JPH07304890A - Electrically-conductive film - Google Patents

Abstract

PURPOSE:To obtain an electrically-conductive film having excellent solvent resistance, excellent appearance free from coating unevenness, no humidity dependence of surface specific resistance, a low surface specific resistance value even at a low humidity, showing stable electrical conductivity. CONSTITUTION:This electrically-conductive film comprises a coated layer obtained by coating one side or both sides of a polymer film with an aqueous coating agent containing (A) electrically-conductive carbon black, (B) a water-soluble or water-dispersible urethane-based binder or a mixture of the binder and another binder, (C) a compound or am amino resin containing two or more oxirane groups in the molecule and (D) a fluorinebased surfactant or the surfactant and another surfactant and satisfying the blending ratios of the component A: the component B=10:90 to 80:20... (1), the component C: (the component A + the component B)=1:99 to 30:70... (2) and the component D: (the component A + the component B + the component C)=1:99 to 20:80... (3) and has 1X10<4> to 1X10<13>OMEGA/square surface resistivity of the coated layer.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a conductive film,
More specifically, it has excellent solvent resistance, good appearance without coating spots, and has stable electrical conductivity with low surface resistivity even at low humidity, especially for magnetic recording media, general industrial products, etc. TECHNICAL FIELD The present invention relates to a conductive film useful for applications.

[0002]

2. Description of the Related Art Polyester films such as polyethylene terephthalate film and polyethylene naphthalate film are excellent in mechanical properties, heat resistance, electrical properties and chemical resistance, and polyethylene terephthalate film is widely used. However, the polyester film has a surface specific resistance value of 10 ¹⁵ to 10 ¹⁶ Ω / □ and is easily charged, and when used as a material such as a magnetic recording medium or an electronic material, it tends to cause a trouble of adsorbing foreign matter.

As a method for preventing the static charge of the polyester film, a method of applying an antistatic coating and a method of kneading an antistatic agent into a base polymer have been conventionally known. As the antistatic agent, an ion conductive type such as a surfactant and an electron conductive type utilizing radical hopping such as a TCNQ-TTF complex,
There is a filler type electron conduction type such as tin oxide-antimony oxide. However, the ion conductive type antistatic agent has a large humidity dependency and has a drawback that its effect is not exhibited in a low humidity atmosphere. An electron conduction type antistatic agent utilizing radical hopping has a drawback that the radical reacts with oxygen molecules in the air and thus the pot life of the coating is short. Further, the filler-type electron conduction type antistatic agent has a drawback that the surface of the coating layer is roughened depending on the particle diameter of the filler.

Therefore, as disclosed in JP-A-2-160552 and JP-A-5-186618, it has been proposed to use carbon having a smaller particle size than tin oxide antimony oxide or the like. Carbon black can be expected to maintain the antistatic property and the flatness of the coating layer. But,
A film coated with carbon black does not always have a good coating appearance, and when this conductive film is used as a magnetic recording medium, there is a drawback in that noise and errors are generated due to this coating appearance.

[0005]

An object of the present invention is to provide a conductive film based on a polymer film, particularly a polyester film, which has excellent solvent resistance, has no coating spots, has a good appearance, and has a surface-specific property. An object of the present invention is to provide a conductive film which has no resistance dependency on humidity, has a low surface resistivity even at low humidity, and exhibits stable electric conductivity.

[0006]

The present invention has the following constitution in order to achieve the above object.

On one or both sides of the polymer film (A)
Conductive carbon black, (B) water-soluble or water-dispersible urethane binder or a mixture of this and other binders, (C) compound having two or more oxirane groups in the molecule or amino resin, and (D) fluorine System surfactant or this and other surfactants are contained, and these ratio (weight%) is following formula (1), (2), (3) A component: B component = 10: 90-80: 20 (1) C component: (A component + B component) = 1: 99 to 30:70 (2) D component: (A component + B component + C component) = 1: 99 to 20:80 ... ( A conductive thin layer coated with an aqueous coating material satisfying 3) is formed, and the surface resistivity of the thin layer is 1 × 10 ⁴ to 1 × 10 ¹³
Ω / □ conductive film.

The polymer film in the present invention is preferably a polyester film. The preferred polyester is a linear saturated polyester synthesized from an aromatic dibasic acid or its ester-forming derivative and a diol or its ester-forming derivative.
Specific examples of such polyesters include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, poly (1,4-cyclohexylene dimethylene) terephthalate, polyethylene-2,6-naphthalene dicarboxylate and the like. These copolymers or their blends with a small proportion of other resins are also included.

The linear saturated polyester can be melt-extruded to form a film by a conventional method, and then oriented and crystallized by heat treatment to form a polyester film. The polyester film is preferably oriented in a crystal form so that the value measured by a scanning calorimeter in a nitrogen stream [at a temperature rising rate of 10 ° C./min] as a heat of fusion of crystal is usually 4 cal / g or more.

Examples of the conductive carbon black as the component (A) in the present invention include furnace black, acetylene black, channel black and Ketjen black.

The hydrophilic binder as the component (B) in the present invention is a hydrophilic (water-soluble or water-dispersible) urethane binder or a mixture of this and other binders. The urethane binder and the other binder may be used alone or in combination of two or more kinds.

Examples of the hydrophilic urethane binders include those having an ionic group (for example, carboxylate group, sulfonate group or sulfuric acid half base) in the molecule, and polyurethane diol having a hydroxyl group in the molecule. preferable. This hydrophilic polyurethane is a carboxylate group,
The hydrophilicity to water is enhanced by a sulfonate group, a sulfuric acid half base, a hydroxyl group, or the like, and such a water affinity imparting group is usually introduced during or after the synthesis of polyurethane.

For example, the introduction of a carboxylic acid group may be carried out by using a carboxylic acid group-containing polyhydroxy compound as one of the starting polyhydroxy compounds during polyurethane synthesis, or by introducing a hydroxyl group-containing carboxylic acid into the isocyanate group of the polyurethane having an unreacted isocyanate group. The reaction can be carried out by reacting an acid or an amino group-containing carboxylic acid, and then adding the reaction product to an alkaline aqueous solution under high speed stirring to neutralize it.

Further, the introduction of a sulfonate group or a sulfuric acid half-ester group usually produces a prepolymer from a polyhydroxy compound, a polyisocyanate and a chain extender, and an amino group or a hydroxyl group capable of reacting with a terminal isocyanate group is added thereto. It can be carried out by adding a compound having a sulfonate group or a sulfuric acid half-ester base in the molecule and reacting it, and finally obtaining a hydrophilic polyurethane having a sulfonate group or a sulfuric acid half-ester base in the molecule. At that time, it is preferable that the formation reaction is carried out in an organic solvent, water is then added, and then the solvent is removed.

As another method, a compound having a sulfonic acid group is used as one of raw materials to synthesize a polyurethane having a sulfonic acid group, and then the polyurethane is added to an alkaline aqueous solution under high speed stirring, Neutralization method, by adding the following sultone compound to the primary or secondary amino group of the main chain or side chain of polyurethane in the presence of an alkali and sulfonate alkali base (eg -SO ₃ Na etc.)
Can be introduced.

As the alkaline aqueous solution, it is preferable to use an aqueous solution of sodium hydroxide, potassium hydroxide, ammonia, alkylamine, etc., but ammonia which does not remain in the conductive thin layer in a state where the alkali is liberated, and dryness conditions Particularly preferred are amines that volatilize at.

The amount of a base such as a carboxylate group, a sulfonate group or a sulfuric acid half ester base is preferably 0.5 to 15% by weight. If the proportion of the base is too small, the water affinity of the polyurethane will be insufficient to make it difficult to adjust the coating solution, and if it is too large, the original characteristics of the polyurethane will be impaired, which is not preferable.

The hydrophilic polyurethane is one which forms a stable aqueous dispersion or an aqueous solution by optionally using a dispersion aid.

Examples of the polyhydroxy compound used for the synthesis of polyurethane include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene glycol, hexamethylene glycol, tetramethylene glycol, 1,5-
Pentanediol, diethylene glycol, triethylene glycol, polycaprolactone, polyhexamethylene adipate, polyhexamethylene sebacate, polytetramethylene adipate, polytetramethylene sebacate, trimethylolpropane, trimethylolethane,
Pentaerythritol, glycerin, etc. can be mentioned.

Examples of the polyisocyanate compound include hexamethylene diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, isophorone diisocyanate, an addition product of tolylene diisocyanate and trimethylolpropane, and an addition product of hexamethylene diisocyanate and trimethylolethane. it can.

Examples of the carboxylic acid group-containing polyol include dimethylolpropionic acid, dimethylolbutyric acid, dimethylolvaleric acid, and trimellitic acid bis (ethylene glycol) ester.

Examples of the amino group-containing carboxylic acid include β-aminopropionic acid, γ-aminobutyric acid and P-aminobenzoic acid.

Examples of the hydroxyl group-containing carboxylic acid include 3
-Hydroxypropionic acid, γ-hydroxybutyric acid, P-
(2-Hydroxyethyl) benzoic acid, malic acid, etc. can be mentioned.

Examples of the compound having an amino group or a hydroxyl group and a sulfone group include aminomethanesulfonic acid,
2-aminoethanesulfonic acid, 2-amino-5-methylbenzene-2-sulfonic acid, sodium β-hydroxyethanesulfonate, propane sultone of an aliphatic diprimary amine compound, butane sultone addition product and the like can be mentioned. And preferably a propane sultone adduct of an aliphatic diprimary amine compound.

Further, as the compound containing an amino group or a hydroxyl group and a sulfuric acid half ester group, for example, aminoethanol sulfuric acid, ethylenediamine ethanol sulfuric acid, aminobutanol sulfuric acid, hydroxyethanol sulfuric acid, γ-hydroxypropanol sulfuric acid, α-hydroxybutanol sulfuric acid, etc. Is mentioned.

The synthesis of polyurethane using these compounds can be carried out by a well-known method.

Other binders that can be used in combination with the hydrophilic polyurethane binder include acrylic resins, polyesters, phenoxy resins, and modified products thereof.

The composition ratio (% by weight) of the conductive carbon black (A) and the hydrophilic polyurethane binder (B) in the present invention is 10 to 80:90 to 20, preferably 10 to 60:90. 40. If the content of the conductive carbon black is less than 10% by weight, the desired surface resistance cannot be achieved, while if it exceeds 60% by weight, the adhesion of the coating film to the base film is lowered and the durability of the coating film is reduced. This is not preferable because the performance will decrease.

The component (C) in the present invention is a compound or amino resin having two or more oxirane groups in the molecule. As a specific example of this compound,

[0030]

[Chemical 1]

[0031]

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[0032]

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[0033]

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[0034]

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[0035]

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[0036]

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[0037]

[Chemical 8]

[0038]

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[0039]

[Chemical 10]

[0040]

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[0041]

[Chemical 12]

[0042]

[Chemical 13]

[0043]

[Chemical 14]

[0044]

[Chemical 15]

And water-soluble or water-dispersible epoxy compounds such as addition condensation products of bisphenol A with epichlorohydrin.

Specific examples of the amino resin include trimethylol melamine and its initial condensation product, hexamethylol melamine and its initial condensation product, dimethylol urea and its initial condensation product, tetramethylol urea and its initial condensation product, and benzoguanamine. Resin etc. can be mentioned.

The amount ratio of the component (C) in the present invention is
Per the total amount of component (A), component (B) and component (C),
It is 1 to 30% by weight, preferably 5 to 30% by weight. If this amount ratio is less than 1% by weight, the solvent resistance of the thin film is inferior, while if it exceeds 30% by weight, the stability of the coating liquid is reduced.

The component (D) in the present invention is a fluorinated surfactant or this and other surfactants. These fluorine-based surfactants and other surfactants can be used alone or in admixture of two or more.

The above-mentioned fluorine-based surfactant uses a fluorocarbon chain as a hydrophobic group of the surfactant. Specific examples thereof include fluoroalkylcarboxylic acid,
Perfluoroalkylcarboxylic acid, perfluorocarboxylic acid salt, perfluorosulfonic acid salt, perfluoroalkylsulfonic acid diethanolamide, perfluoroalkyl phosphoric acid ester, perfluoroalkylethylene oxide adduct, perfluoroalkylsulfonyl glutamate disodium, 3- [Fluoroalkyloxy]
Sodium -1-alkyl sulfonate, sodium 3- [ω-fluoroalkanoyl-N-ethylamino] -1-propane sulfonate, N- [3- (perfluoroalkylsulfonamido) propyl] -N, N-dimethyl-
N-carboxymethylene ammonium betaine, N-propyl-N- (2-hydroxyethyl) perfluoroalkylsulfonamide, perfluoroalkylsulfonamidopropyltrimethylammonium salt, perfluoroalkyl-N-ethylsulfonylglycine salt, bis (phosphate) N-perfluorooctylsulfonyl-N-ethylaminoethyl) and the like.

As the other surfactant used in combination with the above-mentioned fluorine-based surfactant, known anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants and the like can be mentioned.

The amount ratio of the component (D) in the present invention is
It is 1 to 20% by weight based on the total amount of the component (A), the component (B), the component (C) and the component (D). If this amount ratio is less than 1% by weight, repellent coating spots are produced, while if it exceeds 20% by weight, the coating liquid foams, causing repelling by bubbles or coating streaks by foam streaks.

The aqueous conductive coating liquid in the present invention includes (A)
In addition to the component, the component (B), the component (C) and the component (D),
If necessary, other additives such as a lubricant, a dispersant, an antistatic agent, a stabilizer, a catalyst, an antifoaming agent and a lubricant can be added. The solid content concentration in the aqueous conductive coating liquid can be freely selected, but is preferably selected from the range of 1 to 30% by weight.

The aqueous conductive coating solution is preferably applied to the polyester film before the crystal orientation is completed. Here, the polyester film before the crystal orientation is completed is an unstretched film obtained by melting a polymer into a film as it is: a uniaxially stretched film in which the unstretched film is oriented in either the longitudinal direction or the transverse direction. : Further, it includes those which have been stretched and oriented in a low ratio in the longitudinal direction and the transverse direction (a biaxially stretched film before being finally re-stretched in the longitudinal direction or the transverse direction to complete the oriented crystallization). . Of these, application to a uniaxially stretched film is preferable from the viewpoints of economy and cleanliness. That is, applying the water-based conductive coating agent in the polyester film forming step is advantageous in terms of quality and cost.

The thickness of the dry coating film of the final coating layer (conductive thin layer) is preferably 0.01 to 1 μm, but can be freely selected. The coating is preferably performed by a roll coating method, a gravure coating method, a kiss coating method, or the like.

The polyester film coated with the aqueous conductive coating liquid needs to be dried, stretched, and heat-treated (heat setting treatment) to complete the crystal orientation. These treatments are conventionally known means, conditions and the like. Can be done using. The surface of the conductive layer on the polyester film thus obtained preferably has a center line surface roughness (Ra) of 1 to 30 nm.

When the aqueous conductive coating liquid is applied to another polymer film, it may be carried out according to the above method and conditions.

Conductive film of the [0057] present invention, the surface resistivity of the conductive layer surface is ^{1 × 10 4 ~1 × 10 1} 3 Ω / □, preferably a ^{10 10 Ω / □ 1 × 10} 4 ~1 ×. Therefore, if you make a magnetic tape (video tape, audio tape, computer tape, etc.) with this conductive film as the base film and the conductive layer surface as the back surface (back surface),
It is possible to adjust the charging while the magnetic tape is running, and it is possible to prevent errors due to electrostatic attraction. Further, when a magnetic tape or a magnetic disk is produced by using the conductive layer surface as the undercoat of the magnetic layer, the conductive filler in the magnetic layer can be eliminated, so that a desired effect such as an increase in S / N ratio can be expected. Design becomes easy. Therefore, this conductive film can be used as a film with an undercoat layer of a magnetic layer of a magnetic disk, a magnetic tape, a magnetic card, etc., and as a film with a back coat layer on the running surface of the magnetic tape. In addition, it can be used as a film for general industrial use that requires electric transformation and antistatic properties.

[0058]

EXAMPLES The present invention will be further described below with reference to examples. In addition, each physical property in an example is measured by the following method.

1. Surface resistivity After leaving the film at 23 ° C. × 50% RH for 24 hours, it was measured with a vibration capacitance type potentiometer TR-84M type (manufactured by Takeda Riken).

2. Center line surface roughness (Ra) According to JIS B0601, using a high precision surface roughness meter SE-3FAT manufactured by Kosaka Laboratory Ltd., the radius of the needle is 2μ.
m, load 30mg, magnification 200,000 times, cut-off
A chart is placed under the condition of 0.08 mm, a portion of the measurement length L is extracted from the film surface roughness curve in the direction of the center line, the center line of the extracted portion is the X axis, and the longitudinal magnification direction is the Y axis. When the roughness curve is expressed as Y = (x), the value given by the following equation is expressed in μm.

[0061]

[Equation 1]

In this measurement, the standard length is 1.25 mm and 4
Individually measured and expressed as an average value.

3. Solvent resistance test One drop (about 0.02 cc) of methyl ethyl ketone was dropped on the surface of the coated film, gauze was placed on it, and a weight of 50 g was put on it.
Move at the speed of seconds. After drying at room temperature, whether or not the surface of the coating layer has a scratch is visually inspected, and a 200 times differential interference micrograph is used to judge as follows. What is not scratched even when seen in the differential interference contrast micrograph: 5 What is scratched when seen in the differential interference contrast microscope photograph: 4 What is seen to be slightly scratched visually: 3 Items that can be seen: 2 Items that are visually visibly scratched: 1

4. Appearance of coating Place the coated film on a white paper and visually observe the appearance, and judge as follows. No coating spots are visible: ○ Some coating spots are present: △ Remarkably poor coating spots: ×

[Example 1] Polyethylene glycol (M
W = 2500), diphenylmethane diisocyanate,
47% by weight of polyurethane (MW = 27000) made from ethylenediamine, sodium dimethylolpropionate, trimethylolpropane triglycidyl ether
An aqueous coating agent having a solid content concentration of 10% was prepared, which was 8% by weight, 40% by weight of furnace black and 5% by weight of Megafac F-142D, a fluorine-based surfactant manufactured by Dainippon Ink and Chemicals, Inc.

Polyethylene terephthalate having an intrinsic viscosity of 0.65 measured in orthochlorophenol at 25 ° C. was melt extruded onto a rotary cooling drum maintained at 20 ° C. to give an unstretched film, which was then machined. After being stretched by 3.6 times in the axial direction, the coating material was applied to both sides of the film by a 4 g / m ² (wet) kiss coat method. Subsequently, the film was stretched in the transverse direction by 3.6 times and further heat-treated at 205 ° C. to obtain a double-sided film biaxially oriented polyester film having a thickness of 75 μm.

[Comparative Example 1] A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that the aqueous coating agent was not applied.

COMPARATIVE EXAMPLE 2 A polyurethane made from the polyethylene glycol of Example 1 (MW = 2500), diphenylmethane diisocyanate, ethylenediamine and sodium dimethylolpropionate (MW = 2700).
0) was set to 52% by weight, and the same procedure as in Example 1 was performed except that Megafac F-142D was omitted.

Comparative Example 3 Polyurethane made from polyethylene glycol of Example 1 (MW = 2500), diphenylmethane diisocyanate, ethylenediamine and sodium dimethylolpropionate (MW = 2700).
0) was changed to 42% by weight and Megafac F-142D was changed to 10% by weight of polyoxyethylene nonylphenyl ether.

COMPARATIVE EXAMPLE 4 Polyurethane made from polyethylene glycol of Example 1 (MW = 2500), diphenylmethane diisocyanate, ethylenediamine and sodium dimethylolpropionate (MW = 2700).
0) was set to 55% by weight, and the same procedure as in Example 1 was performed except that trimethylolpropane triglycidyl ether was not used.

Example 2 A polyurethane made from the polyethylene glycol of Example 1 (MW = 2500), diphenylmethane diisocyanate, ethylenediamine and sodium dimethylolpropionate (MW = 2700).
0) to 44% by weight, and Megafac F-142D to 3
% By weight, polyoxyethylene nonyl phenyl ether 5
The same procedure as in Example 1 was carried out except that the weight% was changed.

[Example 3] Example 1 was repeated except that polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.64 was used in place of the polyethylene terephthalate in Example 1.
I went the same way.

The results obtained in Examples 1 to 3 and Comparative Examples 1 to 4 are shown in Table 1.

[0074]

[Table 1]

[0075]

EFFECTS OF THE INVENTION According to the present invention, excellent solvent resistance, good appearance without coating spots, humidity dependence of surface resistivity, and low surface resistivity even at low humidity are exhibited. ,
It is possible to provide a conductive film that exhibits stable electrical conductivity.

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Claims (5)

[Claims] 1. A polymer film on one or both sides of which (A) conductive carbon black, (B) a water-soluble or water-dispersible urethane binder or a mixture thereof and another binder, and (C) 2 in the molecule. Containing a compound or amino resin having one or more oxirane groups and (D) a fluorosurfactant or this and other surfactants, and the proportion (% by weight) of these formulas (1) and (2) ,
(3) A component: B component = 10: 90 to 80:20 (1) C component: (A component + B component) = 1: 99 to 30:70 (2) D component: (A component + B) Component + C component) = 1: 99 to 20:80 ... Having a coating layer obtained by coating an aqueous coating agent satisfying (3),
The surface resistivity of the coating layer is 1 × 10 ⁴ to 1 × 10 ¹³ Ω /
□ is a conductive film. 2. The conductive film according to claim 1, wherein the coating layer has a thickness of 0.01 to 1 μm, and the center line surface roughness (Ra) of the coating layer surface is 30 nm or less. 3. The conductive film according to claim 1, wherein the polymer film is a polyester film. 4. The conductive material according to claim 1, wherein the water-based coating composition according to claim 1 is applied to at least one surface of the film before the crystal orientation is completed, and then the film is dried, stretched and heat-treated to complete the crystal orientation. Sex film. 5. A magnetic recording medium in which a magnetic layer is provided on at least one side of the conductive film according to claim 1.