JP2016185632A - Laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated polyester film which has little scratches and whitening, and has high transparency and high quality.SOLUTION: There is provided a laminated polyester film having a laminated film provided on at least one surface of a polyester film (substrate layer), where a resin composition constituting a laminated film contains inorganic particles and organic particles, and when an average particle diameter of the inorganic particles is represented by Da (μm) and an average particle diameter of the organic particles is represented by Db (μm), a relationship of Da<Db is satisfied, and when an area occupation rate of the inorganic particles on a laminated film surface is represented by Fa (%) and an area occupation rate of the organic particles on the laminated film surface is represented by Fb (%), a relationship of 0.3%≤Fb≤Fa≤1.4% is satisfied.SELECTED DRAWING: None

Description

The present invention relates to a laminated polyester film capable of suppressing scratches during the film production process, and further capable of suppressing whitening due to air bleed when the film is wound and rubbing of the film after winding. It is.

Polyester film is excellent in transparency, dimensional stability, mechanical properties, heat resistance, electrical properties, chemical resistance, etc., packaging materials, electrical insulation materials, metal deposition materials, plate making materials, magnetic recording materials, display materials, It is used in many applications such as transfer materials and window paste materials. Especially recently, functions such as anti-static, anti-reflection, and electromagnetic wave shielding for pasting the front panel glass surface of so-called flat displays such as LCDs and PDPs for transparent touch panels and prism sheets used in liquid crystal display devices. Polyester films are widely used in various optical applications such as protective film base films with layers, but when processed into functional films or used by general consumers after finishing into final products as displays. In order to prevent scratches on the surface, the hard coat layer having excellent scratch resistance is provided on the film surface in order to prevent the surface from being damaged. In order to enhance the adhesion with the hard coat layer, it is generally known to provide a laminated film on the film base material in order to impart easy adhesion with the hard coat layer. In addition, in optical applications that require transparency, if an additive is included in the substrate, the transparency of the entire film may be deteriorated. It is done. Moreover, the film provided with the laminated film is wound into a roll shape in the film forming process, and once wound, the roll is slit to a desired width while being rolled back, and is wound and shipped again. The particles contained in the laminated film are used as a support in the winding process, during product storage, during transportation, and during the secondary processing of the product. In order to prevent generation and wrinkling of the film, it is practiced to contain an appropriate amount of particles in the laminated film (for example, Patent Document 1 and Patent Document 2).

Japanese Patent Laid-Open No. 2000-272003 JP 2009-241374 A

However, in patent document 1 and patent document 2, although the generation | occurrence | production of the damage | wound during the film forming process of a film can be suppressed, when winding up as a roll, the particle | grains of a laminated film will damage the film opposite surface, and a film will become thin. There is a problem of whitening. In particular, due to the recent increase in displays such as smart phones and tablets that stare at the screen from a short distance, the required level of the appearance of the polyester film has been remarkably improved, and even such thin whitening has been a problem in appearance.
The present invention has been made in view of such problems, and is to provide a laminated polyester film that has few scratches and whitening, is highly transparent and has high quality, and is preferably used particularly for optical applications.

The present invention employs the following means in order to solve such problems. That is, the laminated polyester film of the present invention is
(A) a laminated polyester film in which a laminated film is provided on at least one side of a polyester film (base material layer),
The resin composition constituting the laminated film contains inorganic particles and organic particles,
When the average particle diameter of the inorganic particles is Da (μm) and the average particle diameter of the organic particles is Db (μm), the relationship of Da <Db is satisfied.
A laminated polyester film satisfying a relationship of 0.3% ≦ Fb ≦ Fa ≦ 1.4%, where the area occupancy of inorganic particles on the surface of the laminated film is Fa (%) and the area occupancy of organic particles Fb (%). .
(Ii) The laminated polyester film according to (a), wherein the polyester film has a haze value of 1.5% or less.
(Iii) When the thickness of the laminated film is L (μm), the laminated polyester film described in (a) or (ii) satisfies the following formulas (1) and (2).
(1) 1.0 ≦ Da / L ≦ 2.0
(2) 1.5 ≦ Db / L ≦ 5.0
(E) The laminated polyester film according to any one of (a) to (u), wherein the base material layer contains substantially no particles.
(O) The laminated polyester film according to any one of (a) to (e), wherein the organic particles include organic particles having a shell core structure and having a core portion whose hardness is harder than external hardness. .
(K) Scratches generated in the polyester film when two laminated polyester films are stacked so that the laminated film is on the inside and then pulled 2.0 mm at a speed of 150 mm / min with a load of 5.0 kg applied The laminated polyester film according to any one of (a) to (o), wherein the area occupancy rate of the layer is 5.0% or less.

The laminated polyester film of the present invention is highly transparent because it can suppress scratches during the manufacturing process of the film, and is less likely to be whitened due to air bleed when the film is wound or rubbed after the film is wound. A high-quality laminated polyester film can be provided. Therefore, it can be particularly preferably used for optical applications requiring a highly transparent and high quality film.

The present invention relates to a laminated polyester film in which a laminated film is provided on at least one surface of a polyester film (base material layer). The polyester constituting the polyester film serving as the base material layer of the present invention is a polyester obtained by condensation polymerization from a diol and a dicarboxylic acid. Representative examples of the dicarboxylic acid include terephthalic acid, isophthalic acid, phthalic acid, naphthalenedicarboxylic acid, adipic acid, sebacic acid, and ester-forming derivatives thereof. Representative examples of the diol include ethylene glycol, trimethylene glycol, tetramethylene glycol, cyclohexanedimethanol and ester-forming derivatives thereof.
Specific examples of such polyester include polymethylene terephthalate, polyethylene terephthalate, polytrimethylene terephthalate, polytetramethylene terephthalate, polyethylene-p-oxybenzoate, poly-1,4-cyclohexanedimethylene terephthalate, and polyethylene-2. , 6-naphthalate. Of course, these polyesters may be homopolymers or copolymers, and examples of copolymer components include diol components such as diethylene glycol, neopentyl glycol and polyalkylene glycol, adipic acid, sebacic acid, and phthalic acid. And dicarboxylic acid components such as isophthalic acid and 2,6-naphthalenedicarboxylic acid.
In the case of the present invention, polyethylene terephthalate and / or polyethylene-2,6-naphthalate are particularly preferably used from the viewpoints of transparency, mechanical strength, and the like. In addition, various additives such as an antioxidant, an antistatic agent, and a crystal nucleating agent may be added to the polyester as necessary.

  The substrate of the polyester film of the present invention may be a single layer or a multilayer film composed of two or more layers.

  The laminated film of the present invention is a layer that is laminated on at least one side of the polyester film that serves as the base material. By laminating the layer, adhesion to a processed layer such as a hard coat layer can be imparted. As a method for laminating the laminated film, there are a co-extrusion method, a coating method, a laminating method, and the like. Lamination by the coating method is preferable because the laminated film can be thinned and transparency can be increased. The resin constituting the laminated film is not particularly limited as long as it provides adhesion, but for example, acrylic resin, urethane resin, polyester resin, olefin resin, fluorine resin, vinyl Resins, chlorine resins, styrene resins, various graft resins, epoxy resins, silicone resins, and the like, and mixtures of these resins can also be used. When the polyester resin is used as an aqueous coating liquid, a water-soluble or water-dispersible polyester resin is used. For such water-solubilization or water-dispersion, a compound containing a sulfonate group or a carboxyl group is used. It is preferable to copolymerize a compound containing an acid base. In the laminated film of the present invention, various crosslinking agents can be used in combination with the resin in order to further improve the adhesion. Examples of the cross-linking agent resin that improves adhesiveness include melamine resins, epoxy resins, and oxazoline resins.

The resin composition constituting the laminated film of the present invention contains inorganic particles and organic particles,
When the average particle diameter of the inorganic particles is Da (μm) and the average particle diameter of the organic particles is Db (μm), it is necessary to satisfy the relationship of Da <Db. By containing said particle | grains, it becomes possible to accelerate | stimulate the air escape at the time of winding prevention at the time of winding up in roll shape prevention by the contact of the roll etc. in the film conveyance at a process.

  Here, from the viewpoint of preventing scratches, it is preferable that the content of particles contained in the resin composition constituting the laminated film is large, and the surface of the laminated film is preferably entirely covered with particles. preferable. From the viewpoint of air escape, it is preferable that the particle size of the particles contained in the resin composition constituting the laminated film is larger in order to make more gaps between the film layers. However, since the effect of light scattering is large for particles having a large particle size, the transparency decreases when the content is large (haze increases). When the transparency is lowered, it cannot be used as an optical member film. Here, by including inorganic particles and organic particles having different average particle sizes in the laminated film, it is possible to improve scratch prevention and air escape while maintaining transparency.

  Further, the polyester film of the present invention has 0.3% ≦ Fb ≦ Fa ≦ 1. It is necessary to satisfy the 4% relationship. If it is the range which satisfy | fills the said relationship, high transparency can be maintained. When the particle area occupation ratio Fa of the inorganic particles is 0.3% or less, the scratch prevention performance is incomplete, and when the area occupation ratio Fb of the organic particles is 0.3% or less, air escape becomes worse. Further, when the organic particles are inorganic particles, if the Fb is 0.2% or more, the films are rubbed when the air is taken out during film winding or storage in a roll state, and the film is whitened. In the present invention, it has been found that whitening does not occur even when Fb is 0.3% or more by making particles having a small particle size hard inorganic particles and particles having a large particle size soft organic particles.

  As the inorganic particles used in the present invention, silica, alumina, kaolin, talc, mica, calcium carbonate, titanium and the like can be used. As the organic particles used in the present invention, silicon, polystyrene, acrylic, polyester, or the like can be used. Among these, particles having a shell core structure (hereinafter sometimes referred to as shell core particles) are preferable. The shell core particle is a polymer fine particle having a multilayer structure in which inner and outer parts are composed of polymers having different properties. In this case, the term “multilayer” refers to two or more layers, and the properties may continuously change in the radial direction. The outside (hereinafter sometimes abbreviated as shell part) reacts with the film base after coating on the film, or reacts, melts, softens or deforms by heat treatment, and has a function of fixing to the film base. (Hereinafter, it may be abbreviated as a core part) is considered to bear a function as a so-called particle which gives the film appropriate slipperiness together with the shell part. From the viewpoint of functional sharing of the shell and core parts, the shell part is required to have excellent affinity with the film base and have appropriate physical, chemical, and thermal properties at the film-forming heat treatment temperature. The core part is required not to be deformed by mechanical friction or the like but to have a relatively large hardness with respect to the shell part.

As a polymer composition for realizing such a function, a thermoplastic resin is generally preferable for the shell portion, and an acrylic resin, a polyester resin, and the like are particularly preferable. Furthermore, in order to increase the affinity with the film base, a functional group having reactivity or affinity with the film base in any proportion in the molecule, specifically, a carboxyl group, a hydroxyl group, a glycidyl group, an amide group, an epoxy group An isocyanate group or the like may be introduced. These functional groups may be used alone or in combination of two or more in some cases. The glass transition temperature (hereinafter abbreviated as Tg) of the shell part is preferably 80 ° C. or lower, more preferably 40 ° C. or lower. When Tg exceeds 80 ° C., the shell core particles fall off from the film. By using the polymer having the above composition in the shell portion, excellent abrasion resistance can be exhibited. Among these, acrylic and / or polyester are preferably used from the viewpoints of affinity with the core polymer, adhesion to the substrate, protrusion holdability, and slipperiness. The acrylic is not particularly limited and may be either a single copolymer or a copolymer, but a copolymer is preferably used because it is easy to change the glass transition point or the film forming temperature. For example, methyl methacrylate (hereinafter sometimes abbreviated as MMA), ethyl acrylate (hereinafter sometimes abbreviated as EA), butyl acrylate and the like are typical examples. If necessary, a crosslinkable monomer such as acrylic acid (hereinafter sometimes abbreviated as AA), N-methylolacrylamide (hereinafter also abbreviated as N-MAM) and the like in an appropriate molar ratio. Copolymerization is possible as long as the effects of the present invention are not impaired. Thereby, a ternary or quaternary acrylic copolymer is obtained. The polyester constituting the shell is preferably a combination of a highly polar group and a hydrophobic group in the molecule. The polar group preferably includes a hydroxyl group, an acid group, an ether, an ester group, an epoxy, a sulfonic acid group, a urethane bond, and the like, and the hydrophobic part includes an aliphatic chain, an aromatic chain, and the like. A ter copolymer, a polyester copolymer containing polyethylene glycol / alkali metal sulfonate, and the like can be used.

  On the other hand, a thermosetting resin such as urea resin, melamine resin, phenol resin, epoxy resin, unsaturated polyester resin, alkyd resin, urethane resin can be used for the core part. Resins, acrylic resins, or high-crosslinkable and / or crosslinkable polymers of the same or different types of these resins are desirable in order to increase strength. Examples of the highly crosslinked polymer include, but are not limited to, organic particles such as styrene / divinylbenzene binary copolymer and styrene / divinylbenzene / ethylenedivinylbenzene terpolymer. In addition, the crosslinkable polymer is not particularly limited, but a self-crosslinkable polymer or a crosslinkable polymer is particularly preferable in terms of projection forming ability. A self-crosslinkable polymer has a crosslinkable functional group in the molecule and can undergo a crosslinking reaction by heat or light to form a three-dimensional network structure. A typical example is acrylic. However, it is not limited to this. However, acrylic is preferably used in the present invention in terms of the miniaturization of the protrusions, the number of protrusions to be formed, slidability, transparency and the like. Examples of the self-crosslinkable acrylic copolymer preferable as the crosslinkable polymer include a functional group-containing vinyl polymerizable monomer, a hydrocarbon vinyl polymerizable monomer, and a hydrocarbon non-conjugated divinyl polymerizable monomer. Although a copolymer compound is mentioned, in this invention, the copolymer of a functional group containing vinyl polymerizable monomer is used preferably. Examples of the functional group-containing vinyl polymerizable monomer include acrylic acid, methacrylic acid, acrylamide, methacrylamide, N-methylolacrylamide, N-butoxymethylacrylamide, diacetone acrylamide, methylol diacetone acrylamide, 2- Hydroxyethyl methacrylate, 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 3-chloro-2-hydroxypropyl methacrylate, and the like are selected, but are particularly limited. Is not to be done. The protrusion preferably contains 70% by weight or more of a crosslinkable polymer, preferably 80% by weight or more, more preferably 90% by weight or more. The crosslinked polymer is a polymer that has already been crosslinked by a crosslinking component, and the polymer species is not particularly limited, but acrylic is preferably used in the present invention. Such protrusions are provided on at least one side of the polyester film. When the protrusions are provided on both sides, the description of the protrusions described below applies to at least one side. As described above, the highly crosslinked polymer in the present invention is a styrene / divinylbenzene binary copolymer, a styrene / divinylbenzene / ethylenedivinylbenzene (copolymerization ratio is, for example, 45/50/5 wt%) terpolymer, or the like. And those that do not thermally deform at normal polyester film forming temperatures are preferred.

Particularly preferable combinations of the shell polymer and the core polymer include a thermoplastic acrylic resin or polyester resin as the shell polymer, and a cross-linkable and / or highly cross-linked acrylic and styrene / divinylbenzene copolymer as the core polymer. .
When the shell core particles are composed of two layers, the shell / core weight ratio can be freely selected, but is preferably 100/1 to 1/10, more preferably 10/1 to 1/3. When the shell / core weight ratio is larger than 100/1, the organic particles having a multilayer structure are more strongly property, and deformation due to heat and mechanical friction is increased. On the other hand, when it is less than 1/10, the properties of inorganic particles become strong, and the adhesion with the film is lowered, and the particles fall off. In either case, the film processability tends to be adversely affected.
The particle shape may be any of a spherical shape, an elliptical shape, a rectangular shape, a cubic shape, and the like, but a spherical particle is particularly preferable.

In the laminated polyester film of the present invention, the thickness of the laminated film is L (μm), the average particle diameter of the inorganic particles contained in the resin composition constituting the laminated film is Da (μm), and the resin composition constituting the laminated film is used. When the average particle diameter of the organic particles contained is Db (μm), it is preferable to satisfy the following formulas (1) and (2).
(1) 1.0 ≦ Da / L ≦ 2.0
(2) 1.5 ≦ Db / L ≦ 5.0
In the inorganic particles, the relationship Da / L between the particle diameter Da and the thickness L of the laminated film is preferably 1.0 or more from the viewpoint of scratch prevention, and is 2.0 or less from the viewpoint of particle dropout. preferable. From the viewpoint of air escape, the relationship Db / L between the inorganic particles B and the thickness L of the laminated film is preferably 1.5 or more, more preferably 2.5 or more. From the viewpoint of transparency, Db / L is preferably 5.0 or less. By using organic particles whose shell part is excellent in affinity with the film substrate, even if Db / L is 2.5 or more, dropping of the particles can be suppressed.

  The total thickness of the laminated film used in the present invention is not particularly limited and is appropriately selected. From the viewpoint of mechanical strength, handling property, etc., usually 20 to 500 nm is preferable, and applications where transparency is required, In particular, 50 nm to 150 nm is more preferable when used as an optical application. If it is less than 20 nm, there is a possibility that sufficient adhesion cannot be obtained when the laminated film is adhered, and if it is more than 500 nm, there is a possibility that problems of blocking or abrasion occur.

  As described above, as a result of intensive studies, the resin composition constituting the laminated film contains inorganic particles and organic particles, the average particle size of the inorganic particles is Da (μm), and the average particle size of the organic particles is When Db (μm) is satisfied, the relationship of Da <Db is satisfied, and when the area occupancy of the inorganic particles on the surface of the laminated film is Fa (%) and the area occupancy Fb (%) of the organic particles, 0.3% When a polyester film satisfying the relationship of ≦ Fb ≦ Fa ≦ 1.4% was obtained, it was possible to obtain a good optical film roll having little scratches and whitening, maintaining low transparency with low haze, and free from wrinkles and interference unevenness. .

  The total thickness of the laminated polyester film of the present invention is preferably 20 μm to 300 μm. In the case of a film of less than 20 μm, the problem of wrinkles occurring when air is taken out during winding or roll storage has become prominent, but by incorporating organic particles having good adhesion to the substrate into the laminated film Even if the particle diameter is increased, the particles do not fall off, the distance between the film layers is increased, air escape is promoted, and the generation of wrinkles is suppressed.

  In the laminated film of the present invention, various additives such as an antioxidant, a heat stabilizer, a weather stabilizer, an ultraviolet absorber, an infrared absorber, a pigment, a dye, as long as the effects of the present invention are not impaired. Fillers, antistatic agents, nucleating agents and the like may be blended.

In the present invention, when used for optical purposes, the haze value of the laminated polyester film is preferably 1.5% or less, more preferably 1.0% or less, and still more preferably 0.9% or less. When used for optical applications, it is preferable that the polyester film as a substrate contains substantially no particles for the purpose of reducing the haze value.
The laminated polyester film of the present invention is desirably used after being stretched. As the stretching method, techniques such as a sequential biaxial stretching method of stretching in the width direction after stretching in the longitudinal direction and a simultaneous biaxial stretching method of stretching the longitudinal direction and the width direction almost simultaneously are used.

Next, although the manufacturing method of the laminated polyester film of this invention is demonstrated, it is not limited to this.
First, a polyester resin containing substantially no particles is supplied to an extruder. In the extruder, the resin that has been heated and melted to a temperature equal to or higher than the melting point passes through a heated pipe connecting a filter, a gear pump, and the like in a molten state to remove foreign matters. The resin sent to the die from the extruder is formed into a target shape by the die and then discharged. The resin temperature at the time of discharge is usually equal to or higher than the melting end temperature of the polyester used. The sheet-like molten resin discharged from the die is cooled and solidified on a casting drum, and an unstretched sheet is obtained by an electrostatic application adhesion method.
The unstretched sheet is heated with a group of heating rolls and stretched in multiple stages of one or two or more stages in the longitudinal direction 2 to 5 times, preferably 2.5 to 4.5 times, more preferably 3 to 4 times. (MD stretching). The stretching temperature is in the range of Tg to (Tg + 60) ° C, more preferably (Tg + 5) to (Tg + 55) ° C, and still more preferably (Tg + 10) to (Tg + 50) ° C. Thereafter, it is cooled by a cooling roll group of 20 to 50 ° C.
Next, a laminated film is applied to at least one surface of the film. A method for coating is not particularly limited, and for example, a reverse coating method, a gravure coating method, a rod coating method, a bar coating method, a Mayer bar coating method, a die coating method, a spray coating method, or the like can be used.
Next, as a stretching method in the width direction following application, for example, a method using a tenter is common. The both ends of this film are gripped with clips, guided to a tenter, and stretched in the width direction (TD stretching). The stretching temperature is preferably Tg to (Tg + 80) ° C., more preferably (Tg + 10) to (Tg + 70) ° C., and further preferably (Tg + 20) to (Tg + 60) ° C. The draw ratio is preferably 2.0 to 6.0 times, more preferably 3.0 to 5.0 times, and still more preferably 3.5 to 4.5 times.
In the present invention, before applying the laminated film, the surface of the base film (in the case of the above example, a uniaxially stretched film) is subjected to a corona discharge treatment or the like, and the wetting tension of the base film surface is preferably 47 mN. / M or more, more preferably 50 mN / m or more, because the adhesion between the laminated film and the substrate film can be further improved.
Next, this stretched film is heat-set under tension or while relaxing in the width direction.
Furthermore, it is preferable to cool this film while relaxing in the width direction in a temperature zone of 40 to 180 ° C. The relaxation rate is preferably 1 to 10% from the viewpoint of reducing the thermal contraction rate in the width direction, more preferably 2 to 8%, and still more preferably 3 to 7%.
Furthermore, the film is cooled and wound up while being relaxed in the longitudinal and width directions to room temperature, if necessary, to obtain a desired laminated polyester film.

A. [Particle area occupancy and number of particles on the laminated film surface]
An arbitrary point is determined on the sample surface of the laminated polyester film.
Next, a square or rectangular section sample of 5 μm or more sharing two sides from the point is obtained. The surface of the sliced film of the slice sample was collected by the VE-7800 type scanning electron microscope (SEM) manufactured by Keyence Co., Ltd. at a magnification of 2000 to 10,000 times, and five photographs of a square area of 5 μm square were collected and laminated. The average particle diameter and area occupancy Fa and Fb of the inorganic particles and the organic particles were calculated from the photograph of the film surface using image analysis type particle size distribution measurement software (Macview).

B. [Total thickness of laminated polyester film]
The thickness of the easily adhesive polyester film was measured using a micrometer M-30 (manufactured by Sony Corporation).

C. [Measurement of scratches]
A sheet-like sample (product width x 1 to 3 m long) is taken from the film roll surface layer of a fixed winding length, and the maximum major axis of scratches is 100 μm or more whether it exists in the dark room in the longitudinal and width directions on the film surface. The number was confirmed by visual observation.

D. [Haze value]
Using a haze meter manufactured by Suga Test Instruments Co., Ltd., it was measured according to JIS K 7105 (1981/3/01 established).

E. [Measurement of air loss (air loss)]
Judgment was made using the roll hardness of the film roll. As for the roll hardness of the film roll, 10 points in the width direction of the film roll were measured using a PAROtester D type manufactured by PROCEQ, and it was determined that the smaller the hardness difference R, the better the air escape. The hardness was measured for five film rolls, and the average value of each measurement R was Rx.
: Rx ≦ 100
○: 100 <Rx ≦ 200
Δ: 200 <Rx ≦ 300
X: Rx> 300
F. [Whitening resistance evaluation (whitening evaluation)]
The whitening resistance of the film was evaluated by the following method. After two polyester films were stacked so that the laminated film was on the inside, a working distance of 2.0 mm was pulled at a speed of 150 mm / min with a 5.0 kg load applied. The obtained film was observed with a VE-7800 scanning electron microscope (SEM) manufactured by Keyence Co., Ltd., and a square area of 5 μm square was observed at 2000 to 10,000 times, and the area occupancy S of scratches was calculated.
A: S ≦ 0.10%
○: 0.10% <S ≦ 0.50%
Δ: 0.50% <S ≦ 1.00%
×: 1.00% <S
[Coating liquid a] Silica particles having an average particle diameter of 80 nm dispersed in water such that polyester resin: 85.7 kg, surfactant: 3.0 kg, particle concentration of 40 wt% with respect to 1000 L of coating liquid (water) : 3.7 Kg, core portion with an average particle diameter of 140 nm dispersed in water so that the particle concentration is 40% by weight has a shell core structure with a crosslinkable acrylic and a shell portion made of thermoplastic acrylic, and the hardness of the core portion Particles whose hardness is harder than the external hardness: 1.1 kg, melamine-based crosslinking agent: 10.5 kg
[Coating liquid b] Silica particles having an average particle diameter of 140 nm dispersed in water such that polyester resin: 106.7 kg, surfactant: 3.0 kg, particle concentration of 40 wt% with respect to 1000 L of coating liquid (water) : 1.1 kg, a core part having an average particle size of 300 nm dispersed in water so that the particle concentration is 40% by weight has a shell core structure in which the core part is made of crosslinkable acrylic and the shell part is made of thermoplastic acrylic, and the hardness of the core part Particles whose hardness is harder than the external hardness: 1.1 kg, melamine-based crosslinking agent: 10.5 kg
[Coating liquid c] A coating liquid in which the polyester resin of the coating liquid a is 106.7 kg per 1000 L and the melamine crosslinking agent is 13.1 kg.
[Coating liquid d] In place of the organic particles in the coating liquid b, the core part having an average particle diameter of 400 nm dispersed in water so that the particle concentration is 40% by weight is made of cross-linkable acrylic and the shell part is made of thermoplastic acrylic. 1.1 kg of organic particles having a shell core structure in which the hardness of the core portion is harder than the external hardness were added.
[Coating liquid e] A coating liquid in which the polyester resin of the coating liquid a is 126.4 kg per 1000 L and the melamine crosslinking agent is 15.5 kg.
[Coating liquid f] Instead of the organic particles in the coating liquid a, silica particles having an average particle diameter of 140 nm dispersed in water so that the particle concentration was 40% by weight: 1.1 kg were added.
[Coating liquid g] A coating liquid in which the polyester resin of the coating liquid a is 158.2 kg per 1000 L and the melamine crosslinking agent is 19.1 kg.
[Coating liquid h] Polyester resin: 67.2 kg, surfactant: 3.0 kg, and silica particles having an average particle diameter of 80 nm dispersed in water so that the particle concentration is 40 wt% with respect to 1000 L of coating liquid (water) : 3.7 kg, melamine-based crosslinking agent: 8.2 kg
Example 1
When polyethylene terephthalate is melted, a stainless steel sintered filter medium having a filtration particle size (initial filtration efficiency: 95%) of 15 μm is used as a filter medium for removing foreign matters from the molten resin, and the filtered polymer is melt extruded at 280 ° C. from an extruder. This was cast on a 20 ° C. cast drum that had been subjected to electrocoating to make an unstretched sheet, which was preheated at 80 ° C., and stretched 3.0 times in the longitudinal direction by roll stretching at this temperature. Thereafter, the coating liquid a was applied to one side of the film while controlling the coating film thickness to be 6 μm. Thereafter, the film was stretched 3.6 times in the width direction at 110 ° C. and heat-treated at 230 ° C. As a result, a 125 μm thick laminated polyester film having a polyethylene terephthalate film with a 65 nm thick laminated film formed on one side as a base material was obtained.

Example 2
A laminated film having a thickness of 81 nm is obtained in the same manner as in Example 1 except that the coating liquid b is used instead of the coating liquid a in Example 1 and the coating film thickness is controlled to be 6 μm. A laminated polyester film having a thickness of 125 μm was obtained using a polyethylene terephthalate film formed on one side as a base material.

Example 3
A laminated film having a thickness of 81 nm is obtained in the same manner as in Example 1 except that the coating liquid c is used in place of the coating liquid a in Example 1 and the coating film thickness is controlled to 6 μm. A laminated polyester film having a thickness of 125 μm was obtained using a polyethylene terephthalate film formed on one side as a base material.

Example 4
A laminated film having a thickness of 81 nm is obtained in the same manner as in Example 1 except that the coating film d is controlled to be 6 μm using the coating liquid d instead of the coating liquid a in Example 1. A laminated polyester film having a thickness of 125 μm was obtained using a polyethylene terephthalate film formed on one side as a base material.

Comparative example 1
A laminated film having a thickness of 96 nm is obtained in the same manner as in Example 1 except that the coating liquid e is used in place of the coating liquid a in Example 1 to control the coating film thickness to 6 μm. A laminated polyester film having a thickness of 125 μm was obtained using a polyethylene terephthalate film formed on one side as a base material. Db / L was as small as 1.46, resulting in poor air escape.

Comparative example 2
A laminate having an easy-adhesion thickness of 65 nm was obtained in the same manner as in Example 1 except that the coating liquid f was used instead of the coating liquid a in Example 1 and the coating film thickness was controlled to 6 μm. A laminated polyester film having a thickness of 125 μm was obtained using a polyethylene terephthalate film having a film formed on one side as a base material. The whitening resistance was inferior.

Comparative example 3
A laminate having an easy-adhesion thickness of 120 nm is obtained in the same manner as in Example 1 except that the coating liquid g is used instead of the coating liquid a in Example 1 and the coating film thickness is controlled to be 6 μm. A laminated polyester film having a thickness of 125 μm was obtained using a polyethylene terephthalate film having a film formed on one side as a base material. The result was a lot of scratches.

Comparative example 4
A laminate having an easy adhesion thickness of 51 nm was obtained in the same manner as in Example 1 except that the coating liquid h was used instead of the coating liquid a in Example 1 to control the coating film thickness to 6 μm. A laminated polyester film having a thickness of 125 μm was obtained using a polyethylene terephthalate film having a film formed on one side as a base material. In the case of a one-particle film, the air escape was poor.
The characteristics of the laminated polyester films obtained from Examples 1 to 4 and Comparative Examples 1 to 4 are shown in Table 1.

The laminated polyester film of the present invention is a film that is excellent in runnability, winding property, and high transparency, has good air escape when used as a film roll, and is suppressed from whitening due to rubbing between films. Is widely used for various optical applications.

Claims (6)

A laminated polyester film in which a laminated film is provided on at least one side of a polyester film (base material layer),
The resin composition constituting the laminated film contains inorganic particles and organic particles,
When the average particle diameter of the inorganic particles is Da (μm) and the average particle diameter of the organic particles is Db (μm), the relationship of Da <Db is satisfied.
A laminated polyester film satisfying a relationship of 0.3% ≦ Fb ≦ Fa ≦ 1.4%, where the area occupancy of inorganic particles on the surface of the laminated film is Fa (%) and the area occupancy of organic particles Fb (%). . The laminated polyester film according to claim 1, wherein the polyester film has a haze value of 1.5% or less. The laminated polyester film according to claim 1 or 2, wherein when the thickness of the laminated film is L (μm), the following formula (1) and formula (2) are satisfied.
(1) 1.0 ≦ Da / L ≦ 2.0
(2) 1.5 ≦ Db / L ≦ 5.0 The laminated polyester film according to any one of claims 1 to 3, wherein the substrate layer contains substantially no particles. The laminated polyester film according to any one of claims 1 to 4, wherein the organic particles include organic particles having a shell core structure and having a core portion whose hardness is harder than an external hardness. Area occupancy rate of scratches generated in polyester film when two sheets of polyester film are stacked so that the laminated film is on the inside and pulled 2.0 mm at a speed of 150 mm / min with a 5.0 kg load applied The laminated polyester film according to any one of claims 1 to 5, wherein the content is 5.0% or less.