Optical laminate, laminated optical film, optical article, and virtual reality display device

Abstract

The present invention addresses the problem of providing: an optical laminate which can be used in a reflective circular polarizer and which causes little ghosting when used in a virtual reality display device, an electronic viewfinder or the like; a laminated optical film provided with a reflective circular polarizer; an optical article provided with the optical laminate; and a virtual reality display device including the optical article. This optical laminate is provided with a first layer, a second layer, a third layer, and a fourth layer in this order, each of the first to fourth layers is a cholesteric liquid crystal layer, each of the first to fourth layers has light reflectivity, the central wavelength of the reflected light of the first layer is in the range of 430-570 nm, the central wavelength of the reflected light of the second layer is in the range of 550-670 nm, and the central wavelength of the reflected light of the third layer is in the range of 550-670 nm. The center wavelength of the reflected light of the third layer is in the range of 430-570 nm, the center wavelength of the reflected light of the fourth layer is in the range of 550-670 nm, and the sign of retardation in the film thickness direction at a wavelength of 550 nm of the first layer is opposite to the sign of retardation in the film thickness direction at a wavelength of 550 nm of the second layer. The sign of retardation in the film thickness direction at a wavelength of 550 nm in the third layer is opposite to the sign of retardation in the film thickness direction at a wavelength of 550 nm in the fourth layer.

Description

Technical Field

[0001] The present invention relates to an optical laminate, a laminated optical film, an optical article and a virtual reality display device. Background Art

[0002] A reflective polarizer is a polarizer that reflects a portion of the polarized light in the incident light and transmits another portion of the polarized light. The reflected light and the transmitted light based on the reflective polarizer are in mutually orthogonal polarization states. Here, mutually orthogonal polarization states refer to polarization states that are located at opposite diameters on the Poincaré sphere, for example, mutually orthogonal linear polarizations, or right-handed circularly polarized light and left-handed circularly polarized light correspond to this.

[0003] As a reflective linear polarizer that converts transmitted light and reflected light into linearly polarized light, for example, a film obtained by stretching a dielectric multilayer film as described in Patent Document 1 and a wire grid polarizer as described in Patent Document 2 are known.

[0004] As a reflective circular polarizer that converts transmitted light and reflected light into circularly polarized light, for example, a film having a light reflecting layer in which a cholesteric liquid crystal phase is fixed as described in Patent Document 3 is known.

[0005] The purpose of using a reflective polarizer is to extract only specific polarized light from incident light, or to separate incident light into two polarized lights. For example, in a liquid crystal display device, it can be used as a brightness enhancement film to improve light utilization efficiency by reflecting unnecessary polarized light from a backlight source and reusing it. In addition, in a liquid crystal projector, it can also be used as a beam splitter that separates light from a light source into two linearly polarized lights and supplies them to a liquid crystal panel respectively.

[0006] In addition, in recent years, a method of using a reflective polarizer has been proposed to generate a virtual image and a real image by reflecting a part of the external light or the light from the image display device. For example, Patent Document 4 discloses a vehicle-mounted rearview mirror (Room Mirror) that uses a reflective polarizer to reflect light from the rear. In addition, Patent Document 5 discloses a method of generating a virtual image, in which light is reflected between a reflective polarizer and a half-reflective mirror and the light is reciprocated, so as to make the display part small and thin in a virtual reality display device, an electronic viewfinder, etc.

[0007] Previous technical literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2011-053705

[0010] Patent Document 2: Japanese Patent Application Publication No. 2015-028656

[0011] Patent Document 3: Japanese Patent No. 6277088

[0012] Patent Document 4: Japanese Patent Application Publication No. 2017-227720

[0013] Patent Document 5: Japanese Patent Application Laid-Open No. 7-120679 Summary of the invention

[0014] Technical issues to be solved by the invention

[0015] Through the research of the present inventors, it was found that when a virtual image and a real image are generated by reflecting a part of the external light and the light from the image display device by a reflective polarizer, the image clarity is reduced in the conventional reflective polarizers described in Documents 1 and 2. In response to this, it was found that a good image clarity can be obtained by using a reflective circular polarizer having a light reflecting layer that fixes a cholesteric liquid crystal phase. The present inventors believe that the reason is that by having a light reflecting layer that fixes a cholesteric liquid crystal phase, a reflective circular polarizer having a high polarization degree can be realized in the form of a thin film, and therefore it is not easily affected by the mixing of foreign matter or the fluctuation caused by the coarseness and density of the material distribution.

[0016] Furthermore, according to the research of the inventors, in virtual reality display devices and electronic viewfinders, in addition to reflected light, transmitted light is also used. In this case, it is important to suppress ghosting that is visually recognized by transmitting the transmitted light that was originally cut off. In the conventional reflective circular polarizer described in Document 3, ghosting suppression was observed, and there is room for further improvement.

[0017] The present invention is completed in view of the above-mentioned problems. The problem to be solved by the present invention is to provide an optical laminate that can be used for a reflective circular polarizer and produces less ghosting when used in a virtual reality display device or an electronic viewfinder, a laminated optical film having the reflective circular polarizer, an optical article having the optical laminate, and a virtual reality display device including the optical article.

[0018] Means for solving technical problems

[0019] The present inventors have conducted intensive studies on the above-mentioned subject and have found that the above-mentioned subject can be achieved by the following configuration.

[0020] <1>

[0021] An optical laminate comprises a first layer, a second layer, a third layer and a fourth layer in this order,

[0022] The first layer to the fourth layer are all cholesteric liquid crystal layers.

[0023] All of the first layer to the fourth layer have light reflectivity,

[0024] The central wavelength of the reflected light of the first layer is within the range of 430 to 570 nm.

[0025] The central wavelength of the reflected light of the second layer is within the range of 550 to 670 nm.

[0026] The central wavelength of the reflected light of the third layer is in the range of 430 to 570 nm.

[0027] The central wavelength of the reflected light of the fourth layer is within the range of 550 to 670 nm.

[0028] The sign of the retardation of the first layer in the film thickness direction at a wavelength of 550 nm is opposite to the sign of the retardation of the second layer in the film thickness direction at a wavelength of 550 nm.

[0029] The sign of the retardation of the third layer in the film thickness direction at a wavelength of 550 nm is opposite to the sign of the retardation of the fourth layer in the film thickness direction at a wavelength of 550 nm.

[0030] <2>

[0031] The optical laminate according to <1>, wherein

[0032] The central wavelength of the reflected light of the first layer is within the range of 430 to 480 nm.

[0033] The central wavelength of the reflected light of the second layer is in the range of 600 to 670 nm.

[0034] The central wavelength of the reflected light from the third layer is within the range of 520 to 570 nm.

[0035] The central wavelength of the reflected light of the fourth layer is within the range of 550 to 620 nm.

[0036] <3>

[0037] The optical laminate according to <1> or <2>, wherein

[0038] One of the first layer and the second layer is a cholesteric liquid crystal layer formed using a rod-shaped liquid crystal compound, and the other is a cholesteric liquid crystal layer formed using a discotic liquid crystal compound.

[0039] One of the third layer and the fourth layer is a cholesteric liquid crystal layer formed using a rod-like liquid crystal compound, and the other is a cholesteric liquid crystal layer formed using a discotic liquid crystal compound.

[0040] <4>

[0041] The optical laminate according to any one of <1> to <3>,

[0042] From the first layer to the fourth layer, the difference in film thickness of each layer is less than 0.5 μm.

[0043] <5>

[0044] A laminated optical film comprises at least a reflective circular polarizer, a phase difference layer for converting circularly polarized light into linearly polarized light, and a linear polarizer in sequence, wherein:

[0045] The reflective circular polarizer is the optical laminate according to any one of <1> to <4>.

[0046] <6>

[0047] The laminated optical film according to <5>, wherein

[0048] The linear polarizer includes at least a light absorption anisotropic layer containing a liquid crystal compound and a dichroic substance.

[0049] <7>

[0050] The laminated optical film according to <5> or <6>, further comprising a positive C plate.

[0051] <8>

[0052] The laminated optical film according to any one of <5> to <7>, further comprising an antireflection layer on the surface.

[0053] <9>

[0054] The laminated optical film according to <8>, wherein

[0055] The anti-reflection layer is a moth-eye film or an AR film.

[0056] <10>

[0057] The laminated optical film according to any one of <5> to <9>, further comprising a resin substrate having a peak temperature of tan δ of 170°C or less.

[0058] <11>

[0059] An optical article comprising the optical laminate according to any one of <1> to <4>.

[0060] <12>

[0061] A virtual reality display device, comprising the optical article described in <11>.

[0062] Effects of the Invention

[0063] The present invention can provide an optical laminate that can be used for a reflective circular polarizer and that generates less ghosting when used in a virtual reality display device or an electronic viewfinder.

[0064] Furthermore, according to the present invention, there can be provided a laminated optical film including the reflective circular polarizer, an optical article including the optical laminate, and a virtual reality display device including the optical article. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 It is a schematic diagram which shows an example of the optical laminated body which concerns on 1st Embodiment of this invention.

[0066] Figure 2 This is an example of a virtual reality display device using the laminated optical film of the present invention.

[0067] Figure 3 This is an example of a virtual reality display device using the laminated optical film of the present invention.

[0068] Figure 4 This is a schematic diagram showing an example of the laminated optical film of the present invention. DETAILED DESCRIPTION

[0069] Hereinafter, the present invention will be described in detail. Although the description of the constituent elements described below may be made based on representative embodiments and specific examples, the present invention is not limited to such embodiments.

[0070] In addition, in this specification, the numerical range expressed using "to" means a range including the numerical values ​​described before and after "to" as the lower limit and the upper limit.

[0071] In this specification, "orthogonal" does not mean 90° in the strict sense, but means 90°±10°, preferably 90°±5°. Also, "parallel" does not mean 0° in the strict sense, but means 0°±10°, preferably 0°±5°. Furthermore, "45°" does not mean 45° in the strict sense, but means 45°±10°, preferably 45°±5°.

[0072] In this specification, the "absorption axis" refers to the polarization direction in which the absorbance in the plane becomes the maximum when linear polarized light is incident. Furthermore, the "reflection axis" refers to the polarization direction in which the reflectivity in the plane becomes the maximum when linear polarized light is incident. Furthermore, the "transmission axis" refers to the direction in the plane that is orthogonal to the absorption axis or the reflection axis. Furthermore, the "slow axis" refers to the direction in which the refractive index in the plane becomes the maximum.

[0073] In this specification, unless otherwise specified, phase difference refers to in-plane retardation, which is recorded as Re(λ). Here, Re(λ) represents in-plane retardation at a wavelength λ, and unless otherwise specified, the wavelength λ is 550 nm.

[0074] In addition, the retardation in the thickness direction at the wavelength λ is described as Rth(λ) in this specification. When Rth(λ) is not described, the wavelength λ is assumed to be 550 nm.

[0075] Re(λ) and Rth(λ) can be measured at a wavelength of λ using AxoScan OPMF-1 (manufactured by Opto Science, Inc.). The average refractive index ((nx+ny+nz) / 3) and the film thickness (d (μm)) can be input into AxoScan to calculate

[0076] Slow axis direction (°)

[0077] Re(λ)=R0(λ)

[0078] Rth(λ)=((nx+ny) / 2-nz)×d.

[0079] As the optical laminate of the present invention, the first embodiment can be mentioned.

[0080] Hereinafter, a first embodiment of the optical laminate of the present invention will be described.

[0081] [First embodiment]

[0082] The optical laminate according to the first embodiment of the present invention includes a first layer, a second layer, a third layer, and a fourth layer in this order.

[0083] The first layer to the fourth layer are all cholesteric liquid crystal layers.

[0084] All of the first to fourth layers have light reflectivity.

[0085] The central wavelength of the reflected light of the first layer is within the range of 430 to 570 nm.

[0086] The central wavelength of the reflected light of the second layer is within the range of 550 to 670 nm.

[0087] The central wavelength of the reflected light of the third layer is in the range of 430 to 570 nm.

[0088] The central wavelength of the reflected light of the fourth layer is within the range of 550 to 670 nm.

[0089] The sign of Rth of the first layer at a wavelength of 550 nm is opposite to the sign of Rth of the second layer at a wavelength of 550 nm.

[0090] The sign of Rth of the third layer at a wavelength of 550 nm is opposite to the sign of Rth of the fourth layer at a wavelength of 550 nm.

[0091] The optical laminate according to the first embodiment of the present invention will be described with reference to the drawings. Figure 1 It is a schematic cross-sectional view showing a structural example of the optical laminate 12 according to the first embodiment.

[0092] exist Figure 1 In the embodiment shown, the optical laminate 12 is sequentially laminated with a first layer 31, a second layer 32, a third layer 33, and a fourth layer 34, which respectively satisfy the above requirements. In addition, the sign of Rth of the first layer 31 is opposite to the sign of Rth of the second layer 32, and the sign of Rth of the third layer 33 is opposite to the sign of Rth of the fourth layer 34.

[0093] The optical laminate of the first embodiment of the present invention can be used for a reflective circular polarizer. It is considered that when the optical laminate has the above structure, the Rth of the first layer and the Rth of the second layer cancel each other, and the Rth of the third layer and the Rth of the fourth layer cancel each other, so that the occurrence of ghosting can be suppressed even for incident light from an oblique direction.

[0094] Hereinafter, a first embodiment of the present invention will be described in detail.

[0095] 〔First to fourth floors〕

[0096] The optical laminate according to the first embodiment of the present invention includes a first layer, a second layer, a third layer, and a fourth layer in this order.

[0097] The first to fourth layers are cholesteric liquid crystal layers having light reflectivity.

[0098] The cholesteric liquid crystal layer is a layer in which a liquid crystal compound is set to a cholesteric liquid crystal phase and the cholesteric liquid crystal phase is fixed. As such a cholesteric liquid crystal layer, a known cholesteric liquid crystal layer can be used, for example, a liquid crystal layer described in Japanese Patent Publication No. 2020-060627 can be used.

[0099] The cholesteric liquid crystal layer is preferably a cholesteric liquid crystal layer formed using a rod-shaped liquid crystal compound or a cholesteric liquid crystal layer formed using a disc-shaped liquid crystal compound. In a cholesteric liquid crystal layer formed using a rod-shaped liquid crystal compound, Rth tends to be positive, and in a cholesteric liquid crystal layer formed using a disc-shaped liquid crystal compound, Rth tends to be negative.

[0100] The cholesteric liquid crystal layer formed using a rod-like liquid crystal compound is a cholesteric liquid crystal layer formed using a first liquid crystal compound substantially composed of a rod-like liquid crystal compound, and is substantially composed of a rod-like liquid crystal compound. In addition, "a cholesteric liquid crystal layer formed using a first liquid crystal compound substantially composed of a rod-like liquid crystal compound" means that the first liquid crystal compound is set as a cholesteric liquid crystal phase and the orientation state of the cholesteric liquid crystal phase is fixed. The above-mentioned "substantially composed of a rod-like liquid crystal compound" means that the liquid crystal compound (first liquid crystal compound) contained in the cholesteric liquid crystal layer formed using a rod-like liquid crystal compound is 95% by mass or more. That is, "the first liquid crystal compound substantially composed of a rod-like liquid crystal compound" means that the content of the rod-like liquid crystal compound is 95% by mass or more relative to the total mass of the first liquid crystal compound. Among them, the first liquid crystal compound is preferably composed only of a rod-like liquid crystal compound.

[0101] Furthermore, the cholesteric liquid crystal layer formed using a discotic liquid crystal compound is a cholesteric liquid crystal layer formed using a second liquid crystal compound substantially composed of a discotic liquid crystal compound, and is substantially composed of a discotic liquid crystal compound. In addition, "a cholesteric liquid crystal layer formed using a second liquid crystal compound substantially composed of a discotic liquid crystal compound" refers to a layer formed by setting the above-mentioned second liquid crystal compound to a cholesteric liquid crystal phase and fixing the orientation state of the cholesteric liquid crystal phase. The above-mentioned "substantially composed of a discotic liquid crystal compound" means that the liquid crystal compound (second liquid crystal compound) contained in the cholesteric liquid crystal layer formed using a discotic liquid crystal compound is 95% by mass or more. That is, "the second liquid crystal compound substantially composed of a discotic liquid crystal compound" means that the content of the discotic liquid crystal compound is 95% by mass or more relative to the total mass of the second liquid crystal compound. Among them, the second liquid crystal compound is preferably composed only of a discotic liquid crystal compound.

[0102] The rod-shaped liquid crystal compound contained in the cholesteric liquid crystal layer formed using the rod-shaped liquid crystal compound is not particularly limited, and a known rod-shaped liquid crystal compound can be used. In addition, the cholesteric liquid crystal layer formed using the rod-shaped liquid crystal compound can be formed as long as the orientation of the rod-shaped liquid crystal compound formed into the cholesteric liquid crystal phase is maintained. It can be formed as follows, that is, after the polymerizable rod-shaped liquid crystal compound having a polymerizable group is made into the orientation state of the cholesteric liquid crystal phase by adding a chiral agent or the like, it is polymerized and cured by ultraviolet irradiation, heating, etc. to form a layer without fluidity. The cholesteric liquid crystal layer formed using the rod-shaped liquid crystal compound as formed above can be formed as long as it becomes a layer in a state where the orientation form will not change due to external fields and external forces. In addition, in the cholesteric liquid crystal layer formed using the rod-shaped liquid crystal compound, as long as the optical properties of the cholesteric liquid crystal phase are maintained in the layer, the rod-shaped liquid crystal compound in the cholesteric liquid crystal layer formed using the rod-shaped liquid crystal compound can no longer show liquid crystal properties. For example, the polymerizable rod-shaped liquid crystal compound can be high molecular weighted by a curing reaction and no longer have liquid crystal properties.

[0103] The center wavelength λ of the reflected light of the cholesteric liquid crystal layer formed using the rod-shaped liquid crystal compound depends on the pitch P (= period of the spiral) of the spiral structure in the cholesteric liquid crystal phase, and is expressed by the relationship of λ=n×P using the average refractive index n of the cholesteric liquid crystal layer formed using the rod-shaped liquid crystal compound. In addition, the center wavelength of the reflected light of the cholesteric liquid crystal layer formed using the rod-shaped liquid crystal compound can be obtained as follows. When the transmission spectrum is measured from the normal direction of the cholesteric liquid crystal layer formed using the rod-shaped liquid crystal compound using the spectrophotometer UV3150 (Shimadzu Corporation), a spectrum with a peak with reduced transmittance in the region near the center wavelength of the reflected light can be obtained. Among them, among the two wavelengths with a transmittance of 1 / 2 of the maximum peak value, the value of the wavelength on the short wavelength side is set to λl (nm) and the value of the wavelength on the long wavelength side is set to λh (nm), and the center wavelength λ of the reflected light is obtained by the following formula.

[0104] λ=(λl+λh) / 2

[0105] The pitch of the cholesteric liquid crystal phase changes by the type of chiral reagent used together with the polymerizable rod-shaped liquid crystal compound and its added concentration. By adjusting any one or more of the above, a cholesteric liquid crystal phase with a desired pitch can be obtained. In addition, the method for measuring the rotation direction and pitch of the spiral can be used in "Introduction to Liquid Crystal Chemistry Experiments" edited by the Liquid Crystal Society of Japan and published by Sigma in 2007, page 46 and "Liquid Crystal Handbook" Liquid Crystal Handbook Editorial Committee Maruzen page 196.

[0106] The disc-shaped liquid crystal compound contained in the cholesteric liquid crystal layer formed by the above-mentioned disc-shaped liquid crystal compound is not particularly limited, and a known disc-shaped liquid crystal compound can be used. In addition, the cholesteric liquid crystal layer formed by the disc-shaped liquid crystal compound can be formed as long as the orientation of the disc-shaped liquid crystal compound formed into the cholesteric liquid crystal phase is maintained. It can be typically formed as follows, that is, by adding a chiral agent or the like to make the polymerizable disc-shaped liquid crystal compound having a polymerizable group become the orientation state of the cholesteric liquid crystal phase, and then polymerize and solidify by ultraviolet irradiation, heating, etc. to form a layer without fluidity. The cholesteric liquid crystal layer formed by the disc-shaped liquid crystal compound formed as described above can be formed as long as it becomes a layer in a state where the orientation morphology will not change due to external fields and external forces. In addition, in the cholesteric liquid crystal layer formed by the disc-shaped liquid crystal compound, as long as the optical properties of the cholesteric liquid crystal phase are maintained in the layer, the disc-shaped liquid crystal compound in the cholesteric liquid crystal layer formed by the disc-shaped liquid crystal compound can no longer show liquid crystal properties. For example, a polymerizable discotic liquid crystal compound may become highly molecular by a curing reaction and no longer have liquid crystallinity.

[0107] The central wavelength λ of reflected light from a cholesteric liquid crystal layer formed using a discotic liquid crystal compound depends on the pitch of the helical structure in the cholesteric liquid crystal phase, and can be defined and measured in the same manner as in the case of a cholesteric liquid crystal layer formed using a rod-like liquid crystal compound.

[0108] The pitch of the cholesteric liquid crystal phase varies with the type of chiral agent used together with the polymerizable discotic liquid crystal compound and its added concentration. By adjusting any one or more of the above, a cholesteric liquid crystal phase with a desired pitch can be obtained. In addition, the above-mentioned literature can be referred to for the method of measuring the rotation direction and pitch of the spiral.

[0109] 〔Reflectivity〕

[0110] In the optical laminate of the first embodiment of the present invention, the center wavelength of the reflected light of the first layer is within the range of 430 to 570 nm, the center wavelength of the reflected light of the second layer is within the range of 550 to 670 nm, the center wavelength of the reflected light of the third layer is within the range of 430 to 570 nm, and the center wavelength of the reflected light of the fourth layer is within the range of 550 to 670 nm. By configuring the light reflecting layers whose center wavelengths of the reflected light are within the above range in the above order, ghosting can be suppressed when used in virtual reality display devices and electronic viewfinders, etc. (hereinafter, also referred to as "suppressing ghosting").

[0111] The center wavelengths of the reflected light from the first and third layers are preferably within the range of 430 to 480 nm and 520 to 570 nm, respectively. Also, the center wavelengths of the reflected light from the second and fourth layers are preferably within the range of 550 to 620 nm and 600 to 670 nm, respectively.

[0112] Furthermore, it is also preferred that the center wavelengths of the reflected light of the first to fourth layers are different from each other. That is, it is more preferred that one of the center wavelengths of the reflected light of the first and third layers is within the range of 430 to 480 nm and the other is within the range of 520 to 570 nm. Furthermore, it is more preferred that one of the center wavelengths of the reflected light of the second and fourth layers is within the range of 550 to 620 nm and the other is within the range of 600 to 670 nm.

[0113] When the center wavelength of the reflected light is 430 to 480 nm, the layer can be used as a blue light reflecting layer. In this case, the reflectance at the center wavelength of the reflected light is preferably 40% or more and less than 50%.

[0114] When the center wavelength of the reflected light is 520 to 570 nm, the layer can be regarded as a green light reflecting layer. In this case, the reflectance at the center wavelength of the reflected light is preferably 40% or more and less than 50%.

[0115] When the center wavelength of the reflected light is 550 to 620 nm, the layer can be used as a yellow light reflecting layer. In this case, the reflectance at the center wavelength of the reflected light is preferably 40% or more and less than 50%.

[0116] When the center wavelength of the reflected light is 600 to 670 nm, the layer can be used as a red light reflecting layer. In this case, the reflectivity at the center wavelength of the reflected light is preferably 40% or more and less than 50%.

[0117] When the reflectivity is 40% or more, ghosting can be further easily suppressed. The reflectivity is a value when a non-polarized light source is incident.

[0118] The reflectance of the optical laminate is a value measured under the following conditions.

[0119] An automatic absolute reflectivity measurement system consisting of a UV-visible near-infrared spectrophotometer V-750 manufactured by JASCO Corporation was used. Polarized light of S waves and P waves with a wavelength of 350 to 900 nm was incident on the optical laminate at an incident angle of 5°. The absolute reflectivity of the S wave and the P wave was measured, and the average value was calculated for each wavelength to obtain a reflection spectrum. Based on the obtained reflectivity spectrum, the average reflectivity of light with a wavelength of 400 to 700 nm was calculated, and it was set as the reflectivity of the optical laminate to light with a wavelength of 400 to 700 nm.

[0120] More preferably, the center wavelength of the reflected light of the first layer is within the range of 430 to 480 nm, the center wavelength of the reflected light of the second layer is within the range of 600 to 670 nm, the center wavelength of the reflected light of the third layer is within the range of 520 to 570 nm, and the center wavelength of the reflected light of the fourth layer is within the range of 550 to 620 nm. By arranging the light reflecting layers whose respective center wavelengths of reflected light are within the above ranges in the above order, ghosting can be further suppressed.

[0121] In the optical laminate of the first embodiment of the present invention, the sign of Rth of the first layer at a wavelength of 550nm is opposite to the sign of Rth of the second layer at a wavelength of 550nm, and the sign of Rth of the third layer at a wavelength of 550nm is opposite to the sign of Rth of the fourth layer at a wavelength of 550nm.

[0122] The method of making the sign of Rth opposite in the first layer and the second layer as described above is not particularly limited. As a method of setting such an Rth relationship, for example, one of the first layer and the second layer is a cholesteric liquid crystal layer formed using a rod-like liquid crystal compound and the other layer is a cholesteric liquid crystal layer formed using a disc-like liquid crystal compound.

[0123] Similarly, the method of making the sign of Rth opposite in the third layer and the fourth layer as described above is not particularly limited, and as a method of setting such an Rth relationship, for example, one of the third layer and the fourth layer is a cholesteric liquid crystal layer formed using a rod-shaped liquid crystal compound and the other layer is a cholesteric liquid crystal layer formed using a disc-shaped liquid crystal compound.

[0124] Furthermore, it is also preferred that the signs of Rth are opposite in the second layer and the third layer. As a method of setting such an Rth relationship, for example, a method in which the first layer and the third layer are cholesteric liquid crystal layers formed using a rod-like liquid crystal compound and the second layer and the fourth layer are cholesteric liquid crystal layers formed using a disc-like liquid crystal compound, and a method in which the first layer and the third layer are cholesteric liquid crystal layers formed using a disc-like liquid crystal compound and the second layer and the fourth layer are cholesteric liquid crystal layers formed using a rod-like liquid crystal compound can be cited.

[0125] The Rth of the cholesteric liquid crystal layer formed using the rod-like liquid crystal compound is preferably 8 to 800 nm, more preferably 16 to 560 nm, and further preferably 24 to 400 nm at a wavelength of 550 nm.

[0126] Regarding the Rth of the cholesteric liquid crystal layer formed using a rod-like liquid crystal compound, only the cholesteric liquid crystal layer formed using a rod-like liquid crystal compound can be taken out from the optical laminate to measure the Rth, or the Rth of a layer produced under the same conditions as when producing the cholesteric liquid crystal layer formed using a rod-like liquid crystal compound can be measured.

[0127] The Rth of the cholesteric liquid crystal layer formed using the discotic liquid crystal compound is preferably -8 to -800 nm, more preferably -16 to -560 nm, and further preferably -24 to -400 nm at a wavelength of 550 nm.

[0128] Regarding the Rth of the cholesteric liquid crystal layer formed using a discotic liquid crystal compound, only the cholesteric liquid crystal layer formed using a discotic liquid crystal compound can be taken out from the optical laminate to measure the Rth, or the Rth of a layer produced under the same conditions as when producing the cholesteric liquid crystal layer formed using a discotic liquid crystal compound can be measured.

[0129] The thickness of the first to fourth layers is preferably 0.1 μm or more, more preferably 0.2 μm or more, and further preferably 0.3 μm or more. In order to further suppress ghosting, the thickness of the first to fourth layers is preferably 10.0 μm or less, more preferably 7.0 μm or less, and further preferably 5.0 μm or less.

[0130] Furthermore, from the viewpoint of further suppressing ghosting, the difference in film thickness of each of the first to fourth layers is preferably less than 0.5 μm, and more preferably less than 0.3 μm.

[0131] The thickness of each layer of the first to fourth layers can be measured by making a cross section of the optical laminate and observing it with a scanning electron microscope. The thickness of each layer is set to a value obtained by averaging the thickness of each layer at any 5 points in the cross section of the optical laminate. In addition, when observing the cross section of the optical laminate with a scanning electron microscope, the regions of each layer of the first to fourth layers can be distinguished by the difference in contrast of the photographic image. In addition, each layer of the first to fourth layers can also be distinguished by performing composition analysis in the film thickness direction using time-of-flight secondary ion mass spectrometry (TOF-SIMS: Time-of-flight SIMS).

[0132] The thicknesses of the first to fourth layers can be measured by preparing a cross section of the optical laminate and observing it with a transmission electron microscope.

[0133] In the optical laminate of the first embodiment of the present invention, the following content is described, namely, the sign of Rth of the first layer is opposite to the sign of Rth of the second layer, and the sign of Rth of the third layer is opposite to the sign of Rth of the fourth layer, so Rth of the first layer and Rth of the second layer cancel each other, and Rth of the third layer and Rth of the fourth layer cancel each other, and the details are described below.

[0134] In an optical laminate having four reflective layers, when the reflective layers are named L1, L2, L3, and L4 in order from the light source side, the sum of the Rths of the layers from reflective layer L1 to reflective layer Li (i is an integer of 4 or less) is SRthi. Specifically, SRthi is represented as follows.

[0135] SRth1=Rth1

[0136] SRth2=Rth1+Rth2

[0137] SRth3=Rth1+Rth2+Rth3

[0138] SRth4=Rth1+Rth2+Rth3+Rth4

[0139] The absolute values ​​of all these SRthi (SRth1 to SRth4) are preferably 0.3 μm or less, more preferably 0.2 μm or less, and further preferably 0.1 μm or less. The Rthi of each layer in the above formula is obtained by the Rth calculation formula described above. In the first embodiment, n is read as 4.

[0140] It is considered that by setting SRthi within the above-mentioned preferred range, the phase difference generated when transmitting each reflective layer can be reduced, and the occurrence of ghost images can be further suppressed for incident light from an oblique direction.

[0141] In the optical laminate of the first embodiment of the present invention, the first to fourth layers can be stacked in direct contact with each other, or can be stacked via other layers. As other layers, there are no particular restrictions, and a close-fitting layer (for example, an adhesive layer, an adhesive layer, etc.), a refractive index adjustment layer, a resin film, a positive C plate, and an orientation layer can be cited. Wherein, the first to fourth layers are preferably stacked in direct contact with each other.

[0142] Furthermore, in the optical laminate of the first embodiment of the present invention, when the first to fourth layers are stacked in direct contact with each other, it is preferred to configure the liquid crystal compound (rod-shaped liquid crystal compound or disc-shaped liquid crystal compound) in such a manner that the orientation direction (slow axis direction) changes continuously at the interface to reduce the refractive index difference. Regarding the configuration as described above, for example, when a second layer of a cholesteric liquid crystal layer formed using a rod-shaped liquid crystal compound is formed on the first layer, which is a cholesteric liquid crystal layer formed using a disc-shaped liquid crystal compound, a coating liquid containing a rod-shaped liquid crystal compound is directly applied to the first layer and can be oriented in such a manner that the slow axis direction is continuous at the interface by the orientation restriction force of the disc-shaped liquid crystal compound contained in the first layer.

[0143] The thickness of the optical laminate according to the first embodiment of the present invention is preferably 30 μm or less, more preferably 15 μm or less. The lower limit is not particularly limited, and for example, it may be 1 μm or more, and preferably 5 μm or more.

[0144] The method for producing the optical laminate according to the first embodiment of the present invention, a laminated optical film using the optical laminate, and the like will be described below.

[0145] [Method for producing optical laminate]

[0146] The optical laminate (first embodiment) of the present invention can be produced by a known method, and the method is not particularly limited.

[0147] For example, as a method for manufacturing an optical laminate according to the first embodiment, the following method can be cited: after applying a composition containing a rod-shaped liquid crystal compound on a substrate to form a cholesteric liquid crystal phase, the orientation state of the cholesteric liquid crystal phase is fixed to form a first cholesteric liquid crystal layer; after applying a composition containing a disc-shaped liquid crystal compound on the first cholesteric liquid crystal layer to form a cholesteric liquid crystal phase, the orientation state of the cholesteric liquid crystal phase is fixed to form a second cholesteric liquid crystal layer; a third cholesteric liquid crystal layer is formed on the second cholesteric liquid crystal layer in the same manner as the first cholesteric liquid crystal layer; and a fourth cholesteric liquid crystal layer is formed on the third cholesteric liquid crystal layer in the same manner as the second cholesteric liquid crystal layer.

[0148] Furthermore, when the optical laminate of the present invention is used for a reflective circular polarizer, when the reflective circular polarizer is stretched or formed, the reflection wavelength region of the reflective circular polarizer may be displaced to the short-wave side, so it is preferred to manufacture the optical laminate by pre-assuming the displacement of the wavelength in the reflection wavelength region. For example, when an optical laminate including a layer formed by fixing a cholesteric liquid crystal phase is used as a reflective circular polarizer, it may be possible that the optical laminate is stretched by stretching or forming and the helical pitch of the cholesteric liquid crystal phase becomes smaller, so the helical pitch of the cholesteric liquid crystal phase may be pre-set to be larger. Furthermore, considering the short-wave displacement of the reflection wavelength region caused by stretching or forming, the optical laminate also preferably has an infrared light reflecting layer having a reflectivity of 40% or more at a wavelength of 800nm.

[0149] Furthermore, when the stretching ratio in the stretching or molding is uneven in the plane, the optical laminate can be manufactured by selecting an appropriate reflection wavelength region at each position in the plane of the optical laminate according to the wavelength displacement caused by stretching. That is, in the plane of the optical laminate, the reflection wavelength region can be different regions. In addition, considering that the stretching ratios at each position in the plane of the optical laminate are different, it is also preferred to preliminarily set the reflection wavelength region to be wider than the desired wavelength region.

[0150] In the above, a method of directly coating the above composition on each cholesteric liquid crystal layer to form a cholesteric liquid crystal layer is shown, but the cholesteric liquid crystal layer can also be formed by coating the cholesteric liquid crystal layer on other substrates respectively and stacking the cholesteric liquid crystal layer via a bonding layer (for example, an adhesive layer, a bonding layer).

[0151] As the adhesive used in the above-mentioned adhesive layer, any commercially available adhesive can be used. From the perspective of thinning and reducing the surface roughness Ra, the thickness is preferably 25 μm or less, more preferably 15 μm or less, and most preferably 6 μm or less. In addition, the adhesive is preferably not easy to outgas. In particular, when stretching or molding is performed, a vacuum process and / or a heating process are sometimes performed, and it is preferred that outgassing is not generated under these conditions.

[0152] As the adhesive used in the adhesive layer, any commercially available adhesive or the like can be used, and for example, an epoxy resin-based adhesive or an acrylic resin-based adhesive can be used.

[0153] From the viewpoint of thinning and reducing the surface roughness Ra of the reflective circular polarizer using the optical laminate, the thickness of the adhesive is preferably 25 μm or less, more preferably 5 μm or less, and most preferably 1 μm or less. In addition, from the viewpoint of thinning the adhesive layer and applying the adhesive to the adherend with a uniform thickness, the viscosity of the adhesive is preferably 300 cP or less, and more preferably 100 cP or less.

[0154] And, when adherend has surface concavoconvex, with respect to the viewpoint of surface roughness Ra of the reflective circular polarizer using optical laminated body for reduction, adhesive or bonding agent can also select suitable viscoelasticity or thickness, so that the surface concavoconvex of the layer being bonded can be embedded.With respect to the viewpoint of embedding surface concavoconvex, the viscosity of adhesive and bonding agent is preferably more than 50cP.And, thickness is preferably thicker than the height of surface concavoconvex.

[0155] As a method for adjusting the viscosity of the adhesive, for example, a method of using an adhesive containing a solvent can be cited. In this case, the viscosity of the adhesive can be adjusted by the ratio of the solvent. In addition, by drying the solvent after applying the adhesive to the adherend, the thickness of the adhesive can be further reduced.

[0156] In a reflective circular polarizer using an optical laminate, from the viewpoint of reducing reflection at the interface and suppressing the decrease in the polarization degree of transmitted light, the adhesive or bonding agent used for bonding each layer preferably has a small refractive index difference with the adjacent layer. The cholesteric liquid crystal layer has birefringence and the refractive index in the fast axis direction and the slow axis direction are different. Therefore, the value obtained by adding the refractive index in the fast axis direction and the refractive index in the slow axis direction and dividing by 2 is set as the average refractive index n of the liquid crystal layer. ave When the refractive index of the adjacent adhesive layer or bonding layer is ave The difference is preferably 0.075 or less, more preferably 0.05 or less, and further preferably 0.025 or less. The refractive index of the binder or adhesive can be adjusted by mixing fine particles such as titanium oxide fine particles and zirconium oxide fine particles, for example.

[0157] Furthermore, regarding the adhesive layer between each layer, the thickness of the adhesive layer is also preferably less than 100nm. When the thickness of the adhesive layer is less than 100nm, the refractive index difference is not easily perceived by light in the visible region, and unnecessary reflection can be suppressed. The thickness of the adhesive layer is more preferably less than 50nm, and further preferably less than 30nm. As a method for forming an adhesive layer with a thickness of less than 100nm, for example, a method of evaporating a ceramic adhesive such as silicon oxide (SiOx layer) onto the bonding surface can be cited. The bonding surface of the bonding component can be subjected to surface modification treatments such as plasma treatment, corona treatment, and saponification treatment before bonding, and a primer layer can be given. Furthermore, in the presence of multiple bonding surfaces, the type and thickness of the adhesive layer can be adjusted for each bonding surface. Specifically, for example, an adhesive layer with a thickness of less than 100nm can be provided according to the steps shown in the following (1) to (3).

[0158] (1) The layers to be laminated are bonded onto a dummy support made of a glass substrate.

[0159] (2) A SiOx layer having a thickness of 100 nm or less is formed by vapor deposition or the like on both the surface of the layer to be laminated and the surface of the layer to be laminated. The vapor deposition can be performed by using SiOx powder as a vapor deposition source and using, for example, a vapor deposition device (model ULEYES) manufactured by ULVAC, Inc. In addition, it is preferred that the surface of the formed SiOx layer be subjected to plasma treatment.

[0160] (3) After the formed SiOx layers are bonded together, the dummy support is peeled off. The bonding is preferably performed at a temperature of 120°C, for example.

[0161] The coating, bonding or lamination of each layer may be performed in a roll-to-roll manner or in a single sheet manner.

[0162] From the viewpoint of improving productivity and reducing axial deviation of each layer, a roll-to-roll method is preferred.

[0163] On the other hand, the single-sheet method is preferred from the viewpoints of suitability for small-volume and high-variety production and the ability to select a special bonding method in which the thickness of the bonding layer is 100 nm or less.

[0164] In addition, as a method for applying the adhesive to the adherend, for example, known methods such as roll coating, gravure printing, spin coating, wire bar coating, extrusion coating, direct gravure coating, reverse gravure coating, die coating, spray coating and inkjet coating can be cited.

[0165] The reflective circular polarizer using the optical laminate of the present invention may include a support and an alignment layer, etc. The support and the alignment layer may be a pseudo support that is peeled off and removed when the laminated optical film described later is produced. In the case of using a pseudo support, the laminated optical film can be thinned by transferring the reflective circular polarizer to another laminate and then peeling off and removing the pseudo support. Furthermore, the phase difference of the pseudo support can eliminate the adverse effect on the polarization degree of the transmitted light, so it is preferred.

[0166] The type of the support is not particularly limited, but is preferably transparent to visible light, and for example, films of cellulose acylate, polycarbonate, polysulfone, polyethersulfone, polyacrylate, polymethacrylate, cyclic polyolefin, polyolefin, polyamide, polystyrene, and polyester can be used. Among them, cellulose acylate films, cyclic polyolefin, polyacrylate, and polymethacrylate are preferred. In addition, commercially available cellulose acetate films (for example, "TD80U" and "Z-TAC" manufactured by FUJIFILM Corporation) can be used.

[0167] When the support is a pseudo support, a support having high tear strength is preferred from the viewpoint of preventing breakage during peeling. For example, a polycarbonate film or a polyester film is preferred.

[0168] Furthermore, from the viewpoint of suppressing the adverse effect on the polarization degree of the transmitted light, the support preferably has a small phase difference. Specifically, the size of Re at 550nm is preferably 10nm or less, and the absolute value of the size of Rth is preferably 50nm or less. Furthermore, even if the support is used as the above-mentioned pseudo support, from the perspective of performing quality inspection of the reflective circular polarizer and other laminates in the manufacturing process of the above-mentioned laminated optical film, it is preferred that the pseudo support has a small phase difference.

[0169] Furthermore, in order to minimize the impact on various sensors that use near-infrared light as a light source, such as eye tracking, expression recognition, and iris authentication, which are incorporated into optical systems such as virtual reality display devices and electronic viewfinders, it is preferred that the reflective circular polarizer used in the optical laminate described later be transmissive to near-infrared light.

[0170] [Laminated optical film]

[0171] The laminated optical film of the present invention comprises at least a reflective circular polarizer, a retardation layer for converting circularly polarized light into linearly polarized light, and a linear polarizer in this order.

[0172] As the reflective circular polarizer, the optical laminate (first embodiment) is used. Preferred embodiments of the optical laminate (first embodiment) are as described above.

[0173] As a preferred use example of the reflective circular polarizer and the laminated optical film including the reflective circular polarizer of the present invention, a virtual reality display device using the laminated optical film of the present invention is given, and the effect of the laminated optical film of the present invention is described in detail.

[0174] Figure 2 Schematic diagram of a virtual reality display device using the laminated optical film of the present invention. Figure 2 In the virtual reality display device of the embodiment shown in FIG. 1 , a laminated optical film 100 having a reflective circular polarizer using the optical laminate, a half mirror 300, a circular polarizer 400, and an image display panel 500 are arranged in order from the visual recognition side. Figure 2As shown, the light 1000 emitted from the image display panel 500 passes through the circular polarizer 400 to become circularly polarized light, and passes through the half mirror 300. Then, it enters the laminated optical film 100 of the present invention from the reflective circular polarizer side and is totally reflected, and is reflected again at the half mirror 300, and is incident on the laminated optical film 100 again. At this time, the light 1000 is reflected at the half mirror and becomes a circularly polarized light with a rotation direction opposite to that of the circularly polarized light when it first enters the laminated optical film 100. Therefore, the light 1000 passes through the laminated optical film 100 and is visually recognized by the user. Furthermore, when the light 1000 is reflected at the half mirror 300, since the half mirror is in the shape of a concave mirror, the image displayed on the image display panel 500 is magnified, and the user can visually recognize the magnified virtual image. The above-mentioned mechanism is called a reciprocating optical system or a folding optical system, etc.

[0175] on the other hand, Figure 3 For the purpose of explaining Figure 2 More specifically, it is a schematic diagram showing a situation in which a light ray 2000 is not reflected but transmitted when it first enters the laminated optical film 100 in the virtual reality display device, thereby causing light leakage. Figure 3 As shown, when the light 2000 is incident on the laminated optical film 100 for the first time, it is not reflected but transmitted, thereby causing light leakage. Figure 3 It is known that the user visually recognizes an image that is not magnified. This image is called a ghost image, and it is required to be reduced.

[0176] Since the laminated optical film 100 of the present invention has a high polarization degree, it is possible to reduce the leakage of transmitted light (ie, ghosting) when light first enters the laminated optical film 100 .

[0177] Furthermore, since the laminated optical film 100 of the present invention also has a high polarization degree for transmitted light, the transmittance of light incident on the laminated optical film 100 for the second time can be increased, and the brightness of the virtual image can be increased to suppress the coloring of the virtual image.

[0178] like Figure 2 and Figure 3 As shown, the laminated optical film 100 is sometimes formed on a curved surface such as a lens.

[0179] The conventional optical film formed by laminating a reflective linear polarizer and a phase difference layer having a phase difference of 1 / 4 wavelength, which is known as a reflective circular polarizer, has optical axes such as a transmission axis, a reflection axis, and a slow axis, so the polarization degree of the transmitted light is reduced due to deformation of the optical axis when stretched or formed into a curved shape. In contrast, in the laminated optical film 100 of the present invention, the reflective circular polarizer (optical laminate) does not have an optical axis, so it is not easy to reduce the polarization degree due to stretching or molding. Therefore, when the laminated optical film 100 is formed into a curved shape, it is not easy to reduce the polarization degree.

[0180] An example of the layer structure of the laminated optical film 100 of the present invention is shown in Figure 4 . Figure 4 In the laminated optical film 100 shown, an antireflection layer 101, a positive C plate 102, a reflective circular polarizer 103, a positive C plate 104, a phase difference layer 105, and a linear polarizer 106 are sequentially arranged. As described above, the reflective circular polarizer 103 uses the above-mentioned optical laminate. Figure 4 In the illustrated embodiment, the antireflection layer 101, the positive C plate 102, and the positive C plate 104 are used, but a part or all of them may be omitted in the above structure.

[0181] The laminated optical film of the present invention sequentially comprises a reflective circular polarizer 103, a phase difference layer 105 for converting circularly polarized light into linearly polarized light, and a linear polarizer 106, so that the leakage light from the reflective circular polarizer 103 can be converted into linearly polarized light and then absorbed by the linear polarizer. Therefore, the polarization degree of the transmitted light can be increased. In addition, when the laminated optical film is stretched or formed, the slow axis of the phase difference layer or the absorption axis of the linear polarizer may be deformed, but as described above, the reflective circular polarizer still has a high polarization degree even if stretched and formed, and the amount of light leakage from the reflective circular polarizer is small, so the increase in leakage light can be suppressed to a small amount.

[0182] Furthermore, the surface roughness Ra of the laminated optical film of the present invention is preferably 100 nm or less. When Ra is small, for example, when the laminated optical film is used in a virtual reality display device, the clarity of the image can be improved. The inventors of the present invention speculate that when light is reflected in the laminated optical film, if there are concave and convex surfaces, it will cause angular distortion of the reflected light, distortion or blurring of the image. The Ra of the laminated optical film is preferably 50 nm or less, more preferably 30 nm or less, and particularly preferably 10 nm or less.

[0183] Furthermore, the laminated optical film of the present invention is made by laminating a plurality of layers. Through research conducted by the present inventors, it was found that when other layers are laminated on a layer having concavoconvexity, the concavoconvexity is amplified. Therefore, in the laminated optical film of the present invention, it is preferred that the Ra of all layers is small. The Ra of each layer of the laminated optical film of the present invention is preferably 50 nm or less, more preferably 30 nm or less, and further preferably 10 nm or less.

[0184] Furthermore, from the viewpoint of improving the image clarity of a reflected image, it is particularly preferred that the Ra of the reflective circular polarizer be small.

[0185] The surface roughness Ra can be measured using, for example, a non-contact surface-layer cross-section shape measuring system VertScan (manufactured by RyokaSystems Inc.). Vertscan is a surface shape measuring method utilizing the phase of the reflected light from the sample, so when measuring a reflective circular polarizer (the above-mentioned optical laminate) consisting of a reflective layer formed by fixing the cholesteric liquid crystal phase, sometimes the reflected light from the inside of the film overlaps and the surface shape cannot be accurately measured. In this case, a metal layer can be formed on the surface of the sample to increase the reflectivity of the surface and thereby suppress reflection from the inside. As a method for forming a metal layer on the surface of the sample, for example, a sputtering method can be used. As a material for sputtering, Au, Al, and Pt can be used.

[0186] The laminated optical film of the present invention preferably has a small number of point defects per unit area. Since the laminated optical film of the present invention is produced by laminating a plurality of layers, the number of point defects in each layer is preferably small to reduce the number of point defects in the laminated optical film as a whole. Specifically, the number of point defects in each layer is preferably 20 or less, more preferably 10 or less, and further preferably 1 or less per square meter. As for the laminated optical film as a whole, the number of point defects is preferably 100 or less, more preferably 50 or less, and further preferably 5 or less per square meter.

[0187] Point defects lead to a decrease in the polarization degree of transmitted light and a decrease in image clarity, and therefore, the number of point defects is preferably small.

[0188] Here, the point defects include foreign matter, scratches, dirt, film thickness variation, poor orientation of liquid crystal compounds, and the like.

[0189] Furthermore, regarding the number of the above-mentioned point defects, it is preferred to count the number of point defects having a size of 100 μm or more, more preferably 30 μm or more, and most preferably 10 μm or more.

[0190] Furthermore, various sensors that use near-infrared light as a light source, such as eye tracking, expression recognition, and iris authentication, are sometimes incorporated into optical systems such as virtual reality display devices and electronic viewfinders. In order to minimize the impact on the sensors, the laminated optical film of the present invention is preferably transmissive to near-infrared light.

[0191] 〔Phase difference layer〕

[0192] The phase difference layer used in the laminated optical film of the present invention has the function of converting the outgoing light into approximately linear polarized light when circularly polarized light is incident. For example, a phase difference layer whose Re is approximately 1 / 4 wavelength at any wavelength in the visible region can be used. In this case, at a wavelength of 550 nm, the in-plane retardation Re (550) is preferably 120 nm to 150 nm, more preferably 125 nm to 145 nm, and further preferably 135 nm to 140 nm.

[0193] Furthermore, a retardation layer having Re of approximately 3 / 4 wavelength or a retardation layer having Re of approximately 5 / 4 wavelength is also preferable because it can convert linearly polarized light into circularly polarized light.

[0194] Furthermore, the phase difference layer used in the laminated optical film of the present invention preferably has inverse wavelength dispersion with respect to the wavelength. When having inverse wavelength dispersion, circularly polarized light can be converted into linearly polarized light in a wide wavelength range in the visible region, so it is preferred. Here, having inverse wavelength dispersion with respect to the wavelength means that as the wavelength increases, the phase difference value at the wavelength also increases.

[0195] The phase difference layer having reverse wavelength dispersion can be produced by uniaxially stretching a polymer film such as a modified polycarbonate resin film having reverse wavelength dispersion, for example, with reference to Japanese Patent Application Laid-Open No. 2017-049574.

[0196] Furthermore, the phase difference layer with anti-wavelength dispersion can be substantially anti-wavelength dispersion. For example, as disclosed in Japanese Patent Gazette No. 06259925, it can be produced by stacking a phase difference layer with Re becoming approximately 1 / 4 wavelength and a phase difference layer with Re becoming approximately 1 / 2 wavelength so that the slow axes of each other are approximately 60°. It is known that at this time, even if the 1 / 4 wavelength phase difference layer and the 1 / 2 wavelength phase difference layer are respectively conventional wavelength dispersion (as the wavelength becomes larger, the phase difference value at this wavelength becomes smaller), circularly polarized light can be converted into linearly polarized light in a wide wavelength range in the visible region, and it can be regarded as substantially having anti-wavelength dispersion. In this case, the laminated optical film of the present invention preferably has a reflective circular polarizer, a 1 / 4 wavelength phase difference layer, a 1 / 2 wavelength phase difference layer and a linear polarizer in sequence.

[0197] Furthermore, the phase difference layer used in the laminated optical film of the present invention also preferably has a layer formed by fixing a uniformly oriented liquid crystal compound. For example, a layer in which a rod-shaped liquid crystal compound is uniformly oriented horizontally relative to the in-plane direction and a layer in which a disc-shaped liquid crystal compound is uniformly oriented vertically relative to the in-plane direction can be used. Furthermore, for example, a phase difference layer with anti-wavelength dispersion can be prepared by uniformly aligning and fixing a rod-shaped liquid crystal compound with anti-wavelength dispersion with reference to Japanese Patent Publication No. 2020-084070.

[0198] Furthermore, the phase difference layer used in the laminated optical film of the present invention also preferably has a layer formed by fixing a liquid crystal compound twisted and oriented with the thickness direction as the helical axis. For example, as disclosed in Japanese Patent No. 5753922 or Japanese Patent No. 5960743, a phase difference layer having a layer formed by fixing a rod-shaped liquid crystal compound or a disc-shaped liquid crystal compound twisted and oriented with the thickness direction as the helical axis can also be used. In this case, the phase difference layer can be regarded as having substantially anti-wavelength dispersion, and therefore is preferred.

[0199] The thickness of the retardation layer is not particularly limited, but is preferably 0.1 to 8 μm, more preferably 0.3 to 5 μm, from the viewpoint of thinning.

[0200] The phase difference layer of the present invention may include a support and an alignment layer, etc. The support and the alignment layer may be a pseudo support that is peeled off and removed when the laminated optical film is made. When a pseudo support is used, the laminated optical film can be thinned by transferring the phase difference layer to another laminate and then peeling off and removing the pseudo support. Furthermore, the phase difference of the pseudo support can eliminate the adverse effect on the polarization degree of the transmitted light, so it is preferred.

[0201] The type of the support is not particularly limited, but is preferably transparent to visible light, and for example, films of cellulose acylate, polycarbonate, polysulfone, polyethersulfone, polyacrylate, polymethacrylate, cyclic polyolefin, polyolefin, polyamide, polystyrene, and polyester can be used. Among them, cellulose acylate films, cyclic polyolefin, polyacrylate, or polymethacrylate are preferred. In addition, commercially available cellulose acetate films (for example, "TD80U" and "Z-TAC" manufactured by FUJIFILM Corporation) can be used.

[0202] When the support is a pseudo support, a support having high tear strength is preferred from the viewpoint of preventing breakage during peeling. For example, a polycarbonate-based or polyester-based film is preferred.

[0203] Furthermore, from the viewpoint of suppressing the adverse effect on the polarization degree of the transmitted light, the support preferably has a small phase difference. Specifically, the size of Re is preferably less than 10 nm, and the absolute value of the size of Rth is preferably less than 50 nm. Furthermore, even if the support is used as the above-mentioned pseudo support, from the perspective of performing quality inspection of the phase difference layer and other laminates in the manufacturing process of the laminated optical film, it is preferred that the pseudo support has a small phase difference.

[0204] Furthermore, in order to minimize the impact on various sensors that use near-infrared light as a light source, such as eye tracking, expression recognition, and iris authentication, which are incorporated into optical systems such as virtual reality display devices and electronic viewfinders, the phase difference layer used in the laminated optical film of the present invention is preferably transmissive to near-infrared light.

[0205] 〔Linear polarizer〕

[0206] The linear polarizer used in the laminated optical film of the present invention is preferably an absorption type linear polarizer. The absorption type linear polarizer absorbs linear polarized light in the absorption axis direction of the incident light and transmits linear polarized light in the transmission axis direction. As the linear polarizer, a general polarizer can be used, for example, a polarizer obtained by dyeing polyvinyl alcohol and other polymer resins with a dichroic substance and orienting it by stretching, or a polarizer obtained by orienting a dichroic substance by orienting a liquid crystal compound. From the viewpoint of availability and the viewpoint of increasing the degree of polarization, a polarizer obtained by dyeing polyvinyl alcohol with iodine and stretching is preferred.

[0207] The thickness of the linear polarizer is preferably 10 μm or less, more preferably 7 μm or less, and further preferably 5 μm or less. When the linear polarizer is thin, cracks and breakages of the film can be prevented when the laminated optical film is stretched or molded.

[0208] Furthermore, the single-element transmittance of the linear polarizer is preferably 40% or more, more preferably 42% or more. Furthermore, the degree of polarization is preferably 90% or more, more preferably 95% or more, and further preferably 99% or more. In addition, in this specification, the single-element transmittance and degree of polarization of the linear polarizer are measured using an automatic polarizing film measuring device: VAP-7070 (manufactured by JASCO Corporation).

[0209] Furthermore, the transmission axis of the linear polarizer is preferably aligned with the polarization axis of the light converted into linear polarized light by the phase difference layer. For example, when the phase difference layer is a layer having a phase difference of 1 / 4 wavelength, the angle between the transmission axis of the linear polarizer and the slow axis of the phase difference layer is preferably approximately 45°.

[0210] The linear polarizer used in the laminated optical film of the present invention is also preferably a light absorption anisotropic layer containing a liquid crystal compound and a dichroic substance. The thickness of the linear polarizer containing a liquid crystal compound and a dichroic substance can be set to be thin, and even if stretched or formed, cracks and breaks are not easily generated, so it is preferred. The thickness of the light absorption anisotropic layer is not particularly limited, but from the viewpoint of thinning, it is preferably 0.1 to 8 μm, and more preferably 0.3 to 5 μm.

[0211] A linear polarizer containing a liquid crystal compound and a dichroic substance can be produced, for example, by referring to Japanese Patent Application Laid-Open No. 2020-023153. From the viewpoint of increasing the polarization degree of the linear polarizer, the orientation degree of the dichroic substance in the light absorption anisotropic layer is preferably 0.95 or more, more preferably 0.97 or more.

[0212] The liquid crystal compound contained in the composition for forming a light absorption anisotropic layer for forming the light absorption anisotropic layer is preferably a liquid crystal compound that does not show dichroism in the visible region.

[0213] As the liquid crystal compound, any of a low molecular liquid crystal compound and a high molecular liquid crystal compound can be used. Here, a "low molecular liquid crystal compound" refers to a liquid crystal compound that does not have a repeating unit in its chemical structure. And, a "high molecular liquid crystal compound" refers to a liquid crystal compound that has a repeating unit in its chemical structure.

[0214] Examples of the polymer liquid crystal compound include thermotropic liquid crystal polymers described in Japanese Patent Application Laid-Open No. 2011-237513. The polymer liquid crystal compound preferably has a crosslinking group (eg, an acryloyl group and a methacryloyl group) at the terminal.

[0215] The liquid crystal compound may be used alone or in combination of two or more. It is also preferred to use a high molecular weight liquid crystal compound and a low molecular weight liquid crystal compound in combination.

[0216] The content of the liquid crystal compound is preferably 25 to 2000 parts by mass, more preferably 33 to 1000 parts by mass, and even more preferably 50 to 500 parts by mass, based on 100 parts by mass of the dichroic material in the present composition. When the content of the liquid crystal compound is within the above range, the degree of orientation of the polarizer is further improved.

[0217] The dichroic substance contained in the light absorption anisotropic layer forming composition for forming the light absorption anisotropic layer is not particularly limited, and examples thereof include visible light absorbing substances (dichroic pigments), ultraviolet absorbing substances, infrared absorbing substances, nonlinear optical substances, carbon nanotubes, etc., and conventionally known dichroic substances (dichroic pigments) can be used.

[0218] In the present invention, two or more dichroic substances may be used in combination. For example, from the viewpoint of obtaining a high degree of polarization in a wider wavelength range, it is preferred to use in combination at least one dichroic substance having a maximum absorption wavelength in the wavelength range of 370 to 550 nm and at least one dichroic substance having a maximum absorption wavelength in the wavelength range of 500 to 700 nm.

[0219] In the case where the linear polarizer of the present invention is composed of a light absorption anisotropic layer containing a liquid crystal compound and a dichroic substance, the linear polarizer may include a support and an alignment layer, etc. The support and the alignment layer may be a dummy support that is peeled off and removed when the laminated optical film is produced. In the case of using a dummy support, the laminated optical film can be thinned by peeling off and removing the dummy support after transferring the light absorption anisotropic layer to another laminate, and further, the phase difference of the dummy support can eliminate the adverse effect on the polarization degree of the transmitted light, so it is preferred.

[0220] The type of the support is not particularly limited, but is preferably transparent to visible light, and for example, the same support as that used for the phase difference layer can be used. The preferred embodiment of the support used in the linear polarizer is the same as that used for the phase difference layer.

[0221] Furthermore, in order to minimize the impact on various sensors that use near-infrared light as a light source, such as eye tracking, expression recognition, and iris authentication, which are incorporated into optical systems such as virtual reality display devices and electronic viewfinders, the linear polarizer used in the laminated optical film of the present invention is preferably transmissive to near-infrared light.

[0222] 〔Other functional layers〕

[0223] The laminated optical film of the present invention may have other functional layers in addition to the reflective circular polarizer, the phase difference layer and the linear polarizer.

[0224] Furthermore, in order to minimize the impact on various sensors that use near-infrared light as a light source, such as eye tracking, expression recognition, and iris authentication, which are incorporated into optical systems such as virtual reality display devices and electronic viewfinders, it is preferred that the other functional layers have near-infrared light transmittance.

[0225] <Positive C plate>

[0226] The laminated optical film of the present invention preferably further has a positive C plate. Here, the positive C plate refers to a phase difference layer in which Re is substantially zero and Rth has a negative value. The positive C plate can be obtained, for example, by vertically aligning a rod-like liquid crystal compound. The details of the manufacturing method of the positive C plate can be referred to, for example, in Japanese Patent Publication No. 2017-187732, Japanese Patent Publication No. 2016-053709, and Japanese Patent Publication No. 2015-200861.

[0227] The positive C plate functions as an optical compensation layer for increasing the polarization degree of transmitted light for light incident from an oblique direction. The positive C plate can be provided at any position of the laminated optical film, and a plurality of positive C plates can be provided.

[0228] The positive C plate can be arranged adjacent to the reflective circular polarizer or arranged inside the reflective circular polarizer. For example, when a reflective layer formed by fixing a cholesteric liquid crystal phase containing a rod-like liquid crystal compound is used as a reflective circular polarizer, the reflective layer has a positive Rth. At this time, when light is incident on the reflective circular polarizer from an oblique direction, sometimes the polarization state of the reflected light and the transmitted light changes due to the action of Rth, and the polarization degree of the transmitted light decreases. When there is a positive C plate inside or near the reflective circular polarizer, it is possible to further suppress the change in the polarization state of the oblique incident light, and further suppress the reduction in the polarization degree of the transmitted light. As a result, ghosting can be further suppressed, so it is preferred. According to the research of the inventors, the positive C plate is preferably arranged on the surface of the blue light reflecting layer on the opposite side of the green light reflecting layer, but it can also be arranged at other positions. In this case, the Re of the positive C plate is preferably approximately less than 10nm, and the Rth is preferably -600 to -100nm, and more preferably -400 to -200nm.

[0229] Furthermore, the positive C plate can be arranged adjacent to the phase difference layer or inside the phase difference layer. For example, when a layer formed by fixing a rod-like liquid crystal compound is used as the phase difference layer, the phase difference layer has a positive Rth. At this time, when light is incident on the phase difference layer from an oblique direction, sometimes the polarization state of the transmitted light changes due to the action of Rth and the polarization degree of the transmitted light decreases. When there is a positive C plate inside or near the phase difference layer, it is possible to suppress changes in the polarization state of the oblique incident light and suppress the reduction in the polarization degree of the transmitted light, so it is preferred. According to the research of the author and others, the positive C plate is preferably arranged on the surface of the phase difference layer on the opposite side of the linear polarizer, but it can also be arranged at other positions. In this case, the Re of the positive C plate is preferably approximately less than 10 nm, and the Rth is preferably -90 to -40 nm.

[0230] <Anti-reflection layer>

[0231] The laminated optical film of the present invention also preferably has an anti-reflection layer on the surface. The laminated optical film of the present invention has the function of reflecting specific circularly polarized light and transmitting circularly polarized light orthogonal to the specific circularly polarized light. The reflection of the surface of the laminated optical film usually includes the reflection of unintended polarized light, thereby sometimes reducing the polarization degree of the transmitted light. Therefore, the laminated optical film preferably has an anti-reflection layer on the surface. The anti-reflection layer can be provided on only one surface of the laminated optical film, or on both surfaces.

[0232] The type of the antireflection layer is not particularly limited, but a moth-eye film or an AR (Anti-Reflective) film is preferred from the viewpoint of further reducing the reflectivity. As the moth-eye film and the AR film, a known film can be used.

[0233] Furthermore, in the case of stretching or molding a laminated optical film, a moth-eye film is preferred because it can maintain high anti-reflection performance even if the film thickness changes due to stretching. Furthermore, the anti-reflection layer includes a support, and in the case of stretching or molding, the peak temperature of Tg of the support is preferably 170°C or less, and more preferably 130°C or less from the viewpoint of facilitating stretching or molding. Specifically, for example, a PMMA film is preferred.

[0234] <Second phase difference layer>

[0235] The laminated optical film of the present invention preferably further comprises a second retardation layer. For example, the laminated optical film may include a reflective circular polarizer, a retardation layer, a linear polarizer, and a second retardation layer in this order.

[0236] The second retardation layer is preferably a layer that converts linearly polarized light into circularly polarized light, and for example, is preferably a retardation layer having Re of 1 / 4 wavelength. The reason for this is described below.

[0237] Light incident on the laminated optical film from the reflective circular polarizer side and transmitted through the reflective circular polarizer, the phase difference layer and the linear polarizer becomes linearly polarized light, a portion of which is reflected on the outermost surface of the linear polarizer side and emitted again from the surface of the reflective circular polarizer side. Such light is redundant reflected light, which may become the main reason for reducing the polarization degree of reflected light, so it is preferably reduced. Therefore, in order to suppress the reflection of the outermost surface of the linear polarizer side, there is a method of laminating an anti-reflection layer, but when the laminated optical film is bonded to a medium such as glass and plastic for use, even if there is an anti-reflection layer on the bonding surface of the laminated optical film, the reflection of the medium surface cannot be suppressed, so it is difficult to obtain an anti-reflection effect.

[0238] On the other hand, when a second phase difference layer is provided to convert linearly polarized light into circularly polarized light, the light reaching the outermost surface of the linear polarizer becomes circularly polarized light, and is converted into orthogonal circularly polarized light when reflected from the outermost surface of the medium. After that, when the light passes through the second phase difference layer again and reaches the linear polarizer, the light becomes linearly polarized light in the absorption axis direction of the linear polarizer and is absorbed by the linear polarizer. This can prevent unnecessary reflection.

[0239] From the viewpoint of more effectively suppressing unnecessary reflection, the second retardation layer preferably has substantially inverse wavelength dispersion properties.

[0240] <Support body>

[0241] The laminated optical film of the present invention may further include a support. The support can be provided at any position, and for example, when the reflective circular polarizer, the phase difference layer or the linear polarizer is a film transferred from a dummy support, the support can be used as the transfer target.

[0242] The type of the support is not particularly limited, but is preferably transparent to visible light, and for example, films of cellulose acylate, polycarbonate, polysulfone, polyethersulfone, polyacrylate, polymethacrylate, cyclic polyolefin, polyolefin, polyamide, polystyrene, and polyester can be used. Among them, cellulose acylate films, cyclic polyolefin, polyacrylate, or polymethacrylate are preferred. In addition, commercially available cellulose acetate films (for example, "TD80U" and "Z-TAC" manufactured by FUJIFILM Corporation) can be used.

[0243] Furthermore, from the viewpoint of suppressing the adverse effect on the polarization degree of transmitted light and facilitating the optical inspection of the laminated optical film, the phase difference of the support is preferably small. Specifically, the size of Re is preferably 10 nm or less, and the absolute value of the size of Rth is preferably 50 nm or less.

[0244] When the laminated optical film of the present invention is a film to be stretched or molded, the peak temperature of tan δ of the support is preferably 170° C. or lower. From the viewpoint of enabling molding at low temperatures, the peak temperature of tan δ is preferably 150° C. or lower, more preferably 130° C. or lower.

[0245] Here, the method for measuring tanδ is described. Using a dynamic viscoelasticity measuring device (DVA-200 manufactured by IT Keisoku Seigyo Co., Ltd.), a film sample that has been humidified in an atmosphere of 25°C and 60% Rh for more than 2 hours is measured under the following conditions: E" (loss elastic modulus) and E' (storage elastic modulus), and the values ​​are used to determine tanδ (=E" / E').

[0246] Device: DVA-200 manufactured by IT Keisoku Seigyo Co., Ltd.

[0247] Sample: 5mm, length 50mm (gap 20mm)

[0248] Measurement conditions: tensile mode

[0249] Measuring temperature: -150℃~220℃

[0250] Heating conditions: 5℃ / min

[0251] Frequency: 1Hz

[0252] In addition, in optical applications, stretched resin substrates are often used, and the peak temperature of tanδ is often high due to the stretching process. For example, the peak temperature of tanδ of TAC (triacetylcellulose) substrate (TG40, manufactured by FUJIFILM Corporation) is 180°C or higher.

[0253] The support having a peak temperature of tanδ of 170°C or less is not particularly limited, and various resin substrates can be used. For example, polyolefins such as polyethylene, polypropylene, and norbornene polymers; cyclic olefin resins; polyvinyl alcohol; polyethylene terephthalate; acrylic resins such as polymethacrylate and polyacrylate; polyethylene naphthalate; polycarbonate; polysulfone; polyethersulfone; polyetherketone; polyphenylene sulfide and polyphenylene oxide. Among them, cyclic olefin resins, polyethylene terephthalate, or acrylic resins are preferred from the viewpoint of being easily available in the market or having excellent transparency, and cyclic olefin resins or polymethacrylates are particularly preferred.

[0254] Examples of commercially available resin substrates include TECHNOLLOY S001G, TECHNOLLOY S014G, TECHNOLLOY S000, TECHNOLLOY C001, TECHNOLLOY C000 (SUMIKA ACRYL CO., LTD.), Lumirror U type, Lumirror FX10, Lumirror SF20 (TORAY INDUSTRIES, INC.), HK-53A (Higashiyama Film Co., Ltd.), TEFLEX FT3 (Teijin DuPont Films Japan Ltd.), ESSINA” and SCA40 (Sekisui Chemical Co., Ltd.), Zeonor Film (Optes CO., LTD.), and Artone Film (JSR Corporation).

[0255] The thickness of the support is not particularly limited, but is preferably 5 to 300 μm, more preferably 5 to 100 μm, and further preferably 5 to 30 μm.

[0256] Furthermore, the laminated optical film may have layers other than the above layers. For example, as the layers other than the above layers, there can be mentioned an adhesive layer formed of a pressure-sensitive adhesive described later, an adhesive layer formed of an adhesive described later, and a refractive index adjustment layer.

[0257] Furthermore, a refractive index adjustment layer having a refractive index difference between the fast axis direction and the slow axis direction smaller than that of the reflective circular polarizer may be provided between the reflective circular polarizer and the adhesive or between the reflective circular polarizer and the adhesive. In this case, it is preferred that the refractive index adjustment layer has a layer formed by fixing the orientation state of the cholesteric liquid crystal compound. By having a refractive index adjustment layer, it is possible to further suppress interface reflection and further suppress the generation of ghosting. Furthermore, it is more preferred that the average refractive index of the refractive index adjustment layer is smaller than the average refractive index of the reflective circular polarizer. Furthermore, the central wavelength of the reflected light of the refractive index adjustment layer may be less than 430 nm or greater than 670 nm, more preferably less than 430 nm.

[0258] [Method of bonding each layer]

[0259] The laminated optical film of the present invention is a laminated body composed of a plurality of layers. Each layer can be bonded by any bonding method, for example, a pressure-sensitive adhesive or an adhesive can be used.

[0260] As the adhesive, any commercially available adhesive can be used. From the viewpoint of thinning and reducing the surface roughness Ra of the laminated optical film, the thickness is preferably 25 μm or less, more preferably 15 μm or less, and most preferably 6 μm or less. In addition, the adhesive is preferably not prone to outgassing. In particular, when stretching or molding is performed, a vacuum process and / or a heating process may be performed, and it is preferred that outgassing is not generated under these conditions.

[0261] As the adhesive, any commercially available adhesive or the like can be used arbitrarily, and for example, an epoxy resin adhesive and an acrylic resin adhesive can be used.

[0262] From the viewpoint of thinning and reducing the surface roughness Ra of the laminated optical film, the thickness of the adhesive is preferably 25 μm or less, more preferably 5 μm or less, and most preferably 1 μm or less. In addition, from the viewpoint of thinning the adhesive layer and applying the adhesive to the adherend with a uniform thickness, the viscosity of the adhesive is preferably 300 cP or less, more preferably 100 cP or less, and further preferably 10 cP or less.

[0263] Furthermore, when the adherend has a surface concavo-convex, from the viewpoint of reducing the surface roughness Ra of the laminated optical film, the adhesive or bonding agent can also select an appropriate viscoelasticity or thickness so as to be able to embed the surface concavo-convex of the bonded layer. From the viewpoint of embedding the surface concavo-convex, the viscosity of the adhesive or bonding agent is preferably 50 cP or more. Furthermore, the thickness is preferably thicker than the height of the surface concavo-convex.

[0264] As a method for adjusting the viscosity of the adhesive, for example, a method of using an adhesive containing a solvent can be cited. In this case, the viscosity of the adhesive can be adjusted by the ratio of the solvent. In addition, by drying the solvent after applying the adhesive to the adherend, the thickness of the adhesive can be further reduced.

[0265] In the laminated optical film, from the viewpoint of reducing unnecessary reflection and suppressing the decrease in the polarization degree of transmitted light and reflected light, the adhesive or bonding agent used for bonding each layer preferably has a small refractive index difference with the adjacent layer. Specifically, the refractive index difference between adjacent layers is preferably 0.1 or less, more preferably 0.05 or less, and further preferably 0.01 or less. The refractive index of the adhesive or bonding agent can be adjusted by mixing particles such as titanium oxide particles and zirconium oxide particles, for example.

[0266] Furthermore, the reflective circular polarizer, phase difference layer and linear polarizer may have in-plane refractive index anisotropy, and preferably the refractive index difference with adjacent layers in all directions in the plane is 0.05 or less. Therefore, the adhesive and pressure-sensitive adhesive may have in-plane refractive index anisotropy.

[0267] Furthermore, regarding the adhesive layer between each layer, the thickness of the adhesive layer is also preferably less than 100nm. When the thickness of the adhesive layer is less than 100nm, the refractive index difference is not easily perceived by light in the visible region, and reflection at the interface can be suppressed. The thickness of the adhesive layer is more preferably less than 50nm. As a method for forming an adhesive layer with a thickness of less than 100nm, for example, a method of evaporating a ceramic adhesive such as silicon oxide (SiOx layer) onto the bonding surface can be cited. The bonding surface of the bonding component can be subjected to surface modification treatments such as plasma treatment, corona treatment, and saponification treatment before bonding, and a primer layer can be given. Furthermore, in the presence of multiple bonding surfaces, the type and thickness of the adhesive layer can be adjusted for each bonding surface. Specifically, for example, an adhesive layer with a thickness of less than 100nm can be provided according to the steps shown in the following (1) to (3).

[0268] (1) The layers to be laminated are bonded onto a dummy support made of a glass substrate.

[0269] (2) A SiOx layer having a thickness of 100 nm or less is formed by vapor deposition or the like on both the surface of the layer to be laminated and the surface of the layer to be laminated. The vapor deposition can be performed by using SiOx powder as a vapor deposition source and using, for example, a vapor deposition device (model ULEYES) manufactured by ULVAC, Inc. In addition, it is preferred that the surface of the formed SiOx layer be subjected to plasma treatment.

[0270] (3) After the formed SiOx layers are bonded together, the dummy support is peeled off. The bonding is preferably performed at a temperature of 120°C, for example.

[0271] The coating, bonding or lamination of each layer may be performed in a roll-to-roll manner or in a single sheet manner. From the viewpoint of improving productivity or reducing axial deviation of each layer, a roll-to-roll method is preferred.

[0272] On the other hand, the single-chip method is preferred in terms of suitability for small-volume and high-variety production and the ability to select a special bonding method in which the thickness of the bonding layer is 100 nm or less.

[0273] In addition, as a method for applying the adhesive to the adherend, for example, known methods such as roll coating, gravure printing, spin coating, wire bar coating, extrusion coating, direct gravure coating, reverse gravure coating, die coating, spray coating and inkjet coating can be cited.

[0274] [Direct coating of each layer]

[0275] It is also preferred that there is no adhesive layer between the layers of the laminated optical film of the present invention. When forming a layer, it can be directly coated on the adjacent layer that has been formed, so that an adhesive layer may not be provided. Furthermore, in the case where one or both of the adjacent layers are layers containing liquid crystal compounds, it is preferred that the orientation direction of the liquid crystal compounds changes continuously at the interface to reduce the refractive index difference in all directions within the plane. For example, it is also possible to directly coat a phase difference layer containing a liquid crystal compound on a linear polarizer containing a liquid crystal compound and a dichroic substance, and the liquid crystal compound of the phase difference layer is oriented in a continuous manner at the interface through the orientation restriction force of the liquid crystal compound of the linear polarizer.

[0276] [Layer stacking order]

[0277] The laminated optical film of the present invention is composed of a plurality of layers, and the order of the steps of laminating these layers is not particularly limited and can be arbitrarily selected.

[0278] For example, when transferring a functional layer from a film composed of a dummy support and a functional layer, by adjusting the stacking order so that the thickness of the film to be transferred becomes 10 μm or more, wrinkles or cracks during transfer can be prevented.

[0279] Furthermore, from the viewpoint of reducing the surface roughness Ra of the laminated optical film, when other layers are laminated on a layer having larger surface roughness, the surface roughness may be further amplified, and therefore, it is preferable to laminate in order starting from the layer having the smallest surface roughness Ra.

[0280] Furthermore, the stacking order can be selected from the perspective of quality evaluation in the manufacturing process of the stacked optical film. For example, after stacking the layers other than the reflective circular polarizer and evaluating the quality through the transmission optical system, the reflective circular polarizer can be stacked and evaluated through the reflection optical system.

[0281] Furthermore, the lamination order can be selected from the viewpoint of improving the manufacturing yield of the laminated optical film or reducing the cost.

[0282] [Application of the laminated optical film of the present invention]

[0283] For example, as described in Patent Documents 4 to 5, the laminated optical film of the present invention can be used as a reflective polarizer assembled in a vehicle-mounted rearview mirror, a virtual reality display device, an electronic viewfinder, etc. In particular, in a virtual reality display device and an electronic viewfinder having a reciprocating optical system that reflects light between a reflective polarizer and a half-reflecting mirror and reciprocates light, the laminated optical film of the present invention is very useful from the viewpoint of improving the clarity of the displayed image. In addition, a virtual reality display device and an electronic viewfinder having a reciprocating optical system sometimes have an optical film such as an absorptive polarizer and a circular polarizer in addition to the reflective polarizer. By using part of the components and bonding methods used for the laminated optical film of the present invention in optical films other than the above-mentioned reflective polarizer, the clarity of the displayed image can be further improved.

[0284] Example

[0285] Below, give embodiment, feature of the present invention is further specifically described.In addition, as long as do not depart from the gist of the present invention, then the material, usage, ratio, processing content, processing step etc. shown below can be changed appropriately.And, as long as do not depart from the gist of the present invention, then can also be set to the structure other than the structure shown below.

[0286] [Preparation of coating solution for reflective layer]

[0287] <Reflective layer coating liquid R-1>

[0288] The composition shown below was stirred and dissolved in a container maintained at 70° C. to prepare a reflective layer coating liquid R-1. Here, R represents a coating liquid using a rod-like liquid crystal compound.

[0289]

[0290] Mixture of rod-like liquid crystal compounds

[0291] [Chemical formula 1]

[0292]

[0293] In the above mixture, the numerical value is mass %, and R is a group bonded via an oxygen atom. Furthermore, the average molar absorption coefficient of the above rod-like liquid crystal compound at a wavelength of 300 to 400 nm is 140 / mol·cm.

[0294] Chiral Reagent A

[0295] [Chemical formula 2]

[0296]

[0297] Surfactant F1

[0298] [Chemical formula 3]

[0299]

[0300] Surfactant F2

[0301] [Chemical formula 4]

[0302]

[0303] Photopolymerization initiator B

[0304] [Chemical formula 5]

[0305]

[0306] The chiral reagent A is a chiral reagent whose helical twisting power (HTP) is reduced by light.

[0307] <Reflective layer coating liquids R-2 to R-6>

[0308] The reflective layer coating liquid R-1 was prepared in the same manner as in the reflective layer coating liquid R-1 except that the amount of the chiral agent A added was changed as shown in Table 1 below.

[0309] Table 1. Amount of chiral agent in coating solution containing rod-shaped liquid crystal compound [Table 1]

[0310]

[0311] <Reflective layer coating liquid D-1>

[0312] The composition shown below was stirred and dissolved in a container maintained at 50° C. to prepare a reflective layer coating liquid D-1. Here, D represents a coating liquid using a discotic liquid crystal compound.

[0313]

[0314] Discotic liquid crystal compound (A)

[0315] [Chemical formula 6]

[0316]

[0317] Discotic liquid crystal compound (B)

[0318] [Chemical formula 7]

[0319]

[0320] Polymerizable monomer E1

[0321] [Chemical formula 8]

[0322]

[0323] Surfactant F4

[0324] [Chemical formula 9]

[0325]

[0326] <Reflective layer coating solutions D-2 to D-5>

[0327] The reflective layer coating liquid D-1 was prepared in the same manner as in Table 2 below, except that the amount of the chiral agent A added was changed.

[0328] Table 2. Amount of chiral agent in coating solution containing discotic liquid crystal compound [Table 2]

[0329]

[0330] [Manufacturing of reflective circular polarizer 1]

[0331] As a pseudo support, a PET (polyethylene terephthalate) film (A4100 manufactured by TOYOBO CO., LTD.) having a thickness of 50 μm was prepared. The PET film had an easy-adhesion layer on one surface.

[0332] The surface of the PET film without the adhesive layer was rubbed, and the reflective layer coating liquid R-1 prepared above was applied by a wire bar coater, and then the coated film was dried at 110°C for 120 seconds. Thereafter, the film was irradiated at 80 mW / cm2 in a low oxygen atmosphere (less than 100 ppm) at 100°C. 2 、Irradiation 500mJ / cm 2 The coating film was cured by light from a metal halide lamp, thereby forming a yellow light reflecting layer (first light reflecting layer) composed of a cholesteric liquid crystal layer. The light irradiation was performed from the cholesteric liquid crystal layer side. At this time, the coating thickness was adjusted so that the film thickness of the yellow light reflecting layer after curing was 2.5 μm.

[0333] Next, the surface of the yellow light reflecting layer was discharged at a rate of 150 W·min / m 2 After the corona treatment, the reflective layer coating liquid D-1 was applied to the corona treated surface using a wire bar coater. The coating film was then dried at 70°C for 2 minutes to vaporize the solvent, and then heated and aged at 115°C for 3 minutes to obtain a uniform orientation state. The coating film was then maintained at 45°C and irradiated with ultraviolet light (300 mJ / cm 2) was cured, thereby forming a green light reflecting layer (second light reflecting layer) on the yellow light reflecting layer. The light irradiation was performed from the cholesteric liquid crystal layer side. At this time, the coating thickness was adjusted so that the film thickness of the green light reflecting layer after curing became 2.4 μm.

[0334] Next, the green light reflecting layer was coated with the reflective layer coating liquid R-2 using a wire bar coater and dried at 110°C for 120 seconds. Thereafter, the green light reflecting layer was irradiated at 80 mW and 500 mJ / cm in a low oxygen atmosphere (less than 100 ppm) at 100°C. 2 The coating film was cured by light from a metal halide lamp, thereby forming a red light reflecting layer (third light reflecting layer) on the green light reflecting layer. The light irradiation was performed from the cholesteric liquid crystal layer side. At this time, the coating thickness was adjusted so that the film thickness of the cured red light reflecting layer was 2.4 μm.

[0335] Next, the discharge rate was 150W·min / m 2 After the surface of the red light reflecting layer was subjected to corona treatment, the reflecting layer coating liquid D-2 was applied to the corona treated surface using a wire bar coater. Then, the coating film was dried at 70°C for 2 minutes to vaporize the solvent, and then heated and aged at 115°C for 3 minutes to obtain a uniform orientation state. Thereafter, the coating film was maintained at 45°C and irradiated with ultraviolet light (300 mJ / cm 2 ) was cured, thereby forming a blue light reflecting layer (fourth light reflecting layer) on the red light reflecting layer. The light irradiation was performed from the cholesteric liquid crystal layer side. At this time, the coating thickness was adjusted so that the film thickness of the blue light reflecting layer after curing became 2.6 μm.

[0336] [Manufacturing of Reflective Circular Polarizers 2 and 4]

[0337] Reflective circular polarizers 2 and 4 were produced by the same production method as that of the reflective circular polarizer 1, except that the reflective layer coating liquid and the film thickness were changed as shown in the following tables (Table 3 and Table 4).

[0338] [Manufacturing of Reflective Circular Polarizer 3]

[0339] In the reflective circular polarizer 3, the reflective layer coating liquid and the film thickness were changed as shown in the following tables (Table 3 and Table 4), and the reflective circular polarizer 3 was produced according to the following production procedure.

[0340] The surface of the PET film without the adhesive layer was rubbed, and the reflective layer coating liquid R-1 prepared above was applied by a wire bar coater, and then the coated film was dried at 110°C for 120 seconds. Thereafter, the film was irradiated at 80 mW / cm2 in a low oxygen atmosphere (less than 100 ppm) at 100°C. 2 、Irradiation 500mJ / cm 2 The coating film was cured by light from a metal halide lamp, thereby forming a yellow light reflecting layer (first light reflecting layer) composed of a cholesteric liquid crystal layer. The light irradiation was performed from the cholesteric liquid crystal layer side. At this time, the coating thickness was adjusted so that the film thickness of the yellow light reflecting layer after curing was 2.5 μm.

[0341] Next, the yellow light reflecting layer was coated with the reflective layer coating liquid R-5 using a wire bar coater, and the coating film was dried at 110°C for 120 seconds. Thereafter, the film was irradiated at 80 mW and 500 mJ / cm2 in a low oxygen atmosphere (less than 100 ppm) at 100°C. 2 The coating film was cured by light from a metal halide lamp, thereby forming a green light reflecting layer (second light reflecting layer) on the yellow light reflecting layer. The light irradiation was performed from the cholesteric liquid crystal layer side. At this time, the coating thickness was adjusted so that the film thickness of the green light reflecting layer after curing was 2.4 μm.

[0342] Next, the green light reflecting layer was coated with the reflective layer coating liquid R-2 using a wire bar coater, and the coating film was dried at 110°C for 120 seconds. Thereafter, the film was irradiated at 80 mW and 500 mJ / cm2 in a low oxygen atmosphere (less than 100 ppm) at 100°C. 2 The coating film was cured by light from a metal halide lamp, thereby forming a red light reflecting layer (third light reflecting layer) on the green light reflecting layer. The light irradiation was performed from the cholesteric liquid crystal layer side. At this time, the coating thickness was adjusted so that the film thickness of the cured red light reflecting layer was 2.4 μm.

[0343] Next, the red light reflecting layer was coated with the reflective layer coating liquid R-6 using a wire bar coater, and the coated film was dried at 110°C for 120 seconds. Thereafter, the film was irradiated at 80 mW and 500 mJ / cm2 in a low oxygen atmosphere (less than 100 ppm) at 100°C. 2 The coating film was cured by light from a metal halide lamp, thereby forming a blue light reflecting layer (fourth light reflecting layer) on the red light reflecting layer. The light irradiation was performed from the cholesteric liquid crystal layer side. At this time, the coating thickness was adjusted so that the film thickness of the blue light reflecting layer after curing became 2.6 μm.

[0344] Table 3. Coating liquid used in the preparation of reflective circular polarizers 1 to 4

[0345] In the following tables, for example, the reflective layer coating liquid R-1 is simply described as "liquid R-1".

[0346] In the table, “1st layer” indicates the 1st light reflecting layer, “2nd layer” indicates the 2nd light reflecting layer, “3rd layer” indicates the 3rd light reflecting layer, and “4th layer” indicates the 4th light reflecting layer.

[0347] [Table 3]

[0348]

[0349] The characteristics of the produced reflective circular polarizers 1 to 4 are shown in Table 3. The reflection center wavelength (center wavelength of reflected light) and Rth of each layer were confirmed by measuring the characteristics of the film produced by coating only a single layer. Here, the reflection center wavelength is used to define the characteristics of a light-reflecting film having a reflection band using a cholesteric liquid crystal phase, and refers to the middle point of the spectral band (spectral band) reflected by the film. Specifically, it is obtained by calculating the average value of the wavelength on the short wavelength side and the wavelength on the long wavelength side showing half the peak reflectivity using the above method.

[0350] In the reflective circular polarizers 1, 2, and 4, the sign of Rth of the first light reflecting layer is opposite to the sign of Rth of the second light reflecting layer, the sign of Rth of the third light reflecting layer is opposite to the sign of Rth of the fourth light reflecting layer, and the sign of Rth of the second light reflecting layer is opposite to the sign of Rth of the third light reflecting layer. On the other hand, in the reflective circular polarizer 3, the sign of Rth is the same from the first light reflecting layer to the fourth light reflecting layer. Furthermore, the SRth of the light reflecting layers of the reflective circular polarizers 1 and 2 is i The absolute values ​​of (i=integer of 1 to 4) were all 0.25 μm or less. The Rth value was measured using AxoScan OPMF-1 (manufactured by Opto Science, Inc.).

[0351] Table 4 shows the film thickness of the produced reflective circular polarizer.

[0352] Table 4. Fabricated reflective circular polarizers 1 to 4 (coating liquid, film thickness) [Table 4]

[0353]

[0354] [Production of laminated optical films]

[0355] A laminated optical film was produced according to the following steps.

[0356] <Production of positive C plate 1>

[0357] The film thickness was adjusted with reference to the method described in paragraphs 0132 to 0134 of Japanese Patent Application Laid-Open No. 2016-053709 to produce a positive C plate 1. In the positive C plate 1, Re=0.2 nm, Rth=-310 nm.

[0358] <Production of phase difference layer 1>

[0359] Referring to the method described in paragraphs 0151 to 0163 of Japanese Patent Application Laid-Open No. 2020-084070, a phase difference layer 1 having reverse wavelength dispersion was produced. In the phase difference layer 1, Re=146 nm, and Rth=73 nm.

[0360] <Production of positive C plate 2>

[0361] A positive C plate 2 was produced in the same manner as the positive C plate 1 except that the film thickness was adjusted. In the positive C plate 2, Re=0.1 nm, Rth=-70 nm.

[0362] <Production of Linear Polarizer>

[0363] A linear polarizer was fabricated according to the following steps.

[0364] (Production of Cellulose Acylate Film 1)

[0365] -Preparation of Core Layer Cellulose Acylate Dope-

[0366] The following composition was placed in a mixing tank and stirred to dissolve the components to prepare a cellulose acetate solution to be used as a core layer cellulose acylate dope.

[0367]

[0368]

[0369] Compound F

[0370] [Chemical formula 10]

[0371]

[0372] -Preparation of outer layer cellulose acylate concentrate-

[0373] To 90 parts by mass of the core layer cellulose acylate dope was added 10 parts by mass of the following matting agent solution to prepare a cellulose acetate solution to be used as an outer layer cellulose acylate dope.

[0374]

[0375] -Production of Cellulose Acylate Film 1-

[0376] After filtering the core layer cellulose acylate concentrate and the outer layer cellulose acylate concentrate with filter paper having an average pore size of 34 μm and a sintered metal filter having an average pore size of 10 μm, the three layers of the core layer cellulose acylate concentrate and the outer layer cellulose acylate concentrates on both sides thereof are simultaneously cast from a casting port onto a drum (belt casting machine) at 20°C.

[0377] Next, the film was peeled off at a solvent content of about 20% by mass, and both ends of the film in the width direction were fixed with tenter clips, and the film was dried while being stretched in the transverse direction at a stretching ratio of 1.1 times.

[0378] Thereafter, the film was further dried by being conveyed between rollers of a heat treatment device to produce an optical film having a thickness of 40 μm, which was referred to as a cellulose acylate film 1. The in-plane retardation of the obtained cellulose acylate film 1 was 0 nm.

[0379] <Formation of Photo-Alignment Layer PA1>

[0380] The coating liquid S-PA-1 for forming an alignment layer described later was continuously coated on the cellulose acylate film 1 using a wire bar. The support body with the coating film formed was dried with warm air at 140° C. for 120 seconds, and then the coating film was irradiated with polarized ultraviolet light (10 mJ / cm 2 , using an ultra-high pressure mercury lamp), thereby forming a photo-alignment layer PA1 with a film thickness of 0.3 μm.

[0381]

[0382] Polymer M-PA-1

[0383] [Chemical formula 11]

[0384]

[0385] Acid Generator PAG-1

[0386] [Chemical formula 12]

[0387]

[0388] Acid Generator CPI-110F

[0389] [Chemical formula 13]

[0390]

[0391] <Formation of light absorption anisotropic layer P1>

[0392] The following coating liquid SP-1 for forming an anisotropic light-absorbing layer was continuously coated on the obtained alignment layer PA1 using a wire bar. Next, the coating layer P1 was heated at 140°C for 30 seconds and cooled to room temperature (23°C). Next, it was heated at 90°C for 60 seconds and cooled to room temperature again. Thereafter, an LED lamp (central wavelength 365nm) was used at an illumination of 200mW / cm 2 The light absorption anisotropic layer P1 was formed on the alignment layer PA1 under the irradiation condition of 2 seconds. The film thickness was 1.6 μm.

[0393]

[0394] Dichroic substance D-1

[0395] [Chemical formula 14]

[0396]

[0397] Dichroic substance D-2

[0398] [Chemical formula 15]

[0399]

[0400] Dichroic substance D-3

[0401] [Chemical formula 16]

[0402]

[0403] Polymer liquid crystal compound MP-1

[0404] [Chemical formula 17]

[0405]

[0406] Low molecular weight liquid crystal compound M-1

[0407] [Chemical formula 18]

[0408]

[0409] Surfactant F-1

[0410] [Chemical formula 19]

[0411]

[0412] <Transfer of reflective circular polarizer>

[0413] The obtained reflective circular polarizer 1 was transferred to the support side of the obtained positive C plate 1. At this time, the transfer was performed in such a way that the layer (fourth light reflecting layer) on the side opposite to the dummy support side of the reflective circular polarizer 1 became the positive C plate 1 side. The dummy support of the reflective circular polarizer 1 was peeled off and removed after the transfer. The transfer of the reflective circular polarizer 1 was performed by the following steps.

[0414] (1) Using a wire bar coater, a UV adhesive chemiseal U2084B (manufactured by Chemitech Inc., with a refractive index of n1.60 after curing) was applied to a thickness of 2 μm on the support side of the positive C plate 1. The reflective circular polarizer 1 was laminated thereon using a laminator so that the side opposite to the dummy support was in contact with the UV adhesive.

[0415] (2) Nitrogen purging was performed in a purge box until the oxygen concentration became 100 ppm or less, and then ultraviolet light from a high pressure mercury lamp was irradiated from the dummy support side of the reflective circular polarizer 1 to perform curing. The illuminance was 25 mW / cm 2 , the irradiation dose is 1000mJ / cm 2 .

[0416] (3) Finally, the dummy support of the reflective circular polarizer 1 is peeled off.

[0417] Next, the positive C plate 2 is bonded to the first light reflecting layer side of the reflective circular polarizer 1. Next, the phase difference layer 1 is bonded to the positive C plate 2.

[0418] Finally, the light absorption anisotropic layer P1 was transferred to the phase difference layer 1 in the same transfer step as above. The phase difference layer 1 was laminated in such a way that the slow axis and the absorption axis of the light absorption anisotropic layer P1 were 45 degrees apart so that the polarization axis of the light emitted from the phase difference layer 1 was parallel to the transmission axis of the light absorption anisotropic layer P1. In this way, a laminated optical film using the reflective circular polarizer 1 of Example 1 was obtained.

[0419] [Evaluation of Double Imaging]

[0420] The lens of the virtual reality display device "Huawei VR Glass" manufactured by Huawei, which uses a reciprocating optical system, was disassembled, and the lens closest to the visual recognition side was removed. The lens is a plano-convex lens with a convex surface on the visual recognition side, and a reflective circular polarizer is bonded to the plane side. The reflective circular polarizer was peeled off from the lens, and instead, the laminated optical film of Example 1 was bonded to the plane side in such a way that the linear polarizer side became the visual recognition side. The lens bonded with the laminated optical film was reassembled into the main body to produce a virtual reality display device. In the produced virtual reality display device, a black and white checkered pattern was displayed on the image display panel, and the visual recognition of ghosting was observed with the naked eye and evaluated in the following three stages.

[0421] A: There is no double image at all.

[0422] B: Although there is a slight double image, it is not annoying.

[0423] C; The ghost image is clearly visible.

[0424] Furthermore, laminated optical films of Example 2, Comparative Example 1 and Comparative Example 2 were prepared in the same manner, and the ghost visibility was evaluated. The types of reflective circular polarizers used in each Example and Comparative Example are shown in Table 5. The evaluation results are shown in Table 6.

[0425] As a result, in the virtual reality display devices of Examples 1 and 2, no ghosting was observed over the entire area of ​​the lens. On the other hand, in the virtual reality evaluation device of Comparative Example 1 using the reflective circular polarizer 3 having the same sign of Rth from the first light reflecting layer to the fourth light reflecting layer, and in the virtual reality evaluation device of Comparative Example 2 in which the layers having the center wavelength of the reflected light in the range of 430 to 570 nm, the layers in the range of 550 to 670 nm, the layers in the range of 430 to 570 nm, and the layers in the range of 550 to 670 nm were not arranged in the following order, ghosting was clearly observed.

[0426] In addition, as a ghosting evaluation method with a higher sensitivity, a black and white checkered pattern was displayed on the image display panel in the manufactured virtual reality display device, and the ghosting visual recognition (photographic image) was evaluated in the following two stages using a photographic image based on a luminance meter (Radiant Vision Systems, Inc., imaging color luminance meter IC-PMI16 with AR / VR lens for head-mounted display evaluation). The above evaluation method can be used to evaluate ghosting at a level that is difficult to confirm with the naked eye in a virtual reality display device.

[0427] A: There is no double image at all.

[0428] B; seeing double.

[0429] As a result, in the virtual reality display device of Example 1, regarding the ghosting visual recognition (photographic image), it is completely invisible throughout the entire area of ​​the lens. On the other hand, in the virtual reality display device of Example 2, in the black display area of ​​the black and white checkered pattern, the light of a part of the white display area is confirmed as a ghost in the photographic image. Thus, according to the evaluation results of the ghosting visual recognition (photographic image) of Examples 1 and 2, it is confirmed that when the difference in the film thickness of each layer from the first layer to the fourth layer is less than 0.5μm, the ghosting can be further suppressed.

[0430] Table 5. Types of reflective circular polarizers used in Examples and Comparative Examples [Table 5]

[0431] Reflective circular polarizer used Example 1 Reflective Circular Polarizer1 Example 2 Reflective Circular Polarizer 2 Comparative Example 1 Reflective Circular Polarizer 3 Comparative Example 2 Reflective Circular Polarizer 4

[0432] Table 6. Evaluation results of ghosting [Table 6]

[0433]

[0434] [Examples 3-4, Comparative Examples 3-4]

[0435] In the step of obtaining the laminated optical film used in the above-mentioned Example 1, the reflective circular polarizer 1 was temporarily transferred to the laminated film with a weak adhesive layer instead of being transferred to the positive C plate 1, thereby obtaining a reflective circular polarizer 1 that was not laminated on the above-mentioned positive C plate 1 but was attached to the laminated film. The same steps as in Example 1 were performed except that the obtained reflective circular polarizer 1 with a laminated film was used, and finally the laminated film was peeled off, thereby obtaining a laminated optical film used in Example 3.

[0436] Furthermore, in the step of obtaining the laminated optical film used in the above-mentioned Example 2, the reflective circular polarizer 2 was temporarily transferred to the laminated film with a weak adhesive layer instead of being transferred to the positive C plate 1, thereby obtaining a reflective circular polarizer 2 that was not laminated on the above-mentioned positive C plate 1 but was attached to the laminated film. The same steps as in Example 2 were performed except that the obtained reflective circular polarizer 2 with a laminated film was used, and finally the laminated film was peeled off, thereby obtaining the laminated optical film used in Example 4.

[0437] In the step of obtaining the laminated optical film used in the above-mentioned Comparative Example 1, the reflective circular polarizer 3 was temporarily transferred to the laminated film with a weak adhesive layer instead of being transferred to the positive C plate 1, thereby obtaining a reflective circular polarizer 3 that was not laminated on the above-mentioned positive C plate 1 but was attached to the laminated film. The same steps as in Comparative Example 1 were performed except that the obtained reflective circular polarizer 3 with a laminated film was used, and finally the laminated film was peeled off, thereby obtaining a laminated optical film used in Comparative Example 3.

[0438] Furthermore, in the step of obtaining the laminated optical film used in the above-mentioned Comparative Example 2, the reflective circular polarizer 4 was temporarily transferred onto the laminated film with a weak adhesive layer instead of being transferred onto the positive C plate 1, thereby obtaining a reflective circular polarizer 4 that was not laminated onto the above-mentioned positive C plate 1 but was bonded to the laminated film. The same steps as in Comparative Example 2 were performed except that the obtained reflective circular polarizer 4 with the laminated film was used, and finally the laminated film was peeled off, thereby obtaining the laminated optical film used in Comparative Example 4.

[0439] The laminated optical films used in Examples 3 and 4 were evaluated for ghosting in the same manner as in the above-described Examples. As a result, the evaluations of ghosting visibility and ghosting visibility (photographed image) were the same as in Examples 1 and 2, respectively.

[0440] The laminated optical films used in Comparative Examples 3 and 4 were evaluated for ghosting in the same manner as in the above-mentioned Comparative Examples. As a result, the evaluations of ghosting visibility and ghosting visibility (photographic image) were the same as in Comparative Examples 1 and 2, respectively.

[0441] Explanation of symbols

[0442] 12-optical laminate, 31-first layer, 32-second layer, 33-third layer, 34-fourth layer, 100-laminated optical film, 101-anti-reflection layer, 102-positive C plate, 103-reflective circular polarizer, 104-positive C plate, 105-phase difference layer, 106-linear polarizer, 300-half-reflecting mirror, 400-circular polarizer, 500-image display panel, 1000-light rays forming virtual images, 2000-light rays forming double images.

Claims

1. An optical laminate comprising a first layer, a second layer, a third layer and a fourth layer in this order, The first layer to the fourth layer are all cholesteric liquid crystal layers, The first layer to the fourth layer all have light reflectivity, The central wavelength of the reflected light of the first layer is in the range of 430 to 570 nm. The central wavelength of the reflected light of the second layer is in the range of 550 to 670 nm. The central wavelength of the reflected light of the third layer is in the range of 430 to 570 nm. The central wavelength of the reflected light of the fourth layer is in the range of 550 to 670 nm. The sign of the retardation of the first layer in the film thickness direction at a wavelength of 550 nm is opposite to the sign of the retardation of the second layer in the film thickness direction at a wavelength of 550 nm. The sign of the retardation of the third layer in the film thickness direction at a wavelength of 550 nm is opposite to the sign of the retardation of the fourth layer in the film thickness direction at a wavelength of 550 nm.

2. The optical laminate according to claim 1, wherein The central wavelength of the reflected light of the first layer is in the range of 430 to 480 nm. The central wavelength of the reflected light of the second layer is in the range of 600 to 670 nm. The central wavelength of the reflected light of the third layer is in the range of 520 to 570 nm. The central wavelength of the reflected light of the fourth layer is in the range of 550 to 620 nm.

3. The optical laminate according to claim 1 or 2, wherein One of the first layer and the second layer is a cholesteric liquid crystal layer formed using a rod-shaped liquid crystal compound, and the other is a cholesteric liquid crystal layer formed using a discotic liquid crystal compound. One of the third layer and the fourth layer is a cholesteric liquid crystal layer formed using a rod-like liquid crystal compound, and the other is a cholesteric liquid crystal layer formed using a discotic liquid crystal compound.

4. The optical laminate according to claim 1 or 2, wherein From the first layer to the fourth layer, the difference in film thickness of each layer is less than 0.5 μm.

5. A laminated optical film, which comprises at least a reflective circular polarizer, a phase difference layer for converting circularly polarized light into linearly polarized light, and a linear polarizer in sequence, wherein: The reflective circular polarizer is the optical laminate according to claim 1 or 2.

6. The laminated optical film according to claim 5, wherein: The linear polarizer includes at least a light absorption anisotropic layer containing a liquid crystal compound and a dichroic substance.

7. The laminated optical film according to claim 5, wherein: The laminated optical film further includes a positive C plate.

8. The laminated optical film according to claim 5, wherein: The laminated optical film further includes an antireflection layer on the surface.

9. The laminated optical film according to claim 8, wherein: The anti-reflection layer is a moth-eye film or an AR film.

10. The laminated optical film according to claim 5, wherein: The laminated optical film further includes a resin substrate having a tan δ peak temperature of 170° C. or less. 11 . An optical article comprising the optical laminate according to claim 1 .

12. A virtual reality display device comprising the optical article according to claim 11.

Images