KR101580346B1 - Light diffusion film and device comprising same - Google Patents

Abstract

A continuous phase comprising a polycarbonate resin and a light diffusing layer formed of a dispersed phase dispersed in this continuous phase and comprising a resin having an absolute value of the refractive index difference with respect to the polycarbonate resin in the range of 0.045 to 0.085 A light-diffusing film is produced. The continuous phase includes a polycarbonate resin having a viscosity average molecular weight of 15000 to 25000, and the dispersed phase may be contained as a cyclic olefin resin. The light-diffusing layer may further comprise a lubricant and / or an antioxidant. The light diffusion film may further include a transparent layer laminated on at least one surface of the light diffusion layer. This light-diffusing film can suppress light leakage even with a high transmittance, so that a surface light source device such as a backlight type liquid crystal display device can be made thinner and brighter.

Description

TECHNICAL FIELD [0001] The present invention relates to a light diffusing film,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light diffusion film for diffusing 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 a 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. Further, a diffusion sheet, a prism sheet, a brightness enhancement sheet (other than a reflection type polarizing plate) and the like are used in order to uniformize the irradiation light for the display panel as a surface light source and increase the luminance of the front surface of the liquid crystal display device. In the liquid crystal display device, a polarizing plate, a retardation plate, a color filter, or the like is also used as a component of the liquid crystal cell.

More specifically, for example, a planar display device (planar display device) in which the image display area is flat (flat) includes a planar display unit (transmissive liquid crystal display unit or the like) 5 as shown in Fig. 1, And a surface light source unit for illuminating the unit from the back side is known. The surface light source unit has one or a plurality of fluorescent discharge tubes (cold cathode tubes) 1. A reflective plate 2 for reflecting light is disposed on the back side of the fluorescent discharge tube 1, A diffusing plate 3 for uniformly illuminating the display unit 5 is disposed between the display unit 5 and the display unit 5. A prism sheet 4 is provided on the display unit side of the diffusing plate 3 Respectively. In the case of the liquid crystal display unit, the planar display unit 5 includes a first polarizing film 6a, a first glass substrate 7a, a first electrode 8a formed on the glass substrate, 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 sequentially As shown in FIG. In such a display device, the display unit can be directly illuminated from the back surface by the built-in fluorescent discharge tube (cold cathode tube) 1.

BACKGROUND OF THE INVENTION [0002] Backlight systems using such a film source (lamp) as a film source have been increasing in weight in liquid crystal display devices with the recent trend toward larger size liquid crystal televisions. In such a surface light source device, the surface light source device having such a structure tends to increase the brightness of the light source and to make the device thinner. However, in the surface light source device having such a structure, the lamp image (image due to the shape of the lamp, The image that can be grasped to be glimpsed of the existence of the more likely to remain.

Further, in the backlight system, since the luminance distribution in the axial direction of the film target light source and in the direction orthogonal to the axial direction is different and uniform illumination of the display unit is difficult, it is difficult to enlarge the viewing angle. As a result, an anisotropic light-diffusing sheet having optically anisotropic scattering characteristics is used as the diffusion sheet, and the brightness is made uniform by using the anisotropic scattering property. For example, by arranging the major axis direction of the dispersed phase of the anisotropic light-diffusing sheet toward the axial direction of the tubular light source, even if a light source having a different luminance distribution in the major axis direction and the minor axis direction is used, And the like are known. However, even if a light diffusion sheet having such an anisotropic scattering property is used, erasing of the lamp image is not sufficient.

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

Japanese Patent No. 4115113 (Patent Document 1) discloses a light diffusion sheet for use in a backlight system, which comprises a tubular light source, a light source for emitting light from the tubular light source from a side surface, And a plurality of anisotropic light scattering films disposed between the light guiding member and the display unit for uniformly illuminating the display unit with light from the tubular light source, Wherein the anisotropic light scattering film comprises a laminated film in which a transparent resin layer is laminated on both sides of an anisotropic light scattering layer, the anisotropic light scattering layer comprises a continuous phase comprising a resin, and a continuous phase having an average aspect ratio of 5 to 1000 And a dispersed phase containing a resin having a refractive index different from that of the continuous phase resin, and the propylene resin And a combination of a propylene resin and a polycarbonate resin, wherein the transparent resin layer is the same resin as the continuous phase and contains a transparent resin having a glass transition temperature or a melting point of 130 to 280 DEG C And a plurality of anisotropic light scattering films are disposed between the light guiding member and the display unit so that the direction of light scattering is different from each other.

However, also in this surface light source unit, in recent backlight type display apparatuses with high brightness and thinness, since the uniformity of brightness on the display surface is insufficient, light leakage occurs with high transmittance and a lamp image remains. Particularly, when a highly transparent resin such as a polycarbonate resin is used, the tendency becomes remarkable. Further, the heat resistance is insufficient, and when used over a long period at a high temperature, the light diffusibility changes. In addition, when a polycarbonate resin is used, it is difficult to industrially efficiently produce a light diffusion film by a melt molding method such as melt extrusion molding because the polycarbonate resin has low melt flowability.

Patent 4115113 (Claim 1)

Accordingly, an object of the present invention is to provide a surface light source device, such as a backlight type liquid crystal display device, which is capable of suppressing light leakage even with a high transmittance and which does not emit a lamp image And a device (a display device such as a surface light source device or a liquid crystal display device) provided with the film.

Another object of the present invention is to provide a light diffusion film and a device (a surface light source device, a display device such as a liquid crystal display device) having the same, which can suppress the change of the light diffusion property even under high temperature.

Another object of the present invention is to provide a light diffusion film which can easily form a film having a uniformly dispersed phase even when a polycarbonate resin having a low affinity for a fluidity and a transparent resin is used and a device A surface 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 diffusion film and a liquid crystal display device including the same, which can cope with the thinning of the apparatus even in a large-sized liquid crystal display apparatus and can easily manufacture the apparatus.

Means for Solving the Problems As a result of intensive studies in order to achieve the above object, the present inventors have found that when a matrix phase (continuous phase) contains a polycarbonate resin and a transparent As a result of including the resin, it has been found that the surface light source device such as the backlight type liquid crystal display device can be made thinner and brighter without suppressing the light leakage even with a high transmittance and not displaying the lamp image Thereby completing the invention.

That is, the light-diffusing film of the present invention comprises a continuous phase containing a polycarbonate resin and a resin dispersed in this continuous phase and having an absolute value of the refractive index difference with respect to the polycarbonate resin of 0.045 to 0.085 And a light diffusing layer formed of a dispersed phase including the light diffusing layer. The continuous phase may contain a polycarbonate resin having a viscosity average molecular weight of 15000 to 25000. The melt flow rate (MFR) of the polycarbonate resin may be in the range of 5 to 30 Cm < 3 > / 10 minutes. The dispersed phase may contain a cyclic olefin resin, and the melt flow rate (MFR) of the cyclic olefin resin may be about 10 to 100 cm 3/10 min under the conditions of 260 ° C and 2.16 kg load in accordance with ISO 1133. 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-diffusing layer may further include at least one selected from a lubricant and an antioxidant. The ratio of the continuous phase to the dispersed phase may be about 99/1 to 50/50 (weight ratio) in the continuous phase / dispersed phase.

The light-diffusing film of the present invention may comprise a particulate dispersed phase in which the dispersed phase has an average aspect ratio of greater than 1 and whose 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 占 퐉, 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 containing at least one selected from an ultraviolet absorber and a light stabilizer. The thickness of the light-diffusing layer is about 3 to 500 mu m, and the total light transmittance of the film may be 60% or more.

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

In the present specification, the term " film " is used to mean a sheet including any thickness.

In the present invention, since the matrix phase (continuous phase) contains a polycarbonate resin and the dispersed phase contains a resin having a specific refractive index difference, light leakage can be suppressed even with a high transmittance, A flat light source device such as a backlight type liquid crystal display device can be made thinner and higher in brightness. Further, the heat resistance is high, and the change of the light diffusion property can be suppressed over a long period of time even when used at a high temperature. In addition, 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. Further, even a large-sized liquid crystal display device can cope with the thinning of the device, and the device can be manufactured easily.

1 is a schematic cross-sectional view showing a planar light source device and a transmissive liquid crystal display device.
2 is a schematic sectional view showing an example of a light diffusion film.
3 is a schematic cross-sectional view showing another example of the light diffusion film.
4 is a conceptual diagram for explaining anisotropic scattering of the light diffusion film.
5 is a schematic view for explaining a method of measuring light scattering characteristics.
6 is a graph of the scattered light intensity against the scattering angle in the light diffusion film with light leakage.
7 is a graph of the scattered light intensity against the scattering angle in the light diffusion film without light leakage.

[Light diffusion film]

The light-diffusing film of the present invention includes a light-diffusing layer including a continuous phase and a dispersed phase. The continuous phase contains a polycarbonate resin in view of both excellent optical properties and high heat resistance.

(Polycarbonate resin)

The polycarbonate resin includes aromatic polycarbonate based on bisphenols and the like. Examples of bisphenols include bisphenols such as dihydroxybiphenyl and the like, bisphenols such as 2,2-bis (4-hydroxyphenyl) propane (bisphenol A), bis (4-hydroxyphenyl) Bis (hydroxyphenyl) alkanes such as bis (4-hydroxyphenyl) ethane and bis (4-hydroxyphenyl) (hydroxy aryl) alkanes [e.g., bis (hydroxy aryl) C _1-10 alkanes, and preferably bis (hydroxy aryl) C _{1 -6} alkanoic acids], bis (hydroxymethyl) cyclohexane bis (hydroxy aryl) cycloalkanes acids [for example, bis (hydroxy aryl) C _3-12 cyclo alkanes, preferably bis (hydroxy aryl) C _4-10 cycloalkane acids], such as, 4, Di (hydroxyphenyl) ethers such as 4'-di (hydroxyphenyl) ether, di (hydroxyphenyl) ethers such as 4,4'- ) Sulfone (bisphenol S) and the like Bis (4-hydroxyphenyl) fluorene, 9,9-bis (4-hydroxy-3-methylphenyl) fluorene, etc.] and the like . These bisphenols may be C _{2 -4} alkylene oxide adducts. These bisphenols may be used alone or in combination of two or more.

The polycarbonate resin may be a polyester carbonate resin copolymerized with a dicarboxylic acid component (an aliphatic, alicyclic or aromatic dicarboxylic acid or an acid halide thereof). These polycarbonate resins may be used alone or in combination of two or more. A preferred polycarbonate resin is a resin based on bis (hydroxyphenyl) C _1-6 alkane, for example, a bisphenol A-type polycarbonate resin.

The molecular weight of the polycarbonate resin is preferably 10,000 or more, more preferably 10,000 or more, more preferably 10,000 to 10,000,000 or more, more preferably 10,000 to 10,000,000 or more, more preferably 10,000 to 10,000,000 or more, more preferably 10,000 to 10,000,000 or more, May be selected from the range of from about 1,000 to about 200,000 (for example, from about 15,000 to about 100,000), and may be a polycarbonate resin having a high molecular weight. In view of the uniformity of the dispersed phase, More preferably from about 18000 to about 22000. If the molecular weight of the polycarbonate resin is too small, the strength of the film is lowered. If the molecular weight is too large, the melt flowability and the uniform dispersibility of the dispersed phase are likely to deteriorate.

The melt flow rate (MFR) of the polycarbonate resin can be selected from the range of about 3 to 30 cm 3/10 min, for example, in accordance with ISO 1133 [300 캜, 1.2 kg load (11.8 N) For example, 5 to 30 cm 3/10 min, preferably 6 to 25 cm 3/10 min (for example, 7 to 20 cm 3/10 min), and more preferably about 8 to 15 cm 3/10 min.

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

These polycarbonate resins are often classified in the product catalog as " medium viscosity products ", " low viscosity products ", and " high flow "

(Dispersed phase)

The dispersed phase is not particularly limited as long as it is an emulsion for the polycarbonate resin constituting the continuous phase and is a resin having a predetermined refractive index difference. The refractive index (n _D ) of the polycarbonate resin may be about 1.50 to 1.65, and the refractive index (n _D ) of a typical bisphenol A-type polycarbonate is 1.59.

The refractive index difference needs to be in the range of 0.045 to 0.085, preferably 0.045 to 0.08 (for example, 0.045 to 0.075), more preferably 0.05 to 0.07 (particularly 0.055 to 0.065) in absolute value. The refractive index of both resins may be any resin, but it is preferable that the resin constituting the continuous phase has a larger refractive index. When such a resin having a refractive index difference is combined with a polycarbonate resin, the light scattering property is improved, and light is scattered in a continuous intensity distribution over a wide angle. When the light diffusion film having such light scattering characteristics is used, the brightness on the display surface is made uniform, and light leakage can be suppressed, so that the remaining of the lamp image can be suppressed.

The dispersed phase usually includes a transparent resin. Examples of the transparent resin constituting the dispersed phase include olefin resins (such as polyethylene), cyclic olefin resins, vinyl resins (polyvinyl chloride, vinyl chloride-vinyl acetate copolymer and polyvinylpyrrolidone), acrylic resins But are not limited to, methyl acrylate, methyl acrylate, polyacrylic acid, polydialkylaminoethyl methacrylate, polycyclohexyl chloroacrylate, polycyclohexyl bromoacrylate, polychloroethyl chloroacrylate, polybutyl thiomethacrylate, Poly (N-methylmethacrylamide), acrylonitrile resin (polyacrylonitrile, polymethacrylonitrile, butadiene-acrylonitrile copolymer), styrene resin (polystyrene, styrene-butadiene copolymer , Styrene-methyl methacrylate copolymer, etc.), polyamide resins (polyamide 6, polyamide 66, polyamide 610 and the like), cellulosic (Nitrocellulose, etc.), synthetic rubbers (polybutadiene, polyisoprene, etc.), and natural rubbers. The transparent resin constituting the dispersed phase is not limited to the above-exemplified resin as long as it has the above refractive index difference, and may be a resin whose refractive index is controlled by introduction of a copolymerization component, for example. Therefore, the transparent resin constituting the dispersed phase may be a polycarbonate-based resin having a refractive index different from that of the continuous phase. These transparent resins may be used alone or in combination of two or more. Among these transparent resins, a cyclic olefin resin, a vinyl resin (e.g., polyvinyl pyrrolidone), a styrene resin (e.g., styrene-butadiene copolymer), a polyamide (For example, polyamide 6, polyamide 66, polyamide 610 and the like) are preferable, and a cyclic olefin resin is particularly preferable in view of having light diffusion property and heat resistance.

(Cyclic olefin resin)

The cyclic olefin resin may be a resin containing 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.

Representative polycyclic olefins include, for example, norbornene, norbornene having a substituent (2-norbornene), a cyclopentadiene multimer, and a cyclopentadiene multimer having a substituent. 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.

Specific examples of the cyclic olefin include 2-norbornene; Norbornenes having alkyl groups such as 5-methyl-2-norbornene, 5,5-dimethyl-2-norbornene, 5-ethyl-2-norbornene and 5-butyl-2-norbornene; Norbornenes having an alkenyl group such as 5-ethylidene-2-norbornene; Norbornenes having 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; Dicyclopentadiene; Derivatives such as 2,3-dihydrodicyclopentadiene, methanooctahydrofluorene, dimethanooctahydronaphthalene, dimethanocyclopentadienonaphthalene, and methanooctahydrocyclopentadienonaphthalene; A derivative having a substituent such as 6-ethyl-octahydronaphthalene; Adducts such as cyclopentadiene and tetrahydroindene, and trimer to tetramer of cyclopentadiene, and the like. These monomers may be used alone or in combination of two or more.

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

The cyclic olefin resin may be a resin obtained by addition polymerization or a resin obtained by ring-opening polymerization (ring-opening metathesis polymerization). The cycloolefin resin (for example, a resin obtained by ring-opening metathesis polymerization) may be a hydrogenated hydrogenated resin. The cyclic olefin-based resin may be a crystalline or amorphous resin, or may be an amorphous resin. The cyclic olefin resin may be produced by an ordinary 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.).

The cyclic olefin resin may be a cyclic olefin alone or a copolymer, or a copolymer of a cyclic olefin and a copolymerizable monomer. A copolymer of a cyclic olefin and a copolymerizable monomer is preferable in that the moldability of the cyclic olefin resin can be improved and the refractive index can be appropriately adjusted.

Examples of the copolymerizable monomers include straight chain C _{2 -10} such as ethylene, propylene, 1-butene, isobutene, 1-pentene, 3-methyl-1-pentene, Olefins; Cyclic C _{4 -12} cycloolefins such as cyclobutene, cyclopentene, cycloheptene, cyclooctene and dicyclopentadiene; Vinyl ester monomers (e.g., vinyl acetate, vinyl propionate and the like); Diene-based monomers (e.g., butadiene, isoprene, etc.); (Meth) acrylic monomers (e.g., (meth) acrylic acid, or derivatives thereof ((meth) acrylic acid esters, etc.)]. These copolymerizable monomers may be used singly or in combination of two or more kinds. Preferred copolymerizable monomers are α-chain C _{2 -8} olefins, particularly α-chain C _{2 -4} olefins such as ethylene.

The ratio (molar ratio) of the cyclic olefin to the copolymerizable monomer (e.g., -olefins such as ethylene) in the cyclic polyolefin-based resin (copolymer) is, for example, 99/1 to 5/95, preferably 90/10 to 10/90, more preferably 80/20 to 10/90 (in particular, 70/30 To 15/85). In particular, in the case where the copolymerizable monomer is ethylene, the ratio (molar ratio) of the cyclic olefin to ethylene in the former / the latter is preferably about 65/35 to 20/80, and more preferably about 60/40 to 30/70 good.

The melt flow rate (MFR) of the cyclic olefin based resin can be selected from the range of, for example, about 10 to 100 cm 3/10 minutes in accordance with ISO 1133 (260 ° C, 2.16 kg load (21.2 N) 20 to 80 cm 3/10 min, preferably 30 to 70 cm 3/10 min, and more preferably 40 to 60 cm 3/10 min.

The ratio of the polycarbonate resin constituting the continuous phase to the MFR of the polycarbonate resin is, for example, the MFR (300 캜, 1.2 kg load) of polycarbonate resin / MFR (260 캜, 2.16 kg load ) = 2/1 to 1/10, preferably 1/1 to 1/8, more preferably 1/2 to 1/7 (particularly 1/3 to 1/6). When the ratio of both MFRs is within this range, both resins can be sufficiently mixed to uniformly form a dispersion layer having a suitable size in the continuous phase.

The softening point or the glass transition temperature of the cyclic olefin resin is, for example, about 80 to 250 占 폚, preferably 100 to 230 占 폚, and more preferably about 110 to 200 占 폚 (particularly 120 to 180 占 폚). Further, the softening point or the glass transition temperature can be controlled by adjusting the ratio of the copolymerization 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, and more preferably about 30,000 to 80,000 (particularly about 40,000 to 70,000).

The cyclic olefin resin can be obtained by copolymerizing a cyclic olefin resin (trade name: "TOPAS", manufactured by Polyplastics Co., Ltd.), "ZEONOR", "ZEONEX" (manufactured by Nippon Zeon Co., ARTON "(manufactured by JSR Corporation)," APEL "(manufactured by Mitsui Chemicals, Inc.) and the like.

In the light-diffusing layer, the ratio of the continuous phase to the dispersed phase can be selected from the range of electron / latter (weight ratio) = 99/1 to 30/70, for example depending on the type of resin, For example, 99/1 to 50/50, preferably 97/3 to 60/40, more preferably 95/5 to 70/30 (particularly 90/10 to 80/20).

(Optional component)

The light-diffusing layer may contain a lubricant if necessary. Particularly, when a cyclic olefin resin is used as the resin constituting the dispersed phase, when a lubricant is added, the dispersed phase is easily deformed at the orientation treatment temperature such as the uniaxial stretching temperature, and a film for anisotropically diffusing the transmitted light is easily obtained Loses. In addition, the aspect ratio of the dispersed phase particles can be controlled by an orientation treatment such as drawing or uniaxial stretching in the extrusion molding step, and a dispersed phase having a large aspect ratio can be easily formed.

The lubricant includes a compound having a hydrocarbon skeleton having a low molecular weight, for example, waxes, lipids, and the like.

Examples of waxes include aliphatic hydrocarbon waxes (such as poly-C _{2 -4} olefin waxes such as polyethylene waxes, ethylene copolymer waxes and polypropylene waxes, paraffin waxes and microcrystalline waxes), vegetable or animal waxes Carnauba wax, beeswax, shellac wax, montan wax and the like). These waxes may be used alone or in combination of two or more kinds.

Examples of lipids, such as fatty acids (eg, caprylic acid, capric acid, lauric acid, C _{8 -35} saturated such as myristic acid, palmitic acid, stearic acid, Oh La Mountain, behenic Fatty acid, C _{10 -35} unsaturated fatty acids such as palmitoleic acid, oleic acid and erucic acid), higher fatty acid salts (for example, barium laurate, zinc laurate, calcium stearate, zinc stearate, stearic acid C _{8 -35} fatty acid metal salts such as magnesium and the like), higher fatty acid esters (e.g., glycerol fatty acid ester, pentaerythritol fatty acid esters, such as di-glycerin fatty acid esters, polyglycerol fatty acid esters _-35 C ₈ fatty acid esters and the like), higher fatty acid amides (e.g., stearic acid amide, erucic acid amide, such as a C _8-35 fatty acid amide, methylenebis stearic acid amide, ethylene bis stearic acid amide, ethylene bis hydroxyl stearic acid amide And the like), and the like.

These lubricants may be used alone or in combination of two or more. Of these lubricants, lipids, particularly C _{8 -35} saturated fatty acids such as lauric acid, palmitic acid, stearic acid and behenic acid, C _{8 -35} saturated fatty acid metal salts such as calcium stearate and magnesium stearate, Fatty acid amides such as polyhydric alcohol C _{8 -35} saturated fatty acid esters such as stearic acid esters and alkylene bis fatty acid amides such as ethylenebisstearic acid amide and ethylenebis hydroxystearic acid amide.

The proportion of the lubricant is, for example, 0.01 to 5 parts by weight, preferably 0.02 to 3 parts by weight, more preferably 0.03 to 2 parts by weight (particularly 0.05 to 1 part by weight) relative to 100 parts by weight of the resin component constituting the light- Parts by weight).

The light-diffusing layer may contain additives for public use, for example, a stabilizer, a plasticizer, an antistatic agent, a flame retardant, and the like within a range that does not impair light scattering properties. These additives may be used alone or in combination of two or more. Among these additives, from the viewpoint of preventing the generation of a gel damaging the appearance of the film, it is preferable to incorporate a stabilizer. The stabilizer includes an antioxidant, an ultraviolet absorber, a heat stabilizer, a light stabilizer, and the like.

In the stabilizer, examples of the antioxidant include phenol-based antioxidants, hydroquinone-based antioxidants, quinoline-based antioxidants, and sulfur-based antioxidants. Examples of the phenolic antioxidant include hindered phenols such as 2,6-di-t-butyl-p-cresol, 2,2'-methylenebis (4-methyl- '- thiobis (4-methyl-6-t-butylphenol); n- octadecyl [3- (3,5-di -t- butyl-4-hydroxyphenyl) propionate], such as the C _10-35 alkyl [3- (3,5-di -t- butyl-4 - hydroxyphenyl) propionate]; 1,6-bis [3- (3,5-di -t- butyl-4-hydroxyphenyl) propionate], such as the C _{2 - 10} alkanediol-bis [3- (3,5- Di-t-butyl-4-hydroxyphenyl) propionate]; Triethylene glycol-bis [3- (3-t- butyl-5-methyl-4-hydroxyphenyl) propionate], such as polyoxy C ₂ of ₄ alkanediol-bis [3- (3,5-di -t-butyl-4-hydroxyphenyl) propionate]; Glycerin tris [3- (3,5-di -t- butyl-4-hydroxyphenyl) propionate], such as C _{3 -8} alkyl rental rheology-tris [3- (3,5-di -t- butyl -4-hydroxyphenyl) propionate]; Pentaerythritol tetrakis [3- (3,5-di -t- butyl-4-hydroxyphenyl) propionate], such as the C ₄ alkane _-8-tetra ol-tetrakis [3- (3,5-di- t-butyl-4-hydroxyphenyl) propionate]; N, N'-C _{2 -10} alkylenebis (3,5-di-t-butyldimethylammonium) such as N, N'-hexamethylenebis (3,5- Butyl-4-hydroxyhydrocinnamamide) and the like are preferable.

Examples of the amine antioxidant include hindered amines such as 1,2-bis (2,2,6,6-tetramethyl-4-piperidyloxy) ethane, phenylnaphthylamine, N, Phenyl-1,4-phenylenediamine, N-phenyl-N'-cyclohexyl-1,4-phenylenediamine and the like.

The hydroquinone antioxidant includes, for example, 2,5-di-t-butylhydroquinone and the quinoline antioxidant includes 6-ethoxy-2,2,4-trimethyl- Dihydroquinoline, and the like. The sulfur-based antioxidant includes, for example, dilauryl thiodipropionate, distearyl thiodipropionate, and the like.

Examples of the ultraviolet absorber include salicylate ester ultraviolet absorbers such as phenyl salicylate and 2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxybenzoate; Benzotriazole, 2- [2-hydroxy-3- (3,4,5,6-tetrahydrophthalimide-methyl) -5-methylphenyl] (2-hydroxy-5-t-butylphenyl) benzotriazole, 2- (3-t-butyl- (2-hydroxy-3,5-bis (?,? - dimethylbenzyl) phenyl) benzotriazole, octyl-3 - [3-t-butyl-4-hydroxy- (5-chloro-2H-benzotriazol- 2-yl) phenyl] propionate, 2- (2H-benzotriazol- (1-methyl-1-phenylethyl) phenol, 2- (2H-benzotriazol- , 3-tetramethylbutyl) phenol, and the like; Benzophenone such as 2-hydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, and 2,2'-dihydroxy- Non - ultraviolet absorber; The reaction product of 2- (4,6-bis (2,4-dimethylphenyl) -1,3,5-triazin-2-yl) Dihydroxyphenyl) -4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine) with 2-ethylhexyl glycidic acid ester, 2,4-bis [2- Hydroxy-4-butoxyphenyl] -6- (2,4-dibutoxyphenyl) -1,3,5-triazine, and other hydroxyphenyltriazine based ultraviolet absorbers.

As light stabilizers (HALS), compounds having 2,2,6,6-tetramethylpiperidine skeleton, 1,2,2,6,6-pentamethyl-4-piperidine skeleton such as N, N, N ', N '', N '' -tetrakis (4,6-bis (butyl- (N-methyl-2,2,6,6- tetramethylpiperidin- (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, these dicarboxylic acid esters corresponding to the C _{4 - 20} alkane-dicarboxylic acid ester (malonate, adipate, etc.) Naphthalenedicarboxylic acid ester (e.g., terephthalate), and the like.

Examples of the heat stabilizer include tris (branched alkyl phenyl) phosphite, bis (alkylaryl) pentaerythritol diphosphite, etc. such as phosphite stabilizers (tris (2,4-di-t-butylphenyl) (Or phosphate esters), sulfur series heat stabilizers, and hydroxylamine series heat stabilizers.

These stabilizers (for example, light stabilizers, etc.) may be of low molecular weight type or high molecular weight type. The stabilizer may be used alone or in 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, a combination of an antioxidant and an ultraviolet absorber and a light stabilizer) It can also be used.

The amount of each stabilizer to be used is 0.01 to 2.5 parts by weight, preferably 0.03 to 2 parts by weight (for example, 0.05 to 1.5 parts by weight), more preferably 0.07 to 1.5 parts by weight, per 100 parts by weight of the resin component constituting the light- 1 part by weight (for example, 0.1 to 0.7 part by weight).

More specifically, the antioxidant is used in an amount of 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, the ultraviolet absorber is used in an amount of 0.1 to 2 parts by weight (For example, about 0.2 to 0.7 part by weight), and the light stabilizer is about 0.03 to 0.5 part by weight (for example, about 0.05 to 0.25 parts by weight) relative to 100 parts by weight of the resin component.

The total amount of the stabilizer may be about 0.05 to 3 parts by weight (for example, about 0.1 to 2 parts by weight), preferably about 0.1 to 1 part by weight, based on 100 parts by weight of the resin component. When a plurality of stabilizers are used in combination, the ratio of the first stabilizer (for example, antioxidant) to the second stabilizer (for example, ultraviolet absorber) is preferably from 95/5 to 10 / 90 (for example, 90/10 to 30/70).

Further, when a molten extrusion molding or a compounding process is carried out by combining a polycarbonate resin and a transparent resin such as a cyclic olefin resin, the die lip (in particular, the wall portion adjacent to the opening portion of the die lip) Part of the water gradually accumulates in the form of snow, and this deposit grows and comes into contact with the molten film extruded from the die lip to form a non-uniform film. As a result, a uniform film can not be continuously produced. In this case, when the stabilizer (for example, an antioxidant and / or an ultraviolet absorber) is contained, formation and growth of the sediments can be prevented remarkably, and a uniform film can be continuously produced. Further, the light-diffusing layer usually contains an antioxidant in many cases.

The shape of the dispersed phase in the light-diffusing layer may be a spherical shape having a ratio (average aspect ratio, L / W) of the average length L of the major axis to the average length W of the minor axis of 1 to 1.25, (An ellipsoid such as a rotating ellipsoid), a flat body, a rectangular parallelepiped, a fibrous body, or a squared body.

In order to enhance the anisotropic light scattering property, it is preferable that the aspect ratio of the dispersed phase particle is large. Particularly, in the present invention, it is preferable that even a high transmittance can be suppressed at a high level of light leakage, and uniformly dispersed in a continuous phase without occurrence of voids or the like between the continuous phase and the continuous phase. The average aspect ratio of the dispersed phase is usually larger than 1 (for example, 1.01 to 20,000), for example, can be selected from the range of about 1.5 to 10000 (for example, 2 to 5000) 3000, preferably from 4 to 2000, and more preferably from 5 to 1000. Further, from the viewpoint of productivity and the like, it may be about 3 to 100, preferably about 3.5 to 50, more preferably about 4 to 30 (particularly about 5 to 20).

In the light diffusing layer that anisotropically optically diffuses the transmitted light, the long axis direction of the dispersed phase is oriented in a predetermined direction of the film, that is, in the X axis direction (pulling direction or machine direction) to form a particulate dispersed phase. Such an anisotropic light diffusion layer can effectively improve the brightness of the display device even in the case of a backlight type liquid crystal display device having a tubular (film subject) light source.

Particularly, in the case of the film target light source, the residual of the lamp image of the light source can be suppressed by orienting the axial direction of the dispersed phase parallel to the axial direction of the light source, but in the present invention, the continuous phase polycarbonate- The refractive index difference of the resin constituting the dispersed phase is adjusted in the above range so that the light scattering effect can be suppressed even if the transmittance is high and the light leakage can be suppressed and the remnant of the highly lamp image can be suppressed.

The average length L of the major axis of the dispersed phase may be in the range of, for example, 0.1 to 1000 탆 (for example, 0.5 to 500 탆), preferably 1 to 100 탆 (for example, 2 to 50 탆) Preferably about 3 to 30 占 퐉 (particularly about 5 to 10 占 퐉). In the case of increasing the anisotropy, for example, it may be about 5 to 800 占 퐉 (particularly, 5 to 500 占 퐉). The average length W of the minor axis of the dispersed phase is, for example, 0.01 to 10 占 퐉 (for example, 0.02 to 5 占 퐉), preferably 0.03 to 5 占 퐉 (for example, 0.05 to 3 占 퐉) And preferably about 0.07 to 1 mu m (e.g., 0.1 to 1 mu m).

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

Orientation coefficient = (3 <cos ² ?> -1) / 2

Represents the angle between the long axis of the particulate dispersed phase and the X axis of the film (when the long axis is parallel to the X axis,? = 0 DEG), and < cos ² > cos ² &amp; thetas; and is expressed by the following formula).

< cos ² &amp; thetas; &gt; = = n (&amp;thetas;) cos ² &

(Wherein, n (?) Represents the ratio (weight ratio) of dispersed phase particles having an angle (?) In the total dispersed phase particles).

The light-diffusing film may have directivity of diffused light. That is to say, having directivity means that there is an angle at which the scattering intensity of the anisotropic diffused light has the maximum value in the direction in which the scattering is strong. When the diffused light has directivity, when the diffuse light intensity F is plotted with respect to the diffuse angle? In the measuring apparatus of Fig. 5 described later, the plot curve is in the range of the specific diffuse angle? = 0 DEG), or a shoulder (in particular, an inflection point such as a maximum point).

The thickness of the light-diffusing layer is, for example, 3 to 500 μm (for example, 10 to 500 μm), preferably 30 to 450 μm (for example, 50 to 400 μm), more preferably 80 to 350 μm (In particular, 100 to 350 mu m).

(Transparent layer)

The light diffusion film may be a single layer film of the light diffusion layer alone (for example, anisotropic light diffusion layer for anisotropically diffusing transmitted light) or may be a light diffusion layer (for example, anisotropic light Diffusing layer), and various transparent materials (for example, glass or the like) can be used for the transparent layer without being limited to the resin layer. The transparent layer is often formed of a transparent resin layer in many cases. In addition, in the light diffusion film having a laminated structure, the transparent resin layer may be laminated on both sides of the light diffusion layer.

As a preferable resin component constituting the transparent resin layer, the transparent resin exemplified in the above section of the dispersed phase can be used. Of the above resins, transparent resins include resins having heat resistance (such as a resin having a high glass transition temperature or high melting point) such as cyclic olefin resins, (meth) acrylic resins, styrene resins, poly Based resins, ester-based resins, polyamide-based resins, polycarbonate-based resins, and the like. Of these, cyclic olefin-based resins or polycarbonate-based resins are particularly preferable from the viewpoints of optical properties and heat resistance. The resin constituting the transparent resin layer may be the same or different from the resin of the continuous phase and / or the dispersed phase constituting the light diffusion layer as long as the adhesiveness and the mechanical properties are not impaired. Or a common (or same system) resin (polycarbonate resin).

Further, the transparent resin layer may contain a common additive such as a stabilizer (an antioxidant, an ultraviolet absorber, a heat stabilizer, a light stabilizer, etc.), a plasticizer, an antistatic agent, a flame retardant and the like. In particular, the transparent layer preferably contains at least one component selected from stabilizers (antioxidants, ultraviolet absorbers, light stabilizers), preferably ultraviolet absorbers and light stabilizers (ultraviolet absorber alone, light stabilizer alone, ultraviolet absorber and light stabilizer) Absorbing agent and a light stabilizer. The same amount of stabilizer can be used as the light-diffusing layer. The amount of each stabilizer and the total amount of the stabilizer relative to 100 parts by weight of the resin component constituting the transparent resin layer is the same as that of the resin component constituting the light- Range. When the ultraviolet absorber and the light stabilizer are used in combination, the ratio of the ultraviolet absorber and the light stabilizer can be selected from the range of about 95/5 to 50/50 (for example, 90/10 to 70/30) have.

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

The total light transmittance of the light diffusion film (or light diffusion layer) is, for example, at least 50% (for example, 50 to 100%), preferably 60% or more (for example, 60 to 100% May be about 70 to 95% (e.g., 75 to 90%). The haze value of the light diffusion film (or light diffusion layer) is preferably 80% or more (for example, 80 to 99.9%), preferably 90% or more (for example, 90 to 99.8% To 99.5%, especially 95 to 99%. If the total light transmittance is small, the luminance tends to lower. If the haze value is small, the light can not be uniformly diffused, and the display quality is degraded.

A releasing agent such as silicone oil may be applied to the surface of the light-diffusing film within a range that does not disturb the optical characteristics, or corona discharge treatment may be performed. The light-diffusing film may be provided with concave-convex portions extending in the X-axis direction (long axis direction of the dispersed phase) of the film. By forming such concave-convex portions, a higher anisotropic light scattering property can be imparted to the film.

2 is a schematic sectional view showing an example of a light diffusion film. The anisotropic light-diffusing film 17 of the single-layer structure includes a plurality of resins having different refractive indices from each other, and a phase separation structure (a) in which the particulate phase dispersed phase 17b is dispersed in the continuous layer 17a containing polycarbonate- Or oceanographic structure).

3 is a schematic cross-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 side of the light diffusion layer. The light diffusing layer 27 is formed of a resin having a phase separation structure (or a sea-island structure) in which a particulate phase dispersed phase 27b is dispersed in a continuous layer 27a containing polycarbonate resin- ). As such an anisotropic light-diffusing film having such a laminated structure, it is possible to protect the light-diffusing layer 27 with the transparent resin layer 29 to prevent the drop-off or adherence of the dispersed phase particles and to improve the scratch resistance and manufacturing stability of the film And at the same time, the strength and handleability of the film can be enhanced.

4 is a conceptual diagram for explaining anisotropy of light diffusion. As shown in Fig. 4, the anisotropic light-diffusing film 37 includes a continuous phase 37a containing a polycarbonate resin and an anisotropic dispersed phase 37b dispersed in the continuous phase. The scattering characteristic [F (?)] Indicating the relationship between the scattering angle [theta] and the scattered light intensity F is Fx ([theta]), the X- The scattering characteristics Fx (?) And Fy (?) Are set such that the scattering angle? Becomes the wide angle (wide angle) when the scattering characteristic in the Y- And the intensity is gently attenuated. The value of Fy (?) / Fx (?) Is 1.01 or more, for example, 1.01 to 200, preferably 1.1 to 150, in the range of scattering angle? = 4 to 30 degrees. The value of Fy (?) / Fx (?) At a scattering angle? = 18 can be selected from the range of about 1.1 to 400, for example, 1.2 to 200, preferably 1.3 to 150, Lt; / RTI &gt; The value of Fy (?) / Fx (?) Is, for example, from 1.2 to 50, preferably from 1.3 to 30, more preferably from 1.5 to 20 (particularly from 1.8 to 10) good.

When the light diffusion film (particularly, an anisotropic light diffusion film) of the present invention having such optical characteristics is used, by arranging to scatter in a direction perpendicular to the axial direction of the light source to be film-formed, It is possible to suppress the decrease in luminance to a minimum. Further, if the value of Fy (?) / Fx (?) And the value of Fy (?) / Fx (?) At the scattering angle? = 18 degrees are excessively large, light leakage (expression of the lamp image) , The decrease in luminance is large. Conversely, when these values are excessively small, a decrease in luminance can be suppressed, but light leakage occurs.

In order to produce a film having such a scattering property, the selection of components (particularly, resins) constituting the continuous phase and the dispersed phase, the molding conditions, particularly the extrusion temperature, the draw ratio after molding and the cooling temperature are important, A film having the light diffusion property of the present invention is obtained.

The X-axis direction of the anisotropic light-diffusing film 37 is generally the long axis direction of the dispersed phase 37b. Accordingly, the X-axis direction of the anisotropic light-diffusing film is disposed in a direction substantially parallel to the axial direction (Y-axis direction) of the tubular light source of the surface light source unit. The X-axis direction of the anisotropic light-diffusing film need not be completely parallel to the axial direction (Y-axis direction) of the tubular light source of the surface light source unit but may be, for example, Deg., In particular, +/- 5 deg.).

The scattering characteristic F (&amp;thetas;) can be measured using, for example, a measuring device as shown in Fig. This apparatus comprises a laser light irradiating device (for example, Nihon Kagaku Enzyme Neo-20MS) 38 for irradiating laser light to the anisotropic light diffusion film 37 and an anisotropic light diffusion film 37 And a detector 39 for measuring the intensity of one laser beam. The intensity of the light diffused by the film (scattered light intensity) F is measured with respect to the scattering angle [theta] by irradiating the surface of the light diffusion film 37 with laser light at an angle of 90 DEG (Plotted), the light scattering characteristic can be obtained.

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

[Method of producing light diffusion film]

The light diffusion film can be produced by dispersing the resin component constituting the dispersed phase in the resin constituting the continuous phase, and the anisotropic light diffusion film can be obtained by modifying and orienting the resin component constituting the dispersed phase. For example, components such as a polycarbonate resin, a cycloolefin resin and, if necessary, a lubricant may be blended by a conventional method (for example, a melt blending method, a tumbler method or the like) And extruded from a T-die ring die or the like and film-formed to disperse the dispersed phase. In addition, a coating method in which a particulate cycloolefin resin as a light scattering component and a composition containing a polycarbonate resin are coated on a substrate (base film or the like), a lamination method in which the composition is laminated, a casting method, A light diffusion film can also be produced by molding using a conventional film forming method such as an extrusion molding method. Usually, a light-diffusing film is often produced by film-forming by an extrusion molding method.

The diffusion film having a laminated structure including a light diffusion layer and a transparent layer (transparent resin layer) laminated on at least one side of the diffusion layer is characterized by comprising a resin composition containing a component corresponding to the light diffusion layer, A method in which the other layer is extruded on one of the previously prepared layers and laminated by a laminate, a method of laminating the prepared light diffusion layer and the transparent resin layer, And the like.

The isotropic light-diffusing film can be produced by subjecting the isotropic light-diffusing film to heat treatment under the conditions of the above extrusion molding (for example, extrusion molding under a mild condition such as picking up in a small draw ratio, For example, a heat treatment for alleviating strain generated in the dispersed phase, or the like).

In the anisotropic light-diffusing layer, the orientation treatment of the dispersed phase can be carried out by, for example, (1) a method of forming a film while drawing an extruded sheet, (2) a method of uniaxially stretching the extruded sheet, (3) (2); (4) a method of solution-blending each of the above-mentioned components and forming the film by a casting method (casting method).

The melting temperature may be selected depending on the type of the resin constituting the dispersed phase. For example, in the case of a cyclic olefin resin, the melting temperature is, for example, 150 to 300 캜, preferably 200 to 290 캜, more preferably 230 to 280 (Particularly 240 to 270 DEG C).

In order to develop an appropriate anisotropy, it is preferable that the light diffusion film of the present invention is formed by drawing an extrusion-molded sheet in a melt film. In order to develop a predetermined anisotropic light diffusion property, it is important to adjust the draw ratio after extrusion. The draw ratio (draft magnification) can be selected from the 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. Uncertainly, The parameter of the anisotropy may be selected from the range of about 30 times, preferably 2.5 to 20 times, and more preferably about 3 to 15 times (particularly 3.5 to 10 times).

When the dispersed phase is a cyclic olefin resin, for example, the cooling temperature by the cast roll or the like is in the range of 30 to 180 DEG C, preferably 50 to 160 DEG C, more preferably 80 to 150 DEG C (particularly 100 to 140 DEG C) good. The light diffusion film of the present invention may be stretched (uniaxially or biaxially stretched, particularly uniaxially stretched). The stretching magnification of the light-diffusing film can be selected according to the aspect ratio of the dispersed phase. For example, the stretching magnification in one direction is 1.1 to 10 times, preferably 1.2 to 5 times, more preferably 1.5 to 3 times .

In the light-diffusing film of the present invention, the transmitted light is scattered and diffused depending on a suitable refractive index difference between the continuous phase and the dispersed phase. Particularly, when the aspect ratio of the dispersed phase becomes large, it can be anisotropically light diffused. Therefore, the light diffusion film of the present invention can be used for various optical applications. For example, an isotropic light-diffusing film can transmit light transmitted from a light source at a uniform luminance even by using a local light source. Particularly, the anisotropic light-diffusing film can diffuse the transmitted light from the light source with a uniform luminance even when using a tubular light source having anisotropy in brightness, and can prevent light leakage. Therefore, The expression 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 uniformly illuminated. Therefore, the light diffusion film of the present invention is useful as a constituent member of a planar light source device or a display device (for example, a flat display device (flat display device) in which an image display area of a liquid crystal display device is flat . Based on the above-described Fig. 1, a liquid crystal display will be described as an example.

[Liquid crystal display device]

1 showing the outline of a liquid crystal display device, the liquid crystal display device includes a planar display unit (a transmissive liquid crystal display unit or a liquid crystal display panel, etc.) 5 serving as an irradiated object having liquid crystal cells sealed with liquid crystal, And a surface light source unit arranged on the back side of the display unit (or panel) for illuminating the display unit 5. [

The planar light source unit includes a tubular light source 1 such as a plurality of fluorescent discharge tubes (cold cathode tubes) disposed directly under the display unit 5 or in parallel with each other, And a reflector 2 for reflecting the light onto the display unit 5 (on the display unit side) and guiding it to the display unit 5. (Not shown) arranged on the front side of the tubular light source 1 and a supporting plate (not shown) disposed on the front side of the tubular light source 1. The supporting plate 1 is located on the exit surface side (the light output surface side of the surface light source unit) (For example, an anisotropic light-diffusing film) 3 for light scattering the light from the display surface side of the anisotropic light-diffusing film 3, And a prism sheet 4 (a microprism is not shown) having a plurality of microprisms formed in parallel in a predetermined direction are successively stacked. The light from the tubular light source 1 is diffused and homogenized by the anisotropic light diffusion film 3 and is converged forward by the prism sheet 4 to increase the brightness and illuminate the display unit 5. [ In addition, the support plate is a transparent plate formed to protect the anisotropic light diffusion film 3, which is a thin film.

The planar 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, 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 Which are sequentially laminated.

In such a display device, the display unit can be directly illuminated from the back surface by the tubular light source 1 such as a built-in fluorescent discharge tube (cold cathode tube). Therefore, the backlight type surface light source device using a tubular light source (lamp) has a very high weight in the liquid crystal display device with the recent enlargement of a liquid crystal display screen of a liquid crystal television or the like.

However, in general, the luminance distribution of the emitted light 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 uneven. In particular, the tubular light source itself disposed directly under 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 if a tubular light source is used, it is necessary to equalize the luminance on the display surface. Particularly, since the anisotropic light-diffusing film 3 is close to the tubular light source 1, stable light diffusing properties are required for the anisotropic light-diffusing film 3 for a long period of time.

When the anisotropic light diffusion film 3 is used in the backlight type surface light source unit or the liquid crystal display device, the brightness on the display surface can be made uniform and the appearance of the lamp image can be suppressed. That is, when the anisotropic light diffusion film 3 is arranged by aligning the major axis direction of the dispersed phase in the long axis direction of the tubular light source 1, light from the tubular light source (fluorescent tube) The light can be scattered in a direction perpendicular to the longitudinal direction of the target light source, and the display surface can be uniformly illuminated by uniformizing the luminance of the emission surface while suppressing the decrease in luminance to a minimum. In particular, since light leakage of diffused light can be prevented by anisotropic light diffusion, a lamp image can be erased even in a backlight type unit requiring thinner and higher brightness. Further, even a large-sized liquid crystal display device can cope with the thinning of the device, and the device can be manufactured easily. That is, even if the light diffusion film of the present invention is thin, the display surface of the large-area liquid crystal display device can be uniformly illuminated with high luminance. Particularly, since the continuous phase and the dispersed phase contain the predetermined resin, it is possible to maintain the predetermined light diffusion for a long period of time even in a direct-type surface light source unit having a high heat resistance and located close to the tubular light source 1, have.

Further, in the liquid crystal display device, the light diffusion film is not limited to anisotropy but may be an isotropic light diffusion film. The light-diffusing film (anisotropic light-diffusing film or the like) may be interposed in the optical path from the light-emitting surface (light-emitting surface) of the surface light source unit, that is, between the surface light source unit and the display unit, Or may be stacked on the light-exiting surface (light-exiting surface) in the form of a laminate. More specifically, the light-diffusing film (anisotropic light-diffusing film or the like) may be disposed on the light-emitting surface (light-emitting surface) side of the surface light source unit or on the incident surface side of the display unit, As shown in FIG. Further, it is not necessary to stack the light source unit on the exit surface of the surface light source unit. Further, it is not necessary to use it in combination with the prism sheet or the brightness enhancement sheet, but the prism sheet is useful for condensing diffused light to illuminate the display unit. When a combination of a prism sheet and a light diffusion film is used, the prism sheet may be disposed on the downstream side of the light path rather than the light diffusion film. The light-diffusing film may be used in combination with (for example, laminated) a retardation film, a polarizing film, a color filter or the like.

Further, in the surface light source unit, the tubular light source need not be positioned directly under the display unit, but may be located on the side. In this case, the light from the tubular light source at the side is incident from the side of the light guide plate, and out of the light guide plate, which is formed so as to face the display unit, the display unit may be illuminated. The number of tubular light sources is not particularly limited, and can be selected depending on the size of the display surface and the like.

The X-axis direction of the anisotropic light-diffusing film is usually the long axis direction of the dispersed phase. Accordingly, the anisotropic light diffusion film is disposed such that its X-axis direction is directed substantially parallel to the axial direction (Y-axis direction) of the tubular light source of the surface light source unit. The X-axis direction of the anisotropic light-diffusing film need not be perfectly parallel to the axial direction (Y-axis direction) of the tubular light source of the surface light source unit but may be, for example, an angle of ± 15 , In particular, within a range of about ± 5 °).

&Lt; Industrial applicability >

The light diffusion film of the present invention is capable of suppressing light leakage even when it is made thinner and has a higher brightness and at the same time has a high heat resistance and can suppress a change in light scattering property over a long period of time even at a high temperature, The display unit can be illuminated uniformly. This is useful as a member of a display device (liquid crystal display device) or a backlight type light source device (surface light source device). Particularly, since the direct-type backlight unit (surface light source unit) in which the light source is disposed directly below the display unit can cope with a display device having display units of various screen sizes, particularly a large screen, Or as a component of a backlight unit. The screen size of the display unit is not particularly limited, and may be, for example, 20 inches or more (for example, 23 to 300 inches, preferably 30 to 200 inches).

<Examples>

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. The characteristics of the light-diffusing film (anisotropic light-diffusing film) used in Examples and Comparative Examples were evaluated according to the following methods.

[Total light transmittance (TT) (%) and haze (%)]

The total light transmittance and haze of the light-diffusing film were measured using a haze meter (NDH-500, manufactured by Nippon Seishin Kogyo Co., Ltd.) in accordance with JIS K 7301.

[Refractive index]

The refractive index of the light-diffusing film was measured using a refractive index meter (manufactured by Atago Co., Ltd., NAR-IT) in accordance with JIS K 7142.

[Melt flow rate (MFR)]

The polycarbonate resin was measured under the conditions of 300 DEG C and 1.2 kg load and the cyclic olefin resin was measured at 260 DEG C under a load of 2.16 kg in accordance with ISO1133.

[This way]

The laser light is irradiated from a direction orthogonal to the surface of the anisotropic light-diffusing film, with the stretching direction of the anisotropic light-diffusing film in the X-axis direction and the direction orthogonal to this direction being the Y-axis direction, The scattered light intensity [Fx ([theta])] with respect to the intensity F, that is, the scattered light intensity Fx ([theta]) with respect to the scattering angle [theta] in the X axis direction and the scattered angle [ . Then, the scattered light intensity ratio [Fy (18) / Fx (18)] at? = 18 was obtained as a numerical value showing the anisotropy of light scattering.

[Aspect ratio of particulate dispersed phase]

The cross section of the anisotropic light-diffusing film was observed by a transmission electron microscope (TEM), and the major axis length and the minor axis length of the dispersed phase particles were measured for five dispersed phase particles and the average of the average aspect ratios was calculated.

[Light leakage]

The light scattering intensity distribution of the anisotropic light-diffusing film was measured using a laser light scattering device (LSD-101, wavelength: 633 nm, manufactured by NEO Arc). The light leakage was evaluated based on a graph in which the abscissa is the scattering angle and the ordinate is the logarithm of the light scattering intensity. FIG. 6 is a graph of a sample that is leaking light, and FIG. 7 is a graph of a sample that is not leaking light. As shown in Fig. 6, in the sample in which light is leaked, the distribution intensity changes discontinuously in the vicinity of 0 DEG, so that the luminance becomes uneven and light leakage occurs, and the lamp image remains. On the other hand, as shown in Fig. 7, even in the vicinity of 0 deg. In the sample without light leakage, the distribution intensity changes continuously, so that the luminance is uniform, light leakage is prevented, and no lamp image remains. The results of evaluating the continuity in the vicinity of 0 DEG in these graphs were evaluated based on the following criteria.

&Amp; cir &amp;: Distribution intensity is continuous, no light leakage, no lamp image remains

A: The distribution intensity is slightly discontinuous near 0 DEG, but the lamp image hardly remains

?: The distribution intensity is slightly discontinuous near 0 °, and the lamp image is slightly left

X: The distribution intensity is discontinuous at around 0 DEG, and the lamp image remains.

Example 1

Bisphenol A type polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd .; &quot; medium viscosity polyphenol S-2000 &quot;, viscosity average molecular weight 18,000 to 20000, melt flow rate 9 to 12 cm 3 / (Trade name: TOPAS 5013, trade name, available from Topas Advanced Polymers GmbH) as a resin constituting the dispersed phase, and 85 parts by weight of a cyclic olefin resin (a copolymer of a norbornene monomer and an olefin monomer, TOPAS Advanced Polymers GmbH , 0.1 part by weight of a lubricant (ethylenebisstearic acid amide, manufactured by Clariant Japan K.K., trade name &quot; E- micropowder &quot;), 15 parts by weight of an antioxidant (hindered phenolic antioxidant, (IRGANOX 1010, manufactured by Shiba Japan Co., Ltd.) were mixed and extruded from a die at a resin temperature of 260 캜 and a die opening of 1.3 mm using an extrusion molding machine, (Drawing magnification) was 5 times, and three cast rolls were used and cooled at 125 占 폚 by an oil temperature controller to produce an anisotropic light-diffusing film having a thickness of 263 占 퐉. As a result of observing a cross section by a transmission electron microscope (TEM), it was found that in this diffusion film, the cyclic polyolefin resin forms scatterers (particulate dispersed phase), the shape of the particulate dispersed phase is an ellipsoid phase The mean length (thickness) of the minor axis was 0.8 mu m and the mean length of the major axis was 6.6 mu m (aspect ratio 8.3).

Example 2

In order to manufacture a two-kind three-layered light diffusion film (a light diffusion film in which an anisotropic light diffusion layer is an intermediate layer and a transparent resin layer as a surface layer is laminated on both sides of the intermediate layer), a bisphenol A- , 0.5 part by weight of a UV absorber (trade name &quot; TINUVIN 234 &quot;, trade name; manufactured by Shiba Japan K.K.) and 100 parts by weight of a light stabilizer [ 0.1 part by weight of a hindered amine light stabilizer manufactured by Shiba Japan Ltd., trade name &quot; KIMASOFF 944FD &quot;, manufactured by Mitsubishi Engineering Plastic Co., Ltd.) as a matrix resin , 15 parts by weight of a cyclic olefin resin (Topas Advanced Polymer GmbH), trade name &quot; Topas 5013 &quot;) as a resin constituting the dispersed phase, 0.1 part by weight of an antioxidant (trade name: "Irganox 1010", manufactured by Shiba Japan K.K.), and 0.1 part by weight of a resin (trade name "E-micropowder" Extruded from a die at a temperature of 260 캜 and a die opening of 1.3 mm and co-extruded at a draw ratio of 3.6, cooled at 125 캜 by using an oil temperature controller using three cast rolls, (Thickness ratio: surface layer / intermediate layer / surface layer = 1/10 / 1). In this anisotropic light-diffusing film, the annular polyolefin resin forms scatterers (particulate dispersed phase) in the intermediate layer, and the shape of the particulate dispersed phase is an ellipsoidal phase (or an elongated linear phase) And an average length of the long axis of 5.3 mu m (aspect ratio 6.5).

Example 3

Anisotropic light diffusion film having a thickness of 323 m (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 annular polyolefin resin forms scatterers (particulate dispersed phase) in the intermediate layer, and the shape of the particulate dispersed phase is an ellipsoidal phase (or an elongated linear phase) And an average length of the major axis of 6.7 mu m (aspect ratio 8.4).

Example 4

Anisotropic light diffusion film having a thickness of 273 탆 (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 changed to 4.8 times. In this anisotropic light-diffusing film, the cyclic polyolefin resin forms a scatterer (particulate dispersed phase) in the intermediate layer, the shape of the particulate dispersed phase is an ellipsoid phase (or an elongated linear phase) And an average length of the major axis of 6.2 mu m (aspect ratio 10.9).

Example 5

Anisotropic light diffusion film having a thickness of 212 mu m (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 changed to 6.1 times. In this anisotropic light-diffusing film, the annular polyolefin resin forms a scatterer (particulate dispersed phase) in the intermediate layer, the shape of the particulate dispersed phase is an ellipsoidal phase (or an elongated linear line) And an average length of the major axis of 7.9 mu m (aspect ratio 16.1).

Further, in Examples 1 to 5, a film was produced without blending the lubricant and the antioxidant of the anisotropic light-diffusing layer, and as a result, a number of gels were produced, resulting in a nonuniform film.

Comparative Example 1

In order to produce a two-kind three-layered light diffusion film (a light diffusion film in which an anisotropic light diffusion layer is formed as an intermediate layer and a transparent resin layer as a surface layer is laminated on both surfaces of the intermediate layer), polycarbonate , 100 parts by weight of an ultraviolet light absorber ("Tinuvin 234", manufactured by Shiba Japan Ltd.) and 100 parts by weight of a light stabilizer (a hindered amine-based ultraviolet light absorber (manufactured by Mitsubishi Engineering Plastics Co., , 84 parts by weight of a polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd., "U.Philon S-2000") as a matrix resin, 0.1 part by weight of a light stabilizer "KIMASOFF 944FD" 16 parts by weight of a polypropylene resin ("WINTECH WFW-4" manufactured by Japan Polypro Corporation) as a resin constituting the dispersed phase and 0.1 part by weight of an antioxidant ("Irganox 1010" manufactured by Shiba Japan Co., Ltd.) Used. The resin compositions constituting each layer were mixed and melted from a die at a resin temperature of 250 DEG C and a die opening of 1.3 mm by a multilayer extrusion molding machine and co-extruded to obtain a draw ratio of 7.8, using three cast rolls, And cooled at 80 캜 by a regulator to produce an anisotropic light diffusion film having a two-kind three-layer structure and having a thickness of 167 탆 (thickness ratio: surface layer / intermediate layer / surface layer = 1/3/1). In this anisotropic light-diffusing film, the polypropylene-based resin forms scatterers (particulate dispersed phase) in the intermediate layer, the shape of the particulate dispersed phase is an ellipsoidal phase (or an elongated linear line), an average length of minor axis is 0.15 탆, (Average aspect ratio: 4700).

Comparative Example 2

As a resin composition for an intermediate layer, 80 parts by weight of a polycarbonate resin (manufactured by Mitsubishi Engineering-Plastics Co., Ltd., "YuPiron S-2000") as a matrix resin, 80 parts by weight of a polypropylene resin Except that 20 parts by weight of an antioxidant ("Wintech WFW-4" manufactured by Shimadzu Corporation) and 0.1 part by weight of an antioxidant ("Irganox 1010" manufactured by Shiba Japan Co., Ltd.) were used and the draw ratio was changed to 8.3 times. , An anisotropic light diffusion film having a two-kind three-layer structure and having a thickness of 157 mu m (thickness ratio: surface layer / intermediate layer / surface layer = 1/3/1) was produced. In this anisotropic light-diffusing film, the polypropylene resin forms scatterers (particulate dispersed phase) in the intermediate layer, the shape of the particulate dispersed phase is an ellipsoidal phase (or an elongated linear line), an average length of minor axis is 0.24 탆, (Aspect ratio 388).

Comparative Example 3

As a resin composition for an intermediate layer, 92 parts by weight of a polycarbonate resin (manufactured by Mitsubishi Engineering Plastics Co., Ltd., "YuPiron S-2000") as a matrix resin, a polypropylene resin Except that 8 parts by weight of "Wintech WFW-4" manufactured by Shin-Etsu Chemical Co., Ltd. and 0.1 part by weight of an antioxidant ("Irganox 1010" And an anisotropic light-diffusing film having a thickness of 167 탆 (thickness ratio: surface layer / intermediate layer / surface layer = 1/3/1) was produced. In this anisotropic light-diffusing film, the polypropylene-based resin forms scatterers (particulate dispersed phase) in the intermediate layer, and the shape of the particulate dispersed phase is an ellipsoid phase (or a slender linear phase).

Example 6

92 parts by weight of a bisphenol A-type polycarbonate resin (manufactured by Mitsubishi Engineering-Plastics Co., Ltd., "YuPiron S-2000") as a resin constituting a continuous phase, 10 parts by weight of a cyclic olefin resin (Topaz Advanced Polymer (Trade name: &quot; PCM30 &quot;, manufactured by Ikei Kogyo Co., Ltd., inner diameter 30 mm ?, L / D = 28.5) was used at a resin temperature of 250 占 폚 The pellets were obtained by compounding. The pellets were impregnated with a single-layer film having a thickness of 280 mu m using a press molding machine (trade name: MINI TEST PRESS 10, manufactured by TOYO SEKI CO., LTD.) Under the conditions of a heat-releasing time of 2 minutes, a pressing time of 2 minutes and a pressing pressure of 10 MPa .

Example 7

Except that a cyclic olefin resin (a copolymer of a norbornene monomer and an olefin monomer, manufactured by Mitsui Chemicals, Inc., trade name: APEL APL6011T) was used as the resin constituting the dispersed phase, Thereby producing a single-layer film having a thickness of 300 mu m.

Example 8

Except that a cyclic olefin resin (ring-opening polymer of norbornene monomer, manufactured by Nippon Zeon Co., Ltd., trade name &quot; Zeonor 330R &quot;, trade name) was used as the resin constituting the dispersed phase. Thereby producing a single layer film.

Comparative Example 4

A single-layer film having a thickness of 200 占 퐉 was produced in the same manner as in Example 6 except that polyethylene terephthalate resin (manufactured by Dainippon Ink and Chemicals, Inc.) was used as a resin constituting the dispersed phase.

Comparative Example 5

A single-layer film having a thickness of 70 占 퐉 was produced in the same manner as in Example 6 except that a polypropylene resin ("Wintech WFW-4" manufactured by Japan Polypro Corporation) was used as a resin constituting the dispersed phase.

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

As is apparent from the table, when the light diffusion film of the embodiment is used, the lamp image does not remain and a high luminance can be obtained. On the contrary, when the film of the comparative example is used, a lamp image remains or a remarkable decrease in luminance is confirmed.

1: Fluorescent discharge tube (cold cathode tube)
2: Reflector
3: diffusion plate
4: prism sheet
5: Planar display unit
6a, 6b: Polarizing film
7a and 7b: glass substrate
8a and 8b:
9a, 9b: alignment film
10: liquid crystal layer
11: Color filter
17, 28: Light diffusion film
27, 37: Anisotropic light-diffusing layer
17a, 27a and 37a:
17b, 27b, 37b: dispersed phase
29: transparent resin layer

Claims (12)

A continuous phase containing a polycarbonate resin having a viscosity average molecular weight of 15000 to 25000 and a continuous phase containing a cyclic olefin based resin dispersed in this continuous phase and having an absolute value of refractive index difference with respect to the polycarbonate resin of 0.045 to 0.085 A light diffusing film comprising a light diffusing layer formed of a dispersed phase,
(MFR) of the polycarbonate resin is 5 to 30 cm &lt; 3 &gt; / 10 min under the conditions of 300 DEG C and 1.2 kg load in accordance with ISO 1133, and the melt flow rate (MFR) 10 to 100 cm &lt; 3 &gt; / 10 min under the conditions of 260 DEG C and 2.16 kg in terms of the ratio of the MFR of the polycarbonate resin / the MFR of the cycloolefin resin = 2 / film. The light-diffusing film according to claim 1, wherein the light-diffusing layer further comprises at least one selected from a lubricant and an antioxidant. The light-diffusing film according to any one of claims 1 to 3, wherein the ratio of the continuous phase to the disperse phase is in the range of from 99/1 to 50/50 (weight ratio). The light-diffusing film according to claim 1 or 2, wherein the dispersed phase comprises a particulate dispersed phase having an average aspect ratio of greater than 1 and whose major axis direction is oriented in a certain direction of the film. 5. The light-diffusing film according to claim 4, wherein the average length of minor axis of the particulate dispersed phase is 0.01 to 10 占 퐉, and the average aspect ratio of the particulate dispersed phase is 3 to 100. The light-diffusing film according to claim 1 or 2, comprising a transparent layer laminated on at least one surface of the light-diffusing layer. The light diffusion film according to claim 6, wherein the transparent layer is a resin layer containing at least one selected from ultraviolet absorbers and light stabilizers. The light-diffusing film according to claim 1 or 2, wherein the thickness of the light-diffusing layer is 3 to 500 μm and the total light transmittance of the film is 60% or more. A surface light source device comprising the light diffusion film of claim 1 or 2. A display device comprising the light-diffusing film of claim 1 or claim 2. delete delete

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