JP6531349B2 - Release film - Google Patents

Description

The present invention relates to a release film, and in particular, to provide a release film having the advantages of excellent visibility after heat treatment and less generation of foreign matter.
It is related.

  The biaxially stretched polyester film is excellent in transparency, dimensional stability, mechanical characteristics, heat resistance, electrical characteristics, etc., and is a release layer mainly composed of a biaxially stretched polyester film and mainly made of silicone resin or the like. The release film provided is used in many fields.

  However, in recent years, the application in which the release film is used is often exposed to high temperatures. For example, in a transparent conductive film provided with an ITO sputtered layer used in a touch panel or the like, heat of about 150 ° C. is applied for one hour or more in the crystallization step of ITO. The pressure-sensitive adhesive layer and the release film for laminating such a transparent conductive film may be laminated on the transparent conductive film before crystallization, and both may go through a crystallization step. However, as a problem of polyester film, when exposed to such high temperature treatment, oligomers contained in the film (low molecular weight components of polyester, particularly cyclic trimer) are precipitated from the inside of the film. The oligomer deposited in this manner passes through the release layer, and is crystallized inside the adhesive layer to become foreign matter, causing a problem that appearance inspection is hindered.

  Therefore, the release film based on the biaxially oriented polyester film did not have sufficient properties to withstand use depending on the application.

Japanese Patent Application Laid-Open No. 2007-200823 JP 2012-150779 A

  The present invention has been made in view of the above-mentioned circumstances, and the problem to be solved is to provide a release film having an effect that the visibility after heat treatment is particularly excellent and the generation of foreign matter is small.

  The present inventor has found that the above-mentioned problems can be solved by using a polyester film substrate, a specific undercoat layer, and a releasing layer as a result of earnestly studying the above-mentioned problems. It came to complete.

That is, the gist of the present invention is that a first undercoat layer, a second undercoat layer, and a release layer containing a curable silicone resin are sequentially laminated on a substrate made of a biaxially stretched polyester film, The first undercoat layer is obtained by applying a coating solution in which the ratio of the crosslinking agent to all the non-volatile components is 70% by weight or more, and then drying it, and the crosslinking agent contains an oxazoline-based crosslinking agent. A coating solution comprising two or more cross-linking agents, wherein the second undercoat layer comprises an organic compound containing at least one metal element selected from aluminum, titanium and zirconium, an organic silicon compound and a metal catalyst after release film, characterized in that is obtained by drying, or the substrate made of a biaxially oriented polyester film, first undercoat layer, second undercoat layer and curable The first subbing layer is obtained by applying a coating solution in which the ratio of the crosslinking agent to the total non-volatile components is 70% by weight or more, and then drying the first undercoat layer. The present invention relates to a release film characterized in that the crosslinking agent is composed of two or more kinds of crosslinking agents containing an oxazoline-based crosslinking agent having an oxazoline group content of 5 to 8 mmol / g .

  According to the laminated polyester film of the present invention, since the oligomer deposition from the film is suppressed even when the treatment is carried out at high temperature for a long time, a product having an excellent appearance without generation of foreign matter on the surface of the release layer It can be obtained and its industrial use value is high.

The base film of the release film of the present invention is made of polyester. Such polyesters include terephthalic acid, isophthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, 4,4'-diphenyldicarboxylic acid, dicarboxylic acids such as 1,4-cyclohexyldicarboxylic acid, or esters thereof A polyester produced by melt polycondensation of ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,4-butanediol, neopentyl glycol, and glycol such as 1,4-cyclohexanedimethanol. The polyester comprising the acid component and the glycol component can be produced by optionally using a commonly used method.
For example, a bis-glycol of a substantially aromatic dicarboxylic acid by transesterification between a lower alkyl ester of an aromatic dicarboxylic acid and a glycol or directly esterifying an aromatic dicarboxylic acid and a glycol A method is employed in which an ester, or a low polymer thereof, is formed, and then this is heated to polycondense under reduced pressure. Depending on the purpose, aliphatic dicarboxylic acids may be copolymerized.

  Typical examples of the polyester of the present invention include polyethylene terephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate and the like, and in addition, the above acid component and glycol component may be used together. It may be a polymerized polyester, and may contain other components and additives as required.

  The polyester film in the present invention is a single layer or multilayer structure. In the case of a multilayer structure, the surface layer and the inner layer, or both surface layers and layers can be made of different polyesters according to the purpose.

  When the additive is added to the film, it can be added to the single layer film or to only a part of the multilayer film. For example, by making the film into a three-layer structure, adding no particles to the inner layer, and adding particles to one or both outer layers, slipperiness and transparency can be made more compatible.

  Moreover, it is preferable when the polyester film of this invention uses polyester with little content of an oligomer. The amount of polyester having a low oligomer content is preferably 80% by weight or more of the total polyester when the film has a single layer structure, and when the film has a multilayer structure, the undercoat layer is used. It is suitable that it is 80 weight% among the surface layer which touches. The polyester having a low content of oligomers refers to a polyester having a cyclic trimer of 0.7% by weight or less. Particularly preferably, the cyclic trimer is 0.5% by weight or less. When the polyester film is heated at a high temperature, a good effect is obtained when the amount is 0.7% by weight or less in order to suppress the precipitation of the oligomer on the film surface. In addition, if the oligomer content is simply reduced, the deposition amount is not reduced accordingly, and in particular, when heating is carried out in a state where an adhesive layer or the like is provided on the film surface, the oligomer content is 0.5% by weight It was found that the amount of precipitation can be significantly reduced on the basis of the degree.

  When the surface layer of the film having a multilayer structure is a polyester having a low oligomer content as described above, the thickness of the surface layer is preferably 4 μm or more, more preferably 5 μm or more. The greater the thickness, the more the precipitation of the oligomer is suppressed, but as a result of testing the release film in various applications through the heating step, when the thickness of the surface layer is thinner than the above range, a sufficient precipitation suppression effect of the oligomer is obtained. It has been found that there may be cases in which

  The polyester film in the present invention can contain particles for the purpose of securing the runnability of the film and preventing the formation of flaws. Examples of such particles include inorganic particles such as silica, calcium carbonate, magnesium carbonate, calcium phosphate, kaolin, talc, aluminum oxide, titanium oxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide and the like Crosslinked polymer particles, organic particles such as calcium oxalate, and particles precipitated in the polyester production process can be used.

  The particle size and content of the particles used are selected according to the application and purpose of the film, but the average particle size (d50) is usually 0.01 μm to 3 μm, preferably 0.02 μm to 2.5 μm, and more preferably Is in the range of 0.03 μm to 2 μm. When the average particle size exceeds 3.0 μm, the surface roughness of the film may be too rough, or the particles may be easily detached from the film surface. If the average particle size is less than 0.01 μm, the surface roughness may be too small to obtain sufficient slipperiness.

  The particle content is usually in the range of 0.0003 to 1.0% by weight, preferably 0.0005 to 0.5% by weight, based on the particle-containing polyester layer. When the particle content is less than 0.0003% by weight, the slipperiness of the film may be insufficient, while when it is added in excess of 1.0% by weight, the transparency of the film is not good. It may be enough. When it is desired to particularly ensure the transparency, smoothness and the like of the film, it may be configured to contain substantially no particles. Also, various stabilizers, lubricants, antistatic agents and the like can be added to the film as appropriate.

  It is preferable that the haze of the polyester film which is a base film of this invention is 10% or less. More preferably, it is 5% or less, more preferably 3% or less. If it is larger than this range, it may be difficult to use it in appearance in optical applications.

  As a film forming method of the film of the present invention, a generally known film forming method can be adopted, and there is no particular limitation. For example, first, a sheet obtained by melt extrusion is stretched by 2 to 6 times at 70 to 145 ° C. by roll stretching to obtain a uniaxially stretched polyester film, and then, in a tenter, it is perpendicular to the above stretching direction. A film is obtained by extending | stretching 2 to 6 times at 80-160 degreeC in a direction, and heat-processing further at 150-250 degreeC for 1 to 600 seconds. Furthermore, in this case, a method of relaxing by 0.1 to 20% in the longitudinal direction and / or the transverse direction in the heat treatment zone and / or the cooling zone at the heat treatment outlet is preferable.

  The first undercoat layer of the present invention can be provided either by so-called off-line coating, in which a coated film is subsequently provided on the formed film, or in-line coating, in which the coating layer is provided in the film formation. However, it is preferably provided by in-line coating, in particular by a coating stretching method in which stretching is performed after coating.

  In-line coating is a method of coating in the process of polyester film production, specifically, a method of coating at any stage from melt extrusion of polyester to biaxial setting, heat setting and winding up. is there. Usually, a substantially amorphous unstretched sheet obtained by melting and quenching, a uniaxially stretched film stretched in a longitudinal direction (longitudinal direction) thereafter, and a biaxially stretched film before heat setting are coated. Do. In particular, as a coating stretching method, a method of stretching in the transverse direction after coating on a uniaxially stretched film is excellent. According to this method, since film formation and coating layer coating can be performed simultaneously, there is a merit on the manufacturing cost, and in order to perform stretching after coating, the characteristics of the coating layer are uniform to form a thin film. Stabilize. In addition, the base film and the coating layer firmly adhere to each other by covering the polyester film before being biaxially stretched with the resin layer constituting the coating layer first and then simultaneously stretching the film and the coating layer. become. In addition, biaxial stretching of the polyester film is carried out by stretching in the lateral direction while holding the film end with a tenter clip, whereby the film is restrained in the longitudinal / lateral direction, and in heat setting, no wrinkles and the like enter. High temperature can be applied while maintaining the sex. Therefore, since the heat treatment applied after coating can be at a high temperature which can not be achieved by other methods, the film forming property of the coated layer is improved, and the coated layer and the polyester film are firmly adhered. As a polyester film provided with a coating layer, the uniformity of the coating layer, the improvement of the film forming property, and the adhesion between the coating layer and the film often produce desirable characteristics.

  In the case of the coating and drawing method, the coating solution to be used is preferably an aqueous solution or a water dispersion for handling, working environment and safety reasons, but water is the main medium and the scope not exceeding the scope of the present invention If it is, you may contain the organic solvent.

  The first undercoat layer of the present invention is preferably obtained by applying and drying a coating solution in which the ratio of the crosslinking agent to the total nonvolatile components is 70% by weight or more. In the coating solution, other components may be contained.

  The crosslinking agent mentioned here is a crosslinking resin which reacts particularly by heat, and examples thereof include an amino resin type, an isocyanate type, an oxazoline type, and an epoxy type. Also included are polymer type crosslinking reactive compounds in which other polymer backbones have reactive groups.

  In the present invention, in particular, it is preferable to use an oxazoline-based crosslinking agent, because it is compatible with suppression of oligomer deposition from the polyester film and good appearance of the undercoat layer.

Moreover, when two or more types of crosslinking agents are used in combination, the effect of suppressing oligomers precipitated from the polyester film at the time of heating becomes high, which is preferable. This is presumably due to the presence of crosslinkers having different reaction rates when the undercoating layer is formed, which more effectively fills the voids of the undercoating layer and becomes a layer that suppresses the precipitation of oligomers. Ru.
As a result of examining various combinations, when an oxazoline type and an epoxy type are used in combination, or when an amino resin type, an oxazoline type and an epoxy type are used in combination, the effect obtained is particularly high.

  The oxazoline-based crosslinking agent is preferably a polymer containing an oxazoline group in the molecule, and can be prepared by polymerization of an addition-polymerizable oxazoline group-containing monomer alone or with another monomer. 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, Examples thereof include 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline and the like, and a mixture of one or more of these can be used. Among these, 2-isopropenyl-2-oxazoline is industrially easily available and suitable, but the other monomer may be a monomer copolymerizable with the addition polymerizable oxazoline group-containing monomer. Moreover, the oxazoline type crosslinking agent in the present invention has a content of oxazoline group of 0.5 to 10 mmol / g, preferably 3 to 9 mmol / g, more preferably 5 to 8 mmol / g. In particular, when two or more types of crosslinking agents are used in combination, the effect obtained is high by selecting the oxazoline-based crosslinking agent within the above range.

  The epoxy type crosslinking agent is a compound having an epoxy group in the molecule, and for example, a condensate of epichlorohydrin and a hydroxyl group or an amino group such as ethylene glycol, polyethylene glycol, glycerin, polyglycerin, bisphenol A or the like These include polyepoxy compounds, diepoxy compounds, monoepoxy compounds, glycidyl amine compounds and the like. Examples of polyepoxy compounds include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, triglycidyl tris (2-hydroxyethyl) isocyanate, glycerol polyglycidyl ether, trimethylolpropane Examples of polyglycidyl ether and diepoxy compound include neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, resorcinol diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether , Polypropylene glycol diglycidyl ether, Examples of tetramethylene glycol diglycidyl ether and monoepoxy compound include allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, and as a glycidyl amine compound, N, N, N ′, N′-tetraglycidyl-m-xylyl. And diamines, 1,3-bis (N, N-diglycidylamino) cyclohexane and the like.

  Among amino resin-based crosslinking agents, those obtained by methylolating the amino group of melamine resin and further methylating a part of the methylol group are water-soluble and easy to handle, highly reactive, and have undercoat layers and groups A release film is obtained which is excellent in the adhesion to the metal film and the durability of the undercoat layer.

  In addition, when it contains this bridge | crosslinking component, the component for accelerating | stimulating bridge | crosslinking simultaneously, for example, a crosslinking catalyst etc. can be used together.

  The coating liquid for providing the first undercoat layer may contain other than the components described above, as necessary. For example, surfactants, other binders, particles, antifoaming agents, coatability improvers, thickeners, antioxidants, ultraviolet light absorbers, blowing agents, dyes, pigments and the like. These additives may be used alone or in combination of two or more as needed.

  In addition, the thickness of the first undercoat layer is generally in the range of 0.003 to 1 μm as the film thickness on the biaxially oriented polyester film. Preferably, it is in the range of 0.005 to 0.5 μm, more preferably 0.01 to 0.2 μm. If the thickness is smaller than this, the amount of oligomers precipitated from the film may not be sufficiently reduced. If the thickness is larger than this range, problems such as deterioration of the appearance of the first undercoat layer and blocking tend to occur.

  The thickness of the first undercoating layer is obtained by dyeing the coated film with a heavy metal such as a ruthenium compound or osmium compound, adjusting the cross section of the coated film by the ultrathin section method, and then cross sectioning the coated film by transmission electron microscopy. It can confirm by observing the application layer of several in several places, and averaging the actual value.

  As a method for applying a coating solution to a polyester film, for example, a coating technique as shown in "Coating system", published by Yuji Harasaki, published by Tsuji Shoten, 1979, can be used. Specifically, air doctor coater, blade coater, rod coater, knife coater, squeeze coater, impregnation coater, reverse roll coater, transfer roll coater, gravure coater, kiss roll coater, cast coater, spray coater, curtain coater, calendar coater , Extrusion coaters and the like.

  In addition, in order to improve the coating property to the film of a coating agent, and adhesiveness, you may perform a chemical treatment, a corona discharge treatment, a plasma treatment etc. to a film before application | coating.

  The coating solution for providing the second undercoat layer of the present invention preferably contains an organic compound containing one or more metal elements selected from aluminum, titanium and zirconium in the coating layer. These metal organic compounds may be used alone or in combination of two or more.

  Specific examples of the organic compound having an aluminum element include aluminum tris (acetylacetonate), aluminum monoacetylacetonate bis (ethylacetoacetate), aluminum-di-n-butoxide-monoethylacetoacetate, and aluminum-di -Iso-propoxide-monomethyl acetoacetate etc. are illustrated.

  Specific examples of the organic compound having a titanium element include, for example, titanium orthoesters such as tetranormal butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, tetramethyl titanate, etc .; titanium acetylacetonate; And titanium chelates such as titanium tetraacetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate, titanium triethanolaminate, titanium ethylacetoacetate and the like.

  Specific examples of the organic compound having a zirconium element include, for example, zirconium acetate, zirconium normal propylate, zirconium normal butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetonate, and zirconium bisacetylacetonate.

  Among them, it is preferable to use an organic compound containing one or two or more metal elements selected from aluminum, titanium, and zirconium, in particular, from the viewpoint that the oligomer precipitation prevention performance is excellent, and more preferably having a chelate structure. Organic compounds are preferred. This is also specifically described in the “Crosslinking Agent Handbook” (Shinzo Yamashita, Taisuke Kaneko Co., Ltd. Taiseisha 1990 edition).

  The second undercoat layer in the present invention is preferably used in combination with an organic silicon compound in order to improve the ability to prevent oligomer deposition and to improve the adhesion between the release layer and the polyester film. As a silicon compound, what is represented by following General formula (1) is preferable.

Si (X) _d (Y) _e (R ¹ ) _f (1)
(Wherein X is an organic group having at least one selected from an epoxy group, a mercapto group, a (meth) acryloyl group, an alkenyl group, a haloalkyl group and an amino group, R ¹ is a monovalent hydrocarbon group, and The carbon number is 1 to 10, Y is a hydrolysable group, d is an integer of 1 or 2, e is an integer of 2 or 3, f is an integer of 0 or 1, and d + e + f = 4 )
The organosilicon compound represented by the above general formula (1) has two (D unit source) or three (D unit source) having a hydrolyzable group Y capable of forming a siloxane bond by hydrolysis / condensation reaction Source) can be used. In the general formula (1), R ¹ is particularly preferably a methyl group, an ethyl group or a propyl group. As the hydrolyzable group Y, conventionally known ones can be used, and the following can be exemplified. Methoxy group, ethoxy group, butoxy group, isopropenoxy group, acetoxy group, butanoxym group, amino group and the like. These hydrolyzable groups may be used alone or in combination of two or more. The application of a methoxy group or an ethoxy group is particularly preferable because it can impart good storage stability to the coating material and has adequate hydrolyzability.

In the present invention, conventionally known organic silicon compounds can be used as the organic silicon compound contained in the coating layer, and specifically, vinyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycid Xypropylmethyldiethoxysilane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, γ -Aminopropyltriethoxysilane, 5-hexenyltrimethoxysilane, p-styryltrimethoxysilane, trifluoropropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyldiisopropenoxysilane Show an example It is possible.

  In the present invention, it is preferable to use a catalyst in combination with the second undercoat layer for the purpose of promoting hydrolysis and condensation reactions. Specific examples of the catalyst include organic acids such as acetic acid, butyric acid, maleic acid and citric acid, inorganic acids such as hydrochloric acid, nitric acid, phosphoric acid and sulfuric acid, basic compounds such as triethylamine, tetrabutyl titanate, dibutyl tin dilaurate, Organometallic salts such as dibutyltin diacetate, dibutyltin dioctate, dibutyltin diolate, diphenyltin diacetate, dibutyltin oxide, dibutyltin dimethoxide, dibutylbis (triethoxysiloxy) tin, dibutyltin benzyl malate, KF, NH4 F And fluorine-containing compounds, and the like. The above catalysts may be used alone or in combination of two or more. Among them, organic metal salts are particularly preferable in that the film durability is improved, and tin catalysts are more preferably used in that the catalyst activity is sustained for a long time.

  Furthermore, inorganic particles may be contained for the purpose of improving the adhesion and slipperiness of the undercoat layer, and specific examples include silica, alumina, kaolin, calcium carbonate, titanium oxide, barium salt and the like.

  Further, if necessary, an antifoamer, a coatability improver, a thickener, an organic lubricant, an organic polymer particle, an antioxidant, an ultraviolet absorber foaming agent, a dye and the like may be contained.

  In the range which does not exceed the scope of the present invention, only one type of organic solvent may be used, or two or more types may be used as appropriate, for the purpose of improving the dispersibility and the film forming property.

  The coating amount of the second undercoat layer in the present invention is usually in the range of 0.005 to 1 μm, preferably 0.005 to 0.5 μm, as the thickness of the film after drying. When the coating amount is less than 0.005 μm, the uniformity of the coating thickness may be insufficient, and after heat treatment, the amount of oligomers deposited from the surface of the coating layer may be large. On the other hand, when it apply | coats exceeding 1 micrometer, fault, such as slipperiness fall, may arise.

  The thickness of the second undercoat layer is obtained by dyeing the coated film with a heavy metal such as a ruthenium compound or an osmium compound, adjusting the cross section of the coated film by the ultrathin section method, and then cross sectioning the coated film by a transmission electron microscope It can confirm by observing the application layer of several in several places, and averaging the actual value.

  In the present invention, as the method for providing the second undercoat layer, for example, a coating technique as shown in "Coating system", published by Yuji Harasaki, published by Tsuji Shoten, 1979, can be used. Specifically, air doctor coater, blade coater, rod coater, knife coater, squeeze coater, impregnation coater, reverse roll coater, transfer roll coater, gravure coater, kiss roll coater, cast coater, spray coater, curtain coater, calendar coater , Extrusion coaters and the like.

  In the present invention, with regard to the curing conditions for forming the second undercoat layer on the polyester film, a heat treatment of 120 ° C. or higher is generally applied, preferably at 120 to 200 ° C. for 3 to 40 seconds, more preferably 120 to 160 Heat treatment is carried out at 3 ° C. for 3 to 40 seconds. Moreover, you may use together heat processing and active energy ray irradiations, such as ultraviolet irradiation, as needed. When the heat treatment is not performed at 120 ° C. or more, the amount of deposited oligomers is large, and the curing of the coating layer is not sufficient, and the variation of the peeling force of the release layer becomes large, which is not preferable.

  In the present invention, a release layer containing a curable silicone resin is further provided on the first undercoat layer and the second undercoat layer on the biaxially oriented polyester film obtained as described above. A type having a curable silicone resin as a main component may be used, or a modified silicone type using graft polymerization with an organic resin such as a urethane resin, an epoxy resin, or an alkyd resin may be used.

  As a kind of curing type silicone resin, any curing reaction type such as addition type, condensation type, ultraviolet curing type, electron beam curing type, non-solvent type can be used.

  To give a specific example, Shin-Etsu Chemical Co., Ltd. KS-774, KS-775, KS-778, KS-779H, KS-847H, KS-856, X-62-2422, X-62-2461, Dow Corning Asia Ltd. DKQ 3-202, DKQ 3-203, DKQ 3-204, DKQ 3-205, DKQ 3-210, Toshiba Silicone Co., Ltd. YSR-3022, TPR-6700, TPR-6720, TPR-6721, Toray Dow Corning Co., Ltd. SD7220, SD7226, SD7229 and the like. Furthermore, in order to adjust the releasability and the like of the release layer, a release control agent may be used in combination.

  In the present invention, as a method of providing a release layer on a polyester film, conventionally known coating methods such as reverse roll coating, gravure coating, bar coating and doctor blade coating can be used.

The coating amount of the release layer in the present invention is usually in the range of 0.01 to 1 g / m ² as a dry film after the release layer is formed. The application amount of the release layer can be calculated from the weight concentration of the paint, the application area, and the use amount of the paint. If the coating amount is smaller than this range, it will be difficult to obtain uniform releasability, and if larger than this range, problems such as blocking may occur.

The application amount can also be determined by confirming the thickness of the release layer from the cross section with a transmission electron microscope as described above and dividing by the specific gravity. Generally, the specific gravity of the curable silicone is about 0.9 to 1.2. The application amount of the release layer having a thickness of 0.1 μm is 0.1 g / m ² at a specific gravity of 1.

EXAMPLES The present invention will be described in more detail by way of examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. In addition, the evaluation method in an Example , a reference example, and a comparative example is as follows.

(1) Measurement Method of Intrinsic Viscosity of Polyester 1 g of polyester was precisely weighed, and 100 ml of mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) was added and dissolved, and measured at 30 ° C.

(2) Measuring method of contained ester cyclic trimer contained in polyester raw material:
About 200 mg of polyester raw material is weighed and dissolved in 2 ml of a mixed solvent of chloroform / HFIP (hexafluoro-2-isopropanol) ratio 3: 2. After dissolution, 20 ml of chloroform is added, and then 10 ml of methanol is added little by little. The precipitate is removed by filtration, and the precipitate is further washed with a mixed solvent of chloroform / methanol 2: 1 ratio, the filtrate and washings are recovered, concentrated by an evaporator and then dried. After dissolving the dried product in 25 ml of DMF (dimethylformamide), this solution is supplied to liquid chromatography ("LC-7A" manufactured by Shimadzu Corporation) to determine the amount of oligomers in DMF, and this value is mixed with chloroform / HFIP. The amount of polyester raw material dissolved in the solvent is divided to obtain the amount of contained oligomer (% by weight). The amount of oligomer in DMF was determined from the peak area ratio of the standard sample peak area and the measurement sample peak area (absolute calibration method).

  The preparation of a standard sample was made by accurately weighing a previously separated oligomer (cyclic trimer) and dissolving it in precisely weighed DMF. The concentration of the standard sample is preferably in the range of 0.001 to 0.01 mg / ml.

The conditions of the liquid chromatograph were as follows.
Mobile phase A: acetonitrile Mobile phase B: 2% aqueous acetic acid column: Mitsubishi Chemical Corporation "MCI GEL ODS 1 HU"
Column temperature: 40 ° C
Flow rate: 1 ml / min Detection wavelength: 254 nm

(3) Measuring method of average particle diameter (d50: μm) 50% of integration (weight basis) in equivalent spherical distribution measured using a centrifugal sedimentation type particle size distribution measuring apparatus (SA-CP type 3 manufactured by Shimadzu Corporation) The value of was taken as the average particle size.

(4) Coating layer thickness The film was fixed with embedding resin, the cross section was cut with a microtome, and the sample was prepared by staining with 2% osmic acid at 60 ° C. for 2 hours. The obtained sample was observed with a transmission electron microscope (JEM 2010, manufactured by JEOL Ltd.) to measure the thickness of the coated layer. A total of 15 points of the film are measured, and an average of nine points excluding three points from the larger one and three points from the smaller one is taken as the coating layer thickness.

(5) Love off test
After leaving a sample of polyester film in a room at 23 ° C / 50% RH for 30 days, the mold release surface is rubbed with a finger several times, the condition of the mold release surface is judged according to the following evaluation criteria, did. ○: No change was observed on the film surface
X: A mark of rubbing with a finger is seen on the film surface, and the peeling force is also changing

(6) Adhesive layer optical defect inspection 1
On the release surface of the release film, an acrylic adhesive COPONYL N-2233 (manufactured by Nippon Synthetic Chemical Co., Ltd.) was applied and dried to a thickness of 3 μm to provide an adhesive layer. The release film was attached to a glass plate through the adhesive layer, and then heated at 160 ° C. for 2.5 hours. Thereafter, foreign substances generated in the adhesive layer were inspected under an optical microscope. In the inspection, an area of 100 mm × 100 mm was selected from 12 arbitrary positions of the sample, and the number of foreign particles having a size of 5 μm or more was counted. Of the 12 inspection ranges, the total number of foreign particles in the 10 inspection ranges was determined according to the following criteria, except for the two locations where the number of foreign particles was the largest.
:: no foreign matter is found △: one or more and less than three foreign matters (a little problem in practical use)
X: 3 or more foreign matter (practical problem)

(7) Adhesive layer optical defect inspection 2
The release film is peeled off from the test piece heated at 160 ° C. for 2.5 hours in the same process as in the adhesive layer optical defect inspection 1 above, and then it is attached to a glass plate, and the adhesive layer is sandwiched between two glass plates Test pieces were prepared. Next, this test piece was subjected to an aging treatment for 10 days in an environment of 60 ° C. and 95% RH. By this aging treatment, the oligomers dissolved in the adhesive layer grow as crystals and become more likely to appear as foreign matter. Foreign substances generated in the adhesive layer of the test piece were inspected under an optical microscope. In the inspection, an area of 100 mm × 100 mm was selected from 12 arbitrary positions of the sample, and the number of foreign particles having a size of 5 μm or more was counted. Of the 12 inspection ranges, the total number of foreign particles in the 10 inspection ranges was determined according to the following criteria, except for the two locations where the number of foreign particles was the largest.
:: no foreign matter is found △: one or more and less than three foreign matters (a little problem in practical use)
X: 3 or more foreign matter (practical problem)

The polyesters used in the examples , reference examples and comparative examples are as follows.
(Polyester 1):
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, 0.09 parts by weight of magnesium acetate tetrahydrate as a catalyst is placed in a reactor, the reaction start temperature is 150 ° C., methanol is distilled off gradually The reaction temperature was raised to 230.degree. C. after 3 hours. After 4 hours, the transesterification was substantially terminated. After 0.04 parts of ethyl acid phosphate was added to the reaction mixture, 0.04 parts of antimony trioxide 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 it was 0.3 mmHg. After the start of the reaction, the reaction was stopped at a point corresponding to an intrinsic viscosity of 0.63 due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure. The limiting viscosity of the obtained polyester 1 was 0.63, and the content of the oligomer (cyclic trimer) was 0.97% by weight.

(Polyester 2):
Polyester 1 is pre-crystallized at 160 ° C. in advance, then solid-phase polymerized under nitrogen atmosphere at a temperature of 220 ° C., polyester having an intrinsic viscosity of 0.75 and an oligomer (cyclic trimer) content of 0.46% by weight I got two.

(Polyester 3):
In the production method of polyester 1, after adding 0.04 parts of ethyl acid phosphate, 0.3 parts of silica particles having an average particle diameter (d50) of 1.6 μm dispersed in ethylene glycol, 0.04 of antimony trioxide Parts were added, and polyester 3 was obtained using the same method as the production method of polyester 1, except that the polycondensation reaction was stopped at a point corresponding to the intrinsic viscosity of 0.65. The obtained polyester 3 had an intrinsic viscosity of 0.65 and an oligomer (cyclic trimer) content of 0.91% by weight.

The following was used as a composition contained in the coating liquid for providing a 1st undercoat layer.
(C1):
Polymer type crosslinking agent (Epocross manufactured by Nippon Shokubai Co., Ltd.) in which an oxazoline group is branched to an acrylic resin. Amount of oxazoline group = 7.7 mmol / g
(C2):
Polymer type crosslinking agent (Epocross manufactured by Nippon Shokubai Co., Ltd.) in which an oxazoline group is branched to an acrylic resin. Amount of oxazoline group = 4.5 mmol / g
(C3):
Polyglycerol polyglycidyl ether having an epoxy content of 5.5 (eq / kg).
(C4):
Hexamethoxymethylolated melamine, wherein the imino group / methylol group / methoxy group has a molar ratio of 1.5 / 2 / 2.5.

(T1):
2-Amino-2-methylpropanol hydrochloride (B1):
Water-soluble acrylic resin methyl methacrylate / isobutyl acrylate / 2-hydroxyethyl methacrylate = 50/30/10 with the following composition and a glass exfoliation at 44 ° C.
(B2):
Acrylic acid alkyl ester, methacrylic acid alkyl ester, methacrylic acid, N-methylol acrylamide as a main component copolymerized in the presence of alkoxy polyethylene glycol methacrylate as reactive emulsifier, glass transition point 50 ° C., acid value 14 mg KOH, Acrylic resin water dispersion having an average particle size of 0.05 μm.

(F1):
Silica particles (S1) having an average particle diameter of 0.07 μm by BET method:
Surfactant Surfynol 465 (made by Air Products)
The following was used as a composition contained in the coating liquid for providing a 2nd undercoat layer.
(A1):
Aluminum tris (acetylacetonate)
(K1):
γ-Glycidoxypropyltrimethoxysilane (T2):
Dibutyltin diacetate

These were mixed as follows to adjust the concentration of the second undercoat layer coating solution to 4% by weight.
(A1): 19.5% by weight
(K1): 80% by weight
(T2): 0.5% by weight
Dilution solvent: toluene / MEK mixed solvent (mixing ratio is 1: 3)

The following were used as a composition of a release layer.
(R1):
Curing type silicone resin (LTC303E: made by Toray Dow Corning)
(R2):
Hardening agent (SRX 212: made by Toray Dow Corning)

<Production example of polyester film>
Production Example 1
A blend of polyester 1 and polyester 3 at a weight ratio of 90/10 is used as a raw material for layer A and only polyester 1 as a raw material for layer B, and each is supplied to two vented twin screw extruders at 285 ° C. Co-extrusion with a layer configuration of two types and three layers (A layer / B layer / A layer) with the A layer split into two layers and the outer layer (surface layer) and the B layer as the intermediate layer Was solidified while being in close contact with a mirror cooling drum with a surface temperature of 40 to 50 ° C. to produce an unstretched polyethylene terephthalate film having a thickness composition ratio of A layer / B layer / A layer = 5/90/5. . This film was stretched 3.7 times in the longitudinal direction while passing through a heating roll group at 85 ° C. to obtain a uniaxially oriented film. Next, this film is introduced into a tenter stretching machine, stretched by 4.0 times in the width direction at 100 ° C., and further heat-treated at 230 ° C., followed by 2% relaxation treatment in the width direction to obtain a film having a thickness of 100 μm. An axially oriented polyethylene terephthalate film was obtained.

Production Example 2
A blend of polyester 2 and polyester 3 at a weight ratio of 93/7 is used as a raw material for layer A and only polyester 1 as raw materials for layer B, and each is supplied to two vented twin screw extruders at 285 ° C. Co-extrusion with a layer configuration of two types and three layers (A layer / B layer / A layer) with the A layer split into two layers and the outer layer (surface layer) and the B layer as the intermediate layer Was solidified while being in close contact with a mirror cooling drum with a surface temperature of 40 to 50 ° C. to produce an unstretched polyethylene terephthalate film having a thickness composition ratio of A layer / B layer / A layer = 5/90/5. . This film was stretched 3.7 times in the longitudinal direction while passing through a heating roll group at 85 ° C. to obtain a uniaxially oriented film. Next, this film is introduced into a tenter stretching machine, stretched by 4.0 times in the width direction at 100 ° C., and further heat-treated at 230 ° C., followed by 2% relaxation treatment in the width direction to obtain a film having a thickness of 100 μm. An axially oriented polyethylene terephthalate film was obtained.

Reference Example 1:
The coating liquid as shown in Table 1 was apply | coated to the single side | surface of the obtained uniaxially oriented film in the process of manufacture example 1. As shown in FIG. Next, this film is introduced into a tenter drawing machine, and the heat is used to dry and heat treat the coating solution, and on the biaxially oriented polyethylene terephthalate film having a film thickness of 100 μm, according to the same process as in Production Example 1. A laminated polyester film provided with a first undercoat layer having a thickness shown in Table 1 was obtained. A second undercoat layer coating solution was further applied to the obtained film so that the applied thickness after drying was 0.01 μm, dried at 130 ° C. for 30 seconds, and heat-treated. Furthermore, the following release layer paint is applied by a reverse gravure coating method so that the applied amount after drying is 0.1 g / m ² , then dried at 150 ° C. for 30 seconds, heat treated, In order to obtain a release film, a first undercoat layer, a second undercoat layer, and a release layer are laminated in order.
(R1) 100 parts (R2) 1 part MEK / toluene mixed solvent (mixing ratio is 1: 2) 1500 parts

Examples 2 to 5, Reference Example 6, Example 7, Reference Example 8 :
The coating solution as shown in Table 1 was apply | coated to the single side | surface of the obtained uniaxially oriented film in the process of manufacture example 2. Next, this film is introduced into a tenter stretching machine, and the heat is used to dry and heat treat the coating solution, and on the biaxially oriented polyethylene terephthalate film having a film thickness of 100 μm, according to the same process as in Production Example 2. A laminated polyester film provided with a first undercoat layer having a thickness shown in Table 1 below was obtained. The obtained film was further coated with a second undercoat layer coating solution to a coating thickness after drying shown in Table 2, dried at 130 ° C. for 30 seconds, and heat-treated. Furthermore, the following release layer paint is applied by a reverse gravure coating method so that the applied amount after drying is 0.1 g / m ² , then dried at 150 ° C. for 30 seconds, heat treated, In order to obtain a release film, a first undercoat layer, a second undercoat layer, and a release layer are laminated in order.
(R1) 100 parts (R2) 1 part MEK / toluene mixed solvent (mixing ratio is 1: 1) 1500 parts

Comparative Examples 1-2:
In the same manner as in Examples 2 to 5, Reference Example 6, Example 7, and Reference Example 8 , except that the second undercoat layer was not provided, the first undercoating was sequentially carried out on the polyester film. A release film having a layer and a release layer laminated thereon was obtained.

Comparative example 3:
A release film in which a release layer was laminated on a polyester film was obtained in the same manner as in Comparative Examples 1 and 2, except that the first undercoat layer was not provided.

  However, the weight ratio in Table 1 represents the weight ratio of non-volatile components of each component in the coating solution.

The characteristics of the films obtained in Examples , Reference Examples , and Comparative Examples are shown in Table 3 below.

  The film of the present invention can be suitably used as a release film in an application requiring an ability to hardly generate foreign matter on an adherend even after being exposed to high temperature.

Claims (4)

A first subbing layer, a second subbing layer, and a release layer containing a curable silicone resin are sequentially laminated on a substrate made of a biaxially oriented polyester film,
The first undercoat layer is obtained by applying a coating solution in which the ratio of the crosslinking agent to all the non-volatile components is 70% by weight or more, and then drying it, and the crosslinking agent is an oxazoline-based crosslinking agent. Ri Do two or more kinds of crosslinking agents, including,
The second undercoat layer is obtained by applying and then drying a coating solution containing an organic compound containing at least one metal element selected from aluminum, titanium, and zirconium, an organic silicon compound, and a metal catalyst. The release film characterized by being. A first subbing layer, a second subbing layer, and a release layer containing a curable silicone resin are sequentially laminated on a substrate made of a biaxially oriented polyester film,
The first undercoat layer is obtained by applying a coating solution in which the ratio of the crosslinking agent to all the non-volatile components is 70% by weight or more, and then drying it, and the crosslinking agent contains an oxazoline group. A release film comprising two or more crosslinkers containing an oxazoline crosslinker in an amount of 5 to 8 mmol / g .   The layer according to claim 1 or 2, wherein the layer constituting the polyester surface in contact with the undercoat layer is a layer having a thickness of 4 μm or more, which is composed of 80% by weight or more of polyester having an oligomer content of 0.7% by weight or less. the film. The laminated body which bonded the release film in any one of Claims 1-3 , and an adhesive and a transparent conductive film.