JP2015068847A - Polarizing plate, image display device, and method of improving bright field contrast of image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate which improves transmittance in a parallel Nicol state, when an image displayed on a liquid crystal display device is viewed through a pair of polarized glasses, compared with a case where a light-transmissive film having in-plane birefringence is placed such that certain visibility in a cross-Nicol state is kept and an angle between a fast axis direction and an absorption axis direction of a polarizer becomes 45 degrees, and which improves bright field contrast when the image display device is viewed with naked eyes and to provide an image display device.SOLUTION: A polarizing plate includes a polarizer 11 and a light-transmissive film 12 having in-plane birefringence and placed on a viewer-side surface of the polarizer 11. The polarizer 11 is positioned such that an absorption axis direction 11A thereof coincides with the horizontal direction. The light-transmissive film 12 is positioned such that, when a slow axis is defined as a direction with a highest refractive index in a plane thereof, an angle α between the absorption axis direction 11A and a fast axis direction 12B is 5 to 40 degrees, inclusive.

Description

  The present invention relates to a polarizing plate, an image display device, and a method for improving bright place contrast in an image display device.

  In a liquid crystal display device, a polarizing plate (upper polarizing plate) is usually disposed on the image display surface side of the liquid crystal cell. The upper polarizing plate is usually composed of a polarizer such as a polyvinyl alcohol film dyed and stretched with iodine or the like, and a protective film that is bonded to one side of the polarizer and protects the polarizer.

  Conventionally, a film made of a cellulose ester typified by triacetyl cellulose has been used as a protective film. This is because cellulose ester is excellent in transparency and optical isotropy, and has appropriate water permeability, so that moisture remaining in the polarizer when the polarizing plate is produced can be dried through the cellulose ester film. It is based on advantages such as being able to.

  However, since the moisture permeability of the cellulose ester is too high, the moisture resistance test has problems such as an increase in transmittance due to discoloration and a decrease in the degree of polarization. In order to solve this problem, a polarizing plate using a cycloolefin resin as a protective film has been proposed (Patent Document 1). In addition to this, in order to improve durability, it is desired to use a versatile film as a protective film that is cheaper than the cellulose ester film, easily available in the market, or that can be manufactured by a simple method. For example, an attempt to use a polyester film such as polyethylene terephthalate instead of a cellulose ester film has been made (see, for example, Patent Document 2).

  Incidentally, a liquid crystal display device such as a notebook personal computer may be used not only indoors but also outdoors. When outdoors, the observer may wear polarized sunglasses, and when the observer visually recognizes the display image of the liquid crystal display device through the polarized sunglasses, the absorption axis of the upper polarizing plate and the absorption axis of the polarized sunglasses Depending on the angle formed, the display image may become dark and difficult to see, and visibility may be reduced. Here, “visibility” in the present specification is used as an index indicating whether or not the display image is difficult to see depending on the observation angle when the viewer visually recognizes the display image through the polarized sunglasses.

  In order to solve this problem, a λ / 4 retardation film is arranged on the viewer side of the upper polarizing plate so that the angle of the fast axis direction with respect to the absorption axis direction of the polarizer of the upper polarizing plate is 45 degrees. It has been proposed (see, for example, Patent Document 3).

  In addition, it is proposed that the angle formed between the slow axis of the polyethylene terephthalate film having a retardation of 3000 to 30000 nm and the absorption axis of the polarizing plate is 45 degrees (see, for example, Patent Document 4). .

JP-A-6-511117 JP 2007-279243 A JP 2009-122454 A JP2011-107198A

  In an image display device that can be used indoors and outdoors, when an observer visually recognizes a display image of a liquid crystal display device through polarized sunglasses, it is of course possible to ensure good visibility regardless of the observation angle. It is desired to improve the bright place contrast when the image display apparatus in the room is observed visually (with polarized sunglasses not attached). Here, when a polarizing plate provided with a protective film made of various materials was tried for an image display device, an image was displayed when a protective film for a polarizing plate made of a polyester film, typically polyethylene terephthalate, was used. It has been discovered that the photopic contrast of the device is improved to a level that can be perceived visually. The inventors of the present invention have made extensive studies on this point and found that there is a correlation between the fast axis of the protective film related to the birefringence that the polyester film normally has and the improvement of the bright contrast of the image display device. It was found that there is. More specifically, it has been found that the direction of the fast axis of the protective film in a state of being incorporated in the image display apparatus can greatly affect the bright place contrast of the image display apparatus.

  Further, since the Brewster angle at which the reflectance is 0% exists in the P-polarized light, when the light is reflected, the P-polarized light decreases, and as a result, the S-polarized light increases. Therefore, if the S-polarized light can be absorbed by the polarized sunglasses, the reflected light can be cut. For this reason, the absorption axis of polarized sunglasses usually exists in the left-right direction. Therefore, the absorption axis of the upper polarizing plate such as the VA mode or the IPS mode in an attitude in which the observer wears polarized sunglasses and observes the display image normally (an attitude in which the absorption axis direction of the polarized sunglasses is substantially horizontal). When the display image of the image display device whose direction is horizontal is visually recognized, the polarized sunglasses and the upper polarizing plate are in a parallel Nicol state. The present inventors have conducted extensive research on the light transmittance when the polarized sunglasses and the upper polarizing plate are in a parallel Nicol state, and the direction of the fast axis of the protective film greatly affects the light transmittance. It was found.

  The present invention is based on such knowledge of the inventors of the present invention, and when a viewer visually recognizes a display image of a liquid crystal display device through polarized sunglasses, while ensuring a certain degree of visibility in a crossed Nicol state, Compared to the case where a light-transmitting film having birefringence is arranged in the plane so that the angle of the fast axis direction with respect to the absorption axis direction of the polarizer is 45 degrees, light in a parallel Nicol state that is usually observed better An object of the present invention is to provide a polarizing plate and an image display device capable of improving the transmittance and improving the bright place contrast when the image display device is visually observed (in a state where the polarized sunglasses are not worn).

  According to one aspect of the present invention, there is provided a polarizing plate comprising: a polarizer; and a light transmissive film having birefringence in a plane provided on a viewer-side surface of the polarizer, The polarizer is arranged so that the absorption axis direction of the polarizer is along the horizontal direction, and the direction having the highest refractive index in the plane of the light transmissive film is defined as the slow axis direction, and the slow phase in the plane is When the direction orthogonal to the axial direction is the fast axis direction, and the light transmissive film is disposed such that the angle of the fast axis direction with respect to the absorption axis direction is not less than 5 degrees and not more than 40 degrees. A polarizing plate is provided.

  According to another aspect of the present invention, there is provided an image display device comprising the above polarizing plate, wherein the polarizing plate is arranged so that an absorption axis direction of the polarizer is along a horizontal direction.

  According to another aspect of the present invention, in the image display device, the polarizing plate is disposed in the image display device so that an absorption axis direction of the polarizer in the polarizing plate is along a horizontal direction. A method for improving photopic contrast is provided.

  According to the polarizing plate of one aspect of the present invention, the polarizer is intentionally used so that the light transmissive film having birefringence is used, the polarizer is disposed so that the absorption axis direction of the polarizer is along the horizontal direction, and the polarizer Since the light transmissive film is arranged so that the angle of the fast axis direction of the light transmissive film with respect to the absorption axis direction is not less than 5 degrees and not more than 40 degrees, the observer can display the display image of the liquid crystal display device through the polarized sunglasses. A light-transmitting film having birefringence in the plane so that the angle in the fast axis direction with respect to the absorption axis direction of the polarizer is 45 degrees while ensuring a certain degree of visibility in the crossed Nicols state when visually observed. Compared to the case where it is arranged, it is possible to improve the transmittance in the parallel Nicol state, which is usually observed well, and to improve the bright place contrast when the image display device is observed visually (with polarized sunglasses not attached). It is possible.

  According to the image display device of another aspect of the present invention, the polarizer is arranged so that the absorption axis direction of the polarizer is along the horizontal direction, and the fast axis direction of the light-transmitting film with respect to the absorption axis direction of the polarizer Since the light-transmitting film is arranged so that the angle of the liquid crystal is 5 degrees or more and 40 degrees or less, when the viewer visually recognizes the display image of the liquid crystal display device through the polarized sunglasses, the visibility in the crossed Nicols state is somewhat Compared to the case where a light-transmitting film having birefringence is arranged in the plane so that the angle of the fast axis direction with respect to the absorption axis direction of the polarizer is 45 degrees, the parallel Nicols that are usually observed better The transmittance in the state can be improved, and the bright place contrast when the image display device is observed visually (with the polarized sunglasses not attached) can be improved.

  According to the method for improving the bright spot contrast in the image display device according to another aspect of the present invention, the polarizer is arranged so that the absorption axis direction of the polarizer is along the horizontal direction, and the light is transmitted through the absorption axis direction of the polarizer. Since the light-transmitting film is arranged so that the angle of the fast axis direction of the conductive film is 5 degrees or more and 40 degrees or less, when the observer visually recognizes the display image of the liquid crystal display device through the polarized sunglasses, the crossed Nicols Compared to the case where a light-transmitting film having birefringence is arranged in the plane so that the angle in the fast axis direction with respect to the absorption axis direction of the polarizer is 45 degrees while ensuring visibility in a state to some extent. It is possible to improve the transmittance in the parallel Nicol state, which is usually observed well, and improve the bright place contrast when the image display device is observed visually (with the polarized sunglasses not attached). It can be.

It is a longitudinal cross-sectional view of the polarizing plate which concerns on embodiment. It is a figure showing the arrangement | positioning relationship of the polarizing plate and polarizing sunglasses which concern on embodiment, and the polarization state of the light which permeate | transmits a polarizing plate. It is a schematic block diagram of the liquid crystal display which is an example of the image display apparatus which concerns on embodiment.

  Hereinafter, a polarizing plate according to an embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a longitudinal sectional view of a polarizing plate according to the present embodiment, and FIG. 2 is a diagram showing the arrangement relationship between the polarizing plate and the polarizing sunglasses according to the present embodiment and the polarization state of light transmitted through the polarizing plate. In the present specification, terms such as “film”, “sheet”, and “plate” are not distinguished from each other only based on the difference in names. Therefore, for example, “film” is a concept including a member that can also be called a sheet or a plate. As a specific example, the “optical film” includes members called “optical sheet”, “optical plate”, and the like.

≪Polarizing plate≫
As shown in FIG. 1, the polarizing plate 10 includes a polarizer 11, a light transmissive film 12 provided on the surface of the polarizer 11 on the viewer side, and a polarizer 11 of the light transmissive film 12. And a functional layer 13 provided on the surface on the opposite side of the surface. The polarizing plate of this invention should just be equipped with the polarizer and the light transmissive film, and does not need to be provided with the functional layer.

<Polarizer>
The polarizer 11 has an absorption axis, but the polarizer 11 is arranged so that the absorption axis direction 11A of the polarizer 11 is along the horizontal direction, as shown in FIG. “The absorption axis direction of the polarizer is along the horizontal direction” means that the absorption axis direction of the polarizer is within a range of less than ± 10 ° with respect to the horizontal direction. The polarizer 11 is preferably arranged so that the absorption axis direction 11A of the polarizer 11 is within a range of less than ± 5 ° with respect to the horizontal direction.

  Examples of the polarizer 11 include a polyvinyl alcohol film, a polyvinyl formal film, a polyvinyl acetal film, and an ethylene-vinyl acetate copolymer saponified film that are dyed and stretched with iodine or the like.

<Light transmissive film>
The light transmissive film 12 functions as a protective film for protecting the polarizer 11. The light transmissive film 12 has birefringence in the plane. Whether a light transmissive film has a birefringence in the plane is the refractive index of the wavelength of _{550nm, Δn (n x -n y} ) what is ≧ 0.0005 has birefringence And those having Δn <0.0005 have no birefringence. The birefringence can be measured by setting a measurement angle of 0 ° and a measurement wavelength of 552.1 nm using KOBRA-WR manufactured by Oji Scientific Instruments. At this time, for calculating the birefringence, the film thickness and the average refractive index are required. The film thickness can be measured using, for example, a micrometer (Digimatic Micrometer, manufactured by Mitutoyo Corporation) or an electric micrometer (produced by Anritsu Corporation). The average refractive index can be measured using an Abbe refractometer or an ellipsometer.

  Δn of TD80UL-M (manufactured by Fuji Film Co., Ltd.) made of triacetyl cellulose and ZF16-100 (made by Nippon Zeon Co., Ltd.) made of cycloolefin polymer, which are generally known as isotropic materials, , 0.0000375, and 0.00005, and it was determined that the film had no birefringence (isotropic).

As another method for measuring birefringence, two polarizing plates are used to determine the orientation axis direction (principal axis direction) of the light-transmitting substrate, and the refractive indexes of the two axes perpendicular to the orientation axis direction. (Nx, ny) can be obtained by an Abbe refractometer (NAGO-4T manufactured by Atago Co., Ltd.), and after a black vinyl tape (for example, Yamato vinyl tape No200-38-21 38 mm width) is pasted on the back surface, Using a spectrophotometer (V7100 type, automatic absolute reflectance measurement unit, VAR-7010, manufactured by JASCO Corporation), polarization measurement: S-polarized light, with slow axis parallel to S-polarized light, fast axis was measured 5 ° reflectance when made into a parallel, the following equation (1) can also calculate the refractive index of each wavelength of the slow axis and the fast axis (n _{x, n y)} .
R (%) = (1-n) ² / (1 + n) ² Formula (1)

The retardation value of the light transmissive film 12 is not particularly limited as long as it is not zero. The "retardation" includes the refractive indices n _x of the in-plane slow axis direction of the light transmissive film, and the refractive index n _y in the fast axis direction in the plane of the light transmissive film, the light transmissive film The thickness d is represented by the following formula (2).
Retardation _{(Re) = (n x -n} y) × d ... formula (2)

  The retardation value is preferably 80 nm to 150 nm, or 3000 nm or more as a retardation value for light having a wavelength of 550 nm. If it is less than 80 nm, there may be a case where sufficient visibility cannot be ensured when an observer visually recognizes the display image of the display device through polarized sunglasses. Moreover, when it exceeds 150 nm and less than 3000 nm, an interference color is observed, and the color of the actual display image may appear to be a different color. Further, the retardation value is particularly preferably 3000 nm or more than 80 nm to 150 nm from the viewpoint that the film thickness accuracy is unnecessary. Specifically, for example, when a material having Δn of 0.1 is used, it is necessary that the retardation value is 80 nm to 150 nm and the thickness d is 0.8 μm to 1.5 μm (variation within 0.7 μm). However, when the retardation value is 3000 nm or more, it is sufficient that the retardation value is 30 μm or more.

The retardation can be measured by, for example, KOBRA-WR manufactured by Oji Scientific Instruments (measurement angle 0 °, measurement wavelength 589.3 nm). Further, the refractive index (n _x , n _y ) of the slow axis and the fast axis of the light transmissive film was measured with an Abbe refractometer (NAR-4T manufactured by Atago Co.), and the light transmissive film thickness d (μm) ) Is measured with an electric micrometer (manufactured by Anritsu), and the unit is converted to nm. And retardation can be calculated | required by Formula (2) using the calculated | required refractive index ( _nx , _ny ) and thickness d. In addition, as described above, the retardation is measured for the reflectivity of 5 degrees when the slow axis is made parallel to the S-polarized light and when the fast axis is made parallel. _x is determined and n _y, and the difference in the the obtained n _x and n _y, can be determined from the product of the thickness of the light transmissive film.

  When the direction with the highest refractive index in the plane of the light transmissive film 12 is the slow axis direction 12A, and the direction orthogonal to the slow axis direction 12A in this plane is the fast axis direction 12B, the light transmissive film. 2, 12 is arranged such that the angle α of the fast axis direction 12B of the light transmissive film 12 with respect to the absorption axis direction 11A of the polarizer 11 is not less than 5 degrees and not more than 40 degrees. Therefore, the fast axis direction 12B of the light transmissive film 12 is positioned with respect to the absorption axis direction 11A of the polarizer 11. The angle α of the fast axis direction 12B of the light transmissive film 12 with respect to the absorption axis direction 11A of the polarizer 11 is 10 degrees or more and 35 degrees from the viewpoint of balance between ensuring visibility through polarized sunglasses and improving bright place contrast. The following is preferable, and 15 degrees or more and 30 degrees or less are more preferable.

Light transmissive film 12, the difference between the refractive indices n _x in the slow axis direction 12A of the light transmissive film 12, the refractive index n _y in the direction perpendicular to the slow axis direction 12A fast axis 12B [Delta] n Is preferably 0.01 or more and 0.30 or less. This is because, when the refractive index difference Δn is less than 0.01, the reflectance difference when the slow axis and the fast axis are installed in the horizontal direction is small, and the obtained bright contrast improvement effect is small. On the other hand, if the refractive index difference Δn exceeds 0.30, the draw ratio needs to be excessively high, so that tearing, tearing, etc. are likely to occur, and the practicality as an industrial material may be significantly reduced. Preferably, the lower limit of the refractive index difference Δn is 0.05, more preferably 0.07. A preferable upper limit of the refractive index difference Δn is 0.27. In addition, when refractive index difference (DELTA) n exceeds 0.27, depending on the kind of light transmissive film, durability of the light transmissive film in a moist heat resistance test may be inferior. From the viewpoint of ensuring excellent durability in the wet heat resistance test, a more preferable upper limit of the refractive index difference Δn is 0.25.

  The light transmissive film 12 is not particularly limited as long as it is a light transmissive film having in-plane birefringence. Examples of such a light transmissive film include a polyester film, a polycarbonate film, a cycloolefin polymer film, and an acrylic film. Among these, a polyester film and a polycarbonate film are preferable from the viewpoint that the refractive index difference Δn developability is large and a bright contrast improvement effect can be easily obtained. In addition, even if it is a cellulose ester film, it can be used if it is a cellulose ester film that has been stretched to have in-plane birefringence.

  Examples of polyester films include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), polyethylene naphthalate (polyethylene-2,6-naphthalate, polyethylene-1,4-naphthalate, polyethylene). -1,5-naphthalate, polyethylene-2,7-naphthalate, polyethylene-2,3-naphthalate) and the like.

  The polyester used in the polyester film may be a copolymer of these polyesters, and the polyester is the main component (for example, a component of 80 mol% or more), and other types in a small proportion (for example, 20 mol% or less). It may be blended with the above resin. Polyethylene terephthalate (PET) or polyethylene-2,6-naphthalate (PEN) is particularly preferable as the polyester because of a good balance between mechanical properties and optical properties. In particular, it is preferably made of polyethylene terephthalate. Polyethylene terephthalate has high versatility, is easily available, and can increase birefringence.

  Examples of the polycarbonate film include aromatic polycarbonate films based on bisphenols (such as bisphenol A) and aliphatic polycarbonate films such as diethylene glycol bisallyl carbonate.

  Examples of the cycloolefin polymer film include films made of polymers such as norbornene monomers and monocyclic cycloolefin monomers.

  Examples of the acrylic film include poly (meth) methyl acrylate film, poly (meth) ethyl acrylate film, methyl (meth) acrylate-butyl (meth) acrylate copolymer film, and the like.

  Examples of the cellulose ester film include a cellulose triacetate film and a cellulose diacetate film. The cellulose ester film is excellent in light transmittance, and among the cellulose acylate films, a triacetyl cellulose film (TAC film) is preferable. A triacetyl cellulose film is a light-transmitting film that can have an average light transmittance of 50% or more in a visible light region of 380 to 780 nm. The average light transmittance of the triacetyl cellulose film is preferably 70% or more, and more preferably 85% or more.

  In addition, as a triacetyl cellulose film, in addition to pure triacetyl cellulose, cellulose acetate propionate or cellulose acetate butyrate may be used in combination with components other than acetic acid as a fatty acid forming an ester with cellulose. . Further, these triacetylcelluloses may be added with other additives such as other cellulose lower fatty acid esters such as diacetylcellulose, or plasticizers, ultraviolet absorbers, and lubricants as necessary.

  The thickness of the light transmissive film 12 is preferably in the range of 5 μm to 300 μm. If it is less than 5 μm, the anisotropy of the mechanical properties becomes remarkable, and it becomes easy to cause tearing, tearing, etc., and the practicality as an industrial material may be remarkably lowered. On the other hand, if it exceeds 300 μm, the light-transmitting film is very rigid, the flexibility specific to the polymer film is lowered, and the practicality as an industrial material is also lowered, which is not preferable. A more preferable lower limit of the thickness of the light transmissive film is 10 μm, a more preferable upper limit is 200 μm, and a further preferable upper limit is 150 μm.

  Further, the light transmissive film 12 preferably has a transmittance in the visible light region of 80% or more, and more preferably 84% or more. In addition, the said transmittance | permeability can be measured by JISK7361-1 (The test method of the total light transmittance of a plastic-transparent material).

  The light transmissive film may be subjected to a surface treatment such as a saponification treatment, a glow discharge treatment, a corona discharge treatment, an ultraviolet (UV) treatment, and a flame treatment without departing from the spirit of the present invention.

  The light transmissive film 12 may be a film that has been subjected to longitudinal uniaxial stretching, tenter stretching, sequential and simultaneous biaxial stretching. Of these, oblique stretching is preferred in which stretching is performed so that the molecular orientation direction is not parallel to the traveling direction and the width direction of the light-transmitting film. Since a roll-shaped polarizer is manufactured while its stretching process is managed with very high accuracy, an absorption axis exists along the longitudinal direction except in special cases. Polarized light having an angle between the absorption axis direction of the polarizer and the fast axis direction of the light-transmitting film other than parallel and orthogonal by bonding the stretched light-transmitting film and the polarizer together A plate can be formed.

<Functional layer>
As described above, the functional layer 13 is provided on the surface of the light transmissive film 12 opposite to the surface on which the polarizer 11 is provided. The functional layer 13 is a layer intended to exhibit a certain function. Specifically, for example, a hard coat property, an antiglare property, an antireflection property, an antistatic property, an antifouling property, or the like is used. Examples include a layer that exhibits the above functions. In the functional layer 13, the refractive index in a direction parallel to the fast axis direction 12 </ b> B of the light transmissive film 12 is lower than the refractive index in the fast axis direction 12 </ b> B of the light transmissive film 12. When a functional layer having a refractive index in a direction parallel to the slow axis direction of the light transmissive film is higher than the refractive index in the slow axis direction of the light transmissive film, the light transmissive film It is preferable to arrange | position so that the slow axis direction of a transparent film may follow a horizontal direction.

  One or more additional functional layers may be provided on the side of the functional layer 13 opposite to the side on which the light transmissive film 12 is provided. As a further functional layer, like the functional layer 13 described above, a layer that exhibits one or more functions such as hard coat properties, antiglare properties, antireflection properties, antistatic properties, and antifouling properties is exemplified. Can do.

(Hard coat layer)
The hard coat layer is a layer that exhibits hard coat properties. Specifically, the hard coat layer has a hardness of “H” or more in a pencil hardness test (4.9 N load) defined in JIS K5600-5-4 (1999). It is what you have.

  The thickness of the hard coat layer is preferably 1.0 μm or more and 10.0 μm or less. If the thickness of the hard coat layer is within this range, a desired hardness can be obtained. In addition, it is possible to reduce the thickness of the hard coat layer, while suppressing the occurrence of cracking and curling of the hard coat layer. The thickness of the hard coat layer can be measured by cross-sectional microscope observation. The lower limit of the thickness of the hard coat layer is more preferably 1.5 μm or more, the upper limit is more preferably 7.0 μm or less, and the thickness of the hard coat layer is 2.0 μm or more and 5.0 μm or less. Further preferred.

  The hard coat layer includes, for example, at least a binder resin. The binder resin is obtained by polymerizing (crosslinking) a photopolymerizable compound by light irradiation. The photopolymerizable compound has at least one photopolymerizable functional group. In the present specification, the “photopolymerizable functional group” is a functional group capable of undergoing a polymerization reaction by light irradiation. Examples of the photopolymerizable functional group include ethylenic double bonds such as a (meth) acryloyl group, a vinyl group, and an allyl group. The “(meth) acryloyl group” means to include both “acryloyl group” and “methacryloyl group”. The light irradiated when polymerizing the photopolymerizable compound includes visible light and ionizing radiation such as ultraviolet rays, X-rays, electron beams, α rays, β rays, and γ rays.

  Examples of the photopolymerizable compound include a photopolymerizable monomer, a photopolymerizable oligomer, and a photopolymerizable polymer, and these can be appropriately adjusted and used. As the photopolymerizable compound, a combination of a photopolymerizable monomer and a photopolymerizable oligomer or photopolymerizable polymer is preferable.

Photopolymerizable monomer The photopolymerizable monomer has a weight average molecular weight of less than 1000. The photopolymerizable monomer is preferably a polyfunctional monomer having two or more photopolymerizable functional groups (that is, bifunctional). In this specification, the “weight average molecular weight” is a value obtained by dissolving in a solvent such as tetrahydrofuran (THF) and converting to polystyrene by a conventionally known gel permeation chromatography (GPC) method.

  Examples of the bifunctional or higher monomer include trimethylolpropane tri (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, and pentaerythritol tri (meth). Acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ditri Methylolpropane tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, tripentaerythritol octa (meth) acrylate, Lapentaerythritol deca (meth) acrylate, isocyanuric acid tri (meth) acrylate, isocyanuric acid di (meth) acrylate, polyester tri (meth) acrylate, polyester di (meth) acrylate, bisphenol di (meth) acrylate, diglycerin tetra ( (Meth) acrylate, adamantyl di (meth) acrylate, isoboronyl di (meth) acrylate, dicyclopentane di (meth) acrylate, tricyclodecane di (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, and these are PO, EO And the like modified.

  Among these, from the viewpoint of obtaining a hard coat layer having high hardness, pentaerythritol triacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), pentaerythritol tetraacrylate (PETTA), dipentaerythritol pentaacrylate (DPPA) and the like are preferable. .

The photopolymerizable oligomer The photopolymerizable oligomer has a weight average molecular weight of 1,000 or more and less than 10,000. The photopolymerizable oligomer is preferably a bifunctional or higher polyfunctional oligomer. Polyfunctional oligomers include polyester (meth) acrylate, urethane (meth) acrylate, polyester-urethane (meth) acrylate, polyether (meth) acrylate, polyol (meth) acrylate, melamine (meth) acrylate, and isocyanurate (meth). Examples include acrylate and epoxy (meth) acrylate.

Photopolymerizable polymer The photopolymerizable polymer has a weight average molecular weight of 10,000 or more, and the weight average molecular weight is preferably 10,000 or more and 80,000 or less, and more preferably 10,000 or more and 40,000 or less. When the weight average molecular weight exceeds 80000, the viscosity is high, so that the coating suitability is lowered, and the appearance of the obtained optical film may be deteriorated. Examples of the polyfunctional polymer include urethane (meth) acrylate, isocyanurate (meth) acrylate, polyester-urethane (meth) acrylate, and epoxy (meth) acrylate.

  In addition to the hard coat layer, if necessary, a solvent-drying resin (a thermoplastic resin, such as a resin that forms a film just by drying the solvent added to adjust the solid content during coating), A thermosetting resin may be added.

  When a solvent-drying type resin is added, film defects on the coating surface of the coating liquid can be effectively prevented when forming the hard coat layer. It does not specifically limit as solvent dry type resin, Generally, a thermoplastic resin can be used. Examples of thermoplastic resins include styrene resins, (meth) acrylic resins, vinyl acetate resins, vinyl ether resins, halogen-containing resins, alicyclic olefin resins, polycarbonate resins, polyester resins, polyamide resins. , Cellulose derivatives, silicone resins and rubbers or elastomers.

  The thermoplastic resin is preferably amorphous and soluble in an organic solvent (particularly a common solvent capable of dissolving a plurality of polymers and curable compounds). In particular, from the viewpoint of transparency and weather resistance, styrene resins, (meth) acrylic resins, alicyclic olefin resins, polyester resins, cellulose derivatives (cellulose esters, etc.) and the like are preferable.

  The thermosetting resin added to the hard coat layer is not particularly limited. For example, phenol resin, urea resin, diallyl phthalate resin, melamine resin, guanamine resin, unsaturated polyester resin, polyurethane resin, epoxy resin, aminoalkyd Examples thereof include resins, melamine-urea cocondensation resins, silicon resins, polysiloxane resins, and the like.

  The hard coat layer is formed by applying a composition for a hard coat layer containing the photopolymerizable compound to a light-transmitting film and drying it, and then irradiating the film-form composition for a hard coat layer with light such as ultraviolet rays. Then, it can be formed by polymerizing (crosslinking) the photopolymerizable compound.

  In addition to the photopolymerizable compound, if necessary, the thermoplastic resin, thermosetting resin, solvent, and polymerization initiator may be added to the hard coat layer composition. Furthermore, the hard coat layer composition includes conventionally known dispersants, surfactants and antistatic agents depending on purposes such as increasing the hardness of the hard coat layer, suppressing cure shrinkage, and controlling the refractive index. , Silane coupling agents, thickeners, anti-coloring agents, colorants (pigments, dyes), antifoaming agents, leveling agents, flame retardants, UV absorbers, adhesion promoters, polymerization inhibitors, antioxidants, surface modification A quality agent, a lubricant, etc. may be added.

  Examples of the method for applying the hard coat layer composition include known coating methods such as spin coating, dipping, spraying, slide coating, bar coating, roll coating, gravure coating, and die coating.

  When ultraviolet rays are used as the light for curing the hard coat layer composition, ultraviolet rays emitted from an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc, a xenon arc, a metal halide lamp, or the like can be used. Moreover, as a wavelength of an ultraviolet-ray, the wavelength range of 190-380 nm can be used. Specific examples of the electron beam source include various electron beam accelerators such as a cockcroft-wald type, a bandegraft type, a resonant transformer type, an insulated core transformer type, a linear type, a dynamitron type, and a high frequency type.

(Anti-glare layer)
The antiglare layer is a layer that exhibits antiglare properties. The surface of the antiglare layer is an uneven surface. By making the surface of the antiglare layer uneven, external light can be diffusely reflected. The “surface of the antiglare layer” means a surface opposite to the surface (back surface) on the light transmissive film side of the antiglare layer. The anti-glare layer can be formed by containing organic fine particles or inorganic fine particles for forming an uneven surface in the hard coat layer composition.

(Antistatic layer)
The antistatic layer is a layer that exhibits antistatic properties. The antistatic layer can be formed by incorporating an antistatic agent into the hard coat layer composition. As the antistatic agent, conventionally known ones can be used. For example, a cationic antistatic agent such as a quaternary ammonium salt, fine particles such as tin-doped indium oxide (ITO), a conductive polymer, or the like can be used. Can do. When using the said antistatic agent, it is preferable that the content is 1-30 mass% with respect to the total mass of all the solid content.

(Anti-fouling layer)
The antifouling layer is a layer that exhibits antifouling properties, and specifically, when dirt (fingerprints, water-based or oily inks, pencils, etc.) is difficult to adhere to or adheres to the outermost surface of the image display device. However, it is a layer that plays the role of being able to wipe off easily. Further, by forming the antifouling layer, it is possible to improve the antifouling property and scratch resistance of the liquid crystal display device. The antifouling layer can be formed of, for example, a composition containing an antifouling agent and a resin.

  The antifouling agent is mainly intended to prevent the outermost surface of the image display device from being stained, and can also impart scratch resistance to the liquid crystal display device. Examples of the antifouling agent include fluorine compounds, silicon compounds, and mixed compounds thereof. More specifically, silane coupling agents having a fluoroalkyl group, such as 2-perfluorooctylethyltriaminosilane, and the like can be mentioned, and those having an amino group can be preferably used.

  The antifouling layer is preferably formed so as to be particularly the outermost surface. The antifouling layer can be replaced, for example, by imparting antifouling performance to the hard coat layer itself.

  A low refractive index layer is preferably formed on the hard coat layer or the antiglare layer.

(Low refractive index layer)
The low refractive index layer is for reducing the reflectance when external light (for example, a fluorescent lamp, natural light, etc.) is reflected on the surface of the polarizing plate. The low refractive index layer has a lower refractive index than the hard coat layer or the antiglare layer. Specifically, for example, the low refractive index layer preferably has a refractive index of 1.45 or less, and more preferably has a refractive index of 1.42 or less.

The thickness of the low-refractive index layer is not limited, but it may be set appropriately from the range of about 30 nm to 1 μm. The thickness d _A (nm) of the low refractive index layer preferably satisfies the following formula (3).
d _A = mλ / (4n _A ) (3)
In the above formula, n _A represents the refractive index of the low refractive index layer, m represents a positive odd number, preferably 1, and λ is a wavelength, preferably a value in the range of 480 nm to 580 nm.

The low refractive index layer preferably satisfies the following formula (4) from the viewpoint of reducing the reflectance.
120 <n _A d _A <145 (4)

  The effect can be obtained with a single layer of the low refractive index layer, but it is also possible to appropriately provide two or more low refractive index layers for the purpose of adjusting a lower minimum reflectance or a higher minimum reflectance. When two or more low refractive index layers are provided, it is preferable to provide a difference in the refractive index and thickness of each low refractive index layer.

  The low refractive index layer is preferably 1) a resin containing low refractive index particles such as silica and magnesium fluoride, 2) a fluorine-based resin which is a low refractive index resin, and 3) fluorine containing silica or magnesium fluoride. 4) It can be composed of any one of a thin film of a low refractive index material such as silica and magnesium fluoride. As for the resin other than the fluorine-based resin, the same resin as the binder resin constituting the hard coat layer described above can be used.

  The silica is preferably hollow silica fine particles, and such hollow silica fine particles can be produced by, for example, a production method described in Examples of JP-A-2005-099778.

<Improvement of bright place contrast by polarizing plate>
In the present embodiment, the polarizing plate 10 includes a polarizer 11 arranged so that the absorption axis direction 11A of the polarizer 11 is along the horizontal direction, and the progress of the light transmissive film 12 with respect to the absorption axis direction 11A of the polarizer 11. And a light transmissive film 12 disposed so that the angle α in the phase axis direction 12B is not less than 5 degrees and not more than 40 degrees. The inventors have confirmed that the polarizing plate 10 is used as a polarizing plate located on the viewer side of the display device, that is, a so-called upper polarizing plate, so that the degree of improvement can be visually detected. The contrast could be increased effectively. The detailed reason why such a phenomenon occurs is unknown, but the following can be considered as one factor. However, the present invention is not limited to the following estimation.

  First, the bright place contrast is calculated as {(brightness of white display + reflection of external light) / (brightness of black display + reflection of external light)}, and the higher the obtained contrast value, the better the contrast. Therefore, if the external light reflection on the surface of the light transmissive film 12 can be reduced, the bright place contrast can be improved. On the other hand, each layer included in the polarizing plate is expected to exhibit various functions, and naturally there are restrictions on the material used for each layer and the refractive index setting of each layer determined by the material. For this reason, except for a special case, a refractive index difference is inevitably generated between the light-transmitting film 12 and the functional layer 13. In addition, unlike the illustrated form, it is assumed that the layer such as the functional layer 13 is not provided on the viewer side of the light transmissive film 12, but in this case also, the refractive index interface that causes reflection is air. And the light transmissive film 12. This difference in refractive index causes reflection of external light at the interface between the light-transmitting film 12 and the functional layer 13, and contributes to a decrease in bright place contrast of the display device.

  On the other hand, there are P-polarized light and S-polarized light as polarization components of light that can enter the display device and cause a bright place contrast. The reflectance of P-polarized light is lower than that of S-polarized light, and there is a Brewster angle at which the reflectance is 0%. For this reason, the polarized light component (S-polarized light) that oscillates in the horizontal direction is inevitably included in the light reflected from the floor surface or ceiling surface and incident on the image display surface of the image display device. . From the above, even if the average refractive index determined depending on the material used is different between the light transmissive film 12 and the functional layer 13, it is aligned along the horizontal direction of the light transmissive film 12. As long as the in-plane refractive index is brought close to the in-plane refractive index along the horizontal direction of the functional layer 13, external light reflection between the light-transmitting film 12 and the functional layer 13 that causes a decrease in contrast in the bright place is caused. It can be effectively prevented.

  Therefore, in the polarizing plate 10 of the present embodiment, the birefringence is set while allowing the average refractive index difference between the light-transmitting film 12 and the functional layer 13 that may inevitably arise due to material selection restrictions. By using the light-transmitting film 12 that is provided, and even by giving the birefringence to the light-transmitting film 12 made of a material that has normally been treated as optically isotropic, The difference in the refractive index in the horizontal direction between the light-transmitting film 12 and the functional layer 13 that governs the reflectance of the polarization component that vibrates rapidly is reduced as much as possible. More specifically, since the average refractive index of the light transmissive film 12 is usually higher than the average refractive index of the functional layer 13, the lowest refractive index among the in-plane refractive indexes of the light transmissive film 12 is obtained. The refractive index difference between the light-transmitting film 12 and the functional layer 13 in the horizontal direction with the fast axis direction 12B in the range of 5 degrees to 40 degrees with respect to the absorption axis direction 11A of the polarizer 11 Is reduced. Thus, by setting the fast axis direction 12B of the light transmissive film 12 included in the polarizing plate 10 to a range of 5 degrees or more and 40 degrees or less with respect to the absorption axis direction 11A of the polarizer 11, the light transmissive film. The light transmissive film 12 allows a difference in refractive index to occur between the average refractive index between the layer 12 and the functional layer 13 and ensures the freedom of selection of materials used for the light transmissive film 12 and the functional layer 13. The horizontal difference that reduces the refractive index difference in the horizontal direction at the interface between the optical layer and the functional layer 13 and causes a decrease in contrast in the bright place when the image display device is observed visually (with the polarized sunglasses not attached). The reflection at the interface between the light transmissive film 12 and the functional layer 13 of the polarization component that vibrates in the direction is effectively reduced. Here, rather than disposing the light-transmitting film so that the angle of the fast axis direction with respect to the absorption axis direction of the polarizer is 45 degrees, the fast phase is advanced with respect to the absorption axis direction 11A of the polarizer 11 as in this embodiment. If the light transmissive film 12 is arranged so that the angle of the axis 12B is 5 degrees or more and 40 degrees or less, the refractive index difference in the horizontal direction at the interface between the light transmissive film 12 and the functional layer 13 is further increased. Since it can reduce, reflection in the interface of the light transmission film 12 and the functional layer 13 of the polarization component which vibrates in a horizontal direction can be reduced more effectively. In the case where the functional layer 13 is not present, the light transmissive substrate 12 comes into contact with air, so that the phase advance is the lowest in the in-plane refractive index of the light transmissive film 12. By setting the axial direction 12B in the range of 5 degrees or more and 40 degrees or less with respect to the absorption axis direction 11A of the polarizer 11, the difference in refractive index from the air can be reduced. As a result, similarly to the above, it is possible to effectively reduce the reflection of the polarization component that vibrates in the horizontal direction, which is the main cause of the decrease in the bright place contrast.

  In addition, the reflection of the polarized component (S-polarized light) that vibrates in the horizontal direction with a large proportion of incidence on the image display surface can be reduced, but as a result, it vibrates in many horizontal directions. The polarizing component to be transmitted is transmitted through the light transmissive film 12. Usually, the polarization component that vibrates in the horizontal direction that has passed through the light-transmitting film is absorbed inside the image display device, or becomes stray light and returns to the viewer side. The stray light that returns to the viewer side creates a brightness distribution different from that of the display image, which is one factor for reducing the bright place contrast. In this regard, in the present embodiment, the polarizer 11 is arranged so that the absorption axis direction 11A of the polarizer 11 is along the horizontal direction, so that the polarization component that vibrates in the horizontal direction transmitted through the light transmissive film 12 is polarized. It can be absorbed by the child 11. Accordingly, since the amount of the polarized component that vibrates in the horizontal direction that returns to the viewer after passing through the light transmissive film 12 can be reduced, the occurrence of stray light can be effectively prevented, and the image display device can be prevented. Can be improved in a bright place when observed visually (with polarized sunglasses not worn).

  As described above, according to the present embodiment, the horizontal direction on the surface of the light transmissive film 12 is more than the case where the light transmissive film is disposed so that the angle of the fast axis direction with respect to the absorption axis direction of the polarizer is 45 degrees. Since the reflection of the polarization component (S-polarized light) oscillating in the direction can be reduced, it is clearer than arranging the light-transmitting film so that the angle of the fast axis direction with respect to the absorption axis direction of the polarizer is 45 degrees. The contrast can be effectively improved. Furthermore, the polarization component that vibrates in the horizontal direction (S-polarized light) transmitted through the light-transmitting film and stray light that returns to the viewer can be absorbed by the polarizer. It is possible to improve the bright place contrast.

  Further, as shown in FIG. 2, the absorption axis direction 11A of the polarizer 11 is a horizontal direction, and therefore the linearly polarized light in the direction parallel to the transmission axis perpendicular to the absorption axis is transmitted through the polarizer 11. The linearly polarized light that has passed through the polarizer 11 changes its polarization state due to the birefringence of the light transmissive film 12 to become elliptically polarized light, and is emitted from the light transmissive film 12 in this elliptically polarized state. And it is radiate | emitted from the polarizing plate 10 through the functional layer 13, maintaining this elliptically polarized light.

  On the other hand, as described above, a polarizer such as a VA mode or an IPS mode is used in a posture in which an observer wears polarized sunglasses and observes a display image normally (an orientation in which the absorption axis direction of polarized sunglasses is substantially horizontal). When the display image of the image display device in which the absorption axis direction is horizontal is viewed, the absorption axis direction 14A of the polarized sunglasses 14 and the absorption axis of the polarizer 11 of the polarizing plate 10 are shown in FIG. Although the direction 11A is in a parallel Nicol state, the polarized sunglasses and the polarizing plate are not in a parallel Nicol state when the observer tilts his / her neck in the left / right direction or when the observer lies down. In particular, when the observer visually recognizes the display image in a state where the absorption axis of the polarized sunglasses is substantially vertical, the polarized sunglasses and the polarizing plate are in a crossed Nicols state.

The transmitted light intensity observed under crossed nicols is when the angle between the absorption axis of the polarizer (the direction of vibration of linearly polarized light) and the slow axis of the light transmissive film having birefringence in the plane is θ. Is represented by the following formula (5).
I = I ₀ · sin ² (2θ) · sin ² (π · Re / λ) (5)
In the above formula (5), I is the intensity of light transmitted through crossed Nicols, I ₀ is the intensity of light incident on a light transmissive film having birefringence in the plane, λ is the wavelength of light, and Re is the light transmission It is retardation of an adhesive film.

When the light transmissive film 12 is not provided, sin ² (2θ) in the above formula (5) is 0, and light is not transmitted through the polarized sunglasses, and thus visibility is deteriorated. On the other hand, in this embodiment, since the light transmissive film 12 is provided, sin ² (2θ) in the above formula (5) takes a value larger than 0. Thereby, even if polarization sunglasses and a polarizing plate are in the state of crossed Nicols, visibility can be secured to some extent.

  Further, in the case where the polarized sunglasses and the polarizing plate are in a parallel Nicol state, λ / having in-plane birefringence so that the angle of the fast axis direction with respect to the absorption axis direction of the polarizer is 45 degrees. When four retardation films are arranged, and when a translucent film having birefringence is arranged in the plane so that the angle of the fast axis direction with respect to the absorption axis direction of the polarizer is 5 degrees or more and 40 degrees or less When the light transmissive film having birefringence is arranged in the plane so that the angle of the fast axis direction with respect to the absorption axis direction of the polarizer is 5 degrees or more and 40 degrees or less, The transmittance is higher than when the λ / 4 retardation film is arranged so that the angle of the fast axis direction with respect to the absorption axis direction of the child is 45 degrees. This is for the following reason. When the λ / 4 retardation film is arranged so that the angle of the fast axis with respect to the absorption axis direction of the polarizer is 45 degrees, the linearly polarized light that has passed through the transmission axis of the polarizer changes its polarization state to circularly polarized light. The state of this circularly polarized light is that of linearly polarized light that can pass through the transmission axis of the polarizer and linearly polarized light that vibrates in a direction perpendicular to the vibration direction of this linearly polarized light (linearly polarized light that is absorbed by the absorption axis of the polarizer). Means the same state as half each. For this reason, even in an ideal state where there is no reflection or absorption, the transmittance is halved when the absorption axis of the polarized sunglasses and the absorption axis of the polarizing plate are in a parallel Nicol state. In contrast, when a light-transmitting film having birefringence is arranged in the plane so that the angle of the fast axis with respect to the absorption axis direction of the polarizer is 5 degrees or more and 40 degrees or less, the transmission of the polarizer The linearly polarized light passing through the axis changes its polarization state to elliptically polarized light. The state of this elliptically polarized light is that linearly polarized light that can pass through the transmission axis of the polarizer vibrates in a direction perpendicular to the vibration direction of this linearly polarized light (linearly polarized light that is absorbed by the absorption axis of the polarizer). It means the same state as the state where there are more than components. For this reason, when the absorption axis of the polarized sunglasses and the absorption axis of the polarizing plate are in a parallel Nicol state, the transmittance does not become half or less, and the angle of the fast axis direction with respect to the absorption axis direction of the polarizer is The transmittance is higher than when a λ / 4 retardation film is arranged to be 45 degrees. In the present embodiment, since the light transmissive film 12 is arranged so that the angle of the fast axis direction 12B with respect to the absorption axis direction 11A of the polarizer 11 is 5 degrees or more and 40 degrees or less, the absorption axis direction of the polarizer The transmittance is higher than that in the case where the λ / 4 retardation film is arranged so that the angle in the fast axis direction with respect to is 45 degrees.

<Image display device and method for improving bright contrast in image display device>
The polarizing plate 20 can be used by being incorporated in an image display device. Examples of the image display device include a liquid crystal display (LCD), a cathode ray tube display device (CRT), a plasma display (PDP), an electroluminescence display (ELD), a field emission display (FED), a touch panel, a tablet PC, and electronic paper. Can be mentioned. FIG. 3 is a schematic configuration diagram of a liquid crystal display which is an example of an image display device incorporating the optical film according to the present embodiment.

  The image display device 20 shown in FIG. 3 is a liquid crystal display. The image display device 20 includes a backlight unit 30 and a liquid crystal panel 40 including the polarizing plate 10 disposed on the viewer side with respect to the backlight unit 30.

  The backlight unit 30 preferably includes a white light emitting diode (white LED) as a backlight light source. The white LED is an element that emits white by combining a phosphor with a phosphor system, that is, a light emitting diode that emits blue light or ultraviolet light using a compound semiconductor. In particular, white light-emitting diodes, which are composed of a combination of blue light-emitting diodes using compound semiconductors and yttrium / aluminum / garnet-based yellow phosphors, have a continuous and broad emission spectrum. In addition to being effective in improving the above, and also excellent in luminous efficiency, it is suitable as the backlight light source in the present invention. Further, since white LEDs with low power consumption can be widely used, it is possible to achieve an energy saving effect.

  A liquid crystal panel 40 shown in FIG. 3 includes a protective film 41 such as a triacetyl cellulose film (TAC film), a polarizer 42, a retardation film 43, and an adhesive layer 44 from the backlight unit 30 side toward the viewer side. The liquid crystal cell 45, the adhesive layer 46, the retardation film 47, and the polarizing plate 10 are laminated in this order. In the liquid crystal cell 45, a liquid crystal layer, an alignment film, an electrode layer, a color filter, and the like are disposed between two glass substrates.

  The polarizing plate 10 is disposed in the image display device 20 so that the absorption axis direction 11A of the polarizer 11 is along the horizontal direction. The light transmissive film 12 of the polarizing plate 10 is disposed such that the angle α in the fast axis direction 12B of the light transmissive film 12 with respect to the absorption axis of the polarizer 11 is not less than 5 degrees and not more than 40 degrees. Needless to say.

  The image display device 20 is preferably a VA mode or IPS mode liquid crystal display device. In the VA (Vertical Alignment) mode, liquid crystal molecules are aligned so as to be perpendicular to the substrate of the liquid crystal cell when no voltage is applied, and dark display is performed. This is an operation mode indicating display. The IPS (In-Plane Switching) mode is a method in which display is performed by rotating the liquid crystal within the substrate surface by a horizontal electric field applied to a pair of comb electrodes provided on one substrate of the liquid crystal cell. is there.

  It is preferable that the image display device is of the VA mode or IPS mode. In the VA mode or IPS mode, the absorption axis of the polarizer placed closer to the viewer than the liquid crystal cell is along the horizontal direction. Because.

  The image display device may be an organic electroluminescence display (organic EL display) in which an absorption axis of a polarizer is installed in the horizontal direction. In this case, the polarizing plate, the λ / 4 retardation plate, and the organic EL element may be laminated in this order from the observer side. As an image display method of an organic EL display, a white light emitting layer is used and a color filter is used to obtain a color display by using a color filter, a blue light emitting layer is used, and a part of the light emission is passed through a color conversion layer. Examples include a color conversion method for obtaining a color display, a three-color method using red, green, and blue light-emitting layers, and a method using a color filter in combination with the three-color method. The material of the light emitting layer may be a low molecule or a polymer.

  In order to describe the present invention in detail, examples will be described below, but the present invention is not limited to these descriptions.

<Light place contrast>
Hereinafter, in each polarizing plate obtained in Examples and Comparative Examples, the bright place contrast was evaluated. The bright place contrast was evaluated as follows. A polarizing plate according to an example and a comparative example, instead of the polarizing plate installed on the observer side of the liquid crystal monitor (FLATRON IPS226V (manufactured by LG Electronics Japan)) so that the absorption axis direction of the polarizer is a horizontal direction. Was placed through a pressure sensitive adhesive (P-3132, manufactured by Lintec Corporation) so that the TD80UL-M side, which will be described later, of the polarizing plate becomes the liquid crystal panel side, and displayed in black at an ambient illuminance of 400 lux (light). From a place about 50 to 60 cm away from the liquid crystal monitor, 15 test subjects visually observed the black display (without wearing polarized sunglasses) and evaluated it according to the following criteria. Evaluation was performed for each polarizing plate formed using the same material, and a polarizing plate in which the angle of the fast axis direction of the light transmissive film with respect to the absorption axis direction of the polarizer was set to 45 degrees was used as a reference.
A: It looked blacker than the reference, and the photopic contrast was very good.
B: It looked blacker than the reference, and the bright place contrast was excellent.
C: The photopic contrast was excellent, although slightly more than the reference.
D: Same as reference or inferior photopic contrast.
Light place contrast: CR = LW / LB
Brightness white brightness (LW): Brightness when the display device displays white in a bright place with ambient light (ambient illuminance 400 lux) Bright place black brightness (LB): Bright place with ambient light (ambient illuminance 400) (Lux)) Luminance when the display device is displayed in black

<Reflectance>
Hereinafter, in each polarizing plate obtained in Examples and Comparative Examples, the reflectance was measured, and the reflectance was measured as follows. A black vinyl tape (Yamato Vinyl Tape No200-38-21, 38 mm wide was applied to the opposite side of the polarizing plate to the light transmissive film side, and then a spectrophotometer (V7100 type, automatic absolute reflectance measurement unit VAR-7010 Japan) Using a spectrophotometer, the reflectivity of 5 degrees was measured when the absorption axis of the polarizer was set parallel to the S-polarized light.

<Visibility evaluation>
Hereinafter, although visibility was evaluated in each polarizing plate obtained in Examples and Comparative Examples, visibility was evaluated as follows. Instead of the polarizing plate installed on the observer side of the liquid crystal monitor (FLATRON IPS 226V (manufactured by LG Electronics Japan)), the polarizing plate according to the example and the comparative example is set so that the absorption axis direction of the polarizer is in the horizontal direction. The polarizing plate was placed through a pressure sensitive adhesive (P-3132, manufactured by Lintec Corporation) so that the TD80UL-M side described later of the polarizing plate was the liquid crystal panel side. In a dark place, the liquid crystal display device displays white, and is rotated so that the angle between the absorption axis of the polarized sunglasses and the absorption axis of the polarizer is 0 ° (parallel Nicols) to 90 ° (crossed Nicols). Evaluation was performed according to the criteria of
A: The display image could be visually recognized at any angle (it was compatible with polarized sunglasses).
B: Depending on the angle, the visibility is slightly lowered, but it is at a level where there is no problem in actual use.
C: Visibility decreases depending on the angle, but the display image can be recognized.
D: There was an angle at which the displayed image could not be visually recognized depending on the angle (corresponding to polarized sunglasses was not made).

<Light transmittance in parallel Nicol state>
Hereinafter, in each polarizing plate obtained in Examples and Comparative Examples, the light transmittance in a parallel Nicol state was measured as follows. A polarizing plate according to an example and a comparative example, instead of the polarizing plate installed on the observer side of the liquid crystal monitor (FLATRON IPS226V (manufactured by LG Electronics Japan)) so that the absorption axis direction of the polarizer is a horizontal direction. Is placed through a pressure-sensitive adhesive (P-3132, manufactured by Lintec Corporation) so that the TD80UL-M side, which will be described later, of the polarizing plate becomes the liquid crystal panel side, white display is performed in the dark, and absorption of polarized sunglasses The front luminance when the angle between the axial direction and the absorption axis direction of the polarizing plate was 0 ° (parallel Nicol) was measured with a luminance meter BM-5A (Topcon Corporation). The transmittance is shown by assuming that the transmittance of a polarizing plate in which TD80UL-M described later is installed on both sides of the polarizer is 100%.

<Comprehensive evaluation>
Comprehensive evaluation was performed according to the following criteria.
(Double-circle): B evaluation or more in bright place contrast evaluation and visibility evaluation.
○: C evaluation or higher in bright place contrast evaluation and visibility evaluation.
X: There is D evaluation in the bright place contrast evaluation and the visibility evaluation.

<Example 1>
(Production of light transmissive film)
The polyethylene terephthalate material was melted at 290 ° C., extruded through a film-forming die, into a sheet form, closely adhered onto a water-cooled and cooled rotating quenching drum, and cooled to produce an unstretched film. This unstretched film is preheated at 120 ° C. for 1 minute using a biaxial stretching test apparatus (manufactured by Toyo Seiki Co., Ltd.) and then stretched uniaxially at a fixed end of 4.0 times at 120 ° C. to have birefringence in the surface A light transmissive film was prepared. The light-transmitting film had a refractive index n _x = 1.701, n _y = 1.6015 at a wavelength of 550 nm, and Δn = 0.0995. The film thickness of this light transmissive film was 75 μm, and Re = 7500 nm.

(Preparation of polarizing plate)
A polyvinyl alcohol film having an average polymerization degree of about 2400 and a saponification degree of 99.9 mol% or more and a thickness of 75 μm was immersed in pure water at 30 ° C., and the weight ratio of iodine / potassium iodide / water was 0.02 / It was immersed in a 2/100 aqueous solution at 30 ° C. Then, it was immersed at 56.5 ° C. in an aqueous solution having a potassium iodide / boric acid / water weight ratio of 12/5/100. Subsequently, it was washed with pure water at 8 ° C. and then dried at 65 ° C. to obtain a polarizer in which iodine was adsorbed and oriented on polyvinyl alcohol. Stretching was mainly performed in the iodine staining and boric acid treatment steps, and the total stretching ratio was 5.3 times.

  An absorption axis of the polarizer and a fast axis of the light-transmitting film are formed on one surface side of the obtained polarizer through a solventless active energy ray-curable adhesive containing an alicyclic epoxy compound. Adhesive bonding was performed so that the angle formed by Next, an isotropic film TD80UL-M (manufactured by Fuji Film Co., Ltd.) is applied to the side opposite to the side where the light transmissive film of the polarizer is laminated, and a solventless active energy containing an alicyclic epoxy compound. Adhesive bonding was carried out via a wire curable adhesive to produce a polarizing plate according to Example 1.

<Example 2>
A polarizing plate according to Example 2 was produced in the same manner as in Example 1 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light-transmitting film was 10 degrees.

<Example 3>
A polarizing plate according to Example 3 was produced in the same manner as in Example 1 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light-transmitting film was 15 degrees.

<Example 4>
A polarizing plate according to Example 4 was produced in the same manner as in Example 1 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light transmissive film was 30 degrees.

<Example 5>
A polarizing plate according to Example 5 was produced in the same manner as in Example 1 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light transmissive film was set to 35 degrees.

<Example 6>
A polarizing plate according to Example 6 was produced in the same manner as in Example 1 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light transmissive film was 40 degrees.

<Comparative Example 1>
A polarizing plate according to Comparative Example 1 was produced in the same manner as in Example 1 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light transmissive film was set to 0 degree.

<Comparative Example 2>
A polarizing plate according to Comparative Example 2 was produced in the same manner as in Example 1 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light transmissive film was 45 degrees.

<Comparative Example 3>
A polarizing plate according to Comparative Example 3 was produced in the same manner as in Example 1 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light transmissive film was 60 degrees.

<Comparative Example 4>
A polarizing plate according to Comparative Example 4 was produced in the same manner as in Example 1 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light transmissive film was 75 degrees.

<Comparative Example 5>
A polarizing plate according to Comparative Example 5 was produced in the same manner as in Example 1 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light-transmitting film was 90 degrees.

<Example 7>
For a hard coat layer in which pentaerythritol triacrylate (PETA) is dissolved in 30% by mass in a methyl isobutyl ketone (MIBK) solvent, and a photopolymerization initiator (Irgacure 184, manufactured by BASF) is added at 5% by mass with respect to the solid content. The composition was applied by a bar coater so that the film thickness after drying was 5 μm, and a coating film was formed on the light transmissive film prepared in Example 1. Next, the formed coating film is heated at 70 ° C. for 1 minute, the solvent is removed, and the coated surface is fixed by irradiating ultraviolet rays onto the coated surface. A permeable film was obtained.

  It is polarized on the surface opposite to the hard coat layer side of the light transmissive film so that the angle between the absorption axis of the polarizer and the fast axis of the light transmissive film with the hard coat layer is 15 degrees. A polarizing plate according to Example 7 was produced in the same manner as in Example 1 except that the child was bonded and bonded.

<Example 8>
A polarizing plate according to Example 8 was produced in the same manner as in Example 7 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light-transmitting film with a hard coat layer was 30 degrees. did.

<Comparative Example 6>
A polarizing plate according to Comparative Example 6 was produced in the same manner as in Example 7 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light-transmitting film with a hard coat layer was 0 degree. did.

<Comparative Example 7>
A polarizing plate according to Comparative Example 7 was produced in the same manner as in Example 7 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light-transmitting film with a hard coat layer was 45 degrees. did.

<Comparative Example 8>
A polarizing plate according to Comparative Example 8 was produced in the same manner as in Example 7 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light-transmitting film with a hard coat layer was 60 degrees. did.

<Comparative Example 9>
A polarizing plate according to Comparative Example 9 was produced in the same manner as in Example 7 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light-transmitting film with a hard coat layer was 90 degrees. did.

<Example 9>
A light-transmitting film having in-plane birefringence was produced in the same manner as in Example 1 except that the film thickness of the unstretched film was adjusted and the fixed-end uniaxial stretching was performed at 120 ° C. by 3.0 times. . The light-transmitting film had a refractive index n _x = 1.6922 and n _y = 1.6123 at a wavelength of 550 nm, and Δn = 0.0799. The film thickness of this light transmissive film was 36 μm, and Re = 2900 nm.

  Example 9 is the same as Example 1 except that this light-transmitting film was used and the angle formed by the absorption axis of the polarizer and the fast axis of the light-transmitting film was 15 degrees. A polarizing plate was produced.

<Example 10>
A polarizing plate according to Example 10 was produced in the same manner as in Example 9, except that the angle formed by the absorption axis of the polarizer and the fast axis of the light-transmitting film was 30 degrees.

<Comparative Example 10>
A polarizing plate according to Comparative Example 10 was produced in the same manner as in Example 9, except that the angle formed between the absorption axis of the polarizer and the fast axis of the light-transmitting film was 0 degree.

<Comparative Example 11>
A polarizing plate according to Comparative Example 11 was produced in the same manner as in Example 9 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light transmissive film was 45 degrees.

<Comparative Example 12>
A polarizing plate according to Comparative Example 12 was produced in the same manner as in Example 9 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light transmissive film was 60 degrees.

<Comparative Example 13>
A polarizing plate according to Comparative Example 13 was produced in the same manner as in Example 9, except that the angle formed between the absorption axis of the polarizer and the fast axis of the light transmissive film was 90 degrees.

<Example 11>
Cellulose acetate propionate (CAP504-0.2 manufactured by Eastman Chemical Co., Ltd.) was dissolved in methylene chloride so as to have a solid concentration of 15%, and then cast on glass, dried, and unstretched film. Got. This unstretched film was uniaxially stretched 1.5 times at 160 ° C. with a biaxial stretching test apparatus (manufactured by Toyo Seiki Co., Ltd.) to produce a light transmissive film having birefringence in the plane. The light-transmitting film had a refractive index n _x = 1.4845 and n _y = 1.4835 at a wavelength of 550 nm, and Δn = 0.001. The film thickness of this light transmissive film was 138 μm, and Re = 138 nm.

  Using this light transmissive film, the polarization according to Example 11 was performed in the same manner as in Example 1 except that the angle formed by the absorption axis of the polarizer and the fast axis of the light transmissive film was 15 degrees. A plate was made.

<Example 12>
A polarizing plate according to Example 12 was produced in the same manner as in Example 11 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light-transmitting film was 30 degrees.

<Comparative example 14>
A polarizing plate according to Comparative Example 14 was produced in the same manner as in Example 11 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light-transmitting film was 0 degree.

<Comparative Example 15>
A polarizing plate according to Comparative Example 15 was produced in the same manner as in Example 11 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light transmissive film was 45 degrees.

<Comparative Example 16>
A polarizing plate according to Comparative Example 16 was produced in the same manner as in Example 11 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light-transmitting film was 60 degrees.

<Comparative Example 17>
A polarizing plate according to Comparative Example 17 was produced in the same manner as in Example 11 except that the angle formed between the absorption axis of the polarizer and the fast axis of the light transmissive film was 90 degrees.

The results are shown in Table 1.

  As shown in Table 1, in Comparative Example 1, the bright place contrast is superior to that of Comparative Example 2 as a reference, and the light transmittance in the parallel Nicol state is higher than that of Comparative Example 2, but the visibility is ensured. It wasn't done. In Comparative Examples 3 and 4, although the light transmittance in the parallel Nicol state was higher than that in Comparative Example 2 and the visibility was secured to some extent, the bright place contrast was equal to or higher than that of Comparative Example 2. It was low. In Comparative Example 5, although the light transmittance in the parallel Nicol state was higher than that in Comparative Example 2, the bright place contrast was equal to or lower than that in Comparative Example 2, and the visibility was not ensured. On the other hand, in Examples 1-6, the bright place contrast was superior to the comparative example 2 which is a reference, and the light transmittance in a parallel Nicol state was also higher than the comparative example 2. Moreover, the visibility was also secured to some extent.

  Further, as shown in Table 1, in Comparative Example 6, the bright place contrast is superior to that of Comparative Example 7 as a reference, and the light transmittance in the parallel Nicol state is higher than that of Comparative Example 7, but the visibility is high. Could not be secured. In Comparative Example 8, the light transmittance in the parallel Nicol state was higher than that of Comparative Example 7 and the visibility was secured to some extent, but the bright place contrast was equal to or lower than that of Comparative Example 7. . In Comparative Example 9, although the light transmittance in the parallel Nicol state was higher than that of Comparative Example 7, the bright place contrast was equal to or lower than that of Comparative Example 7, and the visibility was not ensured. On the other hand, in Examples 7 and 8, the bright place contrast was superior to that of Comparative Example 7 as a reference, and the light transmittance in the parallel Nicol state was higher than that of Comparative Example 7. Moreover, the visibility was also secured to some extent.

  Further, as shown in Table 1, in Comparative Example 10, the bright place contrast is superior to that of Comparative Example 11 as a reference, and the light transmittance in the parallel Nicol state is higher than that of Comparative Example 11, but the visibility is high. Could not be secured. In Comparative Example 12, the light transmittance in the parallel Nicol state was higher than that of Comparative Example 11 and the visibility was ensured to some extent, but the bright place contrast was equal to or lower than that of Comparative Example 11. . In Comparative Example 13, although the light transmittance in the parallel Nicol state was higher than that of Comparative Example 11, the bright place contrast was equal to or lower than that of Comparative Example 11, and the visibility was not ensured. On the other hand, in Examples 9 and 10, the bright place contrast was superior to that of Comparative Example 11 as a reference, and the light transmittance in the parallel Nicol state was higher than that of Comparative Example 11. Moreover, the visibility was also secured to some extent.

  Further, as shown in Table 1, in Comparative Example 14, the bright place contrast is superior to that of Comparative Example 15 as a reference, and the light transmittance in the parallel Nicol state is higher than that of Comparative Example 11, but the visibility is high. Could not be secured. In Comparative Example 16, the light transmittance in the parallel Nicol state was higher than that of Comparative Example 15 and the visibility was secured to some extent, but the bright place contrast was equal to or lower than that of Comparative Example 15. . In Comparative Example 17, although the light transmittance in the parallel Nicol state was higher than that of Comparative Example 15, the bright place contrast was equal to or lower than that of Comparative Example 15, and the visibility was not ensured. On the other hand, in Examples 11 and 12, the bright place contrast was superior to that of Comparative Example 15 as a reference, and the light transmittance in the parallel Nicol state was higher than that of Comparative Example 15. Moreover, the visibility was also secured to some extent.

  In the above examples, the angle of the fast axis of the light transmissive film with respect to the absorption axis of the polarizer is positive, that is, when the polarizing plate is viewed from the front, the left side of the fast axis of the light transmissive film is polarized. The light transmission film is arranged so that it is above the absorption axis of the polarizer, but the angle of the fast axis of the light transmission film with respect to the absorption axis of the polarizer is negative, that is, when the polarizing plate is viewed from the front. For the polarizing plate arranged so that the left side of the fast axis is below the absorption axis of the polarizer, the same evaluation and measurement as described above were performed, and the same result as in the above example was obtained.

DESCRIPTION OF SYMBOLS 10 ... Polarizing plate 11 ... Polarizer 11A ... Absorption axis direction 12 ... Light transmissive film 12A ... Slow axis direction 12B ... Fast axis direction 13 ... Functional layer 14 ... Polarized sunglasses 14A ... Absorption axis direction 20 ... Image display apparatus

Claims (9)

A polarizing plate provided with a polarizer and a light-transmitting film having birefringence in a plane provided on a viewer-side surface of the polarizer,
The polarizer is arranged so that the absorption axis direction of the polarizer is along a horizontal direction, and the direction having the highest refractive index in the plane of the light transmissive film is defined as a slow axis direction, and the retardation in the plane is When the direction orthogonal to the phase axis direction is the fast axis direction, the light-transmitting film is disposed so that the angle of the fast axis direction with respect to the absorption axis direction is 5 degrees or more and 40 degrees or less. A polarizing plate that is characterized.   The polarizing plate according to claim 1, wherein the light transmissive film is a polyester film.   The light transmissive film has a refractive index in a direction parallel to the fast axis direction of the light transmissive film, which is formed on the surface opposite to the surface on which the polarizer is formed in the light transmissive film. The polarizing plate according to claim 1, further comprising a functional layer having a refractive index lower than the refractive index in the fast axis direction.   The polarizing plate according to claim 3, wherein the functional layer is a hard coat layer or an antiglare layer.   An image display device comprising the polarizing plate according to claim 1, wherein the polarizing plate is arranged so that an absorption axis direction of the polarizer is along a horizontal direction.   The image display device according to claim 5, wherein the image display device is a VA mode or IPS mode liquid crystal display device.   The image display apparatus of Claim 5 or 6 provided with a light emitting diode as a light source.   6. The organic electroluminescence display according to claim 5, wherein the image display device is an organic electroluminescence display further including a λ / 4 phase difference plate, wherein the polarizing plate is disposed closer to an observer than the λ / 4 phase difference plate. Image display device.   5. The image display device, wherein the polarizing plate according to claim 1 is disposed in the image display device so that an absorption axis direction of the polarizer in the polarizing plate is along a horizontal direction. To improve contrast in bright places.

Images