阅读说明：本技术 透明电磁屏蔽面板和包含其的组件 (Transparent electromagnetic shielding panel and assembly comprising same ) 是由 郑晋周 朴凤俊 迈克尔·J·戴维 于 2019-02-13 设计创作，主要内容包括：一种用于家用电器的观察面板(30、40、50、60、70、80)包括基板(33、43、53、63、73、83)和设置在基板上的导电层(35、45、55、65、75、85)；导电层包括形成图案的导线(31、41、51、61、71、81)。观察面板的特征在于：基板包括聚合物材料；导线具有由Olympus MX61显微镜确定的0.5微米至10微米的高度(H)；并且图案具有通过Olympus MX61显微镜确定的0.008平方毫米至0.06平方毫米的平均孔面积；其中观察面板具有：对波长在360纳米至750纳米范围内的光的大于70％的总透射率；和在2.45Ghz下的大于30dB的电磁屏蔽效率。(A viewing panel (30, 40, 50, 60, 70, 80) for a domestic appliance comprises a substrate (33, 43, 53, 63, 73, 83) and a conductive layer (35, 45, 55, 65, 75, 85) disposed on the substrate; the conductive layer includes patterned conductive lines (31, 41, 51, 61, 71, 81). The viewing panel is characterized in that: the substrate comprises a polymeric material; the wire has a height (H) of 0.5 to 10 microns as determined by Olympus MX61 microscope; and the pattern has an average pore area of 0.008 to 0.06 square millimeters as determined by an Olympus MX61 microscope; wherein the viewing panel has: a total transmission of greater than 70% for light having a wavelength in the range of 360 nanometers to 750 nanometers; and an electromagnetic shielding effectiveness of greater than 30dB at 2.45 Ghz.)

1. A viewing panel (30, 40, 50, 60, 70, 80) for a household appliance, comprising:

substrates (33, 43, 53, 63, 73, 83) and

a conductive layer (35, 45, 55, 65, 75, 85) disposed on the substrate; the conductive layer comprising patterned conductive lines (31, 41, 51, 61, 71, 81), the viewing panel being characterized in that:

the substrate comprises a polymeric material;

the wire has a height (H) of 0.5 to 10 microns as determined by an Olympus MX61 microscope; and is

The pattern has an average aperture area of 0.008 to 0.06 square millimeters as determined by an Olympus MX61 microscope;

wherein the viewing panel has:

a total transmission of greater than 70% for light having a wavelength in the range 360 nm to 750 nm, as determined using a Haze-Gard test apparatus at a sample thickness of 0.15 mm according to ASTM D-1003-00, procedure a, under D65 illumination, using a 10 degree observer; and an electromagnetic shielding effectiveness of greater than 30dB at 2.45Ghz as measured by ASTM D4935.

2. The viewing panel of claim 1, wherein one or more of the following conditions are used:

the viewing panel has a surface resistance of less than or equal to 1.0 ohm/sq;

under loaded conditions, the viewing panel has a weight of less than 1.0mW/cm at 2.45Ghz as defined in UL923²The electromagnetic leakage of (1); or

The polymeric material has a glass transition temperature equal to or greater than the maximum surface temperature of the substrate during microwave operation, and wherein optionally the polymeric material has a glass transition temperature of 100 ℃ to 250 ℃, preferably 140 ℃ to 250 ℃, and more preferably 150 ℃ to 250 ℃, as determined by Differential Scanning Calorimetry (DSC) at a heating rate of 20 ℃/min according to ASTM D3418.

3. The viewing panel of claim 1 or claim 2, wherein the polymeric material comprises polycarbonate; and the wire comprises at least one of silver, copper, nickel and aluminum; preferably the wire comprises an alloy of at least one of silver, copper, nickel and aluminium.

4. The viewing panel of any one of claims 1 to 3, wherein the polymeric material comprises a copolycarbonate having bisphenol A carbonate units and benzo [ c ] pyrrolone carbonate units.

5. The viewing panel of any one of claims 1 to 4, wherein the wires are disposed directly on a surface of the substrate.

6. The viewing panel of any of claims 1 to 4, wherein the conductive layer further comprises a polymer film (32, 42, 52, 62), and the conductive lines are embossed on the polymer film.

7. An assembly (200, 300, 400, 500, 600) for a household appliance, comprising:

the viewing panel (260, 360, 460, 560, 660) of any one of claims 1 to 6; and

a metal frame (240, 340, 440, 540, 640);

wherein the wires of the viewing panel are electrically grounded to the metal frame; and optionally wherein the assembly is a microwave oven door or a door for a microwave oven and convection oven combination unit.

8. The assembly of claim 7, further comprising a conductive adhesive (250, 550, 650) electrically connecting the wires of the viewing panel to the metal frame, and optionally wherein the conductive adhesive (250, 550, 650) comprises a silicone-based adhesive.

9. The assembly of claim 7, wherein the wire is in direct electrical contact with the metal frame.

10. The assembly of any of claims 7 to 9, further comprising a thermoplastic molded component (370, 470) disposed on a surface of the substrate (330, 430) opposite the conductive lines.

11. The assembly of any of claims 7-10, wherein the wire in direct electrical contact with the metal frame or in direct electrical contact with the conductive adhesive has a width (W2) greater than 10 millimeters.

12. The assembly of any of claims 7 to 11, further comprising a first glass layer disposed on the wire, or a second glass layer (585) disposed on a surface of the substrate (520), or a combination thereof.

13. The assembly of any of claims 7 to 11, further comprising a first glass layer (635) and a second glass layer (655), wherein the viewing panel is disposed between the first glass layer and the second glass layer; and preferably wherein a first air gap is provided between the first glass layer and the viewing panel and a second air gap is provided between the second glass layer and the viewing panel.

14. A method of forming a viewing panel (30, 40, 50, 60, 70, 80) for a household appliance, comprising:

-forming an electrically conductive pattern directly on a substrate (33, 43, 53, 63, 73, 83) or on a polymer film (32, 42, 52, 62) provided on a surface of said substrate via a wire (31, 41, 51, 61, 71, 81), said method being characterized in that:

the wire has a height (H) of 0.5 to 10 microns as determined by an Olympus MX61 microscope;

the conductive pattern has an average aperture area of 0.008 mm to 0.06 mm as determined by an Olympus MX61 microscope, and

the base substrate comprises a polymeric material that is,

wherein the viewing panel has:

a total transmission of greater than 70% of light having a wavelength in the range of 360 nm to 750 nm, determined according to ASTM D-1003-00, procedure A, under D65 illumination, using a 10 degree observer, using a Haze-Gard test device at a sample thickness of 0.15 mm; and

an electromagnetic shielding effectiveness of greater than 30dB at 2.45Ghz as determined by ASTM D4935.

15. A method of forming an assembly (200, 300, 400, 500, 600) for a domestic appliance, comprising:

-forming an electrically conductive pattern directly on a substrate (33, 43, 53, 63, 73, 83) or on a polymer film (32, 42, 52, 62) provided on a surface of said substrate via wires (31, 41, 51, 61, 71, 81) and integrating said viewing panel with a metal frame (240, 340, 440, 540, 640), said method being characterized in that;

the wire has a height (H) of 0.5 to 10 microns as determined by an Olympus MX61 microscope;

the conductive pattern has an average aperture area of 0.008 to 0.06 square millimeters as determined by an Olympus MX61 microscope;

the substrate comprises a polymeric material; and is

The viewing panel is electrically grounded to the metal frame;

wherein the viewing panel has a total transmission of greater than 70% for light having a wavelength in the range of 360 to 750 nanometers, as determined using a Haze-Gard test apparatus at a sample thickness of 0.15 millimeters using a 10 degree observer according to ASTM D-1003-00, procedure a, under D65 illumination; and an electromagnetic shielding effectiveness of greater than 30dB at 2.45Ghz as determined by ASTM D4935.

Technical Field

The present disclosure relates to electromagnetically shielded panels and assemblies incorporating the same, and more particularly to transparent electromagnetically shielded panels and assemblies and methods of making the same.

Background

To meet industry or government regulations, microwave oven doors typically have some electromagnetic interference (EMI) shielding capability to limit the transmission of electromagnetic radiation from outside the oven. Conventional microwave oven doors typically include a perforated metal panel for this purpose. However, while perforated metal sheets can effectively limit microwave radiation transmission, they can also limit transmission of light visible to the human eye. As a result, a microwave oven door having a perforated metal plate may obscure an image of a food item placed within the oven cavity, which may be undesirable to consumers. WO 2015/145355 discloses a method of forming a viewing panel for a microwave oven. The method includes placing a film including a conductive coating in a mold and molding a substrate onto a surface of the film having the conductive coating to form a viewing panel, or injection molding the substrate and applying the conductive coating to the surface of the substrate after molding to form the viewing panel. GB2322276 discloses a microwave oven door having a wire mesh screen which reflects microwave energy back into the cooking chamber, and a microwave absorbing film spaced from the screen. JP2006170578 discloses a microwave heating device comprising a transparent window with heat resistant glass and a metal slit plate with small holes. WO2018/038390 discloses a cooking appliance comprising: a door having a shielding member braided with a wire; and a fixing member electrically connecting the shielding member and the door frame.

Due to the widespread use of microwave oven doors, there remains a need in the art for viewing panels having increased visible light transmission. It would be a further advantage if the viewing panel had further enhanced electromagnetic shielding capabilities.

Disclosure of Invention

A viewing panel (30, 40, 50, 60, 70, 80) for a domestic appliance, comprising a substrate (33, 43, 53, 63, 73, 83) and a conductive layer (35, 45, 55, 65, 75, 85) provided on the substrate; the conductive layer includes patterned conductive lines (31, 41, 51, 61, 71, 81). The viewing panel is characterized in that: the substrate comprises a polymeric material; the wire has a height (H) of 0.5 to 10 microns as determined by an OlympusMX61 microscope; the pattern had an average pore area of 0.008 to 0.06 square millimeters as determined by an Olympus MX61 microscope; wherein the viewing panel has: a total transmission of greater than 70% for light having a wavelength in the range 360 to 750 nanometers, as determined using a Haze-Gard test apparatus at a sample thickness of 0.15 millimeters using a 10 degree observer according to ASTM D-1003-00, procedure a, under D65 illumination; and an electromagnetic shielding effectiveness of greater than 30dB at 2.45Ghz as determined by astm d 4935.

An assembly for a domestic appliance is also disclosed. The assembly includes the above-described viewing panel and a metal frame, wherein the wires of the viewing panel are electrically grounded to the metal frame.

A method of forming a viewing panel (30, 40, 50, 60, 70, 80) for a household appliance, comprising: a conductive pattern is formed directly on a substrate (33, 43, 53, 63, 73, 83) or on a polymer film (32, 42, 52, 62) provided on a surface of the substrate via a wire (31, 41, 51, 61, 71, 81). The method is characterized in that: the wire has a height (H) of 0.5 to 10 microns as determined by Olympus MX61 microscope; the conductive pattern has an average aperture area of 0.008 to 0.06 square millimeters as determined by an Olympus MX61 microscope, and the base substrate comprises a polymeric material, wherein the viewing panel has: a total transmission of greater than 70% for light having a wavelength in the range 360 to 750 nanometers, as determined using a Haze-Gard test apparatus at a sample thickness of 0.15 millimeters using a 10 degree observer according to ASTM D-1003-00, procedure a, under D65 illumination; and an electromagnetic shielding effectiveness of greater than 30dB at 2.45Ghz as determined by ASTM D4935.

A method of forming an assembly for a domestic appliance comprising forming a viewing panel according to the above method; and integrating the viewing panel with the metal frame, electrically grounding the viewing panel to the metal frame.

Drawings

The description is provided for the purpose of illustration and not limitation of the figures, in which:

fig. 1A is a microscope image of an exemplary conductive pattern according to an embodiment of the present disclosure;

fig. 1B is a microscope image of an exemplary conductive pattern according to another embodiment of the present disclosure;

FIG. 2A is a cross-sectional view of a portion of an exemplary viewing panel having a substrate and a conductive layer, wherein the conductive layer has a concave shape and contains conductive lines with uniform line widths;

FIG. 2B is a cross-sectional view of a portion of the exemplary viewing panel of FIG. 3A along the A-A' direction, the viewing panel having conductive lines with non-uniform line widths;

FIG. 2C is a cross-sectional view of a portion of an exemplary viewing panel having a substrate and a conductive layer, wherein the conductive layer has a convex shape and contains conductive lines with uniform line widths;

FIG. 2D is a cross-sectional view of a portion of an exemplary viewing panel having a substrate and a conductive layer, wherein the conductive layer has a convex shape and contains conductive lines with non-uniform line widths;

FIG. 2E is a cross-sectional view of a portion of a viewing panel having a substrate and conductive lines of uniform line width disposed directly on the substrate;

FIG. 2F is a cross-sectional view of a portion of an observation panel having a substrate and conductive lines with non-uniform line widths disposed directly on the substrate;

FIG. 3A is a top view of an exemplary viewing panel having non-uniform line widths;

FIG. 3B is a top view of another exemplary viewing panel having non-uniform line widths;

FIG. 4A is a cross-sectional view of an exemplary assembly having a viewing panel, a metal frame, and a conductive adhesive layer disposed between the viewing panel and the metal frame

FIG. 4B is a cross-sectional view of a portion of an exemplary assembly having a viewing panel, a metal frame, and a molded thermoplastic component;

FIG. 4C is a cross-sectional view of a portion of an exemplary assembly having a viewing panel, a metal frame, a molded thermoplastic component, and a mechanical device that integrates the viewing panel, the metal frame, and the molded thermoplastic component;

FIG. 4D is a cross-sectional view of a portion of an exemplary assembly having a viewing panel, a metal frame, a molded thermoplastic component, and a protective layer;

FIG. 5 is an exploded view of an exemplary assembly according to an embodiment of the present disclosure;

figure 6 is an illustration of a microwave oven door having a viewing panel as described herein;

FIG. 7 depicts the electromagnetic shielding effectiveness as a function of frequency as measured for the viewing panel of examples 1-5 and an original metal frame for a microwave oven door;

FIG. 8 depicts electromagnetic leakage as a function of number of loading cycles for the assembly of example 8;

FIG. 9 depicts electromagnetic leakage as a function of cycle number for the assembly of example 9 under unloaded conditions;

FIG. 10 depicts electromagnetic leakage of the assembly of example 9 as a function of the number of loading cycles under loaded conditions.

Detailed Description

A viewing panel having balanced visible light transmission and electromagnetic shielding efficiency is provided. Advantageously, the viewing panel also has long term reliability in terms of microwave radiation leakage and heat resistance. The viewing panel includes a substrate and a conductive layer disposed on the substrate.

The conductive layer has conductive lines forming a pattern, which may be regular or irregular. Exemplary patterns include rectangles, honeycombs, hexagons, polygons, and the like. The pattern has a variety of apertures having an average aperture area of 0.008 mm to 0.06 mm or 0.008 mm to 0.04 mm as determined by Olympus MX61 microscope. As used herein, a hole refers to the smallest unit formed by a wire. In other words, the space between adjacent lines. The pore area was determined using an Olympus MX61 microscope. The inventors of the present invention have found that a viewing panel having balanced visible light transmittance and EMI shielding efficiency can be provided by adjusting the size of the apertures formed by the conductive wires. Without being bound by theory, it is believed that electromagnetic shielding effectiveness is compromised when the average aperture area is greater than 0.06 square millimeters. Furthermore, without being bound by theory, it is believed that when the average aperture area is less than 0.008 square millimeters, the electromagnetic shielding effectiveness is no longer increased any more, and the transmission of visible light is severely deteriorated.

Fig. 1A and 1B are microscope images of exemplary conductive patterns. In fig. 1A, a wire 11 having a width W forms a regular pattern 15 having various holes 10. In fig. 1B, the conductive lines 21 form an irregular pattern 25 having various holes 20.

The wire includes at least one of silver, copper, nickel, and aluminum. Preferably, the wire includes at least one of silver alloy, copper alloy, nickel alloy, and aluminum alloy. The thickness or height (H) of the wire was 0.5 to 10 microns as measured using an Olympus MX61 microscope. The conductive lines may have a uniform width. Alternatively, the width of the conductive lines falls within two ranges, one of which is, for example, 5 to 12 microns and the other of which is greater than 10 millimeters. The wider wires provide better electrical contact with the metal frame when the viewing panel is incorporated into the assembly.

The wires may be disposed directly on, i.e., in physical contact with, the surface of the substrate. The wires may also be provided on a polymer film, which in turn is deposited on the surface of the substrate, wherein the wires and the polymer film together form a conductive layer. The polymer film may have the same polymer material as the substrate or may comprise a different polymer material. In one embodiment, the polymer film comprises a UV curable polymer material.

The substrate can comprise a polymeric material, such as a thermoplastic polymer, a thermoset polymer, or a combination comprising at least one of the foregoing.

The polymer material is selected based on microwave oven door requirements such as transparency and heat resistance. Possible polymeric materials include, but are not limited to, oligomers, polymers, ionomers, dendrimers, and copolymers, such as graft copolymers, block copolymers (e.g., star block copolymers, random copolymers, etc.), or a combination comprising at least one of the foregoing. Examples of such polymeric materials include, but are not limited to, polyesters, polycarbonates, polystyrenes (e.g., copolymers of polycarbonate and styrene, polyphenylene ether-polystyrene blends), polyimides (e.g., polyetherimides), acrylonitrile-styrene-butadiene (ABS), polyarylates, polyalkylmethacrylates (e.g., Polymethylmethacrylate (PMMA)), polyolefins (e.g., polypropylene (PP) and polyethylene, High Density Polyethylene (HDPE), Low Density Polyethylene (LDPE), Linear Low Density Polyethylene (LLDPE)), polyamides (e.g., polyamideimide), polyarylates, polysulfones (e.g., polyarylsulfone, polysulfonamide), polyphenylene sulfide, polytetrafluoroethylene, polyethers (e.g., Polyetherketone (PEK), Polyetheretherketone (PEEK), Polyethersulfone (PES)), polyacrylates, polystyrene blends of poly (phenylene ether)), and poly (propylene oxide) copolymers, Polyacetals, polybenzoxazoles (e.g., polybenzothiazine, polybenzothiazole), polyoxadiazole, polypyrazinoquinoxaline, pyromellitic polyimide, polyquinoxaline, polybenzimidazole, polyoxoindole, polyoxyisoindoline (e.g., polydioxoisoindoline), polytriazine, polypyridazine, polypiperazine, polypyridine, polypiperidine, polytriazole, polypyrazole, polypyrrolidone, polycarboborane, polyoxabicyclononane, polydibenzofuran, polyphthalamide, polyacetal, polyanhydride, polyvinyl compounds (e.g., polyvinyl ether, polyvinyl thioether, polyvinyl alcohol, polyvinyl ketone, polyvinyl halide, polyvinyl nitrile, polyvinyl ester, polyvinyl chloride), polysulfonates, polysulfides, polyureas, polyphosphazenes, polysilazanes, polysiloxanes, fluoropolymers (e.g., polyvinyl fluoride (PVF)), Polyvinylidene fluoride (PVDF), polyvinylidene fluoride (PVF), fluorinated ethylene-propylene (FEP), polyethylene tetrafluoroethylene (ETFE), or a combination comprising at least one of the foregoing. In order to balance light transmission and heat resistance, high heat polycarbonates, in particular high heat polycarbonate homopolymers, high heat copolycarbonates and high heat polycarbonate copolymers comprising carbonate units and ester units (also referred to as poly (ester carbonates)), are particularly preferred.

The polymeric material has a glass transition temperature equal to or greater than the maximum surface temperature of the substrate during microwave operation. As used herein, microwave operation refers to operation of a microwave oven or operation of a combination microwave and convection oven unit. Exemplary operations include, but are not limited to, microwave mode, grill mode, convection mode, crisping mode, or combinations thereof.

In one embodiment, the polymeric material has a glass transition temperature of from 100 ℃ to 250 ℃ or from 140 ℃ to 250 ℃, preferably from 140 ℃ to 195 ℃, and more preferably from 150 ℃ to 250 ℃ or from 150 ℃ to 175 ℃, as determined by Differential Scanning Calorimetry (DSC) at a heating rate of 20 ℃/min according to ASTM D3418. As used herein, a high thermal material refers to a material having a glass transition temperature as defined herein. The polymeric material may also have excellent transparency. For example, the polymeric material can have a Haze of less than 10% or less than 5% and a total transmission of greater than 70% or greater than 75% for light having a wavelength in the range of 360 nanometers to 750 nanometers, each measured using a Haze-Gard test apparatus according to ASTM D1003-00 procedure a under D65 illumination with a 10 degree observer at a sample thickness of 0.15 millimeters or 0.175 millimeters. Without wishing to be bound by theory, it is believed that the improved thermal stability of the substrate at high temperatures, such as 140 ℃ -250 ℃, allows the conductive layer to have a reduced height because there is less need to dissipate the heat generated during microwave operation.

In one embodiment, the substrate comprises a transparent and high heat phthalimidine copolycarbonate comprising bisphenol A carbonate units and phthalimidine carbonate units of formula (1)

Wherein R is^aAnd R^bEach independently is C_1-12Alkyl radical, C_2-12Alkenyl radical, C_3-8Cycloalkyl or C_1-12Alkoxy, preferably C_1-3Alkyl radical, each R³Independently is C_1-6Alkyl radical, R⁴Is hydrogen, C_1-6Or C_2-6Alkyl or optionally substituted by 1 to 5C_1-6Alkyl-substituted phenyl, and p and q are each independently 0 to 4, preferably 0 to 1. For example benzo [ c]The pyrrolone carbonate unit may have the formula (1a)

Wherein R is⁵Is hydrogen, optionally substituted by up to five C_1-6Alkyl-substituted phenyl or C_1-4Alkyl radicals, e.g. methyl or C_2-4An alkyl group. In one embodiment, R⁵Is hydrogen or phenyl, preferably phenyl. Wherein R is⁵The carbonate units (1a) which are phenyl groups may be derived from 2-phenyl-3, 3' -bis (4-hydroxyphenyl) benzo [ c]Pyrrolones (also known as 3, 3-bis (4-hydroxyphenyl) -2-phenylisoindolin-1-one, or N-phenylphenolphthalein bisphenol or "PPPBP"). The bisphenol A carbonate units have formula (2).

The phthalimidine copolycarbonate comprises 15 to 90 mole percent (mol%) of bisphenol a carbonate units and 10 to 85 mol% of phthalimidine carbonate units, preferably the copolycarbonate comprises 50 to 90 mol% of bisphenol a carbonate units and 10 to 50 mol% of phthalimidine carbonate units, and more preferably the copolycarbonate comprises 50 to 70 mol% of bisphenol a carbonate units and 30 to 50 mol% of phthalimidine carbonate units, or 60 to 70 mol% of bisphenol a carbonate units and 30 to 40 mol% of phthalimidine carbonate units, each based on the total number of carbonate units in the phthalimidine copolycarbonate. Optionally, the phthalimidine copolycarbonate is blended with a bisphenol A homopolycarbonate.

A combination of glass and polymer materials may be used. For example, the substrate may be glass laminated with a film comprising a polymeric material.

The polymer substrate may include various additives that are commonly incorporated into polymer compositions of this type, provided that the additives are selected so as not to adversely affect the desired properties of the polymer, particularly clarity, flexibility, stress, and flexural rigidity. Such additives may be mixed at an appropriate time during mixing of the components for forming the substrate and/or film. Exemplary additives include impact modifiers, fillers, reinforcing agents, antioxidants, heat stabilizers, light stabilizers, Ultraviolet (UV) light stabilizers, plasticizers, lubricants, mold release agents, antistatic agents, colorants (such as carbon black and organic dyes), surface effect additives, radiation stabilizers (e.g., infrared absorbing), flame retardants, and anti-drip agents. Combinations of additives may be used, for example, a combination of a heat stabilizer, mold release agent, and ultraviolet light stabilizer. The total amount of additives (other than any impact modifiers, fillers, or reinforcing agents) may be 0.001 weight percent (wt%) to 5 wt%, based on the total weight of the composition of the substrate and/or film.

The substrate may be a sheet, film or moulding. The perimeter shape of the substrate may be any shape, such as a circle, an ellipse, or a polygon shape with straight or curved edges. The thickness of the substrate may vary. In one embodiment, the substrate has a thickness equal to or greater than 0.1 millimeters, for example, 0.1 to 5 millimeters, 0.1 to 2 millimeters, 0.1 to 1 millimeter, or 0.1 to 0.8 millimeters.

An exemplary viewing panel is shown in fig. 2A-3B. The viewing panels (30, 40, 50, 60, 70, and 80) have substrates (33, 43, 53, 63, 73, and 83) and conductive lines (31, 41, 51, 61, 71, and 81) disposed on the polymer films (32, 42, 52, and 62) shown in fig. 2A-2D or directly on the substrates shown in fig. 2E and 2F. The wires together with the polymer film (if present) form conductive layers (35, 45, 55, 65, 75, and 85). The conductive layer has a height (H1) or thickness that is 0.1 to 12 microns or 0.5 to 10 microns. The thickness or height (H) of the conductive lines is 0.5 to 10 microns. The width of the conductive lines may be uniform or non-uniform. Fig. 2A, 2C, and 2E show a viewing panel having conductive lines with a uniform line width W. Fig. 2B, 2D and 2F show a viewing panel having conductive lines of at least a first width W and a second width W2, wherein the second width is significantly greater than the first width. A wire having a width W2 may be provided at the perimeter of the viewing panel as shown in fig. 3A and 3B. It should be understood that the wire having the width W2 may be disposed at other positions. In the case where the wire is provided on the polymer film, the wire and the polymer film together may have a concave shape (fig. 2A and 2B) or a convex shape (fig. 2C and 2D).

The viewing panel can be manufactured by forming a conductive pattern directly on the substrate or on a polymer film provided on the surface of the substrate. The substrate may be formed by extrusion, calendaring, molding (e.g., injection molding), thermoforming, vacuum forming, or other desired forming process. The substrate may be made as a flat plate. The substrate may be formed with a curvature.

The conductive lines (e.g., conductive metal nanoparticle layers) can be applied to the substrate or polymer film by a variety of techniques, including printing conductive inks (e.g., stamp, screen, flexo, screen, ink jet, gravure offset, reverse offset, and photolithography), coatings, and patterning, such as silver halide emulsions that can be reduced to silver particles, and self-assembly of silver nanoparticle dispersions or emulsions. If present, the polymer film may be laminated to the substrate before the wires are disposed on the polymer film or after the wires are disposed on the polymer film.

The viewing panels disclosed herein can have excellent transparency. In one embodiment, the viewing panel has a total transmission of greater than 70% for light having a wavelength in the range of 360 nm to 750 nm, measured using a Haze-Gard test apparatus according to ASTM D1003-00, procedure a, under D65 illumination with a 10 degree observer, at a thickness of 0.15 mm or 0.175 mm. The viewing panel can have a Haze of less than 10% as measured using a Haze-Gard test equipment according to astm D1003-00, procedure a, under D65 illumination with a 10 degree observer at a thickness of 0.15 millimeters or 0.175 millimeters.

The viewing panel may also have excellent electromagnetic shielding effectiveness. In one embodiment, the viewing panel has an electromagnetic shielding effectiveness of greater than 30 decibels (dB) at 2.45 gigahertz (GHz), as determined by ASTM D4935. The viewing panel can also have less than 1.0 milliwatts per square centimeter (mW/cm) at 2.45Ghz under load conditions defined by underwriters laboratories standard 923(UL923)²) The electromagnetic leakage of (1).

The viewing panel has a low surface resistance. Without being bound by theory, it is believed that low sheet resistance contributes to improved electromagnetic shielding efficiency. In one embodiment, the surface resistance of the viewing panel is less than or equal to 1.0ohm per square (ohm/sq).

The viewing panel may be integrated with a metal frame to provide a component for a household appliance. In this assembly, the wires of the viewing panel are electrically grounded to the metal frame. The percentage of ground contact area may vary depending on the size of the assembly (particularly the size of the viewing panel).

The electrical connection between the wires and the metal frame may be accomplished by a variety of techniques including, but not limited to, conductive inks or pastes, conductive tapes such as copper tape, solder connections, conductive adhesives, or direct electrical contacts. One end of the connector may be connected to the metal frame, and the other end of the connector may be connected to the wire. The electrical attachment to the wires may be made at multiple locations, or even continuously around the perimeter, to provide adequate connection to all portions of the conductive pattern. The width of the wire in direct electrical contact with the metal frame or in direct electrical contact with the conductive adhesive is greater than 10 millimeters. In one embodiment, the total contact area between the wires and the metal frame is greater than 15% of the surface area of the substrate. A larger contact area may lead to better shielding performance and stronger adhesion between the viewing panel and the metal frame. The maximum total contact area between the wires and the metal frame can be adjusted according to the desired viewing panel size.

The metal frame may abut a peripheral edge of the viewing panel. The metal frame may extend along a portion of the perimeter of the viewing panel. The metal frame may also extend along the entire perimeter of the viewing panel so that it surrounds the viewing panel.

Fig. 4A-5 illustrate various exemplary components. The assembly 200 has a metal frame 240, a viewing panel 260 including a substrate 230 and a conductive layer 220, and a conductive adhesive 250 disposed between the metal frame 240 and the conductive layer 220 and electrically connecting the metal frame 240 and the conductive layer 220. A double-sided Pressure Sensitive Adhesive (PSA) type conductive adhesive, conductive paste, or conductive foam may be used. The type of adhesive depends on the application. If high heat resistance properties are required (e.g. over 170 ℃), the conductive adhesive may comprise a silicone-based material to achieve long term stability.

In fig. 4B, assembly 300 has a metal frame 340, a thermoplastic molded part 370, and a viewing panel 360, which includes a substrate 330 and a conductive layer 320. In assembly 300, conductive layer 320 is in direct electrical contact with metal frame 340. A thermoplastic molded part 370 is disposed on the surface of the substrate 330 opposite the conductive layer 320. The thermoplastic molded part may be a housing that integrates the metal frame 340 with the viewing panel 360.

In the assembly 400 shown in fig. 4C, a fastening device 480 is used to integrate the metal frame 440 with the molded thermoplastic component 470 and the viewing panel 460 including the substrate 430 and the conductive layer 420. The fixing means is not particularly limited. In one embodiment, the fastening means is a screw. In assembly 400, conductive layer 420 is in direct electrical contact with metal frame 440.

Additional layers may be included in the assembly if desired. The assembly may further include a first protective layer disposed on the wires, or a second protective layer disposed on the surface of the substrate, or a combination thereof. The protective layer can provide an underlayer having abrasion resistance, ultraviolet radiation resistance, microbial resistance, bacterial resistance, corrosion resistance, or a combination comprising at least one of the foregoing. In one embodiment, the protective layer is a glass layer.

The conductive pattern may be placed on the outside or inside of the assembly. When the conductive pattern is included in a component of a household appliance, the pattern may be placed as a layer within a multi-layer window, for example sandwiched between two or more transparent substrates, to provide protection for the conductive network.

Fig. 4D shows an assembly 500 that includes a viewing panel 560, a metal frame 540, a conductive adhesive layer 550 that electrically connects the conductive layer 530 to the metal frame 540, an inner glass layer 585, and an optically clear adhesive 575 disposed between the substrate 520 and the inner glass layer 585.

As shown in fig. 5, in a particular embodiment, the assembly 600 includes a viewing panel 660, a conductive adhesive 650 that integrates the viewing panel 660 with the metal frame 640. The assembly further includes a cover frame 665 and an inner glass layer 655 disposed between the metal frame 640 and the cover frame 665. The assembly may further include a thermoplastic component, such as a housing 645 that holds the assembly. An outer glass layer 635 may be disposed inside the housing 645 to provide protection to the viewing panel 660. In one embodiment, there is a first air gap (also referred to as an inner air gap) between the inner glass layer 655 and the viewing panel 660, and a second air gap between the outer glass layer 635 and the viewing panel 660. The size of the internal air gap may be determined by the coefficient of thermal expansion of the substrate, the maximum temperature that the substrate can reach during microwave operation, and the heat dissipation requirements of the substrate.

The assembly may be a microwave oven door or a door of a combination microwave and convection oven unit. Figure 6 is an illustration of a microwave oven door 700 having a viewing panel 760 as described herein.

Viewing panels and assemblies having balanced light transmission and electromagnetic shielding effectiveness are further illustrated by the following non-limiting examples.