JP2023135935A - release film - Google Patents

Abstract

To provide a heavy release film that can suppress heavy peeling over time even after applying an adhesive layer, and is suitable for various optical applications such as the case that requires releasability in a heavy peeling area and the situation that dislikes heavy peeling over time after adhesive bonding.SOLUTION: There is provided a release film in which a release layer is laminated on at least one side of a polyester film, in which the release layer is a cured product of a release layer composition containing a curable silicone resin (A) (excluding MQ resin (B)), MQ resin (B), and a catalyst, where the curable silicone resin satisfies the following (1) and (2) simultaneously: (1) it contains polyorganosiloxane containing an alkenyl group having 6 to 10 carbon atoms in a molecule; and (2) 2.5≤SiH group/alkenyl group (molar ratio)≤9.SELECTED DRAWING: None

Description

The present invention relates to a release film, and more particularly, to a release film useful for protecting an adhesive layer.

Conventionally, release films based on polyester films have excellent properties such as mechanical strength, dimensional stability, chemical resistance, and optical properties, and are excellent in cost performance, so they are used for various purposes. . For example, for manufacturing polarizing plates for liquid crystal displays (hereinafter abbreviated as LCD), for manufacturing retardation plates, for manufacturing components of plasma display panels (hereinafter abbreviated as PDP), and for organic electroluminescence (hereinafter abbreviated as organic EL). It is used for various optical applications, such as for manufacturing component parts, various display component parts, etc.

In recent years, with the rapid advancement of the IT (Information Technology) field, display materials such as LCDs, PDPs, and organic ELs have made remarkable progress.As requirements for quality, such as flexibility, have become more sophisticated, adhesives used for bonding materials have increased. specifications that satisfy a wide variety of characteristics are also required. Therefore, the release film used to protect the adhesive layer is also required to have properties that provide release force suitable for a wide variety of purposes. In order to meet these demands, it is assumed that the addition-type silicone resin and the release film will be bonded with an adhesive for a long period of time, so that variations in peeling over time after the adhesive layer is applied are minimized. It is also necessary to In particular, since heavy peeling over time causes various problems due to poor peeling, it is required to suppress heavy peeling over time.

In order to meet such demands, a method is known in which a release force control agent is added to an additive silicone resin as a release film to adjust the release force. In particular, when increasing the peeling force, a method of adding MQ resin is used. In addition-type silicone resins, a release layer crosslinked in a three-dimensional network is formed through the addition polymerization reaction of SiH groups and alkenyl groups, but residual unreacted components (SiH groups or alkenyl groups) remain in the release layer. Because the adhesive reacts with the components in the adhesive, it tends to become heavily peeled over time after the adhesive layer is applied. In particular, when the peeling force is heavy, heavy peeling is noticeable, so it is necessary to suppress heavy peeling over time after application of the adhesive layer.

For example, the process of using a base material-less double-sided pressure-sensitive adhesive sheet is given as an example. The base material-less double-sided pressure-sensitive adhesive sheet is provided with a structure sandwiched between two release films having different peeling strengths. As the two release films, one is used with a light release force, and the other is a release film with a higher release force than the above-mentioned release film. As for the peeling procedure, the release film with light peeling force is peeled off, and then the release film with heavy peeling force is peeled off. However, if the peeling force ratio of these two release films is not appropriate, the adhesive layer The adhesive layer may be deformed or broken, the adhesive layer may be transferred to the release film, and the adhesive layer may float between the other release film and the other release film, resulting in a so-called "breakup". . In addition, in recent years, films have become thinner for the purpose of improving visibility and reducing costs, making it easier for "break-ups" to become apparent. In particular, a release film with a heavy peeling force often contributes to adjusting the ratio, and it is necessary to have the property of suppressing peeling fluctuations over time (heavy peeling) while satisfying the heavy peeling force range. be done.

Therefore, as a measure to improve this, a release film is disclosed that is subjected to an aging treatment at a temperature of 70° C. or more and less than 100° C. for 24 hours or more (Patent Document 1). Furthermore, as another improvement measure, a release film is disclosed that has a release layer made of a cured product formed from a curable silicone resin and inert particles on at least one side of a polyester film (Patent Documents 2 and 3). ).

Japanese Patent Application Publication No. 2016-185674 Japanese Patent Application Publication No. 6-246880 WO2018/079596 publication

The present invention was made in view of the above circumstances, and the problem to be solved is to be able to suppress heavy peeling over time even after application of the adhesive layer, and to suppress mold release properties in the heavy peeling area in various optical applications. It is an object of the present invention to provide a heavy release type film suitable for applications in which heavy peeling over time after bonding with an adhesive is undesirable.

In view of the above-mentioned circumstances, the present inventors have made extensive studies and have found that the above-mentioned problems can be solved by using a release film having a specific configuration, and have completed the present invention. That is, the present invention provides the following [1] to [8].

[1] A release film in which a release layer is laminated on at least one side of a polyester film, the release layer being a curable silicone resin (A) that simultaneously satisfies (1) and (2) below (provided that MQ (excluding resin (B)), MQ resin (B), and a catalyst.
(1) Contains polyorganosiloxane containing an alkenyl group having 6 to 10 carbon atoms in the molecule (2) 2.5≦SiH group/alkenyl group (molar ratio)≦9
[2] The release film according to [1] above, wherein the release layer and acrylic pressure-sensitive adhesive have a rate of heavy peeling over time of 100% or less, as evaluated by the following method.
<Evaluation method>
An acrylic pressure-sensitive adhesive having the following pressure-sensitive adhesive composition is applied to the surface of the release layer of the release film in a coating amount (before drying) of 2 mil, and heat treated at 150° C. for 3 minutes. The adhesive surface after heat treatment is bonded to an untreated biaxially stretched polyethylene terephthalate film (thickness 100 μm) using a rubber roller with a load of 2 kg to produce a release film with adhesive. The peeling force is 180° peeling at a tensile speed of 300 mm/min.
Next, the peeling force after leaving the bonded release film with adhesive at room temperature for 1 day is (F1), and the peeling force after leaving it in a hot air circulation oven at 80°C for 4 days is (F1). F2), and the rate of change in peeling force is determined by the following formula.
Heavy peeling rate over time %=(F2-F1)/F1×100
<Adhesive composition>
Base agent: AT352 (manufactured by Siden Chemical Co., Ltd.) 100 parts by mass Curing agent: AL (manufactured by Siden Chemical Co., Ltd.) 0.25 parts by mass Additive: X-301-375SK (manufactured by Saiden Chemical Co., Ltd.) 0.25 Parts by mass Additive: X-301-352S (manufactured by Saiden Chemical Co., Ltd.) 0.4 parts by mass Toluene 40 parts by mass [3] The above [1] comprising a cured resin layer between the polyester film and the release layer. ] or the release film according to [2].
[4] The release film according to any one of [1] to [3] above, comprising a cured resin layer on the surface of the film opposite to the surface on which the release layer is provided.
[5] A film laminate in which another release film is bonded to the release surface of the release film according to any one of [1] to [4] above via an adhesive layer.
[6] The film laminate according to [5] above, wherein the adhesive layer is OCA.
[7] The film laminate according to any one of [5] or [6] above, in which the other release film is peeled off and then the exposed adhesive layer surface and the optical member are bonded together. How to use.
[8] The method of using the film laminate according to [7] above, wherein the optical member is a polarizing plate.

According to the above structure of the present invention, it is possible to suppress heavy peeling over time even after applying the adhesive layer, and when releasability in the heavy peeling area is required in various optical applications, and after bonding the adhesive. It is possible to provide a heavy release type film suitable for applications where heavy release over time is undesirable.

Hereinafter, an example of an embodiment of the present invention will be described in detail. However, the present invention is not limited to the embodiments described below, and can be implemented with arbitrary modifications within the scope of the gist of the present invention.

<Polyester film>
The polyester film constituting the release film of the present invention may have a single-layer structure or a multi-layer structure, and in addition to the two-layer or three-layer structure, four or more layers may be used as long as the gist of the present invention is not exceeded. It may have multiple layers, and is not particularly limited. In the present invention, a polyester film having at least three layers is preferred. Further, as the polyester film, a biaxially stretched polyester film is preferable from the viewpoint of thinning and dimensional stability.

The polyester used in the present invention may be a homopolyester or a copolyester. When consisting of a homopolyester, one obtained by polycondensing an aromatic dicarboxylic acid and an aliphatic glycol is preferable. Examples of aromatic dicarboxylic acids include terephthalic acid and 2,6-naphthalene dicarboxylic acid, and examples of aliphatic glycols include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Typical polyesters include polyethylene terephthalate and the like.
On the other hand, the dicarboxylic acid component of the copolymerized polyester includes isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, oxycarboxylic acid (for example, p-oxybenzoic acid, etc.), etc. Examples of the glycol component include one or more of ethylene glycol, diethylene glycol, propylene glycol, butanediol, 4-cyclohexanedimethanol, neopentyl glycol, and the like.

The polyester polymerization catalyst is not particularly limited, and conventionally known compounds can be used, such as antimony compounds, titanium compounds, germanium compounds, manganese compounds, aluminum compounds, magnesium compounds, calcium compounds, etc.

In order to suppress the amount of oligomer components precipitated, the film may be manufactured using polyester with a low content of oligomer components as a raw material. As a method for producing polyester with a low content of oligomer components, various known methods can be used, such as a method in which solid phase polymerization is performed after producing polyester.

Further, the amount of precipitation of the oligomer component may be suppressed by forming the polyester film to have a structure of three or more layers, and making the outermost layer of the polyester film a layer using a polyester raw material with a low content of the oligomer component. Further, polyester may be obtained by performing esterification or transesterification reaction and then further increasing the reaction temperature and performing melt polycondensation under reduced pressure.

It is also possible to incorporate an ultraviolet absorber into the polyester film in order to improve the weather resistance of the film and prevent deterioration of adherends (for example, liquid crystal). The ultraviolet absorber is a compound that absorbs ultraviolet rays and is not particularly limited as long as it can withstand the heat added during the polyester film manufacturing process.

As the ultraviolet absorber, there are organic ultraviolet absorbers and inorganic ultraviolet absorbers, and organic ultraviolet absorbers are preferable from the viewpoint of transparency. Examples of organic ultraviolet absorbers include, but are not limited to, cyclic iminoesters, benzotriazoles, benzophenones, and the like. From the viewpoint of durability, cyclic iminoester type and benzotriazole type are more preferable. It is also possible to use two or more types of ultraviolet absorbers in combination.

It is also possible to incorporate particles into the polyester layer of the polyester film for the main purpose of imparting slipperiness and preventing scratches in each step. When blending particles, the types of particles to be blended are not particularly limited as long as they can impart slipperiness; specific examples include silica, calcium carbonate, magnesium carbonate, barium carbonate, and sulfuric acid. Examples include inorganic particles such as calcium, calcium phosphate, magnesium phosphate, kaolin, aluminum oxide, zirconium oxide, and titanium oxide, and organic particles such as acrylic resin, styrene resin, urea resin, phenol resin, epoxy resin, and benzoguanamine resin. Furthermore, precipitated particles in which a part of a metal compound such as a catalyst is precipitated and finely dispersed during the polyester manufacturing process can also be used. Among these, silica particles and calcium carbonate particles are particularly preferred because they are effective even in small amounts.

Further, the average particle diameter of the particles is preferably 5.0 μm or less, more preferably in the range of 0.01 to 3.0 μm. When the average particle size is 5.0 μm or less, the surface roughness of the film will not become too rough, and problems will not occur in various post-processing processes. In addition, by using it within the above range, haze can be kept low and transparency can be easily ensured as a whole film.

Furthermore, the particle content in the polyester layer is preferably less than 5% by weight, more preferably in the range from 0.0003 to 3% by weight, even more preferably in the range from 0.0005 to 1% by weight. If there are no particles or a small number of particles, the film will have high transparency and a good film, but the slipperiness may be insufficient. In some cases, it may be necessary to take measures such as improving the In addition, if the particle content is below the above upper limit, the haze will not increase and sufficient transparency will be obtained, so for example, the difficulty of inspecting for defects such as foreign objects will increase during various inspections. Nor.
In addition, in the case of a structure of three or more layers, the content of particles in the polyester layers on both surfaces may be within the above range.

There are no particular limitations on the shape of the particles used, and any shape such as spherical, lumpy, rod-like, flat, etc. may be used. Furthermore, there are no particular limitations on its hardness, specific gravity, color, etc. Two or more types of these series of particles may be used in combination as necessary.

The method of adding particles into the polyester layer is not particularly limited, and any conventionally known method may be employed. For example, it can be added at any stage of producing the polyester constituting each layer, but it is preferably added after the esterification or transesterification reaction is completed.

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

The thickness of the polyester film constituting the release film of the present invention is not particularly limited as long as it can be formed into a film, but it is usually 5 to 250 μm, more preferably 15 to 200 μm, and even more preferably It is 20 to 188 μm, more preferably 38 to 125 μm.

Regarding the polyester film constituting the release film of the present invention, the initial film haze is preferably 5.0% or less. When the initial film haze is 5.0% or less, visibility is good, and it is suitable for applications that require high visibility, such as touch panels.

In the present invention, the polyester film can be formed by any commonly known film forming method, and is not particularly limited.
For example, when producing a biaxially oriented polyester film, the polyester raw material described above is first melted and extruded from a die using an extruder, and the molten sheet is cooled and solidified with a cooling roll to obtain an 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 rotating cooling drum, and an electrostatic application adhesion method or a liquid application adhesion method is preferably employed. Next, the obtained unstretched sheet is stretched in one direction using a roll or tenter type stretching machine. The stretching temperature is usually 70 to 120°C, preferably 80 to 110°C, and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, the film is stretched in a direction perpendicular to the first-stage stretching direction, usually at 70 to 170°C, and at a stretching ratio of usually 2.5 to 7 times, preferably 3.0 to 6 times. Subsequently, heat treatment is performed at a temperature of 180 to 270° C. under tension or relaxation within 30% to obtain a biaxially oriented film. In the above-mentioned stretching, a method of stretching in one direction in two or more stages can also be adopted. In that case, it is preferable to carry out the stretching so that the final stretching ratios in both directions fall within the above ranges.

Moreover, a simultaneous biaxial stretching method can also be employed for manufacturing the polyester film. The simultaneous biaxial stretching method is a method in which the above-mentioned unstretched sheet is stretched and oriented simultaneously in the machine direction and the width direction under temperature control, usually at 70 to 120°C, preferably 80 to 110°C, and the stretching ratio is is usually 4 to 50 times, preferably 7 to 35 times, more preferably 10 to 25 times in area magnification. Subsequently, heat treatment is performed at a temperature of 170 to 270° C. under tension or relaxation within 30% to obtain a stretched oriented film. Regarding the simultaneous biaxial stretching apparatus that employs the above-mentioned stretching method, conventionally known stretching methods such as a screw method, a pantograph method, and a linear drive method can be employed.

<Release layer>
The formation of the release layer in the present invention will be explained below.
The release layer constituting the release film in the present invention refers to a layer having release properties, and specifically, a curable silicone resin (A) that simultaneously satisfies the following (1) and (2); This is a cured product of a release layer composition containing MQ resin (B) and a catalyst.
(1) Contains polyorganosiloxane containing an alkenyl group having 6 to 10 carbon atoms in the molecule (2) 2.5≦SiH group/alkenyl group (molar ratio)≦9

The release layer constituting the release film in the present invention may be provided on the polyester film during the film manufacturing process such as the above-mentioned coating/stretching method (in-line coating), or it may be applied outside the system onto the film once manufactured. So-called off-line coating may be employed, or any method may be employed. The coating/stretching method (in-line coating) is not limited to the following, but for example, in sequential biaxial stretching, the coating treatment may be applied after the first stage of stretching is completed and before the second stage of stretching. can. In off-line coating, for example, it is common for the aforementioned composition to be once blended as a solvent composition such as toluene or toluene/MEK, and then provided on a polyester film, which is also preferred in the present invention.

The curable silicone resin (A) may be a resin whose main component is a curable silicone resin, or may be a modified silicone obtained by graft polymerization with an organic resin such as a urethane resin, an epoxy resin, or an alkyd resin. good.

From the viewpoint of productivity, the type of curable silicone resin (A) may be any type that can form a coating film through an addition reaction, such as an addition type, an ultraviolet curable type, an electron beam curable type, or a non-solvent type. may also be used.

The curable silicone resin (A) used in the present invention is a polyorganosiloxane containing an alkenyl group having 6 to 10 carbon atoms in the molecule, and a polyorganosiloxane containing an SiH group in the molecule. It is preferable that the alkenyl group has at least two carbon atoms, and at least two hydrosilyl groups in each molecule. Those forming the main chain or skeleton of polyorganosiloxane include, but are not particularly limited to, polydimethylsiloxane, polydiethylseloxane, polydiphenylsiloxane, and the like.

The curable silicone resin (A) is a polyorganosiloxane containing an alkenyl group having 6 to 10 carbon atoms and an SiH group in the molecule, and is exemplified by those represented by the following general formula (1).
R _3-a X _a SiO-(RXSiO)m-(R ₂ SiO)n-SiX _a R _3-a ...(1)

In the general formula (1), R is a monovalent hydrocarbon group having 1 to 10 carbon atoms, and X is an alkenyl group-containing organic group. a is an integer from 0 to 3, preferably 1, m is 0 or more, but when a = 0, m is 2 or more, and m and n are numbers that each satisfy 100≦m+n≦20000. Also, the above formula does not mean a block copolymer. Specific examples of R include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, cycloalkyl groups such as cyclohexyl group, aryl groups such as phenyl group and tolyl group, but especially methyl group, A phenyl group is preferred. X is an alkenyl group-containing organic group preferably having 6 to 10 carbon atoms, and examples of the alkenyl group include vinyl group, allyl group, hexenyl group, octenyl group, acryloylpropyl group, acryloylmethyl group, and methacryloylpropyl group. group, cyclohexenylethyl group, vinyloxypropyl group, etc., with hexenyl group being particularly preferred.

Polyorganosiloxanes containing SiH groups include organohydrogenpolysiloxanes having at least two, preferably three or more hydrogen atoms bonded to silicon atoms in one molecule, and are linear, branched, or cyclic. etc. can be used. Examples include, but are not limited to, compounds represented by the following general formula (2).
H _b R ¹ _(3-b) SiO-(HR ¹ SiO)x-(R ¹ ₂ SiO)y-SiR ¹ _(3-b) H _b ...(2)

In the general formula (2), R ¹ is a monovalent hydrocarbon group having 1 to 6 carbon atoms and containing no aliphatic unsaturated bond. b is an integer from 0 to 3, and x and y are each integers. Specific examples include methylhydrogenpolysiloxane with trimethylsiloxy groups blocked at both molecular chain ends, dimethylsiloxane/methylhydrogensiloxane copolymer with trimethylsiloxy groups blocked on both molecular chain ends, and methyl blocked with dimethylhydrogensiloxy groups at both molecular chain ends. Examples include hydrogen polysiloxane and dimethyl siloxane/methyl hydrogen siloxane copolymer with dimethyl hydrogen siloxy groups endblocked at both molecular chain ends.

In the curable silicone resin (A) used in the present invention, the molar ratio of SiH groups to alkenyl groups is in the range of 2.5 to 9.0, preferably 3.0 to 7.0, more preferably 3. It is 0 to 5.0. When it is less than 2.5, many unreacted alkenyl groups remain in the release layer, which may cause heavy peeling over time. On the other hand, if it is larger than 9.0, many unreacted SiH groups remain in the release layer, which may cause heavy peeling over time.

Examples of specific commercially available curable silicone resins (A) include KS-774, KS-775, KS-778, KS-779H, KS-847H, and KS manufactured by Shin-Etsu Chemical Co., Ltd. -856, X-62-2422, X-62-2461, X-62-1387, X-62-5039, X-62-5040, KNS-3051, -1574A/B, X-62-7052, X-62-7028A/B, X-62-7619, X-62-7213, X-41-3035, as manufactured by Momentive Performance Materials, YSR-3022, TPR-6700, TPR-6720, TPR-6721, TPR6500, TPR6501, UV9300, UV9425, XS56-A2775, XS56-A2982, UV9430, TPR6600, TPR6604, TPR6605, manufactured by Dow Corning Toray Co., Ltd. As, SRX357, SRX211 , SD7220, SD7292, LTC750A, LTC760A, LTC303E, LTC856, LTC851, LTC762, LTC761, LTC310, SP7259, BY24-468C, SP7248S, BY24-452, DKQ3-202, DKQ3 -203, DKQ3-204, DKQ3-205, DKQ3 -210, DEHESIVE 636, 919, 920, 921, 924, and 929 of the DEHESIVE series manufactured by Asahi Kasei Wacker Silicone Co., Ltd. are exemplified.

MQ resin (B) contains a siloxane unit represented by an M unit [R ₃ SiO _1/2 (in the formula, R is a monovalent hydrocarbon group)] and a siloxane unit represented by a Q unit [SiO _4/2 ]. It is silicone resin. The MQ resin may be used alone or in combination of two or more, and includes D units [R ₂ SiO _2/2 (in the formula, R is a monovalent hydrocarbon)] and T units [RSiO _3/2 (in the formula, R is a monovalent hydrocarbon)]. , R is a monovalent hydrocarbon)]. Furthermore, it is preferable that the functional groups contained in the molecule include neither alkenyl groups nor SiH groups. If the MQ resin contains either alkenyl groups or SiH groups, unreacted components (SiH groups or alkenyl groups) remaining in the release layer tend to increase, and heavy peeling tends to occur.

The ratio of M units to Q units in the MQ resin (B) is preferably M units:Q units (molar ratio), 0.1:1.0 to 1.0:1.0, more preferably is 0.7:1.0 to 1.0:1.0. When the M unit (molar ratio) is less than 0.1, the crosslinking density decreases and the peeling force may not be sufficiently strong. On the other hand, if the Q unit (molar ratio) is larger than 1.0, the coating film may become too hard and brittle.

Examples of specific commercial products of MQ resin (B) include KS-3800, X-92-183 manufactured by Shin-Etsu Chemical Co., Ltd., SD7292 manufactured by Dow Corning Toray Co., Ltd. Examples include BY24-843 and BY24-4980.

The mass ratio ((B)/(A)) of curable silicone resin (A) and MQ resin (B) is preferably in the range of 0.01 to 1.5, more preferably 0.05 to 1. More preferably, it is 0. When (B)/(A) is 0.01 or more, the peeling force can be sufficiently increased. On the other hand, when (B)/(A) is 1.5 or less, poor appearance of the release layer due to poor film-growing properties of the MQ resin does not occur.

The catalyst used in the release layer of the present invention is preferably a platinum-based catalyst that promotes addition-type reactions. Therefore, it is preferable that the silicone resin composition further contains a platinum-based catalyst. This component includes platinum-based compounds such as chloroplatinic acid, alcoholic solution of chloroplatinic acid, complexes of chloroplatinic acid and olefins, complexes of chloroplatinic acid and alkenylsiloxane, platinum black, platinum-supported silica, and platinum-supported activated carbon. is exemplified. The content of the platinum catalyst in the release layer is preferably in the range of 0.01 to 10.0% by mass, preferably 0.01 to 5.0% by mass. If the platinum-based catalyst content in the release layer is less than 0.01% by mass, the reaction is slow and curing is likely to be insufficient, and if it is more than 10.0% by mass, the pot life of the solvent composition may be shortened.

In the release layer constituting the release film, an organic silicon compound may be used in combination in order to improve the adhesion of the coating between the release layer and the polyester film. It is preferable to use together an organic silicon compound.
Si(X) _f (Y) _g (R ₂ ) _h ...(3)
(In the above formula (3), 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, Y is a hydrolyzable group, and R ₂ is a monovalent hydrocarbon group having 1 to 10 carbon atoms, f is an integer of 1 or 2, g is an integer of 2 or 3, h is an integer of 0 or 1, and f+g+h=4.)

As the organosilicon compound represented by the general formula (3), one having two or three hydrolyzable groups Y capable of forming a siloxane bond through hydrolysis and condensation reaction can be used.

In general formula (3), examples of the hydrolyzable group Y include the following. That is, they include methoxy group, ethoxy group, butoxy group, isopropenoxy group, acetoxy group, butanoxime group, and amino group. These hydrolyzable groups may be used alone or in combination. It is particularly preferable to use a methoxy group or an ethoxy group because it can impart good storage stability to the coating material and has appropriate hydrolyzability.

In the general formula (3), the monovalent hydrocarbon group R ₂ has 1 to 10 carbon atoms, with methyl, ethyl, and propyl groups being particularly preferred.

Specific examples of organosilicon compounds contained in the release layer include vinyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, and β-(3,4-epoxycyclohexyl). ) Ethyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, 5-hexenyltrimethoxysilane, p-styryl Examples include trimethoxysilane, trifluoropropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, and γ-glycidoxypropylmethyldiisopropenoxysilane.

The content of the organosilicon compound in the release layer is more preferably 0.5 to 5.0 parts by mass, and even more preferably 0.5 to 2.0 parts by mass per 100 parts by mass of the curable silicone resin. Part by mass. If the range is 0.5 parts by mass or more, desired adhesion can be ensured, while if it is 5.0 parts by mass or less, the adhesion to the other resin layer to be bonded will not be too strong. , it can be easily peeled off in situations where it is necessary to peel it off.

Furthermore, within the scope of the present invention, the release layer may contain surfactants, antifoaming agents, coating properties improvers, thickeners, inorganic/organic particles, organic lubricants, electrostatic charges, etc. as necessary. It may contain inhibitors, conductive agents, ultraviolet absorbers, antioxidants, blowing agents, dyes, pigments, and the like.

In the present invention, methods for providing a release layer on a polyester film include, for example, air doctor coating, blade coating, rod coating, bar coating, knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, and gravure coating. Conventionally known coating methods such as kiss roll coating, cast coating, spray coating, curtain coating, calendar coating, and extrusion coating can be used.

The drying and curing conditions when forming a mold release layer on a polyester film are not particularly limited. For example, when a mold release layer is provided by off-line coating, the drying and curing conditions are usually 80° C. or higher for 10 seconds or more, preferably The heat treatment is preferably carried out at 100 to 200°C for 3 to 40 seconds, more preferably at 120 to 180°C for 3 to 40 seconds.

On the other hand, when a mold release layer is provided by in-line coating, heat treatment is usually carried out at 70 to 270°C for 3 to 200 seconds, more preferably at 100 to 250°C for 10 to 100 seconds.

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

The thickness of the delamination is usually 0.005 μm or more and 1.0 μm or less, preferably 0.01 μm or more and 0.5 μm or less, more preferably 0.05 μm or more and 0.5 μm or less, and even more preferably 0.05 μm or more and 0.2 μm or less. It is. When it is 0.005 μm or more, coating properties are excellent and a uniform coating film can be stably obtained. On the other hand, if it is 1.0 μm or less, the coating film adhesion and curability of the release layer itself will not deteriorate.

The peeling force of the release layer is preferably 15 to 500 mN/cm, more preferably 15 to 300 mN/cm, even more preferably 15 to 200 mN/cm, even more preferably 15 to 150 mN/cm. When it is 500 mN/cm or less, peeling from the adherend can be performed smoothly.

In the release film of the present invention, in order to suppress heavy peeling over time after application of the adhesive layer, the rate of heavy peeling over time between the release layer and the acrylic adhesive evaluated by the following method is 100. % or less. More preferably it is 60% or less. When the rate of heavy peeling over time is 100% or less, when the adhesive layer and the release layer of the release film are left together for a long period of time, the fluctuation in peeling over time is small, and it is not necessary to peel it off. In some situations, problems such as difficulty in peeling do not occur.

<Evaluation method>
An acrylic pressure-sensitive adhesive having the following pressure-sensitive adhesive composition is applied to the surface of the release layer of the release film in a coating amount (before drying) of 2 mil, and heat treated at 150° C. for 3 minutes. The adhesive surface after heat treatment is bonded to an untreated biaxially stretched polyethylene terephthalate film (thickness 100 μm) using a rubber roller with a load of 2 kg to produce a release film with adhesive. The peeling force is 180° peeling at a tensile speed of 300 mm/min.
Next, the peeling force after leaving the bonded release film with adhesive at room temperature for 1 day is (F1), and the peeling force after leaving it in a hot air circulation oven at 80°C for 4 days is (F1). F2), and the rate of change in peeling force is determined by the following formula.
Heavy peeling rate over time %=(F2-F1)/F1×100

<Adhesive composition>
Base agent: AT352 (manufactured by Siden Chemical Co., Ltd.) 100 parts by mass Curing agent: AL (manufactured by Siden Chemical Co., Ltd.) 0.25 parts by mass Additive: X-301-375SK (manufactured by Saiden Chemical Co., Ltd.) 0.25 Parts by mass Additive: X-301-352S (manufactured by Saiden Chemical Co., Ltd.) 0.4 parts by mass Toluene 40 parts by mass Other adhesives may be used as long as they have the same adhesive properties as the above adhesive composition. It can be measured by replacing it with the composition.

<Cured resin layer>
The release film of the present invention preferably includes a cured resin layer as an undercoat layer between the polyester film and the release layer.

The cured resin layer is used for the purpose of improving the adhesion between the polyester film and the mold release layer, and is not particularly limited as long as it has good adhesion. Antistatic performance to suppress peeling charge in the process of peeling off functional layers such as adhesive layers, and prevent the adhesion of foreign substances, and to prevent oligomer precipitation from polyester films when heat treatment is performed at high temperatures and for long periods of time. It is preferable to have oligomer sealing performance for sealing.
Note that the cured resin layer may be a single layer or may have a structure of two or more layers.

Further, the cured resin layer can be provided on the surface of the film opposite to the surface on which the release layer is provided. By providing the cured resin layer on the opposite side of the mold release layer, there are advantages such as prevention of foreign matter from outside during the manufacturing process.

As a cured resin layer having antistatic properties, for example, a polymer made by doping a compound made of thiophene or a thiophene derivative with another anionic compound, or a self-doped polymer having an anionic group in a compound made of thiophene or a thiophene derivative Alternatively, a polymer containing as a component a monomer having an alkyl sulfonate ion as a counter ion can be used.
In addition, in the present invention, even if the mold release layer is formed on the cured resin layer containing a compound made of thiophene or a thiophene derivative, this is a preferable embodiment because curing failure of the mold release layer does not occur.

Examples of polymers obtained by doping a compound consisting of thiophene or a thiophene derivative with another anionic compound, or self-doped polymers having an anionic group in a compound consisting of thiophene or a thiophene derivative include the following formula ( 4) or those obtained by polymerizing the compound of the following formula (5) in the presence of a polyanion are exemplified.

In formula (4), R ¹ and R ² each independently represent hydrogen, an aliphatic hydrocarbon group having 1 to 20 carbon atoms, an alicyclic hydrocarbon group, an aromatic hydrocarbon group, or the like.

In formula (5), n represents an integer of 1 to 4.

A specific example of the polymer includes, for example, a polymer having a constituent represented by formula (6) as a repeating unit. These homopolymers and copolymers, as well as a plurality of other components, may be copolymerized. From the viewpoint of improving antistatic properties, a homopolymer is preferable.

As for the structure of the polymer, for example, in the above formula (6), substituent R ¹ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, R ² is -O- or -NH-, and R ³ is a carbon number 1 to 6 alkylene groups or other structures that can establish the structure of formula (6), at least one of R ⁴ , R ⁵ , and R ⁶ is a hydrogen atom, and the other substituents are alkyl groups having 1 to 3 carbon atoms or a hydroxyalkyl group in which the alkyl group has 2 to 3 carbon atoms, and an alkylsulfonic acid ion in which X ^- has an alkyl group having 1 to 4 carbon atoms.

The thickness of the cured resin layer having antistatic properties is preferably 0.005 μm or more and 0.25 μm or less, more preferably 0.008 μm or more and 0.15 μm or less, and still more preferably 0.01 μm or more and 0.10 μm or less. If the thickness of the cured resin layer is within the above range, good antistatic properties can be imparted. It is assumed that unreacted substances of various compounds of the resin composition, compounds after reaction, or a mixture thereof are present in the cured resin layer.

The surface resistivity of the surface of the cured resin layer having antistatic properties is not particularly limited, but is, for example, 1×10 ¹² Ω/□ or less, preferably 1×10 ⁸ Ω/□ or less, more preferably 1×10 ⁶ Ω. /□ or less. Although there is no particular lower limit to the surface resistivity, it is preferably 1×10 ⁴ Ω/□ or more in consideration of the cost of the antistatic agent. The lower the surface resistivity of the undercoat layer, the better the antistatic property.For example, it suppresses peeling static electricity in the process of peeling off a functional layer such as an adhesive layer provided on the release layer, and prevents the adhesion of foreign substances. can be prevented.

Furthermore, for the purpose of suppressing the precipitation of oligomers, a cured resin layer having oligomer sealing properties and containing an organic compound containing one or more metal elements selected from aluminum, titanium, and zirconium may be provided.

The cured resin layer having oligomer sealing properties may be provided directly on the polyester film, or may be provided on the cured resin layer having antistatic properties.

The cured resin layer can be formed by curing a cured resin composition. The cured resin composition may include a binder, and examples of the binder include polyurethane resin, polyester resin, and acrylic resin. Therefore, when the cured resin composition has antistatic properties, it may contain, for example, a compound made of thiophene or a thiophene derivative and a binder.
Further, the cured resin composition may appropriately contain conventionally known additives that can be used in the cured resin layer.

The cured resin layer is formed by coating the film with a coating liquid of the cured resin composition, and may be formed by in-line coating within the film manufacturing process, or by coating it outside the system once it has been manufactured. A so-called off-line coating may be employed.

Examples of methods for applying coating liquid to polyester film include air doctor coating, blade coating, rod coating, bar coating, knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, and kiss roll coating. Conventionally known coating methods such as cast coating, spray coating, curtain coating, calendar coating, and extrusion coating can be used.

The drying and curing conditions when forming a cured resin layer on a polyester film are not particularly limited. For example, when a cured resin layer is provided by off-line coating, the drying and curing conditions are usually 80 to 200 ° C. for 3 to 40 seconds. Preferably, heat treatment is carried out at 100 to 180° C. for 3 to 40 seconds.
On the other hand, when providing a cured resin layer by in-line coating, heat treatment is usually carried out at 70 to 270°C for 3 to 200 seconds, more preferably at 100 to 250°C for 10 to 100 seconds.

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

When a cured resin layer is provided by in-line coating, it is preferable to manufacture a laminated polyester film by using an aqueous solution or dispersion of the above-mentioned series of compounds and applying a coating liquid onto the polyester film. Further, within a range that does not impair the gist of the present invention, the coating solution may contain a small amount of an organic solvent for the purpose of improving dispersibility in water, improving film-forming properties, etc. Only one type of organic solvent may be used, or two or more types may be used as appropriate.

The organic solvent content of the coating liquid is preferably 10% by mass or less, more preferably 5% by mass or less. Specific examples of organic solvents include aliphatic or alicyclic alcohols such as n-butyl alcohol, n-propyl alcohol, isopropyl alcohol, ethyl alcohol, and methyl alcohol; glycols such as propylene glycol, ethylene glycol, and diethylene glycol. Glycol derivatives such as n-butyl cellosolve, ethyl cellosolve, methyl cellosolve, 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; N-methylpyrrolidone Amides such as

The components in the release layer and cured resin layer can be analyzed by, for example, TOF-SIMS, ESCA, fluorescent X-ray analysis, or the like.

Regarding the release film of the present invention, a coating layer such as an adhesive layer, an antistatic layer, an oligomer precipitation prevention layer, etc. may be provided on the surface on which the release layer is not provided, as long as the gist of the present invention is not impaired.

[Film laminate]
The release film in the present invention may have a laminate structure, for example, a form in which an adhesive layer is bonded on the release layer. A preferred form is one in which the present invention is used as a first release film, an adhesive layer, and a second release film having a different peel strength are laminated in this order. A more preferred form is one in which the adhesive layer is an optical transparent adhesive sheet (OCA) and the present invention is laminated as a release film on the heavy release side.
The adhesive layer is preferably formed using a known adhesive. Examples of the adhesive include acrylic adhesives, urethane adhesives, silicone adhesives, polyester adhesives, and among these, acrylic adhesives are preferred.
A highly flexible adhesive is sometimes used as the adhesive layer so that it can conform to uneven adherends, but if the release film of the present invention is used, Also, heavy peeling can be suppressed.

[How to use film laminate]
The above-mentioned film laminate is suitable for applications where releasability in the heavy release area is required and where peeling strength is not expected to increase over time after adhesive bonding, for example, for manufacturing capacitive touch panels. and various uses for bonding through an adhesive layer, for manufacturing LCD component parts such as polarizing plates and retardation plates used in liquid crystal displays (LCDs), for manufacturing plasma display panel (PDP) component parts, and for organic electroluminescence. It is suitable for manufacturing various display components such as (organic EL) components, as well as various adhesive protection uses.
In particular, the above-mentioned film laminate may be preferably used by, for example, bonding an optical member to the exposed adhesive layer surface after peeling off the other release film. This is particularly preferred when the optical member is a polarizing plate.
As described above, the present invention relates to a release film, and specifically provides a release film useful for protecting an adhesive layer.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. Moreover, the measurement method used in the present invention is as follows.

(1) Measurement of intrinsic viscosity of polyester 1 g of polyester from which other polymer components and pigments that are incompatible with polyester have been removed was accurately weighed, and 100 ml of a mixed solvent of phenol/tetrachloroethane = 50/50 (mass ratio) was added. It was dissolved and measured at 30°C.

(2) Measurement of average particle diameter (d50: μm) 50% of the integrated (mass basis) in the equivalent spherical distribution measured using a centrifugal sedimentation type particle size distribution analyzer (Model SA-CP3 manufactured by Shimadzu Corporation) The value was taken as the average particle size.

(3) Measurement of peeling force (F) of release film After pasting one side of double-sided adhesive tape (Nitto Denko Corporation "No. 502") on the release layer surface of the sample film, it was cut into a size of 50 mm x 300 mm. The sample was cut and left at room temperature for 1 hour, and then the peeling force was measured. The peeling force was measured by using a tensile tester (Intesco Model 2001 model manufactured by Intesco Co., Ltd.) and performing 180° peeling at a tensile speed of 300 mm/min.

(4) Evaluation of the rate of heavy peeling over time (%) of the release film Apply an acrylic adhesive composed of the following adhesive composition to the release layer surface of the release film so that the coating amount (before drying) is 2 mil. It was coated on the surface using a baker type applicator and heat treated at 150°C for 3 minutes in a hot air circulation oven. The adhesive surface after heat treatment was bonded to an untreated biaxially stretched polyethylene terephthalate film (thickness 100 μm) using a rubber roller with a load of 2 kg to produce a release film with adhesive.
Next, after leaving the bonded release film with adhesive under each condition, it was cut into a size of 50 mm x 300 mm, and the peeling force (F1) after standing for 1 day at room temperature and 4 days at 80 ° C. The peeling force (F2) after standing was measured. The peeling force was determined by using a tensile tester (Intesco Model 2001 model manufactured by Intesco Co., Ltd.) and performing 180° peeling at a tensile speed of 300 mm/min. The rate was evaluated. In this evaluation, the portion of the peel force profile with the maximum peel force value recorded at the start of peeling was targeted for evaluation.
Rate of heavy peeling over time (%) = {(F2-F1)/F1}×100 (7)

<Adhesive composition>
Base agent: AT352 (manufactured by Siden Chemical Co., Ltd.) 100 parts by mass Curing agent: AL (manufactured by Siden Chemical Co., Ltd.) 0.25 parts by mass Additive: X-301-375SK (manufactured by Saiden Chemical Co., Ltd.) 0.25 Part by mass Additive: X-301-352S (manufactured by Saiden Chemical Co., Ltd.) 0.4 parts by mass Toluene 40 parts by mass

Thereafter, heavy peeling over time was evaluated based on the following criteria.
"Judgment criteria"
◎: 60% or less (practically acceptable level, particularly good)
○: 100% or less (level with no practical problems)
×: Exceeds 100% (practically problematic level)

(5) Evaluation of SiH group/alkenyl group (molar ratio) of curable silicone resin Compositional analysis of the curable silicone resin was performed using 400 MHz-NMR (Bruker Avance 400M). ¹ H-NMR measurements were carried out at a temperature of 30° C. using CDCl ₃ as a solvent and using the peak derived from the methyl group of dimethylsiloxane as a chemical shift standard. The SiH group/alkenyl group (molar ratio) was evaluated based on the integral ratio based on the methyl group.

(6) Method for measuring film thickness of cured resin layer and mold release layer The surfaces of the cured resin layer and mold release layer were dyed with RuO ₄ and embedded in epoxy resin. Thereafter, the section prepared by the ultrathin section method was stained with RuO ₄ and the cross section of the coated layer was measured using a TEM (H-7650 manufactured by Hitachi High-Technologies Corporation, acceleration voltage 100 kV).

The polyester used in the Examples and Comparative Examples was prepared as follows.
<Method for producing polyester (A)>
Using 100 parts by mass of dimethyl terephthalate and 60 parts by mass of ethylene glycol as starting materials, 0.09 parts by mass of magnesium acetate tetrahydrate as a catalyst was placed in a reactor, the reaction initiation temperature was set at 150°C, and the reaction temperature was gradually increased as methanol was distilled off. The reaction temperature was increased to 230° C. after 3 hours. After 4 hours, the transesterification reaction was substantially completed. After adding 0.04 parts by mass of ethyl acid phosphate to this reaction mixture, 0.04 parts by mass of antimony trioxide was added, and a polycondensation reaction was carried out 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 to 0.3 mmHg. After the reaction started, the reaction was stopped at a time point corresponding to an intrinsic viscosity of 0.65 by changing the stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure to obtain polyester (A) having an intrinsic viscosity of 0.65.

<Method for producing polyester (B)>
In the method for producing polyester (A), after adding 0.04 parts by mass of ethyl acid phosphate, 0.2 parts by mass of silica particles dispersed in ethylene glycol having an average particle size of 2.3 μm, and 0.04 parts by mass of antimony trioxide. Polyester (B) was obtained using the same method as that for producing polyester (A), except that part by mass was added and the polycondensation reaction was stopped at a time point corresponding to an intrinsic viscosity of 0.65. The obtained polyester (B) had an intrinsic viscosity of 0.65.

[material]
Examples of compounds constituting the release layer are as follows.
(Curing silicone resin)
A1: A curable silicone resin in which hexenyl groups are introduced into the side chains and/or ends of the main chain consisting of siloxane bonds, and Si-H groups are introduced into the side chains and/or ends of the main chain consisting of siloxane bonds. A mixture containing a crosslinking agent. SiH group/alkenyl group (molar ratio) = 6.7
A2: A curable silicone resin in which vinyl groups are introduced into the side chains and/or ends of the main chain consisting of siloxane bonds, and Si-H groups introduced into the side chains and/or ends of the main chain consisting of siloxane bonds. A mixture containing a crosslinking agent. SiH group/alkenyl group (molar ratio) = 10.0
A3: A curable silicone resin in which hexenyl groups are introduced into the side chains and/or ends of the main chain consisting of siloxane bonds, and Si-H groups are introduced into the side chains and/or ends of the main chain consisting of siloxane bonds. A mixture containing a crosslinking agent. SiH group/alkenyl group (molar ratio) = 2.1
A4: A curable silicone resin in which hexenyl groups are introduced into the side chains and/or ends of the main chain consisting of siloxane bonds, and Si-H groups are introduced into the side chains and/or ends of the main chain consisting of siloxane bonds. A mixture containing a crosslinking agent. SiH group/alkenyl group (molar ratio) = 1.1

(Peeling force control agent)
B1: KS-3800 (manufactured by Shin-Etsu Chemical)
B2: BY24-4980 (manufactured by Toray Dow Corning)
B3: X-92-128 (manufactured by Shin-Etsu Chemical)

(catalyst)
C1: PL-5000 (manufactured by Shin-Etsu Chemical)
C2: SRX212 (manufactured by Toray Dow Corning)

The above mold release agent was diluted with a MEK/toluene mixed solvent (mixing ratio: 1:1) to prepare a coating liquid with a concentration of 2.0% by mass.

Examples of compounds constituting the cured resin layer are as follows.
XA: A conductive agent made of polyethylene dioxythiophene and polystyrene sulfonic acid (Orgacon ICP1010, manufactured by Agfagewald) was neutralized with concentrated ammonia water to a pH of 9, non-volatile components; 1.2% by mass, solvent; Water XB: A compound having an average of 4 molecules of polyethylene oxide added to a polyglycerin skeleton with n=4 on average, as shown in the following formula.

XC: Urethane resin aqueous dispersion polymerized with the following composition A polyester polyol containing 282 parts by mass of terephthalic acid, 282 parts by mass of isophthalic acid, 62 parts by mass of ethylene glycol, and 250 parts by mass of neopentyl glycol was designated as (C1a). A polyester polyurethane containing 876 parts by mass of (C1a), 244 parts by mass of tolylene diisocyanate, 81 parts by mass of ethylene glycol, and 67 parts by mass of dimethylolpropionic acid is neutralized with ammonia and dispersed in water. Non-volatile components: 20% by mass, viscosity at 25°C 50 mPa·s.

XD: Nonionic surfactant with a structure having polyethylene oxide in the side chain as shown in the following formula

[Example 1]
A mixed raw material obtained by mixing polyester (A) and polyester (B) at a ratio of 90% by mass and 10% by mass, respectively, is used as the raw material for the outermost layer (surface layer), and polyester (A) is used as the raw material for the middle layer, and two extruders are used. After each was melted at 290°C, it was placed on a cooling roll set at 25°C with a layer configuration of 2 types and 3 layers (surface layer/middle layer/surface layer = 1:18:1 discharge rate). An unstretched sheet was obtained by extrusion, cooling, and solidification. Next, the film was stretched 3.4 times in the machine direction at a film temperature of 85°C using the difference in circumferential speed of the rolls, then introduced into a tenter, stretched 4.7 times in the transverse direction at 120°C, and heat-treated at 225°C. Thereafter, the film was relaxed by 2% in the transverse direction to obtain a biaxially stretched polyester film having a thickness of 38 μm.

Subsequently, a mold release agent solution No. 1 was applied onto the obtained polyester film. A release film having a release layer laminated thereon was obtained by coating by a bar coating method using 4 bars, drying at a temperature of 150° C. for 30 seconds, heat-treating, and curing.
As shown in Table 2, the deterioration of the peeling rate over time of the obtained release film was small and good, and the peeling force of the release layer was also good.

[Examples 2 to 4]
A release film was obtained in the same manner as in Example 1 except that the composition of the release agent was changed to the composition shown in Table 1 below.
As shown in Table 2, all of the release films showed good results with little deterioration in the peeling rate over time, and the results of the release force of the release layer were also good.

[Example 5]
A mixed raw material prepared by mixing polyester (A) and polyester (B) at a ratio of 90% and 10%, respectively, was used as the raw material for the outermost layer (surface layer), and polyester (A) was used as the raw material for the middle layer, and each was put into two extruders. are supplied and melted at 290°C, then coextruded and cooled on a cooling roll set at 25°C in a layer configuration of 2 types and 3 layers (surface layer/middle layer/surface layer = 1:18:1 discharge rate). It was solidified to obtain an unstretched sheet. Next, the longitudinally stretched film was stretched 3.4 times in the longitudinal direction at a film temperature of 85°C using the difference in peripheral speed of the rolls, and then a coating liquid having the following composition was applied to the longitudinally stretched film, and the film was introduced into a tenter and stretched in the transverse direction. After stretching 4.7 times at 120°C and heat-treating at 225°C, the biaxial film is 38 μm thick and has a cured resin layer that is 2% relaxed in the transverse direction and has a film thickness (after drying) of 0.05 μm. A stretched polyester film was obtained.

<Cured resin layer composition>
The coating liquid constituting the cured resin layer is as follows.
(XA)/(XB)/(XC)/(XD)=10% by mass/35% by mass/50% by mass/5% by mass

Subsequently, a mold release agent solution No. 1 was applied onto the cured resin layer of the obtained polyester film. The film was coated by a bar coating method using a 4 bar, dried at a temperature of 150° C. for 30 seconds, heat treated, and cured to obtain a release film in which a cured resin layer and a release layer were sequentially laminated.
As shown in Table 2, even when the curable resin layer was provided as an undercoat layer, the deterioration of the release rate over time of the obtained release film was small and good, and the release force of the release layer was also good. there were.

[Comparative Examples 1 to 6]
A release film was obtained in the same manner as in Example 1 except that the composition of the release agent was changed to the composition shown in Table 1 below.
As shown in Table 2, the deterioration of the peeling rate over time was large for all of the release films, and there was a concern that they would fail.

Tables 1 and 2 show the characteristics of each release film obtained in the above Examples and Comparative Examples.

The release film of the present invention has good releasability in the heavy release area and can suppress heavy release over time even after application of the adhesive layer. In addition to other uses, it can be suitably used to protect various adhesive layers, where releasability in the heavy release area is required, and where it is preferable for the release force to increase over time after bonding with the adhesive.

Claims (8)

A release film in which a release layer is laminated on at least one side of a polyester film, and the release layer is a curable silicone resin (A) that simultaneously satisfies (1) and (2) below (with the exception of MQ resin (B)). ), MQ resin (B), and a catalyst.
(1) Contains polyorganosiloxane containing an alkenyl group having 6 to 10 carbon atoms in the molecule (2) 2.5≦SiH group/alkenyl group (molar ratio)≦9 The release film according to claim 1, wherein the release layer and acrylic pressure-sensitive adhesive have a rate of heavy peeling over time of 100% or less, as evaluated by the following method.
<Evaluation method>
An acrylic pressure-sensitive adhesive having the following pressure-sensitive adhesive composition is applied to the surface of the release layer of the release film in a coating amount (before drying) of 2 mil, and heat treated at 150° C. for 3 minutes. The adhesive surface after heat treatment is bonded to an untreated biaxially stretched polyethylene terephthalate film (thickness 100 μm) using a rubber roller with a load of 2 kg to produce a release film with adhesive. The peeling force is 180° peeling at a tensile speed of 300 mm/min.
Next, the peeling force after leaving the bonded release film with adhesive at room temperature for 1 day is (F1), and the peeling force after leaving it in a hot air circulation oven at 80°C for 4 days is (F1). F2), and the rate of heavy peeling over time is determined by the following formula.
Heavy peeling rate over time %=(F2-F1)/F1×100
<Adhesive composition>
Base agent: AT352 (manufactured by Siden Chemical Co., Ltd.) 100 parts by mass Curing agent: AL (manufactured by Siden Chemical Co., Ltd.) 0.25 parts by mass Additive: X-301-375SK (manufactured by Saiden Chemical Co., Ltd.) 0.25 Part by mass Additive: X-301-352S (manufactured by Saiden Chemical Co., Ltd.) 0.4 parts by mass Toluene 40 parts by mass The release film according to claim 1 or 2, further comprising a cured resin layer between the polyester film and the release layer. The release film according to any one of claims 1 to 3, comprising a cured resin layer on the surface of the film opposite to the surface on which the release layer is provided. A film laminate obtained by laminating another release film to the release surface of the release film according to any one of claims 1 to 4 via an adhesive layer. The film laminate according to claim 5, wherein the adhesive layer is an optical transparent adhesive sheet (OCA). 7. A method of using the film laminate according to claim 5 or 6, which comprises peeling off the other release film and then bonding the exposed adhesive layer surface to an optical member. The method of using a film laminate according to claim 7, wherein the optical member is a polarizing plate.