JPH0340448B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to articles having good electrical conductivity and optionally colored coatings. Conventionally, it has been well known that conductive coatings made by blending conductive fillers such as carbon black, graphite, carbon fibers or flakes, metal-coated glass fibers or glass beads with paint resins can be used for antistatic purposes, electromagnetic shielding, etc. Are known.
However, these conductive fillers are black or close to gray, and even if pigments are mixed and dispersed, only gray or grayish and unclear hues can be obtained.In order to obtain a clear hue, it is necessary to add more pigment. In this case, the concentration of the conductive filler in the solid content is relatively reduced, resulting in an extremely low conductivity. Furthermore, when carbon fiber is used, it is possible to color it arbitrarily if the conductivity is low, that is, there are few carbon fibers and the conductivity is low, but if the conductivity is good, the amount of carbon fiber added increases and the color becomes gray. In reality, only a shaky and indistinct colored coating film could be obtained. Therefore, the inventor of the present invention conducted extensive research to obtain a paint film that has good conductivity and can be colored arbitrarily, and found that a paint film containing carbon fibers has extremely high conductivity in the thickness direction compared to the surface conductivity. The present invention has been developed based on the discovery that this can improve That is, the present invention
A conductive layer having a volume resistivity of 10 ⁸ Ωcm or less is provided on a non-conductive base material, and the conductive layer contains carbon fibers, pigments, and resins and has a volume resistivity lower than that of the conductive layer.
This invention relates to an article having an optionally colored conductive surface with a coating greater than or equal to 10 Ωcm. Non-conductive substrates used in the present invention include various plastics, paper, woven fabrics, non-woven fabrics, wood, glass,
It also includes materials that are not conductive per se, such as gypsum board, and those coated with non-conductive plastic or paint. The conductive layer according to the present invention has a volume resistivity of 10 ⁸ Ω.
cm or less, and may be a coating layer or an adhesive layer containing a conductive filler, a vapor-deposited layer or a plating layer of metal, metal oxide, etc. Examples of the conductive filler include carbon black, carbon fibers, graphite, metal powder, metal fibers or flakes, metal-coated glass fibers or glass beads. The coating film used as the upper layer of the present invention has a volume resistivity value that is 10 Ωcm or more larger than that of the conductive layer,
The coating thickness is 10-200μ, preferably 10-100μ
It is. The paint for forming the coating film on the conductive layer contains carbon fiber, pigment, and resin as essential components, but if necessary, plasticizers, additives,
Solvents etc. can be added. The resins used in the above paint include thermoplastic acrylic resin, linear polyurethane resin, linear polyester resin, nitrified cotton, cellulose acetate, chlorinated polyolefin resin, vinyl chloride resin, vinyl acetate resin, vinyl chloride-vinyl acetate. Thermoplastic resins such as copolymers, water-soluble resins that dry at room temperature, emulsion resins that dry at room temperature, thermosetting acrylic resins, thermosetting alkyd resins, epoxy resins,
These include thermosetting resins such as phenolic resin, polyamide resin, two-component polyurethane resin, unsaturated polyester resin, and melamine resin, and electron beam curing type and ultraviolet curing type resins can also be used. These resins can be used singly or in a suitable combination of two or more depending on the adhesion to the conductive layer and the heat resistance of the base material. The carbon fibers preferably have a common single yarn diameter of 5 to 25 μm and a fiber length of 3 mm or less, preferably 0.7 mm or less.
If the length is 3 mm or more, it is difficult to disperse, and 0.7
mm or less is preferable in terms of coatability (spray, roll coater, etc.). Spray coating for objects between 0.7 mm and 3 mm may cause problems such as clogging, but
Can be applied by brushing, troweling, etc. All pigments normally used for paints can be used, but transparent pigments will show through and the blackness of the carbon fiber will appear and become unclear, so if used in combination with pigments with hiding power such as titanium oxide or Bengara. good. It is also possible to use a coloring agent in which a pigment is dispersed in a predetermined resin in advance. The amount of pigment blended is determined so that the weight ratio to carbon fiber is in the range of 20/80 to 90/10. It goes without saying that a larger amount of pigment is preferable from the viewpoint of coloring power, but excessive use is not preferable since it may lead to instability of the conductivity or impair the physical properties of the coating film. The volume resistivity value of the coating film of the present invention is 10 Ωcm or more larger than that of the conductive layer, and preferably 10 ² Ωcm or more larger in consideration of colorability. However, a coating film having an excessively large volume resistivity value is not preferable because even if the conductive layer itself has sufficient conductivity, sufficient conductivity to ensure antistatic performance cannot be obtained. In the present invention, various methods such as spraying, brushing, troweling, roll coater, dipping, flow coater, etc. can be used to form a coating film on the conductive layer. Create a coating film with
A method of pasting or transferring this onto the conductive layer may also be used. The conductive coating film of the present invention is characterized in that the coating film itself does not necessarily have sufficient electrical conductivity, and sufficient electrical conductivity occurs only when it is formed on a conductive layer. For example, according to Table 1, which measured the resistance value of only a coating film made of resin mixed with carbon fiber in terms of surface resistance value and thickness direction, it is found that the surface resistance value and thickness method vary depending on the amount of carbon fiber blended in a coating film of the same thickness. Different trends in resistance are observed. In other words, as the amount of carbon fiber blended decreases, the surface resistance value increases, but there is almost no effect on the resistance value in the thickness direction, and when the amount of carbon fiber blended is small, the conductivity clearly changes gender is recognized.

[Table] This fact indicates that among the carbon fibers in the coating film, those distributed in the thickness direction contribute to the conductivity in the thickness direction when the amount of carbon fiber blended is small. This is thought to be because the length of the carbon fibers is about the same as or a fraction of the thickness of the coating film, and in some cases is longer than the thickness of the coating film. Therefore, in the coating film of the present invention, the flow of electricity does not occur in the surface layer of the coating film, but occurs mainly between the coating film and the conductive layer. According to the present invention, the required level of conductivity is achieved by appropriately controlling the volume resistivity of the conductive layer and the overlying coating itself. In other words, when aiming for a volume resistivity of 10 ⁰ Ωcm, for example, the conductive layer should be 10 ⁰ Ωcm, and the upper layer should be 10 ¹ Ω.
cm or more, even if the upper layer is 10 ³ Ωcm, it is 10 ⁰ Ωcm
A volume resistivity value of is obtained. Articles formed according to the present invention can be used for floors and walls where static electricity must be prevented, workbenches in precision equipment assembly factories, computers and home appliances that need to be shielded from EMI, and other places where conductivity is required. I can do things. The target conductivity level is 10 ⁵ to 10 ⁸ Ωcm in terms of volume resistivity for antistatic materials, and 10 ¹ to 10 ⁴ Ω for conductive materials such as high-voltage cable sheathing materials.
cm, 10 ¹ Ωcm or less is required for EMI shielding. Hereinafter, the present invention will be explained in more detail with reference to Examples. In the examples, "part" and "%" indicate parts by weight and weight %. Example 1 An ABS resin board was spray-painted as a lower layer with a paint formulated as shown below, after diluting it with thinner, to a dry film thickness of 45μ. Thermoplastic acrylic resin (40% non-volatile content, main component: polymethyl methacrylate with an average molecular weight of approximately 60,000) 100 parts Butylbenzyl phthalate 10 parts Nickel powder (average particle size 4μ) 90 parts After setting for 5 minutes, apply on this lower layer. For the upper layer, a paint formulated as shown below was diluted with thinner and then spray-painted to a dry film thickness of 30 μm. Thermoplastic acrylic resin (40% non-volatile content, main component: polymethyl methacrylate with average molecular weight of approximately 60,000) 39 parts butylbenzyl phthalate 4 parts carbon fiber (single fiber diameter 14.5μ, fiber length 0.7mm) 19 parts green paste (phthalocyanine) green 9
18 parts CAB resin, 3 parts butylbenzyl phthalate, 70 parts solvent) 17 parts white paste (37 parts titanium white,
10 parts CAB resin, 3 parts butylbenzyl phthalate
When the volume resistivity of the dried coating film thus obtained was measured by contacting one of the electrodes with the upper layer and the other with the lower layer, it was 7 × 10 ^-3 Ωcm, and the hue was The color is a bright young grass color, and when measured as a color difference between L, a, and b systems, L = 55.8, a = -32.46, b = 8.34
It was hot. The EMI shielding effect of this painted board was 20 to 50 dB, which was sufficient. The volume resistivity values of only the upper layer and only the lower layer were 1×10 ⁰ Ωcm and 2×10 ^-3 Ωcm, respectively. Comparative Example 1 In addition to 100 parts of the paint mixed for the lower layer in Example 1, 65 parts of green paste and 83 parts of white paste were added.
109 parts of nickel powder (both of which were the same as those used in Example 1) were mixed and dispersed to obtain a paint having a nickel content of 64% in the solid content of the paint. Spray paint this paint onto an ABS board and dry the film.
A coating film of 70μ was obtained. The volume resistivity value of this coating film was measured by bringing two electrodes into contact with both surfaces of the coating film, and found to be 1.5×10 ^-3 Ωcm. In addition, the hue is an unclear green close to gray, L = 15.6, a =
-9.85, b=1.05 and ΔE= for the coating of Example 1
It was 46.7. Comparative Example 2 34 parts of the carbon fiber used in Example 1 was further mixed and dispersed in 100 parts of the paint formulated for the upper layer in Example 1, and the mixture was spray-painted on an ABS board to obtain a dry coating film of 70 μm. The volume resistivity value of this coating film was measured in the same manner as in Comparative Example 1 and found to be 1.2×10 ^-2 Ωcm, but the hue was an indistinct green with a hint of gray; L = 25.9, a = 11.52, b=1.56 and ΔE=37.1 for the coating film of Example 1. Comparative Example 3 100 parts of the paint mixed for the lower layer in Example 1 was further mixed with 38 parts of green paste and 50 parts of white paste (both of which were the same as those used in Example 1), dispersed, and applied to an ABS board. A coating film with a dry film thickness of 70 μm was obtained by spray painting. The hue of this paint film is a slightly rough green, L=30.6, a=-
15.64, b=3.66 and ΔE= for the coating film of Example 1
30.7, but the volume resistivity value measured in the same manner as in Comparative Example 1 was 3×10 ⁴ Ωcm. Example 2 Chromium was vacuum-deposited on an ABS resin plate to a thickness of 10μ,
A conductive treated ABS board was obtained. Next, 20 parts of carbon fiber with a single fiber diameter of 10μ and a fiber length of 0.2mm were placed on this chromium-deposited surface.
10 parts of Bengara mixed and dispersed with 100 parts of Hitaloid 3008 (manufactured by Hitachi Chemical Co., Ltd., non-volatile content 50%) and 89 parts of an isocyanate-based curing agent Sumidyur N-75 (manufactured by Sumitomo Bayer Urethane Co., Ltd., non-volatile content) 75%) were mixed, spray-painted to a dry film thickness of 35μ, and baked at 80°C for 30 minutes. The volume resistivity value of the coated board after being left at room temperature overnight was 1 x 10 ^-3 . The volume resistivity value of the coating film alone was 7×10 ⁵ Ωcm. Example 3 As an upper layer on release paper, 200 parts of linear polyurethane resin (non-volatile content 25%), 15 parts of titanium white, 0.1 part of phthalocyanine blue, and Shinkasha Red.
After mixing and dispersing 16 parts of carbon fiber with Y0.3 parts, single fiber diameter 12 μ, and fiber length 0.1 mm, apply it with a bar coater and dry to the touch. Acrylic acid alkyl ester (non-volatile content 30
%), 2 parts of graphite, and 10 parts of the same carbon fiber as above were mixed and applied, and after drying at 100°C for 3 minutes, the release paper was removed and the coating film was attached to a wooden board.
The volume resistivity value of this material was 8×10 ⁶ Ωcm. The volume resistivity values of the upper layer and the lower layer alone were 4×10 ⁹ Ωcm and 6×10 ⁶ Ωcm, respectively.
Also, the hue was a beautiful light purple. This article could be used as an anti-static wall material.

Claims (1)

[Claims] 1 Volume resistivity value is 10 ⁸ Ω on a non-conductive base material
It has a conductive layer of cm or less, and carbon fiber, on the conductive layer,
An article having an arbitrarily colored conductive surface comprising a coating film containing a pigment and a resin and having a volume resistivity 10 Ωcm or more larger than that of the conductive layer.