1. The plaintiff's appeal is dismissed.

2. The independent party intervenor's claim raised in the trial shall be dismissed;

3...

1. Underlying facts, each of the following facts is acknowledged either as a dispute between the parties or as a whole by considering the overall purport of the pleadings in Gap evidence (including a serial number).

[1] An independent party intervenor (hereinafter "the intervenor") is a company established on March 14, 2005 for the purpose of manufacturing and selling advertising materials using ELD (LED, Right Emitt, and luminous dives) and is engaged in the business of distributing and selling advertising materials. The plaintiff is working as the representative director of the intervenor from the time when the intervenor was established.

The defendant is a company established for the purpose of manufacturing advertisements.

[2] On May 1, 2009, the intervenor entered into a contract with C (hereinafter “C”) with a third party designated by C or C to deliver PE channel signboards, such as PCB (Pinted Ciritcard, printed circuit board), and the contract term is from May 1, 2009 to December 31, 2009, but the contract term is automatically extended one year unless the intervenor expresses his/her intention of refusal to renew the contract in writing one month prior to the expiration date.

The Intervenor supplied the PCB supplied by Korea LELD Co., Ltd. under the above contract with C to the signboard company including the Defendant, which is the signboard company designated by C, including the Defendant (hereinafter “Defendant, etc.”). The Defendant, etc.’s signboard company has installed the signboard using the above PCB, and then installed it to the C franchise store.

[3] However, from May 2010, there was a problem such as the occurrence of a transparent yellow phenomenon that changes in the light of the signboards installed as above in a yellow color.

C Around June 201, a written agreement was made between the Intervenor and the Intervenor on the share of responsibility for the issue arising from the signboard as above, and the key contents of which are ① With respect to non-standard PCB and defective PCB established without C’s approval, the Intervenor and the Defendant et al.