JPS62132940A - Formation of plasma polymerization thin film on high polymer base material - Google Patents

Abstract

PURPOSE:To form a plasma polymerization thin film having improved durability on the surface of a high polymer base material, by initially carrying out the first plasma treatment by a nonpolymerizable gas on the surface of the high polymer base material, plasma polymerization treatment under reduced pressure and then the second plasma treatment. CONSTITUTION:The surface of a high polymer base material is subjected to the first plasma treatment by glow discharge in an atmosphere of a nonpolymerizable gas, e.g. rare gas, H2, CO, N2, O2, etc., or a mixed gas thereof, etc., under reduced pressure, e.g. 0.05-5Torr, at 5-500W discharge output for 30sec-20min treatment time and then plasma polymerization treatment by glow discharge while feeding a monomer under sustained reduced pressure and subsequently to the second plasma treatment by glow discharge while feeding a nonpolymerizable gas, preferably rare gas of H2 under sustained reduced pressure to form a plasma polymerization thin film having improved durability thereon.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method of forming a polymeric thin film on the surface of a polymer substrate using a plasma excitation reaction, and more specifically, a method of forming a thin polymer film on the surface of a polymer substrate using a plasma excitation reaction. This invention relates to a method for forming a plasma-polymerized thin film with excellent durability.

[Conventional technology and problems]

In recent years, research on the formation of polymer thin films or surface modification using plasma-induced reactions has been active. The plasma polymerization reaction carried out by glow discharge under reduced pressure occurs only in the surface layer of the substrate, and can modify the surface layer and impart a wide variety of functionalities without changing the bulk properties.

For example, adhesiveness is improved by subjecting the surface of a molded article made of polyolefin resin or fluororesin to plasma polymerization treatment with an organosilicon compound or an organotin compound.

(Japanese Patent Application Laid-Open No. 57-147527) Furthermore, antistatic properties are imparted to molded articles of fluororesin or vinyl chloride resin by subjecting them to plasma polymerization treatment of organosilicon compounds.

(Unexamined Japanese Patent Publication No. 57-123232, No. 57-202323)
Alternatively, a plasma polymerized film of tetrafluoroethylene or methyl methacrylate monomer is formed on the surface of the fiber structure to improve the depth of the color of the fiber. (Unexamined Japanese Patent Publication No. 5
3-111192) In this way, plasma polymerization treatment
By employing appropriate monomers, properties such as adhesiveness, wettability, optical properties, insulation properties, and substance permeability of the substrate surface can be changed. However, the plasma polymerized thin film formed on the surface of a substrate has problems with durability due to the following two main reasons. One is that the adhesion to the polymer base material is not necessarily good depending on the type of base material, and it often peels off easily from the base material due to heat or friction.

The other is the base material surface J/? : There was a problem that the properties of the formed plasma-polymerized thin film changed over time and deteriorated. For these two reasons, the practical application of plasma polymerized thin films has been extremely limited.

[Means for solving problems]

As a result of intensive study to solve the above problems, the present inventor first performed a first plasma treatment on the surface of a polymeric substrate using glow discharge in a non-polymerizable gas atmosphere, and then supplied a monomer under reduced pressure. Then, by performing plasma polymerization treatment by glow discharge, and then continuing to supply a non-polymerizable gas and performing a second plasma treatment by glow discharge while reducing production,
The present invention was completed based on the discovery that a highly durable plasma polymerized thin film could be formed on the surface of a substrate.

[Effect]

The present invention will be explained starting from the first plasma treatment. First, the surface of the substrate is subjected to plasma treatment under reduced pressure using glow discharge in a non-polymerizable gas atmosphere. This plasma treatment cleans the substrate surface and generates active sites due to free radicals. Such a highly active surface significantly increases the adhesion between the subsequently formed plasma-polymerized thin film and the substrate.

These depend on the physical and chemical effects of ions, electrons, radicals, excited molecules, and ultraviolet rays in plasma.

The gas used in this first plasma treatment is Ar,
Noble gases such as He, Hl, CO1CO, Teeth, O2, N
Examples include Hs and HgO. Rare gas, H2, is a non-reactive gas, and due to sputtering phenomenon and excited decomposition of the surface layer,
Cleans the surface of the base material. On the other hand, other gases are reactive gases, and some of them become carbonyl groups, carboxyl groups, amino groups, and OH groups and are incorporated into the surface of the polymer base material, forming a highly active surface layer. The operating conditions are:
Although it varies depending on the oscillation power source and device shape used, the pressure is generally in the range of 0.05 Torr to 5 Torr, the discharge output is 5 W to 500 W, and the processing time is between 30 seconds and 30 minutes.

The higher the power and the lower the pressure, the stronger the physical effects of the sputtering phenomenon. After this first plasma treatment, plasma polymerization treatment is subsequently performed while maintaining the reduced pressure atmosphere. This is because free radicals react with atmospheric components and disappear when the pressure is returned to -, and the effectiveness of the active surface is impaired.

In plasma polymerization treatment, a monomer is supplied and a polymerization reaction is performed under glow discharge to form a polymerized thin film on the surface of a substrate. Plasma polymerization treatment can impart various functionalities to the surface of the substrate. For example, if you want to impart hydrophilicity, you can use allylamine, vinyl pyridine, or a heptamine containing nitrogen or oxygen atoms such as propargyl alcohol or methyl methacrylate; conversely, if you want to impart hydrophobicity, use: Tetrafluoroethylene or an organosilicon compound may be used. Tetrafluoroethylene and organosilicon compounds are commonly used to modify insulation, corrosion resistance, and material permeability. In plasma polymerization treatment, film quality and thickness are controlled by changing discharge output, gas flow rate, gas pressure, and polymerization time. Since plasma polymerization treatment is performed under reduced pressure, there are no pinholes in the polymerized film, and a variety of functions can be imparted with a thin coating. In the present invention, after forming this plasma polymerized thin film,
A second plasma treatment is then performed while maintaining the reduced pressure atmosphere. The second plasma treatment enhances the durability of the plasma polymerized film. Plasma polymerized thin films are susceptible to changes over time. Several reasons have been pointed out as the cause. One is intramolecular rotation of functional groups. For example, even if parent wood groups are added by plasma polymerization, if left in the air,
The parent wood group sinks below the surface and the hydrophilicity regresses. One more
One point to note is the presence of low molecular weight polymers.

Plasma-polymerized thin films generally have a network structure, but are not homogeneous and also contain low molecular weight portions. Deterioration of these parts becomes a problem during use. The second plasma treatment has the effect of volatilizing or crosslinking the low molecular weight portions, highly crosslinking the entire polymerized thin film, and making it a rigid structure. Therefore, by performing a second plasma treatment, the functionality of the plasma-polymerized thin film becomes less susceptible to changes over time. The second plasma treatment is desirably performed using a rare gas or H2 in order not to impair the original function of the plasma polymerized thin film.

The operating conditions will be similar to the first plasma treatment.

As mentioned above, 1st. By performing a series of operations including the plasma treatment, the plasma polymerization treatment, and the second plasma treatment, a plasma polymerized thin film with excellent durability can be formed on the polymer substrate. The present invention will be explained below with reference to Examples.

Example A tetrafluoroethylene resin sheet was placed in a plasma device, and after the pressure was reduced to 1O-3 Torr, N2 was introduced and the system was made Q.
After maintaining the pressure at 1 Torr, a discharge treatment was performed at 100 W for 5 minutes using a 13.56 MH2 high frequency power source.

After the treatment, the pressure in the system was reduced to 10 Torr, 4-vinylpyridine was introduced, and the pressure in the system was reduced to 0.2 Torr.
After maintaining the temperature at r 2 , discharge was performed at 80 W for 10 minutes to form a plasma polymerized thin film on the substrate. Subsequently, after reducing the pressure in the system to 10-3 Torr again, Ar was introduced and the pressure was reduced to 0. I
Discharge treatment was performed at 100 W for 5 minutes in a Torr atmosphere.

The water contact angle and adhesive strength of the sample subjected to this series of treatments were measured. This measurement is
Durability was investigated under three conditions: (1) carried out within 1 hour after treatment; (2) carried out 30 days after treatment; and (2) carried out after being left in the air at 200°C for 1 hour after treatment.

The results are shown in Table-1.

Table 1 To measure the adhesive strength, cut the sample into two sheets with a width of 25 mm and a length of 75 mm, apply Araldite (manufactured by Ciba Geigy) to the area of 25 mm in the tip end of one sheet, and After adhering to the test piece and leaving it at 5σC for 7 days, the test piece was peeled off at
It was determined by peeling off at 0 V minutes.

Comparative Example The same sheet used in the example was placed in a plasma apparatus, and after the pressure was reduced to 10-' Torr, a plasma polymerized thin film was formed under the same conditions as in the example without plasma treatment, that is, by introducing K4-vinylpyridine. was formed, and then taken out into the air and subjected to the same measurements as in the example.

The results are shown in Table-2.

Table 2 [Effects of the present invention] The method of forming a plasma polymerized thin film on the surface of a polymer substrate according to the present invention cleans and activates the surface of the substrate in the first plasma treatment with a non-polymerizable gas, Next, while under reduced pressure, a monomer is supplied to form a plasma polymerized thin film to impart functionality to the surface of the substrate, followed by a second plasma treatment with a non-polymerizable gas while remaining under reduced pressure. By performing a series of treatments to remove the low molecular weight portion of the formed plasma-polymerized thin film and increase the crosslinking density, a highly durable plasma-polymerized thin film can be provided on the surface of the polymer substrate.

Claims (3)

[Claims] (1) When forming a plasma-polymerized thin film on a polymer substrate, the surface of the polymer substrate is first subjected to a first plasma treatment using glow discharge in a non-polymerizable gas atmosphere, and then left under reduced pressure. , to a polymer base material characterized in that a monomer is supplied and plasma polymerization treatment is performed by glow discharge, and then a non-polymerizable gas is supplied under reduced pressure and a second plasma treatment is performed by glow discharge. plasma polymerized thin film formation method. (2) In the first plasma treatment, the non-polymerizable gas
Noble gas, H_2, CO, CO_2, N_2, O_2, N
2. The method of forming a plasma polymerized thin film on a polymer substrate according to claim 1, wherein the gas is one of H_3, H_2O, or a mixture thereof. (3) The method for forming a plasma-polymerized thin film on a polymer substrate according to claim 1, wherein in the second plasma treatment, the non-polymerizable gas is a rare gas or H_2.