JP5428868B2 - Easy-adhesive polyester film for optics - Google Patents

Description

  The present invention relates to an easily adhesive polyester film for optics that has few optical defects and high transparency, and is excellent in adhesion and heat and moisture resistance. Specifically, as a base material for optical functional films such as hard coat films, antireflection films, light diffusion sheets, prismatic lens sheets, near-infrared shielding films, transparent conductive films, and antiglare films, which are mainly used for displays and the like. The present invention relates to a suitable optically easy-adhesive polyester film.

  In general, the base material of an optical functional film used as a member of a liquid crystal display (LCD) is a transparent thermoplastic made of polyethylene terephthalate (PET), acrylic, polycarbonate (PC), triacetyl cellulose (TAC), polyolefin, or the like. A resin film is used.

  When using the thermoplastic resin film as a base material for various optical functional films, functional layers corresponding to various applications are laminated. For example, in a liquid crystal display (LCD), a protective film (hard coat layer) that prevents scratches on the surface, an antireflection layer (AR layer) that prevents reflection of external light, and a prism layer that is used to collect and diffuse light And a functional layer such as a light diffusion layer for improving luminance. Among such substrates, particularly polyester films are widely used as substrates for various optical functional films because they are excellent in transparency, dimensional stability and chemical resistance and are relatively inexpensive.

  In general, in the case of a biaxially oriented thermoplastic film such as a biaxially oriented polyester film or a biaxially oriented polyamide film, the film surface is highly crystallized, so it has good adhesion to various paints, adhesives, inks, etc. There is a disadvantage of being scarce. For this reason, methods for imparting easy adhesion to the biaxially oriented thermoplastic resin film surface by various methods have been proposed.

  For example, by providing a coating layer containing various resins such as polyester, acrylic, polyurethane, and acrylic graft polyester on the surface of the thermoplastic resin film of the base material as the main component of the coating layer, the base film can be easily adhered. The method of giving is generally known. Among these coating methods, an aqueous coating solution containing the resin solution or a dispersion obtained by dispersing the resin in a dispersion medium is coated on a thermoplastic resin film before completion of crystal orientation, and dried. Thereafter, the film is stretched at least in a uniaxial direction and then subjected to heat treatment to complete the orientation of the thermoplastic resin film (so-called in-line coating method), or after the production of the thermoplastic resin film, the film is water-based or solvent-based. A method of drying after applying a coating solution (so-called off-line coating method) has been industrially implemented.

  A display such as an LCD or PDP, or a portable device using a hard coat film as a member is used in various environments regardless of indoors or outdoors. In particular, portable devices may require moisture and heat resistance that can withstand a bathroom, a hot and humid area, and the like. The optical functional film used for such applications is required to have high adhesion such that delamination does not occur even under high temperature and high humidity. Therefore, in the following patent document, an easy-adhesive thermoplastic resin film imparted with moisture and heat resistance is disclosed by adding a crosslinking agent to the coating solution and forming a crosslinked structure in the coating layer resin when forming the coating layer by the in-line coating method. Has been.

JP 2000-141574 A Japanese Patent No. 3773738 Japanese Patent No. 3900191 JP 2007-253512 A

  Longer life expectancy is expected for home appliances with a display to reduce the global environmental impact. Therefore, it was considered that the optical functional film used as a member also needs to maintain adhesiveness for a long time even under high temperature and high humidity. However, the easy-adhesion film as disclosed in the above-mentioned patent document shows good adhesion at first, but a decrease in adhesion strength is inevitable in long-term use under high temperature and high humidity. . Due to such a decrease in adhesion, there is a problem that the initial performance is not maintained for a long time.

  In addition, the display resolution has been dramatically improved, and minute scratches and foreign matters that are not considered to be conventional problems have been recognized as optical defects. In addition, due to the improvement in productivity, the line speed in the processing process and the film forming process has been dramatically improved, and it has become necessary to reduce optical defects even under high-speed processing conditions. Thus, there is a need for a high-quality easy-adhesive film with few optical defects that can cope with future high definition and productivity improvement.

  In view of the above problems, the present invention has high transparency with few optical defects, and deterioration of the coating layer under high temperature and high humidity, which has been considered to be unavoidable in the past, in other words, adhesiveness under high temperature and high humidity. It is an object of the present invention to provide an easily adhesive polyester film for optical use that hardly causes a decrease.

  In addition, the adhesiveness under high temperature and high humidity referred to in the present invention is a layer of a photocurable acrylic layer, placed in an environment of 80 ° C., 95% RH, 48 hours, and using a cutter guide with a gap interval of 2 mm, Apply 100 cell-shaped cuts that penetrate the photocurable acrylic layer to the base film on the surface of the photocurable acrylic layer, and then apply cellophane adhesive tape to the cell-shaped cut surface and rub it with an eraser to complete Means the adhesiveness when the same part is peeled off 5 times vigorously, and is adhesiveness according to stricter criteria than the evaluation method described in JIS K5600-5-6, which is generally used. Therefore, it is a problem that the adhesiveness under such high temperature and high humidity shows the adhesiveness equal to or higher than the initial adhesiveness.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor uses a coating film containing a polyester resin having a specific molecular weight and a resin having an oxazoline group, and further using a base film having a specific layer structure. The present inventors have found that the conventional technical common sense that adhesion is improved under high temperature and high humidity while maintaining high transparency with few optical defects. As described in the above-mentioned patent document, in order to improve the adhesion of the coating layer in the conventional technical common sense, it is mixed with a crosslinking agent and a resin having a functional group capable of reacting with it, and a highly crosslinked structure is formed when the coating layer is formed. It has been considered desirable to form. However, the present invention is a new technology contrary to the prior art, in which adhesion is improved under high temperature and high humidity by using a polyester resin that has substantially no carboxylic acid group that is a functional group that reacts with an oxazoline group. It is an easily adhesive film for optics based on the idea.

The above-described problem can be achieved by the following solution means. (1) An easily-adhesive polyester film having a coating layer on at least one surface of a base film, wherein the base film has a laminated structure of three or more layers by a coextrusion method, and both outermost layers are inert particles. A polyester film having a haze of 2.5% or less, wherein the coating layer has a number average molecular weight of 15000 or more and has substantially no carboxylic acid group, and a resin having an oxazoline group Easy-adhesive polyester film for optical use.
(2) The average particle size of the inert particles contained in the outermost layer is 2.1 to 2.5 μm, the thickness of the outermost layer is equal to or greater than the average particle size of the inert particles, and the center of the outermost layer surface The said easily adhesive polyester film for optics whose surface average roughness (SRa) is 0.008-0.015 micrometer, and 10-point average roughness (SRz) is 0.5-1.5 micrometers.
(3) The easily adhesive polyester film for optics, wherein the resin having an oxazoline group is water-soluble.
(4) The inert particles in the outermost layer are amorphous bulk silica having a pore volume of 1.5 to 2.0 ml / g, and the inert particle content in the outermost layer is 0.015 to 0.030. The said easily-adhesive polyester film for optics which is the mass%.
(5) At least one layer selected from a hard coat layer, a light diffusion layer, a prismatic lens layer, an electromagnetic wave absorption layer, a near-infrared blocking layer, and a transparent conductive layer is formed on the coating layer of the optically easy-adhesive polyester film. An optical laminated polyester film obtained by laminating optical functional layers.

  The easily adhesive polyester film for optics of the present invention is excellent in adhesion (moisture heat resistance) to the optical functional layer under high temperature and high humidity while maintaining high transparency with few optical defects. Therefore, as a preferred embodiment, the adhesion at the high temperature and high humidity treatment is equal to or improved from the initial adhesion. As a preferred embodiment of the present invention, when the optically easy-adhesive polyester film of the present invention is used as a substrate for a lens sheet, the adhesion with the lens layer under high temperature and high humidity is good.

(Polyester film)
The polyester resin constituting the substrate in the present invention includes polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polymethylene terephthalate, and copolymerization components such as diethylene glycol, neopentyl glycol, and polyalkylene glycol. A diol component, a polyester resin copolymerized with a dicarboxylic acid component such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, or 2,6-naphthalenedicarboxylic acid can be used.

  The polyester resin suitably used in the present invention mainly contains at least one of polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate as a constituent component. Among these polyester resins, polyethylene terephthalate is most preferable from the balance between physical properties and cost. Moreover, these polyester films can improve chemical resistance, heat resistance, mechanical strength, etc. by biaxially stretching.

  When the film of the present invention is used for a base film of an optical member, high transparency is required. Therefore, the haze value of the base film of the present invention is preferably 2.5% or less, more preferably 2.0% or less, and further preferably 1.5% or less. When the haze value of the substrate film exceeds the upper limit, not only the high transparency required for optical applications is exhibited, but also optical defects due to powdered off inert particles tend to occur.

  In order to achieve both the high transparency and excellent processability, the film of the present invention has a laminated structure of three or more layers by a coextrusion method, and contains inert particles in both outermost layers. Thereby, it becomes possible to give uneven | corrugated shape to the outermost layer surface, and the workability (slidability) by film processing becomes favorable. As the laminated structure of the present invention, for example, when the outermost layer is the B layer, the other layers are the A layer, and the C layer, the layer structure in the film thickness direction is B / A / B, B / A / C / B, Alternatively, a configuration such as B / A / C / A / B is conceivable. Each layer of the A to C layers may have the same or different polyester resin composition, but in order to suppress the occurrence of curling due to the bimetal structure, the polyester resin of each layer is made the same structure. And / or a B / A / B configuration (two-kind three-layer configuration).

  In the present invention, the polyester resin constituting the central layer other than the outermost layer (for example, the A layer in the B / A / B configuration) may contain particles, but in order to obtain high transparency, the central layer is used. It is preferable that the constituent polyester resin does not substantially contain particles. By containing inert particles only in the outermost layer, high transparency can be obtained more suitably. When particles are added to the central layer other than the outermost layer, it is preferably 50 ppm or less, preferably 10 ppm or less.

  The inert particles contained in the outermost layer include calcium carbonate, calcium phosphate, amorphous silica, spherical silica, crystalline glass filler, kaolin, talc, titanium dioxide, alumina, silica-alumina composite oxide particles, barium sulfate, fluoride. Inorganic particles such as calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide, mica, crosslinked polystyrene particles, crosslinked acrylic resin particles, crosslinked methyl methacrylate particles, benzoguanamine / formaldehyde condensate particles, melamine / formaldehyde condensate particles, Examples thereof include heat-resistant polymer fine particles such as polytetrafluoroethylene particles. Of these, silica is most suitable in that it can ensure a film with higher transparency because its refractive index is relatively close to that of polyester.

  The average particle size of the inert particles contained in the outermost layer of the film of the present invention is preferably 2.1 to 2.5 μm, more preferably 2.2 to 2.4 μm. If the average particle diameter of the inert particles is less than 2.1 μm, the agglomeration force of the particles is very large, and coarse abnormal particles are easily generated due to the aggregation of the particles, which is not preferable. In this case, an optical defect having a major axis of 20 μm or more may occur on the film surface due to the aggregated particles. Furthermore, in order to construct a surface shape as described later, it is desirable that the average particle diameter of the inert particles is 2.1 μm or more. Moreover, when the average particle diameter is 2.5 μm or more, the content of coarse particles as a single particle increases, which is not preferable. In this case, optical defects having a major axis of 20 μm or more may occur on the film surface due to coarse particles. In order to reduce the coarse particles that cause optical defects to the utmost limit, it is desirable to use a specific very narrow range of particles.

  The range of the average particle diameter of an inert particle here is measured with the measuring method mentioned later. For example, in the case of secondary particles in which primary particles are aggregated as described later, it means the average particle size of the secondary particles. That is, the average particle diameter of the inert particles here is an average particle diameter in an aspect that can actually exist as inert particles in the film.

  In order to suppress the occurrence of optical defects due to powdering off of the inert particles, the thickness of the outermost layer is preferably equal to or greater than the average particle size of the inert particles. Further, the content of the inert particles in the outermost layer is desirably 0.015 to 0.03% by mass, and more preferably 0.02 to 0.025% by mass. When the content of the inert particles is 0.015% by mass or more, it is preferable from the viewpoint of exhibiting an effective slipping property to the extent that fine scratches are reduced. When content of an inert particle is 0.03 mass% or less, it is preferable when maintaining high transparency.

  In the present invention, the thickness of the inert particle-containing layer and the particle diameter of the inert particles are specified in order to maintain high transparency while further suppressing optical defects due to powder falling generated in the processing step and the film forming step. By setting the range, it is possible to control a surface protrusion having a ratio of a specific protrusion diameter to a protrusion height.

  Specifically, both outermost layers contain inert particles having an average particle size of 2.1 to 2.5 μm, and the thickness of the outermost layer is not less than 5 times and less than 11 times the average particle size of the inert particles, Of the surface protrusions having a height of 2 nm or more observed by the atomic force microscope (AFM) on the outermost surface, the surface protrusions having a ratio L / h of the surface protrusion diameter L to the surface protrusion height h of 50 or less. By setting the ratio of the number to 30% or less, it is possible to obtain a film with less optical defects.

  In other words, in addition to improving processability by imparting surface irregularities, we examined how to reduce powder loss caused by high-speed processing, and when both have a specific surface structure, both of these characteristics are remarkably compatible. I found that I could do it. That is, the ratio L / h of the diameter L of the surface protrusion to the height h of the surface protrusion is 50 or less among the surface protrusions having a height of 2 nm or more observed by the atomic force microscope (AFM) on the outermost surface. By setting the ratio of the number of protrusions to be 30% or less, it is possible to suitably achieve both reduction of optical defects and reduction of powder falling caused by high speed processing.

  In order to achieve more suitable slipping property, it is preferable to have surface protrusions having a protrusion height of 2 nm or more due to inert particles. However, when the surface protrusions become high, particles forming the protrusions may fall off due to rubbing between rolls or films in ultra-high speed processing. A slight powder fall off during such a process can cause the process to become dirty due to long-term operation and cause micro scratches. Therefore, as a result of examining the surface shape that causes powder falling off, the present inventor does not determine the ease of particle removal depending on the height of the surface protrusion, but the shape of the peak of the surface protrusion is that of the inert particle. It was found that it affects the ease of dropping off. That is, among the surface protrusions having a height of 2 nm or more, the surface protrusion having a gentle skirt in which the ratio L / h of the diameter L of the surface protrusion to the height h of the surface protrusion exceeds 50 is less likely to drop off particles. On the other hand, surface protrusions having a relatively small base where the ratio L / h of the diameter L of the surface protrusions to the height h of the surface protrusions is 50 or less are likely to drop off particles.

  When the required characteristics due to powder fall are high, it is desirable to increase the number of surface protrusions having a gentle crest as described above. Therefore, the thickness of the outermost layer needs to be at least 5 times the average particle diameter of the inert particles. The surface protrusions are formed by inert particles present in the outermost layer. In order to form gentle surface protrusions, it is desirable that the particles having a certain size or more exist with an appropriate depth, rather than the inert particles being directly below the surface. When the thickness of the outermost layer is less than 5 times the average particle diameter of the inert particles, the shape of the surface protrusions due to the inert particles becomes relatively sharp, so that powder falling easily occurs. The upper limit of the thickness of the outermost layer is not particularly provided from the viewpoint of occurrence of powder falling, but if the thickness becomes too thick, the amount of inactive particles inside the film becomes too large, and scattering of light generated inside the film is large. This is not preferable because the transparency is lowered. The upper limit of the thickness of the outermost layer was set to less than 11 times from the range in which the haze increase can be allowed. Here, the thickness of the outermost layer is the thickness of one side of the outermost layer laminated on both sides of the film.

  By controlling the thickness of the inert particles and the layer containing the inert particles as described above, it is possible to suitably control the shape of the protrusions on the surface of the film, and to reduce the inclination angle of each protrusion as much as possible. It is possible to reduce optical defects more suitably while suppressing as much as possible.

  Furthermore, in order to form the specific surface shape more preferably, for example, (1) a method of smoothing the surface shape by increasing the intrinsic viscosity of the polyester resin, and (2) processing at a high heat setting temperature. It is also possible to combine the method of smoothing the surface shape. In addition, as will be described later, it is also preferable to use (3) inert particles that are likely to undergo follow-up deformation when the film is stretched.

Inactive particles that are likely to undergo follow-up deformation when the film is stretched are secondary particles in which primary particles of several to several hundred nm are aggregated and have a pore volume of 1.5 ml / g or more. Is preferred. In particular, amorphous bulk silica is preferable from the viewpoints of transparency, handleability, and cost. By setting the pore volume of the inert particles to 1.5 ml / g or more, deformation of the particles due to stretching is likely to occur, and the shape of the protrusions can be easily controlled. The pore volume of the inert particles can be calculated by known nitrogen desorption such as BJH method. If the inert particles are present in the film, for example, dissolve them with a phenol / tetrachloroethane mixed solution, collect the inert particles that are the residue, dry well, and calculate by known nitrogen desorption such as the BJH method. Can do.
The

  As a method of blending the inert particles with polyester, a known method can be adopted. For example, it can be added at any stage for producing the polyester, but it is preferably added as a slurry dispersed in ethylene glycol or the like at the stage of esterification or after the end of the ester exchange reaction and before the start of the polycondensation reaction. The polycondensation reaction may proceed. Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester raw material, or a method of blending dried particles and a polyester raw material using a kneading extruder It can be carried out.

  Among them, in the present invention, after the aggregated inorganic particles are homogeneously dispersed in the monomer liquid that is part of the polyester raw material, the filtered material is the polyester raw material before the esterification reaction, during the esterification reaction, or after the esterification reaction. The method of adding to the remainder of is preferable. According to this method, since the monomer liquid has a low viscosity, homogeneous dispersion of particles and high-accuracy filtration of the slurry can be easily performed, and when added to the remainder of the raw material, the dispersibility of the particles is good and new aggregation is achieved. Aggregation is unlikely to occur.

  In particular, in the case of using the above-mentioned amorphous bulk silica, the particles may be aggregated and aggregated coarse particles may be generated by adding and mixing the slurry. Since silica agglomeration is likely to occur at high temperatures, an esterification reaction or a transesterification reaction is required when adding an ethylene glycol solution containing the above-mentioned irregularly-shaped bulk silica in order to reduce aggregated coarse particles that cause optical defects. In the step before the production of the oligomer, it is preferably blended with the polyester raw material while maintaining the temperature within the range of 10 to 50 ° C, more preferably 10 to 30 ° C. By adding the slurry at this timing, it becomes possible to add the slurry while keeping the slurry temperature at a low temperature, and generation of new aggregates can be suppressed.

  In general, the particle size of the inert particles shows a distribution having a certain width, but the inert particles used in the present invention preferably have 1% or less of the total number of inert particles having a particle size of 10 μm or more. Is preferred. When the number of inert particles having a particle diameter of 10 μm or more exceeds 1%, the number of coarse particles that cause optical defects may increase. As a method for bringing the distribution of the inert particles into the above range, (1) a method of microfiltration of ethylene glycol or polyester in which inert particles are dispersed, and (2) a batch of ethylene glycol or polyester in which inert particles are dispersed. For example, a method of processing with a centrifugal separator of a type or an intermittent type, (3) a method of selecting inert particles having a predetermined particle size distribution, and the like can be used.

  The ten-point average roughness (SRz) of the outermost layer surface of the film of the present invention is preferably 0.5 μm or more. Since the film of the present invention has such a specific protrusion shape, it is excellent in processability (slidability) in post-processing. Furthermore, the three-dimensional center plane average roughness (SRa) of the film of the present invention is preferably 0.008 to 0.015 μm. Further, the ten-point average roughness (SRz) is preferably 0.5 to 1.5 μm, and more preferably 0.6 to 1.0 μm. It is preferable that the three-dimensional center plane average roughness (SRa) or the ten-point average roughness (SRz) is within the above range because transparency can be maintained while effectively suppressing minute scratches.

(Coating layer)
It is important to provide a coating layer containing a polyester resin having a number average molecular weight of 15000 or more and substantially having no carboxylic acid group and a resin having an oxazoline group in the optically easy-adhesive film of the present invention. is there.

  Conventionally, it has been considered desirable to positively introduce a crosslinked structure from the viewpoint of improving the heat and moisture resistance of the coating layer. However, in the present invention, it has been found that the moisture and heat resistance is improved by making the coating layer as described above. Although the mechanism by which the adhesiveness under high temperature and high humidity is improved by such a configuration is not well understood, the present inventor thinks as follows. Since the coating layer of the present invention is substantially free of carboxylic acid groups that are functional groups that react with oxazoline groups, unreacted oxazoline groups remain in the coating layer when the coating layer is formed. On the other hand, under high temperature and high humidity, the polyester resin in the coating layer undergoes hydrolysis, the ester bond is broken, and carboxylic acid group terminals are generated. Here, the unreacted oxazoline group reacts with the generated carboxylic acid terminal to form a crosslink. In other words, it is considered that the deterioration of the coating film strength under high temperature and high humidity can be prevented by self-healing the deterioration of the coating film strength due to hydrolysis.

  According to the above aspect, the present invention can improve the adhesiveness (humidity heat resistance) with a lens layer and other optical functional layers under high temperature and high humidity. Further, the configuration of the present invention will be described in detail below.

  The coating layer of the present invention needs to contain a polyester resin. Adhesion can be improved by containing a polyester resin.

  The polyester resin preferably has fewer carboxylic acid groups which are reactive groups with oxazoline groups. More preferably, it has substantially no carboxylic acid group. Here, “having substantially no carboxylic acid group” means that no carboxylic acid group other than the terminal group is contained. As a method for defining a carboxylic acid group, an acid value can be measured. However, the polyester resin having substantially no carboxylic acid group has an acid value of 3 KOHmg / g or less, more preferably 2 KOHmg / g or less. More preferably, it is a polyester resin of 1 KOHmg / g or less.

  The number average molecular weight of the polyester resin needs to be 15000 or more. When the number average molecular weight is low, the terminal carboxylic acid group increases, which may cause a reaction with the oxazoline group. In addition, the hydrolysis is accelerated, the coating film is not sufficiently repaired, and not only the adhesiveness under high temperature and high humidity is not obtained, but also the adhesiveness with the substrate film is lowered. Further, the number average molecular weight is more preferably 20000 or more, and it is preferably higher as long as it can be produced. However, when the number average molecular weight is increased, the solubility in the coating solution may be lowered. Therefore, the lower limit of the number average molecular weight is preferably 30000 or less.

  The polyester resin has acid components such as terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, trimellitic acid, pyromellitic acid, Examples include dimer acid, 5-sodium sulfoisophthalic acid, 4-sodium sulfonaphthalene-2,7-dicarboxylic acid, and the like. Examples of the diol component include ethylene glycol, propane glycol, 1,4-butanediol, neopentyl glycol, diethylene glycol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, xylene glycol, ethylene oxide adduct of bisphenol A, etc. Is mentioned.

  The polyester resin is based on water or a water-soluble organic solvent (for example, an aqueous solution containing less than 50% by weight of alcohol, alkyl cellosolve, ketone, or ether) or an organic solvent (for example, toluene, ethyl acetate, etc.). Those dissolved or dispersed can be used.

  When the polyester resin is used as an aqueous coating liquid, a water-soluble or water-dispersible polyester resin is used. For such water-solubilization or water-dispersion, a compound containing a sulfonate group or a carboxyl group is used. It is preferable to copolymerize a compound containing an acid base. Therefore, in addition to the dicarboxylic acid component described above, in order to impart water dispersibility to the polyester, it is preferable to use 5-sulfoisophthalic acid or an alkali metal salt thereof in the range of 1 to 10 mol%. Mention may be made of acid, 5-sulfoisophthalic acid, 4-sulfonaphthaleneisophthalic acid-2,7-dicarboxylic acid and 5- (4-sulfophenoxy) isophthalic acid or alkali metal salts thereof.

  The polyester resin preferably has a low glass transition temperature from the viewpoint of adhesion. The glass transition temperature of the polyester resin is preferably 10 to 100 ° C, and more preferably 30 to 70 ° C. When the glass transition temperature is higher than 100 ° C., the melt viscosity becomes high, and it is difficult to obtain a product having a sufficient molecular weight, so that the adhesiveness is lowered. When the glass transition temperature is lower than 10 ° C., the blocking resistance of the film is lowered.

  In order to set the number average molecular weight of the polyester resin to 15000 or more and make the glass transition temperature in the above range, it is preferable to introduce a branched structure into the polyester resin. However, as the number of branched structures increases, the acid value tends to increase. Therefore, in the polyester resin of the present invention, the molar ratio of the third component having 3 or more carboxyl groups / one molecule or 3 or more hydroxyl groups / 1 molecule is 5.0 mol% or less in the total dicarboxylic acid component. Preferably, it is 1.0 mol% or less more preferably.

  The polyester resin is preferably contained in the coating layer in an amount of 10% by mass to 90% by mass. When high adhesiveness is required, it is more preferably 20% by mass or more and 80% by mass or less. When the content of the polyester resin is large, the adhesiveness under high temperature and high humidity decreases, and conversely, when the content is small, the adhesiveness with the base film decreases.

  In this invention, in order to improve adhesiveness, you may contain other than a polyester resin. Examples of such a resin include an acrylic resin and a urethane resin. Preferably, the carboxylic acid group content is low. More preferably, it does not contain a carboxylic acid group. When there are many carboxylic acid groups, it will react with an oxazoline group, and the oxazoline group which reacts with the carboxylic acid group generated from a polyester resin under high temperature and high humidity will decrease.

  In the present invention, it is necessary to contain a resin having an oxazoline group. Examples of the resin having an oxazoline group include water dispersibility and water solubility. The resin having an oxazoline group is preferably water-soluble because it has good compatibility with other water-soluble resins and improves the transparency of the coating layer and the crosslinking reaction efficiency. The above water-soluble means to dissolve in water or an aqueous solution containing less than 50% by mass of a water-soluble organic solvent.

  In order to make the resin having an oxazoline group water-soluble, it is preferable to contain a hydrophilic monomer. As the hydrophilic monomer, a monomer having a polyethylene glycol chain such as 2-hydroxyethyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, a monoester compound of (meth) acrylic acid and polyethylene glycol, (Meth) acrylic acid 2-aminoethyl and its salts, (meth) acrylamide, N-methylol (meth) acrylamide, N- (2-hydroxyethyl) (meth) acrylamide, (meth) acrylonitrile, sodium styrenesulfonate, etc. Can be mentioned. Especially, it is preferable to contain the monomer which has polyethyleneglycol chains, such as (meth) acrylic-acid methoxypolyethylene glycol with high solubility to water, and the monoester compound of (meth) acrylic acid and polyethyleneglycol.

  The resin having an oxazoline group is preferably contained in the coating layer in an amount of 5% by mass to 90% by mass. In particular, when high adhesion is required as in a lens layer, it is more preferably 10% by mass or more and 70% by mass or less. When the content of the resin having an oxazoline group is large, the adhesion with the optical functional layer is lowered, and conversely, when the content is small, the carboxylic acid group generated from the polyester resin under high temperature and high humidity Since the reacting oxazoline group is reduced, the restoration function of the coating film is lowered, and the adhesiveness is lowered.

  In the present invention, in order to improve the coating film strength, the coating layer may contain a crosslinking agent different from the resin having an oxazoline group or a resin having a crosslinking group. Examples of the crosslinking agent include urea, epoxy, melamine, isocyanate, and silanol. Moreover, in order to promote a crosslinking reaction, a catalyst etc. are used suitably as needed.

  In the present invention, particles may be contained in the coating layer. Particles are (1) silica, kaolinite, talc, light calcium carbonate, heavy calcium carbonate, zeolite, alumina, barium sulfate, carbon black, zinc oxide, zinc sulfate, zinc carbonate, titanium dioxide, satin white, aluminum silicate, diatomaceous earth Inorganic particles such as soil, calcium silicate, aluminum hydroxide, hydrous halloysite, magnesium carbonate, magnesium hydroxide, (2) acrylic or methacrylic, vinyl chloride, vinyl acetate, nylon, styrene / acrylic, styrene / Butadiene, polystyrene / acrylic, polystyrene / isoprene, polystyrene / isoprene, methyl methacrylate / butyl methacrylate, melamine, polycarbonate, urea, epoxy, urethane, phenol, di Rirufutareto systems include organic particles of polyester or the like.

  The average particle diameter of the particles is not particularly limited, but from the viewpoint of maintaining the transparency of the film, the average particle diameter of the particles is preferably 1 to 500 nm, and more preferably 1 to 100 nm. The average particle diameter is an average particle diameter measured by using a Coulter Counter (manufactured by Beckman Coulter, Multisizer II type) dispersed in a solvent that does not swell.

  Two or more kinds of particles having different average particle diameters may be used as the particles.

  As content of particle | grains, 0.5 mass% or more and 20 mass% or less are preferable. When the amount is small, sufficient blocking resistance cannot be obtained. Further, scratch resistance is deteriorated. When the amount is large, not only the transparency of the coating layer is deteriorated, but also the coating strength is lowered.

  The coating layer may contain a surfactant for the purpose of improving leveling properties during coating and defoaming the coating solution. The surfactant may be any of cationic, anionic and nonionic surfactants, but is preferably a silicon-based, acetylene glycol-based or fluorine-based surfactant. These surfactants are preferably contained in the coating layer within a range that does not impair the adhesion to the optical functional layer.

  The optically easy-adhesive polyester film of the present invention preferably has a haze value of 3.5% or less, more preferably 3.0% or less, and even more preferably 2.5% or less. In order to obtain high transparency, the thickness of the inert particles and the outermost layer of the base film is set to a specific range, and the resin having an oxazoline group contained in the coating layer is made water-soluble. Thus, compatibility with other resins is improved, and high transparency is obtained.

  In order to impart other functionality to the coating layer, various additives may be contained within a range that does not impair the adhesion to the optical functional layer. Examples of the additive include fluorescent dyes, fluorescent brighteners, plasticizers, ultraviolet absorbers, pigment dispersants, foam suppressors, antifoaming agents, preservatives, and antistatic agents.

  In the present invention, examples of the method for providing the coating layer on the polyester film include a method in which a coating solution containing a solvent, particles and a resin is applied to the polyester film and dried. Examples of the solvent include organic solvents such as toluene, water, and a mixed system of water and a water-soluble organic solvent. Preferably, water alone or a mixture of a water-soluble organic solvent and water is used from the viewpoint of environmental problems. preferable.

  The optically laminated polyester film of the present invention is selected from a hard coat layer, a light diffusing layer, a prismatic lens layer, an electromagnetic wave absorbing layer, a near-infrared blocking layer, and a transparent conductive layer on at least one side of the polyester film coating layer. It is obtained by at least one optical functional layer.

  The material used for the optical function layer is not particularly limited.

(Manufacture of easily adhesive polyester film for optics)
The method for producing an optically easy-adhesive polyester film of the present invention will be described using a polyethylene terephthalate (hereinafter abbreviated as PET) film as an example, but is not limited to this.

  After sufficiently drying the PET resin in a vacuum, it is supplied to an extruder, melted and extruded at about 280 ° C. from a T-die into a rotating cooling roll into a sheet, cooled and solidified by an electrostatic application method, and unstretched PET. Get a sheet. The unstretched PET sheet is preferably formed into a multilayer structure by a co-extrusion method, and a lubricant for the purpose of imparting slipperiness is preferably added to the outermost layer.

  The obtained unstretched PET sheet is stretched 2.5 to 5.0 times in the longitudinal direction with a roll heated to 80 to 120 ° C. to obtain a uniaxially stretched PET film. Furthermore, the edge part of a film is hold | gripped with a clip, it guide | induces to the hot air zone heated at 70-140 degreeC, and is extended | stretched 2.5 to 5.0 times in the width direction. Then, it guide | induces to the heat processing zone of 160-240 degreeC, and heat-processes for 1 to 60 seconds, and completes crystal orientation.

  In an arbitrary stage of the film manufacturing process, a coating solution is applied to at least one surface of the PET film to form the coating layer. There is no particular problem even if the coating layer is formed on both sides of the PET film. The solid content concentration of the resin composition in the coating solution is preferably 2 to 35% by weight, particularly preferably 4 to 15% by weight.

  Any known method can be used as a method for applying the coating solution to the PET film. For example, reverse roll coating method, gravure coating method, kiss coating method, die coater method, roll brush method, spray coating method, air knife coating method, wire bar coating method, pipe doctor method, impregnation coating method, curtain coating method, etc. It is done. These methods are applied alone or in combination.

  In the present invention, the coating layer is formed by coating the coating solution on an unstretched or uniaxially stretched PET film, drying it, stretching in at least a uniaxial direction, and then performing a heat treatment.

In the present invention, the finally obtained coating layer preferably has a thickness of 20 to 350 nm, and the coating amount after drying is preferably 0.02 to 0.5 g / m ² . When the coating amount of the coating layer is less than 0.02 g / m ² , the effect on adhesiveness is almost lost. On the other hand, when the coating amount exceeds 0.5 g / m ² , haze increases.

  The coating layer of the optically easy-adhesive polyester film obtained in the present invention has good adhesion to a hard coat layer, a light diffusion layer, a prismatic lens layer, an electromagnetic wave absorption layer, a near-infrared shielding layer, and a transparent conductive layer. Have By laminating these optical functional layers, it is possible to provide an optical laminated polyester film that can maintain an initial function for a long time even under high temperature and high humidity. Also, good adhesive strength can be obtained even for applications other than optical applications. Specifically, adhesion such as photographic photosensitive layer, diazo photosensitive layer, matte layer, magnetic layer, inkjet ink receiving layer, hard coat layer, UV curable resin, thermosetting resin, printing ink and UV ink, dry laminate, extrusion laminate, etc. Examples thereof include vacuum deposition, electron beam deposition, sputtering, ion plating, CVD, plasma polymerization and the like of an agent, a metal or an inorganic substance, or an oxide thereof, and an organic barrier layer.

  EXAMPLES Next, although this invention is demonstrated in detail using an Example and a comparative example, naturally this invention is not limited to a following example. The evaluation method used in the present invention is as follows.

(1) Intrinsic viscosity Based on JIS K7367-5, it measured at 30 degreeC, using the mixed solvent of phenol (60 mass%) and 1,1,2,2-tetrachloroethane (40 mass%) as a solvent.

(2) Reduced viscosity It measured at 30 degreeC using 25 mL of mixed solvents of phenol (60 mass%) and 1,1,2,2-tetrachloroethane (40 mass%) as a solvent with respect to 0.1 g of resin.

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

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

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

(6) Acid value 1 g (solid content) of a sample was dissolved in 30 ml of chloroform or dimethylformamide, and titrated with 0.1 N potassium hydroxide ethanol solution using phenolphthalein as an indicator to determine the carboxyl groups per gram of the sample. The amount (mg) of KOH required for neutralization was determined.

(7) Haze, total light transmittance A base film prepared without providing a coating layer in each example and comparative example, and an easily adhesive polyester film for optics were prepared, and a turbidimeter (according to JIS-K7105) NHD2000, manufactured by Nippon Denshoku Industries Co., Ltd.) was used to measure the haze and total light transmittance of the substrate film.

(8) Thickness of outermost layer (inert particle-containing layer) The obtained optically easy-adhesive polyester film for optical use was cut out perpendicular to the flow direction of the film and embedded with a photocurable resin. The embedded sample was made into an ultrathin section having a thickness of about 70 to 100 nm with a microtome and stained in ruthenium tetroxide vapor for 30 minutes. This dyed ultrathin section was cross-sectionally observed using a transmission electron microscope (TEM 2010, manufactured by JEOL Ltd.), and the thickness of the outermost layer (inactive particle-containing layer) was determined from the position of the inert particles. The observation magnification was appropriately set in the range of 1500 to 10,000 times.

(9) Average particle diameter of inert particles, number of particles of 10 μm or more Inactive particles are observed with a scanning electron microscope (manufactured by Hitachi, Ltd., S-51O type), and the magnification is appropriately changed according to the size of the particles. An enlarged copy of the photo was taken. Next, the outer circumference of each particle was traced for at least 200 particles selected at random, the equivalent circle diameter of the particles was measured from these trace images with an image analyzer, and the average of these was taken as the average particle diameter. Further, the ratio of particles of 10 μm or more was calculated from the particle diameter of 200 or more particles thus obtained.

(10) Adhesiveness 100 squares reaching the base film through the photocurable acrylic layer using a cutter guide with a gap distance of 2 mm on the photocurable acrylic layer surface of the obtained optical laminated polyester film Make a cut. Next, a cellophane adhesive tape (manufactured by Nichiban Co., Ltd., No. 405; 24 mm width) was attached to the cut surface of the grid and rubbed with an eraser for complete adhesion. Then, after the work of peeling the cellophane adhesive tape vertically from the photocurable acrylic layer surface of the optical laminated polyester film was performed once, the number of grids peeled off from the photocurable acrylic layer surface of the optical laminated polyester film was visually observed. The adhesion between the photocurable acrylic layer and the substrate film was determined from the following formula. In addition, what peeled partially among squares was also counted as the square which peeled, and was ranked according to the following references | standards.
Adhesiveness (%) = (1−number of peeled squares / 100) × 100
A: 100%, or material breakage of photocurable acrylic layer B: 99-90%
Δ: 89-70%
X: 69 to 0%

(11) Heat-and-moisture resistance The obtained laminated polyester film for optics was left in an environment of 80 ° C. and 95% RH for 48 hours in a high-temperature and high-humidity tank. Next, the laminated polyester film for optics was taken out and allowed to stand at room temperature and humidity for 12 hours. Thereafter, the contact between the photocurable acrylic layer and the substrate film was carried out in the same manner as in (10) except that the cellophane adhesive tape was peeled off from the photocurable acrylic layer surface of the laminated polyester film for optics five times. The adhesion was determined and ranked according to the following criteria.
A: 100%, or material breakage of photocurable acrylic layer B: 99-90%
Δ: 89-70%
X: 69 to 0%

(12) Three-dimensional surface roughness (SRa, SRz) of the outermost layer surface
A base film prepared without providing a coating layer in each example and comparative example was prepared, and the outermost surface of the film was measured with a stylus type three-dimensional roughness meter (SE-3AK, manufactured by Kosaka Laboratory Co., Ltd.). , Measured at a needle feed rate of 0.1 mm / sec over a measurement length of 1 mm with a cut-off value of 0.25 mm in the longitudinal direction of the film under the conditions of a needle radius of 2 μm and a load of 30 mg, at a pitch of 2 μm Dividing into 500 points, the height of each point was taken into a three-dimensional roughness analyzer (SPA-11). The same operation was performed 150 times continuously at intervals of 2 μm in the width direction of the film, that is, over 0.3 mm in the width direction of the film, and the data was taken into the analyzer. Next, the center plane average roughness (SRa) and the ten-point average roughness (SRz) were determined using an analyzer.

(13) Evaluation of protrusion shape on outermost layer surface After cutting out the film at an arbitrary place, using an atomic force microscope (SII, SPI3800), observation mode = DFM mode, scanner = FS-20A, cantilever = Surface morphology was observed at DF-3, observation field of view = 5 × 5 μm ² , resolution of 1024 × 512 pixels to obtain an observation image. Subsequently, the cross-sectional profile display mode of the same measurement visual field was displayed. On the cross-sectional movement screen, the cursor was moved at both ends so as to be along the longitudinal direction of the surface protrusion having a height of 2 nm or more and so as to pass through the maximum height position of the surface protrusion. The distance between two intersections where the cross-sectional profile curve and the 0 nm-high line that is the average height line within the measurement range intersect was read, and the diameter of the surface protrusion was measured. Furthermore, the height of the surface protrusion is measured with a height of 0 nm which is an average height line within the measurement range. From the observation image thus obtained, for at least 100 protrusions having a height of 2 nm or more, the diameter L of the protrusions and the height h of the protrusions are measured to calculate the ratio L / h of the diameter and the height. The ratio of protrusions where h is 50 or less was calculated.

(14) Optical defect detection method (evaluation of foreign matters having a major axis of 20 μm or more)
The produced film piece is sandwiched between two polarizing plates to form a crossed Nicol state and set to a state where the vanishing position is maintained. In this state, the Nikon universal projector V-12 (projection lens 50x, transmitted illumination light beam switching knob 50x, transmitted light inspection) is used for inspection. When there were scratches and foreign matter on the film piece, light having passed through the part and having a major axis of 20 μm or more that appeared to shine was detected.
A: No defects of 20 μm or more are observed at all.
○: Defects of 20 μm or more are hardly observed, and there is no practical problem at all.
X: A defect of 20 μm or more is slightly observed, which may cause a practical problem.

(Production Example 1-Polyester A)
When the temperature of the esterification reactor was raised to 200 ° C., 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were charged and 0.017 parts by mass of antimony trioxide as a catalyst while stirring. 0.064 parts by mass of magnesium acetate tetrahydrate and 0.16 parts by mass of triethylamine were charged. Subsequently, the pressure was raised and the esterification reaction was performed under the conditions of a gauge pressure of 0.34 MPa and 240 ° C., and then the esterification reaction vessel was returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. Furthermore, it heated up to 260 degreeC over 15 minutes, and 0.012 mass part of trimethyl phosphate was added. Next, after 15 minutes, dispersion treatment was performed with a high-pressure disperser, and 0.1 mass% of sodium tripolyphosphate aqueous solution was contained as sodium atoms with respect to the silica particles. 0.2 parts by mass of an ethylene glycol slurry of silica particles having an average particle diameter of 2.3 μm and a pore volume of 1.6 ml / g, filtered through a metal filter having an opening of 5 μm, was added. After 15 minutes, the obtained esterification reaction product was transferred to a polycondensation reaction can and subjected to a polycondensation reaction at 280 ° C. under reduced pressure.
After completion of the polycondensation reaction, it is filtered through a NASRON filter with a 95% cut diameter of 5 μm, extruded into a strand from a nozzle, and cooled and solidified using cooling water that has been filtered (pore diameter: 1 μm or less) in advance. And cut into pellets. The obtained polyethylene terephthalate resin (A) had an intrinsic viscosity of 0.62 dl / g and contained substantially no inert particles and internally precipitated particles. (Hereafter, abbreviated as PET (A).)

(Production Example 2-Polyester B)
On the other hand, in the production of PET (A), a polyethylene terephthalate resin (B) having an intrinsic viscosity of 0.62 dl / g and containing no silica particles was obtained. (Hereafter, abbreviated as PET (B).)

(Production Example 3-Polyester C)
In the production of PET (A), a polyethylene terephthalate resin (C) having an intrinsic viscosity of 0.62 dl / g was used in the same manner except that silica particles having an average particle size of 2.4 μm and a pore volume of 2.0 ml / g were used. ) (Hereafter, abbreviated as PET (C).)

(Production Example 4-Polyester D)
In the production of PET (A), a polyethylene terephthalate resin (D) having an intrinsic viscosity of 0.62 dl / g was used in the same manner except that silica particles having an average particle size of 3.5 μm and a pore volume of 1.6 ml / g were used. ) (Hereafter, abbreviated as PET (D).)

(Production Example 5-Polyester E)
A polyethylene terephthalate resin (E) having an intrinsic viscosity of 0.62 dl / g was produced by the same method except that silica particles having an average particle size of 2.0 μm and a pore volume of 1.2 ml / g were used in the production of PET (A). ) (Hereafter, abbreviated as PET (E).)

(Polymerization of polyester resin for coating layer)
In a stainless steel autoclave equipped with a stirrer, a thermometer, and a partial reflux condenser, 194.2 parts by weight of dimethyl terephthalate, 184.5 parts by weight of dimethyl isophthalate, 14.8 parts by weight of dimethyl-5-sodium sulfoisophthalate, 233.5 parts by mass of diethylene glycol, 136.6 parts by mass of ethylene glycol, and 0.2 parts by mass of tetra-n-butyl titanate were charged, and a transesterification reaction was performed from 160 ° C. to 220 ° C. over 4 hours. Next, the temperature was raised to 255 ° C., and the pressure of the reaction system was gradually reduced, followed by reaction for 1 hour 30 minutes under a reduced pressure of 30 Pa to obtain a copolymerized polyester resin (A-1). The obtained copolyester resin (A-1) was light yellow and transparent. It was 0.70 dl / g when the reduced viscosity of the obtained copolyester resin (A-1) was measured. The glass transition temperature by DSC was 40 ° C.

In the same manner, copolymer polyester resins (A-2) to (A-5) having different compositions were obtained. Table 1 shows the composition (mole% ratio) and other characteristics measured by ¹ H-NMR for these copolymer polyester resins.

(Adjustment of polyester aqueous dispersion)
30 parts by mass of polyester resin (A-1) and 15 parts by mass of ethylene glycol n-butyl ether were placed in a reactor equipped with a stirrer, a thermometer and a reflux device, and heated and stirred at 110 ° C. to dissolve the resin. After the resin was completely dissolved, 55 parts by mass of water was gradually added to the polyester solution while stirring. After the addition, the solution was cooled to room temperature while stirring to prepare a milky white polyester aqueous dispersion (B-1) having a solid content of 30% by mass. Similarly, using the polyester resins (A-2) to (A-5) instead of the polyester resin (A-1), water dispersions were prepared, and the water dispersions (B-2) to (B- 5).

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

Example 1
(1) Adjustment of coating liquid The following coating agent was mixed and the coating liquid was created. The polyester resin has a number average molecular weight of 20000.
49.41% by mass of water
Isopropanol 30.00% by mass
Polyester aqueous dispersion (B-1) 12.64% by mass
Water-soluble resin (C) having an oxazoline group 6.32% by mass
Particles 1.58% by mass
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Surfactant 0.05% by mass
(Silicon, solid content concentration of 100% by mass)

(2) Production of optically easy-adhesive polyester film PET (B) resin pellets containing no particles as a base film intermediate layer raw material were dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours, and then an extruder 2 (intermediate layer) II layer), PET (A) and PET (B) are mixed and adjusted so that the content of silica particles is 0.020% by mass, dried by a conventional method, and then the extruder 1 (outer layer I layer and For outer layer III) and dissolved at 285 ° C. After filtering these two kinds of polymers with a filter medium made of a sintered stainless steel (nominal filtration accuracy of 10 μm particles 95% cut), laminating them in a two-kind / three-layer confluence block, and extruding them into a sheet form from a die, The film was wound around a casting drum having a surface temperature of 30 ° C. using an electrostatic application casting method, and then cooled and solidified to produce an unstretched film. At this time, the discharge amount of each extruder was adjusted so that the ratio of the thickness of the I layer, the II layer, and the III layer was 8: 82: 8.

  This unstretched film was heated to 100 ° C. with a heated roll group and an infrared heater, and then stretched 3.4 times in the longitudinal direction with a roll group having a peripheral speed difference to obtain a uniaxially oriented PET film.

Next, the coating solution is microfiltered with a felt type polypropylene filter medium having a filtration particle size (initial filtration efficiency 95%) of 25 μm, and the coating amount after drying on one side of a uniaxially oriented PET film is 0.2 g / m by the reverse roll method. After coating so as to be ² , it was dried at 80 ° C. for 20 seconds.

  The uniaxially stretched film on which the coating layer was formed was guided to a tenter stretching machine, guided to a hot air zone at a temperature of 125 ° C. while being gripped by a clip, and stretched 4.2 times in the width direction. Next, while maintaining the width stretched in the width direction, it was treated at a temperature of 245 ° C. for 30 seconds, and further 3% relaxation treatment was performed in the width direction to obtain a polyester film having a thickness of 188 μm. The evaluation results are shown in Table 2.

(3) Manufacture of optical laminated polyester film About 5 g of the following photocurable acrylic coating solution is placed on a 1 mm thick SUS plate (SUS304) kept clean, and the coating layer surface of the film sample and the photocurable acrylic system The coating solutions were overlapped so that they were in contact with each other, and pressure-bonded so that the photocurable acrylic coating solution was stretched by a manually loaded rubber roller having a width of 10 cm and a diameter of 4 cm from above the film sample. Subsequently, 800 mJ / cm < ² > of ultraviolet rays were irradiated from the film surface side using the high pressure mercury lamp, and the photocurable acrylic resin was hardened. A film sample having a photocurable acrylic layer having a thickness of 20 μm was peeled from the SUS plate to obtain an optical laminated polyester film.
Photo-curing acrylic coating solution Photo-curing acrylic resin 81.00% by mass
(Arakawa Chemical Industries Beam Set 505A-6)
Light-curing acrylic resin 9.00% by mass
(Arakawa Chemical Beam Set 550)
Photopolymerization initiator 10.00% by mass
(Irgacure 184 manufactured by Ciba Specialty Chemicals)

Comparative Example 1
An optically easily adhesive polyester film and an optically laminated polyester film were obtained in the same manner as in Example 1 except that the polyester aqueous dispersion was changed to a polyester aqueous dispersion (B-4) having a molecular weight of 8000.

Comparative Example 2
An optically easy-adhesive polyester film and an optically laminated polyester film were obtained in the same manner as in Example 1 except that the polyester aqueous dispersion was changed to a polyester aqueous dispersion (B-5) having an acid value of 50 KOHmg / g.

Example 2
A school-adhesive polyester film and an optically laminated polyester film were obtained in the same manner as in Example 1 except that the polyester water dispersion was changed to a polyester water dispersion (B-2) having a molecular weight of 15000.

Example 3
An optically easily adhesive polyester film and an optically laminated polyester film were obtained in the same manner as in Example 1 except that the polyester aqueous dispersion was changed to a polyester aqueous dispersion (B-3) having a molecular weight of 23000.

Example 4
Except having changed the coating liquid into the following, it carried out similarly to Example 1, and obtained the easily adhesive polyester film for optics, and the laminated polyester film for optics.
Water 51.92 mass%
Isopropanol 30.00% by mass
Polyester aqueous dispersion (B-1) 2.63% by mass
Water-soluble resin (C) having an oxazoline group 13.82% by mass
Particles 1.58% by mass
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Surfactant 0.05% by mass
(Silicon, solid content concentration of 100% by mass)

Example 5
Except having changed the coating liquid into the following, it carried out similarly to Example 1, and obtained the easily adhesive polyester film for optics, and the laminated polyester film for optics.
Water 51.26% by mass
Isopropanol 30.00% by mass
Polyester water dispersion (B-1) 5.26 mass%
Water-soluble resin (C) having an oxazoline group 11.85% by mass
Particles 1.58% by mass
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Surfactant 0.05% by mass
(Silicon, solid content concentration of 100% by mass)

Example 6
Except having changed the coating liquid into the following, it carried out similarly to Example 1, and obtained the easily adhesive polyester film for optics, and the laminated polyester film for optics.
Water 48.10% by mass
Isopropanol 30.00% by mass
Polyester water dispersion (B-1) 17.90 mass%
Water-soluble resin (C) having an oxazoline group 2.37% by mass
Particles 1.58% by mass
(Silica sol with an average particle size of 100 nm, solid content concentration of 40% by mass)
Surfactant 0.05% by mass
(Silicon, solid content concentration of 100% by mass)

Example 7
Except having changed the coating liquid into the following, it carried out similarly to Example 1, and obtained the easily adhesive polyester film for optics, and the laminated polyester film for optics.
Water 46.89 mass%
Isopropanol 30.00% by mass
Polyester water dispersion (B-1) 20.76 mass%
Water-soluble resin (C) having an oxazoline group 0.82% by mass
0.82% by mass of particles
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
Particle 0.66% by mass
(Silica sol with an average particle size of 450 nm, solid content concentration of 40% by mass)
Surfactant 0.05% by mass
(Silicon, solid content concentration of 100% by mass)

Example 8
Except having changed the coating liquid into the following, it carried out similarly to Example 1, and obtained the easily adhesive polyester film for optics, and the laminated polyester film for optics.
51.81% by mass of water
Isopropanol 30.00% by mass
Polyester water dispersion (B-1) 1.09 mass%
Water-soluble resin having oxazoline group (C) 15.57% by mass
0.82% by mass of particles
(Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass)
Particle 0.66% by mass
(Silica sol with an average particle size of 450 nm, solid content concentration of 40% by mass)
Surfactant 0.05% by mass
(Silicon, solid content concentration of 100% by mass)

Example 9
Optically easy-adhesive polyester film and optical material in the same manner as in Example 1 except that the water-soluble resin (C) having an oxazoline group was changed to Nippon Shokubai Epocross K-2010E (emulsion, solid content concentration 40% by mass). A laminated polyester film was obtained.

Example 10
An easily adhesive polyester film for optics and a laminated polyester film for optics were obtained in the same manner as in Example 1 except that the ratio of the intermediate layer to the outer layer of the base film was 3: 94: 3.

Comparative Example 3
An optically easy-adhesive polyester film and an optically laminated polyester film were prepared in the same manner as in Example 1 except that PET (D) resin pellets were used instead of the PET (A) resin pellets used for the outer layer of the base film. Obtained.

Comparative Example 4
An optically easy-adhesive polyester film and an optically laminated polyester film were prepared in the same manner as in Example 1 except that PET (E) resin pellets were used instead of the PET (A) resin pellets used for the outer layer of the base film. Obtained.

Comparative Example 5
Optically easily adhesive polyester film and optical material in the same manner as in Example 1 except that PET (A) and PET (B) used for the outer layers I and III were mixed so that the silica concentration was 0.050% by mass. A laminated polyester film was obtained.

Comparative Example 6
An optically easily adhesive polyester film and an optically laminated polyester film were obtained in the same manner as in Example 1 except that only PET (B) containing no particles was used as the raw material for the outer layer of the base film.

Example 11
An optically easy-adhesive polyester film and an optically laminated polyester film are obtained in the same manner as in Example 1 except that PET (C) resin pellets are used instead of the PET (A) resin pellets used for the outer layer of the base film. It was.

Example 12
An optically easy-adhesive polyester film and an optically laminated polyester film are obtained in the same manner as in Example 1 except that PET (C) resin pellets are used instead of the PET (A) resin pellets used for the outer layer of the base film. It was.

Example 13
Instead of PET (A) resin pellets used for the outer layer of the base film in which PET (A) and PET (B) used for the outer layers I and III are mixed so that the silica concentration is 0.030% by mass, PET ( C) An easily adhesive polyester film for optics and a laminated polyester film for optics were obtained in the same manner as in Example 1 except that resin pellets were used.

Example 14
An optically easy-adhesive polyester film and an optical laminated polyester film were obtained in the same manner as in Example 1 except that the ratio between the intermediate layer and the outer layer of the base film was 12:76:12.

  The optically easy-adhesive polyester film of the present invention has transparency with few optical defects, and is excellent in adhesion with an optical functional layer and adhesion under high temperature and high humidity (moisture and heat resistance). Suitable as a base film for an optical functional film such as a hard coat film and an antireflection film, a light diffusion sheet, a prismatic lens sheet, a near-infrared shielding film, a transparent conductive film, an antiglare film, etc. It is.

Claims (5)

An easy-adhesive polyester film having a coating layer on at least one side of the base film,
The base film is a polyester film having a laminated structure of three or more layers by a coextrusion method, containing inert particles in both outermost layers, and having a haze of 2.5% or less,
An easily adhesive polyester film for optical use, wherein the coating layer has as a main component a polyester resin having a number average molecular weight of 15000 or more and having substantially no carboxylic acid group and a resin having an oxazoline group. The average particle diameter of the inert particles contained in the outermost layer is 2.1 to 2.5 μm,
The thickness of the outermost layer is equal to or greater than the average particle diameter of the inert particles,
The center surface average roughness (SRa) of the outermost layer surface is 0.008 to 0.015 μm,
The easily adhesive polyester film for optics according to claim 1, wherein the ten-point average roughness (SRz) is 0.5 to 1.5 µm.   The easily adhesive polyester film for optical use according to claim 1 or 2, wherein the resin having an oxazoline group is water-soluble. The inert particles in the outermost layer are amorphous bulk silica having a pore volume of 1.5 to 2.0 ml / g,
The easily adhesive polyester film for optics according to any one of claims 1 to 3, wherein the content of inert particles in the outermost layer is 0.015 to 0.030 mass%.   From the hard coat layer, the light diffusing layer, the prismatic lens layer, the electromagnetic wave absorbing layer, the near infrared ray blocking layer, and the transparent conductive layer to the coating layer of the optically easy-adhesive polyester film according to any one of claims 1 to 4. An optically laminated polyester film obtained by laminating at least one selected optical functional layer.