ARTICLES INCLUDING INFRARED ABSORPTIVE MATERIAL AND COMPRISING RADIATION-TREATED AND NON-RADIATION-TREATED REGIONS

Techniques are described in which articles (e.g., security documents, traffic signage and personal protective equipment) are formed to include an infrared absorptive material. In some instances, the infrared absorptive material includes a reduced tungsten oxide, such as cesium tungsten oxide, calcium tungsten oxide, potassium tungsten oxide, or the like, and exposed to radiation such that one or more regions of the security document has a modified appearance, thereby providing a visual marking or information on the article. Example articles include at least one layer including a polymer and an infrared absorptive material including a reduced tungsten oxide. The layer includes a radiation-treated region that exhibits a first appearance under visible light and at least one non-radiation-treated region that exhibits a second, different appearance under visible light. The at least one radiation-treated region may be formed by exposing the at least one radiation-treated region to infrared light to change at least one property of the reduced tungsten oxide in the radiation-treated region compared to the reduced tungsten oxide in the non-radiation-treated region. The first appearance may be whiter than the second appearance.