New Film Design for Eye Cream

Pola Chemical Industries, Inc. (Headquarters: Yokohama, Kanagawa, President: Takayuki Katagiri), which is responsible for the research, development, and production of the Pola Orbis Group, has achieved both "smooth spreadability that melts into the skin during application" and "firmness after application," which were previously difficult to achieve, through a new film technology that collapses when force is applied and returns to its original state when the force is removed.

Difficulty in Achieving Both Smooth Spreadability and Firmness

Eye creams are required to provide a feeling of firmness while also spreading smoothly without rubbing the eye area. However, achieving both of these simultaneously has been a challenge. Oils and film-forming agents with high firmness are hard and do not deform easily during application, resulting in poor spreadability. Conversely, oils with good spreadability are soft and lack firmness. Therefore, with the conventional approach of combining these, it was difficult to achieve the ideal user experience (Supplementary Material 1).

"Structure-Restoring Oil" Whose Structure Changes According to Force

To achieve both smooth spreadability during application and firmness after application, Pola Chemical Industries focused on an oil whose structure changes according to applied force and then returns to its original state. This oil has a property where plate-like crystals form a three-dimensional structure, like a "card house" of leaning playing cards, which temporarily collapses when force is applied and naturally reassembles when the force is removed (Figure 1).

Composition and Manufacturing Method of Structure-Restoring Oil

To maximize the characteristics of this structure, we investigated combinations and manufacturing methods for the oil. As a result, we found an optimal composition that temporarily lowers its viscosity and becomes softer when force is applied, and recovers its viscosity when the force is removed (Supplementary Material 2). This composition suggests the possibility of achieving both smooth spreadability during application and high firmness after application, which was difficult with conventional oils (Figure 2).

Furthermore, using proprietary high-performance equipment introduced at Pola Chemical Industries, we confirmed that high-speed dispersion processing finely disperses the plate-like crystals, making the structure denser and stronger (Figure 3). As a result, the viscosity recovery rate increased, leading to the realization of higher firmness (Supplementary Material 3).

Achieving a Firm Film After Melting and Spreading

Formulations containing this technology have confirmed a higher viscosity recovery rate compared to conventional technologies (Supplementary Material 4). In addition, user tests conducted by expert evaluators showed high satisfaction in both "a feeling of melting into the skin" and "firmness" (Supplementary Material 5). Pola Chemical Industries will continue to develop new technologies that balance usability and functionality.

[Supplementary Material 1] Structure and Challenges of Conventional Oils

As a component for imparting firmness, hard oils were traditionally used. However, hard oils have a strong structure and do not deform easily during application, resulting in poor spreadability. On the other hand, oils with good spreadability lack structure, are fluid, and are soft, thus lacking firmness (Figure 4).

[Supplementary Material 2] Search for Optimal Oil Composition to Achieve Both Smooth Spreadability and Firmness

The oils forming the card house structure are combined in a way that plate-like crystals interlock. The bonds are not too strong, so they easily collapse when force is applied, but when the force is removed, they touch again, return to their original structure, and viscosity recovers. This behavior changes depending on the combination of oils.

We evaluated the viscosity change with and without force for various oil combinations (Figure 5). As a result, we observed different behaviors, such as compositions where viscosity significantly decreases with force and easily recovers but has low initial viscosity (Composition 1), and compositions that are highly viscous at rest and show little change with force (Composition 2). This is because the ease of structure collapse and recovery differs depending on the type of oil. By combining these, we found a composition (Composition 3) that is initially highly viscous but whose viscosity decreases when force is applied and increases again when the force is removed.

[Supplementary Material 3] Comparison with Conventional Oils

Conventional oils with good spreadability have low viscosity and do not change with the presence or absence of force. This is because they are fluid without forming any particular structure. In contrast, structure-restoring oils are expected to melt and spread during application due to their viscosity changing with force, and lead to high firmness after application (Figure 6).

[Supplementary Material 4] Improvement of Firmness by Dispersion Control of Plate-like Crystals

The card house structure is formed by plate-like crystals interlocking, so the structure becomes denser as the contact points between crystals increase. Therefore, sufficiently dispersing and refining the crystals is important to fully utilize the function of the structure.

We investigated the effect on viscosity recovery (ease of structure return) by improving the dispersibility of plate-like crystals through higher-speed dispersion processing than usual using proprietary high-performance equipment introduced at the Technical Development Center (TDC). When the designed structure-restoring oil was dispersed using the equipment at TDC and the viscosity change when force was applied was evaluated, it was confirmed that the viscosity recovered more easily after force was applied (Figure 7). This is thought to be because the crystals were dispersed more finely, forming a denser card house structure. As a result, higher firmness is expected.

[Supplementary Material 5] Verification in Formulations

An evaluation of a development product containing the designed structure-restoring oil was conducted. As a result, the formulation also showed high viscosity recovery (Figure 8). Furthermore, approximately 70% of expert evaluators reported a greater "feeling of melting into the skin," and approximately 60% reported a greater "firming sensation that tightens the eye area" compared to conventional products (Figure 9). These results confirmed that the developed product achieves both a melting sensation and firmness.