JP5034538B2 - Method for manufacturing electromagnetic shielding film - Google Patents

Description

  The present invention relates to an electromagnetic wave shielding film having a recess formed on the surface of a metal layer.

  Electromagnetic waves are emitted to the outside from the display surface of a CRT (cathode ray tube) or PDP (plasma display panel) used for a display screen of an information processing apparatus or the like. Such electromagnetic waves may cause noise in peripheral devices and may have an effect on the human body.

  For this reason, various techniques for preventing leakage of electromagnetic waves generated from the display screen to the outside have been proposed. As a general leakage prevention measure, a highly conductive metal such as copper or nickel on a transparent substrate. A method of forming a metal pattern layer made of is known.

In particular, when used in a display, it is necessary to improve electromagnetic wave shielding properties while maintaining display characteristics.
However, when the electromagnetic wave shielding film having the metal pattern layer is provided on the entire surface of the display screen, the light from the display screen and external light are reflected on the surface of the metal pattern layer, thereby reducing the visibility of the display screen. There was a problem.
In order to solve this problem, a blackened film is conventionally formed on the surface of the metal pattern layer by blackening treatment (Patent Document 1).

In addition, for the purpose of improving visibility, a technique for roughening the surface of the metal pattern layer during blackening is known (Patent Document 2).
JP 2006-60171 A JP 2000-286594 A

Visibility is improved as the blackened film on the surface of the metal layer is thicker, that is, as the degree of blackening is higher. However, increasing the degree of blackening increases the surface resistance of the electromagnetic wave shielding film.
When the surface resistance is increased, it is difficult to generate a dome-shaped magnetic field over the entire surface of the electromagnetic wave shielding film, resulting in a problem that the electromagnetic wave shielding property is lowered.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an electromagnetic shielding material having a low surface resistance even when the degree of blackening is increased, that is, good visibility and excellent electromagnetic shielding properties. And

The present invention includes an electrically insulating transparent base material, a metal layer formed on the transparent base material, and having a plurality of openings, and one or more recesses on a non-contact surface with the transparent base material, A method for producing an electromagnetic wave shielding film comprising a blackening film formed on a surface of a metal layer, wherein a plurality of photosensitive resist films are formed on a metal layer having a copper foil pasted on a transparent substrate, The resist film on which the pattern of the openings is formed is developed and etched to form a metal layer having a plurality of openings and one or more recesses on the non-contact surface with the transparent substrate, and then blackened In the portion where the concave portion of the surface of the metal layer pattern formed by the etching of the metal layer is to be formed, an exposed portion from the etching resistant film made of a resist film remaining after development is used as an opening. that is obtained by the smaller than It is a manufacturing method of the electromagnetic wave shielding film according to symptoms.

Moreover, the said electromagnetic wave shielding film WHEREIN: The said recessed part may be arrange | positioned spaced apart.

  Moreover, the said electromagnetic wave shielding film WHEREIN: The said recessed part may be formed in groove shape.

  Furthermore, in the electromagnetic wave shielding film, the concave portion may be formed on the entire surface of the metal layer, or may be formed on a portion of the metal layer corresponding to the peripheral edge of the transparent substrate.

  Furthermore, in the electromagnetic wave shielding film, the metal layer may have a flat surface roughness with an Ra value of 0.36 or less, or an Rz value of 2.50 or less.

According to the method for producing an electromagnetic wave shielding film of the present invention, a blackened film is formed on the surface of a metal layer having irregularities, thereby developing an electromagnetic wave shielding film having a low surface resistance value and developing a resist film having a pattern of a plurality of openings. In doing so, it can be easily manufactured by forming a concave pattern together .

Moreover, in the electromagnetic wave shielding film, since the openings of the metal layer are in a matrix shape, uniform electromagnetic wave shielding properties can be obtained over the entire surface.
Further, since the width of the concave portion is about three-fourths of the metal layer, the unevenness formed is considerably larger than the unevenness that is naturally formed during the blackening treatment as shown in Patent Document 2. be able to. Due to the intentionally formed large irregularities, the thickness of the blackened layer is increased and the effect of lowering the surface resistance value can be increased.

  Moreover, in the electromagnetic wave shielding film, since the concave portions are arranged apart from each other, a large surface area can be obtained and a large number of blackened layers can be formed, leading to improved visibility.

  Moreover, in the electromagnetic wave shielding film, since the concave portion is formed in a groove shape, a stable blackened layer shape can be obtained, leading to improved visibility.

  Moreover, in the electromagnetic wave shielding film, since the concave portion is formed in the metal layer at the peripheral portion of the transparent substrate, the thickness of the blackened layer at the central portion can be maintained and good visibility can be maintained.

  Moreover, in the electromagnetic wave shielding film, a good shielding magnetic field can be obtained by forming the recesses on the entire surface of the metal layer.

  Moreover, in the electromagnetic wave shielding film, when the Ra value of the surface roughness of the metal layer is 0.36 or less, the intended amount of irregularities can be formed on the surface of the metal layer.

  Further, in the electromagnetic wave shielding film, when the Rz value of the surface roughness of the metal layer is 2.50 or less, the intended amount of irregularities can be formed on the surface of the metal layer.

  As shown in FIGS. 1 and 2, the electromagnetic wave shielding film 1 of the present invention includes a transparent substrate 2 and a metal layer 3.

The transparent substrate 2 only needs to be electrically insulating, and is preferably a transparent plastic substrate.
Transparent plastic substrates include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate, polyolefins such as polyethylene, polypropylene, polystyrene, and EVA, vinyl resins such as polyvinyl chloride and polyvinylidene chloride, polysulfone, and polyether A film made of plastic such as sulfone, polycarbonate, polyamide, polyimide, acrylic resin, etc., having a total visible light transmittance of 70% or more.
Among these, a polyethylene terephthalate film is preferable in terms of transparency, heat resistance, ease of handling, and price.
The transparent substrate 2 may be colored to such an extent that the visibility is not lowered, and may be used as a multilayer film in which two or more layers are combined.

The transparent substrate 2 can have an adhesive layer (not shown) on one surface layer.
The adhesive layer can be made of an adhesive such as acrylic resin, polyester resin, polyurethane resin, polyvinyl alcohol resin, vinyl chloride / vinyl acetate copolymer resin, or ethylene-vinyl acetate copolymer resin.
The adhesive may be made of a thermosetting resin or an ionizing radiation curable resin (such as an ultraviolet curable resin or an electron beam curable resin).

For the metal layer 3, an alloy in which one or a combination of two or more of metals such as copper, aluminum, nickel, iron, gold, silver, stainless steel, tungsten, chromium, and titanium can be used.
In the material group, the metal layer is preferably made of copper, aluminum, or nickel from the viewpoints of conductivity, pattern processing, and cost.

The metal layer 3 has openings 4 arranged in a matrix.
The shape of the opening 4 is not limited, and may be a polygon such as a triangle or a quadrangle, a circle, an ellipse, or the like alone, or a combination of two or more shapes. It is also possible to do.

  In the metal layer 3, for example, as shown in FIG. 2, one or more recesses 5 are formed on the non-contact surface with the transparent substrate 2, and the metal layer 3 is blackened to form the recesses 5. A blackened film 6 can be formed along. The recesses 5 are arranged in a matrix on the metal layer.

  The shape of the recess 5 in plan view is not limited to a circle as shown in FIG. 1, and may be a polygon such as an ellipse, a quadrangle, or a triangle.

As a modification, as shown in FIG. 3, the recess 5 may be formed in a groove shape in plan view. In the drawing, the lattice-shaped metal layer 3 is provided with a lattice-shaped groove, but the shape is not limited to this, and a stripe-shaped groove may be used. Note that the width of the groove in the direction orthogonal to the extending direction of the groove may vary.
That is,
It can be said that the planar shape and depth of the concave portion, which is a feature of the present invention, may be appropriately set according to the shape, film thickness, type of blackened film, and degree of blackening of the metal layer.

  A blackening film 6 is provided on the metal layer 3. The blackening film 6 refers to an oxide film formed on the surface of the metal film by exposing the metal layer 3 to an oxidizing agent.

The electromagnetic wave shielding film 1 is incorporated in an image display panel such as an optical filter, a liquid crystal display panel, or a plasma display panel. When pasted on the surface of the image display panel, an adhesive layer made of an adhesive is provided on one side of the transparent substrate, for example, the surface to which the metal layer is fixed, and is bonded via the adhesive layer.
The adhesive preferably has a refractive index of 1.40 or more and 1.70 or less. The reason for limiting the refractive index is the relationship between the refractive indexes of the transparent substrate and the adhesive layer. The smaller the difference between the refractive indexes of the two, the lower the visible light transmittance can be prevented.

The pressure-sensitive adhesive is preferably one that flows by heating or pressurization, and is particularly preferably a pressure-sensitive adhesive that exhibits fluidity by heating at 200 ° C. or less or pressurization by ¹ kgf / cm ² or more.
By making it flow, lamination and pressure molding become possible, and it is possible to adhere to an adherend having a phase or a complicated shape.
Moreover, since the environment in which the electromagnetic wave shielding film is used is usually less than 80 ° C., the softening temperature of the adhesive layer is preferably 80 ° C. or higher.

  Examples of the adhesive layer having a refractive index of 1.40 or more and 1.70 or less and flowing by heating or pressurization include thermoplastic resins. For example, (di) enes such as poly-1,2 butadiene, polyethers such as polyvinyl ethyl ether, polyesters such as polyvinyl acetate, and poly (meth) acrylates such as polymethyl methacrylate can be used. If necessary, two or more kinds may be copolymerized, or two or more kinds may be blended and used.

  Next, an example of a method for producing the above-described electromagnetic wave shielding film will be described.

A copper foil is stuck on a transparent substrate having an adhesive layer on one surface layer to form a metal layer. After a photosensitive resist solution is disposed on the metal layer to form a photosensitive resist film, the pattern is baked and developed through an exposure mask having a predetermined pattern. Thereafter, a metal layer pattern is formed by a photoetching method in which the resist film remaining after development is used as an etching resistant film and etching is performed on the metal layer portion exposed from the etching resistant film. At this time, in the portion where the concave portion on the surface of the metal layer pattern is to be formed, the etching amount is reduced by making the exposed portion from the etching resistant film smaller than the opening portion, and the concave portion is formed simultaneously with the metal pattern. To do. Further, blackening treatment is performed, and a blackening film is attached to the metal layer.
In the blackening treatment, the raw material of the electromagnetic wave shielding film with the resist film peeled off is immersed in a blackening bath having a blackening solution, exposed to the blackening solution, washed and dried to form a blackened film. The composition of the blackening solution is, for example, an aqueous solution of about 30% by weight of an oxidizing agent and about 6% by weight of caustic soda, and the temperature is about 50 ° C.

Example 1
In a copper metal layer having a width between the openings of 12 μm and a height from the transparent substrate of 10 μm, a non-contact surface with the transparent substrate (in this embodiment, a metal pattern facing the surface in contact with the transparent substrate) A concave portion having a width of 9 μm and a depth of 2 to 4 μm was formed on the surface of the layer by half etching, and then blackening treatment was performed to prepare an electromagnetic wave shielding film. Table 1 shows the results of measuring the surface resistance at this time using a milliohm high tester.

(Comparative Example 1)
A copper metal layer having a width between the openings of 12 μm and a height from the transparent substrate of 10 μm was subjected to blackening treatment without forming a recess on the surface of the metal layer, thereby producing an electromagnetic wave shielding film. Table 1 shows the results of measuring the surface resistance at this time using a milliohm high tester.

  From Table 1, it was confirmed that a stable low surface resistance value was obtained by intentionally forming irregularities on the surface of the metal layer.

It is a partial top view which shows an example of the electromagnetic wave shielding film by this invention. It is a fragmentary sectional view in the A-A 'line in FIG. It is a partial top view which shows another example of the electromagnetic wave shielding film by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electromagnetic wave shielding film 2 Transparent base material 3 Metal layer 4 Opening part 5 Recessed part 6 Blackening film

Claims (7)

An electrically insulating transparent substrate, a metal layer formed on the transparent substrate, having a plurality of openings, and one or more recesses on a non-contact surface with the transparent substrate, and the surface of the metal layer A method for producing an electromagnetic wave shielding film comprising:
After forming a photosensitive resist film on a metal layer with a copper foil affixed on a transparent substrate, the resist film on which a pattern of a plurality of openings is formed is developed and etched to form a plurality of openings , After forming a metal layer having one or more recesses on the non-contact surface with the transparent substrate, blackening treatment is performed ,
In the portion where the concave portion on the surface of the metal layer pattern formed by etching the metal layer is to be formed, the exposed portion from the etching resistant film made of a resist film remaining after development is made smaller than the opening. A method for producing an electromagnetic wave shielding film, comprising:   The method for producing an electromagnetic wave shielding film according to claim 1, wherein the recesses of the metal layer are arranged apart from each other.   The method for producing an electromagnetic wave shielding film according to claim 1, wherein the concave portion of the metal layer is formed in a groove shape.   The method for producing an electromagnetic wave shielding film according to claim 1, wherein the recess is formed on at least the metal layer at the peripheral edge of the transparent substrate.   The method of manufacturing an electromagnetic wave shielding film according to claim 4, wherein the recess is formed over the entire surface of the metal layer.   The method for producing an electromagnetic wave shielding film according to claim 1, wherein the surface roughness of the metal layer has an Ra value of 0.36 or less.   The method for producing an electromagnetic wave shielding film according to claim 1, wherein the surface roughness of the metal layer has an Rz value of 2.50 or less.

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