KR20090046884A - Multilayer film to be used as base film of luminance-enhancing sheet - Google Patents

Abstract

In the laminated | multilayer film which consists of a polyester film and the application layer formed in the at least single side | surface, the application layer consists of binder resin and organic microparticles | fine-particles, the average particle diameter of organic microparticles | fine-particles is 20-1000 nm, and the average particle diameter of organic microparticles | fine-particles is By the laminated | multilayer film used as the base film of a brightness improving sheet which exceeds 3 times of the thickness of an application layer, and the refractive index difference of organic microparticles | fine-particles and binder resin is less, thermal warpage is small even when using in a high temperature environment. And the laminated | multilayer film used as a base film of a brightness improving sheet provided with blocking resistance in high temperature environment.

Description

Laminated film used as base film of luminance improvement sheet {MULTILAYER FILM TO BE USED AS BASE FILM OF LUMINANCE-ENHANCING SHEET}

This invention relates to the laminated | multilayer film used as a base film of the brightness improvement sheet arrange | positioned in a liquid crystal display device in order to improve the brightness of the display of a liquid crystal display device.

The polyester film is used as a base film of the optical member of a flat panel display device. For example, it is used for the use of the brightness improvement sheet of a liquid crystal display device (generally called a "prism lens sheet"), the base film of an antireflection film, and the base film of the electromagnetic wave shielding film of a plasma display.

In recent years, large screen and high brightness of a liquid crystal display device advance, the quantity of heat emitted from a light source increases, and it became necessary to suppress deformation of the optical member by heat. In particular, the vehicle liquid crystal display device is used at a high temperature in a car under salt water, and the optical member therein is exposed to high heat.

The brightness enhancement sheet is composed of a base film and a prism lens layer formed thereon. This prism lens layer is formed by forming ultraviolet-curable resin which does not contain a solvent in the shape of a prism lens by a metal mold | die, irradiating and hardening an ultraviolet-ray on a base film. For this reason, the base film of a brightness improving sheet is not exposed to heat at the time of formation of a prism lens layer, and when used in a high temperature environment, it is easy to produce thermal warpage.

As a technique for suppressing thermal warpage, an optical polyester film in which the heat shrinkage property of the film is set to a certain range is proposed, and it is known that this film is excellent in adhesion to an active energy ray-curable resin (Japanese Patent Laid-Open No. 2003- 201357). However, this film has insufficient dimensional stability, and when used under high temperature, large thermal warpage occurs.

A polyester film for light diffusing films in which the coefficient of thermal expansion of a film is set within a certain range is proposed, and this film is known to have good adhesion with the light diffusing layer and less warpage (Japanese Patent Laid-Open No. 2002-350617). . However, this film has a very high thermal contraction rate and can prevent thermal warpage at temperatures up to about 60 ° C., but dimensional stability is very insufficient in a high temperature environment of about 78 ° C. or more, and large thermal warpage occurs. This is because the glass transition point of polyethylene terephthalate is at about 78 ° C., and at this temperature or higher, the deformation of the film is governed by the thermal contraction rate rather than the thermal expansion coefficient.

It is known that the film for luminance improvement sheets which set the thermal contraction rate of a film to a certain range is proposed, and this film improves adhesiveness with the lens layer under high temperature, and reduces the deformation | transformation by heat (Japanese Unexamined Patent Publication 2000). -141574). However, when the film is used in a high temperature environment, blocking is very likely to occur and the handling properties are inferior. In addition, in order to manufacture this film, it is necessary to extend | stretch to three-stage or four-stage multistage extending | stretching in the longitudinal direction, the film manufacturing equipment of special longitudinal multistage stretching is needed, and the film production of general sequential biaxial stretching is performed. Manufacturing is difficult with equipment.

A biaxially stretched polyester film in which the refractive index, film thickness, and spectral reflectance of a coating film is set to a certain range is proposed, and this film has excellent ultraviolet transmittance and a lens layer that can withstand fine pitch, continuous production, and large area. It is known that adhesiveness can be obtained (Unexamined-Japanese-Patent No. 2006-137046). However, this film has a high longitudinal shrinkage rate, so that when used in a high temperature environment, large thermal warpage occurs, and blocking is likely to occur, resulting in inferior handling properties.

Disclosure of the Invention

In the liquid crystal display device, a brightness improving sheet is generally overlapped with two sheets, and is arrange | positioned at the position adjacent to other members, such as a diffusion plate, and is used. In the conventional brightness improving sheet, when used in a vehicle-mounted application, for example, in a high temperature environment, the opposite surface of the prism lens (the surface on which the prism lens layer is not formed) of the brightness improving sheet is adjacent to the adjacent member constituting the liquid crystal display device. Is blocked. In the blocked point, the display surface is white and the display quality of the liquid crystal display device is degraded.

The 1st subject of this invention is providing the laminated | multilayer film used as a base film of a brightness improving sheet which is equipped with the blocking resistance in high temperature environment, and can obtain high adhesiveness with a prism lens layer, maintaining high transparency. It is in doing it.

The 2nd subject of this invention is the brightness improvement which is easy to obtain high adhesiveness with a prism lens layer, maintaining high transparency, having low thermal warpage, and having blocking resistance in a high temperature environment, even when using in a high temperature environment. It is providing the laminated | multilayer film used as a base film of a sheet | seat.

That is, the present invention

In the laminated | multilayer film containing a polyester film and the application layer formed in the at least single side | surface,

The coating layer is made of binder resin and organic fine particles,

The average particle diameter of the organic fine particles is 20 to 1000 nm,

The average particle diameter of the organic fine particles exceeds 3 times the thickness of the coating layer,

The refractive index difference of organic fine particles and binder resin is 0.03 or less, It is a laminated | multilayer film used as a base film of a brightness improving sheet.

Best Mode for Carrying Out the Invention

Hereinafter, the present invention will be described in detail.

(Polyester film)

Polyester which comprises a polyester film in this invention is linear saturated polyester synthesize | combined from aromatic dibasic acid or its ester formable derivative, and diol or its ester formable derivative. Specific examples of such polyesters include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate and poly (1,4-cyclohexylenedimethylene terephthalate).

The polyester used for a polyester film may be a copolymer of these polyesters, or may be a blend with other resin. In any case, it is preferable to make the said polyester main (for example, 80 mol% or more component), and to make a copolymerization component or a blend component into a low ratio (for example, 20 mol% or less component). As the polyester, polyethylene terephthalate is particularly preferred because of its good balance between mechanical and optical properties.

Although the polyester film may contain a coloring agent, an antistatic agent, antioxidant, a lubricating agent, and a catalyst, it is preferable from a transparency point of view that it does not contain internal fine particles.

In order to acquire the intensity | strength required as a base film of a brightness improvement sheet, the thickness of a polyester film becomes like this. Preferably it is 25-350 micrometers, More preferably, it is 50-250 micrometers.

Preferably the thermal contraction rate of the longitudinal direction when the laminated | multilayer film of this invention is heat-processed at 150 degreeC for 30 minutes is 1.5 to 0.0%, More preferably, it is 1.0 to 0.0%, Especially preferably, it exists in the range of 0.5 to 0.0%. . If the longitudinal heat shrinkage exceeds 1.5%, thermal dimensional stability is inferior, which is not preferable. On the other hand, when it is less than 0.0% and it becomes negative thermal contraction rate, since deformation becomes easy to occur by thermal expansion, it is unpreferable. Hereinafter, the glass transition temperature is abbreviated as Tg.

In the present invention, since the heat shrinkage rate of the laminated film is governed by the heat shrinkage rate of the polyester film, it is preferable that the polyester film in the present invention has the same heat shrinkage rate as that of the laminated film.

The thermal contraction rate in the horizontal direction when the laminated film of the present invention is heat treated at 150 ° C. for 30 minutes is preferably 1.0 to -0.5%, and more preferably 0.5 to -0.3%. If it exceeds 1.0%, thermal dimensional stability is inferior, thermal warpage deteriorates, which is not preferable. If it is less than -0.5%, deformation is easily caused by thermal expansion, which is not preferable.

(Coating layer)

The laminated | multilayer film used as a base film of the brightness improvement sheet of this invention is equipped with the application layer on the said polyester film. An application layer may be provided in one surface or may be provided in both surfaces, Preferably it is provided in both surfaces. And an application layer consists of binder resin and organic fine particles.

The binder resin per 100 weight% of the composition constituting the coating layer is preferably 60% by weight or more, more preferably 60 to 94.9% by weight, particularly preferably 65 to 89.9% by weight. If binder resin is less than 60 weight%, blocking property will become inferior and it is not preferable. When it exceeds 94.9 weight%, adhesiveness with a prism lens layer will become inferior easily, and it is unpreferable.

The prism lens layer which performs a brightness | luminance improvement effect in a brightness improving sheet generally uses energy curable resin, and is usually formed using an ultraviolet curable acrylic resin. In order to obtain favorable adhesiveness to this acrylic resin, it is preferable that binder resin of an application layer consists of acrylic resin.

The coating layer thickness is preferably 20 to 150 nm, more preferably 30 to 120 nm, and particularly preferably 40 to 90 nm. If the thickness of the coating layer exceeds 150 nm, blocking tends to occur, and if it is less than 20 nm, the adhesion with the prism lens layer formed thereon tends to be inferior, which is not preferable.

(Acrylic resin)

When using acrylic resin as binder resin, the refractive index of an acrylic resin becomes like this. Preferably it is 1.45-1.55, More preferably, it is 1.46-1.53, Especially preferably, it is 1.48-1.51. When the refractive index of the acrylic resin exceeds 1.55, high transmittance of ultraviolet light cannot be obtained, and it is difficult to form a prism lens using an ultraviolet curable acrylic resin when producing a brightness enhancement sheet, while it is technically difficult to make it less than 1.45. Do.

In this invention, the light transmittance of wavelength 400nm can be made into 90% or more by using this acrylic resin. On the other hand, when the light transmittance of wavelength 400nm is less than 90%, a film will not fully transmit an ultraviolet-ray, and when ultraviolet curable resin is used for formation of a prism lens layer, it will become hard to be hardened | cured, and it is difficult to process into a brightness improving sheet.

Glass transition point (Tg) of the acrylic resin of the coating layer in this invention becomes like this. Preferably it is 20-80 degreeC, More preferably, it is 25-70 degreeC. If the glass transition point is less than 20 ° C., the blocking resistance deteriorates, which is not preferable. On the other hand, if the glass transition point is more than 80 ° C., the film preparation properties deteriorate, and the oligomer precipitation sealing property deteriorates, which is not preferable. It is preferable that an acrylic resin is soluble or dispersible in water.

As this acrylic resin, the polymer and copolymer of the acryl monomer illustrated below can be used, for example. As an acryl monomer, Alkyl acrylate and alkyl methacrylate (as an alkyl group, methyl group, an ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group And cyclohexyl group); Hydroxy-containing monomers such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, and 2-hydroxypropyl methacrylate; Epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate and allyl glycidyl ether; Monomers containing carboxyl groups or salts thereof such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt and the like); Styrenesulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); Acrylamide, methacrylamide, N-alkylacrylamide, N-alkyl methacrylamide, N, N-dialkylacrylamide, N, N-dialkyl methacrylate (as an alkyl group, methyl group, ethyl group, n-propyl Group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, etc.), N-alkoxy acrylamide, N-alkoxy methacrylamide, N, N-di Alkoxy acrylamide, N, N- dialkoxy methacrylamide (as an alkoxy group, a methoxy group, an ethoxy group, butoxy group, isobutoxy group, etc.), acryloyl morpholine, N-methylol acrylamide, N-methylol Monomers containing amide groups such as methacrylamide, N-phenylacrylamide, and N-phenylmethacrylamide; Monomers of acid anhydrides such as maleic anhydride and itaconic anhydride; Vinyl isocyanate, allyl isocyanate, styrene, α-methyl styrene, vinyl methyl ether, vinyl ethyl ether, vinyl trialkoxysilane, alkyl maleic acid monoester, alkyl fumaric acid monoester, alkyl itaconic acid monoester, acrylonitrile, methacryl Monomers such as ronitrile, vinylidene chloride, ethylene, propylene, vinyl chloride, vinyl acetate, butadiene, and the like.

Acrylic resin can be manufactured according to the method as described in manufacture examples 1-3 of Unexamined-Japanese-Patent No. 63-37167, for example. That is, a predetermined amount of sodium lauryl sulfonate and a predetermined amount of ion-exchanged water were injected into the four-necked flask as a surfactant, and the temperature was raised to 60 ° C in a nitrogen stream, followed by addition of 0.5 part of ammonium persulfate and 0.2 part of sodium hydrogen nitrite as polymerization initiators. The mixture of monomers constituting the acrylic resin is added dropwise while adjusting the liquid temperature to be 60 to 70 ° C over 3 hours. After completion of the dropwise addition, the reaction is continued under stirring while maintaining the same temperature range for 2 hours, followed by cooling to obtain an aqueous dispersion of an acrylic resin.

(Bridge)

It is preferable that the coating layer in this invention consists of a composition of the acrylic resin containing a crosslinking agent. As the crosslinking agent, any one or more of epoxy, oxazoline, melamine and isocyanate can be used. These may use one type and may use two or more types.

As an epoxy crosslinking agent, a polyepoxy compound, a diepoxy compound, a monoepoxy compound, a glycidylamine compound is mentioned, for example.

As a polyepoxy compound, for example, sorbitol, polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris (2-hydride) Oxyethyl) isocyanate, glycerol polyglycidyl ether, and trimethylol propane polyglycidyl ether.

As a diepoxy compound, for example, neopentyl glycol diglycidyl ether, 1, 6- hexanediol diglycidyl ether, resorcinol diglycidyl ether, ethylene glycol diglycidyl ether, polyethyleneglycol digly Cyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and polytetramethylene glycol diglycidyl ether.

As a monoepoxy compound, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, and phenyl glycidyl ether is mentioned, for example.

As the glycidylamine compound, for example, N, N, N ', N'-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N-diglycidylamino) cyclohexane Can be mentioned.

As an oxazoline crosslinking agent, it is preferable to use the polymer containing an oxazoline group. This can be manufactured by polymerizing an addition polymerizable oxazoline group containing monomer independently or copolymerizing with another monomer.

As an addition polymerizable oxazoline group containing monomer, 2-vinyl-2- oxazoline, 2-vinyl-4-methyl-2- oxazoline, 2-vinyl-5-methyl-2- oxazoline, 2 -Isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, and 2-isopropenyl-5-ethyl-2-oxazoline are mentioned. These may use 1 type and may use 2 or more types. Especially, 2-isopropenyl-2-oxazoline is easy to obtain industrially, and is preferable.

As another monomer used for copolymerization with an oxazoline group containing copolymer, what is necessary is just a monomer copolymerizable with an addition polymeric oxazoline group containing monomer, For example, an alkylacrylate, an alkyl methacrylate (as an alkyl group, a methyl group, (Meth) acrylic acid esters such as ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group and cyclohexyl group); Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrenesulfonic acid and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt and the like); Unsaturated nitriles such as acrylonitrile and methacrylonitrile; Acrylamide, methacrylamide, N-alkylacrylamide, N-alkyl methacrylamide, N, N-dialkylacrylamide, N, N-dialkyl methacrylate (as an alkyl group, methyl group, ethyl group, n-propyl Unsaturated amides such as groups, isopropyl groups, n-butyl groups, isobutyl groups, t-butyl groups, 2-ethylhexyl groups, cyclohexyl groups, and the like; Vinyl esters such as those in which polyalkylene oxide is added to ester portions of vinyl acetate, vinyl propionate, acrylic acid, and methacrylic acid; Vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; Α-olefins such as ethylene and propylene; Halogen-containing alpha, beta -unsaturated monomers such as vinyl chloride, vinylidene chloride and vinyl fluoride; (Alpha), (beta)-unsaturated aromatic monomers, such as styrene and (alpha) -methylstyrene, are mentioned. 1 type may be used for these monomers and they may use 2 or more types together.

As a melamine crosslinking agent, the compound and ether mixture which etherified by lower alcohol to the methylol melamine derivative obtained by condensing melamine and formaldehyde are preferable. As the lower alcohol, for example, methyl alcohol, ethyl alcohol, isopropyl alcohol can be used.

Examples of the methylol melamine derivatives include monomethylolmelamine, dimethylolmelamine, trimethylolmelamine, tetramethylolmelamine, pentamethylolmelamine, and hexamethylolmelamine.

As an isocyanate crosslinking agent, for example, tolylene diisocyanate, diphenylmethane-4,4'- diisocyanate, metaxylylene diisocyanate, hexamethylene-1,6- diisocyanate, 1, 6- diisocyanate hexane, tolylene di Adducts of isocyanate and hexanetriol, adducts of tolylene diisocyanate and trimethylolpropane, polyol modified diphenylmethane-4,4'-diisocyanate, carbodiimide modified diphenylmethane-4,4'-diisocyanate, Isophorone diisocyanate, 1,5-naphthalene diisocyanate, 3,3'-bittolylene-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, metaphenylenedi Isocyanate is mentioned.

When a coating layer contains a crosslinking agent, content of a crosslinking agent becomes like this. Preferably it is 5-30 weight%, More preferably, it is 10-25 weight% per 100 weight% of compositions of an application layer. If it is less than 5 weight%, blocking resistance will deteriorate easily and it is unpreferable. On the other hand, when it exceeds 30 weight%, a coating film will harden | cure very hardly, and it is easy to whiten in an extending process, and inferior transparency is unpreferable.

(Organic fine particles)

In the present invention, the coating layer needs to contain organic fine particles in order to obtain blocking resistance in a high temperature environment.

As organic fine particles, the fine particles of an acrylic resin, a styrene resin, a silicone resin, a fluororesin, a benzoguanamine resin, a phenol resin, a nylon resin are mentioned, for example. These may use one type and may use two or more types. Fine particles of an acrylic resin and a fluororesin are preferable, and fine particles of an acrylic resin are particularly preferable.

Content of the organic fine particle in an application layer becomes like this. Preferably it is 0.1-10 weight% per 100 weight% of compositions of an application layer. If it is less than 0.1 weight%, sufficient activity and abrasion resistance are not obtained, and if it is more than 10 weight%, the cohesion force of a coating film will become low and adhesiveness will deteriorate and it is unpreferable.

The average particle diameter of the organic fine particles contained in the coating layer is 20 to 1000 nm, preferably 20 to 400 nm, more preferably 40 to 350 nm, more preferably 150 to 300 nm, particularly preferably 180 to 250 nm. to be. If it is less than 20 nm, sufficient activity and scratch resistance are not obtained, and blocking resistance deteriorates, which is not preferable. On the other hand, when 1000 nm is exceeded, the fall of organic fine particles will arise easily.

In order to obtain blocking resistance in a high temperature environment, the average particle diameter of the organic fine particles needs to exceed 3 times the thickness of the coating layer, and preferably 3 times and 10 times or less. If it is 3 times or less, since blocking property is inferior, it is unpreferable. On the other hand, when it exceeds 10 times, it will become easy to drop out at the time of the handling at the time of a production process or processing, and is unpreferable. In addition, although the average particle diameter is large, organic microparticles | fine-particles are supported by the acrylic resin of a binder component in the state mix | blended in the composition of an application layer, and apply | coated to a film, and it does not fall out practically in the scope of the present invention.

In this invention, the difference of the refractive index of the acrylic resin used as a binder component and the refractive index of organic microparticles | fine-particles is 0.03 or less, Preferably it is 0.02 or less, More preferably, it is 0.01 or less. When the difference in refractive index exceeds 0.03, light scattering in the coating film becomes high, haze rises, and high transparency cannot be maintained.

(Production method)

The polyester film in this invention can be manufactured by carrying out a relaxation heat treatment further after biaxial stretching. It is preferable to perform this relaxation heat processing by putting a sheath in the vicinity of the both ends of a film downstream from the drawing zone of a tenter, and peeling a film from a clip holding part. In addition, the polyester film in this invention can also be manufactured by the simultaneous biaxial stretching method. Hereinafter, the manufacturing method of a polyester film is demonstrated in detail.

First, the polyester is melt-extruded into a film form, cooled and solidified in a casting drum to obtain an unstretched film, and the unstretched film is once or twice or more in the longitudinal (length) direction at Tg to (Tg + 60) ° C. After longitudinal stretching so that the total magnification may be 3 to 6 times, and then transversely stretched so that the magnification is 3 to 5 times in the transverse (width) direction at Tg to (Tg + 60) ° C., and the resulting biaxially stretched film is used. If necessary, the heat treatment is further performed in a tenter at 180 to 240 ° C. for 1 to 60 seconds, and the relaxation heat treatment is further performed while shrinking 0 to 20% in the longitudinal and transverse directions at a temperature of 10 to 20 ° C. lower than the heat treatment temperature. It can be obtained by.

In this stretching method, a thermal treatment is performed by narrowing the clip interval in the longitudinal direction using a pantograph or linear motor tenter as a tenter. However, when a tenter that cannot reduce the clip interval in the longitudinal direction is used, Sheaths are placed near both ends of the film on the downstream side of the stretching zone to remove the film from the clip holding portion, and the desired relaxation heat treatment can be performed by slowing the take-up roll by 0 to 5% below the maximum speed of the clip in the tenter. .

Moreover, the polyester film of the thermal contraction rate of this range melt-extrudes polyester to a film form, it solidifies by cooling in a casting drum, and makes it an unstretched film, and this unstretched film is seeded at Tg-(Tg + 60) degreeC. Simultaneously biaxially stretch the direction and the lateral direction simultaneously so that the surface magnification becomes 6 times to 25 times, preferably 10 times to 20 times, and further performs a heat treatment for 1 to 60 seconds at 180 to 240 ° C. as needed, It can also be obtained by performing a relaxation heat treatment between the tenter and a pair of take-up rolls subsequent to this at a temperature lower than the temperature of 10 to 20 ° C while shrinking 0 to 10% in the longitudinal and transverse directions.

In this method, since the film is less likely to contact the rolls, minute scratches and the like on the surface of the film are less likely to occur than those described above, which is advantageous for application to optical applications.

In any stretching method, in the relaxation heat treatment, specifically, a cut is placed near both ends of the film on the downstream side of the stretching zone of the tenter, the film is separated from the clip holding portion, and the speed of the take-up roll is set to the maximum speed of the clip in the tenter. It can implement preferably by making it 0 to 5% slower.

In this invention, in order to form an application layer, the application liquid used for application | coating formation of an application layer is preferably used in the form of an aqueous application liquid, such as aqueous solution, aqueous dispersion, or emulsion liquid. In order to form an application layer, you may mix | blend an antistatic agent, a coloring agent, surfactant, and a ultraviolet absorber further as needed.

Solid content concentration of the coating liquid used for this invention is 20 weight% or less normally, Preferably it is 1-10 weight%. If it is less than 1 weight%, the wettability with respect to a polyester film may run short, and it is not preferable. On the other hand, when it exceeds 20 weight%, the stability of a coating liquid and the external appearance of a coating layer may deteriorate, and it is unpreferable.

Although application | coating to the polyester film of a coating liquid can be performed at arbitrary stages, it is preferable to carry out in the manufacturing process of a polyester film, In this case, to apply to the polyester film before orientation crystallization is completed desirable.

Here, the polyester film before a crystal orientation is completed is uniaxially oriented film which orientated the unstretched film and the unstretched film to either one of a longitudinal direction or a transverse direction, and also low magnification extending | stretching to two directions of a longitudinal direction and a transverse direction. Orientated (biaxially stretched film before finally reoriented in the longitudinal direction and in the transverse direction to complete the orientation crystallization) and the like. Especially, it is preferable to apply | coat a coating liquid to the unstretched film or the uniaxial stretched film orientated in 1 direction, and to perform longitudinal stretch and / or lateral stretch and heat setting as it is. Moreover, it is preferable to apply | coat a coating liquid to an unstretched film, to extend | stretch simultaneously simultaneously as a longitudinal direction and a transverse direction, and to further heat-set.

When applying the coating liquid to the film, pretreatment for improving the coating property is to perform physical treatment such as corona surface treatment, flame treatment, plasma treatment on the surface of the film, or to mix the surfactant as a wetting agent in the coating liquid. desirable. When mix | blending surfactant with a coating liquid, it is preferable to set it as 1 to 10 weight% per 100 weight% of solid content of a coating liquid.

The surfactant promotes the wetting of the coating liquid, particularly the aqueous coating liquid, on the polyester film, and improves the stability of the coating liquid. Examples of the surfactant include anionic and nonionic surfactants such as polyoxyethylene-fatty acid esters, sorbitan fatty acid esters, glycerin fatty acid esters, fatty acid metal soaps, alkyl sulfates, alkylsulfonates, and alkylsulfosuccinates. .

As the coating method, any known coating method can be applied. For example, the roll coating method, the gravure coating method, the roll brush method, the spray coating method, the air knife coating method, the impregnation method, and the curtain coating method can be applied. These may be applied alone or in combination.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Various physical properties were measured and evaluated according to the following method.

(1) refractive index

The refractive index of the binder component was made to dry the coating agent at plate shape at 90 degreeC, and it measured with the Abbe refractometer (sodium D line).

The refractive index of the fine particles was suspended in various 25 ° C. liquids having different refractive indexes at 90 ° C., and the refractive index of the liquid in which the suspension was most transparent was measured with an Abbe refractometer (sodium D line).

The refractive index of an application layer calculates | requires the spectral reflectance of wavelength 633nm on the conditions of a scanning speed of 200 nm / min, a slit width of 20 nm, and a sampling pitch of 1.0 nm using a spectrophotometer (UV-3101PC by Shimadzu Corporation), and Abe refractive index The surface direction average refractive index of the film was calculated | required using the system (sodium D line | wire), and it calculated | required using the following formula using the coating layer thickness calculated | required according to the method of following (5).

R = 1-4 n ₁ ² n ₀ / (n ₁ ² (1 + n ₀ ) ² + (1-n ₁ ² ) (n ₀ ² -n ₁ ² ) sin ² (2πn ₁ d ₁ / λ))

    R: Spectral reflectance of the film at 633 nm

    λ: wavelength (633 nm)

n ₀ : average refractive index of the plane of the film

n ₁ : refractive index of the coating layer

d ₁ : coating layer thickness

(2) heat shrinkage

Samples of widths of 350 mm and widths of 50 mm are cut out in the longitudinal direction and the width direction of the film, respectively, and the marks of 300 mm intervals are stamped near both ends of the samples, and one end is fixed to an oven adjusted to a temperature of 150 ° C. The other end was left free and allowed to stand for 30 minutes. After taking this out and allowing it to cool to room temperature, the distance between gage marks was measured (this length is set to S), and the thermal contraction rate was calculated | required by the following formula.

Thermal Shrinkage (%) = ((300-S) / 300) × 100

(3) haze

According to JIS K7136, the haze value of the film was measured using the haze measuring instrument NDH-2000 by Nippon Denshoku Industries Co., Ltd. product. In addition, haze value was evaluated based on the following criteria.

◎: Haze value <1.0% (very good)

○: 1.0% ≤ haze <1.2% (good)

X: 1.2% ≤ haze value (bad)

(4) light transmittance with a wavelength of 400 nm

The light transmittance of wavelength 400nm was measured on the conditions of the scanning speed 200nm / min, slit width 20nm, and sampling pitch 1.0nm using the Shimadzu Corporation spectrophotometer UV-3101PC.

(5) coating layer thickness

The film was cut out small, embedded with an epoxy resin, and the film cross section was cut into 50 nm thickness with a microtome. It was stained with 2% osmium acid at 60 ° C. for 2 hours. The cross section of the dyed film was observed 200,000 times with a transmission electron microscope (LEM-2000) to measure the coating layer thickness.

(6) average particle diameter of fine particles

The measurement similar to the measurement of the coating layer thickness was performed, the particle diameter of 100 microparticles | fine-particles was measured, and the average value was made into the average particle diameter.

(7) thermal warpage

The ultraviolet curable acrylic resin which consists of the following composition is poured into the mold | die which formed the pattern of a prism lens, and the application surface of the polyester film obtained on it was made to contact with the resin side, and it adhere | attached on 30 cm distance from the polyester film surface side, Irradiation intensity 80W / cm, 6.4KW) was used for 30 seconds to cure the resin, and a prism lens layer having a vertex angle of 90 degrees, a pitch of 50 µm, and a height of 30 µm was formed to obtain a brightness improving sheet. The obtained luminance-improving sheet was cut into sheets so as to have a diagonal length of 30 inches (39 cm / 64 cm), and treated in an oven heated at 95 ° C. for 30 minutes while fixing the four sides of the sheet in a frame. , Deformation (thermal warpage state of the film) was visually observed and evaluated according to the following criteria.

(Circle): A bending state is not observed.

(Triangle | delta): Slight bending is observed in part.

X: There exists a bending part, and the unevenness | corrugation of a bending is observed as a bump of 5 mm or more.

(8) Blocking resistance in high temperature environment (in the table, simply referred to as "blocking resistance")

Two films were overlapped so that the coating layer forming surfaces could contact each other, and the resultant was applied with a pressure of 0.6 kg / cm 2 over 17 hours in an atmosphere of 80 ° C. and 80% RH. It peeled after that and evaluated the blocking resistance on the basis of the peeling force at the time of peeling.

○: Peel force <98mN / 5cm width (good)

△: 98 mN / 5 cm width ≤ peel force <196 mN / 5 cm width (slightly good)

×: 196mN / 5cm Width ≤ Peeling Force (Poor)

(9) Adhesiveness with Prism Lens Layer

The ultraviolet curable acrylic resin which consists of the following composition is poured into the mold | die which formed the pattern of a prism lens, and the application surface of the polyester film obtained on it was made to contact with the resin side, and it adhere | attached on 30 cm distance from the polyester film surface side, Irradiation intensity 80W / cm, 6.4KW) was used for 30 seconds to cure the resin, and a prism lens layer having a vertex angle of 90 degrees, a pitch of 50 µm, and a height of 30 µm was formed to obtain a brightness improving sheet. A cross cut of a checkerboard scale (100 pieces of 1 mm 2 scale) was applied to the processed surface of the obtained brightness enhancement sheet, and a cellophane tape (manufactured by Nichiban Co., Ltd.) having a width of 24 mm was attached thereon, and rapidly at a peeling angle of 90 °. After peeling, the peeling surface was observed and evaluated by the following reference | standard.

(Circle): Peeling area is 5% or less (adhesive force is favorable)

X: Peeling area exceeds 5% (adhesive force is bad)

<Ultraviolet curing type acrylic resin>

Ethylene Oxide Modified Bisphenol A Dimethacrylate

(FA-321M made by Hitachi Kasei Kogyo Co., Ltd.)

46 wt%

Neopentylglycol-modified trimethylolpropanediacrylate

(R-604 manufactured by Nippon Kayaku Chemical Industry Co., Ltd.)

25 wt%

Phenoxyethyl acrylate

(Osaka Organic Chemical Industry Co., Ltd. biscoat 192)

27 wt%

2-hydroxy-2-methyl-1-phenylpropan-1-one

(Dark Merc1173, manufactured by Merck)

2 wt%

(10) Composition of Coating Layer

The following were used as a component which comprises the coating liquid for forming an application layer.

Acrylic resin:

Acrylic resin is comprised from 60 mol% of methyl methacrylate / 30 mol% of ethyl acrylate / 5 mol% of 5-hydroxyethyl acrylate / 5 mol% of N-methylol acrylamide (Tg = 40 degreeC). This acrylic resin was manufactured according to the method of manufacture example 1-3 of Unexamined-Japanese-Patent No. 63-37167 as follows. That is, 302 parts of ion-exchange water was injected into a four neck flask, and it heated up to 60 degreeC in nitrogen stream, Then, 0.5 part of ammonium persulfate and 0.2 part of sodium hydrogen sulfite were added as a polymerization initiator, and the methyl methacrylate of the monomer of an acrylic resin 46.7 The mixture of 23.3 parts of ethyl acrylate, 4.5 parts of 2-hydroxyethyl acrylate and 3.4 parts of N-methylol acrylamide was added dropwise while adjusting the liquid temperature to be 60 to 70 ° C over 3 hours. After completion of the dropwise addition, the reaction was continued while stirring in the same temperature range for 2 hours, followed by cooling to obtain an aqueous dispersion of an acrylic resin having a solid content of 25%.

Polyester Resin:

The polyester resin has an acid component of 2,6-naphthalenedicarboxylic acid 75 mol% / isophthalic acid 20 mol% / 5-sodium sulfoisophthalic acid 5 mol%, glycol component is 90 mol% / diethylene glycol 10 It is comprised by mol% (Tg = 80 degreeC, average molecular weight 15000). This polyester resin was manufactured as follows. That is, 51 parts of dimethyl 2,6-naphthalenedicarboxylic acid, 11 parts of dimethyl isophthalate, 4 parts of dimethyl 5-sodium sulfoisophthalate, 31 parts of ethylene glycol, and 2 parts of diethylene glycol are injected into the reactor, and tetra 0.05 parts of butoxytitanium was added to control the temperature to 230 ° C. under a nitrogen atmosphere, and the resulting methanol was distilled off and a transesterification reaction was carried out. Subsequently, in a polymerization kiln with a high motor torque of the stirrer, the temperature of the reaction system was gradually raised to 255 ° C, the system was subjected to a polycondensation reaction at a reduced pressure of 1 mmHg, and a polyester resin having an intrinsic viscosity of 0.56 was obtained. 25 parts of this polyester resin were dissolved in 75 parts of tetrahydrofuran, and 75 parts of water were added dropwise to the obtained solution under high speed stirring at 10000 revolutions / minute to obtain a milky dispersion, and then the dispersion was distilled off under reduced pressure of 20 mmHg, Tetrahydrofuran was distilled off. The water dispersion of the polyester resin was obtained.

Crosslinker:

Glycerol Polyglycidyl Ether (Nagase Chemtex Co., Ltd. product name Denacor EX-313)

Wetting Agent:

Polyoxyethylene (n = 7) lauryl ether (Sanyo Chemical Co., Ltd. product name naroakty N-70)

Particulate 1:

Acrylic filler (average particle diameter: 220 nm)

(Nippon catalyst company make brand name MX-200W)

Particulate 2:

Acrylic filler (average particle diameter: 130 nm)

(Nippon catalyst company make brand name MX-100W)

Particulate 3:

Silica Filler (Average Particle Size: 40nm)

(Nissan Chemical Co., Ltd. product name snow techs OL)

Particulate 4:

Silica Filler (Average Particle Size: 120nm)

(Brand name SI-120P made by Shokubai Kasei Corporation)

Particulate 5:

Conductor filler (average particle diameter: 200 nm)

(Nissan Chemical Co., Ltd. brand name MP-2040)

Particulate 6:

Silica Filler (Average Particle Size: 500nm)

(Nippon catalyst company make brand name KE-W50)

Example 1

The molten polyethylene terephthalate ([η] = 0.62 dl / g, Tg = 78 ° C.) is extruded from the die, cooled in a cooling drum according to a conventional method to obtain an unstretched film, and then stretched 3.2 times in the longitudinal direction. The aqueous coating liquid of 4 weight% of density | concentration of the coating agent shown in Table 1 was apply | coated uniformly to the both surfaces by the roll coater. As the molten polyethylene terephthalate, one containing no fine particles as a lubricant was used.

The film on which the coating film was formed was subsequently dried at 110 ° C., stretched 3.6 times at 140 ° C. in the transverse direction, and heat-set at 235 ° C., and then laterally in the tenter while cooling the film in steps from 180 ° C. to 90 ° C. 3% relaxation heat processing was performed in the direction, and the laminated | multilayer film which is 125 micrometers in thickness, and a coating layer thickness of 60 nm was obtained.

Moreover, the prism lens layer was formed in the obtained laminated | multilayer film using the ultraviolet curable acrylic resin, and the brightness improving sheet was obtained. Table 2 shows the results of the evaluation.

Example 2

After forming a coating film using the coating agent of Table 1, and heat-setting at 225 degreeC, a sheath is put in the vicinity of both ends of a film in a tenter, the film is removed from a clip holding part, and the speed of a take-up roll is set to the clip speed in a tenter. A laminated film having a thickness of 125 µm and a coating layer thickness of 60 nm was obtained in the same manner as in Example 1 except that it was slower by 2.5% and relaxed heat treatment at 185 ° C.

Moreover, the prism lens layer was formed in the obtained laminated | multilayer film using the ultraviolet curable acrylic resin, and the brightness improving sheet was obtained. Table 2 shows the results of the evaluation.

Example 3

Molten polyethylene terephthalate ([η] = 0.61 dl / g, Tg = 78 ° C) is extruded from the die, cooled in a cooling drum according to a conventional method to obtain an unstretched film, and then the coating agent shown in Table 1 on both surfaces thereof. An aqueous coating liquid having a concentration of 6% by weight was uniformly applied with a roll coater. The coated film was subsequently dried at 95 ° C., stretched 3.4 times in the longitudinal direction and 3.6 times in the transverse direction at 110 ° C. and heat-set at 225 ° C., and then 2.5% in the longitudinal and width directions at 190 ° C., respectively. Relaxing heat treatment was performed to obtain a laminated film having a thickness of 100 μm and a coating layer thickness of 60 nm.

Moreover, the prism lens layer was formed in the obtained laminated | multilayer film using the ultraviolet curable acrylic resin, and the brightness improving sheet was obtained. Table 2 shows the results of the evaluation.

Example 4 and Comparative Examples 1-6

A laminated | multilayer film was obtained like Example 1 except having formed the coating layer of the predetermined thickness using the coating agent of Table 1.

Moreover, the prism lens layer was formed in the obtained laminated | multilayer film using the ultraviolet curable acrylic resin, and the brightness improving sheet was obtained. Table 2 shows the results of the evaluation.

Moreover, in the laminated | multilayer film of the comparative example 4, microparticles | fine-particles were too large to hold | maintain a coating film, fell out at the time of handling of a film, and the blocking resistance of a laminated | multilayer film was very bad.

Example 5

A laminated film was obtained in the same manner as in Example 2 except that the coating layer was formed using the coating agent shown in Table 1, and the film thickness was 188 µm. Table 2 shows the results of the evaluation.

Moreover, the prism lens layer was formed in the obtained laminated | multilayer film using the ultraviolet curable acrylic resin, and the brightness improving sheet was obtained. Table 2 shows the results of the evaluation.

Comparative Example 7

A polyester film was obtained in the same manner as in Example 1 except that the coating layer was not formed. Table 2 shows the results of the evaluation.

Moreover, using the obtained polyester film as a base film, the prism lens layer was formed on this using the ultraviolet curable acrylic resin, and the brightness improving sheet was obtained. Table 2 shows the results of the evaluation.

The obtained brightness improving sheet had poor adhesiveness of the polyester film of a base film and a prism lens layer, and was not able to be used satisfactorily as a brightness improving sheet.

Effects of the Invention

ADVANTAGE OF THE INVENTION According to this invention, the laminated | multilayer film used as a base film of a brightness improving sheet which is equipped with the blocking resistance in high temperature environment, and can obtain high adhesiveness with a prism lens layer, maintaining high transparency can be provided. .

According to the present invention, the base of the brightness improvement sheet which has little thermal warpage even in use in a high temperature environment, has blocking resistance in a high temperature environment, and can obtain high adhesiveness with a prism lens layer while maintaining high transparency. The laminated film used as a film can be provided.

The laminated | multilayer film used for the base film of the brightness improvement sheet of this invention can form a prism lens layer on an application layer, and can be set as a brightness improvement sheet. This can be used suitably in a high temperature environment especially as a large screen, a high brightness liquid crystal display device, and a vehicle liquid crystal display device.

Claims (12)

In the laminated | multilayer film containing a polyester film and the application layer formed in the at least single side | surface, The coating layer is made of binder resin and organic fine particles, The average particle diameter of the organic fine particles is 20 to 1000 nm, The average particle diameter of the organic fine particles exceeds 3 times the thickness of the coating layer, The refractive index difference of organic fine particles and binder resin is 0.03 or less, The laminated | multilayer film used as a base film of a brightness improving sheet. The method of claim 1, The laminated film whose binder resin is an acrylic resin. The method of claim 1, The laminated | multilayer film whose refractive index of an acrylic resin is 1.45-1.55. The method of claim 1, The laminated film whose organic microparticles | fine-particles are microparticles | fine-particles of an acrylic resin. The method of claim 1, The laminated | multilayer film whose average particle diameter of organic microparticles | fine-particles is 20-400 nm. The method of claim 1, The laminated | multilayer film whose average particle diameter of organic microparticles | fine-particles exceeds 3 times of the application layer thickness, and is 10 times or less. The method of claim 1, The laminated | multilayer film whose thermal contraction rate of the longitudinal direction at the time of heat processing at 150 degreeC for 30 minutes is 1.5 to 0.0%. The method of claim 1, The laminated | multilayer film whose thermal contraction rate in a horizontal direction when it heat-processes at 150 degreeC for 30 minutes is 1.0 to -0.5%. The brightness improvement sheet which formed the prism lens layer on the application layer of the laminated | multilayer film in any one of Claims 1-8. The method according to any one of claims 1 to 6, The laminated | multilayer film which is a biaxially stretched polyester film which further relaxed-annealed after a polyester film is biaxially stretched. The method of claim 10, The laminated | multilayer film which relaxes heat processing is performed by putting a sheath in the vicinity of the both ends of a film downstream from the drawing zone of a tenter, and peeling a film from a clip holding part. The method of claim 10, The laminated | multilayer film by which biaxial stretching of a polyester film is performed by the simultaneous biaxial stretching method.