JPH0211606B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a smooth coating on a substrate as an ablator shell for fuel globules in nuclear fusion. In particular, it relates to a method of forming by plasma polymerization.

Conventionally, various methods of forming a film on a substrate are known, including a method of forming a film by plasma polymerization. However, it is difficult to form a smooth film, especially on non-planar substrates, such as fibrous, spherical, cylindrical, and other complex-shaped substrates, and it takes a long time to form it. It took a long time. For example, in nuclear fusion, inertial confinement fusion has been rapidly developed in recent years, and in particular, fusion reactions using laser beams, electron beams, and ion beams as energy drivers are being realized. In this nuclear fusion, a laser beam is directed from around a small sphere of fuel consisting of deutorium and tritium sealed in a glass ^or gold pusher (a spherical shell-like container ⁾ . The aim is to achieve a temperature of 100 million degrees by compressing it to an ultra-high density of 10 ²⁶ ions/cm ³ . For compression, ``explosive compression'' involves converting pushers into plasma using a laser beam and using the impact force of this plasma.
In contrast, ``blowout type compression'' is being considered. In the former, the shell, which acts as a pusher that encloses the fuel, is made of a material with a high specific gravity and is thin, and the energy from the laser is used to uniformly heat the entire body in a short time using X-ray radiation or high-speed electrons. , the temperature rise is more significant than the density, making it difficult to compress ultra-high densities. The latter uses fuel globules with a thick layer of lower-density material on the outside of the fuel, applies laser irradiation, and compresses the fuel using the rocket action of the plasma that ejects outward. Fuel globules with various structures have been developed depending on the scale of the experiment. For example, it consists of a vacuum from the center, a solid fuel shell (solidified at low temperature), a high atomic number material shell, a low density material shell, an outer pusher shell, and an ablator shell, with the outer pusher shell having various densities. Consists of layers. Among these, the high atomic number material shell blocks electrons with a large charge in the heat shielding layer and absorbs X-ray radiation, and the low density material shell electrostatically shields high-speed electrons, forming an ablator shell. When it is turned into plasma by laser irradiation, the thermal effect on the fuel shell is reduced, and the compression effect of plasma formation is effectively transmitted.

The ablator shell (low atomic number material shell) used here has been formed by plasma polymerization as a polymer film of tetrafluoroethylene or trans-2-butene. Since this ablator shell needs to be uniformly converted into plasma, it is required to have a uniform thickness of about 50 to 100 μm and a surface smoothness of 0.1 μm. In order to meet this requirement, it is said that the formation rate of the polymer coating must be 1 μm/hr or less. As a method with a high film formation rate, a method is known in which parylene is thermally polymerized to form a film meeting the above requirements at a rate of about 5 μm/hr. However, heating above 100℃ is prohibited, so
Thermal polymerization is not preferred.

The object of the present invention is to produce a relatively thick film with a smooth and uniform thickness that meets the above requirements by plasma polymerization.
It is an object of the present invention to provide a method of forming at a higher forming speed than conventional methods.

The object is achieved by plasma polymerization of alkyl (meth)acrylates or fluoroalkyl (meth)acrylates on a substrate.
As used herein, (meth)acrylate refers to methacrylate or acrylate.

As a result, a relatively thick coating that is extremely smooth and has a uniform thickness can be formed on the substrate in a short time. Specifically, a film having a uniform thickness of 30 to 100 μm and a smoothness of 0.1 μm can be formed at a rate of 6 μm/hr.

The alkyl (meth)acrylate used in the present invention is preferably one in which a linear, branched or cyclic alkyl group having 1 to 20 carbon atoms and a (meth)acrylate group are bonded. Preferably, the alkyl group has 1 to 12 carbon atoms, and most preferably, the alkyl group has 1 to 6 carbon atoms. Examples of alkyl (meth)acrylates used in the present invention include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloro-ethyl acrylate, These include phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, and ethyl α-ethyl acrylate.

The fluoroalkyl (meth)acrylate used in the present invention is a straight chain having 1 to 20 carbon atoms,
In the branched or cyclic alkyl group, a (meth)acrylate group is preferably bonded to an alkyl group in which hydrogens other than the hydrogen bonded to the carbon having a bond are partially or completely substituted with fluorine.
Preferably the number of carbon atoms in the fluoroalkyl group is 1 to 12
The fluoroalkyl group preferably has 1 to 6 carbon atoms. To illustrate the fluoroalkyl (meth)acrylate used in the present invention, the formula: R _f R ² OCOOR ¹ = CH ₂ (wherein, R _f is a linear or branched perfluorocarbon having 1 to 15 carbon atoms). an alkyl group or a group in which one or more fluorine atoms thereof are replaced by a hydrogen atom and has at least one fluorine atom, R ¹
is a hydrogen atom or a methyl group, and R ² is a divalent hydrocarbon residue). The R _f group has 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, and has at least 1 fluorine atom, preferably equal to the number of carbon atoms in the R _f group and the number of carbon atoms in the R ² group. at least 1/2 of the sum. The R ² group is for connecting the acrylate group or methacrylate group and the R _f group, and the number of carbon atoms thereof is preferably 1 to 10, preferably 1 to 5, but is not critical.

More specific examples of the fluoroalkyl (meth)acrylate used in the present invention include CH ₂ =C(CH ₃ )COOCH ₂ (CF ₂ ) ₂ H CH ₂ =C(CH ₃ )COOC(CH ₃ ) ₂ ( CF ₂ ) ₂ H CH ₂ =C(CH ₃ )COOCH ₂ CHFCF ₃ CH ₂ =C(CH ₃ )COOCH ₂ CF ₂ CHFCF ₃ CH ₂ =C(CH ₃ )COOCH(CH ₃ )
CF ₂ CHFCF ₃ CH ₂ =C(CH ₃ )COOCH(C ₂ H ₅ )
CF ₂ CHFCF ₃ CH ₂ =C(CH ₃ )COOCH(C ₃ H ₇ )
CF ₂ CHFCF ₃ CH ₂ = C (CH ₃ ) COOC (CH ₃ ) ₂ CF ₂ CHFCF ₃ CH ₂ = C (CH ₃ ) COOC (CH ₃ ) (C ₂ H ₅ )
CF ₂ CHFCF ₃ CH ₂ = C(CH ₃ ) COOCH ₂ (CF ₂ CF ₂ ) _o H n is 2 to 5 CH ₂ = C(CH ₃ )COOC(CH ₃ ) ₂ (CF ₂ CF ₂ ) _o H n is 2 _~ 5 _CH2 =C( _CH3 )COOC( _CH3 ) _2CF2CH
(CF ₃ ) ₂ CH ₂ =C(CH ₃ ) COOCH ₂ CH ₂ (CF ₂ CF ₂ ) _o CF
( _CF3 ) _2n is 1-5 _CH2 =C( _{CH3 ) COOCH2CH2} ( _CF2 ) _oFn is 1-10.

In addition, preferred alkyl (meth)acrylates or fluoroalkyl (meth)acrylates have a boiling point of 400°C or less at atmospheric pressure or 70°C at 40 Torr.
℃ or below.

Therefore, in order to plasma-polymerize alkyl (meth)acrylate or fluoroalkyl (meth)acrylate on a substrate, a low-pressure gas mixture of alkyl (meth)acrylate or fluoroalkyl (meth)acrylate and an inert gas is polymerized. Either place the substrate and generate a glow discharge around it, or place the substrate in a gas flow of a low-pressure gas mixture of an inert gas and alkyl (meth)acrylate or fluoroalkyl (meth)acrylate excited by glow discharge (afterglow). law).

The inert gas can be helium, neon, argon, krypton, xenon, preferably argon and krypton.

Glow discharge is performed by placing two parallel plate electrodes inside the reaction tube or by placing an induction coil outside the reaction tube and applying a high frequency voltage or current. No matter which type of discharge is performed, whether by placing a substrate in the discharge area or using the afterglow method, it should be performed at a temperature of 0 to 200°C and a pressure of 10 to 10 ^-4 Torr, preferably 1 to 10 ^-2 Torr. , the flow rate of the inert gas is 0.1 to 100 cm ³ STP/min, and the flow rate of monomers such as alkyl acrylate is 0.5 to 50% of the inert gas flow rate, and it is particularly recommended to supply it at a rate of 1 to 20%. preferable. Also, the glow discharge is 0.1
It is preferable to carry out the discharge under a high frequency electric field of ~100 MHz with a discharge power of 1~500 W.

The shape of the substrate may be spherical, flat, fibrous, etc., and the material may be solid such as metal, glass, or resin.

For plasma polymerization apparatus, the reaction tube is also preferably heated to prevent polymer formation on the tube wall, and the electrodes are preferably cooled as shown in the Examples below.

In addition, as a plasma polymerization method, after polymerizing for a certain period of time, the discharge is stopped for a certain period of time and only an inert gas or a monomer is allowed to flow through the reaction tube to prevent the formation of a polymer in the gas phase. This is an effective way to maintain

In addition, some of the monomers may be replaced with chlorine, silium, gold, thallium, silver, copper, etc. (in the case of chlorine or silium), or in the form of a combination of these elements (in the case of metal elements, salts or complexes). These elements can be incorporated into the coating as derivatives of (form) as a means of diagnosis during nuclear fusion. In this case, it can be observed by the generation of x-rays when plasma is generated by a laser beam. For diagnosis, there are other methods such as performing metal vapor deposition during plasma polymerization for metals such as gold, and separately using chlorine or chlorine such as p-chlorostyrene, vinyl chloride, p-chloroacrylanilide, vinylidene chloride, etc. Monomers containing silium can also be introduced by plasma polymerization.

Next, examples of the film forming method of the present invention will be shown, but the present invention is not limited thereto.

Example 1 Polymerization was carried out using a plasma polymerization apparatus, the main part of which is shown in the drawing. The apparatus includes, in order from one end, an argon supply port, a monomer supply port, a polytetrafluoroethylene insert 1 installed inside, an electrode 2 installed inside, a polytetrafluoroethylene insert 3 installed inside, and the other end. The main part is a glass tube 4 equipped with an exhaust port that connects to a vacuum pump through a liquid nitrogen trap.

The electrodes are two copper parallel plate electrodes (length 15.4
cm, width 6.5 cm, interval 3.5 cm), and was placed in the glass tube (inner diameter 8 cm) as described above, and a glass capillary tube with a diameter of 200 μm was placed on the longitudinal center line of the interelectrode space. The electrodes were each shaped like a semi-cylindrical box so that water could pass through the space formed by the glass tube wall that was not between the electrodes, and the electrodes were cooled with water.

The inside of the glass tube was evacuated (0.05 Torr), argon was flowed at 2.8 cm ³ STP/min and about 0.45 Torr, and the monomer was further flowed to carry out plasma polymerization under the following conditions.

Electrode temperature 19℃ Argon flow rate 2.8cm ³ STP/min Monomer (2,2,3,4,4,4-hexafluorobutyl methacrylate) flow rate
0.3cm ³ STP/min Gas pressure 0.5Torr Discharge power 7 Watts Discharge frequency 13.56MHz Discharge time 420min After plasma polymerization, the glass tube was taken out, metal evaporated (gold) was deposited, and observed with an electron microscope. A cylindrical polymer with a diameter of 285 μm was formed around a glass capillary. The irregularities on the outer periphery were 0.1 μm or less, and the coating speed was about 6 μm/hr.

Example 2 In the same manner as in Example 1, the following substrate was subjected to plasma polymerization in the center between the electrodes.

The substrate used was a 200 μm glass bulb (manufactured by Tokyo Shibaura Electric Co., Ltd., GB705) adhered to the tip of a glass capillary tube with an outer diameter of 70 μm using Araldite. The glass bulb was coated with a polymer coating, had a diameter of 285 μm, had a smooth surface, and had an uneven surface of 0.1 μm or less, and a uniform coating with a thickness of 40 μm was formed around the glass capillary. Coating speed is approximately 6μm/
It was hot at hr.

Example 3 Plasma polymerization was carried out in the same manner as in Example 1 except that methyl methacrylate was used as the monomer. A cylindrical polymer with an outer diameter of 275 μm was formed around a glass capillary. The unevenness of the outer periphery is 0.1μ
The coating speed was approximately 5.5 μm/hr.

[Brief explanation of drawings]

The drawing is a schematic diagram of the main parts of a plasma polymerization apparatus used in the method of the present invention. Explanation of symbols in the drawings: 1, 3: polytetrafluoroethylene insert, 2: electrode, 4: glass tube.

Claims (1)

[Claims] 1. A method for forming a smooth coating of an ablator shell on a substrate as an ablator shell for fuel globules in nuclear fusion, which comprises plasma polymerizing an alkyl (meth)acrylate or a fluoroalkyl (meth)acrylate on the substrate.