Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-04-01
2002-01-01
Crispino, Richard (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S238000, C156S247000, C156S254000, C156S345420, C118S035000, C428S001100, C428S001200, C428S001600, C428S458000
Reexamination Certificate
active
06334922
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a coated material having an isotropic coating layer that is obtained by peeling a portion of a film press-fitted to a base material such as a metal foil and made of a polymer capable of forming an optically anisotropic melt phase, and a method of making the coated material. The present invention also relates to a metal-polymer laminate obtained by peeling a portion of the polymer film firmly sandwiched between metal foils, in a direction thicknesswise thereof, and a method of making the metal-polymer laminate.
In the description of the present invention, the polymer capable of forming an optically anisotropic melt phase is referred to as a “liquid crystal polymer”; the film made of the liquid crystal polymer is referred to as a “liquid crystal polymer film”; and the coated material is intended to mean an article of manufacture formed with the liquid crystal polymer coating layer by coating the liquid crystal polymer to the base material.
2. Description of the Prior Art
The liquid crystal polymer has been well known which has various advantageous features including (1) a capability of being thermally bonded directly to a metallic foil layer; (2) a high resistance to heat; (3) a low moisture absorbability; (3) an excellent dimensional stability to thermal change in size; (5) an excellent resistance to change in size brought about by moisture; (6) an excellent property in high frequency characteristic; (7) a fire-proof property with no need to add a flame retardant containing a toxic halogen, phosphorus, antimony and others; (8) an excellent resistance to chemicals; (9) an excellent resistance to radiations; (10) having a controllable thermal expansion coefficient; (11) a flexibility at low temperatures; (12) a property of a high gas barrier (a considerably low permeability to a gaseous material such as, for example, oxygen), and so on.
In recent years, demands have been arisen to use such excellent liquid crystal polymer as a coating material to be applied in the form of a thin film to a metallic foil layer, a silicon plate or a ceramics plate to provide a base material for a precision circuit substrate, a multi-layered circuit substrate, a sealing material or a package can. In addition, because of the resistance to heat and chemicals, the low moisture absorbability and the gas barrier property, demands have increased for the use of the liquid crystal polymer as a coating material that can be utilized to form a protective layer on a metal susceptible to corrosion.
The first problem in utilizing the liquid crystal polymer as a coating material will first be discussed:
To form a thin skin film of, for example, a synthetic resin over the surface of an article of manufacture, various methods have been known such as, for example, a lining process and a coating process. The lining process and the coating process are known to be distinct from each other because of the following reasons. Specifically, the coating process has a primary objectivity in decorative purpose to form a continuous skin film over the article to thereby protect the article from corrosion and contamination and also to provide the article with an appealing ornament and is also often used to form a film for imparting a non-adhesive property and a low frictional property. On the other hand, the lining process is a process of forming a protective thick film on vessels (baths) and tubes or pipes that are used in the chemically and/or physically severe environment where corrosion and/or erosion are strictly desired to be avoided. However, the coating and lining processes have features so common to each other that the line of distinction can hardly be drawn therebetween. It is generally recognized that the skin layer having a thickness of 0.5 mm or more is classified as a lining whereas the skin film having a thickness of 0.5 mm or less is classified as a coating. It is also generally recognized that the coating is to form a film of several tens microns mainly on a surface of a structure whereas the lining is to form a film of several hundreds microns.
In either case, the present invention pertains to a technique of forming on a base material a very thin film of a liquid crystal polymer to a thickness of 25 &mgr;m or less, particularly 15 &mgr;m or less and may therefore be said to pertain to the coating technique.
As one of important properties of the coating, attention is centered on the durability of the coating against change in temperature and, however, this leads to a problem of how the difference in thermal expansion coefficient between the coating and the base material bearing the coating should be resolved. While the coating process includes, inter alia, (1) a dipping method, (2) a flow coating method, (3) a curtain coating method, (4) a roll coating method, (5) an electro-deposition method, (6) a brush coating method, (7) a spray coating method and (8) a gas-phase coating method, none of these known methods can be utilized to form a film of a liquid crystal polymer by the following reason. Specifically, due to a unique property of the liquid crystal polymer in that molecules of the liquid crystal polymer have a propensity of orienting in the same direction, the liquid crystal polymer molecules tend to be oriented in the same direction when a force is applied to a molten liquid crystal polymer being applied to form a thin film. Considering that the physical property such as thermal expansion coefficient measured in a direction conforming to the molecular orientation is considerably different from that measured in a direction transverse to the molecular orientation, that is, the liquid crystal polymer has an anisotropy, it is impossible to render the coating-bearing base material and the layer of the liquid crystal polymer to have the same or substantially same thermal expansion coefficient in all directions on a plane. Although the prior art coating process is capable of providing a liquid crystal polymer layer of a large thickness of, for example, 50 &mgr;m or more, it has been found that the resultant liquid crystal polymer layer has an anisotropy and is therefore incapable of being used as a practically utilizable coating. Nonetheless, no technique of forming a layer of a liquid crystal polymer having an improved isotropy to a thickness of 15 &mgr;m or less have hitherto been made available.
The second problem will now be discussed:
Circuit substrates or the like that are generally utilized in the field of electronics make use of a metal-resin laminate prepared by press-bonding together a foil layer of an electroconductive metal and a film-like insulating material (a film or a sheet with or without a metallic foil layer coated thereon) having an electrically insulating property. The metal-resin laminate is available in the form of a double-sided metal-resin laminate in which an electric insulating layer is sandwiched between two metallic foil layers and of a single-sided met al-resin laminate in which a single metallic foil layer and a single electric insulating layer are bonded together. The liquid crystal polymer having the excellent properties as discussed above is generally recognized as an ideal material for the electric insulating layer used in the laminates.
As a method of making a metal-polymer laminate without diminishing the excellent properties of the liquid crystal polymer, various methods have been well known. (i) Specifically, in the case of the double-sided metal-polymer laminate, the method is known to comprise sandwiching a liquid crystal polymer layer between two metallic foil layers, and hot-pressing the resultant sandwich structure with the use of a hot plate or a hot roll to cause the liquid crystal polymer to melt so that the metallic foil layers and the liquid crystal polymer layer can be thermally bonded together to eventually provide the double-sided metal-polymer laminate upon solidification of the liquid crystal polymer. (ii) On the other hand, in the case of the single-sided metal-polymer laminat
Onodera Minoru
Sato Toshiaki
Tanaka Yoshinobu
Tsudaka Takeichi
Crispino Richard
Kuraray Co. Ltd.
Lorengo J. A.
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