Coating processes – Direct application of electrical – magnetic – wave – or... – Plasma
Reexamination Certificate
2000-06-09
2001-09-25
Pianalto, Bernard (Department: 1762)
Coating processes
Direct application of electrical, magnetic, wave, or...
Plasma
C118S050000, C118S500000, C118S7230IR, C118S7230VE, C427S248100, C427S585000
Reexamination Certificate
active
06294227
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of forming a protective film with scratch-proofness and ultraviolet cutting characteristic on a surface of a plastic car part.
2. Description of the Related Art
Thermoplastic materials which can be easily recycled are widely used for car-use parts, or the like, in order to reduce weight and protect the environment. For example, a polycarbonate resin is mainly used as a lens material for a car headlamp to reduce weight and provide high impact strength. If such a plastic material is used for an exterior part of a car, there is, however, a weak point that the exterior part is apt to be scratched because the material itself is low in surface hardness and that the exterior part is deteriorated by ultraviolet rays and heat radiated from the sun to thereby cause discoloration, deformation and reduction in strength.
To compensate for the weak point, a protective film with scratch-proofness and ultraviolet cutting characteristic was heretofore formed mainly on a plastic surface, for example, by spraying acrylic paint.
The shape of such a plastic part used in a car was, however, a diversified and complex three-dimensional shape. In a surface coating process for spraying paint onto such an part, it was difficult to form a protective film with a uniform thickness. Moreover, coating efficiency onto a plastic surface was so low that most of an organic solvent might be wastefully released into the atmosphere or the paint might be deposited on an undesirable surface.
Therefore, it is required that a protective film of uniform thickness and good quality with scratch-proofness and ultraviolet cutting characteristic and the like be formed on a plastic part having a diversified and complex three-dimensional shape while wasteful release of an organic solvent, or the like, into the atmosphere can be avoided.
SUMMARY OF THE INVENTION
In order to achieve the above object, according to a first aspect of the invention, there is provided a method of forming a protective film on a car-use plastic part by use of a plasma chemical vapor deposition apparatus in which a shape of at least one part of a surface of a cathode provided in a reaction chamber coincides with a shape of a surface of a thin car-use plastic part, the method comprising the steps of: attaching the plastic part to the cathode in a condition that the two surfaces coincident in shape come into contact with each other; and performing plasma chemical vapor deposition by supplying high-frequency electric power between the reaction chamber and the cathode while importing a hydrogen gas and an organic silicon gas into the reaction chamber. According to this method, the organic solvent, or the like, is not wastefully released into the atmosphere because the protective film is formed by plasma chemical vapor deposition in the reaction chamber. Moreover, the efficient dissociative ionization of the organic silicon gas is efficiently dissociated so as to be ionized by the action of hydrogen radicals in the hydrogen gas; the potential of the cathode becomes a negative bias value so that an ion sheath is formed with ions concentrated in the periphery of the cathode; and the plastic part can be disposed in the ion sheath so that ions in the ion sheath are attracted toward the cathode uniformly and slowly and deposited, as a film of approximately uniform thickness, on a surface of the plastic part. Hence, a protective film of approximately uniform thickness and good quality can be formed on the surface of the plastic part having such a complex three-dimensional shape. Moreover, the organic silicon is a high-safety material which has molecules containing Si—C bonds for providing hardness and absorbing ultraviolet rays. Hence, the protective film with scratch-proofness and ultraviolet cutting characteristic can be obtained safely and easily.
According to a second aspect of the invention, the organic silicon gas is hexamethyldisilane. Hexamethyldisilane is a fire-resistant high-safety material which contains Si—Si bonds and Si—C bonds. Hence, the Si—Si bonds are first broken by the action of the hydrogen radicals to thereby form a precursor. The precursor is deposited on the surface of the plastic part to thereby form a protective film more efficiently. Moreover, the protective film obtained by this method can transmit visible light so as to be kept highly transparent while cutting ultraviolet rays.
According to a third aspect of the invention, the organic silicon gas is composed of monosilane and hexamethyldisilane in the condition that the molar ratio of monosilane to hexamethyldisilane is in a range of from 0:1 to 5:1. The protective film thus obtained can cut ultraviolet rays more sufficiently because the addition of monosilane permits the protective film to contain a large amount of Si having a function of making ultraviolet absorption good.
According to a fourth aspect of the invention, the hexamethyldisilane is imported together with a helium carrier gas into the reaction chamber. Hence, even hexamethyldisilane low in vapor pressure at room temperature can be imported into the reaction chamber sufficiently as long as it is mixed with the helium carrier gas.
According to a fifth aspect of the invention, a car-use plastic headlamp lens has a protective film formed on a surface of the lens by a method defined as above. The car headlamp lens has good scratch-proofness and ultraviolet light resistance because the protective film of approximately uniform thickness and good quality with scratch-proofness and ultraviolet cutting characteristic is formed on a surface of the lens. Moreover, a contribution to the protection of the environment can be made because an organic solvent, or the like, is not wastefully released into the atmosphere when the protective film is formed. In addition, the lens does not suffer from deformation and deterioration due to heat at the time of the formation of the protective film.
According to the present invention, a protective film containing an SiC (silicon carbide) polymer is formed on a surface of a car-use plastic part by a cathode deposition method using plasma chemical vapor deposition (hereinafter referred to as plasma CVD) in order to give scratch-proofness, ultraviolet light resistance, etc. to a plastic material such as a polycarbonate resin.
REFERENCES:
patent: 4998968 (1991-03-01), Misumi
patent: 5554418 (1996-09-01), Ito et al.
patent: 5840374 (1998-11-01), Ito et al.
patent: 6025013 (2000-02-01), Heming et al.
patent: 6070551 (2000-06-01), Li et al.
Anma Hidetaka
Hatanaka Yoshinori
Koito Manufacturing Co. Ltd.
Pianalto Bernard
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Method of forming protective film on plastic part for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of forming protective film on plastic part for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of forming protective film on plastic part for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2464567