention.

[0040] Figure 7 This is a schematic diagram showing an overview of light emitted from a display projection device entering the functional glass of the present invention at an angle close to the Brewster angle.

[0041] Figure 8 This is a graph showing the reflection spectrum of each light reflecting layer produced in Examples.

[0042] Fig. 9 This is a graph showing the spectral characteristics of the natural light transmittance and the polarized light transmittance of the two-layer half-wave plate produced in Test Example 1 of the embodiment.

[0043] Fig.10 This is a graph showing the spectral characteristics of natural light transmittance and polarized light transmittance of the single-layer half-wave plate produced in Test Example 2 of the embodiment. DETAILED DESCRIPTION

[0044] Below, while referring to the attached Figure 1 The embodiments of the present invention are described below. In addition, the following embodiments are only examples of several representative embodiments of the present invention, and various changes can be implemented within the scope of the present invention. In addition, the term "for head-up display" is sometimes omitted and only recorded as optical functional film, optical laminate, functional glass. In addition, the terms "(meth)acryl", "(meth)acrylate" and the like represent "acryl" or "methacryl", "acrylate" or "methacrylate", respectively. In addition, "head-up display" is sometimes recorded as HUD.

[0045] [(A) Optical functional film]

[0046] In order to obtain the desired polarization, the optical functional film of the present invention has at least one optical functional layer, which has the function of converting the polarization axis of the incident light. The optical functional layer can be a phase difference film such as a 1 / 2 wavelength plate or a 1 / 4 wavelength plate, a laminate of multiple phase difference films, or a laminate of these and a circularly polarized light reflecting layer. Specifically, it can be mentioned: (A-1) a 1 / 2 wavelength plate, (A-2) a 1 / 4 wavelength plate, (A-3) a laminate of a 1 / 2 wavelength plate and a circularly polarized light reflecting layer, and (A-4) a laminate of a 1 / 4 wavelength plate and a circularly polarized light reflecting layer. Among these, the optical functional film is preferably a laminate formed by sandwiching (A-1) 1 or more 1 / 2 wavelength plates, or (A-4) 1 or more circularly polarized light reflecting layers by 2 1 / 4 wavelength plates. The circularly polarized light reflecting layer is preferably a cholesterol liquid crystal layer, for example, using a cholesterol liquid crystal.

[0047] The optical functional film of the present invention is an optical functional film for a head-up display, which has two or more slow axis bands with different slow axis angles in the same plane, and the maximum slow axis angle difference is more than 5° and less than 30°. Here, the slow axis refers to the optical axis in the direction of the axis where the refractive index becomes the largest for polarized light incident on a plane perpendicular to the direction of travel of light, and the slow axis angle refers to the angle of the slow axis, that is, it means the angle of the slow axis relative to the axis (longitudinal axis) in the length direction of the optical functional film. In addition, the optical functional film of the present invention has two or more slow axis bands with different slow axis angles. If there are more than two slow axis bands, their number is not limited, and can be hundreds to thousands of slow axis bands, that is, a substantial slow axis gradient can be formed. In addition, the maximum slow axis angle difference refers to the difference between the maximum slow axis angle and the minimum slow axis angle in the same plane of a piece of optical functional film, that is, it means that among the slow axis angles in the same plane, the slow axis angle difference is the largest value. Furthermore, since the optical functional film of the present invention is a film for a head-up display, when there is a portion having a slow axis angle difference of 30° or more in a region other than the portion used as a display portion, the slow axis angle in the region is not considered as the maximum slow axis angle difference.

[0048] Figure 1 This is an example of an embodiment of an optical functional film having two slow axis bands in the same plane. Figure 1In the two regions of the optical functional film 30, if one region is a slow axis band A and the other region is a slow axis band B, the slow axis angle in the slow axis 32 of the slow axis band A and the slow axis angle in the slow axis 34 of the slow axis band B represent different angles. Next, the difference between the slow axis angle 31 in the slow axis band A and the slow axis angle 33 in the slow axis band B is more than 5° and less than 30°, that is, the maximum slow axis angle difference is more than 5° and less than 30°. In this embodiment, the lower limit of the maximum slow axis angle difference is more preferably 6°, more preferably 7°, and more preferably 8°, particularly preferably 10°, and most preferably 15° or 16°. In addition, the upper limit of the maximum slow axis angle difference is more preferably 28°, more preferably 27°, and more preferably 26°, particularly preferably 25°, and most preferably 22°. Therefore, the most preferred maximum slow axis angle difference is more than 16° and less than 22°.

[0049] in addition, Figure 2 This is an example of an embodiment of an optical functional film having three slow axis zones in the same plane. Figure 2 In the three regions of the optical functional film 30, if the left region is the slow axis band C, the central region is the slow axis band D, and the right region is the slow axis band E, then among the slow axis angles in the slow axis 42 of the slow axis band C, the slow axis angles in the slow axis 44 of the slow axis band D, and the slow axis angles in the slow axis 46 of the slow axis band E, at least two slow axis angles represent different angles. Assuming that among the slow axis angles, the slow axis angle 41 in the slow axis band C < the slow axis angle 43 in the slow axis band D < the slow axis angle 45 in the slow axis band E, then the difference between the slow axis angle 41 in the slow axis band C and the slow axis angle 45 in the slow axis band E is more than 5° and less than 30°, that is, the maximum slow axis angle difference is more than 5° and less than 30°. In this embodiment, the lower limit of the maximum slow axis angle difference is more preferably 6°, more preferably 7°, and even more preferably 8°, particularly preferably 10°, and most preferably 15° or 16°. The upper limit of the maximum slow axis angle difference is more preferably 28°, more preferably 27°, still more preferably 26°, particularly preferably 25°, and most preferably 22°. Therefore, the most preferred maximum slow axis angle difference is 16° or more and 22° or less.

[0050] In addition, the optical functional film of the present invention is a film having three or more slow axis zones with different slow axis angles in the same plane, and the slow axis angles between adjacent slow axis zones may differ by 5° or more and 20° or less. Figure 2In the slow axis band D adjacent to the slow axis band C, the slow axis angle 43 is different from the slow axis angle 41 by 5° or more and 20° or less, that is, there is a deviation in the slow axis angle. Similarly, in the slow axis band E adjacent to the slow axis band D, the slow axis angle 45 is different from the slow axis angle 43 by 5° or more and 20° or less, that is, there is a deviation in the slow axis angle. The lower limit of the deviation of the slow axis angle between the adjacent slow axis bands is more preferably 6°, more preferably 7°, and particularly preferably 8°. In addition, the upper limit of the deviation of the slow axis angle between the adjacent slow axis bands is more preferably 19°, more preferably 18°, and particularly preferably 17°. That is, the most preferred deviation of the slow axis angle between the adjacent slow axis bands is 8° or more and 17° or less.

[0051] In the optical functional film of the present invention, it is more preferred to have three or more slow axis zones with different slow axis angles in the same plane, and it is more preferred to have slow axis zones with different slow axis angles. Figure 2 The slow axis band C, the slow axis band D and the slow axis band E have different slow axis angles, and preferably the slow axis angles 41, 43 and 45 are all different. Here, the slow axes are all different, for example, the slow axis in the slow axis band C is 25°, the slow axis in the slow axis band D is 30°, and the slow axis in the slow axis band E is 35°.

[0052] The preferred embodiment of the optical functional film of the present invention is as follows: (i) when the optical functional layer is a 1 / 2 wavelength plate, the maximum slow axis angle difference is preferably 7° to 13°, and more preferably 9° to 11°. Also, (ii) when the optical functional layer is a stack of multiple (especially 2) 1 / 2 wavelength plates, the maximum slow axis angle difference is preferably 10° to 25°, and more preferably 18° to 22°. Furthermore, (iii) when the optical functional layer is a stack of 1 or more circularly polarized light reflecting layers sandwiched by 2 1 / 4 wavelength plates, the maximum slow axis angle difference is preferably 10° to 25°, and more preferably 18° to 22°.

[0053] <1 / 2 Wavelength Plate>

[0054] When using a 1 / 2 wavelength plate as an optical functional film, the 1 / 2 wavelength plate is a phase difference element having the function of converting P polarization to S polarization or converting S polarization to P polarization, that is, having the function of converting the polarization axis, for example, the film composed of polycarbonate or cycloolefin polymer can be uniaxially extended in a manner that the phase difference becomes 1 / 2 of the wavelength, or the horizontally aligned polymerizable liquid crystal is aligned in a thickness that the phase difference becomes 1 / 2 of the wavelength, and is obtained accordingly. Generally speaking, a 1 / 2 wavelength plate using a horizontally aligned polymerizable liquid crystal is composed of a polymerizable liquid crystal layer as a layer having the function of converting the polarization axis, and a supporting substrate coated with a coating liquid that forms the polymerizable liquid crystal layer. However, the supporting substrate is not a necessary component of the optical functional film of the present invention, and the polymerizable liquid crystal layer can also be transferred to other substrates (such as an intermediate film or a glass plate) for use. From the perspective of the orientation of the liquid crystal, the upper limit of the thickness of the 1 / 2 wavelength plate is preferably less than 10 μm, and more preferably less than 5 μm. On the other hand, from the perspective of the polymerization of liquid crystal, the lower limit of the thickness of the 1 / 2 wavelength plate is preferably greater than 0.3 μm, and more preferably greater than 0.5 μm. When light is incident from a position inclined relative to the main surface of the 1 / 2 wavelength plate, there will be a situation where the phase difference changes according to the incident angle of the light. At this time, in order to more accurately make the phase difference appropriate, for example, a phase difference element in which the refractive index of the phase difference element has been adjusted can be used, thereby suppressing the phase difference change caused by the incident angle. For example, when the refractive index of the phase difference element in the slow axis direction in the plane is nx, the refractive index of the phase difference element in the direction orthogonal to nx in the plane is ny, and the refractive index of the phase difference element in the thickness direction is nz, the coefficient Nz shown by the following formula (1) is preferably greater than 0.3 and less than 1.0, and more preferably greater than 0.5 and less than 0.8.

[0055] Nz=(nx-nz) / (nx-ny) (1)

[0056] When the 1 / 2 wavelength plate contains a polymerizable liquid crystal layer, the liquid crystal composition constituting the polymerizable liquid crystal layer is coated on a supporting substrate. When the 1 / 2 wavelength plate is used for HUD, in order to maintain the observability of the displayed image, the supporting substrate is preferably transparent in the visible light region, specifically, the visible light transmittance of a wavelength of 380 to 780 nm is 50% or more, preferably 70% or more, and more preferably 85% or more. In addition, although the supporting substrate can be colored, it is more preferably uncolored or less colored. In addition, the refractive index of the supporting substrate is more preferably 1.2 to 2.0, and more preferably 1.4 to 1.8. The thickness of the supporting substrate can be appropriately selected according to the purpose, preferably 5μm to 1000μm, more preferably 10μm to 250μm, and particularly preferably 15μm to 150μm.

[0057] The supporting substrate may be a laminate of a single layer or two or more layers. Examples of the supporting substrate include triacetylcellulose (TAC), acrylic, polycarbonate, polyvinyl chloride, polyolefin, and polyethylene terephthalate (PET). Among these, triacetylcellulose (TAC), polyolefin, and acrylic, which have less birefringence, are more preferred.

[0058] Next, a method for making a 1 / 2 wavelength plate using the above-mentioned nematic liquid crystal monomer having a polymerizable group is described. This method, for example, dissolves the nematic liquid crystal monomer having a polymerizable group in a solvent, and then adds a photopolymerization initiator. The solvent is not particularly limited as long as it can dissolve the liquid crystal monomer used, but examples thereof include cyclopentanone, toluene, methyl ethyl ketone, methyl isobutyl ketone, etc., and cyclopentanone and toluene are more preferred. Thereafter, the solution is applied to a plastic substrate such as a PET film or a TAC film used as a supporting substrate in a manner that is as uniform as possible in thickness, and the solution is placed for a certain period of time at a temperature condition that allows liquid crystals to be formed and aligned on the supporting substrate while removing the solvent by heating. At this time, the surface of the plastic film may be subjected to a rubbing treatment in the desired alignment direction before coating, or a photo-alignment material that will exert photo-alignment properties by irradiating polarized light may be formed on the surface of the plastic film and irradiated with polarized light, thereby making the alignment of the liquid crystal more uniform. Thus, the slow axis of the 1 / 2 wavelength plate can be controlled at a desired angle and the haze value of the 1 / 2 wavelength plate can be reduced. Then, while maintaining the alignment, ultraviolet rays are irradiated to the nematic liquid crystal monomer using a high pressure mercury lamp or the like to fix the alignment of the liquid crystal, thereby obtaining a 1 / 2 wavelength plate having a desired slow axis.

[0059] The main purpose of the half-wave plate is to convert the S-polarized light or P-polarized light that is transmitted without being reflected on the surface into P-polarized light or S-polarized light. This can reduce the reflection from the supporting substrate arranged on the outside and suppress double images.

[0060] <1 / 4 Wavelength Plate>

[0061] A quarter wavelength plate can be used as an optical functional layer in response to the design of the HUD system. The quarter wavelength plate is a phase difference element having the function of converting circular polarization into linear polarization. For example, a film composed of polycarbonate or cycloolefin polymer can be uniaxially stretched in a manner that the phase difference becomes 1 / 4 of the wavelength, or a horizontally aligned polymerizable liquid crystal can be aligned in a thickness that the phase difference becomes 1 / 4 of the wavelength, thereby obtaining it. In addition, similar to the half wavelength plate, the quarter wavelength plate is preferably provided with a polymerizable liquid crystal layer. At this time, the quarter wavelength plate is composed of a polymerizable liquid crystal layer as a layer having the function of converting the polarization axis, and a supporting substrate to which a coating liquid that forms the polymerizable liquid crystal layer is applied. The polymerizable liquid crystal layer and the supporting substrate can use the same materials as the nematic liquid crystal monomer and the supporting substrate used in the above-mentioned half wavelength plate.

[0062] When the phase difference deviation caused by wavelength dispersion is large, the 1 / 4 wavelength plate may also use a phase difference element called a broadband 1 / 4 wavelength plate. A broadband 1 / 4 wavelength plate refers to a phase difference element in which the wavelength dependence of the phase difference has been reduced. For example, a phase difference element in which a 1 / 2 wavelength plate and a 1 / 4 wavelength plate with the same wavelength dispersion are stacked in such a way that the angle formed by each slow axis is 60°, and a polycarbonate phase difference element (made by Teijin: PUREACE WR-S) in which the wavelength dependence of the phase difference has been reduced. In addition, as in a HUD, when the incident angle of light is obliquely incident relative to the 1 / 4 wavelength plate, it depends on the phase difference element, and the phase difference will change according to the incident angle of the light. At this time, as a method of making the phase difference more strictly appropriate, for example, a phase difference element in which the refractive index of the phase difference element has been adjusted can be used, thereby suppressing the phase difference change associated with the incident angle. As an example, when the refractive index of the phase difference element in the slow axis direction within the plane is nx, the refractive index of the phase difference element in the direction orthogonal to nx within the plane is ny, and the refractive index of the phase difference element in the thickness direction is nz, the coefficient Nz shown by the above formula (1) is preferably controlled to be greater than 0.3 and less than 1.0, and more preferably greater than 0.5 and less than 0.8.

[0063] From the perspective of the alignment of the liquid crystal, the upper limit of the thickness of the 1 / 4 wavelength plate is preferably less than 10 μm, and more preferably less than 5 μm. On the other hand, the lower limit of the thickness of the 1 / 4 wavelength plate is more preferably more than 0.3 μm, and more preferably more than 0.5 μm. In addition, from the perspective of the alignment of the liquid crystal, the upper limit of the thickness of the circularly polarized light reflecting layer is more preferably less than 10 μm, and more preferably less than 5 μm. On the other hand, from the perspective of the polymerization of the liquid crystal, the lower limit of the thickness of the circularly polarized light reflecting layer is more preferably more than 0.3 μm, and more preferably more than 0.5 μm.

[0064] When the optical functional film of the present invention contains a phase difference film of a 1 / 2 wavelength plate or a 1 / 4 wavelength plate, these phase difference films preferably contain a polymerizable liquid crystal layer having a polymerizable liquid crystal compound. A polymerizable liquid crystal compound refers to a nematic liquid crystal monomer having a polymerizable group in the molecule and expressing liquid crystal properties in a certain temperature range or concentration range. The polymerizable group can be exemplified by (meth) acryloyl, vinyl, chalcone, cinnamoyl, and epoxy groups. In addition, in order to make the polymerizable liquid crystal display liquid crystal properties, it is more preferred to have a mesogen group in the molecule. The mesogen group refers to a rod-shaped, plate-shaped substituent such as a biphenyl, a terphenyl, a (poly) benzoic acid phenyl ester group, a (poly) ether group, a benzylidene aniline group, or a acenaphthene and quinoxaline group, or a disc-shaped substituent such as a triphenylene, a phthalocyanine group, or an azacrown group, that is, a group having the ability to induce liquid crystal phase behavior. Liquid crystal compounds having rod-shaped or plate-shaped substituents are publicly known in the art as calamitic liquid crystals. Examples of the nematic liquid crystal monomers having polymerizable groups include polymerizable liquid crystals described in Japanese Patent Application Publication No. 2003-315556 and Japanese Patent Application Publication No. 2004-29824, polymerizable liquid crystals such as PALIOCOLOR series (manufactured by BASF) and RMM series (manufactured by Merck). These nematic liquid crystal monomers having polymerizable groups can be used alone or in combination.

[0065] Furthermore, a polymerizable compound having no liquid crystallinity and capable of reacting with a nematic liquid crystal monomer having a polymerizable group may be added. Examples of such a compound include ultraviolet curable resins.Examples of the ultraviolet curable resin include dipentaerythritol hexa(meth)acrylate, a reaction product of dipentaerythritol penta(meth)acrylate and 1,6-hexamethylene diisocyanate, a reaction product of a triisocyanate having an isocyanuric acid ring and pentaerythritol tri(meth)acrylate, a reaction product of pentaerythritol tri(meth)acrylate and isophorone diisocyanate, dipentaerythritol penta(meth)acrylate, dipentaerythritol tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, tri(acryloyloxyethyl)isocyanurate, tri(methyl)acrylate acrylate, a reaction product of propylene glycol diglycidyl ether and (meth)acrylic acid, a reaction product of 1,6-hexanediol ... 6-hexanediol di(meth)acrylate, glyceryl di(meth)acrylate, reaction product of ethylene glycol diglycidyl ether and (meth)acrylic acid, reaction product of diethylene glycol diglycidyl ether and (meth)acrylic acid, bis(acryloyloxyethyl)hydroxyethyl isocyanurate, bis(methacryloyloxyethyl)hydroxyethyl isocyanurate, reaction product of bisphenol A diglycidyl ether and (meth)acrylic acid, tetrahydrofurfuryl (meth)acrylate, caprolactone-modified tetrahydrofurfuryl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, polypropylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, phenoxyhydroxy (meth)acrylate propyl (meth)acrylate, acryloyl morpholine, methoxypolyethylene glycol (meth)acrylate, methoxytetraethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate, methoxyethyl (meth)acrylate, glycidyl (meth)acrylate, glyceryl (meth)acrylate, ethyl carbitol (meth)acrylate, 2-ethoxyethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, 2-cyanoethyl (meth)acrylate, a reaction product of butyl glycidyl ether and (meth)acrylic acid, butoxytriethylene glycol (meth)acrylate, and butanediol mono(meth)acrylate, and these can be used alone or in combination of two or more.These non-liquid crystal UV-curable resins need to be added to such an extent that the composition containing the nematic liquid crystal monomer does not lose its liquid crystal properties. Preferably, the amount is 0.1 parts by mass to 20 parts by mass, and more preferably 1.0 parts by mass to 10 parts by mass, relative to 100 parts by mass of the nematic liquid crystal monomer having a polymerizable group.

[0066] When the nematic liquid crystal monomer having a polymerizable group and the polymerizable compound having no liquid crystallinity are ultraviolet curable, a photopolymerization initiator is added in order to cure the composition containing them by ultraviolet rays. The photopolymerization initiator may be exemplified by 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinylpropane-1-one (IRGACURE 907 manufactured by BASF), 1-hydroxycyclohexylphenylketone (IRGACURE 184 manufactured by BASF), 4-(2-hydroxyethoxy)-phenyl(2-hydroxy-2-propyl)ketone (IRGACURE 2959 manufactured by BASF), 1-(4-dodecylphenyl)-2-hydroxy-2-methylpropane-1-one (DAROCUR 953 manufactured by Merck), 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropane-1-one (DAROCUR 1116 manufactured by Merck), 2-hydroxy-2-methyl-1-phenylpropane-1-one (IRGACURE 184 manufactured by BASF), and the like. 1173) and acetophenone compounds such as diethoxyacetophenone; benzoin compounds such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether and 2,2-dimethoxy-2-phenylacetophenone (IRGACURE 651 manufactured by BASF); diphenyl ketone compounds such as benzoylbenzoic acid, benzoylbenzoic acid methyl ester, 4-phenyldiphenyl ketone, hydroxydiphenyl ketone, 4-benzoyl-4'-methyldiphenyl sulfide, 3,3'-dimethyl-4-methoxydiphenyl ketone (KAYACURE MBP manufactured by Nippon Kayaku Co., Ltd.); and thioxanthone, 2-chlorothioxanthone (KAYACURE CTX manufactured by Nippon Kayaku Co., Ltd.), 2-methylthioxanthone, 2,4-dimethylthioxanthone (KAYACURE Thioxanthone compounds such as 2,4-dichlorothioxanthone (KAYACURE CTX manufactured by Nippon Kayaku Co., Ltd.), 2,4-diethylthioxanthone (KAYACURE DETX manufactured by Nippon Kayaku Co., Ltd.), and 2,4-diisopropylthioxanthone (KAYACURE DITX manufactured by Nippon Kayaku Co., Ltd.) are also included.More preferably, the photopolymerization initiator includes Irgacure TPO, Irgacure TPO-L, Irgacure OXE01, Irgacure OXE02, Irgacure 1300, Irgacure 184, Irgacure 369, Irgacure 379, Irgacure 819, Irgacure 127, Irgacure 907 and Irgacure 1173 (all manufactured by BASF), and particularly preferably, Irgacure TPO, Irgacure TPO-L, Irgacure OXE01, Irgacure OXE02, Irgacure 1300 and Irgacure 907. These photopolymerization initiators may be used alone or in combination of two or more in any proportion.

[0067] When a phenyl ketone compound or a thioxanthone compound is used as a photopolymerization initiator, an auxiliary agent may be used in combination to promote the photopolymerization reaction. Examples of the auxiliary agent include amine compounds such as triethanolamine, methyldiethanolamine, triisopropanolamine, n-butylamine, N-methyldiethanolamine, diethylaminoethyl methacrylate, Michler's ketone, 4,4'-diethylaminobenzophenone, ethyl 4-dimethylaminobenzoate, (n-butoxy)ethyl 4-dimethylaminobenzoate, and isoamyl 4-dimethylaminobenzoate.

[0068] The amount of the photopolymerization initiator and the auxiliary agent added is preferably within a range that does not affect the liquid crystallinity of the composition, and the amount is preferably 0.5 to 10 parts by mass, more preferably 2 to 8 parts by mass, relative to 100 parts by mass of the ultraviolet-curable compound in the composition. In addition, the auxiliary agent is preferably 0.5 to 2 times the amount of the photopolymerization initiator.

[0069] More than 2 optical functional layers can be provided in the optical functional film of the present invention. At this time, no other layers can be used between the optical functional layers, that is, each optical functional layer can be directly stacked, but it is more preferred to provide an adhesive layer or a bonding layer between each optical functional layer. The adhesive used to form the adhesive layer can include an acrylic or rubber adhesive, and it is more preferred to include an acrylic adhesive that is easy to adjust adhesion, retention, etc. The bonding agent can include an ultraviolet curing resin composition, a thermosetting resin composition, and a mixture of these. In the case of an ultraviolet curing resin, a plurality of monomers with an acryloyl group or an epoxy group can be mixed to form a composition, and the composition is irradiated with ultraviolet rays in the presence of a photopolymerization initiator to harden it, thereby bonding the optical functional layers. In the case of a thermosetting resin composition, a plurality of monomers with an epoxy group can be mixed to form a composition, and the composition is heated in the presence of an acid catalyst to harden it, thereby bonding the optical functional layers. Alternatively, a composition composed of a plurality of monomers or polymers having an amino group, a carboxyl group, or a hydroxyl group is heated and cured in the presence of a compound having an isocyanate group or melamine, thereby bonding the optical functional layers.

[0070] [Method for producing optical functional film]

[0071] The optical functional film of the present invention is preferably realized by a phase difference film and multiple slow axis bands, that is, it is more preferably a phase difference film having multiple slow axes. At this time, it does not mean combining multiple phase difference films, but means having a structure with multiple slow axes in one phase difference film. In order to realize more than two slow axis bands with different slow axis angles, multiple slow axes are controlled to the desired angles in the same surface of the optical functional film. This method can be cited as a friction treatment of each predetermined area in the desired orientation direction on the surface of the optical functional layer. In addition, the optical alignment material that can exert the optical alignment property corresponding to the polarization angle by irradiating polarized light can be formed on the surface of the predetermined optical functional layer, and it is set in advance in a manner that the angle of polarized light irradiation is aligned at the desired angle in each predetermined area when irradiating polarized light, thereby making the orientation angle of the optical alignment material in each predetermined area on the surface of the optical functional layer different angles, and aligning and fixing the liquid crystal on these orientation treatment surfaces. By performing the alignment treatment on the same surface of the optical functional film, an optical functional film having two or more slow axis zones having different slow axis angles can be produced.

[0072] [(B) Optical laminate]

[0073] In the optical laminate of the present invention, an intermediate film is laminated on the optical functional film. The intermediate film is preferably a resin film of a thermoplastic resin, and is particularly preferably a film of polyvinyl butyral. The intermediate film may be one or more sheets, but is preferably an optical laminate having a structure in which the optical functional film is sandwiched by two intermediate films. In addition, the optical laminate is preferably made of two optical functional films. At this time, the difference in the slow axis angles of the two optical functional films in the same plane is particularly preferably the same.

[0074] Figure 3 One embodiment of the optical laminate of the present invention is shown. The optical laminate 10 is formed by sandwiching an optical functional film 101 between two intermediate films 102. The optical functional film 101 corresponds to, for example, Figure 1 or Figure 2 The optical functional films (30, 40) are shown. Figure 3 In the optical layered body 10 , two optical functional films 101 having the same difference in slow axis angles in the same plane may be provided.

[0075] [Intermediate film]

[0076] The intermediate film can use a thermoplastic resin, and it is more preferred to use a generally used vehicle-mounted intermediate film. The vehicle-mounted intermediate film can be, for example, polyvinyl butyral resin (PVB), polyvinyl alcohol resin (PVA), ethylene / vinyl acetate copolymer resin (EVA), or cycloolefin polymer (COP). The intermediate film made of these resins is commonly used as an intermediate film for laminated glass, so it is more preferred. In addition, the thickness of the intermediate film is not particularly limited as long as it is within the range that does not affect the reflection of the display light when the optical laminate is used in the HUD system described later, and can be appropriately designed according to the application.

[0077] The interlayer used in the present invention may be appropriately added with ultraviolet absorbers, antioxidants, antistatic agents, heat stabilizers, colorants, bonding regulators, etc., and the interlayer dispersed with infrared absorbing microparticles is particularly important in the production of high-performance heat-insulating laminated glass. The infrared absorbing microparticles are microparticles of conductive materials such as metals such as Sn, Ti, Zn, Fe, Al, Co, Ce, Cs, In, Ni, Ag, Cu, Pt, Mn, Ta, W, V, and Mo, oxides of the metals, nitrides of the metals, or composites containing at least two of these. In addition, these materials may be doped with Sn, Sb, F, etc. In particular, tin-doped indium oxide (ITO), antimony-doped tin oxide (ATO), and fluorine-doped tin oxide, which are transparent in the visible light region, are more preferred when used as windows for buildings and automobiles that require transparency. The particle size of the infrared absorbing microparticles dispersed in the interlayer is preferably 0.2 μm or less. If the particle size of the microparticles is less than 0.2 μm, light scattering in the visible light region can be suppressed and infrared rays can be absorbed, radio wave permeability and transparency can be ensured without generating haze, and physical properties such as bonding, transparency, and durability equivalent to those of an unadded interlayer can be maintained, and laminated glass processing can be performed by operation on a general laminated glass production line. In addition, when PVB is used as an interlayer, in order to keep the moisture content of the interlayer at the most preferred level, the lamination process is performed in a constant temperature and humidity room. In addition, the interlayer can use a partially colored film, a film with a layer having a sound insulation function sandwiched therebetween, a film (wedge-shaped) with an inclined thickness to reduce the ghosting phenomenon (double image) in the HUD, etc.

[0078] The lamination method of the intermediate film and the optical functional film is not particularly limited, and an example of lamination method is to use a nip roller to press the intermediate film and the optical functional film at the same time. When laminating, if the nip roller can be heated, it is also possible to press while heating. In addition, if the adhesion between the intermediate film and the optical functional film is poor, surface treatment such as corona treatment and plasma treatment can be performed in advance before lamination.

[0079] The intermediate film can be directly laminated on one or both sides of the optical functional film in a state of being dissolved in a solvent. When using polyvinyl butyral resin (PVB), the lower limit of butyralization degree is preferably 40 mol%, more preferably 55 mol%, and particularly preferably 60 mol%. On the other hand, the upper limit of butyralization degree is more preferably 85 mol%, more preferably 80 mol%, and particularly preferably 75 mol%. In addition, the butyralization degree can be measured by infrared absorption spectroscopy (IR), for example, FT-IR can be used for measurement.

[0080] The lower limit of the hydroxyl content of the polyvinyl butyral resin is preferably 15 mol%, and the upper limit is preferably 35 mol%. If the hydroxyl content is less than 15 mol%, the bonding between the interlayer film for laminated glass and the glass will be reduced, or the penetration resistance of the laminated glass will be reduced. On the other hand, if the hydroxyl content exceeds 35 mol%, the interlayer film will become hard.

[0081] The polyvinyl butyral resin can be prepared by acetalizing polyvinyl alcohol with an aldehyde. Polyvinyl alcohol is usually obtained by saponifying polyvinyl acetate, and polyvinyl alcohol having a saponification degree of 80 mol% or more and 99.8 mol% or less is generally used. In addition, the upper limit of the degree of polymerization of the polyvinyl alcohol is preferably 4000, more preferably 3000, and particularly preferably 2500. If the degree of polymerization exceeds 4000, it is difficult to form an intermediate film.

[0082] [(C) Functional glass]

[0083] The functional glass of the present invention is laminated with the above-mentioned optical functional film or optical laminate and a glass plate. The glass plate may be one or more, but it is more preferably a functional glass having a structure in which the above-mentioned optical functional film or optical laminate is sandwiched by two glass plates. The functional glass is suitable for use as a display medium in a HUD system.

[0084] Functional glass can be produced, for example, by bonding the optical functional film or optical laminate to a glass plate. As an example of a method for bonding an optical functional film or optical laminate to a glass plate, an adhesive or bonding agent can be applied to one or both sides of the optical functional film or optical laminate, and then the glass plate is bonded, thereby obtaining the functional glass. The adhesive or bonding agent is not particularly limited, but is preferably a material with good adhesion that is excellent in reworkability when it is peeled off later, such as a silicone adhesive, an acrylic adhesive, etc.

[0085] [glass plate]

[0086] The glass plate is not particularly limited as long as it has a transparency that allows the scenery ahead to be fully observed even when the functional glass of the present invention is used as a windshield. In addition, the refractive index of the glass plate is preferably greater than 1.2 and less than 2.0, and more preferably greater than 1.4 and less than 1.8. In addition, the thickness, shape, etc. of the glass plate are not particularly limited as long as they are within the range that does not affect the reflection of the display light, and can be appropriately designed according to the application. In addition, a reflection-enhancing film composed of a multilayer film and a metal thin film layer having a heat-insulating function can be provided on the reflective surface of these glass plates. These films can increase the reflectivity of the incident polarized light, but when the functional glass of the present invention is used as a windshield for an automobile, for example, it is more preferred to adjust the reflectivity in a manner that the visible light transmittance of the functional glass is greater than 70%.

[0087] When the optical functional film or optical laminate of the present invention is used, the optical functional film or optical laminate is placed between two glass plates and pressed together at high temperature and high pressure to obtain functional glass having the optical laminate placed in laminated glass. Figure 4 One embodiment of the functional glass of the present invention is shown. Figure 4 The functional glass 20 shown is a structure in which an optical laminate 10 is sandwiched between two glass plates 201. The optical laminate 10 is equivalent to, for example, Figure 3 The optical laminate has an optical functional film 101 sandwiched between two intermediate films 102. Figure 4 As shown, when the optical laminate 10 constitutes the functional glass 20 , the intermediate film 102 also functions as an adhesive or bonding agent for maintaining the close adhesion between the two glass plates 201 and the optical laminate 10 .

[0088] An example of a method for making functional glass using the optical functional film or optical laminate of the present invention is specifically described. First, two glass plates are prepared. When used as laminated glass for automobile windshields, soda-lime glass made by the float process is used. The glass can be any of transparent and green-colored glass, without particular restrictions. The thickness of these glass plates is usually about 2 mmt, but in response to the demand for lighter glass in recent years, glass plates slightly thinner than 2 mmt can also be used. The glass plate is cut into a predetermined shape, and the edges of the glass are chamfered and washed. When a black frame or dot-shaped printing is required, it is printed on the glass plate. When a curved surface shape is required like a windshield, the glass plate is heated to above 650°C, and then shaped in a manner that the two sheets have the same surface shape by pressing with a mold or bending due to its own weight, and then the glass is cooled. At this time, if the cooling rate is too fast, stress distribution will be generated in the glass plate to form tempered glass, so it is cooled slowly. One of the glass plates prepared as described above is placed horizontally, and the optical functional film or optical laminate of the present invention is overlapped thereon, and another glass plate is further placed. Next, the optical functional film and the intermediate film protruding from the edge of the glass are cut and removed with a cutting machine. Thereafter, the air existing between the glass plates, optical functional films or optical laminates stacked in a sandwich shape is degassed while the temperature is heated from 80°C to 100°C to perform preliminary bonding. There are two methods for degassing the air: a wrapping method in which the glass plate / optical functional film or optical laminate / glass plate laminate is wrapped with a rubber bag made of heat-resistant rubber or the like, and a ring method in which only the end of the glass plate is covered and sealed with a rubber ring. Either method can be used. After the preliminary bonding is completed, the glass plate / optical functional film or optical laminate / glass plate laminate taken out of the rubber bag, or the laminate with the rubber ring removed, is placed in an autoclave and heated at 10 to 15 kg / cm 2The glass plate is heated to 120°C to 150°C under high pressure, and the heating and pressurizing treatment is performed for 20 minutes to 40 minutes under this condition. After the treatment, the glass plate is cooled to below 50°C, and the pressure is released, and the functional glass of the present invention composed of the glass plate / optical functional film or the optical laminate / glass plate is taken out from the autoclave.

[0089] The functional glass obtained in this way can be used as windshields, side glasses, rear windshields, and skylight glasses for ordinary cars, small cars, light cars, etc., as well as large special cars and small special cars. In addition, it can also be used as windows for railway vehicles, ships, and airplanes, and can also be used as building materials and industrial window materials. As a form of use, it can be used by laminating or bonding with components having UV resistance or dimming functions.

[0090] [Head-up display system]

[0091] Figure 5 An embodiment of the HUD system of the present invention is shown in a schematic diagram. Figure 5 The HUD system shown comprises a display image projection device (display) 2 that causes display light that indicates a display image to be S-polarized light or P-polarized light and then emitted, a reflector 3 that reflects the display light emitted by the display image projection device 2, and a functional glass for a head-up display of the present invention (functional glass 4) on which the S-polarized light or P-polarized light emitted by the display image projection device 2 is incident. The S-polarized light or P-polarized light emitted by the display image projection device 2 is reflected by the reflector 3, and the reflected display light is irradiated on the functional glass 4 that functions as a windshield, whereby the S-polarized light or P-polarized light reaches the observer 1 via the optical path 5, and a virtual image 6 of the display image can be observed. In addition, Figure 5 In the HUD system shown, the display light emitted by the display image projection device 2 is incident on the functional glass 4 via the reflector 3, but it can also be directly incident on the functional glass 4 from the display image projection device 2. In addition, the display light representing the display image can be emitted from the display image projection device 2 as random light and reflected on the reflector 3. The reflected light passes through a polarizing plate before reaching the functional glass 4, thereby adjusting the polarization emitted by the display image projection device 2 and irradiating the functional glass 4 with the desired polarization.

[0092] <Display Image Projection Device>

[0093] The display image projection device 2 is not particularly limited as long as it can emit the desired P polarization or S polarization until it finally reaches the functional glass 4, and examples thereof include a liquid crystal display device (LCD), an organic EL display (OELD), etc. When the display image projection device 2 is a liquid crystal display device, the emitted light is usually linearly polarized, so it can be used directly. On the other hand, when the display image projection device 2 is an organic EL display, for example, the display image projection device 2 can be composed of a light source and a polarizing plate that can emit P polarization or S polarization. In addition, when the HUD system is used in a car, for example, an optical component such as a polarizing plate and a 1 / 2 wavelength plate is configured at a light outlet such as an instrument panel, and a liquid crystal display device or an organic EL display can be adjusted in such a way that P polarization or S polarization can be emitted from the display image projection device 2. In addition, the light source used by the display image projection device 2 is not particularly limited, and a laser light source or an LED light source can be used. In addition, the central reflection wavelength of the phase difference element constituting the optical functional layer is set to correspond to the luminous spectrum of the above-mentioned light source, thereby making the display image more vivid.

[0094] <Reflector>

[0095] The HUD system of the present invention may optionally include a reflector 3. The reflector 3 is not particularly limited as long as it can reflect the display light from the display image projection device 2 toward the functional glass 4, and may be composed of, for example, a plane mirror, a concave mirror, etc. When a concave mirror is used as the reflector 3, the concave mirror can also amplify the display light from the display at a predetermined magnification.

[0096] In the HUD system of the present invention, the angle formed by the slow axis of the incident angle 90° where the light emitted by the display image projection device is perpendicularly incident on the optical functional film, and the slow axis of the incident angle 80° where the light emitted by the display image projection device is incident from a position of the optical functional film inclined 10° in the horizontal direction from the axis perpendicular to the surface, that is, the deviation range of the slow axis of the incident angle 80° relative to the incident angle 90° is preferably 5° or more and 20° or less. In addition, if Figure 6 As shown, the incident angle 7 means the angle formed by the surface of the optical functional film 101 and the light incident on the surface of the optical functional film 101. For example, when the light emitted by the display image projection device 2 is incident on the front of the optical functional film 101 through the reflector 3, that is, when it is incident on the surface of the optical functional film 101 vertically, the incident angle 7 is 90°. When it is incident from a position where the axis of the optical functional film 101 is tilted 10° to the right or left in the horizontal direction from the axis perpendicular to the surface, the incident angle 7 is 80°. That is, Figure 6In the embodiment, the deviation between the slow axis angle in the display part 9A and the slow axis angle in the display part 9B is 5° to 20°, which is a more preferred embodiment of the head-up display of the present invention. In addition, the deviation between the slow axis angle in the display part 9A and the slow axis angle in the display part 9B is more preferably 7° to 13°, and even more preferably 9° to 11°.

[0097] In the present invention, the polarization conversion efficiency of the optical functional film caused by the inclination of the incident angle 7 can be improved by the correction of the above-mentioned slow axis, which helps to reduce the generation of double images. The lower limit of the angle formed by the slow axis at an incident angle of 90° and the slow axis at an incident angle of 80° is preferably 7°, more preferably 8°, and particularly preferably 9°. In addition, the upper limit of the angle formed by the slow axis at an incident angle of 90° and the slow axis at an incident angle of 80° is preferably 19°, more preferably 18°, and particularly preferably 17°. That is, the angle formed by the slow axis at an incident angle of 90° and the slow axis at an incident angle of 80° is most preferably 8° or more and 17° or less.

[0098] In addition, in the HUD system of the present invention, the angle formed by the slow axis of the incident angle 90° at which the light emitted by the display image projection device is perpendicularly incident on the optical functional film, and the slow axis of the incident angle 70° at which the light emitted by the display image projection device is incident from the optical functional film at a position inclined 20° in the horizontal direction from the axis perpendicular to the surface, that is, the deviation range of the slow axis of the incident angle 70° relative to the slow axis of the incident angle 90° is preferably 10° or more and 30° or less. The lower limit of the angle formed by the slow axis of the incident angle 90° and the slow axis of the incident angle 70° is more preferably 14°, and particularly preferably 16°. In addition, the upper limit of the angle formed by the slow axis of the incident angle 90° and the slow axis of the incident angle 70° is more preferably 28°, and particularly preferably 24°. That is, the angle formed by the slow axis of the incident angle 90° and the slow axis of the incident angle 70° is most preferably 16° or more and 24° or less.

[0099] like Figure 7 As shown, in the HUD system of the present invention, when the Brewster angle of S-polarized light or P-polarized light relative to the functional glass 4 is α, the incident angle 8 of the light emitted by the display image projection device 2 incident on the functional glass 4 as the display medium is preferably in the range of α-10° to α+10°, and more preferably in the range of α-5° to α+5°. In addition, as Figure 7 As shown, the incident angle 8 means the angle formed by the "axis perpendicular to the surface of the display medium (functional glass 4)" and the "light incident on the surface of the display medium" (hereinafter, this incident angle is also referred to as the "incident angle X").

[0100] In one embodiment of the HUD system of the present invention, when a 1 / 2 wavelength plate is used as an optical functional film, and the display medium is a functional glass 4, and the display light emitted by the display image projection device 2 is S-polarized light, the S-polarized light emitted by the display image projection device 2 is incident through the reflector 3 at a range of α-10° to α+10°, that is, incident at an angle near the Brewster angle relative to the axis perpendicular to the surface of the functional glass 4, preferably incident at an incident angle 8 of the Brewster angle α, thereby suppressing the reflection of the P-polarized light converted by the functional glass 4 due to the outer glass plate of the vehicle, and suppressing the generation of double images. That is, if the incident angle 8 of the S-polarized light is less than α-10° or exceeds α+10°, the incident angle 8 of the S-polarized light will deviate from the angle near the Brewster angle, so the reflection of the P-polarized light converted by the 1 / 2 wavelength plate will increase, and there is a situation where a double image is generated.

[0101] In addition, in other embodiments of the HUD system of the present invention, when a laminated body formed by one or more circularly polarized reflective layers (cholesterol liquid crystal layers) sandwiched by two 1 / 4 wavelength plates is used as an optical functional film, and the display medium is a functional glass 4, and the display light emitted by the display image projection device 2 is P polarized light, the same as above. Generally speaking, the reflected light from the road surface is S polarized light, so polarized sunglasses are designed to absorb S polarized light. Therefore, in the previous HUD system using S polarized light, the observability of the display image of the HUD through the polarized sunglasses will be extremely reduced. On the other hand, if P polarized light reaches the observer in the HUD system using P polarized light, the generation of double images can be suppressed, and the observability of the display image can be improved even when wearing polarized sunglasses. In addition, when the circularly polarized light reflecting layer is a cholesterol liquid crystal layer, the circularly polarized light that passes through the circularly polarized light reflecting layer is converted into the original P polarized light by passing through the second 1 / 4 wavelength plate, and the slow axis of the second 1 / 4 wavelength plate is set in a positional relationship orthogonal to the slow axis of the first 1 / 4 wavelength plate. The converted P polarized light is also incident at an angle close to the Brewster angle with respect to the vehicle outer side glass surface outside the second 1 / 4 wavelength plate. Therefore, the reflection of the P polarized light on the vehicle outer side glass surface outside the second 1 / 4 wavelength plate can also be greatly reduced, and as a result, the generation of double images can be greatly improved.

[0102] In the head-up display system of the present invention, for example, when a functional glass including an optical functional film having a half-wave plate is provided, in order to efficiently perform polarization conversion (for example, converting P polarization into S polarization, or converting S polarization into P polarization), it is preferred to control the angle θ formed by the polarization axis of S polarization or P polarization incident from a position of the functional glass inclined from an axis perpendicular to the surface by 45° or more and 65° or less and the slow axis of the optical functional film to be 35° or more and 47° or less. By setting the incident angle of S polarization or P polarization incident on the functional glass to a range of 45° or more and 65° or less, when P polarization is incident on the functional glass, the reflectivity of the surface of the functional glass can be theoretically suppressed to less than 2%. The transmitted P polarization is converted into S polarization by the half-wave plate, and the converted S polarization is reflected at the interface between the functional glass and the air on the opposite side of the incident side. The reflected S polarization is converted into P polarization again by the half-wave plate, and the P polarization reaches the observer. In addition, when S-polarized light is incident on the functional glass, the S-polarized light will be reflected on the surface of the functional glass, and the S-polarized light will reach the observer. A portion of the S-polarized light that penetrates will be converted into P-polarized light by the 1 / 2 wavelength plate, and the converted P-polarized light will not be reflected on the functional glass on the opposite side of the incident side or on the interface between the functional glass and the air, but will pass through. As described above, by controlling the incident angle X of the S-polarized light or P-polarized light incident on the functional glass, the generation of double images can be suppressed. In addition, when the angle θ is less than 35° or exceeds 47°, the polarization axis conversion performance of converting the P-polarized light incident on the functional glass into S-polarized light or converting the S-polarized light into P-polarized light is low, resulting in the worry of generating double images. By appropriately controlling the angle θ, the 1 / 2 wavelength plate can show good polarization axis conversion performance, resulting in a clearer observation of the displayed image.

[0103] When the optical functional film has a 1 / 2 wavelength plate, in order to properly control the polarization axis conversion performance, the angle θ is preferably a value calculated by the following formulas (2) and (3). The technical significance of the following formulas (2) and (3) is explained here. When the S-polarized light or P-polarized light incident on the functional glass passes through the 1 / 2 wavelength plate belonging to a medium with a refractive index different from that of air, the incident angle X incident on the 1 / 2 wavelength plate will change. Here, the incident angle X of the S-polarized light or P-polarized light relative to the functional glass is α, the actual incident angle X incident on the 1 / 2 wavelength plate, that is, the refractive angle of the 1 / 2 wavelength plate is β, and the refractive index of air is n. α , the refractive index of the 1 / 2 wavelength plate is n β According to Snell's law, sinα / sinβ=n β / n αWill hold, if this formula is simplified to an equation for obtaining β, then formula (3) can be derived. On the other hand, when the polarization axis of the S polarized light incident on the functional glass is the x-axis, the polarization axis of the P polarized light is the y-axis, and the phase difference value when the angle formed by the y-axis and the slow axis of the 1 / 2 wavelength plate is θ is Re, through vector analysis, the y-axis is expressed as Re·cosθ, and the x-axis is expressed as Re·sinθ. Here, it is known that the polarization axis conversion performance of the 1 / 2 wavelength plate will be the maximum when the incident light is at 45° relative to the slow axis of the 1 / 2 wavelength plate, so in theory, the angle θ formed by the polarization axis of the S polarized light or the P polarized light and the slow axis of the optical functional film is preferably 45°. However, as mentioned above, even if the angle formed by the polarization axis of the S polarized light or the P polarized light incident on the functional glass and the slow axis of the optical functional film is set to θ, the actual angle incident on the 1 / 2 polarizing plate is β. Therefore, regarding the y-axis of Re·cosθ (theoretical y-axis), if the y-axis is obtained when it is tilted at an angle β with the x-axis as the center (the actual y-axis), then Re·cosθ / actual y-axis=sin(90°-β) will hold, and the actual y-axis is expressed as Re·cosθcosβ. As mentioned above, the angle formed by the slow axis of the 1 / 2 wavelength plate and the polarization axis of the S polarized light or the polarization axis of the P polarized light is preferably 45°. In order to set the angle formed by the polarization axis of the S polarized light or the P polarized light incident on the functional glass and the slow axis of the 1 / 2 wavelength plate to 45°, the x-axis (Re·sinθ) needs to be equal to the actual y-axis (Re·cosθcosβ), so Re·sinθ=Re·cosθcosβ is obtained, and this formula is simplified to derive formula (2). As described above, by strictly controlling the angle θ based on the values ​​calculated by the following equations (2) and (3) in relation to the angle β actually incident on the half-wave plate, the polarization axis conversion performance of the half-wave plate can be utilized to the maximum extent.

[0104] tanθ=cosθ(2)

[0105]

[0106] θ: Angle formed by the slow axis of the half-wave plate and the polarization axis of S-polarized light or P-polarized light incident on the functional glass at an arbitrary incident angle α.

[0107] α: The incident angle of S-polarized light or P-polarized light relative to the functional glass.

[0108] n α :The refractive index of air.

[0109] n β :Refractive index of 1 / 2 wavelength plate.

[0110] The range of the angle θ is preferably controlled within the range of ±5° of the value of the angle θ, and more preferably within the range of ±3°. If the angle θ is outside the range of ±5° of the angle calculated by the above formulas (2) and (3), the polarization conversion efficiency represented by the 1 / 2 wavelength plate will become lower. By controlling the range of the angle θ according to the value calculated by the above formulas (2) and (3), the decrease in the polarization conversion efficiency of the 1 / 2 wavelength plate can be suppressed.

[0111] Regarding the refractive index of the 1 / 2 wavelength plate substituted into formula (3), the refractive index in the slow axis direction of the 1 / 2 wavelength plate is nx, the refractive index in the direction orthogonal to nx in the plane of the 1 / 2 wavelength plate is ny, and the refractive index in the thickness direction of the 1 / 2 wavelength plate is nz, and the average value of the sum is used as the average refractive index. In addition, when using a commercially available 1 / 2 wavelength plate, the average refractive index may also use the value recorded in the catalog, etc. In addition, when using the polymerizable liquid crystal described later as the material of the 1 / 2 wavelength plate, if the ordinary light refractive index no and the extraordinary light refractive index ne of the liquid crystal are used, the average refractive index is expressed as (nx+ny+nz) / 3=(no+no+ne) / 3. If a specific example of θ calculated by formulas (2) and (3) is shown, for example, when the refractive index of air is set to 1.00, a 1 / 2 wavelength plate with a refractive index of 1.55 is used, and the incident angle X of S-polarized light or P-polarized light is 45°, according to formulas (2) and (3), the value of θ is 42°, so the range of θ is preferably 37° to 47°, and more preferably 39° to 45°. When the incident angle X of S-polarized light or P-polarized light is 50°, according to formulas (2) and (3), the value of θ is 41°, so the range of θ is preferably 36° to 46°, and more preferably 38° to 44°. In addition, when the incident angle X of S-polarized light or P-polarized light is 56° or 60°, according to formulas (2) and (3), the value of θ is 40°, so the range of θ is preferably 35° to 45°, and more preferably 37° to 43°. When the incident angle X of S-polarized light or P-polarized light is 65°, according to equations (2) and (3), the value of θ is 39°, so the range of θ is preferably 34° to 44°, and more preferably 36° to 42°.

[0112] As described above, in the present invention, by controlling the angle θ formed by the polarization axis of the S polarization or P polarization incident on the optical functional film and the slow axis of the 1 / 2 wavelength plate, the polarization axis conversion performance represented by the 1 / 2 wavelength plate can be further improved. At this time, from the perspective of the controllability of the slow axis of the 1 / 2 wavelength plate and the production cost, it is particularly preferred to use a 1 / 2 wavelength plate containing a polymerizable liquid crystal layer as a layer having the function of converting the polarization axis. In addition, as long as the wavelength dispersion of the 1 / 2 wavelength plate described above is suitable for head-up display purposes, there is no particular restriction, but in order to correctly perform polarization conversion within a wide wavelength range in the visible light region, it is more preferred to have reverse wavelength dispersion. Generally speaking, polymers are normal dispersions in which the absolute value of birefringence increases on the short wavelength side, but if it is a liquid crystal compound in which the birefringence increases on the long wavelength side by controlling the value of the birefringence Δn of each wavelength of visible light, reverse wavelength dispersion can be obtained. In addition, by stacking a combination of appropriate slow axes of multiple phase difference plates with appropriate phase difference values ​​corresponding to the wavelength dispersion characteristics of the compound, reverse wavelength dispersion can also be obtained. When using a 1 / 2 wavelength plate formed by stacking a combination of multiple phase difference plates as described above, with respect to the slow axis angle of each phase difference plate, the angle θ formed by the polarization axis of the S polarization or P polarization incident on the optical functional film and the slow axis of the 1 / 2 wavelength plate is appropriately controlled in the above manner, thereby enabling the 1 / 2 wavelength plate to exhibit good polarization axis conversion performance, and as a result, the displayed image can be further observed clearly.

[0113] (Example)

[0114] The present invention is described in detail below by way of examples. In the examples, "parts" means parts by mass. In addition, the present invention is not limited to the following examples within the scope of the gist thereof. In addition, unless otherwise specified, the room temperature is within the range of 20°C ± 5°C.

[0115] <Test Example Using a Quarter Wavelength Plate>

[0116] [Preparation of coating liquid (cholesteric liquid crystal composition)]

[0117] A coating liquid (R1) having the composition shown in Table 1 was prepared.

[0118] [Table 1]

[0119] Material(type) Material name (manufacturer name) Prescription quantity (servings) Nematic Liquid Crystal Monomer LC242 (BASF) 20.00 Chiral Agent LC756 (BASF) 1.54 Photopolymerization initiator Irgacure TPO (BASF) 1.00 Solvents Cyclopentanone 80.00

[0120] Next, except that the amount of the chiral agent in the coating liquid (R1) was changed to the amount shown in Table 2, coating liquids (R2), (R3) and (R4) were prepared with the same formulations.

[0121] [Table 2]

[0122] Coating liquid Chiral agent prescription quantity (parts) Coating liquid (R2) 1.26 Coating liquid (R3) 1.04 Coating liquid (R4) 0.70

[0123] In addition, the coating solution (QWP) having the composition shown in Table 3 used for the production of the quarter-wavelength plate was adjusted.

[0124] [Table 3]

[0125] Material(type) Material name (manufacturer name) Prescription quantity (servings) Nematic Liquid Crystal Monomer LC242 (BASF) 24.69 Photopolymerization initiator Irgacure TPO (BASF) 1.23 Solvents Cyclopentanone 74.07

[0126] [Example 1]

[0127] <Production of optical functional film>

[0128] Using the prepared coating liquids (R1), (R2), (R3) and (R4), light reflection layers PRL-1, PRL-2, PRL-3 and PRL-4 were prepared according to the following steps, and then these layers were stacked to prepare circularly polarized light reflection layers. Next, a quarter wavelength plate was further stacked on both sides of the obtained circularly polarized light reflection layer to prepare a light control laminate. The plastic substrate used as a supporting substrate was a PET film (trade name A4100, thickness 50 μm) manufactured by Toyobo Co., Ltd., the surface without a primer layer being previously rubbed by the method described in Example 1 of Japanese Patent Publication No. 2002-90743.

[0129] (1) Each of the coating solutions (R1), (R2), (R3) and (R4) shown in Tables 1 and 2 was applied to the rubbed surface of each PET film at room temperature using a wire bar coater so that the thickness of each light reflecting layer obtained after drying would be 0.5 μm.

[0130] (2) Each of the obtained coating films was heated at 80°C for 2 minutes to remove the solvent and form a cholesteric liquid crystal phase. Then, a high-pressure mercury lamp (manufactured by HARISON TOSHIBA LIGHTING Co., Ltd.) was used to irradiate UV light at an output of 120 W for 5 to 10 seconds to fix the cholesteric liquid crystal phase, and cholesteric liquid crystal layers formed by coating liquids (R1), (R2), (R3) and (R4) were formed on each PET film, that is, light reflection layer PRL-1, light reflection layer PRL-2, light reflection layer PRL-3 and light reflection layer PRL-4 were formed, respectively.

[0131] (3) The coating liquid shown in Table 3 is applied to the friction-treated surface of each PET film at room temperature using a wire rod coater in such a manner that the thickness of the 1 / 4 wavelength plate obtained after drying becomes 1 μm. Next, the surface of each PET film is divided into three regions of P, Q, and R from the left with a width of 20 cm each, and the friction angle is set for each individual region so that the angle formed by the axis in the longitudinal direction of the PET film (vertical axis) and the slow axis of the 1 / 4 wavelength plate becomes a predetermined angle as shown in Table 4, and the friction treatment is performed. In addition, the longitudinal direction refers to, for example, Figure 2The longitudinal direction (short side) in the diagram refers to the longitudinal direction (short side), and the width direction refers to the transverse direction (long side). The following definitions are the same.

[0132] [Table 4]

[0133]

[0134]

[0135] (4) Each obtained coating film was heated at 80°C for 2 minutes to remove the solvent and form a liquid crystal phase. Then, a high-pressure mercury lamp (manufactured by HARISON TOSHIBA LIGHTING Co., Ltd.) was used to irradiate UV for 5 to 10 seconds at an output of 120W to fix the liquid crystal phase, and a total of 14 1 / 4 wavelength plates with a predetermined slow axis band formed on a PET film with a polymerizable liquid crystal layer were prepared. The 1 / 4 wavelength plate was cut into a size of 60 cm in the width direction and 50 cm in the length direction, including all regions of regions P, Q and R. The slow axis bands of regions P, Q and R were formed in the same plane from the left at 20 cm each in the width direction (consistent with the range shown in Table 4). In addition, the phase difference value of each region of the obtained 1 / 4 wavelength plate was measured with an automatic birefringence meter ("KOBRA-21ADH" manufactured by Oji Measurement Co., Ltd.), and the phase difference value at 546nm was 136nm.

[0136] (5) The light reflecting layer PRL-1 (using the coating liquid (R1)) and the light reflecting layer PRL-2 (using the coating liquid (R2)) on the PET film produced in (1) to (2) are laminated on each light reflecting layer side using an acrylic adhesive (manufactured by Soken Chemical Co., Ltd., acrylic adhesive SK-Dyne 906).

[0137] (6) The PET film of the light reflecting layer PRL-2 is peeled off.

[0138] (7) The light reflecting layer side of the light reflecting layer PRL-3 (using the coating liquid (R3)) on the PET film produced from (1) to (2) and the light reflecting layer side of the PET film peeled off in the light reflecting layer PRL-2 in (6) are laminated together using the same acrylic adhesive as the adhesive used in (5).

[0139] (8) The light reflecting layer side of the light reflecting layer PRL-4 (using the coating liquid (R4)) was laminated on the light reflecting layer PRL-3 in the same manner as in (7).

[0140] (9) The PET films located outside the light reflecting layers PRL-1 and PRL-4 were peeled off respectively to prepare circularly polarized light reflecting layers including four cholesterol liquid crystal layers.

[0141] (10) Using the quarter-wave plates whose slow axis angles in the regions P, Q and R are represented by X-4 and Y-4 in Table 4 as the polymerizable liquid crystal layer on the PET film produced in (3) and (4), the quarter-wave plates were stacked in the width direction via the same acrylic adhesive as the adhesive used in (5) on both sides of the produced circularly polarized light reflecting layer, with the polymerizable liquid crystal layer facing the circularly polarized light reflecting layer and the regions in the width direction of the plane being combinations of X-4 P and Y-4 R, X-4 Q and Y-4 Q, and X-4 R and Y-4 P in Table 4. Next, the PET film of each quarter-wave plate was peeled off to perform the following measurements and evaluations.

[0142] An optical functional film is prepared as described above, and the optical functional film has a circularly polarized light reflecting layer in which light reflecting layer PRL-1, light reflecting layer PRL-2, light reflecting layer PRL-3 and light reflecting layer PRL-4 are stacked in sequence, and two 1 / 4 wavelength plates are stacked on both sides of the circularly polarized light reflecting layer. Figure 8 This is a graph obtained by plotting the relationship between the wavelength and reflectivity of each light reflecting layer when forming a single light reflecting layer PRL-1, PRL-2, PRL-3 and PRL-4. Figure 8 As shown in Table 5, the central reflection wavelengths of the light reflecting layers PRL-1, PRL-2, PRL-3 and PRL-4 are 450nm (half-value width is 123nm), 540nm (half-value width is 131nm), 650nm (half-value width is 148nm) and 800nm ​​(half-value width is 178nm), respectively, and the reflectivity of the light reflecting layers PRL-1, PRL2, PRL-3 and PRL-4 at the central reflection wavelength is approximately 20%, approximately 21%, approximately 22% and approximately 20%, respectively.

[0143] [Table 5]

[0144] Light reflecting layer PRL-1 PRL-2 PRL-3 PRL-4 Maximum reflectivity (%) 20.2 20.8 22.4 19.6 Central reflection wavelength λ2(nm) 450 540 650 800 50% short wavelength side wavelength (nm) 397 479 578 722 50% long wavelength side wavelength (nm) 520 610 726 900 Half value width (nm) 123 131 148 178

[0145] The average transmittance of each light reflecting layer in the front direction (incident angle 0°) was about 77%, and the reflectance at about 550 nm was about 22%. In addition, even when each light reflecting layer was viewed from a position tilted 50° from the front, the transmittance of the red region did not change, and the color tone was the same as that in the front direction. In addition, the phase difference value when each light reflecting layer was tilted 50° was measured with an automatic birefringence meter ("KOBRA-21ADH" manufactured by Oji Instruments Co., Ltd.), and the phase difference value at 546 nm was 55 nm.

[0146] <Production of Optical Laminated Body>

[0147] A transparent polyvinyl butyral intermediate film with a thickness of 0.38 mm and containing triethylene glycol di-2-ethylhexanoate as a plasticizer is cut into the same size as the optical functional film to be produced, and the above-mentioned optical functional film is arranged between two polyvinyl butyral intermediate films, and then pressurized and crimped by a laminator to produce an optical laminate.

[0148] <Production of functional glass>

[0149] The optical laminate is placed between two glass plates of the same size as the optical laminate and 2 mm thick, and then pressurized and heated to obtain functional glass. First, the optical laminate and the transparent glass plate are stacked on a transparent glass plate in sequence. They are wrapped in a rubber bag and degassed in an autoclave heated to 90°C for 10 minutes for preliminary bonding. After cooling to room temperature, they are taken out of the rubber bag and placed in an autoclave again at 135°C, 12 kg / cm 2 The functional glass having an optical laminate inserted therein and having a good appearance was produced by heating and pressing at a high pressure of 100°C for 30 minutes. The visible light transmittance of the obtained functional glass was 72%.

[0150] <Production of Head-Up Display and Evaluation of Display Images>

[0151] As Figure 5 The head-up display is manufactured in the configuration shown. In addition, as for the display image projection device 2 and the reflector 3, a liquid crystal display panel capable of emitting P polarized light to the functional glass 4 is provided, and the functional glass manufactured as described above is used as the functional glass 4. In a dark room, the width direction of the optical functional film in the composition of the functional glass 4 is adjusted in such a manner that the P polarized light emitted by the display image projection device 2 is incident at a Brewster angle (about 56°) relative to the functional glass 4 at an incident angle X of the P polarized light. The glass on the 1 / 4 wavelength plate side containing Y-4 in Table 4 is arranged on the side where the P polarized light from the display image projection device is incident, and the display image can be projected brightly and clearly when projecting an image.

[0152] <Evaluation of Double Image Brightness Ratio: Evaluation of Polarization Conversion Performance of 1 / 4 Wavelength Plate>

[0153] by Figure 7The configuration shown projects a line image from an image projection device (display image projection device 2) onto a functional glass 4 under the condition of emitting P polarized light, captures a reflected image with a colorimeter (Prometric IC-PMI) manufactured by KONICA MINOLTA, and evaluates the display image. For three points of position I (combined area of ​​X-4 P and Y-4 R) 5 cm from the left, position II (combined area of ​​X-4 Q and Y-4 Q) 30 cm from the left, and position III (combined area of ​​X-4 R and Y-4 P) 43 cm from the left in a width of 60 cm, the evaluation image of position I is captured from point X, which is 142 cm vertically away from the glass surface with position I as the starting point. The evaluation image of position II is captured from a position where the brightness meter is tilted 10° to the right from the vertical line from point X to position I. The evaluation image of position III is captured from a position where the brightness meter is tilted 15° to the right from the vertical line from point X to position I. By analyzing the captured images at each position, the double image brightness ratio was calculated by dividing the reflection brightness (main image) of the line image on the optical functional film surface in the composition of the functional glass by the reflection brightness (double image) of the line image at the air interface of the glass on the back side relative to the image projection device by 100. The results are shown in Table 6. In addition, in the examples with low double image brightness ratios shown in Table 6, the images projected on the functional glass are not easily observed as double, and it can be judged that the observability of the image is good.

[0154] [Example 2]

[0155] Regarding the polymerizable liquid crystal layer on the PET film produced by the above (3) to (4), the optical functional film, optical laminate and functional glass were produced in the same manner as in Example 1 except that the 1 / 4 wavelength plates whose slow axis angles in the regions P, Q and R are represented by X-5 and Y-5 in Table 4 were respectively laminated on both sides of the circularly polarized light reflecting layer. In addition, the double image brightness ratio was evaluated in the same manner using the obtained functional glass. The results are shown in Table 6.

[0156] [Example 3]

[0157] Regarding the polymerizable liquid crystal layer on the PET film produced by the above (3) to (4), the optical functional film, optical laminate and functional glass were produced in the same manner as in Example 1 except that the quarter-wavelength plates whose slow axis angles in the regions P, Q and R are represented by X-6 and Y-6 in Table 4 were respectively laminated on both sides of the circularly polarized light reflecting layer. In addition, the double image brightness ratio was evaluated in the same manner using the obtained functional glass. The results are shown in Table 6.

[0158] [Example 4]

[0159] Regarding the polymerizable liquid crystal layer on the PET film produced by the above (3) to (4), the optical functional film, optical laminate and functional glass were produced in the same manner as in Example 1 except that the quarter-wavelength plates whose slow axis angles in the regions P, Q and R are represented by X-3 and Y-3 in Table 4 were respectively laminated on both sides of the circularly polarized light reflecting layer. In addition, the double image brightness ratio was evaluated in the same manner using the obtained functional glass. The results are shown in Table 6.

[0160] [Comparative Example 1]

[0161] Regarding the polymerizable liquid crystal layer on the PET film produced by the above (3) to (4), the optical functional film, optical laminate and functional glass were produced in the same manner as in Example 1 except that the 1 / 4 wavelength plates whose slow axis angles in the regions P, Q and R are represented by X-1 and Y-1 in Table 4 were respectively laminated on both sides of the circularly polarized light reflecting layer. In addition, the double image brightness ratio was evaluated in the same manner using the obtained functional glass. The results are shown in Table 6.

[0162] [Comparative Example 2]

[0163] Regarding the polymerizable liquid crystal layer on the PET film produced by the above (3) to (4), the optical functional film, optical laminate and functional glass were produced in the same manner as in Example 1 except that the quarter-wavelength plates whose slow axis angles in the regions P, Q and R are represented by X-2 and Y-2 in Table 4 were respectively laminated on both sides of the circularly polarized light reflecting layer. In addition, the double image brightness ratio was evaluated in the same manner using the obtained functional glass. The results are shown in Table 6.

[0164] [Comparative Example 3]

[0165] Regarding the polymerizable liquid crystal layer on the PET film produced by the above (3) to (4), the optical functional film, optical laminate and functional glass were produced in the same manner as in Example 1 except that the quarter-wavelength plates whose slow axis angles in the regions P, Q and R are represented by X-7 and Y-7 in Table 4 were respectively laminated on both sides of the circularly polarized light reflecting layer. In addition, the double image brightness ratio was evaluated in the same manner using the obtained functional glass. The results are shown in Table 6.

[0166] [Table 6]

[0167]

[0168] The slow axis angle difference P is used as a reference and is therefore set to 0°.

[0169] The slow axis angle difference Q is the difference between the slow axis angle of the region P and the slow axis angle of the region Q.

[0170] The slow axis angle difference R is the difference between the slow axis angle of the region P and the slow axis angle of the region R.

[0171] From the results of Examples 1 to 4 and Comparative Examples 1 to 3, it can be seen that in Comparative Example 1, which does not have more than two slow axis bands with different slow axis angles in the same plane, and Comparative Examples 2 to 3, which have more than two slow axis bands with different slow axis angles in the same plane but the maximum slow axis angle difference is outside the range of more than 5° and less than 30°, due to different projection positions, when the incident P polarized light penetrates the optical functional film, the S polarized light component will increase, so the S polarized light will be reflected at the glass plate interface on the opposite side of the incident plane. Therefore, the double image brightness ratio will increase, and the image projected on the functional glass will be easily observed as double. As a result, the unevenness of the double image generation will increase, and the observability of the image in a wide range will be reduced.

[0172] <Test Example 1 Using a Half Wavelength Plate>

[0173] <Example 5>

[0174] In the above (3), the coating liquid shown in Table 3 was applied to the rubbed surface of each PET film at room temperature using a wire bar coater so that the thickness of each 1 / 2 wavelength plate obtained after drying was about 2 μm. The surface of each PET film was divided into three regions of P, Q, and R from the left with a width of 20 cm each, and the rubbing angle was set for each individual region so that the angle formed by the longitudinal axis (vertical axis) of the PET film and the slow axis of the 1 / 2 wavelength plate became a predetermined angle as shown in Table 7, and the rubbing treatment was performed.

[0175] [Table 7]

[0176]

[0177] Each obtained coating film was heated at 80°C for 2 minutes to remove the solvent and form a liquid crystal phase. Then, a high-pressure mercury lamp (manufactured by HARISON TOSHIBA LIGHTING Co., Ltd.) was irradiated with UV for 5 to 10 seconds at an output of 120W to fix the liquid crystal phase, and 7 pieces of each of the X group and Y group of 1 / 2 wavelength plates with a predetermined slow axis band formed on a PET film with a polymerizable liquid crystal layer were made, totaling 14 pieces. The 1 / 2 wavelength plate was cut to a size of 60cm in the width direction and 50cm in the length direction including all regions of regions P, Q and R. The slow axis bands of P, Q and R were formed in the same plane from the left at 20cm each in the width direction (consistent with the range shown in Table 7). In addition, the phase difference value of each region of the obtained 1 / 2 wavelength plate was measured with an automatic birefringence meter ("KOBRA-21ADH" manufactured by Prince Measurement Co., Ltd.), and the phase difference value at 546nm was 290nm for 7 pieces of the X group and 250nm for 7 pieces of the Y group.

[0178] The 1 / 2 wavelength plates whose slow axis angles in the regions P, Q and R are represented as X-4 and Y-4 in Table 4 were used as the polymerizable liquid crystal layer on the produced PET film, and the same acrylic adhesive as the adhesive used in the above (5) was used to laminate the 1 / 2 wavelength plates in the width direction on the polymerizable liquid crystal layer sides so that the regions in the width direction of the plane became a combination of X-4 P and Y-4 R, X-4 Q and Y-4 Q, and X-4 R and Y-4 P. Next, the PET film of each 1 / 2 wavelength plate was peeled off for the following measurement and evaluation.

[0179] An optical functional film having two 1 / 2 wavelength plates laminated thereon was prepared in the above manner. The spectral characteristics of the natural light transmittance and polarized light transmittance of the obtained two-layer 1 / 2 wavelength plate were measured, and the results are shown in FIG. Fig. 9 . In addition, in the double-layer 1 / 2 wavelength plate, the average transmittance in the visible light wavelength region in the front direction (incident angle 56°) is about 79%, and the polarized light transmittance is about 10%. In addition. Using the "UV-Visible-Near Infrared Spectrophotometer UV-3600" manufactured by Shimadzu Corporation, the double-layer 1 / 2 wavelength plate is set between parallel polarizing plates at an incident angle of 56° and the polarized light transmittance is measured.

[0180] <Production of Optical Laminated Body>

[0181] A transparent polyvinyl butyral intermediate film with a thickness of 0.38 mm and containing triethylene glycol di-2-ethylhexanoate as a plasticizer is cut into the same size as the double-layer 1 / 2 wavelength plate to be produced, and the above-mentioned double-layer 1 / 2 wavelength plate is arranged between two polyvinyl butyral intermediate films, and then pressurized and crimped using a laminating machine to produce an optical laminate.

[0182] <Production of functional glass>

[0183] The optical laminate is placed between two glass plates of the same size as the double-layer 1 / 2 wavelength plate and 2 mm thick, and then pressurized and heated to obtain functional glass. First, the optical laminate and the transparent glass plate are stacked on the transparent glass plate in sequence. It is wrapped in a rubber bag and degassed in an autoclave heated to 90°C for 10 minutes for preliminary bonding. After cooling to room temperature, it is taken out of the rubber bag and placed in the autoclave again at 135°C, 12 kg / cm 2 The functional glass with good appearance and inserted optical laminate was produced by heating and pressing under high pressure for 30 minutes. The average transmittance of the obtained functional glass in the visible light wavelength region in the front direction (incident angle 56°) was about 72%, and the polarized light transmittance was about 6%.

[0184] <Production of Head-Up Display and Evaluation of Display Images>

[0185] As Figure 5 A head-up display is produced in the configuration shown. In addition, as for the display image projection device 2 and the reflector 3, a liquid crystal display panel capable of emitting S-polarized light to the functional glass 4 is provided, and the functional glass produced as described above is used as the functional glass 4. In a dark room, the width direction of the optical functional film in the composition of the functional glass 4 is adjusted in such a manner that the S-polarized light emitted by the display image projection device 2 is incident at a Brewster angle (about 56°) relative to the functional glass 4 at an incident angle X of the S-polarized light. The glass on the side of the 1 / 2 wavelength plate containing the Y group of Table 7 is provided on the side where the S-polarized light is emitted from the display image projection device, and when projecting an image, the display image can be projected brightly and clearly.

[0186] <Evaluation of Double Image Brightness Ratio: Evaluation of Polarization Conversion Performance of Half Wavelength Plate>

[0187] by Figure 7 The configuration shown projects a line image from an image projection device (display image projection device 2) onto a functional glass 4 under the condition of emitting with S polarized light, and photographs a reflected image with a colorimeter (Prometric IC-PMI) manufactured by KONICA MINOLTA, and evaluates the display image. For three points of position I (combination area of ​​X-4 P and Y-4 R) 5 cm from the left, position II (combination area of ​​X-4 Q and Y-4 Q) 30 cm from the left, and position III (combination area of ​​X-4 R and Y-4 P) 43 cm from the left, the evaluation image of position I is photographed from point X which is 142 cm vertically away from the glass surface with position I as the starting point. The evaluation image of position II is photographed from a position where the brightness meter is tilted 10° to the right from the vertical line from point X to position I. The evaluation image of position III is photographed from a position where the brightness meter is tilted 15° to the right from the vertical line from point X to position I. By analyzing the captured images at each position, the double image brightness ratio was calculated by dividing the reflection brightness (main image) of the line image of the air interface of the glass on the image projection device side in the composition of the functional glass by the reflection brightness (double image) of the line image of the air interface of the glass on the back side relative to the image projection device by 100. The results are shown in Table 8. In addition, in the examples with low double image brightness ratios shown in Table 8, the images projected on the functional glass are not easily observed as double, and it can be judged that the observability of the image is good.

[0188] [Example 6]

[0189] The polymerizable liquid crystal layer on the PET film was stacked with 1 / 2 wavelength plates having slow axis angles X-5 and Y-5 in Table 7, respectively, and an optical functional film, an optical laminate, and a functional glass were prepared in the same manner as in Example 5. In addition, the double image brightness ratio was evaluated in the same manner using the obtained functional glass. The results are shown in Table 8.

[0190] [Example 7]

[0191] The optical functional film, optical laminate and functional glass were prepared in the same manner as in Example 5 except that the polymerizable liquid crystal layer on the PET film was stacked with 1 / 2 wavelength plates having slow axis angles in the regions P, Q and R as shown in Table 7, respectively. In addition, the double image brightness ratio was evaluated in the same manner using the obtained functional glass. The results are shown in Table 8.

[0192] [Example 8]

[0193] The optical functional film, optical laminate and functional glass were prepared in the same manner as in Example 5 except that the polymerizable liquid crystal layer on the PET film was laminated with 1 / 2 wavelength plates having slow axis angles in the regions P, Q and R as shown in Table 7, respectively. In addition, the double image brightness ratio was evaluated in the same manner using the obtained functional glass. The results are shown in Table 8.

[0194] [Comparative Example 4]

[0195] The optical functional film, optical laminate and functional glass were prepared in the same manner as in Example 5 except that the polymerizable liquid crystal layer on the PET film was stacked with 1 / 2 wavelength plates whose slow axis angles in the regions P, Q and R were indicated as X-1 and Y-1 in Table 7. In addition, the double image brightness ratio was evaluated in the same manner using the obtained functional glass. The results are shown in Table 8.

[0196] [Comparative Example 5]

[0197] The optical functional film, optical laminate and functional glass were prepared in the same manner as in Example 5 except that the polymerizable liquid crystal layer on the PET film was stacked with 1 / 2 wavelength plates whose slow axis angles in the regions P, Q and R were indicated as X-2 and Y-2 in Table 7. In addition, the double image brightness ratio was evaluated in the same manner using the obtained functional glass. The results are shown in Table 8.

[0198] [Comparative Example 6]

[0199] The optical functional film, optical laminate and functional glass were prepared in the same manner as in Example 5 except that the polymerizable liquid crystal layer on the PET film was stacked with 1 / 2 wavelength plates having slow axis angles in the regions P, Q and R as shown in Table 7, respectively. In addition, the double image brightness ratio was evaluated in the same manner using the obtained functional glass. The results are shown in Table 8.

[0200] [Table 8]

[0201]

[0202] The slow axis angle difference P is used as a reference and is therefore set to 0°.

[0203] The slow axis angle difference Q is the difference between the slow axis angle of the region P and the slow axis angle of the region Q.

[0204] The slow axis angle difference R is the difference between the slow axis angle of the region P and the slow axis angle of the region R.

[0205] From the results of Examples 5 to 8 and Comparative Examples 4 to 6, it can be seen that in Comparative Example 4, which does not have more than two slow axis bands with different slow axis angles in the same plane, and Comparative Examples 5 to 6, which have more than two slow axis bands with different slow axis angles in the same plane but the maximum slow axis angle difference is outside the range of more than 5° and less than 30°, due to different projection positions, when the incident S-polarized light penetrates the optical functional film, it will not be converted into P-polarized light, and more S-polarized light components will remain. Therefore, the S-polarized light will be reflected at the air interface of the glass plate on the opposite side of the incident surface. Therefore, the double image brightness ratio will increase, and the image projected on the functional glass will be easily observed as double. As a result, the unevenness of the double image generation will become larger, and the observability of the image in a wide range will be reduced.

[0206] <Test Example 2 Using a Half Wavelength Plate>

[0207] <Example 9>

[0208] In the above (3), the coating liquid shown in Table 3 was applied to the rubbed surface of each PET film at room temperature using a wire bar coater so that the thickness of each 1 / 2 wavelength plate obtained after drying was about 2 μm. The surface of each PET film was divided into three regions of P, Q, and R from the left side with each region having a width of 20 cm, and the rubbing angle was set for each individual region so that the angle formed by the longitudinal axis (vertical axis) of the PET film and the slow axis of the 1 / 2 wavelength plate became a predetermined angle as shown in Table 9, and the rubbing treatment was performed.

[0209] [Table 9]

[0210]

[0211] Each obtained coating film was heated at 80°C for 2 minutes to remove the solvent and form a liquid crystal phase. Then, a high-pressure mercury lamp (manufactured by HARISON TOSHIBA LIGHTING Co., Ltd.) was irradiated with UV for 5 to 10 seconds at an output of 120W to fix the liquid crystal phase, and 7 1 / 2 wavelength plates with a predetermined slow axis band formed on a PET film with a polymerizable liquid crystal layer were made. The 1 / 2 wavelength plate was cut to a size of 60 cm in the width direction and 50 cm in the length direction including all regions of regions P, Q and R. The slow axis bands of P, Q and R were formed in the same plane from the left side at 20 cm each in the width direction (consistent with the range shown in Table 9). In addition, the phase difference value of each region of the obtained 1 / 2 wavelength plate was measured with an automatic birefringence meter ("KOBRA-21ADH" manufactured by Prince Measurement Co., Ltd.), and the phase difference value at 546nm was 275nm.

[0212] A half-wave plate having slow axis angles in regions P, Q, and R represented by X-4 in Table 9 was used as a polymerizable liquid crystal layer on the produced PET film, and the same acrylic adhesive as the adhesive used in (5) was applied to the polymerizable liquid crystal layer, and the layer was bonded to a flat glass plate having the same size as the half-wave plate and a thickness of 2 mm. Thereafter, the PET film was peeled off from the half-wave plate in order to carry out the following measurements and evaluations.

[0213] An optical functional film containing one half-wave plate was prepared in the above manner. The spectral characteristics of the natural light transmittance and polarized light transmittance of the obtained half-wave plate were measured, and the results are shown in FIG. Fig.10 . In addition, the average transmittance of the obtained 1 / 2 wavelength plate in the visible light wavelength region in the front direction (incident angle 56°) was about 84%, and the polarized light transmittance was about 18%. In addition, using the "UV-3600 Ultraviolet-Visible-Near Infrared Spectrophotometer" manufactured by Shimadzu Corporation, the 1 / 2 wavelength plate was set between parallel polarizing plates at an incident angle of 56° and the polarized light transmittance was measured.

[0214] <Production of Optical Laminated Body>

[0215] A transparent polyvinyl butyral intermediate film with a thickness of 0.38 mm and containing triethylene glycol di-2-ethylhexanoate as a plasticizer is cut into the same size as the 1 / 2 wavelength plate to be produced, and a piece of polyvinyl butyral intermediate film is arranged on the polymerizable liquid crystal layer side of the above-mentioned 1 / 2 wavelength plate, and then pressurized and crimped by a laminating machine to obtain an optical laminate.

[0216] <Production of functional glass>

[0217] The polyvinyl butyral intermediate film side of the produced optical laminate is placed on a glass plate of the same size as the 1 / 2 wavelength plate and 2 mm thick, and then pressurized and heated to obtain functional glass. First, the optical laminate is overlapped on a transparent glass plate. It is wrapped in a rubber bag and degassed in an autoclave heated to 90°C for 10 minutes for preliminary bonding. After cooling to room temperature, it is taken out of the rubber bag and again in the autoclave at 135°C, 12 kg / cm 2 The functional glass with good appearance and inserted optical laminate was heated and pressed for 30 minutes under high pressure. The average transmittance of the obtained functional glass in the visible light wavelength region in the front direction (incident angle 56°) was about 73%, and the polarized light transmittance was about 14%.

[0218] <Production of Head-Up Display and Evaluation of Display Images>

[0219] As Figure 5 The head-up display is manufactured in the configuration shown. In addition, as for the display image projection device 2 and the reflector 3, a liquid crystal display panel capable of emitting S polarized light to the functional glass 4 is provided, and the functional glass manufactured as described above is used as the functional glass 4. In a dark room, the width direction of the optical functional film in the composition of the functional glass 4 is adjusted in such a manner that the S polarized light emitted by the display image projection device 2 is incident at a Brewster angle (about 56°) relative to the functional glass 4 at an incident angle X of the S polarized light. The glass on the 1 / 2 wavelength plate side containing X-4 in Table 9 is arranged on the side where the S polarized light is emitted from the display image projection device, and the display image can be projected brightly and clearly when projecting an image.

[0220] <Evaluation of Double Image Brightness Ratio: Evaluation of Polarization Conversion Performance of Half Wavelength Plate>

[0221] by Figure 7The configuration shown projects a line image from an image projection device (display image projection device 2) onto a functional glass 4 under the condition of emitting with S polarized light, captures a reflected image with a colorimeter (Prometric IC-PMI) manufactured by KONICA MINOLTA, and evaluates the display image. For three points of position I (the region of P of X-4) 18 cm from the left, position II (the region of Q of X-4) 30.5 cm from the left, and position III (the region of R of X) 43 cm from the left in a width of 60 cm, the evaluation image of position I is captured from point X, which is 142 cm vertically away from the glass surface with position I as the starting point. The evaluation image of position II is captured from a position where the brightness meter is tilted 5° to the right from the vertical line from point X to position I. The evaluation image of position III is captured from a position where the brightness meter is tilted 10° to the right from the vertical line from point X to position I. By analyzing the captured images at each position, the double image brightness ratio was calculated by dividing the reflection brightness (main image) of the line image of the air interface of the glass on the image projection device side in the composition of the functional glass by the reflection brightness (double image) of the line image of the air interface of the glass on the back side relative to the image projection device by 100. The results are shown in Table 10. In addition, in the examples with low double image brightness ratios shown in Table 10, the images projected on the functional glass are not easily observed as double, and it can be judged that the observability of the image is good.

[0222] [Example 10]

[0223] The polymerizable liquid crystal layer on the PET film was prepared in the same manner as in Example 9 except that a half-wavelength plate having a slow axis angle represented by X-5 in Table 9 in the regions P, Q, and R was used. In addition, the double image brightness ratio was evaluated in the same manner using the obtained functional glass. The results are shown in Table 10.

[0224] [Example 11]

[0225] The polymerizable liquid crystal layer on the PET film was prepared in the same manner as in Example 9 except that a half-wavelength plate having a slow axis angle represented by X-6 in Table 9 in the regions P, Q, and R was used. In addition, the double image brightness ratio was evaluated in the same manner using the obtained functional glass. The results are shown in Table 10.

[0226] [Example 12]

[0227] The polymerizable liquid crystal layer on the PET film was prepared in the same manner as in Example 9 except that a half-wavelength plate having a slow axis angle represented by X-3 in Table 9 in the regions P, Q, and R was used. In addition, the double image brightness ratio was evaluated in the same manner using the obtained functional glass. The results are shown in Table 10.

[0228] [Comparative Example 7]

[0229] The polymerizable liquid crystal layer on the PET film was prepared in the same manner as in Example 9 except that a half-wavelength plate having a slow axis angle represented by X-1 in Table 9 in the regions P, Q, and R was used. In addition, the double image brightness ratio was evaluated in the same manner using the obtained functional glass. The results are shown in Table 10.

[0230] [Comparative Example 8]

[0231] The polymerizable liquid crystal layer on the PET film was prepared in the same manner as in Example 9 except that a half-wavelength plate having a slow axis angle represented by X-2 in Table 9 in the regions P, Q, and R was used. In addition, the double image brightness ratio was evaluated in the same manner using the obtained functional glass. The results are shown in Table 10.

[0232] [Table 10]

[0233]

[0234] The slow axis angle difference P is used as a reference and is therefore set to 0°.

[0235] The slow axis angle difference Q is the difference between the slow axis angle of the region P and the slow axis angle of the region Q.

[0236] The slow axis angle difference R is the difference between the slow axis angle of the region P and the slow axis angle of the region R.

[0237] From the results of Examples 9 to 12 and Comparative Examples 7 to 8, it can be seen that in Comparative Example 7, which does not have more than two slow-axis bands with different slow-axis angles in the same plane, and in Comparative Example 8, which has more than two slow-axis bands with different slow-axis angles in the same plane but the maximum slow-axis angle difference is outside the range of more than 5° and less than 30°, due to different projection positions, when the incident S-polarized light penetrates the optical functional film, it will not be converted into P-polarized light, and more S-polarized light components will remain. Therefore, the S-polarized light will be reflected at the air interface of the glass plate on the opposite side of the incident surface. Therefore, the double image brightness ratio will increase, and the image projected on the functional glass will be easily observed as double. As a result, the unevenness of the double image generation will become larger, and the observability of the image in a wide range will be reduced.

[0238] As can be seen from the above, by using the optical functional film for head-up display of the present invention, S polarized light or P polarized light incident at any incident angle can be more efficiently converted back to the original S polarized light or P polarized light. Therefore, an optical functional film having excellent polarization conversion efficiency in a wide range can be obtained. In addition, by using the optical functional film of the present invention in a HUD system, a very clear display image can be observed in a wide range.

[0239] (Industrial Applicability)

[0240] The head-up display system including the optical functional film of the present invention can eliminate uneven generation of double images due to the projection position, that is, can suppress the generation of double images without depending on the shooting position. Therefore, the observer can use the head-up display system without stress.

[0241] Description of Reference Numerals

[0242] 1 Observer

[0243] 2 Display image projection device

[0244] 3 Reflector

[0245] 4 Functional glass

[0246] 5 Optical Path

[0247] 6 virtual image

[0248] 7 Angle of incidence

[0249] 8 Angle of incidence

[0250] 9A Display section

[0251] 9B Display section

[0252] 10 Optical laminate

[0253] 101 Optical Functional Film

[0254] 102 Intermediate film

[0255] 20 Functional glass

[0256] 201 Glass Plate

[0257] 30 Optical functional film

[0258] 31 Slow axis angle in slow axis band A

[0259] 32 Slow axis with A

[0260] 33 Slow axis angle in slow axis band B

[0261] 34 Slow axis with slow axis B

[0262] 40 Optical functional film

[0263] 41 Slow axis angle in slow axis band C

[0264] 42 Slow axis with C slow axis

[0265] 43 Slow axis angle in slow axis band D

[0266] 44 Slow axis with D

[0267] 45 Slow axis angle in slow axis band E

[0268] 46 Slow axis The slow axis of band E.

Claims

1. A head-up display system, comprising an optical functional film for a head-up display, wherein the optical functional film for a head-up display has two or more slow axis zones with different slow axis angles in the same plane, and the maximum slow axis angle difference is more than 5° and less than 30°; Regarding the slow axis with an incident angle of 90° where the light emitted from the image display projection device is vertically incident on the optical functional film, and the slow axis with an incident angle of 80° where the light is incident from a position where the axis is inclined 10° in the horizontal direction from the axis perpendicular to the surface of the optical functional film, the angle formed by these two slow axes is greater than 5° and less than 20°.

2. A head-up display system, comprising an optical laminate for a head-up display, the optical laminate for a head-up display comprising: an optical functional film for a head-up display, having two or more slow axis zones with different slow axis angles in the same plane, and the maximum slow axis angle difference is more than 5° and less than 30°; and an intermediate film; Regarding the slow axis with an incident angle of 90° where the light emitted from the image display projection device is vertically incident on the optical functional film, and the slow axis with an incident angle of 80° where the light is incident from a position where the axis is inclined 10° in the horizontal direction from the axis perpendicular to the surface of the optical functional film, the angle formed by these two slow axes is greater than 5° and less than 20°.

3. A head-up display system, comprising a functional glass for a head-up display, the functional glass for a head-up display comprising: an optical functional film for a head-up display, having two or more slow axis zones with different slow axis angles in the same plane, and the maximum slow axis angle difference is more than 5° and less than 30°; an intermediate film; and a glass plate; Regarding the slow axis with an incident angle of 90° where the light emitted from the image display projection device is vertically incident on the optical functional film, and the slow axis with an incident angle of 80° where the light is incident from a position where the axis is inclined 10° in the horizontal direction from the axis perpendicular to the surface of the optical functional film, the angle formed by these two slow axes is greater than 5° and less than 20°.

4. The head-up display system according to any one of claims 1 to 3, wherein: The maximum slow axis angle difference is greater than or equal to 10° and less than or equal to 25°.

5. The head-up display system according to any one of claims 1 to 3, wherein: Regarding the slow axis with an incident angle of 90° where the light emitted from the image display projection device is vertically incident on the optical functional film, and the slow axis with an incident angle of 70° where the light is incident from a position where the axis is inclined 20° in the horizontal direction from the axis perpendicular to the surface of the optical functional film, the angle formed by these two slow axes is greater than 10° and less than 30°.

6. The head-up display system according to any one of claims 1 to 3, comprising the functional glass, wherein the incident angle of the light emitted from the display image projection device incident on the functional glass is in the range of α-10° to α+10° relative to the Brewster angle α.

Images