Abstract: A glass-ceramic substrate for a magnetic disk suitable for use as a contact recording type magnetic disk includes alpha-cristobalite (alpha-SiO.sub.2) and lithium disilicate (Li.sub.2 O . 2SiO.sub.2) as main crystal phases. The ratio of alpha-cristobalite/lithium disilicate is within a range from 0.25 to 0.35, a grain diameter of crystal grains is within a range from 0.1 .mu.m to 1.0 .mu.m, surface roughness (Ra) of the substrate after polishing is within a range from 2 .ANG. to 10 .ANG. and abrasion resistance index (Aa) of the substrate is within a range from 5 to 15.

Abstract: An adjuvant composition for agricultural chemicals comprising at least one sorbitan/fatty acid ester surfactant (A) and at least one surfactant (B) selected from the group consisting of resin acid surfactants and anionic oligomer or polymer type quaternary ammonium salt surfactants can be used for various crops in safety without causing injury thereof to the crops, and can enhance the efficacies of various agricultural chemicals.

Abstract: A magnetic disk substrate is made of a glass-ceramic having crystal phases of lithium disilicate (Li.sub.2 O.2SiO.sub.2) and alpha-quartz (SiO.sub.2). The crystal phase of alpha-quartz is formed of grown crystal grains each having a globular grain structure made of aggregated particles. Each globular grain has a size within a range from 0.3 .mu.m to 3 .mu.m. Surface roughness (Ra) of a polished surface of the magnetic disk substrate is within a range from 15 .ANG. to 50 .ANG. which is an optimum range of surface roughness for the magnetic disk.

Abstract: A method for detecting a defect in a glass-ceramic for magnetic disks includes steps of forming a colored glass-ceramic having Munsell value within the range of 0 to 7 in the CIE color system by subjecting to heat treatment a base glass comprising in weight percent:______________________________________ SiO.sub.2 65-83% Li.sub.2 O 8-13% K.sub.2 O 0-7% MgO + ZnO + PbO 0.5-5.5% in which MgO 0.5-5.5% ZnO 0-5% PbO 0-5% P.sub.2 O.sub.5 1-4% Al.sub.2 O.sub.3 0-7% As.sub.2 O.sub.3 + Sb.sub.2 O.sub.3 0-2% a coloring agent of at least one ingredient 0.5-5% selected from the group consisting of metal oxides of V, Cu, Mn, Cr, Co, Mo, Ni, Fe, Te, Ce, Pr, Nd and Er ______________________________________and checking the glass-ceramic visually or by means of an automatic checking device for detecting a defect in the glass-ceramic.

Abstract: A magnetic disk substrate is made of a glass-ceramic having crystal phases of lithium disilicate (Li.sub.2 O.2SiO.sub.2) and alpha-quartz (SiO.sub.2). The crystal phase of alpha-quartz is formed of grown crystal grains each having a globular grain structure made of aggregated particles. Each globular grain has a size within a range from 0.3 .mu.m to 3 .mu.m. Surface roughness (Ra) of a polished surface of the magnetic disk substrate is within a range from 15 .ANG. to 50 .ANG. which is an optimum range of surface roughness for the magnetic disk.

Abstract: A glass-ceramic for a magnetic disk substrate in which the grain size can be controlled and the surface roughness after polishing is within the range from 15 .ANG. to 50 .ANG. is provided by heat treating a base glass including in weight percent:______________________________________ SiO.sub.2 65-83% Li.sub.2 O 8-13% K.sub.2 O 0-7% Mgo + ZnO + PbO 0.5-5.5% in which MgO 0.5-5.5% ZnO 0-5% PbO 0-5% P.sub.2 O.sub.5 1-4% Al.sub.2 O.sub.3 0-7% As.sub.2 O.sub.3 + Sb.sub.2 O.sub.3 0-2% ______________________________________The glass-ceramic contains lithium disilicate (Li.sub.2 O. 2SiO.sub.2) and alpha-quartz (SiO.sub.2) as the main crystal phases.

Abstract: An optical glass which is a SiO.sub.2 -Nb.sub.2 O.sub.5 -R'.sub.2 O (where R' is an alkali metal element)-F system of a specific composition range exhibits optical constants of a refractive index (Nd) of about 1.52-1.67 and an Abbe number (.upsilon. d) of about 32-50, is free of PbO and has an improved light transmissivity.

Abstract: An optical glass which is a SiO.sub.2 --TiO.sub.2 --K.sub.2 O--RO (where R represents Mg, Ca, Sr, Ba and Zn metal elements) system glass of a specific content range exhibits optical constants of a refractive index (Nd) of about 1.58-1.78 and Abbe number (.nu.d) of about 28-45, is free of PbO and has an improved property against devitrification.

Abstract: An optical glass which is a SiO.sub.2 --B.sub.2 O.sub.3 --(TiO.sub.2 +ZrO.sub.2)--SrO--BaO--R'.sub.2 O system of a specific composition range exhibits optical constants of a refractive index (Nd) of 1.57-1.75 and Abbe number (.nu.d) of 30-55, is free of PbO and has improved stability against devitrification and tinting and improved chemical durability.

Abstract: A polyester film for printed circuits to be used as a base in a printed circuit base plate or as a base and/or cover layer in a printed circuit board, which undergoes a degree of dimensional stability of not more than 1% in both the longitudinal and transverse directions when kept at 150.degree. C. for 30 minutes, and which is obtained by heat treating an extrusion molded and stretched polyester film at 150.degree. C. to 240.degree. C. without applying tension.

Abstract: A siloxane-modified polyimide precursor which can be converted into a polyimide having excellent adhesion and moisture resistance is produced by simultaneously polymerizing a diaminosiloxane and a diamine containing no silicon atoms in its molecule with 3,3',4,4'-biphenyltetracarboxylic dianhydride, wherein the diaminosiloxane is used in an amount of 1 to 4 mole % per mole of the total diamino compounds and such that the silicon content in the final reaction product is 0.5 wt % or less. The thus obtained precursor solution is further heat aged to reduce the molecular weight of the precursor so that solution viscosity is decreased to a proper level suitable for coating operation.

Abstract: A process for producing a polyimide precursor having excellent adhesion property and improved moisture resistance by polymerization of an organic tetracarboxylic acid component and a diamine is disclosed. A portion of the organic tetracarboxylic acid is reacted with an aminosilane compound in which H in an amino group is substituted with a monovalent organic group containing a hydrophobic aromatic ring, to produce a silane-modified polycarboxylic acid component and the resulting silane-modified polycarboxylic acid component is polymerized with a diamine together with the residual organic tetracarboxylic acid component.

Abstract: A method for stabilizing a water-soluble resin composition which comprises adding, as a stabilizing agent, a carbonate and/or an organic carboxylate of a basic nitrogenous compound to the water-soluble composition in an amount of from about 0.01 to about 10 parts by weight based on 100 parts by weight of the resin content in the water-soluble composition, the water-soluble composition being prepared by condensation reacting an acid component consisting of 1,2,3,4-butane tetracarboxylic acid alone or a polycarboxylic acid component containing at least about 50 mol% of 1,2,3,4-butane tetracarboxylic acid and a diamine in the presence of a water-soluble solvent or, optionally, in the presence of the water-soluble solvent and water to obtain a condensation product having a residual acid value ratio of about 3 to about 50% of the acid value before condensation followed by formation of a salt of the condensation product with a basic nitrogenous compound.

Abstract: A polyester having imide rings in the molecule comprising the reaction product of (1) a polyhydric alcohol component comprising an imide ring containing diol represented by the formula (I) ##STR1## wherein Ar.sub.1 represents a trivalent aromatic group; Ar.sub.2 represents a divalent aromatic group; and m and n each represents an integer of 1 to 6; with the diol comprising the reaction product of 2 moles of an aromatic tricarboxylic acid anhydride of the formula (II) ##STR2## wherein Ar.sub.1 has the same meaning as above, with 1 mole of a diamine of the formula (III)h.sub.2 n -- ar.sub.1 -- NH.sub.2 (III)wherein Ar.sub.2 has the same meaning as above, in the presence of ethylene carbonate; with (2) a polycarboxylic acid component comprising at least one of a polycarboxylic acid and a lower alkyl ester thereof; and a wire enamel containing at least one polyester having imide rings in the molecule as described above.

Abstract: An imide-ring containing polyester comprising the reaction product of(A) (1) a dicarboxylic acid of the formula ##EQU1## wherein R.sub.1 represents a divalent organic group, R.sub.2 represents a trivalent organic group, and n.gtoreq.1, the dicarboxylic acid of the formula (I) comprising the reaction product of 1 mole of an imide compound having terminal amino groups of the formula (II) ##EQU2## wherein R.sub.1 has the same meaning as above, or of an imide precursor thereof, with 2 moles of a tricarboxylic acid anhydride of the formula (III) ##EQU3## wherein R.sub.2 has the same meaning as above, the imide compound of the formula (II) being prepared by reacting n moles of 1,2,3,4-butanetetracarboxylic acid (hereinafter referred to as BTC) with (n+1) moles of a diamine of the formula (IV)h.sub.2 n--r.sub.1 --nh.sub.2 (iv)wherein R.sub.