JPH02160552A - Conductive film - Google Patents

Abstract

PURPOSE:To obtain a low facial intrinsic resistant value under low humidity and stabilized electric conductivity, by a method wherein an aqueous coating agent containing conductive carbon black and polyurethane ionomer at a specific ratio is applied to one side of a polyester film and crystalline orientation is completed by performing drying, stretching and heat treatment. CONSTITUTION:An aqueous conductive agent is applied to a polyester film prior to completion of crystalline orientation. A constituent ratio (wt.% ratio) between conductive carbon black and polyurethane ionomer in the said coating a;gent is made 10-80:90-20. A matter whose tensile strength of a dried film is not exceeding 300kg/cm<2> is preferable as the polyurethane ionomer. A polyester film to which the aqueous conductive agent is applied is completed in the crystalline orientation by performing drying, stretching and heat treatment (thermal fixation treatment). Surface roughness on the center line of the surface of a conductive layer on an obtained polyester film is 5-30nm and the kinetic coefficient of friction between the conductive layer and polyester film is 0.5 or lower. A facial intrinsic resistance value of the surface of the conductive layer is 10<4>-1X10<12>OMEGA/square in a conductive film.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a conductive film, and more specifically, it has a low surface resistivity value even at low humidity, exhibits stable conductivity, and is particularly suitable for magnetic recording. The present invention relates to a conductive film useful for applications such as media and electronic components.

<Prior Art> Polyester films such as polyethylene terephthalate films and polyethylene naphthalate films have excellent mechanical properties, heat resistance, electrical properties, chemical resistance, etc., and polyethylene terephthalate films in particular are used for a wide range of purposes. However, polyester film has a surface resistivity value of 1015 to 10'Ω/□ and is easily charged, and is used, for example, as a magnetic recording medium.

When used as a material for electronic materials, etc., it tends to cause troubles such as foreign matter adsorption.

As a method to prevent static electricity on polyester film,
Conventionally, methods of applying an antistatic paint and methods of kneading an antistatic agent into a base polymer have been known. These antistatic agents include ion conductive ones such as surfactants, and electronic conductive ones that utilize radical hopping such as TCNQ-TTF complexes. but,
Ion-conducting antistatic agents have the disadvantage that they are highly dependent on humidity and do not exhibit their effects in low-humidity environments, and electron-conducting antistatic agents have the disadvantage that radicals react with oxygen molecules in the air. The drawback is that the pot life of the paint is short.

<Object of the invention> The object of the present invention is to provide a conductive film based on polyester film, which has no humidity dependence of surface resistivity, has a low surface resistivity even at low humidity, and is stable. An object of the present invention is to provide a conductive film that exhibits high electrical conductivity.

<Configuration/Effects of the Invention> According to the present invention, an object of the present invention is to apply conductive carbon black and polyurethane ionomer to at least one side of a polyester film at a rate of 10/90 to 8G/2G (by weight) before the crystal orientation is completed. A conductive film having a surface resistivity value of 1x10' to 1x1012 Ω/□, which is coated with a water-based paint containing a composition ratio of %), and then dried, stretched, and heat-treated to complete crystal orientation. achieved by

In the present invention, 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-Schiff0hexylene dimethylene) terephthalate, and polyethylene-2,6
Examples include -naphthalenedicarboxylate, and copolymers thereof or blends of these with small proportions of other resins are also included.

A polyester film can be obtained by melt-extruding such a linear saturated polyester, forming it into a film by a conventional method, and subjecting it to oriented crystallization and heat treatment crystallization. This polyester film was measured as the heat of crystal fusion in a nitrogen stream [at a heating rate of 10°C/min] using a scanning calorimeter.
It is preferable that the crystals are oriented to such an extent that the measured value is usually 4 cal/g or more.

Examples of the conductive carbon black in the present invention include furnace black and acetylene black.

Examples include channel black and Ketchen black. Among these, Ketchen black is particularly preferred from the viewpoint of electrical conductivity. The average particle size of such conductive carbon black is preferably 20 to 100 mμ, more preferably 30 to 60 mμ. If the average particle size of the conductive carbon black is less than 20 mμ, agglomerated particles are likely to occur, while if it exceeds 100 mμ, the surface of the coating layer will become extremely rough, which is not preferable.

In the present invention, polyurethane ionomer is used as a binder for such conductive carbon black,
Examples of the polyhydroxy compound used in the polyurethane ionomer synthesis include polyethylene glycol, polypropylene glycol, polyethylene propylene glycol, polytetramethylene glycol, hexamethylene glycol, tetramethylene glycol, 1.5-
Bentanediol, diethylene glycol, triethylene glycol, polycabrolactone, polyhexamethylene adipate, polyhexamethylene sebacate, polytetramethylene adipate, polytetramethylene sebacate, trimethylene propane, trimethyl o-lethane,
Examples include pentaerythritol and glycerin. Examples of the polyisocyanate compound include hexamethylene diisocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, isophorone diisocyanate, an adduct of tolylene diisocyanate and trimethylolpropane, and an adduct of hexamethylene diisocyanate and trimethylolethane.

Furthermore, examples of compounds that ionomerize polyurethane include sulfonic acid and carboxylic acid-containing polyols. Examples include carboxylic acid-containing polyols, dimethylolbutyric acid, dimethylolbutyric acid,
Dimethylolvaleric acid.

Trimellitic acid bis(ethylene glycol) ester and the like can be mentioned.

The degree of ionomerization of polyurethane is preferably 30 to 70%. If this ionomerization is extremely small, the crosslinking density will be low and the solvent resistance will be insufficient, which is not preferable. On the other hand, if this ionomerization is too large, dispersibility deteriorates, which is not preferable.

The polyurethane ionomer used in the present invention is preferably one whose dry film has a tensile strength of 300 to 9/cd or less. This tensile strength is 300D/CI! When it gets bigger,
This is not preferable because it causes cranking in the coating film during the drying/stretching process and increases the surface resistance value.

The composition ratio (weight % ratio) of conductive carbon black and polyurethane ionomer in the present invention is 10 to 80:
90-20, preferably 15-60:85-4
It is 0. If the content of 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 decreases and the durability of the coating film decreases. This is not preferable because performance deteriorates. The aqueous conductive coating agent containing the solid content having the above composition ratio may contain lubricants, surfactants, stabilizers,
Curing agent, catalyst.

Other additives such as dispersants and the like can be added. Although the solid content concentration in the aqueous D2I coating can be freely selected, it is preferably selected from within the range of 5 to 30% by weight.

The water-based conductive coating is applied to the polyester film before crystal orientation is completed. Here, the polyester film before crystal orientation is completed means an unstretched film obtained by melting a polymer and forming it into a film as it is; a uniaxially stretched film in which an unstretched film is oriented in either the longitudinal or transverse direction. Film: Also includes films that have been stretched and oriented at low magnification in both the vertical and horizontal directions (two-wheel stretched films before being finally re-stretched in the vertical or horizontal direction to complete oriented crystallization), etc. . Among these, it is preferable to apply it to a -axially stretched film from the viewpoint of economy and cleanliness. That is, since the conductive coating agent is applied during the polyester film forming process, it is advantageous in terms of quality and cost.

The thickness of the final coating layer (conductive layer) after drying is 0.1~
It is preferable to employ 2μ, but the selection can be made freely. The coating is preferably performed by a roll coating method, a gravure coating method, or the like.

A polyester film coated with an aqueous conductive coating needs to be dried, stretched, and heat treated (heat setting treatment) to complete crystal orientation, but these treatments can be carried out using conventionally known means 1 conditions, etc. It can be carried out. The surface of the conductive layer on the polyester film thus obtained preferably has a center line surface roughness of 5 to 3001. Further, the coefficient of dynamic friction between the conductive layer and the polyester film is preferably 0.5 or less.

The conductive film of the present invention has a surface resistivity value of 1×104 to 1×10I2Ω/□, preferably 1xi
o4~1×101′Ω/□. Therefore, when a magnetic tape, especially a video tape, is made using this conductive film as a base film and the conductive layer surface is the back surface, it becomes possible to adjust the charge on the magnetic tape while it is running, thereby eliminating errors caused by charge adsorption. It can be prevented. Furthermore, when a magnetic tape is manufactured by using the conductive layer surface as a sublayer of the magnetic layer, the amount of conductive filler in the magnetic layer can be reduced, and the design of the magnetic layer becomes easier.

<Example> The present invention will be further explained below with reference to Examples.

In addition, each physical property in an example was measured by the following method.

1. Surface resistivity: 24hrtli conductive film at 23℃ x 50%RH
After placing the sample, it is measured using a vibrating capacitive potentiometer model TR-84M (manufactured by Takeda Riken Co., Ltd.).

2. Urethane ionomer 7 - Dry film strength The urethane ionomer is air-dried on a Teflon-treated plate to create a film with a thickness of about 0.3 mm, and then completely dried in an oven at 80°C before being machined. Physical properties are measured using a Shimadzu Autograph at a tensile rate of 500 tpm/min.

3. Center line surface roughness (Ra) According to JIS 80601, using a high-precision surface roughness meter 5E-3FAT manufactured by Koita Research Institute, the needle radius was 2 μm.
, 7ft weight 30cm, magnification magnification 200,000 times, cut-off 0°08mm. When the roughness curve is expressed as Y-(X) with the center line of the cut portion being the X axis and the direction of 111 magnification being the Y axis, the value given by the following formula is expressed in μm.

Ra − (1/L) f l f(x) ldx
Riko's measurements were made using 4 pieces with a reference length of 1.25 as.
Expressed as an average value.

4. Coefficient of Dynamic Friction According to ASTM 01894-63, use a slippery measuring device manufactured by Toyo Tester Co., Ltd. to measure the coated surface and polyethylene terephthalate film (non-coated surface). Measure the friction coefficient (μS). However, the thread plate is a glass plate, and the load is I kg.

Example 1 Ketchen Black (Lion Akzo Ketchen Black EC-600JD) was mixed with polyurethane ionomer (
Dainippon Ink■, Hytran HW301, tensile strength 220
9/aJ”) mixed and dispersed in an aqueous solution to a solid content concentration of 15
Weight%, carbon black/binder weight ratio 20/
80 water-based conductive coatings were prepared.

Intrinsic viscosity (orthochlorophenol, 35°C) 0.66
Polyethylene terephthalate was melt-extruded onto a rotating cooling drum maintained at 20°C to form an unstretched film, and then the unstretched film was stretched 3.6 times in the machine axis direction.
The above coating material was applied to one side of the film in an amount of 89/m (wet) by a kiss coating method. Subsequently, it was stretched 3.9 times in the transverse direction at 105°C and further heat-treated at 205°C to a thickness of 14 μm.
A single-sided coated biaxially oriented polyester film was obtained. Surface specific resistance of coated surface O5-4X10'Ω/□, RRa-
20n, the coefficient of dynamic friction between the coating layer and the polyester film was 0.32.

Comparative Example 1 A biaxially oriented polyester film was obtained in the same manner as in Example 1 except that no water-based conductive coating material was applied.

The surface resistivity (ρS) of this film is 3.5×101
5Ω/□, and the center line surface roughness (Ra) is 1501
And the movement between the film surfaces! The friction coefficient was 0.52.

Example 2 Furnace black was used instead of Ketschen black, and the carbon black/binder weight ratio was 40/
The same procedure as in Example 1 was carried out except that the temperature was changed to 60.

The obtained film (conductive film) has a surface specific resistance value ρS-6X10'Ω/□, and a center line surface roughness Ra = 1
6 nm, and the coefficient of dynamic friction between the coated surface and the polyester film surface was 0.29.

A magnetic paint prepared by the method described later was applied to the non-applied surface of the conductive film to a thickness of 1 μm. The resulting magnetically coated film was useful as a videotape.

[Adjustment of 1i paint] Nitrocellulose R81/2 as lacquer thinner for paint
(Flakes containing 25% isopropanol.

Daicel @ J] was dissolved to prepare a 40 wt% solution,
43.8 parts by weight of the liquid, followed by 32.5 parts by weight of polyester resin (manufactured by Bayer),
200 parts of chromium dioxide powder, 1 weight each of soybean oil fatty acid (Legion P, manufactured by Riken Vitamin ■), cationic surfactant (Cation A8, manufactured by Nippon Oil & Fats ■), and squalene (shark liver oil) as a dispersant/wetting agent. part, 0.5 part by weight, and 0.8 part by weight into a ball mill. 282 parts by weight of a mixed solvent consisting of methyl ethyl ketone/Schiff 0 hexanone/toluene-3/4/3 (weight ratio) is further mixed and sufficiently pulverized to prepare a mother liquor paint (45 wt%). To 50 parts by weight of this mother liquor, 1 part by weight of 48 parts of a reaction product of trimethyl0-propane and toluylene diisocyanate (Co-0-nate L: manufactured by Nippon Polyurethane) and 6 parts by weight of butyl acetate.
．． Add 25 parts by weight to obtain a final magnetic coating composition of 42.75 wt%.

Example 3 The same procedure as Example 1 was carried out except that the carbon black/binder weight ratio was changed to 10/90.

Surface specific resistance value of one side of the obtained film ρS -5X
108Ω/□, Ra-11n (dynamic friction coefficient between the coated surface and the film surface was 0.39).

Claims (1)

[Claims] 1. An aqueous coating agent containing conductive carbon black and polyurethane ionomer in a composition ratio of 10/90 to 80/20 (wt%) on at least one side of a polyester film before crystal orientation is completed. A conductive film having a surface resistivity value of 1 x 10^4 to 1 x 10^1^2 Ω/□, which is coated with a coating layer and then subjected to drying, stretching, and heat treatment to complete crystal orientation. 2. The tensile strength of the polyurethane ionomer dry film is 3.
The conductive film according to claim 1, which has a weight of 00 kg/cm^2 or less. 3. The center line surface roughness (Ra) of the coating layer surface is 5 to 30n
2. The conductive film according to claim 1, wherein the conductive film has a coefficient of dynamic friction of 0.5 or less between the coating layer and the polyester film.