JP2007227532A - Electromagnetic wave shielding sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic wave shielding sheet that is controlled in reflectivity of external light and has improved close contact with the other laminated film. <P>SOLUTION: In the electromagnetic wave shielding sheet wherein at least a mesh-type conductor layer 12 is provided to a surface of a transparent base material 11, the relevant conductor layer 12 includes a metal plated layer 14. In the relevant metal plated layer 14, a crystal grain diameter at the front surface in the opposite side of the transparent base material 11 is increased in comparison with a crystal grain diameter at the front surface in the side of the transparent base material 11 facing to the thickness direction x. <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.

  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. A plasma display panel is a combination of a glass having a data electrode, 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, a front plate including an electromagnetic wave shielding sheet is provided 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. In the present specification, the term “electromagnetic wave” simply means an electromagnetic wave having a frequency in the kHz to GHz band centered on the above range, and does not include infrared rays, visible rays, ultraviolet rays, X-rays, and the like. (For example, electromagnetic waves having a frequency in the infrared band are referred to as infrared rays).

The electromagnetic wave shielding sheet used for such applications is required to have optical transparency as well as electromagnetic shielding performance. Therefore, as an electromagnetic wave shielding sheet, a transparent conductive ITO (Indium Tin Oxide) film provided on the entire surface of a transparent substrate (Patent Document 1, etc.) or a transparent substrate made of a resin film is bonded with an adhesive. A metal foil such as copper foil is etched to form a mesh (Patent Document 2 etc.).
However, those using a transparent conductive film of ITO have a problem that it is difficult to achieve both high light transmittance and high electromagnetic shielding properties. In addition, when the metal foil is bonded to a transparent base material and etched into a mesh shape, a rough surface transferred from the metal foil is formed on the adhesive surface exposed in the opening, and the transmission image becomes cloudy, and When another substrate such as an infrared absorption filter is laminated on the mesh surface via an adhesive layer, there is a problem in that the adhesive is not completely filled in the opening, and bubbles remain, which further causes white turbidity.

  In order to solve this problem, it has been attempted to form a metal layer, which becomes a conductive layer, directly on the transparent substrate without using an adhesive layer by a plating method. For example, (1) a method in which conductive ink is printed in a pattern on a transparent substrate, and metal plating is performed on the patterned conductive ink layer (Patent Document 3, etc.); A method in which a photosensitive coating solution containing ink or a chemical plating catalyst is applied to the entire surface, the coating layer is made into a mesh by photolithography, and then metal plating is performed on the mesh (Non-Patent Document 1, etc.), (3) A method in which a conductive treatment layer is applied on a transparent substrate, a metal plating layer is formed thereon by electrolytic plating, and then the metal plating layer and the conductive treatment layer are meshed by a photolithography method (Patent Document 4). Are known. When the metal layer to be the conductive layer is formed by plating, it is less likely to warp than when the metal foil bonded with an adhesive is used as the conductive layer, and is transferred to the adhesive surface of the mesh opening. There is no deterioration in transparency due to the roughness of the metal foil, and it is possible to form a thin film, and there is an advantage that bubbles are less likely to be mixed into the mesh opening when the optical filter and the mesh are bonded as described later. .

  In addition to the electromagnetic wave shielding function, the front plate placed on the front of the display blocks unnecessary light emitted from the display (for example, light with a wavelength of about 590 nm due to neon light emission in PDP), and adjusts the hue of the image to reproduce the color. There are cases where a function to improve the performance, a function to suppress unnecessary reflection of external light, a function to suppress unnecessary infrared radiation from the display and to prevent malfunction of an infrared using device may be required. Therefore, as the actual front plate, an electromagnetic wave shielding sheet and an optical filter having other filter functions, for example, a color filter, an antireflection filter, a near-infrared absorption filter, etc., laminated and integrated into a composite filter are used. (For example, Patent Document 5).

JP-A-1-278800 Japanese Patent Laid-Open No. 10-41682 JP 2000-13088 A Japanese Patent Laid-Open No. 2004-241761 JP 2003-86991 A 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. Month 7 Search], Internet <URL: http: // www. socnb. com / product / hproduct / display. html>

When the conductor layer is formed by the plating method as described above, it has the above-mentioned merits, but on the other hand, the gloss of the surface of the metal plating layer is usually high, and the metal that reflects and reflects external light as a mirror. There is a problem that the gloss reduces the bright room contrast of the fluoroscopic image. Further, in this case, the surface smoothness is usually high, and there are cases in which the adhesive force is insufficient when another layer is laminated on the surface of the metal plating layer via an adhesive layer. These were thought to be due to the small crystal grain size of the metal plating layer.
However, in order to increase the crystal grain size on the surface of the metal plating layer more than desired, for example, in the case of electrolytic plating, a large current density is required. Therefore, a transparent substrate, an underlayer of a thin film for plating, or precipitation There has been a problem that the thin film plating layer or the like that is started generates heat due to Joule heat and is dissolved or altered.

  The present invention has been made in consideration of the above problems, and provides an electromagnetic wave shielding sheet in which the reflectance of external light is suppressed and the adhesion to other laminated films is improved. Objective.

The electromagnetic wave shielding sheet provided by the present invention is an electromagnetic wave shielding sheet in which at least a mesh-like electric conductor layer is provided on one surface of a transparent substrate, and the electric conductor layer includes a metal plating layer, In the metal plating layer, the crystal grain size on the surface opposite to the transparent base material is increased as compared with the crystal grain size on the surface of the transparent base material facing the thickness direction.
In the electromagnetic wave shielding sheet according to the present invention, in the metal plating layer, the crystal grain size of the surface opposite to the transparent substrate is increased compared to the crystal grain size of the surface of the transparent substrate facing the thickness direction. Therefore, when forming the interface between the transparent substrate and the conductor layer, it is possible to form a metal plating layer with a large crystal grain size on the conductor layer surface side without dissolving or altering the interface by reducing the crystal grain size. Therefore, the roughness and unevenness of the surface of the conductor layer are increased, the reflectance of external light is suppressed, and the adhesion with other laminated films is improved by the anchoring effect.

  In the electromagnetic wave shielding sheet according to the present invention, in the metal plating layer, the crystal grain size of the surface opposite to the transparent substrate is increased compared to the crystal grain size of the surface of the transparent substrate facing the thickness direction. Therefore, when forming the interface between the transparent substrate and the conductor layer, it is possible to form a metal plating layer with a large crystal grain size on the conductor layer surface side without dissolving or altering the interface by reducing the crystal grain size. Therefore, the roughness and unevenness of the surface of the conductor layer are increased, the reflectance of external light is suppressed, and the adhesion with other laminated films is improved.

Hereinafter, the present invention will be described in detail.
The electromagnetic wave shielding sheet provided by the present invention is an electromagnetic wave shielding sheet in which at least a mesh-like electric conductor layer is provided on one surface of a transparent substrate, and the electric conductor layer includes a metal plating layer, In the metal plating layer, the crystal grain size on the surface opposite to the transparent base material is increased as compared with the crystal grain size on the surface of the transparent base material facing the thickness direction.
Here, in the present invention, the crystal grain size is an average crystal grain size, for example, on a specific surface of the metal plating layer or on a plane parallel to the transparent substrate at a specific position in the thickness direction of the metal plating layer. These crystal grains were measured by observing the crystal grains under a microscope and averaging the individual crystal grain sizes. (Average value {D (x)} in which crystal grain diameter D (x) existing on a plane parallel to the transparent substrate at a position x in the thickness direction is averaged in the plane) In the present invention, therefore, metal The average crystal grain size of the surface opposite to the transparent substrate in the plating layer is increased as compared with the average crystal grain size of the portion on the surface of the transparent substrate facing the thickness direction of the portion. The function {D (x)} in the thickness direction x is an increasing function when the transparent substrate surface is x = 0 and the growth direction of the metal plating layer is x> 0. The increasing function includes a monotonically increasing function in a narrow sense or a broad sense, and a one-step or multi-step step function including a region having a slope of zero.

An example of the electromagnetic wave shielding sheet according to the present invention is shown in FIG. FIG. 1A is a plan view of an example of an electromagnetic wave shielding sheet used in the present invention, and FIG. 1B is a cross-sectional view of an example of an electromagnetic wave shielding sheet used in the present invention.
As shown in FIG. 1A, the electromagnetic wave shielding sheet 1 of the present invention includes a mesh region 101 that can cover all image display regions of a display to be applied in the plane direction, and the mesh region. A conductor layer 12 having a grounding region 102 is formed on at least a part of the periphery of the substrate.
The mesh area 101 has a size and a shape that can cover the entire image display area of the applied display, and always includes a portion 30 that faces the image display area of the applied display. The outer edge portion that is an area outside the portion 30 facing the image display area of the display may include the mesh-shaped area 101 or may include only the grounding area 102. The grounding region 102 normally has the same layer configuration as the mesh region 101 but does not form an opening, and is provided to facilitate grounding when installed on a display. The grounding region 102 may have a mesh shape in which an opening is formed. The grounding region 102 is often provided in a frame shape around the four sides in a portion that does not affect image display, which is an outer edge portion that is an outer region of the portion 30 facing the image display region of a rectangular display, The form may be provided not only on the entire periphery of the mesh region 101 but on a part of the periphery, or may be provided on only three sides, two sides, or one side.

As shown in FIG. 1B, the electromagnetic wave shielding sheet 1 of the present invention is a conductor having a mesh region 101 and a grounding region 102 on one surface of a transparent substrate 11 in the thickness direction. The layer 12 is formed by stacking at least. In the example of FIG. 1B, the conductor layer 12 includes a conductive treatment layer 13 that is a base layer in addition to the metal plating layer 14. The conductor layer 12 in this example includes a conductive treatment layer 13 that is a base layer and a metal plating layer 14 that is a main part of the conductor layer. The conductor layer 12 may be composed of only a mesh-like metal plating layer, or may include other layers other than the conductive treatment layer 13. The electromagnetic wave shielding sheet of the present invention may be formed by further laminating a non-conductive layer on the front and back surfaces of the conductor layer. Examples of the non-conductive layer include a rust preventive layer and a blackened layer that do not have conductivity. Even if it is a rust prevention layer, a blackening layer, etc., as long as it has electroconductivity, it is contained in a conductor layer in this invention. The non-conductive layer further laminated on the front and back surfaces of the conductor layer is integrated with the conductor layer to form a mesh region and a grounding region.
The electromagnetic wave shielding sheets shown in the figure are all formed into single sheets. However, in the present invention, the electromagnetic wave shielding sheets are in a state of a continuous belt-like sheet including sections of two or more single sheets. Also good.

Hereinafter, the electromagnetic wave shielding sheet of the present invention will be described in order from the transparent substrate 11.
[Transparent substrate]
The transparent substrate 11 is a layer for reinforcing a 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. As a specific example of the transparent substrate, for example, a plate, sheet, or film made of a transparent material such as resin or glass is used.
Examples of the resin include polyester resins such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, terephthalic acid-isophthalic acid-ethylene glycol copolymer, terephthalic acid-cyclohexanedimethanol-ethylene glycol copolymer, nylon 6, and the like. Polyamide resins, polyolefin resins such as polypropylene and polymethylpentene, acrylic resins such as polymethyl methacrylate, styrene resins such as polystyrene and styrene-acrylonitrile copolymers, cellulose resins such as triacetyl cellulose, and imides Examples thereof include resins and polycarbonate resins.
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.

Examples of the glass include quartz glass, borosilicate glass, and soda lime glass. More preferably, the glass has a low coefficient of thermal expansion, excellent dimensional stability and workability in high-temperature heat treatment, and does not contain an alkali component in the glass. Examples include alkali-free glass and the like, which can also be used as an electrode substrate used 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, if the thickness is less than the above, the mechanical strength is insufficient, causing warping, sagging, breakage, etc. If the thickness exceeds the above, it becomes excessive performance and high cost, and thinning is difficult. .

The transparent substrate may also be used as a front substrate which is a component of the display main body, but as a front filter disposed in front of the front substrate, an electromagnetic shield filter to which a function other than the electromagnetic shield is added is used. Then, 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 does not break.
In addition, the transparent base material is preferably 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 produced and productivity can be improved. .
In this respect, a resin sheet is a preferable material for the transparent substrate. In addition, when using a flexible resin sheet as a transparent base material compared to the case of using a rigid transparent base material such as a glass plate, there is a risk that the metal plating layer may be damaged when the intermediate product is processed. large. Therefore, the present invention is particularly preferably applied to an electromagnetic wave shielding sheet using a resin sheet as the transparent substrate.

Among the resin sheets, polyester resin sheets such as polyethylene terephthalate and polyethylene naphthalate are particularly preferable in terms of transparency, heat resistance, cost, and the like, and more preferably a biaxially stretched polyethylene terephthalate sheet. 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.
In addition, a transparent substrate such as a resin sheet is appropriately coated on the surface thereof with known easy processes such as corona discharge treatment, plasma treatment, ozone treatment, flame treatment, primer treatment, pre-heat treatment, dust removal treatment, vapor deposition treatment, and alkali treatment. An adhesion treatment may be performed.

[Conductor layer]
The conductor layer 12 is a layer having conductivity, and is a layer responsible for an electromagnetic wave shielding function. Even if the conductive layer 12 itself is opaque, the presence of an opening in a mesh shape causes an electromagnetic wave shield. It balances performance and light transmission. An example of the conductor layer 12 forming the mesh region 101 is shown in FIG. The conductor layer 12 forming the mesh-like region 101 has a mesh shape in which the openings 103 are densely arranged, and the mesh-like region forms a frame that divides the opening 103 from each opening. The line unit 104 is configured.

In the present invention, the conductor layer 12 includes a metal plating layer 14 as a main layer and may consist of only the metal plating layer 14. It includes a conductive treatment layer 13 to be a ground layer, and optionally further includes a blackening layer and a rust prevention layer having conductivity as described later.
The shape of the mesh is arbitrary and not particularly limited, but the shape of the opening is typically a 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 gaps between the openings are usually line portions having a uniform width. Usually, the openings and the line portions have the same shape and the same size on the entire surface. As an example of a specific size, the width of the line portion 104 between the openings is referred to as a line width W as shown in FIG. 2 in terms of the aperture ratio and the mesh invisibility, and is 25 μm or less, preferably 20 μm or less. It is preferable that However, it is preferable to secure a line width W of at least 5 μm or more in order to exhibit the electromagnetic wave shielding effect and prevent 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 the present invention, the total thickness of the line portions in the finally obtained mesh region, that is, the height H of the line portions 104 between the openings is 20 μm or less, and 1 μm or more from the viewpoint of electromagnetic shielding properties. The thickness is preferably 2 μm or more and 10 μm or less, and particularly preferably about 3 μm from the viewpoint of preventing bubbles from remaining in the openings when the adhesive layer is applied on the mesh region.
In addition, the height H of the line part of a mesh-shaped area | region says the total thickness including all the thickness of the layer which forms the line part 104. FIG. For example, when the line part 104 is composed of only a conductor layer, the height of the line part is equal to the thickness of the conductor layer. For example, the line part has a conductor layer, a non-conductive blackening layer, and a non-conductive layer. In the case of the conductive rust preventive layer, the height of the line portion is the total thickness of the conductor layer, the nonconductive blackened layer, and the nonconductive rust preventive layer.
If the total thickness of the line portion is too large, the level difference between the line portion and the opening becomes large when processed into a mesh, and bubbles tend to remain when the adhesive layer is laminated. Further, if the thickness of the line portion is further increased, it becomes difficult to obtain a desired high-definition mesh shape by side etching or the like during etching.
In contrast, when the total thickness of the line portion including the metal plating layer is 20 μm or less, it is possible to save the amount of copper used and flatten the mesh surface. In particular, when the total thickness of the line portion is about 3 μm, the flattening effect is great. In such a case, even when the step of flattening the mesh surface is omitted in advance before the lamination with the optical filter, the adhesive is placed in the opening of the metal mesh when the electromagnetic wave shielding sheet and the optical filter are laminated and bonded. This is because the layer easily enters uniformly, and bubbles do not easily remain in the opening. In this case, the disadvantage that the haze of the composite filter due to the light scattering of the bubbles can be avoided, and a composite filter with high transparency can be obtained with high production efficiency.
On the other hand, if the total thickness H of the line portion is too small, the thickness of the conductor layer is too small, so that the electric resistance value of the metal is increased and the electromagnetic wave shielding effect is easily impaired. Considering the electromagnetic shielding function, the thickness of the conductor layer including the metal plating layer is preferably 1 μm or more, and more preferably 2 μm or more in the case of the line width and line pitch. Therefore, the height of the line part of the mesh region is preferably 1 μm or more, and more preferably 2 μm or more.
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. .

As a method for preparing an electromagnetic wave shielding sheet including at least a conductor layer having a mesh-like region and including a metal plating layer having a different crystal grain size in the thickness direction in the conductor layer, It does not restrict | limit in particular, For example, the following three methods are 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) A conductive film is formed by forming a metal thin film on one surface of the transparent substrate by sputtering or the like, and a transparent substrate having a metal plating layer formed thereon by electrolytic plating is prepared. The metal plating layer and the conductive treatment layer on the 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).

Among these, in the present invention, the method of (3) above is particularly advantageous because the display image can be seen well because it is excellent in transparency and mesh accuracy, and can be manufactured in a short process with good yield and low cost. It is particularly preferable to use Therefore, a method for forming a mesh-like conductor layer by the method (3) will be described in detail.
An example of an electromagnetic wave shielding sheet formed by the method (3) above, in which a conductive layer forming a mesh-like region is laminated on one surface of a transparent substrate, is shown in FIG. 3 is a cross-sectional view taken along line AA and BB in FIG. In each figure, the scale in the thickness direction (vertical direction in the figure) is greatly enlarged from the actual size as compared with the scale in the plane direction (horizontal direction in the figure). In addition, the scale of the conductive layer 12 is exaggerated and greatly enlarged as compared with the scale of the transparent substrate 11. 3A shows an AA cross section that crosses the opening, and the openings 103 and the lines 104 are alternately formed. FIG. 3B shows a BB cross section that runs through the line 104 and is formed of the conductor layer 12. Lines 104 are formed continuously. In FIG. 3, the conductor layer 12 has a conductive treatment layer 13, a first blackening layer 15 </ b> A, a metal plating layer 14, a second blackening layer 15 </ b> B, and a rust prevention layer 16 from the side close to the transparent substrate 11. However, it has the structure laminated | stacked in this order. Of these layers, the minimum required one is the metal plating layer 14. Other layers are provided as necessary.

(Formation of conductive treatment layer)
In the above method (3), a conductive treatment layer is formed on the transparent substrate 11 as described above prior to metal electroplating described later. As a method for the conductive treatment, a thin film of a known conductive material may be formed. Examples of the conductive material include metals such as gold, silver, copper, nickel, and chromium, or alloys of these metals (for example, nickel-chromium alloy). Moreover, transparent metal oxides, such as a tin oxide, ITO, and ATO, may be sufficient. The conductive treatment may be a single layer or multiple layers (for example, a laminate of a nickel-chromium alloy and a copper layer), and these materials are formed by a known vacuum deposition method, sputtering method, electroless plating method, or the like. The conductive treatment layer 13 is used. The thickness of the conductive treatment layer 13 is preferably an extremely thin layer of about 0.001 to 1 μm, as long as necessary conductivity can be obtained at the time of plating.

(Metal plating layer)
The metal plating layer is an essential layer in the conductor layer of the electromagnetic wave shielding sheet according to the present invention, and refers to a metal layer formed by an electrolytic plating method. Regardless of whether it is formed by the above method (3), it has the following characteristics.
In FIG. 4, the partial expanded cross-section schematic diagram of an example of the electromagnetic wave shielding sheet used for this invention is shown. The conductor layer 12 of the present invention includes a metal plating layer 14, and in the metal plating layer 14, the crystal grain size of the surface 21 opposite to the transparent substrate is the transparent substrate side surface 22 facing the thickness direction x. It is increased compared to the crystal grain size. If the crystal grain size of the surface 21 opposite to the transparent substrate is larger than the crystal grain size of the transparent substrate side surface 22 facing the thickness direction x, as described above, how to increase the crystal grain size Is not particularly limited, but preferably increases in the direction 23 away from the transparent substrate 11 side in the thickness direction. In such a case, since the crystal grain size is large on the outer surface (surface 21 opposite to the transparent substrate) of the conductor layer 12 facing the viewer side of the display device, the specular reflection of extraneous light is reduced. , Preventing whitening of the image and improving the contrast. On the other hand, since the crystal grain size on the surface of the transparent substrate can be reduced, the current density at the time of electrolytic plating can be suppressed, and dissolution or alteration during the production of the metal plating layer can be prevented.

The manner in which the crystal grain size increases as the distance from the transparent substrate 11 increases in the thickness direction may be continuously increased gradually or may be increased discontinuously and gradually. When continuously increasing gradually, stress applied to the metal plating layer does not concentrate at the interface where the crystal grain size changes discontinuously, so that the electromagnetic shielding sheet is less likely to warp or peel off at the interface. It is preferable from the point. In the present invention, if the crystal grain size of the surface 21 opposite to the transparent substrate is larger than the crystal grain size of the transparent substrate side surface 22, the crystal grain size in the thickness direction is not necessarily Even if it does not increase monotonously, a portion where the crystal grain size partially decreases in the thickness direction may be included.
In addition, as a method of obtaining the average crystal grain size {D (X)} in the in-plane direction at the position of the thickness direction x = X, a portion of x> X is polished or corroded from the surface of the metal plating layer. , X = X surface is exposed, and the exposed surface is lightly corroded or dyed as necessary to emphasize the grain boundary and then take a micrograph to measure the particle size. is there. In addition, in the manufacturing process of the metal plating layer, the plating may be stopped when the metal plating layer has grown to x = X, and the x = X plane may be measured by the same method as described above.

In the electromagnetic wave shielding sheet according to the present invention, in the metal plating layer, the crystal grain size on the surface opposite to the transparent substrate has a suitable value depending on the layer thickness of the metal plating layer. % To about 67% is preferable. On the other hand, the crystal grain size on the transparent substrate side surface is preferably 1.5 μm or less. In such a case, even when the metal plating layer is manufactured by electrolytic plating, the reflectance of outside light is suppressed without causing the problem of dissolution or alteration at the interface with the transparent substrate, and other laminated layers An electromagnetic wave shielding sheet having improved adhesion to the film can be suitably obtained. In the metal plating layer, the crystal grain size on the surface opposite to the transparent substrate is more preferably 50% to 60% of the layer thickness of the metal plating layer. The crystal grain size on the surface opposite to the transparent substrate is usually 20 μm or less from the viewpoint of suitability for etching. On the other hand, the crystal grain size on the transparent substrate side surface is more preferably 1.0 μm or less. The crystal grain size on the transparent substrate side surface is usually 0.5 μm or more from the viewpoint of the suitability for etching and the efficiency of plating time.
Further, in the electromagnetic wave shielding sheet according to the present invention, the difference between the crystal particle size of the surface of the metal plating layer on the transparent substrate side and the crystal particle size of the surface opposite to the transparent substrate is a layer of the metal plating layer. The reflectance of external light is suppressed by the large crystal grain size on the surface of the metal plating layer while preventing the problem of dissolution or alteration in manufacturing that the thickness is about 30 to 60%, and further about 40 to 60%. From the point that the adhesion with other laminated films is improved.

  In the metal plating layer 14, if the crystal grain size of the surface 21 opposite to the transparent substrate is larger than the crystal grain size of the transparent substrate side surface 22 facing the thickness direction x, the transparent substrate becomes a transparent substrate. The distribution of the crystal grain size in the parallel plane is not particularly limited, but the crystal grain size in the plane parallel to the transparent substrate is from the point of uniformity of physical properties such as light reflectivity and mechanical strength of the metal plating layer. Preferably they are substantially the same. As described above, since the metal plating layer is deposited by growing metal crystals upward from the base surface, it is considered that the crystals in the plane parallel to the transparent substrate are usually grown almost simultaneously. The crystal grain size in the plane parallel to the transparent substrate is usually aligned to a value close to the average value (statistical dispersion is small).

An example of a method for forming the metal plating layer 14 on the surface of the conductive treatment layer 13 is an electrolytic plating method. In the present invention, by forming a metal layer by a plating method, the metal layer can be formed efficiently without requiring a step of bonding a metal foil such as a copper foil. In particular, when it is desired to form an extremely thin metal layer (for example, 5 μm or less), it is very difficult to handle the metal foil in the step of laminating the metal foil, and damage is likely to occur. A thin metal layer can be easily formed.
As a material of the metal plating layer 14, for example, gold, silver, copper, iron, nickel, chromium, cobalt, or the like having a conductivity sufficient to shield electromagnetic waves, or a mixture of two or more of these metals may be used. An alloy containing a metal is applicable. The metal plating layer 14 may not be a simple substance, but may be a multilayer, and copper or a copper alloy is preferable from the viewpoint of ease of electrolytic plating and conductivity. Examples of the copper alloy include those mainly containing copper and containing other metals such as gold, silver, copper, iron, nickel, chromium, and cobalt. When the metal plating layer is a mixture of copper and another metal or a copper alloy, the copper content is preferably 90% by weight or more of the total metal components, and more preferably 95% by weight or more. preferable.

The metal plating layer is considered to be deposited and formed by growing metal crystals upward from the base surface. Therefore, as a method for increasing the crystal grain size of the surface 21 opposite to the transparent substrate in the metal plating layer as compared with the crystal grain size of the transparent substrate side surface 22 facing the thickness direction x, for example, There is a method of increasing the current density sequentially as the metal grows in the thickness direction using the electrolytic plating method. In this case, for example, the current density is set to 0.1 to 0.5 A / dm ² at the start of plating, and thereafter gradually increased or gradually increased stepwise, and at the end of plating, the current density is set to 5 to 10 A / dm ^2. it can be a dm ^2. By continuously increasing the current density increasing method, the crystal grain size can be increased continuously in the thickness direction. Further, by increasing the current density stepwise, the crystal grain size can be increased stepwise in the thickness direction. Another method for increasing the crystal grain size of the surface 21 opposite to the transparent substrate relative to the crystal grain size of the transparent substrate side surface 22 opposite to the thickness direction x is to crystallize the metal in the thickness direction. A method of sequentially changing the plating bath composition as it grows can be mentioned. Examples of the change in the plating bath composition in this case include changing the concentration of the compound that supplies metal ions to be deposited, such as the copper sulfate concentration, and the type and amount of the additive.

As the metal plating solution in the case of using the electrolytic plating method, a known plating bath such as a copper sulfate bath, a copper bromide bath, a copper borofluoride bath, a copper pyrophosphate bath, etc. can be used. A copper sulfate bath is used. As the composition of the copper sulfate bath, for example, a copper sulfate and an aqueous solution containing sulfuric acid and a plating additive for adjusting crystals are added. The sulfuric acid concentration is about 150 to 220 g / L (liter), and the copper sulfate concentration is about 50 to 85 g / L for pentahydrate.
Examples of the crystal controlling component contained in the plating additive include known compounds such as hydrocarbon polymer compounds, sulfur-containing hydrocarbon compounds, proteins, glues, amines, alkaloids, mercaptans, sulfides, and various dye compounds. . One or two or more such crystal controlling components may be appropriately selected and used. The addition amount of the crystal adjusting component is about 1 to 100 g / L. This type of additive generally reduces the crystal grain size as the amount added is increased. Further, if necessary, hydrochloric acid may be added at a chlorine concentration of about 40 to 80 mg / L in order to roughen the surface of the metal plating layer.

Specific examples of plating conditions include a bath temperature of 20 to 30 ° C., a current density of 0.1 to 10 A / dm ² , a plating time of 30 minutes to 2 hours, and stirring of the plating bath. After the plating layer is deposited, it is preferable to perform an annealing treatment as necessary in order to stabilize the crystal orientation. The annealing conditions are, for example, 100 to 200 ° C., 30 minutes to 2 hours.

  The thickness of the metal plating layer is preferably as thin as possible within a range where sufficient shielding performance and physical properties that do not break during the processing process can be obtained, but the thickness of the entire conductor layer including the metal plating layer is not limited. It is determined in consideration of the thickness of other layers within the range. From this viewpoint, the thickness of the metal plating layer 14 included in the conductor layer is preferably 20 μm or less, more preferably 5 μm or less, and the inside of the opening when the adhesive layer is applied on the mesh region. It is particularly preferable that the thickness be about 3 μm from the viewpoint of preventing residual bubbles. In addition, the thickness of the metal plating layer 14 is preferably 1 μm or more, and more preferably 2 μm or more from the viewpoint of electromagnetic shielding properties.

Further, the total light reflectance was measured in accordance with JIS Z8722 of the metal plating layer surface _{(R SCI)} is less than 40%, not more than an additional 30% conform to JIS Z8722 mesh-like conductor layer surface Therefore, it is easy to make the total light reflectance ( _RSCI ) measured in this way 20% or less, which is preferable from the viewpoint of improving the bright room contrast of the fluoroscopic image.

(Blackening layer)
The present invention is intended to improve the bright room contrast by increasing the crystal grain size on the side opposite to the transparent base material of the conductor layer. In order to further improve such contrast, It is preferable that a blackening process is performed on the observation side of the conductor layer 12 forming the mesh-like region so that external light incident on the electromagnetic wave shielding sheet is absorbed by the blackened surface. Further, the blackening layer may be provided on the display surface side. In this case, since the stray light generated from the display can be suppressed, the visibility of the image is further improved. For this purpose, as shown in FIG. 3A, a blackening layer 15A and / or 15B is provided on at least one surface of the metal plating layer 14 as necessary. The blackening layer is carried out by either roughening the surface of the metal plating layer 14, providing light absorption over the entire visible light spectrum (blackening), or using both in combination. Further, when a blackened layer is provided on the surface of the transparent substrate 11, the metal plated layer 14 may be provided after conducting a conductive treatment with the transparent conductive thin film on the transparent substrate and providing the black plated layer. .

A preferable blackening layer forming method when the metal plating layer contains copper is a cathode in which copper is subjected to cathodic electrolysis in an electrolytic solution composed of sulfuric acid, copper sulfate, cobalt sulfate, and the like, to attach cationic particles. Dick electrodeposition is an example. By providing the cationic particles, the surface becomes more rough, and at the same time, black is obtained. As the cationic particles, copper particles and alloy particles of copper and other metals can be used, but copper-cobalt alloy particles are preferred. The average particle diameter of the cationic particles is preferably about 0.1 to 1 μm from the viewpoint of black density.
In addition, as the blackening layer forming method, nickel-zinc alloy, nickel sulfide, or blackening nickel plating composed of a composite thereof, and copper oxide can also be suitably used.

  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.

(Rust prevention layer)
Furthermore, it is preferable to provide the rust preventive layer 16 so as to cover the surface of the metal plating layer 14 and when the blackened layer is provided, so as to cover the surface of the blackened layer 15B.
The rust preventive layer 16 is preferably provided at least on the blackened layer in order to prevent the rust preventing function and the blackened layer from dropping or deforming. As the rust preventive layer 16, an oxide of nickel, zinc and / or copper, or a chromate treatment layer can be applied. The nickel, zinc, and / or copper oxide may be formed by a known plating method, and the thickness is about 0.001 to 1 μm, preferably 0.001 to 0.1 μm.

(Mesh processing)
Next, the process of making the conductor layer on the transparent substrate provided as described above into a mesh by a photolithography method will be described.
First, a resist layer is provided on the surface of the conductive layer 12 on the transparent substrate prepared as described above, meshed, and the portion of the conductive layer 12 not covered with the resist layer is removed by etching. A mesh-like metal layer is formed by a so-called photolithography method for removing the layer. Furthermore, existing equipment can be used, and by performing many of these manufacturing processes continuously, quality is high, production efficiency is high, yield is high, and production can be performed at low cost.

(Masking process)
First, the surface on the conductor layer side of the laminate of the transparent base material 11 and the conductor layer 12 is made into a mesh shape by a photolithography method, and the mesh-like region 101 is formed. Also in this step, it is preferable to process a roll-shaped laminated body continuously wound in a band shape (referred to as a winding process or a roll-to-roll process). While the laminate is conveyed continuously or intermittently, masking, etching, and resist peeling are performed in a stretched state without looseness. When glass is used as the transparent substrate 11, it is processed one by one (referred to as single wafer processing or single wafer processing).
First, in the masking, for example, a photosensitive resist is applied onto the conductor layer 12 forming the mesh-like region, and after drying, contact exposure is performed with a photomask having a predetermined pattern, water development is performed, and film hardening is performed. Etc. and baking. Note that either a negative type or a positive type of photosensitive resist can be used. When the photosensitive resist is a negative type, it is assumed that the line portion of the mesh pattern of the photomask is transparent. When the photosensitive resist is a positive type, the mesh pattern of the photomask has a transparent opening. Further, the exposure pattern is a desired pattern as an electromagnetic wave shielding sheet, and is composed of a pattern of a mesh area at a minimum. Further, as necessary, a grounding area pattern is added to the outer periphery of the mesh area as shown in FIG.
In the winding process, the resist is applied by winding the belt-like laminated body (laminated body of the transparent base material 11 and the conductive layer 12) continuously or intermittently while forming the mesh-like region on the surface of the conductive layer 12 A resist such as casein, PVA, or gelatin is dipped (immersed), curtain coated, or poured. Moreover, a dry film resist may be used instead of application | coating, and workability | operativity can be improved. In the case of a casein resist, baking is performed at 200 to 300 ° C., but the lowest possible temperature is preferable in order to prevent warping of the laminate.

(Etching process)
Etching is performed after masking. As the etching solution used for the etching, an aqueous solution of ferric chloride or cupric chloride that can be easily circulated is preferable in the present invention in which etching is continuously performed. The etching is basically the same as the equipment for manufacturing a shadow mask for a color TV cathode ray tube that etches a strip-like continuous steel material, particularly a thin plate having a thickness of 20 to 80 μm. In other words, the existing manufacturing equipment for the shadow mask can be diverted, and from masking to etching can be produced consistently and continuously, which is extremely efficient. Single-wafer processing in the case of using glass as the transparent substrate 11 has also been performed for a long time. After etching, the substrate may be dried after washing with water, stripping the resist with an alkaline solution, and washing. Since the transparent base material is exposed on the surface of the mesh opening thus formed, the transparency of the mesh opening is good.
By the above mesh processing, a mesh-like conductor layer is formed and an electromagnetic wave shielding sheet is obtained.

(Physical property value)
Above manner, the total light reflectance of the obtained electric conductor layer surface (R _SCI) is evaluated by the value measured according to JIS Z8722 in the non-mesh portion is preferably 20% or less. In such a case, the external light reflectance after sticking the antireflection film is lowered, and the antireflection function is excellent. The total light reflectance ( _RSCI ) is preferably 3% or less.

  In addition, on the surface of the mesh-like conductor layer, a re-peelable protective film is usually temporarily laminated on the surface of the conductor layer until the next step (lamination of an antireflection film, etc.) starts. Moreover, it is preferable that the peeling resistance value with respect to the said protective film in the non-mesh part of the conductor layer surface is 0.1-3.3N / 25mm. In such a case, when another laminated film is laminated, the adhesiveness is sufficiently high so that it does not fall off spontaneously and can be easily peeled and removed when re-peeling is necessary. The peel resistance value for the protective film on the surface of the mesh-like conductor layer is preferably 0.1 to 0.5 N / 25 mm. Here, the peel resistance value for the protective film can be measured as follows. For example, a commercially available protective film (for example, C200 manufactured by Sanei Kaken Co., Ltd.) is cut out to a length of 150 mm and a width of 25 mm so that the adhesive layer side faces the mesh-like conductor layer surface side. Affixed to the degreased mesh-like conductor layer surface side, and using a tensile tester at a room temperature of 18-25 ° C., the mesh-like conductor layer surface and the protective film have an angle of 180 °. It can be measured as a tensile strength at the time of peeling by pulling in an atmosphere of 20 to 25 ° C. at a pulling speed of 300 mm / min.

(Addition of optical filter)
In the electromagnetic wave shielding sheet of the present invention, an optical filter may be further laminated and bonded to the side having the mesh-like conductor layer. As an optical filter, on the transparent base material of the optical filter, various function expressing layers such as a near infrared absorption layer (NIR layer), a neon light absorption layer, an ultraviolet absorption layer, an antireflection layer (AR layer), a hard coat layer. (HC layer), antiglare layer (AG layer), antifouling layer, etc., one or two or more laminated are used.
When the optical filter is laminated on the electromagnetic wave shielding sheet of the present invention, if the thickness of the conductor layer is relatively thick or the fluidity of the adhesive is relatively low, bubbles remain in the adhesive in the mesh opening. There are things to do. In this case, a planarizing layer is coated on the mesh-like conductor layer, and an optical filter is bonded onto the planarizing layer using an adhesive. The flattening layer may be one having high transparency, good adhesion to the conductive layer of the mesh, and good adhesion to the adhesive in the next step. The resin used for the flattening layer is not particularly limited, and various natural or synthetic resins can be applied. From the viewpoint of durability, applicability, ease of flattening, flatness, and the like, acrylic ultraviolet curable resins are used. Is preferred.

  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.

<Example 1>
(1) Production of Electromagnetic Wave Shielding Sheet 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 as the transparent substrate 11.
On the primer layer of the transparent substrate, a nickel-chromium alloy layer having a thickness of 0.1 μm and a copper layer having a thickness of 0.2 μm (a part of the conductor layer) are sequentially provided by sputtering. Treatment layer 13 was obtained.

A copper metal plating layer 14 (the remaining part of the conductor layer) having a thickness of 18.0 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 metal plating layer are provided. Both layers 14 were formed as the conductor layer 12. As a plating solution, water is used as a solvent, copper sulfate pentahydrate: 75 g / liter, sulfuric acid: 180 g / liter, chlorine (added as hydrochloric acid): 60 mg / liter, hydrocarbon polymer plating additive 1: A mixture of 40 ml / liter was used. The plating conditions are as follows. Bath volume: 500 ml, stirring: air stirring, bath temperature: 25 ° C., plating time: 40 min (target film thickness: 18 μm). The current density was 0.5 A / dm ² at the start of plating, and then gradually increased to 10 A / dm ² at the end of plating.
The crystal grain size immediately after the start of plating, that is, immediately above the conductive treatment layer surface (near the transparent substrate side surface of the metal plating layer) was 1 μm. A scanning electron micrograph immediately after the start of plating is shown in FIG. The crystal grain size at the end of plating was evaluated to be 12 μm. A scanning electron micrograph at the end of plating is shown in FIG.
The evaluation of the crystal grain size is based on a scanning electron micrograph of the surface of the metal plating layer, which is obtained by randomly extracting and measuring 10 in-plane crystal particle diameters, and calculating the arithmetic average value (unit: μm). ) Was calculated. When the particle shape was non-spherical, the calculation was performed by approximating the circumscribed circle diameter of the particle on the photograph.

Next, the conductive layer of the laminated sheet is etched by using a photolithography method to form a mesh region composed of the opening 103 and the line portion 104 and an outer edge portion that surrounds the four circumferences of the mesh region. A frame-shaped grounding area was formed.
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 shape of the mesh in the mesh area is as follows: the line width of the linear part whose opening is a square and non-opening is 10 μm, the line interval (pitch) is 300 μm, and the height of the line is 18.3 μm, rectangular When the sheet was cut into a single sheet, the bias angle defined as the subordinate angle with respect to the long side of the rectangle was 49 degrees. Further, when the completed composite filter 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 mesh region 101 is located at the periphery of the mesh region. Is designed in such a pattern that when the electromagnetic wave shielding sheet is cut into a rectangular sheet, a frame portion having a width of 15 mm without an opening is left as a grounding region on the outer periphery of the four sides. In this way, an electromagnetic wave shielding sheet was obtained.

<Comparative Example 1>
An electromagnetic wave shielding sheet was obtained in the same manner as in Example 1 except that the current density was 0.5 A / dm ² from the start to the end of plating when the metal plating layer 14 was formed. The crystal grain size immediately after the start of plating, that is, immediately above the conductive treatment layer surface (near the transparent substrate side surface of the metal plating layer) was evaluated in the same manner as in Example 1, and found to be 1 μm. Further, when the crystal grain size at the end of plating was evaluated in the same manner as in Example 1, it was 1 μm.

<Evaluation>
About the electromagnetic wave shielding sheets obtained in the above examples and comparative examples, reflection characteristics (external light reflectance by a single substance), antireflection performance (external light reflectance after applying an antireflection layer), and other laminated films The adhesion with was evaluated.
In addition, the reflection characteristics, light reflection prevention performance and adhesion of the conductor layer (in the above examples and comparative examples) are evaluated on the mesh layer surface of the non-mesh part on the outer periphery of the mesh part of the mesh layer. did. In addition, the anti-reflection performance can be eliminated at the non-mesh part (however, the inner part where the anti-reflective film is laminated through the transparent resin layer and has a wet color) because the influence of the opening of the mesh part can be eliminated. It was.

(1) Reflection characteristics The total light reflectance (%) measured in accordance with JIS Z8722 of the conductor layer is set by the spectrocolorimeter (manufactured by Konica Minolta Sensing Co., Ltd., CM-3600d) in the reflection mode. Uses a standard light D65 and a field of view of 2 °, and the detector measures the (integral) intensity of the total reflection light, which is the total of both diffuse reflection light and specular reflection light. The Y value (Y of tristimulus values XYZ) was measured by setting the mode (Component Included).

(2) Light reflection prevention performance The light reflection prevention performance of the electromagnetic wave shielding filter was evaluated by measuring the total light reflectance on the conductor layer side in a state of a wet color after laminating the transparent resin layer and the light reflection prevention film. (%) Was measured from the antireflection film side. The measuring method of the total light reflectance was the same as the measuring method of the total light reflectance in (1). The total light reflectivity (AR) in the wet color state is preferably small, and the case where the total light reflectivity is less than 5% is an allowable range for the light reflection preventing performance.

(3) Adhesiveness It evaluated by the peeling resistance value at the time of sticking an adhesive protective film (Transparent PET film / Acrylic adhesive layer; Sanei Kaken make, C200). That is, the adhesive protective film is cut out to a length of 150 mm and a width of 25 mm, and the adhesive layer side is directed to the conductor layer surface side so that the surface is degreased to the conductor layer surface side. Using a tensile tester, the conductor layer surface and the adhesive protective film are pulled in an atmosphere of 20 to 25 ° C. at a pulling speed of 300 mm / min in a direction where the angle between the two becomes 180 °, and at the time of peeling. Tensile strength was measured.

(Evaluation results)
Table 1 shows the test results for each electromagnetic wave shielding sheet.

  From the evaluation results, the electromagnetic wave shielding sheet having a conventional metal plating layer in which the crystal grain size on the transparent substrate side surface is 1 μm and the crystal grain size on the surface opposite to the transparent substrate is 1 μm has a high external light reflectance. Further, the light reflection preventing performance was also outside the allowable range, and the adhesion with other laminated films was also low. On the other hand, although the crystal grain size of the transparent substrate side surface is 1 μm, the crystal grain size of the surface opposite to the transparent substrate is 12 μm, the electromagnetic wave shielding sheet of Example 1 having the metal plating layer according to the present invention is The external light reflectance was lowered, the light reflection preventing performance was excellent within an allowable range, and the adhesion with other laminated films was also improved.

FIG. 1A is a plan view of an example of an electromagnetic wave shielding sheet used in the present invention, and FIG. 1B is a cross-sectional view of an example of an electromagnetic wave shielding sheet used in the present invention. It is a perspective view which shows an example of the mesh-like area | region 101 of the conductor layer of this invention. FIG. 3A is a lateral view of a line portion in an example of the electromagnetic wave shielding sheet used in the present invention, and FIG. 3B is a vertical cross section of the line portion in an example of the electromagnetic wave shielding sheet used in the present invention. FIG. FIG. 4 is a partially enlarged schematic cross-sectional view of an example of the electromagnetic wave shielding sheet used in the present invention. FIG. 5 is a scanning electron micrograph of the surface of the metal plating layer immediately after the start of plating. FIG. 6 is a scanning electron micrograph of the surface of the metal plating layer immediately after the end of plating.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electromagnetic wave shielding sheet 11 Transparent base material 12 Conductor layer 13 Conductive treatment layer 14 Metal plating layer 15 Blackening layer 16 Antirust layer 21 Surface opposite to a transparent base material 22 Transparent base material side surface 101 Mesh area 102 Grounding area 103 Opening 104 Line part x Thickness direction

Claims (1)

  An electromagnetic wave shielding sheet comprising at least a mesh-like conductor layer on one surface of a transparent substrate, the conductor layer including a metal plating layer, and the metal plating layer on the side opposite to the transparent substrate An electromagnetic wave shielding sheet, wherein the crystal grain size of the surface is increased compared to the crystal grain size of the transparent substrate side surface facing the thickness direction.

Images