Abstract: Ultra high molecular weight epoxy resins are produced in a short time by polymerizing a difunctional epoxy resin having two epoxy group per molecule and a dihydric phenol by heating the difunctional epoxy resin and the dihydric phenol which are present in quantities which provide a ratio of phenolic hydroxyl groups to epoxy groups of from 1:0.9 to 1:1.1, in an amide solvent, in the presence of a polymerization catalyst, and the ultra high molecular weight epoxy resins are linearly polymerized so highly as to have the capability of being formed into films having high strength.

Abstract: An epoxy resin film which is so strong as to have a tensile strength of not less than 10 MPa and an elongation of not less than 5% is formed by using a substantially linear high molecular weight epoxy resin which is synthesized by polymerizing a difunctional epoxy resin having two epoxy groups per molecule and a dihydric phenol in an aprotic polar solvent, in the presence of a solvent, at a reaction temperature ranging from 80.degree. to 130.degree. C., the difunctional epoxy resin and the dihydric phenol being used in quantities which provide a ratio of phenolic hydroxyl groups to epoxy groups of from 1:0.9 to 1:1.1 and a proportion of the total of them of at most 50% by weight based on the total of them and the aprotic polar solvent.

Abstract: An epoxy resin film which is so strong as to have a tensile strength of not less than 10 MPa and an elongation of not less than 5% is formed by using a substantially linear high molecular weight epoxy resin which is synthesized by polymerizing a difunctional epoxy resin having two epoxy groups per molecule and a dihydric phenol in an aprotic polar solvent, in the presence of a solvent, at a reaction temperature ranging from 80.degree. to 130.degree. C., the difunctional epoxy resin and the dihydric phenol being used in quantities which provide a ratio of phenolic hydroxyl groups to epoxy groups of from 1:0.9 to 1:1.1 and a proportion of the total of them of at most 50% by weight based on the total of them and the aprotic polar solvent.

Abstract: A switching regulator including a control circuit including a deviation detector for detecting a deviation between the detection value of the controlled variable and the reference value, a phase difference signal generator for generating a phase difference signal having a pulse width corresponding to the deviation, a reference signal shaper for shaping two reference signals of the same waveform having a phase difference corresponding to the pulse width of the phase difference signal, and a control signal generator for ON/OFF control of switching elements corresponding to the reference signals for controlling a switching circuit having transistors connected as the switching elements in a bridge formation, the switching elements are all driven with an equal ON/OFF ratio, the phase difference between the ON instructions to the two sets of the switching elements is controlled to control the output so that the control of the switching regulator is accomplished not by the pulse width for driving the switching eleme

Abstract: Copper-clad laminates for printed wiring boards with almost no warpage can be produced continuously without using a solvent by continuously running a continuous, fibrous substrate, supplying partially and intermittently a solventless thermosetting resin mixture to the running substrate, laminating a copper foil at least one surface of the running substrate, pressure molding with heating the copper foil laminated substrate in a mold comprising a pair of flat plates at least one of which has projecting portions tapered to the center of the flat plate at the periphery thereof, taking off and cutting the molded laminate.