JP7331400B2 - FLEXIBLE IMAGE DISPLAY DEVICE AND METHOD FOR MANUFACTURING CIRCULARLY POLARIZED PLATE USED THEREOF - Google Patents

Description

The present invention relates to a flexible image display device and a method for manufacturing a circularly polarizing plate used therein.

In the image display device, there is a problem that extraneous light is reflected on the surfaces of constituent materials such as the image display cell and the touch sensor, wiring portions thereof, and the like, resulting in deterioration of visibility. To address these problems, a method has been proposed in which an optical layered body is arranged on the exit surface of an image display device to reduce the reflection of external light. A circularly polarizing plate in which a linear polarizing plate and a 1/4 wavelength retardation plate are laminated is generally used for this optical layered body.

In recent years, as an image display device, there has been developed a flexible display device that 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, or can be wound up into a roll shape for carrying. Proposed.

A polyester film having an in-plane retardation of 3000 to 30000 nm has been proposed as a polarizer protective film for a polarizing plate (see, for example, Patent Document 1). Compared to cellulose or acrylic films, polyester films have lower moisture permeability, superior mechanical properties (high impact resistance and high elastic modulus), and superior chemical properties (solvent resistance, etc.). Therefore, it is suitably used for an image display device. However, the polyester film has a drawback that iridescence tends to occur due to its birefringence.
Therefore, in order to suppress iridescent unevenness and provide sufficient in-plane retardation using a polyester film, it is necessary to increase the thickness of the film. When a circularly polarizing plate in which a retardation plate is laminated on a polarizing plate having such a polyester film as a protective film is used in a flexible image display device, sufficient bending performance cannot be obtained due to its thickness, and repeated When the film is folded or left in a hot place such as the interior of an automobile, there are problems such as the film being easily peeled off and the bending marks being easily left.
Furthermore, in order to suppress the influence of the wavelength dispersion of the refractive index and obtain a circularly polarizing plate with better color reproducibility, a technique of combining a quarter-wave plate and a half-wave plate has been proposed (Patent Document 2). However, when a plurality of such retardation plates are laminated on a polarizing plate, the above problem becomes more conspicuous.

JP 2012-256057 A JP-A-10-68816

The present invention has been made against the background of such problems of the prior art. That is, an object of the present invention is to provide a flexible image display device that has excellent visibility, is resistant to peeling of laminated members even when repeatedly bent or left in a high temperature state, and is resistant to creases, and a circularly polarizing plate. It is to provide a manufacturing method of

The inventors of the present invention have made intensive studies to develop a flexible image display device that has excellent visibility, that is resistant to peeling of laminated members even when repeatedly bent or left in a high temperature state, and that is resistant to creases. As a result, by using a base film having a specific in-plane retardation and using a circularly polarizing plate in which the number of self-supporting films present between the polarizer and the retardation layer is one or less, the above object is achieved. found that it can be done. The present invention has been completed based on such findings.

That is, the present invention relates to a flexible image display device and a method for manufacturing a circularly polarizing plate, which are described in Items 1 to 7.
Section 1.
A flexible image display device comprising an image display cell and a circularly polarizing plate arranged on the viewing side of the image display cell,
The circularly polarizing plate has a retardation layer, a polarizer, and a base film,
(1) The in-plane retardation of the base film is 3000 to 30000 nm, and (2) there is no or only one self-supporting film between the polarizer and the retardation layer (here, the polarizer and the retardation layer includes the retardation layer itself)
Flexible image display device.
Section 2.
2. The flexible image display device according to Item 1, wherein the thickness of the polarizer is 12 μm or less.
Item 3.
3. The flexible image display device according to item 1 or 2, wherein the polarizer comprises a polymerizable liquid crystal compound and a dichroic dye.
Section 4.
4. The flexible image display device according to any one of items 1 to 3, wherein the retardation layer is made of a liquid crystal compound.
Item 5.
The following process:
(1) a step of preparing a base film having an in-plane retardation of 3000 to 30000 nm, (2) a step of providing a polarizer on the base film by either method (a) or (b), (a) separation a method of transferring a polarizer provided on a moldable support substrate to a substrate film;
(b) A method of coating a substrate film with a polarizing film composition comprising a polymerizable liquid crystal compound and a dichroic dye and orienting it to form a polarizer, and (3) forming a retardation layer on the polarizer. laminating,
A method for manufacturing a circularly polarizing plate.
Item 6.
The following process:
(1) a step of preparing a base film having an in-plane retardation of 3000 to 30000 nm, (2) a step of laminating a polarizer on the base film, and (3) (c) or (d) on the polarizer. A step of providing a retardation layer by any of the methods of
(c) a method of transferring a retardation layer provided on a releasable supporting substrate onto a polarizer;
(d) a method of applying a retardation layer composition comprising a liquid crystal compound onto a polarizer and orienting the composition to form a retardation layer;
A method for manufacturing a circularly polarizing plate.
Item 7.
The step of laminating the retardation layer includes
(c) a method of transferring a retardation layer provided on a releasable support substrate onto a polarizer; a method of forming a retardation layer,
6. The method for producing a circularly polarizing plate according to item 5, wherein

The flexible image display device of the present invention uses a base film having an in-plane retardation of 3000 to 30000 nm, and the number of self-supporting films present between the polarizer and the retardation layer is 1 or less. Circularly polarized light. Since a plate is used, the visibility is excellent, and even when repeatedly bent or left in a high-temperature state, the laminated members are less likely to separate from each other, and creases are less likely to be left.

A flexible image display device of the present invention includes an image display cell and a circularly polarizing plate arranged on the viewing side of the image display cell. By arranging the circularly polarizing plate on the viewing surface of the flexible image display device, it is possible to reduce deterioration in visibility due to extraneous light reflected by the surface of the image display cell or wiring. The circularly polarizing plate has a base film, a polarizer, and a retardation layer. First, the circularly polarizing plate used in the present invention will be described.

A. Circularly polarizing plate1. Base Film First, the base film of the circularly polarizing plate will be described.
(Material of base film)
As the resin for the base film used in the present invention, any resin can be used without particular limitation as long as it causes birefringence upon orientation. Polyester, polycarbonate, polystyrene and the like are preferable, and polyester is more preferable, in that the retardation can be increased. Preferable polyesters include polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), among which PET and PEN are more preferable. By using a polyester film as the base film, it is possible to obtain a flexible image display device having a circularly polarizing plate excellent in moisture permeability resistance, dimensional stability, mechanical strength and chemical stability.

In the case of PET, the intrinsic viscosity (IV) of the resin constituting the base film is preferably 0.58 to 1.5 dL/g. The lower limit of IV is more preferably 0.6 dL/g, still more preferably 0.65 dL/g, and particularly preferably 0.68 dL/g. The upper limit of IV is more preferably 1.2 dL/g, still more preferably 1 dL/g. If the IV of PET is less than 0.58 dL/g, it may tend to leave bending traces due to repeated bending. If the IV of PET exceeds 1.5 dL/g, it may become difficult to produce the film. The intrinsic viscosity (IV) in the present invention is a value measured at a temperature of 30° C. using a mixture of phenol and 1,1,2,2-tetrachloroethane at a mass ratio of 6:4 as a solvent. do.

The base film preferably has a light transmittance of 20% or less at a wavelength of 380 nm. The light transmittance at a wavelength of 380 nm is more preferably 15% or less, even more preferably 10% or less, and particularly preferably 5% or less. When the light transmittance is 20% or less, deterioration of iodine or dichroic dye in the polarizer due to ultraviolet rays can be suppressed. The transmittance in the present invention is measured in the direction perpendicular to the plane of the film, and can be measured using a spectrophotometer (for example, Hitachi U-3500).

The light transmittance of the base film at a wavelength of 380 nm is set to 20% or less by adding an ultraviolet absorber to the base film, applying a coating liquid containing the ultraviolet absorber to the surface of the base film, It can be achieved by appropriately adjusting the type or concentration of the ultraviolet absorber and the thickness of the base film. In the present invention, substances known in the art can be used as UV absorbers. Examples of the ultraviolet absorbent include organic ultraviolet absorbents and inorganic ultraviolet absorbents, and organic ultraviolet absorbents are preferred from the viewpoint of transparency.

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

It is also preferable to add particles having an average particle diameter of 0.05 to 2 μm to the base film in order to improve slipperiness. Particles include inorganic particles such as titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, and calcium fluoride; Examples include organic polymer particles such as styrene, acrylic, melamine, benzoguanamine, and silicone particles. The average particle size was calculated by observing particles in the cross section of the film with a scanning electron microscope. Specifically, 100 particles in the cross section of the film were observed with a scanning electron microscope, the diameter (d) of each particle was measured, and the average value thereof was taken as the average particle diameter.
These particles can be added throughout the base film. Alternatively, the substrate may be a skin-core coextruded multilayer structure and the particles may be added to the skin layer only.

(In-plane retardation of base film)
The substrate film has an in-plane retardation of 3000-30000 nm. It is one of the characteristics of the flexible image display device of the present invention that the substrate film of the circularly polarizing plate has an in-plane retardation of 3000 to 30000 nm. If the in-plane retardation of the substrate film is less than 3000 nm, it may not be possible to ensure good visibility when observing from a direction oblique to the normal direction. Further, when the purpose is to prevent blackout or coloration when viewing an image with polarized sunglasses, if the in-plane retardation of the substrate film is less than 3000 nm, iridescence may be observed. A preferable lower limit of the in-plane retardation is 4500 nm, and a more preferable lower limit is 6000 nm.

On the other hand, the upper limit of in-plane retardation is preferably 30000 nm. Even if the base film has a retardation exceeding that, not only is the effect of further improving visibility not substantially obtained, the thickness of the base film becomes considerably thick, and the handleability as an industrial material decreases. do. The upper limit of the in-plane retardation is more preferably 15,000 nm or less, still more preferably 11,000 nm, and particularly preferably 9,000 nm or less, from the viewpoint of reducing the thickness of the film to ensure repetitive flexibility.

The retardation of the base film can be determined by measuring the refractive index and thickness in the biaxial directions, and can also be determined using a commercially available automatic birefringence measuring device such as KOBRA-21ADH (Oji Scientific Instruments Co., Ltd.). . The refractive index is a value measured at the wavelength of the sodium D line (589 nm).

The substrate film preferably has a ratio of in-plane retardation (Re) to thickness direction retardation (Rth) within a specific range. The thickness direction retardation means the average retardation obtained by multiplying the two birefringences (ΔNxz and ΔNyz) when the film is viewed from the thickness direction section by the film thickness d. The smaller the difference between the in-plane retardation and the thickness direction retardation, the more isotropic the action of birefringence depending on the viewing angle, and the smaller the change in retardation due to the viewing angle. Therefore, it is considered that rainbow-like color spots due to viewing angles are less likely to occur.

The ratio of in-plane retardation to thickness direction retardation (Re/Rth) of the base film is preferably 0.2 or more, more preferably 0.5 or more, and still more preferably 0.6 or more. . As the ratio of in-plane retardation to thickness direction retardation (Re/Rth) increases, the birefringence action becomes more isotropic, and rainbow-like color spots due to viewing angles are less likely to occur. The ratio (Re/Rth) of the in-plane retardation to the thickness direction retardation is 2 in a perfect uniaxial (uniaxially symmetrical) film. However, as described above, the mechanical strength in the direction perpendicular to the orientation direction decreases significantly as the film approaches a perfect uniaxial (uniaxially symmetrical) film.

On the other hand, the ratio of in-plane retardation to thickness direction retardation (Re/Rth) of the substrate film is preferably 1.5 or less, more preferably 1.2 or less, and still more preferably 1 or less. . In order to completely suppress the occurrence of rainbow-like color spots depending on the viewing angle, the ratio of the in-plane retardation to the thickness direction retardation (Re/Rth) does not need to be 2, but is 1.5 or less, or 1.2 or less is also sufficient. Further, even if the above ratio is 1 or less, it is sufficiently possible to satisfy the viewing angle characteristics (about 180 degrees left and right and 120 degrees up and down) required for a liquid crystal display device.

(Nz coefficient)
The base film preferably has an Nz coefficient represented by |ny-nz|/|ny-nx| of 1.7 or less. The Nz coefficient can be obtained as follows. The orientation axis direction of the film is determined using a molecular orientation meter (MOA-6004 type molecular orientation meter manufactured by Oji Keisoku Co., Ltd.), and the biaxial refractive indices (ny, nx, ny>nx) and the refractive index (nz) in the thickness direction are determined by an Abbe refractometer (NAR-4T manufactured by Atago Co., Ltd., measurement wavelength 589 nm). The Nz coefficient can be obtained by substituting nx, ny, and nz obtained in this way into the expression represented by |ny-nz|/|ny-nx|.

If the Nz coefficient of the base film exceeds 1.7, iridescence may occur depending on the angle when the liquid crystal display device is observed obliquely. The Nz coefficient is more preferably 1.65 or less, still more preferably 1.63 or less. The lower limit of the Nz coefficient is 1.2. This is because it is technically difficult to obtain a film with an Nz coefficient of less than 1.2. In order to maintain the mechanical strength of the film, the lower limit of the Nz coefficient is preferably 1.3 or more, more preferably 1.4 or more, and still more preferably 1.45 or more.

(degree of plane orientation)
It is preferable that the base film has a degree of planar orientation represented by (nx+ny)/2-nz equal to or less than a specific value. Here, the values of nx, ny and nz are determined in the same manner as the Nz coefficient. The degree of plane orientation of the substrate film is preferably 0.13 or less, more preferably 0.125 or less, and still more preferably 0.12 or less. If the degree of plane orientation exceeds 0.13, iridescence may be observed depending on the angle when the liquid crystal display device is viewed obliquely. If the degree of plane orientation is less than 0.08, the film thickness may fluctuate and the retardation value may become non-uniform in the film plane.

(Method for manufacturing base film)
A predetermined in-plane retardation can be imparted by stretching the film serving as the base material. The stretching may be uniaxial or biaxial as long as the properties are obtained. The slow axis of the base film may be in the longitudinal direction of the base film, in a direction orthogonal to the longitudinal direction, or in an oblique direction. The longitudinal direction here means the running direction in the case of continuous film production. The angle formed by the longitudinal direction of the base film and the slow axis is preferably 10 degrees or less, particularly preferably 7 degrees or less, when the slow axis is in the longitudinal direction of the base film. When the slow axis of the base film is perpendicular to the longitudinal direction, the angle formed by the longitudinal direction of the base film and the slow axis is preferably 80 to 100 degrees, particularly preferably 83 to 97 degrees. When the slow axis of the base film is oblique, the angle formed by the longitudinal direction of the base film and the slow axis is preferably in the range of 35 to 55 degrees.
The stretching conditions will be specifically described by taking as an example a PET base film having a slow axis in the direction perpendicular to the longitudinal direction.
Both ends of an unstretched raw material obtained by extruding molten PET onto cooling rolls are gripped with clips and introduced into a tenter, preheated, and then stretched in the transverse direction while being heated. In addition, before stretching in the horizontal direction, the film may be stretched in the longitudinal direction with continuous rolls. Simultaneous biaxial stretching may also be carried out. The longitudinal stretching temperature and the transverse stretching temperature are preferably 80 to 130°C, particularly preferably 90 to 120°C. The longitudinal draw ratio is preferably 1 to 3.5 times, particularly preferably 1 to 3 times. The transverse draw ratio is preferably 2.5 to 6 times, particularly preferably 3 to 5.5 times. In order to control the retardation within the above range, it is preferable to control the ratio between the longitudinal draw ratio and the transverse draw ratio. If the difference in draw ratio between the vertical and horizontal directions is too small, it becomes difficult to increase the retardation. Setting the stretching temperature low is also a preferable measure for increasing the retardation. In the subsequent heat treatment, the treatment temperature is preferably 100-250°C, particularly preferably 180-245°C.
In order to obtain a substrate film having a slow axis in the longitudinal direction, longitudinal stretching is preferably performed with continuous rolls. Lateral stretching may be performed before the longitudinal stretching step.

The angle between the principal orientation axis of the substrate film and the longitudinal direction or the direction orthogonal to the longitudinal direction is preferably 20 degrees or less, more preferably 15 degrees or less, further preferably 10 degrees or less, and 5 degrees or less. is particularly preferred. When the angle between the principal orientation axis of the substrate film and the longitudinal direction or the direction perpendicular to the longitudinal direction exceeds 20 degrees, iridescence becomes easily visible, and when observed through polarized sunglasses or the like, the brightness varies greatly depending on the angle. Become. In the case of stretching in the longitudinal direction, the main orientation direction is the longitudinal direction, so the angle between the main orientation axis and the longitudinal direction is set. do.

The thickness of the substrate film is preferably 30 to 300 μm, more preferably 40 to 150 μm, even more preferably 50 to 100 μm. The upper limit of the thickness is preferably 80 μm or less, and more preferably 70 μm or less, in terms of ensuring repetitive flexibility. When the thickness of the substrate film is less than 30 μm, it becomes difficult to achieve a high in-plane retardation, and when it exceeds 300 μm, it becomes difficult to handle, has poor flexibility, and is difficult to fold.
The substrate film may be subjected to a treatment for improving adhesiveness, such as corona treatment, flame treatment, plasma treatment, or the like.

(Easy adhesion layer)
The substrate film may be provided with an easy-adhesion layer (easy-adhesion layer P1) in order to improve adhesion with a polarizing film or an orientation layer, which will be described later.
Resins used for the easy adhesion layer include polyester resins, polyurethane resins, polyester polyurethane resins, polycarbonate resins, polycarbonate polyurethane resins, acrylic resins, etc. Among them, polyester resins, polyester polyurethane resins, polycarbonate polyurethane resins and acrylic resins. Resins are preferred. The easy-adhesion layer is preferably crosslinked. Examples of cross-linking agents include isocyanate compounds, melamine compounds, epoxy resins, oxazoline compounds, and the like. Addition of a resin similar to the resin used for the orientation layer or the polarizing film, such as polyvinyl alcohol, polyamide, polyimide, polyamideimide, etc., is also a useful means for improving adhesion.

The easy-adhesion layer can be provided by coating the substrate film with a water-based coating containing these resins and, if necessary, a cross-linking agent, particles, etc., and then drying. Examples of the particles include those used in the base material described above.
The easy-adhesion layer can be provided off-line on the stretched base film, or can be provided in-line during the film-forming process. The easy-adhesion layer is preferably provided in-line during the film-forming process. When the easy-adhesion layer is provided in-line, it may be provided before longitudinal stretching or transverse stretching. In particular, it is preferable to apply the water-based coating immediately before transverse stretching, preheat and heat with a tenter, and dry and crosslink during the heat treatment step to provide an easy-adhesion layer in-line. In the case of in-line coating immediately before longitudinal stretching by rolls, it is preferable to apply the water-based paint, dry it with a vertical dryer, and then introduce it to the stretching rolls.
The coating amount of the water-based paint is preferably 0.01 to 1.0 g/m ² , more preferably 0.03 to 0.5 g/m ² .

(functional layer)
It is also preferable that a functional layer such as a hard coat layer, an antireflection layer, a low reflection layer, an antiglare layer, and an antistatic layer is provided on the side of the substrate film opposite to the side on which the polarizing film is laminated. form.
The thickness of these functional layers can be appropriately set, preferably 0.1 to 50 μm, more preferably 0.5 to 20 μm, still more preferably 1 to 10 μm. Note that a plurality of these layers may be provided.

When providing a functional layer, you may provide an easy-adhesion layer (easy-adhesion layer P2) between a base film. For the easy adhesion layer P2, the resins, cross-linking agents, and the like mentioned for the easy adhesion layer P1 are preferably used. Also, the easy-adhesion layer P1 and the easy-adhesion layer P2 may have the same composition, or may have different compositions.
It is preferable that the easily bonding layer P2 is also provided in-line. The easy-adhesion layer P1 and the easy-adhesion layer P2 can be formed by sequentially coating and drying. Moreover, it is also a preferable form to simultaneously apply the easy-adhesion layer P1 and the easy-adhesion layer P2 on both sides of the base film.

In the following description, the term "base film" includes not only a film without an easy-adhesion layer, but also a film with an easy-adhesion layer. Similarly, the base film also includes a film provided with a functional layer.

2. Polarizer In the circularly polarizing plate used in the present invention, a polarizer is provided on the substrate film.
The polarizer (polarizing film) may be directly provided on the base film, or may be provided on the base film with an orientation layer provided thereon. In the present invention, the combination of the alignment layer and the polarizing film may be collectively referred to as a polarizer. Moreover, when a polarizing film is provided without providing an orientation layer on the substrate film, the polarizing film is sometimes referred to as a polarizer.

(polarizing film)
A polarizing film has a function of transmitting polarized light in only one direction. The polarizing film includes stretched films such as polyvinyl alcohol (PVA) blended with iodine or dichroic dyes, dichroic dye films or coating films blended with dichroic dyes in polymerizable liquid crystal compounds, polyene A stretched film, a wire grid, or the like can be used without particular limitation.
Among these, a polarizing film obtained by adsorbing iodine to PVA and a polarizing film obtained by blending a dichroic dye with a polymerizable liquid crystal compound are preferable examples.

First, a polarizing film in which iodine is adsorbed on PVA will be described.
A polarizing film in which iodine is adsorbed on PVA is generally produced by immersing an unstretched PVA film in an iodine-containing bath and then uniaxially stretching it, or by immersing a uniaxially stretched film in an iodine-containing bath. It can be obtained by immersion and then cross-linking treatment in a boric acid bath.

The thickness of the polarizing film is preferably 1 to 30 μm, more preferably 1.5 to 20 μm, still more preferably 2 to 15 μm. If the thickness of the polarizing film is less than 1 μm, sufficient polarizing properties cannot be obtained, and the film may be too thin to be handled easily. If the thickness of the polarizing film exceeds 30 μm, it does not meet the purpose of thinness for ensuring flexibility.

When laminating a polarizing film and a substrate film, in which iodine is adsorbed to PVA, it is preferable to bond the substrate film and the polarizing film together. As the adhesive for bonding, conventionally used adhesives can be used without limitation. Among them, PVA-based water-based adhesives and UV-curable adhesives are preferable examples, and UV-curable adhesives are more preferable.

Thus, the polarizing film obtained by adsorbing iodine to PVA can be laminated with a base film using a film as a polarizer alone. Alternatively, a polarizer is laminated on a releasable supporting substrate obtained by coating PVA on a releasable supporting substrate and stretching in that state (releasable supporting substrate laminated polarized light It is also possible to laminate by a method of transferring a polarizing film to a base film using a method using a component). This method of laminating by transfer is also preferable as a method of laminating the polarizer and the substrate film, like the above-described bonding method. When using this transfer method, the thickness of the polarizer is preferably 12 μm or less, more preferably 10 μm or less, even more preferably 8 μm or less, and particularly preferably 6 μm or less. Even such a very thin polarizer can be easily handled due to the presence of the releasable supporting substrate, and the polarizer can be easily laminated on the substrate film. By using such a thin polarizer, repeated flexibility can be ensured. Techniques for laminating a polarizer and a base film are known, and for example, Japanese Unexamined Patent Publication No. 2001-350021 and Japanese Unexamined Patent Publication No. 2009-93074 can be referred to.

A method for laminating a polarizer and a substrate film by transfer will be specifically described. First, PVA is applied to a releasable support base material of a thermoplastic resin that is unstretched or uniaxially stretched perpendicularly to the longitudinal direction, and a laminate of the obtained releasable support base material of a thermoplastic resin and PVA is obtained. is stretched 2 to 20 times, preferably 3 to 15 times in the longitudinal direction. The stretching temperature is preferably 80 to 180°C, more preferably 100 to 160°C. The stretched laminate is subsequently immersed in a bath containing a dichroic dye to adsorb the dichroic dye. Dichroic dyes include, for example, iodine and organic dyes. When iodine is used as the dichroic dye, it is preferable to use an aqueous solution containing iodine and potassium iodide as the dyeing bath. Subsequently, it is treated by immersing it in an aqueous solution of boric acid, washed with water, and then dried. It should be noted that the film may be stretched 1.5 to 3 times as a preliminary stretch before adsorption of the dichroic dye. The above method is only an example, and the dichroic dye may be adsorbed before stretching, or the treatment with boric acid may be performed before the dichroic dye is adsorbed. It is also possible to carry out the drawing in a bath containing a dichroic dye or in a bath of aqueous boric acid. Also, these steps may be divided into multiple stages and combined.

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

Lamination of the base film and the polarizer by bonding the polarizer surface of the polarizer to the base film with a pressure-sensitive adhesive or adhesive, and then peeling off the release support base material. you get a body The thickness of the commonly used pressure-sensitive adhesive is 5 to 50 μm, while the thickness of the adhesive is 1 to 10 μm. For thinning, it is preferable to use an adhesive, and among them, it is more preferable to use an ultraviolet curable adhesive. It is also preferable to use a pressure-sensitive adhesive from the aspect of the process that a special device is not required.

Next, a polarizing film obtained by blending a dichroic dye with a polymerizable liquid crystal compound will be described.

A dichroic dye is a dye that has different absorbances in the long-axis direction and the short-axis direction of the molecule.

The dichroic dye preferably has an absorption maximum wavelength (λMAX) in the range of 300-700 nm. Examples of such dichroic dyes include organic dichroic dyes such as acridine dyes, oxazine dyes, cyanine dyes, naphthalene dyes, azo dyes and anthraquinone dyes. Among these, azo dyes are preferred. Examples of azo dyes include monoazo dyes, bisazo dyes, trisazo dyes, tetrakis azo dyes, and stilbenazo dyes. Among these, bisazo dyes and trisazo dyes are preferred. Dichroic dyes may be used alone or in combination. In order to adjust the color tone (achromatic color), it is preferable to combine two or more, more preferably three or more. In particular, it is preferable to use three or more azo compounds in combination.

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

A preferred embodiment of the dichroic dye is a dichroic dye polymer introduced into the side chain of a polymer such as acrylic. Examples of these dichroic dye polymers include the polymers mentioned in JP-A-2016-4055, the polymers obtained by polymerizing the compounds of [Chem. 6] to [Chem. 12] in JP-A-2014-206682, and the like. can be done.

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, in the polarizing film from the viewpoint of improving the orientation of the dichroic dye. , more preferably 1.0 to 15% by mass, particularly preferably 2.0 to 10% by mass.

The polarizing film contains a polymerizable liquid crystal compound in order to improve film strength, degree of polarization, film homogeneity, and the like. In addition, the polymerizable liquid crystal compound includes a polymerized liquid crystal compound as a film.
A polymerizable liquid crystal compound is a compound having a polymerizable group and exhibiting liquid crystallinity.
A polymerizable group means a group that participates in a polymerization reaction, and is preferably a photopolymerizable group. Here, the photopolymerizable group means a group capable of undergoing a polymerization reaction with an active radical generated from a photopolymerization initiator to be described later, an acid, or the like. Examples of the polymerizable group include vinyl group, vinyloxy group, 1-chlorovinyl group, isopropenyl group, 4-vinylphenyl group, acryloyloxy group, methacryloyloxy group, oxiranyl group and oxetanyl group. Among these, an acryloyloxy group, a methacryloyloxy group, a vinyloxy group, an oxiranyl group and an oxetanyl group are preferred, and an acryloyloxy group is more preferred. The compound exhibiting liquid crystallinity may be thermotropic liquid crystal or lyotropic liquid crystal, and may be nematic liquid crystal or smectic liquid crystal in thermotropic liquid crystal.

The polymerizable liquid crystal compound is preferably a smectic liquid crystal compound, and more preferably a high-order smectic liquid crystal compound, in that higher polarizing properties can be obtained. When the liquid crystal phase formed by the polymerizable liquid crystal compound is a high-order smectic phase, a polarizing film with a higher degree of orientational order can be produced.

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

The content 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, more preferably 80% by mass, from the viewpoint of increasing the orientation of the polymerizable liquid crystal compound. ~97% by mass is more preferred, and 83 to 95% by mass is particularly preferred.

A polarizing film containing a polymerizable liquid crystal compound and a dichroic dye can be provided by applying a composition for a polarizing film.
In addition to the polymerizable liquid crystal compound and the dichroic dye, the polarizing film composition may contain a solvent, a polymerization initiator, a sensitizer, a polymerization inhibitor, a leveling agent, a polymerizable non-liquid crystal compound, a cross-linking agent, and the like. .

Any solvent can be used without limitation as long as it dissolves the polymerizable liquid crystal compound. Specific examples of solvents include water; alcohol solvents such as methanol, ethanol, isopropyl alcohol, ethylene glycol, propylene glycol and cellosolve; ester solvents such as ethyl acetate, butyl acetate and γ-butyrolactone; acetone, methyl ethyl ketone and cyclopentanone. , ketone solvents such as 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 can be used without limitation as long as it polymerizes the polymerizable liquid crystal compound. As the polymerization initiator, a photopolymerization initiator that generates active radicals upon exposure to light is preferred. Examples of polymerization initiators include benzoin compounds, benzophenone compounds, alkylphenone compounds, acylphosphine oxide compounds, triazine compounds, iodonium salts, sulfonium salts and the like.

A photosensitizer is preferred as the sensitizer. Examples of photosensitizers include xanthone compounds, anthracene compounds, phenothiazine, rubrene and the like.

Polymerization inhibitors include hydroquinones, catechols, and thiophenols.
Examples of leveling agents include various known surfactants.

As the polymerizable non-liquid crystal compound, those that are copolymerized with the polymerizable liquid crystal compound are preferred. For example, when the polymerizable liquid crystal compound has a (meth)acryloyloxy group, the polymerizable non-liquid crystal compound includes (meth)acrylates. (Meth)acrylates may be monofunctional or polyfunctional. By using polyfunctional (meth)acrylates, the strength of the polarizing film can be improved. When a polymerizable non-liquid crystal compound is used, it is preferably 1 to 15% by mass, more preferably 2 to 10% by mass, even more preferably 3 to 7% by mass in the polarizing film. If the content of the polymerizable non-liquid crystal compound exceeds 15% by mass, the degree of polarization may decrease.

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

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

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

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

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

Since the polarizing film composition contains a polymerizable liquid crystal compound, it is preferably cured. Curing methods include heating and light irradiation, and light irradiation is preferred. Curing can fix the dichroic dye in an oriented state. Curing is preferably performed in a state in which a liquid crystal phase is formed in the polymerizable liquid crystal compound, and curing may be performed by light irradiation at a temperature exhibiting a liquid crystal phase.
Examples of the light for light irradiation include visible light, ultraviolet light, laser light, and the like. Ultraviolet light is preferred because it is easy to handle.

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

The polarizing film is formed by applying a composition for a polarizing film onto an orientation layer provided as necessary, so that the dye is oriented along the orientation direction of the orientation layer and, as a result, has a polarization transmission axis in a predetermined direction. Become. When the polarizing film composition is applied directly to the substrate without providing an orientation layer, the polarizing film can be oriented by curing the polarizing film composition by irradiating it with polarized light. At this time, polarized light oblique to the longitudinal direction of the base film is irradiated. Furthermore, it is preferable that the dichroic dye is strongly aligned along the alignment direction of the polymer liquid crystal by heat treatment after that.

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

When laminating a polarizing film containing a polymerizable liquid crystal compound and a dichroic dye and a substrate film, in addition to the method of laminating the polarizing film directly on the substrate film, the above-described method may be used on another release film. A method of providing a polarizing film according to the method and transferring it to the substrate film is also preferred. Preferable examples of the release film include the release support substrate used in the release support substrate laminated with the release support substrate described above and the release support substrate used in the laminated polarizer, such as a polyester film and a polypropylene film. is a particularly preferred release film. The release force can be adjusted by subjecting the release film to corona treatment, or by providing a release coat, an easy-adhesion coat, or the like.

The method of transferring the polarizing film to the substrate film is also the same as the above-described method for the releasing supporting substrate-laminated polarizer laminated with the releasing supporting substrate.

(Orientation layer)
As described above, the polarizer used in the present invention may be a polarizing film alone, or may be a combination of a polarizing film and an alignment layer.
The orientation layer controls the orientation direction of the polarizing film, and the provision of the orientation layer can provide a polarizer with a higher degree of polarization.
As the alignment layer, any alignment layer may be used as long as it can bring the polarizing film into the desired alignment state. Examples of methods for imparting an orientation state to the orientation layer include rubbing the surface, oblique vapor deposition of an inorganic compound, formation of a layer having microgrooves, and the like. Further, a method of forming a photo-alignment layer in which molecules are aligned by irradiating polarized light to produce an alignment function is also preferable.
Two examples of the rubbing treatment alignment layer and the photo-alignment layer are described below.

Rubbing Treatment Orientation Layer As the polymer material used for the orientation layer formed by the rubbing treatment, polyvinyl alcohol and its derivatives, polyimide and its derivatives, acrylic resins, polysiloxane derivatives and the like are preferably used.

First, after coating a substrate film with a rubbing treatment orientation layer coating solution containing the polymer material described above, heat drying or the like is performed to obtain an orientation layer before rubbing treatment. The alignment layer coating liquid may contain a cross-linking agent. Examples of cross-linking agents include compounds containing a plurality of isocyanate groups, epoxy groups, oxazoline groups, vinyl groups, acryl groups, carbodiimide groups, alkoxysilyl groups and the like; amide resins such as melamine compounds; phenol resins and the like.

As the solvent for the coating liquid for the rubbing treatment alignment layer, any solvent that dissolves the polymer material can be used without limitation. Specific examples of solvents include water; alcohol solvents such as methanol, ethanol, isopropyl alcohol, ethylene glycol, propylene glycol and cellosolve; ester solvents such as ethyl acetate, butyl acetate and γ-butyrolactone; acetone, methyl ethyl ketone and cyclopentanone. , ketone solvents such as 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 rubbing treatment alignment layer coating liquid can be appropriately adjusted depending on the type of polymer, the thickness of the alignment layer to be produced, etc., and is represented by a solid concentration of 0.2 to 20% by mass. Preferably, the range of 0.3 to 10% by mass is more preferable.
As the coating method, known methods such as coating methods such as gravure coating method, die coating method, bar coating method and applicator method; and printing methods such as flexo method are employed.
The temperature for drying by heating depends on the substrate film, but in the case of PET, it is preferably in the range of 30 to 170°C, more preferably in the range of 50 to 150°C, and even more preferably in the range of 70 to 130°C. If the drying temperature is too low, a long drying time may be required, resulting in poor productivity. If the drying temperature is too high, the orientation state of the base film is affected, retardation is lowered, or the heat shrinkage of the base film is increased, so that the optical function as designed cannot be achieved and the flatness is deteriorated. etc. problems arise. The heat drying time is usually 0.5 to 30 minutes, preferably 1 to 20 minutes, more preferably 2 to 10 minutes.

The thickness of the rubbed alignment layer is preferably 0.01 to 10 μm, more preferably 0.05 to 5 μm, and even more preferably 0.1 to 1 μm.

The rubbing treatment can generally be carried out by rubbing the surface of the polymer layer with paper or cloth in one direction. In general, the surface of the alignment film is subjected to rubbing treatment using a rubbing roller made of a cloth made of nylon, polyester, acrylic, or the like.
In order to provide a polarizing film having a transmission axis in a predetermined direction oblique to the longitudinal direction of the long base film, it is necessary to adjust the rubbing direction of the orientation layer to a suitable angle. The angle can be adjusted by adjusting the angle between the rubbing roller and the base film, adjusting the conveying speed of the base film and the rotation speed of the roller, and the like.

In addition, it is also possible to perform a rubbing treatment directly on the substrate film so that the surface of the substrate film has an orientation layer function. This case is also included in the technical scope of the present invention.

Photo-alignment layer The photo-alignment layer is applied to the substrate film with a coating liquid containing a polymer or monomer having a photoreactive group and a solvent, and is irradiated with polarized light, preferably polarized ultraviolet light, to impart alignment control force. Alignment film A photoreactive group refers to a group capable of aligning a liquid crystal by irradiation with light. Specifically, it causes a photoreaction that is the origin of the liquid crystal alignment ability, such as orientation induction of molecules or isomerization reaction, dimerization reaction, photocrosslinking reaction, or photodecomposition reaction caused by light irradiation. be. Among the photoreactive groups, those that cause a dimerization reaction or a photocrosslinking reaction are preferable from the viewpoint of excellent orientation and maintaining the smectic liquid crystal state of the polarizing film. As the photoreactive group capable of causing the above reaction, an unsaturated bond, particularly a double bond is preferable, and from the group consisting of C=C bond, C=N bond, N=N bond and C=O bond Groups having at least one selected are particularly preferred.

Photoreactive groups having a C═C bond include, for example, vinyl groups, polyene groups, stilbene groups, stilbazole groups, stilbazolium groups, chalcone groups and cinnamoyl groups. Photoreactive groups 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 azobenzene group, an azonaphthalene group, an aromatic heterocyclic azo group, a bisazo group, a formazan group, and azoxybenzene. A benzophenone group, a coumarin group, an anthraquinone group, a maleimide group and the like can be mentioned as the photoreactive group having a C═O bond. 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 halogenated alkyl groups.
Among these, a photoreactive group that can cause a photodimerization reaction is preferable, and a cinnamoyl group and a chalcone group are relatively small in the amount of polarized light irradiation required for photoalignment, and photoalignment with excellent thermal stability or stability over time It is preferable because a layer is easily obtained. Furthermore, as a polymer having a photoreactive group, a polymer having a cinnamoyl group having a cinnamic acid structure at the end of the polymer side chain is particularly preferable. Examples of the structure of the main chain include polyimide, polyamide, (meth)acryl, polyester and the like.

Specific alignment layers include, for example, JP-A-2006-285197, JP-A-2007-76839, JP-A-2007-138138, JP-A-2007-94071, JP-A-2007-121721, and JP-A-2007-121721. JP 2007-140465, JP 2007-156439, JP 2007-133184, JP 2009-109831, JP 2002-229039, JP 2002-265541, JP 2002 -317013, JP 2003-520878, JP 2004-529220, JP 2013-33248, JP 2015-7702, orientation layer described in JP 2015-129210, etc. is mentioned.

As the solvent for the coating solution for forming the photo-alignment layer, any solvent can be used without limitation as long as it dissolves the polymer and monomer having a photoreactive group. Specific examples of the solvent include those mentioned for the rubbing treatment alignment layer. If necessary, a photopolymerization initiator, a polymerization inhibitor, various stabilizers, and the like can be added to the coating solution for forming the photo-alignment layer. In addition, a polymer other than a polymer and a monomer having a photoreactive group, a monomer having no photoreactive group copolymerizable with a monomer having a photoreactive group, and the like may be added to the coating solution for forming a photo-alignment layer. .

As for the concentration, coating method, drying conditions, etc. of the coating solution for forming the photo-alignment layer, those mentioned for the rubbing treatment alignment layer can be exemplified. The thickness of the photo-alignment layer is also the same as the preferred thickness of the rubbed alignment layer.

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

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

The wavelength of the polarized light is preferably in a wavelength range in which the photoreactive group of the polymer or monomer having a photoreactive group can absorb light energy. Specifically, ultraviolet light with a wavelength in the range of 250 to 400 nm is preferred.
Examples of the polarized light source include xenon lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, and ultraviolet lasers such as KrF and ArF. High-pressure mercury lamps, ultra-high-pressure mercury lamps and metal halide lamps are preferred.

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

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

The irradiation intensity varies depending on the type or amount of polymerization initiator or resin (monomer), and is preferably 10 to 10,000 mJ/cm ² and more preferably 20 to 5,000 mJ/cm ² at 365 nm.

(Angle between the transmission axis of the polarizer and the slow axis of the base film)
The angle between the transmission axis of the polarizer and the slow axis of the base film is not particularly limited. For the purpose of preventing blackout or coloring when an image is viewed with polarized sunglasses, the range is preferably 30 to 60 degrees, more preferably 35 to 55 degrees. In order to reduce the slight iridescence when observed from an oblique direction with a shallow angle with the naked eye, the angle should be 10 degrees or less, or 7 degrees or less, or 80 to 100 degrees, or 83 to 97 degrees. preferably. These angles can be adjusted by the bonding angle between the base film and the polarizer, the direction of oblique drawing of the base film, or the orientation control angle of the orientation layer.

3. Retardation Layer In the circularly polarizing plate used in the present invention, a retardation layer is present on the opposite side of the polarizer to the substrate film surface. There is no self-supporting film between the polarizer and the retardation layer, or there is only one self-supporting film (here, the retardation layer itself is included between the polarizer and the retardation layer). , is one of the features of the flexible image display device of the present invention. Here, the self-supporting film refers to a film that exists as a film independently during the process.
In addition, the "retardation layer" referred to here is intended to have a function as a circularly polarizing plate, and specifically means a quarter-wave layer, a half-wave layer, a C-plate layer, or the like. do.
The absence of a self-supporting film between the polarizer and the retardation layer means that the retardation layer, which is not a self-supporting film, is directly laminated on the polarizer. The term "directly" as used herein means that there is no layer existing between the polarizer and the retardation layer and between the retardation layers, or if there is only an adhesive layer or adhesive layer. means that
The presence of one self-supporting film between the polarizer and the retardation layer means that only one of the polarizer protective film and all the retardation layers is a self-supporting film.

The 1/4 wavelength layer is a coating-type 1/4 wavelength layer that is separately prepared on an oriented film (self-supporting film) such as polycarbonate or cycloolefin or a triacetyl cellulose (TAC) film, which will be described later. It can be obtained by laminating together retardation films (self-supporting films). However, in terms of thickness reduction, it is preferable to provide a direct coating type quarter-wave layer on the polarizer.
The coated quarter-wave layer is a quarter-wave layer itself formed by coating, and does not stand alone as an independent layer. As a method of providing a 1/4 wavelength layer, a method of coating a retardation compound on a polarizer, a 1/4 wavelength layer is separately provided on a base material having releasability, and this is placed on a polarizer. A transfer method and the like can be mentioned. The quarter-wave layer is preferably a layer made of a liquid crystal compound. Examples of liquid crystal compounds include rod-like liquid crystal compounds, polymer liquid crystal compounds, liquid crystal compounds having reactive functional groups, and the like. As a method of coating a retardation compound on a polarizer, the polarizer may be subjected to a rubbing treatment, or the polarizer may be provided with an alignment layer as described above to give the polarizer an alignment control power, and then the liquid crystal may be applied. It is preferred to apply the compound.

In the method of separately providing a coating type 1/4 wavelength layer on a releasable substrate and transferring it onto a polarizer, a releasable substrate is subjected to a rubbing treatment, or a releasable group is added. It is preferable to apply the liquid crystal compound (1/4 wavelength layer) after providing the alignment layer as described above on the material to give alignment control power.
As a transfer method, a method of applying a birefringent resin to a releasable base material and stretching the base material together with the base material to form a 1/4 wavelength layer is also preferable.

After the thus-obtained transfer type quarter-wave layer is attached to a polarizer using an adhesive or pressure-sensitive adhesive, the release substrate is peeled off. For thinning, it is preferable to use an adhesive, especially an ultraviolet curable adhesive, for bonding. It is also preferable to use a pressure-sensitive adhesive from the aspect of the process that a special device is not required.
Since the polarizer is not easily affected by the coating solvent of the 1/4 wavelength layer, there is a method of separately providing a coating type 1/4 wavelength layer on a release substrate and transferring it onto the polarizer. preferable.

The front retardation of the quarter-wave layer is preferably 100-180 nm, more preferably 120-150 nm.

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

In addition, the 1/4 wavelength layer alone does not provide a 1/4 wavelength in a wide wavelength range of visible light, which may cause coloring. In such a case, an additional half-wave layer may be provided. In this case, it is preferable to provide a half-wave layer between the polarizer and the quarter-wave layer.

Preferred materials, forms, manufacturing methods, lamination methods, etc. of the half-wave layer are the same as those of the above-described quarter-wave layer.
The front retardation of the half-wave layer is preferably 200 to 360 nm, more preferably 240 to 300 nm.

When only a quarter-wave layer is used as the retardation layer, the angle between the orientation axis (slow axis) of the quarter-wave layer and the transmission axis of the polarizer is preferably 35 to 55 degrees, more preferably 40 to 50 degrees. Preferably, 42 to 48 degrees is more preferable.

When a 1/4 wavelength layer and a 1/2 wavelength layer are used in combination as a retardation layer, the angle (θ) between the orientation axis (slow axis) of the 1/2 wavelength layer and the transmission axis of the polarizer is 5 to 20 degrees is preferred, and 7 to 17 degrees is more preferred. The angle between the orientation axis (slow axis) of the half-wave layer and the orientation axis (slow axis) of the quarter-wave layer is preferably in the range of 2θ+45°±10°, and preferably in the range of 2θ+45°±5°. More preferably, the range is 2θ+45°±3°.

These angles can be adjusted by the bonding angle, the stretching direction of the oriented film, etc., when the oriented film is bonded.
In the case of a coating type 1/4 wavelength layer and 1/2 wavelength layer, it can be controlled by the rubbing angle, the irradiation angle of polarized ultraviolet rays, and the like.
In the method of providing a coating type 1/4 wavelength layer on the substrate and transferring it onto the polarizer, the rubbing angle or polarized ultraviolet light is adjusted so that a predetermined angle is obtained when the roll-to-roll bonding is performed. It is preferable to control the irradiation angle.
In the case of using an oriented film, or in the case of applying a birefringent resin to the base film and stretching the base film together, the film should be tilted at an angle so as to form a predetermined angle when the base film is laminated together by roll-to-roll. It is preferred to stretch in the direction.

Furthermore, in order to reduce changes in coloration when viewed obliquely, it is also a preferred form to provide a C-plate layer on the quarter-wave layer. A positive or negative C plate layer is used for the C plate layer according to the characteristics of the quarter wavelength layer or the half wavelength layer. The C-plate layer is preferably a liquid crystal compound layer. The C-plate layer may be provided by applying a coating liquid to be the C-plate layer directly on the quarter-wave layer, or may be provided by transferring a separately prepared C-plate layer.

Various methods can be adopted as these lamination methods. For example, the following methods are mentioned.
- A method of providing a 1/2 wavelength layer on a polarizer by transfer, and further providing a 1/4 wavelength layer thereon by transfer.
- A method in which a 1/4 wavelength layer and a 1/2 wavelength layer are provided in this order on a release film and transferred onto a polarizer.
A method of providing a half-wave layer on a polarizer by coating and providing a quarter-wave layer by transfer.
- A method of preparing a film-like 1/2 wavelength layer, providing a 1/4 wavelength layer thereon by coating or transferring, and bonding this onto a polarizer.

Also, various methods can be adopted when laminating the C plate layer. For example, a method of applying or transferring a C-plate layer on a quarter-wave layer provided on a polarizer, a method of preliminarily laminating a C-plate layer on a quarter-wave layer to be transferred or laminated, and the like. mentioned.
In the present invention, between the polarizer and the quarter-wave layer (including the quarter-wave layer), all layers from the polarizer to the C-plate layer if the C-plate layer is present (the C-plate layer is containing) is preferably the coating layer. This means that there is no free standing film on the opposite side of the polarizer from the base film. Specifically, on the side opposite to the base film of the polarizer, there is only an arbitrary combination of an adhesive layer, a pressure-sensitive adhesive layer, a protective coating layer, an orientation layer, and a coated retardation layer. That is. With such a configuration, the thickness of the circularly polarizing plate can be reduced.

As a specific preferred lamination example between the polarizer and the quarter-wave layer,
polarizer/adhesive layer/quarter wavelength layer,
polarizer/protective coat layer/adhesive layer/quarter wavelength layer,
Polarizer/half wavelength layer/adhesive layer/quarter wavelength layer,
polarizer/adhesive layer/half wavelength layer/adhesive layer/quarter wavelength layer,
Polarizer/protective coat layer/half wavelength layer/adhesive layer/quarter wavelength layer,
Polarizer/protective coat layer/adhesive layer/half wavelength layer/adhesive layer/quarter wavelength layer and the like.
In addition, the adhesive layer may be an adhesive layer. The quarter-wave and half-wave layers can also include alignment layers on either side thereof.

As the pressure-sensitive adhesive layer, rubber-based, acrylic-based, urethane-based, olefin-based, silicone-based pressure-sensitive adhesives, etc. are used without limitation. Among these, acrylic adhesives are preferred. The adhesive can be applied to an object such as the polarizer surface of a polarizing plate. A preferred method is to provide a pressure-sensitive adhesive layer by peeling off the release film on one side of a substrate-less optical transparent pressure-sensitive adhesive (release film/adhesive layer/release film) and then laminating it to the polarizer surface. As the adhesive, ultraviolet curable, urethane and epoxy adhesives are preferably used.
The adhesive layer or pressure-sensitive adhesive layer is used for bonding a polarizer, a protective coat layer, a coated retardation layer, or an image display cell.

In the above, the retardation layer (1/4 wavelength layer or 1/2 wavelength layer) is attached to the object after being provided in the laminate of the base film and the polarizer, but the object A retardation layer (a quarter-wave layer or a half-wave layer) may be provided in advance, and the laminate of the base film and the polarizer may be attached to this. The same applies to the case of providing a C plate layer.

The thickness of the circularly polarizing plate thus obtained is preferably 130 μm or less, more preferably 100 μm or less, still more preferably 90 μm or less, and particularly preferably 85 μm or less.

B. Image Display Cell The flexible image display device of the present invention has the aforementioned circularly polarizing plate on the viewing side of the image display cell. As the image display cell, a flexible image display cell such as a liquid crystal cell, an organic electroluminescence (EL) cell, an inorganic EL cell, or the like can be used without particular limitation. Among these, an organic EL cell is preferable because it is thin and has excellent flexibility. The image display cell and the circularly polarizing plate are preferably bonded together with an adhesive.
As the image display device, an image display device that can be folded into a V-shape, a Z-shape, a W-shape, a double door shape, or the like (folding-type image display device) when carried, or an image display device that can be wound into a roll. (roll-up type image display device).

When the foldable image display device has the display section on the inner side of the fold, the bending radius of the circularly polarizing plate in the folded state becomes small. In the case of such an image display device, by arranging the main orientation direction of the base film in the direction perpendicular to the folding direction (the direction of the folding operation), the occurrence of folding traces due to repeated folding operations can be effectively reduced. be able to. In the vertical direction, the angle between the main orientation direction of the substrate film and the folding direction is preferably 75 to 105 degrees, more preferably 80 to 100 degrees, and even more preferably 83 to 97 degrees.

The reason why the occurrence of folding marks can be reduced is that the base film is stretched by repeated folding operations, and the direction of stretching is perpendicular to the main orientation direction of the molecules, so the base film is easier to stretch. be done. The flexible image display device of the present invention can be suitably used for a foldable image display device having a bending radius of 5 mm or less, further 4 mm or less, particularly 3 mm.
When the foldable image display device has a display part on the folded outer surface side of the device, or when the bending radius is not small even on the inner surface, or in the case of a rollable image display device, the base film The main orientation direction can be used without any particular limitation. However, in such a case, it is also preferable to make the main orientation direction of the base film parallel to the folding direction. The parallel arrangement tends to improve the flatness of the entire image display device when spread out. In this case, the angle 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 even more preferably 7 degrees or less.
The flexible image display device of the present invention does not peel off even when it is repeatedly bent or left in a high temperature state, does not easily leave creases, and has excellent visibility. Furthermore, when a polyester film is used as the base film of the circularly polarizing plate, it provides an image display device having a circularly polarizing plate with excellent moisture permeability resistance, dimensional stability, mechanical strength, and chemical stability. can be done.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. Appropriate modifications may be made within the scope of the gist of the present invention, and they are all included in the technical scope of the present invention.
Methods for evaluating physical properties in Examples are as follows.

(1) Retardation (Re)
The retardation is a parameter defined by the product (ΔNxy×d) of the anisotropy of the biaxial refractive index on the film (ΔNxy=|nx-ny|) and the film thickness d (nm). , which is a measure of optical isotropy and anisotropy. The biaxial refractive index anisotropy (ΔNxy) was obtained by the following method. Using a molecular orientation meter (MOA-6004 type molecular orientation meter manufactured by Oji Keisoku Co., Ltd.), the orientation axis direction of the film is determined, and a rectangle of 4 cm × 2 cm is cut out so that the orientation axis direction is the long side, and the measurement is performed. was used as a sample. For this sample, the biaxial refractive indices (nx, ny) orthogonal to each other and the refractive index (nz) in the thickness direction were measured using an Abbe refractometer (manufactured by Atago, NAR-4T, measurement wavelength 589 nm). , the absolute value of the biaxial refractive index difference (|nx−ny|) was defined as the refractive index anisotropy (ΔNxy). The thickness d (nm) of the film was measured using an electric micrometer (Millitron 1245D, manufactured by Finereuf Co.) and converted into nm. The retardation (Re) was obtained from the product (ΔNxy×d) of the refractive index anisotropy (ΔNxy) and the film thickness d (nm).

(2) Nz Coefficient A value obtained by |ny−nz|/|ny−nx| was used as the Nz coefficient. However, the values of ny and nx were selected such that ny>nx.

(3) Degree of plane orientation (ΔP)
A value obtained by (nx+ny)/2-nz was defined as the degree of planar orientation (ΔP).

(4) Thickness direction retardation (Rth)
The retardation in the thickness direction is obtained by multiplying the two birefringences ΔNxz (=|nx-nz|) and ΔNyz (=|ny-nz|) when viewed from the cross section in the thickness direction of the film by the film thickness d. is a parameter that indicates the average retardation obtained by Obtain nx, ny, nz and film thickness d (nm) in the same manner as for measuring retardation, and calculate the average value of (ΔNxz × d) and (ΔNyz × d) to obtain thickness direction retardation (Rth ).

(5) Light transmittance at a wavelength of 380 nm Using a spectrophotometer (U-3500, manufactured by Hitachi, Ltd.), the light transmittance of each film in a wavelength range of 300 to 500 nm is measured with the air layer as a standard, and light at a wavelength of 380 nm. Transmittance was determined.
The various properties of the base film described above are average values obtained by sampling at three points in the width direction (three points at the center and at both ends).

(6) Angle between film orientation principal axis and longitudinal direction or direction perpendicular to longitudinal direction It is expressed as an angle between the longitudinal direction and the orthogonal direction.

(7) r = 3 bending resistance A circularly polarizing plate sample with a size of 50 mm × 100 mm is prepared, and a no-load U-shaped expansion tester (manufactured by Yuasa System Equipment Co., Ltd., DLDMLH-FS) is used to set the bending radius to 3 mm. , and flexed 100,000 times at a speed of 1 time/second. At that time, the position of the sample is fixed at 10 mm on both ends on the long side, the bending part is 50 mm × 80 mm, the inside of the bending is on the base film side, and the slow axis of the base film and the bending direction are orthogonal. I made it After the bending process was completed, the samples were placed on a flat surface with the inside of the bend facing down and visually inspected. Evaluation criteria are as follows.
A: Deformation of the sample cannot be confirmed.
◯: The sample is deformed, but the maximum floating height is less than 5 mm when placed horizontally.
x: The sample has creases or has a maximum floating height of 5 mm or more when placed horizontally.

(8) r = 5 bending resistance r = 3 resistance except that the bending radius was set to 5 mm, the outside of the bending was on the base film side, and the slow axis of the base film and the bending direction were parallel. It was performed in the same manner as the flexibility test.

(9) Compatible with polarized sunglasses The display was observed while wearing polarized sunglasses. Evaluation criteria are as follows.
○: Image can be seen (the slow axis direction of the base film and the absorption axis direction of the polarizer are about 45 degrees)
×: Those with an angle where the image is blacked out and invisible (the slow axis direction of the base film and the absorption axis direction of the polarizer are orthogonal or parallel)

(10) Heat-resistant bending resistance A sample with a size of 50 mm × 100 mm was bent 180 degrees in the direction of the long side so that the base film surface was inside so that the bending radius was 3 mm, and fixed with a jig, and the temperature was 60 ° C. , and RH 65% for 3 hours. After that, the fixture was removed at room temperature, and the state after 1 hour was observed. The slow axis of the base film and the bending direction were made perpendicular to each other. Evaluation criteria are as follows.
◎: Returned to almost flat ○: Slightly bent (less than 20 degrees)
×: Bent state (20 degrees or more)

(11) Thickness of base film and circularly polarizing plate The thickness of the base film and the circularly polarizing plate was measured with a commercially available digital thickness meter.

(12) Thickness of each layer by coating The thickness of each layer by coating is obtained by embedding the coated PET film (PET that has been subjected to an easy-adhesion treatment if necessary) with epoxy resin under the same coating conditions. was cut out and observed under a microscope. An optical microscope, a transmission electron microscope, or a scanning electron microscope was used depending on the thickness.

<Production of easy-adhesion layer component>
(Polymerization of polyester resin)
194.2 parts by weight of dimethyl terephthalate, 184.5 parts by weight of dimethyl isophthalate, and 14.8 parts by weight of dimethyl-5-sodium sulfoisophthalate were added to a stainless steel autoclave equipped with an agitator, thermometer, and partial reflux condenser. , 233.5 parts by mass of diethylene glycol, 136.6 parts by mass of ethylene glycol, and 0.2 parts by mass of tetra-n-butyl titanate were charged, and transesterification was carried out at a temperature of 160° C. to 220° C. over 4 hours. Then, the mixture was heated to 255° C., the pressure of the reaction system was gradually reduced, and the mixture was reacted under a reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain a copolymerized polyester resin. The resulting copolymerized polyester resin was pale yellow and transparent. When the reduced viscosity of the copolymerized polyester resin was measured, it was 0.70 dl/g. The reduced viscosity was measured at 30 ° C. using 25 mL of a mixed solvent of phenol (60% by mass) and 1,1,2,2-tetrachloroethane (40% by mass) as a solvent with respect to 0.1 g of resin. value. The glass transition temperature by DSC was 40°C.

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

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

(Polymerization of blocked polyisocyanate cross-linking agent used in easy adhesion layer P1)
In a flask equipped with a stirrer, a thermometer and a reflux condenser, 100 parts by mass of a polyisocyanate compound having an isocyanurate structure made from hexamethylene diisocyanate (manufactured by Asahi Kasei Chemicals, 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) were charged, and held at 70° C. for 4 hours in a nitrogen atmosphere. After that, the temperature of the reaction solution was lowered to 50° C., and 47 parts by mass of methyl ethyl ketoxime was added dropwise. By measuring the infrared spectrum of the reaction solution, it was confirmed that the absorption of isocyanate groups had disappeared, and an aqueous blocked polyisocyanate dispersion having a solid content of 75% by mass was obtained.

(Preparation of coating liquid for easy adhesion layer P1)
A coating liquid was prepared by mixing the following raw materials.
Water 40.61% by mass
Isopropanol 30.00% by mass
Polyester water dispersion 11.67% by mass
Polyvinyl alcohol aqueous solution 15.00% by mass
Block isocyanate-based cross-linking agent 0.67% by mass
Particles (silica sol with an average particle diameter of 100 nm, solid content concentration of 40% by mass) 1.25% by mass
Catalyst (organotin compound solid content concentration 14% by mass) 0.30% by mass
Surfactant (silicon type, solid content concentration 10% by mass) 0.50% by mass

(Polymerization of urethane resin used in easy adhesion layer P2)
A urethane resin containing an aliphatic polycarbonate polyol as a constituent component was produced by the following procedure. 43.75 parts by mass of 4,4-diphenylmethane diisocyanate, 12.85 parts by mass of dimethylolbutanoic acid, a number of 153.41 parts by mass of polyhexamethylene carbonate diol having an average molecular weight of 2,000, 0.03 parts by mass of dibutyltin dilaurate, and 84.00 parts by mass of acetone as a solvent were added, and the mixture was stirred at 75°C for 3 hours under a nitrogen atmosphere to form a reaction solution. reached the desired amine equivalent weight. Next, after lowering the temperature of this reaction liquid to 40° C., 8.77 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water is added to a reaction vessel equipped with a homodisper capable of high-speed stirring, the temperature is adjusted to 25° C., and the polyurethane prepolymer solution is added and dispersed while stirring and mixing water at 2000 min ⁻¹ . Ta. After that, acetone and part of the water were removed from the mixture under reduced pressure to prepare a water-soluble polyurethane resin having a solid content of 35%. The resulting polyurethane resin containing aliphatic polycarbonate polyol as a constituent component had a glass transition temperature of -30°C.

(Polymerization of oxazoline-based cross-linking agent used in easy-adhesion layer P2)
A mixture of 58 parts by mass of ion-exchanged water as an aqueous medium and 58 parts by mass of isopropanol, and a polymerization initiator (2, 4 parts by mass of 2'-azobis(2-amidinopropane).dihydrochloride) was added. On the other hand, in a dropping funnel, 16 parts by mass of 2-isopropenyl-2-oxazoline as a polymerizable unsaturated monomer having an oxazoline group, methoxypolyethylene glycol acrylate (average number of added moles of ethylene glycol: 9 mol, Shin-Nakamura Kagaku A mixture of 32 parts by mass of the product (manufacturer) and 32 parts by mass of methyl methacrylate was added and added dropwise over 1 hour at 70°C under a nitrogen atmosphere. After completion of the dropwise addition, the reaction solution was stirred for 9 hours and cooled to obtain a water-soluble resin having an oxazoline group with a solid content concentration of 40% by mass.

(Preparation of coating liquid for easy adhesion layer P2)
A coating liquid for forming a coating layer having excellent adhesion to the functional layer was prepared by mixing the following raw materials.
Water 55.62% by mass
Isopropanol 30.00% by mass
Polyurethane resin 11.29% by mass
Oxazoline-based cross-linking agent aqueous solution 2.26% by mass
Particles (silica sol with an average particle diameter of 40 nm, solid content concentration of 40% by mass) 0.71% by mass
Particles (silica sol with an average particle diameter of 450 nm, solid content concentration of 40% by mass) 0.07% by mass
Surfactant (silicon type, solid content concentration 100% by mass) 0.05% by mass

<Production of polyester resin for base film>
(Production Example 1-Polyester X)
When the temperature of the esterification reactor reaches 200° C., 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol are charged, and 0.017 parts by mass of antimony trioxide as a catalyst and acetic acid are added while stirring. 0.064 parts by mass of magnesium tetrahydrate and 0.16 parts by mass of triethylamine were charged. Then, the pressure was increased and the temperature was increased, and the pressure esterification reaction was performed under the conditions of gauge pressure 0.34 MPa and 240° C., then the pressure in the esterification reactor was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. . Furthermore, the temperature was raised to 260° C. over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. After 15 minutes, dispersion treatment was performed with a high-pressure disperser. After 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reactor, and polycondensation reaction was performed at 280°C under reduced pressure.

After completion of the polycondensation reaction, the product is filtered through a NASLON filter with a 95% cut diameter of 5 μm, extruded from a nozzle in the form of a strand, and cooled and solidified using cooling water that has been previously filtered (pore size: 1 μm or less). , cut into pellets. The intrinsic viscosity (intrinsic viscosity) of the resulting polyethylene terephthalate resin (X) was 0.73 dL/g, and substantially no inert particles and internal precipitated particles were contained (hereinafter referred to as polyethylene terephthalate resin (X) Abbreviated as PET(X)).

(Production Example 2 - Polyester Y)
10 parts by weight of dried UV absorber (2,2′-(1,4-phenylene)bis(4H-3,1-benzoxazinone-4-one) and 90 parts by weight of PET (X) are mixed. Using a kneading extruder, a polyethylene terephthalate resin (Y) containing an ultraviolet absorber was obtained (hereinafter, polyethylene terephthalate resin (Y) is abbreviated as PET (Y)).

(Manufacture of base film)
As a raw material for the base film intermediate layer, 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 at 135° C. for 6 hours under reduced pressure (1 Torr ), then supplied to extruder 2 (for intermediate layer II layer), and PET (X) was dried by a conventional method and supplied to extruder 1 (for outer layer I layer and outer layer III), and 285 ° C. dissolved in These two types of polymers are each filtered with a stainless sintered filter material (nominal filtration accuracy: 10 μm, 95% cut of particles), laminated in a two-type, three-layer confluence block, extruded in a sheet form from a nozzle, An unstretched film was made by winding on a casting drum having a surface temperature of 30° C., cooling and solidifying using an electrostatic casting method. At this time, the discharge rate of each extruder was adjusted so that the thickness ratio of the I layer, the II layer, and the III layer was 10:80:10.

Next, the unstretched PET film was coated with the P1 coating solution on one side and the P2 coating solution on the opposite side by a reverse roll method so that the coating amount after drying was 0.12 g/m ² . C. for 20 seconds.

The unstretched film with the coating layer formed thereon was guided to a tenter stretching machine, and while holding the ends of the film with clips, was guided to a hot air zone at a temperature of 135° C. and stretched 3.8 times in the width direction. Next, while maintaining the width stretched in the width direction, it was treated at a temperature of 225 ° C. for 30 seconds, and then both ends of the film cooled to 130 ° C. were cut with a shear blade and a tension of 0.5 kg / mm ² was applied. After cutting off the ears, the film was wound up to obtain a uniaxially oriented PET film (TD) having a film thickness of 70 μm. The intrinsic viscosity of the entire film was 0.70 dL/g. Table 1 shows the properties of the obtained uniaxially oriented PET film (TD).

An unstretched film obtained in the same manner was heated to 105° C. using a group of heated rolls and an infrared heater, and then stretched 4 times in the running direction with a group of rolls having different circumferential speeds. Then, the PET film stretched in the longitudinal direction was coated with P1 on one side and P2 on the opposite side by a reverse roll method so that the coating amount after drying was 0.12 g / m ² , and then a tenter stretching machine. , hold the edge of the film with a clip, dry it at a temperature of 135 ° C. while maintaining the width, then treat it at a temperature of 220 ° C. for 30 seconds, cool it to 130 ° C. and wind it up, uniaxially oriented with a film thickness of 70 μm. A PET film (MD) was obtained. Table 1 shows the properties of the obtained uniaxially oriented PET film (MD).

(Lamination of hard coat layer)
Urethane acrylate hard coating agent (manufactured by Arakawa Chemical Industries, Ltd., Beamset (registered trademark) 577, solid content concentration 100%) 95 parts by mass, photopolymerization initiator (manufactured by BASF Japan, Irgacure (registered trademark) 184, solid content Concentration 100%) 5 parts by mass and a leveling agent (BYK307 manufactured by BYK Chemie Japan, solid concentration 100%) 0.1 part by mass, diluted with a solvent of toluene / MEK = 1/1, concentration A 40% coating solution was prepared.
Using a Meyer bar, the hard coat coating liquid is applied to the easily adhesive layer P2 surface of the base film so that the film thickness after drying is 5.0 μm, dried at 80 ° C. for 1 minute, and then irradiated with ultraviolet rays. (cumulative amount of light: 200 mJ/cm ² ).

(Lamination of polarizer)
As a method of providing a polarizer on a substrate film, the following four methods were performed.
(A) A method of providing a rubbing alignment layer on a base film and providing a polarizing film comprising a liquid crystal compound and a dichroic dye thereon (polarizer lamination method A)
(B) A method of providing a photo-alignment layer on a substrate film and providing a polarizing film comprising a liquid crystal compound and a dichroic dye thereon (polarizer lamination method B)
(C) A method of providing a polarizing film made of PVA/iodine on a thermoplastic substrate and then transferring it to a substrate film (polarizer lamination method C).
(D) A method of preparing a polarizing film made of PVA/iodine and laminating it to a substrate film (polarizer lamination method D)
Details of each method are described below.

Polarizer lamination method A
(Formation of rubbing alignment layer)
A rubbing alignment layer coating composition having the following composition was applied to the easy adhesion layer P1 surface of the substrate film using a bar coater and dried at 120° C. for 3 minutes to form a film having a thickness of 200 nm. Subsequently, the surface of the obtained film was treated with a rubbing roll wrapped with a nylon raised cloth to obtain a substrate film laminated with a rubbed orientation layer. The rubbing direction was set at 45 degrees with respect to the direction of the film.

Paint for rubbing alignment layer Fully saponified polyvinyl alcohol Molecular weight 800 2 parts by mass Ion-exchanged water 100 parts by mass

(Synthesis of polymerizable liquid crystal compound)
The description of paragraph [0134] of JP 2007-510946, and Lub et al. Recl. Trav. Chim. A compound (a) represented by the following formula (1) and a compound (b) represented by the following formula (2) were synthesized with reference to Pays-Bas, 115, 321-328 (1996).

A dye (c) represented by the following formula (3) was synthesized with reference to Example 1 of JP-A-63-301850.

A dye (d) represented by the following formula (4) was synthesized with reference to Example 2 of JP-B-5-49710.

A dye (e) represented by the following formula (5) was synthesized with reference to the method for producing the compound of general formula (1) in JP-B-63-1357.

(Formation of polarizing film)
Compound (a) 75 parts by mass, compound (b) 25 parts by mass, dye (c) 2.5 parts by mass, dye (d) 2.5 parts by mass, dye (e) 2.5 parts by mass, Irgacure (registered trademark) 6 parts by mass of 369E (manufactured by BASF) and 250 parts by mass of ortho-xylene, a polarizing film coating is applied to the base film on which the rubbing alignment layer is laminated using a bar coater, and dried at 110 ° C. for 3 minutes. , a film having a thickness of 2 μm was formed, followed by irradiation with UV light, and a polarizer was provided on the substrate film.

Polarizer lamination method B
(Synthesis of paint for photo-alignment layer)
Based on the descriptions of Example 1, Example 2, and Example 3 of JP-A-2013-33248, a 5% by mass solution of the polymer (f) represented by the following formula (6) in cyclopentanone was produced. did.

(Formation of photo-alignment layer)
The photo-alignment layer coating composition having the above composition was applied to one side of the substrate film using a bar coater and dried at 80° C. for 1 minute to form a film having a thickness of 150 nm. Subsequently, it was irradiated with polarized UV light to obtain a substrate film laminated with a photo-alignment layer. The polarization direction of the UV light was 45 degrees with respect to the longitudinal direction of the film.
The aforementioned coating material for polarizing film was applied onto the photo-alignment layer, and a polarizing layer was provided on the substrate film laminated with the alignment layer in the same manner.

Polarizer lamination method C
(Manufacturing of substrate-laminated polarizer)
An unstretched film having a thickness of 100 μm is prepared using polyester X as a thermoplastic resin substrate, and an aqueous solution of polyvinyl alcohol having a degree of polymerization of 2400 and a degree of saponification of 99.9 mol % is applied to one side of the unstretched film and dried. to form a PVA layer.
The resulting laminate was stretched twice in the longitudinal direction between rolls having different peripheral speeds at 120° C. and wound up. Next, the obtained laminate was treated with a 4% boric acid aqueous solution for 30 seconds, and then immersed in a mixed aqueous solution of iodine (0.2%) and potassium iodide (1%) for 60 seconds. After dyeing, it was treated with a mixed aqueous solution of potassium iodide (3%) and boric acid (3%) for 30 seconds.
Furthermore, this laminate was uniaxially stretched in the longitudinal direction in a mixed aqueous solution of boric acid (4%) and potassium iodide (5%) at 72°C. The stretched laminate was washed with a 4% potassium iodide aqueous solution, dried in an oven at 80°C after removing the aqueous solution with an air knife, slitted at both ends, and wound up to obtain a 30 cm wide and 1000 m long film. A substrate-laminated polarizer 1 was obtained. The total draw ratio was 6.5 times, and the thickness of the polarizer was 5 µm. The thickness was read by embedding the base-material-laminated polarizer 1 in an epoxy resin, cutting out a section, and observing it with an optical microscope.

(Lamination of polarizing layer)
After applying an ultraviolet-curing acrylic adhesive to the base film, the polarizer surface of the base-layered polarizer 1 is pasted together, and the base film is irradiated with ultraviolet rays from the side of the base-layered polarizer 1. A substrate-laminated polarizer 1 was laminated. After that, the thermoplastic resin substrate was peeled off, and a polarizer was provided on the substrate film.

Polarizer lamination method D
(Manufacture of single-layer polarizer)
A polyvinyl alcohol resin film having a degree of saponification of 99.9% was led to rolls with a difference in peripheral speed, and uniaxially stretched at 100° C. to 3 times. The obtained stretched polyvinyl alcohol stretched film was dyed in a mixed aqueous solution of potassium iodide (0.3%) and iodine (0.05%), and then treated with a 10% boric acid aqueous solution at 72°C. It was uniaxially stretched 8 times. Thereafter, the film was washed with ion-exchanged water, immersed in a 6% potassium iodide aqueous solution, and dried at 45° C. to obtain a polarizer after removing the aqueous solution with an air knife. The thickness of the polarizer was 18 μm.

(Lamination of polarizer)
After applying an ultraviolet-curing acrylic adhesive to the base film, a single-layer polarizer was attached, and ultraviolet rays were irradiated from the side of the base-laminated polarizer to form a polarizer on the base film.

(Lamination of retardation layer)
The following four methods were used to form the retardation layer on the polarizer.
(F) A method of providing a half-wave layer and a quarter-wave layer on a polarizer by coating (Lamination method F of retardation layer)
(G) A method of transferring the 1/2 wavelength layer provided on the release film onto the polarizer and transferring the 1/4 wavelength layer provided on the release film thereon (method of laminating the retardation layer G)
(H) A method of providing a 1/4 wavelength layer and a 1/2 wavelength layer on a release film and transferring this onto a polarizer (Lamination method H of retardation layer)
(I) Method of bonding a quarter-wave layer to a polarizer (Lamination method I of retardation layer)
Details of each method are described below.

Lamination method F of retardation layer
On the polarizer provided on the base film, polyvinyl alcohol (polyvinyl alcohol 1000 completely saponified type 2% by mass aqueous solution (surfactant 0.2%) is applied and dried to obtain a polyvinyl alcohol with a thickness of about 100 nm. After obtaining the film, the surface of the polyvinyl alcohol film was rubbed at an angle of 15 degrees with respect to the absorption axis of the polarizer.
Subsequently, a retardation layer-forming solution having the following composition was applied to the rubbed surface by a bar coating method. The applied film was dried, subjected to orientation treatment, and cured by irradiation with ultraviolet rays to form a half-wave layer.
Retardation layer forming solution LC242 (manufactured by BASF) 75 parts by mass The following compound 20 parts by mass

Trimethylolpropane triacrylate 5 parts by mass Irgacure 379 3 parts by mass Surfactant 0.1 parts by mass Methyl ethyl ketone 250 parts by mass

Subsequently, a polyvinyl alcohol film was formed in the same manner on the half-wave layer, and a rubbing treatment was performed. The angle of the rubbing treatment was 73 degrees with respect to the absorption axis of the polarizer. A solution for forming a retardation layer was applied by a bar coating method, dried, subjected to alignment treatment, and then cured by irradiation with ultraviolet rays. The thickness of the bar coat was adjusted so as to form a 1/4 wavelength layer.

Lamination method G of retardation layer
A biaxially oriented polyethylene terephthalate (PET) film having a thickness of 50 μm was rubbed. A solution for forming a retardation layer is applied to the rubbing-treated surface by a bar coating method, dried, subjected to orientation treatment, then cured by irradiation with ultraviolet rays, and a 1/2 wavelength layer is formed on the biaxially stretched polyethylene terephthalate film. was established. Next, the light release liner of the optical transparent pressure-sensitive adhesive sheet is peeled off, the pressure-sensitive adhesive surface and the 1/2 wavelength layer surface are adhered together, and then the heavy release liner of the optical transparent pressure-sensitive adhesive sheet is peeled off and provided on the base film. It was laminated with a polarizer. After that, the biaxially stretched PET film was peeled off. The bonding was performed at 15 degrees with respect to the absorption axis of the polarizer.
Similarly, a quarter-wave layer was provided on the biaxially stretched PET film, and was attached to the previous half-wave layer using an optical transparent pressure-sensitive adhesive sheet. The bonding was performed at 75 degrees with respect to the absorption axis of the polarizer.

Lamination method H of retardation layer
A biaxially oriented polyethylene terephthalate (PET) film having a thickness of 50 μm was rubbed. A solution for forming a retardation layer is applied to the rubbing-treated surface by a bar coating method, dried, subjected to orientation treatment, then cured by irradiation with ultraviolet rays, and a quarter-wave layer is formed on the biaxially stretched polyethylene terephthalate film. was established. Furthermore, polyvinyl alcohol (2 mass% aqueous solution of polyvinyl alcohol 1000 completely saponified type (surfactant 0.2%) was applied on the quarter-wave layer and dried to obtain a polyvinyl alcohol film with a thickness of about 100 nm. Subsequently, the surface of the polyvinyl alcohol film was subjected to rubbing treatment, and the rubbing-treated surface of PVA was coated with a solution for forming a retardation layer by a bar coating method, dried, subjected to alignment treatment, and then irradiated with ultraviolet rays. The angle between the rubbing direction when providing the quarter-wave layer and the rubbing direction when providing the half-wave layer was 60 degrees. The light release liner of the optical transparent pressure-sensitive adhesive sheet is peeled off, the pressure-sensitive adhesive surface and the 1/2 wavelength layer surface are bonded together, then the heavy release liner of the optical transparent pressure-sensitive adhesive sheet is peeled off, and the polarizer provided on the base film After that, the biaxially stretched PET film was peeled off.The lamination was such that the absorption axis of the polarizer and the rubbing direction of the half-wave layer were 15 degrees, and the rubbing direction of the quarter-wave layer was 75 degrees. I made it

Lamination method I of retardation layer
The quarter wave film was unwound from a roll of quarter wave film with the slow axis along its length and cut to the required length. On the other hand, the light release liner of the transparent pressure-sensitive adhesive sheet for optical use was peeled off, the pressure-sensitive adhesive surface and the quarter-wave film were laminated together, and then the heavy release liner of the transparent pressure-sensitive adhesive sheet for optical use was peeled off, and provided on the base film. It was laminated with a polarizer. The 1/4 wavelength film was prepared by extruding a propylene-ethylene random copolymer (5% ethylene content) into a sheet and stretching it in the length direction with rolls (thickness: 20 μm). The lamination was performed so that the slow axis of the quarter-wave film was 45 degrees with respect to the absorption axis of the polarizer.

The thickness of the retardation layer formed by the above coating was 1.2 μm for the quarter-wave layer and 2.3 μm for the half-wave layer. The thickness of the adhesive layer was 3 μm.

Examples 1-18
A polarizer and a retardation layer were provided on the base film shown in Table 2 by the method shown in Table 2 to prepare a circularly polarizing plate.

Comparative example 1
After laminating a polarizer on the substrate film by the polarizer lamination method D, a TAC film having a thickness of 80 μm was adhered on the polarizer using a PVA adhesive to prepare a polarizing plate. Further, a retardation layer was provided on the TAC film of this polarizing plate by lamination method I of the retardation layer to prepare a circularly polarizing plate.

Comparative example 2
After laminating a polarizer on the substrate film by the polarizer lamination method A, a 1/2 wavelength film was laminated on the polarizer, and a 1/4 wavelength film was further laminated thereon. The 1/2 wavelength film was double the thickness of the 1/4 wavelength film, and each layer was laminated according to the lamination method I of the retardation layer. The half-wave plate was arranged at 15 degrees to the absorption axis of the polarizer, and the quarter-wave layer was arranged to be at 75 degrees to the absorption axis of the polarizer.

Table 2 shows the characteristics of the circularly polarizing plates obtained in Examples 1-18 and Comparative Examples 1-2.

The prepared circularly polarizing plate was attached to an organic EL module via an adhesive layer with a thickness of 25 μm to create a smartphone-type foldable display that can be folded in half at the center with a radius of 3 mm, which corresponds to the bending radius. . The circularly polarizing plate is arranged on the surface of one continuous display through the folded portion, the hard coat layer is positioned on the surface of the display, and the slow axis of the base film is arranged so as to be orthogonal to the folding direction. ing.
The smartphones using the circularly polarizing plate of each example satisfies the operation and visibility as a smartphone that can be folded in half at the center and carried, and no rainbow spots were observed. In addition, when using a circularly polarizing plate in which the angle between the slow axis direction of the base film and the absorption axis direction of the polarizer is set to 45 degrees, blackout or rainbow spots are not observed even when observed with polarized sunglasses. did not occur. On the other hand, the foldable display using the circularly polarizing plate of each comparative example was unfavorable because it seemed that the foldable portion of the display caused image distortion as the frequency of use increased.

The flexible image display device of the present invention does not peel off even when it is repeatedly bent or left in a high temperature state, does not easily leave creases, and has excellent visibility. Furthermore, when a polyester film is used as the base film of the circularly polarizing plate, it provides an image display device having a circularly polarizing plate with excellent moisture permeability resistance, dimensional stability, mechanical strength, and chemical stability. can be done.

Claims (5)

A flexible image display device comprising an image display cell and a circularly polarizing plate arranged on the viewing side of the image display cell,
The circularly polarizing plate has a retardation layer, a polarizer, and a base film,
The in-plane retardation of the base film is 3000 to 30000 nm,
There is no self-supporting film between the polarizer and the retardation layer, or there is only one self-supporting film (here, the retardation layer itself is included between the polarizer and the retardation layer),
The image display device is a foldable type,
Having a display part on the folded inner surface side, the angle between the main orientation direction of the base film and the folding direction is 75 to 105 degrees,
Flexible image display device. A flexible image display device comprising an image display cell and a circularly polarizing plate arranged on the viewing side of the image display cell,
The circularly polarizing plate has a retardation layer, a polarizer, and a base film,
The in-plane retardation of the base film is 3000 to 30000 nm,
There is no self-supporting film between the polarizer and the retardation layer, or there is only one self-supporting film (here, the retardation layer itself is included between the polarizer and the retardation layer),
The image display device is a foldable type,
A flexible image display device having a display part on the folded outer surface, wherein the angle between the main orientation direction of the base film and the folding direction is 15 degrees or less. 3. The flexible image display device according to claim 1, wherein said polarizer has a thickness of 12 [mu]m or less. 4. The flexible image display device according to claim 1, wherein said polarizer comprises a polymerizable liquid crystal compound and a dichroic dye. 5. The flexible image display device according to claim 1, wherein said retardation layer is made of a liquid crystal compound.