JP2014046570A - Laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated polyester film excellent in adhesiveness with a functional layer such as a hard coat layer and also hardly causing an interference spot (irregular color feeling) of light.SOLUTION: The laminated polyester film includes a coating layer containing the following copolymerization polyester of 70 mass% or more on the basis of the mass of a coating layer on at least one surface of an oriented polyethylene terephthalate film. The copolymerization polyester comprises: a naphthalene dicarboxylic acid component of 60-90 mol%; a 6-12c alkylene dicarboxylic acid component of 0-40 mol%; a 4-10c alkylene glycol component of 0-50 mol% (where, the total of the alkylene dicarboxylic acid component and the alkylene glycol component is 15-50 mol%.); and an ethylene oxide adduct component of bisphenol fluorene of 5 mol% or more and less than 20 mol%.

Description

The present invention relates to a laminated polyester film. More specifically, it is excellent in adhesiveness when laminating functional layers such as a hard coat layer, and does not easily cause light interference spots (color spot feeling), and is particularly suitable for use as an easily adhesive film for optics. The present invention relates to a laminated polyester film that can be produced.

Polyester films, particularly stretched films of polyethylene terephthalate, have recently been used in various optical films, and are used for applications such as protective films for flat panel displays, antireflection films, and touch panels. However, even if a functional layer such as a hard coat layer for suppressing the occurrence of scratches on the film surface or an antireflection layer for suppressing light reflection is attempted to be laminated, the adhesion is poor, so in-line coating is usually applied to the film surface. Or it is common to set it as the laminated film which provided the easily bonding layer by offline coating. In this case, when the difference between the refractive index of the polyester film or the functional layer and the refractive index of the easy-adhesion layer increases, a problem of color spots due to light interference spots occurs (this interference spots are sunlight or (It is more perceived under a special fluorescent lamp called a three-wavelength fluorescent lamp than an incandescent lamp)
In order to solve this problem, it has been proposed to increase the refractive index of the easy-adhesion layer so that the refractive index is intermediate between the polyester film and the functional layer, and to adjust the thickness.

For example, in Patent Document 1, the easy-adhesion layer has a refractive index of 1.55 to 1.62 that is an intermediate between the refractive index of the stretched polyester film and the hard coat layer, and has a thickness of 50 to 50.
A method of 150 nm is proposed, and it is described that a high glass transition temperature polyester having a 2,6-naphthalenedicarboxylic acid component and a low glass transition temperature polyester containing a trimellitic acid component are used in combination as an easy adhesion layer. ing. Patent Document 2 discloses a method of providing an easy-adhesion layer mainly composed of a copolyester containing a naphthalenedicarboxylic acid component and a glycol component having a bisphenol A skeleton, and Patent Document 3 discloses 2,6-naphthalene dicarboxylic acid. A method has been proposed in which a copolyester containing an acid component and an ethylene oxide adduct component of bisphenolfluorene is contained as one component, and an easy adhesion layer having a thickness of 50 to 200 nm is provided.

Usually, the easy-adhesion layer using the above-mentioned copolymer polyester is formed by an in-line coating method in which orientation crystallization is completed after coating on a polyester film before orientation completion. However, according to our study, it was estimated that when coated on a polyethylene terephthalate film, it was presumed to be due to cracks in the coating layer that occurred in the stretching process, but it was found that there was a need for further improvement in adhesion. .

JP 2007-253512 A JP 2009-126035 A JP 2010-284944 A

The present invention has been made in view of the above-described background art, and an object of the present invention is a laminated polyester that is excellent in adhesiveness to a functional layer such as a hard coat layer and that hardly causes light interference spots (color spots). To provide a film.

As a result of intensive studies to solve the above problems, the present inventors have found that the copolymerization component of the copolymerized polyester used for increasing the refractive index of the coating layer is the same as that for forming the coating layer in order to increase the glass transition temperature. Since the film properties deteriorate, when an in-line coating method is used to form a coating layer, the coating layer cracks under the stretching conditions of the polyethylene terephthalate film, which results in insufficient adhesion of the resulting laminated polyester film. As a result of further investigations, the present invention has been completed.

That is, the object of the present invention is “a laminated polyester film having a coating layer on at least one side of an oriented polyethylene terephthalate film, wherein the coating layer comprises 70% by mass or more of the following copolyester based on the mass of the coating layer. This is achieved by the "containing laminated polyester film".

Copolyester:
(A1) 60-90 mol% of naphthalenedicarboxylic acid component,
(B1) 0 to 40 mol% of an alkylene dicarboxylic acid component having 6 to 12 carbon atoms and 4 to 1 carbon atoms
0 to 50 mol% of the alkylene glycol component of 0, the total of the alkylene dicarboxylic acid component and the alkylene glycol component is 15 to 50 mol%, and (C1) a glycol component having a fluorene structure represented by the following formula (I) Copolyester containing 5 mol% or more and less than 20 mol%.
(However, the above mol% is a value with respect to 100 mol% of all dicarboxylic acid components of the copolyester.)

（Ｒ_１は炭素数２〜４のアルキレン基、Ｒ_２、Ｒ_３、Ｒ_４、およびＲ_５は、水素、炭素数
１〜４のアルキル基、アリール基またはアラルキル基であり、それぞれ同じであっても異
なっていてもよい。）

(R ₁ is an alkylene group having 2 to 4 carbon atoms, R ₂ , R ₃ , R ₄ , and R ₅ are hydrogen, an alkyl group having 1 to 4 carbon atoms, an aryl group, or an aralkyl group. Or different.)

In addition, the copolymer polyester of the present invention has, as a preferred embodiment thereof, “The copolymer polyester further contains (D2) bisphenol A ethylene oxide adduct component in an amount of 5 to 25 mol%.
The ratio of the copolymerized polyester containing (A3) naphthalenedicarboxylic acid component is 60 to 80 mol%, and (B3) the proportion containing an alkylenedicarboxylic acid component having 6 to 12 carbon atoms is 0 mol%, Further, (E3) 20 of terephthalic acid and / or isophthalic acid component is added.
˜40 mol% ”,“ the coating layer contains 1-30% by mass of a crosslinking agent based on the mass of the coating layer ”,“ to be used as an optically easy-adhesive polyester film ” Includes those with one requirement.

Since the laminated polyester film of the present invention is provided with a coating layer using a specific copolymerized polyester as described above, even in a normally employed in-line coating, it is difficult for the coating layer crack to occur in the stretching process. For example, it has excellent adhesion to a functional layer such as a hard coat layer, and also has a feature that light interference spots (color spots) hardly occur. Therefore, it can be particularly suitably used as an easily adhesive polyester film for optics.

The laminated polyester film of the present invention has a coating layer described later on at least one side of an oriented polyethylene terephthalate film.

[Polyethylene terephthalate film]
Oriented polyethylene terephthalate in the present invention (hereinafter sometimes abbreviated as PET)
The polyester constituting the film is a polyester having an ethylene terephthalate unit of 95 mol% or more, preferably 98 mol% or more, based on all repeating units, and particularly preferably a homopolyester not using a copolymerization component. In the case of copolymerized polyethylene terephthalate, for example, a dicarboxylic acid component such as isophthalic acid or naphthalenedicarboxylic acid or a glycol component such as diethylene glycol, butanediol, or cyclohexanediol can be used as the copolymerization component.

The intrinsic viscosity of polyethylene terephthalate is 35 ° C in o-chlorophenol,
It is preferably 0.40 dl / g or more, and more preferably 0.50 to 0.90 dl / g. When the intrinsic viscosity is less than 0.40 dl / g, cutting may occur frequently during film formation, or the strength of the product after forming may be insufficient. On the other hand, if the intrinsic viscosity becomes too high, the melt viscosity becomes high, so that melt extrusion is difficult, and the polymerization takes a long time and the productivity may be deteriorated.
The polyethylene terephthalate may contain a small amount of other polymers and additives as long as the object of the present invention is not impaired. For example, lubricants such as inert particles, colorants such as pigments and dyes, stabilizers, Examples of the additive include a flame retardant, a foaming agent, and an ultraviolet absorber.

The laminated polyester film of the present invention preferably contains no inert particles in the PET film from the viewpoint of maintaining high transparency. However, prevention of minute scratches in the manufacturing process,
In order to improve the winding property of the film, a small amount of inert particles may be contained as a lubricant. As the inert particles, for example, particles having an average particle diameter of 0.01 to 2 μm, further 0.05 to 1 μm, and particularly 0.1 to 0.3 μm may be used. The blending ratio is preferably 100 ppm or less, more preferably 10 ppm or less, and particularly preferably 1 ppm or less, based on the weight of the layer to be blended.

The oriented polyethylene terephthalate film made of such a polyester may be a uniaxially stretched film or a biaxially stretched film, but it is a biaxially stretched film from the standpoint of uniformity of mechanical characteristics and thermal characteristics in the in-plane direction. Preferably there is. At that time, the refractive index in the plane direction (in the film plane, the average refractive index of the refractive index in any one direction and the refractive index in the direction perpendicular thereto)
Can be arbitrarily set from the viewpoints of mechanical properties, thermal properties, dimensional stability, etc. required for the film, but is usually in the range of 1.6 to 1.7 with an Abbe refractometer. If it exists, even if functional layers, such as a hard-coat layer, are provided on the laminated polyester film of this invention which provided the application layer mentioned later, generation | occurrence | production of the light interference spot (color spot feeling) can be suppressed.

[Coating layer]
The laminated polyester film of the present invention is 70% by mass or more, preferably 80% by mass or more, based on the mass of the coating layer of the following copolyester on at least one side of the oriented polyethylene terephthalate film or on both sides as necessary. , More preferably 85
It has a coating layer containing not less than mass%, particularly preferably not less than 90 mass%. When the ratio of the copolyester is 70% by mass or more, the adhesion with a functional layer such as a hard coat layer is improved, and the refractive index of the coating layer can be within an appropriate range, so that the light interference. Spots can be suppressed. Furthermore, the glass transition temperature (Tg) of the coating layer is also in an appropriate range, the film forming property is improved, the cracking of the coating layer is reduced, and the adhesiveness deterioration due to the cracking can be suppressed, and the adhesiveness A laminated polyester film excellent in the above can be obtained.

In addition, since the refractive index of the oriented polyethylene terephthalate film is usually about 1.66, and the refractive index of the acrylic resin hard coat layer usually used as the functional layer is about 1.52, the refractive index of the coating layer is The range of 1.57 to 1.62 is preferred, and 1.58 to 1.2.
The range of 61 is more preferable, and the range of 1.59 to 1.60 is particularly preferable. Such a refractive index can be easily achieved by employing a copolyester described later.
The thickness of the coating layer is preferably 50 to 100 nm, more preferably 70 to 90 nm. By setting the thickness of the coating layer within this range, when a functional layer such as an acrylic hard coat layer is provided thereon, the effect of suppressing light interference spots is further increased, which is preferable.

(Copolymerized polyester)
The copolymerized polyester contained in the coating layer of the present invention is an alkylene having a naphthalenedicarboxylic acid component of 60 to 90 mol% and a carbon number of 6 to 12 based on the total dicarboxylic acid component (100 mol%) of the copolymerized polyester. 0 to 40 mol% of dicarboxylic acid component, 4 to 10 carbon atoms
0 to 50 mol% of the alkylene glycol component, 5 mol% or more and less than 20 mol% of the glycol component having the fluorene structure represented by the formula (I), and the alkylene dicarboxylic acid component having 6 to 12 carbon atoms and the above The total of alkylene glycol components having 4 to 10 carbon atoms is 15 to 50 mol%.

When the ratio of the naphthalenedicarboxylic acid component is within the above range, the refractive index of the copolyester can be increased, the refractive index of the coating layer can be easily set within the above-described preferable range, and light interference spots can be reduced. Can be suppressed. Moreover, the swelling resistance of the coating layer with respect to a solvent also becomes favorable. If the proportion of the naphthalenedicarboxylic acid component is less than the lower limit, the refractive index of the copolyester is lowered, and as a result, the refractive index of the coating layer is lowered and the effect of suppressing light interference spots is insufficient. In addition, since swelling with organic solvents increases (solvent resistance deteriorates), interference spots caused by swelling of the coating layer due to swelling caused by swelling with the organic solvent in the functional layer coating solution such as a hard coat layer. This is not preferable because not only is easy to occur, but also blocking resistance is reduced. On the other hand, as the proportion of the naphthalenedicarboxylic acid component increases, the refractive index of the copolyester increases, so that the proportion of other (such as a crosslinking agent and other components described later) as the coating layer can be increased. However, at the same time, the glass transition temperature (Tg) of the copolyester tends to be high and the glass transition temperature of the coating layer tends to be high, the film forming property of the coating layer is lowered, and the adhesion of the resulting laminated polyester film is reduced. It tends to decrease.
Therefore, the preferable lower limit of the content of the naphthalenedicarboxylic acid component is 65 mol%,
The upper limit is preferably 85 mol%, more preferably 80 mol%, particularly preferably 70 mol%.

Here, examples of the naphthalenedicarboxylic acid component include 2,7-naphthalenedicarboxylic acid component, 2,6-naphthalenedicarboxylic acid component, 1,4-naphthalenedicarboxylic acid component, and the like, among which 2,6-naphthalenedicarboxylic acid component. Ingredients are preferred.

Moreover, 0-40 mol% of C6-C12 alkylene dicarboxylic acid components and C4-C10 alkylene glycol components are used on the basis of the total acid components of the copolyester.
Since 50 mol% is contained, and the total of the alkylene dicarboxylic acid component and the alkylene glycol component is 15 to 50 mol%, the Tg of the copolyester can be lowered, and the coating layer Tg can be lowered. As a result, the in-line coating method that is usually employed when forming a coating layer on an oriented polyethylene terephthalate film is also excellent in the film-forming property of the coating layer, so it cracks in the coating layer under dry / stretch conditions. Generation | occurrence | production is suppressed and the laminated polyester film excellent in adhesiveness is obtained. In particular, when the simultaneous biaxial stretching method is used for the production of the oriented polyester film and the in-line coating method is used for forming the coating layer, the preheating / drying temperature tends to be relatively low, so the effect of the present invention is large. Particularly preferred. Moreover, it is excellent also in adhesiveness and blocking resistance.

When the total amount of the alkylene dicarboxylic acid component and the alkylene glycol component is less than the lower limit, the Tg of the copolyester is not sufficiently lowered, so that the resulting laminated polyester film has insufficient adhesion. On the other hand, if the alkylene dicarboxylic acid component or alkylene glycol component exceeds the upper limit, or the total of both exceeds the upper limit,
Not only the blocking resistance is lowered, but also the content of other copolymer components is reduced. As a result, the refractive index of the copolymer polyester is lowered and the effect of suppressing the light interference spots becomes insufficient. In addition, the solvent resistance of the coating layer may be reduced. From such a viewpoint, the total amount of the alkylene dicarboxylic acid component and the alkylene glycol component is preferably in the range of 20 to 50 mol%.

Preferred examples of the alkylene dicarboxylic acid component having 6 to 12 carbon atoms (dicarboxylic acid component having an alkylene group having 4 to 10 carbon atoms) include 1,4-butanedicarboxylic acid component, 1,6-hexanedicarboxylic acid component, 1,4-cyclohexanedicarboxylic acid component,
A 1,8-octane dicarboxylic acid component, a 1,10-decanedicarboxylic acid component, etc. can be mentioned. Among these, from the viewpoint that an appropriate Tg can be obtained, a dicarboxylic acid component having an alkylene group having 4 to 8 carbon atoms is preferable, and a dicarboxylic acid component having an alkylene group having 4 to 6 carbon atoms is more preferable.

Moreover, as a C4-C10 alkylene glycol component preferably used, for example, a 1,4-butanediol component, a 1,6-hexanediol component, a 1,4-cyclohexanediol component, a 1,8-octanediol component, Examples include 1,10-decanediol component. Among these, an alkylene glycol component having 4 to 8 carbon atoms is preferable, and an alkylene glycol component having 4 to 6 carbon atoms is more preferable from the viewpoint that an appropriate Tg can be obtained.

In addition, when trying to add other copolymerization components to the copolymerized polyester to impart other functions, it is easy to add them as an acid component, and it is easy to carry out a polymerization reaction, so there is room for copolymerization in the acid component. From the viewpoint of keeping the above, it is more preferable to contain the alkylene dicarboxylic acid component and the alkylene glycol component as an alkylene glycol component.

Further, since the glycol component having the fluorene structure represented by the formula (I) is contained in an amount of 5 mol% or more and less than 20 mol% based on the total acid component of the copolymerized polyester, the Tg of the copolymerized polyester is appropriately low. While maintaining the temperature, the refractive index can be in a preferred range. When the content of the glycol component having the fluorene structure represented by the formula (I) is less than 5 mol%, it is difficult to make the refractive index of the copolymer polyester within a preferable range, and light interference spots cannot be suppressed. . On the other hand, in the case of 20 mol% or more, the Tg of the copolyester becomes too high, so that not only the transparency of the laminated polyester film obtained by reducing the film forming property of the coating layer is lowered, but also the adhesiveness is lowered. To do. From such a viewpoint, the preferred lower limit is 3 mol%, more preferably 5%, and the preferred upper limit is 15 mol%, more preferably 10%.

Examples of the glycol component having a fluorene structure represented by the formula (I) preferably used include a 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene component and a 9,9-bis [4- (2 -Hydroxyethoxy) -2-methylphenyl] fluorene component.

The above-described copolymer polyester of the present invention preferably contains 5 to 25 mol%, more preferably 10 to 20 mol% of an ethylene oxide adduct component of bisphenol A in addition to the above components. Thus, while maintaining the refractive index, Tg can be made a more preferable range, and the adhesiveness is also improved. In addition, the range of 2-4 mol is suitable for the average addition mole number of ethylene oxide with respect to 1 mol of bisphenol A.

In addition to the above components, 20-40 mol% of terephthalic acid and / or isophthalic acid is used in order to bring the Tg of the copolyester into a more preferable range while maintaining the refractive index.
In particular, it is preferably contained in an amount of 24 to 34 mol%. Among these, an isophthalic acid component is preferable because it is easy to obtain a more suitable Tg.

Furthermore, the copolyester of the present invention preferably contains 1 to 10 mol% of a dicarboxylic acid component having a sulfonate group, based on the total acid component. Thereby, the solubility at the time of making copolymer polyester into aqueous coating liquid thru | or water dispersibility can be improved. Moreover, the solvent resistance (swelling resistance) of the coating layer can be improved. However, if the amount is too large, the water resistance and blocking resistance of the coating layer tend to be low, so the range of 2 to 8 mol% is particularly preferable.

Examples of the aromatic dicarboxylic acid component having a sulfonate group include a 5-sodium sulfoisophthalic acid component, a 5-potassium sulfoisophthalic acid component, a 5-lithium sulfoisophthalic acid component, and a 5-phosphonium sulfoisophthalic acid component. However, the 5-sodium sulfoisophthalic acid component is most preferable from the viewpoint of improving water dispersibility.

The copolymerized polyester of the present invention may contain an acid component or a diol component other than those described above, and examples of the acid component include phthalic acid and phthalic anhydride, and examples of the diol component include , Ethylene glycol, diethylene glycol, dipropylene glycol, xylene glycol, dimethylolpropane and the like. If the amount is slightly more, unsaturated acid components such as maleic acid and itaconic acid, polyfunctional acid components such as trimellitic acid and pyromellitic acid, polyfunctional hydroxy components such as glycerin and trimethylolpropane, and poly (ethylene oxide) Poly (alkylene oxide) glycol components such as glycol and poly (tetramethylene oxide) glycol may be used.

The range of preferable intrinsic viscosity (sometimes abbreviated as IV) of the copolymerized polyester of the present invention is 0.2 to 0.8 dl / g, and the lower limit is further 0.3 dl / g, particularly 0.4 dl / g.
The upper limit is preferably 0.7 dl / g, particularly preferably 0.6 dl / g. Here, the intrinsic viscosity is a value measured at 35 ° C. using orthochlorophenol.

Further, the glass transition temperature (Tg) of the copolymerized polyester of the present invention is preferably 70 ° C. or less from the viewpoint of coating film formability (film forming property) and adhesiveness when in-line coating on a polyethylene terephthalate film. From the viewpoint of blocking resistance, it is preferably 40 ° C or higher, particularly 45 ° C or higher. Further, the refractive index of the copolyester makes it easy to suppress light interference spots (color spots) by setting the refractive index of the coating layer to the above-mentioned preferable range.
. It is preferably in the range of 58 to 1.65, more preferably in the range of 1.60 to 1.63, and particularly preferably in the range of 1.61 to 1.62. In order to satisfy the Tg and refractive index of the copolyester at the same time, the above-described requirements regarding the copolyester may be adopted.

Examples of the copolymer polyester preferably used include the following copolymer polyesters.

[Preferred Embodiment 1 of Copolyester]
(A2) 60-90 mol% of naphthalene dicarboxylic acid component
(B2) 0 to 40 mol% of an alkylenedicarboxylic acid component having 6 to 12 carbon atoms and 4 to 1 carbon atoms
0 to 50 mol% of 0 alkylene glycol component, and 15 to 50 mol% of the total of the alkylene dicarboxylic acid component and the alkylene glycol component
(C2) 5 mol% or more and less than 20 mol% of the glycol component having the fluorene structure represented by the formula (I), and (D2) 5 to 25 mol% of the bisphenol A ethylene oxide adduct component.
(However, the above mol% is a value with respect to 100 mol% of all dicarboxylic acid components of the copolyester.)
Copolyester containing.

[Preferred embodiment 2 of copolymerized polyester]
(A3) Naphthalenedicarboxylic acid component is 60 to 80 mol%
(B3) 15 to 50 mol% of an alkylene glycol component having 4 to 10 carbon atoms
(C3) 5 mol% or more and less than 20 mol% of the glycol component having the fluorene structure represented by the formula (I) (D3) 5 to 25 mol% of the bisphenol A ethylene oxide adduct component
(E3) 20-40 mol% of terephthalic acid component and / or isophthalic acid component
(However, the above mol% is a value with respect to 100 mol% of all dicarboxylic acid components of the copolyester.)
Copolyester containing.

[Preferred embodiment 3 of copolymerized polyester]
(A4) Naphthalenedicarboxylic acid component is 60 to 80 mol%
(B4) 15 to 50 mol% of an alkylene glycol component having 4 to 10 carbon atoms
(C4) 5 mol% or more and less than 20 mol% of the glycol component having the fluorene structure represented by the formula (I) (E4) 20 to 40 mol% of the terephthalic acid component and / or isophthalic acid component
(However, the above mol% is a value with respect to 100 mol% of all dicarboxylic acid components of the copolyester.)
Copolyester containing.

[Preferred embodiment 4 of copolymerized polyester]
(A5) The naphthalene dicarboxylic acid component is 60 to 70 mol%.
(B5) 15 to 50 mol% of an alkylene glycol component having 4 to 10 carbon atoms
(C5) 5 mol% or more and less than 20 mol% of the glycol component having the fluorene structure represented by the formula (I) (D5) 5 to 25 mol% of the bisphenol A ethylene oxide adduct component
(E5) 24-34 mol% of terephthalic acid component and / or isophthalic acid component
(F5) 6-8 mol% of dicarboxylic acid component having a sulfonate group
(However, the above mol% is a value with respect to 100 mol% of all dicarboxylic acid components of the copolyester.)
Copolyester containing.

The copolyester of the present invention described in detail above can be produced by a conventionally known polyester production technique. For example, 2,6-naphthalenedicarboxylic acid or an ester-forming derivative thereof, isophthalic acid or an ester-forming derivative thereof and 5-sodium sulfoisophthalic acid or an ester-forming derivative thereof are converted to tetramethylene glycol, 9,9-
A copolymer polyester having a predetermined intrinsic viscosity by reacting with bis [4- (2-hydroxyethoxy) phenyl] fluorene, a bisphenol A ethylene oxide adduct component to form a monomer or oligomer, and then polycondensing under vacuum. It can manufacture by the method to do. In this case, a catalyst for promoting the reaction, for example, an esterification or transesterification catalyst,
A polycondensation catalyst can be used, and various additives such as stabilizers can also be added.

The copolymerized polyester of the present invention is applied to at least one surface of a polyethylene terephthalate film, but since the in-line coating method applied when forming the polyester film is preferable, the copolymerized polyester is preferably used as an aqueous dispersion. . The method for forming the aqueous dispersion is not particularly limited, and a conventionally known method may be adopted.

(Crosslinking agent)
The coating layer of the present invention preferably contains a crosslinking agent in addition to the above-described copolymer polyester. As the crosslinking agent preferably used, an epoxy crosslinking agent, an oxazoline crosslinking agent,
A melamine type crosslinking agent, an isocyanate type crosslinking agent, etc. can be illustrated, These may use 1 type and may use 2 or more types together.

Examples of the epoxy-based crosslinking agent include polyepoxy compounds, diepoxy compounds, monoepoxy compounds, glycidylamine compounds, etc. Examples of the polyepoxy compounds include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether. , Diglycerol polyglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, diepoxy compound, for example, neopentyl glycol diglycidyl ether, 1,6-hexanediol Diglycidyl ether, resorcin diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene group Call diglycidyl ether, propylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, poly-1,4
Examples of butanediol 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-
Examples include m-xylylenediamine and 1,3-bis (N, N-diglycidylamino) cyclohexane.

As the oxazoline-based crosslinking agent, a polymer containing an oxazoline group is preferable. It can be prepared by polymerization with addition polymerizable oxazoline group-containing monomers alone or with other monomers. Addition polymerizable oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-vinyl
And isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, and the like. One or a mixture of two or more of these may be used. Can be used. Among these, 2-isopropenyl-2-oxazoline is preferred because it is easily available industrially. The other monomer may be any monomer that can be copolymerized with an addition-polymerizable oxazoline group-containing monomer, such as alkyl acrylate, alkyl methacrylate (the alkyl group includes a methyl group, an ethyl group, n
(Meth) acrylic acid esters such as -propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group); acrylic acid, methacrylic acid, itaconic acid, maleic acid, Unsaturated carboxylic acids such as fumaric acid, crotonic acid, styrenesulfonic acid and salts thereof (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); unsaturated nitriles such as acrylonitrile, methacrylonitrile; acrylamide, Methacrylamide, N-alkylacrylamide, N-alkylmethacrylamide, N, N-dialkylacrylamide, N, N-dialkylmethacrylate (alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl Group,
Unsaturated amides such as isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, etc .; those obtained by adding polyalkylene oxide to the ester part of vinyl acetate, vinyl propionate, acrylic acid, methacrylic acid, etc. Vinyl esters; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α and β-unsaturated monomers such as vinyl chloride, vinylidene chloride and vinyl fluoride; styrene, α- An α, β-unsaturated aromatic monomer such as methylstyrene can be used, and one or more of these monomers can be used.

As the melamine-based crosslinking agent, a compound obtained by reacting methyl alcohol melamine derivative obtained by condensing melamine and formaldehyde with methyl alcohol, ethyl alcohol, isopropyl alcohol or the like as a lower alcohol and a mixture thereof are preferable. Examples of the methylol melamine derivative include monomethylol melamine, dimethylol melamine, trimethylol melamine, tetramethylol melamine, pentamethylol melamine, hexamethylol melamine and the like.

Examples of the isocyanate-based crosslinking agent include tolylene diisocyanate, diphenylmethane-4,4′-diisocyanate, metaxylylene diisocyanate, hexamethylene-1,6-diisocyanate, 1,6-diisocyanate hexane, tolylene diisocyanate and hexanetriol. Adduct, adduct of tolylene diisocyanate and trimethylolpropane, polyol-modified diphenylmethane-4,4'-diisocyanate, carbodiimide-modified diphenylmethane-4,4'-diisocyanate, isophorone diisocyanate, 1,5-naphthalene diisocyanate, 3,3 ' -Bitrylene-4,4 'diisocyanate, 3,3'dimethyldiphenylmethane-4,4'-diisocyanate, metaphenylene diisocyanate and the like.
Of these cross-linking agents, oxazoline-based cross-linking agents are particularly preferred from the viewpoints of ease of handling, pot life of the coating liquid, and the like.

By including a cross-linking agent in the coating layer, the solvent resistance (swelling resistance) and blocking resistance of the coating layer can be improved. In addition to the difficulty of suppressing light interference spots due to a decrease in the refractive index of the coating layer, the coating layer tends to be hard and the adhesiveness tends to decrease. It is preferable to be in the range of 1 to 30% by mass, particularly 5%.
It is preferable to set it as the range of 10 to 10 weight%.

(Other ingredients)
Various additives can be blended in the coating layer of the present invention within a range not impairing the object of the present invention. For example, to improve film slipperiness, scratch resistance, wettability during coating,
Particles, waxes, surfactants, wetting regulators and the like may be added, and other antistatic agents, ultraviolet absorbers and the like may be added.
For example, by adding particles, the slipperiness and scratch resistance of the film can be improved. Such particles may be any of organic particles, inorganic particles, and organic-inorganic composite particles. From the viewpoint of improving scratch resistance while maintaining transparency, large particles (particles), It is preferable to contain both small particles (small particles).

The average particle size of the large particles is suitably in the range of 80 to 1000 nm, more preferably 100
It is in the range of ˜400 nm, more preferably in the range of 130 to 350 nm. Thereby, it is excellent in lubricity and scratch resistance. In addition, since a large particle is easy to drop | omit from an application layer, it is preferable that it is an organic inorganic composite particle which coat | covered the inorganic particle surface with organic substance (for example, acrylic).
The content of the large particles in the coating layer is preferably 0.1 to 5% by mass, more preferably 0.1 to 1% by mass with respect to the mass of the coating layer, and the effect of adding large particles is further obtained. Cheap.

The average particle size of the small particles is suitably in the range of 10 nm or more and less than 100 nm, more preferably 20 to 80 nm, still more preferably 30 to 60 nm. Thereby, it is excellent in blocking resistance. From the viewpoint of hardness, the small particles are preferably inorganic particles, and are preferably metal oxide particles. Examples of the metal oxide particles include silica particles, alumina particles, titania particles, and zirconia particles. Among these, silica particles and titania particles are preferable from the viewpoint of excellent cost.
The content of the small particles in the coating layer is preferably 0.1 to 5% by mass, more preferably 1 to 3% by mass with respect to the mass of the coating layer, and the effect of adding small particles is more easily obtained.

[Production method of laminated polyester film]
The laminated polyester film of the present invention described above can be produced, for example, by the following method. That is, it is easy to obtain a thin coating layer uniformly by manufacturing by an in-line coating method in which an unstretched film before orientation is completed or a partially oriented film is provided with a coating film and then heat-fixed. Moreover, a strong coating layer is obtained, and further, productivity is excellent, which is preferable. The film forming method may be a sequential biaxial stretching method or a simultaneous biaxial stretching method. From the viewpoint of suppressing damage to the film, the simultaneous biaxial stretching method is preferred. On the other hand, in the simultaneous biaxial stretching method, since the biaxial stretching is performed at the same time, when the coating liquid for forming the coating layer is stretched after coating, the film forming property of the coating layer becomes more severe. for that reason,
The present invention is particularly useful especially in such a case.

Hereinafter, a preferable method when the simultaneous biaxial stretching method is employed will be described. First, fully dried polyethylene terephthalate is mixed with Tm + 10 ° C. to Tm + 30 ° C. (however, Tm
Is melted at a temperature of the melting point of polyethylene terephthalate, extruded into a sheet, and cooled with a cooling drum to form an unstretched film. Next, a coating solution for forming a coating layer is applied to the surface of the unstretched film on which the coating layer is to be formed by a roll coater to obtain an unstretched film having a coating film. At this time, it is applied so that the thickness of the coating layer in the obtained laminated polyester film is preferably 50 to 100 nm, more preferably 70 to 90 nm. Next, this is preheated at 90 to 110 ° C. and simultaneously in the biaxial direction with a simultaneous biaxial stretching machine.
The temperature is Tg to Tg + 70 ° C. (where Tg is the glass transition temperature of polyethylene terephthalate), and preferably 2.5 to the longitudinal direction (the film forming machine axial direction; hereinafter, sometimes referred to as the longitudinal direction or MD). 5.0 times, more preferably 3.0 to 4.0 times, preferably 2.5 in the lateral direction (direction perpendicular to the film forming machine axis direction; hereinafter referred to as width direction or TD). After stretching at ~ 5.0 times, more preferably at 3.0 to 4.0 times, (Tg + 60
A laminated polyester film having a coating layer on an oriented polyethylene terephthalate film can be obtained by heat setting at a temperature of from [deg.] C. to Tm, and preferably by heat relaxation treatment to adjust the heat shrinkage rate. In addition, it is preferable that this extending | stretching temperature is 45 degreeC or more higher than the glass transition temperature of the copolyester in an application layer, More preferably, it is 50 degreeC or more, More preferably, it is 55 degreeC or more higher temperature. . Thereby, the film forming property of the coating layer becomes more excellent, and the effect of improving adhesiveness can be enhanced. Further, the temperature is preferably 40 ° C. or more higher than the glass transition temperature of the coating layer, more preferably 45 ° C. or more, and still more preferably 53 ° C. or more. The adhesiveness is more excellent and the effect of improving the adhesiveness can be increased. Next, for heat setting, for example, a polyethylene terephthalate film is preferably subjected to heat setting at a temperature in the range of 210 to 240 ° C. for 1 to 60 seconds. In addition, the coating film is dried by the heat applied in the above step, and is cured as necessary to form a coating layer.

In addition, the coating liquid for forming an application layer mixes each component which comprises an application layer, and adjusts it suitably diluted in consideration of a viscosity, application | coating thickness, etc. The solvent used for dilution is preferably water, that is, the coating liquid is preferably aqueous. The solid content concentration of the coating liquid is preferably 5 to 20% by mass, and a good coating appearance can be obtained.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited only to these Examples. Each characteristic value was measured by the following method.

(1) Glass transition temperature of copolymerized polyester 10 mg of a copolymerized polyester sample is sealed in an aluminum pan for measurement and attached to a differential calorimeter (DuPont V4.OB2000 type DSC). The temperature was raised to 300 ° C. at a rate of / min, held at 300 ° C. for 5 minutes, taken out, immediately transferred onto ice and rapidly cooled. The pan was again attached to the differential calorimeter, and the glass transition temperature was measured by increasing the temperature from 25 ° C. to 20 ° C./min.

(2) Refractive Index of Copolyester A solution or dispersion of the copolyester was dried into a plate at 90 ° C. and measured with an Abbe refractometer (D line 589 nm).

(3) Glass transition temperature of coating layer 10 mg of a sample obtained by drying a coating solution for forming a coating layer in a plate shape at 90 ° C. is enclosed in an aluminum pan for measurement, and a differential calorimeter (manufactured by DuPont)・ V4.OB2000 DS
C), the glass transition temperature was measured by raising the temperature from 25 ° C. to 300 ° C. at a rate of 20 ° C./min.

(4) Refractive index of coating layer The coating liquid for forming the coating layer is dried at 90 ° C. in a plate shape, and Abbe refractometer (D-line 58).
9 nm) as the refractive index of the coating layer.

(5) Coating layer thickness The film is fixed with an embedding resin, the cross section is cut with a microtome, and 60% with 2% osmic acid.
After dyeing at 2 ° C. for 2 hours, the thickness of the coating layer was measured using a transmission electron microscope (JEM2010 manufactured by JEOL Ltd.).

(6) Haze value of laminated film According to JIS K7136, the haze value of the film was measured using the Nippon Denshoku Industries Co., Ltd. haze measuring device (NDH-2000). In addition, the aspect of the crack on the coating layer surface can be evaluated by the height of the haze. If the conditions are the same, the higher the haze, the more surface cracks, and preferably 0.8% or less, more Preferably it is 0.7% or less, More preferably, it is 0.6% or less, Most preferably, it is 0.5% or less.

(7) Blocking resistance Two films were overlapped so that the coating surfaces were in contact with each other.
A pressure of 0.6 kg / cm ² was applied for 17 hours under an atmosphere of RH, and then the film was peeled off. The blocking resistance was evaluated according to the following criteria based on the peeling force.
A: Peeling force <98 mN / 5 cm: very good blocking resistance B: 98 mN / 5 cm ≦ peeling force <147 mN / 5 cm—good blocking resistance Δ: 147 mN / 5 cm ≦ peeling force <196 mN / 5 cm Slightly good blocking resistance x: 196 mN / 5 cm ≦ peeling force: poor blocking resistance

(8) Swelling resistance The thickness of the coating layer of the film after laminating the hard coat layer was measured in the same manner as in the above (5). When the coating layer thickness before laminating the hard coat layer was d0 and the coating layer thickness after laminating was dh, the swelling rate E (%) of the coating layer was determined by the following formula 1.
E = dh / d0 × 100
The swelling ratio E was evaluated as follows.
A: 100 ≦ E <130: Very good swelling property ○: 130 ≦ E ≦ 200: Good swelling property Δ: 200 <E: Poor swelling property

(9) Adhesion of hard coat layer 10 mm of 1 mm ² cross cut is applied to the hard coat layer of the film on which the hard coat layer is formed.
After putting 0 pieces, a cellophane tape (manufactured by Nichiban Co., Ltd.) was applied thereon, strongly pressed with a finger, peeled in the direction of 90 °, and evaluated according to the number of remaining hard coat layers as follows.
◎: 90 <remaining number ≦ 100: very good adhesion ○: 80 <remaining number ≦ 90 ... good adhesion Δ: 70 <remaining number ≦ 80 ... slightly good adhesion ×: remaining number ≦ 70 ... Adhesive failure

(10) Light interference spots Using a film on which a hard coat layer is formed, the surface opposite to the surface on which the hard coat layer is formed is painted with black magic so as to eliminate the influence of reflected light from the opposite surface. The spectral reflectance was measured using a spectrophotometer (UV-3101PC manufactured by Shimadzu Corporation). Wavelength 500 ~
The reflectance at 600 nm was measured, and the amplitude of the reflectance was evaluated according to the following criteria. At that time, the evaluation was performed with the short-period amplitude obtained by correcting the long-period fluctuation of the reflectance. As the amplitude of the measured reflectance is larger, interference spots are generated, and the visibility as a display is lowered.
◎: Reflectance amplitude ≦ 0.5% ・ ・ ・ Interference spots extremely good ○: 0.5% <Reflectance amplitude ≦ 1.0% ・ ・ ・ Interference spots good ×: 1.0% <Reflectance amplitude・ Impaired interference spots

[Examples 1-8, Comparative Examples 1-4]
Molten polyethylene terephthalate ([η] = 0.63 dl / g, Tg = 78 ° C.) is extruded from a die and cooled with a cooling drum by a conventional method to form an unstretched film.
An aqueous coating liquid having a solid content of 10% by mass having a composition shown in Table 1 was uniformly applied with a roll coater so that the thickness of the coating layer obtained after stretching was 75 nm.
Next, this coated film was preheated at a temperature of 100 ° C., dried, and stretched simultaneously in the longitudinal and transverse directions at a magnification of 3.2 times in the longitudinal direction and 3.7 times in the transverse direction at 120 ° C. in a simultaneous biaxial stretching machine. And heat-fixed for 60 seconds to obtain a laminated polyester film having coating layers on both sides of a 125 μm thick biaxially oriented polyethylene terephthalate film. Table 2 shows the characteristics of the obtained laminated polyester film.
Furthermore, on the coating layer of the film sample cut out to B4 size from the obtained laminated film, a UV curable composition having the following composition was diluted with methyl ethyl ketone to a solid content concentration of 40% by mass, Then, it was immediately dried at 70 ° C. for 1 minute, and cured by irradiating with an ultraviolet ray with an intensity of 80 W / cm for 30 seconds to form a hard coat layer. The count of the Meyer bar was adjusted so that the hard coat layer thickness after curing was 5 μm.

(UV curable composition)
Pentaerythritol acrylate: 45% by weight
N-methylolacrylamide: 40% by weight
N-vinylpyrrolidone: 10% by weight
1-hydroxycyclohexyl phenyl ketone: 5% by weight
Table 2 shows the results of interference spots and adhesion of the film having the hard coat layer laminated thereon.

In Table 1, NDCA is a 2,6-naphthalenedicarboxylic acid component, TA is a terephthalic acid component,
IA is an isophthalic acid component, NSIA is a 5-sodium sulfoisophthalic acid component, C4G is tetramethylene glycol, C8G is octamethylene glycol, BPA-4 is an ethylene oxide 4 mol adduct component of bisphenol A manufactured by Sanyo Chemical Industries (New Pole) BPE
-40), BPEF means 9,9-bis [4- (2-hydroxyethoxy) phenyl] fluorene component, and EG means ethylene glycol.

Further, as a crosslinking agent, an oxazoline crosslinking agent (trade name EPOCROSS WS-70 manufactured by Nippon Shokubai Co., Ltd.)
0), as silica particles 1 (silica acrylic composite fine particles (average particle size: 250 nm) (product name: Soliostar, manufactured by Nippon Shokubai Co., Ltd.), and as particles 2, silica filler (50 nm) (product name: Snowtex, manufactured by Nissan Chemical Co., Ltd.), As the surfactant, polyoxyethylene (n = 7) lauryl ether (trade name NAROACTY N-70, manufactured by Sanyo Chemical Industries, Ltd.) was used.
IV in the table represents the intrinsic viscosity measured under conditions of o-chlorophenol and 35 ° C.

The laminated polyester film of the present invention has excellent adhesiveness with a functional layer such as a hard coat layer, and is less likely to cause light interference spots (color spots). It can be suitably used as an easily adhesive polyester film for various optical applications. Moreover, it can paste | paste on liquid crystal display surfaces, such as a touchscreen, for example, and it can use suitably also as a base film for providing various functions to a display surface.

Claims (5)

A laminated polyester film having a coating layer on at least one side of an oriented polyethylene terephthalate film, wherein the coating layer contains 70% by mass or more of the following copolymerized polyester based on the mass of the coating layer.
Copolyester:
(A1) 60-90 mol% of naphthalenedicarboxylic acid component,
(B1) 0 to 40 mol% of an alkylene dicarboxylic acid component having 6 to 12 carbon atoms and 4 to 1 carbon atoms
0 to 50 mol% of the alkylene glycol component of 0, the total of the alkylene dicarboxylic acid component and the alkylene glycol component is 15 to 50 mol%, and (C1) a glycol component having a fluorene structure represented by the following formula (I) Copolyester containing 5 mol% or more and less than 20 mol%.
(However, the above mol% is a value with respect to 100 mol% of all dicarboxylic acid components of the copolyester.)

(R ₁ is an alkylene group having 2 to 4 carbon atoms, R ₂ , R ₃ , R ₄ , and R ₅ are hydrogen, an alkyl group having 1 to 4 carbon atoms, an aryl group, or an aralkyl group. Or different.) The copolymerized polyester further contains (D2) bisphenol A ethylene oxide adduct component in an amount of 5 to 25 mol%.
(However, the above mol% is a value with respect to 100 mol% of all dicarboxylic acid components of the copolyester.)
The laminated polyester film according to claim 1, comprising: The copolymer polyester is
(A3) The ratio including the naphthalenedicarboxylic acid component is 60 to 80 mol%,
(B3) The proportion of the alkylene dicarboxylic acid component having 6 to 12 carbon atoms is 0 mol%,
further,
(E3) containing 20 to 40 mol% of terephthalic acid and / or isophthalic acid component,
(However, the above mol% is a value with respect to 100 mol% of all dicarboxylic acid components of the copolyester.)
The laminated polyester film according to claim 1 or 2. The coating layer contains 1 to 30% by mass of a crosslinking agent based on the mass of the coating layer.
The laminated polyester film according to any one of 3 above. The laminated polyester film according to any one of claims 1 to 4, which is used as an easily adhesive polyester film for optics.