CN117460976A - Optical laminates, laminated optical films, optical articles, virtual reality display devices - Google Patents

Abstract

An object of the present invention is to provide an optical laminate that can be used as a reflective circular polarizer and that can be used as a reflective circular polarizer, which reduces the occurrence of ghost images when used in a virtual reality display device, an electronic viewfinder, etc. A film and an optical article including an optical laminate, and a virtual reality display device including the optical article. The optical laminate of the present invention has two or more laminated reflective layers. The laminated reflective layers include one each of the following reflective layers: the reflective layer A includes at least one layer using a first liquid crystal compound that is substantially composed of a rod-shaped liquid crystal compound. The cholesteric liquid crystal layer formed does not include a cholesteric liquid crystal layer formed using a second liquid crystal compound substantially composed of a disk-shaped liquid crystal compound; and the reflective layer B includes at least one layer using a second liquid crystal compound substantially composed of a disk-shaped liquid crystal compound. A cholesteric liquid crystal layer formed by using a second liquid crystal compound composed of a discotic liquid crystal compound, excluding a cholesteric liquid crystal layer formed by using a first liquid crystal compound substantially composed of a rod-shaped liquid crystal compound, and meeting the prescribed necessary conditions .

Description

Optical laminates, laminated optical films, optical articles, virtual reality display devices

Technical field

The present invention relates to an optical laminate, a laminated optical film, an optical article, and a virtual reality display device.

Background technique

A reflective polarizer is a polarizer that has the function of reflecting one polarization of incident light and transmitting the other polarization. The reflected light and transmitted light by the reflective polarizer have polarization states that are orthogonal to each other. Here, mutually orthogonal polarization states refer to polarization states located at antipodal points with each other on the Poincar sphere, for example, mutually orthogonal linearly polarized light, right-handed circularly polarized light, and left-handed circularly polarized light. etc. correspond to this.

As a reflective linear polarizer in which transmitted light and reflected light become linearly polarized light, for example, a thin film formed of a stretched dielectric multilayer film as described in Patent Document 1 and a metal film as described in Patent Document 2 are known Wire grid polarizer, etc.

Furthermore, as a reflective circular polarizer in which transmitted light and reflected light become circularly polarized light, a thin film having a light reflective layer in which a cholesteric liquid crystal phase is fixed is known, for example, as described in Patent Document 3.

Reflective polarizers are used to extract only specific polarized light from incident light, splitting the incident light into 2 polarized lights. For example, in a liquid crystal display device, unnecessary polarized light from a backlight is reflected and reused, thereby serving as a brightness enhancement film that improves light utilization efficiency. Furthermore, 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 each to a liquid crystal panel.

Furthermore, in recent years, a method using a reflective polarizer has been proposed for the purpose of reflecting part of external light and light from an image display device to generate a virtual image and a real image. For example, Patent Document 4 discloses a vehicle-mounted rearview mirror (Rear view mirror) that uses a reflective polarizer to reflect light from the rear. Furthermore, Patent Document 5 discloses a method for generating a virtual image by reflecting and reciprocating light between a reflective polarizer and a half mirror in order to reduce the size and thickness of the display section in a virtual reality display device, an electronic viewfinder, etc. method.

Previous technical literature

patent documents

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

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

Patent Document 3: Japanese Patent No. 6277088

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

Patent Document 5: Japanese Patent Application Laid-Open No. 7-120679

Contents of the invention

The technical problem to be solved by the invention

According to research by the present inventors, it was found that when a part of external light and light from an image display device is reflected by a reflective polarizer to generate a virtual image and a real image, the conventional reflective polarization described in Patent Document 1 and Patent Document 2 is The clarity of the image may sometimes be reduced. On the other hand, it was found that good image clarity can be obtained by using a reflective circular polarizer having a light reflective layer in which a cholesteric liquid crystal phase is fixed. The inventors of the present invention believe that this reason is because having a light reflective layer in which a cholesteric liquid crystal phase is fixed makes it possible to realize a reflective circular polarizer with a high degree of polarization using a thin film, and is therefore less susceptible to contamination of foreign matter or material distribution. The influence of fluctuations caused by roughness.

Moreover, according to the research of the present inventor, in a virtual reality display device, an electronic viewfinder, etc., transmitted light is used in addition to reflected light. However, in this case, the transmitted light that was originally intended to be cut is prevented from being transmitted and a ghost image is visually recognized. become important. In the conventional reflective circular polarizer described in Document 3, ghost suppression was observed, and there is room for further improvement.

The present invention has been made in view of the above-mentioned problems, and the technical problem to be solved by the present invention is to provide a reflective circular polarizer that produces less ghost images when used in a virtual reality display device, an electronic viewfinder, etc. An optical laminate, 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.

Means used to solve technical issues

The present inventors conducted in-depth research on the above-mentioned subject and found that the above-mentioned subject can be achieved by the following structure.

[1] An optical laminate having two or more laminated reflective layers, wherein:

The above-mentioned laminated reflective layer includes one of the following reflective layers each: the reflective layer A includes at least one cholesteric liquid crystal layer formed using a first liquid crystal compound that is essentially composed of a rod-shaped liquid crystal compound, and does not include using a first liquid crystal compound that is essentially composed of a rod-shaped liquid crystal compound. A cholesteric liquid crystal layer formed from a second liquid crystal compound composed of a discoidal liquid crystal compound; and

The reflective layer B includes at least one layer of cholesteric liquid crystal layer formed using the above-mentioned second liquid crystal compound substantially composed of a discoidal liquid crystal compound, and does not include the above-mentioned first liquid crystal layer composed essentially of a rod-shaped liquid crystal compound. A cholesteric liquid crystal layer formed from compounds,

Among the two or more laminated reflective layers mentioned above, when the reflective layers A are opposed to each other in two adjacent laminated reflective layers in the stacking direction, the two adjacent laminated reflective layers include The above-mentioned reflective layers A have different center wavelengths of reflected light,

Among the two or more laminated reflective layers described above, when the reflective layers B are opposed to each other in two adjacent laminated reflective layers in the stacking direction, the two adjacent laminated reflective layers B include The reflection layers B have different center wavelengths of reflected light.

[2] The optical laminate according to [1], wherein:

The reflective layers A and B are alternately arranged in the stacking direction of the optical laminate.

[3] The optical laminate according to [1] or [2], wherein:

The total number of the above-described laminated reflective layers is 20 or less.

[4] The optical laminate according to any one of [1] to [3], wherein:

The reflectivity of light with a wavelength of 400 to 700 nm is 40% or more and less than 50%.

[5] The optical laminate according to any one of [1] to [4], wherein:

The above-mentioned laminated reflective layer is composed of one of the above-mentioned reflective layers A and one of the above-mentioned reflective layers in direct contact with each other, or is composed of one of the above-mentioned reflective layers A, one of the above-mentioned reflective layers B, and a plurality of reflective layers arranged between the above-mentioned reflective layers A and the above-mentioned reflective layers. It is composed of a tight layer between layers B.

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

The above-mentioned first layer to the above-mentioned fourth layer are all cholesteric liquid crystal layers,

The above-mentioned first layer to the above-mentioned fourth layer all have light reflectivity,

The central wavelength of the reflected light from the above-mentioned first layer to the above-mentioned fourth layer is within any one of the ranges of 430 to 480 nm, 520 to 570 nm, 570 to 620 nm, and 620 to 670 nm, respectively.

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

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

[7] The optical laminate according to [6], wherein:

Either 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 disk-shaped liquid crystal compound,

Either 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 is a cholesteric liquid crystal layer formed using a disk-shaped liquid crystal compound.

[8] The optical laminate according to [6] or [7], wherein:

In any one of the first layer and the fourth layer, the center wavelength of the reflected light is in the range of 430 to 480 nm, and the center wavelength of the other of the reflected light is in the range of 620 to 670 nm.

[9] The optical laminate according to any one of [6] to [8], wherein:

The central wavelength of the reflected light of the above-mentioned first layer is in the range of 430 to 480 nm.

The central wavelength of the reflected light of the above-mentioned second layer is in the range of 520 to 570nm,

The central wavelength of the reflected light of the third layer is in the range of 570 to 620nm.

The center wavelength of the reflected light of the fourth layer is in the range of 620 to 670 nm.

[10] An optical laminate including a first layer, a second layer, and a third layer in this order,

The above-mentioned first layer to the above-mentioned third layer are all cholesteric liquid crystal layers,

The above-mentioned second layer is a pitch gradient layer formed by changing the spiral pitch in the film thickness direction.

The above-mentioned first layer to the above-mentioned third layer are all light reflective,

The center wavelength of the reflected light from the above-mentioned first layer to the above-mentioned third layer is within any one of the ranges of 430 to 480 nm, 520 to 620 nm, and 620 to 670 nm, respectively.

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

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

[11] The optical laminate according to [10], wherein:

The above-mentioned first layer is a cholesteric liquid crystal layer formed using a rod-shaped liquid crystal compound, the above-mentioned second layer is a cholesteric liquid crystal layer formed using a discoidal liquid crystal compound, and the above-mentioned third layer is formed using a rod-shaped liquid crystal compound. cholesteric liquid crystal layer, or,

The above-mentioned first layer is a cholesteric liquid crystal layer formed using a discoidal liquid crystal compound, the above-mentioned second layer is a cholesteric liquid crystal layer formed using a rod-shaped liquid crystal compound, and the above-mentioned third layer is formed using a discoidal liquid crystal compound. The cholesteric liquid crystal layer formed.

[12] The optical laminate according to [10] or [11], wherein:

The central wavelength of the reflected light of the above-mentioned first layer is in the range of 430 to 480 nm.

The central wavelength of the reflected light of the above-mentioned second layer is in the range of 520 to 620nm,

The center wavelength of the reflected light of the third layer is in the range of 620 to 670 nm.

[13] A laminated optical film having at least a reflective circular polarizer, a phase difference layer that converts circularly polarized light into linearly polarized light, and a linear polarizer in this order, wherein:

The reflective circular polarizer is the optical laminate described in any one of [1] to [12].

[14] The laminated optical film according to [13], wherein:

The linear polarizer includes at least a light-absorbing anisotropic layer including a liquid crystal compound and a dichroic substance.

[15] The laminated optical film according to [13] or [14], further including a positive C plate.

[16] The laminated optical film according to any one of [13] to [15], further including an antireflection layer on the surface.

[17] The laminated optical film according to [16], wherein:

The above-mentioned anti-reflective layer is a moth eye film or AR film.

[18] The laminated optical film according to any one of [13] to [17], which contains:

A resin base material with a tan δ peak temperature of 170°C or lower.

[19] An optical article including the optical laminate according to any one of [1] to [12].

[20] A virtual reality display device including the optical article described in [19].

Invention effect

The present invention can provide an optical laminate that can be used as a reflective circular polarizer, which causes less ghosting when used in a virtual reality display device, an electronic viewfinder, or the like.

Furthermore, according to the present invention, it is possible to provide 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.

Description of the drawings

FIG. 1 is a schematic diagram showing an example of an optical laminate according to the first embodiment of the present invention.

FIG. 2 is a schematic diagram showing an example of the optical laminate according to the first embodiment of the present invention.

FIG. 3 is a schematic diagram showing an example of the second embodiment of the optical laminate of the present invention.

FIG. 4 is a schematic diagram showing an example of an optical laminate according to a third embodiment of the present invention.

FIG. 5 is an example of a virtual reality display device using the laminated optical film of the present invention.

FIG. 6 is an example of a virtual reality display device using the laminated optical film of the present invention.

FIG. 7 is a schematic diagram showing an example of the laminated optical film of the present invention.

Detailed ways

Hereinafter, the present invention will be described in detail. The description of the components described below may be based on representative embodiments or specific examples, but the present invention is not limited to such embodiments.

In addition, in this specification, the numerical range expressed using "～" means the range including the numerical value written before and after "～" as a lower limit value and an upper limit value.

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

In this specification, the "absorption axis" refers to the polarization direction in which the in-plane absorbance becomes maximum when linearly polarized light is incident. Furthermore, the “reflection axis” refers to the polarization direction in which the in-plane reflectance becomes maximum when linearly polarized light is incident. In addition, the “transmission axis” refers to the direction orthogonal to the absorption axis or the reflection axis in the plane. In addition, the “slow axis” refers to the direction in which the in-plane refractive index becomes maximum.

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

In addition, the retardation in the thickness direction at wavelength λ is described as Rth(λ) in this specification.

For Re(λ) and Rth(λ), values measured at wavelength λ using AxoScan OPMF-1 (manufactured by Opto Science, Inc.) can be used. Calculated by inputting the average refractive index ((nx+ny+nz)/3) and film thickness (d(μm)) using AxoScan

Slow axis direction (°)

Re(λ)=R0(λ)

Rth(λ)=((nx+ny)/2-nz)×d.

Examples of the optical laminate of the present invention include the first embodiment, the second embodiment, and the third embodiment.

Hereinafter, the first, second and third embodiments of the optical laminate of the present invention will be described.

[First Embodiment]

The optical laminate according to the first embodiment of the present invention has two or more laminated reflective layers,

The above-mentioned laminated reflective layer includes one of the following reflective layers:

The reflective layer A includes at least one cholesteric liquid crystal layer (hereinafter also referred to as "liquid crystal layer 1") formed using a first liquid crystal compound substantially composed of a rod-shaped liquid crystal compound, and does not include a layer using substantially a rod-shaped liquid crystal compound. A cholesteric liquid crystal layer (hereinafter also referred to as "liquid crystal layer 2") formed of a second liquid crystal compound composed of a discoidal liquid crystal compound; and

Reflective layer B includes at least one layer of liquid crystal layer 2 and does not include liquid crystal layer 1,

Among the two or more laminated reflective layers mentioned above, when the reflective layers A are opposed to each other in two adjacent laminated reflective layers in the stacking direction, the two adjacent laminated reflective layers include The above-mentioned reflective layers A have different center wavelengths of reflected light,

Among the two or more laminated reflective layers described above, when the reflective layers B are opposed to each other in two adjacent laminated reflective layers in the stacking direction, the two adjacent laminated reflective layers B include The reflection layers B have different center wavelengths of reflected light.

The optical laminate according to the first embodiment of the present invention will be described using the drawings. FIG. 1 is a schematic cross-sectional view showing an example of the structure of the optical laminate 10 according to the first embodiment.

In the form shown in FIG. 1 , the optical laminated body 10 is composed of a first laminated reflective layer 25 and a second laminated reflective layer 26 . The first laminated reflective layer 25 is composed of a reflective layer A21 a and a reflective layer B22 b . Layer 26 is composed of reflective layer A23a and reflective layer B24b. In the optical laminate 10 of the form shown in FIG. 1 , the reflective layer A21a, the reflective layer B22b, the reflective layer A23a, and the reflective layer B24b are laminated in this order.

The optical laminate according to the first embodiment of the present invention can be used as a reflective circular polarizer. If the optical laminate has the above structure, the reflective layer A has a positive Rth and the reflective layer B has a negative Rth. Therefore, it is considered that the Rths of each other cancel each other, and ghosting can be suppressed even for incident light from an oblique direction. produce.

Hereinafter, the first embodiment of the present invention will be described in detail.

[Laminated reflective layer]

The optical laminate according to the first embodiment of the present invention has two or more laminated reflective layers, each of which includes a reflective layer A and a reflective layer B, which will be described in detail later. That is, the optical laminate according to the first embodiment of the present invention includes two or more layers of reflective layer A and reflective layer B respectively.

In the laminated reflective layer, the reflective layer A and the reflective layer B may be in direct contact, or the reflective layer A and the reflective layer B may be laminated via another layer. The other layers are not particularly limited, but examples include an adhesive layer (for example, an adhesive layer, an adhesive layer, etc.), a refractive index adjustment layer, a resin film, a positive C plate, an alignment layer, and the like.

Furthermore, the laminated reflective layer may be composed of one reflective layer A and one reflective layer B in direct contact, or may be composed of one reflective layer A, one reflective layer B, and a reflective layer disposed between the reflective layer A and the reflective layer B. Composed of tight layers. Among them, the laminated reflective layer is preferably composed of one reflective layer A and one reflective layer B in direct contact.

In the optical laminate, the laminated reflective layers may be stacked so that the reflective layers A and B are alternately arranged, or may be stacked such that the reflective layers A face each other, or may be stacked such that the reflective layers B face each other. .

For example, when the optical laminate of the first embodiment has two laminated reflective layers, the reflective layer A, the reflective layer B, the reflective layer A, and the reflective layer B may be laminated in this order. The layer B, the reflective layer B, and the reflective layer A may be stacked in this order, or the reflective layer B, the reflective layer A, the reflective layer A, and the reflective layer B may be stacked in this order.

However, among the two laminated reflective layers adjacent to each other in the stacking direction, when the reflective layers A are opposed to each other (for example, the reflective layer B, the reflective layer A, the reflective layer A, and the reflective layer B are stacked in this order) ), the center wavelengths of the reflected light of the reflective layers A contained in the two adjacent laminated reflective layers are different from each other, and among the above-mentioned 2 or more laminated reflective layers, the two adjacent ones in the stacking direction are In the laminated reflective layer, when the reflective layers B are opposed to each other (for example, when the reflective layer A, the reflective layer B, the reflective layer B, and the reflective layer A are laminated in this order), two adjacent laminated layers The reflection layers B included in the reflection layer have different center wavelengths of reflected light.

Hereinafter, an optical laminate in which the reflective layers A face each other among the two laminated reflective layers adjacent to each other in the stacking direction will be described using the drawings. The optical laminate 11 shown in FIG. 2 is composed of a first laminated reflective layer 25 and a second laminated reflective layer 26. The first laminated reflective layer 25 is composed of a reflective layer B21b and a reflective layer A22a, and the second laminated reflective layer 26 is composed of a reflective layer B21b and a reflective layer A22a. It is composed of layer A23a and reflective layer B24b. In the optical laminate 11 of the form shown in FIG. 2 , the reflective layer B21b, the reflective layer A22a, the reflective layer A23a, and the reflective layer B24b are laminated in this order. However, the center wavelength of the reflected light from the reflective layer A22a is different from the center wavelength of the reflected light from the reflective layer A23a. Furthermore, in the optical laminated body 11 shown in FIG. 2 , the reflective layer A22 a is included in the first laminated reflective layer 25 , and the reflective layer A23 a is included in the second laminated reflective layer 26 .

That is, as will be described in detail later, the reflective layer A may include two or more liquid crystal layers 1 having different center wavelengths of reflected light. However, in the optical laminate, when two or more liquid crystal layers 1 are continuously arranged , use reflective layer A and stacked reflective layers to maximize the number of stacked reflective layers.

Similarly, as will be described in detail later, the reflective layer B may include two or more liquid crystal layers 2 having different center wavelengths of reflected light. However, in the optical laminate, two or more liquid crystal layers 2 are continuously arranged. Below, use reflective layer B and stack reflective layers to maximize the number of stacked reflective layers.

Among them, the above-mentioned stacking method of stacking the reflective layers is preferably a stacking method in which the reflective layers A and the reflective layers B are alternately arranged. That is, it is preferable that the reflective layers A and B are alternately arranged in the thickness direction of the optical laminate.

The optical laminate of the first embodiment includes two or more laminated reflective layers, but may include three or more laminated reflective layers, or may include four or more layers. That is, the optical laminate includes two or more layers of the reflective layer A and the reflective layer B, but may include three or more layers of the reflective layer A and the reflective layer B, or may include four or more layers.

The total number of laminated reflective layers included in the optical laminate is preferably 30 or less layers, more preferably 20 or less layers, and even more preferably 10 or less layers. That is, the total number of layers of the reflective layer A and the reflective layer B in the optical laminate is preferably 60 layers or less, preferably 40 layers or less, and more preferably 20 layers or less.

The thickness of the laminated reflective layer is preferably 0.2 μm or more, more preferably 0.4 μm or more, still more preferably 0.6 μm or more. Furthermore, the thickness of the laminated reflective layer is preferably 20.0 μm or less, more preferably 14.0 μm or less, and still more preferably 10.0 μm or less.

The thickness of the laminated reflective layer is measured in the same manner as the reflective layer A and the reflective layer B described below.

Hereinafter, the reflective layer A and the reflective layer B will be described.

[Reflective layer A]

The laminated reflective layer included in the optical laminate according to the first embodiment of the present invention includes at least one liquid crystal layer 1 and a reflective layer A that does not include the liquid crystal layer 2 .

The liquid crystal layer 1 is a cholesteric liquid crystal layer formed using a first liquid crystal compound substantially composed of a rod-shaped liquid crystal compound, and is substantially composed of a rod-shaped liquid crystal compound. In addition, "a cholesteric liquid crystal layer formed using a first liquid crystal compound substantially composed of a rod-shaped liquid crystal compound" means that the above-mentioned first liquid crystal compound is a cholesteric liquid crystal phase, and the orientation of the cholesteric liquid crystal phase is A layer with a fixed state. The above "consisting essentially of a rod-shaped liquid crystal compound" means that the rod-shaped liquid crystal compound accounts for 95 mass % or more of the liquid crystal compound (first liquid crystal compound) contained in the liquid crystal layer 1 . That is, the "first liquid crystal compound substantially composed of a rod-shaped liquid crystal compound" means that the content of the rod-shaped liquid crystal compound is 95 mass % or more based on the total mass of the first liquid crystal compound. Among them, the first liquid crystal compound is preferably composed only of rod-shaped liquid crystal compounds.

Furthermore, the liquid crystal layer 2 is a cholesteric liquid crystal layer formed using a second liquid crystal compound substantially composed of a discoidal liquid crystal compound, and is substantially composed of a discoidal liquid crystal compound. In addition, "a cholesteric liquid crystal layer formed using a second liquid crystal compound substantially composed of a disk-shaped liquid crystal compound" means that the above-mentioned second liquid crystal compound is a cholesteric liquid crystal phase, and the cholesteric liquid crystal phase is The orientation state of the layer is fixed. The above "consisting essentially of a discoidal liquid crystal compound" means that the discoidal liquid crystal compound accounts for 95% by mass or more of the liquid crystal compound (second liquid crystal compound) contained in the liquid crystal layer 2 . That is, the "second liquid crystal compound substantially composed of a discoidal liquid crystal compound" means that the content of the discoidal liquid crystal compound is 95% by mass or more based on the total mass of the second liquid crystal compound. Among them, the second liquid crystal compound is preferably composed only of a discoidal liquid crystal compound.

The reflective layer A only needs to include one or more liquid crystal layers 1, or may include two or more layers. When the reflective layer A includes two or more liquid crystal layers 1 , layers other than the liquid crystal layer 2 may or may not be included between the two or more liquid crystal layers 1 . The other layers are not particularly limited, but examples include an adhesive layer (for example, an adhesive layer, an adhesive layer, etc.), a refractive index adjustment layer, a resin film, a positive C plate, an alignment layer, and the like.

The number of liquid crystal layers 1 included in the reflective layer A is preferably 5 or less, more preferably 3 or less, and still more preferably 2 or less. The number of liquid crystal layers 1 included in the reflective layer A is preferably one layer.

In addition, for example, when two liquid crystal layers 1 have different center wavelengths of reflected light, they are regarded as two liquid crystal layers 1 . Furthermore, as long as the center wavelength of the reflected light of two or more liquid crystal layers 1 is the same, they are regarded as one layer of liquid crystal layer 1 regardless of whether they are formed by sequential coating or separated by the other layers mentioned above.

When the reflective layer A includes two or more liquid crystal layers 1, the center wavelength of the reflected light of the reflective layer A is the center wavelength of the reflected light of the entire reflective layer A. The method of measuring the center wavelength of reflected light will be described later.

The thickness of the reflective layer A is preferably 0.1 μm or more, more preferably 0.2 μm or more, and still more preferably 0.3 μm or more. In order to further suppress ghosting, the thickness of the reflective layer A is preferably 10.0 μm or less, more preferably 7.0 μm or less, and even more preferably 5.0 μm or less.

The thickness of the reflective layer A is measured by making a cross section of the optical laminate and observing it with a scanning electron microscope. The thickness of the reflective layer A is a value obtained by averaging the thicknesses of the reflective layer A at five arbitrary locations in the cross section of the optical laminate. In addition, when the cross section of the optical laminate is observed with a scanning electron microscope, a region of the reflective layer A and a region of the reflective layer B described below can be distinguished based on the difference in contrast of the captured image. Furthermore, by using component analysis in the film thickness direction based on TOF-SIMS (Time-of-flight-Secondary Ion MassSpectrometry), the regions of the reflective layer A and the reflective layer B can also be distinguished.

The Rth of the reflective layer A is preferably 8 to 800 nm at a wavelength of 550 nm, more preferably 16 to 560 nm, and even more preferably 24 to 400 nm.

The Rth of the reflective layer A may be measured by taking out only the reflective layer A from the optical laminate, or the Rth of a layer produced under the same conditions as when the reflective layer A was produced may be measured.

The rod-shaped liquid crystal compound contained in the liquid crystal layer 1 is not particularly limited, and known rod-shaped liquid crystal compounds can be used. Furthermore, the liquid crystal layer 1 only needs to be a layer in which the orientation of a rod-shaped liquid crystal compound that becomes a cholesteric liquid crystal phase is maintained. Typically, a polymerizable rod-shaped liquid crystal compound having a polymerizable group can be made into a layer by adding a chiral reagent or the like. The alignment state of the cholesteric liquid crystal phase is then polymerized and solidified by ultraviolet irradiation, heating, etc. to form a layer without fluidity. The liquid crystal layer 1 formed as described above only needs to be a layer that changes into a state in which the alignment form is not changed due to an external field, external force, or the like. In addition, in the liquid crystal layer 1, it is sufficient that the optical properties of the cholesteric liquid crystal phase can be maintained in the layer, and the rod-shaped liquid crystal compound in the liquid crystal layer 1 may no longer exhibit liquid crystallinity. For example, the polymerizable rod-shaped liquid crystal compound may be polymerized into a high molecular weight through a curing reaction, thereby losing liquid crystallinity.

The center wavelength λ of the reflected light of the liquid crystal layer 1 depends on the pitch P (= period of the spiral) of the spiral structure in the cholesteric liquid crystal phase. Using the average refractive index n of the liquid crystal layer 1, the relationship is λ = n × P express. In addition, the center wavelength of the reflected light of the liquid crystal layer 1 can be obtained as follows. When the transmission spectrum of the reflective layer A was measured from the normal direction of the liquid crystal layer 1 using a spectrophotometer UV3150 (SHIMADZU CORPORATION), a spectrum having a peak with reduced transmittance was obtained in a region near the center wavelength of the reflected light. Among the two wavelengths at which the transmittance is 1/2 of the maximum peak value, let the value of the wavelength on the short wavelength side be λ _l (nm), and let the value of the wavelength on the long wavelength side be λ _h ( nm), the center wavelength λ of the reflected light is calculated by the following formula.

λ=(λ _l +λ _h )/2

The pitch of the cholesteric liquid crystal phase changes depending on the type of chiral reagent used together with the polymerizable rod-shaped liquid crystal compound and its addition concentration. By adjusting any one or more of the above, a cholesteric liquid crystal phase with a desired pitch can be obtained. . In addition, regarding the measurement method of the rotation direction and pitch of the spiral, you can use "Introduction to Liquid Crystal Chemistry Experiments" published by Sigma Publishing, Japan Liquid Crystal Society, 2007, page 46 and "Liquid Crystal Handbook" Liquid Crystal Handbook Editorial Committee Maruzen, page 196 documented methods.

[Reflective layer B]

The laminated reflective layer included in the optical laminate according to the first embodiment of the present invention includes at least one liquid crystal layer 2 and includes a reflective layer B that does not include the liquid crystal layer 1 .

The liquid crystal layer 2 and the liquid crystal layer 1 are defined as above.

The reflective layer B only needs to include one or more layers of the liquid crystal layer 2, or may include two or more layers. When the reflective layer B includes two or more liquid crystal layers 2 , layers other than the liquid crystal layer 1 may or may not be included between the two or more liquid crystal layers 2 . The other layers are not particularly limited, but examples include an adhesive layer (for example, an adhesive layer, an adhesive layer, etc.), a refractive index adjustment layer, a resin film, a positive C plate, an alignment layer, and the like.

The number of liquid crystal layers 2 included in the reflective layer B is preferably 5 or less, more preferably 3 or less, and even more preferably 2 or less. The number of liquid crystal layers 2 included in the reflective layer B is preferably one layer.

In addition, for example, when two liquid crystal layers 2 have different center wavelengths of reflected light, they are regarded as two liquid crystal layers 2 . Furthermore, as long as the center wavelength of the reflected light of two or more liquid crystal layers 2 is the same, they are regarded as one layer of liquid crystal layer 2 regardless of whether they are formed by sequential coating or separated by the other layers mentioned above.

When the reflective layer B includes two or more liquid crystal layers 2, the center wavelength of the reflected light of the reflective layer B is the center wavelength of the reflected light of the entire reflective layer B. The center wavelength of the reflected light of each liquid crystal layer 2 is measured according to the above-described method of measuring the center wavelength of the reflected light of the liquid crystal layer 1 .

The thickness of the reflective layer B is preferably 0.1 μm or more, more preferably 0.2 μm or more, still more preferably 0.3 μm or more. In order to further suppress ghosting, the thickness of the reflective layer B is preferably 10.0 μm or less, more preferably 7.0 μm or less, and even more preferably 5.0 μm or less.

The thickness of the reflective layer B is measured by making a cross section of the optical laminate and observing it with a transmission electron microscope.

The Rth of the reflective layer B is preferably -8 to -800 nm at a wavelength of 550 nm, more preferably -16 to -560 nm, and further preferably -24 to -400 nm.

The Rth of the reflective layer B may be measured by taking out only the reflective layer B from the optical laminate, or the Rth of the layer produced under the same conditions as when the reflective layer B was produced may be measured.

The discoidal liquid crystal compound contained in the liquid crystal layer 2 is not particularly limited, and known discotic liquid crystal compounds can be used. Furthermore, the liquid crystal layer 2 only needs to be a layer in which the orientation of a discoidal liquid crystal compound that becomes a cholesteric liquid crystal phase is maintained. Typically, a polymerizable disc having a polymerizable group can be made by adding a chiral reagent or the like. The liquid crystal compound is oriented into a cholesteric liquid crystal phase, and is then polymerized and solidified by ultraviolet irradiation, heating, etc. to form a layer without fluidity. The liquid crystal layer 2 formed as described above only needs to be a layer that changes into a state in which the alignment form is not changed due to an external field, external force, or the like. In addition, in the liquid crystal layer 2, it is sufficient that the optical properties of the cholesteric liquid crystal phase can be maintained in the layer, and the discoidal liquid crystal compound in the liquid crystal layer 2 may no longer exhibit liquid crystallinity. For example, the polymerizable discoidal liquid crystal compound can be polymerized into a high molecular weight through a curing reaction, thereby no longer having liquid crystallinity.

The center wavelength λ of the reflected light of the liquid crystal layer 2 depends on the pitch of the helical structure in the cholesteric liquid crystal phase, can be defined in the same manner as in the case of the liquid crystal layer 1, and can be measured by the same method.

The pitch of the cholesteric liquid crystal phase changes depending on the type of chiral reagent used together with the polymerizable discoidal liquid crystal compound and its addition concentration. By adjusting any one or more of the above, a cholesteric liquid crystal phase with a desired pitch can be obtained. Liquid crystal phase. In addition, for the measurement method of the spiral direction and pitch, the above-mentioned documents can be referred to.

〔Reflectivity〕

The optical laminate according to the first embodiment of the present invention preferably has a reflectance of light having a wavelength of 400 to 700 nm of 40% or more and less than 50%. When the reflectivity is 40% or more, ghost images can be easily suppressed further. In addition, the light with a wavelength of 400 to 700 nm refers to unpolarized light.

The reflectance of the optical laminate for light having a wavelength of 400 to 700 nm was measured under the following conditions.

An automatic absolute reflectance measurement system consisting of a UV-visible-near-infrared spectrophotometer V-750 manufactured by JASCO Corporation was used. In the optical laminate, polarized light of S wave and P wave having a wavelength of 350 to 900 nm is incident at an incident angle of 5°. The absolute reflectance for each of the S wave and the P wave is measured, and the average value is calculated for each wavelength, thereby obtaining the reflection spectrum. From the obtained reflectance spectrum, the average reflectance with respect to light with a wavelength of 400 to 700 nm was calculated, and was set as the reflectance of the optical laminate with respect to light with a wavelength of 400 to 700 nm.

[Types and arrangements of reflective layer A and reflective layer B]

The optical laminate according to the first embodiment of the present invention includes the above-mentioned reflective layer A and reflective layer B, but preferably includes at least a blue light reflective layer with a reflectance of 40% or more at a wavelength of 460 nm, and a reflectance of 40% or more at a wavelength of 550 nm. The green light reflective layer has a reflectivity of more than 40% at a wavelength of 600 nm, a yellow light reflective layer has a reflectivity of more than 40% at a wavelength of 650 nm, and a red light reflective layer has a reflectivity of more than 40% at a wavelength of 650 nm. The above-mentioned blue light reflective layer, green light reflective layer, yellow light reflective layer and red light reflective layer may respectively correspond to any one of the reflective layer A and the reflective layer B. For example, when the reflective layer A corresponds to the blue light reflective layer, the central wavelength of the reflected light from the reflective layer A can be adjusted by the above method to set the central wavelength of the reflected light to about 460 nm. In addition, when the reflective layer B corresponds to the blue light reflective layer, the center wavelength of the reflected light by the reflective layer B is adjusted by the above method to set the center wavelength of the reflected light to about 460 nm. In addition, the above-mentioned reflectance is the reflectance when unpolarized light is incident on the reflective layer at respective wavelengths.

When the optical laminate includes the above-described blue light reflective layer, green light reflective layer, yellow light reflective layer, and red light reflective layer, it may have two or more blue light reflective layers, or may have two or more green light reflective layers. The layer may have two or more yellow light-reflecting layers, or may have two or more red light-reflecting layers.

The center wavelength of the reflected light of the blue light reflective layer is preferably in the range of 430 to 480 nm.

The center wavelength of the reflected light of the green light reflective layer is preferably in the range of 520 to 570 nm.

The center wavelength of the reflected light of the yellow light reflective layer is preferably in the range of 570 to 620 nm.

The center wavelength of the reflected light of the red light reflective layer is preferably in the range of 620 to 670 nm.

The method for measuring the center wavelength of reflected light is as described above.

Furthermore, in the optical laminate according to the first embodiment of the present invention, the center wavelength of the reflected light of the reflective layer A and the reflective layer B included in the optical laminate may be individually adjusted so as to cover the entire visible light range (wavelength 400~700nm), so that the reflectivity becomes more than 40%.

Furthermore, the optical laminate preferably has the above-described blue light reflective layer, green light reflective layer, yellow light reflective layer, and red light reflective layer laminated in this order. Furthermore, when the optical laminate in the above-mentioned stacking sequence is applied to a reflective circular polarizer described later, in order to obtain sufficient reflectivity in the reflective layer on the long wavelength side (for example, the red light reflective layer) As the required thickness of the reflective layer becomes thicker and the Rth of the reflective layer itself has a greater influence on the light transmitted through the reflective layer, the reflective layer disposed on the light source side is preferably a reflective layer on the short wavelength side (for example, blue light reflective layer).

In the optical laminate according to the first embodiment of the present invention, the reflective layer A has a positive Rth and the reflective layer B has a negative Rth. Therefore, their Rths cancel each other out, as described above. However, the details are explained below.

In an optical laminate having n layers of reflective layers, when the reflective layers are named L ₁ , L ₂ , L ₃ , ..., L _n in order from the light source side (n is an integer of 4 or more), the reflective layer L is The sum of Rth of each layer from ₁ to the reflective layer Li ( _i is an integer equal to or smaller than n) is set to SRth _i . Specifically, SRth _i is expressed as follows.

SRth ₁ =Rth ₁

SRth ₂ =Rth ₁ +Rth ₂

…

SRth _i =Rth ₁ +Rth ₂ +…+Rth _i

…

SRth _n =Rth ₁ +Rth ₂ +…+Rth _i +…+Rth _n

The absolute values of all these SRth _i (SRth ₁ to SRth _n ) are preferably 0.3 μm or less, more preferably 0.2 μm or less, and still more preferably 0.1 μm or less. The Rth _i of each layer in the above formula is determined by the formula for calculating Rth described above.

It is considered that by setting SRth _i 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.

Furthermore, in the case where the reflective layer A and the reflective layer B are in direct contact with each other in the laminated reflective layer, in order to reduce the difference in refractive index, it is preferable to align the liquid crystal compound (rod-shaped liquid crystal compound or disc-shaped liquid crystal compound) in the orientation direction ( Slow axis direction) is configured in a continuously changing manner at the interface. In the arrangement as described above, for example, when the reflective layer A is formed on the reflective layer B, a coating liquid containing a rod-shaped liquid crystal compound can also be directly applied on the reflective layer B. The orientation restricting force of the disk-shaped liquid crystal compound orients in such a way that the slow axis direction is continuous at the interface.

The thickness of the optical laminate according to the first embodiment of the present invention is preferably 30 μm or less, and more preferably 15 μm or less.

The lower limit is not particularly limited. For example, it is 1 μm or more, and preferably 5 μm or more.

The manufacturing method of the optical laminate according to the first embodiment of the present invention, the laminated optical film using the optical laminate, and the like will be described later.

[Second Embodiment]

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

The above-mentioned first layer to the above-mentioned fourth layer are all cholesteric liquid crystal layers,

The above-mentioned first layer to the above-mentioned fourth layer all have light reflectivity,

The central wavelength of the reflected light from the above-mentioned first layer to the above-mentioned fourth layer is within any one of the ranges of 430 to 480 nm, 520 to 570 nm, 570 to 620 nm, and 620 to 670 nm, respectively.

The sign of Rth at the wavelength of 550 nm in the above-mentioned first layer is opposite to the sign of Rth at the wavelength of 550 nm in the above-mentioned second layer,

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

The optical laminate according to the second embodiment of the present invention will be described using the drawings. FIG. 3 is a schematic cross-sectional view showing an example of the structure of the optical laminate 12 according to the second embodiment.

In the form shown in FIG. 3 , the optical laminate 12 has a first layer 31 , a second layer 32 , a third layer 33 , and a fourth layer 34 laminated in this order, each of which satisfies the above-mentioned necessary conditions. In addition, the sign of Rth in the first layer 31 is opposite to the sign of Rth in the second layer 32, and the sign of Rth in the third layer 33 is opposite to the sign of Rth in the fourth layer 34.

The optical laminate according to the second embodiment of the present invention can be used as a reflective circular polarizer. It is considered that if 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 fourth layer cancel each other, it is considered that from the Incident light in oblique directions can also suppress the generation of ghost images.

Hereinafter, the second embodiment of the present invention will be described in detail.

[First floor to fourth floor]

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

The first to fourth layers are light-reflective cholesteric liquid crystal layers.

The cholesteric liquid crystal layer is a layer in which a liquid crystal compound is 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, the liquid crystal layer described in Japanese Patent Application Laid-Open No. 2020-060627 and the like can be used.

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 disk-shaped liquid crystal compound. In a cholesteric liquid crystal layer formed using a rod-shaped liquid crystal compound, Rth tends to have a positive value, and in a cholesteric liquid crystal layer formed using a discoidal liquid crystal compound, Rth tends to have a negative value.

Furthermore, the center wavelengths of the reflected light of the first layer to the fourth layer are respectively within any one of the ranges of 430 to 480 nm, 520 to 570 nm, 570 to 620 nm, and 620 to 670 nm. It is also preferable that the center wavelengths of the reflected light of the first layer to the fourth layer are different from each other.

When the center wavelength of reflected light is 430 to 480 nm, this layer can correspond to the blue light reflecting layer described in the first embodiment. In this case, the reflectance in the center wavelength of the reflected light is preferably 40% or more and less than 50%.

When the center wavelength of reflected light is 520 to 570 nm, this layer can correspond to the green light reflective layer described in the first embodiment. In this case, the reflectance in the center wavelength of the reflected light is preferably 40% or more and less than 50%.

When the center wavelength of reflected light is 570 to 620 nm, this layer can correspond to the yellow light reflective layer described in the first embodiment. In this case, the reflectance in the center wavelength of the reflected light is preferably 40% or more and less than 50%.

When the center wavelength of reflected light is 620 to 670 nm, this layer can correspond to the red light reflective layer described in the first embodiment. In this case, the reflectance in the center wavelength of the reflected light is preferably 40% or more and less than 50%.

The method of measuring reflectance is as described above.

The central wavelength of the reflected light of the first layer to the fourth layer may be within any of the above-mentioned wavelength ranges. However, in the first layer and the fourth layer, it is preferable that the central wavelength of the reflected light of any one of the first layer and the fourth layer is within the range of 430 to 480 nm. , the center wavelength of the other reflected light is in the range of 620~670nm.

Furthermore, it is also preferable that the center wavelength of the reflected light of the first layer is in the range of 430 to 480 nm, the center wavelength of the reflected light of the second layer is in the range of 520 to 570 nm, and the center wavelength of the reflected light of the third layer is in the range of 570 to 570 nm. Within the range of 620 nm, the central wavelength of the reflected light of the fourth layer is within the range of 620 to 670 nm.

That is, it is also preferable that the first layer corresponds to the blue light reflective layer, the second layer corresponds to the green light reflective layer, the third layer corresponds to the yellow light reflective layer, and the fourth layer corresponds to the red light reflective layer.

Furthermore, when the optical laminate in the above-mentioned stacking sequence is applied to a reflective circular polarizer described later, in order to obtain sufficient reflectivity in the reflective layer on the long wavelength side (for example, the red light reflective layer) As the required thickness of the reflective layer becomes thicker and the Rth of the reflective layer itself has a greater influence on the light transmitted through the reflective layer, the reflective layer disposed on the light source side is preferably a reflective layer on the short wavelength side (for example, blue light reflective layer).

In the optical laminate according to the second embodiment of the present invention, the sign of Rth at the wavelength of 550 nm in the first layer is opposite to the sign of Rth at the wavelength of 550 nm in the second layer, and the sign of Rth at the wavelength of 550 nm in the third layer is opposite. The sign is opposite to that of Rth at the wavelength of 550 nm in the fourth layer.

As described above, the method of inverting the signs of Rth in the first layer and the second layer is not particularly limited. An example of a method of establishing such a relationship of Rth is the first layer and the second layer. Among them, one 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 disk-shaped liquid crystal compound.

Similarly, as mentioned above, there is no particular limitation on the method of inverting the signs of Rth in the third layer and the fourth layer. As a method of establishing such a relationship of Rth, for example, the third layer and Among the fourth layers, one 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 disk-shaped liquid crystal compound.

Furthermore, it is preferable that the signs of Rth are opposite in the second layer and the third layer. An example of establishing such a relationship between Rth and the like is as follows: the first layer and the third layer are cholesteric liquid crystal layers formed using rod-shaped liquid crystal compounds, and the second layer and the fourth layer are formed using cylindrical liquid crystal compounds. The first and third layers are cholesteric liquid crystal layers formed using discotic liquid crystal compounds, and the second and fourth layers are formed using rod-shaped liquid crystals. A cholesteric liquid crystal layer formed from compounds.

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

The thickness of the first to fourth layers can be measured by making a cross section of the optical laminate and observing it with a transmission electron microscope.

Furthermore, in the optical laminate of the second embodiment, it is preferable that the absolute value of SRth _i described in the optical laminate of the first embodiment is within the above range. In addition, in the above definition explained in the optical laminate of the first embodiment, n may be replaced with 4.

Specifically, the absolute value of SRth _i is preferably 0.3 μm or less, more preferably 0.2 μm or less, and still more preferably 0.1 μm or less.

It is considered that by setting SRth _i 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.

In the optical laminate according to the second embodiment of the present invention, the first to fourth layers may be laminated in direct contact with each other, or may be laminated via other layers. The other layers are not particularly limited, but examples include an adhesive layer (for example, an adhesive layer, an adhesive layer, etc.), a refractive index adjustment layer, a resin film, a positive C plate, an alignment layer, and the like. Among them, it is preferable that the first to fourth layers are laminated in direct contact with each other.

Furthermore, in the optical laminate according to the second embodiment of the present invention, when the first to fourth layers are laminated in direct contact with each other, in order to reduce the refractive index difference, it is preferable to use a liquid crystal compound (rod-shaped liquid crystal compound) Or a disk-shaped liquid crystal compound) is arranged so that the orientation direction (slow axis direction) changes continuously at the interface. In the arrangement 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 a first layer which is a cholesteric liquid crystal layer formed using a disc-shaped liquid crystal compound, It is also possible to directly apply a coating liquid containing a rod-shaped liquid crystal compound on the first layer, and perform the process in such a manner that the slow axis direction is continuous at the interface due to the orientation regulating force of the discoidal liquid crystal compound contained in the first layer. orientation.

The thickness of the optical laminate according to the second embodiment of the present invention is preferably 30 μm or less, and more preferably 15 μm or less.

The lower limit is not particularly limited. For example, it is 1 μm or more, and preferably 5 μm or more.

The manufacturing method of the optical laminated body of the 2nd Embodiment of this invention, the laminated optical film using the optical laminated body, etc. are demonstrated later.

[Third Embodiment]

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

The above-mentioned first layer to the above-mentioned third layer are all cholesteric liquid crystal layers,

The above-mentioned second layer is a pitch gradient layer formed by changing the spiral pitch in the film thickness direction.

The above-mentioned first layer to the above-mentioned third layer are all light reflective,

The center wavelength of the reflected light from the above-mentioned first layer to the above-mentioned third layer is within any one of the ranges of 430 to 480 nm, 520 to 620 nm, and 620 to 670 nm, respectively.

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

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

The optical laminate according to the third embodiment of the present invention will be described using the drawings. FIG. 4 is a schematic cross-sectional view showing an example of the structure of the optical laminate 13 according to the third embodiment.

In the form shown in FIG. 3 , the optical laminate 13 has the first layer 27 , the second layer 28 , and the third layer 29 laminated in this order, and each of them satisfies the above-mentioned necessary conditions. In addition, the sign of Rth of the first layer 27 is opposite to the sign of Rth of the second layer 28, and the sign of Rth of the second layer 28 is opposite to the sign of Rth of the third layer 29.

The optical laminate according to the third embodiment of the present invention can be used as a reflective circular polarizer. It is considered that if 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 second layer and the Rth of the third layer cancel each other, it is considered that from the Incident light in oblique directions can also suppress the generation of ghost images.

Hereinafter, the third embodiment of the present invention will be described in detail.

〔First floor to third floor〕

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

The above-mentioned first to third layers are light-reflective cholesteric liquid crystal layers.

The cholesteric liquid crystal layer is a layer in which a liquid crystal compound is a cholesteric liquid crystal phase and the cholesteric liquid crystal phase is fixed. As such a cholesteric liquid crystal layer, the cholesteric liquid crystal layer used in the first to fourth layers of the second embodiment can be used.

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 disk-shaped liquid crystal compound. In a cholesteric liquid crystal layer formed using a rod-shaped liquid crystal compound, Rth tends to have a positive value, and in a cholesteric liquid crystal layer formed using a discoidal liquid crystal compound, Rth tends to have a negative value.

In addition, the second layer is a pitch gradient layer in which the spiral pitch changes in the film thickness direction. The pitch gradient layer can be produced by a known method. For example, it can be produced with reference to Japanese Patent Application Laid-Open No. 2020-060627 and the like.

In the pitch gradient layer, since the pitch of the spiral changes in the film thickness direction, it can reflect light in a plurality of wavelength ranges.

Furthermore, the center wavelengths of the reflected light of the first layer to the third layer are respectively within any one of the ranges of 430 to 480 nm, 520 to 620 nm, and 620 to 670 nm. It is also preferable that the center wavelengths of the reflected light from the first layer to the third layer are different from each other.

When the center wavelength of reflected light is 430 to 480 nm, this layer can correspond to the blue light reflecting layer described in the first embodiment. In this case, the reflectance in the center wavelength of the reflected light is preferably 40% or more and less than 50%.

When the center wavelength of reflected light is 520 to 620 nm, this layer can correspond to the green light reflective layer or the yellow light reflective layer described in the first embodiment. In this case, the reflectance in the center wavelength of the reflected light is preferably 40% or more and less than 50%.

When the center wavelength of reflected light is 620 to 670 nm, this layer can correspond to the red light reflective layer described in the first embodiment. In this case, the reflectance in the center wavelength of the reflected light is preferably 40% or more and less than 50%.

The method of measuring reflectance is as described above.

The center wavelength of the reflected light from the first layer to the third layer can be within any of the above-mentioned wavelength ranges, but preferably the center wavelength of the reflected light from the first layer is within the range of 430 to 480 nm, and the center wavelength of the other reflected light is preferably within the range of 430 to 480 nm. The wavelength is in the range of 620 to 670 nm, the center wavelength of the reflected light of the second layer is in the range of 520 to 620 nm, and the center wavelength of the reflected light of the third layer is in the range of 620 to 670 nm.

That is, it is preferable that the first layer corresponds to the blue light reflective layer, the second layer corresponds to the green light reflective layer and the yellow light reflective layer, and the third layer corresponds to the red light reflective layer. Since the second layer is a pitch gradient layer, the first layer can function as a green light reflective layer and a yellow light reflective layer.

Furthermore, when the optical laminate with the above-mentioned stacking sequence is applied to a reflective circular polarizer described later, in order to obtain sufficient reflectivity in the reflective layer on the long wavelength side (for example, the red light reflective layer) As the required thickness of the reflective layer becomes thicker and the Rth of the reflective layer itself has a greater influence on the light transmitted through the reflective layer, the reflective layer arranged on the light source side is preferably a reflective layer on the short wavelength side (for example, blue light reflective layer).

In the optical laminate according to the third embodiment of the present invention, the sign of Rth of the first layer at a wavelength of 550 nm is opposite to the sign of the Rth of the second layer at a wavelength of 550 nm, and the sign of Rth of the second layer at a wavelength of 550 nm is The sign is opposite to that of Rth at the wavelength of 550 nm in the third layer.

As described above, there is no particular limitation on the method of inverting the signs of Rth in the first layer and the second layer, and inverting the signs of Rth in the second layer and the third layer. For example, the relationship is as follows: the first layer is a cholesteric liquid crystal layer formed using a rod-shaped liquid crystal compound, the second layer is a cholesteric liquid crystal layer formed using a disk-shaped liquid crystal compound, and the third layer is a cholesteric liquid crystal layer formed using a disc-shaped liquid crystal compound. The layer is a cholesteric liquid crystal layer formed using a rod-shaped liquid crystal compound. Furthermore, as a method of establishing the relationship between Rth as described above, for example, there is also a method in which the first layer is a cholesteric liquid crystal layer formed using a discoidal liquid crystal compound, and the second layer is formed using a rod-shaped liquid crystal. The third layer is a cholesteric liquid crystal layer formed using a discoidal liquid crystal compound.

Furthermore, in the optical laminate of the third embodiment, it is preferable that the absolute value of SRth _i described in the optical laminate of the first embodiment is within the above range. In addition, in the above definition explained in the optical laminate of the first embodiment, n may be replaced with 3.

Specifically, the absolute value of SRth _i is preferably 0.3 μm or less, more preferably 0.2 μm or less, and still more preferably 0.1 μm or less.

It is considered that by setting SRth _i 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.

In the optical laminate according to the third embodiment of the present invention, the first to third layers may be laminated in direct contact with each other, or may be laminated via other layers. The other layers are not particularly limited, but examples include an adhesive layer (for example, an adhesive layer, an adhesive layer, etc.), a refractive index adjustment layer, a resin film, a positive C plate, an alignment layer, and the like. Among them, it is preferable that the first layer to the third layer are laminated in direct contact with each other.

Furthermore, in the optical laminate according to the third embodiment of the present invention, when the first to third layers are laminated in direct contact with each other, in order to reduce the refractive index difference, it is preferable to use a liquid crystal compound (rod-shaped liquid crystal compound) Or a disk-shaped liquid crystal compound) is arranged so that the orientation direction (slow axis direction) changes continuously at the interface. In the arrangement 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 a first layer which is a cholesteric liquid crystal layer formed using a disc-shaped liquid crystal compound, It is also possible to directly apply a coating liquid containing a rod-shaped liquid crystal compound on the first layer, and perform the process in such a manner that the slow axis direction is continuous at the interface due to the orientation regulating force of the discoidal liquid crystal compound contained in the first layer. orientation.

The thickness of the optical laminate according to the third embodiment of the present invention is preferably 30 μm or less, and more preferably 15 μm or less.

The lower limit is not particularly limited. For example, it is 1 μm or more, and preferably 5 μm or more.

The manufacturing method of the optical laminated body of the 3rd Embodiment of this invention, the laminated optical film using the optical laminated body, etc. are demonstrated later.

[Method for manufacturing optical laminate]

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

For example, as a method of manufacturing the optical laminate of the first and second embodiments, a method of applying a composition containing a rod-shaped liquid crystal compound to a base material to form a cholesteric liquid crystal phase can be cited. , fixing the orientation state of the cholesteric liquid crystal phase to form a first cholesteric liquid crystal layer, and coating a composition containing a discoidal liquid crystal compound on the first cholesteric liquid crystal layer to produce cholesteric liquid crystal After that, the orientation state of the cholesteric liquid crystal phase is fixed to form a second cholesteric liquid crystal layer, and 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. The 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.

In addition, the above-mentioned first cholesteric liquid crystal layer and the third cholesteric liquid crystal layer correspond to the reflective layer A of the first embodiment, and the above-mentioned second cholesteric liquid crystal layer and the fourth cholesteric liquid crystal layer correspond to the first embodiment. way of reflective layer B. Furthermore, the first to fourth cholesteric liquid crystal layers described above correspond to the first to fourth layers of the second embodiment, respectively.

Furthermore, as a method for manufacturing the optical laminate according to the third embodiment, the following method can be cited: forming the first cholesteric liquid crystal layer on the base material in the same manner as above, and referring to the above method for the first cholesteric liquid crystal layer. A second cholesteric liquid crystal layer (pitch gradient layer) is formed on the cholesteric liquid crystal layer, and 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.

In addition, the first to third cholesteric liquid crystal layers described above correspond to the first to third layers of the second embodiment, respectively.

Furthermore, when the optical laminate of the present invention is used for a reflective circular polarizer, or when the reflective circular polarizer is stretched or molded, the reflection wavelength range of the reflective circular polarizer may be shifted to the short-wavelength side, so the reflection It is preferable to manufacture an optical laminate assuming a wavelength shift in the wavelength range. For example, when an optical laminate including a layer in which a cholesteric liquid crystal phase is fixed is used as a reflective circular polarizer, the optical laminate is stretched by stretching or molding, so that the cholesteric liquid crystal phase The helical pitch of the cholesteric liquid crystal phase may become smaller, so the helical pitch of the cholesteric liquid crystal phase can be set larger. Furthermore, assuming a short-wavelength shift in the reflection wavelength range due to stretching or molding, the optical laminate preferably has an infrared light reflective layer with a reflectance of 40% or more at a wavelength of 800 nm.

Furthermore, when the stretch magnification during stretching or molding is not uniform in the plane, the optical laminate can be manufactured by selecting an appropriate reflection wavelength region based on the wavelength shift caused by stretching at each position in the plane of the optical laminate. . That is, the reflection wavelength regions may be different regions within the plane of the optical laminate. Furthermore, it is also preferable to set the reflection wavelength range to be wider than the required wavelength range in advance, assuming that the stretching magnification is different at each position within the plane of the optical laminate.

In the above, the method of directly applying the above composition on each cholesteric liquid crystal layer to form a cholesteric liquid crystal layer is shown. However, the cholesteric liquid crystal layer can also be applied on different substrates. To form, a cholesteric liquid crystal layer is laminated via an adhesive layer (for example, an adhesive layer or an adhesive layer).

As the adhesive used in the adhesive layer, any commercially available adhesive can be used. However, from the viewpoint of thinning and reduced surface roughness Ra, the thickness is preferably 25 μm or less, and more preferably It is 15 micrometers or less, and it is most preferable that it is 6 micrometers or less. Furthermore, the binder is preferably one that does not easily generate outgassing. In particular, when stretching or molding is performed, a vacuum process or a heating process may be performed, and it is preferable that outgassing does not occur even under these conditions.

As the adhesive used in the adhesive layer, any commercially available adhesive can be used. For example, an epoxy resin-based adhesive or an acrylic resin-based adhesive can be used.

From the viewpoint of thinning and reducing the surface roughness Ra of a reflective circular polarizer using an 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. Furthermore, 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.

Furthermore, when the adherend has surface irregularities, from the viewpoint of reducing the surface roughness Ra of the reflective circular polarizer using the optical laminate, an appropriate viscoelasticity or adhesive can be selected. Thickness to cover the surface irregularities of the bonded layer. From the viewpoint of covering surface irregularities, the viscosity of the adhesive or bonding agent is preferably 50 cP or more. Furthermore, the thickness is preferably greater than the height of the surface irregularities.

An example of a method of adjusting the viscosity of the adhesive is a method of using an adhesive containing a solvent. In this case, the viscosity of the adhesive can be adjusted according to the ratio of the solvent. Furthermore, by applying the adhesive to the adherend and then drying the solvent, the thickness of the adhesive can be further reduced.

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

Moreover, the thickness of the adhesive layer between each layer is preferably 100 nm or less. When the thickness of the adhesive layer is 100 nm or less, the difference in refractive index is less likely to be felt by light in the visible region, and unnecessary reflection can be suppressed. The thickness of the adhesive layer is more preferably 50 nm or less, further preferably 30 nm or less. An example of a method of forming an adhesive layer having a thickness of 100 nm or less is a method of vapor-depositing a ceramic adhesive such as silicon oxide (SiOx layer) on the bonding surface. The bonding surface of the bonded parts can be subjected to surface modification treatment such as plasma treatment, corona treatment, saponification treatment, etc. before bonding, or a primer layer can be provided. Furthermore, when there are a plurality of bonding surfaces, the type, thickness, etc. of the adhesive layer can be adjusted for each bonding surface. Specifically, for example, an adhesive layer having a thickness of 100 nm or less can be provided by the steps shown in (1) to (3) below.

(1) The laminated layer is bonded to a pseudo support made of a glass base material.

(2) Form a SiOx layer with a thickness of 100 nm or less on both the surface of the stacked layer and the surface of the layer to be laminated by evaporation or the like. Vapor deposition can be performed using SiOx powder as a vapor deposition source, for example, using a vapor deposition device (model ULEYES) manufactured by ULVAC, Inc., or the like. Furthermore, it is preferable that the surface of the formed SiOx layer is subjected to plasma treatment in advance.

(3) After bonding the formed SiOx layers to each other, the dummy support is peeled off. Bonding is preferably performed at a temperature of, for example, 120°C.

The coating, bonding or lamination of each layer can be done on a roll-to-roll basis or in a single sheet.

From the viewpoint of improving productivity or reducing axis deviation of each layer, the roll-to-roll method is preferred.

On the other hand, the single sheet method is preferable from the viewpoint of being suitable for small-volume, multi-variety production, or being able to select a special bonding method such that the thickness of the adhesive layer is 100 nm or less.

Examples of methods for applying the adhesive to the adherend include roll coating, gravure printing, spin coating, wire bar coating, extrusion coating, and direct gravure coating. , reverse gravure coating method, die coating method, spray coating method and inkjet method and other well-known methods.

A reflective circular polarizer using the optical laminate of the present invention may include a support, an alignment layer, and the like. However, the support and the alignment layer may be dummy supports that are peeled off and removed when producing a laminated optical film described below. When a dummy support is used, by transferring the reflective circular polarizer to another laminated body and then peeling and removing the dummy support, the laminated optical film can be made thinner and the phase difference of the dummy support can be removed. It has a bad effect on the polarization degree of transmitted light, so it is preferred.

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

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

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

In addition, the impact on various sensors that use near-infrared light as a light source, such as eye tracking, expression recognition, and iris authentication, incorporated in optical systems such as virtual reality displays and electronic viewfinders, is minimized. The reflective circular polarizer using the optical laminate used in the above-mentioned laminated optical film preferably has transmissivity with respect to near-infrared light.

[Laminated optical film]

The laminated optical film of the present invention has at least a reflective circular polarizer, a phase difference layer that converts circularly polarized light into linearly polarized light, and a linear polarizer in this order.

As the reflective circular polarizer, the above-mentioned optical laminate (first embodiment, second embodiment, or third embodiment) is used. Preferred aspects of the optical laminate (first embodiment, second embodiment, or third embodiment) are as described above.

As a preferable use example of the reflective circular polarizer of the present invention and the laminated optical film including the reflective circular polarizer, a virtual reality display device using the laminated optical film of the present invention can be cited. The function of the laminated optical film of the present invention will be described in detail. illustrate.

5 is a schematic diagram of a virtual reality display device using the laminated optical film of the present invention. In the virtual reality display device of the form shown in FIG. 5 , the laminated optical film 100 having the reflective circular polarizer using the optical laminated body, the half mirror 300 , the circular polarizing plate 400 and the image are arranged in order from the viewing side. Display panel 500. As shown in FIG. 5 , the light 1000 emitted from the image display panel 500 passes through the circularly polarizing plate 400 and becomes circularly polarized light, and then passes through the half mirror 300 . Next, it enters the laminated optical film 100 of the present invention from the reflective circular polarizer side and is totally reflected. It is reflected again by the half mirror 300 and enters the laminated optical film 100 again. At this time, by being reflected by the half mirror, the light 1000 becomes circularly polarized light in a direction opposite to the rotation direction of the circularly polarized light when incident on the laminated optical film 100 for the first time. Therefore, the light 1000 transmits the laminated optical film 100 and is visually recognized by the user. In addition, when the light 1000 is reflected by the half-mirror 300, since the half-mirror has a concave mirror shape, the image displayed on the image display panel 500 is magnified, so that the user can visually recognize the magnified virtual image. The above-mentioned mechanism is called a reciprocating optical system, a reentrant optical system, or the like.

On the other hand, FIG. 6 is a schematic diagram for explaining the occurrence of ghost images in the virtual reality display device shown in FIG. 5 . More specifically, this is a schematic diagram illustrating a situation where, in a virtual reality display device, when light 2000 is incident on the laminated optical film 100 for the first time, it is transmitted without being reflected, and becomes light leakage. As shown in FIG. 6 , when the light 2000 is incident on the laminated optical film 100 for the first time, it is transmitted without being reflected, and light leakage occurs. As shown in FIG. 6 , the user can visually recognize the unmagnified image. This image is called ghosting, etc., and is required to be reduced.

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

In addition, since the laminated optical film 100 of the present invention also has a high degree of polarization for transmitted light, the transmittance when light is 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 coloring of the virtual image.

As shown in FIGS. 5 and 6 , the laminated optical film 100 may be formed on a curved surface such as a lens.

As a conventionally known reflective circular polarizer, a conventional optical film in which a reflective linear polarizer and a phase difference layer having a phase difference of 1/4 wavelength are laminated has optical properties such as a transmission axis, a reflection axis, and a slow axis. axis, so when extending and molding into a curved surface shape, the optical axis will be deformed, thereby reducing the polarization degree of the transmitted light. In contrast, in the laminated optical film 100 of the present invention, since the reflective circular polarizer (optical laminate) does not have an optical axis, it is difficult to reduce the degree of polarization due to stretching or molding. Therefore, even when the laminated optical film 100 is molded into a curved shape, the degree of polarization is less likely to decrease.

An example of the layer structure of the laminated optical film 100 of the present invention is shown in FIG. 7 . In the laminated optical film 100 shown in FIG. 7 , an antireflection layer 101 , a positive C plate 102 , a reflective circular polarizer 103 , a positive C plate 104 , a retardation layer 105 , and a linear polarizer 106 are arranged in this order. As described above, the above-mentioned optical laminate is used as the reflective circular polarizer 103 . In the form shown in FIG. 7 , the anti-reflection layer 101 , the positive C plate 102 and the positive C plate 104 are used, but part or all of the above structure may be omitted.

The laminated optical film of the present invention has a reflective circular polarizer 103, a phase difference layer 105 that converts circularly polarized light into linearly polarized light, and a linear polarizer 106 in this order. Therefore, the leaked light from the reflective circular polarizer 103 is converted into linearly polarized light. Afterwards, it can be absorbed by a linear polarizer. Therefore, the degree of polarization of transmitted light can be increased. In addition, when the laminated optical film is stretched or molded, the slow axis of the retardation layer or the absorption axis of the linear polarizer may be deformed. However, as mentioned above, the reflective circular polarizer still has a high degree of polarization even if it is stretched or molded. Furthermore, the amount of light leakage from the reflective circular polarizer is small, so the increase in light leakage can be suppressed to a small amount.

Furthermore, the surface roughness Ra of the laminated optical film of the present invention is preferably 100 nm or less. If Ra is small, for example, when the laminated optical film is used in a virtual reality display device or the like, the clarity of the image can be improved. The present inventors speculate that when light is reflected in a laminated optical film, if there are irregularities, this will cause angular deformation of the reflected light and distortion or blurring of the image. 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.

Furthermore, the laminated optical film of the present invention is produced by laminating a plurality of layers. According to research by the present inventors, it was found that when another layer is laminated on a layer having unevenness, unevenness may be enlarged. Therefore, in the laminated optical film of the present invention, it is preferable that Ra of all layers be 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 even more preferably 10 nm or less.

Furthermore, from the viewpoint of improving the image clarity of the reflected image, it is particularly preferable that the Ra of the reflective circular polarizer is small.

Surface roughness Ra can be measured using a non-contact surface layer cross-sectional shape measuring system VertScan (manufactured by Ryoka Systems Inc.), for example. Since Vertscan is a surface shape measurement method that utilizes the phase of reflected light from a sample, when measuring a reflective circular polarizer (the above-mentioned optical laminate) composed of a reflective layer in which a cholesteric liquid crystal phase is fixed, Sometimes the reflected light from inside the film is superimposed and the surface shape cannot be accurately measured. In this case, in order to increase the reflectivity of the surface and thereby suppress reflection from the interior, a metal layer can be formed on the surface of the sample. As a method of forming a metal layer on the surface of a sample, a sputtering method can be used, for example. As a material for sputtering, Au, Al, Pt, etc. can be used.

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, in order to reduce the number of point defects in the entire laminated optical film, it is preferable that the number of point defects in each layer is also small. Specifically, the number of point defects per layer per square meter is preferably 20 or less, more preferably 10 or less, and still more preferably 1 or less. The number of point defects in the entire laminated optical film is preferably 100 or less per square meter, more preferably 50 or less, and still more preferably 5 or less.

Since point defects can cause a decrease in the polarization degree of transmitted light or a decrease in image clarity, fewer are preferred.

Here, point defects include foreign matter, scratches, dirt, film thickness fluctuations, poor alignment of liquid crystal compounds, and the like.

Furthermore, it is preferable that the number of point defects described above has a count size of 100 μm or more, more preferably 30 μm or more, and most preferably 10 μm or more.

In addition, 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 displays or electronic viewfinders. In order to minimize the impact on the sensors, this paper The laminated optical film of the invention preferably has near-infrared light transmittance.

[Phase difference layer]

The retardation layer used in the laminated optical film of the present invention has a function of converting emitted light into substantially linearly polarized light when circularly polarized light is incident thereon. For example, a retardation layer whose Re becomes approximately 1/4 wavelength at any wavelength in the visible region can be used. At this time, 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 even more preferably 135 nm to 140 nm.

In addition, a retardation layer whose Re is about 3/4 wavelength or about 5/4 wavelength is preferable because it can also convert linearly polarized light into circularly polarized light.

Furthermore, it is preferable that the retardation layer used in the laminated optical film of the present invention has reverse wavelength dispersion with respect to wavelength. It is preferable if it has reverse wavelength dispersion property because it can convert circularly polarized light into linearly polarized light in a wide wavelength range of the visible region. Here, having inverse wavelength dispersion with respect to wavelength means that as the wavelength becomes larger, the phase difference value at that wavelength also becomes larger.

The retardation 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 with reference to Japanese Patent Application Publication No. 2017-049574 and the like.

In addition, the retardation layer having inverse wavelength dispersion property may substantially have inverse wavelength dispersion property. For example, as disclosed in Japanese Patent No. 06259925, a retardation layer having Re of about 1/4 wavelength can also be formed by stacking Re. The retardation layer that becomes about 1/2 wavelength of Re and Re is produced so that their slow axes form an angle of about 60°. At this time, it is known that even if the 1/4-wavelength retardation layer and the 1/2-wavelength retardation layer respectively have normal wavelength dispersion (as the wavelength becomes larger, the value of the phase difference at that wavelength becomes smaller), the visible Converting circularly polarized light into linearly polarized light within a wide wavelength range of the region is considered to have essentially reverse wavelength dispersion. In this case, the laminated optical film of the present invention preferably has a reflective circular polarizer, a 1/4 wavelength retardation layer, a 1/2 wavelength retardation layer, and a linear polarizer in this order.

Furthermore, the retardation layer used in the laminated optical film of the present invention preferably has a layer in which a uniformly aligned liquid crystal compound is fixed. For example, a layer in which a rod-shaped liquid crystal compound is uniformly oriented horizontally with respect to the in-plane direction or a layer in which a disc-shaped liquid crystal compound is uniformly oriented vertically in the in-plane direction can be used. In addition, for example, by referring to Japanese Patent Application Laid-Open No. 2020-084070 or the like, a rod-shaped liquid crystal compound having reverse wavelength dispersion can be uniformly oriented and fixed, thereby producing a retardation layer having reverse wavelength dispersion.

Furthermore, the retardation layer used in the laminated optical film of the present invention preferably has a layer in which a liquid crystal compound that is twisted and oriented with the thickness direction as a spiral axis is fixed. For example, as disclosed in Japanese Patent No. 05753922, Japanese Patent No. 05960743, etc., a rod-shaped liquid crystal compound or a disk-shaped liquid crystal compound fixed with a twist orientation with the thickness direction as the spiral axis can be used. In this case, it can be considered that the retardation layer substantially has reverse wavelength dispersion properties, which is preferable.

The thickness of the retardation 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.

The retardation layer of the present invention may include a support, an alignment layer, etc., but the support and the alignment layer may be a dummy support that is peeled off and removed when producing a laminated optical film. When a dummy support is used, by transferring the retardation layer to another laminated body and then peeling and removing the dummy support, the laminated optical film can be made thin, and the phase difference of the dummy support can be removed. The degree of polarization of transmitted light has a negative impact, so it is preferred.

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

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

Furthermore, from the viewpoint of suppressing adverse effects on the polarization degree of transmitted light, the support preferably has a small phase difference. 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. Furthermore, even if the support is used as the above-mentioned pseudo support, in the manufacturing process of the laminated optical film, after quality inspection of the retardation layer or other laminated bodies, it is preferable that the retardation of the pseudo support is small.

In addition, in order to minimize the impact on various sensors that use near-infrared light as a light source such as eye tracking, expression recognition, iris authentication, etc. incorporated in optical systems such as virtual reality displays and electronic viewfinders, the laminate of the present invention The retardation layer used in the optical film preferably has transmissivity with respect to near-infrared light.

[Linear polarizer]

The linear polarizer used in the laminated optical film of the present invention is preferably an absorption-type linear polarizer. An absorptive linear polarizer absorbs linearly polarized light in the direction of the absorption axis among incident light, and transmits linearly polarized light in the direction of the transmission axis. As the linear polarizer, a general polarizer can be used. For example, a polarizer obtained by dyeing polyvinyl alcohol or other polymer resin with a dichroic substance and then stretching it to orient it, or a polarizer that utilizes the orientation of a liquid crystal compound. A polarizer that orients dichroic substances. From the viewpoint of accessibility or improvement in polarization degree, a polarizer obtained by dyeing polyvinyl alcohol with iodine and stretching it is preferred.

The thickness of the linear polarizer is preferably 10 μm or less, more preferably 7 μm or less, and still more preferably 5 μm or less. If the linear polarizer is thin, cracking or breakage of the film can be prevented when the laminated optical film is stretched or molded.

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

Furthermore, it is preferable that the direction of the transmission axis of the linear polarizer coincides with the direction of the polarization axis of the light converted into linearly polarized light by the retardation layer. For example, when the retardation layer is a layer having a retardation of 1/4 wavelength, the angle formed by the transmission axis of the linear polarizer and the slow axis of the retardation layer is preferably about 45°.

The linear polarizer used in the laminated optical film of the present invention is also preferably a light-absorbing anisotropic layer containing a liquid crystal compound and a dichroic substance. A linear polarizer containing a liquid crystal compound and a dichroic substance is preferred because the thickness of the linear polarizer can be reduced and the linear polarizer is less likely to be cracked or broken even if stretched or molded. 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.

A linear polarizer containing a liquid crystal compound and a dichroic material can be produced by referring to Japanese Patent Application Laid-Open No. 2020-023153 and the like. From the viewpoint of increasing the polarization degree of the linear polarizer, the light-absorbing anisotropic layer preferably has an orientation degree of the dichroic substance of 0.95 or more, and more preferably 0.97 or more.

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

As the liquid crystal compound, either a low molecular weight liquid crystal compound or a high molecular weight liquid crystal compound can be used. Here, the "low molecular weight liquid crystal compound" refers to a liquid crystal compound that does not have a repeating unit in its chemical structure. Here, the "polymer liquid crystal compound" refers to a liquid crystal compound having repeating units in its chemical structure.

Examples of the polymer liquid crystal compound include the thermotropic liquid crystal polymer described in Japanese Patent Application Laid-Open No. 2011-237513. Furthermore, the polymeric liquid crystal compound preferably has a crosslinkable group (for example, an acryl group and a methacryloyl group) at the terminal.

One type of liquid crystal compound may be used alone, or two or more types may be used in combination. It is also preferable to use a high molecular weight liquid crystal compound and a low molecular weight liquid crystal compound in combination.

The content of the liquid crystal compound is preferably 25 to 2000 parts by mass, more preferably 33 to 1000 parts by mass, and still more preferably 50 to 500 parts by mass relative to 100 parts by mass of the dichroic substance in the composition. When the content of the liquid crystal compound is within the above range, the orientation degree of the polarizer is further improved.

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

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

When the linear polarizer of the present invention is composed of a light-absorbing anisotropic layer containing a liquid crystal compound and a dichroic substance, the linear polarizer may include a support, an alignment layer, etc., but the support and the alignment layer may also be The pseudo support is peeled off and removed when manufacturing laminated optical films. When a dummy support is used, by transferring the light-absorbing anisotropic layer to another laminated body and then peeling and removing the dummy support, the laminated optical film can be made thinner, and the phase difference of the dummy support can be reduced It is preferable because it can remove the negative influence on the polarization degree of transmitted light.

The type of the support is not particularly limited, but it is preferably transparent to visible light. For example, the same support as used for the retardation layer can be used. The preferred aspect of the support used for the linear polarizer is the same as the preferred aspect of the support used for the retardation layer.

In addition, in order to minimize the impact on various sensors that use near-infrared light as a light source such as eye tracking, expression recognition, iris authentication, etc. incorporated in optical systems such as virtual reality displays and electronic viewfinders, the laminate of the present invention The linear polarizer used in the optical film preferably has transmissivity with respect to near-infrared light.

[Other functional layers]

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.

In addition, in order to minimize the impact on various sensors that use near-infrared light as light sources such as eye tracking, expression recognition, and iris authentication incorporated in optical systems such as virtual reality displays and electronic viewfinders, other functional layers It is preferable to have transmissivity with respect to near-infrared light.

＜Positive C board＞

The laminated optical film of the present invention preferably has a positive C plate. Here, the positive C plate refers to a retardation layer in which Re is substantially zero and Rth has a negative value. The positive C plate is obtained, for example, by vertically aligning a rod-shaped liquid crystal compound. For details on the manufacturing method of the positive C plate, please refer to the descriptions of Japanese Patent Application Laid-Open No. 2017-187732, Japanese Patent Application Laid-Open No. 2016-053709, Japanese Patent Application Laid-Open No. 2015-200861, and the like.

The positive C plate functions as an optical compensation layer for increasing the polarization degree of transmitted light with respect to light incident from an oblique direction. The positive C plate can be installed at any position of the laminated optical film, and multiple sheets can be installed.

The positive C plate may be adjacent to the reflective circular polarizer, or may be disposed inside the reflective circular polarizer. As the reflective circular polarizer, for example, when a reflective layer in which a cholesteric liquid crystal phase containing a rod-shaped liquid crystal compound is immobilized is used, the reflective layer has a positive Rth. At this time, when light is incident on the reflective circular polarizer from an oblique direction, the polarization state of the reflected light and transmitted light changes due to the effect of Rth, and the polarization degree of the transmitted light may decrease. If a positive C plate is provided inside or near the reflective circular polarizer, the change in the polarization state of obliquely incident light can be further suppressed, and the decrease in the polarization degree of the transmitted light can be further suppressed. As a result, ghost images can be further suppressed, which is preferable. . According to the research of the author and others, the positive C plate is preferably disposed on the side opposite to the green reflective layer with respect to the blue light reflective layer, but it can also be disposed at other positions. At this time, Re of the positive C plate is preferably about 10 nm or less, and Rth is preferably -600 to -100 nm, more preferably -400 to -200 nm.

Furthermore, the positive C plate may be adjacent to the retardation layer, or may be provided inside the retardation layer. When a layer obtained by fixing a rod-shaped liquid crystal compound is used as the retardation layer, for example, the retardation layer has a positive Rth. At this time, when light is incident on the retardation layer from an oblique direction, the polarization state of the transmitted light changes due to the effect of Rth, and the polarization degree of the transmitted light may decrease. It is preferable to have a positive C plate inside or near the retardation layer because it can suppress changes in the polarization state of obliquely incident light and suppress decreases in the degree of polarization of transmitted light. According to the research of the author and others, the positive C plate is preferably disposed on the opposite side of the linear polarizer with respect to the retardation layer, but it may be disposed at other positions. At this time, Re of the positive C plate is preferably approximately 10 nm or less, and Rth is preferably -90 to -40 nm.

＜Anti-reflection layer＞

The laminated optical film of the present invention preferably has an antireflection 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 thereto. However, reflection in the surface of the laminated optical film often includes reflection of unexpected polarized light, which sometimes reduces transmission. The degree of polarization of light. Therefore, the laminated optical film preferably has an antireflection layer on the surface. The anti-reflection layer may be provided on only one surface of the laminated optical film, or may be provided on both surfaces.

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

Furthermore, when a laminated optical film is stretched or molded, high antireflection performance can be maintained even if the film thickness varies due to stretching, so a moth-eye film is preferred. In addition, the anti-reflection layer includes a support, and when stretching or molding is performed, the Tg peak temperature of the support is preferably 170°C or lower, and more preferably 130°C or lower from the viewpoint of easy stretching or shaping. . Specifically, for example, a PMMA film or the like is preferred.

<Second phase difference layer>

The laminated optical film of the present invention preferably has a second retardation layer. For example, a reflective circular polarizer, a retardation layer, a linear polarizer, and a second retardation layer may be included in this order.

The second retardation layer preferably converts linearly polarized light into circularly polarized light, and is preferably a retardation layer having Re of 1/4 wavelength, for example. The reason for this will be explained below.

The light incident on the laminated optical film from the reflective circular polarizer side and transmitted through the reflective circular polarizer, the retardation layer and the linear polarizer becomes linearly polarized light, part of which is reflected from the outermost surface of the linear polarizer side and is circularly polarized again from the reflective circular polarizer. surface on the side of the device. Such light is unnecessary reflected light and may cause a decrease in the polarization degree of the reflected light, so it is preferably reduced. Therefore, in order to suppress the reflection on the outermost surface of the linear polarizer side, there is also a method of laminating an anti-reflection layer. However, if the laminated optical film is bonded to a medium such as glass or plastic and used, even if the laminated optical film is bonded Even if the surface has an anti-reflective layer, it cannot suppress reflection on the medium surface, so it is difficult to obtain the anti-reflective effect.

On the other hand, when a second phase difference layer that converts linearly polarized light into circularly polarized light is provided, the light reaching the outermost surface on the linear polarizer side becomes circularly polarized light and is converted into positive light when reflected by the outermost surface of the medium. Crossed circularly polarized light. After that, when it passes through the second retardation layer again and reaches the linear polarizer, the light becomes linearly polarized light in the direction of the absorption axis of the linear polarizer and is absorbed by the linear polarizer. Therefore, unnecessary reflection can be prevented.

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

＜Support＞

The laminated optical film of the present invention may further have a support. The support can be provided anywhere. For example, when the reflective circular polarizer, retardation layer, or linear polarizer is a film used for transfer from a pseudo support, the support can be used as the transfer destination. .

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

Furthermore, the support preferably has a small retardation from the viewpoint of suppressing adverse effects on the polarization degree of transmitted light and facilitating optical inspection of the laminated optical film. 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.

When the laminated optical film of the present invention is 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.

Here, the measurement method of tan δ is described. Using a dynamic viscoelasticity measuring device (DVA-200 manufactured by IT Keisoku Seigyo Co., Ltd.), measure E" under the following conditions on a film sample that has been previously humidified for more than 2 hours in an atmosphere of 25°C and 60% Rh. (loss modulus) and E' (storage modulus), and use them as values to calculate tan δ (=E"/E').

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

Sample: 5mm, length 50mm (gap 20mm)

Measurement conditions: Tensile mode

Measuring temperature: -150℃～220℃

Heating conditions: 5℃/min

Frequency: 1Hz

In addition, generally in optical applications, resin base materials that have been stretched are often used, and the peak temperature of tan δ often becomes high due to stretching. For example, the peak temperature of tan δ of a TAC (triacetyl cellulose) base material (TG40, manufactured by FUJIFILM Corporation) is 180° C. or higher.

The support having a tan δ peak temperature of 170° C. or less is not particularly limited, and various resin base materials can be used. Examples include polyolefins such as polyethylene, polypropylene, and norbornene-based polymers; cyclic olefin-based resins; polyvinyl alcohol; polyethylene terephthalate; polymethacrylates; and polyacrylates. Such as acrylic resin; polyethylene naphthalate; polycarbonate; polysulfone; polyethersulfone; polyetherketone; polyphenylene sulfide and polyphenylene oxide. Among them, cyclic olefin-based resins, polyethylene terephthalate, or acrylic resins are preferred from the viewpoint of being readily available on the market or having excellent transparency, and particularly preferred are cyclic olefin-based resins or polymethacrylate resins. base acrylate.

Examples of commercially available resin base materials include TECHNOLLOY S001G, TECHNOLLOY S014G, TECHNOLLOY S000, TECHNOLLOY C001, TECHNOLLOY C000 (Copyright Sumika Acryl Co., Ltd), Lumirror U type, Lumirror FX10, Lumirror SF20 (TORAY INDUSTRIES, INC. ), HK-53A (HYNT. Company), TEFLEX FT3 (Teijin DuPont Films Japan Ltd.), ESSINA" and SCA40 (SEKISUICHEMICAL CO., LTD.), ZEONOR film (ZEON CORPORATION.), ARTON film (JSR Corporation), etc. .

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

Furthermore, the laminated optical film may have layers other than the above-mentioned layers. For example, examples of layers other than the above include an adhesive layer formed of an adhesive agent to be described later, an adhesive layer and a refractive index adjustment layer formed of an adhesive agent to be described later.

Furthermore, a refractive index adjustment layer in which the difference in refractive index between the fast axis direction and the slow axis direction is 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, the refractive index adjustment layer preferably has a layer in which the alignment state of cholesteric liquid crystal is fixed. By having the refractive index adjustment layer, interface reflection can be further suppressed, and the occurrence of ghost images can be further suppressed. Furthermore, the average refractive index of the refractive index adjustment layer is more preferably smaller than the average refractive index of the reflective circular polarizer. Furthermore, the center wavelength of the reflected light of the refractive index adjustment layer may be smaller than 430 nm or larger than 670 nm, and is more preferably smaller than 430 nm.

[How to bond each layer]

The laminated optical film of the present invention is a laminate composed of a plurality of layers. Each layer can be bonded by any bonding method, for example, an adhesive or adhesive can be used.

As the adhesive, any commercially available adhesive can be used. However, 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 15 μm or less. It is preferably 6 μm or less. Furthermore, the binder is preferably one that does not easily generate outgassing. In particular, when stretching or molding is performed, a vacuum process or a heating process may be performed, and it is preferable that outgassing does not occur even under these conditions.

As the adhesive, any commercially available adhesive can be used. For example, an epoxy resin-based adhesive or an acrylic resin-based adhesive can be used.

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. Furthermore, the adhesive has a viscosity of preferably 300 cP or less, more preferably 100 cP or less, and still more preferably from the viewpoint of thinning the adhesive layer and applying the adhesive to the adherend with a uniform thickness. It is below 10cP.

In addition, when the adherend has surface irregularities, from the viewpoint of reducing the surface roughness Ra of the laminated optical film, the adhesive or adhesive can also have an appropriate viscoelasticity or thickness selected so as to cover all the surface roughness Ra. The surface of the bonded layer is uneven. From the viewpoint of covering surface irregularities, the viscosity of the adhesive or bonding agent is preferably 50 cP or more. Furthermore, the thickness is preferably greater than the height of the surface irregularities.

An example of a method of adjusting the viscosity of the adhesive is a method of using an adhesive containing a solvent. In this case, the viscosity of the adhesive can be adjusted according to the ratio of the solvent. Furthermore, by applying the adhesive to the adherend and then drying the solvent, the thickness of the adhesive can be further reduced.

In the laminated optical film, from the viewpoint of reducing unnecessary reflection and suppressing reduction in the polarization degree of transmitted light and reflected light, the adhesive or adhesive used for bonding each layer is preferably the same as that of the adjacent layer. The refractive index difference is small. Specifically, the difference in refractive index between adjacent layers is preferably 0.1 or less, more preferably 0.05 or less, and even more preferably 0.01 or less. The refractive index of the binder or adhesive agent can be adjusted by mixing, for example, titanium oxide fine particles or zirconium oxide fine particles.

Furthermore, the reflective circular polarizer, retardation layer, and linear polarizer may have in-plane refractive index anisotropy. However, the refractive index difference with adjacent layers is preferably 0.05 or less in all directions within the plane. Therefore, the adhesive or adhesive may also have in-plane refractive index anisotropy.

Moreover, the thickness of the adhesive layer between each layer is preferably 100 nm or less. If the thickness of the adhesive layer is 100 nm or less, the difference in refractive index is less likely to be felt by light in the visible region, and reflection at the interface can be suppressed. The thickness of the adhesive layer is more preferably 50 nm or less. An example of a method of forming an adhesive layer having a thickness of 100 nm or less is a method of vapor-depositing a ceramic adhesive such as silicon oxide (SiOx layer) on the bonding surface. The bonding surface of the bonded parts can be subjected to surface modification treatment such as plasma treatment, corona treatment, saponification treatment, etc. before bonding, or a primer layer can be provided. Furthermore, when there are a plurality of bonding surfaces, the type, thickness, etc. of the adhesive layer can be adjusted for each bonding surface. Specifically, for example, an adhesive layer having a thickness of 100 nm or less can be provided by the steps shown in (1) to (3) below.

(1) The laminated layer is bonded to a pseudo support made of a glass base material.

(2) Form a SiOx layer with a thickness of 100 nm or less on both the surface of the stacked layer and the surface of the layer to be laminated by evaporation or the like. Vapor deposition can be performed using SiOx powder as a vapor deposition source, for example, using a vapor deposition device (model ULEYES) manufactured by ULVAC, Inc., or the like. Furthermore, it is preferable that the surface of the formed SiOx layer is subjected to plasma treatment in advance.

(3) After bonding the formed SiOx layers to each other, the dummy support is peeled off. Bonding is preferably performed at a temperature of, for example, 120°C.

The coating, bonding or lamination of each layer can be done on a roll-to-roll basis or on a single sheet. From the viewpoint of improving productivity or reducing axis deviation of each layer, the roll-to-roll method is preferred.

On the other hand, the single sheet method is preferable from the viewpoint of being suitable for small-volume, multi-variety production, or being able to select a special bonding method such that the thickness of the adhesive layer is 100 nm or less.

Examples of methods for applying the adhesive to the adherend include roll coating, gravure printing, spin coating, wire bar coating, extrusion coating, and direct gravure coating. , reverse gravure coating method, die coating method, spray coating method and inkjet method and other well-known methods.

[Direct coating of each layer]

It is preferable that the laminated optical film of the present invention does not have an adhesive layer between the respective layers. When forming a layer, the adhesive layer can be eliminated by coating directly on an already formed adjacent layer. Furthermore, when one or both of the adjacent layers are layers containing a liquid crystal compound, in order to reduce the refractive index difference in all directions within the plane, it is preferable that the orientation direction of the liquid crystal compound continuously changes at the interface. For example, a linear polarizer containing a liquid crystal compound and a dichroic substance can be directly coated with a retardation layer containing a liquid crystal compound, and the liquid crystal compound of the retardation layer can be caused to orient by the orientation restricting force of the liquid crystal compound of the linear polarizer. Oriented in a continuous manner at the interface.

[Stacking order of each layer]

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

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

In addition, from the viewpoint of reducing the surface roughness Ra of the laminated optical film, when another layer is laminated on a layer with large surface irregularities, since the surface irregularities may further amplify, it is preferable to reduce the surface roughness Ra from the larger surface roughness Ra. Smaller layers begin to stack one on top of the other.

Furthermore, the order of lamination can also be selected from the viewpoint of quality evaluation in the production process of the laminated optical film. For example, after stacking layers other than the reflective circular polarizer and performing quality evaluation based on the transmission optical system, the reflective circular polarizer can be stacked and quality evaluation based on the reflective optical system can be performed.

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

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

For example, as described in Patent Documents 4 and 5, the laminated optical film of the present invention can be used as a reflective polarizer incorporated in vehicle rearview mirrors, virtual reality display devices, electronic viewfinders, and the like. In particular, in a virtual reality display device or an electronic viewfinder having a reciprocating optical system that reflects and reciprocates light between a reflective polarizer and a half mirror, the present invention is useful from the viewpoint of improving the clarity of the displayed image. Laminated optical films are very useful. In addition, a virtual reality display device or an electronic viewfinder having a reciprocating optical system may have an optical film such as an absorptive polarizer or a circular polarizer in addition to a reflective polarizer. However, by using the laminated optical film of the present invention, Part of the component or the bonding method is also used in optical films other than the above-mentioned reflective polarizer, which can further improve the clarity of the displayed image.

Example

Hereinafter, the features of the present invention will be described in further detail using examples. In addition, the materials, usage amounts, ratios, processing contents, processing steps, etc. shown below can be appropriately changed as long as they do not deviate from the gist of the present invention. In addition, as long as it does not deviate from the gist of the present invention, it may be configured as other structures than those shown below.

[Preparation of coating liquid for reflective layer]

<Coating liquid for reflective layer R-1>

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

mixture of rod-shaped liquid crystal compounds

[Chemical formula 1]

In the above mixtures, numerical values are mass %. Moreover, R is a group bonded through an oxygen atom. Furthermore, the average molar absorption coefficient of the rod-shaped liquid crystal at a wavelength of 300 to 400 nm is 140/mol·cm.

Chiral Reagent A

[Chemical formula 2]

Surfactant F1

[Chemical formula 3]

Surfactant F2

[Chemical formula 4]

Photopolymerization initiator B

[Chemical formula 5]

Chiral reagent A is a chiral reagent whose helical twisting power (HTP: Helical Twisting Power) is reduced by light.

<Coating liquids for reflective layer R-2～R-6, R-11～R-17>

The preparation was performed in the same manner as the reflective layer coating liquid R-1 except that the added amount of the chiral reagent A was changed to Table 1 shown later.

＜Coating liquid for reflective layer R-7＞

It was prepared in the same manner as the coating liquid R-1 for reflective layers except that the chiral reagent A was changed to the chiral reagent B shown below for the synthesis method. The synthesis method of chiral reagent B is shown below.

(Synthesis of Intermediate 1)

55.0 g of (S)-binaphthol (manufactured by Tokyo Chemical Industry Co., Ltd.) and 485 g of butyl acetate (manufactured by WakoPure Chemical, Ltd.) were added to a 1L three-necked flask and dissolved, and then the mixture was dissolved in ice water. The solution was cooled. 82.9 g of bromine (manufactured by Wako Pure Chemical, Ltd.) was added dropwise at 0 to 10° C., and the mixture was further stirred at 0 to 10° C. for 3 hours. Next, sodium bisulfite water (18.28 g of sodium bisulfite (manufactured by Wako Pure Chemical, Ltd.), 275 mL of water) was added to the obtained reaction liquid while maintaining it at 10° C. or lower, and then the temperature was raised to room temperature. The water layer was removed. The organic layer was washed sequentially with 275 mL of water and sodium bicarbonate water (11.0 g of sodium bicarbonate (manufactured by Wako Pure Chemical, Ltd.), 275 mL of water). After the washed solution was dried over magnesium sulfate, the solvent was distilled under reduced pressure until the liquid volume became 160 g, and then transferred to a three-necked flask.

Next, into the above-mentioned three-necked flask, 66.2g of DMF (N,N-dimethylformamide, manufactured by Wako Pure Chemical, Ltd.), 79.7g of potassium carbonate (manufactured by NIPPON SODA CO., LTD.) and dibromomethane ( Wako Pure Chemical, Ltd.) 43.4g, heated to 90°C, and stirred directly at 90 to 95°C for 8 hours. Thereafter, the reaction liquid was cooled to room temperature, and the solid was filtered while washing with 170 mL of ethyl acetate (manufactured by Wako Pure Chemical, Ltd.). The solution after filtering the solid was concentrated under reduced pressure to a liquid volume of 215 g, and then 550 mL of methanol (manufactured by Wako Pure Chemical, Ltd.) was added at 45 to 50° C. to precipitate crystals. After cooling the solution to 0 to 5°C, the crystals were filtered and washed with 220 mL of methanol. The obtained crude crystal was suspended in 550 mL of methanol and stirred at 0 to 5° C. for 30 minutes. The crystal was filtered out by filtration under reduced pressure and washed with 220 mL of methanol. The obtained crystal was dried under reduced pressure at 55° C. for 24 hours to obtain Intermediate 1 (63.1 g, yield: 72%).

(Synthesis of Intermediate 2)

13.8 g of intermediate 1, 46.8 g of butyl acrylate (manufactured by Wako Pure Chemical, Ltd.), 42.2 g of potassium carbonate (manufactured by NIPPON SODA CO., LTD.), and tetrabutylammonium bromide (Wako Pure Chemical, Ltd.) were mixed. (manufactured by Wako Pure Chemical, Ltd.) 39.2g, 2,2,6,6-tetramethylpiperidine 1-oxyl radical (TEMPO, Wako Pure Chemical, Ltd.) 0.19g, DMF (N,N-dimethylformamide, Wako Pure Chemical, Ltd.) 47.0 g was added to a 1 L three-necked flask, and nitrogen gas was bubbled for 2 hours and degassed. Thereafter, 12.3 g of triethylamine (manufactured by Wako Pure Chemical, Ltd.), 0.41 g of palladium acetate (manufactured by Wako Pure Chemical, Ltd.), and 11 g of DMF were added, followed by stirring at room temperature for 1 hour while flowing nitrogen, and then The internal temperature was 80 to 85°C and the mixture was further stirred for 1 hour. While maintaining the internal temperature at 80 to 85°C, a solution of 41.8 g of intermediate 1 dissolved in 127.0 g of DMF by bubbling nitrogen for 2 hours was added dropwise to the reaction liquid, and the solution was further heated to 90 to 85°C. Stirred at 95°C for 1 hour. After the reaction was completed, the mixture was cooled to room temperature, 420 mL of toluene (manufactured by Wako Pure Chemical, Ltd.) was added, and the solid was removed by celite filtration, and further washed with 305 mL of toluene. The solution after filtering the solid was washed twice with a mixture of 77.8 g of sodium chloride, 11.84 g of concentrated hydrochloric acid, and 440 mL of water, and then with a mixture of 103 g of sodium chloride and 415 mL of water. The washed solution was dried over magnesium sulfate, 110 g of silica gel (Wakogel C200, manufactured by Wako Pure Chemical, Ltd.) was added, and the mixture was stirred for 1 hour and then filtered through diatomaceous earth to remove the solid while washing with 490 mL of toluene. To the solution after filtering the solid, 0.19 g of TEMPO was added, and the solvent was distilled off under reduced pressure. After adjusting the liquid volume to 100 mL, it was transferred to a three-necked flask, 40 mL of toluene was added, and the temperature was raised to 60°C. To this solution, 355 mL of methanol (manufactured by Wako Pure Chemical, Ltd.) was added dropwise at 50 to 60°C, and then the temperature was lowered to 45°C to precipitate crystals. After the solution was cooled to 0 to 5° C. over 2 hours, the crystals were filtered and washed with a mixed solvent of 72 mL of toluene, 290 mL of methanol, and 360 mL of methanol in this order. The obtained crystal was air-dried at 40° C. for 24 hours to obtain Intermediate 2 (47.6 g, yield: 71%).

(Synthesis of Chiral Reagent B)

In a 2L three-necked flask, 45 g of intermediate 2 was dissolved in 900 mL of ethyl acetate. To this solution, 27.8 g of a 20% ethanol solution of sodium ethoxide (manufactured by NIPPON SODA CO., LTD.) was dropwise added at room temperature, and the mixture was stirred at 20 to 25° C. for 2 hours. Prepare a mixed solution of 41.4g sodium chloride, 8.97g concentrated hydrochloric acid, and 240mL of water in another 2L three-necked flask, cool it to below 15°C, and add the previous reaction solution while keeping the internal temperature below 30°C. . Furthermore, 45 mL of ethyl acetate was added, and after stirring, the mixture was allowed to stand and the water layer was removed. The obtained organic layer was washed with a mixture of 54 g of sodium chloride and 215 mL of water, a mixture of 5.1 g of sodium bicarbonate, 41 g of sodium chloride, and 230 mL of water, and then a mixture of 54 g of sodium chloride and 215 mL of water. 2 times. The washed solution was dried over magnesium sulfate, and the solvent was distilled under reduced pressure until the liquid volume became 140 g. The solution was then transferred to a three-necked flask, and the temperature was raised to 65°C. At 60 to 45°C, 210 mL of methanol (manufactured by Wako Pure Chemical, Ltd.) was added dropwise to precipitate crystals. After the solution was cooled to 0 to 5°C, the crystals were filtered and mixed with 30 mL of ethyl acetate and 90 mL of methanol. Mixed solvents were used for cleaning. The obtained crystal was air-dried at 40° C. for 24 hours, and chiral reagent B (34.4 g, yield: 85%, HPLC purity 96.9%) was obtained.

¹ H NMR of chiral reagent B (heavy solvent: CDCl ₃ ): δ8.02 (4H, d), 7.84 (2H, d), 7.50 (6H, m), 6.52 (2H, d), 5.71 (2H, s), 4.28 (4H, m), 1.35 (6H, t)

The reaction diagram of the synthesis method of the above-mentioned chiral reagent B is shown below.

[Chemical formula 6]

In addition, chiral reagent B can also be synthesized by the following synthesis method.

[Another synthesis method of chiral reagent B]

Intermediate 1 was used, except that butyl acrylate in the synthesis method of Intermediate 2 in Synthesis Example 1 was changed to ethyl acrylate. Reaction, liquid separation, and adsorption were carried out in the same manner as in the synthesis method of Intermediate 2. After treatment with the reagent, the chiral reagent B was directly synthesized by using ethyl acetate/methanol to precipitate and filter the solid. It was confirmed that chiral reagent B can be synthesized by the above method. (Yield: 61%, HPLC purity 99.0%).

Table 1. Amount of chiral reagent for coating liquid containing rod-shaped liquid crystal compound [Table 1]

<Coating liquid D-1 for reflective layer>

The composition shown below was stirred and dissolved in a container maintained at a temperature of 50° C. to prepare a coating liquid D-1 for a circularly polarized light reflecting layer. Here, D represents a coating liquid using discoidal liquid crystal.

Disc-shaped liquid crystal compound (A)

[Chemical Formula 7]

Disc-shaped liquid crystal compound (B)

[Chemical formula 8]

Polymerizable monomer E1

[Chemical Formula 9]

Surfactant F4

[Chemical formula 10]

<Coating liquids for reflective layer D-2～D-5, D-11～D-16>

The preparation was carried out in the same manner as the coating liquid D-1 for the reflective layer except that the added amount of the chiral reagent A was changed to the following Table 2.

Table 2. Amount of chiral reagent in coating liquid containing discoidal liquid crystal compound [Table 2]

[Preparation of reflective circular polarizer 1]

As a pseudo support, a 50 μm-thick PET (polyethylene terephthalate) film (A4100, manufactured by Toyobo Co., Ltd.) was prepared. This PET film has an easy-adhesion layer on one side.

The surface of the PET film without the easy-adhesion layer shown above was rubbed, and the reflective layer coating liquid R-1 prepared above was applied with a wire bar coater, and then dried at 110° C. for 120 seconds. . Thereafter, in a low oxygen atmosphere (100 ppm or less), at 100°C, light from a metal halide lamp with an illumination intensity of 80 mW/cm ² and an irradiation dose of 500 mJ/cm ² was irradiated and cured, thereby forming a cholesteric A red light reflective layer (first light reflective layer) composed of a liquid crystal layer. Light is irradiated from the cholesteric liquid crystal layer side. At this time, the coating thickness was adjusted so that the film thickness of the red light reflective layer after curing would be 4.5 μm.

Next, after the red light reflective layer was corona treated at a discharge amount of 150W·min/ ^m2 , the reflective layer coating liquid D-1 was applied to the corona-treated surface using a wire bar coater. . Then, the coated film was dried at 70° C. for 2 minutes and the solvent was vaporized, 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 cured by irradiation with ultraviolet rays (300mJ/cm ² ) using a metal halide lamp in a nitrogen atmosphere, thereby forming a yellow light reflection on the red light reflection layer. layer (second light reflective layer). Light is irradiated from the cholesteric liquid crystal layer side. At this time, the coating thickness was adjusted so that the film thickness of the yellow light reflective layer after curing would be 3.3 μm.

Next, the reflective layer coating liquid R-2 was applied on the yellow light reflective layer using a wire bar coater, and then dried at 110° C. for 120 seconds. Thereafter, in a low oxygen atmosphere (less than 100 ppm), at 100°C, the light of a metal halide lamp with an illumination intensity of 80 mW and an irradiation dose of 500 mJ/cm ² was irradiated and cured, thereby forming a green layer on the yellow light reflective layer. Light reflective layer (third light reflective layer). Light is irradiated from the cholesteric liquid crystal layer side. At this time, the coating thickness was adjusted so that the film thickness of the green light reflective layer after curing would be 2.7 μm.

Next, after the green light reflective layer was corona treated at a discharge amount of 150W·min/ ^m2 , the light reflective layer coating liquid D- was applied on the corona-treated surface using a wire bar coater. 2. Then, the coated film was dried at 70° C. for 2 minutes and the solvent was vaporized, and then heated and aged at 115° C. for 3 minutes to obtain a uniform orientation state. After that, the coating film was maintained at 45°C and cured by irradiating it with ultraviolet rays (300mJ/cm ² ) using a metal halide lamp in a nitrogen atmosphere, thereby forming a blue light reflection on the green light reflection layer. layer (the fourth light reflective layer). Light is irradiated from the cholesteric liquid crystal layer side. At this time, the coating thickness was adjusted so that the film thickness of the cured blue light reflective layer would be 2.5 μm.

[Production of reflective circular polarizers 2 to 7 and reflective circular polarizers 10 to 13]

The reflective circular polarizers 2 to 7 and the reflective circular polarizer 10 were produced by the same manufacturing method as the reflective circular polarizer 1 except that the coating liquid for the reflective layer and the film thickness were changed as shown in the table below. In addition, the number of layers of the reflective circular polarizers 11 to 13 was increased to 6, 8, and 16 layers, and the coating liquid and film thickness for the reflective layer were changed as shown in the table below. In addition, the reflective circular polarizers 11 to 13 were configured in the same manner as the reflective circular polarizers. Make it using the same method as Device 1.

Table 3-1. Coating liquids used in the production of reflective circular polarizers 1 to 10

Table 3-2. Coating liquid used in the production of reflective circular polarizer 11

Table 3-3. Coating liquid used in the production of reflective circular polarizer 12

Table 3-4. Coating liquid used in the production of reflective circular polarizer 13

In addition, in the following table, the coating liquid R-1 for a reflective layer is abbreviate|omitted and expressed as "liquid R-1".

[Table 4]

[table 5]

[Table 6]

[Production of reflective circular polarizer 8]

The reflective circular polarizer 8 is formed by laminating and coating two light reflective layers on a dummy support. Among the two layers of film 1 and film 2, the light reflective layer of film 2 is transferred to the light reflective layer of film 1. And made. The film 1 is formed by sequentially forming a first light reflective layer and a second light reflective layer on a pseudo support. Furthermore, the thin film 2 is formed by sequentially forming a third light reflective layer and a fourth light reflective layer on a dummy support. Follow the steps below to transfer the light reflective layer.

(1) First, the light reflective layer of film 2 is transferred to the laminated film. Transfer to the laminated film is performed by laminating the laminated film with an adhesive on the surface opposite to the pseudo support of the film 2 and then peeling off the pseudo support.

(2) On the surface opposite to the pseudo support of the film 1, UV adhesive chemiseal U2084B (manufactured by Chemitech Inc., after curing) was applied using a wire bar coater to a thickness of 2 μm. Refractive index n: 1.60). Laminate it with a laminator so that the light reflective layer transferred to the laminate film comes into contact.

(3) After the purge box is purged with nitrogen until the oxygen concentration becomes 100 ppm or less, ultraviolet rays from a high-pressure mercury lamp are irradiated from the pseudo support side of the film 1 to be cured. The illumination intensity is 25mW/cm ² and the irradiation dose is 1000mJ/cm ² . As a result, the reflective circular polarizer 8 in which the first to fourth light reflective layers are formed is obtained.

[Production of reflective circular polarizer 9]

The reflective circular polarizer 9 is formed such that the spiral pitch of the second light reflective layer is continuously deformed in the thickness direction. A pitch gradient layer with gradient is formed. The first light reflective layer and the third light reflective layer are manufactured using the same manufacturing method as the reflective circular polarizer 1 . The pitch gradient layer was formed through the following steps.

After forming the first light reflective layer on the rubbed PET film, the reflective layer coating liquid R-6 was applied using a wire bar coater. Next, the film was heated and aged at 105° C. for 2 minutes to obtain a uniform orientation state. Thereafter, the coating film was maintained at 75° C. and irradiated with ultraviolet rays (30 mJ/cm ² ) using a metal halide lamp in a low-oxygen atmosphere (100 ppm or less). In addition, a bandpass filter that transmits only light with a wavelength of 300 nm to 350 nm during ultraviolet irradiation was placed between the metal halide lamp and the sample. The amount of ultraviolet irradiation was measured through a bandpass filter. Next, the coating film was maintained at 75° C. and heated and aged for 10 seconds. Next, the coating film was maintained at 75° C., and cured by irradiating light from a metal halide lamp with an illumination intensity of 25 mW/cm ² and an irradiation amount of 500 mJ/cm ² in a low-oxygen atmosphere (100 ppm or less). A second light reflective layer composed of a cholesteric liquid crystal layer is formed. Light is irradiated from the cholesteric liquid crystal layer side. At this time, the coating thickness was adjusted so that the film thickness of the second light reflective layer after curing would be 7.0 μm.

The characteristics of the produced reflective circular polarizers 1 to 10 are shown in the following Table 4-1. Furthermore, the characteristics of the produced reflective circular polarizers 11 to 13 are shown in the following Tables 4-2, 4-3, and 4-4, respectively. The reflection center wavelength (center wavelength of reflected light) is confirmed by making a film in which only a single layer is applied. Here, the reflection center wavelength is used to define the characteristics of a light-reflective film having a reflection band using cholesteric liquid crystal, and refers to the midpoint of the 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 that show half value with respect to the peak reflectance using the method described above. Furthermore, the absolute values of SRth _i of the light reflection layers of the reflective circular polarizer 1 and the reflective circular polarizers 4 to 11 are all 0.25 μm or less. The absolute values of SRth _i of the light reflective layers of the reflective circular polarizers 12 to 13 are all 0.20 μm or less. In addition, the value of Rth was measured using AxoScan OPMF-1 (manufactured by Opto Science, Inc.).

Table 4-1. Fabricated reflective circular polarizers 1 to 10 (coating liquid, film thickness)

Table 4-2. Fabricated reflective circular polarizer 11 (coating liquid, film thickness)

Table 4-3. Fabricated reflective circular polarizer 12 (coating liquid, film thickness)

Table 4-4. Fabricated reflective circular polarizer 13 (coating liquid, film thickness)

[Table 8]

[Table 9]

[Table 10]

[Production of laminated optical films]

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

＜Preparation of positive C board 1＞

The positive C plate 1 was produced by adjusting the film thickness with reference to the method described in paragraphs 0132 to 0134 of Japanese Patent Application Laid-Open No. 2016-053709. Positive C plate 1 has Re=0.2nm and Rth=-310nm.

＜Preparation of phase difference layer 1＞

The retardation layer 1 with reverse wavelength dispersion was produced by referring to the method described in paragraphs 0151 to 0163 of Japanese Patent Application Laid-Open No. 2020-084070. The phase difference layer 1 has Re=146nm and Rth=73nm.

＜Preparation of positive C board 2＞

Positive C plate 2 was produced in the same manner as positive C plate 1 except that the film thickness was adjusted. Positive C plate 2 has Re=0.1 nm and Rth=-70 nm.

＜Preparation of linear polarizer＞

Follow the steps below to create a linear polarizer.

(Preparation of cellulose acylate film 1)

-Preparation of core layer cellulose acylate dope-

The following composition was put into a mixing tank and stirred to dissolve each component, thereby preparing a cellulose acetate solution used as a core layer cellulose acylate dope.

Compound F

[Chemical formula 11]

-Preparation of outer layer cellulose acylate dope-

10 parts by mass of the following matting agent solution were added to 90 parts by mass of the core layer cellulose acylate dope to prepare a cellulose acetate solution used as the outer layer cellulose acylate dope.

-Production of cellulose acylate film 1-

After filtering the above-mentioned core layer cellulose acylate dope and the above-mentioned outer layer cellulose acylate dope using filter paper with an average pore size of 34 μm and a sintered metal filter with an average pore size of 10 μm, the above-mentioned core layer cellulose acylate dope and The three outer layers of cellulose acylate dope on both sides are simultaneously cast from the casting port onto a drum at 20°C (belt casting machine).

Next, the film was peeled off in a state where the solvent content was approximately 20% by mass, and both ends in the width direction of the film were fixed with tenter clamps, and dried while stretching in the transverse direction at a draw ratio of 1.1 times.

Then, the film was conveyed between rollers of a heat treatment device and further dried to produce an optical film with a thickness of 40 μm, which was used as cellulose acylate film 1. The in-plane retardation of the obtained cellulose acylate film 1 was 0 nm.

<Formation of Photo Alignment Layer PA1>

The coating liquid S-PA-1 for forming an alignment layer described later was continuously applied on the cellulose acylate film 1 using a wire bar. The support with the coating film formed on it was dried using 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 ultrahigh-pressure mercury lamp), thereby forming the photo-alignment layer PA1 . The film thickness is 0.3μm.

Polymer M-PA-1

[Chemical formula 12]

Acid generator PAG-1

[Chemical formula 13]

Acid generator CPI-110F

[Chemical formula 14]

<Formation of light absorption anisotropic layer P1>

The following coating liquid SP-1 for forming the light absorption anisotropic layer was continuously applied to the obtained alignment layer PA1 using a wire bar. Next, the coating layer P1 was heated at 140°C for 30 seconds, and the coating layer P1 was cooled to room temperature (23°C). Next, it was heated at 90°C for 60 seconds and cooled to room temperature again. Then, the light absorption anisotropic layer P1 was formed on the alignment layer PA1 by irradiating it for 2 seconds using an LED lamp (center wavelength: 365 nm) under irradiation conditions with an illumination intensity of 200 mW/cm ² . The film thickness is 1.6 μm.

Dichroic substance D-1

[Chemical formula 15]

Dichroic substance D-2

[Chemical formula 16]

Dichroic substance D-3

[Chemical formula 17]

Polymer liquid crystal compound M-P-1

[Chemical formula 18]

Low molecular weight liquid crystal compound M-1

[Chemical formula 19]

Surfactant F-1

[Chemical formula 20]

＜Transfer of reflective circular polarizer＞

The obtained reflective circular polarizer 1 was transferred to the support side of the obtained positive C plate 1 . At this time, transfer is performed so that the layer on the side opposite to the dummy support side of the reflective circular polarizer 1 (the fourth light reflective layer) becomes the positive C plate 1 side. The dummy support of the reflective circular polarizer 1 is peeled off and removed after transfer. The reflective circular polarizer 1 was transferred by the following steps.

(1) On the support side of the positive C plate 1, UV adhesive chemiseal U2084B (manufactured by Chemitech Inc., refractive index n1.60 after curing) was applied using a wire bar coater so as to have a thickness of 2 μm. It is bonded with a laminator so that the side opposite to the dummy support of the reflective circular polarizer 1 is in contact with the UV adhesive.

(2) After the purge box is purged with nitrogen until the oxygen concentration becomes 100 ppm or less, ultraviolet rays from a high-pressure mercury lamp are irradiated from the dummy support side of the reflective circular polarizer 1 to be cured. The illumination intensity is 25mW/cm ² and the irradiation dose is 1000mJ/cm ² .

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

Next, the positive C plate 2 is bonded to the first light reflection layer side of the reflective circular polarizer 1 . Next, the C plate 2 is aligned and the retardation layer 1 is bonded.

Finally, the light-absorbing anisotropic layer P1 is transferred to the retardation layer 1 in the same transfer step as described above. However, the retardation layer 1 is laminated so that the slow axis of the retardation layer 1 and the absorption axis of the light-absorbing anisotropic layer P1 are at 45°, so that the polarization axis of the light emitted from the retardation layer 1 is aligned with the light-absorbing anisotropic layer P1 The transmission axis is parallel. In this way, the laminated optical film using the reflective circular polarizer 1 of Example 1 was obtained.

[Evaluation of ghosting]

The lens of the virtual reality display device "Huawei VR Glass" manufactured by Huawei Technologies Co., Ltd., which is a virtual reality display device using a reciprocating optical system, was disassembled and the lens on the side closest to the visual recognition was removed. The visual recognition side of the lens is a convex plano-convex lens, and a reflective circular polarizer is attached to the flat side. The reflective circular polarizer was peeled off from the lens, and the laminated optical film of Example 1 was bonded so that the linear polarizer side became the visible side instead of the flat side. The lens with the laminated optical film attached was reassembled onto the main body to create a virtual reality display device. In the created virtual reality display device, a black and white checkered pattern was displayed on the image display panel, and ghost visibility was visually observed, and evaluation was conducted in the following three stages.

A; completely invisible

B; Although it seems very little, I don’t care.

C; clearly visible

Furthermore, the laminated optical films of Examples 2 to 11 and Comparative Example 1 were produced through the same procedures, and ghost visibility was evaluated. Table 5 shows the types of reflective circular polarizers used in each Example and Comparative Example. And the evaluation results are shown in Table 6.

As a result, in the virtual reality display devices of Examples 1 to 11, the entire area of the lens is completely invisible or indifferent. On the other hand, in the virtual reality display device of Comparative Example 1, in the black display area of the black and white checkered pattern, part of the light in the white display area was clearly visible as a ghost.

Furthermore, as a more sensitive ghosting evaluation method, in the virtual reality display device produced, a black-and-white checkered pattern in black and white is displayed on the image display panel, and a luminance meter (manufactured by Radiant Vision Systems, Inc., equipped with a head-mounted display) was used for evaluation. The ghost visibility (photographed image) was evaluated in the following two stages using the captured image of the AR/VR lens imaging colorimeter IC-PMI16).

A; completely invisible

B; visible

As a result, in the virtual reality display devices of Examples 9 to 11, ghost visibility (captured image) spread over the entire area of the lens and was completely invisible. On the other hand, in the virtual reality display devices of Comparative Example 1 and Examples 1 to 8, in the black display area of the black and white checkered pattern, the light of a part of the white display area was confirmed as a ghost in the captured image.

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

[Table 11]

Table 6. Evaluation results of ghosting

[Table 12]

[Examples 12 to 15]

In the step of obtaining the laminated optical film used in the above-mentioned Example 1, except that the above-mentioned positive C plate 1 was not laminated, the laminated optical film used in the Example 12 was obtained in the same manner as in Example 1. .

In addition, in the step of obtaining the laminated optical film used in the above-mentioned Examples 9 to 11, except that the above-mentioned positive C plate 1 was not laminated, the process was carried out in the same manner as in Examples 9 to 11, respectively, to Example 13. Laminated optical films used in ~15.

The laminated optical films used in Examples 12 to 15 were evaluated for ghosting in the same manner as in each of the above examples. As a result, evaluation of ghost visibility and ghost visibility (photographed image) The same as Examples 1 and 9 to 11 respectively.

Symbol Description

10～13-Optical laminate, 21a, 22a, 23a-Reflective layer A, 21b, 22b, 24b-Reflective layer B, 25, 26-Laminated reflective layer, 31-First layer, 32-Second layer, 33 -Third layer, 34-Fourth layer, 27-First layer, 28-Second layer, 29-Third layer, 100-Laminated optical film, 101-Anti-reflective layer, 102-Positive C plate, 103-Reflection Circular polarizer, 104-positive C plate, 105-phase difference layer, 106-linear polarizer, 300-half mirror, 400-circular polarizer, 500-image display panel, 1000-light that forms a virtual image, 2000-formation Ghosting light.

Claims (20)

1. An optical laminate having 2 or more laminated reflection layers, wherein,

the laminated reflective layer includes 1 each of the following reflective layers:

a reflective layer A including at least 1 or more cholesteric liquid crystal layers formed using a 1 st liquid crystal compound substantially composed of a rod-like liquid crystal compound, and not including a cholesteric liquid crystal layer formed using a 2 nd liquid crystal compound substantially composed of a discotic liquid crystal compound; and

A reflective layer B comprising at least 1 layer of a cholesteric liquid crystal layer formed using the 2 nd liquid crystal compound substantially composed of a discotic liquid crystal compound and not comprising a cholesteric liquid crystal layer formed using the 1 st liquid crystal compound substantially composed of a rod-like liquid crystal compound,

Of the 2 or more laminated reflection layers, among the 2 adjacent laminated reflection layers in the lamination direction, when the reflection layers a face each other, the center wavelengths of the reflection light of the reflection layers a included in the adjacent 2 laminated reflection layers are different from each other,

among the 2 or more laminated reflection layers, among the 2 adjacent laminated reflection layers in the lamination direction, when the reflection layers B are opposed to each other, the center wavelengths of the reflected light of the reflection layers B included in the adjacent 2 laminated reflection layers are different from each other.

2. The optical laminate according to claim 1, wherein,

the reflective layers a and the reflective layers B are alternately arranged in the lamination direction of the optical laminate.

3. The optical laminate according to claim 1, wherein,

the total number of layers of the laminated reflecting layers is 20 or less.

4. The optical laminate according to claim 1, wherein,

the reflectance of light having a wavelength of 400-700 nm is 40% or more and less than 50%.

5. The optical laminate according to claim 1, wherein,

the laminated reflection layer is configured by directly contacting 1 reflection layer a and 1 reflection layer B, or is configured by 1 reflection layer a, 1 reflection layer B, and an adhesion layer disposed between the reflection layer a and the reflection layer B.

6. 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 each have light reflectivity,

the central wavelength of the reflected light of the first layer to the fourth layer is respectively in any one of 430-480 nm, 520-570 nm, 570-620 nm and 620-670 nm,

the sign of the retardation in the film thickness direction at the wavelength of 550nm of the first layer is opposite to the sign of the retardation in the film thickness direction at the wavelength of 550nm of the second layer,

the sign of the retardation in the film thickness direction at the wavelength of 550nm of the third layer is opposite to the sign of the retardation in the film thickness direction at the wavelength of 550nm of the fourth layer.

7. The optical laminate according to claim 6, wherein,

either one of the first layer and the second layer is a cholesteric liquid crystal layer formed using a rod-like liquid crystal compound, the other is a cholesteric liquid crystal layer formed using a discotic liquid crystal compound,

either 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.

8. The optical laminate according to claim 6, wherein,

the center wavelength of the reflected light of either one of the first layer and the fourth layer is in the range of 430 to 480nm, and the center wavelength of the reflected light of the other layer is in the range of 620 to 670 nm.

9. The optical laminate according to claim 6, wherein,

the central wavelength of the reflected light of the first layer is in the range of 430 to 480nm,

the reflected light of the second layer has a central wavelength in the range of 520 to 570nm,

the center wavelength of the reflected light of the third layer is in the range of 570 to 620nm,

the center wavelength of the reflected light of the fourth layer is in the range of 620 to 670 nm.

10. An optical laminate comprising a first layer, a second layer and a third layer in this order,

the first layer to the third layer are all cholesteric liquid crystal layers,

the second layer is a pitch gradient layer formed by changing the spiral pitch in the film thickness direction,

the first layer to the third layer each have light reflectivity,

the central wavelength of the reflected light of the first layer to the third layer is in any one of 430 to 480nm, 520 to 620nm and 620 to 670nm,

the sign of the retardation in the film thickness direction at the wavelength of 550nm of the first layer is opposite to the sign of the retardation in the film thickness direction at the wavelength of 550nm of the second layer,

The sign of the retardation in the film thickness direction at the wavelength of 550nm of the second layer is opposite to the sign of the retardation in the film thickness direction at the wavelength of 550nm of the third layer.

11. The optical laminate according to claim 10, wherein,

the first layer is a cholesteric liquid crystal layer formed using a rod-like liquid crystal compound, the second layer is a cholesteric liquid crystal layer formed using a discotic liquid crystal compound, the third layer is a cholesteric liquid crystal layer formed using a rod-like liquid crystal compound, or,

the first layer is a cholesteric liquid crystal layer formed using a discotic liquid crystal compound, the second layer is a cholesteric liquid crystal layer formed using a rod-like liquid crystal compound, and the third layer is a cholesteric liquid crystal layer formed using a discotic liquid crystal compound.

12. The optical laminate according to claim 10, wherein,

the central wavelength of the reflected light of the first layer is in the range of 430 to 480nm,

the reflected light of the second layer has a central wavelength in the range of 520 to 620nm,

the center wavelength of the reflected light of the third layer is in the range of 620 to 670 nm.

13. A laminated optical film comprising, in order, at least a reflective circular polarizer, a phase difference layer for converting circularly polarized light into linearly polarized light, and a linear polarizer,

The reflective circular polarizer is the optical laminate according to any one of claims 1 to 12.

14. The laminated optical film of claim 13 wherein,

the linear polarizer includes at least a light absorbing anisotropic layer including a liquid crystal compound and a dichroic substance.

15. The laminated optical film of claim 13 further comprising a positive C plate.

16. The laminated optical film of claim 13 wherein,

an anti-reflection layer is also included on the surface.

17. The laminated optical film of claim 16 wherein,

the anti-reflection layer is a moth-eye film or an AR film.

18. The laminated optical film of claim 13, comprising:

a resin substrate having a peak temperature of tan delta of 170 ℃ or lower.

19. An optical article comprising the optical laminate of any one of claims 1 to 12.

20. A virtual reality display device comprising the optical article of claim 19.