JP2012162075A - Laminated polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated polyester film that is suitably used as a member for a microlens or a prism sheet used in a backlight unit of a liquid crystal display and has good adhesion to various functional layers.
SOLUTION: A laminated polyester film having a coating layer, wherein the coating layer is formed of a coating solution containing an acrylic resin, a carbodiimide compound, and an oxazoline compound. the film.
[Selection figure] None

Description

  The present invention relates to a laminated polyester film. Specifically, the laminated polyester film is suitably used as a member for a microlens or a prism sheet used in a backlight unit of a liquid crystal display, etc., and has good adhesion to various functional layers. It relates to a polyester film. Note that an optical functional layer that scatters or collects transmitted light on a transparent film, for example, a microlens sheet or a prism sheet in which a microlens layer or a prism layer is formed, is collectively referred to as an optical functional film. A typical example of “layer” is an optical functional layer in an optical functional film.

  In recent years, liquid crystal displays have been widely used as display devices for televisions, personal computers, digital cameras, mobile phones and the like. Since these liquid crystal displays do not have a light emitting function by a liquid crystal display unit alone, a method of displaying by irradiating light using a backlight from the back side is widespread.

  The backlight system has a structure called an edge light type or a direct type. Recently, there is a tendency to reduce the thickness of liquid crystal displays, and an edge light type is increasingly used. The edge light type is generally configured in the order of a reflection sheet, a light guide plate, a light diffusion sheet, and a prism sheet. As the flow of light, the light incident on the light guide plate from the backlight is reflected by the reflection sheet and emitted from the surface of the light guide plate. The light beam emitted from the light guide plate enters the light diffusion sheet, is diffused and emitted by the light diffusion sheet, and then enters the next existing prism sheet. The light beam is condensed in the normal direction by the prism sheet and emitted toward the liquid crystal layer.

  The prism sheet used in this configuration is for improving luminance by improving the optical efficiency of the backlight. As the transparent base film, a polyester film is generally used in consideration of transparency and mechanical properties. In order to improve the adhesion between the base polyester film and the prism layer, these intermediate layers are easily bonded. In general, a conductive coating layer is provided. As an easily adhesive coating layer, for example, polyester resin, acrylic resin, and urethane resin are known (Patent Documents 1 to 3).

  As a method for forming the prism layer, for example, an active energy ray-curable coating material is introduced into a prism type, irradiated with active energy rays while being sandwiched between polyester films, the resin is cured, and the prism type is removed to remove polyester. The method of forming on a film is mentioned. In the case of such a method, it is necessary to use a solventless active energy ray-curable coating material in order to form the prism type with precision. However, solventless paints are less permeable and swellable to the easy-adhesion layer laminated on the polyester film than solvent-based paints, and tend to have insufficient adhesion. A coating layer made of a specific urethane resin has been proposed to improve the adhesion, but even with such a coating layer, the adhesion is not necessarily sufficient for solventless paints. (Patent Document 4).

JP-A-8-281890 Japanese Patent Laid-Open No. 11-286092 JP 2000-229395 A JP-A-2-158633

  The present invention has been made in view of the above circumstances, and the problem to be solved is that it is suitably used as a member for a microlens or a prism sheet used in a backlight unit of a liquid crystal display and the like, and is in close contact with various functional layers. It is in providing the laminated polyester film with favorable property.

  As a result of intensive studies in view of the above circumstances, the present inventors have found that the use of a laminated polyester film having a specific configuration can easily solve the above-described problems, and have completed the present invention.

  That is, the first gist of the present invention is a laminated polyester film having a coating layer, wherein the coating layer is formed of a coating solution containing an acrylic resin, a carbodiimide compound, and an oxazoline compound. It exists in the laminated polyester film characterized by this.

  And the second gist of the present invention is a laminated polyester film in which a functional layer is formed using a solventless active energy ray-curable coating on the surface of the coated layer of the laminated polyester film having the coated layer, The coating layer is formed of a coating solution containing an acrylic resin, a carbodiimide compound, and an oxazoline compound.

  According to the laminated polyester film of the present invention, when a microlens, a prism layer or the like is formed, a laminated polyester film having excellent adhesion can be provided, and its industrial value is high.

  The polyester film constituting the laminated polyester film in the present invention may have a single layer structure or a multilayer structure, and may have four or more layers as long as it does not exceed the gist of the present invention other than a two-layer or three-layer structure. It may be a multilayer, and is not particularly limited.

  The polyester used in the present invention may be a homopolyester or a copolyester. In the case of a homopolyester, those obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol are preferred. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Typical polyester includes polyethylene terephthalate and the like. On the other hand, the dicarboxylic acid component of the copolyester includes isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxybenzoic acid, etc.), etc. 1 type or 2 types or more are mentioned, As a glycol component, 1 type or 2 types or more, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexane dimethanol, neopentyl glycol, is mentioned.

  In the polyester layer of the film of the present invention, it is preferable to blend particles mainly for the purpose of imparting slipperiness and preventing scratches in each step. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Examples of the particles include magnesium, kaolin, aluminum oxide, and titanium oxide. Further, the heat-resistant organic particles described in JP-B-59-5216, JP-A-59-217755 and the like may be used. Examples of other heat-resistant organic particles include thermosetting urea resins, thermosetting phenol resins, thermosetting epoxy resins, benzoguanamine resins, and the like. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

  On the other hand, the shape of the particles to be used is not particularly limited, and any of a spherical shape, a block shape, a rod shape, a flat shape, and the like may be used. Moreover, there is no restriction | limiting in particular also about the hardness, specific gravity, a color. These series of particles may be used in combination of two or more as required.

  Moreover, the average particle diameter of the particle | grains to be used is 0.01-5 micrometers normally, Preferably it is the range of 0.1-3 micrometers. If the average particle size is less than 0.01 μm, the slipperiness may not be sufficiently imparted, or the particles may be aggregated to make the dispersibility insufficient, thereby reducing the transparency of the film. On the other hand, if it exceeds 5 μm, the surface roughness of the film becomes too rough, and a problem may occur when a functional layer such as a microlens layer or a prism layer is formed in a later step.

  Further, the content of particles in the polyester layer is usually in the range of 0.001 to 5% by weight, preferably 0.005 to 3% by weight. When the particle content is less than 0.001% by weight, the slipperiness of the film may be insufficient. On the other hand, when the content exceeds 5% by weight, the transparency of the film is insufficient. There is a case.

  The method for adding particles to the polyester layer is not particularly limited, and a conventionally known method can be adopted. For example, it can be added at any stage for producing the polyester constituting each layer, but it is preferably added after completion of esterification or transesterification.

  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 blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  In addition to the above-mentioned particles, conventionally known antioxidants, antistatic agents, ultraviolet absorbers, heat stabilizers, lubricants, dyes, pigments, etc. may be added to the polyester film in the present invention as necessary. Can do.

  Although the thickness of the polyester film in this invention will not be specifically limited if it can be formed into a film as a film, Usually, 10-350 micrometers, Preferably it is the range of 50-250 micrometers.

  Next, although the manufacture example of the polyester film in this invention is demonstrated concretely, it is not limited to the following manufacture examples at all. That is, a method of using the polyester raw material described above and cooling and solidifying a molten sheet extruded from a die with a cooling roll to obtain an unstretched sheet is preferable. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction. In that case, first, the unstretched sheet is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3 to 6 times. Next, the film is stretched in a direction perpendicular to the first-stage stretching direction. In that case, the stretching temperature is usually 70 to 170 ° C., and the stretching ratio is usually 3 to 7 times, preferably 3.5 to 6 times. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or under relaxation within 30% to obtain a biaxially oriented film. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges.

  In the present invention, the simultaneous biaxial stretching method can be adopted for the production of the polyester film constituting the laminated polyester film. The simultaneous biaxial stretching method is a method in which the above-mentioned unstretched sheet is usually stretched and oriented in the machine direction and the width direction at a temperature controlled normally at 70 to 120 ° C., preferably 80 to 110 ° C. Is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in terms of area magnification. Subsequently, heat treatment is performed at a temperature of 170 to 250 ° C. under tension or under relaxation within 30% to obtain a stretched oriented film. With respect to the simultaneous biaxial stretching apparatus that employs the above-described stretching method, a conventionally known stretching method such as a screw method, a pantograph method, or a linear driving method can be employed.

  Next, formation of the coating layer which comprises the laminated polyester film in this invention is demonstrated. Regarding the coating layer, it may be provided by in-line coating which treats the film surface during the process of forming a polyester film, or offline coating which is applied outside the system on a once produced film may be adopted. Since the coating can be performed simultaneously with the film formation, the production can be handled at a low cost, and therefore in-line coating is preferably used.

  The in-line coating is not limited to the following, but for example, in the sequential biaxial stretching, the coating treatment can be performed particularly before the lateral stretching after the longitudinal stretching is finished. When the coating layer is provided on the polyester film by in-line coating, it is possible to apply at the same time as the film formation, and the coating layer can be processed at a high temperature in the heat treatment process of the polyester film after stretching. Performances such as adhesion to various surface functional layers that can be formed on the layer and heat-and-moisture resistance can be improved. Moreover, when coating before extending | stretching, the thickness of an application layer can also be changed with a draw ratio, and compared with off-line coating, uniform coating can be performed with a thin film. That is, a film suitable as a polyester film can be produced by in-line coating, particularly coating before stretching.

  In the present invention, it is an essential requirement to have a coating layer formed of a coating solution containing an acrylic resin, a carbodiimide compound, and an oxazoline compound on at least one surface of the polyester film.

  The coating layer in the present invention can improve the adhesion with various surface functional layers, but can particularly improve the adhesion with the solventless active energy ray-curable coating layer. For example, a microlens layer or a prism layer can be formed.

  The acrylic resin used in the present invention is a polymer comprising a polymerizable monomer having a carbon-carbon double bond, as typified by acrylic and methacrylic monomers. These may be either a homopolymer or a copolymer. Moreover, the copolymer of these polymers and other polymers (for example, polyester, polyurethane, etc.) is also included. For example, a block copolymer or a graft copolymer. Alternatively, a polymer (possibly a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyester solution or a polyester dispersion is also included. Similarly, a polymer (in some cases, a mixture of polymers) obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in a polyurethane solution or polyurethane dispersion is also included. Similarly, a polymer obtained by polymerizing a polymerizable monomer having a carbon-carbon double bond in another polymer solution or dispersion (in some cases, a polymer mixture) is also included.

  The polymerizable monomer having a carbon-carbon double bond is not particularly limited, but particularly representative compounds include, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, citracone. Various carboxyl group-containing monomers such as acids, and salts thereof; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, monobutyl hydroxyl fumarate, Various hydroxyl group-containing monomers such as monobutylhydroxy itaconate; various monomers such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, lauryl (meth) acrylate ( (Meth) acrylic acid esters; Various nitrogen-containing vinyl monomers such as (meth) acrylimide, diacetone acrylamide, N-methylol acrylamide or (meth) acrylonitrile; various styrene derivatives such as styrene, α-methylstyrene, divinylbenzene, vinyltoluene, Various vinyl esters such as vinyl acetate and vinyl propionate; various silicon-containing polymerizable monomers such as γ-methacryloxypropyltrimethoxysilane and vinyltrimethoxysilane; phosphorus-containing vinyl monomers; vinyl chloride And various vinyl halides such as biliden chloride; and various conjugated dienes such as butadiene.

  An acrylic resin containing a functional group such as a carboxyl group, a hydroxyl group, an amino group, or an amide group can be used in order to improve adhesion with various surface functional layers.

  For forming the coating layer in the film of the present invention, the coating layer of the coating layer is strengthened, and has sufficient adhesion with the microlens layer, the prism layer, etc., and heat and moisture resistance after forming the microlens layer, the prism layer, etc. In order to improve the above, a carbodiimide compound or an oxazoline compound is used as a crosslinking agent.

  The carbodiimide compound used in the present invention is a compound having a carbodiimide structure, and improves adhesion to a surface functional layer such as a prism layer that can be formed on the coating layer, and improves the heat and humidity resistance of the coating layer. It is used for. The carbodiimide-based compound is a compound having one or more carbodiimide structures in the molecule and a reaction product thereof, but a compound having two or more in the molecule and a reaction product thereof are more preferable for better adhesion and the like.

  A compound having a carbodiimide structure can be synthesized by a conventionally known technique, and generally a condensation reaction of a diisocyanate compound is used. The diisocyanate compound is not particularly limited, and any of aromatic and aliphatic compounds can be used. Specifically, tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate, naphthalene diisocyanate, hexa Examples include methylene diisocyanate, trimethylhexamethylene diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, isophorone diisocyanate, dicyclohexyl diisocyanate, and dicyclohexylmethane diisocyanate.

  The oxazoline-based compound is a compound having an oxazoline group in the molecule, and particularly a compound using a polymer containing an oxazoline group is preferred, and by polymerization with an addition polymerizable oxazoline group-containing monomer alone or with another monomer. Can be created. Addition polymerizable oxazoline group-containing monomers include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, and the like can be mentioned, and one or a mixture of two or more thereof can be used. Among these, 2-isopropenyl-2-oxazoline is preferred because it is easily available industrially. The other monomer is not limited as long as it is a monomer copolymerizable with an addition polymerizable oxazoline group-containing monomer. For example, alkyl (meth) acrylate (the alkyl group includes a methyl group, an ethyl group, an n-propyl group, an isopropyl group, (meth) acrylic acid esters such as n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group); acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, styrene Unsaturated carboxylic acids such as sulfonic acid and its salts (sodium salt, potassium salt, ammonium salt, tertiary amine salt, etc.); methoxy polyethylene glycol (meth) acrylate, polyethylene glycol, ethoxy polyethylene glycol (meth) acrylate ( (Meth) acrylate polyethylene Glycol adducts; Unsaturated nitriles such as acrylonitrile and methacrylonitrile; (meth) acrylamide, N-alkyl (meth) acrylamide, N, N-dialkyl (meth) acrylamide, (alkyl groups include methyl group, ethyl group , N-propyl group, isopropyl group, n-butyl group, isobutyl group, t-butyl group, 2-ethylhexyl group, cyclohexyl group, etc.); vinyl esters such as vinyl acetate and vinyl propionate; Vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; α-olefins such as ethylene and propylene; halogen-containing α, β-unsaturated monomers such as vinyl chloride, vinylidene chloride and vinyl fluoride; styrene, α-methylstyrene, etc. Of α, β-unsaturated aromatic monomers Can be, these can be used of one or more monomers.

  Moreover, in order to improve slipperiness and blocking, it is preferable to use particles in combination with the formation of the coating layer. The content of the particles is preferably in the range of 3 to 25%, more preferably in the range of 5 to 15%, and in the range of 5 to 10% in terms of the weight ratio of the entire coating layer. Further preferred. If it is less than 3%, the effect of imparting slipperiness or preventing blocking may be insufficient. On the other hand, if it exceeds 25%, the transparency of the coating layer may be lowered, the coating film strength may be lowered due to the loss of the continuity of the coating layer, or the easy adhesion may be lowered.

  Examples of the particles used include inorganic particles such as silica, alumina, and metal oxide, or organic particles such as crosslinked polymer particles. In particular, silica particles are preferred from the viewpoint of dispersibility in the coating layer and transparency of the resulting coating film.

  For the coating layer in the present invention, other than the acrylic resin described above in order to improve the coating surface shape, improve the visibility when various microlens layers and prism layers are formed on the coating surface, and improve the transparency. These binder polymers can also be used in combination.

  In the present invention, the “binder polymer” is a number average molecular weight (Mn) measured by gel permeation chromatography (GPC) according to a polymer compound safety evaluation flow scheme (sponsored by the Chemical Substance Council in November 1985). It is defined as a polymer compound of 1000 or more and having a film-forming property.

  Specific examples of the binder polymer include polyester resin, urethane resin, polyalkylene glycol, polyalkyleneimine, methylcellulose, hydroxycellulose, starches and the like.

  Further, in the range not impairing the gist of the present invention, the anti-foaming agent, the coating property improving agent, the thickening agent, the organic lubricant, the antistatic agent, the ultraviolet absorber, the antioxidant, and the foaming agent are used for forming the coating layer. , Dyes, pigments and the like may be used in combination.

  In this invention, content of the said acrylic resin in a coating liquid is 10 to 95 weight% normally as a ratio with respect to all the non-volatile components, Preferably it is 20 to 90 weight%, More preferably, it is 30 to 85 weight%. If the amount is less than 10% by weight, the adhesion may not be sufficient due to the small amount of the acrylic resin component. If the amount exceeds 95% by weight, the coating layer becomes brittle due to the small amount of the crosslinking agent component, and the adhesion is not sufficient. In some cases, the heat and humidity resistance may not be sufficient.

  In the present invention, the content of the carbodiimide compound in the coating solution is usually 1 to 50% by weight, preferably 3 to 40% by weight, more preferably 5 to 30% by weight as a ratio to the total nonvolatile components. . When the amount is less than 1% by weight, the coating layer becomes brittle and may not sufficiently withstand humidity and heat. When the amount exceeds 50% by weight, the adhesion may not be sufficient.

  In the present invention, the content of the oxazoline-based compound in the coating solution is usually 1 to 50% by weight, preferably 3 to 40% by weight, more preferably 5 to 30% by weight as a ratio to the total nonvolatile components. . When the amount is less than 1% by weight, the coating layer becomes brittle and may not sufficiently withstand humidity and heat. When the amount exceeds 50% by weight, the adhesion may not be sufficient.

  In the polyester film of the present invention, a coating layer can also be provided on the surface opposite to the surface on which the coating layer is provided. For example, when a functional layer such as an anti-sticking layer, a light diffusion layer, or a hard coat layer is formed on the opposite side of the prism layer or the microlens layer, it is possible to improve the adhesion with the functional layer. . A conventionally well-known thing can be used as a component of the coating layer formed in the surface on the opposite side. For example, a binder polymer such as a polyester resin, an acrylic resin, a urethane resin, a carbodiimide compound, an oxazoline compound, an epoxy compound, a melamine compound, a crosslinking agent such as an isocyanate compound, and the like, and these materials may be used alone. Multiple types may be used in combination. Further, it may be a coating layer (coating layer having the same surface on both sides of the polyester film) containing the acrylic resin, carbodiimide compound, and oxazoline compound as described above.

  Analysis of various components in the coating layer can be performed by surface analysis such as TOF-SIMS.

  When providing a coating layer by in-line coating, the above-mentioned series of compounds is applied as an aqueous solution or dispersion, and the coating solution adjusted to a solid content concentration of about 0.1 to 50% by weight as a guide is applied onto the polyester film. It is preferable to produce a laminated polyester film. Moreover, in the range which does not impair the main point of this invention, a small amount of organic solvents may be contained in the coating liquid for the purpose of improving dispersibility in water, improving film-forming properties, and the like. Only one type of organic solvent may be used, or two or more types may be used as appropriate.

Regarding the laminated polyester film in the present invention, the coating amount after drying of the coating layer provided on the polyester film is usually 0.002 to 1.0 g / m ² , more preferably 0.005 to 0.5 g / m ² , More preferably, it is the range of 0.01-0.2 g / m < ² >. If the coating amount is less than 0.002 g / m ^2, sufficient adhesion may not be obtained, and if it exceeds 1.0 g / m ² , the appearance, transparency, and film blocking properties may be deteriorated. There is sex.

  In the present invention, as a method for providing the coating layer, a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating or the like can be used. Regarding the coating method, there is a description example in “Coating method” published by Yasuharu Harasaki in 1979.

  In the present invention, the drying and curing conditions for forming the coating layer on the polyester film are not particularly limited. For example, when the coating layer is provided by off-line coating, it is usually 3 to 40 at 80 to 200 ° C. The heat treatment may be performed for 2 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds.

  On the other hand, when the coating layer is provided by in-line coating, heat treatment is usually performed at 70 to 280 ° C. for 3 to 200 seconds as a guide.

  Further, irrespective of off-line coating or in-line coating, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as required. The polyester film constituting the laminated polyester film in the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

  Generally, a prism layer, a microlens layer, or the like is provided on the coated layer of the laminated polyester film of the present invention in order to improve luminance. In recent years, various shapes have been proposed for the prism layer in order to improve the luminance efficiently. Generally, prism layers are formed by arranging prism rows having a triangular cross section in parallel. Similarly, various shapes of the microlens layer have been proposed, but in general, a large number of hemispherical convex lenses are provided on the film. Any layer can have a conventionally known shape.

  Examples of the shape of the prism layer include a triangular cross section having a thickness of 10 to 500 μm, a prism row pitch of 10 to 500 μm, and an apex angle of 40 to 100 °. As the material used for the prism layer, conventionally known materials can be used, for example, those made of an active energy ray-curable paint, such as polyester resin, epoxy resin, polyester (meth) acrylate, epoxy Examples include (meth) acrylate resins such as (meth) acrylate and urethane (meth) acrylate.

  Examples of the shape of the microlens layer include a hemispherical shape having a thickness of 10 to 500 μm and a diameter of 10 to 500 μm, but may have a shape such as a cone or a polygonal pyramid. As the material used for the microlens layer, conventionally known materials can be used as in the prism layer, and examples thereof include an active energy ray-curable coating material.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measurement method and evaluation method used in the present invention are as follows.

(1) Measurement of intrinsic viscosity of polyester:
1 g of polyester from which other polymer components and pigments incompatible with polyester were removed was precisely weighed, 100 ml of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) was added and dissolved, and measurement was performed at 30 ° C.

(2) Measurement of average particle diameter (d ₅₀ : μm):
The value of 50% of integration (weight basis) in the equivalent spherical distribution measured using a centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type manufactured by Shimadzu Corporation) was defined as the average particle size.

(3) Adhesion evaluation method:
In order to form a prism layer, an active energy ray-curable paint composed of the following coating agent composition is placed on a mold member in which a large number of prism rows with a pitch of 50 μm and an apex angle of 65 ° are arranged in parallel, and a coating layer is formed thereon. The laminated polyester film is laminated in the direction in which the resin comes into contact with the resin, the active energy ray-curable coating composition is uniformly stretched by a roller, and the resin is cured by irradiating ultraviolet rays from an ultraviolet irradiation device with a mercury lamp 160W at 300 mJ / cm ² . . Subsequently, the film was peeled off from the mold member to obtain a film on which a prism layer was formed. Scratches at 5 mm intervals with a cutter knife, affixed 24 mm wide tape (Cello Tape (registered trademark) CT-24 manufactured by Nichiban Co., Ltd.), peeled off sharply at a peeling angle of 180 degrees, and observed the peeled surface. When the peeled area was less than 3%, it was evaluated as ◯, when the peeled area was 3% to 50%, Δ, and when it exceeded 50%, it was marked as x.

<Active energy ray-curable coating composition>
KAYARAD-DPHA (Nippon Kayaku Co., Ltd.) 40 parts DPHA-40H (Nippon Kayaku Co., Ltd.) 20 parts BPP-4 (Daiichi Kogyo Seiyaku Co., Ltd.) 30 parts R-128H (Nippon Kayaku) 10 parts Irgacure 651 (manufactured by BASF Corporation) 3 parts

The polyester used in the examples and comparative examples was prepared as follows.
<Method for producing polyester (A)>
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, adding tetrabutoxy titanate as a catalyst to the reactor, setting the reaction start temperature to 150 ° C., and gradually increasing the reaction temperature as methanol is distilled off. It was 230 degreeC after 3 hours. After 4 hours, the transesterification reaction was substantially completed, and then a polycondensation reaction was performed for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.63 due to a change in stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester (A) having an intrinsic viscosity of 0.63.

<Method for producing polyester (B)>
Starting from 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol, magnesium acetate / tetrahydrate is added as a catalyst to the reactor, the reaction start temperature is set to 150 ° C., and the reaction temperature is gradually increased as methanol is distilled off. Was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. This reaction mixture was transferred to a polycondensation tank, orthophosphoric acid was added, and germanium dioxide was added to carry out a polycondensation reaction for 4 hours. That is, the temperature was gradually raised from 230 ° C. to 280 ° C. On the other hand, the pressure was gradually reduced from normal pressure, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time corresponding to an intrinsic viscosity of 0.65 due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure to obtain a polyester (B) having an intrinsic viscosity of 0.65.

<Method for producing polyester (C)>
In the method for producing polyester (A), 0.2 part of silica particles having an average particle diameter of 2 μm dispersed in ethylene glycol was added, and the polycondensation reaction was stopped at a time corresponding to an intrinsic viscosity of 0.66. A polyester (C) having an intrinsic viscosity of 0.66 was obtained using a method similar to the method for producing polyester (A).

Examples of compounds constituting the coating layer are as follows.
(Example compounds)
Acrylic resin: (IA) Aqueous dispersion of acrylic resin polymerized with the following composition: ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylol acrylamide / acrylic acid = 65/21/10/2/2 (% by weight) Emulsion polymer (emulsifier: anionic surfactant)

Acrylic resin: (IB) Aqueous dispersion of acrylic resin polymerized with the following composition: ethyl acrylate / methyl methacrylate / 2-hydroxyethyl methacrylate / N-methylol acrylamide / acrylic acid = 65/28/3/2/2 (% by weight ) Emulsion polymer (emulsifier: anionic surfactant)

Polyester resin: (II) A water dispersion of a polyester resin copolymerized with the following composition: Monomer composition: (acid component) terephthalic acid / isophthalic acid / 5-sodium sulfoisophthalic acid // (diol component) ethylene glycol / 1 4-butanediol / diethylene glycol = 56/40/4 // 70/20/10 (mol%)

・ Carbodiimide compounds: (IIIA)
Polycarbodiimide compound Carbodilite V-02 (Nisshinbo Co., Ltd.)

・ Carbodiimide compounds: (IIIB)
Polycarbodiimide compound Carbodilite E-04 (Nisshinbo Co., Ltd.)

・ Oxazoline compounds: (IVA)
Oxazoline group-containing acrylic polymer Epocros WS-500 (manufactured by Nippon Shokubai Co., Ltd.)

・ Oxazoline compounds: (IVB)
Oxazoline group-containing acrylic polymer Epocros WS-300 (manufactured by Nippon Shokubai Co., Ltd.)

Epoxy compound: (V) Denacol EX-521 (manufactured by Nagase ChemteX Corporation), which is polyglycerol polyglycidyl ether

-Particles: (VI) Silica sol with an average particle size of 65 nm

Example 1:
A mixed raw material obtained by mixing polyesters (A), (B), and (C) at a ratio of 85%, 5%, and 10%, respectively, is used as a raw material of the outermost layer (surface layer), and polyesters (A) and (B) are each 95 %, 5% mixed raw materials were used as intermediate layer raw materials, each was supplied to two extruders, melted at 290 ° C, and then on a cooling roll set at 40 ° C. Coextruded with a layer structure of layers (surface layer / intermediate layer / surface layer = 1: 18: 1 discharge amount) and cooled and solidified to obtain an unstretched sheet. Next, the film was stretched 3.4 times in the longitudinal direction at a film temperature of 85 ° C. using the difference in peripheral speed of the roll, and then the coating solution 1 shown in Table 1 below was applied to one side of the longitudinally stretched film, which was led to a tenter. Stretch 4.0 times at 120 ° C in the transverse direction, heat treatment at 225 ° C, relax 2% in the transverse direction, and the coating amount (after drying) has a coating layer whose thickness is 188 μm as shown in Table 2 A polyester film was obtained.

  It was favorable when adhesiveness was evaluated regarding the obtained polyester film. The properties of this film are shown in Table 2 below.

Examples 2-10:
In Example 1, it manufactured similarly to Example 1 except having changed the coating agent composition into the coating agent composition shown in Table 1, and obtained the polyester film. The finished polyester film was as shown in Table 2 and had good adhesion.

Comparative Examples 1-5:
In Example 1, it manufactured similarly to Example 1 except having changed the coating agent composition into the coating agent composition shown in Table 1, and obtained the polyester film. When the completed laminated polyester film was evaluated, it was as shown in Table 2 and had poor adhesion.

  The film of the present invention can be suitably used for applications that require good adhesion to a microlens layer or a prism layer, such as a backlight unit of a liquid crystal display.

Claims (8)

  A laminated polyester film having a coating layer, wherein the coating layer is formed of a coating solution containing an acrylic resin, a carbodiimide compound, and an oxazoline compound.   As a ratio with respect to all the non-volatile components in the coating liquid, the content of the acrylic resin is 10 to 95% by weight, the content of the carbodiimide compound is 1 to 50% by weight, and the content of the oxazoline compound is 1 to 50% by weight. The laminated polyester film according to claim 1.   The laminated polyester film according to claim 1 or 2, wherein the functional layer is an optical functional layer.   The laminated polyester film according to claim 3, wherein the optical functional layer is a microlens layer or a prism layer.   A laminated polyester film in which a functional layer is formed on the surface of a coated polyester film having a coating layer using a solvent-free active energy ray-curable coating, wherein the coated layer is an acrylic resin or a carbodiimide compound. And a laminated polyester film formed by a coating solution containing an oxazoline-based compound.   As a ratio with respect to all the non-volatile components in the coating liquid, the content of the acrylic resin is 10 to 95% by weight, the content of the carbodiimide compound is 1 to 50% by weight, and the content of the oxazoline compound is 1 to 50% by weight. The laminated polyester film according to claim 5.   The laminated polyester film according to claim 5 or 6, wherein the functional layer is an optical functional layer.   The laminated polyester film according to claim 7, wherein the optical functional layer is a microlens layer or a prism layer.