JP2979020B2 - EMI shielding material and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an EMI shielding material for shielding electromagnetic waves emitted from an image display device or the like and used for applications requiring good transparency, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, electromagnetic waves (hereinafter, referred to as CRTs and plasma displays) emitted from video display devices such as plasma displays.
The influence of EMI) on the human body is becoming a serious problem, and the necessity of an EMI shield for shielding it has been emphasized.

Conventionally, as an EMI shielding material disposed on a display screen, an earth portion 7 made of metal centering on copper and a shield made of a grid-like pattern surrounded by the earth portion are provided on a transparent glass plate. A part 8 (see FIG. 6) and a structure directly formed by plating,
After aluminum or ITO is formed on the entire surface of a transparent glass plate or a transparent film using a vapor deposition method or a sputtering method, and an etching resist is formed thereon so as to cover a part to be left as the earth part 7 or the shield part 8, Aluminum and ITO not covered with etching resist
Was removed with an etching solution.

However, the above-mentioned plating method, vapor deposition method,
The formation of conductors by the sputtering method has low productivity and high production costs. In addition, aluminum and ITO formed by the vapor deposition method or the sputtering method are peeled or disconnected during etching due to low adhesion to the transparent substrate. And other problems.

[0005] In view of the demand for high productivity, low cost, and high adhesion between the conductor and the transparent substrate, the transparent substrate 1 made of polyethylene terephthalate or the like used as a material for flexible printed wiring boards has been developed. It has been conceived to use a material in which a metal foil layer 3 such as a copper foil is adhered to one surface via an adhesive layer 2 for producing an EMI shielding material. After the etching resist 5 is formed on the metal foil layer 3 bonded to the transparent base material 1, the metal foil layer 3 in a portion not covered with the etching resist 5 is removed with an etching solution to form the metal foil layer 3. An EMI shielding material is obtained by patterning a frame-shaped ground portion and a shield portion such as a lattice pattern surrounded by the ground portion, and finally stripping the resist (see FIG. 7).

[0006]

However, the EMI shielding material in which the metal foil layer 3 is bonded to the transparent substrate 1 is as follows.
Since the surface of the metal foil layer 3 in contact with the adhesive layer 2 is formed with irregularities in order to further enhance the adhesion between the metal foil layer 3 and the adhesive layer 2, the adhesive layer after the metal foil layer 3 is removed by etching. The unevenness of the metal foil layer 3 is transferred to the portion where the surface 2 is exposed. As a result, when the transparent substrate is placed on the display screen with the EMI shielding material on the screen side, the light 6 that has entered the adhesive layer 2 from the display screen through the transparent substrate 1 and immediately before exiting into the air is emitted. The scattering or reflection due to the unevenness of the adhesive layer 2 causes a part thereof to be returned to the display screen side, which causes a decrease in the light transmittance of the EMI shielding material and a problem of greatly reducing the visibility of the display screen. (See FIG. 8).

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems, and at low cost, excellent in productivity,
E, which has high adhesion between the conductor constituting the grounding part and the shielding part and the adhesive layer, and also has excellent visibility of the display screen
It is to provide an MI shielding material.

[0008]

In order to achieve the above object, an EMI shielding material according to the present invention is provided with an adhesive layer on one side of a transparent substrate, and a ground, a grid, a stripe, or the like on the adhesive layer. A metal foil layer having a shield portion formed of a pattern such as a honeycomb shape was provided, and a transparent overcoat layer was provided so as to cover at least an exposed portion of the adhesive layer.

In the above structure, a transparent overcoat layer is provided so as to cover at least the shield part of the metal foil layer.

In each of the above structures, the material of the metal foil layer is a copper foil, and at least the surface of the shield is blackened.

Further, in the method of manufacturing an EMI shielding material according to the present invention, a material having a three-layer structure in which a metal foil layer is bonded to one side of a transparent substrate via an adhesive layer is prepared, and then the material is etched on the metal foil layer. After the resist is formed, the metal foil layer in a portion not covered with the etching resist is removed with an etching solution to form the metal foil layer with a ground portion and a lattice shape,
A transparent overcoat layer was formed so as to cover the exposed portion of the adhesive layer before or after the etching resist was stripped, or after patterning into a shield portion having a stripe or honeycomb pattern.

Further, in the configuration of the manufacturing method, a transparent overcoat layer is formed so as to cover at least the shield part of the metal foil layer.

In each of the above-described manufacturing methods, a copper foil is used as a material of the metal foil layer, and at least the surface of the shield portion of the metal foil layer is blackened after the etching resist is removed.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an EMI shielding material of the present invention will be described in detail with reference to the drawings.

In the EMI shielding material shown in FIG. 1, an adhesive layer 2 is entirely provided on one surface of a transparent base material 1.
Metal foil layer 3 having a ground portion and a shield portion having a pattern such as a lattice shape, a stripe shape, or a honeycomb shape thereon
Is provided, and a transparent overcoat layer 4 is provided so as to cover an exposed portion of the adhesive layer 2.

In order to obtain such an EMI shielding material, first, a material having a three-layer structure in which a metal foil layer 3 is entirely bonded to one surface of a transparent substrate 1 via an adhesive layer 2 is prepared (FIG. 2a). As a material of the transparent substrate 1, a transparent film such as a polyethylene terephthalate resin, a polypropylene resin, or a polyester resin, a transparent glass plate, or the like can be used. As a material of the adhesive layer 2, an epoxy resin, an acrylic resin, or the like can be used, and is formed by a method such as a screen printing method, a roll coater method, and a die coater method. As a material of the metal foil layer 3, a copper foil, an aluminum foil, a stainless steel foil, or the like can be used.

Next, after an etching resist 5 is formed on the metal foil layer 3 (see FIG. 2B), a portion of the metal foil layer 3 not covered with the etching resist 5 is removed with an etching solution to thereby form the metal foil layer 3. Is patterned into a ground portion having a frame-like pattern and a shield portion having a grid-like, stripe-like, or honeycomb-like pattern surrounded by the ground portion (see FIG. 2C).

Further, before or after the etching resist 5 is stripped (see FIG. 2d), a transparent overcoat layer 4 is formed so as to cover the exposed portion of the adhesive layer 2 (see FIG. 2e). The transparent overcoat layer 4 covers the exposed portion of the adhesive layer 2 as shown in FIG.
May be formed (see FIG. 3), or may be formed so as to cover a part or all of the ground part of the metal foil layer 3. When the surface of the metal foil layer 3 is covered, the adhesion between the metal foil layer 3 and the adhesive layer 2 is further improved, and the metal foil layer 3 is prevented from being corroded. Examples of the method of forming the transparent overcoat layer 4 include screen printing, gravure printing, and roll coating of a transparent resin such as a liquid polyester or acrylic resin, a polyethylene terephthalate resin having an adhesive layer or an adhesive layer on one surface,
There is a method of bonding a transparent film such as a polypropylene resin or a polyester resin with a roll laminator. Further, the etching resist 5 may be left without being stripped.

In the EMI shielding material as described above, the transparent overcoat layer 4 is buried in the unevenness on the surface of the exposed portion of the adhesive layer 2 and flattened. Even if the light 6 emitted from the display screen is not scattered or reflected in the portion where the metal foil layer is not formed, the light transmittance in the front direction is improved (see FIG. 4). That is, the visibility is excellent.

When the material of the metal foil layer is a copper foil, at least the surface of the shield portion of the metal foil layer may be blackened after the etching resist 5 is removed (not shown). In the blackening treatment, the copper surface is immersed in a mixed solution of sodium chlorite, sodium hydroxide and sodium phosphate at 95 ° C. for about 2 minutes. As a result, the copper surface is oxidized and C
It becomes uO and turns black. The blackened EMI shielding material has low visibility because the blackened surface suppresses the reflection of light emitted from other than the display at the shield part when the transparent substrate is placed on the display screen with the transparent substrate facing the screen. Further improve.

[0021]

EXAMPLE A three-layer structure in which a metal foil layer made of an electrolytic copper foil having a thickness of 18 μm is entirely adhered to one surface of a transparent substrate made of a polyethylene terephthalate film having a length of 200 mm, a width of 300 mm and a thickness of 100 μm with an adhesive layer. Commercially available materials were prepared. A dry film etching resist having a thickness of 25 μm is formed on the surface of the metal foil layer of this material by roll lamination, exposed and developed, and then the metal foil layer which is not covered with the etching resist is removed with an etching solution. The foil layer was patterned into a frame-shaped ground portion having a width of 16 mm, and a shield portion surrounded by a grid-shaped pattern having a line width of 70 μm and a line pitch of 280 μm. After the resist is removed, the surface of the metal foil layer is blackened, and finally, a liquid acrylic resin is printed by a screen printing method so as to cover the exposed portions of the metal foil layer and the adhesive layer, and dried at 80 ° C. for 30 minutes. To form a transparent overcoat layer
An MI shielding material was obtained.

With respect to the EMI shielding material obtained as described above, a material having no transparent overcoat layer was used as a comparative example, and the light transmittance in the front direction at a portion where the metal foil layer was not formed was 400 to 700 nm. Was measured in the wavelength range. As a result, the transmittance in the frontal direction when the transparent overcoat layer is not provided is only 1 to 2%, but by providing the transparent overcoat layer as in this embodiment, the transmittance is 68 to 82%. (Fig. 5
reference).

[0023]

The EMI shielding material of the present invention has the above-described configuration and operation, and has the following effects.

That is, in the EMI shielding material of the present invention, a metal foil layer such as a copper foil is adhered to one surface of a transparent substrate via an adhesive layer, and the metal foil layer is etched to form a ground portion and a grid-like pattern. Because it is patterned with a shield part, it is low cost, excellent in productivity,
The adhesive force between the conductor constituting the ground portion and the shield portion and the adhesive layer is high.

Also, since the transparent overcoat layer is buried in the unevenness on the surface of the exposed portion of the adhesive layer and flattened,
Even when the transparent substrate is placed on the display screen with the screen side, scattering or reflection of the light emitted from the display screen at the portion where the metal foil layer is not formed is suppressed,
The display screen has excellent visibility.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment of an EMI shielding material according to the present invention.

FIG. 2 is a cross-sectional view showing one embodiment of a method for manufacturing an EMI shielding material according to the present invention.

FIG. 3 is a cross-sectional view showing another embodiment of the EMI shielding material according to the present invention.

FIG. 4 is a diagram showing a light transmission state in a portion of the EMI shielding material according to the present invention where a metal foil layer is not formed.

FIG. 5 is a diagram showing the results of measuring the light transmittance in the front direction in a portion where a metal foil layer is not formed in Examples and Comparative Examples of the present invention.

FIG. 6 is a sectional view showing a shield part and an earth part of an EMI shield material.

FIG. 7 is a cross-sectional view illustrating a method for manufacturing an EMI shielding material according to the related art.

FIG. 8 is a diagram showing a state of light transmission in a portion where a metal foil layer of an EMI shielding material according to the related art is not formed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent base material 2 Adhesive layer 3 Metal foil layer 4 Transparent overcoat layer 5 Etching resist 6 Light 7 Earth part 8 Shield part

Claims (6)

(57) [Claims] An adhesive layer is provided on one surface of a transparent substrate, and a metal foil layer having a ground portion and a shield portion formed of a grid, stripe, or honeycomb pattern is provided on the adhesive layer, and at least a metal foil layer is provided. An EMI shielding material, wherein a transparent overcoat layer is provided so as to cover an exposed portion of the adhesive layer. 2. A transparent overcoat layer is provided so as to cover at least a shield part of the metal foil layer.
EMI shielding material as described. 3. The EMI shielding material according to claim 1, wherein the material of the metal foil layer is a copper foil, and at least the surface of the shielding portion is blackened. 4. A material having a three-layer structure in which a metal foil layer is attached to one side of a transparent base material via an adhesive layer, and then an etching resist is formed on the metal foil layer, and then covered with the etching resist. By removing the metal foil layer of the non-portion portion with an etching solution, the metal foil layer is patterned into a ground portion and a shield portion formed of a lattice, a stripe or a honeycomb shape, and further before the etching resist is removed or A method for producing an EMI shielding material, comprising forming a transparent overcoat layer so as to cover an exposed portion of an adhesive layer after peeling. 5. The method for manufacturing an EMI shielding material according to claim 4, wherein a transparent overcoat layer is formed so as to cover at least the shield part of the metal foil layer. 6. The EMI shield according to claim 4, wherein a copper foil is used as a material of the metal foil layer, and at least the surface of the shield portion of the metal foil layer is blackened after the etching resist is removed. Material manufacturing method.