JP2013155315A - Substrate-less double-sided adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate-less double-sided adhesive sheet whose releasing polyester films of both faces laminated on an adhesive layer can easily be distinguished visually when being used in a step of binding members.SOLUTION: A substrate-less double-sided adhesive sheet has polyester films each having a releasing layer laminated on both faces of an adhesive layer, and one of the polyester films contains a compound to be colored by laser light.

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 surface of the layer is bonded to a different object surface, whereby the objects are surface bonded (Patent Document 1).

  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 step of pasting the base material-less double-sided PSA sheet with the member, the release film with a light release force is first peeled off, but when the release films on both sides have the same thickness, in the release film made of a colorless and transparent polyester film, It has a problem that it is difficult to determine which surface has a release film having a light peeling force. In this case, a technique of using a colored film as a release film is conceivable (Patent Document 2).

  Also, in such applications, one of the release films may be peeled off, and the foreign material, dirt, and scratches may be inspected when pasted to another member while leaving the remaining release film on the heavy release side. There is a case. At that time, when a colored film is used as the release film (Patent Document 2), there is a possibility that the transmittance and the visibility are lowered, and there is a high possibility of causing a problem during the above inspection. Desirably, it is colored only under certain conditions, that is, only the laser irradiation part is colored (Patent Document 3), only the UV irradiation part is colored (Patent Document 4), or only the UV irradiation part emits light (Patent Document 3). It is desirable to be able to apply techniques such as 5), but there are many and many hurdles to be overcome, such as thermal stability and cost during film production.

JP 2009-220296 A Japanese Patent Application No. 2011-208327 JP 2010-189504 A JP 2010-174135 A JP 2010-174086 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 polyester films having a release layer are laminated on both sides of the pressure-sensitive adhesive layer, and one polyester film contains a compound that is colored by laser light. It exists in the base-material-free double-sided adhesive sheet characterized by the above-mentioned.

  According to the present invention, the release film 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 members and inspectability problems in the subsequent process are solved. Therefore, 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 1st release film 31 is what is called a light release sheet, Comprising: The 1st mold release agent layer 15 is provided in the polyester film 13, and the 1st mold release agent layer 15 is temporarily attached to the adhesive layer 11 so that peeling is possible. Yes. The light release sheet may be provided with a coating layer 14 or 14 'or double-sided coating layers 14 and 14' in order to enhance functionality depending on the application. At this time, as long as it does not affect the release layer formation, the coating layer may be provided with any function such as oligomer sealing, antistatic, easy adhesion, and colorability.

  The second release film 32 is a so-called heavy release sheet. The second release agent layer 25 is provided on the polyester film 23, and the second release agent layer 25 is temporarily attached to the adhesive layer 11 so as to be peelable. ing. The heavy release sheet may be provided with a coating layer 24 or 24 'or double-sided coating layers 24 and 24' in order to enhance functionality depending on the application. At this time, as long as it does not affect the release layer formation, the coating layer may be provided with any function such as oligomer sealing, antistatic, easy adhesion, and colorability. In this invention, the layer which shows a coloring function by laser irradiation is mentioned as an example.

  The polyester film referred to in the present invention is a film which is melt-extruded from an extrusion die, and is subjected to stretching and heat treatment as necessary after cooling a molten polyester sheet extruded by a so-called extrusion method.

  Examples of the polyester forming the release film substrates 13 and 23 include polyethylene terephthalate in which 80 mol% or more of the structural units are ethylene terephthalate, and polyethylene in which 80 mol% or more of the structural units is ethylene-2,6-naphthalate. Examples include -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, etc. These series of particles may be used in combination of two or more as required.

  Moreover, the average particle diameter of the particle | grains to be used is 0.05-5 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.

  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 is preferably employed. Next, the obtained unstretched sheet is stretched in the biaxial direction. In that case, first, the unstretched sheet is stretched in one direction by a roll or a tenter type stretching machine. The stretching temperature is usually 70 to 120 ° C., preferably 80 to 110 ° C., and the stretching ratio is usually 2.5 to 7 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.

  The present invention is characterized in that a polyester film used for one release film laminated on both surfaces of a pressure-sensitive adhesive sheet is colored partially and when necessary by laser irradiation. The film of the present invention is characterized by being irreversibly colored by laser light.

  If you decide in advance whether to use a polyester film that is colored by laser light on the light release side or the heavy release side, there is no need to remove the release film from the adhesive sheet, making it easy to identify the release film, It is possible to prevent mistakes in the joining process.

  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.

  For the polyester film used in the present invention, it is preferable to use either a method of containing a compound colored by laser light at the time of extrusion of the polyester or a coating layer provided by coating.

  In the present invention, a compound that is colored by laser light is used. Specific examples thereof include laser marking pigments, and the following compounds are preferred as usable ones.

  As a specific example of the compound colored by laser light, the metal oxide is preferably at least one selected from a copper compound, a molybdenum compound, an iron compound, a nickel compound, a chromium compound, a zirconium compound, and an antimony compound. More preferably, it is at least one selected from a compound and an antimony compound. In addition, supplementary use and use of inorganic metal compounds such as titanium oxide, zinc sulfide, zinc oxide, precipitated barium sulfate, barium carbonate and precipitated calcium carbonate and dyes such as carbon black, graphite and black lake, and leuco dye It is desirable to select and use it according to the environment.

  In this invention, when the compound colored with a laser beam is kneaded in a film, content of the compound colored with the laser beam in a film is the range of 0.025 to 0.25 weight%. When the content is less than 0.025% by weight, the discoloration effect of the film is inferior. On the other hand, when it contains exceeding 0.25 weight%, a malfunction arises with the degraded material in a film.

  Next, examples of the method of incorporating the compound colored by laser light in the present invention into polyester include a kneading method and a coating method. When the method of kneading into polyester is used, these compounds are preferably used as a masterbatch kneaded into polyester resin, but may be added directly to the polyester resin.

  Further, for the polyester film colored by laser irradiation in the present invention, the layer structure of the compound colored by the laser beam is kneaded as described above, the laser marking pigment can be kneaded into either the surface layer or the intermediate layer of the homopolyester film. I do not care. What is necessary is just to adjust content of a surface layer or an intermediate | middle layer so that it may become said content as the whole film.

  In the present invention, when a compound colored by laser light is contained not in the film but in the attached coating layer, a method for forming the coating layer will be described. For coating layers containing compounds that are colored by laser light, it may be provided by in-line coating, which treats the film surface during the stretching process of the polyester film, and is applied outside the system on the film once produced. May be employed, or both may be used in combination. In-line coating is preferably used in that it can be applied at the same time as film formation, and thus can be manufactured at low cost, and the thickness of the coating layer can be changed by the draw ratio.

  The in-line coating is not limited to the following, but for example, in the sequential biaxial stretching, the coating treatment can be performed particularly before the lateral stretching after the longitudinal stretching is finished. When a coating layer is provided on a polyester film by in-line coating, coating can be performed simultaneously with film formation, and the coating layer can be processed at a high temperature, and a film suitable as a polyester film can be produced.

  In the present invention, it is an indispensable requirement to use a laser marking pigment-containing water / organic solvent mixed solution as a coating solution on one side or both sides of a polyester film and apply them in-line as a coating layer. Is. In addition, this coating is not limited by the coating, and if the liquid stability is sufficient when mixed with a coating solution having various functions such as adhesion, it is used with those liquids to provide further performance. Can be provided.

The structure of the coating liquid which consists of a laser marking pigment containing water / organic solvent mixed solution contained in the coating layer in the present invention will be described. Examples of the organic solvent having a certain degree of compatibility with water include alcohols, ketones, and esters. Further, it is desirable to use a small amount of a solvent rich in anthracene such as toluene as a mixed solvent with a solvent of alcohols, ketones or esters. Examples of alcohols include solvents having an alkyl chain typified by ethanol, propanol, isopropanol and the like, alcohols having an aryl group as a substituent, and the like. Examples of ketones include acetone and methyl ethyl ketone. Examples of the esters include ethyl acetate.
Furthermore, it is desirable to perform ultrasonic treatment of the solution if the uniform dispersion of the coating solution or a uniform solution is aimed.

  In addition, when the coated layer in the present invention is made into a polyester film and then rolled into a roll, the film is sticking to the front and back, and so-called blocking is likely to occur. In order to prevent blocking, it is preferable to contain particles. The content of the particles is preferably in the range of 3 to 25%, more preferably in the range of 5 to 15%, and in the range of 5 to 10% in terms of the weight ratio of the entire coating layer. Further preferred. If it is less than 3%, the effect of preventing blocking may be insufficient. On the other hand, when it exceeds 25%, although the blocking prevention effect is high, there is a concern that the transparency of the coating layer is lowered and the coating film strength is lowered due to the loss of the continuity of the coating layer. By using the particles in the above range, it has anti-blocking performance.

  As the particles, for example, inorganic particles such as silica, alumina, and metal oxide, or organic particles such as crosslinked polymer particles can be used. In particular, silica particles are preferred from the viewpoint of dispersibility in the coating layer and transparency of the resulting coating film.

  If the particle size is too small, the effect of preventing blocking is difficult to obtain, and if it is too large, dropping off from the coating film tends to occur. The average particle size is preferably about 1/2 to 10 times the thickness of the coating layer. Furthermore, if the particle size is too large, the transparency of the coating layer may be inferior, so the average particle size is preferably 300 nm or less, and more preferably 150 nm or less. The average particle diameter of the particles described here can be obtained by measuring the 50% average diameter of the number average of the particle dispersion with Microtrac UPA (Nikkiso Co., Ltd.).

  When providing a coating layer by in-line coating, the above-mentioned series of compounds is used as a water / organic solvent mixed solution, and a coating solution adjusted with a solid content concentration of about 0.1 to 50% by weight as a guide is applied onto a polyester film. It is preferable to produce a polyester film having coloring performance in the manner described above. Moreover, in the range which does not impair the main point of this invention, a small amount of organic solvents may be contained in the coating liquid for the purpose of improving dispersibility in water, improving film-forming properties, and the like. Only one type of organic solvent may be used, or two or more types may be used as appropriate.

The film thickness of the coating layer provided on the polyester film of the present invention is usually 0.002~1.0g / ^{m 2,} more preferably 0.005 to 0.5 / ^{m 2,} more preferably 0.01 to 0. The range is ² g / m ² . If the film thickness is less than 0.002 g / m ^2, sufficient laser photosensitive coloring performance may not be obtained, and if it exceeds 1.0 g / m ² , the appearance, transparency, and film blocking properties deteriorate. there's a possibility that.

  In the present invention, as a method for providing the coating layer, a conventionally known coating method such as reverse gravure coating, direct gravure coating, roll coating, die coating, bar coating, curtain coating or the like can be used. Regarding the coating method, there is a description example in “Coating method” published by Yasuharu Harasaki in 1979.

  In the present invention, the drying and curing conditions for forming the coating layer on the polyester film are not particularly limited. For example, when the coating layer is provided by off-line coating, it is usually 3 to 40 at 80 to 200 ° C. The heat treatment should be performed for 2 seconds, preferably 100 to 180 ° C. for 3 to 40 seconds.

  On the other hand, when the coating layer is provided by in-line coating, it is usually preferable to perform heat treatment at 70 to 280 ° C. for 3 to 200 seconds as a guide.

  In addition, regardless of offline coating or in-line coating, as long as the laser marking pigment does not decompose, heat treatment and irradiation with active energy rays such as ultraviolet irradiation may be used in combination. The polyester film constituting the polyester film coated with the laser marking pigment in the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

  The content of the laser marking pigment in the coating layer is in the range of 1.0 to 10% by weight. When the content is less than 1.0% by weight, the colorability of the film is inferior. On the other hand, when it contains exceeding 10 weight%, a malfunction arises with the degraded material in a film.

  In some applications, the release film used in the present invention may be subjected to a visual inspection of polarized light such as a scratch or a foreign substance or an in-line polarized light inspection after peeling the light release sheet and bonding it to a member to be used. In this case, in order to realize high inspection properties, the orientation angle of the film is required to have a low orientation angle. The orientation angle at this time is an index that qualitatively represents the direction in which molecular chains are aligned with respect to the longitudinal direction after stretching. In addition, as other elements for realizing high inspectability, there are few foreign matters inside and outside the film and low haze. The film haze 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 first release film 15 and the second release film 25 is not particularly limited as long as it contains a material having release properties. 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, or the adhesive may remain on the second release film 32 or may be zipped.

  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, adhesive residue or zipping may occur on the release film.

  When processed into a substrate-less double-sided pressure-sensitive adhesive sheet according to the present invention, there is an operation of bonding to another member. Coloring by laser irradiation is performed in order to distinguish a release film having transparent light peeling and heavy peeling ability at that time. Is used as one method. Coloring in the present invention is a color change in the film appearance. Specifically, it can be expressed by the contrast ratio in the luminance measurement. Specifically, the relative luminance obtained from the ratio of the laser irradiated part to the unirradiated part is about 102 to 200, preferably 200 or more. Further, coloring can also be expressed by ΔE obtained from L * a * b * color difference evaluation, and the ΔE value is preferably about 0.5 to 6.0, more preferably 6.0 or more. is there.

  In the present invention, in order to achieve the above value, a compound that is stable on film formation and colored by laser light is appropriately selected so as not to cause haze reduction, poor color, and sufficient coloring performance. The content must be adjusted.

In carrying out the present invention, the laser light source and the irradiation method thereof are not particularly limited, and various known Nd: YAG lasers, CO ₂ lasers, various excimer lasers, and the like can be used. Among these, the effect becomes remarkable in the marking using the Nd: YAG laser.

  The strength of coloring by laser irradiation using the substrate-less double-sided pressure-sensitive adhesive sheet in the present invention for distinction is that only an appropriate portion can be colored at an appropriate timing and place. In addition, when a film with light release and heavy release ability has the same transparency and the same thickness, it is also epoch-making that it can be easily distinguished after laser irradiation by including a laser marking pigment in either of them. It is.

  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) Measurement of amount of metal in coating layer Using a fluorescent X-ray analyzer (model “XRF-1500” manufactured by Shimadzu Corporation), the amount of elements in the film was determined by single film measurement by the film FP method. . The detection limit in this method is usually about 1 ppm.

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

(6) Evaluation of release film release force (F) After attaching one side of a double-sided adhesive tape (Nitto Denko "No. 502") to the release layer surface of the sample film, cut into a size of 50 mm x 300 mm After that, the peel strength after standing for 1 hour at room temperature is measured. 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.

(7) Peeling ratio of first and second release films Peeling force ratio means second releasing film peeling force / first releasing film peeling force measured in (4) above.
○: 2.0 times or more.
X: Lower than 2.0 times.

(8) Evaluation of polyester film after laser irradiation The laser marking conditions are as follows.
Laser marking device: Keyence Co., Ltd. laser marker MD-V9900
Laser type: YVO ₄ laser (wavelength 1064 nm)
Irradiation method: XYZ 3-axis simultaneous scanning method (CW (continuous oscillation), Q switch frequency 1 to 400 kHz)
Marking power: 13W
Scanning speed: 1500mm / s

-Contrast evaluation of the coloring intensity after laser irradiation of the polyester film Using a luminance meter, the contrast ratio between the uncolored portion of the film before laser irradiation and the colored portion after laser irradiation was evaluated. Specifically, a sample is placed on a flat illuminator manufactured by Dentsu Sangyo Co., Ltd .: HF-SL-A48LCF, and further, using Konica Minolta Sensing Co., Ltd. CS-200, the measurement viewing angle is 1 °, and the distance between the sample and the luminance meter is measured. The luminance value (cd / m ² ) was measured at 500 mm. The relative luminance (%) was obtained from the following formula.
Relative luminance = (measured value of the laser non-irradiated portion) ÷ (measured value of the laser irradiated portion) × 100 Evaluation was made according to the following criteria from the obtained relative luminance value.
○: Over 200 (strong coloring).
Δ: 102 to 200 (colored).
X: Less than 102 (almost not colored).

・ L * a * b * Color Difference Evaluation of Coloring Strength after Laser Irradiation of Polyester Film About the obtained polyester film after laser irradiation, using a color difference meter, uncolored portions of the film before laser irradiation and after laser irradiation The L * a * b * color difference of the colored portion was evaluated. Specifically, according to JIS Z 8729, L * a * b * color difference values of the laser irradiated portion and the non-irradiated portion were measured using a color difference meter CR-410 (sample diameter 50 mm) manufactured by Konica Minolta. At this time, the light source was C / D65, the back surface was white, and measurement was performed by a reflection method. The measurement was performed three times, and an average value was adopted. ΔL * (irradiated portion L * value−non-irradiated portion L * value), Δa * (irradiated portion a * value−non-irradiated portion a * value), Δb * (irradiated portion b * value−non-irradiated portion) (Part b * value) was calculated, and ΔE value was calculated and evaluated.
The ΔE value was determined from the following formula.
ΔE = {(ΔL *) ² + (Δa *) ² + (Δb *) ² } ^1/2
Evaluation was performed based on the following criteria from the obtained ΔE value.
○: More than 6.0 (strong coloring).
Δ: 0.5 to 6.0 (colored).
X: Less than 0.5 (almost not colored).

(9) 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-time production, and continuous production is possible.
X: A problem that the production cannot be continued occurs, and the continuous production is impossible.
<Discrimination 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 heavy release side was used on.
○: After the laser irradiation, the release film on the heavy release side could be identified.
X: A release film on the heavy release side cannot be formed after laser irradiation.

<Foreign matter inspection>
The light release film was peeled off, the pressure-sensitive adhesive side of the light release side was bonded to a float plate glass (manufactured by Sekiya Rika Co., Ltd.), and polarized light was applied to visually inspect the foreign matter.
○: Foreign matter in the film 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 very smoothly, no peeling streaks, and no peeling noise.
Δ: Slight peeling streaks are observed, peeling noise is slightly generated, and slight zipping occurs.
X: Stripping streaks are observed, peeling sound is generated, and 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 lifting is observed at the interface between the second release layer and the pressure-sensitive adhesive, but it is at a level that causes no practical problems.
X: A clear float is seen in a 2nd mold release layer and an adhesive interface.

(10) Comprehensive evaluation An evaluation is performed in consideration of film forming properties, processability, functionality, and the like. Judgment is based on the following criteria.
○: Even if it is produced, it can be sufficiently supplied as a product.
X: Productivity is poor. There are many problems with optical inspection. Visually visible and poor in appearance.
Lack of sex.

The polyester used in the examples and comparative examples was prepared as follows.
<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.

<Production of first release film substrate>
Using polyester A as the raw material for the intermediate layer, the surface layer polyester B and the mixed raw material for the intermediate layer were each fed to two extruders at a ratio of 1: 9, melted at 290 ° C., and then set to 40 ° C. On the cooling roll, it coextruded by the layer structure of 2 types, 3 layers (surface layer / intermediate layer / surface layer), it was made to cool and solidify, and the unstretched sheet was obtained. Next, the film was stretched 3.4 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, then led to a tenter, stretched 4.0 times at 120 ° C. in the transverse direction, and heat-treated at 225 ° C. Thereafter, the film was relaxed by 2% in the lateral direction to obtain a transparent polyester film having a thickness of 38 μm (surface layer: 1.9 μm, intermediate layer: 34.2 μm).
<Production of second release film substrate>
A mixed raw material obtained by mixing polyester A and a laser marking pigment copper and molybdenum composite oxide (CuO · xMoO ₃ : Toago Material Technology Co., Ltd.) at a ratio of 99.97: 0.03 is used as a raw material for the intermediate layer. Each of the surface layer polyester B and the intermediate layer mixed raw material was supplied to two extruders at a ratio of 1: 9, melted at 290 ° C., respectively, and then on a cooling roll set at 40 ° C. Coextruded with a layer structure (surface layer / intermediate layer / surface layer) and cooled and solidified to obtain an unstretched sheet. Next, the film was stretched 3.4 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, then led to a tenter, stretched 4.0 times at 120 ° C. in the transverse direction, and heat-treated at 225 ° C. Thereafter, the film was relaxed by 2% in the lateral direction to obtain a transparent polyester film having a thickness of 50 μm (surface layer: 2.5 μm, intermediate layer: 45 μm). The obtained polyester film was a colorless and transparent film.

<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
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

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 properties of the obtained release film are shown in Table 1 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.

About the obtained base-material-free double-sided pressure-sensitive adhesive sheet, YVO ₄ laser (Keyence Corporation: MD-V9900) was irradiated with light (1064 nm) and the coloring performance was evaluated. Only the second release film was changed to a gray colored state. Was good. The obtained film had a relative luminance of 210% and ΔE of 5.73 (L * = 82.81, a * = 1.86, b * = 2.04). The obtained results are shown in Table 1.

Example 2:
A film was obtained in the same manner as in Example 1 except that the content of the laser marking pigment in the second release film was changed. The obtained results are summarized in Table 1 below.

Example 3:
A film was obtained in the same manner as in Example 1 except that the method for containing the laser marking pigment in the second release film was changed to the following. The results obtained are summarized in Table 2 below.
<Production of second release film substrate>
Using polyester A as the raw material for the intermediate layer, the surface layer polyester B and the mixed raw material for the intermediate layer were each fed to two extruders at a ratio of 1: 9, melted at 290 ° C., and then set to 40 ° C. On the cooling roll, it coextruded by the layer structure of 2 types, 3 layers (surface layer / intermediate layer / surface layer), it was made to cool and solidify, and the unstretched sheet was obtained. Next, the film was stretched 2.8 times in the machine direction at a film temperature of 85 ° C. using the difference in peripheral speed of the roll, and then 50 parts by weight of the following resin I having an easy adhesion function was added to one side of the machined film. Copper / molybdenum complex oxide, which is a laser marking pigment, in a mixed solution of water and ethanol (mixing ratio is 4: 6) containing 45 parts by weight and 5 parts by weight of inert particles III: CuO.xMoO3 (east (Coated with Material Technology Co., Ltd.) is applied, guided to a tenter, stretched 5.1 times at 120 ° C in the transverse direction, heat treated at 225 ° C, and then relaxed by 2% in the transverse direction. A transparent polyester film having a thickness of 50 μm (a surface layer of 2.5 μm and an intermediate layer of 45 μm) containing 9.8% by weight of CuO.xMoO3 in the coating layer after drying was obtained. About the obtained base-material-free double-sided pressure-sensitive adhesive sheet, YVO ₄ laser (Keyence Corporation: MD-V9900) was irradiated with light (1064 nm) and the coloring performance was evaluated. Only the second release film was changed to a gray colored state. Was good. The obtained film had a relative luminance of 210% and ΔE of 5.73 (L * = 82.81, a * = 1.86, b * = 2.04). The obtained results are shown in Table 1.
-Contents of coating agent Binder resin I: Copolyester water-soluble resin II containing terephthalic acid, isophthalic acid, 5-sodium sulfoisophthalic acid as dicarboxylic acid components, and ethylene glycol and diethylene glycol as diol components II: Saponification Polyvinyl alcohol inert particles III having a degree of polymerization of 88 mol% and a degree of polymerization of 1700: silica sol having an average particle diameter of 0.05 μm Thereafter, a baseless double-sided pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1.

Examples 4-5:
A film was obtained in the same manner as in Example 3, except that the content of the laser marking pigment in the second release film of Example 3 was changed and the surface of the coating layer was changed. The results obtained are summarized in Table 2 below.

Comparative Examples 1-6:
Example 1 except changing the content of the laser marking pigment in the second release film, changing the stretching conditions of the first and second release films, and changing the release layer composition of the first and second release films. A film was obtained in the same manner as above. The obtained results are summarized in Tables 3 and 4 below.

Comparative Examples 7-8:
A film was obtained in the same manner as in Example 3, except that the content of the laser marking pigment in the second release film of Example 3 was changed and the surface of the coating layer was changed. The results obtained are summarized in Table 5 below.

  Since the substrate-less double-sided pressure-sensitive adhesive sheet of the present invention can easily distinguish between release films provided on both sides of the pressure-sensitive adhesive sheet, production loss in the process of joining members can be suppressed, and foreign matter inspection is also possible. Since it is excellent, it can be suitably used as a substrate-less double-sided pressure-sensitive adhesive sheet for optics.

DESCRIPTION OF SYMBOLS 10 Substrate-less double-sided adhesive sheet 11 Adhesive layer 13 1st release film base material 14 1st application layer 14 '1' application layer 15 1st release agent layer 23 2nd release film base material 24 2nd application | coating Layer 24 'Second' coating layer 25 Second release agent layer 31 First release film (light release sheet)
32 Second release film (heavy release sheet)

Claims (1)

A substrate-less double-sided pressure-sensitive adhesive sheet in which a polyester film having a release layer is laminated on both sides of an adhesive layer, and one polyester film contains a compound that is colored by laser light. Double-sided adhesive sheet.

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