JP5679787B2 - Polyester film for double-sided pressure-sensitive adhesive sheets - Google Patents

Description

  The present invention relates to a polyester film for a base-less double-sided pressure-sensitive adhesive sheet suitable for optical applications.

  Conventionally, various pressure-sensitive adhesive sheets for surface bonding between objects are known, and a base-less double-sided pressure-sensitive adhesive sheet is known as one of pressure-sensitive adhesive sheets. The substrate-less double-sided pressure-sensitive adhesive sheet is configured by laminating a light release sheet having a relatively low peeling force and a heavy release sheet having a relatively high peeling force on both sides of the pressure-sensitive adhesive layer, and removing the double-sided release sheet. The latter is a double-sided pressure-sensitive adhesive sheet that only has a pressure-sensitive adhesive layer that does not have a supporting substrate. The substrate-less double-sided PSA sheet is first peeled off from the light release sheet, and one side of the exposed PSA layer is bonded to the object surface. The other side of the layer is bonded to a different object surface, thereby surface bonding between the objects.

  In recent years, substrate-less double-sided PSA sheets are being used for various optical applications because of their advantages in that they can be stored for each unit, resulting in higher yields and versatility. Yes. For example, as the LCD member, peel off the release film with the lighter peeling force of the base-less double-sided pressure-sensitive adhesive sheet, paste the polarizing plate on the surface, and release the heavy release force on the opposite side. May be used.

  Due to workability in production, the difference in peel force between release films must be large. However, since there is a problem that it is difficult to control the release force of the release film on the heavy release side, the release force of the release film on the light release side is required to be as light as possible.

  Moreover, in order to reduce the peeling force of a release film, as one method, there is a method using the migration of a low molecular component. However, if the migration of the low molecular component is too high, it is transferred to a polarizing plate with an adhesive to which the component cause adheres, causing problems such as foreign matter, dirt, reduced adhesive strength, and defects such as dents. I am concerned about this.

JP 2009-220296 A JP 2003-231214 A JP 2002-361737 A Japanese Patent Application No. 2001-301024 Japanese Patent Application No. 2010-121101 JP 2009-220296 A JP 2010-13561 A Japanese Patent Laid-Open No. 10-158519

  The present invention has been made in view of the above circumstances, and the problem to be solved is that when the substrate-less double-sided pressure-sensitive adhesive sheet is used in optical applications such as a touch panel, a liquid crystal deflecting plate, a retardation plate, etc. A low-cost base material that provides low-cost films and enables the migration of low-molecular-weight silicone components that can cause various defects to be as low as possible, solving problems such as productivity and cost. It is providing the polyester film for double-sided adhesive sheets.

  As a result of intensive studies in view of the above circumstances, the present inventor has found that the above problem can be easily solved by a polyester film having a specific configuration, and has completed the present invention.

That is, the gist of the present invention is that a coating agent containing a solventless addition reaction curable silicone having a viscosity at 25 ° C. of 150 to 250 mPa · s is applied in a range of 0.12 to 1 g / m ^2. The release film has a release layer provided on one side, and the content of the solventless addition reaction curable silicone in the release layer is 0 with respect to 100 parts by weight of the resin constituting the release layer. 5 to 5.0 parts by weight, and the adhesive tape No. The peel strength by 31B is 15 mN / cm or less, and the adhesive tape No. It exists in the polyester film for base-material-free double-sided adhesive sheets characterized by the adhesive evaluation rate of the transferability of the silicone type component by 31B being 90% or more.

  According to the present invention, it is possible to provide a release polyester film that has a light peeling force, a low migration property of a low molecular silicone component, and an excellent air exposure property. Therefore, its industrial value is high.

  The polyester film referred to in the present invention is a film obtained by stretching a sheet melt-extruded from an extrusion die according to a so-called extrusion method.

The polyester constituting the film refers to a polymer containing an ester group obtained by polycondensation from dicarboxylic acid and diol or from hydroxycarboxylic acid.
Examples of dicarboxylic acids include terephthalic acid, isophthalic acid, adipic acid, azelaic acid, sebacic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and diols include ethylene glycol and 1,4-butane. Examples include diol, diethylene glycol, triethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, polyethylene glycol and the like, and examples of hydroxycarboxylic acid include p-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid. be able to. Typical examples of such a polymer include polyethylene terephthalate and polyethylene-2,6-naphthalate.

  In the film of the present invention, it is preferable to blend particles mainly for the purpose of imparting slipperiness and preventing the occurrence of scratches in each step. The kind of the particle to be blended is not particularly limited as long as it is a particle capable of imparting slipperiness. Specific examples thereof include silica, calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, calcium phosphate, and phosphoric acid. Examples of the particles include magnesium, kaolin, aluminum oxide, and titanium oxide. Further, heat-resistant organic particles as 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. These series of particles may be used in combination of two or more as required.

  Moreover, the average particle diameter of the particle | grains to be used is 0.01-3 micrometers normally, Preferably it is the range of 0.1-2 micrometers. When the average particle size is less than 0.01 μm, the slipperiness may not be sufficiently imparted. On the other hand, when the thickness exceeds 3 μm, transparency may be lowered due to the aggregate of the particles when the film is formed, and it is easy to cause breakage, which causes a problem in terms of productivity. There is.

  Furthermore, the content of particles in the polyester 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. On the other hand, when the content exceeds 5% by weight, the transparency of the film is insufficient. There is a case.

  The method for adding particles to the polyester layer 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 raw material, or a blending of dried particles and a polyester raw material using a kneading extruder. It is done by methods.

  In addition to the above-mentioned particles, conventionally known antioxidants, antistatic agents, thermal stabilizers, lubricants, dyes, pigments, and the like can be added to the polyester film in the present invention as necessary.

  Although the thickness of the polyester film in this invention will not be specifically limited if it is a range which can be formed into a film as a film, Usually, 10-350 micrometers, Preferably it is the range of 15-100 micrometers.

  Next, although the manufacture example of the polyester film in this invention is demonstrated concretely, it is not limited to the following manufacture examples at all. 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 90 to 140 ° C., preferably 95 to 120 ° C., and the stretching ratio is usually 2.5 to 7 times, preferably 3.0 to 6 times. Next, the film is stretched in the direction perpendicular to the first stretching direction. In that case, the stretching temperature is usually 90 to 170 ° C., and the stretching ratio is usually 3.0 to 7 times, preferably 3.5 to 6 times. is there. 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 of the present invention, a simultaneous biaxial stretching method can also be employed. The simultaneous biaxial stretching method is a method in which the unstretched sheet is usually stretched and oriented in the machine direction and the width direction at 90 to 140 ° C., preferably 80 to 110 ° C., and the stretching ratio is as follows. Is 4 to 50 times, preferably 7 to 35 times, and 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.

  Although the method in particular of forming a coating layer on the surface of a polyester film is not restrict | limited, The method of apply | coating a coating liquid in the process of manufacturing a polyester film is employ | adopted suitably. Specifically, a method of applying and drying a coating solution on the surface of an unstretched sheet, a method of applying and drying a coating solution on the surface of a uniaxially stretched film, and a method of applying and drying a coating solution on the surface of a biaxially stretched film Etc. Among these, it is economical to apply a coating solution on the surface of an unstretched film or a uniaxially stretched film, and then simultaneously dry and cure the coating layer in the process of heat-treating the film. Moreover, as a method for forming the coating layer, a method in which some of the above-described coating methods are used in combination can be adopted as necessary. Specifically, a method of applying a first layer on the surface of an unstretched sheet and drying, then stretching in a uniaxial direction, and then applying and drying a second layer can be used. Use the reverse roll coater, gravure coater, rod coater, air doctor coater, etc. shown in “Coating Method” by Yuji Harasaki, Tsuji Shoten, published in 1979, as a method of applying the coating solution to the surface of the polyester film. Can do.

  The coating solution used in the present invention is usually preferably adjusted with water as the main medium from the viewpoint of safety and hygiene. As long as water is the main medium, a small amount of an organic solvent may be contained for the purpose of improving the dispersion in water or improving the film forming performance. The organic solvent is preferably used as long as it is dissolved in water when mixed with water, which is the main medium. However, if it is a stable emulsion (emulsion) that does not separate after standing for a long time, Alternatively, it may be used in a state where it does not dissolve in water. The organic solvent may be used alone or in combination of two or more as necessary.

  The release layer formed on one outermost layer of the polyester film obtained in the present invention contains a material having releasability, and specifically contains a solventless addition reaction curable silicone. It is a release layer provided by applying a coating agent, and the release layer is preferable because the release property is improved. 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.

  As a kind of the curable silicone resin used in the present invention, an addition type is mainly used, and an emulsion type is possible, but a solventless addition reaction curing type having a relatively small molecular weight is mainly used.

Examples of the silicone resin used in the present invention include the following. (A) Polydiorganosiloxane having two or more alkenyl groups in one molecule (B) Polyorganosiloxane containing SiH groups Here, component (A) has two or more alkenyl groups in one molecule Examples of such alkenyl group-containing polydiorganosiloxanes include polydiorganosiloxanes represented by the following general formula (1).
General formula (1)
_{R (3-a) X a} SiO- (RXSiO) m - (R 2 SiO) n - (RXSiO) p -R (3-a) X a SiO
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 0 or more, but when a = 0, m is 2 or more, and m and n are numbers satisfying 100 ≦ m + n ≦ 20000, respectively. , P is 2 or more. 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. An aryl group such as, for example, is mentioned, and a methyl group and a phenyl group are particularly preferable. X is an alkenyl group-containing organic group, preferably having 2 to 10 carbon atoms, specifically vinyl, allyl, hexenyl, octenyl, acryloylpropyl, acryloylmethyl, methacryloylpropyl, cyclohexenylethyl. Group, vinyloxypropyl group, and the like, among which vinyl group and hexenyl group are particularly preferable.

  The polydiorganosiloxane may be in the form of oil or raw rubber, and the viscosity of the component (A) is preferably 100 mPa · s or more, particularly 1000 mPa · s or more at 25 ° C. In addition, although it does not specifically limit as an upper limit, It is preferable to select so that a polymerization degree may be 20000 or less from the ease of mixing with another component. Moreover, (A) component may be used individually by 1 type, and may use 2 or more types together.

The (B) component SiH group-containing polyorganosiloxane is a crosslinking agent, and is an organohydropolysiloxane having at least 2, preferably 3 or more, hydrogen atoms bonded to silicon atoms in one molecule. , Branched, annular, etc. can be used. (B) As a component, although the compound represented by following General formula (2) can be mentioned, it is not limited to these.
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
In the general formula (2), R1 is a monovalent hydrocarbon group containing no C1-C6 aliphatic unsaturated bond. b is an integer of 0 to 3, and x and y are integers, respectively, and indicate the number at which the viscosity of this organohydropolysiloxane at 25 ° C. is 1 to 5000 mPa · s. The viscosity of this organohydropolysiloxane at 25 ° C. is preferably 1 to 5000 mPa · s, particularly 5 to 1000 mPa · s, and may be a mixture of two or more.

  Crosslinking by addition reaction occurs between the component (A) and the component (B) of the crosslinking agent, and the gel fraction of the adhesive layer after curing is determined by the ratio of the crosslinking component. Component (B) is used so that the molar ratio of SiH groups in component (B) to alkenyl groups in component (A) is in the range of 0.5 to 20, particularly 0.8 to 15. It is preferable. If it is less than 0.5, the crosslinking density is lowered, and the holding force may be lowered accordingly. On the other hand, if it exceeds 20, the adhesive strength may decrease, or the usable time of the treatment liquid may be shortened.

  In addition, in order to improve the heat resistance such as heat resistance and solvent resistance such as suppression of solvent penetration, the proportion of the cross-linking component in the composition may be increased. There may be effects such as reduced flexibility. From such a point, the blending mass ratio of the component (A) / (B) may be 20/80 to 80/20, and is particularly preferably 45/55 to 70/30. When the blending ratio of the component (A) is less than 20/80, the adhesive property may be deteriorated, and when it is more than 80/20, sufficient heat resistance may not be obtained.

  In the present invention, in order to achieve the described peeling force and silicone migration, a solventless addition reaction curable silicone formulated as described above must be used. The blended solventless addition reaction curable silicone has a viscosity at 25 ° C. of preferably 5 to 1000 mPa · s, more preferably 20 to 500 mPa · s, and still more preferably 50 to 250 mPa · s. The viscosity at 25 ° C. of the solventless addition reaction curable silicone used in Examples and Comparative Examples was in the range of 150 to 250 mPa · s.

Specific examples of the solventless type silicone resin coating material include DEHESIVE ^R 636, 919, 920, 921, 924, 929 and the like in the DEHESIVE series manufactured by Asahi Kasei Wacker Silicone Co., Ltd. Further, a release control agent may be used in combination to adjust the release property of the release layer. Further, as described above, a silane compound having an amino group may be added to the release layer.

  In the polyester film of the present invention, the content of the solventless addition reaction curable silicone in the release layer is usually in the range of 0.5 to 5.0 parts by weight. Preferably, it is 1.0 to 3.0 parts by weight. If the content is less than 0.5 parts by weight, the intended light release may not be satisfied. On the other hand, when the value is larger than 5.0 parts by weight, there is a large amount of low molecular weight silicone migratory component, which may affect productivity.

In the present invention, as a method for providing a release layer on the polyester film, a conventionally known coating method such as reverse roll coating, gravure coating, bar coating, doctor blade coating, or the like can be used. The application amount of the release layer in the present invention is usually in the range of 0.01 to 1 g / m ² .

  In the present invention, a coating layer such as an adhesive layer, an antistatic layer and an oligomer precipitation preventing layer may be provided on the surface where the release layer is not provided, and the polyester film may be subjected to corona treatment, plasma treatment, etc. A surface treatment may be applied.

  Moreover, drying and / or curing (thermal curing, ionizing radiation curing, etc.) of the coating film of the pressure-sensitive adhesive layer or the release layer can be performed individually or simultaneously. When performing simultaneously, it is preferable to carry out at the temperature of 80 degreeC or more. The drying and curing conditions are preferably 80 ° C. or higher and 10 seconds or longer. When the drying temperature is less than 80 ° C. or the curing time is less than 10 seconds, the coating film is not completely cured, and the coating film tends to fall off, which is not preferable.

  In the polyester film in the present invention, a platinum-based catalyst that promotes an addition-type reaction is used to make the release layer clean and strong. 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.

  In addition, since the addition-type reaction is very reactive, acetylene alcohol may be added as an unreactive inhibitor in some cases. The component is an organic compound having a carbon-carbon triple bond and a hydroxyl group, and preferably 3-methyl-1-butyn-3-ol, 3,5-dimethyl-1-hexyn-3-ol and phenylbuty It is a compound selected from the group consisting of nor.

  In the present invention, the peeling force refers to a double-sided pressure-sensitive adhesive tape (“No. 31B” manufactured by Nitto Denko) attached to the release layer surface and left at room temperature for 1 hour, and then the substrate film and the peeling angle of 180 °. The value measured with a tensile tester when the tape is peeled off at the tensile speed. The method for adjusting the specific peeling force in the present invention can be achieved by selecting the composition in the release layer, but other means can also be adopted, mainly the type of release agent for the silicone release layer. Is preferably changed according to the desired peeling force, and furthermore, since the peeling force largely depends on the application amount of the release agent to be used, a method of adjusting the application amount of the release agent is more preferable. The peeling force in the release film of the present invention is in the range of 10 to 15 mN / cm. When the peeling force is less than 10 mN / cm, the peeling force becomes too light, and the problem of peeling easily occurs even in a scene where it is not necessary to peel off. The means for achieving the above peeling force in the polyester film according to the present invention is a polyester film outer layer comprising, as a coating film, a silicone containing a certain amount of solvent-free addition reaction curable silicone having a viscosity at 25 ° C. of 5 to 1000 mPa · s. It is to be laminated.

  The migration rate evaluation adhesion rate of the silicone-based component of the release layer in the present invention is an adhesive tape (“No” manufactured by Nitto Denko Corporation) when pressed for 2 hours under the conditions of a temperature of 60 ° C. and a pressure of 1 MPa. .31B ") is measured, and the ratio of the peel force to that before the treatment is calculated. The peeling force was “Intesco Model 2001” manufactured by Intesco Co., Ltd., and 180 ° peeling was performed under the condition of a tensile speed of 0.3 (m / min). The migration evaluation adhesion rate needs to be 90% or more. When the transferability evaluation adhesion rate is lower than 90%, the transfer component becomes a defect such as a foreign substance, or moves to the surface opposite to the release coat surface during winding, and the release film is peeled off in the previous step. Or cause problems.

  In the present invention, the means for achieving the above-mentioned transferability in the polyester film is, for example, by using a silicone containing a certain amount of a solvent-free addition reaction curable silicone having a viscosity at 25 ° C. of 5 to 1000 mPa · s as a coating film. Laminating on the outer layer of a film is mentioned.

  In the present invention, the release layer was exposed to air in a non-clean room with a room temperature of 23 ° C. and a humidity of 50% RH for 24 hours (exposure), and then an adhesive tape (“No. 31B” manufactured by Nitto Denko Corporation). ) Is used to measure the peel force and the ratio of the peel force before the exposure is taken. The peeling force was “Intesco Model 2001” manufactured by Intesco Co., Ltd., and 180 ° peeling was performed under the condition of a tensile speed of 0.3 (m / min). The peel force after exposure to air is preferably less than 15 mN / cm, and the peel force fluctuation before and after exposure is preferably within ± 10%. If it is out of this range, the product may be a film that is extremely weak against changes in temperature and humidity, which may cause problems such as difficulty in storage control.

  In the present invention, the means for achieving the above air exposure resistance in the polyester film is, for example, a coating film made of a silicone containing a certain amount of a solventless addition reaction curable silicone having a viscosity at 25 ° C. of 5 to 1000 mPa · s. And laminating on the outer layer of the polyester film.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is exceeded. The measurement method and evaluation method used in the present invention are as follows.

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

(2) Measurement of average particle size (d50: μm) 50% integrated (weight basis) in equivalent spherical distribution measured using centrifugal sedimentation type particle size distribution measuring device (SA-CP3 type manufactured by Shimadzu Corporation) The value was defined as the average particle size.

(3) Measurement of transmittance of polyester film According to JIS-K7105, the total light transmittance of the polyester film was measured with an integrating sphere turbidimeter NDH-300A manufactured by Nippon Denshoku Industries Co., Ltd. Judgment is based on the following criteria.

(4) Measurement of haze (turbidity) of polyester film According to JIS-K7105, the haze of the film was measured with an integrating sphere turbidimeter NDH-20D manufactured by Nippon Denshoku Industries Co., Ltd.

(5) Measurement of heat shrinkage rate of polyester film The polyester film was sampled at an arbitrary length L (cm) in the longitudinal direction (hereinafter abbreviated as MD) and the lateral width direction (hereinafter abbreviated as TD). To do. Subsequently, the sample is heated in an oven at 160 ° C. for 5 minutes, and the sample is taken out of the oven and the length l (cm) is measured. This operation is performed three times, and the average value is adopted as the value of the heat shrinkage rate. The heat shrinkage rate can be calculated by the following formula.
Heat shrinkage (%) = {(L−l) / L} × 100

(6) Measurement of catalyst amount in coating layer Using SAICAS, the sample film was obliquely cut to expose the cross section. Then, the amount of catalyst containing platinum contained in the polyester film coating layer was determined using TOF-SIMS (time-of-flight mass spectrometry mass spectrum).

(7) Measurement of amount of catalyst in coating layer Using SAICAS, the sample film was obliquely cut to expose the cross section. Then, the amount of catalyst containing platinum contained in the polyester film coating layer was determined using TOF-SIMS (time-of-flight mass spectrometry mass spectrum).

(8) Evaluation of peeling force (F) of release film After applying one side of a double-sided adhesive tape (Nitto Denko "No. 31B") to the release layer surface of the sample film, cut into a size of 50 mm x 300 mm After that, the peel strength after standing for 1 hour at room temperature is measured. The peeling force was 180 ° peeled at a tensile speed of 300 mm / min using a tensile tester (“Intesco Model 2001” manufactured by Intesco Corporation). Judgment is based on the following criteria.
○: 15 mN / cm or less ×: Greater than 15 mN / cm

(9) Evaluation of silicone low molecular weight component transferability of release film (XRF)
A surface on which a release layer of a release film is provided under the following measurement conditions by an FP (Fundamental Parameter Method) method using an X-ray fluorescence measurement apparatus (Shimadzu Corporation, model “XRF-1500”). And the amount of silicon element on the surface without the release layer was measured, and the difference was taken as the amount of silicon element in the release layer. Next, the coating amount (Si) (g / m ² ) as a unit of —SiO (CH ₃ ) ₂ was calculated using the obtained amount of silicon element.
"Measurement condition"
Spectral crystal: PET (pentaerythritol)
2θ: 108.88 °
Tube current: 95 mA
Tube voltage: 40 kv

(10) Evaluation of silicone low molecular weight component transferability of release film Cut sample film into A4 size, and put 75μm thick biaxially stretched PET film (Mitsubishi Resin Co., Ltd .: Diafoil T100-75) on the release surface. Press for 2 hours under conditions of a temperature of 60 ° C. and a pressure of 1 MPa. A 75 μm-thick film pressed against this release surface is used as a migration evaluation film. Similarly, a 75 μm-thick biaxially stretched PET film (same as above) is pressed against an untreated PET film as a reference film. Adhesive tape (“No. 31B” manufactured by Nitto Denko Corporation) is applied to the pressed surface of each film, then cut to a size of 50 mm × 300 mm, and the peel strength after standing for 1 hour at room temperature. It was measured. The peeling force was “Intesco Model 2001” manufactured by Intesco Co., Ltd., and 180 ° peeling was performed under the condition of a tensile speed of 0.3 (m / min).
Transferability evaluation adhesion rate (%) = (Peeling force of transferability evaluation film / Peeling force of reference film) × 100
The obtained results are judged according to the following criteria.
○: 90% or more ×: Less than 90%

(11) Evaluation of air release resistance of release film A sample film is cut to A4 size, and hung on a string passed into a laboratory (non-clean environment) adjusted to room temperature 23 ° C. and humidity 50% RH for 24 hours. An adhesive tape (“No. 31B” manufactured by Nitto Denko Co., Ltd.) was attached to the release surface, then cut to a size of 50 mm × 300 mm, and the peel force after standing at room temperature for 1 hour was measured. The peeling force was “Intesco Model 2001” manufactured by Intesco Co., Ltd., and 180 ° peeling was performed under the condition of a tensile speed of 0.3 (m / min). Judgment is based on the following criteria.
○: 15 mN / cm or less ×: Greater than 15 mN / cm

(12) Release characteristics The release characteristics were evaluated from the situation when the release film was peeled off from the laminated film having the adhesive layer.
○: Peeling of the release film neatly, causing the adhesive to adhere to the release layer, or the silicone low molecular weight component derived from the release layer not attaching to the adhesive Δ: The release film is peeled off but peeling at a high speed The adhesive adheres to the release layer, or a small amount of the silicone low molecular component derived from the release layer adheres to the adhesive. ×: Adhesive adheres to the release film, does not peel off well, or Silicone low-molecular components derived from the release layer adhere to the adhesive

(13) Comprehensive evaluation An evaluation is performed in consideration of all film forming properties, productivity, and inspection characteristics. Judgment is based on the following criteria.
○: Even if it is produced, it can be sufficiently supplied as a product. Δ: Productivity is good and the frequency of defects is low. ×: Productivity is poor. Trouble occurs frequently

The polyester used in the examples and comparative examples was prepared as follows.
<Method for producing polyester (a)>
Using 100 parts by weight of dimethyl terephthalate and 60 parts by weight of ethylene glycol as starting materials, adding tetrabutoxy titanate as a catalyst to the reactor, setting the reaction start temperature to 150 ° C., and gradually increasing the reaction temperature as methanol is distilled off. It was 230 degreeC after 3 hours. After 4 hours, the transesterification reaction was substantially completed, and then a polycondensation reaction was performed 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 corresponding to an intrinsic viscosity of 0.61 due to a change in the stirring power of the reaction vessel, and the polymer was discharged under nitrogen pressure to obtain a polyester (a) having an intrinsic viscosity of 0.61.

<Method for producing polyester (b)>
In the production method of polyester (a), 0.2 part of silica particles having an average particle diameter of 2.0 μm dispersed in ethylene glycol was added, and the polycondensation reaction was stopped at a time corresponding to an intrinsic viscosity of 0.61. A polyester (b) having an intrinsic viscosity of 0.61 was obtained using a method similar to the method for producing polyester (a).

Example 1:
<Manufacture of polyester film>
Mixing 77% by weight of polyester (a) and 23% by weight of polyester (b) as the raw material for the surface layer, using polyester (a) as the raw material for the intermediate layer, and supplying each to two vented extruders, After melt extrusion at 290 ° C., an unstretched sheet was obtained by cooling and solidifying on a cooling roll whose surface temperature was set to 40 ° C. using an electrostatic application adhesion method. Next, the film was stretched 3.2 times in the longitudinal direction at 100 ° C., then subjected to a preheating step in the tenter and 4.3 times transverse stretching at 120 ° C., followed by heat treatment at 220 ° C. for 10 seconds, 4% relaxation was added in the width direction at 180 ° C. to obtain a master roll having a width of 4000 mm. A slit was made from a position of 1400 mm from the end of the master roll, and the core roll was wound up 1000 m to obtain a polyester film. The total thickness of the obtained film was 38 μm (layer constitution: surface layer 4 μm / intermediate layer 30 μm / surface layer 4 μm).

A release agent composed of release agent composition-A shown below was applied to the obtained polyester film by a reverse gravure coating method so that the coating amount (after drying) was 0.12 g / m ² , and the dryer temperature was 120. A roll-shaped release polyester film was obtained under the conditions of ° C and a line speed of 30 m / min. The resulting release polyester film is a release film having a release force of 12 mN / cm, a migration evaluation adhesion rate of silicone-based components of 95%, and a peel force of 13 mN / cm after one day of air exposure in an air resistance test. Hereinafter, the peel force fluctuation ratio before and after exposure to air was 8%.

<Releasing agent composition-A>
Addition-type cured silicone resin (BY24-561 30%: manufactured by Toray Dow Corning)
6.7 parts solvent-free addition-type cured silicone resin (DEHEISIVE 929 solid content concentration 100
% By weight: manufactured by Asahi Kasei Wacker Silicone Co., Ltd.) 1.0 part Curing agent (V24, solid content concentration: 100% by weight: manufactured by Asahi Kasei Wacker Silicone Co., Ltd.)
0.08 parts addition type platinum catalyst (BY24-835 solid content concentration: 100% by weight: manufactured by Toray Dow Corning) 0.30 parts MEK / toluene / n-heptane mixed solvent (mixing ratio is 1: 1: 1.5) )

  For the obtained polyester film, a polarizing plate was prepared by the following method, and the peeling characteristics were evaluated. The obtained release film peeled off the polarizing plate cleanly, and no phenomenon such as the generation of foreign matter in the adhesive caused by the low molecular weight silicone component was observed, where the adhesive adhered to the release layer.

<Manufacture of polarizing plate with release film>
The acrylic adhesive shown below is applied to the polarizing plate so that the thickness after drying is 25 μm, and after passing through a 130 ° C. drying oven in 30 seconds, the release film is bonded, and the adhesive is interposed. Thus, a polarizing plate with a release film in which the release film and the polarizing film were adhered to each other was prepared. The laminating direction of the film was performed so that the width direction of the release film was parallel to the orientation axis of the polarizing film.

Acrylic adhesive coating solution Acrylic adhesive (Olivein BPS429-4: manufactured by Toyo Ink) 100 parts Curing agent (BPS8515: manufactured by Toyo Ink) 3 parts MEK / toluene mixed solvent (mixing ratio is 1: 1) 50 parts

Examples 2-4:
In Example 1, a polyester film was obtained in the same manner as in Example 1 except that the solvent-free silicone content of the release agent composition in the coating layer during the production of the polyester film was changed. The obtained results are summarized in Table 1 below.

Comparative Examples 1-3:
In Example 1, it is produced in the same manner as in Example 1 except that the solventless silicone content of the release agent composition in the coating layer during the production of the polyester film is changed, or the application amount of the release agent is changed. A polyester film was obtained. The results obtained are summarized in Table 2 below.

  The polyester film of the present invention can be suitably used as a release polyester film having good productivity and low peeling force in the field of substrate-less double-sided pressure-sensitive adhesive sheets in optical applications where demand is great.

Claims (1)

A release layer provided by applying a coating agent containing a solventless addition reaction curable silicone having a viscosity at 25 ° C. of 150 to 250 mPa · s in a range of 0.12 to 1 g / m ^2. A release film on one side, and the content of the solventless addition reaction curable silicone in the release layer is 0.5 to 5.0 parts by weight with respect to 100 parts by weight of the resin constituting the release layer. , and the adhesive tape of the release layer No. The peel strength by 31B is 15 mN / cm or less, and the adhesive tape No. The polyester film for base material-less double-sided pressure-sensitive adhesive sheets, wherein the adhesive rate of migration evaluation of silicone-based components by 31B is 90% or more.