PTC unit for vehicle heater and PTC heater including the same

A positive temperature coefficient unit for a vehicle heater comprising:

• a heat generation part which includes positive temperature coefficient elements;
• a heat radiation part which is provided on at least one surface of the heat generation part and includes a heat radiation base material and a heat radiation film provided on at least a portion of an outer surface of the heat radiation base material to improve heat radiation performance;
• wherein the heat radiation base material includes a heat radiation plate disposed adjacent to the heat generation part and a heat radiation fin portion disposed on the heat radiation plate, and the heat radiation film is provided on outer surfaces of both of the heat radiation fin portion and the heat radiation plate;
• wherein the heat radiation film is composed of an oxide film and a heat radiation coating layer formed on the oxide layer;
• wherein the heat radiation coating layer is formed through an insulating heat radiation coating composition which includes a coating layer-forming component including a main resin which includes a compound represented by Formula 1 below, an insulating heat radiation filler included in an amount of 25-70 parts by weight with respect to 100 parts by weight of the main resin, which is silicon carbide and in which the insulating heat radiation filler has an average particle diameter is 10 nm to 15 μm and a ratio of a particle diameter at 50% to a particle diameter at 97% in a volume-based particle size distribution of the insulating heat radiation filler is less than or equal to 1:4.5, a physical property-improving component which is a silane-based compound included in an amount of 0.5 to 20 parts by weight, an antioxidant included in an amount of 0.1 to 3 parts by weight, a dispersant included in an amount of 0.5 to 20 parts by weight and a UV stabilizer included in an amount of 0.05 to 2 parts by weight;
• wherein the coating layer-forming component further includes a curing agent included in an amount of 25-100 parts by weight with respect to 100 parts by weight of the main resin;
• wherein the curing agent includes one or more selected from the group consisting of an aliphatic polyamine-based curing agent, an aromatic polyamine-based curing agent, an acid anhydride-based curing agent, and a catalyst-based curing agent;
• and
• wherein the curing agent includes a first curing agent and a second curing agent in a weight ratio of 1:0.5 to 1:1.5, wherein the first curing agent includes an aliphatic polyamine-based curing agent and the second curing agent includes one or more selected from the group consisting of an aromatic polyamine-based curing agent, an acid anhydride-based curing agent, and a catalyst-based curing agent:
• wherein R1 and R2 are each independently a hydrogen atom, a C1-C5 linear alkyl group or a C3-C5 branched alkyl group, and R3 and R4 are each independently a hydrogen atom, a C1-C5 linear alkyl group or a C3-C5 branched alkyl group, and n is a rational number which allows a weight average molecular weight of the compound represented by Formula 1 above to be in a range of 400 to 4,000.