TWI448740B - Polyester film for brightness enhancement sheet - Google Patents

Description

Polyester film for brightness enhancement sheet

The present invention relates to a polyester film for a brightness enhancement sheet (generally referred to as "strip") of a liquid crystal display.

In recent years, polyester film has been widely used for optical films, such as a brightness enhancement sheet for liquid crystal display devices, a substrate film such as a touch panel and a backlight, a matrix film for an antireflection film, an electromagnetic wave shielding film for a plasma display, and an organic EL. The use of a substrate film for a display, an explosion-proof substrate film for a display, and the like.

The matrix film used for such use requires excellent transparency and adhesion and adhesion to a ruthenium layer, a hard coat layer, an adhesive layer, an antireflection layer, a sputter layer, and the like provided on the substrate film.

However, the polyester film, particularly the biaxially stretched polyester film, generally has poor adhesion to other materials, and is, for example, poorly adhered to a enamel layer or a hard coat layer containing an acrylic resin as a main component.

In the above, as a method of improving the adhesion between the polyester film and the ruthenium layer, it is proposed to provide a bonding layer on the surface of the polyester film to improve the adhesion (Japanese Unexamined Patent Publication No. Hei No. Hei No. Hei. Japanese Laid-Open Patent Publication No. 2005-89622, JP-A-2006-137046.

However, the heat resistance of the bonding layer of the conventional technology is insufficient, and exposure to a high temperature environment seriously impairs the adhesion, that is, the heat-resistant adhesiveness is insufficient. Therefore, it is not possible to use, for example, a component of a machine that is a vehicle-mounted material such as a navigation system and a high-intensity large-screen display whose temperature is likely to rise.

The present invention provides a brightness-increasing sheet (sheet) which is suitable for use in a vehicle-mounted material, a high-brightness large-screen display, has sufficient heat-resistant adhesiveness, and has high transparency and high adhesion of display and enamel layer. A polyester film of a matrix film.

That is, the present invention is formed of a polyester film and a coating layer disposed thereon, and is characterized in that the coating layer is a brightness enhancement sheet made of an acrylic resin, a crosslinking agent, and a polyoxyalkylene ether. Use a polyester film.

Hereinafter, the present invention will be described in detail.

Polyester film

The polyester constituting the polyester film of the present invention is a linear saturated polyester synthesized from an aromatic dibasic acid or an ester-forming derivative thereof and a diol or an ester-forming derivative thereof. Specific examples of such polyesters include, for example, polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, and polybutylene terephthalate. .

The polyester used in the polyester film may be a copolymer of such a polyester or may be blended with other resins. In either case, it is preferred that the polyester is a main component (for example, a component of 80 mol% or more) as a copolymerization component or a mixture of components (for example, a component of 20 mol% or less). As the polyester, polyethylene terephthalate is particularly preferable because it has a good balance of mechanical properties, optical properties, and the like.

The polyester film may contain a colorant, a charge preventive agent, an oxidation preventive agent, a lubricant, and a catalyst, and those having no added fine particles are preferable in terms of transparency.

The thickness of the polyester film is preferably from 25 to 350 μm, more preferably from 50 to 250 μm, in order to obtain a desired strength when used as a brightness enhancement sheet.

Coating layer

In the polyester film for a brightness enhancement sheet of the present invention, a coating layer is provided on the polyester film. The coating layer may be provided on one side or on both sides, and is preferably provided on both sides.

The thickness of the coating layer of the present invention is preferably from 20 to 150 nm, more preferably from 30 to 120 nm, still more preferably from 40 to 90 nm, and when the thickness of the coating layer exceeds 150 nm, agglomeration tends to occur, which is not preferable. When the thickness is less than 20 nm, the adhesion to the ultraviolet curable resin tends to be deteriorated, which is not preferable.

The coating layer is formed of an acrylic resin, a crosslinking agent, and a polyoxyalkylene ether. Among them, the acrylic resin functions as a binder, and the crosslinking agent imparts heat-resistant adhesiveness.

When the brightness-enhancing sheet is formed, the enamel layer provided on the polyester film for brightness enhancement sheet is generally used as an energy-hardening type, particularly an ultraviolet-curable type acrylic resin, and it is required to have good adhesion to the acrylic resin. Therefore, an acrylic resin is used as a binder component of the coating layer.

Acrylic

The acrylic resin of the coating layer of the present invention is preferably a glass transition temperature (hereinafter referred to as "Tg"), preferably 30 to 80 ° C, more preferably 35 to 70 ° C. By using an acrylic resin of this range of Tg, a film having good agglomeration properties and excellent transparency can be obtained.

As the acrylic resin, for example, a polymer obtained by polymerizing an acrylic monomer exemplified below or an acrylic resin obtained by copolymerization can be used.

As the acrylate monomer, for example, an alkyl acrylate or an alkyl methacrylate (as an alkyl group such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, butyl, 2) -ethylhexyl, cyclohexyl, etc.); 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, etc., hydroxyl-containing monomers; An epoxy group-containing monomer such as glyceride, glycidyl methacrylate or allyl glycidyl ether; acrylic acid, methacrylic acid, methylene succinic acid, maleic acid, fumaric acid a monomer containing a carboxyl group or a salt thereof, such as 2-butenoic acid and a salt thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); styrenesulfonic acid and a salt thereof (sodium salt, potassium salt, Ammonium salt, tertiary amine salt, etc.); acrylamide, methacrylamide, N-alkyl acrylamide, N-alkyl methacrylamide, N,N-dialkyl acrylamide, N , N-dialkylmethacrylamide (as alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, butyl, 2-ethylhexyl, Cyclohexyl, etc.) N-alkoxypropenylamine, N-alkoxymethylpropenylamine, N,N-dialkoxypropenylamine, N,N-dialkoxymethylpropenylamine (as alkoxy group) , for example, methoxy, ethoxy, butoxy, isobutoxy, etc.), acryloyl morpholine, N-methylol acrylamide, N-methylol methacrylamide, N-benzene a monomer containing a guanamine group such as acrylamide or N-phenylmethacrylamide; a monomer of an acid anhydride such as maleic anhydride or methylene succinic anhydride; isocyanate, isocyanic acid Allyl ester, styrene, α-methylstyrene, vinyl methyl ether, vinyl ethyl ether, vinyl trialkoxy decane, alkyl maleic acid monoester, alkyl antibutene Monomers such as acid monoester, alkylmethylene succinic acid monoester, acrylonitrile, methacrylonitrile, vinylidene chloride, ethylene, propylene, ethylene chloride, vinyl acetate, butadiene.

In order to obtain high adhesion between the coating layer and the processing layer such as the ruthenium layer provided in the subsequent processing, and at the same time, sufficient adhesion between the coating layer and the substrate, the acrylic resin is a polymer of a monomer component containing a nitrogen atom. Or a copolymer of acrylic resin is preferred. The content of the monomer component containing a nitrogen atom in the acrylic resin is preferably from 1 to 30 mol% based on the total amount of the monomer components constituting the acrylic resin in order to achieve the above object.

As a monomer component containing a nitrogen atom, for example, acrylamide, methacrylamide, N-alkyl acrylamide, N-alkyl methacrylamide, N, N-dialkyl acrylamide, N , N-dialkyl methacrylate (as alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, butyl, 2-ethylhexyl, ring Hexyl, etc.), N-alkoxypropenylamine, N-alkoxymethylpropenylamine, N,N-dialkoxypropenylamine, N,N-dialkoxymethylpropenamide ( As alkoxy group, for example, methoxy, ethoxy, butoxy, isobutoxy, etc.), acryloylmorpholine, N-methylol acrylamide, N-methylol methacrylamide A monomer containing a guanamine group such as N-phenyl acrylamide or N-phenylmethacrylamide. The reason why the adhesiveness can be improved by using an acrylic resin containing these monomers as a monomer component is that the nitrogen atom has an unpaired electron, has a high polarity, and has high intermolecular force and reactivity.

Acrylic resins are preferably water soluble or dispersible in water. The acrylic resin can be produced, for example, according to the methods described in Production Examples 1 to 3 of JP-A-63-37167. That is, a predetermined amount of sodium lauryl sulfonate as a surfactant and a predetermined amount of ion-exchanged water were placed in a 4-necked flask, and the temperature was raised to 60 ° C in a nitrogen gas stream, and then added as a polymerization initiator. 0.5 parts by weight of ammonium persulfate and 0.2 parts by weight of sodium hydrogen nitrite were added, and the mixture of the monomers for polymerization of the acrylic resin was allowed to drip while adjusting the liquid temperature to 60 to 70 ° C over 3 hours. After the completion of the dropwise addition, the mixture was kept at the same temperature for 2 hours, and the reaction was continued with stirring, followed by cooling to obtain an aqueous dispersion of an acrylic resin.

The refractive index of the acrylic resin of the present invention is preferably from 1.45 to 1.55, more preferably from 1.46 to 1.53, still more preferably from 1.48 to 1.51. When the refractive index of the acrylic resin exceeds 1.55, the transmittance of UV light does not increase, and when the brightness-enhancing sheet is produced, it is difficult to form an ultraviolet curable acrylic resin, and on the other hand, it is difficult to form 1.45.

The acrylic resin is preferably 100% by weight to the total of 100% by weight of the composition constituting the coating layer, and particularly preferably 65 to 87% by weight. By containing the acrylic resin in the coating layer in this range, excellent adhesion and heat-resistant adhesiveness between the coating layer and the ruthenium layer provided after the processing can be obtained.

Crosslinker

The coating layer of the present invention contains a crosslinking agent. As the crosslinking agent, any one or more of an epoxy resin, an oxazoline, a melamine, and an isocyanate can be used. These may be used alone or in combination of two or more.

As the epoxy crosslinking agent, for example, a polyepoxy compound, a diepoxide compound, a monoepoxy compound, or a glycidylamine compound.

As the polyepoxy compound, for example, sorbitol, polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerin polyglycidyl ether, triglycidyl tris(2-hydroxyethyl) isocyanate, glycerin Polyglycidyl ether, trimethylolpropane polyglycidyl ether.

As the diepoxy compound, for example, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcinol diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol II Glycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, polybutylene glycol diglycidyl ether.

As the monoepoxy compound, for example, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether.

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

As the oxazoline crosslinking agent, a polymer containing an oxazoline group is preferred. The monomer containing an addition-polymerizable oxazoline group may be produced by polymerization alone or may be produced by copolymerization with another monomer.

As a monomer containing an addition polymerizable oxazoline group, for example, 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, 2-isopropenyl-5-ethyl-2- Oxazoline. These may be used alone or in combination of two or more. Among them, 2-isopropenyl-2-oxazoline is industrially easy to obtain and is suitable.

The other monomer used for the copolymerization with the oxazoline group-containing copolymer may be a monomer copolymerizable with a monomer having an addition polymerizable oxazoline group, for example, an alkyl acrylate, a An alkyl acrylate (as an alkyl group such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, butyl, 2-ethylhexyl, cyclohexyl), etc. Acrylates; acrylic acid, methacrylic acid, methylene succinic acid, maleic acid, fumaric acid, 2-butenoic acid, styrene sulfonic acid and salts thereof (sodium salt, potassium salt) Unsaturated carboxylic acid such as ammonium salt or tertiary amine salt; unsaturated nitrile such as acrylonitrile or methacrylonitrile; acrylamide, methacrylamide, N-alkyl acrylamide, N -alkyl methacrylamide, N,N-dialkyl acrylamide, N,N-dialkyl methacrylate (as alkyl group, such as methyl, ethyl, n-propyl, isopropyl Unsaturated guanamine such as n-butyl, isobutyl, butyl, 2-ethylhexyl, cyclohexyl, etc.; ester of vinyl acetate, vinyl propionate, acrylic acid, methacrylic acid Poly epoxy Vinyl esters such as methyl vinyl ether and vinyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α, β-non such as vinyl chloride, vinylidene chloride and vinyl fluoride Saturated monomer; α,β-unsaturated aromatic monomer such as styrene or α-methylstyrene. These monomers may be used alone or in combination of two or more.

As the melamine crosslinking agent, a methylol melamine derivative obtained by condensing melamine with formaldehyde, a compound which reacts a lower alcohol and etherified, and a mixture thereof are preferable. As the lower alcohol, for example, methanol, ethanol, or isopropyl alcohol can be used.

As the methylol melamine derivative, for example, monomethylol melamine, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, hexamethylol melamine.

As an isocyanate crosslinking agent, for example, toluene diisocyanate, diphenylmethane-4,4'-diisocyanate, m-xylene diisocyanate, hexamethylene-1,6-diisocyanate, 1,6-di Isocyanate hexane, adduct of toluene diisocyanate and hexanetriol, adduct of toluene diisocyanate and trimethylolpropane, polyol modified diphenylmethane-4,4'- Diisocyanate, carbodiimide modified triphenylmethane-4,4'-diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, 3,3'-dimethyl phenyl-4,4 '-Diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, m-phenylene diisocyanate.

The content ratio of the crosslinking agent contained in the coating layer is preferably from 5 to 30% by weight, more preferably from 10 to 25% by weight, based on 100% by weight of the composition of the coating layer. When the content of the crosslinking agent is 5 to 30% by weight, a good heat-resistant adhesiveness can be obtained, and a coating film having a suitable hardness can be obtained, the coating film is not too hard, and the film whitening does not occur in the stretching step. A film with good transparency.

Polyoxyalkylene ether

The coating layer of the present invention contains a polyoxyalkylene alkyl phenyl ether.

As polyoxyalkylene alkyl phenyl ether, such as polyoxyethylene nonylphenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene styrene phenyl ether, polyoxyethylene distyryl phenyl ether, polyoxyethylene Tristyrenated phenyl ether, polyoxyethylene benzyl phenyl ether, polyoxyethylene diphenylmethyl phenyl ether, polyoxyethylene trityl phenyl ether, polyoxypropylene decyl phenyl ether, polyoxygen Propylene octyl phenyl ether, polyoxypropylene distyrenated phenyl ether, polyoxypropylene triphenylmethyl phenyl ether. These monomers may be used alone or in combination of two or more.

Among these polyoxyalkylene ethers, a polyoxyalkylene phenyl ether having a plurality of aromatic groups is preferred, and a polyoxyalkylene phenyl ether having a plurality of aromatic groups on the phenyl group is more preferred. As the polyoxyalkylene alkyl phenyl ether, for example, polyoxyethylene styrenated phenyl ether, polyoxyethylene distyryl phenyl ether, polyoxyethylene tristyryl phenyl ether, polyoxyethylene benzyl phenyl ether, Polyoxyethylene diphenylmethylphenyl ether, polyoxyethylene triphenylmethylphenyl ether. These polyoxyalkylene phenyl ethers having a plurality of aromatic groups are preferred because they have good compatibility with components constituting the coating layer and can reduce the haze of the coating layer.

As the polyoxyalkylene phenyl ether, a polyoxyalkylene phenyl ether having a plurality of styrene groups and/or benzyl groups on the phenyl group is particularly preferable. As the polyoxyalkylene alkyl phenyl ether, for example, polyoxyethylene distyrenated phenyl ether, polyoxyethylene tristyryl phenyl ether, polyoxyethylene diphenylmethyl phenyl ether, polyoxyethylene triphenylmethyl benzene Ether.

The content of the polyoxyalkylene ether to be contained in the coating layer is preferably from 2 to 15% by weight, more preferably from 3 to 10% by weight, based on 100% by weight of the composition of the coating layer. A film having good heat-resistant adhesiveness and excellent blocking resistance can be obtained by 2 to 15% by weight.

The polyoxyalkylene phenyl ether has an effect of promoting the wettability of the aqueous coating liquid of the polyester film, and a wetting agent can also be added.

The formation of the coating layer is preferably carried out using an aqueous coating liquid. In this case, the surface tension of the aqueous coating liquid is preferably 50 dynes/cm or less, more preferably 40 dynes/cm or less. In order to obtain the surface tension, a surfactant such as an anionic surfactant, a cationic surfactant, or a nonionic surfactant is preferred as a preferred surfactant, such as polyethylene oxide ‧ polyoxypropylene Block copolymer, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene ether ether, polyoxyethylene alkyl ether, polyoxyethylene-fatty acid ester, sorbitol fatty acid Ester, glycerin fatty acid ester, fatty acid metal soap, alkane sulfonate, alkyl sulfate, alkyl benzene sulfonate, alkyl sulfonate, alkyl diphenyl ether disulfonate, alkyl sulfo amber An acid salt, a 4-grade ammonium chloride salt, an alkylamine hydrochloric acid or the like.

Microparticle

The coating layer of the present invention preferably contains fine particles having an average particle diameter of from 100 to 400 nm from the viewpoint of suppressing agglomeration. In particular, in order to obtain the non-caking property used at a high temperature, the average particle diameter of the fine particles contained in the coating layer is more than three times the thickness of the coating layer. In addition, even if the average particle diameter is large, the fine particles are supported by the acrylic resin of the binder component in a state in which the composition is applied to the coating layer, and the range of the present invention does not fall off practically.

In the case where the coating layer contains fine particles, it is preferred to use organic fine particles having a property of being difficult to fall off from the coating layer. Examples of the organic fine particles include fine particles of an acrylic resin, a styrene resin, a polyoxyn resin, a fluororesin, a benzoguanamine resin, a phenol resin, and a nylon resin. These monomers may be used alone or in combination of two or more. Among these, fine particles of acrylic resin are preferred.

In the case of containing fine particles, it is preferably 0.1 to 10 parts by weight based on 100 parts by weight of the total of the composition of the coating layer other than the fine particles. When the amount is less than 0.1%, sufficient lubricity and scratch resistance are not obtained, and it is not preferable from the viewpoint of scratch resistance. On the other hand, when it exceeds 10 parts by weight, transparency is deteriorated, which is not preferable.

Production method

In the coating liquid used for coating the coating layer of the present invention, in order to form a coating film on the film, an aqueous coating liquid such as an aqueous solution, an aqueous dispersion or an emulsion is preferably used. For the coating liquid, for example, a charging inhibitor or a surfactant may be blended as needed.

The solid content concentration of the coating liquid is usually 20% by weight or less, preferably 1 to 10% by weight or less. When the amount is less than 1% by weight, the coating property to the polyester film is insufficient. Therefore, when the amount is more than 20% by weight, the stability of the coating liquid and the appearance of the coating layer are deteriorated, which is not preferable.

The application of the coating liquid to the polyester film can be carried out at any stage, but it is preferably carried out in the production process of the polyester film, and in particular, it is preferred to coat the polyester film before the completion of the alignment crystallization. Here, the polyester film before the completion of the crystallization is an axially stretched film including an unstretched film and an unstretched film in either the longitudinal direction or the transverse direction, and a two-direction low magnification in the longitudinal direction and the transverse direction. The concept of extending the aligned biaxially stretched film (the biaxially stretched film before the alignment crystallization is finally extended in the longitudinal direction or the transverse direction). Among them, the uncoated film or the one-direction alignment one-axis stretching film is preferably coated on the coating liquid. In this case, it is preferable to apply longitudinal extension and/or lateral extension and heat fixation as they are. Further, it is an ideal production method for producing a biaxially stretched film by stretching the film coating liquid without stretching in the longitudinal direction and the transverse direction as it is, and then thermally fixing it.

When the coating liquid is applied to the film, physical treatment such as corona surface treatment, flame treatment, or plasma treatment may be applied, and it is preferable to prepare for the improvement of the coating property.

As the coating method, any conventional coating method can be applied. For example, a roll coating method, a gravure printing method, a rolling brush coating method, a spray coating method, an air knife coating method, a dipping method, and a curtain coating method can be applied. These can be used individually or in combination.

Example

Hereinafter, the present invention will be described in more detail by way of examples.

Various physical properties were evaluated by the following methods.

(1) Haze

The haze of the film was measured according to JIS K7136 using a haze meter NDH-2000 manufactured by Nippon Denshoku Industries Co., Ltd.

(2) Transparency

The transparency was evaluated by the haze value obtained in the above (1) on the basis of the following criteria.

◎: Haze value <0.8% (excellent transparency)

○: 0.8% haze value <1.0% (good transparency)

×: 1.0% haze value (poor transparency)

(3) Thickness of coating layer

The film was cut into small pieces, wrapped in epoxy resin, and sliced into a film profile of 50 nm thickness by a microtome. This was dyed with 2% citric acid at 60 ° C for 2 hours. The cross section of the dyed film was measured by a transmission electron microscope (LEM-2000) at a magnification of 200,000 times to measure the thickness of the coating layer.

(4) Average particle size of the microparticles

It was cut into small pieces, wrapped in epoxy resin, and sliced into a film profile of 50 nm thickness by a microtome. This was dyed with 2% citric acid at 60 ° C for 2 hours. The cross section of the dyed film was measured by a transmission electron microscope (LEM-2000) at a magnification of 500,000 times, and the particle diameter of any 100 fine particles was measured, and the average value of the particle diameters was used as the average particle diameter.

(5) Production of brightness enhancement sheet

The ultraviolet curable acrylic resin formed by the following composition is formed in a mold having a pattern, and the coating layer of the polyester film of the present invention is disposed on the acrylic resin side so that the two are adhered to each other. From the surface side of the polyester film, the distance from the surface of the polyester film was 30 cm, and the resin was cured by irradiation with an ultraviolet lamp (irradiation intensity: 80 W/cm, 6.4 kW) for 30 seconds to form a ruthenium layer having a apex angle of 90 degrees, a pitch of 50 μm, and a height of 30 μm. Brightness enhancement sheet.

As the ultraviolet curable acrylic resin, those having the following composition are used.

Ethylene oxide modified bisphenol A dimethacrylate

(FA-321M, manufactured by Hitachi Chemical Co., Ltd.) 46% by weight

Neopentyl glycol modified trimethylolpropane diacrylate

(R-604, manufactured by Hitachi Chemical Chemical Co., Ltd.) 25 wt%

Phenoxyethyl acrylate

(BIS-COAT192 manufactured by Osaka Organic Chemical Industry Co., Ltd.) 27% by weight

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

(Darocurl 173 made by Merck) 2% by weight

(6) Adhesion to the enamel layer

In the processing surface of the brightness enhancement sheet obtained in the above (5), a cross cut of a checkerboard (100 squares of 1 mm ² ) is applied, and a 24 mm wide celluloid tape is attached thereto (NICHIBAN company, Saiyan Fan) The tape CT405AP-18) was attached by a metal roll of 5 kg/5/5 cm wide, and the peeling angle of 90 degree was peeled off rapidly, and the peeling surface was observed, and it evaluated on the following basis.

○: The peeling area is 5% or less (good adhesion)

×: The peeling area exceeds 5% (poor adhesion)

(7) heat-resistant adhesiveness

The brightness-enhancing sheet obtained in the above (5) was subjected to heat treatment in an oven at 100 ° C for 12 hours, taken out from the oven, and left to stand at room temperature for 10 minutes, and then subjected to the same peeling test as in the above (6) to observe peeling. The surface was evaluated on the basis of the following criteria.

○: The peeling area is 5% or less (heat-resistant adhesiveness is good)

△: The peeling area is 5 to 20% (the heat-resistant adhesiveness is slightly poor)

×: The peeling area exceeds 20% (the heat-resistant adhesiveness is completely poor)

Example 1

The molten polyethylene terephthalate ([η]=0.60 dl/g, Tg=78 °C) was extruded from a die, cooled by a cooling method in a general method, and formed into an unstretched film, and then in the longitudinal direction. After extending 3.3 times, an aqueous coating liquid having a concentration of 5% of the coating agent A having the composition shown in Table 1 was uniformly applied by roller coating on both sides thereof. Further, in the case of molten polyethylene terephthalate, those which do not contain fine particles as a lubricant are used.

a film provided with a coating layer, followed by drying at 120 ° C, extending 3.6 times in the transverse direction at 135 ° C, and after heat setting at 235 ° C, the film is cooled stepwise from 180 ° C to 90 ° C, and the tenter is stretched. The inside of the machine was subjected to a 3.5% relaxation heat treatment in the lateral direction to obtain a polyester film for a brightness-enhancing sheet having a thickness of 125 μm and a coating layer thickness of 75 nm. The evaluation results are shown in Table 2.

Further, a ruthenium layer was formed on the obtained polyester film using an ultraviolet curable acrylic resin to obtain a brightness-enhancing sheet. The evaluation results are shown in Table 2.

Example 2

The molten polyethylene terephthalate ([η] = 0.61 dl/g, Tg = 78 ° C) was extruded from a die, cooled by a cooling method in a conventional manner, and formed into an unstretched film, and then on both sides thereof. An aqueous coating liquid having a concentration of 7% of the coating agent A of the composition shown in Table 1 was uniformly applied by a roll coating method. The coated film was then dried at 95 ° C, extended at 3.4 times in the longitudinal direction at 113 ° C, 3.6 times in the transverse direction, and thermally fixed at 230 ° C, then at 185 ° C in the longitudinal direction and the width direction, respectively. A 2.2% relaxation heat treatment was carried out to obtain a polyester film for a brightness enhancement sheet having a thickness of 125 μm and a coating layer thickness of 75 nm. The evaluation results are shown in Table 2.

To the obtained polyester film, an ultraviolet curable acrylic resin was used to form a ruthenium layer, and a brightness enhancement sheet was obtained. The evaluation results are shown in Table 2.

Example 3

A polyester film for brightness enhancement sheet was obtained in the same manner as in Example 2 except that the coating film A was used to form a coating film and the thickness of the film was 188 μm, and a brightness enhancement sheet was produced. The evaluation results are shown in Table 2.

Examples 4 to 11

A polyester film for brightness enhancement sheet was produced in the same manner as in Example 1 except that the coating materials B, C or D, J, K, L, N or O described in Table 1 were used to form a coating film having a predetermined thickness. It is also used to make a brightness enhancement sheet. The evaluation results are shown in Table 2.

Comparative Examples 1 to 5

A polyester film for a brightness enhancement sheet was obtained in the same manner as in Example 1 except that the coating materials E, F, G, H or I described in Table 1 were used to form a coating film having a predetermined thickness. It is also used to make a brightness enhancement sheet. The evaluation results are shown in Table 2.

Comparative Example 6

A polyester film for brightness enhancement sheet was obtained in the same manner as in Example 1 except that the coating layer was not formed, and a layer of the coating layer was directly provided, and a brightness enhancement sheet was produced. The evaluation results are shown in Table 2.

Further, the obtained brightness-enhancing sheet has poor adhesion between the base film and the enamel layer, and cannot satisfy the brightness-enhancing sheet.

The following components were used to constitute a component for setting the coating liquid for the coating layer.

Acrylic resin 1: consisting of methyl methacrylate 60 mol % / ethyl acrylate 30 mol % / 2-hydroxyethyl acrylate 5 mol % / N-methylol acrylamide 5 mol%. The acrylic method is produced as follows according to the methods described in Production Examples 1 to 3 of JP-A-63-37167. That is, 302 parts of ion-exchanged water was placed in a 4-necked flask, and the temperature was raised to 60 ° C in a nitrogen gas stream, and then 0.5 parts by weight of ammonium persulfate as a polymerization initiator and 0.2 parts by weight of sodium hydrogen nitrite were added. a mixture of 59.9 parts by weight of methyl methacrylate, 30.0 parts by weight of ethyl acrylate, 5.8 parts by weight of 2-hydroxyethyl acrylate, and 4.3 parts by weight of N-methylol acrylamide as a monomer, for 3 hours. While adjusting the liquid temperature to 60 to 70 ° C, it was dripped. After the completion of the dropwise addition, the mixture was kept at the same temperature for 2 hours, and the reaction was continued with stirring, followed by cooling to obtain an aqueous dispersion of the acrylic resin 1 having a solid content of 25%.

Acrylic resin 2: consisting of methyl methacrylate 60 mol % / ethyl acrylate 30 mol % / 2-hydroxyethyl acrylate 5 mol % / acrylamide 5 mol %. The acrylic method is produced as follows according to the methods described in Production Examples 1 to 3 of JP-A-63-37167. That is, 302 parts of ion-exchanged water was placed in a 4-necked flask, and the temperature was raised to 60 ° C in a nitrogen gas stream, and then 0.5 parts by weight of ammonium persulfate as a polymerization initiator and 0.2 parts by weight of sodium hydrogen nitrite were added. Further, a mixture of 60.8 parts by weight of methyl methacrylate, 30.4 parts by weight of ethyl acrylate, 5.9 parts by weight of 2-hydroxyethyl acrylate, and 2.9 parts by weight of acrylamide as a monomer was adjusted for liquid temperature over 3 hours. It is dropped at 60 to 70 ° C. After the completion of the dropwise addition, the mixture was kept at the same temperature for 2 hours, and the reaction was continued with stirring, followed by cooling to obtain an aqueous dispersion of the acrylic resin 2 having a solid content of 25%.

Acrylic resin 3: consisting of methyl methacrylate 60 mol % / ethyl acrylate 30 mol % / 2-hydroxyethyl acrylate 5 mol % / acrylonitrile 5 mol%. The acrylic method is produced as follows according to the methods described in Production Examples 1 to 3 of JP-A-63-37167. That is, 302 parts of ion-exchanged water was placed in a 4-necked flask, and the temperature was raised to 60 ° C in a nitrogen gas stream, and then 0.5 parts by weight of ammonium persulfate as a polymerization initiator and 0.2 parts by weight of sodium hydrogen nitrite were added. Further, a mixture of 61.4 parts by weight of methyl methacrylate, 30.7 parts by weight of ethyl acrylate, 5.9 parts by weight of 2-hydroxyethyl acrylate, and 2.0 parts by weight of acrylonitrile as a monomer was adjusted to adjust the liquid temperature over 3 hours. 60 to 70 ° C, while dropping. After the completion of the dropwise addition, the mixture was kept at the same temperature for 2 hours, and the reaction was continued with stirring, followed by cooling to obtain an aqueous dispersion of the acrylic resin 3 having a solid content of 25%.

Crosslinking agent 1: glycerol polyglycidyl ether (manufactured by Nagase Chemtex, DENACOL EX-313)

Crosslinking agent 2: oxazoline-containing polymer (manufactured by Nippon Shokubai Co., Ltd., EPOCROS K-2030E)

Crosslinking agent 3: methylolated melamine (manufactured by Sanwa Chemical Co., Ltd., NIKALAC MX-035)

Crosslinking agent 4: isocyanate (manufactured by Daiichi Kogyo Co., Ltd., ELASTRON H-3)

Microparticles: acrylate filler (average particle size: 160 nm, manufactured by Nippon Shokubai Co., Ltd., MX-100W)

Wetting agent 1: Polyoxyethylene distyryl phenyl ether (made by Kao Corporation, EMULGEN A-60)

Wetting agent 2: polyoxyethylene tristyryl phenyl ether (made by Kao Corporation, EMULGEN B-66)

Wetting agent 3: polyoxyalkylene alkyl ether (made by Sanyo Chemical Co., Ltd., NAROACTIE N-70)

Wetting agent 4: polyoxyalkylene ether ether (made by Takemoto Oil Co., Ltd., BIONINE D-1504)

Wetting agent 5: polyoxyethylene distyrenated phenyl ether (made by Kao Corporation, EMULGEN A-90)

Effect of the invention

According to the present invention, it is possible to provide a brightness-increasing sheet (sheet) which is suitable for use in a vehicle-mounted material, a high-brightness large-screen display, has sufficient heat-resistant adhesiveness, and has high transparency and high adhesion of display and enamel layer. A polyester film of a matrix film.

Industrial utilization possibility

The polyester film for a brightness enhancement sheet of the present invention can be suitably used for various optical applications. In particular, it is suitable for use in a substrate for a liquid crystal display that is moving toward a large screen and a high brightness, and a substrate for a brightness enhancement sheet that is used at a high temperature for use in a vehicle.

Claims (6)

A polyester film for brightness enhancement sheet characterized by a polyester film and a coating layer disposed thereon, and the coating layer is formed of an acrylic resin, a crosslinking agent, and a polyoxyalkylene ether. Wherein the polyoxyalkylene phenyl ether is a polyoxyalkylene phenyl ether having a plurality of aromatic groups. The polyester film for brightness enhancement sheet according to claim 1, wherein the polyoxyalkylene ether phenyl group has a plurality of polystyrene alkyl phenyl ethers having a styryl group and/or a benzyl group. The polyester film for brightness-enhancing sheets according to the first aspect of the invention is applied by coating a coating liquid constituting the coating layer and then sequentially stretching by a biaxial stretching method. The polyester film for brightness enhancement sheet according to the first aspect of the invention is produced by coating a coating liquid constituting the coating layer and then stretching it by a biaxial stretching method. The polyester film for a brightness enhancement sheet according to the first aspect of the invention, wherein the acrylic resin of the coating layer is an acrylic resin containing a monomer having a nitrogen atom as a monomer component. A brightness enhancement sheet provided with a ruthenium layer on a polyester film for a brightness enhancement sheet according to any one of claims 1 to 5.