JPS6340201B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a thin polymer film on the surface of a substrate.

In recent years, organic polymer thin films with a thickness of several microns or less,
The field of application of inorganic (compound) thin films is expanding, and there is a demand for the development of ultrathin films with uniform film quality and high reliability, as well as the development of methods for producing the same. For example, pinholes are used for applications such as thin film dielectric layers in thin film capacitors, thin film insulator layers as passivation films for ICs, surface damage prevention coatings for glasses and camera lenses, and antirust protective coatings for vapor-deposited magnetic tapes. A very high degree of reliability is required in terms of non-existence, uniformity of film thickness, uniformity of film quality, etc.

Methods for forming thin films that meet these demands include plasma polymerization, sputtering deposition, ion plating, and plasma CVD (Chemcal).
Vapor-Deposition) method and the like are known.

However, while the latter three are methods for forming inorganic (compound) thin films and have already been put into practical use in a fairly wide range, plasma polymerization has only been proposed as a method for forming organic polymer thin films. .

The plasma polymerization method that has been proposed so far involves introducing an inert gas such as argon or helium and a monomer, and maintaining the vacuum chamber at a low vacuum of 10 torr to 10 ^-2 torr, causing glow discharge in almost the entire area of the vacuum chamber. Since the system generates gas and deposits a gas phase polymer on a substrate placed during glow discharge, it has the following drawbacks.

(a) The adhesion strength between the base material and the formed polymer thin film is low, especially the adhesion strength with the inorganic base material is extremely low.

(b) As a result of constant exposure to plasma during the thin film formation process, polymerization and decomposition occur simultaneously due to generation of excessive active species, heating of the substrate, etc., resulting in coloring of the formed polymer film, and long-lived radicals. remains and lacks stability over time.

(c) During the thin film formation process, the film growth rate is slow due to sputtering caused by constantly introduced gas ions.

(d) The polymer thin film formed is porous, has a low packing density, and is prone to pinholes.

In order to solve these drawbacks and problems, the present invention has been made by discovering a new method of forming a thin polymer film as a result of intensive research, and has arrived at the present invention. The purpose is to provide a method for forming a homogeneous polymeric thin film with high density, high film strength, and no pinholes. The present invention aims to provide a method for forming molecular thin films.

That is, the gist of the present invention is to inject monomer vapor having carbon and carbon double bonds into a vacuum chamber in a high vacuum state, and to deposit the monomer on a cooled base material and simultaneously irradiate it with an electron beam. The present invention provides a method for forming a thin polymer film, which comprises forming a highly densely crosslinked polymer film on the surface of the substrate.

The present invention will be explained below based on the drawings. 1st
The figure is a schematic diagram showing an example of a device used in the present invention.

In Fig. 1, 1 is a vacuum chamber, which is connected to an exhaust pipe 2 by an exhaust system device (composed of an oil rotary pump, an oil diffusion pump, a cold trap, etc., but not shown). It is designed so that it can be evacuated to a high vacuum of up to 1×10 ^-7 torr.

Reference numeral 3 designates a capillary nozzle for ejecting monomer vapor in a specific direction, and in order to align the movement direction of the monomer vapor, the nozzle is shaped like a capillary with a diameter of 3 mm or less. Monomer gas is introduced from a monomer cylinder 4 located outside the vacuum chamber 1 through a pressure reducing valve 5, an introduction pipe 6, and a slow leak valve 7.

8 is a supply roll for the base film, and 9 is a take-up roll thereof.

The base film 10 is a cooled cylindrical drum 11
It is set up so that it can be moved along. 12
is an electron irradiation device, which heats a filament 13 by energizing it with an AC power source 14 to generate thermoelectrons, and then applies a negative high voltage to the filament 13 with a DC power source 15 to obtain accelerated electrons.

Next, a method for forming a polymer thin film based on the present invention using the above-mentioned apparatus will be explained. First, the inside of the vacuum chamber 1 is evacuated to a high vacuum of 8×10 ^-4 torr or less, preferably 1×10 ^-4 torr or less using an exhaust system. At this time, the pressure reducing valve 5 is closed, the slow leak valve 7 is kept open, and the inside of the monomer gas introduction pipe 6 is sufficiently exhausted. To introduce the monomer gas, open the pressure reducing valve 5 attached to the gas cylinder 4, adjust the amount of introduction by adjusting the slow leak valve 7, and inject it into the vacuum chamber 1 through the thin tube nozzle 3. However, at this time, the movement directions are aligned due to the arrangement relationship between the thin tube nozzle 3 and the exhaust direction,
Even after exiting the nozzle 3, the particles enter the surface of the base film 10 as a relatively oriented molecular stream or aggregate stream.

The monomer incident on the surface of the base film adheres to the film surface, and a portion of it is re-evaporated in the vacuum region.

At this time, in order to increase the adhesion efficiency of the monomer to the film surface, the base film temperature must be cooled to a temperature below which the monomer vapor pressure is 1/10 of the vapor pressure at room temperature (20°C). Preferably, the temperature of the drum is controlled.

Simultaneously with or before the injection of the monomer vapor, the electron irradiation device 12 is operated to irradiate the monomer attached to the film surface with an electron beam. The energy of the electron beam at this time is 5eV
From the above, it is preferable to set it to 10 eV or more,
This can be easily achieved by controlling the negative DC voltage applied to the filament 13 using the power supply 15.

The monomers that are continuously incident on and attached to the base film 10 generate ionized monomers, ionized molecules, dissociated molecules, radicals, excited molecules, etc. by electron beam irradiation, and the polymerization reaction progresses due to the action of the various active species. A densely crosslinked polymer thin film is formed.

The formation of the above-mentioned polymeric thin film is carried out on the surface of a continuously moving film, and the film is moved by a drive system including a supply roll 8, a take-up roll 9, and a cylindrical drum 11.

The following types of monomers having carbon and carbon double bonds may be used in the present invention.

(a) Olefins and their derivatives such as ethylene, propylene, isobutylene, and trichloropropylene (b) Dienes and their derivatives such as butadiene and trichlorobutadiene, and vinyl acetylenes such as vinyl acetylene and chlorvinylacetylene (c) Vinyl chloride and vinylidene chloride , dichloroethylene, trichloroethylene, allyl chloride, and other halogenated ethylenes (d) Acrylic acid, methacrylic acid, acrylic morpholine, acrylic pyrrolidine, and other acrylic acids and methacrylic acids and their derivatives (e) Ethyl acrylate, butyl acrylate, etc. Acrylic esters (f) Methacrylic esters such as methyl methacrylate, β-chloroethyl methacrylate, and β-ethoxyethyl methacrylate (g) Acrylamide and its derivatives such as acrylamide and N-n-butoxycarbonylacrylamide (h ) Methacrylamide and its derivatives such as N-o-anisylmethacrylamide (i) Acrylonitrile, methacrylonitrile, α
- Acrylo or methacrylonitriles such as chloroacrylonitrile and α-ethyl acrylonitrile (j) Vinyl esters such as vinyl acetate, monochlorovinyl acetate, and vinyl trifluoroacetate (k) Unsaturated dichloromethane such as methyl acrylic maleate and vinyl ethyl fumarate Basic acids and their esters (l) Allyl esters such as allyl acetate and diallyl phthalate (m) Vinyl ketones and their derivatives such as methyl vinyl ketone and divinyl ketone (n) Allyl esters such as allyl vinyl ether, ethyl vinyl ether, and divinyl ether Saturated ethers (o) Styrene and its derivatives such as styrene, chlorostyrene and methylstyrene (p) Vinyl amines and their derivatives such as vinyl isocyanate and N-vinylethyleneamine (q) Maleimide and its derivatives (r) Vinyl thioether, thio Sulfur-containing compounds such as vinyl acetate and vinyl sulfone (s) Vinyl compounds having polycyclic hydrocarbons and heterocycles such as N-vinylpyridine and chlorvinylnaphthalene (t) Silicon-containing compounds such as trichlorovinylsilane (u) Vinyl Phenol and its derivatives such as phenol The method for forming a polymer thin film of the present invention differs from the plasma polymerization method, plasma CVD method, etc. described above, and has the following effects.

First, since the thin film is formed in a high vacuum region, there is less incorporation of residual gases and reactions, and a thin polymer film with fewer impurities can be obtained, as well as less reaction with reactive gases such as residual oxygen gas, resulting in less oxidation. It is possible to reduce the generation of long-lived peroxide radicals, etc., which cause discoloration of the thin film due to oxidation and oxidative deterioration after the formation of the polymer thin film. Furthermore, since the process is carried out in a high vacuum, the mean free path of the monomer particles becomes large, and as a result, the monomer vapor injected from the capillary nozzle in the same direction does not diffuse into the entire area of the vacuum chamber. A relatively focused molecular stream can travel toward the substrate. Second, the present invention is a method in which a monomer vapor stream is ionized and activated by bombardment of accelerated electrons immediately after it enters the surface of a base material, and is polymerized. Introduced all areas of vacuum chamber
This method differs from the method of maintaining a low vacuum of 10 torr to ^{10 -2} torr and ionizing this inert gas with a high frequency or direct current high voltage electric field to generate a glow discharge, so it has the following effects.

(a) Since no glow discharge is used, the sputtering phenomenon caused by plasma particles, which adversely affects the thin film formation rate, can be prevented.

(b) Since there is no sputtering phenomenon, there is no heat generation caused by this phenomenon, and unnecessary thermal decomposition of the formed polymer can be prevented.

(c) The concentration of the active species required for polymerization and polymerization on the substrate can be easily controlled by the electron density, that is, the output of the irradiating electron beam. Further, since the uniformity of the irradiation distribution of the electron beam irradiation amount can be controlled relatively easily, the properties of the formed polymer thin film can be made uniform over a wide area.

Thirdly, the present invention uses a method in which monomers are ionized and activated by being bombarded with accelerated electrons at the time they adhere to the surface of the substrate or near the surface of the substrate. Compared to polymerization, it requires significantly less energy,
5eV or more, 10eV at most is fine.

In other words, 1/ of the energy required in conventional electron beam polymerization
About 1000 is sufficient.

Fourthly, since the high molecular weight polymer obtained by the present invention is highly crosslinked, it is particularly suitable for applications requiring strength.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an example of an apparatus used in the present invention. 1... Vacuum chamber, 2... Exhaust pipe, 3... Thin tube nozzle, 4... Monomer cylinder, 6... Inlet pipe, 8...
... Supply roll, 9 ... Take-up roll, 10 ... Base film, 11 ... Cooled cylindrical drum, 12
...Electron irradiation device, 13...Filament, 14
...AC power supply, 15...DC power supply.

Claims (1)

[Claims] 1. Monomer vapor having carbon and carbon double bonds is injected into a vacuum chamber in a high vacuum state, and the monomer is deposited on a cooled base material, and simultaneously irradiated with an electron beam. A method for forming a thin polymer film, which comprises forming a highly densely crosslinked polymer film on the surface of the substrate. 2 The temperature of the base material and the vapor pressure of the monomer used are 20
2. The method for forming a thin polymer film according to claim 1, wherein the temperature is lower than the temperature at which the vapor pressure is 1/10 of the vapor pressure at ℃.