JP5167181B2 - Electromagnetic wave shielding filter - Google Patents

Description

  The present invention relates to an electromagnetic wave shielding filter that is disposed on the front surface of an image display device (display) and shields electromagnetic waves generated from the display.

Currently, the electromagnetic wave shielding member is used for applications such as disposing on the front surface of the display, and among them, there is typically a plasma display (also referred to as PDP) application. 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. The metal pattern (EMI shielding mesh) is obtained by bonding metal foil to a transparent substrate with a transparent adhesive, and then chemically etching the metal foil (which is often used with inexpensive copper foil) into a mesh by photolithography. (For example, refer to Patent Document 1).
In addition, it is desirable that the metal mesh is difficult to be seen in order not to impair the image quality of the display device. In addition to thinning, the brightness and chromaticity of the surface are reduced in order to prevent screen whitening and image contrast degradation due to external light reflection. It needs to be small and have little pattern and unevenness. Therefore, in order to reduce the brightness and chromaticity of the surface of the metal mesh, the metal foil is generally blackened (see, for example, Patent Document 2).

The PDP is characterized by a large screen, for example, 37 type, 42 type, and even a large size. For this reason, the number of lines (wires) of the electromagnetic wave shielding filter is usually several thousand in the vertical and horizontal directions, and the width of the lines must be within a certain range. If the variation (distribution) of the line width (line width) is large, black and white dot defects, line defects, or rectangular defects occur on the mesh surface, and the visibility of the image is not good.
Further, when the variation in the L ^* value of the black layer surface of the electromagnetic wave shielding filter (Commission Internationale de l'Eclairage (CIE) defined in L ^* a ^* b ^* color system of L ^*) is large, the blackening degree mesh surface Unevenness is visible, and the visibility of the image is not good.

JP 2003-318596 A Republished in 2005/066732

  Therefore, the present invention has been made to solve such problems, and the object thereof is to arrange on the front surface of a display such as a CRT or PDP, shield electromagnetic waves generated from the display, and mesh. Black and white spot defects, line defects or rectangular defects are unlikely to occur on the metal pattern surface represented by To provide a filter.

As a result of various studies to solve the above problems, the present inventors have found that the composition and properties of the blackening layer applied to the metal foil are related to the ease of chemical etching and affect the variation in line width. By selecting the composition and properties of the blackened layer with good chemical etching suitability and making the line width variation less than the predetermined value, black and white spot defects, linear defects on the metal pattern surface, Alternatively, it has been found that an electromagnetic wave shielding filter that is less likely to have a rectangular defect and has good image visibility is provided.
In addition, by selecting the composition and properties of the blackened layer applied to the metal foil and setting the variation of the L ^* value on the blackened layer surface to a predetermined value or less, unevenness in the degree of blackening is not visually observed, and image visibility is improved. It has been found that a good electromagnetic shielding filter is provided.

The electromagnetic wave shielding filter according to the first invention is an electromagnetic wave shielding filter formed by laminating at least an adhesive layer and a metal pattern layer in this order on a transparent substrate, and the metal pattern layer is a transparent copper layer. It consists of a layer structure in which a blackening layer is laminated on one side or both sides of the substrate side or the transparent substrate, and the blackening layer is composed of a first colored layer made of copper, cobalt and zinc, nickel, cobalt and A second colored layer made of molybdenum is formed on a copper layer in this order, and the blackening layer surface has a lightness of L ^* of 20 to 40, and chromaticity of a ^* and b ^* of 0 to 10, respectively. In addition, the line width variation of the wire ridges constituting the metal pattern layer is 2.0 μm or less.
An electromagnetic wave shielding filter according to a second invention is an electromagnetic wave shielding filter formed by laminating at least an adhesive layer and a metal pattern layer in this order on a transparent substrate, and the metal pattern layer is a transparent copper layer. It consists of a layer structure in which a blackening layer is laminated on one side or both sides of the substrate side or the transparent substrate, and the blackening layer is composed of a first colored layer made of copper, cobalt and zinc, nickel, cobalt and A second colored layer made of molybdenum is formed on a copper layer in this order, and the blackening layer surface has a lightness of L ^* of 20 to 40, and chromaticity of a ^* and b ^* of 0 to 10, respectively. And the variation of the L ^* value (value measured in the PET film laminate state) on the surface of the metal mesh layer is 0.5 or less.
In both inventions, the total content of copper, cobalt, zinc, nickel and molybdenum in the blackened layer is 1 to 3 mg / dm ² , and the content ratio is 30 to 45% for copper and 15 for cobalt. It is preferable that it is ˜25%, zinc is 10 to 25%, nickel is 5 to 15%, and molybdenum is 10 to 20%.

According to the first invention, electromagnetic waves generated from a display such as a CRT or PDP are shielded, the wire ridges of the metal pattern are invisible, satisfy both electromagnetic wave shielding properties and transparency, and Electromagnetic wave shielding that makes it difficult to generate black and white spot defects, line defects, or rectangular defects on the metal pattern surface, and allows an image to be viewed well, because the line width variation of the portion is less than a certain value A filter is provided.
According to the second invention, electromagnetic waves generated from a display such as a CRT or PDP are shielded, the wire ridges of the metal pattern are invisible, satisfy both electromagnetic shielding properties and transparency, and the metal When the variation in the L ^* value on the surface of the pattern layer is equal to or less than a certain value, an electromagnetic wave shielding filter is provided in which unevenness in the degree of blackening of the metal pattern is not visually recognized and the image can be viewed well.

The electromagnetic wave shielding filter of the present invention is formed by laminating at least an adhesive layer and a metal pattern layer in this order on a transparent substrate, and the metal pattern layer is opposite to the transparent substrate side of the copper layer or the transparent substrate. It has a layer structure in which a blackening layer is laminated on one side or both sides of the side. The blackening layer includes a first colored layer made of copper, cobalt and zinc, and a second colored layer made of nickel, cobalt and molybdenum. It is formed on the layer in this order, and the lightness of the blackened layer surface is 20 to 40 for L ^* and 0 to 10 for chromaticity a ^* and b ^* , respectively.
Moreover, in the first invention, the line width variation of the wire ridges constituting the metal pattern layer is not more than a predetermined value, and in the second invention, the variation of the L ^* value of the blackened layer is not more than a certain value. .

In the electromagnetic wave shielding filter of the present invention, first, a copper layer provided with a blackening layer (hereinafter also referred to as a blackening treatment layer) is prepared at least on the viewer side, and the copper layer is applied to one surface of the transparent substrate. After laminating via an adhesive, a resist layer is provided on the copper layer surface in a desired pattern such as a mesh, and after removing the blackened copper layer not etched by the resist layer by etching, the resist layer It is manufactured by a so-called photolithographic method for removing water.
Hereinafter, the material and formation of each layer of the electromagnetic wave shielding filter of the present invention will be described.

(Copper layer)
As the copper layer for shielding electromagnetic waves, rolled copper foil and electrolytic copper foil can be used. From the viewpoint of uniformity of thickness, adhesion to the blackening treatment layer, and thinning of 10 μm or less, the electrolytic copper foil is preferable.
The thickness of the copper layer is about 1 to 100 μm, preferably 5 to 20 μm. If the thickness is less than this, pattern processing by the photolithographic method becomes easy, but the electric resistance value of the metal is increased and the electromagnetic wave shielding effect is impaired, and if it is more than this, the desired high-definition pattern shape cannot be obtained. In addition, the electromagnetic shielding filter has disadvantages that the flexibility of the electromagnetic wave shielding filter is lowered, the workability is lowered due to the increase in weight, and the manufacturing cost is increased by using an excessive amount of copper in terms of performance.
The surface roughness of the copper layer is preferably 0.5 to 10 μm in terms of Rz value. Below this, even if the blackening process is performed, the external light is specularly reflected, and the visibility of the image is deteriorated. Above this, when the adhesive or resist is applied, the entire surface is not spread or bubbles are generated. The surface roughness Rz is an average value of 10 points measured according to JIS-B0601.

(Blackening treatment layer)
A blackening treatment layer is formed on the surface of the copper layer to reduce its light reflectance.
The blackening treatment layer of the present invention is obtained by forming a first coloring layer made of copper, cobalt and zinc and a second coloring layer made of nickel, cobalt and molybdenum in this order on the copper layer, and the surface of the blackening treatment layer The lightness of L ^* is 20 to 40 at L ^* and the chromaticity is 0 to 10 at a ^* and b ^* , respectively.

  Here, the surface means the upper surface and the lower surface, and the surface in contact with the transparent adhesive in the presence of the transparent adhesive layer is the lower surface. In order to use the electromagnetic wave shielding filter with the upper surface side of the image observer, it is preferable to form a blackening treatment layer on at least the upper surface, and more preferably, the lower surface on the image display element side is also blackened. A layer may be formed.

Lightness and chromaticity are measured with a color difference meter. In the present invention, the brightness and chromaticity are defined by the L ^* a ^* b ^* color system (also adopted in JIS Z 8729) defined by the International Commission on Illumination (CIE). The lightness means that the smaller the value is, the more black it is and it is hard to see without reflecting light, and the theoretical minimum value is zero. Chromaticity represents coordinates on the chromaticity diagram, and represents hue and saturation. In the L ^* a ^* b ^* color system, coordinates where the values of a ^* b ^* are both 0 represent a theoretical achromatic color.
When the brightness is in the range of 20 to 40 with L ^* , the surface of the copper foil appears black. On the other hand, if the chromaticity is a ^* and b ^* of 0 to 10, respectively, an achromatic color appears. When a ^* exceeds 10, the copper mesh appears red, when it is less than 0, it appears green, when b ^* exceeds 10, it appears yellow, and when it is less than 0, it appears blue. The preferred range for a ^* is 0-5, and the preferred range for b ^* is 0-5.

The first colored layer made of copper, cobalt, zinc, the second colored layer made of nickel, cobalt, molybdenum is formed in this order on the copper layer, and the blackened layer of the present invention, copper, cobalt, zinc, The total content of nickel and molybdenum is preferably 1 to 3 mg / dm ² , and the content is preferably 30 to 45% for copper, preferably 15 to 25% for cobalt, and preferably 10 for zinc. -25%, nickel is preferably 5-15%, and molybdenum is preferably 10-20%.

The first colored layer made of copper, cobalt and zinc can be formed by simultaneously plating copper, cobalt and zinc by electroplating.
The plating solution used for forming the first colored layer containing copper, cobalt, and zinc is a copper compound containing copper, such as copper sulfate, copper chloride, copper carbonate, copper hydroxide, cobalt sulfate, cobalt chloride, cobalt carbonate, water. An aqueous solution containing a cobalt compound containing cobalt such as cobalt oxide and a zinc compound containing zinc such as zinc sulfate, zinc chloride, zinc carbonate, and zinc hydroxide. It is preferable to add a non-plated electrolyte metal salt such as sodium sulfate to the plating solution and a buffering agent such as boric acid for the purpose of stabilizing the pH of the plating solution.

The copper ion concentration of the plating bath for forming the first colored layer is preferably 2.0 to 6.0 g / L, more preferably 3.0 to 4.5 g / L, and the cobalt ion concentration is preferably 1.0 to 4.0 g / L, more preferably 2.0 to 3.0 g / L, and the zinc ion concentration is preferably 1.0 to 5.0 g / L, more preferably 2.5. -4.0 g / L. For example, the plating is performed at a current density of 2.0 to 10.0 A / dm ² , preferably 5.0 to 8.0 A / dm ² , a plating bath temperature of 20 to 40 ° C., a plating time of 1 to 5 seconds, preferably 1 to It is desirable to carry out under conditions of 3 seconds.
The total content of copper, cobalt, and zinc in the formed first colored layer is preferably 0.5 to 1.5 mg / dm ² , and the content ratio is preferably 50 to 75% for copper. Cobalt is preferably 5 to 15%, and zinc is preferably 15 to 40%.

After forming the first colored layer, a second colored layer made of nickel, cobalt, and molybdenum is formed.
The second colored layer made of nickel, cobalt and molybdenum can be formed by simultaneously plating nickel, cobalt and molybdenum by electroplating.
As a plating solution used for forming the second colored layer containing nickel, cobalt, and molybdenum, a tartaric acid bath, a citric acid bath, a gluconic acid bath, a sulfamic acid bath, a pyrophosphoric acid bath, or the like can be applied. The metal ion source includes nickel compounds such as nickel sulfate, nickel chloride, nickel acetate, nickel carbonate and nickel sulfamate, and cobalt compounds containing cobalt such as cobalt sulfate, cobalt chloride, cobalt carbonate, cobalt sulfamate and cobalt gluconate. And molybdenum compounds containing molybdenum such as potassium molybdate, sodium molybdate, and ammonium molybdate.
The nickel ion concentration of the plating bath for forming the second colored layer is preferably 1.0 to 20.0 g / L, more preferably 1.0 to 5.0 g / L, and the cobalt ion concentration is preferably 1.0 to 20.0 g / L, more preferably 2.0 to 10.0 g / L, and the molybdenum ion concentration is preferably 0.2 to 10.0 g / L, more preferably 0.5. -5.0 g / L. Taking a citric acid bath as an example, a sodium citrate concentration of 20 to 50 g / L is preferable. For example, the plating is performed at a current density of 1.0 to 20.0 A / dm ² , preferably 2.0 to 5.0 A / dm ² , a plating bath temperature of 20 to 40 ° C., a plating time of 1 to 30 seconds, preferably 2 to 2. It is desirable to carry out under the condition of 10 seconds.
The total content of nickel, cobalt and molybdenum in the formed second colored layer is preferably 0.5 to 1.5 mg / dm ² , and the content ratio is preferably 25 to 50% for nickel. Cobalt is preferably 20 to 30%, and molybdenum is preferably 25 to 50%.

After forming the second colored layer, a rust preventive layer can be formed to improve the rust preventive property during storage of the copper foil and chemical resistance in the chemical treatment in the manufacturing process such as etching. The rust prevention treatment is not particularly limited as long as it does not affect the hue, and various rust prevention treatments used for copper foils for printed wiring board applications can be applied. Rust prevention treatment with chromium is suitable because it does not affect the hue.
The copper layer on which the blackening treatment layer obtained as described above is formed is laminated on a transparent substrate using a transparent adhesive.

(Transparent substrate)
The transparent substrate 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. Transparent materials such as glass and ceramics It may be a plate-like rigid body such as an inorganic plate or a resin plate. 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 and supplied from a winding (roll), appropriately processed, and then wound and stored in the winding.

Examples of resins for resin films and resin plates include polyesters such as polyethylene terephthalate, polyethylene naphthalate, ethylene glycol-1,4 cyclohexanedimethanol-terephthalic acid copolymer, and ethylene glycol-terephthalic acid-isophthalic acid copolymer. Examples thereof include resins, acrylic resins such as polymethyl methacrylate, polyolefin resins such as polypropylene and cycloolefin polymers, cellulose resins such as triacetyl cellulose, polycarbonate resins, and polyimide resins. 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.
Examples of the transparent inorganic material include soda glass, potash glass, borosilicate glass, lead glass, and other transparent ceramics such as PLZT and quartz.

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 the case of using a resin or transparent inorganic plate, the thickness is, for example, about 500 to 5000 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.
The transparent base material may be obtained by performing known easy adhesion treatment such as corona discharge treatment, primer treatment, or flame treatment on the surface thereof.

(Transparent adhesive layer)
The transparent adhesive layer is a layer for fixing the metal pattern layer to the transparent substrate. For example, when the metal pattern is formed from copper foil, the transparent adhesive layer is used to bond and fix the copper foil to the transparent substrate. .
The transparent adhesive layer may be a transparent adhesive so as not to impair the light transmission through the opening of the metal pattern layer, and a known transparent adhesive may be appropriately used. 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.
The transparent adhesive layer can be formed by applying a transparent adhesive to one or both of a copper foil and a transparent substrate by a known forming method, and then laminating them with the adhesive interposed therebetween. The forming method includes a coating method and a printing method.

(Photolithographic method)
The resist layer is provided in a mesh pattern on the blackened copper layer surface, and after removing the copper layer not covered with the resist layer by etching, the resist layer is removed by a photolithographic method. To do.
Masking is performed, for example, by applying a photosensitive resist onto a blackened copper layer, drying, and then performing close contact exposure with an original plate (photomask) of a predetermined pattern (pattern line portion), developing with water, Bake with hardening.

  After masking, etching (corrosion and removal of the copper layer where the resist is not formed) is performed. As the etching solution used for the etching, a solution of ferric chloride or cupric chloride that can be easily circulated is preferable in the present invention in which etching is continuously performed. After the etching, the substrate is dried after washing with water, removing the resist with an alkaline solution, and washing.

(Metal pattern)
The metal pattern portion is formed by forming a desired pattern made of a fine line having an opening in order to give visible light transparency to a metal layer made of copper without impairing the electromagnetic wave shielding property. Such a pattern is appropriately selected from shapes such as a mesh (mesh or lattice), a switch (a group of parallel lines or a striped pattern), a spiral (spiral or spiral), and the mesh is representative and general-purpose. In the specification of the present application, the term “electromagnetic wave” means, in a broad sense, an electromagnetic wave radiated from an image display device in particular in the kHz to GHz band. Among electromagnetic waves in a broad sense, those other than the above frequency bands such as visible light, infrared light, and ultraviolet light are referred to as visible light, infrared light, and ultraviolet light, respectively.
The mesh is composed of a plurality of openings surrounded by lines. The shape of the opening is not particularly limited. For example, a triangle such as a regular triangle, an isosceles triangle, a square such as a square, a rectangle, a rhombus, and a trapezoid, a pentagon, a hexagon (tortoise), an octagon, etc. Polygon, circle, ellipse, etc. can be applied. A plurality of these openings are combined into a mesh.
The line width of the line portion of the mesh pattern is, for example, 5 to 50 μm, and is 5 to 30 μm, more preferably 5 to 20 μm, in terms of the effect of the present invention. The line interval (pitch), which is a line repetition period, is, for example, 100 to 500 μm. The aperture ratio (ratio of the total area of the openings in the total area of the electromagnetic shielding pattern) is usually about 50 to 95%. In the case of patterns other than meshes, the line width, aperture ratio, etc. may be selected from an equivalent numerical range.

(Line width variation)
In the first invention, the variation in the line width of the line portion of the pattern (three times the standard deviation (3σ)) needs to be 2.0 μm or less.
Usually, several thousand or more straight lines are formed on an electromagnetic wave shielding sheet for a large plasma display panel, and each of them intersects. By suppressing the variation of the line width to 2.0 μm or less, it has electromagnetic wave shielding properties and appropriate transparency, there is little unevenness in the density of the metal pattern, and especially black and white dots and line defects In addition, it is possible to obtain an electromagnetic wave shielding filter that has less display light glare, or suppresses reflection of external light and has excellent image visibility.
As described above, in order to set the line width variation (three times the standard deviation (3σ)) to a predetermined value or less, it is important to select the composition and properties of the blackened layer having good etching suitability as described above. In addition to this, it is controlled by the type of resist and the conditions of the etching process. For example, a dry resist film or a liquid resist is used as a method for forming a resist film. Etching conditions include a baume degree of an etching solution of 35 degrees or more, or cupric chloride or chloride chloride as an etching solution. Etching by using a ferric aqueous solution and setting the etching solution temperature to 35 ° C. or higher, the spray flow rate of the etching solution to 2000 mL / min or more, and swinging the spray nozzle or swinging left and right. It is desirable.

(L ^* value variation on the blackened layer surface)
In the second invention, the variation 3σ of the L ^* value (value measured in the PET film laminate state) on the blackened layer surface is required to be 0.5 or less.
By suppressing the variation in the L ^* value on the surface of the blackened layer to 0.5 or less, it is possible to obtain an electromagnetic wave shielding filter in which the unevenness of the degree of blackening of the metal pattern is not visually recognized and the image can be viewed well.
Thus, in order to make the variation of the L ^* value (three times the standard deviation (3σ)) of the blackened layer surface below a predetermined value, it is necessary to select the composition and properties of the blackened layer as described above. It is.

(Optical filter layer)
The thus obtained electromagnetic wave shielding filter can be used as a composite filter having both an electromagnetic wave shielding function and an optical function by providing an optical filter layer. As the optical filter layer, a conventionally known layer may be used as it is, and examples thereof include a near infrared absorption layer, a neon light absorption layer, an ultraviolet absorption layer, an antireflection layer, and an antiglare layer.
In addition, if necessary, the composite filter can be further combined with a functional layer that expresses functions other than the optical function. Examples of such a layer include an impact resistant layer, an antistatic layer, a hard coat layer, and an antifouling layer.
Here, when an optical filter layer such as an antireflection layer is directly formed on a transparent base material on which a metal pattern layer is formed, unevenness between the metal pattern layer and the transparent base material may cause uneven coating of the antireflection layer or mixing of bubbles. Occurring, the bubbles scatter the image light, resulting in a decrease in image quality, and the antireflection effect is insufficient. In order to solve this problem, it is preferable to provide a transparent flattening layer for filling the unevenness of the metal mesh layer and the transparent base material and flattening, and to provide an optical filter layer such as an antireflection layer on the upper surface. . The resin used for the flattening layer is not particularly limited, and various natural or synthetic resins, heat or ionizing radiation curable resins can be applied, but from the durability of the resin, applicability, ease of flattening, flatness, etc. Acrylic ultraviolet curable resins are preferred.
In addition, a near-infrared absorber, a neon light absorber, an ultraviolet absorber, etc. can also be added to resin used for a planarization layer.

And, the electromagnetic wave shielding filter of the present invention or the composite filter having the electromagnetic wave shielding filter has little variation in the line width of the wire ridge portion constituting the metal pattern layer, and the image unevenness when the image is observed through this is practically problematic. Since it is suppressed to a certain extent, it is mounted on the image display surface (front surface) of a display panel such as a plasma display device (PDP), a cathode ray tube (CRT) display device, an electroluminescence (EL) display device, etc. It can be a device.
Moreover, the electromagnetic wave shielding filter of the present invention can be applied to various other uses. For example, windows for buildings such as houses, offices, hospitals, stores, etc., windows for vehicles such as vehicles, ships, aircraft, home appliances other than image display devices such as microwave ovens, copiers, various instruments, office equipment, electricity It can be used as a member that shields electromagnetic waves in parts that require visible light transmission, such as windows of products and optical openings.

EXAMPLES Next, although an Example demonstrates this invention still in detail, this invention is not limited at all by these examples.
In the following examples, since a mesh is used as the metal pattern, the “(metal) pattern” is exclusively referred to as “(metal) mesh”.

(Evaluation method)
"Evaluation method of reflection chromaticity of copper foil":
The reflection chromaticity at 27 locations in the plane was measured using a C-3600d manufactured by Konica Minolta at a copper foil width of 50 cm × 1215 mm.
“Evaluation method of mesh line width variation 3σ”:
The mesh line widths at 27 locations in the surface of one electromagnetic wave shielding mesh sheet were measured with a microscope in a magnification of 500 and a transmitted light mode.
"Mesh appearance (line width variation) sensory evaluation method":
A white mount was placed on an inspection table whose peripheral wall surface was covered with a white cloth, and an electromagnetic wave shielding mesh sheet was placed on the white mount with the black surface facing up. A fluorescent lamp was placed immediately above the electromagnetic shielding mesh sheet (100 cm above the floor) so that the illuminance on the surface of the mount was 1000 lux. Under the fluorescent lamp, it was visually confirmed with reflected light. The position of the eyes of the observer is a position where the angle formed from the surface of the electromagnetic wave shielding mesh sheet is 80 degrees and the height from the surface of the electromagnetic wave shielding mesh sheet (measured in the normal direction) is 70 cm. did.
The evaluation was classified into levels by comparing the unevenness of appearance (three items of streaks, rough (with), and spots) with the limit sample. Levels were measured in 8 levels: A, A, AB, B, BC, C, CD, D. The closer to A, the better the appearance defects are less noticeable. The closer to D, the more conspicuous the appearance defects are.
In the evaluation method, for example, the degree of streaking was visually compared with a predetermined limit sample mesh as B, and the case where it was recognized as the same degree as B was defined as B. The same applies to A and the like. A case where it was judged that it was an intermediate level between A and B was defined as AB. A and above are A and D and below are also D.
Here, the “streak” refers to an appearance defect that has a line width region along the product flow direction and looks like a streak. If the line is thick, it looks like a black line, and if it is thin, it looks like a white line.
“Zara” refers to an appearance defect in which areas with different line widths are present in a relatively large rectangular shape and appear to be uneven as if they are rough.
The “stain” refers to an appearance defect in which areas having different line widths exist in a relatively small circular or elliptical shape and look like a stain (stain). A thick line looks like a black spot, and a thin line looks like a white spot.
“Evaluation method for variation in L ^* value (value measured in the PET film laminate state) on the blackened layer surface”:
A biaxially stretched PET film having a thickness of 100 μm is adhered to the black surface of the electromagnetic wave shielding mesh sheet via an acrylic resin adhesive, and the L ^* value of reflected light is measured at 10 locations on the blackened layer surface from the PET film side. taking measurement. Three times the standard deviation of the measured value, that is, 3σ is defined as the variation of L ^* .
"Mesh appearance (unevenness of blackening degree) sensory evaluation method":
The same PET film laminated electromagnetic wave shielding mesh sheet with the L ^* value variation evaluated was installed with the black side up, and under the same conditions as when the mesh appearance sensory evaluation was performed, under a 1000 lux fluorescent lamp, Visual confirmation with reflected light.
It is confirmed whether or not the unevenness of the blackening degree can be visually confirmed, and OK (unevenness of the blackening degree is not visible) or NG (unevenness of the blackening degree is visible) is determined.

(Production Example 1)
Using a plating solution having a composition of cobalt sulfate heptahydrate 12 g / L, zinc sulfate heptahydrate 14 g / L, copper sulfate pentahydrate 13 g / L, and boric acid 20 g / L, current density 6.0 A / dm ² First, the glossy surface of the electrolytic copper foil (manufactured by Nihon Electrolytic Co., Ltd., thickness 18 μm, glossy center line average roughness Ra = 0.20 μm) is subjected to a plating treatment in the energization time 1.5 seconds, and is subjected to the first coloring. A layer was formed. The total amount of metal content of the first colored layer was 1.4 mg / dm ² , and the content ratio was 62% for copper, 14% for cobalt, and 24% for zinc. After forming the first colored layer, a plating solution having a composition comprising cobalt sulfate heptahydrate 28 g / L, nickel sulfate hexahydrate 8.8 g / L, sodium molybdate 2.4 g / L, and sodium citrate 30 g / L Was used to form a second colored layer by plating at a current density of 3.0 A / dm ² and an energization time of 5.0 seconds, and a blackened copper foil A for an electromagnetic wave shielding filter was produced. The total content of the metal content of the second colored layer was 0.7 mg / dm ² , and the content ratio was 26% for cobalt, 27% for nickel, and 47% for molybdenum.
The total metal content of the colored layer is 2.1 mg / dm ² , and the content ratio is 41% for copper, 18% for cobalt, 16% for zinc, 9% for nickel, and 16% for molybdenum. there were.
Further, the lightness of the surface of the blackened copper foil was 29.5 in L ^* , and the chromaticity was a ^* 3.9, b ^* 5.0.

(Production Example 2)
Electrolytic copper of the same type as in Production Example 1 using a plating solution having a composition of cobalt sulfate heptahydrate 14 g / L, zinc sulfate heptahydrate 15 g / L, copper sulfate pentahydrate 13 g / L, and boric acid 30 g / L On the glossy surface of the foil, a colored layer was formed by plating at a current density of 5.0 A / dm ² and an energization time of 5.0 seconds to prepare a blackened copper foil B for an electromagnetic wave shielding filter.
The blackened layer of the blackened copper foil B is made of copper, cobalt, and zinc. The total metal content is 5.4 mg / dm ² , and the content ratio is 63% for copper and 12 for cobalt. %, Zinc was 25%, surface lightness was L ^* 16.0, chromaticity was a ^* 0.6, b ^* 0.8.

Example 1
As a transparent base material, a continuous belt-like uncolored transparent biaxially stretched polyethylene terephthalate film having a polyester resin primer layer formed on one side was prepared.
Subsequently, the primer layer surface of the transparent base material and the glossy surface of the blackened copper foil A produced in Production Example 1 were combined with a transparent two-component curable urethane resin adhesive (polyester polyurethane having an average molecular weight of 30,000 as a main ingredient) After dry lamination with 12 parts by mass of polyol (including 1 part by mass of xylylene diisocyanate-based prepolymer as a curing agent), the film is cured at 50 ° C. for 3 days, and transparent with a thickness of 7 μm between the copper foil and the transparent substrate. A continuous strip-shaped copper foil laminate sheet having an adhesive layer was obtained.
Next, the copper foil of the copper foil laminate sheet is subjected to a chemical etching process using a photolithographic method, and a frame region including an opening portion and a line portion, and a frame on an outer edge portion surrounding the mesh region. A pattern having a grounding region with no opening 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 to the entire copper foil surface 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 copper foil in the resist layer non-formed portion is etched with an etching solution of an acidic aqueous solution containing ferric chloride (temperature 40 ° C., concentration 40 baume, processing time 60 seconds). ) To form a pattern having a mesh-shaped opening, and then sequentially washed with water, stripped resist, washed, and dried.
The mesh shape of the mesh area (image display area) is such that the line width of the linear line portion having a square opening and a non-opening portion 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. In this way, an electromagnetic wave shielding filter having a width dimension of 605 mm was produced.
The obtained pattern had a mesh line width variation 3σ of 1.5 μm, and the sensory evaluation of unevenness of the mesh appearance was streaks AB, rough AB, spot A, and comprehensive evaluation AB.
The variation 3σ of the L ^* value (measured in the PET film laminate state) of the blackened layer surface of the electromagnetic wave shielding mesh was 0.24, and the blackness unevenness was OK.

(Example 2)
In Example 1, an electromagnetic wave shielding filter was produced in the same manner except that the etching conditions were a temperature of 45 ° C., a concentration of 35 Baume, and a treatment time of 45 seconds.
The obtained pattern had a mesh line width variation 3σ of 1.3 μm, and the sensory evaluation of unevenness of the mesh appearance was streak A, rough A, spot A, and comprehensive evaluation A.
The variation 3σ of the L ^* value (value measured in the PET film laminate state) of the blackened layer surface of the electromagnetic wave shielding mesh was 0.23, and the blackness unevenness was OK.

(Comparative Example 1)
An electromagnetic wave shielding filter was produced in the same manner as in Example 1 except that the blackened copper foil B produced in Production Example 2 was used as the copper foil.
The obtained pattern had a mesh line width variation 3σ of 2.6 μm, and the sensory evaluation of unevenness of the mesh appearance was streak C, rough B, spot A, and overall evaluation C.
The variation 3σ of the L ^* value (value measured in the PET film laminate state) of the blackened layer surface of the electromagnetic wave shielding mesh was 0.07, and the blackness unevenness was OK.

(Comparative Example 2)
An electromagnetic wave shielding filter was produced in the same manner as in Comparative Example 1 except that the etching conditions were a temperature of 45 ° C., a concentration of 35 Baume, and a treatment time of 45 seconds.
The obtained pattern had a mesh line width variation 3σ of 2.2 μm, and the sensory evaluation of unevenness in the mesh appearance was streak BC, rough AB, spot A, and comprehensive evaluation BC.
The variation 3σ of the L ^* value (value measured in the PET film laminate state) of the blackened layer surface of the electromagnetic wave shielding mesh was 0.05, and the blackness unevenness was OK.

(Comparative Example 3)
In Example 1, an electrolytic copper foil having a thickness of 18 μm was prepared as a copper foil, and fine copper particles were first provided on the glossy surface by copper plating at an adhesion amount of 9.9 mg / dm ² . Next, an alloy fine roughened particle layer made of copper, cobalt, and nickel was attached to the surface of the fine copper particles under the following plating conditions to form a blackened layer.
The total metal content of the blackened layer was 11.2 mg / dm ² , and the content ratio was 30% for copper, 56% for cobalt, and 14% for nickel.
(Plating conditions)
(Plating bath composition) Copper sulfate 2 g / L, Cobalt sulfate 8 g / L, Nickel sulfate 8 g / L, Ammonium sulfate 40 g / L, Boric acid 20 g / L
(Plating conditions) Temperature 30 ° C., pH 3.5, current density 15 A / dm ² , plating time 3 seconds Except for using the blackened copper foil (referred to as blackened copper foil C) obtained above. An electromagnetic wave shielding filter was produced.
In addition, the lightness of the blackened layer surface of the blackened copper foil C was 3 ^* in L ^* , and the chromaticity was a ^* 1.9 and b ^* 3.9.
The obtained pattern had a mesh line width variation 3σ of 1.5 μm, and the sensory evaluation of unevenness of the mesh appearance was streaks AB, rough AB, spot A, and comprehensive evaluation AB.
The variation 3σ of the L ^* value (value measured in the PET film laminate state) of the blackened layer surface of the electromagnetic wave shielding mesh was 0.79, and the blackness unevenness was NG.

(Comparative Example 4)
An electromagnetic wave shielding filter was produced in the same manner as in Comparative Example 3 except that the etching conditions were a temperature of 45 ° C., a concentration of 35 Baume, and a treatment time of 45 seconds.
The obtained pattern had a mesh line width variation 3σ of 1.4 μm, and the sensory evaluation of unevenness of the mesh appearance was streak A, rough A, spot A, and comprehensive evaluation A.
The variation 3σ of the L ^* value (value measured in the PET film laminate state) of the blackened layer surface of the electromagnetic wave shielding mesh was 0.81, and the blackness unevenness was NG.

Claims (5)

An electromagnetic wave shielding filter formed by laminating at least an adhesive layer and a metal pattern layer in this order on a transparent substrate, the metal pattern layer being on the transparent substrate side of the copper layer or on the opposite side of the transparent substrate It has a layer structure in which a blackening layer is laminated on one or both sides, and the blackening layer has a first colored layer made of copper, cobalt and zinc, and a second colored layer made of nickel, cobalt and molybdenum on the copper layer. The lightness of the blackened layer surface is 20 to 40 for L ^* , the chromaticity is 0 to 10 for a ^* and b ^* , and constitutes the metal pattern layer. An electromagnetic wave shielding filter having a line width variation of 2.0 μm or less at a wire rod part. An electromagnetic wave shielding filter formed by laminating at least an adhesive layer and a metal pattern layer in this order on a transparent substrate, the metal pattern layer being on the transparent substrate side of the copper layer or on the opposite side of the transparent substrate It has a layer structure in which a blackening layer is laminated on one or both sides, and the blackening layer has a first colored layer made of copper, cobalt and zinc, and a second colored layer made of nickel, cobalt and molybdenum on the copper layer. In this order, the lightness of the blackened layer surface is 20 to 40 in terms of L ^* , the chromaticity is 0 to 10 in terms of a ^* and b ^* , respectively, and the surface of the blackened layer is L ^* An electromagnetic wave shielding filter having a variation in value (measured in a PET film laminate state) of 0.5 or less. The total content of copper, cobalt, zinc, nickel and molybdenum in the blackening layer is 1 to 3 mg / dm ² , and the content ratio is 30 to 45% for copper, 15 to 25% for cobalt, and zinc for 15%. The electromagnetic wave shielding filter according to claim 1 or 2, wherein 10 to 25%, nickel is 5 to 15%, and molybdenum is 10 to 20%.   A composite filter comprising an optical filter layer and / or a functional layer laminated on one or both sides of the front and back of the electromagnetic wave shielding filter according to claim 1.   An image display device comprising the electromagnetic wave shielding filter according to claim 1 or the composite filter according to claim 4 installed on an observer side of the screen.