WO2008053592A1

WO2008053592A1 - Anisotropic light diffusing film, and display device and liquid crystal display device using the anisotropic light diffusing film

Info

Publication number: WO2008053592A1
Application number: PCT/JP2007/001185
Authority: WO
Inventors: Kensaku Higashi; Yasuhiko Motoda
Original assignee: Tomoegawa Co., Ltd.
Priority date: 2006-10-31
Filing date: 2007-10-30
Publication date: 2008-05-08
Also published as: TW200837392A

Abstract

This invention provides an anisotropic light diffusing film comprising a plurality of anisotropic light diffusing layers stacked on top of each other so that the direction of a scattering central axis varies depending upon each anisotropic light diffusing layer. The anisotropic light diffusing layer is formed of a cured product of a composition containing a photopolymerizable compound. Each of the anisotropic light diffusing layers has such an incident light diffusion through property that each has a scattering central axis and has an incident angle dependency which varies depending upon the angle at which the scattering central axis and the incident light axis cross each other.

Description

Specification

Anisotropic light diffusing film, display device using the same, and liquid crystal display device

Technical field

TECHNICAL FIELD [0001] The present invention relates to an anisotropic light diffusion film capable of expanding a viewing angle, a display device using the same, and a liquid crystal display device.

Background art

[0002] Examples of the display device that can be used include a liquid crystal display panel, a plasma display panel (PDP), an organic electroluminescence panel (EL), a rear projector, and a field emission display. It is done. Among these, liquid crystal display devices using liquid crystal display panels are used in many products.

[0003] In a liquid crystal display panel in a conventional liquid crystal display device, nematic liquid crystal is sandwiched between a pair of transparent glass substrates on which transparent electrodes are formed, and a pair of polarizing plates is provided on both sides of the glass substrate. It is the structure which was made. However, in the liquid crystal display device using the liquid crystal display panel having such a configuration, although the display direction is good with respect to the normal direction of the liquid crystal display panel, the vertical or horizontal direction with respect to the normal line of the liquid crystal display panel However, there is a problem that the display characteristic is remarkably deteriorated in a direction inclined more than a specific angle.

[0004] As one of the causes of the remarkable deterioration of the display characteristics, a good contrast between dark and light is good in the normal direction of the panel, but it is remarkable in the direction inclined above or below or right and left with respect to the normal. In some cases, the brightness of the screen may be reversed. This phenomenon is called screen gradation inversion.

[0005] To solve these display characteristics problems including gradation inversion, a plurality of refractive index distribution type microlenses formed by reaction of a photopolymerizable monomer are formed in a transparent polymer substrate. A microlens array is disclosed in which the viewing angle of a liquid crystal display device can be expanded by having a region of (see, for example, Patent Document 1). . ) In addition, a bundle of many glass fibers is thinly cut at a surface where the optical axis of the fiber is inclined at a specific angle with respect to the normal of the fiber plate. A liquid crystal display device in which the emitted light has directivity by being laminated as a glass substrate on the side is disclosed (for example, see Patent Document 2).

[0006] However, these techniques are merely techniques for directing emitted light in the normal direction of the display panel in a specific direction, and the expansion of the viewing angle in an arbitrary direction in the liquid crystal display device is not sufficient.

[0007] In addition, as a technique for changing the amount of linearly transmitted light according to the incident angle of incident light, the resin layer made of a cured product of a composition containing a photopolymerizable compound, all in a predetermined direction P An anisotropic diffusion film in which an aggregate of a plurality of bar-shaped hardened regions extending in parallel is disclosed (see, for example, Patent Document 3). It is known that this anisotropic diffusion film can slightly improve the viewing angle by being applied to the viewing surface side of a liquid crystal display device. Hereinafter, in the present specification, the terms “photopolymerization” and “curing” will be used as the photopolymerizable compound undergoes a polymerization reaction with light, and both are used interchangeably.

Patent Document 1: Japanese Patent Application Laid-Open No. 6_59 10 2

Patent Document 2: JP-A-6-2 5 8 6 2 7

Patent Document 3: Japanese Patent Laid-Open No. 2 0 0 _ 2 6 5 9 1 5

Disclosure of the invention

Problems to be solved by the invention

[0009] As described above, the conventional anisotropic light diffusion film can slightly improve the viewing angle in the direction close to the predetermined direction P, but has not yet sufficiently improved the viewing angle. Accordingly, an object of the present invention is to provide an anisotropic light diffusion film capable of sufficiently expanding the viewing angle of a display panel, particularly a liquid crystal display panel, in an arbitrary direction, and a liquid crystal display device using the same.

Means for solving the problem

[0010] In view of the above prior art, the present inventor has determined that the transmission diffusibility of incident light is anisotropic light diffusion. The scattering central axis projected on the surface of the anisotropic light diffusing layer has an incident angle dependency that changes depending on the angle at which the scattering central axis of the scattering layer intersects the optical axis of the incident light to the anisotropic light diffusing layer. By using an anisotropic light diffusing layer whose length direction is close to the direction in which the viewing angle is desired to be enlarged, by stacking multiple anisotropic light diffusing layers, the viewing angle of a display panel, in particular a liquid crystal display panel, can be set in any direction. The present invention has been completed. Therefore, the anisotropic light diffusing film of the present invention comprises a plurality of anisotropic light diffusing layers made of a cured product of a composition containing a photopolymerizable compound, and each of the anisotropic light diffusing layers has one scattering center axis, The transmission diffusivity of incident light to the anisotropic light diffusing layer has an incident angle dependency that changes depending on the angle at which the scattering central axis of the anisotropic light diffusing layer and the optical axis of the incident light intersect. However, it is characterized in that the direction of the scattering central axis differs depending on each anisotropic light diffusion layer.

The invention's effect

[001 1] According to the present invention, by stacking a plurality of anisotropic light diffusing layers having different scattering center axes, light emitted from a display panel, particularly a liquid crystal display panel, is distributed in a direction around a plurality of scattering center axes. As a result, the viewing angle of the display panel including the liquid crystal display panel can be sufficiently expanded in an arbitrary direction.

Such an effect is considered to be obtained as follows. First, as shown in FIG. 2, the anisotropic light diffusing layer in the anisotropic light diffusing film of the present invention has an assembly of a plurality of rod-like hardened regions 3 in the anisotropic light diffusing layer 1, and a scattering center in the length direction. The plurality of rod-shaped hardened regions 3 are formed so as to be parallel to the axis P, and the refractive index is different from the periphery thereof. Therefore, a part of the light emitted from the display panel, particularly the liquid crystal display panel, The viewing angle is expanded in a direction that is parallel to the direction in which the scattering center axis P is projected onto the surface of the anisotropic light diffusion layer, and the emitted light is diffused around the scattering center axis. Then, by performing this action with a plurality of anisotropic light diffusion layers, the light emitted from the display panel including the liquid crystal display panel is distributed and diffused around a plurality of scattering central axes. Can do. Furthermore, light directed in a direction different from the direction in which the scattering center axis P is projected onto the surface of the anisotropic light diffusion layer is further directed to another direction by the plurality of anisotropic light diffusion layers. As a result, not only can the viewing angle of a display panel including a liquid crystal display panel be sufficiently expanded in any direction by adjusting the scattering center axis, but also in a direction different from the direction in which the scattering center axis is directed. Can be expanded up to the viewing angle.

Brief Description of Drawings

FIG. 1 is a diagram schematically showing an example of an anisotropic light diffusion film of the present invention.

FIG. 2 is a view schematically showing an anisotropic light diffusion layer in the present invention.

FIG. 3 is a three-dimensional polar coordinate display for explaining the scattering center axis in the present invention.

FIG. 4 is a diagram schematically showing an example of a liquid crystal display device of the present invention.

FIG. 5 is a diagram schematically showing another example of the liquid crystal display device of the present invention.

FIG. 6 is a schematic diagram showing a conventional light control plate.

FIG. 7 is a diagram showing that the anisotropic light diffusion film of the present invention can expand the luminance of the backlight in an arbitrary direction.

Explanation of symbols

[0014] 1 ... Anisotropic light diffusing layer, 2 ... Adhesive, 3 ... Bar-shaped cured region, 10 ... Anisotropic light diffusing film, 1 1, 1 2 ... Glass substrate, 1 3 ... Nematic liquid crystal, 1 4, 1 5 … Polarizing plate, P… scattering central axis.

BEST MODE FOR CARRYING OUT THE INVENTION

[0015] The anisotropic light diffusing film of the present invention has, for example, a configuration in which a plurality of anisotropic light diffusing layers 1 are laminated with an adhesive 2 as shown in FIG. For the pressure-sensitive adhesive layer 2, generally known adhesives and pressure-sensitive adhesives are appropriately used. The anisotropic light diffusing layer in the present invention is made of a cured product of a composition containing a photopolymerizable compound, and an assembly of a plurality of rod-shaped cured regions is parallel to the scattering central axis in the length direction. It is formed as follows. In such a configuration, for example, a composition containing a photopolymerizable compound is provided in a sheet form, and a light beam parallel to the desired scattering center axis P is irradiated from a light source to the sheet, and the composition is cured. Can be formed. [0016] Here, the length direction of the rod-shaped region aggregate and the scattering center axis are parallel as long as they satisfy the law of refractive index (S ne II's law) and are strictly parallel. There is no need. Law of S ne II, when the light to the interface of the medium refractive index n ₂ from a medium of refractive index _{eta iota} incident, between the incident angle of 0 and a refractive angle of 0 _2, _{η ι} si _η Θ , = n ₂ sin 0 ₂ is established. For example, if ΓΗ = 1 (air) and η ₂ = 1.51 (anisotropic light diffusing layer), if the inclination of the scattering center axis (incident angle) is 30 °, the length direction of the rod-shaped region aggregate The (refraction angle) is about 19 °. However, even if the incident angle and the refraction angle are different from each other as long as the Sne II law is satisfied, the present invention includes the parallel concept.

[0017] Note that the aggregate of rod-shaped cured regions referred to in the present invention is schematically shown in Fig. 2, but a large number of rod-shaped or columnar cured regions have their length directions parallel to the scattering center axis. In addition, although the rod shape is estimated from the irradiation light source and the cross section is schematically shown in a circular shape in FIG. 2, it is formed in a rod shape parallel to the scattering center axis. The cross-sectional shape is not particularly limited, such as a circular shape, a polygonal shape, or an indefinite shape.

[0018] According to the three-dimensional polar coordinate display as shown in FIG. 3, the scattering central axis P in the present invention has a polar angle of 0 when the anisotropic light diffusion layer surface is the X y plane and the normal is the z axis. It can be expressed by the azimuth angle ø. That is, P _{xy in} FIG. 3 can be said to be the length direction of the scattering central axis projected onto the surface of the anisotropic light diffusion layer. In the anisotropic light diffusing film of the present invention, the viewing angle of a display panel including a liquid crystal display panel can be sufficiently enlarged if the azimuth angle ø in at least a plurality of anisotropic light diffusing layers is different.

In the present invention, the polar angle 0 of the scattering center angle P is preferably 10 to 60 °, more preferably 30 to 45 °. If the polar angle 0 is less than 10 °, the viewing angle of the display panel including the liquid crystal display panel cannot be expanded sufficiently. -On the other hand, if the polar angle 0 exceeds 60 °, it is necessary to irradiate the composition containing the photopolymerizable compound provided in the form of a sheet in the manufacturing process from a deep inclination, and the absorption efficiency of the irradiated light is increased. Since it is bad and disadvantageous in manufacture, it is not preferable. [0020] The anisotropic light diffusing film of the present invention is formed by laminating a plurality of anisotropic light diffusing layers made of a cured product of a composition containing a photopolymerizable compound. The laminated body is formed on a transparent substrate. It is also possible to adopt a configuration in which a transparent substrate is laminated on both sides of the laminated body. Here, as the transparent substrate, the higher the transparency, the better, and the total light transmittance (JIS K736 1-1) is 80% or more, more preferably 85 <½ or more, most preferably 90 <½ or more. In addition, those having a haze value (JISK 7 136) of 3.0 or less, more preferably 1.0 or less, and most preferably 0.5 or less can be suitably used. A transparent plastic film or glass plate can be used, but a plastic film is preferred because it is thin, light, difficult to break, and has excellent productivity. Specifically, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), triacetyl cellulose (TAC), polystrength Ponate (PC), polyester sulphone (P ES), cellophane, polyethylene (PE) Polypropylene (PP), polyvinyl alcohol (PVA), cycloolefin resin and the like can be mentioned, and these can be used alone or in combination or further laminated. The thickness of the substrate is 1 m to 5 mm, preferably 10 to 500; Um, more preferably 50 to 15 in consideration of use and productivity.

Next, the anisotropic light diffusing film of the present invention includes an anisotropic light diffusing layer obtained by curing a composition containing a photopolymerizable compound, and the following combinations can be used as this composition. .

(1) Using a single photopolymerizable compound described later

(2) A mixture of a plurality of photopolymerizable compounds described later

(3) One or a plurality of photopolymerizable compounds mixed with a polymer compound that does not have photopolymerizability

In any combination, it seems that a fine structure of micron order with different refractive index is formed in the anisotropic light diffusion layer by light irradiation, and this makes the unique anisotropic light diffusion shown in the present invention. It seems that the characteristics can be expressed. Therefore, in (1) above, the larger the refractive index change before and after photopolymerization, In (2) and (3), it is preferable to combine a plurality of materials having different refractive indexes. Here, the refractive index change and the difference in refractive index specifically indicate a change or difference of 0.11 or more, preferably 0.05 or more, more preferably 0.110 or more. is there.

[0023] The photopolymerizable compound, which is an essential material for forming the anisotropic light diffusion layer of the present invention, is a photopolymerization selected from a polymer having a radically polymerizable or cationically polymerizable functional group, an oligomer, and a monomer. It is a material that is composed of an organic compound and a photoinitiator, and is polymerized and cured by irradiation with ultraviolet rays and visible light.

[0024] The radical polymerizable compound mainly contains one or more unsaturated double bonds in the molecule, and specifically includes epoxy acrylate, urethane acrylate, polyester acrylate, poly Acryl oligomers called ether acrylates, polybutadiene acrylates, silicone acrylates, and 2-ethyl hexyl acrylate, isoamyl acrylate, butoxy shetyl acrylate, ethoxydiethylene glycol acrylate , Phenoxychetyl acrylate, Tetrahydrofurfuryl acrylate, Isonol phenyl acrylate, 2-Hydroxyethyl acrylate, 2-Hydroxypropyl acrylate, 2-Acryloyl oxyphthalic acid, Dicyclopentenyl Acrylate, triethyleneglycol Rudiacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, EO adduct of bisphenol A diacrylate, trimethylolpropane triacrylate, EO modified trimethylolpropane triacrylate, pentaerythritol | lutriacrylate, Acrylate monomers such as pentaerythritol | rutetraacrylate, ditrimethylolpropane tetraacrylate, and dipentaerythritol hexacrylate. In addition, these compounds may be used alone or in combination. Similarly, the ability to use methacrylates is generally preferable to methacrylates because of higher photopolymerization rate than methacrylates.

[0025] The cationically polymerizable compound includes an epoxy group and a vinyl ether group in the molecule. A compound having one or more oxetane groups can be used. Compounds having an epoxy group include 2-ethylhexyl diglycol glycidyl ether, biphenyl glycidyl ether, bisphenol A, hydrogenated bisphenol A, bisphenol F, bisphenol AD, bisphenol S, tetramethyl. Diglycidyl ethers of bisphenols such as Rubisphenol A, Tetramethylbisphenol ", Tetrachlorobisphenol 8, Tetrabromobisphenol A, Phenolic nopolac, Cresolol nopolac, Bromoヱ Polyglycidyl ethers of nopolak resins such as nornolacol and orthocresol nopolac, ethylene glycol, polyethylene glycol, polypropylene glycol, butanediol, 1,6-hexanediol, neopentyl glycol Diglycidyl ethers of alkylene glycols such as trimethylolpropane, 1,4-cyclohexanedimethanol, EO adduct of bisphenol A, PO adduct of bisphenol A, glycidyl esters and dimers of hexahydrophthalic acid Examples thereof include glycidyl esters such as diglycidyl ester of acid.

In addition, 3,4-epoxycyclohexylmethyl- 3 ', 4'-epoxy cyclohexylcarboxylate, 2-((3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy) cycloto Di (3,4-epoxycyclohexylmethyl) adipate, Di (3,4-epoxy-1-methylcyclohexylmethyl) adipate, 3,4-epoxy 6-methylcyclohexyl luo 3 ', 4 'mono-epoxy 1' 6-methyl hexane carboxycarboxylate, methylenebis (3,4-epoxycyclohexane), dicyclopentadiene epoxide, diethylene glycol (3,4 mono-epoxycyclohexylmethyl) Ether, ethylene bis (3,4-epoxycyclohexanecarboxylate), lactone modified 3,4-epoxy Chlohexylmethyl- 3 ', 4' monoepoxy cyclohexyl carboxylate, tetra (3, 4-epoxycyclohexylmethyl) butanetetra force lpoxylate, di (3, 4-epoxycyclohexylmethyl) one 4, 5, Although alicyclic epoxy compounds, such as epoxy tetrahydrophthalate, are also mentioned, it is not limited to these.

[0027] Examples of the compound having a vinyl ether group include diethylene glycol divinyl ether, triethylene glycol divinyl ether, butanediol divinyl ether, hexanediol divinyl ether, cyclohexanedimethanol divinyl ether. Ter, hydroxy butyl vinyl ter, ethyl vinyl ter, dodecyl vinyl ter, trimethylol propane trivinyl ether, propenyl ether propylene, etc. It is not limited. The vinyl ether compound is generally cationically polymerizable but can be radically polymerized by combining with acrylate.

As the compound having an oxetane group, 1,4-bis [(3-ethyl-3-oxetanylmethoxy) methyl] benzene, 3-ethyl-3- (hydroxymethyl) monoxetane, and the like can be used.

[0029] The above cationically polymerizable compounds may be used alone or in combination. The photopolymerizable compound is not limited to the above. Further, in order to produce a sufficient refractive index difference, the photopolymerizable compound may be introduced with fluorine atoms (F) in order to reduce the refractive index, and in order to increase the refractive index. In addition, a sulfur atom (S), a bromine atom (Br), and various metal atoms may be introduced. In addition, as disclosed in Special Table 2 0 0 5— 5 1 4 4 8 7, such as titanium oxide (T i 0 ₂ ), zirconium oxide (Z r 0 ₂ ), tin oxide (S n O _x ), etc. It is also possible to add functional ultrafine particles in which photopolymerizable functional groups such as acrylic group, methacrylyl group, and epoxy group are introduced to the surface of ultrafine particles made of a metal compound having a high refractive index to the photopolymerizable compound. It is valid.

[0030] Photoinitiators capable of polymerizing radically polymerizable compounds include benzophenone, benzyl, Michler's ketone, 2-chlorodithioxanthone, 2,4-diethylthioxanthone, benzoinethyl ether, benzoinisopropyl Ether, benzoin isobutyl ether, 2, 2-ethoxy Acetophenone, benzyldimethyl ketal, 2,2-dimethoxy-1,2-diphenylethane_1_one, 2-hydroxy-2-methyl-1,1-phenylpropane-1-one, 1-hydroxycyclohexyl phenyl ketone , 2 —Methyl mono 1_ [4— (Methylthio) phenyl] _2_morpholinopropanone _1, 11 [41 (2-hydroxyethoxy) -phenyl] _2—hydroxy 2-methyl-1-propan _1 _one Bis (cyclopentadienyl) bis (2, 6-difluoro-3- (pill_1_yl) titanium, 2 monobenzyl 2-dimethylamino 1 (4-morpholinophenyl) 1 Thanone 1, 2, 4, 6-trimethylbenzoyldiphenylphosphine oxide etc. These compounds may be used alone or in combination. May be.

In addition, the photoinitiator of a cationic polymerizable compound is a compound that generates an acid by light irradiation and can polymerize the above cationic polymerizable compound by the generated acid. Mouthcene complexes are preferably used. Dionium salts, sulfonium salts, sodium salts, phosphonium salts, selenium salts, etc. are used as onium salts, and these counter ions include BF ₄ _, PF ₆ _, A s F ₆ _, S b F ₆ Anions such as _ are used. Specific examples include 4-chlorobenzene benzene hexafluorophosphate, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, ( (4-phenylthiophenyl) diphenylsulfonium hexafluoroantimonate, (41-phenylthiophenyl) diphenylsulfonium hexafluorophosphate, bis [41- (diphenylsulfonio ) Phenyl] sulfi dobis monohexafluoroanmonate, bis [41 (diphenylsulfonio) phenyl] sulfido monobis monohexafluorophosphate, (4-methoxyphenyl) diphenylsulfonhexaful Oloantimonate, (4-methoxyphenyl) phenfluorohexafluoroanti Ne one, bis (4_T_ Petit Rufueniru) hexa to ® one Doniumu full O b phosphate, benzyl triflate et Nylphosphonium hexafluoroantimonate, triphenylselenium hexafluorophosphate, (7? 5-isopropylbenzene) (7? 5-cyclopentagenyl) iron (II) hexafluoro Examples include, but are not limited to, phosphates. These compounds may be used alone or in combination.

[0032] In the present invention, the photoinitiator is 0.01 to 10 parts by weight, preferably 0.1 to 7 parts by weight, more preferably 0 to 100 parts by weight of the photopolymerizable compound. About 1 to 5 parts by weight are blended. This is because if less than 0.1 part by weight, the photocuring property is lowered, and if more than 10 parts by weight is blended, only the surface is cured and the internal curability is lowered. Because it comes. These photoinitiators are usually used by directly dissolving a powder in a photopolymerizable compound, but if the solubility is poor, a photoinitiator dissolved in a very small amount of solvent in advance at a high concentration is used. It can also be used. Such a solvent is more preferably photopolymerizable, and specific examples thereof include propylene carbonate, and r-peptilolactone. It is also possible to add various known dyes and sensitizers in order to improve photopolymerization. Further, a thermosetting initiator capable of curing the photopolymerizable compound by heating can be used in combination with the photoinitiator. In this case, by heating after photocuring, it can be expected that polymerization curing of the photopolymerizable compound is further promoted and completed.

In the present invention, an anisotropic light diffusing layer can be formed by curing the above-mentioned photopolymerizable compound alone or by mixing a mixture of a plurality thereof. The anisotropic light diffusion layer of the present invention can also be formed by curing a mixture of a photopolymerizable compound and a polymer resin that does not have photocurability. Polymer resins that can be used here include acrylic resin, styrene resin, styrene-acrylic copolymer, polyurethane resin, polyester resin, epoxy resin, cellulose resin, vinyl acetate resin, and vinyl chloride vinyl chloride copolymer. And polyvinyl ptylal resin. These polymer resins and photopolymerizable compounds must have sufficient compatibility before photocuring, but various organic solvents must be used to ensure this compatibility. It is also possible to use an agent or a plasticizer. When acrylate is used as the photopolymerizable compound, it is preferable from the viewpoint of compatibility that the polymer resin is selected from acryl resins.

[0034] The anisotropic light diffusing film of the present invention is provided with a composition containing the above-mentioned photopolymerizable compound in a sheet form, and a light beam parallel to the desired scattering center axis P is irradiated from the light source to the sheet. And is produced by curing the composition. Here, as a method of providing the composition containing the photopolymerizable compound in a sheet form on the substrate, a normal coating method or printing method is applied. Specifically, air coating, bar coating, blade coating, knife coating, river coating, transfer coating, gravure mouth coating, kisco coating, cast coating Coating, spray coating, slot orifice coating, calendar coating, dam coating, dip coating, die coating, etc., intaglio printing such as gravure printing, stencil printing such as screen printing, etc. Can be used. In addition, when the composition has a low viscosity, a weir of a certain height can be provided around the substrate, and the composition can be cast inside the weir.

[0035] As a light source for irradiating a composition containing a photopolymerizable compound provided in a sheet form, a short arc ultraviolet light source is usually used. Specifically, a high pressure mercury lamp, a low pressure mercury lamp Metahalide lamps, xenon lamps, etc. can be used. Note that a light source having a rod-like light emitting surface is inappropriate in the present invention. When such a rod-shaped light source is used, a plate-like hardened region is formed, resulting in the conventional light diffusion medium shown in FIG. In the present invention, it is necessary to irradiate the composition containing the photopolymerizable compound formed in the form of a sheet with a light beam parallel to the desired scattering center axis P. Is preferably used. In addition, when producing a small size, it is possible to irradiate from a sufficiently long distance using an ultraviolet spot light source.

[0036] The light applied to the sheet of the composition containing the photopolymerizable compound needs to have a wavelength capable of curing the photopolymerizable compound, and is usually a mercury lamp. Light with a wavelength centering around 365 nm is used. When the anisotropic light diffusion layer of the present invention is produced using this wavelength band, the illuminance is preferably in the range of 0.01 to 1 OO mW / cm ² , more preferably 0.1 to 20. it is in the range of mW / cm ^2. Illuminance 0. 0 1 mW / cm ² it takes a long time to a be a cured or less, the production efficiency becomes poor, 1 0 O mW / cm ² or more curing is the photopolymerizable compound is too fast structure This is because no formation occurs and the desired transmission diffusivity of incident light cannot be expressed.

[0037] Regarding the above-mentioned light irradiation, it is possible to directly irradiate a composition containing a sheet-like photopolymerizable compound with ultraviolet rays, but in order to prevent oxygen damage due to the material of the photopolymerizable compound, It is preferable that a transparent glass film is brought into close contact with the surface of the composition containing the photopolymerizable compound, and ultraviolet irradiation is performed through the glass. It is also possible to attach a mask having a transmitted light intensity distribution to the surface of a composition containing a sheet-like photopolymerizable compound and to irradiate ultraviolet rays through this mask. In ultraviolet irradiation through a mask having this transmitted light intensity distribution, a photopolymerization reaction corresponding to the irradiation intensity occurs in a composition containing a sheet-like photopolymerizable compound. This is effective in producing the anisotropic light diffusion layer of the present invention. Such transmitted light intensity distribution type masks can be produced by vapor deposition, printing, or coating.

[0038] A display device according to another aspect of the present invention is applicable as long as the display performance has a viewing angle dependency. Examples of the display device that can be used include a liquid crystal display panel, a PDP panel, an organic EL panel, a rear projector, a field emission display, and the like. Here, the viewing performance depends on the viewing angle. When viewing from the front direction (normal direction of the viewing surface of the display device, viewing angle 0 °) and oblique viewing (direction larger than viewing angle 0 °) This means that the display performance such as contrast ratio, gradation characteristics, and chromaticity is different, and the brightness changes greatly. In particular, such viewing angle dependence is strongly observed in the TN mode of the liquid crystal display panel or STN mode, but the anisotropic light diffusion of the present invention is present on the observation surface side of these display devices. By providing a film, good display performance can be expanded in any direction.

[0039] In addition, the liquid crystal display device according to another aspect of the present invention has a configuration in which the above-described anisotropic light diffusion film is provided on the outgoing light side of the liquid crystal display panel. As shown in FIG. 5, a nematic liquid crystal 13 is sandwiched between a pair of transparent glass substrates 11 and 12 on which transparent electrodes are formed, and a pair of glass substrates 11 and 12 are placed on both sides. In the conventional liquid crystal display panel provided with the polarizing plates 14 and 15, the anisotropic light diffusion film 10 is placed on the polarizing plate 14 or between the glass substrate 11 and the polarizing plate 14. This is a configuration provided. For the above-mentioned transparent glass substrate, nematic liquid crystal, polarizing plate, etc., generally known ones can be used.

Example

Next, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

A partition wall with a height of 0.5 mm was formed with a curable resin using a dispenser on the entire periphery of the 76 x 26 mm size slide glass. A composition containing the following photopolymerizable compound was dropped into this and covered with another slide glass.

[Photopolymerizable compound]

■ 2- (Perfluorooctyl) -Ethyl acrylate (Kyoeisha Chemical Co., Ltd., trade name: Light acrylate FA— 1 08) 50 parts by weight

■ 1,9—Nonanediol diacrylate (Kyoeisha Chemical Co., Ltd., trade name: Light acrylate 1.9 N D— A) 50 parts by weight

[Photoinitiator]

■ 2-Hydroxy-1, 2-Methyl-1- 1-Phenylpropane-1-one (Ciba ■ Specialty ■ Chemicals, product name: D aro cure 1 1 73)

4 parts by weight

[0041] With respect to a liquid film having a thickness of 0.3 mm sandwiched between both sides of the slide glass, Using an epi-illumination system with a UV spot light source (manufactured by Hamamatsu Photonics, product name: L 2859 _ 01), ultraviolet rays with an irradiation intensity of 8 mW / cm ² were irradiated for 1 minute at an inclination of 30 ° from the normal. Thereafter, the slide glass on both sides was removed to obtain an anisotropic light diffusion layer.

[0042] Next, using an adhesive (trade name: TD06A, manufactured by Yodogawa Paper Co., Ltd.), the azimuth angles ø when laminated on the liquid crystal display panel are 0 ° and 180 °, respectively. An anisotropic light diffusion film of Example 1 was produced by laminating two anisotropic light diffusion layers.

[0043] Next, the anisotropic light diffusing film described above is applied to an 1.8 inch color S TN panel.

Adhering to the upper side (vertical viewing angle 40 °, left and right viewing angle 40 °) using the above-mentioned adhesive so that the azimuth angle ø is 0 ° and 180 °, respectively. A liquid crystal display device was produced. At this time, the directions of azimuth angles 0 = 0 ° and 1 80 ° were defined as the right and left directions of the panel, respectively.

[0044] <Comparative Example 1>

An anisotropic light diffusing film is not laminated 1. An 8-inch color STN panel was used as the liquid crystal display device of Comparative Example 1.

[0045] <Comparative Example 2>

Instead of the anisotropic light diffusing film of Example 1, Lumisty MFZ-2555 (manufactured by Sumitomo Chemical Co., Ltd.) was used as the anisotropic light diffusing film of Comparative Example 2, and was laminated on the 1.8-inch force STN panel. A liquid crystal display device was obtained.

Instead of the anisotropic light diffusing film of Example 1, a diffusion film BS _ 037 (manufactured by Keiwa) was used as the anisotropic light diffusing film of Comparative Example 3, and the liquid crystal display device of Comparative Example 3 was laminated on an 8-inch column STN panel. It was.

[0047] With respect to the liquid crystal display devices of Example 1 and Comparative Examples 1 to 3 manufactured as described above, the vertical and horizontal viewing angles and the gradation inversion angle described below were confirmed. The tone reversal angle here refers to the angle at which tone reversal starts to occur when the screen is viewed from a position inclined with respect to the normal of the screen. As the direction of tilting at this time, Up and down direction of the screen corresponding to the azimuth angle 90 ° and 270 ° direction, diagonal direction of the screen corresponding to the azimuth angle 45 ° and 235 ° direction, left and right direction of the screen corresponding to the azimuth angle 0 ° and 1 80 ° direction, It confirmed about each of. The viewing angle in this measurement was the maximum polar angle at which the contrast ratio represented by the ratio of white luminance to black luminance was 2 or more. In addition, the presence or absence of image blur was also confirmed, and the results are shown in Table 1.

[0048] [Table 1]

As a result, as shown in Table 1, the viewing angle of the liquid crystal display device of Comparative Example 1 is 40 ° with respect to the vertical and diagonal directions and the horizontal direction, and the gradation inversion angles are vertical and diagonal and left and right. It was 50 ° to the direction. The viewing angle of the liquid crystal display device of Comparative Example 2 is 40 ° in the vertical and diagonal directions, and the horizontal direction is 65 °. The gradation inversion angle is 50 ° in the vertical and diagonal directions, and 75 in the horizontal direction. °. The viewing angle of the liquid crystal display device of Comparative Example 3 was 50 ° in the vertical, diagonal, and horizontal directions, and the gradation inversion angle was 60 ° in the vertical, diagonal, and horizontal directions. Even within 50 °, the screen was blurred, and the outline of the image was not clear. On the other hand, in the liquid crystal display device of the example of the present invention, the viewing angle in the vertical, diagonal, and horizontal directions was 55 °, and the gradation inversion angle was 65 ° in the vertical and diagonal directions. That is, the anisotropic light diffusing film and the liquid crystal display device of the present invention can expand the viewing angle by 15 ° with respect to the vertical, diagonal, and horizontal directions as compared with the conventional liquid crystal display device.

[0050] Next, the present invention will be specifically described using examples of other embodiments.

Z r (OP r) ₄ 65. Place 4 parts by weight in a 250 m I three-necked flask and ice bath Cooled in. While stirring this, 17.2 parts by weight of methacrylic acid (MAA) was gradually added dropwise over 15 minutes. The whole amount is added dropwise and stirred for another 10 minutes, and then the three-necked flask is removed from the ice bath and stirred at 25 ° C for another 10 minutes, Zr (OPr) ₄ / MAA (1: 1) Was prepared.

[0051] Next, 24.8 parts by weight of methacryloxypropyl trimethoxysilane, 14.8 parts by weight of dimethyljetoxysilane, polyvinyl propylal solution (concentration 30% by weight ethanol solution) 1 33.6 parts by weight and tri Ethylene glycol (2_ethylhexanoate) 1 1 0.6 parts by weight were mixed and stirred at 25 ° C. for 15 minutes to prepare a mixed solution for the photopolymerizable composition. To this mixed solution for photopolymerizable composition, 4.50 parts by weight of 0.1 N HCI was added, and the mixture was stirred at room temperature for 10 minutes until the cloudy reaction mixture became clear. Then, while stirring, using a submerged funnel, gradually add the above Zr (OPr) ₄ / MAA (1: 1) 41.6 parts by weight, and after complete addition, For 4 hours. Thereafter, 1.9 parts by weight of water was added dropwise to the mixed solution for photopolymerizable composition, and stirred at room temperature. Furthermore, the product name: C rodamer UVA 42 1 was added 6.7 5 parts by weight, then diluted with 86.3 parts by weight of isopropanol, and the product name: Byk 306 was added 6.5 parts by weight, completely The mixture was stirred until homogenized to prepare a photopolymerizable composition.

[0052] On the transparent PET film having a thickness of 10 Om, the photopolymerizable composition prepared as described above was applied to provide a coating film having a dry film thickness of 50 m. Furthermore, a 38 m thick release PET film (trade name: 38 X, manufactured by Lintec) was laminated on this coating film, and parallel UV light was irradiated from above on a direction with an incident angle of 30 °. Thus, an anisotropic light diffusion film having a scattering central axis of 30 ° was produced.

[0053] Next, two sheets of the anisotropic light diffusing film described above were placed so that the azimuth angles of the scattering center axes thereof were 0 ° and 1800 ° of the outgoing light surface of the backlight, and Example 2 An anisotropic light diffusing film was prepared.

The anisotropic light diffusion layer having a diffusion center axis of 30 ° in Example 2 is The anisotropic light diffusing film of Comparative Example 4 was produced by placing the azimuth of the light so that it coincides with the 0 ° direction of the light exit surface of the backlight (the horizontal right direction of the light exit surface).

[0055] A commercially available backlight was placed on a rotating table with its light emitting surface standing upright, and a luminance meter was placed in front of it. The rotation table was intermittently rotated at 0 ° in the normal direction of the light exit surface, the luminance at each angle was measured, and the luminance distribution characteristic was measured only for the backlight with nothing on it.

[0056] Next, the anisotropic light diffusing film of Example 2 was overlaid on the backlight so that the azimuth angle of the scattering center axis was 0 ° and 180 ° of the light exit surface of the backlight. The luminance distribution characteristics were measured in the same manner as described above.

[0057] Further, on this backlight, the anisotropic light diffusing film of Comparative Example 4 is arranged such that the azimuth angle of the scattering center axis thereof coincides with 0 ° (horizontal direction of the light exit surface) of the exit surface of the backlight. The luminance distribution characteristics were measured in the same manner as described above.

[0058] These results are shown in FIG. As can be seen from Fig. 7, compared with the brightness distribution characteristics of the backlight 卜 alone, the anisotropic light diffusing film of Comparative Example 4 using one anisotropic light diffusing layer shows a significant increase in the angle region of + 32 ° or more. Although the brightness was improved, the brightness was not improved at all in the minus angle region. In contrast, in the anisotropic light diffusing film of Example 2 using two anisotropic light diffusing layers, not only in the plus side but also in the minus side angle region, the brightness is greatly increased in an angle region of about 30 ° or more. An improvement was shown.

Note that each luminance in FIG. 7 is standardized assuming that the luminance in the 0 ° direction of the backlight is 100%, and the actual luminance data is shown in Table 2. According to this data, the anisotropic light diffusing film of the present invention shows that the luminance in the scattering central axis direction is improved, although the luminance in the front direction is slightly lowered. In other words, the anisotropic light diffusing film of the present invention induces light in the front direction in the direction of the scattering center axis.

[0060] 2

As described above, according to the present invention, an anisotropic light diffusion film capable of sufficiently expanding the viewing angle of a display device, particularly a liquid crystal display panel, in an arbitrary direction, a display device using the same, and a liquid crystal display device are provided. be able to.

Claims

The scope of the claims

[1] A plurality of anisotropic light diffusion layers made of a cured product of a composition containing a photopolymerizable compound,

Each of the anisotropic light diffusion layers has one scattering center axis,

The transmission diffusivity of incident light to the anisotropic light diffusing layer depends on the incident angle depending on the angle at which the scattering central axis of the anisotropic light diffusing layer intersects the optical axis of the incident light. Have

An anisotropic light diffusing film characterized in that the direction of the scattering central axis is different depending on each anisotropic light diffusing layer.

[2] The anisotropic light diffusing film according to [1], wherein an azimuth angle of the scattering central axis is different for each anisotropic light diffusing layer.

[3] The anisotropic light diffusion film according to [1], wherein a polar angle of the scattering central axis is different for each of the anisotropic light diffusion layers.

[4] A display device comprising the anisotropic light diffusing film according to claim 1 arranged on an observation surface side of a display device having viewing angle dependence on display performance.

[5] A liquid crystal is sandwiched between a pair of transparent substrates on which a transparent electrode is formed, and a pair of polarizing plates is provided on both sides of the transparent substrate opposite to the side where the liquid crystal is sandwiched. A liquid crystal display device comprising a liquid crystal display panel,

2. A liquid crystal display device comprising the anisotropic light diffusing film according to claim 1 provided on an outgoing light side of the liquid crystal panel.