JP2001138462A - Easily adhesive film for optics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easily adhesive film which shows superb transparency and easy adhesive properties and improved film conveying performance in a thermal processing step at the time of after-processing such as prismatic lens fabrication, hard coat application or AR formation and further, reliable suitability for fabrication. SOLUTION: This easily adhesive film for optics is a biaxially oriented polyester film as a base having a thickness of 100 μm or more, with an easily adhesive layer consisting of a copolymer polyester resin and a polyurethane resin laminated on at least one of the faces of the base. In addition, the film is characterized in that the difference between the maximum value and the minimum value of the coefficient of heat shrinkage in the longitudinal direction of the film is 0.2% or less in the width direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented polyester film for optical use, and more particularly to a biaxially oriented polyester film for optical use having excellent processability.

[0002]

2. Description of the Related Art Biaxially oriented polyester films are widely used as various optical films because of their excellent transparency, dimensional stability and chemical resistance. In particular, the use of a base film for a prism lens sheet used for an LCD, a hard coat process, a base film for an AR (anti-reflection; anti-glare) film, and a shatterproof film for a CRT are:
100 μm because of excellent strength and dimensional stability
The above relatively thick films are suitably used.
Films used for such optical films have excellent transparency and prism lens processing and hard coat processing,
In addition to being required to have excellent easy adhesion to a resin laminated at the time of post-processing such as AR processing, a film having excellent workability at the time of post-processing is required.

[0003]

However, when a conventional polyester film is used as an optical film in a post-processing heat treatment step such as prism lens processing, hard coat processing, and AR processing, the longitudinal direction of the film is reduced. The heat shrinkage is different depending on the position in the film width direction, and the film is subjected to a heat treatment step during post-processing, and the length of the product end changes due to the difference in the heat shrinkage in the longitudinal direction. There is a problem in that the film may deteriorate at the end of the film in the post-processing step, such as scratching the end portion by being rubbed with the frame of the machine frame or the like, and furthermore, the productivity may be reduced. In particular, in recent years, large screens such as notebook personal computers and cathode ray tubes of CRTs have been developed, and this problem has become more important when products are widened.

Further, in general, polyester films have a problem that adhesion to other materials such as a prism lens containing acrylate as a main component or a hard coat is poor. Therefore, on the surface of the polyester film is formed an easy-adhesion layer made of polyurethane resin or the like,
For example, it has been proposed in JP-A-6-340049. However, in the case of forming an easy-adhesion layer made of polyurethane resin, although the adhesive force with the outer layer such as the hard coat layer is improved, the adhesive force with the polyester film as the base material is not sufficient, and as a result, However, there was a problem that sufficient adhesiveness could not be obtained.

That is, an object of the present invention is to provide a film which has excellent transparency and easy adhesion in the heat treatment step at the time of post-processing such as prism lens processing, hard coat processing, and AR processing. An object of the present invention is to provide an optically easy-to-adhesive film having improved transportability and excellent workability.

[0006]

As a result of intensive studies to achieve the above-mentioned objects, the present inventors have found that they have high transparency, have excellent adhesive properties, and have excellent workability with a small difference in heat shrinkage in the width direction. An optically easy-to-use adhesive film was obtained. That is, the present invention has the following configuration. A. A biaxially oriented polyester film having a biaxially oriented polyester film having a thickness of 100 μm or more as a base material and an easy-adhesion layer made of a copolymerized polyester resin and a polyurethane resin laminated on at least one surface of the base material, An easy-to-use optical film, wherein the difference between the maximum value and the minimum value of the heat shrinkage in the longitudinal direction of the film is 0.2% or less in the width direction. B. A light-adhesive film for optical use, wherein the light-adhesive acrylic coating layer provided on the light-adhesive layer according to A has an adhesiveness of 85% or more. The above-mentioned adhesiveness refers to JI
It means the value obtained from the following formula based on the test method according to 8.5.1 of S-K5400. Adhesion (%) = (1−peeled area / evaluated area) × 100 A film according to A or B, wherein the film has a haze value of 1.0% or less.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the optically easy-to-adhesive film of the present invention will be described below. The biaxially oriented polyester film which is the base film of the present invention is made of polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate or a copolymer mainly composed of these resin components. Biaxially oriented films formed from polyethylene terephthalate are particularly preferred.

When a polyester copolymer is used as the resin forming the biaxially oriented polyester film, the dicarboxylic acid component includes aliphatic dicarboxylic acids such as adipic acid and sebacic acid, terephthalic acid, isophthalic acid, phthalic acid, and the like. Aromatic dicarboxylic acids such as 2,6-naphthalenedicarboxylic acid and the like and polyfunctional carboxylic acids such as trimellilotic acid and pyromellilotic acid are used. As the glycol component, fatty acid glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, propylene glycol and neopentyl glycol;
aromatic glycols such as p-xylene glycol; 1,4
Alicyclic glycols such as cyclohexanedimethanol;
For example, polyethylene glycol having an average molecular weight of 150 to 20,000 is used. Preferred copolymer ratio is 20%
Is less than. If it is 20% or more, the film strength, transparency, and heat resistance may be poor. Further, the polyester-based resin may contain various additives. Examples of the additive include an antistatic agent, a UV absorber, and a stabilizer. Further, it is preferable that particles for the purpose of imparting lubricity are not added to the polyester base film of the present invention.

The intrinsic viscosity of polyester resin pellets, which is a raw material of a biaxially oriented polyester film, is 0.1.
The range of 45 to 0.70 dl / g is preferred. When the intrinsic viscosity is less than 0.45 dl / g, the effect of improving the tear resistance deteriorates. On the other hand, if the intrinsic viscosity exceeds 0.70 dl / g, the increase in filtration pressure becomes large, and high-precision filtration becomes difficult.

The easy-adhesion layer of the optically-adhesive film of the present invention is laminated on at least one side of the biaxially oriented polyester film, and provided on at least one side of the unstretched or uniaxially stretched polyester film, It is preferable to laminate by an in-line coating method of stretching and heat-setting at least in a uniaxial direction. By adding fine particles of an appropriate particle size to the easy-adhesion layer laminated by the in-line coating method and forming irregularities on the surface of the easy-adhesion layer, it is possible to impart good slipperiness, winding property, and scratch resistance. it can. For this reason, since it is not necessary to contain fine particles in the biaxially oriented polyester, it is particularly effective for obtaining a highly transparent film having a haze value of 1.0% or less.

The term "easy adhesion" as used in the present invention refers to the adhesion between the photocurable acrylic coat layer and the photocurable acrylic coat layer when measured according to the method described in "Adhesion with Photocurable Acrylic Coat Layer" below. Is 85% or more, preferably 90% or more, particularly preferably 95% or more.

The easy-adhesion layer of the easy-adhesion film for optical use of the present invention is composed of a copolymerized polyester resin and a polyurethane resin as main resin components. When the copolymerized polyester resin alone is used, the adhesiveness with the polyester base film is sufficient, but the adhesiveness with the acrylic resin used for the prism lens or the hard coat is insufficient. Further, although the polyurethane resin alone has excellent adhesiveness to the acrylate resin, the adhesiveness to the polyester base film is insufficient.

The copolymerized polyester resin used in the easy-adhesion layer of the present invention comprises a dicarboxylic acid component and a branched glycol component as constituent components. The branched glycol component is, for example, 2,2-dimethyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, 2-methyl-2-butyl-1,3. -Propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-2-isopropyl-1,3
-Propanediol, 2-methyl-2-n-hexyl-
1,3-propanediol, 2,2-diethyl-1,3
-Propanediol, 2-ethyl-2-n-butyl-
1,3-propanediol, 2-ethyl-2-n-hexyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, 2-n-butyl-2
-Propyl-1,3-propanediol, and 2,2-
Di-n-hexyl-1,3-propanediol and the like.

The above-mentioned branched glycol component is contained in all the glycol components preferably in a proportion of 10 mol% or more, more preferably in a proportion of 20 mol% or more. As the glycol component other than the above compounds, ethylene glycol is most preferable. If the amount is small, diethylene glycol, propylene glycol, butanediol, hexanediol, 1,4-cyclohexanedimethanol, or the like may be used.

As the dicarboxylic acid component contained as a component in the copolymerized polyester resin, terephthalic acid and isophthalic acid or salts thereof are most preferred. If the amount is small, another dicarboxylic acid component, for example, an aromatic dicarboxylic acid such as diphenylcarboxylic acid or 2,6-naphthalenedicarboxylic acid may be added and copolymerized.

In addition to the dicarboxylic acid component, 5-sulfoisophthalic acid is used in an amount of 1 to 10 to impart water dispersibility.
It is preferably used in the range of mol%, for example, sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfonaphthaleneisophthalic acid-2,7-dicarboxylic acid and 5-
(4-Sulfophenoxy) isophthalic acid or salts thereof can be mentioned.

The polyurethane resin used in the easy-adhesion layer of the present invention is, for example, a resin containing a block type isocyanate group, in which a terminal isocyanate group is blocked with a hydrophilic group (hereinafter referred to as a block), and is a heat-reactive type. And water-soluble urethane. Examples of the isocyanate group blocking agent include bisulfites and phenols containing sulfonic acid groups, alcohols, lactams, oximes, and active methylene compounds. The blocked isocyanate group can make the urethane prepolymer hydrophilic or water-soluble. Among the above blocking agents, bisulfites are most preferable as those which are appropriate for the temperature and time during the heat treatment and widely used industrially.

Further, when heat energy is given to the polyurethane resin in the drying step or the heat setting treatment step in the production of the film, the blocking agent separates from the isocyanate group, so that the polyurethane resin is mixed with the self-crosslinked stitches. While immobilizing the water-dispersible copolymerized polyester resin, it reacts with the terminal groups of the resin.
The resin under coating liquid adjustment is poor in water resistance because it is hydrophilic, but when the thermal reaction is completed by applying, drying and heat fixing,
Since the hydrophilic group of the urethane resin, that is, the blocking agent comes off, a coating film having good water resistance can be obtained.

The urethane prepolymer used in the polyurethane resin includes (1) an organic polyisocyanate having two or more active hydrogen atoms in a molecule or a molecular weight having at least two active hydrogen atoms in a molecule. 200 to 20,000 compounds, (2) an organic polyisocyanate having two or more isocyanate groups in the molecule, or (3) a chain extender having at least two active hydrogen atoms in the molecule. The resulting compound having a terminal isocyanate group is exemplified.

The compound (1) is generally known to contain two or more hydroxyl groups, carboxyl groups, amino groups or mercapto groups at the terminal or in the molecule. Particularly preferred compounds are Examples include polyether polyols and polyether ester polyols.

Examples of the polyether polyol include (a) alkylene oxides such as ethylene oxide and propylene oxide, (b) a compound obtained by polymerizing styrene oxide, epichlorohydrin, and the like; (c) a random polymer or a block polymer thereof; d) Compounds obtained by addition polymerization to polyhydric alcohols are exemplified.

The polyester polyol and the polyether ester polyol include mainly linear or branched compounds. These include polyvalent saturated or unsaturated carboxylic acids such as succinic acid, adipic acid, phthalic acid, and maleic anhydride, or the carboxylic anhydrides, and ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl. Polyhydric saturated and unsaturated alcohols such as glycol, 1,6-hexanediol, trimethylolpropane, etc .; polyalkylene ether glycols such as relatively low molecular weight polyethylene glycol and polypropylene glycol; or alcohols thereof Can be obtained by condensation with a mixture of

Further, as polyester polyols, polyesters obtained from lactone and hydroxy acid, and as polyether ester polyols,
Polyetheresters obtained by adding ethylene oxide or propylene oxide to polyesters produced in advance can also be used.

As the organic polyisocyanate (2), isomers of toluylene diisocyanate, 4,4
-Diphenylmethane diisocyanate, aromatic diisocyanates such as xylylene diisocyanate, isophorone diisocyanate, alicyclic diisocyanates such as 4,4-dicyclohexylmethane diisocyanate,
Hexamethylene diisocyanate, and 2,2,4-
Examples thereof include aliphatic diisocyanates such as trimethylhexamethylene diisocyanate, and polyisocyanates in which these compounds are added alone or in combination with trimethylolpropane or the like in advance.

Examples of the chain extender having at least two active hydrogens in the above (3) include glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol and 1,6-hexanediol, glycerin, trimethylolpropane and the like. And polyhydric alcohols such as pentaerythritol, diamines such as ethylenediamine, hexamethylenediamine, and piperazine; aminoalcohols such as monoethanolamine and diethanolamine; thiodiglycols such as thiodiethylene glycol; and water.

In order to synthesize the urethane polymer of the above (3), usually a single-stage or multi-stage isocyanate polyaddition method using the above-mentioned chain extender is carried out at a temperature of 150 ° C. or less, preferably 70 to 120 ° C. Let react for minutes to several hours. The ratio of isocyanate groups to active hydrogen atoms can be freely selected as long as it is 1 or more, but it is necessary that free isocyanate groups remain in the obtained urethane prepolymer.

The content of the free isocyanate group may be 10% by weight or less, but preferably 7% by weight or less in consideration of the stability of the aqueous urethane polymer solution after blocking.

The obtained urethane prepolymer is preferably subjected to blocking using bisulfite.
The mixture is mixed with an aqueous bisulfite solution, and the reaction is allowed to proceed with good stirring for 5 minutes to 1 hour. The reaction temperature is preferably set to 60 ° C. or lower. Thereafter, the mixture is diluted with water to an appropriate concentration to obtain a heat-reactive water-soluble urethane composition. When using this composition, adjust to the appropriate concentration and viscosity,
Usually, when heated to 80 to 200 ° C., the bisulfite of the blocking agent is dissociated, and the active isocyanate group is regenerated, so that a polyurethane polymer is formed by a polyaddition reaction occurring within or between molecules of the prepolymer. , Or to other functional groups.

As an example of the resin (B) containing a blocked isocyanate group described above, Elastron (trade name) manufactured by Daiichi Kogyo Seiyaku Co., Ltd. is typical. Elastron is obtained by blocking an isocyanate group with sodium bisulfite, and is water-soluble due to the presence of a carbamoyl sulfonate group having strong hydrophilicity at the molecular terminal.

When preparing a coating solution by mixing the copolymerized polyester resin (A) containing a branched glycol component and the resin (B) containing a blocked isocyanate group used in the present invention, the resin (A) ) And the resin (B) preferably have a weight ratio of (A) :( B) = 90: 10 to 10:90, particularly preferably (A) :( B) = 80: 20.
20:80. When the ratio of the resin (A) is
When less than 10% by weight based on the total solid content of the coating layer,
The applicability to the base film is insufficient, and the adhesion between the application layer and the film is insufficient. The ratio of the resin (B) is 1 to the total solid weight of the coating layer.
When the amount is less than 0% by weight, practical adhesiveness cannot be obtained with the UV-curable hard coat layer.

A catalyst may be added to the aqueous coating solution used in the present invention in order to promote a thermal crosslinking reaction. Examples of the catalyst include inorganic substances, salts, organic substances, alkaline substances, acidic substances and metal-containing organic compounds. Various chemical substances are used. In order to adjust the pH of the aqueous solution, an alkaline substance or an acidic substance may be added.

When the aqueous coating solution is applied to the surface of the substrate film, a known anionic activator and a nonionic active agent are used to increase the wettability to the substrate film and uniformly coat the coating solution. A required amount of a surfactant can be added. The solvent used for the coating solution may be mixed with alcohols such as ethanol, isopropyl alcohol, and benzyl alcohol, in addition to water, until the proportion of the solvent in the total coating solution is less than 50% by weight. Further, when the content is less than 10% by weight, an organic solvent other than alcohols may be mixed in a range where it can be dissolved. However, the total of alcohols and other organic solvents in the coating liquid is preferably less than 50% by weight.

When the addition amount of the organic solvent is less than 50% by weight, the drying property is improved at the time of coating and drying, and the effect of improving the appearance of the coating film is obtained as compared with the case where only water is used. When the addition amount of the organic solvent is 50% by weight or more, the evaporation rate of the solvent is increased, and the concentration of the coating solution easily changes during coating. As a result, since the viscosity of the coating solution increases and the coating property decreases, there is a possibility that the appearance of the coating film may be deteriorated. Further, it is not preferable in terms of danger such as fire and health of workers. .

In the composition of the aqueous coating solution, an antistatic agent, an ultraviolet absorption inhibitor, a plasticizer, inorganic and / or organic inactive particles, a pigment,
Various additives such as an organic lubricant and an antibacterial agent may be mixed. Further, since the coating liquid is aqueous, other water-soluble resins, water-dispersible resins, emulsions, and the like may be added to the coating liquid for improving the performance as long as the contribution effect is not lost.

In the present invention, since inert particles for the purpose of imparting lubricity are not substantially contained in the base film,
It is preferable that inert particles are added to the aqueous coating solution to form appropriate projections on the film surface. Examples of inert particles added to the aqueous coating solution include inorganic particles such as calcium carbonate, calcium phosphate, silica, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, and molybdenum sulfide. And organic particles such as crosslinked polymer particles and calcium oxalate. Among these, silica is the most preferable because the refractive index is relatively close to that of the polyester resin, and a highly transparent film is easily obtained.

The average particle size (observed by an electron microscope) of the inert particles added to the aqueous coating solution is 0.01 to 1.0 μm.
m is preferable, and more preferably 0.02 to 0.5 μm
m, particularly preferably 0.03 to 0.1 μm. When the average particle size of the inert particles exceeds 1.0 μm, the film surface tends to be rough, and the transparency of the film tends to decrease. On the other hand, if the average particle size of the inert particles is less than 0.01 μm, the slipperiness of the film becomes insufficient, which is not preferable.

The content of the inert particles in the coating layer after drying the coating solution is 0.01 to 60% by weight.
Is particularly preferable, and 0.1 to 40% by weight is particularly preferable. If the content of the inert particles in the coating layer exceeds 60% by weight, the adhesion to the film may be impaired. On the other hand, when the content of the inert particles is less than 0.01% by weight, the slipperiness of the film becomes insufficient, which is not preferable.

In the present invention, it is preferable that two types of particles (particle A and particle B) are contained in the easily adhesive layer. Particle A
Has an average particle size of preferably from 20 to 300 nm, more preferably from 30 to 100 nm. Particle A has an average particle size of 2
If it is less than 0 nm, the scratch resistance tends to deteriorate. On the other hand, when the average particle diameter of the particles A exceeds 300 nm, the haze value tends to increase.

Since the particle A alone has insufficient scratch resistance, in order to further improve the scratch resistance,
It is preferable that the particles B are contained in the easy adhesion layer in combination with the particles A. The average particle size of the particles B is 300 to 1000 nm
And more preferably 400 to 800 nm. If the average particle diameter of the particles B is less than 300 nm, the scratch resistance tends to be deteriorated. On the other hand, when the average particle diameter of the particles B exceeds 1000 nm, the haze value tends to increase. Further, the particles B are preferably aggregated particles in which primary particles are aggregated, and the ratio of the average particle size in the aggregated state to the average particle size of the primary particles is preferably 6 times or more from the viewpoint of scratch resistance. .

Further, the content ratio (A / B) of the particles A and the particles B in the easy-adhesion layer is set to 5 to 30, and the content of the particles B is set to 0.1 to 0.1 with respect to the solid content of the easy-adhesion layer. The content of 1% by weight is suitable for obtaining an optically easy-to-adhesive film having a small haze value and excellent in slipperiness and scratch resistance. It is preferable to set the content of each particle so as to fall within the above range. In particular, for the solid content of the easily adhesive layer,
When the content of the particles B exceeds 1% by weight, transparency tends to deteriorate. The solid content of the easy-adhesion layer described above means the total of the solid contents of the resin A, the resin B, the particles A, and the particles B. As inert particles to be contained in the easy adhesion layer,
Using two types of silica particles having different particle diameters and forms, spherical monodisperse silica as particles A and aggregated silica as particles B are set to the contents and ratios in the above ranges, respectively, and the coating amount is set in the above range. This is particularly suitable for obtaining an optically easy-to-adhesive film having a small haze value and excellent in slipperiness and scratch resistance.

At the time of applying the coating solution, a filter medium is arranged so that the coating solution is subjected to microfiltration immediately before the application in order to remove coarse aggregates or contaminants due to precipitation of particles and resin in the coating solution. Is preferred.

It is preferable that the filter medium for finely filtering the coating solution used in the present invention has a filter particle size of 25 μm or less (initial filtration efficiency: 95%). When a filter medium having a filtration particle size exceeding 25 μm is used, coarse aggregates and contaminants cannot be sufficiently removed, and many coarse aggregates that cannot be removed are subjected to a uniaxial stretching or biaxial stretching process after coating and drying. In some cases, it may be recognized as an aggregate having a size of 100 μm or more due to the stretching stress, and may cause an optical defect in addition to an increase in the haze value of the film.

The type of the filter medium for finely filtering the coating liquid is not particularly limited as long as it has the above-described foreign matter removing performance, and examples thereof include a filament type, a felt type, and a mesh type. The material of the filter medium for finely filtering the coating solution is not particularly limited as long as it has the above-described foreign matter removing performance and does not adversely affect the coating solution, and examples thereof include stainless steel, polyethylene, polypropylene, and nylon.

Next, the method for producing the optically-adhesive polyester film of the present invention will be described with reference to polyethylene terephthalate (hereinafter abbreviated as PET) as an example.
Of course, it is not limited to this.

After sufficiently drying PET pellets substantially containing no inert particles, the pellets are fed to an extruder, melt-extruded into a sheet at about 280 ° C., and solidified by cooling to produce an unstretched PET sheet. Film. At this time, high-precision filtration is performed at an arbitrary place where the molten resin is maintained at about 280 ° C. in order to remove foreign substances contained in the resin. The filter medium used for high-precision filtration of the molten resin is not particularly limited, but the filter medium of the stainless sintered body is made of Si, Ti, Sb, G
It is excellent in the performance of removing aggregates containing e and Cu as main components and high-melting organic matter, and is suitable. The above “PET substantially free of inert particles” means that the content of inert particles in PET is less than the detection limit when analyzed by fluorescent X-ray. I do.

Further, the size of the filter particles of the filter medium (initial filtration efficiency 95%) is preferably 15 μm or less. If it is 15 μm or more, foreign substances of 20 μm or more cannot be sufficiently removed. The size of the filter particles of the filter medium (initial filtration efficiency 95%) is 15 μm
Productivity may be reduced by performing high-precision filtration of the molten resin using the following filter media, but it is indispensable to obtain an optical film with few optical defects.

Even in the case of fine foreign matter passing through the filter medium in the step of extruding the molten resin, crystallization proceeds around the foreign matter in the process of cooling the sheet-like molten material, which causes unevenness in stretching in the stretching step, A slight difference in thickness occurs. In the part where this minute thickness difference exists,
The light is refracted or scattered as if it has a lens, and when viewed with the naked eye, appears larger than an actual foreign object. This minute difference in thickness can be observed as a difference between the height of the projection and the depth of the depression. The height of the projection is 1 μm or more, and the depth of the depression adjacent to the projection is 0.5 μm or more. In this case, due to the lens effect, an object having a size of 20 μm may be visually recognized as a size of 50 μm or more, and may be further recognized as an optical defect having a size of 100 μm or more. In order to obtain a highly transparent film, it is desirable not to include particles for imparting lubricity in the base film, but as the particle content is lower and the transparency is higher,
Optical defects due to minute irregularities tend to be sharper.

Further, in the case of a thick film, the cooling efficiency in the film thickness direction is insufficient compared with the thin film, and crystallization tends to proceed. Is required. As a method of cooling the unstretched sheet, a known method of extruding a molten resin into a sheet shape from a die on a rotary cooling drum (chill roll), and rapidly cooling the sheet-like melt into a sheet while closely contacting the sheet-like molten material on the chill roll. Can be applied. As a method of cooling the air surface (the surface opposite to the surface that comes into contact with the chill roll) of the sheet-like material, for example, a method of bringing the sheet surface into contact with a cooling liquid in a tank, a method of evaporating the sheet air surface with a spray nozzle And a method of cooling by blowing high-speed airflow. Above all, a method of cooling by blowing a high-speed airflow is effective.
In particular, when producing a thick optical film having a final thickness of 188 μm or more, it is preferable to use both of them. Further, as a method of bringing the sheet-like melt into close contact with the chill roll, for example, a method of using an air knife or a method of imposing an electrostatic charge on the sheet-like melt is preferable. Among these methods, the latter method of impressing the electrostatic charge is particularly preferable.

The obtained unstretched sheet is longitudinally stretched 2.5 to 5.0 times in the longitudinal direction by a roll heated to 80 to 120 ° C. to obtain a uniaxially oriented PET film. The longitudinal stretching may be performed in one step, but may be performed in at least two or more steps from the viewpoint of productivity and reduction of uneven thickness. Furthermore, the end of the film is gripped with a clip and guided to a hot air zone heated to 80 to 180 ° C., and is laterally stretched 2.5 to 5.0 times in the width direction. Subsequently, the resultant is guided to a heat-setting treatment zone at 200 to 240 ° C. and subjected to a heat treatment for 1 to 60 seconds to complete the crystal orientation. During this heat-setting treatment step, a relaxation treatment of 1 to 12% may be performed in the width direction or the longitudinal direction as necessary. Furthermore, when the film is cooled to Tg or less after the heat setting, if the tension in the film flow direction is applied, the effect of the heat setting is reduced, so that it is preferable to provide a nip roll or a quenching zone for cutting the tension. At any stage during this step, an aqueous solution of the above-mentioned copolymerized polyester and polyurethane resin is applied to at least one surface of the polyester film.

The aqueous coating solution can be applied by any known method. For example, reverse roll coating, gravure coating, kiss coating, roll brushing, spray coating, air knife coating, wire barber coating, pipe doctor method,
Examples include an impregnation / coating method and a curtain coating method, and these methods can be performed alone or in combination.

The step of applying the aqueous coating solution may be a usual coating step, that is, an off-line step of applying the film to a base film which has been biaxially stretched and heat-fixed, but may be applied during the above-described film production step. In-line coating is preferred. Further, it is more preferable to apply the composition to the base film before the completion of the crystal orientation. When the above coating solution is applied to a polyester film substrate after unstretching or uniaxial stretching, and then dried and stretched, only a solvent such as water is removed in the drying step after coating, and the crosslinking reaction of the coating layer does not proceed. It is important to choose temperature and time. The drying temperature is preferably performed at 70 to 140 ° C.,
The drying time is adjusted according to the coating solution and the amount of coating.
It is preferable that the temperature product of (° C.) and time (second) be 1000 to 3000.

The solid content in the aqueous coating solution is 30% by weight.
Or less, particularly preferably 10% by weight
It is as follows. The aqueous coating solution is 1 m of running film.
^The coating is carried out so that 0.04 to 5 g, preferably 0.2 to 4 g per ² is adhered. The film to which the aqueous coating solution has been applied and dried is guided to a tenter for stretching and heat fixing, where it is heated to form a stable film by a thermal crosslinking reaction, and becomes a polyester-based laminated film. In order to obtain good adhesion to the ink, heat treatment is performed at 100 ° C. or more for 1 minute or more in the heat treatment step, and the coating amount of the easy-adhesion layer after the heat treatment is adjusted to 0.05 g / m ² or more. It is preferable to work.

In the optically easy-adhesive film of the present invention, the difference between the maximum value and the minimum value of the heat shrinkage in the longitudinal direction is 0.1 mm in the width direction.
It is necessary to be 2% or less, preferably 0.1%
Or less, particularly preferably 0.06% or less. In order to set the difference between the maximum value and the minimum value of the heat shrinkage in the longitudinal direction of the film to 0.2% or less in the width direction, the temperature in the film width direction in the heat fixing zone is set from the center to the edge. It is preferable to increase the height over the part.

More specifically, a shielding plate is placed over a plenum duct (hot air blowing portion) arranged at a certain interval in the film advancing direction, and the width of the shielding plate is gradually increased with respect to the film advancing direction. It is preferable that the air flow in the width direction of the film is increased from the center to the edge of the film by spreading (the opening is narrowed), and the temperature in the width direction of the film is increased from the center to the edge. . Further, the temperature in the film width direction may be increased from the center to the ends by using an infrared heater.

The thickness of the obtained optically easy-to-adhere film of the present invention needs to be 100 μm or more.
It is preferably from 0 to 300 μm, particularly preferably from 125 to 2
50 μm. If the film thickness is less than 100 μm,
The rigidity is insufficient, which is not preferable.

(Function) The present inventors ran a conventional biaxially stretched polyethylene terephthalate film in a post-processing step with a specific tension and temperature applied to the film, and then placed the film on a flat surface. It was found that one of the ends of the film was sagged. This is because when heated under tension in the post-processing step, the length of the end having a large heat shrinkage in the longitudinal direction is shortened due to the difference in the heat shrinkage at both ends in the width direction. Was not applied,
It is considered that sagging occurred.

Even if an attempt is made to remove the slack by applying an excessive tension to the end where the slack has occurred, the heat in the processing step causes the film to stretch, causing distortion to be present therein. Distortion becomes apparent, which degrades the quality of products such as prism lenses, hard coat products, and AR products.

As a result of further intensive studies, the present inventors have found that the tenter has a distribution of strain in the width direction of the film, and that the strain increases from the center to the end. It is considered that the reason is that the end is hardly deformed and the distortion is large because the tenter is gripped by the clip. As a result, the heat shrinkage in the vertical direction changes in the width direction, so that it appears as a slack when heat-treated in a post-processing step. The above-mentioned distortion can be reduced by increasing the temperature during the heat setting process during film production, and by increasing the temperature in the width direction from the center to the edge of the film, the distortion in the width direction of the film can be reduced. Can be made uniform.

In order to suppress the occurrence of the sag,
When slitting from the mill roll to the customer's product size,
At any position, it is necessary to reduce the difference in the heat shrinkage in the longitudinal direction at both ends of the slit roll in the film width direction. Specifically, the difference between the maximum value and the minimum value of the heat shrinkage in the longitudinal direction of the film is 0.2% in the width direction.
It must be: By doing so, it is possible to perform processing without applying excessive tension in the post-processing step.
Further, the film can be conveyed without sagging on one side of the film at the time of running the film in the post-processing step and the frame or other parts of the machine base during the step.

[0060]

EXAMPLES Hereinafter, the present invention will be described with reference to Examples, but it should be understood that the present invention is not limited to these Examples. “Parts” in Examples and Comparative Examples means “parts by weight” unless otherwise specified.

Example 1 (1) Preparation of coating solution A coating solution used in the present invention was prepared according to the following method.
95 parts of dimethyl terephthalate, 95 parts of dimethyl isophthalate, 35 parts of ethylene glycol, 145 parts of neopentyl glycol, 0.1 part of zinc acetate and 0.1 part of antimony trioxide are charged into a reaction vessel, and the ester is added at 180 ° C. for 3 hours. An exchange reaction was performed. Next, 6.0 parts of 5-sodium isophthalic acid was added, and the esterification reaction was carried out at 240 ° C. for 1 hour, and then reduced pressure (13 ° C.) at 250 ° C.
To 0.3 hPa) for 2 hours to obtain a polyester resin having a molecular weight of 19,500 and a softening point of 60 ° C.

30% of the obtained polyester resin (A)
6.7 parts of an aqueous dispersion, 40 parts of a 20% aqueous solution of a self-crosslinkable polyurethane resin (B) containing isocyanate groups blocked with sodium bisulfite (product name: Elastron H-3, manufactured by Daiichi Kogyo Seiyaku), 0.5 part of catalyst for Elastron (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd .: Cat64) and 47.
8 parts and 5 parts of isopropyl alcohol were mixed, and 1% by weight of an anionic surfactant and 5% by weight of spherical silica particles (Snowtex OL manufactured by Nissan Chemical Industries, Ltd.) were added thereto. (Abbreviated as liquid AB)
And

(2) Production of Easy Adhesive Film As a film raw material, polyethylene terephthalate resin pellets having an intrinsic viscosity of 0.62 dl / g and containing substantially no inert particles were dried under reduced pressure at 135 ° C. for 6 hours. (1.3 hPa), and then fed to an extruder,
It was melt-extruded into a sheet at 0 ° C. and quenched and solidified on a chill roll maintained at a surface temperature of 20 ° C. to obtain a cast film having a thickness of 1400 μm.

At this time, a stainless sintered filter medium having a filtration particle size (initial filtration efficiency: 95%) of 15 μm was used as a filter medium for removing foreign matters from the molten resin. Next, the cast film was heated to 100 ° C. by a heated roll group and an infrared heater.
And stretched 3.5 times in the longitudinal direction with a group of rolls having a difference in peripheral speed to obtain a uniaxially oriented PET film.

Thereafter, the coating liquid AB was finely filtered through a felt-type polypropylene filter medium having a filtration particle size (initial filtration efficiency: 95%) of 25 μm, and applied to both sides of a uniaxially oriented PET film by a reverse roll method. Subsequently, after coating, the end of the film was gripped with a clip and the coated layer was dried at 80 ° C. for 20 seconds in the preheating zone of the tenter, and then stretched 4.0 times at 130 ° C. in the width direction in the transverse stretching zone. . Subsequently, a heat setting treatment is performed at 230 ° C.
A lateral relaxation treatment of 3% was performed at 0 ° C. to obtain a biaxially oriented PET film having a thickness of 100 μm. The coated amount of the obtained film after drying was 0.10 g / m ² .

In the heat setting zone, plenum ducts were arranged vertically at 400 mm intervals in the film traveling direction in the width direction of the film, and hot air was blown from the upper and lower plenum ducts onto the film. In this embodiment, a shielding plate is placed over the opening of the plenum duct at the center of the film width direction, and the width of the shielding plate is gradually increased with respect to the plenum duct in the film advancing direction. In other words, the amount of air that hits the film in the width direction strongly hits the end because the opening of the plenum duct gradually narrows in the film advancing direction. Specifically, the width of the shielding plate was changed so that the air volume was 20 m / sec near the entrance of the heat fixing zone and about 40 m / sec at the highest speed near the exit. Table 1 shows the obtained results.

Example 2 A film was obtained in the same manner as in Example 1 except that the thickness of the unstretched sheet was 1750 μm and the thickness after film formation was 125 μm. Table 1 shows the obtained results.

Example 3 The thickness of the unstretched sheet was 2632 μm, and the thickness after film formation was 1
A film was obtained in the same manner as in Example 1 except that the unstretched sheet was cooled by blowing a high-speed airflow onto the air surface (the surface opposite to the surface contacting the chill roll) of the unstretched sheet. Table 1 shows the obtained results.

Comparative Example 1 33.5 parts of a 30% aqueous dispersion of the polyester resin (A) obtained in Example 1, 47.8 parts of water and 18.7 parts of isopropyl alcohol were mixed, and anion was further added. 1% by weight of a water-soluble surfactant and 5% by weight of spherical silica particles (Snowtex OL, manufactured by Nissan Chemical Industries, Ltd.) to obtain a coating solution (hereinafter referred to as a coating solution A), and a heat fixing zone. Example 2 except that the width of the shielding plate over the plenum duct was gradually reduced in the film advancing direction, and the air flow was gradually reduced from the center to the end.
A film having a thickness of 125 μm was obtained in the same manner as described above. Table 1 shows the obtained results.

Comparative Example 2 A 20% aqueous solution of a self-crosslinkable polyurethane resin (B) containing isocyanate groups blocked with sodium bisulfite (Elastron H-3, trade name, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) was used.
Part, elastron catalyst (Daiichi Kogyo Seiyaku Co., Ltd .: trade name Ca
t64), 37.8 parts of water and 11.7 parts of isopropyl alcohol, respectively, and further 1% by weight of an anionic surfactant, spherical silica particles (Nissan Chemical Industries, Ltd .: Snowtex) OL) was added in an amount of 5% by weight to obtain a coating liquid (hereinafter referred to as coating liquid B), and a 125 μm thick film was obtained in the same manner as in Comparative Example 1. Table 1 shows the obtained results.

Comparative Example 3 A film having a thickness of 188 μm was obtained in the same manner as in Example 3, except that no shielding plate was provided in the plenum duct in the heat fixing zone. Table 1 shows the obtained results.

(Evaluation Method) The evaluation method used in the present invention will be described below.

(1) Heat Shrinkage In accordance with the method specified in JIS C-2318, the width of a product is sampled at 100 mm intervals in the horizontal direction.
The heat shrinkage in the longitudinal direction was measured. The difference between the maximum and minimum values of the heat shrinkage in the machine direction in the film width direction was determined.

(2) Film Permeability A product having a film width of 1000 mm was heated at a temperature of 100 using a coater in which the interval between two rolls was 1500 mm.
The heat treatment was performed by setting the temperature in the furnace at 98 ° C. and the furnace tension at 98 N. Next, in order to evaluate the flatness of the film, the film was passed through two horizontally arranged rolls having a roll interval of 2000 mm under a tension of 98N. At the center position between the rolls having a roll interval of 2000 mm, an iron bar was arranged such that the upper surface of the iron bar was positioned at a position 30 mm below a common tangent to the horizontally arranged roll upper surface, and the film was passed through. When the film does not contact the iron bar,
And when it came into contact with an iron bar, it was evaluated as x. These steps were continuously performed, and whether or not the film was in contact with the iron bar was visually confirmed.

(3) Adhesion with Photocurable Acrylic Coating Layer A hard coating agent (manufactured by Dainichi Seika Co., Ltd., Seika Beam EXF01) was applied to the easily adhesive layer surface of the films obtained in Examples and Comparative Examples.
(B)) was applied with a # 8 wire bar, dried at 70 ° C. for 1 minute to remove the solvent, and then 200 mJ /
A hard coat layer having a thickness of 3 μm was formed under the conditions of cm ² , irradiation distance of 15 cm and running speed of 5 m / min. The adhesiveness of the obtained film was determined by a test method according to the description of JIS-K5400, 8.5.1. Specifically, 100 square-shaped cuts penetrating the easy-adhesion layer and reaching the base film were made using a cutter guide with a gap of 2 mm. Next, a cellophane adhesive tape (405 made by Nichiban Co., Ltd.)
No .: 24 mm width) was attached to the cut-shaped cut surface, rubbed with an eraser and completely adhered, and then peeled off vertically to visually determine the adhesiveness from the following formula. Adhesiveness (%) = (1−peeled area / evaluated area) × 100

(4) Measurement of film haze value The haze value was measured using a haze meter (Model TC-H3DP manufactured by Tokyo Denshoku Industries Co., Ltd.) according to JIS-K7105.

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[Table 1]

[0078]

The optically easy-adhesive film of the present invention has excellent transparency and easy-to-adhere properties, and can be used in a heat treatment step during post-processing such as prism lens processing, hard coating processing, and AR processing. Because of its excellent post-processing suitability such as transportability, the product yield can be increased. Furthermore, since there are few optical defects, as optical films used throughout various optical members, in particular, base films for prism lens sheets, base films for backlights, base films for AR (anti-reflection) films, and for CRTs It is suitable for a crush prevention film and the like.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F100 AK25D AK41B AK41C AK42A AK51B AK51C AL01B AL01C BA02 BA03 BA06 BA07 BA10B BA10C CC00D EJ38A JA03 JB14D JL11 JL11B JL11C JN01 YY00

Claims (3)

[Claims] 1. A biaxially oriented polyester comprising a biaxially oriented polyester film having a thickness of at least 100 μm as a base material and an easy-adhesion layer comprising a copolymerized polyester resin and a polyurethane resin laminated on at least one surface of the base material. A film for optical use, wherein the difference between the maximum value and the minimum value of the heat shrinkage in the longitudinal direction of the film is 0.2% or less in the width direction. 2. An easy-to-use optically-adhesive film having an adhesive property of 85% or more when a photocurable acrylic coating layer is provided on the easily-adhesive layer according to claim 1. The adhesiveness described above means a value obtained from the following formula based on a test method according to JIS-K5400, 8.5.1. Adhesiveness (%) = (1−peeled area / evaluated area) × 100 3. The easily adhesive film for optical use according to claim 1, wherein the haze value of the film is 1.0% or less.