WO2018079596A1

WO2018079596A1 - Mold release film

Info

Publication number: WO2018079596A1
Application number: PCT/JP2017/038499
Authority: WO
Inventors: 俊啓開
Original assignee: 三菱ケミカル株式会社
Priority date: 2016-10-25
Filing date: 2017-10-25
Publication date: 2018-05-03
Also published as: TWI741053B; JP7031601B2; KR20190076955A; CN109789678A; JPWO2018079596A1; TW201827230A; CN109789678B

Abstract

A mold release film having a mold release layer comprising a cured material formed from a curable silicone resin and inert particles on at least one surface of a polyester film, the peel force between the mold release layer and an acrylic adhesive measured by a predetermined method being 50 g/25 mm to 150 g/25 mm.

Description

Release film

The present invention relates to a release film, and more particularly relates to a release film that allows easy adjustment of the peel force and has a stable release property even in a state of being bonded to an adhesive over a long period of time. It is.

Release films based on polyester films are used in various applications from the viewpoints of mechanical strength, heat resistance, thermal dimensional stability, chemical resistance and economy. For example, optical clear adhesives used in touch panels For manufacturing (OCA), for manufacturing LCD components such as polarizing plates / retardation plates used in liquid crystal displays (LCD), for manufacturing plasma display panel (PDP) components, for manufacturing organic electroluminescence (organic EL) components For various display component manufacturing applications, medical adhesive film applications such as poultice / patch, ceramic sheet applications, molding process applications such as polyvinyl chloride sheets and carbon fibers, labels, adhesive tapes, decorative boards, transfer tapes Industrial applications such as are exemplified.

In the manufacture of LCD components, commercial distribution is carried out by a method in which a polarizing plate maker cuts a polarizing plate to a panel maker, or a method called Roll to Panel in which a polarizing plate is delivered from the polarizing plate maker to the panel maker in a roll state. Is configured. Here, the release film is coated on the surface to protect the polarizing plate until the polarizing plate is incorporated into the member in the manufacturing process, for example. In recent years, due to the inventory adjustment of the polarizing plate, in any of the methods, the period from the production of the polarizing plate to the peeling off of the release film for incorporation into the member has been prolonged. Therefore, it has been demanded that the release film has stable release properties even in a state where the release film is bonded to the adhesive for a long period of time (Patent Document 1).

JP-A-6-246880

However, in the conventional release film, in the pasting with the adhesive for a long time, the reaction between the silicone resin and the adhesive contained in the release layer of the release film proceeds on the surface of the release layer. At the same time, the peeling force increased and sometimes it was difficult to peel off.

The present invention has been made in view of the above circumstances, and the solution to the problem is that the peel force with time does not change greatly even in a state of being bonded to the adhesive over a long period of time, and the releasability (peel force) is stable. It is to provide a release film.

As a result of intensive studies in view of the above circumstances, the present inventor has found that if a release film having a specific configuration is used, it is possible to greatly improve the temporal stability of the peeling force in a situation where it is bonded to an adhesive from the prior art, The present invention has been completed.

That is, the gist of the present invention is to provide a release layer comprising a cured product formed from a curable silicone resin and inert particles on at least one surface of a polyester film, and the release layer measured by the following method. And the acrylic adhesive are in a release film having a peeling force of 50 g / 25 mm or more and 150 g / 25 mm or less (first preferred embodiment).
<Measurement method>
An acrylic pressure-sensitive adhesive composed of the following pressure-sensitive adhesive composition is applied to the release layer surface of the release film so that the coating amount (before drying) is 2 mil, and heat-treated at 150 ° C. for 3 minutes. The pressure-sensitive adhesive surface after the heat treatment is bonded to an untreated polyethylene terephthalate biaxially stretched film (thickness: 188 μm) with a rubber roller with a load of 2 kg to produce a release film with a pressure-sensitive adhesive.
Next, the peeling force after leaving the bonded release film with pressure-sensitive adhesive at room temperature for 1 hour is measured. The peeling force is 180 ° peeling under the condition of a tensile speed of 300 mm / min.
<Adhesive composition>
Main agent: AT352 (manufactured by Seiden Chemical Co., Ltd.) 100 parts by weight Curing agent: AL (manufactured by Seiden Chemical Co., Ltd.) 0.25 parts by weight Additive: X-301-375SK (manufactured by Seiden Chemical Co., Ltd.) 0.25 Part by weight Additive: X-301-352S (manufactured by Seiden Chemical Co., Ltd.) 0.4 part by weight Toluene 40 part by weight

Alternatively, the gist of the present invention is that the polyester film has a release layer composed of a cured product formed from a curable silicone resin and inert particles on at least one side, and the release using a scanning electron microscope In the release film, the area occupied by the inert particles on the layer surface is 4% or more and 12% or less (second preferred embodiment).

According to the above-described configuration of the present invention, a release film that has been a problem of the prior art and has a stable releasability without a change in peeling force over time even in a state of being bonded to an adhesive over a long period of time. For example, it is suitable for manufacturing various optical members such as liquid crystal polarizing plate manufacturing and touch panel manufacturing.

2 is an SEM image obtained by photographing the release layer surface of the release film of Example 1. FIG. It is the SEM image which image | photographed the mold release layer surface of the mold release film of Example 9. FIG. It is a SEM image which image | photographed the mold release layer surface of the mold release film of the comparative example 3.

Hereinafter, the present invention, its components, and preferred embodiments for carrying out the present invention will be described in detail.

(Polyester film)
The polyester in the polyester film used for the release film is preferably obtained by polycondensation of aromatic dicarboxylic acid and aliphatic glycol, and consists of one kind of aromatic dicarboxylic acid and one kind of aliphatic glycol. It may be a polyester or a copolyester obtained by copolymerizing one or more other components. Examples of the aromatic dicarboxylic acid include terephthalic acid and 2,6-naphthalenedicarboxylic acid, and examples of the aliphatic glycol include ethylene glycol, diethylene glycol, and 1,4-cyclohexanedimethanol. Typical polyester includes polyethylene terephthalate and the like. On the other hand, examples of the dicarboxylic acid used as a component of the copolyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and the like, and glycol components include ethylene glycol, diethylene glycol, Examples include propylene glycol, butanediol, 1,4-cyclohexanedimethanol, neopentyl glycol and the like. Oxycarboxylic acids such as p-oxybenzoic acid can also be used. Further, it may be a polyester copolymerized with other acid components or glycol components. If necessary, conventionally known colorants (dyes / pigments), ultraviolet absorbers, antioxidants, antistatic agents, conductive agents, heat Various functionalizing components and additives such as stabilizers and lubricants may be contained.

In addition, in the polyester film constituting the release film, in order to reduce the amount of oligomers contained in the film precipitated or crystallized on the surface of the film due to thermal history during film processing, etc., a multilayer structure film It is also possible to use a polyester with a reduced amount of oligomer in the outermost layer. As a method for reducing the amount of oligomer in the polyester, for example, a solid phase polymerization method or the like can be used.

The polyester film constituting the release film can contain particles mainly for the purpose of imparting slidability, ensuring the running property of the film in each step, and preventing scratches. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness, and specific examples include, for example, silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, calcium phosphate. , Calcium fluoride, calcium oxalate, lithium fluoride, zeolite, magnesium phosphate, kaolin, talc, aluminum oxide, alumina, titanium oxide, molybdenum sulfide, and the like. Further, the heat-resistant organic particles described in JP-B-59-5216, JP-A-59-217755 and the like may be used. Examples of other heat-resistant organic particles include thermosetting urea resins, thermosetting phenol resins, thermosetting epoxy resins, benzoguanamine resins, and the like. Furthermore, precipitated particles obtained by precipitating and finely dispersing a part of a metal compound such as a catalyst during the polyester production process can also be used.

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

The particle size and content of the particles are selected according to the use and purpose of the film, but the average particle size when used in optical applications is usually in the range of 0.01 to 5 μm, preferably 0.01 to 2 μm. It is. When the average particle size is less than 0.01 μm, the particles tend to aggregate and the dispersibility may be insufficient. On the other hand, when the average particle size exceeds 5 μm, the surface roughness of the film becomes too rough and Problems may occur when various surface functional layers are applied in the process.

Furthermore, the particle content when used in optical applications is usually in the range of 0.001 to 5% by weight, preferably 0.005 to 3% by weight. When the particle content is less than 0.001% by weight, the slipperiness of the film may be insufficient, while when it exceeds 5% by weight, the transparency of the film may be insufficient.

When there are no or few particles, the transparency of the film becomes high and it becomes a good film, but it may be difficult to handle, such as insufficient slipping, so put particles in the knurling or coating layer Etc. may be necessary.

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

Also, a method of blending a slurry of particles dispersed in ethylene glycol or water with a vented kneading extruder and a polyester material, or a method of blending dried particles and a polyester material using a kneading extruder Etc.

The polyester film constituting the release film may be a single layer structure or a laminated structure of two or more layers, and is not particularly limited.

The release film may contain a UV absorber in the polyester film in order to improve the weather resistance of the film. The ultraviolet absorber is not particularly limited as long as it is a compound having ultraviolet absorbing ability and can withstand the heat applied in the production process of the polyester film.

As the ultraviolet absorber, there are an organic ultraviolet absorber and an inorganic ultraviolet absorber, and an organic ultraviolet absorber is preferable from the viewpoint of transparency. Although it does not specifically limit as an organic type ultraviolet absorber, For example, a cyclic imino ester type, a benzotriazole type, a benzophenone type etc. are mentioned. From the viewpoint of durability, a cyclic imino ester type and a benzotriazole type are more preferable. It is also possible to use two or more ultraviolet absorbers in combination.

The thickness of the polyester film constituting the release film is not particularly limited as long as it can be formed as a film, but is usually 400 μm or less, preferably 5 to 250 μm, more preferably 12 to 200 μm. It is.

The transparency of the polyester film is not particularly limited. However, in the case of optical applications that require transparency, the haze is preferably 1.8% or less, and more preferably 1.2% or less.

The total light transmittance of the polyester film is not particularly limited, but is preferably 80% or more, and more preferably 85% or more in the case of optical use where transparency is required.

The production example of the polyester film constituting the release film will be described in detail, but is not limited to the following production example, and a generally known polyester film forming method can be adopted. That is, a method of using the polyester raw material described above and cooling and solidifying a molten sheet extruded from a die with a cooling roll to obtain an unstretched sheet is preferable. In this case, in order to improve the flatness of the sheet, it is preferable to improve the adhesion between the sheet and the rotary cooling drum, and an electrostatic application adhesion method and / or a liquid application adhesion method is preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction. In that case, first, the unstretched sheet is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7.0 times, preferably 3.0 to 6.0 times. Next, the film is stretched in the direction perpendicular to the first stretching direction. In this case, the stretching temperature is usually 70 to 170 ° C., and the stretching ratio is usually 3.0 to 7.0 times, preferably 3.5 to 6 times. .0 times. Subsequently, heat treatment is performed at a temperature of 180 to 270 ° C. under tension or under relaxation within 30% to obtain a biaxially oriented film. In the above-described stretching, a method in which stretching in one direction is performed in two or more stages can be employed. In that case, it is preferable to carry out so that the draw ratios in the two directions finally fall within the above ranges.

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

(Functional layer)
In the release film of the present invention, a functional layer may be interposed between the polyester film and the release layer. Functional layers include easy adhesion layer, antistatic layer, conductive layer, antifouling layer, bleed-out component sealing layer, refractive index adjusting layer, light transmittance improving layer, light absorbing layer, antifogging layer, barrier coat layer , A hard coat layer, a pressure-sensitive adhesive layer, and a layer in which these functionalities are combined. In addition, the functional layer may be a single layer or may be composed of two or more layers. With respect to the functional layer, it may be provided by in-line coating which treats the film surface during the stretching process of the polyester film, or offline coating which is applied outside the system on the once produced film may be adopted.

Although the in-line coating is not limited to the following, for example, in the sequential biaxial stretching, the coating treatment can be performed especially after the stretching in the flow direction is completed, that is, before the stretching in the width direction. When a functional layer is provided on a polyester film by in-line coating, the functional layer can be processed at a high temperature while being simultaneously formed with a film, and a film suitable as a polyester film can be produced.

When the functional layer is provided by in-line coating, it is preferable to produce a laminated polyester film by applying a coating solution on the polyester film by using a series of compounds described later as an aqueous solution or an aqueous dispersion. Moreover, in the range which does not impair the main point of this invention, a small amount of organic solvents may be contained in the coating liquid for the purpose of improving dispersibility in water, improving film-forming properties, and the like. Only one type of organic solvent may be used, or two or more types may be used as appropriate.

The organic solvent content of the coating solution is preferably 10% by weight or less, more preferably 5% by weight or less. Specific examples of the organic solvent 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 And amides.

In addition, regardless of off-line coating or in-line coating, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as necessary.

Examples of the method for forming the functional layer include gravure coating, reverse roll coating, die coating, air doctor coating, blade coating, rod coating, bar coating, curtain coating, knife coating, transfer roll coating, squeeze coating, curtain coating, Conventionally known coating methods such as impregnation coating, kiss coating, spray coating, calendar coating, and extrusion coating can be used.

Examples of the polymer used for forming the functional layer include polyester resins, polyurethane resins, acrylic resins, polyvinyl alcohol and other vinyl resins, epoxy resins, melamine resins, polyether resins, amide resins, aramid resins, phenol resins, imide resins, A fluororesin, a silicone resin, etc. are mentioned.
In addition, these skeleton structures may have a composite structure substantially by copolymerization or the like, and examples of the polymer having a composite structure include acrylic resin graft polyester, acrylic resin graft polyurethane, and vinyl resin graft. Examples thereof include polyester and vinyl resin graft polyurethane.

Various known resins can be used as the crosslinking agent for forming the functional layer. For example, melamine compounds, guanamine compounds, alkylamide compounds, polyamide compounds, glyoxal compounds, carbodiimide compounds, epoxy compounds, oxazoline compounds, Aziridine compounds, isocyanate compounds, silane coupling agents, dialcohol aluminate coupling agents, dialdehyde compounds, zircoaluminate coupling agents, peroxides, heat or photoreactive vinyl compounds and photosensitive resins, etc. Can be mentioned.

The functional layer may contain particles for the purpose of improving slipperiness. The average particle size is not particularly limited, but for example, when used for optical applications, it is preferably in the range of 1.0 μm or less, more preferably 0.5 μm or less, particularly preferably 0.2 μm from the viewpoint of film transparency. The range is as follows. Specific examples of the particles include inert inorganic particles such as silica, alumina, calcium carbonate, and titanium dioxide, fine particles obtained from polystyrene resins, polyacrylic resins, and polyvinyl resins, or organic particles represented by these crosslinked particles. Is mentioned.

Other functional layers include surfactants, antifoaming agents, coatability improvers, mold release agents, thickeners, organic lubricants, antistatic agents, conductive agents, refractive index adjusters, ultraviolet rays, depending on the purpose. An iso-light absorber, an antioxidant, a foaming agent, a dye, a pigment and the like may be contained.

Analysis of the components in the functional layer can be performed by analysis of TOF-SIMS, ESCA, fluorescent X-rays, etc., for example.

The thickness of the functional layer provided on the polyester film in the present invention, when seen as a final coating, usually 0.01 ~ 3g / m ^2, preferably 0.02 ~ 1g / m ^2, more preferably The range is 0.03 to 0.3 g / m ² . When the thickness of the functional layer is less than 0.01 g / m ² , sufficient performance may not be obtained in the easy adhesion performance to the release layer, and the functional layer exceeding 3 g / m ² It tends to cause cost increase due to deterioration of transparency, film blocking, and line speed reduction. The coating amount can be determined by calculation from the weight of the liquid applied before coating (before drying), the concentration of the coating liquid non-volatile content, the coating width, the draw ratio, the line speed, and the like.

The polyester film may be subjected to various surface treatments separately from the functional layer. Conventionally known techniques can be used for various surface treatments. For example, the surface treatment includes surface activation treatment such as corona discharge treatment, flame treatment, ultraviolet treatment, high frequency treatment, microwave treatment, glow discharge treatment, active plasma treatment, and laser treatment.

(Release layer)
The release layer constituting the release film will be described below.

It is important that the release film of the present invention contains a curable silicone resin and inert particles from the viewpoint of obtaining good release performance. However, there are no particular restrictions on the constituent components of the release layer excluding the curable silicone resin and the inert particles, as long as they have good release performance at the time of peeling from the adhesive layer. A type having a curable silicone resin as a main component may be used, or a modified silicone type by graft polymerization with an organic resin such as a urethane resin, an epoxy resin, or an alkyd resin may be used. When the pressure-sensitive adhesive layer is a silicone pressure-sensitive adhesive or the like, it is preferable to contain a fluorosilicone resin or the like.

As the type of the curable silicone resin, any type of curing reaction such as an addition type or a condensation type can be used. Also, any curing reaction type of electron beam curing type such as thermosetting type and ultraviolet curing type can be used. A plurality of types of curable silicone resins may be used in combination. Further, there is no particular limitation on the application form of the curable silicone resin when forming the release layer, and any form of dissolving in an organic solvent, an aqueous emulsion, or a solventless form may be used.
As a specific embodiment in which a plurality of types of curable silicone resins are used in combination, as described later, for example, by using a curable silicone resin containing an alkenyl group and a curable silicone resin containing a SiH group together, the release film is peeled off. There is a case where the force can be adjusted to an appropriate range, or a change with time of the peeling force can be suppressed.
In addition, as a coating solution used for the release layer, a release film is peeled off by using a curable silicone resin-containing coating solution containing inert particles and a curable silicone resin-containing coating solution containing no inert particles. There is a case where the force can be adjusted to an appropriate range, or a change with time of the peeling force can be suppressed.

Although there is no restriction | limiting in the kind of curable silicone resin, From the viewpoint of the mold release characteristics which were excellent in peelability etc., use of the curable silicone resin containing an alkenyl group is preferable in this invention. Examples of the curable silicone resin containing an alkenyl group include diorganopolysiloxane 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 organic group containing an alkenyl group. a is an integer of 0 to 3, preferably 1, and m is an integer of 0 or more, but when a = 0, m is 2 or more, and m and n are integers satisfying 100 ≦ m + n ≦ 20000, respectively. In addition, the above formula includes a random copolymer and does not mean a block copolymer.
R is a monovalent hydrocarbon group having 1 to 10 carbon atoms, specifically, an alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group, a cycloalkyl group such as a cyclohexyl group, a phenyl group or a tolyl group. And allyl groups such as methyl group and phenyl group are particularly preferable. X is an alkenyl group-containing organic group, preferably having 2 to 10 carbon atoms, specifically, vinyl group, allyl group, hexenyl group, octenyl group, acryloylpropyl group, acryloylmethyl group, methacryloylpropyl group, cyclohexenylethyl group. Group, vinyloxypropyl group and the like are mentioned, and vinyl group and hexenyl group are particularly preferable. Specifically, a trimethylsiloxy group-capped dimethylsiloxane / methylhexenylsiloxane copolymer (96 mol% dimethylsiloxane unit, 4 mol% methylhexenylsiloxane unit), dimethylvinylsiloxy group-capped dimethyl with both molecular chain ends. Siloxane / methylhexenylsiloxane copolymer (97 mol% dimethylsiloxane unit, 3 mol% methylhexenylsiloxane unit), dimethylsiloxane / methylhexenylsiloxane copolymer blocked with dimethylhexenylsiloxy group at both ends of molecular chain (95 mol% dimethylsiloxane unit) Methylhexenylsiloxane unit 5 mol%).

Next, in order to react with the alkenyl group contained in the curable silicone resin to form a stronger silicone release layer, the curable silicone resin preferably contains a SiH group. For example, the polyorganosiloxane containing SiH group is an organohydrogenpolysiloxane having at least 2, preferably 3 or more hydrogen atoms bonded to a silicon atom in one molecule, and is linear, branched or cyclic. Can be used, and examples include compounds represented by the following general formula (2), but are not limited thereto.
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 containing no aliphatic unsaturated bond having 1 to 6 carbon atoms. b is an integer of 0 to 3, and x and y are integers. Specifically, molecular chain both ends trimethylsiloxy group-capped methylhydrogenpolysiloxane, molecular chain both ends trimethylsiloxy group-capped dimethylsiloxane / methylhydrogensiloxane copolymer, molecular chain both ends dimethylhydrogensiloxy group-capped methyl Examples thereof include hydrogen polysiloxane and dimethylhydrogensiloxy group-blocked dimethylsiloxane / methylhydrogensiloxane copolymer having both molecular chain terminals.

Next, specific examples of the curable silicone resin used in the present invention include KS-774, KS-775, KS-778, KS-779H, KS-847H, KS-856, X, manufactured by Shin-Etsu Chemical Co., Ltd. -62-2422, X-62-2461, X-62-1387, X-62-5039, X-62-5040, KNS-3051, X-62-1496, KNS320A, KNS316, X-62-1574A / B X-62-7052, X-62-7028A / B, X-62-7619, X-62-7213, X-41-3035; YSR-3022, TPR-6700, TPR manufactured by Momentive Performance Materials -6720, TPR-6721, TPR6500, TPR6501, UV9300, UV9425, XS56-A277 XS56-A2982, UV9430, TPR6600, TPR6604, TPR6605; SRX357, SRX211, SD7220, SD7292, LTC750A, LTC760A, LTC760A, LTC303E, SP7259, BY24-468C, SP2448S, BY24, manufactured by Toray Dow Corning 202, DKQ3-203, DKQ3-204, DKQ3-205, DKQ3-210; DEHESIVE 636, 919, 920, 921, 924, 929 and the like are exemplified in the DEHESIVE series manufactured by Asahi Kasei Wacker Silicone Co., Ltd.

In the composition constituting the release layer, it is preferable to use a platinum-based catalyst that promotes an addition-type reaction in order to ensure strength. As this component, chloroplatinic acid, alcohol solution of chloroplatinic acid, a complex of chloroplatinic acid and olefin, a platinum compound such as a complex of chloroplatinic acid and alkenylsiloxane, platinum black, platinum-supported silica, platinum-supported activated carbon Is exemplified. The platinum-based catalyst content in the composition constituting the release layer is preferably from 0.3 to 3.0% by weight, more preferably from 0.5 to 2.0% by weight. When the platinum-based catalyst content in the composition constituting the release layer is lower than 0.3% by weight, the peeling force is defective, and the curing reaction at the release layer becomes insufficient. May cause problems. On the other hand, when the platinum-based catalyst content in the composition constituting the release layer exceeds 3.0% by weight, the reactivity may increase and problems may occur in the process of generating gel foreign matter. .

In addition, since the addition type reaction is very reactive, acetylene alcohol may be added as an addition reaction inhibitor in some cases. The component is an organic compound having a carbon-carbon triple bond and a hydroxyl group, preferably 3-methyl-1-butyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol and phenylbutynol. A compound selected from the group consisting of:

In the composition constituting the release layer, it is possible to use a catalyst other than the platinum-based catalyst in combination for the purpose of promoting hydrolysis and condensation reaction. Specific examples of the catalyst include organic acids such as acetic acid, butyric acid, maleic acid and citric acid; inorganic acids such as hydrochloric acid, nitric acid, phosphoric acid and sulfuric acid; basic compounds such as triethylamine; tetrabutyl titanate, dibutyltin dilaurate, Organometallic salts such as dibutyltin diacetate, dibutyltin dioctate, dibutyltin diolate, diphenyltin diacetate, dibutyltin oxide, dibutyltin dimethoxide, dibutylbis (triethoxysiloxy) tin, dibutyltin benzylmalate; KF, NH ₄ F Fluorine element-containing compounds such as The above catalysts may be used alone or in combination of two or more. Among these, organometallic salts are preferable in that the coating film durability is particularly good.

In the second preferred embodiment of the present invention, the release force of the release layer is adjusted to a desired release force, and the desired release force can be stably maintained even when pasted with an adhesive for a long period of time. In addition, the release layer contains a curable silicone resin and inert particles, and the area occupied by the inert particles when the surface of the release layer is observed using a scanning electron microscope (SEM) under the following conditions: Is an essential requirement of 4% or more and 12% or less.
<< Scanning electron microscope observation conditions >>
-Equipment used: S-3400N (manufactured by Hitachi, Ltd.)
・ Observation mode: Secondary electron (observation) mode ・ Acceleration voltage: 15 kV
Probe current: 30
・ Aperture stop: 3
・ Working distance (WD): 10mm
・ Magnification: 20000 times

When the occupied area ratio of the inert particles is 4% or more as in the release film of the present invention, the inert particles can inhibit or suppress the reaction on the surface of the release layer, and the desired release force is stabilized. Can be maintained. The occupied area ratio of the inert particles is preferably 5% or more, more preferably 7% or more.
On the other hand, the upper limit of the occupied area ratio of the inert particles is 12% or less. When the occupied area ratio of the inert particles exceeds 12%, the peeling force becomes very large immediately after the release film is formed, and the release film and the pressure-sensitive adhesive are difficult to peel off. The peel force over time remains very large.

The occupied area ratio of the inert particles in the present invention indicates the ratio of the area where the inert particles can exist in the vicinity of the surface of the release layer. The occupied area ratio of the inert particles is controlled by a coating method and a curing condition when forming the release layer. By forming the release layer by the coating method and curing conditions described later, the inert particles appear on the surface of the release layer, and the occupied area ratio of the inert particles can be satisfied within the specified range.
Therefore, the occupied area ratio of the inert particles is not determined only by the content of the inert particles in the release layer coating liquid. Even if the release layer contains a large amount of inert particles, if the inert particles do not appear on the surface of the release layer and the occupied area ratio of the inert particles is less than 4%, the inert particles are released. The reaction with the pressure-sensitive adhesive cannot be inhibited or suppressed on the surface of the layer, and the peeling force with time increases. Further, even if the release layer contains only a small amount of inert particles, if the inert particles appear on the surface of the release layer and the occupied area ratio of the inert particles is within the specified range, the inert particles However, it is possible to inhibit or suppress the reaction with the pressure-sensitive adhesive on the surface of the release layer, and to suppress an increase in peel strength with time.
In addition, as long as it measures by said prescription | regulation, it is not necessary to target only the inert particle contained in a mold release layer. For example, when the surface layer of the polyester film contains inert particles, or when the functional layer that can be optionally provided contains inert particles, it is not necessary to identify the inert particles contained in these layers. .

As the inert particles used in the release layer, any substance may be used. Specifically, particles that can be used for imparting the slipperiness of the polyester film described above may be used in the same manner. it can. Among these, inorganic particles are preferable, and silica particles are more preferable from the viewpoint of versatility. Specific examples include BY24-312 and BY24-4980 manufactured by Toray Dow Corning, “Snowtex” manufactured by Nissan Chemical Industries, “OSCAL” manufactured by JGC Catalysts & Chemicals, Inc. The

From the viewpoint of compatibility with the silicone resin in the release layer and the distribution of the silica particles in the release layer, the surface of the silica particles is more preferably a structure of general formula (3), and all are methyl groups. A structure that is trimethylsilylated is particularly preferred.
Si—O—Si— (Rα) _c (Rβ) _d (Rγ) _e (3)
(In the general formula (3), Rα, Rβ, and Rγ are each independently an alkyl group or phenyl group having 1 to 6 carbon atoms, c, d, and e are integers, and c + d + e = 3.)

The average particle diameter of the inert particles used in the release layer is usually 0.01 to 5 μm, preferably 0.01 to 2 μm. When the average particle size of the inert particles is within the specified range, the occupied area ratio of the surface of the release layer is satisfied, and the peeling force is adjusted to an appropriate range, or the change of the peeling force with time is suppressed. can do.

The content of the inert particles used in the release layer is usually 1 to 50% by weight, preferably 2 to 40% by weight, more preferably 3 to 30% by weight. When the content of the inert particles is within the specified range, the occupied area ratio of the surface of the release layer is satisfied, and the peeling force is adjusted to an appropriate range, or the change of the peeling force with time is suppressed. be able to.

In addition to the inert particles, a peeling force adjusting agent may be used in combination. In order to increase the release force, generally a heavy release agent such as organopolysiloxane or a silicone species that increases the release force is added to the composition constituting the release layer in an appropriate content. Specific examples of the heavy release agent include KS-3800 and X-92-183 manufactured by Shin-Etsu Chemical Co., Ltd.
In order to reduce the peeling force, various low molecular weight siloxane compounds are selected, and an appropriate content is added to the release layer so that the siloxane migration component exhibits the release performance. Examples of the low molecular siloxane compound include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and the like. In addition, as other compounds of the low molecular siloxane compound, there are a trimethylsiloxy group-capped dimethylsiloxane oligomer having both molecular chains and a dimethylhydroxysiloxy group-capped dimethylsiloxane oligomer having both molecular chains, and the compounds may be mixed as necessary. May be used. These low-molecular-weight siloxane compounds are usually contained in a silicone resin in an amount of 0.1 to 15% by weight, preferably 0.1 to 10% by weight, more preferably 0.1 to 5% by weight, thereby achieving a desired release property. can do. If the content of the low-molecular siloxane compound is less than 0.1% by weight, the releasability is hardly exhibited because there are few migratory components. On the other hand, when the content of the low-molecular siloxane is larger than 15% by weight, the migratory component is excessively precipitated, so that it tends to cause process contamination.

In the release layer constituting the release film, an organic silicon compound may be used in combination in order to improve the coating film adhesion between the release layer and the polyester film, and is represented by the following general formula (4). It is preferable to use an organosilicon compound in combination.
Si (X) _f (Y) _g (R ² ) _h (4)
(In the above formula (4), 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, 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 (4), one having two or three hydrolyzable groups Y capable of forming a siloxane bond by hydrolysis and condensation reaction can be used.

In the general formula (4), examples of the hydrolyzable group Y include the following. That is, a methoxy group, an ethoxy group, a butoxy group, an isopropenoxy group, an acetoxy group, a butanoxime group, an amino group, and the like. These hydrolyzable groups may be used alone or in combination. The application of a methoxy group or an ethoxy group is particularly preferable because it can impart good storage stability to the coating material and has suitable hydrolyzability.

In the general formula (4), the monovalent hydrocarbon group R ² has 1 to 10 carbon atoms, and is particularly preferably a methyl group, an ethyl group, or a propyl group.

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

The content of the organosilicon compound in the release layer is preferably 0.5 to 5.0 parts by weight, more preferably 0.5 to 2.0 parts by weight with respect to 100 parts by weight of the curable silicone resin. Parts by weight. If the range is less than 0.5 parts by weight, it may be difficult to ensure the desired adhesion. On the other hand, if it exceeds 5.0 parts by weight, the adhesion to the mating resin layer is too strong. In a scene that originally needs to be peeled off, there may be a problem that it cannot be easily peeled off.

Further, within the range that does not impair the gist of the present invention, the release layer is optionally provided with a surfactant, an antifoaming agent, a coating property improving agent, a thickener, an inorganic organic particle, an organic lubricant, a charging agent. An inhibitor, a conductive agent, an ultraviolet absorber, an antioxidant, a foaming agent, a dye, a pigment and the like may be contained.

The release layer is formed by coating the coating solution on the film. Even if it is provided by in-line coating performed within the film manufacturing process, it is also applied to the once manufactured film outside the system, so-called offline coating. May be adopted.

As a method for controlling the occupation area ratio, adjustment of the coating method and curing conditions of the release layer may be mentioned.
Reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating, knife coating, transfer roll coating, squeeze coating, impregnation coating, kiss coating, spray coating, calendar coating, extrusion coating. The conventionally known coating methods described above can be used. Regarding the coating method, there is a description example in “Coating method” (Tsubaki Shoten, Yuji Harasaki, published in 1979).

The curing conditions for forming the release layer are not particularly limited. When the release layer is provided by off-line coating, it is usually 80 ° C. or more and 10 seconds or more, preferably 100 to 200 ° C. for 3 to 40. The heat treatment is preferably carried out for 2 seconds, more preferably at 120 to 180 ° C. for 3 to 40 seconds.
Examples of the heat source used for curing the release layer include contact with a hot roll, contact with a heating medium such as air, infrared heating, microwave heating, and the like. Among them, it is preferable to use infrared heating capable of removing and curing the solvent in a short time because the inert particles are likely to appear on the surface of the release film, and the area occupied by the inert particles in a predetermined range can be obtained.
Moreover, you may use together heat processing and active energy ray irradiation, such as ultraviolet irradiation, as needed. In addition, as an energy source for hardening by active energy ray irradiation, a well-known apparatus and an energy source can be used.
The coating amount (after drying) of the release layer is usually 0.005 to 5 g / m ² , preferably 0.005 to 1 g / m ² , more preferably 0.005 to 0. The range is 1 g / m ² . If the coating amount (after drying) is less than 0.005 g / m ² , the coating property may be less stable and it may be difficult to obtain a uniform coating film. On the other hand, when the coating is thicker than 5 g / m ² , the coating layer adhesion and curability of the release layer itself may decrease.

About the release film obtained in this way, it is preferable that the peeling force of the release layer and acrylic adhesive layer which were measured with the following method is 50 g / 25mm or more. The release film of the present invention exhibits particularly excellent peeling stability over time when the peeling force is 50 g / 25 mm or more.
The release film of the present invention includes the release force between the release layer and the acrylic pressure-sensitive adhesive layer within a predetermined range by adjusting the occupied area ratio of the inert particles contained in the release layer. it can. However, the means for obtaining the peeling force is not limited to the method for adjusting the area ratio of the inert particles contained in the release layer.

<Measurement method>
An acrylic pressure-sensitive adhesive composed of the following pressure-sensitive adhesive composition is applied to the release layer surface of the release film so that the coating amount (before drying) is 2 mil, and heat-treated at 150 ° C. for 3 minutes. The pressure-sensitive adhesive surface after the heat treatment is bonded to an untreated polyethylene terephthalate biaxially stretched film (thickness: 188 μm) with a rubber roller with a load of 2 kg to produce a release film with a pressure-sensitive adhesive.
Next, the peeling force after leaving the bonded release film with an adhesive at room temperature for 1 hour is measured. The peeling force is 180 ° peeling under the condition of a tensile speed of 300 mm / min.
<Adhesive composition>
Main agent: AT352 (manufactured by Seiden Chemical Co., Ltd.) 100 parts by weight Curing agent: AL (manufactured by Seiden Chemical Co., Ltd.) 0.25 parts by weight Additive: X-301-375SK (manufactured by Seiden Chemical Co., Ltd.) 0.25 Part by weight Additive: X-301-352S (manufactured by Seiden Chemical Co., Ltd.) 0.4 part by weight Toluene 40 parts by weight Other adhesives as long as they have the same adhesive properties as the above adhesive composition It can be measured by replacing the composition.

On the other hand, the upper limit of the peeling force between the release layer and the acrylic pressure-sensitive adhesive layer is preferably 150 g / 25 mm or less. The release film of the present invention has a release force of 150 g / 25 mm or less, so that it can exhibit the release stability particularly over time, and can maintain the release force stably during long-term transportation and inventory. be able to.

In the first preferred embodiment of the present invention, it is an essential requirement that the peeling force between the release layer and the acrylic pressure-sensitive adhesive layer is 50 g / 25 mm or more and 150 g / 25 mm or less.

Regarding the release force over time, the release film of the present invention preferably has a peel force of 150 g / 25 mm or less after being left in a thermostatic chamber at 23 ° C. and 50% RH for 2 months, more preferably 100 g / 25 mm or less. preferable. When the peeling force is 150 g / 25 mm or less, the peeling force can be stably maintained when transporting or stocking for a long period of time.
Further, from the viewpoint of the change in peel force with time, the peel force after leaving the release film in a thermostatic chamber at 23 ° C. and 50% RH for 3 months is more preferably 100 g / 25 mm or less, and 85 g / 25 mm or less. Is particularly preferred. Here, the measuring method of peeling force is the same as the above.

The release film of the present invention can be used as a release film with an adhesive having an acrylic adhesive layer on the release layer surface of the release film.
Moreover, the release film of this invention can be utilized suitably as a protective film of optical members, such as a liquid crystal polarizing plate and a touch panel, for example.

The acrylic pressure-sensitive adhesive to be bonded to the release film of the present invention is a resin containing an acrylic monomer as a constituent component. Only one type of acrylic resin may be used, or two or more types may be used. Moreover, only 1 type may be sufficient as an acryl-type monomer, and 2 or more types may be sufficient as it.
The acrylic resin preferably contains (meth) acrylic acid alkyl ester as a monomer component constituting the resin. Examples of the (meth) acrylic acid alkyl ester include hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl ( Alkyl having 6 to 14 carbon atoms such as (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecyl (meth) acrylate, n-tridecyl (meth) acrylate, n-tetradecyl (meth) acrylate, etc. Examples include (meth) acrylic acid alkyl esters having a group. Only one (meth) acrylic acid alkyl ester may be used, or two or more may be used.

In addition, the constituent component of the acrylic resin may contain, for example, a polyfunctional monomer from the viewpoint that a crosslinked structure can be introduced into the acrylic resin and an appropriate cohesive force can be obtained.
Specifically, ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, Examples include trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, divinylbenzene, and N, N′-methylenebisacrylamide. Only one type of polyfunctional monomer may be used, or two or more types may be used.

The present invention will be described in more detail with reference to the following examples, comparative examples, and production examples. However, the present invention is not limited to the following examples, comparative examples, and production examples as long as the gist thereof is not exceeded. . In addition, the evaluation method and the processing method of a sample in an Example, a comparative example, and a manufacture example are as follows.

(1) Intrinsic viscosity of polyester (inherent viscosity)
1 g of polyester was precisely weighed, 100 mL of a mixed solvent of phenol / tetrachloroethane = 50/50 (weight ratio) was added and dissolved, and measurement was performed at 30 ° C.

(2) Average particle diameter (d50: μm)
The average particle size was defined as a 50% integrated (weight basis) value in an equivalent spherical distribution measured using a centrifugal sedimentation type particle size distribution analyzer (“SA-CP3 type” manufactured by Shimadzu Corporation).

(3) Evaluation of peel strength with time of release film Baker type applicator so that the amount of acrylic adhesive composed of the following adhesive composition (before drying) is 2 mil on the release layer surface of the release film And then heat-treated at 150 ° C. for 3 minutes in a hot air circulating furnace. The pressure-sensitive adhesive surface after the heat treatment was bonded to an untreated polyethylene terephthalate biaxially stretched film (thickness: 188 μm) with a rubber roller having a load of 2 kg to prepare a release film with a pressure-sensitive adhesive.
Next, the adhesive release film with adhesive was left to stand under each standing condition, then cut to a size of 50 mm × 300 mm, and the peel strength after standing for 1 hour at room temperature was measured. Peeling force was determined by using a tensile tester (“Intesco Model 2001” manufactured by Intesco Corporation), peeling at 180 ° under a tensile speed of 300 mm / min, and evaluating the peel strength over time according to the following evaluation criteria. It was. In this evaluation, in the peeling force profile, the site of the maximum peeling force value recorded at the start of peeling was set as the evaluation target.

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

<Leaving condition of release film with adhesive>
Condition 1: Immediately after forming the release film Condition 2: The release film is left in a constant temperature and humidity chamber at 23 ° C. and 50% RH for one month. Condition 3: The release film is at 23 ° C. and 50% RH. Leave in a constant temperature and humidity chamber for 2 months Condition 4: Leave the release film in a constant temperature and humidity chamber at 23 ° C and 50% RH for 3 months

<< Evaluation criteria for peel strength over time >>
A: Peeling force under condition 4 is 85 g / 25 mm or less B: Peeling force under condition 4 exceeds 85 g / 25 mm and 100 g / 25 mm or less C: Peeling force under condition 3 exceeds 100 g / 25 mm and is 150 g / 25 mm or less D : Peeling force under condition 3 exceeds 150 g / 25 mm

(4) Evaluation of occupied area ratio of silica particles The surface of the release layer of the produced release film was observed with a scanning electron microscope (manufactured by Hitachi, Ltd., S-3400N), and the obtained SEM of 5 square μm The image was subjected to automatic binarization processing using two-dimensional image analysis software (manufactured by Mitani Shoji Co., Ltd., WinRoof), and then the occupied area ratio of silica particles in a SEM image of 5 square μm was obtained.

<< Scanning electron microscope observation conditions >>
-Equipment used: S-3400N
・ Observation mode: Secondary electron (observation) mode ・ Acceleration voltage: 15 kV
Probe current: 30
・ Aperture stop: 3
・ Working distance (WD): 10mm
・ Magnification: 20000 times

The raw materials of the polyester film used in the following production examples are as follows.
<Method for producing polyester (I)>
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, 0.09 parts by weight of magnesium acetate tetrahydrate as a catalyst is placed in the reactor, the reaction start temperature is set to 150 ° C., and the methanol is distilled off gradually. The reaction temperature was raised to 230 ° C. after 3 hours. After 4 hours, the transesterification reaction was substantially terminated. After adding 0.04 part by weight of ethyl acid phosphate to this reaction mixture, 0.04 part by weight 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, and finally 0.3 mmHg. After the start of the reaction, the reaction was stopped at a time when the intrinsic viscosity was 0.63 dL / g due to a change in stirring power of the reaction tank, and the polymer was discharged under nitrogen pressure. The intrinsic viscosity of the obtained polyester (I) was 0.63 dL / g.

<Method for producing polyester (II)>
In the method for producing polyester (I), 0.04 part by weight of ethyl acid phosphate was added, and then 0.3 part by weight of silica particles having an average particle diameter of 1.6 μm dispersed in ethylene glycol, 0.04 part of antimony trioxide, 0.04 part. Polyester (II) was obtained using the same method as the production method of polyester (I) except that the polycondensation reaction was stopped at the time when the parts by weight were added and the intrinsic viscosity was 0.65 dL / g. The obtained polyester (II) had an intrinsic viscosity of 0.65 dL / g.

Moreover, the following was used as a composition of the functional layer formed in the polyester film surface.
(A1) Copolymerized polyester resin having an acid component having a condensed polycyclic aromatic structure and an aliphatic acid component: Monomer composition of an aqueous dispersion of a polyester resin copolymerized with the following composition: (acid component) 2,6-naphthalene Dicarboxylic acid / sebacic acid / 5 sodium 5-sulfoisophthalate // (diol component) ethylene glycol / hexanediol / diethylene glycol = 37/11/3 // 27/17/5 (mol%)
(A2) Acrylic resin: Aqueous dispersion of acrylic resin polymerized with the following composition: ethyl acrylate / n-butyl acrylate / methyl methacrylate / N-methylol acrylamide / acrylic acid = 65/21/10/2/2 (% by weight) Emulsion polymer (emulsifier: anionic surfactant)
(B1) 3-glycidoxypropyltrimethoxysilane (B2) epoxy compound: polyglycerol polyglycidyl ether (B3) hexamethoxymethylolmelamine

[Example 1]
Two extruders using a mixed raw material in which polyesters (I) and (II) are mixed at a ratio of 90% by weight and 10% by weight, respectively, as a raw material for the outermost layer (surface layer) and polyester (I) as a raw material for the intermediate layer Each is supplied to each and melted at 285 ° C., then co-extruded on a cooling roll set at 40 ° C. in a layer configuration of two types and three layers (surface layer / intermediate layer / surface layer), cooled and solidified, and unstretched A sheet was obtained. Next, the film was stretched 3.4 times in the flow direction (longitudinal direction) at a film temperature of 85 ° C. using the roll peripheral speed difference, then led to a tenter, and stretched 4.3 times at 120 ° C. in the width direction (transverse direction). After heat treatment at 225 ° C., a laminated polyester film having a thickness of 38 μm (surface layer 5 μm, intermediate layer 28 μm) was obtained.
The obtained laminated polyester film was applied off-line by a reverse gravure coating method so that the coating amount (after drying) was 0.13 g / m ² by using an offline dryer. A release film was obtained after drying at a temperature of 166 ° C. and a line speed of 50 m / min.
Table 2 shows the results of evaluation of the occupied area ratio of the silica particles distributed on the surface of the release layer of the obtained release film and the peel strength with time. Moreover, the SEM image which image | photographed the mold release layer surface of the mold release film is shown in FIG.

<Releasing agent composition A>
(I) Addition-type curable silicone resin (X62-5039, manufactured by Shin-Etsu Chemical Co., Ltd.): 15 parts by weight (a mixture of a curable silicone resin containing a vinyl group and a curable silicone resin containing a SiH group)
(Ii) Silica particle-containing addition-type curable silicone resin (BY24-312, manufactured by Toray Dow Corning Co., Ltd.): 5 parts by weight (containing silica particles, alkenyl group-containing curable silicone resin and SiH group) A mixture with curable silicone resin)
(Iii) Addition type platinum catalyst (CAT-PL-50T, manufactured by Shin-Etsu Chemical Co., Ltd.): 0.5 part by weight (iv) Methyl ethyl ketone / toluene mixed solvent (mixing volume ratio is 1: 1)

[Example 2] to [Example 8]
As in Example 1, the unstretched sheet was stretched 3.4 times in the longitudinal direction, and then coating liquids 1 to 7 having the composition shown in Table 1 below were coated on one side of the film so that the coating amount (after drying) was a predetermined amount. After each coating, the film was led to a tenter, stretched 4.3 times in the transverse direction at 120 ° C., and heat treated at 225 ° C., and then a functional layer having a thickness of 38 μm (surface layer 5 μm, intermediate layer 28 μm) was provided. A laminated polyester film was obtained.
The obtained laminated polyester film was provided with a release layer on the functional layer in the same manner as in Example 1 to obtain a release film. Table 2 shows the results of evaluation of the occupied area ratio of the silica particles distributed on the surface of the release layer of the obtained release film and the peel strength with time.

[Example 9]
The laminated polyester film obtained in Example 1 was applied off-line by a reverse gravure coating method so that the application amount (after drying) of the release agent composition A was 0.13 g / m ² . After heat treatment at 180 ° C. for 10 seconds, a release film was obtained.
Table 2 shows the results of evaluation of the occupied area ratio of the silica particles distributed on the surface of the release layer of the obtained release film and the peel strength with time. Moreover, the SEM image which image | photographed the mold release layer surface of the mold release film is shown in FIG.

[Comparative Example 1]
Using polyester (I) as a raw material for the outermost layer (surface layer) and the intermediate layer, each was supplied to two extruders, melted at 285 ° C., and then on a cooling roll set at 40 ° C. Coextruded with a layer structure and cooled and solidified to obtain an unstretched sheet. Next, the film was stretched 3.4 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, then led to a tenter, stretched 4.3 times at 120 ° C. in the transverse direction, and heat-treated at 225 ° C. Thereafter, a polyester film having a thickness of 38 μm was obtained.
The obtained polyester film is applied off-line by a reverse gravure coating method so that the coating amount of the release agent composition B containing no inert particles is 0.13 g / m ² (after drying). After applying and heat-treating at 180 ° C. for 10 seconds, a release film was obtained. Table 2 shows the results of evaluation of the occupied area ratio of the silica particles distributed on the surface of the release layer of the obtained release film and the peel strength with time.

<Releasing agent composition B>
(I) Addition-type curable silicone resin (X62-5039, manufactured by Shin-Etsu Chemical Co., Ltd.): 15 parts by weight (a mixture of a curable silicone resin containing a vinyl group and a curable silicone resin containing a SiH group)
(Ii) Organopolysiloxane resin (KS-3800, manufactured by Shin-Etsu Chemical Co., Ltd.): 5 parts by weight (iii) Addition type platinum catalyst (CAT-PL-50T, manufactured by Shin-Etsu Chemical Co., Ltd.): 0.5 Part by weight (iv) Methyl ethyl ketone / toluene mixed solvent (mixing volume ratio is 1: 1)

[Comparative Example 2]
As in Comparative Example 1, the unstretched sheet was stretched 3.4 times in the longitudinal direction, and then the coating liquid 1 having the coating composition shown in Table 1 below was coated on one side of the film so that the coating amount (after drying) was a predetermined amount. After coating, the film was led to a tenter, stretched 4.3 times at 120 ° C. in the transverse direction, and heat treated at 225 ° C., and then a functional layer having a thickness of 38 μm (surface layer 5 μm, intermediate layer 28 μm) was provided. A laminated polyester film was obtained.
The obtained laminated polyester film was provided with a release layer on the functional layer in the same manner as in Comparative Example 1 to obtain a release film. Table 2 shows the results of evaluation of the occupied area ratio of the silica particles distributed on the surface of the release layer of the obtained release film and the peel strength with time.

[Comparative Example 3]
A release liquid was obtained by applying a coating solution composed of the release agent composition C offline so that the coating amount (after drying) was 0.10 g / m ² and heat-treating at 130 ° C. for 10 seconds. Table 3 shows the evaluation results of the occupied area ratio of the silica particles distributed on the surface of the release layer of the obtained release film and the peel strength with time. Moreover, the SEM image which image | photographed the mold release layer surface of the mold release film is shown in FIG.

<Releasing agent composition C>
(I) Silica particle-containing addition-type curable silicone resin (BY24-312, manufactured by Toray Dow Corning Co., Ltd.): 5.3 parts by weight (silica particle-containing curable silicone resin containing alkenyl group and SiH group With curable silicone resin containing
(Ii) Addition type platinum catalyst (CAT-PL-50T, manufactured by Shin-Etsu Chemical Co., Ltd.): 0.11 part by weight (iii) Methyl ethyl ketone / toluene mixed solvent (mixed part by weight is 70:30)

The release films of Examples 1 to 8 were practically useful release films because the release force was maintained without excessively increasing the release force after 3 months after being bonded to the adhesive. . The release film of Example 9 was a release film that could be used practically without causing heavy peeling that would cause a problem even after 2 months had elapsed after bonding with the adhesive.
On the other hand, the release films of Comparative Examples 1 and 2 had a performance that could cause problems in cases such as transportation and inventory over a long period of time, after one month after bonding with the pressure-sensitive adhesive. Moreover, the release film of Comparative Example 3 had a performance that could cause a problem as a release film since the pressure-sensitive adhesive and peeling force increased immediately after production.

The present invention can be suitably used for manufacturing optical members such as liquid crystal polarizing plate manufacturing and touch panel manufacturing.

Claims

At least one surface of the polyester film has a release layer made of a cured product formed from a curable silicone resin and inert particles, and the release layer and the acrylic pressure-sensitive adhesive measured by the following method are peeled off. A release film having a force of 50 g / 25 mm or more and 150 g / 25 mm or less.
<Measurement method>
An acrylic pressure-sensitive adhesive composed of the following pressure-sensitive adhesive composition is applied to the release layer surface of the release film so that the coating amount (before drying) is 2 mil, and heat-treated at 150 ° C. for 3 minutes. The pressure-sensitive adhesive surface after the heat treatment is bonded to an untreated polyethylene terephthalate biaxially stretched film (thickness: 188 μm) with a rubber roller with a load of 2 kg to produce a release film with a pressure-sensitive adhesive.
Next, the peeling force after leaving the bonded release film with pressure-sensitive adhesive at room temperature for 1 hour is measured. The peeling force is 180 ° peeling under the condition of a tensile speed of 300 mm / min.
<Adhesive composition>
Main agent: AT352 (manufactured by Seiden Chemical Co., Ltd.) 100 parts by weight Curing agent: AL (manufactured by Seiden Chemical Co., Ltd.) 0.25 parts by weight Additive: X-301-375SK (manufactured by Seiden Chemical Co., Ltd.) 0.25 Part by weight Additive: X-301-352S (manufactured by Seiden Chemical Co., Ltd.) 0.4 part by weight Toluene 40 part by weight
The polyester film has a release layer composed of a cured product formed from a curable silicone resin and inert particles on at least one side of the polyester film, and the occupation of the inert particles on the surface of the release layer using a scanning electron microscope A release film having an area ratio of 4% or more and 12% or less.
The release film according to claim 1 or 2, wherein the curable silicone resin includes a curable silicone resin containing an alkenyl group.
The release film according to any one of claims 1 to 3, wherein the curable silicone resin includes a curable silicone resin containing a SiH group.
The release film according to any one of claims 1 to 4, wherein the cured product contains a platinum catalyst.
The release film according to any one of claims 1 to 5, wherein a functional layer is interposed between the polyester film and the release layer.
A release film with a pressure-sensitive adhesive having an acrylic pressure-sensitive adhesive layer on the surface of the release layer of the release film according to any one of claims 1 to 6.
The release film according to any one of claims 1 to 6, which is used as a protective film for an optical member.