CN111869323B - Electroluminescence display device - Google Patents

Abstract

An electroluminescent display device comprising: an electroluminescent element, and a circular polarizing plate disposed on the visible side of the electroluminescent element, wherein the circular polarizing plate has a retardation layer, a polarizing plate, and a substrate film in sequence, (1) the refractive index ny in the fast axis direction of the substrate film is not less than 1.568 and not greater than 1.63; itself); and, (3) the light transmission axis of the polarizer is approximately parallel to the fast axis of the substrate film.

Description

Electroluminescence display device

technical field

The present invention relates to electroluminescent (EL) display devices.

Background technique

In an EL display device, external light is reflected on the surface of constituent materials such as an image display element and a touch sensor, these wiring parts, etc., and there is a problem that visibility is reduced. To address these problems, a method has been proposed in which an optical layered body is disposed on the output surface of an image display device to reduce reflection of external light. Usually used for this optical laminate is a circular polarizing plate in which a linear polarizing plate and a 1/4 wavelength retardation plate are laminated.

As a polarizer protective film for a polarizing plate, a polyester film having an in-plane retardation of 3000 to 30000 nm has been proposed (for example, refer to Patent Document 1). Compared with cellulose-based or acrylic films, polyester films have low moisture permeability, excellent mechanical properties (high impact resistance and high elastic modulus), and excellent chemical properties (solvent resistance, etc.), so they are suitable for use in image display devices. However, a polyester film has birefringence, and thus has a disadvantage that rainbow spots are easily generated. Therefore, in order to suppress iridescence and provide sufficient in-plane retardation using a polyester film, it is necessary to thicken the film.

Furthermore, in order to suppress the influence of the wavelength dispersion of the refractive index and obtain a circular polarizing plate with better color reproducibility, a technique combining a 1/4 wavelength plate and a 1/2 wavelength plate has been proposed (Patent Document 2). However, when such a plurality of retardation plates are stacked on a polarizing plate, the problem of the thickness described above becomes more prominent. In addition, a circular polarizing plate is laminated with a plurality of films. Therefore, when the circular polarizing plate is wound up and stored in the manufacturing process, curling is easily given, and handling in the subsequent bonding process with the EL element may become difficult.

In this way, a circular polarizing plate in which a retardation plate is laminated on a polarizing plate with a base film having a high retardation as a protective film has to be thick, so it cannot sufficiently cope with the thinning required in recent years, and troubles are easily caused in the manufacturing process. In particular, in a large-sized image display device such as a size over 40 (diagonal length of the display part is 40 inches), the circular polarizing plate becomes large, and the problem of curling tends to arise.

In addition, in recent years, flexible EL display devices that have a wide display surface and can be folded into a V-shape, Z-shape, W-shape, double-door shape, etc. when carried, or rolled into a roll shape have been proposed as image display devices. If a circular polarizing plate is used in such a foldable (foldable) or rollable (rollable) EL display device, there are problems such as that sufficient bending performance cannot be obtained due to its thickness; the film is easily peeled off when repeated bending operations or placed in a high-temperature place such as the interior of a car; and it is easy to give bending marks.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2012-256057

Patent Document 2: Japanese Patent Application Laid-Open No. 10-68816

Contents of the invention

The problem to be solved by the invention

The present invention has been made against the background of the above-mentioned problems of the prior art. That is, it is an object of the present invention to provide an EL display device that can be thinned while ensuring visibility, does not easily cause trouble in the manufacturing process, and does not easily peel off laminated members when it is repeatedly bent or placed in a high-temperature state when it is a flexible EL display device, and does not easily give creases.

solutions to problems

The inventors of the present invention have conducted intensive studies to develop an EL display device that is thinner while ensuring visibility, does not cause trouble in the manufacturing process, and is not prone to peeling or creases after being repeatedly bent or placed in a high-temperature state in the case of a flexible EL display device. As a result, it has been found that the above object can be achieved by using a circular polarizing plate that uses a base film having a specific value of refractive index ny in the fast axis direction and reduces the number of self-supporting films present between the polarizing plate and the retardation layer. It is 1 sheet or less, and the light transmission axis of a polarizing plate is substantially parallel to the fast axis of a base film. The present invention has been accomplished based on such knowledge.

That is, the present invention relates to the EL display device described in Item 1 to Item 6.

Item 1.

An electroluminescent display device comprising: an electroluminescent element, and a circular polarizing plate arranged on the visible side of the electroluminescent element,

The aforementioned circular polarizing plate has a retardation layer, a polarizer and a substrate film in sequence,

(1) The refractive index ny of the fast axis direction of the base film is 1.568 or more and 1.63 or less;

(2) There is no self-supporting film between the polarizer and the retardation layer, or there is only one self-supporting film (here, the retardation layer itself is also included between the polarizer and the retardation layer); and,

(3) The light transmission axis of the polarizing plate is approximately parallel to the fast axis of the base film.

Item 2.

The electroluminescence display device according to the above item 1, wherein the in-plane birefringence ΔNxy of the base film is 0.06 or more and 0.2 or less.

Item 3.

The electroluminescence display device according to item 1 or 2 above, wherein the tear strength of the base film in the slow-axis direction and the fast-axis direction according to the right-angle tearing method is smaller than 250 N/mm.

Item 4.

The electroluminescence display device according to any one of items 1 to 3 above, wherein the polarizing plate has a thickness of 12 μm or less.

Item 5.

The electroluminescence display device according to any one of items 1 to 4, wherein the polarizing plate is formed of a polymerizable liquid crystal compound and a dichroic dye.

Item 6.

The electroluminescent display device according to any one of items 1 to 5, wherein the retardation layer is formed of a liquid crystal compound.

The effect of the invention

The EL display device of the present invention utilizes a circular polarizing plate using a substrate film having a refractive index ny in the fast axis direction of 1.568 to 1.63, the number of self-supporting films present between the polarizing plate and the retardation layer is 1 or less, and the light transmission axis of the polarizing plate is approximately parallel to the fast axis of the substrate film. Therefore, visibility is excellent (suppression of rainbow spots), thinning is possible, and troubles in the manufacturing process are less likely to occur.

In addition, in the case of a flexible EL display device, the laminated members are not easily separated from each other even when repeatedly bent or placed in a high-temperature state, and creases are not easily given.

Detailed ways

The EL display device of the present invention includes: an EL element; and a circular polarizing plate disposed on the viewing side of the EL element. By arranging the circular polarizing plate on the viewing surface of the EL display device, it is possible to reduce the reduction in visibility due to external light reflected on the surface of the EL element or wiring. In addition, the EL display device of the present invention is thin. This circular polarizing plate has a retardation layer, a polarizing plate, and a base film in this order.

First, the circular polarizing plate used in the present invention will be described. A circular polarizing plate has a retardation layer, a polarizing plate, and a base film in this order. In this circular polarizing plate, the retardation layer, the polarizing plate, and the base film are basically laminated in this order, but it is a concept that includes the case where other layers are present between the respective layers.

A. Circular polarizer

1. Substrate film

First, the base film of the circular polarizing plate will be described. This circular polarizing plate has a base film on the visible side of the polarizing plate.

(Material of base film)

The resin of the base film used in the present invention is not particularly limited as long as birefringence occurs due to orientation. In the aspect that the amount of retardation can be increased, polyester, polycarbonate, polystyrene, etc. are preferable, and polyester is more preferable. Preferred polyesters include polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN). Among them, PET and PEN are more preferred. By using a polyester film as a base film, an EL display device having a circularly polarizing plate excellent in moisture permeability resistance, dimensional stability, mechanical strength, and chemical stability can be obtained.

In the case of PET, the intrinsic viscosity (IV) of the resin constituting the base film is preferably 0.58 to 1.5 dL/g. The lower limit of IV is more preferably 0.6 dL/g, still more preferably 0.65 dL/g, particularly preferably 0.68 dL/g. The upper limit of IV is more preferably 1.2 dL/g, still more preferably 1 dL/g. If the IV of PET is less than 0.58 dL/g, it may be easy to give bending marks under repeated bending. When the IV of PET exceeds 1.5 dL/g, it may become difficult to produce a film. In addition, as intrinsic viscosity (IV) in this invention, the value obtained by mixing phenol and 1,1,2,2-tetrachloroethane at a mass ratio of 6:4 as a solvent, and using the value measured at temperature 30 degreeC was used.

The light transmittance of the base film at a wavelength of 380 nm is desirably 20% or less. The light transmittance at a wavelength of 380 nm is more preferably 15% or less, further preferably 10% or less, particularly preferably 5% or less. If the light transmittance is 20% or less, deterioration of iodine or a dichroic dye in a polarizing plate due to ultraviolet rays can be suppressed. It should be noted that the transmittance in the present invention is measured along a direction perpendicular to the plane of the film, and can be measured using a spectrometer (for example, Hitachi U-3500).

In order to make the light transmittance of the wavelength 380nm of the substrate film below 20%, it can be achieved by the following methods: adding an ultraviolet absorber to the substrate film; coating the coating solution containing the ultraviolet absorber on the surface of the substrate film; suitably adjusting the type or concentration of the ultraviolet absorber and the thickness of the substrate film; etc. In the present invention, those known in the technical field can be used as the ultraviolet absorber. Examples of the ultraviolet absorber include organic ultraviolet absorbers and inorganic ultraviolet absorbers. From the viewpoint of transparency, an organic ultraviolet absorber is preferable.

The organic ultraviolet absorber can be used without particular limitation as long as it can make the light transmittance of the base film at a wavelength of 380 nm 20% or less. Examples of such organic ultraviolet absorbers include benzotriazole-based, benzophenone-based, cyclic iminoester-based, and combinations thereof.

In addition, it is also preferable to add particles having an average particle diameter of 0.05 to 2 μm to the base film in order to improve slipperiness. Examples of particles include inorganic particles such as titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, and calcium fluoride; organic polymer particles such as styrene, acrylic, melamine, benzoguanamine, and silicone. In addition, the average particle diameter was calculated by the method of observing the particle|grains of the cross-section of a film with the scanning electron microscope. Specifically, 100 particles in the cross section of the thin film were observed with a scanning electron microscope, the diameter (d) of each particle was measured, and the average value thereof was defined as the average particle diameter.

These particles may be added to the entire base film. Alternatively, the substrate can also be formed into a sheath-core coextruded multilayer structure, adding particles only to the sheath layer.

The lower limit of the refractive index ny in the fast axis direction of the base film is preferably 1.568, more preferably 1.578, still more preferably 1.584, particularly preferably 1.588. The upper limit of the refractive index ny in the fast axis direction of the base film is preferably 1.63, more preferably 1.62, still more preferably 1.615, particularly preferably 1.61. In the case of a PET film, when ny is less than 1.58, it is close to complete uniaxiality (uniaxial symmetry), and therefore, the mechanical strength in the direction parallel to the orientation direction is remarkably reduced. In addition, in a thin film having ny larger than 1.62, iridescent unevenness becomes easy to be observed when viewed from an oblique direction.

Generally, polyvinyl alcohol or a polymerizable liquid crystal compound is used as a matrix substance in a polarizing plate. In the above case, although it is not certain, the reason why rainbow spots are not easily observed is that the refractive index in the transmission axis direction of these polarizing plates is close to the refractive index of the base film, and reflection at the interface is suppressed.

The in-plane birefringence ΔNxy of the base film is preferably from 0.06 to 0.2, more preferably from 0.07 to 0.19, still more preferably from 0.08 to 0.18. When ΔNxy is less than 0.06, iridescent unevenness becomes easy to be observed when viewed from an oblique direction. In addition, in a film with ΔNxy greater than 0.2, iridescent spots do not occur, but as described above, it is close to complete uniaxiality (uniaxial symmetry), so the mechanical strength in the direction parallel to the orientation direction is significantly reduced.

The in-plane birefringence ΔNxy is the absolute value of the difference between the refractive index (nx) in the slow axis direction and the refractive index (ny) in the fast axis direction. In addition, the measurement wavelength of the refractive index was 589 nm.

The value of the smaller of the tear strengths in the slow axis direction and the fast axis direction of the base film by the rectangular tearing method is preferably 250 N/mm or more, more preferably 280 N/mm or more, and still more preferably 300 N/mm or more. In a film having a high value of ΔNxy, the value of tear strength in the slow axis direction tends to be smaller than that in the fast axis direction. When the tear strength is less than 250 N/mm, the film is easily broken, and the stability at the time of film production or processing decreases. On the other hand, as the tear strength becomes higher, the stability during film formation and processing increases, but the biaxiality (biaxial symmetry) becomes higher, and iridescent spots become generated. Therefore, it is preferable to increase the above-mentioned tear strength within a range in which iridescent spots do not occur, and it is actually preferably 500 N/mm or less.

In addition, tear strength is as follows: It measures according to the rectangular tear method (JISK-7123), and the tear strength (N/mm) per unit film thickness was calculated|required.

The Nz coefficient of the base film is preferably from 1.5 to 2.5, more preferably from 1.6 to 2.3, still more preferably from 1.7 to 2.1. The smaller the Nz coefficient, the less likely it is to produce iridescent spots caused by the viewing angle. In addition, the Nz coefficient becomes 1 in a completely uniaxial (monoaxially symmetric) thin film. However, as described above, the mechanical strength in the direction parallel to the orientation direction tends to decrease as the film approaches a completely uniaxial (uniaxially symmetric) film.

The Nz coefficient can be obtained as follows. Using a molecular orientation meter (manufactured by Oji Scientific Instruments Co Ltd., MOA-6004 molecular orientation meter), the orientation main axis direction (slow axis direction) of the film was obtained, and the biaxial refractive index (refractive index nx in the slow axis direction, and refractive index in the fast axis direction) in the orientation main axis direction and the direction (fast axis direction) orthogonal to it was obtained using an Abbe refractometer (ATAGO CO., LTD., NAR-4T, measurement wavelength 589 nm). rate ny, where nx>ny), and the refractive index in the thickness direction (nz). Substituting nx, ny, and nz obtained in this way into the expression shown by |nx-nz|/|nx-ny|, the Nz coefficient is obtained. In addition, the measurement wavelength of the refractive index was 589 nm.

From the viewpoint of further reducing rainbow spots, the base film preferably has a retardation of 1500 to 9000 nm. The lower limit of the amount of retardation is preferably 2000 nm, more preferably 2500 nm.

On the other hand, the upper limit of retardation is preferably 9000 nm. Even if a base film having a retardation exceeding this value is used, in an organic EL display device widely used in flexible image display devices, not only is the further improvement effect of visibility not substantially obtained, but the thickness of the base film becomes thicker, and the handleability of a circular polarizing plate for a thin flexible image display device decreases, or creases may be easily given by repeated folding operations caused by long-term use. The preferable upper limit of retardation is 8000 nm, the more preferable upper limit is 6000 nm, the more preferable upper limit is 5500 nm, and the most preferable upper limit is 5000 nm.

In addition, birefringence can also be calculated|required by measuring the refractive index in a biaxial direction, or can also be calculated|required using a commercially available automatic birefringence measuring apparatus, such as KOBRA-21ADH (Oji Scientific Instruments Co Ltd.). In addition, the measurement wavelength of the refractive index was 589 nm.

The base film used in the present invention can be obtained according to a general film production method of each raw material. Hereinafter, the case where a base film is polyester is demonstrated as an example. The polyester base film (hereinafter, may be simply referred to as the base film) can be produced in accordance with a general method for producing a polyester film. As a method for producing a polyester film, for example, a method of melting a polyester resin, extruding it into a sheet and molding it to obtain a non-oriented polyester, stretching the obtained non-oriented polyester at a temperature equal to or higher than the glass transition temperature in the longitudinal direction and the transverse direction, and performing heat treatment.

The base film may be a uniaxially stretched film or a biaxially stretched film. When using a biaxially stretched film as the base film, if the biaxiality is increased, there will be no iridescent stains when viewed from directly above the film surface, but iridescent spots may be observed when viewed from an oblique direction, so caution is required.

This phenomenon is caused by the fact that the biaxially stretched film is composed of refractive index ellipsoids having different refractive indices in the traveling direction, width direction, and thickness direction, and there is a direction in which the amount of retardation becomes zero (observing that the refractive index ellipsoid is a perfect circle) depending on the transmission direction of light at the inside of the film. Therefore, when the display screen is viewed from a specific direction in an oblique direction, there may be a point where the retardation amount becomes zero, and rainbow-like color irregularities may be concentrically generated around this point. Furthermore, when θ is the angle from directly above the film surface (normal direction) to the position where iridescent stains are visible, the larger the birefringence in the film surface is, the larger the angle θ becomes, and iridescent spots become less visible. Since the angle θ tends to be smaller in a biaxially stretched film, it is more preferable than a uniaxially stretched film at the point that iridescent unevenness is less likely to be seen.

However, a completely uniaxial (uniaxially symmetric) film is not preferable since the mechanical strength in the direction perpendicular to the orientation direction is remarkably lowered. In the present invention, it is preferable to have biaxiality (biaxial symmetry) within a range in which iridescent unevenness does not substantially occur, or within a range in which iridescent unevenness does not occur within a range of viewing angles required for a liquid crystal display screen.

The main orientation axis (slow axis in the case of polyester) of the base film may be the traveling direction of the film (longitudinal direction, MD direction) or a direction perpendicular to the longitudinal direction (orthogonal direction, TD direction).

The film forming conditions of the base film may be sequential biaxial stretching or simultaneous biaxial stretching. First, a film forming method in the case of sequential biaxial stretching will be described.

First, when the slow axis is perpendicular to the direction, the melted PET is extruded onto a cooling roll, and the obtained unstretched billet is longitudinally stretched with continuous rolls. Thereafter, both ends of the film are fixed with clips, introduced into a tenter, preheated, and then stretched in the transverse direction while heating. When the slow axis is the longitudinal direction, the same procedure as above can be followed, but it is preferable to stretch the unstretched raw material in the transverse direction with a tenter, and then stretch it longitudinally with continuous rolls.

The longitudinal stretching temperature and the transverse stretching temperature are preferably 80 to 130°C, more preferably 90 to 120°C. The draw ratio in the direction perpendicular to the main orientation direction performed first is preferably 1.2 to 3 times, more preferably 1.8 to 2.5 times. In addition, the draw ratio in the main orientation direction is preferably 2.5 to 6 times, more preferably 3 to 5.5 times.

In general sequential biaxial stretching, since longitudinal stretching becomes roll stretching, it is easy to give scratches to the film. Therefore, from the viewpoint of preventing scratches during stretching, simultaneous biaxial stretching without using rollers is preferable. When the film forming conditions of simultaneous biaxial stretching are demonstrated concretely, longitudinal stretching temperature and transverse stretching temperature are preferably 80-150 degreeC, More preferably, they are 90-140 degreeC. When the slow axis direction is the longitudinal direction, the longitudinal stretch ratio is preferably 5.5 to 7.5 times, more preferably 6 to 7 times, particularly preferably 6.5 to 7 times. In addition, the lateral stretch ratio is preferably 1.5 to 3 times, more preferably 1.8 to 2.8 times. When making the slow axis direction a perpendicular direction, the longitudinal stretch ratio and the lateral stretch ratio are opposite to the above.

In addition, in the case of uniaxial stretching, stretching may be performed only in the direction of the slow axis in the above.

In addition, from the viewpoint of making it difficult to give scratches to the film and general-purpose stretching equipment can be used, only transverse uniaxial stretching using a tenter may be used.

In order to control the direction of the slow axis, ΔNxy, Nz coefficient, and tear strength within the above-mentioned ranges, it is preferable to control the respective magnifications of the longitudinal stretch magnification and the transverse stretch magnification. If the difference between the vertical and horizontal stretch ratios is too small, it becomes difficult to increase ΔNxy. In addition, in terms of increasing ΔNxy, setting the stretching temperature lower is also a preferable response.

In order to increase the tear strength, it is preferable to moderately impart biaxiality to a completely uniaxial film under the condition that ΔNxy satisfies the range defined in the present specification.

In the subsequent heat treatment, the treatment temperature is preferably 100 to 250°C, more preferably 180 to 245°C.

The thickness of the base film is arbitrary, but is preferably in the range of 15 to 90 μm, more preferably in the range of 15 to 80 μm. In a base film having a thickness of less than 15 μm, the mechanical properties of the film are significantly lowered, cracks, cracks, etc. are likely to occur, and the practicality tends to be significantly reduced. A particularly preferable lower limit of the thickness is 20 μm. On the other hand, when the upper limit of the thickness of the base film exceeds 90 μm, the thickness of the circular polarizing plate becomes thick, which is not preferable. In addition, the thicker the thickness, the easier it is to give traces due to repeated bending with a small radius. Therefore, the upper limit of the thickness is preferably 80 μm, more preferably 70 μm, more preferably 60 μm, and particularly preferably 50 μm.

In the above thickness range, in order to control ΔNxy, Nz coefficient and tear strength to the range of the present invention, suitable polyester used as the base film is polyethylene terephthalate.

In addition, as a method of compounding an ultraviolet absorber in the polyester film in this invention, a well-known method can be used in combination. For example, the polyester film can be compounded with a UV absorber by a method such as: blending the dried UV absorber and polymer raw materials with a kneading extruder in advance to prepare a masterbatch in advance, and mixing the masterbatch and polymer raw materials at a predetermined ratio during film formation.

In the above case, in order to uniformly disperse the ultraviolet absorber and mix it economically, the concentration of the ultraviolet absorber in the masterbatch is preferably 5 to 30% by mass. As conditions for preparing the masterbatch, it is preferable to extrude at a temperature of not less than the melting point of the polyester raw material and not more than 290° C. for 1 to 15 minutes using a kneading extruder. If the extrusion temperature exceeds 290° C., the ultraviolet absorber will have a large decrease in weight, and the viscosity of the masterbatch will decrease greatly. If the extrusion time is less than 1 minute, uniform mixing of the ultraviolet absorber will become difficult. At this time, a stabilizer, a color tone adjuster, an antistatic agent, etc. may be added as needed.

In addition, in the present invention, it is preferable that the film has a multilayer structure of at least three layers, and an ultraviolet absorber is added to the middle layer of the film. Specifically, the film of the three-layer structure which contains an ultraviolet absorber in an intermediate layer can be produced as follows. Polyester pellets are used alone for the outer layer, and a masterbatch containing an ultraviolet absorber for the intermediate layer and polyester pellets are mixed at a predetermined ratio, dried, supplied to a known extruder for melt lamination, extruded into a sheet form from a slit-shaped die, and cooled and solidified on a casting roll to form an unstretched film. That is, two or more extruders, a three-layer manifold or a junction block (for example, a junction block having a square-shaped confluence part) are used to stack the film layers constituting the two outer layers and the film layer constituting the middle layer, extrude a three-layer sheet from the tube head, and cool it on a casting roll to form an unstretched film. In addition, in this invention, in order to remove the foreign matter contained in the raw material polyester which becomes a cause of an optical defect, it is preferable to perform high-precision filtration at the time of melt extrusion. The filtration particle size (initial filtration efficiency 95%) of the filter medium used for high-precision filtration of molten resin is preferably 15 μm or less. By setting the filtration particle size of the filter medium to 15 μm or less, foreign matter having a particle size of 20 μm or more can be sufficiently removed.

The substrate film may be subjected to corona treatment, flame treatment, plasma treatment, or other treatment for improving adhesion.

(easy bonding layer)

In order to improve the adhesiveness with the polarizing film or alignment layer mentioned later, you may provide an easily bonding layer (easy bonding layer P1) on a base film.

Examples of the resin used in the easily bonding layer include polyester resins, polyurethane resins, polyester polyurethane resins, polycarbonate resins, polycarbonate polyurethane resins, and acrylic resins. Among these, polyester resins, polyester polyurethane resins, polycarbonate polyurethane resins, and acrylic resins are preferred. The easily bonding layer is preferably crosslinked. As a crosslinking agent, an isocyanate compound, a melamine compound, an epoxy resin, an oxazoline compound, etc. are mentioned. In addition, in order to improve the adhesiveness, it is also a useful means to add a resin similar to the resin used for the alignment layer or the polarizing film, such as polyvinyl alcohol, polyamide, polyimide, and polyamideimide.

The easily bonding layer can be provided by forming a water-based paint to which these resins and, if necessary, a crosslinking agent, particles, and the like are added, and applying to a base film and drying. As the particles, users among the above-mentioned substrates can be exemplified.

The easily bonding layer may be provided on the stretched base film off-line, or may be provided on-line in the film forming process. The easily bonding layer is preferably provided in-line in the film forming step. When providing the easily bonding layer in-line, it may be either before longitudinal stretching or before lateral stretching. It is particularly preferable to apply the above-mentioned water-based paint immediately before transverse stretching, preheat and heat it with a tenter, and dry and crosslink it in this heat treatment step to form an easily bonding layer in-line. In addition, when performing in-line coating immediately before longitudinal stretching with a roll, it is preferable to introduce|transduce to a stretching roll after applying the said water-based coating material, drying it with a vertical dryer.

The coating amount of the aforementioned water-based paint is preferably 0.01 to 1.0 g/m ² , more preferably 0.03 to 0.5 g/m ² .

(functional layer)

It is also a preferable embodiment to provide functional layers such as a hard coat layer, an antireflection layer, a low reflection layer, an antiglare layer, and an antistatic layer on the opposite side of the base film to which the polarizing film is laminated.

The thickness of these functional layers can be appropriately set, but is preferably 0.1 to 50 μm, more preferably 0.5 to 20 μm, and still more preferably 1 to 10 μm. It should be noted that these layers can be set in multiple layers.

When providing a functional layer, you may provide an easily bonding layer (easy bonding layer P2) between a base film and a base film. In the easily bonding layer P2, the resin, a crosslinking agent, etc. mentioned in the said easily bonding layer P1 can be used suitably. In addition, the easily bonding layer P1 and the easily bonding layer P2 may have the same composition or different compositions.

It is also preferable that the easily bonding layer P2 is provided in-line. The easily bonding layer P1 and the easily bonding layer P2 can be applied sequentially and dried. In addition, it is also a preferable aspect to coat both surfaces of the base film with the easily bonding layer P1 and the easily bonding layer P2 at the same time.

In addition, when referring to a base film in the following description, not only the case where an easily bonding layer is not provided, but also the case where an easily bonding layer is provided is included. Similarly, those provided with a functional layer are also included in a base film.

2. Polarizer

In the circular polarizing plate used in the present invention, a polarizing plate is provided on a base film.

As the polarizer, for example, a polarizing film can be used. The polarizing film may be directly provided on the base film, or an orientation layer may be provided on the base film, and a polarizing film may be provided thereon. It should be noted that, in the present invention, the alignment layer and the polarizing film are sometimes collectively referred to as a polarizer. Moreover, when a polarizing film is provided without providing an orientation layer on a base film, a polarizing film can be called a polarizing plate.

(polarizing film)

The polarizing film has the function of allowing polarized light to pass in only one direction. The polarizing film can be used without particular limitation: a stretched film such as polyvinyl alcohol (PVA) in which iodine or a dichroic dye is blended, a dichroic dye film or a coated film obtained by blending a dichroic dye in a polymerizable liquid crystal compound, a polyene stretched film, a wire grid, and the like.

Among them, a polarizing film in which iodine is adsorbed to PVA, and a polarizing film in which a dichroic dye is blended in a polymerizable liquid crystal compound are preferable examples.

First, a polarizing film in which iodine is adsorbed on PVA will be described.

A polarizing film in which iodine is adsorbed to PVA can generally be obtained by uniaxially stretching an unstretched PVA film after being immersed in a bath containing iodine, or by immersing the uniaxially stretched film in a bath containing iodine, and then performing a crosslinking treatment in a boric acid bath.

The thickness of the polarizing film obtained by the above method is preferably 1 to 30 μm, more preferably 1.5 to 20 μm, and even more preferably 2 to 15 μm. If the thickness of the polarizing film is less than 1 μm, sufficient polarizing properties cannot be exhibited, and it may be difficult to handle if it is too thin. When the thickness of the polarizing film exceeds 30 μm, it does not meet the purpose of thinness.

When laminating the polarizing film in which iodine is adsorbed in PVA, and the base film, it is preferable to stick the base film and the polarizing film together. As an adhesive for pasting, conventional users can be used without limitation. Among these, PVA-based water-based adhesives, ultraviolet curable adhesives, and the like are preferred examples, and ultraviolet curable adhesives are more preferred.

In this way, the polarizing film in which iodine is adsorbed to PVA can be laminated with the base film using a separate film as a polarizer. Alternatively, it can also be laminated by a method in which a polarizing plate is laminated on a releasable support base obtained by coating PVA on a releasable support base and stretching it in this state (laminated polarizer on a releasable support base), and transferring the polarizing film to a base film. This method of laminating by transfer is also preferable as a method of laminating a polarizing plate and a base film, similarly to the above-mentioned method of pasting. When using this transfer method, the thickness of the polarizing plate is preferably 12 μm or less, more preferably 10 μm or less, further preferably 8 μm or less, particularly preferably 6 μm or less. Even if it is such a very thin polarizing plate, since it is a releasable support base material, handling is easy, and a polarizing plate can be easily laminated|stacked on a base film. By using such a thin polarizing plate, it is possible to cope with further reduction in thickness and to ensure flexibility.

In addition, the technique of laminating a polarizing plate and a base film is well-known, for example, JP-A-2001-350021 and JP-A-2009-93074 can be referred to.

The method of laminating a polarizing plate and a base film by transfer printing is demonstrated concretely. First, PVA is coated on a thermoplastic resin release support substrate that has been unstretched or uniaxially stretched perpendicular to the longitudinal direction, and the obtained laminate of the thermoplastic resin release support substrate and PVA is stretched 2 to 20 times, preferably 3 to 15 times, in the longitudinal direction. The stretching temperature is preferably 80 to 180°C, more preferably 100 to 160°C. Next, the stretched laminate is immersed in a bath containing a dichroic dye to adsorb the dichroic dye. As a dichroic dye, iodine, an organic dye, etc. are mentioned, for example. When using iodine as a dichroic dye, it is preferable to use an aqueous solution containing iodine and potassium iodide as a dyeing bath. Next, after immersing in an aqueous solution of boric acid for treatment, washing with water, and drying. It should be noted that stretching by 1.5 to 3 times may be performed as pre-stretching before the adsorption of the dichroic dye. In addition, the above-mentioned method is an example, and adsorption of a dichroic dye may be performed before stretching, and the treatment with boric acid may be performed before adsorption of a dichroic dye. Stretching may also be performed in a bath containing a dichroic dye or in a bath of an aqueous boric acid solution. In addition, these steps may be divided into multiple stages and combined.

As the releasable support substrate (release film) of thermoplastic resin, polyester films such as polyethylene terephthalate, polyolefin films such as polypropylene and polyethylene, polyamide films, polyurethane films, and the like can be used. The release force can be adjusted by corona treatment, release coating, easy-adhesion coating, etc. for the thermoplastic resin release supporting base material (release film).

A laminate of the base film and the polarizer can be obtained by affixing the polarizer surface of the releasable support base-laminated polarizer to the base film with an adhesive or adhesive, and then peeling the releasable support base. The thickness of the commonly used adhesive is 5-50 μm, and the thickness of the adhesive is 1-10 μm. For thinning, it is preferable to use an adhesive, and among them, it is more preferable to use an ultraviolet-curable adhesive. It is also preferable to use an adhesive in terms of a process that does not require a special device.

Next, a polarizing film in which a dichroic dye is mixed with a polymerizable liquid crystal compound will be described.

A dichroic dye is a dye that has a property in which the absorbance in the long-axis direction and the absorbance in the short-axis direction of the molecule are different.

The dichroic dye preferably has an absorption maximum wavelength (λMAX) in the range of 300 to 700 nm. Examples of such dichroic dyes include organic dichroic dyes such as acridine dyes, oxazine dyes, cyanine dyes, naphthalene dyes, azo dyes, and anthraquinone dyes, among which azo dyes are preferable. Examples of the azo dyes include monoazo dyes, disazo dyes, trisazo dyes, tetrazo dyes, and stilbene azo dyes, among which disazo dyes and trisazo dyes are preferable. Dichroic dyes may be used alone or in combination. In order to adjust (achromatic) color tone, it is preferable to combine 2 or more types, and it is more preferable to combine 3 or more types. It is particularly preferable to use a combination of three or more azo compounds.

Preferred azo compounds include dyes described in JP-A-2007-126628 , JP-A 2010-168570 , JP-A 2013-101328 , JP-A 2013-210624 and the like.

It is also a preferable embodiment that the dichroic dye is a dichroic dye polymer introduced into a side chain of a polymer such as acrylic. Examples of these dichroic dye polymers include polymers listed in JP-A-2016-4055 and polymers obtained by polymerizing compounds of [Chem. 6] to [Chem. 12] in JP-A-2014-206682.

The content of the dichroic dye in the polarizing film is preferably 0.1 to 30% by mass, more preferably 0.5 to 20% by mass, still more preferably 1.0 to 15% by mass, and particularly preferably 2.0 to 10% by mass in the polarizing film from the viewpoint of making the orientation of the dichroic dye good.

In order to improve film strength, degree of polarization, film homogeneity, etc., a polymerizable liquid crystal compound is contained in the polarizing film. It should be noted that the polymerizable liquid crystal compound also includes those polymerized in the form of a film.

The polymerizable liquid crystal compound refers to a compound that has a polymerizable group and exhibits liquid crystallinity.

A polymerizable group refers to a group that participates in a polymerization reaction, and is preferably a photopolymerizable group. Here, the photopolymerizable group refers to a group that can undergo a polymerization reaction by an active radical, an acid, or the like generated from a photopolymerization initiator described later. Examples of the polymerizable group include vinyl group, vinyloxy group, 1-chlorovinyl group, isopropenyl group, 4-vinylphenyl group, acryloyloxy group, methacryloyloxy group, oxiranyl group, oxetanyl group and the like. Among them, acryloyloxy group, methacryloyloxy group, ethyleneoxy group, oxiranyl group and oxetanyl group are preferable, and acryloyloxy group is more preferable. The compound exhibiting liquid crystallinity may be a thermotropic liquid crystal or a lyotropic liquid crystal, and may be a nematic liquid crystal or a smectic liquid crystal among thermotropic liquid crystals.

The polymerizable liquid crystal compound is preferably a smectic liquid crystal compound, more preferably a higher-order smectic liquid crystal compound, since higher polarization characteristics can be obtained. If the liquid crystal phase formed by the polymerizable liquid crystal compound is a high-order smectic phase, a polarizing film with a higher degree of orientation order can be produced.

Specific examples of preferred polymerizable liquid crystal compounds include, for example, JP-A-2002-308832, JP-A-2007-16207, JP-A-2015-163596, JP-A-2007-510946, JP-A-2013-114131, WO2005/045485, Lub Substances described in etal. Recl. Trav. Chim. Pays-Bas, 115, 321-328 (1996) and the like.

The content ratio of the polymerizable liquid crystal compound in the polarizing film is preferably 70 to 99.5% by mass, more preferably 75 to 99% by mass, further preferably 80 to 97% by mass, and particularly preferably 83 to 95% by mass in the polarizing film from the viewpoint of improving the orientation of the polymerizable liquid crystal compound.

A polarizing film containing a polymerizable liquid crystal compound and a dichroic dye can be provided by applying a composition for a polarizing film.

The composition for a polarizing film may further contain a solvent, a polymerization initiator, a sensitizer, a polymerization inhibitor, a leveling agent, a polymerizable non-liquid crystal compound, a crosslinking agent, and the like in addition to the polymerizable liquid crystal compound and the dichroic dye.

As the solvent, any solvent can be used without limitation as long as it dissolves the polymerizable liquid crystal compound. Specific examples of the solvent include water; alcohol-based solvents such as methanol, ethanol, isopropanol, ethylene glycol, propylene glycol, and cellosolve; ester-based solvents such as ethyl acetate, butyl acetate, and γ-butyrolactone; ketone-based solvents such as acetone, methyl ethyl ketone, cyclopentanone, and cyclohexanone; aromatic hydrocarbon solvents such as toluene and xylene; and ether-based solvents such as tetrahydrofuran and dimethoxyethane. These solvents may be used alone or in combination.

The polymerization initiator can be used without limitation as long as it polymerizes the polymerizable liquid crystal compound. As the polymerization initiator, a photopolymerization initiator that generates active radicals by light is preferable. Examples of the polymerization initiator include benzoin compounds, benzophenone compounds, alkylphenone compounds, acylphosphine oxide compounds, triazine compounds, iodonium salts, sulfonium salts, and the like.

As the sensitizer, a photosensitizer is preferable. Examples of the photosensitizer include xanthone compounds, anthracene compounds, phenothiazines, rubrene and the like.

Examples of the polymerization inhibitor include hydroquinones, catechols, and thiophenols.

Various well-known surfactants are mentioned as a leveling agent.

As the polymerizable non-liquid crystal compound, one copolymerized with a polymerizable liquid crystal compound is preferable. For example, when the polymerizable liquid crystal compound has a (meth)acryloyloxy group, examples of the polymerizable non-liquid crystal compound include (meth)acrylates. (Meth)acrylates may be monofunctional or polyfunctional. The strength of the polarizing film can be improved by using polyfunctional (meth)acrylates. When using a polymerizable non-liquid crystal compound, it is preferable to set it as 1-15 mass % in a polarizing film, it is more preferable to set it as 2-10 mass %, and it is still more preferable to set it as 3-7 mass %. When the content of the polymerizable non-liquid crystal compound exceeds 15% by mass, the degree of polarization may decrease.

As a crosslinking agent, the compound etc. which can react with the functional group of a polymerizable liquid crystal compound and a polymerizable non-liquid crystal compound are mentioned. As a crosslinking agent, an isocyanate compound, a melamine, an epoxy resin, an oxazoline compound, etc. are mentioned specifically,.

A polarizing film can be provided by directly applying the composition for a polarizing film on a base film or on an alignment layer, drying if necessary, heating, and curing.

As the coating method, known methods such as coating methods such as gravure coating, die coating, bar coating, and applicator; and printing methods such as flexographic printing can be used.

Drying is carried out by introducing the coated substrate film into a hot air dryer, an infrared dryer, or the like, preferably at 30 to 170°C, more preferably at 50 to 150°C, and even more preferably at 70 to 130°C. The drying time is preferably 0.5 to 30 minutes, more preferably 1 to 20 minutes, and still more preferably 2 to 10 minutes.

Heating may be performed to more firmly align the dichroic dye and the polymerizable liquid crystal compound in the polarizing film. The heating temperature is preferably within a temperature range in which the polymerizable liquid crystal compound forms a liquid crystal phase.

Since the composition for polarizing films contains a polymerizable liquid crystal compound, it is preferable to harden it. As a curing method, heating and light irradiation are mentioned, and light irradiation is preferable. Fixing can be performed in a state where the dichroic dye is oriented by curing. Curing is preferably carried out in a state where a liquid crystal phase is formed in the polymerizable liquid crystal compound, but it may be cured by irradiating light at a temperature at which a liquid crystal phase is formed.

Examples of light in light irradiation include visible light, ultraviolet light, and laser beams. In terms of ease of handling, ultraviolet light is preferred.

The irradiation intensity varies depending on the type or amount of a polymerization initiator or resin (monomer), but is preferably 100 to 10000 mJ/cm ² , more preferably 200 to 5000 mJ/cm ² based on 365 nm.

Polarizing Film The composition for a polarizing film is applied to an alignment layer provided if necessary, and the dye is aligned along the alignment direction of the alignment layer. As a result, the polarized light transmission axis has a predetermined direction. When directly coating the composition for polarizing films on a base material without providing an alignment layer, the composition for polarizing films can also be oriented by irradiating polarized light and curing the composition for polarizing films. It is more preferable to perform a heat treatment thereafter so as to orient the dichroic dye firmly along the orientation direction of the polymer liquid crystal.

The thickness of the polarizing film at this time is usually 0.1 to 5 μm, preferably 0.3 to 3 μm, more preferably 0.5 to 2 μm.

When laminating a polarizing film containing a polymerizable liquid crystal compound and a dichroic dye on a base film, not only a method of directly providing a polarizing film on the base film and laminating it, but also a method of providing a polarizing film on another release film according to the above-mentioned method and transferring it to the base film is preferable. As a release film, a release support base used for laminating a polarizing plate with a release support base laminated with the above-mentioned release support base is mentioned as a preferable example, and a polyester film, a polypropylene film, etc. are mentioned as a particularly preferable release film. The release film can be adjusted by corona treatment, release coating, easy-adhesion coating, etc., to adjust the release force.

The method of transferring the polarizing film to the base film is also the same as the method for the polarizing plate laminated on the release support base and the release support base.

(orientation layer)

The polarizing plate used in the present invention may not only be a polarizing film as described above, but may also have a combination of a polarizing film and an alignment layer.

The alignment layer is used to control the alignment direction of the polarizing film, and by providing the alignment layer, a polarizer with a higher degree of polarization can be provided.

As an orientation layer, any orientation layer may be used as long as it can make a polarizing film into a desired orientation state. As a method of providing an alignment state to an alignment layer, for example, surface brushing treatment, oblique vapor deposition of an inorganic compound, formation of a layer having microgrooves, and the like are mentioned. Furthermore, a method of forming a photo-alignment layer that functions as an alignment function by aligning molecules by irradiation with polarized light is also preferable.

Hereinafter, two examples of the brushing treatment alignment layer and the photo alignment layer will be described.

Brushing Treatment Alignment Layer

As the polymer material used in the alignment layer formed by brushing treatment, polyvinyl alcohol and its derivatives, polyimide and its derivatives, acrylic resin, polysiloxane derivatives, and the like are preferably used.

First, after coating the coating liquid for brushing treatment alignment layer containing the above-mentioned polymer material on the substrate film, heat drying etc. are performed to obtain the alignment layer before brushing treatment. The coating liquid for an alignment layer may have a crosslinking agent. Examples of the crosslinking agent include compounds containing a plurality of isocyanate groups, epoxy groups, oxazoline groups, vinyl groups, acryloyl groups, carbodiimide groups, alkoxysilyl groups, etc.; amide resins such as melamine compounds; and phenolic resins.

As the solvent for the brushing treatment alignment layer coating liquid, any solvent can be used without limitation as long as it dissolves the polymer material. Specific examples of the solvent include water; alcohol solvents such as methanol, ethanol, isopropanol, ethylene glycol, propylene glycol, and cellosolve; ester solvents such as ethyl acetate, butyl acetate, and γ-butyrolactone; ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, and cyclohexanone; aromatic hydrocarbon solvents such as toluene and xylene; ether solvents such as tetrahydrofuran and dimethoxyethane. These solvents may be used alone or in combination.

The concentration of the brushing treatment alignment layer coating liquid can be appropriately adjusted depending on the type of polymer, the thickness of the alignment layer to be produced, etc., and is expressed as a solid content concentration, preferably in the range of 0.2 to 20% by mass, more preferably 0.3 to 10% by mass.

As the coating method, known coating methods such as gravure coating, die coating, bar coating, and applicator; printing methods such as flexographic printing can be used.

The temperature of heat drying also depends on the base film, and in the case of PET, it is preferably in the range of 30 to 170°C, more preferably in the range of 50 to 150°C, and still more preferably in the range of 70 to 130°C. When the drying temperature is too low, a long drying time is required, and productivity may be poor. If the drying temperature is too high, the orientation state of the substrate film will be affected, the retardation will decrease, or the thermal shrinkage of the substrate film will increase, so that the designed optical function cannot be achieved, and problems such as poor planarity will occur. The heat drying time is usually 0.5 to 30 minutes, preferably 1 to 20 minutes, more preferably 2 to 10 minutes.

The brushing-treated alignment layer has a thickness of preferably 0.01 to 10 μm, more preferably 0.05 to 5 μm, even more preferably 0.1 to 1 μm.

The brushing treatment can generally be performed by rubbing the surface of the polymer layer with paper or cloth in a constant direction. Usually, the surface of the alignment film is subjected to a brushing treatment using a brushing roller of a raised cloth made of fibers such as nylon, polyester, and acrylic.

In order to provide a polarizing film having a light transmission axis in a predetermined direction with respect to the longitudinal direction of the elongated base film, the brushing direction of the alignment layer also needs to form an angle corresponding to it. Adjustment of the angle can be performed by adjusting the angle between the brush roller and the base film, adjusting the conveying speed of the base film, the rotation speed of the roll, and the like.

It should be noted that the base film may also be directly subjected to brushing treatment so that the surface of the base film may function as an alignment layer. The above situation is also included in the protection scope of the present invention.

photo-alignment layer

The photo-alignment layer refers to an alignment film that imparts orientation-regulating force by applying a coating liquid containing a polymer or monomer having a photoreactive group and a solvent to a substrate film, and irradiating polarized light, preferably polarized ultraviolet rays. The photoreactive group means a group that produces liquid crystal alignment ability by light irradiation. Specifically, photoreactions which are the origin of liquid crystal orientation ability, such as orientation induction of molecules by irradiation with light, or isomerization reaction, dimerization reaction, photocrosslinking reaction, or photodecomposition reaction. Among the photoreactive groups, those that cause a dimerization reaction or a photocrosslinking reaction are preferable in terms of maintaining the smectic liquid crystal state of the polarizing film having excellent orientation. As the photoreactive group capable of generating the above reaction, an unsaturated bond is preferred, a double bond is particularly preferred, and a group having at least one selected from the group consisting of a C=C bond, a C=N bond, an N=N bond and a C=O bond is particularly preferable.

As a photoreactive group which has a C=C bond, a vinyl group, a polyalkenyl group, a stilbene group, a stilbazolyl group, a stilbazolium group, a chalcone group, a cinnamoyl group etc. are mentioned, for example. Examples of the photoreactive group having a C=N bond include groups having structures such as aromatic SchiFF bases and aromatic hydrazones. Examples of the photoreactive group having an N=N bond include azophenyl, azonaphthyl, aromatic heterocyclic azo, disazo, formazan, azoxybenzene and the like as its basic structure. Examples of the photoreactive group having a C=O bond include a benzophenone group, a coumarin group, an anthraquinone group, and a maleimide group. These groups may have substituents such as alkyl, alkoxy, aryl, allyloxy, cyano, alkoxycarbonyl, hydroxyl, sulfonic acid, and haloalkyl.

Among them, photoreactive groups capable of inducing photodimerization reactions are preferred, and cinnamoyl groups and chalcone groups are preferred because they are easy to obtain a photoalignment layer that requires less irradiation of polarized light required for photoalignment and has excellent thermal stability or stability over time. Furthermore, as a polymer which has a photoreactive group, what has a cinnamoyl group in which the terminal part of this polymer side chain becomes a cinnamic acid structure is especially preferable. Examples of the main chain structure include polyimide, polyamide, (meth)acrylic acid, polyester and the like.

As a specific alignment layer, for example, JP-A 2006-285197, JP-A 2007-76839, JP-A 2007-138138, JP-A 2007-94071, JP-A 2007-121721, JP-A 2007-140465, JP-A 20 07-156439 Gazette, JP 2007-133184 Gazette, JP 2009-109831 Gazette, JP 2002-229039 Gazette, JP 2002-265541 Gazette, JP 2002-317013 Gazette, JP 2003-520878 Gazette, JP Alignment layers described in Table 2004-529220 A, JP-A No. 2013-33248, JP-A No. 2015-7702, JP-A No. 2015-129210, etc.

As a solvent of the coating liquid for photo-alignment layer formation, the polymer and monomer which have a photoreactive group can be used without limitation, and can be used without limitation. As a specific example of a solvent, what was mentioned in the brushing process alignment layer can be illustrated. A photopolymerization initiator, a polymerization inhibitor, various stabilizers, etc. can also be added to the coating liquid for photo-alignment layer formation as needed. In addition, a polymer having a photoreactive group and a polymer other than a monomer, a monomer having no photoreactive group copolymerizable with a monomer having a photoreactive group, etc. may be added to the coating liquid for forming a photoalignment layer.

The concentration of the coating solution for forming a photo-alignment layer, the coating method, the drying conditions, and the like can be exemplified by those listed in the brushing treatment of the alignment layer. The thickness of the photo-alignment layer is also the same as the preferred thickness of the brush-treated alignment layer.

By irradiating the thus-obtained photo-alignment layer before alignment with polarized light in a predetermined direction with respect to the longitudinal direction of the base film, a photo-alignment layer in which the direction of the alignment regulating force is in a predetermined direction with respect to the longitudinal direction of the elongated base film can be obtained.

Polarized light may be directly irradiated to the photo-alignment layer before alignment, or may be irradiated through the substrate film.

The wavelength of the polarized light is preferably in the wavelength region where the photoreactive group of the polymer or monomer having a photoreactive group can absorb light energy. Specifically, ultraviolet rays having a wavelength of 250 to 400 nm are preferable.

The light sources of polarized light include xenon lamps, high-pressure mercury lamps, ultra-high pressure mercury lamps, metal halide lamps, ultraviolet lasers such as KrF and ArF, and are preferably high-pressure mercury lamps, ultra-high pressure mercury lamps, and metal halide lamps.

Polarized light can be obtained, for example, by passing light from the aforementioned light source through a polarizing plate. By adjusting the polarization angle of the aforementioned polarizer, the direction of polarized light can be adjusted. Examples of the aforementioned polarizing plate include polarizing filters; polarizing prisms such as Glan-Thompson and Glan-Taylor; and wire grid-type polarizing plates. Polarized light is preferably substantially parallel light.

By adjusting the angle of the polarized light to be irradiated, the direction of the alignment-regulating force of the photo-alignment layer can be adjusted arbitrarily.

The irradiation intensity varies depending on the type or amount of a polymerization initiator or resin (monomer), but is preferably 10 to 10000 mJ/cm ² , more preferably 20 to 5000 mJ/cm ² based on 365 nm.

(the angle between the light transmission axis of the polarizer and the fast axis of the substrate film)

It is preferable that the light transmission axis of a polarizing plate and the fast axis of a base film are substantially parallel. Substantially parallel here means that the angle formed by the light transmission axis of the polarizing plate and the fast axis of the base film is 10 degrees or less. The angle formed by the light transmission axis of the polarizing plate and the fast axis of the base film is preferably 7 degrees or less, more preferably 5 degrees or less. When the angle formed by the transmission axis of the polarizing plate and the fast axis of the base film exceeds 10 degrees, rainbow spots may become easily visible when viewed from an oblique direction.

In the case of a polarizing plate obtained by stretching polyvinyl alcohol, the polarizing plate is usually stretched in the longitudinal direction, and the transmission axis direction becomes a direction perpendicular to it. Therefore, a base film having a slow axis in the longitudinal direction (in the case of polyester, having a main orientation axis in the longitudinal direction) is a suitable combination in terms of productivity. On the other hand, in the case of a polarizing plate obtained by orienting a polymerized liquid crystal compound, the direction of the transmission axis of the polarizing plate can be adjusted in the rubbing direction or the polarization direction of ultraviolet rays. Therefore, any combination in which the base film has a slow axis in either the longitudinal direction or the perpendicular direction is suitable.

On the opposite side of the polarizing plate to the base film, a protective coating may be provided to prevent scratches in the next step and to prevent deterioration of the polarizing plate due to adhesives, adhesives, solvents for coating the retardation layer, and the like. As the overcoat layer, PVA, other resins, ultraviolet curable resins, and the like can be appropriately selected within the range that does not adversely affect the polarizing plate. The thickness of the overcoat layer is preferably 0.01 to 10 μm, more preferably 0.1 to 5 μm.

3. Phase difference layer

In the circular polarizing plate used in the present invention, a retardation layer is present on the side of the polarizing plate opposite to the surface of the base film. That is, this circular polarizing plate has a retardation layer on the electroluminescent (EL) element side of the polarizing plate. One of the characteristics of the EL display device of the present invention is that there is no self-supporting film between the polarizer and the retardation layer, or only one self-supporting film (here, the retardation layer itself is also included between the polarizer and the retardation layer). Here, the self-supporting thin film refers to a form that exists independently in the form of a thin film in terms of process.

In addition, the term "retardation layer" here refers to one used to function as a circular polarizing plate, and specifically refers to a 1/4 wavelength layer, a 1/2 wavelength layer, a C plate layer, and the like.

The fact that no self-supporting film is present between the polarizing plate and the retardation layer means that the retardation layer is directly laminated on the polarizing plate instead of laminating the self-supporting film. Here, "directly" means that there is no layer between the polarizing plate and the retardation layer, and between the retardation layers, or even if there is, it is only an adhesive layer or an adhesive layer.

The fact that one self-supporting film exists between the polarizing plate and the retardation layer means that only one of the polarizing plate protective film and all the retardation layers is a self-supporting film.

The 1/4 wavelength layer can be obtained by pasting a separately prepared retardation film (self-supporting film) provided with a coating type 1/4 wavelength layer described later on an oriented film (self-supporting film) such as polycarbonate or cycloolefin, or a cellulose triacetate (TAC) film. However, it is preferable to provide a coating type 1/4 wavelength layer directly on the polarizer from the viewpoint of thinning or ensuring flexibility.

The coating-type 1/4 wavelength layer means that the 1/4 wavelength layer itself is a 1/4 wavelength layer formed by coating, and does not become an independent state. As a method of providing a 1/4 wavelength layer, the following methods can be mentioned: a method of coating a retardation compound on a polarizing plate; a method of separately providing a 1/4 wavelength layer on a base material with mold release properties, and transferring it to a polarizing plate. As the 1/4 wavelength layer, a layer formed of a liquid crystal compound is preferable. Examples of the liquid crystal compound include rod-like liquid crystal compounds, polymer-like liquid crystal compounds, liquid crystal compounds having reactive functional groups, and the like. As a method of coating the retardation compound on the polarizing plate, it is preferable to brush the polarizing plate, or apply the liquid crystal compound after providing the above-mentioned alignment layer on the polarizing plate so as to have an alignment control force.

In addition, in the method of providing a coating type 1/4 wavelength layer on a release substrate and transferring it to a polarizing plate, it is preferable to perform a brushing treatment on the release substrate, or to apply the liquid crystal compound (1/4 wavelength layer) after providing the above-mentioned alignment layer on the release substrate so that it has orientation control force.

In addition, as a transfer method, a method in which a birefringent resin is coated on a releasable base material and stretched together with the base material to form a 1/4 wavelength layer is also preferable.

After affixing the transfer-type 1/4 wavelength layer obtained in this way to a polarizing plate with an adhesive or an adhesive, the release base material is peeled off. In order to reduce the thickness, it is preferable to stick it with an adhesive, especially an ultraviolet-curable adhesive.

Since the polarizing plate is not easily affected by the coating solvent of the 1/4 wavelength layer, a method of separately providing a coating type 1/4 wavelength layer on a release base material and transferring it to the polarizing plate is preferable.

The front retardation of the 1/4 wavelength layer is preferably 100 to 180 nm, more preferably 120 to 150 nm.

For these methods and retardation layers, for example, JP-A-2008-149577, JP-A-2002-303722, WO2006/100830, JP-A-2015-64418, etc. can be referred to.

In addition, when the 1/4 wavelength layer is alone, the 1/4 wavelength may not be obtained in the wide wavelength range of visible light, and coloring may occur. In such a case, a 1/2 wavelength layer may be further provided. In the above case, it is preferable to provide a 1/2 wavelength layer between the polarizing plate and the 1/4 wavelength layer.

Preferable raw materials, forms, manufacturing methods, lamination methods, etc. of the 1/2 wavelength layer are the same as the above-mentioned 1/4 wavelength layer.

The front retardation of the 1/2 wavelength layer is preferably 200 to 360 nm, more preferably 240 to 300 nm.

When only the 1/4 wavelength layer is used as the retardation layer, the angle formed by the orientation axis (slow axis) of the 1/4 wavelength layer and the transmission axis of the polarizer is preferably 35 to 55 degrees, more preferably 40 to 50 degrees, and even more preferably 42 to 48 degrees.

When using a 1/4 wavelength layer and a 1/2 wavelength layer in combination as a retardation layer, the angle (θ) formed by the orientation axis (slow axis) of the 1/2 wavelength layer and the transmission axis of the polarizer is preferably 5 to 20 degrees, more preferably 7 to 17 degrees. The angle formed by the orientation axis (slow axis) of the 1/2 wavelength layer and the orientation axis (slow axis) of the 1/4 wavelength layer is preferably within the range of 2θ+45°±10°, more preferably within the range of 2θ+45°±5°, even more preferably within the range of 2θ+45°±3°.

In the case of pasting an oriented film, these angles can be adjusted by the angle of pasting, the stretching direction of the oriented film, and the like.

In the case of the coating type 1/4 wavelength layer and 1/2 wavelength layer, it can be controlled by the angle of brushing, the irradiation angle of polarized ultraviolet rays, and the like.

In the method of providing a coating type 1/4 wavelength layer on a base material and transferring it to a polarizing plate, in the case of roll-to-roll bonding, it is preferable to control the angle of brushing or the irradiation angle of polarized ultraviolet rays to a predetermined angle in advance.

In addition, when an oriented film is used or when a birefringent resin is applied to a base film and stretched together with the base material, it is preferable to stretch in an oblique direction so that a predetermined angle is obtained when sticking by roll-to-roll.

Furthermore, it is also a preferable aspect to provide a C plate layer on the 1/4 wavelength layer in order to reduce the change in coloring when viewed from an oblique view. Among the C-plate layers, positive or negative C-plate layers can be used depending on the characteristics of the 1/4 wavelength layer or the 1/2 wavelength layer. The C plate layer is preferably a liquid crystal compound layer. The C-plate layer can be provided by directly coating the coating solution to be the C-plate layer on the 1/4 wavelength layer, or by transferring a separately produced C-plate layer.

As these stacking methods, various methods can be employed. For example, the following methods can be mentioned.

- A method of providing a 1/2 wavelength layer by transfer on a polarizing plate, and further providing a 1/4 wavelength layer thereon by transfer.

- A method in which a 1/4 wavelength layer and a 1/2 wavelength layer are sequentially provided on a release film and transferred to a polarizing plate.

・A method in which a 1/2 wavelength layer is provided on a polarizing plate by coating, and a 1/4 wavelength layer is provided by transfer printing.

- A method of preparing a film-like 1/2 wavelength layer, applying or transferring a 1/4 wavelength layer on top of it, and sticking it on a polarizing plate.

In addition, in the case of laminating the C-plate layers, various methods can also be employed. For example, the following methods can be mentioned: the method of applying or transferring the C plate layer on the 1/4 wavelength layer provided on the polarizing plate; the method of pre-stacking the C plate layer on the 1/4 wavelength layer to be transferred or pasted.

In the present invention, when there is a C plate between the polarizer and the 1/4 wavelength layer (including the 1/4 wavelength layer), all the layers from the polarizer to the C plate (including the C plate) are preferably coating layers. This means that no self-supporting film is present on the opposite side of the polarizing plate to the base film. Specifically, it means that only any combination of an adhesive layer, an adhesive layer, a protective coating layer, an orientation layer, and a coating-type retardation layer exists on the opposite side of the polarizing plate from the base film. With such a configuration, the thickness of the circular polarizing plate can be reduced or flexibility can be ensured.

As a specific preferred lamination example between the polarizing plate and the 1/4 wavelength layer, the following can be mentioned:

polarizer/1/2 wavelength layer/adhesive layer/1/4 wavelength layer,

polarizer/adhesive layer/1/2 wavelength layer/adhesive layer/1/4 wavelength layer,

polarizer/protective coating layer/1/2 wavelength layer/adhesive layer/1/4 wavelength layer,

Polarizer/protective coating layer/adhesive layer/1/2 wavelength layer/adhesive layer/1/4 wavelength layer, etc.

It should be noted that the above-mentioned middle adhesive layer may be an adhesive layer. In addition, the 1/4 wavelength layer and the 1/2 wavelength layer may contain an alignment layer on either side.

As the adhesive layer, rubber-based, acrylic-based, urethane-based, olefin-based, silicone-based, and other adhesives can be used without limitation. Among them, acrylic adhesives are preferable. The adhesive can be applied to an object, for example, a polarizer surface of a polarizing plate. A preferred method is to provide an adhesive layer by peeling off the release film on one side of the substrate-less optically transparent adhesive (release film/adhesive layer/release film) and affixing it to the surface of the polarizer. As the adhesive, ultraviolet curing type, urethane type, and epoxy type are preferably used.

The adhesive layer or the pressure-sensitive adhesive layer is used for bonding a polarizing plate, a protective coating layer, a coating-type retardation layer, or an EL element.

It should be noted that, in the above, the retardation layer (1/4 wavelength layer and 1/2 wavelength layer) can be exemplified as follows: the laminated body of the substrate film and the polarizing plate is attached to the object after being installed, but the retardation layer (1/4 wavelength layer and 1/2 wavelength layer) can be provided on the object in advance, and the laminated body of the substrate film and the polarizing plate is pasted thereon. The same applies to the case where the C layer is provided.

The thickness of the circular polarizing plate thus obtained is preferably 100 μm or less, more preferably 80 μm or less, further preferably 70 μm or less, particularly preferably 60 μm or less.

Furthermore, a circularly polarized reflection layer made of a liquid crystal compound may be provided on the retardation layer of the circularly polarizing plate (the surface opposite to the polarizing plate). The circularly polarized light reflecting layer is preferably a cholesteric liquid crystal layer. The cholesteric liquid crystal layer may be one layer, but the cholesteric liquid crystal layer has wavelength selectivity in reflection characteristics, so that a uniform reflection characteristic is formed in a wide range of visible light, and it is preferable to provide a plurality of cholesteric liquid crystal layers. The cholesteric liquid crystal layer is more preferably two or more layers, further preferably three or more layers. The cholesteric liquid crystal layer is preferably seven or less, more preferably six or less, particularly preferably five or less.

The circularly polarized light reflecting layer is preferably provided by coating or transferring a circularly polarized light reflecting layer containing a liquid crystal compound.

Examples of the liquid crystal compound used in the circularly polarized light reflection layer include the liquid crystal compound used in the aforementioned polarizing film or retardation layer.

Furthermore, in order to align the circularly polarized light reflective layer with cholesteric liquid crystals, it is preferable that the coating material for the circularly polarized light reflective layer contains a chiral agent. By containing a chiral agent, the helical structure of a cholesteric liquid crystal phase is induced, and a cholesteric liquid crystal phase becomes easy to obtain.

The chiral agent is not particularly limited, and known chiral agents can be used. Examples of the chiral agent include liquid crystal device handbook, chapter 3, item 4-3, chiral agents for TN (Twisted Nematic), STN (Super-twisted nematic display), page 199, edited by the 142nd Committee of the Japan Society for the Promotion of Science, 1989, compounds, isosorbide, isomannitol derivatives, and the like. The chiral agent preferably has a polymerizable group. It is preferable that the compounding quantity of a chiral agent is 1-10 mass parts with respect to 100 mass parts of liquid crystal compounds.

When the circularly polarized light reflective layer is provided on the retardation layer by coating, it may be directly coated on the retardation layer, or an alignment layer may be provided and coated thereon. When the circularly polarized light reflective layer is provided by transfer, it may be directly coated on the release base material, or an orientation layer may be provided on the release base material and the coating material for the circularly polarized light reflective layer may be coated thereon. Alternatively, a circularly polarized light reflection layer and a retardation layer may be sequentially provided on a releasable substrate and transferred to a polarizing plate. It is also possible to sequentially provide a circularly polarized light reflection layer and a part of a retardation layer on a releasable substrate, place another part of the retardation layer on a separate polarizing plate, and transfer it to the retardation layer. As the alignment layer, the above-mentioned alignment layer is preferably used.

The circularly polarized light reflecting layer can be described, for example, in JP-A-1-133003, JP-A-3416302, JP-A-3363565, JP-A-8-271731, International Publication No. 2016/194497, JP-A-2018-10086, etc., which are referred to herein.

The thickness of the circularly polarized light reflecting layer is preferably 2.0 to 150 μm, more preferably 5.0 to 100 μm. It should be noted that, when the circularly polarized light reflecting layer is multilayered, the total thickness is also preferably within the above-mentioned range.

By combining the circularly polarized light reflection layer with the circularly polarizing plate, it is possible to reduce the decrease in luminance when the circularly polarizing plate for anti-reflection is provided in the EL display device. Furthermore, the polarizing plate, the retardation layer, and the circularly polarized light reflecting layer are provided by coating or transfer printing, and by forming a structure without a self-supporting film between the polarizing plate and the circularly polarized light reflecting layer (including the polarizing plate itself and the circularly polarized light reflecting layer), the circular polarizing plate can be thinned, and it becomes easy to cope with the thinning of the EL display device. In addition, such a structure is optimal as a flexible EL display device such as foldable or rollable.

B. EL element

The EL display device of the present invention includes the aforementioned circular polarizing plate on the visible side of the EL element. Known ones can be used without limitation as the EL element, and among them, an organic EL element is preferable because it is thin. The EL element and the circular polarizing plate are preferably bonded with an adhesive.

The EL display device of the present invention uses a circular polarizing plate having a base film whose refractive index Ny in the fast axis direction is 1.568 to 1.63, the number of self-supporting films present between the polarizing plate and the retardation layer is 1 or less, and the transmission axis of the polarizing plate is approximately parallel to the fast axis of the base film, so that visibility is excellent (suppression of rainbow spots), thinning can be achieved, and troubles in the manufacturing process are less likely to occur. In particular, it is suitable for use in large EL display devices of size 40 (diagonal length of the display portion is 40 inches) or larger and size 50 (diagonal length of the display portion is 50 inches).

In addition, in the case of forming a flexible EL display device, the laminated members are less likely to be peeled off and creases are less likely to be formed even when repeatedly bent or placed in a high-temperature state.

As a flexible EL display device, it is preferably used in any of an EL display device that can be folded into a V shape, a Z shape, a W shape, a double door shape, etc. (folding type EL display device), or an EL display device that can be rolled up into a roll shape (rolling type EL display device).

In the case where the foldable EL display device has a display portion on the inner side of the fold, the bending radius of the circular polarizing plate in the folded state becomes small. In the case of such an EL display device, the main orientation direction of the base film is arranged perpendicular to the folding direction (direction of folding operation), thereby effectively reducing the occurrence of creases caused by repeated folding operations. It should be noted that, in the vertical direction, the angle formed by the main orientation direction of the substrate film and the folding direction is preferably 75-105 degrees, more preferably 80-100 degrees, and even more preferably 83-97 degrees.

The reason why creases can be reduced is that the substrate film is stretched by repeated folding operations, or the stretched direction is perpendicular to the main molecular orientation direction, so the substrate film becomes easy to elongate. The flexible EL display device of the present invention can be suitably used for a foldable EL display device having a bending radius of 5 mm or less, further 4 mm or less, particularly 3 mm.

In the case of a foldable EL display device having a display portion on the folded outer side of the device, or in the case where the bending radius does not become small even if it is an inner surface, or in the case of a roll-up type EL display device, the main orientation direction of the base film can be used without particular limitation. However, in such a case, it is also a preferred aspect to make the main orientation direction of the base film parallel to the folding direction. By making them parallel, the flatness of the entire EL display device at the time of expansion tends to be improved. In the above case, the angle formed by the main orientation direction of the base film and the folding direction is preferably 15 degrees or less, more preferably 10 degrees or less, and still more preferably 7 degrees or less.

The flexible EL display device of the present invention does not peel off even when it is repeatedly bent or placed in a high-temperature state, it is difficult to give creases, and it has excellent visibility. Further, when a polyester film is used as a base film of a circular polarizing plate, an EL display device having a circular polarizing plate excellent in moisture permeability resistance, dimensional stability, mechanical strength, and chemical stability can be provided.

Example

Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples. It can also be appropriately modified and implemented within the range that can meet the gist of the present invention, and these are all included in the protection scope of the present invention.

The evaluation method of the physical property in an Example is as follows.

(1) Evaluation of the slow axis and fast axis directions of the film

Evaluation of the axial direction of the film was measured with a molecular orientation meter (molecular orientation meter MOA-6004, manufactured by Oji Scientific Instruments Co Ltd.).

(2) ΔNxy and delay (Re)

The retardation is a parameter defined by the product (ΔNxy×d) of the refractive index anisotropy (ΔNxy=|nx-ny|) of the orthogonal biaxial axes on the film and the film thickness d (nm), and is a scale representing optical isotropy and anisotropy. The biaxial refractive index anisotropy (ΔNxy) was obtained by the following method. Using a molecular orientation meter (manufactured by Oji Scientific Instruments Co Ltd., MOA-6004 molecular orientation meter), the slow axis direction of the film was obtained, and the film was cut into a rectangle of 4 cm x 2 cm so that the slow axis direction was parallel to the long side of the measurement sample, and used as a measurement sample. The sample was measured with an Abbe refractometer (manufactured by ATAGO CO., LTD., NAR-4T, measurement wavelength 589 nm) to measure the refractive index of the orthogonal biaxial axis (refractive index in the slow axis direction: nx, the refractive index in the direction perpendicular to the slow axis direction in the plane (that is, the refractive index in the fast axis direction): ny), and the refractive index in the thickness direction (nz), and the absolute value of the difference between the aforementioned biaxial refractive indices (|nx-ny|) Anisotropy (ΔNxy) as refractive index. The thickness d (nm) of the film was measured with an electronic micrometer (Millitron 1245D, manufactured by Fine Ryuf Co., Ltd.), and the unit was converted into nm. The retardation (Re) was obtained from the product (ΔNxy×d) of the anisotropy of the refractive index (ΔNxy) and the thickness d (nm) of the film.

(3) Nz coefficient

The values of nx, ny, and nz measured by the Abbe refractometer in (2) above were substituted into |nx-nz|/|nx-ny| to obtain the Nz coefficient.

(4) Observation of rainbow spots

The polarizing plate obtained as follows was arranged in an organic EL display so that the PET film was positioned on the visible side instead of a commercially available organic EL display (Organic EL TV C6P 55 inches manufactured by LG Corporation) except for the circular polarizing plate (the circular polarizing plate was placed closer to the visible side than the organic EL element). The organic EL display was visually observed from the front and oblique directions, and the presence or absence of occurrence of rainbow spots was determined as follows.

◯: No rainbow spots are observed when observed from any direction.

Δ: When viewed from an oblique direction of 60 degrees or more relative to the normal direction, a shallow rainbow spot is observed.

×: When viewed from an oblique direction of 60 degrees or more relative to the normal direction, rainbow spots are observed.

(5) Thickness of substrate film and circular polarizer

The thickness of the substrate film and circular polarizing plate was measured with a commercially available digital thickness gauge.

(6) Based on the thickness of each layer applied

The thickness of each layer based on coating is as follows: Under the same coating conditions, PET film (PET with easy-adhesive treatment is performed if necessary) is embedded and coated with epoxy resin, cut into slices, and observed with a microscope. As the microscope, an optical microscope, a transmission electron microscope, or a scanning electron microscope is used depending on the thickness.

(7) Operability

The produced circular polarizing plate was cut into an A5 equivalent, and a paper tube with an outer diameter of 6 inches and a biaxially stretched PET film with a thickness of 50 μm was wound up so that the longitudinal direction became the winding direction. The winding was carried out by inserting the circular polarizing plate sample when the PET film was wound by 3 m, and further winding the PET film by 7 m. In addition, as a blank, only the base film was prepared. These were stored at 40° C. for 3 days, returned to room temperature, unrolled, and the convex portion of the curl was turned upward, and placed on a glass plate to observe the state of the curl after 30 minutes. Also, I tested whether it becomes easy to flatten by pressing from above. The evaluation criteria are as follows.

◎: Almost the same as the blank, and almost no curl.

◯: Compared with the blank, the curl is slightly strong, but it is easy to flatten.

Δ: Compared with the blank, the curl is stronger, but can be flattened.

×: Compared with the blank, the curl is considerably stronger and it is difficult to flatten.

(8) Tear strength

Using Autograph (AG-X plus) manufactured by Shimadzu Corporation, the tear strength (N/mm) per unit film thickness was measured for each film according to the rectangular tearing method (JIS K-7128-3). The tear strength was measured in two directions parallel to and perpendicular to the main axis (slow axis) of the film (i.e., two directions, the slow axis direction and the fast axis direction), and the smaller numerical value was recorded in Table 1 as the tear strength. In addition, the measurement of the orientation principal axis direction (slow axis direction) was measured using the molecular orientation meter (MOA-6004 molecular orientation meter made by Oji Scientific Instruments Co Ltd.).

(9) r=3 bending resistance

A circular polarizing plate sample with a size of 50 mm×100 mm was prepared, and it was bent 100,000 times at a rate of 1 time/second with a bending radius of 3 mm using a no-load U-shaped stretch tester (manufactured by Yuasa System Co., Ltd., DLDMLH-FS). At this time, for the sample, the positions of 10 mm at both ends of the long side were fixed, the bent portion was 50 mm×80 mm, the inside of the bend was the base film side, and the slow axis of the base film was perpendicular to the bending direction. After the bending treatment is completed, place the sample on a flat surface with the inside of the bend facing down, and perform a visual inspection. The evaluation criteria are as follows.

⊚: Deformation of the sample could not be confirmed.

◯: There is deformation of the sample, but when placed horizontally, the maximum height of the float is less than 5 mm.

X: There are creases in the sample, or when the sample is placed horizontally, the maximum height of the float is 5 mm or more.

(10) r=5 bending resistance

The bending radius was set to 5 mm, the bent outer side was the base film side, and the slow axis of the base film was parallel to the bending direction, and the bending resistance test was performed in the same manner as r=3.

(11) heat resistance bending

With the base film surface on the inside, bend a 50mm×100mm sample 180 degrees along the long side so that the bending radius becomes 3mm, fix it with a jig, and place it at 60°C and RH65% for 3 hours. After that, the fixture was removed at room temperature, and the state after 1 hour was observed. The slow axis of the base film is perpendicular to the bending direction. The evaluation criteria are as follows.

◎: basically return to plane

○: In a slightly bent state (less than 20 degrees)

×: In a bent state (20 degrees or more)

＜Manufacture of easy-adhesive layer components＞

(polymerization of polyester resin)

194.2 parts by mass of dimethyl terephthalate, 184.5 parts by mass of dimethyl isophthalate, 14.8 parts by mass of 5-sodium dimethyl isophthalate, 233.5 parts by mass of diethylene glycol, 136.6 parts by mass of ethylene glycol, and 0.2 parts by mass of tetra-n-butyl titanate were put into a stainless steel autoclave equipped with a stirrer, a thermometer, and a partial reflux condenser. The transesterification reaction was carried out in 4 hours. Next, the temperature of the mixture was raised to 255° C., and the reaction system was gradually decompressed, followed by a reaction under a reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain a copolyester resin. The obtained copolyester resin was pale yellow and transparent. The reduced viscosity of the copolyester resin was measured and found to be 0.70 dl/g. The reduced viscosity is a value measured at 30° C. using 25 mL of a mixed solvent of phenol (60 mass %) and 1,1,2,2-tetrachloroethane (40 mass %) as a solvent with respect to 0.1 g of the resin. The glass transition temperature based on DSC was 40°C.

(Preparation of Polyester Water Dispersion)

In a reactor equipped with a stirrer, a thermometer, and a reflux device, 30 parts by mass of polyester resin and 15 parts by mass of ethylene glycol n-butyl ether were placed, and stirred while heating at 110° C., to dissolve the resin. After the resin was completely dissolved, the polyester solution was stirred, and 55 parts by mass of water was slowly added. After completion of the addition, the mixed liquid was stirred and cooled to room temperature to obtain a milky white polyester aqueous dispersion having a solid content of 30% by mass.

(Preparation of Polyvinyl Alcohol Aqueous Solution)

In a container equipped with a stirrer and a thermometer, 90 parts by mass of water was placed, and 10 parts by mass of polyvinyl alcohol resin (manufactured by Kuraray, 500 degree of polymerization and 74% of saponification degree) was slowly added while stirring. After completion of the addition, the mixed liquid was heated to 95° C. while stirring to dissolve the resin. After the resin was dissolved, the liquid mixture was cooled to room temperature while stirring to obtain an aqueous solution of polyvinyl alcohol having a solid content of 10% by mass.

(Polymerization of blocked polyisocyanate crosslinking agent used in the easy-adhesion layer P1)

Into a flask equipped with a stirrer, a thermometer, and a reflux condenser, 100 parts by mass of a polyisocyanate compound having an isocyanurate structure (manufactured by Asahi Kasei Chemicals Corporation, Duranate TPA) using hexamethylene diisocyanate as a raw material, 55 parts by mass of propylene glycol monomethyl ether acetate, and 30 parts by mass of polyethylene glycol monomethyl ether (average molecular weight 750) were charged, and kept at 70° C. for 4 hours under a nitrogen atmosphere. Thereafter, the temperature of the reaction liquid was lowered to 50° C., and 47 parts by mass of methyl ethyl ketone oxime was added dropwise. When the infrared spectrum of the reaction liquid was measured, it was confirmed that the absorption of the isocyanate group disappeared, and an aqueous dispersion of blocked polyisocyanate having a solid content of 75% by mass was obtained.

(Preparation of coating solution for easy bonding layer P1)

The following raw materials were mixed to prepare a coating liquid.

(Polymerization of urethane resin used in the easy bonding layer P2)

A urethane resin containing an aliphatic polycarbonate polyol as a constituent is produced in the following procedure. 43.75 parts by mass of 4,4-diphenylmethane diisocyanate, 12.85 parts by mass of dimethylol butyric acid, 153.41 parts by mass of polyhexamethylene carbonate diol with a number average molecular weight of 2000, 0.03 parts by mass of dibutyltin dilaurate, and 84.00 parts by mass of acetone as a solvent were put into a four-necked flask equipped with a stirrer, a serpentine condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer. It was stirred at 75° C. for 3 hours, and it was confirmed that the reaction liquid had reached the predetermined amine equivalent. Next, after lowering the temperature of this reaction liquid to 40 degreeC, 8.77 mass parts of triethylamines were added, and the polyurethane prepolymer solution was obtained. Next, 450 g of water was added to a reaction vessel equipped with a homodisperser capable of high-speed stirring, adjusted to 25° C., and the polyurethane prepolymer solution was added and dispersed while stirring and mixing the water at 2000 min ⁻¹ . Thereafter, acetone and part of water were removed from the mixed solution under reduced pressure to prepare a water-soluble polyurethane resin having a solid content of 35%. The glass transition point temperature of the obtained polyurethane resin comprising aliphatic polycarbonate polyol as a constituent component was -30°C.

(Polymerization of the oxazoline-based crosslinking agent used in the easy-adhesion layer P2)

A mixture of 58 parts by mass of ion-exchanged water and 58 parts by mass of isopropanol as an aqueous medium and 4 parts by mass of a polymerization initiator (2,2'-azobis(2-amidinopropane) dihydrochloride) were charged into a flask equipped with a thermometer, a nitrogen gas introduction tube, a reflux condenser, a dropping funnel, and a stirrer. On the other hand, a mixture of 16 parts by mass of 2-isopropenyl-2-oxazoline as a polymerizable unsaturated monomer having an oxazoline group, 32 parts by mass of methoxypolyethylene glycol acrylate (average number of added moles of ethylene glycol: 9 moles, manufactured by Shin-Nakamura Chemical Co., Ltd.), and 32 parts by mass of methyl methacrylate was put into the dropping funnel, and was added dropwise at 70° C. for 1 hour under a nitrogen atmosphere. After completion of the dropwise addition, the reaction solution was stirred for 9 hours and cooled to obtain a water-soluble resin having an oxazoline group having a solid content concentration of 40% by mass.

(Preparation of Coating Liquid for Easy Adhesion Layer P2)

The following raw materials were mixed to prepare a coating solution for forming a coating layer having excellent adhesion to the functional layer.

<Manufacture of polyester resin for base film>

(Manufacturing example 1-polyester X)

The esterification reactor was heated up, and when it reached 200°C, 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were added, and 0.017 parts by mass of antimony trioxide, 0.064 parts by mass of magnesium acetate tetrahydrate, and 0.16 parts by mass of triethylamine were added as catalysts while stirring. Next, pressurization was performed and temperature was raised, and after pressurized esterification reaction was performed on the conditions of 0.34 MPa gauge pressure and 240 degreeC, the esterification reactor was returned to normal pressure, and 0.014 mass parts of phosphoric acid was added. Furthermore, it heated up to 260 degreeC over 15 minutes, and added 0.012 mass parts of trimethyl phosphates. Next, after 15 minutes, dispersion treatment was performed with a high-pressure disperser, and after 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reactor, and polycondensation reaction was performed at 280° C. under reduced pressure.

After the polycondensation reaction is completed, filter through a filter made of Naslon with a 95% cut-off diameter of 5 μm, extrude from a nozzle in strands, cool and solidify with cooling water previously filtered (pore size: 1 μm or less), and cut into pellets. The obtained polyethylene terephthalate resin (X) had an intrinsic viscosity (intrinsic viscosity) of 0.73 dL/g, and contained substantially no inert particles and internal precipitated particles (hereinafter, the polyethylene terephthalate resin (X) will be abbreviated as PET (X)).

(Manufacturing example 2-polyester Y)

10 parts by mass of the dried ultraviolet absorber (2,2'-(1,4-phenylene)bis(4H-3,1-benzoxazin-4-one) and 90 parts by mass of PET (X) were mixed, and a polyethylene terephthalate resin (Y) containing an ultraviolet absorber was obtained by using a kneading extruder. (Hereafter, the polyethylene terephthalate resin (Y) will be abbreviated as PET (Y).)

(Manufacture of base film 1)

As raw materials for the intermediate layer of the base film, 90 parts by mass of PET (X) resin pellets not containing particles and 10 parts by mass of PET (Y) resin pellets containing ultraviolet absorbers were dried under reduced pressure at 135°C (1 Torr) for 6 hours, and then supplied to extruder 2 (for intermediate layer II). PET (X) was dried by a conventional method, and supplied to extruder 1 (for outer layer I and outer layer III), respectively, and dissolved at 285°C. The two kinds of polymers were respectively filtered with stainless steel sintered filter media (nominal filtration precision 10 μm particles 95% cut-off), laminated in two kinds of three-layer confluence blocks, formed into sheets from the pipe head and extruded, and then wound up to a casting drum with a surface temperature of 30° C. by electrostatic application casting method, cooled and solidified, and an unstretched film was produced. At this time, the discharge rate of each extruder was adjusted so that the thickness ratio of the I layer, II layer, and III layer became 10:80:10.

Next, P1 was applied to one side of the unstretched PET film and P2 coating solution was applied to the opposite side by the reverse roll method so that the coating amount after drying was 0.12 g/ ^m2 , and then introduced into a dryer and dried at 80° C. for 20 seconds.

The unstretched film on which the coating layer was formed was introduced into a simultaneous biaxial stretching machine, and introduced into a hot air zone at a temperature of 125°C while fixing the ends of the film with clips, and stretched 6.5 times in the traveling direction and 2.2 times in the width direction. Next, while maintaining the stretched width in the width direction, treatment was performed at a temperature of 225° C. for 30 seconds to obtain a biaxially oriented PET film having a film thickness of 35 μm. This was wound up into a roll to form a film roll. The slow axis of the obtained film deviated from the traveling direction within 3°.

(Manufacture of Base Film 2)

The thickness of the unstretched film was changed, and stretched in the traveling direction and the width direction by the same method as the production method of the above-mentioned base film 1 to obtain a biaxially oriented PET film with a film thickness of 50 μm. This was wound up into a roll to form a film roll. The slow axis of the obtained film deviated from the traveling direction within 3°.

(Manufacture of base film 3)

The thickness of the unstretched film was changed, and stretched in the traveling direction and the width direction by the same method as the production method of the above-mentioned base film 1 to obtain a biaxially oriented PET film with a film thickness of 80 μm. This was wound up into a roll to form a film roll. The slow axis of the obtained film deviated from the traveling direction within 3°.

(Manufacture of Base Film 4)

The thickness of the unstretched film was changed, and stretched 2.2 times in the traveling direction and 6.0 times in the width direction by the same method as the production method of the above-mentioned base film 1 to obtain a biaxially oriented PET film with a film thickness of 35 μm. This was wound up into a roll to form a film roll. The slow axis of the obtained film deviated from the traveling direction within 5°.

(Manufacture of Base Film 5)

An unstretched film was produced in the same manner as the above-mentioned base film 1 production method, stretched 6.5 times in the row direction on a roller set with a peripheral speed difference using a sequential biaxial stretcher, and then stretched 2.2 times in the width direction in a tenter to obtain a biaxially oriented PET film with a film thickness of 35 μm. This was wound up into a roll to form a film roll. The slow axis of the obtained film deviated from the traveling direction within 5°.

(Manufacture of Base Film 6)

Except for changing the thickness, an unstretched film was produced in the same manner as the above-mentioned method for producing the base film 1, and stretched 3.6 times in the width direction in a tenter to obtain a biaxially oriented PET film with a film thickness of 35 μm. This was wound up into a roll to form a film roll. The slow axis of the obtained film deviated from the traveling direction within 5°.

(Manufacture of base film 7)

Except for changing the thickness, an unstretched film was produced in the same manner as the above-mentioned method for producing the base film 1, and stretched 3.8 times in the row direction on a roller group having a peripheral speed difference with a sequential biaxial stretcher, and then heat-fixed without stretching in the width direction in a tenter to obtain a biaxially oriented PET film with a film thickness of 35 μm. This was wound up into a roll to form a film roll. The slow axis of the obtained film deviated from the traveling direction within 5°.

(Manufacture of Base Film 8)

The thickness of the unstretched film was changed, and stretched 4.5 times in the traveling direction and 2.5 times in the width direction by the same method as the production method of the above-mentioned base film 1 to obtain a biaxially oriented PET film with a film thickness of 35 μm. This was wound up into a roll to form a film roll. The slow axis of the obtained film deviated from the traveling direction within 5°.

Table 1 shows the properties of the obtained base films 1 to 8.

[Table 1]

(lamination of hard coat)

95 parts by mass of a urethane acrylate hard coat agent (manufactured by Arakawa Chemical Industry Co., Ltd., BEAMSET (registered trademark) 577, solid content concentration 100%), photopolymerization initiator (manufactured by BASF Japan Co., Ltd., Irgacure (registered trademark) 184, solid content concentration 100%) 5 parts by mass and leveling agent (manufactured by BYK Japan Co., Ltd., BYK307, solid content concentration 100%) 0.1 Parts by mass were mixed, and diluted with a solvent of toluene/MEK=1/1 to prepare a coating liquid having a concentration of 40%.

The hard coat coating solution was applied to the easily bonding layer P2 surface of the base film with a Meyer rod so that the film thickness after drying was 5.0 μm, dried at 80° C. for 1 minute, and then irradiated with ultraviolet light (cumulative light intensity: 200 mJ/cm ² ).

(Lamination of Polarizers)

As a method of providing a polarizing plate on a base film, the following four methods were performed.

(A) A method in which a brushed alignment layer is provided on a substrate film, and a polarizing film formed of a liquid crystal compound and a dichroic dye is provided thereon (polarizer lamination method A)

(B) A method in which a photo-alignment layer is provided on a substrate film, and a polarizing film formed of a liquid crystal compound and a dichroic dye is provided thereon (polarizer lamination method B)

(C) A method of providing a polarizing film made of PVA/iodine on a thermoplastic substrate and transferring it to a substrate film (polarizer lamination method C)

(D) A method of making a polarizing film made of PVA/iodine and sticking it to a base film (polarizer lamination method D)

The details of each method are described below.

Polarizer Lamination Method A

(Formation of brushing alignment layer)

On the easily bonding layer P1 surface of the base film, a coating material for a rubbing alignment layer having the following composition was coated with a bar coater, and dried at 120° C. for 3 minutes to form a film with a thickness of 200 nm. Next, the surface of the obtained film was treated with a brush roll wrapped with a nylon raised cloth to obtain a base film on which a brush alignment layer was laminated. The brushing direction was set at 0 degrees or 90 degrees with respect to the longitudinal direction of the film.

Paint for brushing alignment layer

Fully saponified polyvinyl alcohol molecular weight 800 2 parts by mass

100 parts by mass of ion-exchanged water

(Synthesis of polymerizable liquid crystal compounds)

With reference to paragraph [0134] of JP 2007-510946 A and Lub et al.

Referring to Example 1 of JP-A-63-301850, a dye (3) represented by the following formula (3) was synthesized.

Referring to Example 2 of Japanese Patent Publication No. 5-49710, a dye (4) represented by the following formula (4) was synthesized.

The dye (5) represented by the following formula (5) was synthesized by referring to the production method of the compound of the general formula (1) in JP-A-63-1357.

(Formation of Polarizing Film)

Using a bar coater, a coating for polarizing film comprising 75 parts by mass of compound (1), 25 parts by mass of compound (2), 2.5 parts by mass of pigment (3), 2.5 parts by mass of pigment (4), 2.5 parts by mass of pigment (5), 6 parts by mass of Irgacure (registered trademark) 369E (manufactured by BASF Corporation) and 250 parts by mass of o-xylene was coated on the substrate film laminated with the brush-polished alignment layer, and dried at 110° C. for 3 minutes to form A film with a thickness of 2 μm. Next, UV light is irradiated to install a polarizing plate on the base film.

Polarizer Lamination Method B

(Synthesis of coating material for photo-alignment layer)

Based on the description of Example 1, Example 2, and Example 3 of JP-A-2013-33248, a 5% by mass solution of cyclopentanone of a polymer (6) represented by the following formula (6) was produced.

(Formation of photo-alignment layer)

Using a bar coater, the coating material for a photo-alignment layer having the above composition was applied to one side of the substrate film, and dried at 80° C. for 1 minute to form a film with a thickness of 150 nm. Next, polarized UV light was irradiated to obtain a base film on which a photo-alignment layer was laminated.

The aforementioned coating material for polarizing film is coated on the photo-alignment layer, and a polarizing layer is similarly provided on the substrate film on which the alignment layer is laminated.

Polarizer Lamination Method C

(Manufacturing of substrate-laminated polarizers)

Using polyester X as a thermoplastic resin substrate, an unstretched film with a thickness of 100 μm was prepared, and an aqueous solution of polyvinyl alcohol with a degree of polymerization of 2400 and a degree of saponification of 99.9 mol % was coated on one side of the unstretched film and dried to form a PVA layer.

The obtained laminate was stretched at 120° C. between rolls having different peripheral speeds to 2 times in the longitudinal direction, and wound up. Next, the obtained laminate was treated in a 4% boric acid aqueous solution for 30 seconds, then immersed in a mixed aqueous solution of iodine (0.2%) and potassium iodide (1%) for 60 seconds to dye, and then treated in a mixed aqueous solution of potassium iodide (3%) and boric acid (3%) for 30 seconds.

Further, this laminate was uniaxially stretched in the longitudinal direction in a mixed aqueous solution of boric acid (4%) and potassium iodide (5%) at 72°C. The stretched laminate was then washed with a 4% potassium iodide aqueous solution, and after removing the aqueous solution with an air knife, it was dried in an oven at 80° C., and both ends were slit and wound up to obtain a base-layer laminated polarizing plate 1 with a width of 30 cm and a length of 1000 m. The total draw ratio was 6.5 times, and the thickness of the polarizing plate was 5 μm. In addition, the thickness is as follows: The substrate laminated polarizing plate 1 was embedded in epoxy resin, cut into slices, and observed and read with an optical microscope.

(lamination of polarizing layers)

After coating the base film with an ultraviolet curable acrylic adhesive, the polarizer surface of the base laminated polarizing plate 1 is bonded, and ultraviolet rays are irradiated from the base laminated polarizing plate 1 side to laminate the base laminated polarizing plate 1 on the base film. Thereafter, the thermoplastic resin substrate is peeled off, and a polarizing plate is provided on the substrate film.

Polarizer Lamination Method D

(Manufacture of single-layer polarizer)

A polyvinyl alcohol resin film having a degree of saponification of 99.9% was introduced to rolls having a peripheral speed difference, and uniaxially stretched to 3 times at 100°C. The obtained stretched polyvinyl alcohol stretched film was dyed in a mixed aqueous solution of potassium iodide (0.3%) and iodine (0.05%), and then uniaxially stretched to 1.8 times in a 10% aqueous solution of boric acid at 72°C. Thereafter, it was washed with ion-exchanged water, further immersed in a 6% potassium iodide aqueous solution, and the aqueous solution was removed with an air knife, followed by drying at 45° C. to obtain a polarizing plate. The thickness of the polarizing plate was 18 μm.

(Lamination of Polarizers)

After coating a UV-curable acrylic adhesive on the base film, a single-layer polarizing plate is attached, and ultraviolet rays are irradiated from the base layer laminated polarizing plate side to install the polarizing plate on the base film.

(Stacking of Retardation Layers)

As a method of providing a retardation layer on a polarizing plate, the following four methods were performed.

(F) A method of coating a 1/2 wavelength layer and a 1/4 wavelength layer on a polarizer (stacking method F of retardation layer)

(G) Method of transferring the 1/2 wavelength layer provided on the release film to a polarizing plate, and further transferring the 1/4 wavelength layer provided on the release film thereon (stacking method G of retardation layer)

(H) A method of providing a 1/4 wavelength layer and a 1/2 wavelength layer on a release film and transferring them to a polarizing plate (stacking method H of retardation layer)

(I) A method of coating a 1/2 wavelength layer on a 1/4 wavelength layer and pasting these 1/2 wavelength layers on a polarizer (lamination method I of retardation layer)

The details of each method are described below.

Lamination method of retardation layer F

On the polarizer set on the base film, polyvinyl alcohol (polyvinyl alcohol 1000 fully saponified 2% by mass aqueous solution (surfactant 0.2%) was applied and dried to obtain a polyvinyl alcohol film with a thickness of about 100 nm. Then, the surface of the polyvinyl alcohol film was subjected to brushing treatment. The brushing treatment was carried out so that the angle of the brushing treatment became 15 degrees with respect to the absorption axis of the polarizer.

Next, a solution for forming a retardation layer having the following composition was applied by a bar coating method on the brushed surface. After the coated film was dried and subjected to an orientation treatment, it was irradiated with ultraviolet rays to be cured to form a 1/2 wavelength layer.

Solution for forming retardation layer

LC242 (manufactured by BASF Corporation) 75 parts by mass

20 parts by mass of the following compounds

5 parts by mass of trimethylolpropane triacrylate

Irgacure379 3 parts by mass

Surfactant 0.1 parts by mass

250 parts by mass of methyl ethyl ketone

Next, a polyvinyl alcohol film was similarly provided on the 1/2 wavelength layer, and brushing treatment was performed. The brushing treatment was carried out so that the angle of the brushing treatment became 73 degrees with respect to the absorption axis of the polarizing plate. The solution for forming a retardation layer was applied by a bar coating method, dried, and after orientation treatment, it was irradiated with ultraviolet rays to be cured. In bar coating, the thickness is adjusted so that it becomes a 1/4 wavelength layer.

Lamination method of retardation layer G

A brushing treatment was performed on a biaxially stretched polyethylene terephthalate (PET) film having a thickness of 50 μm. On the brushed surface, a solution for forming a retardation layer was applied by bar coating and dried, and after orientation treatment, it was cured by irradiating ultraviolet rays, and a 1/2 wavelength layer was formed on a biaxially stretched polyethylene terephthalate film. Next, using an ultraviolet curable adhesive, the 1/2 wavelength layer was bonded to the polarizer surface provided on the base film. Thereafter, the biaxially stretched PET film was peeled off. Sticking was performed so that it might become 15 degrees with respect to the absorption axis of a polarizing plate.

Similarly, a 1/4 wavelength layer was provided on a biaxially stretched PET film, and the above-mentioned 1/2 wavelength layer was pasted with an optical transparent adhesive sheet. Sticking was performed so that it might become 75 degrees with respect to the absorption axis of a polarizing plate.

Lamination Method H of Retardation Layer

A brushing treatment was performed on a biaxially stretched polyethylene terephthalate (PET) film having a thickness of 50 μm. On the brushed surface, a solution for forming a retardation layer was applied by bar coating and dried, and after orientation treatment, it was cured by irradiating ultraviolet rays, and a 1/4 wavelength layer was formed on a biaxially stretched polyethylene terephthalate film. Furthermore, polyvinyl alcohol (polyvinyl alcohol 1000 fully saponified 2% by mass aqueous solution (surfactant 0.2%) was applied on the 1/4 wavelength layer and dried to obtain a polyvinyl alcohol film with a thickness of about 100 nm. Then, the surface of the polyvinyl alcohol film was subjected to brushing treatment. On the brushed surface of PVA, a solution for forming a retardation layer was coated by bar coating and dried. The angle between the brushing direction of the 2-wavelength layer is 60 degrees. Furthermore, the 1/2 wavelength layer is bonded to the polarizer surface provided on the base film using an ultraviolet curing adhesive. After that, the biaxially stretched PET film is peeled off. During the pasting, the absorption axis of the polarizer and the brushing direction of the 1/2 wavelength layer are 15 degrees, and the absorption axis of the polarizer and the brushing direction of the 1/4 wavelength layer are 75 degrees.

Lamination Method I of Retardation Layer

The 1/4 wavelength film is unwound from a roll of the 1/4 wavelength film having a slow axis in the longitudinal direction, cut to a desired length, and the surface is subjected to brushing treatment. A 1/2 wavelength layer was provided on the brushed surface by the same method as the lamination method F of the retardation layer. Furthermore, the 1/2 wavelength layer was bonded to the polarizer surface provided on the base film using an ultraviolet curable adhesive. It should be noted that the 1/4 wavelength film used was produced by extruding a propylene-ethylene random copolymer (5% ethylene content) into a sheet and stretching it with a roll in the longitudinal direction (thickness: 20 μm). During pasting, the absorption axis of the polarizer and the brushing direction of the 1/2 wavelength layer were 15 degrees, and the absorption axis of the polarizer and the slow axis direction of the 1/4 wavelength layer were 75 degrees.

It should be noted that the thickness of the retardation layer based on the above coating is 1.2 μm in the 1/4 wavelength layer and 2.3 μm in the 1/2 wavelength layer. The thickness of the adhesive layer was 3 μm.

Examples 1-23

On the base film shown in Table 2, a polarizing plate and a retardation layer were provided by the method shown in Table 2 to prepare a circular polarizing plate.

Comparative example 1

After laminating a polarizing plate on the base film by polarizing plate lamination method D, a TAC film with a thickness of 80 μm was bonded to the polarizing plate with a PVA adhesive to prepare a polarizing plate. A retardation layer is further arranged on the TAC film of the polarizing plate by using the lamination method I of the retardation layer to produce a circular polarizing plate.

Comparative example 2

After laminating a polarizing plate on a base film by polarizing plate lamination method A, a 1/2 wavelength film is laminated on the polarizing plate, and a 1/4 wavelength film is further laminated thereon. The 1/2 wavelength film was used in which the thickness of the 1/4 wavelength film was doubled, and each lamination was performed according to the lamination method I of the retardation layer. The absorption axis of the 1/2 wavelength plate with respect to the polarizing plate was set at 15 degrees, and the absorption axis of the 1/4 wavelength layer with respect to the polarizing plate was set at 75 degrees.

Comparative example 3-5

By the method shown in Table 2, a polarizing plate and a retardation layer were provided on the base film shown in Table 2 to prepare a circular polarizing plate.

Table 2 shows the properties of the circular polarizing plates obtained in Examples 1 to 23 and Comparative Examples 1 to 5.

[Table 2]

The resulting circular polarizing plate is attached to an organic EL device with an adhesive layer of 25 μm thick, and a smartphone-type foldable display that can be folded in two at the center of the whole with a radius of 3 mm corresponding to the bending radius is manufactured. The circular polarizing plate is arranged on the surface of one continuous display through the folded portion, the hard coat layer is located on the surface of the display, and the slow axis of the base film is arranged to be perpendicular to the folding direction. Table 3 shows the evaluation results of the circular polarizing plates used.

[table 3]

When the circular polarizing plate of each example is used, it is folded in two at the central part to make a portable smartphone, which satisfies the operation and visibility, and no rainbow spots can be observed.

(Formation of coating for circularly polarized light reflection layer)

A methyl ethyl ketone/cyclohexanone (95/5 mass ratio) solution having a solid content concentration of 5% of the following composition was prepared.

・LC242 (manufactured by BASF Corporation) 100 parts by mass

・LC756 (manufactured by BASF Corporation) 5 parts by mass

・Irgacure 819 4 parts by mass

· 0.75 parts by mass of the following fluorine-containing compound (1)

0.075 parts by mass of the following fluorine-containing compound (2)

(Formation of circularly polarized light reflection layer)

The coating material for the circularly polarized light reflecting layer was coated on the retardation layer of the circularly polarizing plate obtained in the examples with a bar coater, and dried at 85°C. Next, ultraviolet rays were irradiated in an oven at 85° C. to form a circularly polarized light reflecting layer.

(Evaluation of Circularly Polarizing Plate Laminated with Circularly Polarized Light Reflecting Layer)

The circular polarizing plate laminated with the circularly polarized light reflecting layer obtained above was similarly incorporated into an EL display and observed visually. As a result, compared with the circular polarizing plate of each example in which the circularly polarized light reflecting layer was not laminated, the effect of improving brightness was confirmed.

In addition, the operability and bending resistance were evaluated in the same manner, and all of them were at the same level as the original examples.

The EL display device of the present invention uses a circular polarizing plate using a substrate film having a refractive index ny in the fast axis direction of 1.568 to 1.63, the number of self-supporting films present between the polarizing plate and the retardation layer is 1 or less, and the light transmission axis of the polarizing plate is approximately parallel to the fast axis of the substrate film. Therefore, it is excellent in visibility (suppression of rainbow spots), can be thinned, and does not easily cause trouble in the manufacturing process.

In addition, the flexible EL display device is not peeled even when repeatedly bent or left in a high-temperature state, and creases are hardly formed, and the visibility is excellent.

Further, when a polyester film is used as a base film of a circular polarizing plate, an EL display device having a circular polarizing plate excellent in moisture permeability resistance, dimensional stability, mechanical strength, and chemical stability can be provided.

Claims (6)

1. An electroluminescent display device comprising: an electroluminescent element, and a circular polarizing plate arranged on the visible side of the electroluminescent element, The circular polarizing plate has a retardation layer, a polarizer and a substrate film in sequence, (1) The refractive index ny of the fast axis direction of the base film is 1.568 or more and 1.63 or less; (2) There is no self-supporting film between the polarizer and the retardation layer, or there is only one self-supporting film, where the retardation layer itself is also included between the polarizer and the retardation layer; and, (3) The light transmission axis of the polarizing plate is approximately parallel to the fast axis of the base film. 2. The electroluminescent display device according to claim 1, wherein the in-plane birefringence ΔNxy of the base film is 0.06 or more and 0.2 or less. 3. The electroluminescent display device according to claim 1 or 2, wherein the value of the smaller of the tear strengths of the slow axis direction and the fast axis direction of the substrate film by the rectangular tearing method is 250 N/mm or more. 4. The electroluminescence display device according to any one of claims 1 to 3, wherein the polarizer has a thickness of 12 μm or less. 5. The electroluminescence display device according to any one of claims 1 to 4, wherein the polarizer is formed of a polymerizable liquid crystal compound and a dichroic dye. 6. The electroluminescence display device according to any one of claims 1 to 5, wherein the retardation layer is formed of a liquid crystal compound.