JP2013067743A - Substrate-less double-sided adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate-less double-sided adhesive sheet in which both surface release polyester films laminated on the self-adhesive layer can be visually judged easily when the substrate-less double-sided adhesive sheet is used in a process of joining members.SOLUTION: This substrate-less double-sided adhesive sheet is composed of two polyester films with a release layer whose release layer surfaces are laminated respectively on both sides of the self-adhesive layer, where one polyester film is colored.

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 There is a problem that it is difficult to determine whether or not a mark is affixed.

JP 2009-220296 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 the two release film surfaces of a polyester film having a release layer are laminated on both sides of the pressure-sensitive adhesive layer, and one polyester film is colored. It exists in the base-material-free double-sided adhesive sheet characterized by having.

  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. .

Typical sectional drawing which shows the base-material-free 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.

  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. 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 0.05-5 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 transparency of the film is insufficient. There is.

  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 a polyester film used for one release film laminated on both sides of an adhesive sheet is colored.

  If you decide whether to use a polyester film colored on the light release side or the heavy release side in advance, there is no need to remove the release film from the adhesive sheet, making it easy to identify the release film and joining the members You can prevent mistakes.

  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.

  The colored polyester film is preferably a film in which at least three or more polyester layers are laminated, and more specifically, all the layers are extruded together by a so-called coextrusion method in which the layers are melted and extruded together from an extrusion die. It is a film. 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 phenomenon that the added dye swells on the film surface (bleed out) and the phenomenon that it sublimates easily occur, and this causes contamination of the film forming machine, In many cases, the production itself cannot be performed, and even if it can be produced, the surface layer has a spring-out from the inside of the film due to bleed-out, thereby often adversely affecting post-processing.

  It is preferable that the polyester film used by this invention contains the dye which melt | dissolves substantially in polyester in the inner layer (intermediate layer) of the laminated structure. The term “substantially dissolved” as used in the present invention means that when the polyester is kneaded in a molten state, no agglomerates or the like are left and mixed uniformly.

  The dye to be used is preferably a dye that is less decomposed at the molding temperature of the polyester. Such dyes are preferably anthraquinone, perinone, perylene, azomethine, and heterocyclic dyes in terms of chemical structure, and dispersible dyes and oil-soluble dyes are suitable in terms of dyeing formulation. Moreover, even if it is generally classified as a pigment, it can be used as a dye in the present invention as long as it is soluble in molten polyester as described above. Examples thereof include complex salt dyes with metal ions such as copper, cobalt, nickel, zinc and chromium such as phthalocyanine.

  The above-mentioned dyes are generally used by appropriately selecting and mixing several kinds of dyes, for example, in order to adjust to gray or brown tones. It can be appropriately selected from the range of 01 to 10.0% by weight, preferably 0.05 to 5.0% by weight.

  The method of adding the dye and other additives in the present invention to the polyester may be a method of adding these powders, pastes or liquids when the film is melt-molded. In consideration of ease of treatment, it is preferable to prepare a masterbatch of a dye or the like in advance and add the masterbatch while diluting with a clear resin at the time of melt molding of the film. In addition, it is particularly preferable to use a twin screw extruder in order to carry out the melt molding while kneading the polyester with good dispersion.

  The film haze of the release film used in the present invention is usually 10% or less, preferably 8% or less. The substrate-less double-sided pressure-sensitive adhesive sheet of the present invention is used for optics, so if there are defects such as foreign matter, it must be removed by visual inspection or an automatic defect detector, etc., but the film haze exceeds 10% May interfere with the detection of defects in foreign matter and the like. For the colored polyester film, the film haze is preferably 10% or less, more preferably 8% or less for the same reason.

  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 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 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 usually 16 μm or more, preferably 20 μm or more. If the thickness of the release film is less than 16 μm, the film is not stiff, and the peel angle increases at the boundary where the pressure-sensitive adhesive and the release film are peeled off when the release film is peeled off. In some cases, the adhesive may remain on the release film or zipping may occur.

  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. <Distinguishability of release film>
The base material-less double-sided pressure-sensitive adhesive sheet provided with release films on both sides was visually observed to determine which side the release film on the light release side was used on.
○: A release film on the light release side could be identified. ×: A release film on the light release side could not be obtained.

<Foreign matter inspection>
The substrate-less double-sided PSA sheet provided with release films on both sides was observed to evaluate the ease of detecting foreign matter.
○: 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

<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, 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, an ethylene glycol slurry containing 2.0 parts of silica particles having an average particle size of 1.4 μm was added to the reaction system, and 0.04 part of ethyl acid phosphate and 0.04 part of antimony trioxide were added. 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 size of 0.8 μm were used instead of silica particles having an average particle size of 1.4 μm. C was obtained.

<Manufacture of polyester D>
Polyester A was subjected to a vented twin-screw extruder, and each concentration of Dialresin Red HS 3.0 wt%, Blue H3G 5.5 wt%, and Yellow F 1.5 wt% manufactured by Mitsubishi Chemical Corporation The resulting mixture was mixed and added, melt-kneaded to form chips, and a dye master batch polyester D was prepared.

<Manufacture of polyester film 1>
Each chip of polyester A and D was charged in an intermediate layer extruder as an intermediate layer resin in a ratio of 92: 2. Apart from this, each chip | tip of polyester A and B was thrown into the extruder for surface layers as a resin for surface layers in the ratio of 70:30. 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 2-4>
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 5>
Each chip of polyester A, B, D was supplied to the extruder with a vent at a ratio of 89: 5: 6, melt-extruded at 290 ° C., and then the surface temperature was set to 40 ° C. using an electrostatic application adhesion method. The film was cooled and solidified on a cooling roll to obtain an amorphous film having a single 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 stretched polyester film having a thickness of 38 μm. It was. This film has a phenomenon in which sublimates gradually adhere to the cooling drum when making a molten sheet (not observed at all in polyester films 1 to 4), and cannot be produced for a long time. 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 Co., Ltd.) 100 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 2
Curable silicone resin (KS-847H: manufactured by Shin-Etsu Chemical) 95 parts Heavy release control agent (SD-7292: manufactured by Toray Dow Corning) 3 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 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.) 95 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
Curable silicone resin (KS-774: manufactured by Shin-Etsu Chemical Co., Ltd.) 100 parts Curing agent (PL-4: manufactured by Shin-Etsu Chemical Co., Ltd.) 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 2 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 2-7, Comparative Example 1:
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 8 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 in Tables 3 and 4 below.

  In Tables 3 and 4, the peel force ratio of * 1 means second release film peel force ÷ first release film peel force.

  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 (3)

A base material-less double-sided pressure-sensitive adhesive sheet in which two release film surfaces of a polyester film having a release layer are laminated on both sides of the pressure-sensitive adhesive layer, and one polyester film is colored. Less double-sided adhesive sheet. The base material-less double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the colored polyester film is a coextruded laminated film composed of at least three layers, and the intermediate layer contains a dye that substantially dissolves in the polyester. The substrate-less double-sided surface according to claim 1 or 2, wherein the peel force between the surface of one adhesive layer and the release layer surface is 2.0 times or more the peel force between the surface of the other adhesive layer and the release layer surface. Adhesive sheet.

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