JP2007095971A - Electromagnetic wave shielding sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic wave shielding sheet including a lamination of adjoining copper mesh layer and an adhesive layer in which discoloration is prevented even after a long term use in a high temperature and high humidity. <P>SOLUTION: The electromagnetic wave shielding sheet 1 comprises a copper mesh layer 14, an adhesive layer 15, and an adherend layer 16 formed sequentially on one surface of a transparent substrate 11 wherein the adhesive layer 15 contains an adhesive having an acid number and an antioxidant. In the electromagnetic wave shielding sheet, the antioxidant is a benzotriazol based antioxidant. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electromagnetic wave shielding sheet that shields (shields) electromagnetic waves generated from a display such as a CRT or PDP, and more particularly to an electromagnetic wave shielding sheet excellent in color reproducibility during long-term use.

In recent years, with the advancement of functions and increasing use of electrical and electronic equipment, electromagnetic noise interference (EMI) has increased, and electromagnetic waves are also generated in displays such as cathode ray tubes (referred to as CRT) and plasma display panels (referred to as PDP). appear. The plasma display panel is a combination of a data electrode, a glass having a fluorescent layer, and a glass having a transparent electrode, and generates a large amount of electromagnetic waves, near infrared rays, and heat when operated.
Usually, an electromagnetic wave shielding sheet is provided as a front plate on the front surface of the plasma display panel in order to shield electromagnetic waves. The shielding property of electromagnetic waves generated from the front surface of the display requires a function of 30 dB or more at 30 MHz to 1 GHz. Furthermore, in order to make the display image easy to see, it is difficult to see the metal (especially copper) mesh (line part) for shielding electromagnetic waves, and the mesh pattern accuracy is good and the mesh is not disturbed. It is necessary to have visible light transmittance.

  As shown in FIG. 1, the electromagnetic wave shielding sheet usually has a copper mesh layer 14 formed on a transparent substrate 11, and further a surface of the transparent substrate 11 on which the copper mesh 14 is formed, and an adherend layer 16. For example, an optical filter such as an antireflection filter and a near-infrared filter, a glass substrate of a PDP screen, and the like can be laminated through an adhesive (adhesive) layer 15. For example, Patent Document 1 discloses a display panel front plate in which an electromagnetic wave shielding filter film and an antireflection film are disposed via an adhesive layer. Such a simple layer structure is excellent in terms of productivity and quality.

  Further, in Patent Document 2, a pattern of a blackened metal layer is formed on a transparent film via an adhesive material layer, and near-infrared absorption is performed on the metal layer pattern via another adhesive material layer. A shielding material including a layer structure provided with a layer is disclosed. Such a layer structure has transparency of the shielding material because the adhesive layer and transparent substrate are not corroded by the presence of the highly chemical-resistant adhesive layer when patterning by etching the metal foil with chemicals. There is an advantage that can be maintained.

Japanese Patent Laid-Open No. 11-12604 JP 2002-009484 A

  In the electromagnetic wave shielding sheet including the structure in which the adherend layer is laminated on the copper mesh layer for electromagnetic wave shielding as described above via an adhesive layer, the copper mesh layer and the adherend layer have sufficient adhesion. is necessary. From the present invention, it has been found that it is effective to use a pressure-sensitive adhesive having sufficient acid value in order to achieve sufficient adhesion. However, when an adhesive having an acid value with high adhesion is used, when the electromagnetic shielding sheet is used for a long time, particularly under high temperature and high humidity, the copper mesh is oxidized and the electromagnetic shielding sheet is discolored. The problem of doing. When the copper mesh is oxidized, the electromagnetic shielding sheet is tinged with blue, which adversely affects the color reproducibility of the display. This problem also occurred when a blackening layer made of a thin film such as copper cobalt alloy particles and nickel sulfide particles was formed on a copper mesh and an adhesive layer was laminated.

On the other hand, it was also found that when an adhesive having no acid value (acid value = 0) was used, such copper oxidation and discoloration did not occur. However, in this case, since the adhesion between copper and the adherend is lowered, it cannot be adopted as a measure for preventing oxidative discoloration of the copper mesh.
The present invention was made to solve the above problems, and is an electromagnetic wave shielding sheet including a structure in which an adherend layer is laminated on an electromagnetic shielding copper mesh layer via an adhesive layer, An object of the present invention is to provide an electromagnetic wave shielding sheet that does not change color even when used for a long period of time, particularly under high temperature and high humidity, while the copper mesh layer and the adherend layer have sufficient adhesion.

  As a result of intensive studies to achieve the above object, the inventor has changed the color of the electromagnetic wave shielding sheet to blue due to the action of the acid component contained in the adhesive and the moisture of the adhesive layer under high temperature and high humidity. In order to prevent this, the inventors have found that an electromagnetic wave shielding sheet containing an antioxidant in a pressure-sensitive adhesive layer can achieve the above-mentioned object, and have completed the present invention.

That is, the electromagnetic wave shielding sheet of the present invention is an electromagnetic wave shielding sheet in which at least a copper mesh layer, an adhesive layer, and an adherend layer are provided in this order on one surface of a transparent substrate, and the adhesive layer Includes an adhesive having an acid value and an antioxidant.
The pressure-sensitive adhesive used in the electromagnetic wave shielding sheet has improved adhesion performance by having an acid such as a carboxyl group that generates an acid value. However, under high temperature and high humidity, it is presumed that the surface of copper is easily oxidized due to the presence of protons and water dissociated from an acid such as a carboxyl group that is not involved in the adhesion contained in the pressure-sensitive adhesive layer. On the other hand, it is estimated that the electromagnetic wave shielding sheet of the present invention can suppress such action and prevent discoloration of the copper mesh layer by containing an antioxidant in the adhesive layer. Further, by adding an antioxidant to the pressure-sensitive adhesive layer, it is possible to omit a separate step of providing a rust-proof layer, and there is an advantage that productivity is improved.

In the electromagnetic wave shielding sheet of the present invention, the antioxidant is preferably a benzotriazole antioxidant.
In the electromagnetic wave shielding sheet of the present invention, it is preferable from the viewpoint of adhesion that the pressure-sensitive adhesive is an acrylic pressure-sensitive adhesive, and the acid value of the pressure-sensitive adhesive is 1 or more.
Further, in the electromagnetic wave shielding sheet of the present invention, the pressure-sensitive adhesive layer contains 1 part by weight or more of the benzotriazole antioxidant with respect to 100 parts by weight of the pressure-sensitive adhesive from the viewpoint of preventing discoloration of the copper surface. preferable.
Moreover, the electromagnetic wave shielding sheet of the present invention is preferably provided with a blackening treatment layer between the copper mesh layer and the pressure-sensitive adhesive layer from the viewpoint of improving visibility.

  The present invention relates to an electromagnetic wave shielding sheet including a configuration in which an adherend layer is laminated on an electromagnetic wave shielding copper mesh layer via an adhesive layer, and even when used for a long time, particularly under high temperature and high humidity. In addition, while the copper mesh layer and the adherend layer have sufficient adhesion, no discoloration due to oxidation of the copper mesh layer occurs, and an electromagnetic wave shielding sheet excellent in color reproducibility can be obtained.

The electromagnetic wave shielding sheet of the present invention is an electromagnetic wave shielding sheet in which at least a copper mesh layer, an adhesive layer, and an adherend layer are provided in this order on one surface of a transparent substrate, and the adhesive layer is an acid layer. A pressure-sensitive adhesive and an antioxidant are included.
The adhesive used for the electromagnetic wave shielding sheet has an adhesion performance that is improved by having an acid such as a carboxyl group. However, under high temperature and high humidity, it is presumed that the surface of copper is easily oxidized due to the presence of protons and water dissociated from an acid such as a carboxyl group that is not involved in the adhesion contained in the pressure-sensitive adhesive layer. And it is thought that the compound containing copper ions, such as a copper complex, will be produced by oxidation, and it will color blue. On the other hand, it is estimated that the electromagnetic wave shielding sheet of the present invention can suppress such action and prevent discoloration of the copper mesh layer by containing an antioxidant in the adhesive layer. Further, by adding an antioxidant to the pressure-sensitive adhesive layer, it is possible to omit a separate step of providing a rust-proof layer, and there is an advantage that productivity is improved.

〔Layer structure〕
FIG. 1 is a cross-sectional view illustrating a basic form of an electromagnetic wave shielding filter according to the present invention.
In FIG. 1A, a copper mesh layer 14 is formed on a transparent base material 11, and the surface of the transparent base material 11 on which the copper mesh 14 is formed and the adherend layer 16 form an adhesive layer 15. It is the structure laminated | stacked through. The adherend layer 16 is, for example, a sheet, plate, or coating film, various filters such as a reflection (including antiglare) filter, a near infrared absorption filter, a protective film, or a component of the display itself. It is a layer having an arbitrary function such as a front substrate.

In addition, another layer may be provided between each of the above layers, and the electromagnetic wave shielding sheet of the present invention is black between the copper mesh layer 14 and the adhesive layer 15 as shown in FIG. It is preferable that the light-emitting layer 17 is provided from the viewpoint of reducing the light reflectance and improving the visibility of the image on the display by providing a contrast feeling.
In these configurations, the copper mesh layer 14 may be laminated on the transparent substrate 11 via an adhesive layer (not shown).

  FIG. 1C is an illustration of a layer structure when an electromagnetic wave shielding sheet is formed by an electrolytic plating method. A conductive treatment layer 13 is formed on the transparent substrate 11, and a copper mesh layer 14 is further formed thereon. The blackening layer 17 is laminated in this order, and the surface of the transparent substrate 11 on which the blackening layer 17 is formed and the adherend 16 are laminated via the adhesive layer 15.

  FIG. 2 is a perspective view illustrating only the transparent base material layer 11, the conductive treatment layer 13, and the copper mesh layer 14 in the electromagnetic wave shielding sheet of FIG. The conductive treatment layer 13 and the copper mesh layer 14 (hereinafter, both layers and other layers having conductivity are also simply referred to as a conductor layer 12) are in a mesh shape in which the openings 103 are closely arranged, The mesh region 101 includes an opening 103 and a line portion 104 that forms a frame. A blackened layer 17 (not shown) further laminated on the surface of the copper mesh layer 14 is integrated with the conductor layer 12 to form the mesh region 101.

3 is a cross-sectional view taken along line AA and BB in FIG. 3A shows a cross section that crosses the opening, the openings 103 and the lines 104 are alternately formed, and FIG. 3B shows a cross section that cuts the line 104 vertically, and the copper mesh layer 14 and the conductive treatment layer 13 line portions 104 are continuously formed. Note that all of the cross-sectional views of the electromagnetic wave shielding filter shown in FIG. 1 correspond to the AA cross-sectional view.
In addition, the above illustration does not limit the aspect of the electromagnetic wave shielding sheet of this invention. Any device that has substantially the same structure as the technical idea described in the claims of the present invention and that exhibits the same effect can be included in the technical scope of the present invention. .
Hereinafter, the electromagnetic wave shielding sheet of the present invention will be described in order from the transparent substrate for each layer.

[Transparent substrate]
The transparent substrate is a layer for reinforcing a copper mesh layer having a low mechanical strength. Therefore, as long as it has light transmittance as well as mechanical strength, it may be selected and used depending on the application, taking into account heat resistance, insulation, etc. as appropriate. Specific examples of the transparent substrate include, for example, plates and sheets (or films; the same applies hereinafter) made of an organic material such as a resin, and plates made of an inorganic material such as glass.

Examples of transparent resins used as plates and sheets made of the above organic materials include, for example, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, terephthalic acid-isophthalic acid-ethylene glycol copolymer, terephthalic acid-cyclohexanedimethanol-ethylene glycol. Polyester resins such as copolymers, polyamide resins such as nylon 6, polyolefin resins such as polypropylene and polymethylpentene, acrylic resins such as polymethyl methacrylate, styrene resins such as polystyrene and styrene-acrylonitrile copolymers And cellulose resins such as triacetyl cellulose, imide resins, polycarbonate resins and the like.
In addition, these resins are used as a single or a plurality of types of mixed resins (including polymer alloys) as a resin material, and as a layer, they are used as a single layer or a laminate of two or more layers. In the case of a resin sheet, a uniaxially stretched or biaxially stretched sheet is more preferable in terms of mechanical strength.
Moreover, you may add additives, such as a ultraviolet absorber, a filler, a plasticizer, an antistatic agent, in these resins suitably as needed.

  Further, as the glass of the glass plate, there are quartz glass, borosilicate glass, soda lime glass, etc. More preferably, the thermal expansion coefficient is small, the dimensional stability and the workability in high-temperature heat treatment are excellent, and the glass contains an alkali. Examples include alkali-free glass that does not contain a component, and can also be used as an electrode substrate that serves as a front substrate of a display.

  The thickness of the transparent substrate is not particularly limited as long as it depends on the application. When the transparent substrate is made of a transparent resin, it is usually about 12 to 1000 μm, preferably 50 to 500 μm. On the other hand, when a transparent base material is a glass plate, about 1-5 mm is usually suitable. In any material, when the thickness is less than the above, the mechanical strength is insufficient and warping, loosening, breakage, and the like occur. When the thickness exceeds the above, the cost is increased due to excessive performance and it is difficult to reduce the thickness.

In addition, the transparent base material may also be used as a front substrate, which is a component of the display main body including the front substrate and the rear substrate, but in the form using an electromagnetic wave shielding filter as a front filter disposed in front of the front substrate. The sheet is superior to the plate in terms of thinness and lightness, and the resin sheet is superior to the glass plate in that it is not broken.
In this respect, a resin sheet is a preferable material for the transparent substrate, but among the resin sheets, in particular, polyester resin sheets such as polyethylene terephthalate and polyethylene naphthalate have transparency, heat resistance, cost, and the like. In view of this, a biaxially stretched polyethylene terephthalate sheet is more preferable. In addition, although the transparency of a transparent base material is so good that it is high, Preferably the light transmittance which becomes 80% or more by visible light transmittance | permeability is good.

[Copper mesh layer]
The copper mesh layer is a layer having electrical conductivity and is responsible for the electromagnetic wave shielding function, and is itself opaque, but the presence of an opening in the shape of a mesh makes the electromagnetic wave shielding performance and Both light transmittance is achieved.
The layer having the conductivity and responsible for the electromagnetic wave shielding function is, for example, a copper mesh layer, a conductive thin layer (hereinafter referred to as a conductive treatment layer), or a conductive layer serving as a base layer for copper plating. There are blackening layers having properties, and these are collectively referred to as a conductor layer. For example, in FIG. 1C, when the blackened layer 17 has conductivity, the conductor layer means the conductive treatment layer 13, the copper mesh layer 14, and the blackened layer 17. On the other hand, when the blackening layer 17 does not have conductivity, the conductor layer means the conductive treatment layer 13 and the copper mesh layer 14.

  The shape of the conductor layer including the copper mesh layer is not particularly limited, but the opening is typically square. Examples of the shape of the opening include a triangle such as a regular triangle, a square such as a square, a rectangle, a rhombus, and a trapezoid, a polygon such as a hexagon, a circle, and an ellipse. The mesh has a plurality of openings having these shapes, and the openings are usually line-like line portions having a uniform width, and the openings and the openings are generally the same shape and the same size on the entire surface. For example, the width of the line part 104 between the openings, that is, the line width W, is preferably 25 μm or less, and preferably 20 μm or less in terms of the aperture ratio and the invisibility of the mesh. However, it is preferable to secure at least 5 μm or more for the expression of the electromagnetic wave shielding effect and prevention of breakage. The opening width of the opening is represented by (line pitch P) − (line width W). In the present invention, the width is 150 μm or more, preferably 200 μm or more. It is preferable from the point that air bubbles hardly remain in the opening during lamination. However, in order to exhibit electromagnetic wave shielding properties in the MHz to GHz band, the maximum is 3000 μm or less.

  In addition, as a method for producing the electromagnetic wave shielding sheet of the present invention, in the case of selecting a method in which the pressure-sensitive adhesive layer is previously applied to the adherend side and then adhered to the copper mesh layer, the final method is selected. It is preferable that the thickness of the mesh region obtained in the above, that is, the height H of the line portion 104 between the openings is 3 μm or less. In such a case, the diluted solvent is also dried, and the pressure-sensitive adhesive layer is pushed into the copper mesh in a state where the fluidity is minimized. Therefore, when the thickness of the line portion exceeds 3 μm, it becomes difficult for the adhesive to sufficiently flow into and fill the copper mesh opening, and bubbles tend to remain in the opening. On the other hand, if the height of the line part is 3 μm or less, the pressure-sensitive adhesive layer easily enters the opening of the mesh region at the time of lamination and adhesion of the electromagnetic wave shielding sheet and the adherend layer, and bubbles remain in the opening. It is difficult. In this case, it is possible to avoid the disadvantage that the haze of the electromagnetic wave shielding sheet due to light scattering of the bubbles is increased, and an electromagnetic wave shielding sheet having high transparency can be obtained with high production efficiency. However, in consideration of the electromagnetic wave shielding function so that the electric resistance value of the metal is not increased and the electromagnetic wave shielding effect is not easily impaired, the thickness of the conductor layer is 1 μm when the size and shape of the mesh region is in the above range. This is necessary. Therefore, when the adhesive layer is previously formed on the adherend side and manufactured, it is more preferable that the height of the line portion of the mesh region is 1 to 3 μm.

On the other hand, as a manufacturing method, when the adhesive layer is applied to the copper mesh side in advance, the fluidity is sufficiently enhanced by solvent dilution of the adhesive during coating. Therefore, there is no problem of remaining bubbles even if the height of the line portion exceeds 3 μm. In addition, the height of the line portion is also increased when a planarization step is performed in which a mesh opening is filled with a transparent resin called a planarization resin and a planarization layer is provided before lamination with the adherend layer. Even if it exceeds 3 μm, there is no problem of residual bubbles.
In addition, the height of the line part of a mesh-like area | region includes all the thickness of the layer which forms the opening part and forms the line part 104 among the conductor layers 12 and the layer which is not further laminated | stacked. Refers to the total thickness. In addition, the bias angle of the mesh region (angle formed between the mesh line portion and the outer periphery of the electromagnetic wave shielding sheet) may be appropriately set to an angle at which moire is difficult to occur in consideration of the pixel pitch of the display and the light emission characteristics. .

[Adhesive layer]
The pressure-sensitive adhesive layer constituting the electromagnetic wave shielding sheet of the present invention includes a pressure-sensitive adhesive and an antioxidant.
(Adhesive)
The pressure-sensitive adhesive according to the present invention refers to one type of adhesive. Among the adhesives, only adhesiveness on the surface is obtained only by pressing moderately, usually lightly by hand, at the time of bonding. It can be glued. In order to develop the adhesive strength of the pressure-sensitive adhesive, usually, physical energy or action such as heating, humidification, radiation (ultraviolet ray, electron beam, etc.) irradiation is unnecessary, and chemical reaction such as polymerization reaction is also unnecessary. In addition, the pressure-sensitive adhesive can maintain the adhesive strength to the extent that it can be re-peeled after bonding.

  Examples of the pressure-sensitive adhesive used in the present invention include those having an acid value among natural rubber and synthetic resins. Examples of the pressure-sensitive adhesive include those composed of a substance having a carboxyl group in the molecule. Specifically, an acrylic pressure-sensitive adhesive is preferable from the viewpoint of high transparency. Moreover, it is preferable that the acid value of an acrylic adhesive is 1 or more from the point that the adhesiveness with the copper mesh in the electromagnetic wave shielding sheet obtained is favorable.

As the acrylic pressure-sensitive adhesive having an acid value contained in the pressure-sensitive adhesive layer according to the present invention, the pressure-sensitive adhesive layer has appropriate adhesive strength, transparency, and coating suitability from those commonly used as known pressure-sensitive adhesives. A material that does not substantially change the transmission spectrum of the electromagnetic wave shielding sheet is appropriately selected. The acrylic pressure-sensitive adhesive having an acid value is a polymer containing at least a (meth) acrylic acid alkyl ester monomer and is a (meth) acrylic acid alkyl ester monomer having an alkyl group of about 1 to 18 carbon atoms. Generally, it is a copolymer of a monomer having a carboxyl group. The adhesive ability of the pressure-sensitive adhesive contained in the pressure-sensitive adhesive layer is manifested by strongly adsorbing carboxyl groups present in the pressure-sensitive adhesive molecules on the surface of the copper mesh layer.
In the present invention, (meth) acrylic acid means acrylic acid and / or methacrylic acid.

Examples of (meth) acrylic acid alkyl ester monomers used here include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, sec-propyl (meth) acrylate, N-butyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, Examples thereof include n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, undecyl (meth) acrylate and lauryl (meth) acrylate. Of these, butyl acrylate and 2-ethylhexyl acrylate are preferable, and butyl acrylate and 2-ethylhexyl acrylate are preferably used in combination.
Moreover, the said (meth) acrylic-acid alkylester is copolymerized in the quantity of 30-99.5 weight part normally in an acrylic adhesive.

  Moreover, as a monomer which has a carboxyl group which forms an acrylic adhesive, monomers containing a carboxyl group such as (meth) acrylic acid, itaconic acid, crotonic acid, maleic acid, monobutyl maleate and β-carboxyethyl acrylate are used. Can be mentioned.

  Furthermore, in addition to the above, the acrylic pressure-sensitive adhesive used in the present invention may be copolymerized with a monomer having another functional group within a range that does not impair the characteristics of the acrylic pressure-sensitive adhesive. Examples of monomers having other functional groups include monomers containing hydroxyl groups such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate and allyl alcohol; (meth) acrylamide, N-methyl Monomers containing amide groups such as (meth) acrylamide and N-ethyl (meth) acrylamide; Monomers containing amide groups and methylol groups such as N-methylol (meth) acrylamide and dimethylol (meth) acrylamide; Monomers having functional groups such as monomers containing amino groups such as (meth) acrylate, dimethylaminoethyl (meth) acrylate and vinylpyridine; epoxy group-containing monomers such as allyl glycidyl ether and (meth) acrylic acid glycidyl ether Be mentionedIn addition to these, fluorine-substituted (meth) acrylic acid alkyl ester, (meth) acrylonitrile, and the like, vinyl group-containing aromatic compounds such as styrene and methylstyrene, vinyl acetate, and vinyl halide compounds can be used.

  Furthermore, in the acrylic pressure-sensitive adhesive used in the present invention, in addition to the monomer having other functional groups as described above, another monomer having an ethylenic double bond can be used. Examples of monomers having an ethylenic double bond include diesters of α, β-unsaturated dibasic acids such as dibutyl maleate, dioctyl maleate and dibutyl fumarate; vinyl esters such as vinyl acetate and vinyl propionate. Vinyl ether; vinyl aromatic compounds such as styrene, α-methylstyrene and vinyl toluene; (meth) acrylonitrile and the like.

  In addition to the monomer having an ethylenic double bond as described above, a compound having two or more ethylenic double bonds may be used in combination. Examples of such compounds include divinylbenzene, diallyl malate, diallyl phthalate, ethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, methylene bis (meth) acrylamide, and the like.

Furthermore, in addition to the above-described monomers, monomers having an alkoxyalkyl chain can be used. Examples of alkoxyalkyl esters of (meth) acrylic acid include 2-methoxyethyl (meth) acrylate, methoxyethyl (meth) acrylate, 2-methoxypropyl (meth) acrylate, and 3-methoxypropyl (meth) acrylate. , 2-methoxybutyl (meth) acrylate, 4-methoxybutyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 3-ethoxypropyl (meth) acrylate, 4-ethoxybutyl (meth) acrylate And so on.
As a commercial item of an acrylic adhesive, the product name: "5407" by Nippon Synthetic Chemical Co., Ltd. is used suitably, for example.

(Antioxidant)
By containing the antioxidant, the pressure-sensitive adhesive layer according to the present invention can prevent discoloration of the copper mesh in the electromagnetic wave shielding sheet while using a pressure-sensitive adhesive having good acidity.
Compounds used as antioxidants are selected from benzotriazole antioxidants, phenolic antioxidants, phosphite antioxidants, amine antioxidants, sulfur-containing organometallic salt antioxidants, etc. However, in the electromagnetic wave shielding sheet according to the present invention, the antioxidant contained in the adhesive layer is preferably a benzotriazole antioxidant from the viewpoint of copper blue discoloration prevention performance.

  Examples of the benzotriazole antioxidant include compounds characterized by containing at least the structure of the following formula (1) as a skeleton, and sodium salts, potassium salts, and amine salts thereof. Examples of the substituent that may be included in the structure of the following formula (1) include an alkyl group that may have a substituent, an aryl group that may have a substituent, and a halogen atom. It is done.

  Specifically, 1,2,3-benzotriazole (1H-benzotriazole), 1H-benzotriazole sodium salt, 4-methyl-1H-benzotriazole, 5-methyl-1H-benzotriazole, 4-methyl-1H -Benzotriazole potassium salt, 5-methyl-1H-benzotriazole potassium salt, 4-methyl-1H-benzotriazoleamine salt, 5-methyl-1H-benzotriazoleamine salt, 2- (3,5-di-t- Butyl-2-hydroxyphenyl) -5-chlorobenzotriazole, 2- (3,5-di-t-amyl-2-hydroxyphenyl) benzotriazole and the like, among which 1,2,3-benzotriazole (1H -Benzotriazole) is preferred.

In the electromagnetic wave shielding sheet of the present invention, the pressure-sensitive adhesive layer has sufficient adhesive force that the pressure-sensitive adhesive layer contains 1 part by weight or more of the benzotriazole-based antioxidant with respect to 100 parts by weight of the pressure-sensitive adhesive. And it is preferable from the point which discoloration of the surface of a copper mesh layer does not occur.
When content of antioxidant is less than the said range, even if it contains the antioxidant mentioned later in an adhesive layer, there exists a possibility that discoloration cannot fully be prevented.

In particular, the acid value of the pressure-sensitive adhesive is preferably 1 or more, and the pressure-sensitive adhesive layer preferably contains 1 part by weight or more of the benzotriazole antioxidant with respect to 100 parts by weight of the pressure-sensitive adhesive.
In addition, as a method of forming a copper mesh layer, when a method of laminating a transparent base material and a metal foil with an adhesive and then meshing the metal foil by a photolithography method (for example, JP-A-11-145678) is selected. In addition, discoloration of the surface of the copper mesh on the transparent substrate side can be prevented by adding the antioxidant to the adhesive.

Furthermore, in the pressure-sensitive adhesive layer according to the present invention, a curing agent (crosslinking agent) such as an isocyanate compound, a tackifier, a silane coupling agent, a filler, and the like can be blended as desired.
Note that the adhesive layer may contain one or more near-infrared absorbing dyes, ultraviolet absorbers, and / or neon light absorbing dyes as described below. In that case, the near infrared light transmittance in the wavelength range of 800 nm to 1100 nm is 20% or less, especially 10% or less, and the light transmittance of the neon emission spectrum in the wavelength region of 560 to 630 nm is 30% or less, especially 25% or less. It is preferable to do so. Further, it is preferable that the light transmittance of ultraviolet rays in a wavelength region of 380 nm or less is 10% or less.

By doing in this way, since the function of a plurality of functional layers can be combined with one layer and integrated with the adhesive layer, the total thickness, the number of steps, and the cost as a composite filter can be reduced. This is possible and preferable.
In this invention, it is preferable that the film thickness of such an adhesive bond layer exists in the range of 5-40 micrometers. This is because, by setting this range, it is possible to satisfactorily flatten the unevenness of the mesh in the electromagnetic wave shielding sheet, particularly when the electromagnetic wave shielding sheet and the optical filter are laminated and bonded.

  As a measure of the adhesion of the electromagnetic wave shielding sheet according to the present invention, the adhesive force of the pressure-sensitive adhesive layer containing the pressure-sensitive adhesive having the acid value and the antioxidant is evaluated as follows. First, the pressure-sensitive adhesive layer coating solution containing the pressure-sensitive adhesive and the antioxidant is coated on the mesh surface of the laminate of the transparent base material and the copper mesh layer so as to have a film thickness of 25 μm after drying, and at 120 ° C. for 2 minutes. PET (thickness 50 μm, easy-adhesive surface of trade name “A4100”, manufactured by Toyobo Co., Ltd.)) is bonded to the dried product using a roller. Next, the bonded sample is cut into a 1 inch width, the PET side is bonded and fixed to a stainless steel plate having a thickness of 1 mm, and set in a tensile tester (trade name “Tensilon”, manufactured by Toyo Seiki Co., Ltd.). Then, PET (A4100) and EMI mesh are peeled at a peeling angle of 180 ° (peeling speed: 200 mm / min, peeling distance: 100 mm), and the adhesive force (N / inch) is measured. The adhesive force is preferably in the range of 20 N / inch or more.

[Blackening layer]
In order to absorb external light incident on the electromagnetic wave shielding sheet and improve the visibility of the display image, the electromagnetic wave shielding sheet of the present invention has a blackened layer between the copper mesh layer and the adhesive layer. It is preferable from the viewpoint of improving contrast. In some blackened layers, the surface of the layer becomes rough and adhesion can be enhanced.

The blackening layer may be any layer that exhibits a dark color such as black, and may be any layer that satisfies basic physical properties such as adhesion, and a known blackening layer may be appropriately employed. Further, it does not matter whether the blackened layer has conductivity.
Therefore, as the blackening layer, an inorganic material such as a metal, an organic material such as a black colored resin, or the like can be used. For example, as the inorganic material, a metal compound such as a metal, an alloy, a metal oxide, or a metal sulfide is used. It is formed as a metal-based layer. As a method for forming the metal layer, various conventionally known blackening methods can be appropriately employed. Especially, the blackening process by a plating method is preferable at adhesiveness, uniformity, ease, etc. As a material for the plating method, for example, a metal such as copper, cobalt, nickel, zinc, molybdenum, tin, or chromium, a metal compound, or the like is used. These are superior to the case of cadmium or the like in terms of adhesion and blackness.

  Moreover, as a blackening layer, black chrome, black nickel, a nickel alloy, etc. are preferable, and as this nickel alloy, they are a nickel-zinc alloy, a nickel-tin alloy, and a nickel-tin-copper alloy. Normally, the blackened layer particles are needle-shaped, and the appearance is likely to change due to external forces, but the nickel alloy blackened layer is less likely to deform and the appearance is less likely to change during post-processing. Can also be obtained.

  A preferable plating method for blackening treatment for forming a blackening layer on the conductive treatment layer is that a conductor layer made of copper is subjected to cathodic electrolysis treatment in an electrolytic solution made of sulfuric acid, copper sulfate, cobalt sulfate or the like. There is a cathodic electrodeposition plating method in which cationic particles are attached. According to this method, the rough surface can be obtained simultaneously with the black color by the adhesion of the cationic particles. Copper particles and copper alloy particles can be adopted as the cationic particles. The copper alloy particles are preferably copper-cobalt alloy particles, and the average particle diameter is preferably 0.1 to 1 μm. A blackened layer composed of a copper-cobalt alloy particle layer is obtained by the copper-cobalt alloy particles. The cathodic electrodeposition method is also preferable in that the average particle size of the cationic particles to be adhered is adjusted to 0.1 to 1 μm. When the average particle diameter exceeds the above range, the density of the adhered particles is reduced, blackness is reduced and unevenness occurs, and particle falling off (powder falling) is likely to occur. On the other hand, even if the average particle diameter is less than the above range, the blackness is lowered. In the cathodic electrodeposition method, when the treatment is performed at a high current density, the treated surface becomes cathodic, and activated by reducing hydrogen generation, the adhesion between the copper surface and the cationic particles is remarkably improved.

When a nickel alloy is used as the material for the blackened layer, the blackened layer may be formed by a known electrolytic or electroless plating method, and the nickel alloy may be formed after nickel plating.
A preferable black density of the blackened layer is 0.6 or more. In addition, the measurement method of black density was set to the density standard ANSIT as an observation viewing angle of 10 degrees, an observation light source D50, and an illumination type using GRETAG SPM100-11 (trade name, manufactured by Kimoto Co., Ltd.) of COLOR CONTROL SYSTEM. The specimen is measured after calibration. Further, the light reflectance of the blackened layer is preferably 5% or less. The light reflectance is measured using a haze meter HM150 (trade name, manufactured by Murakami Color Co., Ltd.) in accordance with JIS-K7105. In addition, instead of measuring the reflectance, the Y value of reflection may be expressed by a color difference meter. In this case, the Y value is preferably 10 or less.

  In addition, when the blackened layer constitutes a completely dense film and covers all the surfaces that come into contact with the adhesive layer of the copper mesh, Contact between acid and copper is blocked. Therefore, in this case, it is possible to prevent copper discoloration without adding an antioxidant to the pressure-sensitive adhesive. However, the blackened layer usually only covers a part of the exposed surface of the copper mesh as shown in FIG. 1B for reasons such as manufacturing cost reduction. Also, the normally used blackening layer is a fine particle or porous body of a metal or a metal compound, the film thickness is thin, or there is a partial non-adherent region, and it is not a complete dense film. There are many. Therefore, in the normal case, even if a blackening layer is present, the discoloration of copper by an acid such as a carboxyl group of the pressure-sensitive adhesive cannot be prevented even if it has a function of delaying the generation to some extent.

[Adherent layer]
The adherend layer constituting the electromagnetic wave shielding sheet of the present invention is, for example, a sheet, plate or coating film, various filters such as a reflection (including antiglare) filter, a near infrared absorption filter, a protective film, or This is a layer having an arbitrary function such as a front substrate which is a component of the display itself.
Hereinafter, a case where the adherend is an optical filter will be described. Although it does not specifically limit as an optical filter, For example, the filter which has a near-infrared absorption function, a neon light absorption function, an ultraviolet-ray absorption function, an antireflection function etc. is mentioned. The layer configuration of the optical filter may be one layer or two or more, and may be in the form of a composite filter in which the above filters are laminated. Further, one layer or each layer may have a plurality of different functions.

  As the near-infrared absorbing filter, a commercially available film having a near-infrared absorber (for example, Toyobo Co., Ltd., trade name No. 2832) is used, or a composition containing a near-infrared absorbing dye in a binder is formed, or The composition may be applied on a transparent substrate. As a near-infrared absorbing dye, when an optical filter is applied to the front surface of a plasma display panel, it absorbs a near-infrared region caused by a xenon gas discharge emitted from the plasma display panel, that is, a wavelength region of 800 nm to 1100 nm. Is used. The near-infrared transmittance of the band is preferably 20% or less, more preferably 10% or less. At the same time, it is desirable that the near-infrared absorbing filter has a sufficient light transmittance in the visible light region, that is, in the wavelength region of 380 nm to 780 nm.

  Specific examples of near-infrared absorbing dyes include polymethine compounds, cyanine compounds, phthalocyanine compounds, naphthalocyanine compounds, naphthoquinone compounds, anthraquinone compounds, dithiol compounds, imonium compounds, diimonium compounds, and aminium. Compounds, pyrylium compounds, cerium compounds, squarylium compounds, copper complexes, nickel complexes, dithiol metal complexes organic near infrared absorbing dyes, tin oxide, indium oxide, magnesium oxide, titanium oxide, chromium oxide Zirconium oxide, nickel oxide, aluminum oxide, zinc oxide, iron oxide, ammonium oxide, lead oxide, bismuth oxide, inorganic near-infrared absorbing dyes such as lanthanum oxide, etc. can be used alone or in combination of two or more. . As the binder resin, a resin such as a polyester resin, a polyurethane resin, an acrylic resin, or an epoxy resin is used. Binder resin drying and curing methods include a drying and solidification method by drying a solvent (or dispersion medium) from a solution (or emulsion), a polymerization method using heat, ultraviolet light, electron beam energy, and a crosslinking reaction. Alternatively, a curing method utilizing a reaction such as crosslinking or polymerization between a functional group such as a hydroxyl group or an epoxy group in a resin and an isocyanate group in a curing agent can be applied.

  The neon light absorption filter is installed to absorb neon light emitted from the plasma display panel, that is, an emission spectrum of neon atoms when the optical filter is used for a plasma display. Since the emission spectrum band of neon light has a wavelength of 550 to 640 nm, the neon light absorbing layer is preferably designed so that the spectral transmittance is 50% or less at a wavelength of 550 to 640 nm. The neon light absorption filter may be formed by dispersing a dye conventionally used as a dye having an absorption maximum in a wavelength region of at least 550 to 640 nm in a binder resin as mentioned in the near infrared absorption filter. it can. Specific examples of the dye include cyanine, oxonol, methine, subphthalocyanine or porphyrin.

  Moreover, as an ultraviolet absorption filter, it can form by disperse | distributing an ultraviolet absorber to binder resin, for example. Examples of the ultraviolet absorber include organic compounds such as benzotriazole and benzophenone, and inorganic compounds composed of particulate zinc oxide, cerium oxide, and the like. As the binder resin, resins such as those listed above for the near infrared absorption filter can be used.

Further, as an antireflection (AR) filter, for example, a multilayer structure in which low refractive index layers and high refractive index layers are alternately laminated is generally used, such as a dry method such as vapor deposition or sputtering, or coating. It can also be formed using a wet method. Note that silicon oxide, magnesium fluoride, fluorine-containing resin, or the like is used for the low refractive index layer, and titanium oxide, zinc sulfide, zirconium oxide, niobium oxide, or the like is used for the high refractive index layer.
In addition, anti-glare (AG) filters can be applied to the surface of the layer by forming a coating using an inorganic filler such as silica in a resin binder, or by shaping using a shaping sheet or shaping plate. It can be formed as a layer provided with fine irregularities that diffusely reflect. As the resin of the resin binder, a curable acrylic resin, an ionizing radiation curable resin, or the like is preferably used in the same manner as the hard coat layer described below because surface strength is desired as the surface layer.

  Further, when the adherend is a protective film, typical examples include a hard coat layer (HC layer) and an antifouling layer. Examples of the hard coat layer include polyfunctional (meth) acrylate prepolymers such as polyester (meth) acrylate, urethane (meth) acrylate, and epoxy (meth) acrylate, or trimethylolpropane tri (meth) acrylate, pentaerythritol tetra An ionizing radiation curable resin in which a trifunctional or higher polyfunctional (meth) acrylate monomer such as (meth) acrylate, dipentaerythritol hexa (meth) acrylate or the like is used alone or in combination of two or more selected from these. It can be formed as a coating film used. Here, (meth) acrylate is a composite notation meaning acrylate or methacrylate.

The antifouling layer is generally a water-repellent or oil-repellent coat, and a siloxane-based, fluorinated alkylsilyl compound or the like can be applied. A fluorine-based or silicone-based resin used as a water-repellent paint can be preferably used. For example, when the low refractive index layer of the antireflection layer is formed of SiO ₂ , a fluorosilicate water-repellent paint is preferably used.
In addition, the transparent base material and adhesive layer which comprise a to-be-adhered body layer can use the material used with the electromagnetic wave shielding sheet mentioned above suitably.

Hereinafter, the manufacturing method of the electromagnetic wave shielding sheet of the present invention will be described.
First, a transparent substrate is prepared. As a transparent base material, it can select and use from the base material mentioned above.
When the transparent base material is a resin base material, it can be handled in the form of a continuous belt-like sheet at least at the initial stage of production, such as mesh layer formation, in that the electromagnetic shielding filter can be continuously manufactured to improve productivity. Is preferred.
The transparent substrate is appropriately 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, alkali treatment, etc. May be.

  Next, a copper mesh layer is formed on the transparent substrate. In the present invention, the method for forming the copper mesh layer is not particularly limited, and various methods for forming a conventionally known light-transmitting electromagnetic wave shielding sheet can be appropriately employed. For example, the following (1) to (4) may be mentioned.

(1) A method in which a conductive ink is printed in a pattern on a transparent substrate, and metal plating is performed on the conductive ink layer (for example, JP 2000-13088 A).
(2) A method in which a conductive ink or a chemical plating catalyst-containing photosensitive coating solution is applied to the entire surface of a transparent substrate, and the coating layer is made into a mesh by photolithography, followed by metal plating on the mesh (for example, , Sumitomo Osaka Cement Co., Ltd. New Materials Division, New Materials Research Institute, New Materials Research Group, “Photoresolvable Chemical Plating Catalyst”, [online], date not listed, Sumitomo Osaka Cement Co., Ltd. [2003 Search on January 7], Internet <URL: http://www.socnb.com/product/hproduct/display.html>).
(3) After laminating a transparent base material and a metal foil with an adhesive, the metal foil is formed into a mesh by a photolithography method (for example, JP-A-11-145678).
(4) On one surface of the transparent substrate, a metal thin film is formed by sputtering or the like to form a conductive treatment layer, and a transparent substrate on which a metal layer is formed as a metal plating layer by electrolytic plating is prepared. The metal plating layer and the conductive treatment layer of the metal-plated transparent base material are formed into a mesh shape by a photolithography method (for example, Japanese Patent No. 3502979, Japanese Patent Application Laid-Open No. 2004-241761).

  In the present invention, in particular, it is possible to obtain a desired thin mesh thickness in the present invention, and it is possible to manufacture a thin metal film on one surface of a transparent substrate because it can be manufactured in a short process with good yield and low cost. A transparent substrate having a metal layer formed thereon as a metal plating layer by electroplating is prepared, and the metal plating layer and the conductive treatment layer of the metal-plated transparent substrate are prepared. It is particularly preferable to use a method of forming a mesh by a photolithography method (for example, Japanese Patent No. 3502979, Japanese Patent Application Laid-Open No. 2004-241761). According to this method, an electromagnetic wave shielding sheet excellent in transparency and mesh accuracy can be obtained.

In the laminate of the copper mesh layer and the transparent substrate thus obtained, a blackening layer may be further formed on the mesh-like conductor layer. The blackening layer roughens the surface of the conductor layer, imparts light absorption over the entire visible light spectrum (blackens), or uses both in combination. This is done according to the processing method.
As described above, a laminated body of a mesh-like conductor layer including at least a copper mesh layer and a transparent substrate is obtained.

On the other hand, the adherend layer according to the present invention is an optical filter having a function such as an antireflection filter or a near-infrared absorption filter, a glass substrate of a PDP screen, or the like as described above. Depending on the method of lamination, it may be a continuous strip or a single wafer.
The method for laminating the laminate having the mesh-like region, the pressure-sensitive adhesive layer, and the adherend layer to obtain the electromagnetic wave shielding sheet shown in FIG. 1C is not particularly limited. FIG. 4 is a schematic view of obtaining the electromagnetic wave shielding sheet shown in FIG. 1C by adhering and laminating the mesh-like region of the laminate 4 and the adherend layer via an adhesive layer. For example, as shown in FIG. 4A, first, the laminate 5 in which the pressure-sensitive adhesive layer 15 is laminated on the laminate 4 is prepared, and the adherend layer 16 is laminated on the pressure-sensitive adhesive layer 15. Alternatively, as shown in FIG. 4B, first, a laminate in which the pressure-sensitive adhesive layer 15 is laminated on the adherend layer 16 may be prepared, and the laminate 4 may be laminated on the pressure-sensitive adhesive layer 15. .

Hereinafter, the method of FIG. 4B will be specifically described.
First, a method of laminating the pressure-sensitive adhesive layer 15 on at least one surface of the adherend layer 16 is a known layer forming method, for example, a coating method such as roll coating, comma coating, gravure coating, or an arbitrary shape. Printing methods such as screen printing and gravure printing, which can be easily formed, can be appropriately employed. If necessary, the adherend after the adhesion processing may be protected with a known separator or the like. As the separator, a resin sheet such as a biaxially stretched polyethylene terephthalate film whose surface is release-treated with silicone or the like may be used.

Furthermore, the method for producing an electromagnetic wave shielding sheet by adhering and laminating the pressure-sensitive adhesive layer 15 laminated on the adherend layer 16 and the mesh-like region of the laminate 4 is not particularly limited. The method of making it adhere | attach and laminate | stack by pressing simultaneously from the transparent base material 11 side and the to-be-adhered body layer 16 side using the laminator provided with a pressurization part is mentioned.
If the example of the lamination is further shown, the roll-to-roll system is used for the adhesive layer side of the resin sheet for the continuous band-shaped optical filter and the conductor layer side of the continuous band-shaped electromagnetic wave shielding sheet in which the mesh-shaped region is formed. And laminating using a roll laminator.
Lamination method using roll-to-roll method is preferable because it has good production efficiency and low cost. However, either one or both of the electromagnetic wave shielding sheet and the adhesive optical filter is made into a single wafer shape and laminated using various laminators. May be.

The laminator may be a roll type, a flat plate type, etc., as long as it can pressurize the optical filter and the electromagnetic wave shielding sheet. However, it is easy to cope with the roll-to-roll method and prevent air bubbles from being mixed. It is preferable to use a roll laminator from a certain point and a point capable of continuous production.
Although the pressurization at the time of lamination is not particularly limited, for example, when a roll laminator is used, the linear pressure is preferably 1 to 20 kgf / cm. Although the temperature of the pressurization part at the time of lamination | stacking is also not specifically limited, From the point of an equipment burden, the one where it is low temperature is preferable and it is more preferable that it is 20 to 80 degreeC. However, you may heat to 80 degreeC or more as needed.
In addition, the manufacturing method of the electromagnetic wave shielding sheet of this invention is not limited to the said embodiment.

Hereinafter, the present invention will be specifically described with reference to examples. These descriptions do not limit the present invention. In the examples, parts represent parts by weight unless otherwise specified.
<Example 1>
An electromagnetic wave shielding sheet 1 shown in FIG. 1 (C) was produced as follows.
As the transparent base material 11, a continuous belt-shaped non-colored transparent biaxially stretched polyethylene terephthalate film having a thickness of 100 μm and a polyester resin primer layer formed on one side was prepared.
On the primer layer of this transparent base material, a nickel-chromium alloy layer having a thickness of 0.1 μm and a copper layer having a thickness of 0.2 μm were sequentially provided by a sputtering method to obtain a conductive treatment layer 13.

  A copper plating layer 14 having a thickness of 2.0 μm is provided on the surface of the conductive treatment layer by an electrolytic plating method using a copper sulfate bath, and the conductive treatment layer 13 and the copper plating layer 14 (hereinafter, both layers are combined to form a metal layer). 18), a copper-clad laminate sheet 2 as shown in FIG. 5A was produced, in which the conductor layer was formed directly on the transparent substrate without interposing the adhesive layer therebetween.

Next, a mesh-like region composed of the opening 103 and the line portion 104 as shown in FIG. 5B is formed on the laminated sheet by etching using the photolithography method of the metal layer 18, and the laminated body 3 was obtained.
Specifically, using a production line for a color TV shadow mask, the etching was performed consistently from masking to etching on the continuous belt-like laminated sheet. That is, after applying a photosensitive etching resist to the entire surface of the conductor layer of the laminated sheet, a desired mesh pattern is closely exposed, developed, hardened, and baked on the area corresponding to the line portion of the mesh. After processing the resist layer into a pattern in which the resist layer remains and there is no resist layer on the area corresponding to the opening, the conductive layer is etched away with an aqueous ferric chloride solution to form a mesh-shaped opening. Then, washing with water, resist stripping, washing and drying were sequentially performed.

  The mesh shape of the mesh region is such that the line width of the linear portion where the opening is a square and a non-opening is 10 μm, the line interval (pitch) is 300 μm, the height of the line is 2.3 μm, rectangular When cut into single sheets, the bias angle defined as the minor angle with respect to the long side of the rectangle was 49 degrees. Further, when the completed electromagnetic shielding sheet is mounted on the front surface of the image display device (display), the mesh region 101 has a portion facing the image display region of the display, and the peripheral portion of the mesh region. For example, when the electromagnetic wave shielding sheet is cut into a rectangular sheet, the pattern is designed to leave a frame portion having a width of 15 mm without an opening as a grounding region on the outer periphery of the four sides. In this way, a mesh metal layer and a ground metal layer were formed on the transparent substrate.

  Next, a blackened layer 17 was formed on the metal layer 18 of the laminate 3. Specifically, a nickel plate is used for the anode, and the mesh-shaped conductor layer is formed on a transparent base material in a blackening plating bath made of a mixed aqueous solution of a nickel ammonium sulfate aqueous solution, a zinc sulfate aqueous solution and a sodium thiocyanate aqueous solution. The laminated sheet formed above is immersed and electroplated to perform blackening treatment, and a blackened layer 17 made of a nickel-zinc alloy is formed on the entire exposed conductor layer to form a conductive layer. The laminated body 4 as shown in FIG. 5C in which the body layer 12 (the conductive treatment layer 13, the copper mesh layer 14, and the blackening layer 17) was laminated was obtained.

Subsequently, the adherend layer 16 for laminating | stacking on the said laminated body 4 via an adhesive layer was prepared. As the structure of the adherend layer, an antireflection filter / ultraviolet absorption filter structure was prepared. “/” Indicates that the left and right layers are laminated and integrated.
As the ultraviolet absorbing filter, a Tetron film (trade name “HB type” manufactured by Teijin Ltd.), which is a transparent biaxially stretched PET film having a thickness of 50 μm and kneaded with an ultraviolet absorber, was used. The ultraviolet absorbing layer is also used as a base material for coating and forming an antireflection layer.
The antireflection filter was formed by sequentially forming a high refractive index layer and a low refractive index layer on the ultraviolet absorption filter.

Here, the high refractive index layer is a cured product having a thickness of 3 μm and a refractive index of 1.69 of a composition (trade name “KZ7973” manufactured by JSR Corporation) in which ultrafine zirconia particles are dispersed in an ultraviolet curable resin. Consists of layers.
The low refractive index resin layer is made of a cured product having a thickness of 100 nm and a refractive index of 1.41 made of a fluororesin-based ultraviolet curable resin (manufactured by JSR Corporation, trade name “TM086”).

  Next, the pressure-sensitive adhesive layer 15 is formed on the ultraviolet absorption filter side of the adherend layer, and the pressure-sensitive adhesive is added to the pressure-sensitive adhesive layer 15 by adding a near-infrared absorber and a neon light absorber. The layer was also used as a near infrared absorption filter and a neon light absorption filter.

The pressure-sensitive adhesive layer coating solution was prepared as follows. Acrylic resin adhesive 1 (Manufacturer: Nippon Synthetic Chemical, trade name: “5407”, acid value: 8, molecular weight (Mw) 700,000, solid content (%): 40 ± 1.5, viscosity (mPa · s / 25 ° C.): 8000 ± 1000) 100 parts by weight and curing agent 1 (manufactured by Nippon Polyurethane Co., Ltd., trade name: “Coronate L-55E”) 4 parts by weight were mixed. Further, 1,2,3-benzotriazole as an antioxidant is 1 part by weight with respect to 100 parts by weight of the pressure-sensitive adhesive, and a cyanine dye (manufactured by Asahi Denka Kogyo Co., Ltd., a product) as a neon light absorber. Name “TY-167”), as a near-infrared absorber, diimonium dye (manufactured by Nippon Carlit Co., Ltd., trade name “CIR1085”), phthalocyanine dye (manufactured by Nippon Shokubai Co., Ltd., trade name “IR12”), and phthalocyanine dye (Nippon Shokubai Co., Ltd., trade name “IR14”) was added and mixed to obtain an adhesive layer coating solution. The pressure-sensitive adhesive layer coating liquid is coated on the UV-absorbing layer side of the adherend layer and dried to obtain a pressure-sensitive adhesive layer / adhesive layer laminate (adhesive layer-attached adherend). It was. The thickness of the pressure-sensitive adhesive layer was 25 μm.
The obtained adherend with an adhesive layer is cut into the same shape as the part (rectangular shape) facing the image display area of the mesh-like area of the laminate 4 and the size is cut large by 4 mm both vertically and horizontally, and one adhesive It was set as the adherend with an agent layer.

  Then, the obtained laminate 4 and the adherend with the adhesive layer are arranged in such a direction that the adhesive layer of the adherend with the adhesive layer faces the mesh-like region of the laminate 4 and with the adhesive layer. The adherends were aligned so as to cover the entire portion of the mesh-like region facing the image display region, and then bonded to each other. As the lamination conditions in this case, the electromagnetic wave shielding sheet of Example 1 was manufactured by applying pressure at a maximum linear pressure of 10 kg / cm with a rubber roller at room temperature (20 ° C.).

<Example 2>
The electromagnetic wave shielding sheet of Example 2 was produced in the same manner as in the electromagnetic wave shielding sheet of Example 1, except that the amount of 1,2,3-benzotriazole added was changed to 3 parts by weight with respect to the adhesive.

<Example 3>
In the electromagnetic wave shielding sheet of Example 1, the electromagnetic wave shielding sheet of Example 3 was produced in the same manner except that the amount of 1,2,3-benzotriazole added was changed to 0.5 parts by weight with respect to the adhesive. did.

<Comparative Example 1>
In the electromagnetic wave shielding sheet of Example 1, the electromagnetic wave shielding sheet of Comparative Example 1 was produced in the same manner except that the antioxidant was not added.
<Comparative example 2>
In the electromagnetic wave shielding sheet of Comparative Example 1, the electromagnetic wave shielding sheet of Comparative Example 2 was produced in the same manner except that the blackening treatment was omitted.

<Comparative Example 3>
In the electromagnetic wave shielding sheet of Comparative Example 1, the electromagnetic wave shielding sheet of Comparative Example 3 was produced in the same manner except that the thickness of the pressure-sensitive adhesive layer was 15 μm.
<Comparative example 4>
In the electromagnetic wave shielding sheet of Comparative Example 3, the acrylic resin-based pressure-sensitive adhesive added to the pressure-sensitive adhesive layer coating solution is pressure-sensitive adhesive 2 (manufacturer: Nippon Synthetic Chemical, trade name: “N-2031B”, acid value: 0.00). 5, molecular weight (Mw) 670000, solid content (%): 40 ± 1.5, viscosity (mPa · s / 25 ° C.): 9000 ± 2000) 100 parts by weight, and curing agent is curing agent 2 An electromagnetic wave shielding sheet of Comparative Example 4 was produced in the same manner except that it was changed to (Isocyanate adduct, manufactured by Nippon Polyurethane Co., Ltd.).

<Comparative Example 5>
In the electromagnetic wave shielding sheet of Comparative Example 3, the acrylic resin-based adhesive added to the coating solution for the adhesive layer is the adhesive 3 (manufacturer: Nippon Synthetic Chemical Co., Ltd., trade name: “N-2260”, acid value: 0, The electromagnetic wave of Comparative Example 5 was similarly changed except that the molecular weight (Mw) was 750,000, the solid content (%): 40 ± 1.5, and the viscosity (mPa · s / 25 ° C.): 6500 ± 2000) 100 parts by weight. A shielding sheet was produced.

[Performance evaluation method]
The following points were evaluated with respect to the above examples and comparative examples. The evaluation results are shown in Table 1.
Regarding environmental reliability (color change ΔE), ΔE> 1.2 (a color difference is slightly above the level of visual judgment x), 0.6 <ΔE ≦ 1.2 (color difference below the level of slight difference by visual judgment) ) And Δ for color change ΔE ≦ 0.6 (a level equal to or lower than the threshold value for color discrimination by visual judgment).

(1) Environmental reliability First, the chromaticity a ^* , b ^* and lightness L ^* (International Lighting Commission (CIE) regulations) of the obtained electromagnetic wave shielding sheet are measured. Next, after exposure to a high temperature and high humidity (60 ° C., 95% RH) atmosphere for 500 hours, the chromaticity and brightness are measured in the same manner. From the above measurement results, the color difference ΔE before and after exposure to a high temperature and high humidity atmosphere was determined. ΔE> 1.2 (a color change is clearly observed when the color difference is slightly higher than a visual difference) x, 0.6 <ΔE ≦ 1.2 (a color difference is less than a slight level as determined visually), Δ Color change ΔE ≦ 0.6 (a level equal to or less than a threshold value for color change discrimination by visual judgment) was evaluated as ◯.

(2) Adhesive strength First, coating the pressure-sensitive adhesive layer coating liquid containing the pressure-sensitive adhesive and antioxidant on the mesh surface of the laminate of the transparent base material and the copper mesh layer so that the film thickness becomes 25 μm after drying, Dry at 120 ° C. for 2 minutes. Next, pressure is applied between a pair of rubber rollers at room temperature (23 ° C.) using a desktop roll pressure laminating machine (Fuji Plastic Machine Industry Co., Ltd., trade name: “Lamipacker”). Release PET was bonded to the surface. Next, the peeled PET was peeled off, and an easy-adhesive surface of PET (manufactured by Toyobo Co., Ltd., trade name: “A4100”)) was bonded to the adhesive surface using a roller. Next, the bonded sample was cut into a 1 inch width, and a double-sided tape was attached to the PET surface. Next, the double-sided tape was peeled off, the sample was attached to a stainless steel plate having a thickness of 1 mm, and set in a tensile tester (trade name: “Tensilon” manufactured by Toyo Seiki Co., Ltd.). Then, PET (A4100) and EMI mesh were peeled at a peeling angle of 180 ° (peeling speed: 200 mm / min, peeling distance: 100 mm), and the adhesive force (N / inch) was measured. The allowable range of adhesive force was 20 N / inch or more.

The pressure-sensitive adhesive and curing agent in the table are as follows.
Adhesive 1: Nippon Synthetic Chemical Co., Ltd., trade name “5407”
Adhesive 2: manufactured by Nippon Synthetic Chemical Co., Ltd., trade name “N-2031B”
Adhesive 3: manufactured by Nippon Synthetic Chemical Co., Ltd., trade name “N-2260”
Curing agent 1: manufactured by Nippon Polyurethane Co., Ltd., trade name: “Coronate L-55E” (adduct of tolylene diisocyanate of trimethylolpropane)
Curing agent 2: Nippon Polyurethane Co., Ltd., adduct of isocyanate

<Summary of results>
The following can be seen from the above examples and comparative examples.
The electromagnetic wave shielding sheets of the present invention obtained in Examples 1, 2 and 3 all have sufficient adhesive strength, and the effect of reducing discoloration of the copper mesh under high temperature and high humidity by adding an antioxidant. Was recognized. In particular, in Example 1 and Example 2, there was little discoloration, it was a level (ΔE <0.6) where color difference discrimination by visual observation was impossible, and the adhesive force was sufficient.

On the other hand, although the electromagnetic wave shielding sheets obtained in Comparative Examples 1 to 4 in which the antioxidant contained in the pressure-sensitive adhesive layer was not added had sufficient adhesion, discoloration was observed.
Further, the electromagnetic wave shielding sheets obtained in Comparative Examples 5 and 6 in which the acid value of the pressure-sensitive adhesive contained in the pressure-sensitive adhesive layer was less than 1, although discoloration was within an acceptable range, had insufficient adhesive force.

It is sectional drawing of an example of the electromagnetic wave shielding sheet which concerns on this invention. It is a perspective view of an example (Drawing 1 (C)) of an electromagnetic wave shielding sheet concerning the present invention. It is sectional drawing of an example (FIG. 2) of the electromagnetic wave shielding sheet which concerns on this invention. It is a schematic diagram which obtains the electromagnetic wave shielding sheet shown in FIG.1 (C) by adhere | attaching and laminating | stacking the mesh-like area | region and adherend layer of the laminated body 4 through an adhesive layer. It is a figure which shows an example of the intermediate | middle laminated body at the time of manufacturing the electromagnetic wave shielding sheet which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electromagnetic wave shielding sheet 2-6 Laminated body 11 Transparent base material 12 Conductor layer 13 Conductive treatment layer 14 Copper mesh layer (copper plating layer)
DESCRIPTION OF SYMBOLS 15 Adhesive layer 16 Adhering body layer 17 Blackening layer 18 Metal layer 101 Mesh area 103 Opening part 104 Line part

Claims (5)

  An electromagnetic wave shielding sheet in which at least a copper mesh layer, an adhesive layer, and an adherend layer are provided in this order on one surface of a transparent substrate, the adhesive layer having an acid value and an antioxidant An electromagnetic wave shielding sheet comprising an agent.   The electromagnetic wave shielding sheet according to claim 1, wherein the antioxidant is a benzotriazole-based antioxidant.   The electromagnetic wave shielding sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive is an acrylic pressure-sensitive adhesive, and the acid value of the pressure-sensitive adhesive is 1 or more.   The electromagnetic wave shielding sheet according to claim 2 or 3, wherein the pressure-sensitive adhesive layer contains 1 part by weight or more of the benzotriazole-based antioxidant with respect to 100 parts by weight of the pressure-sensitive adhesive.   The electromagnetic wave shielding sheet according to claim 1, wherein a blackening treatment layer is provided between the copper mesh layer and the pressure-sensitive adhesive layer.

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