CN111869323A

CN111869323A - Electroluminescent display device

Info

Publication number: CN111869323A
Application number: CN201980019195.5A
Authority: CN
Inventors: 柴野博史; 山下达郎; 村田浩一; 中瀬胜贵; 早川章太; 佐佐木靖; 本乡有记; 西尾正太郎
Original assignee: Toyobo Co Ltd
Current assignee: Toyobo Co Ltd
Priority date: 2018-03-23
Filing date: 2019-03-22
Publication date: 2020-10-30
Anticipated expiration: 2039-03-22
Also published as: JP2019169470A; TW201940906A; WO2019182120A1; JP7259452B2; CN111869323B; TWI814797B; KR20200133786A

Abstract

An electroluminescent display device, comprising: an electroluminescent element and a circularly polarizing plate disposed on the visible side of the electroluminescent element, the circularly polarizing plate comprising a retardation layer, a polarizing plate and a base film in this order, wherein (1) the refractive index ny in the fast axis direction of the base film is 1.568 or more and 1.63 or less; (2) no self-supporting film or only 1 self-supporting film (here, the phase difference layer itself is also included between the polarizing plate and the phase difference layer); and (3) the transmission axis of the polarizing plate is substantially parallel to the fast axis of the base film.

Description

Electroluminescent display device

Technical Field

The present invention relates to an Electroluminescent (EL) display device.

Background

In the EL display device, external light is reflected on the surface of the constituent materials such as the image display element and the touch sensor, and the wiring portion, and the like, and there is a problem that visibility is lowered. In order to solve these problems, the following methods are proposed: an optical laminate is disposed on the emission surface of the image display device to reduce reflection of external light. As the optical laminate, a circular polarizing plate in which a linear polarizing plate and an 1/4-wavelength phase difference plate are laminated is generally used.

As a polarizer protective film of a polarizing plate, a polyester film having an in-plane retardation of 3000 to 30000nm has been proposed (for example, see patent document 1). Polyester films are suitable for use in image display devices because they have low moisture permeability, excellent mechanical properties (high impact resistance and high elastic modulus), and further excellent chemical properties (solvent resistance, etc.) as compared with cellulose-based or acrylic films. However, the polyester film has a disadvantage that rainbow unevenness is easily generated because it has birefringence. Thus, in order to provide a sufficient in-plane retardation while suppressing rainbow unevenness by using a polyester film, it is necessary to thicken the film.

Further, in order to obtain a circularly polarizing plate having a better color reproducibility by suppressing the influence of the wavelength dispersion of the refractive index, a technique of combining an 1/4 wavelength plate and a 1/2 wavelength plate has been proposed (patent document 2). However, when a plurality of such retardation plates are stacked on a polarizing plate, the problem of the thickness becomes more significant. Further, since a plurality of films are laminated on the circularly polarizing plate, curling is easily applied when the circularly polarizing plate is wound and stored in a manufacturing process, and handling in a subsequent step of attaching the circularly polarizing plate to an EL element becomes difficult.

As described above, a circular polarizing plate in which a retardation plate is laminated on a polarizing plate using a base film having a high retardation as a protective film is required to have a thickness, and therefore, there are problems that it is not possible to sufficiently cope with the thinning required in recent years, and that trouble is easily caused in the manufacturing process. In particular, in a large-sized image display device such as a display device of more than 40 type (the length of the diagonal line of the display portion is 40 inches), the circularly polarizing plate becomes large, and a problem of curling is likely to occur.

In recent years, as an image display device, a flexible EL display device has been proposed which has a wide display surface and can be folded into a V-shape, a Z-shape, a W-shape, a double-door shape, or the like when carried or rolled up in a roll shape. If a circularly polarizing plate is used in such an EL display device that can be folded (foldable) or rolled (rollable), the following problems arise: sufficient bending properties cannot be obtained due to its thickness; the film is easily peeled off when the film is repeatedly bent or placed in a high-temperature place such as the interior of an automobile; easily giving a bending mark, etc.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 2012 and 256057

Patent document 2: japanese laid-open patent publication No. 10-68816

Disclosure of Invention

Problems to be solved by the invention

The present invention was made in view of the above-mentioned problems of the prior art. That is, an object of the present invention is to provide: an EL display device which can be thinned while securing visibility, is less likely to cause trouble in the manufacturing process, and is flexible, wherein the members after lamination are less likely to be separated from each other when repeatedly bent or left in a high temperature state, and is less likely to be creased.

Means for solving the problems

The present inventors have conducted extensive studies to develop an EL display device which can be thinned while securing visibility, is less likely to cause trouble in the manufacturing process, and is flexible, and in which repeated bending or separation of members stacked when the device is left in a high-temperature state is less likely to occur, and a fold line is less likely to be formed, and as a result, they have found that: the above object can be achieved by using a circular polarizing plate in which a base film having a specific value of the refractive index ny in the fast axis direction is used, the number of self-supporting films present between a polarizing plate and a retardation layer is 1 sheet or less, and the transmission axis of the polarizing plate is substantially parallel to the fast axis of the base film. The present invention has been completed based on such findings.

That is, the present invention relates to the EL display device described in any one of items 1 to 6.

Item 1.

An electroluminescent display device, comprising: an electroluminescent element, and a circularly polarizing plate disposed on the viewing side of the electroluminescent element,

the circularly polarizing plate comprises a retardation layer, a polarizing plate and a base film in this order,

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

(2) no self-supporting film or only 1 self-supporting film (here, the phase difference layer itself is also included between the polarizing plate and the phase difference layer); and the combination of (a) and (b),

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

Item 2.

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

Item 3.

The electroluminescent display device according to item 1 or 2 above, wherein the smaller of the tear strengths in the slow axis direction and the fast axis direction of the base film by the square tear method is 250N/mm or more.

Item 4.

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

Item 5.

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

ADVANTAGEOUS EFFECTS OF INVENTION

The EL display device of the present invention uses a circular polarizing plate in which a base film having a refractive index ny in the fast axis direction of 1.568 or more and 1.63 or less is used, the number of self-supporting films present between a polarizing plate and a retardation layer is 1 or less, and the transmission axis of the polarizing plate is substantially parallel to the fast axis of the base film, so that the circular polarizing plate is excellent in visibility (suppression of rainbow unevenness), can be made thin, and is less likely to cause trouble in the production process.

In the case of a flexible EL display device, stacked members are not easily peeled off from each other even when repeatedly bent or left in a high temperature state, and thus cannot be easily provided with a fold.

Detailed Description

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

First, a circularly polarizing plate used in the present invention will be described. The circularly polarizing plate comprises a retardation layer, a polarizing plate and a base film in this order. In this circularly polarizing plate, the retardation layer, the polarizing plate and the base film are basically laminated in this order, but the concept also includes the case where other layers are present between the respective layers.

A. Circular polarizing plate

1. Base film

First, a base film of a circularly polarizing plate will be described. The circularly polarizing plate has a base film on the viewing side of a 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 is generated by orientation. In terms of the retardation being increased, polyester, polycarbonate, polystyrene and the like are preferable, and polyester is more preferable. Preferable polyesters include polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and the like, and among these, PET and PEN are more preferable. By using a polyester film as a base film, an EL display device having a circularly polarizing plate excellent in moisture permeation 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 0.6dL/g, still more preferably 0.65dL/g, particularly preferably 0.68 dL/g. The upper limit of IV is more preferably 1.2dL/g, still more preferably 1 dL/g. If the IV of PET is less than 0.58dL/g, bending marks may be easily imparted by repeated bending. When the IV of PET exceeds 1.5dL/g, it sometimes becomes difficult to produce a film. As the Intrinsic Viscosity (IV) in the present invention, a value obtained as follows is used: will be measured at 6: 4, 1,2, 2-tetrachloroethane as a solvent, and measured at 30 ℃.

The substrate film desirably has a light transmittance at a wavelength of 380nm of 20% or less. The light transmittance at a wavelength of 380nm is more preferably 15% or less, still more preferably 10% or less, and particularly preferably 5% or less. When the light transmittance is 20% or less, the deterioration of iodine or a dichroic dye in the polarizing plate due to ultraviolet rays can be suppressed. The transmittance in the present invention is measured in a direction perpendicular to the plane of the film, and can be measured by using a spectrometer (for example, hitachi U-3500 type).

The light transmittance of the substrate film at a wavelength of 380nm is 20% or less, and can be achieved by: adding an ultraviolet absorber to the base film; coating the coating liquid containing the ultraviolet absorber on the surface of the base material film; the kind or concentration of the ultraviolet absorbent and the thickness of the substrate film are properly adjusted; and the like. In the present invention, a substance known in the art can be used as the ultraviolet absorber. Examples of the ultraviolet absorber include an organic ultraviolet absorber and an inorganic ultraviolet absorber. From the viewpoint of transparency, an organic ultraviolet absorber is preferable.

The organic ultraviolet absorber is not particularly limited as long as it can make the light transmittance of the base film at a wavelength of 380nm 20% or less. Examples of such an organic ultraviolet absorber include: benzotriazole, benzophenone, cyclic imino ester, and combinations thereof.

Further, it is preferable to add particles having an average particle diameter of 0.05 to 2 μm to the base film for improving the slidability. Examples of the particles include inorganic particles such as titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconium oxide, tungsten oxide, lithium fluoride, and calcium fluoride; organic polymer particles such as styrene, acrylic, melamine, benzoguanamine, and silicone particles. The average particle diameter is calculated by observing the particles in the cross section of the thin film with a scanning electron microscope. Specifically, 100 particles in the cross section of the thin film were observed by a scanning electron microscope, the diameter (d) of each particle was measured, and the average value of the diameters was defined as the average particle diameter.

These particles may be added to the bulk of the substrate film. Alternatively, the substrate may be formed into a skin-core coextruded multilayer structure with particles added only to the skin layer.

The lower limit of the refractive index ny in the fast axis direction of the substrate film is preferably 1.568, more preferably 1.578, still more preferably 1.584, and particularly preferably 1.588. The upper limit of the refractive index ny in the fast axis direction of the substrate film is preferably 1.63, more preferably 1.62, still more preferably 1.615, and particularly preferably 1.61. In the case of a PET film, ny lower than 1.58 is nearly completely uniaxial (uniaxial symmetry), and therefore, the mechanical strength in the direction parallel to the orientation direction is significantly reduced. In addition, in the film having ny of more than 1.62, rainbow-like color spots are easily observed when viewed from an oblique direction.

In general, a polarizing plate uses polyvinyl alcohol or a polymerizable liquid crystal compound as a matrix material. In the above case, although not clear, the reason why the rainbow unevenness is not easily observed is considered to be that the refractive index in the transmission axis direction of these polarizing plates and the refractive index of the base film become close to each other, and reflection at the interface is suppressed.

The in-plane birefringence Δ Nxy of the base film is preferably 0.06 or more and 0.2 or less, more preferably 0.07 or more and 0.19 or less, and further preferably 0.08 or more and 0.18 or less. When Δ Nxy is less than 0.06, iridescent stains are easily observed when viewed from an oblique direction. In addition, in the thin film having Δ Nxy larger than 0.2, although the rainbow-like color unevenness does not occur, as described above, the mechanical strength in the direction parallel to the orientation direction is remarkably reduced because the uniaxial property (uniaxial symmetry) is close to perfect.

The in-plane birefringence Δ Nxy is an absolute value of a difference between a refractive index (nx) in the slow axis direction and a refractive index (ny) in the fast axis direction. The measurement wavelength of the refractive index was 589 nm.

The smaller of the tear strengths in the slow axis direction and the fast axis direction of the base film by the square tear method is preferably 250N/mm or more, more preferably 280N/mm or more, and still more preferably 300N/mm or more. In a film having a high Δ Nxy value, the 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 250N/mm, the film is easily broken, and the stability during film formation or processing is lowered. On the other hand, as the tear strength becomes higher, the stability during film formation or processing is increased, but the biaxiality (biaxial symmetry) becomes higher, and thus rainbow-like color unevenness is generated. Therefore, the tear strength is preferably increased within a range where no rainbow-like color spots are generated, and practically, 500N/mm or less is preferable.

The tear strength is as follows: the tear strength (N/mm) per thickness of the film was measured by the rectangular tear method (JISK-7123).

The Nz coefficient of the base film is preferably 1.5 or more and 2.5 or less, more preferably 1.6 or more and 2.3 or less, and further preferably 1.7 or more and 2.1 or less. The smaller the Nz coefficient is, the less likely the rainbow color spot generated at the observation angle is generated. In a completely uniaxial (uniaxially symmetric) film, the Nz coefficient is 1. However, as described above, the mechanical strength in the direction parallel to the orientation direction tends to decrease as the film approaches perfect uniaxiality (uniaxial symmetry).

The Nz coefficient can be obtained as follows. The orientation main axis direction (slow axis direction) of the film was determined by a molecular orientation meter (MOA-6004 type molecular orientation meter manufactured by Oji Scientific Instruments Co Ltd.), and the biaxial refractive indices (refractive index nx in the slow axis direction, refractive index ny in the fast axis direction, where nx > ny) and the thickness direction (nz) in the orientation main axis direction and the direction (fast axis direction) orthogonal thereto were determined by an Abbe refractometer (ATAGOCO., LTD. manufactured by NAR-4T, measurement wavelength 589 nm). The nx, ny and Nz thus obtained are substituted into a formula shown by | nx-Nz |/| nx-ny | to obtain an Nz coefficient. The measurement wavelength of the refractive index was 589 nm.

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

On the other hand, the upper limit of the retardation is preferably 9000 nm. Even if a base film having a retardation exceeding the above is used, in an organic EL display device widely used in a flexible image display device, not only a further improvement effect of visibility cannot be substantially obtained, but also the thickness of the base film becomes thick, so that the operability of a circular polarizing plate for a thin flexible image display device is lowered, and a crease is likely to be given by a repeated folding operation due to long-term use. The upper limit of the retardation is preferably 8000nm, more preferably 6000nm, still more preferably 5500nm, and most preferably 5000 nm.

The birefringence may be determined by measuring the refractive index in the 2-axis direction, or may be determined using a commercially available automatic birefringence measurement device such as KOBRA-21ADH (Oji Scientific Instruments Co Ltd). The measurement wavelength of the refractive index was 589 nm.

The base film used in the present invention can be obtained by a general film production method using each raw material. Hereinafter, a case where the base film is a polyester will be described as an example. The polyester base film (hereinafter, may be simply referred to as base film) can be produced by a general method for producing a polyester film. Examples of the method for producing a polyester film include the following methods: the polyester resin is melted, extruded into a sheet shape, molded to obtain a non-oriented polyester, and the obtained non-oriented polyester is stretched in the longitudinal and transverse directions at a temperature equal to or higher than the glass transition temperature, and subjected to a heat treatment.

The substrate film may be a uniaxially or biaxially stretched film. When a biaxially stretched film is used as a base film, if the biaxial properties are increased, no rainbow-like color spots are observed even when the film is viewed from directly above the film surface, but the rainbow-like color spots are observed in some cases when the film is viewed from an oblique direction, and therefore, attention is required.

This phenomenon is caused as follows: the biaxially stretched film is composed of refractive index ellipsoids having different refractive indices in the traveling direction, the width direction, and the thickness direction, and is caused by the presence of a direction in which the retardation amount becomes zero (the refractive index ellipsoids are observed to be perfect circles) depending on the light transmission direction in the film. Therefore, if the display screen is viewed from a specific direction in an oblique direction, a point where the retardation amount becomes zero may occur, and the rainbow-like color spots may occur concentrically around this point. When an angle from directly above the film surface (normal direction) to a position where the rainbow-like color spots are visible is represented by θ, the larger the birefringence in the film surface, the larger the angle θ becomes, and the more the rainbow-like color spots are less likely to be visible. The biaxially stretched film tends to have a smaller angle θ, and therefore is preferable in that it is less likely to cause rainbow-like color spots than the uniaxially stretched film.

However, a completely uniaxial (uniaxially symmetric) film is not preferable because the mechanical strength in the direction perpendicular to the orientation direction is significantly reduced. In the present invention, it is preferable that the liquid crystal display device has biaxiality (biaxial symmetry) in a range where substantially no rainbow-like color spots are generated or in a range where no rainbow-like color spots are generated in a viewing angle range 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 film running direction (longitudinal direction, MD direction) or may be the direction perpendicular to the longitudinal direction (perpendicular 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 sequential biaxial stretching will be described.

First, when the slow axis is perpendicular, the molten PET is extruded onto a cooling roll, and the obtained undrawn material is longitudinally drawn with a continuous roll. Thereafter, both ends of the film were fixed by clips and introduced into a tenter, and after preheating, the film was stretched while heating in the transverse direction. When the slow axis is the longitudinal direction, the same procedure as described above can be applied, but it is preferable that the unstretched material is stretched in the transverse direction in a tenter and then longitudinally stretched by continuous rolls.

The longitudinal stretching temperature and the transverse stretching temperature are preferably 80-130 ℃, and more preferably 90-120 ℃. The stretching ratio in the direction orthogonal to the primary orientation direction is preferably 1.2 to 3 times, more preferably 1.8 to 2.5 times. 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 is roll stretching, scratches are easily given to the film. Therefore, from the viewpoint of preventing scratches during stretching, simultaneous biaxial stretching without using a roll is preferable. Specifically, when the conditions for the film formation by the simultaneous biaxial stretching are described, the longitudinal stretching temperature and the transverse stretching temperature are preferably 80 to 150 ℃, more preferably 90 to 140 ℃. When the slow axis direction is the longitudinal direction, the longitudinal draw ratio is preferably 5.5 to 7.5 times, more preferably 6 to 7 times, and particularly preferably 6.5 to 7 times. The transverse draw ratio is preferably 1.5 to 3 times, more preferably 1.8 to 2.8 times. When the slow axis direction is made orthogonal to the slow axis direction, the longitudinal stretching magnification and the lateral stretching magnification are opposite to those described above.

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

Further, from the viewpoint that it becomes difficult to impart scratches to the film and from the viewpoint that a general stretching apparatus can be used, only transverse uniaxial stretching by a tenter may be used.

In order to control the direction of the slow axis, the Δ Nxy, the Nz coefficient, and the tear strength within the above ranges, it is preferable to control the respective magnifications of the longitudinal stretching magnification and the lateral stretching magnification. If the difference in the longitudinal and lateral draw ratios is too small, it becomes difficult to increase Δ Nxy. In addition, in terms of increasing Δ Nxy, it is also preferable to set the stretching temperature lower.

In order to improve the tear strength, it is preferable to appropriately impart biaxial properties to a completely uniaxial film under the condition that Δ Nxy satisfies the range defined in the present specification.

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

The thickness of the base film is arbitrary, and is preferably in the range of 15 to 90 μm, and 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 remarkably reduced, and cracking, breakage, or the like is likely to occur, and the practicability tends to be remarkably reduced. The lower limit of the thickness is particularly preferably 20 μm. On the other hand, if the upper limit of the thickness of the base film exceeds 90 μm, the thickness of the circular polarizing plate becomes large, which is not preferable. Further, since repeated bending with a small radius is likely to impart marks as the thickness is thicker, the upper limit of the thickness is preferably 80 μm, more preferably 70 μm, still more preferably 60 μm, and particularly preferably 50 μm.

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

In addition, as a method of blending an ultraviolet absorber in the polyester film of the present invention, a known method can be used in combination. For example, the ultraviolet absorber can be blended in the polyester film by the following method or the like: the dried ultraviolet absorber and the polymer material are blended in advance by a kneading extruder to prepare a master batch, and the master batch and the polymer material are mixed at a predetermined ratio in film formation.

In the above case, the concentration of the ultraviolet absorber in the masterbatch is preferably 5 to 30% by mass in order to uniformly disperse the ultraviolet absorber and to economically blend the ultraviolet absorber. The master batch is preferably prepared by extruding the polyester raw material in a kneading extruder at an extrusion temperature of not less than the melting point of the polyester raw material and not more than 290 ℃ for 1 to 15 minutes. If the extrusion temperature exceeds 290 ℃, the weight loss of the ultraviolet absorber becomes large and the viscosity of the master batch decreases greatly. When the extrusion time is less than 1 minute, uniform mixing of the ultraviolet absorber becomes difficult. At this time, a stabilizer, a color tone adjuster, an antistatic agent, and the like may be added as necessary.

In the present invention, it is preferable that the thin film has a multilayer structure of at least 3 layers and that an ultraviolet absorber is added to an intermediate layer of the thin film. The film having a 3-layer structure in which the ultraviolet absorber is contained in the intermediate layer can be specifically produced as follows. Pellets of polyester alone were used for the outer layer, and a master batch containing an ultraviolet absorber for the intermediate layer and pellets of polyester were mixed at a predetermined ratio, dried, supplied to a known melt lamination extruder, extruded from a slit die into a sheet, and cooled and solidified on a casting roll to give an unstretched film. That is, the film layers constituting the two outer layers and the film layer constituting the intermediate layer were laminated by using 2 or more extruders and 3-layer manifolds or confluence blocks (for example, confluence blocks having a square confluence part), and 3-layer sheets were extruded from a pipe head and cooled on a casting roll to prepare an unstretched film. In the present invention, in order to remove foreign matters contained in the raw material polyester, which cause optical defects, it is preferable to perform high-precision filtration during melt extrusion. The filter medium used for high-precision filtration of the molten resin preferably has a filter particle size (initial filtration efficiency 95%) of 15 μm or less. Foreign matter having a particle size of 20 μm or more can be sufficiently removed by setting the filter particle size of the filter medium to 15 μm or less.

The base film may be subjected to a treatment for improving adhesiveness such as corona treatment, flame treatment, plasma treatment, or the like.

(easy adhesion layer)

In order to improve the adhesiveness to the polarizing film or the alignment layer described later, an easy-adhesion layer (easy-adhesion layer P1) may be provided on the base film.

Examples of the resin used for the easy adhesion layer include polyester resin, polyurethane resin, polyester polyurethane resin, polycarbonate polyurethane resin, and acrylic resin, and among these, polyester resin, polyester polyurethane resin, polycarbonate polyurethane resin, and acrylic resin are preferable. The easy-bond layer is preferably crosslinked. Examples of the crosslinking agent include isocyanate compounds, melamine compounds, epoxy resins, oxazoline compounds, and the like. In addition, in order to improve the adhesion, it is also useful to add a resin similar to the resin used for the alignment layer or the polarizing film, such as polyvinyl alcohol, polyamide, polyimide, or polyamideimide.

The easy adhesion layer may be provided as follows: an aqueous coating material containing these resins and, if necessary, a crosslinking agent, particles, etc. is formed, applied to a base film, and dried, whereby the coating material can be provided. As the particles, the users in the above-described substrate can be exemplified.

The easy-adhesion layer may be provided off-line to the stretched base film or may be provided on-line in the film-forming step. The easy adhesion layer is preferably provided in-line in the film forming step. When the easy adhesive layer is provided on-line, it may be either before longitudinal stretching or before transverse stretching. In particular, it is preferable that the water-based paint is applied immediately before the transverse stretching, and the water-based paint is preheated and heated by a tenter, and dried and crosslinked in the heat treatment step, thereby providing the easy-adhesion layer in-line. In the case of in-line coating with a roll immediately before longitudinal drawing, it is preferable that the water-based coating material is applied and then dried in a vertical dryer before being introduced into a drawing roll.

The coating amount of the water-based coating material is preferably 0.01 to 1.0g/m²More preferably 0.03 to 0.5g/m²。

(functional layer)

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

The thickness of these functional layers can be set as appropriate, 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 may be provided in a plurality of layers.

When the functional layer is provided, an easy-adhesion layer (easy-adhesion layer P2) may be provided between the functional layer and the base film. The easy adhesive layer P2 can be suitably formed using the resins and crosslinking agents listed for the easy adhesive layer P1. The easy-adhesive layer P1 and the easy-adhesive layer P2 may have the same composition or different compositions.

The easy adhesion layer P2 is also preferably provided in-line. The easy adhesion layer P1 and the easy adhesion layer P2 may be formed by coating and drying in sequence. Further, it is also preferable to coat both sides of the base film with the easy-adhesion layer P1 and the easy-adhesion layer P2.

In the following description, the term "base film" includes not only a case where the easy-adhesion layer is not provided but also a case where the easy-adhesion layer is provided. Similarly, the functional layer is also included in the base film.

2. Polarizing plate

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

As the polarizing plate, for example, a polarizing film can be used. The polarizing film may be provided directly on the base film, or an alignment layer may be provided on the base film and the polarizing film may be provided thereon. In the present invention, the alignment layer and the polarizing film may be collectively referred to as a polarizing plate. In the case where a polarizing film is provided on the base film without providing an alignment layer, the polarizing film may be referred to as a polarizing plate.

(polarizing film)

The polarizing film has a function of passing polarized light only in a single direction. The polarizing film may be used without particular limitation: a stretched film of polyvinyl alcohol (PVA) or the like mixed with iodine or a dichroic dye, a coated film of a dichroic dye film or a polymerizable liquid crystal compound mixed with a dichroic dye, a stretched film of polyene, a wire grid, or the like.

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

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

A polarizing film having iodine adsorbed in PVA can be generally obtained as follows: the PVA film may be obtained by immersing an unstretched PVA film in an iodine-containing bath and then uniaxially stretching the film, or immersing a uniaxially stretched film in an iodine-containing bath and then crosslinking the film 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 further preferably 2 to 15 μm. If the thickness of the polarizing film is less than 1 μm, sufficient polarization characteristics cannot be exhibited, and if it is too thin, handling may become difficult. If the thickness of the polarizing film exceeds 30 μm, the purpose of thinning is not satisfied.

When the polarizing film having iodine adsorbed in PVA is laminated with the base film, the base film is preferably adhered to the polarizing film. As the adhesive for sticking, a conventional user can use without limitation. Among these, PVA-based aqueous adhesives, ultraviolet-curable adhesives and the like are preferred examples, and ultraviolet-curable adhesives are more preferred.

In this way, the polarizing film having iodine adsorbed to PVA can be used as a single polarizing film and laminated on a base film. Alternatively, the layers may be laminated by the following method: the polarizing film is transferred to a substrate film by using a releasable support substrate obtained by coating PVA on a releasable support substrate and stretching the releasable support substrate in this state, and laminating a polarizing plate on the releasable support substrate (releasable support substrate laminated polarizing plate). The method of laminating by transfer is also preferable as a method of laminating a polarizing plate and a base film, in the same manner as the above-described method of pasting. When this transfer method is used, the thickness of the polarizing plate is preferably 12 μm or less, more preferably 10 μm or less, further preferably 8 μm or less, and particularly preferably 6 μm or less. Even in such a very thin polarizing plate, since the support substrate is releasable, handling is easy, and the polarizing plate can be easily laminated on the substrate film. By using such a thin polarizing plate, it is possible to further cope with the reduction in thickness and to ensure flexibility.

A technique of laminating a polarizing plate and a base film is known, and for example, japanese patent laid-open nos. 2001-350021 and 2009-93074 can be referred to.

A method of laminating the polarizing plate and the base film by transfer will be specifically described. First, PVA is coated on a releasable supporting base material of a thermoplastic resin which is not stretched or uniaxially stretched perpendicularly to the longitudinal direction, and the resulting laminate of the releasable supporting base material of a thermoplastic resin and PVA is stretched 2 to 20 times, preferably 3 to 15 times in the longitudinal direction. The stretching temperature is preferably 80-180 ℃, and more preferably 100-160 ℃. Next, the stretched laminate is immersed in a bath containing a dichroic dye to adsorb the dichroic dye. Examples of the dichroic dye include iodine and an organic dye. When iodine is used as the dichroic dye, an aqueous solution containing iodine and potassium iodide is preferably used as the dyeing bath. Subsequently, the substrate was immersed in an aqueous solution of boric acid, treated, washed with water, and dried. The stretching may be performed by 1.5 to 3 times before the adsorption of the dichroic dye. In the above method, the dichroic dye may be adsorbed before stretching, or may be treated with boric acid before adsorbing the dichroic dye. The stretching may be performed in a bath containing a dichroic dye or in a bath containing an aqueous solution of boric acid. These steps may be performed in a combination of a plurality of stages.

As the releasable supporting base (release film) of the thermoplastic resin, a polyester film such as polyethylene terephthalate, a polyolefin film such as polypropylene or polyethylene, a polyamide film, a polyurethane film, or the like can be used. The release force can be adjusted by subjecting a releasable supporting base (release film) of a thermoplastic resin to corona treatment, or by providing a release coating or an easy-adhesion coating.

The polarizing plate surface of the laminated polarizing plate is bonded to the base film with an adhesive or bonding agent, and then the releasable supporting base is peeled off to obtain a laminate of the base film and the polarizing plate. The thickness of the adhesive used is generally 5 to 50 μm, and the thickness of the adhesive is 1 to 10 μm. For thinning, an adhesive is preferably used, and among them, an ultraviolet-curable adhesive is more preferably used. From the viewpoint of the process without requiring a special apparatus, it is also preferable to use an adhesive.

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

The dichroic dye is a dye having a property that the absorbance of molecules in the major axis direction is different from the absorbance of molecules in the minor axis direction.

The dichroic dye preferably has an absorption maximum wavelength (λ MAX) within a range of 300 to 700 nm. Examples of such dichroic pigments include organic dichroic pigments such as acridine pigments, oxazine pigments, cyanine pigments, naphthalene pigments, azo pigments, and anthraquinone pigments, and among them, azo pigments are preferable. Examples of the azo dye include monoazo dyes, disazo dyes, trisazo dyes, tetraazo dyes, and stilbene azo dyes, and among them, disazo dyes and trisazo dyes are preferable. The dichroic dyes may be used alone or in combination. In order to adjust the (achromatic) hue, 2 or more kinds are preferably combined, and more preferably 3 or more kinds are combined. Particularly, 3 or more azo compounds are preferably used in combination.

Preferred azo compounds include pigments described in, for example, Japanese patent application laid-open Nos. 2007-126628, 2010-168570, 2013-101328, and 2013-210624.

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 an acrylic polymer. Examples of the dichroic dye polymers include polymers exemplified in Japanese patent application laid-open Nos. 2016 and 4055, and polymers obtained by polymerizing compounds of formulae 6 to 12 in Japanese patent application laid-open Nos. 2014 and 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, even more preferably 1.0 to 15% by mass, and particularly preferably 2.0 to 10% by mass, in view of improving the orientation of the dichroic dye in the polarizing film.

The polarizing film contains a polymerizable liquid crystal compound for the purpose of improving film strength, polarization degree, film homogeneity, and the like. The polymerizable liquid crystal compound also includes a film-polymerized product.

The polymerizable liquid crystal compound is a compound having a polymerizable group and exhibiting liquid crystallinity.

The polymerizable group is a group participating in a polymerization reaction, and is preferably a photopolymerizable group. Here, the photopolymerizable group means a group capable of undergoing 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 a vinyl group, a vinyloxy group, a 1-chloroethenyl group, an isopropenyl group, a 4-vinylphenyl group, an acryloyloxy group, a methacryloyloxy group, an oxirane group, and an oxetanyl group. Among them, acryloxy, methacryloxy, vinyloxy, oxirane and oxetanyl groups are preferable, and acryloxy group is more preferable. The compound exhibiting liquid crystallinity may be thermotropic liquid crystal or lyotropic liquid crystal, and may be nematic liquid crystal or smectic liquid crystal among thermotropic liquid crystals.

The polymerizable liquid crystal compound is preferably a smectic liquid crystal compound, and more preferably a higher order smectic liquid crystal compound, in terms of obtaining higher polarization characteristics. If the liquid crystal phase formed by the polymerizable liquid crystal compound is a higher order smectic phase, a polarizing film having a higher degree of alignment order can be produced.

Specific examples of preferable polymerizable liquid crystal compounds include those described in, for example, Japanese patent laid-open Nos. 2002-308832, 2007-16207, 2015-163596, 2007-510946, 2013-114131, WO2005/045485, Lub et al Recl. Travv. 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, even more preferably 80 to 97% by mass, and particularly preferably 83 to 95% by mass, in terms of improving the alignment property of the polymerizable liquid crystal compound.

The polarizing film including the polymerizable liquid crystal compound and the dichroic pigment may be provided by coating the composition for a polarizing film.

The composition for a polarizing film may further include 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.

The solvent may be used without limitation as long as it dissolves the polymerizable liquid crystal compound. 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 polymerization initiator may be used without limitation as long as it is capable of polymerizing the polymerizable liquid crystal compound. As the polymerization initiator, a photopolymerization initiator which generates an active radical 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 preferred. Examples of the photosensitizing agent include xanthone compounds, anthracene compounds, phenothiazine, rubrene, and the like.

Examples of the polymerization inhibitor include hydroquinones, orthophthalic diphenols and thiophenols.

Examples of the leveling agent include various known surfactants.

The polymerizable non-liquid crystal compound is preferably a compound copolymerized with a polymerizable liquid crystal compound. For example, when the polymerizable liquid crystal compound has a (meth) acryloyloxy group, examples of the polymerizable non-liquid crystal compound include (meth) acrylates. The (meth) acrylates may be monofunctional or polyfunctional. By using a polyfunctional (meth) acrylate, the strength of the polarizing film can be improved. When a polymerizable non-liquid crystal compound is used, the amount of the polymerizable non-liquid crystal compound in the polarizing film is preferably 1 to 15% by mass, more preferably 2 to 10% by mass, and still more preferably 3 to 7% by mass. If the content of the polymerizable non-liquid crystal compound exceeds 15 mass%, the degree of polarization may be reduced.

Examples of the crosslinking agent include compounds capable of reacting with functional groups of the polymerizable liquid crystal compound and the polymerizable non-liquid crystal compound. Specific examples of the crosslinking agent include isocyanate compounds, melamine, epoxy resins, oxazoline compounds, and the like.

The composition for a polarizing film may be applied directly to a base film or an alignment layer, dried as needed, and then heated and cured to provide a polarizing film.

As the coating method, coating methods such as a gravure coating method, a die coating method, a bar coating method, and an applicator method; a known method such as a printing method such as a flexographic printing method.

Drying was carried out as follows: the coated base film is introduced into a hot air dryer, an infrared dryer, or the like, and is preferably conducted at 30 to 170 ℃, more preferably 50 to 150 ℃, and still more preferably 70 to 130 ℃. The drying time is preferably 0.5 to 30 minutes, more preferably 1 to 20 minutes, and further preferably 2 to 10 minutes.

The heating may be performed in order 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.

The composition for a polarizing film preferably contains a polymerizable liquid crystal compound and is thus cured. Examples of the curing method include heating and light irradiation, and light irradiation is preferable. The fixing may be performed in a state where the dichroic dye is aligned by curing. The curing is preferably performed in a state where a liquid crystal phase is formed in the polymerizable liquid crystal compound, and may be performed by irradiating light at a temperature at which the liquid crystal phase is present.

Examples of the light in the irradiation include visible light, ultraviolet light, and laser beam. In terms of ease of handling, ultraviolet light is preferable.

The irradiation intensity varies depending on the kind or amount of the polymerization initiator or the resin (monomer), and is preferably 100 to 10000mJ/cm in 365nm, for example²More preferably 200 to 5000mJ/cm²。

In the polarizing film, the composition for a polarizing film is applied to an alignment layer provided as needed, and the dye is aligned in the alignment direction of the alignment layer, so that the polarizing film has a polarized light transmission axis in a predetermined direction. In the case where the composition for a polarizing film is directly applied to a substrate without providing an alignment layer, the composition for a polarizing film may be irradiated with polarized light to be cured, thereby aligning the polarizing film. It is further preferable that the dichroic dye is firmly aligned in the alignment direction of the polymer liquid crystal by performing heat treatment thereafter.

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

When a polarizing film containing a polymerizable liquid crystal compound and a dichroic dye is laminated on a base film, not only a method of directly providing a polarizing film on a base film and laminating them but also a method of providing a polarizing film on another releasable film according to the above method and transferring it to a base film is preferable. The release film includes a releasable supporting base material used for a releasable supporting base material laminated polarizing plate laminated with the releasable supporting base material, and particularly preferable release films include a polyester film, a polypropylene film, and the like. The release film may be subjected to corona treatment, or may be provided with release coating, easy adhesion coating, or the like, so that the peeling force can be adjusted.

The method of transferring the polarizing film to the substrate film is also the same as the method of laminating the polarizing film to the releasable supporting substrate laminated polarizing plate.

(alignment layer)

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

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

The alignment layer may be any alignment layer as long as the polarizing film can be brought into a desired alignment state. Examples of the method for providing the alignment layer with an alignment state include: brushing the surface, oblique deposition of an inorganic compound, formation of a layer having microgrooves, and the like. Further, a method of forming a photo-alignment layer for generating an alignment function by molecular alignment by irradiation of polarized light is also preferable.

Hereinafter, 2 examples of the rubbing treatment of the alignment layer and the photo-alignment layer will be described.

Brushing treatmentAlignment layer

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

First, a coating liquid for an alignment layer to be brushed containing the polymer material is applied to a substrate film, and then heated and dried to obtain an alignment layer before being brushed. The coating liquid for 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, and the like; amide resins such as melamine compounds; phenolic resins, and the like.

The solvent used for the coating liquid for rubbing treatment of the alignment layer can be used without limitation as long as the polymer material is dissolved. 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 coating liquid for the rubbing treatment of the alignment layer may be suitably adjusted depending on the kind of the polymer, the thickness of the alignment layer to be produced, and the like, and is preferably in the range of 0.2 to 20 mass%, more preferably 0.3 to 10 mass%, in terms of the solid content concentration.

As a method for performing coating, coating methods such as a gravure coating method, a die coating method, a bar coating method, and an applicator method; a known method such as a printing method such as a flexographic printing method.

The temperature for the heat drying depends on the base film, and in the case of PET, it is preferably in the range of 30 to 170 ℃, more preferably in the range of 50 to 150 ℃, and further preferably in the range of 70 to 130 ℃. If the drying temperature is too low, the drying time is required to be long, and the productivity is sometimes poor. If the drying temperature is too high, the orientation state of the base film is affected, the retardation is reduced, or the heat shrinkage of the base film is increased, so that the optical function conforming to the design cannot be achieved, and the flatness is deteriorated. The heating and drying time is usually 0.5 to 30 minutes, preferably 1 to 20 minutes, and more preferably 2 to 10 minutes.

The thickness of the alignment layer after the rubbing treatment is preferably 0.01 to 10 μm, more preferably 0.05 to 5 μm, and still more preferably 0.1 to 1 μm.

The brushing treatment may be generally carried out by rubbing the surface of the polymer layer with paper or cloth in a constant direction. In general, the surface of the alignment film is subjected to brushing treatment using a brush roller of a napped cloth of fibers such as nylon, polyester, acrylic, or the like.

In order to provide a polarizing film having a light transmission axis in a predetermined direction with respect to the longitudinal direction of the long base film, the brushing direction of the alignment layer also needs to be at an angle corresponding thereto. The angle can be adjusted by adjusting the angle between the brush-grinding roller and the base material film, adjusting the conveyance speed of the base material film, the rotation speed of the roller, and the like.

The base film may be directly subjected to a brushing treatment so that the surface of the base film has a function as an alignment layer. The above-mentioned cases are also included in the scope of the present invention.

Photo-alignment layer

The photo-alignment layer is an alignment film to which an alignment regulating force is applied by applying a coating liquid containing a polymer or monomer having a photoreactive group and a solvent to a base film and irradiating the coating liquid with polarized light, preferably polarized ultraviolet light. The photoreactive group is a group that generates liquid crystal alignment ability by light irradiation. Specifically, the alignment of molecules by light irradiation induces a photoreaction, such as an isomerization reaction, a dimerization reaction, a photocrosslinking reaction, or a photolysis reaction, which is a source of the alignment ability of liquid crystals. Among these photoreactive groups, those causing dimerization reaction or photocrosslinking reaction are preferable in terms of maintaining a smectic liquid crystal state of the polarizing film having excellent alignment properties. The photoreactive group that can cause the reaction is preferably an unsaturated bond, particularly preferably a double bond, and particularly preferably 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.

Examples of the photoreactive group having a C ═ C bond include a vinyl group, a polyene group, a stilbene azolium (Stilbazolium) group, a chalcone group, and a cinnamoyl group. 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 those having a basic structure such as an azophenyl group, an azonaphthyl group, an aromatic heterocyclic azo group, a bisazo group, a formazan (formazan) group, and an azoxybenzene (azoxybenzene). 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 groups, alkoxy groups, aryl groups, allyloxy groups, cyano groups, alkoxycarbonyl groups, hydroxyl groups, sulfonic acid groups, and haloalkyl groups.

Among them, a photoreactive group which causes a photodimerization reaction is preferable, and a cinnamoyl group and a chalcone group are preferable because a photo-alignment layer which requires a small amount of polarized light for photo-alignment and is excellent in thermal stability and stability with time can be easily obtained. Further, as the polymer having a photoreactive group, a polymer having a cinnamoyl group in which a terminal portion of a side chain of the polymer has a cinnamic acid structure is particularly preferable. Examples of the main chain structure include polyimide, polyamide, (meth) acrylic acid, and polyester.

Specific examples of the alignment layer include: an alignment layer described in Japanese patent laid-open Nos. 2006-285197, 2007-76839, 2007-138138, 2007-94071, 2007-121071, 2007-121721, 2007-140465, 2007-156439, 2007-133184, 2009-109831, 2002-229039, 2002-265541, 2002-317013, 2003-520878, 2004-529220, 2013-33248, 2015-7702, 2015-129210, and the like.

As the solvent of the coating liquid for forming a photo-alignment layer, a polymer having a photoreactive group and a monomer can be dissolved and used without limitation. Specific examples of the solvent include those listed as the alignment layer subjected to the brushing treatment. A photopolymerization initiator, a polymerization inhibitor, various stabilizers, and the like may be added to the coating liquid for forming a photo-alignment layer, if necessary. In addition, a polymer having a photoreactive group, a polymer other than a monomer, a monomer having no photoreactive group copolymerizable with the monomer having a photoreactive group, or the like may be added to the coating liquid for forming a photoalignment layer.

The concentration of the coating liquid for forming the photo-alignment layer, the coating method, the drying conditions, and the like may be exemplified by those of the alignment layer subjected to the brushing treatment. The thickness of the photo-alignment layer is also the same as the preferred thickness of the alignment layer after the brushing treatment.

By irradiating the photo-alignment layer before alignment thus obtained with polarized light having 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 a predetermined direction with respect to the longitudinal direction of the long base film can be obtained.

The polarized light may be irradiated directly to the photo-alignment layer before alignment or may be irradiated through the base film.

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

Examples of the light source of polarized light include an ultraviolet laser such as a xenon lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a metal halide lamp, KrF, ArF, and the like, and a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, and a metal halide lamp are preferable.

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

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

The irradiation intensity varies depending on the kind or amount of the polymerization initiator or the resin (monomer), and is preferably 10 to 10000mJ/cm in 365nm, for example²More preferably 20 to 5000mJ/cm²。

(Angle formed by transmission axis of polarizing plate and fast axis of base film)

The transmission axis of the polarizer is preferably substantially parallel to the fast axis of the base film. Here, the term "substantially parallel" means that the angle formed by the transmission axis of the polarizing plate and the fast axis of the base film is 10 degrees or less. The angle formed by the 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, the rainbow unevenness may be easily seen when viewed from an oblique direction.

In the case of a polarizing plate obtained by stretching polyvinyl alcohol, the polarizing plate is generally stretched in the longitudinal direction, and the light transmission axis direction is perpendicular to the longitudinal direction. Therefore, the 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 aligning a polymerized liquid crystal compound, the light transmission axis direction of the polarizing plate can be adjusted in the brushing direction or the polarization direction of ultraviolet rays, and therefore, a base film having a slow axis in either the longitudinal direction or the orthogonal direction is a suitable combination.

A protective coating layer may be provided on the side opposite to the base film of the polarizing plate in order to prevent scratches after the next step and to prevent the polarizing plate from being deteriorated by an adhesive, a coating solvent for the retardation layer, and the like. As the protective coating layer, PVA, other resins, ultraviolet-curable resins, and the like can be appropriately selected within a range that does not adversely affect the polarizing plate. The thickness of the protective coating is preferably 0.01 to 10 μm, more preferably 0.1 to 5 μm.

3. Retardation layer

In the circularly polarizing plate used in the present invention, a retardation layer is present on the side opposite to the substrate film side of the polarizing plate. That is, the circularly polarizing plate has a retardation layer on the Electroluminescence (EL) element side of the polarizer. The EL display device of the present invention is characterized in that no independent film is present between the polarizing plate and the retardation layer, or only 1 independent film is present (here, the retardation layer itself is also included between the polarizing plate and the retardation layer). Here, the self-supporting film is a film that is independent from the process.

The "retardation layer" is used to function as a circular polarizing plate, and specifically refers to an 1/4 wavelength layer, a 1/2 wavelength layer, a C-plate layer, and the like.

The absence of an independent film between the polarizing plate and the retardation layer means that the retardation layer is directly laminated on the polarizing plate, and the independent film is not laminated. The term "directly" as used herein means that there is no layer present between the polarizing plate and the retardation layer or between the retardation layers, or only an adhesive layer or an adhesive layer if present.

When 1 self-supporting film is present between the polarizing plate and the retardation layer, only 1 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 attaching a retardation film (self-supporting film) provided with a coating type 1/4 wavelength layer described later, which is prepared separately, to an oriented film (self-supporting film) such as polycarbonate or cycloolefin or a cellulose Triacetate (TAC) film. However, in order to reduce the thickness and ensure flexibility, it is preferable to provide the coating type 1/4 wavelength layer directly on the polarizing plate.

The coating type 1/4 wavelength layer is a 1/4 wavelength layer in which the 1/4 wavelength layer itself is formed by coating, and is not in a separate state. As a method for providing the 1/4 wavelength layer, the following method can be given: a method of coating a phase difference compound on a polarizing plate; and a method of providing an 1/4 wavelength layer on a releasable substrate and transferring the layer to a polarizing plate. The 1/4 wavelength layer is preferably a layer formed of a liquid crystal compound. Examples of the liquid crystal compound include a rod-like liquid crystal compound, a polymer-like liquid crystal compound, and a liquid crystal compound having a reactive functional group. As a method for applying a retardation compound to a polarizing plate, it is preferable to brush-polish the polarizing plate, or apply a liquid crystal compound after providing the above-mentioned alignment layer to the polarizing plate to impart an alignment controlling force.

In a method of separately providing a coating type 1/4 wavelength layer on a releasable substrate and transferring the layer onto a polarizing plate, it is preferable to brush-polish the releasable substrate, or to provide the above-mentioned alignment layer on the releasable substrate so as to have an alignment controlling force and then coat a liquid crystal compound (1/4 wavelength layer).

Further, as a method for performing transfer, the following method is also preferable: a birefringent resin was applied to a releasable substrate, and the resultant was stretched together with the substrate to form an 1/4 wavelength layer.

The transfer-type 1/4 wavelength layer thus obtained was attached to a polarizing plate with an adhesive or a pressure-sensitive adhesive, and then the releasable substrate was peeled off. For thinning, it is preferable to apply the adhesive, particularly an ultraviolet-curable adhesive.

In terms of the polarizer being less susceptible to the coating solvent of the 1/4 wavelength layer, the following method is preferable: a coating-type 1/4 wavelength layer was separately provided on a releasable substrate, and transferred onto a polarizing plate.

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

These methods and phase difference layers can be referred to, for example, japanese patent application laid-open nos. 2008-149577, 2002-303722, WO2006/100830, 2015-64418, and the like.

When the 1/4 wavelength layer alone is used, the wavelength is not 1/4 in a wide wavelength range of visible light, and coloring may occur. In this case, 1/2 wavelength layers 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.

1/2 preferred materials, forms, production methods, lamination methods and the like of the wavelength layer are the same as those of the 1/4 wavelength layer.

The front retardation of the 1/2 wavelength layer is preferably 200 to 360nm, 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 polarizing plate is preferably 35 to 55 degrees, more preferably 40 to 50 degrees, and still more preferably 42 to 48 degrees.

When an 1/4-wavelength layer and a 1/2-wavelength layer are used in combination as a retardation layer, the angle (θ) between the alignment axis (slow axis) of the 1/2-wavelength layer and the transmission axis of the polarizing plate 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 in the range of 2 θ +45 degrees ± 10 degrees, more preferably in the range of 2 θ +45 degrees ± 5 degrees, and still more preferably in the range of 2 θ +45 degrees ± 3 degrees.

In the case of attaching an oriented film, these angles can be adjusted by the angle of attachment, 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, the angle of brushing, the irradiation angle of polarized ultraviolet rays, and the like can be controlled.

In the method of providing the coating type 1/4 wavelength layer on the substrate and transferring the layer onto the polarizing plate, when the layer is pasted roll to roll, it is preferable to control the angle of rubbing or the irradiation angle of the polarized ultraviolet ray to a predetermined angle in advance.

In the case of using an oriented film or in the case of applying a birefringent resin to a base film and stretching the film together with the base film, it is preferable to stretch the film in an oblique direction so that the film is at a predetermined angle when roll-to-roll bonding is performed.

Further, in order to reduce a change in coloring or the like when viewed obliquely, it is also preferable to provide the 1/4 wavelength layer with a C plate layer. Among the C plate layers, a positive or negative C plate layer may be used according to 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 may be provided by directly applying a coating liquid for the C plate layer on the 1/4 wavelength layer, or by transferring a separately prepared C plate layer.

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

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

A method of sequentially providing an 1/4-wavelength layer and a 1/2-wavelength layer on a release film and transferring them onto a polarizing plate.

A method of providing 1/2 wavelength layers by coating on a polarizer and providing 1/4 wavelength layers by transfer.

A method of preparing a 1/2 wavelength layer in the form of a film, applying or transferring a 1/4 wavelength layer thereon, and attaching the layer to a polarizing plate.

In addition, when the C sheet layers are laminated, various methods can be used. For example, the following methods may be mentioned: a method of disposing a C plate layer on the 1/4 wavelength layer disposed on the polarizing plate by coating or transfer printing; a method of laminating a C plate layer in advance on the 1/4 wavelength layer to be transferred or pasted, and the like.

In the present invention, when a C plate layer is present between the polarizer and the 1/4 wavelength layer (including the 1/4 wavelength layer), all layers (including the C plate layer) from the polarizer to the C plate layer are preferably coating layers. This means that no independent film is present on the side of the polarizing plate opposite to the base film. Specifically, the polarizing plate has only an arbitrary combination of an adhesive layer, a protective coating layer, an alignment layer, and a coating-type retardation layer on the side opposite to the base film. With such a configuration, the circular polarizing plate can be thinned and flexibility can be ensured.

Specific preferable examples of the lamination between the polarizing plate and the 1/4 wavelength layer include:

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.

The adhesive layer may be an adhesive layer. The 1/4 wavelength layer and the 1/2 wavelength layer may include an alignment layer on either side thereof.

As the pressure-sensitive adhesive layer, a pressure-sensitive adhesive of rubber type, acrylic type, urethane type, olefin type, silicone type, or the like can be used without limitation. Among them, acrylic adhesives are preferable. The adhesive can be applied to the polarizing plate surface of an object such as a polarizing plate. The following method is preferred: the pressure-sensitive adhesive layer was provided by peeling off a release film on one surface of a transparent pressure-sensitive adhesive for optical use (release film/pressure-sensitive adhesive layer/release film) without a base material, and then attaching the release film to the surface of the polarizer. As the adhesive, those of ultraviolet curing type, urethane type and epoxy type are preferably used.

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

In the above, examples of the retardation layer (1/4 wavelength layer and 1/2 wavelength layer) include the following: the retardation layer (1/4 wavelength layer and 1/2 wavelength layer) may be provided in advance on the object, and the laminate of the base film and the polarizing plate may be bonded thereto. The same applies to the case where the C plate layer is provided.

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

Further, a circularly polarizing light reflecting layer made of a liquid crystal compound may be provided on the retardation layer (the surface opposite to the polarizing plate) of the circularly polarizing plate. The circularly polarized light reflecting layer is preferably a cholesteric liquid crystal layer. The cholesteric liquid crystal layer may be 1 layer, but since the cholesteric liquid crystal layer has wavelength selectivity in reflection characteristics, it is preferable to provide a plurality of cholesteric liquid crystal layers in order to form uniform reflection characteristics in a wide region of visible light. The cholesteric liquid crystal layer is more preferably 2 or more layers, and further preferably 3 or more layers. The cholesteric liquid crystal layer is preferably 7 layers or less, more preferably 6 layers or less, and particularly preferably 5 layers 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 with a paint.

Examples of the liquid crystal compound used for the circularly polarizing light reflecting layer include the liquid crystal compounds used for the polarizing film and the retardation layer.

Further, in order to align the cholesteric liquid crystal in the circularly polarized light reflective layer, it is preferable that the coating material for a circularly polarized light reflective layer contains a chiral agent. By containing the chiral agent, the helical structure of the cholesteric liquid crystal phase is induced, and the cholesteric liquid crystal phase is easily obtained.

The chiral agent is not particularly limited, and a known chiral agent can be used. Examples of the chiral agent include a liquid crystal device manual, chapter 3, items 4 to 3, TN (twisted chemical), a chiral agent for STN (Super-twisted chemical display), 199 pages, a compound described in 142 th committee of Japan society for academic Press, 1989, isosorbide, and an isomannide derivative. The chiral agent preferably has a polymerizable group. The amount of the chiral agent is preferably 1 to 10 parts by mass per 100 parts by mass of the liquid crystal compound.

In the case where the circularly polarized light reflecting 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 polarizing light reflecting layer is provided by transfer, the coating material for the circularly polarizing light reflecting layer may be directly applied to a releasable substrate, or may be applied by providing an alignment layer on a releasable substrate and applying the alignment layer thereon. A circularly polarized light reflecting layer and a retardation layer may be provided in this order on a releasable substrate and transferred onto a polarizing plate. Alternatively, a circularly polarized light reflecting layer and a part of the retardation layer may be provided in this order on a releasable substrate, and the other part of the retardation layer may be provided on a separate polarizing plate and transferred onto the retardation layer. The alignment layer is preferably the one described above.

The circularly polarizing light reflecting layer can be described in, for example, Japanese patent laid-open Nos. H1-133003, 3416302, 3363565, 8-271731, 2016/194497, 2018-10086, and the like, which are incorporated herein by reference.

The thickness of the circularly polarized light reflecting layer is preferably 2.0 to 150 μm, more preferably 5.0 to 100 μm. When the circularly polarizing light reflecting layer is a multilayer, the total thickness is preferably within the above range.

By combining the circularly polarizing light reflecting layer with the circularly polarizing plate, it is possible to reduce the decrease in luminance when the circularly polarizing plate for antireflection is provided in the EL display device. Further, by providing a polarizing plate, a retardation layer, and a circularly polarizing light reflecting layer by coating or transfer, and by forming a structure without an independent thin film between the polarizing plate and the circularly polarizing light reflecting layer (including the polarizing plate itself and the circularly polarizing light reflecting layer), the circularly polarizing plate can be made thin, and it becomes easy to cope with the thinning of the EL display device. Such a structure is preferable as a flexible EL display device which is foldable or rollable.

B.EL element

The EL display device of the present invention includes the circularly polarizing plate on the viewing side of the EL element. The EL element can be any known one without limitation, and among them, an organic EL element is preferable in terms of being thin. The EL element and the circularly polarizing plate are preferably bonded with an adhesive.

The EL display device of the present invention uses a circular polarizing plate using a base film in which the refractive index Ny in the fast axis direction of the base film is 1.568 or more and 1.63 or less, and 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 substantially parallel to the fast axis of the base film, so that the EL display device is excellent in visibility (suppression of rainbow unevenness), can be made thin, and is less likely to cause troubles in the production process. The display device is particularly suitable for use in a large-sized EL display device of 40-type (the length of the diagonal line of the display portion is 40 inches) or more, and further 50-type (the length of the diagonal line of the display portion is 50 inches) or more.

In addition, in the case of forming a flexible EL display device, when the EL display device is repeatedly bent or left in a high temperature state, the members after lamination are not easily peeled off from each other, and a fold is not easily provided.

The flexible EL display device is preferably used for any of an EL display device (a folding EL display device) which can be folded into a V shape, a Z shape, a W shape, a double-door shape, or the like when carried, and an EL display device (a roll EL display device) which can be rolled into a roll.

When the foldable EL display device has a display portion on the folded inner surface side, the bending radius of the circularly polarizing plate in the folded state is reduced. In the case of such an EL display device, the main orientation direction of the base film is arranged in a direction perpendicular to the folding direction (direction of the folding operation), and the occurrence of creases due to repeated folding operations can be effectively reduced. In the vertical direction, the angle formed between the main orientation direction of the base film and the folding direction is preferably 75 to 105 degrees, more preferably 80 to 100 degrees, and still more preferably 83 to 97 degrees.

The reason why the occurrence of the crease can be reduced is considered to be that the base film is stretched by the repeated folding operation, or the stretched direction is perpendicular to the main orientation direction of the molecules, and therefore the base film is easily stretched. The flexible EL display device of the present invention can be suitably used for a folding EL display device having a bend radius of 5mm or less, further 4mm or less, and particularly 3 mm.

In the case of a folding EL display device having a display portion on the outer surface side of the device to be folded, or in the case of a bending radius not becoming small even when the device is on the inner surface side, or in the case of a roll-up EL display device, the main orientation direction of the substrate film can be used without particular limitation. However, in such a case, it is also preferable that the main orientation direction of the base film is parallel to the folding direction. By forming the parallel portions, the planarity of the entire EL display device tends to be improved when the EL display device is expanded. In the above case, the angle formed between 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 is not peeled off even when repeatedly bent or left in a high temperature state, is not easily creased, and has excellent visibility. When a polyester film is further used as a base film of the circularly polarizing plate, an EL display device having a circularly polarizing plate excellent in moisture permeation resistance, dimensional stability, mechanical strength, and chemical stability can be provided.

Examples

The present invention will be described more specifically with reference to examples, but the present invention is not limited to the examples. The present invention can be suitably modified within the scope of the present invention, and these modifications are included in the scope of the present invention.

The evaluation methods of physical properties in examples are as follows.

(1) Evaluation of film in Slow and fast axes directions

The evaluation of the axial direction of the film was carried out by using a molecular orientation meter (MOA-6004 type molecular orientation meter, manufactured by Oji Scientific Instruments Co Ltd.).

(2) Δ Nxy and retardation (Re)

The retardation is a parameter defined by the product (Δ Nxy × d) of the refractive index anisotropy (Δ Nxy ═ nx-ny |) of the orthogonal biaxial refractive indices on the film and the film thickness d (nm), and is a measure representing the optical isotropy and the anisotropy. The biaxial refractive index anisotropy (Δ Nxy) is obtained by the following method. The slow axis direction of the film was determined by a molecular orientation meter (MOA-6004 molecular orientation meter, manufactured by Oji scientific instruments Co Ltd.), and the film was cut into a rectangle of 4 cm. times.2 cm so that the slow axis direction was parallel to the long side of the measurement sample to obtain a measurement sample. For this sample, refractive indices of biaxial directions perpendicular to each other (refractive index in the slow axis direction: nx, refractive index in the direction perpendicular to the slow axis direction in the plane (i.e., refractive index in the fast axis direction: ny) and refractive index in the thickness direction (nz) were measured by an Abbe refractometer (ATAGO CO., manufactured by LTD., NAR-4T, measurement wavelength 589nm), and the absolute value (| nx-ny |) of the difference between the refractive indices of the aforementioned biaxial directions was used as anisotropy of refractive index (Δ Nxy). The thickness d (nm) of the film was measured with an electronic micrometer (Fine Ryuf co., ltd., mill 1245D), and the unit was converted to nm. The retardation (Re) is determined from the product (Δ Nxy × d) of the anisotropy of the refractive index (Δ Nxy) and the thickness d (nm) of the thin film.

(3) Coefficient of Nz

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

(4) Iridescent speckle Observation

The polarizing plate obtained below was disposed in an organic EL display so that the PET film was positioned on the visible side instead of the circularly polarizing plate (circularly polarizing plate disposed on the visible side of the organic EL element) removed from a commercially available organic EL display (organic EL television C6P 55 inches, LG corporation). The presence or absence of the occurrence of the rainbow unevenness was determined as follows by visual observation from the front and oblique directions of the organic EL display.

O: no iridescent spots were observed when viewed from any direction.

And (delta): when observed from an oblique direction of 60 degrees or more with respect to the normal direction, a shallow rainbow spot can be observed.

X: when observed from an oblique direction of 60 degrees or more with respect to the normal direction, the rainbow unevenness can be observed.

(5) Thickness of base film and circular polarizing plate

The thicknesses of the base film and the circularly polarizing plate were measured by a commercially available digital thickness meter.

(6) Based on the thickness of the applied layers

The thicknesses of the layers based on the coating were as follows: the coating was carried out under the same coating conditions by embedding a PET film (optionally treated with an easy-adhesion PET) with an epoxy resin, cutting the film into sections, and observing the sections with a microscope. The microscope is an optical microscope, a transmission electron microscope, or a scanning electron microscope depending on the thickness.

(7) Operability of

The circularly polarizing plate thus obtained was cut into pieces corresponding to A5, and a paper tube having an outer diameter of 6 inches was wound together with a biaxially stretched PET film having a thickness of 50 μm so that the longitudinal direction was the winding direction. The winding was carried out as follows: the circularly polarizing plate sample was inserted at a timing of 3m after the PET film was wound up, and a 7mPE film was further wound up. Further, as a blank, one obtained by winding only the base film was prepared. These were stored at 40 ℃ for 3 days, returned to room temperature, and then uncoiled so that the curled convex portions were directed upward, and placed on a glass plate, and the state of curling after 30 minutes was observed. In addition, whether or not the sheet is easily flattened by pressing from above was attempted. The evaluation criteria are as follows.

Very good: substantially the same as the blank and substantially no curl.

O: the curl was slightly stronger but flattened easily compared to the blank.

And (delta): the curl was strong but could be flattened compared to the blank.

X: the curl was quite strong compared to the blank and was difficult to flatten.

(8) Tear strength

The tear strength (N/mm) per thickness of each film was measured by the angle tear method (JIS K-7128-3) using an Autograph (AG-X plus) manufactured by Shimadzu corporation. The tear strength was measured in 2 directions (i.e., 2 directions of the slow axis direction and the fast axis direction) parallel and perpendicular to the orientation major axis (slow axis) direction of the film, and the smaller numerical value is shown in table 1 as the tear strength. The measurement of the orientation main axis direction (slow axis direction) was performed by using a molecular orientation meter (MOA-6004 type molecular orientation meter manufactured by Oji Scientific Instruments Co ltd.).

(9) r 3 bending resistance

A circular polarizing plate sample having a size of 50mm × 100mm was prepared, and the sample was bent 10 ten thousand times at a speed of 1 time/second with a bending radius of 3mm using a no-load U-shaped stretching machine (DLDMLH-FS, manufactured by Yuasasystem). In this case, the sample was fixed at positions of 10mm at both ends on the long side, the bent portion was 50mm × 80mm, the inner side of the bend was set to the base film side, and the slow axis of the base film was set to be orthogonal to the bending direction. After the bending treatment was completed, the sample was placed on a flat surface with the bent inner side facing downward, and subjected to visual inspection. The evaluation criteria are as follows.

Very good: no deformation of the sample could be confirmed.

O: there was deformation of the sample, but the maximum height of the float was below 5mm when placed horizontally.

X: the maximum height of the sample floating is 5mm or more when the sample is creased or placed horizontally.

(10) Bending resistance of 5 ═ r

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

(11) Resistance to thermal bending

A sample having a size of 50mm X100 mm was bent at 180 degrees in the longitudinal direction so that the bending radius became 3mm with the film surface of the substrate being the inner side, fixed with a jig, and left at 60 ℃ and RH 65% for 3 hours. After that, the holder was detached at room temperature, and the state after 1 hour was observed. The slow axis of the base film is orthogonal to the bending direction. The evaluation criteria are as follows.

Very good: return to substantially flat

O: in a slightly bent state (less than 20 degree)

X: is bent (more than 20 degrees)

< production of easily bondable layer component >

(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 dimethyl isophthalate 5-sulfonic acid sodium salt, 233.5 parts by mass of diethylene glycol, 136.6 parts by mass of ethylene glycol, and 0.2 part by mass of tetra-n-butyl titanate were charged into a stainless autoclave equipped with a stirrer, a thermometer, and a partial reflux condenser, and ester exchange reaction was carried out at 160 to 220 ℃ for 4 hours. Subsequently, the mixture was heated to 255 ℃ and the reaction system was slowly reduced in pressure, followed by reaction under a reduced pressure of 30Pa for 1 hour and 30 minutes to obtain a copolyester resin. The obtained copolyester resin is light 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 obtained as follows: as for 0.1g of the resin, 25mL of a mixed solvent of phenol (60 mass%) and 1,1,2, 2-tetrachloroethane (40 mass%) was used as a solvent, and the value was measured at 30 ℃. The glass transition temperature based on DSC is 40 ℃.

(preparation of an aqueous polyester Dispersion)

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

(preparation of aqueous polyvinyl alcohol solution)

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

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

100 parts by mass of a polyisocyanate compound having an isocyanurate structure (manufactured by Asahi Kasei Chemicals Corporation, Duranate TPA), 55 parts by mass of propylene glycol monomethyl ether acetate, and 30 parts by mass of polyethylene glycol monomethyl ether (average molecular weight 750) each of which was prepared from hexamethylene diisocyanate were charged into a flask equipped with a stirrer, a thermometer, and a reflux condenser, and the flask was held at 70 ℃ for 4 hours under a nitrogen atmosphere. Then, the temperature of the reaction solution was lowered to 50 ℃ and 47 parts by mass of methyl ethyl ketoxime was added dropwise. The infrared spectrum of the reaction mixture was measured, and it was confirmed that the absorption of isocyanate groups was lost, thereby obtaining an aqueous dispersion of a blocked polyisocyanate having a solid content of 75 mass%.

(preparation of coating liquid for easy adhesive layer P1)

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

(polymerization of urethane resin used for easy adhesion layer P2)

A urethane resin containing an aliphatic polycarbonate polyol as a constituent was produced in the following manner. 43.75 parts by mass of 4, 4-diphenylmethane diisocyanate, 12.85 parts by mass of dimethylolbutyric acid, 153.41 parts by mass of polyhexamethylene carbonate diol having 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 introduction tube, a silica gel drying tube, and a thermometer, and stirred at 75 ℃ for 3 hours under a nitrogen atmosphere, confirming that the reaction solution had reached a predetermined amine equivalent. Subsequently, the temperature of the reaction solution was lowered to 40 ℃, and 8.77 parts by mass of triethylamine was added to the reaction solution to obtain a polyurethane prepolymer solution. Next, 450g of water was added to a reaction vessel equipped with a homogeneous disperser capable of high-speed stirring, and the temperature was adjusted to 25 ℃ while the water was kept for 2000min^-1The polyurethane prepolymer solution was added and dispersed while stirring and mixing. Then, under reduced pressure, a part of the acetone and water was removed from the mixed solution, thereby preparing a water-soluble polyurethane resin having a solid content of 35%. The glass transition temperature of the obtained polyurethane resin containing the aliphatic polycarbonate polyol as a constituent component was-30 ℃.

(polymerization of oxazoline crosslinking agent used in easy adhesion layer P2)

Into a flask equipped with a thermometer, a nitrogen inlet, a reflux condenser, a dropping funnel, and a stirrer, a mixture of 58 parts by mass of ion exchange water and 58 parts by mass of isopropyl alcohol as an aqueous medium, and 4 parts by mass of a polymerization initiator (2, 2' -azobis (2-amidinopropane) · dihydrochloride) were charged. 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 moles of ethylene glycol added: 9 moles, manufactured by shinkanji chemical Co., Ltd.), and 32 parts by mass of methyl methacrylate was charged into a dropping funnel and dropped at 70 ℃ for 1 hour under a nitrogen atmosphere. After the completion of the dropwise addition, the reaction solution was stirred for 9 hours and cooled to obtain an oxazoline group-containing water-soluble resin having a solid content concentration of 40 mass%.

(preparation of coating solution for easy adhesion layer P2)

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

< production of polyester resin for base film >

Production example 1 polyester X

The esterification reaction kettle was heated up, and when the temperature reached 200 ℃, 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 as a catalyst, 0.064 parts by mass of magnesium acetate tetrahydrate, and 0.16 parts by mass of triethylamine were added while stirring. Subsequently, the pressure and temperature were increased to perform the pressure esterification reaction under the conditions of a gauge pressure of 0.34MPa and 240 ℃ and then the esterification reaction vessel was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. Further, the temperature was raised to 260 ℃ over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. Then, after 15 minutes, the resulting mixture was dispersed with a high-pressure disperser, and after 15 minutes, the resulting esterification reaction product was transferred to a polycondensation reaction vessel, and polycondensation reaction was carried out at 280 ℃ under reduced pressure.

After the completion of the polycondensation reaction, the mixture was filtered through a NasEn filter having a 95% cutoff diameter of 5 μm, extruded in strand form through a nozzle, cooled and solidified with cooling water having been subjected to a filtration treatment (pore diameter: 1 μm or less), and cut into pellets. The obtained polyethylene terephthalate resin (X) had an intrinsic viscosity (intrinsic viscosity) of 0.73dL/g and contained substantially no inactive particles and internal precipitated particles (hereinafter, the polyethylene terephthalate resin (X) will be referred to as PET (X)).

Production 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 the ultraviolet absorber was obtained using a kneading extruder (hereinafter, the polyethylene terephthalate resin (Y) will be referred to simply as PET (Y))

(production of base film 1)

As the base film intermediate layer raw material, 90 parts by mass of PET (X) resin pellets containing no particles and 10 parts by mass of PET (Y) resin pellets containing an ultraviolet absorber were dried under reduced pressure at 135 ℃ for 6 hours (1Torr), and then supplied to the extruder 2 (for the intermediate layer II), and further, PET (X) was dried by a conventional method and supplied to the extruder 1 (for the outer layer I and the outer layer III), respectively, and dissolved at 285 ℃. The 2 kinds of polymers were each filtered with a filter medium of a stainless steel sintered body (nominal filtration accuracy 10 μm particle 95% cutoff), laminated in 2 kinds of 3-layer flow blocks, formed into a sheet from a pipe head and extruded, and then wound up to a casting drum having a surface temperature of 30 ℃ by an electrostatic casting method, cooled and solidified to prepare an unstretched film. At this time, the discharge amount of each extruder was adjusted so that the ratio of the thicknesses of the layer I, the layer II, and the layer III became 10: 80: 10.

Next, P1 was applied to one side of the unstretched PET film and P2 was applied to the opposite side thereof by the reverse roll method so that the application amounts after drying became 0.12g/m²Then, the mixture was introduced into a dryer and dried at 80 ℃ for 20 seconds.

The unstretched film on which the coating layer was formed was introduced into a simultaneous biaxial stretching machine, and while the end of the film was fixed with a jig, the film was introduced into a hot air zone at a temperature of 125 ℃ and stretched 6.5 times in the running direction and 2.2 times in the width direction. Subsequently, the film was treated at 225 ℃ for 30 seconds while keeping the width of the film stretched in the width direction, to obtain a biaxially oriented PET film having a film thickness of 35 μm. The film is wound into a roll form to form a film roll. The slow axis of the obtained film is within 3 DEG from the advancing direction.

(production of base film 2)

The thickness of the unstretched film was changed, and the film was stretched in the running direction and the width direction in the same manner as in the above-described method for producing the base film 1, to obtain a biaxially oriented PET film having a film thickness of 50 μm. The film is wound into a roll form to form a film roll. The slow axis of the obtained film is within 3 DEG from the advancing direction.

(production of base film 3)

The thickness of the unstretched film was changed, and the film was stretched in the running direction and the width direction in the same manner as in the above-described method for producing the base film 1, to obtain a biaxially oriented PET film having a film thickness of 80 μm. The film is wound into a roll form to form a film roll. The slow axis of the obtained film is within 3 DEG from the advancing direction.

(production of base film 4)

The thickness of the unstretched film was changed, and the film was stretched 2.2 times in the running direction and 6.0 times in the width direction in the same manner as in the above-described method for producing the base film 1, to obtain a biaxially oriented PET film having a film thickness of 35 μm. The film is wound into a roll form to form a film roll. The slow axis of the obtained film is within 5 DEG from the running direction.

(production of base film 5)

An unstretched film was produced in the same manner as in the production method of the base film 1, and was stretched 6.5 times in the advancing direction on a roll group having a peripheral speed difference by a sequential biaxial stretcher, and then was stretched 2.2 times in the width direction in a tenter to obtain a biaxially oriented PET film having a film thickness of 35 μm. The film is wound into a roll form to form a film roll. The slow axis of the obtained film is within 5 DEG from the running direction.

(production of base film 6)

An unstretched film was produced in the same manner as in the above-described method for producing the base film 1 except that the thickness was changed, and the film was stretched 3.6 times in the width direction in a tenter to obtain a biaxially oriented PET film having a film thickness of 35 μm. The film is wound into a roll form to form a film roll. The slow axis of the obtained film is within 5 DEG from the running direction.

(production of base film 7)

Except for changing the thickness, an unstretched film was produced in the same manner as in the above-described method for producing the base film 1, and was stretched 3.8 times in the advancing direction on a roll group having a peripheral speed difference by a sequential biaxial stretcher, and thereafter, only heat-set without stretching in the width direction in a tenter to obtain a biaxially oriented PET film having a film thickness of 35 μm. The film is wound into a roll form to form a film roll. The slow axis of the obtained film is within 5 DEG from the running direction.

(production of base film 8)

The thickness of the unstretched film was changed, and the film was stretched 4.5 times in the advancing direction and 2.5 times in the width direction in the same manner as in the production method of the base film 1 to obtain a biaxially oriented PET film having a film thickness of 35 μm. The film is wound into a roll form to form a film roll. The slow axis of the obtained film is within 5 DEG from the running direction.

The properties of the obtained base films 1 to 8 are shown in Table 1.

[ Table 1]

(lamination of hard coat layer)

95 parts by mass of a urethane acrylate hard coat agent (manufactured by mitaka chemical industries, BEAMSET (registered trademark) 577, solid content concentration 100%), 5 parts by mass of a photopolymerization initiator (manufactured by BASF Japan, Irgacure (registered trademark) 184, solid content concentration 100%), and 0.1 part by mass of a leveling agent (manufactured by BYK Japan, BYK307, solid content concentration 100%) were mixed, and the mixture was diluted with a solvent of toluene/MEK ═ 1/1 to prepare a coating solution having a concentration of 40%.

A hard coat coating liquid was applied on the easy-adhesion layer P2 surface of the base film with a Meyer bar so that the film thickness after drying became 5.0. mu.m, and after drying at 80 ℃ for 1 minute, ultraviolet rays were irradiated (cumulative light amount 200 mJ/cm)²)。

(lamination of polarizing plate)

As a method for providing a polarizing plate on a base film, the following 4 methods were performed.

(A) A method in which a rubbing alignment layer is provided on a base film, and a polarizing film comprising a liquid crystal compound and a dichroic dye is provided thereon (polarizing plate laminating method A)

(B) A method in which a photo-alignment layer is provided on a base film, and a polarizing film comprising a liquid crystal compound and a dichroic dye is provided thereon (polarizing plate laminating method B)

(C) A method in which a polarizing film made of PVA/iodine is provided on a thermoplastic substrate and then transferred to a substrate film (polarizing plate laminating method C)

(D) A method of preparing a polarizing film comprising PVA/iodine and bonding the polarizing film to a substrate film (polarizing plate laminating method D)

The details of each method are described below.

Polarizing plate laminating method A

(formation of alignment layer by brushing)

A coating material for an alignment layer was applied to the surface of the easy-adhesion layer P1 of the base film by a bar coater, followed by drying at 120 ℃ for 3 minutes to form a 200nm thick film. Next, the surface of the obtained film was treated with a brush roll wound with a nylon-made napped cloth to obtain a base material film on which a brush-rubbed alignment layer was laminated. The brushing direction was set to 0 degree or 90 degrees with respect to the longitudinal direction of the film.

Coating for brushing alignment layer

Molecular weight of completely saponified polyvinyl alcohol 8002 parts by mass

100 parts by mass of ion-exchanged water

(Synthesis of polymerizable liquid Crystal Compound)

A compound (1) represented by the following formula (1) and a compound (2) represented by the following formula (2) were synthesized with reference to the description of paragraph [0134] of Japanese patent application laid-open No. 2007 & 510946 and Lub et al.

A dye (3) represented by the following formula (3) was synthesized with reference to example 1 of Japanese patent application laid-open No. 63-301850.

A dye (4) represented by the following formula (4) was synthesized by referring to example 2 of Japanese examined patent publication No. 5-49710.

A dye (5) represented by the following formula (5) was synthesized by referring to a method for producing a compound of the general formula (1) of Japanese patent publication No. 63-1357.

(formation of polarizing film)

A coating material for a 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 applied to a base film on which a brush-rubbing alignment layer was laminated by a bar coater, and dried at 110 ℃ for 3 minutes to form a film having a thickness of 2 μm. Next, UV light was irradiated, and a polarizing plate was placed on the base film.

Polarizing plate laminating method B

(Synthesis of coating Material for photo-alignment layer)

A5 mass% solution of cyclopentanone of a polymer (6) represented by the following formula (6) was prepared based on the descriptions of example 1, example 2 and example 3 in Japanese patent application laid-open No. 2013-33248.

(formation of photo-alignment layer)

The coating material for a photo-alignment layer having the above composition was applied to one surface of a base film by a bar coater, and dried at 80 ℃ for 1 minute to form a film having a thickness of 150 nm. Subsequently, the substrate film on which the photo-alignment layer was laminated was obtained by irradiating polarized UV light.

The coating for a polarizing film is applied to a photo-alignment layer, and a polarizing layer is similarly provided on a base film on which the alignment layer is laminated.

Polarizing plate laminating method C

(production of substrate laminated polarizing plate)

An unstretched film having a thickness of 100 μm was prepared using polyester X as a thermoplastic resin substrate, and an aqueous solution of polyvinyl alcohol having a polymerization degree of 2400 and a saponification degree of 99.9 mol% was applied to one surface of the unstretched film and dried to form a PVA layer.

The obtained laminate was stretched at 120 ℃ between rolls having different peripheral speeds by 2 times in the longitudinal direction and wound. 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 be dyed, and then treated in a mixed aqueous solution of potassium iodide (3%) and boric acid (3%) for 30 seconds.

The laminate was uniaxially stretched in the longitudinal direction in a mixed aqueous solution of boric acid (4%) and potassium iodide (5%) at 72 ℃. The stretched laminate was then washed with a 4% aqueous solution of potassium iodide, the aqueous solution was removed with an air knife, and the laminate was dried in an oven at 80 ℃ to obtain a substrate laminated polarizing plate 1 having a width of 30cm and a length of 1000m, which was cut at both ends and wound up. The total draw ratio was 6.5 times, and the thickness of the polarizing plate was 5 μm. Note that, the thicknesses are as follows: the substrate laminated polarizing plate 1 was embedded in an epoxy resin and cut into slices, observed with an optical microscope and read.

(lamination of polarizing layers)

After an ultraviolet-curable acrylic adhesive is applied to the base film, the polarizing plate surface of the base laminated polarizing plate 1 is bonded, and ultraviolet light is 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 was peeled off, and a polarizing plate was provided on the substrate film.

Polarizing plate laminating method D

(production of Single-layer polarizing plate)

A polyvinyl alcohol resin film having a degree of saponification of 99.9% was introduced into a roll having a difference in peripheral speed, and uniaxially stretched at 100 ℃ by a factor of 3. The obtained stretched polyvinyl alcohol 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 boric acid 10% aqueous solution at 72 ℃. Thereafter, the sheet was washed with ion-exchanged water, and further immersed in a 6% aqueous solution of potassium iodide, and the aqueous solution was removed with a gas knife, followed by drying at 45 ℃. The thickness of the polarizer was 18 μm.

(lamination of polarizing plate)

After an ultraviolet-curable acrylic adhesive is applied to a base film, a single-layer polarizing plate is bonded, and ultraviolet light is irradiated from the base-laminated polarizing plate side, thereby providing a polarizing plate on the base film.

(lamination of retardation layer)

As a method for providing a retardation layer on a polarizer, the following 4 methods were performed.

(F) Method of providing 1/2-wavelength layer and 1/4-wavelength layer on polarizer by coating (method of laminating phase difference layer F)

(G) A method in which the 1/2 wavelength layer provided on the release film was transferred onto a polarizing plate, and the 1/4 wavelength layer provided on the release film was further transferred thereon (method of laminating retardation layers G)

(H) A method in which an 1/4-wavelength layer and a 1/2-wavelength layer are provided on a release film and transferred to a polarizing plate (method for laminating a retardation layer H)

(I) Method of coating and disposing 1/2 wavelength layer on 1/4 wavelength layer and attaching 1/2 wavelength layer to polarizing plate (method I for laminating retardation layer)

The details of each method are described below.

Method for laminating retardation layer F

A polyvinyl alcohol (2 mass% aqueous solution of polyvinyl alcohol 1000 completely saponified type (surfactant 0.2%) was applied to a polarizing plate provided on a base film and dried to obtain a polyvinyl alcohol film having a thickness of about 100nm, and then the surface of the polyvinyl alcohol film was subjected to a brushing treatment at an angle of 15 degrees with respect to the absorption axis of the polarizing plate.

Next, a solution for forming a retardation layer having the following composition was applied to the surface subjected to the brushing treatment by a bar coating method. The coated film was dried, subjected to alignment treatment, and then cured by irradiation with ultraviolet light to obtain an 1/2 wavelength layer.

Solution for forming phase difference layer

LC242 (manufactured by BASF corporation) 75 parts by mass

20 parts by mass of the following compound

Trimethylolpropane triacrylate 5 parts by mass

Irgacure 3793 parts by mass

0.1 part by mass of a surfactant

Methyl ethyl ketone 250 parts by mass

Subsequently, a polyvinyl alcohol film was similarly provided on the 1/2 wavelength layer, and a brushing treatment was performed. The rubbing was performed at an angle of 73 degrees with respect to the absorption axis of the polarizing plate. The phase difference layer forming solution was applied by a bar coating method, dried, subjected to alignment treatment, and then irradiated with ultraviolet rays to be cured. In the bar coating, the thickness was adjusted so that the layer became 1/4 wavelength.

Method G for laminating retardation layer

A biaxially stretched polyethylene terephthalate (PET) film having a thickness of 50 μm was subjected to brushing treatment. The retardation layer forming solution was applied to the brushed surface by a bar coating method, dried, subjected to an alignment treatment, and then cured by irradiation with ultraviolet light, thereby forming an 1/2 wavelength layer on the biaxially stretched polyethylene terephthalate film. Next, the 1/2 wavelength layer was bonded to the polarizer surface provided on the base film using an ultraviolet-curable adhesive. After that, the biaxially stretched PET film was peeled. The attachment was performed at 15 degrees with respect to the absorption axis of the polarizing plate.

Similarly, an 1/4 wavelength layer was provided on a biaxially stretched PET film, and the film was bonded to the 1/2 wavelength layer with an optically transparent adhesive sheet. The attachment was performed at 75 degrees with respect to the absorption axis of the polarizing plate.

Method for laminating retardation layer H

A biaxially stretched polyethylene terephthalate (PET) film having a thickness of 50 μm was subjected to brushing treatment. The retardation layer forming solution was applied to the brushed surface by a bar coating method, dried, subjected to an alignment treatment, and then cured by irradiation with ultraviolet light, thereby providing an 1/4 wavelength layer on the biaxially stretched polyethylene terephthalate film. Further, a polyvinyl alcohol (2 mass% aqueous solution (surfactant 0.2%) of polyvinyl alcohol 1000 completely saponified type was applied to the 1/4 wavelength layer and dried to obtain a polyvinyl alcohol film having a thickness of about 100nm, then, the surface of the polyvinyl alcohol film was subjected to a brushing treatment, a retardation layer forming solution was applied to the brushed surface of the PVA by a bar coating method and dried, after an orientation treatment, the polyvinyl alcohol film was irradiated with ultraviolet rays to be cured to provide a 1/2 wavelength layer, the rubbing direction in the case of providing the 1/4 wavelength layer and the rubbing direction in the case of providing the 1/2 wavelength layer were set to an angle of 60 degrees, and further, the 1/2 wavelength layer was bonded to the polarizer surface provided to the base film by using an ultraviolet-curable adhesive, and thereafter, the biaxially stretched PET film was peeled off, and in the bonding, the absorption axis of the polarizer and the rubbing direction of the 1/2 wavelength layer were set to 15 degrees, The absorption axis of the polarizer was 75 degrees from the brushing direction of the 1/4 wavelength layer.

Method I for laminating retardation layer

A 1/4 wavelength film was unwound from a roll of 1/4 wavelength film having a slow axis in the longitudinal direction, cut to a desired length, and subjected to a brushing treatment on the surface. An 1/2 wavelength layer was provided on the brushed surface by the same method as the method F for laminating a retardation layer. Further, an 1/2 wavelength layer was bonded to the surface of the polarizing plate provided on the base film using an ultraviolet-curable adhesive. The 1/4-wavelength film was produced as follows: the propylene-ethylene random copolymer (ethylene content: 5%) was extruded into a sheet form and stretched in the longitudinal direction with a roll to produce a propylene-ethylene random copolymer (thickness: 20 μm). In the pasting, the rubbing direction of the absorption axis of the polarizing plate and the 1/2 wavelength layer was set to 15 degrees, and the slow axis direction of the polarizing plate and the 1/4 wavelength layer was set to 75 degrees.

The thickness of the retardation layer formed by the above coating was 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 to 23

A polarizing plate and a retardation layer were provided on the base film shown in table 2 by the methods shown in table 2 to prepare a circularly polarizing plate.

Comparative example 1

After a polarizing plate was laminated on the base film by the polarizing plate laminating method D, a TAC film having a thickness of 80 μm was bonded to the polarizing plate with a PVA adhesive, thereby obtaining a polarizing plate. Further, a retardation layer was formed on the TAC film of the polarizing plate by the phase difference layer lamination method I to produce a circular polarizing plate.

Comparative example 2

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

Comparative examples 3 to 5

A polarizing plate and a retardation layer were provided on the base film shown in table 2 by the methods shown in table 2 to obtain a circularly polarizing plate.

The properties of the circularly polarizing plates obtained in examples 1 to 23 and comparative examples 1 to 5 are shown in table 2.

[ Table 2]

The circularly polarizing plate thus obtained was attached to an organic EL element via an adhesive layer having a thickness of 25 μm, and a folding display of a smart phone type was produced in which the entire center portion having a radius of 3mm corresponding to the bending radius was folded in two. The circularly polarizing plate was disposed on the surface of 1 continuous display by means of a folded portion, and the hard coat layer was disposed on the surface of the display so that the slow axis of the base film was orthogonal to the folding direction. The evaluation results of the circularly polarized plate used are shown in table 3.

[ Table 3]

When the circular polarizing plate of each example was used, the central portion was folded into two, and a portable smartphone was produced, satisfying the operation and visibility, and no rainbow unevenness was observed.

(preparation of coating for circular polarization light reflection layer)

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

100 parts by mass of LC242 (manufactured by BASF corporation)

LC756 (manufactured by BASF corporation) 5 parts by mass

Irgacure 8194 parts by mass

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

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

(formation of a circularly polarized light reflective layer)

The coating material for a circularly polarizing light reflecting layer was applied to the retardation layer of the circularly polarizing plate obtained in the example by a bar coater, and dried at 85 ℃. Subsequently, the inside of an oven at 85 ℃ was irradiated with ultraviolet rays, and a circularly polarized light reflecting layer was provided.

(evaluation of circularly polarizing plate having circularly polarizing light reflecting layer laminated thereon)

When the circularly polarizing plate laminated with the circularly polarizing reflective layer obtained in the above was similarly incorporated into an EL display and observed by visual observation, the effect of improving the luminance was observed as compared with the circularly polarizing plates of the respective examples in which the circularly polarizing reflective layer was not laminated.

The workability and the bending resistance were evaluated in the same manner, and the results were all at a level equivalent to those of the original examples.

The EL display device of the present invention uses a circular polarizing plate using a base film having a refractive index ny in the fast axis direction of 1.568 or more and 1.63 or less, wherein the number of self-supporting films present between a polarizing plate and a retardation layer is 1 or less, and the transmission axis of the polarizing plate is substantially parallel to the fast axis of the base film, so that the EL display device is excellent in visibility (suppression of rainbow unevenness), can be made thin, and is less likely to cause troubles in the production process.

In addition, the flexible EL display device is not peeled off even when repeatedly bent or left in a high-temperature state, is not easily creased, and is excellent in visibility.

When a polyester film is further used as a base film of the circularly polarizing plate, an EL display device having a circularly polarizing plate excellent in moisture permeation resistance, dimensional stability, mechanical strength, and chemical stability can be provided.

Claims

1. An electroluminescent display device, comprising: an electroluminescent element, and a circularly polarizing plate disposed on the viewing side of the electroluminescent element,

(2) No self-supporting film or only 1 self-supporting film is present between the polarizing plate and the retardation layer, and the retardation layer itself is also included between the polarizing plate and the retardation layer; and the combination of (a) and (b),

2. The electroluminescent display device according to claim 1, wherein the in-plane birefringence Δ Nxy 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 smaller of the tear strengths based on the square tear method in the slow axis direction and the fast axis direction of the base material film is 250N/mm or more.

4. The electroluminescent display device according to any one of claims 1 to 3, wherein the thickness of the polarizing plate is 12 μm or less.

5. The electroluminescent display device according to any one of claims 1 to 4, wherein the polarizing plate is formed of a polymerizable liquid crystal compound and a dichroic pigment.

6. The electroluminescent display device according to any one of claims 1 to 5, wherein the phase difference layer is formed of a liquid crystal compound.