JP2017177681A - Laminate film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminate film that allows the interference unevenness caused by light reflection to be reduced at a high level, and also has good adhesiveness to a surface functional layer such as a light-diffusing layer or an antisticking layer and can be, therefore, suitably used in optical applications including a backlight unit of a liquid crystal display device.SOLUTION: A laminate film has a coating layer containing a resin having a benzyl group on at least one side of a film.SELECTED DRAWING: None

Description

  The present invention relates to a laminated film, for example, a liquid crystal display backlight unit or the like, which reduces interference unevenness due to light reflection, and has good adhesion to a surface functional layer such as a light diffusion layer or an anti-sticking layer. The present invention relates to a laminated film suitable for various necessary optics.

  In recent years, liquid crystal displays have been widely used as display devices for televisions, personal computers, digital cameras, mobile phones and the like. Since these liquid crystal displays do not have a light emitting function by a liquid crystal display unit alone, a method of displaying by irradiating light using a backlight from the back side is widespread.

  The backlight system has a structure called an edge light type or a direct type. Recently, there is a tendency to reduce the thickness of liquid crystal displays, and an edge light type is increasingly used. The edge light type is generally configured in the order of a reflection sheet, a light guide plate, a light diffusion sheet, and a prism sheet. As the flow of light, the light incident on the light guide plate from the backlight is reflected by the reflection sheet and emitted from the surface of the light guide plate. The light beam emitted from the light guide plate enters the light diffusion sheet, is diffused and emitted by the light diffusion sheet, and then enters the next existing prism sheet. The light beam is condensed in the normal direction by the prism sheet and emitted toward the liquid crystal layer.

  The light diffusion sheet used in this configuration is used for uniformly diffusing transmitted light in multiple directions, and needs to have high light diffusibility and high light transmission. As the light diffusing sheet, the surface of the sheet is roughened by heating and pressing during finishing, so-called embossing, or a light diffusing layer made of a transparent resin containing particles on a transparent base film The one made by coating is known. In the light diffusion sheet, a binder and a small amount of beads are used to prevent sticking (partial adhesion) between the light diffusion sheet and the light guide plate on the surface of the transparent base film opposite to the light diffusion layer. It has also been proposed to form a sticking-preventing layer containing Pt (Patent Documents 1 to 3).

  As a transparent substrate film for forming a light diffusion sheet, in order to improve adhesion to the light diffusion layer or the anti-sticking layer, an easily adhesive coating layer is generally provided as an intermediate layer thereof. .

  In recent years, in the field of liquid crystal displays, there has been a demand for larger screens and higher image quality. Along with this, the level of demand for suppression of iris-like colors (interference unevenness) particularly under fluorescent lamps is increasing. In addition, fluorescent lamps have become a three-wavelength type for daylight color reproducibility, and interference unevenness is more likely to occur. Because light is diffused to the light diffusion layer side, interference unevenness is unlikely to occur.However, because the sticking prevention layer side is not highly diffusible, interference unevenness is likely to occur compared to the light diffusion layer. is there. Therefore, especially on the anti-sticking layer side, the optical design of the coating layer laminated on the polyester film has become important. Specifically, a coating layer having a higher refractive index adjusted to be between the refractive index of the film substrate and the refractive index of the resin used for the light diffusion layer or the anti-sticking layer is required.

  If the refractive index of the coating layer is not adjusted, the occurrence of uneven interference may not be sufficiently suppressed. When a film in which interference unevenness is conspicuously generated is used as a liquid crystal display, various problems due to deterioration in visibility may become apparent. In addition, various problems caused by the deterioration of visibility caused by interference unevenness may cause eye fatigue and health problems.

  Therefore, it is desired to improve interference unevenness by increasing the refractive index of the coating layer. For example, as a method of reducing interference unevenness on the light diffusion layer side, a method of increasing the refractive index of the coating layer by combining an aqueous polyester resin and a metal chelate compound such as a water-soluble titanium chelate compound has been proposed ( Patent Document 4). However, due to the instability of the metal chelate compound in an aqueous solution, depending on the combination, the stability of the coating solution may not be sufficient, and when performing production for a long time, there is a possibility of increasing the liquid exchange work. Moreover, in the said coating layer structure, adhesiveness may not be enough depending on resin used for a light-diffusion layer, or the conditions of an endurance test.

  It is also known to use a compound having a condensed polycyclic aromatic as another technique for increasing the refractive index of the coating layer (Patent Documents 5 and 6). In recent years, however, hard coat layers and antireflection layers formed on coating layers for antireflection films are generally refracted compared to light diffusion layers and antisticking layers formed for light diffusion films. The rate is high. Therefore, the refractive index of the coating layer suitably used for the antireflection film is very high. On the contrary, for the light diffusing sheet, the refractive index is too high, thereby causing interference unevenness. Further, the hard coat layer or antireflection layer formed for the antireflection film and the light diffusion layer or antisticking layer formed for the light diffusion film have different components.

  For this reason, even if a coating layer showing good adhesion is used for an antireflection film, it does not necessarily show perfect adhesion to be used for a light diffusion film, so some device is required.

JP 2000-89007 A JP 2004-4598 A JP 2007-286166 A JP 2006-20993 A JP 2006-175628 A JP 2007-181994 A

  The present invention has been made in view of the above circumstances, and its solution is to reduce the occurrence of interference unevenness due to reflection of light and to provide good adhesion to surface functional layers such as a light diffusion layer and an anti-sticking layer. It is intended to provide a laminated film that can be suitably used in, for example, a backlight unit of a liquid crystal display.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the use of a laminated film having a specific configuration can easily solve the above-described problems, and have completed the present invention.

  That is, the gist of the present invention resides in a laminated film having a coating layer containing a resin having a benzyl group on at least one surface of the film.

  According to the film of the present invention, when various surface functional layers such as a light diffusing layer and an anti-sticking layer are formed, there is little interference unevenness due to reflection of external light, and excellent adhesion to various surface functional layers. A material film can be provided, and its industrial value is high.

  As the film base of the laminated film in the present invention, conventionally known ones can be used, for example, polyester film, polycarbonate film, fluororesin film, polyimide film, triacetyl cellulose film, polyolefin film, polyacrylate film, Examples thereof include a polystyrene film, a polyvinyl chloride film, a polyvinyl alcohol film, an ethylene vinyl acetate copolymer film, an ethylene-vinyl alcohol copolymer film, and a nylon film. In particular, in order to develop into various applications, it is preferable to have heat resistance, and polyester film, polycarbonate film, fluororesin film, and polyimide film are preferably used, and polyester is further considered in view of transparency, moldability, and versatility. A film is used more suitably.

  The film constituting the laminated film in the present invention may have a single-layer structure or a multilayer structure, and may have a multilayer structure of four or more layers as long as the gist of the present invention is not exceeded other than the two-layer or three-layer structure. There is no particular limitation.

  As a polyester film used as the film of the present invention, the corresponding polyester may be a homopolyester or a copolyester. In the case of a homopolyester, those obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol are preferred. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Typical polyester includes polyethylene terephthalate and the like. On the other hand, the dicarboxylic acid component of the copolyester includes isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxybenzoic acid, etc.), etc. 1 type or 2 types or more are mentioned, As a glycol component, 1 type or 2 types or more, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexane dimethanol, neopentyl glycol, is mentioned.

  There is no restriction | limiting in particular as a polymerization catalyst of polyester, A conventionally well-known compound can be used, For example, an antimony compound, a titanium compound, a germanium compound, a manganese compound, an aluminum compound, a magnesium compound, a calcium compound etc. are mentioned. Among these, titanium compounds and germanium compounds are preferable because they have high catalytic activity, can be polymerized in a small amount, and the amount of metal remaining in the film is small, so that the brightness of the film becomes high. Furthermore, since a germanium compound is expensive, it is more preferable to use a titanium compound.

  In the case of polyester using a titanium compound, the titanium element content is preferably 50 ppm or less, more preferably 1 to 20 ppm, and still more preferably 2 to 10 ppm. If the content of the titanium compound is too high, the polyester may be deteriorated in the process of melt-extruding the polyester, resulting in a strong yellowish film. If the content is too low, the polymerization efficiency is poor and the cost is low. In some cases, a film having a sufficient strength or a sufficient strength cannot be obtained. Moreover, when using the polyester by a titanium compound, it is preferable to use a phosphorus compound in order to reduce the activity of a titanium compound for the purpose of suppressing deterioration in the step of melt extrusion. As the phosphorus compound, orthophosphoric acid is preferable in view of the productivity and thermal stability of the polyester. The phosphorus element content is preferably in the range of 1 to 300 ppm, more preferably 3 to 200 ppm, and still more preferably 5 to 100 ppm with respect to the amount of polyester to be melt-extruded. If the content of the phosphorus compound is too large, it may cause gelation or foreign matter. If the content is too small, the activity of the titanium compound cannot be lowered sufficiently, and the yellowish It may be a film.

  As the polycarbonate film that can be used as the laminated film of the present invention, a conventionally known polycarbonate can be used, but a type containing a bisphenol A structure is particularly preferable.

  As the fluororesin film that can be used as the laminated film of the present invention, a conventionally known fluororesin can be used. For example, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetra Examples include fluoroethylene-perfluoroalkyl vinyl ether copolymers.

  The film of the present invention may contain an ultraviolet absorber for improving the weather resistance of the film and preventing the deterioration of the liquid crystal and the like. The ultraviolet absorber is not particularly limited as long as it is a compound that absorbs ultraviolet rays and can withstand the heat applied in the film production process.

  As the ultraviolet absorber, there are an organic ultraviolet absorber and an inorganic ultraviolet absorber. From the viewpoint of transparency, an organic ultraviolet absorber is preferable. Although it does not specifically limit as an organic type ultraviolet absorber, For example, a cyclic imino ester type, a benzotriazole type, a benzophenone type etc. are mentioned. From the viewpoint of durability, a cyclic imino ester type and a benzotriazole type are more preferable. It is also possible to use two or more ultraviolet absorbers in combination.

  In the film of the present invention, particles can be blended mainly for the purpose of imparting slipperiness and preventing the occurrence of scratches in each step. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Examples include inorganic particles such as magnesium, kaolin, aluminum oxide, and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin, and benzoguanamine resin. Furthermore, it is also possible to use precipitated particles in which a part of a metal compound such as a catalyst is precipitated and finely dispersed during the film production process.

The shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color, etc.
These series of particles may be used in combination of two or more as required.

  The average particle diameter of the particles is preferably 5 μm or less, more preferably 0.01 to 3 μm. By using the average particle diameter within the above range, an appropriate surface roughness is imparted to the film, and in the case where various functional layers and the like are formed in a subsequent process, problems are unlikely to occur.

  Furthermore, the particle content in the film is preferably less than 5% by weight, more preferably in the range of 0.0003 to 3% by weight. When there are no or few particles, the transparency of the film becomes high and the film becomes a good film, but the slipperiness may be insufficient. There are cases where improvement is required. Moreover, when there is too much particle content, even if a functional layer is formed, haze will not fully fall, and transparency of a film may be inadequate.

  The method for adding particles to the film is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at an arbitrary stage for producing a film constituting each layer, but it is preferably added after completion of esterification or transesterification.

  In addition to the above-mentioned particles, conventionally known antioxidants, antistatic agents, thermal stabilizers, lubricants, dyes, pigments and the like can be added to the film in the present invention as necessary.

  The thickness of the film in the present invention is not particularly limited as long as it can be formed as a film, but is 10 to 350 μm, more preferably 15 to 300 μm, and still more preferably 20 to 250 μm.

  Next, although the manufacture example of the film in this invention is demonstrated concretely, it is not limited to the following manufacture examples at all. In general, the resin is melted, formed into a sheet, and stretched for the purpose of increasing the strength and the film is formed. As an example, the case where the polyester film mentioned above is manufactured is introduced. A method of drying the pellet-shaped polyester raw material and cooling and solidifying the molten film extruded from the die with a cooling roll using an extruder is preferred. In this case, in order to improve the flatness of the film, it is preferable to improve the adhesion between the film and the rotary cooling drum, and an electrostatic application adhesion method or a liquid application adhesion method is preferably employed. Next, the obtained unstretched film is stretched in the biaxial direction. In that case, first, the unstretched film is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, the film is stretched in the direction perpendicular to the first stretching direction. In that case, the stretching temperature is usually 70 to 170 ° C., and the stretching ratio is usually 3.0 to 7 times, preferably 3.5 to 6 times. is there. Subsequently, heat treatment is performed at a temperature of 180 to 250 ° C. under tension or under relaxation within 30% to obtain a biaxially oriented film. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges.

  In the present invention, the simultaneous biaxial stretching method can be adopted for the production of the film constituting the laminated film. The simultaneous biaxial stretching method is a method in which the above-mentioned unstretched sheet is usually stretched and oriented in the machine direction and the width direction at a temperature controlled normally at 70 to 120 ° C., preferably 80 to 110 ° C. Is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in terms of area magnification. Subsequently, heat treatment is performed at a temperature of 170 to 250 ° C. under tension or under relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, a conventionally known stretching method such as a screw method, a pantograph method, or a linear driving method can be employed.

  Next, formation of the coating layer which comprises the laminated | multilayer film in this invention is demonstrated. Regarding the coating layer, it may be provided by in-line coating, which treats the film surface during the film formation process, or may be applied off-system on a once manufactured film. More preferably, it is formed by in-line coating.

  In-line coating is a method in which coating is performed within the film production process, and specifically, a method in which coating is performed at any stage from melt extrusion of a resin to heat setting after stretching and winding up. Usually, it is coated on any of an unstretched sheet obtained by melting and quenching, a stretched uniaxially stretched film, a biaxially stretched film before heat setting, and a film after heat setting and before winding. Although not limited to the following, for example, in sequential biaxial stretching, a method of stretching in the transverse direction after coating a uniaxially stretched film stretched in the longitudinal direction (longitudinal direction) is particularly excellent. According to such a method, film formation and coating layer formation can be performed at the same time, so there is an advantage in manufacturing cost. In addition, in order to perform stretching after coating, the thickness of the coating layer can be changed by the stretching ratio. Compared to offline coating, thin film coating can be performed more easily. Further, by providing the coating layer on the film before stretching, the coating layer can be stretched together with the base film, whereby the coating layer can be firmly adhered to the base film. Furthermore, in the manufacture of biaxially stretched films, the film can be restrained in the vertical and horizontal directions by stretching while gripping the film edges with clips, etc., and flatness is not generated in the heat setting process. High temperature can be applied while maintaining 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 can be improved, and the coating layer and the base film can be more firmly adhered to each other. Furthermore, it can be set as a firm coating layer, and performances such as adhesion to various functional layers that can be formed on the coating layer and wet heat resistance can be improved.

  In the present invention, it is an essential requirement to have a coating layer containing a resin having a benzyl group on at least one surface of the film.

  In the present invention, the coating layer is provided for the purpose of adjusting the refractive index. It is preferable that the optimum refractive index of the coating layer in which interference unevenness hardly occurs is designed to be close to the geometric mean of the refractive index of the film and the refractive index of the surface functional layer such as the light diffusion layer or the anti-sticking layer. For example, in the case of a polyester film, when the refractive index is about 1.65 and the refractive index of the resin used for the light diffusion layer or the anti-sticking layer is about 1.50, the polyester film is positioned in the middle of these layers. The ideal refractive index of the coating layer to be applied is about 1.57, which is usually a high refractive index that is difficult to achieve with only the acrylic resin as the coating layer component used for imparting easy adhesion. . Therefore, it is necessary to use a resin having a benzyl group, which requires a higher refractive index adjustment and can be designed with a compound that can prevent a decrease in adhesion. A method of forming a layer is effective.

  The resin having a benzyl group is not particularly limited as long as it is a resin having a benzyl group as a substitution, and examples thereof include conventionally known resins such as acrylic resins, polyester resins, and urethanes. Among these, acrylic resins are preferred because they are easy to synthesize, can introduce many benzyl groups, and have good adhesion.

  The acrylic resin having a benzyl group is a polymer composed of a polymerizable monomer having a carbon-carbon double bond, as typified by an acrylic or methacrylic monomer having a benzyl group. These may be a homopolymer or copolymer of a polymerizable monomer having a benzyl group-containing acrylic or methacrylic carbon-carbon double bond, and may be an acrylic or methacrylic carbon-carbon having a benzyl group. A copolymer of a polymerizable monomer having a double bond and an acrylic monomer having no benzyl group or a polymerizable monomer having a methacrylic carbon-carbon double bond may be used. From the viewpoint of being able to contain many benzyl groups and obtaining a higher refractive index, homopolymerization of a polymerizable monomer having a benzyl group-containing acrylic or methacrylic carbon-carbon double bond or A copolymer is more preferred.

  Moreover, the copolymer of said polymer and other polymers (for example, polyester, polyurethane, etc.) is also contained. For example, a block copolymer or a graft copolymer. Alternatively, it may be a polymer obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyester solution or a polyester dispersion (in some cases, a mixture of polymers). Similarly, a polymer (in some cases, a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyurethane solution or polyurethane dispersion is also included. Similarly, a polymer obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in another polymer solution or dispersion (in some cases, a polymer mixture) is also included. Moreover, in order to improve adhesiveness more, it is also possible to contain a hydroxyl group and an amino group.

  The polymerizable monomer having a carbon-carbon double bond having no benzyl group is not particularly limited, but as typical compounds, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, Various carboxyl group-containing monomers such as fumaric acid, maleic acid, citraconic acid, and salts thereof; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, Various hydroxyl group-containing monomers such as monobutyl hydroxyl fumarate and monobutyl hydroxy itaconate; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) Various (meth) such as acrylate Crylates; various nitrogen-containing compounds such as (meth) acrylamide, diacetone acrylamide, N-methylolacrylamide or (meth) acrylonitrile; various styrenes such as styrene, α-methylstyrene, divinylbenzene, vinyltoluene Various vinyl esters such as derivatives, vinyl propionate; various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane; phosphorus-containing vinyl monomers; vinyl chloride, Examples include various vinyl halides such as biliden chloride; various conjugated dienes such as butadiene.

  The ratio of the benzyl group contained in the resin having a benzyl group is preferably 10% by weight or more, more preferably 15% by weight or more, and further preferably 20 to 60% by weight as the ratio of the entire resin. By using it in the above range, the refractive index of the coating layer can be increased, and interference unevenness can be reduced.

  In the present invention, in order to supplementarily adjust the refractive index of the coating layer, a high refractive index material other than a resin having a benzyl group can be used in combination. For example, condensed polycyclic aromatic-containing compounds such as naphthalene structure and fluorene structure, fine particles of metal oxide, compounds containing many aromatic structures such as bisphenol A structure, compounds containing sulfur element and halogen element, etc. Is mentioned.

  In the laminated film of the present invention, when a surface functional layer such as a light diffusing layer and an anti-sticking layer is laminated on the coating surface, adhesion is improved, interference unevenness is reduced, transparency is improved, and the coating appearance is improved. For example, various polymers can be used in combination.

  Specific examples of the polymer include acrylic resin having no benzyl group, polyester resin, urethane resin, polyvinyl (polyvinyl alcohol, polyvinyl chloride, vinyl chloride vinyl acetate copolymer, etc.), polyalkylene glycol, polyalkyleneimine, methylcellulose. , Hydroxycellulose, starches and the like. Among these, an acrylic resin, a polyester resin, and a urethane resin that do not have a benzyl group are more preferably used from the viewpoint of improving the adhesion between the light diffusion layer and the surface functional layer such as an anti-sticking layer.

  In the laminated film of the present invention, a crosslinking agent may be used in combination in the formation of the coating layer as long as the gist of the present invention is not impaired. Various known crosslinking agents can be used as the crosslinking agent, and examples include melamine compounds, oxazoline compounds, epoxy compounds, carbodiimide compounds, isocyanate compounds, silane coupling compounds, hydrazide compounds, aziridine compounds, and the like. Among these, melamine compounds, oxazoline compounds, carbodiimide compounds, and isocyanate compounds are preferable from the viewpoint of improving adhesion. Further, the melamine compound has a high refractive index and is a useful compound for adjusting the refractive index of the coating layer.

  The melamine compound is a compound having a melamine skeleton in the compound. For example, an alkylolized melamine derivative, a compound partially or completely etherified by reacting an alcohol with an alkylolated melamine derivative, and these Mixtures can be used. As alcohol used for etherification, methyl alcohol, ethyl alcohol, isopropyl alcohol, n-butanol, isobutanol and the like are preferably used. Moreover, as a melamine compound, either a monomer or a multimer more than a dimer may be sufficient, or a mixture thereof may be used. Further, a product obtained by co-condensing urea or the like with a part of melamine can be used, and a catalyst can be used to increase the reactivity of the melamine compound.

  The oxazoline compound is a compound having an oxazoline group in the molecule, and a polymer containing an oxazoline group is particularly preferable, and can be prepared by polymerization of an addition polymerizable oxazoline group-containing monomer alone or with another monomer. Addition polymerizable oxazoline group-containing monomers include 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, and the like can be mentioned, and one or a mixture of two or more thereof can be used. Among these, 2-isopropenyl-2-oxazoline is preferred because it is easily available industrially. The other monomer is not limited as long as it is a monomer copolymerizable with an addition polymerizable oxazoline group-containing monomer. For example, alkyl (meth) acrylate (the alkyl group includes a methyl group, an ethyl group, an n-propyl group, an isopropyl group, (meth) acrylic acid esters such as n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group); acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrene Unsaturated carboxylic acids such as sulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); Unsaturated nitriles such as acrylonitrile, methacrylonitrile; (meth) acrylamide, N-alkyl ( (Meth) acrylamide, N, N-dialkyl (meth) acrylamide, As the alkyl group, unsaturated amides such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group and cyclohexyl group); vinyl acetate Vinyl esters such as vinyl propionate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α, β-unsaturated monomers such as vinyl chloride, vinylidene chloride and vinyl fluoride And α, β-unsaturated aromatic monomers such as styrene and α-methylstyrene, and the like, and one or more of these monomers can be used.

  The content of the oxazoline group contained in the oxazoline compound is usually 0.5 to 10 mmol / g, preferably 1 to 9 mmol / g, more preferably 3 to 8 mmol / g, and further preferably 4 to 6 mmol in terms of the amount of the oxazoline group. / G. Use within the above range is preferable because adhesion to various functional layers is improved.

  A carbodiimide-based compound is a compound having a carbodiimide structure, and is a compound having one or more carbodiimide structures in the molecule, but for better adhesion, etc., the polycarbodiimide having two or more in the molecule More preferred are system compounds.

  The carbodiimide compound can be synthesized by a conventionally known technique, and generally a condensation reaction of a diisocyanate compound is used. The diisocyanate compound is not particularly limited, and any of aromatic and aliphatic compounds can be used. Specifically, tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, hexa Examples include methylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl diisocyanate, and dicyclohexylmethane diisocyanate.

  Furthermore, in order not to lose the effect of the present invention, in order to improve the water solubility and water dispersibility of the polycarbodiimide compound, adding a surfactant, polyalkylene oxide, quaternary ammonium salt of dialkylamino alcohol, You may add and use hydrophilic monomers, such as a hydroxyalkyl sulfonate.

  The content of the carbodiimide group contained in the carbodiimide-based compound is a carbodiimide equivalent (weight of the carbodiimide compound to give 1 mol of carbodiimide group [g]) and is usually 100 to 1000, preferably 250 to 800, more preferably 300. It is -700, More preferably, it is the range of 350-650. By using it within the above range, adhesion to various functional layers is improved.

  The isocyanate compound is a compound having an isocyanate derivative structure typified by isocyanate or blocked isocyanate. Examples of the isocyanate include aromatic isocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate, and aromatic rings such as α, α, α ′, α′-tetramethylxylylene diisocyanate. Aliphatic isocyanates such as aliphatic isocyanate, methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, methylene bis (4-cyclohexyl isocyanate), isopropylidene dicyclohexyl diisocyanate Ne Alicyclic isocyanates such as bets are exemplified. Further, polymers and derivatives such as burettes, isocyanurates, uretdiones, and carbodiimide modified products of these isocyanates are also included. These may be used alone or in combination. Among the above isocyanates, aliphatic isocyanates or alicyclic isocyanates are more preferable than aromatic isocyanates in order to avoid yellowing due to ultraviolet rays.

  When used in the state of blocked isocyanate, the blocking agent includes, for example, bisulfites, phenolic compounds such as phenol, cresol, and ethylphenol, and alcohols such as propylene glycol monomethyl ether, ethylene glycol, benzyl alcohol, methanol, and ethanol. Compounds, active methylene compounds such as dimethyl malonate, diethyl malonate, methyl acetoacetate, ethyl acetoacetate, acetylacetone, mercaptan compounds such as butyl mercaptan and dodecyl mercaptan, lactam compounds such as ε-caprolactam and δ-valerolactam , Amine compounds such as diphenylaniline, aniline, ethyleneimine, acetanilide, acid amide compounds of acetic acid amide, formaldehyde, acetoald Examples include oxime compounds such as oxime, acetone oxime, methyl ethyl ketone oxime, and cyclohexanone oxime, and these may be used alone or in combination of two or more.

  In addition, the isocyanate compound in the present invention may be used alone, or may be used as a mixture or bond with various polymers. In the sense of improving the dispersibility and crosslinkability of the isocyanate compound, it is preferable to use a mixture or a bond with a polyester resin or a urethane resin.

  The epoxy compound is a compound having an epoxy group in the molecule, and examples thereof include condensates of epichlorohydrin with ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A and the like hydroxyl groups and amino groups, There are polyepoxy compounds, diepoxy compounds, monoepoxy compounds, glycidylamine compounds, and the like. Examples of the polyepoxy compound include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, trimethylolpropane. Examples of the polyglycidyl ether and diepoxy compound include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and propylene glycol diglycidyl ether. , Polypropylene glycol diglycidyl ether, poly Examples of tetramethylene glycol diglycidyl ether and monoepoxy compounds include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and glycidyl amine compounds such as N, N, N ′, N′-tetraglycidyl-m-xylyl. Examples include range amine and 1,3-bis (N, N-diglycidylamino) cyclohexane.

  Further, in forming the coating layer in the film of the present invention, two or more kinds of crosslinking agents can be used in combination for improving the coating appearance, transparency, adhesion and the like.

  These cross-linking agents are used in a design that improves the performance of the coating layer by reacting in the drying process or film forming process. It can be inferred that unreacted products of these crosslinking agents, compounds after the reaction, or mixtures thereof exist in the finished coating layer.

  In addition, in the formation of the coating layer, particles can be used in combination for the purpose of blocking and improving slipperiness. The average particle diameter is in the range of 1 μm or less, preferably 0.7 μm or less, more preferably 0.5 μm or less from the viewpoint of the transparency of the film. Further, from the viewpoint of adhesion and slipperiness, the average particle size is preferably in the range of 0.01 μm or more, more preferably 0.03 μm or more, and further preferably 0.05 μm or more. Specific examples of the particles include silica, alumina, kaolin, calcium carbonate, titanium oxide, and organic particles. Among them, silica is particularly preferable.

  Further, in the range not impairing the gist of the present invention, an antifoaming agent, a coating property improver, a thickener, an organic lubricant, an antistatic agent, an ultraviolet absorber, and an antioxidant are formed as necessary for forming the coating layer. , Foaming agents, dyes, pigments and the like may be used in combination.

  The content of the resin having a benzyl group is preferably in the range of 20% by weight or more as a ratio of the resin containing a benzyl group to the total nonvolatile components used in the coating layer constituting the laminated film in the present invention. More preferably, it is in the range of 30 to 90% by weight, and further preferably in the range of 40 to 80% by weight. By using in these ranges, the refractive index of the coating layer can be easily adjusted, and interference unevenness after forming a surface functional layer such as a light diffusion layer or an anti-sticking layer can be easily reduced. The ratio of the benzyl group can be determined by, for example, dissolving and extracting the coating layer with an appropriate solvent or warm water, separating by chromatography, analyzing the structure by NMR or IR, and further pyrolysis GC-MS (gas chromatography mass spectrometry). ) Or optical analysis.

  As a ratio with respect to all the non-volatile components in the coating liquid forming the coating layer constituting the laminated film in the present invention, the crosslinking agent is preferably in the range of 5 to 70% by weight, more preferably in the range of 10 to 60% by weight, More preferably, it is the range of 15-50 weight%. If it is out of these ranges, the adhesiveness with the surface functional layer such as the light diffusion layer or the anti-sticking layer may deteriorate, the coating appearance may deteriorate, or the visibility due to interference unevenness may deteriorate.

  In the polyester film of the present invention, a coating layer can also be provided on the surface opposite to the surface on which the coating layer is provided. For example, when a functional layer such as a microlens layer, a prism layer, an anti-sticking layer, a light diffusion layer, or a hard coat is formed on the opposite side of forming a surface functional layer such as a light diffusion layer and an anti-sticking layer, the functional layer It is possible to improve the adhesiveness. A conventionally well-known thing can be used as a component of the coating layer formed in the surface on the opposite side. For example, binder polymers such as polyester resins, acrylic resins, urethane resins, carbodiimide compounds, oxazoline compounds, melamine compounds, epoxy compounds, carbodiimide compounds, crosslinkers such as isocyanate compounds, and the like can be mentioned. You may use and may use multiple types together. Further, it may be a coating layer (a coating layer having the same surface on both sides) formed from a resin having a benzyl group as described above.

  The analysis of the components in the coating layer can be performed by surface analysis such as TOF-SIMS, ESCA, and fluorescent X-ray.

  When providing a coating layer by in-line coating, the above-mentioned series of compounds is applied as an aqueous solution or dispersion, and the coating solution adjusted to a solid content concentration of about 0.1 to 50% by weight as a guide is applied onto the polyester film. It is preferable to produce a laminated polyester film. Moreover, in the range which does not impair the main point of this invention, a small amount of organic solvents may be contained in the coating liquid for the purpose of improving dispersibility in water, improving film-forming properties, and the like. Only one type of organic solvent may be used, or two or more types may be used as appropriate.

  Regarding the laminated polyester film in the present invention, the thickness of the coating layer provided on the polyester film is preferably 0.04 to 0.20 μm, more preferably 0.05 to 0.17 μm, and still more preferably 0.07 to 0. The range is 15 μm. When the film thickness is out of the above range, visibility may deteriorate due to interference unevenness after the surface functional layer is formed.

  Examples of the method for forming the coating layer of the present invention include gravure coating, reverse roll coating, die coating, air doctor coating, blade coating, rod coating, bar coating, curtain coating, knife coating, transfer roll coating, squeeze coating, and impregnation. Conventionally known coating methods such as coat, kiss coat, spray coat, calendar coat, and extrusion coat can be used.

  In the present invention, the drying and curing conditions for forming the coating layer on the polyester film are not particularly limited. For example, when the coating layer is provided by off-line coating, it is usually 3 to 40 at 80 to 200 ° C. The heat treatment may be performed for 2 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds.

  On the other hand, when the coating layer is provided by in-line coating, heat treatment is usually performed at 70 to 280 ° C. for 3 to 200 seconds as a guide.

  Further, irrespective of off-line coating or in-line coating, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as required. The polyester film constituting the laminated polyester film in the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

  The coating layer in the present invention has a refractive index adjusted in order to suppress the occurrence of interference unevenness, and the refractive index is a synergistic effect of the base polyester film and a surface functional layer such as a diffusion layer or an anti-sticking layer. It is designed around the average. The refractive index of the coating layer and the reflectance of the coating layer are closely related. In the film thickness within the range of the present invention, it is preferable that a graph showing the wavelength on the horizontal axis and the reflectance on the vertical axis is drawn, and one minimum value of the reflectance appears in the wavelength range of 400 to 800 nm. If they appear at the same wavelength, the minimum reflectivity is high when the refractive index is high, and low when the refractive index is low. In the present invention, the reflectance of the minimum value varies depending on the wavelength range of the minimum value even if the material design of the coating layer is exactly the same. Specifically, comparing the case where the wavelength range of the minimum value exists in the short wavelength region and the case where it exists in the long wavelength region, the reflectance is lower in the case where it exists in the long wavelength region.

  In the present invention, the favorable reflectance means that the absolute value has a minimum value in a wavelength range of 400 nm or more and less than 750 nm, and the value of the minimum value is preferably 3.0 to 4.7%, more preferably It is 3.2 to 4.4%, more preferably in the range of 3.4 to 4.2%. When there is no minimum value between wavelengths of 400 nm and 750 nm, or when the absolute reflectance of the minimum value is outside the above value, interference unevenness occurs after the formation of a surface functional layer such as a light diffusion layer or anti-sticking layer And the visibility of a film may fall.

  In general, the laminated film of the present invention is provided with a surface functional layer such as a light diffusion layer or an anti-sticking layer on the coating layer. The light diffusing layer contains particles and a binder.

  The particles to be included in the light diffusion layer may be any particles having a property of diffusing light, such as organic particles such as acrylic resin, acrylic urethane resin, urethane resin, polyester resin, and polyvinyl resin, silica, and metal oxide. And inorganic particles such as barium sulfate can be used. Of these, acrylic resins and acrylic urethane resins having good transparency are preferably used. Moreover, the particle size of these particles is not particularly limited, but the average particle size is 1 to 50 μm, more preferably 5 to 15 μm.

  The binder contained in the light diffusing layer is used to fix particles and develop light diffusibility. For example, polyester resin, acrylic resin, polyurethane resin, fluororesin, silicone resin, epoxy resin, UV curable type Examples thereof include resins. In consideration of processability, a polyol compound, an ultraviolet curable resin, or the like is preferably used, and examples thereof include acrylic polyol, polyester polyol, and various (meth) acrylates. In particular, from the viewpoint of increasing the hardness, an ultraviolet curable resin is preferable to a thermosetting resin. In addition, the description of (meth) acrylate in this specification represents an acrylate and a methacrylate.

  When a polyol compound is used as a binder, it is preferable to contain isocyanate as a curing agent. By containing isocyanate, a stronger cross-linked structure can be formed, and physical properties as a light diffusion layer are improved. Further, when an ultraviolet curable resin is used as the binder, a (meth) acrylate resin is preferable, which can be used for improving the hardness of the light diffusion layer.

  The ultraviolet curable (meth) acrylate is not particularly limited. For example, a known active energy ray-curable monofunctional (meth) acrylate, bifunctional (meth) acrylate, or a mixture of one or more types of polyfunctional (meth) acrylate, or a resin material for ultraviolet curable hard coats. In addition to these, in addition to these, other additives may be used as long as the object of the present embodiment is not impaired.

  The UV-curable monofunctional (meth) acrylate is not particularly limited, but for example, methyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate , Alkyl (meth) acrylates such as stearyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate and other hydroxyalkyl ( Alkoxy alcohols such as meth) acrylate, methoxyethyl (meth) acrylate, ethoxyethyl (meth) acrylate, methoxypropyl (meth) acrylate, ethoxypropyl (meth) acrylate, etc. Amino group-containing (meth) acrylates such as aromatic (meth) acrylates such as ru (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, diaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate, Methoxyethylene glycol (meth) acrylate, phenoxy polyethylene glycol (meth) acrylate, ethylene oxide modified (meth) acrylate such as phenylphenol ethylene oxide modified (meth) acrylate, glycidyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, Examples include (meth) acrylic acid.

  Although it does not specifically limit as ultraviolet curable bifunctional (meth) acrylate, For example, 1, 4- butanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1, 6-hexanediol Di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, alkanediol di (meth) acrylate such as tricyclodecane dimethylol di (meth) acrylate, bisphenol A ethylene oxide modified di (meth) acrylate, bisphenol F Bisphenol-modified di (meth) acrylate such as ethylene oxide-modified di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, urethane di (meth) acrylate, epoxy Sidi (meth) acrylate etc. are mentioned.

  The UV curable polyfunctional (meth) acrylate is not particularly limited, but for example, dipentaerythritol hexa (meth) acrylate, pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, penta Isocyanuric acid modified tri (meth) acrylates such as erythritol tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, isocyanuric acid ethylene oxide modified tri (meth) acrylate, ε-caprolactone modified tris (acryloxyethyl) isocyanurate, Pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane prepolymer Mer, urethane acrylates such as dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, and the like.

  Among these (meth) acrylates, a surface functional layer having a highly cross-linked structure can be formed, and therefore there is a merit such as high hardness and resistance to scratches, so a material having a larger number of functional groups is used. Ideally, a bifunctional or higher (meth) acrylate is preferable, and a tetrafunctional or higher (meth) acrylate is more preferable.

  In addition, the above-mentioned compound may be used independently and may be used together 2 or more types.

  Other components contained in the composition containing ultraviolet curable (meth) acrylate are not particularly limited. Examples thereof include inorganic or organic fine particles, polymerization initiators, polymerization inhibitors, antioxidants, antistatic agents, dispersants, surfactants, light stabilizers, and leveling agents. In addition, when the film is dried after film formation in the wet coating method, an arbitrary amount of solvent can be added.

  The light diffusing layer may contain a surfactant, a fine inorganic filler, a plasticizer, a curing agent, an antioxidant, an ultraviolet absorber, a rust preventive agent, etc. within a range not impairing the light diffusion performance. .

  The mixing ratio of the binder and the particles in the light diffusion layer can be appropriately set depending on the light diffusibility to be obtained, and is not particularly limited. For example, the binder / particles are in the range of 0.1 to 50 by weight ratio, More preferably, it is the range of 0.5-20.

  Examples of the method for forming the light diffusion layer include a method in which a coating liquid containing a binder and particles is prepared, applied and dried. As a coating method, a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, spray coating, spin coating or the like can be used. Although the thickness of a light-diffusion layer is not specifically limited, Considering light diffusibility, film | membrane intensity | strength, etc., it is the range of 1-100 micrometers, More preferably, it is the range of 3-30 micrometers.

  It is preferable that an anti-sticking layer is formed on the surface opposite to the light diffusion layer. The anti-sticking layer contains the same compound and particles as the light diffusing layer, and the content of the particles is not intended to be light diffusive, so a method of incorporating a smaller amount with a smaller particle size is common. It is. The formation method can also be formed by coating similarly to the light diffusion layer, and the thickness is not particularly limited, but is preferably in the range of 1 to 10 μm.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measurement method and evaluation method used in the present invention are as follows.

(1) Method for measuring the intrinsic viscosity of polyester 1 g of polyester from which other polymer components and pigments incompatible with polyester have been removed are precisely weighed, and 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) is added. And dissolved at 30 ° C.

(2) Measuring method of average particle diameter The coating layer was observed using TEM (H-7650 made by Hitachi, acceleration voltage 100 kV), and the average value of the particle diameter of 10 particles was defined as the average particle diameter.

(3) Method for measuring film thickness of coating layer The surface of the coating layer was dyed with RuO ₄ and embedded in an epoxy resin. Thereafter, the section prepared by ultramicrotomy stained with RuO _4, a coating layer cross-section was measured by using a TEM (Hitachi Ltd. H-7650, accelerating voltage 100 kV).

(4) Evaluation method of absolute reflectance from the coating layer surface in the polyester film In order to measure the absolute reflectance on one side of the polyester film, in order to suppress the reflection from the back surface, black tape is applied to the measurement back surface of the polyester film in advance. (Nichiban Co., Ltd. vinyl tape VT-50) is applied, synchronized mode and incidence using a spectrophotometer (UV-spectrophotometer V-570 and automatic absolute reflectance measuring device ARM-500N manufactured by JASCO Corporation) The absolute reflectance of the coating layer surface with a wavelength range of 400 to 800 nm was measured at an angle of 5 °, N polarization, response Fast, data collection interval of 1.0 nm, bandwidth of 10 nm, and scanning speed of 1000 m / min. Bottom wavelength) and reflectance were evaluated.

(5) Interference unevenness evaluation method As a light diffusion layer coating solution, 60 parts by weight of dipentaerythritol hexaacrylate, 20 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate, a photopolymerization initiator (trade names: Irgacure 184, Ciba 5 parts by weight of specialty chemicals), 20 parts by weight of acrylic resin particles having an average particle size of 15 μm (MBX-15 manufactured by Sekisui Plastics Industry) and 200 parts by weight of methyl ethyl ketone were applied so that the dry film thickness was 5 μm. A light diffusing layer having a refractive index of 1.49 was formed by curing by irradiation with ultraviolet rays. Further, acrylic resin particles having an average particle size of 15 μm used in the coating solution for the light diffusion layer as an anti-sticking layer on the side opposite to the light diffusion layer were replaced with acrylic resin particles having an average particle size of 5 μm (manufactured by Sekisui Plastics Co., Ltd.). MBX-5) A double-sided product was prepared in the same manner except that a layer having a thickness of 3 g / m ² was formed instead of 7 parts. A black tape (vinyl tape VT-50 manufactured by Nichiban Co., Ltd.) is attached to the light diffusion layer side of the obtained film, and interference unevenness is visually observed under a three-wavelength fluorescent lamp from the sticking prevention layer side. ◎ if the interference unevenness can not be confirmed, ◯ if the interference unevenness of the color is confirmed, △ if the interference unevenness that can distinguish the color is △, strong interference unevenness that can distinguish the color Those which were confirmed and confirmed to have interference unevenness even under a white fluorescent lamp were evaluated as x. In the case of a normal light diffusing layer, since the light diffusibility is high like the above light diffusing layer, interference unevenness is hardly observed. However, in the case of a light diffusion layer with low light diffusibility, interference unevenness may be observed, so that the refractive index adjustment of the coating layer is more important. On the other hand, the anti-sticking layer is formed of particles and a binder in the same manner as the light diffusion layer, but generally has a smaller amount of particles and a smaller film thickness than the light diffusion layer. For this reason, the light diffusibility is lowered, and interference unevenness may be observed. Therefore, it is very important to adjust the refractive index of the coating layer.

(6) Adhesive evaluation method By the same method as the interference unevenness evaluation method, a light diffusion layer was formed on one side of the laminated polyester film and a sticking prevention layer was formed on the other side. After being left for 100 hours (adhesion 2) in an environment of 80 ° C. and 85% RH in an initial temperature (adhesion 1) and a constant temperature and humidity chamber for the obtained film (adhesion 2), the light diffusion layer and the anti-sticking layer respectively On the other hand, a 10 × 10 cross cut was made, and an 18 mm wide tape (Cello Tape (registered trademark) CT-18 manufactured by Nichiban Co., Ltd.) was applied thereon, and the tape was peeled off rapidly at a peeling angle of 180 degrees. After that, the peeled surface was observed, and for the larger peeled area, if the peeled area is 0%, ◎, if it exceeds 0% and 5% or less, ○ if it exceeds 5% and 20% or less, Δ, 20% X was exceeded if it exceeded. In general, the anti-sticking layer has less surface irregularities, and therefore has better adhesion to the tape to be peeled, and therefore the peel area tends to be larger than the light diffusion layer.

The polyester used in the examples and comparative examples was prepared as follows.
<Method for producing polyester (A)>
100 parts by weight of dimethyl terephthalate, 60 parts by weight of ethylene glycol, 30 ppm of ethyl acid phosphate with respect to the resulting polyester, and 100 ppm of magnesium acetate tetrahydrate with respect to the resulting polyester as the catalyst at 260 ° C. in a nitrogen atmosphere at 260 ° C. The reaction was allowed to proceed. Subsequently, 50 ppm of tetrabutyl titanate was added to the resulting polyester, the temperature was raised to 280 ° C. over 2 hours and 30 minutes, the pressure was reduced to 0.3 kPa in absolute pressure, and melt polycondensation was further carried out for 80 minutes. 0.63 polyester (A) was obtained.

<Method for producing polyester (B)>
100 parts by weight of dimethyl terephthalate, 60 parts by weight of ethylene glycol, and magnesium acetate tetrahydrate as a catalyst were subjected to an esterification reaction at 225 ° C. in a nitrogen atmosphere at 900 ppm with respect to the produced polyester. Subsequently, 3500 ppm of orthophosphoric acid was added to the produced polyester, and 70 ppm of germanium dioxide was added to the produced polyester. The temperature was raised to 280 ° C. over 2 hours and 30 minutes, and the pressure was reduced to an absolute pressure of 0.4 kPa. After 85 minutes of melt polycondensation, polyester (B) having an intrinsic viscosity of 0.64 was obtained.

<Method for producing polyester (C)>
In the production method of polyester (A), polyester (C) is obtained using the same method as the production method of polyester (A), except that 0.3 part by weight of silica particles having an average particle diameter of 2 μm is added before melt polymerization. It was.

Examples of compounds constituting the coating layer are as follows.
(Example compounds)
・ Acrylic resin with benzyl group: (IA)
Acrylic resin aqueous dispersion with a benzyl group ratio of 52% by weight synthesized with the following composition benzyl methacrylate homopolymer (dispersant: polyethylene glycol)

・ Acrylic resin with benzyl group: (IB)
Acrylic resin aqueous dispersion with a benzyl group ratio of 56% by weight synthesized with the following composition benzyl acrylate homopolymer (dispersant: polyethylene glycol)

・ Acrylic resin with benzyl group: (IC)
Acrylic resin aqueous dispersion having a benzyl group ratio of 44% by weight synthesized with the following composition: benzyl methacrylate / ethyl acrylate / n-butyl acrylate = 70/16/14 (% by weight) polymer (dispersant: polyethylene glycol) )

・ Acrylic resin: (IIA)
Aqueous dispersion of acrylic resin polymerized with the following composition Ethyl acrylate / n-butyl acrylate / methyl methacrylate = 67/23/10 (wt%) polymer (dispersant: polyethylene glycol)

・ Acrylic resin: (IIB)
Aqueous dispersion of acrylic resin polymerized with the following composition: Emulsion polymer of ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylol acrylamide / acrylic acid = 65/21/10/2/2 (% by weight) (emulsifier: Anionic surfactant)

・ Melamine compounds: (IIIA)
Hexamethoxymethylolmelamine

・ Oxazoline compounds: (IIIB)
Acrylic polymer having an oxazoline group and a polyalkylene oxide chain Epocross (Oxazoline group amount = 4.5 mmol / g, manufactured by Nippon Shokubai Co., Ltd.)

・ Epoxy compounds: (IIIC)
Polyglycerol polyglycidyl ether.

・ Carbodiimide compounds: (IIID)
Carbodiimide compound Carbodilite (carbodiimide equivalent: 380) (Nisshinbo Co., Ltd.)

・ Isocyanate compounds: (IIIE)
1000 parts of hexamethylene diisocyanate was stirred at 60 ° C., and 0.1 part of tetramethylammonium caprylate was added as a catalyst. After 4 hours, 0.2 part of phosphoric acid was added to stop the reaction, and an isocyanurate type polyisocyanate composition was obtained. 100 parts of the obtained isocyanurate type polyisocyanate composition, 42.3 parts of methoxypolyethylene glycol having a number average molecular weight of 400, and 29.5 parts of propylene glycol monomethyl ether acetate were charged and maintained at 80 ° C. for 7 hours. Thereafter, the reaction solution temperature was kept at 60 ° C., 35.8 parts of methyl isobutanoyl acetate, 32.2 parts of diethyl malonate, and 0.88 part of 28% methanol solution of sodium methoxide were added and kept for 4 hours. Block polyisocyanate obtained by adding 58.9 parts of n-butanol, maintaining the reaction solution temperature at 80 ° C. for 2 hours, and then adding 0.86 part of 2-ethylhexyl acid phosphate.

-Particles: Silica particles (IV) with an average particle size of 0.07 μm

Example 1:
A mixed raw material in which polyesters (A), (B), and (C) were mixed in proportions of 91%, 3%, and 6%, respectively, was used as a raw material for the outermost layer (surface layer), and polyesters (A) and (B) were each 97 %, 3% of the mixed raw material is used as an intermediate layer raw material, each is supplied to two extruders, melted at 285 ° C., and then on a cooling roll set at 40 ° C. Coextruded with a layer structure of layers (surface layer / intermediate layer / surface layer = 1: 18: 1 discharge amount) and cooled and solidified to obtain an unstretched sheet. Next, the film was stretched 3.4 times in the longitudinal direction at a film temperature of 85 ° C. using the difference in peripheral speed of the roll, and then the coating liquid 1 shown in Table 1 below was applied to both sides of the longitudinally stretched film, and led to a tenter. Thickness having a coating layer in which the film is stretched 4.0 times at 120 ° C. in the transverse direction and heat-treated at 225 ° C. and then relaxed by 2% in the transverse direction and the coating layer thickness (after drying) is 0.10 μm. A 125 μm polyester film was obtained.

  When the obtained polyester film was evaluated, the minimum value of the absolute reflectance of the coating layer was 600 nm, the reflectance was 3.7%, and after the surface functional layers such as the light diffusion layer and the anti-sticking layer were formed No interference unevenness was observed in this film. The properties of this film are shown in Table 2 below.

Examples 2-16:
In Example 1, it manufactured similarly to Example 1 except having changed the coating agent composition into the coating agent composition shown in Table 1, and obtained the polyester film. As shown in Table 2, the finished polyester film had a good level of interference unevenness and good adhesion.

Comparative Examples 1-6:
In Example 1, it manufactured similarly to Example 1 except having changed the coating agent composition into the coating agent composition shown in Table 1, and obtained the polyester film. When the finished laminated polyester film was evaluated, as shown in Table 2, there were cases where clear interference unevenness could be observed and adhesion was not good.

  The film of the present invention can be suitably used for applications that need to reduce interference unevenness due to light reflection, such as a backlight unit of a liquid crystal display.

Claims (2)

A laminated film comprising a coating layer containing a resin having a benzyl group on at least one side of the film. The laminated film according to claim 1, wherein the film is a film made of polyester.