JPS63265636A - Laminated polyester film - Google Patents

Abstract

PURPOSE:To enhance transparency, an easy slip property, easy adhesiveness and smoothness, by applying a water-soluble or water-dispersible acrylic resin containing specific inorg. colloid to a polyester film to stretch said film and bringing the particle size of the inorg colloid particle and a lamination thickness to specific correlation. CONSTITUTION:Inorg. colloid contains 10<5>-10<9> atoms/one particle and is obtained as metal colloid, oxide colloid or hydroxide colloid according to an element. The average particle size thereof is pref. 0.11-0.4mum. A water- dispersible or water-soluble acrylic resin is based on alkyl acrylate or alkyl methacrylate and pref. contains 30-90 mol.% of said main component and 70-10 mol.% of a vinyl monomer component copolymerizable therewith and having a functional group. The haze (turbidity) of the polyester film constituting this film is pref. 4.0% or less and the ratio D/d of the average particle size D of the inorg. colloid particle in a coating layer and the thickness (d) of said coating layer is set to 1.1-80.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a laminated polyester film. Specifically, the present invention relates to a laminated polyester film having excellent transparency, easy sliding properties, easy adhesion properties, and smoothness.

[Prior Art] Polyester biaxially stretched film has excellent properties such as mechanical properties, electrical properties, dimensional stability, and transparency, so it can be used as a magnetic recording material, a packaging material, an electrically insulating material,
It is widely used as a base film for many applications such as graphic arts materials and photographic materials. However, recently,
These applications are all technologically oriented toward miniaturization, weight reduction, and high precision, and along with this, the requirements and quality of the base film are also becoming stricter. For example, in the field of graphic arts, the requirements for transparency, easy slippage, easy adhesion, and smoothness are increasing, and there is a long-awaited base film that simultaneously maintains each of these properties. However, in terms of transparency and slipperiness, polyester film, which is highly transparent, has very poor slipping properties between films, which can cause surface defects such as blocking and scratches, and may cause problems with winding properties. It is known that this causes deterioration in the appearance of the roll, and furthermore, poor workability during processing. Moreover, these drawbacks tend to become more noticeable as the base film becomes thinner. In this way, in polyester films, transparency and ease of slipping are in a contradictory relationship, and it is difficult to satisfy both properties at the same time.Furthermore, it is difficult to obtain a film that has both easy adhesion and smoothness at the same time. It was difficult. Various studies have been made in the past in order to create a film that has such excellent properties.

(1> Polyester film in which an organic polymer binder containing inorganic particles and silica sol is coated on the surface of a transparent film (JP-A-61-2528, JP-A-60-
61259).

(2) A polyester film in which fine longitudinal protrusions are formed by stretching and breaking a resin layer coated on the surface of a transparent film (Japanese Patent Application Laid-Open No. 61-204240).

[Problems to be Solved by the Invention] However, the above-mentioned polyester film has the following problems.

In the film of (1) above, when inorganic particles are used,
Uniform dispersion into the organic polymer binder is difficult, resulting in variations in film properties and coarse protrusions caused by agglomerated particles on the coating film, resulting in decreased transparency and smoothness, and even more protrusions. The harm caused by falling off is likely to increase. Furthermore, when silica sol is used as a lubricant, since the silica sol known in the art is fine, slipperiness can only be achieved by adding a large amount of silica sol, but on the other hand, it tends to cause a decrease in transparency and easy adhesion. Furthermore, if the base film becomes thin, sufficient slipping effect cannot be achieved.

In the film of (2) above, since the protrusions are fine, if the base film becomes thin, not only the slipperiness becomes insufficient, but also the transparency tends to decrease due to cracks generated in the coating film.

The present invention solves the drawbacks of these conventional techniques and provides a laminated polyester film that has excellent transparency, easy slipping, easy adhesion, and smoothness, and also has excellent durability and abrasion resistance of easy slipping. We aim to provide the following.

[Means for Solving the Problems] The present invention provides at least one side of the polyester film,
A laminated polyester film comprising a coating layer mainly composed of an inorganic colloid with an average particle size of 0.11 to 0.4 μm and a water-soluble or water-dispersible acrylic resin, the film having an average particle size of the inorganic colloid ( The present invention relates to a laminated polyester film characterized in that the ratio (D/d) between D) and the thickness (d) of the coating layer is in the range of 1.1 to 80.

In the present invention, polyester refers to well-known polyesters,
Specifically, at least one difunctional carboxylic acid such as terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid, bis-α, β(2-chlorophenoxy)ethane-4,4-dicarboxylic acid, adipic acid, and sebacic acid. and at least one type of glycol such as ethylene glycol, triethylene glycol, tetramethylene glycol, hexamethylene glycol, and decamethylene glycol.

In addition, the polyester may be blended or copolymerized with other polymers within a range that does not impede the purpose of the present invention, and may contain antioxidants, heat stabilizers, lubricants, pigments, ultraviolet absorbers, etc. It may be

The intrinsic viscosity of the polyester (measured in orthochlorophenol at 25°C) is 0.4 to 2.0, preferably 0.
．． A value in the range of 5 to 1.0 is usually used.

In the present invention, particularly excellent effects can be obtained when polyethylene terephthalate or polyethylene-2,6-naphthalate is used as the polyester.

The coating layer in the present invention is a layer mainly composed of an inorganic colloid and a water-soluble or water-dispersible acrylic resin. The term "main component" means that the component itself occupies 70% or more of the coating layer. In the present invention, such a coating layer is provided on at least one side of the polyester film, but when it is provided on both sides, the following description of the layer applies to at least one side.

The inorganic colloid as used in the present invention is defined in the Imori Publishing Co., Ltd. Chemistry Dictionary, and contains 105 to 109 atoms in one particle. Depending on the element, it can be obtained as a metal colloid, oxide colloid, or hydroxide colloid. Preferably used metal colloids include gold, palladium, platinum, silver, and sulfur; examples of oxide colloids, hydroxide colloids, carbonate colloids, and sulfate colloids include zinc, magnesium, silicon, calcium, aluminum, Oxide colloids, hydroxide colloids, carbonate colloids, sulfate colloids such as strontium, barium, zirconium, titanium, manganese, iron, cobalt, nickel, tin, etc. are preferably used in the present invention. For example, silicic acid colloids obtained by adding silicon tetrahalide to water or gradually adding concentrated hydrochloric acid to an aqueous solution of alkali silicate are very preferably used in the present invention.

The average particle size of the inorganic colloid is 0.11 to 0.4 μm, preferably 0.13 to 0.3 μm, more preferably 0.15 μm.
It is necessary that it is in the range of ~0.25 μm. If the average particle size is 0.11 μm or less, the slipperiness of the laminated film will be insufficient. Furthermore, since the agglomeration of the particles increases, the transparency tends to decrease due to the generation of coarse foreign matter. If the thickness exceeds 0.4 μm, not only will the surface of the laminated film become noticeably rough and the abrasion resistance will deteriorate;
The stability of the inorganic colloid particles in an aqueous solution deteriorates significantly, and in some cases, precipitation, aggregation, gelation, etc. of the particles occur. Furthermore, during the recovery and reuse of film flakes, the surface roughness of the film is promoted due to the contamination of particles.
Smoothness deteriorates.

The average particle diameter here refers to the inorganic colloid aqueous solution measured using a centrifugal sedimentation particle size distribution analyzer (Shimadzu Corporation 5).
A-CP2 type).

Water-dispersible or water-soluble acrylic resin (
The acrylic resin (hereinafter abbreviated as acrylic resin) is preferably one containing alkyl acrylate or alkyl methacrylate as a main component, with 30 to 90 mol% of this component and a vinyl metatarsal component copolymerizable with these components and having a functional group. 7
Water-soluble or water-dispersible resins containing 0 to 10 mol% are preferred.

A vinyl monobase that is copolymerizable with alkyl acrylate or alkyl methacrylate and has a functional group imparts hydrophilicity to the resin and improves the water dispersibility of the resin.
Alternatively, it is preferable to have a functional group that improves the adhesion between the resin and the polyester film or the coating layer provided on the undercoat layer. Preferred functional groups include a carboxyl group or a salt thereof, an acid anhydride group, and a sulfone. acid group or its salt, amide group or alkylolated amide group,
These include amino groups (including substituted amino groups), alkylolated amino groups, salts thereof, hydroxyl groups, and epoxy groups. Particularly preferred are carboxyl groups or salts thereof, acid anhydride groups, epoxy groups, and the like. Two or more types of these groups may be contained in the resin.

The reason why the content of fulkyl acrylate or alkyl methacrylate in the acrylic resin is preferably 30 mol % or more is because the coating film formability, coating film strength, and blocking resistance are improved. It is preferable that the content of alkyl acrylate or alkyl methacrylate in the acrylic resin is 90 mol% or less because it can be made water-soluble or water-dispersible by introducing a compound having a specific functional group into the acrylic resin as a copolymerization component. This is to make the coating easier and to keep the condition stable for a long period of time.It also improves the adhesion between the coating layer and the polyester film layer, and improves the strength, water resistance, and chemical resistance of the coating layer due to reactions within the coating layer. This is because it is possible to improve the adhesion between the film of the present invention and other materials.

Examples of alkyl groups in alkyl acrylates and alkyl methacrylates include methyl group, edyl group, n-propyl group, isopropyl group, lobutyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, lauryl group, stearyl group, and cyclohexyl group. Examples include bases.

As the vinyl monomer having a functional group copolymerizable with alkyl acrylate or alkyl methacrylate, the following compounds having functional groups such as a reactive functional group, a self-crosslinking functional group, and a hydrophilic group can be used.

Examples of compounds having a carboxyl group or a salt thereof, or an acid anhydride group include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, metal salts of these carboxylic acids with sodium etc., ammonium salts, Alternatively, maleic anhydride may be used.

Examples of compounds having a sulfonic acid group or a salt thereof include vinyl sulfonic acid, styrene sulfonic acid, metal salts of these sulfonic acids with sodium, and ammonium salts.

Examples of compounds having an amide group or an alkylolated amide group include acrylamide, methacrylamide, tomethylmethacrylamide, methylolated acrylamide, methylolated methacrylamide, ureido vinyl ether, β-ureido isobutyl vinyl ether, ureido ethyl acrylate, etc. It will be done.

Examples of compounds having an amino group or an alkylolated amine group or a salt thereof include diethylaminoedyl vinyl ether, 3-aminopropyl vinyl ether, 2-aminobutyl vinyl ether, dimedylaminoethyl methacrylate, dimedylaminoethyl vinyl ether, and the like. Examples include those in which the amino group of is methylolated, and those in which the amino group is converted into a quaternary chloride with an alkyl halide, dimethyl sulfate, sultone, etc.

Examples of compounds having a hydroxyl group include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate,
β-hydroxypropyl acrylate, β-hydroxypropyl methacrylate, β-hydroxy vinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monoacrylate, polypropylene glycol monomethacrylate, etc. There is a storm.

Examples of compounds having an epoxy group include glycidyl acrylate and glycidyl methacrylate.

Furthermore, in addition to the above compounds, the following compounds may be used in combination. That is, acrylonitrile, methacrylate trile,
Styrenes, butyl vinyl ether, mono- or dialkyl maleic acid esters, mono- or dialkyl fumaric acid esters, mono- or dialkyl itaconic acid esters, methyl vinyl ketone, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl pyridine, vinyl pyrrolidone, vinyl trimethoxysilane Examples include, but are not limited to, these.

The acrylic resin may contain a surfactant, but the low molecular weight surfactant contained in the acrylic resin may be concentrated during the film-growing process, accumulate at the interface between particles, or be difficult to coat. It may migrate to the interface between layers, causing problems with the mechanical strength, water resistance, and adhesion of the coating layer to the laminate. In such a case, a polymer obtained by so-called soap-free polymerization that does not contain a surfactant can be used.

However, among these, water containing 35/65 to 65/35 (mole ratio) copolymer of methyl meucrylate and ethyl 7 acrylate as the backbone polymer, and introducing 1 to 5% by weight of -COOI-1 and -CH2O8 each. Dispersible acrylic is particularly suitable in terms of easy adhesion and transparency of the laminated film.

The concentration of the inorganic colloid in the coating layer is preferably from 0.1 to 30% by weight, more preferably from 0.5 to 20% by weight, and even more preferably from 1.0 to 15% by weight. If the concentration of the inorganic colloid is less than 0.1%, it is difficult to obtain a laminated film having the desired slipperiness. If it exceeds 30% by weight, the transparency, easy adhesion, and abrasion resistance of the laminated film will deteriorate, and the adhesion of the coating layer to the base film will decrease, which is not preferable.

In addition, in order to improve the adhesion, water resistance, solvent resistance, and mechanical strength of the coating layer, methylolated or alkylolated urea-based melamine-based, acrylamide-based, polyamide-based, etc. are used as crosslinking agents. It may also contain reactive compounds such as resins, epoxy compounds, aziridine compounds, block polyisocyanates, and vinyl compounds.

Furthermore, if necessary, an antifoaming agent, a coating property improver, a binder, an antistatic agent, an antioxidant, an ultraviolet absorber, a dye, a pigment, etc. may be contained.

The polyester film constituting the film of the present invention is at least biaxially oriented by a conventional method, and the thickness is preferably 2 to 300 μm, more preferably 5 to 150 μm for practical handling as a base material. Excellent in sex. Furthermore, the haze (turbidity) of the polyester film is preferably 4.0% or less, more preferably 3.0%.
% or less.

The laminated thickness of the coating layer constituting the film of the present invention is 0.00
The range is preferably 5 to 0.15 μm, more preferably 0.01 to 0.1 μm. When the lamination thickness is less than 0.005 μm, it is not only difficult to uniformly laminate the film, but also the adhesion properties are lowered, and the adhesion of the inorganic colloid particles is also lowered, making it difficult to obtain a @layer film that is easy to slip and has durability. If the thickness exceeds 0.15 μm, transparency and slipperiness may decrease, and in some cases, blocking may easily occur due to moisture absorption of the coating layer.

The film of the present invention has a ratio (D/d) of the average particle diameter (D) of inorganic colloid particles in the coating layer to the thickness (d) of the coating layer of 1.1.
Must be ~80. Preferably 2.0 to 40,
More preferably, it is in the range of 3.0 to 15. If the ratio of particle size to film thickness is less than 1.0, the slipperiness and transparency of the laminated film will deteriorate, and problems such as surface defects will increase, which is not preferable. If the ratio of particle size to film thickness is 80 or more, not only the easy adhesion and smoothness deteriorate, but also the abrasion resistance of the coating layer deteriorates, making it easier to generate white powder, or conversely, the slipperiness deteriorates. So I don't like it.

The film of the present invention has a haze of 4.0% in terms of transparency.
The content is preferably below, more preferably 3.0% or less, still more preferably 2.5% or less.

Next, a case where a polyethylene terephthalate (hereinafter abbreviated as PET) film is used will be described as a representative A manufacturing method of the present invention, but the method is not limited thereto.

First, PET chips polymerized by a conventional method were heated to 260.
It is melt-extruded through a slit-shaped die at ~310'C and cooled to 20-80C while applying an electrostatic charge to produce an unstretched film. At this time, the intrinsic viscosity of the unstretched film is
From the viewpoint of film properties, it is desirable that it be 0.5 or more. Next, the unstretched film or the unstretched film is
On a film stretched 2.0 to 5.0 times at ~120°C,
An aqueous solution prepared by adjusting a predetermined amount of a mixed composition of inorganic = 10 oid and water-soluble or water-dispersible acrylic resin in advance is coated with a coating film.
After drying the paint film and applying the prescribed 15 layers, 70
~150°C, when using an unstretched film, stretch 2.0 to 5.0 times in the machine direction and 2° to 5.0 times in the transverse direction, and when using a -axially stretched film, 2.0～
5.0 (8 horizontal stretching.

Alternatively, the biaxially oriented film may be stretched 1.1 to 3.5 times in at least one direction at 100 to 180°C. Further, the biaxially oriented film is treated at 150 to 240°C for 1 to 60 seconds while giving 0 to 10% relaxation as necessary.

The coating method is not particularly limited, and extrusion lamination and melt coating methods may be used, but gravure coating using a water-soluble or water-dispersed coating material is preferred because it enables high-speed thin film coating. It is preferable to apply known methods such as the method, reverse coat method, spray coat method, kit coat method, die coat method, and metal ring bar code method. In this case, coating properties can only be improved by subjecting the PET film to a known surface treatment such as corona discharge treatment in air or various atmospheres as necessary before coating. First, the coating layer can be formed more firmly on the film surface. In addition, the coating material'Q degree,
The coating film drying conditions are not particularly limited, but it is desirable that the coating film drying conditions be within a range that does not adversely affect the properties of the laminated polyester film.

[Evaluation method] The characteristic values of the present invention are based on the following measurement method and evaluation criteria.

(1) Blocking resistance The blocking property of the laminated film surface is in accordance with JIS-Z-02.
50℃, 80~90RH%, load 500 according to 19
q/12ctK was applied to evaluate the blocking property of 24-hour shun. The criteria are Q: Good, Δ: Slightly poor, X:
It was marked as defective.

(2) Adhesion of coating film The adhesion strength of the coating layer/base film is
- After pasting the adhesive tape with a width of 18 mm specified in C-2338, apply a load of approximately 5 kg using a hand roller, press it back and forth twice in the length direction (approximately 10 cm), and then apply the adhesive tape by hand. The coating layer was peeled off and the degree of peeling of the coating layer was observed and evaluated. The criteria are: O: Good (Peeling area less than 5%), Δ: Slightly poor (Peeling area 5% or more and less than 20%), ×
: Defective (peeling area 20% or more).

(3) Sliding property (μS) The coefficient of static friction μs between the laminated surface and the non-laminated surface was measured according to ASTM-D-1894-63.

(4) The surface of the ff1fff1 surface of the film in the form of a durable and easily slippery tape was repeatedly run in contact with a metal (SUS) fixed guide (5 mm, ff) 100 times, and then the μS in (3) above was measured. . If the difference is within 0.2 from μS when traveling,
The durability is evaluated as good (○), and if the difference exceeds 0.2, the durability is evaluated as poor (X).

(5) The surface of the coating layer of the abrasion-resistant tape-shaped film is made of metal (SUS).
After repeatedly running in contact with a fixed guide (5 mm O) 100 times, the amount of scratches attached to the film was observed.
Judgments were made based on the number as follows.

◎ Very few varnish scratches (very good durability) ○ Few varnish scratches (good durability) X Many varnish scratches (poor durability) (8) Transparent 5EP-H-2 type thermometer (Japan Haze (turbidity) was measured based on J Is-6714-58 using Seimitsu Kogaku Co., Ltd. The criterion was that an increase in haze relative to the base film of less than 0.3% was considered good (0). , 0.3% or more was considered defective (X).

(7) Thickness d (μ) of coating layer Cellophane tape is applied to the coating layer, and the coating layer at the end of the cellophane tape is dissolved and removed using a solvent such as dimethylformamide. Next, the cellophane tape was peeled off, and the boundary between the surface protected by the cellophane tape and the surface that had been dissolved and removed was measured using an ET-10 high-precision step measuring device manufactured by Kosaka Institute to determine the thickness.

If the above method was difficult, an ultra-thin section of the laminated film was observed using a transmission electron microscope model HU-12 manufactured by Hitachi, Ltd., and the thickness was determined.

(8> Ratio of average particle diameter (D) to lamination thickness (d) (D
/d) Average particle diameter (D) and lamination thickness (d) measured in (7) above
>, the ratio (D/d) was determined.

(9) Smoothness According to J15-B-0601, a stylus-type surface roughness tester model 5D-3 manufactured by Kosaka Laboratory Co., Ltd. was used with a cutoff of 0.
The average roughness Ra (μ) was measured with a length of 25 mm and a measurement length of 1 mm. Ra is less than 0.020μm, good smoothness, 0.0
A thickness of 20 μm or more was determined to have poor smoothness.

0 mouth) Coating film using the following three types of coating materials on adhesive laminated film [After forming the layer, cross cut (100 pieces/ml) on the coating film
, apply cellophane tape (CT-24 manufactured by Chiban Co., Ltd.) to 450 on the cross-cut surface, and apply the above (2)
The cellophane tape was peeled off by hand to observe and evaluate the degree of peeling of the coating layer. The judgment criteria are: O: not peeled off well), △: somewhat poor (less than 20% peeled area), X: poor (
peeled area of 20% or more).

■ Gravure printing ink Commercially available gravure ink for cellophane printing: Cellocolor ST
(Toyo Ink Manufacturing Co., Ltd., diluted with a mixed solvent of toluene/edyl acetate/methyl edyl ketone (2:1:1),
After binding the density 10 weight 0%, barcode and 100'CX
It was dried for 1.5 minutes to form a coating layer with a thickness of 1.5 μm.

■ Cellulose for diazo binder CA338 is a commercially available cellulose for diazo binder.
1-05 (manufactured by Nagase Sangyo Co., Ltd.) was dissolved in ethyl acetate to a concentration of 10% by weight, barcoded, and heated at 110°C.
It was dried for 1.5 minutes to form a coating layer with a thickness of 5.0 μm.

■ Magnetic coating material composition: ・T-Fe203 powder 68 double cells ・Carbon fluff 7 double cells ・Vinyl chloride-vinyl acetate-vinyl alcohol copolymer
26 parts by weight, 5 parts by weight of acrylonitrile-butadiene copolymer, 2 parts by weight of polyisocyanate, 75 parts by weight of methyl ethyl ketone, and 75 parts by weight of toluene.
The coating material consisting of 75 parts was barcoded, dried for 2 minutes at 120"C, and then heated at 50℃ for 1
It was aged for 2 hours to form a coating layer with a thickness of 2.5 μm.

[Effects of the Invention] The present invention provides a polyester film that is coated with a water-soluble or water-dispersible acrylic resin containing a specific inorganic colloid, and then stretched, so that the particle diameter of the inorganic colloid particles and the lamination thickness have a specific correlation. Since the coating layer was formed, the following excellent effects could be achieved without deteriorating the properties of the base film.

(1) The laminated polyester film has excellent transparency, easy slipping, easy adhesion, and smoothness.

(2) The laminated polyester film has excellent slipperiness, durability, and abrasion resistance.

(3) The laminated polyester film maintains excellent transparency and slipperiness even at FaP;L, so it has excellent windability and form during the film forming process, and ease of handling during post-processing. ing.

(4) Laminated polystyrene film has excellent adhesion properties, so when a coating layer made of various resins is provided in post-processing, the resin layer is firmly formed, eliminating the need for an anchor coat and simplifying the process. can be achieved.

The laminated polyester film of the present invention can be applied to base films for magnetic recording media, base films for electrical disconnection, base films for capacitors, base films for packaging, various photographic base films, optical base films, graphic base films, etc. However, especially U
It is preferable to use it for a base material that requires transparency, easy slipperiness, and easy adhesion, such as a base film for v-printing.

[Example 1] The present invention will be explained using the following examples and comparative examples, but the present invention is not limited thereto.

Example 1 A PET homopolymer dip (intrinsic viscosity 0.62, melting point 259°C) produced by a conventional method was dried under reduced pressure at 180'C for 2 hours (3 mmllc+>L/).

This chip was supplied to an extruder at 280'C, melted and extruded from a T-shaped nozzle, and wound around a cooling drum with a surface temperature of 20°C using an electrostatic application method to cool and solidify it to form an unstretched film. The film was stretched 3.3 times in the machine direction by roll stretching at 90°C.

Next, as inorganic colloids, silica sol "Cataroid'° (manufactured by Catalysts Kasei Kogyo Co., Ltd.) with an average particle size of 0.12 μm and water-dispersible acrylic resin "Nicazol" A-oa (manufactured by Nippon Carbide Industries Co., Ltd.) were used. A binder consisting of Eli
Concentration 1 uniformly dispersed with a composition of ffl solid content ratio of 5:95
．． After applying 0% by weight of the coating material to one side of the above-mentioned -axially stretched film using a metering bar, the 5 layers of the coating were stretched 3.6 times in the transverse direction at 100'C while drying. Heat treatment was performed at 210°C for 5 seconds while relaxing 2% in the direction to form a coating layer of 0.
A laminated film with a thickness of 15 μm in which 0.026 μm was laminated was prepared.

The coating layer thus formed had a ratio of the average particle diameter of the silica sol to the layer thickness (D/d) of 4.6.

Furthermore, the properties of the laminated film are as shown in Table 1, and it has excellent transparency, slipperiness, adhesion, and smoothness, and the coating layer has excellent sliding durability, abrasion resistance, blocking resistance,
Both adhesion was excellent.

Examples 2 to 5, Comparative Examples 1 to 2 Using the same PET as in Example 1 and the same composition as in Example 1, coating materials were made with different average particle diameters and composition ratios of silica sol. Laminated films with different ratios (D/d) of the average particle diameter of the silica sol to the laminated thickness in the coating layer were obtained using the same method as described above. The properties of these laminated films are shown in Table 1. As shown in Table 1, when the laminated film is within the scope of the present invention (Examples 2 to 6), 1q of films with an excellent balance of slipperiness, transparency, adhesiveness, and smoothness can be used. However, if it is outside the scope of the present invention (Comparative Example 1)
．． It can be seen that in case 2), a film having excellent transparency, slipperiness, adhesiveness and smoothness cannot be obtained.

Example 6 Titanium oxide sol “Queen Titanic” with an average particle diameter of 0.20 μm as an inorganic colloid (Catalysts & Chemicals Co., Ltd.)
The film was formed and evaluated in the same manner as in Example 1, except that the film was manufactured using the following method. As shown in Table 1, it was possible to obtain a laminated film that similarly maintained excellent transparency, slipperiness, adhesiveness, and smoothness.

Claims (2)

[Claims] (1) A laminated polyester film having a coating layer mainly composed of an inorganic colloid with an average particle size of 0.11 to 0.4 μm and a water-soluble or water-dispersible acrylic resin on at least one side of the polyester film. The ratio of the average particle diameter (D) of the inorganic colloid to the thickness (d) of the coating layer (
A laminated polyester film characterized in that D/d) is in the range of 1.1 to 80. (2) The laminated polyester film according to claim 1, wherein the optical haze of the laminated polyester film is 4% or less.