JP2009277965A - Electromagnetic wave shield filter, multifunctional filter, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive and practical electromagnetic wave shield filter which uses aluminum by eliminating a pattern precision defect of chemical etching caused when a material of a metal pattern is changed from copper to inexpensive aluminum, and to reduce cost in a multifunctional filter and an image forming apparatus using the electromagnetic shield filter. <P>SOLUTION: The electromagnetic wave shield filter 10 is characterized in that the metal pattern on a transparent base 1 is an aluminum pattern 2 and an oxide film 3 of aluminum on at least an upper surface (a surface in the same direction with a side where the aluminum pattern is formed on the transparent base) of the aluminum pattern is 0 to 13 &angst; thick. Further, the electromagnetic wave shield filter and an optical filter are stacked to form the multifunctional filter, and the image display includes the electromagnetic wave shield filter or multifunctional filter disposed on the front. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an electromagnetic wave shielding filter suitable for being disposed on the front surface of an image display device (display), a multi-function filter using the same, and an image display device.

  Currently, electromagnetic wave shielding filters are used for applications such as disposing on the front surface of a display, and among them, there are typically plasma display (also referred to as PDP) applications. In an electromagnetic wave shielding filter for a plasma display, a mesh pattern is often used as a metal pattern that achieves both electromagnetic wave shielding performance and light transmittance. A metal pattern (EMI mesh) can be formed by bonding a metal foil to a transparent substrate with a transparent adhesive, and then chemically etching the metal foil into a mesh by a photolithography method (Patent Documents 1 and 2). ).

  As a metal material of the metal foil, there are many documents that are not particularly limited in Patent Documents (Patent Documents 1 and 2). Examples of metals include high conductivity such as aluminum (Patent Document 2) in addition to copper. However, in actuality, the EMI mesh of the electromagnetic wave shielding filter distributed in the market uses only copper, specifically, copper foil, and does not use aluminum foil and has not been put into practical use.

JP 2003-318596 A Japanese Patent No. 3388682

In recent years, an expensive electromagnetic shielding filter has been a hindrance in promoting the spread of image display devices. In order to reduce the cost of the electromagnetic shielding filter, it is conceivable to use an aluminum foil that is cheaper than a copper foil.
Therefore, we aimed at cost reduction, and examined the electromagnetic wave shielding filter using aluminum foil cheaper than copper foil as the metal material of the metal pattern (EMI mesh). Actually, it turned out that there are the following problems to be solved. The following problems are conspicuous when the pattern line width and thickness are about 100 μm or more. In order to pursue transparency for use in high-quality image display devices, the pattern line width and thickness dimensions may become particularly evident when the dimensions are reduced to about 10 to 20 μm or less. found.

(A) Aluminum itself has high activity, and an aluminum oxide film is present on the surface, which becomes a corrosion-resistant film and inhibits chemical etching.
(B) When a portion of the oxide film in the region in contact with the etching solution is removed, the removed portion is rapidly etched with respect to the portion that has not yet been removed, and uniform and stable etching is difficult. is there.
(C) As a result of the above (a) and (b), the contour of the line portion of the metal pattern has a zigzag shape. In other words, aluminum is inferior in the pattern accuracy of the line compared to the case of copper foil.

  As a result, a fine pattern (for example, a line width of 10 to 20 μm and a pattern thickness of about 10 to 20 μm) required by the image display device cannot be obtained as compared with the copper foil. Then, the unevenness leads to unevenness in the area ratio of the opening that realizes light transmittance, leading to unevenness in the surface of the display screen, and disconnection leads to deterioration in electromagnetic wave shielding performance.

  Here, with reference to FIG. 4 and FIG. 5, the unstable etching at the time of making an aluminum foil into an aluminum pattern by chemical etching and the pattern accuracy defect caused thereby will be described.

FIG. 4A shows a state before corrosion due to etching progresses, and FIG. 4B shows a state where corrosion due to etching progresses. FIGS. 4A and 4B show a state in which the aluminum foil 54 exposed in the region where the resist pattern 52 is not formed is etched with the etching solution 51.
4A and 4B, the aluminum foil 54 having the aluminum oxide film 3 on both the front and back sides of the upper and lower surfaces of the aluminum layer 53 is transparently bonded to one side of the transparent substrate 1. The adhesive layer 4 is adhesively fixed and laminated to form an aluminum foil laminate 55.

  Then, as shown in FIG. 4B, when etching proceeds, the oxide film 3 on the exposed portion of the aluminum foil 54 that contacts the etching solution 51 in the non-formed portion of the resist pattern 52 is uniformly etched on the entire exposed portion. However, the etching is partially preceded, and the aluminum layer 53 is etched from the corrosion preceding portion 56.

  As a result, when the etching is completed, pattern accuracy defects such as burrs and disconnections frequently occur in the lines of the aluminum pattern 2 as conceptually shown in the plan view of FIG.

That is, an object of the present invention is to solve the pattern accuracy defect of an aluminum pattern formed by chemical etching, which occurs when the material of the metal pattern is changed from copper to inexpensive aluminum, and to provide an inexpensive and practical electromagnetic wave using aluminum. It is to provide a shielding filter.
Moreover, it is providing the multifunction filter using this electromagnetic wave shielding filter, and the image display apparatus using these filters.

  Therefore, in the electromagnetic wave shielding filter of the present invention, in the electromagnetic wave shielding filter in which the metal pattern is formed on the transparent substrate, the metal pattern is an aluminum pattern, and at least the upper surface of the aluminum pattern (the aluminum pattern is formed on the transparent substrate). An electromagnetic wave shielding filter having a thickness of 0 to 13 mm of an aluminum oxide film on the same direction as that of the coated side.

In this way, by defining the thickness of at least the aluminum oxide film on the upper surface side to be thin, stable etching is possible when the aluminum pattern is formed by chemical etching, and the etching quality is improved. In addition, the defect that causes disconnection is eliminated, the pattern accuracy is improved, and as a result, variations in electromagnetic shielding properties (surface resistance value) and haze (cloudiness value) can be avoided. As a result, an electromagnetic wave shielding filter that is inexpensive in terms of material can be put into practical use by using aluminum that is less expensive than copper.
Also, in terms of manufacturing, since the aluminum oxide film can be chemically etched as it is, the removal process is unnecessary, and the manufacturing process is not complicated and the cost is increased.

The multifunction filter of the present invention is a multifunction filter in which the electromagnetic wave shielding filter and an optical filter are stacked.
With this configuration, it is possible to achieve multi-functionality including an optical filter function as well as an electromagnetic wave shielding function, so that a transparent substrate can be made common and a filter can be thinned, and thus cost can be reduced.

Moreover, the image display device of the present invention is an image display device in which the electromagnetic wave shielding filter or the multifunction filter is disposed on the front surface.
With this configuration, the cost can be reduced and the spread of the image display apparatus can be promoted.

(1) According to the electromagnetic wave shielding filter of the present invention, even when aluminum which is cheaper than copper is used for the metal pattern, the line contour zigzag and disconnection at the time of chemical etching formation are eliminated, and the pattern accuracy is improved. Thus, variations in electromagnetic wave shielding properties (surface resistance value) and increase in haze can be avoided, and an inexpensive electromagnetic wave shielding filter can be practically used.
Moreover, since the aluminum oxide film can be chemically etched as it is in terms of production, an additional removal process of the oxide film is unnecessary, and the manufacturing process is not complicated and the cost is increased.
(2) According to the multi-function filter of the present invention, it becomes a multi-function filter from which the effects of the electromagnetic wave shielding filter such as cost reduction can be obtained.
(3) According to the image display device of the present invention, it becomes an image display device from which the effects of the electromagnetic wave shielding filter or the multifunction filter such as cost reduction can be obtained, and the spread of the image display device can be promoted.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the electromagnetic wave shielding filter 10 illustrated in the cross-sectional view of FIG. 1 shows an embodiment of the electromagnetic wave shielding filter of the present invention. In the case of the same figure, the aluminum pattern 2 has an aluminum oxide film on the upper and lower surfaces. 3 and at least the thickness of the oxide film on the upper surface is in the range of 0 to 13 mm. And in the example of the figure, this aluminum pattern 2 is a thing of the structure bonded and fixed to the transparent base material 1 by the transparent adhesive layer 4 on the lower surface of the oxide film 3 of the lower surface side. The transparent adhesive layer 4 is formed on the entire surface of the transparent substrate 1 including the opening of the aluminum pattern.

  In the present invention, the “upper surface” means a surface that is the same direction as the side on which the aluminum pattern is formed with respect to the transparent substrate (also a surface facing upward in the drawing), and the “lower surface” means “ It means the surface opposite to the “upper surface” (also the surface facing downward in the drawing).

[Transparent substrate]
The transparent substrate 1 may be appropriately selected from known materials and thicknesses in consideration of required physical properties such as transparency in the visible region (light transmittance), heat resistance, and mechanical strength, such as glass and ceramics. A plate-like rigid body such as a transparent inorganic plate or a resin plate may be used. However, a flexible resin film (or sheet) is preferable in consideration of suitability for continuous processing with a roll-to-roll having excellent productivity. The roll-to-roll refers to a processing method in which the material is unwound from a take-up (roll), supplied, appropriately processed, and then taken up and stored.

  Examples of resins for resin films and resin plates include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, acrylic resins such as polymethyl methacrylate, polyolefin resins such as cycloolefin polymers, and cellulose resins such as triacetyl cellulose. Resins, polycarbonate resins, polyimide resins and the like. Among them, polyethylene terephthalate is a transparent base material whose biaxially stretched film is preferable in terms of heat resistance, mechanical strength, light transmittance, cost, and the like.

  The thickness of the transparent substrate is basically not particularly limited and is appropriately selected depending on the application. When a flexible resin film is used, it is, for example, about 12 to 500 μm, preferably about 25 to 200 μm.

In addition, known additives such as an ultraviolet absorber, a colorant, a filler, a plasticizer, and an antistatic agent can be appropriately added to the resin of the transparent substrate as necessary.
Further, the transparent substrate may be obtained by subjecting the surface thereof to known easy adhesion treatment such as corona discharge treatment, primer treatment, and ground treatment.

[Aluminum pattern]
The aluminum pattern 2 is a pattern layer formed of aluminum. Although the layer itself is opaque, the electromagnetic wave shielding performance and the light transmittance are made compatible by forming a pattern in which a non-formation portion of the layer such as an opening is provided. Is a layer. Moreover, the aluminum pattern 2 of the present invention has an aluminum oxide film 3 having a specific thickness range of 0 to 13 mm on at least the upper surface thereof. Note that 1Å = 0.1 nm.

  Aluminum in the aluminum pattern is mainly composed of aluminum, and may be aluminum alloy in addition to aluminum pure metal. These are collectively referred to as aluminum in the present invention. However, since the conductivity decreases when the purity of aluminum is low, the purity is shielded against electromagnetic waves. Higher is preferable in terms of performance, and aluminum having a purity of 99.0% or more is preferable. The aluminum pattern using aluminum having a purity of 99.0% or more is made of a foil conforming to the aluminum foil defined in JIS H4160 (aluminum and aluminum alloy foil) and JIS H4170 (high purity aluminum foil). It can be formed by using it.

  The aluminum pattern is not formed from an aluminum foil, but an aluminum pattern formed from an aluminum vapor deposition film formed on a transparent substrate by a vapor phase growth method such as a vacuum vapor deposition method may be used.

  The thickness of the aluminum pattern may be appropriately selected from the viewpoints of electromagnetic wave shielding performance, processability, mechanical strength, and the like, specifically 1 to 100 μm, preferably 5 to 20 μm, more preferably 8 to 15 μm. If the thickness is thin, electromagnetic wave shielding performance, mechanical strength and the like are lowered, and if the thickness is thick, workability is lowered.

  The shape of the aluminum pattern in plan view is, for example, a known pattern in which both electromagnetic wave shielding performance and light transmittance such as a mesh shape and a stripe shape are compatible. Among them, a mesh shape and a square lattice shape are typical, and in addition, examples of the lattice shape include a rectangular lattice, a rhombus lattice, a hexagonal lattice, and a triangular lattice. The mesh has a plurality of openings having these shapes, and the openings are line portions (line portions or line portions) that define the openings. The line portions are usually line-shaped with a uniform width, and usually the openings and the spaces between the openings are all the same shape and the same size.

  In addition, in the display application, the above pattern is a solid pattern that does not have an opening for grounding continuity around the four sides that do not affect the image display of the electromagnetic wave shielding filter, or grounding that has a small occupied area ratio. An area may be provided around an internal image display area having an opening.

  The line width of the line portion of the pattern is 5 to 50 μm, for example, and 5 to 30 μm, which is finer in terms of the effect of the present invention, and the line interval (pitch), which is a line repetition period, is 100 to 500 μm, for example.

(Pattern formation)
In order to form the pattern of the aluminum pattern, it can be formed by chemical etching after laminating an aluminum layer such as an aluminum foil on the transparent base material before pattern formation. For pattern formation of the resist pattern during chemical etching, a known pattern formation method such as a photolithography method (pattern exposure method) or a printing method may be appropriately selected. Among these, the photolithography method is a preferable method compared to the printing method in that a highly accurate pattern such as a line width required for the electromagnetic wave shielding filter and its uniformity can be stably formed.

A known etching solution may be appropriately selected and used as an etching solution for chemically etching the aluminum pattern. For example, an acidic etching solution containing ferric chloride.
Etching is performed including an aluminum oxide film in the resist pattern non-formation portion on the upper surface of the aluminum layer. It is not particularly necessary to remove the aluminum oxide film on the upper surface as a pretreatment for etching.
Then, the aluminum oxide film 3 on the upper and lower surfaces corresponding to the resist pattern forming portion remains as the oxide film 3 on the upper and lower surfaces of the aluminum pattern 2.

[Aluminum oxide film]
An aluminum oxide film is a layer containing an aluminum oxide. When an aluminum pattern is formed using an aluminum foil, the aluminum oxide film exists on both the top and bottom surfaces of the foil. When the pattern is formed, the thickness of the etched side, that is, the upper surface side is defined. The upper limit of the thickness of the aluminum oxide film on at least the upper surface of the aluminum pattern is 13 mm, preferably 12 mm, more preferably 10 mm, and even more preferably 8 mm.
By setting the upper limit of the thickness of the aluminum oxide film on at least the upper surface as described above, stable chemical etching is possible even if the oxide film is still present, and copper is changed to inexpensive aluminum. The pattern accuracy defect can be avoided.

  By the way, normally manufactured aluminum foil is manufactured by a rolling method, and manufactured and stored at room temperature (20 ° C., around 50% RH), such as aluminum ingot rolling process, foil manufacturing process through annealing process, and subsequent storage in air. By doing so, an active aluminum irreversibly forms an oxide film of aluminum on the surface. However, it does not become a thin oxide film as in the present invention, but is thicker than 15 mm, usually about 20 to 100 mm. It becomes an oxide film.

Further, the lower limit of the thickness of the aluminum oxide film on the upper surface of the aluminum pattern is 0 (zero), that is, no oxide film may be present from the viewpoint of not inhibiting chemical etching.
However, the oxide film of aluminum is said to be a passive film, and during the process of processing, transporting and storing the aluminum foil, oxidation or corrosion (inadvertently or undesired) inside the aluminum foil. In this respect, an oxide film as a dense aluminum passivating film may be formed in this respect.

  For aluminum patterns that do not have an aluminum oxide film on the upper surface, the aluminum layer before pattern formation is formed on a transparent substrate in vacuum and in an inert gas, and the upper surface of the aluminum layer is coated with a resin before forming the oxide film. This can be achieved by blocking the oxidation reaction. Thereafter, if a predetermined pattern is formed by chemical etching, an aluminum pattern having no aluminum oxide film on the upper surface is obtained.

  There are various ways to reduce the thickness of the aluminum oxide film as described above, but when aluminum foil is used for the aluminum pattern, the aluminum foil is made by rolling, and then manufactured by annealing. However, it can adjust to the target thickness by adjusting rolling conditions and annealing conditions.

  For example, when removing the rolling oil adhering to the surface of the aluminum foil after rolling during annealing, the gas composition of the annealing atmosphere is controlled so that the surface is not oxidized (the oxygen concentration is lowered), aluminum There are methods such as removing the aluminum oxide film on the foil surface with chemicals. Although there is a method of not annealing, rolling oil is not preferable because it adversely affects the photolithography method.

  The thickness of the aluminum oxide film is measured by X-ray photoelectron spectroscopy (XPS), which is a kind of Hunter Hall method and X-ray fluorescence analysis.

The aluminum oxide film is usually formed on both the front and back surfaces of the foil, that is, both the upper surface and the lower surface from the foil manufacturing process. Among these, since it is the oxide film on the upper surface that affects the chemical etching for pattern formation of the aluminum pattern, the present invention defines a specific thickness (thinness) for at least the aluminum oxide film on the upper surface. It should be noted that the aluminum oxide film on the lower surface does not need to be specified in terms of pattern accuracy because the contribution to the generation of mesh shape burrs during chemical etching is usually negligible compared to the aluminum oxide film on the upper surface. . However, if the film thickness is too thick, an adverse effect on the mesh shape due to the aluminum oxide film remaining in the opening may occur, and the transparency of the opening may be reduced. For this reason, it is recommended that the aluminum oxide film on the lower surface is preferably less than the minimum visible light wavelength of 380 nm, more preferably 200 nm or less. For example, the film thickness of the aluminum oxide film on the lower surface is set to 0 to 13 mm similarly to the upper surface. As one form of the present invention, by adjusting the film thickness of the aluminum oxide film on the lower surface before chemical etching and the processing conditions of chemical etching, the minimum wavelength of visible light in the pattern opening is less than 380 nm (for example, 3 to 13 mm). The transparent aluminum oxide film having a thickness of 2) remains, and the transparent adhesive layer or transparent substrate exposed to the opening during chemical etching can be protected from coloring by the corrosive liquid.
However, if the lower surface aluminum oxide film has the same thickness as that of the upper surface oxide film, the thickness of the lower surface aluminum oxide film is defined to be the same as the thickness of the upper surface aluminum oxide film. be able to.

(Blackening treatment layer)
The aluminum pattern may have a blackened layer on the surface.
The blackening treatment layer is a layer for improving external light absorption and image contrast by suppressing light reflection by the aluminum pattern and the oxide film on the surface. The blackening treatment layer is provided when external light absorption and image contrast improvement are required. When there is an oxide film on the surface or surface of the aluminum pattern, the blackening treatment layer is a layer that is provided on the surface of the film to reduce the light reflectance.

  Here, the surface refers to a surface such as an upper surface, a lower surface, or a side surface. The surface on which the blackening treatment is performed to form the blackening treatment layer may be surfaces according to demand, such as the upper surface only, the upper surface and both side surfaces, the lower surface only, the upper surface, both side surfaces, and the entire lower surface. This is the same as a known blackening process. Among these, the surface in contact with the transparent adhesive in the presence of the transparent adhesive layer is the lower surface. Further, in order to use the electromagnetic wave shielding filter with the upper surface side of the observer side, it is preferable to form a blackening treatment layer on at least the upper surface, more preferably on both side surfaces, and on the lower surface on the image display element side described later. Also, a blackening treatment layer is preferably formed.

  As the blackening treatment layer, any known electromagnetic shielding filter may be adopted as appropriate. For example, as the blackening treatment layer, an inorganic material such as a metal, an organic material such as a black resin, or the like can be used. The inorganic material is, for example, a metal compound such as a metal or an alloy, a metal oxide, or a metal sulfide, and can be formed by a known blackening process such as a plating method. Moreover, as black resin, it can form as a layer which contained the black coloring agent in resin, for example.

[Transparent adhesive layer]
The transparent adhesive layer 4 is a layer for fixing the aluminum pattern to the transparent substrate. For example, when the aluminum pattern is formed from an aluminum foil, the transparent adhesive layer 4 is used for bonding and fixing the aluminum foil to the transparent substrate. . In addition, a transparent adhesive bond layer can be abbreviate | omitted when forming from the aluminum layer which laminated | stacked the aluminum pattern directly on the transparent base material by aluminum vapor deposition.

  The transparent adhesive layer may be a transparent adhesive so as not to impair the light transmission through the openings of the aluminum pattern, and a known transparent adhesive may be used as appropriate. For example, urethane adhesive, acrylic adhesive, epoxy adhesive, rubber adhesive, and the like. Among these, urethane adhesives, for example, two-component curable urethane adhesives are preferable in terms of adhesive strength. As the two-component curable urethane-based adhesive, an adhesive using a polyol as a main agent and a polyisocyanate compound as a curing agent can be used. Examples of the polyol include acrylic polyol, polyester polyol, polyurethane polyol, polyether polyol, and polyester polyurethane polyol. Examples of the polyisocyanate compound include tolylene diisocyanate, xylylene diisocyanate, and hexamethylene diisocyanate. A plurality of polyols and polyisocyanates may be used.

  The transparent adhesive layer can be formed by applying a transparent adhesive to one or both of an aluminum foil and a transparent substrate by a known forming method, and then laminating these with an adhesive interposed therebetween. The forming method includes a coating method and a printing method.

[Multi-function filter]
The multi-function filter 20 is a filter having an optical filter function as well as an electromagnetic wave shielding function by further laminating an optical filter on the above-described electromagnetic wave shielding filter. FIG. 2 is a cross-sectional view showing one embodiment of such a multifunction filter 20, which is a filter having a configuration in which the optical filter 5 is directly laminated on one surface of the electromagnetic wave shielding filter 10.
The laminated surface may be either one surface of the electromagnetic wave shielding filter 10 or both surfaces. In addition, when a lamination | stacking surface is single side | surface, any of the surface by the side of the lower surface of a transparent base material and the surface by the side of the upper surface of an aluminum pattern may be sufficient.

  By making a multi-function filter in which an optical filter is further laminated on an electromagnetic wave shielding filter, the multi-functionality is provided with an optical filter function as well as an electromagnetic wave shielding function, making it possible to share a transparent base material and reduce the thickness of the filter. Cost reduction is also possible.

(Optical filter)
As the optical filter 5, a known optical filter having an optical filter function may be appropriately selected. Examples of the optical filter function include a near-infrared absorption function that absorbs near-infrared light, an ultraviolet absorption function that absorbs ultraviolet light, a neon light absorption function that absorbs neon light of a PDP display, and color correction that corrects a display image to a desired color tone. A thin film having a specific light transmission function such as a function, an antireflection function (any of antiglare, antireflection, antiglare and antireflection), or a contrast enhancement function by antireflection of external light described in JP-A-2007-272161 It is a minute louver.
The optical filter 5 has one function or two or more functions among the various optical filter functions such as the above-described near-infrared absorption function, antireflection function, and contrast enhancement function.

These various optical filter functions, for example, near infrared absorption function, neon light absorption function, color correction function, etc., using dyes corresponding to these functions (near infrared absorption dye, neon light absorption dye, color correction dye), The ultraviolet absorbing function can be realized by a known material / method such as using an ultraviolet absorber. For example, a resin layer in which these materials are dispersed in a resin can be formed as an optical filter layer by a known coating method, extrusion method, or the like. In addition, the resin layer can be used for a plurality of functions depending on a single layer or a multilayer structure.
Further, the optical filter layer having an optical filter function including an antireflection function may be appropriately laminated on a transparent substrate to form an optical filter. In addition, as a transparent base material here, the material listed with the transparent base material of the above-mentioned electromagnetic wave shielding filter can be used.

[Other layers]
The electromagnetic wave shielding filter and the multi-function filter described above include other layers such as a flattening resin layer for flattening the unevenness on the upper surface side of the aluminum pattern, a surface protective layer for protecting the surface, a hard coat layer, and a contamination prevention function. In these filters, known layers such as a layer, an antistatic functional layer, and an adhesive layer can be laminated. These layers can be combined.

[Image display device]
The image display device of the present invention is an image display device in which the above-described electromagnetic wave shielding filter or multi-functional filter is disposed on the front surface, and more specifically, the above-described electromagnetic wave shielding filter or multi-functional filter is disposed on the observer side of the image display element. It is the display device arranged in. The front surface is the observer side of the image display device. Moreover, arrangement | positioning should just follow a well-known form.

  By using such an image display device, the cost can be reduced, and the spread of the image display device can be promoted.

(Image display element)
Examples of the image display element include a plasma display panel (also referred to as PDP), a cathode ray tube (also referred to as CRT), a liquid crystal display element (also referred to as LCD), an electroluminescent element (also referred to as EL), and the like that generate electromagnetic waves. is there. For example, in PDP, unnecessary electromagnetic waves in a band of 30 MHz to 1 GHz are generated.

(Arrangement form)
The electromagnetic wave shielding filter or the multi-functional filter is arranged on the observer side of the image display element, and is roughly divided into the electromagnetic wave shielding filter or the multi-functional filter on the observer side of the image display element without a space, However, a configuration in which the electromagnetic wave shielding filter or the multi-functional filter is disposed on the viewer side of the image display element through a space [FIG. 3 (b)].

  The image display device 40 in the form of being directly laminated as shown in FIG. 3A has the electromagnetic wave shielding filter 10 or the multi-function filter 20 directly without leaving a gap on the surface of the image display element 30 on the viewer side. It is a laminated display device. The electromagnetic wave shielding filter 10 or the multi-function filter 20 can be obtained by directly pasting the surface of the image display element 30 on the viewer side. In that case, it laminates | stacks through a transparent adhesive agent as needed. The adhesive (including the pressure-sensitive adhesive) may be a known one such as an adhesive layer provided as a part of the electromagnetic wave shielding filter 10 or the multi-function filter 20, or an adhesive layer applied between the layers during lamination. As the transparent adhesive, the adhesive listed in the transparent adhesive layer described above can be used.

  On the other hand, in the case of the image display apparatus 40 arranged in the space shown in FIG. 3B, a plate-like laminate in which the electromagnetic wave shielding filter 10 or the multifunction filter 20 is once laminated directly on the surface of the transparent substrate 6. 21 is arranged with a space on the viewer side of the image display element 20.

As shown in FIG. 3B, in the form in which the electromagnetic wave shielding filter 10 or the multi-function filter 20 is disposed with a space therebetween, the electromagnetic wave shielding filter 10 or the multi-function filter 20 is not a rigid plate-like body but a sheet or When the film shape is flexible and the shape cannot be maintained, the plate-like laminate 21 laminated with the transparent substrate 6 is preferable in that the shape can be maintained.
3B, the electromagnetic wave shielding filter 10 or the multi-function filter 20 is laminated on the surface on the observer side with respect to the transparent substrate 6 in the form illustrated in FIG. Further, it may be laminated on the surface on the image display element side.

(Transparent substrate)
As the transparent substrate 6, a plate-like body capable of maintaining its shape, for example, an inorganic plate such as glass or ceramics, a resin plate, or the like can be used. Examples of the resin for the resin plate include polyester resins such as polyethylene terephthalate and polyethylene naphthalate, acrylic resins such as polymethyl methacrylate, polyolefin resins such as cycloolefin polymers, cellulose resins such as triacetyl cellulose, and polycarbonate. Resin, polyimide resin and the like.
In the resin of the transparent substrate, known additives such as an ultraviolet absorber, a colorant, a filler, a plasticizer, and an antistatic agent can be appropriately added as necessary.

[Example 1]
First, a continuous strip-shaped rolled aluminum foil having a thickness of 12 μm was prepared as a metal foil for an aluminum pattern. When the thickness of the oxide film on the surface of this aluminum foil was measured, it was 8 mm on both the upper and lower surfaces.
Further, as a transparent substrate, a continuous belt-like uncolored transparent biaxially stretched polyethylene terephthalate film having a polyester resin primer layer formed on one side was prepared.

  Next, the primer layer surface of the transparent substrate and the glossy surface of the aluminum foil are cured with respect to 12 parts by mass of a transparent two-component curable urethane resin-based adhesive (polyester polyurethane polyol having an average molecular weight of 30,000 as a main component). (Including 1 part by mass of xylylene diisocyanate-based prepolymer as an agent), followed by curing at 50 ° C. for 3 days, and a continuous strip of aluminum having a 7 μm thick transparent adhesive layer between the aluminum foil and the transparent substrate A foil laminated sheet was obtained.

  Next, the aluminum foil of the aluminum foil laminated sheet is subjected to a chemical etching process using a photolithographic method, and a mesh-like region composed of an opening and a line portion, and a frame shape on the outer edge surrounding the mesh-like region. An aluminum pattern having a grounding region with no opening was formed.

  More specifically, the etching was performed consistently from masking to etching on the continuous belt-like laminated sheet using a production line for a color TV shadow mask. That is, after applying a photosensitive etching resist on the entire surface of the aluminum foil of the laminated sheet, a desired mesh pattern is closely exposed, developed, hardened, and baked to form a resist on the area corresponding to the mesh opening. After forming the resist pattern in which the layer is not formed, the aluminum foil in the resist layer non-formed part is removed by etching with an acid aqueous etchant containing ferric chloride to have a mesh-like opening. An aluminum pattern was formed, and then washing with water, stripping of the resist, washing, and drying were sequentially performed.

  The mesh shape of the mesh area (image display area) is such that the line width of the linear line portion whose opening is a square and non-opening is 20 μm, the line interval (pitch) is 300 μm, and the height of the line portion. When cut into a rectangular sheet of 12 μm, the bias angle defined as the minor angle formed by the line portion and the long side of the rectangle was 49 degrees. Thus, the intermediate body of the electromagnetic wave shielding filter of width dimension 605mm was obtained, and it wound up in roll shape.

  The obtained roll-shaped electromagnetic shielding filter intermediate is continuously supplied to the blackening device using rolls, tows, and rolls, and a nickel compound blackening layer is formed on the aluminum pattern surface of the intermediate. And wound up to obtain an electromagnetic wave shielding filter.

  Regarding the pattern accuracy of the obtained aluminum pattern, the variation in the line width of the mesh was 4.5 μm, the surface unevenness had no problem in appearance, and there was almost no variation in the surface resistance value.

[Comparative Example 1]
An electromagnetic wave shielding filter was obtained in the same manner as in Example 1 except that an aluminum foil having a surface oxide film thickness of 15 mm was used.
As for the pattern accuracy of the obtained aluminum pattern, breakage occurred frequently in the mesh line (line width variation of 20 μm or more), surface irregularity was conspicuous visually, and the surface resistance value varied greatly.

Sectional drawing which shows one form of the electromagnetic wave shielding filter by this invention. Sectional drawing which shows one form of the multifunction filter by this invention. Sectional drawing which shows the example of a form of the image display apparatus by this invention. Sectional drawing explaining the cause which a pattern precision defect produces at the time of etching an aluminum pattern. The top view which illustrates the pattern accuracy defect of an aluminum pattern notionally.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent base material 2 Aluminum pattern 3 Oxide film 4 Transparent adhesive layer 5 Optical filter 6 Transparent substrate 10 Electromagnetic wave shielding filter 20 Multifunctional filter 21 Plate-shaped laminated body 30 Image display element 40 Image display apparatus 51 Etching liquid 52 Resist pattern 53 Aluminum Layer 54 Aluminum foil 55 Aluminum foil laminate (sheet)
56 Corrosion preceding part

Claims (3)

In an electromagnetic wave shielding filter in which a metal pattern is formed on a transparent substrate,
Electromagnetic wave shielding, wherein the metal pattern is an aluminum pattern, and the thickness of the aluminum oxide film on at least the upper surface of the aluminum pattern (the surface facing the same direction as the side on which the aluminum pattern is formed with respect to the transparent substrate) is 0 to 13 mm filter.   A multi-function filter in which the electromagnetic wave shielding filter according to claim 1 and an optical filter are laminated. The image display apparatus which has arrange | positioned the electromagnetic wave shielding filter of Claim 1, or the multifunction filter of Claim 2 in the front surface.

Images