JP2003036729A - Conductive material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive material maintaining high conductivity and improved in durability against abrasion, as a material of an apparatus in a clean room, especially as a material for a viewing window of a machine. SOLUTION: On one side of a transparent plastic film having an anchor coat if necessary, is formed a conductible layer containing conductive particles and an ionizing radiation cured resin, covered with an inorganic pellicle of silica or the like. The width of the inorganic pellicle is set so as to prevent reflection of visible light. With an adhesive layer on the other side of the plastic film, it is used to adhere to a material to be adhered to such as a glass material constituting the viewing window of the machine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive material for imparting an antistatic function to various base materials, and is particularly suitable as a structural material for a clean room or a material for equipment used in the clean room. Regarding

[0002]

2. Description of the Related Art In a room such as an industrial dust-free room (clean room) where fine powder is disliked, an antistatic material is used as a structural material for walls and floors and a machine material installed in the room. ing. As such a material, for example, a material in which an antistatic film (conductive film) is attached or thermocompression-bonded to a synthetic resin material is widely used, and particularly for applications where transparency such as a peep window of a machine is required. As the conductive film, a transparent substrate provided with a conductive layer in which a transparent conductive filler such as ITO is dispersed in a binder resin is used.

Conductive films for clean rooms are required to have higher conductivity than ordinary antistatic films.
A predetermined conductivity is obtained by increasing the conductive filler / resin ratio. However, if the ratio of the conductive filler / resin is increased, there is a problem that the mechanical strength of the conductive layer, especially the scratch resistance of the surface is lowered.

In order to prevent such a decrease in mechanical strength, it has been proposed to use an ionizing radiation curable resin as the resin of the conductive layer or to provide a hard coat layer between the conductive layer and the base material. However, the mechanical strength such as flexibility is improved. However, regarding the scratch resistance of the surface of the conductive layer, sufficient performance has not been obtained by these techniques.

On the other hand, it is possible to provide a scratch-resistant layer such as a hard coat layer in order to impart scratch resistance to the surface of the conductive layer. In this case, the conductivity may be impaired. It is highly likely.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a conductive material having high conductivity, which has improved mechanical strength such as scratch resistance. Another object of the present invention is to provide a conductive material having high transparency, which is particularly suitable for applications requiring light transmission such as a peep window of a machine used in a clean room.

[0007]

In order to achieve the above object, the inventors of the present invention have earnestly studied about a film material formed on a conductive layer, and as a result, by providing an inorganic thin film such as silica, the conductivity and the transparency are improved. The mechanical strength of the conductive layer can be significantly improved without impairing the reflectivity, and the reflectivity can be prevented by setting the thickness of such an inorganic thin film within a specific range. The inventors of the present invention have found that a conductive material suitable for a window can be obtained and have reached the present invention.

That is, the conductive material of the present invention is characterized in that it is provided on a base material and has a conductive layer containing conductive particles and an inorganic thin film formed on the conductive layer. is there. Further, the conductive material of the present invention is characterized in that it is provided on a transparent substrate and has a transparent conductive layer containing conductive particles and an inorganic thin film formed on the conductive layer. .

Further, the conductive material of the present invention is characterized in that the inorganic thin film is made of silica. The thickness of the inorganic thin film is preferably 0.01 μm to 1.0 μm. Further, in the conductive material of the present invention, the base material has an anchor coat layer made of an ionizing radiation curable resin between the base material and the conductive layer. Further, in the conductive material of the present invention, the base material has an adhesive layer on the surface opposite to the surface on which the conductive layer is provided.

The conductive material of the present invention is provided with an inorganic thin film such as silica on the conductive layer to improve the mechanical strength of the conductive layer, especially the scratch resistance, without impairing the conductivity. You can Further, by setting the thickness of this inorganic thin film within a predetermined range, when the conductive material is transparent, the high transparency can be maintained and the reflectivity can be prevented. Accordingly, when the conductive material of the present invention is applied to a peep window for machinery, the inside can be made extremely easy to see.

The conductive material of the present invention will be described in detail below. The conductive material of the present invention has a base material, a conductive layer, and an inorganic thin film as a basic configuration. As the base material used for the conductive material of the present invention, a base material such as a plastic film, a plastic plate or a glass plate can be used. As the plastic film, for example, a film made of an acrylic resin such as polycarbonate, polyolefin, polyester or polyacrylate, or a resin such as polyvinyl chloride, polyvinylidene chloride or triacetyl cellulose can be used. As a plastic plate,
A plate made of polycarbonate, acrylic resin, polyvinyl chloride or the like can be used.

When the conductive material of the present invention is a film, a polyester film is preferable among the above materials from the viewpoint of processability such as solvent resistance and heat resistance and optical characteristics such as transparency. The surface of the base material may be subjected to an easy adhesion treatment for the purpose of improving the adhesiveness to the conductive layer or the anchor coat layer described later.

The thickness of the substrate is not particularly limited, but in the case of a film attached to another member, it is usually about 50 μm to 300 μm. By setting it as such a range, the handling property and the workability at the time of sticking to other members will become favorable.

In the conductive material of the present invention, the conductive layer may be directly provided on the base material, but preferably, an anchor coat layer containing an ionizing radiation curable resin is provided between the base material and the conductive layer. . By providing the anchor coat layer, the mechanical strength can be improved.

The ionizing radiation curable resin constituting the anchor coat layer is a resin which is cross-linked and cured by irradiation with ionizing radiation (ultraviolet ray or electron beam), and specifically, epoxy-based acrylate, polyester-based acrylate, polyurethane-based acrylate, A resin having an acrylic group such as a polyhydric alcohol acrylate, or a photopolymerizable prepolymer such as a polythiol polyene resin can be used.

Although these can be used alone, it is preferable to add a photopolymerizable monomer in order to improve the crosslinkability and the hardness of the crosslinked cured film. As the photopolymerizable monomer, a monofunctional acrylic monomer such as 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, butoxyethyl acrylate, 1,6-hexanediol acrylate, neopentyl glycol diacrylate, diethylene glycol diacrylate. One or two kinds of bifunctional acrylic monomers such as acrylate, polyethylene glycol diacrylate, hydroxypivalic acid ester neopentyl glycol acrylate, etc., and polyfunctional acrylic monomers such as dipentaerythritol hexaacrylate, trimethylpropane triacrylate, pentaerythritol triacrylate, etc. The above is used.

In the anchor coat layer, in addition to the above-mentioned photopolymerizable prepolymer and photopolymerizable monomer, it is preferable to add a photopolymerization initiator, an ultraviolet sensitizer or the like when it is cured by ultraviolet irradiation. Further, the anchor coat layer may contain a resin other than an ionizing radiation curable resin such as an acrylic resin or an epoxy resin. Further, in addition to the above-mentioned ionizing radiation curable resin and the like, additives such as a UV absorber and a light stabilizer may be contained.

For the anchor coat layer, an ionizing radiation curable resin coating material containing the above-mentioned photopolymerizable prepolymer, photopolymerizable monomer and, if necessary, a photopolymerization initiator, an ultraviolet sensitizer and the like is applied on a substrate. After that, it can be formed by irradiating with an ultraviolet ray or an electron beam. The thickness of the anchor coat layer is not particularly limited, but is preferably 2 μm or more, more preferably 4 μm to 12 μm.

The conductive layer contains a binder resin and conductive particles. As the binder resin, it is preferable to use a thermosetting resin such as phenol resin, urethane resin, unsaturated polyester, or N-methylolated polyacrylamide, or an ionizing radiation curable resin similar to the resins mentioned as the resin for the anchor coat layer. . High coating strength can be obtained by using such a resin. In particular, from the viewpoint that a layer can be formed at a relatively low temperature and that it has excellent scratch resistance, an ionizing radiation curable resin or a polymer having an N-methylol group at the terminal or side chain as described below and the terminal or side chain are used. A mixed polymer with a polymer having a carboxyl group is preferable.

As the polymer having an N-methylol group at the terminal or side chain, a copolymer of N-methylol acrylamide and (meth) acrylic acid ester, N-methylol acrylamide and an ethylenically unsaturated double bond are used. Examples thereof include a copolymer with a compound having the same. (Meta)
Examples of the acrylate ester monomer include ethyl acrylate, butyl acrylate, methyl methacrylate and the like, and examples of the monomer having an ethylenically unsaturated double bond include vinyl acetate, styrene and the like.

As the polymer having a carboxyl group at the terminal or side chain, a copolymer of (meth) acrylic acid and (meth) acrylic acid ester, a compound having (meth) acrylic acid and an ethylenically unsaturated double bond And copolymers thereof.

The mixing ratio of the polymer having an N-methylol group at the terminal or side chain and the polymer having a carboxyl group at the terminal or side chain is such that the ratio of the N-methylol group to the carboxyl group is 50: 1 to 1:20. , Preferably from 5: 1
The ratio is preferably 1: 3. With such a ratio, it becomes possible to cure the conductive layer by heating at a relatively low temperature.

As the conductive particles, fine powder of metal such as aluminum and zinc, fine powder of metal oxide such as titanium oxide, zinc oxide, tin oxide, fine powder of indium oxide, mixed fine powder of tin oxide and antimony oxide, For example, tin oxide doped with antimony can be used. In addition, needle-shaped conductive particles obtained by coating the surface of the needle-shaped substance with a metal or a metal oxide may be used. Examples of the acicular conductive particles include acicular potassium titanate whose surface is extremely thinly coated with aluminum, chromium, silver, antimony, indium, tin oxide doped with antimony oxide, or the like. For applications requiring transparency, fine oxide powders such as tin oxide or a mixture of tin oxide and antimony oxide are suitable. These may be used alone or in admixture of two or more.

The particle diameter of the conductive particles is preferably 0.2 μm or less. By using particles of 0.2 μm or less, it is possible to suppress scattering of visible light and ensure transparency. The amount of the conductive particles added is preferably 50 to 90% by weight, more preferably 60 to 85% by weight, based on the conductive layer (the entire material constituting the conductive layer). By adding 50% by weight or more, the surface resistivity can be made 10 ⁴ to 10 ⁹ Ω, and it can be applied to applications requiring extremely high antistatic properties. When acicular conductive particles are used, the above surface resistivity can be obtained even if the amount of addition is about 35% by weight or more. Further, when the content is 90% by weight or less, the strength of the coating film can be prevented from lowering and the transparency can be maintained.

The conductive layer may contain additives such as a UV absorber, a UV absorbing resin, and a light stabilizer in addition to the binder resin and the conductive particles described above as long as the conductivity is not impaired.

The conductive layer is formed by applying a binder resin coating containing conductive particles on a base material or an anchor coat layer formed on the base material, and then applying a predetermined temperature when the binder resin is a thermosetting resin. By heat-curing (about 100 ° C. to 150 ° C.), an ionizing radiation-curable resin can be formed by irradiation with ultraviolet rays or electron beams. The thickness of the conductive layer is preferably 1.0 μm to 5.0 μm, more preferably 1.5 μm to 3.0 μm.

The inorganic thin film is provided on the above-mentioned conductive layer in order to improve the scratch resistance of the conductive layer without impairing the conductivity of the conductive layer. Materials for forming such an inorganic thin film include oxides of Si, which are relatively low-refractive index materials, fluorides such as Li, Na, Mg, Al, Ca, La, Nd, and Pb, and relatively high refractive index. Materials Ti, Cr, Z
simple substance such as r, Ni, Mo, Ti, Zn, Y, Zr, I
Examples thereof include oxides of n, Sn, Sb, Hf, Ta, Ce, Pr, Nd and the like. In particular, by using a low-refractive index material such as Si oxide (silica), it is possible to reduce the reflectance on the surface of the conductive layer and impart antireflection property to the surface of the conductive material. In this way, the conductive film with improved anti-reflection property prevents external light from being reflected and facilitates internal visibility when applied to a member that sees through the inside, such as a peep window of a machine. be able to.

The thickness of the inorganic thin film is preferably 0.01 μm to
The thickness is 1.0 μm, more preferably 0.05 μm to 0.5 μm. In such a range, the scratch resistance can be improved without impairing the conductivity of the conductive layer. Further, according to the theory of antireflection of light, when the thickness d satisfies the following equation, high antireflection property is obtained. d = (a + 1) λ / 4n In the formula, a is 0 or a positive even number, λ is the wavelength of light for which reflection is to be prevented, and n is the refractive index of the inorganic thin film.

When the inorganic thin film is a silica thin film, the refractive index n is
Since it is 1.40, the antireflection property can be improved by setting the range of approximately 0.15 μm to 0.07 μm with respect to the wavelength range of visible light (780 nm to 380 nm).

The inorganic thin film may be a single layer, but two or more layers made of a material having a high refractive index and a layer made of a material having a high refractive index are laminated so as to have a predetermined film thickness according to the wavelength to prevent reflection. It is also possible to improve the property. However, in order not to impede conductivity, the overall film thickness should be within the above range (1.0 μm).
m or less) is preferable.

The inorganic thin film can be formed by forming the above-mentioned materials by a vacuum film forming method such as a vacuum vapor deposition method, a sputtering method, an ion plating method or the like. Alternatively, a silicon alkoxide such as tetraethoxysilane, tetramethoxysilane, tetratriethoxysilane, or methyltrimethoxysilane, or an oxidation prepared by hydrolyzing a metal alkoxide other than silicon such as zirconia propoxide, aluminum isopropoxide, or titanium budoxide. It can also be formed by applying a silicon sol or a metal oxide sol by a known coating method such as a blade coater method, a rod coater method or a gravure coater method.

The conductive material of the present invention has an adhesive layer or a heat-sensitive adhesive on the back surface of the base material (the surface opposite to the surface on which the conductive layer is formed) so that it can be attached to other members. An agent layer can be provided. For the pressure-sensitive adhesive layer, a commonly used pressure-sensitive adhesive such as an acrylic pressure-sensitive adhesive, a silicone pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, a rubber pressure-sensitive adhesive can be used. Also, an adhesive containing an antistatic agent may be used.

Since the conductive material of the present invention constructed as described above has high antistatic property and scratch resistance, it is used as a structural material of a clean room, a pallet used in a clean room, various cases, and the like. In addition to being used by adhering to, it is suitable for a peep window of a machine installed in a clean room due to its high transparency and antireflection property.

[0034]

EXAMPLES The conductive material of the present invention will be further described below based on examples. In the following examples, "parts" means "parts by weight" unless otherwise specified.

[Example] Polyester film (thickness 100μ
m) was coated with a coating solution for conductive layer having the following formulation, dried and then irradiated with ultraviolet rays (120 W) for 20 seconds to form a conductive layer having a thickness of 2.8 μm. <Coating liquid for conductive layer> -Tin dioxide-antimony pentoxide 10.4 parts-Ionizing radiation curable resin 3.3 parts (solid content 80% by weight) (Unidick 17-813: Dainippon Ink and Chemicals, Inc.) -Photopolymerization initiator 0.08 part (Irgacure 184: Ciba Specialty Chemicals Co.)-Propylene glycol monomethyl ether 12.8 parts-Toluene 38.5 parts

A hydrolyzed solution of tetraethoxysilane was applied onto this conductive layer by a blade coater method and dried to form a silica thin film having a dry thickness of 0.1 μm to obtain a conductive film.

Comparative Example 1 A conductive film was obtained by forming a conductive layer in the same manner as the conductive film of Example except that the silica thin film was not formed.

Comparative Example 2 Polyester film (thickness 100
(μm) on one side, a conductive layer is formed in the same manner as the conductive film of the example, and a hard coat layer coating solution having the following formulation is further applied onto the conductive layer, and after drying, ultraviolet rays (120 W) are applied for 10 seconds. Irradiation was performed to form a UV curable resin layer having a thickness of 2.0 μm to obtain a conductive film. <Coating liquid for hard coat layer> -Ionizing radiation curable resin 47 parts (solid content 80% by weight) (Unidick 17-813: Dainippon Ink and Chemicals, Inc.)-Photopolymerization initiator 1.1 parts (Irgacure 184) : Ciba Specialty Chemicals) ・ Propylene glycol monomethyl ether 34 parts ・ Toluene 34 parts

The following characteristics were evaluated and compared with respect to each conductive film obtained in Examples and Comparative Examples 1 and 2. The results are shown in Table 1. Scratch resistance: 1 cm ² area with # 0000 steel wool
Was reciprocated 10 times with a load of 300 gf. As a result, the case where scars were scarcely generated was evaluated as ◯, and the case where scratches were generated was evaluated as Δ. Surface resistivity (Ω): 4329A HIGH RESISTANCE METER, 160
08A RESISTIVITY CELL (Yokogawa Hewlett-Packard Company) (JIS-K6911) Total light transmittance (%): SM color computer HGM
-Measured using 2K (Suga Test Instruments Co., Ltd.) (JIS-K7105-198
1) Haze value (%): SM color computer HGM-2
Measurement using K (Suga Test Instruments Co., Ltd.) (JIS-K7105-1981) Reflectance (%): Shimadzu spectrophotometer (UV-31101)
PC: Shimadzu Corporation) is used to measure the reflectance at a wavelength of 550 nm

[0040]

[Table 1]

As is clear from the results shown in Table 1, by providing the inorganic thin film on the conductive layer, the scratch resistance is improved, the surface resistivity is not increased so much, and sufficient conductivity is obtained. I understood it. On the other hand, the optical characteristics such as light transmittance and haze value were improved by providing the inorganic thin film, and in particular, the reflectance was significantly reduced, and excellent antireflection property was obtained. Further, in the conductive film of Comparative Example 2 in which the hard coat layer was provided instead of the inorganic thin film, the scratch resistance was improved, but the surface resistivity was increased, and sufficient conductivity was not obtained.

[0042]

According to the present invention, by providing an inorganic thin film on a conductive layer provided on a substrate, it is possible to significantly improve scratch resistance without impairing conductivity. . Further, the antireflection property can be enhanced by setting the thickness of the inorganic thin film within a predetermined range. ADVANTAGE OF THE INVENTION According to this invention, the electrically conductive material which is excellent in antistatic property, transparency, abrasion resistance, and antireflection property, and is suitable for the peep window of the apparatus or machine installed in a clean room is provided.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Susumu Kurishima             4-63 Suzuya, Saitama City, Saitama Prefecture Stock             Kimoto Technology Development Center F-term (reference) 4F100 AA01C AA20C AA28 AA29                       AH06 AK01D AK42 AR00E                       AT00A BA03 BA04 BA05                       BA07 BA10A BA10C BA10E                       DE01B GB90 JB14D JG01                       JG01B JG03 JK12 JL13E                       JM02C JN01 JN01A JN01B                       YY00C                 5G307 FA01 FA02 FB01 FB02 FC09                       FC10

Claims (6)

[Claims] 1. A conductive material comprising a conductive layer provided on a base material and containing conductive particles, and an inorganic thin film formed on the conductive layer. 2. The conductive material according to claim 1, wherein the base material and the conductive layer are substantially transparent. 3. The conductive material according to claim 1, wherein the inorganic thin film is made of silica. 4. The thickness of the inorganic thin film is 0.01 μm to 1.0 μm.
The conductive material according to any one of claims 1 to 3, which is m. 5. The conductive material according to any one of claims 1 to 4, wherein the base material has an anchor coat layer made of an ionizing radiation curable resin between the base material and the conductive layer. 6. The conductive material according to claim 1, wherein the base material has an adhesive layer on the surface opposite to the surface on which the conductive layer is provided.