JPH11170378A - Manufacture of minute-hole film using electron beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a large number of holes by a method wherein an electron beam narrowed down to the size of a diameter 0.2 nm-200 μm is cast on the surface of a film and then chemical etching is applied to the surface. SOLUTION: In a method for manufacturing a minute-hole film wherein a large number of holes are formed by casting an electron beam on the surface of the film and then by applying thereto chemical etching by an alkali solution, an acid solution, an oxidizing agent, etc., the electron beam having the energy of 20-2000 keV and a total current value of 10 μA-1 mA is narrowed down to the size of a diameter 0.2 nm 200 μm and cast.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION
After irradiating the film surface with an electron beam focused to the size of um diameter,
The present invention relates to a method for manufacturing a microporous film in which a large number of holes are formed by performing a chemical etching process.

[0002]

2. Description of the Related Art Various techniques have been used to increase added value, such as forming a through hole in a polymer film or a contact lens to impart functionality. For example, polymer films have been applied in a wide range of fields as porous membranes such as microfiltration membranes and extraocular filtration membranes. Method. A chemical method that utilizes the difference in solubility of polymers. A method in which solid fine particles soluble in a solvent are mixed and then eluted. It is performed by a method such as sintering or a method by crushing a bubbled polymer sheet.

In recent years, high-energy charged particles (ions) including neutrons generated from a nuclear reactor are irradiated on a polymer film to form a track in which a polymer chain is cut, and the track is converted into an alkaline solution or an acidic solution. An etching method for obtaining a porous film by processing (etching) using a solution or the like has been proposed (for example, Japanese Patent Publication No. 52-39).
No. 87, Japanese Patent Application Laid-Open No. 54-11971, Japanese Patent Application Laid-Open
4-117546 and JP-A-5-51479.

Further, in contact lenses, as a means for increasing oxygen permeability or improving tear passage so as not to hinder cell respiration of the cornea, perforation by discharge, laser beam or ion irradiation, etc. For example, Japanese Patent Application Laid-Open Nos. 49-53451, 49-75348, 58-29627, 1-500577, and 1-29 have been proposed.
8312, and JP-A-5-19132).

[0005]

What is obtained by a perforation technique performed in a method for producing a porous membrane such as a microfiltration membrane or an ultrafiltration membrane is a three-dimensional mesh, a closed-cell type, a communicating type or the like. There are various types such as those having irregular pores and those having continuously changing pore diameters, and the pore diameters are also non-uniform.

In the perforation technique for producing a porous film by chemical etching after ion irradiation, a film having a uniform hole diameter and a substantially perfect cylindrical hole can be obtained. Shape control is not possible. Moreover, the ion irradiation device is large and expensive, and its operation is not easy.

Further, in the perforation technique using a laser beam, it is difficult to control the position, size, shape, number, etc. of the holes, and there is a problem in reproducibility. In this case, the pore diameter becomes 500 μm or more, and it is impossible to produce fine pores smaller than 500 μm.

Accordingly, an object of the present invention is to produce a microporous film having uniform holes in which the positions, sizes, shapes, numbers, etc. of the holes are controlled. Specifically, the microporous membrane referred to here is a membrane having a pore size from nanometer size (nm) to micrometer size (μm).

Similar to the microporation technique of the present invention, there is a perforation technique by an etching method in which holes are formed by performing a chemical etching treatment after ion irradiation. This technology involves irradiating the film surface with heavy ions such as argon ions, krypton ions, xenon ions, gold ions, and uranium ions that have energy, and then irradiating the film in an alkaline solution such as sodium hydroxide or potassium hydroxide. The holes are formed by immersion. As a result, a membrane having a substantially perfect cylindrical hole with a uniform hole diameter can be obtained.

[0010] However, in this technique, the holes generated by etching overlap or separate, and the positions of the holes are uneven (non-uniform distribution) because the irradiation is not a method of controlling and irradiating each ion individually. Moreover, the shape of the hole is only cylindrical, and the shape cannot be changed even by using techniques such as selection and adjustment of ions.

[0011]

In order to solve these problems, a perforation technique using an electron beam instead of an ion beam has been established. The electron beam device is smaller and easier to operate than the ion irradiation device. This perforation of the film using an electron beam is performed by irradiating the film surface with an electron beam and then performing a chemical etching process.When the electron beam is used, the damage to a substance is extremely low compared to heavy ions. There are features.

That is, the present invention provides a method for producing a microporous film in which a large number of holes are formed by irradiating an electron beam on the surface of the film and then performing a chemical etching treatment with an alkaline solution, an acidic solution, an oxidizing agent or the like. The electron beam irradiation has an energy of 20 to 2000 keV,
An electron beam having a total current value of A to 1 mA
The irradiation is performed by irradiating with a diameter of 200 μm.

[0013]

DETAILED DESCRIPTION OF THE INVENTION Originally, this etching method irradiates high-energy charged particles (ions) to form a track in which a polymer chain is cut, and treats the track using an alkaline solution or an acidic solution (etching). ) To obtain a porous membrane. Therefore, since the role of ion irradiation here is to cut the polymer chain, pore formation after the etching process is determined by how much the irradiated ions damage the substance. . Generally, the higher the degree of polymer chain breakage (the degree of damage to a substance),
Also, ions having lower energy are larger.

[0014] Furthermore, heavy ions and electrons cause damage by a factor of several thousand to several hundred thousand times. This indicates that holes cannot be formed simply by irradiating the film surface with an electron beam. How can pore formation be possible? One idea is to irradiate an amount that gives the same effect (same degree of damage) as heavy ions.
For this purpose, if the beam diameter of the electron beam is reduced and the irradiation is performed at a single point, the same damage state as the ions can be created in a short time. Unlike an ion irradiation device, an electron beam generator can easily reduce the beam diameter. With this electron beam irradiation technique and etching technique, it has become possible to produce a microporous film.

In this case, the hole diameter can be changed from nanometer size (nm) to micrometer size (μm) by controlling the electron beam diameter and the etching condition. The position of the hole can be arbitrarily selected by moving the irradiation sample stage (stage) and scanning the electron beam. Further, the shape of the hole can be changed to an arbitrary shape, for example, a square, a rhombus, an ellipse, etc. by scanning the electron beam.

The membrane used in the present invention is, for example, polyethylene terephthalate, polydiethylene glycol bisallyl carbonate, polyethylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, polysterene, polymethyl methacrylate, polyimide, poly Ether ether ketone, polyethylene naphthalate and the like can be mentioned,
The type does not matter.

Examples of the etching agent used in the present invention include alkaline solutions such as sodium hydroxide and potassium hydroxide, acidic solutions such as sulfuric acid and nitric acid, and oxidizing agents such as potassium dichromate and potassium permanganate. And the like. In particular, sulfuric acid solution of potassium dichromate, alkaline solution containing potassium permanganate,
An oxidizing solution such as an alkaline solution of sodium hypochlorite is preferred. Further, a product obtained by adding an alcohol or a surfactant to the oxidizing solution etching treatment agent can also be used. Next, the present invention will be specifically described based on examples.

[0018]

Examples 1 and 2 An electron beam having an accelerating voltage of 200 KeV and a total current value of 100 μA was applied to a film of polyethylene terephthalate having a thickness of 12 μm (Example 1) and a film of polyethylene naphthalate having a thickness of 6 μm (Example 2). 1
Irradiation was performed for 5 seconds with a diameter of μm. Thereafter, the irradiated film is immersed in a 6N aqueous sodium hydroxide solution,
C. for 1 hour. After the treatment, the film was washed with water, dried, and observed with an electron microscope. As a result, cylindrical through holes were obtained. Result Polyethylene terephthalate (Example 1) 18 μm diameter through hole Polyethylene naphthalate (Example 2) 6 μm diameter through hole

[0019]

Examples 3 to 6 An electron beam having an accelerating voltage of 200 KeV and a total current value of 100 μA was applied to a 12 μm thick polyethylene terephthalate film by a 0.4 μm diameter (Example 3), a 1 μm diameter (Example 4), and a 10 μm diameter. (Example 5) Irradiation was performed for 5 seconds while focusing on a 100 μm diameter (Example 6). Thereafter, the irradiated film was immersed in a 6N aqueous sodium hydroxide solution and treated at 60 ° C. for 10 minutes. After the treatment, the film was washed with water, dried, and observed with an electron microscope. As a result, cylindrical through holes were obtained. Result 0.4 μm beam diameter (Example 3) 0.7 μm diameter through hole 1 μm beam diameter (Example 4) 1.2 μm diameter through hole 10 μm beam diameter (Example 5) 13 μm diameter through hole 100 μm beam diameter Example 6) 50 μm diameter through-hole

[0020]

EXAMPLE 7 An electron beam having an accelerating voltage of 200 KeV and a total current value of 100 μA was focused on a polyimide film having a thickness of 7 μm for 5 seconds with a diameter of 1 μm. Thereafter, the irradiated film was immersed in a 6% sodium hydroxide solution of 30% sodium hypochlorite and treated at 60 ° C. for 1 hour. After the treatment, the film was washed with water, dried, and observed with an electron microscope. As a result, a cylindrical through hole having a diameter of 2 μm was obtained.

[0021]

According to the present invention, since a large number of holes are formed by irradiating the surface of a film with an electron beam and then performing a chemical etching treatment, the hole is formed by using a conventional heavy ion. There is an advantage that it is possible to use an electron beam with extremely low damage to the substance to be treated as compared with the conversion technology, and to use a small-sized device such as an electron beam device which is easy to operate.

Further, according to the present invention, when the surface of the film is irradiated with an electron beam, an energy of 20 to 2000 keV, 1
An electron beam having a total current value of 0 μA to 1 mA is 0.2 n
By irradiating with a diameter of m to 200 μm, there is an advantage that a microporous film having uniform holes in which the position, size, shape, number, and the like of the holes are controlled can be produced.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Takeshi Suwa 1233 Watanukicho, Takasaki City, Gunma Prefecture Inside the Japan Atomic Energy Research Institute Takasaki Research Institute (72) Inventor Tadao Seguchi 1233 Watanukicho Takasaki City, Gunma Prefecture Japan Atomic Energy Research Institute Takasaki Research Inside

Claims (3)

[Claims] 1. A method for producing a microporous film, wherein a large number of holes are formed by irradiating the surface of the film with an electron beam. 2. A method for producing a microporous film, comprising subjecting the film of claim 1 to a chemical etching treatment. 3. Energy of 20 to 2000 keV, 1
An electron beam having a total current value of 0 μA to 1 mA is 0.2 n
A method for producing a microporous membrane, characterized in that irradiation is performed with a diameter of m to 200 μm.