TW202403363A - Circular polarizing plate and image display device including a polarizer, a retardation layer, and a liquid crystal alignment film - Google Patents

Abstract

A circular polarizing plate (10) is arranged on a viewing side of an image display unit such as an organic EL unit (70), and is used as an anti-reflection device for image display devices with flexible parts. The circular polarizing plate includes a polarizer (11) and a retardation layer (13) laminated on one surface of the polarizer. The retardation layer (13) is a laminate of two or more retardation layers (131, 132) and has a thickness of 20 [mu]m or less. The circular polarizing plate includes one or less layer of a liquid crystal alignment film. The retardation layer (13) includes a first retardation layer having a refractive index anisotropy of nx>ny≥nz and a second retardation layer having a refractive index anisotropy of nz>nx≥ny.

Description

Circular polarizing plate and image display device

The present invention relates to circular polarizing plates and image display devices.

Flat panel displays such as liquid crystal display devices and organic EL display devices are used in display devices such as mobile phones, smartphones, navigation devices, personal computer monitors, and televisions. In recent years, organic EL elements using bendable substrates (flexible substrates) such as resin films have been put into practical use, and foldable displays have been developed.

An organic EL display device using an organic EL element as a display body disposes a circular polarizing plate on the viewing side surface of the organic EL element (organic EL unit) to prevent light reflected by metal electrodes, etc. from being re-emitted and viewed (for example, Refer to patent document 1).

In a foldable display, in addition to the foldability of the organic EL element, the circular polarizing plate disposed on the surface of the foldable display is also required to have excellent bending properties. Therefore, it is necessary to reduce the thickness of the circular polarizing plate. In order to reduce the thickness of the circular polarizing plate, it is necessary to reduce the thickness of the polarizer, retardation layer, polarizer protective film, adhesive layer and other components that constitute the circular polarizing plate. As the retardation layer, liquid crystal is widely used An oriented liquid crystal layer formed by orienting materials in a predetermined direction. existing technical documents patent documents

Patent document 1: Japanese Patent Application Publication No. 2015-163938

The problem to be solved by the invention In a foldable display, since the foldable display repeatedly bends at the same position, breakage or cracks are likely to occur in the constituent members at the bent portion. A circular polarizing plate having an oriented liquid crystal layer as a retardation layer has a small thickness and excellent bending properties, but has the problem that breakage or cracks easily occur in the bent portion. In view of this problem, the object of the present invention is to provide a circular polarizing plate that, when used in an image display device with a flexible portion such as a foldable display, is less prone to cracks in the flexed portion and is resistant to deflection. Excellent performance.

Means used to solve problems The present invention relates to an image display device with a flexible portion and a circular polarizing plate used for anti-reflection thereof. The circular polarizing plate can also be provided in the form of a circular polarizing plate with an adhesive layer attached to the surface on the side of the retardation layer.

The circularly polarizing plate has a polarizer and a phase difference layer attached to one surface of the polarizer. The retardation layer is a laminate of two or more retardation layers, and the thickness is 20 μm or less. The liquid crystal alignment film contained in the circularly polarizing plate is less than 1 layer. Circular polarizing plates may also contain no liquid crystal alignment film.

In one embodiment, the retardation layer of the circular polarizing plate includes a first retardation layer with a refractive index anisotropy of nx>ny≥nz and a second retardation layer with a refractive index anisotropy of nz>nx≥ny. layer. nx is the refractive index in the slow axis direction of the plane, ny is the refractive index in the fast axis direction of the plane, and nz is the refractive index in the thickness direction.

The arrangement of the first retardation layer and the second retardation layer is not particularly limited. In one embodiment, the first retardation layer and the aforementioned second retardation layer are arranged in order from the polarizer side.

At least one of the first phase difference layer and the second phase difference layer is preferably a directional liquid crystal layer. Both the first retardation layer and the second retardation layer may be oriented liquid crystal layers. The alignment liquid crystal layer may be formed without using a liquid crystal alignment film.

In one embodiment, the first retardation layer is an oriented liquid crystal layer in which liquid crystal compounds are oriented along the surface. The second retardation layer may also be an oriented liquid crystal layer in which liquid crystal compounds are vertically aligned, or a film composed of a non-liquid crystalline resin with negative intrinsic birefringence and a thickness of 10 μm or less.

Invention effect Since the thickness of the retardation layer of the present invention is small and the liquid crystal alignment film is one layer or does not contain a liquid crystal alignment film, the circularly polarizing plate of the present invention has excellent flexibility resistance and can also be used in image display devices with flexible parts.

The image display device of the present invention has a flexible part. An example of a display device having a flexible portion is a foldable display.

FIG. 1 is a cross-sectional view of a circularly polarizing plate according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of a circularly polarizing plate having an adhesive layer 21 on one surface of the circularly polarizing plate 10 . 3 is a cross-sectional view of an image display device according to an embodiment of the present invention, showing an organic EL display device in which a circular polarizing plate 10 is bonded to the light capture surface of an organic EL element 70 (organic EL unit) through an adhesive layer 21 .

The organic EL unit 70 may be a top emission type or a bottom emission type. A top-emitting organic EL unit is composed of a metal electrode, an organic light-emitting layer, and a transparent electrode in order on a substrate, and captures light from the surface opposite to the substrate. The bottom-emitting organic EL unit is composed of a transparent electrode, an organic light-emitting layer, and a metal electrode in order on a substrate, and captures light from the surface of the substrate.

As the substrate of the organic EL unit, a glass substrate or a plastic substrate is used. A flexible plastic substrate can be suitably used as the substrate in a foldable display.

In a top-emitting organic EL unit, the substrate does not have to be transparent, and a highly heat-resistant film such as a polyimide film can also be used as the substrate. In addition to the organic layer that functions as a light-emitting layer, the organic light-emitting layer may also have an electron transport layer, a hole transport layer, and the like. The transparent electrode is a metal oxide layer or metal film used to transmit light from the organic light-emitting layer.

The metal electrode of the organic EL unit is light reflective. Therefore, when external light is incident into the interior of the organic EL unit, the light will be reflected on the metal electrode, and the reflected light will be visible from the outside like a mirror. By arranging the circular polarizing plate 10 on the viewing side surface of the organic EL unit 70, the light reflected by the metal electrode can be prevented from being re-emitted to the outside, thereby improving the visibility and design of the screen.

[Circular polarizing plate] The circularly polarizing plate 10 includes a retardation layer 13 laminated on one surface of the polarizer 11 . A transparent film 15 can also be bonded on the other surface of the polarizer 11 . The circularly polarizing plate 10 is arranged so that the surface on the retardation layer 13 side faces the organic EL unit 70 . The polarizer 11 and the retardation layer 13 are preferably bonded together through an appropriate adhesive or adhesive. An appropriate transparent protective film may also be disposed between the polarizer 11 and the retardation layer 13 .

The phase difference layer 13 includes two or more phase difference layers. As described in detail later, by stacking a plurality of retardation layers, the three-dimensional refractive index anisotropy of the retardation layer can be adjusted, thereby reducing retardation changes caused by viewing angles. In addition, by stacking a plurality of retardation layers, the wavelength dispersion of the retardation of the retardation layer 13 can be adjusted, and the circular polarizing plate can be broadened to a wider frequency range.

The thickness of the retardation layer 13 is 20 μm or less. The thickness of the retardation layer 13 is the total thickness of each of the plurality of retardation layers and the thickness of the adhesive layer bonded between the respective layers. Since the thickness of the retardation layer 13 is small and the thickness of the circular polarizing plate 10 is also small, the bending property of the flexible portion of the image display device is excellent. The thickness of the retardation layer 13 is preferably 15 μm or less, more preferably 10 μm or less. In order to keep the thickness of two or more retardation layers laminated within the above range, it is preferable that at least one of the plurality of retardation layers 131 and 132 constituting the retardation layer 13 be an oriented liquid crystal layer, and it is preferable that all the retardation layers be oriented. Liquid crystal layer.

The circular polarizing plate 10 contains less than one layer of liquid crystal alignment film. In addition to the small thickness of the retardation layer 13 as mentioned above, because the circular polarizing plate 10 contains one layer of liquid crystal alignment film or the circular polarizing plate 10 does not contain a liquid crystal alignment film, the circular polarizing plate has excellent flexibility resistance. .

An oriented liquid crystal layer in which a liquid crystal compound is oriented in a predetermined direction is usually formed by coating a composition containing a liquid crystal compound on a substrate provided with a liquid crystal alignment film and orienting the liquid crystal compound. When the liquid crystal alignment layer is peeled off from the substrate, peeling usually occurs at the interface between the liquid crystal alignment film and the substrate because the liquid crystal alignment film and the alignment liquid crystal layer are firmly adhered to each other. In cases where a liquid crystal alignment film is attached to the alignment liquid crystal layer condition.

When this oriented liquid crystal layer is used for the retardation layer 13, the circularly polarizing plate 10 includes an oriented liquid crystal film. When the retardation layer 13 is a stacked structure of a plurality of oriented liquid crystal layers, since the retardation layer 13 may include a plurality of liquid crystal oriented films, the circular polarizing plate will include a plurality of liquid crystal oriented films. When the circularly polarizing plate contains a liquid crystal alignment film, the liquid crystal alignment film tends to be easily broken or cracked at the bending portion of the image display device, resulting in reduced flexibility resistance. In particular, when the circularly polarizing plate contains a plurality of liquid crystal alignment films, the occurrence of fractures or cracks at the bending position becomes obvious. As mentioned above, by including one layer of liquid crystal alignment film in the circular polarizing plate 10 or by not including the liquid crystal alignment film in the circular polarizing plate 10 , the bending resistance of the circular polarizing plate due to breakage or cracks in the liquid crystal alignment film can be suppressed. Sexuality is reduced. From the viewpoint of improving flexibility resistance, it is particularly preferable that the circularly polarizing plate 10 does not contain a liquid crystal alignment film.

The thickness of the circularly polarizing plate 10 , that is, the total thickness of the polarizer 11 , the retardation layer 13 , the transparent film 15 , and the adhesive layer (not shown) used to bond these layers is preferably 80 μm or less. The thickness of the circularly polarizing plate 10 is preferably 70 μm or less, more preferably 60 μm or less, and may also be 55 μm or less. Since the circular polarizing plate has a small thickness, it tends to have excellent bending properties and resistance to bending at the bends of the image display device. The thickness of the circular polarizing plate 10 may be above 30 μm, above 40 μm, or above 45 μm.

＜Polarizer＞ Examples of the polarizer 11 include hydrophilic polymer films such as polyvinyl alcohol-based films, partially formalized polyvinyl alcohol-based films, and ethylene-vinyl acetate copolymer-based partially saponified films that adsorb iodine or dichroic dyes. and other dichroic substances and uniaxially stretched; polyene-based oriented films such as dehydrated products of polyvinyl alcohol or dehydrochloric acid-treated products of polyvinyl chloride, etc. Among them, a polarizer obtained by adsorbing iodine on a polyvinyl alcohol-based film is preferred because it can achieve a high degree of polarization.

In the manufacturing steps of polarizers, water washing, swelling, cross-linking and other treatments may also be carried out as needed. Extension can be performed at any time before or after iodine staining, or it can be extended while dyeing. The stretching may be either stretching in the air (dry stretching) or stretching in water or in an aqueous solution containing boric acid, potassium iodide, etc. (wet stretching), or a combination of these may be used.

The thickness of the polarizer 11 is not particularly limited, and is generally about 1 to 50 μm. From the viewpoint of reducing the thickness of the circularly polarizing plate 10 , the thickness of the polarizer 11 is preferably 30 μm or less, more preferably 20 μm or less, and more preferably 15 μm or less. The polarizer 11 may be a thin polarizer with a thickness of 10 μm or less. The thickness of the polarizer 11 can also be 3~10 μm or 4~8 μm.

Examples of thin polarizers with a thickness of 10 μm or less include Japanese Patent Application Laid-Open No. Sho 51-069644, Japanese Patent Application Laid-Open No. 2000-338329, WO2010/100917, Japanese Patent No. 4691205, and Japanese Patent No. 4751481. No., the polarizing element described in Japanese Patent Application Laid-Open No. 2012-73580. A thin polarizing element can be obtained, for example, by iodine dyeing and stretching a laminate in which a polyvinyl alcohol-based resin layer is formed on a stretching resin base material. In this production method, even if the polyvinyl alcohol-based resin layer is thin, it can be stretched without problems such as breakage due to stretching since it is supported by the resin base material for stretching.

＜Phase difference layer＞ As described above, the circularly polarizing plate 10 is configured by disposing the retardation layer 13 on one surface of the polarizer 11 .

The phase difference layer 13 is a 1/4 wavelength plate (λ/4 plate). The front retardation R (550) at a wavelength of 550nm is preferably 100~180nm, more preferably 110~170nm, more preferably 120~150nm, or it can be is 125~145nm. The angle formed by the slow axis direction of the phase difference layer 13 and the absorption axis direction of the polarizer 11 is 10° to 90°, preferably 40° to 50°, and may also be 43° to 47° or 44° to 46°.

The retardation layer 13 has a laminated structure of two or more retardation layers. The retardation layer 13 as the laminated body has the above-mentioned front retardation and arrangement angle. The laminated body of the polarizer 11 and the retardation layer 13 serves as a circular polarizing plate. Function.

In the circularly polarizing plate 10 shown in FIG. 1 , the retardation layer 13 has two layers: a first retardation layer 131 disposed on the side close to the polarizer 11 and a second retardation layer 132 disposed on the side away from the polarizer 11 . . In one embodiment, among the first phase difference layer 131 and the second phase difference layer 132, one of the phase difference layers has a refractive index anisotropy of nx>ny≥nz, and the other phase difference layer has a refractive index anisotropy of nz>nx≥ny. The refractive index anisotropy. nx is the refractive index in the slow axis direction of the plane, ny is the refractive index in the fast axis direction of the plane, and nz is the refractive index in the thickness direction.

By stacking a plurality of phase difference layers with different refractive index anisotropies, the three-dimensional refractive index anisotropy can be adjusted and the retardation changes caused by the viewing angle can be reduced. In the case of a positive C plate in which the retardation layer 131 has a refractive index anisotropy of nx>ny≥nz and the retardation layer 132 has a refractive index anisotropy of nz>nx≒ny, the retardation layer 132 has a negative thickness. The direction is blocked, so the oblique phase difference of the phase difference layer 131 will be eliminated by the phase difference layer 132 . Therefore, the retardation layer 13 which is a laminate of the retardation layer 131 and the retardation layer 132 has a refractive index anisotropy of nx>nz>ny, and the retardation change due to the viewing angle is small. Even oblique reflected light can be reduced. In the case of a negative B plate in which the retardation layer 132 has a refractive index anisotropy of nz>nx>ny, the retardation layer 132 has negative thickness direction retardation, so the oblique phase difference of the retardation layer 131 can be eliminated. , which can reduce the obstruction changes caused by the visual angle.

As mentioned above, the thickness of the retardation layer 13 is 20 μm or less, preferably 15 μm or less, more preferably 10 μm or less. From the viewpoint of handleability and retardation visibility, the thickness of the retardation layer 13 is preferably 3 μm or more, and may be 5 μm or more or 8 μm or more. The total light transmittance of the phase difference layer 13 is preferably above 80%, more preferably above 85%, and more preferably above 90%.

As described above, by reducing the thickness of the retardation layer 13 in which a plurality of retardation layers 131 and 132 are laminated, the thickness of the circular polarizing plate 10 can be reduced. In order to reduce the thickness of the retardation layer 13, it is preferable to reduce the thickness of each retardation layer constituting the retardation layer 13, that is, the first retardation layer 131 and the second retardation layer 132. The thickness of each of the first phase difference layer 131 and the second phase difference layer 132 is preferably 10 μm or less, and may be 8 μm or less or 5 μm or less.

If each of the first retardation layer 131 and the second retardation layer 132 constituting the retardation layer 13 is an oriented liquid crystal layer, the thickness can be small and the retardation layer 13 can have required retardation characteristics. The oriented liquid crystal layer with refractive index anisotropy, which is oriented in a predetermined direction by the liquid crystal compound, has large birefringence, so the required retardation can be displayed with a small thickness. For example, if a homogeneous orientation liquid crystal layer with a refractive index anisotropy of nx>ny≒nz is used as the first phase difference layer 131, and a refractive index with nz>nx≒ny is used as the second phase difference layer 132, The anisotropic vertically aligned liquid crystal layer can form a retardation layer with a small thickness.

However, when the first retardation layer 131 is a creeping alignment liquid crystal layer having a liquid crystal alignment film, and the second retardation layer 132 is a homeotropic alignment liquid crystal layer having an alignment liquid crystal film, the circular polarizing plate will contain a plurality of liquid crystal alignment films. film, and the flex resistance is reduced. In order to improve the flexibility resistance of the circularly polarizing plate 10, it is preferable that the first retardation layer 131 and the second retardation layer 132 are oriented liquid crystal layers, and one or both of them are oriented liquid crystal layers formed without using a liquid crystal oriented film. , or either one of the first retardation layer 131 and the second retardation layer 132 is a thin film made of a non-liquid crystalline resin material.

Hereinafter, the first retardation layer 131 disposed on the side close to the polarizer 11 has a refractive index anisotropy of nx>ny≥nz, and the second retardation layer 132 disposed on the side far from the polarizer 11 has a refractive index anisotropy of nz>nx. The structure of the refractive index anisotropy of ≥ny will be explained by taking specific examples of the first retardation layer 131 and the second retardation layer 132 respectively. In addition, the circularly polarizing plate of the present invention is not limited to the following example. A phase difference layer with refractive index anisotropy of nz>nx≥ny can also be disposed on the side close to the polarizer 11, and a retardation layer with nx can be disposed on the side away from the polarizer 11. > retardation layer with refractive index anisotropy of ny≥nz. In addition, the phase difference layer 13 may include three or more phase difference layers.

<First phase difference layer> Examples of the retardation layer having a refractive index anisotropy of nx>ny≥nz include a positive A plate having a refractive index anisotropy of nx>ny≒nz and a refractive index anisotropy of nx>ny>nz. The negative B plate.

Examples of the first retardation layer 131 include an aligned liquid crystal layer in which a liquid crystal compound is aligned along the surface, or a thin film of a non-liquid crystalline resin material (polymer) having positive intrinsic birefringence.

A polymer with positive intrinsic birefringence refers to a polymer whose refractive index in the direction of orientation increases relatively when the polymer is oriented by stretching or the like. Examples of the polymer having positive intrinsic birefringence include polycarbonate resins, polyester resins such as polyethylene terephthalate or polyethylene naphthalate, polyarylate resins, and polyester resins. Polyurethane, polyether sulfide and other sulfide-based resins, polyphenylene sulfide and other sulfide-based resins, polyimide-based resins, cyclic polyolefin-based (polynorphenyl-based) resins, polyamide resins, polyethylene or polyamide resins Polyolefin resins such as propylene, cellulose esters, etc.

The first phase difference layer 131 is preferably a 1/4 wavelength plate, and the front-side retardation R(550) at a wavelength of 550nm is preferably 100~180nm, more preferably 110~170nm, more preferably 120~150nm, or 125~ 145nm. In addition, when the second retardation layer 132 is a positive B plate with refractive index anisotropy of nz>nx>ny, the front retardation of the first retardation layer 131 is adjusted so that the retardation layer 131 and the retardation layer 132 The front retardation of the retardation layer 13 of the laminated body only needs to be within the above range.

The first retardation layer 131 may also have a characteristic that the longer the wavelength, the greater the blocking (so-called “reverse wavelength dispersion”). When the first retardation layer 131 has reverse wavelength dispersion, in the wide wavelength range of visible light, since the difference between the front-side retardation of the retardation layer and 1/4 wavelength is small, the circular polarizing plate will be widened in frequency range, and can be realized Excellent anti-reflective properties.

The ratio Re(450)/Re(550) of the front-side retardation Re(450) at a wavelength of 450 nm and the front-side retardation Re(550) at a wavelength of 550 nm of the retardation layer with reverse wavelength dispersion characteristics is less than 1. Re(450)/Re(550) is preferably 0.65~0.99, more preferably 0.70~0.95, more preferably 0.75~0.90, or 0.80~0.85.

As mentioned above, the first phase difference layer 131 may be a thin film of non-liquid crystalline resin or a directional liquid crystal layer. However, from the viewpoint of having a small thickness, that is, having front retardation of 1/4 wavelength, the first phase difference layer 131 is preferably The difference layer 131 is a surface-aligned liquid crystal layer. The surface-aligned liquid crystal layer is formed, for example, by coating a liquid crystal composition containing a liquid crystal compound on a support substrate, aligning the liquid crystal compound along the surface, and then fixing the alignment state.

Examples of liquid crystal compounds include rod-shaped liquid crystal compounds, disk-shaped liquid crystal compounds, and the like. The liquid crystal compound is preferably a rod-shaped liquid crystal compound because it is easily oriented along the plane due to the orientation control force of the supporting substrate. The rod-shaped liquid crystal compound can be a main chain liquid crystal or a side chain liquid crystal. The rod-shaped liquid crystal compound may be a liquid crystal polymer or a polymer of a polymerizable liquid crystal compound. If the liquid crystal compound (monomer) exhibits liquid crystallinity before polymerization, it may not exhibit liquid crystallinity after polymerization.

The liquid crystal compound is preferably a thermotropic liquid crystal that exhibits liquid crystallinity by heating. Thermotropic liquid crystals undergo phase transitions between crystalline phase, liquid crystal phase, and isotropic phase as temperature changes. Examples of rod-shaped liquid crystal compounds showing thermotropic properties include methine azo compounds, oxy azo compounds, cyanobiphenyl compounds, cyanophenyl esters, benzoate esters, and cyclohexanecarboxylic acid. Phenyl esters, cyanophenylcyclohexane, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldiodesanes, diphenylethynes, alkenylcyclohexylbenzonitriles wait.

Examples of the polymerizable liquid crystal compound include a polymerizable liquid crystal compound that can fix the alignment state of a rod-shaped liquid crystal compound using a polymer binder, and a polymerizable liquid crystal compound that has a polymerizable functional group that can fix the alignment state of the liquid crystal compound by polymerization. Compounds etc. Among them, a photopolymerizable liquid crystal compound having a photopolymerizable functional group is preferred.

The photopolymerizable liquid crystal compound (liquid crystal monomer) has a mesogen group and at least one photopolymerizable functional group in one molecule. The temperature at which the liquid crystal monomer exhibits liquid crystallinity (liquid crystal phase transition temperature) is preferably 40 to 200°C, more preferably 50 to 150°C, and more preferably 55 to 100°C.

Examples of the mesogen group of the liquid crystal monomer include a biphenyl group, a phenyl benzoate group, a phenylcyclohexyl group, an oxyazophenyl group, a methine azo group, and an azophenyl group. Phenylpyrimidinyl, diphenylethynyl, diphenylbenzoate, dicyclohexyl, cyclohexylphenyl, terphenyl and other cyclic structures. The terminals of these cyclic units may also have substituents such as cyano group, alkyl group, alkoxy group, and halogen group.

Examples of photopolymerizable functional groups include (meth)acrylyl groups, epoxy groups, vinyl ether groups, and the like. Among them, a (meth)acrylyl group is preferred. The photopolymerizable liquid crystal monomer preferably has two or more photopolymerizable functional groups in one molecule. By using a liquid crystal monomer containing two or more photopolymerizable functional groups, a cross-linked structure is introduced into the liquid crystal layer after photocuring, thereby tending to improve the durability of the aligned liquid crystal layer.

As the photopolymerizable liquid crystal monomer, any appropriate liquid crystal monomer can be used. Examples include International Publication No. 00/37585, U.S. Patent No. 5211877, U.S. Patent No. 4388453, International Publication No. 93/22397, European Patent No. 0261712, German Patent No. 19504224, German Patent No. 4408171, British Patent No. 2280445, Japanese Patent Publication No. 2017-206460, International Publication No. 2014/126113, International Publication No. 2016/114348, International Publication No. 2014/010325, Japanese Patent Publication No. 2015-200877, Japanese Patent Application Publication No. 2010-31223, International Publication No. 2011/050896, Japanese Patent Application Publication No. 2011-207765, Japanese Patent Application Publication No. 2010-31223, Japanese Patent Application Publication No. 2010-270108, International Publication No. Compounds described in Japanese Patent Application Publication No. 2008/119427, Japanese Patent Application Publication No. 2008-107767, Japanese Patent Application Publication No. 2008-273925, International Publication No. 2016/125839, Japanese Patent Application Publication No. 2008-273925, etc. By selecting the liquid crystal monomer, the development of birefringence or the wavelength dispersion of retardation can also be adjusted.

The liquid crystal composition is prepared by mixing the liquid crystal monomer and various orientation control agents, polymerization initiators, leveling agents, etc. with a solvent, and then coating the liquid crystal composition on a support substrate to orient the liquid crystal compound, thereby forming an aligned liquid crystal layer. By using a flexible film as a support substrate, a series of steps from coating the liquid crystal composition on the support substrate to photohardening of the liquid crystal monomer and subsequent heat treatment can be implemented in a roll-to-roll manner, thus improving the Productivity.

The supporting substrate may also have an orientation energy for orienting the liquid crystal compound in a predetermined direction. For example, by using a stretched film as a supporting substrate, the liquid crystal compound can be aligned along its extending direction. The elongation of the stretched film is sufficient as long as the directional energy can be exerted, for example, about 1.1 times to 5 times. The stretched film may also be a biaxially stretched film. Even if it is a biaxially stretched film, if the stretching ratio in the longitudinal direction and the transverse direction are different, the liquid crystal compound can be oriented in the direction with a large stretching ratio. The stretched film may also be an obliquely stretched film. By using an obliquely stretched film as a support substrate, the liquid crystal compound can be oriented in a direction that is not parallel to either the longitudinal direction or the width direction of the support substrate.

The support substrate may also have an alignment film on the surface where the alignment liquid crystal layer is to be formed. The orientation film can be appropriately selected according to the type of liquid crystal compound or the material of the supporting substrate. As the alignment film for orienting the liquid crystal compound along the surface in a predetermined direction, it is preferable to use a polyimide-based or polyvinyl alcohol-based alignment film that has been rubbed. In addition, a light alignment film can also be used. Instead of providing an alignment film, the resin film serving as the supporting substrate may be subjected to rubbing treatment.

When the liquid crystal compound is thermotropic liquid crystal, the liquid crystal composition is coated on the support substrate and heated to orient the liquid crystal compound in a liquid crystal state. The liquid crystal composition layer formed on the support substrate is heated to form a liquid crystal phase, whereby the liquid crystal compound is oriented. Specifically, after the liquid crystal composition is coated on the support substrate, the liquid crystal composition is heated to a temperature higher than the N (nematic phase) - I (isotropic liquid phase) phase transition temperature of the liquid crystal composition, so that the liquid crystal composition becomes isotropic. liquid state. Then, if necessary, it is slowly cooled to allow the nematic phase to appear. At this time, it is preferable to temporarily maintain the temperature at which the liquid crystal phase appears so that the liquid crystal phase region grows and becomes a single domain (mono-domain). Alternatively, the liquid crystal composition may be coated on the support substrate and then maintained at a temperature within a temperature range in which the nematic phase appears for a certain period of time to orient the liquid crystal compound in a predetermined direction.

The heating temperature when orienting the liquid crystal compound in a predetermined direction can be appropriately selected according to the type of the liquid crystal composition, and is usually about 40 to 200°C. When the heating temperature is too low, there is a tendency for the phase transition to liquid crystal phase to become insufficient; when the heating temperature is too high, orientation defects may increase. The heating time can be adjusted to allow the liquid crystal phase region to fully grow, usually about 30 seconds to 30 minutes.

After the liquid crystal compound is oriented by heating, it is preferable to cool it to a temperature below the glass transition temperature. The cooling method is not particularly limited. For example, it may be taken out from a heated gas environment to room temperature. Forced cooling such as air cooling and water cooling can also be performed.

By irradiating the liquid crystal layer with light, the photopolymerizable liquid crystal compound (liquid crystal monomer) is photocured in a state having liquid crystal regularity. It is sufficient to irradiate light to polymerize the photopolymerizable liquid crystal compound, and usually ultraviolet light or visible light with a wavelength of 250 to 450 nm is used. When the liquid crystal composition is photocured, the liquid crystal compound can also be oriented in a predetermined direction by using polarized light in a predetermined direction. As mentioned above, when the liquid crystal compound is oriented by the orientation control force of the supporting substrate, the irradiating light may also be non-polarized light (natural light).

The polymer after the liquid crystal monomer is photohardened by light irradiation is non-liquid crystalline and will not undergo phase transitions between the liquid crystal phase, the glass phase, and the crystalline phase due to temperature changes. Therefore, a liquid crystal layer that is photohardened with the liquid crystal monomers oriented in a predetermined direction is less likely to undergo changes in molecular orientation due to temperature changes. In addition, the oriented liquid crystal layer has an extremely large birefringence compared with a film made of non-liquid crystal material, so the thickness of the first phase difference layer 131 having front retardation of 1/4 wavelength can be extremely reduced. When the first retardation layer 131 is a surface-aligned liquid crystal layer, its thickness is about 0.5~10 μm. The thickness of the surface-aligned liquid crystal layer may also be 8 μm or less or 5 μm or less.

<Second phase difference layer> Examples of the retardation layer having a refractive index anisotropy of nz>nx≥ny include a positive C plate having a refractive index anisotropy of nz>nx≒ny and a refractive index anisotropy of nz>nx>ny. The positive B board of the opposite sex.

Examples of the second retardation layer 132 include an aligned liquid crystal layer in which a liquid crystal compound is homeotropically aligned, or a thin film of a non-liquid crystalline resin material (polymer) having negative intrinsic birefringence.

A polymer with negative intrinsic birefringence refers to a polymer whose refractive index in the orientation direction is relatively reduced when the polymer is oriented by stretching or the like. Examples of polymers having negative intrinsic birefringence include polymers in which chemical bonds or functional groups with large polarization anisotropy, such as aromatic or carbonyl groups, are introduced into the side chains of the polymer. Specific examples include acrylic resins, Styrene-based resin, maleimide-based resin, fumarate-based resin, etc.

The manufacturing method of the resin film is not particularly limited, and either a solution method or a melting method can be used. When a resin film is formed by a solution method, the molecular chains of the polymer tend to be oriented in the in-plane direction. When the molecular chain of a polymer with negative intrinsic birefringence is oriented in the plane, the refractive index nz in the thickness direction of the coating film will be relatively reduced relative to the refractive index in the plane, showing a refractive index with nz>nx≒ny. Positive C plate characteristics of anisotropy (thickness direction retardation Rth is negative). Furthermore, by biaxially stretching a film of a polymer having negative intrinsic birefringence so that the front retardation becomes approximately 0, a positive C plate with approximately 0 front retardation can be obtained. In addition, nx≒ny is not limited to the case where nx and ny are exactly the same, as long as the front-side retardation Re(550) at the wavelength of 550nm is 10nm or less. The front retardation Re(550) of the positive C plate should be 5nm or less, or it can be 3nm or less or 1nm or less.

As mentioned above, the second phase difference layer 132 may also be a positive B plate having refractive index anisotropy of nz>nx>ny. For example, a positive C plate can be obtained by biaxially stretching a film of a polymer with negative intrinsic birefringence in such a way that the front-side retardation reaches approximately zero. In addition, when a polymer film with a refractive index anisotropy of nz>nx≒ny obtained by coating is uniaxially stretched at the free end, the refractive index ny in the stretching direction will decrease, and the refractive index ny in the direction orthogonal to the stretching direction will decrease. The refractive index nx and the refractive index nz in the thickness direction will increase, but the relationship of nz>ny will still be maintained after stretching, so a film with refractive index anisotropy of nz>nz>ny can be obtained.

From the viewpoint of reducing the thickness of the retardation layer, the second retardation layer 132 is preferably a homeotropic alignment liquid crystal layer having refractive index anisotropy of nz>nx≒ny. The homeotropically aligned liquid crystal layer is formed, for example, by coating a liquid crystal composition containing a liquid crystal compound on a support substrate, allowing the liquid crystal compound to be homeotropically aligned, and then fixing the alignment state. For details of the homeotropic alignment liquid crystal layer, refer to Japanese Patent Application Laid-Open No. 2008-216782, for example.

The liquid crystal compound is preferably a thermotropic liquid crystal as described above for the surface-aligned liquid crystal layer. The support substrate used in forming the homeotropic liquid crystal layer may be provided with an alignment film for homeotropic alignment of the liquid crystal molecules. Examples of the orienting agent used to form an alignment film with homeotropic alignment (homeotropic alignment film) include lecithin, stearic acid, cetyltrimethylammonium bromide, and stearylamine hydrochloride. , monocarboxylic acid chromium complex, silane coupling agent or siloxane compound and other organosilanes, perfluorodimethylcyclohexane, tetrafluoroethylene, polytetrafluoroethylene, etc.

In addition to the liquid crystal monomer, the liquid crystal composition used to form the vertically aligned liquid crystal layer may also contain a compound that controls the orientation of the liquid crystal monomer. For example, by including a side chain type liquid crystal polymer in a liquid crystal composition, the liquid crystal compound (monomer) can be vertically aligned. Therefore, even when a support substrate without a liquid crystal alignment film is used, vertical alignment can still be formed. Oriented liquid crystal layer.

The side chain liquid crystal polymer may be a homopolymer or a copolymer. The side chain type liquid crystal polymer may contain only monomer units having liquid crystalline fragment side chains, or may contain, in addition to monomer units having liquid crystalline fragment side chains, side chains without liquid crystalline fragments. Single unit. Examples of the monomer unit that does not have a liquid crystalline segment in the side chain include a monomer unit that does not have a side chain and a monomer unit that has a non-liquid crystalline segment in the side chain.

The polymer exhibits liquid crystallinity by having a liquid crystalline segment in the side chain. When the liquid crystalline composition is heated to a predetermined temperature, the polymer tends to be oriented in a predetermined direction. In addition, since the polymer has a non-liquid crystalline segment in the side chain, it exerts an orientation force that orients the photopolymerizable liquid crystal monomer contained in the liquid crystal composition together with the polymer in a homeotropic alignment. By orienting the liquid crystal monomer according to the orientation of the side-chain liquid crystal polymer and fixing the orientation state, a vertically aligned liquid crystal layer can be obtained.

Examples of the monomer having a liquid crystalline segment side chain include polymerizable compounds having a nematic liquid crystalline substituent containing a mesogen group. Examples of the mesogen group include those previously exemplified as the mesogen group as the liquid crystal monomer. Among them, the mesogen group preferably has a biphenyl group or a phenyl benzoate group.

Examples of the monomer having a non-liquid crystalline segment side chain include polymerizable compounds having a linear substituent such as a long-chain alkyl group having 7 or more carbon atoms. Examples of the polymerizable functional groups of the liquid crystalline monomer and the non-liquid crystalline monomer include (meth)acrylyl groups.

As the side chain type liquid crystal polymer, a copolymer having a liquid crystalline monomer unit represented by the general formula (I) and a non-liquid crystalline monomer unit represented by the general formula (II) is preferably used.

In formula (I), R ¹ is a hydrogen atom or a methyl group, R ² is a cyano group, a fluoro group, an alkyl group with 1 to 6 carbon atoms, or an alkoxy group with 1 to 6 carbon atoms, and X ¹ is - CO ₂ -or-OCO-. a is an integer from 1 to 6, b and c are each independently 1 or 2.

In formula (II), R ³ is a hydrogen atom or a methyl group, and R ⁴ is an alkyl group with 7 to 22 carbon atoms, a fluoroalkyl group with 1 to 22 carbon atoms, or a group represented by the following general formula (III) group.

In formula (III), R ⁵ is an alkyl group having 1 to 5 carbon atoms, and d is an integer of 1 to 6.

The ratio of liquid crystalline monomer units to non-liquid crystalline monomer units in the side-chain liquid crystal polymer is not particularly limited. When the ratio of non-liquid crystalline monomer units is small, orientation of the side-chain liquid crystal polymer may be caused. The orientation of the liquid crystal monomer will become insufficient, and the orientation of the liquid crystal layer after photohardening will become uneven. On the other hand, when the ratio of liquid crystalline monomer units is small, it is difficult for the side chain type liquid crystal polymer to exhibit single-region liquid crystal orientation. Therefore, the molar ratio of the non-liquid crystalline monomer to the total of the liquid crystalline monomer units and the non-liquid crystalline monomer units is preferably 0.01 to 0.8, more preferably 0.1 to 0.6, and more preferably 0.15 to 0.5. From the viewpoint of balancing the film-forming properties and orientation properties of the liquid crystal composition, the weight average molecular weight of the side chain type liquid crystal polymer is preferably about 2,000 to 100,000, more preferably about 2,500 to 50,000.

Side-chain liquid crystal polymers can be polymerized by various known methods. For example, when the monomer unit has a (meth)acrylyl group as a polymerizable functional group, a side-chain liquid crystal polymer having a liquid crystalline segment and a non-liquid crystalline segment can be obtained by radical polymerization using light or heat.

The liquid crystal composition is prepared by mixing the above-mentioned liquid crystal monomer and the side-chain liquid crystal polymer as an orientation control agent, a polymerization initiator, a leveling agent, etc. with a solvent, and then coating the liquid crystal composition on the supporting substrate to make the liquid crystal The compounds are oriented to form a vertically aligned liquid crystal layer. The amount of the side chain type liquid crystal polymer in the liquid crystal composition is preferably about 5 to 50 parts by weight relative to 100 parts by weight of the liquid crystal monomer.

Except that the liquid crystal composition contains a side-chain liquid crystal polymer, the manufacturing method of the aligned liquid crystal layer (orientation by heating, photohardening, etc.) is the same as the above-mentioned fabrication of the surface-aligned liquid crystal layer, so the description of these details is omitted. . When the second phase difference layer 132 is a vertically aligned liquid crystal layer, its thickness is about 0.5~10 μm. The thickness of the vertically aligned liquid crystal layer may also be below 8 μm or below 5 μm.

The thickness direction retardation Rth of the second retardation layer 132 represented by Rth=(nx-nz)×d is less than 0. In addition, nz and nz are as mentioned above, and d is the thickness. The thickness direction retardation Rth of the second retardation layer 132 is, for example, -30~-200nm, preferably -50~-150nm. The sum of the thickness direction retardation of the first retardation layer 131 and the thickness direction retardation of the second retardation layer 132 is preferably 30~110 nm, more preferably 40~100 nm, more preferably 50~90 nm.

＜Polarizer protective film＞ In the circularly polarizing plate 10 , a transparent film 15 may be bonded to the viewing side surface of the polarizer 11 (the surface opposite to the surface where the retardation layer 13 is disposed) as a polarizer protective film.

When the transparent film 15 is bonded to the polarizer 11, its thickness is about 1 to 50 μm. From the viewpoint of reducing the thickness of the circularly polarizing plate 10, the thickness of the transparent film 15 is preferably 45 μm or less, more preferably 40 μm or less, and may also be 35 μm or less. From the viewpoint of handleability, surface protection, etc., the thickness of the transparent film 15 is preferably 5 μm or more, more preferably 10 μm or more, and may be 15 μm or more or 20 μm or more.

Examples of the resin material of the transparent film 15 include those described above as the resin material of the retardation layer 13 . The transparent film 15 may also have functional layers such as a hard coat layer, an anti-reflection layer, and an anti-adhesion layer on the surface of the resin film (the surface opposite to the polarizer 11). When the transparent film 15 has functional layers on the resin film, the thickness including the functional layers is preferably within the above range.

The transparent film 15 should absorb less visible light and be transparent. The total light transmittance of the transparent film 15 is preferably above 80%, more preferably above 85%, and more preferably above 90%. The light transmittance of the transparent film 15 at a wavelength of 440 nm is preferably more than 80%, more preferably more than 85%, and more preferably more than 90%.

＜Adhesive layer＞ The polarizer 11, the retardation layer 13 and the transparent film 15 constituting the circular polarizing plate 10 are preferably bonded together through appropriate adhesive layers (not shown). The thickness of the adhesive layer is, for example, about 0.01~30 μm.

The first phase difference layer 131 and the second phase difference layer 132 are preferably bonded together through an adhesive layer. From the viewpoint of reducing the thickness of the retardation layer 13 , it is preferable to use an adhesive for bonding the first retardation layer 131 and the second retardation layer 132 . The thickness of the adhesive layer bonding the first retardation layer 131 and the second retardation layer 132 is preferably 5 μm or less, preferably 3 μm or less, and may also be 2 μm or less.

As the adhesive, various forms such as water-based adhesives, solvent-based adhesives, hot-melt adhesives, and active energy ray-curable adhesives can be used. Among these, water-based adhesives or active energy ray-curable adhesives are preferred because they can reduce the thickness of the adhesive layer. When using an adhesive that exhibits adhesion through a hardening reaction after coating, the thickness of the adhesive layer is preferably 0.01 to 5 μm, more preferably 0.03 to 3 μm, and may also be 2 μm or less.

Examples of the polymer component of the water-based adhesive include vinyl polymer, gelatin, vinyl latex, polyurethane, polyester, epoxy, and the like. Among these, vinyl polymers are preferable, and polyvinyl alcohol-based resins are particularly preferable because of their excellent adhesion between the easily adhered film and the polarizer. Among the polyvinyl alcohol resins, polyvinyl alcohol containing an acetyl acetyl group is preferred.

Active energy ray-curable adhesives are adhesives that undergo radical polymerization, cationic polymerization, or anionic polymerization by irradiation with active energy rays such as electron beams or ultraviolet rays. Among them, a photoradically polymerizable adhesive that initiates polymerization by ultraviolet irradiation, a photocationically polymerizable adhesive, or a hybrid adhesive that uses both photocationic polymerization and photoradical polymerization are preferred because they can be cured with low energy. agent.

Examples of the monomer of the radically polymerizable adhesive include a compound having a (meth)acrylyl group or a compound having a vinyl group. Among these, compounds having a (meth)acrylyl group are preferred. Examples of the curable component of the cationic polymerizable adhesive include compounds having an epoxy group or an oxetanyl group. The compound having an epoxy group is not particularly limited as long as it has at least two epoxy groups in the molecule, and various generally known curable epoxy compounds can be used.

As the adhesive, those based on polymers such as acrylic polymers, polysiloxane polymers, polyesters, polyurethanes, polyamides, polyethers, fluorine-based or rubber-based polymers can be appropriately selected and used. . In particular, an acrylic adhesive is suitable because it has excellent optical transparency, exhibits moderate wettability and cohesiveness, and has excellent weather resistance or heat resistance.

From the perspective of reducing the thickness of the circularly polarizing plate 10, the thickness of the adhesive layer used in the bonding of the polarizer 11 and the transparent film 15 and the bonding of the polarizer 11 and the retardation layer 13 is preferably 20 μm or less. Preferably it is 15 μm or less. As mentioned above, by using the adhesive layer, the thickness of the adhesive layer can be reduced. When using adhesive, the thickness of the adhesive layer can be 1~10μm or 2~7μm.

[Organic EL display device] The organic EL display device 100 is formed by disposing the circular polarizing plate 10 on the viewing side surface of the organic EL unit 70 . As shown in FIG. 3 , the organic EL unit 70 and the circular polarizing plate 10 can be bonded together through an appropriate adhesive layer 21 . As the adhesive layer 21, a hardening adhesive or an adhesive (pressure-sensitive adhesive) can be used. The thickness of the adhesive layer 21 is, for example, about 0.1 to 50 μm.

From the viewpoint of handleability and the like, the adhesive layer 21 is preferably an adhesive. As the adhesive, acrylic polymers, polysiloxane polymers, polyesters, polyurethanes, polyamides, polyethers, fluorine polymers, rubber polymers, etc. can be used as base polymers. object person. In particular, an adhesive such as an acrylic adhesive or a rubber adhesive that has excellent transparency, moderate wettability, cohesiveness, adhesion, weather resistance, or heat resistance is preferred.

The thickness of the adhesive layer 21 is, for example, about 1 to 50 μm. From the viewpoint of thinning and bendability, the thickness of the adhesive layer 21 bonding the organic EL unit 70 and the circular polarizing plate 10 is preferably 30 μm or less, more preferably 25 μm or less, more preferably 20 μm or less, and may be Below 18μm.

As shown in FIG. 2 , an adhesive layer 21 can also be provided on the surface of the circular polarizing plate 10 on the phase difference layer 13 side in advance to produce a circular polarizing plate with an adhesive layer. The thickness of the circular polarizing plate with the adhesive layer (the total thickness of the circular polarizing plate 10 and the thickness of the adhesive layer 21) is preferably 100 μm or less, more preferably 90 μm or less, and may also be 80 μm or less or 75 μm or less.

In a polarizing plate with an adhesive layer, a release liner (not shown) may be temporarily attached to the surface of the adhesive layer 21 in order to prevent contamination of the adhesive layer. As a release liner, it is preferable to use one in which the surface of a plastic film is coated with a release agent such as a silicone release agent, a long-chain alkyl release agent, or a fluorine release agent.

The organic EL display device may include any optical components in addition to the organic EL unit 70 and the circular polarizing plate 10 . For example, a hard coating layer, an anti-reflection layer, an antifouling layer, a surface protection layer (covering window), etc. may also be provided on the viewing side surface of the circularly polarizing plate 10 . In addition, the organic EL display device may also include a touch panel sensor. The touch panel sensor can also be disposed on the back of the organic EL unit 70 , inside the organic EL unit 70 , between the organic EL unit 70 and the circular polarizing plate 10 , or at a position closer to the viewing side than the circular polarizing plate 10 . Anywhere.

As mentioned above, the image display device of the present invention has a flexible part. Since the thickness of the retardation layer 13 is small and includes only one layer of liquid crystal alignment film or no liquid crystal alignment film, the circular polarizing plate 10 has excellent flexibility resistance and is difficult to break or crack even if it is repeatedly flexed at the same place. .

Example The present invention will be explained in more detail below using examples, but the present invention is not limited to these specific examples.

[Example of manufacturing phase difference layer] <Manufacturing Example 1: Polycarbonate-based stretched film> Into the reaction vessel, bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane: 38.06 parts by weight, isosorbide ("POLYSORB" manufactured by ROQUETTE FRERES): 53.73 parts by weight, 1,4 - Cyclohexane dimethanol (cis-trans mixture, manufactured by SK Chemical): 9.64 parts by weight, diphenyl carbonate (manufactured by Mitsubishi Chemical): 81.28 parts by weight, and calcium acetate monohydrate as a catalyst, and reduced After replacement with pressurized nitrogen, the mixture was stirred at 150° C. for about 10 minutes under a nitrogen stream to dissolve the raw materials. After the temperature was raised to 220°C, the reaction was performed under normal pressure for 60 minutes. Thereafter, the pressure was reduced from normal pressure to 13.3 kPa and maintained for 30 minutes, and the generated phenol was pumped out of the reaction system. Next, while raising the temperature to 240° C., the pressure was reduced to 0.10 kPa or less, and the produced phenol was discharged out of the reaction system. After reaching the predetermined stirring torque, the reaction was stopped after the pressure was restored to normal pressure with nitrogen. The generated polycarbonate is extruded into water, and the bundles are cut to obtain polycarbonate (PC) resin pellets.

Using the above-mentioned polycarbonate resin pellets, an unstretched film with a thickness of 100 μm was produced by a melt extrusion method. Using a tenter-type stretching machine that can independently control the traveling speed of the left and right clamps, the film is stretched diagonally at a temperature of 137°C and a stretching ratio of about 2.5 times, so that the slow axis direction is 45° relative to the long side of the film. Extended retardation film (thickness 47μm, front retardation Re(550)=140nm).

<Manufacturing Example 2: Surface-aligned liquid crystal film> A photopolymerizable liquid crystal compound ("Paliocolor LC242" manufactured by BASF) showing a nematic liquid crystal phase was dissolved in cyclopentanone to prepare a solution with a solid content concentration of 30% by weight. A surfactant ("BYK-360" manufactured by BYK) and a photopolymerization initiator ("Omnirad907" manufactured by IGM Resins) were added to this solution to prepare a liquid crystal composition solution. The added amounts of the leveling agent and the polymerization initiator were respectively 0.01 parts by weight and 3 parts by weight relative to 100 parts by weight of the photopolymerizable liquid crystal compound.

A biaxially stretched norzolene-based film ("Zeonor Film" manufactured by Zeon, Japan, thickness: 33 μm, front retardation: 135 nm) was used as a base material, and the above-mentioned liquid crystal composition was coated on the base material using a bar coater and dried. The thickness is 3 μm, and the liquid crystal is oriented by heating at 100°C for 3 minutes. After cooling to room temperature, the ultraviolet light with a cumulative light intensity of 400 mJ/cm ² was irradiated in a nitrogen environment for photohardening, thereby obtaining a laminate with a surface-aligned liquid crystal layer on the film base material without an alignment film interposed therebetween. <Manufacture Example 3: In-plane alignment liquid crystal film with liquid crystal alignment film> A composition for forming a photo-alignment film was applied to a biaxially stretched polyethylene terephthalate (PET) film and dried at 80° C. for 1 minute. , use a polarized UV irradiation device to perform polarized UV exposure with a cumulative light amount of 100mJ/cm ² to form a liquid crystal alignment film. The same liquid crystal composition solution as in Production Example 2 was applied thereon, heated and photocured to obtain a laminate in which a surface-aligned liquid crystal layer was provided on a film base material via an alignment film.

<Manufacture Example 4: Homeographically Aligned Liquid Crystal Film> 20 parts by weight of a side chain type liquid crystal polymer having a weight average molecular weight of 5,000 and a polymerizable liquid crystal compound showing a nematic liquid crystal phase ("Paliocolor manufactured by BASF") having the following chemical formula (n=0.35, expressed as a block polymer for convenience) 80 parts by weight of LC242") and 5 parts by weight of a photopolymerization initiator ("Omnirad 907" manufactured by IGM Resins) were dissolved in 400 parts by weight of cyclopentanone to prepare a liquid crystal composition.

A biaxially stretched norzolene-based film ("Zeonor Film" manufactured by Zeon, Japan, thickness: 52 μm, front retardation: 50 nm) was used as a base material, and the above-mentioned liquid crystal composition was coated on the base material using a bar coater and dried. The thickness is 3.5 μm, and it is heated at 80°C for 2 minutes to orient the liquid crystal and cooled to room temperature. Then, it is irradiated with ultraviolet light of 700mJ/ ^cm2 in a nitrogen environment to photoharden the liquid crystal monomer, and obtains no barrier on the film substrate. A laminate with vertically aligned aligned liquid crystal layers attached to an alignment film.

<Manufacture Example 5: Homeotropic alignment liquid crystal film with liquid crystal alignment film> A commercially available film ("MCP-N (80)" manufactured by Dainippon Printing) was prepared, in which a vertically aligned liquid crystal layer was provided on a PET film via an alignment film.

<Production Example 6: Poly(nitrostyrene)-based coating film> In a reaction vessel, dissolve 50 parts by weight of polystyrene in a mixed solvent of 900 parts by weight of nitrobenzene and 300 parts by weight of 1,2-dichloroethane, and drop 86 parts by weight of nitric acid and concentrated nitric acid over 30 minutes while stirring. 100 parts by weight of sulfuric acid mixed acid. After the reaction was carried out for 22 hours while stirring at room temperature, the reaction liquid was poured into a sodium hydroxide aqueous solution, and the organic phase was separated and precipitated in methanol. The precipitate is dissolved in N,N-dimethylformamide (DMF), reprecipitated in methanol, filtered, washed repeatedly with methanol, and dried under vacuum to obtain poly(nitro) Styrene)-based resin fibrous powder.

The obtained poly(nitrostyrene)-based resin was dissolved in cyclopentanone to prepare a 20% solution, and was coated on a PET film and dried to obtain a 6 μm-thick film on the PET film (coating phase difference thin film) laminate. The front-side retardation of the coated film after peeling off the PET film is 0nm, and the thickness-direction retardation is -85nm.

[Production of polarizing plates] Corona treatment was performed on one side of an amorphous polyester film (polyethylene terephthalate/polyethylene isophthalate; glass transition temperature: 75°C) with a thickness of 100 μm. Resin 100 containing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetate-acetyl-modified polyvinyl alcohol ("GOHSEFIMER Z410" manufactured by Nippon Synthetic Chemical Industry) in a weight ratio of 9:1 Add 13 parts by weight of potassium iodide to prepare a PVA aqueous solution. This aqueous solution was applied to the corona-treated surface of the amorphous polyester film and dried at 60° C. to prepare a laminate in which a 13 μm-thick PVA-based resin layer was provided on the amorphous polyester film base material.

The free end of the laminated body was uniaxially extended to 3.0 times in the long side direction using aerial auxiliary stretching in an oven at 130°C, and then sequentially immersed in a 4% boric acid aqueous solution at 40°C for 30 seconds while being rolled. , Soak in 40℃ dyeing solution (0.2% iodine, 1.4% potassium iodide aqueous solution) for 60 seconds. Next, while conveying the laminate in a roll, it was immersed in a cross-linking solution (5% boric acid, 3% potassium iodide aqueous solution) at 40°C for 30 seconds to perform cross-linking treatment, and then in 4% boric acid, 5% potassium iodide solution at 70°C. While immersed in the aqueous solution, the free end is uniaxially extended toward the long side to achieve a total extension ratio of 5.5 times. Thereafter, the laminated body was immersed in a cleaning solution (4% potassium iodide aqueous solution) at 20°C.

The laminated body was transported to an oven at 60° C. for 1 minute to dry. During this period, it was brought into contact with a SUS heated roller with a surface temperature of 75°C placed in the oven for about 2 seconds. Through the above steps, a laminate in which a PVA-based polarizer with a thickness of about 5 μm is provided on an amorphous polyester film base material can be obtained.

The non-hard-coat layer surface of a triacetylcellulose (TAC) film (thickness 32 μm) with a hard-coat layer formed on one side was bonded to the polarizer side of the above-mentioned laminate using an ultraviolet curable adhesive. Thereafter, the amorphous polyester film base material was peeled off from the polarizer, and a polarizing plate (total thickness 38 μm) in which a hard-coat film was bonded to one side of the polarizer was obtained.

[Circular polarizing plate] ＜Comparative example 1＞ The polycarbonate film of Production Example 1 and the vertically aligned liquid crystal film of Production Example 5 were bonded together using an ultraviolet curing adhesive to produce a laminated phase difference plate.

The surface of the polycarbonate film side of the laminated phase difference plate was bonded to the surface of the TAC film side of the polarizing plate without the hard coating layer through an acrylic adhesive layer with a thickness of 5 μm, and then the film base material was lifted from the vertical side. Peeling from surface aligned liquid crystal film. At this time, the liquid crystal alignment film is peeled off at the interface with the film substrate, and the liquid crystal alignment film remains on the vertically aligned liquid crystal layer. The thickness of the homeotropic aligned liquid crystal layer including the liquid crystal alignment layer is 4 μm. The angle formed by the extension direction of the polycarbonate film (slow axis direction) and the extension direction of the polarizer (absorption axis direction) is 45°.

An acrylic adhesive sheet with a thickness of 15 μm was bonded to the surface on the side of the vertically aligned liquid crystal layer of the above-mentioned circular polarizing plate to obtain a circular polarizing plate with an adhesive layer.

＜Comparative example 2＞ The creeping alignment liquid crystal film of Production Example 3 and the homeotropic alignment liquid crystal film of Production Example 5 were bonded together using an ultraviolet curing adhesive to produce a laminated phase difference plate.

The film base material was peeled off from the surface-aligned liquid crystal film of the laminated retardation plate, and pasted on the TAC film side of the polarizing plate of Production Example 6 through an acrylic adhesive layer with a thickness of 5 μm. , the film base material is peeled off from the vertically aligned liquid crystal film to produce a circular polarizing plate. Regardless of whether it is a vertically aligned liquid crystal film or a vertically aligned liquid crystal film, when the film substrate is peeled off, the liquid crystal alignment film remains on the aligned liquid crystal layer after the interface between the liquid crystal alignment film and the film substrate is peeled off. The thickness of the surface aligned liquid crystal layer including the liquid crystal alignment layer is 4 μm. The angle formed by the orientation direction (slow axis direction) of the surface-aligned liquid crystal layer and the extension direction (absorption axis direction) of the polarizer is 45°.

An acrylic adhesive sheet with a thickness of 15 μm was bonded to the surface on the side of the vertically aligned liquid crystal layer of the above-mentioned circular polarizing plate to obtain a circular polarizing plate with an adhesive layer.

<Example 1> The surface-aligned liquid crystal film without a liquid crystal alignment film of Production Example 2 was used instead of the surface-aligned liquid crystal film of Production Example 3. In addition, a circular polarizing plate was produced in the same manner as Comparative Example 2, and an acrylic adhesive sheet with a thickness of 15 μm was bonded to the vertically aligned liquid crystal layer to obtain an adhesive-attached circular polarizing plate.

<Example 2> The vertical alignment liquid crystal film without a liquid crystal alignment film of Production Example 4 was used instead of the vertical alignment liquid crystal film of Production Example 5. In addition, a circular polarizing plate was produced in the same manner as Comparative Example 2, and an acrylic adhesive sheet with a thickness of 15 μm was bonded to the vertically aligned liquid crystal layer to obtain an adhesive-attached circular polarizing plate.

<Example 3> The orthogonal alignment liquid crystal film without a liquid crystal alignment film of Production Example 2 was used instead of the orthogonal alignment liquid crystal film of Production Example 3, and the vertical alignment liquid crystal film without a liquid crystal alignment film of Production Example 4 was used instead of the vertical alignment liquid crystal film of Production Example 5. Alignment of oriented liquid crystal films. In addition, a circular polarizing plate was produced in the same manner as Comparative Example 2, and an acrylic adhesive sheet with a thickness of 15 μm was bonded to the vertically aligned liquid crystal layer to obtain an adhesive-attached circular polarizing plate.

<Example 4> The poly(nitrostyrene)-based resin film of Production Example 6 was used instead of the homeotropically aligned liquid crystal film of Production Example 5, and the surface-aligned liquid crystal layer and the poly(nitrostyrene)-based resin film were bonded together through an ultraviolet curable adhesive. , and make a laminated phase difference plate. Thereafter, a circular polarizing plate was produced in the same manner as in Comparative Example 2, and an acrylic adhesive sheet with a thickness of 15 μm was bonded to the poly(nitrostyrene) resin film to obtain an adhesive-attached circular polarizing plate.

[Evaluation of Flexibility] The circular polarizing plates of the Examples and Comparative Examples were cut into rectangles of 30 mm × 100 mm, and pasted onto a desktop durability testing machine (clamshell type flexure testing machine) manufactured by YUASA SYSTEM Co., Ltd. through an acrylic adhesive sheet. "DR11MR4-CS-m") on the jig. Arrange the sample on the stage of the jig so that the short side direction becomes the deflection axis, and attach polyimide tape to the long side of the sample to fix it on the jig. There is no acrylic adhesive sheet on the flexure.

Conduct a 100,000-fold flexural test under the conditions of flexural radius: 1.5mm and flexural speed: 30 cycles/minute, and visually confirm the flexural part of the sample after the test. Those where no cracks or breaks were observed were evaluated as 0, and those where cracks or breaks were observed were evaluated as ×.

The evaluation results of the lamination structure and flex resistance of the circularly polarizing plates of Examples and Comparative Examples are shown in Table 1. The phase difference layer 1 is a λ/4 plate arranged on the side close to the polarizer, and the phase difference layer 2 is a positive C plate arranged on the side far from the polarizer. Table 1 shows whether the material of retardation layers 1 and 2 is a resin material or a liquid crystal material, and also describes the thickness of each retardation layer and the presence or absence of a liquid crystal alignment film.

[Table 1]

In Comparative Example 1 in which the retardation layer 1 (λ/4 plate) is a stretched polycarbonate film, the thickness of the retardation layer is large and the flexibility resistance is poor. In Comparative Example 2, although the thickness of the retardation layer was small, like Comparative Example 1, the flexibility resistance was poor. We believe that in Comparative Example 2, both the retardation layers 1 and 2 include a liquid crystal alignment film, which is the reason for the decrease in flexibility resistance.

Example 1 in which only the retardation layer 2 includes a liquid crystal alignment film, Examples 2 and 4 in which only the retardation layer 1 includes a liquid crystal alignment film, and Example 3 without a liquid crystal alignment film all show good flexibility resistance.

10: Circular polarizing plate 11:Polarizer 13: Phase difference layer 131: First phase difference layer (1/4 wavelength plate) 132: Second phase difference layer (positive C plate) 15:Transparent film 21: Adhesive layer 50: Circular polarizing plate with adhesive layer 70: Organic EL element (organic EL unit) 100:Image display device

FIG. 1 is a cross-sectional view of a circularly polarizing plate according to an embodiment. 2 is a cross-sectional view of a circularly polarizing plate with an adhesive layer attached thereto according to an embodiment. FIG. 3 is a cross-sectional view of an image display device according to an embodiment.

10: Circular polarizing plate

11:Polarizer

13: Phase difference layer

131: First phase difference layer (1/4 wavelength plate)

132: Second phase difference layer (positive C plate)

15:Transparent film

21: Adhesive layer

70: Organic EL element (organic EL unit)

100:Image display device

Claims (10)

A circular polarizing plate, which is used as an anti-reflection device for image display devices with flexible parts; The aforementioned circularly polarizing plate includes a polarizer and a phase difference layer bonded to one surface of the polarizer; The aforementioned retardation layer is a laminate of two or more retardation layers, and the thickness is 20 μm or less; The liquid crystal alignment film is one layer or less. The circular polarizing plate of claim 1, wherein the phase difference layer includes a first phase difference layer with a refractive index anisotropy of nx>ny≥nz and a second phase with a refractive index anisotropy of nz>nx≥ny poor layer; However, nx is the refractive index in the slow axis direction of the plane, ny is the refractive index in the fast axis direction of the plane, and nz is the refractive index in the thickness direction. The circular polarizing plate of claim 2, wherein the first phase difference layer is an oriented liquid crystal layer formed by orienting liquid crystal compounds along the surface. Such as the circular polarizing plate of claim 2 or 3, wherein the second phase difference layer is an oriented liquid crystal layer formed by vertically oriented liquid crystal compounds, or is composed of a non-liquid crystalline resin with negative intrinsic birefringence and has a thickness of Films below 10μm. The circularly polarizing plate of claim 2 or 3 is provided with the first retardation layer and the second retardation layer in order from the polarizer side. The circularly polarizing plate according to any one of claims 1 to 3, which does not contain a liquid crystal alignment film. For example, the thickness of the circularly polarizing plate according to any one of claims 1 to 3 is 80 μm or less. A circular polarizing plate with an adhesive layer, including the circular polarizing plate according to any one of claims 1 to 3 and an adhesive layer disposed on the surface of the circular polarizing plate on the side of the retardation layer. For example, the total thickness of the circularly polarizing plate with adhesive layer in claim 8 is less than 100 μm. An image display device having a flexible part; and The viewing side surface of the organic EL unit is provided with a circular polarizing plate according to any one of claims 1 to 7.