KR101516030B1 - Polyester film for brightness enhancement sheet - Google Patents

Abstract

A base film of a brightness enhancement sheet (prism lens sheet) having sufficient heat-resistant adhesiveness which can be suitably used for a vehicle-use substrate or a high-luminance large-screen display, exhibiting high transparency and exhibiting high adhesion with a prism lens layer A polyester film for a brightness enhancement sheet, characterized by comprising a polyester film and a coating layer formed thereon in order to provide a polyester film to be used, characterized in that the coating layer is composed of an acrylic resin, a crosslinking agent and polyoxyalkylene phenyl ether Lt; / RTI >

Description

POLYESTER FILM FOR BRIGHTNESS ENHANCEMENT SHEET BACKGROUND OF THE INVENTION [0001]

The present invention relates to a polyester film used in a brightness enhancement sheet (sometimes referred to as a " prism lens sheet " in some cases) of a liquid crystal display.

BACKGROUND ART [0002] Polyester films are widely used in recent optical films. For example, base films such as brightness enhancement sheets, touch panels, and backlights used in liquid crystal displays, base films for antireflection films, electromagnetic shielding films for plasma displays, A base film of an organic EL display, and a base film for explosion-proofing a display.

The base film used for such applications is required to have excellent transparency and is required to have adhesiveness and adhesion to a prism lens layer, a hard coat layer, an adhesive layer, an antireflection layer, a sputter layer, etc. formed on a base film.

However, the polyester film, particularly the biaxially stretched polyester film, has poor adhesiveness with other materials and has poor adhesion with, for example, a prism lens layer or a hard coat layer mainly composed of an acrylic resin.

As a method for improving the adhesion between the polyester film and the prism lens layer, a number of proposals have been made to improve the adhesiveness by forming an anchor coat layer on the surface of the polyester film (JP-A-11-271503 Japanese Unexamined Patent Publication No. 2000-141574, Japanese Unexamined Patent Publication No. 2005-89622, Japanese Unexamined Patent Publication No. 2006-137046).

However, in the prior art, the heat resistance of the anchor coat layer is not sufficient, and when exposed under a high temperature environment, the adhesion is greatly impaired, that is, the heat-resistant adhesiveness is insufficient. Therefore, it can not be used as a member of a vehicle-use base material such as a car navigation system or a member of a large-brightness large-screen display base which tends to rise in temperature.

The present invention relates to a brightness enhancing sheet (prism lens sheet) having a high heat resistance and a high transparency which can be preferably used for a vehicle-use substrate or a high-brightness large-screen display, It is an object of the present invention to provide a polyester film used as a base film.

That is, the present invention is a polyester film for a brightness enhancement sheet comprising a polyester film and a coating layer formed thereon, wherein the coating layer comprises an acrylic resin, a crosslinking agent, and a polyoxyalkylene phenyl ether.

According to the present invention, it is possible to provide a brightness enhancement sheet (prismatic lens sheet) which has sufficient heat-resistant adhesiveness that can be suitably used for a vehicle-use base material and a high-brightness large-screen display, exhibits high transparency, ). ≪ / RTI >

Hereinafter, the present invention will be described in detail.

Polyester film

The polyester constituting the polyester film in 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 polyethylene terephthalate, polyethylene naphthalene dicarboxylate, polybutylene terephthalate and poly (1,4-cyclohexylene dimethylene terephthalate).

The polyester used in the polyester film may be a copolymer of these polyester, or it may be blended with another resin. In either case, it is preferable that the polyester is a main component (for example, 80 mol% or more) and the copolymerization component or the blend component is a small proportion (for example, 20 mol% or less). As the polyester, polyethylene terephthalate is particularly preferable because it has good balance of mechanical properties and optical properties.

The polyester film may contain a colorant, an antistatic agent, an antioxidant, a lubricant, and a catalyst, but it is preferable not to contain internally-contained fine particles from the viewpoint of transparency.

The thickness of the polyester film is preferably 25 to 350 占 퐉, more preferably 50 to 250 占 퐉 in order to obtain the strength required for use as a brightness enhancement sheet.

Coating layer

The polyester film for a brightness enhancement sheet of the present invention has a coating layer on the polyester film. The coating layer may be provided on one surface or on both surfaces, preferably on both surfaces.

The thickness of the coating layer in the present invention is preferably 20 to 150 nm, more preferably 30 to 120 nm, particularly preferably 40 to 90 nm. When the thickness of the coating layer exceeds 150 nm, blocking tends to occur, which is undesirable. On the other hand, if it is less than 20 nm, adhesion with the ultraviolet curable resin tends to be deteriorated.

The coating layer is composed of an acrylic resin, a crosslinking agent and a polyoxyalkylene phenyl ether. Among them, the acrylic resin acts as a binder, and the cross-linking agent acts to impart heat-resistant adhesion.

In producing the brightness improving sheet, an energy-curable type, in particular, an ultraviolet curing type acrylic resin is generally used for the prism lens layer formed on the polyester film for brightness enhancement sheet, and therefore good adhesion to the acrylic resin is required . Therefore, an acrylic resin is used as a binder component of the coating layer.

Acrylic resin

In the acrylic resin of the coating layer in the present invention, the glass transition temperature of the polymer (hereinafter, the glass transition temperature is sometimes referred to as " Tg ") is preferably 30 to 80 캜, more preferably 35 to 70 캜 Of acrylic resin. By using an acrylic resin having a Tg within this range, a film having good blocking properties and excellent transparency can be obtained.

As this acrylic resin, for example, an acrylic resin which is a polymer obtained by polymerizing an acrylic monomer or copolymer which is exemplified below can be used.

-메틸스티렌, 비닐메틸에테르, 비닐에틸에테르, 비닐트리알콕시실란, 알킬말레산모노에스테르, 알킬푸마르산모노에스테르, 알킬이타콘산모노에스테르, 아크릴로니트릴, 메타크릴로니트릴, 염화비닐리덴, 에틸렌, 프로필렌, 염화비닐, 아세트산비닐, 부타디엔 등의 모노머를 들 수 있다. Examples of the acrylic monomer include alkyl acrylate and alkyl methacrylate (examples of the alkyl group include a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, , Cyclohexyl group and the like); 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 a carboxyl group or a salt 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); Styrene sulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); Acrylamide, N, N-dialkyl acrylamide, N, N-dialkyl methacrylate (examples of the alkyl group include methyl group, ethyl group, n- propyl acrylate, An isopropyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group and a cyclohexyl group), N-alkoxyacrylamide, N-alkoxymethacrylamide, (Methoxy group, ethoxy group, butoxy group, isobutoxy group and the like), acryloylmorpholine, N-methylol acrylamide, N-methylol acrylamide, 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,

-Methylstyrene, vinylmethylether, vinylethylether, vinyltrialkoxysilane, alkylmaleic acid monoester, alkylfumaric acid monoester, alkyl itaconic acid monoester, acrylonitrile, methacrylonitrile, vinylidene chloride, ethylene, propylene , Vinyl chloride, vinyl acetate, and butadiene.

In order to obtain a high adhesion between the coating layer and a processing layer such as a prism lens layer formed in the subsequent processing and at the same time to obtain sufficient adhesion between the coating layer and the substrate, the acrylic resin contains a monomer component containing a nitrogen atom Polymer or an acrylic resin which is a copolymer. The content of the monomer component containing a nitrogen atom in the acrylic resin is preferably 1 to 30 mol% based on the total amount of the monomer components constituting the polymer of the acrylic resin in order to achieve the above object.

Examples of the monomer containing nitrogen atom include acrylamide, methacrylamide, N-alkyl acrylamide, N-alkyl methacrylamide, N, N-dialkyl acrylamide, N, N-dialkyl methacrylate Examples of the alkyl group include an alkyl group such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, (Methoxy group, ethoxy group, butoxy group, isobutoxy group and the like), N, N-dialkoxy acrylamide, N, N-dialkoxy methacrylamide (the alkoxy group is exemplified by acryloxyethyl methacrylate, And monomers containing amide groups such as N-methylol acrylamide, N-methylol methacrylamide, N-phenylacrylamide and N-phenylmethacrylamide. The reason why the adhesiveness is improved by using an acrylic resin containing these monomers as the monomer component is considered to be that the nitrogen atom has a high polarity and relatively high intermolecular force and reactivity because it has hole electrons.

The acrylic resin is preferably soluble or dispersible in water. The acrylic resin can be produced, for example, in accordance with the methods described in Production Examples 1 to 3 of JP-A-63-37167. That is, a four-necked flask was charged with a predetermined amount of sodium laurylsulfonate as a surfactant and a predetermined amount of ion-exchange water, and the temperature was raised to 60 ° C in a nitrogen stream. Then, 0.5 part by weight of ammonium persulfate and 0.2 part by weight of sodium hydrogen nitrate And the mixture of the monomers used for polymerization of the acrylic resin is added dropwise over 3 hours while adjusting the liquid temperature to 60 to 70 占 폚. After completion of the dropwise addition, the reaction is continued under stirring in the same temperature range for 2 hours, and then cooled to obtain an acrylic resin aqueous dispersion.

The refractive index of the acrylic resin in the present invention is preferably 1.45 to 1.55, more preferably 1.46 to 1.53, and particularly preferably 1.48 to 1.51. When the refractive index of the acrylic resin exceeds 1.55, the transmittance of the UV light does not rise. Therefore, it is difficult to form the prism lens by using the ultraviolet curable acrylic resin in the production of the brightness improving sheet, .

The acrylic resin accounts for 55 to 93% by weight, particularly preferably 65 to 87% by weight, based on the total 100% by weight of the composition constituting the coating layer. By containing the acrylic resin in the coating layer in this range, excellent adhesion and heat-resistant adhesion can be obtained between the coating layer and the prism lens layer formed in the subsequent processing.

Cross-linking agent

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

Examples of the epoxy crosslinking agent include polyepoxy compounds, diepoxy compounds, monoepoxy compounds, and glycidyl amine compounds.

As the polyepoxy compound, for example, sorbitol, polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris (2-hydro Hydroxyethyl) isocyanate, glycerol polyglycidyl ether, and trimethylolpropane polyglycidyl ether.

Examples of the diepoxy compound include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcinediglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, Propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and polytetramethylene glycol diglycidyl ether can be given.

Examples of the monoepoxy compound include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, and phenyl glycidyl ether.

Examples of the glycidylamine compound include N, N, N ', N', -tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N-diglycidylamino) Hexane.

As the oxazoline crosslinking agent, it is preferable to use a polymer containing an oxazoline group. This can be produced by polymerizing an addition polymerizable oxazoline group-containing monomer alone, or by copolymerizing with other monomers.

Examples of the addition polymerizable oxazoline group-containing monomer include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2- Isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline and 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 preferable because it is easily available industrially.

-올레핀 ; 염화비닐, 염화비닐리덴, 불화비닐 등의 함할로겐

,β-불포화 모노머 ; 스티렌,

-메틸스티렌 등의

,β-불포화 방향족 모노머를 들 수 있다. 이들 모노머는 1 종을 사용해도 되고, 2 종 이상을 병용해도 된다. The other monomer used for copolymerization with the oxazoline group-containing copolymer may be any monomer copolymerizable with the addition polymerizable oxazoline group-containing monomer, and examples thereof include alkyl acrylates and alkyl methacrylates (Meth) acrylates such as ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, 2-ethylhexyl and cyclohexyl; Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrenesulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt and the like); Unsaturated nitriles such as acrylonitrile and methacrylonitrile; Acrylamide, N, N-dialkyl acrylamide, N, N-dialkyl methacrylate (examples of the alkyl group include methyl group, ethyl group, n- propyl acrylate, Unsaturated amides such as a isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a 2-ethylhexyl group, a cyclohexyl group and the like; Vinyl esters such as those obtained by adding a polyalkylene oxide to the ester moiety of vinyl acetate, vinyl propionate, acrylic acid and methacrylic acid; Vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; Ethylene, propylene, and the like

Olefins; Halogen halides such as vinyl chloride, vinylidene chloride and vinyl fluoride

, beta -unsaturated monomers; Styrene,

- methylstyrene

, and? -unsaturated aromatic monomers. These monomers may be used alone or in combination of two or more.

The melamine crosslinking agent is preferably a compound obtained by etherifying a methylol melamine derivative obtained by condensing melamine and formaldehyde with a lower alcohol and a mixture thereof. As the lower alcohol, for example, methyl alcohol, ethyl alcohol and isopropyl alcohol can be used.

Examples of the methylol melamine derivative include monomethylol melamine, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, and hexamethylol melamine.

Examples of the isocyanate crosslinking agent include tolylene diisocyanate, diphenylmethane-4,4'-diisocyanate, meta xylylenediisocyanate, hexamethylene-1,6-diisocyanate, 1,6-diisocyanate hexane, Adducts of isocyanate and hexanetriol, adducts of tolylene diisocyanate and trimethylol propane, polyol-modified diphenylmethane-4,4'-diisocyanate, carbodiimide-modified diphenylmethane-4,4'-diisocyanate, Isophorone diisocyanate, 1,5-naphthalene diisocyanate, 3,3'-bitolylene 4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, .

The content of the crosslinking agent contained in the coating layer is preferably 5 to 30% by weight, more preferably 10 to 25% by weight, per 100% by weight of the composition of the coating layer. When the content of the crosslinking agent is 5 to 30% by weight, good heat-resistant adhesion can be obtained and a coating film with appropriate hardness can be obtained, and the coating film is not excessively stiff and the film is not whitened in the stretching step , A film excellent in transparency can be obtained.

Polyoxyalkylene phenyl ether

The coating layer in the present invention contains polyoxyalkylene phenyl ether.

Examples of the polyoxyalkylene phenyl ether include polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene styrenated phenyl ether, polyoxyethylene distyrenated phenyl ether, polyoxyethylene triesterified phenyl ether, Polyoxyethylene dibenzylphenyl ether, polyoxyethylene tribenzyl phenyl ether, polyoxypropylene nonyl phenyl ether, polyoxypropylene octyl phenyl ether, polyoxypropylene distyrenated phenyl ether, polyoxypropylene tribenzyl Phenyl ether. These may be used alone or in combination of two or more.

Of these polyoxyalkylene phenyl ethers, preferred are polyoxyalkylene phenyl ethers having a plurality of aromatic groups, more preferably polyoxyalkylene phenyl ethers having a plurality of aromatic groups on a phenyl group. Examples of the polyoxyalkylene phenyl ether include polyoxyethylene styrenated phenyl ether, polyoxyethylene distyrenated phenyl ether, polyoxyethylene triesterified phenyl ether, polyoxyethylene benzylphenyl ether, polyoxyethylene dibenzyl Phenyl ether, and polyoxyethylene tribenzyl phenyl ether. These polyoxyalkylene phenyl ethers having a plurality of aromatic groups are preferable because they have good compatibility with components constituting the coating layer and can lower the haze of the coating layer.

 Particularly preferred as the polyoxyalkylene phenyl ether is a polyoxyalkylene phenyl ether having a plurality of styrene groups and / or benzyl groups on the phenyl group. Examples of the polyoxyalkylene phenyl ether include polyoxyethylene distyrenated phenyl ether, polyoxyethylene triesterified phenyl ether, polyoxyethylene dibenzylphenyl ether, and polyoxyethylene tribenzylphenyl ether.

The content of the polyoxyalkylene phenyl ether contained in the coating layer is preferably 2 to 15% by weight, more preferably 3 to 10% by weight, based on 100% by weight of the composition of the coating layer. 2 to 15% by weight, it is possible to obtain a film having good heat-resistant adhesion and excellent blocking resistance.

The polyoxyalkylene phenyl ether has an effect of promoting the wettability of the aqueous coating liquid to the polyester film. In addition to this, a wetting agent may be further 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 dyne / cm or less, more preferably 40 dyne / cm or less. In order to obtain the surface tension, surfactants such as anionic surfactants, cationic surfactants and nonionic surfactants are preferred as the preferred surfactants, and examples thereof include polyethylene oxide / polypropylene oxide block copolymer, polyoxyethylene lauryl Ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene alkyl ether, polyoxyethylene-fatty acid ester, sorbitan fatty acid ester, glycerin fatty acid ester, fatty acid metal soap, Alkyl sulfates, alkylsulfonates, alkyldiphenyl ether disulfonates, alkylsulfosuccinates, quaternary ammonium chloride salts, alkylaminate salts, and the like.

Particulate

The coating layer in the present invention preferably contains fine particles having an average particle diameter of 100 to 400 nm from the viewpoint of inhibiting blocking. Particularly, in order to obtain properties that are not blocked in use at high temperatures, it is preferable that the average particle diameter of the fine particles contained in the coating layer exceeds 3 times the thickness of the coating layer. Further, even if the average particle size of the fine particles is large, the fine particles are supported on the acrylic resin of the binder component in the state where the fine particles are blended in the composition of the coating layer and applied to the film, so that they do not fall out practically in the scope of the present invention.

When fine particles are contained in the coating layer, it is preferable to use organic fine particles having such properties that they do not fall off well from the coating layer. Examples of the organic fine particles include fine particles of acrylic resin, styrene resin, silicone resin, fluororesin, benzoguanamine resin, phenol resin, and nylon resin. These may be used alone or in combination of two or more. Of these, fine particles of an acrylic resin are preferable.

When the fine particles are contained, the amount is preferably 0.1 to 10 parts by weight based on 100 parts by weight of the total of the coating layer compositions other than the fine particles. When the amount is less than 0.1 part by weight, sufficient activity and scratch resistance can not be obtained and it is not preferable from the viewpoint of improving scratch resistance. On the other hand, if it exceeds 10 parts by weight, transparency deteriorates.

Manufacturing method

In order to form a coating film on a film, the coating liquid used for coating formation of the coating layer in the present invention is preferably used in the form of an aqueous coating liquid such as an aqueous solution, an aqueous dispersion or an emulsion. If necessary, the coating liquid may further contain, for example, an antistatic agent or a surfactant.

The solid content concentration of the coating liquid is usually 20% by weight or less, preferably 1 to 10% by weight. If the content is less than 1% by weight, the coating property to the polyester film may be insufficient. If the content is more than 20% by weight, the stability of the coating liquid and the appearance of the coating layer may deteriorate.

The application of the coating liquid to the polyester film can be carried out at an arbitrary stage, and is preferably carried out during the production of the polyester film, particularly preferably to the polyester film before the orientation crystallization is completed Do. The polyester film before the orientation crystallization is completed is a uniaxially stretched film, a uniaxially stretched film in which the unoriented film is oriented in either the longitudinal direction or the transverse direction, And a biaxially oriented film (a biaxially oriented film which is finally stretched in a longitudinal direction or a transverse direction to complete orientation crystallization). Among them, it is preferable to apply the coating liquid to an unstretched film or a monoaxially stretched film oriented in one direction. In this case, it is preferable to further perform longitudinal stretching and / or transverse stretching and heat fixing in this state. It is also a preferable manufacturing method to apply a coating liquid to an unstretched film, simultaneously stretch the film in the longitudinal direction and the transverse direction in this state, and heat fix it again to produce a biaxially oriented film.

When the coating liquid is applied to a film, it is preferable to perform physical treatment such as corona surface treatment, flame treatment and plasma treatment on the surface of the film as a preliminary treatment for improving the coatability.

As the coating method, any known coating method can be applied. For example, a roll coat method, a gravure coat method, a roll brush method, a spray coat method, an air knife coat method, an impregnation method, and a curtain coat method can be applied. These may be applied alone 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) Hayes

The haze value of the film was measured using a haze meter NDH-2000 manufactured by Nippon Denshoku Industries Co., Ltd. according to JIS K 7136.

(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% (transparency is very good)

헤이즈값 ＜ 1.0 ％ (투명성 양호) ?: 0.8%

Haze value < 1.0% (good transparency)

헤이즈값 (투명성 불량) ×: 1.0%

Haze value (poor transparency)

(3) Thickness of Coating Layer

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

(4) Average particle diameter of fine particles

The film was cut into small pieces and embedded in an epoxy resin, and the cross section of the film was cut to a thickness of 50 nm with a microtome. This was stained with 2% osmium acid at 60 DEG C for 2 hours. The cross-section of the dyed film was observed at 500,000 times using a transmission electron microscope (LEM-2000) to arbitrarily measure the particle diameters of 100 fine particles, and the average value of the particle diameters was taken as the average particle diameter.

(5) Fabrication of brightness enhancement sheet

An ultraviolet curable acrylic resin having the following composition was poured into a frame having a prism lens pattern formed thereon and the coated layer side of the polyester film of the present invention was placed so as to be on the acrylic resin side, The resin was cured by irradiating with a ultraviolet lamp (irradiation intensity: 80 W / cm, 6.4 KW) from a distance of 30 cm from the surface side for 30 seconds to form a prism lens layer having a vertex angle of 90 degrees, a pitch of 50 占 퐉 and a height of 30 占 퐉 To obtain a luminance improving sheet.

As the ultraviolet curable acrylic resin, one having the following composition was used.

Ethylene oxide-modified bisphenol A dimethacrylate

(FA-321M manufactured by Hitachi Chemical Co., Ltd.) in an amount of 46 wt%

Neopentyl glycol-modified trimethylolpropane diacrylate

(R-604, manufactured by Nippon Kayaku Kagaku Kogyo) 25 wt%

Phenoxy ethyl acrylate

(Biscoat 192, manufactured by Osaka Organic Chemical Industry Co., Ltd.) 27 wt%

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

(Darocur 1173 manufactured by Merck & Co., Inc.) 2%

(6) Adhesion to prism lens layer

Cross cuts (100 pieces of 1 mm 2 square) were formed on the processed surface of the brightness enhancement sheet obtained in the above (5), and a 24 mm wide cellophane adhesive tape (Nicoty reflective manufacturing cell tape CT405AP- 18) were adhered to each other by weighting two reciprocations with a metal roll having a width of 5 kg / 5 cm, followed by abrupt peeling at a peeling angle of 90 °, and peeling was observed.

?: The peeled area was 5% or less (good adhesion)

X: The peeled area exceeding 5% (poor adhesion)

(7) Heat Resistance Adhesion

The brightness enhancement sheet obtained in the above (5) was heat treated in an oven at 100 캜 for 12 hours, removed from the oven, and cooled at room temperature for 10 minutes. Thereafter, the same peeling test as in the above (6) And evaluated by the following criteria.

?: The peeled area was 5% or less (good heat-resistant adhesion)

?: Peeling area is 5% to 20% (heat-resistant adhesion is slightly poor)

X: The peeled area exceeded 20% (heat-resistant adhesiveness was completely poor)

Example 1

The melt polyethylene terephthalate ([?] = 0.60 dl / g, Tg = 78 占 폚) was extruded from the die and cooled with a cooling drum by an ordinary method to form an unstretched film, followed by stretching 3.3 times in the machine direction , And an aqueous coating solution having a concentration of Coating Agent A of the composition shown in Table 1 of 5% on both surfaces thereof was uniformly coated with a roll coater. Further, a molten polyethylene terephthalate containing no fine particles as a lubricant was used.

The film formed with the coating layer was successively dried at 120 ° C, stretched in the transverse direction at 135 ° C to 3.6 times, heat-set at 235 ° C and then cooled in a stepwise manner from 180 ° C to 90 ° C, 3.5% relaxation heat treatment was performed in the transverse direction to obtain a polyester film for a brightness enhancement sheet having a thickness of 125 탆 and a coating layer thickness of 75 nm. The evaluation results are shown in Table 2.

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

Example 2

(Η) = 0.61 dl / g, Tg = 78 ° C.) was extruded from the die and cooled with a cooling drum by a conventional method to form an unstretched film. Subsequently, the composition shown in Table 1 By weight of a coating agent A having a concentration of 7% was uniformly coated with a roll coater. The coated film was successively dried at 95 ° C. and simultaneously stretched 3.4 times in the longitudinal direction and 3.6 times in the transverse direction at 113 ° C. and thermally fixed at 230 ° C. and then stretched at 185 ° C. in the longitudinal direction and in the transverse direction at 2.2% And subjected to relaxation heat treatment to obtain a polyester film for a brightness enhancement sheet having a thickness of 125 탆 and a coating layer thickness of 75 nm. The evaluation results are shown in Table 2.

A prism lens layer was formed on the obtained polyester film using an ultraviolet curable acrylic resin to obtain a brightness enhancement sheet. The evaluation results are shown in Table 2.

Example 3

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

Examples 4 to 11

A brightness enhancement sheet was produced in the same manner as in Example 1 except that a coating film having a predetermined thickness was formed using the coating agents B, C or D, J, K, L, N or O described in Table 1. 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 a coating film having a predetermined thickness was formed using the coating agents E, F, G, H, or I described in Table 1. Further, a brightness enhancement sheet was produced using this. The evaluation results are shown in Table 2.

Comparative Example 6

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

Further, the obtained brightness enhancing sheet had poor adhesion between the base film and the prism lens layer, and thus could not be satisfactorily used as the brightness enhancing sheet.

The following components were used as ingredients for forming a coating liquid for forming a coating layer.

Acrylic resin 1:

Methyl methacrylate 60 mol% / ethyl acrylate 30 mol% / 2-hydroxyethyl acrylate 5 mol% / N-methylol acrylamide 5 mol%. Further, acryl was prepared 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 injected into a four-necked flask, and the temperature was raised to 60 占 폚 in a nitrogen stream. Then, 0.5 parts by weight of ammonium persulfate and 0.2 parts by weight of sodium hydrogen sulfite were added as polymerization initiators, A mixture of 59.9 parts by weight of acrylate, 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 was adjusted to have a solution temperature of 60 to 70 ° C over 3 hours . After completion of the dropwise addition, the reaction was continued under stirring in the same temperature range for 2 hours, followed by cooling to obtain an aqueous dispersion of acrylic resin 1 having a solid content of 25%.

Acrylic resin 2:

60 mol% of methyl methacrylate / 30 mol% of ethyl acrylate / 5 mol% of 2-hydroxyethyl acrylate / 5 mol% of acrylamide. Further, acryl was prepared 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 injected into a four-necked flask, and the temperature was raised to 60 DEG C in a stream of nitrogen. Then, 0.5 part by weight of ammonium persulfate and 0.2 part by weight of sodium hydrogen sulfite were added as a polymerization initiator, 60.8 parts by weight of acrylate, 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 was added dropwise over 3 hours while adjusting the solution temperature to 60 to 70 占 폚. After completion of the dropwise addition, the reaction was continued under stirring in the same temperature range for 2 hours, followed by cooling to obtain an aqueous dispersion of acrylic resin 2 having a solid content of 25%.

Acrylic resin 3:

60 mol% of methyl methacrylate / 30 mol% of ethyl acrylate / 5 mol% of 2-hydroxyethyl acrylate / 5 mol% of acrylonitrile. Further, acryl was prepared 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 injected into a four-necked flask, and the temperature was raised to 60 占 폚 in a nitrogen stream. Then, 0.5 parts by weight of ammonium persulfate and 0.2 parts by weight of sodium hydrogen sulfite were added as polymerization initiators, A mixture of 61.4 parts by weight of acrylate, 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 was added dropwise over 3 hours while adjusting the solution temperature to 60 to 70 ° C . After completion of the dropwise addition, the reaction was continued under stirring in the same temperature range for 2 hours, followed by cooling to obtain an aqueous dispersion of acrylic resin 3 having a solid content of 25%.

Cross-linking agent 1:

Glycerol polyglycidyl ether (Denacol EX-313 manufactured by Nagase Chemtech)

Cross-linking agent 2:

The oxazoline group-containing polymer (Epochros K-2030E, manufactured by Nippon Shokubai Co., Ltd.)

Cross-linking agent 3:

Methylol melamine (NIKARAK MX-035 manufactured by Sanwa Chemical Co., Ltd.)

Cross-linking agent 4:

Isocyanate (Elastron H-3 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.)

Particulate matter:

Acrylic filler (average particle diameter 160 nm, MX-100W manufactured by Nippon Shokubai Co., Ltd.)

Wet 1:

Polyoxyethylene distyrenated phenyl ether (Margen A-60 manufactured by Kao Corporation)

Wet 2:

Polyoxyethylene tribenzyl phenyl ether (Margen B-66 manufactured by Kao Corporation)

Wet third:

Polyoxyalkylene alkyl ether (NARO ACTIVE N-70 manufactured by Sanyo Chemical Industries, Ltd.)

Wet Fourth:

Polyoxyalkylene oleyl ether (Pionein D-1504 manufactured by Takemoto Oil & Fats Co.)

Wet 5:

Polyoxyethylene distyrenated phenyl ether (Margen A-90 manufactured by Kao Corporation)

The polyester film for a brightness enhancement sheet of the present invention can be suitably used for various optical uses. And can be suitably used for applications such as a liquid crystal display in which a large screen and a high luminance are advanced, and a luminance improvement sheet base used under high temperature such as a vehicle.

Claims (7)

A polyester film for a brightness enhancement sheet, comprising a polyester film and a coating layer formed thereon, wherein the coating layer comprises an acrylic resin, a crosslinking agent and a polyoxyalkylene phenyl ether,
Wherein the polyoxyalkylene phenyl ether is a polyoxyalkylene phenyl ether having a plurality of aromatic groups. The method according to claim 1,
Wherein the polyoxyalkylene phenyl ether is a polyoxyalkylene phenyl ether having a plurality of styrene groups and / or benzyl groups on the phenyl group. The method according to claim 1,
A polyester film for a brightness enhancement sheet produced by applying a coating liquid constituting a coating layer and then stretching by a sequential biaxial stretching method. The method according to claim 1,
A polyester film for a brightness enhancement sheet produced by applying a coating liquid constituting a coating layer, followed by stretching by a simultaneous biaxial stretching method. A brightness enhancement sheet having a prism layer formed on a polyester film for a brightness enhancement sheet according to any one of claims 1 to 4. The method according to claim 1,
Wherein the acrylic resin of the coating layer is an acrylic resin containing a monomer containing a nitrogen atom as a monomer component. delete