JPH0637571B2 - Surface hardened polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a surface-cured polyester film. More specifically, the present invention relates to a surface-cured polyester film which is less likely to be scratched on the surface of the film and which maintains good appearance and transparency of the film.

[Problems to be solved by conventional technology and invention]

The biaxially stretched polyester film, especially the biaxially stretched polyethylene terephthalate film is widely used due to its excellent mechanical strength, dimensional stability, heat resistance, transparency, chemical resistance, etc., but the film comes into contact with objects. As a result, the surface of the film is scratched, the appearance of the surface,
If the gloss and the transparency decrease, there are some drawbacks. As a method of improving the susceptibility of the surface of the plastic to scratches, a method using a so-called surface-hardening coating is well known. Typical surface-curing paints are acrylic resins, urethane resins, amino resins, alkyd resins, and silicone resins, which are applied by heating or crosslinking reaction by active rays such as ultraviolet rays and electron beams. The property is exhibited by increasing the hardness of the layer.
Thermosetting resin by heating requires a solvent for coating,
There are also safety and health problems. In addition, since the thermosetting resin requires high temperature for crosslinking and a long reaction time, there is a problem that dimensional change of the polyester film, deterioration of flatness, deterioration of transparency and the like are likely to occur. Among surface-curable coating materials, silicone-based resins are useful when highly attempting to harden the surface, but have the problem of being expensive. Therefore, the actinic radiation-crosslinking type surface-curing paint in which the solvent itself of the coating agent is a so-called reactive diluent is attracting attention, and among them, the acrylic resin which is easily actinic radiation crosslinkable is attracting attention. . However, the adhesiveness between the actinic radiation crosslinkable acrylic resin and the polyester film is not industrially sufficiently satisfactory, and there is a problem in practical durability.

[Means for solving problems]

The present inventors have formed an actinic radiation crosslinkable acrylic resin layer on a polyester film having good adhesion to an actinic radiation crosslinkable acrylic resin, and put a surface-cured polyester film with good durability into practical use. The present invention has been achieved as a result of earnest research conducted for the purpose of providing the same.

That is, the gist of the present invention is to apply a polyurethane having an anionic group to at least one side of a polyester phenol, and then form an actinic radiation-crosslinking acrylic resin on the coating layer of a stretched polyester film. It exists in polyester film.

Hereinafter, the present invention will be described in detail.

The polyester of the polyester film in the present invention means polyethylene terephthalate in which 80 mol% or more of its constituent units is ethylene terephthalate, or
80 mol% or more of the constitutional unit is polyethylene naphthalate, which is ethylene naphthalate.

The polyester film of the present invention may contain inorganic particles, organic particles, organic lubricants, antistatic agents, stabilizers, dyes, pigments, organic polymers and the like as a composition, if necessary.

The polyurethane having an anionic group in the present invention means JP-B-42-24194, JP-B-46-7720 and JP-B-46-10.
193, Japanese Patent Publication No. 49-37839, Japanese Patent Laid-Open No. 50-123197, Japanese Patent Laid-Open No.
Polyurethane resins known in JP-A-53-126058, JP-A-54-138098 and the like or polyurethane resins similar thereto can be used.

The main constituents of the polyurethane-forming component are polyisocyanates, polyols, chain extenders, crosslinkers and the like.

Examples of polyisocyanates include tolylene diisocyanate, phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate and the like.

Examples of polyols include polyethers such as polyoxyethylene glycol, polyoxypropylene glycol, polyoxytetramethylene glycol, polyethylene adipate, polyethylene-butylene adipate, polyesters such as polycaprolactone, acrylic polyols, castor oil, etc. There is.

Examples of the chain extender or crosslinking agent include ethylene glycol, propylene glycol, butanediol, diethylene glycol, trimethylolpropane, hydrazine, ethylenediamine, diethylenetriamine, 4,
4'-diaminodiphenylmethane, 4,4'-diaminodicyclohexylmethane, water and the like.

The polyurethane-based resin having an anionic group is a method of using a compound having an anionic group as a polyurethane-forming component such as a polyol, a polyisocyanate compound, and a chain extender, and the unreacted isocyanate group and anionic group of the generated polyurethane are It can be produced by a method of reacting a compound having the same, a method of reacting a group having an active hydrogen of polyurethane with a specific compound, or the like.

In the method of using a compound having an anionic group as the polyurethane-forming component, for example, a compound obtained by a method of sulfonating an aromatic isocyanate compound, a diaminocarboxylic acid salt, a sulfuric acid ester salt of amino alcohols, or the like can be used.

The method of reacting an unreacted isocyanate group of polyurethane with a compound having an anionic group is, for example, bisulfite, aminosulfonic acid and salts thereof, aminocarboxylic acid and salts thereof, sulfuric acid ester of aminoalcohols and salts thereof, hydroxy and the like. Acetic acid and its salts can be used.

The method of reacting the group having an active hydrogen of polyurethane with a specific compound is, for example, dicarboxylic acid anhydride, tetracarboxylic acid anhydride, sultone, lactone, epoxycarboxylic acid, epoxysulfonic acid, 2,4-dioxooxazolidine, isato. A 3- to 7-membered cyclic compound showing a salt-type group such as an acid anhydride, hoston, or carbyl sulfate or a group capable of forming a salt after ring opening can be used.

Polyurethane resin has a molecular weight of 300 to 2000
A resin comprising a compound having 0 polyol, polyisocyanate, a chain extender having a reactive hydrogen atom and a group reactive with an isocyanate group, and at least one anionic group is preferable.

Anionic groups in the polyurethane-based resin, -SO ₃ H, -OS
O ₃ H, -COOH or their ammonium salts, lithium salts, sodium salts, is used as the potassium salt or magnesium salt.

A particularly preferred sulfonate group.

The amount of anionic groups in the polyurethane resin is preferably 0.05% by weight to 8% by weight. With a small amount of anionic group,
The polyurethane resin has poor water solubility or water dispersibility,
This is because when the amount of anionic group is large, the water resistance of the undercoat layer after coating is poor, or moisture is absorbed and the films are easily fixed to each other.

When the polyurethane having an anionic group in the present invention is insufficient in coatability or adhesiveness to the polyester film as the base due to its chemical structural characteristics, the polyester having an anionic group is used together with the polyurethane in the present invention. This makes it possible to remedy these drawbacks.

However, among polyurethanes, those containing a large amount of polyester units as constituent components do not necessarily require the blending of the above-described polyester having an anionic group.
The polyester having an anionic group (hereinafter, abbreviated as "polyester resin") refers to Japanese Patent Publication No. 47-40873.
JP-A-50-83497, JP-A-50-121336, JP-A-52-1556
Polyesters known in JP-A-40, etc. or polyesters similar thereto can be used.

For example, the dicarboxylic acid component of polyester is terephthalic acid, isophthalic acid, as an example of aromatic dicarboxylic acid,
2,6-naphthalenedicarboxylic acid and ester-forming derivatives thereof are used, and examples of the aliphatic dicarboxylic acid include adipic acid, azelaic acid, sebacic acid and ester-forming derivatives thereof, and oxymonocarboxylic acid. For example, oxybenzoic acid and its ester-forming derivative are used.

Further, as the glycol component of the polyester, aliphatic, alicyclic, aromatic diol and the like can be used, and examples thereof include ethylene glycol, 1,4-butanediol, diethylene glycol, triethylene glycol, 1,4-cyclohexanedimethanol. , P-xylene diol, etc. are used, and so-called polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. are used as examples of poly (oxyalkylene) glycol.

As the polyester, not only the saturated linear polyester including the ester-forming component described above but also a polyester including a compound having three or more ester-forming components or a polyester having a reactive unsaturated group can be used.

The polyester having a sulfonate group can be produced by using a compound having a sulfonate group which can be a polyester component together with the above-mentioned polyester forming component.

Examples of the compound having a sulfonate group include sulfoisophthalic acid, sulfoterephthalic acid, sulfonaphthalene-
There are metal salts such as 2,6-dicarboxylic acid and its ester-forming derivatives. As the metal of the metal salt, lithium,
Sodium, potassium, magnesium and the like are preferable. Among these, very suitable compounds are 5-sodiosulfoisophthalic acid or 5-sodiosulfodimethylisophthalate.

Another method of introducing a sulfonate group into the polyester is to sulfonate the unsaturated group of the polyester containing an ester-forming aliphatic unsaturated compound as a copolymerization component with a sulfonating agent such as sodium hydrogen sulfite or sodium metabisulfite. The method can also be illustrated.

The amount of aromatic dicarboxylic acid in the dicarboxylic acid component of the polyester resin is preferably in the range of 50 mol% to 100 mol%. This is to increase the softening point of the polyester resin and improve the adhesiveness.

The sulfonate group in the polyester resin needs to be present in an amount necessary for making the resin water-soluble or water-dispersible, and the dicarboxylic acid having a sulfonate group is contained in an amount of 2 mol% to 20 mol% in the dicarboxylic acid. It is preferably used in the range.

If the amount of the sulfonate group is less than 2 mol%, the water solubility or water dispersibility is insufficient, and if the amount of the sulfonate group is more than 20 mol%, the water resistance of the undercoat layer after coating is poor or the film absorbs moisture to form a film. This is because they tend to stick to each other.

Further, as the polyester resin, not only the saturated linear polyester consisting of the above-mentioned ester-forming component,
A polyester formed of a compound having a trivalent or higher valent ester-forming component or a polyester having a reactive unsaturated group can also be used.

The proportion of the polyurethane having an anionic group and the polyester resin in the present invention is 30% by weight of polyurethane.
To 100% by weight (solid content ratio), more preferably 50% to 100% by weight. If the proportion of polyurethane is less than 30% by weight, the adhesiveness to the actinic radiation-crosslinking acrylic resin will be insufficient.

The medium containing a polyurethane having an anionic group as a main component after coating in the present invention, which contains water as a main component, has improved aggregation stability of the polymer, improved coatability of the substrate to the polyester film, and film formation. Organic compounds such as alcohols, cellosolves, and N-methylpyrrolidone may be contained in addition to water in order to improve properties.

A reverse roll coater described as "coating method" by Yuji Harasaki, Maki Shoten, issued in 1979, is known as a method of applying a coating solution containing a polyurethane having an anionic group as a main component in the present invention to a polyester film as a base. A gravure coater, a rod coater, an air doctor coater, or a coating device other than these can be used. The coating step, before sequential biaxial stretching in the film forming step, before simultaneous biaxial stretching, before re-stretching after biaxial stretching,
That is, it is a coating and stretching method in which a coating agent is coated on at least one side of a polyester film and then appropriately dried or stretched without drying. As a specific example of this method, a coating agent is applied to a uniaxially stretched polyester film by a roll stretching method, subjected to appropriate drying, or without drying, immediately stretched in a direction perpendicular to the previous stretching direction, and heat treated. Is the way to do it. According to this method, the coating layer can be dried simultaneously with stretching, and the thickness of the coating layer can be reduced according to the stretching ratio.

The coating thickness of the coating layer containing polyurethane having an anionic group as a main component in the present invention is preferably in the range of 0.01 μ to 1 μ, and more preferably in the range of 0.01 μ to 0.1 μ. If the thickness of the coating layer is less than 0.01, it is difficult to apply the coating uniformly, so that coating unevenness is likely to occur in the product, and if it is thicker than 1 μ, slipperiness may be rather deteriorated.

The coating layer containing a polyurethane having an anionic group as a main component in the present invention has a methylol group or an alkylol group as a cross-linking agent in order to improve the adhesion (blocking property), water resistance, solvent resistance and mechanical strength of the coating layer. Urea-based, melamine-based, guanamine-based, acrylamide-based, polyamide-based compounds, epoxy compounds, aziridine compounds, block polyisocyanates, silane coupling agents, titanium coupling agents, zircoaluminate coupling agents, heat, It may contain a vinyl compound or a photosensitive resin that is reactive with peroxides, actinic rays and the like. Further, this coating layer is silica, silica sol, alumina, alumina sol, zirconium sol, kaolin, talc, calcium carbonate, titanium oxide, barium salt, carbon black, molybdenum sulfide, as inorganic fine particles for improving adhesion and slipperiness. It may contain antimony oxide sol and the like.

In addition, this coating layer contains an organic polymer, an antifoaming agent, a coating property improving agent, a thickener, an antistatic agent, an organic lubricant, an organic polymer particle, an antioxidant, an ultraviolet absorber, if necessary. It may contain agents, foaming agents, dyes, pigments and the like.

The coating layer containing a polyurethane having an anionic group as a main component in the present invention may be formed on only one side of the polyester film or may be formed on both sides. When this coating layer has only one surface, a coating layer other than the polyurethane having an anionic group according to the present invention may be formed on the opposite surface to impart characteristics other than the effects of the present invention to the polyester film of the present invention. . It is also possible to improve the coatability of the coating liquid to the film and the adhesiveness of the coating layer to the base film by subjecting the polyester film before coating the coating liquid in the present invention to chemical treatment or discharge treatment.

The coating property and the adhesive property of the actinic radiation-crosslinking acrylic resin may be improved by performing discharge treatment on the coating layer containing the polyurethane having an anionic group as the main component of the polyester film of the present invention.

In the present invention, the polyester film as the base is
Those having a thickness of 3 μ to 500 μ can be used.

The actinic radiation of the actinic radiation crosslinkable acrylic resin in the present invention means an electromagnetic wave such as an ultraviolet ray, an electron beam, or a radiation that polymerizes an acrylic vinyl group, and the ultraviolet ray is practically convenient. The electron beam method is useful because the apparatus is expensive and the operation under an inert gas is required, but the photopolymerization initiator and the photosensitizer may not be contained in the coating layer.

The actinic radiation cross-linking acrylic resin in the present invention contains an acrylic oligomer and a reactive diluent as actinic radiation polymerization components, and optionally contains a photoinitiator, a photosensitizer, and a modifier. Good. Acrylic oligomers include those in which a reactive acrylic group is bonded to an acrylic resin skeleton, as well as polyester acryl, urethane acryl, epoxy acryl, polyether acryl, and rigid skeletons such as melamine and isocyanuric acid. Examples thereof include those having an acrylic group bonded thereto, but are not limited thereto. The reactive diluent serves as a solvent for the coating agent and functions as a solvent in the coating step.
As such, it has a group capable of reacting with a monofunctional or polyfunctional acrylic oligomer and serves as a copolymerization component of a coating film. Further, particularly in the case of crosslinking by ultraviolet rays, since the light energy is small, a photopolymerization initiator and a sensitizer are necessary for promoting the conversion and initiation of light energy. These acrylic oligomers, reactive diluents, photopolymerization initiators,
Specific examples of the sensitizer, the crosslinking device, etc. are written by Shinzo Yamashita and Tosuke Kaneko, "Crosslinker Handbook", published by Taiseisha in 1981.
Pages 267 to 275, pages 562 to 59
Although page 3 can be referred to, it is not limited thereto. As a multifunctional acrylic UV-curable coating as a commercial product, Mitsubishi Rayon Co., Fujikura Kasei Co., Dainichi Seika Kogyo Co., Dainippon Ink and Chemicals, Toa Gosei Chemical Co.,
Products such as Nitto Kasei can be used, but are not limited to these. Examples of modifiers for the surface-hardened layer include coatability improvers, defoamers, thickeners, antistatic agents, inorganic particles, organic particles, organic lubricants, organic polymers, dyes, pigments, stabilizers. And the like, and these are used as the composition of the coating layer within a range that does not inhibit the reaction due to actinic radiation, and the characteristics of the surface-hardened layer can be improved depending on the application.

The thickness of the acrylic resin layer in the present invention is preferably 0.5 μ to 50 μ.

〔The invention's effect〕

The surface-cured polyester film of the present invention has good adhesiveness between the polyester film layer of the substrate and the actinic radiation-crosslinking acrylic resin, and enables the surface-curing characteristics of the acrylic resin to be exhibited for a long period of time. . The surface-cured polyester film of the present invention is a protective film laminated on glass such as membrane switches, buildings, automobiles and furniture.
It is used for light-shielding films, labels, nameplates, color filters, home appliances plastic sheet laminates, and anti-glare filters for display.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples as long as the gist thereof is not exceeded.

The effect of the present invention is evaluated by the following method.

1 Formation of surface-hardened acrylic resin layer Urethane acrylate-based Unideck 1 in “UV-curable resin for scratch resistant paint” by Dainippon Ink and Chemicals, Inc. 1
The 7-806 (trade name) system was used. The compounding composition of this product is 30 parts of Unidix 17-806, 50 parts of Unidix Shin-An # 001, 1.2 parts of a photopolymerization initiator, and 0.012 part of an additive. This was coated on a polyester film substrate using a bar coater and pre-dried at 60 ° C. for 5 minutes, and the curing condition was 80 W / c with UVH-2000 type (trade name) which is an ultraviolet irradiation device manufactured by Ushio Inc.
A cured layer having a thickness of 5 μm was formed with m, irradiation distance of 15 cm, and irradiation time of 5 seconds. The surface hardenability of this hardened layer is 7H in pencil hardness (JIS K-5400), which is extremely high. Taber abrasion (ASTM D-1044), falling sand abrasion (ASTM D-673), steel wool abrasion. Even with (# 000 line), 500 g / cm load, 100 reciprocations of rubbing), the increase in transparency is extremely small, but the hardness is so high that the adhesion to the polyester film is poor as described later.

2 Adhesiveness evaluation method Put a 2mm square square in a surface-hardened acrylic resin tank,
18 mm wide cellophane tape (trade name) manufactured by Nichiban Co., Ltd. is attached to a length of 7 cm so as to prevent air bubbles from entering, and a constant load is applied on this with a manual load roll of 3 kg. Fix the film,
Connect one end of the cellophane tape to the 500g weight with a string,
Observe the presence or absence of peeling by a method in which the weight starts to peel in the direction of 180 degrees after naturally dropping at a distance of 45 cm.

3 Durability evaluation method Two films are fixed using a spacer. The film interval is 100 μ, and the space is 2 cm × 2 cm. Use a rod with a load of 200g and rubber at the tip 7R for 3Hz.
The key is pressed from the surface-cured acrylic resin layer side, and the change in transparency of the film is observed.

Comparative Example Polyethylene terephthalate was melt extruded at 285 ° C. and cast on a cooling drum at 60 ° C. to give a thickness of 820.
An amorphous film of μ was obtained. This film was stretched 3.3 times in the longitudinal direction at 95 ° C., further 3.3 times in the transverse direction at 110 ° C., and heat-treated at 210 ° C. to obtain a film having a thickness of 75 μ.

A surface-hardened acrylic resin layer was formed on this film.
In the evaluation of the adhesiveness using the cellophane tape, it was completely peeled off at the interface between the polyester base layer and the acrylic resin layer. In the durability evaluation by hitting the keys with a rod, the deterioration of the transparency was observed about 10,000 times.

Example 1 Hydran AP-40 (trade name) manufactured by Dainippon Ink and Chemicals, Inc., which is a water-dispersed polyurethane having a carboxylate group
A coating solution consisting of 80 parts (the same as the solid content weight and below) and 20 parts of Hua Intex ES-670 (trade name) manufactured by Dainippon Ink and Chemicals, Inc., which is a water-dispersed polyester having a sulfonate group, was stretched in the transverse direction after longitudinal stretching in Comparative Example. It was applied to one side of the film before stretching. The thickness of this coating layer was 0.04 g / m ² .

A surface-cured acrylic resin layer was formed on the coating layer of this film. In the evaluation of the adhesiveness with the cellophane tape, peeling occurred at the interface between the cellophane tape and the acrylic resin layer, and the acrylic resin did not fall off. In the durability evaluation by hitting keys with a rod, the transparency was not deteriorated even after 30,000 times.
That is, the surface-cured polyester film of the present invention,
The adhesiveness between the surface-cured acrylic resin and the substrate polyester was good, and it was useful for applications such as membrane switches.

Example 2 Polyethylene terephthalate in which the content of inorganic particles was reduced as much as possible was extruded in the same manner as in Comparative Example to obtain an amorphous film of 340μ, and further stretched 3.7 times in the longitudinal direction at 95 ° C.
Hydran AP-40 (trade name) from Dainippon Ink and Chemicals, Inc., which is a water-dispersed polyurethane having a carboxylate group, is subjected to corona discharge treatment on both sides of this film.
A coating solution consisting of 5 parts and 5 parts of silica gel is applied to both sides of the film and immediately stretched 3.7 times in the transverse direction at 110 ° C.
Furthermore, it heat-processed at 220 degreeC. The thickness of this film is 2
The coating layer had a thickness of 5 μm and a thickness of 0.06 g / m ² .

A surface-hardened acrylic resin layer was formed on one side of this film. The evaluation of the adhesiveness with the cellophane tape was good without peeling at the interface between the cellophane tape and the acrylic resin and the acrylic resin did not fall off. That is, the surface-cured polyester film of the present invention has good adhesion between the surface-cured acrylic resin and the polyester of the substrate, and is useful for glass lamination applications and the like.

Example 3 Polyethylene terephthalate was extruded at 285 ° C. and
The film was cast on a cooling drum at 0 ° C. to obtain an amorphous film having a thickness of 900 μ, and further stretched 3.0 times in the machine direction at 95 ° C. One side of this film is a water-dispersed polyurethane having a sulfonate group, Inbranil DL manufactured by Bayer.
Coating consisting of 65 parts of H (trade name), 20 parts of Polyester XWR-901 (trade name) of Japan Synthetic Chemical Industry Co., Ltd., which is a water-dispersed polyester having a sulfonate group, 10 parts of alkylol melamine, and 5 parts of silica sol. Apply the liquid,
Immediately, it was stretched 3.0 times in the transverse direction and heat-treated at 210 ° C. The thickness of this film is 100μ, and the thickness of the coating layer is 0.
It was 09 g / m ² . This film was slightly hazy due to the fine roughness of the coating layer surface, but when a surface-cured acrylic resin layer was provided on this film, it was as transparent as the base film without the polyurethane layer of the present invention. Sexuality. The acrylic resin layer of this film was found to have good adhesiveness to the base film as evaluated by cellophane tape. That is, the surface-cured polyester film of the present invention was also useful in applications such as labels.

Continuation of front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display location B29L 9:00 4F (72) Inventor Nariaki Okajima 1000 Kamoshida-cho, Midori-ku, Yokohama-shi, Kanagawa Daifoil Co., Ltd. Research In-house (56) References JP 62-127328 (JP, A) JP 61-261326 (JP, A)

Claims (1)

[Claims] 1. A surface-cured polyester comprising a polyester film coated with a polyurethane having an anionic group on at least one surface thereof, and then an actinic radiation-crosslinking acrylic resin layer formed on the coated layer of the stretched polyester film. Film.