JP2011154854A - Transparent planar heating element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flexible transparent planar heating element which is superior in transparency and visibility, hard to generate a moire phenomenon, and has high quality surface heating characteristics capable of uniform heat generation. <P>SOLUTION: The transparent planar heating element has one pair or more of electrodes on a conductive layer of a conductive substrate, and the conductive substrate has a transparent substrate and the conductive layer laminated thereon, and the conductive layer has an irregular network form. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a transparent sheet heating element having high-quality sheet heating characteristics that are excellent in transparency and capable of generating uniform heat.

  Conventionally, refrigeration and refrigeration showcases need to prevent condensation on the glass surface that constitutes the window portion. For this reason, a transparent conductive film is formed on the glass surface, and predetermined power is applied to the window surface. It is done to warm up. Similarly, defrosters using a transparent conductive film are used in automobile window glass to prevent fogging and condensation. Also, in cold regions, use of a transparent sheet heating element to prevent snow melting and freezing in order to prevent the visibility of road signs and the like due to snow accumulation and freezing on road signs and traffic lights, and in low temperature environments in cold regions The necessity of providing a transparent sheet heating element for temperature control is increasing in order to prevent malfunction of the liquid crystal display element used in the above, and to assist startup.

  As a liquid crystal display element used in a low-temperature environment such as a cold region, for example, as proposed in Patent Document 1, a mesh-like heating resistor is disposed and heated, as in Patent Document 2, and the like. Transparent surface heating using a transparent conductive film such as silver, copper or indium tin oxide (ITO) provided on a transparent substrate as a heating surface, and a pair of metal electrodes for energizing the transparent conductive film The body has been reported. However, in the method of Patent Document 1, it is difficult to uniformly heat the entire liquid crystal element, and a heating resistor made of an opaque metal tends to be an obstacle when viewing a liquid crystal display. Also, in the method of Patent Document 2, it is not always easy to uniformly heat the entire liquid crystal element, and when a heating element made of a transparent conductive film that increases haze and reflection as the thickness increases, It may interfere with viewing the LCD display. In addition, when the thickness is thin enough to ensure transparency, the conductivity is inferior, so that the amount of flowing current is small and the rise of heat generation may be slow. Furthermore, when a sputtering method, a vapor deposition method, or the like is used, the manufacturing cost is high, and the ITO transparent conductive film has a problem that it is poor in bending resistance and easily cracked.

  Further, Patent Document 3 discloses that a solution of an organic silver compound or the like is spray-coated on a substrate to form a fine network structure film, and this is irradiated with radiation to reduce and precipitate silver to form a fine silver network structure. It is described that a transparent conductive film having a slag is obtained, which can be used as a transparent planar heating element. In this method, since a transparent conductive film having a fine network structure is used, a moire interference pattern does not occur, but in order to obtain the conductive film, a method of reducing silver by irradiation with ultraviolet rays or the like is taken. There is a problem in stable reproducibility.

  Patent Document 4 proposes a method of forming a mesh-like conductive layer made of a conductive paste by photolithography, but this method requires a complicated process to obtain a mesh-like conductive layer. In order to remove excess conductive paste, there are many problems in terms of material recycling and manufacturing costs.

  Therefore, a high-quality transparent sheet heating element with high flexibility, which has high transparency and visibility, has a low resistance value of the conductive portion, is less likely to cause moire phenomenon, and can generate uniform heat, is desired. ing.

: JP-A-58-126517 : JP-A-9-306647 : JP-A-10-312715 : JP 2006-49006 A

  The present invention is a flexible transparent sheet heating element that has high transparency and visibility, is less susceptible to moire phenomenon, has a low resistance value of a conductive part, and has high-quality surface heat generation characteristics capable of uniform heat generation. Is to provide.

The present invention employs the following means in order to solve such problems. That is:
1) A transparent planar heating element comprising one or more pairs of electrodes on a conductive layer of a conductive substrate,
The conductive substrate is a laminate of a transparent substrate and a conductive layer,
A transparent planar heating element, wherein the conductive layer has an irregular network shape.
2) The transparent sheet heating element according to 1) above, wherein a transparent protective layer is provided on the surface of the conductive substrate on the conductive layer side.
3) The transparent sheet heating element according to 1) or 2) above, wherein the conductive layer has a surface resistivity of 1 to 100Ω / □.
4) The transparent sheet heating element according to any one of 1) to 3) above, wherein the total light transmittance is 50% or more.
5) The conductive layer is a conductive layer in which a metal is laminated on a transparent substrate in an irregular network shape by applying a metal dispersion on the transparent substrate. The transparent sheet heating element according to any one of the above.

  According to the present invention, a transparent transparent surface having high transparency and visibility, less likely to cause moire phenomenon, a low resistance value of a conductive portion, and high-quality surface heat generation characteristics capable of uniform heat generation. A heating element can be provided. The transparent sheet heating element according to the present invention has high transparency and visibility, and has a high level of conductivity. For example, the liquid crystal display element is activated in a low-temperature environment such as a cold region, road signs, It can be suitably used for snow melting and freezing prevention of traffic lights etc., window portions of freezing and refrigerated showcases, and defrosters for automobile window glass. Moreover, since it has flexibility, it can be used for a member having a curved surface.

  The present invention is a flexible, high-quality surface heat generation characteristic that is high in the above problems, i.e., high transparency and visibility, hardly causes moire phenomenon, has a low resistance value of the conductive portion, and can generate uniform heat. With regard to the transparent sheet-shaped heating element, the above problems can be solved all at once by providing at least one pair of electrodes on the conductive layer of a conductive substrate having a conductive layer in which a conductive compound is laminated in an irregular network shape. It has been investigated to solve. That is, a transparent planar heating element provided with one or more pairs of electrodes in a conductive layer of a conductive substrate, the conductive substrate is a laminate of a transparent substrate and a conductive layer, and the conductive layer is It is an invention of a transparent planar heating element characterized by having an irregular network shape.

  It is important that the conductive substrate used in the transparent sheet heating element of the present invention is a laminate of a transparent substrate and a conductive layer. The conductive layer is preferably formed from a conductive compound. Examples of the conductive compound suitably used for the conductive layer include gold, silver, copper, platinum, iron, aluminum, nickel, cobalt, zinc, tin, palladium, rhodium, ruthenium, bismuth, and other metals, polythiophene, and polyacetylene. Any conductive compound such as polyaniline and polypyrrole, carbon nanotubes and the like can be used as long as the compound exhibits conductivity. However, from the viewpoint of conductivity, the conductive compound is preferably a metal, and one type of metal is used. You may use, and may use it in combination of 2 or more type. Moreover, even if the metal is not a pure metal, any metal may be used as long as a predetermined conductivity can be finally obtained by a known conductive treatment described later, such as a metal oxide, an organic acid metal salt, a fatty acid metal salt, A metal compound coated and bound with a compound can also be selected.

  The shape of the metal is not particularly limited as long as an irregular network-like conductive layer can be formed. From the viewpoint of easy formation of the network structure, the shape of fine particles, powder, fibers, wires, and the like is preferable.

  It is important that the conductive layer in the transparent sheet heating element of the present invention has an irregular network shape. That is, the conductive substrate is a laminate of a transparent substrate and an irregular network-like conductive layer.

  Here, the network-like structure of the irregular network-like conductive layer indicates a structure in which several points are connected by several line segments. That is, the network-like conductive layer in the present invention means a structure in which line segments composed of a conductive compound and various additives described later are connected at a plurality of points. For example, in the case of a wire-like conductive compound such as a carbon nanotube, the wire-like conductive compound exhibits conductivity by being entangled or overlapping with at least one contact point. A line segment is formed, and a portion surrounded by the line segment becomes an opening, and becomes an irregular network-like conductive layer. Here, the opening part enclosed by the line segment contributes to transparency. In the case of a particulate conductive compound, a number of particulate conductive compounds are connected, contacted, and bonded to form a line segment, and the line segment formed from these particulate conductive compounds has several points. As a result of overlapping and surrounded by the openings, an irregular network-like structure can be obtained.

  Here, irregularity in an irregular network-like structure can be specified by an observation image such as a differential interference microscope, and the shape and size of the structure of the opening surrounded by the line segment are uneven. For example, it shows a state in which the sizes are irregular, such as a circle, an ellipse, a polygon such as a quadrangle, a pentagon, and a hexagon, or a combination of these. For example, examples of the irregular shape include shapes described in JP-A Nos. 10-31715 and 2008-243547.

  It is important that the structure of the network-like conductive layer used in the present invention is irregular. This is because the conductive layer has an irregular network-like structure, so that the moiré phenomenon does not occur when the conductive layer is overlaid with the regularly distributed layer. Here, the moire phenomenon is “a striped pattern generated when overlapping regularly distributed points or lines geometrically”, and according to Kojien, “a point or line is geometrically Striped pattern mottles that occur when superposedly distributed objects are superimposed. This is likely to occur when a halftone is reproduced using a halftone print as a manuscript. Therefore, for example, in the case of applying a transparent planar heating element having a regular network-like structure conductive layer to prevent freezing of the display surface portion where the elements are regularly arranged such as a liquid crystal display element, Although the moiré phenomenon is likely to occur, the moiré phenomenon does not occur when the transparent sheet heating element having the irregular network-like conductive layer of the present invention is applied, so that the network-like conductivity used in the present invention is not affected. It is important that the layer structure is irregular.

  The irregular network-like conductive layer in the present invention is a layer composed of the above-described conductive compound, and if necessary to form an irregular network-like conductive layer, the conductive layer is In addition to conductive compounds, various other additives such as dispersants, surfactants, protective resins, thermosetting resins, ultraviolet curable resins, antioxidants, heat stabilizers, weathering stabilizers, ultraviolet absorbers, It can contain inorganic components and organic components such as pigments, dyes, organic or inorganic fine particles, fillers, antistatic agents and the like. In addition, an irregular network-like conductive layer is not necessary for forming the conductive layer, but is necessary for using the conductive substrate having the conductive layer as the transparent planar heating element of the present invention. In this case, various additives as described above may be contained.

  The transparent sheet heating element of the present invention preferably has a transparent protective layer on the surface of the conductive substrate on the conductive layer side. The resin forming the transparent protective layer is not particularly limited, and examples thereof include an ultraviolet curable resin and a thermosetting resin. Examples of the ultraviolet curable resin include polyester acrylate, urethane acrylate, epoxy acrylate, and the like. Examples of thermosetting resins include unsaturated polyester resins, epoxy resins, urethane resins, and silicone resins. The transparent protective layer may be formed by directly laminating the aforementioned ultraviolet curable resin or thermosetting resin from the conductive layer side of the transparent sheet heating element. Moreover, after providing an adhesive layer or an adhesive layer on the conductive layer, a thermoplastic resin film may be laminated as a transparent protective layer.

  The thermoplastic resin film is not particularly limited, but polyester film, polyolefin film, polylactic acid film, polycarbonate film, acrylic film, polyamide film, polyvinyl chloride film, polyurethane film, fluorine film, polyphenylene A sulfide film or the like can be used.

  The transparent protective layer only needs to be protected so that the irregular network-like conductive layer in the present invention is not peeled off or scraped. Further, since the transparent sheet heating element is energized to generate heat, the transparent protective layer also has an effect as an insulator. Therefore, the thickness of the transparent protective layer is not particularly limited as long as the thickness of the transparent protective layer is greater than the thickness of the conductive layer as long as the conductive film can serve as a protection and insulator.

  In the transparent planar heating element of the present invention, it is important that one or more pairs of electrodes are provided on the conductive layer of the conductive substrate. The transparent sheet heating element of the present invention functions as a heating element by energizing this electrode. The term “one or more pairs of electrodes” means that there are one or more pairs of electrodes for energizing the transparent sheet heating element of the present invention. By providing one or more pairs of electrodes, even when the transparent sheet heating element is enlarged, it is possible to energize electricity from a plurality of locations, so that uneven conduction is less likely to occur. Therefore, temperature unevenness of the entire transparent sheet-shaped heating element hardly occurs, and the temperature can be generated uniformly.

  Any electrode can be used as long as it has conductivity. Examples of preferable electrodes include conductive resins, metal foils, and metal plating layers. A mixed layer can be used as an electrode. From the viewpoint of contact resistance, it is preferable to use an electrode having a lower resistance value.

  The thickness of the electrode may be a thickness that can be used for the transparent planar heating element of the present invention, so that an irregular network-like conductive layer functions as a heating surface, and can be energized with current. Usually, it is 0.1 micrometer or more, Preferably it is 0.5-100 micrometers, More preferably, it is 1-50 micrometers, More preferably, it is 5-20 micrometers.

  The surface specific resistance value of the conductive layer of the conductive substrate used for the transparent sheet heating element of the present invention is preferably 1 to 100Ω / □. More preferably, it is 1-30 ohm / square, More preferably, it is 1-10 ohm / square, Especially preferably, it is 1-5 ohm / square. Even if the surface specific resistance value is greater than 100Ω, it is possible to generate heat, but this is not preferable because high power application is required. Although the lower surface specific resistance value is preferable, the lower limit that can be practically achieved is considered to be about 1Ω / □, and therefore, about 1Ω / □ is considered the lower limit.

  When the conductive layer is formed from a metal dispersion and the conductive layer contains an insulating compound in addition to the metal, an organic solvent treatment, an acid treatment, a heat treatment, a current treatment, etc. You may perform the process which raises the electroconductivity of this conductive layer and makes a surface specific resistance value small using a well-known method.

  The above-mentioned measurement of the surface specific resistance value of the conductive layer is, for example, in the form conforming to JIS-K-7194 (established in 1994) in the normal condition (23 ° C., relative humidity 65%) after standing for 24 hours. Thus, measurement can be performed using Loresta-EP (manufactured by Mitsubishi Chemical Corporation, model number: MCP-T360). In addition, when the conductive substrate of the present invention has a transparent protective layer on the surface on the conductive layer side, the surface specific resistance value of the conductive layer is measured by removing the transparent protective layer if it can be removed. In the case where it cannot be removed, it is a value measured before laminating the transparent protective layer.

  The conductive layer of the conductive substrate of the transparent sheet heating element of the present invention was formed by applying a metal dispersion on the transparent substrate so that the metal in the metal dispersion was laminated on the transparent substrate in an irregular network shape. A conductive layer is preferred. As a method for applying the metal dispersion, known coating methods such as a die coating method, an applicator method, a micro gravure method, a comma coating method, a spray method, a dipping method, and the like can be used. When using a contact-type coating method that contacts the substrate when applying the metal dispersion, scratches occur on the part that contacts the substrate, and when the metal dispersion is applied, streaks appear on the part that contacts the substrate. Therefore, a non-contact coating method that does not come into contact with the substrate is preferable.

  In the present invention, since the conductive layer has an irregular network structure, it is possible to obtain a substrate that is highly transparent and highly visible and hardly causes the moire phenomenon. The total light transmittance of the transparent sheet heating element in the present invention is preferably 50% or more, more preferably 60% or more. If the total light transmittance is less than 50%, there may be a problem in terms of transparency of the transparent sheet heating element. In addition, although the total light transmittance of a transparent planar heating element is so preferable that it is high, since it is difficult to make it higher than 95% practically, an upper limit is considered to be about 95%.

  As described above, the conductive layer of the conductive substrate of the transparent sheet heating element of the present invention is formed on the transparent substrate in such a manner that the metal in the metal dispersion is irregularly formed by applying the metal dispersion on the transparent substrate. It is preferable that the conductive layer is laminated. The method for applying the metal dispersion on the transparent substrate is not particularly limited as described above, but is not limited as long as an irregular network-like conductive layer can be formed. For example, as a metal dispersion, a method of printing a metal fine particle dispersion, a metal oxide fine particle dispersion, an organometallic compound dispersion, or a metal dispersion obtained by mixing two or more of these in a network form, irregularly A method of applying a metal dispersion that forms a network-like structure, and after applying the above-mentioned metal dispersion on the entire surface of the substrate, the conductive layer is physically scraped to form a network or chemically etched Or by digging or embossing the substrate, creating a network-like groove on at least one side of the substrate in advance, and filling the above-described solution therewith to form a network-like conductive layer For example, various methods can be selected.

  In this case, as a metal dispersion, various additives other than metal, for example, a dispersant, a surfactant, a protective resin, a thermosetting resin, an ultraviolet curing, are necessary in order to form a network-like conductive layer. Inorganic components such as resins, antioxidants, heat stabilizers, weathering stabilizers, ultraviolet absorbers, pigments, dyes, organic or inorganic fine particles, fillers, antistatic agents, and the like can be contained. Also, when necessary for use as the transparent planar heating element of the present invention, various additives as described above may be contained in the metal dispersion.

  As the solvent for the metal dispersion, water and various organic solvents can be used in consideration of the dispersibility of the metal compound, the solubility of various additives, etc., in order to form an irregular network structure In addition, a solvent containing both water and various organic solvents can also be used. Examples of such a metal dispersion include metal dispersions described in JP-A-2006-127828 and JP-A-2006-127929.

  In addition, for the purpose of forming an irregular network structure before applying the metal dispersion, corona discharge treatment, flame treatment, plasma treatment, glow discharge treatment, roughening treatment on the surface of the transparent substrate, The degree of hydrophobicity and hydrophilicity of the surface of the transparent substrate may be adjusted by performing surface treatment such as chemical treatment or coating with an anchor coat agent or a primer.

  As the transparent substrate of the conductive substrate used in the transparent sheet heating element of the present invention, a thermoplastic resin film can be used. When the transparent substrate which comprises a conductive substrate is a thermoplastic resin film, it is preferable at points, such as transparency, a softness | flexibility, and workability. The thermoplastic resin film as used in the present invention is a general term for films that are melted or softened by heat, and is not particularly limited, but representative examples include polyolefins such as polyester films, polypropylene films, and polyethylene films. Films, polylactic acid films, polycarbonate films, acrylic films such as polymethyl methacrylate films and polystyrene films, polyamide films such as nylon, polyvinyl chloride films, polyurethane films, fluorine films, polyphenylene sulfide films, and the like can be used.

  These may be homopolymers or copolymerized polymers. Of these, polyester films, polypropylene films, polyamide films and the like are preferable in terms of mechanical properties, dimensional stability, transparency, and polyester films are particularly preferable in terms of mechanical strength and versatility.

  In the polyester film, polyester is a general term for polymers having an ester bond as a main bond chain, and includes ethylene terephthalate, propylene terephthalate, ethylene-2,6-naphthalate, butylene terephthalate, propylene-2,6. A compound having at least one component selected from naphthalate, ethylene-α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate as a main component can be preferably used. . These constituent components may be used alone or in combination of two or more. However, when quality, economy and the like are comprehensively judged, polyester having ethylene terephthalate as a main constituent, that is, polyethylene terephthalate is used. It is particularly preferable to use it. In addition, when heat or shrinkage stress acts on the substrate, polyethylene-2,6-naphthalate having excellent heat resistance and rigidity is more preferable. These polyesters may further be partially copolymerized with other dicarboxylic acid components and diol components, preferably 20 mol% or less.

  The polyester also contains various additives such as antioxidants, heat stabilizers, weathering stabilizers, UV absorbers, organic lubricants, pigments, dyes, organic or inorganic fine particles, fillers, antistatic agents. An agent, a nucleating agent, etc. may be added to such an extent that the properties are not deteriorated.

  The intrinsic viscosity (measured in o-chlorophenol at 25 ° C.) of the above polyester is preferably 0.4 to 1.2 dl / g, more preferably 0.5 to 0.8 dl / g. This is suitable for carrying out the present invention.

  The polyester film using the polyester is preferably biaxially oriented. A biaxially oriented polyester film is generally an unstretched polyester sheet or film that is stretched about 2.5 to 5 times in the longitudinal direction and in the width direction, and then subjected to heat treatment to complete crystal orientation. It is a thing which shows a biaxially oriented pattern by wide-angle X-ray diffraction.

  The thickness of the polyester film is not particularly limited and is appropriately selected depending on the application and type, but from the viewpoint of mechanical strength, handling properties, etc., it is usually preferably 10 to 500 μm, more preferably 38 to 250 μm, most preferably 75 to 150 μm. Further, the polyester film substrate may be a composite film by coextrusion. On the other hand, the obtained film can also be used by bonding by various methods.

  On the surface where the conductive layer of the transparent substrate used in the transparent sheet heating element of the present invention is not laminated, and on the transparent protective layer, various functional layers such as an adhesive layer, a release layer, an adhesion-imparting layer, Further, a weather resistant layer or the like may be provided.

  Although the manufacturing method of the electroconductive board | substrate which comprises the transparent planar heating element of this invention is illustrated and demonstrated more concretely, this invention is not limited to this. A silver fine particle solution is applied to the biaxially stretched polyester film by a known method to form a conductive layer containing an insulating compound in an irregular network structure. Thereafter, in order to treat the conductive layer with an organic solvent, the biaxially stretched polyester film is immersed in the organic solvent and left for about 0.1 seconds to 60 minutes. Then, after taking out the biaxially stretched polyester film, the organic solvent is dried at 30 ° C., and heat treatment is performed at 100 ° C. or higher. Thereby, the electroconductive board | substrate with which the irregular network-like electroconductive layer was laminated | stacked can be obtained.

  Next, although the manufacturing method of the transparent planar heating element of this invention is illustrated and demonstrated more concretely, this invention is not limited to this. A transparent surface provided with a transparent protective layer by taking a pair of electrodes by laminating a copper foil with a uniform width in parallel on both ends of a conductive substrate and laminating a hard coat agent by a known method Can be obtained.

[Method for measuring characteristics and method for evaluating effects]
The method for measuring the characteristics of the conductive substrate prepared in each example and comparative example and the method for evaluating the effect are as follows.
(1) Conductivity The conductivity of the conductive layer of the conductive substrate was evaluated by the surface specific resistance value. The surface specific resistance value is measured in a normal condition (23 ° C., relative humidity 65%) for 24 hours, and in that atmosphere, in compliance with JIS-K-7194 (established in 1994), Loresta-EP (Mitsubishi This was carried out using Chemical Co., Ltd., model number: MCP-T360. The unit is Ω / □. In addition, this measuring device can measure 1 × 10 ⁵ Ω / □ or less.
(2) Total light transmittance The total light transmittance is measured according to JIS-K-7375 (established in 2008) after leaving the conductive substrate for 2 hours in the normal state (23 ° C., relative humidity 65%). , Using a fully automatic direct reading haze computer “HGM-2DP” manufactured by Suga Test Instruments Co., Ltd. The average value measured three times was defined as the total light transmittance of the transparent sheet heating element. If the total light transmittance is 50% or more, the transparency is good. In the case of a transparent sheet heating element in which a conductive layer is laminated only on one side of the transparent substrate, the transparent sheet heating element is installed so that light enters from the side where the conductive layer is laminated.
(3) Surface observation (shape observation)
Using a differential interference microscope (LEICA DMLM manufactured by Leica Microsystems) or a scanning electron microscope (S-2100A type Hitachi scanning electron microscope, Hitachi, Ltd.)) on the surface of the conductive layer of the conductive substrate Observation was performed to confirm whether or not an irregular network-like conductive layer was formed. In addition, the surface observation is carried out on three arbitrarily selected surfaces, and when an irregular network structure is confirmed in any place, the transparent sheet heating element having the observed conductive layer is irregular. It was judged to have a conductive network-like layer.
(4) Exothermic evaluation For evaluating the exothermic property of the transparent sheet heating element, copper tape was attached to both ends of the conductive layer side of a 15 cm x 15 cm conductive substrate (network-like metal fine particle laminated substrate) and electrodes were taken. A predetermined current was applied.

  The center surface temperature (exothermic temperature) 5 minutes after applying the current was measured with a radiation temperature sensor (manufactured by KEYENCE, model number FT-H20). When the measured temperature on the conductive substrate is equal to or higher than the temperature before energization, it can be used as a transparent sheet heating element, and “o” is indicated, and the temperature below the energization is “x”.

Next, the present invention will be described based on examples.
(Metal dispersion)
As the metal dispersion, XA-9053 manufactured by Fujikura Kasei Co., Ltd., which is a silver fine particle solution, was used.
(Transparent resin layer solution)
As the transparent protective layer, a resin solution obtained by diluting a commercially available hard coat agent (“OPSTAR” (registered trademark) Z7534, manufactured by JSR Corporation) with methyl isobutyl ketone so as to have a solid content concentration of 40% by weight was used.
Example 1
A biaxially stretched polyethylene terephthalate film (Lumirror (registered trademark) U46 manufactured by Toray Industries, Inc.) was coated with a metal dispersion with a wire bar to a wet thickness of 30 μm, and a 150 ° C. hot air oven (Tabaye Spec Corp. ) Manufactured by PHH-200) for 2 minutes to form a conductive layer (silver fine particle layer) on one side of the transparent substrate. A photoresist was laminated on the conductive layer (silver fine particle layer) surface of this laminated substrate, and after exposure, the resist was developed so as to form an irregular network. Next, etching was performed to remove silver fine particles in a portion where the resist did not remain, washed with water, and dried. Finally, the photoresist was removed to obtain a conductive substrate having an irregular network-like conductive layer.

  The laminated substrate is immersed in 25 ° C. acetone (manufactured by Sasaki Chemical Co., Ltd.) for 2 seconds, and the laminated substrate is taken out and dried at 25 ° C. for 3 minutes. The laminated substrate is then heated in a 150 ° C. hot air oven (Tabay Espec Corp.). ) PHH-200) for 60 seconds. The obtained conductive substrate having an irregular network-like conductive layer (network-like conductive layer laminated substrate) had a surface specific resistance value of 8.0Ω / □ and a total light transmittance of 75%.

Next, the obtained conductive substrate having an irregular network-like conductive layer is cut to a size of 15 cm × 15 cm, and copper tape is applied to both end portions of the conductive layer side surface of the conductive substrate at 5 mm. Then, a pair of electrodes was provided. Thereafter, the transparent resin layer solution was applied with a wire bar and laminated in the shape of the conductive layer to obtain a transparent sheet heating element having a transparent protective layer. When this transparent sheet heating element was evaluated for exothermicity when a current of 1 A was applied, the exothermic temperature was 30 ° C., and the temperature before energization was 20 ° C., so the exothermic property was “◯”. .
(Example 2)
On a biaxially stretched polyethylene terephthalate film (Lumirror (registered trademark) U46 manufactured by Toray Industries, Inc.), the metal dispersion was printed in an irregular network form by screen printing, and a hot air oven at 150 ° C. An irregular network-like conductive layer (silver fine particle layer) was formed on one side of the transparent substrate by performing a heat treatment for 2 minutes using PHH-200).

  The laminated substrate is immersed in 25 ° C. acetone (manufactured by Sasaki Chemical Co., Ltd.) for 2 seconds, and the laminated substrate is taken out and dried at 25 ° C. for 3 minutes. The laminated substrate is then heated in a 150 ° C. hot air oven (Tabay Espec Corp.). ) PHH-200) for 60 seconds. The obtained conductive substrate having an irregular network-like conductive layer (network-like conductive layer laminated substrate) had a surface specific resistance value of 7.4Ω / □ and a total light transmittance of 70%.

Next, the obtained conductive substrate having an irregular network-like conductive layer is cut into a size of 15 cm × 15 cm, and copper tape is applied to both end portions of the conductive layer side surface of the conductive substrate at 5 mm. A pair of electrodes was provided. Thereafter, the transparent resin layer solution was applied with a wire bar and laminated in the shape of the conductive layer to obtain a transparent sheet heating element having a transparent protective layer. When this transparent sheet heating element was evaluated for exothermicity when a current of 1 A was applied, the exothermic temperature was 30 ° C., and the temperature before energization was 20 ° C., so the exothermic property was “◯”. .
(Example 3)
On the surface of the biaxially stretched polyethylene terephthalate film (Lumirror (registered trademark) U46 manufactured by Toray Industries, Inc.) to which the metal dispersion is applied, the primer solution is applied with a wire bar to a wet thickness of 12 μm, and the hydrophilic treatment layer is applied. Formed. A metal dispersion containing a 30 wt% aqueous solution in which a surfactant is dissolved is applied to the substrate with a wire bar so that the wet thickness is 30 μm, and is heated in a hot air oven at 150 ° C. (PHH-200 manufactured by Tabai Espec Co., Ltd.). Heat treatment was performed for 2 minutes to form a conductive layer (silver fine particle layer) on one side of the transparent substrate. The conductive layer (silver fine particle layer) of this multilayer substrate was in an irregular network shape, the total light transmittance was 80%, and the surface specific resistance value was 30.4Ω / □.

  Next, the laminated substrate was immersed in acetone (manufactured by Sasaki Chemical Co., Ltd.) at 25 ° C. for 2 seconds, and the laminated substrate was taken out and dried at 25 ° C. for 3 minutes. Next, this laminated substrate was heat-treated for 60 seconds in a hot air oven (PHH-200, manufactured by Tabai Espec Co., Ltd.) at 150 ° C. The obtained conductive substrate having an irregular network-like conductive layer (network-like conductive layer laminated substrate) had a surface specific resistance value of 7.1Ω / □ and a total light transmittance of 80%.

Next, the obtained conductive substrate having an irregular network-like conductive layer is cut into a size of 15 cm × 15 cm, and copper tape is applied to both end portions of the conductive layer side surface of the conductive substrate at 5 mm. A pair of electrodes was provided. Thereafter, the transparent resin layer solution was applied with a wire bar and laminated in the shape of the conductive layer to obtain a transparent sheet heating element having a transparent protective layer. When this transparent sheet heating element was evaluated for exothermicity when a current of 1 A was applied, the exothermic temperature was 30 ° C., and the temperature before energization was 20 ° C., so the exothermic property was “◯”. .
Example 4
When the exothermic evaluation when a current of 2 A was applied to the transparent sheet heating element obtained by the same method as in Example 3 was performed, the heating temperature was 45 ° C., and the temperature before energization was 20 ° C. Therefore, the exothermic property was “◯”.
(Example 5)
When the exothermic evaluation was performed when a current of 2.5 A was applied to the transparent sheet heating element obtained by the same method as in Example 3, the exothermic temperature was 55 ° C., and the temperature before energization was Since it was 20 ° C., the exothermic property was “◯”.

  The present invention relates to a transparent sheet heating element that can generate heat uniformly, and more particularly to a transparent sheet heating element used in liquid crystal display elements, refrigerated showcases, frozen showcases, automotive defrosters, and the like. .

Claims (5)

A transparent planar heating element comprising a pair of electrodes on a conductive layer of a conductive substrate,
The conductive substrate is a laminate of a transparent substrate and a conductive layer,
A transparent planar heating element, wherein the conductive layer has an irregular network shape.   The transparent sheet heating element according to claim 1, further comprising a transparent protective layer on a surface of the conductive substrate on the conductive layer side.   The transparent sheet heating element according to claim 1, wherein the conductive layer has a surface specific resistance value of 1 to 100Ω / □.   The transparent sheet heating element according to claim 1, wherein the total light transmittance is 50% or more.   5. The conductive layer according to claim 1, wherein the conductive layer is a conductive layer in which a metal is laminated on the transparent substrate in an irregular network by applying a metal dispersion on the transparent substrate. A transparent planar heating element according to claim 1.