Image display device

Abstract

The present invention addresses the problem of providing an image display device which a viewer can watch even when the viewer wears polarized sunglasses that cut linearly polarized light, and in which the light emitted from a display and reflected from an object can be sensed by an in-cell optical sensor. The above problem is solved by an image display device comprising an image display unit, an optical sensor that detects visible light, a polarizer, and a depolarization film. The optical sensor, the polarizer, and the depolarization film are disposed in this order, and the depolarization film is disposed closer to the viewing side than the polarizer is.

Description

Image display device

[0001] This invention relates to an image display device.

[0002] Conventionally, phase difference films such as quarter-wave plates have been used to impart optical functions to image display devices. For example, when an observer wearing polarized sunglasses views an image displayed on an image display device that uses a polarizing plate on the light-emitting side, the screen appears completely black, which is a problem (blackout). In response to this, it is known that by installing a quarter-wave plate on the light-emitting side of an image display device such that the angle between the absorption axis of the polarizer of the polarizing plate of the image display device and the slow axis of the quarter-wave plate is approximately 45 degrees, the emitted light is made approximately circularly polarized, thereby preventing blackout (Patent Document 1).

[0003] Japanese Patent Publication No. 2019-174636

[0004] Polarized sunglasses absorb one type of linearly polarized light and transmit the other type of linearly polarized light whose polarization direction is perpendicular to it. Therefore, blackout can be suppressed by making the light emitted from an image display device circularly polarized. On the other hand, it has been found that when a quarter-wave plate is installed on the light emission side of an in-cell type image display device that has a light sensor within the image display area of ​​the image display device for fingerprint detection, etc., and the emitted light is made approximately circularly polarized, the reflected light from objects such as fingerprints cannot be detected by the light sensor.

[0005] Therefore, the present invention aims to provide an image display device that can be viewed even when wearing polarized sunglasses that cut linearly polarized light, and that can sense reflected light from objects emitted from the display using an in-cell optical sensor.

[0006] The inventors of the present invention have conducted extensive research on the above-mentioned problems and have found that the above problems can be achieved with the following configuration.

[0007] [1] An image display device comprising an image display unit, a light sensor for detecting visible light, a polarizer, and a depolarization film, wherein the light sensor, polarizer, and depolarization film are arranged in this order, and the depolarization film is positioned on the viewing side of the polarizer. [2] The image display device according to [1], wherein the depolarization film has a phase difference layer A, and the in-plane retardation of the phase difference layer A at a wavelength of 550 nm is from 3,000 nm to 100,000 nm. [3] The image display device according to [1], wherein the depolarization film has a phase difference layer B, and the phase difference layer B has a slow axis distribution or a phase difference distribution in the plane. [4] The image display device according to [1], wherein the depolarization film has a phase difference layer A and a phase difference layer B, and the in-plane retardation of the phase difference layer A at a wavelength of 550 nm is from 3,000 nm to 100,000 nm, and the phase difference layer B has a slow axis orientation distribution or a phase difference distribution in the plane. [5] The image display device according to [3] or [4], wherein the phase difference layer B is a layer formed using a liquid crystal compound. [6] The image display device according to any one of [3] to [5], wherein the slow axis distribution is a random slow axis distribution. [7] The image display device according to [6], wherein when the domain size of the phase difference layer B is defined as the autocorrelation length × 3, the domain size is 32 μm or less. [8] The image display device according to any one of [1] to [7], wherein the image display unit is an organic EL cell. [9] The image display device according to [8], wherein the light sensor is located between the pixels of the organic EL cell.

[10] The image display device according to [9], wherein the light sensor is an organic photodetector.

[0008] According to the present invention, it is possible to provide an image display device that can be viewed even when wearing polarized sunglasses that cut linearly polarized light, and that can sense reflected light from an object using an in-cell optical sensor.

[0009] This is a schematic diagram showing an example of the image display device of the present invention. This is a schematic diagram showing an example of the image display device of the present invention, including a phase difference layer A and a phase difference layer B. This is a schematic diagram showing a phase difference layer B, which is an example of the depolarization film of the present invention, as viewed from approximately the direction normal to the surface of the film. This is a schematic diagram showing a phase difference layer B, which is an example of the depolarization film of the present invention, as viewed from a cross-section of the film. This is a schematic diagram showing the case when phase difference layers B are laminated. This is a photograph of the fabricated phase difference layer B taken under crossed nicols using an optical microscope. Figure 7 is a schematic diagram showing an interference exposure method for fabricating a master mold, as an example of a method for fabricating phase difference layer B, namely replica exposure.

[0010] The present invention will now be described in detail. The following descriptions of constituent elements may be based on representative embodiments and specific examples, but the present invention is not limited to such embodiments. In this specification, numerical ranges expressed using "~" mean a range that includes the numbers written before and after "~" as the lower and upper limits.

[0011] In this specification, "orthogonal" does not mean exactly 90°, but rather 90°±10°, preferably 90°±5°. Similarly, "parallel" does not mean exactly 0°, but rather 0°±10°, preferably 0°±5°. Furthermore, "45°" does not mean exactly 45°, but rather 45°±10°, preferably 45°±5°.

[0012] In this specification, the "absorption axis" refers to the polarization direction in which the absorbance is maximum when linearly polarized light is incident on the surface. The "reflection axis" refers to the polarization direction in which the reflectance is maximum when linearly polarized light is incident on the surface. The "transmission axis" refers to the direction perpendicular to the absorption axis or reflection axis in the surface. Furthermore, the "latent axis" refers to the direction in which the refractive index is maximum in the surface. In this specification, unless otherwise specified, the phase difference refers to the in-plane retardation and is denoted as Re(λ). Here, Re(λ) represents the in-plane retardation at wavelength λ, and unless otherwise specified, wavelength λ is 550 nm. The retardation in the thickness direction at wavelength λ is denoted as Rth(λ) in this specification. Unless otherwise specified, wavelength λ is 550 nm. Re(λ) and Rth(λ) can be measured at wavelength λ using an AxoScan OPMF-1 (OptoScience Co., Ltd.). By inputting the average refractive index ((nx + ny + nz) / 3) and film thickness (d (μm)) into AxoScan, the following can be calculated: Re(λ) = R0(λ) Rth(λ) = ((nx + ny) / 2 - nz) × d in the slow phase axis direction (°).

[0013] The image display device of the present invention will be described below.

[0014] The image display device of the present invention comprises an image display unit, a light sensor for detecting visible light, a polarizer, and a depolarizing film, wherein the light sensor, polarizer, and depolarizing film are arranged in this order, and the depolarizing film is positioned on the viewing side of the polarizer.

[0015] The image display device of the present invention displays an image, and also has a light sensor within the image display area of ​​the image display device. For example, when a finger is brought close to the image display area, light from the image display unit is shone onto the finger, and the light sensor detects the reflected light from the finger, thereby acquiring a fingerprint image, which can be used for fingerprint authentication.

[0016] As described in Patent Document 1 above, it has been found that when a quarter-wave plate is installed on the light-emitting side of an image display device, reflected light from objects such as fingerprints cannot be detected by the optical sensor. When the light emitted from the image display unit of an image display device irradiates an object, the light is circularly polarized by passing through the polarizer and the quarter-wave plate. When this circularly polarized light is reflected by the object, the direction of rotation of the circular polarization is reversed. Therefore, when the circularly polarized light reflected from the object passes through the quarter-wave plate towards the optical sensor, it is converted to linear polarization, and this linear polarization is approximately parallel to the absorption axis of the polarizer. Consequently, the linearly polarized light, which is reflected light from the object, is absorbed by the polarizer. It is thought that this is the reason why reflected light from an object cannot be detected by the optical sensor. In contrast, the image display device of the present invention described above has suitability for polarized sunglasses and enables sensing by an optical sensor.

[0017] Figure 1 is a schematic diagram showing an example of the image display device of the present invention. The image display device 100 comprises an image display unit 4, a light sensor 3, a polarizer 2, and a depolarization film 1. The light sensor 3, polarizer 2, and depolarization film 1 are arranged in this order, with the depolarization film 1 positioned on the viewing side of the polarizer 2. The image display unit 4 is positioned on the opposite side of the polarizer 2 from the depolarization film 1. The image display device 100 also has a plurality of light sensors 3. In the illustrated example, the plurality of light sensors 3 are arranged two-dimensionally within the plane of the image display unit 4, spaced apart from each other. The plurality of light sensors 3 arranged within the plane can acquire an image by detecting the light incident on the image display device 100. Since the light sensors 3 detect visible light, they can detect light emitted from the image display unit 4 and reflected by objects, as well as ambient light.

[0018] By positioning the depolarizing film 1 on the viewing side relative to the polarizer 2, the polarized light emitted from the image display unit 4 passes through the polarizer 2 and is then depolarized by the depolarizing film 1, reaching the eye as natural light. As a result, even when viewing this image display device through polarized sunglasses, there is no blackout, allowing the displayed image to be viewed. Furthermore, by positioning the light sensor 3 on the image display unit 4 side relative to the polarizer 2 and the depolarizing film 1 on the viewing side relative to the polarizer 2, when an object such as a finger is brought close to the image display area, the light emitted from the image display unit 4 is first linearly polarized by the polarizer 2 and then depolarized by the depolarizing film 1, so that natural light reaches the object. Since almost all of the natural light is reflected from the object irradiated with natural light, only half is absorbed by the absorption axis of the polarizer when it passes through the depolarizing film 1 and polarizer 2 again. As a result, the remaining half of the reflected light reaches the light sensor 3, enabling object detection. This allows for applications such as fingerprint detection within the image display area.

[0019] The image display device of the present invention may have the same configuration as known image display devices, except that it has a light sensor for detecting visible light, a polarizer, and a depolarizing film. Examples include liquid crystal display devices, organic EL display devices, and LED (light-emitting diode) display devices. Applications of the image display device include smartphones, tablets, notebook PCs, monitors, and televisions.

[0020] Furthermore, the objects detected using the sensor 3 in the image display device 100 of the present invention are not limited to objects near the image display area, such as fingerprints. For example, the sensor 3 may detect ambient light around the image display device 100. The brightness and / or color information of the ambient light detected by the sensor 3 can be used to adjust the brightness and / or color tone of the image displayed by the image display device 100. In this case, it is sufficient to have at least one sensor 3.

[0021] [Image Display Unit] Various known image display methods can be used as the image display unit of the image display device of the present invention. Examples include liquid crystal cells, organic EL (electroluminescent) cells, and LED (Light Emitting Diode) display cells. Organic EL cells are particularly preferred because a light sensor using an organic photodetector can be formed in the same process as the pixel light-emitting unit and placed alongside the pixel light-emitting unit. Here, an organic EL cell is a light-emitting element using an organic material that self-illuminates when a voltage is applied. Organic materials include low molecular weight materials, organic polymers, and combinations thereof. Materials and structures with high luminous efficiency and long lifespan are preferred.

[0022] In an image display unit, it is preferable to have a narrow spectral width for each color of light. Narrowing the spectral width increases the color gamut. Examples of image display units with a narrow spectral width include those using quantum dots and lasers as light sources.

[0023] <Spectrum when displaying white> The image display unit preferably has two or more maximum values ​​in the visible range (visible light wavelength range) when displaying white. Here, the visible range refers to the wavelength range of 380 to 780 nm. The spectrum when displaying white preferably has maximums in at least two wavelength ranges: the red range, the green range, and the blue range. The red range (R) preferably has a maximum at a wavelength of 600 nm or higher. The green range (G) preferably has a maximum between wavelengths of 510 to 570 nm. The blue range (B) preferably has a maximum between wavelengths of 430 to 470 nm. The image display unit preferably uses a light source in which the full width at half maximum of the peaks corresponding to each maximum value is 20 nm or less. Examples of such light sources include quantum dots and lasers as described above. By using an organic EL display device (depolarization film) in an image display device using such a light source, the polarization state of the emitted light can be changed from place to place, so that polarization can be depolarized even for light sources with a narrow spectral width, and blackout can be suppressed.

[0024] [Optical Sensor] An optical sensor refers to a light detection device built into an image display device. Optical sensors detect visible light. This allows them to detect the amount of light in the surrounding environment of the display device and acquire a two-dimensional image (e.g., fingerprint detection). Optical sensors are usually composed of photodetectors such as photodiodes and phototransistors, which convert light into electrical signals. These photodetectors can be made from inorganic semiconductors such as silicon and organic semiconductor materials. Photodetectors made from inorganic semiconductors are generally called photodetectors, and photodetectors made from organic semiconductor materials are generally called organic photodetectors. In particular, with regard to organic semiconductors, it is preferable to place the organic photodetector on the same plane as the organic EL cell, which is the image display unit, from the viewpoint of thinning and simplifying the manufacturing process. For example, in the in-cell method, the optical sensor is directly incorporated as part of the image display device, eliminating the need for additional external components and enabling thinning and integration of the device. Therefore, optical sensors support functions such as automatic brightness adjustment according to ambient light and fingerprint detection, improving the user experience. It is preferable to have the optical sensor between the pixels of the organic EL cell. Furthermore, it is preferable that the light sensor is an organic photodetector.

[0025] The arrangement of the light sensor is not limited to the above. For example, the light sensor may be placed on the back side of the image display unit, that is, on the opposite side from the polarizer. In this case, the image display unit only needs to have a region that transmits light (visible light). The light sensor may also be placed between the image display unit and the polarizer.

[0026] [Polarizer] A polarizer can be any component that has the function of converting natural light in the visible range (unpolarized) into a specific linearly polarized light, for example, an absorption polarizer. There are no particular restrictions on the type of polarizer, and commonly used polarizers can be used, for example, iodine-based polarizers, dye-based polarizers using dichroic dyes, and polyene-based polarizers. Iodine-based polarizers and dye-based polarizers are generally made by adsorbing iodine or a dichroic dye onto polyvinyl alcohol and then stretching it. A protective film may be placed on one or both sides of the polarizer. Furthermore, as described in International Publication No. 2019 / 131943 and Japanese Patent Publication No. 2017-83843, a coated polarizer may be used, which is made by coating a liquid crystal compound and a dichroic organic dye (for example, a dichroic azo dye used in the light-absorbing anisotropic film described in International Publication No. 2017 / 195833) without using polyvinyl alcohol as a binder. In other words, the polarizer may be a polarizer formed using a composition containing a polymerizable liquid crystal compound. This coated polarizer is a technique that utilizes the orientation of the liquid crystal compound to orient the dichroic organic dye. As described in Japanese Patent Publication No. 2012-83734, it is preferable from the viewpoint of increasing the degree of orientation if the polymerizable liquid crystal compound exhibits smectic properties. Alternatively, as described in International Publication No. 2018 / 186503, it is also preferable from the viewpoint of increasing the degree of orientation if the dye is crystallized. International Publication No. 2019 / 131943 describes a preferred polymer liquid crystal structure for increasing the degree of orientation. Polarizers in which dichroic organic dyes are oriented using the orientation properties of liquid crystals without stretching have the following characteristics: they can be made into very thin layers with a thickness of about 0.1 μm to 5 μm, they are resistant to cracking when bent as described in Japanese Patent Application Publication No. 2019-194685, they have little thermal deformation, and they have excellent durability even in polarizers with high transmittance exceeding 50% as described in Japanese Patent No. 6483486. These are just some of the many advantages. Taking advantage of these advantages, they can be used in applications requiring high brightness, small size and light weight, fine optical systems, molding for curved surfaces, and flexible parts. Of course, it is also possible to peel off the support and transfer the polarizer for use.From the viewpoint of power saving, the transmittance of the polarizer should preferably be 40% or more, more preferably 44% or more, and even more preferably 50% or more. The transmittance of the polarizer with luminous efficiency correction is measured using an automatic polarizing film measuring device: VAP-7070 (manufactured by JASCO Corporation). The transmittance with luminous efficiency correction can be measured as follows: A sample (5 cm x 5 cm) is prepared by attaching a polarizer to glass via an adhesive. At this time, a polarizing plate protective film is attached to the polarizer so that it is on the side opposite to the glass (air interface). The glass side of this sample is set facing the light source and measured. The polarizer may also be further modified to form a circular polarizer by laminating a quarter-wave plate. The quarter-wave plate may be formed directly adjacent to the polarizer, or it may be attached with an adhesive and glue. In addition, other optical components with a small in-plane phase difference may be placed between the quarter-wave plate and the polarizer. This can provide the function of a circular polarizer. By positioning a quarter-wave plate between the polarizer and the image display unit, reflected light from the image display unit can be prevented, thereby improving the visibility of the image display device.

[0027] Furthermore, if the display device includes a polarizer, such as when the image display unit is a liquid crystal cell of a liquid crystal display device, the polarizer on the viewing side of the liquid crystal cell may be used as the polarizer in this invention.

[0028] [Depolarizing Film] The depolarizing film has the effect of reducing the degree of polarization of light emitted from the image display device. The depolarizing film may have the characteristic of ideal depolarizing, which depolarizes any polarization state, or it may have the characteristic of depolarizing according to the polarization state when the light emitted from the image display unit passes through the polarizer. The degree of polarization of the light emitted from the image display device is preferably less than 30%, more preferably less than 20%, and most preferably less than 10%. A lower degree of polarization is preferable because it improves the visibility of the image display device when observed while wearing polarized sunglasses, and also improves the detection efficiency of reflected light from objects by the light sensor. The degree of polarization includes the degree of linear polarization for linearly polarized light, the degree of circular polarization for circularly polarized light, and the degree of polarization for all polarizations including linear and circular polarization. In the present invention, a low degree of polarization for all polarizations is preferred.

[0029] Various films with different depolarizing properties can be used as the depolarizing film. Principles for achieving a depolarized state include, for example, the wavelength scrambling method, the spatial scrambling method, and the time scrambling method, all of which are applicable to the present invention. The wavelength scrambling method achieves a depolarized state by increasing the change in polarization state with respect to wavelength changes. An example of a means to achieve wavelength scrambling is to use a high-reducation film with a retardation of 3000 nm or more at a wavelength of 550 nm. The spatial scrambling method achieves a depolarized state by providing a polarization state distribution within a plane. A means to achieve spatial scrambling is to provide a phase difference layer and distribute at least one of the slow axis orientation and retardation (phase difference) value of the phase difference layer within the plane. The time scrambling method achieves a polarized state by rapidly switching the polarization state over time. One method for achieving time scrambling is to rapidly switch the orientation state of the liquid crystal using a liquid crystal cell consisting of a transparent electrode and a liquid crystal material, thereby changing at least one of the retardation (phase difference) value and the slow axis orientation. Among these, the spatial scrambling method is more preferable because it can efficiently obtain a lower degree of polarization, and the combination of the wavelength scrambling method and the spatial scrambling method is even more preferable. Furthermore, since the spatial scrambling method also has an in-plane distribution of scattering characteristics, a phenomenon called glare occurs where pixels appear distorted and visible. However, by using the spatial scrambling method and the wavelength scrambling method in combination, the change in the in-plane distribution of scattering characteristics can be made finer, thereby improving glare. Phase difference layer A in this invention utilizes the wavelength scrambling method. Phase difference layer B in this invention utilizes the spatial scrambling method. Therefore, it is preferable to use phase difference layer B, and it is more preferable to use both phase difference layer A and phase difference layer B. Moreover, when using both phase difference layer A and phase difference layer B, it is most preferable to have phase difference layer A on the polarizer side.

[0030] Figure 2 is a schematic diagram showing another example of the image display device of the present invention, and shows an example in which the depolarization film 1 includes a phase difference layer A and a phase difference layer B. Preferably, the depolarization film 1 includes a phase difference layer A5 and a phase difference layer B6, with the phase difference layer A5 being on the polarizer 2 side. Such a depolarization film in the present invention is suitable for applications where the displayed image of the image display device is observed while wearing polarizing glasses. That is, the depolarization film in the present invention can effectively eliminate the polarization of incident light. Therefore, whether the image display device of the present invention is viewed while wearing polarizing glasses that cut linearly polarized light, such as polarized sunglasses, or while wearing polarizing glasses that cut circularly polarized light, such as AR glasses, an image display without blackout can be achieved. Note that the configuration of the depolarization film is not limited to the above example, and it may have a configuration having only a phase difference layer A, or a configuration having only a phase difference layer B. Also, the depolarization film may have a configuration having multiple phase difference layers A, or a configuration having multiple phase difference layers B. Furthermore, the depolarizing film may have layers other than phase difference layer A and / or phase difference layer B.

[0031] Phase Difference Layer A: As described above, Phase Difference Layer A utilizes a wavelength scrambling method and is a high-reducing film with a retardation of 3000 nm or more at a wavelength of 550 nm. Furthermore, within the plane of Phase Difference Layer A, the direction of retardation and the slow axis is approximately constant.

[0032] <In-plane retardation of retardation layer A in the normal direction> Retardation layer A is preferably a high retardation film having a phase difference of several times or more the wavelength of visible light. The in-plane retardation of retardation layer A in the normal direction at a wavelength of 550 nm is preferably from 300 nm to 100000 nm, more preferably from 5000 nm to 50000 nm, and most preferably from 7000 nm to 20000 nm. When the value is greater than 3000 nm, the depolarization ability due to wavelength scrambling increases, so color unevenness and blackout can be suppressed. On the other hand, when the value is smaller than 100000 nm, the decrease in transmittance and the deterioration of transmitted image clarity caused by excessively thick retardation layer A can be suppressed. Here, the retardation of retardation layer A can be adjusted by formation conditions, forming materials, film thickness, lamination of a plurality of retardation films, and the like.

[0033] <Lamination of a plurality of retardation films> Retardation layer A may comprise two or more retardation films. The number of retardation films included in retardation layer A is not limited, but in order to obtain reduced interface reflection and high transmitted image clarity, it is preferably less than 20 layers, more preferably less than 10 layers, still more preferably less than 6 layers, and most preferably less than 3 layers.

[0034] By laminating a plurality of retardation films, a high retardation value can be obtained while precisely controlling the oblique retardation, so that a favorable depolarization effect can be achieved for polarized light in various states and light sources with various spectra. That is, in the configuration in which a plurality of retardation films are laminated, as described above, each retardation film can have different retardations. Therefore, by adjusting the film thickness of each layer according to the retardation of the combined retardation films, the difference between the normal direction retardation and the oblique direction retardation of the composite comprising the depolarization element and the retardation layer can be reduced, so that blackout can be suppressed while suppressing color unevenness when observed through polarized sunglasses.

[0035] <Optical Properties of Laminated Retardation Films> Each retardation film of the laminated retardation film is preferably designed to exhibit a desired retardation at a specific wavelength. This enables effective elimination of the polarization state of light regardless of the polarization state of incident light. This retardation may be adjusted by known methods such as the thickness of the film and the degree of optical anisotropy (birefringence) of the optically anisotropic material.

[0036] Furthermore, a plurality of retardation layers A may be provided. There is no limitation on the number of retardation layers A. From the viewpoint of the depolarization function, a larger number of laminated retardation layers A is preferable because higher retardation can be obtained and blackout suppression performance is further improved. On the other hand, from the viewpoints of luminance of an image observed through a polarizing element and sharpness of a transmitted image, a smaller number of laminated retardation films is advantageous.

[0037] <Material for Retardation Layer A> There is no particular limitation on the composition and material of a film that satisfies the optical properties of the retardation layer A used in the depolarization element of the present invention. The materials constituting the retardation layer A are described below.

[0038] As a material constituting the retardation layer A, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, etc. (e.g., a polyester resin or a polycarbonate resin) can be used as a main component. The term "main component" refers to a material that constitutes 50% by mass or more of the retardation layer A.

[0039] The retardation layer A may contain one or more any appropriate additives in addition to the thermoplastic resin material described above. Examples of the additives include ultraviolet absorbers, particles, lubricants, antiblocking agents, thermal stabilizers, antioxidants, antistatic agents, light stabilizers, impact resistance improvers, lubricants, dyes, and pigments. The content of the thermoplastic resin in the retardation layer A is preferably 50 to 100% by mass, more preferably 50 to 99% by mass, still more preferably 60 to 98% by mass, and particularly preferably 70 to 97% by mass. When the content of the thermoplastic resin in the retardation layer A is 50% by mass or more, the high transparency inherently possessed by the thermoplastic resin can be sufficiently exhibited.

[0040] The phase difference layer A may be a single-layer film or a multilayer film. Furthermore, both or one side of these single-layer or multilayer films may be surface-treated. This surface treatment may include surface modification by corona treatment, saponification, heat treatment, ultraviolet irradiation, electron beam irradiation, etc., or thin film formation by coating or vapor deposition of polymers and metal compounds. Additionally, to improve adhesion with other components, an easy-adhesion layer, as described later, may be formed.

[0041] There are no restrictions on the material used to form the phase difference layer A; various known materials used for forming phase difference films can be used. Examples include birefringent particles, birefringent polymers, and liquid crystal compounds. Among these, birefringent polymers that can obtain high retardation values ​​in a simple process are preferred. Polyester resins and polycarbonate resins, in particular, are preferred due to their high birefringence exhibiting properties.

[0042] --Polyester Resin-- The phase difference layer A is preferably a polyester film containing polyester resin as the main component. Furthermore, it is preferable that the phase difference layer A is a polyester film stretched in at least one axial direction. Examples of polyester resins include polyethylene terephthalate, polyethylene isophthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, and 1,4-cyclohexanedimethylene terephthalate, and two or more of these may be used as needed. Among these, polyethylene terephthalate and polyethylene-2,6-naphthalate are preferably used. From the viewpoint of material cost, it is more preferable to use polyethylene terephthalate.

[0043] Polyethylene terephthalate is a polyester having structural units derived from terephthalic acid as a dicarboxylic acid component and structural units derived from ethylene glycol as a diol component, preferably with 80 mol% or more of the total repeating units being ethylene terephthalate, and may also contain structural units derived from other copolymer components. Examples of other copolymer components include dicarboxylic acid components such as isophthalic acid, p-β-oxyethoxybenzoic acid, 4,4'-dicarboxydiphenyl, 4,4'-dicarboxybenzophenone, bis(4-carboxyphenyl)ethane, adipic acid, sebacic acid, 5-sodium sulfisoisophthalic acid, and 1,4-dicarboxycyclohexane, and diol components such as propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanediol, ethylene oxide adduct of bisphenol A, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. Two or more of these dicarboxylic acid components and / or diol components may be used in combination as needed. Furthermore, it is possible to use oxycarboxylic acids such as p-oxybenzoic acid in combination with the above-mentioned carboxylic acid component and / or diol component. As other copolymer components, dicarboxylic acid components and / or diol components containing small amounts of amide bonds, urethane bonds, ether bonds, carbonate bonds, etc., may be used. As a method for producing polyethylene terephthalate, any production method can be applied, such as the so-called direct polymerization method in which terephthalic acid and ethylene glycol, and optionally other dicarboxylic acids and / or other diols are reacted directly, or the so-called transesterification method in which dimethyl ester of terephthalic acid and ethylene glycol, and optionally dimethyl ester of other dicarboxylic acids and / or other diols are transesterified.

[0044] --Polycarbonate resin-- The phase difference layer A may also preferably contain polycarbonate resin as its main component.

[0045] Any known polycarbonate resin can be used. For example, a polycarbonate resin having a bisphenol A skeleton can be used, which is obtained by reacting a dihydroxy component with a carbonate precursor by interfacial polymerization or melt polymerization. For example, those described in Japanese Patent Publication No. 2006-277914, Japanese Patent Publication No. 2006-106386, and Japanese Patent Publication No. 2006-284703 can be preferably used. As a commercially available product, "Toughlon MD1500" (manufactured by Idemitsu Kosan Co., Ltd.) can be used. Two or more of these may be used as needed.

[0046] --Ultraviolet Absorber-- It is preferable to include an ultraviolet absorber in the phase difference layer A to prevent the polarizing plate protective film of the image display device from degrading due to ultraviolet light. The ultraviolet absorber is a compound having ultraviolet absorbing ability and is not particularly limited as long as it can withstand the heat added during the manufacturing process of the phase difference layer A.

[0047] UV absorbers include organic and inorganic UV absorbers, but organic UV absorbers are preferred from the viewpoint of transparency. Suitable organic UV absorbers include, for example, benzotriazole, hydroxyphenyltriazine, and benzoxazine UV absorbers. In the present invention, for example, 2,2'-(p-phenylene)di-3,1-benzoxazine-4-one (manufactured by Fujifilm Fine Chemicals Co., Ltd., product name UVSORB 101) is preferably used as the UV absorber. In addition, two or more UV absorbers with different maximum absorption wavelengths may be used in combination to broaden the UV absorption range. The amount of UV absorber added is preferably 0.01 to 2% by mass of the resin contained in the phase difference layer A, and more preferably 0.01 to 1.5% by mass.

[0048] Furthermore, if the phase difference layer A is a multilayer film, it is preferable to have at least three layers, and it is preferable to incorporate the UV absorber in the intermediate layer. By incorporating the UV absorber in the intermediate layer, it is possible to prevent the UV absorber from bleeding out to the film surface, and as a result, the properties of the film, such as adhesion, can be maintained.

[0049] -Method for manufacturing the phase difference layer A- There are no particular restrictions on the method for manufacturing the phase difference layer A, but in order to impart the above characteristics, it is preferable to manufacture it by the following method. First, the resin to be used for the phase difference layer A (for example, polyester resin) is melt-extruded into a film shape, cooled and solidified in a casting drum to obtain an unstretched film, and then, if necessary, a coating liquid for forming an easy-adhesion layer is applied, and it is preferable to stretch this unstretched film at a temperature of Tg to (Tg + 60)°C of the polyester film so that it is 3 to 10 times, preferably 3 to 7 times, in the width direction. The phase difference layer A is preferably a polyester film stretched in at least one axial direction, and it is more preferable from the viewpoint of greatly exhibiting in-plane retardation Re.

[0050] Next, it is preferable to perform a heat treatment (referred to here as thermal setting) at 140°C to 220°C for 1 to 60 seconds. The thermal setting temperature is more preferably 150°C to 220°C, and particularly preferably 150°C to less than 220°C.

[0051] Furthermore, it is preferable to perform a reheat treatment (referred to as a relaxation treatment) at a temperature 10 to 20°C lower than the heat-fixing temperature while shrinking the film by 0 to 20% in the longitudinal and / or widthwise directions. In this method, the film comes into contact with the roll less, so minute scratches and other defects are less likely to occur on the film surface than in the method described above, which is advantageous for optical applications. The glass transition temperature of the film is denoted as Tg. When the heat-fixing temperature is 150°C or higher and less than 220°C, the displacement of the orientation direction of the resin used in the phase difference layer A becomes smaller, and the thermal dimensional change also becomes smaller, which is preferable. In particular, when the phase difference layer A has a hard coat layer as described later, peeling and cracking of the hard coat layer are less likely to occur.

[0052] 《Phase Difference Layer B》 In the present invention, phase difference layer B is preferably a pattern phase difference layer in which the characteristics change within the plane. The changing characteristics may be the slow axis orientation, retardation (phase difference), or both. The distribution pattern of the characteristics in phase difference layer B can be random, stripe, continuous change, checkerboard, etc., but random is particularly preferred because it can suppress the generation of moiré due to interference with pixels.

[0053] One embodiment of phase difference layer B is a patterned phase difference layer having an in-plane distribution of slow axis orientations. The pattern of the slow axis orientation distribution can be selected from random, stripe, continuous change, checkerboard, etc., but random is particularly preferred because it suppresses the generation of moiré due to interference with pixels. In the first embodiment of phase difference layer B, a manufacturing method for imparting an in-plane distribution to the slow axis orientation is to irradiate a photo-alignment film that responds to the polarization direction of polarized exposure with light of different polarization directions in the plane. Specifically, different polarizations may be irradiated twice through a light-shielding mask having a pattern. Alternatively, a distribution of linear polarization may be imparted by interfering right-circularly polarized and left-circularly polarized laser light. Alternatively, the axis distribution may be drawn by irradiating different polarizations in each region using a polarizing light source with a small exposure spot, such as a laser. The second embodiment of phase difference layer B is a patterned phase difference layer having an in-plane distribution of phase differences. Here, "the phase difference has an in-plane distribution" means that the phase difference Re1 at one point and the phase difference Re2 at another point have different values.

[0054] <Structure of Phase Difference Layer B Having a Random Axis Distribution> In the present invention, it is preferable that the phase difference layer B has a random axis distribution. Having a random axis distribution means, as described above, that the orientation of the axes (slow axis) in the phase difference film, i.e., the axial orientation, is oriented in various directions without regularity within the plane, i.e., it is randomly distributed.

[0055] Figure 3 is a conceptual diagram of the phase difference layer B viewed from the direction normal to the film surface. Figure 4 is a conceptual diagram of the phase difference layer B viewed from the side. The orientation (direction) of the slow axis 13 of the phase difference layer B (11) differs depending on the location in the plane. In the phase difference layer B (11), the distribution of the slow axis may be separated into domains or it may be continuous. The dotted line 12 in Figure 3 schematically represents the boundary line when the distribution of the slow axis is separated into domains. The double arrow 13 in Figure 3 represents the direction of the slow axis. The phase difference layer B includes a first phase difference film in which the orientation of the slow axis 13 is directed in various directions without regularity in the plane, i.e., it has a random (slow) axis distribution. It is preferable that the thickness of the phase difference layer B is almost uniform in the plane and that the slow axis direction changes in the plane. By making the thickness almost uniform in the plane, light scattering can be suppressed, resulting in good image clarity.

[0056] Here, in the present invention, a domain in the phase difference layer B is a region where the axes (slow axes) in the plane of the pattern phase difference film are oriented in a similar direction. In the example shown in Figure 3, the phase difference layer B is divided into multiple domains in the plane, and the direction of the slow axis 13 (direction in the plane) in each domain is randomly different. Also, in the example shown in Figure 3, the size and shape of each domain are different from each other, and their arrangement is irregular. Also, in the example shown in Figure 4, the direction of the slow axis in the thickness direction is approximately constant in each domain. Also, in the example shown in Figure 4, the size, shape, and arrangement of each domain are constant in the thickness direction. In such a phase difference layer B, the direction of the slow axis in each domain is random, but the retardation (phase difference) in each domain is approximately constant. Hereinafter, the retardation (phase difference) of each domain in the phase difference layer B will also be referred to as the retardation (phase difference) of the phase difference layer B.

[0057] The fact that phase difference layer B has a random axial distribution can be confirmed, for example, by using a Nikon ECLIPSE LV100POL polarizing microscope, setting polarizers on the light source side and the detector side, arranging them in a crossed nicol configuration, placing phase difference layer B between the two polarizers, and observing phase difference layer B at 50x magnification to see if an irregular pattern of light and dark appears (see Figure 6).

[0058] The above describes a phase difference layer B having a random axis distribution. As will be described later, even in a configuration having multiple phase difference layers B having a random axis distribution, the preferred configuration of each phase difference layer B having a random axis distribution is the same as that described above.

[0059] In this invention, a random axis distribution refers to a state in which the optical anisotropy axes (slow axis) of the phase difference layer B, for example, the orientation direction of the liquid crystal compounds, do not follow any specific rules and patterns, but are statistically evenly distributed. In other words, a random axis distribution means that the optical anisotropy axes of the phase difference layer B, for example, the orientation of each liquid crystal compound, are unpredictable, and orientation in any direction occurs with equal probability. Such randomness is realized by specific conditions during the manufacturing process and has a significant impact on the properties of the film.

[0060] The randomness of the axis distribution is measured as follows: Using a Nikon ECLIPSE LV100POL polarizing microscope, the phase difference and axis distribution (in-plane distribution of axis angles) of the phase difference layer are measured at multiple points in the plane using the rotational compensator method (reference: Spectroscopic Ellipsometry, by Hiroyuki Fujiwara). The axis angles are considered random, i.e., to have a random axis distribution, if the average value of the axis orientations at multiple points in the plane is within the range of -5° to 5°, and the standard deviation of the axis orientations is within the range of 45° to 55°. For the phase difference, the in-plane phase difference Re and the phase difference Rth in the thickness direction are measured. For the axis distribution, the axis orientations at multiple points in the plane are measured in an evaluation system in which the axis orientations are obtained as values ​​in the range of -90° to 90°.

[0061] <Structure of Phase Difference Layer B Having a Regular Axis Distribution> In the present invention, it is also preferable that the phase difference layer B has a regular axis distribution. Having a regular axis distribution means that the orientation of the axes (slow axis) in the phase difference film, i.e., the axial orientation, is distributed with regularity (periodicity) within the plane.

[0062] The orientation (direction) of the slow axis in phase difference layer B varies depending on the location within the plane. In phase difference layer B, the distribution of slow axes may be separated by domain or continuous. Phase difference layer B includes a first phase difference film in which the orientation of the slow axis is oriented in various directions with regularity (periodicity) within the plane, i.e., it has a regular (slow) axis distribution. It is preferable that the thickness of phase difference layer B is almost uniform within the plane and that the orientation of the slow axis changes within the plane. By making the thickness almost uniform within the plane, light scattering can be suppressed, resulting in good image clarity.

[0063] The fact that phase difference layer B has a regular axial distribution can be confirmed, for example, by using a Nikon ECLIPSE LV100POL polarizing microscope, setting polarizers on the light source side and the detector side, arranging them in a crossed nicol configuration, placing phase difference layer B between the two polarizers, and observing phase difference layer B at 50x magnification to see if a regular pattern of light and dark appears.

[0064] The phase difference layer B, having a regular axial distribution, is preferably formed using a liquid crystal composition containing a liquid crystal compound. It is preferable that the orientation of the optical axes derived from the liquid crystal compound changes periodically along at least one direction in the plane. The orientation of the optical axes of the liquid crystal compound can take the form of a periodic pattern in which it continuously rotates clockwise or counterclockwise along one direction, or a periodic pattern in which it alternately rotates clockwise and counterclockwise along one direction. In particular, having a periodic pattern in which it alternates clockwise and counterclockwise rotation is preferable from the viewpoint of suppressing diffraction rainbows. The liquid crystal layer only needs to have a region having the above periodic pattern in at least a part of the in-plane direction of the main surface, and may also include regions without the periodic pattern. Furthermore, the phase difference layer B may have other layers. For example, it may have a support, an alignment film, etc.

[0065] As an example, in a phase difference layer B (liquid crystal layer) having a periodic pattern, the liquid crystal compounds are arranged two-dimensionally within the plane of a principal surface parallel to a certain direction X and a direction Y that is perpendicular to this X direction.

[0066] Specifically, in a preferred embodiment, the liquid crystal layer has a periodic pattern in which the orientation of the optical axis originating from the liquid crystal compound changes alternately between rightward and leftward rotation along a certain direction X within the plane of the main surface of the liquid crystal layer. In the following description, "rightward (leftward) rotation of the optical axis" will also be simply referred to as "rightward (leftward) rotation of the optical axis".

[0067] Specifically, the statement that the orientation of the optical axis of a liquid crystal compound changes by alternately rotating clockwise and counterclockwise along a certain direction X means that the liquid crystal compound alternately has regions where the orientation of the optical axis is arranged to rotate clockwise along a certain direction X, and regions where it is arranged to rotate counterclockwise along a certain direction X.

[0068] In other words, when we say that the orientation of the optical axis of a liquid crystal compound changes by alternating clockwise and counterclockwise rotations along a certain direction X, it means that the angle between the optical axis of the liquid crystal compound, which is arranged along direction X, and direction X differs depending on the position in direction X. Along direction X, the angle between the optical axis and direction X gradually changes from an angle θ0 to θ0+θ, and then gradually changes from θ0+θ to θ0, repeating this process alternately. That is, within a certain angular range θ, the angle between the optical axis and direction X repeatedly increases and decreases along direction X.

[0069] Furthermore, the difference in the angle of the optical axes of adjacent liquid crystal compounds in one direction X is preferably 45° or less, more preferably 15° or less, and even more preferably a smaller angle.

[0070] Furthermore, in this invention, the rotation direction of the optical axis of the liquid crystal compound in a certain direction X is assumed to be such that the liquid crystal compound rotates in a direction that reduces the angle between the optical axes of liquid crystal compounds adjacent to each other in that direction X.

[0071] On the other hand, in the liquid crystal compound forming the phase difference layer B, in the Y direction perpendicular to the one direction X, that is, in the Y direction perpendicular to the one direction in which the optical axis alternates between clockwise and counterclockwise rotation, liquid crystal compounds with the same optical axis orientation are arranged at equal intervals.

[0072] In other words, in liquid crystal compounds that form a liquid crystal layer, the angle between the optical axis and the X direction is equal for liquid crystal compounds arranged in the Y direction.

[0073] An optical film having a liquid crystal layer with such a periodic pattern can be placed on the display surface of an image display device and used as a depolarizing film.

[0074] <Optical Characteristics of Phase Difference Layer B> It is preferable to design the phase difference layer B to exhibit a desired phase difference at a specific wavelength. This effectively eliminates the polarization state of the incident light. The phase difference of the phase difference layer B can be adjusted by known methods such as the thickness of the film and the degree of optical anisotropy (birefringence) of the optical anisotropic material. In this regard, the same applies to other phase difference layers B when there are multiple phase difference layers B. There are no restrictions on the phase difference of the phase difference layer B, and it can be set appropriately according to the image display device application of the present invention. As an example, it is preferable that the phase difference of the phase difference layer B at a wavelength of 550 nm is 235 to 315 nm. By setting the phase difference of the phase difference layer B within this range, it is possible to effectively depolarize polarized light. The phase difference of the phase difference layer B at a wavelength of 550 nm is more preferably 255 to 295 nm, and even more preferably 265 to 285 nm. When the phase difference layer B is used as a single layer, that is, when the image display device of the present invention has only one layer of phase difference layer B as a depolarizing film, it is preferable that the phase difference of the phase difference layer B is within the above range. Such characteristics are preferable for suppressing the decrease in brightness when the image display device is observed while wearing polarizing glasses and for improving contrast when reflected light from an object is detected by a light sensor.

[0075] <Lamination of Phase Difference Layer B> The depolarizing film in the present invention may have multiple layers of phase difference layer B. There is no limit to the number of phase difference layers B, but two layers are preferred.

[0076] Figure 5 is a schematic diagram showing an example of a polarizing film having two phase difference layers B. The polarizing film 1 shown in Figure 5 has two phase difference layers B (31) and two phase difference layers B (32) laminated together with an adhesive 33 in between.

[0077] As shown in Figure 5, phase difference layer B(31) and phase difference layer B(32) each have a random axis distribution. Furthermore, the randomness in phase difference layer B(31) and the randomness in phase difference layer B(32) are different from each other. For example, the size and magnitude of the domains in phase difference layer B(31) are different from the size and magnitude of the domains at the corresponding positions in phase difference layer B(32). Therefore, in the in-plane direction, one domain in phase difference layer B(31) overlaps with one or more domains in phase difference layer B(32), and one domain in phase difference layer B(32) overlaps with one or more domains in phase difference layer B(31). The orientation of the slow axis of a domain in phase difference layer B(31) and the orientation of the slow axis of the overlapping domain in phase difference layer B(32) may be the same or different from each other. Also, the thickness of phase difference layer B(31) and the thickness of phase difference layer B(32) may be the same or different from each other. Furthermore, the retardation of phase difference layer B(31) and the retardation of phase difference layer B(32) may be the same or different from each other.

[0078] When multiple phase difference layers B are laminated, as shown in Figure 5, each phase difference layer B may be laminated via an adhesive or directly. There are no particular restrictions on the adhesive, and known adhesives and bonding agents can be used. Alternatively, two phase difference layers B may be laminated by forming a base layer on top of the first phase difference layer B and then forming a second phase difference layer B on top of that.

[0079] By stacking multiple phase difference layers B, it is possible to accommodate a wide bandwidth of light sources and achieve a suitable depolarization effect for various states of polarization. When multiple phase difference layers B are stacked, the composite phase difference layer obtained by stacking can be given a different composite phase difference distribution in addition to the axial distribution of each phase difference layer B. This makes it possible to more effectively improve the depolarization ability for various types of polarization (e.g., linear polarization, circular polarization, elliptic polarization). In addition, it is possible to improve the depolarization ability over a wide wavelength range. That is, if there are two phase difference layers B, depending on the state of the incident polarization, even if the depolarization is insufficient in one phase difference layer B, it is possible to achieve sufficient depolarization by depolarizing the other phase difference layer B with a different phase difference. As a result, regardless of whether the incident polarization is linear, circular, or elliptic, it can be suitably depolarized. Such characteristics are desirable for suppressing brightness reduction when observing an image display device while wearing polarizing glasses and for improving contrast when detecting reflected light from an object with a photosensor.

[0080] As described above, when the image display device of the present invention has multiple phase difference layers B, there is no limit to the number of phase difference layers B. Here, in terms of the polarization depolarization function, a larger number of layered phase difference layers B is preferable. On the other hand, in terms of the brightness and image clarity of the image observed through polarizing glasses, a smaller number of layered phase difference layers B is advantageous. From these viewpoints, when there are multiple phase difference layers B, the number of layers is preferably two or three, and more preferably two.

[0081] <Optical properties of the laminated phase difference layer B> It is preferable to design the laminated phase difference layer B to exhibit a desired phase difference at a specific wavelength. This effectively eliminates the polarization state of light, regardless of the polarization state of the incident light. This phase difference can be adjusted by known methods, such as the thickness of the film and the degree of optical anisotropy (birefringence) of the optical anisotropic material.

[0082] For example, if the depolarizing film has two phase difference layers B, a combination of a quarter-wave plate with a random axial distribution and a half-wave plate with a random axial distribution is preferred. In this case, the first phase difference layer B may be a quarter-wave plate with a random axial distribution and the second phase difference layer B may be a half-wave plate with a random axial distribution, or the first phase difference layer B may be a half-wave plate with a random axial distribution and the second phase difference layer B may be a quarter-wave plate with a random axial distribution.

[0083] The phase difference at a wavelength of 550 nm for the quarter-wave plate (e.g., the first phase difference layer B) is preferably 100 to 180 nm, more preferably 120 to 160 nm, and even more preferably 130 to 150 nm. The phase difference at a wavelength of 550 nm for the half-wave plate (e.g., the second phase difference layer B) is preferably 235 to 315 nm, more preferably 255 to 295 nm, and even more preferably 265 to 285 nm. Such characteristics are preferable for suppressing brightness reduction and color change when observing the image display device while wearing polarizing glasses.

[0084] In the case of lamination of three or more layers, the preferred embodiment of the two-layer lamination may further include a quarter-wave plate and / or a half-wave plate with a random axial distribution. Furthermore, in the case of lamination of three or more layers with a random axial distribution, a phase difference film other than the quarter-wave plate and half-wave plate may be included, such as a three-quarter-wave plate with a random axial distribution. Such configurations can be appropriately designed in accordance with the purpose required of the depolarization film.

[0085] <Control of Rth> When the depolarizing film in the present invention has a plurality of phase difference layers B, it is preferable to control the value of Rth (thickness direction retardation) of each phase difference film. By controlling the value of Rth of each phase difference film, the phase difference in the oblique direction can also be suitably controlled. As a result, the depolarizing ability can be improved not only when the image display device is observed from the front, i.e., when light is incident on the depolarizing film from the front, but also when the image display device is observed from an oblique angle, i.e., when light is incident on the depolarizing film from an oblique angle.

[0086] In the present invention, when the depolarizing film has a phase difference layer B, a preferred method for controlling Rth is to laminate a phase difference layer B having a negative Rth value and a phase difference layer B having a positive Rth value. A phase difference layer B having a negative Rth value can be produced, for example, by using a liquid crystal compound having positive birefringence in the production of the phase difference layer B. Examples of liquid crystal compounds having positive birefringence include rod-shaped liquid crystal compounds. On the other hand, a phase difference layer B having a positive Rth value can be produced, for example, by using a liquid crystal compound having negative birefringence in the production of the phase difference layer B. Examples of liquid crystal compounds having negative birefringence include disc-shaped liquid crystal compounds.

[0087] Furthermore, when the depolarizing film in the present invention has a phase difference layer B, the control of Rth is not limited to a configuration in which a phase difference layer B having a negative Rth value and a phase difference layer B having a positive Rth value are laminated, as described above, and various configurations can be used. For example, when the depolarizing film has a phase difference film consisting of a first phase difference layer B and a second phase difference layer B as described above, the first phase difference layer B and the second phase difference layer B may have positive birefringence, the first phase difference layer B and the second phase difference layer B may have negative birefringence, the first phase difference layer B may have positive birefringence and the second phase difference layer B may have negative birefringence, or the first phase difference layer B may have negative birefringence and the second phase difference layer B may have positive birefringence. When light is incident on the depolarizing film from an oblique direction, that is, when the image display device is observed from an oblique direction, it is preferable that the first phase difference layer B has negative birefringence and the second phase difference layer B has positive birefringence, or that the first phase difference layer B has positive birefringence and the second phase difference layer B has negative birefringence.

[0088] The positive or negative nature of birefringence can be determined by measuring Rth. When Rth is negative, there is positive birefringence. When Rth is positive, there is negative birefringence.

[0089] <Materials for Phase Difference Layer B> There are no restrictions on the materials used to form Phase Difference Layer B, and various known materials used for forming Phase Difference Films can be used. Examples include birefringent particles, birefringent polymers, and liquid crystal compounds. Among these, liquid crystal compounds that can form a Phase Difference Film with uniform thickness and a high aspect ratio (in-plane length / thickness), and that also have high optical anisotropy are preferred. Liquid crystal compounds having polymerizable groups are particularly suitable. By using liquid crystal compounds to form Phase Difference Layer B, in addition to excellent Phase Difference characteristics, processability and durability can also be improved.

[0090] Liquid crystal compounds can be easily immobilized by heating and UV irradiation, and maintain stable optical properties over long periods. Moreover, liquid crystal compounds allow for precise adjustment of desired phase difference characteristics, and because they exhibit a liquid crystal phase within a specific temperature range, their phase difference characteristics can be optimized through temperature control during the manufacturing process.

[0091] While there are no restrictions on the birefringence wavelength dispersion characteristics of liquid crystal compounds, inverse wavelength dispersion is preferred. Inverse wavelength dispersion is defined as Re(450) / Re(550) < 1.00 and Re(650) / Re(550) ≥ 1.00. Therefore, by fabricating the phase difference layer B using a liquid crystal compound with inverse wavelength dispersion, color changes when observing an image display device that emits polarized light while wearing polarizing glasses can be suppressed.

[0092] Furthermore, when selecting liquid crystal compounds, it is preferable to pay attention to physical properties such as heat resistance, light resistance, and moisture resistance, and to select materials with durability appropriate to the operating environment. This makes it possible to ensure long-term reliability in image display devices such as liquid crystal displays, and other optical devices.

[0093] The phase difference layer B preferably contains a liquid crystal compound. Even when the depolarizing film in the present invention has multiple phase difference layers B, it is preferable that each phase difference layer B contains a liquid crystal compound. For example, as described above, when the depolarizing film has a first phase difference layer B and a second phase difference layer B, it is preferable that both the first phase difference layer B and the second phase difference layer B contain a liquid crystal compound. The preferred embodiment of the liquid crystal compound in each phase difference layer B is the same as described above.

[0094] <Domain Size> As described above, in phase difference layer B having a random axis distribution, the distribution of slow axes may be separated into domains or may be continuous. Furthermore, a domain in phase difference layer B is, as described above, a region in the plane of the phase difference film where the axes (slow axes) are oriented in a similar direction. In Figure 3, to make the structure of phase difference layer B having a random axis distribution easier to understand, the boundary lines when it is divided into domains are schematically shown by dotted lines 12. However, in reality, it is difficult to clearly determine the boundaries of domains in a second phase difference film having a random axis distribution.

[0095] Here, the axial distribution in the phase difference layer B having a random axial distribution can be adjusted by the formation conditions of the phase difference film, the forming material, the characteristics of the underlying orientation film, etc. Furthermore, in the phase difference B having a random axial distribution, the state of the axial distribution, the size of the domains, and the degree of distribution in the axial distribution do not fluctuate significantly within the plane of the phase difference film. Accordingly, in the present invention, in the phase difference layer B having a random axial distribution, regardless of whether the distribution of the slow axis (axial distribution) is separated for each domain or continuous, the autocorrelation coefficient of the luminance distribution measured with the phase difference layer B placed between polarizers arranged in crossed nicols is determined, and the value obtained by multiplying this autocorrelation length by three is defined as the domain size.

[0096] Specifically, as described above, a polarizing microscope is used, with polarizers set in crossed nicols on the light source side and the detector side, and a phase difference layer B is placed between the polarizers for observation at 50x magnification. In this case, if the phase difference film has a random axial distribution, an irregular pattern of light and dark will appear in the observed image as described above (see Figure 6). A luminance profile on an arbitrary line in this observed image is extracted, and the autocorrelation coefficient of this luminance profile is calculated. Then, the distance at which the autocorrelation coefficient becomes 0.5 is defined as the autocorrelation length in the luminance profile of the phase difference layer B. In this invention, the value obtained by multiplying this autocorrelation length by three is defined as the domain size in the phase difference layer B having a random axial distribution.

[0097] As described above, when the phase difference layer B has a random axis distribution, an irregular light-dark pattern appears in the observed image of the phase difference layer B when observed with a polarizing microscope under polarizers arranged in crossed nicols. This light-dark pattern in the observed image corresponds to the direction of the slow axis at each position in the plane of the phase difference layer B, which has a random axis distribution and is placed between the polarizers arranged in crossed nicols. Therefore, this light-dark pattern in the observed image changes depending on the state of the random axis distribution in the phase difference layer B. In other words, this domain size is one of the numerical values ​​that indicate the state of the axis distribution in the phase difference layer B of the depolarization film in the present invention.

[0098] In the phase difference layer B having a random axial distribution, it is preferable to control the domain size. This can improve optical uniformity. The domain size is preferably 32 μm or less, more preferably 30 μm or less, even more preferably 25 μm or less, and particularly preferably 20 μm or less. Also, it is preferably 0.5 μm or more, more preferably 1.5 μm or more, even more preferably 2.5 μm or more, and particularly preferably 4 μm or more. In particular, the domain size is preferably 0.5 to 32 μm, more preferably 1.5 to 30 μm, even more preferably 2.5 to 25 μm, and particularly preferably 4 to 20 μm.

[0099] On the other hand, the preferred range of domain sizes for phase difference layers with random axis distributions varies depending on the application and structure of the image display device.

[0100] A. When an antipolarizing film is placed near a pixel, i.e., an image display device, the preferred range of domain size can be estimated from the following viewpoints. A-(1) Image blur reduction; The degree of image blur is determined from the relationship between the scattering angle θ (∝ 1 / domain size), the light diffusion distance obtained from the distance L between the pixel and the antipolarizing film, and the pixel period d. Specifically, if the light diffusion distance is as large as the pixel period, the image will appear blurred. From the viewpoint of reducing image blur, the preferred range of domain size can be expressed by the formula: Domain size [μm] > (8π / 180) / tan -1 (d / 2L) A-(2) Pixel occlusion suppression; The degree of pixel occlusion can be determined from the relationship between the pixel period d and the domain size. If the domain size is larger than the subpixels (RGB), some pixels will be occluded, causing a color change. From the viewpoint of pixel occlusion suppression (color change), the preferred range of domain size can be expressed by the formula: Domain size [μm] < d / 3.

[0101] The domain size can be measured by the method described above, that is, by the method described in the examples below. Furthermore, if the domain size is greater than or equal to the lower limit of each range described above, the diffraction angle of light diffraction caused by the PBP (Pancharatnam Berry Phase) phase due to the difference in axial orientation can be kept small, resulting in a clear image. On the other hand, if the domain size is less than or equal to the upper limit of each range described above, the variation in light intensity from pixel to pixel can be kept low, thus suppressing noise.

[0102] The following shows examples of preferred domain sizes corresponding to the applications and structures of image display devices.

[0103] <For Tablet Surfaces> As a first example, consider the case where a phase difference layer B is placed as an anti-polarization film on the surface of a tablet PC (the front side of the touch panel). This example corresponds to the case where an anti-polarization film is placed near the pixels shown in 'A' above. As an example, the distance L between the pixel and the phase difference layer B is 1000 μm, and the pixel period d is 96 μm. In this case, the domain size is preferably 32 μm or less, more preferably 30 μm or less, even more preferably 25 μm or less, particularly preferably 24 μm or less, even more preferably 20 μm or less, and most preferably 16 μm or less. Also, 1.5 μm or more is preferred, 2.5 μm or more is more preferred, 2.9 μm or more is even more preferred, 3.9 μm or more is particularly preferred, even more preferably 4 μm or more, and most preferably 6 μm or more. In particular, the domain size is preferably 1.5 to 32 μm, more preferably 1.5 to 30 μm, even more preferably 2.5 to 30 μm, even more preferably 2.5 to 25 μm, particularly preferably 3.9 to 24 μm, even more preferably 4 to 20 μm, and most preferably 6 to 16 μm. Furthermore, even when there are multiple phase difference layers B having a random axial distribution, it is preferable to control the domain size of each phase difference film, and the domain size is preferably within the above range. For example, the domain sizes of the first phase difference layer B and the second phase difference layer B are preferably within the above range.

[0104] <In the case of being directly above the display> As a second example, consider the case where the phase difference layer B is placed as an anti-polarization film directly above the display device of a smartphone (on the back of the touch panel). This example also corresponds to the case where the anti-polarization film is placed near the pixels as shown in 'A' above. As an example, the distance L between the pixel and the phase difference layer B is 100 μm, and the pixel period d is 55 μm. In this case, the domain size is preferably 20 μm or less, more preferably 14 μm or less, and most preferably 9 μm or less. Also, it is preferably 0.5 μm or more, more preferably 0.7 μm or more, and most preferably 1.0 μm or more. In particular, the domain size is preferably 0.5 to 20 μm, more preferably 0.7 to 14 μm, and most preferably 1.0 to 9 μm. The domain size can be measured by the method described in the examples below. Furthermore, even when there are multiple phase difference layers B having a random axis distribution, it is preferable to control the domain size of each phase difference layer B, and the domain size is preferably within the above range. For example, the domain sizes of the first phase difference layer B and the second phase difference layer B are preferably within the range described above.

[0105] <Methods for controlling domain size> Domain size can be controlled by appropriately adjusting the conditions during the orientation process of the liquid crystal compound, such as temperature, time, and UV irradiation intensity. Domain size can also be controlled by appropriately adjusting the physical properties of the liquid crystal compound, such as the elastic constant. Furthermore, domain size can also be controlled by the distance from the underlying layer. The distance from the underlying layer can also be controlled by the thickness of the phase difference layer. When the thickness of the phase difference layer is thin, the domain size becomes smaller, and when the thickness is thick, the domain size becomes larger.

[0106] Another method for controlling domain size involves using the following materials as the underlying layer for the orientation film, and pre-applying a distribution of orientation directions to achieve the desired domain size. Specific examples of methods for applying a distribution of orientation directions (methods for controlling domain size) are shown below.

[0107] (1) As a method for imparting a distribution of orientation directions, first, a photo-alignment film is used as the underlying layer, and linearly polarized light, such as laser light, is exposed to each minute region of this photo-alignment film while changing the direction of polarization. By forming a liquid crystal layer as a phase difference layer on such an alignment film, it becomes possible to obtain a phase difference layer having any domain size.

[0108] (2) When a liquid crystal layer formed on a substrate without orientation-restricting force is used as the base layer, the domain size can be controlled by the distance from the substrate without orientation-restricting force and the elastic modulus of the layer. The distance from the substrate without orientation-restricting force can be controlled by the thickness of the liquid crystal layer. When the thickness of the liquid crystal layer is thin, the domain size becomes small, and when the thickness is thick, the domain size becomes large. Also, when the elastic modulus of the liquid crystal layer is high, the domain size becomes small, and when the elastic modulus is low, the domain size becomes large. The elastic modulus of the liquid crystal layer can also be controlled by the type of material and the temperature of the liquid crystal layer during drying and UV curing. When the temperature of the layer during drying and UV curing is high, the elastic modulus becomes low, and therefore the domain size becomes large. By using such a liquid crystal layer as a base and forming a liquid crystal layer on top of it as a phase difference layer, it is possible to obtain a phase difference layer with an arbitrary domain size.

[0109] (3) As a method for imparting a distribution of orientation directions, a method can also be used in which a cholesteric liquid crystal layer is used as the underlayer and the director orientation of the liquid crystal compound on the outermost surface of the cholesteric liquid crystal layer is changed in the plane. Methods for changing the director orientation of the liquid crystal compound on the outermost surface of the cholesteric liquid crystal layer in the plane include changing the film thickness of the cholesteric liquid crystal layer in the plane and changing the helical pitch of the cholesteric liquid crystal layer in the plane. Methods for changing the film thickness of the cholesteric liquid crystal layer in the plane include wind unevenness caused by applying air, step unevenness caused by pump pulsation, streaks caused by bar coating, Marangoni convection, and, when a photo-alignment film is used as an underlayer for the cholesteric liquid crystal layer, methods for imparting a distribution to the height of the photo-alignment film make it possible to generate a fine film thickness distribution. On the other hand, one method for changing the helical pitch of a cholesteric liquid crystal layer in-plane is to change the helical twisting power (HTP) of the chiral agent added to induce cholesteric liquid crystal properties in-plane by the intensity of isomerization exposure after coating the cholesteric liquid crystal layer but before curing. By using a cholesteric liquid crystal layer obtained by such methods as a base and forming a liquid crystal layer as a phase difference layer on top of it, it becomes possible to form liquid crystal layers with orientations facing various directions.

[0110] These methods for controlling domain size may be used in combination.

[0111] Furthermore, the above description regarding domain size applies not only to the first phase difference layer B having a random axis distribution, but also to the second phase difference layer B having a random axis distribution. In other words, the above description regarding domain size applies to all phase difference films, both when the depolarizing film of the present invention has only one phase difference layer B and when the depolarizing film of the present invention has multiple phase difference layers B.

[0112] <Method for Manufacturing Phase Difference Layer B> There are no restrictions on the method for manufacturing the phase difference layer B, and known methods can be used depending on the material used to form the phase difference layer B. As an example, a method is exemplified in which a liquid crystalline material having crosslinkable groups is uniformly applied to a support, then heat-treated at a specific temperature, and cured by ultraviolet irradiation or the like to produce the phase difference layer B. In other words, a liquid crystalline material having crosslinkable groups is a liquid crystal composition containing a liquid crystal compound having crosslinkable groups.

[0113] A typical phase difference film using liquid crystal compounds is manufactured by applying a liquid crystal composition to a substrate (alignment film) that has liquid crystal alignment restricting force and a uniform orientation restricting direction, and then curing it to form a phase difference layer. Methods for making the orientation restricting direction uniform in the plane include rubbing the substrate and uniform linearly polarized light irradiation of the photo-alignment film. In contrast, to manufacture a phase difference layer B with a random axial distribution, a substrate without orientation restricting force, or with a random orientation restricting direction in the plane, is used. An example of a substrate without orientation restricting force is a substrate obtained by applying a composition containing crosslinkable non-liquid crystal molecules and then curing it. Furthermore, a plastic film that has not been rubbed can also be used as a substrate with a random orientation restricting direction.

[0114] Furthermore, in order to create a phase difference in the phase difference layer B, it is preferable to orient the rod-shaped liquid crystal compounds horizontally or the disc-shaped liquid crystal compounds vertically. To achieve this, it is preferable to control the surface energy of the underlying layer. Specifically, when creating a phase difference layer B consisting of rod-shaped liquid crystal compounds, it is preferable to make the underlying layer hydrophobic. On the other hand, when creating a phase difference layer B consisting of disc-shaped liquid crystal compounds, it is preferable to make the underlying layer hydrophilic.

[0115] The phase difference layer B in the present invention may consist only of a patterned phase difference film, or it may have the support (substrate) and underlayer described above. As the support, various known materials can be used as long as they can support the patterned phase difference film and transmit the target light, such as visible light. For example, examples of materials for forming a transparent support include cellulose polymers (hereinafter referred to as cellulose acylates), such as triacetylcellulose, thermoplastic norbornene resins (such as Zeonex and Zeonor from Nippon Zeon Co., Ltd., and Arton from JSR Corporation), acrylic resins, and polyester resins, as well as plastic films and glass. As the underlayer, various known materials can be used as long as they do not have the orientation-restricting power of liquid crystal compounds and transmit the target light, such as visible light. Examples of the underlying layers include a layer formed by curing a crosslinkable non-liquid crystal molecules (hard coat layer), a layer formed by curing a crosslinkable liquid crystal compound (liquid crystal layer), a plastic film layer made of polymer, and photo-alignment films such as azo and cinnamate. In addition, in the depolarization film of the present invention, the underlying layer may also serve as a support, as in the plastic film without the rubbing treatment described above. Furthermore, in addition to these layers, the depolarization film of the present invention may have various layers (films) as needed, such as an anti-reflective layer, a phase difference layer, a depolarization layer made of a high birefringence material, a polarizer layer, a color absorption layer, a transparent conductive layer, and an antistatic layer. Here, the retardation of the phase difference layer B can be adjusted by the formation conditions of the phase difference film, the forming material, the film thickness of the phase difference film, and the lamination of multiple phase difference films.

[0116] The present invention will be specifically described below based on examples. The materials, reagents, amounts and proportions of substances, and procedures shown in the following examples can be modified as appropriate, as long as they do not depart from the spirit of the present invention. Therefore, the present invention is not limited to the following examples.

[0117] <Preparation of Phase Difference Layer A-1> A polyethylene terephthalate (PET) film with a thickness of 100 μm was prepared by the following method.

[0118] —Synthesis of raw material polyester— —Raw material polyester 1— As shown below, raw material polyester 1 (Sb catalyst-based PET) was obtained by a continuous polymerization apparatus using a direct esterification method in which terephthalic acid and ethylene glycol were directly reacted, water was removed by distillation, esterification was performed, and then polycondensation was carried out under reduced pressure.

[0119] (1) Esterification reaction: In the first esterification reactor, 4.7 tons of high-purity terephthalic acid and 1.8 tons of ethylene glycol were mixed over 90 minutes to form a slurry, which was continuously supplied to the first esterification reactor at a flow rate of 3800 kg / h. Furthermore, an ethylene glycol solution of antimony trioxide was continuously supplied, and the reaction was carried out at a reactor temperature of 250°C, under stirring, with an average residence time of approximately 4.3 hours. At this time, antimony trioxide was continuously added so that the amount of Sb added was 150 ppm in terms of elemental value.

[0120] The reactants were transferred to a second esterification reactor and reacted under stirring at a reactor temperature of 250°C for an average residence time of 1.2 hours. Ethylene glycol solutions of magnesium acetate and ethylene glycol solutions of trimethyl phosphate were continuously supplied to the second esterification reactor so that the amounts of Mg and P added were 65 ppm and 35 ppm, respectively, on an elemental basis.

[0121] (2) Polycondensation reaction The esterification reaction product obtained above is continuously supplied to the first polycondensation reaction vessel and stirred, at a reaction temperature of 270°C and a reaction vessel pressure of 20 torr (2.67 × 10⁻¹⁰). －３ Polycondensation was performed at MPa with an average residence time of approximately 1.8 hours.

[0122] Furthermore, the mixture is transferred to a second condensation reactor, where it is stirred, with a reactor temperature of 276°C and a reactor pressure of 5 torr (6.67 × 10⁻¹⁰). －４ The reaction (polycondensation) was carried out under conditions of MPa with a residence time of approximately 1.2 hours.

[0123] Next, the mixture is transferred to a third condensation reactor, where the reactor temperature is 278°C and the reactor pressure is 1.5 torr (2.0 × 10⁻¹⁰). －４ The reaction (polycondensation) was carried out under conditions of MPa with a residence time of 1.5 hours to obtain the reactant (polyethylene terephthalate (PET)).

[0124] Next, the resulting reaction product was extruded in strand form into cold water and immediately cut to produce polyester pellets (cross-section: major diameter approximately 4 mm, minor diameter approximately 2 mm, length: approximately 3 mm). The resulting polymer had an intrinsic viscosity IV = 0.63. This polymer was designated as raw material polyester 1.

[0125] The intrinsic viscosity IV was determined by dissolving the raw material polyester 1 in a 1,1,2,2-tetrachloroethane / phenol (= 2 / 3 [mass ratio]) mixed solvent and measuring the viscosity of the solution in this mixed solvent at 25°C.

[0126] --Raw material polyester 2-- 10 parts by mass of dried ultraviolet absorber (2,2'-(1,4-phenylene)bis(4H-3,1-benzoxazinon-4-one) and 90 parts by mass of raw material polyester 1 (IV = 0.63) were mixed, and raw material polyester 2 containing the ultraviolet absorber was obtained using a kneading extruder.

[0127] ―Film Forming Process― Raw material polyester 1 (90 parts by mass) and raw material polyester 2 (10 parts by mass) containing an ultraviolet absorber were dried to a moisture content of 20 ppm or less, then placed into the hopper 1 of a 50 mm diameter single-screw kneading extruder 1, and melted at 300°C in the extruder 1. The molten resin was extruded from the die through a gear pump and a filter (pore size 20 μm) under the following extrusion conditions. The extrusion conditions for the molten resin were set to a pressure fluctuation of 1% and a temperature distribution of molten resin of 2%, and the molten resin was extruded from the die. Specifically, the back pressure was increased by 1% relative to the average pressure inside the extruder barrel, and the extruder piping temperature was heated to a temperature 2% higher than the average temperature inside the extruder barrel. The molten resin extruded from the die was extruded onto a cooling cast drum set to a temperature of 25°C, and adhered to the cooling cast drum using an electrostatic application method. The film was peeled off using a peeling roll positioned opposite the cooling cast drum to obtain an unstretched polyester film 1.

[0128] —Transverse stretching process— —Preheating section— The preheating temperature was set to 90°C, and the unstretched polyester film 1, to which the polarizer-side easy-adhesion layer had been applied, was heated to a temperature at which it could be stretched.

[0129] --Stretching Section-- A preheated, unstretched polyester film 1 was guided into a tenter (transverse stretcher), and while holding the ends of the film with clips, it was transversely stretched in the TD direction (film width direction, transverse direction) under the following conditions and by the following method and conditions to obtain a transversely stretched polyester film 1. <Conditions> ・Transverse stretching temperature: 90°C ・Transverse stretching ratio: 4.3 times

[0130] --Thermal Fixation Section-- Next, a thermal fixation process was performed while controlling the surface temperature of the transversely stretched polyester film 1 to the following temperature: <Conditions> ・Thermal fixation temperature: 180°C ・Thermal fixation time: 15 seconds

[0131] --Thermal Relaxation Section-- The heat-set transversely stretched polyester film 1 was heated to the following temperature to relax the film. • Thermal relaxation temperature: 170°C • Thermal relaxation rate: 2% in the TD direction (film width direction, transverse direction)

[0132] --Cooling Section-- Next, the transversely stretched polyester film 1, after heat relaxation, was cooled at a cooling temperature of 50°C.

[0133] In this way, a phase difference layer A-1, which is a transversely stretched polyester film after thermal relaxation, was obtained. When the in-plane retardation of phase difference layer A-1 was measured with Axoscan, the in-plane retardation Re(550) = 10000 nm at a wavelength of 550 nm was found to be. Phase difference layer A-1 corresponds to phase difference layer A.

[0134] <Formation of Substrate 1> A PET film with a thickness of 100 μm (Cosmoshine A4265, manufactured by Toyobo Co., Ltd.) was prepared as a support. This PET film has an easy-adhesion layer on one side. Substrate coating liquid 1 with the following composition was applied to the side of the PET film without the easy-adhesion layer using a #3.6 wire bar coater. After that, it was dried at 45°C for 60 seconds, and then exposed to ultraviolet light at 25°C using a mercury lamp as the ultraviolet light source at a rate of 500 mJ / cm². 2 A support having a 1.4 μm thick underlayer 1 was fabricated by irradiating it with ultraviolet light.

[0135] [Coating liquid for base layer 1] KAYARAD PET30 (manufactured by Nippon Kayaku Co., Ltd.) 100 parts by mass IRGACURE 907 (manufactured by Ciba-Geigy) 3.0 parts by mass Kayacure DETX (manufactured by Nippon Kayaku Co., Ltd.) 1.0 part by mass The following surfactant F1 0.01 parts by mass Methyl isobutyl ketone 243 parts by mass

[0136] Surfactant F1

[0137] <Preparation of Phase Difference Layer B-1> A phase difference layer coating liquid 1 with the following composition was applied to the base layer 1 using a wire bar coater. Then, it was dried at 25°C for 30 seconds, and then heated at 80°C for 120 seconds for liquid crystal alignment. At 40°C, it was irradiated with ultraviolet light at 500 mJ / cm using a mercury lamp as the ultraviolet light source. 2 Phase difference layer B-1 was fabricated by irradiating with ultraviolet light to form a phase difference layer with a thickness of 0.85 μm. Phase difference layer B-1 has positive birefringence. Phase difference layer B-1 corresponds to phase difference layer B.

[0138] [Coating solution for phase difference layer 1] Methyl ethyl ketone 144.9 parts by mass Mixture X of the following rod-shaped liquid crystal compounds 100.0 parts by mass Photopolymerization initiator A 0.02 parts by mass Photopolymerization initiator B 1.00 parts by mass The above surfactant F1 0.027 parts by mass The following surfactant F2 0.067 parts by mass

[0139] Rod-shaped liquid crystal compound mixture X

[0140] In the above mixture, the values ​​are in mass percent. R represents a group bonded to an oxygen atom. Furthermore, the average molar extinction coefficient of the above rod-shaped liquid crystal compound at wavelengths of 300-400 nm was 140 / mol·cm.

[0141] Photopolymerization initiator A: IRGACURE 907 (manufactured by Ciba-Geigy) Photopolymerization initiator B: Kayacure DETX (manufactured by Nippon Kayaku Co., Ltd.)

[0142] Surfactant F2

[0143] <Fabrication of Phase Difference Layer B-2> Phase difference layer B-2 was fabricated using the same procedure as phase difference layer B-1, except that the thickness of the phase difference layer was changed to 1.7 μm. Phase difference layer B-2 has positive birefringence. Phase difference layer B-2 corresponds to phase difference layer B.

[0144] <Preparation of Phase Difference Layer-1> Phase difference layer-1 was prepared using the same procedure as for phase difference layer B-1, except that the substrate to which the coating solution for the phase difference layer was applied was changed from base layer 1 to a rubbed PET film. Phase difference layer-1 has an in-plane retardation of 140 nm and exhibits positive birefringence.

[0145] <Measurement> The following measurements were performed on each fabricated phase difference film (phase difference layer). Each measurement was performed by transferring each phase difference film to glass. The transfer method involved first bonding the coated side to the glass via an adhesive. Next, the PET support was peeled off. This created an optical object consisting of glass / phase difference layer / underlayment layer.

[0146] 《Measurement of Phase Difference and Axis Distribution》 Using a Nikon ECLIPSE LV100POL polarizing microscope, the phase difference and axis distribution (in-plane distribution of axis angles) were measured using the rotational compensator method (reference: Spectroscopic Ellipsometry, by Hiroyuki Fujiwara). For the phase difference, the in-plane phase difference Re and the phase difference Rth in the thickness direction were measured. For the axis distribution, the axis orientation was measured at multiple points in the plane in an evaluation system where the axis orientation is obtained as a value in the range of -90° to 90°, and the mean and standard deviation of these axis orientations were evaluated. Measurements were performed at 4.4 μm intervals in a 200 x 200 point (880 μm x 880 μm square) area. If the mean value of the axis orientation is in the range of -5° to 5°, and the standard deviation of the axis orientation is in the range of 45° to 55°, the axis angles are random, i.e., the axis distribution is random. Note that the above angles are defined as 90 degrees in the direction from the observer to the measuring instrument (depth direction), and 0 degrees in the direction perpendicular to that, to the right.

[0147] 《Domain Size Measurement》 Using a Nikon ECLIPSE LV100POL polarizing microscope, polarizers were set on both the light source and detector sides, and a phase difference film was placed between the two polarizers in a crossed nicol configuration. The phase difference film was then observed at 50x magnification. As an example of an image obtained using this method, an image of phase difference film B-1 is shown in Figure 6. The appearance of an irregular pattern of light and dark under the crossed nicol configuration indicates that the axes of the phase difference layer have a distribution within the plane (random axis distribution). A luminance profile on an arbitrary line in this image was extracted, and the autocorrelation coefficient of this luminance profile was calculated. The domain size was defined as three times the autocorrelation length, where the distance at which the autocorrelation coefficient is 0.5 is defined as the autocorrelation length.

[0148] Table 1 shows the measurement results for each phase difference film. Since a light / dark pattern was observed under crossed nicols, phase difference layers B-1 and B-2 had random axis orientations (distribution of slow phase axis orientations), and the average value of their azimuth angles was 0 degrees. Furthermore, phase difference layers B-1 and B-2 had domains. On the other hand, the azimuth angle of the slow phase axis of phase difference layer B-1, which had a liquid crystal layer formed on rubbing PET, was 45 degrees, and there were no domains. Also, since a light / dark pattern could not be observed under crossed nicols, phase difference layers A-1 and B-1 did not have a random axis distribution. Note that the angle of the slow phase axis was defined as 90 degrees in the direction from the observer to the measuring instrument (depth direction), and 0 degrees in the direction perpendicular to that to the right.

[0149]

[0150] <Fabrication of Image Display Device for Comparative Example 1> As the image display device 1, a commercially available Apple smartphone, the iPhone (registered trademark; hereinafter the same) 15, was used. Since the iPhone 15 emits approximately circularly polarized light, a polarizing plate was bonded to the front glass to emit linearly polarized light, and the image display device 1 of Comparative Example 1 was prepared without a polarizing film. The degree of polarization was evaluated using the following procedure. A Topcon Techno House SR-UL2 spectroradiometer was used as the spectroradiometer. A linearly polarizing plate was set on a rotating stage directly in front of the lens of the spectroradiometer, and the brightness was acquired at each angle while rotating it in 1-degree increments from 0 to 90°, and the maximum value Imax and minimum value Imin of the brightness were obtained. The degree of linear polarization was obtained using the following formula. Linear polarization degree = (Imax - Imin) / (Imax + Imin) × 100 [%] Next, a right circular polarizer and a left circular polarizer were sequentially set in front of the lens of the spectroradiometer. The brightness IR of the right circular polarization component obtained by setting the right circular polarizer so that only the right circular polarization component could be detected, and the brightness IL of the left circular polarization component obtained by setting the left circular polarizer so that only the left circular polarization component could be detected, were obtained. The circular polarization degree was obtained using the following formula: Circular polarization degree = |IR - IL| / (IR + IL) × 100 [%] Finally, the polarization degree was obtained using the following formula: Polarization degree = √(Linear polarization degree^2 + Circular polarization degree^2) This measurement confirmed that the light emitted from the image display device 1 had a linear polarization degree of 100% and a polarization degree of 100%.

[0151] <Fabrication of Image Display Device in Example 1> Next, the phase difference layer A-1 was bonded to the surface of the image display device 1 via an adhesive, and the degree of polarization was measured in the same manner as above. As a result, it was confirmed that the degree of polarization was 10%. This will be referred to as Example 1 when a depolarizing film is provided.

[0152] <Fabrication of Image Display Devices in Examples 2-6 and Comparative Example 2> The phase difference film to be laminated or transferred to the image display device 1 was changed to the configuration shown in Table 2. Here, phase difference layer A-1 was laminated, and after lamination, phase difference layers B-1, B-2 and phase difference layer-1 were peeled off the PET support.

[0153] 《Blackout Evaluation》 Visual evaluation of blackout was performed on the examples and comparative examples according to the following criteria. The results are shown in Table 2. This evaluation corresponds to the suitability of polarized sunglasses in Table 2. The evaluation was performed according to the following criteria: A: No blackout, no color unevenness, and no glare. B: No blackout, no color unevenness, but slight glare. C: No blackout, no color unevenness, but glare. D: No blackout, but color unevenness. E: Blackout occurs.

[0154] In Comparative Example 1, an image display device without an anti-polarization film, blackout occurred when observed through polarized sunglasses. On the other hand, in Examples 1 to 6, image display devices with an anti-polarization film, no blackout occurred. The image display unit of the iPhone 15 is an organic EL cell. Image display device 1 does not have a light sensor, but it has an image display unit, and by adding a polarizer and an anti-polarization film to it, it is possible to evaluate the degree of polarization of the displayed image. Since the presence or absence of a light sensor does not affect the degree of polarization of the displayed image, it is thought that the same evaluation results can be obtained even when using the image display device of the present invention which has a light sensor. Among these, Examples 2 to 6, which used phase difference layer B, were better because there was no color unevenness. Furthermore, Example 4, which used two types of phase difference layer B, was better because the degree of glare was reduced. Furthermore, it was found that glare was further improved and even more preferable by combining phase difference layer A with phase difference layer B to form an anti-polarization film.

[0155]

[0156] <Preparation of a glass laminate for fingerprint authentication evaluation in Example 1> To evaluate the feasibility of fingerprint authentication, a polarizing plate and phase difference layer A-1 were laminated to glass in that order. The side with phase difference layer A-1 was pressed against a finger, and a light was shone from the glass surface side to visually evaluate whether the fingerprint was visible. This is Example 1, which simulates the parts of an image display device such as a light sensor, polarizer, and depolarization film, and it is thought that the feasibility of detection by the light sensor can be determined by evaluating the feasibility of visibility by the eye. As a result, it was confirmed that the fingerprint was visible. Based on these results, it is considered that the image display device of the present invention, which has an image display unit, a light sensor, a polarizer, and a depolarization film (phase difference layer A-1), can detect reflected light from light hitting an object with the light sensor when light is shone from the image display unit.

[0157] 《Evaluation of Fingerprint Recognition Simulation Test》 Visual evaluation of the fingerprint recognition simulation test was performed on the example and comparative examples according to the following criteria. The results are shown in Table 2. A: Fingerprint is clearly visible and has high contrast. B: Fingerprint is clearly visible. C: Fingerprint is visible but somewhat unclear. D: Fingerprint is visible but unclear. E: Fingerprint is not visible.

[0158] In Comparative Example 2, an image display device having a quarter-wave plate on the viewing side of the polarizer, fingerprints could not be seen due to the anti-reflective effect of the polarizer and the quarter-wave plate. On the other hand, in Examples 1 to 6, which have a depolarizing film, fingerprints could be seen. The visibility of fingerprints was clearer in Examples 4 to 6, where the degree of polarization was lower.

[0159] Next, we will describe an example in which a phase difference layer B having a regular axial distribution is used as the depolarizing film.

[0160] <Fabrication of Phase Difference Layer B-11> (Formation of Alignment Film) A glass substrate was prepared as a support. The following alignment film forming coating solution 1 was applied to the glass substrate by spin coating. The support on which the alignment film forming coating solution 1 was applied was dried on a 60°C hot plate for 60 seconds to form an alignment film. The thickness of the alignment film was measured by optical interferometry (analysis using the least squares method with OPTM-A1 manufactured by Otsuka Electronics Co., Ltd.) and found to be 50 nm.

[0161] Coating liquid 1 for alignment film formation ―――――――――――――――――――――――――――――――― Photoalignment material A 4.00 parts by mass Water 48.00 parts by mass Butoxyethanol 24.00 parts by mass Propylene glycol monomethyl ether 24.00 parts by mass ――――――――――――――――――――――――――――――――

[0162] Photoalignment material A

[0163] (Exposure of alignment film) The alignment film was exposed using a multi-step exposure method (in this case, two-step exposure was used, which is irradiation with first polarized light (periodic intensity distribution) + irradiation with second polarized light (periodic intensity distribution)), to form an alignment film P-1 having an alignment pattern.

[0164] Specifically, as the first-step pattern exposure, the illuminance was 12 mW / cm ２ , and polarized UV light (wavelength: 365 nm) with an exposure dose of 50 mJ / cm ２ was irradiated from the alignment film side through a mask having an in-plane transmittance distribution. Polarized UV light with a wavelength of 365 nm was obtained by transmitting ultraviolet light emitted from a mercury lamp through a bandpass filter having a transmission band at 365 nm and a wire-grid polarizer. The mask having a transmittance distribution was produced by an etching method, and a mask for multi-step exposure having a transmittance distribution with a period of 115 μm was produced by changing the area ratio of transmission parts / light-shielding parts by dot density. The etching method was carried out in the following sequence: (1) sputtering chromium metal onto a glass substrate, (2) applying a resist photosensitive material, (3) drawing a dot pattern with an electron beam, (4) developing, (5) etching treatment. In this process, the grid direction of the wire-grid polarizer is taken as a reference (set as 0 degrees). At this time, linearly polarized light in the 90-degree direction is irradiated onto the glass.

[0165] As the second-step pattern exposure, the illuminance was 12 mW / cm ２ , and the exposure dose was 50 mJ / cm ２Polarized UV light (wavelength 365 nm) was irradiated from the alignment film side through a mask having a transmittance distribution in its plane. The 365 nm polarized UV light was obtained by transmitting ultraviolet light emitted from a mercury lamp through a bandpass filter with a transmission band at 365 nm and a wire grid polarizer. The mask with the transmittance distribution was the same mask used in the first stage of pattern exposure, and was positioned with a half-period shift relative to the sample in the periodic direction of the transmittance distribution. At this time, by setting the grid direction of the wire grid polarizer to 90 degrees, linearly polarized light in the 0-degree direction was irradiated onto the glass.

[0166] Through the two-stage exposure described above, an orientation film P-1 was formed in which the direction of the orientation restricting force changed triangularly from 0° to 90° to 0° along one direction in the plane. In other words, the direction of the orientation restricting force alternately rotated clockwise and counterclockwise with a rotation angle of 90°, and the rate of change of the rotation angle was constant. The period Λ was 115 μm. Note that the period Λ is the length along one direction in the region where the direction of the orientation restricting force rotates clockwise once and counterclockwise once.

[0167] (Formation of liquid crystal layer) A liquid crystal layer was formed on the alignment film P-1 to create a phase difference layer B-11. At this time, the liquid crystal layer was formed by dividing it into two regions in the thickness direction. These are referred to as the first region and the second region from the alignment film side.

[0168] <<Formation of the First Region>> The following phase difference layer coating solution 2 was prepared as a liquid crystal composition for forming the first region of the liquid crystal layer.

[0169] Coating solution for phase difference layer 2 -------------------------------------------------- Liquid crystal compound L-1 80.00 parts by mass Liquid crystal compound L-2 10.00 parts by mass Liquid crystal compound L-3 10.00 parts by mass Polymerization initiator P-1 1.00 parts by mass Leveling agent T-1 0.20 parts by mass Leveling agent T-2 0.10 parts by mass Chiral agent C-1 0.20 parts by mass Methyl ethyl ketone 345.00 parts by mass Cyclopentanone 345.00 parts by mass --------------------------------------------------

[0170] Liquid crystal compound L-1

[0171] Liquid crystal compound L-2

[0172] Liquid crystal compound L-3 (the number next to the structure represents mass %)

[0173] Photopolymerization initiator P-1

[0174] Leveling agent T-1

[0175] Leveling agent T-2

[0176] Chiral agent C-1

[0177] The phase difference layer coating solution 2 is applied to the alignment film P-1, the coating film is heated to 85°C on a hot plate, and then, under a nitrogen atmosphere, ultraviolet light with a wavelength of 365 nm is applied using a high-pressure mercury lamp at an irradiance of 10 mW / cm². ２ , irradiation amount 200mJ / cm ２ The orientation of the liquid crystal compound was fixed by irradiating the coating film under these conditions. In this way, the first region was formed.

[0178] The product of the refractive index difference and thickness of the cured layer of the phase difference layer coating liquid 2, Δn × d, was measured by applying the phase difference layer coating liquid 2 to a support with an alignment film prepared separately for retardation measurement, aligning the liquid crystal compound director so that it was horizontal to the substrate, and then fixing it by ultraviolet irradiation. The resulting liquid crystal fixed layer (cured layer) was then measured by performing field-of-view analysis at the target wavelength using an AxoScan from Axometrix.

[0179] In the first region of the liquid crystal layer of phase difference layer B-11, the liquid crystal Δn ５５０ ×d (=Re(550)) was 222.8 nm, and the torsion angle in the thickness direction of the liquid crystal compound in the first region was 63°. Furthermore, a striped pattern of light and dark areas was confirmed to be formed in a planar view using a polarizing microscope.

[0180] Unless otherwise specified, the following is 'Δn'. 550 Measurements such as 'thickness' were performed in the same manner.

[0181] <<Formation of the second region>> A phase difference layer coating solution 3 was prepared in the same manner as the phase difference layer coating solution 2, except that the following chiral agent C-2 was used instead of chiral agent C-1, and the content of the chiral agent was set to 0.343 parts by mass.

[0182] Apart from using the phase difference layer coating solution 3, a second region of the liquid crystal layer was formed on the first region in the same manner as the first region, thereby producing an optical film 1 having a liquid crystal layer consisting of the first region and the second region.

[0183] Chiral agent C-2

[0184] The second region is ultimately the Δn of the liquid crystal. 550 The thickness (=Re(550)) was 222.8 nm, and the torsion angle in the thickness direction of the liquid crystal compound was -63°. The linear retardation (phase difference) of the liquid crystal layer obtained by laminating the first and second regions was 275 nm.

[0185] Furthermore, the fabricated liquid crystal layer had a periodic pattern in which the optical axis of the liquid crystal compound alternately rotated clockwise and counterclockwise along one direction in the plane, with a rotation angle of 90° and a period Λ of 115 μm. In addition, the rate of change of the rotation angle was constant in both clockwise and counterclockwise rotations.

[0186] <Fabrication of Phase Difference Layers B-12 to B-13> Based on the fabrication method for Phase Difference Layer B-11, Phase Difference Layers B-12 to B-13 were fabricated by changing the period Λ of the liquid crystal layer's periodic pattern, rotation angle, rate of change of rotation angle, azimuth angle (unidirectional direction) in which the pattern changes, and phase difference. The characteristics of each Phase Difference Layer are shown in Table 3.

[0187] Here, phase difference layers B-12 and B-13 were exposed using a multi-stage exposure method ((i) two stages: irradiation with a first polarization (uniform intensity distribution) + irradiation with a second polarization (periodic intensity distribution)). In the second stage of mask exposure, the pattern of the transmittance mask and the amount of polarized UV irradiation were changed to adjust the period Λ of the periodic pattern of the liquid crystal layer, the rotation angle, and the rate of change of the rotation angle.

[0188] In the phase difference layer B-13, the rate of change of the rotation angle was adjusted so that the waveform in the graph between the angle of the optical axis of the liquid crystal compound and its position along one direction in the plane becomes a trapezoidal wave.

[0189] [Measurement] The following measurements were performed on each fabricated phase difference layer. Each measurement was performed by transferring each optical film to a PMMA (polymethyl methacrylate) film. The transfer method involved first applying an adhesive layer to the liquid crystal layer side of the optical film, and then bonding the coated side to the PMMA film via the adhesive. Next, the glass substrate and alignment film were peeled off. This created an optical object for optical property evaluation consisting of the optical film / adhesive / PMMA film.

[0190] <Measurement of Phase Difference and Period Λ of Periodic Pattern> Using a Nikon ECLIPSE LV100POL polarizing microscope, the phase difference and period Λ of the periodic pattern at a wavelength of 550 nm were measured using the rotational compensator method (reference: Spectroscopic Ellipsometry, by Hiroyuki Fujiwara). The in-plane phase difference Re was measured. The phase difference of phase difference layer B-11 was 275 nm. Of the various phase differences obtained here (total retardation, linear retardation, circular retardation), the value of linear retardation was adopted.

[0191] Measurements using a polarizing microscope confirmed that the periodic pattern in the liquid crystal layer of phase difference layer B-11 changes along one direction within the plane, with the optical axis originating from the liquid crystal compound alternating between clockwise and counterclockwise rotations. The length of one period (Λ) was 115 μm.

[0192] Similar measurements were performed on phase difference layers B-12 and B-13. The measurement results are shown in Table 3.

[0193] <Fabrication of phase difference layers B-14 to B-15>

[0194] Below, we describe a method for creating patterns where the rotation angle relative to the position is linear, specifically using the replica method. In the replica method, a master model with a pattern in which the slow axis orientation changes periodically is used as a mask.

[0195] <Fabrication of Master Molds 1 and 2> A glass substrate was prepared as the support. The following master mold alignment film forming coating solution was applied to the glass substrate by spin coating. The support with the alignment film forming coating solution applied was dried on a 60°C hot plate for 60 seconds to form the alignment film. The thickness of the alignment film was measured by optical interferometry (analysis using the least squares method with an OPTM-A1 manufactured by Otsuka Electronics Co., Ltd.) and was found to be 50 nm.

[0196] Coating solution for forming alignment film for master mold ---------------------------------------------------------------- Photo-alignment material A 4.00 parts by mass Water 48.00 parts by mass Butoxyethanol 24.00 parts by mass Propylene glycol monomethyl ether 24.00 parts by mass ----------------------------------------------------------------

[0197] Photo alignment material A

[0198]

[0199] (Exposure of the alignment film) An alignment film MP-1 having an alignment pattern was formed by exposing the alignment film using the interference exposure method shown in Figure 7. More specifically, the support 21 with the alignment film 22 formed by the above method was placed in the exposure section of the exposure apparatus, and the alignment film was exposed by irradiating it with interference light from two light rays 23 (one circularly polarized) and light ray 24 (circularly polarized opposite to light ray 23). In the exposure apparatus, a laser emitting laser light with a wavelength of 355 nm was used. The exposure amount to the alignment film 22 by interference light was 1000 mJ / cm². ２ This was done. At this time, a mirror and a polarizing beam splitter were placed in the optical path from the laser to the alignment film 22 so that the angle θ between the paths of the two light rays was 0.088 degrees, thereby forming an orientation-regulating force orientation distribution with a period of 230 μm on the alignment film 22. As a result, an alignment film MP-1 was formed having an orientation pattern in which the orientation state changes periodically with a period of 230 μm.

[0200] (Formation of liquid crystal layer) A liquid crystal layer was formed on the alignment film MP-1 using the phase difference layer coating solution 1, following the same process as described above for the phase difference layer B-1. Finally, the Δn of the liquid crystal was formed. 550 The thickness (=Re(550)) was 82 nm, and the twist angle in the thickness direction of the liquid crystal compound was 0°. Δn at a wavelength of 550 nm 550 ×By setting the thickness to this value, the Δn at a light source wavelength of 313 nm, which will be used later in the replica method, is determined from the wavelength dispersion characteristics of the liquid crystal material. 313The goal was to achieve a thickness of 156.5 nm (HWP characteristics at a wavelength of 313 nm). A film with a slight adhesive (support) was bonded to this liquid crystal layer, and then peeled off again to detach the liquid crystal layer from the glass. At this time, the detachment interface was the interface between the liquid crystal layer and the photoalignment film. Next, the adhesive was bonded to the liquid crystal layer side of the detached liquid crystal layer / slight adhesive / support, and this adhesive side was bonded to a glass plate (Corning Eagle XG, t1.1) that is transparent in the ultraviolet region. Finally, by peeling off the slight adhesive / support, a master type 1 with a period of 230 μm consisting of glass / adhesive / liquid crystal layer was fabricated. Using a similar method, a master type 2 with a period of 190 μm was fabricated by changing the exposure optical system so that the angle θ between the paths of the two light rays during interference exposure was 0.107 degrees.

[0201] <Fabrication of phase difference layers B-14 and B-15>

[0202] (Formation of alignment film P-14) A photo-alignment film forming solution E2 with the following composition was continuously applied to one side of the cellulose acylate film using a wire bar. The support with the formed coating was dried with 134°C hot air for 75 seconds. Subsequently, the aforementioned master mold 1 was placed on the coating and polarized ultraviolet irradiation (8 mJ / cm²) was applied. ２ An orientation film P-14 was formed by using an ultra-high pressure mercury lamp. The thickness of the orientation film P-14 was 0.8 μm. By irradiating the master mold with light having a uniform polarization direction in the plane, the transmitted light changes to a state in which the polarization direction changes periodically in the plane. This period is half the period of the master mold. As a result, an orientation film P-14 was formed having an orientation pattern in which the orientation state changes periodically with a period of 115 μm.

[0203] ------------------------------------------------------------------- Photo-alignment film forming coating solution E2 ------------------------------------------------------------------- ・100.00 parts by mass of the polymer PA-1 below ・6.00 parts by mass of the acid generator PAG-1 below ・0.60 parts by mass of diisopropylethylamine ・625.4 parts by mass of butyl acetate ・156.3 parts by mass of methyl ethyl ketone -------------------------------------------------------------------

[0204] Polymer PA-1 [In the formula below, the numerical values ​​listed for each repeating unit represent the content (mass%) of each repeating unit relative to the total number of repeating units. Weight-average molecular weight: 45,000]

[0205] Acid Generator PAG-1

[0206] (Formation of liquid crystal layer) Phase difference layer B-14 was fabricated using the same method as for forming the liquid crystal layer in phase difference layer B-11. Similar to phase difference layer B-11, a striped liquid crystal alignment pattern with a period of 115 μm was confirmed to be formed in a planar view using a polarizing microscope.

[0207] <Fabrication of Phase Difference Layer B-15> Except for changing the master mold used to master mold 2 (period 190 μm), phase difference layer B-15 was fabricated using the same method as phase difference layer B-14.

[0208] [Measurement] For the fabricated phase difference layers B-14 and B-15, the phase difference and the period of one period Λ of the periodic pattern were measured using the same method as for phase difference layer B-11. Measurements using a polarizing microscope confirmed that the periodic pattern in the liquid crystal layer of phase difference layer B-14 changed linearly with a clockwise rotation along one direction in the plane, with the optical axis originating from the liquid crystal compound. The length of one period (Λ) of phase difference layer B-14 was 115 μm. The length of one period (Λ) of phase difference layer B-15 was 95 μm. These measurement results are shown in Table 3.

[0209]

[0210] [Evaluation] For phase difference layers B-11 to B-15, image display devices and glass laminated products for fingerprint authentication evaluation were fabricated in the same manner as for phase difference layer A-1, and evaluations of polarization degree, suitability for polarized sunglasses, and fingerprint detection simulation tests were conducted. The results are shown in Table 4. Both suitability for polarized sunglasses and fingerprint detection performance were good.

[0211]

[0212] 1 Polarization-depolarizing film 2 Polarizer 3 Light sensor 4 Image display unit 5 Phase difference layer A 6 Phase difference layer B 11 Phase difference layer B with random axis distribution 12 Domain boundary of phase difference layer B with random axis distribution 13 Slow axis 21 Support 22 Alignment film 23, 24 Light rays 31 First phase difference layer B 32 Second phase difference layer B 33 Adhesive layer 100 Image display device

Claims

1. An image display device comprising an image display unit, a light sensor for detecting visible light, a polarizer, and a depolarizing film, wherein the light sensor, the polarizer, and the depolarizing film are arranged in this order, and the depolarizing film is positioned on the viewing side of the polarizer.

2. The image display device according to claim 1, wherein the depolarizing film has a phase difference layer A, and the in-plane retardation of the phase difference layer A at a wavelength of 550 nm is from 3,000 nm to 100,000 nm.

3. The image display device according to claim 1, wherein the depolarizing film has a phase difference layer B, and the phase difference layer B has a slow axis distribution or a phase difference distribution in its plane.

4. The image display device according to claim 1, wherein the depolarization film has a phase difference layer A and a phase difference layer B, the in-plane retardation of the phase difference layer A at a wavelength of 550 nm is from 3,000 nm to 100,000 nm, and the phase difference layer B has an in-plane distribution of slow axis orientation or a phase difference distribution.

5. The image display device according to claim 3 or 4, wherein the phase difference layer B is a layer formed using a liquid crystal compound.

6. The image display device according to claim 3 or 4, wherein the slow axis distribution is a random slow axis distribution.

7. The image display device according to claim 6, wherein when the domain size of the phase difference layer B is defined as the autocorrelation length × 3, the domain size is 32 μm or less.

8. The image display device according to any one of claims 1 to 4, wherein the image display unit is an organic EL cell.

9. The image display device according to claim 8, wherein the light sensor is located between the pixels of the organic EL cell.

10. The image display device according to claim 9, wherein the light sensor is an organic photodetector.

Images