JP2014062204A - Substrate-less double-sided adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate-less double-sided adhesive sheet by which in a step for bonding members with each other using the substrate-less double-sided adhesive sheet, release films laminated on both sides of an adhesive layer can be easily distinguished from each other.SOLUTION: The substrate-less double-sided adhesive sheet is produced by laminating release polyester films having peel forces different from each other individually on both sides of an adhesive layer, and one of the release polyester films is a film having a film haze of 6% or more.

Description

  The present invention relates to a substrate-less double-sided pressure-sensitive adhesive sheet, for example, a substrate-less double-sided pressure-sensitive adhesive sheet suitably used for bonding an optical member such as a touch panel.

  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, the use of a baseless double-sided pressure-sensitive adhesive sheet has been spreading, and is also used for members for various optical applications. For example, a touch panel as an optical application is a laminated body in which members such as a transparent conductive film are laminated, and a baseless double-sided pressure-sensitive adhesive sheet is used to join the members.

  In the process of bonding the substrate-less double-sided PSA sheet to the member, the release film with a light release force is peeled off first, but with a release film made of a colorless and transparent polyester film, the release film with a light release force on either side It has a problem that it is difficult to determine whether or not a mark is affixed.

JP 2011-189589 A JP 2011-245739 A JP 2011-224896 A JP 2011-224904 A JP 2012-025030 A

  The present invention has been made in view of the above circumstances, and the problem to be solved is to easily visually check the release films on both sides laminated on the adhesive layer in the step of joining the members using the baseless double-sided adhesive sheet. An object of the present invention is to provide a substrate-less double-sided pressure-sensitive adhesive sheet that can be discriminated.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be easily solved according to the base material-less double-sided pressure-sensitive adhesive sheet having a specific configuration, and have completed the present invention. .

  That is, the gist of the present invention is a substrate-less double-sided pressure-sensitive adhesive sheet in which release polyester films having different peeling forces are laminated on both sides of an adhesive layer, respectively, and one release polyester film is a film of 6% or more. It exists in the base-material-free double-sided adhesive sheet characterized by being a film which has a haze.

  According to the present invention, the release films laminated on both sides of the pressure-sensitive adhesive sheet can be easily discriminated, and problems such as production loss in the process of joining the members are solved, and the industrial value of the present invention is high. .

It is typical sectional drawing which shows the base material-less double-sided adhesive sheet which concerns on embodiment of this invention.

  As shown in FIG. 1, the substrateless double-sided pressure-sensitive adhesive sheet 10 is configured by laminating first and second release films on both sides of a pressure-sensitive adhesive layer 11.

  The first release film 31 is a so-called light release sheet, in which the first release agent layer 14 is provided on the polyester film 13, and the first release agent layer 14 is temporarily attached to the adhesive layer 11 so as to be peelable. Yes.

  The second release film 32 is a so-called heavy release sheet. The second release agent layer 24 is provided on the polyester film 23, and the second release agent layer 24 is temporarily attached to the adhesive layer 11 so as to be peelable. ing.

  Examples of the polyester forming the base material used for the release films 13 and 14 include polyethylene terephthalate in which 80 mol% or more of the structural units are ethylene terephthalate, and 80 mol% or more of the structural units are ethylene-2,6-naphthalate. Specific polyethylene-2,6-naphthalate and poly-1,4-cyclohexanedimethylene terephthalate in which 80 mol% or more of the structural unit is 1,4-cyclohexanedimethylene terephthalate. Other examples include polyethylene isophthalate and poly-1,4-butylene terephthalate.

  Examples of copolymer components other than the above-described dominant component include propylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, neopentyl glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, diethylene glycol, Diol components such as triethylene glycol, polyethylene glycol, polytetramethylene glycol, polyalkylene glycol, isophthalic acid, 2,7-naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, malonic acid, succinic acid, adipic acid, Esterogenic derivatives such as azelaic acid, sebacic acid, diphenyl ether dicarboxylic acid and oxymonocarboxylic acid can be used.

  Further, as the polyester, in addition to a homopolymer or a copolymer, a small proportion of a blend with another resin can also be used. Examples of resins blended with polyethylene terephthalate include various copolymerized polyethylene terephthalates such as isophthalic acid copolymer, cyclohexanedimethylene terephthalate copolymer, polyethylene glycol copolymer, polyethylene naphthalate and copolymerized polyethylene naphthalate, poly Examples include butylene terephthalate.

  The intrinsic viscosity of the polyester film of the present invention is usually in the range of 0.40 to 0.90, preferably 0.45 to 0.80, and more preferably 0.50 to 0.70. If the intrinsic viscosity is less than 0.40, the mechanical strength of the film tends to be weakened. If the intrinsic viscosity exceeds 0.90, the melt viscosity becomes high, the load on the extruder is increased, and the production cost increases. Problems may occur.

  It is preferable to mix | blend particle | grains in the polyester layer which comprises the polyester film of this invention for the main purpose of provision of slipperiness. 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.

  In order to facilitate the identification of the release film provided on both sides of the pressure-sensitive adhesive layer, the present invention needs to control the film haze of the polyester film used for the release film. As a method, a method of controlling the film haze with particles contained in the film is preferably used.

  Particles to be blended in order to obtain a polyester film having a film haze of 6% or more used in the present invention are preferably particles whose film haze is appropriately increased according to the blending amount, and specifically, calcium carbonate is preferred. Since silica particles have a lower film haze than calcium carbonate particles, it is necessary to increase the amount of addition in order to obtain the desired film haze. is there. When the film surface becomes rough, the pressure-sensitive adhesive surface to which the release film is bonded is deformed, and defects such as bubbles occur due to protrusions or the like when the pressure-sensitive adhesive layer is bonded to the substrate.

  Titanium oxide has a very high hiding power, so the film haze is high even with a small amount of compounding, and when inspecting a substrate-less double-sided PSA sheet with a release film attached to both sides, the testability is high. There is a tendency to be inferior.

  Moreover, the average particle diameter of the particle | grains to be used is 0.05-5 micrometers normally, Preferably it is the range of 0.05-3 micrometers. If the average particle size is less than 0.05 μm, the particles tend to aggregate and the dispersibility may be insufficient. On the other hand, if it 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.

  Further, the content of particles in the polyester layer 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 roughness of the film surface increases. The adhesive layer may be deformed.

  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.

  The present invention is characterized in that the film haze of one release film laminated on both surfaces of the pressure-sensitive adhesive sheet is 6% or more, preferably 10% or more.

  If the film haze is 6% or more, the surface of the release film is visually checked to determine whether to use a release film with a high film haze on the light release side or the heavy release side in advance. It is not necessary to peel off the release film from the sheet, making it easy to distinguish the release film and preventing errors in the process of joining the members.

  In the member joining step, conditions such as the speed at which the release film is peeled off are set in accordance with the peeling force of the release film.

  If the film haze of any release film is less than 6%, the discrimination on the surface of the release film is insufficient, and it is necessary to peel off the release film from the pressure-sensitive adhesive layer, which is not preferable.

  In the method of using the substrate-less double-sided pressure-sensitive adhesive sheet of the present invention, the release film on the light release side is first peeled off, and the pressure-sensitive adhesive layer surface from which the release film has been peeled off is bonded to a panel substrate or the like. When performing an optical inspection to detect foreign matter at this time, the release film bonded to the heavy release side of the base material-less double-sided pressure-sensitive adhesive sheet is required to be transparent, which is not preferable when the film haze is high. Sometimes.

  In order to achieve both distinguishability and optical inspection properties, it is preferable to increase the film haze of the release film on the lightly peeled side that is peeled first during use.

  In order to improve discrimination, it is preferable to increase the release film on the light release side. However, if the film haze exceeds 20%, a large amount of particles are added, so the roughness of the film surface is large. When the substrate-less double-sided PSA sheet is inspected in a state where the release film is bonded to both sides, the inspectability may be inferior.

  The difference in film haze between the release films provided on both sides of the pressure-sensitive adhesive is usually 6% or more, preferably 10% or more from the distinguishability on the release film surface. If the haze difference of the release film is less than 6%, the distinguishability on the release film surface may be insufficient.

  The polyester film used for the release film having a high haze is preferably a film in which at least three or more polyester layers are laminated. More specifically, all the layers are melt-extruded together from an extrusion die, so-called common film. It is a film extruded by an extrusion method. Further, the film is not an unstretched state or a uniaxially stretched film, but needs to be a film that is stretched and oriented in the biaxial directions of the longitudinal direction and the transverse direction and then heat-set. Such a laminated film has a coextruded surface layer on both sides and a coextruded intermediate layer therebetween, but the coextruded intermediate layer itself may have a laminated structure.

  When the polyester fill has a single-layer configuration, the particles added to increase haze increase the roughness of the film surface, deforming the surface of the pressure-sensitive adhesive layer to which the release film is bonded, When the layer is applied to a substrate or the like, there may be defects such as bubbles.

  As the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer 11, an acrylic pressure-sensitive adhesive is usually used. The acrylic pressure-sensitive adhesive is composed mainly of an acrylic copolymer obtained by copolymerizing a functional group-containing monomer and another monomer such as an acrylic ester or methacrylic ester, and if necessary, a solvent , A crosslinking agent, a tackifier, a filler, a colorant, an antioxidant, an antistatic agent, an ultraviolet absorber and the like may be further contained.

  Examples of the functional group-containing monomer include carboxyl group-containing monomers such as acrylic acid and methacrylic acid. The functional group-containing monomer preferably includes 0.3 to 5.0% by mass as a monomer unit based on the whole monomer constituting the acrylic copolymer (100% by mass).

  By containing functional groups, acrylic copolymers can adjust the cohesive force by reaction with the crosslinking agent, and prevent the adhesive from sticking out from the base material and improve the adhesive strength and heat resistance. Can be made. There is no restriction | limiting in particular as a crosslinking agent used for an adhesive, It uses suitably selecting from what was conventionally used in the acrylic adhesive conventionally, for example, a polyisocyanate compound, an epoxy resin, a melamine resin, a urea resin , Dialdehydes, methylol polymers, aziridine compounds, metal chelate compounds, metal alkoxides, metal salts and the like, preferably polyisocyanate compounds are used.

  The release layer of the 1st release film 14 and the 2nd release film 24 will not be specifically limited if the material which has mold release property is contained. 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 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 peeling force of the first release film 31 corresponding to the light peeling side is usually 3 to 50 mN / cm, preferably 5 to 25 mN / cm. Even if the peeling force of the 2nd release film 32 is made low by suppressing the peeling force of the 1st release film 31, the peeling force difference of both the release films 31 and 32 can be enlarged.

  Further, by setting the peeling force of the first release film 31 to a certain value or more, the first release film 31 is unexpectedly peeled off from the adhesive layer 11 before use, or the first release film 31 is an adhesive. Floating from the layer 11 is prevented.

  The peeling force of the second release film 32 corresponding to the heavy peeling side is preferably in the range of 20 to 100 mN / cm, more preferably 30 to 70 mN / cm. By suppressing the peeling force of the second release film 32 to a low level, it is possible to prevent the adhesive from remaining on the second release film 32, zipping, and the like that occur when the second release film 2 is peeled off. .

  The peeling force of the second release film 32 is usually 2.0 times or more, preferably 2.5 times or more, more preferably 3.0 times or more of the peeling force of the first release film 31. When the peeling force of the second release film 32 is less than 2.0 times the peeling force of the first release film 31, the second release film 32 adheres when the first release film 31 on the light release side is peeled off. The phenomenon of floating from the agent layer 11 may occur, the adhesive may remain on the second release film 32, or zipping may occur.

  The thickness of the biaxially oriented polyester film used as the base material of the first release film 31 and the second release film 32 of the present invention is 16 μm or more, preferably 20 μm or more. When the thickness of the release film is 15 μm or less, the film has no stiffness and the peeling angle increases at the boundary where the pressure-sensitive adhesive and the release film are peeled off when the release film is peeled off, so the pressure-sensitive adhesive layer is thick. In some cases, the adhesive remains on the release film or zipping occurs.

  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, in the case of a polyester film composed of three layers using the polyester raw material described above, a plurality of extruders, a multi-layer multi-manifold die or a feed block are used to laminate the respective polyesters, and the die A method in which a multi-layered molten sheet is extruded from and cooled and solidified with a cooling roll to obtain an unstretched sheet is preferred.

  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.

  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) Film haze The turbidity of the film was measured according to JIS-K6714 using a Nippon Denshoku Industries Co., Ltd. ball-type turbidimeter NDH-20D.

(4) Evaluation of release film release force (F) After applying 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.

(5) Practical properties <Continuous film forming property of polyester film>
It was evaluated from the production status of polyester film.
○: No problem is observed in long-term production, and continuous production is possible. ×: A problem that production cannot be continued occurs, and continuous production is impossible.

<Identification of release film>
The release film surface of the base-less double-sided pressure-sensitive adhesive sheet provided with release films on both sides was observed, and the distinguishability of the release film was evaluated from the difference in the surface of the release film.
○: The release film stuck on both sides could be easily identified. Δ: The release film stuck on both sides could be identified somehow.
X: The release film stuck on both surfaces could not be identified.

<Foreign matter inspection>
Remove the release film on the light release side from the substrate-less double-sided pressure-sensitive adhesive sheet provided with release films on both sides, and paste the adhesive layer on the light release side to which the release film was peeled off on the glass. The substrate-less double-sided PSA sheet was observed from the release film side, and the ease of detection of foreign matters was evaluated.
○: Foreign matter in the film can be easily detected Δ: Not easy, but foreign matter can be detected ×: Foreign matter cannot be detected

<Ziping occurrence>
When measuring the peeling force, the peeling state of the pressure-sensitive adhesive and the release film was observed, and the occurrence of zipping was evaluated in three stages.
○: Peeling extremely smoothly, no peeling streaking, no peeling noise △: Slight peeling streaks, slight peeling noise, slight zipping ×: Peeling streaks , Peeling sound occurs, zipping occurs

<Peelability of first and second release films>
The evaluation was made according to the situation of the interface between the second release layer and the adhesive when the first release film on the light release side was peeled off.
○: No abnormality is observed at the interface between the second release layer and the pressure-sensitive adhesive. Δ: Slight floating is observed at the interface between the second release layer and the pressure-sensitive adhesive, but there is no practical problem. There is a clear float at the interface of the adhesive

<Deformation of adhesive layer>
From the substrate-less double-sided pressure-sensitive adhesive sheet provided with a release film on both sides, the release film on the light release side is peeled off, and the adhesive layer on the light release side where the release film is peeled off to the glass, and the adhesive layer and The interface with the glass was observed, and the situation of defects due to deformation of the adhesive layer was evaluated.
○: No abnormality is observed at the interface between the glass and the adhesive.
Δ: Very fine bubbles are observed at the interface between the glass and the pressure-sensitive adhesive.
X: Air bubbles are easily seen at the interface between the glass and the pressure-sensitive adhesive.

<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, and the temperature is raised while heating, the methanol is distilled off, a transesterification reaction is performed, and it takes 4 hours from the start of the reaction. The temperature was raised to 230 ° C. to substantially complete the transesterification reaction. Next, 0.04 part of ethyl acid phosphate and 0.04 part of antimony trioxide were added, and then the temperature was 280 ° C. and the pressure was 15 mmHg in 100 minutes. The pressure was gradually reduced thereafter, and finally 0.3 mmHg 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, and the temperature is raised while heating and methanol is distilled off. The temperature was raised to 230 ° C. to substantially complete the transesterification reaction. Next, an ethylene glycol slurry containing 1.0 part of synthetic calcium carbonate particles having an average particle diameter of 0.8 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. Then, 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 resulting polyester B had a silica particle content of 1.0% by weight. The intrinsic viscosity of this polyester was 0.70.

<Manufacture of polyester C>
In the production method of polyester B, the same method as the production method of polyester B was used except that synthetic calcium carbonate particles having an average particle diameter of 1.4 μm were used instead of synthetic calcium carbonate particles having an average particle diameter of 0.8 μm. Thus, polyester C was obtained.

<Manufacture of polyester D>
In the production method of polyester B, polyester was used in the same manner as the production method of polyester B, except that silica particles having an average particle size of 1.4 μm were used instead of synthetic calcium carbonate particles having an average particle size of 0.8 μm. D was obtained.

<Manufacture of polyester E>
In the production method of polyester B, the same method as the production method of polyester B was used except that titanium dioxide particles having an average particle size of 0.3 μm were used instead of synthetic calcium carbonate particles having an average particle size of 0.8 μm. Polyester E was obtained.

<Manufacture of polyester film 1>
Each chip of polyester A and B was charged in an intermediate layer extruder at a ratio of 78:22 as an intermediate layer resin. Separately, each chip of polyester A and B was put into a surface layer extruder as a surface layer resin at a ratio of 92: 8. Each of the extruders was a bi-directional extruder with a vent, and the resin was extruded at a melting temperature of 290 ° C. without drying, and then the molten polymers were merged in a feed block and laminated. Thereafter, it was cooled and solidified on a cooling roll whose surface temperature was set to 40 ° C. using an electrostatic application adhesion method, to obtain a laminated amorphous sheet having a three-layer structure and a thickness of about 1500 μm. The obtained sheet was stretched 3.3 times in the longitudinal direction at 85 ° C., stretched 3.6 times in the transverse direction at 100 ° C., and heat-set at 210 ° C. to obtain a biaxially oriented film having a thickness of 38 μm. It was. The thickness of each layer of this film was 3/32/3 μm.

<Manufacture of polyester films 2-7>
In the production of the polyester film, a polyester film was obtained in the same manner as the polyester film 1 except that the raw material composition was as shown in Table 1.

<Manufacture of polyester film 8>
After each chip of polyester A and B was supplied to the extruder with a vent at a ratio of 78:22 and melt-extruded at 290 ° C., the surface temperature was set to 40 ° C. using an electrostatic application adhesion method. Upon cooling and solidification, an amorphous film having a single layer structure with a thickness of about 1500 μm was obtained. The obtained sheet was stretched 3.3 times in the longitudinal direction at 85 ° C, stretched 3.6 times in the transverse direction at 100 ° C, and heat-set at 210 ° C to obtain a biaxially stretched polyester film having a thickness of 38 µm. It was.

<Release layer>
A biaxially oriented polyester film obtained by the production of a polyester film is provided with a paint having a release layer composition shown below so that the coating amount is 0.1 g / m ² (after drying). Obtained.

-Release layer composition 1
Curing type silicone resin (KS-847H: manufactured by Shin-Etsu Chemical) 100 parts Curing agent (PL-50T: manufactured by Shin-Etsu Chemical) 1 part MEK / toluene mixed solvent (mixing ratio is 1: 1) 1500 parts

-Release layer composition 2
Curable silicone resin (KS-847H: manufactured by Shin-Etsu Chemical Co., Ltd.) 97 parts Heavy release control agent (SD-7292: manufactured by Toray Dow Corning) 3 parts Curing agent (PL-50T: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part MEK / toluene mixed solvent (Mixing ratio is 1: 1) 1500 parts

-Release layer composition 3
Curable silicone resin (KS-847H: manufactured by Shin-Etsu Chemical Co., Ltd.) 95 parts Heavy release control agent (SD-7292: manufactured by Dow Corning Toray) 5 parts Curing agent (PL-50T: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part MEK / toluene mixed solvent (Mixing ratio is 1: 1) 1500 parts

-Release layer composition 4
Curable silicone resin (KS-847H: manufactured by Shin-Etsu Chemical Co., Ltd.) 90 parts Heavy release control agent (SD-7292: manufactured by Toray Dow Corning) 10 parts Curing agent (PL-50T: manufactured by Shin-Etsu Chemical Co., Ltd.) 1 part MEK / toluene mixed solvent (Mixing ratio is 1: 1) 1500 parts

-Release layer composition 5
Curing type silicone resin (KS-774: manufactured by Shin-Etsu Chemical) 100 parts Curing agent (PL-4: manufactured by Shin-Etsu Chemical) 10 parts MEK / toluene mixed solvent (mixing ratio is 1: 1) 1500 parts

-Release layer composition 6
Curable silicone resin (KS-723A: manufactured by Shin-Etsu Chemical) 100 parts Curable silicone resin (KS-723B: manufactured by Shin-Etsu Chemical) 5 parts Curing agent (PS-3: manufactured by Shin-Etsu Chemical) 5 parts MEK / toluene mixed solvent (mixed) The ratio is 1: 1) 1500 parts

Example 1:
<Manufacture of first release film>
A release composition 1 was provided on the polyester film 1 such that the coating amount was 0.1 g / m ² (after drying) to obtain a first release film. The characteristics of the obtained release film are shown in Tables 1 to 3 below.
<Manufacture of second release film>
A release composition 5 was provided on the polyester film 5 so that the coating amount was 0.1 g / m ² (after drying) to obtain a first release film. The characteristics of the obtained release film are shown in Tables 1 to 3 below.
<Manufacture of substrate-less double-sided PSA sheet>
On the release agent layer of the obtained second release film, the acrylic pressure-sensitive adhesive solution was applied using an applicator so that the film thickness after drying was 25 μm. The adhesive layer was formed by drying at 120 ° C. for 1 minute. 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 1st release film were bonded together, and the base material-less double-sided adhesive sheet of Example 1 was obtained.

Examples 2-11, Comparative Examples 1-3:
In the production of the first release film of Example 1 and the production of the second release film, Example 1 except that the polyester used in the release film and the release layer composition were changed as shown in Table 2 below. Similarly, a first release film and a second release film were obtained.

  Using the obtained release film, the substrate-less double-sided pressure-sensitive adhesive sheets of Examples 2 to 11 and Comparative Examples 1 to 3 were obtained in the same manner as in Example 1.

  The evaluation results of the films obtained in each Example and Comparative Example are summarized and shown in Tables 3 to 5 below.

  In Table 3, * 1 peel force ratio means second release film peel force / first release film peel force. The following Tables 4-6 are also synonymous.

  The substrate-less double-sided pressure-sensitive adhesive sheet of the present invention makes it easy to distinguish between release films provided on both sides of the pressure-sensitive adhesive sheet. Therefore, it can be suitably used as a substrate-less double-sided pressure-sensitive adhesive sheet for optical use.

DESCRIPTION OF SYMBOLS 10 Substrate-less double-sided adhesive sheet 11 Adhesive layer 13 1st release film base material 14 1st release agent layer 23 2nd release film base material 24 2nd release agent layer 31 1st release film (light release) Sheet)
32 Second release film (heavy release sheet)

Claims (4)

The release polyester films having different peeling forces are substrate-less double-sided pressure-sensitive adhesive sheets laminated on both sides of the pressure-sensitive adhesive layer, and one release polyester film is a film having a film haze of 6% or more. The base material-less double-sided pressure-sensitive adhesive sheet. The base material-less double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the difference in film haze between the release polyester films laminated on both surfaces of the pressure-sensitive adhesive layer is 6% or more. The base material-less double-sided pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the release force difference of the release polyester film laminated on both surfaces of the pressure-sensitive adhesive layer is 2.0 times or more. The base material-less double-sided pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the release polyester film having a higher film haze has a base material of coextruded polyester having at least three layers.

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