An exhaust gas purification filter includes a honeycomb structure part and sealing parts. The honeycomb structure part has a porous partition wall and a plurality of cells defined by the partition wall to form exhaust gas flow paths. The sealing parts seal alternately a gas inflow-side end face or a gas outflow-side end face of the cells. The exhaust gas purification filter includes fine pores with diameters of 10 μm or less measured by the mercury intrusion method that account for 5% or more of all pores by volume in the honeycomb structure part. The partition wall has a plurality of communication pores communicating between the cells adjacent to the partition wall and has constricted communication pore of which a largest diameter Φ.sub.1 and a smallest diameter Φ.sub.2 satisfy relationships Φ.sub.1≥50, 100×Φ.sub.2/Φ.sub.1≤20.

A pillar-shaped honeycomb structure including an outer peripheral side wall, a plurality of first cells provided on an inner peripheral side of the outer peripheral side wall, the first cells extending from a first end surface to a second end surface, each opening on the first end surface and having a sealing portion with an average void ratio of 4% or less on the second end surface, and a plurality of second cells provided on the inner peripheral side of the outer peripheral side wall, the second cells extending from the first end surface to the second end surface, each having a sealing portion with an average void ratio of 4% or less on the first end surface and opening on the second end surface, the first cells and the second cells being alternately arranged adjacent to each other with a partition wall interposed therebetween.

A pillar-shaped honeycomb structure filter including a plurality of first cells and a plurality of second cells, the first cells and the second cells being alternately arranged adjacent to each other with a porous partition wall interposed therebetween, wherein a ceramic porous film, in which an average film thickness T (unit: μm) is 2 to 50 μm, a porosity P (unit: %) is 65 to 90%, and the average film thickness T and the porosity P satisfy a relational expression of 0.36T+60≤P≤0.75T+72, is formed on a surface of each of the first cells.

A ceramic filter having a pillar-shaped honeycomb structure, wherein when observing a plurality of pores from a surface of partition walls with a laser microscope and plotting an equivalent circle diameter (μm) of each pore on an X-axis and a pore depth (μm) of each pore on a Y-axis on a two-dimensional coordinate system, a slope of a regression line (y/x) obtained by a least squares method in a range of 20≤x≤40 is 0 to 0.20, an average value of the pore depth of the plurality of pores is 2.5 μm to 5.0 μm, and a number density of the plurality of pores is 600/mm.sup.2 to 2450/mm.sup.2.

A honeycomb structure comprising a pillar-shaped honeycomb structure body having a porous partition wall disposed so as to surround a plurality of cells, wherein let that A denotes an absolute value of open frontal area (%) in a plane of the honeycomb structure body orthogonal to the extending direction of the cells and P denotes an absolute value of porosity (%) of the partition wall, the honeycomb structure has a value represented by the following expression (1) that is 0.05 to 0.12, let that D denotes an average pore diameter (m) of the partition wall and G denotes a geometric surface area (mm.sup.2/mm.sup.3) of the partition wall, the honeycomb structure has a value represented by the following expression (2) that is 8 to 50 (μm×mm.sup.2/mm.sup.3), and the honeycomb structure has a hydraulic diameter of the cells that is 1.1 mm or more,

(1−A/100)×(1−P/100),  Expression (1)

D×G.  Expression (2)

A honeycomb body with a honeycomb structure having an inner zone of a first plurality of walls and an outer zone of a second plurality of walls at least partially surrounding the inner zone. The honeycomb structure has Pi that is greater than Po and MPSi that is greater than MPSo, wherein Pi is an average bulk porosity of the first plurality of walls, Po is an average bulk porosity of the second plurality of walls, MPSi is a median pore size of pores in the first plurality of walls, and MPSo is a median pore size of pores in the second plurality of walls. Various honeycomb structures, honeycomb extrusion apparatus, and co-extrusion methods are disclosed.

The honeycomb structure includes a pillar-shaped honeycomb structure body that includes a porous partition wall. When the thickness (μm) of the partition wall is defined as T.sub.1 and, among pores formed in the partition wall, the value of an average pore diameter (μm) of specific pores whose pore diameters measured by a mercury press-in method are 20 to 100 μm is defined as D.sub.(20 to 100), T.sub.1/D.sub.(20 to 100) that is a value obtained by dividing T.sub.1 by D.sub.(20 to 100) is not less than 2.4, a ratio of a pore volume of the specific pores to an overall pore volume of the partition wall is 5 to 45%, and a ratio of a pore volume of large pores whose pore diameters are not less than 100 μm to the overall pore volume of the partition wall is not more than 5%.

A honeycomb filter includes a pillar-shaped honeycomb structure body having a porous partition wall disposed to surround a plurality of cells and a plugging portion, wherein the partition wall is composed of a material containing cordierite as a main component thereof, porosity of the partition wall measured by a mercury press-in method is 60 to 68%, an average pore diameter of the partition wall measured by a mercury press-in method is 8 to 12 and in a pore diameter distribution which indicates a cumulative pore volume of the partition wall measured by a mercury press-in method, with a pore diameter (μm) on an abscissa axis and a log differential pore volume (cm.sup.3/g) on an ordinate axis, a first peak that includes a maximum value of the log differential pore volume has a pore diameter value of 10 μm or less, the pore diameter value corresponding to a ⅓ value width of the maximum value.

A honeycomb filter includes a pillar-shaped honeycomb structure body having a porous partition wall disposed to surround a plurality of cells and a plugging portion, wherein the partition wall is composed of a material containing cordierite as a main component thereof, porosity of the partition wall measured by a mercury press-in method is 60 to 68%, an average pore diameter of the partition wall measured by a mercury press-in method is 13 to 18 μm, and in a pore diameter distribution indicating a cumulative pore volume of the partition wall measured by a mercury press-in method, with a pore diameter (μm) on an abscissa axis and a log differential pore volume (cm.sup.3/g) on an ordinate axis, a first peak including a maximum value of the log differential pore volume has a pore diameter value of 15 μm or less, the pore diameter value corresponding to a ⅓ value width of the maximum value.

A honeycomb filter includes a pillar-shaped honeycomb structure body having a porous partition wall disposed, surrounding a plurality of cells which serve as fluid through channels extending from a first end face to a second end face; and a plugging portion provided at an open end on the first end face side or the second end face side of each of the cells, wherein the partition wall is composed of a material containing cordierite as a main component thereof, an average pore diameter of the partition wall is 20 to 30 μm, an average equivalent circle diameter of pores existing at a surface of the partition wall and having equivalent circle diameters exceeding 3.0 μm is 18 to 30 μm, and a number per unit area of pores existing at a surface of the partition wall and having equivalent circle diameters exceeding 3.0 μm is 400 per mm.sup.2 or more.