JP2015199265A - Release film for substrate-less double-sided adhesive sheets - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a release film suitable for substrate-less double-sided adhesive sheets which is imparted with smoothness of an adhesive layer, does not cause blocking, with slipperiness improved even when being superimposed on a hard coat layer, allows easy detection of defects by an automatic inspection machine and is usable in protective films for prevention of scattering.SOLUTION: A release film for substrate-less double-sided adhesive sheets has a structure composed of at least two layers and is provided, on one side of a polyester film, with a release layer of a thickness of 50-150 μm and an inclination (orientation angle) of the main axis of the orientation of 12 degrees or smaller. The surface roughness is different between the front and back surfaces of the release layer; the surface roughness (Ra) of the front surface of the release layer is 10-20 nm; and the surface roughness Ra of the back surface of the release layer is 20-40 nm.

Description

  TECHNICAL FIELD The present invention relates to a release film used for a substrate-less double-sided pressure-sensitive adhesive sheet, and in particular, a substrate-less double-sided pressure-sensitive adhesive for bonding a protective film for preventing scattering of glass of a portable information terminal such as a mobile phone or a touch panel to a substrate of a touch panel. The present invention relates to a release film suitable for a sheet.

  Mobile terminal devices such as touch panels and mobile phones tend to be thinner than the demand for portability, and when glass panels are used, protective films for preventing scattering are used. The protective film used to prevent scattering is provided with a hard coat layer to prevent scratches on the surface. Poor property and there is a problem in handling property in each process.

  In order to improve the slipperiness, it is effective that the surface on which the hard coat layer is superposed is a surface having an appropriate surface roughness.

  If the reverse release surface of the release film that is bonded to the substrate-less double-sided pressure-sensitive adhesive sheet for bonding the protective film having the hard coat layer to the panel substrate is superimposed on the hard coat layer, In the surface roughness that improves the slipperiness with the coat layer, in order to deform the adhesive that the release layer side comes into contact with, the release film is peeled off, and when the protective film is bonded to the base material, bubbles are involved, etc. There's a problem.

  In addition, the inspection by the automatic inspection machine is performed by crossed Nicols inspection of polarized transmitted light in order to detect more minute defects, and the release film is required to be compatible with the crossed Nicols inspection. It is.

Japanese Patent Application No. 2010-56884 Japanese Patent Application No. 2010-121101 Japanese Patent Application No. 2010-97765 Japanese Patent Application No. 2010-97925 Japanese Patent Application No. 2010-165733 Japanese Patent Application No. 2011-48410 Japanese Patent Application No. 2011-75120

  The present invention has been made in view of the above circumstances, and its solution is to provide smoothness to the adhesive layer, and at the same time, even when superimposed on the hard coat layer, the slipperiness is improved and blocking occurs. Another object of the present invention is to provide a release film suitable for a substrate-less double-sided pressure-sensitive adhesive sheet used for a protective film for preventing scattering, which can be easily detected by an automatic inspection machine.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor has found that the above-mentioned problems can be easily solved by a release film having a specific configuration, and has completed the present invention.

  That is, the gist of the present invention is a group having a release layer on one side of a polyester film having a thickness of 50 to 150 μm, having a structure consisting of at least two layers, and having an inclination angle (orientation angle) of 12 degrees or less. It is a release film for a material-less double-sided PSA sheet, the surface roughness of the front and back is different, the surface roughness (Ra) of the release layer surface is in the range of 10 to 20 nm, and the surface roughness Ra of the anti-release layer surface Exists in the mold release film for base-material-free double-sided pressure-sensitive adhesive sheets, characterized by being in the range of 20 to 40 nm.

  According to the present invention, if the release film of the present invention is used for the base material-less double-sided pressure-sensitive adhesive sheet constituting the protective film for preventing touch panel scattering having a hard coat layer, the smoothness to the pressure-sensitive adhesive is maintained and the hard film is hard. Even when it is overlapped with the coat layer, it has good slipperiness, easy defect detection with an automatic inspection machine, and the industrial value of the present invention is high.

  The polyester used for the polyester film in the present invention may be a homopolyester or a copolyester. In the case of a homopolyester, those obtained by polycondensation of an aromatic dicarboxylic acid and an aliphatic glycol are preferred. 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. Representative polyester includes polyethylene terephthalate (PET) and the like. On the other hand, examples of the dicarboxylic acid component of the copolyester include isophthalic acid, phthalic acid, terephthalic acid, 2,6-naphthalenedicarboxylic acid, adipic acid, sebacic acid, and oxycarboxylic acid (eg, P-oxybenzoic acid). 1 type or 2 types or more are mentioned, As a glycol component, 1 type or 2 types or more, such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, 1, 4- cyclohexane dimethanol, neopentyl glycol, is mentioned. In any case, the polyester referred to in the present invention refers to a polyester which is polyethylene terephthalate or the like in which 60 mol% or more, preferably 80 mol% or more is an ethylene terephthalate unit.

  In the present invention, the polyester film constituting the release film is characterized by having at least a two-layer structure in order to obtain films having different surface roughnesses on the front and back sides.

  The surface roughness that differs between the front and back is that the surface of the releasable release layer that requires slipperiness is specifically 2 nm or more higher in surface roughness (Ra) than the surface of the release layer that requires smoothness. Point to.

  The surface roughness (Ra) of the release layer is in the range of 10 to 20 nm, and the surface roughness (Ra) of the anti-release layer is in the range of 20 to 40 nm.

  When the surface roughness of the release layer is less than 10 nm, the film surface has small protrusions, the film becomes less slippery, the appearance when wound with a roll is deteriorated, or the film is in contact with the roll in the film forming process. Since the surface is damaged, it is not preferable.

  When the surface roughness (Ra) of the release layer exceeds 20 nm, it is not preferable because the adhesive layered as a release film is provided with irregularities that are disadvantageous. In particular, base material-less double-sided pressure-sensitive adhesive sheets for preventing scattering of mobile touch panels tend to use a soft adhesive to fill the level difference or become thin, and are easily affected by the surface roughness of the release film. .

  Since the releasable layer is used as a part of the protective film of the anti-scattering film having the hard coat layer, the surface roughness (Ra ) Needs to be 20 nm or more, and if it is less than 20 nm, the protrusion on the film surface is small, and the slipperiness when the smooth hard coat layer is overlaid is insufficient, which is not preferable.

  When the surface roughness (Ra) of the anti-release layer exceeds 40 nm, the surface roughness of the film becomes too rough, and protrusions may be transferred to the surface of the release layer or particles may become foreign matters. Absent.

  In the polyester layer constituting the polyester film of the present invention, particles are blended for the main purpose of imparting easy slipperiness, but the blended particles differ depending on the polyester layer serving as the release layer surface and the anti-release layer surface.

  The polyester layer used as the release layer surface has a mean particle size of usually 0.1 to 2.0 μm, preferably 0.5 to 1.0 μm, in order to give a specific surface roughness that suppresses deformation of the pressure-sensitive adhesive. To do. When the average particle size is less than 0.1 μm, the surface roughness (Ra) of the release layer required in the present invention may not be obtained, and the slipperiness of the film may be deteriorated. Even when the average particle diameter exceeds 2.0 μm, it may not be possible to obtain the surface roughness (Ra) of the release layer required in the present invention, and give the unevenness that becomes a defect to the bonded adhesive. There is.

  The polyester layer serving as the releasable mold surface has a mean particle size of usually 2.0 to 4.0 μm, preferably 3.0 to 4.0 μm, in order to give slipperiness when overlaid with the hard coat layer. use. Average particle size is 2.0. If it is less than μm, the surface roughness Ra of the releasable film required in the present invention may not be obtained, and the slipperiness when the smooth hard coat layers are stacked may be insufficient. Even when the average particle diameter exceeds 4.0 μm, the surface roughness (Ra) of the releasable layer necessary for the invention may not be obtained, and the bonded adhesive may be provided with irregularities that become defects. There is.

  The content of particles in the polyester layer serving as the release layer is preferably in the range of 0.05 to 0.50% by weight. When the particle content is less than 0.05% by weight, there are few protrusions on the film surface, the slipping property of the film is poor, the appearance when wound with a roll is deteriorated, or the film is in contact with the roll in the film forming process. The surface may be damaged.

  The particle content in the polyester layer to be the releasable layer is preferably in the range of 0.10 to 0.50% by weight. When the particle content is less than 0.10% by weight, there are few protrusions on the film surface, and the slipperiness when the smooth hard coat layer is overlaid may be insufficient. When the amount of the particles exceeds 0.50% by weight, the surface roughness of the film becomes too rough, and the protrusions may be transferred to the surface of the release layer or the particles may become foreign matters.

  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, 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, it is possible to use precipitated particles in which a part of a metal compound such as a catalyst is precipitated and finely dispersed during the manufacturing process of the film raw material.

  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.

  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 of producing the polymer constituting each layer.

  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.

  In order that the release film for base material-less double-sided pressure-sensitive adhesive sheets of the present invention has a role of protecting the base-material-less double-sided pressure-sensitive adhesive sheet, the film thickness is preferably 50 to 150 μm. If the film thickness is less than 50 μm, the pressure-sensitive adhesive may be deformed when it comes into contact with the protrusions in the manufacturing process. When film thickness exceeds 150 micrometers, the intensity | strength of a polyester film becomes strong and the roll external appearance after bonding a release film to an adhesive may worsen, or cost may become high.

  A major feature of the present invention is that the surface of the release layer and the surface of the release layer are constituted by the laminated polyester, and the thickness ratio of each laminated polyester is usually in the range of 5 to 95%, preferably 10 It is in the range of -90%, more preferably in the range of 20-80%. When the thickness ratio of each laminated polyester is less than 5% or exceeds 95%, it may be affected by the opposite surface and may not play its original role. When the laminated polyester on the release layer side is less than 5%, there are cases where protrusions appearing on the surface of the release layer that cause problems with the adhesive due to the influence of particles contained in the laminated polyester on the side of the release layer. is there. When the laminated polyester on the side of the release layer is less than 5%, the surface roughness becomes low, and the slipperiness with the hard coat layer may be deteriorated.

  The biaxially oriented polyester film used for the release film of the present invention needs to satisfy that the inclination of the orientation main axis is 12 degrees or less, preferably 10 degrees or less. In addition, the inclination of the orientation principal axis here is also called an orientation angle, and is the inclination of the principal axis with respect to the film width direction or the longitudinal direction.

  When the release film of the present invention is bonded to the film for scattering prevention via the substrate-less pressure-sensitive adhesive and the inspection is performed by the crossed Nicols method for polarized transmitted light, the orientation angle is determined in this inspection step. In a mold release film using a biaxially oriented polyester film having an angle of more than 12 degrees, light leakage is large, which hinders detection of defects such as foreign matter and scratches.

  In the biaxially oriented polyester film used for the second release film 9 of the present invention, the orientation of the orientation main axis is to change the conditions such as the temperature in the longitudinal stretching and the stretching ratio, the temperature and the stretching ratio in the transverse stretching, and the relaxation treatment. Can be adjusted.

  The release layer of the present invention is not particularly limited as long as it contains a material having releasability. Among them, the one containing a curable silicone resin is preferable because the releasability 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 the type of the curable silicone resin, any of the curing reaction types such as an addition type, a condensation type, an ultraviolet ray curable type, an electron beam curable type, and a solventless type can be used.

  Specific examples include KS-774, KS-775, KS-778, KS-779H, KS-847H, KS-856, X-62-2422, X-62-2461, Dow, manufactured by Shin-Etsu Chemical Co., Ltd. -Corning Asia Co., Ltd. DKQ3-202, DKQ3-203, DKQ3-204, DKQ3-205, DKQ3-210, Toshiba Silicone Co., Ltd. YSR-3022, TPR-6700, TPR-6720, TPR-6721, Toray Dow Corning Co., Ltd. SD7220, SD7226, SD7229, etc. are mentioned. Further, a release control agent may be used in combination to adjust the release property of the release layer.

  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 or a coating layer may be provided on the surface where the release layer is not provided, and the polyester film is subjected to a surface treatment such as corona treatment or plasma treatment. May be applied.

  The release force of the release film corresponding to the light release side is preferably 3 to 50 mN / cm, and more preferably 5 to 25 mN / cm.

  Even if the release force of the release film on the heavy release side is lowered by keeping the release force of the release film corresponding to the light release side low, the difference in release force between the release film on the light release side and the release side of the heavy release side Can be increased.

  Also, by setting the release force of the release film on the light release side to a certain value or more, the release film may be unexpectedly peeled off from the adhesive layer before use, or the release film may float from the adhesive layer. Is prevented.

  The release force of the release film corresponding to the heavy release side is preferably 10 to 100 mN / cm, and more preferably 15 to 50 mN / cm.

  By suppressing the release force of the release film on the heavy release side to a low level, it is possible to prevent the adhesive from remaining on the release film, zipping, and the like that occur when the release film is released.

  The baseless double-sided pressure-sensitive adhesive sheet is, for example, a light release release film is pasted after a pressure-sensitive adhesive is provided on the release layer surface on the heavy release side, and a light release and heavy release release film are attached to both sides. It becomes a product in the state of being used, and is used for a protective film for preventing scattering.

  The base-less double-sided PSA sheet that has become a product is peeled off from the release film on the light release side, and the release film on the anti-hard coat layer side of the anti-scattering protective film with a hard coat layer. The peeled adhesive surface is bonded, and the opposite surface of the hard coat layer surface is the configuration of the releasable layer surface. At this time, since the hard coat layer and the releasable layer surface are overlapped, the hard coat layer and the releasable layer surface must be slippery.

  Light release and heavy release release films are used for the substrate-less double-sided pressure-sensitive adhesive sheet, but the release film of the present invention is used at least as a release film on the side of heavy release to be overlaid with the hard coat layer. There is a need.

  However, since the surface of the release layer has a flat surface roughness even on the light release side of the substrate-less double-sided pressure-sensitive adhesive sheet, the adhesive can be given smoothness. Even if it is used on the light release side, the effect of the present invention can be obtained.

  Next, although the manufacture example of the polyester film used as the base material of the release film of 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 necessary 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 are 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 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 70 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.

  In the present invention, the simultaneous biaxial stretching method can be adopted for the production of the polyester film constituting the release film. 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 70 to 120 ° C., preferably 80 to 110 ° C., and stretch ratio. As an area magnification, it is 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times. 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.

  Next, the present description will be further described with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In addition, the evaluation method of the physical property in a following example and a comparative example is as follows.

(1) Measurement of Intrinsic Viscosity of Polyester 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)
The average particle size d50 was defined as the particle size having an integrated volume fraction of 50% in an equivalent spherical distribution measured using a centrifugal sedimentation type particle size distribution analyzer (SA-CP3 type) manufactured by Shimadzu Corporation.

(3) Surface roughness Ra
The center line average roughness Ra (μm) is defined as the surface roughness Ra. It calculated | required as follows using the Kosaka Laboratory Co., Ltd. surface roughness measuring machine (SE-3F). That is, a portion having a reference length L (2.5 mm) is extracted from the film cross-section curve in the direction of the center line, the center line of the extracted portion is the x axis, and the direction of the vertical magnification is the y axis. When represented by (x), the value given by the following equation is represented by [μm]. The center line average roughness was represented by the average value of the center line average roughness of the extracted portion obtained from 10 cross section curves obtained from the sample film surface. The tip radius of the stylus was 2 μm, the load was 30 mg, and the cutoff value was 0.08 mm.
Ra = (1 / L) ∫ 0 L | f (x) | dx

(4) Measurement of orientation (orientation angle) of orientation main axis Using a polarization microscope manufactured by Carl Zeiss, the orientation of the polyester film is observed, and the direction of the main orientation axis in the polyester film plane is relative to the width direction of the polyester film. The number of tilts was measured to determine the orientation angle. This measurement was carried out at a total of three locations on the center and both ends of the film, and the largest orientation angle value among the three locations was taken as the maximum orientation angle.

(5) Evaluation of release film peeling force (F) After attaching one side of a double-sided adhesive tape (Nitto Denko “No. 502”) to the surface of the release layer of the sample film, cut into a size of 50 mm × 300 mm After that, the peel strength after standing for 1 hour at room temperature is measured. For the peeling force, a tensile tester (“Intesco model 2001 type” manufactured by Intesco Co., Ltd.) was used, and 180 ° peeling was performed under the condition of a tensile speed of 300 mm / min.

(6) Practical properties <Deformation of adhesive>
The adhesive surface after peeling the release film from the substrate-less double-sided adhesive sheet was visually observed, and the state of the adhesive surface was evaluated. ○: Unevenness that becomes a problem when bonded to a substrate is very flat. Not seen △: Slight irregularities are seen, but it is a level that will be buried when pasted on the base material, and can be judged as having no problem in practical use. Become a practical problem

<Roll rollability>
The roll winding property was evaluated from the roll winding situation in the production process shown below and the rolled roll appearance.
-Polyester film production process-Release film production process-Substrate-less double-sided PSA sheet production process ◎: A roll having a problem-free appearance is obtained in any production process, and there is no problem under a wide range of winding conditions A roll having an appearance was obtained. ○: A roll having a satisfactory appearance was obtained, and a production process with a narrow range of winding conditions was observed. △: A range of winding conditions in each process was narrow, and the appearance was occasionally Bad rolls occurred ×: It is difficult to obtain rolls with good appearance through each production process

<Cross Nicol inspection of polarized transmitted light>
A release film is sandwiched between two polarizing plates whose optical axes are crossed, and the polarized light transmitted through the polarizing plate / release film / polarizing plate is visually observed from a light source, and a determination is made based on the detection status of defects. It was.
<Criteria>
○: The base part of the release film is dark and the defects are easily seen as bright spots. ×: The base part of the release film is bright and the defects are not seen as bright spots.

<Manufacture of polyester>
-Manufacture of polyester A 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate are placed in a reactor, heated to a temperature and distilled off of methanol to conduct a transesterification reaction. The temperature was raised to 230 ° C. over 4 hours, and the transesterification reaction was substantially completed. Next, 0.04 part of ethyl acid phosphate and 0.04 part of antimony trioxide were added, the temperature was 280 ° C. and the pressure was 15 mmHg in 100 minutes. It was. After 4 hours, the system was returned to normal pressure to obtain polyester A substantially free of fine particles. The intrinsic viscosity of this polyester was 0.70.

-Manufacture of polyester B 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate are placed in a reactor, heated to a temperature and distilled off of methanol to conduct a transesterification reaction. The temperature was raised to 230 ° C. over 4 hours, and the transesterification reaction was substantially completed. Next, an ethylene glycol slurry containing 1.0 part of synthetic calcium carbonate particles having an average particle diameter of 0.7 μm was added to the reaction system, and 0.04 part of ethyl acid phosphate and 0.04 part of antimony trioxide were further added. Thereafter, in 100 minutes, the temperature was 280 ° C. and the pressure was 15 mmHg, and thereafter the pressure was gradually reduced to finally 0.3 mmHg. After 4 hours, the system was returned to normal pressure to obtain polyester B. The obtained polyester B had a synthetic calcium carbonate particle content of 1.0% by weight. The intrinsic viscosity of this polyester was 0.65.

-Production of polyester C The production method of polyester B is the same as the production method of polyester B, except that silica particles having an average particle size of 3.4 µm were used instead of synthetic calcium carbonate particles having an average particle size of 0.70 µm. Polyester C was obtained using the method. The silica particle content of the obtained polyester C was 1.0% by weight. The intrinsic viscosity of this polyester was 0.65.

-Production of polyester D The production method of polyester B is the same as the production method of polyester B, except that calcium carbonate particles having an average particle size of 1.50 µm were used instead of synthetic calcium carbonate particles having an average particle size of 0.70 µm. Polyester D was obtained using the method. The resulting polyester D had a calcium carbonate particle content of 1.0% by weight. The intrinsic viscosity of this polyester was 0.65.

-Production of polyester E The production method of polyester B is the same as the production method of polyester B, except that silica particles having an average particle size of 2.2 µm were used instead of synthetic calcium carbonate particles having an average particle size of 0.70 µm. Polyester E was obtained using this method. The resulting polyester E had a silica particle content of 1.0% by weight. The intrinsic viscosity of this polyester was 0.65.

-Production of polyester F In the production method of polyester B, the synthetic calcium carbonate particles having an average particle size of 0.27 µm were used instead of the synthetic calcium carbonate particles having an average particle size of 0.70 µm. Polyester E was obtained using the same method. The obtained polyester F had a synthetic calcium carbonate particle content of 1.0% by weight. The intrinsic viscosity of this polyester was 0.65.

・ Polyester film forming condition-1
Polyesters A to F were mixed into raw materials of layer A and layer B in the mixing ratio shown in Table 1, and each was supplied to two twin-screw extruders and melted at 285 ° C. A non-oriented sheet was obtained by co-extrusion on a casting drum cooled to 20 ° C. in a two-layer / two-layer configuration so that the thickness ratio of the layer and the B layer was the composition ratio shown in Table 2. Next, the film was stretched 2.9 times in the longitudinal direction at 85 ° C., then subjected to a preheating step in the tenter and subjected to transverse stretching of 5.4 times at 125 ° C., followed by heat treatment at 215 ° C. for 10 seconds, 4.5% relaxation was added in the width direction at 180 ° C. to obtain polyester films having thicknesses shown in Tables 1 to 3 below.

・ Polyester film forming condition-2
Polyesters A to F were mixed into raw materials of layer A and layer B in the mixing ratio shown in Table 1, and each was supplied to two twin-screw extruders and melted at 285 ° C. A non-oriented sheet was obtained by co-extrusion on a casting drum cooled to 20 ° C. in a two-layer / two-layer configuration so that the thickness ratio of the layer and the B layer was the composition ratio shown in Table 2. Next, the film was stretched 3.4 times in the longitudinal direction at 85 ° C., then subjected to a preheating step in the tenter and subjected to 4.0 times transverse stretching at 125 ° C., followed by heat treatment at 230 ° C. for 10 seconds, 4.5% relaxation was added in the width direction at 180 ° C. to obtain polyester films having thicknesses shown in Tables 1 to 3 below.

<Manufacture of release film>
A release layer having the following composition was provided on the obtained polyester film so that the coating amount was 0.1 g / m @ 2 (after drying), followed by heat treatment at 120 DEG C. for 30 seconds, and light release with a peeling force of 15 mN / cm. A release film for the side and a release film for the heavy release side having a peeling force of 80 mN / cm were obtained.
・ Releasing agent composition of release film for light release side Curing type silicone resin (KS-847H: manufactured by Shin-Etsu Chemical) 100 parts Hardening agent (PL-50T: manufactured by Shin-Etsu Chemical) 1 part MEK / toluene mixed solvent (mixing ratio is 1: 1) 1500 parts / release agent composition of release film for heavy release side curable silicone resin (KS-847H: manufactured by Shin-Etsu Chemical Co., Ltd.) 90 parts heavy release control agent (SD-7292: manufactured by Dow Corning Toray) 10 Part Curing agent (PL-50T: manufactured by Shin-Etsu Chemical) 1 part MEK / toluene mixed solvent (mixing ratio is 1: 1) 1500 parts

<Manufacture of substrate-less double-sided PSA sheet>
On the release agent layer of the obtained release film for heavy release side, the acrylic pressure-sensitive adhesive solution is applied using an applicator so that the film thickness after drying is 25 μm, and then the coating is performed. The film was dried at 120 ° C. for 1 minute to form an adhesive layer. The acrylic pressure-sensitive adhesive solution was prepared by adding polyisocyanate-based crosslinking to 100 parts by mass of a copolymer solution (solvent: toluene, solid content concentration: 40% by mass) having a monomer-based mass ratio of butyl acrylate and acrylic acid of 99: 1. It was obtained by adding 1 part by weight of an agent (manufactured by Toyo Ink Manufacturing Co., Ltd., trade name “BHS8515”, solid content concentration 37.5% by mass). Subsequently, the release agent layer and adhesive layer of the release film for light peeling side were bonded together, and the base material-less double-sided adhesive sheet of Example 1 was obtained.

  The release film of the present invention can easily detect defects even when used in a film for preventing scattering having a hard coat layer, has good slidability with the hard coat surface, and can suppress deformation of the adhesive. As a release film for a base-less double-sided pressure-sensitive adhesive sheet used for scattering prevention, it can be suitably used.

Claims (3)

Mold release for substrate-less double-sided pressure-sensitive adhesive sheets having a release layer on one side of a 50-150 μm thick polyester film having a structure composed of at least two layers and having a tilt angle (orientation angle) of 12 degrees or less. The surface roughness of the front and back surfaces is different, the surface roughness (Ra) of the release layer surface is in the range of 10 to 20 nm, and the surface roughness Ra of the anti-release layer surface is in the range of 20 to 40 nm. A release film for a substrate-less double-sided pressure-sensitive adhesive sheet, characterized by that. The polyester layer on the release layer side contains particles with an average particle size of 0.1 to 2.0 μm, and the polyester layer on the anti-release layer side contains particles with an average particle size of 2.0 to 4.0 μm. The release film for base-material-less double-sided adhesive sheets of Claim 1. 3. The release film for a substrate-less double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the release film is used for a heavy release side of the substrate-less double-sided pressure-sensitive adhesive sheet.