Abstract: The present invention relates to A backlight system including an adherend for outgoing light, an optical film subjected to embossing or roughening processing treatment so as to increase the surface area thereof, and a pressure-sensitive adhesive layer containing a pressure-sensitive adhesive polymer having a gel fraction of 35 to 85%, in which the adherend and the optical film are joined through the pressure-sensitive adhesive layer. Further, the invention relates to a process for producing the backlight system, an optical sheet with a pressure-sensitive adhesive which is used in the backlight system, and an image display and an illuminating system using the backlight system.

Abstract: A negative photoresist composition is disclosed which is excellent in sensitivity and resolution, tenaciously adheres to substrates, and can be advantageously used in practical production processes. Two 1,4-dihydropyridine derivatives each having a specific structure are incorporated as photosensitizers into a polyamic acid to obtain the negative photoresist composition.

Abstract: A polyimide-metal foil composite film comprising a conductive metal foil having directly laminated on at least one surface thereof a polyimide resin layer which comprises repeating units represented by formulae (1) and (2) as described hereinabove. The polyimide-metal foil composite film can be used as a circuit substrate having excellent dimensional stability under high temperature.

Abstract: A heat-resistant negative-working photoresist composition comprising a resin component having a carbodiimide unit in the molecule, and a compound capable of inducing a basic compound by irradiation with actinic rays. The photosensitive layer formed by the photoresist composition shows a sufficient sensitivity even by a lower irradiation energy and can give a sharp negative-type pattern by irradiation with actinic rays such as ultraviolet rays.

Abstract: A heat-resistant negative-working photoresist composition comprising a resin component having a carbodiimide unit in the molecule, and a compound capable of inducing a basic compound by irradiation with actinic rays. The photosensitive layer formed by the photoresist composition shows a sufficient sensitivity even by a lower irradiation energy and can give a sharp negative-type pattern by irradiation with actinic rays such as ultraviolet rays.

Abstract: A heat-resistant adhesive film, an adhesion structure obtained using the same, and an adhesion method using the same are disclosed, the film comprising a polyisoimide resin containing at least 40 mol % of an isoimide unit represented by formula (I): ##STR1## wherein R.sub.1 represents a tetravalent aromatic or aliphatic residue; R.sub.2 represents a divalent aromatic or aliphatic residue; and the arrow represents a bond replaceable on isomerization, in the molecule thereof. The isoimide unit of the polyisoimide resin is easily converted to an imide unit on heating, e.g., hot pressing with an adherend, to provide a cover-lay film or a single-sided or double-sided base for printed circuit boards having excellent adhesion, heat resistance, dimensional precision, and workability.

Abstract: An anisotropic electrically conductive adhesive film having fine through holes independently electroconductively passing through an insulating film in the thickness direction, at least one end portion of both the end portions of the each through hole on the front and back surfaces of said film being blocked with a bump-form metal projection having a larger base area than the area of the opening portion of the through hole, wherein the insulating film comprises a thermoplastic polyimide resin having a melt viscosity at 400.degree. C. of not higher than 1.times.10.sup.8 poise is disclosed. The film is interposed between materials to be connected to provide a connection structure.

Abstract: A flexible printed substrate imparted with an adhesive property for loading on an external substrate, a double printed substrate having formed on both surfaces thereof a metal layer or a wiring circuit, and a multilayer substrate having a multilayer structure are disclosed. The flexible printed substrate comprises an insulating resin layer comprising a low-linear expansion polyimide resin layer and a thermoplastic polyimide resin layer, and a metal layer or a wiring circuit formed on the low-linear expansion polyimide resin layer of the insulating resin layer, wherein a mixed region of the polyimide resin components is formed in the interface between the low-linear expansion polyimide resin layer and the thermoplastic polyimide resin layer.

Abstract: An intra-ocular lens comprising a lens part and a fixing part for fixing the lens part in an eye, the lens part comprising a colorless and transparent polyimide containing at least one of repeating units represented by formulae (I) to (IV): ##STR1## wherein X.sub.1 represents ##STR2## X.sub.2 represents ##STR3## X.sub.3 represents ##STR4## Further, the lens part and the fixing part may be integrally molded together, if desired.

Abstract: An intra-ocular lens comprising a lens part and a fixing part is disclosed, said lens part comprising a colorless transparent polyimide consisting mainly of a repeating unit represented by formula (I): ##STR1## The intra-ocular lens exhibits compatibility with the organism, chemical inactivity, and insusceptibility to modification or deterioration by the organism, has a refractive index of 1.6 or higher, completely absorbs ultraviolet rays while exhibiting substantial transparency to visible rays, and possesses heat resistance enough to withstand autoclaving.

Abstract: A polyamide acid solution is disclosed, comprising a polyamide acid comprising as main components at least one recurring unit selected from the recurring units of the formulae (I) to (IV) and a recurring unit of formula (V), dissolved in an organic solvent comprising as a main component an amide type polar solvent having a boiling point of 170.degree. C. or less. The solution is capable of forming a polyimide film which has colorless transparency free from coloration and strong adhesion to a substrate for liquid crystal cell enough to prevent penetration of water into interface between the substrate and film. The solution is particularly useful for forming a liquid crystal oriented film.

Abstract: A colorless transparent polyimide shaped article having as a main component at least one recurring unit selected from the recurring units of the formulae (I) to (IX). It is useful, for example, as an oriented film in liquid crystal display devices. The polyimide shaped article is produced by a process which comprises preparing a solution of a polyamide acid having as a main component at least one recurring unit selected from the recurring units of the formulae (V) to (VIII) in an amide-type organic polar solvent, forming a shaped article of the polyamide acid from the solution, and imidizing the resulting shaped article of the polyamide acid.

Abstract: A colorless transparent polyimide shaped article having as a main component at least one recurring unit selected from the recurring units of the formulae (I) to (III), which is useful, for example, as an oriented film in liquid crystal display devices. The polyimide shaped article is produced by a process which comprises preparing a solution of (A) a polyimide precursor obtained by reacting a diamino compound comprising as a main component at least one aromatic diamine having amino groups at the m-position selected from diamines of formulae (IV) to (VI) with a tetracarboxylic acid compound comprising as a main component a tetracarboxylic acid dianhydride of formula (VII) dissolved in (B) at least one organic polar solvent selected from N,N-dimethylacetamide, N,N-dimethylformamide, bis(2-methoxyethyl)ether, cresol and halogenated phenols; forming a shaped article of the polyimide precursor from the solution; and imidizing the resulting shaped article.