JP6191099B2 - Polarizer - Google Patents

Description

The present invention relates to a polarizing plate using an easy-adhesive polyester film as a polarizer protective film , and in particular, has excellent adhesion and appearance with a functional layer mainly composed of a water-soluble / hydrophilic resin. The present invention relates to a polarizing plate using an easily adhesive polyester film as a polarizer protective film .

  In the liquid crystal display device, polarizing plates are arranged on both sides of a glass substrate that forms the surface of the liquid crystal panel due to the image forming method. The polarizing plate generally has a configuration in which a polarizer protective film is bonded to both surfaces of a polarizer made of a dichroic material such as a polyvinyl alcohol film and iodine via a hydrophilic adhesive such as a polyvinyl alcohol resin. have. As a protective film used for protecting 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 at high temperature or high humidity, the performance of the polarizing plate such as the degree of polarization and hue deteriorates. There is a case. In recent years, there has been a demand for thinning the polarizing plate in order to cope with the thinning of the display. However, from the viewpoint of maintaining moisture barrier properties, there has been a limit to thinning the triacetyl cellulose film. Therefore, it has been proposed to use a polyester film as a polarizer protective film having durability and moisture barrier properties (see Patent Documents 1 to 5).
The triacetyl cellulose film used as a polarizer protective film is subjected to alkali treatment or the like on its surface, and has an extremely high affinity with a hydrophilic adhesive. Therefore, the protective film made of a triacetyl cellulose film has extremely high adhesiveness with a polarizer coated with a hydrophilic adhesive.
However, the polyester film has insufficient adhesion to the hydrophilic adhesive, and this tendency becomes more prominent particularly in the case of a polyester film having orientation by a stretching treatment. Therefore, Patent Documents 1 to 3 and 5 propose providing a polyester film with an easy-adhesion layer in order to improve the adhesion to the polarizer or the hydrophilic adhesive applied to the polarizer.

JP-A-8-271733 JP-A-8-271734 JP 2009-157361 A JP 2010-277028 A JP 2011-8170 A

  A polyester film has a low affinity for water, and this tendency is particularly remarkable in a polyester film having an aromatic dicarboxylic acid as a dicarboxylic acid component. Moreover, the polyester film which has crystal orientation by extending | stretching has a low affinity with water further. On the other hand, the polarizer and the adhesive applied on the polarizer are mainly composed of a polyvinyl alcohol-based resin and have high hydrophilicity. Due to the difference in properties, the polyester film, the polarizer, and the adhesive have low affinity, and it is difficult to firmly bond the two. Therefore, even if it is a polyester film which has an easily bonding layer disclosed by patent documents 1-3 and 5, compared with a triacetyl cellulose film, sufficient adhesiveness is not yet acquired. Therefore, when a polarizing plate using a conventional polyester film as a protective film is used as a display member for a long time, floating or peeling occurs between the protective film and the polarizer, and the polarization characteristics deteriorate due to a change in the amount of moisture in the polarizer. Visibility such as white spots may deteriorate.

In addition, in order to improve the durability of the adhesive layer and the like compared to the conventional polarizing plate, the thickness of the adhesive for bonding the polarizer and the polarizer protective film has been reduced, and the surface of the polarizer protective film has become minute. Unevenness or the like has become a factor that deteriorates the adhesion with the adhesive layer.

Under such circumstances, the object of the present invention is to improve the appearance and reduce the unevenness of the surface, and to strengthen the polyester film and the polyvinyl alcohol-based resin layer such as an adhesive applied on the polarizer or the polarizer. It aims at providing the polarizing plate which used the polyester film provided with the means to adhere to as a polarizer protective film .

  As a result of intensive studies to solve the above problems, the present inventor surprisingly contains a polyvinyl alcohol resin and a blocked isocyanate, the dissociation temperature of the blocked isocyanate is 130 ° C. or lower, and the boiling point of the blocking agent. By using a coating layer having a temperature of 180 ° C. or higher, it has been found that adhesion and appearance are improved, and the present invention has been achieved.

That is, the said subject can be achieved by the following solution means.
(1) A polarizing plate using an easy-adhesive polyester film having a coating layer on at least one side as a polarizer protective film , wherein the coating layer contains a polyvinyl alcohol resin and a blocked isocyanate, and the dissociation of the blocked isocyanate A polarizing plate having a temperature of 130 ° C. or lower, the blocking agent is a pyrazole compound, and the blocking agent has a boiling point of 180 ° C. or higher.
(2) The said polarizing plate whose saponification degree of the said polyvinyl alcohol-type resin is 95 mol% or less.
(3) The said polarizing plate whose mass ratio (polyvinyl alcohol-type resin / block isocyanate) of the polyvinyl alcohol-type resin and blocked isocyanate in the said application layer is 20/1-1/1.
(4) The said polarizing plate whose haze of a polyester film is 2.0% or less.
(5) A hard coat layer, an antiglare layer (AG), an antireflection layer (AR), a low reflection layer (LR), a low reflection antiglare layer (on the surface opposite to the coating layer of the easy-adhesive polyester film) The polarizing plate in which at least one functional layer selected from the group consisting of (AG / LR), an antireflection antiglare layer (AG / AR), and an antistatic layer is laminated.
( 6 ) A liquid crystal display device using the polarizing plate.

The easily-adhesive polyester film in the present invention is excellent in adhesion and appearance, and particularly excellent in adhesion with water-soluble and hydrophilic resins. Therefore, the easily-adhesive polyester film in the present invention is suitable as a base film for an optical member such as a display, and is particularly excellent in adhesion with a polarizer and is suitable as a polarizer protective film.

(Polyester film)
The polyester resin constituting the substrate in the present invention includes polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polymethylene terephthalate, and copolymerization components such as diethylene glycol, neopentyl glycol, and polyalkylene glycol. A diol component, a polyester resin copolymerized with a dicarboxylic acid component such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, or 2,6-naphthalenedicarboxylic acid can be used.

The polyester film in the present invention can be obtained by, for example, a method in which the above polyester resin is melt-extruded into a film shape and cooled and solidified with a casting drum to form a film. As the polyester film of the present invention, either a non-stretched film or a stretched film can be used, but a stretched film is preferable 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 a longitudinal uniaxial stretching method, a transverse uniaxial stretching method, a longitudinal and transverse sequential biaxial stretching method, a longitudinal and transverse simultaneous biaxial stretching method, and the like can be employed.

  The stretched polyester film may be a single layer or a multilayer. Moreover, as long as it exists in the range with the effect of this invention, each of these layers can contain various additives in a polyester resin as needed. Examples of the additive include an antioxidant, a light resistance agent, an antigelling agent, an organic wetting agent, an antistatic agent, an ultraviolet absorber, an infrared absorber, and a surfactant.

When used as a polarizer protective film, the addition of an ultraviolet absorber is particularly preferable, and the light transmittance at a wavelength of 380 nm of the easily adhesive polyester film is preferably 20% or less, more preferably 15% or less, and more preferably 10% or less. More preferred.

In addition, in order to improve handling properties such as slipperiness, rollability and blocking resistance of the film, and wear characteristics such as wear resistance and scratch resistance, inert particles may be included in the polyester film. However, since the film in the present invention is used as a base film for an optical member, it is required to have excellent handling properties while maintaining high transparency. Specifically, when used as a substrate film for an optical member, the total light transmittance of the easily adhesive polyester film is preferably 85% or more, more preferably 87% or more, and even more preferably 88% or more. 89% or more is more preferable, and 90% or more is particularly preferable.

  For high definition, the content of inert particles in the base film is preferably as small as possible. Therefore, it is a preferred embodiment that a multilayer structure in which particles are contained only in the surface layer of the film is used, or that the particles are substantially not contained in the film and fine particles are contained only in the coating layer.

  In particular, from the viewpoint of transparency, when an inert particle is practically not contained in the polyester film, an inorganic and / or heat-resistant polymer particle is contained in the aqueous coating solution in order to improve the handleability of the film. It is also preferable.

  Note that “substantially no inert particles” means, for example, in the case of inorganic particles, when the element derived from the particles is quantitatively analyzed by fluorescent X-ray analysis, 50 ppm or less, preferably 10 ppm or less, Preferably, the content is below the detection limit. This means that even if particles are not actively added to the base film, contaminants derived from foreign substances and raw material resin or dirt adhering to the line or equipment in the film manufacturing process will be peeled off and mixed into the film. It is because there is a case to do.

  In addition, from the viewpoint of achieving both high transparency and handling properties, it is also a preferred embodiment to add inert particles only to the surface layer. For example, in the case of a three-layer structure, it is preferable that particles are contained in the outermost layer (A layer in the case of A layer / B layer / A layer), and the center layer (B layer) is substantially free of particles. .

  The type and content of the particles contained in the outermost layer may be inorganic particles or organic particles, and are not particularly limited, but include metal oxidation such as silica, titanium dioxide, talc, and kaolinite. Examples thereof include inorganic particles that are inert to polyesters such as products, calcium carbonate, calcium phosphate, and barium sulfate. Any one of these inert inorganic particles may be used alone, or two or more thereof may be used in combination.

  The particles preferably have an average particle size of 0.1 to 3.5 μm. If the average particle size is less than the lower limit, sufficient handling properties may not be obtained. If the upper limit is exceeded, the transparency may decrease. The content of inorganic particles in the outermost layer is preferably 0.01 to 0.20 mass% with respect to the polyester constituting the outermost layer. If it is less than the lower limit, sufficient handling properties cannot be obtained. When the upper limit is exceeded, the transparency decreases.

  The thickness of the base film used in the present invention is not particularly limited, but can be arbitrarily determined in the range of 12 to 350 μm according to the standard to be used. The upper limit of the thickness of the base film is preferably 250 μm, particularly preferably 125 μm. On the other hand, the lower limit of the film thickness is preferably 12 μm, more preferably 25 μm, and particularly preferably 38 μm. When the film thickness is less than the lower limit, rigidity and mechanical strength tend to be insufficient. On the other hand, when the film thickness exceeds the upper limit, the cost may increase.

(Coating layer)
It is important that the easy-adhesive polyester film in the present invention has a coating layer containing a polyvinyl alcohol resin and a blocked isocyanate having a dissociation temperature of 130 ° C. or lower and a blocking agent having a boiling point of 180 ° C. or higher on at least one surface. It is.

As in the above-mentioned patent document, a polyvinyl alcohol resin was suitably used for imparting easy adhesion with a hydrophilic resin, but a cross-linked structure was positively introduced from the point of improving the adhesion of the coating layer, It was considered desirable to have a hard coating layer. Therefore, as in Japanese Patent No. 4130964, an example using an isocyanate as a crosslinking agent has been proposed. However, since these cross-linking agents are highly reactive, they tend to react with water in an aqueous coating solution to lose the cross-linking reactivity or to react with the polyvinyl alcohol resin to easily generate aggregates. For this reason, the so-called pot life is short, and it has been difficult to stably apply for a long period of time. Therefore, as in JP-A-11-301104, an isocyanate having a functional group blocked with a blocking agent that is dissociated by heat addition may be used. However, when the surface of the resulting easy-adhesive film is observed in detail under a fluorescent lamp, there are cases where minute irregularities are present on the coated surface. Such minute irregularities may not only impair the appearance of the resulting film, but may also affect the adhesion in some cases.
Then, when the unevenness | corrugation of the coating surface was earnestly examined, it turned out that it was surprisingly that such a fine coating surface unevenness | corrugation originated in the above blocked isocyanate. This was thought to be because minute uneven pinholes were formed on the coated surface when the dissociated blocking agent volatilized at a high temperature.

  Thus, as a result of intensive studies, the present inventor is excellent by adopting a coating layer containing a polyvinyl alcohol resin and a blocked isocyanate having a dissociation temperature of 130 ° C. or lower and a blocking agent having a boiling point of 180 ° C. or higher. It was found that good adhesion and appearance can be obtained. That is, when the dissociation temperature exceeds the above temperature, it is considered that the dissociation of the blocking agent due to heat addition becomes insufficient and a sufficient cross-linked structure cannot be obtained, resulting in a decrease in adhesion. Moreover, when the boiling point of a blocking agent is less than the said temperature, it is thought that the blocking agent which remained in the application layer volatilizes by heat addition, and an application | coating external appearance falls.

According to the above aspect, the present invention can improve the appearance and improve the adhesion between the water-soluble and hydrophilic resin, particularly the polarizer and the adhesive with the polarizer. Further, the configuration of the present invention will be described in detail below.

(Polyvinyl alcohol resin)
The polyvinyl alcohol resin used in the present invention is not particularly limited. For example, polyvinyl alcohol obtained by saponifying polyvinyl acetate; a derivative thereof; and a copolymer of vinyl acetate and a copolymerizable monomer. And saponified products of polyvinyl alcohol, modified polyvinyl alcohol obtained by acetalization, urethanization, etherification, grafting, phosphoric esterification, etc. of polyvinyl alcohol. Examples of the monomer include unsaturated carboxylic acids such as (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, (meth) acrylic acid, and esters thereof; α-olefins such as ethylene and propylene, (meth) Examples include allyl sulfonic acid (soda), sulfonic acid soda (monoalkyl malate), disulfonic acid soda alkyl maleate, N-methylol acrylamide, acrylamide alkyl sulfonic acid alkali salt, N-vinyl pyrrolidone, N-vinyl pyrrolidone derivatives, and the like. . These polyvinyl alcohol resins may be used alone or in combination of two or more.

  Examples of the polyvinyl alcohol resin used in the present invention include vinyl alcohol-vinyl acetate copolymer, vinyl alcohol-vinyl butyral copolymer, and ethylene-vinyl alcohol copolymer. Among these, vinyl alcohol-vinyl acetate copolymer An ethylene-vinyl alcohol copolymer is 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 from the viewpoint of the coating solution viscosity.

  The copolymerization ratio of vinyl alcohol is represented by the degree of saponification. The saponification degree of the polyvinyl alcohol resin is preferably 60 mol% or more and 95 mol% or less, more preferably 65 mol% or more and 90 mol% or less, further preferably 68 mol% or more and 85 mol% or less, and 70 mol% or more and 80 mol% or less. Less than is even more preferable. When the degree of saponification of the polyvinyl alcohol resin is within the above range, a crosslinked structure can be more suitably formed with the isocyanate crosslinking agent. Further, when the saponification degree of the polyvinyl alcohol resin exceeds the upper limit, the adhesion to the polyester film is lowered, and when it is less than the lower limit, the adhesion to the water-soluble / hydrophilic resin and the polarizer may be lowered. . The degree of saponification of the polyvinyl alcohol-based resin can be determined by the alkali consumption required for hydrolysis of copolymer units such as vinyl acetate or the composition analysis by NMR.

  As content of polyvinyl alcohol-type resin, 10 to 80 mass% is preferable in an easily bonding layer, 12 to 70 mass% is more preferable, 15 to 60 mass% is more preferable, 20 mass% or more and 50 mass% or less are still more preferable. When the content of the polyvinyl alcohol-based resin is not less than the above lower limit, it is suitable for adhesiveness with a polarizer / water-based resin, and when it is not more than the above upper limit, it is suitable for adhesiveness with a polyester film substrate.

(Block isocyanate)
In the present invention, it is necessary to contain a blocked isocyanate having a dissociation temperature of 130 ° C. or lower and a blocking agent having a boiling point of 180 ° C. or higher in the coating layer. The blocked isocyanate can be obtained by reacting a polyisocyanate and a blocking agent. The dissociation temperature and boiling point can be measured by differential thermal analysis.

  The dissociation temperature of the blocked isocyanate is preferably 130 ° C or lower, more preferably 125 ° C or lower, and still more preferably 120 ° C or lower. In the case of a drying step after application of the coating solution or an in-line coating method, the blocking agent is dissociated from the functional group by heat addition in the film forming step, and a regenerated isocyanate group is generated. For this reason, a crosslinking reaction with a polyvinyl alcohol-based resin or the like proceeds, and adhesion at normal temperature, high temperature and high humidity is improved. When the dissociation temperature of the blocked isocyanate is equal to or lower than the above temperature, the dissociation of the blocking agent proceeds sufficiently, so that the adhesiveness, particularly the moist heat resistance is improved. The lower limit of the dissociation temperature is not particularly limited as long as it is room temperature or higher for stabilization of the coating solution, but is preferably 50 ° C. or higher, more preferably 80 ° C. or higher, and further preferably 100 ° C. or higher.

  As the blocking agent, a compound having one active hydrogen in the molecule is preferably used. In this case, in order to make the dissociation temperature relatively low as described above, it is preferable to employ a blocking agent capable of obtaining a high electron density. For example, a blocking agent having a heterocyclic ring or a similar structure in the molecule is preferably used.

  The boiling point of the blocking agent is preferably 180 ° C or higher, more preferably 190 ° C or higher, further preferably 200 ° C or higher, and further preferably 210 ° C or higher. The higher the boiling point of the blocking agent, the more the drying of the coating solution after coating and the in-line coating method, the volatilization of the blocking agent is suppressed by heat addition in the film forming process, and the coating surface appearance defects due to minute unevenness of the coating surface The coating appearance and transparency are improved. The upper limit of the boiling point of the blocking agent is not particularly limited, but it seems that the upper limit is about 300 ° C. from the viewpoint of productivity. Since the boiling point is related to the molecular weight, in order to increase the boiling point of the blocking agent, it is preferable to use a blocking agent having a large molecular weight. The molecular weight of the blocking agent is preferably 50 or more, more preferably 60 or more, and more preferably 80 or more. preferable.

The dissociation temperature used for the blocked isocyanate in the present invention is 130 ° C. or lower, and the blocking agent has a boiling point of 180 ° C. or higher.
Pyrazole compounds: 3,5-dimethylpyrazole, 3-methylpyrazole, 4-bromo-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, etc.
Active methylene type: Malonic acid diester (dimethyl malonate, diethyl malonate, di-n-butyl malonate, di-2-ethylhexyl malonate), etc.
Triazole compounds: 1,2,4-triazole and the like.
Of these, pyrazole compounds are preferred from the viewpoints of heat and humidity resistance and yellowing. Bisulfite compounds such as sodium bisulfite are also included in this range, but if the salt remains in the coating layer, it may be inferior in terms of water resistance.
Details.

The polyisocyanate which is a precursor of the blocked isocyanate in the present invention is obtained by introducing diisocyanate. Examples thereof include urethane-modified products, allophanate-modified products, urea-modified products, biuret-modified products, uretdione-modified products, uretoimine-modified products, isocyanurate-modified products, and carbodiimide-modified products.

  Diisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 1,5-naphthylene diene Isocyanate, 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, 4,4'-diphenylpropane diisocyanate, 3,3'-dimethoxydiphenyl-4, Aromatic diisocyanates such as' -diisocyanate, aromatic aliphatic diisocyanates such as xylylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate and 4,4-dicyclohexylmethane diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane , Hexamethylene diisocyanate, and aliphatic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate. From the viewpoints of transparency, adhesiveness, and heat and humidity resistance, aliphatic and alicyclic isocyanates and modified products thereof are preferred. When aromatic isocyanate is used, there is a problem of yellowing, which may not be preferable for optical use requiring high transparency. Moreover, since it becomes a hard coating film compared with an aliphatic type | system | group, it becomes impossible to relieve | moderate the stress by shrinkage | contraction and swelling of various resin etc., and adhesiveness may fall.

The blocked isocyanate in the present invention can introduce a hydrophilic group into the polyisocyanate which is a precursor in order to impart water solubility or water dispersibility. Hydrophilic groups include (1) quaternary ammonium salts of dialkylamino alcohols and quaternary ammonium salts of dialkylaminoalkylamines, (2) sulfonates, carboxylates, phosphates, etc. (3) alkoxy groups Examples thereof include polyethylene glycol and polypropylene glycol blocked at one end. When a hydrophilic site is introduced, it becomes (1) cationic, (2) anionic, and (3) nonionic. Especially, since many other water-soluble resins are anionic, the anionic property and nonionic property which can be easily compatible are preferable. In addition, anionic properties are excellent in compatibility with other resins, and nonionic properties are preferred for improving heat and moisture resistance because they have no ionic hydrophilic groups. In addition, anionic and cationic ones aggregate with other resins or self-aggregate, which may affect transparency and appearance, and among these, nonionic ones are more preferable.

  As the anionic hydrophilic group, those having a hydroxyl group for introduction into polyisocyanate and a carboxylic acid group for imparting hydrophilicity are preferred. Examples include glycolic acid, lactic acid, tartaric acid, citric acid, oxybutyric acid, oxyvaleric acid, hydroxypivalic acid, dimethylolacetic acid, dimethylolpropionic acid, dimethylolbutanoic acid, and polycaprolactone having a carboxylic acid group. An organic amine compound is preferable for neutralizing the carboxylic acid group. For example, ammonia, methylamine, ethylamine, propylamine, isopropylamine, butylamine, 2-ethylhexylamine, cyclohexylamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, trimethylamine, triethylamine, triisopropylamine, tributylamine , Linear, branched 1, 2 or tertiary amines having 1 to 20 carbon atoms such as ethylenediamine, morpholine, N-alkylmorpholine, cyclic amines such as pyridine, monoisopropanolamine, methylethanolamine, methylisopropanolamine, Dimethylethanolamine, diisopropanolamine, diethanolamine, triethanolamine, diethylethanolamine, triethanol A hydroxyl group-containing amines such as triethanolamine and the like.

  The nonionic hydrophilic group is preferably 3 to 50, more preferably 5 to 30, of ethylene glycol and polypropylene oxide ethylene oxide and / or propylene oxide capped at one end with an alkoxy group. When the repeating unit is small, the compatibility with the resin is deteriorated and the haze is increased. When the repeating unit is large, the adhesiveness under high temperature and high humidity may be decreased.

The blocked isocyanate in the present invention may contain a nonionic, anionic, cationic or amphoteric surfactant for improving water dispersibility. For example, nonionics such as polyethylene glycol and polyhydric alcohol fatty acid esters, fatty acid salts, alkyl sulfates, alkylbenzene sulfonates, sulfosuccinates, alkyl phosphates and other anionic systems, alkylamine salts, cationic systems such as alkyl betaines, Examples thereof include surfactants such as carboxylic acid amine salts, sulfonic acid amine salts, and sulfate ester salts.

  In addition to water, a water-soluble organic solvent can be contained. For example, the organic solvent used in the reaction or it can be removed and another organic solvent can be added.

  As content of block isocyanate, 5 mass% or more and 100 mass% or less are preferable with respect to polyvinyl alcohol-type resin. More preferably, it is 15 mass% or more and 70 mass% or less. When the amount is small, the coating layer is insufficiently cross-linked, and the adhesion with the water-soluble resin, hydrophilic resin or polarizer decreases.When the amount is large, the amount of hydroxyl groups of the polyvinyl alcohol-based resin decreases, and Adhesiveness with water-soluble resin, hydrophilic resin or polarizer is lowered. Two or more types of blocked isocyanates may be combined, or two or more types of blocking agents may be combined. In that case, at least one blocked isocyanate must satisfy the provisions of the present invention.

  In the present invention, two kinds of crosslinking agents may be mixed in order to improve the coating film strength. Examples of the crosslinking agent to be mixed include melamine, epoxy, carbodiimide, and oxazoline. A carbodiimide type and an oxazoline type are preferable from the viewpoint of the stability over time of the coating liquid and the effect of improving adhesion. Moreover, in order to promote a crosslinking reaction, a catalyst etc. are used suitably as needed.

In the easy-adhesion layer in the present invention, a resin other than the polyvinyl alcohol-based resin may be contained in order to improve the adhesion to the polyester film. For example, an acrylic resin, a polyester resin, a urethane resin, etc. are mentioned. In particular, it is preferable to add a polyester resin from the viewpoint of obtaining adhesion with a polyester film.

(Polyester resin)
The polyester resin contained in addition to the polyvinyl alcohol resin is not particularly limited, and conventionally known polyester resins can be used. The polyester resin will be described below. The polyester resin used for the easy-adhesion layer of the present invention is a copolymer obtained by polycondensation of a dicarboxylic acid component and a diol component, and known materials can be used as the dicarboxylic acid component and the diol component. From the viewpoint of improving the adhesion to the polyester film substrate, it is preferable to use a dicarboxylic acid component having the same or similar structure and properties as the dicarboxylic acid component in the polyester film as the dicarboxylic acid component of the polyester resin. Therefore, for example, when an aromatic dicarboxylic acid is employed as the dicarboxylic acid component of the polyester film, it is preferable to use the 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 preferred. Other aromatic dicarboxylic acids may be added and copolymerized within a range of 10 mol% or less with respect to the total dicarboxylic acid component.
The glycol component of the polyester resin is preferably composed of ethylene glycol and branched glycol. By having a branched structure, it is considered that it contributes to stress relaxation in the easy-adhesion layer, and it is possible to suitably exhibit adhesion. Examples of the branched glycol component include 2,2-dimethyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, and 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, Such as 2-di-n-butyl-1,3-propanediol, 2-n-butyl-2-propyl-1,3-propanediol, and 2,2-di-n-hexyl-1,3-propanediol. And the like.

  The molar ratio of the branched glycol component is preferably 10 mol%, particularly preferably 20 mol%, based on the total glycol component. On the other hand, the upper limit is preferably 80 mol%, more preferably 70 mol%, and particularly preferably 60 mol%. 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 the polyvinyl alcohol resin. In order to make the polyester resin water-soluble or water-dispersed, it is preferable to copolymerize a compound containing a hydrophilic group such as a sulfonate group or a carboxylate group. Of these, a dicarboxylic acid component having a sulfonate group is preferred from the viewpoint of imparting hydrophilicity while maintaining the acid value of the polyester resin low and controlling the reactivity with the crosslinking agent. Examples of the dicarboxylic acid component having a sulfonate group include sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfonaphthaleneisophthalic acid-2,7-dicarboxylic acid, and 5- (4-sulfophenoxy) isophthalic acid or an alkali thereof. Examples of the metal salt include 5-sulfoisophthalic acid. 1-15 mol% is preferable in the dicarboxylic acid component of a polyester resin, as for the dicarboxylic acid component which has a sulfonate group, 1.5-12 mol% is more preferable, and 2-10 mol% is further more preferable. When the dicarboxylic acid component having a sulfonate group is at least the above lower limit, it is suitable for making the polyester resin water-soluble or water-dispersed. Moreover, when the dicarboxylic acid component which has a sulfonate group is below the said upper limit, it is suitable for adhesiveness with a polyester film base material.

  The polyester resin preferably has fewer carboxylic acid groups which are reactive groups with the blocked isocyanate. By reducing the number of carboxyl groups that are reactive with the blocked isocyanate, the reactivity with the blocked isocyanate is lowered, so that the blocked isocyanate and the polyvinyl alcohol-based resin can be effectively crosslinked. From such a viewpoint, the acid value of the polyester resin is 20 KOH mg / g or less, preferably 15 KOH mg / g or less, more preferably 10 KOH mg / g or less, still more preferably 8 KOH mg / g or less, and still more preferably 5 KOH mg / g or less. is there. The acid value of the polyester resin can be theoretically determined from the result of component analysis by titration method described later or NMR.

  In order to control the acid value of the polyester resin within the above range, the introduction amount of carboxylic acid base for water solubilization or water dispersion is reduced, a hydrophilic group other than carboxylic acid base is adopted, polyester It is preferable to lower the carboxylic acid terminal concentration of the resin. As a method for lowering the carboxylic acid terminal concentration of the polyester resin, it is preferable to employ a polyester resin in which a carboxylic acid terminal group is modified, or a polyester resin having a large number average molecular weight of the polyester resin. For this reason, the number average molecular weight of the polyester resin is preferably 5000 or more, more preferably 6000 or more, and further preferably 10,000 or more. Moreover, it is preferable to make low content of the acid component which has a polyester resin as a structural component and has three or more carboxyl groups.

  Although the glass transition temperature of a polyester resin is not specifically limited, It is preferable that it is 20-90 degree | times, and it is more preferable that it is 30-80 degree | times. When the glass transition temperature is not less than the above lower limit, it is suitable for blocking resistance, and when the glass transition temperature is not more than the above upper limit, it is suitable for adhesiveness to a polyester film substrate.

  10 mass% or more and 90 mass% or less are preferable, as for content of the polyester resin in an easily bonding layer, 45 mass% or more and 85% mass% or less are more preferable, and 50 mass% or more and 80 mass% or less are more preferable. When the content of the polyester resin is not less than the above lower limit, it is suitable for adhesion to the polyester film substrate, and when it is not more than the above upper limit, it is suitable for adhesion to the polarizer / water-based resin.

  The blending ratio (PEs) / (PVA) of the polyester resin (PEs) and the polyvinyl alcohol resin (PVA) is preferably 0.8 to 5, more preferably 1 to 4, and 2 to 2. 4 is more preferable, and 2.5 to 3.5 is particularly preferable. When (PEs) / (PVA) is at least the above lower limit, it is suitable for adhesion to a polyester film substrate, and when it is at most the above upper limit, it is suitable for adhesion to a polarizer / water-based resin.

(Additive)
In the present invention, particles may be contained in the coating layer. Particles are (1) silica, kaolinite, talc, light calcium carbonate, heavy calcium carbonate, zeolite, alumina, barium sulfate, carbon black, zinc oxide, zinc sulfate, zinc carbonate, zirconium dioxide, titanium dioxide, satin white, silicic acid Inorganic particles such as aluminum, diatomaceous earth, calcium silicate, aluminum hydroxide, hydrous halloysite, magnesium carbonate, magnesium hydroxide, (2) acrylic or methacrylic, vinyl chloride, vinyl acetate, nylon, styrene / acrylic , Styrene / butadiene, polystyrene / acrylic, polystyrene / isoprene, polystyrene / isoprene, methyl methacrylate / butyl methacrylate, melamine, polycarbonate, urea, epoxy, urethane , Phenolic, diallyl phthalate, and organic particles of a polyester or the like.

The average particle diameter of the particles is not particularly limited, but is preferably 1 to 500 nm, and more preferably 1 to 100 nm from the viewpoint of maintaining film transparency.

  The particles may contain two or more kinds of particles having different average particle diameters.

  In addition, said average particle diameter measures the maximum diameter of the 10 or more particle | grains which exist in the cross section of a coating layer by image | photographing the cross section of a laminated film at a magnification of 120,000 times using a transmission electron microscope (TEM). And can be obtained as an average value of them.

  The content of the particles is preferably 0.5% by mass or more and 20% by mass or less in the coating layer. When the amount is small, sufficient blocking resistance cannot be obtained. Further, scratch resistance is deteriorated. When the amount is large, not only the transparency of the coating layer is deteriorated, but also the coating strength is lowered.

  The coating layer may contain a surfactant for the purpose of improving leveling properties during coating and defoaming the coating solution. The surfactant may be any of cationic, anionic and nonionic surfactants, but is preferably a silicon-based, acetylene glycol-based or fluorine-based surfactant. These surfactants are also preferably contained in a range that does not impair the adhesion to the optical functional layer, for example, in the range of 0.005 to 0.5% by mass in the coating solution.

The easily adhesive polyester film in the present invention preferably has a haze value of 2.0% or less, more preferably 1.5% or less, and still more preferably 1.2% or less.

  In order to impart other functionality to the coating layer, various additives may be contained within a range that does not impair the adhesion to the polarizer / water-based resin. Examples of the additive include fluorescent dyes, fluorescent brighteners, plasticizers, catalysts, ultraviolet absorbers, pigment dispersants, foam suppressors, antifoaming agents, preservatives, and antistatic agents.

In the easily adhesive polyester film of the present invention, various functional layers can be provided on the surface opposite to the coating layer for the purpose of preventing reflection, suppressing glare, and suppressing scratches. Such a functional layer is not particularly limited, but includes a hard coat layer, an antiglare layer (AG), an antireflection layer (AR), a low reflection layer (LR), a low reflection antiglare layer (AG / LR), and a reflection. Examples thereof include an antiglare layer (AG / AR) and an antistatic layer. As for these layers, only 1 type may be provided on the polyester film, and may be laminated | stacked combining 2 or more types as needed. As these functional layers, various types known in the technical field can be used, and the type is not particularly limited.

In the polyester film of the present invention, in order to improve adhesion with the functional layer, between the functional layer and the polyester film, in addition to physical treatment such as corona discharge treatment, plasma discharge treatment, oxidation treatment, It is preferable to have an anchor coat layer. The anchor coat layer can be formed by applying one or more kinds of resins such as polyester resin, polyurethane resin, acrylic resin, and polyvinyl alcohol resin. The method for coating is not particularly limited. For example, the coat layer described in Japanese Patent No. 3300909, Japanese Patent No. 3632044, Japanese Patent No. 4770971, Japanese Patent Publication No. 6-81714, and Japanese Patent Application Laid-Open No. 2009-143226 is also suitable as the anchor coat layer.

  In the present invention, examples of the method for providing the coating layer on the polyester film include a method in which a coating solution containing a solvent, particles and a resin is applied to the polyester film and dried. Examples of the solvent include organic solvents such as toluene, water, and a mixed system of water and a water-soluble organic solvent. Preferably, water alone or a mixture of a water-soluble organic solvent and water is used from the viewpoint of environmental problems. preferable.

(Manufacture of easily adhesive polyester film)
The method for producing an easy-adhesive polyester film in the present invention will be described by taking a polyethylene terephthalate (hereinafter abbreviated as PET) film as an example, but is not limited to this.

  The coating layer is formed by coating a coating solution on at least one surface of a PET film at any stage of the formed film or film manufacturing process. In particular, coating (in-line coating method) in a film production process capable of high heat addition for dissociation of the blocking agent is preferable. The coating layer may be formed on both sides of the PET film. The solid content concentration of the resin composition in the coating solution is preferably 2 to 35% by weight, particularly preferably 4 to 15% by weight.

  Any known method can be used as a method of applying the coating liquid to the PET film. 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, etc. It is done. These methods are applied alone or in combination.

  In the case of the in-line coating method, the coating layer is formed by applying the coating solution to an unstretched or uniaxially stretched PET film, drying it, stretching it at least in a uniaxial direction, and then performing a heat treatment.

In the present invention, the finally obtained coating layer preferably has a thickness of 20 to 350 nm, and the coating amount after drying is preferably 0.02 to 0.5 g / m ² . When the coating amount of the coating layer is less than 0.02 g / m ² , the effect on adhesiveness is almost lost. On the other hand, when the coating amount exceeds 0.5 g / m ² , haze increases.

  The film used as the substrate can be obtained as follows, taking a PET film as an example. After sufficiently drying the PET resin in a vacuum, it is supplied to an extruder, melted and extruded at about 280 ° C. from a T-die into a rotating cooling roll into a sheet, cooled and solidified by an electrostatic application method, and unstretched PET. Get a sheet. The unstretched PET sheet may have a single layer structure or a multilayer structure by a coextrusion method. Moreover, it is preferable not to contain an inert particle substantially in PET resin.

  The obtained unstretched PET sheet 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. Furthermore, the edge part of a film is hold | gripped with a clip, it guide | induces to the hot air zone in the tenter heated at 70-140 degreeC, and it extends | stretches 2.5 to 5.0 times in the width direction. Guidance and heat treatment. In order that the blocking agent of the present invention is suitably dissociated by heat addition, the maximum temperature in the tenter and the heat treatment time during heat treatment are preferably 160 ° C. or higher and 1 second or longer, and 180 ° C. or higher and 5 seconds or longer. More preferred. In order to suitably suppress volatilization of the blocking agent, the maximum temperature in the tenter and the heat treatment time during heat treatment are preferably 250 ° C. or less and 60 seconds or less, and more preferably 240 ° C. or less and 50 seconds or less. In addition, the said heat processing time says the residence time from the heat processing zone in a tenter after extending | stretching to a cooling zone.

Highly adhesive polyester film roll formed by winding a highly adhesive polyester film of the present invention are also preferred embodiments in the present invention. Since the coating layer of the present invention has good anti-blocking properties due to the addition of a crosslinking agent, it can be suitably used even when it is a roll for improving productivity.

Although the thickness of the easily-adhesive polyester film in this invention is not specifically limited, It can be arbitrarily determined in the range of 12-350 micrometers according to the specification of the use to be used. The upper limit of the thickness of the easily adhesive polyester film is preferably 250 μm, and particularly preferably 125 μm. On the other hand, the lower limit of the film thickness is preferably 25 μm, particularly preferably 38 μm. If the film thickness is less than 12 μm, the mechanical strength tends to be insufficient. On the other hand, if the film thickness exceeds 350 μm, it tends to be difficult to wind it into a roll.

When the easily adhesive polyester film in the present invention is used as a roll, the winding length and width are appropriately determined depending on the use of the film roll. The winding length of the film roll is preferably 1500 m or more, more preferably 1800 m or more. The upper limit of the winding length is preferably 5000 m. Moreover, it is preferable that the width | variety of a film roll is 500 mm or more, More preferably, it is 800 mm. The upper limit of the film roll width is preferably 2500 mm.

(Polarizer)
The polarizing plate of this invention is a polarizing plate which has a polarizer protective film on both surfaces of a polarizer, Comprising: The polarizer protective film of at least one surface is the said easily-adhesive polyester film for polarizer protection Is preferred. The other polarizer protective film may be an easily adhesive polyester film for protecting a polarizer of the present invention, or a film having no birefringence such as a triacetyl cellulose film, an acrylic film, or a norbornene-based film. It is also preferable to use

  Examples of the polarizer include a polyvinyl alcohol film containing a dichroic material such as iodine. The polarizer protective film is bonded to the polarizer directly or via an adhesive layer, but it is preferable to bond the polarizer protective film via an adhesive from the viewpoint of improving adhesiveness. In that case, it is preferable to arrange | position the easily bonding layer of this invention to a polarizer surface or an adhesive bond layer surface. As a preferable polarizer for bonding the polyester film of the present invention, for example, iodine or dichroic material is dyed and adsorbed on a polyvinyl alcohol film, uniaxially stretched in a boric acid aqueous solution, and the stretched state is maintained. The polarizer obtained by performing washing | cleaning and drying is mentioned. The draw ratio of uniaxial stretching is usually about 4 to 8 times. Polyvinyl alcohol is suitable as the polyvinyl alcohol film. “Kuraray Vinylon” [manufactured by Kuraray Co., Ltd.], “Tosero Vinylon” [manufactured by Toh Cello Co., Ltd.], “Nichigo Vinylon” [Nippon Synthetic Chemical Co., Ltd.] Commercial products such as “made” can be used. Examples of the dichroic material include iodine, a disazo compound, and a polymethine dye.

  From the viewpoint of thinning the adhesive layer, the adhesive applied to the polarizer is preferably an aqueous one, that is, an adhesive component dissolved in water or dispersed in water. For example, a polyvinyl alcohol resin, a urethane resin, or the like is used as a main component, and a composition containing an isocyanate compound, an epoxy compound, or the like can be used as necessary in order to improve adhesiveness. The thickness of the adhesive layer is preferably 5 μm or less, more preferably 1 μm or less, and even more preferably 0.5 μm or less.

  When using polyvinyl alcohol resin as the main component of the adhesive, in addition to partially saponified polyvinyl alcohol and fully saponified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, methylol group-modified polyvinyl alcohol, amino group-modified A modified polyvinyl alcohol resin such as polyvinyl alcohol may be used. 1-10 mass% is preferable and, as for the density | concentration of the polyvinyl alcohol-type resin in an adhesive agent, 2-7 mass% is more preferable.

EXAMPLES Next, although this invention is demonstrated in detail using an Example, a comparative example, and a reference example, this invention is not limited to a following example naturally. Hereinafter, Example 16 will be read as Reference Example 16. The evaluation method used in the present invention is as follows.

(1) Intrinsic viscosity Based on JIS K7367-5, it measured at 30 degreeC, using the mixed solvent of phenol (60 mass%) and 1,1,2,2-tetrachloroethane (40 mass%) as a solvent.

(2) Dissociation temperature and boiling point The dissociation temperature of blocked isocyanate was measured by DSC analysis using a differential scanning calorimeter (Seiko Instruments Inc., DSC6200), and the boiling point of the blocking agent was thermogravimetric / differential thermal analysis (TG / DTA). It was measured by. The boiling point was measured at 1 atm.
(3) Glass transition temperature In accordance with JIS K7121, using a differential scanning calorimeter (Seiko Instruments, DSC6200), 10 mg of a resin sample was heated at a rate of 20 ° C / min over a temperature range of 25 to 300 ° C. The extrapolated glass transition start temperature obtained from the curve was defined as the glass transition temperature.

(4) Number average molecular weight 0.03 g of resin was dissolved in 10 ml of tetrahydrofuran, and GPC-LALLS apparatus low-angle light scattering photometer LS-8000 (manufactured by Tosoh Corporation, tetrahydrofuran solvent, reference: polystyrene) was used at a column temperature of 30 ° C. The number average molecular weight was measured using a flow rate of 1 ml / min and a column (showex KF-802, 804, 806 manufactured by Showa Denko KK).

(5) Resin composition The resin is dissolved in deuterated chloroform, 1H-NMR analysis is performed using a nuclear magnetic resonance analyzer (NMR) Gemini-200 manufactured by Varian, and the mol% ratio of each composition is determined from the integration ratio. did.

(6) Acid value 1 g (solid content) of a sample was dissolved in 30 ml of chloroform or dimethylformamide, and titrated with 0.1 N potassium hydroxide ethanol solution using phenolphthalein as an indicator to determine the carboxyl groups per gram of the sample. The amount (mg) of KOH required for neutralization was determined.

(7) Saponification degree Residual acetate groups (mol%) of the polyvinyl alcohol resin were quantified using sodium hydroxide according to JIS-K6726, and the value was defined as the saponification degree (mol%). The sample was measured three times, and the average value was defined as the saponification degree (mol%).

(8) Total light transmittance of easy-adhesive polyester film The total light transmittance of the easy-adhesive polyester film was measured using a turbidimeter (Nippon Denshoku, NDH2000) in accordance with JIS K 7105.

(9) Haze of easy-adhesive polyester film The haze of the easy-adhesive polyester film was measured using a turbidimeter (Nippon Denshoku, NDH2000) according to JIS K7136.

(10) PVA adhesion On the surface of the easy-adhesive layer of the easy-adhesive polyester film, a polyvinyl alcohol aqueous solution (PVA117 manufactured by Kuraray Co., Ltd.) adjusted to a solid content concentration of 5% by mass is used. It was applied with a wire bar and dried at 70 ° C. for 5 minutes. As the polyvinyl alcohol aqueous solution, a solution in which a red dye was added so as to facilitate the determination was used. The prepared evaluation target film was attached to a glass plate having a thickness of 5 mm to which a double-sided tape was attached, and the opposite surface of the evaluation target laminated film on which the polyvinyl alcohol resin layer was formed was attached to the double-sided tape. Next, 100 grid-like cuts that penetrated through the polyvinyl alcohol resin layer and reached the base film were made using a cutter guide with a gap interval of 2 mm. Then, an adhesive tape (Nichiban Co., Ltd. cello tape (registered trademark) CT-24; 24 mm width) was attached to the grid-shaped cut surface. The air remaining at the interface at the time of pasting was pressed with an eraser to bring it into close contact, and then the adhesive tape was peeled off vigorously and vertically five times. The number of squares on which the polyvinyl alcohol resin layer was not peeled was counted to determine PVA adhesion. That is, when the PVA layer was not peeled off at all, the PVA adhesion rate was 100, and when all the PVA layer was peeled off, the PVA adhesion rate was 0. In addition, what was partially peeled within one square was also included in the number of peeled.
Adhesiveness (%) = (1−number of peeled squares / 100) × 100
A: 100% or material breakage of PVA117 layer B: 99-90%
Δ: 89-60%
X: 59 to 0%
(9) Appearance With the easy-adhesive surface of the prepared easy-adhesive polyester film facing upward, visual observation was carried out in the range of 10 ° to 45 ° with respect to the film surface under a three-wavelength fluorescent lamp on a black mat. Evaluation was made in the following three stages.
○: There is no defect of the coated layer surface due to the coated surface microprotrusions.
(Triangle | delta): There are some faults of the coating layer surface resulting from a coating surface microprotrusion.
X: The defect of the coating layer surface resulting from a coating surface microprotrusion is scattered.

(Polyester resin polymerization)
In a stainless steel autoclave equipped with a stirrer, a thermometer, and a partial reflux condenser, 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, The mixture was charged with 233.5 parts by mass of diethylene glycol, 136.6 parts by mass of ethylene glycol, and 0.2 parts by mass of tetra-n-butyl titanate, and subjected to a transesterification reaction at a temperature of 160 to 220 ° C. over 4 hours. Next, the temperature was raised to 255 ° C., and the pressure of the reaction system was gradually reduced, followed by reaction for 1 hour 30 minutes under a reduced pressure of 30 Pa to obtain a copolymerized polyester resin (A-1). The obtained copolyester resin (A-1) was light yellow and transparent. It was 0.70 dl / g when the reduced viscosity of copolyester resin (A-1) was measured. The glass transition temperature by DSC was 40 ° C.

  In the same manner, copolymer polyester resins (A-2) to (A-4) having different compositions were obtained. Table 1 shows the composition (mole% ratio) and other characteristics measured by 1H-NMR for these copolymer polyester resins.

(Adjustment of polyester aqueous dispersion)
30 parts by mass of polyester resin (A-1) and 15 parts by mass of ethylene glycol n-butyl ether were placed in a reactor equipped with a stirrer, a thermometer and a reflux device, and heated and stirred at 110 ° C. to dissolve the resin. After the resin was completely dissolved, 55 parts by mass of water was gradually 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 aqueous dispersion (Aw-1) having a solid content of 30% by mass. Similarly, using the polyester resins (A-2) to (A-4) instead of the polyester resin (A-1), water dispersions are prepared, and the polyester water dispersions (Aw-2) to (Aw) are respectively produced. -4).

(Preparation of aqueous polyvinyl alcohol 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 polyvinyl alcohol resin (manufactured by Kuraray) (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 with stirring to prepare a polyvinyl alcohol aqueous solution (Bw-1) having a solid content of 10% by mass. Similarly, polyvinyl alcohol resins (B-2) to (B-7) were used instead of the polyvinyl alcohol resin (B-1) to prepare aqueous solutions, which were designated as (Bw-2) to (Bw-7), respectively. . Table 2 shows the degree of saponification of the polyvinyl alcohol resins (B-1) to (B-7).

(Polymerization of block polyisocyanate crosslinking agent C-1)
A flask equipped with a stirrer, thermometer, reflux condenser, and polyisocyanate compound having an isocyanurate structure using hexamethylene diisocyanate as a raw material (manufactured by Asahi Kasei Chemicals, Duranate TPA) with 52.21 parts by mass of polyethylene glycol monomethyl ether (average molecular weight) 1000) 20.72 parts by mass were added dropwise and kept at 70 ° C. for 5 hours under an atmosphere. Thereafter, 27.08 parts by mass of 3,5-dimethylpyrazole (dissociation temperature: 120 ° C., boiling point: 218 ° C.) was added dropwise. After measuring the infrared spectrum of the reaction solution and confirming that the absorption of the isocyanate group had disappeared, 25 parts by mass of dipropylene glycol dimethyl ether and 125 parts by mass of water were added, and the mixture was stirred at 30 ° C. at a high speed. A block polyisocyanate aqueous dispersion (C-1) was obtained.

(Polymerization of block polyisocyanate crosslinking agent C-2)
A flask equipped with a stirrer, a thermometer, a reflux condenser, and a polyisocyanate compound having a biuret structure made of hexamethylene diisocyanate as a raw material (manufactured by Asahi Kasei Chemicals Co., Ltd., Duranate 24A-100) was added to 52.54 parts by mass of polyethylene glycol monomethyl ether (average (Molecular weight 1000) 19.78 mass parts It hold | maintained for 5 hours at 70 degreeC by the atmosphere. Thereafter, 27.67 parts by mass of 3,5-dimethylpyrazole (dissociation temperature: 120 ° C., boiling point: 218 ° C.) was added dropwise. After measuring the infrared spectrum of the reaction solution and confirming that the absorption of the isocyanate group had disappeared, 25 parts by mass of dipropylene glycol dimethyl ether and 125 parts by mass of water were added, and the mixture was stirred at 30 ° C. at a high speed, and the solid content was 40% by mass. A block polyisocyanate aqueous dispersion (C-2) was obtained.

(Polymerization of block polyisocyanate crosslinking agent C-3)
A polyisocyanate compound having an isocyanurate structure using hexamethylene diisocyanate as a raw material in a flask equipped with a stirrer, thermometer, and reflux condenser (66,04 parts by mass, manufactured by Asahi Kasei Chemicals, Duranate TPA), 17.50 N-methylpyrrolidone 25.19 parts by mass of 3,5-dimethylpyrazole (dissociation temperature: 120 ° C., boiling point: 218 ° C.) was added dropwise to parts by mass, and the mixture was held at 70 ° C. for 1 hour in an atmosphere of atmosphere. Thereafter, 5.27 parts by mass of dimethylolpropanoic acid was added dropwise. After measuring the infrared spectrum of the reaction solution and confirming that the absorption of the isocyanate group disappeared, 5.59 parts by mass of N, N-dimethylethanolamine and 132.5 parts by mass of water were added, and the solid content was 40% by mass. A block polyisocyanate aqueous dispersion (C-3) was obtained.

(Polymerization of block polyisocyanate crosslinking agent C-4)
Except for changing 3,5-dimethylpyrazole (dissociation temperature: 120 ° C., boiling point: 218 ° C.) of the block polyisocyanate aqueous dispersion (C-1) to diethyl malonate (dissociation temperature: 120 ° C., boiling point 199 ° C.). In the same manner, a block polyisocyanate aqueous dispersion (C-4) having a solid content of 40% was obtained.

(Polymerization of block polyisocyanate crosslinking agent C-5)
Except for changing 3,5-dimethylpyrazole (dissociation temperature: 120 ° C., boiling point: 218 ° C.) of the block polyisocyanate aqueous dispersion (C-1) to methyl ethyl ketoxime (dissociation temperature: 140 ° C., boiling point: 152 ° C.) A block polyisocyanate aqueous dispersion (C-5) having a solid content of 40% was obtained in the same manner.

(Polymerization of block polyisocyanate crosslinking agent C-6)
Except for changing 3,5-dimethylpyrazole (dissociation temperature: 120 ° C., boiling point: 218 ° C.) of the block polyisocyanate aqueous dispersion (C-3) to methyl ethyl ketoxime (dissociation temperature: 140 ° C., boiling point: 152 ° C.). A block polyisocyanate aqueous dispersion (C-6) having a solid content of 40% was obtained in the same manner.

Example 1
(1) Adjustment of coating liquid The coating liquid of the following composition was adjusted.
Water 28.60% by mass
Isopropanol 30.00% by mass
Polyester water dispersion (Aw-1) 12.00% by mass
Polyvinyl alcohol aqueous solution (Bw-4) 24.00% by mass
Block polyisocyanate aqueous dispersion (C-1) 3.00 mass%
Particles 1.50% by mass
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Catalyst (Organic tin compound solid content concentration 14% by mass) 0.30% by mass
Surfactant 0.60% by mass
(Silicone, solid content concentration 10% by mass)

(2) Production of easy-adhesive polyester film PET film pellets having an intrinsic viscosity (solvent: phenol / tetrachloroethane = 60/40) of 0.62 dl / g and substantially free of particles are used as a film raw material polymer. The film was dried at 135 ° C. under reduced pressure of 133 Pa for 6 hours. Thereafter, the sheet was supplied to an extruder, melted and extruded into a sheet at about 280 ° C., and rapidly cooled and solidified on a rotating cooling metal roll maintained at a surface temperature of 20 ° C. to obtain an unstretched PET sheet.

  This unstretched PET sheet was heated to 100 ° C. with a heated roll group and an infrared heater, and then stretched 3.5 times in the longitudinal direction with a roll group having a difference in peripheral speed to obtain a uniaxially stretched PET film.

Subsequently, after apply | coating the said coating liquid to the single side | surface of PET film by the roll coat method, it dried at 80 degreeC for 15 second. The coating amount after drying (after biaxial stretching) was adjusted to 0.12 g / m ² . Subsequently, the film was stretched 4.0 times in the width direction at 150 ° C. with a tenter, and heated at 230 ° C. for 0.5 seconds with the length in the width direction fixed, and further at 230 ° C. for 10 seconds. % Relaxation treatment in the width direction was performed to obtain a polarizer protective polyester film having a thickness of 38 μm. The evaluation results are shown in Table 3.

Example 2
An easily adhesive polyester film was obtained in the same manner as in Example 1 except that the polyester aqueous dispersion of the coating solution was changed to Aw-2.

Example 3
An easily adhesive polyester film was obtained in the same manner as in Example 1 except that the polyester aqueous dispersion of the coating solution was changed to Aw-3.

Example 4
An easy-adhesive polyester film was obtained in the same manner as in Example 1 except that the polyester aqueous dispersion of the coating solution was changed to Aw-4.

Example 5
An easy-adhesive polyester film was obtained in the same manner as in Example 1 except that the coating solution was changed to the following composition.
Water 28.60% by mass
Isopropanol 30.00% by mass
Polyurethane resin 12.00% by mass
(HUX350, made by ADEKA, solid content 30%)
Polyvinyl alcohol aqueous solution (Bw-4) 24.00% by mass
Block polyisocyanate aqueous dispersion (C-1) 3.00 mass%
Particles 1.50% by mass
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Catalyst (Organic tin compound solid content concentration 14% by mass) 0.30% by mass
Surfactant 0.60% by mass
(Silicone, solid content concentration 10% by mass)

Example 6
An easily adhesive polyester film was obtained in the same manner as in Example 1 except that the polyvinyl alcohol aqueous solution of the coating solution was changed to Bw-3.

Example 7
An easily adhesive polyester film was obtained in the same manner as in Example 1 except that the polyvinyl alcohol aqueous solution of the coating solution was changed to Bw-2.

Example 8
An easily adhesive polyester film was obtained in the same manner as in Example 1 except that the polyvinyl alcohol aqueous solution of the coating solution was changed to Bw-1.

Example 9
An easy-adhesive polyester film was obtained in the same manner as in Example 1 except that the coating solution was changed to the following composition.
Water 33.35% by mass
Isopropanol 30.00% by mass
Polyester water dispersion (Aw-1) 14.00 mass%
Polyvinyl alcohol aqueous solution (Bw-4) 18.00 mass%
Block polyisocyanate aqueous dispersion (C-1) 2.25% by mass
Particles 1.50% by mass
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Catalyst (Organic tin compound solid content concentration 14% by mass) 0.30% by mass
Surfactant 0.60% by mass
(Silicone, solid content concentration 10% by mass)

Example 10
An easy-adhesive polyester film was obtained in the same manner as in Example 1 except that the coating solution was changed to the following composition.
Water 38.10% by mass
Isopropanol 30.00% by mass
Polyester water dispersion (Aw-1) 16.00 mass%
Polyvinyl alcohol aqueous solution (Bw-4) 12.00% by mass
Block polyisocyanate aqueous dispersion (C-1) 1.50 mass%
Particles 1.50% by mass
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Catalyst (Organic tin compound solid content concentration 14% by mass) 0.30% by mass
Surfactant 0.60% by mass
(Silicone, solid content concentration 10% by mass)

Example 11
An easy-adhesive polyester film was obtained in the same manner as in Example 1 except that the coating solution was changed to the following composition.
23.85% by mass of water
Isopropanol 30.00% by mass
Polyester water dispersion (Aw-1) 10.00 mass%
Polyvinyl alcohol aqueous solution (Bw-4) 30.00 mass%
Block polyisocyanate aqueous dispersion (C-1) 3.75% by mass
Particles 1.50% by mass
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Catalyst (Organic tin compound solid content concentration 14% by mass) 0.30% by mass
Surfactant 0.60% by mass
(Silicone, solid content concentration 10% by mass)

Example 12
An easy-adhesive polyester film was obtained in the same manner as in Example 1 except that the coating solution was changed to the following composition.
27.10% by weight of water
Isopropanol 30.00% by mass
Polyester water dispersion (Aw-1) 12.00% by mass
Polyvinyl alcohol aqueous solution (Bw-4) 24.00% by mass
Block polyisocyanate aqueous dispersion (C-1) 4.50 mass%
Particles 1.50% by mass
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Catalyst (Organic tin compound solid content concentration 14% by mass) 0.30% by mass
Surfactant 0.60% by mass
(Silicone, solid content concentration 10% by mass)

Example 13
An easy-adhesive polyester film was obtained in the same manner as in Example 1 except that the coating solution was changed to the following composition.
Water 30.10% by mass
Isopropanol 30.00% by mass
Polyester water dispersion (Aw-1) 12.00% by mass
Polyvinyl alcohol aqueous solution (Bw-4) 24.00% by mass
Block polyisocyanate aqueous dispersion (C-1) 1.50 mass%
Particles 1.50% by mass
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Catalyst (Organic tin compound solid content concentration 14% by mass) 0.30% by mass
Surfactant 0.60% by mass
(Silicone, solid content concentration 10% by mass)

Example 14
An easily adhesive polyester film was obtained in the same manner as in Example 1 except that the block polyisocyanate aqueous dispersion of the coating solution was changed to C-2.

Example 15
An easily adhesive polyester film was obtained in the same manner as in Example 1 except that the block polyisocyanate aqueous dispersion of the coating solution was changed to C-3.

Example 16
An easily adhesive polyester film was obtained in the same manner as in Example 1 except that the block polyisocyanate aqueous dispersion of the coating solution was changed to C-4.

Example 17
An easily adhesive polyester film was obtained in the same manner as in Example 1 except that the polyvinyl alcohol aqueous solution of the coating solution was changed to Bw-5.

Example 18
An easily adhesive polyester film was obtained in the same manner as in Example 1 except that the polyvinyl alcohol aqueous solution of the coating solution was changed to Bw-6.

Example 19
An easy-adhesive polyester film was obtained in the same manner as in Example 1 except that the coating solution was applied after 24 hours had elapsed.

Example 20
An easy-adhesive polyester film was obtained in the same manner as in Example 1 except that the coating solution was changed to the following composition.
19.10% by mass of water
Isopropanol 30.00% by mass
Polyester water dispersion (Aw-1) 8.00 mass%
Polyvinyl alcohol aqueous solution (Bw-4) 36.00% by mass
Block polyisocyanate aqueous dispersion (C-1) 4.50 mass%
Particles 1.50% by mass
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Catalyst (Organic tin compound solid content concentration 14% by mass) 0.30% by mass
Surfactant 0.60% by mass
(Silicone, solid content concentration 10% by mass)

Comparative Example 1
An easy-adhesive polyester film was obtained in the same manner as in Example 1 except that the coating liquid was formulated as follows.
44.60% by mass of water
Isopropanol 30.00% by mass
Polyester aqueous dispersion (Aw-1) 20.00% by mass
Block polyisocyanate aqueous dispersion (C-1) 3.00 mass%
Particles 1.50% by mass
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Catalyst (Organic tin compound solid content concentration 14% by mass) 0.30% by mass
Surfactant 0.60% by mass
(Silicone, solid content concentration 10% by mass)
Comparative Example 2
An easy-adhesive polyester film was obtained in the same manner as in Example 1 except that the coating liquid was formulated as follows.
Water 31.90% by mass
Isopropanol 30.00% by mass
Polyester water dispersion (Aw-1) 12.00% by mass
Polyvinyl alcohol aqueous solution (Bw-4) 24.00% by mass
Particles 1.50% by mass
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Surfactant 0.60% by mass
(Silicone, solid content concentration 10% by mass)

Comparative Example 3
An easy-adhesive polyester film and an optically laminated polyester film were obtained in the same manner as in Example 1 except that the block polyisocyanate aqueous dispersion was changed to the block polyisocyanate aqueous dispersion (C-5).

Comparative Example 4
An easily adhesive polyester film and an optically laminated polyester film were obtained in the same manner as in Example 1 except that the block polyisocyanate aqueous dispersion was changed to the block polyisocyanate aqueous dispersion (C-6).

Comparative Example 5
The block polyisocyanate aqueous dispersion was changed to a polyisocyanate aqueous dispersion having an isocyanurate structure (WT30-100, manufactured by Asahi Kasei Chemicals) using hexamethylene diisocyanate as a raw material, and a coating solution was prepared and applied 24 hours later. In the same manner as in Example 1, an easily adhesive polyester film was obtained.

Comparative Example 6
An easily adhesive polyester film was obtained in the same manner as in Example 1 except that the polyvinyl alcohol aqueous solution of the coating solution was changed to Bw-7 and the blocked isocyanate aqueous dispersion was changed to (C-5).

The easily-adhesive polyester film in the present invention is excellent in adhesion and appearance, and particularly excellent in adhesion with water-soluble and hydrophilic resins. Therefore, the easily-adhesive polyester film in the present invention is suitable as a base film for an optical member such as a display, and is particularly excellent in adhesion with a polarizer and is suitable as a polarizer protective film.

Claims (6)

A polarizing plate using an easy-adhesive polyester film having a coating layer on at least one side as a polarizer protective film ,
The coating layer contains a polyvinyl alcohol resin and a blocked isocyanate,
A polarizing plate in which the dissociation temperature of the blocked isocyanate is 130 ° C. or lower, the blocking agent is a pyrazole compound, and the boiling point of the blocking agent is 180 ° C. or higher. The polarizing plate of Claim 1 whose saponification degree of the said polyvinyl alcohol-type resin is 95 mol% or less. The polarizing plate according to claim 1 or 2, wherein a mass ratio of the polyvinyl alcohol resin and the blocked isocyanate (polyvinyl alcohol resin / block isocyanate) in the coating layer is 20/1 to 1/1.   The polarizing plate in any one of Claims 1-3 whose haze of a polyester film is 2.0% or less. On the surface opposite to the coating layer of the easy-adhesive polyester film, a hard coat layer, an antiglare layer (AG), an antireflection layer (AR), a low reflection layer (LR), and a low reflection antiglare layer (AG / LR) ), a polarizing plate according to claim 1 formed by laminating at least one functional layer selected from the group consisting of anti-reflection anti-glare layer (AG / AR) and the antistatic layer. At least one reference liquid crystal display device and the polarizing plate according to any one of claims 1 to 5.