JP2009290054A - Electromagnetic-wave shielding sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic-wave shielding sheet hardly turning to yellow, allowing little mixing of minute bubbles, high in image definition, capable of suppressing increase of haze, and provided with an adhesive layer excelling in an optical characteristic. <P>SOLUTION: In this electromagnetic-wave shielding sheet provided with a conductive pattern layer on one surface of a transparent base material through an adhesive layer, the adhesive layer is formed of an adhesive containing (I) as a base compound, polyester urethane polyol containing a soft segment (A) and a hard segment (B), and (II) a curing agent containing isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI). The electromagnetic wave shielding sheet is characterized in that, in the base compound, the weight ratio ((A):(B)) of the soft segment (A) to the hard segment (B) is 60:40 to 90:10; and the weight ratio (IPDI:HDI) of the isophorone diisocyanate (IPDI) to the hexamethylene diisocyanate (HDI) is 50:50 to 80:20. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electromagnetic wave shielding sheet that shields (shields) electromagnetic waves generated from a display (image display device) such as a PDP (plasma display panel).

  In recent years, with the advancement of functions and increased 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. In order to shield this electromagnetic wave, an electromagnetic wave shielding sheet disposed on the front surface of the display is known. In the electromagnetic wave shielding sheet used for such applications, light transmittance is also required in addition to the electromagnetic wave shielding performance. Therefore, an electromagnetic wave shielding sheet that uses a transparent base material such as a resin film or a glass plate as a base material, and is provided with light transmittance by forming a conductive pattern layer made of a metal such as copper on the transparent base material. It has been known. Note that a mesh (conductive mesh layer) is usually used as the pattern.

  The conductive pattern layer is formed in a mesh shape by etching a metal foil laminated on a transparent substrate. Since the mesh-like metal foil obtained by etching as described above is difficult to handle by itself, usually a laminated body in which an unprocessed metal foil is laminated on a transparent substrate via an adhesive layer is produced. The pattern-like etching is performed on the metal foil on the laminate.

For the adhesive layer, an adhesive containing a polyester resin (typically a polyester polyol) and an isocyanate compound is used.
Patent Document 1 discloses an adhesive containing a curing agent containing saturated polyester and xylylene diisocyanate (XDI). The surface of the metal foil used for this kind of application has minute irregularities to enhance the adhesive force by the anchoring effect, so when using this adhesive to bond the metal foil on the transparent substrate, The air between them is not completely removed, and microbubbles are generated between the surface of the metal foil and the surface of the adhesive. Then, in the process of curing the saturated polyester and xylylene diisocyanate (XDI), microbubbles are mixed in the adhesive layer. Therefore, when the electromagnetic wave shielding sheet obtained in this way is arranged on the front surface of the display, there is a problem that image light is scattered by the microbubbles mixed in the adhesive layer and haze (cloudiness value) is increased.

  In addition, when an adhesive containing a saturated polyester and a curing agent containing hexamethylene diisocyanate (HDI) is used, the surface of the adhesive layer after curing is caused by uneven curing shrinkage of the adhesive layer during coating. Due to the lack of flow flattening, etc., the flatness is lowered, and minute distorted irregularities (other than the minute irregularities of the metal foil for improving the anchoring effect) are generated. When the metal foil is etched and formed into a mesh shape, the surface of the adhesive layer having minute distorted irregularities is exposed at the portion where the metal foil is removed. Therefore, when the electromagnetic wave shielding sheet obtained in this way is arranged on the front surface of the display, the transmitted light from the back surface of the backlight inside the PDP is emitted by the minute distorted irregularities on the surface of the adhesive layer of the electromagnetic wave shielding sheet. There is a problem that the so-called “image sharpness” is lowered, that is, the image is distorted and does not go straight and appears to be distorted.

In addition, when the line width of a mesh is reduced (about 5 to 30 μm) with the increase in image quality and resolution, the fine line width is processed stably, with good reproducibility and without defects. For this, it is necessary to immerse a laminated body in which a metal foil is laminated on a transparent substrate via an adhesive layer in a low concentration etching solution for a long time. However, when the laminate is immersed in an etching solution for a long time, an etching solution typified by a ferric chloride aqueous solution or the like is likely to penetrate into the adhesive layer, and the adhesive layer is yellowed. Moreover, when the electromagnetic wave shielding sheet obtained in this way is arranged on the front surface of the display, there is a problem that haze increases.
As described above, in the conventional adhesive, all of the electromagnetic wave shielding sheets required for the electromagnetic wave shielding sheet, such as that microbubbles are not mixed, the adhesive layer is hardly yellowed, the haze is low, and the image definition is high. The optical properties could not be satisfied.

JP 2003-198181 A

  The present invention has been made in view of the above problems, and is an adhesive having excellent optical characteristics that is difficult to yellow, does not easily contain microbubbles, has high image definition, and can suppress an increase in haze. An object of the present invention is to provide an electromagnetic wave shielding sheet having a layer.

As a result of intensive studies, the present inventors have found that the above problems can be solved by using a specific adhesive, and have completed the present invention.
That is, the electromagnetic wave shielding sheet according to the present invention is an electromagnetic wave shielding sheet provided with a conductive pattern layer on one surface of a transparent substrate via an adhesive layer.
The adhesive layer is
(I) formed from an adhesive containing a polyester urethane polyol containing a soft segment (A) and a hard segment (B) as a main agent, and (II) a curing agent containing isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI) And the weight ratio of the soft segment (A) to the hard segment (B) ((A) :( B)) in the main agent is 60:40 to 90:10, and the isophorone diisocyanate (IPDI) A weight ratio (IPDI: HDI) of the hexamethylene diisocyanate (HDI) is 50:50 to 80:20.

In the adhesive of the present invention, a polyester urethane polyol containing a soft segment (A) and a hard segment (B) is used as a main agent, and the weight ratio of the soft segment (A) and the hard segment (B) is set to a specific range. By doing so, even if it hardens the adhesive layer after hardening to etching liquid for a long time, it can make it hard to yellow. Further, by using a curing agent containing isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI), and setting the weight ratio of the isophorone diisocyanate (IPDI) and the hexamethylene diisocyanate (HDI) to a specific range, an adhesive layer Mixing of microbubbles into the inside can be suppressed, and minute distortions can be made difficult to occur on the surface of the adhesive layer.
Therefore, according to the present invention, it is possible to provide an electromagnetic wave shielding sheet that is excellent in image definition and can suppress an increase in haze.

  In the electromagnetic wave shielding sheet according to the present invention, the glass transition temperature of the polyester urethane polyol is preferably in the range of 20 to 40 ° C. from the viewpoint of making the cured adhesive layer difficult to be yellowed by the etching solution. .

  In the electromagnetic wave shielding sheet according to the present invention, the amount of the curing agent is in the range of 4 to 30 parts by weight with respect to 100 parts by weight of the main agent, yellowing after etching, blocking, and conductivity. This is preferable from the viewpoint of pattern adhesion.

  According to the present invention, by using a specific adhesive, the cured adhesive layer is hardly yellowed, microbubbles are hardly mixed, and minute distortions are not easily generated on the surface of the adhesive layer. Therefore, it is possible to provide an electromagnetic wave shielding sheet that has high image definition and can suppress an increase in haze.

The present invention is described in detail below.
The electromagnetic wave shielding sheet of the present invention is an electromagnetic wave shielding sheet provided with a conductive pattern layer on one side of a transparent substrate via an adhesive layer.
The adhesive layer is
(I) formed from an adhesive containing a polyester urethane polyol containing a soft segment (A) and a hard segment (B) as a main agent, and (II) a curing agent containing isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI) And the weight ratio of the soft segment (A) to the hard segment (B) ((A) :( B)) in the main agent is 60:40 to 90:10, and the isophorone diisocyanate (IPDI) A weight ratio (IPDI: HDI) of the hexamethylene diisocyanate (HDI) is 50:50 to 80:20.

In the electromagnetic wave shielding sheet provided with the conductive pattern layer on one surface of the transparent substrate, the adhesive layer is yellowed by the etching liquid depending on the adhesive forming the adhesive layer. Or haze increases due to microbubbles mixed in the adhesive layer, or fine distortion on the surface of the adhesive layer, resulting in a decrease in image definition. was there.
On the other hand, the adhesive used for the electromagnetic wave shielding sheet of the present invention uses a polyester urethane polyol containing a soft segment (A) and a hard segment (B) as a main agent, and the soft segment (A) and the hard segment. By setting the weight ratio of (B) within a specific range, it is possible to make yellowing hardly occur even if the cured adhesive layer is immersed in an etching solution for a long time. Further, by using a curing agent containing isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI), and setting the weight ratio of the isophorone diisocyanate (IPDI) and the hexamethylene diisocyanate (HDI) to a specific range, an adhesive layer Mixing of microbubbles into the inside can be suppressed, and minute distortions can be made difficult to occur on the surface of the adhesive layer.
Therefore, according to the present invention, it is possible to provide an electromagnetic wave shielding sheet that is excellent in image definition and can suppress an increase in haze.

The adhesive layer of the present invention is hardly yellowed, is difficult to mix microbubbles, and can make it difficult to produce minute distortions on the surface of the adhesive layer for the following reasons. Conceivable.
The temperature of the etching solution when etching the laminate in which the metal foil is laminated on the transparent substrate via the adhesive layer is usually 40 to 50 ° C. On the other hand, the glass transition temperature of conventionally used adhesives is usually in the range of 15 to 100 ° C., which is comparable to or lower than the temperature of the etching solution. Therefore, when the laminate is immersed in an etching solution for a long time, the etching solution is likely to penetrate into the adhesive layer, and the adhesive layer is yellowed. On the other hand, when the hard segment (B) is added to the soft segment (A) which is the main component of the adhesive, the glass transition temperature becomes high. Therefore, by adjusting the blending ratio of the soft segment (A) and the hard segment (B) so that the glass transition temperature of the adhesive is sufficiently higher than the temperature of the etching solution, the etching processing time can be reduced. Even if the length is increased, it is considered that the etching solution hardly penetrates into the adhesive layer, yellowing can be suppressed, and haze increase can be suppressed.
Moreover, as a result of experiments by the present inventors, xylylene diisocyanate (XDI) contained in the curing agent of the adhesive has a high viscoelasticity and is rapidly solidified, and has a fast curing reaction rate. It was also found that hexamethylene diisocyanate (HDI) has low viscoelasticity and is slow to solidify, and tends to cure and shrink during the curing reaction with the main agent.
Therefore, the adhesive containing the xylylene diisocyanate (XDI) is not easily deformed, and the curing reaction between the main agent of the adhesive and the xylylene diisocyanate (XDI) proceeds rapidly, so that the metal foil surface and the adhesive surface It is considered that the microbubbles generated in the middle are easily mixed in the cured adhesive layer. In addition, the adhesive containing hexamethylene diisocyanate (HDI) is soft and easily deformed, and curing shrinkage easily occurs in the curing reaction process of the main agent of the adhesive and the hexamethylene diisocyanate (HDI). This is considered to cause uneven distortion.
From such a viewpoint, in order to make it difficult to mix microbubbles in the adhesive layer after curing, it is effective to use a curing agent containing an isocyanate compound that is low in viscoelasticity and slow to solidify, On the other hand, in order to make it difficult to produce minute irregularities on the surface of the adhesive layer after curing, it is presumed that it is effective to use a curing agent containing an isocyanate compound that hardly undergoes curing shrinkage. The inventors of the present application may first improve all of yellowing, mixing of microbubbles, and microscopic distortion as long as the viscoelasticity and the slowness of the curing reaction are adjusted to an appropriate range. Judged that there was. However, as a result of various trials and errors made by the inventors of the present application, it has not been possible to find a curing agent having such a variety of conflicting properties in an appropriate balance with a single isocyanate compound.
Therefore, in the present invention, the cross-linking point formed by the curing reaction with the main agent is highly viscoelastic and hardly moves, so that isophorone diisocyanate (IPDI), which is difficult to cause shrinkage by curing, is in a solidified state with low viscoelasticity. By using slow hexamethylene diisocyanate (HDI) in combination and adjusting the blending ratio, it is difficult for microbubbles to be mixed in the cured adhesive layer, and it is difficult to produce minute irregularities on the surface of the adhesive layer. It is considered possible.
Here, the “solidified state” is a state where tan σ is 1. The “soft segment” is a soft and flexible segment, and the “hard segment” is a hard and rigid segment.

〔Layer structure〕
FIG. 1 is a cross-sectional view illustrating a basic form of an electromagnetic wave shielding sheet according to the present invention. In the cross-sectional view shown in FIG. 1, for ease of explanation, the scale in the thickness direction (vertical direction in the figure) is greatly enlarged and exaggerated in comparison with the scale in the plane direction (left and right direction in the figure). The scale in the thickness direction of the electromagnetic wave shielding sheet is illustrated in a greatly enlarged manner than the scale in the thickness direction of the plasma display panel (hereinafter also referred to as PDP). In the electromagnetic wave shielding sheet 1, a mesh-like conductive pattern layer 12 is laminated on one surface of a transparent substrate 10 with an adhesive layer 11 interposed therebetween. The conductive pattern layer 12 has a blackened layer 13 by blackening the surface opposite to the surface on the transparent substrate 10 side (side facing the viewer or viewer of the image).
If the electromagnetic wave shielding sheet 1 according to the present invention is disposed on the front surface of the plasma display panel 20, the electromagnetic wave shielding sheet 1 is directly attached to the plasma display panel using an adhesive layer, although not shown in FIG. Alternatively, it may be disposed on the front surface of the plasma display after being attached to another plate-like transparent substrate that may have an optical function or the like.
Hereinafter, the electromagnetic wave shielding sheet of the present invention will be described in order from a transparent substrate.

(Transparent substrate)
The transparent substrate is a part of the layer constituting the electromagnetic wave shielding sheet, and is a layer serving as a substrate for laminating the conductive pattern layer via the adhesive layer. Moreover, you may add an ultraviolet-ray absorption function as needed. Therefore, as the transparent base material, if it has an ultraviolet absorbing ability as well as mechanical strength and light transmission property, a material that appropriately considers performance such as heat resistance may be selected according to the application. Specific examples of such a transparent substrate include a sheet (or film; the same applies hereinafter) or a plate made of an organic material such as resin or an inorganic material such as glass. The higher the transparency of the transparent substrate, the better. However, the light transmittance in the visible light region of 380 to 780 nm is preferably 70% or more, more preferably 80% or more. The light transmittance can be measured using a spectrophotometer (for example, UV-3100PC manufactured by Shimadzu Corporation) and a value measured in the air at room temperature.

  Examples of the resin used as the material for the transparent substrate include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, terephthalic acid-isophthalic acid-ethylene glycol copolymer, and terephthalic acid-cyclohexanedimethanol-ethylene glycol copolymer. Polyester resins such as polyester resins, polyamide resins such as nylon 6, polyolefin resins such as polypropylene, polymethylpentene, and cycloolefin polymers, acrylic resins such as polymethyl methacrylate, styrene resins such as polystyrene and styrene-acrylonitrile copolymers, Examples thereof include cellulose resins such as triacetyl cellulose, imide resins, and polycarbonate resins.

  These resins are used alone or as a plurality of types of mixed resins (including polymer alloys), and the layer structure of the transparent resin substrate is used as a single layer or a laminate of two or more layers. In the case of a resin film, a uniaxially stretched or biaxially stretched film is more preferable in terms of mechanical strength. Moreover, you may add additives, such as a filler, a plasticizer, and an antistatic agent, in these resins suitably as needed. Examples of the glass include soda glass, potash glass, borosilicate glass, and quartz glass. Usually, glass is used in the form of a thick plate.

The thickness of the transparent substrate may be basically selected according to the use and is not particularly limited, but is usually 12 to 5000 μm, preferably 50 to 500 μm in the case of a film, more preferably 50 to 200 μm, plate In this case, the thickness is 500 to 3000 μm. Within such a thickness range, the mechanical strength is sufficient, warping, loosening, breakage, etc. are prevented, and it is easy to supply and process in a continuous belt shape.
In the present invention, as the transparent substrate, a material made of a flexible resin film or plate is particularly preferable in terms of good manufacturing processability and reduced weight and cost. In particular, a base material made of these resins is referred to as a transparent resin base material, which will be described below as an example.

  As a form of the transparent resin substrate, a transparent resin film is preferable to a resin plate. Among the resin films, polyester resin films such as polyethylene terephthalate and polyethylene naphthalate are preferable in terms of transparency, heat resistance, cost, and the like, and more preferably a biaxially stretched polyethylene terephthalate film.

In the present invention, when the transparent resin substrate has an ultraviolet absorbing function, the transparent resin substrate is kneaded with an ultraviolet absorber in the resin of the transparent resin substrate, or the transparent resin substrate is configured. A surface coat layer containing an ultraviolet absorber may be provided on the surface as part of the layer, or a combination of both may be used. The surface on which the surface coat layer is provided may be either one of the front and back surfaces or both sides.
In addition, the transparent resin base material may be provided with an undercoat layer appropriately provided with various functions such as an adhesion improving function, a durability improving function, a printability improving function, and a solvent resistance improving function.

(Adhesive layer)
The adhesive layer is a layer that adheres the conductive pattern layer and the transparent substrate. The adhesive layer of the present invention includes an adhesive containing a polyester urethane polyol containing a soft segment (A) and a hard segment (B) as a main agent, and a curing agent containing isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI). Formed from. The composition of the adhesive will be described below.

[Main agent]
The main agent contained in the adhesive used in the present invention is a polyester urethane polyol containing two components of a soft segment (A) and a hard segment (B). The weight ratio ((A) :( B)) of the soft segment (A) and the hard segment (B) is in the range of 60:40 to 90:10, preferably in the range of 60:40 to 80:20. It is. By setting the weight ratio ((A) :( B)) within the above range, the cured adhesive layer can be hardly yellowed even when immersed in an etching solution for a long time, and microbubbles can be obtained. Mixing and minute distortions on the surface of the adhesive layer can also be suppressed without hindrance.

The glass transition temperature (also abbreviated as Tg) of the polyester urethane polyol is preferably in the range of 20 to 40 ° C, and more preferably in the range of 25 to 35 ° C. If the glass transition temperature is less than 20 ° C., yellowing may occur after etching, while if it exceeds 40 ° C., the mesh adhesion may be reduced.
Here, when only the hard segment of the polyester urethane polyol is polymerized alone, the glass transition temperature is 20 ° C. or higher, preferably 40 ° C. or higher, more preferably 80 ° C. or higher. In general, it is preferable to include an aromatic ring in the molecule. Further, when only the soft segment of the polyester urethane polyol is polymerized alone, the glass transition temperature is 40 ° C. or lower, preferably 20 ° C. or lower, more preferably 10 ° C. or lower. In general, it is preferable that no aromatic ring is contained in the molecule.
And when combining the hard segment and the soft segment,
Tg of the polymer of only the hard segment> Tg of the polymer of only the soft segment is selected and combined.
Specific materials constituting the hard segment and the soft segment include, for example, polyvalent carboxylic acids such as aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, isophthalic acid, phthalic acid, 2,6- Aromatic dicarboxylic acids such as naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid, bis (p-carboxyphenyl) methane, anthracene dicarboxylic acid, 4,4-diphenyl ether dicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4 -One or more selected from alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, cyclopentanedicarboxylic acid, 4,4'-bis (cyclohexyl) dicarboxylic acid, or ester-forming derivatives thereof, as a polyhydric alcohol, ethylene Glycol, propylene glycol, 1 , 4-butanediol, hexamethylene glycol, decamethylene glycol, cyclohexanedimethanol, or the like, or polyisocyanates such as tolylene diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, etc., aromatic isocyanate, hexa Examples thereof include one or more selected from aliphatic to alicyclic isocyanates such as methylene diisocyanate, hydrogenated tolylene diisocyanate, and isophorone diisocyanate.
These components are selectively mixed in accordance with the design criteria for the Tg of the hard segment and the soft segment, and a polymerization reaction is performed so that a polyester urethane polyol is obtained.

The glass transition temperature is simply calculated by the following formula based on the glass transition temperature Tg (K) of each homopolymer described in “POLYMERHANDBOOK 3rd edition” (published by John Wiley & Sons, Ink.). Besides, it can be obtained by DSC (Differential Scanning Calorimetry) or DTA (Differential Thermal Analysis).
1 / Tg (K) = W ₁ / Tg ₁ + W ₂ / Tg ₂ +... + Wn / Tgn
Wn; weight fraction Tgn of each monomer; Tg (K) of homopolymer of each monomer, in the polymer handbook (3rd Ed., J. Brandrup and EH Immergut, WILEY INTERSCIENCE) Use publicly available listings such as values.

[Curing agent]
The curing agent contained in the adhesive used in the present invention includes isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI), and the weight ratio of the isophorone diisocyanate (IPDI) to hexamethylene diisocyanate (HDI) (IPDI: HDI). Is 50: 50-80: 20, preferably 60: 40-80: 20. By setting the weight ratio (IPDI: HDI) within the above range, it is possible to suppress the entry of microbubbles into the adhesive layer and to make it difficult for micro unevenness to occur on the surface of the adhesive layer.

  Moreover, it is preferable that the compounding quantity of the said hardening | curing agent is the range of 4-30 weight part with respect to 100 weight part of said base agents, and also it is preferable that it is the range of 10-20 weight part. If the amount is less than 4 parts by weight, yellowing after etching, blocking may occur, and the conductive pattern adhesion may be reduced. If the amount exceeds 30 parts by weight, the conductive pattern adhesion may be reduced.

(Conductive pattern layer)
The conductive pattern layer is a layer that can have an electromagnetic wave shielding function by being conductive, and is itself made of an opaque material, but has a pattern shape in which a large number of openings exist for image light transmission. By processing, it is a layer that achieves both electromagnetic wave shielding performance and light transmittance.
Since the conductive pattern layer has a low mechanical strength, it is difficult to exist as an independent layer. Therefore, the conductive pattern layer is usually formed by laminating a conductive layer on the surface of a transparent base material (transparent resin base material or transparent glass base material) and forming the conductive layer into a pattern shape by etching (corrosion). The

  The conductive pattern layer is not particularly limited as long as it is a substance having sufficient conductivity to exhibit electromagnetic wave shielding performance, but usually a metal layer is preferable in terms of good conductivity. Examples of the metal material for the metal layer include gold, silver, copper, aluminum, iron, nickel, and chromium. The metal of the metal layer may be an alloy, and the metal layer may be a single layer or a multilayer. For example, in the case of iron, low carbon steel such as low carbon rimmed steel and low carbon aluminum killed steel, Ni-Fe alloy, Invar alloy, and the like are preferable. On the other hand, when the metal is copper, the metal material is copper or a copper alloy. There are rolled copper foil and electrolytic copper foil as the copper foil, but the thinness and uniformity thereof, the adhesion with the blackened layer, etc. Is preferably an electrolytic copper foil.

  In addition, the thickness of the electroconductive pattern layer by a metal layer is about 1-50 micrometers, Preferably it is 2-15 micrometers. If the thickness is too thin, it will be difficult to obtain sufficient electromagnetic wave shielding performance due to an increase in electrical resistance, and if the thickness is too thick, it will be difficult to obtain a high-definition pattern shape, which will reduce the uniformity of the pattern shape. . The thickness of the conductive pattern layer is 2 to 10 μm from the viewpoint that it is easy to flatten the conductive pattern layer, and there is little air bubble mixing when flattening, and it is easy to obtain an electromagnetic wave shielding sheet excellent in transparency. It is preferable that it is a grade.

[Mesh shape]
The pattern shape of the conductive pattern layer is not particularly limited, and various types such as a mesh (lattice or net), stripe (parallel line group), and spiral can be used. A mesh that can exhibit shielding properties with respect to the vibration direction (polarization direction) is frequently used.
In the following, the present invention will be described by mainly exemplifying a typical conductive mesh layer as the conductive pattern layer. However, the conductive pattern of the present invention is not limited to the mesh shape.
The shape of the opening of the mesh is typically a square. The plan view shape of the opening is, for example, a triangle such as a regular triangle, a square such as a square, a rectangle, a rhombus, or a trapezoid, a polygon such as a hexagon, a circle, an ellipse, or the like. The mesh has a plurality of openings with these shapes, and between the openings is usually a line (line) with a uniform width (line), and usually the opening and the line have the same shape on the entire surface. They are the same size. As an example of a specific size, the width of the line portion between the openings is preferably 5 to 30 μm from the viewpoint of high aperture ratio and invisibility of the mesh. The size of the opening is [line interval or line pitch] − [line width]. In terms of this [line interval or line pitch], the opening size is 100 μm to 500 μm, and the opening ratio (total area of opening / mesh area) The total area) is preferably 50 to 97% from the viewpoint of compatibility between light transmittance and electromagnetic wave shielding properties. In order to prevent moire fringes, the line pitch may be random between 100 μm and 500 μm.
The bias angle (the 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 fringes are not likely to occur in consideration of the pixel pitch of the display and the light emission characteristics.

[Grounding area and mesh area]
In addition, the conductive pattern layer 12 has a grounding region other than the mesh region 121 at the center in the planar direction, like the conductive pattern layer 12 conceptually illustrated in the plan view of FIG. The layer provided with 122 is more preferable in terms of easy grounding. The grounding area is formed on a part or all of the periphery of the image display area so as not to disturb the image display. The mesh area is an area that can cover the entire image display area of the display to which the electromagnetic wave shielding sheet is applied. The grounding area is an area for grounding. The image display area means at least an area in which the display substantially displays an image (substantially image display area), but when the display is viewed from an observer, the entire inside of the frame by the outer frame body of the display is displayed. An area may be included for convenience. The reason is that if a black area (border) exists inside the frame and outside the substantial image display area, it is outside the image display area, but the appearance is substantially the image display area as long as it is touched. The difference is that a sense of incongruity occurs.
The grounding region basically does not require a mesh, but a mesh composed of openings may be present for the purpose of preventing warpage of the grounding region.

[Blackening treatment]
The blackening treatment is for preventing light reflection on the surface of the conductive pattern layer, and the black level of the fluoroscopic image due to reflection of external light on the surface of the conductive pattern layer by the blackening treatment surface formed by the blackening treatment. Is reduced, and the bright room contrast of the fluoroscopic image is improved, thereby improving the visibility of the image on the display. The blackened surface is preferably provided on all surfaces of the line portion (linear portion) of the conductive pattern layer, but at least the observer side of the front and back surfaces and the external light incident side surface are blackened. A surface is preferred. Both the front and back surfaces and the side surfaces (both sides or one side) of the line portion may be further blackened. The blackening layer may be provided at least on the viewer side. However, when the blackening layer is also provided on the display surface side, stray light generated from the display can be suppressed, so that the visibility of the image is further improved.
As the blackening treatment, at least the outermost surface is black (color) by either roughening the surface of the conductive pattern layer, imparting light absorption over the entire visible light spectrum, or using both in combination. ). In particular, when the blackening process is performed by forming a layer, such a layer is referred to as a blackened layer. As a specific blackening treatment, a blackening layer is additionally provided on the conductive pattern layer by plating or the like, and the surface of the layer constituting the surface is roughened from the surface to the inside by etching or the like. It may be changed to a blackened layer.
Note that the color of the “blackening layer” to “blackening treatment” here does not have to be completely black, and if it is a low-lightness (dark) chromatic or achromatic color, that is, a so-called dark color, it is blackened. The effect equivalent to the purpose of the layer (blackening treatment) is achieved. Specific examples of such dark colors include achromatic colors such as black and dark (low lightness) gray, and low-lightness chromatic colors such as dark blue, brown, dark green, rosy and dark purple.

  Moreover, the blackening layer should just exhibit dark colors, such as black, and should satisfy | fill basic physical properties, such as adhesiveness, and can employ | adopt a well-known blackening layer suitably. 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, examples of the inorganic material include a metal compound such as a metal, an alloy, a metal oxide, and a metal sulfide. 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.

Although the electromagnetic wave shielding sheet of the present invention can be installed as a single product on the front surface of the image display device, it is usually laminated with a filter substrate to constitute an electromagnetic wave shielding filter plate, or various functional layers and After stacking to form a composite (multifunctional) filter, it can also be installed in front of the image display device.
The filter substrate may be appropriately selected from the same substrates as those described above as the transparent substrate of the electromagnetic wave shielding sheet.
As the functional layer, one or more of an optical filter layer, a hard coating layer (hard coat) layer, an antistatic layer, an antifouling layer, an impact resistant layer and the like are appropriately selected and laminated. As an optical filter layer, a filter layer having functions such as ultraviolet ray absorption, near infrared ray absorption, neon light absorption, antireflection, antiglare, coloring, antireflection of outside light by a fine louver structure (shade or harpoon) or a viewing angle regulating function Is mentioned. These functional layers may be appropriately laminated with a transparent substrate, or two or more functions may be imparted to one layer as necessary. These functional layers are appropriately selected from known various structures.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

  Hereinafter, the present invention will be described more specifically with reference to examples. These descriptions do not limit the present invention.

(Example 1)
As a transparent substrate, a continuous strip-shaped uncolored transparent biaxially stretched polyethylene terephthalate (PET) film (A4300: trade name, manufactured by Toyobo Co., Ltd.) having a thickness of 100 μm was prepared.
Next, an adhesive layer having the following composition was coated on one surface of the base material so that the thickness when dried was 4 μm to form an adhesive layer.
[composition]
(Main agent)
A1151: Trade name, manufactured by Mitsui Chemicals Polyurethanes Co., Ltd. (weight ratio of soft segment (A) and hard segment (B) ((A) :( B)) is 75:25): 100 parts by mass (curing agent)
D140N, trade name, manufactured by Mitsui Chemicals Polyurethanes Co., Ltd. (containing isophorone diisocyanate (IPDI)): 8 parts by mass A3070, trade name, manufactured by Mitsui Chemicals Polyurethanes Co., Ltd. (containing hexamethylene diisocyanate (HDI)): 2 parts by mass Part The weight ratio of IPDI to HDI (IPDI: HDI) is 8: 2.

  Next, a continuous strip-shaped electrolytic copper foil having a thickness of 10 μm was dry-laminated and laminated on one side of the PET film via the adhesive layer to obtain a continuous strip-shaped laminate. After dry laminating, the adhesive was cured by curing at 50 ° C. for 3 days.

(Example 2)
In the formation of the adhesive layer of Example 1, as a curing agent, except that D140N was 5 parts by mass, A3070 was 5 parts by mass, and the weight ratio of IPDI to HDI (IPDI: HDI) was 5: 5. A continuous belt-like laminate was obtained in the same manner as in Example 1.

(Comparative Example 1)
In the formation of the adhesive layer of Example 1, as the curing agent, 4 parts by mass of D140N and 6 parts by mass of A3070, except that the weight ratio of IPDI to HDI (IPDI: HDI) was 4: 6, A continuous belt-like laminate was obtained in the same manner as in Example 1.

(Comparative Example 2)
The formation of the adhesive layer of Example 1 was performed in the same manner as in Example 1 except that 10 parts by mass of D140N was used as a curing agent and A3070 was not used.

(Comparative Example 3)
In the formation of the adhesive layer of Example 1, a continuous belt-like laminate was obtained in the same manner as in Example 1 except that 10 parts by mass of A3070 was used as the curing agent without using D140N.

(Comparative Example 4)
In the formation of the adhesive layer of Example 1, A310: trade name, product of Mitsui Chemicals Polyurethanes Co., Ltd. (weight ratio of soft segment (A) and hard segment (B) ((A) :( A continuous belt-like laminate was obtained in the same manner as in Example 1 except that B)) was 100: 0).

(Evaluation results)
The following points were evaluated with respect to the above examples and comparative examples. The results are listed in Table 1. (1) Presence / absence of yellowing of the adhesive layer after the etching treatment Presence / absence of yellowing of the adhesive layer after the etching process using the photolithography method is performed on the above-described continuous band-shaped laminate according to the following conditions. Was visually observed.
<Judgment>
-The adhesive layer did not turn yellow: ○
・ Yellowing of the adhesive layer was observed, but the degree was minor: △
・ Adhesive layer turns yellow, remarkable: ×
(Condition 1)
Etching using the photolithography method is performed on the above-described continuous strip-shaped laminate by forming a conductive pattern layer including an opening portion and a line portion as a conductive pattern layer, and an outer edge that surrounds the four circumferences of the conductive pattern layer. A frame-shaped non-forming area for grounding was formed in the part. The mesh shape was a square lattice having square openings, the line width was 10 μm, and the opening width (side length of the square) was 300 μm. One rectangular area having the mesh shape corresponds to one screen of the PDP. Such rectangular mesh-like areas are arranged on one side at intervals of 30 mm in the form of a continuous band, and margins having a width of 15 mm are formed on both sides of the arrangement of the mesh-like areas, and the width of the grounding area at the peripheral part is increased. It was 15 mm.
Specifically, the etching was performed consistently from resist formation, masking to etching on the laminate using a production line for a color TV shadow mask. That is, after applying a photosensitive etching resist to the entire surface of the conductive layer of the laminate, a mask with a desired mesh pattern is closely exposed, developed, hardened, and baked on the area corresponding to the line portion of the mesh. After the resist layer is processed into a pattern in which the resist layer remains and there is no resist layer on the region corresponding to the opening, the resist layer is formed in a non-resist layer formation region by dipping in a ferric chloride aqueous solution at 50 ° C. for 1 minute. The conductive layer was removed by etching to form a mesh-shaped opening, and then washed with water, stripped of the resist, washed, and dried sequentially.
(Condition 2)
In condition 1, etching was performed in the same manner as in condition 1 except that the laminate was immersed in a ferric chloride aqueous solution at 50 ° C. for 2 minutes.
(2) Haze Transparent adhesive TD-06A / Toyo of Yodogawa Paper Mill using Vinciroll, a handler minator made by DNK, on the adhesive layer surface of the laminate subjected to the whole surface etching treatment according to the above conditions 1 and 2. A spinning PET film A4300 (100 μm) was bonded. After the pasting, a clearing treatment was performed under the conditions of 70 ° C., 0.5 MPA, 30 min using an autoclave treatment apparatus HP-9515OMA manufactured by Kyoshin Engineering. About the sample which carried out the transparent process, HM-150 which is HAZEMETER of Murakami Color Research Laboratory was used, incident light source from PET surface, and measured HAZE.
<Judgment>
・ 5% or less: ○
・ Over 5%: ×
(3) Image sharpness Transparent adhesive TD-06A / Toyo from the Yodogawa Paper Mill using Vinciroll, a DNK handlerminator, on the adhesive layer surface of the laminate subjected to the whole surface etching treatment according to the above condition 1 A spinning PET film A4300 (100 μm) was bonded. After the pasting, a clearing treatment was performed under the conditions of 70 ° C., 0.5 MPA, 30 min using an autoclave treatment apparatus HP-9515OMA manufactured by Kyoshin Engineering. PDP (Pioneer's product name “PDP-435HDL (42 inches)”, image quality (brightness and contrast) set to “standard” mode) is displayed as an image, and transparent of each example and comparative example is displayed on the front. All the samples subjected to the conversion processing were placed side by side, and the image sharpness was determined by visually observing whether the black-and-white boundary of the pattern was clearly visible without any image distortion or distortion.
<Judgment>
・ The image looks clear with no distortion or distortion: ○
・ You can see slack and distortion in the image: ×
(4) Microbubbles About the laminated body which performed the whole surface etching process according to said conditions 1, the microbubble was observed from the PET surface using the digital microscope VHX-100F by Keyence Corporation.
<Judgment>
・ Microbubbles were not mixed in the adhesive layer: ○
・ Microbubbles were mixed in the adhesive layer: ×
(5) Mesh adhesion strength For the laminate subjected to the whole surface etching treatment according to the above condition 1, a cellophane adhesive tape was stuck on the mesh and peeled by hand, and it was confirmed that there was no peeling.
<Judgment>
・ Cellophane tape did not come off: ○
・ Cellophane tape peeled off: ×

(Summary of results)
From Table 1 above, in Examples 1 and 2, the adhesive layer after curing does not turn yellow, it is possible to suppress the mixing of microbubbles into the adhesive layer, and suppress the increase in haze, The image sharpness and the adhesion with the conductive pattern layer could be excellent. On the other hand, in Comparative Example 1 in which the weight ratio of the curing agent was outside the range specified in the present invention, the image was distorted and the image sharpness was lowered. Moreover, in Comparative Example 2 using only the curing agent containing IPDI, since there is no initial adhesion, the electrolytic copper foil cannot be dry-laminated on one side of the PET film via the adhesive layer. Each evaluation could not be performed. In Comparative Example 3 using only the curing agent containing HDI, the image was distorted and the image sharpness was lowered. Further, in Comparative Example 4 using the main agent containing only the soft segment, yellowing occurred to the extent that it can be visually discerned as compared with the Examples, even when etched and processed under the same conditions as in each Example.

It is a cross-sectional schematic diagram of an example of the electromagnetic wave shielding sheet for a display according to the present invention. It is a top view of an example of the electroconductive pattern layer used for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electromagnetic wave shielding sheet 10 Transparent base material 11 Adhesive layer 12 Conductive pattern (mesh) layer 13 Blackening layer 20 Plasma display panel 121 Mesh area 122 Grounding area

Claims (3)

In one surface of the transparent substrate, an electromagnetic wave shielding sheet provided with a conductive pattern layer via an adhesive layer,
The adhesive layer is
(I) formed from an adhesive containing a polyester urethane polyol containing a soft segment (A) and a hard segment (B) as a main agent, and (II) a curing agent containing isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI) And the weight ratio of the soft segment (A) to the hard segment (B) ((A) :( B)) in the main agent is 60:40 to 90:10, and the isophorone diisocyanate (IPDI) The electromagnetic wave shielding sheet, wherein a weight ratio (IPDI: HDI) of the hexamethylene diisocyanate (HDI) is 50:50 to 80:20.   2. The electromagnetic wave shielding sheet according to claim 1, wherein the polyester urethane polyol has a glass transition temperature in the range of 20 to 40 ° C. 3.   3. The electromagnetic wave shielding sheet according to claim 1, wherein an amount of the curing agent is in a range of 4 to 30 parts by weight with respect to 100 parts by weight of the main agent.

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