Viewing angle switching system and image display device

Abstract

The present invention addresses the problem of providing a viewing angle switching system that, when applied to an image display device, excels in brightness in a predetermined oblique direction when in a sharing mode and excels in a light shielding property in the predetermined oblique direction when in a privacy mode. A viewing angle switching system according to the present invention comprises a light-absorbing anisotropic layer, a polarization conversion unit that includes one or more liquid crystal cells, and a polarizer, in that order, and: the angle formed by a transmittance central axis of the light-absorbing anisotropic layer and a normal line of the light-absorbing anisotropic layer is 0-45°; and it is possible to switch between a predetermined first state and second state regarding the intensity of a P-polarization component and the intensity of an S-polarization component via a voltage applied to a liquid crystal layer included in the liquid crystal cell.

Description

Viewing angle switching system, image display device

[0001] The present invention relates to a viewing angle switching system, and also to an image display device including the viewing angle switching system.

[0002] In recent years, display devices such as liquid crystal display devices have been widely used as displays for personal computers, smartphones, and the like. Displays are also often adopted in mobile devices. Devices with such displays are often used in public places, and therefore there is a demand for technology to prevent others from peeking at them.

[0003] Furthermore, in recent years, liquid crystal display devices have come to be used as in-vehicle displays inside automobiles. As in-vehicle displays have become larger, images displayed on the displays may be reflected on the windshield or other surfaces, obstructing the driver's field of vision, and therefore there is a demand for technology to prevent such reflections.

[0004] Furthermore, it is also preferable that the width of the viewing angle of such a display can be switched as needed. For example, Patent Document 1 discloses a viewing angle switching system that is capable of switching the width of the viewing angle and includes a substrate in which dyes are vertically aligned and a switching cell.

[0005] US Patent Application Publication No. 2021 / 0349335

[0006] A viewing angle switching system is required to be applied to an image display device and be able to switch between a share mode in which an image is visible and a privacy mode in which the image is difficult to view when observed from an oblique direction at a specific azimuth angle. Recently, there has been a demand for the share mode to have superior brightness when observed from a specific oblique direction. Furthermore, there has been a demand for the privacy mode to have superior light-blocking properties when observed from a specific oblique direction. The inventors have studied the share mode and privacy mode and found that the technology described in Patent Document 1 does not meet the standards currently required and that further improvement is necessary.

[0007] Therefore, an object of the present invention is to provide a viewing angle switching system that, when applied to an image display device, provides excellent brightness in a predetermined oblique direction in a share mode and excellent light-blocking properties in a predetermined oblique direction in a privacy mode. Another object of the present invention is to provide an image display device using the above viewing angle switching system.

[0008] The present inventors have conducted extensive research to solve the above problems and have completed the present invention. That is, they have found that the above problems can be solved by the following configuration.

[0009] [1] A viewing angle switching system having, in this order, an optically absorptive anisotropic layer, a polarization conversion unit including one or more liquid crystal cells, and a polarizer, wherein the angle between the transmittance central axis of the optically absorptive anisotropic layer and a normal to the optically absorptive anisotropic layer is 0 to 45°, and the viewing angle switching system is switchable between the following first and second states by a voltage applied to a liquid crystal layer included in the liquid crystal cell. First state: A laminate obtained by peeling off the optically absorptive anisotropic layer from the viewing angle switching system is used as a measurement sample, and when light is incident from the polarizer side of the measurement sample, the intensity of the S-polarized component contained in the light that has passed through the polarization conversion unit when the light is incident at an azimuth angle parallel to the absorption axis of the polarizer and at a polar angle of 45° is 55% or more, and the intensity of the P-polarized component contained in the light that has passed through the polarization conversion unit when the light is incident at an azimuth angle perpendicular to the absorption axis of the polarizer and at a polar angle of 45° is 55% or more. Second state: When light is incident from the polarizer side of the measurement sample, the intensity of the S-polarized component contained in the light transmitted through the polarization conversion unit is 55% or more when the light is incident at an azimuth angle parallel to the absorption axis of the polarizer and at a polar angle of 45°, and when the light is incident at an azimuth angle orthogonal to the absorption axis of the polarizer and at a polar angle of 45°, the intensity of the S-polarized component contained in the light transmitted through the polarization conversion unit is 55% or more. [2] The viewing angle switching system according to [1], wherein the liquid crystal cell included in the polarization conversion unit is a twisted nematic liquid crystal cell, wherein Δnd of the liquid crystal layer in the liquid crystal cell is 500 to 700 nm, and wherein the viewing angle switching system can be switched between the following third and fourth states by a voltage applied to the liquid crystal layer in the liquid crystal cell, wherein the first state is realized by the third state, and the second state is realized by the fourth state. Third state: A state in which the angle formed between the average alignment direction of the liquid crystal compound in the liquid crystal layer in the liquid crystal cell and the thickness direction of the liquid crystal cell is within the range of 0±10°.Fourth state: A state in which the twist angle of the liquid crystal compound in the liquid crystal layer of the liquid crystal cell is 140 to 220°, the angle formed by the in-plane slow axis of the surface of the liquid crystal layer on the polarizer side of the liquid crystal cell and the absorption axis of the polarizer is 20° or less, and the angle formed by the in-plane slow axis of the surface of the liquid crystal layer on the light absorption anisotropic layer side of the liquid crystal cell and the absorption axis of the polarizer is 20° or less. [3] The viewing angle switching system according to [1], wherein the polarization conversion unit includes a first liquid crystal cell and a second liquid crystal cell, and both the first liquid crystal cell and the second liquid crystal cell are vertical alignment type liquid crystal cells or electric field controlled birefringence type liquid crystal cells, and the viewing angle switching between the following fifth and sixth states is possible depending on a voltage applied to the liquid crystal layers of the first liquid crystal cell and the second liquid crystal cell, and the first state is realized by the fifth state, and the second state is realized by the sixth state. Fifth state: A state selected from the group consisting of state 1 in which the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer in the first liquid crystal cell and the absorption axis of the polarizer is within a range of 0±10°, and state 2 in which the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer in the liquid crystal cell and the thickness direction of the liquid crystal cell is within a range of 0±10°. Sixth state: The angle formed by the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the first liquid crystal cell and the second liquid crystal cell and the thickness direction of the first liquid crystal cell and the second liquid crystal cell is 15 to 75°, respectively; the angle formed by the in-plane direction of the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the first liquid crystal cell and the absorption axis of the polarizer is within a range of 0±10°; the angle formed by the in-plane direction of the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the second liquid crystal cell and the absorption axis of the polarizer is within a range of 0±10°; and the angle formed by the in-plane direction orientation of the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the first liquid crystal cell and the in-plane orientation orientation of the average alignment direction of the liquid crystal compounds in the liquid crystal layer of the second liquid crystal cell is within a range of 180°±10°.[4] A viewing angle switching system having, in this order, an optically absorptive anisotropic layer, a liquid crystal cell, and a polarizer, wherein the angle between the transmittance central axis of the optically absorptive anisotropic layer and a normal to the optically absorptive anisotropic layer is 0 to 45°, the liquid crystal cell is a twisted nematic liquid crystal cell, and Δnd of the liquid crystal layer in the liquid crystal cell is 500 to 700 nm, and the viewing angle switching system is switchable between the following third and fourth states by a voltage applied to the liquid crystal layer in the liquid crystal cell: Third state: A state in which the angle between the average alignment direction of liquid crystal compounds in the liquid crystal layer in the liquid crystal cell and the thickness direction of the liquid crystal cell is within the range of 0±10°. Fourth state: A state in which the twist angle of the liquid crystal compound in the liquid crystal layer in the liquid crystal cell is 140 to 220°, the angle formed by the in-plane slow axis of the surface of the liquid crystal layer in the liquid crystal cell facing the polarizer and the absorption axis of the polarizer is 20° or less, and the angle formed by the in-plane slow axis of the surface of the liquid crystal layer in the liquid crystal cell facing the optically absorptive anisotropic layer and the absorption axis of the polarizer is 20° or less. [5] A viewing angle switching system having an optically absorptive anisotropic layer, a first liquid crystal cell, a second liquid crystal cell, and a polarizer in this order, wherein the angle between the transmittance central axis of the optically absorptive anisotropic layer and a normal to the optically absorptive anisotropic layer is 0 to 45°, and both the first liquid crystal cell and the second liquid crystal cell are vertical alignment type liquid crystal cells or electric field controlled birefringence type liquid crystal cells, and the viewing angle switching system is switchable between the following fifth and sixth states by voltages applied to the liquid crystal layers of the first liquid crystal cell and the second liquid crystal cell. Fifth state: A state selected from the group consisting of state 1 in which the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer in the first liquid crystal cell and the absorption axis of the polarizer is within a range of 0±10°, and state 2 in which the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer in the liquid crystal cell and the thickness direction of the liquid crystal cell is within a range of 0±10°.Sixth state: The angle formed by the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the first liquid crystal cell and the second liquid crystal cell and the thickness direction of the first liquid crystal cell and the second liquid crystal cell is 15 to 75°, respectively; the angle formed by the in-plane direction of the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the first liquid crystal cell and the absorption axis of the polarizer is within a range of 0±10°; the angle formed by the in-plane direction of the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the second liquid crystal cell and the absorption axis of the polarizer is within a range of 0±10°; and the angle formed by the in-plane direction orientation of the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the first liquid crystal cell and the in-plane orientation orientation of the average alignment direction of the liquid crystal compounds in the liquid crystal layer of the second liquid crystal cell is within a range of 180°±10°. [6] The viewing angle switching system according to [5], wherein, when the liquid crystal cell is in a fifth state, an angle formed between an average alignment direction of liquid crystal compounds in the liquid crystal layer of the liquid crystal cell on the optically absorptive anisotropic layer side and an absorption axis direction of the polarizer is within a range of 0±10°, and an angle formed between an average alignment direction of liquid crystal compounds in the liquid crystal layer of the liquid crystal cell on the polarizer side and a thickness direction of the liquid crystal cell is within a range of 0±10°. [7] The viewing angle switching system according to any one of [1] to [6], wherein the optically absorptive anisotropic layer contains a liquid crystal compound and a dichroic dye. [8] An image display device, comprising the viewing angle switching system according to any one of [1] to [6].

[0010] According to the present invention, a viewing angle switching system can be provided that, when applied to an image display device, provides excellent brightness in a predetermined oblique direction in a share mode and excellent light-blocking properties in a predetermined oblique direction in a privacy mode. Furthermore, according to the present invention, an image display device using the above-mentioned viewing angle switching system can be provided.

[0011] FIG. 1 is a cross-sectional view showing one aspect of an image display device using the viewing angle switching system of the first embodiment. FIG. 2 is a perspective view of a laminate obtained by peeling off a light absorption anisotropic layer from the viewing angle switching system of the aspect shown in FIG. 1. FIG. 3 is a cross-sectional schematic view showing one aspect of an image display device of the present invention. FIG. 4 is a cross-sectional schematic view showing one aspect of an image display device of the present invention. FIG. 5 is a diagram showing the orientation relationship when a laminate including a liquid crystal cell and a polarizer is viewed from the liquid crystal cell side. FIG. 6 is a diagram showing the S angle of the Poincare sphere to explain polarization conversion when polarized light oscillating in a direction 45° counterclockwise with respect to direction D1 is incident. ３ 9 is a cross-sectional view of the laminate shown in FIG. 8; FIG. 10 is a cross-sectional view of the laminate shown in FIG. 9; FIG. 11 is a cross-sectional view of the laminate shown in FIG. 10; FIG. 12 is a cross-sectional view of the laminate shown in FIG. 11; FIG. 13 is a cross-sectional view of the laminate shown in FIG. 12; FIG. 14 is a cross-sectional view of the laminate shown in FIG. 13;

[0012] The present invention will be described in detail below. The following description of the components may be based on representative embodiments of the present invention, but the present invention is not limited to such embodiments.

[0013] The meaning of each description in this specification is as follows: In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0014] In this specification, "parallel" and "orthogonal" do not mean "parallel" or "orthogonal" in the strict sense, but mean a range of ±5° from parallel or orthogonal. Furthermore, in this specification, unless otherwise specified, "polar angle" means the angle with respect to the normal direction of the film.

[0015] In this specification, the liquid crystal composition and liquid crystal compound conceptually include those that no longer exhibit liquid crystallinity due to curing or the like.

[0016] In addition, in this specification, each component may use a single substance corresponding to the component, or two or more substances may be used in combination. Here, when two or more substances are used in combination for each component, the content of that component refers to the total content of the substances used in combination, unless otherwise specified. In addition, in this specification, "(meth)acrylate" is a notation representing "acrylate" or "methacrylate", "(meth)acrylic" is a notation representing "acrylic" or "methacrylic", and "(meth)acryloyl" is a notation representing "acryloyl" or "methacryloyl".

[0017] In this specification, Re(λ) and Rth(λ) represent the in-plane retardation and the thickness direction retardation, respectively, at a wavelength λ. Unless otherwise specified, the wavelength λ is 550 nm. In the present invention, Re(λ) and Rth(λ) are values ​​measured at a wavelength λ using an AxoScan OPMF-2 (manufactured by Axometrics). By inputting the average refractive index ((nx + ny + nz) / 3) and film thickness (d) into AxoScan, the following slow axis direction (°) is calculated: Re(λ) = R0(λ) Rth(λ) = ((nx + ny) / 2 - nz) × d. Note that R0(λ) is displayed as a numerical value calculated using the AxoScan OPMF-2, but it means Re(λ).

[0018] In this specification, the term "transmittance central axis" refers to the direction that exhibits the highest transmittance when the transmittance is measured by changing the tilt angle (polar angle) and tilt direction (azimuthal angle) relative to the normal direction of the optically absorptive anisotropic layer surface. Specifically, an AxoScan OPMF-2 (manufactured by Axometrics) is used to measure the Mueller matrix at a wavelength of 550 nm. More specifically, during measurement, the azimuthal angle at which the transmittance central axis is tilted is first found, and then, within a plane containing the normal direction of the optically absorptive anisotropic layer along that azimuthal angle (a plane containing the transmittance central axis and perpendicular to the layer surface), the polar angle, which is the angle relative to the normal direction of the optically absorptive anisotropic layer surface, is changed in 1° increments from -70 to 70°, while measuring the Mueller matrix at a wavelength of 550 nm, to derive the transmittance of the optically absorptive anisotropic layer. The resulting direction with the highest transmittance is designated the transmittance central axis. The transmittance central axis means the direction of the absorption axis (the direction of the long axis of the molecule) of the dichroic material contained in the light absorption anisotropic layer.

[0019] In this specification, the refractive indices nx, ny, and nz are measured using an Abbe refractometer (NAR-4T, manufactured by Atago Co., Ltd.) with a sodium lamp (λ = 589 nm) as a light source. Wavelength dependency can be measured using a multi-wavelength Abbe refractometer DR-M2 (manufactured by Atago Co., Ltd.) in combination with an interference filter. Values ​​from the Polymer Handbook (John Wiley & Sons, Inc.) and catalogs of various optical films can also be used. Examples of average refractive index values ​​for major optical films are listed below: cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).

[0020] In this specification, Δnd refers to the retardation caused by a layer in which rod-shaped or discotic liquid crystal compounds are twisted and aligned along the thickness direction, and is expressed as the product of the thickness d of the liquid crystal layer and the birefringence Δn of the liquid crystal. The twist angle of the liquid crystal compound from one surface to the other surface of the layer in which the liquid crystal compound is twisted and aligned is also referred to as the twist angle of the liquid crystal compound. Unless otherwise specified, Δn is the value at a wavelength of 550 nm.

[0021] The viewing angle switching system of the present invention can be exemplified by a first embodiment, a second embodiment, and a third embodiment. Each aspect of the viewing angle switching system of the present invention will be described below.

[0022] <First Embodiment of Viewing Angle Switching System> A first embodiment of the viewing angle switching system of the present invention (hereinafter also simply referred to as the "viewing angle switching system of the first embodiment") comprises, in this order, an optically absorptive anisotropic layer, a polarization conversion unit including one or more liquid crystal cells, and a polarizer. Here, the angle between the transmittance central axis of the optically absorptive anisotropic layer and the normal to the optically absorptive anisotropic layer is 0 to 45°. Furthermore, the viewing angle switching system can be switched between the following first and second states by applying a voltage to a liquid crystal layer included in the liquid crystal cell. First state: A laminate obtained by peeling off the optically absorptive anisotropic layer from a viewing angle switching system is used as a measurement sample, and when light is incident from the polarizer side of the measurement sample, the intensity of the S-polarized component contained in the light that has passed through the polarization conversion unit when the light is incident at an azimuth angle parallel to the absorption axis of the polarizer and at a polar angle of 45° is 55% or more, and the intensity of the P-polarized component contained in the light that has passed through the polarization conversion unit when the light is incident at an azimuth angle perpendicular to the absorption axis of the polarizer and at a polar angle of 45° is 55% or more. Second state: When light is incident from the polarizer side of the measurement sample, the intensity of the S-polarized component contained in the light that passes through the polarization conversion unit when the light is incident at an azimuth angle parallel to the absorption axis of the polarizer and at a polar angle of 45° is 55% or more, and the intensity of the S-polarized component contained in the light that passes through the polarization conversion unit when the light is incident at an azimuth angle perpendicular to the absorption axis of the polarizer and at a polar angle of 45° is 55% or more.

[0023] In the first state, when light is incident from the polarizer side of the measurement sample at an azimuth angle parallel to the absorption axis of the polarizer and at a polar angle of 45°, the intensity of the S-polarized component contained in the light transmitted through the polarization conversion unit is preferably 60% or more, more preferably 65% ​​or more, and even more preferably 70% or more. The intensity of the S-polarized component is often 99% or less. In the first state, when light is incident from the polarizer side of the measurement sample at an azimuth angle perpendicular to the absorption axis of the polarizer and at a polar angle of 45°, the intensity of the P-polarized component contained in the light transmitted through the polarization conversion unit is preferably 70% or more, more preferably 80% or more, and even more preferably 85% or more. The intensity of the P-polarized component is often 99% or less. In the second state, when light is incident from the polarizer side of the measurement sample at an azimuth angle parallel to the absorption axis of the polarizer and at a polar angle of 45°, the intensity of the S-polarized component contained in the light transmitted through the polarization conversion unit may be 60% or more, or may be 70% or more. Furthermore, the intensity of the S-polarized component is often 99% or less, more often 80% or less, and even more often 75% or less. In the second state, when light is incident at an azimuth angle orthogonal to the absorption axis of the polarizer and at a polar angle of 45°, the intensity of the S-polarized component contained in the light transmitted through the polarization conversion unit may be 60% or more, or may be 70% or more, or may be 90% or more. Furthermore, the intensity of the S-polarized component is often 99% or less.

[0024] The viewing angle switching system of the first embodiment is used as a component of an image display device, constituting the image display device of the present invention. FIG. 1 is a cross-sectional view showing one aspect of an image display device using the viewing angle switching system of the first embodiment. The image display device 100a shown in FIG. 1 includes a viewing angle switching system 10a and a display panel 20. Note that the viewer side of the image display device 100a is the side opposite the display panel 20 side of the viewing angle switching system 10a. The viewing angle switching system 10a includes, from the side opposite the display panel 20 side (viewer side), an optically absorptive anisotropic layer 12, a polarization conversion unit 14a, and a polarizer 16, in this order. Note that the angle between the transmittance central axis of the optically absorptive anisotropic layer 12 and the normal to the optically absorptive anisotropic layer 12 is 0 to 45°. 1 is a twisted nematic (TN) liquid crystal cell that includes a liquid crystal layer and can switch the alignment state of the liquid crystal compound included in the liquid crystal layer between a twisted alignment and a vertical alignment. Although the components are shown spaced apart in FIG. 1, the components may be in close contact with each other.

[0025] The polarization conversion unit 14a (TN-type liquid crystal cell) included in the viewing angle switching system 10a can be switched between the first and second states by applying a voltage to the liquid crystal layer of the TN-type liquid crystal cell. The first and second states will be described below with reference to FIG. 2. FIG. 2 is a perspective view of a laminate 30 obtained by peeling off the optically absorptive anisotropic layer 12 from the viewing angle switching system 10a of FIG. 1. Note that FIG. 2 illustrates the polarization conversion unit 14a and the polarizer 16 without any separation. The laminate 30 includes the polarization conversion unit 14a (TN-type liquid crystal cell) and the polarizer 16. The absorption axis direction A16 of the polarizer 16 is the left-right direction on the page (see the black double-headed arrow in FIG. 2). The first and second states are defined by the laminate 30 shown in FIG. 2. In FIG. 2, the dashed line indicates the normal direction to the surface of the polarization conversion unit 14a. 2, two dashed lines drawn on the surface of the polarization conversion unit 14a respectively represent a direction parallel to the absorption axis direction A16 of the polarizer 16 and a direction orthogonal to the absorption axis direction A16 of the polarizer 16 on the surface of the polarization conversion unit 14a. First, the first state will be described.

[0026] In FIG. 2 , the direction of light traveling at an azimuth angle parallel to the absorption axis direction A16 of the polarizer 16 and at a polar angle of 45° is defined as the first light traveling direction L1. Also, in FIG. 2 , the direction of light traveling at an azimuth angle perpendicular to the absorption axis direction A16 of the polarizer 16 and at a polar angle of 45° is defined as the second light traveling direction L2. That is, θ1 is 45° and θ2 is 45°. In the first state, when the laminate 30 is used as a measurement sample and light is incident from the polarizer 16 side, the intensity of the S-polarized component contained in the light transmitted through the polarization conversion unit 14a in the first light traveling direction L1 is 55% or more. In the first state, when the laminate 30 is used as a measurement sample and light is incident from the polarizer 16 side, the intensity of the P-polarized component contained in the light transmitted through the polarization conversion unit 14a in the second light traveling direction L2 is 55% or more. The S-polarized component is a polarized component that vibrates in an in-plane direction perpendicular to the first light traveling direction L1 and in a direction parallel to the surface of the polarization conversion unit 14a. The P-polarized component is a polarized component that vibrates in an in-plane direction perpendicular to the first light traveling direction L1 and in a direction perpendicular to the vibration direction of the S-polarized component. The S-polarized component and the P-polarized component in the second light traveling direction L2 are also defined in the same way as in the first light traveling direction L1.

[0027] In this specification, the intensity of the S-polarized component and the intensity of the P-polarized component can be measured using a spectroradiometer or spectrometer (e.g., a polarization phase difference analyzer, AxoScan, manufactured by AXOMETRICS) equipped with a polarizing plate. More specifically, the intensity of the S-polarized component in the first light traveling direction L1 is measured by irradiating light from the polarizer 16 side of the laminate 30 along the first light traveling direction L1, and a polarizing plate is disposed between the light receiver of the measuring device and the laminate 30. Here, the detected intensity of light measured by disposing a polarizing plate so that the vibration direction of the S-polarized component in the first light traveling direction L1 and the absorption axis of the disposed polarizing plate are orthogonal when viewed from the first light traveling direction L1 is defined as DIs. Furthermore, the detected intensity of light measured by disposing a polarizing plate so that the vibration direction of the P-polarized component in the first light traveling direction L1 and the absorption axis of the disposed polarizing plate are orthogonal when viewed from the first light traveling direction L1 is defined as DIp. The intensity Is of the S-polarized light component in the first light traveling direction L1 can be calculated by the following formula (1s): Is = DIs / (DIs + DIp) Formula (1s) Furthermore, the intensity Ip of the P-polarized light component in the first light traveling direction L1 can be calculated by the following formula (1p): Ip = DIp / (DIs + DIp) Formula (1p)

[0028] Furthermore, the intensity of the S-polarized component and the intensity of the P-polarized component in the second light propagation direction L2 are measured in the same manner as the intensity of the S-polarized component and the P-polarized component in the first light propagation direction L1.

[0029] On the other hand, in the second state, when the laminate 30 is used as a measurement sample and light is incident from the polarizer 16 side, the intensity of the S-polarized component contained in the light that has passed through the polarization conversion unit 14a in the first light traveling direction L1 is 55% or more. Also, in the second state, when the laminate 30 is used as a measurement sample and light is incident from the polarizer 16 side, the intensity of the S-polarized component contained in the light that has passed through the polarization conversion unit 14a in the second light traveling direction L2 is 55% or more. The method for measuring the intensity of the S-polarized component is the same as the method for measuring the intensity of the S-polarized component in the first state, and therefore description thereof will be omitted.

[0030] As described above, the viewing angle switching system 10a can switch between the first state and the second state by applying a voltage to the liquid crystal layer included in the liquid crystal cell (TN-type liquid crystal cell). That is, by controlling the alignment direction of the liquid crystal compound included in the liquid crystal layer of the liquid crystal cell, the image display device 100a can switch between the privacy mode and the share mode when viewed from an oblique direction at a predetermined azimuth angle. Hereinafter, with reference to FIGS. 3 and 4, it will be described that the image display device 100a shown in FIG. 1 can switch between the privacy mode and the share mode.

[0031] FIG. 3 is a cross-sectional view of the image display device 100a. Note that FIG. 3 is a cross-sectional view of the image display device 100a taken along a plane parallel to the zx plane in FIG. 2. The white arrows in FIG. 3 indicate panel light emitted from the display panel 20 and obliquely emitted at a predetermined azimuth angle. The configuration of the image display device 100a is similar to that shown in FIG. 1. However, in FIG. 3, the absorption axis direction A16 of the polarizer 16 is oriented horizontally relative to the paper. Furthermore, the angle between the central transmittance axis of the optically absorptive anisotropic layer 12 and the normal to the optically absorptive anisotropic layer 12 is 0°. Furthermore, the traveling direction of the panel light in FIG. 3 coincides with the first light traveling direction L1 in FIG. 2. When the viewing angle switching system 10a is in the first state, the panel light passes through the laminate of the polarizer 16 and the polarization conversion unit 14a, resulting in an increase in the S-polarized component (the component extending into and out of the paper) as described above. Furthermore, when the viewing angle switching system 10a is in the second state, the S-polarized component (component in the back-to-front direction of the page) of light passing through the laminate of the polarizer 16 and the polarization conversion unit 14a is increased, as described above. Here, as described above, the angle between the transmittance central axis of the optically absorptive anisotropic layer 12 and the normal to the optically absorptive anisotropic layer 12 is 0°. That is, for light emitted in an oblique direction, the optically absorptive anisotropic layer 12 is less likely to absorb light polarized in the back-to-front direction of the page, but is more likely to absorb light polarized in the left-to-right direction of the page. Therefore, when the viewing angle switching system 10a is in the first state and the second state, panel light polarized in the back-to-front direction of the page that enters the optically absorptive anisotropic layer 12 is less likely to be absorbed by the optically absorptive anisotropic layer 12 and is more likely to exit to the viewing side.

[0032] FIG. 4 is a cross-sectional view of the image display device 100a. Note that FIG. 4 is a cross-sectional view of the image display device 100a taken along a plane parallel to the yz plane in FIG. 2. The white arrows in FIG. 4 indicate panel light emitted from the display panel 20 and obliquely emitted at a predetermined azimuth angle. The configuration of the image display device 100a is similar to that shown in FIG. 1. However, in FIG. 4, the absorption axis direction A16 of the polarizer 16 is directed toward the front of the paper. Furthermore, the angle between the central transmittance axis of the optically absorptive anisotropic layer 12 and the normal to the optically absorptive anisotropic layer 12 is 0°. Furthermore, the traveling direction of the panel light in FIG. 4 coincides with the second light traveling direction L2 in FIG. 2. When the viewing angle switching system 10a is in the first state, the panel light passes through the laminate of the polarizer 16 and the polarization conversion unit 14a, resulting in an increase in the P-polarized component (the component in the direction of the black arrow in FIG. 4), as described above. As described above, the angle between the central axis of transmittance of the optically absorptive anisotropic layer 12 and the normal to the optically absorptive anisotropic layer 12 is 0°. That is, for light emitted in oblique directions, the optically absorptive anisotropic layer 12 does not easily absorb light polarized in the direction toward the front of the paper, but does easily absorb light polarized in the direction to the left of the paper. Therefore, when the viewing angle switching system 10a is in the first state, panel light polarized in the direction to the left of the paper and incident on the optically absorptive anisotropic layer 12 is easily absorbed by the optically absorptive anisotropic layer 12 and does not easily exit to the viewing side.

[0033] 4, when the viewing angle switching system 10a is in the second state, the panel light passes through the laminate of the polarizer 16 and the polarization conversion unit 14a, and as described above, the S-polarized component (component polarized in the direction toward the front of the page) increases. Therefore, when the viewing angle switching system 10a is in the second state, the panel light polarized in the left-right direction of the page and incident on the optically absorptive anisotropic layer 12 is less likely to be absorbed by the optically absorptive anisotropic layer 12 and is more likely to exit to the viewing side.

[0034] To summarize the above, when the viewing angle switching system 10a is in the first state, light in the first light traveling direction L1 in FIG. 2 is easily transmitted, and light in the second light traveling direction L2 is less likely to be transmitted. That is, the state in which the viewing angle switching system 10a is in the first state is the privacy mode. On the other hand, when the viewing angle switching system 10a is in the second state, light in the first light traveling direction L1 in FIG. 2 is easily transmitted, and light in the second light traveling direction L2 is easily transmitted. That is, the state in which the viewing angle switching system 10a is in the second state is the share mode. Therefore, as described above, when the first state and the second state can be switched by the voltage applied to the liquid crystal layer included in the liquid crystal cell, switching between the privacy mode and the share mode is possible.

[0035] Furthermore, even when the angle between the central transmittance axis of the optically absorptive anisotropic layer 12 and the normal to the optically absorptive anisotropic layer 12 is not 0°, it is possible to switch between the privacy mode and the share mode by switching between the first state and the second state using the voltage applied to the liquid crystal layer included in the liquid crystal cell included in the polarization conversion unit 14 a, based on the above-mentioned principle. Note that in the direction of the central transmittance axis of the optically absorptive anisotropic layer 12, panel light emitted from the display panel 20 is easily transmitted, making it easy to view images displayed on the display panel 20.

[0036] Since the viewing angle switching system of the first embodiment can switch between the first and second states, it is considered to have excellent brightness in a specified oblique direction in share mode and excellent light-blocking properties in a specified oblique direction in privacy mode.

[0037] 1 to 4, the viewing angle switching system 10a has, in this order from the side opposite the display panel 20 (the viewing side), the light-absorbing anisotropic layer 12, the polarization conversion unit 14a (TN-type liquid crystal cell), and the polarizer 16. However, the viewing angle switching system of the first embodiment is not limited to the above embodiment and may be modified in various ways. For example, the polarization conversion unit 14a may include two or more liquid crystal cells. Furthermore, the liquid crystal cell may be another type of liquid crystal cell, as will be described later in the third embodiment.

[0038] The following describes the configuration included in the viewing angle switching system of the first embodiment. Note that in the aspects shown in FIGS. 1 to 4 and the aspects described above, each configuration included in the viewing angle switching system can be modified as shown in the following configuration examples, and modified configurations can also be combined. Additionally, the viewing angle switching system of the first embodiment may further include the elements described below. Hereinafter, excellent brightness in a predetermined oblique direction in share mode will also be referred to as "excellent transparency," and excellent light-blocking ability in a predetermined oblique direction in privacy mode will also be referred to as "excellent light-blocking."

[0039] [Light-Absorbing Anisotropic Layer] In the light-absorbing anisotropic layer of the viewing angle switching system of the first embodiment, the angle between the transmittance central axis of the light-absorbing anisotropic layer and the normal to the light-absorbing anisotropic layer is 0 to 45°. The light-absorbing anisotropic layer preferably contains a dichroic material. When the light-absorbing anisotropic layer contains a dichroic material, the transmittance central axis and the orientation direction of the dichroic material usually coincide. The angle can be adjusted depending on the direction in which the image is desired to be viewed. For example, when providing an image display device with an anti-peeping function, it is preferable to maximize the transmittance in the front direction. In this case, the angle is preferably 0 to 10°. The transmittance central axis of the light-absorbing anisotropic layer may be oriented in different directions depending on the location within the plane of the light-absorbing anisotropic layer. For example, in an in-vehicle display having a curved display surface, in order to prevent emitted light from any position from being reflected on the windshield or the like and to ensure that the displayed image is properly visible to the driver, it is preferable to adjust the direction of the central axis of transmittance of the light-absorbing anisotropic layer to match the curved surface.

[0040] The term "transmittance central axis" refers to the direction in which transmittance is highest when transmittance is measured by varying the tilt angle (polar angle) and tilt direction (azimuthal angle) relative to the normal direction of the optically absorbing anisotropic layer surface. When measuring this angle, an AxoScan OPMF-2 (manufactured by Axometrics) is used to first detect the azimuthal angle at which the transmittance central axis is tilted. Then, in the direction of this azimuthal angle, the Mueller matrix is ​​measured while varying the polar angle to derive the transmittance. The direction in which transmittance is highest (polar angle) is defined as the direction of the transmittance central axis of the optically absorbing anisotropic layer. This polar angle is the angle between the transmittance central axis in the optically absorbing anisotropic layer and the normal direction to the optically absorbing anisotropic layer. The transmittance central axis (polar angle) of the optically absorptive anisotropic layer is measured at 15 arbitrarily selected points in the optically absorptive anisotropic layer, and the average of the polar angles is taken as the transmittance central axis of the optically absorptive anisotropic layer. In the present invention, these optical measurements are performed using light with a wavelength of 550 nm, unless otherwise specified.

[0041] The light transmittance of the optically absorptive anisotropic layer in a direction parallel to the central axis of transmittance is preferably 50% or more, more preferably 70%. The upper limit of the transmittance is not particularly limited, but may be, for example, 95% or less, and is often 90% or less. The transmittance in a direction tilted 30° from the central axis of transmittance of the optically absorptive anisotropic layer is preferably 30% or less, more preferably 15% or less. The lower limit of the transmittance is not particularly limited, but may be, for example, 0.5% or more, and is often 5% or more.

[0042] The optically absorptive anisotropic layer of the present invention preferably contains at least one dichroic material (e.g., a dichroic dye). The dichroic material is not particularly limited as long as it exhibits dichroism, and examples thereof include dichroic dyes, dichroic azo dye compounds, ultraviolet-absorbing materials, infrared-absorbing materials, nonlinear optical materials, carbon nanotubes, anisotropic metal nanoparticles, and inorganic materials. The optically absorptive anisotropic layer may contain two or more dichroic materials. For example, it preferably contains a cyan dye exhibiting dichroism in the red wavelength range, a magenta dye exhibiting dichroism in the green wavelength range, and a yellow dye exhibiting dichroism in the blue wavelength range. The inclusion of multiple dichroic materials can neutralize the color and provide a viewing angle control effect across the entire wavelength range of visible light. A dichroic material is a material that exhibits dichroism, and dichroism refers to the property of varying absorbance depending on the polarization direction. The degree of orientation of the dichroic material at a wavelength of 550 nm is preferably 0.95 or greater. When the degree of orientation of the dichroic material is 0.95 or more, the transmittance in the direction of the absorption axis (i.e., the direction in which light is to be transmitted) can be increased. Furthermore, in order to achieve a neutral color, the degree of orientation of the dichroic material at a wavelength of 420 nm is preferably 0.93 or more. The thickness of the optically absorptive anisotropic layer is not particularly limited, but from the viewpoint of flexibility, it is preferably 100 to 8000 nm, and more preferably 300 to 5000 nm. Hereinafter, a dichroic dye will be described as an example of the dichroic material.

[0043] (Dichroic Dye) As the dichroic substance, a dichroic dye is preferred, and a dichroic azo dye compound is more preferred. In the present invention, a dichroic azo dye compound refers to an azo dye compound whose absorbance varies depending on the direction. A dichroic azo dye compound may or may not exhibit liquid crystallinity. When a dichroic azo dye compound exhibits liquid crystallinity, it may exhibit either a nematic liquid crystal phase or a smectic liquid crystal phase. The temperature range in which the liquid crystal phase is exhibited is preferably room temperature (approximately 20 to 28°C) to 300°C, and more preferably 50 to 200°C from the viewpoints of handleability and manufacturing suitability.

[0044] In the present invention, from the viewpoint of improving pressure resistance, it is preferable that the dichroic azo dye compound in the optically absorptive anisotropic layer-forming composition used in forming the optically absorptive anisotropic layer described below has a crosslinkable group. Specific examples of the crosslinkable group include a (meth)acryloyl group, an epoxy group, an oxetanyl group, and a styryl group, and among these, a (meth)acryloyl group is preferred.

[0045] Examples of preferred dichroic azo dye compounds for use in the present invention include a first dichroic azo dye compound, a second dichroic azo dye compound, and a third dichroic azo dye compound. The first dichroic azo dye compound is a dichroic azo dye compound having a maximum absorption wavelength in the wavelength range of 560 nm to 700 nm. The second dichroic azo dye compound is a dichroic azo dye compound having a maximum absorption wavelength in the wavelength range of 455 nm to less than 560 nm. The third dichroic azo dye compound is a dichroic azo dye compound having a maximum absorption wavelength in the wavelength range of 380 nm to 455 nm. Specific examples of the first dichroic azo dye compound, the second dichroic azo dye compound, and the third dichroic azo dye compound include, for example, the compounds described in paragraphs

[0161] to

[0171] of WO 2022 / 138548, the compounds described in paragraphs

[0172] to

[0180] of WO 2022 / 138548, and the compounds described in paragraphs

[0183] to

[0206] of WO 2022 / 138548.

[0046] The content of the dichroic material is preferably from 1 to 30% by mass, more preferably from 5 to 25% by mass, and even more preferably from 10 to 20% by mass, based on the total solid mass of the light absorption anisotropic layer.

[0047] (Liquid Crystal Compound) The optically absorptive anisotropic layer is preferably formed using a liquid crystal composition containing a dichroic substance and a liquid crystal compound. Therefore, the optically absorptive anisotropic layer preferably contains a component derived from the liquid crystal compound. By forming the optically absorptive anisotropic layer using the liquid crystal composition, the dichroic substance can be aligned with a high degree of orientation while preventing precipitation of the dichroic substance. As the liquid crystal compound, either a low-molecular-weight liquid crystal compound or a high-molecular-weight liquid crystal compound can be used, and it is also preferable to use both in combination. Here, "low-molecular-weight liquid crystal compound" refers to a liquid crystal compound that does not have a repeating unit in its chemical structure. Furthermore, "high-molecular-weight liquid crystal compound" refers to a liquid crystal compound that has a repeating unit in its chemical structure.

[0048] The low-molecular-weight liquid crystal compound may be either a compound exhibiting a nematic liquid crystal phase or a compound exhibiting a smectic liquid crystal phase, but from the viewpoint of increasing the degree of orientation, a compound exhibiting a smectic liquid crystal phase is preferred. For example, the liquid crystal compounds described in JP-A-2013-228706 can be mentioned.

[0049] Examples of polymeric liquid crystalline compounds include the thermotropic liquid crystalline polymers described in JP 2011-237513 A. Furthermore, from the viewpoint of excellent strength (particularly the flex resistance of the film), the polymeric liquid crystalline compound preferably has a repeating unit having a crosslinkable group at its terminal. Examples of crosslinkable groups include the polymerizable groups described in paragraphs

[0040] to

[0050] of JP 2010-244038 A. Among these, from the viewpoint of improving reactivity and synthetic suitability, acryloyl groups, methacryloyl groups, epoxy groups, oxetanyl groups, and styryl groups are preferred, with acryloyl groups and methacryloyl groups being more preferred.

[0050] When the light absorption anisotropic layer contains a polymeric liquid crystalline compound, the polymeric liquid crystalline compound preferably forms a nematic liquid crystalline phase. The temperature range in which the polymeric liquid crystalline compound exhibits the nematic liquid crystalline phase is preferably from room temperature (23°C) to 450°C, and from the viewpoints of handling and manufacturing suitability, preferably from 50 to 400°C.

[0051] The content of the component derived from the liquid crystal compound in the light absorption anisotropic layer is preferably 25 to 2,000 parts by mass, more preferably 100 to 1,300 parts by mass, and even more preferably 200 to 900 parts by mass, relative to 100 parts by mass of the dichroic substance. When the content of the liquid crystal compound is within the above range, the degree of orientation of the dichroic substance is further improved. The liquid crystal compound may be contained alone, or two or more types may be contained. When two or more types of liquid crystal compounds are contained, the content of the component derived from the liquid crystal compound means the total content of the liquid crystal compounds.

[0052] (Additives) The liquid crystal composition used for forming the light absorption anisotropic layer may further contain additives such as a solvent, a vertical alignment agent, an interfacial improver, a leveling agent, a polymerizable component, a polymerization initiator (e.g., a radical polymerization initiator), a durability improver, etc. Known additives can be used as appropriate.

[0053] The viewing angle switching system of the first embodiment may include another layer different from the optically absorbing anisotropic layer and the layer described later. However, the other layer is a layer that is in direct contact with the optically absorbing anisotropic layer or indirectly in contact with the optically absorbing anisotropic layer via a layer different from the optically absorbing anisotropic layer and the layer described later. Hereinafter, the other layer that is in direct or indirect contact with the optically absorbing anisotropic layer will be described.

[0054] (Substrate Layer) The viewing angle switching system of the first embodiment may include a substrate layer as another layer. The substrate layer is not particularly limited, but a transparent film or sheet is preferred. Known transparent resin films, transparent resin plates, transparent resin sheets, and glass can be used. Examples of transparent resin films that can be used include cellulose acylate films (e.g., cellulose triacetate films, cellulose diacetate films, cellulose acetate butyrate films, and cellulose acetate propionate films), polyethylene terephthalate films, polyethersulfone films, polyacrylic resin films, polyurethane resin films, polyester films, polycarbonate films, polysulfone films, polyether films, polymethylpentene films, polyether ketone films, and (meth)acrylonitrile films. Among these, cellulose acylate films are preferred because they have high transparency, low optical birefringence, and are easy to manufacture. These films are commonly used as protective films for polarizers. Cellulose triacetate films are particularly preferred. The thickness of the transparent resin film is preferably 20 μm to 100 μm.

[0055] (Alignment Film) The viewing angle switching system of the first embodiment may have an alignment film between the substrate layer and the light-absorbing anisotropic layer as another layer. The alignment film may be any layer that can align the dichroic substance (liquid crystal compound) in a desired state on the alignment film. For example, a film formed from a polyfunctional acrylate compound or polyvinyl alcohol may be used. Polyvinyl alcohol is particularly preferred. The alignment film may be a photo-alignment film. Note that by irradiating a photo-alignment film containing an azo compound or a cinnamoyl compound with UV light from an oblique direction, the dichroic substance can be aligned at an angle relative to the normal direction of the film.

[0056] (Barrier Layer) The viewing angle switching system of the first embodiment may include a barrier layer as another layer. Here, the barrier layer is also called a gas barrier layer (oxygen barrier layer) and has the function of protecting the light absorption anisotropic layer from gases such as oxygen in the atmosphere, moisture, or compounds contained in adjacent layers. For details of the barrier layer, see, for example, paragraphs

[0014] to

[0054] of JP 2014-159124 A, paragraphs

[0042] to

[0075] of JP 2017-121721 A, paragraphs

[0045] to

[0054] of JP 2017-115076 A, paragraphs

[0010] to

[0061] of JP 2012-213938 A, and paragraphs

[0021] to

[0031] of JP 2005-169994 A.

[0057] (Refractive Index Adjustment Layer) The optically absorptive anisotropic layer may have a problem of internal reflection due to its high refractive index. In such a case, a refractive index adjustment layer may be used. The refractive index adjustment layer is preferably disposed in contact with the optically absorptive anisotropic layer and serves as a layer for so-called index matching. The in-plane average refractive index of the refractive index adjustment layer at a wavelength of 550 nm is preferably 1.55 or more and 1.70 or less.

[0058] (Method for forming optically absorbing anisotropic layer) The method for forming the optically absorbing anisotropic layer is not particularly limited, and examples thereof include a method including, in this order, a step of applying a composition for forming an optically absorbing anisotropic layer to form a coating film (hereinafter also referred to as a "coating film forming step") and a step of orienting a liquid crystalline component and a dichroic substance contained in the coating film (hereinafter also referred to as an "orientation step"). Note that the liquid crystalline component is a component that includes not only the above-mentioned liquid crystalline compound, but also the dichroic substance having liquid crystallinity, if the above-mentioned dichroic substance has liquid crystallinity.

[0059] -Coating film forming step- The coating film forming step is a step of forming a coating film by applying a composition for forming an optically absorbing anisotropic layer. The composition for forming an optically absorbing anisotropic layer can be easily applied by using a composition for forming an optically absorbing anisotropic layer that contains a solvent, or by using a composition for forming an optically absorbing anisotropic layer that has been converted into a liquid such as a molten liquid by heating or the like. Specific examples of methods for applying the composition for forming an optically absorbing anisotropic layer include known methods such as roll coating, gravure printing, spin coating, wire bar coating, extrusion coating, direct gravure coating, reverse gravure coating, die coating, spraying, and inkjet printing.

[0060] Orientation Process—The orientation process is a process for orienting the liquid crystalline component contained in the coating film. This results in an optically absorptive anisotropic layer. The orientation process may include a drying process. Components such as the solvent can be removed from the coating film by the drying process. The drying process may be performed by leaving the coating film at room temperature for a predetermined time (e.g., natural drying), or by heating and / or blowing air. Here, the liquid crystalline component contained in the composition for forming an optically absorptive anisotropic layer may be aligned by the above-described coating film formation process or drying process. For example, in an embodiment in which the composition for forming an optically absorptive anisotropic layer is prepared as a coating liquid containing a solvent, the coating film is dried to remove the solvent from the coating film, thereby obtaining a coating film with optical absorptive anisotropy (i.e., an optically absorptive anisotropic layer). When the drying process is performed at a temperature equal to or higher than the temperature at which the liquid crystalline component contained in the coating film transitions from a liquid crystal phase to an isotropic phase, the heat treatment described below may not be performed.

[0061] The transition temperature from the liquid crystal phase to the isotropic phase of the liquid crystalline component contained in the coating film is preferably 10 to 250°C, more preferably 25 to 190°C, from the viewpoint of manufacturability, etc. A transition temperature of 10°C or higher is preferred because it eliminates the need for a cooling process or the like to lower the temperature to a temperature range in which the liquid crystal phase is exhibited. Furthermore, a transition temperature of 250°C or lower is preferred because it does not require a high temperature even when heating to an isotropic phase in order to suppress alignment defects, thereby reducing waste of thermal energy and deformation and deterioration of the substrate.

[0062] The orientation step preferably includes a heat treatment. This allows the liquid crystalline component contained in the coating film to be oriented, and the heat-treated coating film can be suitably used as a light absorption anisotropic layer. From the viewpoint of manufacturability, the heat treatment is preferably performed at a temperature of 10 to 250°C, more preferably 25 to 190°C. The heating time is preferably 1 to 300 seconds, more preferably 1 to 60 seconds.

[0063] The alignment step may include a cooling treatment carried out after the heating treatment. The cooling treatment is a treatment in which the coated film after heating is cooled to about room temperature (20 to 25°C). This makes it possible to fix the alignment of the liquid crystalline component contained in the coated film. The cooling method is not particularly limited and can be carried out by a known method.

[0064] Other Steps The method for forming the optically absorbing anisotropic layer may include a step of curing the optically absorbing anisotropic layer (hereinafter also referred to as a "curing step") after the above-described alignment step. For example, when the compound contained in the optically absorbing anisotropic layer has a crosslinkable group (polymerizable group), the curing step is performed by heating and / or light irradiation (exposure). Among these, from the viewpoint of productivity, the curing step is preferably performed by light irradiation. Various light sources, such as infrared light, visible light, or ultraviolet light, can be used as the light source for curing, but ultraviolet light is preferred. Furthermore, ultraviolet light may be irradiated while heating during curing, or ultraviolet light may be irradiated through a filter that transmits only specific wavelengths. When exposure is performed while heating, the heating temperature during exposure is preferably 25 to 140°C, although this depends on the transition temperature of the liquid crystal component contained in the liquid crystal film. Furthermore, exposure may be performed under a nitrogen atmosphere. When the curing of the liquid crystal film proceeds by radical polymerization, exposure under a nitrogen atmosphere is preferred because inhibition of polymerization by oxygen is reduced.

[0065] The optically absorptive anisotropic layer may contain a dichroic dye and a guest-host liquid crystal material, and may be capable of electrically driving the alignment direction of the dichroic dye, as described in, for example, JP-A No. 2013-541727. In this case, it becomes possible to electrically switch the alignment direction of the dichroic dye.

[0066] [Polarization conversion unit] The viewing angle switching system of the first embodiment includes a polarization conversion unit including one or more liquid crystal cells. The polarization conversion unit may include one liquid crystal cell, or two or more liquid crystal cells. In many cases, the polarization conversion unit includes four or fewer liquid crystal cells. The liquid crystal cells included in the polarization conversion unit will be described below.

[0067] (Liquid Crystal Cell) The liquid crystal cell included in the polarization conversion section is disposed between the light absorption anisotropic layer and the polarizer. As described above, the liquid crystal cell includes a liquid crystal layer, and can be switched between a first state and a second state by a voltage applied to the liquid crystal layer in the liquid crystal cell. The liquid crystal cell is not particularly limited as long as the laminate can be switched between the first state and the second state, and any known liquid crystal cell can be used. It is preferable that the alignment direction of the liquid crystal compound in the liquid crystal cell can be controlled by a voltage applied to the liquid crystal layer. As described above, the liquid crystal cell can be switched between a privacy mode and a share mode by switching between the first state and the second state.

[0068] The liquid crystal cell may have a plurality of regions in which the alignment direction of the liquid crystal compound can be controlled. When the liquid crystal cell has a plurality of regions in which the alignment direction of the liquid crystal compound can be controlled, the alignment direction of the liquid crystal compound in each region can be controlled independently, and the regions of the display panel corresponding to each region can be switched between a privacy mode and a share mode.

[0069] The type of the liquid crystal cell is not particularly limited, and known types can be used. Examples of the liquid crystal cell include, in addition to the TN type liquid crystal cell described above, an in-plane switching (IPS) type liquid crystal cell, a vertical alignment (VA) type liquid crystal cell, an ECB (Electrically Controlled Birefringence) type liquid crystal cell, and an OCB (Opticaly Compensated Bend) type liquid crystal cell. The liquid crystal cell may be a super twisted nematic (STN) liquid crystal cell having a twist angle of 180° or more, or a vertically aligned twisted nematic (VATN) liquid crystal cell disclosed in Japanese Patent Laid-Open No. 10-123576, in which rod-shaped liquid crystal molecules are substantially vertically aligned when no voltage is applied and the liquid crystal layer is twisted at 60 to 120° when a voltage is applied. Of these, the liquid crystal cell is preferably selected from the group consisting of a TN liquid crystal cell, an ECB liquid crystal cell, and a VA liquid crystal cell.

[0070] When the polarization conversion unit includes a TN-type liquid crystal cell, the polarization conversion unit preferably includes one liquid crystal cell. When the polarization conversion unit includes at least one selected from the group consisting of an ECB-type liquid crystal cell and a VA-type liquid crystal cell, the polarization conversion unit preferably includes two liquid crystal cells.

[0071] A preferred embodiment of the TN-type liquid crystal cell will be described in the section on the viewing angle switching system of the second embodiment, and a preferred embodiment of the ECB-type liquid crystal cell and a preferred embodiment of the VA-type liquid crystal cell will be described in the section on the viewing angle switching system of the third embodiment.

[0072] [Polarizer] The polarizer included in the viewing angle switching system of the first embodiment is not particularly limited, and a known polarizer (linear polarizer) can be used. For example, examples of linear polarizers (absorbing polarizers) include polarizers in which a dichroic substance is dyed onto polyvinyl alcohol or other polymer resins and stretched to align the dichroic substance horizontally, and polarizers in which a dichroic substance is oriented horizontally by utilizing the alignment of liquid crystals.

[0073] The polarizer may be a reflective polarizer or a laminate of an absorbing polarizer and a reflective polarizer. A reflective polarizer is a polarizer that reflects one polarized light and transmits the other polarized light. Note that a reflective polarizer has a reflection axis and a transmission axis in its plane, but the reflection axis functions similarly to the absorption axis in a normal polarizer (absorption polarizer) in the sense that it does not transmit polarized light in that direction. Therefore, in this specification, the reflection axis of a reflective polarizer can be read as the absorption axis.

[0074] [Other Layers] The viewing angle switching system of the first embodiment may include layers (other layers) other than those described above. Examples of the other layers include a protective film, a pressure-sensitive adhesive layer, an adhesive layer, an optical compensation layer, a diffusion sheet, a prism sheet, and a reflective sheet. Known layers can be used for the other layers. For example, examples of the optical compensation layer include an A plate, a B plate, and a C plate.

[0075] <Second Embodiment of Viewing Angle Switching System> A second embodiment of the viewing angle switching system of the present invention (hereinafter also simply referred to as "the viewing angle switching system of the second embodiment") has, in this order, an optically absorptive anisotropic layer, a liquid crystal cell, and a polarizer. Here, the angle between the central axis of transmittance of the optically absorptive anisotropic layer and the normal to the optically absorptive anisotropic layer is 0 to 45°. The liquid crystal cell is a twisted nematic (TN) liquid crystal cell, and the Δnd of the liquid crystal layer in the liquid crystal cell is 500 to 700 nm. Furthermore, the liquid crystal cell can be switched between the following third and fourth states by applying a voltage to the liquid crystal layer. Third state: A state in which the angle between the average alignment direction of liquid crystal compounds in the liquid crystal layer in the liquid crystal cell and the thickness direction of the liquid crystal cell is within the range of 0±10°. Fourth state: A state in which the twist angle of the liquid crystal compound in the liquid crystal layer of the liquid crystal cell is 140 to 220°, the angle formed by the in-plane slow axis of the surface of the liquid crystal layer in the liquid crystal cell facing the polarizer and the absorption axis of the polarizer is 20° or less, and the angle formed by the in-plane slow axis of the surface of the liquid crystal layer in the liquid crystal cell facing the optically absorptive anisotropic layer and the absorption axis of the polarizer is 20° or less.

[0076] An image display device using the viewing angle switching system of the second embodiment is similar to the image display device using the viewing angle switching system of the first embodiment shown in FIG. 1, and therefore a description thereof will be omitted.

[0077] Here, in the description of the viewing angle switching system of the first embodiment, it was explained that if the viewing angle switching system can be switched between a first state and a second state, it can switch between a privacy mode and a share mode. It was also explained that the viewing angle switching system has excellent transmittance and excellent light-blocking properties. Hereinafter, it will be explained that in a third state of the viewing angle switching system of the second embodiment, the first state of the viewing angle switching system of the first embodiment is realized, and in a fourth state of the viewing angle switching system of the second embodiment, the second state of the viewing angle switching system of the first embodiment is realized. That is, it will be explained that in the third state of the viewing angle switching system of the second embodiment, when light is incident at an azimuth angle parallel to the absorption axis of the polarizer and from a polar angle of 45°, the intensity of the S-polarized component of light that has passed through a laminate including a polarizer and a liquid crystal cell is increased. It will also be explained that in the third state of the viewing angle switching system of the second embodiment, when light is incident at an azimuth angle orthogonal to the absorption axis of the polarizer and from a polar angle of 45°, the intensity of the P-polarized component of light that has passed through a laminate including a polarizer and a liquid crystal cell is increased. In addition, in the fourth state of the viewing angle switching system of the second embodiment, when light is incident at an azimuth angle parallel to the absorption axis of the polarizer and from a polar angle of 45°, the intensity of the S-polarized component in the light transmitted through the laminate including the polarizer and the liquid crystal cell is increased. In addition, in the fourth state of the viewing angle switching system of the second embodiment, when light is incident at an azimuth angle orthogonal to the absorption axis of the polarizer and from a polar angle of 45°, the intensity of the S-polarized component in the light transmitted through the laminate including the polarizer and the liquid crystal cell is increased.

[0078] First, in the third state of the viewing angle switching system of the second embodiment, when light is incident at an azimuth angle parallel to the absorption axis of the polarizer and from a polar angle of 45°, the intensity of the S-polarized component in light transmitted through a laminate including a polarizer and a liquid crystal cell is increased. When light is incident at an azimuth angle parallel to the absorption axis of the polarizer and from a polar angle of 45°, polarized light vibrating perpendicular to the absorption axis of the polarizer exits the polarizer. If the polarized light exiting the polarizer does not undergo polarization conversion, it contains a large amount of S-polarized component. In the third state, the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer of the liquid crystal cell and the thickness direction of the liquid crystal cell is within the range of 0±10°. Therefore, when the liquid crystal compound is a rod-shaped liquid crystal compound, the thickness direction of the liquid crystal cell is the slow axis direction in the third state. Here, it is easy to understand that the light emitted from the polarizer is emitted from the liquid crystal cell without undergoing any polarization conversion by the liquid crystal cell, since the thickness direction of the liquid crystal cell is the slow axis direction. Therefore, the above-mentioned state is achieved.

[0079] Next, we will explain why, in the third state of the viewing angle switching system of the second embodiment, when light is incident at an azimuth angle perpendicular to the absorption axis of the polarizer and from a polar angle of 45°, the intensity of the P-polarized component in light transmitted through a laminate including a polarizer and a liquid crystal cell increases. When light is incident at an azimuth angle parallel to the absorption axis of the polarizer and from a polar angle of 45°, polarized light vibrating in a direction perpendicular to the absorption axis of the polarizer exits the polarizer. If the polarized light exiting the polarizer does not undergo polarization conversion, it contains a large amount of P-polarized component. As described above, in the third state, the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer of the liquid crystal cell and the thickness direction of the liquid crystal cell is within the range of 0±10°. Therefore, when the liquid crystal compound is a rod-shaped liquid crystal compound, the thickness direction of the liquid crystal cell is the slow axis direction in the third state. Here, it is easy to understand that the light emitted from the polarizer is emitted from the liquid crystal cell without undergoing any polarization conversion by the liquid crystal cell, since the thickness direction of the liquid crystal cell is the slow axis direction. Therefore, the above-mentioned state is achieved.

[0080] Next, it will be explained that in the fourth state of the viewing angle switching system of the second embodiment, when light is incident at an azimuth angle parallel to the absorption axis of the polarizer and from a polar angle of 45°, the intensity of the S-polarized component in the light transmitted through the laminate including the polarizer and the liquid crystal cell becomes large. At the same time, it will be explained that in the fourth state of the viewing angle switching system of the second embodiment, when light is incident at an azimuth angle orthogonal to the absorption axis of the polarizer and from a polar angle of 45°, the intensity of the S-polarized component in the light transmitted through the laminate including the polarizer and the liquid crystal cell becomes large.

[0081] When light is incident at an azimuth angle parallel to the absorption axis of the polarizer and at a polar angle of 45°, polarized light vibrating in a direction perpendicular to the absorption axis of the polarizer exits the polarizer. The polarized light exiting the polarizer contains a large S-polarized component if it does not undergo polarization conversion. On the other hand, when light is incident at an azimuth angle parallel to the absorption axis of the polarizer and at a polar angle of 45°, polarized light vibrating in a direction perpendicular to the absorption axis of the polarizer exits the polarizer. The polarized light exiting the polarizer contains a large P-polarized component if it does not undergo polarization conversion. Here, as an example of the fourth state, consider a state in which the twist angle of the liquid crystal compound in the liquid crystal layer of the liquid crystal cell is 200°, the angle between the in-plane slow axis of the surface of the liquid crystal layer facing the polarizer in the liquid crystal cell and the absorption axis of the polarizer is 10°, and the angle between the in-plane slow axis of the surface of the liquid crystal layer facing the optically absorptive anisotropic layer in the liquid crystal cell and the absorption axis of the polarizer is 10°. The orientation relationship in the above state is shown in FIG. 5. FIG. 5 is a diagram showing the orientation relationship when a laminate including a liquid crystal cell and a polarizer is viewed from the liquid crystal cell side. That is, FIG. 5 is a diagram showing the orientation relationship when the laminate 30 of FIG. 2 is viewed in a direction parallel to the z axis of FIG. 2 and from the liquid crystal cell side. In FIG. 5, direction DA is a direction parallel to the absorption axis direction A16 of the polarizer 16. In FIG. 5, direction D1 is a direction parallel to the in-plane slow axis of the surface of the liquid crystal layer in the liquid crystal cell facing the polarizer, and φ1 is the angle between direction DA and direction D1, which is 10°. In FIG. 5, direction D2 is a direction parallel to the in-plane slow axis of the surface of the liquid crystal layer in the liquid crystal cell facing the optically absorptive anisotropic layer, and φ2 is the angle between direction DA and direction D2, which is 10°. Also, in FIG. 5, direction D2 is a direction 200° clockwise with respect to direction D1 when viewed from the optically absorptive anisotropic layer side. The incident direction of light when light is incident from a direction at an azimuth angle parallel to the absorption axis of the polarizer and at a polar angle of 45° (the first light traveling direction L1) corresponds to direction DX in Fig. 5. The incident direction of light when light is incident from a direction at an azimuth angle perpendicular to the absorption axis of the polarizer and at a polar angle of 45° (the second light traveling direction L2) corresponds to direction DY in Fig. 5. When light is incident on a laminate including a liquid crystal cell and a polarizer from direction DX, a large amount of polarized light vibrating in a direction perpendicular to direction DA tends to exit the polarizer.Furthermore, when light is incident from the direction DY onto a laminate including a liquid crystal cell and a polarizer, a large amount of polarized light vibrating in a direction perpendicular to the direction DA tends to exit from the polarizer.

[0082] In the above laminate, light emitted from the polarizer undergoes polarization conversion by the liquid crystal cell. In the liquid crystal layer of the liquid crystal cell, the liquid crystal compound is twisted and aligned at a twist angle of 220° from direction D1 to direction D2. Here, it is assumed that Δnd of the liquid crystal layer in the liquid crystal cell is 630 nm. Polarization conversion by a layer containing a twistedly aligned liquid crystal compound is generally understood by the locus of a rolling cone. Here, Figure 6 shows the S of the Poincaré sphere to explain the polarization conversion when polarized light oscillating in a direction at an angle of 45° counterclockwise to direction D1 is incident. ３ 6 shows a projection view from the axial direction. In Fig. 6, point P1a represents polarized light vibrating in a direction at an angle of 45° counterclockwise relative to direction D1. In the liquid crystal cell, the Δnd of the liquid crystal layer is 630 nm and the twist angle is 220°, so at a wavelength of 550 nm, the apex angle of the rolling cone is approximately 90°. Therefore, it can be said that the light represented by point P1a is converted into a polarization state represented by point P2a by the liquid crystal cell, as shown in Fig. 6.

[0083] Here, when light is incident from the direction of incidence of light at an azimuth angle parallel to the absorption axis of the polarizer and a polar angle of 45° (corresponding to direction DX in FIG. 5 ), it can be said that direction D1 (in-plane slow axis direction) is perceived as being at a position of about 75° counterclockwise to the incident light. Similarly, it can be said that direction D2 (in-plane slow axis direction) is perceived as being at a position of about 75° clockwise to the incident light. In other words, when light is incident obliquely from a direction corresponding to direction DX in FIG. 5 , it can be said that the twist angle of the liquid crystal compound in the liquid crystal layer in the liquid crystal cell is perceived as being greater than 220° to the incident light. Therefore, when light is incident from the above direction, it can be said that the apex angle of the rolling cone is greater than 90°. Therefore, when light is incident obliquely from a direction corresponding to direction DX in FIG. 5 , it can be said that the polarization state is converted by the liquid crystal cell to the polarization state represented by point P2b in FIG. 6 . The light represented by point P2b contains many components that are similar to the polarization state before entering the liquid crystal cell, and therefore has a large intensity of the S-polarized component. Therefore, when light is incident at an azimuth angle parallel to the absorption axis of the polarizer and from a polar angle of 45°, the intensity of the S-polarized component is large in the light that has passed through the laminate including the polarizer and the liquid crystal cell.

[0084] On the other hand, when light is incident from a direction of incidence at an azimuth angle orthogonal to the absorption axis of the polarizer and a polar angle of 45° (corresponding to direction DY in FIG. 5 ), direction D1 (in-plane slow axis direction) can be perceived as a position of approximately 85° counterclockwise to the incident light. Similarly, direction D2 (in-plane slow axis direction) can be perceived as a position of approximately 85° clockwise to the incident light. In other words, when light is incident obliquely from a direction corresponding to direction DY in FIG. 5 , the twist angle of the liquid crystal compound in the liquid crystal layer in the liquid crystal cell can be perceived as being smaller than 220° to the incident light. Therefore, when light is incident from the above direction, the apex angle of the rolling cone can be perceived as being smaller than 90°. Therefore, when light is incident obliquely from a direction corresponding to direction DY in FIG. 5 , it can be said that the light is converted into the polarization state represented by point P2c in FIG. 6 after being subjected to polarization conversion by the liquid crystal cell. The light represented by point P2c contains many components in a polarization state orthogonal to the polarization state before entering the liquid crystal cell, and therefore has a large intensity of the S-polarized component. Therefore, when light is incident at an azimuth angle parallel to the absorption axis of the polarizer and from a polar angle of 45°, the intensity of the S-polarized component is large in the light that has passed through the laminate including the polarizer and the liquid crystal cell.

[0085] From the above, it can be understood that in the third state of the viewing angle switching system of the second embodiment, the first state of the viewing angle switching system of the first embodiment is realized, and in the fourth state of the viewing angle switching system of the second embodiment, the second state of the viewing angle switching system of the first embodiment is realized. Therefore, if it is possible to switch between the third state and the fourth state, it is possible to switch between the privacy mode and the share mode, and it has excellent transparency and light-blocking properties. Even in a configuration other than the above, it is easily understood that the viewing angle switching system of the second embodiment can switch between the privacy mode and the share mode using the same principle as above, and has excellent transparency and light-blocking properties.

[0086] [Liquid Crystal Cell] The liquid crystal cell included in the viewing angle switching system of the second embodiment is a TN-type liquid crystal cell. The liquid crystal compound included in the liquid crystal layer of the TN-type liquid crystal cell is not particularly limited, and any conventionally known liquid crystal compound can be used. A rod-shaped liquid crystal compound is preferred as the liquid crystal compound. The liquid crystal compound used in the TN-type liquid crystal cell may have either positive or negative dielectric anisotropy. When a liquid crystal compound with positive dielectric anisotropy is used, the TN-type liquid crystal cell is likely to enter the third state when no voltage is applied to the electrodes, and is likely to enter the fourth state when a voltage is applied to the electrodes. On the other hand, when a liquid crystal compound with negative dielectric anisotropy is used, the TN-type liquid crystal cell is likely to enter the fourth state when no voltage is applied to the electrodes, and is likely to enter the third state when a voltage is applied to the electrodes.

[0087] The twist angle and average alignment direction of the liquid crystal compound can be measured using AxoScan OPMF-2 (manufactured by Axometrics).

[0088] TN type liquid crystal cells are most commonly used as color TFT (Thin Film Transistor) liquid crystal display devices, and are described in many publications.

[0089] In the third state, when light is incident from the polarizer side of the measurement sample at an azimuth angle parallel to the absorption axis of the polarizer and at a polar angle of 45°, the intensity of the S-polarized component contained in the light transmitted through the polarization conversion unit is preferably 60% or more, more preferably 65% ​​or more, and even more preferably 70% or more. The intensity of the S-polarized component is often 99% or less. In the third state, when light is incident from the polarizer side of the measurement sample at an azimuth angle perpendicular to the absorption axis of the polarizer and at a polar angle of 45°, the intensity of the P-polarized component contained in the light transmitted through the polarization conversion unit is preferably 70% or more, more preferably 80% or more, and even more preferably 85% or more. The intensity of the P-polarized component is often 99% or less. In the fourth state, when light is incident from the polarizer side of the measurement sample at an azimuth angle parallel to the absorption axis of the polarizer and at a polar angle of 45°, the intensity of the S-polarized component contained in the light transmitted through the polarization conversion unit may be 60% or more, or may be 70% or more. Furthermore, the intensity of the S-polarized component is often 99% or less, more often 80% or less, and even more often 75% or less. In the fourth state, when light is incident at an azimuth angle orthogonal to the absorption axis of the polarizer and at a polar angle of 45°, the intensity of the S-polarized component contained in the light transmitted through the polarization conversion unit may be 60% or more, or may be 70% or more, or may be 90% or more. Furthermore, the intensity of the S-polarized component is often 99% or less.

[0090] In the TN-type liquid crystal cell, the liquid crystal layer has a thickness of 500 to 700 nm, preferably 550 to 675 nm, and more preferably 600 to 650 nm. In the third state, the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer of the TN-type liquid crystal cell and the thickness direction of the liquid crystal cell is within a range of 0±10°, and preferably within a range of 0±5°.

[0091] In the fourth state, the twist angle of the liquid crystal compound in the liquid crystal layer of the TN-type liquid crystal cell is 140 to 220°, and may be 150° or more, or 180° or more. The twist angle may be 200° or less. In the fourth state, the angle between the in-plane slow axis of the surface of the liquid crystal layer on the polarizer side in the TN-type liquid crystal cell and the absorption axis of the polarizer is 20° or less, or may be 15° or less, or may be 10° or less, or may be 7° or less. The angle is often 1° or more, but may be 3° or more, or 5° or more. In the fourth state, the angle between the in-plane slow axis of the surface of the liquid crystal layer on the light absorption anisotropic layer side in the TN-type liquid crystal cell and the absorption axis of the polarizer is 20° or less, or may be 15° or less, or may be 10° or less, or may be 7° or less. Furthermore, the angle is often 1° or more, but may be 3° or more, or may be 5° or more.

[0092] [Light-absorbing anisotropic layer] The aspects and preferred aspects of the light-absorbing anisotropic layer included in the viewing angle switching system of the second embodiment are the same as those of the light-absorbing anisotropic layer included in the viewing angle switching system of the first embodiment, so explanations will be omitted.

[0093] [Polarizer] The aspects and preferred aspects of the polarizer included in the viewing angle switching system of the second embodiment are the same as those of the polarizer included in the viewing angle switching system of the first embodiment, and therefore description thereof will be omitted.

[0094] [Other Layers] The viewing angle switching system of the second embodiment may have layers (other layers) other than those described above. The other layers are similar to the other layers that may be included in the viewing angle switching system of the first embodiment, and therefore, description thereof will be omitted.

[0095] <Third Embodiment of Viewing Angle Switching System> A third embodiment of the viewing angle switching system of the present invention (hereinafter also simply referred to as the "viewing angle switching system of the third embodiment") includes an optically absorptive anisotropic layer, a first liquid crystal cell, a second liquid crystal cell, and a polarizer, in this order. Here, both the first liquid crystal cell and the second liquid crystal cell are vertical alignment type liquid crystal cells or field-controlled birefringence type liquid crystal cells. Furthermore, the first liquid crystal cell and the second liquid crystal cell can be switched between the following fifth and sixth states by applying a voltage to the liquid crystal layer. Fifth state: A state in which the first liquid crystal cell and the second liquid crystal cell are each selected from the group consisting of State 1, in which the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer of the liquid crystal cell and the absorption axis of the polarizer is within a range of 0±10°, and State 2, in which the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer of the liquid crystal cell and the thickness direction of the liquid crystal cell is within a range of 0±10°. Sixth state: A state in which the angle formed between the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the first liquid crystal cell and the second liquid crystal cell and the thickness direction of the liquid crystal cell is 15 to 75°, the angle formed between the in-plane direction of the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the first liquid crystal cell and the absorption axis of the polarizer is within a range of 0±10°, the angle formed between the in-plane direction of the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the second liquid crystal cell and the absorption axis of the polarizer is within a range of 0±10°, and the angle formed between the in-plane direction orientation of the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the first liquid crystal cell and the in-plane direction orientation of the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the second liquid crystal cell is within a range of 180°±10°.

[0096] The viewing angle switching system of the third embodiment is used as a component of an image display device, constituting the image display device of the present invention. Figure 7 shows a cross-sectional view of one aspect of an image display device using the viewing angle switching system of the third embodiment. The image display device 100b shown in Figure 7 includes a viewing angle switching system 10b and a display panel 20. The image display device 100b has a viewing angle switching system 10b and a display panel 20. The viewing side of the image display device 100b is the side opposite the display panel 20 side of the viewing angle switching system 10b. The viewing angle switching system 10b includes, in this order from the side opposite the display panel 20 side (the viewing side), an optically absorptive anisotropic layer 12, a first liquid crystal cell 142, a second liquid crystal cell 144, and a polarizer 16. The angle between the transmittance central axis of the optically absorptive anisotropic layer 12 and the normal to the optically absorptive anisotropic layer 12 is 0 to 45°. 7 are either vertical alignment type liquid crystal cells or field controlled birefringence type liquid crystal cells. In FIG. 7, the components are shown spaced apart from each other, but the components may be in close contact with each other.

[0097] Here, in the description of the viewing angle switching system of the first embodiment, it was explained that if the viewing angle switching system can be switched between a first state and a second state, it can switch between a privacy mode and a share mode. It was also explained that the viewing angle switching system has excellent transparency and excellent light-blocking properties. Hereinafter, it will be explained that in the fifth state of the viewing angle switching system of the third embodiment, the first state of the viewing angle switching system of the first embodiment is realized, and in the sixth state of the viewing angle switching system of the third embodiment, the second state of the viewing angle switching system of the first embodiment is realized. That is, it will be explained that in the fifth state of the viewing angle switching system of the third embodiment, when light is incident at an azimuth angle parallel to the absorption axis of the polarizer and from a polar angle of 45°, the intensity of the S-polarized component increases in light that has passed through a laminate including the polarizer, the first liquid crystal cell, and the second liquid crystal cell. Furthermore, in a fifth state of the viewing angle switching system of the third embodiment, when light is incident at an azimuth angle orthogonal to the absorption axis of the polarizer and from a polar angle of 45°, the intensity of the P-polarized component of the light transmitted through a laminate including the polarizer, the first liquid crystal cell, and the second liquid crystal cell is increased. In a sixth state of the viewing angle switching system of the third embodiment, when light is incident at an azimuth angle parallel to the absorption axis of the polarizer and from a polar angle of 45°, the intensity of the S-polarized component of the light transmitted through a laminate including the polarizer, the first liquid crystal cell, and the second liquid crystal cell is increased. In a sixth state of the viewing angle switching system of the third embodiment, when light is incident at an azimuth angle orthogonal to the absorption axis of the polarizer and from a polar angle of 45°, the intensity of the S-polarized component of the light transmitted through a laminate including the polarizer, the first liquid crystal cell, and the second liquid crystal cell is increased.

[0098] First, in the fifth state of the viewing angle switching system of the third embodiment, when light is incident at an azimuth angle parallel to the absorption axis of the polarizer and from a polar angle of 45°, the intensity of the S-polarized component in light transmitted through a laminate including the polarizer and the first and second liquid crystal cells is described. When light is incident at an azimuth angle parallel to the absorption axis of the polarizer and from a polar angle of 45°, polarized light vibrating perpendicular to the absorption axis of the polarizer exits the polarizer. The polarized light exiting the polarizer contains a large amount of S-polarized component if it does not undergo polarization conversion. As described above, in the fifth state, the first and second liquid crystal cells are in a state selected from the group consisting of State 1, in which the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer of the liquid crystal cell and the absorption axis of the polarizer is within a range of 0±10°, and State 2, in which the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer of the liquid crystal cell and the thickness direction of the liquid crystal cell is within a range of 0±10°. Therefore, when the liquid crystal compound is a rod-shaped liquid crystal compound, in the fifth state, the slow axis directions of the first and second liquid crystal cells are respectively in the thickness direction of the liquid crystal cell or perpendicular to the S-polarized light component. Therefore, it is easily understood that the light emitted from the polarizer is hardly subjected to polarization conversion by the first and second liquid crystal cells and is emitted from the first and second liquid crystal cells. Therefore, the above-mentioned state is achieved.

[0099] Next, in the fifth state of the viewing angle switching system of the third embodiment, when light is incident from a direction at an azimuth angle perpendicular to the absorption axis of the polarizer and a polar angle of 45°, the intensity of the P-polarized component in light transmitted through a laminate including the polarizer and the first and second liquid crystal cells will be described. When light is incident from a direction at an azimuth angle parallel to the absorption axis of the polarizer and a polar angle of 45°, polarized light vibrating in a direction perpendicular to the absorption axis of the polarizer exits the polarizer. The polarized light exiting the polarizer contains a large amount of P-polarized component if it does not undergo polarization conversion. As described above, in the fifth state, the first and second liquid crystal cells are in a state selected from the group consisting of State 1, in which the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer of the liquid crystal cell and the absorption axis of the polarizer is within a range of 0±10°, and State 2, in which the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer of the liquid crystal cell and the thickness direction of the liquid crystal cell is within a range of 0±10°. Therefore, when the liquid crystal compound is a rod-shaped liquid crystal compound, in the fifth state, the slow axis directions of the first and second liquid crystal cells are respectively in the thickness direction of the liquid crystal cell or perpendicular to the S-polarized light component. Therefore, it is easily understood that the light emitted from the polarizer is hardly subjected to polarization conversion by the first and second liquid crystal cells and is emitted from the first and second liquid crystal cells. Therefore, the above-mentioned state is achieved.

[0100] Next, it will be explained that in the sixth state of the viewing angle switching system of the third embodiment, when light is incident at an azimuth angle parallel to the absorption axis of the polarizer and from a polar angle of 45°, the intensity of the S-polarized component in the light transmitted through the laminate including the polarizer and the first and second liquid crystal cells becomes large. In addition, it will be explained that in the sixth state of the viewing angle switching system of the third embodiment, when light is incident at an azimuth angle orthogonal to the absorption axis of the polarizer and from a polar angle of 45°, the intensity of the S-polarized component in the light transmitted through the laminate including the polarizer and the first and second liquid crystal cells becomes large.

[0101] First, we will explain the case where light is incident on the viewing angle switching system of the third embodiment from a direction at an azimuth angle parallel to the absorption axis of the polarizer and a polar angle of 45°. FIG. 8 is a perspective view of a laminate 32 obtained by peeling off the optically absorptive anisotropic layer 12 from the viewing angle switching system 10b of FIG. 7. Note that FIG. 8 illustrates the first liquid crystal cell 142, the second liquid crystal cell 144, and the polarizer 16 without any separation. The laminate 32 includes the first liquid crystal cell 142, the second liquid crystal cell 144, and the polarizer 16 in this order. In FIG. 8, the dashed-dotted line indicates the normal direction to the surface of the first liquid crystal cell 142. Furthermore, in FIG. 8, the two dashed lines on the surface of the first liquid crystal cell 142 represent the direction parallel to the absorption axis direction A16 of the polarizer 16 and the direction perpendicular to the absorption axis direction A16 of the polarizer 16, respectively, on the surface of the first liquid crystal cell 142.

[0102] In Fig. 8, the direction of light traveling at an azimuth angle parallel to the absorption axis direction A16 of the polarizer 16 and at a polar angle of 45° is defined as a third light traveling direction L3. Also in Fig. 8, the direction at an azimuth angle perpendicular to the absorption axis direction A16 of the polarizer 16 and at a polar angle of 45° is defined as a fourth light traveling direction L4. That is, θ3 is 45° and θ4 is 45°.

[0103] Next, the sixth state will be described with reference to the drawings. FIG. 9 is a cross-sectional view of the laminate 32 shown in FIG. 8. FIG. 9 shows an example of the average alignment direction of the liquid crystal compound in the liquid crystal layer in each of the first liquid crystal cell 142 and the second liquid crystal cell 144 in the sixth state. The laminate 32 shown in FIG. 9 includes a polarizer 16, a second liquid crystal cell 144, and a first liquid crystal cell 142, in this order. Note that FIG. 9 is a cross-sectional view of the laminate 32 taken along a plane parallel to the zx plane in FIG. 8. Therefore, the absorption axis direction A16 of the polarizer 16 is aligned horizontally on the paper. The black arrow in FIG. 9 indicates the average alignment direction D3 of the liquid crystal compound in the liquid crystal layer in the first liquid crystal cell 142. The angle between the average alignment direction D3 and the thickness direction of the first liquid crystal cell 142 is 35°. That is, θ5 shown in FIG. 9 is 35°. In Fig. 9, the average alignment direction D3 is represented as a direction extending from the surface on the polarizer side toward the surface opposite the polarizer side. The white arrow in Fig. 9 indicates the average alignment direction D4 of the liquid crystal compound in the liquid crystal layer of the second liquid crystal cell 144. The angle between the average alignment direction D4 and the thickness direction of the second liquid crystal cell 144 is 35°. In other words, θ6 in Fig. 9 is 35°. In Fig. 9, the average alignment direction D4 is represented as a direction extending from the surface on the polarizer side toward the surface opposite the polarizer side.

[0104] On the other hand, Figure 10 is a cross-sectional view of the laminate 32 shown in Figures 8 and 9. That is, the laminate 32 shown in Figure 10 has a polarizer 16, a second liquid crystal cell 144, and a first liquid crystal cell 142, in this order. Note that Figure 10 is a cross-sectional view of the laminate 32 taken along a plane parallel to the yz plane of Figure 8. Therefore, the absorption axis direction A16 of the polarizer 16 is directed toward the front of the paper. The solid arrows in Figure 10 indicate the average alignment direction D3 of the liquid crystal compound in the liquid crystal layer of the first liquid crystal cell 142. The hollow arrows in Figure 10 indicate the average alignment direction D4 of the liquid crystal compound in the liquid crystal layer of the second liquid crystal cell 144. In the cross-sectional view shown in Figure 10, the average alignment directions D3 and D4 appear to coincide with the thickness directions of the first liquid crystal cell 142 and the second liquid crystal cell 144.

[0105] On the other hand, Figure 11 is a diagram showing the orientation relationship when the laminate 32 shown in Figures 8 to 10 is viewed from the first liquid crystal cell 142 side. That is, Figure 11 is a diagram showing the orientation relationship when the laminate 32 of Figures 8 to 10 is viewed in a direction parallel to the z axis of Figure 8 and from the first liquid crystal cell 142 side. In Figure 11, direction DA is a direction parallel to the absorption axis direction A16 of the polarizer 16. In Figure 11, direction D3P is a direction parallel to the z axis of Figure 8 and is the average alignment direction of the liquid crystal compound in the liquid crystal layer of the first liquid crystal cell 142 in the sixth state when viewed from the first liquid crystal cell 142 side. That is, direction D3P shown in Figure 11 coincides with the in-plane direction of the average alignment direction (average alignment direction D3) of the liquid crystal compound in the liquid crystal layer of the first liquid crystal cell 142. 11 , direction D4P is a direction parallel to the z-axis in FIG. 8 and is the average alignment direction of the liquid crystal compounds in the liquid crystal layer of the second liquid crystal cell 144 in the sixth state when viewed from the first liquid crystal cell 142 side. That is, direction D4P shown in FIG. 11 coincides with the in-plane direction of the average alignment direction (average alignment direction D4) of the liquid crystal compounds in the liquid crystal layer of the second liquid crystal cell 144. In an example of the sixth state, as shown in FIG. 11 , the angle formed between the in-plane direction (direction D3P) of the average alignment direction (average alignment direction D3) of the liquid crystal compounds in the liquid crystal layer of the first liquid crystal cell 142 and the absorption axis direction A16 (direction DA) of the polarizer 16 is 0°. 11 , in an example of the sixth state, the angle formed between the in-plane direction (direction D4P) of the average alignment direction (average alignment direction D4) of the liquid crystal compounds in the liquid crystal layer of the second liquid crystal cell 144 and the absorption axis direction A16 (direction DA) of the polarizer 16 is 0°. Additionally, in an example of the sixth state, the directions D3P and D4P are opposite to each other in FIG. 11 . That is, in an example of the sixth state, the angle formed between the in-plane direction (direction D3P) of the average alignment direction of the liquid crystal compounds in the liquid crystal layer of the first liquid crystal cell 142 and the in-plane direction (direction D4P) of the average alignment direction of the liquid crystal compounds in the liquid crystal layer of the second liquid crystal cell 144 in FIG. 11 is 180°.11 , the angle formed by the azimuth angle when direction D3P is projected from the z-axis direction onto the xy plane and the azimuth angle when direction D4P is projected from the z-axis direction onto the xy plane is 180°. That is, the angle formed by the azimuth angle when direction D3P is projected from the normal direction to the surface of first liquid crystal cell 142 onto the surface of first liquid crystal cell 142 and the azimuth angle when direction D4P is projected from the normal direction to the surface of first liquid crystal cell 142 onto the surface of second liquid crystal cell 144 is 180°.

[0106] Based on the above, in the sixth state, when light incident from the third light traveling direction L3 and light incident from the fourth light traveling direction L4 in Figure 8 exits the laminate 32, the intensity of the S-polarized component will be explained. As shown in Figure 8, light containing a large amount of P-polarized component incident from the third light traveling direction L3 is incident toward the zx plane from a direction tilted 45° from the y-axis in the yz plane in Figure 9. As is clear from Figure 9, to light containing a large amount of P-polarized component incident from the third light traveling direction L3, the average alignment direction D4 of the liquid crystal compound in the liquid crystal layer in the second liquid crystal cell 144 and the average alignment direction D3 in the liquid crystal layer in the first liquid crystal cell 142 each appear to be oriented at an angle of 45° with the vibration direction of the P-polarized component. In this case, light containing a large amount of P-polarized components incident from the third light propagation direction L3 undergoes polarization conversion by the first liquid crystal cell 142 and the second liquid crystal cell 144, and when it exits the laminate 32, the intensity of the S-polarized components increases.

[0107] On the other hand, light containing a large amount of S-polarized light entering from the fourth light traveling direction L4 shown in Fig. 8 enters the y-z plane from a direction tilted 45° from the z-axis in the z-x plane in Fig. 10. As is clear from Fig. 10, the light containing a large amount of S-polarized light entering from the fourth light traveling direction L4 appears to be aligned at a 90° angle with the vibration direction of the S-polarized light component, with the average alignment direction D4 of the liquid crystal compound in the liquid crystal layer of the second liquid crystal cell 144 and the average alignment direction D3 in the liquid crystal layer of the first liquid crystal cell 142. As a result, the light containing a large amount of S-polarized light entering from the fourth light traveling direction L4 undergoes almost no polarization conversion by the first liquid crystal cell 142 and the second liquid crystal cell 144, and the intensity of the S-polarized light component increases when it exits the laminate 32.

[0108] From the above, it can be understood that the fifth state of the viewing angle switching system of the third embodiment realizes the first state of the viewing angle switching system of the first embodiment, and the sixth state of the viewing angle switching system of the third embodiment realizes the second state of the viewing angle switching system of the first embodiment. Therefore, if the fifth state and the sixth state can be switched, the privacy mode and the share mode can be switched, and the viewing angle switching system has excellent transparency and excellent light-blocking properties. Even in other aspects, it can be easily understood that the viewing angle switching system of the third embodiment can switch between the privacy mode and the share mode using the same principle as above, and has excellent transparency and light-blocking properties.

[0109] [Liquid Crystal Cells] The liquid crystal cells (first and second liquid crystal cells) included in the viewing angle switching system of the third embodiment are both vertical alignment (VA) type liquid crystal cells or electric field controlled birefringence (ECB) type liquid crystal cells. The first and second liquid crystal cells may be liquid crystal cells of different configurations or liquid crystal cells of the same configuration.

[0110] In VA-mode liquid crystal cells, rod-shaped liquid crystal molecules are generally aligned substantially vertically when no voltage is applied. VA-mode liquid crystal cells include (1) narrowly defined VA-mode liquid crystal cells in which rod-shaped liquid crystal molecules are aligned substantially vertically when no voltage is applied and substantially horizontally when voltage is applied (disclosed in JP-A-2-176625), (2) multi-domain VA-mode (MVA-mode) liquid crystal cells (disclosed in SID97, Digest of Tech. Papers (Proceedings) 28 (1997) 845), (3) n-ASM-mode liquid crystal cells in which rod-shaped liquid crystal molecules are aligned substantially vertically when no voltage is applied and are aligned in a twisted multi-domain manner when voltage is applied (disclosed in Proceedings of the Japan Liquid Crystal Symposium 58-59 (1998)), and (4) SURVIVAL-mode liquid crystal cells (disclosed at LCD International 98). In addition, any of a PVA (Patterned Vertical Alignment) method, an optical alignment method, and a PSA (Polymer-Sustained Alignment) method may be used. Details of these methods are described in detail in JP-A-2006-215326 and JP-A-2008-538819.

[0111] In a VA-type liquid crystal cell, the alignment direction of the liquid crystal compound can be changed by applying a voltage. For example, when no voltage is applied, the state 2 of the fifth state is easily realized, and by adjusting the applied voltage, the sixth state is easily realized. In addition, in a VA-type liquid crystal cell, when a predetermined voltage is applied, the liquid crystal compound is aligned horizontally, so the state 1 of the fifth state may be realized by applying the predetermined voltage. Note that the azimuth angle at which the liquid crystal compound tilts in the in-plane direction due to the application of a voltage to the VA-type liquid crystal cell can be controlled by the pretilt azimuth angle.

[0112] In an ECB-type liquid crystal cell, an electric field is generated perpendicular to the substrate surface, and the alignment direction of the liquid crystal compound is changed by the electric field. In an ECB-type liquid crystal cell, the liquid crystal compound generally aligns along the thickness direction of the cell when an electric field is generated. In an ECB-type liquid crystal cell, for example, State 2 of the fifth state is easily realized when a predetermined voltage is applied, and State 6 is easily realized by adjusting the applied voltage. Furthermore, in an ECB-type liquid crystal cell, the liquid crystal compound is easily aligned in the in-plane direction of the liquid crystal cell when no voltage is applied, so State 1 of the fifth state may be realized when no voltage is applied. The azimuth angle at which the liquid crystal compound rises in the thickness direction of the ECB-type liquid crystal cell when a voltage is applied to the ECB-type liquid crystal cell can be controlled by the pretilt azimuth angle.

[0113] The Δnd of the liquid crystal layer in the first liquid crystal cell and the second liquid crystal cell is preferably 300 nm or more, more preferably 350 nm or more, and even more preferably 400 nm or more, and is preferably 700 nm or less, more preferably 650 nm or less, and even more preferably 550 nm or less.

[0114] As described above, in the fifth state, the first liquid crystal cell may be in State 1 and the second liquid crystal cell may be in State 1, the first liquid crystal cell may be in State 1 and the second liquid crystal cell may be in State 2, the first liquid crystal cell may be in State 2 and the second liquid crystal cell may be in State 1, or the first liquid crystal cell may be in State 2 and the second liquid crystal cell may be in State 2. Among these, in the fifth state, it is preferable that the first liquid crystal cell be in State 1 and the second liquid crystal cell be in State 2, or that the first liquid crystal cell be in State 2 and the second liquid crystal cell be in State 1. In terms of superior light-blocking properties, it is more preferable that the first liquid crystal cell be in State 2 and the second liquid crystal cell be in State 1.

[0115] In the sixth state, the angle formed between the average alignment direction of the liquid crystal in the liquid crystal layer of the first liquid crystal cell and the second liquid crystal cell and the thickness direction of the liquid crystal cell is 30 to 55°, preferably 35 to 50°, and more preferably 35 to 45°. Furthermore, in the sixth state, the angle formed between the in-plane direction of the average alignment direction of the liquid crystal compound in the liquid crystal layer of the first liquid crystal cell and the absorption axis of the polarizer is within a range of 0±10°, preferably 0±5°. Furthermore, in the sixth state, the angle formed between the in-plane direction of the average alignment direction of the liquid crystal compound in the liquid crystal layer of the second liquid crystal cell and the absorption axis of the polarizer is within a range of 0±10°, preferably 0±5°. Furthermore, in the sixth state, the angle between the in-plane direction of the average alignment direction of the liquid crystal compound in the liquid crystal layer in one liquid crystal cell and the in-plane direction of the average alignment direction of the liquid crystal compound in the liquid crystal layer in the second liquid crystal cell is within the range of 180°±10°, but is preferably within the range of 180°±5°.

[0116] <Image Display Device> The image display device of the present invention includes the viewing angle switching system of the present invention (first embodiment, second embodiment, and third embodiment). The image display device is not particularly limited, and examples thereof include a liquid crystal display device, an electroluminescence display device, and a plasma display device. The image display device may be used as, for example, a display, a head-up display, a head-mounted display, etc. The image display device of the present invention may be used in combination with a configuration commonly used in this field. For example, the image display device of the present invention may be combined with a protective film, a depolarizing film, an optical compensation film, etc.

[0117] As shown in Figures 1 and 7, the image display device of the present invention includes a viewing angle switching system and a display panel. Examples of the display panel include a display panel using a liquid crystal display element, an electroluminescent display element, or a plasma display element. When a liquid crystal display element is used as the display element, it may be equipped with a backlight, or it may be a transmissive liquid crystal display element without a backlight. Examples of the electroluminescent display element include an organic electroluminescent (organic EL) display element, an inorganic electroluminescent (inorganic EL) display element, and a light-emitting diode display element, with an organic EL display element or a light-emitting diode display element being preferred.

[0118] As described above, the image display device of the present invention can switch between a privacy mode and a share mode when viewed from an oblique direction at a predetermined azimuth angle. Furthermore, the image display device of the present invention has excellent light-blocking properties and transparency. Due to the above characteristics, the image display device of the present invention can be used as an image display device that can change visibility from an oblique direction at a predetermined azimuth angle. For example, when the image display device of the present invention is applied to an in-vehicle display, by setting the predetermined azimuth angle to the driver's side, it is possible to switch whether or not an image displayed on the display panel is visible when viewed from the driver's side. It is also preferable that the above switching be controlled based on the driving state of the vehicle. The image display device can also be preferably applied to image display devices for mobile applications (e.g., laptop PCs, smartphones, tablet devices, portable game consoles, etc.).

[0119] The present invention will be described in more detail below with reference to examples. The materials, amounts used, ratios, treatment details, treatment procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the examples shown below.

[0120] Example 1 [Fabrication of Viewing Angle Control System A1] The viewing angle control system A1 was fabricated in the following manner.

[0121] (Formation of Alignment Film Layer) The following composition for forming an alignment film 1 was applied to the surface of a commercially available cellulose acylate film (manufactured by Fujifilm Corporation, product name Fujitac TG60UL) using a wire bar. The support on which the coating film was formed was dried with hot air at 140°C for 120 seconds to form an alignment film AL1, thereby obtaining an alignment film-coated cellulose acylate film 1. The thickness of the alignment film AL1 was 1 μm.

[0122] ------------------------------------------------------------------ Composition 1 for forming alignment film -------------------------------------------------- Polymer PA-1 (described below) 100.00 parts by mass Acid generator PAG-1 (described below) 8.25 parts by mass Stabilizer DIPEA (described below) 0.6 parts by mass Butyl acetate 1001.42 parts by mass Methyl ethyl ketone 250.36 parts by mass

[0123] Polymer PA-1 (wherein the numerical value for each repeating unit represents the content (% by mass) of each repeating unit relative to all repeating units)

[0124] Acid generator PAG-1

[0125] Stabilizer DIPEA

[0126] (Formation of Optically Absorbent Anisotropic Layer) The following composition P1 for forming an optically absorbent anisotropic layer was continuously applied onto the obtained cellulose acylate film 1 with an alignment layer using a wire bar, heated at 120°C for 60 seconds, and then cooled to room temperature (23°C). Next, the composition was heated at 80°C for 60 seconds and cooled again to room temperature. Thereafter, an LED lamp (center wavelength 365 nm) was used to illuminate the film from the normal direction to the film at an illuminance of 200 mW / cm. ２ The optically absorptive anisotropic layer was formed on the alignment film AL1 by irradiating the film for 2 seconds under the irradiation conditions of 1. The thickness of the optically absorptive anisotropic layer was 4.5 μm.

[0127] 0.17 parts by mass of dichroic substance D-2 below; 1.13 parts by mass of dichroic substance D-3 below; 8.67 parts by mass of polymer liquid crystal compound P-1 below; 1.97 parts by mass of liquid crystal compound L-1 below; 0.20 parts by mass of IRGACURE OXE-02 (manufactured by BASF); 0.16 parts by mass of alignment agent E-1 below; 0.16 parts by mass of alignment agent E-2 below; 0.007 parts by mass of surfactant F-1 below; 78.17 parts by mass of cyclopentanone; 8.69 parts by mass of benzyl alcohol ----------------------------------------------------------------------------------

[0128] Dichroic substance D-1

[0129] Dichroic substance D-2

[0130] Dichroic substance D-3

[0131] Polymer liquid crystal compound P-1 (polymerization average molecular weight 21,000)

[0132] Liquid crystal compound L-1 [a mixture of the following liquid crystal compounds (RA), (RB) and (RC) in a mass ratio of 84:14:2]

[0133] Orientation agent E-1

[0134] Orientation agent E-2

[0135] Surfactant F-1 (In the following formula, TMS represents a trimethylsilyl group.)

[0136] (Formation of Protective Layer B1) The following protective layer-forming composition B1 was continuously applied to the obtained optically absorptive anisotropic layer using a wire bar to form a coating film. The support on which the coating film was formed was then dried with hot air at 60°C for 60 seconds and then with hot air at 100°C for 120 seconds to form a protective layer B1, thereby producing an optically absorptive anisotropic film having an optically absorptive anisotropic layer. The thickness of the protective layer was 0.5 μm.

[0137] -------------------------------------------------- Protective layer forming composition B1 -------------------------------------------------- 3.80 parts by mass of modified polyvinyl alcohol PVA-1 shown below 0.20 parts by mass IRGACURE 2959 70 parts by mass Water 30 parts by mass Methanol --------------------------------------------------

[0138] Modified polyvinyl alcohol PVA-1

[0139] The azimuthal angle and polar angle of the central transmittance axis of the fabricated optically absorbing anisotropic layer were determined by the following procedure. Using an AxoScan OPMF-2 (manufactured by Axometrics), the transmittance was measured while changing the azimuthal angle and polar angle at which light was incident on the optically absorbing anisotropic layer, as described above, to determine the direction of the central transmittance axis of the optically absorbing anisotropic layer. The angle between the central transmittance axis of the optically absorbing anisotropic layer and the normal to the optically absorbing anisotropic layer was 0°.

[0140] [Fabrication of TN-Type Liquid Crystal Cell 1] Two glass substrates with ITO electrodes were coated with a horizontally aligned polyimide alignment film and dried at high temperature to form the alignment film. The substrates were then rubbed to form a TN-type liquid crystal cell. Specifically, the rubbing treatment was performed to achieve a 190° twisted alignment from one glass substrate toward the other. Next, a thermosetting sealant was applied to one of the two substrates, and bead spacers (5 μm in diameter) were applied to the other. The two substrates were then bonded together, vacuum-packed, and heat-treated to form an empty liquid crystal cell. A liquid crystal compound (MLC-9100 manufactured by Merck) with positive dielectric anisotropy, refractive index anisotropy (birefringence) Δn = 0.0854 (589 nm, 20°C), and Δε = approximately +8.5 was injected into the empty cell using a vacuum liquid crystal injector. TN-type liquid crystal cell 1 with a liquid crystal layer Δnd of 620 nm was then fabricated by sealing. Furthermore, since the inner surfaces of the upper and lower glass substrates were subjected to a rubbing treatment, the liquid crystal layer was twisted and aligned at a twist angle of 190° between the upper and lower glass substrates when no voltage was applied, and the liquid crystal compound was aligned vertically when a voltage was applied, thereby obtaining a TN-type liquid crystal cell 1. Note that by adjusting the spacer diameter, the value of Δnd of the liquid crystal layer in the TN-type liquid crystal cell can be adjusted.

[0141] [Preparation of Polarizing Plate] A polarizing plate having a polarizer thickness of 8 μm and one surface of the polarizer (other optically absorptive anisotropic layer) exposed was prepared in the same manner as in the preparation of polarizing plate 02 with a one-side protective film described in WO 2015 / 166991.

[0142] [Preparation of viewing angle control system A1] The polarizing plate was attached to one surface of the TN-type liquid crystal cell 1 using a pressure-sensitive adhesive layer (Opteria (registered trademark) NCF-D692 (film thickness: 15 μm, manufactured by Lintec Corporation)) so that the polarizer side of the polarizing plate faced the TN-type liquid crystal cell 1. The attachment was performed so that the angle formed between the in-plane slow axis of the surface of the liquid crystal layer on the polarizer side in the TN-type liquid crystal cell 1 and the absorption axis of the polarizer was 5°, and the angle formed between the in-plane slow axis of the surface of the liquid crystal layer on the light absorption anisotropic layer side in the TN-type liquid crystal cell 1 and the absorption axis of the polarizer was also 5°.

[0143] For the laminate of the TN-type liquid crystal cell 1 and the polarizer thus prepared, the intensities of the S-polarized component and the P-polarized component in the first light propagation direction and the second light propagation direction were measured using a spectrometer equipped with a polarizing plate. The method for measuring the intensities of the S-polarized component and the P-polarized component was as described above.

[0144] After the above measurements were carried out, the optically absorptive anisotropic film prepared above was attached to the surface of the TN-type liquid crystal cell 1 opposite to the surface to which the polarizing plate was attached, using an adhesive layer (Opteria (registered trademark) NCF-D692 (film thickness: 15 μm, manufactured by Lintec Corporation)) so that the support surface side of the optically absorptive anisotropic film faced the TN-type liquid crystal cell 1, thereby producing a viewing angle control system A1.

[0145] [Fabrication of Image Display Device A1] Cosmoshine (registered trademark) Super Birefringent Type (SRF, manufactured by Toyobo Co., Ltd., corresponding to a depolarizing film) was attached to the display screen of a dynabook (manufactured by Toshiba Corporation), a notebook computer equipped with a liquid crystal display device, using an adhesive layer (Opteria (registered trademark) NCF-D692 (film thickness: 15 μm, manufactured by Lintec Corporation)). Next, the viewing angle control system A1 prepared above was placed on the depolarizing film to fabricate an image display device A1 with a viewing angle control function. It was confirmed that the viewing angle of the fabricated image display device A1 could be switched between omnidirectional transmission (share mode) and left-right light blocking (privacy mode) by turning the voltage of the TN-type liquid crystal cell 1 on and off. Note that the image display device A1 was obtained by aligning the absorption axis direction of the polarizer of the viewing angle control system A1 with the vertical direction of the liquid crystal display device.

[0146] Example 2 [Preparation of TN-type liquid crystal cell 2] TN-type liquid crystal cell 2 was prepared in the same manner as TN-type liquid crystal cell 1 in Example 1, except that Δnd was adjusted to 675 nm.

[0147] [Fabrication of Image Display Device A2] Image display device A2 was fabricated in the same manner as image display device A1, except that in the fabrication of image display device A1 of Example 1, the TN-type liquid crystal cell 1 was changed to TN-type liquid crystal cell 2 to obtain viewing angle control system A2, and viewing angle control system A2 was used instead of viewing angle control system A1. It was confirmed that image display device A2 was also capable of switching between share mode and privacy mode.

[0148] Example 3 [Preparation of TN-type liquid crystal cell 3] TN-type liquid crystal cell 3 was prepared in the same manner as TN-type liquid crystal cell 1 in Example 1, except that the Δnd of the liquid crystal layer was adjusted to 550 nm.

[0149] [Fabrication of Image Display Device A3] Image display device A3 was fabricated in the same manner as image display device A1, except that in the fabrication of image display device A1 of Example 1, TN-type liquid crystal cell 1 was changed to TN-type liquid crystal cell 3 to obtain viewing angle control system A3, and viewing angle control system A3 was used instead of viewing angle control system A1. It was confirmed that image display device A3 was also capable of switching between share mode and privacy mode.

[0150] Example 4 [Preparation of TN-type liquid crystal cell 4] TN-type liquid crystal cell 4 was prepared in the same manner as TN-type liquid crystal cell 1 in Example 1, except that the Δnd of the liquid crystal layer was adjusted to 625 nm and the twist angle to 220°.

[0151] [Preparation of viewing angle control system A4] Viewing angle control system A4 was prepared in the same manner as viewing angle control system A1 in Example 1, except that in the preparation of viewing angle control system A1 in Example 1, the angle formed between the in-plane slow axis of the surface of the liquid crystal layer on the polarizer side in the TN-type liquid crystal cell 4 and the absorption axis of the polarizer was 20°, and the angle formed between the in-plane slow axis of the surface of the liquid crystal layer on the optically absorptive anisotropic layer side in the TN-type liquid crystal cell 4 and the absorption axis of the polarizer was 20°.

[0152] [Fabrication of image display device A4] Image display device A4 was fabricated in the same manner as image display device A1 in Example 1, except that viewing angle control system A1 was changed to viewing angle control system A4. It was confirmed that image display device A4 was also capable of switching between share mode and privacy mode.

[0153] Example 5 [Preparation of TN-type liquid crystal cell 5] TN-type liquid crystal cell 5 was prepared in the same manner as TN-type liquid crystal cell 1 in Example 1, except that the Δnd of the liquid crystal layer was adjusted to 600 nm and the twist angle to 150°.

[0154] [Preparation of viewing angle control system A5] A viewing angle control system A5 was prepared in the same manner as the viewing angle control system A1 of Example 1, except that in the preparation of the viewing angle control system A1 of Example 1, the angle formed between the in-plane slow axis of the surface of the liquid crystal layer on the polarizer side in the TN-type liquid crystal cell 5 and the absorption axis of the polarizer was 15°, and the angle formed between the in-plane slow axis of the surface of the liquid crystal layer on the optically absorptive anisotropic layer side in the TN-type liquid crystal cell 5 and the absorption axis of the polarizer was 15°.

[0155] [Fabrication of Image Display Device A5] Image display device A5 was fabricated in the same manner as image display device A1 in Example 1, except that viewing angle control system A1 was changed to viewing angle control system A5. It was confirmed that image display device A5 was also capable of switching between share mode and privacy mode.

[0156] Comparative Example 1 [Preparation of TN-type liquid crystal cell 6] TN-type liquid crystal cell 6 was prepared in the same manner as TN-type liquid crystal cell 1 in Example 1, except that the Δnd of the liquid crystal layer was adjusted to 450 nm and the twist angle to 90°.

[0157] [Preparation of viewing angle control system B1] In preparation of the viewing angle control system A1 of Example 1, the viewing angle control system B1 was prepared in the same manner as the viewing angle control system A1, except that in the preparation of the viewing angle control system A1 of Example 1, the angle formed between the in-plane slow axis of the surface of the liquid crystal layer in the TN type liquid crystal cell 6 facing the polarizer and the absorption axis of the polarizer was 0°, and the angle formed between the in-plane slow axis of the surface of the liquid crystal layer in the TN type liquid crystal cell 6 facing the light absorption anisotropic layer and the absorption axis of the polarizer was 90°.

[0158] [Fabrication of image display device B1 with viewing angle control function] Image display device B1 was fabricated in the same manner as image display device A1 in Example 1, except that the viewing angle control system A1 was changed to viewing angle control system B1.

[0159] Comparative Example 2 [Preparation of TN-type liquid crystal cell 7] TN-type liquid crystal cell 7 was prepared in the same manner as TN-type liquid crystal cell 1 in Example 1, except that the Δnd of the liquid crystal layer was adjusted to 620 nm and the twist angle to 240°.

[0160] [Preparation of viewing angle control system B2] Viewing angle control system B2 was prepared in the same manner as viewing angle control system A1 in Example 1, except that in the preparation of viewing angle control system A1 in Example 1, the angle formed between the in-plane slow axis of the surface of the liquid crystal layer in the TN-type liquid crystal cell 7 facing the polarizer and the absorption axis of the polarizer was 30°, and the angle formed between the in-plane slow axis of the surface of the liquid crystal layer in the TN-type liquid crystal cell 7 facing the optically absorptive anisotropic layer and the absorption axis of the polarizer was 30°.

[0161] [Fabrication of Image Display Device B2] Image display device B2 was fabricated in the same manner as image display device A1 in Example 1, except that viewing angle control system A1 was changed to viewing angle control system B1.

[0162] Example 6 [Preparation of VA-Type Liquid Crystal Cell 1] A glass substrate with electrodes was immersed in a solution of household neutral detergent diluted with 50 cc of water for 30 seconds and allowed to air dry. A liquid crystal alignment film (JALS-2021-R1, manufactured by JSR Corporation) was formed on a separately cleaned glass substrate, and the formed alignment film was then rubbed. The glass substrate with electrodes and the glass substrate with the alignment film formed on it were assembled into a liquid crystal cell, with the rubbed surface facing inward. The liquid crystal cell was fabricated by dropwise injecting and sealing a liquid crystal material with negative dielectric anisotropy (MLC6608, manufactured by Merck) between the substrates, forming a liquid crystal layer between the substrates with vertical alignment. The gap between the substrates was adjusted to achieve a Δnd of 450 nm at a wavelength of 550 nm. Using the above procedure, a VA-type liquid crystal cell, VA-type liquid crystal cell 1, was obtained. In the VA-type liquid crystal cell 1, the alignment direction of the liquid crystal material (liquid crystal compound) in the liquid crystal layer changed from vertical alignment (0 V) to horizontal alignment (20 V) upon application of a voltage. Furthermore, when a voltage of 3 V was applied to the liquid crystal layer of the VA-type liquid crystal cell 1, the average alignment direction of the liquid crystal compound was analyzed using an AxoScan OPMF-2 (manufactured by Axometrics), and the polar angle (the angle with the thickness direction of the VA-type liquid crystal cell 1) was 35°.

[0163] [Preparation of Viewing Angle Control System A6] The polarizing plate was bonded to one surface of the VA-type liquid crystal cell 1 prepared above using a pressure-sensitive adhesive layer (Opteria (registered trademark) NCF-D692 (film thickness: 15 μm, manufactured by Lintec Corporation)) so that the polarizer side of the polarizing plate faced the VA-type liquid crystal cell 1. The bonding was performed so that, when a voltage was applied to the VA-type liquid crystal cell 1, the angle between the average alignment direction of the liquid crystal in the liquid crystal layer in the liquid crystal cell and the absorption axis of the polarizer was 0°. Next, a newly prepared VA-type liquid crystal cell 1 was superimposed on the surface of the VA-type liquid crystal cell 1 to which the polarizing plate had been bonded, opposite to the surface to which the polarizing plate had been bonded. The VA-type liquid crystal cell 1 thus bonded was positioned so that, when a voltage was applied to the superimposed VA-type liquid crystal cell 1, the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer in the liquid crystal cell and the absorption axis of the polarizer was 0°. Furthermore, when the voltage of the two VA-type liquid crystal cells 1 was set to 3 V, the two VA-type liquid crystal cells were stacked so that the angle formed between the in-plane direction of the average alignment direction of the liquid crystal compound in the liquid crystal layer of one VA-type liquid crystal cell 1 and the in-plane direction of the average alignment direction of the liquid crystal compound in the liquid crystal layer of the other VA-type liquid crystal cell 1 was 180°. Next, the intensities of the S-polarized component and the P-polarized component were measured in the same manner as described in Example 1.

[0164] Next, the optically absorbing anisotropic film prepared above was attached to the surface of the VA-type liquid crystal cell to which no polarizing plate was attached, opposite to the polarizing plate side. The attachment was performed using a pressure-sensitive adhesive layer (Opteria (registered trademark) NCF-D692 (film thickness: 15 μm, manufactured by Lintec Corporation)) so that the support side of the optically absorbing anisotropic film faced the VA-type liquid crystal cell 1. By the above procedure, a viewing angle control system A6 was prepared.

[0165] [Fabrication of Image Display Device A6] Image display device A6 was fabricated in the same manner as image display device A1 in Example 1, except that viewing angle control system A1 was changed to viewing angle control system A6. It was confirmed that image display device A6 was also capable of switching between share mode and privacy mode.

[0166] Example 7 An image display device A6 similar to the image display device A6 of Example 6 was obtained.

[0167] Comparative Example 3 [Preparation of viewing angle control system B3] In the preparation of the image display device A6 of Example 6, after laminating a polarizing plate to the VA-type liquid-crystal cell 1, a new VA-type liquid-crystal cell 1 was not prepared, and the above-prepared optically absorbing anisotropic film was laminated to the surface of the VA-type liquid-crystal cell 1 opposite to the surface to which the polarizing plate was laminated, thereby obtaining a viewing angle control system B1. In the lamination of the optically absorbing anisotropic film, the optically absorbing anisotropic film was laminated using a pressure-sensitive adhesive layer (Opteria (registered trademark) NCF-D692 (film thickness: 15 μm, manufactured by Lintec Corporation)) so that the support side of the optically absorbing anisotropic film faced the VA-type liquid-crystal cell 1.

[0168] [Fabrication of image display device B3 with viewing angle control function] Image display device B3 was fabricated in the same manner as image display device A1 in Example 1, except that the viewing angle control system A1 was changed to viewing angle control system B3.

[0169] Comparative Example 4 [Preparation of VA-type liquid crystal cell 2] VA-type liquid crystal cell 2 was prepared in the same manner as VA-type liquid crystal cell 1 in Example 6, except that the Δnd of the liquid crystal layer was adjusted to 140 nm.

[0170] [Preparation of viewing angle control system B4] Viewing angle control system B4 was prepared in the same manner as viewing angle control system B3 of Comparative Example 3, except that when the voltage to VA-type liquid crystal cell 2 was turned on, the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer in VA-type liquid crystal cell 2 and the absorption axis of the polarizer was 45°.

[0171] [Fabrication of Image Display Device B4] Image display device B4 was fabricated in the same manner as image display device A1 in Example 1, except that viewing angle control system A1 was changed to viewing angle control system B4.

[0172] <Evaluation of Viewing Angle Control System> Each of the manufactured image display devices was observed, and the viewing angle control system included in each image display device was evaluated. Note that, in the modes shown in Table 1 below, the share mode refers to the mode when the voltage applied to the liquid crystal layer of the liquid crystal cell is 0 V, and the privacy mode refers to the mode when the voltage applied to the liquid crystal layer of the liquid crystal cell is 5 V. Furthermore, in the modes shown in Table 2 below, the share mode refers to the mode when the voltage applied to the liquid crystal layer of each liquid crystal cell is 3 V, and the privacy mode refers to the mode when the voltage applied to the liquid crystal layer of each liquid crystal cell is 0 V or 20 V.

[0173] [Observation of brightness in share mode] A: When viewed from all directions at a polar angle of 45°, the image can be seen in all directions and the brightness of the image is not noticeable. B: When viewed from all directions at a polar angle of 45°, the image can be seen in all directions, but the image appears a little dark in all directions. C: When viewed from all directions at a polar angle of 45°, the image is dark and difficult to see in some directions.

[0174] [Observation of light blocking properties in privacy mode] A: When viewed from a polar angle of 45° in the horizontal direction, the image is not recognizable, and when viewed from diagonally above, the image is also not recognizable. B: When viewed from a polar angle of 45° in the horizontal direction, the image is not recognizable, but when viewed from a diagonal polar angle of 45°, the image is slightly recognizable.

[0175] <Results> The configuration of each image display device and the evaluation results of the viewing angle control system included in each image evaluation device are shown in Tables 1 and 2. In Tables 1 and 2, the "horizontal direction" refers to the measurement results of the intensity of each polarized component when light is incident from a direction with an azimuth angle perpendicular to the absorption axis of the polarizer and a polar angle of 45°. The "vertical direction" refers to the measurement results of the intensity of each polarized component when light is incident from a direction with an azimuth angle parallel to the absorption axis of the polarizer and a polar angle of 45°. In Table 2, the "liquid crystal compound-absorption axis angle" refers to the angle between the absorption axis of the polarizer and the azimuth angle in the in-plane direction of the average alignment direction of the liquid crystal compounds in the liquid crystal layer when a voltage is applied to the liquid crystal cell. In Table 2, the "angle between the azimuth angles of the liquid crystal compounds in the second state" refers to the angle between the in-plane direction of the average alignment direction of each liquid crystal compound when a voltage of 3 V is applied to the liquid crystal layers of the first and second liquid crystal cells. In Table 1, "State 1" refers to the first state described in the first embodiment of the viewing angle switching system, which is achieved by applying a voltage to each TN-type liquid crystal cell. Furthermore, applying a voltage to the liquid crystal layer of each TN-type liquid crystal cell results in the third state described in the second embodiment. In Table 1, "State 2" refers to the second state described in the first embodiment of the viewing angle switching system, which is achieved by not applying a voltage to TN-type liquid crystal cells 1 to 5. Furthermore, not applying a voltage to TN-type liquid crystal cells 1 to 5 results in the fourth state described in the second embodiment. In Table 2, "State 1" refers to the first state described in the first embodiment of the viewing angle switching system, which is achieved by applying a voltage of 20 V to the liquid crystal layer of each VA-type liquid crystal cell or by not applying a voltage to each VA-type liquid crystal cell. Furthermore, applying a voltage of 20 V to the liquid crystal layer of each VA-type liquid crystal cell or by not applying a voltage to each VA-type liquid crystal cell results in the fifth state described in the third embodiment. In Table 1, "second state" refers to the second state described in the first embodiment of the viewing angle switching system, which is achieved by applying a voltage of 3 V to the liquid crystal layer of the VA-type liquid crystal cell 1. Furthermore, applying a voltage of 3 V to the liquid crystal layer of the VA-type liquid crystal cell 1 results in the sixth state described in the third embodiment.

[0176]

[0177]

[0178] The results shown in Table 1 confirm that in the viewing angle switching systems of each Example, when it is possible to switch between the third state and the fourth state by applying a voltage to the liquid crystal layer of the TN-type liquid crystal cell, the system, when applied to an image display device, exhibits excellent brightness in a predetermined oblique direction in the share mode and excellent light-blocking properties in a predetermined oblique direction in the privacy mode. On the other hand, in the viewing angle switching systems of each Comparative Example, when the requirements for the fourth state are not met, the system exhibits inferior brightness, particularly in the share mode. Furthermore, the results shown in Table 2 confirm that in the viewing angle switching systems of each Example, when it is possible to switch between the fifth state and the sixth state, the system, when applied to an image display device, exhibits excellent brightness in a predetermined oblique direction in the share mode and excellent light-blocking properties in a predetermined oblique direction in the privacy mode. On the other hand, in the viewing angle switching systems of each Comparative Example, when the requirements for the sixth state are not met, the system exhibits inferior brightness, particularly in the share mode. A comparison between Example 6 and Example 7 confirms that when the first liquid crystal cell is in State 2 and the second liquid crystal cell is in State 1, the system exhibits superior light-blocking properties in the privacy mode.

[0179] REFERENCE SIGNS LIST 10a, 10b Viewing angle switching system 12 Light absorption anisotropic layer 14a Liquid crystal cell 142 First liquid crystal cell 144 Second liquid crystal cell 16 Polarizer 18 Optical compensation layer 20 Display panel 30, 32 Laminated body 100a, 100b Image display device

Claims

1. A viewing angle switching system having, in this order, an optically absorptive anisotropic layer, a polarization conversion unit including one or more liquid crystal cells, and a polarizer, wherein the angle between the transmittance central axis of the optically absorptive anisotropic layer and the normal to the optically absorptive anisotropic layer is 0 to 45°, and the viewing angle switching system is switchable between the following first and second states by applying a voltage to a liquid crystal layer included in the liquid crystal cell. First state: A laminate obtained by peeling off the optically absorptive anisotropic layer from the viewing angle switching system is used as a measurement sample, and when light is incident from the polarizer side of the measurement sample, the intensity of the S-polarized component contained in the light that has passed through the polarization conversion unit when the light is incident at an azimuth angle parallel to the absorption axis of the polarizer and at a polar angle of 45° is 55% or more, and the intensity of the P-polarized component contained in the light that has passed through the polarization conversion unit when the light is incident at an azimuth angle perpendicular to the absorption axis of the polarizer and at a polar angle of 45° is 55% or more. Second state: When light is incident from the polarizer side of the measurement sample, the intensity of the S-polarized component contained in the light that has passed through the polarization conversion unit is 55% or more when the light is incident at an azimuth angle parallel to the absorption axis of the polarizer and at a polar angle of 45°, and the intensity of the S-polarized component contained in the light that has passed through the polarization conversion unit is 55% or more when the light is incident at an azimuth angle perpendicular to the absorption axis of the polarizer and at a polar angle of 45°.

2. The viewing angle switching system according to claim 1, wherein the liquid crystal cell included in the polarization conversion unit is a twisted nematic liquid crystal cell, wherein Δnd of the liquid crystal layer in the liquid crystal cell is 500 to 700 nm, and wherein the liquid crystal cell is switchable between the following third and fourth states by a voltage applied to the liquid crystal layer, wherein the first state is realized by the third state, and the second state is realized by the fourth state. Third state: A state in which the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer in the liquid crystal cell and the thickness direction of the liquid crystal cell is within the range of 0±10°. Fourth state: A state in which the twist angle of the liquid crystal compound in the liquid crystal layer in the liquid crystal cell is 140 to 220°, the angle formed by the in-plane slow axis of the surface of the liquid crystal layer in the liquid crystal cell facing the polarizer and the absorption axis of the polarizer is 20° or less, and the angle formed by the in-plane slow axis of the surface of the liquid crystal layer in the liquid crystal cell facing the optically absorptive anisotropic layer and the absorption axis of the polarizer is 20° or less.

3. The viewing angle switching system of claim 1, wherein the polarization conversion unit includes a first liquid crystal cell and a second liquid crystal cell, wherein the first liquid crystal cell and the second liquid crystal cell are both vertical alignment type liquid crystal cells or electric field controlled birefringence type liquid crystal cells, and wherein the viewing angle switching system can be switched between the following fifth and sixth states by voltages applied to the liquid crystal layers of the first liquid crystal cell and the second liquid crystal cell, wherein the first state is realized by the fifth state, and the second state is realized by the sixth state. Fifth state: A state selected from the group consisting of state 1 in which the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer in the first liquid crystal cell and the absorption axis of the polarizer is within a range of 0±10°, and state 2 in which the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer in the liquid crystal cell and the thickness direction of the liquid crystal cell is within a range of 0±10°. Sixth state: The angle formed by the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the first liquid crystal cell and the second liquid crystal cell and the thickness direction of the first liquid crystal cell and the second liquid crystal cell is 15 to 75°, respectively; the angle formed by the in-plane direction of the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the first liquid crystal cell and the absorption axis of the polarizer is within a range of 0±10°; the angle formed by the in-plane direction of the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the second liquid crystal cell and the absorption axis of the polarizer is within a range of 0±10°; and the angle formed by the in-plane direction orientation of the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the first liquid crystal cell and the in-plane orientation orientation of the average alignment direction of the liquid crystal compounds in the liquid crystal layer of the second liquid crystal cell is within a range of 180°±10°.

4. A viewing angle switching system having, in this order, an optically absorptive anisotropic layer, a liquid crystal cell, and a polarizer, wherein the angle between the central axis of transmittance of the optically absorptive anisotropic layer and a normal to the optically absorptive anisotropic layer is 0 to 45°, the liquid crystal cell is a twisted nematic liquid crystal cell, and Δnd of the liquid crystal layer in the liquid crystal cell is 500 to 700 nm, and the viewing angle switching system is switchable between the following third state and fourth state by a voltage applied to the liquid crystal layer in the liquid crystal cell. Third state: a state in which the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer in the liquid crystal cell and the thickness direction of the liquid crystal cell is within a range of 0±10°. Fourth state: a state in which the twist angle of the liquid crystal compound in the liquid crystal layer in the liquid crystal cell is 140 to 220°, the angle between the in-plane slow axis of the surface of the liquid crystal layer on the polarizer side in the liquid crystal cell and the absorption axis of the polarizer is 20° or less, and the angle between the in-plane slow axis of the surface of the liquid crystal layer on the optically absorptive anisotropic layer side in the liquid crystal cell and the absorption axis of the polarizer is 20° or less.

5. A viewing angle switching system having, in this order, an optically absorptive anisotropic layer, a first liquid crystal cell, a second liquid crystal cell, and a polarizer, wherein the angle between the transmittance central axis of the optically absorptive anisotropic layer and a normal to the optically absorptive anisotropic layer is 0 to 45°, and both the first liquid crystal cell and the second liquid crystal cell are vertical alignment type liquid crystal cells or electric field controlled birefringence type liquid crystal cells, and the viewing angle switching system is switchable between the following fifth and sixth states by voltages applied to the liquid crystal layers of the first liquid crystal cell and the second liquid crystal cell. Fifth state: A state selected from the group consisting of state 1 in which the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer in the first liquid crystal cell and the absorption axis of the polarizer is within a range of 0±10°, and state 2 in which the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer in the liquid crystal cell and the thickness direction of the liquid crystal cell is within a range of 0±10°. Sixth state: The angle formed by the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the first liquid crystal cell and the second liquid crystal cell and the thickness direction of the first liquid crystal cell and the second liquid crystal cell is 15 to 75°, respectively; the angle formed by the in-plane direction of the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the first liquid crystal cell and the absorption axis of the polarizer is within a range of 0±10°; the angle formed by the in-plane direction of the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the second liquid crystal cell and the absorption axis of the polarizer is within a range of 0±10°; and the angle formed by the in-plane direction orientation of the average alignment direction of the liquid crystal compounds in the liquid crystal layer in the first liquid crystal cell and the in-plane orientation orientation of the average alignment direction of the liquid crystal compounds in the liquid crystal layer of the second liquid crystal cell is within a range of 180°±10°.

6. The viewing angle switching system of claim 5, wherein, when the liquid crystal cell is in the fifth state, the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer in the liquid crystal cell on the light absorption anisotropic layer side and the absorption axis direction of the polarizer is within the range of 0±10°, and the angle between the average alignment direction of the liquid crystal compound in the liquid crystal layer in the liquid crystal cell on the polarizer side and the thickness direction of the liquid crystal cell is within the range of 0±10°.

7. The viewing angle switching system according to any one of claims 1 to 6, wherein the light absorption anisotropic layer contains a liquid crystal compound and a dichroic dye.

8. An image display device comprising the viewing angle switching system according to any one of claims 1 to 6.

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