JP5625625B2 - Adhesive sheet for metal sticking - Google Patents

Description

  The present invention is a metal with excellent durability that is difficult to cause discoloration or alteration of the pressure-sensitive adhesive caused by the metal member even when affixed to the metal member for a long time, and is difficult to cause deterioration of the metal member due to the pressure-sensitive adhesive. The present invention relates to an adhesive sheet for sticking.

  In recent years, there has been an increasing demand for plasma display panels (hereinafter abbreviated as PDPs) as display panels for various electronic devices such as large televisions. In PDP, an electromagnetic wave shield is used to prevent leakage of electromagnetic waves. In general, the electromagnetic wave shield is attached to the front surface of the PDP through an adhesive layer.

  However, when the metal surface of the electromagnetic wave shield and the pressure-sensitive adhesive layer are in contact with each other, metal ions derived from the electromagnetic wave shield react with the organic material constituting the pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer may be discolored or deteriorated. there were. In addition, the acid component derived from the pressure-sensitive adhesive layer and the metal of the electromagnetic wave shield may react to denature the metal. Therefore, the pressure-sensitive adhesive used for attaching the electromagnetic wave shield is required to have characteristics that do not change with the metal and do not change the metal.

  So far, an acrylic pressure-sensitive adhesive having an acrylic polymer having a specific composition as a base polymer has been reported as an adhesive having a property of not corroding a metal (see Patent Document 1). Here, an adhesive that does not corrode the copper foil even when exposed to a high-humidity environment has been proposed, but there is no description about the characteristics of the adhesive that does not deteriorate due to metal.

International Publication No. 2000/074937 Pamphlet JP 2009-73866 A

  The present invention has been made in view of the above circumstances, and the object of the present invention is that, even when affixed to a metal member for a long time, discoloration or alteration of the adhesive caused by the metal member is difficult to occur, and It is an object of the present invention to provide a pressure-sensitive adhesive sheet for metal sticking that is difficult to cause deterioration of a metal member due to the pressure-sensitive adhesive and has excellent durability.

  The present inventor has made extensive studies to solve the above-mentioned problems. As a result, the pressure-sensitive adhesive layer-forming material contains an acrylic polymer, a crosslinking agent, and a specific rust preventive agent. The present inventors have found that the problem can be solved and have completed the present invention.

  Until now, for certain rust inhibitors, deterioration of near-infrared absorbing dye caused by contact between the pressure-sensitive adhesive layer and the metal member is caused by inclusion in the pressure-sensitive adhesive layer forming material together with the acrylic polymer and near-infrared absorbing dye. Has been reported to be able to be suppressed (see Patent Document 2). However, there is no report that all rust preventives have such an effect, and according to the rust preventives, discoloration and alteration of the adhesive itself that does not contain near-infrared absorbing dyes can be suppressed, and optical properties can be maintained over a long period of time. There is no report that the light transmittance in the visible region of the sheet can be maintained.

  Specifically, the present invention provides the following.

  (1) It has at least an adhesive layer made of an adhesive layer forming material containing an acrylic polymer, a crosslinking agent, and carboxybenzotriazole and / or 1,2,4-triazole as a rust inhibitor. A pressure-sensitive adhesive sheet for sticking metal.

  (2) The acrylic polymer is mainly obtained by copolymerization of an acrylic ester with the acrylic ester and a copolymerizable hydroxyl group-containing monomer, and contains substantially no carboxyl group (1 ) The adhesive sheet for metal sticking as described in.

  (3) When the pressure-sensitive adhesive layer and the metal surface are bonded together, the chromaticity change (Δy) before and after the heat resistance test at a temperature of 80 ° C. and a test time of 2000 hours is less than 0.002, and The pressure-sensitive adhesive sheet for metal sticking according to (1) or (2), wherein the chromaticity change (Δy) before and after the wet heat resistance test at a temperature of 60 ° C., a humidity of 90%, and a test time of 2000 hours is less than 0.002.

  (4) An optical film for a plasma display panel, wherein the pressure-sensitive adhesive layer surface of the pressure-sensitive adhesive sheet according to any one of (1) to (3) and the metal surface of the electromagnetic wave shield are bonded together.

  (5) The optical film for a plasma display panel according to (4), wherein the electromagnetic wave shield is formed by printing a conductive ink containing a resin and a conductive metal.

  (6) A plasma display in which the optical film according to (4) or (5) is disposed on the front surface of the image display glass plate of the plasma display panel.

  The pressure-sensitive adhesive sheet for metal sticking of the present invention is less likely to cause discoloration or alteration of the pressure-sensitive adhesive due to the metal member even if the pressure-sensitive adhesive layer surface is in contact with the metal surface of the metal member. Deterioration of metal members is difficult to occur. Furthermore, the pressure-sensitive adhesive sheet for sticking metal of the present invention is excellent in durability and can maintain stable optical characteristics even when used for a long time under high temperature conditions or high temperature and high humidity conditions.

  Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and may be implemented with appropriate modifications within the scope of the object of the present invention. be able to.

  The pressure-sensitive adhesive sheet for metal sticking (hereinafter referred to as pressure-sensitive adhesive sheet) of the present invention contains an acrylic polymer, a crosslinking agent, and carboxybenzotriazole and / or 1,2,4-triazole as a rust preventive agent. It has at least an adhesive layer made of an agent layer forming material. That is, the pressure-sensitive adhesive sheet of the present invention may have a structure in which a pressure-sensitive adhesive layer is formed on a substrate, for example, a substrate / pressure-sensitive adhesive layer / release film, or a release film / pressure-sensitive adhesive layer / The structure may be a double-sided pressure-sensitive adhesive sheet that is a substrate-less type like a release film. Even if the pressure-sensitive adhesive sheet of the present invention is applied so that the pressure-sensitive adhesive layer surface is in contact with the metal surface of the metal member, discoloration or alteration of the pressure-sensitive adhesive caused by the metal member hardly occurs. Alteration is unlikely to occur. Hereinafter, an adhesive layer, a base material, a peeling film, and an adhesive sheet are demonstrated in order.

[Adhesive layer]
In the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive layer is made of a pressure-sensitive adhesive layer forming material containing an acrylic polymer, a crosslinking agent, and carboxybenzotriazole and / or 1,2,4-triazole as a rust preventive agent. It is characterized by becoming.

  In the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive layer forming material contains, as a main ingredient, an acrylic polymer that is excellent in transparency, heat resistance, heat and humidity resistance, durability, coating suitability, and the like and is low in cost. The acrylic polymer is not particularly limited, and examples thereof include an acrylic ester copolymer obtained by copolymerizing an acrylic ester and another monomer. Examples of the acrylate ester include ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, hydroxylethyl acrylate, propylene glycol acrylate, acrylamide, and glycidyl acrylate. It is done. These can be used alone or in combination of two or more. In the present invention, among the above acrylate esters, in particular, n-butyl acrylate and 2-ethylhexyl acrylate are excellent in transparency, heat resistance, moist heat resistance, durability, suitability for coating, etc. This is preferable in terms of cost.

  Other monomers include, for example, methyl acrylate, methyl methacrylate, styrene, acrylonitrile, vinyl acetate, acrylic acid, methacrylic acid, itaconic acid, hydroxylethyl acrylate, hydroxylethyl methacrylate, propylene glycol acrylate, acrylamide Methacrylamide, glycidyl acrylate, glycidyl methacrylate, dimethylaminoethyl methacrylate, tert-butylaminoethyl methacrylate, and n-ethylhexyl methacrylate. These can be used alone or in combination of two or more. In the present invention, methacrylic acid-n-ethylhexyl is preferable among the other monomers.

  When the acrylic polymer is an acrylic acid ester copolymer, the weight average molecular weight (Mw) of the acrylic acid ester copolymer is not particularly limited as long as it exhibits a desired adhesive force. To 300,000 to 1,500,000, and more preferably 300,000 to 1,300,000. The weight average molecular weight is a value in terms of polystyrene when measured by gel permeation chromatography (GPC).

  Examples of commercially available products include SK Dyne 2094 (manufactured by Soken Chemical Co., Ltd.), SK Dyne 1811L (manufactured by Soken Chemical Co., Ltd.), SK Dyne 1442 (manufactured by Soken Chemical Co., Ltd.), and SK Dyne 2147 (Soken Chemical Co., Ltd.). SK Dyne 1435 (manufactured by Soken Chemical Co., Ltd.), SK Dyne 1415 (manufactured by Soken Chemical Co., Ltd.), Olivevine EG-655 (manufactured by Toyo Ink Manufacturing Co., Ltd.) and the like can be suitably used.

  In the pressure-sensitive adhesive sheet of the present invention, the acrylic polymer is obtained by copolymerization of an acrylic ester as a main component, the acrylic ester and a copolymerizable hydroxyl group-containing monomer, and substantially has a carboxyl group. It is preferable not to contain. Here, the main component means that the copolymerization ratio is 51% by mass or more, and preferably 65% by mass or more.

  The copolymerizable hydroxyl group-containing monomer is not particularly limited as long as it has a copolymerizable polymerizable group and a hydroxyl group in its structure. For example, 2-hydroxyethyl acrylate, 2-hydroxyacrylate Examples thereof include hydroxypropyl, 2-hydroxybutyl acrylate, 3-chloro-2-hydroxypropyl acrylate, polyethylene glycol acrylate, and the like.

  The copolymerization ratio (mass ratio) between the acrylate ester and the copolymerizable hydroxyl group-containing monomer is not particularly limited as long as the acrylate ester is a main component, and is appropriately set so as to exhibit a desired adhesive strength. However, it is preferably 99/1 to 70/30 from the viewpoint of durability, adhesiveness, optical properties, and the like. The copolymerization ratio can be measured with a nuclear magnetic resonance apparatus (NMR).

  Moreover, it is preferable that the said acrylic polymer does not contain a carboxyl group substantially. This is because when the pressure-sensitive adhesive layer forming material contains an acid component, the acid component reacts with the metal of the electromagnetic wave shield, and the metal is easily altered. Here, “not containing substantially” means that the content of carboxyl groups in the acrylic polymer is less than 25 ppm. By not containing 25 ppm or more of carboxyl groups in the acrylic polymer, a pressure-sensitive adhesive sheet having more excellent optical properties (light transmission, chromaticity, brightness, etc.) can be formed. In addition, as a method of confirming content of the carboxyl group in an acrylic polymer, the measuring method by a nuclear magnetic resonance apparatus (NMR) is mentioned. Specifically, a carboxyl group and a silylating agent are reacted, and a peak derived from the silylated product is measured by 1H-NMR (600 MHz) (lower limit of quantification: 25 ppm).

  Commercially available pressure-sensitive adhesive which is an acrylic polymer which is mainly composed of an acrylic ester and is obtained by copolymerization of the acrylic ester with a copolymerizable hydroxyl group-containing monomer and which does not substantially contain a carboxyl group. For example, SK Dyne 1811L (manufactured by Soken Chemical Co., Ltd.), SK Dyne 2147 (manufactured by Soken Chemical Co., Ltd.), SK Dyne 1435 (manufactured by Soken Chemical Co., Ltd.), SK Dyne 1415 (manufactured by Soken Chemical Co., Ltd.), Orivine EG-655 (Toyo Ink Manufacturing Co., Ltd.) etc. are mentioned.

  In the pressure-sensitive adhesive sheet of the present invention, the crosslinking agent is not particularly limited, and examples thereof include an isocyanate crosslinking agent and an epoxy crosslinking agent. As an isocyanate type crosslinking agent, for example, a polyisocyanate compound, a trimer of a polyisocyanate compound, a urethane prepolymer having a terminal isocyanate group obtained by reacting a polyisocyanate compound and a polyol compound, 3 of the urethane prepolymer Examples include a polymer. Examples of the polyisocyanate compound include 2,4-tolylene diisocyanate, 2,5-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane-4,4′-diisocyanate, 3 -Methyldiphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, dicyclohexylmethane-2,4'-diisocyanate, lysine isocyanate and the like.

  Examples of the epoxy-based crosslinking agent include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, neopentyl glycol diester. Examples include polyfunctional epoxy compounds such as glycidyl ether, 1,6-hexanediol diglycidyl ether, hydrogenated bisphenol A diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, and polybutadiene diglycidyl ether.

  The crosslinking agent can be used alone or in combination of two or more, and may be appropriately selected according to the type of the acrylic polymer. In addition, when using an isocyanate type crosslinking agent, it is preferable to select the kind which does not yellow a pressure sensitive adhesive layer.

  In addition, as a commercial item of the said isocyanate type crosslinking agent, L45 (made by Soken Chemical Co., Ltd.), TD75 (made by Soken Chemical Co., Ltd.), BXX5627 (made by Toyo Ink Manufacturing Co., Ltd.), X-301-422SK (Siden), for example. (Made by Kagaku Co., Ltd.) etc. can be used suitably. Moreover, as a commercial item of the said epoxy-type crosslinking agent, E-5XM (made by Soken Chemical Co., Ltd.), E-5C (made by Soken Chemical Co., Ltd.) etc. can be used suitably, for example.

  The blending amount of the crosslinking agent is preferably 0.01 to 10 parts by mass and preferably 0.01 to 5 parts by mass with respect to 100 parts by mass of the adhesive solid content in the adhesive layer forming material. More preferred. If it is the said range, a suitable crosslinking density will be obtained and the adhesive layer which has moderate elasticity and adhesive strength can be formed. Moreover, since an excess crosslinking agent does not arise, there is no possibility of causing the flexibility fall resulting from the coupling | bonding of crosslinking agents.

  In the pressure-sensitive adhesive sheet of the present invention, the pressure-sensitive adhesive layer-forming material contains carboxybenzotriazole and / or 1,2,4-triazole as a rust inhibitor. In the present invention, the pressure-sensitive adhesive layer-forming material contains carboxybenzotriazole and / or 1,2,4-triazole as a rust preventive agent, so that even if affixed to a metal member for a long time, the pressure-sensitive adhesive caused by the metal member It is possible to obtain a pressure-sensitive adhesive sheet that hardly causes discoloration or alteration of the agent, and that hardly changes the quality of the metal member due to the pressure-sensitive adhesive. In particular, when an acrylic polymer having a carboxyl group is used as a main component of the pressure-sensitive adhesive layer forming material, the metal of the electromagnetic wave shield is easily altered, but carboxybenzotriazole and / or 1,2,4-triazole is used as the pressure-sensitive adhesive layer. By containing it in the forming material, the alteration can be suppressed.

  Carboxybenzotriazole and 1,2,4-triazole have low compatibility with the acrylic polymer and the crosslinking agent, and even when added directly, precipitation occurs and does not dissolve or disperse well. Therefore, when preparing a coating solution for forming an adhesive layer, carboxybenzotriazole and / or 1,2,4-triazole is preliminarily improved with respect to carboxybenzotriazole and / or 1,2,4-triazole. After dissolving and dispersing in a solvent, it is necessary to mix with the acrylic polymer and the crosslinking agent. As the good solvent, for example, toluene, ethyl acetate, methyl isobutyl ketone, tetrahydrofuran, a mixed solvent of toluene, methyl ethyl ketone, and tetrahydrofuran can be suitably used.

  As a commercially available product of carboxybenzotriazole, for example, CBT-1 (manufactured by Johoku Chemical Industry Co., Ltd.) can be suitably used. Moreover, as a commercial item of 1,2,4-triazole, for example, 1,2,4-triazole (manufactured by Johoku Chemical Industry Co., Ltd.), 1,2,4-triazole (manufactured by Tokyo Chemical Industry Co., Ltd.), etc. It can be used suitably.

  The blending amount of carboxybenzotriazole or 1,2,4-triazole is preferably 0.01 to 10% by mass with respect to the solid content of the pressure-sensitive adhesive in the pressure-sensitive adhesive layer forming material. More preferably, it is mass%. Moreover, when it contains carboxybenzotriazole and 1,2,4-triazole, the total compounding quantity is 0.01-10 mass% with respect to adhesive solid content in an adhesive layer forming material. It is preferable that it is 0.1-5 mass%. If it is the said range, even if the supply of the metal ion from a metal surface to an adhesive layer surface increases and the high temperature and high temperature / humidity conditions, an optical characteristic does not deteriorate easily.

  In addition, a silane coupling agent, a tackifier, a metal chelating agent, a surfactant, an antioxidant, an ultraviolet absorber, a pigment, a dye, a colorant, and an anti-electricity resistance are added as necessary without departing from the object of the present invention. Various additives such as an agent, an antiseptic, an antifoaming agent, and a wettability adjusting agent can be blended.

  In the pressure-sensitive adhesive sheet of the present invention, the silane coupling agent that can be blended in the pressure-sensitive adhesive layer forming material is not particularly limited, but is an organosilicon compound having at least one alkoxysilyl group in the molecule. Those having good compatibility with the pressure-sensitive adhesive are preferred. Examples include tetraethoxysilane, trimethoxysilane, dimethylethoxysilane, methyltrimethoxysilane, aminosilane, chlorosilane, dichlorosilane, etc., and can be selected as appropriate in consideration of the properties of the adherend surface, the type of adhesive, etc. it can. In addition, you may use these individually or in combination of 2 or more types. The blending amount of the silane coupling agent is preferably 0.01 to 1.5 parts by mass with respect to 100 parts by mass of the adhesive solid content in the adhesive layer forming material, and preferably 0.1 to 1.2. More preferably, it is part by mass. If it is the said range, favorable adhesiveness, adhesiveness, heat resistance, moist heat resistance, durability, and workability | operativity can be provided to an adhesive layer.

  The thickness of an adhesive layer is not specifically limited, According to a use, it can select suitably. Usually, it is 5-100 micrometers, Preferably it is 10-50 micrometers. If it is the said range, adhesive physical property will be stabilized. If the thickness is less than 5 μm, sufficient adhesive strength may not be obtained. If the thickness exceeds 100 μm, optical characteristics such as light transmittance may be adversely affected.

[Base material]
In the pressure-sensitive adhesive sheet of the present invention, a base material is not essential, but when it is provided as a configuration, it needs to be transparent. Here, the transparent does not necessarily need to be colorless and transparent, and may be colored and transparent, but the light transmittance in the visible region (380 to 780 nm) must be 80% or more. The higher the light transmittance of the substrate, the better, and the light transmittance in the visible region is preferably 85% or more. The light transmittance can be measured (based on JIS-Z8701) using a commercially available spectrophotometer, for example, UV-3100PC manufactured by Shimadzu Corporation.

  A base material will not be specifically limited if it has the above light transmittances, required intensity | strength, and a softness | flexibility, According to a use, it can select suitably. Generally, a synthetic resin film is used. Synthetic resin film materials include polyester resins, polypropylene resins, polyvinyl chloride resins, fluorine resins, polystyrene resins, poly (meth) acrylic resins, cellulose resins, polycarbonate resins, polyamide resins, Known resins such as polyolefin resins, polyester resins, polyvinyl alcohol resins, polyimide resins, phenol resins, polyurethane resins and the like can be mentioned. These can be used alone or in combination of two or more. Moreover, a single layer may be sufficient and the laminated body of two or more layers may be sufficient. From the viewpoint of mechanical strength, a uniaxially stretched or biaxially stretched film is preferred. In the present invention, among the synthetic resins, it is particularly preferable to use a polyester-based resin from the viewpoints of transparency, heat resistance, dimensional stability, rigidity, flexibility, suitability for stacking, price, and the like.

  Examples of the polyester-based resin include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, polyarylate, polytetramethylene terephthalate, etc. Among these, the viewpoint that it is easy to handle and is inexpensive. Therefore, polyethylene terephthalate is particularly preferable.

  The thickness of a base material is not specifically limited, According to a use, it can select suitably. Usually, it is about 12 to 188 μm, preferably 25 to 188 μm. If it is the said range, mechanical strength is enough, it is hard to produce a curvature, a slack, a fracture | rupture, etc., and workability | operativity is favorable. It is also possible to supply and process in a continuous belt shape. If the thickness exceeds the above-mentioned thickness, excessive performance may increase the cost.

  The formation method of a base material is not specifically limited, For example, conventionally well-known film forming methods, such as a solution casting method, a melt extrusion method, and a calender method, can be used. Moreover, you may use the commercially available base material previously formed into a film form by the said method.

  The base material may be subjected to known easy adhesion treatment such as corona discharge treatment, plasma treatment, ozone treatment, flame treatment, primer treatment, pre-heat treatment, dust removal treatment, vapor deposition treatment, and alkali treatment.

[Peeling film]
In the pressure-sensitive adhesive sheet of the present invention, a release film may be provided on one or both surfaces of the pressure-sensitive adhesive layer. In the pressure-sensitive adhesive sheet of the present invention, the release film is made of a release member having releasability, has a function of protecting the surface of the pressure-sensitive adhesive layer, and is peeled and removed during use. The release member is not particularly limited as long as it has the necessary strength and flexibility. For example, a film made of a resin such as polyethylene terephthalate, polypropylene, or polyethylene, or a foamed film thereof, silicone-based, fluorine-based, long Examples thereof include those subjected to release treatment with a release agent such as a chain alkyl group-containing carbamate. Although the thickness of a peeling film is not specifically limited, Preferably it is 12-188 micrometers.

[Adhesive sheet]
The pressure-sensitive adhesive sheet of the present invention is used for attaching a metal to be attached to a metal surface of a metal member. The metal to which the pressure-sensitive adhesive sheet of the present invention is attached is not particularly limited, and includes, for example, a single metal such as copper, iron, nickel, cobalt, aluminum, titanium, silver, gold, indium, tin, or two or more of these. An alloy etc. are mentioned. These may be used alone or in combination of two or more. Specific examples of objects to be applied include conductive meshes formed from metal foil, conductive meshes formed by plating methods, and metal for electromagnetic shielding such as conductive patterns in which conductive paste is printed in mesh by screen printing or the like. Examples thereof include a surface, a transparent conductive film (ITO) film, ITO glass, and a window material having a metal surface at least partially.

  The pressure-sensitive adhesive sheet of the present invention has an average light transmittance change (ΔT) at each wavelength before and after a heat resistance test at a temperature of 80 ° C. and a test time of 2000 hours when the pressure-sensitive adhesive layer surface and the metal surface are bonded together. The average value of the change in light transmittance (ΔT) at each wavelength before and after the heat and humidity resistance test with a value of 3% or less in the wavelength range of 380 to 500 nm and a temperature of 60 ° C., a humidity of 90%, and a test time of 2000 hours However, it is preferable that it is 2.5% or less in a wavelength range 380-500 nm. More preferably, the average value of the light transmittance change (ΔT) at each wavelength before and after the heat resistance test at a temperature of 80 ° C. and a test time of 2000 hours is 2.5% or less in the wavelength range of 380 to 500 nm. And the average value of the light transmittance change (ΔT) at each wavelength before and after the wet heat resistance test at a temperature of 60 ° C., a humidity of 90%, and a test time of 2000 hours is 2.5% or less in the wavelength range of 380 to 500 nm. is there.

  The pressure-sensitive adhesive sheet of the present invention has a light transmittance change (ΔT) at each wavelength before and after a heat resistance test at a temperature of 80 ° C. and a test time of 2000 hours when the pressure-sensitive adhesive layer surface and the metal surface are bonded. Of the light transmittance change (ΔT) at each wavelength before and after the heat and humidity resistance test at a temperature of 60 ° C., a humidity of 90%, and a test time of 2000 hours. The average value is preferably 3% or less in the wavelength region of 600 to 780 nm. More preferably, the average value of the light transmittance change (ΔT) at each wavelength before and after the heat resistance test at a temperature of 80 ° C. and a test time of 2000 hours is 2.8% or less in the wavelength region of 600 to 780 nm. And the average value of the light transmittance change (ΔT) at each wavelength before and after the heat and humidity resistance test at a temperature of 60 ° C., a humidity of 90%, and a test time of 2000 hours is 2.8% or less in the wavelength region of 600 to 780 nm. is there. If the average value of the light transmittance change (ΔT) is the above, it can be suitably used as an optical sheet.

  The light transmittance (T) in the present invention can be measured (based on JIS-Z8701) using a commercially available spectrophotometer, for example, UV-3100PC manufactured by Shimadzu Corporation.

The light transmittance change (ΔT) is calculated by the following equation.
Light transmittance change (ΔT) = | T _{int (W)} −T _{end (W)} |

Here, T _{int (W)} is the light transmittance at the wavelength W before the heat resistance test or before the heat resistance test, and T _{end (W)} is the light transmission at the wavelength W after the heat resistance test or after the heat resistance test. Represents a rate.

  The electromagnetic wave shield is attached to the front surface of the PDP through an adhesive layer. When the metal surface of the electromagnetic wave shield is in contact with the pressure-sensitive adhesive layer surface, the pressure-sensitive adhesive layer may be discolored or deteriorated. This is considered to be a phenomenon caused by the reaction between metal ions and the organic material constituting the pressure-sensitive adhesive layer to form a complex. Under high temperature and high temperature and high humidity conditions, the supply of metal ions from the metal surface to the pressure-sensitive adhesive layer surface increases, so that the pressure-sensitive adhesive layer is likely to be discolored or altered. Such discoloration or alteration of the pressure-sensitive adhesive layer causes a decrease in light transmittance, which is not preferable. In particular, when the pressure-sensitive adhesive layer turns yellow, the light transmittance in the visible region (380 to 500 nm) on the short wavelength side decreases. If it does so, the yellowness of the image projected on PDP will become strong, and as a result, the color tone balance of an image will be impaired. However, the pressure-sensitive adhesive sheet of the present invention is excellent in durability, and even if it is applied to a metal member for a long period of time under high temperature or high temperature and high humidity conditions, the pressure-sensitive adhesive layer is unlikely to discolor or change in quality. Not likely to occur. In particular, according to the pressure-sensitive adhesive sheet of the present invention, yellowing of the pressure-sensitive adhesive layer is unlikely to occur, so that the light transmittance in the visible region (380 to 500 nm) on the short wavelength side is unlikely to decrease. Moreover, according to the adhesive sheet of this invention, the fall of the light transmittance considered to originate in metal oxidation, especially the fall of the light transmittance in the visible region (600-780 nm) of a long wavelength side does not arise.

  The pressure-sensitive adhesive sheet of the present invention has a chromaticity change (Δy) of less than 0.002 before and after a heat resistance test at a temperature of 80 ° C. and a test time of 2000 hours when the pressure-sensitive adhesive layer and the metal surface are bonded together. And the change in chromaticity (Δy) before and after the heat and humidity resistance test at a temperature of 60 ° C., a humidity of 90%, and a test time of 2000 hours is preferably less than 0.002. More preferably, the change in chromaticity (Δy) before and after the heat resistance test at a temperature of 80 ° C. and a test time of 2000 hours is less than 0.0015, and the temperature is 60 ° C., the humidity is 90%, and the test time is 2000 hours. The change in chromaticity (Δy) before and after the wet heat resistance test is less than 0.0015.

  The chromaticity (y) in the present invention can be measured (based on JIS-Z8722) using a commercially available spectral colorimeter, for example, SD 5000 manufactured by Nippon Denshoku Industries Co., Ltd.

The chromaticity change (Δy) is calculated by the following equation.
Chromaticity change (Δy) = | y _int −y _end |

Here, y _int represents the chromaticity of the transmitted light before the heat resistance test or the wet heat resistance test, and y _end represents the chromaticity of the transmitted light after the heat resistance test or after the heat resistance test.

  As described above, under high temperature and high temperature and high humidity conditions, the pressure-sensitive adhesive layer is likely to be discolored as the amount of metal ions supplied from the metal surface to the pressure-sensitive adhesive layer surface increases. However, the pressure-sensitive adhesive sheet of the present invention is excellent in durability, and the chromaticity hardly changes even if it is applied to a metal member for a long time under high temperature or high temperature and high humidity conditions.

  Furthermore, the pressure-sensitive adhesive sheet of the present invention has a lightness change (ΔY) of less than 2 before and after a heat resistance test at a temperature of 80 ° C. and a test time of 2000 hours when the pressure-sensitive adhesive layer and the metal surface are bonded together. Moreover, it is preferable that the change in brightness (ΔY) before and after the heat and humidity resistance test at a temperature of 60 ° C., a humidity of 90%, and a test time of 2000 hours is less than 2. More preferably, the change in brightness (ΔY) before and after the heat resistance test at a temperature of 80 ° C. and a test time of 2000 hours is less than 1.8, and the humidity resistance at a temperature of 60 ° C., a humidity of 90%, and a test time of 2000 hours. The change in brightness (ΔY) before and after the thermal test is less than 1.8.

  The brightness (Y) in the present invention can be measured (based on JIS-Z8722) using a commercially available spectral colorimeter, for example, SD 5000 manufactured by Nippon Denshoku Industries Co., Ltd.

The brightness change (ΔY) is calculated by the following equation.
Lightness change (ΔY) = | Y _int −Y _end |

Here, Y _int represents the brightness before the heat resistance test or before the wet heat resistance test, and Y _end represents the lightness after the heat resistance test or after the heat resistance test.

  Discoloration or alteration of the pressure-sensitive adhesive layer causes not only a decrease in light transmittance but also a decrease in brightness. However, as described above, the pressure-sensitive adhesive sheet of the present invention is excellent in durability, and even when applied to a metal member for a long time under high temperature or high temperature and high humidity conditions, the pressure-sensitive adhesive layer is unlikely to discolor or change in quality. Is unlikely to occur.

[Method for producing adhesive sheet]
The method for producing the pressure-sensitive adhesive sheet of the present invention is not particularly limited except for the preparation of the pressure-sensitive adhesive layer-forming coating solution, and a conventionally known method can be used. Here, the case of the adhesive sheet of the structure by which the adhesive layer is formed on the base material is demonstrated. In general, in the preparation of a coating solution for forming a pressure-sensitive adhesive layer, all the materials of the pressure-sensitive adhesive are mixed at once, diluted with a solvent and dispersed as necessary. However, as described above, carboxybenzotriazole and 1,2,4-triazole have low compatibility with the acrylic polymer and the cross-linking agent, and even when added directly, precipitation, aggregation, etc. occur, which is good. Does not dissolve or disperse. Therefore, first, carboxybenzotriazole and / or 1,2,4-triazole is converted into a good solvent for the carboxybenzotriazole and / or 1,2,4-triazole, for example, a mixed solvent of toluene and methyl ethyl ketone (mass ratio 1 1) is sufficiently dissolved and dispersed to prepare a solution of carboxybenzotriazole and / or 1,2,4-triazole. Next, the acrylic polymer is blended with the crosslinking agent, diluted with a solvent such as toluene and sufficiently dispersed, and then the carboxybenzotriazole and / or 1,2,4-triazole solution is added, By further dispersing, a coating liquid is obtained. Then, the entire surface of the coating liquid is coated on the substrate with an applicator or the like to form an adhesive layer. Thereafter, the pressure-sensitive adhesive sheet of the present invention can be formed by drying and laminating the release film.

  Although the thickness of the adhesive sheet of this invention is not specifically limited, It is preferable that it is 17-350 micrometers, and it is more preferable that it is 35-238 micrometers. If it is the said range, since it has moderate softness | flexibility, handling becomes easy.

  The pressure-sensitive adhesive sheet of the present invention can be suitably used as an optical film for a plasma display panel by bonding to a metal surface of an electromagnetic wave shield, that is, a conductive mesh or a conductive pattern surface. The pressure-sensitive adhesive sheet of the present invention has little change in light transmittance, chromaticity, and lightness in the visible region even when used for a long time under high temperature or high temperature and high humidity conditions, and maintains stable optical properties. It can be used suitably. Further, according to the pressure-sensitive adhesive sheet of the present invention, it is difficult to alter the conductive mesh or the metal of the conductive pattern, so that the electromagnetic waves radiated from the display can be shielded stably. Therefore, in the plasma display panel in which the optical film is disposed in front of the image display glass plate, the color tone emitted from the display and the electromagnetic wave shielding effect are not changed. In addition, although it does not specifically limit as a method of affixing the adhesive sheet of this invention on the image display glass plate front surface of a plasma display panel, Usually, a crimping | compression-bonding system is used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention does not receive a restriction | limiting at all by these description.

<Production Example 1>
As the metal foil, a continuous strip-shaped electrolytic copper foil having a thickness of 10 μm in which a blackening layer made of alloy particles of copper, cobalt, chromium and nickel was formed by electrolytic plating was used. After both surfaces of this electrolytic copper foil were galvanized, a known chromate treatment was performed by a dipping method to form rust prevention layers on both the front and back surfaces. Next, 12 parts by mass of a main agent (polyester polyurethane polyol having an average molecular weight of 30,000) and 1 part by mass of a curing agent (xylylene diisocyanate prepolymer) are formed on the primer layer of the base material on the blackened layer surface side of the copper foil. After dry laminating with a transparent two-component curable urethane resin-based adhesive consisting of the above, it is cured at 50 ° C. for 3 days, and has a 7 μm thick transparent adhesive layer between the copper foil and the transparent resin substrate A continuous belt-shaped electromagnetic shielding sheet was formed. As the base material, a continuous belt-shaped uncolored transparent biaxially stretched polyethylene terephthalate film having a thickness of 100 μm and having a polyester resin primer layer formed on one surface was used.

  Then, the blackened layer of the copper foil of the above-described continuous band-shaped electromagnetic wave shielding sheet is etched by a photolithography method, and a mesh region composed of an opening (opening width 300 μm) and a line portion (line width 15 μm), and a mesh-shaped region An electromagnetic wave shield sheet (A) was obtained in which a conductive mesh layer (aperture ratio 95%) having a frame-shaped mesh-free grounding region was formed on the outer edge surrounding four circumferences. Specifically, after applying a photosensitive etching resist to the entire surface of the copper foil, the desired mesh pattern is closely exposed, developed, hardened, and baked, and the resist layer remains on the area corresponding to the line portion of the mesh. Then, after processing the resist layer into a pattern in which there is no resist layer on the region corresponding to the opening, the copper foil provided with the blackening layer and the rust prevention layer is etched away with an aqueous ferric chloride solution. A mesh-shaped opening was formed, and then a conductive mesh layer was formed by sequentially performing water washing, resist peeling, washing, and drying.

<Production Example 2>
A non-sol type UV curable resin was coated on one surface of a base material made of an uncolored transparent biaxially stretched polyethylene terephthalate film having a thickness of 100 μm. Next, an ink (conductive paste) in which 92 parts by mass of silver particles having an average particle diameter of about 1 μm and 8 parts by mass of a polyester resin are dispersed in ethylene glycol monobutyl ether acetate is prepared. After screen printing on the resin coating surface, it was dried with hot air at 150 ° C. to volatilize the solvent, and a sheet having a mesh-like conductive pattern layer (opening ratio: 87%) having a line width of 13 μm, a pitch of 250 μm, and a thickness of 10 μm was formed. . This sheet was pressed by a roll press at a linear pressure of 600 kg / cm at room temperature (23 ° C.) to obtain a sheet having a thickness of 8.6 μm.

  The obtained sheet was dipped in a copper sulfate plating solution, and electrolytic copper plating was performed by using a mesh-like conductive pattern layer formed on the surface of the sheet as a cathode and a copper plate as an anode, with a current of 2 A / dm 2 flowing. And the electromagnetic wave shield sheet (B) in which the copper plating film | membrane with a thickness of 2 micrometers was selectively formed on the conductive pattern layer was obtained.

< Reference Example 1>
Acrylic adhesive (trade name: SK Dyne 1811L, main monomer: butyl acrylate, acrylic ester (mainly butyl acrylate) and an acrylic polymer obtained by copolymerization of a hydroxyl group-containing monomer, mass average molecular weight (Mw ): About 650,000, dispersity (Mw / Mn): 6.3, carboxyl group content in acrylic polymer: less than 25 ppm (measured by NMR), solid content: 23%, manufactured by Soken Chemical Co., Ltd.) 100 0.2 parts by mass of crosslinking agent (trade name: TD75, isocyanate-based crosslinking agent, solid content: 75%, manufactured by Soken Chemical Co., Ltd.) and 0.09 parts by mass of silane coupling agent (product) Name: A50, solid content: 50%, manufactured by Soken Chemical Co., Ltd.), diluted with 10 parts by mass of toluene and sufficiently dispersed. To this, 0.5% by mass of a rust inhibitor (carboxybenzotriazole, trade name: CBT-1, solid content: 100%, manufactured by Johoku Chemical Industry Co., Ltd.) with respect to the solid content of the acrylic pressure-sensitive adhesive, 0.5% of the antioxidant (2 ′, 3-bis [[3- [3,5-di-tert-butyl-4-hydroxyphenyl] propionyl]] propiyl based on the solid content of the acrylic adhesive. Onohydrazide, trade name: IRGANOX MD1024, manufactured by BASF) and a solution obtained by dissolving and dispersing in 50 ml of a mixed solvent of toluene and methyl ethyl ketone (trade name: KT11, mass ratio 1: 1, manufactured by DIC Graphics Co., Ltd.) It was added and further dispersed to prepare a coating solution for forming an adhesive layer.

And the film thickness after drying is 25 μm on the easy adhesion surface side of the substrate (PET film, trade name: Cosmo Shine A4100, film thickness: 100 μm, total light transmittance: 92%, manufactured by Toyobo Co., Ltd.) The pressure-sensitive adhesive layer-forming coating solution was coated on the entire surface with an applicator to form a pressure-sensitive adhesive layer. Then, it was made to dry and the peeling film (PET separator, brand name: Therapy MFA, film thickness: 38 micrometers, the Toray Film processing company make) was laminated, and the adhesive sheet of the reference example 1 was obtained.

< Reference Example 2>
Acrylic adhesive (trade name: SK Dyne 2094, main monomer: butyl acrylate, acrylic ester (mainly butyl acrylate) and an acrylic polymer obtained by copolymerization with a carboxyl group-containing monomer, mass average molecular weight ( Mw): about 850,000, dispersity (Mw / Mn): 5.8, solid content: 25%, 100 parts by mass of Soken Chemical Co., Ltd.) 0.27 parts by mass of a crosslinking agent (trade name: E-5XM, epoxy crosslinking agent, solid content: 5%, manufactured by Soken Chemical Co., Ltd.), diluted with 10 parts by mass of toluene and sufficiently dispersed. To this, 0.5% by mass of a rust preventive (carboxybenzotriazole, trade name: CBT-1) based on the solid content of the acrylic pressure-sensitive adhesive, and 0. Add 5% antioxidant (trade name: IRGANOX MD1024) and 50ml of a mixed solvent of toluene and methyl ethyl ketone (trade name: KT11). A pressure-sensitive adhesive sheet of Reference Example 2 was obtained in the same manner as in Reference Example 1 except that the coating liquid was prepared.

<Example 1 >
0.2 parts by mass of a crosslinking agent (trade name: TD75, isocyanate-based crosslinking agent) and 0.09 parts by mass of a silane coupling agent (100 parts by mass of an acrylic pressure-sensitive adhesive (trade name: SK Dyne 1811L)) Product name: A50) was mixed, diluted with 10 parts by mass of toluene and sufficiently dispersed. In addition, 0.5% by mass of a rust inhibitor (1,2,4-triazole, trade name: 1,2,4-triazole, solid content: 100%, Johoku, based on the solid content of the acrylic pressure-sensitive adhesive) Chemical Industry Co., Ltd.), 0.5% antioxidant (trade name: IRGANOX MD1024) based on the solid content of the acrylic pressure-sensitive adhesive, and 50 ml of a mixed solvent of toluene and methyl ethyl ketone (trade name: KT11) A pressure-sensitive adhesive sheet of Example 1 was obtained in the same manner as in Reference Example 1 except that a solution dissolved and dispersed in was added and further dispersed to prepare a coating solution for forming a pressure-sensitive adhesive layer.

<Comparative Example 1>
0.2 parts by mass of a crosslinking agent (trade name: TD75, isocyanate-based crosslinking agent) and 0.09 parts by mass of a silane coupling agent (100 parts by mass of an acrylic pressure-sensitive adhesive (trade name: SK Dyne 1811L)) Product name: A50) was mixed, diluted with 10 parts by mass of toluene and sufficiently dispersed. To this, 0.5% by mass of a rust preventive agent (2- (2-heptadec-8-enyl-2-imidazolin-1-yl) ethanol based on the solid content of the acrylic pressure-sensitive adhesive, trade name: AMINE O , Solid content: 100%, manufactured by BASF) and 0.5% antioxidant (trade name: IRGANOX MD1024) with respect to the solid content of the acrylic pressure-sensitive adhesive, and further dispersed, A pressure-sensitive adhesive sheet of Comparative Example 1 was obtained in the same manner as in Reference Example 1, except that a coating liquid for forming a pressure-sensitive adhesive layer was prepared.

<Comparative example 2>
0.27 parts by mass of a crosslinking agent (trade name: E-5XM, epoxy-based crosslinking agent) is blended with 100 parts by mass of an acrylic pressure-sensitive adhesive (trade name: SK Dyne 2094), and 10 parts by mass of toluene. Diluted and fully dispersed. In addition, 0.5% by mass of a rust preventive (trade name: AMINE O) based on the solid content of the acrylic pressure-sensitive adhesive and 0.5% of the anti-oxidant based on the solid content of the acrylic pressure-sensitive adhesive. The pressure-sensitive adhesive sheet of Comparative Example 2 was prepared in the same manner as in Reference Example 1 except that an agent (trade name: IRGANOX MD1024) was added and further dispersed to prepare a coating solution for forming a pressure-sensitive adhesive layer. Obtained.

<Comparative Example 3>
0.27 parts by mass of a crosslinking agent (trade name: E-5XM, epoxy-based crosslinking agent) is blended with 100 parts by mass of an acrylic pressure-sensitive adhesive (trade name: SK Dyne 2094), and 10 parts by mass of toluene. Diluted and fully dispersed. In addition, 0.5% by mass of a rust inhibitor (2-mercaptobenzothiazole, trade name: Sunbit M, solid content: 100%, manufactured by Sanshin Chemical Industry Co., Ltd.) with respect to the solid content of the acrylic adhesive. ) And 0.5% of an antioxidant (trade name: IRGANOX MD1024) with respect to the solid content of the acrylic pressure-sensitive adhesive are dissolved and dispersed in 50 ml of a mixed solvent of toluene and methyl ethyl ketone (trade name: KT11). The pressure-sensitive adhesive sheet of Comparative Example 3 was obtained in the same manner as in Reference Example 1 except that the solution was added and further dispersed to prepare a pressure-sensitive adhesive layer-forming coating solution.

<Comparative example 4>
0.2 parts by mass of a crosslinking agent (trade name: TD75, isocyanate-based crosslinking agent) and 0.09 parts by mass of a silane coupling agent (100 parts by mass of an acrylic pressure-sensitive adhesive (trade name: SK Dyne 1811L)) Product name: A50) was mixed, diluted with 10 parts by mass of toluene and sufficiently dispersed. To this, 0.5% by mass of a rust inhibitor (3- (2-benzothiazylthio) propionic acid, trade name: Sunbit PBT, solid content: 100%, based on the solid content of the acrylic pressure-sensitive adhesive, Sanshin Chemical Industry Co., Ltd.) and 0.5% antioxidant (trade name: IRGANOX MD1024) based on the solid content of the acrylic pressure-sensitive adhesive, and a mixed solvent of toluene and methyl ethyl ketone (trade name: KT11) ) A pressure-sensitive adhesive sheet of Comparative Example 4 was obtained in the same manner as in Reference Example 1 except that a solution dissolved / dispersed in 50 ml was added and further dispersed to prepare a coating solution for forming a pressure-sensitive adhesive layer. It was.

<Comparative Example 5>
0.27 parts by mass of a crosslinking agent (trade name: E-5XM, epoxy-based crosslinking agent) is blended with 100 parts by mass of an acrylic pressure-sensitive adhesive (trade name: SK Dyne 2094), and 10 parts by mass of toluene. Diluted and fully dispersed. In addition to this, 0.5% by mass of a rust preventive (trade name: Sunbit PBT) based on the solid content of the acrylic pressure-sensitive adhesive and 0.5% oxidation on the solid content of the acrylic pressure-sensitive adhesive. An inhibitor (trade name: IRGANOX MD1024) and a solution obtained by dissolving and dispersing in 50 ml of a mixed solvent of toluene and methyl ethyl ketone (trade name: KT11) are added and further dispersed to obtain a coating solution for forming an adhesive layer. A pressure-sensitive adhesive sheet of Comparative Example 5 was obtained in the same manner as in Reference Example 1 except that it was prepared.

<Comparative Example 6>
0.2 parts by mass of a crosslinking agent (trade name: TD75, isocyanate-based crosslinking agent) and 0.09 parts by mass of a silane coupling agent (100 parts by mass of an acrylic pressure-sensitive adhesive (trade name: SK Dyne 1811L)) Product name: A50) was mixed, diluted with 10 parts by mass of toluene and sufficiently dispersed. To this, 0.5% by mass of a rust inhibitor (2,3-bis (3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyl) based on the solid content of the acrylic pressure-sensitive adhesive Propionohydrazide, trade name: CDA10, solid content: 100%, manufactured by ADEKA Co., Ltd.), and 0.5% antioxidant (trade name: IRGANOX MD1024) with respect to the solid content of the acrylic pressure-sensitive adhesive, a mixed solvent of toluene and methyl ethyl ketone (trade name: KT11) was added a solution prepared by dissolving and dispersing in 50 ml, was further dispersed, except that to prepare a pressure-sensitive adhesive layer forming coating solution, the same as reference example 1 By the method, the adhesive sheet of Comparative Example 6 was obtained.

<Comparative Example 7>
0.27 parts by mass of a crosslinking agent (trade name: E-5XM, epoxy-based crosslinking agent) is blended with 100 parts by mass of an acrylic pressure-sensitive adhesive (trade name: SK Dyne 2094), and 10 parts by mass of toluene. Diluted and fully dispersed. To this, 0.5% by mass of a rust inhibitor (2,4,6-trimercapto-s-triazole, trade name: TSH, solid content: 100%, Kawaguchi Chemical Co., Ltd.) Manufactured by Kogyo Co., Ltd.) and 0.5% of antioxidant (trade name: IRGANOX MD1024) with respect to the solid content of the above acrylic pressure-sensitive adhesive in 50 ml of a mixed solvent of toluene and methyl ethyl ketone (trade name: KT11) A pressure-sensitive adhesive sheet of Comparative Example 7 was obtained in the same manner as in Reference Example 1 except that the dissolved / dispersed solution was added and further dispersed to prepare a coating solution for forming a pressure-sensitive adhesive layer.

<Comparative Example 8>
0.2 parts by mass of a crosslinking agent (trade name: TD75, isocyanate-based crosslinking agent) and 0.09 parts by mass of a silane coupling agent (100 parts by mass of an acrylic pressure-sensitive adhesive (trade name: SK Dyne 1811L)) Product name: A50) was mixed, diluted with 10 parts by mass of toluene and sufficiently dispersed. In addition to this, 0.5% by mass of a rust inhibitor (a mixture of 4-methyl-1H-benzotriazoleamine salt and 5-methyl-1H-benzotriazoleamine salt, commercial product, based on the solid content of the acrylic pressure-sensitive adhesive) Name: TA-286, solid content: 97%, manufactured by Cypro Kasei Co., Ltd.) and 0.5% antioxidant (trade name: IRGANOX MD1024) with respect to the solid content of the acrylic adhesive. and methyl ethyl ketone mixed solvent (trade name: KT11) was added a solution prepared by dissolving and dispersing in 50 ml, was further dispersed, except that to prepare a pressure-sensitive adhesive layer forming coating solution, the same method as in reference example 1 Thus, a pressure-sensitive adhesive sheet of Comparative Example 8 was obtained.

[Heat resistance test]
The pressure-sensitive adhesive sheets obtained in Reference Examples 1 and 2, Example 1 and Comparative Examples 1 to 8 were cut into 100 mm × 50 mm to obtain test pieces. The test piece was applied to the surface of the conductive mesh layer of the electromagnetic wave shield (A) formed by the method of Production Example 1 and the surface of the conductive pattern layer of the electromagnetic wave shield (B) formed by the method of Production Example 2, respectively. After laminating using a 2 kg roller, laminating using an autoclave device (processing conditions: 0.6 MPa, 80 ° C., 0.5 hours), and leaving for 2000 hours under heating conditions at a temperature of 80 ° C. .

[Moisture and heat resistance test]
The pressure-sensitive adhesive sheets obtained in Reference Examples 1 and 2, Example 1 and Comparative Examples 1 to 8 were cut into 100 mm × 50 mm to obtain test pieces. This test piece was bonded to each metal surface of the electromagnetic wave shield (A) formed by the method of Production Example 1 and the electromagnetic wave shield (B) formed by the method of Production Example 2 using a 2 kg roller. Then, pasting was performed using an autoclave apparatus (processing conditions: 0.6 MPa, 80 ° C., 0.5 hour), and the mixture was left for 2000 hours under heating and humidification conditions of a temperature of 60 ° C. and a humidity of 90%.

[Evaluation]
Spectral colorimeter (product name: SD 5000, manufactured by Nippon Denshoku Industries Co., Ltd.) is used to measure the chromaticity (y) and lightness (Y) of the pressure-sensitive adhesive sheet subjected to the heat resistance test and the moist heat resistance test before and after being left. (Light source: C light source, light entry angle: 2 °, illumination / light reception conditions: transmission, measurement area: 28 mmφ, JIS-Z8722 compliant). Then, from the measured values of chromaticity (y) and lightness (Y) before and after standing, the chromaticity change (Δy) and the lightness change (ΔY) were obtained. The evaluation criteria for chromaticity change (Δy) were as follows. ◯: Change in chromaticity (Δy) is less than 0.002, x: Change in chromaticity (Δy) is 0.002 or more. The chromaticity change (Δy) and lightness change (ΔY) before and after being left are shown in Table 1 (bonding target: electromagnetic wave shield (A)) and Table 2 (bonding target: electromagnetic wave shield (B)).

  Further, the light transmittance (T) of the pressure-sensitive adhesive sheet subjected to the heat resistance test and the wet heat resistance test before and after being left was measured with a spectrophotometer (product name: UV-3100PC, manufactured by Shimadzu Corporation). . The measurement was based on JIS-Z8701. Then, the light transmittance change (ΔT) was determined from the measured value of the light transmittance (T) before and after being left. The measurement wavelength range was 380 to 780 nm. Table 3 shows the average value of the light transmittance change (ΔT) before and after being left in the visible region (380 to 500 nm) on the short wavelength side. Table 4 shows the average value of the light transmittance change (ΔT) before and after being left in the visible region (600 to 780 nm) on the long wavelength side.

  Furthermore, the discoloration of the metal surface of each electromagnetic wave shield after standing was visually confirmed. The result is shown in Table 5 (bonding object: electromagnetic wave shield (A)) and Table 6 (bonding object: electromagnetic wave shield (B)).

Whether the pressure-sensitive adhesive sheet ( Reference Examples 1 and 2) formed of a pressure-sensitive adhesive layer-forming material containing carboxybenzotriazole as a rust preventive is an electromagnetic wave shield (A) (B ), Changes in chromaticity, lightness, and light transmittance were small under any conditions of high temperature and high temperature and high humidity (Tables 1 to 4). In addition, the pressure-sensitive adhesive sheet ( Reference Example 1) using an acrylic polymer substantially not containing a carboxyl group has chromaticity and lightness compared to the pressure-sensitive adhesive sheet ( Reference Example 2) using an acrylic polymer containing a carboxyl group. And the change in light transmittance was smaller (Tables 1 to 4). As for the pressure-sensitive adhesive sheet (Example 1 ) on which a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive layer-containing material containing 1,2,4-triazole as a rust preventive agent is applied, the object to be applied is the electromagnetic wave shield (A). Regardless of whether (B) or (B), changes in chromaticity, lightness, and light transmittance were small under either high temperature or high temperature and high humidity conditions (Tables 1 to 4).
On the other hand, the pressure-sensitive adhesive sheet (Comparative Examples 1 to 6) in which the pressure-sensitive adhesive layer made of the pressure-sensitive adhesive layer-forming material containing another rust preventive agent is formed has at least chromaticity, lightness, and light transmittance. One or more changes were large and exhibited undesirable properties for optical applications (Tables 1 to 4).
In addition, the pressure-sensitive adhesive sheet (Comparative Example 7) using 2,4,6-trimercapto-s-triazole as a rust inhibitor and 4-methyl-1H-benzotriazoleamine salt and 5-methyl-1H-benzotriazoleamine salt Since the pressure-sensitive adhesive sheet (Comparative Example 8) using the mixture became cloudy when the pressure-sensitive adhesive layer was formed, none of the items of chromaticity change, lightness change, and light transmittance change was evaluated.

  In the adhesive sheet (Comparative Examples 1 to 6) having a large change in at least one of chromaticity, brightness, and light transmittance under high temperature conditions and high temperature and high humidity conditions, discoloration was observed on the metal surface of the electromagnetic wave shield (Table). 5, 6).

  From the above results, by selecting at least an acrylic polymer, a crosslinking agent, and carboxybenzotriazole or 1,2,4-triazole as a rust preventive agent as the pressure-sensitive adhesive layer forming material, Even when affixed to a metal surface for a long time under the conditions, a pressure-sensitive adhesive sheet is obtained in which the adhesive layer is not easily discolored or deteriorated due to the metal member, and the metal member is not easily discolored due to the adhesive layer. Became clear. And it became clear by selecting the thing which does not contain a carboxyl group substantially as an acrylic polymer, and the heat resistance and heat-and-moisture resistance of an adhesive sheet improve more.

Claims (6)

An acrylic polymer, a crosslinking agent, 1 as a rust inhibitor for metal sticking adhesive sheet characterized by having a 2,4-triazole, an adhesive layer comprising the pressure-sensitive adhesive layer forming material containing at least .   2. The acrylic polymer as a main component, comprising an acrylic ester as a main component, obtained by copolymerization of the acrylic ester and a copolymerizable hydroxyl group-containing monomer, and containing substantially no carboxyl group. Adhesive sheet for metal sticking.   When the pressure-sensitive adhesive layer and the metal surface are bonded, the change in chromaticity (Δy) before and after the heat resistance test at a temperature of 80 ° C. and a test time of 2000 hours is less than 0.002, and the temperature is 60 ° C. The pressure-sensitive adhesive sheet for metal sticking according to claim 1 or 2, wherein the change in chromaticity (Δy) before and after the humidity and heat resistance test at a humidity of 90% and a test time of 2000 hours is less than 0.002.   The optical film for plasma display panels by which the adhesive layer surface of the adhesive sheet in any one of Claims 1-3 and the metal surface of an electromagnetic wave shield are bonded together.   The optical film for a plasma display panel according to claim 4, wherein the electromagnetic wave shield is formed by printing a conductive ink containing a resin and a conductive metal.   A plasma display in which the optical film according to claim 4 or 5 is disposed in front of an image display glass plate of a plasma display panel.