CN115093595A

CN115093595A - Laminated polyester film

Info

Publication number: CN115093595A
Application number: CN202210771647.9A
Authority: CN
Inventors: 田川理惠; 山口洋平; 广瀬友香
Original assignee: Toyobo Co Ltd
Current assignee: Toyobo Co Ltd
Priority date: 2017-09-22
Filing date: 2018-09-07
Publication date: 2022-09-23
Anticipated expiration: 2038-09-07
Also published as: TW202325551A; JP7052854B2; KR102376858B1; CN111051404B; TW202323059A; JP6981482B2; JP2021062619A; CN111051404A; KR102371651B1; JP7052854B6; TWI795442B; JPWO2019058999A1; KR20200027542A; TW201919907A; JP7136172B2; JP7230994B2; JP2021043470A; WO2019058999A1; CN115093595B; JP2020063457A

Abstract

A laminated polyester film using an easily adhesive polyester film which has low interference properties capable of suppressing rainbow unevenness, has excellent adhesion to a hard coat layer or the like which is required to have a high degree of dimension in various optical applications, and has excellent blocking resistance and transparency, and further has high slidability. A laminated polyester film having a coating layer on at least one surface of a polyester film, wherein the coating layer contains a polyurethane resin having a polycarbonate skeleton and a polyester resin having a naphthalene skeleton, and wherein the coating layer contains 1 or more functional layers selected from the group consisting of a hard coat layer, an antiglare antireflection layer, an antireflection layer and a low reflection layer, and wherein when the total solid content of the coating layer is 100% by mass, the content of the polyurethane resin component is a, the content of the polyester resin component having a naphthalene skeleton is b, and the total content of the components other than these is c, and when the total content is represented by a triangular chart, a, b and c are within a region surrounded by 4 specific straight lines.

Description

Laminated polyester film

The present application is a divisional application of an application having an application date of 2018, 9/7, an application number of 201880056954.0, and an invention name of "easy-adhesion polyester film".

Technical Field

The present invention relates to: an easily adhesive polyester film which has low interference and excellent adhesion to various functional layers, blocking resistance and transparency and can eliminate the problem of rainbow unevenness can be secured. More specifically, the present invention relates to: an easily adhesive polyester film which can be suitably used for high definition optical applications.

Background

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

The hard coat film is required to have temperature, humidity, light durability, transparency, chemical resistance, abrasion resistance, stain resistance, and the like. Further, since they are often used for surfaces of displays, decorative materials, and the like, visibility and design are required. Therefore, in order to suppress glare, iridescent coloring, 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 stacked on each other is provided on the hard coat layer.

However, in applications such as displays and decorative materials, further screen enlargement (area enlargement) and high definition have been demanded in recent years, and along with this, the level of demand for suppression of iridescent colors (uneven interference) particularly under fluorescent lamps has been increasing. In addition, due to the reproducibility of daylight color, the 3 wavelengths of fluorescent lamps become the mainstream, and interference unevenness is more likely to occur. Further, the demand for cost reduction by simplifying the antireflection layer is also increasing. Therefore, it is required to suppress interference unevenness as much as possible only with a hard coat film without an antireflection layer.

Further, with the development of mobile office (mobile) technology, the use of portable devices such as mobile phones, automatic navigation systems, and electronic books in outdoor areas has been expanding. In addition, the mobile device is basically a display based on a liquid crystal panel in view of reduction in thickness. In such a field, for example, in a mobile phone having a touch panel mounted thereon, as a hard coat film for protecting a display surface, a defect of visibility due to interference fringes has been more conspicuous in applications in which design is applied to a back surface of the hard coat film, such as interference fringes due to reflected light from both interfaces in contact with an applied surface and a protective tape.

The iridescent color (interference unevenness) of the hard coating film is caused by a large difference between the refractive index (for example, 1.62 to 1.65) of the polyester film of the base material and the refractive index (for example, 1.49) of the hard coating layer formed of an acrylic resin or the like. In order to reduce the refractive index difference between the layers and prevent the occurrence of interference unevenness, a method has been proposed in which a coating layer having a relatively high refractive index is provided on a polyester film as a base material, thereby reducing the refractive index difference between the polyester film and the coating layer and the refractive index difference between the coating layer and a hard coating layer.

Conventionally, in the field of an optical easy-adhesion film, as a method for increasing the refractive index of an easy-adhesion layer, the following methods are known: a method of including specific high refractive index fine particles in the coating layer; a method of increasing the refractive index of the resin of the coating layer, and the like. In particular, a polyester resin using a naphthalenedicarboxylic acid component containing naphthalenedicarboxylic acid as a copolymerization component is excellent in adhesion to a base polyester film, and has been proposed as a suitable example (for example, see patent document 1). However, a polyester resin having a high refractive index generally has a high glass transition temperature and lacks flexibility of the resin, so that there is a problem that the adhesion is poor, and the blocking resistance sometimes deteriorates when the polyester resin is increased. On the other hand, a method of using a polyurethane resin having a polycarbonate component as a resin having excellent flexibility and high adhesion has been proposed (for example, see patent document 2), and patent document 1 has a problem that a polyurethane resin having a polycarbonate component is compounded, but if the amount of the polyurethane component is increased, low interference and poor transparency are caused. As described above, no easy-to-adhere polyester film has been obtained which satisfies the high-level low interference property in recent years and has all of the properties of adhesion to a hard coat layer, blocking resistance and transparency in a high balance.

Documents of the prior art

Patent document

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

Patent document 2: japanese patent laid-open publication No. 2011-168053

Disclosure of Invention

Problems to be solved by the invention

The present invention was made in view of the above-mentioned problems of the prior art. That is, an object of the present invention is to provide: the easily adhesive polyester film is excellent in low interference property for suppressing rainbow unevenness, adhesion to a hard coat layer or the like which is required to have a high degree of dimension in various optical applications, blocking resistance, and transparency, further has high slidability, and is suitably used in optical applications having excellent workability in subsequent steps such as production of a polarizing plate of a liquid crystal display device and the like.

Means for solving the problems

That is, the present invention includes the following configurations.

1. An easily adhesive polyester film having a coating layer on at least one surface of a polyester film, wherein the coating layer contains a polyurethane resin having a polycarbonate skeleton and a polyester resin having a naphthalene skeleton, and when the total solid content of the coating layer is set to 100 mass%, the content (mass%) of the polyurethane resin component is a, the content (mass%) of the polyester resin component having a naphthalene skeleton is b, and the total amount (mass%) of the components other than these is c, and the sum is represented by a triangular chart, a, b, and c are in a region surrounded by 4 straight lines, i.e., a straight line P1, a straight line Q1, a straight line R1, and a straight line S1.

The straight line P1, the straight line Q1, the straight line R1, and the straight line S1 are as follows.

Line P1: a straight line passing through points where a is 10 mass%, b is 55 mass%, and c is 35 mass%, and points where a is 10 mass%, b is 10 mass%, and c is 80 mass%

Straight line Q1: a straight line passing through points a, b and c of 10, 10 and 80 mass% and points a, b and c of 70, 10 and 20 mass% respectively

Straight line R1: a straight line passing through points where a is 70 mass%, b is 10 mass%, and c is 20 mass%, and points where a is 50 mass%, b is 40 mass%, and c is 10 mass%

Straight line S1: a straight line passing through points where a is 45 mass%, b is 45 mass%, and c is 10 mass%, and points where a is 10 mass%, b is 55 mass%, and c is 35 mass%

2. The easy-adhesion polyester film according to the above 1, wherein the coating layer contains a crosslinking agent.

3. The easy-adhesive polyester film according to the above 1 or 2, wherein the coating layer contains metal oxide particles (particles A) having a refractive index of 1.7 or more.

4. The easily bondable polyester film according to any one of the above 1 to 3, wherein the coating layer contains lubricant particles (particles B).

5. A laminated polyester film comprising 1 or more functional layers selected from the group consisting of a hard coat layer, an antiglare and antireflection layer, an antireflection layer, and a low-reflection layer on a coating layer of the easy-adhesion polyester film described in any one of items 1 to 4.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, there can be provided: an easily adhesive polyester film which has low interference, transparency, blocking resistance, adhesion to various functional layers, and sliding properties and can be suitably used for optical applications.

Drawings

Fig. 1 is a triangular chart showing a preferred range of the easy-adhesion polyester film of the present invention.

Description of the reference numerals

P1: straight line passing through coordinates (10, 55, 35) and (10, 10, 80)

Q1: straight line passing through coordinates (10, 10, 80) and (70, 10, 20)

R1: straight line passing through coordinates (70, 10, 20) and (50, 40, 10)

S1: straight line passing through coordinates (45, 45, 10) and (10, 55, 35)

O: plotting of the examples

□: plotting of each comparative example

Numerical values in the trigonometric chart: numbering of examples or comparative examples

Detailed Description

(polyester film)

The polyester film used as the substrate in the present invention is a film made of a polyester resin, and preferably a polyester film mainly containing at least 1 of polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate as a constituent component. Further, the polyester may be a film formed of a copolyester obtained by copolymerizing the above-mentioned polyester with a third component monomer. Among these polyester films, polyethylene terephthalate films are most preferable from the viewpoint of balance between physical properties and cost.

The polyester film may be a single layer or a multilayer. In addition, in these layers, various additives may be contained in the polyester resin as necessary as long as the effect of the present invention is exerted. Examples of the additives include antioxidants, light stabilizers, anti-gelling agents, organic wetting agents, antistatic agents, ultraviolet absorbers, and surfactants.

(coating layer)

The easily adhesive polyester film of the present invention is obtained by laminating an easily adhesive coating layer on the above-mentioned polyester base film.

In the coating layer of the present invention, it is preferable that when the content (mass%) of the polyurethane resin component having a polycarbonate skeleton is "a", the content (mass%) of the polyester resin component having a naphthalene skeleton is "b", and the total amount (mass%) of the components other than these is "c" in a triangular chart, a, b, and c are in the range of the region surrounded by 4 straight lines, i.e., the straight line P1, the straight line Q1, the straight line R1, and the straight line S1, assuming that the total amount (solid content) of the coating layer is 100 mass%.

Here, the straight line P1, the straight line Q1, the straight line R1 and the straight line S1 are as follows.

Straight line P1: a straight line passing through points where a is 10 mass%, b is 55 mass%, and c is 35 mass%, and points where a is 10 mass%, b is 10 mass%, and c is 80 mass%

Straight line Q1: a straight line passing through points where a is 10 mass%, b is 10 mass%, and c is 80 mass%, and points where a is 70 mass%, b is 10 mass%, and c is 20 mass%

By setting the above range, low interference (interference fringe improvement), adhesion, blocking resistance, and transparency can be maintained in a well-balanced manner at a high level.

The preferred range will be described briefly with reference to a triangular chart shown in fig. 1. Three sides of the triangular chart respectively show coordinate axes in which the content of the polyurethane resin component having a polycarbonate skeleton is a (mass%), the content of the polyester resin component having a naphthalene skeleton is b (mass%), and the other components are c (mass%). Here, if coordinates inside the triangular chart are expressed in the order of (a, b, c), 5 coordinates (10, 55, 35), (10, 10, 80), (70, 10, 20), (50, 40, 10), and (45, 45, 10) are shown within the triangular chart. Further, 4 lines of a line P1 passing through (10, 55, 35) and (10, 10, 80), a line Q1 passing through (10, 10, 80) and (70, 10, 20), a line R1 passing through (70, 10, 20) and (50, 40, 10), and a line S1 passing through (45, 45, 10) and (10, 55, 35) are shown, and the range inside the line surrounded by the 4 lines shows a range in which low interference (interference fringe improvement), adhesion, blocking resistance, and transparency can be provided with good balance.

Further, further preferable ranges on the respective straight lines are explained below.

Instead of the straight line P1, a straight line P2 (a straight line passing through a point where a is 15 mass%, b is 55 mass%, and c is 30 mass%, and a point where a is 15 mass%, b is 10 mass%, and c is 75 mass%) is preferably used.

Instead of the straight line Q1, a straight line Q2 (a straight line passing through a point where a is 10 mass%, b is 20 mass%, and c is 70 mass%, and a point where a is 70 mass%, b is 10 mass%, and c is 20 mass%) and a further straight line Q3 (a straight line passing through a point where a is 20 mass%, b is 20 mass%, and c is 60 mass%, and a point where a is 70 mass%, b is 10 mass%, and c is 20 mass%) are preferably used.

Instead of the straight line R1, a straight line R2 (a straight line passing through a point where a is 65 mass%, b is 10 mass%, and c is 25 mass%, and a point where a is 45 mass%, b is 40 mass%, and c is 15 mass%) and a further straight line R3 (a straight line passing through a point where a is 60 mass%, b is 10 mass%, and c is 30 mass%, and a point where a is 40 mass%, b is 40 mass%, and c is 20 mass%) are preferably used.

Instead of the straight line S1, a straight line S2 (a straight line passing through a point where a is 50 mass%, b is 40 mass%, and c is 10 mass%, and a point where a is 10 mass%, b is 50 mass%, and c is 40 mass%), a further straight line S3 (a straight line passing through a point where a is 52 mass%, b is 38 mass%, and c is 10 mass%, and a point where a is 10 mass%, b is 48 mass%, and c is 42 mass%), and particularly S4 (a straight line passing through a point where a is 55 mass%, b is 35 mass%, and c is 10 mass%, and a point where a is 10 mass%, b is 45 mass%, and c is 45 mass%) are preferably used.

The lower limit of the content a of the urethane resin component having a polycarbonate skeleton is preferably 10 mass%, more preferably 13 mass%, and still more preferably 15 mass%. When the content a of the urethane resin component having a polycarbonate skeleton is 10% by mass or more, the adhesiveness can be satisfied without deteriorating the transparency, and it is preferable.

The upper limit of the content a of the urethane resin component having a polycarbonate skeleton is preferably 70% by mass, more preferably 60% by mass, still more preferably 50% by mass, and particularly preferably 40% by mass. The content a of the urethane resin component having a polycarbonate skeleton is preferably 70% by mass or less because the refractive index can be maintained high and low interference can be obtained.

The lower limit of the content b of the polyester resin component having a naphthalene skeleton is preferably 10% by mass, more preferably 15% by mass, and still more preferably 20% by mass. When the content b of the polyester resin component having a naphthalene skeleton is 10% by mass or more, the adhesiveness can be satisfied, and it is preferable.

The upper limit of the content b of the polyester resin component having a naphthalene skeleton is preferably 55 mass%, more preferably 50 mass%, still more preferably 48 mass%, particularly preferably 45 mass%. The content b of the polyester resin component having a naphthalene skeleton is preferably 55% by mass or less because the blocking resistance can be exhibited.

The lower limit of the content c of the other component is preferably 10% by mass, more preferably 20% by mass, still more preferably 25% by mass, and particularly preferably 30% by mass. When the content c of the other component is 10% by mass or more, if the component for increasing the refractive index of the coating layer is contained, the low interference property is improved, and it is preferable. As a result, the content a of the polyurethane resin having a polycarbonate skeleton is not excessively increased, and blocking can be prevented, which is preferable.

The upper limit of the content c of the other component is preferably 80% by mass, more preferably 70% by mass, still more preferably 60% by mass, and particularly preferably 55% by mass. When the content c of the other component is 80% by mass or less, the balance between the content a of the polyurethane resin component having a polycarbonate skeleton and the content b of the polyester resin component having a naphthalene skeleton can be easily obtained, the adhesion can be maintained, and the balance between the blocking resistance and the refractive index (low interference) can be easily obtained, which is preferable.

(polyurethane resin having polycarbonate skeleton)

The diol component, which is a constituent component of the polyurethane resin having a polycarbonate skeleton, preferably contains an aliphatic polycarbonate polyol having excellent heat resistance and hydrolysis resistance. In the optical use of the present invention, an aliphatic polycarbonate polyol is also preferably used in view of preventing yellowing.

The aliphatic polycarbonate polyol includes aliphatic polycarbonate diol, aliphatic polycarbonate triol, and the like, and aliphatic polycarbonate diol can be suitably used. The aliphatic polycarbonate diol which is a constituent component of the polyurethane resin of the present invention includes, for example: and aliphatic polycarbonate diols obtained by reacting 1 or 2 or more kinds of diols such as ethylene glycol, propylene glycol, 1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, 3-methyl-1, 5-pentanediol, 1, 6-hexanediol, 1, 9-nonanediol, 1, 8-nonanediol, neopentyl glycol, diethylene glycol, dipropylene glycol, 1, 4-cyclohexanediol, and 1, 4-cyclohexanedimethanol with carbonates such as dimethyl carbonate, diphenyl carbonate, ethylene carbonate, and phosgene.

1460cm of an aliphatic polycarbonate-derived component measured by infrared spectroscopy with respect to a polyurethane resin having a polycarbonate skeleton ^-1 The absorbance (A1460) in the vicinity and 1530cm of the absorbance derived from the urethane component ^-1 The ratio (A1460/A1530) of the absorbance (A1530) in the vicinity is preferably 0.40 to 2.30.

When the ratio (a1460/a1530) is 0.40 or more, the amount of the hard urethane component does not become excessively large, the stress relaxation of the coating layer does not decrease, and the moist heat resistance does not decrease, and thus it is preferable. When the ratio (a1460/a1530) is 2.30 or less, the solvent resistance of the coating layer can be maintained without excessively increasing the aliphatic component of the soft aliphatic polycarbonate, and the moist heat resistance is not lowered, which is preferable.

The number average molecular weight of the aliphatic polycarbonate diol is preferably 1500 to 4000, more preferably 2000 to 3000, in order to set the ratio (A1460/A1530) in the range of 0.40 to 2.30. When the number average molecular weight of the aliphatic polycarbonate diol is small, the ratio of the aliphatic polycarbonate component constituting the polyurethane resin is relatively small.

Examples of the polyisocyanate that is a constituent component of the polyurethane resin of the present invention include: aromatic aliphatic diisocyanates such as xylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate and 4, 4-dicyclohexylmethane diisocyanate, 1, 3-bis (isocyanatomethyl) cyclohexane, aliphatic diisocyanates such as hexamethylene diisocyanate and 2,2, 4-trimethylhexamethylene diisocyanate, or polyisocyanates obtained by previously adding one or more of these compounds to trimethylolpropane or the like. The polyisocyanate does not have a problem of yellowing, and is preferably used for optical applications requiring high transparency. The polyisocyanate is preferably one that can relax stress caused by shrinkage and swelling of a photocurable resin or the like without making the coating film excessively hard, and can maintain adhesion.

In order to impart water solubility to the polyurethane resin, (co) sulfonic acid (salt) group or carboxylic acid (salt) group may be introduced into the urethane molecular skeleton. Since a sulfonic acid (salt) group is strongly acidic and moisture resistance is sometimes difficult to maintain due to its hygroscopic property, a carboxylic acid (salt) group which is weakly acidic is preferably introduced. Further, a nonionic group such as a polyoxyalkylene group may be introduced.

In order to introduce a carboxylic acid (salt) group into the polyurethane resin, for example, a polyol compound having a carboxylic acid group such as dimethylolpropionic acid or dimethylolbutyric acid as a polyol component is introduced as a copolymerization component, and neutralized with a salt forming agent. Specific examples of the salt-forming agent include trialkylamines such as ammonia, trimethylamine, triethylamine, triisopropylamine, tri-N-propylamine and tri-N-butylamine, N-alkylmorpholines such as N-methylmorpholine and N-ethylmorpholine, and N-dialkylalkanolamines such as N-dimethylethanolamine and N-diethylethanolamine. These may be used alone, or 2 or more kinds may be used in combination.

In the case where a polyol compound having a carboxylic acid (salt) group is used as a copolymerization component in order to impart water solubility, the composition molar ratio of the polyol compound having a carboxylic acid (salt) group in the polyurethane resin is preferably 3 to 60 mol%, and preferably 5 to 40 mol%, based on 100 mol% of the total polyol component of the polyurethane resin. When the composition molar ratio is 3 mol% or more, the water dispersibility is good and is preferable. When the molar ratio of the above-mentioned composition is 60 mol% or less, the water resistance and the moist heat resistance can be maintained, and therefore, it is preferable.

The glass transition point temperature of the polyurethane resin of the present invention is preferably lower than 0 deg.C, more preferably lower than-5 deg.C. When the glass transition point temperature is lower than 0 ℃, it is preferable that the coating layer easily exhibits appropriate flexibility in terms of stress relaxation.

(polyester resin having naphthalene skeleton)

The acid component of the polyester resin contained in the coating layer contains a component derived from naphthalenedicarboxylic acid, whereby the refractive index is increased, and the iridescent color under a fluorescent lamp can be easily controlled. In addition, the moist heat resistance can be improved.

As such a naphthalenedicarboxylic acid, 2, 6-naphthalenedicarboxylic acid is preferred. The content of the naphthalenedicarboxylic acid in the total dicarboxylic acid components constituting the polyester resin is preferably 20 mol% or more, more preferably 30 mol% or more, still more preferably 50 mol% or more, and still more preferably 60 mol% or more.

In addition, as long as the effect of the present invention is exerted, as the acid component in the polyester resin, terephthalic acid, isophthalic acid, phthalic anhydride, 1, 4-cyclohexanedicarboxylic acid, trimellitic acid, pyromellitic acid, dimer acid, isophthalic acid-5-sodium sulfonate, naphthalene-4-sodium sulfonate-2, 7-dicarboxylic acid, adipic acid, azelaic acid, sebacic acid, and the like can be used. When these are copolymerized, the aromatic dicarboxylic acid component including naphthalenedicarboxylic acid is preferably 70 mol% or more, more preferably 80 mol% or more, in terms of moist heat resistance and high refractivity. In particular, when the moist heat resistance and high refractivity are important, the aromatic dicarboxylic acid component is preferably 90 mol% or more, more preferably 95 mol% or more, and particularly preferably 100%.

As the diol component in the polyester resin, ethylene glycol, 1, 3-propanediol, propylene glycol, 1, 4-butanediol, 1, 6-hexanediol, neopentyl glycol, diethylene glycol, 1, 4-cyclohexanedimethanol, xylene glycol, an ethylene oxide adduct of bisphenol a, or the like can be used insofar as the effects of the present invention are exerted.

In addition, when the content of the polyurethane resin having a polycarbonate skeleton in the coating layer is reduced, the flexibility of the coating film is deteriorated, and there is a fear that chips and particles of the coating layer may be detached in a post-processing treatment or the like. In this case, it is one of preferable embodiments to include a dicarboxylic acid component represented by the following formula (1) and/or a diol component represented by the following formula (2) in the polyester resin.

(1) HOOC- (CH2) n-COOH (wherein n is an integer of 4. ltoreq. n.ltoreq.10)

(2) HO- (CH2) n-OH (wherein n is an integer of 4. ltoreq. n. ltoreq.10)

By containing the acid component and/or the glycol component having the carbon component of a specific length in this manner, flexibility can be imparted to the polyester resin, and even large particles can be easily held, and chipping and particle shedding of the coating layer can be suppressed.

Examples of the dicarboxylic acid component of formula (1) include adipic acid, sebacic acid, azelaic acid, and the like. Examples of the diol component of formula (2) include butanediol and hexanediol.

The polyester resin can be obtained by dissolving or dispersing in water, a water-soluble organic solvent (for example, an aqueous solution containing less than 50% by mass of an alcohol, an alkyl cellosolve, a ketone, or an ether), or an organic solvent (for example, toluene or ethyl acetate).

When a polyester resin is used as the aqueous coating liquid, when a water-soluble or water-dispersible polyester resin is used, it is preferable to copolymerize a compound having a sulfonate group and a compound having a carboxylate group because of the water-solubility or water-dispersibility.

The number average molecular weight of the polyester resin is preferably 5000 to 40000 in view of the strength of the coating film and the ease of water dispersion. Further preferably 10000 to 30000, particularly preferably 12000 to 25000.

The polyester resin containing a naphthalenedicarboxylic acid component may be a single one or a blend of 2 or more. In the case of a blend of 2 or more types, the above-mentioned composition is preferably the total amount of the polyester resin components.

Examples of the other components contained in the coating layer include a binder resin other than a polyurethane resin having a polycarbonate skeleton and a polyester resin containing a naphthalenedicarboxylic acid component, a crosslinking agent, lubricant particles, metal oxide particles for increasing the refractive index of the coating layer, a surfactant, and the like. Although the coating liquid may contain a solvent and a surfactant, the amount of the solvent and the amount of the solid content of the surfactant remaining after drying and curing are extremely small, and when the composition of each component is calculated from the coating liquid, the amount of the solvent and the amount of the solid content of the surfactant may not necessarily be included in the amount of the solid content of the entire coating layer, and the composition of the example is described based on the above calculation.

In order to form a crosslinked structure in the coating layer, the coating layer may be formed including a crosslinking agent. By containing the crosslinking agent, the adhesion under high temperature and high humidity can be further improved. Specific examples of the crosslinking agent include urea-based, epoxy-based, melamine-based, isocyanate-based, oxazoline-based, and carbodiimide-based crosslinking agents. Among them, melamine-, isocyanate-, oxazoline-and carbodiimide-based crosslinking agents are preferable from the viewpoint of the stability of the coating liquid with time and the effect of improving the adhesion under high-temperature and high-humidity treatment. In addition, a catalyst or the like may be suitably used as necessary to promote the crosslinking reaction.

When the coating layer is formed by including a crosslinking agent, the content of the crosslinking agent is preferably 5 mass% or more and 50 mass% or less of the entire solid content of the coating layer. More preferably 10% by mass or more and 40% by mass or less. If the content is 10% by mass or more, the strength of the resin of the coating layer can be maintained, and the adhesion under high temperature and high humidity is good, and if the content is 40% by mass or less, the flexibility of the resin of the coating layer can be maintained, and the adhesion under normal temperature, high temperature and high humidity can be maintained, and is preferable.

The coating layer preferably contains metal oxide particles (particles a) having a high refractive index of 1.7 or more. Examples of such a metal oxide include TiO ₂ Refractive index of 2.7, ZnO refractive index of 2.0, Sb ₂ O ₃ (refractive index 1.9) SnO ₂ (refractive index 2.1) ZrO ₂ (refractive index 2.4) and Nb ₂ O ₅ (refractive index 2.3), CeO ₂ (refractive index 2.2), Ta ₂ O ₅ (refractive index 2.1), Y ₂ O ₃ (refractive index 1.8) La ₂ O ₃ (refractive index 1.9) In ₂ O ₃ (refractive index 2.0) and Cr ₂ O ₃ (refractive index 2.5), and composite oxide particles containing these metal atoms.

The lower limit of the refractive index of the particle a is preferably 1.7, more preferably 1.75. The upper limit of the refractive index of the particle a is preferably 3.0, more preferably 2.7, and further preferably 2.5. By setting the above range, a good balance among low interference, transparency, adhesion, and blocking resistance can be obtained.

The composite oxide particles used as the particles A are preferably TiO ₂ Particles of/ZnO (mixed particles of zirconia/titania). The zirconia/titania mixed particles are a group of particles containing both zirconia and titania in such an aggregated state that zirconia and titania do not form a composite body are separately dispersed in a single liquid. Of course, in the coating layer, the liquid component is substantially evaporated and disappears in the drying step and the curing step. By including such particles a in the coating layer, the balance between the sliding property and the transparency is excellent, and high transparency and low interference can be ensured. The liquid is preferably an aqueous liquid because the coating layer can be easily formed by a so-called inline coating method described later.

The zirconia/titania mixed particles may contain other components than zirconia/titania, and may be inorganic particles or organic particles, and are not particularly limited, and examples thereof include inorganic particles inactive to polyester, such as metal oxides, e.g., silica, titania (titania), zirconia (zirconia), talc, and kaolinite, calcium carbonate, calcium phosphate, and barium sulfate.

The average particle diameter of the particles A is preferably 5nm or more, more preferably 10nm or more, further preferably 15nm or more, particularly preferably 20nm or more. The average particle diameter of the particles A is preferably 5nm or more, since the particles A are less likely to aggregate.

The average particle diameter of the particles A is preferably 200nm or less, more preferably 150nm or less, still more preferably 100nm or less, and particularly preferably 60nm or less. The average particle diameter of the particles A is preferably 200nm or less because the transparency is good.

In the present invention, the coating layer preferably contains lubricant particles (particles B).

Examples of the particles B include (1) inorganic particles such as silica, kaolinite, talc, light calcium carbonate, heavy calcium carbonate, zeolite, alumina, barium sulfate, carbon black, zinc oxide, zinc sulfate, zinc carbonate, titanium dioxide, satin white, aluminum silicate, diatomaceous earth, calcium silicate, aluminum hydroxide, hydrolyzed halloysite, magnesium carbonate, and magnesium hydroxide; (2) organic particles such as acrylic or methacrylic, vinyl chloride, vinyl acetate, nylon, styrene/acrylic, styrene/butadiene, polystyrene/acrylic, polystyrene/isoprene, methyl methacrylate/butyl methacrylate, melamine, polycarbonate, urea, epoxy, urethane, phenol, diallyl phthalate, and polyester, and silica is particularly preferably used in order to provide a suitable sliding property to the coating layer.

The average particle diameter of the particles B is preferably 200nm or more, more preferably 250nm or more, further preferably 300nm or more, particularly preferably 350nm or more. The average particle diameter of the particles B is preferably 200nm or more, since aggregation is less likely to occur and the sliding property can be secured.

The average particle diameter of the particles B is preferably 2000nm or less, more preferably 1500nm or less, still more preferably 1000nm or less, and particularly preferably 700nm or less. When the average particle diameter of the particles B is 2000nm or less, the transparency can be maintained and the particles are not exfoliated, which is preferable.

The surface treatment of the particles a and B may be performed, and as the surface treatment method, there are: physical surface treatment such as plasma discharge treatment and corona discharge treatment, and chemical surface treatment using a coupling agent, preferably using a coupling agent. As the coupling agent, an organic alkoxy metal compound (e.g., titanium coupling agent, silane coupling agent) is preferably used. In the case where the particles B are silica, the silane coupling treatment is particularly effective. The surface treatment agent for the particles B may be used for surface treatment in advance before the layer coating solution is prepared, or may be further added as an additive to the layer when the layer coating solution is prepared. Of course, may be used for the particles a.

The content of the particles a in the coating layer is preferably 2% by mass or more, more preferably 3% by mass or more, further preferably 4% by mass or more, and particularly preferably 5% by mass or more. When the content of the particles a in the coating layer is 2% by mass or more, the refractive index of the coating layer can be maintained high, and low interference can be effectively obtained, which is preferable.

The content of the particles a in the coating layer is preferably 50% by mass or less, more preferably 40% by mass or less, further preferably 30% by mass or less, and particularly preferably 20% by mass or less. When the content of the particles A in the coating layer is 50% by mass or less, the film-forming property can be maintained, and it is preferable.

The content of the particles B in the coating layer is preferably 0.01 mass% or more, more preferably 0.05 mass% or more, and further preferably 0.1 mass% or more. When the content of the particles B in the coating layer is 0.01% by mass or more, a proper sliding property can be maintained, and it is preferable.

The content of the particles B in the coating layer is preferably 2% by mass or less, more preferably 1.5% by mass or less, and further preferably 1% by mass or less. When the content of the particles B in the coating layer is 2% by mass or less, the haze can be kept low, and the transparency is preferable.

The film thickness of the coating layer is preferably 0.001 μm or more, more preferably 0.01 μm or more, further preferably 0.02 μm or more, and particularly preferably 0.05 μm or more. When the film thickness of the coating layer is 0.001 μm or more, the adhesiveness is good, and it is preferable.

The film thickness of the coating layer is preferably 2 μm or less, more preferably 1 μm or less, still more preferably 0.8 μm or less, and particularly preferably 0.5 μm or less. When the film thickness of the coating layer is 2 μm or less, blocking is not likely to occur, and it is preferable.

The coating layer may contain a surfactant for the purpose of improving leveling property during coating and defoaming of the coating liquid. The surfactant may be any of 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 coating layer within a range not to impair the effect of suppressing iridescent color under fluorescent lamps and the adhesion.

In order to impart other functionality to the coating layer, various additives may be contained within a range not to impair the effect of suppressing iridescent color under a fluorescent lamp and the adhesion. Examples of the additives include fluorescent dyes, fluorescent brighteners, plasticizers, ultraviolet absorbers, pigment dispersants, foam inhibitors, antifoaming agents, and preservatives.

As the coating method, any of a so-called inline coating method in which coating is performed simultaneously when the film is formed into a polyester base film and a so-called offline coating method in which coating is performed separately by a coater after the film is formed into a polyester base film can be applied, and the inline coating method is effective, and is more preferable.

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

In the present invention, a method of providing a coating layer on a polyester film includes a method of applying a coating liquid containing a solvent, particles, and a resin to a polyester film and drying the coating liquid. Examples of the solvent include an organic solvent such as toluene, water, or a mixed system of water and a water-soluble organic solvent, and it is preferable that water is mixed with a water-soluble organic solvent alone or in water from the viewpoint of environmental problems.

The solid content concentration of the coating liquid depends on the type of the binder resin, the type of the solvent, and the like, and is preferably 2% by mass or more, and more preferably 4% by mass or more. 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 coating is preferably 80 ℃ or higher and preferably 250 ℃ or lower, depending on the type of binder resin, the type of solvent, the presence or absence of a crosslinking agent, the solid content concentration, and the like.

The surface roughness (Ra) of the coating layer is preferably 0.01nm or more, more preferably 0.1nm or more, further preferably 0.2nm or more, and particularly preferably 0.5nm or more, depending on the slipperiness of the surface of the coating layer. On the other hand, the upper limit of the surface roughness (Ra) of the coating layer is preferably 200nm or less, more preferably 100nm or less, further preferably 80nm or less, and particularly preferably 50nm or less.

(production of an easily adhesive polyester film for optical use)

The optical easy-adhesive polyester film of the present invention can be produced by a general method for producing a polyester film. For example, the following methods can be mentioned: the polyester resin is melted, extruded and molded into a sheet form to obtain a non-oriented polyester, the obtained non-oriented polyester is stretched in the longitudinal direction at a temperature of not less than the glass transition temperature by a speed difference of a roller, and then stretched in the transverse direction by a tenter, and heat treatment is performed.

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

This phenomenon is caused by the fact that the biaxially stretched film is composed of refractive index ellipsoids having different refractive indices in the traveling direction, the width direction, and the thickness direction, and exists in a direction in which the in-plane retardation amount becomes zero (the refractive index ellipsoids are visible as a perfect circle) depending on the light transmission direction inside the film. Therefore, if the liquid crystal display screen is viewed from a specific direction in the oblique direction, a point where the in-plane retardation amount becomes zero may occur, and the rainbow-like color unevenness may occur concentrically around the point. Further, if the angle of the position where the rainbow-like color unevenness is observed from directly above the film surface (normal direction) is represented by θ, the larger the birefringence in the film surface is, the larger the angle θ becomes, and the more difficult the rainbow-like color unevenness is to be observed. Since the biaxially stretched film tends to have a smaller angle θ, it is preferable that iridescent unevenness is less likely to be observed in the case of a uniaxially stretched film.

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 where substantially no rainbow-like color unevenness occurs or in a range where no rainbow-like color unevenness occurs in a viewing angle range required for a liquid crystal display screen.

(laminated polyester film)

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

It is also a preferable embodiment to provide a functional layer on the coating layer of the easy-adhesion polyester film of the present invention. The functional layer is a layer having functionality, such as an antiglare layer, an antiglare antireflection layer, an antireflection layer, a low reflection layer, and an antistatic layer, in addition to the hard coat layer, for the purpose of preventing reflection of light, suppressing glare, suppressing rainbow unevenness, and suppressing scratches. As the functional layer, various substances known in the art can be used, and the kind thereof is not particularly limited. Hereinafter, each functional layer will be explained.

For example, in the formation of the hard coat layer, a known hard coat layer may be used, and a resin compound which is polymerized and/or reacted by drying, heat, a chemical reaction, or irradiation with any of electron beams, radiation, and ultraviolet rays may be used without particular limitation. Examples of such curable resins include melamine-, acrylic-, silicone-and polyvinyl alcohol-based curable resins, and photocurable acrylic curable resins are preferred for 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 acrylates, epoxy acrylates, urethane acrylates, polyether acrylates, polybutadiene acrylates, silicone acrylates, and the like. By mixing a reactive diluent, a photopolymerization initiator, a sensitizer and the like with these acrylic curable resins, a coating composition for forming the optically 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%, and particularly preferably 0 to 30%. Of course, 0% is preferable, and may be 0.2% or more, or may be 0.5% or more.

Therefore, the film of the present invention can be suitably used for all applications of films for optical use, including prism lens sheets, AR (anti-reflection) films, hard coat films, diffusion plates, and shatter-proof films, as base films for optical members such as LCDs, flat TVs, and CRTs, near infrared absorption filters as members for front panels for plasma displays, touch panels, and 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 functional group, for example, there can 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 (meth) acrylate or the like containing a polyfunctional compound such as a polyol, and a monofunctional monomer and a polyfunctional monomer such as ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, methylstyrene, and N-vinylpyrrolidone as reactive diluents, for example, 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, and neopentyl glycol di (meth) acrylate.

Among them, in the case of an electron beam or ultraviolet ray curable resin, acetophenones, benzophenones, Michler's benzoyl benzoate, α -aminooxime ester, tetramethylthiuram monosulfide, thioxanthone, etc., which are photopolymerization initiators, may be mixed with the resin, or n-butylamine, triethylamine, tri-n-butylphosphine, etc., which are photosensitizers, may be mixed with the resin.

The silicone (siloxane) thermosetting resin can be produced by hydrolyzing and condensing 2 or more organosilane compounds alone or in combination under an acid or alkali catalyst. In particular, in the case of low reflection, when 1 or more kinds of fluorosilane compounds are mixed and subjected to hydrolysis and condensation reaction, the composition is further excellent in the improvement of low refractive index property, stain resistance and the like.

(production of laminated polyester film)

The method for producing the laminated polyester film of the present invention is described by taking an easily adhesive polyester film as an example, but is not limited thereto.

The electron beam or ultraviolet ray curable acrylic resin or silicone thermosetting resin is applied on the surface of the coating layer of the easy-adhesion polyester film. In the case of coating layers on both sides, the coating is applied to at least one coated side. The coating liquid is not particularly diluted, but if necessary, the viscosity, wettability, coating thickness, and the like of the coating liquid are diluted with an organic solvent. The coating layer is formed by applying the coating liquid to the film, drying the coating liquid if necessary, and then curing the coating layer by irradiation with electron beams or ultraviolet rays and heating the coating liquid according to the curing conditions of the coating liquid, thereby forming a hard coat layer.

In the present invention, the thickness of the hard coat layer is preferably 1 to 15 μm. When the thickness of the hard coat layer is 1 μm or more, the effects of chemical resistance, abrasion resistance, stain resistance and the like as the hard coat layer are effectively exerted, 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 cracking or the like, and it is preferable.

As scratch resistance, it is preferable that scratches are not visually apparent when the coated surface is abraded with black lining paper. In the above evaluation, if the scratch is not obvious, the scratch is not easily generated when the sheet passes through the guide roll, and the scratch is preferable from the viewpoint of workability and the like.

The lower limit of the coefficient of static friction (. mu.s) is preferably 0.3, and if it is 0.3 or more, there is no problem of excessive slip, and therefore, the hard chrome plated roller or the like tends to be easily wound up in the production process. The workability and blocking resistance can be maintained, and preference is given. The upper limit of the coefficient of static friction (. mu.s) is preferably 0.5, and if it is 0.5 or less, there is no fear of scratching the film which is to be a contact target surface at the time of rolling.

The lower limit of the coefficient of dynamic friction (. mu.d) is preferably 0.4, and if it is 0.4 or more, there is no problem of excessive slip, and therefore, the hard chrome plated roller or the like tends to be easily wound up in the production process. The workability and blocking resistance can be maintained, and preference is given. The upper limit of the dynamic friction coefficient (. mu.d) is preferably 0.6, and if it is 0.6 or less, the film to be a contact target surface is not scratched when rolled up, and it is preferable.

The polyester film of the present invention is preferably highly transparent as long as it is used as an easily adhesive film for optical use. The lower limit of the haze is desirably 0%, and the lower limit is more preferably closer to 0%. The upper limit of the haze is preferably 2%, and when the haze is 2% or less, the light transmittance is good, and a clear image can be obtained in the liquid crystal display device, which is preferable. The haze of the polyester film can be measured, for example, by the method described later.

The adhesion between the coating layer having easy adhesion and the hard coat layer is preferably 80% in the lower limit and 100% in the upper limit, according to the evaluation by the measurement method described later. If the content is 80% or more, the adhesion between the coating layer and the hard coat layer can be said to be sufficiently maintained.

The lower limit of the adhesion between the easy-adhesion layer and the hard coat layer under high-temperature and high-humidity conditions, which is evaluated by the method described later, is preferably 10%, and the upper limit of the adhesion under high-temperature and high-humidity conditions is preferably 100%. If the content is 10% or more, the adhesion between the easy-adhesion layer and the hard coat layer can be satisfied at one time under high temperature and high humidity conditions, and the passability in the subsequent processing steps can be satisfied at one time. More preferably 50% or more.

The polyester film for protecting a polarizing plate on which a hard coat layer is formed is preferably one in which interference unevenness by an evaluation method described later is not observed, and if interference unevenness by the evaluation method is not observed, visibility of the liquid crystal image device is good, and it is preferable.

The easy-adhesion polyester film of the present invention can be used for various applications, is preferably used in a process for producing a polarizing plate used in a liquid crystal display device, and is particularly preferably used as a protective film for a polarizing plate constituting the polarizing plate. In general, most polarizing plates are made of polyvinyl alcohol, and the easy-adhesion polyester film of the present invention is bonded to the polarizing plate with an adhesive made of polyvinyl alcohol and containing a crosslinking agent or the like as necessary. In this case, the coating layer of the easy-adhesion polyester film of the present invention is more preferably used so as to face not the surface to be adhered to the polarizing plate but the opposite surface. The easy-adhesive polyester film of the present invention is preferably laminated with an easy-adhesive layer containing a polyester resin, a polyvinyl alcohol resin, and a crosslinking agent, as described in, for example, international publication No. 2012/105607, on the surface to be adhered to a polarizing plate.

Examples

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

(1) Average particle diameter

[ measurement method based on scanning Electron microscope ]

The average particle diameter of the particles can be measured by the following method. The particles are photographed by a Scanning Electron Microscope (SEM), the maximum particle diameter (distance between 2 points farthest from each other) of 300 to 500 particles is measured at a magnification of 2 to 5mm in the size of 1 particle which is the smallest, and the average particle diameter is defined as the average particle diameter. The average particle diameter of the particles present in the coating layer in the present invention can be measured by this measurement method.

[ dynamic light scattering method ]

The average particle diameter of the particles can be determined by a dynamic scattering method in the production of particles and films. The sol was diluted with a dispersion medium, and the average particle diameter was obtained by calculation by an accumulation method using the parameters of the dispersion medium and measured by a submicron particle analyzer N4 PLUS (manufactured by Beckman Coulter). In the dynamic light scattering method, the average particle diameter of particles in a sol is observed, and when the particles are aggregated, the average particle diameter of the aggregated particles is observed.

(2) Refractive index of the particles

The refractive index of the particles can be measured by the following method. After drying the inorganic particles at 150 ℃, the inorganic particles were pulverized in a mortar to obtain a powder, the obtained powder was immersed in a solvent 1 (having a refractive index lower than that of the particles), and then a solvent 2 (having a refractive index higher than that of the particles) was added little by little until the fine particles were substantially transparent. The refractive index of the solution was measured with an abbe refractometer (atagaco, abbe refractometer by ltd.). The measurement was carried out at 23 ℃ under D-ray (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 1,1,1,3,3, 3-hexafluoro-2-propanol, chloroform, carbon tetrachloride, toluene, and glycerol, depending on the refractive index.

(3) Haze of easily adhesive polyester film

Haze of easy-adhesion polyester film was measured according to JIS K7136: 2000, measured by a turbidimeter (Nippon Denshoku Kogyo, NDH 2000).

(4) Adhesion Property

The hard coat layer described in the above-mentioned item of formation of the hard coat layer was formed on the easy-adhesion layer of the polyester film obtained in the examples. The adhesion between the hard coat layer and the base film was determined on the easy-adhesion polyester film having the hard coat layer formed thereon in accordance with JIS-K5400-1990's 8.5.1.

Specifically, 100 mesh scratches reaching the base film were formed on the surface of the hard coat layer by passing through the hard coat layer with a cutter guide having a gap of 2 mm. Subsequently, a cellophane tape (No. 405, manufactured by Nichiban; 24mm wide) was adhered to the mesh-like scratched surface, and wiped with an eraser to completely adhere thereto. After that, the cellophane tape was vertically peeled off from the hard coat layer surface of the hard coat laminated polarizer protective film, and the number of meshes peeled off from the hard coat layer surface of the hard coat laminated polarizer protective film was visually counted to obtain the adhesion between the hard coat layer and the base film from the following formula. Note that some of the peeled cells in the mesh are also counted as peeled cells.

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

(5) Interference fringe improvement (Rainbow-like color)

A hard coat layer was formed on the easy-adhesion layer of the optical easy-adhesion polyester film obtained in each example. The optical easy-adhesive polyester film having the hard coat layer formed thereon was cut into an area of 10cm (film width direction) × 15cm (film length direction), to prepare a sample film. A black gloss tape (ethylene base tape No21, manufactured by Rido electric Co., Ltd.; black) was attached to the surface of the obtained sample film opposite to the hard coat layer surface. The hard-coated surface of the sample film was set to the upper surface, and the film was observed from obliquely above with a positional relationship (angle of 15 to 45 degrees at a distance of 40 to 60cm from the light source) in which the reflection was most visible, using a 3-wavelength daylight color (National Palook, F.L 15 EX-N15W) as the light source.

The results observed by visual observation were ranked according to the following criteria. Note that the observation was performed in 5 of the subjects skilled in the evaluation, and the maximum rating was defined as the evaluation rating. Assuming that the same number is used in 2 ranks, the center is divided into 3 ranks. For example, when 2 and 1 are each x and Δ, respectively, o is adopted, when 1 is x and 2 is Δ and Δ, when 2 is x, 2 is x and Δ and 1 is Δ, respectively, o is adopted.

Very good: no iridescent coloration is observed from all angles

O: slightly visible iridescent colors according to a certain angle

And (delta): slightly iridescent coloration was observed

X: clear iridescent colors were observed

(6) Blocking resistance

The coated surfaces of 2 laminated films were superposed and opposed to each other, and 5kg/cm was applied ² The load of (3) was left in an atmosphere at 50 ℃ for 24 hours. The films after the overlapping were peeled off, and the peeled state was judged by the following criteria.

Very good: can be peeled off lightly

O: the peeling was resistant, but the coating layer was not transferred to the object surface.

And (delta): a peeling sound is generated, and part of the coating layer is transferred to the target surface

X: 2 sheets of the film were fixed and could not be peeled off, or even if peeled off, the base film was cleaved

(7) Glass transition temperature

10mg of a resin sample was heated at 20 ℃/min in a temperature range of 25 to 300 ℃ by a differential scanning calorimeter (DSC 6200, Seiko Instruments) according to JIS K7121-1987, and the extrapolated glass transition starting temperature obtained from the DSC curve was taken as the glass transition temperature.

(8) Number average molecular weight

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

(9) Resin composition

The resin was dissolved in deuterated chloroform, and 1H-NMR analysis was performed using a nuclear magnetic resonance analyzer (NMR) Gemini-200 (manufactured by Varian corporation), and the molar% ratio of each composition was determined based on the integrated ratio.

(polymerization of polyester resin)

Polymerization of copolyester resins (B1) to (B3) for coating layer

342.0 parts by mass of dimethyl 2, 6-naphthalenedicarboxylate, 35.0 parts by mass of dimethyl terephthalate, 35.5 parts by mass of sodium dimethyl isophthalate-5-sulfonate, 198.6 parts by mass of ethylene glycol, 118.2 parts by mass of 1, 6-hexanediol, and 0.4 part by mass of tetra-n-butyl titanate were charged into a stainless steel autoclave equipped with a stirrer, a thermometer, and a partial reflux condenser, and ester exchange reaction was carried out at 160 ℃ to 220 ℃ for 4 hours. Further, 60.7 parts by mass of sebacic acid was added to carry out an esterification reaction. Subsequently, the temperature was raised to 255 ℃ and the pressure of the reaction system was gradually reduced, followed by reaction under a reduced pressure of 30Pa for 1 hour and 30 minutes to obtain a copolyester resin (B1). The obtained copolyester resin is light yellow and transparent.

The composition of the copolyester resin (B1) is shown in table 1.

Further, copolyester resins (B2) and (B3) having the compositions shown in table 1 were obtained in the same manner with changing the raw materials.

[ Table 1]

(production of an aqueous polyester Dispersion)

30 parts by mass of the copolyester resin (B1) 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 unit, and the resins were dissolved by heating and stirring at 110 ℃. After the resin was completely dissolved, the resin solution was slowly added while stirring 55 parts by mass of water in the polyester solution. After the addition, the solution was cooled to room temperature while stirring, to prepare a milky-white aqueous polyester dispersion (Bw1) containing 25 mass% of a solid content.

An aqueous polyester dispersion Bw2 was similarly obtained from the copolyester resin B2, and an aqueous polyester dispersion Bw3 was obtained from the copolyester resin B3.

(production of aqueous polyurethane Dispersion)

Polymerization of Water-soluble polyurethane resin (A1) containing aliphatic polycarbonate polyol as component

43.75 parts by mass of 4, 4-diphenylmethane diisocyanate, 12.85 parts by mass of dimethylolbutyric acid, 153.41 parts by mass of polyhexamethylene carbonate diol having a number average molecular weight of 2000, 0.03 parts by mass of dibutyltin dilaurate and 84.00 parts by mass of acetone as a solvent were put into a four-necked flask equipped with a stirrer, a serpentine condenser, a nitrogen inlet, a silica gel drying tube and a thermometer, and stirred at 75 ℃ for 3 hours under a nitrogen atmosphere, whereby it was confirmed that the reaction solution reached a predetermined amine equivalent. Subsequently, the reaction solution was cooled to 40 ℃ and 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 homogeneous disperser capable of high-speed stirring, and the temperature was adjusted to 25 ℃ for 2000min ^-1 The polyurethane prepolymer solution was added while stirring and mixing, and dispersed in water. Then, under reduced pressure, acetone and water were partially removed to prepare a water-soluble urethane resin (a1) having a solid content of 37 mass%. The glass transition point temperature of the obtained polyurethane resin was-30 ℃.

Polymerization of Water-soluble polyurethane resin (A2) containing aliphatic polycarbonate polyol as component

A water-soluble polyurethane resin (a2) was prepared in the same manner as in the polymerization of a1, except that 38.41 parts by mass of isophorone diisocyanate, 6.95 parts by mass of dimethylolpropionic acid, 158.99 parts by mass of polyhexamethylene carbonate diol having a number average molecular weight of 2000, 0.03 parts by mass of dibutyltin dilaurate, and 84.00 parts by mass of acetone as a solvent were used.

(polymerization of blocked polyisocyanate-based crosslinking agent)

100 parts by mass of a polyisocyanate compound having an isocyanurate structure (manufactured by Asahi Kasei Chemicals Corporation, Duranate TPA), 55 parts by mass of propylene glycol monomethyl ether acetate, and 30 parts by mass of polyethylene glycol monomethyl ether (average molecular weight 750) each of which was prepared from hexamethylene diisocyanate were charged into a flask equipped with a stirrer, a thermometer, and a reflux condenser, and the flask was held at 70 ℃ for 4 hours under a nitrogen atmosphere. Thereafter, the temperature of the reaction solution was lowered to 50 ℃ and 47 parts by mass of methyl ethyl ketoxime was added dropwise. The infrared spectrum of the reaction solution was measured, and it was confirmed that the absorption of isocyanate groups was lost, thereby obtaining an aqueous dispersion of a blocked polyisocyanate (Cx1) having a solid content of 40 mass%.

(polymerization of oxazoline-based crosslinking agent)

Into a flask equipped with a thermometer, a nitrogen inlet, a reflux condenser, a dropping funnel, and a stirrer, a mixture of 58 parts by mass of ion exchange water and 58 parts by mass of isopropyl alcohol as an aqueous medium, and 4 parts by mass of a polymerization initiator (2, 2' -azobis (2-amidinopropane) · dihydrochloride) were charged. On the other hand, a mixture of 16 parts by mass of 2-isopropenyl-2-oxazoline as a polymerizable unsaturated monomer having an oxazoline group, 32 parts by mass of methoxypolyethylene glycol acrylate (an average number of moles of ethylene glycol added, manufactured by shinkanko chemical Co., Ltd.), and 32 parts by mass of methyl methacrylate was charged into a dropping funnel, and was dropwise added at 70 ℃ for 1 hour under a nitrogen atmosphere. After the completion of the dropwise addition, the reaction solution was stirred for 9 hours and cooled to obtain an oxazoline group-containing water-soluble resin (Cx2) having a solid content concentration of 40 mass%.

(polymerization of carbodiimide-based crosslinking agent)

168 parts by mass of hexamethylene diisocyanate and 220 parts by mass of polyethylene glycol monomethyl ether (M400, average molecular weight 400) were put into a flask equipped with a stirrer, a thermometer and a reflux condenser, and stirred at 120 ℃ for 1 hour, and then 26 parts by mass of 4, 4' -dicyclohexylmethane diisocyanate and 3.8 parts by mass of 3-methyl-1-phenyl-2-phosphorus-1-oxide (2% by mass relative to the total isocyanate) as a carbodiimidization catalyst were added thereto, and further stirred under nitrogen flow at 185 ℃ for 5 hours. The infrared spectrum of the reaction solution was measured, and the wavelength of 2200 to 2300cm was confirmed ^-1 The absorption of (2) disappears. Naturally cooled to 60 ℃ and then added with 567 parts by mass of ion-exchanged water to obtain a carbodiimide water-soluble resin (Cx3) having a solid content of 40 mass%.

(epoxy crosslinking agent)

As the epoxy crosslinking agent, Denacol (registered trademark) EX-521 (solid content concentration 100%) manufactured by Nagase ChemteX Corporation (epoxy crosslinking agent (Cx4)) was used.

(Melamine crosslinking agent)

As the melamine-based crosslinking agent, Beckamine (registered trademark) M-3 (solid content concentration 60%) manufactured by DIC corporation (melamine-based crosslinking agent (Cx5)) was used.

(zirconia particles)

The procedure is as follows with reference to example 8 of Japanese patent application laid-open No. 2008-290896.

In a 3-liter glass vessel, 2283.6g of pure water and 403.4g of oxalic acid dihydrate were charged, and heated to 40 ℃ to prepare a 10.72 mass% oxalic acid aqueous solution. While stirring the aqueous solution, zirconium oxycarbonate powder (ZrOCO) was slowly added ₃ Preparation of, and conversion to, ZrO by AMR International Corp ₂ The content was 39.76% by mass. )495.8g, mixed for 30 minutes and then heated at 90 ℃ for 30 minutes. Then, 1747.2g of a 25.0 mass% aqueous tetramethylammonium hydroxide solution (manufactured by Moore chemical Co., Ltd.) was slowly added over 1 hour. At this point, the mixed solution is in the form of slurry containing ZrO ₂ The content was 4.0% by mass in terms of conversion. The slurry was transferred to a stainless steel autoclave vessel and subjected to hydrothermal treatment at 145 ℃ for 5 hours. The product after this hydrothermal treatment was completely solated without unplocculations. The sol obtained is ZrO ₂ The content of the particles was 4.0% by mass based on pH6.8, and the average particle diameter obtained by a dynamic light scattering method was 19 nm. Further, the sol was adjusted to ZrO with pure water ₂ The concentration was 2.0 mass%, and the measured transmittance was 88%. The particles were observed by a transmission electron microscope, and as a result, ZrO was substantially around 7nm ₂ Aggregated particles of primary particles. With respect to ZrO obtained by the above hydrothermal treatment ₂ 4000g of 4.0 mass% zirconia sol, washed and concentrated using an ultrafiltration apparatus while slowly adding pure water, and then the resultant solution was subjected to concentration on ZrO 2 ₂ At a concentration of 13.1 mass% and pH4.9, ZrO was obtained ₂ 953g of a zirconia sol having a transmittance of 76% at a concentration of 13.1% by mass.

ZrO obtained after the above washing and concentration ₂ Oxygen at a concentration of 13.1 mass%After adding 3.93g of a 20 mass% citric acid aqueous solution and 11.0g of a 25 mass% tetramethylammonium hydroxide aqueous solution to 300g of the zirconium oxide sol, the mixture was further concentrated by an ultrafiltration apparatus, whereby ZrO was obtained ₂ 129g of a high-concentration zirconia sol (Cpz1) having a concentration of 30.5 mass%. The resulting high-concentration zirconia sol had a pH of 9.3 and an average particle diameter of 19nm as determined by a dynamic light scattering method. The zirconia sol is free from precipitates and stable at 50 ℃ for 1 month or more.

Further, Cpz2 having an average particle size of 32nm was obtained in example 2 of Japanese patent application laid-open No. 2008-290896, and Cpz3 having an average particle size of 48nm was obtained in example 1.

(titanium dioxide particles)

Example 1 of japanese patent application laid-open publication No. 2011-132484 is performed as follows.

Will be made of TiO ₂ 12.09kg of an aqueous Titanium tetrachloride solution containing 7.75 mass% of Titanium tetrachloride (Osaka Titanium Technologies Co., Ltd., manufactured by Ltd.) and 4.69kg of aqueous ammonia (manufactured by Utsu corporation) containing 15 mass% of ammonia were mixed on a reduced basis to prepare a white slurry having a pH of 9.5. Subsequently, the slurry was filtered and washed with pure water to obtain 9.87kg of a hydrous titanic acid cake having a solid content of 10 mass%. Then, 11.28kg of a hydrogen peroxide solution (manufactured by Mitsubishi gas chemical corporation) containing 35 mass% of hydrogen peroxide and 20.00kg of pure water were added to the cake, and then the mixture was heated at 80 ℃ for 1 hour under stirring, and 57.52kg of pure water was further added thereto to obtain a TiO complex ₂ 98.67kg of an aqueous solution of peroxotitanic acid containing 1 mass% peroxotitanic acid as converted to the standard. The aqueous solution of peroxotitanic acid was transparent tan and had a pH of 8.5.

Next, 4.70kg of cation exchange resin (manufactured by Mitsubishi chemical corporation) was mixed with 98.67kg of the aqueous solution of peroxotitanic acid, and SnO was slowly added thereto under stirring ₂ 12.33kg of an aqueous solution of potassium stannate containing 1% by mass of potassium stannate (available from Showa Kagaku K.K.) in terms of the standard. Next, the cation exchange resin doped with potassium ion or the like was separated, and the resulting mixture was placed in an autoclave (120L, manufactured by pressure-resistant Nitro industries, Ltd.) at a temperature of 165 ℃Heated at temperature for 18 hours.

Subsequently, the obtained mixed aqueous solution was cooled to room temperature, and then concentrated by an ultrafiltration membrane apparatus (ACV-3010, manufactured by Asahi chemical Co., Ltd.) to obtain 9.90kg of an aqueous dispersion sol (Cpt1) containing titanium-based fine particles (hereinafter referred to as "P-1") and having a solid content of 10 mass%. The solid content in the sol thus obtained was measured by the above-described 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, the content of each metal component in terms of oxide was as follows: TiO 2 ₂ 87.2% by mass SnO ₂ 11.0 mass% and K ₂ O1.8 mass%. The pH of the mixed aqueous solution was 10.0. Further, the aqueous dispersion sol containing the titanium-based fine particles was transparent and milky, and the titanium-based fine particles contained in the aqueous dispersion sol had an average particle diameter of 35nm by a dynamic light scattering method and a distribution frequency of coarse particles having a particle diameter of 100nm or more was 0%. The refractive index of the obtained titanium fine particles was 2.42.

Further, Cpt2 having an average particle size of 32nm was obtained in example 2 of Japanese patent application laid-open No. 2011-132484, and Cpt3 having an average particle size of 42nm was obtained in example 4.

(zirconia/titania mixed particles)

The zirconia particles (Cpz1) and titania particles (Cpt1) obtained in the above were mixed at a mass ratio of 75/25 to prepare zirconia/titania mixed particles having a solid content concentration of 13 mass ((Cp 1): average particle diameter 23 nm).

Similarly, Cp2 (average particle size 32nm) was obtained from Cpz2 and Cpt2, and Cp3 (average particle size 46nm) was obtained from Cpz3 and Cpt 3.

(cerium oxide particles)

The experiment was carried out as follows, with reference to Japanese patent application laid-open No. 2011-132107.

216g of cerium (III) chloride heptahydrate was put into 10L of distilled water and dissolved by stirring. While further stirring was continued, the temperature was raised to 93 ℃ and a total amount of 5.6kg of a 1.0% aqueous solution of sodium hydroxide was added at once. After further stirring at 93 ℃ for 6 hours, it was cooled to 25 ℃ to obtain a white precipitate.

The precipitate was separated by a centrifugal separator, 15L of distilled water was added to the obtained precipitate, and after stirring and redispersion, the precipitate was separated by a centrifugal separator. This operation was performed 3 times in total, and the precipitate was washed.

Distilled water was added to the obtained precipitate to adjust the pH to 9.2, and the mixture was dispersed by an ultrasonic disperser to obtain a cerium oxide particle dispersion (Cp4) having a solid content concentration of 12 mass%. The average particle diameter obtained by the dynamic light scattering method was 34 nm.

(formation of hard coat layer)

A hard coat layer-forming coating liquid having the following composition was applied to a surface of a polyester film produced in examples described below, which was opposite to the surface to be bonded to the polarizing plate, with a #10 wire bar, and dried at 70 ℃ for 1 minute to remove the solvent. Next, the film coated with the hard coat layer was irradiated with 300mJ/cm of light from a high-pressure mercury lamp ² The obtained protective film had a hard coat layer having a thickness of 5 μm.

Coating liquid for hard coat layer formation

Methyl ethyl ketone 65.00% by mass

Dipentaerythritol hexaacrylate 27.20% by mass

(Xinzhongcun chemical A-DPH)

6.80% by mass of polyethylene diacrylate

(Xinzhongcun chemical A-400)

Photopolymerization initiator 1.00% by mass

(Irgacure 184, product of Ciba Specialty Chemicals Inc.)

(example 1)

Coating liquid raw material

Aqueous dispersion of particles a: zirconia/titania mixed particles having an average particle diameter of 23nm (Cp1)

(zirconia content in zirconia/titania 75 mass%, solid content concentration 13 mass%)

Aqueous dispersion of particles B: silica sol having an average particle diameter of 450nm (solid content concentration: 4% by mass)

Aqueous polyester dispersion ((Bw1), solid content concentration 25% by mass)

Aqueous polyurethane dispersion ((A1), solid content concentration 37% by mass)

Blocked isocyanate-based crosslinking agent ((Cx1), solid content concentration 40% by mass)

(1) Coating liquid adjustment of easy adhesion layer

The coating liquid having the following composition was prepared.

(2) Production of easily bondable polyester film

PET resin pellets having an intrinsic viscosity (solvent: phenol/tetrachloroethane: 60/40) of 0.62dl/g and containing substantially no particles were dried at 135 ℃ under reduced pressure of 133Pa for 6 hours as a film raw material polymer. Thereafter, the sheet was fed to an extruder, melt-extruded at about 280 ℃ into a sheet form, and cooled and closely solidified on a rotating cooling metal roll whose surface temperature was kept at 20 ℃ to obtain an undrawn 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 the roll set having a peripheral speed difference to obtain a uniaxially stretched PET film.

Subsequently, the coating liquid was applied to one surface of a PET film by roll coating, and then dried at 80 ℃ for 15 seconds. The coating weight after drying after the final stretching was adjusted to 0.12g/m ² . Then, the film was stretched at 150 ℃ in the width direction by a tenter to 4.0 times, and while the length of the film in the width direction was constant, the film was heated at 230 ℃ for 0.5 second, and further subjected to relaxation treatment at 230 ℃ for 3% in the width direction for 10 seconds to obtain an easily adhesive polyester film for optical use having a thickness of 38 μm. The urethane resin component, the polyester resin component, and other components in the coating layer were 20 mass%, 30 mass%, and 50 mass%, respectively, as shown in table 2.

(examples 2, 3, 18 to 25, comparative examples 1 to 7)

An easily adhesive polyester film was obtained in the same manner as in example 1, except that the ratio of the urethane resin component, the polyester resin component, and the other components in the coating layer was changed to table 2 or 3.

(examples 4 to 7)

An easily adhesive polyester film was obtained in the same manner as in example 1, except that the composition of each component in the coating layer was changed as shown in table 2 by changing the crosslinking agent of the coating liquid.

(examples 8 to 12)

An easily adhesive polyester film was obtained in the same manner as in example 1, except that the kind of the particles a in the coating liquid was changed and the composition of each component in the coating layer was changed as shown in table 2.

(examples 13 to 15)

An easily adhesive polyester film was obtained in the same manner as in example 1 except that the film thickness of the coating layer was changed as shown in table 2.

(examples 16 and 17)

An easily adhesive polyester film was obtained in the same manner as in example 1, except that the amount of the particles B in the coating layer was changed as shown in table 2.

(examples 26 and 27)

An easily adhesive polyester film was obtained in the same manner as in example 1 except that the kind of the copolyester resin component was changed as shown in table 3.

(example 28)

An easily adhesive polyester film was obtained in the same manner as in example 1, except that the kind of the urethane resin component was changed as shown in table 3.

The respective results are shown in tables 2 and 3. Fig. 1 shows plots on triangular charts of examples and comparative examples.

[ Table 2]

[ Table 3]

(coefficient of static Friction, coefficient of dynamic friction (. mu.s,. mu.d))

The friction coefficients of the polyester films obtained in examples and comparative examples were measured by Tensilon (Toyo Baldwin, RTM-100) according to JIS K7125-1999 Plastic film and sheet friction coefficient test method, and were all in the range of 0.35 to 0.5 in terms of static friction coefficient (. mu.s) and 0.45 to 0.6 in terms of kinetic friction coefficient (. mu.d), and there was no problem in terms of windup property and handling property.

Industrial applicability

According to the present invention, there can be provided: a polyester film which has low interference, transparency, blocking resistance, adhesion to various functional layers, and excellent sliding properties and which is suitable for use in optical applications, particularly polarizing plate protective films, and a laminated polyester film using the same.

Claims

1. A laminated polyester film having a coating layer on at least one surface of a polyester film, wherein the coating layer contains a polyurethane resin having a polycarbonate skeleton and a polyester resin having a naphthalene skeleton, and 1 or more functional layers selected from the group consisting of a hard coat layer, an antiglare antireflection layer, an antireflection layer and a low reflection layer are provided on the coating layer, wherein when the total solid content of the coating layer is 100 mass%, the content (mass%) of the polyurethane resin component is a, the content (mass%) of the polyester resin component having a naphthalene skeleton is b, and the total amount (mass%) of the components other than these is c, and the values a, b and c are in a region surrounded by 4 straight lines of a straight line P1, a straight line Q1, a straight line R1 and a straight line S1,

here, the straight line P1, the straight line Q1, the straight line R1, and the straight line S1 are as follows:

straight line P1: a straight line passing through points a, b, and c of 10, 55, and 35 mass%, and points a, b, and c of 10, and 80 mass%, respectively

Line Q1: a straight line passing through points where a is 10 mass%, b is 10 mass%, and c is 80 mass%, and points where a is 70 mass%, b is 10 mass%, and c is 20 mass%

Straight line S1: a straight line passing through points where a is 45 mass%, b is 45 mass%, and c is 10 mass%, and points where a is 10 mass%, b is 55 mass%, and c is 35 mass%.

2. A laminated polyester film as claimed in claim 1, wherein the coating layer contains a crosslinking agent.

3. The laminated polyester film according to claim 1 or 2, wherein the coating layer contains particles a which are metal oxide particles having a refractive index of 1.7 or more.

4. A laminated polyester film according to any one of claims 1 to 3, wherein the coating layer contains lubricant particles, i.e., particles B.