JP2000246856A - Optical easy-to-adhere film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical easy-to-adhere film having excellent transparency and easy adhesiveness in an optical film use requiring easy adhesive layers on both surfaces and having excellent scratch resistance in a process applying post-processing treatment to both surfaces of a base material film such as a process providing a vapor deposition layer of a transparent conductive layer on a single surface and providing a hard coat layer for anti-reflection(AR) to other surface. SOLUTION: In a biaxially oriented polyester film having easy-to-adhere layers each consisting of a copolyester resin and a polyurethane resin formed on both surfaces thereof, the total light transmissivity of this film is 90% or more and the three-dimensional center average surface roughness (SRa) of the easy adhesive layers is 0.002-0.010 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical adhesive film, and more particularly to an optical adhesive film having excellent transparency, adhesive property and scratch resistance.

[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, base films for prism lens sheets, touch panel base films, backlight base films, AR (anti-reflection) film base films, and C films for use in liquid crystal display devices.
Since the application of the crush prevention film for RT requires excellent strength and dimensional stability, a relatively thick film having a thickness of 100 μm or more is suitably used. Films used for such optical films are required to have excellent transparency and excellent adhesion to prism lens processing, hard coat processing, and AR processing. Therefore, it is desirable that the amount be as small as possible.

[0004]

However, it is generally known that a biaxially oriented polyester film generally has poor adhesion to other materials, for example, a prism lens or a hard coat mainly composed of an acrylic resin. . For this reason, various types of polyester films having an easily adhesive layer formed of a polyurethane resin or the like on the surface thereof have been proposed (for example, 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.

On the other hand, inert inorganic particles and the like are generally added to the base film in order to improve the slipperiness (easy slipperiness). Tend to hinder the transparency of Furthermore, when the particles are not contained in the base film or are added only in such a small amount that the transparency is not impaired, it is generally necessary to add particles for the purpose of imparting lubricity to the easily adhesive layer. is there. At this time, in order to ensure transparency, it is necessary to use particles having an extremely small average particle size equal to or smaller than the wavelength of visible light. However, although transparency can be ensured only by such fine particles having a small average particle diameter, for example, in the case of a base film for a touch panel that requires an easy-adhesion layer on both sides, a step of depositing a transparent conductive layer (ITO film) on one side. In the subsequent process such as laminating a hard coat layer for anti-reflection (AR) on other surfaces, the film surface is easily scratched by a contacting roll (hereinafter referred to as scratching property). It is becoming.

In view of the above problems, an object of the present invention is to provide a transparent conductive layer having excellent transparency and adhesion on one side in an optical film application requiring an easy adhesion layer on both sides. A vapor deposition layer is provided, and anti-reflection (A
An object of the present invention is to provide an easily adhesive optical film having excellent scratch resistance in a step of post-processing both surfaces of a base film such as providing a hard coat layer for R).

[0007]

The above object of the present invention is achieved by the following means.

[0008] 1. A biaxially oriented polyester film having an easy-adhesion layer made of a copolymerized polyester resin and a polyurethane resin formed on both surfaces, wherein the film has a total light transmittance of 90% or more, and further has a three-dimensional structure. Surface roughness (SRa) 0.002 to 0.010μ
m.

[0009] 2. 3. An optical adhesive film having an adhesive property of 85% or more when a photocurable acrylic coating layer is provided on the adhesive layer according to 1 above.

Here, the adhesiveness means a value obtained from the following equation. Adhesiveness (%) = (peeled area / evaluated area) × 100

[0011]

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 as the substrate 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. However, among them, a biaxially oriented film formed from polyethylene terephthalate is 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 the polyester resin pellet, which is a raw material of the 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 easy-adhesion film of the present invention is laminated on both sides of the biaxially oriented polyester film, and the easy-adhesion layers are provided on both sides of the unstretched or uniaxially stretched polyester film. It is preferable to laminate by an inline coating method in which the film is stretched in the direction and heat-set. If the easy-adhesion layer laminated on both sides of the film by the in-line coating method is provided with a slipperiness by containing fine particles having an appropriate particle diameter, a good winding property and a function of preventing scratching can be imparted. For this reason,
There is no need to include fine particles in the biaxially oriented polyester, and high transparency can be maintained.

The term "easy adhesion" as used in the present invention means that the adhesiveness to the acrylate coat layer obtained when measured according to the method described in [0059] is 85% or more, preferably 90% or more. And particularly preferably 95% or more.

The adhesive layer of the optical adhesive film of the present invention contains a copolyester resin and a polyurethane resin as main resin components. When the copolymerized polyester resin alone is used, the adhesion to the polyester base film is sufficient, but the adhesion to the acrylic resin used for the prism lens or the hard coat is poor. Also,
The polyurethane resin alone has excellent adhesiveness with the acrylate resin but is inferior in adhesiveness with the polyester base film.

The copolymerized polyester resin used in the easily adhesive layer of the present invention comprises a dicarboxylic acid component and a branched glycol component as constituents. 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 it is a small amount, diethylene glycol, propylene glycol, butanediol,
Hexanediol or 1,4-cyclohexanedimethanol may be used.

As the dicarboxylic acid component contained as a constituent component in the copolymerized polyester resin, terephthalic acid and isophthalic acid are most preferred. In small amounts, other dicarboxylic acids, especially diphenylcarboxylic acid and 2,2
An aromatic dicarboxylic acid such as 6-naltalenedicarboxylic acid may be added for copolymerization. In addition to the dicarboxylic acid component, 5-sulfoisophthalic acid is preferably used in an amount of 1 to 10 mol% in order to impart water dispersibility,
Examples thereof include sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfonaphthaleneisophthalic acid-2,7-dicarboxylic acid, 5- (4-sulfophenoxy) isophthalic acid and salts thereof.

The polyurethane resin used for the adhesive layer of the optical adhesive film of the present invention is, for example, a resin containing a block type isocyanate group, and the terminal isocyanate group is blocked with a hydrophilic group (hereinafter referred to as a block). did,
Thermal reaction-type water-soluble urethane is exemplified. 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 renders the urethane prepolymer hydrophilic or water-soluble. When thermal energy is given to the resin during the drying or heat setting process during film production, the blocking agent separates from the isocyanate group, so that the resin fixes the water-dispersible copolymerized polyester resin mixed with the self-crosslinked stitches. And also reacts with the terminal groups of the resin. The resin being adjusted for coating liquid has poor water resistance because it is hydrophilic,
When the thermal reaction is completed by coating, drying and heat setting, the hydrophilic group of the urethane resin, that is, the blocking agent comes off,
A coating film having good water resistance is obtained.

Among the above blocking agents, those which are suitable for heat treatment temperature and heat treatment time and are widely used industrially include:
Bisulfites are most preferred. As the chemical composition of the urethane prepolymer used in the above resin,
(1) Organic polyisocyanate having two or more active hydrogen atoms in a molecule, or having a molecular weight of 200 to 20,000 having at least two active hydrogen atoms in a molecule.
(2) an organic polyisocyanate having two or more isocyanate groups in the molecule, or (3)
A compound having a terminal isocyanate group obtained by reacting a chain extender having at least two active hydrogen atoms in the molecule.

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 compounds obtained by polymerizing alkylene oxides such as ethylene oxide and propylene oxide, or compounds obtained by polymerizing styrene oxide and epichlorohydrin, or by random polymerization, block polymerization, or addition polymerization to a polyhydric alcohol. There are compounds.

The polyester polyol and the polyether ester polyol include mainly linear or branched compounds. Succinic acid, adipic acid,
Polyvalent saturated or unsaturated carboxylic acids such as phthalic acid and maleic anhydride, or the carboxylic anhydrides and the like, ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol and It can be obtained by condensing polyhydric saturated and unsaturated alcohols such as trimethylolpropane, polyalkylene ether glycols such as relatively low molecular weight polyethylene glycol and polypropylene glycol, or a mixture of these alcohols. .

Further, as the polyester polyol,
Polyesters obtained from lactones and hydroxy acids, and polyetherester polyols also include polyetheresters obtained by adding ethylene oxide or propylene oxide to polyesters produced in advance.

As the organic polyisocyanate (2), isomers of toluylene diisocyanate, 4,4
Aromatic diisocyanates such as diphenylmethane diisocyanate, aromatic aliphatic diisocyanates such as xylylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate and 4,4-dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and 2,2,4 -Aliphatic diisocyanates such as trimethylhexamethylene diisocyanate, or polyisocyanates in which one or more of these compounds are previously added to trimethylolpropane or the like.

The chain extender having at least two active hydrogens of the above (3) includes ethylene glycol, diethylene glycol, 1,4-butanediol, and 1,6
Glycols such as hexanediol, polyhydric alcohols such as glycerin, trimethylolpropane, and pentaerythritol; diamines such as ethylenediamine, hexamethylenediamine and piperazine; aminoalcohols such as monoethanolamine and diethanolamine; thiodiethylene Thiodiglycols such as glycol, and water.

In order to synthesize the urethane prepolymer, 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., for 5 minutes to several hours. Let react. 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. Further, the content of free isocyanate groups may be 10% by weight or less, but in consideration of the stability of the aqueous urethane polymer solution after blocking,
It is preferably at most 7% by weight.

The obtained urethane prepolymer is preferably blocked using bisulfite. The mixture is mixed with an aqueous bisulfite solution, and the reaction is allowed to proceed with good stirring for about 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 the composition is used, it is adjusted to an appropriate concentration and viscosity.
When heated to about 200 ° C., the bisulfite of the blocking agent is dissociated, and the active isocyanate group is regenerated. Thus, a polyurethane polymer is generated by a polyaddition reaction occurring within or between molecules of the prepolymer, or It has the property of causing addition 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 typically exemplified.
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, more preferably (A) :( B) = 80: 20 to.
20:80. If the ratio of the resin (A) to the weight of the solid content is less than 10% by weight, the applicability to the substrate film is poor, and the adhesiveness between the surface layer and the film becomes insufficient. When the ratio of the resin (B) to the solid content is less than 10% by weight, a practically applicable adhesiveness cannot be obtained in a UV-curable hard coat.

In the present invention, it is preferable to use an aqueous coating liquid as the coating liquid for forming the easily adhesive layer. Various additives such as an antistatic agent, a UV absorber plasticizer, a pigment, an organic filler, and a lubricant may be mixed with the composition of the aqueous coating solution as long as the adhesive property is not lost. 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.

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 substances. Various chemical substances such as compounds 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 base film, a known anionic surfactant and a nonionic surfactant are used to increase the wettability of the film and uniformly coat the coating solution. The necessary amount of the agent can be added and used. The solvent used for the coating liquid is ethanol,
Alcohols such as isopropyl alcohol and benzyl alcohol may be mixed until the proportion of the total coating liquid 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 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 appearance of the coating film is improved as compared with the case where only water is used. If the content is 50% by weight or more, the solvent evaporates at a high rate, the concentration of the coating solution changes during coating, the viscosity increases, and the coating property decreases, which may cause poor appearance of the coating film. May be a danger such as fire.

The coating amount (weight of solids per unit area of the film) of the easily adhesive layer is 0.05 to 0.50 g / m ^2.
Is preferred. When the coating amount is less than 0.05 g / m ² ,
Poor adhesion. If the coating amount is more than 0.50 g / m ² , the total light transmittance decreases, which is not preferable.

The total light transmittance of the easily adhesive optical film of the present invention must be 90% or more, preferably 91% or more, particularly preferably 92% or more. When the total light transmittance is less than 90%, when the film is used as a base film for a touch panel, a base film for an AR (anti-reflection) film, or the like, the sharpness of the screen deteriorates, which is not preferable. In the present invention, the easy-adhesion layers are formed on both surfaces of the biaxially oriented polyester film. This is the base film for touch panel, AR (anti-reflection) film, shatterproof film for CRT, etc.
This is because easy adhesion is often required on both surfaces.

In order to make the total light transmittance of the easily adhesive optical film of the present invention 90% or more, it is preferable that particles for imparting lubricity are not contained in the base film. When the base film does not contain particles for imparting lubricity, it is preferable to include appropriate particles in the easy-adhesion layer in order to improve the scratch resistance of the easy-adhesion layer and the winding property of the film. .

Examples of such particles include inorganic particles such as calcium carbonate, calcium phosphate, silica, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite and molybdenum disulfide, and crosslinked polymers. And organic particles such as calcium oxalate. Among them, silica particles are most preferable because they have a refractive index relatively close to that of the polyester resin and can easily obtain a highly transparent film.

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 total light transmittance tends to decrease.

In the present invention, it is preferable to add the particles B in order to further improve the scratch resistance, which is insufficient with the particles A alone. The average particle size of the particles B is 300 to 1000
nm, more preferably 400 to 800 nm
It is. When the average particle size of the particles B is less than 300 nm,
The scratch resistance tends to deteriorate. On the other hand, when the average particle diameter of the particles B exceeds 1000 nm, the total light transmittance tends to decrease. 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 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 1 with respect to the solid content of the easy-adhesion layer. % By weight means that the three-dimensional center plane average surface roughness (SR
a) is preferably set to 0.002 to 0.010 μm, and it is necessary to set the respective particle contents 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, the total light transmittance is significantly reduced. The solid content of the easy adhesion layer described above,
It means the total of the solid contents of the resin A, the resin B, the particles A, and the particles B.

Furthermore, in order to make the total light transmittance of the optically easy-adhesive film of the present invention 90% or more, it is necessary to remove foreign substances in the coating liquid and the base film and to prepare an unstretched sheet as a whole (especially a chill roll). It is effective to rapidly cool the surface which does not come into contact with.

The filter medium for finely filtering the coating solution preferably has a filter particle size (initial filtration efficiency: 95%) of 25 μm or less. If the filtration particle size exceeds 25 μm, the removal of coarse aggregates tends to be insufficient. Therefore, the coarse aggregates that could not be removed by filtration are spread by the stretching stress in the uniaxial stretching or the biaxial stretching process after coating and drying, and are recognized as aggregates of 100 μm or more, and lower the total light transmittance of the film. Cause.

There is no particular limitation on the type of filter medium for finely filtering the coating solution as long as it has the above-mentioned performance.
Filament type, felt type and mesh type are mentioned. The material of the filter medium for finely filtering the coating solution is not particularly limited as long as it has the above performance and does not adversely affect the coating solution, and examples thereof include stainless steel, polyethylene, polypropylene, and nylon.

The base film is also subjected to high-precision filtration at any place where the molten resin is maintained at about 280 ° C. during the melt extrusion in order to remove foreign substances contained in the raw material resin. Filter media used for high precision filtration of molten resin are:
Although not particularly limited, a filter material of a sintered stainless steel is suitable because it has excellent performance of removing aggregates containing Si, Ti, Sb, Ge, and Cu as main components and organic substances having a high melting point. The filtration particle size (initial filtration efficiency 95%) of the filter medium used for high-precision filtration of the molten resin is preferably 15 μm or less. When the filtration particle size of the filter medium exceeds 15 μm, the removal of foreign substances of 20 μm or more tends to be insufficient. Although the productivity may be reduced by performing high-precision filtration of the molten resin using a filter medium having a filtration particle size (initial filtration efficiency of 95%) of 15 μm or less, an optical film having a high total light transmittance is obtained. Is very suitable for

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 non-uniform stretching in the stretching step. A minute difference in thickness is caused, resulting in a lens state. Here, the light is refracted or scattered as if there is a lens, and when observed with the naked eye, it appears larger than an actual foreign substance. 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. , Due to the lens effect, an object having a shape of 20 μm is visually 50 μm.
m and may be 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 the smaller the amount of added particles and the higher the transparency, the higher the optical defects due to minute irregularities. It tends to be sharper. Also, the surface of a thick film is less likely to be quenched than a thin film, and crystallization tends to proceed. Therefore, it is necessary to quench the entire film when preparing an unstretched sheet. As a method of cooling the unstretched sheet, a known method in which a molten resin is extruded from a die onto a rotary cooling drum onto a sheet, and the sheet-like molten material is rapidly cooled while being in close contact with the rotary cooling drum to form a sheet can be applied. . As a method for cooling the air surface (the surface opposite to the surface in contact with the cooling drum) of the sheet-like material, a method of blowing a high-speed airflow to cool the sheet is effective.

Next, the method for producing the optically easy-to-adhere film of the present invention will be described with reference to polyethylene terephthalate (hereinafter P
ET), but the present invention is not limited to this. PET pellets substantially free of particles for the purpose of imparting lubricity are sufficiently vacuum-dried, fed to an extruder, melt-extruded into a sheet at about 280 ° C., cooled and solidified, and then dried. A stretched PET sheet is formed into a film. At this time, the high-precision filtration is performed at an arbitrary place where the molten resin is kept at about 280 ° C. in order to remove foreign substances contained in the resin.

The obtained unstretched sheet is heated at 80 to 120 ° C.
And stretched 2.5 to 5.0 times in the longitudinal direction with a roll heated to obtain a uniaxially oriented PET film. Further, the end of the film is gripped with a clip, guided to a hot air zone heated to 80 to 180 ° C., and dried to a width of 2.5 to 5.0 in the width direction.
Stretch twice. Subsequently, it is led to a heat treatment zone of 160 to 240 ° C. and heat treated for 1 to 60 seconds to complete the crystal orientation. During this heat treatment step, if necessary, a 1 to 12% relaxation treatment may be performed in the width direction or the longitudinal direction.

At any stage during this process, an aqueous solution of the above-mentioned copolymerized polyester and polyurethane resin is applied to one side of the polyester film. The aqueous coating solution can be applied by any known method. For example, a reverse roll coating method, a gravure coating method, a kiss coating method, a roll brushing method, a spray coating method, an air knife coating method, a wire barber coating method, a pipe doctor method, an impregnation / coating method, a curtain coating method, etc. These methods can be performed alone or in combination.

The step of applying the aqueous coating solution may be a normal coating step, that is, a step of coating a base film which has been biaxially stretched and heat-set, but an in-line coating method of coating during the production step of the film may be used. preferable. More preferably, it is applied to the base film before the completion of the crystal orientation. The solid content concentration in the aqueous coating solution is preferably 30% by weight or less, particularly preferably 10% by weight or less. The amount of the aqueous coating liquid applied The film coated with the aqueous coating liquid 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 a polyester-based laminated film Becomes In order to obtain good adhesion to the ink, the coating amount at this time should be 0.
The heat treatment is not less than 05 g / m ² and 100 ° C. for 1 minute or more.

The three-dimensional center plane average surface roughness (SRa) of the easy-adhesion layer in the easy-adhesion film for optical use of the present invention is 0.1.
002-0.010 μm, 0.002
5 to 0.0080 μm is preferable, and 0.0030 to 0.
0060 μm is particularly preferred. SRa is 0.002 μm
If the surface is smooth, the scratch resistance is deteriorated, which is not preferable. On the other hand, if SRa exceeds 0.010 μm, the total light transmittance is reduced and the transparency is deteriorated, so that it is not preferable as an optical film.

It is preferable that the content of the particles A and the particles B, the ratio thereof, and the coating amount are within the above ranges, so that the SRa and the total light transmittance specified in the present invention are within the ranges. This is effective for achieving both good resistance and scratch resistance.

The thickness of the easily adhesive optical film in the present invention is preferably from 50 to 300 μm, particularly preferably 10 to 300 μm.
0 to 250 μm. If the film thickness is less than 50 μm, the rigidity becomes insufficient, which is not preferable. On the other hand, if the thickness of the film exceeds 300 μm, it is not preferable because foreign substances which are optical defects existing in the film increase and the total light transmittance decreases.

The optically easy-adhesive film thus obtained is
In optical film applications that require easy adhesion layers on both sides,
It has the characteristics of excellent transparency, easy adhesion, and excellent scratch resistance in the process of post-processing both sides of the base film. A transparent conductive layer (ITO film) is laminated on one side of the base film. It can be suitably used for a base film for a touch panel having a hard coat layer for anti-reflection (AR) laminated on the other surface.

[0056]

Next, a method for producing an easily adhesive polyester film for optics of the present invention will be described with reference to polyethylene terephthalate (hereinafter abbreviated as PET) as an example, but is not limited thereto. The evaluation of the characteristics in the present specification was performed by the following methods.

(1) Measurement of total light transmittance Haze meter (Model TC-H3D manufactured by Tokyo Denshoku Industries Co., Ltd.)
P).

(2) Three-dimensional center plane average surface roughness (SR
a) The three-dimensional center plane average roughness (SRa) of the surface of the easily adhesive layer is measured by a stylus type three-dimensional surface roughness meter (ET-30H) manufactured by Kosaka Laboratory Co., Ltd.
K) and a three-dimensional roughness analyzer (SPA-11), stylus tip radius: 2 μm, stylus load: 20 mg, cutoff value: 0.08 mm, measurement length: 1 mm, feed speed: 100 μm / It was measured under the conditions of seconds and a feed pitch of 2 μm.

(3) Adhesion with Photocurable Acrylic Coating Layer The easy-adhesion layer surface of the films obtained in Examples and Comparative Examples was applied to a hard coating agent (Seika Beam EXF01 manufactured by Dainichi Seika Co., Ltd.).
(B)) using a # 8 wire bar, and
After drying for a minute to remove the solvent, 200mJ with a high pressure mercury lamp
/ Cm ² , an irradiation distance of 15 cm, and a running speed of 5 m / min, to form a hard coat layer having a thickness of 3 μm. The adhesiveness of the obtained film was determined by a test method according to 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) Scratch resistance An optically easy-to-adhesive film slit to a width of 1000 mm was measured for a diameter of 220 m using a film running tester.
m, and run on a free roll (surface roughness: 100 nm in Ra) which has been subjected to hard chrome plating and has a rotation resistance of 1 kg. The running conditions at this time were: running speed: 10 m / min, winding angle: 60 °, running tension: 10 kg. Scratches entering the film surface due to this treatment are observed with a microscope after platinum deposition, and when there are less than 10 scratches with a width of 3 μm or more and a length of 500 μm or more per m ² , it is excellent and 10 or more and less than 20 Was determined to be good, and to be 20 or more was determined to be defective. Although excellent is desirable, even good is practically usable.

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 sulfoisophthalic acid was added, and
After performing the esterification reaction over time, a polycondensation reaction was performed at 250 ° C. under reduced pressure (10 to 0.2 mmHg) 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 an isocyanate group-containing self-crosslinkable polyurethane resin (B) blocked with sodium bisulfite (Daiichi Kogyo Seiyaku Co., Ltd., trade name: Elastron H-3), 0.5 parts catalyst for Elastron (Daiichi Kogyo Seiyaku; product name Cat64) and 4 parts water
4.3 parts and 5 parts of isopropyl alcohol were respectively mixed, and 0.6% by weight of a 10% aqueous solution of an anionic surfactant, particles A (Nissan Chemical Industries: Snowtex OL, average particle size 40 nm) 1.8 parts of a 20% aqueous dispersion of the particles B (manufactured by Nippon Aerosil Co., Ltd .; Aerosil O)
X50, average particle size 500 nm, average primary particle size 40 nm)
1.1 parts of a 4% aqueous dispersion was added to obtain a coating liquid.

(2) Production of Easy Adhesive Film Example As a raw material polymer, polyethylene terephthalate resin pellets containing no particles and having an intrinsic viscosity of 0.62 dl / g were dried under reduced pressure at 135 ° C. for 6 hours (1 Torr).
After r), the mixture was supplied to an extruder, melted and extruded into a sheet at about 280 ° C., and quenched and solidified on a metal roll maintained at a surface temperature of 20 ° C. to obtain a cast film having a thickness of 1400 μm. At this time, as a filter material for foreign matter removal of the molten resin,
A stainless sintered filter medium having a filtration particle size (initial filtration efficiency: 95%) of 15 μm was used. Next, the cast film was heated for 100 hours by a heated roll group and an infrared heater.
C., and then 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. Next, the coating liquid was filtered to a particle size (initial filtration efficiency of 95%).
%) Precisely filtered through a 25 μm felt-type polypropylene filter medium, applied to both sides of a uniaxially oriented PET film by a reverse roll method, and dried. At this time, the content ratio of the particles A and the particles B was 8, and the content of the particles B was 0.42% by weight in terms of the solid content ratio of the easily adhesive layer. The coating amount was 0.10 g / m ² as a solid content. Subsequently, after coating, the end of the film is gripped with a clip and guided to a hot air zone heated to 130 ° C., dried and stretched 4.0 times in the width direction to obtain a biaxially oriented PET film having a thickness of 100 μm. Was.
Table 1 shows the results.

Example 2 In the preparation of the coating solution, except that the content ratio of the particles A and the particles B was 20, and the content of the particles B was 0.17% by weight based on the solid content of the easily adhesive layer. In the same manner as in Example 1, an easily adhesive film for optical was obtained. The amounts of water and isopropyl alcohol were adjusted while keeping the ratio between the two so that the solid content concentration in the coating solution was the same as in Example 1. Table 1 shows the results.

Example 3 In the preparation of the coating solution, except that the content ratio of the particles A and the particles B was 12, and the content of the particles B was 0.41% by weight with respect to the solid content of the easily adhesive layer. In the same manner as in Example 1, an easily adhesive film for optical was obtained. The amounts of water and isopropyl alcohol were adjusted while keeping the ratio between the two so that the solid content concentration in the coating solution was the same as in Example 1. Table 1 shows the results.

Comparative Example 1 Example 1 was repeated except that the polyester resin (A) was not added in preparing the coating solution.
An easy-to-use optical adhesive film was obtained in the same manner as described above. At this time, the content ratio of the particles A and the particles B was 8, and the content of the particles B was 0.52% by weight based on the solid content of the easily adhesive layer. In addition,
The amounts of water and isopropyl alcohol were adjusted while keeping the ratio of the amounts added so that the solid content concentration in the coating solution was the same as in Example 1. Table 1 shows the results.

(Comparative Example 2) An easy-to-use optical adhesive film was obtained in the same manner as in Example 1 except that the urethane resin (B) was not added in the preparation of the coating solution. At this time, the content ratio of the particles A and the particles B was 8, and the content of the particles B was 1.82% by weight based on the solid content of the easily adhesive layer. The amounts of water and isopropyl alcohol were adjusted while keeping the ratio between the two so that the solid content concentration in the coating solution was the same as in Example 1. Table 1 shows the results.

(Comparative Example 3) In the preparation of the coating solution, the average particle size of the particles A was 1400 nm (31, manufactured by Fuji Silysia Limited).
An easily adhesive film for optical use was obtained in the same manner as in Example 1 except that the particles of No. 0) were used. Particles A and B at this time
Was 8 and the content of particles B was 0.42% by weight based on the solid content of the easily adhesive layer. The amounts of water and isopropyl alcohol were adjusted while keeping the ratio between the two so that the solid content concentration in the coating solution was the same as in Example 1. Table 1 shows the results.

(Comparative Example 4) In preparing the coating solution, except that the content ratio of the particles A and the particles B was 2, and the content of the particles B was 1.60% by weight based on the solid content of the easily adhesive layer. In the same manner as in Example 1, an easily adhesive film for optical was obtained. In addition,
The amounts of water and isopropyl alcohol were adjusted while keeping the ratio of the amounts added so that the solid content concentration in the coating solution was the same as in Example 1. Table 1 shows the results.

(Comparative Example 5) An easily adhesive optical film was obtained in the same manner as in Example 1 except that particles A and B were not added in the preparation of the coating solution. The amounts of water and isopropyl alcohol were adjusted while keeping the ratio between the two so that the solid content concentration in the coating solution was the same as in Example 1. Table 1 shows the results.

(Comparative Example 6) An easy-to-use optical adhesive film was obtained in the same manner as in Example 1, except that the coating solution was applied only on one side of the uniaxially oriented PET film. Table 1 shows the results
Shown in

[0072]

[Table 1]

[0073]

According to the present invention, the optical film having an easy-adhesion layer formed on both surfaces has a resin component and a three-dimensional center plane average surface roughness (SRa) of the easy-adhesion layer within a specific range, and has a total light transmittance. Is more than a certain value, it is possible to obtain a film having excellent adhesion, scratch resistance and transparency. The use of the film of the present invention covers all kinds of optical films, and is particularly useful for a base film for a touch panel which requires post-processing on both surfaces of the film of the present invention, an AR (anti-reflection) film, a crush prevention film for a CRT, and the like. .

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C08L 23:10 67:00 75:00 F term (Reference) 4F006 AA35 AB24 AB35 AB37 BA01 CA05 DA04 4F071 AA45 AA46 AA53 AF27Y AF30Y AH19 BA01 BB06 BB08 BC01 BC16 BC17 4F100 AK25D AK41A AK41B AK41C AK42 AK51A AK51C AK51G AL01A AL01C BA03 BA04 BA06 BA07 BA10A BA10C BA10D BA16 EH46 EJ38B GB90 JB14D JK14A JK14C JL11A JL11C JN01B YY00B

Claims (2)

[Claims] 1. A biaxially oriented polyester film having an easy-adhesion layer made of a copolymerized polyester resin and a polyurethane resin formed on both sides, wherein the film has a total light transmittance of 90% or more, and The three-dimensional center plane average surface roughness (SRa) of the adhesive layer is 0.002 to 0.0
An optical adhesive film having a thickness of 10 μm. 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.