US-12623481-B2 - Identification medium, article, and identification medium use method

US12623481B2US 12623481 B2US12623481 B2US 12623481B2US-12623481-B2

Abstract

An identification medium including a light reflection layer and a patterned phase difference layer, wherein the light reflection layer is a layer that reflects incident light as circularly polarized light or linearly polarized light, and the patterned phase difference layer is a layer that includes an area having a phase difference, and is a layer provided in the identification medium so that the area having a phase difference occupies a partial area of a display surface of the identification medium. Also provided are an article including the identification medium, and a method for using the identification medium wherein, in observation of the reflected light, a linear polarization component or a circular polarization component of the reflected light is selectively observed, or linearly polarized light, circularly polarized light, or elliptically polarized light is made incident as the incident light.

Inventors

Natsumi FUJIWARA

Assignees

ZEON CORPORATION

Dates

Publication Date: 20260512
Application Date: 20210129
Priority Date: 20200131

Claims (17)

1 . An identification medium comprising a light reflection layer and a patterned phase difference layer, wherein the light reflection layer is a reflection-type circular polarizer, the patterned phase difference layer is a layer that includes an area having a phase difference, and is a layer provided in the identification medium so that the area having a phase difference occupies a partial area of a display surface of the identification medium, and the patterned phase difference layer includes, as the area having a phase difference, an area that functions as a λ/4 wave plate.
2 . The identification medium according to claim 1 , wherein the patterned phase difference layer is provided at a position on a side closer to a viewing side than the light reflection layer.
3 . The identification medium according to claim 1 , comprising one or more single patterned phase difference layers as the patterned phase difference layer, the single patterned phase difference layer consisting of a single area that has a smaller size than that of the display surface of the identification medium, and has a certain phase difference.
4 . The identification medium according to claim 1 , comprising a plurality of areas having irregularly different directions of slow axes as the area having a phase difference.
5 . The identification medium according to claim 1 , wherein the light reflection layer is a cut piece of a material having cholesteric regularity.
6 . The identification medium according to claim 1 , wherein the light reflection layer include two or more areas giving different polarization states to reflected light.
7 . The identification medium according to claim 1 , wherein a reflectance ratio of an unpolarized light having been incident on one or more areas of the light reflection layer and reflected by the light reflection layer is 35 to 50% at all wavelengths in a wavelength region of 420 nm to 650 nm.
8 . The identification medium according to claim 1 , further comprising a light absorption layer on a side of the light reflection layer opposite to a viewing side.
9 . The identification medium according to claim 1 , further comprising a diffusion layer provided at a position on a side closer to a viewing side than the patterned phase difference layer.
10 . The identification medium according to claim 1 , further comprising a transparent resin member, in which part or all members other than the transparent resin member are embedded.
11 . The identification medium according to claim 1 , further comprising a mounting member for attachment to an article.
12 . An article comprising the identification medium according to claim 1 .
13 . The article according to claim 12 , further comprising a polarizer viewer.
14 . A method for using the identification medium according to claim 1 , comprising: causing incidence of incident light on the display surface of the identification medium and reflection of the incident light by the light reflection layer to convert the incident light into reflected light, and observing the reflected light, wherein unpolarized light is made incident as the incident light, and in observation of the reflected light, a linear polarization component or a circular polarization component of the reflected light is selectively observed.
15 . The method for using the identification medium according to claim 14 , wherein the selective observation is performed by visually observing the reflected light via a linear polarizer being separated away from the identification medium.
16 . The method for using the identification medium according to claim 15 , wherein the linear polarizer is polarized sunglasses.
17 . A method for using the identification medium according to claim 1 , comprising: causing incidence of incident light on the display surface of the identification medium and reflection of the incident light by the light reflection layer to convert the incident light into reflected light, and observing the reflected light, wherein linearly polarized light, circularly polarized light, or elliptically polarized light is made incident as the incident light.

Description

FIELD The present invention relates to an identification medium, an article, and a method for using an identification medium. BACKGROUND As a general practice, an identification medium is provided to an article for facilitating determination of whether or not the article is an authentic article. The identification medium is required to have anti-counterfeit performance and an identification function. The anti-counterfeit performance of the identification medium as referred to herein is performance that prevents the identification medium from being easily copied by means of a general technique such as printing. The identification function of the identification medium is a function that can allow an authentic identification medium to be distinguished by some means with high reliability from a counterfeit identification medium deceptively produced by means of a general technique. In many cases, determination of authenticity of an identification medium is performed by observation through a special determination tool including an optical member such as a circular polarizer and a linear polarizer (for example, Patent Literatures 1 to 3). On the other hand, some identification media can be subjected to determination by observation with the naked eye without the need for a special determination tool. For example, there is an identification medium, such as a so-called hologram, that can be subjected to determination on the basis of whether or not a stereoscopic image of a pattern shape on the identification medium can be viewed (for example, Patent Literature 4). CITATION LIST Patent Literature Patent Literature 1: Japanese Patent Application Laid-Open No. 2010-221650 APatent Literature 2: Japanese Patent Application Laid-Open No. 2010-113249 A (Corresponding publication: specification of U.S. Patent Application Publication No. 2010/119738)Patent Literature 3: International Publication No. 2005/059597Patent Literature 4: Japanese Patent No. 5915838 B SUMMARY Technical Problem As to an identification medium that requires a special determination tool for determination of authenticity, the persons who perform the determination are limited. That is, only special identifiers, such as customs staff, that possess special determination tools can perform the determination, whereas general article users who buy, sell, possess, or use articles cannot perform the determination since the users do not possess such special determination tools. In addition, determination of authenticity for an identification medium in Patent Literatures 1 and 2 requires a special operation of bringing a determination tool close to the identification medium. As to an identification medium that can be subjected to determination with a so-called hologram that does not require a special determination tool, while the persons who perform the determination are less limited, anti-counterfeit performance may be insufficient since an identification medium that can provide a relatively similar effect can be produced by means of a hologram technique that has already been commonly used. In a case of employing a method of observing a hologram through a special determination tool, a configuration with further improved anti-counterfeit performance can be achieved. However, in this case, the persons who perform the determination are limited as in the aforementioned case. Therefore, an object of the present invention is to provide an identification medium that has high anti-counterfeit performance and that can provide an identification function without the need for a special determination tool, an article including an identification medium, and a method for determining authenticity. Solution to Problem In their study to solve the aforementioned problem, the present inventors have conceived of configuring an identification medium that can provide an identification function by using a general tool, such as polarized sunglasses and a device such as a liquid crystal display device that emits polarized light, in its normal use mode. As a result of further study based on the idea, the present inventors have arrived at the present invention upon discovering that, in a case where a specific identification medium is constituted, the identification function thereof can be used by using the general tool, and that favorable anti-counterfeit performance can also be obtained. That is, the Present Invention Includes the Following. (1) An identification medium comprising a light reflection layer and a patterned phase difference layer, wherein the light reflection layer is a layer that reflects incident light as circularly polarized light or linearly polarized light, andthe patterned phase difference layer is a layer that includes an area having a phase difference, and is a layer provided in the identification medium so that the area having a phase difference occupies a partial area of a display surface of the identification medium. (2) The identification medium acco