JP2010221614A - Coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester film which has optically excellent characteristics, is excellent in easily adhesive property for a finish coating agent and can be suitably used in various uses. <P>SOLUTION: In the polyester film having coating layers obtained by a coating stretching method on both surfaces, one coating layer contains a fluorine-containing resin as one of constitutional components, and another coating layer has a polyurethane resin which contains polycarbonate structures and carboxyl groups and has a glass transition temperature of 10°C or less and contains a crosslinking agent with functional groups of 10 mmol/g or more, by not greater than 20 wt.%. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polyester film having an application layer with improved optical properties and excellent adhesion to various topcoats.

  Biaxially stretched polyester film is excellent in transparency, dimensional stability, mechanical properties, heat resistance, electrical properties, etc., and in recent years it is used as a base material for antireflection sheets and various protections used in liquid crystal displays such as computers and televisions. Widely used as a base material for optical films such as materials and lens sheets. In these applications, a surface functional layer such as a hard coat layer and an antireflection layer is usually laminated on the film.

  For example, a lens sheet is a sheet-like optical member provided with a prism-like or micro-lens-like lens layer, and is incorporated inside a surface light source device to collect light incident from the light source in the normal direction. This is an optical member that improves the luminance in the viewing direction. In general, a material in which a lens shape or a diffusion surface is formed on one surface of a base film such as polyester is often used.

  Moreover, when using as a surface protection material which has the role which affixes on the surface of another member and protects the member surface, it adheres one side of a film and the member to protect through an adhesive or an adhesive agent.

  However, the biaxially stretched polyester film has an extremely high refractive index in the plane direction, and therefore has a characteristic that the reflectance of light rays is high or the amount of transmitted light is small at the interface with air. May cause problems. For example, a sheet of PMMA or triacetylcellulose has a refractive index of about 1.5 and a visible light reflectance at the air interface of about 4%, whereas a biaxially stretched polyethylene terephthalate film has a refractive index of 1 .65, and the reflectance reaches about 6%.

  In order to solve this problem, for example, Patent Document 1 proposes a method in which a functional layer is provided on one side of a film and an antireflection coating is provided on the opposite side. As this antireflection coating, it is also conceivable to apply one as disclosed in Patent Document 2.

  However, this method has a problem in that it lacks industrial practicality due to an increase in the number of processing steps, resulting in a decrease in yield and an increase in cost.

  In addition, in such applications, when a functional layer is provided on the surface of a polyester film as a base material, there is another drawback that the adhesiveness to the base film is poor depending on the material used as the functional layer.

  As one method for improving the adhesiveness of a biaxially stretched polyester film, a method is known in which various resins are applied to the surface of the polyester film and an application layer having an easy adhesion property is provided.

  For example, Patent Document 3, Patent Document 4, Patent Document 5, and the like disclose the use of a polyester resin, an acrylic resin, a polyurethane resin, or a specific crosslinking agent.

  However, such an existing easily-adhesive coating layer may still not have sufficient adhesion depending on the type of the topcoat layer. For example, in manufacturing a lens sheet, a so-called solventless UV curable paint is often used as a lens layer forming material. However, such a solvent-free top coat has a lower permeation and swelling effect on the easy-adhesion layer than solvent-based top coats, and tends to have insufficient adhesion. In patent document 6, the application layer which consists of a specific polyurethane resin is disclosed and the improvement of adhesiveness is aimed at. However, for such a solventless topcoat, even such a coating layer does not necessarily have sufficient adhesiveness.

Japanese Patent Laid-Open No. 2001-21706 JP 11-305007 A JP-A-8-281890 Japanese Patent Laid-Open No. 11-286092 JP 2000-229395 A JP-A-2-158633

  The present invention has been made in view of the above circumstances, and the problem to be solved is a polyester film having optically excellent characteristics, excellent adhesion to a top coat, and suitable for use in various applications. Is to provide.

  As a result of intensive studies on the above problems, the present inventors have found that the above problems can be solved by providing a coating layer containing a specific type of compound, and the present invention has been completed. .

  That is, the gist of the present invention is a polyester film having coating layers on both sides obtained by a coating stretching method, one coating layer having a fluorine-containing resin as one of the constituent components, and the other coating layer being a polycarbonate. The coating film is characterized in that it contains a polyurethane resin having a structure and a carboxyl group-containing glass transition point of 10 ° C. or less, and does not contain 20% by weight or more of a crosslinking agent having a functional group amount of 10 mmol / g or more.

Hereinafter, the present invention will be described in detail.
The base film of the coated film of the present invention is made of polyester. Such polyesters include dicarboxylic acids such as terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, 4,4′-diphenyldicarboxylic acid, 1,4-cyclohexyldicarboxylic acid or esters thereof. It is a polyester produced by melt polycondensation with glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, and 1,4-cyclohexanedimethanol. Polyesters composed of these acid components and glycol components can be produced by arbitrarily using a commonly used method.
For example, a transesterification reaction between a lower alkyl ester of an aromatic dicarboxylic acid and a glycol, or a direct esterification of an aromatic dicarboxylic acid and a glycol, to form a substantially bisglycol of an aromatic dicarboxylic acid A method is employed in which an ester or a low polymer thereof is formed and then polycondensed by heating under reduced pressure. Depending on the purpose, an aliphatic dicarboxylic acid may be copolymerized.

  Typical examples of the polyester of the present invention include polyethylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, and the like. It may be a polymerized polyester and may contain other components and additives as necessary.

  The polyester film in the present invention can contain particles for the purpose of ensuring the film runnability and preventing scratches. Examples of such particles include inorganic particles such as silica, calcium carbonate, magnesium carbonate, calcium phosphate, kaolin, talc, aluminum oxide, titanium oxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, and molybdenum sulfide. Further, organic particles such as crosslinked polymer particles and calcium oxalate, and precipitated particles during the polyester production process can be used.

  The particle size and content of the particles used are selected according to the use and purpose of the film, but the average particle size is usually in the range of 0.01 to 5.0 μm. If the average particle size exceeds 5.0 μm, the surface roughness of the film becomes too rough, or the particles are likely to fall off from the film surface. When the average particle size is less than 0.01 μm, the surface roughness is too small and sufficient slipperiness may not be obtained. About particle | grain content, it is 0.0003 to 1.0 weight% normally with respect to polyester, Preferably it is the range of 0.0005 to 0.5 weight%. When the particle content is less than 0.0003% by weight, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 1.0% by weight, the transparency of the film is poor. It may be enough. In addition, when it is particularly desired to ensure transparency, smoothness, etc. of the film, it can also be configured so as not to substantially contain particles. Further, various stabilizers, lubricants, antistatic agents and the like can be appropriately added to the film.

  As a film forming method of the film of the present invention, a generally known film forming method can be adopted, and there is no particular limitation. For example, a sheet obtained by melt extrusion is first stretched 2 to 6 times at 70 to 145 ° C. by a roll stretching method to obtain a uniaxially stretched polyester film, and then perpendicular to the previous stretching direction in the tenter. A film is obtained by extending | stretching 2 to 6 times at 80-160 degreeC to the direction, and also heat-processing at 150-250 degreeC for 1 to 600 seconds. Further, at this time, a method of relaxing 0.1 to 20% in the longitudinal direction and / or the transverse direction in the heat treatment zone and / or the cooling zone at the heat treatment outlet is preferable.

  The polyester film in the present invention has a single layer or multilayer structure. In the case of a multilayer structure, the surface layer and the inner layer, or both the surface layer and each layer can be made of different polyesters depending on the purpose.

  The polyester film of the present invention has a coating layer (hereinafter sometimes abbreviated as X) having a fluorine-containing resin as one of the constituent components on one side, and an easily adhesive coating layer (hereinafter, referred to as X). Y may be abbreviated as Y).

  The coating layers (X) and (Y) of the film of the present invention are provided by so-called in-line coating in which a coating layer is provided during film formation, in particular by a coating stretching method in which stretching is performed after coating.

  In-line coating is a method of coating within the process of manufacturing a polyester film. Specifically, it is a method of coating at any stage from melt extrusion of polyester to biaxial stretching and then heat setting and winding. is there. Normally, it is coated on either a substantially amorphous unstretched sheet obtained by melting and quenching, then a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction), or a biaxially stretched film before heat setting. To do. In particular, as a coating stretching method, a method of stretching in the transverse direction after coating on a uniaxially stretched film is excellent. According to such a method, since film formation and coating layer coating can be performed at the same time, there is a merit in manufacturing cost. Stabilize. Moreover, the polyester film before biaxial stretching is first covered with a resin layer constituting the coating layer, and then the base film and the coating layer are firmly adhered by stretching the film and the coating layer simultaneously. become. In addition, the biaxial stretching of the polyester film is achieved by stretching the film in the lateral direction while holding the film end with a tenter clip, so that the film is constrained in the longitudinal / lateral direction and is flat without wrinkles or the like in heat setting. High temperature can be applied while maintaining the nature. Therefore, since the heat treatment performed after coating can be performed at a high temperature that cannot be achieved by other methods, the film forming property of the coating layer is improved, and the coating layer and the polyester film are firmly adhered. As the polyester film provided with the coating layer, the uniformity of the coating layer, the improvement of the film forming property, and the adhesion between the coating layer and the film often produce preferable characteristics.

  In this case, the coating solution to be used is preferably an aqueous solution or an aqueous dispersion for safety reasons in terms of handling, working environment, and water as the main medium, as long as it does not exceed the gist of the present invention. An organic solvent may be contained.

  Next, the coating layer (X) will be described.

  Examples of the fluorine-containing resin used in the coating layer (X) include a copolymer of a fluoroolefin and an alkyl vinyl ether, or a polymer containing a polyfluoroalkyl group. For example, polytetrafluoroethylene, tetrafluoroethylene / perfluoroalkyl vinyl ether polymer, tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / ethylene copolymer, copolymerization of tetrafluoroethylene and heterocyclic fluorine-containing monomer Polymer, polychlorotrifluoroethylene, fluoroalkyl (meth) acrylate polymer, fluoroalkyl (meth) acrylate and other alkyl (meth) acrylate copolymer, vinylidene fluoride, vinylidene fluoride and tetrafluoroethylene copolymer, fluorine Vinylidene chloride and perfluoroalkyl vinyl ether copolymer. In particular, a polymer obtained by reacting a polyfluoroalkyl group-containing ethylenically unsaturated monomer with another ethylenically unsaturated monomer has an affinity with a polyester film, ease of production of a dispersion, etc. From this aspect, it can be suitably used. The polyfluoroalkyl group is usually a hydrocarbon group such as a linear or branched alkyl group or alkenyl group, or an oxygen-containing hydrocarbon group having an oxygen atom ether-bonded to a carbon atom. The hydrocarbon group has a structure in which part or all of the hydrogen atoms are substituted with fluorine atoms. In this case, the number of carbon atoms is preferably 4 to 20, and among these carbon atoms, the number of carbons to which one or more fluorine atoms are bonded is 2 or more, preferably 4 to 18, and particularly preferably 6 to 16. Individual is good. Further, the ratio of the number of fluorine atoms to the number of all atoms bonded to carbon is preferably 60% or more, particularly preferably 80% or more. A perfluoroalkyl group having 6 to 16 carbon atoms is particularly preferable.

  In a film having a coating layer (X) having a fluorine-containing resin as one of the constituent components, when a laminated film having a functional layer on the surface opposite to the coating layer (X) is used, a film having excellent optical characteristics is obtained. can get.

  That is, in the lens sheet in which the lens is formed on the easy-adhesive coating layer (Y) on the opposite surface of the coating layer (X), the lens sheet has a higher luminance than a normal polyester film.

  In addition, the coating layer (X) having the fluorine-containing resin of the present invention as one of the constituent components is characterized by low adhesion to other materials due to its low surface energy. The coating layer X is provided when the easily adhesive coating layer on the opposite surface is likely to cause blocking problems as will be described later, and various measures are required to achieve both easy adhesion performance and anti-blocking performance. Thus, the blocking problem can be easily solved without impairing various characteristics of the easy-adhesion layer.

  Since the biaxially stretched polyester film has a high refractive index, usually a large amount of incident light is reflected, resulting in a decrease in optical properties. By applying an antireflection coating to this surface, it is possible in principle to increase the transmitted light and improve the luminance, but this increases the number of steps, which increases the processing cost and is not realistic. In the present invention, by providing the anti-blocking coating layer with the function of reducing the reflected light at the same time, the optical characteristics can be improved as a method that is extremely easy and industrially practical. In order to reduce the reflected light, it is optimal that the approximate coating layer has a refractive index that is the square root of the refractive index of the polyester film. However, the refractive index in the in-plane direction of the biaxially stretched polyethylene terephthalate film is usually around 1.65, and the material that can efficiently form a coating layer with a square root of less than 1.3 in a large area is Currently not in practical use. Among them, the fluorine-containing resin in the present invention is a material having a relatively low refractive index and excellent anti-blocking performance, and the method of providing a coating layer containing such a resin solves the problems of the present invention. It is suitable for. The thickness of the coating layer for reducing surface reflection is preferably such that the product of the thickness of the coating layer and the refractive index is 1/4 of the wavelength of the target incident light. Although the refractive index of the coating layer is difficult to measure, the thickness of the coating layer is preferably in the range of about 80 to 120 nm. Alternatively, it can be substituted by measuring the surface reflectance. For example, for the purpose of improving the luminance when a lens sheet is used, the absolute reflectance from the surface of the coating layer (X) side of the approximate film should be within the range where the thickness of the coating layer (X) is approximately 40 to 500 nm. For example, it has a minimum value in the visible light range of wavelength 300 to 800 nm. At this time, the minimum wavelength in the visible light region is in the range of 400 to 600 nm, preferably in the range of 450 to 580 nm, whereby the luminance can be improved efficiently. It is possible to determine the optimum thickness by measuring the surface reflectance of the film with the thickness of the coating layer changed depending on which wavelength range the optical characteristics are to be improved in particular.

  In this invention, it has an easily-adhesive coating layer (Y) on the surface opposite to said coating layer (X). The coating layer (Y) contains a polyurethane resin having a polycarbonate structure and a carboxyl group and having a glass transition point of 10 ° C. or less and a crosslinking agent having a functional group amount of 10 mmol / g or more.

  The polyurethane having a polycarbonate structure in the present invention is obtained by using a polycarbonate as one of the main constituent polyols of polyurethane.

  Examples of the polyisocyanate component of the polyurethane having a polycarbonate structure in the present invention include tolylene diisocyanate, phenylene diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, Examples include isophorone diisocyanate.

  Examples of polyol components other than polycarbonates include polyethers such as polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol, polyethylene adipate, polyethylene-butylene adipate, polyesters such as polycaprolactone, acrylic There are polyols and castor oil.

  Examples of chain extenders or crosslinking agents include ethylene glycol, propylene glycol, butanediol, diethylene glycol, trimethylolpropane, hydrazine, ethylenediamine, diethylenetriamine, isophoronediamine, 4,4′-diaminodiphenylmethane, 4,4′- Diaminodicyclohexylmethane, water, etc.

  The polycarbonate polyol can be obtained, for example, by a reaction from diphenyl carbonate and diol, a reaction from dialkyl carbonate and diol, a reaction from alkylene carbonate and diol, or the like. Examples of the diol include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, , 6-hexanediol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, neo Examples include pentyl glycol, 3-methyl-1,5-pentanediol, 3,3-dimethylol heptane and the like.

  Polycarbonate diol is a polystyrene-equivalent number average molecular weight by gel permeation chromatography (GPC), and is preferably 300 to 5,000.

  The polyurethane containing polycarbonate as a constituent component in the present invention may use a solvent as a medium, but preferably uses water as a medium. In order to disperse or dissolve polyurethane in water, there are a forced emulsification type using an emulsifier, a self-emulsification type in which a hydrophilic group is introduced into a polyurethane resin, and a water-soluble type. In particular, a self-emulsification type in which an ionic group is introduced into a skeleton of a polyurethane resin to form an ionomer is preferable because it is excellent in storage stability of the liquid and water resistance, transparency, and adhesiveness of the obtained coating layer. Examples of the ionic group to be introduced include a carboxyl group, sulfonic acid, phosphoric acid, phosphonic acid, quaternary ammonium, and the like, and a carboxyl group is preferable. As a method for introducing a carboxyl group into a urethane resin, various methods can be taken in each stage of the polymerization reaction. For example, at the time of prepolymer synthesis, a resin having a carboxyl group can be used as a copolymerization component, or a component having a carboxyl group can be used as one component such as a polyol, polyisocyanate, or chain extender. In particular, a method in which a desired amount of carboxyl groups is introduced using a carboxyl group-containing diol depending on the amount of this component charged is preferred. For example, dimethylolpropionic acid, dimethylolbutanoic acid, bis- (2-hydroxyethyl) propionic acid, bis- (2-hydroxyethyl) butanoic acid, and the like are copolymerized with a diol used for polymerization of a urethane resin. Can do. The carboxyl group is preferably in the form of a salt neutralized with ammonia, amine, alkali metal, inorganic alkali or the like. Particularly preferred are ammonia, trimethylamine and triethylamine. In such a polyurethane resin, a carboxyl group from which a neutralizing agent is removed in a drying step after coating can be used as a crosslinking reaction point by another crosslinking agent. Thereby, it is possible to further improve the durability, solvent resistance, water resistance, blocking resistance and the like of the obtained coating layer, as well as excellent stability in a liquid state before coating.

  In particular, the polyurethane used in the present invention is preferably a resin comprising a polycarbonate and a polyol, a polyisocyanate, a chain extender having a reactive hydrogen atom, a group that reacts with an isocyanate group, and a compound having at least one anionic group. Moreover, a carboxyl group is contained in resin. The carboxyl group in this case may be a carboxyl group contained as the ionic group for self-emulsification described above.

  The amount of anionic groups in the polyurethane is preferably 0.05% by weight to 8% by weight. When the amount of the anionic group is small, the water solubility or water dispersibility of the polyurethane is poor, and when the amount of the anionic group is large, the water resistance of the coating layer after coating is poor or the film tends to stick to each other due to moisture absorption. Because.

  The content of the polycarbonate component in the polyurethane is usually 20 to 95% by weight, preferably 40 to 90% by weight. When the content is less than 20% by weight, the effect of improving the adhesiveness of polyurethane is poor, and when it exceeds 95% by weight, the coating property is deteriorated.

  The polyurethane resin in the present invention has a glass transition point (hereinafter sometimes abbreviated as Tg) of 10 ° C. or less. When Tg is higher than 10 ° C., easy adhesion is insufficient. The measurement of Tg mentioned here refers to a temperature at which E ″ is maximized by preparing a dry film of polyurethane resin and performing dynamic viscoelasticity measurement.

  Moreover, when the coating layer containing a polyurethane having a low Tg as described above is formed into an easy-adhesive film and then rolled into a roll shape, the front and back of the film stick, and so-called blocking is likely to occur. In order to prevent blocking, a method of increasing the hardness of the coating layer by using a cross-linking agent as a constituent component of the coating layer is generally performed. However, the technique for preventing blocking by the cross-linking agent is the Tg in the present invention. It should be noted that the effect of improving the easy adhesion by the polyurethane resin containing polycarbonate that defines the upper limit of the above may be hindered.

Commonly used crosslinking agents include amino resin-based melamine, benzoguanamine, oxazoline-based, carbodiimide-based, epoxy-based, isocyanate-based, etc., and other cross-linking functional groups as described above in the polymer skeleton. Copolymerized so-called polymer type crosslinking agents are exemplified, but when a crosslinking agent is used in the present invention, it is important not to lower the easy adhesion. In order to crosslink the coating layer while maintaining easy adhesion, it is necessary not to make the density of crosslinking in the coating layer too high. For this purpose, it is preferable not to use too much amount of the crosslinking agent or to use a crosslinking agent having a small amount of functional groups. Here, the functional group amount represents how many cross-linking functional groups exist per weight of the cross-linking agent molecule. For example, the ratio of the cross-linking functional group per molecular weight of the cross-linking agent can be determined by assigning the structure of the cross-linking agent by ¹³ C-NMR and determining the amount ratio of functional groups by ¹ H-NMR. If a cross-linking agent with a high functional group is used, it should be kept in a small amount. A cross-linking agent having a low functional group amount is preferable because its characteristics are easily stabilized regardless of the amount of the functional group used. In the present invention, it is essential that a crosslinking agent having a functional group amount exceeding 10 mmol / g is not contained in an amount of 20% by weight or less based on the entire coating layer. On the other hand, the polymer type crosslinking agent has a low functional group amount and is easy to use. In the present invention, the most preferable mode is to use a polymer type crosslinking agent having an oxazoline group for a polyurethane containing a carboxyl group.

  Moreover, in this invention, in order to increase the slipperiness of a coating film and to prevent blocking, you may contain particle | grains. The content of the particles is not particularly specified, but if it is too small, the effect is not exerted. If it is too much, the effect of slipperiness and blocking resistance is high, but the transparency of the coating layer is reduced, or the coating layer The continuity of the film may be impaired, and the coating film strength may be reduced, or the easy adhesion may be reduced. Specifically, the lower limit is preferably 1% by weight, more preferably 3% by weight. The upper limit is preferably 15% by weight or less, more preferably 10% by weight or less. By this method, it is possible to achieve both easy adhesion performance and easy slipperiness and anti-blocking performance.

  As the particles, for example, inorganic particles such as silica, alumina, and metal oxide, or organic particles such as crosslinked polymer particles can be used. In particular, silica particles are preferred from the viewpoint of dispersibility in the coating layer and transparency of the resulting coating film.

  If the particle size is too small, the effect of preventing blocking is difficult to obtain, and if it is too large, dropping off from the coating film tends to occur. The average particle size is preferably about 1/2 to 10 times the thickness of the coating layer. Furthermore, if the particle size is too large, the transparency of the coating layer may be inferior, so the average particle size is preferably 300 nm or less, and more preferably 150 nm or less. The average particle diameter of the particles described here can be obtained by measuring the 50% average diameter of the number average of the particle dispersion with Microtrac UPA (Nikkiso Co., Ltd.).

  The ratio of the polyurethane resin in the coating layer is not limited. This is because the coating layer may be composed of polyurethane as a main component, but the adhesion can be improved by simply mixing the polyurethane with a coating layer mainly composed of other easily adhesive resin. , And can be selected as appropriate within the range in which the desired characteristics appear. However, if the amount is too small, it is difficult to obtain the effect. Therefore, if the lower limit is 20% or 40%, more preferably 50% or more, the effect is high.

  The coating solution for providing the coating layer can contain components other than those described above as necessary. For example, surfactants, other binders, antifoaming agents, coatability improvers, thickeners, antioxidants, ultraviolet absorbers, foaming agents, dyes, pigments and the like. These additives may be used alone or in combination of two or more as necessary.

The coating amount of the coating layer provided on the polyester film (Y), when viewed as a final coating, typically 0.002~1.0g / ^{m 2,} preferably from 0.005 to 0.5 / ^{m 2} More preferably, it is 0.01 to 0.2 g / m ² . If the coating amount is less than 0.002 g / m ^2, sufficient adhesion performance may not be obtained, and a coating layer exceeding 1.0 g / m ² tends to deteriorate the appearance and transparency and increase the cost. .

  As a method for applying the coating solution to the polyester film, for example, a coating technique as shown in “Coating system” published by Yuji Harasaki, Tsuji Shoten, published in 1979 can be used. Specifically, air doctor coater, blade coater, rod coater, knife coater, squeeze coater, impregnation coater, reverse roll coater, transfer roll coater, gravure coater, kiss roll coater, cast coater, spray coater, curtain coater, calendar coater And a technique such as an extrusion coater.

  In addition, in order to improve the applicability | paintability to the film of a coating agent and adhesiveness, you may give a chemical process, a corona discharge process, a plasma process, etc. to a film before application | coating.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In addition, the evaluation method in an Example and a comparative example is as follows.

(1) Glass transition point (Tg)
The polyurethane resin solution or aqueous dispersion is dried in a Teflon (registered trademark) petri dish so that the film thickness after drying is 500 μm to obtain a film. As drying conditions, after drying at room temperature for one week, further drying at 120 ° C. for 10 minutes. The obtained film was cut into a width of 5 mm, and set in a measuring device so that the distance between chucks was 20 mm in a dynamic viscoelasticity measuring device (DVA-200 type) manufactured by IT Measurement Control Co., Ltd. Until the temperature is increased at a rate of 10 ° C./min, measurement is performed at a frequency of 10 Hz. The point where E ″ was the maximum was taken as Tg.

(2) Absolute reflectance A black tape (vinyl tape VT-50 manufactured by Nichiban Co., Ltd.) was applied from one side to the surface opposite to the reflectance measurement surface of the film while being weighted with a roller from one side and placed for 12 hours. Using UV-visible spectrophotometer V-570 and automatic absolute reflectance measuring device AM-500N manufactured by Co., Ltd., synchronous mode, incident angle 5 °, N-polarized light, response Fast, data collection interval 1.0 nm, bandwidth 10 nm, The absolute reflectance from the film measurement surface was measured at a scanning speed of 1000 m / min and a wavelength range of 300 to 800 nm.

(3) Formation of the lens layer The cross section is an isosceles triangle having an apex angle of 100 degrees and a low angle of 40 degrees, and a UV cured acrylate is used as a lens layer forming resin on a steel sheet having a prism shape with a pitch of 50 μm. Z9002A (manufactured by JSR) was dropped, and then the lens-forming surface of the film was placed on the steel plate onto which the lens layer-forming resin was dropped, and the film was superposed while being pressed with a 2 kg weight roller.
Then, immediately, using a high-pressure mercury lamp with an energy of 160 W / cm, curing is performed by irradiating with ultraviolet rays through the film side for about 10 seconds at an irradiation distance of 100 mm, peeling off the film from the prism mold, and one side of the film A lens sheet provided with a lens layer was prepared.

(4) Adhesiveness The lens layer of the lens sheet prepared in the above (3) is cross-cut so that there are 100 grids in an inch width, and immediately, using the cello tape (registered trademark) three times at the same location. A quick peel test was performed, and the adhesion was evaluated by the peel area. The judgment criteria are as follows.
A: Number of cross-cuts = 0
○: 1 ≦ Number of cross cuts ≦ 10
Δ: 11 ≦ number of cross-cuts ≦ 20
×: 21 <Number of cross-cuts peeled ××: Whole surface peeled

(5) Blocking resistance Two polyester films to be measured are prepared, one surface of one film and the other surface of the other film are overlapped, and an area of 12 cm × 10 cm is pressed. The conditions are 40 ° C., 80% RH, 10 kg / cm ² , 20 hours. Thereafter, the films are peeled according to the method specified in ASTM-D-1893, and the peel load is measured. It can be said that the lighter the peeling load, the better the blocking. If the load is less than 150 g / 10 cm, it can be said that there is no problem, and if it is less than 100 g / 10 cm, it can be said that it is good. When the load exceeds 150 g / 10 cm, there may be a problem in practice.

(5) Luminance of lens sheet The lens sheet prepared by the method of (3) above was placed on a flat illuminator HF-SL-A48LCF manufactured by Dentsu Sangyo with the lens as the upper surface. Using a CS-200 manufactured by Konica Minolta Sensing Co., Ltd., the measurement angle was 1 °, the distance between the sample and the luminance meter was 500 mm, and the luminance value (cd / m ² ) was measured.

The polyester raw materials used in Examples and Comparative Examples are as follows.
(Polyester 1): Polyethylene terephthalate having an intrinsic viscosity of 0.66 substantially free from particles (Polyester 2): containing 0.3% by weight of amorphous silica having an average particle diameter of 1.6 μm 61 polyethylene terephthalate

Moreover, the following was used as a coating composition. However, “part” in the text represents the weight ratio in the resin solid content.
(L1): Dickguard F-90N (manufactured by Dainippon Ink & Chemicals), which is a water-dispersed resin containing a perfluoro group
(L2): Fluorosurf FS-6030 (manufactured by Fluoro Technology), which is a fluorine-based aqueous coating agent
(L3): Asahi Guard AG-E060 (manufactured by Asahi Glass), which is a water-dispersed resin containing a perfluoro group

(U1): 400 parts of polycarbonate polyol composed of 1,6-hexanediol and diethyl carbonate having a number average molecular weight of 2000, 10.4 parts of neopentyl glycol, 58.4 parts of isophorone diisocyanate, and 74. parts of dimethylolbutanoic acid. A polyurethane resin aqueous dispersion (U2) obtained by neutralizing a 3 part prepolymer with triethylamine and extending the chain with isophoronediamine, and having a Tg of −30 ° C .: consisting of 1,6-hexanediol and diethyl carbonate It is obtained by neutralizing a prepolymer comprising 320 parts of polycarbonate polyol having a number average molecular weight of 800, 505.7 parts of hydrogenated diphenylmethane diisocyanate and 148.6 parts of dimethylolbutanoic acid with triethylamine and extending the chain with isophoronediamine. , Tg Aqueous dispersion of 7 ° C. of the polyurethane resin (U3): RU-40-350 having a carboxyl group, Tg is -20 ° C. Water-dispersible polycarbonate polyurethane resin (manufactured by Stahl)
(U4): Takelac W-511 (Mitsui Chemical Polyurethane Co., Ltd.), which is a water-dispersed polycarbonate polyurethane resin having a carboxyl group and a Tg of 35 ° C.
(U5): 180 parts of a polycarbonate polyol composed of 1,6-hexanediol and diethyl carbonate having a number average molecular weight of 400, 520 parts of a polyester polyol composed of terephthalic acid and ethylene glycol, and 420. methylenebis (4-cyclohexylisocyanate). An aqueous dispersion of polyurethane resin having a Tg of 60 ° C. obtained by neutralizing a prepolymer comprising 4 parts and 121.8 parts of dimethylolbutanoic acid with triethylamine and extending the chain with isophoronediamine (U6): 3- 400 parts of a polyester polyol having a number average molecular weight of 3000 consisting of methyl-1,5-pentanediol and adipic acid, 41.7 parts of neopentyl glycol, 133 parts of isophorone diisocyanate, and 29.7 parts of dimethylolbutanoic acid. The The polymer was neutralized with triethylamine, is obtained by chain extension with isophorone diamine, aqueous dispersion of Tg is -47 ° C. the polyurethane resin

(F1): Silica sol aqueous dispersion having an average particle size of 0.07 μm (F2): Silica sol aqueous dispersion having an average particle size of 0.44 μm

(C1): Epocross WS-500 (manufactured by Nippon Shokubai Co., Ltd.), which is a polymer type cross-linking agent in which an oxazoline group is branched to an acrylic resin. Oxazoline group amount = 4.5 mmol / g
(C2): Becamine J-101 (Dainippon Ink Chemical Co., Ltd.) which is methoxymethylol melamine. Functional group (methoxy, methylol, imino group) amount = 18 mmol / g
(S1): Surfactant Surfynol 465 (manufactured by Air Products)

Example 1:
A blend of polyester 1 and polyester 2 at a weight ratio of 90/10 was used as a raw material for layer A, and polyester 1 alone was used as a raw material for layer B. To the outer layer (surface layer) and the B layer as an intermediate layer, and coextruded in a layer configuration of two types and three layers (A / B / A) using an electrostatic adhesion method. The film was cooled and solidified in close contact with a mirror surface cooling drum having a surface temperature of 40 to 50 ° C. to prepare an unstretched polyethylene terephthalate film. This film was stretched 3.7 times in the longitudinal direction while passing through a heating roll group at 85 ° C. to obtain a uniaxially oriented film. The coating composition (X-1) as shown in the following Table 1 is applied to one surface (referred to as the first surface) of this uniaxially oriented film, and the coating composition (Y) as defined on the opposite surface (referred to as the second surface). -1) was applied. Next, the film was guided to a tenter stretching machine, and the coating composition was dried using the heat, stretched 4.0 times in the width direction at 100 ° C., and further subjected to heat treatment at 230 ° C. The film was subjected to a relaxation treatment of 2% to obtain a coated film in which a coating layer having an amount as shown in Table 2 below was provided on a biaxially oriented polyethylene terephthalate film having a film thickness of 100 μm. The properties of this film are shown in Table 3 below. However, the coating amount in Table 2 is a value in terms of solid content of the coating layer in the state of the finally obtained biaxially oriented polyethylene terephthalate film. In Table 3, the adhesion evaluation was performed on the second surface, and the luminance evaluation was performed by forming a lens layer on the second surface. The blocking resistance evaluation was performed in such a manner that the first surface and the second surface face each other. The same applies to the following examples and comparative examples.

Comparative Example 1:
In the same process as Example 1, the coating film which provided the coating layer of the quantity shown in Tables 1 and 2 only on one side (second side) on the substrate film whose film thickness is 100 micrometers was obtained. The properties of this film are shown in Table 3.

Examples 2-16, Comparative Examples 2-6:
In the same process as in Example 1, the coating solution was changed as shown in Tables 1 and 2, and a coating film in which the coating layer of the amount shown in Tables 1 and 2 was provided on a base film having a film thickness of 100 μm was prepared. Obtained. The properties of this film are shown in Table 3.

Comparative Example 7:
In the same process as Example 1, the coating film which provided the coating layer of the quantity shown in Tables 1 and 2 only on one side (the 1st side) on the substrate film whose film thickness is 100 micrometers was obtained. As shown in Tables 1 and 2 on the second surface side of the film, the coating composition having the same component ratio (Y-1) was barred off-line so that the coating amount after drying was 0.05 g / m ^2. The coated film was applied and heat treated at a dryer set temperature of 100 ° C. for 5 seconds to obtain a coated film. As shown in Table 3, the characteristics of this film were insufficient adhesiveness due to insufficient drying and curing of the easy adhesion layer.

Comparative Example 8:
A coating film was obtained in the same manner as in Comparative Example 7, except that the dryer set temperature for offline coating was 180 ° C. This film was extremely inferior in flatness due to shrinkage of the film in the dryer and wrinkling. Other characteristics are shown in Table 3.

  The coating amount in Table 2 is in terms of dry solid content on the finally obtained biaxially stretched polyester film.

  The adhesion evaluation in Table 3 was performed on the second surface. The blocking resistance evaluation was performed in such a manner that the first surface and the second surface face each other. The luminance evaluation was performed by forming a lens layer on the second surface.

  The film of the present invention can be suitably used as a biaxially stretched polyester film in applications requiring excellent optical properties and adhesion.

Claims (1)

It is a polyester film having a coating layer obtained on both sides by a coating stretching method, one coating layer having a fluorine-containing resin as one of the constituent components, and the other coating layer having a polycarbonate structure and a glass transition having a carboxyl group A coated film comprising a polyurethane resin having a point of 10 ° C. or lower and a crosslinking agent having a functional group amount of 10 mmol / g or more and not containing 20 wt% or more.