JPH0257150B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for plating polyethylene terephthalate film with ferromagnetic metal, and more specifically, polyethylene terephthalate film (hereinafter simply referred to as PET film). By applying palladium colloid with a certain high catalytic activity to the surface of the PET film, and then chemically plating a ferromagnetic metal in a magnetic field, excellent adhesion and magnetic properties can be achieved with a simple operation on the surface of the PET film. The present invention relates to a ferromagnetic metal plating method that makes it possible to form a ferromagnetic metal plating film with good reproducibility.

A ferromagnetic metal coating according to the present invention is formed.
The main use of PET film is in high-density magnetic recording media.

[Conventional technology]

Recently, ferromagnetic metal-plated thin films have been attracting attention as high-density magnetic recording media with excellent reproduction output and sensitivity. It is necessary for the coating to have excellent adhesion and to have excellent magnetic properties by being magnetically anisotropic.

Since the PET film surface is generally inert,
In order to form a ferromagnetic metal film on the surface of PET film by chemical plating,
After etching the PET film surface, it is necessary to apply palladium to the PET film surface as a catalyst to cause a reduction reaction of metal ions.

Conventionally, methods for adding palladium to the surface of PET films include, for example, the Journal of Applied Physics.
There is a method described on page 948 of Volume 36 (1965) of Physics.

This method consists of a sensitization treatment in which a PET film etched with chromic acid-sulfuric acid and sodium hydroxide is immersed in an acidic hydrochloric acid solution of tin chloride, and then washed with water. The activation process consists of two steps: immersion in an acidic solution of hydrochloric acid to deposit palladium on the surface of the PET film.

Furthermore, as a method for imparting palladium in one step, there are, for example, the methods described in US Pat.

The method described in US Pat. No. 3,011,920 involves contacting a substrate with a strongly acidic palladium-tin colloidal solution to provide palladium that acts as a catalyst for chemical plating. This strongly acidic palladium-tin colloidal solution can be used, for example, in the Transaction of the Institute of Metal Finishing.
Institute of Metal Finishing) Volume 51 (1973)
As described on page 63, it is used for the activation treatment of ABS resin, etc., but it is not used for PET film. The method described in JP-A No. 52-117242 involves treating an insulator with an acidic solution containing a hydrated oxide of a noble metal such as palladium, which acts as a catalyst for chemical plating. It imparts oxides.

[Problem that the invention seeks to solve]

The method described in the aforementioned Journal of Applied Physics requires two baths of stannous chloride and palladium chloride, and must be washed with water after each treatment to prevent the two baths from mixing. The process is extremely complicated. Moreover, since the catalytic activity for chemical plating is low, sufficient palladium cannot be applied to induce a reduction reaction of metal ions unless the same treatment is repeated two or three times.

In the case of the method described in the above-mentioned US Pat. No. 3,011,920, in addition to palladium, which acts as a catalyst for chemical plating, a large amount of tin hydroxide is also applied to the substrate, so these impurities are removed from the chemical plating. This hinders the reduction reaction during bonding, and also causes a weakening of the adhesion strength between the formed metal film and the substrate. Therefore, after bringing the substrate into contact with a strongly acidic palladium-tin colloidal solution to remove impurities other than palladium, a further process such as immersing the substrate in an acid or alkaline solution (acceleration treatment) is required. Moreover, this strongly acidic palladium-tin colloidal solution changes over time and begins to precipitate 3 to 4 months after its preparation, and has the drawback of lacking stability and reproducibility. The method described in JP-A-52-117242 is
Due to their composition, they have the disadvantage of insufficient catalytic activity for chemical plating.

Furthermore, since the ferromagnetic metal plating films obtained by these known methods are magnetically isotropic, they are inferior in magnetic recording properties such as reproduction output and sensitivity when used as magnetic recording media.

As mentioned above, by applying palladium, which has a certain high catalytic activity, to the surface of the PET film by a simple operation, and then chemically plating a ferromagnetic metal with magnetic anisotropy, the adhesion and Establishment of a method for forming ferromagnetic metal plating films with excellent magnetic properties with good reproducibility is currently most needed.

[Means to solve the problem]

The present inventor has studied various methods of applying palladium, which has a certain high catalytic activity, to the surface of a PET film by a simple operation, and then chemically plating a ferromagnetic metal by imparting magnetic anisotropy. As a result of repeated efforts, the present invention was arrived at.

That is, in the present invention, the surface of the target PET film is etched with an aqueous solution of an alkali metal hydroxide, then treated with an aqueous cationic surfactant solution or a metal oxide hydrosol (colloidal solution), and then anionically etched. Palladium colloid is applied to the surface of the PET film by immersing it in a palladium hydrosol containing one or more selected from ionic surfactants, nonionic surfactants, and water-soluble polymers. Then, by chemically plating ferromagnetic metal in a magnetic field.
This is a method for plating PET film with ferromagnetic metal.

[Effect]

First, the most important point in the present invention is that PET
etching the film with an aqueous solution of an alkali metal hydroxide, and then treating it with an aqueous cationic surfactant solution or a metal oxide hydrosol;
When applying palladium, which acts as a catalyst for chemical plating, to the surface of PET film, one or more selected from anionic surfactants, nonionic surfactants, and water-soluble polymers are used. The method consists of using a palladium hydrosol containing palladium and chemically plating a ferromagnetic metal in a magnetic field.

In the present invention, palladium hydrosol containing one or more selected from anionic surfactants, nonionic surfactants, and water-soluble polymers is extremely stable. It can be stored for a long time and can be used at any time, and since it does not contain impurities that would interfere with the catalytic action, it does not require accelerating treatment as in conventional methods. A palladium colloid having a constant high catalytic activity can be obtained by a simple operation of etching a PET film with an oxide aqueous solution, treating it with a cationic surfactant aqueous solution or metal oxide hydrosol, and then immersing it in the palladium hydrosol. Furthermore, by chemically plating ferromagnetic metal in a magnetic field, it can be made magnetically anisotropic, resulting in excellent magnetic properties.
A ferromagnetic film can be obtained as a high-density magnetic recording medium.

Next, various conditions for carrying out the method of the present invention will be described.

In the etching treatment of the PET film in the present invention, the PET film is placed in an aqueous alkali metal hydroxide solution at a temperature ranging from room temperature to a boiling point, preferably 50 to 50 ml.
This is done by soaking at a temperature of 90°C for 10 minutes or more. The PET film used is preferably previously degreased with ethanol or the like, washed with water, and dried.

As the alkali metal hydroxide aqueous solution used in the etching process in the present invention, a sodium hydroxide or potassium hydroxide aqueous solution is suitable, and the concentration thereof is 1.
~10 mol/ is desirable.

As the cationic surfactant aqueous solution in the present invention, a quaternary ammonium salt type such as stearyltrimethylammonium chloride or dodecylpyridinium chloride dissolved in an aqueous solution at a concentration of 0.1 to 5% can be used.

Examples of the metal hydroxide hydrosol in the present invention include iron hydroxide hydrosol obtained by rapidly hydrolyzing an aqueous iron chloride solution in boiling pure water, and commercially available iron hydroxide hydrosol produced by a gas phase method. A hydrated aluminum oxide hydrosol prepared by dispersing aluminum oxide in water can be used.

In the present invention, the etched PET film can be treated with a cationic surfactant or metal hydroxide hydrosol by immersing it at a temperature in the range from room temperature to 100°C for 5 minutes or more.

The palladium hydrosol in the present invention is a palladium salt aqueous solution such as palladium chloride (),
With a water-soluble reducing agent such as sodium borohydride or hydrazine in the presence of one or more types selected from anionic surfactants, nonionic surfactants, and water-soluble polymers as protective agents. It can be obtained by reduction treatment (for example, JP-A-59
-120249 Publication).

Examples of anionic surfactants include sulfonic acid type surfactants such as sodium dodecylbenzenesulfonate, nonionic surfactants such as polyethylene glycol-P-monononyl phenyl ether, and water-soluble polymers such as polyvinyl. Pyrrolidone and the like can be used, and when used, these surfactants and water-soluble polymers can be used alone or in combination of two or more.

The concentration of surfactant and water-soluble polymer is 0.002
A range of ~0.1% is preferred.

The palladium concentration in the palladium hydrosol used in the present invention is preferably in the range of 0.1 to 2 mg-atom/.

The PET film in the present invention can be immersed in palladium hydrosol at a temperature in the range from room temperature to 100° C. for 1 minute or more, preferably 10 minutes or more, and then pulled out and washed with water.

Chemical plating of ferromagnetic metal in the present invention is performed in a magnetic field. That is, in a solution containing ferromagnetic metal ions and a reducing agent, the metal ions are reduced in the palladium colloid part, and the ferromagnetic metal is precipitated. At this time, by applying a directional magnetic field from the outside, , which improves magnetic properties by adjusting the arrangement of magnetic domains to provide anisotropy.

The object of the present invention can be achieved if the strength of the magnetic field is 1 kOe or more, but in consideration of the magnetic properties of the resulting ferromagnetic metal plating film, it is preferably 3 kOe or more.

The ferromagnetic metal plating film in the present invention can be made to have anisotropy in any direction by changing the direction of the magnetic field.

As the ferromagnetic metal for chemical plating in a magnetic field according to the present invention, one or more water-soluble salts such as nickel, cobalt, iron, and chromium can be used.

As the reducing agent for chemical plating in the present invention, sodium hypophosphite, formaldehyde, etc. can be used.

〔Example〕

Next, the present invention will be explained by examples.

The magnetism in the examples was measured in a magnetic field of 10 kOe.

To measure SFD, use the differentiator circuit of a magnetic measuring instrument to obtain a differential curve of coercive force, measure the half-width of this curve, and divide this value by the coercive force at the peak value of the curve. Ta.

To check the adhesion of plating, use Scotch Mending Tape (manufactured by Sumitomo 3M Ltd.) 1 hour after plating is completed.
The test was performed by strongly pasting the material onto a plated object and peeling it off.

Example 1 After washing with ethanol for 10 minutes, washing with water and drying PET film for magnetic tape (manufactured by Toray Industries, Inc., thickness:
Etching treatment was carried out by immersing a 20.8 μm, 4 cm x 2.5 cm) in an aqueous solution at 50° C. containing 6 mol of sodium hydroxide, and removing it after 60 minutes and washing it with water.

A hydrated aluminum oxide hydrosol was prepared by dispersing 0.2 g of aluminum oxide powder ("Aluminum Oxide C" manufactured by Nippon Aerosil Co., Ltd.) in 100 ml of pure water at room temperature. The above PET film was immersed in this hydrosol at a temperature of 80°C. After 30 minutes, the film was pulled out and thoroughly washed with water.

Separately, 50 μmol of palladium chloride ()
It was dissolved in 2.5 ml of an aqueous solution containing 250 μmol of sodium chloride, and then diluted to 94 ml with pure water. While vigorously stirring this solution, 1 ml of an aqueous solution containing 10 mg of polyethylene glycol mono-P-nonyl phenyl ether (polymerization degree of the polyethylene glycol moiety: 10) was added, followed by 5 ml of an aqueous solution containing 200 μmol of sodium borohydride. When added dropwise, the color of the solution suddenly changed, and a transparent black-brown palladium hydrosol containing a nonionic surfactant was obtained.

The above PET film treated with hydrated aluminum oxide hydrosol was immersed in this palladium hydrosol at a temperature of 80°C for 30 minutes, and then the film was pulled up and washed with water to obtain a PET film with palladium colloid applied to the surface. It was done.

Next, 0.03 mol of cobalt sulfate () heptahydrate, 0.25 mol of sodium hypophosphite, 0.50 mol
Sodium tartrate dihydrate and 0.50 mol of boric acid are dissolved in pure water to make 1, and 3.3 mol/
The PET film to which the palladium colloid was applied was immersed in a cobalt chemical plating solution whose pH was adjusted to 9.0 by adding an aqueous sodium hydroxide solution at a temperature of 63° C. in an applied magnetic field of 5 kOe parallel to the film. After 7 minutes of soaking, the film is pulled out, washed with water, and dried to a thickness of 0.55 μm on the PET film surface.
A ferromagnetic metal cobalt film with good adhesion of m was formed.

Even when the mending tape was strongly pressed against the surface of this PET film and removed, the cobalt film did not peel off.

Also, the residual magnetic flux density of this PET film is
5740 Gauss, coercive force 766 Oe, squareness ratio 0.64, S.
FD was 0.28.

Example 2 Palladium colloid was applied in the same manner as in Example 1, except that the magnetic field strength was 15 kOe.
Coating of PET film was performed.

The surface of the obtained PET film was silvery white, and the ferromagnetic cobalt film did not peel off even when the mending tape was strongly pressed and removed. Also, the residual magnetic flux density of this PET film is
6000Gauss, coercive force 790Oe, squareness ratio 0.66, S.
FD was 0.19.

Comparative Example Co was applied to PET film in the same manner as in Example 1, except that no magnetic field was applied during chemical plating.
I went to meet someone.

The residual magnetic flux density of this PET film is
4320 Gauss, coercive force 800 Oe, squareness ratio 0.52, S.
FD was 0.40.

〔effect〕

In the method for plating PET film with ferromagnetic metal according to the present invention, as shown in the above example, the palladium hydrosol used in the present invention does not contain impurities that interfere with the catalytic action of chemical plating.
In addition, since it is stable over a long period of time, it is possible to add palladium colloid that has a certain high catalytic activity, so it has excellent adhesion to the PET film surface and is magnetically different. Due to the ability to impart orientation, it is possible to form a ferromagnetic metal plating film with excellent magnetic properties.

Claims (1)

[Claims] 1. When forming a ferromagnetic metal coating on the surface of a polyethylene terephthalate film by chemical plating, the target polyethylene terephthalate film is etched with an aqueous solution of an alkali metal hydroxide, and then a cationic interface is formed. After treatment with an activator aqueous solution or metal hydroxide hydrosol, it is added to a palladium hydrosol containing one or more selected from anionic surfactants, nonionic surfactants, and water-soluble polymers. A method for plating a polyethylene terephthalate film with a ferromagnetic metal, the method comprising applying palladium colloid to the surface of the polyethylene terephthalate film by immersion, and then chemically plating a ferromagnetic metal in a magnetic field.