JP2014156070A - Substrateless double-sided adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrateless double-sided adhesive sheet capable of easily discriminating a double-sided releasing film laminated on an adhesive layer through visual observation, in a step of bonding a member by using the substrateless double-sided adhesive sheet.SOLUTION: In a substrateless double-sided adhesive sheet in which each of polyester films having releasing layers is laminated on both surfaces of an adhesive layer through the releasing layers, at least one polyester film has a laminated structure, and contains a laser marking compound in an intermediate layer excluding the outermost layer in the laminated structure.

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). Although it is desirable to be able to apply techniques such as 5), the hurdles to be overcome during film production are high and many.

  One of the hurdles to be exceeded is that the color pigment or dye to be selected requires sufficient heat resistance during film production through the melting step. In order to maintain the optical properties of the film, an organic compound having a relatively low molecular weight is often selected. In that case, it decomposes immediately by heat applied in the melting process, for example, 200 ° C. or higher, or When passing through the melting process many times, if the deterioration is severe, it is not suitable as a material.

  Another hurdle to overcome is the bleeding out of the colored pigment or dye to the adhesive material that occurs when using the colored pigment or dye. The low molecular weight component used may pass through the polymer film and transfer to the adhesive material, thereby adversely affecting the adhesive material component. Such adverse effects become a problem in particularly severe applications among polarizing plates and touch panel members.

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 a polyester film having a release layer is laminated on both sides of the pressure-sensitive adhesive layer via the release layer, and at least one polyester film has a laminated structure. And having a laser marking compound in an intermediate layer excluding the outermost layer in the laminated structure.

  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 first release film 31 is a so-called light release sheet. The first release agent layer 15 is provided on the laminated polyester films 13 and 14, and the first release agent layer 15 is temporarily peelable from the adhesive layer 11. It is worn.

  The second release film 32 is a so-called heavy release sheet, and the second release agent layer 25 is provided on the laminated polyester films 23 and 24 so that the second release agent layer 25 can be peeled off from the pressure-sensitive adhesive layer 11. Temporarily worn. This heavy release sheet may be provided with a double-sided coating layer 24 ′ in order to enhance functionality depending on the application. At this time, as long as the release layer formation is not affected, 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 that forms the release film bases 13, 14, 23, and 24 include polyethylene terephthalate in which 80 mol% or more of the structural unit is ethylene terephthalate, and 80 mol% or more of the structural unit is ethylene-2,6- Examples thereof include polyethylene-2,6-naphthalate, which is 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 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. .

  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 this invention, in order to prevent the compound added in order to give the laser coloring function mentioned later to bleed out, it is preferable to provide a coating layer in both outermost layer surfaces of the layer which consists of polyester. The coating layer also has an inhibitory effect on oligomers precipitated from polyester (hereinafter abbreviated as OL).

  In the present invention, an oligomer is defined as a cyclic trimer among low molecular weight substances that crystallize and precipitate on the film surface after heat treatment.

  The method for forming the coating layer of the coating layer 24 ′ is not particularly limited, but a method of coating the coating solution in the process of manufacturing the polyester film is suitably employed. Specifically, a method of applying and drying a coating solution on the surface of an unstretched sheet, a method of applying and drying a coating solution on the surface of a uniaxially stretched film, and a method of applying and drying a coating solution on the surface of a biaxially stretched film Etc. Among these, it is economical to apply a coating solution on the surface of an unstretched film or a uniaxially stretched film, and then simultaneously dry and cure the coating layer in the process of heat-treating the film. Moreover, as a method for forming the coating layer, a method in which some of the above-described coating methods are used in combination can be adopted as necessary. Specifically, a method of applying a first layer on the surface of an unstretched sheet and drying, then stretching in a uniaxial direction, and then applying and drying a second layer can be used. Use the reverse roll coater, gravure coater, rod coater, air doctor coater, etc. shown in “Coating Method” by Yuji Harasaki, Tsuji Shoten, published in 1979, as a method of applying the coating solution to the surface of the polyester film. Can do.

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

  The 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 normal to use a binder polymer for the coating layer 24 ′, but the binder polymer is based on a polymer compound safety evaluation flow scheme (sponsored by the Chemical Substance Council in November 1985), It is defined as a polymer compound having a number average molecular weight (Mn) of 1000 or more as measured by gel permeation chromatography (GPC) and having film-forming properties.

  Analysis of the components in the coating layer can be performed by surface analysis such as TOF-SIMS.

  When providing a coating layer by in-line coating, the above-mentioned series of compounds is applied as an aqueous solution or dispersion, and the coating solution adjusted to a solid content concentration of about 0.1 to 50% by weight as a guide is applied onto the polyester film. It is preferable to produce a laminated polyester film. 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.

  In order to achieve the above object, in the present invention, a low molecular component precipitation preventing layer is formed on the film surface by coating, and the layer comprises 10 to 100% by weight of polyvinyl alcohol, preferably 20 to 90% by weight, more preferably. It shall contain 30-90weight%. If the content of polyvinyl alcohol is less than 10% by weight, the effect of preventing the precipitation of low molecular components is insufficient, which is not preferable.

  The polyvinyl alcohol used in the present invention can be synthesized by a normal polymerization reaction and is preferably water-soluble. The degree of polymerization of polyvinyl alcohol is not particularly limited, but is usually 100 or more, preferably 300 to 40,000. When the degree of polymerization is 100 or less, the water resistance of the coating layer tends to decrease. The degree of saponification of the polyvinyl alcohol used in the present invention is not particularly limited, but a polyvinyl acetate saponified product that is usually 70 mol% or more, preferably 80 mol% or more and 99.9 mol% or less is practically used. It is done.

  In the coating layer 24 ′ in the present invention, a water-soluble or water-dispersible binder resin other than the above polyvinyl alcohol may be used in combination as necessary. Examples of the binder resin include polyester, polyurethane, acrylic resin, vinyl resin, epoxy resin, amide resin, acrylate resin, and the like. In these, each skeleton structure may have a composite structure substantially by copolymerization or the like. Examples of the binder resin having a composite structure include acrylic resin graft polyester, acrylic resin graft polyurethane, vinyl resin graft polyester, vinyl resin graft polyurethane, and acrylate resin graft polyethylene glycol. The blending amount of the binder component is preferably 50 parts by weight or less, and more preferably 30 parts by weight or less in terms of parts by weight with respect to the coating layer. Furthermore, the coating layer of the film of the present invention may contain a crosslinking reactive compound as required.

  Crosslinking reactive compounds include methylolated or alkylolated urea, melamine, guanamine, acrylamide, polyamide and other compounds, polyamines, epoxy compounds, oxazoline compounds, aziridine compounds, blocked isocyanate compounds, silane cups Polyfunctional low molecular weight compounds such as ring agents, titanium coupling agents, zirco-aluminate coupling agents, metal chelates, organic acid anhydrides, organic peroxides, thermally or photoreactive vinyl compounds and photosensitive resins, and It is selected from polymer compounds.

  Crosslinkable compounds improve the cohesiveness, surface hardness, scratch resistance, solvent resistance, and water resistance of the easy-adhesive resin layer mainly by cross-linking reaction with the functional groups of the resin contained in the easy-adhesive resin layer. can do. For example, when the functional group of the easily adhesive resin is a hydroxyl group, the crosslinking reactive compound is preferably a melamine compound, a blocked isocyanate compound, an organic acid anhydride, or the like, and the functional group of the easily adhesive polyester is an organic acid or an anhydride thereof. In this case, epoxy-based compounds, melamine-based compounds, oxazoline-based compounds, metal chelates and the like are preferable as the cross-linking reactive compound. It is preferable to select and use a functional group contained in the easily adhesive resin and one having a high crosslinking reaction efficiency. Examples of the melamine compound in the present invention include methoxymethylated melamine and butoxymethylated melamine which are alkylol or alkoxyalkylolated melamine compounds, and those obtained by co-condensing urea or the like with a part of melamine can also be used. .

  The cross-linking reactive compound may be either a low molecular weight compound or a high molecular polymer having a reactive functional group as long as the reactive functional group is always contained in two or more functional groups in one molecule. The compounding amount of the crosslinking reactive compound is preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and particularly preferably 15 parts by weight or less in terms of parts by weight with respect to the easily adhesive resin layer. Furthermore, the easily adhesive resin layer of the present invention may contain inert particles for improving the slipperiness of the coating layer, if necessary.

Examples of the inert particles include inorganic inert particles and organic inert particles. Examples of the inorganic inert particles include silica sol, alumina sol, calcium carbonate, and titanium oxide.
Examples of the organic inert particles include fine particles containing a single or copolymer of polystyrene resin, polyacrylic resin, and polyvinyl resin, or organic particles represented by crosslinked particles in which these and a crosslinking component are combined. These inert particles preferably have a softening temperature or decomposition temperature of about 200 ° C. or higher, more preferably 250 ° C. or higher, particularly 300 ° C. or higher. The average particle diameter (d) of the inert particles is 1/3 ≦ d / L ≦ 3, and further 1/2 ≦ d / L ≦ 2, when the average film thickness of the easily adhesive resin layer is (L). It is preferable to select so as to satisfy the relationship.

  The coating layer 24 ′ of the present invention is optionally provided with a surfactant, an antifoaming agent, a coating property improving agent, a thickener, a low molecular antistatic agent, an organic lubricant, an antioxidant, an ultraviolet absorber, and foaming. A small amount of additives such as additives, dyes and pigments may be contained. These additives may be used alone or in combination of two or more as necessary. The coating layer of the film of the present invention may be formed only on one side of the polyester film or on both sides. In the case of forming only on one side, another type of coating layer can be formed on the opposite side as required, and further properties can be imparted. In addition, in order to improve the applicability | paintability and adhesiveness to the film of a coating liquid, you may give a chemical process, an electrical discharge process, etc. to the film before application | coating.

Respect polyester film of the present invention, the thickness of the coating layer provided on the polyester film is usually 0.002~1.0g / ^{m 2,} more preferably 0.005 to 0.5 / ^{m 2,} more preferably 0 The range is from 0.01 to 0.2 g / m ² . If the film thickness is less than 0.002 g / m ^2, sufficient adhesion may not be obtained, and if it exceeds 1.0 g / m ² , the appearance, transparency, and film blocking properties may deteriorate. There is.

  In the present invention, the drying and curing conditions for forming the coating layer 24 ′ on the polyester film are not particularly limited. For example, when the coating layer is provided by off-line coating, it is usually at 80 to 200 ° C. The heat treatment may be performed for 3 to 40 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, heat treatment is usually performed at 70 to 280 ° C. for 3 to 200 seconds as a guide.

  Further, irrespective of off-line coating or in-line coating, heat treatment and active energy ray irradiation such as ultraviolet irradiation may be used in combination as required. The polyester film constituting the laminated polyester film in the present invention may be subjected to surface treatment such as corona treatment or plasma treatment in advance.

  The coating layer 24 'of the polyester film of the present invention is preferably formed by blending a binder resin and a crosslinking agent in an arbitrary ratio. In this case, since the layer forms a barrier layer densely, a low molecular weight analysis is performed. Can be prevented from coming out. For this reason, there is an effect that the OL from the polyester film and the precipitation of the compound used for the purpose of coloring are not attached to the adhesive as much as possible and are not produced in the previous processing step. Therefore, the layer structure of the coating layer 14 'of the polyester film of the present invention is preferably double-sided.

  The release film used in the present invention is formed by providing at least a biaxially oriented polyester film (release film substrate) and a release agent layer in this order. In order to prevent production process contamination, it is preferable that an application layer including OL sealing is provided. In that case, the biaxially oriented polyester films 23 and 24, the coating layer 24 ', and the release agent layer 25 are provided in this order.

  When the coating layer is not provided, depending on the compound used for the purpose of coloring in the release film, the production process of the base-less double-sided pressure-sensitive adhesive sheet, and the step of bonding to another member of the pressure-sensitive adhesive sheet for optical substrates Process contamination and OL of the film are likely to occur, which is not preferable.

  In the base material-less double-sided pressure-sensitive adhesive sheet used in the present invention, for example, a pressure-sensitive adhesive is coated on a release layer of a release film, and then dried to form a pressure-sensitive adhesive layer. It is manufactured by laminating release films having different peeling forces on the surface, but when the coating layer is not provided, in addition to process contamination, OL generated in the manufacturing process and compounds used for coloring purposes When the pressure-sensitive adhesive layer is bonded to the electronic base material, it is not preferable because a problem occurs in the electronic component due to the influence of OL or a compound used for coloring.

In the present invention, when the release film has a coating layer, after heat-treating those release films (180 ° C., 10 minutes), the amount of OL extracted from the release layer surface with the coating layer by dimethylformamide is: It is preferably 1.0 mg / m ² or less. When OL exceeds 1.0 mg / m ² , there is a process contamination, and when the adhesive is bonded, a foreign matter may be generated, resulting in a problem such as a decrease in product yield.

  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 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.

  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 a method in which a compound that is colored by laser light (hereinafter referred to as a laser marking compound) is contained during the extrusion of the polyester.

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

  As a specific example of the laser marking compound, 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 compounds. 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 a laser marking compound 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 for incorporating the laser marking compound into the polyester in the present invention 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, in the kneading of the laser marking compound into the polyester, the compound belongs to an organic compound or an organometallic complex, and is generally known to have low heat resistance around 300 ° C. In the present invention, it is necessary to appropriately select a compound having heat resistance that can withstand a high amount of heat at the time of forming a polyester film or at the time of heat history in raw material recycling. One of the features of the laser marking compound of the present invention is that it is excellent in heat history characteristics that repeats regeneration.

  In the present invention, when the laser marking compound is kneaded into the film, the content of the laser marking compound in the film is usually in the range of 0.025 to 0.25% by weight. When the content is less than 0.025% by weight, the discoloration effect of the film tends to be inferior. On the other hand, when it contains exceeding 0.25 weight%, a malfunction may arise by the degraded material in a film.

  Furthermore, about the polyester film in this invention, the layer structure of the laser marking compound knead | mixing to an intermediate | middle layer except an outermost layer is preferable. In that case, 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. When kneaded into the surface layer, a double-sided pressure-sensitive adhesive sheet is formed, and when stored for a long time, the kneaded compound bleeds out and shifts to the adhesive material side. In the present invention, bleed out refers to a phenomenon in which a low molecular compound migrates to the film surface layer.

  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, more preferably 5% 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% Hinders the detection of defects in foreign matter and the like.

  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-mentioned value, a laser marking compound that is stable on film formation is appropriately selected, and the content is set so as not to cause haze reduction, poor color appearance, and sufficient coloring performance. 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 According to JIS-K6714, the turbidity of the film was measured with the Nippon Denshoku Industries Co., Ltd. divisional 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) Measurement of OL extracted from the coating layer side surface An unheat-treated release film is heated in air at 180 ° C. for 10 minutes in advance. After that, the heat-treated film is brought into close contact with the inner surface of a box having a top and width of 10 cm and a height of 3 cm, and the box shape is obtained. When the coating layer is provided, the coating layer surface is set to the inside. Next, 4 ml of DMF (dimethylformamide) is placed in the box prepared by the above method and left for 3 minutes, and then DMF is recovered. The recovered DMF was supplied to liquid chromatography (manufactured by Shimadzu Corporation: LC-7A) to determine the amount of OL in DMF, and this value was divided by the area of the film in contact with DMF to obtain the amount of film surface OL (mg / M ² ).

  The amount of oligomer in DMF was determined from the peak area ratio between the standard sample peak area and the measured sample peak area (absolute calibration curve method). The standard sample was prepared by accurately weighing OL (cyclic trimer) collected in advance and dissolving it in DMF accurately weighed. The concentration of the standard sample is preferably in the range of 0.001 to 0.01 mg / ml. The conditions for the liquid chromatograph were as follows.

Mobile phase A: Acetonitrile Mobile phase B: 2% acetic acid aqueous solution Column: “MCI GEL ODS 1HU” manufactured by Mitsubishi Chemical Corporation
Column temperature: 40 ° C
Flow rate: 1 ml / min Detection wavelength: 254 nm

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

(8) 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.

(9) 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).

(10) Practical properties <Continuous film forming properties 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 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 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 mold release layer and the pressure-sensitive adhesive, but the level is practically satisfactory. Clear float at the mold layer and adhesive interface

(11) Comprehensive evaluation An evaluation taking film forming properties, workability, functionality, etc. into consideration is performed. Judgment is based on the following criteria.
○: Can be supplied as a product even after production ×: Productivity is poor, optical inspection malfunctions occur frequently, or visual transmission is poor in appearance

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 complex oxide of copper and molybdenum (CuO · xMoO ₃ : Dongguan Material Technology Co., Ltd.) in a ratio of 99.96: 0.04 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 2.8 times in the machine direction at a film temperature of 85 ° C. using the roll peripheral speed difference, then led to a tenter, stretched 5.1 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.

Examples 2-7:
A film was obtained in the same manner as in Example 1 except that the content of the laser marking compound in the second release film was changed. The obtained results are summarized in Tables 1 and 2 below.

Example 8:
A sheet was obtained in the same manner as in Example 1 except that the production method of the second release substrate was changed and a coating layer was added (the following). The results obtained are summarized in Table 2.
<Production of second release film substrate>
A mixed raw material obtained by mixing polyester A and compound 1 of Table 1 at a ratio of 99.64: 0.36 was used as a raw material for the intermediate layer, and a mixed raw material of polyester B of the surface layer and the intermediate layer was provided at a ratio of 1: 9. Each was supplied to an extruder and melted at 290 ° C., then co-extruded in a layer configuration of two types and three layers (surface layer / intermediate layer / surface layer) on a cooling roll set at 40 ° C., and cooled and solidified. A stretched 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 roll peripheral speed, and then the following coating agent was applied on both surfaces of the machine film (after drying) to 0.03 g. / M ² , then led to a tenter, stretched 5.1 times at 120 ° C. in the transverse direction, heat treated at 225 ° C., relaxed 2% in the transverse direction, and 50 μm thick ( A transparent polyester film having a surface layer of 2.5 μm and an intermediate layer of 45 μm was obtained. The obtained polyester film was a colorless and transparent film. However, in the case of the present invention, only when a coating layer (corresponding to 24 'in the figure) intended for bleed-out sealing of the compound mixed for the purpose of coloring is provided, the coating processing is performed after stretching in the longitudinal direction as necessary. However, stretching in the transverse direction shall be performed.

<Coating layer>
Examples of compounds constituting the coating layer 24 'are as follows.
(Example compounds)
-Polyvinyl alcohol binder polymer having a saponification degree of 88 mol% and a polymerization degree of 350: A
Emulsion polymer of methyl methacrylate / ethyl acrylate / acrylonitrile / N-methylol methacrylamide = 45/45/5/5 (molar ratio) (emulsifier: anionic surfactant) Binder polymer: B
・ Crosslinking agent Hexamethoxymelamine crosslinking agent: C
・ Particulate colloidal silica (average particle diameter: 70 nm): D
Solid content ratio: A / B / C / D = 30/24/42/4

Comparative Example 1:
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 and contained in the outermost layer. The obtained results are summarized in Table 3 below.

Comparative Example 2:
The sheet | seat was obtained by the method of adding the coating layer by the method of Example 8 for the comparative example 1. FIG. The results obtained are summarized in Table 3.

  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 intermediate layer 14 1st release film base material outermost layer 15 1st release agent layer 23 2nd release film base material intermediate layer 24 1st 2 Release film substrate outermost layer 24 Second release film coating layer 25 Second release agent layer 31 First release film (light release sheet)
32 Second release film (heavy release sheet)

Claims (4)

A polyester film having a release layer is a substrate-less double-sided pressure-sensitive adhesive sheet that is laminated on both sides of the pressure-sensitive adhesive layer via a release layer, and at least one polyester film has a laminated structure, A baseless double-sided pressure-sensitive adhesive sheet comprising a laser marking compound in an intermediate layer excluding the outermost layer. The substrate-less double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the content of the laser marking compound in the polyester film is 0.025 to 0.25 wt%. The substrate-less double-sided pressure-sensitive adhesive sheet according to claim 1 or 2, further comprising a coating layer obtained by coating a coating liquid containing polyvinyl alcohol on both sides of the polyester film according to claim 1. The peeling force between the surface of one adhesive layer and the release layer surface is 2.0 times or more of the peeling force between the surface of the other adhesive layer and the release layer surface. Substrate-less double-sided adhesive sheet.

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