JP2012185469A - Optical sheet and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical sheet which prevents or reduces rainbow-like unevenness generated on a surface material of an image display device, and to provide an image display device having the optical sheet mounted thereon as the surface material.SOLUTION: In the optical sheet arranged in an observer side of an image generation panel, the optical sheet includes a transparent base material A and a polarized light scattering particle layer, the polarized light scattering particle layer being arranged in the image generation panel side of the transparent base material A. The image display device has the optical sheet mounted thereon as a surface material.

Description

  The present invention relates to a surface material on an image observer side surface of an image display device, and more particularly to an optical sheet used as the surface material and an image display device equipped with the optical sheet as a surface material.

The image display device improves the quality of the generated image on the back side and / or the image viewer side of a panel (referred to as an “image generation panel” in the present invention) that is a central unit that generates and controls an image. An optical functional layer for the display, other functional layers for improving quality other than the display quality of the image display device, or a light source on the back side of the liquid crystal panel when the panel does not have self-luminous properties It is constituted by providing. Hereinafter, “image observer (side)” is also simply referred to as “observer (side)”.
An image display device is required to display a high-luminance image as one of the viewpoints of display quality, and various means have been proposed to increase the luminance.
On the observer side surface of the image display device (hereinafter also simply referred to as “surface”), optical functions or optical properties such as antireflection and antiglare properties, hard coat properties and antifouling properties, etc. A laminated structure including one layer or two or more layers for providing some function useful for the image display device such as a function or property other than the optical function (hereinafter sometimes referred to as “function”) is provided. It is done. Such a laminated structure is referred to as a “surface material” in the present invention.
The surface material usually has at least one transparent base material as a support, and is formed by laminating one or two or more functional layers on one side or both sides of the transparent base material. The surface material may take the form of an independent optical sheet or plate-like material, and may be fixed to the observer-side surface of the image display device by a method such as pasting or fitting, or one layer on the image generation panel. Alternatively, two or more layers may be directly formed by a method such as coating. Furthermore, two or more surface materials may be overlapped on the observer side surface of the image display device with a space (that is, via an air layer).
On the other hand, Patent Document 1 describes an optical filter including a crystalline polymer having a spherulite structure (particularly, particles of the crystalline polymer) and a liquid crystal display device equipped with the optical filter. The optical filter described in Patent Document 1 has the property of converting polarized light incident from the surface on the image generation panel side to non-polarized light close to natural light with high efficiency and emitting it from the side of the viewer on the opposite side. When looking directly at the emitted light, eyestrain is reduced as compared to looking directly at the polarized light before entering. Since the liquid crystal display device displays an image formed by polarized light in principle, it is possible to display a non-polarized image when the optical filter is attached, and the eye strain of the viewer is reduced. .
Further, when viewing an image by wearing glasses such as sunglasses having a polarizing filter function, there is a problem that the image looks dark when the angular relationship between the observer and the image display device changes. The filter can also eliminate such problems.
However, Patent Document 1 only describes that an optical filter including a crystalline polymer having a spherulitic structure can convert polarized light into non-polarized light with high efficiency, and a rainbow generated on the surface material of the image display device. Nothing is described about the influence or action on the unevenness of the shape and the brightness of the image display device.

Special Table 2007-119592

As a result of intensive research on the surface material of the image display device, the present inventors convert the polarized light into non-polarized light on the image generating panel side (the surface opposite to the observer side) of the transparent substrate that the surface material has. When laminating a layer containing particles, rainbow-like unevenness that occurs on the surface material of the image display device is prevented compared to the case where a layer containing particles that convert such polarized light into non-polarized light is not laminated. Or found that it can be mitigated.
In addition, when using a transparent substrate made of a material with small optical anisotropy, it contains particles that convert polarized light into non-polarized light on the image generation panel side (the surface opposite to the observer side) It has been found that when the layer to be laminated is laminated, the luminance is increased in displaying the image as compared with the case where the layer containing particles that convert such polarized light into non-polarized light is not laminated.

  The present invention has been accomplished based on such discovery, and an optical sheet for preventing or reducing rainbow-like unevenness generated on a surface material of an image display device, and an image display device equipped with the optical sheet as a surface material It is a first object to provide

  In addition, a second object of the present invention is to provide an optical sheet that can improve the luminance of the image display device, and a high-luminance image display device in which the optical sheet is mounted as a surface material.

  The optical sheet according to the present invention is an optical sheet disposed on the viewer side of the image generation panel, and includes a transparent substrate A and a polarized light scattering particle layer, and the polarized light scattering particle layer is formed of the transparent substrate A. It is arranged on the image generation panel side.

  In the optical sheet according to the present invention, it is preferable that the transparent base material A has Re ≦ 1200 nm from the viewpoint of preventing rainbow-like unevenness while ensuring visibility.

  In the optical sheet according to the present invention, the transparent substrate A preferably has Re ≦ 800 nm and Rth ≦ 800 nm from the viewpoint of excellent luminance.

In the optical sheet according to the present invention, a functional layer is disposed on the observer side of the transparent substrate A, and the polarized light scattering particle layer is disposed on the image generation panel side of the transparent substrate A. it can.
In the optical sheet according to the present invention, the polarized light scattering particle layer and the functional layer are arranged in this order from the side close to the transparent substrate A on the image generation panel side of the transparent substrate A. be able to.

  The optical sheet according to the present invention uniformly improves the luminance of the image display device by defining | Re1-Re2 | ≦ 400 nm when Re is defined as Re1 and Re2, respectively, on the optical sheet surface. It is preferable from the point which can be made.

  In the optical sheet according to the present invention, the occupation ratio of the polarized light scattering particles in the polarized light scattering particle layer is preferably 55% or less from the viewpoint of excellent visibility.

  The image display device according to the present invention comprises a laminated structure including a transparent base material A and a polarized light scattering particle layer on the viewer side of the image generation panel, and the polarized light scattering particle layer generates an image of the transparent base material A. It is arranged on the panel side.

  In the image display device according to the present invention, it is preferable that the transparent base material A has Re ≦ 1200 nm from the viewpoint of preventing rainbow-like unevenness while ensuring visibility.

  In the image display device according to the present invention, it is preferable that the transparent substrate A has Re ≦ 800 nm and Rth ≦ 800 nm from the viewpoint of excellent luminance.

In the image display device according to the present invention, the polarized light scattering particle layer, the transparent substrate A, and the functional layer may be arranged from the side close to the image generation panel.
In the image display device according to the present invention, the functional layer, the polarized light scattering particle layer, and the transparent substrate A may be arranged from the side close to the image generation panel.

  According to the present invention, an optical sheet that prevents or reduces rainbow-like unevenness generated on the surface material of the image display device by being arranged on the viewer side of the image generation panel, and the optical sheet mounted as the surface material An image display device can be provided.

  In addition, when the optical sheet of the present invention is made of a material having a small optical anisotropy as a transparent substrate, it is arranged on the observer side of the image generation panel to improve the luminance of the image display device. be able to.

FIG. 1 is a diagram schematically illustrating an example of an optical sheet according to the present invention and an image display device including the optical sheet. FIG. 2 is a diagram schematically illustrating another example of the optical sheet according to the present invention and an image display device including the optical sheet. FIG. 3 is a diagram schematically illustrating another example of the optical sheet according to the present invention and an image display device including the optical sheet. FIG. 4 is a diagram schematically showing an example of an image display device according to the present invention. FIG. 5 is a diagram schematically showing another example of the image display device according to the present invention. FIG. 6 is a graph showing the largest Re value among the Re values of the transparent substrate A or other layer on the viewer side of the polarized light scattering particle layer and the polarized light necessary for eliminating rainbow unevenness in the optical sheet according to the present invention. It is the conceptual diagram which showed the relationship figure of the polarization scattering particle occupation rate of a scattering particle layer.

  Next, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and various modifications can be made within the scope of the spirit thereof.

In the present invention, (meth) acrylic resin represents acrylic resin and / or methacrylic resin, and (meth) acrylate represents acrylate and / or methacrylate.
In the present invention, the resin is a concept including a polymer in addition to a monomer and an oligomer.
In the definition of film and sheet in JIS-K6900, a sheet is thin and generally refers to a flat product whose thickness is small for the length and width, and the film is extremely thick compared to the length and width. A thin, flat product that is small and has an arbitrarily limited maximum thickness, typically supplied in the form of a roll. Therefore, it can be said that a film with a particularly thin thickness among the sheets is a film, but the boundary between the sheet and the film is not clear and is difficult to distinguish clearly. Is defined as “sheet”.
In the present invention, the molecular weight means a weight average molecular weight which is a polystyrene equivalent value measured by gel permeation chromatography (GPC) in a THF solvent when having a molecular weight distribution, and when having no molecular weight distribution, It means the molecular weight of the compound itself.

In the present invention, Re represents an in-plane refractive index anisotropy (retardation) value, and is defined by the following formula (1).
Re = (nx−ny) × d (1)
In formula (1), nx is the refractive index in the slow axis direction in the plane of the layer, substrate or sheet (hereinafter referred to as a sheet or the like) (maximum refractive index in the plane), and ny is the sheet or the like. It is the refractive index in the direction perpendicular to the in-plane slow axis, and d is the thickness (nm) of the sheet or the like. In general, ny gives the minimum refractive index in the surface of a sheet or the like. Here, the xy coordinate system is set so that the xy plane is located within the surface of the sheet or the like.

In the present invention, Rth represents a refractive index anisotropy (retardation) value in the thickness direction, and is defined by the following formula (2).
Rth = {(nx + ny) / 2−nz} × d (2)
In the formula (2), nx, ny and d are the same as those defined in the formula (1). Nz is the refractive index in the thickness direction of the sheet or the like.
If there is no need to specifically discuss the phase advance or delay of the electric field of light oscillating in the slow axis (X axis) direction, the fast axis (Y axis) direction, and the thickness (Z axis) direction. , Re and Rth are expressed by absolute values of the formulas (1) and (2), and the sign is not particularly given. In the present specification, unless otherwise specified, the units of Re and Rth are expressed in nm. In-plane refractive index anisotropy (Re) and thickness direction refractive index anisotropy (Rth) are also collectively referred to as “optical anisotropy”.
Further, as the Re or Rth of a sheet or the like increases, the unevenness of Re of the sheet or the like increases.

(Optical sheet)
The optical sheet according to the present invention is an optical sheet disposed on the viewer side of the image generation panel, and includes a transparent substrate A and a polarized light scattering particle layer, and the polarized light scattering particle layer is formed of the transparent substrate A. It is arranged on the image generation panel side.

The optical sheet according to the present invention is generated on the surface of the image display device when the polarization scattering particle layer is disposed on the image generation panel side of the transparent substrate A and used as a surface material of the image display device. It is possible to prevent or reduce rainbow-colored appearance unevenness (hereinafter sometimes simply referred to as “rainbow unevenness”). When observing an image display device, if glasses such as sunglasses having a polarizing filter function are passed, rainbow unevenness is particularly easily observed. However, by using the optical sheet according to the present invention, the glasses are passed through. Even in this case, rainbow unevenness is not observed on the surface of the image display device, or is difficult to observe.
Further, when the optical sheet of the present invention is made of a material having a small optical anisotropy as the transparent substrate A, the brightness of the image display device is increased when used as a surface material of the image display device. improves.
At present, the principle and mechanism of the reason why the generation of rainbow unevenness or the improvement of luminance is prevented by the polarized light scattering particle layer containing specific polarized light scattering particles is unknown.

The layer structure of the optical sheet according to the present invention will be described with reference to the drawings. The optical sheet 200 according to the present invention can be configured as shown in FIGS.
In these drawings, for the convenience of illustration, the scale of each member and the dimensional ratio between the members may be illustrated as enlarged, reduced, or changed from the original size as appropriate. Also, the details of the surface of each member and the fine structure inside are omitted for the purposes of the present invention.
FIG. 1 shows an optical sheet 200 in which a polarized light scattering particle layer 20 is disposed on the transparent substrate A10 on the image generation panel 100 side.

  In FIG. 2, the functional layer 30 is disposed on the observer side of the transparent substrate A10, and the polarized light scattering particle layer 20 is disposed on the image generation panel 100 side of the transparent substrate A10. The functional layer 30 may be one layer or two or more layers. Although not shown, one or more functional layers may be provided between the transparent substrate A10 and the polarized light scattering particle layer 20 or on the image generation panel 100 side of the polarized light scattering particle layer 20. .

  In FIG. 3, the polarized light scattering particle layer 20 and the functional layer 30 are arranged in this order from the side close to the transparent substrate 10 on the image generation panel 100 side of the transparent substrate A10. The functional layer 30 may be one layer or two or more layers. Further, although not shown, one or more functional layers may be further provided between the transparent substrate A10 and the polarized light scattering particle layer 20 or on the observer side of the transparent substrate A10.

  In the optical sheet according to the present invention, when two Re are defined on the surface of the optical sheet, and Re1 and Re2, respectively, | Re1-Re2 | ≦ 400 nm, more preferably | Re1-Re2 | ≦ 50 nm. This is preferable because the luminance of the image display device can be improved uniformly.

Although the thickness of the optical sheet which concerns on this invention is not specifically limited, Usually, it is 31-550 micrometers.
Further, the transmittance of the optical sheet according to the present invention is not particularly limited, but is preferably 60% or more, and more preferably 80% or more. In the present invention, the transmittance means an average value of light transmittance in the visible light region of 380 to 780 nm. The light transmittance can be measured using a value measured in the air at room temperature using an ultraviolet-visible spectrophotometer (for example, UV-3100PC (product name) manufactured by Shimadzu Corporation).

  The haze of the optical sheet according to the present invention is not particularly limited, but is preferably 90% or less. In particular, when image sharpness and brightness are required, 70% or less is more preferable, and 60% or less is more preferable. In the present invention, haze is a haze value determined in accordance with JIS K7136, using a general haze meter (for example, product number: HM-150, manufactured by Murakami Color Research Laboratory), Values measured in the air at room temperature can be used.

  Hereinafter, the transparent substrate A, the polarized light scattering particle layer, and the functional layer constituting the optical sheet according to the present invention will be described.

(Transparent substrate A)
The transparent substrate A is a member used as a substrate of the optical sheet according to the present invention.
It does not specifically limit as the transparent base material A used in this invention, The well-known transparent base material used for the surface material of an image display apparatus can be used.
The transparent substrate A used in the present invention is not particularly limited, but preferably Re ≦ 1200 nm. When Re of the transparent substrate A is larger than 1200 nm, it is necessary to contain a large amount of polarized light scattering particles in the polarized light scattering particle layer in order to eliminate rainbow unevenness generated in the image display device. It is because the transparency of an optical sheet will fall and the visibility of the screen of an image display device will fall when there is too much content. In the present invention, “visibility” means transmission clarity (measurable in accordance with JISK-7105).
Further, from the viewpoint of improving luminance, the transparent substrate A used in the present invention preferably has Re ≦ 1200 nm, particularly preferably Re ≦ 800 nm and Rth ≦ 800 nm. By combining a transparent base material with small optical anisotropy and a polarized light scattering particle layer described later, the brightness of an image incident from the polarized light scattering particle layer side is improved.
As the transparent substrate A used in the present invention, Re ≦ 400 nm and Rth ≦ 400 nm are preferable, and Re ≦ 150 nm and Rth ≦ 150 nm are more preferable from the viewpoint of further improving the luminance. More preferably, Re ≦ 50 nm and Rth ≦ 50 nm.

The material of the transparent substrate A is not particularly limited, and for example, a resin substrate can be used, and a glass substrate can be used as a material having small optical anisotropy. Examples of the resin base material include (meth) acrylic resin, polystyrene resin, polycarbonate (PC) resin, polyethylene terephthalate (PET), polybutylene terephthalate, polyester resin such as polyethylene naphthalate, triacetyl cellulose (TAC), and the like. General-purpose plastics such as cellulose resin, urethane resin, vinyl chloride-vinyl acetate copolymer, polypropylene (PP), and cycloolefin polymer (COP). Among these, as a material for obtaining a resin base material having a small optical anisotropy, polypropylene, cycloolefin polymer, polycarbonate, triacetyl cellulose (TAC), or the like can be used.
Further, a glass substrate can be used as the transparent substrate A having a small optical anisotropy. As a material for the glass substrate, soda glass, potash glass, quartz glass, lead glass and the like are used.

  Although the thickness of the said transparent base material A is not specifically limited, Usually, it is 30-500 micrometers. Among them, from the viewpoint of improving luminance and maintaining high transmittance, although depending on the material, 30 to 300 μm is preferable, and 30 to 150 μm is more preferable.

  The transmittance of the transparent resin substrate A is not particularly limited, but is preferably 80% or more.

(Polarized scattering particle layer)
The polarized light scattering particle layer used in the present invention is a layer containing polarized light scattering particles, and even if the polarized light scattering particles are dispersed in a matrix, they are attached in layers to the interface of other layers. It may be a thing. The brightness of the image display device can be improved by disposing the transparent resin substrate A having a small specific optical anisotropy on the viewer side of the polarized light scattering particle layer.

[Polarized scattering particles]
Polarized scattering particles refer to particles that can convert linearly polarized light into non-polarized light close to natural light with high efficiency when used as the polarized light scattering particle layer.
The action of the polarized light scattering particles is described in terms of phenomenon as follows. For example, two polarizing plates that transmit only specific linearly polarized light are prepared, and the direction of the transmission axis (that is, the direction in which the light (component) in which the electric field vector vibrates can be transmitted) is orthogonal to these polarizing plates. When superposed, light is not transmitted at all. On the other hand, when a polarization scattering particle layer is interposed between two polarizing plates whose transmission axes are orthogonal to each other, very bright light is transmitted though the transmission axis directions are orthogonal. This phenomenon is caused by the fact that linearly polarized light that has passed through the polarizing plate on the back side passes through the polarized light scattering particle layer, and is non-polarized light that is close to natural light, that is, polarized light that is orthogonal to the polarization component parallel to the transmission axis direction of the observer-side polarizing plate. Non-polarized light is incident on the polarizing plate on the viewer side, and the transmission axis direction of the polarizing plate on the viewer side coincides with the vibration direction of the electric field vector. It means that light (component) reaches the observer.
According to the present invention, by arranging a layer containing polarized scattering particles having the above-described characteristics on the observer side on the image generation panel side, rainbow unevenness generated on the surface material of the image display device can be prevented or reduced. Further, when a transparent substrate A having a small optical anisotropy is used, the luminance can be improved.

The polarized light scattering particles used in the present invention include crystalline polymers having a spherulite structure.
In the present invention, the spherulite structure is a structure unique to a crystalline polymer formed by three-dimensional isotropic or radial growth of polymer fibrils from one or more cores.
Among the polarized scattering particles, among the crystalline polymers having a spherulite structure, it is preferable that the single particle itself has a spherulite structure. In the present invention, the single particle itself has a spherulite structure is a spherulite structure formed by three-dimensionally or radially growing polymer fibrils from a single or a plurality of cores near the center of one single particle. It means that.
The spherulite structure can be confirmed by observing the cross section of the particle using a scanning electron microscope (SEM) or a transmission electron microscope (TEM).

The polarized light scattering particles are preferably polyamide from the viewpoint of thermal stability.
Examples of the polyamide include thermoplastic polyamides obtained by ring-opening polymerization of cyclic amides, polycondensation of amino acids, polycondensation of dicarboxylic acid and diamine, and the like. Examples of raw materials used for ring-opening polymerization of cyclic amides include ε-caprolactam, ω-laurolactam, and the like, and raw materials used for polycondensation of amino acids include ε-aminocaproic acid, ω-aminododecanoic acid, ω- Examples of the raw material used for polycondensation of dicarboxylic acid and diamine include dicarboxylic acids such as succinic acid, adipic acid, sebacic acid, 1,4-cyclohexyldicarboxylic acid, and derivatives thereof, ethylenediamine, hexa Examples include diamines such as methylene diamine, 1,4-cyclohexyl diamine, pentamethylene diamine, and decamethylene diamine.

These polyamides may be further copolymerized with a small amount of an aromatic component such as terephthalic acid, isophthalic acid, and m-xylylenediamine. Of these combinations of monomers, those having a melting point of the polyamide after polymerization of 280 ° C. or higher are preferable because of high thermal stability. The polyamide resin of the present invention preferably has a melting point of 280 to 330 ° C, and most preferably has a melting point of 290 to 310 ° C.
Specific examples of the polyamide include polyamide 46 (melting point Tm = 290 ° C.), polyamide 6T / 66 (Tm = 310 ° C.), polyamide 6T / 6I (Tm = 320 ° C.), polyamide 6T / 6I / 66 (Tm = 310 ° C), polyamide 6T / N-5T (Tm = 305 ° C), polyamide 9T (Tm = 306 ° C), and mixtures or copolymer resins thereof. Among these, polyamide 46, polyamide 9T, and polyamide 6T / 66 are preferable because they have high crystallinity and easily form a spherulite structure.
In the name of the polyamide, each polyamide has the following structure.
Polyamide 46: Copolymer of 1,4-tetramethylenediamine and adipic acid.
Polyamide 6T / 66: A copolymer of 1,6-hexamethylenediamine, terephthalic acid and adipic acid.
Polyamide 6T / 6I: A copolymer of 1,6-hexamethylenediamine, terephthalic acid and isophthalic acid.
Polyamide 6T / 6I / 66: A copolymer of 1,6-hexamethylenediamine, terephthalic acid, isophthalic acid and adipic acid.
Polyamide 6T / N-5T: A copolymer of 1,6-hexamethylenediamine, 1,5-pentamethylenediamine and terephthalic acid.
Polyamide 9T: A copolymer of 1,9-nonanediamine and terephthalic acid.

  The molecular weight of the polyamide is usually 2,000 to 100,000, preferably 5,000 to 40,000.

  The shape of the polarized light scattering particles is not particularly limited, but the envelope shape preferably includes spherical or substantially spherical particles such as spheres, spheroids, and polyhedrons. In the present invention, the substantially spherical particles include true spherical particles, particles having irregular surfaces, and particles having a shape similar to a desert rose as described in JP 2010-132768 A And Among these, 70% by mass or more of the polarized light scattering particles are preferably substantially spherical particles, and more preferably 80% by mass or more are substantially spherical particles. When substantially spherical particles are present in the above range or more, the fluidity as a powder material is improved.

The polarized light scattering particles preferably have a ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn) of 1.0 to 2.0, 1.0 to 1 .8 is more preferable, and 1.0 to 1.5 is still more preferable. If Dv / Dn is smaller than 2.0, the dispersion of the particle diameter is small and it can be uniformly dispersed.
The volume average particle size and the number average particle size of the polarized light scattering particles can be measured using, for example, a particle size analyzer (trade name “Multisizer” manufactured by Beckman Coulter).

  The particle diameter of the polarized light scattering particles is not particularly limited, but the number average particle diameter is preferably 0.1 to 30 μm, more preferably 0.5 to 20 μm, and still more preferably 1 to 15 μm. . When the number average particle diameter is smaller than the above range, it may be difficult to form a spherulite structure. When the number average particle diameter is larger than the above range, it may be difficult to form a uniform polarized light scattering particle layer.

The polarized light scattering particles are preferably porous particles because they easily scatter polarized light.
Among them, the porous particles preferably have a BET specific surface area of 0.1 to ²⁰⁰ m ² / g, more preferably 1 to 180 m ² / g, and particularly preferably ² to 150 m ² / g. This is because within this range, there is little aggregation of the polarized light scattering particles, and handling at the time of dry powder is easy.
The porous particles preferably have an average pore diameter of 0.01 to 0.5 μm, more preferably 0.02 to 0.3 μm.

  The refractive index of the polarized light scattering particles is not particularly limited, but is usually 1.30 to 1.70.

  Various materials can be used as the polarized light scattering particles used in the present invention. In particular, porous spherical particles made of a transparent resin are preferable. Typically, polyamide resin, polyester resin, polyurethane resin, acrylic resin, polycarbonate resin are used. Spherical particles of a crystalline polymer having a spherulite structure having a geometric structure as described in WO 2007/119959 republished publication, JP 2010-132768 A, etc. are preferable. Among them, porous spherical particles (hereinafter also referred to as polyamide porous substantially spherical particles) made of polyamide resin spherulites, as described in WO2007 / 119959 republished publication, JP2010-132768A, and the like. ) Is preferred. Hereinafter, the polyamide porous substantially spherical particles which are preferable polarized light scattering particles will be described.

<Polyamide porous substantially spherical particles>
The polyamide porous substantially spherical particles have a porosity index (RI) of preferably 3 to 180, more preferably 5 to 150. If the porosity index is smaller than the above range, the degree of porosity may be low, and the light scattering property may be insufficient. On the other hand, if the porosity index is larger than the above range, the shape as particles may become unstable.

  Here, the porosity index (RI) is defined as the ratio of the specific surface area of the porous spherical particles to the specific surface area of the spherical particles having a smooth surface having the same particle diameter. Can be represented.

RI = S / S ₀ (3)
(In formula (3), RI is the porosity index, S is the specific surface area of the porous particles [m ² / g], and S ₀ is the specific surface area of the spherical particles having the same particle diameter and smooth surface [m ^2]. / G], which is calculated by the following equation (4).)

S ₀ = 6 / (ρd _obs ) (4)
(In formula (4), d _obs is the observed number average spherical particle diameter [m], and ρ is the density of the polyamide [kg / m ³ ].)

The bulk density of the polyamide porous substantially spherical particles is preferably 0.01 to 0.5 g / cm ³ . More preferably, it is 0.02-0.4 g / cm < ³ >.

  The amount of boiled linseed oil absorbed by the method according to JIS K 5101 of the polyamide porous substantially spherical particles is 150 to 800 ml / 100 g, more preferably 200 to 700 ml / 100 g. If the amount of oil absorption is too small, the surface of the polyamide porous substantially spherical particles may be crushed, and the light scattering property may decrease.

  The degree of crystallinity of the polyamide porous substantially spherical particles is not particularly limited, but is preferably 35% or more, and more preferably 40% or more. When the crystallinity is 35% or more, the thermal stability is excellent and the polarization scattering property can be improved. The degree of crystallinity can be determined from the ratio of the heat of fusion measured using a differential scanning calorimeter (DSC) to the heat of crystal fusion.

The polyamide porous substantially spherical particles can be produced by dissolving the polyamide in a good solvent, lowering the solubility of the solution in the polyamide, and precipitating the polyamide. For example, although it is a non-solvent for polyamide at low temperatures, it is dissolved by using a solvent that sufficiently dissolves polyamide at high temperatures and dispersing the polyamide in the solvent, then increasing the temperature and increasing the solubility of the solvent in polyamide. After that, by reducing the temperature of the solution to reduce the solubility of the solvent in the polyamide, the polyamide was dissolved in a method of precipitating the polyamide or in a good solvent that dissolves the polyamide in the range from about room temperature to about 100 ° C. The method of reducing the solubility with respect to the polyamide of a solvent by mixing the polyamide solution with the non-solvent which cannot dissolve polyamide at room temperature vicinity is mentioned.
Moreover, as the polyamide porous substantially spherical particles, commercially available products such as POMP manufactured by Ube Industries, Ltd. can be used.

  The polarized light scattering particle layer of the present invention may contain additives such as conventionally known light diffusing agents, polymerization initiators, leveling agents and the like as necessary in addition to the polarized light scattering particles.

The polarized light scattering particle layer used in the present invention may be formed by dispersing the polarized light scattering particles in a matrix.
Examples of the matrix used in this case include (meth) acrylic resin, polystyrene resin, polycarbonate resin, polyester resin, cellulose resin, urethane resin, vinyl chloride-vinyl acetate copolymer, and the like. One type of resin selected from these resins or a mixture of two or more types is used.

The polarized light scattering particle layer used in the present invention is not particularly limited. For example, a polarized light scattering particle composition containing at least the polarized light scattering particles in a solvent is applied to the surface of another layer and dried. Thus, a polarized light scattering particle layer can be formed. The polarized light scattering particle composition may contain the above-described additives and a resin that serves as a matrix.
Further, the polarized light scattering particle layer is formed by pasting a polarized light scattering particle layer previously formed into a sheet shape onto a transparent substrate via a general adhesive such as urethane, acrylic or polyester adhesive. You can also

  The thickness of the polarized light scattering particle layer is not particularly limited, but is usually 3 to 50 μm.

  The occupation ratio of the polarized light scattering particles in the polarized light scattering particle layer is preferably 55% or less. This is because if the occupation ratio of the polarized light scattering particles is larger than this, the transparency of the optical sheet is lowered and the visibility is poor.

The occupancy ratio of the polarized light scattering particles can be generally measured by using an optical microscope (or a digital microscope) and calculating the projected area ratio of the polarized light scattering particles.
The occupation ratio of the polarized light scattering particles in the polarized light scattering particle layer can be adjusted by the content of the polarized light scattering particles in the polarized light scattering particle layer. When the content of the polarized light scattering particles is large, the occupation ratio of the polarized light scattering particles is increased, and when the content of the polarized light scattering particles is small, the occupation ratio of the polarized light scattering particles is decreased.

The occupation ratio of the polarized light scattering particles in the polarized light scattering particle layer is appropriately adjusted depending on the optical properties of the transparent substrate A or other layers on the viewer side of the polarized light scattering particle layer.
Specifically, the Re value of the transparent substrate A or the Re value of the other layer on the viewer side of the polarized light scattering particle layer is the largest Re value (hereinafter, sometimes simply referred to as “Re value”). In order to eliminate rainbow unevenness, the larger the is, the higher the occupancy ratio of the polarized light scattering particles in the polarized light scattering particle layer (hereinafter sometimes simply referred to as “particle occupation ratio”). That is, the particle occupancy is adjusted according to the Re value so as to be within the range of the shaded portion shown in FIG. This is because rainbow unevenness is more likely to occur on the surface of the image display device as the Re value is larger, and the effect of eliminating rainbow unevenness is improved as the particle occupancy is higher. FIG. 6 is a conceptual diagram showing the relationship between the Re value and the particle occupancy, and does not specify a numerical value.
As described above, the particle occupancy is appropriately adjusted according to the Re value. However, when Re ≦ 1200 nm, the particle occupancy is generally 20 to 75%.

(Functional layer)
The optical sheet of the present invention preferably has a functional layer. In the present invention, the functional layer is a layer that is disposed on the viewer side of the image generation panel and imparts some capable function to the image display device. For example, an optical function for improving the quality of the generated image And other functional layers for improving quality other than the display quality of the image display device.
Specifically, such as an antireflection layer, an antiglare layer, a neon light absorption layer, a colored filter layer, an optical functional layer for improving the quality of the generated image, an ultraviolet absorption layer, a near infrared absorption layer. Other functional layers for improving quality other than the display quality of the image display device, such as a hard coat layer and an antifouling layer, can be mentioned. In the present invention, the functional layer may be a single layer or a laminated structure of two or more layers.
Hereinafter, specific examples of main functional layers will be described, but the functional layers of the present invention are not limited thereto.

[1. Hard coat layer]
The functional layer used in the present invention can be a hard coat layer. The hard coat layer is a layer that imparts scratch resistance and abrasion resistance to the object surface. In the present invention, the hard coat layer exhibits a hardness of H or higher in the pencil hardness test shown in JIS K5600-5-4: 1999. Say.

The hard coat layer is usually formed using an ionizing radiation curable resin. As the ionizing radiation curable resin for forming the hard coat layer, a resin having an acrylate functional group is preferable. Specific examples include relatively low molecular weight polyester resins, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol polyether resins, and polyhydric alcohols. . Also, di (meth) acrylates such as ethylene glycol di (meth) acrylate and pentaerythritol di (meth) acrylate monostearate; tri (meth) such as trimethylolpropane tri (meth) acrylate and pentaerythritol tri (meth) acrylate Acrylates; tetrafunctional or higher polyfunctional (meth) acrylates such as pentaerythritol tetra (meth) acrylate derivatives and dipentaerythritol penta (meth) acrylates; monomers of polyfunctional compounds such as; oligomers such as epoxy acrylate and urethane acrylate, etc. Can also be mentioned.
In addition, inorganic particles made of silica, alumina, etc. whose surface is coated to the extent that transparency is not impaired, or organic particles made of polyamide resin, silicon resin, urea resin, etc. are used to form a covalent bond between the particles and the hard coat component. Alternatively, a hard coat layer with improved hardness may be used.

  The film thickness after curing of the hard coat layer is preferably 0.1 μm or more, more preferably 0.8 μm or more, while the film thickness is preferably 100 μm or less, more preferably 20 μm or less. If the film thickness is 0.1 μm or more, sufficient hard coat performance can be easily obtained, and if it is 100 μm or less, sufficient strength can be easily obtained against external impacts.

[2. Antiglare layer]
The functional layer used in the present invention can be an antiglare layer. The antiglare layer can be formed by forming light diffusive fine irregularities on the surface of the resin layer not containing particles, but is usually composed of an ionizing radiation curable resin and antiglare layer particles. By including particles for the antiglare layer, antiglare performance can be imparted in addition to scratch resistance.

  The ionizing radiation curable resin can be appropriately selected from those preferably used for the hard coat layer.

  The anti-glare layer particles prevent specular reflection of light incident on the anti-glare layer from the viewer side, and scatter and reflect, thereby preventing glare on the surface of the optical sheet and reflection of room lighting. As the shape of the particles for the antiglare layer, for example, a spherical shape may be used. Examples of the spherical shape include a true spherical shape and an elliptical shape. Preferably, a spherical shape is used.

  The material for the antiglare layer particles may be either inorganic or organic. The particles for the antiglare layer usually exhibit antiglare properties, and it is preferable to use a transparent material. Examples of such antiglare layer particles include silica beads and the like as inorganic beads, and plastic beads made of a resin such as (meth) acrylic resin as organic beads.

  When plastic beads are used, those having a refractive index of 1.40 to 1.60 are preferably used. The reason for limiting the refractive index of the plastic beads to the above range is as follows. That is, the refractive index of an ionizing radiation curable resin, particularly an acrylate or methacrylate resin is usually 1.45 to 1.55, and plastic beads having a refractive index as close as possible to the refractive index of the ionizing radiation curable resin should be selected. This is because the antiglare property can be improved without impairing the transparency of the coating film.

  Specific examples of plastic beads having a refractive index close to that of ionizing radiation curable resin include acrylic beads (refractive index: 1.49) such as polymethyl methacrylate beads, polycarbonate beads (refractive index: 1.58), Polystyrene beads (refractive index: 1.59), melamine beads (refractive index: 1.57), polyvinyl chloride beads (refractive index: 1.54), polyacryl styrene beads (refractive index: 1.57), acrylic- Examples thereof include styrene beads (refractive index: 1.54) and polyethylene beads (refractive index: 1.53). As long as the refractive index is in the above range, other materials can be used.

  The particle diameter of these antiglare layer particles is preferably 3 μm or more and 8 μm or less. Further, the content of the particles for the antiglare layer is preferably 2 parts by weight or more, more preferably 10 parts by weight or more with respect to 100 parts by weight of the ionizing radiation curable resin. Part or less, more preferably 25 parts by weight or less.

  When the antiglare layer is formed by applying and curing the coating liquid, it is preferable to ensure dispersion of the particles for the antiglare layer in the coating liquid. Specifically, in the coating liquid in which the particles for the antiglare layer are mixed in the ionizing radiation curable resin, it may be necessary to well agitate and disperse the particles for the antiglare layer that are precipitated during use. In order to eliminate such inconvenience, silica beads having a particle size of usually 0.5 μm or less, preferably 0.1 μm or more and 0.25 μm or less as an anti-settling agent in the coating solution to form an antiglare layer. May be added. In addition, although this silica bead is effective in preventing sedimentation of the organic filler as it is added, it may affect the transparency of the coating film. Therefore, it is preferable that the content of the silica beads is within a range that does not impair the transparency of the coating film and can prevent sedimentation. Specifically, it is preferable to add silica beads less than about 0.1 parts by weight with respect to 100 parts by weight of the ionizing radiation curable resin.

  The film thickness after curing of the antiglare layer is preferably 0.1 μm or more, more preferably 0.8 μm or more, while the film thickness is preferably 100 μm or less, more preferably 20 μm or less. If the film thickness is 0.1 μm or more, sufficient hard coat performance can be easily obtained, and if it is 100 μm or less, sufficient strength can be easily obtained against external impact.

In the antiglare layer, the average particle diameter of the particles for the antiglare layer is R (μm), the ten-point average roughness of the unevenness on the surface of the antiglare layer is Rz (μm), and the unevenness average interval on the surface of the antiglare layer is When Sm (μm) is set and the average inclination angle of the concavo-convex portion is θa, it is preferable to satisfy the following four expressions simultaneously.
30 ≦ Sm ≦ 200,
0.90 ≦ Rz ≦ 1.60,
1.3 ≦ θa ≦ 2.5,
0.3 ≦ R ≦ 10

According to another preferred embodiment of the antiglare layer, when the refractive indexes of the antiglare layer particles and the ionizing radiation curable resin are n1 and n2, respectively, the following formula is satisfied: An antiglare layer having a haze value inside the antiglare layer of 55% or less is preferred.
Δn = | n1-n2 | <0.1

[3. Antistatic layer]
The functional layer used in the present invention can be an antistatic layer. The antistatic layer is a layer that provides a function of suppressing the generation of static electricity to prevent adhesion of dust or preventing external static electricity damage when incorporated in a liquid crystal display or the like. As the performance of the antistatic layer in this case, the surface resistance is preferably 10 ¹² Ω / □ or less. However, even when the surface resistance is 10 ¹² Ω / □ or more, by providing the antistatic layer, dust adhesion can be suppressed more easily than the surface material having no antistatic layer.

  When the antistatic layer is formed of a resin, the antistatic layer contains a resin and an antistatic agent. Here, as the resin for forming the antistatic layer, the same resin as the ionizing radiation curable resin used in the hard coat layer can be used.

  Examples of the antistatic agent contained in the antistatic layer-forming resin include various cationic antistatic agents having a cationic group such as a quaternary ammonium salt, a pyridinium salt, and first to third amino groups; sulfonic acid Anionic antistatic agents having anionic groups such as bases, sulfate ester bases, phosphate ester bases, phosphonate bases; amphoteric antistatic agents such as amino acids and aminosulfate esters; amino alcohols, glycerols, polyethylene glycols Nonionic antistatic agents such as those based on conductive polymers such as polyacetylene, polyaniline, polythiophene, etc. combined with a dopant (eg, 3,4-ethylenedioxythiophene (PEDOT)); tin and titanium Such as organometallic compounds such as alkoxides and their acetylacetonate salts Various surfactant type antistatic agents such as genus chelate compounds; and the above-mentioned antistatic agent increasing the molecular weight of the polymeric antistatic agent and the like. In addition, a tertiary amino group, a quaternary ammonium group, a monomer or oligomer having a metal chelate portion and polymerizable by ionizing radiation, and an organometallic compound such as a coupling agent having a functional group polymerizable by ionizing radiation And other polymerizable antistatic agents.

  Examples of other antistatic agents include fine particles having a particle size of 100 nm or less, such as tin oxide, tin-doped indium oxide (ITO), antimony-doped tin oxide (ATO), indium-doped zinc oxide (AZO), antimony oxide, and indium oxide. be able to. In particular, when the particle size is 100 nm or less, which is less than the wavelength of visible light, it is easy to ensure the transparency of the antistatic layer, and the advantage that the transparency of the surface material is hardly impaired is exhibited.

  By mixing the antistatic agent in the coating liquid for forming the hard coat layer and the antiglare layer, two properties of antistatic performance and hard coat performance, or two properties of antistatic performance and antiglare performance are provided. It becomes easy to obtain a coating film having improved properties at the same time.

[4. Antireflection layer]
The functional layer used in the present invention can be an antireflection layer. Such an antireflection layer has as its essential layer a low refractive index layer made of a material having a relatively lower refractive index than the layer immediately below it (such as the transparent substrate A or the high refractive index layer). Ideally, the refractive index of the low refractive index layer is the square root of the refractive index of the layer immediately below, as already known in the field of optics. For example, when the transparent substrate A is made of polyethylene terephthalate having a refractive index of 1.65, 1.29 (= (1.65) ^−1/2 ) is an ideal value for the refractive index of the low refractive index layer. . However, it is often difficult to select a material having such an optimum refractive index from materials that are actually available, have other physical properties such as durability, and have an appropriate price. In that case, a material close to this ideal value is selected as much as possible from materials that can be actually selected.

(Low refractive index layer)
The low refractive index layer used in the present invention usually contains mainly an ionizing radiation curable resin and low refractive index particles for adjusting the refractive index. As the ionizing radiation curable resin, the same as the hard coat layer can be used. Moreover, what is necessary is just to make it the same as a hard-coat layer also about the photoinitiator used as needed, various additives, a formation method, etc.
Examples of the low refractive index particles for adjusting the refractive index include fine particles having a particle diameter of 100 nm or less, and silicon oxide, fluoride and the like are used. Specifically, SiO ₂ (refractive index n = 1.45), MgF ₂ (refractive index n = 1.38), LiF (refractive index n = 1.36), NaF (refractive index n = 1.33). , CaF ₂ (refractive index n = 1.44), 3NaF · AlF ₃ (refractive index n = 1.4), AlF ₃ (refractive index n = 1.37), Na ₃ AlF ₆ (refractive index n = 1. 33). Examples of the organic material include a fluorine-based organic compound (fluororesin), a silicon-based organic compound, and the like.
Further, fine particles having voids may be used for the low refractive index particles. The fine particles having voids form a structure in which fine particles are filled with gas and / or a porous structure containing gas, and are in inverse proportion to the gas occupancy ratio in the fine particles compared to the original refractive index of the fine particles. It means fine particles having a reduced refractive index.
The low refractive index layer may be a layer formed by forming a material listed as the material of the low refractive index particles by a vapor deposition method such as chemical vapor deposition (CVD) or physical vapor deposition (PVD). .

(High refractive index layer)
The antireflection layer used in the present invention has a refractive index relatively higher than that of the transparent substrate A between the low refractive index layer and the transparent substrate A, in addition to the essential low refractive index layer. By inserting a high refractive index layer made of a material, the relationship between the refractive indices of the low refractive index layer and the layer immediately below can be brought close to the optimum value, and better antireflection can be imparted. The high refractive index layer usually contains mainly an ionizing radiation curable resin and high refractive index particles for adjusting the refractive index. As the ionizing radiation curable resin, the same as the hard coat layer can be used. Moreover, what is necessary is just to make it the same as a hard-coat layer also about the photoinitiator used as needed, various additives, a formation method, etc.

  Examples of the high refractive index particles for adjusting the refractive index include fine particles having a particle diameter of 100 nm or less, such as zinc oxide (refractive index: 1.90), titania (refractive index: 2.3 to 2.7). ), Ceria (refractive index: 1.95), tin-doped indium oxide (refractive index: 1.95), antimony-doped tin oxide (refractive index: 1.80), yttria (refractive index: 1.87), zirconia (refractive) Rate: 2.0).

  The particles for adjusting the refractive index are preferably those having a refractive index higher than that of the ionizing radiation curable resin. The refractive index is determined by the content of particles for adjusting the refractive index in the high refractive index layer. That is, since the refractive index increases as the content of the particles for adjusting the refractive index increases, the refractive index can be freely adjusted in the range of 1.46 to 2.00 by changing the composition ratio of the ionizing radiation curable resin and the particles. Can be controlled.

  The high refractive index layer may be a layer formed by forming a material listed as the material of the high refractive index particles by a vapor deposition method such as chemical vapor deposition (CVD) or physical vapor deposition (PVD). .

  In the optical sheet according to the present invention, when the high refractive index layer is provided, the high refractive index layer is provided at a position closer to the image generation panel than the low refractive index layer. Moreover, in this form, when providing a hard-coat layer further, the said hard-coat layer is provided in the surface at the side of the transparent base material A of the said high refractive index layer.

  The functional layer is formed of a transparent base material, a polarized light scattering particle layer, and other functional layers through a general adhesive such as a urethane-based, acrylic-based, or polyester-based adhesive. It can also be formed by pasting together.

  In addition, it is preferable that the optical sheet of this invention does not have a layer which is Re> 1200nm on the observer side rather than the said polarized light scattering particle layer from the point which is excellent in the visibility of the screen of an image display apparatus. Further, from the viewpoint of improving the luminance of the image display device, it is preferable not to include a layer satisfying Re> 800 nm or Rth> 800 nm.

(Image generation panel)
In the present invention, an image generation panel is a panel-like member that is a central unit that generates and controls an image. For example, a liquid crystal display panel, a plasma display panel (PDP), etc. are mentioned.
When the image generation panel is a liquid crystal display panel, it is composed of a rear side polarizing plate / liquid crystal cell / observer side polarizing plate, and in the case of a plasma display panel, a cellular discharge having a rear glass substrate / dielectric layer / phosphor. This is a PDP module comprising a space / dielectric layer / observer side glass substrate.

(Image display device)
The image display device according to the present invention comprises a laminated structure including a transparent base material A and a polarized light scattering particle layer on the viewer side of the image generation panel, and the polarized light scattering particle layer generates an image of the transparent base material A. It is arranged on the panel side.

The image display apparatus according to the present invention includes a laminated structure including a transparent base material A and a polarized light scattering particle layer on the viewer side of the image generation panel, and the polarized light scattering particle layer generates an image of the transparent base material A. By being arranged on the panel side, rainbow unevenness generated on the surface can be prevented or reduced.
Moreover, the brightness | luminance improves the image display apparatus of this invention, when using what consists of a material with small optical anisotropy as the transparent base material A. FIG.
At present, the principle and mechanism of the reason why the generation of rainbow unevenness or the improvement of luminance is prevented by the polarized light scattering particle layer containing specific polarized light scattering particles is unknown.

The stacked structure of the image display device can be the same as the structure of FIGS. 1 to 3 similar to the optical sheet according to the present invention. In addition to the optical sheet, as shown in FIG. 4, for example, an air layer 40 may be interposed between the polarized light scattering particle layer 20 and the transparent substrate A10. Further, in this case, a second transparent substrate 11 may be used separately from the transparent substrate A10 as shown in FIG. The second transparent substrate 11 can also be arranged on the image generation panel side further than the polarized light scattering particle layer 20 as shown in FIG.
In addition to the image generation panel and the optical sheet of the present invention, the image display device according to the present invention includes the functional layer disposed as necessary, or further, constituent members (components) of various known image display devices. Appropriate combinations are configured. Such components include a backlight (back light source), a power source, circuits such as a tuning circuit and a video signal processing circuit, an electromagnetic shielding material, a housing, and the like.

As the transparent substrate A, the polarized light scattering particle layer, and the other layers constituting the image display device of the present invention, the same materials as the optical sheet of the present invention described above can be used.
In addition, it is preferable that the transparent base material A used for the image display apparatus of this invention is Re <= 1200nm from the point which is excellent in the visibility of the screen of an image display apparatus. From the same viewpoint, it is preferable not to have a layer with Re> 1200 nm closer to the viewer than the polarized light scattering particle layer.
From the viewpoint of improving the luminance of the image display device, the transparent substrate A preferably has Re ≦ 800 nm and Rth ≦ 800 nm. From the same viewpoint, it is preferable not to have a layer with Re> 800 nm or Rth> 800 nm closer to the viewer than the polarized light scattering particle layer.

(Use)
The image display device according to the present invention can be used for various applications. In particular, it can be used for display units of television receivers, measuring instruments, instruments, office equipment, medical equipment, computer equipment, telephones, electronic signboards, game machines, and the like.

  Hereinafter, the present invention will be described more specifically with reference to examples. These descriptions do not limit the present invention.

[Example A series]
Hereinafter, examples in which the evaluation of the presence or absence of rainbow unevenness and the measurement of the luminance ratio were performed will be shown as Example A series.

[Example A1]
(Preparation of polarization scattering particle composition)
Components of the following composition were sufficiently mixed in a mixer, and then filtered through a polypropylene filter having a pore size of 100 μm to prepare a polarized light scattering particle composition.
<Composition of polarization scattering particle composition>
-Matrix resin: Dipentaerythritol hexaacrylate (DPHA, 6 functional): 8 parts by weight-Polarized light scattering particle: PMP-DP (particle size: 10 μm, refractive index: 1.56) manufactured by Ube Industries, Ltd .: 2.1 weights Part / polymerization initiator: Ciba Japan Co., Ltd., Irgacure 184: 0.3 parts by weight Leveling agent: Dainichi Seika Co., Ltd., silicone (Part No. 10-28): 0.2 parts by weight Solvent: methyl isobutyl ketone: 30 parts by weight

(Production of optical sheet)
The polarized scattering particle composition obtained above on one side of a transparent substrate A, triacetylcellulose (TAC) film (manufactured by Fuji Film Holding, TF-80UL, film thickness 80 μm, Re: 5 nm, Rth: 40 nm) Was adjusted and applied so that the film thickness after drying was 25 μm, and dried at 70 ° C. for 60 seconds. Subsequently, it is cured by irradiating with an ultraviolet ray at an irradiation dose of 10 mJ / cm ² using an ultraviolet ray irradiating apparatus (manufactured by Fusion UV System Japan Co., Ltd., light source H bulb), and polarized scattering with a film thickness of 25 μm on the transparent substrate A. A particle layer was formed to obtain an optical sheet having a thickness of 105 μm.

[Example A2]
An optical sheet was produced in the same manner as in Example A1, except that a polycarbonate (PC) film (Pure Ace manufactured by Teijin Chemicals, film thickness: 100 μm, Re: 577 nm, Rth: 280 nm) was used as the transparent substrate A.

[Example A3]
An optical film further bonded onto a transparent substrate A of the optical sheet obtained in Example A1 via a PC film (Pure Ace manufactured by Teijin Chemicals Co., Ltd., film thickness 100 μm, Re: 135 nm, Rth: 80 nm) via an acrylic adhesive. A sheet was obtained. Hereinafter, a film that is further laminated on the transparent substrate A may be referred to as a “laminated film”, and is also referred to as a “laminated film (observer side)” in Table 1.

[Example A4]
An optical sheet was produced in the same manner as in Example A3, except that a PC film (Pure Ace manufactured by Teijin Chemicals Co., Ltd., film thickness: 100 μm, Re: 577 nm, Rth: 280 nm) was used as the transparent substrate A and the laminated film.

[Example A5]
In the preparation of the polarized light scattering particle composition, the addition amount of the polarized light scattering particles is 2.0 parts by weight, and the transparent substrate A is a PC film (Pure Ace manufactured by Teijin Chemicals, film thickness 100 μm, Re: 345 nm, Rth: 220 nm). An optical sheet was produced in the same manner as in Example A4, except that

[Example A6]
In the preparation of the polarized light scattering particle composition, the addition amount of the polarized light scattering particles is 2.2 parts by weight, and the transparent substrate A is a PC film (Pure Ace manufactured by Teijin Chemicals, film thickness 100 μm, Re: 810 nm, Rth: 320 nm). An optical sheet was produced in the same manner as in Example A4, except that

[Example A7]
In the preparation of the polarized light scattering particle composition, the amount of added polarized light scattering particles is 2.3 parts by weight, and the transparent substrate A is a PC film (Pure Ace manufactured by Teijin Chemicals, film thickness 100 μm, Re: 990 nm, Rth: 440 nm). An optical sheet was produced in the same manner as in Example A4, except that

[Example A8]
In the preparation of the polarization scattering particle composition, the addition amount of the polarization scattering particle is 2.4 parts by weight, and the transparent substrate A is a PC film (Pure Ace manufactured by Teijin Chemicals, film thickness 100 μm, Re: 1200 nm, Rth: 460 nm). An optical sheet was produced in the same manner as in Example A4, except that

[Comparative Example A1]
PC film (Pure Ace manufactured by Teijin Chemicals, film thickness 100 μm, Re: 577 nm, Rth: 280 nm) was used as the laminated film, and in the preparation of the polarized light scattering particle composition, the polarized light scattering particles (POMP-DP manufactured by Ube Industries, Ltd.) Instead, an optical sheet was prepared in the same manner as in Example A3, except that 2.1 parts by weight of GE Toshiba Silicone Tospearl (particle size: 10 μm, refractive index: 1.43) was added.

[Reference Example A1]
An optical sheet was prepared in the same manner as in Example A3, except that a polyethylene terephthalate (PET) film (A4100, film thickness 50 μm, Re: 1200 nm, Rth: 6000 nm) was used as the laminated film.

[Reference Example A2]
An optical sheet was produced in the same manner as in Example A1, except that a PET film (Toyobo, A4100, film thickness 50 μm, Re: 1200 nm, Rth: 6000 nm) was used as the transparent substrate A.

[Reference Example A3]
An optical sheet was produced in the same manner as in Reference Example A2, except that the amount of the polarized scattering particles added was 2.4 parts by weight in the preparation of the polarized scattering particle composition.

[Reference Example A4]
An optical sheet was prepared in the same manner as in Example A2, except that the amount of the polarized scattering particles added was 2.0 parts by weight in the preparation of the polarized scattering particle composition.

[Reference Example A5]
An optical sheet was produced in the same manner as in Example A4, except that the amount of the polarized light scattering particles added was 2.0 parts by weight in the preparation of the polarized light scattering particle composition.

[Reference Example A6]
An optical sheet was produced in the same manner as in Example A5 except that the amount of the polarized scattering particles added was 2.4 parts by weight in the preparation of the polarized scattering particle composition.

[Reference Example A7]
An optical sheet was produced in the same manner as in Example A6, except that the amount of added polarized scattering particles was 2.0 parts by weight in the preparation of the polarized scattering particle composition.

[Reference Example A8]
An optical sheet was produced in the same manner as in Example A7, except that the addition amount of the polarized light scattering particles was 2.2 parts by weight in the preparation of the polarized light scattering particle composition.

[Reference Example A9]
An optical sheet was produced in the same manner as in Example A7, except that in the preparation of the polarization scattering particle composition, the addition amount of the polarization scattering particles was 2.4 parts by weight.

[Reference Example A10]
An optical sheet was produced in the same manner as in Example A8, except that in the preparation of the polarized light scattering particle composition, the addition amount of the polarized light scattering particles was 2.1 parts by weight.

(Measurement of particle occupancy)
The particle occupancy ratio of the polarized light scattering particle layer of the optical sheet obtained in each example and each reference example of Example A series was measured. The particle occupancy was measured by calculating the projected area ratio of the polarized light scattering particles using an optical microscope.
Further, in the optical sheet obtained in Comparative Example A1, the particle occupancy of the particle layer containing Tospearl was measured by the same method as the measurement of the particle occupancy.

(Measurement of physical properties of optical sheet)
The transmittance and haze of the optical sheets obtained in each Example of the Example A series, Comparative Example A1, and each Reference Example were measured. The transmittance was measured in the atmosphere at room temperature using HM-150 manufactured by Murakami Color Research Laboratory. Haze was measured at room temperature and in the atmosphere using HM-150 manufactured by Murakami Color Research Laboratory Co., Ltd. according to JIS K 7136.

(With or without rainbow unevenness)
The surface of the polarizing plate which is not the light source side of the liquid crystal television (AQUAS (20 inches) manufactured by Sharp Corporation) which is not the light source side of the optical sheet obtained in each example of the example A series, comparative example A1 and each reference example. A polarizing scattering particle layer was placed on the (observer side surface) so as to be on the liquid crystal television side, and was bonded via an acrylic adhesive to obtain a liquid crystal television with an optical sheet. The white display state of the liquid crystal television with the optical sheet was visually observed through sunglasses having a polarizing filter function to evaluate the presence or absence of rainbow-like unevenness. The evaluation results obtained in each Example and Comparative Example are shown in Table 1, and the evaluation results obtained in each Reference Example are shown in Table 2.

(Luminance ratio)
The surface of the polarizing plate which is not the light source side of the liquid crystal television (AQUAS (20 inches) manufactured by Sharp Corporation) which is not the light source side of the optical sheet obtained in each example of the example A series, comparative example A1 and each reference example. A polarizing scattering particle layer was placed on the (observer side surface) so as to be on the liquid crystal television side, and was bonded via an acrylic adhesive to obtain a liquid crystal television with an optical sheet. The front luminance in white display of the liquid crystal television with the optical sheet was measured in the atmosphere at room temperature using BM-7 manufactured by Topcon Corporation. The relative value (%) of the luminance value when the luminance value measured in Comparative Example A1 is 100% is defined as the luminance ratio, the luminance ratio of each Example and Comparative Example is shown in Table 1, and the luminance ratio of each Reference Example Is shown in Table 2.

[Discussion (Example A Series)]
Regarding the evaluation results of the presence / absence of rainbow unevenness and the luminance ratio in Example A series, the discussion is shown below.

The optical sheets of Examples A1 to A8 include a transparent substrate A and a polarized light scattering particle layer, and the polarized light scattering particle layer is disposed on the image generation panel side of the transparent substrate A. Since it is the optical sheet of the invention, no rainbow-like unevenness was observed on the image display device by disposing it on the viewer side of the image generation panel. On the other hand, since the optical sheet of Comparative Example A1 has a particle layer containing Tospearl instead of the polarized light scattering particle layer, rainbow-like unevenness is observed on the image display device even if it is arranged on the viewer side of the image generation panel. It was done. Accordingly, it was found that when the optical sheet according to the present invention having a polarized light scattering particle layer is used as a surface material of an image display device, rainbow unevenness generated on the surface of the image display device can be prevented or reduced.
In addition, the optical sheets of Examples A1 to A6 are optical sheets according to the present invention including the transparent base material A and the polarization scattering particle layer, and the transparent base material A having a small optical anisotropy is used. By arranging on the viewer side of the panel, the brightness of the image display device could be improved as compared with the optical sheet of Comparative Example A1 having a particle layer containing Tospearl instead of the polarized light scattering particle layer. .
Among them, in Examples A1 to A5, the transparent substrate A has Re ≦ 800 nm and Rth ≦ 800 nm, and does not have a layer with Re> 800 nm or Rth> 800 nm closer to the viewer than the polarized light scattering particle layer. As compared with Comparative Example A1, the luminance was greatly improved.
In Example A8 and Example A9, the Re value of the transparent substrate A was high, and it was necessary to increase the particle occupancy of the polarized light scattering particle layer in order to eliminate rainbow unevenness. Therefore, the luminance was higher than that of Comparative Example A1. Although no improvement was observed, the luminance was practical enough for an image display device.
In the optical sheets of Reference Examples A1, A2, A4, A5, A7, A8, and A10, the particle occupancy of the polarized light scattering particle layer was too small with respect to the Re value of the transparent substrate A or the laminated film, so that rainbow unevenness occurred. did. In the optical sheets of Reference Examples A3, A6, and A9, although rainbow unevenness did not occur, the particle occupancy of the polarized light scattering particle layer was large, so that the haze was high and the luminance of the image display device was lowered.

[Example B series]
Hereinafter, examples where the luminance ratios of 1 to 3 were measured are shown as Example B series.

[Example B1]
(Preparation of polarization scattering particle composition)
Components of the following composition were sufficiently mixed in a mixer, and then filtered through a polypropylene filter having a pore size of 100 μm to prepare a polarized light scattering particle composition.
<Composition of polarization scattering particle composition>
-Matrix resin: Dipentaerythritol hexaacrylate (DPHA, 6 functional): 8 parts by weight-Polarized light scattering particles: manufactured by Ube Industries, Ltd., POMP-DP (particle size 10 μm, refractive index 1.56): 2 parts by weight Polymerization initiator: Ciba Japan Co., Ltd., Irgacure 184: 0.3 parts by weight Leveling agent: Dainichi Seika Co., Ltd. silicone (Part No. 10-28): 0.2 parts by weight Solvent: Methyl isobutyl ketone: 30 weights Part

(Formation of optical sheet)
On the single side of a polycarbonate (PC) film (Pure Ace manufactured by Teijin Chemicals, film thickness: 100 μm, Re: 138 nm, Rth: 75 nm), which is a transparent substrate A, the dried film of the polarized light scattering particle composition is dried. The coating was adjusted to a thickness of 25 μm and dried at 70 ° C. for 60 seconds. Subsequently, it is cured by irradiating with an ultraviolet ray at an irradiation dose of 10 mJ / cm ² using an ultraviolet ray irradiating apparatus (manufactured by Fusion UV System Japan Co., Ltd., light source H bulb), and polarized scattering with a film thickness of 25 μm on the transparent substrate A. A particle layer was formed to obtain an optical sheet having a thickness of 125 μm.

(Measurement of physical properties of optical sheet)
The | Re1-Re2 | value, transmittance and haze of the obtained optical sheet were determined.
Arbitrary two locations Re were determined on the surface of the obtained optical sheet, were set to Re1 and Re2, respectively, and the absolute value | Re1-Re2 | of the difference between Re1 and Re2 was determined to be 30 nm. In addition, Re is calculated | required by above-mentioned Formula (1), but the refractive index (nx) of the slow axis direction in the surface of an optical sheet, and the refractive index (ny) of a direction perpendicular | vertical to the slow axis in a surface are Using KOBRA-WR manufactured by Oji Scientific Instruments, room temperature was measured in the atmosphere.
The transmittance of the obtained optical sheet was 88.5%. The transmittance was measured in the atmosphere at room temperature using HM-150 manufactured by Murakami Color Research Laboratory.
The haze of the obtained optical sheet was 46.0%. The haze was measured at room temperature and in the atmosphere using HM-150 manufactured by Murakami Color Research Laboratory in accordance with JIS K 7136.

[Example B2]
As the transparent substrate A, instead of a PC film (Pure Ace manufactured by Teijin Chemicals, film thickness: 100 μm, Re: 138 nm, Rth: 75 nm), a triacetyl cellulose (TAC) film (manufactured by Fuji Film Holding, TF-80UL, An optical sheet was prepared in the same manner as in Example B1 except that a film thickness of 80 μm, Re: 5 nm, and Rth: 40 nm were used, and physical properties were measured. The obtained optical sheet had a thickness of 105 μm, | Re1-Re2 | was 2 nm, the transmittance was 89.8%, and the haze was 46.9%.

[Comparative Example B1]
Instead of polarized light scattering particles (POMP-DP manufactured by Ube Industries, Ltd.), Tospearl manufactured by GE Toshiba Silicone (particle size: 10 μm, refractive index: 1.43) is used as a transparent substrate A, and a PC film (Teijin Chemicals Pure) Example except that polyethylene terephthalate (PET) film (Toyobo, A4100, film thickness 50 μm, Re: 1200 nm, Rth: 6000 nm) was used instead of Ace, film thickness: 100 μm, Re: 138 nm, Rth: 75 nm) An optical sheet was prepared in the same manner as B1, and the physical properties were measured. The obtained optical sheet had a thickness of 75 μm, | Re1-Re2 | was 500 nm, transmittance was 91.2%, and haze was 45.3%.

[Comparative Example B2]
As the transparent substrate A, instead of a PET film (Toyobo, A4100, film thickness 50 μm, Re: 1200 nm, Rth: 6000 nm), a TAC film (Fuji Film Holding, TF-80UL, film thickness 80 μm, Re: 5 nm) , Rth: 40 nm) was used, and an optical sheet was prepared in the same manner as in Comparative Example B1, and physical properties were measured. The obtained optical sheet had a thickness of 105 μm, | Re1-Re2 | was 1 nm, transmittance was 91.4%, and haze was 46.9%.

[Comparative Example B3]
As the transparent substrate A, instead of a PC film (Pure Ace manufactured by Teijin Chemicals, film thickness: 100 μm, Re: 138 nm, Rth: 75 nm), a PET film (Toyobo, A4100, film thickness 50 μm, Re: 1200 nm, Rth: An optical sheet was prepared in the same manner as in Example B1 except that 6000 nm) was used, and physical properties were measured. The obtained optical sheet had a thickness of 75 μm, | Re1-Re2 | was 600 nm, the transmittance was 90.8%, and the haze was 45.2%.

  Luminance ratios 1 to 3 were determined under the following conditions using a liquid crystal television bonded with the optical sheets obtained in each Example and each Comparative Example of Example B series. Table 3 shows the obtained luminance ratio. In addition, each luminance ratio described the relative value (%) of the luminance value when the luminance value measured in Comparative Example B2 was 100%.

(Luminance ratio 1)
The optical sheet obtained in each Example and each Comparative Example of Example B series is a surface that is not on the liquid crystal cell side of the polarizing plate that is not on the light source side of the liquid crystal television (AQUAOS (20 inches) manufactured by Sharp Corporation) (observer side) The liquid crystal television with an optical sheet was obtained by arranging the polarizing scattering particle layer on the surface) so as to be on the side of the liquid crystal television and pasting with an acrylic adhesive. The front luminance in white display of the liquid crystal television with the optical sheet was measured in the atmosphere at room temperature using BM-7 manufactured by Topcon Corporation.

(Luminance ratio 2)
Further, a TAC film (manufactured by FUJIFILM Holdings, TF-80UL, film thickness 80 μm, Re: 5 nm, Rth: on the transparent base material A of the optical sheet obtained in each Example and each Comparative Example of Example B series. 40 nm) was bonded via an acrylic adhesive to obtain an optical sheet with a TAC film. The optical sheet with the TAC film is arranged on the observer side surface of the liquid crystal television (AQUAOS (20 inches) manufactured by Sharp Corporation) so that the polarized light scattering particle layer is on the liquid crystal television side, and an acrylic adhesive is interposed therebetween. To obtain a liquid crystal television with a TAC film / optical sheet. The front luminance in white display of the obtained TAC film / optical sheet-equipped liquid crystal television was measured in the same manner as the luminance ratio 1.

(Luminance ratio 3)
On the transparent substrate A of the optical sheet obtained in each Example and each Comparative Example of Example B series, a PET film (Toyobo, A4100, film thickness 50 μm, Re: 1200 nm, Rth: 6000 nm) was further acrylic. Bonding via a system adhesive, an optical sheet with a PET film was obtained. The optical sheet with the PET film is arranged on the viewer side surface of the liquid crystal television (AQUAOS (20 inches) manufactured by Sharp Corporation) so that the polarization scattering particle layer is on the liquid crystal television side, and an acrylic adhesive is interposed therebetween. To obtain a liquid crystal television with a PET film and an optical sheet. The front luminance in white display of the obtained liquid crystal television with PET film and optical sheet was measured in the same manner as the luminance ratio 1.

[Discussion (Example B Series)]
The consideration is shown below about the evaluation result of the luminance ratio 1-3 of Example B series.

(Luminance ratio 1)
The optical sheets of Example B1 and Example B2 using specific polarized light scattering particles and having a transparent substrate A having a small optical anisotropy in a specific arrangement can realize high front luminance and are based on Comparative Example 2 ( 100%), 4% and 5% higher brightness was obtained respectively. In addition, the optical sheets of Example 1 and Comparative Example B2 in which | Re1-Re2 | ≦ 400 nm did not have in-plane variations (unevenness) in luminance that can be recognized by visual observation. On the other hand, the optical sheet obtained in Comparative Example B1 is provided with a particle layer containing Tospearl instead of the polarized light scattering particle layer, and as the transparent substrate A, a PET film having a large optical anisotropy was used. Was low. In addition, the optical sheet of Comparative Example 1 in which | Re1-Re2 |> 400 nm exhibited in-plane variations (unevenness) in luminance that can be recognized by visual observation.
Since the optical sheet obtained in Comparative Example B2 was provided with a particle layer containing Tospearl instead of the polarized light scattering particle layer, a TAC film having a small optical anisotropy was used as the transparent substrate A. Was low.
Since the optical sheet obtained in Comparative Example B3 used a PET film having a large optical anisotropy as the transparent substrate A, the brightness ratio of the polarizing scattering particle layer was low, and almost the same as Comparative Examples B1 and B2. The brightness was equivalent.

(Luminance ratio 2)
In the measurement of the luminance ratio 2, the TAC film was laminated on the transparent base material A of the optical sheet obtained in each Example and each Comparative Example of Example B series. Therefore, the luminance ratio is low in Comparative Examples B1 to B3, and the luminance ratio is high in Examples B1 and B2.

(Luminance ratio 3)
In the measurement of the luminance ratio 3, a PET film was laminated and laminated on the transparent base material A of the optical sheet obtained in each Example and each Comparative Example of Example B series. The PET film was optically anisotropic. Due to the large nature, the luminance ratio was as low in all Examples and Comparative Examples of the Example B series.

10 Transparent substrate A
11 Second transparent substrate 20 Polarized light scattering particle layer 30 Functional layer 40 Air layer 100 Image generation panel 200 Optical sheet 300 Image display device

Claims (12)

An optical sheet disposed on the viewer side of the image generation panel,
An optical sheet comprising a transparent substrate A and a polarized light scattering particle layer, wherein the polarized light scattering particle layer is disposed on the image generating panel side of the transparent substrate A.   The optical sheet according to claim 1, wherein the transparent substrate A has Re ≦ 1200 nm.   The optical sheet according to claim 1, wherein the transparent substrate A has Re ≦ 800 nm and Rth ≦ 800 nm.   The functional layer is arrange | positioned at the observer side of the said transparent base material A, and the said polarization | polarized-light scattering particle layer is arrange | positioned at the image generation panel side of the said transparent base material A. Optical sheet.   The polarized light scattering particle layer and the functional layer are arranged in this order from the side close to the transparent substrate A on the image generation panel side of the transparent substrate A. Optical sheet.   The optical sheet according to any one of claims 1 to 5, wherein | Re1-Re2 | ≦ 400 nm when Re is defined as Re at two arbitrary positions on the surface of the optical sheet, and Re2 and Re2, respectively. .   The optical sheet according to any one of claims 1 to 6, wherein an occupation ratio of the polarized light scattering particles in the polarized light scattering particle layer is 55% or less. On the viewer side of the image generation panel, a transparent substrate A, and a laminated structure including a polarized light scattering particle layer,
The image display device, wherein the polarized light scattering particle layer is disposed on an image generation panel side of the transparent substrate A.   The image display device according to claim 8, wherein the transparent substrate A has Re ≦ 1200 nm.   10. The image display device according to claim 8, wherein the transparent substrate A has Re ≦ 800 nm and Rth ≦ 800 nm.   The image display device according to any one of claims 8 to 10, wherein the polarized light scattering particle layer, the transparent base material A, and the functional layer are arranged from a side close to the image generation panel.   11. The image display device according to claim 8, wherein the functional layer, the polarized light scattering particle layer, and the transparent base material A are disposed from a side close to the image generation panel.

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