Abstract: An air filter medium includes a first porous PTFE membrane and a second porous PTFE membrane. The air filter medium has a first main surface and a second main surface, and the first porous PTFE membrane and the second porous PTFE membrane are arranged so that an air flow moving from the first main surface to the second main surface passes through the first porous PTFE membrane and subsequently through the second porous PTFE membrane. A proportion of areas occupied by the plurality of nodes on a surface of the first porous PTFE membrane is in the range of 1.5 to 3.0% and an average of the areas of the plurality of nodes is 200 ?m2 or more.

Abstract: An air filter medium includes a first porous PTFE membrane and a second porous PTFE membrane. The air filter medium has a first main surface and a second main surface, and the first porous PTFE membrane and the second porous PTFE membrane are arranged so that an air flow moving from the first main surface to the second main surface passes through the first porous PTFE membrane and subsequently through the second porous PTFE membrane. A contact angle of the first porous PTFE membrane with water is in the range of 154° to 165°.

Abstract: An air filter medium includes a first porous PTFE membrane and a second porous PTFE membrane. The air filter medium (10) has a first main surface and a second main surface, and the first porous PTFE membrane and the second porous PTFE membrane are arranged so that an air flow moving from the first main surface to the second main surface passes through the first porous PTFE membrane and subsequently through the second porous PTFE membrane. A thickness of the first porous PTFE membrane is in the range of 4 to 40 ?m and a specific surface area of the first porous PTFE membrane is 0.5 m2/g or less.

Abstract: An air filter medium includes a first porous PTFE membrane and a second porous PTFE membrane. An average fiber diameter of fibers included in the first porous PTFE membrane is 0.24 to 0.45 ?m, an average fiber diameter of fibers included in the second porous PTFE membrane is 0.04 to 0.23 ?m, the air filter medium has a first main surface and a second main surface, and the first porous PTFE membrane and the second porous PTFE membrane are arranged so that an air flow moving from the first main surface to the second main surface passes through the first porous PTFE membrane and subsequently through the second porous PTFE membrane.

Abstract: A filter medium includes a first porous PTFE membrane, a first air-permeable support member, a second porous PTFE membrane, and a second air-permeable support member. A surface of the filter medium is formed by the first porous PTFE membrane. A bond strength, as measured by a 180° peel test, between the first porous PTFE membrane and the first air-permeable support member is higher than 1.2 N/25 mm. The first air-permeable support member is an embossed non-woven fabric having one or more recessed portions and one or more projecting portions. A ratio of the area of the recessed portion or the total area of the recessed portions to the area of the embossed non-woven fabric serving as the first air-permeable support member is more than 15%.

Abstract: An air filter medium includes a first porous PTFE membrane and a second porous PTFE membrane. The air filter medium has a first main surface and a second main surface, and the first porous PTFE membrane and the second porous PTFE membrane are arranged so that an air flow moving from the first main surface to the second main surface passes through the first porous PTFE membrane and subsequently through the second porous PTFE membrane. A proportion of areas occupied by the plurality of nodes on a surface of the first porous PTFE membrane is in the range of 1.5 to 3.0% and an average of the areas of the plurality of nodes is 200 ?m2 or more.

Abstract: An air filter medium includes a first porous PTFE membrane and a second porous PTFE membrane. The air filter medium has a first main surface and a second main surface, and the first porous PTFE membrane and the second porous PTFE membrane are arranged so that an air flow moving from the first main surface to the second main surface passes through the first porous PTFE membrane and subsequently through the second porous PTFE membrane. A contact angle of the first porous PTFE membrane with water is in the range of 154° to 165°.

Abstract: An air filter medium includes a first porous PTFE membrane and a second porous PTFE membrane. The air filter medium (10) has a first main surface and a second main surface, and the first porous PTFE membrane and the second porous PTFE membrane are arranged so that an air flow moving from the first main surface to the second main surface passes through the first porous PTFE membrane and subsequently through the second porous PTFE membrane. A thickness of the first porous PTFE membrane is in the range of 4 to 40 ?m and a specific surface area of the first porous PTFE membrane is 0.5 m2/g or less.

Abstract: An air filter medium includes a first porous PTFE membrane and a second porous PTFE membrane. An average fiber diameter of fibers included in the first porous PTFE membrane is 0.24 to 0.45 ?m, an average fiber diameter of fibers included in the second porous PTFE membrane is 0.04 to 0.23 ?m, the air filter medium has a first main surface and a second main surface, and the first porous PTFE membrane and the second porous PTFE membrane are arranged so that an air flow moving from the first main surface to the second main surface passes through the first porous PTFE membrane and subsequently through the second porous PTFE membrane.

Abstract: A filter medium includes a first porous polytetrafluoroethylene membrane, a first air-permeable support member, a second porous polytetrafluoroethylene membrane, and a second air-permeable support member. A surface of the filter medium is formed by the first porous polytetrafluoroethylene membrane. A bond strength, as measured by a 180° peel test, between the first porous polytetrafluoroethylene membrane and the first air-permeable support member is higher than 1.2 N/25 mm and higher than a bond strength, as measured by the 180° peel test, between the first air-permeable support member and the second porous polytetrafluoroethylene membrane.

Abstract: A filter medium includes a first porous polytetrafluoroethylene membrane, a first air-permeable support member, a second porous polytetrafluoroethylene membrane, and a second air-permeable support member. A surface of the filter medium is formed by the first porous polytetrafluoroethylene membrane. A bond strength, as measured by a 180° peel test, between the first porous polytetrafluoroethylene membrane and the first air-permeable support member is higher than 1.2 N/25 mm and higher than a bond strength, as measured by the 180° peel test, between the first air-permeable support member and the second porous polytetrafluoroethylene membrane.

Abstract: A filter medium includes a first porous PTFE membrane, a first air-permeable support member, a second porous PTFE membrane, and a second air-permeable support member. A surface of the filter medium is formed by the first porous PTFE membrane. A bond strength, as measured by a 180° peel test, between the first porous PTFE membrane and the first air-permeable support member is higher than 1.2 N/25 mm. The first air-permeable support member is an embossed non-woven fabric having one or more recessed portions and one or more projecting portions. A ratio of the area of the recessed portion or the total area of the recessed portions to the area of the embossed non-woven fabric serving as the first air-permeable support member is more than 15%.