A method for the adjustment of the viscosity of a dispersion material containing fine particles of a crystalline polymer as a dispersed particle with a dispersant by changing the temperature of the dispersion material, wherein the dispersant comprises a copolymer of a first monomer with a second monomer, in which: the first monomer is a monomer crystallizable as a polymer having a molecular structure identical to the dispersed particle, the first monomer is one or more than one selected from: ethylene; a (meth)acrylate, a (meth)acrylamide, a vinylether, a vinylester, a siloxane, an α-olefine and a substituted styrene, each having a straight-chained alkyl side chain having at least eight carbon atoms; a (meth)acrylate, a (meth)acrylamide, a vinylether, a vinylester, a siloxane, an α-olefine and a substituted styrene, each having an at least partially fluorinated straight-chained alkyl side chain having at least eight carbon atoms; and polypropylene, and the second monomer is one or more than one selected from: a (meth)acrylate, a vinylether, a vinylester, a maleic ester, an itaconic ester, an acrylamide, and a substituted styrene, each having a straight-chained alkyl side chain having seven carbon atoms or less than seven carbon atoms; a (meth)acrylate, a vinylether, a vinylester, a maleic ester, an itaconic ester, an acrylamide, and a substituted styrene, each having a branched alkyl side chain having seven carbon atoms or less than seven carbon atoms; a (meth)acrylate, a vinylether, a vinylester, a maleic ester, an itaconic ester, and an acrylamide, each having an aryl group; a (meth)acrylate, a vinylether, a vinylester, a maleic ester, an itaconic ester, an acrylamide, and a substituted styrene, each having an oxyethylenic structure or an oxypropionic structure; styrene; acrylic acid; methacrylic acid; vinyl acetate; a (meth)acrylate having a dimethylsiloxane side chain, and a (meth)acrylate having a fluorinated alkyl side chain. the first monomer is a monomer crystallizable as a polymer having a molecular structure identical to the dispersed particle, the first monomer is one or more than one selected from: ethylene; a (meth)acrylate, a (meth)acrylamide, a vinylether, a vinylester, a siloxane, an α-olefine and a substituted styrene, each having a straight-chained alkyl side chain having at least eight carbon atoms; a (meth)acrylate, a (meth)acrylamide, a vinylether, a vinylester, a siloxane, an α-olefine and a substituted styrene, each having an at least partially fluorinated straight-chained alkyl side chain having at least eight carbon atoms; and polypropylene, and ethylene; a (meth)acrylate, a (meth)acrylamide, a vinylether, a vinylester, a siloxane, an α-olefine and a substituted styrene, each having a straight-chained alkyl side chain having at least eight carbon atoms; a (meth)acrylate, a (meth)acrylamide, a vinylether, a vinylester, a siloxane, an α-olefine and a substituted styrene, each having an at least partially fluorinated straight-chained alkyl side chain having at least eight carbon atoms; and polypropylene, and the second monomer is one or more than one selected from: a (meth)acrylate, a vinylether, a vinylester, a maleic ester, an itaconic ester, an acrylamide, and a substituted styrene, each having a straight-chained alkyl side chain having seven carbon atoms or less than seven carbon atoms; a (meth)acrylate, a vinylether, a vinylester, a maleic ester, an itaconic ester, an acrylamide, and a substituted styrene, each having a branched alkyl side chain having seven carbon atoms or less than seven carbon atoms; a (meth)acrylate, a vinylether, a vinylester, a maleic ester, an itaconic ester, and an acrylamide, each having an aryl group; a (meth)acrylate, a vinylether, a vinylester, a maleic ester, an itaconic ester, an acrylamide, and a substituted styrene, each having an oxyethylenic structure or an oxypropionic structure; styrene; acrylic acid; methacrylic acid; vinyl acetate; a (meth)acrylate having a dimethylsiloxane side chain, and a (meth)acrylate having a fluorinated alkyl side chain. a (meth)acrylate, a vinylether, a vinylester, a maleic ester, an itaconic ester, an acrylamide, and a substituted styrene, each having a straight-chained alkyl side chain having seven carbon atoms or less than seven carbon atoms; a (meth)acrylate, a vinylether, a vinylester, a maleic ester, an itaconic ester, an acrylamide, and a substituted styrene, each having a branched alkyl side chain having seven carbon atoms or less than seven carbon atoms; a (meth)acrylate, a vinylether, a vinylester, a maleic ester, an itaconic ester, and an acrylamide, each having an aryl group; a (meth)acrylate, a vinylether, a vinylester, a maleic ester, an itaconic ester, an acrylamide, and a substituted styrene, each having an oxyethylenic structure or an oxypropionic structure; styrene; acrylic acid; methacrylic acid; vinyl acetate; a (meth)acrylate having a dimethylsiloxane side chain, and a (meth)acrylate having a fluorinated alkyl side chain.