A positive-type photosensitive resin composition, a pattern forming method, a thin film transistor array substrate, and a liquid crystal display device are provided. The positive-type photosensitive resin includes a novolac resin (A), an alkali-soluble resin (B), an ester (C) of an o-naphthoquinone diazide sulfonic acid, and a solvent (D). The alkali-soluble resin (B) includes a first alkali-soluble resin (B-1) produced by polymerizing a mixture. The mixture includes an epoxy compound (i) and a compound (ii), wherein the epoxy compound (i) has at least two epoxy groups, and the compound (ii) has at least one carboxylic acid group and at least one ethylenically unsaturated group.
Positive-type photosensitive resin composition, pattern forming method, thin film transistor array substrate, and liquid crystal display device