JPH10119215A - Polyester film for cathode-ray tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provided superior transparency and securing properties and improve adhesive properties to a hard cost layer by providing a coated layer containing a specific amount of a polyester resin, an acryl resin, a crosslinking agent resin and particles on one side of a biaxially stretched polyester whose film phase is a specific value or less. SOLUTION: A polyester film for a cathode-ray tube comprises a coated layer containing 10 to 85wt.% of a polyester resin, 5 to 60wt.% of an acryl resin, 1 to 50wt.% of a crosslinging agent resin and 0.5 to 10wt.% of particles that is provided on at least one side of a biaxially stretched polyester film having a film haze of 0.2 or less. A method is used to form the coated layer that comprises the steps of coating a thin film forming liquid on the surface of a non-stretched film and thereafter stretching it biaxially. Alternately, a method can be used that comprises the steps of coating a thin film forming liquid on the surface of a mono-axially stretched film and thereafter stretching it in right angles directions, or a combination of these two methods may be used. Furthermore, a film so obtained is then extended, limit shrunk or thermally treated under a constant length.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to productivity, transparency,
The present invention relates to a polyester film for a cathode ray tube having a novel coating layer having excellent adhesiveness, particularly excellent adhesiveness with a hard coat layer.

[0002]

2. Description of the Related Art In recent years, cathode ray tubes, particularly color cathode ray tubes, have been mass-produced for general household televisions, industrial televisions, computer displays, and the like. These glass panels for cathode ray tubes are produced by molding molten glass in a mold.However, the surface of the panel glass during molding is uneven, so the panel glass surface is polished before use. It is. A polishing step is indispensable for obtaining a panel glass surface of a cathode ray tube as smooth as required. In the manufacturing process of the cathode ray tube, the time and cost occupied by this process are 20 to 30% of the entire process.
It is important to rationalize this polishing process.

[0003] Cathode rays can be obtained by bringing a biaxially stretched polyester film having excellent properties in mechanical strength, dimensional stability, flatness, smoothness, heat resistance, chemical resistance, transparency and the like into close contact with the face surface of a cathode ray tube. It has been proposed to simplify the tube manufacturing process. However, while having such excellent properties, polyester films generally have the disadvantage of being inert and poor in adhesiveness. As a method for improving the adhesiveness of the biaxially stretched polyester film, physical treatment (for example, corona treatment, ultraviolet treatment, plasma treatment, EB treatment, etc.), flame treatment, or chemical treatment (for example, alkali, aqueous amine, trichloroacetic acid or phenol) Treatment with a chemical such as a class) is known.
However, these methods have practical disadvantages such as deterioration of the adhesive force with time and contamination of the working environment due to volatilization of the chemical.

[0004] As another means, there is a method in which an easily adhesive coating agent is applied to the film surface by a process other than the ordinary polyester film manufacturing process to form a coating layer. However, in this method, an organic solvent is usually used as a solvent for the coating agent, and it is difficult to say that the coating atmosphere is sufficiently clean. safety,
There are hygiene issues.

[0005] Therefore, if the coating process is performed in the polyester film forming process using an aqueous coating agent, no dust adheres in a clean environment, and there is no danger of explosion or environmental deterioration due to the aqueous solvent. This is advantageous in terms of film performance, economy, and safety. Many proposals have been made as a coating agent used for the coating and stretching method, such as polyester, polyurethane, acrylic resin, and vinyl resin. However, although polyester as a coating agent has good adhesiveness to a polyester film as a substrate, when laminated with another material thereon, the adhesiveness is often insufficient,
When the amount of the copolymer component or the amount of the copolymer is increased in order to improve the adhesive property, there is a problem that the fixability (blocking property) is deteriorated.

According to Japanese Patent Application Laid-Open No. 58-124651, a polyester film which is obtained by applying a coating solution containing a polyester and an acrylic resin to a film and then stretching the film is proposed, and is confirmed to be practically effective. . However, when a coating solution containing only these resins is used as a polyester film for a cathode ray tube, a film which simultaneously satisfies the adhesiveness, the transparency, and the adhesiveness cannot be obtained. In order to use it as a polyester film for a cathode ray tube, it is essential to provide an adhesive used for bonding to a panel glass and a thin film layer having good adhesion to an ultraviolet-curable hard coat layer. In particular, if the adhesiveness with the hard coat layer is poor, the interface between the polyester film and the hard coat layer is lifted or peeled off, resulting in a significant reduction in commercial value in appearance.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyester film for a cathode ray tube which is excellent in transparency and sticking property and can improve adhesion to a hard coat layer. is there.

[0008]

Means for Solving the Problems As a result of intensive studies on the above problems, the present inventor has found that a film obtained by applying a coating layer having a specific composition on at least one surface of a polyester film solves the above problems, In addition, they have found that unexpected effects can be obtained, and have completed the present invention. That is, the gist of the present invention is that the film haze is 2.
On at least one side of a biaxially stretched polyester film of 0% or less, 10 to 85% by weight of a polyester resin,
5 to 60% by weight of acrylic resin and 1 to 5 of crosslinking agent resin
A polyester film for a cathode ray tube, comprising a coating layer containing 0% by weight and 0.5 to 10% by weight of particles.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The polyester constituting the film of the present invention is a polyester obtained by using an aromatic dicarboxylic acid or an ester thereof and a glycol as main starting materials. For example, 80% or more of the repeating structural units are ethylene terephthalate units or ethylene-2, Refers to a polyester having 6-naphthalate units or 1,4-cyclohexane terephthalate. Then, other conditions may be contained as long as the conditions do not deviate from the above range.

As the aromatic dicarboxylic acid component, for example, in addition to terephthalic acid and 2,6-naphthalenedicarboxylic acid, for example, isophthalic acid, phthalic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxyethoxy) Benzoic acid and the like can be used. As the glycol component, other than ethylene glycol, for example, diethylene glycol, propylene glycol, butanediol, 1,4-cyclohexanedimethanol,
One or more of neopentyl glycol and the like can be used. The limiting viscosity of the polyester used in the present invention is usually 0.45 to 1.0, preferably 0.50 to 1.0.
1.0, more preferably 0.52 to 0.80.
If the intrinsic viscosity is less than 0.45, the productivity during film production may be reduced, or the mechanical strength of the film may be reduced. If the intrinsic viscosity exceeds 1.0, the melt extrusion stability of the polymer tends to be poor.

The polyester film of the present invention may contain particles in the polyester and form appropriate projections on the film surface for the purpose of giving the film a slipperiness and improving the handleability. Examples of such particles include inorganic particles such as calcium carbonate, calcium phosphate, silica, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, and molybdenum sulfide, crosslinked polymer particles, and oxalic acid. Organic particles such as calcium and precipitated particles formed during the polymerization of polyester can be exemplified. In the present invention, the average particle size of the particles contained in the film is usually 3.0 μm or less, preferably 2.5 μm or less, more preferably 2.
0 μm or less. When the average particle size exceeds 5.0 μm,
The film surface tends to be rough and the transparency tends to decrease.

The content of the particles in the polyester is usually 1.0% by weight or less, preferably 0.1% by weight or less, more preferably 0.01% by weight or less. If the particle content exceeds 1.0% by weight, the transparency of the film may be impaired. Two or more kinds of the above particles may be compounded in the film, and particles of the same kind but different in particle diameter may be compounded. In any case, it is preferable that the average particle diameter of all the particles contained in the film and the total content satisfy the above-mentioned range.

In the production of polyester containing particles,
The particles may be added during the polyester synthesis reaction or may be added directly to the polyester. When it is added during the synthesis reaction, a method in which the particles are added as a slurry in which the particles are dispersed in ethylene glycol or the like at an arbitrary stage of polyester synthesis is preferable. On the other hand, when it is directly added to the polyester, it is used as dried particles or water or a compound having a boiling point of 2%.
It is preferable to use a twin-screw kneading extruder to add and mix a slurry dispersed in an organic solvent having a temperature of 00 ° C. or lower. In addition, the particles to be added may be subjected to processing such as crushing, dispersion, classification, and filtration as needed.

As a method for adjusting the content of particles, a master material containing particles at a high concentration is prepared in the above-described manner, and is diluted with a material substantially free of particles during film formation. A method of adjusting the particle content is effective. In addition, as additives other than the above-mentioned projection-forming agent, as necessary, an antistatic agent, a stabilizer, a lubricant, a crosslinking agent, an antiblocking agent, an antioxidant, a coloring agent (dye, pigment),
It may contain a light-blocking agent, an ultraviolet absorber and the like.
The polyester film of the present invention may have a multilayer structure as long as the properties finally obtained satisfy the requirements of the present invention. For example, it may be a co-extruded laminated film. In this case, the above description regarding the base film applies to the polyester of the outermost layer.

The production of a biaxially stretched polyester film comprises:
It is carried out by either simultaneous biaxial stretching or sequential biaxial stretching, and in particular, sequential biaxial stretching is often performed. That is,
The melt-extruded polyester is cooled on a cooling drum to form an unstretched film, which is stretched (longitudinal stretching) by a group of rolls having a difference in peripheral speed, and then clipped in a direction perpendicular to the longitudinal direction of the film. Stretching (lateral stretching) while holding. As this modification, the longitudinal stretching and the transverse stretching may be performed by dividing into several times. Further, the stretching may be divided and a part thereof may be alternately performed. For example, a method of manufacturing a high-strength film by a re-stretching method corresponds to this.

The biaxially stretched polyester film of the present invention has a film haze measured at a film thickness of 188 μm of 2.0% or less, preferably 1.5% or less, more preferably 1.0% or less. Film haze is 2.
If it exceeds 0%, when the film is brought into close contact with a glass panel to form a cathode ray tube, the sharpness of the screen is undesirably reduced.

The polyester resin constituting the coating layer of the film of the present invention comprises, as main constituents, the following polyvalent carboxylic acids and polyvalent hydroxy compounds. That is, polycarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 4,4′-diphenyldicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4- Cyclohexanedicarboxylic acid, 2-potassium sulfoterephthalic acid, 5-sodium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutaric acid, succinic acid, trimellitic acid, trimesic acid, pyromellitic acid, anhydride Trimellitic acid, phthalic anhydride, p
-Hydroxybenzoic acid, monopotassium trimellitate and ester-forming derivatives thereof can be used. Examples of the polyvalent hydroxy compound include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, , 3-propanediol, 1,4
-Butanediol, 1,6-hexanediol, 2-methyl-1,5-pentaneddiol, neopentyl glycol, 1,4-cyclohexanedimethanol, p-xylylene glycol, bisphenol A -Ethylene glycol adduct, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytetramethylene oxide glycol, dimethylolpropionic acid, glycerin, trimethylolpropane , Dimethylo-
Sodium ruethylsulfonate, potassium dimethylolpropionate and the like can be used.

Of these compounds, 1
One or more may be selected and a polyester resin may be synthesized by a conventional polycondensation reaction. In addition, in addition to the above,
A composite polymer having a polyester component such as a so-called acrylic graft polyester or a polyester polyurethane obtained by chain-extending a polyester polyol with an isocyanate, which is described in JP-A-165633, is also included in the polyester resin that can be used in the present invention.
As the acrylic resin constituting the coating layer of the film of the present invention, those containing alkyl acrylate or alkyl methacrylate as a main component are preferable, and those components are 30 to 90 mol% and a vinyl monomer having a functional group. A water-soluble or water-dispersible resin obtained by copolymerizing 70 to 10 mol% of a monomer component is preferred.

The vinyl monomer having a functional group copolymerizable with an alkyl acrylate or an alkyl methacrylate can impart hydrophilicity to the resin to improve the water dispersibility of the resin, or can be used to improve the water dispersibility of the resin or the polyester film or the coating layer. Those having a functional group having good adhesion to another coating layer provided thereon, or having good affinity with other resins and reactivity with oxazoline groups to be blended as a coating agent are preferable. A carboxyl group or a salt thereof, an acid anhydride group, a sulfonic acid group or a salt thereof, an amide group or an alkylolated amide group, an amino group (including a substituted amino group) or an alkylolated amino group, or Examples thereof include a salt, a hydroxyl group, an epoxy group and the like, particularly, a carboxyl group or a salt thereof, an acid anhydride group, an epoxy group, and the like. Preferred. Two or more of these groups may be contained in the resin.

When the content of the alkyl acrylate or alkyl methacrylate in the acrylic resin is 30 mol% or more, the coating formability, the strength of the coating film and the blocking resistance are particularly good. When the alkyl acrylate or alkyl methacrylate in the acrylic resin is 90 mol% or less, a compound having a compound having a specific functional group is introduced as a copolymer component into the acrylic resin to facilitate water solubility and water dispersion. In addition, it can stabilize the condition for a long period of time, further improve the adhesion between the coating layer and the polyester film layer, improve the strength, water resistance, chemical resistance of the coating layer due to the reaction in the coating layer, and The adhesiveness between the film of the invention and other materials can be improved.

Examples of the alkyl group of the alkyl acrylate and the alkyl methacrylate include a methyl group and n-
Examples include a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a 2-ethylhexyl group, a lauryl group, a stearyl group, and a cyclohexyl group. As the vinyl monomer having a functional group copolymerizable with the alkyl acrylate or alkyl methacrylate, compounds having a functional group such as a reactive functional group, a self-crosslinkable functional group, and a hydrophilic group can be used. Specific examples include alkali metal salts such as acrylic acid, methacrylic acid, itaconic acid, and maleic acid, or alkaline earth metal salts, ammonium salts, and maleic anhydride.

Examples of the compound having a sulfonic acid group or a salt thereof include vinyl sulfonic acid, styrene sulfonic acid, metal salts of these sulfonic acids with sodium and the like, and ammonium salts. Examples of the compound having an amide group or an alkylolated amide group include acrylamide, methacrylamide, N-methylmethacrylamide, methylolated acrylamide, methylolated methacrylamide, ureido vinyl ether, β-ureido isobutyl vinyl ether, ureido ethyl acrylate, and the like. No.

Examples of the compound having an amino group or an alkylolated amino group or a salt thereof include diethylaminoethyl vinyl ether, 2-aminoethyl vinyl ether, 3-aminopropyl vinyl ether,
-Aminobutyl vinyl ether, dimethylaminoethyl methacrylate, dimethylaminoethyl vinyl ether, methylolated amino groups thereof, alkyl halides, quaternized with dimethyl sulfate, sultone and the like.

Examples of the compound having a hydroxyl group include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, β-hydroxypropyl acrylate,
-Hydroxypropyl methacrylate, β-hydroxyvinyl ether, 5-hydroxypentyl vinyl ether, 6-hydroxyhexyl vinyl ether, polyethylene glycol monoacrylate, polyethylene glycol monomethacrylate, polypropylene glycol monoacrylate, polypropylene glycol monomethacrylate and the like. Examples of the compound having an epoxy group include glycidyl acrylate and glycidyl methacrylate.

Further, in addition to the above, the following compounds may be used in combination. That is, acrylonitrile, styrenes, butyl vinyl ether, mono or dialkyl maleate, mono or dialkyl fumarate, mono or dialkyl itaconate, methyl vinyl ketone, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl pyridine, vinyl pyrrolidone,
Examples include, but are not limited to, vinyltrimethoxysilane. The acrylic resin may contain a surfactant, but a low molecular weight surfactant is concentrated during the film formation process and accumulates at the interface between particles or migrates to the interface of the coating layer. Therefore, problems may occur in the mechanical strength, water resistance, and adhesion to the laminate of the coating layer. In such a case, no surfactant is contained,
A polymer obtained by so-called soap-free polymerization can be used.

A method for producing an acrylic resin containing no surfactant is described in "Comprehensive Technical Data for Water-Soluble Polymers / Water-Dispersible Resins", edited by the Business Development Center Publishing Division, published in January 1981. Use the method shown in p. 309 or the textbook of the lecture "Looking forward into the future from the latest research results-New development of emulsion and future technical issues" sponsored by the Industrial Technology Research Association (December 1981) Can be. For example, use of an oligomer or a polymer surfactant instead of a low molecular weight surfactant, introduction of a hydrophilic group into a polymer by use of a polymerization initiator such as potassium persulfate or ammonium persulfate, having a hydrophilic group Copolymerization of monomers, use of reactive surfactants, so-called shell-core type polymers in which the structure of the inner layer and outer layer of the dispersion particles are changed, and so-called water-dispersible acrylics containing no surfactant It can be used as a resin manufacturing technique.

Examples of the crosslinking agent resin constituting the coating layer of the film of the present invention include methylolated or alkylolated urea-based, melamine-based, guanamine-based, acrylamide-based, polyamide-based compounds, polyamines, epoxy compounds, and the like. Oxazoline compounds, aziridine compounds, blocked isocyanate compounds, silane coupling agents,
Examples thereof include a titanium coupling agent, a zircol aluminate coupling agent, a metal chelate, an organic acid anhydride, an organic peroxide, a thermally or photoreactive vinyl compound, and a photosensitive resin. The crosslinking agent resin is usually selected from these polyfunctional low molecular weight compounds and high molecular weight compounds. Among these, melamine-based, epoxy-based, and oxazoline-based compounds are particularly preferable in terms of improving applicability and adhesion.

As the particles constituting the coating layer of the film of the present invention, either inorganic particles or organic particles may be used. Examples of the inorganic particles include silicon dioxide, alumina, zirconium oxide, kaolin, talc, calcium carbonate, titanium oxide, barium oxide, carbon black, molybdenum sulfide, and antimony oxide. Among them, silicon dioxide is inexpensive and has a wide variety of particle sizes, so that it is easy to use. The surface of these particles may be treated with an organic substance. For example, it may be surface-treated with a surfactant, a polymer as a dispersant, a silane coupling agent, a titanium coupling agent, or the like.

Examples of the organic particles include polystyrene or polyacrylate polymethacrylate in which a crosslinked structure is achieved by a compound containing two or more carbon-carbon double bonds in one molecule (for example, divinylbenzene). Further, as thermosetting resin particles synthesized by the condensation reaction, melamine-formaldehyde, benzoguanamine-
Formaldehyde, phenol-formaldehyde, epoxy and the like. Further, polytetrafluoroethylene, tetrafluoroethylene-ethylene copolymer, polyvinylidene fluoride, tetrafluoroethylene-
Examples include particles of a fluororesin such as hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, and polychlorotrifluoroethylene, and particles of a crosslinked silicone resin. The surface of these particles may be surface-treated with an organic substance. For example, it may be surface-treated with a surfactant, a polymer as a dispersant, a silane coupling agent, a titanium coupling agent, or the like.

Other additives may include an antistatic agent, an antifoaming agent, a coating improver, a thickener, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, a pigment, and the like. The amount of the polyester resin in the coating layer of the present invention is 10 to 85.
% By weight, preferably 30 to 70% by weight. If the amount is less than 10% by weight, sufficient adhesive strength will not be exhibited, and if it exceeds 85% by weight, blocking resistance will be insufficient. The amount of the acrylic resin in the coating layer of the present invention is 5 to 60% by weight, preferably 10 to 40% by weight. When the amount is less than 5% by weight, the adhesion to the hard coat layer is insufficient. When the amount is more than 60% by weight, the stretchability of the coating layer itself is deteriorated, so that the uniformity of the coating film is deteriorated.

The compounding amount of the crosslinking agent resin in the coating layer of the present invention is 1 to 50% by weight, preferably 5 to 30% by weight. When the amount is less than 1% by weight, sufficient adhesiveness under high temperature and high humidity is not exhibited, and the effect of improving solvent resistance is insufficient. On the other hand, if it exceeds 50% by weight, sufficient adhesiveness is not exhibited. The compounding amount of the particles in the coating layer of the present invention is 0.5 to 10% by weight, preferably 1 to 5% by weight. If the amount is less than 0.5% by weight, the blocking resistance is insufficient. If the amount exceeds 10% by weight, transparency is impaired, and the sharpness of the image is undesirably reduced.

The coating solution for obtaining the coating layer of the present invention contains a small amount of an organic solvent for the purpose of improving dispersion in water or improving film forming performance, as long as water is the main medium. You may. When the organic solvent is used by mixing with water as a main medium, it is necessary to use the organic solvent within a range that dissolves in water. As the organic solvent, n-butyl alcohol, n-propyl alcohol, isopropyl alcohol, ethyl alcohol, aliphatic or alicyclic alcohols such as methyl alcohol, propylene glycol, ethylene glycol, glycols such as diethylene glycol, n-butyl cellosolve, Ethyl cellosolve, methyl cellosolve, glycol derivatives such as propylene glycol monomethyl ether, ethers such as dioxane and tetrahydrofuran, esters such as ethyl acetate and amyl acetate, ketones such as methyl ethyl ketone and acetone, and amides such as N-methylpyrrolidone. But not limited to these. These organic solvents may be used alone or in combination of two or more as necessary.

As a method of forming the coating layer, there are a method of forming the biaxially stretched film at the time of production and a method of forming the film by biaxial stretching. The former is more preferable. As a specific example of the former, for example, after a thin film forming liquid is applied to the surface of an unstretched film, the film is stretched biaxially. Alternatively, a method of applying a thin film forming liquid on the surface of a uniaxially stretched film and then stretching the film in the perpendicular direction may be mentioned, but a method of using this in combination is also suitable. When the stretching treatment is not performed after the application, the adhesion between the formed coating layer and the base film tends to be weak, and the adhesiveness suitable for practical use may not be obtained. In order to achieve these industrially advantageously, it is preferable to apply in the manufacturing process of the biaxially stretched film, but it is not limited thereto.

As a method of applying the above-mentioned coating solution to a polyester film, for example, the following method can be used.
A reverse roll coater, a gravure coater, a rod coater, an air doctor coater or a coating device other than these can be used as shown in "Coating System" published in 979. The coating layer in the present invention may be laminated on only one side of the polyester film, or may be laminated on both sides. When laminating only on one side, a coating layer different from the above-mentioned coating layer may be formed on the opposite surface, if necessary, to further impart other characteristics to the polyester film of the present invention. Note that the film may be subjected to a chemical treatment or a discharge treatment before coating in order to improve the coating property and adhesion of the coating solution to the film. Further, in order to further improve the surface characteristics of the biaxially stretched polyester film of the present invention, a discharge treatment may be performed after forming the coating layer.

The thickness of the coating layer in the present invention is in the range of 0.02 to 0.5 μm as a final dry thickness, and more preferably 0.1 to 0.5 μm.
The range of from 03 to 0.3 μm is preferred. If the thickness of the coating layer is less than 0.02 μm, the effects of the present invention may not be obtained. If the thickness exceeds 0.5 μm, the films are likely to be mutually blocked, and the coating is particularly performed for the purpose of increasing the strength of the film. When re-stretching the treated film,
During the process, it may be easy to stick to the roll. The problem of blocking is particularly noticeable when the same coating layer is provided on both sides of the film. Next, the method for producing the film of the present invention will be specifically described.

The polyester raw material is supplied to an extruder,
It is melt-extruded at a temperature equal to or higher than the melting point of the polyester and extruded as a molten sheet from a slit die. Next, the molten sheet is quenched and solidified on a rotary cooling drum so as to have a temperature equal to or lower than the glass transition temperature, thereby obtaining a substantially amorphous unstretched sheet. In this case, in order to improve the flatness of the sheet, it is preferable to increase the adhesion between the sheet and the rotary cooling drum. In the present invention, the electrostatic application adhesion method and / or the liquid application adhesion method are preferably employed.

The thus-obtained coated unstretched sheet is first stretched in the machine direction. The stretching temperature range is 70-1
It is preferable that the stretching ratio is 50 ° C. and the stretching ratio is 2.5 to 6 times. Stretching can be performed in one step or two or more steps. After forming a longitudinally uniaxially stretched film, a coating liquid is applied to at least one side of the film, and is appropriately dried or undried, and the glass transition point of the uniaxially oriented film in the horizontal direction, that is, in the direction orthogonal to the vertical direction, is once performed. Cooling to below or without cooling, e.g. preheating to a temperature range of 90-150C,
The film is stretched 5 times, preferably 3.0 to 4.5 times to obtain a biaxially oriented film.

The film thus obtained is heat-treated for 1 second to 5 minutes under elongation, limited shrinkage or constant length within 30%. At this time, a method of performing a relaxation treatment within 10%, preferably within 5% in the longitudinal direction in or after the heat treatment step can be also adopted particularly in order to keep the heat shrinkage in the longitudinal direction within a suitable range. . The heat treatment temperature is preferably from 180 to 250C, more preferably from 200 to 230C, although it depends on the stretching conditions. Heat treatment temperature is 250 ℃
If it exceeds, the film density tends to be too high.
Further, a part of the coating layer may be thermally decomposed. On the other hand, when the temperature is lower than 180 ° C., the heat shrinkage of the film is undesirably large. Note that the film may be subjected to a chemical treatment or a discharge treatment before application in order to improve the coating property and adhesion of the coating agent to the film. Further, in order to improve the adhesiveness, applicability and the like of the coating layer of the biaxially stretched polyester film of the present invention, the coating layer may be subjected to a discharge treatment after the formation of the coating layer.

[0039]

The present invention will be described below in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist. In addition, the evaluation method in an Example is as follows. In Examples and Comparative Examples, “parts” means “parts by weight”.

(1) Intrinsic viscosity of polymer [η] (d
1 / g) 1 g of the polymer is phenol / tetrachloroethane = 50
/ 50 (weight ratio) in 100 ml of a mixed solvent.
Measured in ° C. (2) Average particle size Centrifugal sedimentation type particle size distribution analyzer SA- manufactured by Shimadzu Corporation
The particle size was measured using a CP3 type by the sedimentation method based on Stokes' resistance law. The average particle size was determined using a value of 50% of the integrated (volume basis) in the equivalent spherical distribution of the particles obtained by the measurement.

(3) Transparency (Film Haze) Film turbidity was measured according to JIS-K6714 using a spectroscopic turbidity meter “NDH-300A (trade name)” manufactured by Nippon Denshoku Industries Co., Ltd. (4) Coatability The surface of the obtained polyester film was visually observed.
The criteria are as follows. ：: coating unevenness is hardly recognized △: coating unevenness is extremely slightly recognized ×: coating unevenness is clearly recognized

(5) Stickiness (Film Blocking Property) The film surfaces to be measured are overlapped, and the temperature is 40 ° C. and the humidity is 80%.
When performing a press treatment at RH and a load of 10 kg / cm ² for 20 hours, and peeling off the pressed film surface in accordance with the method of measuring and quantifying the degree of blocking between plastic films determined by ASTM D 1893. The degree of blocking was determined from the load of. The criteria are as follows. Less than 100 g: ○ (good) 100 or more, less than 250 g: △ (normal) 250 or more: × (poor)

(6) Adhesion to Hard Coat Layer Evaluation of Adhesion (Method A) A hard coat agent having the following composition was applied to the surface of a polyester film using a # 20 bar, and dried at 90 ° C. for 1 minute to remove the solvent. After that, the composition was cured with a high-pressure mercury lamp under the conditions of 120 W / cm, irradiation distance of 15 cm, and 10 m / min to form a hard coat layer of 8 μm. Immediately after the formation of the hard coat layer, a cross cut was made on the hard coat layer so as to have 100 grids in a width of 1 inch. The criteria are as follows. ○: Number of cross-cut strips <5 △: 5 ≦ Number of cross-cut strips ≦ 20 ×: 20 <Number of cross-cut strips

[0044]

[Table 1] [Hard coat agent composition] ─────────────────────────────────── Seika Beam EXY-26 ( S) (manufactured by Dainichi Seika Kogyo Co., Ltd.) 30 parts Methyl ethyl ketone 35 parts Toluene 35 parts ────────────────────────────── ─────

Evaluation of Adhesion (Method B) Immediately after the formation of the hard coat layer, storage was carried out for 5 days in an environment of 50 ° C. and 90% RH, and the same method as in the evaluation of adhesion (Method A) was used, except that cellophane tape was peeled off. evaluated.

(7) Screen State The panel glass to which the polyester sheet was adhered was visually observed. ：: No abnormality is observed on the surface of the panel glass at all. △: Irregularity is observed on the surface of the panel glass. ×: Image clarity is deteriorated. (Adjustment of coating agent) Aqueous solution shown in Table 1-1 and Table 1-2 below A paint stock solution was blended to prepare a water-based paint having a composition shown in Table 2 below.

[0047]

[Table 2]

[0048]

[Table 3]

[0049]

[Table 4]

Example 1 Polyethylene terephthalate having an intrinsic viscosity of 0.65 and containing 15 ppm of silica particles having an average particle diameter of 1.5 μm was dried by a conventional method, supplied to an extruder, melted at 290 ° C. and extruded into a sheet. Then, it was rapidly cooled on a cooling roll by using an electrostatic application contact method to obtain an amorphous sheet having a sheet thickness of 1950 μm. The obtained unstretched sheet is stretched 2.5 times at 85 ° C. in the machine direction by a roll stretching method, and further 1.3 at 95 ° C.
After the double stretching, before the transverse stretching by the tenter, the aqueous coating composition P1 shown in Table 2 was applied, the film was guided to the tenter, and the film was stretched 3.2 times at 120 ° C. in the transverse direction, and 225
Heat treatment was carried out at ℃ to obtain a biaxially stretched polyester film having a film thickness of 188 μm. The intrinsic viscosity of the obtained film was 0.59. In addition, the aqueous paint composition P1
The haze of the film before application was 0.9%.

Comparative Example 1 The average particle diameter of the silica particles in Example 1 was 2.3 μm.
m, and a biaxially stretched polyester film having a film thickness of 188 μm was obtained in the same manner as in Example 1 except that the content was changed to 120 ppm. Water-based paint composition P1
The haze of the film before application was 4.5%. Examples 2 to 6 and Comparative Examples 2 to 9 In Examples 1, the water-based paint compositions were changed to the following Tables 3-1 and 3
A biaxially stretched polyester film having a film thickness of 188 μm was obtained in the same manner as in Example 1 except that the composition was changed to the composition shown in -2.

Comparative Example 10 A film thickness of 18 was obtained in the same manner as in Example 1 except that the aqueous paint was not applied after the longitudinal stretching and before the transverse stretching.
An 8 μm biaxially stretched polyester film was obtained. Table 3 summarizes the properties of the obtained biaxially stretched polyester film.
-1 and Table 3-2.

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[Table 5]

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Industrial Applicability The film of the present invention is a polyester film required for a polyester film for a cathode ray tube, which is excellent in properties such as transparency and sticking property, especially adhesion to a hard coat layer, and has an industrial value. Extremely large.

Claims (1)

[Claims] 1. A biaxially stretched polyester film having a film haze of 2.0% or less is provided on at least one surface with 10 to 85% by weight of a polyester resin, 5 to 60% by weight of an acrylic resin, and 1% of a crosslinking agent resin. A polyester film for a cathode ray tube, comprising a coating layer containing 50 to 50% by weight and 0.5 to 10% by weight of particles.