A diamine monomer compound with a structural formula of

##STR00001##

wherein n.sub.1 is an integer greater than 1, forms the basis of a dielectric material with reduced dielectric losses for improved signals transmission. A method for preparing the compound, a polyimide resin made from the compound, a flexible film, and an electronic device including the polyimide resin are also disclosed. The compound has a long but flexible even numbered carbon chain and a liquid crystal unit structure. The reduced regularity and rigidity of the molecular chain make the polyimide resin convenient for film-forming. Dimensional stability is improved, the coefficient of thermal expansion of the materials is reduced, and the materials have good mechanical and thermal properties, the electron loss factor and coefficient of thermal expansion of the materials being reduced.

In a first aspect, a polyimide film includes a polyimide derived from a dianhydride and a diamine. The dianhydride includes pyromellitic dianhydride, the diamine includes a benzimidazole, the molar ratio of dianhydride to diamine that forms the polyimide is in a range of from 0.85:1 to 0.99:1, and the polyimide film has a T.sub.g of 400° C. or higher, a tensile modulus of 6.0 GPa or more, and a coefficient of thermal expansion of 15 ppm/° C. or less over a temperature range of 50 to 500° C. In a second aspect, an electronic device includes the polyimide film of the first aspect.

An electronic device including a flexible substrate, a plurality of light emitting units, and a plurality of supporting elements is provided. The flexible substrate has a first surface and a second surface opposite to each other. The light emitting units are disposed on the first surface. The supporting elements are disposed on the second surface. The supporting element includes an arc-shaped structure.

A polyimide composite film for use in a flexible metal clad substrate, comprising: a polyimide base material film; a fluorine polymer layer, formed on at least one surface of the polyimide base material film, comprising polyimide resins and fluorine polymers, wherein the polyimide resin accounts for 2 to 20 wt % of the total solid content of the fluorine polymer layer, the aromatic functional group ratio of the polyimide resin in the fluorine polymer layer is greater than 35%, and the absorption onset wavelength (λonset) of the ultraviolet-visible spectrum is greater than 360 nm; a thickness ratio of the polyimide base material film to one layer of the fluorine polymer layers is 8:1 to 1:4; and a total thickness of the polyimide composite film is between 18 and 175 microns. Thus, the polyimide composite film has a low dielectric constant, low loss factor, and has good drilling processability.

A metal substrate includes a first insulating substrate, a second insulating substrate, a first metal layer, a second metal layer and a release layer. The first insulating substrate has a first modified surface and a second surface opposite to the first modified surface. The first metal layer faces the second surface. The release layer is bonded on the first modified surface. The second insulating substrate is bonded on a side of the release layer, such that the release layer is between the first modified surface and the second insulating substrate. The second metal layer is disposed on a side of the second insulating substrate, such that the second insulating substrate is between the release layer and the second metal layer. An original surface roughness of the first modified surface has a variation substantially less than 10% after the first modified surface is released from the release layer.

A flexible printed circuit board includes a base film having an insulating property and a conductive pattern laminated on one surface of the base film, and has a terminal connecting area toward one end edge of the conductive pattern, the flexible printed circuit board including a reinforcement member laminated on an opposite surface of the base film and situated at least at a position opposite the terminal connecting area, wherein the reinforcement member has one or more lines of hollow holes aligning with a width direction thereof.

The conductive composition of the present embodiment contains metal nanoparticles having an average particle diameter of 30 nm to 600 nm, metal particles having an average particle diameter larger than that of the metal nanoparticles, a thermosetting resin having an oxirane ring in a molecule, a curing agent, and a cellulose resin. Then, the specific resistance of the conductor formed by applying and calcining the conductive composition on the substrate is preferably 5.0×10.sup.−6 Ω.Math.cm or less, and the conductor does not peel from the substrate when a tape having an adhesive force of 3.9 N/10 mm to 39 N/10 mm is pressed against the conductor and peeled off.

The present disclosure relates to a printed circuit and an electronic device including the same. The printed circuit board includes a first substrate having a through portion, a second substrate disposed in the through portion of the first substrate, and in which at least a portion of a side surface thereof is surrounded by the first substrate, and a flexible substrate disposed in the through portion of the first substrate and connecting the first and second substrates.

A planar antenna includes: a radiating element; a flexible dielectric film portion; a power feeder line provided for the dielectric film portion, and configured to feed power to the radiating element; a first ground conductor facing against the radiating element; and an antenna base having a dielectric layer disposed between the radiating element and the first ground conductor. The dielectric film portion extends from a side surface of the antenna base. The dielectric layer is thicker than the dielectric film portion.

A flexible and/or stretchable structural system for transmitting electrical signal between first and second rigid portions comprises a body structure and said first and second portions arranged to said body structure. The modulus of elasticity of said first portion is lower than the corresponding modulus of elasticity of said second portion. In addition the modulus of elasticity of said body structure is lower than the corresponding modulus of elasticity of said second portion. The system comprises also an interface portion, such as e.g. an electrically conducting fabric, textile or knit, which is arranged to said body structure and between said first and second portions. The interface portion electrically connects said first and second portions. The modulus of elasticity of said interface portion is lower than the corresponding modulus of elasticity of said second portion.