JP2008120864A - Double-sided pressure-sensitive adhesive sheet, module for touch panel and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a double-sided pressure-sensitive adhesive sheet that can suitably suppress deformation of a uniaxially stretched film caused in a high temperature high humidity environment, and a module for a touch panel suppressed in peeling from a substrate caused by deformation of a sheet for the touch panel. <P>SOLUTION: The double-sided pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer comprising an acrylic polymer and an epoxy crosslinking agent, where the gel fraction of the pressure-sensitive adhesive layer increases with time, is 50-80% initially and 80-95% after pasted on an object to be pasted on and left for 200 hr in an environment of 80-90°C and a relative humidity of 80-90% and the difference of the initial gel fraction and the gel fraction left after 200 hr is at least 15%. The module for the touch panel comprises a glass substrate or a transparent resin substrate and, fixed thereto via the double-sided pressure-sensitive adhesive sheet, a side peripheral part of an ITO film of the sheet, for the touch panel, comprised of the uniaxially stretched film and the ITO film laminated thereon. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a double-sided pressure-sensitive adhesive sheet that does not peel off when a strong force is applied in the peeling direction from the outside in a high-temperature and high-humidity environment, a touch-panel module that does not curl and peel off from the substrate, and the manufacture of the module Regarding the method.

  Liquid crystal display devices have been widely used in various products such as personal computers and televisions. Especially, electronic notebooks, mobile phones, and the like have been increasingly miniaturized, and all of them are widely used as display devices for electronic devices. Such a liquid crystal display device or the like includes a so-called touch panel module in which a display screen functions as a touch panel sheet and an operator designates an operation by touching a predetermined position on the display screen with a finger. . As such a touch panel module, for example, a typical one having a structure in which a touch panel sheet is bonded to a glass substrate through a double-sided pressure-sensitive adhesive sheet also serving as a spacer is cited.

  As such a touch panel module, for example, a polarizing plate and an ITO film are laminated, and if necessary, an adhesive layer is provided so that a touch panel plate having a retardation plate in the middle and another ITO film have a gap. There is disclosed a module joined via a cable (see, for example, Patent Document 1 and FIG. 2). Conventionally, a polarizing plate used in such a module for a touch panel is obtained by laminating a glass substrate and a polarizing film on the entire surface. For this reason, even if the uniaxially stretched polarizing film is to be deformed under high temperature and high humidity, the touch panel itself is not deformed because it is laminated on the entire surface of the glass substrate. Even if it is used, it can be used stably.

  On the other hand, in order to reduce the cost of the touch panel module, an attempt has been made to use a touch panel sheet in which a polarizing film and an ITO film are laminated without using a glass substrate. However, when such a touch panel sheet is used, there arises a problem that the polarizing film is curled and deformed in a high temperature and high humidity environment. When creating a touch panel module, it is necessary to join the touch panel sheet with a gap between the conductive glass substrate, the laminate of the conductive film and the resin substrate, etc. It is necessary to bond only at the adhesive part. For this reason, when the said touch panel sheet is used, it is necessary to use the double-sided adhesive sheet which can suppress the deformation | transformation of the said sheet | seat in a high-temperature, high-humidity environment by the frame-shaped adhesion | attachment of a surrounding part.

  As an adhesive for fixing a polarizing plate, for example, an adhesive containing an acrylic resin, an alkoxysilane, and a crosslinking agent is disclosed as an adhesive used for a polarizing plate having an adhesive layer excellent in durability at high temperature and high humidity. (See Patent Document 2). However, the durability at high temperature and high humidity in fixing the polarizing plate is realized by applying an adhesive to the entire surface of the polarizing plate and sticking the entire surface to the glass. For this reason, when the polarizing film is bonded only at the frame-shaped bonding portion as described above by the pressure-sensitive adhesive using the isocyanurate-based crosslinking agent disclosed in the Examples of the document, the high-temperature and high-humidity environment is used. The deformation of the polarizing film cannot be suppressed, and the polarizing film is easily peeled off. In addition, this document discloses that an epoxy compound can be used as a cross-linking agent, but the description merely lists epoxy compounds generally used for pressure-sensitive adhesives.

In addition, as an adhesive tape having excellent resilience even when used in a frame shape, for example, a double-sided adhesive tape using an adhesive containing an acrylic copolymer and an isocyanate crosslinking agent is disclosed. (See Patent Document 3). The adhesive tape has good repulsion resistance when used as a frame-like double-sided tape in an LCD module for a mobile phone, and does not peel off even in a long-term environmental test. However, the adhesive tape does not peel off in a relatively small area panel such as an LCD module for a mobile phone, but it is a uniaxial shaft that causes a large deformation as described above in a large area module for car navigation or the like. When the stretched film is fixed, the adhesive sheet having a small adhesion area may be peeled off in order to reduce the number of adhesion sites that become the dead space of the image display unit. In addition, if the polarizing film is distorted, its polarizing properties will deteriorate, so it is necessary to suppress the distortion. However, when a polarizing film with a large area is bonded in a frame shape with the adhesive tape, There was a problem that a slight float occurred.
JP 2003-342542 A JP-A-9-292526 JP 2006-010931 A

  The problem to be solved by the present invention is to provide a double-sided pressure-sensitive adhesive sheet that does not peel or float even in a high-temperature environment, particularly a double-sided pressure-sensitive adhesive sheet that can suitably suppress deformation of a uniaxially stretched film that occurs in a high-temperature and high-humidity environment. It is in. Moreover, this invention makes it a subject to provide the manufacturing method of this module which can suppress peeling of the panel for touch panels from the module which suppressed peeling from the board | substrate by the deformation | transformation of the sheet | seat for touch panels, and this module.

  The deformation of a uniaxially stretched film in a high-temperature and high-humidity environment is very large, so a double-sided PSA sheet that attaches a uniaxially stretched film only in a small area such as a frame shape requires extremely strong adhesive strength. . However, when a relatively soft adhesive is used as a strong adhesive, stringing occurs when a strong peeling force is applied, and the adhesive tears and peels off. In order to prevent this, if a hard pressure-sensitive adhesive having a high degree of crosslinking is used, peeling at the interface between the double-sided pressure-sensitive adhesive sheet and the object to be bonded occurs due to the peeling force due to deformation of the uniaxially stretched film. For this reason, in the conventional double-sided pressure-sensitive adhesive sheet, it has been extremely difficult to suppress the peeling of the uniaxially stretched sheet under a high temperature and high humidity with a small adhesion area.

  The present inventors have studied in detail the deformation behavior of a uniaxially stretched film in a high-temperature and high-humidity environment and the accompanying peeling behavior of the pressure-sensitive adhesive, and have a specific pressure-sensitive adhesive composition in which the degree of crosslinking of the pressure-sensitive adhesive layer changes over time. It has been found that peeling due to deformation of the uniaxially stretched film can be suppressed by the double-sided pressure-sensitive adhesive sheet. According to the double-sided pressure-sensitive adhesive sheet, the uniaxially stretched film is fixed with a strong adhesive force at the beginning of application, and the degree of crosslinking increases in a high temperature and high humidity environment where the uniaxially stretched film is deformed. Even when a force is applied to the adhesive, when the peeling force is generated by the tearing of the adhesive due to stringing, the peeling can be suppressed following the deformation.

  That is, the present invention is a double-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing an acrylic polymer and an epoxy crosslinking agent, wherein the gel fraction of the pressure-sensitive adhesive layer increases with time, and the initial gel of the pressure-sensitive adhesive layer The gel fraction of the pressure-sensitive adhesive layer is 80 to 95% after being left for 200 hours in an environment having a relative humidity of 80 to 90% at 80 to 90 ° C. A double-sided PSA sheet is provided.

  In the present invention, the ITO film side peripheral portion of the sheet for a touch panel in which a uniaxially stretched film and an ITO film are laminated is fixed to a glass substrate or a transparent resin substrate via an adhesive layer, and the touch panel sheet and glass A module for a touch panel in which a portion where the adhesive layer between the substrate or the transparent resin substrate is not provided is a gap, and the adhesive layer is a double-sided adhesive sheet. is there.

  Furthermore, the present invention provides an ITO film side peripheral portion of a touch panel sheet in which a uniaxially stretched film and an ITO film are laminated, a glass substrate or a transparent resin substrate, and an adhesive containing an acrylic polymer and an epoxy crosslinking agent. The manufacturing method of the module for touchscreens which has the process affixed with the double-sided adhesive sheet which has the adhesive layer which becomes and the gel fraction of the said adhesive layer is 50 to 80% is provided.

  The double-sided pressure-sensitive adhesive sheet of the present invention does not cause peeling due to tearing of the adhesive or interfacial peeling even when peeling force occurs in a high-temperature and high-humidity environment, thus firmly fixing the object to be stuck even in harsh environments it can. Moreover, even if it is sticking of a very small area, the sticking target can be firmly fixed in a high-temperature and high-humidity environment, so that even when used in a touch panel module, dead space caused by an adhesion site can be extremely reduced.

  Furthermore, the touch panel module of the present invention does not use a glass substrate, is composed of an inexpensive resin film, and does not peel off the touch panel sheet even in a high-temperature and high-humidity environment, so it is used in a harsh environment. It can be suitably used as a car navigation module.

[Double-sided adhesive sheet]
The initial gel fraction of the pressure-sensitive adhesive layer used in the present invention is 50 to 80%, particularly preferably 60 to 75%. If it is this range, the initial adhesive force with a resin film or a glass plate can be made higher, and it is easy to follow the deformation | transformation of the uniaxially stretched film in a high-temperature, high-humidity environment especially. In addition, in this invention, an initial stage gel fraction refers to the gel fraction when the prepared adhesive is stored still at 40 degreeC for 48 hours.

  The increase rate of the gel fraction may be appropriately designed according to the object to be used based on the above concept, but it is preferable that the gel fraction is not too fast. In the case of suppressing peeling due to deformation of the uniaxially stretched film, the pressure-sensitive adhesive after storage for 200 hours at 80 to 90 ° C. and relative humidity of 80 to 90%, if the initial gel fraction of the pressure-sensitive adhesive layer is 50 to 80% The gel fraction of the layer is 80 to 95%, preferably 85 to 95%. The difference between the initial gel fraction and the gel fraction after storage for 200 hours under the above conditions is preferably 15% or more, more preferably 15 to 30%, and more preferably 20 to 25%. Particularly preferred. The increase in gel fraction is preferably increased over time up to 200 hours. Moreover, it is preferable that the gel fraction is designed so that the gel fraction does not exceed 90%, preferably 85% before 100 hours have passed under the above conditions. The increase rate of the gel fraction can be adjusted by adjusting the type or amount of the crosslinking agent.

  As described above, the pressure-sensitive adhesive layer used in the double-sided pressure-sensitive adhesive sheet of the present invention increases the degree of crosslinking over time or with heating, so the gel fraction changes over time in a high-temperature environment, and in the peeling direction under a high-temperature and high-humidity environment. Even when a force is applied, suitable adhesiveness can be maintained following the peeling force.

In addition, the gel fraction of the pressure-sensitive adhesive layer is obtained by immersing the composition of the pressure-sensitive adhesive layer after curing in toluene, measuring the mass of the insoluble matter remaining after being left for 24 hours, and measuring the percentage of the original mass. expressed.
That is, the pressure-sensitive adhesive layer used in the present invention has a gel fraction that increases with time. Here, increasing the gel fraction means that the tangent or slope of the curve obtained by plotting the graph with the horizontal axis representing time and the vertical axis representing the gel fraction is 0 or more.

  It is considered that there are generally two types of peeling behavior between the pressure-sensitive adhesive layer and the adherend. That is, there are peeling at the interface between the pressure-sensitive adhesive layer and the adherend, and peeling due to the pressure-sensitive adhesive layer itself being broken due to stringing or the like. Peeling at the interface tends to occur when the pressure-sensitive adhesive layer is hard. If the pressure-sensitive adhesive layer is hard, it is considered that the force to be peeled off does not disperse inside the pressure-sensitive adhesive layer, and this force concentrates on the interface between the pressure-sensitive adhesive layer and the object to be deposited, causing peeling from the interface. On the other hand, peeling due to breakage of the pressure-sensitive adhesive layer is likely to occur when the pressure-sensitive adhesive layer is soft, and when the force to be peeled is applied to the pressure-sensitive adhesive layer, the pressure-sensitive adhesive itself is stretched, causing stringing and breaking.

  In a high temperature and high humidity environment, the pressure-sensitive adhesive layer is in a soft state, and it is considered that when a force to peel off with time is generated, the pressure-sensitive adhesive layer is stringed and peeled off. In order to prevent this, if the pressure-sensitive adhesive layer is in a hard state, that is, in a state where the gel fraction is high and the degree of crosslinking is high, there is a possibility that the adhesive force at the initial bonding may not be sufficient, and that interface peeling may occur in a room temperature environment. is there. Adhesive that suppresses debonding due to breakage and interfacial debonding under both high temperature and room temperature conditions when the pressure of the pressure-sensitive adhesive layer is to be peeled off from the target in an environment where environmental conditions change A layer is required.

  Usually, strong adhesive and repulsion-resistant adhesives that are commercially available are based on the design philosophy of appropriately adjusting the balance between the property that does not cause peeling due to breakage and the property that does not cause interface peeling. there were. However, even if these are adjusted as appropriate, there is a limit to preventing peeling, and sufficient peel resistance is exhibited in heat cycle tests in high-temperature and high-humidity environments and at room temperature, which are tests that reproduce harsh environments. Difficult to do.

  On the other hand, in the present invention, a pressure-sensitive adhesive layer having a gel fraction that changes with time, particularly a gel fraction that increases when overheated is used. Thereby, the adhesive force with the object to be adhered can be suitably secured at the initial stage of adhesion or at room temperature, and peeling at the interface between the pressure-sensitive adhesive layer and the object to be adhered does not occur. After that, when force is generated in the peeling direction over time or in a high temperature and high humidity environment, the gel fraction increases, so that crosslinking progresses as appropriate and suppresses the destruction of the adhesive layer due to stringing of the adhesive layer. it can. Thereby, it is possible to realize a double-sided pressure-sensitive adhesive sheet that does not peel even when placed in a high temperature and high humidity environment as well as in a room temperature environment. In addition, peeling at the interface between the pressure-sensitive adhesive layer and the object to be deposited is less likely to occur with time, so peeling does not occur at the interface after a long period of time, and there is no breakage because it is stable at a high degree of crosslinking. .

  Since the pressure-sensitive adhesive used for the double-sided pressure-sensitive adhesive sheet is preferably one having stable characteristics from the viewpoint of quality control, it is usually designed so that the characteristics do not change significantly with time. In the present invention, the pressure-sensitive adhesive layer is designed based on a completely different idea from the conventional idea, thereby achieving prevention of peeling in a high-temperature and high-humidity environment that could not be achieved conventionally.

  The double-sided pressure-sensitive adhesive sheet of the present invention can suitably adjust the change in the gel fraction by containing an acrylic polymer and an epoxy crosslinking agent, and particularly contains 8 to 12 parts by mass of a carboxyl group-containing copolymer monomer unit. What consists of an adhesive containing 100 mass parts of acryl-type polymers and 0.6-1.5 mass parts of epoxy crosslinking agents suitably, and a gel fraction rises with time.

  Examples of the monomer that gives a carboxyl group-containing copolymerizable monomer unit include (meth) acrylic acid, acrylic acid dimer, itaconic acid, crotonic acid, maleic acid, maleic anhydride, and the like. Of these, acrylic acid or methacrylic acid is preferable, and acrylic acid is particularly preferable. In this specification, (meth) acrylic acid means acrylic acid or methacrylic acid, and the same applies to derivatives of acrylic acid or methacrylic acid.

  When the carboxyl group-containing copolymer monomer unit is contained in an amount of 5 to 15 parts by mass in 100 parts by mass of the acrylic polymer, the release can be suitably suppressed when a large peeling force is applied over time. By setting it as 12 parts by mass, the deformation of the uniaxially stretched film can be followed particularly well.

  As a monomer that gives other monomer units constituting the acrylic polymer, (meth) acrylic acid alkyl ester can be preferably used, and among them, (meth) acrylic acid alkyl ester having an alkyl side chain having 4 to 14 carbon atoms is preferred. It is preferable to use it.

  Specific examples of the (meth) acrylic acid alkyl ester having an alkyl side chain having 4 to 14 carbon atoms include n-butyl acrylate, sec-butyl acrylate, t-butyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, isodecyl acrylate, lauryl acrylate, isobornyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, sec -Butyl methacrylate, t-butyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, n-octyl methacrylate DOO, isooctyl methacrylate, 2-ethylhexyl methacrylate, isononyl methacrylate, isodecyl methacrylate, lauryl methacrylate, isobornyl methacrylate, and the like.

  Among these, a methacrylic acid alkyl ester having an alkyl side chain having 4 to 9 carbon atoms or an acrylic acid alkyl ester having an alkyl side chain having 4 to 9 carbon atoms is preferable, and further having 4 to 9 carbon atoms. An acrylic acid alkyl ester having an alkyl side chain is more preferred. Specifically, n-butyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, and isononyl acrylate are preferable.

  Further, by copolymerizing with the above (meth) acrylic acid alkyl ester using a monoethylenic copolymerizable monomer other than the above carboxyl group-containing copolymerizable monomer or (meth) acrylic acid alkyl ester, a functional group or The cohesive force and Tg can be adjusted by adjusting the adhesive force by introducing a polar group and controlling the maximum value of the loss tangent (tan δ) of the copolymer.

  Such monoethylenic copolymerizable monomers include hydroxyl group-containing copolymerizable monomers such as 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate, N -Amide group-containing copolymerizable monomers such as vinyl-2-pyrrolidone, N-vinylcaprolactam, morpholine acrylate, N, N-dimethyl (meth) acrylamide, imide group-containing copolymerizable monomers such as cyclohexylmaleimide, isopropylmaleimide, 2- (Perhydrophthalimido-N-yl) ethyl acrylate, styrene, vinyl acetate, acrylonitrile and the like can be mentioned. When using such a copolymerizable monomer, it is preferable to contain 2-40 mass% as a monomer unit in the acrylic polymer obtained.

  The mass average molecular weight of the acrylic polymer is 400,000 to 2,000,000, preferably 600,000 to 1,300,000 in terms of standard polystyrene conversion measured by gel permeation chromatography (GPC). If the mass average molecular weight is less than 400,000, the cohesive force is lowered, which is not preferable. On the other hand, if it exceeds 2 million, it is necessary to lower the solid content concentration to adjust the viscosity of the pressure-sensitive adhesive solution. This is because it takes a long time and is not preferable.

  This acrylic polymer can be produced by a known radical polymerization method such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization or supercritical polymerization.

  Polymerization can be initiated by peroxides such as benzoyl peroxide and lauroyl peroxide, thermal initiation using azo initiators such as azobisisobutyronitrile, acetophenone, benzoin, benzyl ketal. The starting method by ultraviolet rays, such as a system, an acyl phosphine oxide system, a benzophenone system, and a maleimide system, and the starting method by an electron beam can be arbitrarily selected. Of these, a heat initiation method using an azo initiator such as azobisisobutyronitrile and an ultraviolet light initiation method using an acylphosphine oxide initiator are preferable.

  During polymerization, other additives are added to the above monomer species as necessary, and these are dissolved in an organic solvent to prepare a pressure-sensitive adhesive material before adding a crosslinking agent and an antioxidant. Make an adhesive solution. The organic solvent is not particularly limited as long as it dissolves the above-described blending components and does not react with the functional group of the cross-linking agent. However, ethyl acetate, toluene, xylene, n-hexane, acetone, methyl ethyl ketone and the like are known. Conventional organic solvents can be used alone or in admixture. Of these, ethyl acetate, n-hexane, acetone, and methyl ethyl ketone are preferable.

  As the epoxy crosslinking agent used in the present invention, a commercially available epoxy crosslinking agent can be used, and a tetrafunctional epoxy crosslinking agent can be particularly preferably used. Examples of the tetrafunctional epoxy crosslinking agent include Tetrad X and Tetrad C manufactured by Mitsubishi Gas Chemical Company, and E-05X manufactured by Soken Chemical Co., Ltd. The epoxy crosslinking agent is preferably contained in an amount of 0.01 to 0.025 parts by mass, more preferably 0.01 to 0.02 parts by mass with respect to 100 parts by mass of the acrylic polymer. Particularly preferred is 013 to 0.017 parts by mass. In the present invention, by containing the content of the epoxy crosslinking agent, the gel fraction changes with time even when force is applied in the peeling direction in a high-temperature and high-humidity environment. Can be held.

  Various additives, antioxidants, ultraviolet absorbers, fillers, pigments, thickeners, tackifying resins and the like may be further added to the pressure-sensitive adhesive layer as long as the performance is not impaired.

  The double-sided pressure-sensitive adhesive sheet of the present invention is a double-sided pressure-sensitive adhesive sheet having the above-mentioned pressure-sensitive adhesive layer, and can be produced by coating the prepared pressure-sensitive adhesive solution on a release paper and drying it. Examples of release paper include glassine paper, fine paper, craft paper, nonwoven fabric, metal foil, polyimide film, polyethylene naphthalate film (PEN), polyether ether ketone film (PEEK), polyparaphenylene sulfide film (PPS), Examples include polytetrafluoroethylene film (PTFE), polyethylene terephthalate film (PET), and laminates thereof. Among these, a resin film can be suitably used, and a PET film is particularly preferable. The surface of the release paper is preferably subjected to a release treatment such as silicone treatment or fluorine treatment in order to improve the peelability from the adhesive. Glassine paper, high-quality paper, and kraft paper are preferably subjected to a sealing treatment with polyethylene in order to perform the mold release process uniformly.

  In the double-sided pressure-sensitive adhesive sheet of the present invention, a resin film can be used as a support, and polyester, polypropylene, polyethylene, polyvinyl carbonate, and laminates thereof can be used as the resin of the resin film. Among these, a polyester resin film such as PET can be preferably used. These resin films are preferably subjected to an easy adhesion surface treatment by corona treatment or the like in order to improve the adhesion to the pressure-sensitive adhesive layer. Moreover, the thing of the double-sided adhesive tape structure which uses a fibrous support as a core material can also be used, and it is suitable when thickness is requested | required of a double-sided adhesive sheet. Specific examples of the fibrous support include non-woven fabrics, and examples thereof include those made of materials such as cotton, hemp, and rayon.

  The thickness of the support used is preferably 5 to 100 μm, particularly preferably 5 to 20 μm when a resin film is used. When a fibrous support is used, it is preferably 20 to 60 μm.

  The coating amount of the pressure-sensitive adhesive layer is appropriately set according to the required performance, but the coating amount on each surface of the support is preferably 5 to 100 μm after drying, and preferably 15 to 70 μm. More preferred. The total thickness is preferably 15 to 300 μm, and particularly preferably 50 to 150 μm.

  This double-sided PSA sheet can be produced by forming a PSA layer and release paper on both sides of the support. The pressure-sensitive adhesive layer can be formed by applying a pressure-sensitive adhesive on a release paper with a roll coater or a die coater, and forming the pressure-sensitive adhesive layer once on the release paper, and then transferring the pressure-sensitive adhesive layer onto the support or directly on the support. A conventionally known method such as a method for performing the method can be appropriately used.

[Touch panel module]
In the touch panel module of the present invention, the ITO film side peripheral portion of the touch panel sheet in which the uniaxially stretched film and the ITO film are laminated is fixed to the glass substrate via the double-sided adhesive sheet, the touch panel sheet, A portion where the double-sided pressure-sensitive adhesive sheet between the glass substrate is not provided is a gap.

Hereinafter, the touch panel module of the present invention will be described in detail with reference to the drawings.
FIG. 1 is an exploded view illustrating a schematic configuration of a touch panel module according to the present invention, and FIG. 2 is a longitudinal sectional view.
The touch panel module 1 includes a touch panel sheet 10 in which a uniaxially stretched film 2 and an ITO film 3 are laminated, an adhesive layer 4 made of the double-sided adhesive sheet described above, and a glass substrate 5.

  The sheet 10 for the touch panel is bonded to the glass substrate 5 through the adhesive layer 4 on the surface on the ITO film 3 side. The adhesive layer 4 is provided along the periphery of the ITO film 3 and the glass substrate 5, and has a frame shape. Accordingly, the portion where the adhesive layer 4 between the ITO film 3 and the glass substrate 5 is not provided is a gap 6, and the adhesive layer 4 also functions as a spacer.

Although the uniaxially stretched film used by this invention will not be specifically limited if it is manufactured by the conventionally well-known method, The uniaxially stretched polarizing film widely used with a liquid crystal display element etc. is preferable.
The ITO (indium tin oxide) film is not particularly limited as long as it is produced by a conventionally known method.

  The touch panel sheet 10 is obtained by a conventionally known method. For example, it can be obtained by bonding the uniaxially stretched film 2 and the ITO film 3 of a predetermined shape with an adhesive. The pressure-sensitive adhesive is not particularly limited as long as it does not deteriorate the visibility of the display device. For example, an acrylic pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a polyester-based pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, and a polyurethane-based pressure-sensitive adhesive Known and commonly used pressure-sensitive adhesives such as pressure-sensitive adhesives can be used, and these pressure-sensitive adhesives may be used alone or in combination of two or more. Moreover, what bonded together what was marketed as a polarizing film with an adhesive layer with an ITO film can also be used.

In the present invention, the thickness of the uniaxially stretched film 2 is preferably 0.15 to 0.30 mm, and the thickness of the ITO film 3 is preferably 0.05 to 0.15 mm. These uniaxially stretched film and ITO film are bonded together with an adhesive having a thickness of about 0.02 to 0.05 μm. And it is preferable that the thickness of the sheet | seat 10 for touchscreens is 0.22-0.5 mm.
Moreover, it is preferable that the thickness of the adhesion layer 4 is 0.05-0.150 mm, and it is preferable that the thickness of the glass substrate 5 is 0.70-1.5 mm.
And it is preferable that the thickness of the module 1 for touch panels is 1-2 mm.

The width (W) of the adhesive layer 4 in the in-plane direction of the adhesive application of the ITO film 3 and the glass substrate 5 is not particularly limited, but the touch panel sheet serving as the image display unit of the touch panel module of the present invention. even the area of about 50 to 250 mM ² area, 1.5 to 5 mm, preferably very small by the width of the double-sided pressure-sensitive adhesive sheet, a high-temperature and high-humidity environment due to the anisotropy of the uniaxially stretched film of 2~3mm Large curl can be suppressed.

  The touch panel module according to the present invention may be formed by bonding the touch panel sheet 10 and the glass substrate 5 via the double-sided pressure-sensitive adhesive sheet 4 having the shape of these peripheral portions. It is preferable to carry out in a state where the gel fraction of the pressure-sensitive adhesive layer of the double-sided pressure-sensitive adhesive sheet 4 is 50 to 80%.

As described above, according to the touch panel module of the present invention, in the initial stage of bonding between the touch panel sheet and the glass substrate, the adhesive layer has flexibility, and the interface between the touch panel sheet and the adhesive layer. In addition, it exhibits good adhesion at the interface between the glass substrate and the adhesive layer, and does not cause interfacial peeling when a force is applied in the peeling direction. And by increasing the gel fraction of the adhesive layer over time or by heating, even when a force is applied in the peeling direction over time in a high temperature environment, breakage due to stringing of the adhesive layer is suppressed, No peeling due to destruction. For this reason, even if it is a case where an adhesion area is very small, the big curl resulting from the anisotropy of the uniaxially stretched film in a high-temperature, high-humidity environment can be suppressed. Therefore, even if the touch panel module of the present invention uses a touch panel sheet that does not use a glass plate for the image display section, the touch panel sheet does not peel off in a high temperature and high humidity environment.
Such a touch panel module of the present invention can limit the dead space in which an image cannot be displayed even in an application used in a high temperature and high humidity environment, and thus is limited in a severe environment such as an in-vehicle car navigation application. Especially effective for use in open spaces.
Further, it can be effectively used in a large-area display panel that is likely to be deformed.

  Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to the following examples.

(Preparation of adhesive solution)
Using a reaction vessel equipped with a stirrer, a cold flow cooler, a thermometer, a dropping funnel and a nitrogen gas inlet, 89.9 parts by mass of butyl acrylate, 10.0 parts by mass of acrylic acid, 0.1 mass of 4-hydroxybutyl acrylate Part and 0.03 part by mass of 2,2-azobisisonitri as a polymerization initiator were dissolved in a mixed solvent consisting of 63 parts by mass of ethyl acetate and 100 parts by mass of acetone. Subsequently, it superposes | polymerizes at 65 degreeC for 6 hours, 0.2 mass part of additional 2, 2- azobis isobutyl nitriles and 45 mass parts of ethyl acetate are added to this, Furthermore, it superposes | polymerizes for 6 hours, and a mass mean molecular weight 900,000 (polystyrene) Conversion) acrylic copolymer solution. Ethyl acetate was added to this acrylic copolymer solution to obtain a pressure-sensitive adhesive solution having a nonvolatile content of 30% by mass.

[Example 1]
To 100 parts by mass of the pressure-sensitive adhesive solution obtained above, 0.64 parts by mass of a crosslinking agent (“E-05X” manufactured by Soken Chemical Co., Ltd., epoxy-based crosslinking agent, solid content: 0.5% by mass) is added, After stirring for 15 minutes, a pressure-sensitive adhesive was applied to a release film of 50 μm thick PET release paper to a thickness of 45 μm, dried at 80 ° C. for 3 minutes, and then double-sided corona with a thickness of 12 μm. Laminated to the treated PET film. Further, an adhesive was applied to the opposite surface of the PET film on a 50 μm PET release paper to a thickness of 45 μm, and an adhesive layer dried at 80 ° C. for 3 minutes was laminated and laminated, and then at 48 ° C. for 48 A double-sided PSA sheet was prepared by heat treatment for a period of time.
Along the outer periphery of a touch panel sheet having a thickness of 0.35 mm and a size of 90 mm × 167 mm, in which the uniaxially stretched film and the ITO film are bonded together with an acrylic pressure-sensitive adhesive, the above double-sided pressure-sensitive adhesive sheet is bonded to each other, Furthermore, it bonded together with the glass substrate of thickness 1.2mm and size 90mmx167mm, and obtained the module for touchscreens.

[Example 2]
A double-sided PSA sheet was prepared in the same manner as in Example 1 except that the addition amount of the crosslinking agent “E-05X” was changed to 0.8 parts by mass. A touch panel module was obtained in the same manner as in Example 1 except that the obtained double-sided PSA sheet was used.

[Example 3]
A double-sided PSA sheet was prepared in the same manner as in Example 1 except that the addition amount of the crosslinking agent “E-05X” was changed to 1.0 part by mass. A touch panel module was obtained in the same manner as in Example 1 except that the obtained double-sided PSA sheet was used.

[Example 4]
A double-sided PSA sheet was prepared in the same manner as in Example 1 except that the addition amount of the crosslinking agent “E-05X” was changed to 1.2 parts by mass. A touch panel module was obtained in the same manner as in Example 1 except that the obtained double-sided PSA sheet was used.

[Comparative Example 1]
A double-sided PSA sheet was prepared in the same manner as in Example 1 except that the addition amount of the crosslinking agent “E-05X” was changed to 0.4 parts by mass. A touch panel module was obtained in the same manner as in Example 1 except that the obtained double-sided PSA sheet was used.

[Comparative Example 2]
A double-sided PSA sheet was prepared in the same manner as in Example 1 except that the addition amount of the crosslinking agent “E-05X” was changed to 0.6 parts by mass. A touch panel module was obtained in the same manner as in Example 1 except that the obtained double-sided PSA sheet was used.

[Comparative Example 3]
A double-sided PSA sheet was prepared in the same manner as in Example 1 except that the addition amount of the crosslinking agent “E-05X” was changed to 2.2 parts by mass. A touch panel module was obtained in the same manner as in Example 1 except that the obtained double-sided PSA sheet was used.

<Measurement of gel fraction (insoluble content)>
The initial gel fraction of the double-sided pressure-sensitive adhesive sheets obtained in Examples 1 to 4 and Comparative Examples 1 to 3 and the gel fraction after being allowed to stand for 200 hours under the conditions of a temperature of 85 ° C./relative humidity of 85%. It was measured.
The gel fraction was measured by the following method.
(1) The weight of the pressure-sensitive adhesive layer that has been cut into a size of 40 mm × 50 mm and from which the release paper of the double-sided pressure-sensitive adhesive sheet has been removed is measured and “mass A”.
(2) The weight of the support cut into a size of 40 mm × 50 mm is measured and “mass B” is measured. (3) The cut adhesive layer is immersed in toluene for 24 hours to separate the insoluble matter, and the separated insoluble matter is dried at 105 ° C. for 1 hour to measure “mass C”.
(4) The gel fraction is calculated by the following formula.
Gel fraction (%) = (CB) / (AB) × 100

<Environmental test>
The following environmental tests are performed on the touch panel modules obtained in Examples 1 to 4 and Comparative Examples 1 to 3, and the touch panel sheet is observed to be peeled off from the lath substrate and the touch panel sheet is observed to be distorted. did. The obtained results are shown in Table 1. Moreover, the time-dependent change of the gel fraction at the time of the high temperature, high humidity environment test of the adhesive tape prepared in Example 1 was shown in FIG.
(1) High-temperature and high-humidity environment test The module for touch panels was stored for 200 hours under the conditions of a temperature of 85 ° C. and a relative humidity of 85%, and peeling and distortion were observed. The judgment criteria are as follows.
Judgment criteria;
(Double-circle): Peeling and distortion are not seen at all.
○: No peeling is observed, and no distortion that affects the visibility of image display is observed.
Δ: Small floating or distortion of the touch panel sheet is observed.
X: Large peeling and curling are observed.
(2) Heat cycle test The module for touch panel was held at -40 ° C for 1 hour and at 85 ° C for 1 hour (1 cycle at 2 hours) was repeated 100 cycles, and peeling and distortion were observed. The determination criteria are the same as in (1) above.

As apparent from Table 1, in Examples 1 to 4, peeling of the touch panel sheet was not observed, and distortion was hardly observed. In particular, those of Examples 2 and 3 were confirmed to have particularly high stability.
On the other hand, in Comparative Examples 1 to 3, peeling of the touch panel sheet and large distortion were observed. In particular, in Comparative Examples 1 and 3, the touch panel sheet was curled and large peeling occurred.

  The present invention can be used for a liquid crystal display device and the like, and is useful in the field of electric appliances.

It is an exploded view which illustrates schematic structure of the module for touchscreens concerning this invention. It is a longitudinal cross-sectional view which illustrates the module for touchscreens which concerns on this invention. It is a graph which shows the time-dependent change of the gel fraction at the time of the high-temperature, high-humidity environmental test of the adhesive tape prepared in Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Touch panel module, 2 ... Uniaxially stretched film, 3 ... ITO film, 4 ... Adhesive layer, 5 ... Glass substrate, 10 ... Touch panel sheet

Claims (9)

  A double-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing an acrylic polymer and an epoxy crosslinking agent, wherein the gel fraction of the pressure-sensitive adhesive layer increases with time, and the initial gel fraction of the pressure-sensitive adhesive layer is 50 to 80 The gel fraction of the pressure-sensitive adhesive layer after leaving for 200 hours in an environment of 80 to 90 ° C. and relative humidity of 80 to 90% after being applied to the object to be applied is 80 to 95%, and the initial gel The double-sided pressure-sensitive adhesive sheet, wherein the difference between the fraction and the gel fraction after being left for 200 hours is 15% or more.   The pressure-sensitive adhesive layer comprises a pressure-sensitive adhesive containing 100 parts by mass of an acrylic polymer containing 8 to 12 parts by mass of a carboxyl group-containing copolymer monomer unit and 0.01 to 0.025 parts by mass of an epoxy crosslinking agent. The double-sided pressure-sensitive adhesive sheet according to claim 1.   The double-sided pressure-sensitive adhesive according to claim 2, wherein 100 parts by mass of the acrylic polymer further contains 88 to 92 parts by mass of a (meth) acrylic acid alkyl ester monomer unit having an alcohol residue having 4 to 14 carbon atoms. Sheet.   The double-sided pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer is provided on both surfaces of the support.   The double-sided pressure-sensitive adhesive sheet according to claim 4, wherein the support is a PET film having a thickness of 5 to 100 μm.   The ITO film side peripheral part of the touch panel sheet in which the uniaxially stretched film and the ITO film are laminated is fixed to the glass substrate or the transparent resin substrate via the adhesive layer, and the touch panel sheet, the glass substrate or the transparent resin substrate, It is the module for touch panels by which the part in which the said adhesive layer between them is not provided was made into the space | gap part, Comprising: The said adhesive layer is the double-sided adhesive sheet in any one of Claims 1-5 characterized by the above-mentioned. Touch panel module.   The touch panel module according to claim 6, wherein the uniaxially stretched film is a uniaxially stretched polarizing film. 8. The touch panel sheet according to claim 6, wherein an area of the touch panel sheet is 50 to 250 cm ² , and a width of the adhesive sheet provided on the ITO film side periphery of the touch panel sheet is 1.5 to 5 mm. module. An ITO film side periphery of a sheet for a touch panel in which a uniaxially stretched film and an ITO film are laminated, and a glass substrate or a transparent resin substrate,
It has the process of sticking with the double-sided adhesive sheet which has an adhesive layer which consists of an adhesive containing an acrylic polymer and an epoxy crosslinking agent, and the gel fraction of the said adhesive layer is 50 to 80%. A method for manufacturing a touch panel module.

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