JP-2026075314-A - Inhibitors of stratum corneum thickening

Abstract

[Problem] To suppress the layering of the stratum corneum. [Solution] The stratum corneum thickening inhibitor is applied to the skin. The stratum corneum thickening inhibitor contains 2% by mass or more of plate-shaped titanium oxide (A1). Preferably, the thickness of the plate-shaped titanium oxide (A1) is 100 nm or more and 200 nm or less. Preferably, the aspect ratio of the plate-shaped titanium oxide (A1) is 50 or more and 150 or less. [Selection Diagram] None

Inventors

• 須藤 美由紀
• 梶原 啓吾
• 我部 有
• 川端 慶吾

Assignees

• 花王株式会社

Dates

Publication Date

20260508

Application Date

20241022

Claims (6)

1. A stratum corneum thickening inhibitor applied to the skin, A stratum corneum multilayering inhibitor containing 2% by mass or more of plate-like titanium dioxide (A1).
2. The stratum corneum layering inhibitor according to claim 1, wherein the thickness of the plate-like titanium oxide (A1) is 100 nm or more and 200 nm or less.
3. The stratum corneum layering inhibitor according to claim 1 or 2, wherein the aspect ratio of plate-shaped titanium oxide (A1) is 50 or more and 150 or less.
4. The stratum corneum layering inhibitor according to claim 1 or 2, further containing 2% by mass or more and 60% by mass or less of a non-volatile oil (B).
5. The stratum corneum stratification inhibitor according to claim 1 or 2, further comprising spherical titanium dioxide (A2).
6. The stratum corneum layering inhibitor according to claim 5, wherein the average particle size of the spherical titanium oxide (A2) is 500 nm or more.

Description

This invention relates to a technology for suppressing the layering of the stratum corneum. Generally, infrared radiation, unlike ultraviolet radiation, is recognized as light with fewer adverse effects on the human body. Therefore, while many positive effects of infrared radiation on human skin are known, negative effects are less widely known. Patent Document 1 discloses the negative effects of infrared radiation exposure on human skin. The invention described in Patent Document 1 addresses the problem of photoaging of the skin caused by infrared radiation exposure to human skin, and provides a topical skin preparation that reduces the amount of infrared radiation incident on the skin. In other words, the topical skin preparation described in Patent Document 1 can suppress adverse effects on the skin caused by infrared radiation, such as photoaging, by reducing the amount of infrared radiation incident on the skin. Japanese Patent Publication No. 2021-070680 This is a photograph showing the state of the stratum corneum before the start of the test to evaluate the effect of inhibiting stratum corneum layering in Example 1.This is a photograph showing the state of the stratum corneum after the completion of the test to evaluate the effect of inhibiting stratum corneum layering in Example 1. The embodiments of the present invention will be described below. The present invention is not limited to the embodiments shown below, and various modifications may be made without departing from the spirit of the invention. [Overall composition of the stratum corneum thickening inhibitor] The inventors of this invention were the first in the field of stratum corneum research to discover that the stratum corneum is prone to thickening due to infrared radiation incident on the skin. Normally, the stratum corneum peels off as dead skin in cycles of several weeks, but in skin that has received a lot of infrared radiation, the old stratum corneum remains on the skin without peeling off, and the inventors found that this tends to lead to thickening of the stratum corneum. Based on this, the inventors of this invention conceived the idea that thickening of the stratum corneum can be suppressed by reducing the amount of infrared radiation incident on the skin. The stratum corneum thickening inhibitor according to this embodiment is intended for use in products (cosmetics, quasi-drugs, pharmaceuticals, etc.) that maintain a normal skin condition by reducing the amount of infrared radiation incident on the skin and suppressing the thickening of the stratum corneum. It should be noted that the stratum corneum thickening inhibitor according to this embodiment has a different purpose from heat-shielding products, photoaging inhibitors, skin temperature rise inhibitors, fatigue inhibitors, and reactive oxygen species production inhibitors currently available on the market, and will therefore occupy a market niche distinct from these topical skin preparations. The stratum corneum layering inhibitor according to this embodiment contains plate-shaped titanium dioxide (A1). Plate-shaped titanium dioxide (A1) is plate-shaped titanium dioxide particles. Here, "plate-shaped" is not particularly limited, but for example, by observing the particles using a scanning electron microscope (SEM), measuring the thickness and length of each cross-section, and calculating the aspect ratio (length/thickness), it refers to a particle shape where the aspect ratio is 5 or greater. Furthermore, "plate-shaped" includes not only plate-shaped particles in the narrow sense, but also powders with shapes such as thin flakes. Plate-shaped titanium dioxide (A1) has the property of reflecting infrared rays through a light interference mechanism. Therefore, in the stratum corneum layering inhibitor according to this embodiment, infrared rays incident on the skin are reflected by plate-shaped titanium dioxide (A1), reducing the amount of infrared rays incident on the skin and thereby suppressing the layering of the stratum corneum. The reason why plate-shaped titanium dioxide (A1) has a stratum corneum layering inhibitory effect is not yet clear, but it is thought to be because plate-shaped titanium dioxide (A1) has the property of selectively interfering with light including wavelengths in the 780 nm to 1800 nm range through a light interference mechanism. This infrared-reflecting property is unique to plate-shaped titanium dioxide (A1). In other words, ultraviolet scattering agents such as fine-particle titanium dioxide and fine-particle zinc oxide, widely used in topical skin preparations intended to reflect ultraviolet rays, such as sunscreens, do not possess the property of efficiently reflecting infrared rays through the light interference mechanism. Furthermore, ultraviolet absorbers, widely used in topical skin preparations intended to absorb ultraviolet rays, do not possess the property of efficiently reflecting infrared rays through the light interference