Ceramic honeycomb filter and its production method

1. A ceramic honeycomb structure having large numbers of flow paths partitioned by porous cell walls, and plugs alternately formed in said flow paths on the exhaust-gas-inlet and outlet sides, an area ratio of pores opening at the cell wall surfaces being 20-28%, porous, cross-linked structures being formed by heat-resistant particles introduced together with a gas into penetrating holes constituted by communicating pores in said cell walls, such that they clog said penetrating holes, and said cross-linked structures being formed more on the exhaust-gas-outlet side of said ceramic honeycomb filter than on the exhaust-gas-inlet side wherein said heat-resistant particles are the same material as that of said cell walls.

2. The ceramic honeycomb filter according to claim 1 , wherein the average diameter of said heat-resistant particles is 2/3 times or less the average pore diameter of said cell walls, and 0.5 μm or more.

3. A method for producing the ceramic honeycomb filter recited in claim 1 , wherein said heat-resistant particles are introduced together with a gas through said exhaust-gas-inlet side.

4. A method for producing the ceramic honeycomb filter recited in claim 1 , wherein water is introduced into said penetrating holes before said heat-resistant particles are introduced into said penetrating holes together with a gas.

5. The method for producing a ceramic honeycomb filter according to claim 3 , wherein only part of said flow paths on the exhaust-gas-inlet side is immersed in water before said heat-resistant particles are introduced, such that water is introduced into said penetrating holes.