CN116438074A

CN116438074A - Easy-to-adhere polyester film

Info

Publication number: CN116438074A
Application number: CN202180076563.7A
Authority: CN
Inventors: 惠岛明纪; 山口洋平
Original assignee: Toyobo Co Ltd
Current assignee: Toyobo Co Ltd
Priority date: 2020-11-24
Filing date: 2021-10-20
Publication date: 2023-07-14
Also published as: TW202229432A; JPWO2022113577A1; KR20230086743A; WO2022113577A1

Abstract

[ problem ]]Provided is an easily adhesive polyester film which is suitable for optical applications and the like by suppressing the decrease in adhesion with time. [ solution ]]An easily adhesive polyester film having a coating layer on at least one side of the polyester film, wherein the coating layer is obtained by curing a composition comprising a polyester having a polycyclic aromatic skeleton and a crosslinking agent having at least one skeleton selected from aliphatic, alicyclic and heterocyclic groups, and the surface of the coating layer on the side not in contact with the polyester film is characterized by 1640cm to be attributed to ureido groups when the surface of the coating layer on the side not in contact with the polyester film is measured by Fourier transform infrared spectrometry (FT-IR) ^‑1 Absorption intensity as peak (I ₁₆₄₀ ) 1410cm from the CH stretch to be attributed to the polyester ^‑1 Absorption intensity as peak (I ₁₄₁₀ ) The relative absorption intensity ratio (I) ₁₆₄₀ /I ₁₄₁₀ ) When the restriction is made, a specific relationship is satisfied.

Description

Easy-to-adhere polyester film

Technical Field

The present invention relates to an easily adhesive polyester film which can ensure low interference properties capable of eliminating the problem of rainbow spots when functional layers such as hard coat layers are laminated, and which is excellent in adhesion to the functional layers, blocking resistance, and transparency. More particularly, the present invention relates to an easily adhesive polyester film suitable for use in more transparent optical applications.

Background

A hard coat film having a transparent hard coat layer laminated thereon is used on the front surface of a display, a decorative material, or the like of a touch panel, a computer, a television, a liquid crystal display, or the like. In addition, as a transparent plastic film of a base material, a transparent polyester film is generally used, and in order to improve adhesion between the polyester film of the base material and a hard coat layer, a coating layer having adhesion is often provided on the surface of the polyester film as an intermediate layer between them.

The hard coat film is required to have temperature, humidity, durability against light, transparency, chemical resistance, abrasion resistance, stain resistance, and the like. In addition, since the composition is often used for a display or a surface of a decorative material, visibility and design are required. Therefore, in order to suppress glare, iridescent color, and the like caused by reflected light when viewed from an arbitrary angle, the following operations are generally performed: an antireflection layer having a multilayer structure in which a high refractive index layer and a low refractive index layer are laminated on each other is provided on the top layer of the hard coat layer.

In recent years, hard coatings having various backbones have been developed, and adhesion of a substrate to the hard coating is discussed every time. Not only the initial adhesion immediately after lamination but also reliability of the product in long-term use with little decrease in humidity and heat resistance, adhesion retention, adhesion with time and the like are required, and products having various evaluation resistances are also required.

In the field of conventional easy-to-adhere polyester films, when a polyester resin using naphthalene dicarboxylic acid as a copolymerization component is used for a coating layer having easy-to-adhere properties, adhesion to a base polyester film is also excellent, and a suitable example is proposed (for example, refer to patent document 1). As a resin having excellent flexibility and high adhesion, a method of using a polyurethane resin having a polycarbonate component has been proposed (for example, see patent document 2).

However, although the adhesion was confirmed, an easily adhesive polyester film which ensured reliability for long-term use was not obtained.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open publication No. 2011-246663

Patent document 2: japanese patent laid-open publication No. 2011-168853

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made in view of the above-described problems of the prior art. That is, an object of the present invention is to provide an easily adhesive polyester film having improved reliability of adhesion, and particularly to provide an easily adhesive polyester film which is suitable for optical applications and the like by suppressing a decrease in adhesion with time.

The present inventors have conducted intensive studies in order to achieve the above object, and as a result, have devised the present invention.

That is, the present invention includes the following configurations.

1. An easily adhesive polyester film having a coating layer on at least one side of the polyester film, wherein the coating layer is obtained by curing a composition comprising a polyester having a polycyclic aromatic skeleton and a crosslinking agent having at least one skeleton selected from aliphatic, alicyclic and heterocyclic groups, and the surface of the coating layer on the side not in contact with the polyester film is characterized by 1640cm to be attributed to ureido groups when the surface of the coating layer on the side not in contact with the polyester film is measured by Fourier transform infrared spectrometry (FT-IR) ^-1 Absorption intensity as peak (I ₁₆₄₀ ) 1410cm from the CH stretch to be attributed to the polyester ^-1 Absorption intensity as peak (I ₁₄₁₀ ) Is strong in relative absorption ofDegree ratio (I) ₁₆₄₀ /I ₁₄₁₀ ) When the restriction is performed, the following relationship is satisfied.

The relative absorption strength ratio (X) obtained by evaluating the film-formed easily adhesive polyester film and the relative absorption strength ratio (Y) obtained by evaluating the polyester film after being left for 24 hours in an environment of 80 ℃ and 90% RH satisfy the following formula (1)

110≤(Y/X)×100≤140···(1)

2. The adhesive polyester film according to item 1 above, wherein the polyester having a polycyclic aromatic skeleton is a polyester having a naphthalene skeleton.

3. The adhesive polyester film according to item 1 or 2, wherein the crosslinking agent having at least one skeleton selected from the group consisting of aliphatic, alicyclic and heterocyclic groups is an isocyanate crosslinking agent having at least one skeleton selected from the group consisting of aliphatic, alicyclic and heterocyclic groups.

4. The adhesive polyester film according to any one of items 1 to 3, wherein the adhesion is 95% or more when a hard coat layer comprising a resin having an aromatic skeleton is provided on the surface of the coating layer.

ADVANTAGEOUS EFFECTS OF INVENTION

The present invention can provide an easily adhesive polyester film which ensures adhesion reliability for a long period of time, and can be widely used for optical applications and the like.

Detailed Description

(polyester film)

The polyester film used as a base material in the present invention is a film mainly composed of a polyester resin. The term "film mainly composed of a polyester resin" as used herein means a film formed from a resin composition containing 50 mass% or more of a polyester resin. Blending with another polymer means that the polyester resin is contained in an amount of 50% by mass or more, and copolymerizing with another monomer means that the polyester resin is contained in an amount of 50% by mole or more. The polyester film preferably contains 90% by mass or more, more preferably 95% by mass or more, still more preferably 100% by mass of the polyester resin.

The material of the polyester resin is not particularly limited, and a copolymer obtained by polycondensing a dicarboxylic acid component and a diol component, or a resin blend thereof may be used. Examples of the dicarboxylic acid component include terephthalic acid, isophthalic acid, phthalic acid, 2, 5-naphthalenedicarboxylic acid, 2, 6-naphthalenedicarboxylic acid, 1, 4-naphthalenedicarboxylic acid, 1, 5-naphthalenedicarboxylic acid, diphenylcarboxylic acid, diphenoxyethane dicarboxylic acid, diphenylsulfone carboxylic acid, anthracene dicarboxylic acid, 1, 3-cyclopentanedicarboxylic acid, 1, 3-cyclohexanedicarboxylic acid, 1, 4-cyclohexanedicarboxylic acid, hexahydroterephthalic acid, hexahydroisophthalic acid, malonic acid, dimethylmalonic acid, succinic acid, 3-diethylsuccinic acid, glutaric acid, 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.

Examples of the diol component constituting the polyester resin include ethylene glycol, propylene glycol, hexamethylene glycol, neopentyl glycol, 1, 2-cyclohexanedimethanol, 1, 4-cyclohexanedimethanol, decamethylene glycol, 1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, 2-bis (4-hydroxyphenyl) propane, and bis (4-hydroxyphenyl) sulfone.

The dicarboxylic acid component and the diol component constituting the polyester resin may be used in an amount of 1 or 2 or more, respectively. In addition, other acid components such as trimellitic acid and other hydroxyl components such as trimethylolpropane may be suitably added.

Specific examples of the polyester resin include polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate, and among these, polyethylene terephthalate is preferable in terms of balance between physical properties and cost. In order to control optical properties such as polarization, it is preferable to include other copolymerizable components and other polymers. From the viewpoint of controlling the optical properties of the polyester film, preferable copolymerization components include diethylene glycol, a copolymerization component having norbornene in a side chain, and the like.

In order to improve the handleability such as slidability and winding property of the polyester film, the film may contain inactive particles, but in order to maintain high transparency, it is preferable that the content of inactive particles in the film is as small as possible. Therefore, it is preferable to have a multilayer structure in which particles are contained only in the surface layer of the film, or to have particles substantially absent in the film, and to have particles contained only in the cover layer laminated on at least one side of the polyester film.

In the case of inorganic particles, for example, the term "substantially free of particles" means a content of 50ppm or less, preferably 10ppm or less, and most preferably a detection limit or less when the element derived from the particles is quantitatively analyzed by fluorescent X-ray analysis. This is because, even if particles are not positively added to the base film, there are cases where foreign matter-derived contaminant components, raw resin, or contaminants adhering to pipelines and devices in the process of producing the film are peeled off and inevitably mixed into the film.

In addition, when the polyester film is formed into a multilayer structure, it is preferable to form two or more layers in which the inner layer contains substantially no inactive particles and only the outermost layer contains inactive particles, so that both transparency and processability can be achieved.

The polyester film as a base material may be a single layer or may be a laminate of 2 or more layers. In addition, various additives may be contained in the film as required within the range of the effect of the present invention. Examples of the additives include antioxidants, photostable agents, antigelling agents, organic wetting agents, antistatic agents, ultraviolet absorbers, and surfactants. When the film has a laminated structure, it is preferable that the film contains additives according to the functions of the respective layers as needed. For example, it is also preferable to add an ultraviolet absorber or the like to the inner layer in order to prevent photodegradation of the polarizing plate.

The polyester film may be manufactured according to a conventional method. For example, the method comprises the following steps: the polyester resin was melt-extruded into a film, and the film was formed by cooling and solidifying the film on a casting drum. As the polyester film in the present invention, either a non-stretched film or a stretched film may be used, but a stretched film is preferable in terms of mechanical strength and durability of chemical resistance. In the case where 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, or the like may be used. In the case of stretching the polyester film, the stretching may be performed before or after the lamination of the later-described easy-to-adhere layer. The uniaxially stretching may be performed in the longitudinal direction or the transverse direction before the lamination of the easy-to-bond layer, and the stretching may be performed in other directions after the lamination of the cover layer.

(coating layer)

The adhesive polyester film of the present invention is obtained by laminating an adhesive coating layer on the polyester base film. The coating layer contains a binder resin and an additive.

The respective compositions of the coating layers are described in detail below.

The binder resin constituting the coating layer is a resin having an easy adhesion property, and from the viewpoints of retention of particles and adhesion, polyester is most preferable, and further, in the present invention, polyester having a polycyclic aromatic skeleton is most preferable. It is also compatible with the composition of a hard coat layer described later, but is also suitable from the standpoint of conjugate interaction when the composition of the hard coat layer has an aromatic skeleton.

Specific examples of the polyester having a polycyclic aromatic skeleton include a polyester having a naphthalene skeleton, a polyester having a fluorene skeleton, a polyester having an anthracene skeleton, a polyester having a phenanthrene skeleton, and the like.

In the present invention, the binder resin constituting the coating layer preferably does not contain a polyurethane resin. From the viewpoint of elasticity and formability of the coating film, it is apparent that the urethane resin is used, but it is preferable that the urethane resin is not contained from the viewpoint of maintaining the stability of adhesion with time, since it is difficult to satisfy the characteristics related to the relative absorption strength ratio described later when the amount of the urea compound present in the coating layer becomes excessive due to the mixing of the urea compound as an impurity.

The polyester is preferably contained in the coating layer in an amount of 10 to 90 mass% based on the percentage by mass of the solid content of the polyester resin relative to the sum of the solid content masses of the resin and the crosslinking agent. More preferably 15% by mass or more and 85% by mass or less. When the content of the polyester resin is 90 mass% or less, the adhesion to the hard coat layer is preferably maintained at high temperature and high humidity. Conversely, if the content is 10 mass% or more, the adhesion to the polyester film at a low temperature and a high humidity is easily maintained, which is preferable.

In the present invention, a crosslinking agent is preferably contained in order to form a crosslinked structure in the coating layer. The crosslinking agent capable of forming urea groups by a side reaction of crosslinking is suitable, and specific examples thereof include isocyanate-based crosslinking agents and carbodiimide-based crosslinking agents. Among these, the isocyanate crosslinking agent is suitable for the stability of the coating liquid with time and the effect of improving the adhesion under high-temperature and high-humidity treatment. Further, in the present invention, an isocyanate having at least one skeleton selected from aliphatic, alicyclic and heterocyclic groups is preferable. In order to promote the crosslinking reaction, a catalyst or the like may be suitably used as needed in the composition for forming a coating layer.

Specific examples of the aliphatic isocyanate include 1, 4-diisocyanato butane, 1, 5-pentamethylene diisocyanate, 2-methyl-1, 5-pentamethylene diisocyanate, 1, 6-hexamethylene diisocyanate, and 1,12& #8722; dodecane diisocyanate, 2, 4-trimethyl-1, 6-hexamethylene diisocyanate, 2, 4& #8722; trimethyl & #8722;1, 6-hexamethylene diisocyanate, 3, 5-trimethyl & #8722;1, 6-hexamethylene diisocyanate, and the like.

Specific examples of the alicyclic isocyanate include cyclohexane diisocyanate, isophorone diisocyanate, 4' -dicyclohexylmethane diisocyanate, 1, 3-bis (isocyanatomethyl) cyclohexane, 1, 4-bis (isocyanatomethyl) cyclohexane, cyclohexyl 1,4& #8722; diisocyanates, 1-bis (isocyanatomethyl) cyclohexane, 2, 4-hexahydrotolylene diisocyanate, 2, 6-hexahydrotolylene diisocyanate, and the like.

Specific examples of the heterocyclic isocyanate include 2, 5-diisocyanatothiophene, 2, 5-bis (isocyanatomethyl) thiophene, 2, 5-diisocyanatotetrahydrofene, 2, 5-bis (isocyanatomethyl) tetrahydrothiophene, 3, 4-bis (isocyanatomethyl) tetrahydrothiophene, 2, 5-diisocyanato-1, 4-dithiane, 2, 5-bis (isocyanatomethyl) -1, 4-dithiane, 4, 5-diisocyanato-1, 3-dithiane, 4, 5-bis (isocyanatomethyl) -1, 3-dithiolane, 4, 5-bis (isocyanatomethyl) -2-methyl-1, 3-dithiolane, 2,6& #8722; di (isocyanatomethyl) furan, 5 '-methylenebis furfuryl isocyanate, 5' -isopropylidene bis furfuryl isocyanate, or trimers of diisocyanates, 2,4, 6-trioxohexahydro-1, 3, 5-triazine-1, 3, 5-trityltri (6, 1-hexanediyl) triisocyanate having a triazine ring called isocyanurate, 1,3, 5-tris [ (5-isocyanato-1, 3-trimethylcyclohexyl) methyl ] -1,3, 5-triazine-2, 4,6 (1H, 3H, 5H) -trione, and the like.

In the present invention, the isocyanate having an aromatic skeleton is highly reactive and easily reacts with moisture in the air, and thus promotes the formation of urea compounds more than necessary, and therefore is preferably not included in the composition for forming a coating layer. Further, from the viewpoint of weather resistance, an isocyanate having at least one skeleton of aliphatic, alicyclic and heterocyclic groups is also preferable.

The solid content of the crosslinking agent in the composition for forming a coating layer is preferably 5% by mass or more and 50% by mass or less, in terms of percentage of the solid content mass of the crosslinking agent relative to the sum of the solid content masses of the resin and the crosslinking agent. More preferably 10 mass% or more and 45 mass% or less. Further preferably 10% by mass or more and 30% by mass or less, and most preferably 10% by mass or more and 20% by mass or less. If the content is 5 mass% or more, the strength of the resin of the coating layer is maintained, and the adhesion at high temperature and high humidity is good, and if the content is 50 mass% or less, the flexibility of the resin of the coating layer is maintained, and the adhesion at normal temperature and high humidity is preferably maintained.

The coating layer in the adhesive polyester film of the present invention is preferably a cured product of a composition comprising a polyester having a polycyclic aromatic skeleton and a crosslinking agent having at least one skeleton selected from aliphatic, alicyclic and heterocyclic groups. The expression of curing the composition is described as such, because it is difficult to appropriately express the chemical composition after the reaction curing due to the crosslinking agent.

(additive)

In the coating layer of the present invention, known additives such as surfactants, antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic slip agents, pigments, dyes, organic or inorganic particles, antistatic agents, nucleating agents, and the like may be added to the extent that the effects of the present invention are not impaired. However, it is preferable not to use an environmentally unfriendly substance or the like.

In the present invention, it is also preferable to add particles to the coating layer in order to further improve the blocking resistance of the coating layer. Examples of the particles contained in the coating layer of the present invention include titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, and the like, or a mixture thereof, and further, examples thereof include: and inorganic particles such as those used in combination with other usual inorganic particles, for example, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, calcium fluoride, etc., and organic polymer particles such as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, silicone-based, etc.

The average particle diameter of the inactive particles in the coating layer (average particle diameter based on the number of SEM: the same shall apply hereinafter) is preferably 0.04 to 2.0. Mu.m, more preferably 0.1 to 1.0. Mu.m. When the average particle diameter of the inactive particles is 0.04 μm or more, irregularities are easily formed on the film surface, and therefore, the film is preferably improved in handleability such as slidability and winding property, and good in workability at the time of bonding. On the other hand, if the average particle diameter of the inactive particles is 2.0 μm or less, the particles are not likely to fall off, which is preferable. The concentration of the particles in the coating layer is preferably 1 to 20% by mass in the solid content.

The thickness of the coating layer in the present invention can be suitably set in the range of 0.001 to 2.00. Mu.m, preferably in the range of 0.01 to 1.00. Mu.m, more preferably in the range of 0.02 to 0.80. Mu.m, still more preferably in the range of 0.05 to 0.50. Mu.m, for the purpose of simultaneously improving the workability and the adhesion. If the thickness of the coating layer is 0.001 μm or more, the adhesion is good, which is preferable. If the thickness of the coating layer is 2.00 μm or less, blocking is less likely to occur, which is preferable.

The present invention is a urea compound whose crosslinking agent component present in a composition for forming a coating layer is deformed by a reaction with moisture in the air or the like, and focuses on a change in the amount of the crosslinking agent component present.

When the surface of the coating layer of the easily adhesive polyester film of the present invention is measured by Fourier transform infrared spectroscopy (FT-IR), the coating layer is classified into 1640cm to be ureido groups ^-1 Absorption intensity as peak (I ₁₆₄₀ ) With 1410cm of CH stretch attributed to polyester having a polycyclic aromatic backbone ^-1 Absorption intensity as peak (I ₁₄₁₀ ) The relative absorption intensity ratio (I) ₁₆₄₀ /I ₁₄₁₀ ) The greater the relative absorption intensity ratio, the more urea compound is formed in the coating layer when the limiting is made. 1640cm ascribed to urea compound ^-1 The peak does not necessarily appear exactly at 1640cm ^-1 There is 1640.+ -.5 cm ^-1 Left and right amplitude. In addition, 1410cm of a polyester resin having a polycyclic aromatic skeleton ^-1 The peak does not necessarily appear exactly at 1410cm ^-1 There is 1410.+ -.5 cm ^-1 Left and right amplitude.

The relative absorption strength ratio (X) obtained by evaluating the film-formed easy-to-adhere polyester film and the relative absorption strength ratio (Y) obtained by evaluating the easy-to-adhere polyester film after being kept in an environment of 80 ℃ and 90% rh for 24 hours preferably satisfy the following relationship (1).

110≤(Y/X)×100≤140···(1)

In the present invention, "after film formation" means that a sample is placed in a certain environment after film production, and is within 240 hours. Specifically, the term "temperature" in the above-mentioned constant environment means 5 ℃ or higher and 40 ℃ or lower, and the term "humidity" means an environment of 30% RH to 60% RH or lower. If the sample is kept in these ranges, it is preferable that the change with time is not confirmed, and that the sample is called an initial state is confirmed.

In the polyester film of the present invention, the (Y/X) ×100 of the coating layer present on the film surface is preferably 140 or less, more preferably 130 or less. If 140 or less, the ratio of urea in the coating layer is not excessively large, and problems of deterioration in the stability and reliability of adhesion with time due to adsorption of more moisture in the air by the urea compound having a polar group can be prevented. If the (Y/X). Times.100 is 110 or more, the content of the crosslinking agent is insufficient, and the reaction such as crosslinking can be properly performed to obtain adhesion and adhesion reliability, which is preferable.

In this case, it is possible to evaluate the adhesion-promoting polyester film by the ratio of the relative absorption strength before and after the film is left in a room temperature environment of about several weeks to several months, but it is preferable that the film is left in a high temperature and high humidity environment of 80 ℃ and 90% rh for 24 hours as an alternative measurement because the film is difficult to be left in a left standing condition.

In order to satisfy the relation (1) of the relative absorption intensity ratio, it is preferable to control the ratio of the resin to the crosslinking agent in the coating layer. By increasing the resin component in the composition for forming a coating layer, the values of X and Y gradually increase, and the total solid content of the resin component and the crosslinking agent component is preferably 70 mass% or more, assuming that the total solid content is 100 mass%. More preferably 75% by mass or more, still more preferably 80% by mass or more. If the amount is 70 mass% or more, the ratio of the crosslinking agent is not excessively large, and the ratio of the excessive urea compound can be reduced, so that it becomes easy to satisfy the relation (1). However, these means are merely examples, and the use of other implementation means is not excluded. When the total solid content of the resin component and the crosslinking agent component is 100% by mass, the solid content of the crosslinking agent component is preferably 30% by mass or less, more preferably 25% by mass or less, and still more preferably 20% by mass or less.

In this case, the value of X is preferably 1.78 or less. More preferably 1.60 or less, and still more preferably 1.41 or less. The resin component is increased, and the crosslinking agent component is reduced, so that the proportion of the excessive urea compound can be reduced, and the hard coat adhesion is preferably improved. On the other hand, the value of X is preferably 1.10 or more, and the addition ratio for the crosslinking reaction with the resin can be satisfied, and the adhesion with the hard coat layer at high temperature and high humidity is preferably satisfied. The value of X is more preferably 1.15 or more, and still more preferably 1.20 or more.

The value of Y is preferably 2.70 or less. More preferably 2.30 or less, and still more preferably 1.85 or less. The crosslinking agent component is reduced, so that the occurrence ratio of the excessive urea compound can be reduced with time, and the hard coat adhesion is preferably improved. On the other hand, if the value of Y is 0.90 or more, the addition ratio for the crosslinking reaction with the resin can be satisfied, and the adhesion with the hard coat layer at high temperature and high humidity is preferably satisfied. The value of Y is more preferably 1.20 or more, and still more preferably 1.40 or more.

The composition for forming a coating layer may contain a surfactant for the purpose of improving leveling property at the time of coating and defoaming of a coating liquid. The surfactant may be cationic, anionic, nonionic, etc., and is preferably a silicone surfactant, an acetylene glycol surfactant or a fluorine surfactant. These surfactants are preferably contained in the composition for forming a coating layer within a range that does not deteriorate the effect of suppressing iridescent color and the degree of adhesion under a fluorescent lamp.

As the coating method, either a so-called in-line coating method in which coating is performed simultaneously when the film is made of a polyester base film, or a so-called off-line coating method in which coating is performed separately by a coater after the film is made of a polyester base film can be applied, and the in-line coating method is effective and more preferable.

As a coating method, a method for applying a coating liquid to a polyethylene terephthalate (hereinafter abbreviated as PET) film may be any known method. Examples thereof include reverse roll coating, gravure coating, kiss coating, die coating, roll brushing, spray coating, air knife coating, bar coating, tube doctor blade coating, impregnation coating, curtain coating, and the like. These methods may be applied singly or in combination.

In the present invention, as a method of providing a coating layer on a polyester film, there is a method of applying a coating liquid containing a solvent, particles, and a resin to a polyester film and drying the same. The solvent may be water or a mixture of water and an organic solvent, and from the viewpoint of environmental problems, water alone or a mixture of water and an organic solvent that is water-soluble is preferable.

Examples of the water-soluble organic solvent include alcohols such as isopropyl alcohol and ethyl alcohol, ketones such as methyl ethyl ketone, ethers such as butyl cellosolve, amines such as triethanolamine, and amides such as N-methylpyrrolidone.

The solid content concentration of the coating liquid also depends on the kind of the binder resin, the kind of the solvent, and the like, and is preferably 2 mass% or more, more preferably 4 mass%. The solid content concentration of the coating liquid is preferably 35% by mass or less, more preferably 15% by mass or less.

The drying temperature after the application is also preferably 80 ℃ or more and preferably 250 ℃ or less depending on the kind of the binder resin, the kind of the solvent, the presence or absence of the crosslinking agent, the solid content concentration, and the like.

(production of easily bondable polyester film)

The polyester film which is the base material of the easy-to-adhere polyester film of the present invention can be produced according to a general production method of a polyester film. For example, the following methods can be mentioned: the polyester resin is melted, extruded and formed into a sheet to obtain an unoriented polyester, the unoriented polyester obtained is stretched in the machine direction at a temperature equal to or higher than the glass transition temperature by using a difference in speed of rolls, and then stretched in the transverse direction by a tenter, and heat treatment is performed.

In the present invention, the polyester film may be a uniaxially stretched film or a biaxially stretched film, and when the biaxially stretched film is used as a protective film on the front surface of a liquid crystal panel, rainbow-like color spots are not observed even when viewed from directly above the film surface, but rainbow-like color spots are sometimes observed when viewed from an oblique direction, and therefore, attention is required.

This phenomenon is because the biaxially stretched film is composed of refractive index ellipsoids having different refractive indices in the advancing direction, the width direction, and the thickness direction, and the retardation amount is zero (the refractive index ellipsoids are visible as perfect circles) depending on the transmission direction of light inside the film. Therefore, if the liquid crystal display screen is viewed from a specific direction of the oblique direction, there is a case where a dot whose retardation amount is zero is generated, and an iridescent color patch is generated concentrically around the dot. If the angle at which the iridescent color spot is observed from directly above (in the normal direction) the film surface is defined as θ, the greater the birefringence in the film surface, the greater the angle θ becomes, and the more iridescent color spot becomes difficult to observe. Since the angle θ tends to be small in the biaxially stretched film, it is preferable that the biaxially stretched film has a structure in which rainbow-like color spots are less likely to be observed.

However, a completely uniaxial (uniaxially symmetric) film is not preferable because the mechanical strength in the direction perpendicular to the orientation direction is significantly reduced. The present invention preferably has biaxiality (biaxiality) in a range in which substantially no rainbow-like color unevenness is generated or in a range in which no rainbow-like color unevenness is generated in a viewing angle range required for a liquid crystal display screen.

(laminated polyester film)

In the present invention, a laminated polyester film mainly used for optical applications is obtained by providing a hard coat layer formed of an electron beam or ultraviolet curable acrylic resin, a silicone thermosetting resin, or the like on the coating layer of the easily adhesive polyester film of the present invention.

It is also preferable to provide a functional layer on the coating layer of the easy-to-adhere polyester film of the present invention. The functional layer is a layer having a functional property such as an antiglare layer, an antiglare antireflection layer, an antireflection layer, a low reflection layer, an antistatic layer, or the like, in addition to the hard coat layer described above, for the purposes of antireflection, glare suppression, iridescence suppression, scratch suppression, or the like. The functional layer may be any of various materials known in the art, and the kind thereof is not particularly limited. Hereinafter, each functional layer will be described.

For example, a known hard coat layer may be used in the formation of the hard coat layer, and a resin compound polymerized and/or reacted by drying, heat, chemical reaction, or irradiation with any of electron beam, radiation, and ultraviolet rays may be used without particular limitation. Examples of such curable resins include melamine-based, acrylic-based, silicone-based, and polyvinyl alcohol-based curable resins, and photocurable acrylic-based curable resins are preferable in terms of obtaining high surface hardness and optical design. As such an acrylic curable resin, a polyfunctional (meth) acrylate monomer and an acrylate oligomer can be used, and examples of the acrylate oligomer include polyester acrylate, epoxy acrylate, urethane acrylate, polyether acrylate, polybutadiene acrylate, and silicone acrylate. By mixing a reaction diluent, a photopolymerization initiator, a sensitizer, and the like with these acrylic curable resins, a coating composition for forming the optical functional layer can be obtained.

The hard coat layer may have an antiglare function (antiglare function) of scattering external light. The antiglare function (antiglare function) can be obtained by forming irregularities on the surface of the hard coat layer. In this case, the haze of the film is preferably 0 to 50%, more preferably 0 to 40%, particularly preferably 0 to 30%. Of course, 0% is preferable, and may be 0.2% or more, or 0.5% or more.

In order to perform a low reflection process (anti-reflection process) for suppressing reflection of light by providing a layer having a different refractive index and changing the light transmission characteristic, it is preferable to adjust the refractive index between the hard coat layer and the functional layer and preferably achieve a reflectance of 0 to 1.0%, more preferably 0 to 0.8%, and particularly preferably 0 to 0.5%. Of course, 0% is preferable, and may be 0.05% or more, or 0.1% or more.

In particular, as the hard coat composition used in the present invention, a resin containing an aromatic component in a proportion of 5 mol% or more and 20 mol% or less relative to the total mole number of the monomers and oligomers constituting the resin is generally used for adjusting the refractive index.

The use of the polyester film having easy adhesion and the laminated polyester film having a functional layer laminated on its coating layer of the present invention mainly covers the entire optical film, and is particularly suitable for use as a base film for optical members such as prism lens sheets, AR (anti-reflection) films, hard coat films, diffusion plates, shatter prevention films, and the like, LCD, flat TV, CRT, and the like, near infrared absorption filters as members in front panels for plasma displays, touch panels, transparent conductive films for electroluminescence, and the like.

As the acrylic resin cured by electron beam or ultraviolet ray for forming the hard coat layer, specifically, one having an acrylate-based functional group, for example, may be used: lower molecular weight polyester resins, polyether resins, acrylic resins, epoxy resins, polyurethane resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins; an oligomer or prepolymer of a (meth) acrylate or the like containing a polyfunctional compound such as a polyol, and a monofunctional monomer such as ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, methylstyrene, N-vinylpyrrolidone or the like as a reactive diluent, a polyfunctional monomer such as trimethylolpropane tri (meth) acrylate, hexanediol (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate or the like.

In the case of an electron beam or ultraviolet curable resin, acetophenones, benzophenones, michler's benzoyl benzoate, a-a Mi Luoji ester (a-amyox ester), tetramethylthiuram monosulfide, thioxanthones, which are photopolymerization initiators, may be mixed with the above resin, or n-butylamine, triethylamine, tri-n-butylphosphine, and the like, which are photosensitizers, may be used.

The silicone-based (siloxane-based) thermosetting resin can be produced by subjecting an organosilane compound alone or in combination with 2 or more of them to hydrolysis and condensation reactions in the presence of an acid or base catalyst. In particular, in the case of low reflection, when 1 or more fluorosilane compounds are mixed and subjected to hydrolysis and condensation reaction, the composition is further excellent in improvement of low refractive index, stain resistance and the like.

(production of laminated polyester film)

The method for producing the laminated polyester film using the easily adhesive polyester film of the present invention is described, but is not limited to the specific examples described.

The electron beam or ultraviolet curable acrylic resin, oligomer, monomer or siloxane thermosetting resin is coated on the coating layer of the adhesive polyester film. In the case of two sides provided with coating layers, the coating is applied on at least one coating layer. The coating liquid does not need to be diluted particularly, but there is no particular problem even if diluted with an organic solvent according to the needs of the viscosity, wettability, coating film thickness, and the like of the coating liquid. The hard coat layer is formed by applying the coating liquid onto the film, drying the film as necessary, and curing the coating layer by electron beam or ultraviolet irradiation and heating in accordance with the curing conditions of the coating liquid.

In the present invention, the thickness of the hard coat layer is preferably 1 to 15. Mu.m. If the thickness of the hard coat layer is 1 μm or more, the effect of chemical resistance, abrasion resistance, stain resistance and the like on the hard coat layer is effectively exhibited, and it is preferable. On the other hand, if the thickness is 15 μm or less, the flexibility of the hard coat layer can be maintained, and there is no fear of occurrence of cracks or the like, which is preferable.

As scratch resistance, it is preferable that the coated surface is not visually scratched when the coated surface is abraded with a black backing paper. If the scratch is not obvious in the above evaluation, it is not easy to scratch when passing through the guide roller, and is preferable from the viewpoint of operability.

The easy-to-adhere polyester film and the laminated polyester film of the present invention are mainly used for optical applications, and therefore, preferably have high transparency. The lower limit of the haze is desirably 0%, and more preferably, the closer to 0%. The upper limit of the haze is preferably 2% or less, and if it is 2% or less, the light transmittance is good, and a clear image can be obtained in the liquid crystal display device. The haze of the polyester film can be measured, for example, by a method described below.

The adhesion between the coating layer having the adhesion-facilitating property and the hard coat layer is preferably 95% or more based on the evaluation by the measurement method described later. More preferably 98% or more, still more preferably 100%. If the content is 95% or more, it can be said that the adhesion between the coating layer and the hard coat layer is sufficiently maintained.

The adhesion between the easy-to-adhere layer and the hard coat layer evaluated by the method described later under the conditions of 80 ℃ and 95% rh high temperature and high humidity is preferably 95% or more as described above. More preferably 98% or more, still more preferably 100%. If the content is 95% or more, the adhesion between the adhesive layer and the hard coat layer under high temperature and high humidity conditions can be satisfied at one time, and the passability in the post-processing step can be satisfied at one time.

In this case, it may be desirable if the easy-to-adhere polyester film can be evaluated for adhesion after being left to stand in a room temperature environment of about several weeks to several months, but since it is difficult to carry out a standing measurement, it is assumed that the easy-to-adhere polyester film is evaluated by being left to stand in a high temperature and high humidity environment of 80 ℃ and 90% rh for 24 hours at an accelerated rate as an alternative measurement.

The adhesive polyester film of the present invention can be used for various applications, and is preferably used in a process for producing a polarizing plate used in a liquid crystal display device, and particularly preferably used as a protective film for a polarizing plate constituting the polarizing plate. In general, the polarizing plate is often made of polyvinyl alcohol, and the easy-to-adhere polyester film of the present invention is adhered to the polarizing plate by an adhesive made of polyvinyl alcohol and having a crosslinking agent or the like added thereto, if necessary. In this case, the coating layer of the easy-to-adhere polyester film of the present invention is more preferably used not to the surface on the side to which the polarizing plate is adhered but to the opposite surface. On the surface of the adhesive polyester film of the present invention to which the polarizing plate is adhered, an adhesive layer containing a polyester resin, a polyvinyl alcohol resin, and a crosslinking agent, for example, as described in international publication No. 2012/105607, is preferably laminated.

Examples

Next, the present invention will be described in detail with reference to examples, comparative examples and reference examples, but the present invention is of course not limited to the following examples. The evaluation method used in the present invention is as follows.

(1) Average particle diameter

[ scanning Electron microscope-based assay ]

The average particle diameter of the particles can be measured by the following method. For the particles, a photograph was taken with a Scanning Electron Microscope (SEM), and the maximum particle diameter (distance between 2 points farthest from) of 300 to 500 particles was measured at a magnification of 2 to 5mm for 1 particle size as the smallest particle, and the average value was taken as the average particle diameter. The average particle size of the particles present in the coating layer in the present invention can be determined by this assay.

[ dynamic light scattering method ]

The average particle diameter of the particles can also be obtained by a dynamic scattering method in the production of the particles and the thin film. The sol was diluted with a dispersion medium, and the average particle diameter was obtained by calculation using a cumulative method by measuring with a submicron particle analyzer N4 PLUS (manufactured by Beckman Coulter Co.) using parameters of the dispersion medium. In the dynamic light scattering method, the average particle diameter of particles in the sol is observed, and when particles are aggregated with each other, the average particle diameter of the aggregated particles is observed.

(2) Refractive index of particles

The refractive index of the particles can be measured by the following method. The inorganic particles were dried at 150 ℃ and pulverized in a mortar to obtain a powder, and the obtained powder was immersed in a solvent 1 (having a lower refractive index than the particles) and then a solvent 2 (having a higher refractive index than the particles) was added little by little until the particles became substantially transparent. The refractive index of the solution was measured with an Abbe refractometer (ATAOCO., LTD. Abbe refractometer). The measurement was performed at 23℃under D-rays (wavelength 589 nm). The solvent 1 and the solvent 2 are selected to be miscible with each other, and examples thereof include solvents such as 1, 3-hexafluoro-2-propanol, chloroform, carbon tetrachloride, toluene, and glycerol, depending on the refractive index.

(3) Haze of easily adhesive polyester film for optical use

Haze of the easy-to-adhere polyester film was in accordance with JIS K7136: 2000, measured by a turbidity meter (NDH 2000, japan electric color system).

(4) Adhesion of

The hard coat layer described in the item of the formation of the hard coat layer was formed on the easy-to-adhere layer of the polyester film obtained in the example. The adhesion between the hard coat layer and the base film was determined according to the disclosure of JIS-K5400-1990, 8.5.1, for the polyester film for easy adhesion on which the hard coat layer was formed.

Specifically, the hard coat layer was penetrated by a cutter rail having a gap of 2mm, and 100 grid-like scratches were formed on the hard coat layer surface. Then, a cellophane tape (manufactured by Nichiban, no. 405; 24mm wide) was adhered to the surface of the scratch in a grid shape, and the scratch was wiped with an eraser to allow the scratch to adhere completely. Then, the cellophane tape was peeled off perpendicularly from the hard coat layer surface of the hard coat layer-laminated polarizing plate protective film, and the number of the cells peeled off from the hard coat layer surface of the hard coat layer-laminated polarizing plate protective film was visually counted, and the adhesion between the hard coat layer and the base film was determined by the following formula. The partial stripper in the mesh is also counted as the stripped mesh.

Adhesion (%) = {1- (number of peeled grids/100) } ×100

(5) Moist heat resistance (adhesion after standing at 80 ℃ and 90% RH)

The obtained adhesive polyester film was left in a high temperature and high humidity tank at 80℃under 90% RH for 24 hours, and then left at room temperature (20℃under 65% RH) for 12 hours. Thereafter, a hard coat layer was formed in the same manner as described above, and adhesion to the base film was obtained.

(6) Number average molecular weight

The resin (0.03 g) was dissolved in tetrahydrofuran (10 ml), and the number average molecular weight was measured by a GPC-LALLS apparatus low angle light scattering photometer LS-8000 (manufactured by Tosoh Co., ltd., tetrahydrofuran solvent, control: polystyrene) using a column (Shodex KF-802, 804, 806 manufactured by Showa electric Co., ltd.) at a column temperature of 30℃and a flow rate of 1 ml/min.

(7) Absorbance determination based on infrared spectroscopy

The obtained optical adhesive polyester film was subjected to FT-IR ATR measurement under the following conditions.

The device comprises: cary670FTIR (Agilent Co., ltd.)

An accessory: specTA-Tech Foundation Thunder Dome Ge45 primary reflection detector: TGS (TGS)

Resolution ratio: 4cm ^-1

Cumulative number of times: 128 times

1640cm ^-1 The peak intensity is from about 1540cm ^-1 Along the horizontal direction, a base line is drawn, and the height (I) of the peak top from the base line is obtained ₁₆₄₀ )。

1410cm ^-1 The peak intensity is about 1420cm to be connected ^-1 Is about 1390cm ^-1 The line of the trough of (a) is used as a base line, and the height (I) of the peak top from the base line is obtained ₁₄₁₀ )。

Relative absorption intensity ratio to calculate I ₁₆₄₀ And I ₁₄₁₀ Ratio (I) ₁₆₄₀ /I ₁₄₁₀ ) And the result was obtained.

For the measurement, data "I" measured and calculated immediately after film formation was obtained ₁₆₄₀ /I ₁₄₁₀ (X) ", and data" I "calculated by using measurement of a sample after film formation, which was left in a high temperature and high humidity tank at 80℃under 90% RH for 24 hours and then left at room temperature (20℃under 65% RH) for 12 hours ₁₆₄₀ /I ₁₄₁₀ (Y) ", and" (Y/X). Times.100 ".

(polymerization of the copolyester resin (A) for coating layer)

Into a stainless steel autoclave equipped with a stirrer, a thermometer and a partial reflux condenser, 342.0 parts by mass of dimethyl 2, 6-naphthalate, 35.0 parts by mass of dimethyl terephthalate, 35.5 parts by mass of dimethyl isophthalate-5-sodium sulfonate, 198.6 parts by mass of ethylene glycol, 118.2 parts by mass of 1, 6-hexanediol, and 0.4 parts by mass of tetra-n-butyl titanate were charged, and transesterification was performed at a temperature of 160℃to 220℃for 4 hours. Further, 60.7 parts by mass of sebacic acid was added to carry out an esterification reaction. Then, the temperature was raised to 255℃and the reaction system was slowly depressurized, followed by reaction under a reduced pressure of 30Pa for 1 hour and 30 minutes to obtain a copolyester resin (A). The resulting copolyester resin (A) was pale yellow transparent. The reduced viscosity of the copolyester resin (A) was measured and found to be 0.72dl/g. The glass transition temperature based on DSC was 40℃and the number average molecular weight was 20000.

(polymerization of the copolyester resin (B) for coating layer)

Into a stainless steel autoclave equipped with a stirrer, a thermometer and a partial reflux condenser, 293.0 parts by mass of dimethyl 2, 6-naphthalate, 128.0 parts by mass of dimethyl terephthalate, 41.6 parts by mass of dimethyl isophthalate-5-sodium sulfonate, 125.0 parts by mass of ethylene glycol, 105.0 parts by mass of diethylene glycol, 142.0 parts by mass of 1, 6-hexanediol, and 0.4 part by mass of tetra-n-butyl titanate were charged, and transesterification was performed at a temperature of 160℃to 220℃for 4 hours. Then, the temperature was raised to 255℃and the reaction system was slowly depressurized, followed by reaction under a reduced pressure of 30Pa for 1 hour and 30 minutes to obtain a copolyester resin (B). The resulting copolyester resin (B) was pale yellow transparent. The reduced viscosity of the copolyester resin (B) was measured and found to be 0.69dl/g. The DSC-based glass transition temperature was 30℃and the number average molecular weight was 21000.

(polymerization of the copolyester resin (C) for coating layer)

Into a stainless steel autoclave equipped with a stirrer, a thermometer and a partial reflux condenser, 145.6 parts by mass of dimethyl terephthalate, 14.8 parts by mass of sodium isophthalate-5-sulfonate, 43.3 parts by mass of dimethyl azelate, 80.7 parts by mass of ethylene glycol, 131.6 parts by mass of 9, 9-bis [4- (2-hydroxyethoxy) phenyl ] fluorene, 70.9 parts by mass of 3-methyl-1, 5-pentanediol and 0.4 parts by mass of tetra-n-butyl titanate were charged, and transesterification was performed at a temperature of 160℃to 220℃for 4 hours. Then, the temperature was raised to 255℃and the reaction system was slowly depressurized, followed by reaction under a reduced pressure of 30Pa for 1 hour and 30 minutes to obtain a copolyester resin (C). The resulting copolyester resin (C) was pale yellow transparent. The reduced viscosity of the copolyester resin (C) was measured and found to be 0.65dl/g. The DSC-based glass transition temperature was 40℃and the number average molecular weight was 19000.

(polymerization of the copolyester resin (D) for coating layer)

A copolyester resin (D) was obtained in the same manner as in the polymerization of the resin (a), except that 194.2 parts by mass of dimethyl terephthalate, 184.5 parts by mass of dimethyl isophthalate, 14.8 parts by mass of dimethyl isophthalate-5-sodium sulfonate, 233.5 parts by mass of diethylene glycol, 136.6 parts by mass of ethylene glycol, and 0.2 part by mass of tetra-n-butyl titanate were used. The reduced viscosity of the resulting copolyester resin (D) was measured and found to be 0.70dl/g. The glass transition temperature based on DSC was 40 ℃.

(preparation of aqueous polyester Dispersion (Aw), (Bw), (Cw), (Dw))

In a reactor equipped with a stirrer, a thermometer and a reflux apparatus, 30 parts by mass of a copolyester resin (A) and 15 parts by mass of ethylene glycol n-butyl ether were placed, and the mixture was heated and stirred at 110℃to dissolve the resin. After the resin was completely dissolved, 55 parts by mass of water was slowly added to the polyester solution with stirring. After the addition, the solution was stirred and cooled to room temperature to prepare an aqueous dispersion (resin a solution) (Aw) of a milky polyester resin (a) having a solid content of 25.0 mass%.

In the same manner, an aqueous polyester resin (B) dispersion (resin B solution) (Bw) in which the copolymerized polyester resin (B) is dissolved was prepared.

In the same manner, an aqueous polyester resin (C) dispersion (resin C solution) (Cw) in which the copolymerized polyester resin (C) is dissolved was produced.

In the same manner, an aqueous dispersion (resin D solution) (Dw) of the polyester resin (D) in which the copolymerized polyester resin (D) is dissolved was prepared.

(production of polyurethane aqueous Dispersion (E))

[ polymerization of Water-dispersible polyurethane resin comprising aliphatic polycarbonate polyol as constituent component ]

43.75 parts by mass of 4,4' -diphenylmethane diisocyanate, 12.85 parts by mass of dimethylol butanoic acid, 153.41 parts by mass of polyhexamethylene carbonate diol having a number average molecular weight of 2000, 0.03 part by mass of dibutyltin dilaurate, and 84.00 parts by mass of acetone as a solvent were charged into a four-necked flask equipped with a stirrer, a serpentine condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, and the mixture was stirred under a nitrogen atmosphere at 75℃for 3 hours, whereby it was confirmed that the reaction solution had reached a predetermined amine equivalent. Subsequently, the reaction solution was cooled to 40℃and then 8.77 parts by mass of triethylamine was added thereto to obtain a polyurethane prepolymer solution. Then, 450g of water was added to a reaction vessel equipped with a high-speed stirring homogenizer, and the temperature was adjusted to 25℃for 2000 minutes ^-1 The polyurethane prepolymer solution was added while stirring and mixing to disperse in water. After that, the process is carried out,a portion of acetone and water was removed under reduced pressure, thereby preparing a water-soluble polyurethane resin solution (resin E solution) having a solid content of 37 mass%. The glass transition temperature of the polyurethane resin obtained was-30 ℃.

(Synthesis of crosslinker P)

To 100 parts by mass of a polyisocyanate compound (NCO concentration 23.1%) having an isocyanurate structure and 17.5 parts by mass of N-methylpyrrolidone, which were produced from 1, 6-hexamethylene diisocyanate by a conventional method, 35.00 parts by mass of 3, 5-dimethylpyrazole was added dropwise to a flask equipped with a stirrer, a thermometer and a reflux condenser, and the mixture was kept at 70℃for 1 hour under a nitrogen atmosphere. After that, 12.50 parts by mass of dimethylolpropionic acid was added dropwise. After confirming the disappearance of the absorption of the isocyanate group by measuring the infrared spectrum of the reaction solution, 8.72 parts by mass of N, N-dimethylethanolamine was added. After stirring for 1 hour in this state, a proper amount of water was added to obtain a blocked isocyanate aqueous dispersion (crosslinker P solution) having a solid content of 40 mass%.

(Synthesis of crosslinker Q)

To 100 parts by mass of a polyisocyanate compound (NCO concentration 23.3%) having an isocyanurate structure and 17.5 parts by mass of N-methylpyrrolidone, which were produced from cyclohexane diisocyanate according to a conventional method, 35.00 parts by mass of 3, 5-dimethylpyrazole was added dropwise to a flask equipped with a stirrer, a thermometer and a reflux condenser, and the mixture was kept at 70℃for 1 hour under a nitrogen atmosphere.

After that, 12.50 parts by mass of dimethylolpropionic acid was added dropwise. After confirming the disappearance of the absorption of the isocyanate group by measuring the infrared spectrum of the reaction solution, 8.72 parts by mass of N, N-dimethylethanolamine was added. After stirring for 1 hour in this state, a proper amount of water was added to obtain a blocked isocyanate aqueous dispersion (crosslinking agent Q solution) having a solid content of 40 mass%.

(Synthesis of crosslinker R)

To 100 parts by mass of a polyisocyanate compound (NCO concentration 23.1%) having an isocyanurate structure and 17.5 parts by mass of N-methylpyrrolidone, which were produced from 2, 5-diisocyanatothiophene according to a conventional method, 35.00 parts by mass of 3, 5-dimethylpyrazole was added dropwise to a flask equipped with a stirrer, a thermometer and a reflux condenser, and the mixture was kept at 70℃for 1 hour under a nitrogen atmosphere.

After that, 12.50 parts by mass of dimethylolpropionic acid was added dropwise. After confirming the disappearance of the absorption of the isocyanate group by measuring the infrared spectrum of the reaction solution, 8.72 parts by mass of N, N-dimethylethanolamine was added. After stirring for 1 hour in this state, a proper amount of water was added to obtain a blocked isocyanate aqueous dispersion (crosslinker R solution) having a solid content of 40 mass%.

(Synthesis of crosslinker S)

Into a flask equipped with a stirrer, a thermometer and a reflux condenser, 168 parts by mass of hexamethylene diisocyanate and 220 parts by mass of polyethylene glycol monomethyl ether (average molecular weight 400) were charged and stirred at 120℃for 1 hour, 26 parts by mass of 4,4' -dicyclohexylmethane diisocyanate and 3.8 parts by mass (2% by mass relative to the total amount of isocyanate) of 3-methyl-1-phenyl-2-phosphorus-1-oxide as a carbodiimidization catalyst were further added, and the mixture was stirred under a nitrogen flow at 185℃for 5 hours. The infrared spectrum of the reaction solution was measured to confirm the disappearance of the absorption of isocyanate groups. Naturally cooled to 60 ℃, 567 parts by mass of ion-exchanged water was added to obtain a carbodiimide-based crosslinking agent (crosslinking agent S solution) having a solid content of 40% by mass.

(Synthesis of crosslinker T)

To 100 parts by mass of a polyisocyanate compound (NCO concentration of 22.3%) having an isocyanurate structure and 17.5 parts by mass of N-methylpyrrolidone, which were produced from 2, 4-toluene diisocyanate by a conventional method, 35.00 parts by mass of 3, 5-dimethylpyrazole was added dropwise to a flask equipped with a stirrer, a thermometer and a reflux condenser, and the mixture was kept at 70℃for 1 hour under a nitrogen atmosphere.

After that, 12.50 parts by mass of dimethylolpropionic acid was added dropwise. After confirming the disappearance of the absorption of the isocyanate group by measuring the infrared spectrum of the reaction solution, 8.72 parts by mass of N, N-dimethylethanolamine was added. After stirring for 1 hour in this state, a proper amount of water was added to obtain a blocked isocyanate aqueous dispersion (crosslinking agent tsolution) having a solid content of 40 mass%.

(zirconia particles)

Into a 3 liter glass vessel, 2283.6g of pure water and 403.4g of oxalic acid dihydrate were charged, and the mixture was heated to 40℃to prepare a 10.72 mass% oxalic acid aqueous solution. While stirring the aqueous solution, zirconium oxychloride powder (ZrOCO) was slowly added ₃ AMR International Corp, converted to ZrO ₂ Contains 39.76 mass%) of 495.8g, and after mixing for 30 minutes, heating was performed at 90℃for 30 minutes. Then, 1747.2g of 25.0% by mass aqueous tetramethylammonium hydroxide (manufactured by Mimo chemical Co., ltd.) was slowly added over 1 hour. At this time, the mixed solution was in the form of a slurry of ZrO ₂ The content in the content was 4.0 mass%. The slurry was transferred to a stainless steel autoclave vessel and subjected to hydrothermal treatment at 145 ℃ for 5 hours. The product after the hydrothermal treatment has no non-peptized matter and is completely dissolved. The sol obtained is obtained as ZrO ₂ The content was 4.0 mass%, the pH was 6.8, and the average particle diameter by the dynamic light scattering method was 19nm. In addition, the sol was adjusted to ZrO with pure water ₂ The transmittance measured at a concentration of 2.0 mass% was 88%. As a result of observation of the particles by a transmission electron microscope, zrO was substantially at about 7nm ₂ Aggregate particles of primary particles. ZrO obtained by performing the above-mentioned hydrothermal treatment ₂ 4000g of zirconia sol having a concentration of 4.0 mass%, and washing and concentrating the sol while slowly adding pure water by using an ultrafiltration device to obtain ZrO ₂ Concentration of 13.1 mass%, pH4.9, zrO ₂ Zirconia sol 953g having a transmittance of 76% at a concentration of 13.1 mass%. The refractive index of the obtained zirconia-based particles was 1.75.

(zirconia sol)

ZrO obtained by the above-mentioned washing and concentration ₂ 300g of zirconia sol having a concentration of 13.1 mass% was added with 3.93g of a 20 mass% aqueous citric acid solution and 11.0g of a 25 mass% aqueous tetramethylammonium hydroxide solution, and then the mixture was further concentrated by an ultrafiltration apparatus to obtain ZrO ₂ 129g of zirconia sol with high concentration and 30.5 mass percent. The obtained high-concentration zirconia sol had a pH of 9.3 and an average particle diameter of 19nm obtained by a dynamic light scattering method. The zirconia sol is stable at 50 ℃ for 1 month or more without sediment.

(titanium dioxide particles)

Will be treated with TiO ₂ 12.09kg of an aqueous titanium tetrachloride solution containing 7.75% by mass of titanium tetrachloride (Osaka Titanium Technologies co., ltd.) and 4.69kg of aqueous ammonia (manufactured by yu-xing corporation) containing 15% by mass of ammonia were mixed with each other to prepare a white paste slurry having a ph of 9.5. Subsequently, this slurry was filtered and washed with pure water to obtain 9.87kg of an aqueous titanic acid cake having a solid content of 10% by mass. Next, 11.28kg of a hydrogen peroxide solution (Mitsubishi gas chemical Co., ltd.) containing 35% by mass of hydrogen peroxide and 20.00kg of pure water were added to the cake, and then heated at 80℃for 1 hour with stirring, and 57.52kg of pure water was further added to obtain TiO ₂ 98.67kg of an aqueous solution of titanic acid peroxide containing 1% by mass of titanic acid peroxide in terms of conversion standard. The aqueous solution of peroxo titanic acid was transparent brown and had a pH of 8.5.

Next, 4.70kg of cation exchange resin (Mitsubishi chemical Co., ltd.) was mixed with 98.67kg of the aqueous solution of the above-mentioned titanium peroxide, and SnO was slowly added thereto with stirring ₂ The standard amount of the solution was 12.33kg containing 1% by mass of potassium stannate (manufactured by Showa chemical Co., ltd.). Then, the cation-exchange resin doped with potassium ions or the like was separated, and then placed in an autoclave (120L, manufactured by Nitro Kagaku Co., ltd.) and heated at 165℃for 18 hours.

(titanium dioxide sol)

Subsequently, the obtained mixed aqueous solution was cooled to room temperature, and then concentrated by an ultrafiltration device (ACV-3010, manufactured by Asahi Kabushiki Kaisha), to obtain 9.90kg of a water-dispersible sol containing titanium-based fine particles (hereinafter referred to as "P-1") in a solid content of 10% by mass. The solid content in the sol thus obtained was measured by the above method, and as a result, titanium-based fine particles (primary particles) having a rutile-type crystal structure and formed of a composite oxide containing titanium and tin were obtained. Further, the content of the metal component contained in the titanium-based fine particles was measured, and as a result, each metal component was as follows in terms of oxide conversion: tiO (titanium dioxide) ₂ 87.2 mass% of SnO ₂ 11.0 mass% and K ₂ O1.8 massThe amount is percent. The pH of the mixed aqueous solution was 10.0. The aqueous dispersion sol containing the titanium-based fine particles was transparent and milky white, and the average particle diameter of the titanium-based fine particles contained in the aqueous dispersion sol was 35nm, and the distribution frequency of coarse particles having a particle diameter of 100nm or more was 0%. Further, the refractive index of the obtained titanium-based fine particles was 2.42.

(zirconia/titania Mixed sol)

The zirconia particles and titania particles obtained in the above were mixed in the respective ratios, to thereby prepare a zirconia/titania mixed sol having a solid content concentration of 13 mass%.

(formation of hard coating)

The surface of the polyester film produced in the example described below opposite to the surface to which the polarizing plate was adhered was coated with a coating liquid for forming a hard coat layer having the following composition by using a #14 wire bar, and dried at 70℃for 1 minute, and the solvent was removed. Next, the film coated with the hard coat layer was irradiated with 300mJ/cm by a high-pressure mercury lamp ² The polarizer protective film having a hard coat layer with a thickness of 7 μm was obtained.

The coating liquid used in the formation of the hard coat is prepared as follows.

(preparation of coating liquid L for Forming hard coating)

The aromatic components in the total resin in the prepared coating liquid for forming a hard coat layer L were 13.3% by mole ratio.

(preparation of coating liquid M for Forming hard coating)

The aromatic components in the total resin in the prepared coating liquid M for forming a hard coat layer were 5.4% by mole ratio.

(preparation of coating liquid N for Forming hard coating)

/>

The aromatic components in the total resin in the prepared coating liquid N for forming a hard coat layer were 19.3% by mole ratio.

Example 1

(adjustment of coating liquid)

The coating liquid having the following composition was adjusted.

(production of easily bondable polyester film)

As a film base polymer, PET resin pellets having an intrinsic viscosity (solvent: phenol/tetrachloroethane=60/40) of 0.62dl/g and substantially no particles were dried at 135℃for 6 hours under a reduced pressure of 133 Pa. Thereafter, the resultant was fed to an extruder, melt-extruded at about 280℃into a sheet form, and cooled and solidified by quenching on a rotating and cooling metal roll maintained at a surface temperature of 20℃to obtain an unstretched PET sheet.

The unstretched PET sheet was heated to 100℃by a heated roll set and an infrared heater, and then stretched 3.5 times in the longitudinal direction by a roll set having a peripheral speed difference to obtain a uniaxially stretched PET film.

Then, the above coating liquid was applied to one side of a PET film by a roll coating method, and then dried at 80℃so that the final coating amount after drying after stretching became 0.12g/m ² Is adjusted by way of the (c). Then, stretched to 4.0 times in the width direction at 150℃in a tenter,the film was heated at 230℃with its length in the width direction fixed, and further subjected to relaxation treatment at 230℃in the width direction, to give an adhesive polyester film having a thickness of 38. Mu.m.

On the adhesive layer of the obtained adhesive polyester film, the absorbance was measured by infrared spectrometry to calculate 1640cm to be attributed to the urea compound ^-1 Absorption intensity as peak (I ₁₆₄₀ ) 1410cm to be attributed to the polyester resin ^-1 Absorption intensity as peak (I ₁₄₁₀ ) Relative absorption intensity ratio "(I) ₁₆₄₀ /I ₁₄₁₀ ) (X) ", and as a result, 1.375.

Next, using the coating liquid a for forming a hard coat layer, a laminated polyester film in which a hard coat layer is formed on the easy-to-adhere layer of the obtained easy-to-adhere polyester film according to the above-described forming method was obtained.

The adhesion of the hard coat layer of the obtained laminated polyester film was evaluated, and as a result, the adhesion was 100%.

The obtained easy-to-adhere polyester film was left to stand in a high-temperature and high-humidity tank at 80℃under 90RH% for 24 hours, and then left to stand at room temperature for 12 hours. Then, absorbance was measured by infrared spectrometry on the easy-to-adhere layer of the treated easy-to-adhere polyester film, and the relative absorption intensity ratio "(I) was calculated ₁₆₄₀ /I ₁₄₁₀ ) (Y) ", as a result, 1.750.

From the result, 127 was calculated when (Y/X). Times.100.

Next, a hard coat layer was formed on the easy-to-adhere layer of the treated easy-to-adhere polyester film using the coating liquid L for forming a hard coat layer, to obtain a laminated polyester film.

The adhesion of the hard coat layer of the obtained laminated polyester film was evaluated, and as a result, the adhesion was 100%. Further, the adhesion (wet heat resistance) of the easy-to-adhere polyester film after being left in an environment of 80℃and 90% RH was evaluated, and found to be 100%.

Example 2

An easily adhesive polyester film was obtained in the same manner as in example 1, except that the coating liquid having the following composition was adjusted.

The evaluation of the obtained adhesive polyester film was carried out in the same manner as in example 1, and the results thereof are shown in table 1.

Example 3

Example 4

An easily bondable polyester film was obtained in the same manner as in example 1, except that the coating liquid was adjusted using the crosslinking agent Q solution. The evaluation of the obtained adhesive polyester film was carried out in the same manner as in example 1, and the results thereof are shown in table 1.

Example 5

An easily bondable polyester film was obtained in the same manner as in example 1, except that the coating liquid was adjusted using the crosslinking agent R solution. The evaluation of the obtained adhesive polyester film was carried out in the same manner as in example 1, and the results thereof are shown in table 1.

Example 6

An easily bondable polyester film was obtained in the same manner as in example 1, except that the coating liquid was adjusted using the crosslinking agent S solution. The evaluation of the obtained adhesive polyester film was carried out in the same manner as in example 1, and the results thereof are shown in table 1.

Example 7

An easily bondable polyester film was obtained in the same manner as in example 1, except that the coating liquid was adjusted using the resin B solution. The evaluation of the obtained adhesive polyester film was carried out in the same manner as in example 1, and the results thereof are shown in table 1.

Example 8

An easily bondable polyester film was obtained in the same manner as in example 1, except that the coating liquid was adjusted using the resin C solution. The evaluation of the obtained adhesive polyester film was carried out in the same manner as in example 1, and the results thereof are shown in table 1.

Example 9

Example 10

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Example 11

Examples 12 to 13

An easy-to-adhere polyester film was obtained in the same manner as in example 1, except that the types of the hard coat liquids applied to the obtained easy-to-adhere polyester films were changed as shown in table 1. The evaluation of the obtained adhesive polyester film was carried out in the same manner as in example 1, and the results thereof are shown in table 1.

Comparative example 1

Comparative example 2

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Comparative example 3

An easily bondable polyester film was obtained in the same manner as in example 1, except that the coating liquid was adjusted using the resin D solution. The evaluation of the obtained adhesive polyester film was carried out in the same manner as in example 1, and the results thereof are shown in table 1.

Comparative example 4

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Comparative example 5

An easily bondable polyester film was obtained in the same manner as in example 1, except that the coating liquid was adjusted using the crosslinking agent tsolution. The evaluation of the obtained adhesive polyester film was carried out in the same manner as in example 1, and the results thereof are shown in table 1.

TABLE 1

Industrial applicability

According to the present invention, there may be provided: an easily adhesive polyester film which ensures adhesion reliability after being left in a high-temperature and high-humidity environment for a long period of time, and which is more easily applied to optical applications and the like.

Claims

1. An easily adhesive polyester film having a coating layer on at least one side of the polyester film, wherein the coating layer is obtained by curing a composition comprising a polyester having a polycyclic aromatic skeleton and a crosslinking agent having at least one skeleton selected from aliphatic, alicyclic and heterocyclic groups, and the coating layer is free of the polyester film as measured by Fourier transform infrared spectrometry (FT-IR)On the surface of the contact side of the film, 1640cm of the urea group was attributed to ^-1 Absorption intensity as peak (I ₁₆₄₀ ) 1410cm from the CH stretch to be attributed to the polyester ^-1 Absorption intensity as peak (I ₁₄₁₀ ) The relative absorption intensity ratio (I) ₁₆₄₀ /I ₁₄₁₀ ) When the restriction is made, the following relationship is satisfied,

the relative absorption strength ratio (X) obtained by evaluating the film-forming, easy-to-adhere polyester film and the relative absorption strength ratio (Y) obtained by evaluating the polyester film after 24 hours of standing at 80 ℃ and 90%RH satisfy the following formula (1),

110≤(Y/X)×100≤140···(1)。

2. the easy-to-adhere polyester film according to claim 1, wherein the polyester having a polycyclic aromatic skeleton is a polyester having a naphthalene skeleton.

3. The easy-to-adhere polyester film according to claim 1 or 2, wherein the crosslinking agent having at least one skeleton selected from the group consisting of aliphatic, alicyclic and heterocyclic groups is an isocyanate crosslinking agent having at least one skeleton selected from the group consisting of aliphatic, alicyclic and heterocyclic groups.

4. The adhesive polyester film according to any one of claims 1 to 3, wherein the adhesion of the hard coat layer comprising a resin having an aromatic skeleton is 95% or more when the hard coat layer is provided on the surface of the coating layer.