JP2023142190A - Laminated polyester film and production method thereof - Google Patents

Abstract

To provide a laminated polyester film provided with an antireflection layer with both antifouling property and low reflectivity.SOLUTION: Provided is a laminated polyester film having an antireflection layer on either surface of a polyester film, in which the antireflection layer is formed of a resin composition comprising two kinds of resin components having different refractive indexes, one resin component (A) of the two kinds of resin components contains a fluorine-based resin, a refractive index of the other resin component (B) of the two kinds of resin components is higher than that of the fluorine-based resin, and when sequential argon (Ar) etching and XPS (X-ray photoelectron spectroscopy) are used to measure concentration distributions of fluorine atoms (F) and oxygen atoms (O) in the thickness direction of the antireflection layer and when the first time at which the amount of the fluorine atoms (F) becomes less than the amount of oxygen atoms (O) is assumed to be X seconds and the amount of fluorine atoms (F) at an etching time of 0 second is assumed to be 100, the amount of fluorine atoms (F) at 1.5X seconds is 10 to 20.SELECTED DRAWING: None

Description

The present invention relates to a laminated polyester film having an antireflection layer and a method for producing the same.

Polyester films are used in a variety of fields due to their excellent transparency, optical properties, dimensional stability, mechanical strength, heat resistance, chemical resistance, electrical properties, etc. Specifically, they are used in magnetic recording. In addition to materials, packaging materials, solar cell applications, separators for liquid crystal polarizing plates, base materials for dry film resists, release films for forming green sheets for multilayer ceramic capacitors, anti-reflection films, diffusion sheets, prism sheets, etc. It is widely used in optical films, label printing films, etc.

For example, Patent Document 1 discloses that it has excellent transparency, makes minute scratches on the base film inconspicuous during the film forming process, eliminates the hazy feeling of laminated films, and has excellent adhesion and moisture-heat resistance. Excellent optical laminated polyester film (for example, the film can be provided with a hard coat layer and used as an anti-reflection laminated film, and can also be used, for example, with a conductive metal oxide layer, such as a laminated film for touch panels or a laminated film for electronic paper) ), a coating layer is provided on at least one side of the polyester film, and the coating layer is made of two types of resins with different refractive indexes, and has a refractive index of 1.53 to 1.65. A layer L1 mainly composed of a certain high refractive index component is located on the polyester film side, and a layer L2 mainly composed of a low refractive index component having a refractive index of 1.43 to 1.56 is located on the opposite side. and the layer L2, a mixed phase region of each layer exists with a thickness of 5 to 100 nm, and has a total light transmittance of 90% or more and a haze of 1.5% or less. An optical laminated film is disclosed.

In recent years, polyester films have also been used as base films for face shields and show windows, and are required to have antifouling properties to improve visibility.

For example, Patent Document 2 describes an antireflection film that has high visible light antireflection properties even when used outdoors and is resistant to ultraviolet deterioration. An antireflection film comprising a light reflection prevention layer and an antifouling layer sequentially provided, wherein the thermoplastic resin film has an ultraviolet shielding property, the ultraviolet transmittance of the antireflection film is 20% or less, and the film reflects visible light. An antireflection film is disclosed that has a haze value of 5% or less and a haze value of 2% or less.

Further, Patent Document 3 discloses that a hard coat layer and an antireflection layer are sequentially laminated on at least one surface of a transparent base material, and the antireflection layer includes alternating layers of a high refractive material and a layer of a low refractive index. In the antireflection film, which is a laminate of four or more layers, the outermost thin film of the antireflection layer is a low refractive index layer, an antifouling layer containing a fluorine-containing silicon compound on the surface of the antireflection layer. It is disclosed that the following is provided. Fluorine-based materials are sometimes used to provide antifouling properties in this way.

Japanese Patent Application Publication No. 2004-107627 Japanese Patent Application Publication No. 2001-315262 Japanese Patent Application Publication No. 2011-69995

Since fluorine compounds have antifouling properties and low refractive index, as in Patent Document 3 mentioned above, providing an antifouling layer containing a fluorine compound on the surface of the antireflection layer can improve low reflectivity and antifouling properties. and can be given.

However, although fluorine compounds have low reflectivity, they have a problem of narrow wavelength selectivity when used alone.When an antifouling layer containing a fluorine compound is provided on the surface of an antireflection layer, the low reflectivity of the antireflection layer is affected. There was a risk that it would
Further, when an antifouling layer containing a fluorine-based material is provided on the surface of the antireflection layer, there is a possibility that a problem may arise in the adhesion between the antireflection layer and the antifouling layer.

Therefore, an object of the present invention is to provide a laminated polyester film provided with an antireflection layer that has both antifouling properties and low reflectivity.

The laminated polyester film of the present invention has the following configuration in order to solve the above problems.

[1] In the first aspect of the present invention, a polyester film has an antireflection layer on at least one surface, and the antireflection layer is formed from a resin composition containing two resin components having different refractive indexes. , one of the two resin components (A) contains a fluororesin, and the other resin component (B) of the two resin components has a refractive index lower than that of the fluororesin. The concentration distribution of fluorine atoms (F) and oxygen atoms (O) in the thickness direction of the antireflection layer was measured using sequential argon (Ar) etching and XPS (X-ray photoelectron spectroscopy). When the first time when the amount of atoms (F) becomes less than the amount of oxygen atoms (O) is set to X seconds, and the amount of fluorine atoms (F) at 0 seconds of etching is set to 100, ) amount is 10 or more and 20 or less.

[2] A second aspect of the present invention is the laminated polyester film according to the first aspect, wherein the fluororesin has a refractive index of 1.39 or more and 1.44 or less.

[3] A third aspect of the present invention is the laminated polyester film according to the first or second aspect, wherein the resin component (B) has a refractive index of 1.57 or more and 1.61 or less.

[4] In a fourth aspect of the present invention, in the first aspect, the antireflection layer includes a fluororesin component (A1) having a refractive index of 1.39 or more and 1.44 or less and a refractive index of 1. It is a laminated polyester film containing a resin component (B) of 57 or more and 1.61 or less and having a layer structure of two or more layers.

[5] A fifth aspect of the present invention is the laminated polyester film according to any one of the first to fourth aspects, wherein the resin component (B) contains polyester.

[6] A sixth aspect of the present invention is the laminated polyester film according to any one of the first to fifth aspects, wherein the antireflection layer has a surface free energy of 50 mN/m or less.

[7] In the seventh aspect of the present invention, a mixed solution containing two or more resin components having different refractive indexes is applied to at least one surface of a polyester film, and an antireflection layer is provided on at least one surface of the polyester film. one of the resin components (A) of the two resin components having different refractive indexes includes a fluororesin, and the other of the two resin components The refractive index of the resin component (B) is higher than that of the fluorine-based resin, and fluorine atoms (F) in the thickness direction of the antireflection layer are removed using sequential argon (Ar) etching and XPS (X-ray photoelectron spectroscopy). and the concentration distribution of oxygen atoms (O), the first time when the amount of fluorine atoms (F) becomes less than the amount of oxygen atoms (O) is set as X seconds, and the amount of fluorine atoms (F) at 0 seconds of etching is 100, the amount of fluorine atoms (F) at 1.5X seconds is 10 or more and 20 or less.

[8] An eighth aspect of the present invention is the method for producing a laminated polyester film according to the seventh aspect, wherein the fluororesin has a refractive index of 1.39 or more and 1.44 or less.

[9] A ninth aspect of the present invention is the method for producing a laminated polyester film according to the seventh or eighth aspect, wherein the resin component (B) has a refractive index of 1.57 or more and 1.61 or less. It is.

[10] A tenth aspect of the present invention is a method for producing a laminated polyester film according to the ninth aspect, wherein the resin component (B) contains polyester.

[11] An eleventh aspect of the present invention is a method for producing a laminated polyester film according to any one of the seventh to tenth aspects, wherein the antireflection layer has a surface free energy of 50 mN/m or less.

According to the present invention, it is possible to provide a laminated polyester film including an antireflection layer that has both antifouling properties and low reflectivity.
Since the polyester film of the present invention is provided with an antireflection layer that has both antifouling properties and low reflectivity, there is no risk of adhesion problems between the antireflection layer and the antifouling layer, and the antireflection layer has low reflectivity. Since it has both antifouling properties and antifouling properties, it has the advantage of having low reflectivity in a wide wavelength range.

FIG. 1 is a cross-sectional photograph of the laminated polyester film of the present invention taken using a transmission electron microscope (TEM) (Example 1). FIG. 2 is a diagram showing the wavelength dependence of the absolute reflectance of the laminated polyester film of the present invention (Examples 1 to 3). FIG. 3 is a diagram showing the distribution of fluorine atomic weight by XPS (X-ray photoelectron spectroscopy) for the antireflection layer of the laminated polyester film of the present invention (Example 1).

<Laminated polyester film>
The laminated polyester film of the present invention (hereinafter also referred to as "this film") has an antireflection layer on at least one surface of the polyester film as a base film.

<Polyester film>
The polyester film is not particularly limited as long as it is a film mainly composed of polyester, and the polyester may be a homopolyester or a copolyester, or a polymer blend mainly containing these polyesters. But that's fine.
Here, "mainly containing polyester" means that the component with the largest mass percentage among the components constituting the polyester film is polyester, and preferably polyester accounts for 50% by mass or more. More preferably, polyester accounts for 70% by mass or more.

(polyester raw material)
The homopolyester is preferably a polycondensation polymer of aromatic dicarboxylic acid and aliphatic glycol. Examples of aromatic dicarboxylic acids include terephthalic acid and 2,6-naphthalene dicarboxylic acid. Examples of aliphatic glycols include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Typical polyesters include polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polymethylene terephthalate, and the like.

The copolymerized polyester is preferably a polycondensation polymer of a dicarboxylic acid component and a glycol component. Examples of the dicarboxylic acid component used in the copolymerized polyester include isophthalic acid, phthalic acid, terephthalic acid, and 2,6-naphthalene dicarboxylic acid. Examples include one or more of acids, adipic acid, sebacic acid, oxycarboxylic acids (eg, p-oxybenzoic acid, etc.).
Examples of the glycol component include one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexanedimethanol, neopentyl glycol, and the like.
In the copolymerized polyester, the dicarboxylic acid component preferably contains terephthalic acid, and the glycol component preferably contains ethylene glycol, and the content of terephthalic acid is, for example, 50 mol% or more, preferably 70 mol% or more, of the dicarboxylic acid component. More preferably, it is 90 mol% or more.
Further, the content of ethylene glycol is 50 mol% or more, preferably 70 mol% or more, more preferably 90 mol% or more of the glycol component.
The copolymer polyester may also contain structural units derived from difunctional compounds other than dicarboxylic acid components and glycol components, and structural units derived from difunctional compounds other than dicarboxylic acid components and glycol components may It is preferably 20 mol% or less, more preferably 10 mol% or less, based on the total mole of all constituent units. Examples of the difunctional compound include various hydroxycarboxylic acids and aromatic diols.

(intrinsic viscosity)
The intrinsic viscosity of the polyester is not particularly limited, but from the viewpoint of film formability, productivity, etc., it is preferably 0.45 to 1.0 dl/g, more preferably 0.5 to 0.9 dl/g.

(Layer structure)
The polyester film may have a single-layer structure or a multi-layer structure, and in the case of a multi-layer structure, it may have a two-layer structure, a three-layer structure, etc., or a multilayer structure of four or more layers, and the number of layers is not particularly limited. .
Further, the polyester film is preferably a uniaxially or biaxially stretched polyester film, and particularly preferably a biaxially stretched polyester film.

(polymerization catalyst)
Polyester is preferably produced by dehydration polycondensation of a polycarboxylic acid such as an aromatic dicarboxylic acid and a polyol such as an aliphatic glycol, but may also be produced by a transesterification method or the like. Examples of the polyester polymerization catalyst include antimony compounds, titanium compounds, germanium compounds, manganese compounds, aluminum compounds, magnesium compounds, and calcium compounds. Among these, it is particularly preferable to use at least one selected from titanium compounds and germanium compounds.
In the case of a polyester using the titanium compound as a polymerization catalyst, the titanium element content in the polyester film is preferably 50 ppm or less, more preferably 1 to 20 ppm, and even more preferably 2 to 10 ppm.
In addition, when the polyester film is multilayered, the titanium element content in the entire film should be within the above range, but it is particularly preferable that the titanium element content in each layer be within the above range. .
By setting the content of the titanium compound to the above upper limit value or less, deterioration of the polyester can be prevented in the process of melt-extruding the polyester, and a film with a strong yellowish tinge can be prevented.
Moreover, when the content is equal to or more than the above lower limit, the polymerization efficiency becomes good, the cost becomes low, and it becomes easy to obtain a film having sufficient strength.
As mentioned above, when using a polyester containing a titanium compound derived from a polymerization catalyst, it is preferable to blend a phosphorus compound into the polyester in order to lower the activity of the titanium compound for the purpose of suppressing deterioration in the melt extrusion process. As the phosphorus compound, alkyl acid phosphates such as orthophosphoric acid and ethyl acid phosphate are preferable in consideration of the productivity and thermal stability of polyester.
The phosphorus element content in the polyester film is preferably in the range of 1 to 300 ppm, more preferably 3 to 200 ppm, and still more preferably 5 to 100 ppm. By controlling the content of the phosphorus compound to be less than or equal to the above upper limit, it is possible to prevent the phosphorus compound from causing gelation or foreign matter.
Further, by setting the amount to be equal to or more than the above lower limit, the activity of the titanium compound can be sufficiently lowered, and a yellowish film can be prevented.
In addition, when the polyester film is multilayered, the phosphorus element content in the layer containing the titanium element is preferably within the above range.

(Prevention of oligomer precipitation)
The polyester film can also be produced using a polyester with a low content of ester cyclic trimers as a raw material in order to suppress the amount of ester cyclic trimers precipitated after heat treatment. As a method for producing a polyester with a low content of ester cyclic trimers, various known methods can be used, such as a method in which solid phase polymerization is performed after producing the polyester.
In addition, by making the polyester film have a structure of three or more layers, and making the outermost layer of the polyester film a layer using a polyester raw material with a low content of ester cyclic trimers, precipitation of ester cyclic trimers after heat treatment can be prevented. You can reduce the amount.
Moreover, after carrying out esterification or transesterification reaction, polyester may be obtained by further raising the reaction temperature and performing melt polycondensation under reduced pressure.

(particle)
Particles may be added to the polyester film for the main purpose of imparting slipperiness and preventing scratches in each step. When blending particles, the types of particles to be blended are not particularly limited as long as they can impart slipperiness; examples 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, zirconium oxide, and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin, and benzoguanamine resin. Furthermore, precipitated particles in which a part of a metal compound such as a catalyst is precipitated and finely dispersed during the polyester manufacturing process can also be used. Among these, silica particles and calcium carbonate particles are particularly preferred because they are effective even in small amounts.

Further, the average particle diameter of the particles is preferably 5.0 μm or less, more preferably in the range of 0.01 to 3.0 μm. By setting the average particle size to 5.0 μm or less, the surface roughness of the film is prevented from increasing, and defects are less likely to occur in various post-processing processes.
Further, by using particles having an average particle size within the above range, haze can be suppressed to a low level, and transparency can be easily ensured as a whole of the laminated polyester film.

Further, the content of particles in the polyester film is preferably less than 5% by mass, more preferably in the range of 0.0003 to 1% by mass, and even more preferably 0.0005 to 0.5% by mass, based on the entire polyester film. is within the range of By setting the particle content to less than 5% by mass, it is possible to prevent haze from increasing and to easily ensure transparency. Therefore, for example, during various inspections, defects such as foreign matter can be easily inspected.
If the polyester film does not contain particles or if the content is small, the polyester film will have high transparency and a good appearance, but the slipperiness may be insufficient. Therefore, it is preferable to improve the slipperiness by adding particles.
There are no particular limitations on the shape of the particles used, and any shape such as spherical, lumpy, rod-like, flat, etc. may be used. Furthermore, there are no particular limitations on its hardness, specific gravity, color, etc.
Two or more types of these series of particles may be used in combination as necessary.

The method of adding particles to the polyester film is not particularly limited, and conventionally known methods can be employed. For example, it can be added at any stage of producing the polyester constituting each layer of the polyester film, but it is preferably added after the esterification or transesterification reaction is completed.
In addition, when performing melt polycondensation, solid phase polymerization, etc. after esterification or transesterification reaction, it is necessary to perform the esterification or transesterification reaction and before melt polycondensation or solid phase polymerization. More preferably, particles are added.
When the polyester film is multilayered, it is preferable that at least one layer contains particles, and it is especially preferable that the outermost layer contains particles. For example, in a multilayer structure including an outermost layer, an intermediate layer, and an outermost layer in this order, particles may be contained in each outermost layer.

(Other additives)
In addition, in addition to the above-mentioned particles, ultraviolet absorbers, antioxidants, heat stabilizers, lubricants, dyes, pigments, etc. can be added to the polyester film of the present invention, if necessary.

(Thickness of polyester film)
The thickness of the polyester film as the base film is usually in the range of 10 to 300 μm, preferably 15 to 250 μm, and more preferably 20 to 200 μm.

(Method for producing polyester film)
As a method for producing the polyester film as the base film, a commonly known production method can be employed, and there are no particular limitations. For example, when producing a biaxially stretched polyester film, the polyester raw material described above is melt-extruded from a die using an extruder, and the molten sheet is cooled and solidified with a cooling roll to obtain an unstretched sheet. In this case, in order to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the rotating cooling drum, and an electrostatic application adhesion method or a liquid application adhesion method is preferably employed. Next, the obtained unstretched sheet is stretched in one direction using a roll or 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 a direction perpendicular to the first-stage stretching direction, usually at 70 to 170°C, and at a stretching ratio of usually 2.5 to 7 times, preferably 3.0 to 6 times. Subsequently, heat treatment is performed at a temperature of 180 to 270° C. under tension or relaxation within 30% to obtain a biaxially stretched film. In the above-mentioned stretching, a method of stretching in one direction in two or more stages can also be adopted. In that case, it is preferable to carry out the stretching so that the final stretching ratios in both directions fall within the above ranges.

Moreover, a simultaneous biaxial stretching method can also be employed for manufacturing the polyester film. The simultaneous biaxial stretching method is a method in which the above-mentioned unstretched sheet is stretched and oriented simultaneously in the machine direction and the width direction under temperature control, usually at 70 to 120°C, preferably 80 to 110°C, and the stretching ratio is The area magnification is 4 to 50 times, preferably 7 to 35 times, more preferably 10 to 25 times. Subsequently, heat treatment is performed at a temperature of 180 to 270° C. under tension or relaxation within 30% to obtain a stretched oriented film. Regarding the simultaneous biaxial stretching apparatus that employs the above-mentioned stretching method, conventionally known stretching methods such as a screw method, a pantograph method, and a linear drive method can be employed.

<Anti-reflection layer>
The antireflection layer of the present invention is a layer that imparts antireflection properties and antifouling properties to the film, and has an appropriate amount of fluorine (F) atoms segregated on the surface of the antireflection layer, and fluorine atoms are present in the polyester film. By having such a configuration, it is possible to have excellent antireflection properties and antifouling properties.
More specifically, the antireflection layer is etched with fluorine atoms (F) and oxygen atoms (O) in the thickness direction of the antireflection layer using sequential argon (Ar) etching and XPS (X-ray photoelectron spectroscopy). When the first time when the amount of fluorine atoms (F) becomes less than the amount of oxygen atoms (O) is X seconds, and the amount of fluorine atoms (F) at 0 seconds of etching is 100, 1 When the amount of fluorine atoms (F) at .5X seconds is 10 or more and 20 or less, it is possible to have both excellent antireflection properties and antifouling properties.
From this point of view, especially from the viewpoint of the balance between antireflection properties and antifouling properties, the amount of fluorine atoms (F) at 1.5X seconds is preferably 10 or more and 20 or less, more preferably 10 or more and 16 or less. It is preferably 10 or more and 14 or less.

The antireflection layer of the present invention has the above-mentioned configuration, that is, "the initial time when the amount of fluorine atoms (F) becomes less than the amount of oxygen atoms (O) is X seconds, and the fluorine atoms ( When the amount of F) is 100, the amount of fluorine atoms (F) at 1.5X seconds is 10 or more and 20 or less.'' (hereinafter also referred to as ``Configuration A''). This means that there is an interface between the resin layer and the polyester layer, and by having the structure A, the fluororesin layer with excellent stain resistance is unevenly distributed on the outermost surface, and the interface between the fluororesin layer and the polyester resin is unevenly distributed. It is surmised that by forming the antireflection layer, the antireflection layer can have excellent antireflection and antifouling properties.

In order for the antireflection layer of the present invention to have the above configuration A, the antireflection layer is preferably formed from a resin composition containing at least two mixed resin components having different refractive indexes, and One of the two resin components (A) contains a fluororesin, and the other resin component (B) of the two resin components has a refractive index higher than that of the fluororesin. Preferably, it is formed from a resin composition containing a high mixed resin component.
By forming the antireflection layer from the resin composition, the fluororesin, which has a lower affinity with the polyester film base material than polyester resin, migrates to the surface side of the antireflection layer and exhibits antifouling properties. . Further, by using another resin component having a refractive index different from that of the fluororesin, specifically, having a higher refractive index than the fluororesin, low reflectivity can also be achieved as described later.
From this viewpoint, the refractive index of the fluororesin is preferably 1.39 or more and 1.44 or less, more preferably 1.39 or more and 1.42 or less, and 1.39 or more and 1.40 or less. It is more preferable that
Here, the content ratio ((A)/(B)) of the resin component (A) containing the fluororesin and the mixed resin component having a higher refractive index than the fluororesin is in the range of 1 to 5. It is preferably in the range of 1.2 to 4, more preferably in the range of 1.5 to 3. When the ratio of component (A) to component (B) is within the above range, an antireflection layer having both antifouling and antireflection properties can be obtained.

Examples of the fluororesin include fluoroolefin copolymer resins containing vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, etc. as monomers; fluoromethylene ether, difluoromethylene ether, Fluorine-based copolymer resins having polyalkylene ether groups in which some or all of the hydrogen atoms are substituted with fluorine atoms, such as fluoroethylene ether, difluoroethylene ether, tetrafluoroethylene ether, hexafluoropropylene ether; hydroxy group-containing Examples include fluorine-based copolymer resins obtained by graft polymerization of fluorine-based resin copolymers and (meth)acrylic acid ester compounds or other monomers; vinyl polymers having perfluoroalkyl groups, and the like.

Among these, preferred are fluoroolefin copolymer resins and fluororesin copolymers containing polyalkylene ether groups in which some or all of the hydrogen atoms are substituted with fluorine atoms, from the viewpoint of antifouling properties and low reflectivity. . A fluorine-based copolymer resin having a polyalkylene ether group in which some or all of the hydrogen atoms are substituted with fluorine atoms is obtained by polymerizing a monomer having the polyalkylene ether group and another monomer. Examples include fluorine-based copolymer resins, and more specifically, urethane resins having polyfluoroalkylene ether groups, polyesters having polyfluoroalkylene ether groups, acrylic resins having polyfluoroalkylene ether groups, and the like.
Other monomers constituting the urethane resin having a polyfluoroalkylene ether group include isocyanate compounds. Isocyanate compounds include aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, methylene diphenyl diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, and tolydine diisocyanate; aromatic rings such as α, α, α', α'-tetramethylxylylene diisocyanate; aliphatic diisocyanates such as methylene diisocyanate, propylene diisocyanate, lysine diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate; cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, isopropylidene dicyclohexy fats such as diisocyanate Examples include cyclic diisocyanates.
Other monomers that make up the urethane resin include polyols that do not contain fluorine atoms, dimethylolpropanoic acid, dimethylolbutanoic acid, bis-(2-hydroxyethyl)propionic acid, and bis-(2-hydroxyethyl)butane. Examples include polyols having a carboxy group such as acids. Among these, it is preferable to include a polyol having a carboxy group from the viewpoint of self-emulsification when water is used as a dispersion solvent, and among them, dimethylolpropanoic acid is more preferable.

In addition, there is no particular restriction on the resin component (B) having a refractive index different from that of the resin component (A), but from the viewpoint of low reflectivity, the resin component (B) has a refractive index different from that of the resin component (A). It is preferable to have another resin component (B) with a high refractive index, and the resin component (B) preferably has a refractive index of 1.57 or more and 1.61 or less, also from the viewpoint of low reflectivity. .
By using a resin (high refractive index resin) whose refractive index is higher than that of the fluororesin, the antireflection layer has a low refractive index layer containing the fluororesin that migrates to the surface side, and a high refractive index layer that remains on the polyester film side. It has a two-layer structure in which a high refractive index layer containing a refractive resin is laminated, and by canceling the interfacial reflection between the layers and preventing the reflection of external light, it can have excellent low reflection characteristics.
As the resin constituting the resin component (B) having a refractive index of 1.57 or more and 1.61 or less, aromatic rings, sulfur atoms, bromine atoms, etc. are introduced into resins such as polyester, acrylic resin, and urethane resin. Among these, polyesters having a fused aromatic ring in the molecule are particularly preferred from the viewpoint of adhesion with the base material and separability from the fluororesin. .
The fused aromatic rings include, for example, naphthalene, acenaphthylene, anthracene, benzanthracene, aceantrylene, phenanthrene, benzophenanthrene, phenalene, fluorene, pentacene, picene, pentaphenylene, pyrene, chrysene, benzochrysene, and s-indacene. , as-indacene, fluoranthene, perylene, triphenylene, benzotriphenylene, spirofluorene, benzofluoranthene, benzochrysene, and the like. Among these, naphthalene and fluorene are preferred in the present invention.

The refractive index difference between the resin component (A) and the resin component (B) is preferably 0.05 or more and 0.3 or less, and 0.1 or more and 0.3 or less, from the viewpoint of low reflectivity. More preferably, it is 0.15 or more and 0.3 or less.

(other ingredients)
The antireflection layer of the present invention may contain other components in addition to the resin component (A) and the resin component (B), and the other components include the resin components (A) and (B). In addition to other resin components (C) (for example, resin component (C) for adjusting the refractive index), metal oxide particles for increasing the refractive index (for example, metal oxide particles with a refractive index of 1.7 or more) ), hollow silica fine particles for lowering the refractive index, inorganic or organic particles for imparting slipperiness, and surfactants for improving coating appearance.

The metal oxides constituting the metal oxide particles include TiO ₂ (refractive index 2.7), ZnO (refractive index 2.0), Sb ₂ O ₃ (refractive index 1.9), SnO ₂ (refractive index 2.1), ZrO ₂ (refractive index 2.4), Nb ₂ O ₅ (refractive index 2.3), CeO ₂ (refractive index 2.2), Ta ₂ O ₅ (refractive index 2.1), Y ₂ O ₃ (refractive index 1.8), La ₂ O ₃ (refractive index 1.9), In ₂ O ₃ (refractive index 2.0), Cr ₂ O ₃ (refractive index 2.5), etc. Examples include composite oxide particles containing metal atoms.

Examples of the inorganic particles for imparting slipperiness include silica, kaolinite, talc, light calcium carbonate, heavy calcium carbonate, zeolite, alumina, barium sulfate, carbon black, zinc oxide, zinc sulfate, zinc carbonate, and dioxide. Examples include titanium, satin white, aluminum silicate, diatomaceous earth, calcium silicate, aluminum hydroxide, hydrated halloysite, magnesium carbonate, magnesium hydroxide, and the like.

The organic particles for imparting slipperiness include acrylic or methacrylic, vinyl chloride, vinyl acetate, nylon, styrene/acrylic, styrene/butadiene, polystyrene/acrylic, polystyrene/isoprene, Examples include polystyrene/isoprene, methyl methacrylate/butyl methacrylate, melamine, polycarbonate, urea, epoxy, urethane, phenol, diallyl phthalate, and polyester.

(Method for forming antireflection layer)
The antireflection layer may be formed by in-line coating, in which the surface of the polyester film is treated during the stretching process, or by off-line coating, in which it is applied outside the system on the film once it has been produced. Often, both may be used in combination.
In addition, since the antireflection layer of the present invention has the above configuration A, the antireflection layer is not formed by successively coating a high refractive index resin component and a low refractive index resin component in multiple stages, but rather It is preferable to form an antireflection layer by collectively coating a resin mixture containing two or more resin components with different values (hereinafter also referred to as "preferred antireflection layer forming method"), and such a method is adopted. As a result, the high refractive index resin such as polyester resin that has high affinity with the polyester film moves to the base material side from the coating to the drying process, and the fluorine atoms segregate on the surface of the antireflection layer, resulting in composition A. can do.

In addition, in the case of the above-mentioned preferable antireflection layer forming method, from the surface side, a low refractive index layer formed from a resin component (A) containing a fluororesin component, and a resin component (A) having a higher refractive index than the fluororesin component; It has a structure in which a high refractive index layer formed from a resin composition containing B) is sequentially laminated, but due to the low affinity between the fluororesin and the polyester resin, there is an interface between the low refractive index layer and the high refractive index layer. can be formed. In addition, by using a low refractive index layer and a high refractive index layer that have high affinity, a mixed layer can be formed between the low refractive index layer and the high refractive index layer, but the reflection on the surface of the antireflection layer It is more preferable to form an interface because light and light reflected from the interface between the layers can interfere with each other.

As described above, according to the preferred method for forming an antireflection layer of the present invention, the antireflection layer can be formed by one coating, and therefore, from the viewpoint of economy, it is preferable to employ in-line coating.
Furthermore, the coating liquid for forming the antireflection layer is preferably a dispersion liquid using water as a dispersion medium, and a surfactant may be added to stabilize the dispersion liquid and improve coating properties. . It is thought that the fluororesin migrates to the surface side of the antireflection layer during the drying stage after coating. In addition, an organic solvent can also be mixed if necessary.
The solid content concentration of the coating liquid is preferably in the range of 1 to 30% by mass, more preferably in the range of 5 to 25% by mass.

(Absolute reflectance of anti-reflection layer)
From the viewpoint of having an excellent antireflection function, the antireflection layer of the present invention preferably has a minimum absolute reflectance of 6.0% or less at a wavelength of 300 to 800 nm, and preferably 3.0% or less. More preferably, it is 1.5% or less.
In addition, from the viewpoint of wavelength selectivity for the antireflection function, the absolute reflectance at wavelengths of 300 to 400 nm and/or 650 to 800 nm is preferably 7.0% or less, and preferably 6.0% or less. More preferably, it is 3.0% or less.
For example, if only one antifouling layer containing a fluorine compound is formed on the antireflection layer and the absolute reflectance is set to the minimum value in the wavelength range of 450 to 500 nm to which the human eye is sensitive, then The absolute reflectance at wavelengths of 650 to 800 nm is high.
The wavelength selectivity of the absolute reflectance of the antireflection layer in the present invention can be achieved, for example, by adjusting the film thickness of the fluororesin layer or polyester layer, so that the light reflected from the surface of the antireflection layer and the interface between the fluororesin layer and the polyester resin layer are controlled. It can be controlled by interfering reflected light, and the absolute reflectance at wavelengths of 300 to 400 nm and/or 650 to 800 nm can be lowered.

(Surface free energy of antireflection layer)
Specifically, the antireflection layer of the present invention preferably has a surface free energy of 50 mN/m or less, more preferably 35 mN/m or less, and 20 mN/m or less, from the viewpoint of having an excellent antifouling function. Most preferably, it is less than or equal to m.
When the surface free energy of the antireflection layer of the present invention is equal to or less than the above value, a water-repellent effect is produced and excellent antifouling properties can be obtained.

<Other layers>
This film may have layers other than the antireflection layer, for example, a hard coat layer may be provided between the polyester film and the antireflection layer, or a hard coat layer may be provided between the polyester film and the antireflection layer, or a hard coat layer may be provided between the polyester film and the antireflection layer. You may also set it up.

<Application>
This film is used in optical display devices such as liquid crystal displays (LCDs), plasma display panels (PDPs), projection displays, and organic electroluminescent displays (organic ELDs), touch panels, optical lenses, eyeglass lenses, and anti-reflection treatment used in photolithography processes. , used as an anti-reflection film for applying anti-reflection treatment to the surface of solar cell panels.

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to the following Examples.
The evaluation methods and sample processing methods in Examples are as follows.

<Evaluation method>
(1) Method for measuring the intrinsic viscosity of polyester The intrinsic viscosity of the polyester used in the laminated polyester film produced in the example was determined by accurately weighing 1 g of polyester from which components incompatible with polyester had been removed, and measuring phenol/tetrachloroethane = 50. 100 ml of a mixed solvent of /50 (mass ratio) was added to dissolve the mixture, and the mixture was measured at 30°C.

(2) Method for measuring refractive index Dry a coating solution containing 97 parts by mass of resin components (components (A) and (B) described below) and 3 parts by mass of additives (particles, surfactant). It was coated onto a polyester film so that the resulting film thickness was 50 to 150 nm.
Thereafter, the absolute reflectance was measured by the method described below, and the refractive index was estimated from the obtained reflectance using Fresnel's equation.

(3) XPS (X-ray photoelectron spectroscopy)
The amount of fluorine atoms (F) and the amount of oxygen atoms (O) in the antireflection layer in the laminated polyester film produced in the examples were determined using an X-ray electron spectrometer (manufactured by Thermo Fisher Scientific Co., Ltd., product name "K-Alpha") ). The excitation X-rays were Al Kα rays, and the detector was measured at a tilt angle (photoelectron escape angle) of 90 degrees with respect to the sample surface.
In addition, after performing etching treatment with argon (Ar) etching treatment (1000 eV) for 20 to 50 seconds, quantitative analysis (atomic %) of the surface of the antireflection layer of the film was performed, and fluorine atoms (F), oxygen atoms (O) The amount was measured. This was repeated and the amount of elements at each depth was measured.
Note that XPS was measured for fluorine atoms (F), oxygen atoms (O), carbon atoms (C), and nitrogen atoms (N), and expressed as relative values (%) to the total amount of these four elements.

(4) Surface free energy The surface free energy of the antireflection layer in the laminated polyester film produced in the example was measured using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., product name "DMo- 501'') to prepare droplets of ion-exchanged water and diiodomethane on the antireflection layer surface of a laminated polyester film, and the contact angle thereof was measured. For the contact angle, the contact angle 5 seconds after dropping each liquid onto the laminated polyester film was adopted.
Regarding the contact angle data of ion-exchanged water and diiodomethane obtained by this method, surface free energy was calculated using the OWRK (Owens-Wendt-Rable-Kaelble) method using analysis software (manufactured by Dataphysics, product name "sca20"). was calculated.

(5) Method for measuring the minimum value of absolute reflectance The absolute reflectance of the antireflection layer in the laminated polyester film produced in the example was determined in advance by attaching a black tape (manufactured by Nichiban Co., Ltd., product name: Vinyl tape VT-50'') was applied, and a spectrophotometer (manufactured by JASCO Corporation, ultraviolet-visible spectrophotometer, product name ``V-570'' and automatic absolute reflectance measurement device, product name ``AM-500N'') was attached. Using synchronous mode, incident angle 5°, N polarization, response Fast, data acquisition interval 1.0 nm, bandwidth 10 nm, scanning speed 1000 m/min, the wavelength range of the anti-reflectance layer surface of the laminated polyester film was measured. The absolute reflectance from 300 to 800 nm was measured, and the wavelength (bottom wavelength) and absolute reflectance at the minimum value (minimum value) were evaluated.

(6) Method for observing cross section of antireflection layer in laminated polyester film The surface of the coating layer was dyed with RuO4 and embedded in epoxy resin. Thereafter, the cross section of the coated layer of the section prepared by the ultra-thin section method was measured using a TEM (H-7650 manufactured by Hitachi High-Technologies Corporation, acceleration voltage 100 kV).

<Materials used>
The polyester raw materials for the polyester film (base film) of the laminated polyester film produced in the examples are as follows.

[Polyester (1)]
Polyethylene terephthalate substantially free of particles and having an intrinsic viscosity of 0.64 dL/g

[Polyester (2)]
Polyethylene terephthalate with an intrinsic viscosity of 0.65 dL/g and containing 0.2% by mass of amorphous silica with an average particle size of 2 μm

The constituent components of the resin composition for forming the antireflection layer of the laminated polyester film produced in the examples are as follows.

<Component (A)>
[Fluorine-containing compound (A1)]
Isophorone diisocyanate/dimethylolpropanoic acid/fluoroether glycol (difluoroethylene oxide: difluoromethylene oxide: tetrafluoroethylene oxide = 5:43:52 (mol%)) = 40/23/37 (mol%), refractive index An aqueous dispersion of fluorine-based polyether urethane resin with a ratio of 1.39

<Component (B)>
[Polyester (B1)]
Aqueous dispersion of polyester with a refractive index of 1.57 copolymerized with the following composition Monomer composition: (acid component) terephthalic acid/isophthalic acid/5-sodium sulfoisophthalic acid // (diol component) ethylene glycol/1, 4-butanediol/diethylene glycol = 56/40/4//70/20/10 (mol%)

[Polyester (B2)]
Aqueous dispersion of polyester with a refractive index of 1.61 copolymerized with the following composition Monomer composition: (acid component) 2,6-naphthalene dicarboxylic acid/5-sodium sulfoisophthalic acid // (diol component) ethylene glycol/diethylene glycol =92/8//80/20 (mol%)

[Polyester (B3)]
Aqueous dispersion of polyester with a refractive index of 1.60, copolymerized with the following composition. Monomer composition: (acid component) 2,6-naphthalenedicarboxylic acid/sebacic acid/sulfonylisophthalic acid//(diol component) ethylene glycol/hexane Diol/diethylene glycol = 37/11/3//27/17/5 (mol%)

<Component (C)>
[Silica particles (C1)]
Silica particles with a particle size of 50 to 80 nm

<Component (D)>
[Surfactant (D1)]
Acetylenic nonionic surfactant with HLB of 8.0 and having polyethylene oxide in the side chain

[Surfactant (D2)]
A nonionic surfactant with an HLB of 13.3 whose main component is polyoxyethylene alkyl ether.

<Example 1>
A blend of the above polyester (1) and polyester (2) at a weight ratio of 92/8 was used as the raw material for layer A, and only polyester (1) was used as the raw material for layer B, and each was supplied to an extruder. Melt by heating at ℃, layer A is divided into two layers to form a layer structure of two types and three layers, with layer A being the outermost layer (surface layer) and layer B being the middle layer, and under extrusion conditions, the thickness composition ratio is surface layer/middle layer/surface layer = 1. :8:1, and cooled and solidified while being brought into close contact with a mirror cooling drum with a surface temperature of 40 to 50°C to produce an unstretched film. This film was stretched 3.4 times in the longitudinal direction while passing through a group of heating rolls at 85° C. to obtain a uniaxially stretched film.
Next, on one side of this uniaxially stretched film, a composition for forming an antireflection layer shown in Table 1 below diluted with water was applied as coating solution 1, and then this film was introduced into a tenter stretching machine and heated to 110°C. After stretching 4.3 times in the width direction at Obtained. Note that the solid content concentration of the coating liquid was 19% by mass.
The evaluation results regarding the laminated polyester film are shown in Tables 2 and 3.
Further, FIG. 1 shows the results of cross-sectional observation, FIG. 2 shows the evaluation results of reflectance characteristics, and FIG. 3 shows the distribution of fluorine atoms by XPS.

In addition, in Table 1, each numerical value of fluorine material, polyester material, particle, and surfactant shows the mass ratio (parts) of each component.

<Example 2 and 3>
As shown in Table 1, Examples 2 and 3 were the same as those in Example 1 except that the composition for forming an antireflection layer, that is, coating liquid 1, was changed to a coating liquid having the composition shown in Table 1. A laminated polyester film (antireflection layer film) was obtained in the same manner as in 1. The evaluation results regarding the laminated polyester film are shown in Tables 2 and 3. Further, the evaluation results of reflectance characteristics are shown in FIG. 2.

As shown in Examples 1 to 3, in the laminated polyester film of the present invention, an antireflection layer is formed using a resin composition containing resin materials with different refractive indexes, and the antireflection layer has a cross-sectional observation result (Fig. 1 As can be seen from the XPS measurement results (see Figure 3), they contain resin components (fluorine resin and polyester) with different refractive indexes, and fluorine atoms are segregated on the surface side. It was confirmed that by having a two-layer structure that gradually decreases toward the film, it has both excellent antifouling properties and low reflection properties.
In FIG. 1, the embedding resin is an epoxy resin for cutting TEM samples, the upper layer is a low refractive index layer containing a large amount of fluororesin, and the lower layer is a high refractive index layer containing a large amount of polyester. PET means polyester film.

(Reflectance characteristics)
FIG. 2 shows the reflectance characteristics of Examples 1 to 3. For comparison with conventional reflective films, the reflectance characteristics of Reference Example 1 below are also shown in FIG. As shown in FIG. 2, the absolute reflectance of the laminated polyester film of Reference Example 1 is low near wavelengths of 450 to 500 nm, but high at wavelengths of 300 to 400 and 650 to 800 nm. This result shows that the laminated polyester film of the present invention has low reflection characteristics with wide wavelength selectivity.

<Reference example 1>
In order to confirm that the laminated polyester film of the present invention has low reflection characteristics with wide wavelength selectivity compared to conventional antireflection films in which an antifouling layer is formed on an antireflection layer, fluorine-based Reflectance characteristics of a laminated polyester film (Reference Example 1) produced in the same manner as in Example 1, except that a resin composition consisting of resin (A1), silica particles (C1), and surfactant (D1) was used. was evaluated.

(Distribution of fluorine atomic weight by XPS)
In order to demonstrate the specificity of the concentration gradient due to the segregation of fluorine atoms in the antireflection layer of the laminated polyester film of the present invention, the antireflection layer of the laminated polyester film of the following Reference Example 2 and the laminated polyester film produced in Example 1 was FIG. 3 shows the distribution of fluorine atomic weight on the surface by XPS.
As shown in FIG. 3, compared to the laminated polyester film of Reference Example 2, the fluorine atomic weight of the laminated polyester film of Example 1 decreases somewhat gradually toward the polyester film; The trend is for the fluorine atomic weight to decrease, and a large amount of fluorine-based resin is present on the surface side, making it possible to maintain low reflection properties while maintaining excellent antifouling properties.

<Reference example 2>
In Example 1, coating liquid (I) containing a resin composition consisting of polyester (B1) and surfactant (D2) was applied to a polyester film base material and dried at 120°C to form a polyester resin layer on the film. Created.
Next, a coating liquid (II) containing a resin composition consisting of a fluororesin (A1) and a surfactant (D2) was applied onto the polyester resin layer and dried at 120°C to produce a laminated polyester film.

The laminated polyester film of the present invention can be suitably used in applications requiring high antifouling properties and high antireflection effects. In particular, it can be used on the surface of optical displays. Examples of the optical display device include a touch panel, liquid crystal display (LCD), plasma display panel (PDP), projection display, organic electroluminescent display (organic ELD), and the like. The laminated polyester film of the present invention can be used directly on the screen surface of the optical display device or in close contact with the front plate disposed in front of the screen via an adhesive layer.

Claims (11)

having an antireflection layer on at least one side of the polyester film,
The antireflection layer is formed from a resin composition containing two types of resin components with different refractive indexes,
One of the two resin components (A) contains a fluororesin,
The other resin component (B) of the two types of resin components has a higher refractive index than the fluororesin,
The concentration distribution of fluorine atoms (F) and oxygen atoms (O) in the thickness direction of the antireflection layer was measured using sequential argon (Ar) etching and XPS (X-ray photoelectron spectroscopy). ) The first time when the amount of oxygen atoms (O) becomes smaller than the amount of oxygen atoms (O) is defined as A laminated polyester film having a molecular weight of 10 or more and 20 or less. The laminated polyester film according to claim 1, wherein the fluororesin has a refractive index of 1.39 or more and 1.44 or less. The laminated polyester film according to claim 1 or 2, wherein the resin component (B) has a refractive index of 1.57 or more and 1.61 or less. The antireflection layer contains a fluororesin component (A1) having a refractive index of 1.39 or more and 1.44 or less, and a resin component (B) having a refractive index of 1.57 or more and 1.61 or less, and 2 The laminated polyester film according to claim 1, having a layer structure of more than one layer. The laminated polyester film according to any one of claims 1 to 4, wherein the resin component (B) contains polyester. The laminated polyester film according to any one of claims 1 to 5, wherein the antireflection layer has a surface free energy of 50 mN/m or less. An antireflection layer forming step of applying a liquid mixture containing two types of resin components having different refractive indexes to at least one surface of a polyester film to form an antireflection layer on at least one surface of the polyester film,
One of the resin components (A) of the two resin components having different refractive indexes contains a fluororesin,
The other resin component (B) of the two types of resin components has a higher refractive index than the fluororesin,
The concentration distribution of fluorine atoms (F) and oxygen atoms (O) in the thickness direction of the antireflection layer was measured using sequential argon (Ar) etching and XPS (X-ray photoelectron spectroscopy). ) The first time when the amount of oxygen atoms (O) becomes smaller than the amount of oxygen atoms (O) is defined as A method for producing a laminated polyester film, wherein the polyester film is 10 or more and 20 or less. The method for producing a laminated polyester film according to claim 7, wherein the fluororesin has a refractive index of 1.39 or more and 1.44 or less. The method for producing a laminated polyester film according to claim 7 or 8, wherein the resin component (B) has a refractive index of 1.57 or more and 1.61 or less. The method for producing a laminated polyester film according to claim 9, wherein the resin component (B) contains polyester. The method for producing a laminated polyester film according to any one of claims 7 to 10, wherein the antireflection layer has a surface free energy of 50 mN/m or less.