阅读说明：本技术 电致发光显示装置 (Electroluminescent display device ) 是由 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 于 2019-03-22 设计创作，主要内容包括：一种电致发光显示装置,其具备：电致发光元件、和配置于比该电致发光元件还靠近可视侧的圆偏光板,前述圆偏光板依次具有相位差层、偏振片和基材薄膜,(1)基材薄膜的快轴方向的折射率ny为1.568以上且1.63以下；(2)在偏振片与相位差层之间不存在自立性薄膜、或仅存在有1张自立性薄膜(此处偏振片与相位差层之间也包括相位差层本身)；和,(3)偏振片的透光轴与基材薄膜的快轴为大致平行。(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.)

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 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),

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

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.

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.

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.