CN114600008B

CN114600008B - Light diffusion film, and polarizing plate having the same

Info

Publication number: CN114600008B
Application number: CN202080074336.6A
Authority: CN
Inventors: 吉川贵博; 三田聪司; 村上夏纪
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2019-10-24
Filing date: 2020-10-14
Publication date: 2024-12-06
Anticipated expiration: 2040-10-14
Also published as: JP7446766B2; TW202119107A; JP2021067849A; KR20220084269A; CN114600008A; WO2021079804A1

Abstract

Provided is a light diffusion film which can contribute to the durability (particularly, the humidification durability) of an optical laminate when the optical laminate is formed by combining with other films. The light diffusion film of the present invention comprises a shaping layer and a light diffusion layer arranged on one surface of the shaping layer, wherein the shaping layer comprises a base material part and a concave-convex part arranged on one surface of the base material part, and the light diffusion layer is arranged on the side of the base material part of the shaping layer.

Description

Light diffusion film and polarizing plate provided with same

Technical Field

The present invention relates to a light diffusion film and a polarizing plate provided with the light diffusion film.

Background

In recent years, there has been a strong demand for thinning of image display devices (e.g., liquid crystal display devices and organic EL display devices) and improvement of design (e.g., narrowing of frames). Along with this, the desire for integration and/or functional integration of optical members and/or optical films for image display devices is also increasing. As an example of such integration or functional integration, it is proposed to apply a light diffusion function to a predetermined optical member or the like by directly bonding a light diffusion film thereto. An excellent optical property and processability, and durability (particularly, humidification durability) of an optical laminate including the light diffusion film are sometimes required for the light diffusion film, but it is difficult to satisfy these properties in a good balance in the light diffusion film used by direct bonding. In particular, a light-diffusing film comprising light-diffusing particles often suffers from breakage or the like during film formation, and is difficult to stably produce, and is difficult to combine processability with other characteristics (e.g., optical characteristics).

Prior art literature

Patent literature

Patent document 1 Japanese patent application laid-open No. 2012-118235

Patent document 2 Japanese patent application laid-open No. 2009-025774

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made to solve the above-described conventional problems, and a main object thereof is to provide a light diffusion film which has excellent processability and optical characteristics and which can contribute to durability (particularly, humidification durability) of an optical laminate when the film is combined with other films to form the optical laminate.

Solution for solving the problem

The light diffusion film of the present invention comprises a shaping layer and a light diffusion layer arranged on one surface of the shaping layer, wherein the shaping layer comprises a base material part and a concave-convex part arranged on one surface of the base material part, and the light diffusion layer is arranged on the side of the base material part of the shaping layer.

In one embodiment, the light diffusion layer and the shaping layer are laminated with an adhesive layer or an adhesive layer.

In one embodiment, the light diffusion layer is directly formed on the shaping layer.

In one embodiment, the light diffusion layer includes light diffusing particles having a volume average particle diameter of 2 μm to 30 μm.

In one embodiment, the haze value of the light diffusion film is 30% -95%.

According to another aspect of the present invention, a polarizing plate may be applied. The polarizing plate includes a polarizer and the light diffusion film laminated on the polarizer via an adhesive layer.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, by providing the shaping layer having the concave-convex portion and the light diffusion layer, it is possible to provide the light diffusion film which has excellent processability and optical characteristics and which can contribute to durability (particularly, humidification durability) of the optical laminate when the optical laminate is constituted by combining with other films.

Drawings

Fig. 1 is a schematic cross-sectional view of a light diffusing film according to an embodiment of the present invention.

Fig. 2 is a schematic plan view showing a typical example of the plan view shape of the convex portion of the concave-convex surface in the light diffusion film according to the embodiment of the present invention.

Fig. 3 is a schematic cross-sectional view of an optical stack according to an embodiment of the present invention.

Fig. 4 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. The drawings are schematically shown for the sake of convenience of observation, and the ratio of the length, width, and thickness, the shape and fineness of the irregularities, and the like are different from those of actual ones.

A. light diffusion film

A-1. Integral constitution

Fig. 1 is a schematic cross-sectional view of a light diffusing film according to an embodiment of the present invention. The light diffusion film 100 illustrated in the drawing includes a shaping layer 10 and a light diffusion layer 20 disposed on one surface of the shaping layer 10. The shaping layer 10 has a base material portion 11 and a concave-convex portion 12 formed on one surface of the base material portion 11. The concave-convex portion 12 has a convex portion 12a and a concave portion 12b. The light diffusion layer 20 is disposed on the substrate portion 11 side (opposite side of the concave-convex portion 12) of the shaping layer 10. In one embodiment, the light diffusion film of the present invention is used by adhering the concave-convex portion 12 to another film.

Fig. 2 is a schematic plan view showing a typical example of the plan view shape of the convex portion of the concave-convex portion in the shaping layer of the light diffusion film according to the embodiment of the present invention. In one embodiment, as shown in fig. 2, the concave portion 12b may have a cell structure surrounded by the convex portion 12a (substantially, a wall surface of the convex portion). By forming the concave portion having the cell structure, intrusion of moisture into the optical laminate can be prevented when the optical laminate is formed by laminating the light diffusion film on another film. Further, by forming the concave portion having a cell structure, a light diffusion film which can be cut with good workability by preventing defects such as breakage and chipping at the cut portion can be obtained. The concave portions may be opened at the end side of the light diffusion film without forming all the concave portions in a cell structure, for example, in the vicinity of the end side of the light diffusion film.

The convex portion 12a of the concave-convex portion may have any suitable shape in plan view. As shown in fig. 2, the convex portion 12a may have a regular shape (e.g., a lattice shape) or an irregular shape in plan view. The pitch of the projections (the interval between projections) is preferably 1000 μm or less, more preferably 500 μm or less, and still more preferably 100 μm or less. When the shape of the convex portion in plan view is regular, an oblique direction having an angle of 1 to 90 degrees may be provided. When the planar shape of the convex portion is irregular, the pitch is an average pitch, and preferably a distribution such as five or more is set to be within ±50% of the average pitch. With such a configuration, when the light diffusion film is laminated on another film, the adhesion strength between the light diffusion film and the other film can be ensured, and good display quality can be ensured. In addition, when the light diffusion film is laminated on another film to form an optical laminate, intrusion of moisture into the optical laminate can be prevented.

In the present invention, by providing the shaping layer having the concave-convex portion, only the convex portion (substantially the upper portion of the convex portion) of the light diffusion film can be bonded to other films when the light diffusion film is laminated to other films to form the optical laminate. In the present specification, for convenience, the bonding of only the convex portions may be referred to as "spot bonding". By such spot bonding, a substantially low refractive index portion generated by the concave portion (air portion or void portion) is defined in the vicinity of the spot bonded portion. As a result, the luminance angle of view can be increased while achieving good light diffusion performance. Conventionally, in an image display device, other films (for example, a polarizing material (polarizing plate)) and a light diffusion film are provided separately, and as a result, an air layer is interposed between the polarizing plate and the light diffusion film. On the other hand, the air layer can maintain a large luminance angle of view by the retroreflection by the air layer. When the other film is integrated with the light diffusion film, the thickness and the function can be integrated, but the air layer is eliminated, so that the luminance angle of view becomes small. By forming the low refractive index portion in the vicinity of the spot-bonded portion, light is efficiently retroreflected as in the case where an air layer is present. Therefore, according to the embodiment of the present invention, by forming the spot bonding, it is possible to maintain a large (wide) luminance angle of view while exhibiting a desired light diffusion performance.

In one embodiment, the shaping layer does not contain light diffusing particles. The shaping layer can be produced by any suitable film forming method, but the shaping layer formed so as not to contain light diffusing particles is less likely to cause breakage during film forming and is excellent in workability. It is one of the achievements of the present invention to make the shaping layer free of light diffusing particles (i.e. even with good processability) achieve good light diffusing properties and to increase the luminance angle of view.

The thickness of the light diffusion film of the present invention is preferably 25 μm to 250 μm, more preferably 30 μm to 100 μm.

The haze value of the light diffusion film of the present invention is preferably 30% to 95%, more preferably 40% to 93%, and further preferably 60% to 90%. According to the present invention, it is possible to provide a light diffusion film which can suppress a decrease in luminance and realize an excellent luminance angle of view despite a high haze value.

A-2 shaping layer

Any suitable resin may be used as the resin constituting the shaping layer. Specific examples of the resin constituting the shaping layer include (meth) acrylic resins, polyester resins (for example, polyethylene terephthalate (PET)), cycloolefin resins (for example, norbornene resins), cellulose resins (for example, triacetyl cellulose (TAC)), polyvinyl alcohol resins, polycarbonate resins, polyamide resins, polyimide resins, polyethersulfone resins, polysulfone resins, polystyrene resins, polyolefin resins, and acetate resins. These resins may be used alone or in combination of two or more. From the viewpoints of optical characteristics, transparency and versatility, (meth) acrylic resins, polyester resins and cycloolefin resins are preferable, and (meth) acrylic resins are more preferable.

In the present specification, "(meth) acrylic acid" means acrylic acid and/or methacrylic acid.

As the (meth) acrylic resin, any suitable (meth) acrylic resin may be used.

For simplicity of description, the (meth) acrylic resin will be hereinafter simply referred to as an acrylic resin. The acrylic resin typically contains an alkyl (meth) acrylate as a main component as a monomer unit. Examples of the alkyl (meth) acrylate constituting the main skeleton of the acrylic resin include alkyl (meth) acrylates having a linear or branched alkyl group with 1 to 18 carbon atoms. They may be used alone or in combination. Further, any suitable comonomer may be introduced into the acrylic resin by copolymerization. The kind, amount, copolymerization ratio, etc. of such comonomers can be appropriately set according to the purpose. The constituent components (monomer units) of the main skeleton of the acrylic resin will be described later with reference to the general formula (2).

The acrylic resin may preferably have at least 1 selected from the group consisting of a glutarimide unit, a lactone ring unit, a maleic anhydride unit, a maleimide unit, and a glutarimide unit. Acrylic resins having lactone ring units are described in, for example, japanese patent application laid-open No. 2008-181078, the description of which is incorporated herein by reference. The glutarimide unit is preferably represented by the following formula (1),

In the general formula (1), R ¹ and R ² each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ³ represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 10 carbon atoms. In the general formula (1), it is preferable that R ¹ and R ² are each independently hydrogen or methyl, and R ³ is hydrogen, methyl, butyl or cyclohexyl. More preferably, R ¹ is methyl, R ² is hydrogen and R ³ is methyl.

The alkyl (meth) acrylate is typically represented by the following formula (2).

In the general formula (2), R ⁴ represents a hydrogen atom or a methyl group, and R ⁵ represents a hydrogen atom or an optionally substituted aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms. Examples of the substituent include halogen and hydroxy. Specific examples of the alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2,3,4,5, 6-pentahydroxyhexyl (meth) acrylate, and 2,3,4, 5-tetrahydroxypentyl (meth) acrylate. In the general formula (2), R ⁵ is preferably a hydrogen atom or a methyl group. Thus, particularly preferred alkyl (meth) acrylates are methyl acrylate or methyl methacrylate.

The acrylic resin may contain only a single glutarimide unit, or may contain a plurality of glutarimide units in which R ¹、R² and R ³ in the general formula (1) are different.

The content ratio of the glutarimide unit in the acrylic resin is preferably 2 mol% to 50 mol%, more preferably 2 mol% to 45 mol%, still more preferably 2 mol% to 40 mol%, particularly preferably 2 mol% to 35 mol%, and most preferably 3 mol% to 30 mol%. If the content is less than 2 mol%, there is a concern that the effect (for example, high optical characteristics, high mechanical strength, and thinning) exhibited by the glutarimide unit cannot be sufficiently exhibited. If the content exceeds 50 mol%, there is a concern that heat resistance and transparency may be insufficient, for example.

The acrylic resin may contain only a single alkyl (meth) acrylate unit, or may contain a plurality of alkyl (meth) acrylate units having different R ⁴ and R ⁵ in the general formula (2).

The content ratio of the alkyl (meth) acrylate unit in the acrylic resin is preferably 50 to 98 mol%, more preferably 55 to 98 mol%, still more preferably 60 to 98 mol%, particularly preferably 65 to 98 mol%, and most preferably 70 to 97 mol%. If the content is less than 50 mol%, the effect (for example, high heat resistance and high transparency) derived from the alkyl (meth) acrylate unit may not be sufficiently exhibited. If the content exceeds 98 mol%, the resin may be brittle and easily broken, and may not sufficiently exhibit high mechanical strength and poor productivity.

The acrylic resin may contain a unit other than the glutarimide unit and the alkyl (meth) acrylate unit.

In one embodiment, the acrylic resin may contain, for example, 0 to 10% by weight of an unsaturated carboxylic acid unit which does not participate in the intramolecular imidization reaction described later. The content ratio of the unsaturated carboxylic acid unit is preferably 0 wt% to 5 wt%, more preferably 0 wt% to 1 wt%. When the content is within such a range, transparency, retention stability and moisture resistance can be maintained.

In one embodiment, the acrylic resin may contain a copolymerizable vinyl monomer unit (other vinyl monomer unit) other than the above. Examples of the other vinyl monomer include acrylonitrile, methacrylonitrile, ethacrylonitrile, allyl glycidyl ether, maleic anhydride, itaconic anhydride, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, aminoethyl acrylate, propylaminoethyl acrylate, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, cyclohexylaminoethyl methacrylate, N-vinyldiethylamine, N-acetylvinylamine, allylamine, methallylamine, N-methallylamine, 2-isopropenyl-oxazoline, 2-vinyl-oxazoline, 2-acryl-oxazoline, N-phenylmaleimide, phenylaminoethyl methacrylate, styrene, α -methylstyrene, p-glycidyl styrene, p-aminostyrene, 2-styryl-oxazoline, and the like. They may be used alone or in combination. Styrene monomers such as styrene and α -methylstyrene are preferable. The content of the other vinyl monomer unit is preferably 0 to 1% by weight, more preferably 0 to 0.1% by weight. If the amount is within this range, the undesired retardation and the decrease in transparency can be suppressed.

The imidization ratio in the acrylic resin is preferably 2.5% to 20.0%. When the imidization ratio is in such a range, a resin excellent in heat resistance, transparency and molding processability can be obtained, and occurrence of scorching and a decrease in mechanical strength during film molding can be prevented. In the acrylic resin, the imidization rate is represented by the ratio of glutarimide units to alkyl (meth) acrylate units. The ratio can be obtained, for example, from NMR spectrum, IR spectrum, etc. of the acrylic resin. In the present embodiment, the imidization rate can be determined by ¹ H-NMR measurement of the resin using ¹ H NMR BRUKER AvanceIII (400 MHz). More specifically, the peak area of the proton of O-CH ₃ derived from alkyl (meth) acrylate in the vicinity of 3.5 to 3.8ppm is defined as A, and the peak area of the proton of N-CH ₃ derived from glutarimide in the vicinity of 3.0 to 3.3ppm is defined as B, which is obtained by the following formula.

Imidization ratio Im (%) = { B/(a+b) } ×100

The Tg (glass transition temperature) of the acrylic resin is preferably 110 ℃ or higher, more preferably 115 ℃ or higher, further preferably 120 ℃ or higher, particularly preferably 125 ℃ or higher, and most preferably 130 ℃ or higher. When Tg is 110 ℃ or higher, a polarizing plate including a light diffusion film obtained from such a resin is likely to be excellent in durability. The upper limit of Tg is preferably 300 ℃ or less, more preferably 290 ℃ or less, further preferably 285 ℃ or less, particularly preferably 200 ℃ or less, and most preferably 160 ℃ or less. When Tg is in such a range, formability is excellent.

The acrylic resin can be produced, for example, by the following method. The method comprises (I) copolymerizing an alkyl (meth) acrylate monomer corresponding to the alkyl (meth) acrylate unit represented by the general formula (2) with an unsaturated carboxylic acid monomer and/or a precursor monomer thereof to obtain a copolymer (a), and (II) treating the copolymer (a) with an imidizing agent to thereby effect intramolecular imidization of the alkyl (meth) acrylate monomer unit in the copolymer (a) with the unsaturated carboxylic acid monomer and/or the precursor monomer unit thereof, and introducing a glutarimide unit represented by the general formula (1) into the copolymer.

Details of the acrylic resin and the method for producing the same are described in, for example, japanese patent application laid-open Nos. 2018-155812 and 2018-155813. The disclosures of these publications are incorporated by reference into this specification.

The height H of the protruding portion 12a is preferably 5% to 40% of the thickness of the shaping layer. If the range is such, good spot bonding can be achieved. In addition, the height of the convex portion is set to the above range, which is also advantageous from the viewpoint of mechanical strength, whereby the concave portion shape can be desirably maintained, and excellent light diffusivity and luminance angle of view can be obtained.

The height H of the protruding portion 12a is more preferably 10% to 30%, and still more preferably 10% to 20% of the thickness of the shaping layer. If the range is such, good spot bonding can be achieved.

The height H of the protruding portion 12a is preferably 2.5 μm to 25 μm, more preferably 5 μm to 20 μm. If the range is such, good spot bonding can be achieved.

The average area of the concave portions having a cell structure is preferably 5000 μm ² or more. When the amount is in this range, a light diffusion film which can suppress a decrease in luminance and realize an excellent luminance angle of view can be obtained. The average area of the concave portions having a cell structure is more preferably 5000 μm ²～50000μm², still more preferably 7000 μm ²～40000μm², particularly preferably 8000 μm ²～30000μm². When the content is within this range, the above-mentioned effects are remarkable, and a light diffusion film excellent in mechanical strength can be obtained. The average area of the concave portions having the cell structure can be obtained using image analysis software (free software "ImageJ"). That is, the inside and outside of the recess are determined by the threshold value of the binary image of the surface of the shaped film, and the outer frame of the recess is determined. The area within the specified frame is calculated and the average value of the calculated areas is calculated, whereby it can be found.

In one embodiment, the maximum length of the concave portion of the cell structure in plan view is preferably 300 μm or more, more preferably 400 μm or more, and still more preferably 500 μm or more. In such a range, even when the light diffusion film is cut for use, the light diffusion film can effectively prevent moisture intrusion, and durability in the vicinity of the end portion of the optical laminate can be improved. The maximum length of the concave portion of the cell structure is the corresponding distance of the portion where the distance between the wall surfaces of the convex portion forming the concave portion is the longest.

The area ratio of the concave portion to the entire area in the planar view of the concave-convex portion is preferably 50% or more, more preferably 60% or more, and still more preferably 70% or more. The upper limit of the area ratio of the concave portion may be 90%, for example. When the area ratio of the concave portion is in such a range, good diffusion performance can be imparted to the light diffusion film while maintaining a wide luminance angle of view, and adhesive strength can be ensured when the light diffusion film is laminated on another film.

In the light diffusion film of the present invention, it is preferable that the wall surface of the convex portion 12a is present in a region within 500 μm from the end edge of the light diffusion film. In the present invention, when the light diffusion film is laminated on another film to form an optical laminate, the convex portion 12a can prevent intrusion of moisture into the optical laminate. By forming the wall surface of the convex portion 12a in the region within 500 μm from the end edge of the light diffusion film, moisture intrusion can be effectively prevented, and durability in the vicinity of the end portion of the optical laminate can be improved. More preferably, the wall surface of the convex portion 12a is present in a region within 400 μm from the end edge of the light diffusion film, and still more preferably, the wall surface of the convex portion 12a is present in a region within 300 μm from the end edge of the light diffusion film. The wall surface of the convex portion 12a is preferably present in all regions within 500 μm (preferably within 400 μm, more preferably within 300 μm) from the end edge of the light diffusion film.

The ratio B/a of the cross-sectional area B of the concave portion to the cross-sectional area a of the entire concave-convex portion is preferably 50% or more, more preferably more than 50%, still more preferably 60% or more, and particularly preferably 70% or more. The upper limit of the ratio B/A may be, for example, 90%. When the ratio B/a is in such a range, good diffusion performance can be imparted to the light diffusion film while maintaining a wide luminance angle of view, and adhesive strength can be ensured when the light diffusion film is laminated on another film. The cross-sectional area a of the entire concave-convex portion is the area of a portion surrounded by a line connecting the surface of the convex portion, a line connecting the bottom of the concave portion, and a line connecting the bottom of the concave portion in the up-down direction of the film (for reference, the outside of this portion is surrounded by a broken line and shown in fig. 1), and the cross-sectional area B of the concave portion is the sum of the cross-sectional areas of the respective concave portions 22 (the area of a portion surrounded by a line connecting the wall portion of the adjacent convex portion, a line connecting the surface of the convex portion, and a line connecting the bottom of the concave portion).

The thickness of the shaping layer is preferably 25 μm to 250 μm, more preferably 40 μm to 100 μm.

The thickness of the base material is preferably 22.5 μm to 225 μm, more preferably 30 μm to 90 μm.

The concave-convex portion (concave-convex shape) may be formed by any suitable method. The concave-convex shape can be formed by, for example, a surface roughening method or a method of imparting concave-convex shape with fine particles. Specific examples of the surface roughening method include embossing and sandblasting. The concave-convex portion (concave-convex shape) can be typically formed by shaping the surface of the melt-extruded film with an embossing roller.

In one embodiment, the base material portion and the concave-convex portion are made of the same material. Preferably, the base material portion and the concave-convex portion are integrally formed of the same material.

A-3 light diffusion layer

The light diffusion layer may be formed of a light diffusion element, or may be formed of a light diffusion adhesive or a light diffusion bonding agent. The light diffusing element may have a structure having a fine uneven structure on the surface (an external diffusion type light diffusing layer), or may have a structure including a matrix and light diffusing fine particles dispersed in the matrix (an internal diffusion type light diffusing layer). The light diffusion element may be a light diffusion cured layer (for example, a layer formed by coating a dispersion liquid (light diffusion layer forming coating liquid) containing a matrix resin, light diffusion fine particles, and an additive as needed on any appropriate substrate and curing and/or drying the same), or may be a light diffusion film (for example, a commercially available film). The matrix of the light diffusing adhesive is composed of an adhesive, and the matrix of the light diffusing adhesive is composed of an adhesive. When the light diffusion layer is made of a light diffusion adhesive or a light diffusion bonding agent, any appropriate protective film may be disposed on the side of the light diffusion layer opposite to the shaping layer in order to protect the surface of the light diffusion layer.

Details of the light diffusing element and the light diffusing adhesive are described in, for example, japanese patent application laid-open publication nos. 2012-83741, 2012-83742, 2012-83743, 2012-83744, 2013-235259, and 2014-224964. The disclosures of these publications are incorporated by reference into this specification. Light diffusing elements with surface relief are known in the art.

The light diffusion layer is directly disposed on the shaping layer or is laminated with the shaping layer via an adhesive layer or an adhesive layer. The directly disposed shaping layer may be formed by coating. Examples of the light diffusion layer thus formed include a light diffusion layer formed by applying the above-mentioned coating liquid for forming a light diffusion layer, and a light diffusion layer composed of a light diffusion adhesive or a light diffusion adhesive. Examples of the light diffusion layer disposed via the pressure-sensitive adhesive layer or the pressure-sensitive adhesive layer include a light diffusion film. The adhesive layer that bonds the shaping layer to the light diffusing layer comprises any suitable adhesive. Examples of the adhesive include rubber adhesives, acrylic adhesives, silicone adhesives, epoxy adhesives, and cellulose adhesives, and acrylic adhesives are preferred. The adhesive layer that bonds the shaping layer to the light diffusion layer may include any suitable adhesive. Examples of the adhesive include an aqueous adhesive (for example, a vinyl alcohol adhesive) and a curable adhesive (for example, an active energy ray curable adhesive or a thermosetting adhesive).

The light diffusing property of the light diffusing layer can be expressed by, for example, a haze value. The haze value of the light diffusion layer is preferably 20% to 90%, more preferably 30% to 87%, and further preferably 40% to 85%. The haze value of the light diffusion layer can be controlled by adjusting the fine uneven structure of the surface, the constituent material of the matrix (binder), the constituent material of the light diffusing fine particles, the volume average particle diameter, the blending amount, and the like.

The total light transmittance of the light diffusion layer is preferably 75% or more, more preferably 80% or more, and further preferably 85% or more.

The thickness of the light diffusion layer may be appropriately adjusted according to the constitution and desired light diffusion performance, etc. Specifically, the thickness of the light diffusion layer is preferably 2 μm to 100 μm, more preferably 5 μm to 30 μm.

In one embodiment, the light diffusing layer is comprised of a light diffusing adhesive. The light diffusing adhesive typically includes an adhesive as a matrix and light diffusing particles dispersed in the adhesive.

As the binder (matrix), any suitable substance may be used. Specific examples of the adhesive include rubber adhesives, acrylic adhesives, silicone adhesives, epoxy adhesives, cellulose adhesives, and the like, and acrylic adhesives are preferred. By using an acrylic adhesive, a light diffusion layer excellent in heat resistance and transparency can be obtained. The binder may be used alone or in combination of 2 or more.

As the acrylic adhesive, any suitable one may be used. The glass transition temperature of the acrylic adhesive is preferably-60 ℃ to-10 ℃, more preferably-55 ℃ to-15 ℃. The weight average molecular weight of the acrylic adhesive is preferably 20 to 200 tens of thousands, more preferably 25 to 180 tens of thousands. By using an acrylic adhesive having such characteristics, appropriate adhesion can be obtained. The refractive index of the acrylic adhesive is preferably 1.40 to 1.65, more preferably 1.45 to 1.60.

The acrylic pressure-sensitive adhesive is generally obtained by polymerizing a main monomer that imparts tackiness, a comonomer that imparts cohesiveness, and a functional group-containing monomer that imparts tackiness and becomes a crosslinking point. The acrylic adhesive having the above-described characteristics can be synthesized by any suitable method, and for example, can be synthesized by reference to "chemistry and application of bonding/adhesion" by the release of the book of large japan (ltd).

The content of the binder in the light diffusion layer is preferably 50 wt% to 99.7 wt%, more preferably 52 wt% to 97 wt%.

As the light diffusing fine particles, any appropriate fine particles can be used. Specific examples of the light diffusing fine particles include inorganic fine particles and polymer fine particles. The light diffusing fine particles are preferably polymer fine particles. Examples of the material of the polymer microparticles include polystyrene resin, polyurethane resin, melamine resin, silicone resin, acrylic resin, and styrene-acrylic copolymer resin. These resins have a desired refractive index difference with respect to the adhesive and have excellent dispersibility with respect to the adhesive, and thus can give a light diffusion layer excellent in light diffusion performance. Polystyrene resin is preferred. The light diffusing particles may have a spherical shape, a flat shape, or an irregular shape, for example. The light diffusing fine particles may be used alone or in combination of 2 or more kinds.

The volume average particle diameter of the light diffusing fine particles is preferably larger than 1 μm and 30 μm or smaller, more preferably 2 μm to 30 μm, still more preferably 2 μm to 25 μm, particularly preferably 3 μm to 20 μm. By setting the volume average particle diameter to the above range, a light diffusion layer having excellent optical characteristics can be obtained. In particular, when light diffusing fine particles having a volume average particle diameter of 2 μm or more are used, a light diffusing layer having remarkably excellent optical characteristics such as prevention of coloring of transmitted light can be obtained. The volume average particle diameter can be measured by using an ultracentrifuge automatic particle size distribution measuring apparatus.

The refractive index of the light diffusing fine particles is preferably 1.50 or more, more preferably 1.55 to 1.70, and still more preferably 1.58 to 1.65.

The absolute value of the refractive index difference between the light diffusing fine particles and the binder (matrix) is preferably 0.05 or more, more preferably 0.07 to 0.15, and still more preferably 0.10 to 0.13.

The content of the light diffusing fine particles in the light diffusing layer is preferably 0.3 to 50 wt%, more preferably 3 to 48 wt%. By setting the blending amount of the light diffusing fine particles to the above range, a light diffusing layer having excellent light diffusing performance can be obtained.

The light diffusing layer may comprise any suitable additive. Examples of the additives include antistatic agents and antioxidants.

In another embodiment, the light diffusion layer is composed of a light diffusion element. At this time, the light diffusion layer typically includes a matrix and light diffusing particles dispersed in the matrix. The substrate is composed of, for example, an ionizing radiation-curable resin. Examples of the ionizing radiation include ultraviolet rays, visible rays, infrared rays, and electron rays. Preferably, the substrate is composed of an ultraviolet curable resin because ultraviolet rays are preferable. Examples of the ultraviolet curable resin include acrylic resins, aliphatic (e.g., polyolefin) resins, and urethane resins. As the light diffusing fine particles, the same fine particles as those that can be used for the light diffusing binder can be used. In the present embodiment, the matrix may contain a resin component and an ultrafine particle component. In this case, a refractive index modulation region having a refractive index that changes substantially continuously may be formed outside the vicinity of the surface of the light diffusing fine particles. The refractive index modulation region may typically be formed by a substantial gradient of the dispersion concentration of the ultrafine particle component in the matrix. By adopting such a constitution, back scattering can be suppressed. As described above, the resin component is preferably composed of an ultraviolet curable resin (for example, an acrylic resin). Specific examples of the monomer component constituting the acrylic resin include pentaerythritol triacrylate (PETA: molecular weight 298), neopentyl glycol diacrylate (NPGDA: molecular weight 212), dipentaerythritol hexaacrylate (DPHA: molecular weight 632), dipentaerythritol pentaacrylate (DPPA: molecular weight 578), and trimethylolpropane triacrylate (TMPTA: molecular weight 296). The ultrafine particle component is preferably composed of an inorganic compound. Preferable inorganic compounds include, for example, metal oxides and metal fluorides. Specific examples of the metal oxide include zirconium oxide (zirconium oxide) (refractive index: 2.19), aluminum oxide (refractive index: 1.56 to 2.62), titanium oxide (refractive index: 2.49 to 2.74), and silicon oxide (refractive index: 1.25 to 1.46). Specific examples of the metal fluoride include magnesium fluoride (refractive index: 1.37) and calcium fluoride (refractive index: 1.40 to 1.43). Details of the light diffusion layer (light diffusion element) including such a matrix are described in, for example, japanese patent application laid-open publication No. 2010-250295 or japanese patent application laid-open publication No. 2012-088692, which are incorporated by reference into the present specification.

B. Optical laminate

B-1. Integral constitution

Fig. 3 is a schematic cross-sectional view of an optical stack according to an embodiment of the present invention. The optical laminate 200 illustrated in the figure includes a light diffusion film 100 and other films 110 disposed on one side of the light diffusion film 100. The light diffusion film 100 and the other films 110 are laminated so that the concave and convex portions 12 of the shaping layer 10 provided in the light diffusion film 100 face the other films 110. Typically, the light diffusion film 100 and the other film 110 are laminated with the adhesive layer 120 interposed therebetween.

As described above, in the concave-convex portion 12 of the light diffusion film 100, the ratio B/a of the cross-sectional area B of the concave portion to the cross-sectional area a of the entire concave-convex portion is preferably 50% or more, more preferably more than 50%, still more preferably 60% or more, and particularly preferably 70% or more. The upper limit of the ratio B/A may be, for example, 90%. The ratio B/a may correspond to the void fraction. When the amount is in this range, an optical laminate having excellent mechanical strength and capable of achieving good light diffusion performance and increasing the luminance angle of view can be obtained.

B-2 other films

As the other film, any suitable film may be used. Examples of the other film include an optical film such as a polarizer, a wavelength conversion film, and a polarizing reflection film, glass (preferably, thin glass), and a resin film (for example, a protective film).

In one embodiment, a polarizer is used as the other film. In this embodiment, the light diffusion film functions as a polarizer protective film, and the optical laminate may be a polarizing plate. Details of the polarizing plate will be described later.

B-3 adhesive layer

The adhesive layer is formed of any suitable adhesive or binder. The adhesive layer is typically formed of an aqueous adhesive (for example, a vinyl alcohol adhesive) or a curable adhesive (for example, an active energy ray curable adhesive or a thermosetting adhesive).

In one embodiment, the adhesive layer includes an active energy ray-curable adhesive. When the adhesive layer is formed using an active energy ray-curable adhesive, an optical laminate can be obtained without impairing the uneven shape of the light diffusion film.

As the active energy ray-curable adhesive, any suitable adhesive may be used as long as it can be cured by irradiation with active energy rays. Examples of the active energy ray-curable adhesive include ultraviolet ray-curable adhesives and electron ray-curable adhesives. Specific examples of the curing form of the active energy ray-curable adhesive include radical curing type, cation curing type, anion curing type, and combinations thereof (for example, a mixture of radical curing type and cation curing type).

Examples of the active energy ray-curable adhesive include adhesives containing a compound (e.g., a monomer and/or an oligomer) having a radically polymerizable group such as a (meth) acrylate group or a (meth) acrylamide group as a curing component.

Specific examples of the active energy ray-curable adhesive and the curing method thereof are described in, for example, japanese patent application laid-open No. 2012-144690. This description is incorporated by reference into this specification.

As a method for applying the active energy ray-curable adhesive, any suitable method may be used depending on the viscosity of the adhesive, the thickness of a desired adhesive layer, and the like. Examples of the coating method include coating by a reverse coater, a gravure coater (direct, reverse, offset), a bar reverse coater, a roll coater, a die coater, a bar coater, and the like. In addition, coating by the dipping method may be used.

As a curing method of the active energy ray-curable adhesive, any suitable method can be used. The conditions such as the wavelength and the irradiation amount of the active energy ray may be set to any appropriate conditions according to the type of the curable compound used.

The thickness of the portion where the thickness of the adhesive layer is the largest is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 5 μm. In such a range, it is preferable to form voids due to the irregularities of the thin film, and an optical laminate excellent in mechanical strength can be obtained. In one embodiment, the portion where the thickness of the adhesive layer is the largest may correspond to a gap from the upper surface of the convex portion of the light diffusion film (the surface facing the other film) to the lower surface of the other film (the surface facing the light diffusion film). In another embodiment, the portion where the thickness of the adhesive layer is the largest may be a position corresponding to the concave portion of the light diffusion film (fig. 4). For example, the adhesive layer may be formed so as to cover at least a part of the wall surface of the convex portion of the light diffusion film. In this case, the adhesive layer is preferably in a so-called meniscus (meniscuses) shape, and is not formed on the concave surface of the light diffusion film. In this embodiment, an optical laminate excellent in adhesion between the light diffusion film and other films can be obtained while securing a gap.

In one embodiment, the thickness T of the adhesive layer formed on the upper surface of the convex portion of the light diffusion film is preferably smaller than the thickness (height) H of the convex portion. The ratio T/H of the thickness T to the height H of the convex portion is preferably 50% or less, more preferably 30% or less. When the ratio T/H is in such a range, good spot bonding can be achieved. The lower limit of the ratio T/H may be, for example, 10%.

The light diffusion film has concave and convex portions, and the convex portions of the light diffusion film are bonded (i.e., spot bonded) to other films and laminated, but the adhesive layer is preferably formed in a void portion of the other films in addition to the portion involved in bonding. In other words, the adhesive layer preferably covers at least a part (preferably all) of the other film surface in the concave portion (void portion) of the light diffusion film. In this way, deterioration of other films can be prevented. This effect is particularly useful when the other film is degraded by moisture, external air, or the like, and is useful when the other film is a polarizing material, for example. The thickness of the adhesive layer at the void portion may or may not be constant. In one embodiment, the adhesive layer of the void portion has a meniscus shape, the thickness of which is not constant. Examples of the method for providing the adhesive layer in the void portion include a method in which an adhesive precursor layer is formed on another film and then the other film is bonded to the light diffusion film.

The storage modulus of the adhesive layer at 25 ℃ is preferably 100kPa or more, more preferably 100kPa to 3GPa, and still more preferably 100kPa to 1GPa. In such a range, voids due to the irregularities of the light diffusion film can be desirably formed, and an optical laminate excellent in mechanical strength can be obtained. The storage modulus can be determined by dynamic viscoelasticity measurement. For example, the dynamic viscoelasticity measurement is performed using a pressure-sensitive adhesive sample having a thickness of 2mm by 8mm, manufactured by Rheometric Scientific company, "Advanced Rheometric Expansion System (ARES)", in a deformation mode, namely, torsion, measurement frequency of 1Hz, temperature rise rate of 5 ℃ per minute, and measurement temperature of-50 ℃ to 150 ℃.

B-4 polarizing plate

As described above, in one embodiment, the optical laminate is a polarizing plate. Fig. 4 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present invention. The polarizing plate 200a illustrated in the drawing includes a polarizer 110a and a polarizer protective film 100a laminated on the polarizer 110a via an adhesive layer 120. The polarizer protective film 100a in this embodiment corresponds to the light diffusion film described above. The polarizer 110a corresponds to the other film. The polarizer protective film 100a is disposed such that the concave-convex portion side is the polarizer 110a side. The adhesive layer is as described above. Practically, another protective film 140 is disposed on the opposite side of the polarizer protective film 100a. Practically, the adhesive layer 150 is further provided as an outermost layer so that the polarizing plate can be attached to the image display unit. A release film (not shown) is temporarily stuck to the surface of the pressure-sensitive adhesive layer 150 in a releasable manner, and the pressure-sensitive adhesive layer can be protected and rolled up until the polarizing plate is actually used. The polarizing plate according to the embodiment of the present invention may be used as a rear-side polarizing plate of an image display device or as a recognition-side polarizing plate. According to the embodiment of the present invention, since the polarizer protective film itself has light diffusing performance and also functions as a light diffusing film, significant thinning can be achieved by a synergistic effect with the effect of eliminating the air layer.

As the polarizing material, any suitable polarizing material may be used. For example, the resin film forming the polarizer may be a single-layer resin film or a laminate of two or more layers.

Specific examples of the polarizing material comprising a single-layer resin film include polarizing materials obtained by dyeing and stretching hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films and ethylene-vinyl acetate copolymer partially saponified films with a dichroic substance such as iodine and a dichroic dye, and multi-functional oriented films such as dehydrated PVA products and desalted polyvinyl chloride products. In view of excellent optical characteristics, a polarizing material obtained by dyeing a PVA-based film with iodine and uniaxially stretching the film is preferably used.

The iodine-based dyeing is performed, for example, by immersing the PVA-based film in an aqueous iodine solution. The stretching ratio of the unidirectional stretching is preferably 3-7 times. Stretching may be performed after dyeing treatment or may be performed while dyeing. In addition, it is also possible to re-dye after stretching. The PVA-based film may be subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, and the like as needed. For example, by immersing the PVA-based film in water and washing it before dyeing, not only stains on the surface of the PVA-based film but also the anti-blocking agent can be washed, and the PVA-based film can be swelled to prevent uneven dyeing.

Specific examples of the polarizing material obtained by using the laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, and a polarizing material obtained by coating a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate. The polarizing plate obtained by using the laminate of the resin substrate and the PVA-based resin layer formed on the resin substrate can be produced, for example, by applying a PVA-based resin solution to the resin substrate, drying the solution to form a PVA-based resin layer on the resin substrate, obtaining a laminate of the resin substrate and the PVA-based resin layer, and stretching and dyeing the laminate to form the PVA-based resin layer into the polarizing plate. In this embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching. Further, stretching may include if necessary, subjecting the laminate to air stretching at a high temperature (for example, 95 ℃ or higher) before stretching in the aqueous boric acid solution. The obtained laminate of the resin substrate and the polarizing element may be used as it is (that is, the resin substrate may be used as a protective layer for the polarizing element), or the resin substrate may be peeled from the laminate of the resin substrate and the polarizing element, and any appropriate protective layer according to the purpose may be laminated on the peeled surface. Details of such a method for producing a polarizing material are described in, for example, japanese patent application laid-open No. 2012-73580. The entire disclosure of this publication is incorporated by reference into this specification.

The thickness of the polarizer is, for example, 1 μm to 80 μm. In one embodiment, the thickness of the polarizer is preferably 1 μm to 20 μm, and more preferably 3 μm to 15 μm.

The polarizer protective film preferably has substantially optical isotropy. In the present specification, "substantially optically isotropic" means that the in-plane retardation Re (550) is 0nm to 10nm. The in-plane retardation Re (550) is more preferably 0nm to 5nm, still more preferably 0nm to 3nm, particularly preferably 0nm to 2nm. When Re (550) of the polarizer protective film is in such a range, adverse effects on display characteristics can be prevented when the polarizing plate including the polarizer protective film is applied to an image display device. Re (550) is the in-plane retardation of the film measured at 23℃with light having a wavelength of 550 nm. Re (550) was obtained by the formula Re (550) = (nx-ny) x d. Here, nx is the refractive index in the direction in which the refractive index in the plane is maximum (i.e., the slow axis direction), ny is the refractive index in the direction orthogonal to the slow axis in the plane (i.e., the fast axis direction), and d is the thickness (nm) of the thin film.

The higher the transmittance at 380nm is, the more preferable is the polarizer protective film thickness of 40 μm. Specifically, the light transmittance is preferably 75% or more, more preferably 80% or more, and further preferably 85% or more. When the light transmittance is in such a range, desired optical characteristics can be ensured. The light transmittance can be measured by, for example, a method according to ASTM-D-1003.

The haze of the polarizer protective film is preferably 50% to 99%, more preferably 70% to 95%.

The polarizer protective film preferably has the following characteristics. When the light transmittance at 550nm is set to 100%, the difference between the light transmittance at 450nm and the light transmittance at 650nm and the light transmittance at 550nm is preferably within.+ -. 5%, more preferably within.+ -. 2%.

The luminance angle of view of the polarizer protective film is preferably 56 ° (one-sided 28 °) or more, more preferably 60 ° -70 ° (one-sided 30 ° -35 °) at a half-value angle of luminance (an angle at which luminance is 50% of the front face). The angle at which the luminance becomes 25% of the front face is preferably 90 ° (45 ° on one side) or more, more preferably 96 ° -120 ° (48 ° -60 ° on one side). According to the embodiment of the present invention, excellent diffusion performance can be imparted to the polarizer protective film, and the luminance angle of view can be maintained wide.

The refractive index n _F of the whole polarizer protective film is preferably 1.3 to 1.8, more preferably 1.4 to 1.6. When the refractive index of the polarizer protective film is in such a range, the refractive index difference between the polarizer protective film and the low refractive index portion defined by the point bonding with the polarizer in the polarizing plate can be set to a desired range.

The moisture permeability of the polarizer protective film is preferably 300g/m ².24 hr or less, more preferably 250g/m ².24 hr or less, still more preferably 200g/m ².24 hr or less, particularly preferably 150g/m ².24 hr or less, and most preferably 100g/m ².24 hr or less. When the moisture permeability of the polarizer protective film is in such a range, a polarizing plate excellent in durability and moisture resistance can be obtained.

C. image display device

The polarizing plate can be applied to an image display device. Accordingly, the present invention also includes an image display device using such a polarizing plate. As typical examples of the image display device, a liquid crystal display device and an organic Electroluminescence (EL) display device are cited. Since the image display device has a structure well known in the art, a detailed description thereof will be omitted.

Examples

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. The measurement methods of the respective characteristics are as follows. Unless otherwise specified, "parts" and "%" in examples are based on weight.

(1) Workability (tear strength)

The tear strength of the shaping layer was measured by the trouser tearing method according to JIS K7128-1. The test piece was cut to a predetermined size under constant temperature conditions (23 ℃ C., 50% humidity), a 75mm slit was cut, and a tear test was performed at a speed of 200 mm/min. The average value of the tear strength of the remaining 50mm was determined except for 20mm at the start of the tear and 5mm before the end of the tear. The test was performed with n=5 and the average value was determined.

When the tear strength is 0.5N or less, the film may break during film formation, and thus is referred to as NG.

(2) Optical characteristics

The content of the light diffusing fine particles was adjusted so that the haze of the light diffusing film became 80%, and the transmittance T (450) at a wavelength of 450nm, the transmittance T (550) at a wavelength of 550nm, and the transmittance T (650) at a wavelength of 650nm were measured.

A value of ((T450) -T (650))/T (550) of within.+ -. 0.5 was defined as acceptable (. Smallcircle.). The quality product was free from coloring of transmitted light and was excellent in optical characteristics.

(3) Humidification durability

After an adhesive was applied to the surface of the polarizing element at 1 μm, the polarizing element was bonded to the concave-convex surface of the light diffusion film (polarizing element protective film) obtained in examples and comparative examples, and then UV irradiation was performed to cure the adhesive, thereby obtaining a polarizing plate composed of a shaping film (polarizing element protective film)/adhesive layer/polarizing element.

The shaping film (polarizing element protective film) of the polarizing plate is laminated with a glass plate via an acrylic adhesive. The resulting laminate was left to stand in an atmosphere of 90% humidity at 60℃for 500 hours. Then, the transmittance of the laminate was measured by an absorptiometer with an integrating sphere (V7100 manufactured by japan spectroscopy).

Regarding the transmittance before heating and humidification, the transmittance after heating and humidification was changed by 10% or more and was determined to be unacceptable (x), and the transmittance after heating and humidification was determined to be acceptable (o).

Example 1]

Methacrylic resin (product name "PARAPET HR-S" manufactured by Kagaku Co., ltd.) was fed into a single screw extruder, and a textured layer (thickness: 50 μm, protrusion height: 10 μm, cell size: 15000 μm ²) was obtained by imparting a textured shape to one surface by an embossing roll while melt-extruding at 260 ℃.

A mixture obtained by blending 10 parts of silica particles having a volume average particle diameter of 10 μm into an acrylic ultraviolet curable resin was applied to the side of the shaping layer having no irregularities. And irradiating ultraviolet rays to the coating layer to cure the ultraviolet curing resin to form a light diffusion layer, thereby obtaining the light diffusion film.

And (3) applying the obtained light diffusion film to the evaluations (1) - (3). The results are shown in Table 1.

Example 2 ]

A light diffusion film was obtained in the same manner as in example 1, except that silica particles having a volume average particle diameter of 6 μm were used as the silica particles of the light diffusion layer.

Example 3 ]

A light diffusion film was obtained in the same manner as in example 1, except that silica particles having a volume average particle diameter of 2 μm were used as the silica particles of the light diffusion layer.

Example 4 ]

A shaping layer was obtained in the same manner as in example 1.

On the side of the shaping layer having no irregularities, the shaping layer and the acrylic film are laminated via an adhesive film (light diffusion adhesive) in which silica particles are dispersed in an acrylic adhesive, to obtain a light diffusion film.

Example 5 ]

A shaping layer was obtained in the same manner as in example 1.

On the side of the shaping layer having no uneven shape, the shaping layer and a light-diffusing film (Kimoto co., ltd., trade name "diffusing film MXE") were laminated via an acrylic adhesive to obtain a light-diffusing film. The light diffusion film is laminated with the surface opposite to the diffusion layer as the shaping layer side.

Comparative example 1]

9 Parts of silicone resin fine particles (volume average particle diameter 4.5 μm) as light diffusing fine particles were fed into a single screw extruder to 100 parts of methacrylic resin (product name "PARAPET HR-S" manufactured by Kagaku Kogyo Co., ltd.) and melt-extruded at 260℃while giving a concave-convex shape to one surface by an embossing roll, to obtain a light diffusing film (thickness: 50 μm, height of convex: 10 μm, cell size: 15000 μm ²).

Comparative example 2 ]

The prism film BEF2-T-155 manufactured by 3M was supplied to the above-mentioned evaluation (3). At this time, after an adhesive was applied to the surface of the polarizer at 1 μm, bonding was performed to the prism side of the prism film.

TABLE 1

Industrial applicability

The light diffusion film of the present invention is useful in various fields as a film capable of imparting a light diffusion function. For example, the light diffusion film of the present invention can be suitably used for a polarizing plate. The polarizing plate of the present invention can be suitably used for an image display device. The image display device of the present invention can be used for various applications such as mobile devices including mobile information terminals (PDA), smart phones, mobile phones, watches, digital cameras, and palm game machines, office automation devices including computer monitors, notebook computers, and copiers, home electric devices including video cameras, televisions, and microwave ovens, in-vehicle devices including rear view displays, displays for car navigation systems, and car audio systems, display devices including digital signage and information displays for shops, security devices including monitor displays, and care/medical devices including care displays and medical displays.

Description of the reference numerals

10. Shaping layer

11. Base material part

12. Concave-convex part

12A convex portion

12B recess

20. Light diffusion layer

100. Light diffusion film

110. Other films

120. Adhesive layer

200. Optical laminate

Claims

1. A light diffusion film comprising a shaping layer and a light diffusion layer disposed on one surface of the shaping layer,

The shaping layer comprises a base material part and a concave-convex part arranged on one surface of the base material part,

The light diffusion layer is disposed on the substrate portion side of the shaping layer,

A wall surface having a convex portion in a region within 500 μm from the end edge of the light diffusion film,

The ratio B/A of the cross-sectional area B of the concave portion to the cross-sectional area A of the entire concave-convex portion is 50% or more,

The haze value of the light diffusion film is 30% -95%.

2. The light diffusing film of claim 1, wherein the light diffusing layer and the shaping layer are laminated with an adhesive layer or an adhesive layer.

3. The light diffusing film of claim 1, wherein the light diffusing layer is formed directly on the shaping layer.

4. The light diffusing film according to any one of claim 1 to 3, wherein the light diffusing layer contains light diffusing fine particles,

The volume average particle diameter of the light diffusing fine particles is 2 μm to 30 μm.

5. A polarizing plate comprising a polarizer and the light diffusion film according to any one of claims 1 to 4 laminated on the polarizer via an adhesive layer.