JP7230994B2 - Easy-adhesive polyester film - Google Patents

Description

TECHNICAL FIELD The present invention relates to an easy-adhesive polyester film that can ensure low interference that can solve the problem of iridescent unevenness, and that is excellent in adhesion to various functional layers, blocking resistance, and transparency.

A hard coat film obtained by laminating a transparent hard coat layer is used on the front surface of touch panels, computers, televisions, displays such as liquid crystal display devices, decorative materials, and the like. In addition, a transparent polyester film is generally used as the transparent plastic film of the base material. In many cases, a coating layer having a

The hard coat film is required to have durability against temperature, humidity and light, transparency, chemical resistance, scratch resistance, antifouling property and the like. In addition, since they are often used on the surfaces of displays and decorative materials, visibility and designability are required. Therefore, in order to suppress glare and iris-like colors due to reflected light when viewed from any angle, a multi-layered anti-reflection structure in which a high refractive index layer and a low refractive index layer are laminated on top of the hard coat layer It is common practice to provide layers.

However, in applications such as displays and decorative materials, in recent years, there has been a demand for even larger screens (larger areas) and higher definition, and along with this, there is a demand for suppression of iris-like colors (interference spots), especially under fluorescent lights. The level is getting higher. In addition, since fluorescent lamps are mainly of the three-wavelength type because of the reproducibility of daylight colors, interference spots are more likely to occur. Furthermore, there is an increasing demand for cost reductions due to the simplification of the antireflection layer. Therefore, there is a demand for a hard coat film without an antireflection layer that suppresses interference spots as much as possible.

Furthermore, with the development of mobile technology, mobile devices such as mobile phones, car navigation systems, and electronic books are being used outdoors. In addition, most of the above-mentioned mobile devices have a liquid crystal panel display from the viewpoint of slimness. In such a field, for example, in mobile phones equipped with touch panels, as a hard coat film to protect the surface of the display, there are interference fringes caused by reflected light from both interfaces in contact with the coated surface, and designs on the back of the hard coat film such as icon sheets. In applications where the effect is applied, the drawback of visibility due to interference fringes is becoming more apparent.

The iris-like color (interference spots) of the hard coat film is determined by the refractive index of the polyester film as the substrate (eg, 1.62 to 1.65) and the refractive index of the hard coat layer made of acrylic resin or the like (eg, 1.49). It is said that this occurs because there is a large difference between In order to reduce the difference in refractive index between layers and prevent the occurrence of interference spots, a coating layer with a relatively high refractive index is provided on the polyester film as the base material, and the difference in refractive index between the polyester film and the coating layer, the coating layer and a method of reducing the refractive index difference between the hard coat layer and the hard coat layer.

Conventionally, in the field of optical easy-adhesive films, methods for increasing the refractive index of the easy-adhesive layer include 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. It has been known. In particular, a polyester resin using a naphthalenedicarboxylic acid as a copolymerization component is excellent in adhesion to a substrate polyester film, and has been proposed as a suitable example (see, for example, Patent Document 1). However, polyester resin with a high refractive index generally has a high glass transition temperature, which may be due to the lack of flexibility of the resin. there were. On the other hand, a method using a polyurethane resin having a polycarbonate component as a resin having excellent flexibility and high adhesion has been proposed (see, for example, Patent Document 2), and Patent Document 1 also incorporates a polyurethane resin having a polycarbonate component. However, when the polyurethane component is increased, there is a problem that the low interference property and the transparency are deteriorated. As described above, conventionally, an easy-adhesive polyester film having a high balance of adhesion to the hard coat layer, blocking resistance, and transparency while meeting the high level of low interference in recent years has not been obtained. I didn't.

JP 2011-246663 A JP 2011-168053 A

The present invention has been made against the background of such problems of the prior art. That is, the object of the present invention is low interference that can suppress iridescent unevenness, adhesion to hard coat layers etc. that are required at a high level in various optical applications, blocking resistance, and transparency. An object of the present invention is to provide an easy-adhesive polyester film which has slipperiness and is excellent in handleability during manufacturing and in post-processes such as manufacturing processes for polarizing plates of liquid crystal display devices.

That is, the present invention consists of the following configurations.
1. A coating containing, on at least one side of a polyester film, a polyurethane resin having a polycarbonate skeleton, a polyester resin having a naphthalene skeleton, a cross-linking agent, metal oxide particles (particles A) having a refractive index of 1.7 or more, and lubricant particles (particles B). The content (% by mass) of the polyurethane resin component having a polycarbonate skeleton when the coating layer has a layer and the total solid content of the coating layer is 100% by mass, and the content (% by mass) of the polyester resin component having a naphthalene skeleton is b, when the total amount (mass%) of other components is represented by a ternary diagram as c, a, b, and c are within the area surrounded by the four straight lines P1, Q1, R1, and S1 and wherein the total amount c of other components is 55% by mass or less when the total solid content of the coating layer is 100% by mass.
Here, straight line P1, straight line Q1, straight line R1, and straight line S1 are as follows.

Straight line P1: A straight line Q1 that passes through a point where a is 10% by mass, b is 55% by mass, and c is 35% by mass, and a point where a is 10% by mass, b is 10% by mass, and c is 80% by mass. : Straight line R1 passing through the point where a is 10% by mass, b is 10% by mass, and c is 80% by mass and the point where a is 70% by mass, b is 10% by mass, and c is 20% by mass: a is 70% by mass, b is 10% by mass, and c is 20% by mass, and a point is 50% by mass, b is 40% by mass, and c is 10% by mass. A straight line passing through the point where mass%, b is 45 mass%, and c is 10 mass%, and the point where a is 10 mass%, b is 55 mass%, and c is 35 mass%

2. 1. The easy-adhesive polyester film as described in 1 above, wherein the metal oxide particles (particles A) having a refractive index of 1.7 or more have an average particle size of 5 nm or more and 200 nm or less.
3. The easy-adhesive polyester film according to the first or second above, wherein the lubricant particles (particles B) have an average particle size of 200 nm or more and 2000 nm or less.
4. The easy-adhesive polyester film for a polarizer protective film according to any one of the first to third items, wherein the coating layer has a thickness of 0.5 μm or less.
5. 4. The easy-adhesive polyester film according to any one of the first to fourth items, wherein the easy-adhesive polyester film is for a polarizer protective film.
6. Selected from the group consisting of a hard coat layer, an antiglare layer, an antiglare antireflection layer, an antireflection layer and a low reflection layer on the coating layer of the easily adhesive polyester film according to any one of the above 1 to 5. A laminated polyester film having one or more functional layers.

INDUSTRIAL APPLICABILITY According to the present invention, it has become possible to provide an easy-adhesive polyester film excellent in low interference, transparency, anti-blocking property, adhesion to various functional layers, and slipperiness, which can suppress iridescent unevenness.

1 is a triangular diagram showing a preferred range for the easily adhesive polyester film of the present invention.

(polyester film)
The polyester film used as a base material in the present invention is a film composed of a polyester resin, and is preferably a polyester film composed mainly of at least one of polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate. . Also, the film may be a film made of a copolymerized polyester obtained by copolymerizing the above polyester with a third component monomer. Among these polyester films, polyethylene terephthalate film is most preferable from the viewpoint of balance between physical properties and cost.

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

(Coating layer)
The easily-adhesive polyester film in the present invention is obtained by laminating an easily-adhesive coating layer on the polyester base film as described above.
In the coating layer of the present invention, the content (mass%) of the polyurethane resin component having a polycarbonate skeleton is a, and the content of the polyester resin component having a naphthalene skeleton ( %) is represented by b, and the total amount (% by mass) of other components is represented by a triangular diagram, where a, b, and c are surrounded by four straight lines: straight line P1, straight line Q1, straight line R1, and straight line S1. It is preferably within the defined region.

Here, straight line P1, straight line Q1, straight line R1, and straight line S1 are as follows.
Straight line P1: A straight line Q1 that passes through a point where a is 10% by mass, b is 55% by mass, and c is 35% by mass, and a point where a is 10% by mass, b is 10% by mass, and c is 80% by mass. : Straight line R1 passing through the point where a is 10% by mass, b is 10% by mass, and c is 80% by mass and the point where a is 70% by mass, b is 10% by mass, and c is 20% by mass: a is 70% by mass, b is 10% by mass, and c is 20% by mass, and a point is 50% by mass, b is 40% by mass, and c is 10% by mass. A straight line passing through the point where mass%, b is 45 mass%, and c is 10 mass%, and the point where a is 10 mass%, b is 55 mass%, and c is 35 mass%

Within the above range, all of low coherence (improvement of interference fringes), adhesion, anti-blocking properties and transparency can be maintained at a well-balanced and high level.

The preferred range will be briefly explained using the ternary chart shown in FIG. The three sides of the triangular chart show the content a (% by mass) of the polyurethane resin component having a polycarbonate skeleton, b (% by mass) the content of the polyester resin component having a naphthalene skeleton, and c (% by mass) the other components. Each coordinate axis is shown. Here, if the coordinates inside the ternary diagram are written in the order of (a, b, c), there are five coordinates (10, 55, 35), (10, 10, 80), (70) in the ternary diagram. , 10,20), (50,40,10) and (45,45,10) are shown. A straight line P1 passing through (10,55,35) and (10,10,80), a straight line Q1 passing through (10,10.80) and (70,10,20), and (70,10,20 ) and (50, 40, 10), and a straight line S1 passing through (45, 45, 10) and (10.55, 35). The inner range surrounded by indicates a range in which low coherence (improvement of interference fringes), adhesion, anti-blocking properties, and transparency can be provided in a well-balanced manner.

Furthermore, a more preferable range for each straight line is described below.
Instead of straight line P1, straight line P2 (the point where a is 15% by mass, b is 55% by mass, and c is 30% by mass, and the point where a is 15% by mass, b is 10% by mass, and c is 75% by mass) It is preferable to adopt a straight line passing through and.

Instead of straight line Q1, straight line Q2 (a point of 10 mass%, b of 20 mass%, c of 70 mass% and a point of a of 70 mass%, b of 10 mass%, c of 20 mass% A straight line passing through), and a straight line Q3 (a is 20% by mass, b is 20% by mass, c is 60% by mass, a is 70% by mass, b is 10% by mass, and c is 20% by mass. It is preferable to adopt a straight line passing through the points of

Instead of the straight line R1, a straight line R2 (the point where a is 65% by mass, b is 10% by mass, and c is 25% by mass, and the point where a is 45% by mass, b is 40% by mass, and c is 15% by mass) A straight line passing through), and a straight line R3 (a is 60% by mass, b is 10% by mass, c is 30% by mass, a is 40% by mass, b is 40% by mass, and c is 20% by mass. It is preferable to adopt a straight line passing through the points of

Instead of the straight line S1, a straight line S2 (the point where a is 50% by mass, b is 40% by mass, and c is 10% by mass, and the point where a is 10% by mass, b is 50% by mass, and c is 40% by mass) A straight line passing through), and a straight line S3 (a point of 52 mass%, b of 38 mass%, c of 10 mass%, a of 10 mass%, b of 48 mass%, c of 42 mass% A straight line passing through the points), especially S4 (the point where a is 55% by mass, b is 35% by mass, c is 10% by mass, a is 10% by mass, b is 45% by mass, and c is 45% by mass. % point) is preferably adopted.

The lower limit of the content a of the polyurethane resin component having a polycarbonate skeleton is preferably 10% by mass, more preferably 13% by mass, and still more preferably 15% by mass. It is preferable that the content a of the polyurethane resin component having a polycarbonate skeleton is 10% by mass or more because the transparency is not impaired and the adhesion is satisfactory.
The upper limit of the content a of the polyurethane 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. When the content a of the polyurethane resin component having a polycarbonate skeleton is 70% by mass or less, the refractive index is kept high and low interference is obtained, which is preferable.

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. It is preferable that the content b of the polyester resin component having a naphthalene skeleton is 10% by mass or more because the adhesion is satisfactory.
The upper limit of the content b of the polyester resin component having a naphthalene skeleton is preferably 55% by mass, more preferably 50% by mass, still more preferably 48% by mass, and particularly preferably 45% by mass. When the content b of the polyester resin component having a naphthalene skeleton is 55% by mass or less, blocking resistance is exhibited, which is preferable.

The lower limit of the content c of other components is preferably 10% by mass, more preferably 20% by mass, even more preferably 25% by mass, and particularly preferably 30% by mass. It is preferable that the content c of other components is 10% by mass or more because the low interference property is improved if a component that increases the refractive index of the coating layer is included. Moreover, as a result, the content a of the polyurethane resin having a polycarbonate skeleton does not become too large, and blocking can be prevented, which is preferable.
The upper limit of the content c of other components 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 components is 80% by mass or less, as a result, it is easy to balance 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, resulting in adhesion. is maintained, and the blocking resistance and the refractive index (low coherence) are easily balanced.

(Polyurethane resin having a polycarbonate skeleton)
The diol component, which is a constituent component of the polyurethane resin having a polycarbonate skeleton, preferably contains an aliphatic polycarbonate polyol which is excellent in heat resistance and hydrolysis resistance. In optical applications of the present invention, it is preferable to use an aliphatic polycarbonate polyol from the viewpoint of preventing yellowing.

Aliphatic polycarbonate polyols include aliphatic polycarbonate diols and aliphatic polycarbonate triols, and aliphatic polycarbonate diols can be preferably used. Examples of aliphatic polycarbonate diols that are constituents of the urethane resin of the present invention include 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, 1,4- Aliphatic polycarbonate diols obtained by reacting one or more diols such as cyclohexanedimethanol with carbonates such as dimethyl carbonate, diphenyl carbonate, ethylene carbonate and phosgene.

Polyurethane resin having a polycarbonate skeleton is the ratio of the absorbance (A1460) around 1460 cm ⁻¹ derived from the aliphatic polycarbonate component and the absorbance (A1530) around 1530 cm ⁻¹ derived from the urethane component measured by infrared spectroscopy (A1460/ A1530) is preferably 0.40 to 2.30.
When the ratio (A1460/A1530) is 0.40 or more, the hard urethane component does not become too much, stress relaxation of the coating layer does not deteriorate, and there is no fear of deterioration in resistance to moist heat, which is preferable. In addition, when the ratio (A1460/A1530) is 2.30 or less, the aliphatic component of the flexible aliphatic polycarbonate does not become too much, and the solvent resistance of the coating layer is maintained, and the wet heat resistance may decrease. It is preferable because there is no

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

Examples of the polyisocyanate that is a component of the urethane resin in the present invention include aromatic-aliphatic diisocyanates such as xylylene diisocyanate, isophorone diisocyanate and 4,4-dicyclohexylmethane diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane. Alicyclic diisocyanates such as hexamethylene diisocyanate, and aliphatic diisocyanates such as 2,2,4-trimethylhexamethylene diisocyanate, or poly prepared by adding a single or multiple of these compounds with trimethylolpropane or the like in advance. Isocyanates can be mentioned. The above polyisocyanates are free from the problem of yellowing and are preferred for optical applications requiring high transparency. In addition, such polyisocyanates are preferable because the coating film does not become too hard, stress due to contraction and swelling of the photocurable resin can be relieved, and adhesion is maintained.

In order to impart water solubility to the urethane resin, a sulfonic acid (salt) group or a carboxylic acid (salt) group can be introduced (copolymerized) into the urethane molecular skeleton. A sulfonic acid (salt) group is strongly acidic, and it may be difficult to maintain moisture resistance due to its hygroscopicity, so it is preferable to introduce a weakly acidic carboxylic acid (salt) group. A nonionic group such as a polyoxyalkylene group can also be introduced.

In order to introduce a carboxylic acid (salt) group into a urethane resin, for example, as a polyol component, a polyol compound having a carboxylic acid group such as dimethylolpropionic acid or dimethylolbutanoic acid is introduced as a copolymerization component to form a salt. Neutralize with an agent. Specific examples of salt-forming agents include ammonia, trialkylamines such as trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine and tri-n-butylamine; -N-dialkylalkanolamines such as alkylmorpholines, N-dimethylethanolamine and N-diethylethanolamine. These can be used alone or in combination of two or more.

When 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 urethane resin is the same as that of the urethane resin. When the total polyol component is 100 mol %, it is preferably 3 to 60 mol %, preferably 5 to 40 mol %. When the composition molar ratio is 3 mol % or more, the water dispersibility is good, which is preferable. In addition, when the composition molar ratio is 60 mol % or less, water resistance is maintained and moist heat resistance is maintained, which is preferable.

The glass transition temperature of the urethane resin in the present invention is preferably less than 0°C, more preferably less than -5°C. When the glass transition temperature is less than 0° C., it is preferable from the viewpoint of stress relaxation of the coating layer because it tends to exhibit suitable flexibility.

(Polyester resin having a naphthalene skeleton)
By including a component derived from naphthalene dicarboxylic acid as the acid component of the polyester resin contained in the coating layer, the refractive index is increased, making it easier to control the iridescent color under a fluorescent lamp. Moreover, it becomes possible to improve moist heat resistance.

As such naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid is preferred. The proportion of the naphthalene dicarboxylic 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 even more preferably 60 mol% or more.

Further, within the range where the effect of the present invention is exhibited, as an acid component in the polyester resin, terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 1,4-cyclohexanedicarboxylic acid, trimellitic acid, pyromellitic acid , dimer acid, 5-sodium sulfoisophthalic acid, 4-sodium sulfonaphthalene-2,7-dicarboxylic acid, adipic acid, azelaic acid, sebacic acid, and the like may be used. When these are copolymerized, the aromatic dicarboxylic acid component including naphthalene dicarboxylic acid is preferably 70 mol % or more, more preferably 80 mol % or more, from the viewpoint of moist heat resistance and high refractive index. Particularly when moist heat resistance and high refractive index are important, the aromatic dicarboxylic acid component is preferably 90 mol % or more, more preferably 95 mol % or more, and particularly preferably 100%.

As long as the effects of the present invention are exhibited, ethylene glycol, 1,3-propane glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, and neopentyl glycol may be used as the diol component in the polyester resin. , diethylene glycol, 1,4-cyclohexanedimethanol, xylene glycol, an ethylene oxide adduct of bisphenol A, and the like may be used.

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 deteriorates, and there is a possibility that the coating layer may be scraped off or particles may come off during post-processing. In such a case, it is one of preferred forms that the polyester resin contains a dicarboxylic acid component represented by the following formula (1) and/or a diyl component represented by the following formula (2).
(1) HOOC-(CH2)n-COOH (wherein n is an integer of 4 ≤ n ≤ 10)
(2) HO-(CH2)n-OH (wherein n is an integer of 4 ≤ n ≤ 10)

Thus, by containing an acid component and/or a diol component having a carbon component with a specific length, flexibility is imparted to the polyester resin, and even relatively large particles can be easily retained and the coating layer It is possible to suppress scraping and falling off of particles.
Examples of the dicarboxylic acid component of formula (1) include adipic acid, sebacic acid and azelaic acid. Examples of the diol component of formula (2) include butanediol and hexanediol.

The polyester resin is water, or a water-soluble organic solvent (e.g., an aqueous solution containing less than 50% by mass of alcohol, alkyl cellosolve, ketone, or ether) or an organic solvent (e.g., toluene, ethyl acetate, etc.) Dissolved or dispersed ones can be used.

When a polyester resin is used as a water-based coating liquid, a water-soluble or water-dispersible polyester resin is used. It is preferred to copolymerize compounds containing acid bases.

The number average molecular weight of the polyester resin is preferably 5,000 to 40,000 from the viewpoint of coating film strength, ease of water dispersion, and the like. More preferably 10,000 to 30,000, particularly preferably 12,000 to 25,000.

Incidentally, the polyester resin containing the naphthalenedicarboxylic acid component may be a single one or a blend of two or more kinds. In the case of a blend of two or more kinds, it is preferable that the total composition of the polyester resin components is as described above.

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 cross-linking agent, lubricant particles, and metal oxide particles that increase the refractive index of the coating layer. , surfactants, and the like. In the present invention, it is preferable to contain a cross-linking agent, lubricant particles, and metal oxide particles that increase the refractive index of the coating layer. The coating liquid contains a solvent and may contain surfactants, etc. However, the mass of the solvent remaining after drying and curing and the mass of the solid content of the surfactant are extremely small. When determining the composition of each component by calculation, the mass of the residual solvent and the mass of the solid content of the surfactant do not necessarily have to be included in the solid content mass of the entire coating layer, and the description of the composition in the examples is based on the above calculation. is based on

The coating layer may contain a cross-linking agent in order to form a crosslinked structure in the coating layer. By containing a cross-linking agent, it becomes possible to further improve adhesion under high temperature and high humidity conditions. Specific cross-linking agents include urea-based, epoxy-based, melamine-based, isocyanate-based, oxazoline-based, carbodiimide-based, and the like. Among these, melamine-based, isocyanate-based, oxazoline-based, and carbodiimide-based cross-linking agents are preferable from the viewpoint of the stability of the coating liquid over time and the effect of improving adhesion under high-temperature and high-humidity treatment. In addition, a catalyst or the like can be appropriately used as necessary in order to accelerate the cross-linking reaction.

When the coating layer contains a cross-linking agent, the content of the cross-linking agent is preferably 5% by mass or more and 50% by mass or less in the total solid components of the coating layer. More preferably, it is 10% by mass or more and 40% by mass or less. When it is 10% by mass or more, the strength of the resin in the coating layer is maintained, and the adhesion under high temperature and high humidity is good. It is preferable because the adhesiveness is maintained at room temperature and under high temperature and high humidity.

Moreover, it is preferable to incorporate high refractive index metal oxide particles (particles A) having a refractive index of 1.7 or more in the coating layer. Examples of such metal oxides include TiO ₂ (refractive index 2.7), ZnO (refractive index 2.0), Sb ₂ O ₃ (refractive index 1.9), SnO ₂ (refractive index 2.1), _ZrO2 (refractive index 2.4), _{Nb2O5 (} refractive index 2.3) _{, CeO2} (refractive index 2.2), _Ta2O5 (refractive index _2.1 ), _Y2O3 (refractive index 1.8), La ₂ O ₃ (refractive index 1.9), In ₂ O ₃ (refractive index 2.0), Cr ₂ O ₃ (refractive index 2.5), etc., and metal atoms thereof Composite oxide particles and the like are included.

The lower limit of the refractive index of the particles A is preferably 1.7, more preferably 1.75. The upper limit of the refractive index of the particles A is preferably 3.0, more preferably 2.7, still more preferably 2.5. A good balance between low interference, transparency, adhesion, and anti-blocking properties can be obtained by setting the above range.

Composite oxide particles used as particles A are preferably TiO ₂ / ZrO ₂ particles (zirconia/titania mixed particles). A zirconia/titania mixed particle is a particle group containing both zirconia and titania in an aggregated state such that zirconia and titania are individually dispersed in a single liquid and do not form a composite. Of course, most of the liquid component in the coating layer is evaporated during the drying and curing steps. By including such particles A in the coating layer, it is possible to ensure an excellent balance between lubricity and transparency, as well as high transparency and low interference. The liquid is preferably a water-based liquid in order to facilitate the formation of a coating layer by a so-called in-line coating method, which will be described later.

The zirconia/titania mixed particles may contain components other than zirconia/titania, may be inorganic particles or organic particles, and are not particularly limited, but may include silica, Metal oxides such as titanium dioxide (titania), zirconium oxide (zirconia), talc and kaolinite, and inorganic particles inert to polyester such as calcium carbonate, calcium phosphate and barium sulfate are exemplified.

The average particle size of the particles A is preferably 5 nm or more, more preferably 10 nm or more, still more preferably 15 nm or more, and particularly preferably 20 nm or more. It is preferable that the particles A have an average particle size of 5 nm or more because aggregation is unlikely to occur.

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

In the present invention, it is preferable to incorporate lubricant particles (particles B) in the coating layer.

Particle B includes (1) 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, and aluminum silicate. , inorganic particles such as diatomaceous earth, calcium silicate, aluminum hydroxide, hydrated halloysite, magnesium carbonate, magnesium hydroxide, etc. (2) acrylic or methacrylic, vinyl chloride, vinyl acetate, nylon, styrene/acrylic, Styrene/butadiene, polystyrene/acrylic, polystyrene/isoprene, polystyrene/isoprene, methyl methacrylate/butyl methacrylate, melamine, polycarbonate, urea, epoxy, urethane, phenol, diallyl phthalate , polyester-based organic particles, etc., and silica is particularly preferably used in order to impart appropriate lubricity to the coating layer.

The average particle size of the particles B is preferably 200 nm or more, more preferably 250 nm or more, still more preferably 300 nm or more, and particularly preferably 350 nm or more. When the average particle diameter of the particles B is 200 nm or more, it is preferable because the particles are less likely to aggregate and the lubricity can be ensured.

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

Particles A and B may be surface-treated, and surface treatment methods include physical surface treatments such as plasma discharge treatment and corona discharge treatment, and chemical surface treatments using a coupling agent. is preferred. As the coupling agent, an organoalkoxymetal compound (eg, titanium coupling agent, silane coupling agent) is preferably used. Silane coupling treatment is particularly effective when the particles B are silica. As a surface treatment agent for the particles B, it may be used for surface treatment prior to the preparation of the coating solution for the layer, or it may be added as an additive during the preparation of the coating solution for the layer so as to be contained in the layer. Of course, you may use for the particle|grains 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, still more 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 kept high, and low interference is effectively obtained, which is preferable.

The content of particles A in the coating layer is preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less, and particularly preferably 20% by mass or less. It is preferable that the content of the particles A in the coating layer is 50% by mass or less because film-forming properties are maintained.

The content of particles B in the coating layer is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and still more preferably 0.1% by mass or more. It is preferable that the content of the particles B in the coating layer is 0.01% by mass or more because a suitable lubricity can be maintained.

The content of particles B in the coating layer is preferably 2% by mass or less, more preferably 1.5% by mass or less, and even more 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 is kept low, which is preferable from the viewpoint of transparency.

The thickness of the coating layer is preferably 0.001 μm or more, more preferably 0.01 μm or more, still more preferably 0.02 μm or more, and particularly preferably 0.05 μm or more. Adhesiveness is favorable in the film thickness of a coating layer being 0.001 micrometer or more, and it is preferable.

The 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, which is preferable.

The coating layer may contain a surfactant for the purpose of improving leveling properties during coating and defoaming the coating solution. The surfactant may be cationic, anionic, or nonionic, but silicone, acetylene glycol, or fluorine-based surfactants are preferred. These surfactants are preferably contained in the coating layer within a range that does not impair the effect of suppressing iridescent coloring under fluorescent light and the adhesion.

In order to impart other functionality to the coating layer, various additives may be added within a range that does not impair the effect of suppressing the iris-like coloration under a fluorescent lamp and the adhesion. Examples of the additives include fluorescent dyes, fluorescent whitening agents, plasticizers, ultraviolet absorbers, pigment dispersants, foam inhibitors, antifoaming agents, preservatives, and the like.

As the coating method, both a so-called in-line coating method in which coating is performed simultaneously with the formation of the polyester base film, and a so-called off-line coating method in which coating is performed with a separate coater after forming the polyester base film can be applied. In-line coating methods are efficient and more preferred.

As a coating method, any known method can be used for coating a polyethylene terephthalate (hereinafter abbreviated as PET) film with a coating solution. For example, reverse roll coating method, gravure coating method, kiss coating method, die coater method, roll brush method, spray coating method, air knife coating method, wire bar coating method, pipe doctor method, impregnation coating method, curtain coating method, etc. be done. These methods are used singly or in combination for coating.

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

The solid content concentration of the coating liquid depends on the type of binder resin, the type of solvent, etc., but is preferably 2% by mass or more, more preferably 4% by mass. The solid content concentration of the coating liquid is 3
It is preferably 5% by mass or less, more preferably 15% by mass or less.

The drying temperature after coating also depends on the type of binder resin, the type of solvent, the presence or absence of a cross-linking agent, the solid content concentration, etc., but is preferably 80° C. or higher and preferably 250° C. or lower.

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

(Manufacturing of easy-adhesive polyester film for optical use)
The easy-adhesive polyester film for optical use in the present invention can be produced according to a general method for producing a polyester film. For example, a polyester resin is melted and a non-oriented polyester extruded into a sheet is stretched in the longitudinal direction using the speed difference between rolls at a temperature equal to or higher than the glass transition temperature, and then stretched in the transverse direction with a tenter, A method of applying a heat treatment can be mentioned.

The polyester film in the present invention may be a uniaxially stretched film or a biaxially stretched film, but when the biaxially stretched film is used as a protective film in front of the liquid crystal panel, the film is observed from directly above the film surface. Although rainbow-like color spots are not observed even when observed from an oblique direction, it is necessary to pay attention to the fact that rainbow-like color spots may be observed in some cases.

This phenomenon occurs because the biaxially stretched film consists of a refractive index ellipsoid with different refractive indices in the running direction, width direction, and thickness direction, and the in-plane retardation becomes zero depending on the direction of light transmission inside the film (refractive This is because there is a direction in which the index ellipsoid looks like a perfect circle. Therefore, when the liquid crystal display screen is observed from a specific oblique direction, a point where the in-plane retardation becomes zero may occur, and rainbow-like color spots appear concentrically around that point. Assuming that the angle from directly above the film plane (normal direction) to the position where the rainbow-like color spots appear is θ, this angle θ increases as the birefringence in the film plane increases, and the rainbow-like colors The spots become less visible. Since the angle θ tends to be small in a biaxially stretched film, a uniaxially stretched film is preferable because rainbow-like color spots are less visible.

However, a completely uniaxial (uniaxially symmetrical) film is not preferable because the mechanical strength in the direction perpendicular to the orientation direction is remarkably lowered. The present invention has biaxiality (biaxial symmetry) in a range in which rainbow-like color spots are not substantially generated, or in a range in which rainbow-like color spots are not generated in the viewing angle range required for liquid crystal display screens. preferably.

(Laminated polyester film)
In the present invention, the laminated polyester film that is mainly used for optical applications is a hard coat made of an electron beam- or ultraviolet-curable acrylic resin, a siloxane-based thermosetting resin, or the like, on the coating layer of the easily-adhesive polyester film of the present invention. It is obtained by providing a layer or the like.

It is also a preferred form to provide a functional layer on the coating layer of the easily adhesive polyester film in the present invention. Functional layers include anti-glare layers, anti-glare anti-reflection layers, anti-reflection layers, low-reflection layers and A functional layer such as an antistatic layer. Various functional layers known in the art can be used, and the type is not particularly limited. Each functional layer will be described below.

For example, for the formation of the hard coat layer, a known hard coat layer can be used and is not particularly limited. and/or reactive resin compounds can be used. Such curable resins include melamine-based, acrylic-based, silicone-based, and polyvinyl alcohol-based curable resins. Resins are preferred. Polyfunctional (meth)acrylate-based monomers and acrylate-based oligomers can be used as such acrylic curable resins. Examples of acrylate-based oligomers include polyester acrylate, epoxy acrylate, urethane acrylate, poly Examples include ether acrylate, polybutadiene acrylate, and silicone acrylate. A coating composition for forming the optical function layer can be obtained by mixing a reactive diluent, a photopolymerization initiator, a sensitizer, and the like with these acrylic curable resins.

The hard coat layer may have an antiglare function (antiglare function) for scattering external light. An anti-glare function (anti-glare function) is obtained by forming unevenness on the surface of the hard coat layer. At this time, the haze of the film is ideally preferably 0 to 50%, more preferably 0 to 40%, and particularly preferably 0 to 30%. Of course, 0% is ideal, and it may be 0.2% or more, or 0.5% or more.

Therefore, the use of the film in the present invention is mainly for optical films in general, and optical films such as prism lens sheets, AR (anti-reflection) films, hard coat films, diffusion plates, crush prevention films, LCDs, flat TVs, CRTs, etc. It can be suitably used for a base film of a display member, a near-infrared absorbing filter which is a member of a front panel for a plasma display, a transparent conductive film for a touch panel or electroluminescence, and the like.

More specifically, the acrylic resin that is cured by electron beams or ultraviolet rays for forming the hard coat layer has an acrylate-based functional group, such as a relatively low-molecular-weight polyester resin, polyether resin, acrylic resin , epoxy resins, urethane resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins, oligomers or prepolymers such as (meth)acrylates of polyfunctional compounds such as polyhydric alcohols, and ethyl (meth) as a reactive diluent. Monofunctional monomers such as acrylates, ethylhexyl (meth)acrylate, styrene, methylstyrene, N-vinylpyrrolidone, and multifunctional monomers 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, etc. can be used.

However, in the case of electron beam or UV curable resins, acetophenones, benzophenones, Michler benzoyl benzoate, α-amyloxime ester, tetramethylthirium monosulfide, and thioxanthone are added to the above resins as photopolymerization initiators. or a mixture of n-butylamine, triethylamine, tri-n-butylphosphine and the like as a photosensitizer.

In addition, silicone-based (siloxane-based) thermosetting resins can be produced by hydrolyzing and condensing organosilane compounds singly or in a mixture of two or more in the presence of an acid or base catalyst. In particular, in the case of low reflection, it is better to mix one or more fluorosilane compounds and carry out hydrolysis and condensation reaction to improve the low refractive index property and stain resistance.

(Manufacture of laminated polyester film)
The method for producing the laminated polyester film of the present invention will be described with an easy-adhesive polyester film as an example, but it is of course not limited to this.

The above-mentioned electron beam- or UV-curable acrylic resin or siloxane-based thermosetting resin is applied to the coating layer surface of the above-mentioned easy-adhesive polyester film. When the coating layer is provided on both sides, it is applied to at least one of the coating layer surfaces. It is not necessary to dilute the coating liquid, but there is no particular problem if it is diluted with an organic solvent depending on the viscosity, wettability, coating thickness, etc. of the coating liquid. The coating layer is formed by applying the coating liquid to the above-mentioned film, drying it if necessary, and then curing the coating layer by irradiating electron beams or ultraviolet rays and heating according to the curing conditions of the coating liquid. , to form 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 effect of the hard coat layer on chemical resistance, scratch resistance, antifouling property, etc. is efficiently exhibited, which is preferable. On the other hand, when the thickness is 15 μm or less, the flexibility of the hard coat layer is maintained, and cracks and the like are not likely to occur, which is preferable.

As for scratch resistance, it is preferable that scratches are not conspicuous visually when the coated surface is abraded with a black backing paper. If no scratches are conspicuous in the above evaluation, it is less likely to be scratched when passing through the guide rolls, which is preferable from the viewpoint of handling.

The lower limit of the coefficient of static friction (μs) is preferably 0.3, and if it is 0.3 or more, there is no problem of excessive slippage, so winding up with a hard chrome-plated roll or the like in the manufacturing process becomes easy. It is preferable because handleability and anti-blocking property are maintained. The upper limit of the coefficient of static friction (μs) is preferably 0.5, and when it is 0.5 or less, there is no fear of scratching the film, which is the contact surface during winding, and this is preferable.

The lower limit of the coefficient of dynamic friction (μd) is preferably 0.4, and if it is 0.4 or more, there is no problem of excessive slippage, so winding up with a hard chrome-plated roll or the like in the manufacturing process becomes easy. It is preferable because handleability and anti-blocking property are maintained. The upper limit of the coefficient of dynamic friction (μd) is preferably 0.6, and when it is 0.6 or less, it is preferable because there is no fear of scratching the film, which is the contact surface during winding.

Since the polyester film in the present invention is mainly used as an easily adhesive film for optics, it preferably has high transparency. The lower limit of haze is ideally 0%, and the closer to 0%, the more preferable. The upper limit of the haze is preferably 2%, and when it 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, according to the method described below.

The adhesion between the easy-adhesive coating layer and the hard coat layer is preferably 80% as a lower limit and 100% as an upper limit, as determined by the measurement method described below. When it is 80% or more, it can be said that the adhesion between the coating layer and the hard coat layer is sufficiently maintained.

Regarding the adhesion between the easy adhesion layer and the hard coat layer under high temperature and high humidity conditions, which is evaluated according to the method described later, the lower limit is preferably 10%, and the upper limit of the high temperature and high humidity adhesion is preferably 100%. be. When it is 10% or more, the adhesion between the easy-adhesion layer and the hard coat layer is generally satisfied under high-temperature and high-humidity conditions, and the passability in post-processing steps is generally satisfied. More preferably, it is 50% or more.

The polyester film for protecting a polarizer with a hard coat preferably has no interference unevenness observed by the evaluation method described below. preferable.

The easy-adhesive polyester film of the present invention can be used for various purposes, and is preferably used in the manufacturing process of polarizing plates used in liquid crystal display devices, and is particularly preferably used as a protective film for a polarizer constituting a polarizing plate. It is something that can be done. Most polarizers are usually made of polyvinyl alcohol, and the easily adhesive polyester film of the present invention is adhered to the polarizer using an adhesive made of polyvinyl alcohol or an adhesive obtained by adding a cross-linking agent or the like to the polarizer, if necessary. In this case, the coating layer of the easy-adhesive polyester film of the present invention is more preferably applied not to the side to be adhered to the polarizer but to the opposite side. The surface of the easy-adhesive polyester film of the present invention to be adhered to a polarizer contains, for example, a polyester-based resin, a polyvinyl alcohol-based resin, and a cross-linking agent as described in International Publication No. 2012/105607. Preferably the layers are laminated.

EXAMPLES Next, the present invention will be described in detail using examples, comparative examples, and reference examples, but the present invention is of course not limited to the following examples. Moreover, the evaluation methods used in the present invention are as follows.

(1) Average particle size [measurement method using a scanning electron microscope]
The average particle size of the above particles can be measured by the following method. The particles are photographed with a scanning electron microscope (SEM) and the largest diameter of 300-500 particles (between the two furthest Distance) is measured, and the average value is taken as the average particle size. The average particle diameter of particles present in the coating layer in the present invention can be measured by the measuring method.

[Dynamic light scattering method]
The average particle diameter of particles can also be determined by a dynamic scattering method during the production of particles and films. The sol was diluted with a dispersion medium, measured with a submicron particle analyzer N4 PLUS (manufactured by Beckman Coulter) using the parameters of the dispersion medium, and calculated by the cumulant method to obtain an average particle size. In the dynamic light scattering method, the average particle size of particles in the sol is observed, and when particles are aggregated, the average particle size of the aggregated particles is observed.

(2) Refractive index of particles
Refractive index measurement of particles can be performed by the following method. After drying the inorganic particles at 150 ° C., the powder ground in a mortar is immersed in solvent 1 (with a lower refractive index than the particles), and then solvent 2 (with a higher refractive index than the particles) is added little by little until the fine particles are almost transparent. was added until The refractive index of this liquid was measured using an Abbe refractometer (Abbe refractometer manufactured by Atago Co., Ltd.). Measurements were made at 23° C. and D-line (wavelength 589 nm). The above solvent 1 and solvent 2 are selected from those that can be mixed with each other, and depending on the refractive index, Solvents such as carbon, toluene, glycerin and the like are included.

(3) Haze of easy-adhesive polyester film The haze of the easy-adhesive polyester film was measured according to JIS K 7136:2000 using a turbidity meter (NDH2000, manufactured by Nippon Denshoku).

(4) Adhesion The hard coat layer described in the section on the formation of the hard coat layer was formed on the easily adhesive layer of the polyester film obtained in the example. Adhesion between the hard coat layer and the base film is determined according to the description of JIS-K5400-1990, 8.5.1 of the easily adhesive polyester film with the hard coat formed thereon.

Specifically, using a cutter guide with a gap interval of 2 mm, 100 grid-like cuts that penetrate the hard coat layer and reach the substrate film are made on the hard coat layer surface. Next, a cellophane adhesive tape (No. 405, 24 mm width, manufactured by Nichiban Co., Ltd.) is attached to the square-shaped cut surface and completely adhered by rubbing with an eraser. After that, the cellophane adhesive tape was peeled off vertically from the hard coat layer surface of the hard coat laminated polarizer protective film, and the number of squares peeled off from the hard coat layer surface of the hard coated laminated polarizer protective film was visually counted, and the following formula was obtained. The adhesion between the hard coat layer and the substrate film is obtained from the above. In addition, a square that is partially peeled off is also counted as a peeled square.
Adhesion (%) = {1-(number of peeled squares/100)} x 100

(5) Improvement of interference fringes (iris color)
A hard coat layer was formed on the easy-adhesion layer of the optical easy-adhesion polyester film obtained in each example. A sample film was prepared by cutting the hard-coated easy-adhesive polyester film for optical use into an area of 10 cm (film width direction)×15 cm (film longitudinal direction). A black glossy tape (vinyl tape No. 21, manufactured by Nitto Denko Corporation; black) was attached to the surface of the obtained sample film opposite to the hard coat layer surface. With the hard-coated side of this sample film facing up, and with a three-wavelength daylight white light (National Park, FL 15EX-N 15W) as the light source, the positional relationship where the strongest reflection can be seen visually from above (distance from the light source: 40 to 60 cm, 15-45° angle).

The results of visual observation are ranked according to the following criteria. The observation was conducted by 5 persons who were familiar with the evaluation, and the most common rank was taken as the evaluation rank. If two ranks had the same number, the center of the three separate ranks was adopted. For example, if there are 2 ◎ and ○ and 1 △, mark ○, if there is 1 ◎ and 2 ○ and △, mark ○, 2 ◎ and △ and 1 ○ In the case of first name, ○ is adopted respectively.
◎: No iris-like color observed from any angle ○: Slight iris-like color observed at certain angles △: Slight iris-like color observed ×: Clear iris-like color observed be done

(6) Blocking Resistance Two laminate films were superimposed so that the coated surfaces faced each other, a load of 5 kg/cm ² was applied, and this was allowed to stand in an atmosphere of 50°C for 24 hours. The superimposed films were peeled off, and the peeled state was evaluated according to the following criteria.
⊚: Can be easily peeled ◯: There is resistance during peeling, but the coating layer does not transfer to the other surface.
△: A peeling sound is generated, and the coating layer is partially transferred to the other surface
×: The two films are adhered and cannot be peeled off, or the base film is cleaved even if they can be peeled off.

(7) Glass transition temperature In accordance with JIS K7121-1987, using a differential scanning calorimeter (manufactured by Seiko Instruments, DSC6200), 10 mg of resin sample was heated at 20 ° C./min over a temperature range of 25 to 300 ° C. , the extrapolated glass transition start temperature obtained from the DSC curve was taken as the glass transition temperature.

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

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

(Polymerization of polyester resin)
Polymerization of Copolyester Resins (B1) to (B3) for Coating Layer In a stainless steel autoclave equipped with a stirrer, a thermometer, and a partial reflux condenser, 342.0 parts by mass of dimethyl 2,6-naphthalenedicarboxylate, 35.0 parts by weight of dimethyl terephthalate, 35.5 parts by weight of dimethyl-5-sodium sulfoisophthalate, 198.6 parts by weight of ethylene glycol, 118.2 parts by weight of 1,6-hexanediol, and 0.2 parts by weight of tetra-n-butyl titanate. 4 parts by mass were charged, and the transesterification reaction was carried out from 160° C. to 220° C. over 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° C., the reaction system was gradually decompressed, and the reaction was allowed to proceed under a reduced pressure of 30 Pa for 1 hour and 30 minutes to obtain a copolymerized polyester resin (B1). The resulting copolymerized polyester resin was pale yellow and transparent.
Table 1 shows the composition of the copolymer polyester resin (B1).
Copolyester resins (B2) and (B3) having the compositions shown in Table 1 were obtained in the same manner by changing the raw materials.

(Production of polyester aqueous dispersion)
A reactor equipped with a stirrer, a thermometer and a reflux device was charged with 30 parts by mass of the copolymer polyester resin (B1) and 15 parts by mass of ethylene glycol-n-butyl ether, heated at 110° C. and stirred to dissolve the resin. After the resin was completely dissolved, 55 parts by mass of water was gradually added to the polyester solution with stirring. After the addition, the liquid was cooled to room temperature while stirring to prepare a milky white polyester water dispersion (Bw1) having a solid content of 25% by mass.
Similarly, an aqueous polyester dispersion Bw2 was obtained from the copolymer polyester resin B2, and an aqueous polyester dispersion Bw3 was obtained from the copolymer polyester resin B3.

(Production of polyurethane aqueous dispersion)
Polymerization of water-soluble polyurethane resin (A1) containing aliphatic polycarbonate polyol as a constituent component In a four-necked flask equipped with a stirrer, a Dimroth condenser, a nitrogen inlet tube, a silica gel drying tube, and a thermometer, 4,4- 43.75 parts by weight of diphenylmethane diisocyanate, 12.85 parts by weight of dimethylolbutanoic acid, 153.41 parts by weight of polyhexamethylene carbonate diol having a number average molecular weight of 2000, 0.03 parts by weight of dibutyltin dilaurate, and 84.00 parts by weight of acetone as a solvent and stirred for 3 hours at 75° C. under a nitrogen atmosphere, and it was confirmed that the reaction solution reached a predetermined amine equivalent weight. Next, after the temperature of this reaction liquid was lowered to 40° C., 8.77 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring, adjusted to 25° C., and while stirring and mixing at 2000 min ⁻¹ , the polyurethane prepolymer solution was added and dispersed in water. . After that, acetone and part of the water were removed under reduced pressure to prepare a water-soluble polyurethane resin (A1) having a solid content of 37% by mass. The glass transition temperature of the obtained polyurethane resin was -30°C.

Polymerization of water-soluble polyurethane resin (A2) containing aliphatic polycarbonate polyol as a constituent component 38.41 parts by mass of isophorone diisocyanate, 6.95 parts by mass of dimethylolpropanoic acid, 158.99 parts by mass of polyhexamethylene carbonate diol having a number average molecular weight of 2000 A water-soluble polyurethane resin (A2) was prepared in the same manner as the polymerization of A1, except that 0.03 parts by weight of dibutyltin dilaurate and 84.00 parts by weight of acetone as a solvent were used.

(Polymerization of block polyisocyanate-based cross-linking agent)
100 parts by mass of a polyisocyanate compound having an isocyanurate structure (manufactured by Asahi Kasei Chemicals, Duranate TPA) made from hexamethylene diisocyanate in a flask equipped with a stirrer, a thermometer and a reflux condenser, 55 parts by mass of propylene glycol monomethyl ether acetate, 30 parts by mass of polyethylene glycol monomethyl ether (average molecular weight: 750) was charged, and the mixture was held at 70°C for 4 hours under a nitrogen atmosphere. After that, the temperature of the reaction solution was lowered to 50° C., and 47 parts by mass of methyl ethyl ketoxime was added dropwise. By measuring the infrared spectrum of the reaction solution, it was confirmed that the absorption of the isocyanate groups had disappeared, and an aqueous blocked polyisocyanate dispersion (Cx1) having a solid content of 40% by mass was obtained.

(Polymerization of oxazoline-based cross-linking agent)
A mixture of 58 parts by mass of ion-exchanged water as an aqueous medium and 58 parts by mass of isopropanol in a flask equipped with a thermometer, a nitrogen gas inlet tube, a reflux condenser, a dropping funnel, and a stirrer, and a polymerization initiator (2, 2 4 parts by mass of '-azobis(2-amidinopropane).dihydrochloride) was added. On the other hand, in a dropping funnel, 16 parts by mass of 2-isopropenyl-2-oxazoline as a polymerizable unsaturated monomer having an oxazoline group, methoxypolyethylene glycol acrylate (average number of moles of ethylene glycol added: 9 mol, Shin-Nakamura Chemical A mixture of 32 parts by mass of the product (manufacturer) and 32 parts by mass of methyl methacrylate was added and added dropwise over 1 hour at 70° C. under a nitrogen atmosphere. After completion of the dropwise addition, the reaction solution was stirred for 9 hours and cooled to obtain a water-soluble resin (Cx2) having a solid content of 40% by mass and having an oxazoline group.

(Polymerization of carbodiimide-based cross-linking agent)
A flask equipped with a stirrer, a thermometer and a reflux condenser was charged with 168 parts by mass of hexamethylene diisocyanate and 220 parts by mass of polyethylene glycol monomethyl ether (M400, average molecular weight: 400), stirred at 120°C for 1 hour, and then stirred for 4 hours. 26 parts by mass of 4′-dicyclohexylmethane diisocyanate and 3.8 parts by mass of 3-methyl-1-phenyl-2-phosphorene-1-oxide as a carbodiimidation catalyst (2% by mass relative to the total isocyanate) were added, and the mixture was stirred under a nitrogen stream at 185°C. °C for an additional 5 hours. The infrared spectrum of the reaction solution was measured, and it was confirmed that absorption at wavelengths of 2200 to 2300 cm ^-1 had disappeared. After allowing to cool to 60° C., 567 parts by mass of ion-exchanged water was added to obtain a carbodiimide water-soluble resin (Cx3) having a solid content of 40% by mass.

(epoxy cross-linking agent)
As an epoxy-based cross-linking agent, Denacol (registered trademark) EX-521 (solid concentration: 100%) manufactured by Nagase ChemteX Corporation was used (epoxy-based cross-linking agent (Cx4)).

(melamine cross-linking agent)
As a melamine-based cross-linking agent, Beccamin (registered trademark) M-3 (solid concentration: 60%) manufactured by DIC was used (melamine-based cross-linking agent (Cx5)).

(zirconia particles)
With reference to Example 8 of JP-A-2008-290896, the following procedure was carried out.
2283.6 g of pure water and 403.4 g of oxalic acid dihydrate were placed in a 3-liter glass container and heated to 40° C. to prepare a 10.72 mass % oxalic acid aqueous solution. While stirring this aqueous solution, 495.8 g of zirconium oxycarbonate powder (ZrOCO ₃ , manufactured by AMR International Corp., containing 39.76% by mass in terms of ZrO ₂ ) was gradually added and mixed for 30 minutes. , 90° C. for 30 minutes. Then, 1747.2 g of a 25.0% by mass tetramethylammonium hydroxide aqueous solution (manufactured by Tama Chemical Industry Co., Ltd.) was gradually added over 1 hour. At this point, the mixed liquid was in the form of a slurry and contained 4.0% by mass in terms of _ZrO2 . This slurry was transferred to a stainless steel autoclave container and hydrothermally treated at 145° C. for 5 hours. The product after this hydrothermal treatment was completely solified with no unpeptized matter. The resulting sol contained 4.0% by mass of ZrO ₂ , had a pH of 6.8, and had an average particle size of 19 nm as determined by the dynamic light scattering method. Also, the transmittance measured by adjusting the sol to a ZrO ₂ concentration of 2.0% by mass with pure water was 88%. Observation of the particles with a transmission electron microscope revealed that most of the particles were agglomerates of ZrO ₂ primary particles of around 7 nm. Using an ultrafiltration device, 4000 g of _zirconia sol having a ZrO concentration of 4.0% by mass obtained by the above hydrothermal treatment was washed and concentrated while gradually adding pure water to obtain a ZrO concentration _of 953 g of a zirconia sol with a transmittance of 76% at a ZrO 2 concentration of 13.1% by weight, pH 4.9 and a ZrO ₂ concentration of 13.1% by weight were obtained.

After adding 3.93 g of a 20% by mass citric acid aqueous solution and 11.0 g of a 25% by mass tetramethylammonium hydroxide aqueous solution to 300 g of _a zirconia sol having a ZrO concentration of 13.1% by mass obtained by performing the above washing and concentration. Furthermore, when concentration was carried out using an ultrafiltration device, 129 g of high-concentration zirconia sol (Cpz1) with a ZrO ₂ concentration of 30.5% by mass was obtained. The obtained high-concentration zirconia sol had a pH of 9.3 and an average particle size of 19 nm as determined by the dynamic light scattering method. Moreover, this zirconia sol had no sediment and was stable at 50° C. for more than one month.

Furthermore, referring to Example 2 of JP-A-2008-290896, Cpz2 with an average particle size of 32 nm was obtained, and Example 1 was referred to obtain Cpz3 with an average particle size of 48 nm.

(Titania particles)
With reference to Example 1 of JP-A-2011-132484, it was carried out as follows.
12.09 kg of titanium tetrachloride aqueous solution containing 7.75% by mass of titanium tetrachloride (manufactured by Osaka Titanium Technologies Co., Ltd.) based on TiO ₂ conversion, and ammonia water containing 15% by mass of ammonia (manufactured by Ube Industries, Ltd.) 4 .69 kg was mixed to prepare a white slurry liquid having a pH of 9.5. Next, after filtering this slurry, it was washed with pure water to obtain 9.87 kg of a hydrous titanate cake having a solid content of 10% by mass. Next, 11.28 kg of hydrogen peroxide solution containing 35% by mass of hydrogen peroxide (manufactured by Mitsubishi Gas Chemical Co., Ltd.) and 20.00 kg of pure water are added to the cake, followed by heating at 80° C. for 1 hour. , and then 57.52 kg of pure water was added to obtain 98.67 kg of an aqueous peroxytitanic acid solution containing 1 mass % of peroxytitanic acid in terms of TiO ₂ . This titanic acid peroxide aqueous solution was transparent, yellowish brown, and had a pH of 8.5.

Next, 4.70 kg of a cation exchange resin (manufactured by Mitsubishi Chemical Corporation) was mixed with 98.67 kg of the aqueous titanate peroxide solution, and potassium stannate (manufactured by Showa Kako Co., Ltd.) was added to SnO ₂ equivalent. 12.33 kg of an aqueous potassium stannate solution containing 1% by mass on a basis was slowly added with stirring. Next, after separating the cation exchange resin containing potassium ions and the like, it was placed in an autoclave (manufactured by Pressure Glass Industry Co., Ltd., 120 L) and heated at a temperature of 165° C. for 18 hours.

Next, after cooling the resulting mixed aqueous solution to room temperature, it is concentrated with an ultrafiltration membrane device (ACV-3010, manufactured by Asahi Kasei Co., Ltd.), and titanium-based fine particles having a solid content of 10% by mass ( Hereafter, 9.90 kg of a water-dispersed sol (Cpt1) containing "P-1") was obtained. When the solid matter contained in the sol thus obtained was measured by the above method, it was found to be titanium-based fine particles (primary particles) composed of a composite oxide containing titanium and tin, having a rutile crystal structure. rice field. Furthermore, when the content of the metal components contained in the titanium-based fine particles was measured, TiO ₂ was 87.2% by mass, SnO ₂ was 11.0% by mass, and K ₂ O was obtained on the basis of oxide conversion of each metal component. It was 1.8% by mass. Moreover, the pH of the mixed aqueous solution was 10.0. Furthermore, the water-dispersed sol containing the titanium-based fine particles is transparent and milky white, and the titanium-based fine particles contained in the water-dispersed sol have an average particle size of 35 nm as determined by a dynamic light scattering method, and particles of 100 nm or more. The distribution frequency of coarse particles having a diameter was 0%. Furthermore, it could be assumed that the obtained titanium-based fine particles had a refractive index of 2.42.
Further, Cpt2 with an average particle size of 32 nm was obtained with reference to Example 2 of JP-A-2011-132484, and Cpt3 with an average particle size of 42 nm with reference to Example 4.

(zirconia/titania mixed particles)
By mixing the zirconia particles (Cpz1) and the titania particles (Cpt1) obtained above at a mass ratio of 75/25, zirconia / titania mixed particles ((Cp1): average particle size 23 nm) having a solid content concentration of 13 mass% It was created.
Further, Cp2 (average particle size: 32 nm) was obtained from Cpz2 and Cpt2, and Cp3 (average particle size: 46 nm) was obtained from Cpz3 and Cpt3 in the same manner.

(Ceria particles)
The following experiments were conducted with reference to JP-A-2011-132107.
216 g of cerium (III) chloride heptahydrate was added to 10 L of distilled water and stirred to dissolve. Further, the temperature was raised to 93° C. while stirring was continued, and the total amount of 5.6 kg of 1.0% sodium hydroxide aqueous solution was added at once. After further stirring at 93° C. for 6 hours, the mixture was cooled to 25° C. to obtain a white precipitate.
The precipitate was separated by a centrifuge, 15 L of distilled water was added to the obtained precipitate, and the mixture was stirred and redispersed, and then separated by a centrifuge. This operation was performed three times in total to wash the precipitate.
Distilled water was added to the resulting precipitate, the pH was adjusted to 9.2, and the mixture was dispersed using an ultrasonic disperser to obtain a ceria particle dispersion (Cp4) having a solid concentration of 12% by mass. The average particle size by dynamic light scattering method was 34 nm.

(Formation of hard coat layer)
A coating solution for forming a hard coat layer having the following composition was applied to the surface of the polyester film produced in Examples described later, opposite to the surface to be adhered to the polarizer, using a #10 wire bar, and the coating solution was applied at 70°C for 1 minute. Dry and remove the solvent. Next, the film coated with the hard coat layer was irradiated with ultraviolet rays of 300 mJ/cm ² using a high-pressure mercury lamp to obtain a polarizer protective film having a hard coat layer with a thickness of 5 μm.
・Coating liquid for forming hard coat layer Methyl ethyl ketone 65.00% by mass
Dipentaerythritol hexaacrylate 27.20% by mass
(Shin Nakamura Chemical A-DPH)
Polyethylene diacrylate 6.80% by mass
(Shin Nakamura Chemical A-400)
Photopolymerization initiator 1.00% by mass
(Irgacure 184 manufactured by Ciba Specialty Chemicals)

(Example 1)
Coating liquid raw material/particle A water dispersion: zirconia/titania mixed particles (Cp1) having an average particle size of 23 nm
(75% by mass of zirconia in zirconia/titania, 13% by mass of solid content)
・ Particle B water dispersion: silica sol with an average particle size of 450 nm (solid content concentration 4% by mass)
・ Polyester water dispersion ((Bw1), solid content concentration 25% by mass)
・Polyurethane water dispersion ((A1), solid content concentration 37% by mass)
・Blocked isocyanate-based cross-linking agent ((Cx1), solid content concentration 40% by mass)

(1) Preparation of Coating Liquid for Easily Adhesive Layer A coating liquid having the following composition was prepared.
Water 36.00 parts by mass Isopropyl alcohol 30.31 parts by mass Particle A Water dispersion 10.99 parts by mass Particle B Water dispersion 0.91 parts by mass Polyester water dispersion 8.80 parts by mass Polyurethane water dispersion 3.96 parts by mass Block isocyanate-based cross-linking agent 5.50 parts by mass High boiling point solvent (NMP) 3.00 parts by mass Surfactant (fluorine-based, solid content concentration 10% by mass) 0.25 parts by mass

(2) Production of easy-adhesive polyester film PET resin pellets having an intrinsic viscosity (solvent: phenol/tetrachloroethane = 60/40) of 0.62 dl/g and containing substantially no particles were used as the raw material polymer for the film. , and dried at 135° C. for 6 hours under reduced pressure of 133 Pa. After that, it was supplied to an extruder, melt-extruded into a sheet at about 280° C., and rapidly cooled and solidified on a rotating cooling metal roll whose surface temperature was maintained at 20° C. to obtain an unstretched PET sheet.

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

Then, the coating liquid was applied to one side of the PET film by a roll coating method, and then dried at 80° C. for 15 seconds. The coating amount after drying after the final stretching was adjusted to 0.12 g/m2. Subsequently, the film was stretched 4.0 times in the width direction at 150°C with a tenter, heated at 230°C for 0.5 seconds while fixing the length of the film in the width direction, and further heated at 230°C for 10 seconds 3. % in the width direction to obtain an easily adhesive polyester film for optical use having a thickness of 38 μm. As shown in Table 2, the polyurethane resin component, polyester resin component, and other components in the coating layer are 20% by mass, 30% by mass, and 50% by mass, respectively.

(Examples 2, 3, 18, Reference Example 19, Examples 20-25 , Comparative Examples 1-7)
An easy-adhesive polyester film was obtained in the same manner as in Example 1 except that the ratio of the polyurethane resin component, polyester resin component and other components in the coating layer was set as shown in Table 2 or 3.

(Examples 4-7)
An easily adhesive polyester film was obtained in the same manner as in Example 1, except that the cross-linking agent in the coating liquid was changed and the composition of each component in the coating layer was changed as shown in Table 2.

(Examples 8-12)
An easily adhesive polyester film was obtained in the same manner as in Example 1, except that the type of 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 13-15)
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 easy-adhesive polyester film was obtained in the same manner as in Example 1, except that the amount of 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 type of the copolymerized polyester 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 type of polyurethane resin component was changed as shown in Table 3.

The respective results are shown in Tables 2 and 3. Also, plots on a ternary chart for each example and comparative example are shown in FIG.

(Static friction coefficient, dynamic friction coefficient (μs, μd))
The coefficient of friction of the polyester films obtained in Examples and Comparative Examples was measured using a Tensilon (Toyo Baldwin, RTM-100) in accordance with JIS K7125-1999 Plastics - Film and Sheet Friction Coefficient Test Method. All of the films had a static friction coefficient (μs) of 0.35 to 0.5 and a dynamic friction coefficient (μd) of 0.45 to 0.6, and had no problem in windability and handling. .

According to the present invention, it has excellent low interference, transparency, anti-blocking property, adhesion with various functional layers, and slipperiness, which can suppress iridescent unevenness, and easy adhesion that can be suitably used in optical applications, especially polarizer protective film applications. It has become possible to provide a polyester film and a laminated polyester film using the above.

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: coordinates (70, 10, 20) and (50, 40, 10) Straight line S1: Straight line passing through coordinates (45, 45, 10) and (10, 55, 35) ○: Plot of each example or reference example □: Numerical values in the plot ternary chart of each comparative example: Number of each example , reference example or each comparative example

Claims (6)

A coating containing, on at least one side of a polyester film, a polyurethane resin having a polycarbonate skeleton, a polyester resin having a naphthalene skeleton, a cross-linking agent, metal oxide particles (particles A) having a refractive index of 1.7 or more, and lubricant particles (particles B). The content (% by mass) of the polyurethane resin component having a polycarbonate skeleton when the coating layer has a layer and the total solid content of the coating layer is 100% by mass, and the content (% by mass) of the polyester resin component having a naphthalene skeleton is b, when the total amount (mass%) of other components is represented by a ternary diagram as c, a, b, and c are within the area surrounded by the four straight lines P1, Q1, R1, and S1 and wherein the total amount c of other components is 55% by mass or less when the total solid content of the coating layer is 100% by mass.
Here, straight line P1, straight line Q1, straight line R1, and straight line S1 are as follows.

Straight line P1: A straight line Q1 that passes through a point where a is 10% by mass, b is 55% by mass, and c is 35% by mass, and a point where a is 10% by mass, b is 10% by mass, and c is 80% by mass. : Straight line R1 passing through the point where a is 10% by mass, b is 10% by mass, and c is 80% by mass and the point where a is 70% by mass, b is 10% by mass, and c is 20% by mass: a is 70% by mass, b is 10% by mass, and c is 20% by mass, and a point is 50% by mass, b is 40% by mass, and c is 10% by mass. A straight line passing through the point where mass%, b is 45 mass%, and c is 10 mass%, and the point where a is 10 mass%, b is 55 mass%, and c is 35 mass% 2. The easy-adhesive polyester film according to claim 1, wherein the metal oxide particles (particles A) having a refractive index of 1.7 or more have an average particle diameter of 5 nm or more and 200 nm or less. The easily adhesive polyester film according to claim 1 or 2, wherein the lubricant particles (particles B) have an average particle size of 200 nm or more and 2000 nm or less. The easily adhesive polyester film for a polarizer protective film according to any one of claims 1 to 3, wherein the coating layer has a thickness of 0.5 µm or less. The easily adhesive polyester film according to any one of claims 1 to 4, which is used for a polarizer protective film. A layer selected from the group consisting of a hard coat layer, an antiglare layer, an antiglare antireflection layer, an antireflection layer and a low reflection layer on the coating layer of the easily adhesive polyester film according to any one of claims 1 to 5. A laminated polyester film having one or more functional layers.

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