An International Guide to
Patent Case Management for Judges

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8.5 Patent infringement

A patentee enjoys the exclusive right to practice their patented invention for business purposes.72 Therefore, any person who is neither a patentee nor an exclusive licensee and who practices a patented invention for business purposes without permission from the patentee or the exclusive licensee is committing an act of infringement.

A patentee can grant exclusive license of the patent right to others73 and an exclusive licensee enjoys the monopoly on the right to exploit the patented invention within the scope of the exclusive license granted by the patentee.74 The grant of exclusive license must be registered to take effect.75 A patentee can grant nonexclusive license as well.76 A nonexclusive license is different from an exclusive license in that a nonexclusive licensee does not enjoy monopoly and nonexclusive licenses can be granted to multiple licensees. Registration is not needed for a nonexclusive license to be effective between the parties but is necessary to be effective against a third party.77

Because a nonexclusive licensee does not have the power to exclude others from exploiting the patent, they may not seek damages or injunction for patent infringement. In contrast, an exclusive licensee has the power to exclude others, and can seek damages or injunction on their own as such. In case exclusive license is granted over the entire scope of the patent right, the common view is that the patentee retains the authority to file for injunction nonetheless, because the patentee has an interest in preventing infringing acts to remove obstacles in exploiting the patent right for their own purpose upon expiration of the exclusive license.78 Meanwhile, the same does not apply to damages. The patentee may not independently seek damages arising from infringement of the patent right for which an exclusive license is granted without joining the exclusive licensee.79,80

Once patent infringement is established, the patentee may seek compensation for damages against the infringer (Article 750 of the Civil Act; Article 128(1) of the Patent Act) or file a claim for restitution of unjust enrichment (Article 741 of the Civil Act). Further, they may also seek a preliminary or permanent injunction against the infringer (Article 126 of the Patent Act) or the recovery of reputation in certain circumstances (Article 131 of the Patent Act). Patent infringement may also incur criminal liability (Article 225 of the Patent Act).

To establish patent infringement, the patentee should contend and prove that they are the owner of the patent and that the defendant has practiced81 the patent, and the defendant’s products or methods must be found as falling within the scope of protection of the patentee’s patent right.

8.5.1 Claim construction Relationship between claims and scope of protection

The scope of protection of a patented invention is the objective scope that the effects of the patent reach and is determined by what is stated in the claims.82 Accordingly, the scope of protection should be determined before the issue of infringement, and such a determination involves claim construction. Claim construction is also done before deciding whether the invention at issue lacks novelty or an inventive step. It is a matter of legal decision or evaluation, not of fact-finding, and thus may not be done via confession. Principles of claim construction

Claims state the scope of the patented invention for which the applicant seeks to receive protection. The scope of the claims must be determined based on what is stated in the claims and cannot be broadened or narrowed based on other statements (e.g., detailed descriptions or drawings). Nevertheless, reference to the descriptions or drawings of the invention is necessary to accurately understand the technical meaning of the claims. Thus, claims should be construed in an objective and reasonable manner based on contemplation of the technical meaning sought to be expressed by the wording of the claims, on the basis of the general meaning of the wording used in the claims but also in reference to the detailed description and drawings.83 In other words, one should mainly look to the wording of the claims for claim construction (the principle of literal interpretation), but the descriptions or drawings of the invention, as well as the general technical knowledge at the time of filing, should also be given weight (the principle of reference to description).

Further, one may also refer to other documents containing the applicant’s arguments in the prosecution history, such as specifications, amendments and written arguments presented by the applicant in the course of filing, as well as opinions presented by the KIPO examiner (the principle of reference to prosecution history). However, reference to these documents should never be used to broaden or narrow the meaning of the wordings used in the claims.

8.5.2 Infringement analysis Comparison of the patented invention with the infringing product or process

A defendant’s product or process infringes the patent only if it falls within the protected scope of the patent. In practice, the plaintiff breaks down the disputed claim into elements and compares them with the corresponding elements of the defendant’s product or process. The defendant provides their answer on whether the elements are appropriately identified and compared, and the court subsequently intervenes to ensure that both parties have the same understanding of the matter. A one-to-one comparison chart is often produced to compare the elements. The elements must be as confirmed in the claim construction process.

For the defendant’s product or process to fall within the scope of protection of the patented invention, every element stated in the claims, and their organic combination, must be included in the defendant’s product or process. If any of the elements is missing, the defendant’s product or process does not fall under the protected scope of the patented invention (all elements rule). Literal infringement

Literal infringement is the most basic type of infringement. It is established when all of the elements and the way the elements are organically combined (as specified by a literal interpretation of the claims) are found in the defendant’s product or process. Infringement by equivalence

Infringement by equivalence is established when the elements of the defendant’s product or process are not literally identical but are equivalent to the corresponding elements of the patented invention.

Infringement by equivalence has positive and negative requirements. In terms of positive requirements, (i) both inventions must have adopted the same principle to solve the problem (identity of solution principles); (ii) in spite of any replacement, the defendant’s product or process must have a substantially identical effect as the patented invention (substantial identity of effects); and (iii) the replacement must be self-evident to the extent that any person of ordinary skill in the art would have easily conceived of it (easiness of replacement). In terms of negative requirements, (iv) the defendant’s product or process must not be a free-to-practice technology that is in the public domain; and (v) the replaced element in the defendant’s product or process must not have been purposefully excluded from the scope of claims in the prosecution process. The patentee has the burden of proof as to the positive requirements, whereas the infringer has the burden of proof as to the negative requirements.

To determine whether the patented invention and the defendant’s product or process use the same principle to solve the problem, the superficial deduction of features recited in the claims does not suffice. Instead, the essence of the technical idea underlying the solution that is unique to the patented invention, in comparison with prior arts, should be identified in reference to the detailed description of the invention along with known technologies at the time of filing and be put under substantive review.84 Indirect infringement

In addition to direct infringement, the Patent Act regulates certain indirect acts as constructively constituting infringement. Under Article 127(1) and (2), the manufacturing, assigning, leasing, importing or offering to assign or lease a product exclusively used for manufacturing a patented product or for practicing a patented process, if done so for business purposes, are also deemed infringement.85 The purpose of this provision is to deem acts that are yet to reach the stage of practicing all elements of the patented invention as constituting infringement under certain circumstances if it is highly plausible that such acts would lead to the practice of all elements of the patented invention. The provision thereby offers effective relief against foreseeable future infringement.86

The patentee has the burden of proof. To prove indirect infringement, the patentee must show that the alleged good is used in practicing the patented invention (the use requirement), that the alleged good is exclusively used in practicing the patented invention (the exclusivity requirement) and that the alleged good is made for business purposes.

8.5.3 Defenses

When the patentee argues and proves all required elements to show infringement under each claim for injunction or damages and so on, the defendant should contend and prove contradicting facts to defeat the claim. The means of defense available to the defendant are classified into “denials,”87 for which the burden of proof lies with the plaintiff, and “defenses,” for which the burden of proof is on the defendant. The following sections focus on defenses.

The accused patent infringer denying infringement must disclose the product or process actually used. Under the amended Patent Act, the defendant denying infringement in spite of a prima facie showing by the plaintiff that the defendant is using the patented product or process must provide details regarding the product or process the defendant is actually using. If the defendant refuses to provide such details without adequate justification, the court may presume that the defendant actually committed the infringing act as claimed by the plaintiff.88 Abuse of rights

Whether the issue of inventive step of a patented invention can be examined and determined in an infringement case was subject to dispute until a Supreme Court decision in 2012. Ruling en banc in its 2010Da95390 decision on January 19, 2012, the Supreme Court expressly upheld the so-called defense of abuse of rights, forbidding the exercise of patent rights in an infringement suit when the patented invention lacks an inventive step, stating that

Even before when the administrative decision invalidating the patent is finalized, claims for damages or injunctions based on the patent may constitute an abuse of the rights and be impermissible when it is clear the patented invention lacks an inventive step and will be invalidated by the administrative invalidation proceeding. When the defense is raised that the patentee’s claim for damages or injunction constitutes an abuse of rights, the court handling the infringement suit is entitled to review and determine the inventive step issue in order to decide whether the defense is well-grounded.89

Deciding when a lack of an inventive step is “clear” may be an issue, but, in practice, the clarity requirement is considered met and is not independently examined so long as the judge finds the patented invention lacks an inventive step in the infringement suit.90

This Supreme Court decision dealt with a case where the inventive step of the patented invention was denied, but it is also considered equally applicable to cases where a patented invention lacks novelty or sufficient description so as to be invalid or is in violation of the first-to-file rule. However, the Supreme Court had held that a patented invention lacking novelty or sufficient description had no protectable scope of right even before the 2010Da95390 decision.91

The plaintiff may submit a reply of correction of the patented invention in response to the defendant’s defense of abuse of rights. It is possible to “correct” a patent to narrow the claims, correct typographical errors or clarify ambiguous language, either during an IPTAB invalidation proceeding or by filing a separate correction petition at the IPTAB, provided that the correction does not substantially alter the nature of what is claimed. Free-to-exploit technology

The defendant may raise a defense of free-to-exploit technology to argue that the defendant’s product or process only implemented technology that was publicly known or could be easily derived from what was publicly known. The Supreme Court has held as follows:

In determining whether the technology the defendant exploits falls within the scope of rights of the patented invention, the comparison between the two is unnecessary to conclude that the exploited technology does not fall within the patented scope if the defendant’s product only consists of publicly known technologies or can be easily practiced by any person of ordinary skill in the pertinent art from publicly known technologies.92

This analysis resembles that given for inventive step but is different in that what is compared with the prior art or publicly known technology is the defendant’s infringing product, not the patented invention. In practice, the defense of free-to-exploit technology is rarely seen in infringement cases because the defendant can use the defense of abuse of rights to argue that the patented invention lacks an inventive step.93 Known technology

As discussed above, the Supreme Court has held that patent rights may not be exercised when the invention consists only of technologies that were already publicly known or in public use at the time of the filing, whether or not the IPTAB has ruled on the invalidity of the patented invention. The defendant bears the burden of contention and proof to demonstrate that the patented invention is a publicly known technology. Such a defense of known technology may be asserted in addition to the defense of free-to-exploit technology, but, in practice, it is less frequently asserted than the defenses of abuse of rights or of free-to-exploit technology.94 Patent exhaustion

Even though it is not expressly stipulated in the Patent Act, reselling or using a patented product is generally deemed acceptable and does not constitute patent infringement so long as the product is lawfully transferred from the patentee. This is called the “exhaustion doctrine” or “first sale doctrine.” A defendant may raise the defense of patent exhaustion in a patent infringement lawsuit.

The Supreme Court has acknowledged the doctrine of patent exhaustion as applicable to product inventions by ruling as follows:

When a patentee or licensee of a product patent lawfully sells the product implementing the patented invention in the territory of the Republic of Korea, the effects of the patent right shall not extend to the acts of using, assigning or leasing the product by the assignee or buyer with regard to the assigned product because the patent right on that product has achieved its purpose and is thus exhausted.95 Limited effect or lawful practice of patent right

In addition to the above defenses, the defendant may also assert defenses such as that:

  • the effect of the patent is limited (Articles 96 and 181 of the Patent Act);
  • the defendant has an exclusive or nonexclusive license granted by the patentee;
  • the defendant has a statutory license granted under Articles 103, 104, 105, 122, 182 or 183 of the Patent Act, or
  • the defendant is granted a compulsory license under Articles 98, 106, 107 and 138 of the Patent Act.96