JP2010056122A - Electromagnetic wave shielding filter, multifunctional filter, and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnetic wave shielding filter which is made of aluminum and inexpensive, and contributes to moire improvement by improving a decrease in precision of a metal pattern, formed by chemical etching, the decrease being caused when a material of the metal pattern is changed from copper to inexpensive aluminum, and to make a multifunctional filter and an image display device inexpensive using the electromagnetic wave shielding filter. <P>SOLUTION: The electromagnetic wave shielding filter has an aluminum pattern 2 as the metal pattern on a transparent base, and satisfies 13 Å<t≤20 Å and 50%<(ΔL/L)×100<100%, where t is the thickness of an oxide film of aluminum at least on an upper surface thereof (on the side where the pattern 2 is formed on the transparent base), L is an average value of the line width of the pattern 2, and ΔL (3σ) is variance. Further, the multifunctional filter is constituted by stacking the electromagnetic wave shielding filter and an optical filter, and the image display device has the electromagnetic wave shielding filter or multifunctional filter arranged in the front. <P>COPYRIGHT: (C)2010,JPO&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 (electromagnetic interference (EMI) shielding mesh, also abbreviated as EMI mesh) is obtained by bonding a metal foil to a transparent substrate with a transparent adhesive, and then chemically etching the metal foil into a mesh by photolithography. It can be made (Patent Document 1, Patent Document 2).
Further, when the mesh pattern is arranged on the front surface of the image display device, moire occurs due to the relationship with the pixel arrangement of the image display device, and in order to improve this, the mesh metal pattern is changed to the pixel arrangement. A method of tilting (also referred to as a bias angle) is well known.

  And as for the 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. And if the degree of a jaggedness is large, it will lead to disconnection, and disconnection will lead to a fall of electromagnetic wave shielding performance.

That is, the object of the present invention is to improve the deterioration of the pattern accuracy 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 while suppressing the occurrence of disconnection, An object of the present invention is to provide an inexpensive and practical electromagnetic wave shielding filter using aluminum in which moiré is improved by actively utilizing a decrease in accuracy.
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). The thickness t of the aluminum oxide film on the surface of the aluminum pattern in the same direction as the formed side is 13 mm <t ≦ 20 mm, and the average value L of the line width of the aluminum pattern and 3σ (σ is the standard deviation) of the line width distribution The electromagnetic wave shielding filter has a variation ΔL of 50% <(ΔL / L) × 100 <100%.

In this way, at least the thickness of the aluminum oxide film on the upper surface side is suitably thin, specifically as described above, and by defining the line width variation ΔL and the average value L as described above, When the aluminum pattern is formed by chemical etching, stable etching can be performed while leaving a line outline scratch to an extent that leads to moire improvement while suppressing the occurrence of line disconnection. As a result, an electromagnetic wave shielding filter that is less expensive in material and leads to improvement in moire can be realized by using aluminum that is cheaper 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 that is cheaper than copper is used for the metal pattern, the occurrence of disconnection is suppressed for the zigzag and disconnection of the line contour during chemical etching formation, Contour scratches allow stable etching that remains to the extent that moire is improved, and an inexpensive electromagnetic shielding filter that improves moire can be 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 t of the oxide film on the upper surface is in the range of 13 mm <t ≦ 20 mm. Moreover, the aluminum pattern 2 has an average value L of the line width and a variation ΔL that is 3σ (σ is a standard deviation) of the distribution of the line width,
50% <(ΔL / L) × 100 <100%.
Note that σ is a standard deviation.
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 oxide film 3 of aluminum having a specific thickness range of 13Å <t ≦ 20Å (t: thickness) on at least the upper surface thereof. Note that 1Å = 0.1 nm.
By setting the thickness range as described above, it is possible to bring out the possibility of stable etching in which the flaws of the outline of the line are left to the extent that moire is improved while the occurrence of disconnection is suppressed.

  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.

Also, in order for the outline of the line portion of the pattern to be a knurl that can reduce moire but suppress the occurrence of disconnection, the line width of the aluminum pattern is expressed by the line width variation ΔL and the average value L of the line width. For the relationship, the value of (ΔL / L) × 100 is
It is preferable to set it to more than 50% and less than 100%. That means
50% <(ΔL / L) × 100 <100%.
In other words, the line width variation ΔL is set to exceed 50% of the average value L of the line width, but considering the prevention of disconnection, 100% which is the same as the average value L is not included and is less than 100%. It is preferable to suppress.

  Here, FIG. 2 is a plan view for conceptually explaining the average value L and the variation ΔL of the line width, and a part of the contour on the right side of the line 2 shown in FIG. FIG. 2B is a partially enlarged view shown. FIG. 2 is for conceptually explaining the meanings of the average value L and variations ΔL, L−ΔL, L + ΔL, etc., and shows the aspect ratio of the drawing, the relationship between the line width and variation, and the degree of unevenness of the line contour. This is not the case. Further, the relationship between L−ΔL, L + ΔL, and L is conceptually shown as a representative line width based on the jagged shape of the one-side outline of the line.

  If the relationship between ΔL and L defined by (ΔL / L) × 100 is 50% or less, the moire improvement effect is excessively lowered, which is not preferable. Note that the value of the above relational expression is preferably over 50%, more preferably over 60%.

By the way, the average value L and the variation ΔL of the line width in the present invention are obtained by measuring the line width of the aluminum pattern at a large number of measurement positions in the same production lot (the number of measurements is at least the number of measurements n ≧ 3, Preferably, the number of measurements is n ≧ 10), the average value of the line widths obtained by statistical processing of the measurement results of the individual line widths is L, and 3σ, which is three times the standard deviation σ with respect to the distribution of the line widths, is a variation ΔL. It is.
As a result, the majority of the line width distribution falls within the range of (L−ΔL) to (L + ΔL) (99.7% assuming that the distribution is a normal distribution).

  In the present invention, the relational expression (ΔL / L) × 100 is such that ΔL is 0.5 L when the minimum is 50%, and the individual line width is 0.5 L <individual line width <1.5 L. Further, when the maximum is 100%, which is not preferable, ΔL is 1.0 L, and the individual line width is 0.0 L ≦ individual line width ≦ 2.0 L. 0.0L means that the line width is zero, that is, disconnection has occurred. Therefore, in order to prevent disconnection, it is preferable that the above relational expression has a maximum value of less than 100% so that it does not exceed 100% at the maximum.

In addition, when the measurement target of multiple line widths is not in the same production lot but can be measured for a plurality of different production lots, a large number of measurement positions are distributed in a plurality of different production lots. However, from the viewpoint of wire breakage suppression and moire suppression, the meanings of the average value L and the variation ΔL are the appearance of transmitted images (moire fringes, unevenness, contrast, etc.) and electromagnetic wave shielding performance when a specific product is evaluated. It is necessary to measure L and ΔL and calculate (ΔL / L) × 100 in one product unit (for one screen of the image display device) in the same lot. There is. However, when evaluating the distribution status of (ΔL / L) × 100 of each product in the same lot, the significance of comparing and evaluating the difference of the numerical values for a plurality of different products in the same lot There is. Further, when comparing and measuring the difference between the numerical values for each production lot, it is meaningful to compare and measure the numerical values of products in a plurality of lots.
Note that the thickness of the aluminum oxide film is set to exceed 13 mm in order to satisfy 50% <(ΔL / L) × 100 <100% with respect to the width of the linear portion (line portion) of the aluminum pattern. At the same time, the etching processing conditions (such as the composition, concentration, liquid temperature, or circulation of the corrosion solution) are controlled so that the value of (ΔL / L) × 100 converges to a predetermined range.

(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. The pattern formation of the resist pattern at the time of chemical etching is a known method such as a photolithography method (for example, a pattern exposure method for a photosensitive resist film), a printing method capable of forming a pattern without using a pattern exposure method using a photosensitive resist film, etc. What is necessary is just to select the pattern formation method suitably. 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 t is defined for the etched side, that is, the upper surface side. Regarding the thickness t of the aluminum oxide film on at least the upper surface of the aluminum pattern, the lower limit is not more than 13 mm not including 13 mm, more preferably 14 mm or more, and further preferably 15 mm or more. On the other hand, the upper limit of the thickness t is 20 mm or less, preferably 18 mm or less, more preferably 17 mm or less, and still more preferably 16 mm or less. If the thickness t of the aluminum oxide film on the upper surface of the aluminum pattern is smaller than the lower limit described above, it is difficult to leave a jagged edge that contributes to the improvement of moire. Although it is likely to remain, disconnection is likely to occur. Therefore, the range of the thickness t is 13Å <t ≦ 20Å.

  For the thickness t of the aluminum oxide film on the upper surface at least, the lower limit and the upper limit range are set as described above, so that even if the oxide film is still present, the disconnection is suppressed and the moiré is improved. Stable chemical etching can be performed so that the remaining pattern accuracy can be obtained, and pattern accuracy defects that lead to disconnection due to the change of copper to inexpensive aluminum can be avoided.

  By the way, normally manufactured aluminum foil is manufactured by a rolling method, and manufactured and stored at normal 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, but it does not become a thin oxide film as in the present invention, but usually becomes an oxide film of more than 20 to 100 mm.

  There are various ways to reduce the thickness of the aluminum oxide film as described above compared to the case of conventional aluminum foil. When aluminum foil is used for an aluminum pattern, the aluminum foil is formed by a rolling method. Although it is made and then annealed, it can be adjusted to the desired thickness by adjusting the 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. As for the aluminum oxide film on the lower surface, 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. There is no need to specify. 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 t of the aluminum oxide film on the lower surface is set to 13 mm <t ≦ 20 mm, similarly to the film thickness t on 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 for chemical etching, the minimum wavelength of visible light is less than 380 nm (for example, 3 例 え ば ≦ t A transparent aluminum oxide film having a thickness of ≦ 13 mm) can be left to protect the transparent adhesive layer or the transparent substrate exposed to the opening during chemical etching 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. 3 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, usually, a configuration in which the electromagnetic wave shielding filter or the multifunction filter is disposed on the viewer side of the image display element through a space [FIG. FIG. 4 (b)].

  The image display device 40 in the form of being directly laminated as shown in FIG. 4A directly connects the electromagnetic wave shielding filter 10 or the multi-function filter 20 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 device 40 arranged in the form shown in FIG. 4B, 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. 4B, 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.
Further, in the plate-like laminate 21, in the form illustrated in FIG. 4B, the electromagnetic wave shielding filter 10 or the multi-function filter 20 is laminated on the surface on the viewer side with respect to the transparent substrate 6. Further, it may be laminated on the surface on the image display element side.

(Transparent substrate)
In addition, as the transparent substrate 6, a plate-like body capable of maintaining the 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 (IN30; JIS H4160 compliant) having a thickness of 12 μm was prepared as a metal foil to be an aluminum pattern. When the thickness of the oxide film on the surface of this aluminum foil was measured, it was 14 mm on both the upper and lower surfaces.
Further, as a transparent substrate, a continuous belt-shaped uncolored transparent biaxially stretched polyethylene terephthalate film having a polyester resin primer layer formed on both surfaces was prepared.

  Next, one primer layer surface of the transparent base material and the glossy surface of the aluminum foil are combined with a transparent two-component curable urethane resin adhesive (based on 12 parts by mass of a polyester polyurethane polyol having an average molecular weight of 30,000 as a main agent). , Including 1 part by mass of xylylene diisocyanate prepolymer as a curing agent), and then heat aging to cure the adhesive, and a transparent adhesive layer having a thickness of 3 μm is formed between the aluminum foil and the transparent substrate. A continuous strip-shaped aluminum 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 (frame region) where no opening was formed was formed.

  Specifically, the etching was consistently performed 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-like region (image display region) is such that the line width (average value) of the linear line portion having a square opening and a non-opening portion is 20 μm, and the line interval (pitch) is 300 μm. The height of the portion was 12 μm, and when cut into a rectangular sheet, the bias angle defined as the minor angle formed by the line portion and the long side of the rectangle was 0 degree. 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 mesh line width has a variation of ± 16 μm with respect to the average value L20 μm, and the relationship between the average value L and the variation ΔL is (ΔL / L) × 100 = 80%. is there. Visually, the uniformity of the mesh region is very high and appears to be free of defects, and no moiré occurs even when installed on the front surface of the PDP.

[Example 2]
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 18 mm was used.
Regarding the pattern accuracy of the obtained aluminum pattern, the mesh line width has a variation of ± 19.2 μm with respect to the average value L20 μm, and the relationship between the average value L and the variation ΔL is (ΔL / L) × 100 = 96. %. The uniformity of the mesh-like region is visually very high and appears to be free of defects, the line portion is not broken, and no moiré occurs even when installed in front of the PDP.

[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 5 mm was used.
Regarding the pattern accuracy of the obtained aluminum pattern, the mesh line width varies ± 1 μm with respect to the average value L20 μm, and the relationship between the average value L and the variation ΔL is (ΔL / L) × 100 = 5. %. Visually, the uniformity of the mesh region is very high and appears to be free of defects, but since the linearity of the outline of the line is high, moire occurs when installed on the front surface of the PDP.

Sectional drawing which shows one form of the electromagnetic wave shielding filter by this invention. The top view explaining notionally about the line of an aluminum pattern by the average value L of line width, and variation (DELTA) L of line width. 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.

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

Claims (3)

In an electromagnetic wave shielding filter in which a metal pattern is formed on a transparent substrate,
The metal pattern is an aluminum pattern, and the thickness t of the aluminum oxide film on at least the upper surface of the aluminum pattern (the surface in the same direction as the side on which the aluminum pattern is formed with respect to the transparent substrate) is 13 mm <t ≦ 20 mm. ,
And the average value L of the line width of the aluminum pattern and the variation ΔL that is 3σ (σ is a standard deviation) of the distribution of the line width,
An electromagnetic wave shielding filter in which 50% <(ΔL / L) × 100 <100%.   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