KR20200078623A - Easy-adhesive polyester film - Google Patents

Abstract

[Problem] The present invention does not substantially contain an organotin compound as a crosslinking/curing catalyst in the composition forming the easily adhesive layer, and has excellent adhesion between a polyester film and a functional layer such as a polarizer or adhesive layer, and condensation. It is to provide a self-adhesive polyester film which does not generate blocking in the presence of water.
[Solution Solution] The present invention is a polyester film having an easily adhesive layer on at least one side, wherein the easily adhesive layer is a composition containing a polyester resin, a polyvinyl alcohol resin, and an active methylene block isocyanate crosslinking agent, to be cured. It is made, and is a self-adhesive polyester film having substantially no organic tin as a curing catalyst for the composition in the easily adhesive layer, and having a peel strength of 2 N/cm or less after water adhesion.

Description

Easy-adhesive polyester film

The present invention relates to a bi-adhesive polyester film that does not generate blocking even when condensation water is adhered, has excellent adhesion to a polarizer or a functional layer, and is excellent in environmental titration. The easily-adhesive polyester film of the present invention is suitable as a base film for optical members such as displays, and is particularly suitable as a polarizer protective film.

In a liquid crystal display device, polarizing plates are disposed on both sides of a glass substrate that forms a liquid crystal panel surface by the image forming method. The polarizing plate generally has a configuration in which a polarizer protective film is pasted through a hydrophilic adhesive such as a polyvinyl alcohol-based resin on both surfaces of a polarizer made of a polyvinyl alcohol-based film and a dichroic material such as iodine. As a protective film used for the protection of a polarizer, a triacetyl cellulose film has been conventionally used from the viewpoint of optical properties and transparency.

However, triacetyl cellulose is not sufficiently durable, and when a polarizing plate using a triacetyl cellulose film as a polarizer protective film is used under high temperature or high humidity, the performance of the polarizing plate such as polarization degree or color may be deteriorated. Further, in order to cope with the thinning of displays in recent years, thinning of polarizing plates is required, but from the viewpoint of maintaining moisture barrier properties, there has been a limit to thinning of triacetyl cellulose films. Therefore, it has been proposed to use a polyester film as a polarizer protective film having durability and moisture barrier properties (for example, see Patent Document 1).

The triacetyl cellulose film used as a polarizer protective film has an alkali treatment or the like applied to the surface, and has an extremely high affinity with a hydrophilic adhesive. Therefore, the protective film made of a triacetyl cellulose film has extremely high adhesion to a polarizer coated with a hydrophilic adhesive. However, the polyester film has insufficient adhesiveness with a hydrophilic adhesive, and the tendency becomes more remarkable, especially in the case of a polyester film having orientation by stretching treatment. Therefore, in order to improve the adhesiveness with the polarizer or the hydrophilic adhesive applied to the polarizer, coating of the surface of the polyester film with a highly hydrophilic material such as the easily adhesive layer disclosed in Patent Document 1 has been performed.

Japanese Patent Application No. 2013-063610

The polyester film has low affinity to water, and a polyester film having an aromatic dicarboxylic acid as a dicarboxylic acid component is particularly prominent in this tendency. Moreover, the polyester film which has crystal orientation by extending|stretching has a lower affinity with water further. On the other hand, the polarizer or the adhesive applied on the polarizer generally has a polyvinyl alcohol-based resin as a main component and has high hydrophilicity. From such a difference in properties, as a means for firmly adhering a polyester film and a polyvinyl alcohol-based resin layer such as an adhesive applied on a polarizer or a polarizer, as used in the easily adhesive layer disclosed in Patent Document 1 Materials such as increased hydrophilicity have been used.

However, if the hydrophilicity of the easily bonding layer is increased, the film roll may be affected by the temperature difference between the indoor temperature and the outside air, especially when transporting film rolls in winter, between indoors and outdoors in factories, etc. In some cases, condensation water adhered, and blocking troubles in which the film surface or the easily adhesive layer adhered to each other occurred. This is different from the blocking that occurs under pressure after standing in air containing normal water vapor, and is generated only through liquid water. That is, it is necessary to increase the hydrophilicity in order to increase the adhesiveness with the adhesive, but on the other hand, since blocking by condensation water occurs, it has been extremely difficult to achieve both this adhesiveness and blocking. To avoid this, seasoning is effective, but is not completely avoidable, and the problem is that the seasoning process is added and the processing is delayed, leading to deterioration in productivity.

In addition, from the viewpoint of durability of the easily adhesive layer, an organic tin catalyst is often used as a raw material to accelerate the crosslinking reaction (hardening of the easily adhesive layer) of the easily adhesive layer. In the literature describing a coating liquid containing a conventional polyvinyl alcohol, a polyester, and an isocyanate crosslinking agent, there are many things that do not mention that a crosslinking/curing catalyst is contained, but it is usually used without a description. However, it is known that organotin is highly toxic and affects organisms even in a small amount, and the use of organotin compounds has been limited in recent years.

Under such development, the problem of the present invention is that the composition forming the easily adhesive layer does not substantially contain an organotin compound as a crosslinking and curing catalyst, and the adhesiveness between the polyester film and a functional layer such as a polarizer or an adhesive layer. An object of the present invention is to provide a self-adhesive polyester film which is excellent and does not generate blocking in the presence of condensation water.

The present inventors have studied earnestly to achieve these objects, and have reached the completion of the present invention. That is, this invention consists of the following structures.

1.A polyester film having an easily adhesive layer on at least one surface, wherein the easily adhesive layer is made of a composition containing a polyester resin, a polyvinyl alcohol resin and an active methylene block isocyanate crosslinking agent, and cured. A self-adhesive polyester film having substantially no organotin as a curing catalyst for the composition, and having a peel force of 2 N/cm or less after water adhesion.

2. The easily-adhesive polyester film according to the above 1, which is used as a polarizer protective film.

According to the present invention, even if condensation water adheres, blocking does not occur, excellent adhesion to a functional layer such as a polarizer or an adhesive layer, and an organic tin catalyst is not used. It became possible to provide a self-adhesive polyester film.

(Polyester film)

The polyester film used as a base material in the present invention is a film mainly composed of a polyester resin. Here, "a film mainly composed of a polyester resin" means a film formed of a resin composition containing 50% by mass or more of a polyester resin. When mixed with other polymers, it means that the polyester resin contains 50 mass% or more, and when copolymerized with other monomers, it means that the polyester structural unit contains 50 mol% or more. Preferably, the polyester film contains 90% by mass or more of the polyester resin, more preferably 95% by mass or more, and even more preferably 100% by mass.

The material of the polyester resin is not particularly limited, but a copolymer formed by polycondensation of a dicarboxylic acid component and a diol component or a mixed resin thereof can be used. As the dicarboxylic acid component, for example, terephthalic acid, isophthalic acid, orthophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5- Naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethanedicarboxylic acid, diphenylsulfoniccarboxylic acid, anthracenedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1 ,4-cyclohexanedicarboxylic acid, hexahydro terephthalic acid, hexahydro isophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3,3-diethylsuccinic acid, glutaric acid, 2,2-dimethylglutaric acid, adipic acid , 2-methyladipic acid, trimethyladipic acid, pimelic acid, azelaic acid, dimer acid, sebacic acid, suberic acid, dodecanedicarboxylic acid and the like.

As the diol component constituting the polyester resin, for example, ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1,2-cyclohexane dimethanol, 1,4-cyclohexane dimethanol, decamethylene glycol , 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-bis(4-hydroxyphenyl)propane, bis(4-hydroxyphenyl) And sulfones.

The dicarboxylic acid component and the diol component constituting the polyester resin may be used alone or in combination of two or more. Moreover, you may add suitably other acid components, such as trimellitic acid, and other hydroxyl group components, such as trimethylolpropane.

Specific examples of the polyester resin include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and among these, polyethylene terephthalate is preferred from a balance between physical properties and cost. Moreover, in order to control optical properties, such as polarization, it is also a preferable aspect to include another copolymerization component or another polymer. Preferred copolymerization components from the viewpoint of controlling the optical properties of the polyester film include diethylene glycol, copolymerization components having norbornene in the side chain, and the like.

When used as a protective film for polarizers, it is preferable that the polyester film of this invention has high transparency. The transparency of the film of the present invention, the total light transmittance is preferably 85% or more, more preferably 87% or more, more preferably 88% or more, even more preferably 89% or more, and 90% The above is particularly preferable. Moreover, haze is preferably 3% or less, more preferably 2.5% or less, further preferably 2% or less, and particularly preferably 1.5% or less.

In order to improve handling properties such as slipperiness and windability of the polyester film, inert particles may be contained in the film, but in order to maintain high transparency, the content of the inert particles in the film is preferably as small as possible. Do. Therefore, it is preferable to make it into a multi-layered structure in which particles are contained only in the surface layer of the film, or to contain fine particles only in the coating layer laminated on at least one side of the polyester film without substantially containing particles in the film.

In addition, "substantially free of particles" means, for example, in the case of inorganic particles, when quantitatively analyzing elements derived from particles by fluorescence X-ray analysis, 50 ppm or less, preferably 10 ppm or less, most preferably Means content below the detection limit. This means that even if the particles are not actively added to the base film, the foreign matter-derived contaminant component or the contamination attached to the line or device in the raw material resin or film production process is peeled off and inevitably incorporated into the film. Because there are cases.

In addition, when the polyester film is formed in a multi-layered structure, the two-layered three-layered structure containing substantially no inert particles in the inner layer and only containing the inert particles in the outermost layer can achieve both transparency and workability. Do.

In the present invention, the thickness of the base film is not particularly limited, but when the thickness of the polarizing plate is thinned for thinning the display, the thickness of the film is preferably 200 μm or less, and more preferably 100 μm or less. On the other hand, from the viewpoint of maintaining the mechanical strength as a protective film, the thickness of the film is preferably 10 µm or more, more preferably 12 µm or more, and even more preferably 20 µm or more.

The polyester film serving as the base material may be a single layer or a layer of two or more layers laminated. Moreover, as long as it is in the range which achieves the effect of this invention, various additives can be contained in a film as needed. Examples of the additives include antioxidants, light fasteners, antigelling agents, organic wetting agents, antistatic agents, ultraviolet absorbers, surfactants, and the like. When the film has a laminated structure, it is also preferable to contain additives depending on the function of each layer, if necessary. For example, in order to prevent light deterioration of the polarizer, it is also preferable to add an ultraviolet absorber or the like to the inner layer.

The polyester film can be produced according to an ordinary method. For example, it is obtained by a method of forming a film by melt-extruding the above-mentioned polyester resin in a film form and cooling and solidifying it with a casting drum. As the polyester film in the present invention, both a non-stretched film and a stretched film can be used, but it is preferably a stretched film from the viewpoint of durability such as mechanical strength and chemical resistance. When the polyester film is a stretched film, the stretching method is not particularly limited, and the longitudinal uniaxial stretching method, the transverse uniaxial stretching method, the longitudinal and lateral difference biaxial stretching method, the vertical and horizontal simultaneous biaxial stretching method, etc. Can be employed. When stretching a polyester film, extending|stretching may be performed before laminating|stacking the easily bonding layer mentioned later, or after laminating|stacking the easily bonding layer. It is also possible to uniaxially stretch in the longitudinal or transverse direction before laminating the adhesive layer, and to stretch in the other direction after laminating the coating layer.

(Easy adhesive layer)

The polyester film of the present invention has an acid value of 20 KOHmg/g or less on at least one side of the polyester film in order to improve adhesion to a polyvinyl alcohol-based resin layer such as a polarizer and a water-based adhesive provided on one or both sides thereof. It is preferable that an easy-adhesion layer formed of a resin composition containing a polyester resin, a polyvinyl alcohol-based resin having a saponification degree of 60 to 85 mol%, and an active methylene block isocyanate crosslinking agent is laminated. This adhesive layer may be provided on both sides of the polyester film, or may be provided only on one side of the polyester film, and a different type of resin coating layer may be provided on the other side.

While not being bound by theory, poly is by combining a specific polyester resin having an acid value of 20 KOHmg/g or less, a specific polyvinyl alcohol resin having a saponification degree of 60 to 85 mol%, and an active methylene block isocyanate crosslinking agent. It is believed that the ester-based resin and the polyvinyl alcohol-based resin form separate domain units in the easily-adhesive layer, thereby forming a phase separation structure, also commonly referred to as a sea-island structure. By taking such a domain-based separation structure, the adhesion to the polyester film by a domain composed of a polyester-based resin and the polyvinyl alcohol-based resin layer by a domain composed of a polyvinyl alcohol-based resin and It is thought that the two functions of adhesiveness are compatible with each other without being damaged. It is thought that the active methylene block isocyanate crosslinking agent promotes and maintains the formation of the domain structure by crosslinking and coagulating with the polyester resin and the polyvinyl alcohol-based resin.

Hereinafter, each composition of the easily adhesive layer will be described in detail.

(Polyester resin)

The polyester resin used for the easily-adhesive layer in the present invention is a copolymer obtained by polycondensing a dicarboxylic acid component and a diol component, and as the dicarboxylic acid component and the diol component, the material of the polyester film as the aforementioned base material can be used. Can. From the viewpoint of improving the adhesion with the polyester film base material, using a dicarboxylic acid component having the same or similar structure and properties as the dicarboxylic acid component in the polyester film as the base material as the dicarboxylic acid component of the polyester-based resin desirable. Therefore, for example, when aromatic dicarboxylic acid is employed as the dicarboxylic acid component of the polyester film, it is preferable to use aromatic dicarboxylic acid as the dicarboxylic acid component of the polyester resin. As such an aromatic dicarboxylic acid component, terephthalic acid and isophthalic acid are most preferable. Other aromatic dicarboxylic acids may be added and copolymerized in the range of 10 mol% or less with respect to all the dicarboxylic acid components.

Moreover, as a glycol component of a polyester resin, it is preferable to use ethylene glycol and branched glycol as a structural component. It is considered that by having a branched structure, it is possible to contribute to stress relaxation in the easily-adhesive layer and suitably exhibit adhesiveness. The branched glycol component is, for example, 2,2-dimethyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, 2-methyl-2-butyl-1, 3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-2-isopropyl-1,3-propanediol, 2-methyl-2-n-hexyl-1,3- Propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, 2-ethyl-2-n-hexyl-1,3-propanediol , 2,2-di-n-butyl-1,3-propanediol, 2-n-butyl-2-propyl-1,3-propanediol, and 2,2-di-n-hexyl-1,3- And propanediol.

The molar ratio of the branched glycol component is preferably 10 mol%, and particularly preferably 20 mol%, with respect to the total glycol component. On the other hand, the upper limit is preferably 80 mol%, more preferably 70 mol%, particularly preferably 60 mol%. Further, if necessary, diethylene glycol, propylene glycol, butanediol, hexanediol, 1,4-cyclohexanedimethanol, or the like may be used in combination.

The polyester resin used in the present invention is preferably a water-soluble or water-dispersible resin from the viewpoint of compatibility with polyvinyl alcohol-based resins. For water solubilization or water oxidation of the polyester resin, it is preferable to copolymerize a compound containing a hydrophilic group such as sulfonic acid base or carboxylic acid base. Among them, a dicarboxylic acid component having a sulfonic acid base is suitable from the viewpoint of maintaining the acid value of the polyester resin (A) low and controlling the reactivity with the crosslinking agent to impart hydrophilicity. As the dicarboxylic acid component having a sulfonic acid base, for example, sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfonaphthaleneisophthalic acid-2,7-dicarboxylic acid and 5-(4-sulfophenoxy)iso Phthalic acid or its alkali metal salt is mentioned, and 5-sulfoisophthalic acid is particularly preferable. The dicarboxylic acid component having a sulfonic acid base is preferably 1 to 15 mol% of the dicarboxylic acid component of the polyester resin (A), more preferably 1.5 to 12 mol%, and even more preferably 2 to 10 mol%. When the dicarboxylic acid component having a sulfonic acid base is greater than or equal to the above lower limit, it is suitable for water solubilization or water oxidation of the polyester resin. Moreover, when the dicarboxylic acid component which has a sulfonic acid base is below the said upper limit, it is suitable for adhesiveness with a polyester film base material.

It is preferable that the polyester resin has less carboxylic acid groups due to reaction with an active methylene block isocyanate crosslinking agent. Since the reactivity with the crosslinking agent is reduced by reducing the carboxyl group that is reactive with the crosslinking agent, as a result, the domain structure formed by the crosslinked polyvinyl alcohol-based resin is not completely mixed with the polyvinyl alcohol-based resin. I think it is possible to maintain. From such a viewpoint, the acid value of the polyester resin is 20 KOHmg/g or less, preferably 15 KOHmg/g or less, more preferably 10 KOHmg/g or less, even more preferably 8 KOHmg/g or less, even more It is preferably 5 KOHmg/g or less. The acid value of the polyester resin can be theoretically obtained from the results of the component analysis by titration method or NMR described later.

In order to control the acid value of the polyester resin to the above range, reduce the amount of introduction of the carboxylic acid base for water solubilization or water oxidation, employ a hydrophilic group other than the carboxylic acid base, or adjust the carboxylic acid terminal concentration of the polyester resin. It is desirable to lower. As a method of lowering the carboxylic acid terminal concentration of the polyester resin, a polyester resin having a terminal modification of the carboxylic acid terminal group is employed, or a polyester resin having a large number average molecular weight of the polyester resin is employed. It is desirable to do. For this reason, the number average molecular weight of the polyester resin is preferably 5000 or more, more preferably 6000 or more, and even more preferably 10000 or more. Moreover, it is preferable to lower the content of the acid component which has three or more carboxyl groups as a constituent component of a polyester resin.

Although the glass transition temperature of a polyester resin is not specifically limited, It is preferable that it is 20-90 degreeC, and it is more preferable that it is 30-80 degreeC. If the glass transition temperature is above the lower limit, it is suitable for blocking resistance, and if the glass transition temperature is below the upper limit, it is suitable for adhesion to the polyester film substrate.

When the total amount of the solid content of the polyester resin, polyvinyl alcohol-based resin, and active methylene block isocyanate crosslinking agent in the coating liquid is 100 mass%, the lower limit of the content of the polyester resin is preferably 30 mass% (in solid content) , More preferably 40 mass%, still more preferably 50 mass%, particularly preferably 60 mass%. When the content of the polyester resin is 30% by mass or more, even if water adheres to the film or the easily adhesive layer, blocking is unlikely to occur and there is no fear that the peel strength is increased. On the other hand, the upper limit of the content of the polyester resin is preferably 99% by mass, more preferably 95% by mass, still more preferably 90% by mass, particularly preferably 85% by mass. When the content of the polyester resin is 99% by mass or less, adhesiveness with a polyvinyl alcohol-based resin such as a polarizer or a hydrophilic adhesive is good, and even if water adheres to the film or the easily adhesive layer, blocking is unlikely to occur and the peel strength is increased. There is no concern.

(Polyvinyl alcohol-based resin)

The polyvinyl alcohol-based resin is not particularly limited, but, for example, polyvinyl alcohol obtained by saponifying polyvinyl acetate; Derivatives thereof; Saponified copolymer of vinyl acetate and a copolymerizable monomer; Modified polyvinyl alcohol obtained by subjecting polyvinyl alcohol to acetalization, urethanization, etherification, grafting, and phosphoric acid esterification; And the like. Examples of the monomers include unsaturated carboxylic acids such as (anhydride) maleic acid, fumaric acid, crotonic acid, itaconic acid and (meth)acrylic acid and esters thereof; Α-olefins such as ethylene and propylene, (meth)allyl sulfonic acid (soda), sulfonic acid soda (monoalkylmaleate), disulfonic acid sodaalkylmaleate, N-methylolacrylamide, acrylamide alkylsulfonic acid alkali salt, N- And vinyl pyrrolidone and N-vinyl pyrrolidone derivatives. As for these polyvinyl alcohol-type resins, only 1 type may be used and 2 or more types may be used together.

As the polyvinyl alcohol-based resin used in the present invention, vinyl alcohol-vinyl acetate copolymer, vinyl alcohol-vinyl butyral copolymer, ethylene-vinyl alcohol copolymer is exemplified, and among these, vinyl alcohol-vinyl acetate copolymer, ethylene- Vinyl alcohol copolymers are preferred. The degree of polymerization of the polyvinyl alcohol-based resin is not particularly limited, but the degree of polymerization is preferably 3000 or less in view of the viscosity of the coating liquid.

The copolymerization ratio of vinyl alcohol is expressed by saponification degree. The saponification degree of the polyvinyl alcohol-based resin of the present invention is preferably 60 mol% or more and 85 mol% or less, more preferably 65 mol% or more and 83 mol% or less, even more preferably 68 mol% or more and 80 mol% or less, 70 mol% or more and less than 80 mol% are more preferable, 71 mol% or more and 78 mol% or less are even more preferable, and 73 mol% or more and 75 mol% or less are particularly preferable. When the saponification degree of the polyvinyl alcohol-based resin is 60 mol% or more, it is preferable because a crosslinked structure can be more suitably formed with an active methylene block isocyanate crosslinking agent. Moreover, when the saponification degree of a polyvinyl alcohol-type resin is 85 mol% or less, compatibility with a polyester-type resin can be demonstrated more suitably, and it is preferable. The saponification degree of the vinyl alcohol-based resin can be obtained by analyzing the amount of alkali consumed for the hydrolysis of copolymerized units such as vinyl acetate, or composition analysis by NMR.

When the total amount of the solid content of the polyester resin, the polyvinyl alcohol-based resin and the active methylene block isocyanate crosslinking agent in the coating liquid is 100 mass%, the lower limit of the content ratio of the polyvinyl alcohol-based resin is preferably 1 mass% (in solid content ), more preferably 5% by mass, still more preferably 10% by mass, particularly preferably 15% by mass, and most preferably 20% by mass. If the content ratio of the polyvinyl alcohol-based resin is 1 mass% or more, the adhesion to a polyvinyl alcohol-based resin such as a polarizer or a hydrophilic adhesive is good, and even if water is adhered to the film, blocking is unlikely to occur and there is no fear of increasing peel strength. desirable. The upper limit of the content ratio of the polyvinyl alcohol-based resin is preferably 60 mass%, more preferably 55 mass%, further preferably 50 mass%, particularly preferably 45 mass%, most preferably 40 It is mass%. When the content ratio of the polyvinyl alcohol-based resin is 60% by mass or less, even if water adheres to the film, blocking is unlikely to occur, and peeling strength is not likely to increase, which is preferable.

(Active methylene block isocyanate crosslinking agent)

In the present invention, the active methylene block isocyanate crosslinking agent used for the formation of the coating layer is one that is made of a strong coating layer and is preferably used to provide stable adhesion and light peeling property upon water adhesion.

As an isocyanate compound which is a precursor of an active methylene block isocyanate crosslinking agent, an aliphatic isocyanate compound, an alicyclic isocyanate compound, an aromatic isocyanate compound, etc. are mentioned, for example.

As the isocyanate compound, a low-molecular or high-molecular diisocyanate or a triisocyanate or higher polyisocyanate can be used. As specific isocyanate compounds, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2' -Diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, 1,4-naphthylene diisocyanate, phenylene diisocyanate, tetramethylxylylene diisocyanate, 4,4'-diphenyl ether diisocyanate, 2 -Nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4, Aromatic diisocyanates such as 4'-diphenylpropane diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, aromatic aliphatic diisocyanates such as xylylene diisocyanate, isophorone diisocyanate And alicyclic diisocyanates such as 4,4-dicyclohexylmethane diisocyanate, 1,3-bis(isocyanate methyl)cyclohexane, hexamethylene diisocyanate, and 2,2,4-trimethylhexamethylene diisocyanate. Aliphatic diisocyanates, and trimers of these isocyanate compounds are mentioned. In addition, excess amounts of these isocyanate compounds and low molecular weight active hydrogen compounds such as ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, monoethanolamine, diethanolamine, and triethanolamine, or polyester polyols, And a terminal isocyanate group-containing compound of a polymer obtained by reacting a polymer active hydrogen compound such as polyether polyols and polyamides. These may be used alone or in combination of two or more.

The active methylene block isocyanate crosslinking agent in the film of the present invention can be synthesized by reacting an isocyanate group of an isocyanate compound with an active methylene compound.

Examples of the active methylene compound include meldrum acid and dialkyl malonate (eg, dimethyl malonate, diethyl malonate, din-butyl malonate, di-t-butyl malonate, di malonate) 2-ethylhexyl, methyl n-butyl malonate, ethyl n-butyl malonate, methyl s-butyl malonate, ethyl s-butyl malonate, methyl t-butyl malonate, ethyl t-butyl malonate, methylmalonic acid Diethyl, dibenzyl malonate, diphenyl malonate, benzylmethyl malonate, ethylphenyl malonate, t-butylphenyl malonate, isopropylidene malonate, etc.), acetoacetate alkyl (e.g. methyl acetoacetate, Acetoacetate ethyl, acetoacetate n-propyl, acetoacetate isopropyl, acetoacetate n-butyl, acetoacetate t-butyl, acetoacetate benzyl, acetoacetate phenyl, etc.), 2-acetoacetoxyethyl methacrylate, acetylacetone, Cyano ethyl acetate, and the like. Dimethyl malonate and diethyl malonate are preferable from the viewpoint of excellent low-temperature curing properties.

In the active methylene block isocyanate crosslinking agent used in the easily-adhesive layer of the easily-adhesive polyester film of the present invention, the active methylene compounds shown above may be used alone or in combination of two or more kinds. As an active methylene compound used in combination, dimethyl malonate and diethyl malonate are preferable from the viewpoint of excellent low-temperature curing properties.

In addition, the active methylene block isocyanate crosslinking agent, if necessary, existing block agents, for example, oxime-based, pyrazole-based, alcohol-based, alkyl phenol-based, phenol-based, mercaptan-based, acid-amide-based, acid-imide-based, already A polyazole-based, urea-based, amine-based, imine-based, and bisulfite-blocking agent may also be used in combination during the blocking reaction. The existing block agents used in combination may be used alone or in combination of two or more.

The compounding ratio of the active methylene block isocyanate crosslinking agent to the block isocyanate using the above-described conventional blocking agent is not limited, but the lower limit is preferably 0.5 or more in solid content. If the amount is less than the above lower limit, the effect of the active methylene block isocyanate crosslinking agent will be dimmed, so adhesion to a polyvinyl alcohol-based resin such as a polarizer or a hydrophilic adhesive deteriorates, or when water adheres to the film, blocking occurs and peel strength is generated. It is not desirable because it becomes large. Of course, it goes without saying that the active methylene block isocyanate crosslinking agent may be used alone as an active methylene blocking agent that does not use other conventional blocking agents.

The active methylene block isocyanate crosslinking agent used in the film of the present invention preferably contains a hydrophilic moiety in order to improve the blendability in the water-based coating, and as a method of adding a hydrophilic moiety to the blocked isocyanate compound, for example And a method of reacting the isocyanate group of the precursor isocyanate compound with a hydrophilic compound having active hydrogen.

Examples of the hydrophilic compound having active hydrogen used in the active methylene block isocyanate crosslinking agent used in the film of the present invention include polyethylene glycol-based compounds, carboxylic acid-containing compounds, sulfonic acid-containing compounds, and amine-containing compounds. These hydrophilic compounds may be used alone or in combination of two or more.

Examples of the polyethylene glycol-based compound include monoalkoxy polyethylene glycol, polyethylene glycol, polyoxypropylene polyoxyethylene copolymer diol, polyoxypropylene polyoxyethylene block polymer diol, and the like. Monoalkoxy polyethylene glycols such as ethoxy polyethylene glycol and monoethoxy polyethylene glycol are preferred.

Examples of the carboxylic acid group-containing compound include monohydroxy carboxylic acid or dihydroxy carboxylic acid or derivatives thereof. Among the carboxylic acid group-containing compounds, monohydroxy carboxylic acid or dihydroxy carboxylic acid is preferred, and more preferably monohydroxy carboxylic acid.

Specific examples of the carboxylic acid-containing compound include, for example, hydroxypivalic acid, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, or polycaprolactone diol or polyether polyol using them as an initiator. And derivatives thereof, and salts thereof.

As the sulfonic acid group-containing compound, aminoethylsulfonic acid, ethylenediamino-propyl-β-ethylsulfonic acid, 1,3-propylenediamine-β-ethylsulfonic acid, N,N-bis(2-hydroxyethyl)-2-amino Ethane sulfonic acid, and salts thereof.

Examples of the amine-containing compound include hydroxyl group-containing amino compounds. Specifically, dimethylethanolamine, diethylethanolamine, and the like can be mentioned.

In addition, the active methylene block isocyanate crosslinking agent used in the present invention is used in a design that improves the performance of the coating layer by reacting during drying or film forming. It can be assumed that an unreacted product of the active methylene block isocyanate crosslinking agent, a compound after the reaction, or a mixture thereof is present in the completed coating layer.

Moreover, the active methylene block isocyanate crosslinking agent in the present invention may be used alone or in a plurality of types.

When a polyester resin, a polyvinyl alcohol-based resin, and an active methylene block isocyanate crosslinking agent are combined, even if they do not contain an organic tin catalyst, they have excellent adhesion to a polarizer or a functional layer, and even if condensation water adheres, blocking does not occur. An adhesive layer can be produced. Although this reason is not necessarily clear, since the transesterification reaction proceeds when an active methylene block isocyanate crosslinking agent is used, the crosslinked mesh structure is densely formed due to a difference in reactivity with the urethanization reaction occurring in the conventional block isocyanate. It is guessed. In this regard, for block isocyanates using other conventional blocking agents alone, it takes too long to crosslink and cure the composition constituting the easily bonding layer in the absence of an organotin catalyst, or water in which the formed easily bonding layer is liquid is present. It is not preferable because a satisfactory thing cannot be obtained from the viewpoint of blocking in the case where it is performed.

When the total amount of the solid content of the polyester resin, the polyvinyl alcohol-based resin and the active methylene block isocyanate crosslinking agent in the coating liquid is 100 mass%, the lower limit of the content of the active methylene block isocyanate crosslinking agent is preferably 0.1 mass% (in solid content ), more preferably 1% by mass, still more preferably 2% by mass, particularly preferably 3% by mass, and most preferably 4% by mass. When the content ratio of the active methylene block isocyanate crosslinking agent is 0.1 mass% or more, even if water adheres to the film or the easily adhesive layer, blocking is unlikely to occur and there is no fear that the peel strength is increased. The upper limit of the content rate of the active methylene block isocyanate crosslinking agent is preferably 60% by mass, more preferably 40% by mass, even more preferably 20% by mass, particularly preferably 15% by mass, most preferably 9.4 It is mass%. When the content of the active methylene block isocyanate crosslinking agent is 60% by mass or less, it is preferable because the adhesiveness with a functional layer such as an adhesive layer is good.

The blending ratio of the polyester resin to the polyvinyl alcohol-based resin is preferably 1 to 30 in mass ratio, more preferably 2 to 6. If the blending ratio is 1 or more, it is suitable for adhesion to the polyester film substrate, and if it is 30 or less, it is suitable for adhesion to a polyvinyl alcohol-based resin layer such as a polarizer or an adhesive.

The sum of the polyester resin and the polyvinyl alcohol-based resin with respect to the active methylene block isocyanate crosslinking agent is preferably 3 to 20 in mass ratio, more preferably 8 to 15. When the mixing ratio is 3 or more, it is suitable for the expression of the adhesive effect by the binder resin component, and when it is 20 or less, it is suitable for the adhesive effect by phase separation.

By adopting the above composition, the easily-adhesive layer in the present invention exhibits high adhesiveness equivalent to triacetyl cellulose to polarizers and water-based adhesives, particularly polyvinyl alcohol-based polarizers and water-based adhesives. Specifically, the remaining area after peeling once with respect to the water-based adhesive by the adhesiveness test mentioned later is preferably 90% or more, more preferably 95% or more, and still more preferably 100%.

(Organic tin catalyst)

Organic tin, especially tributyl tin, is listed in the ``List of Chemicals Suspected to Have Endocrine Disruption Actions'' published by the Ministry of Environment in 2000, and has been designated as a substance that prioritizes the risk. Although, of course, the use thereof is avoided, in the future, even if it is an organic tin that is not listed in the list, it is necessary to avoid using as much as possible and reduce the risk to the human body or the environment as much as possible. For this reason, it is preferable that the organic tin is not intentionally used as a crosslinking/curing catalyst for the easily adhesive layer. However, it is not intended to deny the content of 100 ppm or less present in the easily adhesive layer without intentional use. That is, in the present invention, the term "substantially does not contain organic tin as a curing catalyst for the composition in the easily adhesive layer" means that the organic tin is 100 ppm or less with respect to the mass of the entire solid content of the easily adhesive layer. In the present invention, by containing the above-mentioned active methylene block isocyanate crosslinking agent in the coating solution for forming an easily adhesive layer, even the non-catalyst is quickly crosslinked and cured upon heating, and thus the easily adhesive polyester film produced is a liquid. Although there is no fear of causing the problem of blocking even in the presence of water, if necessary, an environmentally-friendly catalyst other than tin may be used. For example, such catalysts include zinc-based compounds such as zinc acetylacetonate, zinc propionate and zinc octanoate, titanium-based compounds such as tetraisopropyl titanate, and tetra-n-butyl titanate, and zirconium tetraisopropoxide And zirconium-based compounds such as seeds and zirconium tetra-n-butoxide, bismuth-based compounds such as bis(acetylacetone)bismuth and bismuth 2-ethylhexanoate, and amines. The content of the organotin catalyst in the adhesive layer was measured as follows. The adhesive layer on the side of the film is wiped off using a solvent that can be wiped off, for example, MEK, etc., and the wiping is completed by performing fluorescence X-ray measurement on the surface of the layer on the side of the side, before the peak intensity of Si is 100 It was supposed to be less than one-third. Then, the weight of the A4 film before and after wiping was measured, and the difference was taken as the application amount after drying of the easy-adhesive layer on the surface. By dissolving the easily-adhesive layer of the film, the content of the organic tin catalyst in the easily-adhesive layer was finally calculated by a method according to Tsuyoshi Kawakami et al, YAKUGAKU ZASSHI 130(2)223-235(2010).

(additive)

Among the easily-adhesive layers of the present invention, known additives, such as surfactants, antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricating agents, in the range that does not impair the effects of the present invention, You may add pigments, dyes, organic or inorganic particles, antistatic agents, nucleating agents, and the like. However, high environmental toxicity is excluded.

In the present invention, in order to further improve the blocking resistance of the easily adhesive layer, it is also a preferred embodiment to add particles to the easily adhesive layer. In the present invention, the particles contained in the easily adhesive layer are, for example, titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, or a mixture thereof, and further, other general Inorganic particles, such as calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, calcium fluoride, and other inorganic particles such as styrene, acrylic, melamine, benzoguanamine, and silicon And organic polymer particles.

The average particle diameter of the particles in the adhesive layer (average particle diameter based on number by SEM. The same applies hereinafter) is preferably 0.04 to 2.0 μm, and more preferably 0.1 to 1.0 μm. When the average particle diameter of the inert particles is 0.04 µm or more, the formation of unevenness on the film surface is facilitated, and thus the handling properties such as the slipperiness and the wrapability of the film are improved, and the processability at the time of bonding is preferable. On the other hand, if the average particle diameter of the inert particles is 2.0 µm or less, dropping of the particles is unlikely to occur, which is preferable. The particle concentration in the adhesive layer is preferably 1 to 20% by mass in the solid component.

In the present invention, the thickness of the easily-adhesive layer can be appropriately set in the range of 0.001 to 2.00 µm, but the range of 0.01 to 1.00 µm is preferable, and more preferably 0.02 to 0.80 µm, further in order to achieve both workability and adhesiveness. It is preferably 0.05 to 0.50 µm. When the thickness of this adhesive layer is 0.001 µm or more, the adhesiveness is good and is preferable. If the thickness of this adhesive layer is 2.00 µm or less, it is difficult to generate blocking, which is preferable.

Conventionally, among polyester films having an easy-adhesive layer containing a polyester resin, a polyvinyl alcohol-based resin, and a crosslinking agent, many satisfy the blocking resistance when left in an environment containing ordinary water vapor. However, in winter, when transported between outdoors and indoors, liquid water may adhere to the surface of the film or the surface of the easily-adhesive layer when it is transported, including polyester-based resins, polyvinyl alcohol-based resins, and crosslinking agents. The polyester film having a self-adhesive layer to be said had a problem of causing blocking. However, the easily-adhesive polyester film of the present invention is not only blocking resistance when left in an environment containing ordinary water vapor, but also an environment for an easily-adhesive polyester film carried between indoors and outdoors in winter. Even when liquid water adheres to the film surface or the surface of the easily-adhesive layer due to condensation with a change in temperature, there is no fear of causing blocking. It can be confirmed from the point that the peeling force after water adhesion by the measuring method described below is 2 N/cm or less. It is more preferably 1.5 N/cm or less, still more preferably 1 N/cm or less, particularly preferably 0.5 N/cm or less, and most preferably 0.3 N/cm or less. It is preferable that the peeling force after water adhesion is small, but it may be 0.01 N/cm or more, or 0.02 N/cm or more. Peeling force after such small water adhesion is a phenomenon that appears specifically when an active methylene block isocyanate crosslinking agent is used, and the same effect cannot be expected from a block isocyanate crosslinking agent using only another blocking agent. In addition, when the active methylene block isocyanate crosslinking agent is used, the small peeling force after water adhesion is particularly effectively obtained when an organic tin curing catalyst is not used.

In the present invention, the easily-adhesive layer formed by curing a composition containing a polyester-based resin, a polyvinyl alcohol-based resin and an active methylene block isocyanate crosslinking agent may be laminated on at least one side of the polyester film, of course, on both sides. You may laminate|stack this adhesive layer. Moreover, the above-mentioned easily-adhesive layer is laminated only on one side of the polyester film, and a resin coating layer of different composition may be laminated on the other film surface. The easily-adhesive layer formed by curing the composition containing the polyester-based resin, the polyvinyl alcohol-based resin and the active methylene block isocyanate crosslinking agent in the present invention is a polarizer made of a polyvinyl alcohol-based film and dichroic materials such as iodine, It is excellent in adhesiveness and adhesiveness with hydrophilic adhesives such as polyvinyl alcohol-based resins, but also has certain adhesiveness and adhesiveness to other functional layers such as hard coat layers.

In addition, in the present invention, the expression that the easily-adhesive layer is made by curing a composition containing a polyester resin, a polyvinyl alcohol-based resin and an active methylene block isocyanate crosslinking agent is used in the easily adhesive layer after crosslinking and curing. , It is thought that the hydroxyl group of polyvinyl alcohol is reacted with an isocyanate group to crosslink and harden, but it is extremely difficult or impossible to accurately express the composition or chemical structure after crosslinking and curing. Therefore, most of the polyester resin, the polyvinyl alcohol-based resin, and the active methylene block isocyanate cross-linking agent in the cross-linked and cured self-adhesive layer do not exist in the same chemical structure.

(Preparation of easily adhesive polyester film for polarizer protection)

Although the polyethylene terephthalate (hereinafter abbreviated as PET) film is demonstrated as an example of the manufacturing method of the easily adhesive polyester film for polarizer protection of this invention, it is of course not limited to this.

After the PET resin is sufficiently vacuum dried, it is supplied to an extruder, melt-extruded molten PET resin at a temperature of about 280°C from a T die into a sheet with a rotary cooling roll, cooled and solidified by electrostatic application, and unstretched PET. Get a sheet The unstretched PET sheet may be of a single layer structure or a multilayer structure by a coextrusion method.

The obtained unstretched PET sheet is subjected to crystal orientation by uniaxial stretching or biaxial stretching. For example, in the case of biaxial stretching, the film is stretched 2.5 to 5.0 times in the longitudinal direction with a roll heated to 80 to 120°C to obtain a uniaxially stretched PET film, and then the end of the film is gripped with a clip, It leads to a hot-air zone heated to 80-180 degreeC, and stretches 2.5-5.0 times in the width direction. Moreover, in the case of uniaxial stretching, it is stretched 2.5 to 5.0 times in a tenter. After extending|stretching, it continues to a heat processing zone, performs heat processing, and completes crystal orientation. In addition, in this invention, when it describes that it is a longitudinal direction or a longitudinal direction of a film, it points to the machine flow direction of a manufacturing process. On the other hand, when it is described as a transverse direction or a width direction of the film, it indicates a direction perpendicular to the machine flow direction.

The lower limit of the temperature of the heat treatment zone is preferably 170°C, more preferably 180°C. If the temperature of the heat treatment zone is 170°C or higher, curing becomes sufficient, and the blocking property in the presence of liquid water is good, which is preferable, and there is no need to lengthen the drying time. On the other hand, the upper limit of the temperature of the heat treatment zone is preferably 230°C, and more preferably 200°C. When the temperature of the heat treatment zone is 230°C or lower, it is preferable that there is no fear that the physical properties of the film are lowered. In the manufacturing process using a polarizer protective film, in order to suppress a decrease in refractive index, it is more preferable to heat-treat at 200°C or lower.

This adhesive layer can be provided after manufacture of a film or in a manufacturing process. In particular, from the viewpoint of productivity, it is preferable to apply an application liquid to at least one side of the PET film after any step of the film production process, that is, unstretched or uniaxially stretched to form an easily adhesive layer.

As a method for applying the coating liquid to the PET film, any known method can be used. For example, reverse roll coating method, gravure coating method, kiss coating method, die coater method, roll brush method, spray coating method, air knife coating method, wire bar coating method, pipe doctor method, impregnation coating method, curtain coating method And the like. These methods can be applied singly or in combination.

(Polarizing plate)

The easily adhesive polyester film of the present invention can be suitably used as a polarizer protective film. Generally, a polarizing plate is formed by arranging a polarizer protective film on both sides of a polarizer, but it is preferable that the polarizer protective film on at least one side of the polarizer is the self-adhesive polyester film for protecting the polarizer. As the other polarizer protective film, the easily-adhesive polyester film of the present invention may be used, and it is also preferable to use a film having no birefringence such as represented by a triacetyl cellulose film, an acrylic film, or a norbornene-based film.

As a polarizer, what contains a dichroic material, such as iodine, in a polyvinyl alcohol-type film is mentioned, for example. The polarizer protective film is pasted directly to the polarizer or via an adhesive layer, but from the viewpoint of improving adhesiveness, it is preferable to adhere via an adhesive. At this time, it is preferable to arrange the easily-adhesive layer of the present invention on the polarizer side or the adhesive layer side. As a preferred polarizer for adhering the polyester film of the present invention, for example, iodine or a dichroic material is dyed and adsorbed on a polyvinyl alcohol-based film, uniaxially stretched in an aqueous solution of boric acid, and maintained in a stretched state. And a polarizer obtained by washing and drying. The draw ratio of uniaxial stretching is usually about 4 to 8 times. As polyvinyl alcohol-based film, polyvinyl alcohol is suitable, and "Kurare Vinylon" [manufactured by Kurare Co., Ltd.], "Dosero Vinylon" [manufactured by Tosero Corporation], "Nichigo Vinylon" [Nippon Kose Commercial products, such as manufactured by Kagaku Co., Ltd., can be used. Examples of the dichroic material include iodine, disazo compounds, and polymethine dyes.

From the viewpoint of thinning the adhesive layer, the adhesive applied to the polarizer is preferably water-based, that is, an adhesive component dissolved in water or dispersed in water. For example, as a main component, a polyvinyl alcohol-based resin, a urethane resin, or the like may be used, and in order to improve adhesiveness, a composition in which an isocyanate-based compound, an epoxy compound, or the like is blended may be used as necessary. The thickness of the adhesive layer is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less.

When a polyvinyl alcohol-based resin is used as the main component of the adhesive, in addition to partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, methylol-modified polyvinyl alcohol, amino group-modified poly A modified polyvinyl alcohol-based resin such as vinyl alcohol may be used. The concentration of the polyvinyl alcohol-based resin in the adhesive is preferably 1 to 10% by mass, more preferably 2 to 7% by mass.

Example

Next, the present invention will be described in detail using Examples, Comparative Examples, and Reference Examples, but the present invention is of course not limited to the following Examples. In addition, the evaluation method used in the present invention is as follows.

(1) Glass transition temperature

According to JIS K7121:2012, using a differential scanning calorimeter (Seiko Instruments Inc., DSC6200), 10 mg of the resin sample was heated to 20°C/min over a temperature range of 25 to 300°C, and extrapolation obtained from the DSC curve () The glass transition initiation temperature was defined as the glass transition temperature.

(2) Number average molecular weight

Dissolve 0.03 g of polyester resin in 10 ml of tetrahydrofuran, and use a low-angle light scattering photometer LS-8000 (manufactured by Tosoh Corporation, tetrahydrofuran solvent, reference: polystyrene) in a GPC-LALLS apparatus, and the column temperature is 30. The number average molecular weight was measured using a column, a flow rate of 1 ml/min, and a column (shodex KF-802 manufactured by Showa Denko Co., 804, 806).

(3) Polyester resin composition

The polyester resin was dissolved in heavy chloroform, and 1H-NMR analysis was performed using a nuclear magnetic resonance analyzer (NMR) Gemini-200 manufactured by Varian Co., Ltd. to determine the mole percent ratio of each composition from the integral ratio.

(4) Acid value of polyester

1 g (solid content) of a polyester sample is dissolved in 30 ml of chloroform or dimethylformamide, titrated with 0.1 N potassium hydroxide ethanol solution using phenolphthalein as an indicator, and the amount of KOH required to neutralize the carboxyl group per 1 g of sample (mg ).

(5) Saponification degree of polyvinyl alcohol

Sodium hydroxide was used according to JIS K6726:1994 to quantify the residual acetic acid group (mol%) of the polyvinyl alcohol resin, and the value was taken as the saponification degree (mol%). The same sample was measured three times, and the average value was taken as the saponification degree (mol%).

(Formation of PVA layer)

The thickness of the polyvinyl alcohol resin layer after drying a polyvinyl alcohol aqueous solution (PVA117 manufactured by Kurare) adjusted to a solid content concentration of 3 mass% on the surface of the easily adhesive layer of the easily adhesive polyester film or the laminated polyester film, which will be described later, It was applied to a wire bar so as to be 200 nm, and dried at 80°C for 5 minutes. As an aqueous polyvinyl alcohol solution, one to which a red dye was added was used to facilitate determination.

(PVA adhesion)

On the easily-adhesive layer of the easily-adhesive polyester film obtained in the examples or on the resin coating layer of the laminated polyester film, the PVA layer described in the above-mentioned item of formation of the PVA layer was formed. The adhesive film of the PVA layer and the base film is calculated|required based on the base material of 8.5.1 of JIS K5400:1990 of the polyester film for easy adhesion which formed PVA.

Specifically, 100 checkered eye-shaped cuts that penetrate the PVA layer and reach the base film are cut out on the surface of the hard coat layer using a cutter guide having a gap of 2 mm. Subsequently, a cellophane adhesive tape (manufactured by Nichiban, No. 405; width of 24 mm) was applied to the checkered surface of the checkered eye shape, and rubbed with an eraser to completely adhere. Thereafter, the cellophane adhesive tape was vertically removed from the PVA layer side of the polarizer protective film, and the number of checkered eyes peeled from the PVA layer side of the polarizer protective film was visually counted, and the adhesiveness between the hard coat layer and the base film from the following equation To get Moreover, partly peeling among the board eyes counts as the peeled board eyes. PVA adhesiveness is set to 70 (%) or more as a pass.

PVA adhesion (%) = {1-(number of stripped checkered eyes/100)}×100

(Formation of hard coat layer)

On the easily-adhesive layer of the easily-adhesive polyester film prepared in Examples described later or on the resin coating layer of the laminated polyester film, a coating solution for forming a hard coat layer having the following composition was applied using a #10 wire bar, and at 70°C. After drying for 1 minute, the solvent was removed. Subsequently, the film coated with the hard coat layer was irradiated with ultraviolet light of 300 mJ/cm 2 using a high pressure mercury lamp to obtain a polarizer protective film having a hard coat layer having a thickness of 5 μm.

·Coating solution for hard coat layer formation

Methyl ethyl ketone #65.00 mass%

Dipentaerythritol hexaacrylate　　　　 27.20% by mass

(A-DPH manufactured by Shin-Nakamura Chemical Co., Ltd.)

Polyethylene diacrylate　　　　　　　 6.80% by mass

(A-400 manufactured by Shin-Nakamura Chemical Co., Ltd.)

Photopolymerization initiator 　　　　　　　 1.00 mass%

(Irgacure 184 manufactured by Chiba Specialty Chemicals)

(Hard coat adhesion)

On the easily-adhesive layer of the polyester film obtained in the examples, the hard coat layer described in the section on formation of the hard coat layer described above was formed. The adhesive film of the hard coat layer and the base film is calculated|required based on the base material of 8.5.1 of JIS K5400:1990 of the polyester film for easy adhesion which formed the hard coat.

Specifically, 100 checkered eye-shaped cuts that penetrate the hard coat layer and reach the base film are cut out on the surface of the hard coat layer using a cutter guide having a gap of 2 mm. Subsequently, a cellophane adhesive tape (manufactured by Nichiban, No. 405; width of 24 mm) was applied to the checkered surface of the checkered eye shape, and rubbed with an eraser to completely adhere. Thereafter, the cellophane adhesive tape was vertically removed from the hard coat layer side of the hard coat laminated polarizer protective film, and the number of checkered eyes peeled from the hard coat layer side of the hard coat laminated polarizer protective film was counted visually and hard from the following formula. The adhesion between the coat layer and the base film is determined. Moreover, partly peeling among the board eyes counts as the peeled board eyes. The hard coat adhesion is 50 (%) or more.

Hard coat adhesion (%) = {1-(number of peeled checkered eyes/100)}×100

(Peeling force after water attachment)

The easily-adhesive polyester film prepared in Examples described later is cut to 10 cm in the width direction and 1.5 cm in the length direction. An arbitrary film of 1.5 cm in the length direction and 1.5 cm in the width direction is superimposed on the end of the surface of the easily-adhesive layer of the cut film. It may be the same as a release paper.) 0.03 g of water droplets are poured on the surface of the adhesive layer on the opposite end. Thereafter, the surfaces of the easily-adhesive layers of the film cut to 10 cm in the width direction and 1.5 cm in the length direction were superimposed, and the roll was evenly wound to prevent air from entering from the side where the water droplets were dropped to the side where the film overlapped. Then, the sample is put into the oven for 6 hours. The taken-out sample is a 1.5 square (cm) cm film sandwiched between them, and the part to which water is not attached is used as a handle of the chuck, and a tensile tester [Shimadzu Sei Co., Ltd. at room temperature according to JIS K 6854-3:1999] A peel test was performed at a tensile speed of 0.3 m/min using an autograph manufactured by Sakusho, part number AGS-X, and the peel force (N/cm) was measured five times to obtain an average.

(Block resistance)

Each film sample was cut into two pieces of 3.5 square cm (length x width of 3.5 cm), and two sheets of each sample were stacked so that the surface of the adhesive layer was in contact with each other, and the film was pressed at a pressure of 0.5 MPa in a direction perpendicular to the surface. It is left in an environment of 80% at 30°C for 1 day. After that, samples were taken out and two samples were peeled off to evaluate the state of each film. Examples In all the samples prepared in the comparative examples, the two films were peeled off without applying force, and no adhesion marks or the like were observed.

(Polymerization of polyester resin)

In a stainless steel autoclave equipped with a stirrer, a thermometer, and a partial reflux cooler, 194.2 parts by weight of dimethyl terephthalate, 184.5 parts by weight of dimethyl isophthalate, 14.8 parts by weight of dimethyl-5-sodium sulfoisophthalate, and 233.5 of diethylene glycol The mass part, 136.6 mass parts of ethylene glycol, and 0.2 mass parts of tetra-n-butyl titanate were added, and the transesterification reaction was performed at a temperature of 160°C to 220°C over 4 hours. Subsequently, the temperature was raised to 255°C, the reaction system was gradually reduced in pressure, and then reacted for 1 hour and 30 minutes under a reduced pressure of 30 Pa to obtain a copolymerized polyester resin (A-1). The obtained copolymerized polyester resin (A-1) was pale yellow transparent. When the reduced viscosity of the copolymerized polyester resin (A-1) was measured, it was 0.70 dl/g. The glass transition temperature by DSC was 40°C.

In the same manner, a copolymerized polyester resin (A-2) having a different composition was obtained. Table 1 shows the composition (molar% ratio) and other properties measured by 1H-NMR for these copolymerized polyester resins.

[Table 1]

(Preparation of polyester water dispersion)

In a reactor equipped with a stirrer, a thermometer, and a reflux device, 15 parts by mass of polyester resin (A-1) and 15 parts by mass of ethylene glycol n-butyl ether were added, heated and stirred at 110°C to dissolve the resin. After the resin was completely dissolved, 70 parts by mass of water was slowly added to the polyester solution while stirring. After the addition, the solution was cooled to room temperature while stirring to prepare a milky white polyester water dispersion (Aw-1) having a solid content of 15% by mass. Similarly, instead of the polyester resin (A-1), a polyester resin (A-2) was used to prepare a water dispersion, and a polyester water dispersion (Aw-2) was used.

(Preparation of polyvinyl alcohol aqueous solution)

In a container equipped with a stirrer and a thermometer, 90 parts by mass of water was added, and 10 parts by mass of a polyvinyl alcohol resin (Curare) (B-1) having a polymerization degree of 500 was gradually added while stirring. After the addition, the solution was heated to 95°C while stirring to dissolve the resin. After dissolution, the mixture was cooled to room temperature while stirring to prepare a polyvinyl alcohol aqueous solution (Bw-1) having a solid content of 10% by mass. Similarly, an aqueous solution was prepared using polyvinyl alcohol resin (B-2) instead of polyvinyl alcohol resin (B-1) to obtain (Bw-2), respectively. Table 2 shows the saponification degree of the polyvinyl alcohol resin (B-1) (B-2).

[Table 2]

(Polymerization of active methylene block isocyanate crosslinking agent)

The inside of a four-necked flask equipped with a stirrer, a thermometer, a reflux cooling tube, and a nitrogen blow tube was set to a nitrogen atmosphere, 1000 parts by mass of HDI, and 22 parts by mass of trimethylolpropane (molecular weight 134), a trivalent alcohol, and the temperature in the reactor under stirring Was maintained at 90° C. for 1 hour to perform urethanization. Thereafter, the reaction solution temperature was maintained at 60°C, and an isocyanurate-catalyzed trimethylbenzylammonium-hydrooxide was added, and phosphoric acid was added at a time when the conversion rate reached 48% to stop the reaction. Thereafter, after the reaction solution was filtered, unreacted HDI was removed by a thin film distillation apparatus.

The viscosity of the obtained polyisocyanate at 25°C was 25,000 mPa·s, the isocyanate group content was 19.9 mass%, the number average molecular weight was 1080, and the average number of isocyanate groups was 5.1. Then, the existence of urethane bond, allophanate bond, and isocyanurate bond was confirmed by NMR measurement.

A stirrer, a thermometer, a reflux cooling tube, a nitrogen blow tube, and a four-neck flask with a dropping funnel were placed in a nitrogen atmosphere, 100 parts by mass of the polyisocyanate obtained above, 42.3 parts of methoxy polyethylene glycol having a number average molecular weight of 400, and dipropylene 76.6 parts of glycol dimethyl ether was added and maintained at 80°C for 6 hours. Thereafter, the reaction temperature was cooled to 60°C, and 72 parts by mass of diethyl malonate and 0.88 parts by mass of a 28% methanol solution of sodium methylate were added and maintained for 4 hours, followed by addition of 0.86 parts by mass of 2-ethylhexyl acid phosphate. .

Subsequently, 43.3 parts by mass of diisopropylamine was added, and the reaction solution temperature was maintained at 70°C for 5 hours. The reaction solution was analyzed by gas chromatography, confirming that the reaction rate of diisopropyl amine was 70%, to obtain an active methylene block isocyanate crosslinking agent (C-1) having a solid content concentration of 70% by mass.(effective NCO group mass 5.3 %)

(Polymerization of oxime block isocyanate crosslinking agent)

100 parts by mass of a polyisocyanate compound having an isocyanurate structure (manufactured by Asahi Kasei Chemicals, Duranate TPA) using hexamethylene diisocyanate as a raw material in a flask equipped with a stirrer, a thermometer, and a reflux cooling tube, propylene glycol monomethyl ether 55 parts by mass of acetate and 30 parts by mass of polyethylene glycol monomethyl ether (average molecular weight 750) were added and maintained at 70°C for 4 hours under a nitrogen atmosphere. Thereafter, the temperature of the reaction solution was lowered to 50°C, and 47 parts by mass of methyl ethyl ketooxime was added dropwise. The infrared spectrum of the reaction solution was measured to confirm that the absorption of the isocyanate group was lost, and an oxime block isocyanate crosslinking agent (C-2) having a solid content of 75% by mass was obtained.

(Carbodiimide-based crosslinking agent polymerization)

In a flask equipped with a stirrer, thermometer, and reflux cooling tube, 168 parts by mass of hexamethylene diisocyanate and 220 parts by mass of polyethylene glycol monomethyl ether (M400, average molecular weight 400) were added, stirred at 120° C. for 1 hour, and additionally 4, 26 parts by mass of 4'-dicyclohexylmethane diisocyanate and 3.8 parts by mass of 3-methyl-1-phenyl-2-phosphorene-1-oxide (2% by mass based on total isocyanate) are added as a carbodiimide catalyst. Then, the mixture was stirred for 5 hours at 185°C under a nitrogen stream. The infrared spectrum of the reaction solution was measured, and it was confirmed that absorption of wavelengths 2200 to 2300 cm ^-1 was lost. It cooled to 60 degreeC, and 567 mass parts of ion-exchanged water was added, and the carbodiimide type crosslinking agent (C-3) of 40 mass% of solid content was obtained.

(Epoxy clock crosslinking agent)

As the epoxy crosslinking agent, Denacol EX-521 (100% solid content) manufactured by Nagase Chemtex Co., Ltd. was used (epoxy crosslinking agent (C-4)).

(Example 1)

(1) Preparation of coating liquid

The following ceramics were mixed, and the solid content ratio of the polyester resin (A-1)/polyvinyl alcohol resin (B-1)/active methylene block isocyanate crosslinking agent (C-1) was 92/3/5. A coating liquid to be used was prepared. As the water dispersion of polyester, an aqueous dispersion (Aw-1) in which a polyester resin having an acid value of 2 KOHmg/g was dispersed was used, and the aqueous solution of polyvinyl alcohol was an aqueous solution in which polyvinyl alcohol having a saponification degree of 88 mol% was dissolved ( Bw-1) was used.

Water: 32.62 mass%

Isopropanol 　　　　　　　　　　　　　30.00 mass%

Polyester water dispersion (Aw-1)　　　　　 　33.59 mass%

Polyvinyl alcohol aqueous solution (Bw-1)　　　　　　 1.46% by mass

Block isocyanate type crosslinking agent (C-1): 0.40 mass%

Particle 　　　　　　　　　　　　　　　　　　 0.49 mass%

(A silica sol having an average particle diameter of 450 nm, a solid content concentration of 4 mass%)

Particle 　　　　　　　　 　　　　　　　　1.29 mass%

(A silica sol having an average particle diameter of 40 nm, solid content concentration of 40 mass%)

Surfactant　　　　　 　　　　　　　　　　0.15 mass%

(Silicone-based, solid content concentration 10% by mass)

(2) Preparation of easily adhesive polyester film

As a film raw material polymer, PET resin pellets having an intrinsic viscosity (solvent: phenol/tetrachloroethane=60/40) of 0.62 dl/g and substantially free of particles, were reduced to 6 at 135° C. under reduced pressure of 133 Pa. Time to dry. Then, it was fed to an extruder, melt-extruded in a sheet form at about 280°C, and rapidly cooled and solidified on a rotary cooling metal roll maintained at a surface temperature of 20°C to obtain an unstretched PET sheet.

Subsequently, the coating solution was applied to one side of the PET film by a roll coating method, and then dried at 80°C for 15 seconds. Further, the coating thickness after final (after stretching) drying was adjusted to be 150 nm. Subsequently, in a tenter, the film was stretched 4.0 times in the width direction at 150°C, and the length in the width direction of the film was fixed, followed by heating at a heat setting temperature of 180°C for 0.5 seconds, and further at 180°C for 10 seconds in a 3% width direction The relaxation treatment was performed to obtain an easily adhesive polyester film having a thickness of 100 µm.

Table 3 shows the results of evaluating the aforementioned polyester film for each of the above items.

(Example 2)

The following ceramics were mixed, and the solid content ratio of the polyester resin (A-1)/polyvinyl alcohol resin (B-1)/active methylene block isocyanate crosslinking agent (C-1) was changed to be 83/5/12. An easily-adhesive polyester film was obtained in the same manner as in Example 1 except for the above.

Water 33.75 mass%

Isopropanol 　　　　　　　　　　　　　 30.40 mass%

Polyester water dispersion (Aw-1): 30.34 mass%

Polyvinyl alcohol aqueous solution (Bw-1)　 　　　　　2.67% by mass

Block isocyanate type crosslinking agent (C-1)　　 　　0.95 mass%

Particle 　　　　　　　　　　　　　　　　　　　0.49 mass%

(A silica sol having an average particle diameter of 450 nm, a solid content concentration of 4 mass%)

Particle 　　　　　　　　　　　　　　　　　　　 1.25 mass%

(A silica sol having an average particle diameter of 40 nm, solid content concentration of 40 mass%)

Surfactant 　　　　　　　　　　　　　　　　 0.15 mass%

(Silicone-based, solid content concentration 10% by mass)

(Example 3)

The easily-adhesive polyester film was obtained like Example 2 except having changed the polyester resin (A-2) and the polyester water dispersion into (Aw-2).

(Example 4)

Example 1 except that the solid content ratio of the polyester resin (A-1)/polyvinyl alcohol-based resin (B-1)/active methylene block isocyanate crosslinking agent (C-1) was changed to 55/20/25. Similarly, an easily adhesive polyester film was obtained.

(Example 5)

The easily-adhesive polyester film was obtained like Example 4 except having changed so that it may become polyvinyl alcohol-type resin (B-2) and polyvinyl alcohol aqueous solution (Bw-2).

(Example 6)

Example 1 except that the solid content ratio of the polyester resin (A-1)/polyvinyl alcohol-based resin (B-1)/active methylene block isocyanate crosslinking agent (C-1) was changed to 45/15/40. Similarly, an easily adhesive polyester film was obtained.

(Example 7)

Example 1 except that the solid content ratio of the polyester resin (A-1)/polyvinyl alcohol-based resin (B-1)/active methylene block isocyanate crosslinking agent (C-1) was changed to 56/37/7. Similarly, an easily adhesive polyester film was obtained.

(Example 8)

Example 1 except that the solid content ratio of the polyester resin (A-1)/polyvinyl alcohol-based resin (B-1)/active methylene block isocyanate crosslinking agent (C-1) was changed to 80/15/5. Similarly, an easily adhesive polyester film was obtained.

(Example 9)

Example 1 except that the solid content ratio of the polyester resin (A-1)/polyvinyl alcohol-based resin (B-1)/active methylene block isocyanate crosslinking agent (C-1) was changed to 65/27/8. Similarly, an easily adhesive polyester film was obtained.

(Example 10)

Example 1 except that the solid content ratio of the polyester resin (A-1)/polyvinyl alcohol-based resin (B-1)/active methylene block isocyanate crosslinking agent (C-1) was changed to 71/18/11. Similarly, an easily adhesive polyester film was obtained.

(Example 11)

Example 1 except that the solid content ratio of the polyester resin (A-1)/polyvinyl alcohol-based resin (B-1)/active methylene block isocyanate crosslinking agent (C-1) was changed to 75/16/9. Similarly, an easily adhesive polyester film was obtained.

(Example 12)

Example 1 except that the solid content ratio of the polyester resin (A-1)/polyvinyl alcohol-based resin (B-1)/active methylene block isocyanate crosslinking agent (C-1) was changed to 45/45/10. Similarly, an easily adhesive polyester film was obtained.

(Example 13)

Example 1 except that the solid content ratio of the polyester resin (A-1)/polyvinyl alcohol-based resin (B-1)/active methylene block isocyanate crosslinking agent (C-1) was changed to 40/30/30. Similarly, an easily adhesive polyester film was obtained.

(Example 14)

Example 1 except that the solid content ratio of the polyester resin (A-1)/polyvinyl alcohol-based resin (B-1)/active methylene block isocyanate crosslinking agent (C-1) was changed to 30/5/65. Similarly, an easily adhesive polyester film was obtained.

(Comparative Example 1)

Except for laminating the resin coating layer in which the solid content ratio of the polyester resin (A-1)/polyvinyl alcohol-based resin (B-1)/active methylene block isocyanate crosslinking agent (C-1) was changed to be 95/0/5 In the same manner as in Example 1, a laminated polyester film was obtained.

(Comparative Example 2)

Example 1 except that the solid content ratio of the polyester resin (A-1)/polyvinyl alcohol-based resin (B-1)/active methylene block isocyanate crosslinking agent (C-1) was changed to 25/65/10. Similarly, an easily adhesive polyester film was obtained.

(Comparative Example 3)

The easily adhesive polyester film was obtained like Example 1 except having changed the composition of a coating liquid as follows.

Water 30.81 mass%

Isopropanol 　　　　　　　　　　　　　30.00 mass%

Polyester water dispersion (Aw-1): 26.46 mass%

Polyvinyl alcohol aqueous solution (Bw-1)　 　　　　　9.69% by mass

Oxime block isocyanate crosslinking agent (C-2) 0.65 mass%

Particle 　　　　　　　　　　　　　　　　　　0.49 mass%

(A silica sol having an average particle diameter of 450 nm, a solid content concentration of 4 mass%)

Particle 　　　　　　　　　　　　　　　　　　 1.27 mass%

(A silica sol having an average particle diameter of 40 nm, solid content concentration of 40 mass%)

Surfactant 　　　　　　　　　　　　　　　 0.15 mass%

(Silicone-based, solid content concentration 10% by mass)

Catalyst 0.48 mass%

(Organic tin-based compound, solid content concentration 10% by mass)

(Comparative Example 4)

The solid content ratio of the polyester resin (A-1)/polyvinyl alcohol-based resin (B-1)/active methylene block isocyanate crosslinking agent (C-1) was changed to 45/45/10, and the easily-adhesive polyester film In the same manner as in Example 1, except that the heat setting temperature and the relaxation treatment temperature were changed from 180°C to 160°C in the production of, a self-adhesive polyester film was obtained.

(Comparative Example 5)

The block isocyanate crosslinking agent was changed to a carbodiimide crosslinking agent (C-3), and the polyester resin (A-1)/polyvinyl alcohol-based resin (B-1)/carbodiimide crosslinking agent (C-3). The easily-adhesive polyester film was obtained like Example 1 except having changed the solid content ratio into 53/24/23.

(Comparative Example 6)

The block isocyanate crosslinking agent was changed to an epoxy crosslinking agent (C-4), and the solid content ratio of the polyester resin (A-1)/polyvinyl alcohol resin (B-1)/epoxy watch crosslinking agent (C-4) was 45/ The easily-adhesive polyester film was obtained like Example 1 except having changed so that it might be 42/13.

[Table 3]

Industrial availability

According to the present invention, even if condensation water of the liquid adheres, blocking does not occur, the adhesiveness with a functional layer such as a polarizer or an adhesive layer is excellent, and an organic tin catalyst is not used, and thus the environmental suitability is excellent. It became possible to provide a self-adhesive polyester film that can be suitably used in film applications.

Claims (2)

A polyester film having an easily adhesive layer on at least one side, wherein the easily adhesive layer is made of a composition containing a polyester resin, a polyvinyl alcohol resin and an active methylene block isocyanate crosslinking agent, and cured. A self-adhesive polyester film that does not substantially contain organic tin as a curing catalyst and has a peel force of 2 N/cm or less after water adhesion. According to claim 1,
An easily adhesive polyester film used as a polarizer protective film.