WO2010084647A1

WO2010084647A1 - Light diffusion film and device comprising same

Info

Publication number: WO2010084647A1
Application number: PCT/JP2009/067390
Authority: WO
Inventors: 義紀薬師神; 透北口; 聡須田
Original assignee: ダイセル化学工業株式会社
Priority date: 2009-01-22
Filing date: 2009-10-06
Publication date: 2010-07-29
Also published as: CN102292658A; TW201035600A; JP5411169B2; JPWO2010084647A1; KR101580346B1; CN102292658B; KR20110106408A; TWI463187B

Abstract

A light diffusion film having a light diffusion layer which is composed of a continuous phase formed of a polycarbonate resin and a dispersed phase which is dispersed in the continuous phase and formed of a resin having an absolute value of the refractive index difference from that of the polycarbonate resin within the range of 0.045-0.085. The continuous phase is formed of a polycarbonate resin having a viscosity average molecular weight of 15,000-25,000, and the dispersed phase may be formed of a cyclic olefin resin. The light diffusion layer may additionally contain a lubricant and/or an antioxidant. The light diffusion film may additionally have a transparent layer arranged on at least one side of the light diffusion layer. The light diffusion film can suppress light leakage even when the transmittance is high, thereby enabling a surface light source device such as a backlight type liquid crystal display device to be formed thinner with higher luminance.

Description

Light diffusing film and apparatus having the same

The present invention relates to a light diffusion film that diffuses transmitted light isotropically or anisotropically, and a surface light source device and a display device (liquid crystal display device, etc.) provided with the light diffusion film.

In a backlight type display device (or liquid crystal display device or the like) that illuminates a display panel (liquid crystal display module or the like) from the back surface, a surface light source unit (or backlight unit) is disposed on the back surface of the display panel. In addition, in order to make the irradiation light to the display panel uniform as a surface light source and to increase the brightness of the front surface of the liquid crystal display device, a diffusion sheet, a prism sheet, a brightness enhancement sheet (a reflective polarizing plate, etc.) and the like are used. Further, in a liquid crystal display device, a polarizing plate, a retardation plate, a color filter, and the like are also used as constituent members of a liquid crystal cell.

More specifically, for example, as a planar display device (flat display device) having a flat (planar) image display area, a planar display unit (such as a transmissive liquid crystal display unit) 5 as shown in FIG. And a surface light source unit for illuminating the unit from the back side are known. The surface light source unit has one or a plurality of fluorescent discharge tubes (cold cathode tubes) 1, and a reflection plate 2 for reflecting light is disposed on the back side of the fluorescent discharge tube 1. Between the discharge tube 1 and the display unit 5, there is disposed a diffusion plate 3 for diffusing light to uniformly illuminate the display unit 5, and a prism sheet 4 is laminated on the display unit side of the diffusion plate 3. Has been. In the case of a liquid crystal display unit, the surface display unit 5 includes a first polarizing film 6a, a first glass substrate 7a, a first electrode 8a formed on the glass substrate, and a first layer laminated on the electrode. The alignment film 9a, the liquid crystal layer 10, the second alignment film 9b, the second electrode 8b, the color filter 11, the second glass substrate 7b, and the second polarizing film 6b are sequentially stacked. . In such a display device, the display unit can be directly illuminated from the back by a built-in fluorescent discharge tube (cold cathode tube) 1.

The backlight system using such a rod-shaped (tubular) light source (lamp) has become very heavy in liquid crystal display devices with the recent increase in size of liquid crystal televisions. In recent years, in such a surface light source device, there is a tendency that the brightness of the light source is increased and the device is thinned. However, in the surface light source device having such a structure, a lamp image (in the shape of a lamp that is a light source). The resulting image and the image in which the presence of the lamp can be easily understood) are more likely to remain.

In the backlight method, the luminance distribution in the axial direction of the rod-shaped light source is different from that in the direction perpendicular to the axial direction, and it is difficult to uniformly illuminate the display unit, so it is difficult to expand the viewing angle. . For this reason, an anisotropic light diffusion sheet having optically anisotropic scattering characteristics is used as the diffusion sheet, and the luminance is made uniform by utilizing the anisotropic scattering characteristics. For example, by arranging the long axis direction of the dispersed phase of the anisotropic light diffusing sheet toward the axial direction of the tubular light source, anisotropic scattering is possible even when using light sources having different luminance distributions in the long axis direction and the short axis direction. A method is known that can make the luminance of transmitted light uniform by utilizing the characteristics. However, even if a light diffusing sheet having such anisotropic scattering characteristics is used, the erasure of the lamp image is not sufficient.

Furthermore, in the backlight system, since the rod-shaped light source is close to the display unit, the display unit is heated, and the diffusion sheet is also required to have heat resistance. A polycarbonate resin is known as a resin having high heat resistance and transparency. However, since the polycarbonate resin has low melt fluidity, it is difficult to industrially efficiently produce a light diffusion film by a melt molding method such as melt extrusion molding. Further, since the polycarbonate resin does not have a high affinity with the components of the dispersed phase, voids are easily generated at the interface with the dispersed phase, and it is difficult to form the dispersed phase uniformly.

Japanese Patent No. 4115113 (Patent Document 1) as a light diffusion sheet used for a backlight system displays a tubular light source and light from the tubular light source incident from the side and emitted from a flat emission surface. A light guide member for illuminating the unit, and a plurality of anisotropic light scattering members disposed between the light guide member and the display unit, and for uniformly illuminating the display unit with light from the tubular light source A surface light source unit comprising a film, wherein the anisotropic light scattering film is composed of a laminated film in which transparent resin layers are laminated on both sides of an anisotropic light scattering layer, and the anisotropic light scattering layer is composed of a resin. And a dispersed phase composed of a resin having an average aspect ratio of 5 to 1000 dispersed in the continuous phase and having a refractive index different from that of the resin of the continuous phase. And a combination of a propylene resin and a styrene resin, or a combination of a propylene resin and a polycarbonate resin, and the transparent resin layer is the same resin as the continuous phase, and has a glass transition temperature or a melting point. A surface light source unit comprising a transparent resin having a temperature of 130 to 280 ° C. and having a plurality of anisotropic light scattering films disposed between the light guide member and the display unit with different light scattering directions. It is disclosed.

However, even in this surface light source unit, in recent backlight type display devices that have been increased in brightness and thinned, luminance uniformity on the display surface is insufficient, so light leakage occurs with high transmittance, The lamp image remains. In particular, when a highly transparent resin such as a polycarbonate resin is used, this tendency becomes remarkable. In addition, the heat resistance is not sufficient, and the light diffusibility changes when used at a high temperature for a long time. Furthermore, when a polycarbonate resin is used, since the polycarbonate resin has low melt fluidity, it is difficult to industrially efficiently produce a light diffusion film by a melt molding method such as melt extrusion molding.

Japanese Patent No. 4115113 (Claim 1)

Accordingly, an object of the present invention is to reduce light leakage even at a high transmittance, and to reduce the thickness and increase the brightness of a surface light source device such as a backlight type liquid crystal display device without developing a lamp image (lamp image). An object of the present invention is to provide a light diffusing film that can be formed and a device (a display device such as a surface light source device or a liquid crystal display device) including the same.

Another object of the present invention is to provide a light diffusing film capable of suppressing changes in light diffusing characteristics even when used at high temperatures and a device (display device such as a surface light source device or a liquid crystal display device) provided with the same. It is in.

Still another object of the present invention is to provide a light diffusing film that can easily form a film having a uniform dispersed phase even when a polycarbonate-based resin having low fluidity and low affinity for a transparent resin is used, and an apparatus (surface) having the same. It is to provide a light source device or a display device such as a liquid crystal display device.

Another object of the present invention is to provide a light diffusing film and a liquid crystal display device including the same, which can cope with the thinning of the device even if it is a large liquid crystal display device and can be easily manufactured.

As a result of intensive studies to achieve the above-mentioned problems, the present inventors have made a transparent resin having a matrix phase (continuous phase) made of a polycarbonate-based resin and a dispersed phase having a predetermined refractive index difference with respect to the polycarbonate-based resin. As a result, it is possible to suppress light leakage even at high transmittance, and to reduce the thickness and brightness of a surface light source device such as a backlight type liquid crystal display device without causing a lamp image (lamp image). As a result, the present invention has been completed.

That is, the light diffusing film of the present invention comprises a continuous phase composed of a polycarbonate resin, a resin dispersed in the continuous phase, and an absolute value of a difference in refractive index from the polycarbonate resin of 0.045 to 0.085. And a light diffusion layer formed of a dispersed phase composed of The continuous phase may be composed of a polycarbonate resin having a viscosity average molecular weight of 15000 to 25000, and the melt flow rate (MFR) of the polycarbonate resin is 5 under the conditions of 300 ° C. and 1.2 kg load in accordance with ISO 1133. it may be about ~ 30cm ^3/10 minutes. Further, the dispersed phase may be composed of a cyclic olefin resin, and the melt flow rate (MFR) of the cyclic olefin resin is 10 to 100 cm under the conditions of 260 ° C. and 2.16 kg load in accordance with ISO 1133. ^It may be about 3/10 minutes. Further, the ratio of the MFR of the polycarbonate resin to the MFR of the cyclic olefin resin may be about the former / the latter = 2/1 to 1/10. The light diffusion layer may further include at least one selected from a lubricant and an antioxidant. The ratio between the continuous phase and the dispersed phase may be about continuous phase / dispersed phase = 99/1 to 50/50 (weight ratio).

The light diffusion film of the present invention may include a particulate dispersed phase in which the dispersed phase has an average aspect ratio greater than 1 and the major axis direction is oriented in a certain direction of the film. The average length of the minor axis of the particulate dispersed phase is about 0.01 to 10 μm, and the average aspect ratio of the particulate dispersed phase is about 3 to 100.

The light diffusion film of the present invention may include a transparent layer laminated on at least one surface of the light diffusion layer. The transparent layer may be a resin layer including at least one selected from an ultraviolet absorber and a light stabilizer. The light diffusion layer may have a thickness of about 3 to 500 μm, and the total light transmittance of the film may be 60% or more.

The present invention includes a surface light source device and a display device (such as a liquid crystal display device) provided with the light diffusion film.

In this specification, “film” is used to mean including a sheet regardless of thickness.

In the present invention, since the matrix phase (continuous phase) is composed of a polycarbonate-based resin and the dispersed phase is composed of a resin having a specific refractive index difference, light leakage can be suppressed even with high transmittance, and the lamp A surface light source device such as a backlight type liquid crystal display device can be made thinner and higher in brightness without developing an image (lamp image). In addition, it has high heat resistance and can suppress changes in light diffusion characteristics over a long period of time even when used at high temperatures. Further, even when a polycarbonate resin having low fluidity and low affinity for a transparent resin is used, a film having a uniform dispersed phase can be easily formed. Furthermore, even a large-sized liquid crystal display device can cope with the thinning of the device and can be easily manufactured.

FIG. 1 is a schematic sectional view showing a surface light source device and a transmissive liquid crystal display device. FIG. 2 is a schematic cross-sectional view showing an example of a light diffusion film. FIG. 3 is a schematic sectional view showing another example of the light diffusion film. FIG. 4 is a conceptual diagram for explaining anisotropic scattering of the light diffusion film. FIG. 5 is a schematic diagram for explaining a method of measuring light scattering characteristics. FIG. 6 is a graph of the scattered light intensity with respect to the scattering angle in a light diffusion film with light leakage. FIG. 7 is a graph of the scattered light intensity with respect to the scattering angle in a light diffusion film having no light omission.

[Light diffusion film]
The light diffusion film of the present invention includes a light diffusion layer composed of a continuous phase and a dispersed phase. The continuous phase is composed of a polycarbonate-based resin from the viewpoint of achieving both excellent optical properties and high heat resistance.

(Polycarbonate resin)
The polycarbonate-based resin includes aromatic polycarbonate based on bisphenols. Examples of bisphenols include biphenols such as dihydroxybiphenyl, 2,2-bis (4-hydroxyphenyl) propane (bisphenol A), bis (4-hydroxyphenyl) methane (bisphenol F), 1,1-bis ( Bis (hydroxyphenyl) alkanes such as 4-hydroxyphenyl) ethane (bisphenol AD), bis (hydroxyaryl) alkanes such as bis (4-hydroxytolyl) alkane, bis (4-hydroxyxylyl) alkane [for example, bis _{(hydroxyaryl) C 1-10} alkanes, preferably bis _{(hydroxyaryl) C 1-6} alkanes, bis bis (hydroxyaryl) cycloalkanes such as (hydroxyphenyl) cyclohexane [e.g., bis (hydroxyalkyl _{Lumpur) C 3-12} cycloalkane, preferably bis _{(hydroxyaryl) C 4-10} cycloalkanes, 4,4'-di (di (hydroxyphenyl) ethers such as hydroxyphenyl) ether, 4, Di (hydroxyphenyl) ketones such as 4'-di (hydroxyphenyl) ketone, di (hydroxyphenyl) sulfones such as bis (4-hydroxyphenyl) sulfone (bisphenol S), bisphenolfluorenes [for example, 9,9 -Bis (4-hydroxyphenyl) fluorene, 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, etc.]. These bisphenols may be C _2-4 alkylene oxide adducts. These bisphenols can be used alone or in combination of two or more.

The polycarbonate resin may be a polyester carbonate resin obtained by copolymerizing a dicarboxylic acid component (such as an aliphatic, alicyclic or aromatic dicarboxylic acid or an acid halide thereof). These polycarbonate resins can be used alone or in combination of two or more. Preferred polycarbonate resins are resins based on bis (hydroxyphenyl) C _1-6 alkanes, for example, bisphenol A type polycarbonate resins.

The molecular weight of the polycarbonate resin has a viscosity average molecular weight (average molecular weight determined by a one-point measurement method based on the correlation between the intrinsic viscosity and the average molecular weight based on the viscosity measured at 20 ° C. using methylene chloride) of 10,000 to 200,000. (For example, it may be selected from a range of about 15000 to 100,000) and may be a high molecular weight polycarbonate resin, but from the viewpoint of the uniformity of the dispersed phase, for example, 15000 to 25000, preferably 17000 to 25000, more preferably Is about 18000-22000. When the molecular weight of the polycarbonate-based resin is too small, the strength of the film is lowered, and when the molecular weight is too large, the melt fluidity and the uniform dispersibility of the dispersed phase are liable to be lowered.

Polycarbonate resin has a melt flow rate (MFR), ISO 1133 (300 ° C., 1.2 kg load (11.8 N)) in compliance with, for example, be selected from the range of about ³ ~ 30cm 3/10 minutes, for example, 5 ~ 30cm ^3/10 minutes, preferably 6 ~ 25cm ^3/10 minutes (e.g., 7 ~ 20cm ^3/10 min), more preferably about 8 ~ 15cm ^3/10 minutes.

The melting point or glass transition temperature of the polycarbonate-based resin is, for example, about 130 to 280 ° C., preferably about 140 to 270 ° C., and more preferably about 150 to 260 ° C.

Such polycarbonate resins are often classified as “medium viscosity products”, “low viscosity products”, and “high flow” grades in product catalogs.

(Dispersed phase)
The dispersed phase is not particularly limited as long as it is incompatible with the polycarbonate resin constituting the continuous phase and has a predetermined refractive index difference. The refractive index of the polycarbonate resin _{(n D)} may be about 1.50 to 1.65, the refractive index of typical bisphenol A type polycarbonate _{(n D)} is 1.59.

The difference in refractive index must be an absolute value in the range of 0.045 to 0.085, preferably 0.045 to 0.08 (for example, 0.045 to 0.075), and more preferably 0.0. It is about 05 to 0.07 (particularly 0.055 to 0.065). Furthermore, the refractive index of both resins may be any resin, but the resin constituting the continuous phase preferably has a higher refractive index. When a resin having such a refractive index difference is combined with a polycarbonate-based resin, light scattering characteristics are improved, and light is scattered with a continuous intensity distribution over a wide angle. When a light diffusion film having such light scattering characteristics is used, the luminance on the display surface is made uniform and light leakage can be suppressed, so that the remaining lamp image can be suppressed.

The dispersed phase is usually composed of a transparent resin. Transparent resins constituting the dispersed phase include olefin resins (polyethylene, etc.), cyclic olefin resins, vinyl-based resins (polyvinyl chloride, vinyl chloride-vinyl acetate copolymers, polyvinyl pyrrolidone, etc.), acrylic resins ( Polymethyl methacrylate, polyacrylic acid, polydialkylaminoethyl methacrylate, polycyclohexyl chloroacrylate, polycyclohexyl bromoacrylate, polychloroethyl chloroacrylate, polybutylthiomethacrylate, polyfurfuryl methacrylate, poly N-methylmethacrylamide), acrylonitrile Resin (polyacrylonitrile, polymethacrylonitrile, butadiene-acrylonitrile copolymer, etc.), styrene resin (polystyrene, styrene-butadiene copolymer, Lene-methyl methacrylate copolymer), polyamide resins (polyamide 6, polyamide 66, polyamide 610, etc.), cellulose derivatives (nitrocellulose, etc.), synthetic rubbers (polybutadiene, polyisoprene, etc.), natural rubber, etc. . The transparent resin constituting the dispersed phase is not limited to the exemplified resin as long as it has the refractive index difference. For example, a resin whose refractive index is controlled by introducing a copolymer component may be used. Therefore, the transparent resin constituting the dispersed phase may be a polycarbonate resin having a refractive index different from that of the continuous phase. These transparent resins can be used alone or in combination of two or more. Among these transparent resins, from the viewpoint of light diffusion characteristics, cyclic olefin resins, vinyl resins (for example, polyvinyl pyrrolidone), styrene resins (for example, styrene-butadiene copolymer), polyamide resins (for example, , Polyamide 6, polyamide 66, polyamide 610, etc.) are preferable, and cyclic olefin-based resins are particularly preferable from the viewpoint of light diffusion characteristics and heat resistance.

(Cyclic olefin resin)
The cyclic olefin-based resin may be a resin having at least a polymerizable cyclic olefin having an ethylenic double bond in the ring as a polymerization component. The cyclic olefin may be a monocyclic olefin, but is preferably a polycyclic olefin.

Typical polycyclic olefins include, for example, norbornene, norbornene having a substituent (2-norbornene), a multimer of cyclopentadiene, a multimer of cyclopentadiene having a substituent, and the like. Examples of the substituent include an alkyl group, an alkenyl group, an aryl group, a hydroxyl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, an acyl group, a cyano group, an amide group, and a halogen atom.

Specifically, as the cyclic olefin, for example, 2-norbornene; 5-methyl-2-norbornene, 5,5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, etc. Norbornenes having an alkyl group; norbornenes having an alkenyl group such as 5-ethylidene-2-norbornene; alkoxycarbonyl groups such as 5-methoxycarbonyl-2-norbornene and 5-methyl-5-methoxycarbonyl-2-norbornene; Norbornenes having a cyano group such as 5-cyano-2-norbornene; norbornenes having an aryl group such as 5-phenyl-2-norbornene and 5-phenyl-5-methyl-2-norbornene; Pentadiene; 2,3-dihydrodi Derivatives such as clopentadiene, methanooctahydrofluorene, dimethanooctahydronaphthalene, dimethanocyclopentadienonaphthalene, methanooctahydrocyclopentadienonaphthalene; derivatives having substituents such as 6-ethyl-octahydronaphthalene; cyclo Examples thereof include adducts of pentadiene and tetrahydroindene, and cyclopentadiene tri- to tetramers. These monomers can be used alone or in combination of two or more.

These cyclic olefins can be used alone or in combination of two or more. Of these cyclic olefins, polycyclic olefins such as norbornenes are preferred.

The cyclic olefin-based resin may be a resin obtained by addition polymerization, or may be a resin obtained by ring-opening polymerization (ring-opening metathesis polymerization or the like). In addition, the cyclic olefin-based resin (for example, a resin obtained by ring-opening metathesis polymerization) may be a hydrogenated hydrogenated resin. In addition, the cyclic olefin resin may be a crystalline or amorphous resin, and may usually be an amorphous resin. The cyclic olefin resin may be prepared by a conventional polymerization method (for example, addition polymerization using a Ziegler type catalyst, addition polymerization using a metallocene catalyst, ring-opening metathesis polymerization using a metathesis polymerization catalyst, etc.). Good.

Furthermore, the cyclic olefin-based resin may be a cyclic olefin homopolymer or a copolymer, or may be a copolymer of a cyclic olefin and a copolymerizable monomer. A copolymer of a cyclic olefin and a copolymerizable monomer is preferable from the viewpoint that the moldability of the cyclic olefin resin can be improved and the refractive index can be appropriately adjusted.

Examples of copolymerizable monomers include chain structures such as ethylene, propylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-hexene and 1-octene. C _2-10 olefins; cyclic C _4-12 cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene, dicyclopentadiene; vinyl ester monomers (for example, vinyl acetate, vinyl propionate, etc.); dienes Examples thereof include monomers (for example, butadiene, isoprene, etc.); (meth) acrylic monomers (for example, (meth) acrylic acid, or derivatives thereof ((meth) acrylic acid ester, etc.)). These copolymerizable monomers may be used alone or in combination of two or more. Preferred copolymerizable monomers are α-chain C _2-8 olefins, particularly α-chain C _2-4 olefins such as ethylene.

In the cyclic polyolefin resin (copolymer), the ratio (molar ratio) between the cyclic olefin and the copolymerizable monomer (for example, α-olefins such as ethylene) is, for example, the former / the latter = 100/0 to For example, the former / the latter = 99/1 to 5/95, preferably 90/10 to 10/90, more preferably 80/20 to 10/90 (particularly 70/30 to 15). / 85) grade. In particular, when the copolymerizable monomer is ethylene, from the viewpoint of optical properties, the ratio (molar ratio) between the cyclic olefin and ethylene is the former / the latter = 65/35 to 20/80, preferably 60/40. It may be about 30/70.

Cyclic olefin resin has a melt flow rate (MFR), ISO 1133 (260 ° C., 2.16 kg load (21.2 N)) in compliance with, for example, be selected from the range of about 10 ~ 100cm ^3/10 min, e.g. , 20 ~ 80cm ^3/10 minutes, preferably from 30 ~ 70cm ^3/10 minutes, more preferably about 40 ~ 60cm ^3/10 minutes.

The ratio of polycarbonate resin constituting the continuous phase to MFR is, for example, polycarbonate resin MFR (300 ° C., 1.2 kg load) / cyclic olefin resin MFR (260 ° C., 2.16 kg load) = 2 / It is about 1 to 1/10, preferably 1/1 to 1/8, more preferably about 1/2 to 1/7 (particularly 1/3 to 1/6). When the ratio of both MFR is in such a range, both resins are sufficiently mixed, and a dispersion layer having an appropriate size can be uniformly formed in the continuous phase.

The softening point or glass transition temperature of the cyclic olefin resin is, for example, about 80 to 250 ° C., preferably 100 to 230 ° C., more preferably 110 to 200 ° C. (especially 120 to 180 ° C.). The softening point or glass transition temperature can be controlled by adjusting the proportion of the copolymer component, the molecular weight, and the like.

The number average molecular weight of the cyclic olefin resin is, for example, about 15,000 to 200,000, preferably about 20,000 to 100,000, more preferably about 30,000 to 80,000 (particularly about 40,000 to 70,000).

Cyclic olefin resins are trade names “TOPAS” (manufactured by Polyplastics Co., Ltd.), trade names “ZEONOR” “ZEONEX” (manufactured by Nippon Zeon Co., Ltd.), and trade names “ARTON” (manufactured by JSR Corporation). The product name “Apel” (manufactured by Mitsui Chemicals, Inc.) can be easily obtained.

In the light diffusion layer, the ratio between the continuous phase and the dispersed phase is, for example, in the range of the former / the latter (weight ratio) = 99/1 to 30/70, depending on the type of resin, fluidity, light diffusibility, and the like. For example, it may be about 99/1 to 50/50, preferably 97/3 to 60/40, more preferably about 95/5 to 70/30 (particularly about 90/10 to 80/20). .

(Optional component)
The light diffusion layer may contain a lubricant as necessary. In particular, when a cyclic olefin resin is used as the resin constituting the dispersed phase, if a lubricant is blended, the dispersed phase easily deforms at an orientation treatment temperature such as a uniaxial stretching temperature, and the transmitted light is diffused anisotropically. A film is easily obtained. In addition, the aspect ratio of the dispersed phase particles can be controlled by an orientation treatment such as draw ratio or uniaxial stretching in the extrusion molding process, and a dispersed phase having a large aspect ratio can be easily formed.

Lubricants include compounds having a low molecular weight hydrocarbon skeleton, such as waxes and lipids.

Examples of the wax include aliphatic hydrocarbon wax (poly C _2-4 olefin wax such as polyethylene wax, ethylene copolymer wax, polypropylene wax, paraffin wax, microcrystalline wax, etc.), vegetable or animal And waxes such as carnauba wax, beeswax, shellac wax, and montan wax. These waxes can be used alone or in combination of two or more.

Examples of lipids include higher fatty acids (for example, _C8-35 saturated fatty acids such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, palmitooleic acid, olein). _C10-35 unsaturated fatty acids such as acids and erucic acids), higher fatty acid salts (eg, C _8-35 fatty acid metal salts such as barium laurate, zinc laurate, calcium stearate, zinc stearate, magnesium stearate, etc.) ), Higher fatty acid esters (eg, C _8-35 fatty acid esters such as glycerin fatty acid ester, pentaerythritol fatty acid ester, diglycerin fatty acid ester, polyglycerin fatty acid ester), higher fatty acid amides (eg, stearic acid amide, erucic acid amide) _{C 8,} such as ₃₅ fatty acid amide, methylene bis stearic acid amide, ethylenebis stearic acid amide, such as alkylene bis fatty acid amides such as ethylene bis-hydroxystearic acid amide) and the like.

These lubricants can be used alone or in combination of two or more. Of these lubricants, lipids, in particular, lauric acid, palmitic acid, stearic acid, C _8-35 saturated fatty acids such as behenic acid, C _8-35 saturated fatty acid metal salts such as calcium stearate and magnesium stearate, pentaerythritol Polyhydric alcohol C _8-35 saturated fatty acid ester such as stearic acid ester, and alkylene bis fatty acid amide such as ethylene bis stearic acid amide and ethylene bishydroxy stearic acid amide are preferable.

The ratio of the lubricant is, for example, 0.01 to 5 parts by weight, preferably 0.02 to 3 parts by weight, and more preferably 0.03 to 2 parts by weight with respect to 100 parts by weight of the resin component constituting the light diffusion layer. (Particularly 0.05 to 1 part by weight).

The light diffusion layer may further contain a conventional additive such as a stabilizer, a plasticizer, an antistatic agent, a flame retardant, etc., as long as the light scattering property is not impaired. These additives can be used alone or in combination of two or more. Of these additives, a stabilizer is preferably blended from the viewpoint of preventing the generation of a gel that impairs the appearance of the film. Stabilizers include antioxidants, ultraviolet absorbers, heat stabilizers, light stabilizers, and the like.

Among the stabilizers, examples of the antioxidant include a phenol-based antioxidant, a hydroquinone-based antioxidant, a quinoline-based antioxidant, and a sulfur-based antioxidant. Phenol antioxidants include hindered phenols such as 2,6-di-tert-butyl-p-cresol, 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2 Alkylphenol antioxidants such as' -thiobis (4-methyl-6-t-butylphenol); C ₁₀ such as n-octadecyl [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] _-35 alkyl [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate]; 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxy) C _2-10 alkanediol-bis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] such as phenyl) propionate]; Polyoxy C _2-4 alkanediol-bis [3- (3,5-di-t-butyl-, such as tylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate] 4-hydroxyphenyl) propionate]; C _3-8 alkylenetriol-tris [3- (3,5-dithiol] such as glycerin tris [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] -T-butyl-4-hydroxyphenyl) propionate]; C _4-8 alkanetetraol tetrakis [3- (pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate]) (3,5-di-tert-butyl-4-hydroxyphenyl) propionate]; N, N′-hexamethylene N, N′-C _2-10 alkylene bis (3,5-di-tert-butyl-4-hydroxyhydrocinnamate) such as bis (3,5-di-tert-butyl-4-hydroxyhydrocinnamamide) Mid).

Amine-based antioxidants include hindered amines such as 1,2-bis (2,2,6,6-tetramethyl-4-piperidyloxy) ethane, phenylnaphthylamine, N, N′-diphenyl-1,4. -Phenylenediamine, N-phenyl-N'-cyclohexyl-1,4-phenylenediamine and the like.

Examples of the hydroquinone antioxidant include 2,5-di-t-butylhydroquinone, and examples of the quinoline antioxidant include 6-ethoxy-2,2,4-trimethyl-1,2. -Dihydroquinoline and the like are included. Examples of the sulfur-based antioxidant include dilauryl thiodipropionate and distearyl thiodipropionate.

Examples of the ultraviolet absorber include salicylic acid ester-based ultraviolet absorbers such as phenyl salicylate and 2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxybenzoate; 2- (2- Hydroxy-5-methylphenyl) benzotriazole, 2- [2-hydroxy-3- (3,4,5,6-tetrahydrophthalimido-methyl) -5-methylphenyl] benzotriazole, 2- (3-t-butyl -2-hydroxy-5-methylphenyl) -5-chlorobenzotriazole, 2- (2-hydroxy-5-tert-butylphenyl) benzotriazole, 2- (2-hydroxy-3,5-di-tert-butyl) Phenyl) benzotriazole, 2- (2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl) benzoto Riazole, octyl-3- [3-tert-butyl-4-hydroxy- (5-chloro-2H-benzotriazol-2-yl) phenyl] propionate, 2- (2H-benzotriazol-2-yl) -4, 6-bis (1-methyl-1-phenylethyl) phenol, 2- (2H-benzotriazol-2-yl) -6- (1-methyl-1-phenylethyl) -4- (1,1,3 Benzotriazole ultraviolet absorbers such as 3-tetramethylbutyl) phenol; 2-hydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2,2′-dihydroxy-4-methoxy Benzophenone UV absorbers such as benzophenone; 2- (4,6-bis (2,4-dimethylpheny ) -1,3,5-triazin-2-yl) -5-hydroxyphenyl and oxirane reaction product, 2- (2,4-dihydroxyphenyl) -4,6-bis (2,4-dimethylphenyl) ) -1,3,5-triazine) and 2-ethylhexylglycidic acid ester, 2,4-bis [2-hydroxy-4-butoxyphenyl] -6- (2,4-dibutoxyphenyl) Examples thereof include hydroxyphenyl triazine-based ultraviolet absorbers such as 1,3,5-triazine.

Examples of the light stabilizer (HALS) include compounds having a 2,2,6,6-tetramethylpiperidine skeleton and a 1,2,2,6,6-pentamethyl-4-piperidine skeleton, such as N, N ′, N '', N '''-tetrakis (4,6-bis (butyl- (N-methyl-2,2,6,6-tetramethylpiperidin-4-yl) amino) triazin-2-yl) -4, 7-diazadecane-1,10-diamine, decanedioic acid bis (2,2,6,6-tetramethyl-1-octyloxy-4-piperidinyloxy) ester, bis (1,2,2,6, 6-pentamethyl-4-piperidinyl) [[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] butyl malonate, bis (1,2,2,6,6-pentamethyl-4 -Piperidinyl) sebacate, this C _4-20 alkane corresponding to the dicarboxylic acid ester of al - such as dicarboxylic acid esters (malonates, such as adipates) or array Nji carboxylate (terephthalate, etc.) can be exemplified.

Examples of heat stabilizers include phosphite stabilizers (tris (branched alkylphenyl) phosphites such as tris (2,4-di-t-butylphenyl) phosphite), bis (alkylaryl) pentaerythritol diphosphites. And the like, phosphorus-based stabilizers (or phosphate esters), sulfur-based heat stabilizers, hydroxylamine-based heat stabilizers, and the like.

These stabilizers (for example, light stabilizers) may be a low molecular weight type or a high molecular weight type. The stabilizer may be used alone, or a combination of two or more components (for example, a combination of an antioxidant and an ultraviolet absorber, a combination of an ultraviolet absorber and a light stabilizer, an antioxidant and an ultraviolet ray). A combination of an absorber and a light stabilizer may be used.

The amount of each stabilizer used is 0.01 to 2.5 parts by weight, preferably 0.03 to 2 parts by weight (for example, 0.05 to 1.0.0 parts by weight) with respect to 100 parts by weight of the resin component constituting the light diffusion layer. 5 parts by weight), more preferably about 0.07 to 1 part by weight (for example, 0.1 to 0.7 parts by weight).

More specifically, the antioxidant is about 0.05 to 1 part by weight (for example, 0.08 to 0.3 part by weight) with respect to 100 parts by weight of the resin component, and the ultraviolet absorber is 100 parts by weight of the resin component. 0.1 to 2 parts by weight (for example, 0.2 to 0.7 parts by weight) with respect to parts, and the light stabilizer is 0.03 to 0.5 parts by weight (for example with respect to 100 parts by weight of the resin component). 0.05 to 0.25 parts by weight).

The total amount of the stabilizer may be 0.05 to 3 parts by weight (for example, 0.1 to 2 parts by weight), preferably about 0.1 to 1 part by weight with respect to 100 parts by weight of the resin component. Good. Further, when a plurality of stabilizers are used in combination, the ratio of the first stabilizer (for example, antioxidant) and the second stabilizer (for example, ultraviolet absorber) is the former / the latter (weight ratio) = It can be selected from a range of about 95/5 to 10/90 (for example, 90/10 to 30/70).

In addition, when an alloy system combining a polycarbonate resin and a transparent resin such as a cyclic olefin resin is melt-extruded or compounded, a part of the extrudate is clearly visible on the die lip (especially the wall adjacent to the opening of the die lip). And the deposit grows into contact with the molten film extruded from the die lip to form a non-uniform film. Therefore, it becomes impossible to produce a uniform film continuously. In such a case, when the stabilizer (for example, an antioxidant and / or an ultraviolet absorber) is contained, the formation and growth of the deposit can be remarkably prevented, and a uniform film can be continuously produced. In many cases, the light diffusion layer usually contains an antioxidant.

In the light diffusion layer, the dispersed phase is in the form of a sphere having a ratio of the average length L of the major axis to the average length W of the minor axis (average aspect ratio, L / W) of about 1 to 1.25. It may be a football type shape (an ellipsoid such as a spheroid), a flat body, a rectangular parallelepiped shape, a fiber shape or a thread shape.

In order to enhance the anisotropic light scattering property, it is preferable that the aspect ratio of the dispersed phase particles is large. In particular, in the present invention, it is preferable to disperse uniformly in the continuous phase without generating voids between the continuous phase and the high-transmittance even when the transmittance is high. The average aspect ratio of the dispersed phase is usually larger than 1 (for example, 1.01 to 20000), and can be selected from a range of about 1.5 to 10,000 (for example, 2 to 5000), for example, 3 to 3000. It is preferably about 4 to 2000, and more preferably about 5 to 1000. From the viewpoint of productivity, it may be about 3 to 100, preferably 3.5 to 50, more preferably about 4 to 30 (especially 5 to 20).

In the light diffusion layer that diffuses the transmitted light anisotropically, the long axis direction of the dispersed phase is oriented in a predetermined direction of the film, that is, the X-axis direction (take-up direction or machine direction) to form a particulate dispersed phase. ing. Such an anisotropic light diffusion layer can effectively improve the luminance of the display device even in a backlight type liquid crystal display device provided with a tubular (bar-shaped) light source.

In particular, in the case of a rod-shaped light source, the residual phase of the lamp image of the light source can be suppressed by orienting the axial direction of the dispersed phase in parallel to the axial direction of the light source. On the other hand, by adjusting the difference in the refractive index of the resin constituting the dispersed phase within the above range, even if the transmittance is high, light leakage can be suppressed without reducing the light scattering effect, and a high degree of lamp image can be achieved. Residual can be suppressed.

The average length L of the major axis of the dispersed phase is, for example, 0.1 to 1000 μm (for example, 0.5 to 500 μm), preferably 1 to 100 μm (for example, 2 to 50 μm), and more preferably 3 to 30 μm. (Especially about 5 to 10 μm). Further, in the case of increasing the anisotropy, for example, it may be about 5 to 800 μm (especially 5 to 500 μm). The average length W of the minor axis of the dispersed phase is, for example, 0.01 to 10 μm (for example, 0.02 to 5 μm), preferably 0.03 to 5 μm (for example, 0.05 to 3 μm), and more preferably Is about 0.07 to 1 μm (for example, 0.1 to 1 μm).

The orientation coefficient of the dispersed phase particles as the degree of alignment is, for example, 0.34 or more (about 0.34 to 1), preferably 0.4 to 1 (for example, 0.5 to 1), more preferably 0.7. It may be about ˜1. Higher anisotropy can be imparted to the scattered light as the orientation coefficient of the dispersed phase particles is higher. The orientation coefficient can be calculated based on the following formula.

Orientation coefficient = (3 <cos ² θ> −1) / 2
(In the formula, θ represents an angle between the major axis of the particulate dispersed phase and the X axis of the film (when the major axis and the X axis are parallel, θ = 0 °), and <cos ² θ> represents each The average cos ² θ calculated for the dispersed phase particles is shown by the following formula).

<Cos ² θ> = ∫n (θ) · cos ² θ · dθ
(In the formula, n (θ) represents the ratio (weight ratio) of dispersed phase particles having an angle θ in all dispersed phase particles).

The light diffusion film may have a directivity of diffused light. That is, having directivity means that there is an angle at which the scattering intensity has a maximum in the direction of strong scattering in anisotropic diffused light. When the diffused light has directivity, when the diffused light intensity F is plotted with respect to the diffusion angle θ in the measurement apparatus of FIG. 5 described later, the plot curve shows a range of a specific diffusion angle θ (θ = It has a maximum or a shoulder (in particular, an inflection point such as a maximum) in an angle range other than 0 °.

The thickness of the light diffusion layer may be, for example, about 3 to 500 μm (for example, 10 to 500 μm), preferably about 30 to 450 μm (for example, 50 to 400 μm), more preferably about 80 to 350 μm (particularly about 100 to 350 μm). Good.

(Transparent layer)
The light diffusion film may be a single layer film of the light diffusion layer alone (for example, an anisotropic light diffusion layer for anisotropically diffusing transmitted light), or a light diffusion layer (for example, transmitting light anisotropically). A laminated body composed of a transparent layer laminated on at least one surface of an anisotropic light diffusing layer that diffuses light into the transparent layer is not limited to a resin layer. Glass, etc.). In many cases, the transparent layer is usually formed of a transparent resin layer. Moreover, in the light-diffusion film which has a laminated structure, you may laminate | stack a transparent resin layer not only on one side of a light-diffusion layer but on both surfaces.

As a preferable resin component constituting the transparent resin layer, the transparent resin exemplified in the section of the dispersed phase can be used. Among the resins, transparent resins include heat-resistant resins (such as resins having a high glass transition temperature or melting point) such as cyclic olefin resins, (meth) acrylic resins, styrene, in order to increase heat resistance and blocking resistance. Resin, polyester resin, polyamide resin, polycarbonate resin and the like can be used, but cyclic olefin resin or polycarbonate resin is particularly preferable from the viewpoint of optical properties and heat resistance. As the resin constituting the transparent resin layer, a resin that is the same as or different from the resin of the continuous phase and / or the dispersed phase constituting the light diffusion layer can be used as long as the adhesion and mechanical properties are not impaired. A resin (polycarbonate resin) that is the same or common (or the same system) as the continuous phase resin is preferred.

Further, the transparent resin layer contains conventional additives such as stabilizers (antioxidants, ultraviolet absorbers, heat stabilizers, light stabilizers, etc.), plasticizers, antistatic agents, flame retardants and the like. Also good. In particular, the transparent layer comprises a stabilizer (antioxidant, ultraviolet absorber, light stabilizer), preferably at least one component selected from an ultraviolet absorber and a light stabilizer (ultraviolet absorber alone, light stabilizer alone, It is preferably composed of a resin layer containing an ultraviolet absorber and a light stabilizer), particularly an ultraviolet absorber and a light stabilizer. The same components as the light diffusion layer can be used as the stabilizer, and the amount of each stabilizer used and the total amount of the stabilizer with respect to 100 parts by weight of the resin component constituting the transparent resin layer are the resin components constituting the light diffusion layer. It can be selected from the same range as the ratio to. Further, when the ultraviolet absorber and the light stabilizer are used in combination, the ratio of the two is from the range of the former / the latter (weight ratio) = 95/5 to 50/50 (for example, 90/10 to 70/30). You can choose.

The thickness of each transparent layer may be approximately the same as that of the light diffusion layer. For example, when the thickness of the light diffusion layer is about 3 to 500 μm, the thickness of each transparent layer can be selected from about 3 to 150 μm. It may be about 5 to 100 μm, preferably about 10 to 50 μm, and more preferably about 15 to 40 μm. The thickness ratio between the light diffusion layer and each transparent layer is, for example, light diffusion layer / transparent layer = 5/95 to 99/1, preferably 30/70 to 99/1, more preferably 40/60 to 95 /. About 5. The thickness of the laminated film may be, for example, about 10 to 600 μm, preferably about 50 to 500 μm, and more preferably about 100 to 400 μm.

The total light transmittance of the light diffusion film (or light diffusion layer) is, for example, 50% or more (for example, 50 to 100%), preferably 60% or more (for example, 60 to 100%), and particularly 70 to 95. % (For example, 75 to 90%). Further, the haze value of the light diffusion film (or light diffusion layer) is 80% or more (for example, 80 to 99.9%), preferably 90% or more (for example, 90 to 99.8%), and more preferably 93%. It is about 99.5%, especially about 95 to 99%. If the total light transmittance is small, the luminance tends to decrease, and if the haze value is small, the light cannot be diffused uniformly and the display quality is deteriorated.

It should be noted that a release agent such as silicone oil may be applied to the surface of the light diffusion film as long as the optical properties are not hindered, or a corona discharge treatment may be performed. Furthermore, you may form the uneven | corrugated | grooved part extended in the X-axis direction (long axis direction of a dispersed phase) of a film in a light-diffusion film. When such an uneven part is formed, high anisotropic light scattering can be imparted to the film.

FIG. 2 is a schematic cross-sectional view showing an example of a light diffusion film. The anisotropic light diffusing film 17 having a single layer structure is composed of a plurality of resins having different refractive indexes, and a phase separation structure in which a particulate dispersed phase 17b is dispersed in a continuous layer 17a composed of a polycarbonate resin (or It has a sea-island structure.

FIG. 3 is a schematic sectional view showing another example of the light diffusion film. In this example, the light diffusion film 28 has a laminated structure including a light diffusion layer 27 and a transparent resin layer 29 laminated on at least one surface of the light diffusion layer. The light diffusion layer 27 is composed of a plurality of resins having different refractive indexes, and a phase separation structure (or sea-island structure) in which the particulate dispersed phase 27b is dispersed in a continuous layer 27a composed of a polycarbonate-based resin. have. In such an anisotropic light diffusing film having a laminated structure, the transparent resin layer 29 protects the light diffusing layer 27 to prevent the dispersed phase particles from falling off and adhering, and the film can be improved in scratch resistance and manufacturing stability. Strength and handleability can be improved.

FIG. 4 is a conceptual diagram for explaining the anisotropy of light diffusion. As shown in FIG. 4, the anisotropic light diffusing film 37 is composed of a continuous phase 37 a composed of a polycarbonate-based resin, and an anisotropic dispersed phase 37 b dispersed in the continuous phase. The light diffusion anisotropy is the scattering characteristic F (θ) indicating the relationship between the scattering angle θ and the scattered light intensity F. The scattering characteristic in the X-axis direction of the film is orthogonal to Fx (θ), the X-axis direction. When the scattering characteristic in the Y-axis direction is Fy (θ), the scattering characteristics Fx (θ) and Fy (θ) show patterns in which the light intensity gently attenuates as the scattering angle θ becomes wider. In the range of scattering angle θ = 4 to 30 °, the value of Fy (θ) / Fx (θ) is 1.01 or more, for example, about 1.01 to 200, preferably about 1.1 to 150. It is. Further, at the scattering angle θ = 18 °, the value of Fy (θ) / Fx (θ) can be selected from the range of about 1.1 to 400, for example, 1.2 to 200, preferably 1.3 to 150. More preferably, it is about 1.5 to 100. The value of Fy (θ) / Fx (θ) is, for example, 1.2 to 50, preferably 1.3 to 30, more preferably 1.5 to 20 (particularly 1.) in terms of productivity. It may be about 8 to 10).

When the light diffusing film of the present invention having such optical characteristics (especially an anisotropic light diffusing film) is used, the rod-shaped light source itself is recognized by being arranged so as to scatter in the direction perpendicular to the axial direction of the rod-shaped light source. The erasing of the lamp image can be achieved with a minimum reduction in brightness. Note that if the value of Fy (θ) / Fx (θ) and the value of Fy (θ) / Fx (θ) at a scattering angle θ = 18 ° are too large, light omission (expression of a lamp image) can be suppressed. On the other hand, when the brightness is greatly reduced and these values are too small, the brightness can be suppressed, but light leakage occurs.

In order to prepare a film having such scattering characteristics, selection of components (particularly resin) constituting the continuous phase and the dispersed phase, molding conditions, particularly extrusion temperature, draw ratio after molding and cooling temperature are important. A film having the light diffusion characteristics of the present invention can be obtained by producing a film under the types and conditions described below.

Note that the X-axis direction of the anisotropic light diffusion film 37 is usually the long-axis direction of the dispersed phase 37b. Therefore, the anisotropic light diffusion film is disposed so that the X-axis direction is substantially parallel to the axial direction (Y-axis direction) of the tubular light source of the surface light source unit. Note that the X-axis direction of the anisotropic light diffusing film does not need to be completely perpendicular to the axial direction (Y-axis direction) of the tubular light source of the surface light source unit, for example, an angle ± 15 ° (for example, ± 10) You may arrange | position toward the diagonal direction within the range of about (degree, especially +/- 5 degree).

The scattering characteristic F (θ) can be measured using, for example, a measuring apparatus as shown in FIG. This apparatus measures the intensity of laser light that has passed through the anisotropic light diffusion film 37 and a laser light irradiation apparatus (for example, NIHONGAKAGAKU ENG NEO-20MS) 38 for irradiating the anisotropic light diffusion film 37 with laser light. And a detector 39. Then, laser light is irradiated (perpendicularly) at an angle of 90 ° with respect to the surface of the light diffusion film 37, and the intensity (scattered light intensity) F of the light diffused by the film is measured (plotted) with respect to the scattering angle θ. ) To obtain light scattering characteristics.

In the anisotropic light diffusion film, when the anisotropy of light scattering is high, the angle dependency of scattering in a predetermined direction can be reduced, and therefore the angle dependency of luminance can be reduced. In the anisotropic light diffusing film, when the angle (90 °) perpendicular to the display surface is 0 °, a decrease in luminance can be suppressed even at an angle of 40 ° or more exceeding the angle 20 ° with respect to the display surface.

[Production method of light diffusion film]
The light diffusion film can be prepared by dispersing the resin component constituting the dispersed phase in the resin constituting the continuous phase, and the anisotropic light diffusion film is obtained by deforming and orienting the resin component constituting the dispersed phase. be able to. For example, a polycarbonate resin, a cyclic olefin resin and, if necessary, a component such as a lubricant are blended by a conventional method (for example, a melt blending method, a tumbler method, etc.) as necessary, and melt-mixed to form a T die or a ring. The dispersed phase can be dispersed by extrusion from a die or the like to form a film. In addition, a coating method in which a composition composed of a particulate cyclic olefin resin as a light scattering component and a polycarbonate resin is applied to a substrate (such as a substrate film) or the composition is laminated. The light diffusing film can also be produced by molding using a conventional film molding method such as a laminating method, a casting method, or an extrusion molding method. Usually, a light diffusing film is often prepared by film forming by an extrusion method.

In addition, the diffusion film which has the laminated structure comprised by the light-diffusion layer and the transparent layer (transparent resin layer) laminated | stacked on at least one surface of this diffusion layer was comprised by the component corresponding to a light-diffusion layer. A resin composition and a resin composition composed of components corresponding to the transparent layer are co-extruded, and a co-extrusion molding method for forming a film. It can be formed by a lamination method, a dry lamination method in which a light diffusion layer and a transparent resin layer, which are respectively produced, are laminated.

The isotropic light diffusing film has the above-mentioned extrusion molding conditions (for example, extrusion under a mild condition such as drawing with a small draw ratio, unstretched processing, etc.), heat treatment of the film after extrusion molding (dispersed with extrusion) It may be prepared by relaxing the form of the dispersed phase into a spherical shape by, for example, heat treatment for relaxing the distortion generated in the phase.

In the anisotropic light diffusing layer, for example, (1) a method of forming a film while drawing an extruded sheet, (2) a method of uniaxially stretching the extruded sheet, (3) the method of (1) The method can be carried out by a method combining the method and the method (2), (4) a method in which the above components are solution-blended, and a film is formed by a casting method.

The melting temperature can be selected according to the type of resin constituting the dispersed phase. For example, in the case of a cyclic olefin resin, for example, 150 to 300 ° C., preferably 200 to 290 ° C., more preferably 230 to 280 ° C. ( In particular, it may be about 240 to 270 ° C.

In order to develop moderate anisotropy, the light diffusion film of the present invention is preferably formed while drawing an extruded sheet in melt film formation. In order to exhibit a predetermined anisotropic light diffusion characteristic, it is important to adjust the draw ratio after extrusion. The draw ratio (draw ratio) can be selected from a range of about 1.5 to 50 times depending on the opening of the die of the extruder, the type of resin, the layer structure, etc., and cannot be uniquely determined. From the range of about 30 times, preferably 2.5-20 times, more preferably 3-15 times (particularly 3.5-10 times), the anisotropy parameter can be selected to be in the range. .

When the dispersed phase is a cyclic olefin resin, the cooling temperature by a cast roll is, for example, about 30 to 180 ° C., preferably 50 to 160 ° C., more preferably 80 to 150 ° C. (especially 100 to 140 ° C.). Also good. Furthermore, the light diffusion film of the present invention may be stretched (uniaxial or biaxial stretching, particularly uniaxial stretching). The draw ratio of the light diffusion film can be selected according to the aspect ratio of the dispersed phase. For example, the draw ratio in one direction is 1.1 to 10 times, preferably 1.2 to 5 times, more preferably 1.5 to It may be about 3 times.

In the light diffusing film of the present invention, transmitted light is scattered and diffused by an appropriate difference in refractive index between the continuous phase and the dispersed phase. In particular, when the aspect ratio of the dispersed phase is increased, the light can be diffused anisotropically. Therefore, the light diffusion film of the present invention can be used for various optical applications. For example, the isotropic light diffusion film can diffuse the transmitted light from the light source to a uniform luminance even when a local light source is used. In particular, anisotropic light diffusing films can reduce the transmission of light from a light source with uniform brightness and prevent light leakage even when a tubular light source having anisotropy in luminance is used. Even if the brightness and brightness are increased, the appearance of the lamp image can be suppressed. Therefore, when applied to a display device such as a liquid crystal display device, the entire display surface can be illuminated uniformly. Therefore, the light diffusing film of the present invention is useful as a constituent member of a surface light source device or a display device (for example, a surface display device (flat display device) having a flat image display area such as a liquid crystal display device). is there. An example of a liquid crystal display device will be described with reference to FIG. 1 described above.

[Liquid Crystal Display]
In FIG. 1 which shows the outline of a liquid crystal display device, the liquid crystal display device includes a surface type display unit (such as a transmission type liquid crystal display unit or a liquid crystal display panel) 5 as an irradiated body including a liquid crystal cell in which liquid crystal is sealed. The surface light source unit is disposed on the back side of the display unit (or panel) and illuminates the display unit 5.

The surface light source unit includes a tubular light source 1 such as a plurality of fluorescent discharge tubes (cold cathode tubes) arranged in parallel or directly below the display unit 5 and light from the tubular light source 1 in the forward direction (display unit). And a reflecting plate 2 for guiding the light to the display unit 5. In front of the tubular light source 1, a support plate (not shown) disposed in front of the tubular light source 1 and an emission surface side (light-emitting surface side of the surface light source unit) of the support plate are arranged to transmit transmitted light. A diffusing plate (for example, anisotropic light diffusing film) 3 for anisotropic light scattering, and a triangular cross section located on the display surface side of the anisotropic light diffusing film 3 with the top facing the direction of the display surface A prism sheet 4 (micro prisms not shown) in which micro prisms are formed in parallel in a predetermined direction is sequentially stacked. The light from the tubular light source 1 is diffused and uniformed by the anisotropic light diffusion film 3 and condensed forward by the prism sheet 4 to illuminate the display unit 5 with increased brightness. In addition, the said support plate is a transparent plate formed in order to protect the anisotropic light-diffusion film 3 which is a thin film.

The surface type display unit (liquid crystal display unit) 5 includes a first polarizing film 6a, a first glass substrate 7a, a first electrode 8a formed on the glass substrate, and a first electrode laminated on the electrode. The first alignment film 9a, the liquid crystal layer 10, the second alignment film 9b, the second electrode 8b, the color filter 11, the second glass substrate 7b, and the second polarizing film 6b are sequentially stacked. Yes.

In such a display device, the display unit can be directly illuminated from the back by a tubular light source 1 such as a built-in fluorescent discharge tube (cold cathode tube). For this reason, the backlight type surface light source device using a tubular light source (lamp) has become very heavy in the liquid crystal display device as the liquid crystal display screen of a liquid crystal television or the like in recent years increases in size.

However, in general, the luminance distribution of light emitted from the tubular light source 1 is not uniform, and the luminance distribution in the direction orthogonal to the axial direction of the tubular light source 1 is not uniform. In particular, the tubular light source itself disposed immediately below the display unit (liquid crystal display unit) 5 is recognized from the display surface side, and a lamp image remains on the display surface. Therefore, even when a tubular light source is used, it is necessary to make the luminance on the display surface uniform. In particular, since the anisotropic light diffusing film 3 is close to the tubular light source 1, the anisotropic light diffusing film 3 is required to have stable light diffusibility for a long period of time.

When the anisotropic light diffusion film 3 is used for a backlight type surface light source unit or a liquid crystal display device, the luminance on the display surface can be made uniform and the expression of the lamp image can be suppressed. That is, when the anisotropic light diffusion film 3 is disposed with the long axis direction of the dispersed phase aligned with the long axis direction of the tubular light source 1, the light from the tubular light source (fluorescent tube) 1 is converted into a rod-shaped light source due to anisotropic light scattering. It is possible to scatter in the direction perpendicular to the length direction of the light source, and to uniformly illuminate the display surface by uniformizing the luminance of the exit surface while minimizing the decrease in luminance. In particular, anisotropic light diffusion can prevent diffused light from being lost, so that the lamp image can be erased even in a backlight unit that is required to be thin and have high brightness. Furthermore, even a large-sized liquid crystal display device can cope with the thinning of the device and can be easily manufactured. That is, even if the light diffusion film of the present invention is thin, the display surface of a large-area liquid crystal display device can be illuminated uniformly with high luminance. In particular, since the continuous phase and the disperse phase are made of a predetermined resin, even a direct type surface light source unit that has high heat resistance, is located in the vicinity of the tubular light source 1 and is subjected to high temperatures can be used for a long time. A predetermined light diffusion can be maintained.

In the liquid crystal display device, the light diffusion film is not limited to anisotropy and may be an isotropic light diffusion film. Further, the light diffusing film (anisotropic light diffusing film, etc.) may be interposed in the light path emitted from the light emitting surface (emission surface) of the surface light source unit, that is, between the surface light source unit and the display unit. You may arrange | position with the lamination | stacking form laminated | stacked on the light emission surface (emitted surface) using the agent. More specifically, the light diffusing film (anisotropic light diffusing film or the like) may be disposed on the light exiting surface (emission surface) side of the surface light source unit or the incident surface side of the display unit. You may arrange | position between display units. In addition, it is not necessary to laminate | stack on the output surface of the said surface light source unit. Further, although it is not necessary to use in combination with the prism sheet or the brightness enhancement sheet, the prism sheet is useful for condensing diffused light and illuminating the display unit. When the prism sheet and the light diffusing film are used in combination, usually, the prism sheet may be disposed on the downstream side of the optical path from the light diffusing film. Moreover, you may use a light-diffusion film in combination with a retardation film, a polarizing film, a color filter, etc. (for example, laminating | stacking).

Furthermore, in the surface light source unit, the tubular light source does not have to be positioned directly below the display unit, and may be positioned on the side portion. In this case, the light from the side tubular light source may be incident from the side of the light guide plate, and may be emitted from the exit surface of the light guide plate formed to face the display unit to illuminate the display unit. . The number of tubular light sources is not particularly limited and can be selected according to the size of the display surface.

Note that the X-axis direction of the anisotropic light diffusion film is usually the long-axis direction of the dispersed phase. Therefore, the anisotropic light diffusing film is disposed so that the X-axis direction thereof is substantially parallel to the axial direction (Y-axis direction) of the tubular light source of the surface light source unit. Note that the X-axis direction of the anisotropic light diffusing film does not need to be completely perpendicular to the axial direction (Y-axis direction) of the tubular light source of the surface light source unit, for example, an angle ± 15 ° (for example, ± 10) You may arrange | position toward the diagonal direction within the range of about (degree, especially +/- 5 degree).

The light diffusing film of the present invention suppresses light leakage even when it is thin and has high brightness, has high heat resistance, and can suppress changes in light scattering characteristics over a long period of time even when used at high temperatures. The display unit can be uniformly illuminated by the light unit (surface light source unit). Therefore, it is useful as a member of a display device (liquid crystal display device or the like) or a backlight type light source device (surface light source device). In particular, a direct type backlight unit (surface light source unit) in which a light source is disposed directly below the display unit can be used for display devices having various screen sizes, particularly large screen display units. It is suitable as a constituent member of the display unit or the backlight unit. The screen size of the display unit is not particularly limited, and may be, for example, about 20 inches or more (eg, 23 to 300 inches, preferably 30 to 200 inches).

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In addition, the characteristic of the light-diffusion film (anisotropic light-diffusion film) used by the Example and the comparative example was evaluated in accordance with the following method.

[Total light transmittance TT (%) and haze (%)]
Based on JIS K7301, the total light transmittance and haze of the light diffusion film were measured using a haze meter (NDH-500, manufactured by Nippon Denshoku Industries Co., Ltd.).

[Refractive index]
In accordance with JIS K 7142, the refractive index of the light diffusion film was measured using a refractometer (manufactured by Atago Co., Ltd., NAR-IT).

[Melt flow rate (MFR)]
In accordance with ISO1133, polycarbonate resin was measured under conditions of 300 ° C. and 1.2 kg load, and cyclic olefin resin was measured under conditions of 260 ° C. and 2.16 kg load.

[Anisotropy]
The stretching direction of the anisotropic light diffusing film is the X-axis direction, the direction orthogonal to this direction is the Y-axis direction, laser light is irradiated from the direction orthogonal to the anisotropic light diffusing film surface, and the scattered light intensity F with respect to the scattering angle θ. That is, the scattered light intensity Fx (θ) with respect to the scattering angle θ in the X-axis direction and the scattered light intensity Fy (θ) with respect to the scattering angle θ in the Y-axis direction were measured. The scattered light intensity ratio Fy (18 °) / Fx (18 °) at θ = 18 ° was determined as a numerical value indicating the anisotropy of light scattering.

[Aspect ratio of particulate dispersed phase]
The cross section of the anisotropic light diffusing film is observed with a transmission electron microscope (TEM), and the long axis length and short axis length of the dispersed phase particles are measured for the 5 dispersed phase particles, and the average is calculated and the average aspect ratio is calculated. did.

[Light loss]
The light scattering intensity distribution of the anisotropic light diffusion film was measured using a laser type light scattering device (manufactured by Neoarc, LSD-101, wavelength 633 nm). The evaluation of light omission was based on a graph in which the horizontal axis represents the scattering angle and the vertical axis represents the logarithm of the light scattering intensity. FIG. 6 is a graph of a sample that has lost light, and FIG. 7 is a graph of a sample that has not lost light. As shown in FIG. 6, in the sample where light is lost, the distribution intensity changes discontinuously near 0 °, so that the luminance becomes non-uniform, light is lost, and the lamp image remains. On the other hand, as shown in FIG. 7, in the sample where light is not lost, since the distribution intensity continuously changes even near 0 °, the luminance is uniform, light is prevented from being lost, and the lamp image does not remain. . The results of evaluating the continuity around 0 ° in such a graph were evaluated according to the following criteria.

◎: Distribution intensity is continuous, no light is lost, and no lamp image remains. ○: Distribution intensity is slightly discontinuous near 0 °, but almost no lamp image remains. △: Distribution intensity is near 0 °. Slightly discontinuous and some lamp image remains ×: The distribution intensity is discontinuous near 0 °, and the lamp image remains.

Example 1
Bisphenol A type polycarbonate resin as the resin constituting the continuous phase (Mitsubishi Engineering Plastics Co., Ltd., "medium viscosity products Iupilon S-2000", viscosity-average molecular weight from 18,000 to 20,000, a melt flow rate 9 ~ 12cm ^3/10 min) 85 parts by weight, the cyclic olefin resin (a copolymer of norbornene monomer and an olefin monomer as a resin constituting the dispersed phase, Topas Advanced polymers GmbH Co., trade name "TOPAS5013", melt flow rate 48cm ^3/10 minutes ) 15 parts by weight, 0.1 parts by weight of lubricant (ethylene bis stearamide, Clariant Japan Co., Ltd., trade name “E-micro powder”), antioxidant (hindered phenol antioxidant, Ciba Japan) Product name "IRGANOX" 1 10 ") 0.1 parts by weight were mixed, and the extrusion temperature was used to melt and extrude from the die at a resin temperature of 260 ° C. and a die opening of 1.3 mm, the draw ratio (draw ratio) was 5 times, and the oil temperature Three-tone cast rolls were cooled at 125 ° C. to produce an anisotropic light diffusion film having a thickness of 263 μm. When the cross section was observed with a transmission electron microscope (TEM), in this diffusion film, the cyclic polyolefin resin formed a scatterer (particulate dispersed phase), and the particulate dispersed phase had an ellipsoidal shape (or The average length (thickness) of the minor axis was 0.8 μm and the average length of the major axis was 6.6 μm (aspect ratio 8.3).

Example 2
As a surface layer resin composition, a two-layer / three-layer light diffusion film (an optical diffusion layer having an anisotropic light diffusion layer as an intermediate layer and a transparent resin layer as a surface layer laminated on both surfaces of the intermediate layer) is prepared. 100 parts by weight of a bisphenol A type polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd., trade name “Iupilon S-2000”), UV absorber (Ciba Japan Co., Ltd., trade name “Tinuvin 234”) 5 parts by weight and 0.1 parts by weight of a light stabilizer (hindered amine light stabilizer, Ciba Japan Co., Ltd., trade name “Kimasoap 944FD”) are used as a resin composition for an intermediate layer, and polycarbonate as a matrix resin Resin (Mitsubishi Engineering Plastics Co., Ltd., trade name “Iupilon S-2000”) 85 parts by weight, constituting the dispersed phase 15 parts by weight of cyclic olefin resin (made by Topas Advanced Polymers GmbH, trade name “TOPAS5013”), 0.1 parts by weight of lubricant (made by Clariant Japan, trade name “E-micro powder”), antioxidant 0.1 parts by weight of an agent (trade name “Irganox 1010” manufactured by Ciba Japan Co., Ltd.) is mixed and melted from the die at a resin temperature of 260 ° C. and a die opening of 1.3 mm using a multilayer extruder. Co-extrusion, draw ratio is 3.6 times, oil temperature control 3 cast rolls are cooled at 125 ° C., have 2 types and 3 layers structure, thickness 364 μm (thickness ratio: surface layer / intermediate layer / surface layer = 1/10) / 1) anisotropic light diffusion film was produced. In this anisotropic light diffusing film, the cyclic polyolefin resin forms a scatterer (particulate dispersed phase) in the intermediate layer, and the particulate dispersed phase has an ellipsoidal shape (or elongated linear shape) and a short axis. The average length (thickness) was 0.8 μm, and the average length of the major axis was 5.3 μm (aspect ratio 6.5).

Example 3
An anisotropic light diffusion film having a thickness of 323 μm (thickness ratio: surface layer / intermediate layer / surface layer = 1/9/1) was produced in the same manner as in Example 2 except that the draw ratio was 4.0 times. In this anisotropic light diffusing film, the cyclic polyolefin resin forms a scatterer (particulate dispersed phase) in the intermediate layer, and the particulate dispersed phase has an ellipsoidal shape (or elongated linear shape) and a short axis. The average length (thickness) was 0.8 μm and the average length of the major axis was 6.7 μm (aspect ratio 8.4).

Example 4
An anisotropic light diffusion film having a thickness of 273 μm (thickness ratio: surface layer / intermediate layer / surface layer = 1/7/1) was produced in the same manner as in Example 2 except that the draw ratio was 4.8 times. In this anisotropic light diffusing film, the cyclic polyolefin resin forms a scatterer (particulate dispersed phase) in the intermediate layer, and the particulate dispersed phase has an ellipsoidal shape (or elongated linear shape) and a short axis. The average length (thickness) was 0.6 μm and the average length of the major axis was 6.2 μm (aspect ratio 10.9).

Example 5
An anisotropic light diffusing film having a thickness of 212 μm (thickness ratio: surface layer / intermediate layer / surface layer = 1/5/1) was produced in the same manner as in Example 2 except that the draw ratio was 6.1 times. In this anisotropic light diffusing film, the cyclic polyolefin resin forms a scatterer (particulate dispersed phase) in the intermediate layer, and the particulate dispersed phase has an ellipsoidal shape (or elongated linear shape) and a short axis. The average length (thickness) was 0.5 μm and the average length of the long axis was 7.9 μm (aspect ratio 16.1).

In Examples 1 to 5, when a film was prepared without blending the lubricant and antioxidant of the anisotropic light diffusion layer, a large number of gels were formed, resulting in a non-uniform film.

Comparative Example 1
As a surface layer resin composition, a two-layer / three-layer light diffusion film (light diffusion film in which an anisotropic light diffusion phase is used as an intermediate layer and transparent resin layers as surface layers are laminated on both surfaces of the intermediate layer) is used. , 100 parts by weight of a polycarbonate resin (Mitsubishi Engineering Plastics Co., Ltd., “Iupilon S-2000”), 0.5 parts by weight of an ultraviolet absorber (Ciba Japan Co., Ltd., “Tinuvin 234”) and a light stabilizer (Hindered amine light stabilizer, “Kimasoap 944FD”) 0.1 parts by weight, and as a resin composition for the intermediate layer, polycarbonate resin as a matrix resin (“Iupilon S-2000” manufactured by Mitsubishi Engineering Plastics Co., Ltd.) 84 parts by weight, polypropylene resin as a resin constituting the dispersed phase (manufactured by Nippon Polypro Co., Ltd., “Winte Click WFW-4 ") 16 parts by weight of an antioxidant (manufactured by Ciba Japan Co., Ltd.," IRGANOX 1010 ") was used 0.1 parts by weight. The resin composition constituting each layer is mixed, and is melted and co-extruded from a die at a resin temperature of 250 ° C. and a die opening of 1.3 mm with a multilayer extruder, the draw ratio is 7.8 times, and the oil temperature control is 3 The cast roll was cooled at 80 ° C. to prepare an anisotropic light diffusion film having a two-type three-layer structure and a thickness of 167 μm (thickness ratio: surface layer / intermediate layer / surface layer = 1/3/1). In this anisotropic light diffusing film, the polypropylene resin forms a scatterer (particulate dispersed phase) in the intermediate layer, and the particulate dispersed phase has an ellipsoidal shape (or elongated linear shape) and a short axis. The average length was 0.15 μm and the average length of the long axis was 700 μm (aspect ratio 4700).

Comparative Example 2
As a resin composition for the intermediate layer, 80 parts by weight of a polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd., “Iupilon S-2000”) as a matrix resin, a polypropylene resin (Nippon Polypro Co., Ltd.) as a resin constituting the dispersed phase ), “Wintech WFW-4”) and 20 parts by weight of antioxidant (Ciba Japan Co., Ltd., “Irganox 1010”) are used, and the draw ratio is 8.3 times. Except for the above, an anisotropic light diffusion film having a two-type three-layer structure and a thickness of 157 μm (thickness ratio: surface layer / intermediate layer / surface layer = 1/3/1) was prepared in the same manner as in Comparative Example 1. In this anisotropic light diffusing film, the polypropylene resin forms a scatterer (particulate dispersed phase) in the intermediate layer, and the particulate dispersed phase has an ellipsoidal shape (or elongated linear shape) and a short axis. The average length was 0.24 μm and the average length of the long axis was 94 μm (aspect ratio 388).

Comparative Example 3
As a resin composition for the intermediate layer, 92 parts by weight of a polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd., “Iupilon S-2000”) as a matrix resin, and a polypropylene resin (Nippon Polypro Co., Ltd.) as a resin constituting the dispersed phase ), "Wintech WFW-4") 8 parts by weight and antioxidant (Ciba Japan Co., Ltd., "Irganox 1010") 0.1 parts by weight were used in the same manner as in Comparative Example 1, An anisotropic light diffusion film having a two-type three-layer structure and a thickness of 167 μm (thickness ratio: surface layer / intermediate layer / surface layer = 1/3/1) was produced. In this anisotropic light diffusing film, the polypropylene resin formed a scatterer (particulate dispersed phase) in the intermediate layer, and the shape of the particulate dispersed phase was an ellipsoid (or elongated linear).

Example 6
92 parts by weight of bisphenol A type polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd., “Iupilon S-2000”) as a resin constituting the continuous phase, cyclic olefin resin (Topas Advanced Polymers GmbH) as the resin constituting the dispersed phase 8 parts by weight of a product name “TOPAS5013” manufactured by the company, using a twin-screw extruder (product name “PCM30”, inner diameter 30 mmφ, L / D = 28.5) manufactured by Ikegai Co., Ltd.) at a resin temperature of 250 ° C. Compounded to obtain pellets. Using a press molding machine (trade name “MINI TEST PRES 10”, manufactured by Toyo Seiki Co., Ltd.), the pellets were 280 μm thick single layer film under conditions of preheating time 2 minutes, pressing time 2 minutes, and pressing pressure 10 MPa. Was made.

Example 7
Except for using a cyclic olefin resin (copolymer of norbornene monomer and olefin monomer, manufactured by Mitsui Chemicals, Inc., trade name “Apel APL6011T”) as the resin constituting the dispersed phase, the same as in Example 6. A single layer film having a thickness of 300 μm was prepared.

Example 8
A 130 μm-thick single resin having a thickness of 130 μm was used in the same manner as in Example 6 except that a cyclic olefin resin (a ring-opening polymer of a norbornene monomer, manufactured by Nippon Zeon Co., Ltd., trade name “ZEONOR330R”) was used as the resin constituting the dispersed phase. A layer film was prepared.

Comparative Example 4
A single-layer film having a thickness of 200 μm was prepared in the same manner as in Example 6 except that polyethylene terephthalate resin (manufactured by Teijin Chemicals Ltd.) was used as the resin constituting the dispersed phase.

Comparative Example 5
A single-layer film having a thickness of 70 μm was produced in the same manner as in Example 6 except that a polypropylene resin (manufactured by Nippon Polypro Co., Ltd., “Wintech WFW-4”) was used as the resin constituting the dispersed phase.

The results are shown in Table 1. In Table 1, symbol TT means total light transmittance (%).

As is clear from the table, when the light diffusion film of the example is used, a high luminance can be obtained without the lamp image remaining. On the other hand, when the film of the comparative example is used, a lamp image remains or a significant reduction in luminance is confirmed.

1. Fluorescent discharge tube (cold cathode tube)
DESCRIPTION OF SYMBOLS 2 ... Reflecting plate 3 ... Diffusing plate 4 ... Prism sheet 5 ...

Planar display unit

6a, 6b ...

Polarizing film

7a, 7b ...

Glass substrate

8a, 8b ...

Electrode

9a, 9b ... Alignment film 10 ... Liquid crystal layer 11 ...

Color filter

17 , 28 ...

Light diffusing film

27, 37 ... Anisotropic

light diffusing layer

17a, 27a, 37a ...

Continuous phase

17b, 27b, 37b ... Dispersed phase 29 ... Transparent resin layer

Claims

A continuous phase composed of a polycarbonate-based resin and a dispersed phase dispersed in this continuous phase and composed of a resin having an absolute difference in refractive index with respect to the polycarbonate-based resin of 0.045 to 0.085. A light diffusion film comprising a light diffusion layer.
2. The light diffusing film according to claim 1, wherein the continuous phase is composed of a polycarbonate resin having a viscosity average molecular weight of 15000 to 25000, and the dispersed phase is composed of a cyclic olefin resin.
Polycarbonate resin of melt flow rate (MFR), in compliance with ISO 1133, 300 ° C., a 5 ~ 30cm 3/10 minutes under the conditions of 1.2kg load, the cycloolefin resin melt flow rate (MFR) , in conformity with ISO1133, 260 ℃, a 10 ~ 100cm 3/10 min under conditions of 2.16kg load, and the ratio of both, the MFR / cyclic olefin resin of polycarbonate resin MFR = 2/1 ~ The light diffusion film according to claim 2, which is 1/10.
The light diffusion film according to any one of claims 1 to 3, wherein the light diffusion layer further comprises at least one selected from a lubricant and an antioxidant.
5. The light diffusing film according to claim 1, wherein the ratio of the continuous phase to the dispersed phase is continuous phase / dispersed phase = 99/1 to 50/50 (weight ratio).
6. The light diffusing film according to claim 1, wherein the dispersed phase includes a particulate dispersed phase having an average aspect ratio larger than 1 and having a major axis direction oriented in a certain direction of the film.
The light diffusion film according to claim 6, wherein the average length of the minor axis of the particulate dispersed phase is 0.01 to 10 µm, and the average aspect ratio of the particulate dispersed phase is 3 to 100.
The light diffusion film according to any one of claims 1 to 7, comprising a transparent layer laminated on at least one surface of the light diffusion layer.
The light diffusion film according to claim 8, wherein the transparent layer is a resin layer containing at least one selected from an ultraviolet absorber and a light stabilizer.
10. The light diffusing film according to claim 1, wherein the light diffusing layer has a thickness of 3 to 500 μm and the total light transmittance of the film is 60% or more.
A surface light source device comprising the light diffusing film according to any one of claims 1 to 10.
A display device comprising the light diffusing film according to any one of claims 1 to 10.