JP7348807B2 - Shaped film and optical laminate including shaped film - Google Patents

Description

The present invention relates to a shaped film and an optical laminate including the shaped film.

In recent years, there has been a strong demand for thinner image display devices (eg, liquid crystal display devices, organic EL display devices) and improved design (eg, narrower bezels). Along with this, there is an increasing demand for integration of optical members and/or optical films used in image display devices and/or integration of functions. As an example of such integration or function integration, it has been proposed to directly bond a light diffusion film to a predetermined optical member or the like to impart a light diffusion function. Light diffusion films are sometimes required to have brightness, brightness viewing angle, processability, and durability (especially humidification durability) of optical laminates that include the light diffusion films, but they are not used by directly bonding. It is difficult to satisfy these characteristics in a well-balanced manner in a light-diffusing film.

Japanese Patent Application Publication No. 2012-118235 JP2009-025774A

The present invention has been made to solve the above-mentioned conventional problems, and its main purpose is to be able to exhibit excellent brightness and brightness viewing angle when combined with another film to form an optical laminate; The object of the present invention is to provide a shaped film that can contribute to the durability (particularly, humidification durability) of the optical laminate and has excellent processability.

The shaped film of the present invention is a shaped film comprising a base material portion and an uneven portion formed on one side of the base material portion, the uneven portion being surrounded by a convex portion and the convex portion. The height of the convex portion is 5% to 40% of the thickness of the shaped film, and the average area of the concave portion having the cell structure is 5000 μm ² or more, and the wall surface of the convex portion exists in a region within 500 μm from the edge of the shaped film.
In one embodiment, the base portion and the uneven portion are made of the same material.
In another aspect of the invention, an optical laminate is provided. This optical laminate includes the above-mentioned shaped film and another film disposed on one side of the shaped film so as to oppose the uneven portion of the shaped film, and has a total cross-sectional area of the uneven portion. The ratio B/A of the cross-sectional area B of the recess to A is 50% or more.
In one embodiment, the optical laminate further includes an adhesive layer between the shaped film and the another film.
In one embodiment, the portion where the adhesive layer has the maximum thickness is located at a position corresponding to the recessed portion of the shaped film.
In one embodiment, the adhesive layer includes an active energy ray-curable adhesive.
In one embodiment, the storage modulus of the adhesive layer at 25° C. is 100 kPa or more.
In one embodiment, the another film is a polarizer, a wavelength conversion film, a polarized light reflective film, glass, or a resin film.
In one embodiment, the optical laminate is a polarizing plate.

According to the present invention, by configuring the surface with irregularities of a specific shape, when an optical laminate is constructed in combination with another film, excellent brightness and brightness viewing angle can be exhibited, and the optical laminate can exhibit excellent brightness and brightness viewing angle. It is possible to provide a shaped film that can contribute to durability (especially humidification durability) and has excellent processability.

FIG. 1 is a schematic cross-sectional view of a shaped film according to one embodiment of the present invention. FIG. 2 is a schematic plan view showing a typical example of the planar shape of the convex portions on the uneven surface of the shaped film according to the embodiment of the present invention. FIG. 1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. 1 is a schematic cross-sectional view of a polarizing plate according to one embodiment of the present invention.

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. Note that the drawings are shown schematically for ease of viewing, and the ratios of length, width, and thickness, the shape and fineness of unevenness, etc. are different from the actual drawings.

A. Shaped film A-1. Overall Configuration FIG. 1 is a schematic cross-sectional view of a shaped film according to one embodiment of the present invention. The shaped film 100 in the illustrated example has a base material part 10 and an uneven part 20 formed on one side of the base material part 10. The uneven portion 20 has a convex portion 21 and a concave portion 22. The shaped film of the present invention can function as a light-diffusing film by attaching the uneven portions 20 to another film.

FIG. 2 is a schematic plan view showing a typical example of the planar shape of the convex portion of the uneven portion in the shaped film according to one embodiment of the present invention. As shown in FIG. 2, the recess 22 may have a cell structure surrounded by the protrusion 21 (substantially, the wall surface of the protrusion). By forming the recesses having a cell structure, when an optical laminate is constructed by laminating the shaped film on another film, it is possible to prevent moisture from entering the optical laminate. Furthermore, by forming the recessed portions having a cell structure, it is possible to prevent defects such as cracking and chipping at the cut portion, and to obtain a shaped film that can be cut with good workability. Note that not all of the recesses need to have a cell structure; for example, in the vicinity of the edges of the shaped film, the recesses may be open toward the edges of the shaped film.

Any suitable shape may be adopted as the shape of the convex portion 21 in the uneven portion in plan view. The shape of the convex portion 21 in plan view may be a regular shape (for example, a lattice shape) or an irregular shape, as shown in FIG. 2, for example. The pitch of the convex portions (the distance between the convex portions) 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, a bias angle of 1 degree to 90 degrees may be provided. When the convex portion has an irregular shape in plan view, the pitch means an average pitch, and it is preferable that the distribution is such that 50% or more is within ±50% of the average value of the pitch. With such a configuration, when the shaped film is laminated on another film, adhesive strength between the shaped film and another film can be ensured, and good display quality can be ensured. Furthermore, when an optical laminate is constructed by laminating the shaped film on another film, it is possible to prevent moisture from entering the optical laminate.

The height H of the convex portion 21 is 5% to 40% of the thickness of the shaped film. In such a range, when an optical laminate is constructed by laminating the excipient film on another film, only the convex portion of the excipient film (substantially the upper part of the convex portion) will overlap with the other film. can be glued to. Note that in this specification, adhesion of only the convex portions may be referred to as "point adhesion" for convenience. Due to such point bonding, a substantial low refractive index portion is defined by a concave portion (air portion or void portion) in the vicinity of the point bonded portion. As a result, it is possible to realize good light diffusion performance and increase the brightness viewing angle. Conventionally, in an image display device, another film (for example, a polarizer (polarizing plate)) and a light diffusing film are placed separately, and as a result, an air layer is interposed between the polarizing plate and the light diffusing film. . While this air layer becomes an obstacle to making the device thinner, the brightness and viewing angle are maintained large due to retroreflection caused by the air layer. Although a reduction in thickness and integration of functions can be achieved by integrating another film and a light-diffusing film, the brightness and viewing angle become smaller due to the elimination of the air layer. By forming a low refractive index portion near the point bonded portion, light is efficiently retroreflected in the same way as when an air layer exists. Therefore, according to the embodiment of the present invention, by forming point adhesion, it is possible to exhibit desired light diffusion performance and maintain a large (wide) brightness viewing angle. Further, setting the height of the convex portion within the above range is advantageous from the viewpoint of mechanical strength, and thereby the shape of the concave portion can be maintained preferably, and excellent light diffusivity and brightness viewing angle can be obtained.

The height H of the convex portion 21 is preferably 10% to 30%, more preferably 10% to 20% of the thickness of the shaped film. Within this range, the above effect becomes significant.

The height H of the convex portion 21 is preferably 2.5 μm to 25 μm, more preferably 5 μm to 20 μm. Within this range, the above effect becomes significant.

The average area of the recesses having a cell structure is 5000 μm ² or more. Within such a range, it is possible to obtain a shaped film that can realize an excellent brightness viewing angle while suppressing a decrease in brightness. The average area of the recesses having a cell structure is preferably 5000 μm ² to 50000 μm ² , more preferably 7000 μm ² to 40000 μm ² , and even more preferably 8000 μm ² to 30000 μm ² . Within this range, the above effects will be significant, and a shaped film with excellent mechanical strength can be obtained. The average area of the recesses having a cell structure can be determined 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 on the surface of the shaped film, and the outer frame of the recess is specified. It can be determined by calculating the area within the specified frame and calculating the average value of the calculated areas.

In one embodiment, the maximum length in plan view of the recessed portion that is the cell structure is preferably 300 μm or more, more preferably 400 μm or more, and still more preferably 500 μm or more. Within this range, even when the shaped film is cut and used, the shaped film effectively prevents moisture intrusion and improves the durability near the edges of the optical laminate. be able to. The maximum length of the concave portion having a cell structure means the distance at the point where the distance between the wall surfaces of the convex portions forming the concave portion is the longest.

The area ratio of the recesses 22 to the entire area of the uneven portion when viewed in plan is preferably 50% or more, preferably 60% or more, and more preferably 70% or more. The upper limit of the area ratio of the recesses may be, for example, 90%. If the area ratio of the recesses is in this range, the shaped film will have good diffusion performance while maintaining a wide brightness viewing angle, and will also improve the adhesive strength when the shaped film is laminated onto another film. can be ensured.

In the shaped film of the present invention, the wall surface of the convex portion 21 exists in a region within 500 μm from the edge of the shaped film. In the present invention, the convex portion 21 can prevent moisture from entering the optical laminate when the shaped film is laminated onto another film to form an optical laminate. By forming the wall surface of the convex portion 21 in a region within 500 μm from the edge of the shaped film, moisture intrusion can be effectively prevented and the durability of the optical laminate near the edge can be improved. It is preferable that the wall surface of the convex portion 21 exists in a region within 400 μm from the edge of the shaped film, and more preferably the wall surface of the convex portion 21 exists in a region within 300 μm from the edge of the shaped film. Preferably, the wall surface of the convex portion 21 is present in all areas within 500 μm (preferably within 400 μm, more preferably within 300 μm) from the edge of the shaped film.

The ratio B/A of the cross-sectional area B of the recessed portion to the cross-sectional area A of the entire uneven portion is preferably 50% or more, more preferably more than 50%, still more preferably 60% or more, and particularly preferably It is 70% or more. The upper limit of the ratio B/A may be, for example, 90%. If the ratio B/A is in this range, the shaped film will have good diffusion performance while maintaining a wide brightness viewing angle, and will also have good adhesive strength when the shaped film is laminated to another film. can be ensured. Note that the cross-sectional area A of the entire uneven portion is the area of the portion surrounded by the line connecting the surface of the raised portion, the line connecting the bottom of the recessed portion, and the vertical line at both ends of the film (for reference, The cross-sectional area B of each recess 22 is defined as the cross-sectional area B of each recess 22 (the line connecting the wall line of the adjacent projection and the surface of the projection and the line connecting the bottom of the recess). (area of the area enclosed by ).

The thickness of the shaped film of the present invention is preferably 25 μm to 250 μm, more preferably 40 μm to 100 μm.

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

In one embodiment, the shaped film does not contain light-diffusing particles. By configuring it without containing light-diffusing particles, a shaped film with excellent processability can be obtained. More specifically, it is possible to obtain a shaped film that is less likely to break during film formation. Further, when cutting the obtained shaped film, it is possible to prevent defects such as cracks and chips at the cut portion, and to cut the end surface with good quality. One of the achievements of the present invention is that even without including light-diffusing particles, good light-diffusing performance can be achieved and the brightness viewing angle can be increased.

The uneven portion (irregular shape) may be formed by any suitable method. The uneven shape can be formed, for example, by a method of roughening the surface or a method of imparting unevenness using fine particles. Specific examples of surface roughening methods include embossing and sandblasting. The uneven portion (irregular shape) can typically be formed by shaping the surface of a melt-extruded film with an embossing roll. Further, a mold having an uneven shape is pressed against the surface of a film precursor formed from an active energy ray (for example, ultraviolet ray) curable resin composition to transfer the uneven shape, and then the composition is cured, A shaped film may also be obtained.

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

A-2. Constituent Materials Any suitable resin may be employed as the resin constituting the shaped film. Specific examples of resins constituting the shaped film include (meth)acrylic resins, polyester resins (e.g. polyethylene terephthalate (PET)), cycloolefin resins (e.g. norbornene resins), cellulose resins (e.g. , triacetyl cellulose (TAC)), polyvinyl alcohol resin, polycarbonate resin, polyamide resin, polyimide resin, polyethersulfone resin, polysulfone resin, polystyrene resin, polyolefin resin, and acetate resin. . These resins may be used alone or in combination of two or more. From the viewpoints of optical properties, transparency, and versatility, (meth)acrylic resins, polyester resins, and cycloolefin resins are preferred, and (meth)acrylic resins are more preferred. In this specification, "(meth)acrylic" means acrylic and/or methacryl.

As the (meth)acrylic resin, any appropriate (meth)acrylic resin may be employed. In addition, for simplification of description, (meth)acrylic resin will be simply referred to as acrylic resin hereinafter. Acrylic resin typically contains 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 linear or branched alkyl groups having 1 to 18 carbon atoms. These can be used alone or in combination. Furthermore, any appropriate copolymerizable monomer may be introduced into the acrylic resin by copolymerization. The type, number, copolymerization ratio, etc. of such copolymerizable monomers can be appropriately set depending on the purpose. The constituent components (monomer units) of the main skeleton of the acrylic resin will be described later with reference to general formula (2).

The acrylic resin may preferably have at least one selected from glutarimide units, lactone ring units, maleic anhydride units, maleimide units, and glutaric anhydride units. Acrylic resins having lactone ring units are described, for example, in JP-A No. 2008-181078, and the description in this publication is incorporated herein by reference. The glutarimide unit is preferably represented by the following general 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, or an alkyl group having 3 to 12 carbon atoms. represents a cycloalkyl group or an aryl group having 6 to 10 carbon atoms. In general formula (1), preferably R ¹ and R ² are each independently hydrogen or a methyl group, and R ³ is hydrogen, a methyl group, a butyl group, or a cyclohexyl group. More preferably, R ¹ is a methyl group, R ² is hydrogen and R ³ is a methyl group.

The above alkyl (meth)acrylate is typically represented by the following general 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. show. Examples of the substituent include halogen and hydroxyl group. Specific examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, and t-(meth)acrylate. Butyl, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, chloromethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (meth)acrylic acid Examples include 3-hydroxypropyl, 2,3,4,5,6-pentahydroxyhexyl (meth)acrylate and 2,3,4,5-tetrahydroxypentyl (meth)acrylate. In general formula (2), R ⁵ is preferably a hydrogen atom or a methyl group. Particularly preferred alkyl (meth)acrylates are therefore 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 , R ² and R ³ in the general formula (1) are different.

The content of glutarimide units in the acrylic resin is preferably 2 mol% to 50 mol%, more preferably 2 mol% to 45 mol%, even more preferably 2 mol% to 40 mol%, particularly preferably 2 mol%. % to 35 mol%, most preferably 3 mol% to 30 mol%. If the content is less than 2 mol %, the effects derived from the glutarimide unit (for example, high optical properties, high mechanical strength, and thinning) may not be sufficiently exhibited. If the content exceeds 50 mol%, for example, heat resistance and transparency may become insufficient.

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

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

The acrylic resin may contain units other than glutarimide units and alkyl (meth)acrylate units.

In one embodiment, the acrylic resin may contain, for example, 0% to 10% by weight of unsaturated carboxylic acid units that do not participate in the intramolecular imidization reaction described below. The content of unsaturated carboxylic acid units is preferably 0% to 5% by weight, more preferably 0% to 1% by weight. If the content is within this range, transparency, retention stability, and moisture resistance can be maintained.

In one embodiment, the acrylic resin can contain copolymerizable vinyl monomer units (other vinyl monomer units) other than those mentioned above. Examples of other vinyl monomers include acrylonitrile, methacrylonitrile, ethacrylonitrile, allyl glycidyl ether, maleic anhydride, itaconic anhydride, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, acrylic aminoethyl acid, propylaminoethyl acrylate, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, cyclohexylaminoethyl methacrylate, N-vinyldiethylamine, N-acetylvinylamine, allylamine, methalylamine, N-methylallylamine, 2 -Isopropenyl-oxazoline, 2-vinyl-oxazoline, 2-acroyl-oxazoline, N-phenylmaleimide, phenylaminoethyl methacrylate, styrene, α-methylstyrene, p-glycidylstyrene, p-aminostyrene, 2-styryl- Examples include oxazoline. These may be used alone or in combination. Styrenic monomers such as styrene and α-methylstyrene are preferred. The content of other vinyl monomer units is preferably 0 to 1% by weight, more preferably 0 to 0.1% by weight. Within this range, it is possible to suppress the development of undesired phase difference and the decrease in transparency.

The imidization rate in the acrylic resin is preferably 2.5% to 20.0%. When the imidization rate is within this range, a resin with excellent heat resistance, transparency, and moldability can be obtained, and the occurrence of burnt and decrease in mechanical strength during film molding can be prevented. In the above acrylic resin, the imidization rate is expressed as the ratio of glutarimide units to alkyl (meth)acrylate units. This ratio can be obtained, for example, from the NMR spectrum, IR spectrum, etc. of the acrylic resin. In this embodiment, the imidization rate can be determined by ¹ H-NMR measurement of the resin using ¹ HNMR BRUKER Avance III (400 MHz). More specifically, A is the peak area derived from the O-CH ₃ proton of alkyl (meth)acrylate around 3.5 to 3.8 ppm, and the peak area derived from the N-CH ₃ proton of glutarimide around 3.0 to 3.3 ppm is defined as A. It is determined by the following formula, where B is the area of the peak derived from protons.
Imidization rate Im (%) = {B/(A+B)}×100

The acrylic resin has a Tg (glass transition temperature) of preferably 110°C or higher, more preferably 115°C or higher, even more preferably 120°C or higher, particularly preferably 125°C or higher, and most preferably 130°C or higher. If Tg is 110° C. or higher, a polarizing plate containing a shaped film obtained from such a resin tends to have excellent durability. The upper limit of Tg is preferably 300°C or less, more preferably 290°C or less, even more preferably 285°C or less, particularly preferably 200°C or less, and most preferably 160°C or less. If Tg is within such a range, moldability can be excellent.

The above acrylic resin can be produced, for example, by the following method. This method comprises (I) an alkyl (meth)acrylate monomer corresponding to the alkyl (meth)acrylate unit represented by general formula (2), an unsaturated carboxylic acid monomer and/or its precursor monomer; and (II) treating the copolymer (a) with an imidizing agent to obtain the copolymer (a). An intramolecular imidization reaction is carried out between the alkyl (meth)acrylate monomer unit and the unsaturated carboxylic acid monomer and/or its precursor monomer unit, and the glutarimide unit represented by the general formula (1) is formed. Incorporating into a polymer.

Details of the acrylic resin and its manufacturing method are described in, for example, JP 2018-155812A and JP 2018-155813A. The descriptions of these publications are incorporated herein by reference.

B. Optical laminate B-1. Overall Configuration FIG. 3 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. The illustrated optical laminate 200 includes a shaping film 100 and another film 110 disposed on one side of the shaping film 100. The shaped film 100 and another film 110 are laminated so that the uneven portions 20 of the shaped film 100 and the other film 110 face each other. Typically, the shaped film 100 and another film 110 are laminated with an adhesive layer 120 interposed therebetween.

As mentioned above, in the uneven portion 20 of the shaped film 100, the ratio B/A of the cross-sectional area B of the recessed portion to the cross-sectional area A of the entire uneven portion is preferably 50% or more, more preferably more than 50%. More preferably, it is 60% or more, 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 porosity. Within this range, it is possible to achieve good light diffusion performance, increase the brightness viewing angle, and obtain an optical laminate with excellent mechanical strength.

B-2. Another film Any suitable film may be employed as the other film. Examples of other films include optical films such as polarizers, wavelength conversion films, and polarized light reflecting films; glass (preferably thin glass); resin films (for example, protective films), and the like.

In one embodiment, a polarizer is used as another film. In this embodiment, the shaping film may function as a polarizer protective film, and the optical laminate may serve as a polarizing plate. Details of the polarizing plate will be described later.

B-3. Adhesive Layer The adhesive layer is comprised of any suitable adhesive or adhesive. The adhesive layer is typically formed of a water-based adhesive (for example, a vinyl alcohol adhesive) or a curable adhesive (for example, an active energy ray-curable adhesive or a heat-curable adhesive).

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

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

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

Specific examples of the active energy ray-curable adhesive and its curing method are described in, for example, JP-A No. 2012-144690. That description is incorporated herein by reference.

As a method for applying the active energy ray-curable adhesive, any appropriate method may be adopted depending on the viscosity of the adhesive, the desired thickness of the adhesive layer, etc. Examples of the coating method include coating using a reverse coater, a gravure coater (direct, reverse, or offset), a bar reverse coater, a roll coater, a die coater, a bar coater, a rod coater, and the like. Further, application by a dipping method may be adopted.

Any suitable method may be employed as a method for curing the active energy ray-curable adhesive. Conditions such as the wavelength of the active energy ray and the irradiation amount may be set to any appropriate conditions depending on the type of curable compound used and the like.

The thickness of the adhesive layer at its maximum thickness is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 5 μm. Within this range, voids due to the unevenness of the shaped film can be preferably formed, and an optical laminate having excellent mechanical strength can be obtained. In one embodiment, the portion where the adhesive layer has the maximum thickness extends from the top surface of the convex portion of the shaped film (the surface facing another film) to the bottom surface of another film (the surface facing the shaped film). This can correspond to a gap of In another embodiment, the portion where the adhesive layer has the maximum thickness may be located at a position corresponding to the recessed portion of the shaped film (FIG. 4). For example, an adhesive layer may be formed to cover at least a portion of the wall surface of the convex portion of the shaped film. At this time, it is preferable that the adhesive layer is not formed on the concave surface of the shaped film and has a so-called meniscus shape. In this embodiment, it is possible to obtain an optical laminate that has excellent adhesiveness between the excipient film and another film while ensuring voids.

In one embodiment, the thickness T of the adhesive layer formed on the upper surface of the convex portion of the shaped film is preferably thinner than the thickness (height) H of the convex portion. The ratio T/H between the thickness T and the height H of the convex portion is preferably 50% or less, more preferably 30% or less. If the ratio T/H is within this range, good point adhesion can be achieved. The lower limit of the ratio T/H may be, for example, 10%.

The above-mentioned shaped film has an uneven part, and the raised part of the shaped film and another film are laminated by adhesion (that is, point adhesion). In addition to the portion contributing to adhesion, it is also preferable that the adhesive be formed in the void portion. In other words, the adhesive layer preferably covers at least a portion (preferably all) of the surface of another film in the recessed portion (gap portion) of the shaped film. In this way, deterioration of other films can be prevented. Such an effect is particularly useful when the other film is degraded by moisture, ambient air, etc., and is useful, for example, when the other film is a polarizer. The thickness of the adhesive layer in the gap portion may be constant or irregular. In one embodiment, the adhesive layer in the gap has a meniscus shape and has an indeterminate thickness. Examples of the method for providing an adhesive layer in the gap include a method in which an adhesive precursor layer is formed on another film and then the other film and the shaped film are bonded together.

The storage modulus of the adhesive layer at 25° C. is preferably 100 kPa or more, more preferably 100 kPa to 3 GPa, still more preferably 100 kPa to 1 GPa. Within this range, voids due to the unevenness of the shaped film can be preferably formed, and an optical laminate having excellent mechanical strength can be obtained. Note that the storage modulus can be determined by dynamic viscoelasticity measurement. Dynamic viscoelasticity measurement is performed, for example, on an adhesive sample with a thickness of 2 mm and a diameter of 8 mm using "Advanced Rheometric Expansion System (ARES)" manufactured by Rheometric Scientific, deformation mode: torsion, measurement frequency: 1 Hz, heating rate 5. C/min, measurement temperature: -50°C to 150°C.

B-4. Polarizing Plate As mentioned 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 one embodiment of the invention. The illustrated polarizing plate 200a 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 above-mentioned shaping film. Moreover, the polarizer 110a corresponds to the above-mentioned another film. The polarizer protective film 100a is arranged so that the uneven portion side faces the polarizer 110a. The adhesive layer is as described above. Practically, another protective film 140 is placed on the opposite side of the polarizer protective film 100a. Practically speaking, an adhesive layer 150 is further provided as the outermost layer to enable attachment of the polarizing plate to the image display cell. A separator (not shown) is removably temporarily attached to the surface of the adhesive layer 150 to protect the adhesive layer until the polarizing plate is actually used and to enable roll formation. The polarizing plate according to the embodiment of the present invention may be used as a back side polarizing plate of an image display device, or may be used as a viewing side polarizing plate. According to the embodiment of the present invention, the polarizer protective film itself has light diffusion performance and also serves as a light diffusion film, so that a remarkable reduction in thickness can be achieved due to the synergistic effect with the effect of eliminating the air layer.

Any suitable polarizer may be employed as the polarizer. 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 polarizers composed of single-layer resin films include hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and partially saponified ethylene/vinyl acetate copolymer films. Examples include those that have been dyed with dichroic substances such as iodine and dichroic dyes and stretched, and polyene-based oriented films such as dehydrated PVA and dehydrochloric acid treated polyvinyl chloride. Preferably, a polarizer obtained by dyeing a PVA film with iodine and uniaxially stretching is used because it has excellent optical properties.

The above-mentioned staining with iodine is performed, for example, by immersing the PVA-based film in an iodine aqueous solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after the dyeing process or may be performed while dyeing. Alternatively, it may be dyed after being stretched. If necessary, the PVA film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, etc. For example, by immersing a PVA film in water and washing it with water before dyeing, you can not only wash dirt and anti-blocking agents from the surface of the PVA film, but also swell the PVA film and prevent uneven dyeing. It can be prevented.

Specific examples of polarizers obtained using a laminate include a laminate of a resin base material and a PVA resin layer (PVA resin film) laminated on the resin base material, or a laminate of a resin base material and the resin Examples include polarizers obtained using a laminate with a PVA-based resin layer coated on a base material. A polarizer obtained using a laminate of a resin base material and a PVA-based resin layer coated on the resin base material can be obtained by, for example, applying a PVA-based resin solution to the resin base material and drying it. Forming a PVA-based resin layer thereon to obtain a laminate of a resin base material and the PVA-based resin layer; stretching and dyeing the laminate to use the PVA-based resin layer as a polarizer; obtain. In this embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching. Furthermore, the stretching may further include stretching the laminate in air at a high temperature (for example, 95° C. or higher) before stretching in the boric acid aqueous solution, if necessary. The obtained resin base material/polarizer laminate may be used as is (that is, the resin base material may be used as a protective layer for the polarizer), or the resin base material may be peeled from the resin base material/polarizer laminate. However, any appropriate protective layer may be laminated on the peeled surface depending on the purpose. Details of the method for manufacturing such a polarizer are described in, for example, Japanese Patent Application Publication No. 2012-73580. The entire description of this publication is incorporated herein by reference.

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, more preferably 3 μm to 15 μm.

The polarizer protective film preferably has substantially optical isotropy. In this specification, "having substantially optical isotropy" means that the in-plane retardation Re (550) is 0 nm to 10 nm. The in-plane retardation Re(550) is more preferably 0 nm to 5 nm, even more preferably 0 nm to 3 nm, particularly preferably 0 nm to 2 nm. If the Re(550) of the polarizer protective film is within such a range, an adverse effect on display characteristics can be prevented when a polarizing plate including the polarizer protective film is applied to an image display device. Note that Re(550) is the in-plane retardation of the film measured with light having a wavelength of 550 nm at 23°C. Re(550) is determined by the formula: Re(550)=(nx-ny)×d. Here, nx is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., slow axis direction), and ny is the refractive index in the in-plane direction perpendicular to the slow axis (i.e., fast axis direction). It is the refractive index, and d is the thickness (nm) of the film.

The higher the light transmittance at 380 nm when the polarizer protective film has a thickness of 40 μm, the better. Specifically, the light transmittance is preferably 75% or more, more preferably 80% or more, and even more preferably 85% or more. If the light transmittance is within this range, desired optical characteristics can be ensured. Light transmittance can be measured, for example, by a method according to ASTM-D-1003.

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

It is preferable that the polarizer protective film has the following characteristics. When the light transmittance at 550 nm is taken as 100%, the difference between the light transmittance at 450 nm and 650 nm and the light transmittance at 550 nm is preferably within ±5%, more preferably within ±2%. be.

Regarding the brightness viewing angle of the polarizer protective film, the half-brightness angle (the angle at which the brightness is 50% of the front brightness) is preferably 56° (28° on one side) or more, and more preferably 60° to 70° (30° on one side). 35°). Further, the angle at which the brightness is 25% of the front brightness is preferably 90° (45° on one side) or more, and more preferably 96° to 120° (48° to 60° on one side). According to the embodiments of the present invention, it is possible to provide a polarizer protective film with excellent diffusion performance and maintain a wide brightness viewing angle.

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

The water vapor permeability of the polarizer protective film is preferably 300 g/m ² ·24 hr or less, more preferably 250 g/m ² ·24 hr or less, even more preferably 200 g/m ² ·24 hr or less, particularly preferably 150 g/m ² ·24 hr Below, most preferably it is 100 g/m ² ·24 hr or less. If the water vapor permeability of the polarizer protective film is within this range, a polarizing plate with excellent durability and moisture resistance can be obtained.

C. Image Display Device The polarizing plate described above can be applied to an image display device. Therefore, the present invention also includes an image display device using such a polarizing plate. Typical examples of image display devices include liquid crystal display devices and organic electroluminescence (EL) display devices. Since the image display device employs a configuration well known in the industry, detailed explanation will be omitted.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples. The method for measuring each characteristic is as follows. Note that unless otherwise specified, "parts" and "%" in the examples are based on weight.

(1) Thickness of the shaped film and height of the convex parts The cross sections of the shaped films obtained in Examples and Comparative Examples were observed with a scanning electron microscope, and the height of the shaped film and the height of the convex parts were determined from the images. The height was measured.
(2) Cell size The surfaces of the shaped films obtained in Examples and Comparative Examples were observed with a scanning electron microscope, and the average area of the recesses was determined from the images using image analysis software (free software "ImageJ"). Ta. More specifically, the inside and outside of the recess are determined using the threshold value of the surface binary image, the outer frame of the recess is specified, the area within the specified frame is calculated, the average value of the calculated area is calculated, and this is It was taken as the average area of the recess.
(3) Distance from the edge of the shaped film to the outermost convex part The surface of the shaped films obtained in the Examples and Comparative Examples was observed with a scanning electron microscope, and the distance from the edge of the shaped film was determined from the image. The distance to the outermost convex portion was measured. Note that the distance was measured over the entire circumference of the shaped film, and Table 1 shows the maximum value.
(4) Point adhesion evaluation After coating the surface of the polarizer with adhesive at a thickness of 1 μm, the polarizer and the uneven surface of the shaped film (polarizer protective film) obtained in the Examples and Comparative Examples are bonded together. Thereafter, the adhesive was cured by UV irradiation to obtain a polarizing plate consisting of a shaped film (polarizer protective film)/adhesive layer/polarizer. Thereafter, the polarizing plate was observed under a microscope to check how well the shaped recesses were filled, and evaluated based on the following criteria.
○: Out of 100 recesses (voids), 80 or more are good (60% or more of the recesses are not filled with adhesive)
△: Out of 100 recesses (voids), 30 to 79 are good. ×: Out of 100 recesses (voids), less than 30 are good (5) Humidification durability Same as (4) above. A polarizing plate was obtained.
The shaped film of the polarizing plate (polarizer protective film) and a glass plate were laminated via an acrylic adhesive. The obtained laminate was left for 500 hours in an environment with a temperature of 60° C. and a humidity of 90%. Thereafter, the transmittance of the laminate was measured using an absorbance photometer with an integrating sphere ("V7100" manufactured by JASCO Corporation).
A case where the transmittance after heating and humidification changed by 10% or more with respect to the transmittance before heating and humidification was judged as a failure (x), and a case where the change was less than 10% was judged as a pass (○).
(6) Brightness A polarizing plate was obtained in the same manner as in (4) above.
The SJ8000 manufactured by LG was disassembled, the liquid crystal panel with a polarizing plate was taken out, and the above light plate was mounted as a polarizing plate on the backlight side. In addition, the light diffusion film provided in the backlight unit of the product was cut out and reassembled only at the mounting location. Regarding the thus obtained mounted product, the brightness in the front direction was measured using Ezconstrat manufactured by ELDIM. The measured brightness was expressed as a ratio (%) when the front brightness when the polarizing plate and the light diffusing film were placed separately was set to 100.
(7) Processability The shaped films obtained in Examples and Comparative Examples were cut using a lever-type cutter. The case where a crack/chip occurred at the end of the film after cutting by 300 μm or more from the end of the film toward the center was judged as a failure (x), and the case where no cracking/chip occurred was judged as a pass (◯).

<Example 1>
A methacrylic resin (manufactured by Kuraray Co., Ltd., product name "Parapet HR-S") is put into a single-screw extruder, and while melt-extruded at 260°C, an uneven shape is formed on one surface with an embossing roll, and a shaped film is formed. (Thickness: 50 μm, convex height: 10 μm, cell size: 15000 μm ² ) was obtained.
The obtained shaped film was subjected to the above evaluations (1) to (7). The results are shown in Table 1.

<Example 2>
A shaped film (thickness: 46 μm, convex height: 5 μm, cell size: 5000 μm ² ) was obtained in the same manner as in Example 1, except that the embossing roll was changed.
The obtained shaped film was subjected to the above evaluations (1) to (7). The results are shown in Table 1.

<Example 3>
A methacrylic resin (manufactured by Kuraray Co., Ltd., product name "Parapet HR-S") was charged into a single-screw extruder and melt-extruded at 260° C. to obtain a substantially flat film with a thickness of 55 μm. On the surface of this film, 95 parts by weight of urethane acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name "NK Oligo U-108A") and a photopolymerization initiator (manufactured by Ciba Specialty Chemical Co., Ltd., trade name "Irgacure 184") were added. After applying a UV curable resin containing 5 parts by weight and transferring an uneven shape to the coated surface, the UV curable resin is cured to form a shaped film (thickness: 55 μm, height of protrusions: 5 μm, cell Size: 10000 μm ² ) was obtained.
The obtained shaped film was subjected to the above evaluations (1) to (7). The results are shown in Table 1.

<Example 4>
A shaped film (thickness: 55 μm, convex height: 20 μm, cell size: 10000 μm ² ) was obtained in the same manner as in Example 3, except that the mold used was changed.
The obtained shaped film was subjected to the above evaluations (1) to (7). The results are shown in Table 1.

<Comparative example 1>
A shaped film (thickness: 42 μm, convex height: 2 μm, cell size: 10000 μm ² ) was obtained in the same manner as in Example 1, except that the embossing roll was changed.
The obtained shaped film was subjected to the above evaluations (1) to (7). The results are shown in Table 1.

<Comparative example 2>
A shaped film (thickness: 40 μm, convex height: 1 μm, cell size: 12000 μm ² ) was obtained in the same manner as in Example 1, except that the embossing roll was changed.
The obtained shaped film was subjected to the above evaluations (1) to (7). The results are shown in Table 1.

<Comparative example 3>
A shaped film (thickness: 50 μm, convex height: 4 μm, cell size: 10000 μm ² ) was obtained in the same manner as in Example 1, except that the embossing roll was changed.
The obtained shaped film was subjected to the above evaluations (1) to (7). The results are shown in Table 1.

<Comparative example 4>
A shaped film (thickness: 50 μm, convex height: 25 μm, cell size: 11000 μm ² ) was obtained in the same manner as in Example 3, except that the mold used was changed.
The obtained shaped film was subjected to the above evaluations (1) to (7). The results are shown in Table 1.

<Comparative example 5>
A shaped film (thickness: 50 μm, convex height: 5 μm, cell size: 3000 μm ² ) was obtained in the same manner as in Example 3 except that the mold used was changed.
The obtained shaped film was subjected to the above evaluations (1) to (7). The results are shown in Table 1.

<Comparative example 6>
A shaped film (thickness: 233 μm, convex height: 50 μm) was obtained in the same manner as in Example 3 except that the mold used was changed. The shaped film had a prism shape and did not have a cell structure concave portion.
The obtained shaped film was subjected to the above evaluations (1), (5) and (7). The results are shown in Table 1.

<Comparative example 7>
In the same manner as in Example 3, a methacrylic resin was extruded to obtain a film. On the surface of this film, 95 parts by weight of urethane acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name "NK Oligo U-108A") and a photopolymerization initiator (manufactured by Ciba Specialty Chemical Co., Ltd., trade name "Irgacure 184") were added. A mixture of 100 parts by weight of a UV curable resin containing 5 parts by weight and 10 parts by weight of particles (silicone particles, manufactured by Momentive, trade name "Tospearl 1110", average particle diameter: 11 μm) was coated with a wire bar. Thereafter, the coating layer was cured by UV to obtain a film (thickness: 199 μm, height of convex portions: 11 μm).The shaped film did not have concave portions with a cell structure.
The obtained shaped film was subjected to the above evaluations (1), (5) and (7). The results are shown in Table 1.

<Evaluation>
As is clear from Table 1, the polarizing plate constructed using the shaped film of the present invention can exhibit excellent brightness and has excellent humidification durability. Further, the shaped film of the present invention has excellent processability.

The shaped film of the present invention can be used in various fields as a film capable of imparting a light diffusing function. For example, the shaped film of the present invention is suitably used for polarizing plates. The polarizing plate of the present invention is suitably used in image display devices. The image display device of the present invention includes portable devices such as personal digital assistants (PDAs), smartphones, mobile phones, watches, digital cameras, and portable game consoles; OA devices such as personal computer monitors, notebook computers, and copy machines; video cameras, and televisions. , household electrical equipment such as microwave ovens; car equipment such as rear view monitors, car navigation system monitors, and car audio; display equipment such as digital signage and information monitors for commercial stores; security equipment such as surveillance monitors; nursing care It can be used for various purposes such as nursing care and medical equipment such as medical monitors and medical monitors.

10 base material part 20 uneven part 21 convex part 22 concave part 100 shaping film 110 another film 120 adhesive layer 200 optical laminate

Claims (7)

A shaped film comprising a base material part and an uneven part formed on one side of the base material part,
The uneven portion has a convex portion and a concave portion surrounded by the convex portion and has a cell structure,
The height of the convex portion is 5% to 40% of the thickness of the shaped film,
The average area of the recesses having the cell structure is 5000 μm ² or more,
The wall surface of the convex portion is present in an area within 500 μm from the edge of the shaped film.
Shaped film;
a polarizer disposed on one side of the shaped film so as to oppose the uneven portions of the shaped film;
The ratio B/A of the cross-sectional area B of the recessed portion to the entire cross-sectional area A of the uneven portion is 50% or more;
Polarizing plate . The polarizing plate according to claim 1 , further comprising an adhesive layer between the shaped film and the another film. The polarizing plate according to claim 2 , wherein a portion where the thickness of the adhesive layer is maximum is a position corresponding to a recessed portion of the shaping film. The polarizing plate according to claim 2 or 3 , wherein the adhesive layer contains an active energy ray-curable adhesive. The polarizing plate according to any one of claims 2 to 4 , wherein the adhesive layer has a storage modulus of 100 kPa or more at 25°C. The polarizing plate according to any one of claims 1 to 5, wherein the base portion and the uneven portion are made of the same material. The polarizing plate according to any one of claims 1 to 6, wherein the shaped film is the polarizer protective film .

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