JP2014141008A - Release polyester film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a release polyester film which is excellent in flatness and peelability and reduces the generation of a siloxane oligomer from a resin layer.SOLUTION: There is provided a release film having a resin layer on at least one surface of a polyester film, wherein the resin layer has an acrylic polymer as a main chain and a silicone based polymer as a side chain and is mainly composed of a silicone-based graft copolymer having a carboxyl group and a hydroxyl group, and has a peeling strength of 0.01 to 0.10 N/cm and a center line average roughness SRa of 20 nm or less.

Description

  The present invention relates to a release polyester film suitable for use in electronic materials and the like.

  Release polyester films are widely used in electronic materials as release papers such as adhesive sheets and adhesive tapes, printed wiring boards, protective films for touch panels, and release films for manufacturing ceramic capacitors.

  Conventional release agents used in the release layer include silicone oil, silicone grease, fluorine compounds such as tetrafluoroethylene oligomer and hexafluoropropylene oxide oligomer, paraffin wax, paraffin hydrocarbons such as n-dodecane, Phosphate esters such as (2-ethylhexyl) phosphate, mineral oil, fatty acid derivatives, glycol, talc, mica, fluorine-based mold release agents and the like are used. However, since conventional mold release agents have low adhesion to a substrate, they are usually used in combination with a curing agent.

  For example, Patent Document 1 describes a coating agent in which a curing agent is added to acrylic-modified silicone. However, when the coating agent of Patent Document 1 is used as a release agent, there is a problem that the silicone oligomer generated from the acrylic-modified silicone resin accumulates on the roller, which causes the peelability to decrease. Moreover, when using a hardening | curing agent, since it needs to manufacture in consideration of pot life, there existed a problem that use was restrict | limited.

  On the other hand, when a protrusion or the like is transferred to the surface of the adherend in a release film used for an electronic material, this may cause a defect on the surface of the adherend. For this reason, in addition to peelability, the release film is required to have flatness on the release surface.

JP-A 63-227670

  An object of the present invention is to solve the above problems, and to provide a release polyester film that is excellent in flatness and releasability and has reduced generation of siloxane oligomers from a resin layer.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved, and have reached the present invention.

That is, the gist of the present invention is as follows.
(1) A release film in which a resin layer is formed on at least one side of a polyester film, the resin layer having an acrylic polymer as a main chain and a silicone polymer as a side chain, and having a carboxyl group and a hydroxyl group And the resin layer has a peel strength of 0.01 to 0.10 N / cm, and the resin layer has a center line average roughness (SRa) of 20 nm or less. Release polyester film characterized by
(2) The release polyester film according to (1), wherein the resin layer does not contain a curing agent.
(3) The release polyester film according to (1) or (2), wherein the amount of siloxane oligomer in the resin layer is 1 ppm or less.
(4) The release polyester film according to any one of (1) to (3), wherein the polyester film is a multilayer film.
(5) A coating liquid containing a silicone-based graft copolymer having an acrylic polymer as a main chain and a silicone polymer as a side chain and having a carboxyl group and a hydroxyl group is applied to a polyester film, and then 180 ° C. The method for producing a release polyester film according to any one of (1) to (4), comprising a step of heat drying at the above temperature.
(6) The method for producing a release polyester film according to (5), wherein a coating liquid whose solvent is water is used.

  ADVANTAGE OF THE INVENTION According to this invention, the mold release polyester film which was excellent in flatness and peelability and the generation | occurrence | production of the siloxane oligomer from the resin layer was reduced can be provided. The release polyester film of the present invention can be suitably used as a film for use in electronic materials. Moreover, according to the manufacturing method of this invention, a mold release polyester film can be obtained by the simple method of apply | coating a coating liquid to a polyester film, and heat-drying above a fixed temperature.

  The release polyester film of the present invention is obtained by forming a resin layer containing a silicone-based graft copolymer as a main component on a polyester film substrate.

  Although it does not specifically limit as a polyester resin used for a polyester film base material, For example, a polyethylene terephthalate, a polybutylene terephthalate, polyethylene-2, 6-naphthalate is mentioned, A polyethylene terephthalate is more preferable. You may copolymerize another component with a polyester resin as needed.

  Examples of other components include a carboxylic acid component, a hydroxycarboxylic acid component, and an alcohol component. Examples of the carboxylic acid component include isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, dimer acid , Maleic anhydride, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, cyclohexanedicarboxylic acid, trimellitic acid, trimesic acid, and pyromellitic acid. Examples of the hydroxycarboxylic acid component include 4-hydroxybenzoic acid, ε-caprolactone, and lactic acid. Examples of the alcohol component include ethylene glycol, diethylene glycol, 1,3-propanediol, neopentyl glycol, 1,6-hexanediol, cyclohexanedimethanol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and bisphenol. Examples include ethylene oxide adducts of A and bisphenol S, trimethylolpropane, glycerin, and pentaerythritol. Two or more of these copolymer components may be used in combination.

  The melting point of the polyester resin is preferably 230 ° C. or higher. By setting the melting point to 230 ° C. or higher, excellent heat resistance can be imparted to the polyester film substrate.

  Examples of the polymerization method of the polyester resin include known production methods such as a direct esterification method and a transesterification method. Examples of the direct esterification method include a method in which a necessary monomer raw material is injected into a reaction vessel, an esterification reaction is performed, and then a polycondensation reaction is performed. In the esterification reaction, the reaction is performed by heating and melting at a temperature of 160 ° C. or higher for 4 hours or longer in a nitrogen atmosphere. At that time, oxides such as magnesium, manganese, zinc, calcium, lithium, titanium, and acetate may be used as the catalyst. In the polycondensation reaction, the polycondensation reaction proceeds under a reduced pressure of 130 Pa or less until a desired molecular weight is reached at a temperature of 220 to 280 ° C. At that time, an oxide such as antimony, titanium, germanium, or acetate may be used as a catalyst. Since the polyester resin after polymerization contains monomers, oligomers, and by-products such as acetaldehyde and tetrahydrofuran, it is preferable to carry out solid phase polymerization at a temperature of 200 ° C. or higher under reduced pressure or inert gas flow.

  When the polyester resin is polymerized, an antioxidant, a heat stabilizer, an ultraviolet absorber, an antistatic agent, or the like may be added as necessary. Examples of the antioxidant include hindered phenol compounds and hindered amine compounds. Examples of the heat stabilizer include phosphorus compounds. Examples of the ultraviolet absorber include benzophenone compounds and benzotriazole compounds.

  The release polyester film of the present invention is obtained by forming a resin layer on a polyester film substrate by applying a coating solution and drying by heating.

  The resin layer can be formed by an inline coating method or a post coating method. The in-line coating method is a method in which a coating solution is applied to a non-stretched film or a uniaxially stretched film, heated and dried, and then stretched. On the other hand, the post-coating method is a method in which an unstretched film is converted into a biaxially stretched film by a sequential biaxial stretching method or a simultaneous biaxial stretching method, and a coating solution is applied to the biaxially stretched film and heated and dried.

  The application method of the coating liquid is not particularly limited, and examples thereof include a gravure roll method, a reverse roll method, an air knife method, a reverse gravure method, a Mayer bar method, an inverse roll method, or various coating methods based on a combination thereof. It is done. Various spraying methods can also be employed. The coating thickness is preferably 0.01 to 2 μm after heating and drying, more preferably 0.03 to 1 μm, still more preferably 0.04 to 0.5 μm, and siloxane oligomer. From the viewpoint of reducing the amount, the thickness is most preferably 0.04 to 0.2 μm. When the thickness after heat drying is less than 0.01 μm, the peelability may be reduced, and when the thickness after heat drying exceeds 2 μm, the curing time becomes long and the productivity may decrease. In order to set the peel strength of the resin layer within the range specified in the present invention, the heat drying temperature is preferably 180 to 240 ° C, and more preferably 200 to 230 ° C. The heat drying time is preferably 5 to 60 seconds, and more preferably 20 to 60 seconds.

  The polyester film substrate of the release polyester film of the present invention may be an unstretched film or a stretched film. The unstretched film is supplied with a sufficiently dried polyester resin raw material to the extruder, melted at a temperature higher than the fluidity, and passed through a filter as necessary. It can be obtained by extruding onto a cooling drum whose temperature is adjusted below the point (Tg).

  In the uniaxial stretching method, the unstretched film is stretched in the temperature range of Tg to (Tg + 50 ° C.) of the polyester resin so that the stretching ratio is about 2 to 6 times in the horizontal direction or the vertical direction. In the simultaneous biaxial stretching method, the unstretched film is biaxially stretched in the temperature range of Tg to (Tg + 50 ° C.) of the polyester resin so that the stretching ratio is about 2 to 4 times in the transverse direction and the longitudinal direction. In this case, preliminary longitudinal stretching of about 1 to 1.2 times may be performed before guiding to the simultaneous biaxial stretching machine. In the sequential biaxial stretching method, the unstretched film is heated with a roll, infrared rays, or the like, and stretched in the longitudinal direction to obtain a longitudinally stretched film. Stretching is preferably performed 2.5 to 4.0 times in a temperature range of Tg to (Tg + 40 ° C.) of the polyester resin by utilizing a difference in peripheral speed of two or more rolls. Subsequently, the longitudinally stretched film is continuously subjected to transverse stretching, heat setting, and thermal relaxation to form a biaxially stretched film. The transverse stretching starts in the temperature range of Tg to (Tg + 40 ° C.) of the polyester resin, and the maximum temperature is preferably in the temperature range of (Tm-100 ° C.) to (Tm-40 ° C.) of the polyester resin (Tm Is the melting point of the polyester resin). The transverse stretching ratio is adjusted depending on the required physical properties of the final film, but is preferably 3.5 times or more, more preferably 3.8 times or more, and 4.0 times or more. Is more preferable. The film can be stretched in the machine direction and the transverse direction, and further stretched in the machine direction and / or the transverse direction to increase the elastic modulus and dimensional stability of the film. Following stretching, heat fixing treatment for several seconds in the temperature range of polyester resin (Tm-50 ° C.) to (Tm-10 ° C.) and relaxation of 1-10% in the lateral direction of the film simultaneously with the heat fixing treatment preferable.

  In general, the in-line coating method has higher productivity and is more economical than the post coating method. In the in-line coating method, since the coating liquid is applied to the stretched film, it can be heated at a high temperature. In the present invention, since it is preferable to heat-treat the resin layer at 180 to 240 ° C., an in-line coating method that can be heated at a high temperature is preferable.

The silicone-based graft copolymer used in the present invention may be a structural unit derived from the (meth) acrylic acid ester (I) represented by the general formula (I) (hereinafter referred to as “structural unit (I)”). ), A structural unit derived from ethylenically unsaturated carboxylic acid (II) and / or a salt thereof (hereinafter sometimes referred to as “structural unit (II)”), and a structural unit derived from silicone macromonomer (III) (Hereinafter, sometimes referred to as “structural unit (III)”) and a structural unit derived from another polymerizable monomer (IV) (hereinafter referred to as “structural unit (IV)”) May be included).
^{_{CH 2 = C (R 1)}} -COO- (R 2 -O) n -R 3 (I)
(In the formula, R ¹ represents a hydrogen atom or a methyl group, R ² represents an ethylene group or a propylene group, R ³ represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms, and n is a number from 1 to 25. (However, when n is 1, R ³ is a monovalent hydrocarbon group of 1 to 6.)

  The trunk of the silicone-based graft copolymer has units derived from the polymerizable unsaturated group at one end of the structural unit (I), the structural unit (II), and the silicone-based macromonomer (III). Furthermore, it has a structural unit derived from another polymerizable monomer, and a silicone polymer that forms the main body of the silicone macromonomer (III) is bonded to the trunk as a branch. . The silicone-based polymer forming the branch portion is branched into the trunk portion by the copolymerization site of the silicone-based macromonomer (that is, the portion copolymerized by the polymerizable unsaturated group at one end of the silicone-based macromonomer (III)). Are connected.

In the silicone-based graft copolymer, the structural unit (I) forms a trunk. In the (meth) acrylic acid ester (I) represented by the general formula (I), R ¹ is preferably a hydrogen atom or a methyl group, and more preferably a methyl group.

When R ¹ is a methyl group, R ² is preferably an ethylene group or a propylene group, and more preferably an ethylene group. R ³ is preferably a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 6 carbon atoms, and a methyl group or an ethyl group. More preferable is the point that the viscosity of the aqueous solution is lowered. n is preferably a number of 1 to 25, more preferably 1 to 20, still more preferably 1 to 10, and particularly preferably 2 to 5. By setting n in the range of 1 to 25, the copolymer can be easily dissolved in water.

Examples of the (meth) acrylic acid ester (I) in which R ¹ is a methyl group include methoxypolyethylene glycol (meth) acrylate and ethoxypolyethyleneglycol (meth) acrylate in which n is 1 to 10 in the general formula (I) , Propoxy polyethylene glycol (meth) acrylate, butoxy polyethylene glycol (meth) acrylate, pentoxy polyethylene glycol (meth) acrylate, hexoxy polyethylene glycol (meth) acrylate, methoxy polypropylene glycol (meth) acrylate, ethoxy polypropylene glycol (meth) acrylate , Propoxypolypropylene glycol (meth) acrylate, butoxypolypropylene glycol (meth) acrylate, pentoxypolypropylene Glycol (meth) acrylate, hexoxycarbonyl polypropylene glycol (meth) acrylate. Among these, methoxypolyethylene glycol (meth) acrylate and ethoxypolyethylene glycol (meth) acrylate, in which n is 2 to 5 in the general formula (I), are preferable from the viewpoint of availability, and methoxypolyethylene glycol (meth) acrylate is more preferable. preferable. These may be used alone or in combination.

Examples of commercially available (meth) acrylic acid ester (I) in which R ¹ is a methyl group include “NK Ester M Series”, “NK Ester AM Series” (trade name) manufactured by Shin-Nakamura Chemical Co., Ltd., Nippon Oil & Fats Co., Ltd. “Blemmer PME series”, “Blemmer AME series” (trade name) manufactured by Kyoeisha Chemical Co., Ltd.

  In the silicone-based graft copolymer, the structural unit (II) forms a trunk. Examples of the ethylenically unsaturated carboxylic acid (II) include ethylene that is copolymerizable with (meth) acrylic acid ester (I) and silicone-based macromonomer (III) and has one or more carboxyl groups. Unsaturated carboxylic acid can be used. Examples of the ethylenically unsaturated carboxylic acid include (meth) acrylic acid, ethacrylic acid, propylacrylic acid, isopropylacrylic acid, crotonic acid, itaconic acid, fumaric acid, citraconic acid, maleic acid, maleic anhydride, ω- Various acid anhydride adducts of carboxypolycaprolactone mono (meth) acrylate, ω-carboxypolyalkylene glycol mono (meth) acrylate, and ω-hydroxymono (meth) acrylate are mentioned, among others, availability, silicone macromonomer From the viewpoint of copolymerization with (III), acrylic acid and methacrylic acid are more preferable, and methacrylic acid is more preferable. These may be used alone or in combination.

  The silicone-based macromonomer (III) that introduces a branch portion of the silicone-based graft copolymer is a silicone-based polymer having a polymerizable unsaturated group at one end.

The silicone macromonomer (III) is a chain-like silicone polymer having releasability and may be a silicone macromonomer having a polymerizable unsaturated group (in particular, a polymerizable double bond) at one end thereof. Although it will not specifically limit, the silicone type macromonomer shown by the following general formula (IIIa) is more preferable from a peelable point.
D—O— [Si (R ⁴ ) (R ⁵ ) —O] _p —X (IIIa)
(Wherein D is a group having a polymerizable unsaturated bond at the terminal (polymerizable unsaturated group), R ⁴ and R ⁵ are each independently a monovalent aliphatic hydrocarbon group or a monovalent aromatic hydrocarbon. Group or monovalent halogenated hydrocarbon group, X is a substituent having no radical polymerizability, and p is the degree of polymerization.)

In the general formula (IIIa), R ⁴ and R ⁵ are preferably an alkyl group having 1 to 3 carbon atoms or a phenyl group, and more preferably a methyl group.

The silicone macromonomer (III) is a dimethylpolysiloxane macromonomer in which both R ⁴ and R ⁵ are methyl groups and a polymerizable unsaturated group is bonded to one end in the general formula (IIIa), diorganopolysiloxane-based macromonomer is preferably substituted by dimethyl polysiloxane portion of R ⁴ and / or R ⁵ in the macromonomer of ethyl or other alkyl and / or phenyl group, R ⁴ and R ⁵ More preferred are dimethylpolysiloxane macromonomers, all of which are methyl groups.

The polymerizable unsaturated group at one end of the silicone-based macromonomer (III) [for example, D in the above general formula (IIIa)] is (meth) acrylic acid ester (I), ethylenically unsaturated carboxylic acid (II) Although it will not specifically limit if it is a polymerizable unsaturated group copolymerizable with (meth) acryloyl from the point of copolymerization with (meth) acrylic acid ester (I) and ethylenically unsaturated carboxylic acid (II) It is preferably a group. Examples of the polymerizable unsaturated group D at one end of the silicone macromonomer include a group represented by the following general formula (IIId).
^{_{CH 2 = C (R 6)}} -COO- (CH 2) q - (O) r - (CH 2) 3 -Si (R 7) (R 8) - (IIId)
Wherein R ⁶ is a hydrogen atom or methyl group, R ⁷ and R ⁸ are alkyl groups having 1 to 4 carbon atoms, alkoxy groups having 1 to 4 carbon atoms or acetoxy groups, and q is 0 to 0 when r is 0. 2. When r is 1, it is 2, and r is 0 or 1.)

  X in the general formula (IIIa) is preferably a trialkylsilyl group, more preferably a trimethylsilyl group, a dimethylethylsilyl group, or a dimethylbutylsilyl group from the viewpoint of the chemical stability of the silicone macromonomer and graft copolymer. .

  The weight average molecular weight of the silicone-based macromonomer (III) is preferably 5,000 to 35,000, more preferably 8,000 to 30,000, and further preferably 10,000 to 20,000. By making the weight average molecular weight of silicone type macromonomer (III) into the range of 5000-35000, the peelability of the said silicone type macromonomer can be improved further. In the present invention, the weight average molecular weight (weight average molecular weight of silicone macromonomer and silicone graft copolymer) refers to a weight average molecular weight determined by gel permeation chromatography using polystyrene as a reference substance.

  As the silicone macromonomer (III), one type of silicone macromonomer may be used, or two or more types of silicone macromonomer may be used. Specific examples of the silicone-based macromonomer include, for example, “AK-5”, “AK-30”, “AK-32” (trade name) manufactured by Toagosei Co., Ltd., and “X-22-174DK” manufactured by Shin-Etsu Chemical Co., Ltd. , “X-24-8201”, “X-22-2426” (trade name).

  When the silicone-based graft copolymer has a structural unit (IV), the structural unit (IV) forms a trunk.

  Other polymerizable monomers (IV) include, for example, alkyl esters of (meth) acrylic acid, alicyclic hydrocarbon esters of (meth) acrylic acid, hydroxyalkyl esters of (meth) acrylic acid, (meth) Examples include acrylamidovinyl, (meth) acrylonitrile, aromatic vinyl compounds, sulfonic acid group-containing monomers, vinyl acetate, and N-vinylpyrrolidone. These may be used alone or in combination. Examples of the alkyl ester of (meth) acrylic acid include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and (meth) acrylate-2-ethylhexyl. Cyclohexyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate.

  The silicone-based graft copolymer used in the present invention is composed of only the three components of (meth) acrylic acid ester (I), ethylenically unsaturated carboxylic acid (salt) (II) and silicone-based macromonomer (III). It may also be included, and other polymerizable monomers may be included in the constitution.

  The silicone-based graft copolymer used in the present invention contains a carboxyl group resulting from the structural unit (II). Therefore, the solubility in water can be improved by neutralizing a part of the carboxyl group with a base. In the silicone-based graft copolymer, 50 mol% or more of all carboxyl groups are preferably neutralized, and 75 mol% or more is more preferably neutralized. Examples of the base used for neutralization include inorganic alkali agents such as alkali metal hydroxides such as potassium hydroxide and sodium hydroxide, and organic amines such as diethanolamine and triethanolamine. Of these, alkali metal hydroxides are preferred.

  The glass transition temperature of the silicone-based graft copolymer is preferably 60 to 100 ° C.

  As a method for producing a silicone-based graft copolymer, for example, a macromonomer method, an ionic polymerization method, a method by introducing a side chain by a polymer reaction, and the like are known. Among these, the macromonomer method is preferable because the degree of polymerization of the trunk and the branch can be easily adjusted and the branch can be easily connected (bonded) to the trunk. As the macromonomer method, (meth) acrylic acid ester (I), ethylenically unsaturated carboxylic acid (II), silicone-based macromonomer (III) and other polymerizable monomer (IV) as necessary, The method of copolymerizing in an organic solvent is mentioned. The copolymerization is preferably performed in a state where the carboxyl group of the ethylenically unsaturated carboxylic acid (II) is not neutralized from the viewpoint of the uniformity of polymerization.

  The silicone-based graft copolymer used in the present invention is self-crosslinked by applying it to a substrate and then drying by heating to form a resin layer having excellent mechanical strength and reduced siloxane oligomer concentration. Can do. The siloxane oligomer concentration is more preferably 1 ppm or less. The resin layer thus formed has a non-uniform phase separation structure in which the surface has a large amount of silicone component and the interface with the substrate has a small amount of silicone component. For this reason, the polyester film base material can exhibit excellent peelability due to silicone while having high adhesion.

  Further, the silicone-based graft copolymer used in the present invention does not proceed with the curing reaction unless heated. Therefore, it can be stored at room temperature for a long time.

  In addition, the silicone graft copolymer used in the present invention can be dissolved in water. Therefore, the burden on the environment can be reduced by using an aqueous solution of the silicone-based graft copolymer.

  Examples of the silicone-based graft copolymer used in the present invention include Saimak US-450 manufactured by Toagosei Co., Ltd.

  The polyester film substrate used in the present invention may have any layer structure such as a single layer, a two-kind two-layer, a two-kind three-layer, a three-kind three-layer, etc., but the surface roughness should be controlled on each side. Therefore, a multilayer is preferable.

  The peel strength of the resin layer of the release polyester film of the present invention by the measurement method described later needs to be 0.01 to 0.10 N / cm, and should be 0.01 to 0.05 N / cm. preferable. A peel strength of less than 0.01 N / cm is not preferable because the film cannot slide and be scraped off. On the other hand, when the peel strength exceeds 0.10 N / cm, the peelability is insufficient and it cannot be used as a release polyester film, which is not preferable. The peel strength can be controlled by adjusting the heating and drying temperature of the coating liquid, the thickness of the resin layer, the content of the curing agent, and the like. As the content of the curing agent increases, the peel strength can be increased. Therefore, in order to obtain a relatively high peel strength within the range of the peel strength of the present invention, it is preferable to use a curing agent. When using a hardening | curing agent, it is preferable to set it as 1-4 mass parts with respect to 100 mass parts of main agents, and it is more preferable to set it as 1-2 mass parts. The curing agent is preferably one that can react with the carboxyl group and / or hydroxyl group of the silicone-based graft copolymer. Examples of such a curing agent include isocyanate, carbodiimide, melamine, epoxy, and lactate. On the other hand, a relatively low peel strength within the range of the peel strength of the present invention can be achieved without using a curing agent.

  The static friction coefficient of the resin layer of the release polyester film of the present invention is preferably 0.50 or less, more preferably 0.40 or less, and further preferably 0.30 or less. In the present invention, the static friction coefficient can be used as an index of slipperiness, and the lower the static friction coefficient, the higher the slipperiness. In the present invention, the static friction coefficient can be appropriately adjusted by selecting the type, particle diameter, and content of the roughening substance.

  The centerline average roughness (SRa) of the resin layer of the release polyester film of the present invention is required to be 20 nm or less, preferably 10 nm or less, and more preferably 5 nm or less. When SRa is larger than 20 nm, if the roughness of the resin layer surface is transferred to the adherend surface, this impairs the flatness of the adherend surface, which is not preferable. In order to reduce the SRa of the resin layer to 20 nm or less, the layer in contact with the resin layer is preferably a resin alone, and even if a material other than a resin, for example, a roughening substance, is contained, The content is preferably 1% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.1% by mass or less. In the present invention, the SRa of the resin layer can be used as an index of flatness, and the lower the SRa of the resin layer, the higher the flatness.

  The SRa on the opposite surface of the resin layer of the release polyester film of the present invention is preferably 10 nm or more, and the ten-point average roughness (Sz) is preferably 3.0 μm or more. By increasing SRa and Sz, the slipperiness can be improved and the roll running property during the film production process can be improved. As a method for setting SRa on the opposite surface of the resin layer to 10 nm or more and a 10-point average roughness Sz to 3.0 μm or more, a roughening substance is included in the polyester resin used for the opposite surface of the resin layer. Is preferred. Examples of the roughening substance include inorganic particles such as silicon dioxide, calcium carbonate, kaolinite, titanium dioxide, and silica alumina, and organic particles such as silicone, polymethyl methacrylate, and ethyl vinylbenzene. A roughening substance may be used independently and may use 2 or more types together. The average particle diameter of the roughening material is not particularly limited, but is preferably 1.0 to 3.0 μm, and more preferably 1.5 to 2.5 μm. Two or more types of roughening substances having different average particle diameters may be used in combination. The surface roughness can be appropriately adjusted by selecting the type, particle diameter, and content of the roughening substance.

  Although the thickness of the release polyester film of this invention is not specifically limited, It is preferable that it is 20-75 micrometers. By setting the thickness to 20 to 75 μm, a film can be produced with high productivity.

  The release polyester film of the present invention is preferably stretched in at least one direction. By being stretched, the flatness and heat resistance of the film can be improved.

  The release polyester film of the present invention is excellent in flatness and releasability, and the generation of siloxane oligomers from the resin layer is reduced. Therefore, the release paper such as pressure-sensitive adhesive sheet and pressure-sensitive adhesive tape, printed wiring board, protection for touch panel The film can be suitably used as a release film for producing a ceramic capacitor.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

1. Material <Polyester resin>
Polyester resin A: Intrinsic viscosity 0.62, Tg 78 ° C., Tm 255 ° C., average particle size of contained silica 2.3 μm, content 0.08 mass%
Polyester resin B: Intrinsic viscosity 0.63, Tg 78 ° C., Tm 255 ° C., average particle diameter of contained silica 1.2 μm, content 0.03 mass%
Polyester resin C: Intrinsic viscosity 0.62, Tg 78 ° C., Tm 255 ° C., average particle diameter of silica contained 1.0 μm, content 0.17% by mass
Polyester resin D: Intrinsic viscosity 0.62, Tg 78 ° C., Tm 255 ° C., average silica particle size 3.5 μm, content 0.08% by mass
Polyester resin E: intrinsic viscosity 0.62, Tg 78 ° C., Tm 255 ° C., silica free

<Coating fluid>
・ Coating fluid a
The main agent “Symac US-450 (manufactured by Toagosei Co., Ltd., silicone-based graft copolymer, having hydroxyl group and carboxyl group, solid content concentration 30% by mass)” was purified so that the solid content concentration was 8% by mass. After dilution with water, the mixture was sufficiently stirred at room temperature to obtain a uniform coating solution.
・ Coating fluid b
The main component “Symac US-450” and the curing agent “Pionin XC-101K (Melamine aqueous solution made by Takemoto Yushi, solid content concentration 70% by mass)” are mixed so that the solid content ratio (mass ratio) becomes 100/2. Then, after diluting with pure water so that the solid content concentration becomes 8% by mass, the mixture was sufficiently stirred at room temperature to obtain a uniform coating solution.
・ Coating liquid c
X-62-2087 (manufactured by Shin-Etsu Chemical Co., Ltd., thermosetting polydimethylsiloxane, hydroxyl group-free carboxyl group) with toluene / 2-butanone (= After diluting with a 1/1 (mass ratio) solution, the mixture was sufficiently stirred at room temperature to obtain a uniform coating solution.
・ Coating fluid d
The main component “Cymac US-450” and the curing agent “Pionin XC-101K (Melamine aqueous solution made by Takemoto Yushi, solid content concentration 70% by mass)” are set so that the solid content ratio (mass ratio) becomes 100/5. After mixing and diluting with pure water so that the solid content concentration was 8% by mass, the mixture was sufficiently stirred at room temperature to obtain a uniform coating solution.

2. Evaluation method (1) Peel strength Adhesive tape 31B (tape width: 50 mm) manufactured by Nitto Denko Corporation was applied to the resin layer surface of the film and left at 70 ° C. for 20 hours under a load of 20 g / cm ² , then 23 ° C., 50% RH. Was conditioned in the atmosphere. Thereafter, the 180 ° peel strength when the pressure-sensitive adhesive tape was peeled off from the surface of the resin layer was measured for the conditioned sample using an autograph at a crosshead speed of 300 mm / min.

(2) Surface roughness SRa and Sz were measured under the following conditions using Talysurf CCI6000 manufactured by Taylor / Hobson.
Measurement length: 0.66mm x 0.66mm
Cut-off: Robust Gaussian filter, 0.25mm
Peak count level: 1.0 μm

(3) Coefficient of static friction (gradient method)
Using a slip tester AN-8 manufactured by Toyo Seiki Seisakusho, the humidity was adjusted at 23 ° C. and 50% RH for 2 hours, and then the friction coefficient of the resin layer was measured. The contact area of the slider was 85 mm × 120 mm, the load was 1000 g, the angle at which the rider began to slide and the rider started to slide was θ (°), and the static friction coefficient was calculated using the following formula. It calculated | required by the average value of the frequency | count of measurement 5 times.
Coefficient of static friction = tanθ

(4) Siloxane oligomer concentration After the polyester film on which the resin layer was formed was cut into 2 cm × 2 cm, 25 mL of chloroform was added and shaken at 150 rpm for 4 hours to completely dissolve the resin layer in the chloroform solution. The shaking solution was filtered using a membrane filter (pore size 0.45 μm), and the filtrate was filtered using a Agilent gas chromatography apparatus Agilent 6890N equipped with a mass spectrometer. Concentration was measured.

Example 1
Polyester resin A ((i) layer) melted at 280 ° C. and fed into an extruder with a screw diameter of 65 mm, and Polyester resin E ((ii) layer) melted at 280 ° C. and fed into an extruder with a screw diameter of 90 mm Were combined in a feed block, adjusted to a total thickness of 380 μm and extruded from a multilayer die into a film, and then rapidly cooled and solidified to obtain an unstretched bilayer film.
The obtained unstretched bilayer film was stretched 3.5 times with a roll type longitudinal stretcher under the condition of 88 ° C., and (ii) the corona treatment was applied to the surface layer of the layer. Thereafter, (ii) the coating liquid a is coated on the surface of the layer with a Mayer bar so that the thickness of the heat-treated resin layer is 0.19 μm, and the sheet end is continuously stretched by a flat type stretching machine. And was stretched 4.5 times at 120 ° C. Thereafter, the film was heat-treated at 230 ° C. for 7 seconds with a lateral relaxation rate of 3% to obtain a film having a thickness of 25 μm.

Examples 2 to 8, Comparative Examples 1 and 3
(I) Layer, (ii) Resin used for layer, type of silica, type of coating liquid used for resin layer, treatment temperature, thickness as shown in Table 1 except that it was changed as shown in Table 1. Then, corona treatment, in-line coating, stretching, thermal relaxation, and heat treatment were performed to obtain a film having a thickness of 25 μm.

Example 9
Polyester resin B, which was put into an extruder with a screw diameter of 65 mm and melted at 280 ° C., was adjusted to a thickness of 380 μm and extruded from a T-die into a film, and then rapidly cooled and solidified to obtain an unstretched monolayer film It was.
The obtained unstretched monolayer film was subjected to corona treatment, in-line coating, stretching, thermal relaxation, and heat treatment in the same manner as in Example 1 to obtain a film having a thickness of 25 μm.

Example 10 and Comparative Example 5
Except for changing the polyester resin to be used, in the same manner as in Example 9, preparation of an unstretched film, corona treatment, in-line coating, stretching, thermal relaxation, and heat treatment were performed to obtain a film having a thickness of 25 μm.

Comparative Example 2
During the production of the release polyester film, an uncoated polyester film was obtained by performing the same operations as in Examples 6 and 7, except that the coating solution a was not subjected to in-line coating by corona treatment.
On the surface of the obtained uncoated polyester film (ii), No. The coating liquid a was post-coated using a 2 Meyer bar and heated and dried at 120 ° C. for 20 seconds to obtain a film having a thickness of 25 μm.

Comparative Example 4
During the production of the release polyester film, an uncoated polyester film was obtained by performing the same operations as in Examples 1 to 4 and 8, except that the coating liquid a was not subjected to in-line coating by corona treatment.
On the surface of the obtained uncoated polyester film (ii), No. The coating liquid c was post-coated using a 2 Meyer bar and heat-dried at 150 ° C. for 20 seconds to obtain a film having a thickness of 25 μm.

  Tables 1 and 2 show the film configuration and the characteristic values of the resin layer.

The release polyester films of Examples 1 to 10 are coated with an acrylic polymer as a main chain, a silicone polymer as a side chain, and a silicone graft copolymer having a carboxyl group and a hydroxyl group as main components. Since it was a film in which a resin layer was formed using a working solution, the peel strength of the resin layer was 0.01 to 0.10 N / cm, SRa was 20 nm or less, and the amount of siloxane oligomer was small.
Since the release polyester films of Examples 1 to 3 and 5 to 10 were within the most preferable range defined by the present invention in the thickness of the resin layer, the amount of siloxane oligomer in the resin layer was slightly higher than in Example 4. There were few.
Moreover, when Example 2, 8 and the comparative example 3 are compared, it turns out that peeling strength can be adjusted with content of a hardening | curing agent.
Moreover, the release polyester films of Examples 1 to 9 had a high surface roughness on the surface opposite to the resin layer and a low coefficient of static friction. Therefore, the roll running property during the film production process was excellent.

Since the polyester film of Comparative Example 1 had a thin resin layer, the peel strength of the resin layer was high.
The polyester film of Comparative Example 2 had poor peelability because the heat drying temperature when forming the resin layer was low.
Since the polyester film of Comparative Example 3 used a large amount of curing agent, the peelability was poor.
Since the polyester film of Comparative Example 4 did not use the acrylic silicone graft copolymer defined in the present invention, the amount of siloxane oligomer was large.
Since the polyester film of Comparative Example 5 contained a large amount of roughening material in the layer in contact with the resin layer, the SRa of the resin layer was large.

Claims (6)

A release film having a resin layer formed on at least one surface of a polyester film, wherein the resin layer has an acrylic polymer as a main chain, a silicone polymer as a side chain, and has a carboxyl group and a hydroxyl group The main component is a silicone-based graft copolymer, the peel strength of the resin layer is 0.01 to 0.10 N / cm, and the center line average roughness (SRa) of the resin layer is 20 nm or less. Release polyester film. 2. The release polyester film according to claim 1, wherein the resin layer does not contain a curing agent. The release polyester film according to claim 1 or 2, wherein the amount of siloxane oligomer in the resin layer is 1 ppm or less. The release polyester film according to claim 1, wherein the polyester film is a multilayer film. A temperature of 180 ° C. or higher is applied to a polyester film after applying a coating liquid containing a silicone-based graft copolymer having an acrylic polymer as a main chain and a silicone polymer as a side chain and having a carboxyl group and a hydroxyl group. A method for producing a release polyester film according to any one of claims 1 to 4, further comprising a step of drying by heating. 6. The method for producing a release polyester film according to claim 5, wherein a coating liquid whose solvent is water is used.