WO2018123838A1

WO2018123838A1 - Viewing angle expansion film, polarizing plate, and liquid crystal display device

Info

Publication number: WO2018123838A1
Application number: PCT/JP2017/046057
Authority: WO
Inventors: 寛哉西岡
Original assignee: 日本ゼオン株式会社
Priority date: 2016-12-28
Filing date: 2017-12-22
Publication date: 2018-07-05
Also published as: CN110036314A; JPWO2018123838A1; JP6977736B2; KR20190096982A; TW201832916A

Abstract

Provided is a viewing angle expansion film for expanding the viewing angle, wherein the viewing angle expansion film is equipped with one or more resin layers among which one or more of the layers is a hole-containing layer equipped with multiple hole-containing sections which are substantially parallel to each other. The hole-containing sections contain holes, and the refractive index of the hole-containing layer is 1.53 or less. Also provided are a polarizing plate and a liquid crystal display device having this viewing angle expansion film.

Description

Viewing angle widening film, polarizing plate, and liquid crystal display device

The present invention relates to a viewing angle widening film, a polarizing plate, and a liquid crystal display device.

TN mode and VA mode liquid crystal display devices are established and can be supplied at a relatively low cost. On the other hand, the display quality when viewing the display surface from an oblique direction is inferior, and the usable viewing angle is often narrow. . Specifically, the relationship between the brightness of the image displayed on the screen and the brightness measured by observing the image is greatly different between when observed from the front and when observed from an oblique direction. Visual recognition can be difficult. For this reason, TN mode liquid crystal display devices have conventionally been mainly employed in display devices that are visually recognized from a fixed angle, such as small and medium-sized televisions and personal computers. However, in recent years, it has been attempted to use liquid crystal displays of these modes together with means for expanding the viewing angle even in devices that require visibility at a wide viewing angle, such as tablet terminals.

As an example of means for enlarging the viewing angle, a retardation layer having a specific phase difference and thereby compensating the viewing angle is known. Various proposals have also been made for a method for producing such a retardation layer (for example, Patent Documents 1 and 2).

JP 2013-151162 A (corresponding application in other countries: US Patent Application Publication No. 2002/180107) International Publication No. 2009/088461 (Application in other countries: US Patent Application Publication No. 2011/039084)

However, there is a demand for a display device that can realize good display in a wider viewing angle. Specifically, while maintaining the contrast ratio of the liquid crystal display device at a high level, and the gradation luminance characteristics (the relationship between the brightness of the image displayed on the screen and the luminance measured by observing the image), There is a demand for a display device in which gradation luminance characteristics observed from an oblique direction are close to gradation luminance characteristics observed from the front.
Accordingly, an object of the present invention is to provide a viewing angle widening film, a polarizing plate, and a liquid crystal display device capable of achieving a high contrast ratio and a wide viewing angle.

As a result of studying to solve the above-mentioned problems, the present inventor applied a film including a layer of a material having a specific refractive index and having a specific structure to the layer as a viewing angle widening film to a display device. The inventors have found that such problems can be solved, and have completed the present invention.
That is, the present invention is as follows.

[1] A viewing angle widening film for widening a viewing angle, wherein the viewing angle widening film includes one or more resin layers,
One or more of the resin layers are pore-containing layers,
The hole-containing layer includes a plurality of hole-containing portions substantially parallel to each other,
The hole-containing part contains a hole,
The pore-containing layer is a viewing angle widening film whose refractive index is 1.53 or less.
[2] The viewing angle widening film according to [1], wherein the resin constituting the pore-containing layer is an amorphous resin.
[3] The viewing angle widening film according to [1] or [2], comprising two or more resin layers.
[4] The viewing angle widening film according to any one of [1] to [3], wherein an interval between the adjacent hole-containing portions is a random interval of 50 μm or less.
[5] The viewing angle widening film according to any one of [1] to [4], comprising an ultraviolet absorber.
[6] The viewing angle widening film according to any one of [1] to [5], wherein the viewing angle widening film is a polarizing plate protective film.
[7] The viewing angle widening film according to any one of [1] to [6], wherein the hole-containing portion is made of craze.
[8] A polarizing plate comprising the viewing angle widening film according to any one of [1] to [7] and a polarizer.
[9] The polarizing plate according to [8], wherein the longitudinal direction of the hole-containing portion is parallel or perpendicular to the absorption axis of the polarizer.
[10] The polarizing plate according to [8], wherein an angle formed between the absorption axis of the polarizer and the longitudinal direction of the hole-containing portion is 45 °.
[11] A TN mode liquid crystal display device comprising the polarizing plate according to [8] or [9] and a TN mode liquid crystal cell in this order from the viewing side,
The polarizing plate is arranged such that the viewing angle expansion film side surface is the viewing side,
A TN mode liquid crystal display device in which an angle formed by an azimuth angle at which a gradation is inverted when a display screen is viewed from an oblique direction and a longitudinal direction of the hole-containing portion is vertical.
[12] A VA mode liquid crystal display device comprising the polarizing plate according to [8] or [9] and a VA mode liquid crystal cell in this order from the viewing side,
The VA mode liquid crystal display device, wherein the polarizing plate is disposed such that a surface on the viewing angle widening film side is a viewing side.

According to the present invention, a viewing angle widening film, a polarizing plate, and a liquid crystal display device capable of achieving a high contrast ratio and a wide viewing angle are provided.

FIG. 1 is a plan view schematically showing an example of a viewing angle widening film. FIG. 2 is an enlarged schematic view showing an example of the structure of the craze. FIG. 3 is a perspective view schematically showing an example of a crazing apparatus. FIG. 4 is a side view schematically showing the vicinity of the blade of FIG. 3 in an enlarged manner.

Hereinafter, the present invention will be described in detail with reference to embodiments and examples. However, the present invention is not limited to the following embodiments and exemplifications, and can be implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof.

In the following description, the “polarizing plate” includes not only a rigid member but also a flexible member such as a resin film.

In the following description, the direction of the component is “45 °”, “parallel”, “vertical”, or “orthogonal” unless otherwise specified, for example, usually ± 5 °. The error may preferably be within a range of ± 2 °, more preferably ± 1 °.

In the following description, the MD direction (machine direction) is the film flow direction in the production line, and the TD direction (transverse direction) is a direction parallel to the film surface and perpendicular to the MD direction. is there. For convenience, the longitudinal direction of the long film may be referred to as the MD direction of the film, and the width direction may be referred to as the TD direction of the film. In the following description, the “long” film means a film having a length of 5 times or more, preferably 10 times or more, and specifically a roll. A film having such a length that it can be wound up and stored or transported. The upper limit of the length of the long film is not particularly limited, and can be, for example, 100,000 times or less with respect to the width.

In the following description, the in-plane retardation Re of a film such as a viewing angle widening film is a value represented by Re = (nx−ny) × d unless otherwise specified. Further, the retardation Rth in the thickness direction of the film is a value represented by Rth = {(nx + ny) / 2−nz} × d unless otherwise specified. Here, nx represents the refractive index in the direction that gives the maximum refractive index in the in-plane direction of the film, that is, the direction perpendicular to the thickness direction. ny represents the refractive index in the in-plane direction and orthogonal to the nx direction. nz represents the refractive index in the thickness direction. d represents the thickness of the film. The measurement wavelength is 590 nm unless otherwise specified.

[1. Overview of viewing angle widening film)
The viewing angle widening film of the present invention is a film for enlarging the viewing angle of a liquid crystal display device.
The viewing angle widening film includes one or more resin layers. One or more of the resin layers are pore-containing layers.

[2. Material of pore-containing layer]
The material of the pore-containing layer can be a resin containing various polymers. Examples of such polymers include polystyrene, polypropylene, polyethylene, polyester, polyamide, polyvinylidene fluoride, and alicyclic structure-containing polymers. From the viewpoint of ease of formation of pore-containing portions, polystyrene, polypropylene, An alicyclic structure-containing polymer is preferred.

Polystyrene is a polymer containing a repeating unit derived from a styrene monomer (hereinafter referred to as “styrene monomer unit” as appropriate). The aforementioned styrene monomer refers to styrene and styrene derivatives. Examples of styrene derivatives include α-methylstyrene, o-methylstyrene, p-methylstyrene, p-chlorostyrene, p-nitrostyrene, p-aminostyrene, p-carboxystyrene, and p-phenylstyrene. . A styrenic monomer may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. Therefore, the styrenic polymer may contain one type of styrenic monomer unit alone, or may contain two or more types of styrenic monomer units in combination at any ratio. .

Further, the polystyrene may be a homopolymer or a copolymer containing only a styrene monomer, or may be a copolymer of a styrene monomer and another monomer. Examples of monomers that can be copolymerized with styrene monomers include ethylene, propylene, butadiene, isoprene, acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, N-phenylmaleimide, methyl acrylate, methyl methacrylate, Examples include ethyl acrylate, ethyl methacrylate, maleic anhydride, acrylic acid, methacrylic acid, and vinyl acetate. These monomers may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

Polypropylene may be a propylene homopolymer or a copolymer with a monomer other than propylene. When the polypropylene is a copolymer, the polypropylene may be a random polymer, a block copolymer, or a graft polymer. However, even when the polypropylene is a copolymer, it is preferable that the content of the propylene-derived repeating unit contained in the polypropylene is high, specifically, 80% by weight or more is preferable, and 85% by weight or more is more preferable. .

Examples of alicyclic structure-containing polymers include (1) norbornene polymers, (2) monocyclic olefin polymers, (3) cyclic conjugated diene polymers, and (4) vinyl alicyclic hydrocarbons. And hydrides of (1) to (4). Among these, norbornene-based polymers and hydrides thereof are preferable from the viewpoints of heat resistance, mechanical strength, and the like.

Examples of the norbornene-based polymer include, for example, a ring-opening polymer of a norbornene monomer, a ring-opening copolymer of a norbornene monomer and another monomer capable of ring-opening copolymerization, and a hydride thereof; an addition polymer of a norbornene monomer; Examples include addition copolymers with other monomers copolymerizable with norbornene monomers. Among these, from the viewpoint of transparency, a hydride of a ring-opening polymer of a norbornene monomer and a hydride of a ring-opening copolymer of a rubornene monomer and another monomer capable of ring-opening copolymerization are particularly preferable.

[2.1. Hydrogenated block copolymer [G]]
As an example of the alicyclic structure-containing polymer, two or more polymer blocks [D] having cyclic hydrocarbon group-containing compound hydride units [I] and chain hydrocarbon compound hydride units [II] Or a hydrogenated block copolymer [G] comprising one or more polymer blocks [E] having a combination of units [I] and units [II].

[2.1.1. Cyclic hydrocarbon group-containing compound hydride unit [I]]
Cyclic hydrocarbon group-containing compound hydride unit [I] polymerizes a cyclic hydrocarbon group-containing compound, and if the unit obtained by such polymerization has an unsaturated bond, the unsaturated bond is It is a structural unit having a structure obtained by hydrogenation. However, the cyclic hydrocarbon group-containing compound hydride unit [I] includes units obtained by any production method as long as it has the structure.

The cyclic hydrocarbon group-containing compound hydride unit [I] is preferably a structural unit obtained by polymerization of an aromatic vinyl compound. More specifically, it is a structural unit (aromatic vinyl compound hydride unit [I]) having a structure obtained by polymerizing an aromatic vinyl compound and hydrogenating an unsaturated bond thereof. However, the aromatic vinyl compound hydride unit [I] includes units obtained by any production method as long as it has the structure.
Similarly, in the present application, for example, a structural unit having a structure obtained by polymerizing styrene and hydrogenating the unsaturated bond may be referred to as a styrene hydride unit. The styrene hydride unit also includes a unit obtained by any production method as long as it has the structure.
Examples of the aromatic vinyl compound hydride unit [I] include structural units represented by the following structural formula (1).

In the structural formula (1), R ^c represents an alicyclic hydrocarbon group. Examples of R ^c include cyclohexyl groups such as cyclohexyl group; decahydronaphthyl groups and the like.

In the structural formula (1), R ¹ , R ² and R ³ are each independently a hydrogen atom, a chain hydrocarbon group, a halogen atom, an alkoxy group, a hydroxyl group, an ester group, a cyano group, an amide group or an imide group. Represents a chain hydrocarbon group substituted with a silyl group or a polar group (halogen atom, alkoxy group, hydroxyl group, ester group, cyano group, amide group, imide group, or silyl group). Among them, R ¹ , R ² and R ³ are preferably a hydrogen atom and a chain hydrocarbon group having 1 to 6 carbon atoms from the viewpoints of heat resistance, low birefringence and mechanical strength. The chain hydrocarbon group is preferably a saturated hydrocarbon group, and more preferably an alkyl group.

Preferable specific examples of the aromatic vinyl compound hydride unit [I] include a structural unit represented by the following formula (1-1). The structural unit represented by the formula (1-1) is a styrene hydride unit.

In the examples of the cyclic hydrocarbon group-containing compound hydride unit [I], any one having a stereoisomer can be used. One type of cyclic hydrocarbon group-containing compound hydride unit [I] may be used, or two or more types may be used in combination at any ratio.

[2.1.2. Chain hydrocarbon compound hydride unit [II]]
The chain hydrocarbon compound hydride unit [II] is obtained by polymerizing a chain hydrocarbon compound and further hydrogenating the unsaturated bond if the unit obtained by the polymerization has an unsaturated bond. Is a structural unit having the structure However, the chain hydrocarbon compound hydride unit [II] includes units obtained by any production method as long as it has the structure.

The chain hydrocarbon compound hydride unit [II] is preferably a structural unit obtained by polymerization of a diene compound. More specifically, a structural unit (diene compound hydrogen) having a structure obtained by polymerizing a diene compound and hydrogenating the unsaturated bond if the unit obtained by such polymerization has an unsaturated bond. Compound unit [II]). However, the diene compound hydride unit [II] includes units obtained by any production method as long as it has the structure.
Similarly, in the present application, for example, a structural unit having a structure obtained by polymerizing isoprene and hydrogenating the unsaturated bond may be referred to as an isoprene hydride unit. The isoprene hydride unit also includes a unit obtained by any production method as long as it has the structure.

The diene compound hydride unit [II] is preferably a structural unit obtained by polymerization of a conjugated diene compound. More specifically, it preferably has a structure obtained by polymerizing a conjugated diene compound such as a chain conjugated diene compound and hydrogenating the unsaturated bond. Examples thereof include a structural unit represented by the following structural formula (2) and a structural unit represented by the structural formula (3).

In the structural formula (2), R ⁴ to R ⁹ are each independently a hydrogen atom, a chain hydrocarbon group, a halogen atom, an alkoxy group, a hydroxyl group, an ester group, a cyano group, an amide group, an imide group, or a silyl group. Or a chain hydrocarbon group substituted with a polar group (halogen atom, alkoxy group, hydroxyl group, ester group, cyano group, amide group, imide group, or silyl group). Among these, R ⁴ to R ⁹ are preferably a hydrogen atom and a chain hydrocarbon group having 1 to 6 carbon atoms from the viewpoints of heat resistance, low birefringence, mechanical strength, and the like. The chain hydrocarbon group is preferably a saturated hydrocarbon group, and more preferably an alkyl group.

In the structural formula (3), R ¹⁰ to R ¹⁵ each independently represent a hydrogen atom, a chain hydrocarbon group, a halogen atom, an alkoxy group, a hydroxyl group, an ester group, a cyano group, an amide group, an imide group, or a silyl group. Or a chain hydrocarbon group substituted with a polar group (halogen atom, alkoxy group, hydroxyl group, ester group, cyano group, amide group, imide group, or silyl group). Among them, R ¹⁰ to R ¹⁵ are preferably a hydrogen atom and a chain hydrocarbon group having 1 to 6 carbon atoms from the viewpoint of heat resistance, low birefringence, mechanical strength, and the like. The chain hydrocarbon group is preferably a saturated hydrocarbon group, and more preferably an alkyl group.

Preferable specific examples of the diene compound hydride unit [II] include structural units represented by the following formulas (2-1) to (2-3). The structural units represented by the formulas (2-1) to (2-3) are isoprene hydride units.

Any of the stereoisomers of the chain hydrocarbon compound hydride unit [II] having a stereoisomer can be used. One type of chain hydrocarbon compound hydride unit [II] may be used, or two or more types may be used in combination at any ratio.

[2.1.3. Details of Hydrogenated Block Copolymer [G]
The hydrogenated block copolymer [G] preferably has a triblock molecular structure having one block [E] per molecule and two blocks [D] per molecule linked to both ends thereof. That is, the hydrogenated block copolymer [G] has one block [E] per molecule; and one end of the block [E] and has a cyclic hydrocarbon group-containing compound hydride unit [I]. One block [D1] per molecule; one block [D2] per molecule having a cyclic hydrocarbon group-containing compound hydride unit [I] connected to the other end of the block [E]; It is preferable that it is a triblock copolymer containing.

In the hydrogenated block copolymer [G] as the triblock copolymer described above, the total of the block [D1] and the block [D2] and the block [D2] are obtained from the viewpoint of easily obtaining a pore-containing layer having preferable characteristics. The weight ratio (D1 + D2) / E to E] is preferably within a specific range. Specifically, the weight ratio (D1 + D2) / E is preferably 45/55 or more, more preferably 50/50 or more, preferably 89/11 or less, more preferably 86/14 or less.

In addition, in the hydrogenated block copolymer [G] as the triblock copolymer described above, the weight ratio of the block [D1] to the block [D2] from the viewpoint of easily obtaining a hole-containing layer having desirable characteristics. D1 / D2 is preferably within a specific range. Specifically, the weight ratio D1 / D2 is preferably 1 or more, more preferably 3 or more, particularly preferably 5 or more, preferably 15 or less, more preferably 14 or less, and particularly preferably 13 or less.

The weight average molecular weight Mw of the hydrogenated block copolymer [G] is preferably 50000 or more, more preferably 55000 or more, particularly preferably 60000 or more, preferably 85000 or less, more preferably 80000 or less, and particularly preferably 75000. It is as follows. When the weight average molecular weight Mw is in the above range, a pore-containing layer having desirable characteristics can be easily obtained.

The molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) of the hydrogenated block copolymer [G] is preferably 2.0 or less, more preferably 1.7 or less, and particularly preferably 1.5. Or less, preferably 1.0 or more. When the weight average molecular weight Mw is in the above range, the polymer viscosity can be lowered and the moldability can be improved.

The weight average molecular weight Mw and the number average molecular weight Mn of the hydrogenated block copolymer [G] can be measured as values in terms of polystyrene by gel permeation chromatography using tetrahydrofuran as a solvent.

It is preferable that the block [D1] and the block [D2] each independently comprise only the cyclic hydrocarbon group-containing compound hydride unit [I], but other than the cyclic hydrocarbon group-containing compound hydride unit [I]. May contain any unit. Examples of arbitrary structural units include structural units based on vinyl compounds other than cyclic hydrocarbon group-containing compound hydride units [I]. The content of any structural unit in the block [D] is preferably 10% by weight or less, more preferably 5% by weight or less, and particularly preferably 1% by weight or less.

The block [E] consists only of the chain hydrocarbon compound hydride unit [II], or only from the cyclic hydrocarbon group-containing compound hydride unit [I] and the chain hydrocarbon compound hydride unit [II]. Although it is preferable, arbitrary units other than the units [I] and [II] can be included. Examples of arbitrary structural units include structural units based on vinyl compounds other than the units [I] and [II]. The content of any structural unit in the block [E] is preferably 10% by weight or less, more preferably 5% by weight or less, and particularly preferably 1% by weight or less.

When the block [E] includes a cyclic hydrocarbon group-containing compound hydride unit [I] and a chain hydrocarbon compound hydride unit [II], the units [I] and [II] in the block [E] The weight ratio [I] / [II] is preferably 0.1 or more, more preferably 0.2 or more, particularly preferably 0.3 or more, preferably 1.5 or less, more preferably 1.4 or less. Particularly preferably, it is 1.3 or less.
The weight ratio [I] / [II] of the units [I] and [II] in the molecule of the hydrogenated block copolymer [G] is preferably 70/30 or more, more preferably 72/28 or more, Particularly preferably, it is 74/26 or more, preferably 89/11 or less, more preferably 85/15 or less, and particularly preferably 83/17 or less. When the ratio of the units [I] and [II] is in the above range, a pore-containing layer having preferable characteristics can be easily obtained.

The manufacturing method of hydrogenated block copolymer [G] is not specifically limited, Arbitrary manufacturing methods can be employ | adopted. The hydrogenated block copolymer [G] is prepared, for example, by preparing monomers corresponding to the cyclic hydrocarbon group-containing compound hydride unit [I] and the chain hydrocarbon compound hydride unit [II]. The polymer [F] obtained by polymerization can be produced by hydrogenation. Specific production can be carried out by appropriately combining, for example, the method described in International Publication No. WO2016 / 152871 and other known methods. The hydrogenation rate in the hydrogenation reaction is usually 90% or more, preferably 95% or more, more preferably 97% or more. By increasing the hydrogenation rate, the low birefringence and thermal stability of the hydrogenated block copolymer [G] can be enhanced. The hydrogenation rate can be measured by ¹ H-NMR.

[2.2. Characteristics of the resin constituting the pore-containing layer)
The weight average molecular weight of the polymer in the resin constituting the pore-containing layer is a weight average molecular weight in terms of polystyrene or polyisoprene measured by gel permeation chromatography, and is usually 5,000 or more, preferably 10,000 or more. More preferably, it is 15,000 or more, usually 50,000 or less, preferably 45,000 or less, more preferably 40,000 or less.

The resin constituting the pore-containing layer may contain an optional component other than the polymer as necessary. Examples of optional components are UV absorbers, antioxidants, heat stabilizers, light stabilizers, antistatic agents, dispersants, chlorine scavengers, flame retardants, crystallization nucleating agents, reinforcing agents, antiblocking agents, antifogging agents Agents, release agents, pigments, organic or inorganic fillers, neutralizing agents, lubricants, decomposing agents, metal deactivators, antifouling agents, and antibacterial agents.

Examples of UV absorbers include oxybenzophenone compounds, benzotriazole compounds, salicylic acid ester compounds, benzophenone UV absorbers, benzotriazole UV absorbers, acrylonitrile UV absorbers, triazine compounds, nickel complex compounds, And inorganic powders. Examples of suitable UV absorbers are 2,2′-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- ( 2′-hydroxy-3′-tert-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2,4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol, Examples include 2,2′-dihydroxy-4,4′-dimethoxybenzophenone and 2,2 ′, 4,4′-tetrahydroxybenzophenone. An example of particularly suitable is 2,2'-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol).

When the resin constituting the pore-containing layer contains an ultraviolet absorber, the content of the ultraviolet absorber is preferably 0.5 to 5% by weight per 100% by weight of the resin.

The resin constituting the pore-containing layer is preferably an amorphous resin. By adopting an amorphous resin, even if the resin to be employed is not a resin having an extremely low refractive index, it is possible to obtain a good viewing angle expansion effect.

The resin crystallinity can be determined using a differential scanning calorimeter (DSC). Specifically, the resin for which the crystallinity is determined can be analyzed at a temperature increase rate (temperature increase mode) of 10 ° C./min according to JIS K7121 using a differential scanning calorimeter (DSC). In this analysis, when an endothermic peak exists, it can be determined that the resin is crystalline.

The resin constituting the pore-containing layer preferably has a tensile elongation of a specific value or less. Specifically, the tensile elongation measured at ISO 527-3 (test speed: 50 mm / min) on a test piece obtained by molding the resin to be measured into a single-layer 20 μm film and punching it into a dumbbell shape, It is preferable that it is below a specific value. Such tensile elongation is preferably 6% or less, more preferably 4% or less. Although the minimum of tensile elongation is not specifically limited, For example, it can be 0.3% or more. By employing such a resin exhibiting a low tensile elongation, it is possible to easily form a craze as a hole-containing part.

[3. Characteristics of pore-containing layer etc.)
The hole-containing layer has a refractive index of 1.53 or less, preferably 1.51 or less. By setting the refractive index of the hole-containing layer to the specific value or less, the effect of widening the viewing angle by the hole-containing layer is enhanced, and the effective effect of the present invention can be obtained. Although the minimum of a refractive index is not specifically limited, For example, it may be 1.48 or more.

The refractive index of the hole-containing layer referred to in the present application is the refractive index of the material that forms the hole-containing layer and that does not have a hole-containing portion. The measurement of the refractive index of the hole-containing layer in the field-of-view expansion film can be performed, for example, by removing the holes of the hole-containing layer with a hot press and measuring the refractive index of the layer with an appropriate measuring device. Specifically, the field-of-view expansion film can be pressed at an appropriate temperature until holes disappear in at least a part of the film and become transparent, and then the refractive index of the area can be measured. The temperature suitable for pressing may be Tg or more or Tm or more of the resin constituting the hole-containing layer, and may be (Tg + 10) ° C. or less or (Tm + 10) ° C. or less of the resin. As the measuring device, for example, a refractive index / film thickness measuring device such as a prism coupler can be used.

When the hole-containing layer has optical anisotropy, its refractive index is (nx + ny) / 2.

The viewing angle widening film of the present invention may have only one hole-containing layer or two or more layers. When the viewing angle widening film of the present invention has two or more pore-containing layers, the materials exemplified above can be used as the material constituting each resin layer.

The thickness of the pore-containing layer is preferably 4 μm or more, more preferably 8 μm or more, preferably 90 μm or less, more preferably 60 μm or less. When the viewing angle widening film includes two or more hole-containing layers, the total thickness of the hole-containing layers is preferably within this range. When the thickness of the hole-containing layer is within such a range, the hole-containing layer having the effects of the present invention can be easily configured.

[4. Resin layer other than pore-containing layer]
The viewing angle widening film of the present invention may include only a hole-containing layer as a resin layer, or may include a combination of a hole-containing layer and an arbitrary resin layer that is not a hole-containing layer. A useful viewing angle widening film can be constituted by combining the hole-containing layer and the other resin layer.

An example of such an optional resin layer is a reinforcing layer having a higher strength than the pore-containing layer. When the hole-containing layer contains holes, the strength can be low. By providing such a reinforcing layer, a viewing angle widening film having both optical performance and strength can be obtained.

As another example of the arbitrary resin layer, a protective layer provided on one or both of the front surface and the back surface of the hole-containing layer may be mentioned. When the hole-containing layer contains holes, the surface thereof may be uneven. By providing such a protective layer, a viewing angle widening film having both optical performance and surface smoothness can be obtained. The protective layer may further have a function as the reinforcing layer described above. For example, the viewing angle widening film of the present invention has a layer configuration of two types and three layers of skin layer / core layer / skin layer, the core layer is a pore-containing layer, and the skin layer is a reinforcing layer and / or protective layer. It can be a layer that can function as

As yet another example of the optional resin layer, an easy-adhesion layer for improving the adhesion between the viewing angle widening film and other members can be mentioned.

When the viewing angle widening film of the present invention has a resin layer other than the hole-containing layer, the resin constituting the layer is not particularly limited, and any material having desired characteristics can be appropriately selected. For example, as the resin constituting the reinforcing layer and the protective layer, a resin having desired characteristics can be appropriately selected from the examples of the resin constituting the hole-containing layer described above.

The thickness of the viewing angle widening film is preferably 5 μm or more, more preferably 10 μm or more, and further preferably 20 μm or more. The upper limit is not particularly limited, but is preferably 100 μm or less, more preferably 70 μm or less, and further preferably 40 μm or less.

[5. Hole containing part)
The hole-containing layer in the viewing angle widening film of the present invention includes a plurality of hole-containing parts that are substantially parallel to each other, and the hole-containing part contains holes.
FIG. 1 is a plan view schematically showing an example of a viewing angle widening film. In the example of FIG. 1, the long viewing angle widening film 1 includes only a single hole-containing layer, and includes a plurality of linear hole-containing portions 20 that are parallel to each other. In FIG. 1, each of the hole-containing portions 20 is illustrated as one thin line, but the hole-containing portion 20 is a region having a width and a depth, and a large number of holes (not shown in FIG. 1) therein. ). In the example of FIG. 1, the longitudinal direction of the hole-containing portion 20 is a direction parallel to the TD direction of the viewing angle widening film 1.

Since the hole-containing part contains holes, the light incident on the hole-containing part is scattered. Moreover, the refractive index of a hole containing part expresses a different refractive index from the location in which the hole containing part of a hole containing layer is not formed by containing a hole. As a result, the angle of the light scattering direction can be expanded. While not being bound by any particular theory, it is believed that viewing angle expansion is achieved by such a wide range of light scattering.

The holes contained in the hole-containing part may or may not penetrate in the thickness direction of the viewing angle widening film. In any case, since the hole-containing portion contains holes, the structure has a depth in the thickness direction of the viewing angle widening film. Each hole-containing part usually has a large number of holes, but the structure of the hole-containing part is not limited to this, and may consist of a single crack-like hole. The depth of the hole-containing portion may extend over the entire thickness direction of the hole-containing layer, or only a part thereof.

The plurality of hole-containing portions are provided substantially parallel to each other. The term “substantially parallel” with respect to the hole-containing portions may be an angle between the angles exceeding 0 ° within a range in which the effect of the present invention can be obtained. Specifically, the error may be preferably within ± 40 °, more preferably within ± 30 °. Since the hole-containing portions that are “substantially parallel” to each other can have such an angular relationship, in the hole-containing layer, the plurality of hole-containing portions may have portions that intersect each other.

Each individual hole-containing part usually has a substantially linear shape. The shape of the hole-containing portion being “substantially linear” includes a case where the hole-containing portion has a curvature within a range in which the effect of the present invention is obtained.

Further, from the viewpoint of easy formation of the hole-containing part, the longitudinal direction of the hole-containing part is preferably substantially parallel to the TD direction of the viewing angle widening film (substantially perpendicular to the MD direction). In this case, as shown in FIG. 1, it is not necessary to form a straight line from one end of the viewing angle widening film 1 to the other end facing the end.

The interval P between adjacent hole-containing portions may be constant or random. For example, in the example shown in FIG. 1, the interval P between adjacent hole-containing portions 20 is not constant but random. From the viewpoint of obtaining a high viewing angle expansion effect, the interval between the hole-containing portions is preferably random.

The interval P between the adjacent hole-containing portions is not particularly limited, but is preferably a narrow interval from the viewpoint of suppressing phenomena such as moire interference and obtaining good display screen quality. Specifically, the interval P may be preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 5 μm or less. When the interval P is random, it is preferable that the maximum value of the interval P in the viewing angle widening film is not more than the upper limit. The lower limit of the interval P is not particularly limited, but may be 0.5 μm or more.

In a preferred embodiment, some or all of the plurality of hole-containing portions provided in the viewing angle widening film are made of craze. From the viewpoint of easy formation of the hole-containing part, the hole-containing part is preferably made of craze.

Craze means a substantially linear crack formed in a film. Crazes usually have fibrils formed between such cracks and voids formed between them. A fibril refers to a fiber obtained by fiberizing molecules constituting a resin.

FIG. 2 is an enlarged schematic diagram showing an example of the structure of the craze. In FIG. 2, the craze 21 has a number of elongated fibrils 211 and voids 212 existing therebetween. The fibril 211 is usually present extending in a direction substantially perpendicular to the longitudinal direction of the craze as the hole-containing portion. The craze having such a structure can be formed by crazing the film. By creasing the film and applying pressure to the film, it is possible to form cracks in the film, and further, in the gaps of the cracks, to fiberize the molecules constituting the resin and form fibrils and voids between them. . Details of the crazing process will be described later.

The diameter of the fibril is usually 5 nm to 50 nm, preferably 10 nm to 50 nm, more preferably 10 nm to 40 nm, and even more preferably 20 nm to 40 nm. The diameter of the void in the craze is usually 5 nm to 45 nm, preferably 10 nm to 30 nm. When the pore-containing part is made of craze, the width of the craze is usually 20 nm to 800 nm, preferably 30 nm to 600 nm, more preferably 40 nm to 300 nm. The craze height is usually 0.3 μm to 50 μm, preferably 0.4 μm to 30 μm, more preferably 0.5 μm to 20 μm. The fibril diameter, void diameter, craze width, and craze height value here are average values, specifically, observing any three locations where crazes are expressed with a scanning electron microscope, It can be determined by measuring the size of fibrils and voids.

[6. (Viewing angle expansion film shape, physical properties, etc.)
The viewing angle widening film of the present invention may be a long film or a single film. Usually, from the viewpoint of increasing the production efficiency, the viewing angle widening film is produced as a long film. Moreover, when manufacturing a sheet viewing angle expansion film, a sheet viewing angle expansion film can be manufactured by cutting out a long viewing angle expansion film into a desired shape.

The viewing angle widening film of the present invention may be a substantially optically isotropic film with small optical anisotropy or an optically anisotropic film. When the viewing angle widening film is optically anisotropic, the anisotropy may be attributed to the hole-containing layer, or may be attributed to a layer other than the hole-containing layer, It may be caused by both of them.
When the viewing angle widening film of the present invention is an optically anisotropic film, the in-plane retardation Re is preferably 360 nm or less, more preferably 330 nm or less, and even more preferably 300 nm or less. Although it does not specifically limit about a minimum, Preferably it is 10 nm or more, More preferably, it is 20 nm or more, More preferably, it is 30 nm or more. The retardation Rth in the thickness direction is preferably 400 nm or less, more preferably 350 nm or less, and still more preferably 300 nm or less. Although it does not specifically limit about a minimum, Preferably it is 10 nm or more, More preferably, it is 20 nm or more, More preferably, it is 30 nm or more.

The total light transmittance of the viewing angle widening film is preferably 70% or more, more preferably 80% or more. The light transmittance can be measured by using a spectrophotometer (manufactured by JASCO Corporation, ultraviolet-visible near-infrared spectrophotometer “V-570”) in accordance with JIS K0115.

[7. Manufacturing method of viewing angle widening film)
The viewing angle widening film of the present invention can be produced by any method such as a known method. For example, after manufacturing the film for use in forming the hole-containing portion, the viewing angle widening film of the present invention can be manufactured by forming the hole-containing portion in one or more layers of the film. In the present application, such a film for forming the hole-containing portion may be referred to as a “material film”.

[7.1. (Manufacture of material film)
The layer structure of the material film is not particularly limited, and may be a layer structure suitable for the layer structure of the desired viewing angle widening film. For example, it can be set as the layer structure containing the layer used as a hole containing layer, and the layer used as the other resin layer. More specifically, a viewing angle widening film including a hole-containing layer and a resin layer other than that is obtained by combining a layer that can become a hole-containing layer by craze processing and a layer that does not generate craze by such craze processing. A material film can be constructed.

Examples of the material film manufacturing method include an injection molding method, an extrusion molding method, a press molding method, an inflation molding method, a blow molding method, a calendar molding method, a casting molding method, and a compression molding method.

The conditions such as the molten resin temperature when manufacturing the material film can be appropriately changed according to the type of the material film, and can be performed under known conditions.

When the material film includes two or more resin layers, examples of the method for producing the material film include coextrusion T-die method, coextrusion inflation method, coextrusion lamination method, dry lamination, co-casting method, and coating molding. Law.

The material film may be an unstretched film that has not been stretched or a stretched stretched film. In general, a stretched film has a smaller tensile elongation and is easier to form a craze. Therefore, for example, a stretched film formed of a certain material and an unstretched film formed of the same material are bonded to form a multilayer material film, and crazing is performed on this, whereby only the stretched film is crazed. Can be expressed. As a stretching method for obtaining a stretched film, either uniaxial stretching or biaxial stretching may be adopted, but biaxial stretching is preferred. Especially, suitable embodiment is biaxial stretching with a high draw ratio in the TD direction of a material film.

Stretching can be performed using a known stretching apparatus. Examples of the stretching apparatus include a longitudinal uniaxial stretching machine, a tenter stretching machine, a bubble stretching machine, and a roller stretching machine.

The stretching temperature is preferably (Tg-30 ° C) or higher, more preferably (Tg-10 ° C) or higher, preferably (Tg + 60 ° C) or lower, more preferably (Tg + 50 ° C) or lower. Here, “Tg” represents the glass transition temperature of the resin.

The draw ratio is preferably 1.2 to 5 times, more preferably 1.5 to 4 times, and even more preferably 2 to 3 times. When stretching in a plurality of different directions such as biaxial stretching, it is preferable that the total stretching ratio represented by the product of the stretching ratios in each stretching direction is within the above range.

[7.2. Formation of pore-containing part)
After producing the material film, a viewing angle widening film can be produced by forming a hole-containing portion on the surface of the material film.
An example of a specific method for forming the hole-containing portion is crazing. By performing the crazing process, it is possible to efficiently produce a viewing angle widening film in which the hole-containing portion is made of crazing.

クレー Crazing can be performed by any method such as a known method. Examples of craze processing include JP-A-6-82607, JP-A-7-146403, JP-A-9-166702, JP-A-9-281306, WO2007 / 046467, and JP-A-2006-313262. Examples thereof include methods described in Japanese Patent Laid-Open No. 2009-298100 and Japanese Patent Laid-Open No. 2012-167159.

A specific example of crazing will be described with reference to FIGS. FIG. 3 is a perspective view schematically showing an example of the crazing apparatus, and FIG. 4 is a side view schematically showing the vicinity of the blade in FIG. 3 in an enlarged manner. In FIG. 4, the apparatus is observed from the TD direction.

In the example of FIG. 3, the crazing apparatus 100 includes a feed roll 41, transport rolls 42 and 43, and a blade 30. The blade 30 includes an edge 30E extending in a direction parallel to the TD direction.
In the operation of the crazing apparatus 100, the material film 10 conveyed in the direction of the arrow A11 from the feeding roll 41 is supported and conveyed by the conveying rolls 42 and 43 while being urged against the edge 30E of the blade 30. The Thereby, pressure can be applied to the material film 10. As a result, deformation due to pressurization occurs on the surface of the material film 10 to form the hole containing portion 20 extending in a direction substantially parallel to the TD direction, and the viewing angle widening film 1 can be manufactured.

In the crazing process, the angle at which the blade 30 contacts the material film 10 can be appropriately adjusted to an angle at which a desired craze is formed. In the example of FIGS. 3 and 4, the angle is represented as an angle θ formed by the center line 30 </ b> C of the blade 30 observed from the extending direction of the edge 30 </ b> E and the downstream surface of the material film 10. The angle θ is preferably 10 ° to 60 °, more preferably 15 ° to 50 °, and even more preferably 20 ° to 40 °.

The tension of the material film when the blade is pressed against the material film can be appropriately adjusted to a value at which a desired craze is formed. The tension is preferably 100 N / m to 1000 N / m, and more preferably 300 N / m to 800 N / m.

When the material film is subjected to a stretching treatment, the crazing process may be performed before the material film is stretched or may be performed simultaneously with the stretching treatment.

When a material film having two or more resin layers is used as the material film, and craze processing is performed on the material film, craze may occur in all of the two or more resin layers. Crazing may occur only on the surface. Furthermore, when craze occurs only in a part of the resin layer, craze may occur in the outermost layer, and craze may occur in the inner layer. For example, if craze processing is performed on a material film consisting of a core layer made of a brittle material with relatively small tensile elongation and a relatively soft skin layer on the front and back surfaces, only the core layer is crazed. Can occur. Such a film can also be used as the viewing angle widening film of the present invention.

[8. (Use of viewing angle widening film: Polarizing plate)
The viewing angle widening film of this invention can be used for the use which expands the viewing angle of a liquid crystal display device. However, the function of the viewing angle widening film of the present invention is not limited to this. For example, the viewing angle widening film of the present invention may exhibit other functions in addition to the function as the viewing angle widening film. Examples of functions other than the viewing angle widening film include a function as a protective film, a function as a retardation film, and a function as an optical compensation film. In particular, as described below, the polarizing plate can be preferably used as a material that also functions as a polarizing plate protective film.

The polarizing plate of the present invention includes the viewing angle widening film of the present invention and a polarizer. In the polarizing plate of the present invention, the viewing angle widening film can also function as a polarizing plate protective film. Such a polarizing plate can be manufactured by bonding a polarizer and a viewing angle widening film, for example. In the polarizing plate of the present invention, the polarizer and the viewing angle widening film may be directly bonded without an adhesive layer, or may be bonded via an adhesive layer formed of an adhesive. . Furthermore, another protective film may be interposed between the polarizer and the viewing angle widening film.

When the viewing angle widening film has a hole-containing portion only on one surface thereof, the surface may be located on the polarizer side or on the opposite side of the polarizer.

The polarizing plate of the present invention may be provided with a viewing angle widening film only on one surface of the polarizer, or on both surfaces. When the viewing angle widening film is provided only on one surface of the polarizer, the polarizing plate can be provided with any film other than the viewing angle widening film that can function as a protective film on the other surface of the polarizer.

In the polarizing plate of the present invention, the field-enlarging film can be in direct contact with the polarizer. Or the polarizing plate of this invention may have further another layer interposed between a visual field expansion film and a polarizer. When the field expansion film is in contact with the polarizer directly or through only the adhesive layer, the field expansion film can function as a protective film for protecting the polarizer in the polarizing plate.
On the other hand, the polarizing plate and the liquid crystal display device of the present invention can also be configured by adding a field-enlarging film to an existing liquid crystal display device. Specifically, the viewing side polarizer and the field of view are enlarged by placing a field of view enlargement film on the display surface of a liquid crystal display device having various components such as a protective film on the side of viewing further than the viewing side polarizer. A polarizing plate and a liquid crystal display device of the present invention can be constituted by combining with a film.

When the polarizing plate of the present invention is used in a VA mode liquid crystal display device to be described later, it is preferable that the longitudinal direction of the hole-containing portion is parallel to the absorption axis of the polarizer. Thereby, the viewing angle of the VA mode liquid crystal display device can be expanded.

Further, when the polarizing plate of the present invention is used in a TN mode liquid crystal display device to be described later, the azimuth angle at which the gradation is inverted when the display screen of the liquid crystal display device is viewed from an oblique direction and the longitudinal direction of the hole-containing portion are formed. The corners are preferably vertical. Thereby, the viewing angle of the TN mode liquid crystal display device can be expanded.

The polarizer can be produced, for example, by adsorbing iodine or a dichroic dye on a polyvinyl alcohol film and then uniaxially stretching in a boric acid bath. Further, for example, it can also be produced by adsorbing iodine or a dichroic dye to a polyvinyl alcohol film and stretching, and further modifying a part of the polyvinyl alcohol unit in the molecular chain to a polyvinylene unit. Furthermore, a polarizer having a function of separating polarized light into reflected light and transmitted light, such as a grid polarizer, a multilayer polarizer, and a cholesteric liquid crystal polarizer, may be used as the polarizer. Among these, a polarizer comprising polyvinyl alcohol is preferable. The polarization degree of the polarizer is preferably 98% or more, more preferably 99% or more. The average thickness of the polarizer is preferably 5 μm to 80 μm.

As the adhesive for bonding the polarizer and the viewing angle widening film, any optically transparent adhesive can be used. Examples of the adhesive include water-based adhesives, solvent-based adhesives, two-component curable adhesives, ultraviolet curable adhesives, and pressure-sensitive adhesives. Among these, a water-based adhesive is preferable, and a polyvinyl alcohol-based water-based adhesive is particularly preferable. Moreover, an adhesive agent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The average thickness of the adhesive layer is preferably 0.05 μm or more, more preferably 0.1 μm or more, preferably 5 μm or less, more preferably 1 μm or less.

There is no limitation on the method for bonding the viewing angle widening film and the polarizer.For example, after applying an adhesive on one surface of the polarizer as necessary, a roll laminator is used to enlarge the polarizer and the viewing angle. A method of laminating the film and drying as necessary is preferable. The drying time and drying temperature are appropriately selected according to the type of adhesive.

[9. Liquid crystal display device)
The viewing angle widening film of the present invention and the polarizing plate of the present invention can be used in a liquid crystal display device. As the liquid crystal cell constituting the liquid crystal display device, known cells such as a TN (Twisted Nematic) mode, a VA (Virtual Alignment) mode, and an IPS (In-Plane Switching) mode can be used, but the viewing angle can be effectively expanded. From the viewpoint, the TN mode and the VA mode are preferable.

[9.1. TN mode liquid crystal display device]
The viewing angle widening film of the present invention or the polarizing plate of the present invention is preferably used for a TN mode liquid crystal display device.

The TN mode liquid crystal display device of the present invention includes the polarizing plate of the present invention and the TN mode liquid crystal cell in this order from the viewing side, and the polarizing plate has a viewing angle expansion film side surface on the viewing side. The angle between the azimuth angle at which the gradation is inverted when the display screen of the liquid crystal display device is viewed from an oblique direction and the longitudinal direction of the hole-containing portion is vertical. Here, the azimuth angle at which the gradation is inverted was observed by providing a polarizing plate having the same configuration as the polarizing plate of the present invention, except that the viewing angle widening film of the present invention was not used instead of the polarizing plate of the present invention. This is the azimuth angle at which the gradation is reversed.

A TN mode liquid crystal display device usually includes a polarizing plate and a light source on the side opposite to the viewing side of the TN mode liquid crystal cell. As the polarizing plate disposed on the side opposite to the viewing side, the polarizing plate of the present invention may be used, or a polarizing plate other than the polarizing plate of the present invention, such as a known polarizing plate, may be used. Moreover, as a light source, arbitrary light sources, such as a well-known light source, can be used.

“Viewing side” refers to the side on which the viewer of the displayed image is located when using the liquid crystal display device.

Normally, when the liquid crystal display device is operated from black display to gradually increase brightness to white display, the luminance of the display screen also gradually increases. For example, when an operation is performed to display an 8-bit gray scale (black display is 0, white display is 255, and intermediate gradation is expressed by a value from 0 to 255) on the display screen of the liquid crystal display device, the scale is 0. The luminance of the display screen also increases with the increase from 255 to 255. However, depending on the direction of observation, when the operation for gradually increasing the brightness is performed, the brightness of the display screen may decrease on the contrary. In this way, the operation of increasing or decreasing the brightness displayed on the display device and the actual increase or decrease of the luminance of the display screen do not coincide with each other is referred to as “gradation inversion”. Gradation inversion may be seen at a certain azimuth angle when the display screen of the liquid crystal display device is viewed from an oblique direction. The TN mode liquid crystal display device according to the present invention has such a gradation inversion by making the angle formed by the azimuth angle at which the gradation is inverted when the display screen is viewed from an oblique direction and the longitudinal direction of the hole-containing portion perpendicular to each other. And the viewing angle can be enlarged.
The azimuth angle for gradation inversion is not limited to one direction, but may be two directions or an angle range having a certain extent. In that case, the direction in which the viewing angle is most desired to be expanded can be determined, and the longitudinal direction of the hole-containing portion can be set in a direction perpendicular to the direction.
In the TN mode liquid crystal display device of the present invention, as the polarizing plate of the present invention, one having an angle formed by the absorption axis of the polarizer and the longitudinal direction of the hole-containing portion is preferably 45 °. Normal TN mode liquid crystal display device (with a rectangular display screen, used in a state where the display screen stands upright in a substantially vertical direction, the long side direction of the rectangle is horizontal and the short side direction is substantially vertical) In many cases, gradation inversion is often observed when viewed from below. In a normal TN mode liquid crystal display device, the angle between the absorption axis of the polarizer and the horizontal direction of the display screen is often 45 °. Therefore, when the polarizing plate of the present invention has an angle of 45 ° between the absorption axis of the polarizer and the longitudinal direction of the hole-containing portion, the angle formed between the absorption axis of the polarizer and the horizontal direction of the display screen Can be easily arranged so that the angle formed by the longitudinal direction of the hole-containing portion and the horizontal direction of the display screen is parallel, so that the viewing angle of the TN mode liquid crystal display device can be easily increased. Can do.

[9.2. VA mode liquid crystal display device]
The viewing angle widening film of the present invention or the polarizing plate of the present invention is also preferably used in a VA mode liquid crystal display device.

The VA mode liquid crystal display device of the present invention comprises the polarizing plate of the present invention and the VA mode liquid crystal cell in this order from the viewing side, and the polarizing plate has a viewing angle expansion film side surface on the viewing side. It is arranged to become.

VA mode liquid crystal display devices usually include a polarizing plate and a light source on the side opposite to the viewing side of the VA mode liquid crystal cell. As the polarizing plate disposed on the side opposite to the viewing side, the polarizing plate of the present invention may be used, or a polarizing plate other than the polarizing plate of the present invention, such as a known polarizing plate, may be used. Moreover, as a light source, arbitrary light sources, such as a well-known light source, can be used.

In the VA mode liquid crystal display device of the present invention, as the polarizing plate of the present invention, those in which the longitudinal direction of the hole-containing portion is parallel or perpendicular to the absorption axis of the polarizer can be preferably used. In the case of arranging such a polarizing plate in a normal liquid crystal display device, the relationship between the longitudinal direction of the hole-containing portion and the long side direction of the display screen is preferably parallel or vertical. The longitudinal direction of the hole-containing portion can be a direction perpendicular to the azimuth direction in which the viewing angle is required to be enlarged. For example, in a display device having a rectangular display screen, when it is required to enlarge the viewing angle in the long side direction, the longitudinal direction of the hole-containing portion should be arranged in a direction parallel to the short side direction. Is preferred. The longitudinal direction of the hole-containing portion can be usually a direction parallel or perpendicular to the absorption axis of the polarizer. With such an arrangement, the viewing angle of the VA mode liquid crystal display device can be increased.

Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the following examples, and can be implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof.

In the following description, “%” and “part” representing the amount are based on weight unless otherwise specified. The following operations were performed in a normal temperature and normal pressure atmosphere unless otherwise specified.

〔Evaluation methods〕
(Refractive index of pore-containing layer)
The field-expanding films obtained in the examples and comparative examples are Tg or Tm or higher of the resin constituting the pore-containing layer, and the craze disappears at an appropriate temperature of (Tg + 20) ° C. or lower or (Tm + 20) ° C. or lower. And pressed until transparent, and then the refractive index of the hole-containing layer was measured. As a refractive index measuring device, a refractive index / film thickness measuring device (“Prism Coupler Model 2010 / M” manufactured by Irix Corporation) was used.

(Determination of crystallinity)
The crystallinity determination object is analyzed using a differential scanning calorimeter (DSC) according to JIS K7121 at a heating rate of 10 ° C./min (temperature increasing mode). It was determined to be a functional resin.

(Tensile elongation)
A film having a single-layer thickness of 20 μm, which is a resin to be measured, was prepared. Except for Example 1, the film for core layer having a thickness of 20 mm obtained in Examples and Comparative Examples was used as it was. In Example 1, a product having the same material as the biaxially stretched polypropylene film used and a thickness of 20 μm was obtained. The film was punched into a dumbbell shape to obtain a test piece. About this, tensile elongation was measured by ISO527-3 (test speed: 50 mm / min).

(White brightness, contrast ratio, and Δγ)
For the liquid crystal display devices of the example and the comparative example, white luminance, contrast ratio, and Δγ were measured.
For the measurement, a spectroradiometer (manufactured by Topcon Corporation, product name “SR-LEDW”) was used. The white luminance and contrast ratio were measured from the front direction (polar angle 0 °) of the display device. In the measurement, the illuminance of light irradiated on the display surface of the apparatus was 0 lux. The luminance during white display was determined as white luminance (unit: cd / m ² ). Further, a ratio of (brightness during white display) / (brightness during black display) was obtained as a contrast ratio. High white luminance indicates good luminance. A high contrast ratio indicates a good contrast ratio. A low Δγ indicates that the viewing angle characteristics are good.

Also, colors of each gradation from 0 (black) to 255 (white) in a 256 gradation gray scale were displayed, and the luminance was observed from the front direction and a polar angle of 75 °. The azimuth angle in the direction of the polar angle of 75 ° was the in-plane direction of the display device perpendicular to the longitudinal direction of the hole-containing portion. In the examples, the in-plane direction of the display device perpendicular to the longitudinal direction of the hole-containing portion was used, and in the comparative example, the in-plane direction of the display device corresponding to each example was used. In the observation in each direction, the normalized luminance was calculated by setting the luminance at the gray scale 0 to 0% and the luminance at the gray scale 255 to 100%, and the relationship between the gray scale and the normalized luminance was obtained. For each grayscale gradation, the absolute value of the difference between the normalized luminance in the front direction and the normalized luminance in the polar angle 75 ° direction is obtained, and the maximum value among these values is obtained as Δγ (%). It was.

[Example 1]
(1-1. Material film)
An unstretched polypropylene film (manufactured by Futamura Chemical Co., Ltd.) having a width of 300 mm and a thickness of 15 μm and a biaxially stretched polypropylene film (manufactured by Futamura Chemical Co., Ltd.) having a thickness of 15 μm were prepared.
It was crystallinity when the crystallinity of resin which comprises a biaxially stretched polypropylene film as a judgment object was judged.
When tensile elongation was measured using a biaxially stretched polypropylene film as a measurement object, the tensile elongation was 5%.
An unstretched polypropylene film and a biaxially stretched polypropylene film were bonded together by a thermal laminating method to obtain a material film.

(1-2. Viewing angle expansion film)
Using the apparatus schematically shown in FIGS. 3 and 4, a viewing angle widening film was produced. In the apparatus, a blade made of SUS (blade tip R = 0.2 mm) was adopted as the blade 30.
The material film obtained in (1-1) is disposed so that the non-stretched polypropylene film side surface is in contact with the blade 30, the material film 10 is pressed against the blade 30, and the tension of the material film 10 is 500 N / m. Crazing was carried out by conveying at a speed of 50 mm / min in the direction of arrow A11.
At the time of crazing, the direction of the edge 30E of the blade 30 was the width direction (TD direction) of the material film. The angle θ formed by the center line 30C of the blade 30 observed from the extending direction of the edge 30E and the downstream surface of the material film 10 was 20 °. This produced the viewing angle expansion film.

The pore-containing part of the obtained viewing angle widening film was expressed on the biaxially oriented polypropylene film side. The hole-containing part was a craze having a substantially linear shape, and the longitudinal directions of the hole-containing part were substantially parallel to each other and substantially parallel to the TD direction of the film. The interval P between the hole-containing portions was a random interval of 20 μm or less. The average value of the width of each hole-containing part was 300 nm, the average value of the depth of the hole-containing part was 15 μm, and the average value of the fibril diameter was 20 nm. These values were determined by selecting three arbitrary points on the craze film and observing a 25 μm square area with a scanning electron microscope.

About the obtained viewing angle expansion film, the refractive index of the biaxially-stretched polypropylene film part which is the hole containing layer was measured.

(1-3. Manufacture of liquid crystal display device)
The viewing angle widening film obtained in (1-2) was bonded to the polarizing plate on the viewing side surface of a linearly polarized VA mode liquid crystal display device (BenQ, 27-inch, model GW2760HS). At the time of pasting, the angle formed by the absorption axis of the polarizer in the viewing side polarizing plate and the longitudinal direction of the hole-containing portion of the viewing angle widening film is 90, and the longitudinal direction of the hole-containing portion is a rectangular display screen These directions were adjusted to be parallel to the short side direction. Further, the viewing angle widening film was bonded so that the surface on which the hole-containing portion was formed became the visual recognition side. Thereby, the liquid crystal display device of the present invention was obtained.

(1-4. Evaluation)
With respect to the liquid crystal display device obtained in (1-3), white luminance, contrast ratio, and Δγ were measured.

[Example 2]
(2-1. Production of block copolymer [F1])
A stainless steel reactor equipped with a stirrer and thoroughly dried and purged with nitrogen was charged with 256 parts of dehydrated cyclohexane, 25.0 parts of dehydrated styrene, and 0.65 part of di-n-butyl ether and stirred at 60 ° C. Then, 0.82 part of n-butyllithium (15% cyclohexane solution) was added to initiate the polymerization reaction. Furthermore, it was made to react at 60 degreeC for 60 minutes, stirring. The polymerization conversion rate at this time was 99.5%. The reaction temperature was maintained at 60 ° C. until the reaction was stopped.
Next, 50 parts of a mixed monomer composed of 25 parts of styrene monomer and 25 parts of isoprene monomer was continuously added to the reaction solution over 150 minutes, and stirring was continued for 20 minutes after completion of the addition. The polymerization conversion rate at this time was 99.5%. Thereafter, 25.0 parts of dehydrated styrene was further added and stirred for 60 minutes. The polymerization conversion rate at this point was almost 100%. Next, 0.5 part of isopropyl alcohol was added to the reaction solution to stop the reaction, and a polymerization reaction solution containing a block copolymer [F1] was obtained. The obtained block copolymer [F1] had a weight average molecular weight (Mw) of 58,000 and a molecular weight distribution (Mw / Mn) of 1.03.

(2-2. Production of hydrogenated block copolymer [G1])
The polymerization reaction solution obtained in (2-1) was transferred to a pressure-resistant reactor equipped with a stirrer, and a silica-alumina supported nickel catalyst (E22U, nickel supported amount 60%; manufactured by JGC Chemical Industries, Ltd.) as a hydrogenation catalyst. ) 4.0 parts and 350 parts dehydrated cyclohexane were added and mixed. The inside of the reactor was replaced with hydrogen gas, and hydrogen was supplied while stirring the solution. A hydrogenation reaction was performed at a temperature of 170 ° C. and a pressure of 4.5 MPa for 6 hours.
After completion of the hydrogenation reaction, the reaction solution was filtered to remove the hydrogenation catalyst. To the filtrate, a phenolic antioxidant pentaerythrityl tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] (product name “AO60”, manufactured by ADEKA) 0. 1.0 part of a xylene solution in which 1 part was dissolved was added and dissolved to obtain a solution.
Next, the above solution is treated at a temperature of 260 ° C. and a pressure of 0.001 MPa or less using a cylindrical concentrating dryer (manufactured by Hitachi, Ltd., product name “Contro”). The volatile component was removed to obtain a molten resin. This was filtered at a temperature of 260 ° C. with a polymer filter (manufactured by Fuji Filter Co., Ltd.) equipped with a stainless sintered filter having a pore diameter of 20 μm connected to a concentration dryer, and then the molten polymer was extruded from the die into a strand shape, cooled, The pellet was formed by a pelletizer. This obtained pellets of resin [G1] containing hydrogenated block copolymer [G1].
The hydrogenated block copolymer [G1] in the obtained resin [G1] is a block in which St, a repeating unit derived from styrene and a repeating unit derived from isoprene coexist (hereinafter referred to as “St / Ip” as appropriate). The weight ratio of each block was St: St / Ip: St = 25: 25/25: 25. The block copolymer had Mw of 59,000, Mw / Mn of 1.05, a hydrogenation rate of almost 100%, and a thermal softening temperature Ts of 110 ° C.

(2-3. Production of block copolymer [F2])
In a reactor equipped with a stirrer and thoroughly purged with nitrogen, 270 parts of dehydrated cyclohexane, 75 parts of dehydrated styrene and 7.0 parts of di-n-butyl ether were placed. While stirring the whole volume at 60 ° C., 5.6 parts of n-butyllithium (15% cyclohexane solution) was added to initiate polymerization. Subsequently, the whole volume was stirred at 60 ° C. for 60 minutes. The reaction temperature was maintained at 60 ° C. until the reaction was stopped.
The polymerization conversion rate at this point (polymerization first stage) was 99.4%.

Next, 15 parts of dehydrated isoprene was continuously added to the reaction solution over 40 minutes, and stirring was continued for 30 minutes as it was after the addition was completed. The polymerization conversion rate at this point (polymerization second stage) was 99.8%.
Thereafter, 10 parts of dehydrated styrene was continuously added to the reaction solution over 30 minutes, and stirred for 30 minutes as it was after completion of the addition. The polymerization conversion rate at this point (polymerization third stage) was almost 100%.

Here, 1.0 part of isopropyl alcohol was added to stop the reaction to obtain a polymer solution containing a block copolymer [F2] of [D1]-[E]-[D2] type. In the obtained block copolymer [F2], Mw [F2] = 82,400, Mw / Mn was 1.32 and wA: wB = 85: 15.

(2-4. Production of hydrogenated block copolymer [G2])
The polymer solution obtained in (2-3) was transferred to a pressure-resistant reactor equipped with a stirrer, and a diatomaceous earth supported nickel catalyst (product name “E22U”, nickel supported amount 60%, JGC catalyst) as a hydrogenation catalyst. 4.0 parts of Kasei Co., Ltd.) and 30 parts of dehydrated cyclohexane were added and mixed. The inside of the reactor was replaced with hydrogen gas, and hydrogen was supplied while stirring the solution. A hydrogenation reaction was performed at a temperature of 190 ° C. and a pressure of 4.5 MPa for 6 hours.
The reaction solution obtained by the hydrogenation reaction contained the hydrogenated block copolymer [G2]. Mw [G2] of the hydrogenated block copolymer [G2] was 71,800, the molecular weight distribution Mw / Mn was 1.30, and the hydrogenation rate was almost 100%.

After completion of the hydrogenation reaction, the reaction solution is filtered to remove the hydrogenation catalyst, and then the phenol-based antioxidant pentaerythrityl tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) ) Propionate] (product name “AO60”, manufactured by ADEKA) 2.0 parts of xylene solution in which 0.3 part was dissolved was added and dissolved to obtain a solution.
Next, the above solution is treated at a temperature of 260 ° C. and a pressure of 0.001 MPa or less using a cylindrical concentrating dryer (product name “Contro”, manufactured by Hitachi, Ltd.), and cyclohexane, xylene and other volatile components are removed from the solution. And a molten resin was obtained. This was extruded from a die into a strand, cooled, and formed into pellets by a pelletizer. As a result, 95 parts of a pellet of the resin [G2] containing the hydrogenated block copolymer [G2] was produced.
The obtained hydrogenated block copolymer [G2] in the resin [G2] had Mw [G2] = 68,500, Mw / Mn = 1.30, and Ts = 139 ° C.
When the crystallinity was determined using the resin [G2] as the determination target, it was amorphous.
When the tensile elongation was measured using the resin [G2] as an object to be measured, the tensile elongation was 4%.

(2-5. Preparation of material film)
As a material film, a multilayer film having a layer structure of two types and three layers of skin layer / core layer / skin layer was formed. For molding, a film forming apparatus for coextrusion molding was used. As the material for the skin layer, the resin [G1] obtained in (2-2) was used. As the material for the core layer, the resin [G2] obtained in (2-4) was used.
The obtained material film had a width of 300 mm, a thickness of each skin layer of 10 μm, a core layer thickness of 20 μm, and a total thickness of the material film of 40 μm.
(2-6. Production of wide viewing angle film)
Using the apparatus schematically shown in FIGS. 3 and 4, a viewing angle widening film was produced. In the apparatus, a blade made of SUS (blade tip R = 0.2 mm) was adopted as the blade 30.
The material film obtained in (2-5) is arranged so that one surface thereof is in contact with the blade 30, the material film 10 is pressed against the blade 30, and the tension of the material film 10 is 450 N / m, and the direction of the arrow A11 Was carried out at a speed of 50 mm / min for crazing.
At the time of crazing, the direction of the edge 30E of the blade 30 was the width direction (TD direction) of the material film. The angle θ formed by the center line 30C of the blade 30 observed from the extending direction of the edge 30E and the downstream surface of the material film 10 was 20 °. This produced the viewing angle expansion film.

The pore-containing part of the obtained viewing angle widening film was expressed in the core layer. The hole-containing part was a craze having a substantially linear shape, and the longitudinal directions of the hole-containing part were substantially parallel to each other and substantially parallel to the TD direction of the film. The interval P between the hole-containing portions was a random interval of 1.2 μm or less. The average value of the width of each hole-containing part was 250 nm, the average value of the depth of the hole-containing part was 20 μm, and the average value of the fibril diameter was 5 nm. These values were determined by selecting three arbitrary points on the craze film and observing a 25 μm square area with a scanning electron microscope.

For the obtained viewing angle widening film, the refractive index of the pore-containing layer was measured. Since the hole-containing layer was a core layer, the refractive index of the core layer was measured in measuring the refractive index of the hole-containing layer.

(2-7. Manufacture of liquid crystal display devices)
The viewing angle widening film obtained in (2-6) is bonded to the polarizing plate on the viewing side surface of the linearly polarized VA mode liquid crystal display device (same as that used in (1-3) of Example 1). did. At the time of pasting, the angle formed by the absorption axis of the polarizer in the viewing side polarizing plate and the longitudinal direction of the hole-containing portion of the viewing angle widening film is 90, and the longitudinal direction of the hole-containing portion is a rectangular display screen These directions were adjusted to be parallel to the short side direction. Thereby, the liquid crystal display device of the present invention was obtained.

(2-8. Evaluation)
The liquid crystal display device obtained in (2-7) was measured for white luminance, contrast ratio, and Δγ.

Example 3
Except for the following changes, a liquid crystal display device and its components were obtained and evaluated by the same operation as in Example 2.
In the production of the viewing angle widening film of (2-6), the blade made of SUS was changed from the one with the tip R = 0.2 mm to the one with the tip R = 0.5 mm.
In the production of the viewing angle widening film (2-6), the tension of the material film was changed from 450 N / m to 300 N / m.

The hole containing part of the viewing angle widening film obtained in Example 3 was expressed in the core layer. The hole-containing part was a craze having a substantially linear shape, and the longitudinal directions of the hole-containing part were substantially parallel to each other and substantially parallel to the TD direction of the film. The interval P between the hole-containing portions was a random interval of 1.8 μm or less. The average value of the width of each hole-containing part was 50 nm, the average value of the depth of the hole-containing part was 20 μm, and the average value of the fibril diameter was 5 nm. In measuring the refractive index of the hole-containing layer, the refractive index of the core layer was measured.

Example 4
(4-1. Preparation of material film)
As a material film, a multilayer film having a layer configuration of two types and three layers of skin layer / core layer / skin layer was formed. For molding, a film forming apparatus for coextrusion molding was used. As a material for the skin layer, an acrylic resin (“HT55X” manufactured by Sumitomo Chemical Co., Ltd., glass transition temperature: 108 ° C.) containing an acrylic polymer and rubber particles was used. As a material for the core layer, polymethyl methacrylate polymer resin (manufactured by Asahi Kasei Corporation, trade name “Delpet” 80NH, glass transition temperature 102 ° C.) was used.
The obtained material film had a width of 300 mm, a thickness of each skin layer of 10 μm, a core layer thickness of 20 μm, and a total thickness of the material film of 40 μm.
When the crystallinity was determined using the polymethyl methacrylate polymer resin as the determination target, it was amorphous.
When tensile elongation was measured using a polymethyl methacrylate polymer resin as a measurement object, the tensile elongation was 5%.

(4-2. Production and evaluation of viewing angle widening film and liquid crystal display device)
Except for the following changes, a liquid crystal display device and its components were obtained and evaluated by the same operations as in (2-6) to (2-8) of Example 2.
In the production of the viewing angle widening film of (2-6), the material film obtained in (4-1) was used instead of the material film obtained in (2-5).

The hole-containing part of the viewing angle widening film obtained in Example 4 was expressed in the core layer. The hole-containing part was a craze having a substantially linear shape, and the longitudinal directions of the hole-containing part were substantially parallel to each other and substantially parallel to the TD direction of the film. The interval P between the hole-containing portions was a random interval of 1.2 μm or less. The average value of the width of each hole-containing part was 50 nm, the average value of the depth of the hole-containing part was 19 μm, and the average value of the fibril diameter was 5 nm. In measuring the refractive index of the hole-containing layer, the refractive index of the core layer was measured.

Example 5
(5-1. Preparation of material film)
As a material film, a multilayer film having a layer configuration of two types and three layers of skin layer / core layer / skin layer was formed. For molding, a film forming apparatus for coextrusion molding was used. As a material for the skin layer, norbornene polymer 1 (trade name: ZEONOR 1600, manufactured by ZEON CORPORATION, glass transition temperature 163 ° C.) was used. As a material for the core layer, norbornene polymer 2 (trade name: Zeonex K26R, manufactured by Nippon Zeon Co., Ltd., glass transition temperature 143 ° C.) was used.
The obtained material film had a width of 300 mm, a thickness of each skin layer of 10 μm, a core layer thickness of 20 μm, and a total thickness of the material film of 40 μm.
When crystallinity was determined using norbornene polymer 2 (Zeonex K26R) as a determination target, it was amorphous.
When the tensile elongation was measured using the norbornene polymer 2 (Zeonex K26R) as a measurement object, the tensile elongation was 2%.

(5-2. Production and evaluation of viewing angle widening film and liquid crystal display device)
Except for the following changes, a liquid crystal display device and its components were obtained and evaluated by the same operations as in (2-6) to (2-8) of Example 2.
In the production of the viewing angle widening film of (2-6), the material film obtained in (5-1) was used instead of the material film obtained in (2-5).
In the production of the viewing angle widening film (2-6), the tension of the material film was changed from 450 N / m to 700 N / m.

The hole-containing part of the viewing angle widening film obtained in Example 5 was expressed in the core layer. The hole-containing part was a craze having a substantially linear shape, and the longitudinal directions of the hole-containing part were substantially parallel to each other and substantially parallel to the TD direction of the film. The interval P between the hole-containing portions was a random interval of 1.5 μm or less. The average value of the width of each hole-containing part was 45 nm, the average value of the depth of the hole-containing part was 19 μm, and the average value of the fibril diameter was 5 nm. In measuring the refractive index of the hole-containing layer, the refractive index of the core layer was measured.

[Comparative Example 1]
In Examples 1 to 5, the liquid crystal display device itself was measured for white luminance, contrast ratio, and Δγ.

[Comparative Example 2]
(C2-1. Preparation of material film)
As a material film, a multilayer film having a layer configuration of two types and three layers of skin layer / core layer / skin layer was formed. For molding, a film forming apparatus for coextrusion molding was used. As a material for the skin layer, an acrylic resin (“HT55X” manufactured by Sumitomo Chemical Co., Ltd., glass transition temperature: 108 ° C.) containing an acrylic polymer and rubber particles was used. As a material for the core layer, a styrene-maleic anhydride copolymer resin (“Dylark D332” manufactured by Nova Chemicals, glass transition temperature: 128 ° C.) was used.
The obtained material film had a width of 300 mm, a thickness of each skin layer of 10 μm, a core layer thickness of 20 μm, and a total thickness of the material film of 40 μm.
When crystallinity was determined using styrene-maleic anhydride copolymer resin as a determination target, it was amorphous.
When tensile elongation was measured using styrene-maleic anhydride copolymer resin as a measurement object, the tensile elongation was 2%.

(C2-2. Manufacturing and evaluation of viewing angle widening film and liquid crystal display)
Except for the following changes, a liquid crystal display device and its components were obtained and evaluated by the same operations as in (2-6) to (2-8) of Example 2.
In the production of the viewing angle widening film of (2-6), the material film obtained in (C2-1) was used instead of the material film obtained in (2-5).
In the production of the viewing angle widening film (2-6), the tension of the material film was changed from 450 N / m to 500 N / m.

The hole containing part of the viewing angle widening film obtained in Comparative Example 2 was expressed in the core layer. The hole-containing part was a craze having a substantially linear shape, and the longitudinal directions of the hole-containing part were substantially parallel to each other and substantially parallel to the TD direction of the film. The interval P between the hole-containing portions was a random interval of 1.2 μm or less. The average value of the width of each hole-containing part was 50 nm, the average value of the depth of the hole-containing part was 19 μm, and the average value of the fibril diameter was 5 nm. In measuring the refractive index of the hole-containing layer, the refractive index of the core layer was measured.

[Comparative Example 3]
(C3-1. Preparation of Material Film)
As a material film, a multilayer film having a layer configuration of two types and three layers of skin layer / core layer / skin layer was formed. For molding, a film forming apparatus for coextrusion molding was used. As a material for the skin layer, polycarbonate resin (trade name “Panlite AD5503”, manufactured by Teijin Limited, glass transition temperature 142 ° C.) was used. As the material for the core layer, another polycarbonate resin (trade name “Iupilon HL8004”, manufactured by Mitsubishi Engineering Plastics Co., Ltd., glass transition temperature 136 ° C.) was used.
The obtained material film had a width of 300 mm, a thickness of each skin layer of 10 μm, a core layer thickness of 20 μm, and a total thickness of the material film of 40 μm.
When crystallinity was determined using styrene-maleic anhydride copolymer resin as a determination target, it was amorphous.
When tensile elongation was measured using styrene-maleic anhydride copolymer resin as a measurement object, the tensile elongation was 2%.

(C3-2. Manufacturing and evaluation of viewing angle widening film and liquid crystal display device)
Except for the following changes, a liquid crystal display device and its components were obtained and evaluated by the same operations as in (2-6) to (2-8) of Example 2.
In the production of the viewing angle widening film of (2-6), the material film obtained in (C3-1) was used instead of the material film obtained in (2-5).
In the production of the viewing angle widening film (2-6), the tension of the material film was changed from 450 N / m to 700 N / m.

The hole containing part of the viewing angle widening film obtained in Comparative Example 3 was expressed in the core layer. The hole-containing part was a craze having a substantially linear shape, and the longitudinal directions of the hole-containing part were substantially parallel to each other and substantially parallel to the TD direction of the film. The interval P between the hole-containing portions was a random interval of 1.5 μm or less. The average value of the width of each hole-containing part was 40 nm, the average value of the depth of the hole-containing part was 19 μm, and the average value of the fibril diameter was 5 nm. In measuring the refractive index of the hole-containing layer, the refractive index of the core layer was measured.

Table 1 summarizes the results of Examples and Comparative Examples.

As is apparent from the results shown in Table 1, in the examples using the field-of-view magnification film made of a material that satisfies the requirements such as the refractive index of the present invention, good characteristics such as a contrast ratio of over 2000 and Δγ of 20 or less. A liquid crystal display device having the following was obtained.

DESCRIPTION OF SYMBOLS 1 Viewing angle expansion film 10 Film 20 Hole containing part 21 Craze (hole containing part)
211 Fibrils 212 Holes 100 Craze processing equipment 30 Blades

Claims

A viewing angle widening film for enlarging a viewing angle, wherein the viewing angle widening film comprises one or more resin layers,
One or more of the resin layers are pore-containing layers,
The hole-containing layer includes a plurality of hole-containing portions substantially parallel to each other,
The hole-containing part contains a hole,
The pore-containing layer is a viewing angle widening film whose refractive index is 1.53 or less.
The viewing angle widening film according to claim 1, wherein the resin constituting the pore-containing layer is an amorphous resin.
The viewing angle expansion film according to claim 1, comprising two or more resin layers.
The viewing angle widening film according to any one of claims 1 to 3, wherein an interval between the adjacent hole-containing portions is a random interval of 50 µm or less.
The viewing angle widening film according to any one of claims 1 to 4, comprising an ultraviolet absorber.
The viewing angle widening film according to any one of claims 1 to 5, wherein the viewing angle widening film is a polarizing plate protective film.
The viewing angle widening film according to any one of claims 1 to 6, wherein the hole-containing portion is made of craze.
A polarizing plate comprising the viewing angle widening film according to any one of claims 1 to 7 and a polarizer.
The polarizing plate according to claim 8, wherein the longitudinal direction of the hole-containing portion is parallel or perpendicular to the absorption axis of the polarizer.
The polarizing plate according to claim 8, wherein an angle formed by the absorption axis of the polarizer and the longitudinal direction of the hole-containing portion is 45 °.
A TN mode liquid crystal display device comprising the polarizing plate according to claim 8 or 9 and a TN mode liquid crystal cell in this order from the viewing side,
The polarizing plate is arranged such that the viewing angle expansion film side surface is the viewing side,
A TN mode liquid crystal display device in which an angle formed by an azimuth angle at which a gradation is inverted when a display screen is viewed from an oblique direction and a longitudinal direction of the hole-containing portion is vertical.
A VA mode liquid crystal display device comprising the polarizing plate according to claim 8 or 9 and a VA mode liquid crystal cell in this order from the viewing side,
The VA mode liquid crystal display device, wherein the polarizing plate is disposed such that a surface on the viewing angle widening film side is a viewing side.