An electrostatic filter according to one embodiment of the present invention is an electrostatic filter including a first layer and a second layer, the first layer being provided with a base and a plurality of firm protuberances extending from a face of the base and adjacent to the second layer, the protuberances including a stem having a root-ward side surface and a tip side surface, the second layer being provided with a base, a first angle constituted by either an angle between the root-ward side surface of the stem and the base of the first layer or an angle between the tip side surface of the stem and the base of the second layer being at least 90° and less than 180, and a second angle constituted by the other of the two angles thereof being at least 45° and less than 180°.

An electrostatic filter according to one embodiment of the present invention is an electrostatic filter including a first layer and a second layer, the first layer being provided with a base and a plurality of firm protuberances extending from a face of the base and adjacent to the second layer, the protuberances including a stem having a root-ward side surface and a tip side surface, the second layer being provided with a base, a first angle constituted by either an angle between the root-ward side surface of the stem and the base of the first layer or an angle between the tip side surface of the stem and the base of the second layer being at least 90° and less than 180, and a second angle constituted by the other of the two angles thereof being at least 45° and less than 180°.

A filtration material of the present invention comprises a bulky fiber sheet layer having a thickness of 0.5 mm or more, and a triboelectrically-charged nonwoven fabric layer in which two or more types of fibers different in constituent resin are mixed, wherein constituent fibers of the triboelectrically-charged nonwoven fabric layer penetrate into the bulky fiber sheet layer. A three-layer filtration material of the present invention comprises bulky fiber sheet layers having a thickness of 0.5 mm or more, and a triboelectrically-charged nonwoven fabric layer, which is located between the bulky fiber sheet layers, wherein the constituent fibers of the triboelectrically-charged nonwoven fabric layer penetrate into the bulky fiber sheet layers, and both bulky fiber sheet layers contain fibers having a limiting oxygen index of 20 or more, and have a mass per unit area 0.5 times or more than that of the triboelectrically-charged nonwoven fabric layer. A filter element of the present invention comprises the filtration material in a pleated state.

An image forming apparatus includes a flow passage associated with a direction of flow and a particle collecting device including a filter to collect particles in a fluid passing through the flow passage in the direction of flow. The flow passage includes a curved portion, and a distribution in particle collecting performance of the filter in a direction perpendicular to the direction of flow results from the curved portion of the flow passage.

An image forming apparatus includes a flow passage associated with a direction of flow and a particle collecting device including a filter to collect particles in a fluid passing through the flow passage in the direction of flow. The flow passage includes a curved portion, and a distribution in particle collecting performance of the filter in a direction perpendicular to the direction of flow results from the curved portion of the flow passage.

Electret webs include a thermoplastic resin and a charge-enhancing additive. The charge-enhancing additive is an arylamino-substituted benzoic acid or an arylamino-substituted benzoic acid salt. The electret webs may be a non-woven fibrous web or a film. The electret webs are suitable for use as filter media.

Electret webs include a thermoplastic resin and a charge-enhancing additive. The charge-enhancing additive is an arylamino-substituted benzoic acid or an arylamino-substituted benzoic acid salt. The electret webs may be a non-woven fibrous web or a film. The electret webs are suitable for use as filter media.

An integrated electrostatic dust collection device for efficiently capturing particles in air and an electret processing technique thereof comprises a main body formed by stacking a plurality of layers of dust collection boards; wherein the dust collection boards are integrated with hole for air to pass through and are formed with micro-foaming, to which plastic materials of an electret enhancement material, a negative ion emission material, and a magnetic material can be added; the upper and lower surfaces of each layer of dust collection board are disposed with an enclosed conductive film applied with a high-voltage electric field, and one or more layers of dust collection boards can be installed with an ion emission device; a stacked structure and a high-voltage power supply are integrally packaged in the outer frame of the protection structure, and a low-voltage direct current or mains power is used externally to supply power.

An integrated electrostatic dust collection device for efficiently capturing particles in air and an electret processing technique thereof comprises a main body formed by stacking a plurality of layers of dust collection boards; wherein the dust collection boards are integrated with hole for air to pass through and are formed with micro-foaming, to which plastic materials of an electret enhancement material, a negative ion emission material, and a magnetic material can be added; the upper and lower surfaces of each layer of dust collection board are disposed with an enclosed conductive film applied with a high-voltage electric field, and one or more layers of dust collection boards can be installed with an ion emission device; a stacked structure and a high-voltage power supply are integrally packaged in the outer frame of the protection structure, and a low-voltage direct current or mains power is used externally to supply power.

An engine air intake dust removal system and method, comprising an air intake dust removal system inlet (1011), an air intake dust removal system outlet and an air intake electric field device (1014). The air intake dust removal system (101) and method can effectively remove particulate matters from air trying to enter the engine, and make the air entering the engine cleaner.