JP6394137B2 - Coating - Google Patents

Description

  It is related with the coating film excellent in magnetic shielding property.

  In recent years, communication devices and electronic devices have become more sophisticated, and the size and weight have been reduced. These communication devices and electronic devices have problems that magnetic noise or electromagnetic noise generated in the device is radiated to the outside, or that the device malfunctions due to electromagnetic interference in the device. In order to prevent the occurrence of such noise and the malfunction of the device, a magnetic shield material is provided in the device.

  It is particularly difficult to shield low-frequency magnetism, and a method such as using a thick metal as a magnetic shield material is sometimes used. However, such a method hinders weight reduction of the device, and therefore a magnetic shield material that can more effectively shield low-frequency magnetism is required.

  In such a situation, for example, a flat soft magnetic powder and an oxide powder made of an Fe-Si-Al alloy have a high surface resistance and a high magnetic permeability at the same time to improve the noise suppression effect. An electromagnetic interference suppressor configured to be dispersed in an organic binder is disclosed (for example, see Patent Document 1).

  However, such a magnetic shield material is generally in the form of a sheet, and in order to give a magnetic shield characteristic to a member having a complicated shape, it is necessary to bond a plurality of sheets along the shape of the member. Therefore, a gap is formed between the sheets, which may cause noise and malfunction of the device. Further, in the process of manufacturing the sheet, it is necessary to press and orient the magnetic material.

JP 2012-2222076 A

  The present invention aims to solve such problems. That is, an object of the present invention is to provide a coating film having excellent magnetic shielding properties that can be formed on a member having a complicated shape by a simple process of painting.

  The present invention relates to a coating film comprising a binder and a magnetic filler and satisfying the conditions (1) and (2).

Condition (1): Three parallel straight lines extending in the film thickness direction are drawn every 3.0 μm on the cross-sectional photograph in the film thickness direction of the coating film taken with a scanning electron microscope, and each straight line intersects with the straight line. When the number of magnetic fillers having a longest length of 1.0 μm or more in the cross-sectional photograph is counted and the number of magnetic fillers is divided by the length of the straight line, the reference number per 1 μm of straight line is calculated. The average value of the reference numbers in the straight line is 0.15 (pieces / μm) or more.

Condition (2): A cross-sectional photograph in the film thickness direction of a coating film taken with a scanning electron microscope is provided with a measurement region formed by 100 unit regions of 3 μm square, and a binder occupies each unit region. When the area is measured, the number of unit regions in which the ratio of the area occupied by the binder to the unit regions is 50% or more is 50 or less.

  The binder is preferably at least one selected from urethane resin, acrylic resin, polyester resin, epoxy resin, polyimide resin, and silicone resin.

  Magnetic filler is Fe-Si-Al alloy, Fe-Si alloy, Fe-Si-Cr alloy, Fe-Cr alloy, Fe-Ni alloy, Fe-Co alloy, Fe-based amorphous, Co-based amorphous, Mn-Zn series It is preferably at least one selected from ferrite and Ni—Zn ferrite.

  The magnetic filler is preferably flat or needle-shaped with a thickness of 1 μm or less and an aspect ratio of 20 or more.

  The mass ratio of the solid content of the binder to the magnetic filler is preferably 30/70 to 5/95.

  According to the present invention, it is possible to provide a coating film that can be formed by a simple process of coating and has excellent magnetic shielding properties.

It is a schematic diagram of the cross-sectional photograph which image | photographed the cross section of the film thickness direction of the coating film concerning embodiment of this invention with the operation type electron microscope (SEM). It is a schematic diagram of the cross-sectional photograph which image | photographed the cross section of the film thickness direction of the coating film concerning embodiment of this invention with the operation type electron microscope (SEM). It is the schematic diagram which expanded the unit area | region provided in the cross-sectional photograph of FIG. 2 is a cross-sectional photograph of the coating film obtained in Example 1 in the film thickness direction. 2 is a cross-sectional photograph of a coating film obtained in Comparative Example 1 in the film thickness direction. 3 is a measurement result of complex permeability of a coating film obtained in Example 1. FIG. 3 is a measurement result of complex permeability of a coating film obtained in Comparative Example 1. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings and the like. However, the coating film of the present invention is not limited to those described in these embodiments.

  The coating film of the present invention contains a binder and a magnetic filler and satisfies the conditions (1) and (2).

  Condition (1) means that three parallel straight lines extending in the film thickness direction are drawn every 3.0 μm on a cross-sectional photograph in the film thickness direction of the coating film taken with a scanning electron microscope. When the number of magnetic fillers that intersect with each other and the length of the longest part in the cross-sectional photograph is 1.0 μm or more is divided by the length of the straight line, the reference number per 1 μm of the straight line is calculated. Further, the average value of the reference numbers in the three straight lines is 0.15 (pieces / μm) or more. The average value of the reference numbers in the three straight lines is preferably 0.15 to 1.0 (pieces / μm) or more, and more preferably 0.15 to 0.5 (pieces / μm) or more. preferable. When the average value of the reference number is smaller than 0.15 (pieces / μm), the density of the magnetic filler in the coating film decreases, and the magnetic shielding properties of the coating film tend to decrease.

  FIG. 1 is a schematic diagram of a cross-sectional photograph obtained by photographing a cross section obtained by cutting a coating film according to an embodiment of the present invention along the film thickness direction with an operation electron microscope (SEM). Hereinafter, the procedure for calculating the reference number will be described with reference to the schematic diagram of FIG. In FIG. 1, the vertical direction of the cross-sectional photograph 100 is the film thickness direction. For example, the closer to the upper surface of the cross-sectional photograph 100, the closer to the surface of the coating film. Approaches the interface.

  First, as shown in FIG. 1, in a cross-sectional photograph 100 taken in a film thickness direction of a coating film taken by a scanning electron microscope, three parallel straight lines (A), (B) and (B) extending in the film thickness direction. C) Draw. For example, the straight line (b), which is the center of the straight lines (b), (b), and (c), is drawn so as to be located at the center in the left-right direction of the cross-sectional photograph 100. The distance between the straight lines (A), (B), and (C) is 3 μm.

  Next, for each of the three straight lines (A), (B), and (C), the length of the longest portion in the cross-sectional photograph is 1.0 μm or more, and the number of magnetic fillers that intersect the straight line is counted. For example, when the number of magnetic fillers 102 is α for a straight line (A), β for a straight line (B), and γ for a straight line (C), by dividing by the length Lμm of the straight line, The reference number per 1 μm of each straight line can be calculated. That is, the reference number in each straight line is α / L (pieces / μm), β / L (pieces / μm), and γ / L (pieces / μm). In this case, the average value of the reference numbers in the three straight lines is (α + β + γ) / 3L (pieces / μm). For example, since the straight line (c) in FIG. 1 intersects with the magnetic fillers 102a to 102e, and the magnetic fillers 102a to 102e all have a longest length of 1.0 μm or more in the cross-sectional photograph, γ is “5”.

  In addition, the condition (2) is that a measurement region in which 100 unit regions of 3 μm square are continuously formed is provided in a cross-sectional photograph in the film thickness direction of a coating film taken by a scanning electron microscope. When the area occupied by the binder is measured, the number of unit regions in which the ratio of the area occupied by the binder to the unit region is 50% or more is 50 or less. The number of unit regions in which the ratio of the area occupied by the binder to the unit region is 50% or more is more preferably 10 to 50, and 10 to 30 in that the magnetic shielding property of the coating film can be improved. More preferably. When the number of unit regions in which the binder occupies 50% or more of the unit region is less than 10, the number of regions in which the binder component is continuously present is small, so the flexibility of the coating film tends to be low. . When the number of unit regions in which the binder occupies 50% or more of the unit regions exceeds 50, the density of the magnetic filler in the coating film decreases, and the magnetic shielding properties tend to be deteriorated.

  FIG. 2 is a schematic diagram of a cross-sectional photograph taken by a scanning electron microscope (SEM) of a cross section obtained by cutting the coating film according to the embodiment of the present invention along the film thickness direction. FIG. 3 shows an enlarged schematic view of a unit region provided in the cross-sectional photograph of FIG. Hereinafter, the procedure for calculating the number of unit regions in which the ratio of the area occupied by the binder to the unit regions is 50% or more will be described using the schematic diagrams of FIGS. 2 and 3.

  First, as shown in FIG. 2, a 30 μm × 30 μm square measurement region 103 is provided in a cross-sectional photograph 100 taken in a film thickness direction (vertical direction) of a coating film taken by a scanning electron microscope. The unit area 104 is a 3 μm × 3 μm square, and the measurement area 103 is composed of 10 (vertical direction) × 10 (left and right direction) unit areas 104. Next, for each unit region 104, the area occupied by the binder 101 in the unit region 104 is measured. For example, as shown in FIG. 3, the number of unit regions 104 in which the area ratio of the binder 101 is 50% or more is counted. In FIG. 2, the unit region 104 in which the area ratio of the binder 101 is 50% or more is indicated by hatching. In FIG. 2, the measurement region 103 is formed in a square shape, but the shape is not particularly limited as long as 100 unit regions 104 are formed in a row.

  The coating film of the present invention can be obtained, for example, by applying and drying a magnetic shield paint containing at least a binder, a magnetic filler, and a solvent.

  It is preferable that the binder used in order to obtain the coating film of this invention is 1 or more selected from a urethane resin, an acrylic resin, a polyester resin, an epoxy resin, a polyimide resin, and a silicone resin. Among these, urethane resin is preferable because the density of the magnetic filler in the coating film is high and a coating film excellent in flexibility and adhesion to the surface to be coated can be easily obtained.

  The urethane resin is obtained by reacting a polyol and a polyisocyanate compound. Examples of the urethane resin include polyether polyurethane, polycarbonate polyurethane, and polyester polyurethane. Among these, polyester-based polyurethane is preferable because it has a high elongation at break and excellent flexibility.

  Polyether polyurethane is a reaction product of a polyether polyol and a polyisocyanate compound. Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, and polytetramethylene glycol.

  Polycarbonate polyurethane is a reaction product of a polycarbonate polyol and a polyisocyanate compound. Examples of the polycarbonate polyol include diols (ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, Neopentyl glycol etc.) and carbonate (dimethyl carbonate, diphenyl carbonate, ethylene carbonate, phosgene etc.) and the polycarbonate diol obtained by reacting.

  Polyester polyurethane is a reaction product of a polyester polyol and a polyisocyanate compound. Examples of the polyester polyol include dicarboxylic acids (phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid, adipic acid, sebacic acid, etc.) and polyhydric alcohols (ethylene glycol, propylene glycol, tetramethylene glycol, 1, And 4-butanediol, 1,6-hexanediol, neopentyl glycol, trimethylolpropane, pentaerythritol, etc.).

  Examples of the polyisocyanate compound include hexamethylene diisocyanate, tolylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, norbornene diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, isophorone diisocyanate trimer, hydrogenated xylylene diisocyanate, Examples thereof include hydrogenated diphenylmethane diisocyanate.

  The weight average molecular weight of the urethane resin is preferably 1000 to 100,000, more preferably 5000 to 50000. When the weight average molecular weight of the urethane resin is less than 1000, the durability of the coating film tends to decrease or the magnetic shielding properties tend to decrease. When the weight average molecular weight of the urethane resin exceeds 100,000, the flexibility of the coating film The adhesion to the surface to be coated tends to decrease, and the orientation of the filler tends to deteriorate.

  The magnetic filler used in the present invention is not particularly limited as long as it is a soft magnetic material. For example, Fe-Si-Al alloy, Fe-Si alloy, Fe-Si-Cr alloy, Fe-Cr alloy, Fe-Ni One or more selected from alloys, Fe—Co alloys, Fe-based amorphous, Co-based amorphous, Mn—Zn based ferrite and Ni—Zn based ferrite are preferable. Among these, an Fe—Si—Al alloy (for example, Sendust) is preferable from the viewpoint of obtaining excellent magnetic shielding characteristics.

  The shape of the magnetic filler is not particularly limited, but is preferably flat or needle-like with a thickness of 1 μm or less. The flat shape has, for example, a shape in which a three-dimensional shape such as a sphere or a rectangular parallelepiped is crushed in one direction, and is a concept including shapes such as a plate shape, a scale shape, and a thin film shape. The needle shape refers to an elongated shape extending linearly in one direction.

  The thickness of the magnetic filler is more preferably 0.5 μm or less, and further preferably 0.3 μm or less. When the thickness of the magnetic filler exceeds 1 μm, the number of magnetic fillers in the film thickness direction decreases and the magnetic shielding characteristics deteriorate.

  The aspect ratio of the magnetic filler is preferably 20 or more. The aspect ratio of the magnetic filler is more preferably 40 or more, and even more preferably 100 or more, in that the number of magnetic fillers in the film thickness direction increases and the gap between the fillers decreases. Here, the aspect ratio means a value obtained by dividing the length of the longest portion of the magnetic filler by the average thickness. When the aspect ratio is less than 20, the number of magnetic fillers in the film thickness direction decreases and the magnetic shield characteristics deteriorate.

  In the magnetic shielding coating used in the present invention, the mass ratio of the solid content of the binder to the magnetic filler is preferably 30/70 to 5/95, more preferably 25/75 to 10/90, and 20 / More preferably, it is 80-10 / 90. When the mass ratio of the solid content of the binder to the magnetic filler is larger than 30/70, that is, when the solid content of the binder is too large, the magnetic shielding properties of the coating film tend to deteriorate, and the solid content of the binder and the magnetic filler If the mass ratio is smaller than 5/95, that is, if the solid content of the binder is too small, the resulting coating film loses its flexibility and becomes brittle, or the contact between the fillers becomes insufficient and the magnetic shielding properties are degraded. .

  In the magnetic shield paint used in the present invention, an organic solvent is used as a solvent. As the organic solvent, for example, toluene, methyl ethyl ketone, isopropanol, butyl acetate, ethyl acetate, butyl cellosolve, butyl carbitol acetate, xylene and the like are used. Of these, toluene, methyl ethyl ketone, and isopropanol are preferable from the viewpoints of drying properties and coating workability.

  The magnetic shield paint used in the present invention includes a binder, a magnetic filler, an organic solvent, a dispersant and an antifoaming agent, as well as pigments, fillers, ultraviolet absorbers, light, and the like within the scope of the present invention. Arbitrary components, such as a stabilizer and antioxidant, may be contained.

  The magnetic shield coating used in the present invention is preferably adjusted to a viscosity of 1.0 to 100 dPa · s, and more preferably adjusted to a viscosity of 2 to 50 dPa · s by adjusting the content of the organic solvent. preferable. If the viscosity of the magnetic shield paint is lower than 1.0 mPa · s, the coating film will sag during application. On the other hand, when the viscosity of the magnetic shield coating is higher than 100 mPa · s, the orientation of the magnetic filler is deteriorated and the number of magnetic fillers in the film thickness direction is reduced.

(Painting method)
The method for applying the magnetic shield paint of the present invention is not particularly limited as long as the coated surface can be uniformly coated, and examples thereof include spray coating. For example, it is preferable to perform spray coating at a pressure of 1.0 to 10 kg / cm ² using a spray gun having a gun diameter of 1.0 to 5.0 mm.

  Also, the drying method after coating is not particularly limited, and it may be dried at room temperature or may be heat-dried, but from the viewpoint of easy orientation of the magnetic filler in the direction perpendicular to the film thickness direction, it is dried at room temperature. It is preferable to do.

(Use)
The coating film of the present invention can be used, for example, for magnetic shields such as inner walls and outer walls of hospitals, office buildings, data centers, etc., battery cases of electric vehicles and hybrid vehicles, motors, transformers, and magnetic devices.

  Hereinafter, the present invention will be described in more detail with reference to examples and the like, but the present invention is not limited to these examples.

Example 1
Urethane resin (manufactured by Arakawa Chemical Industries, Ltd., polyester polyurethane “Yuriano 2456”, weight average molecular weight 30000) 22.97 parts by mass, Sendust (manufactured by Daido Special Steel Co., Ltd., “DAPMSA10”, thickness 1.0 μm, aspect ratio 40) 38.28 parts by mass, 0.31 part by mass of a phosphoric acid polyester-based dispersant (Bikchem-Japan Co., Ltd., “BYK-111”) as a dispersant, 38.28 parts by mass of toluene as an organic solvent, and antifoaming 0.15 parts by mass of a non-silicone antifoaming agent (manufactured by Big Chemi Japan Co., Ltd., “BYK-1752”) as an agent was mixed using a disper to obtain a magnetic shield paint. The obtained magnetic shielding paint had a nonvolatile content of 45% and a viscosity of 5.0 dPa · s. Apply the magnetic shield paint to a glass plate with a spray gun with a gun diameter of 1.5 mm at a pressure of 4.0 kg / cm ² so that the thickness of the coating after drying is 200 μm, and dry at room temperature. Thus, a coating film of Example 1 was obtained.

(Average number of reference numbers on three straight lines)
About the cross section of the said coating film, the cross-sectional photograph of the film thickness direction of the coating film was image | photographed by the scanning electron microscope (the JEOL Co., Ltd. make, JSM-6360LV) at 1000-times multiplication factor. FIG. 4 shows a cross-sectional photograph taken with a scanning electron microscope. Three parallel straight lines extending in the film thickness direction were drawn every 3.0 μm on the photographed cross-sectional photograph. For each straight line, count the number of magnetic fillers that intersect the straight line and the longest length in the cross-sectional photograph is 1.0 μm or more, and divide the counted number by the length of the straight line to obtain the reference number per 1 μm of the straight line. The average value of the reference numbers in the three straight lines was calculated. The results are shown in Table 1.

(Number of unit regions where the percentage of the area occupied by the binder is 50% or more)
In the same manner as the measurement of the reference number, the cross-sectional photograph in the film thickness direction of the coating film taken by the scanning electron microscope has 100 unit areas of 3 μm square (10 in the vertical direction × 10 in the horizontal direction). When the measurement area formed in a row was provided and the area occupied by the binder was measured for each unit area, the number of unit areas where the ratio of the area occupied by the binder to the unit area was 50% or more was determined. The results are shown in Table 1.

(Complex permeability)
About the coating film obtained in Example 1, the real part μr ′ and the imaginary part μr of the complex permeability in the frequency band of 1 M to 1 GHz using an RF impedance material analyzer device (E4991A, manufactured by Agilent Technologies). ”Was measured. The measurement results are shown in FIG.

(Comparative Example 1)
Acrylic resin (Fujikura Kasei Co., Ltd., “Acrybase LH101”, weight average molecular weight 40000) 22.97 parts by mass, Sendust (Daido Special Steel Co., Ltd., “DAPMSA10”, thickness 1.0 μm, aspect ratio 40) 38 .28 parts by mass, 0.31 part by mass of a phosphoric acid polyester-based dispersant (BIC Chemi Japan Co., Ltd., “BYK-111”) as a dispersant, 38.28 parts by mass of toluene as an organic solvent, and non-defoamer 0.15 parts by mass of a silicone-based antifoaming agent (Bikchem-Japan Co., Ltd., “BYK-1752”) was mixed using a disper to obtain a magnetic shield paint.

  The obtained magnetic shielding paint was applied in the same manner as in Example 1 to obtain a coating film of Comparative Example 1. About the obtained coating film, the number of unit regions in which the average value of the reference numbers in the three straight lines and the area ratio occupied by the binder were 50% or more were calculated in the same manner as in Example 1. The results are shown in Table 1. About the coating film of the comparative example 1, the cross-sectional photograph of the film thickness direction of the coating film image | photographed with the scanning electron microscope is shown in FIG. Further, the complex permeability of the coating film of Comparative Example 1 was measured by the same method as in Example 1. The measurement results are shown in FIG.

  As can be seen from the cross-sectional photographs of FIGS. 4 and 5 and the results in Table 1, the coating film of Example 1 has a higher density of magnetic filler than Comparative Example 1, and is oriented in a direction perpendicular to the film thickness direction. ing. Moreover, as can be seen from the results of the complex permeability measurement shown in FIGS. 6 and 7, the coating film of Example 1 is superior to the coating film of Comparative Example 1 in particular in the low frequency band. .

100 Cross-sectional photograph 101 Binder 102 Magnetic filler 103 Measurement area 104 Unit area

Claims (4)

A coating film comprising a binder and a magnetic filler, wherein the binder is a urethane resin and satisfies the conditions (1) and (2).
Condition (1): Three parallel straight lines extending in the film thickness direction are drawn every 3.0 μm on the cross-sectional photograph in the film thickness direction of the coating film taken with a scanning electron microscope, and each straight line intersects with the straight line. When the number of magnetic fillers having a longest length of 1.0 μm or more in the cross-sectional photograph is counted and the number of magnetic fillers is divided by the length of the straight line, the reference number per 1 μm of straight line is calculated. The average value of the reference numbers in the straight line is 0.15 (pieces / μm) or more.
Condition (2): A cross-sectional photograph in the film thickness direction of a coating film taken with a scanning electron microscope is provided with a measurement region formed by 100 unit regions of 3 μm square, and a binder occupies each unit region. When the area is measured, the number of unit regions in which the ratio of the area occupied by the binder to the unit regions is 50% or more is 50 or less. Magnetic filler is Fe-Si-Al alloy, Fe-Si alloy, Fe-Si-Cr alloy, Fe-Cr alloy, Fe-Ni alloy, Fe-Co alloy, Fe-based amorphous, Co-based amorphous, Mn-Zn series it is one or more selected from ferrite and Ni-Zn ferrite, coating of claim 1. The coating film according to claim 1 or 2 , wherein the magnetic filler has a thickness of 1 µm or less and is flat or needle-shaped and has an aspect ratio of 20 or more. Mass ratio of solids and the magnetic filler binder is 30/70 to 5/95, the coating film according to any one of claims 1-3.