Identification medium, article, and method for using the same

Abstract

To provide an identification medium, an article including the identification medium, and an authenticity determination method using the article, the identification medium having high anti-counterfeiting performance, high identification capability, high design effect, and high confidentiality.SOLUTION: The present invention relates to an identification medium including a light reflection layer and a retardation layer, the light reflection layer being a layer that reflects, as reflected light, a specific polarization component of incident light, the specific polarization component being either one of a circularly polarized component and a linearly polarized component, the retardation layer being divided into at least three regions, each of the at least three regions being a layer that emits, as an observation-target polarization component, a part or all of the specific polarization component incident from the light reflection layer, the at least three regions having mutually different emission ratios of the observation-target polarization component, and the retardation layer having a substantially uniform thickness.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an identification medium, an article, and a method for using the identification medium. [Background technology]

[0002] It is common practice to provide an identification medium on an item to make it easier to determine whether the item is genuine. The identification medium is required to have anti-counterfeiting properties and an identification function. The anti-counterfeiting properties of the identification medium here refer to the ability of the identification medium to be difficult to replicate using common printing or other techniques. The identification function of the identification medium refers to the ability to distinguish, with a high degree of reliability, a genuine identification medium from a counterfeit identification medium forged using common techniques.

[0003] It is sometimes desirable for an identification medium to have a concealed identification function, i.e., a high probability that the presence of a portion having an identification function will not be detected by normal observation. In other words, if the presence of a portion having an identification function is not detected by normal observation, counterfeiters will not recognize the identification medium as an identification medium, but only as a normal display medium, and in that case, counterfeiters will not even think of imitating the identification function of the identification medium. Therefore, an identification medium in which the portion having the identification function is concealed reduces the possibility of counterfeits being produced that imitate the identification function. In an identification medium, an image that cannot be observed by normal observation and can only be observed in a specific manner for authenticity verification is called a latent image.

[0004] In addition, there are cases where an identification medium is required to function as a decorative medium while exhibiting an identification function. That is, the optical properties of an identification medium can be used not only as an identification medium function but also as a property that is aesthetically pleasing and exhibits a design effect. For example, in the case of an identification medium that allows general users to identify its authenticity, it is sometimes desired that the latent image be appreciated by users as an aesthetic design. In particular, since the items to be authenticated are often items with high added value, the latent image indicating the authenticity may also be required to have a high design quality that reflects the high added value of the item.

[0005] In many cases, the identification medium comprises components such as an optically anisotropic layer and a reflective polarizer layer, which exert optical effects. In many cases, the authenticity of the identification medium is determined by observing it through a special determination tool that includes an optical element such as a circular polarizer or a linear polarizer (for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2021 / 153761 [Patent Document 2] International Publication No. 2022 / 209852 [Patent Document 3] International Publication No. 2008 / 018560 Summary of the Invention [Problem to be solved by the invention]

[0007] From the viewpoint of exhibiting high anti-counterfeiting performance and high identification function, as well as from the viewpoint of exhibiting high design effects, it is required that the identification medium be capable of displaying a complex latent image. However, in the identification media of Patent Documents 1 and 2, the latent image is basically displayed using two types of regions, namely, a light region and a dark region, so there are limitations on the complexity of the latent image.

[0008] Patent Document 3 describes the use of a combination of multiple types of retardation layers with different thicknesses, and forming such a thickness distribution may result in a complex latent image. However, when such retardation layers with different thicknesses are combined, the difference in thickness becomes easily detectable even under normal observation, thereby compromising confidentiality.

[0009] Therefore, an object of the present invention is to provide an identification medium, an article equipped with an identification medium, and a method for determining authenticity using the same, which have high anti-counterfeiting performance, high identification function, the ability to produce high design effects, and high confidentiality. [Means for solving the problem]

[0010] In the course of investigations to solve the above-mentioned problems, the present inventors came up with the idea that the above-mentioned problems can be solved by employing a specific retardation layer in an identification medium having a light-reflecting layer and a retardation layer. The present invention was completed based on this idea. That is, the present invention includes the following.

[0011] (1) An identification medium comprising a light-reflecting layer and a retardation layer, the light reflecting layer is a layer that reflects a specific polarized component of incident light as reflected light, the specific polarized component being either a circularly polarized component or a linearly polarized component; The retardation layer is divided into three or more regions, each of the three or more types of regions is a layer that outputs a part or all of the specific polarized component incident from the light reflecting layer as an observation target polarized component; the three or more regions have different emission rates of the polarized component to be observed, and the emission rate of the polarized component to be observed is a ratio of the amount of emission of the polarized component to the amount of incident light to the identification medium per unit area; The retardation layer has a substantially constant film thickness. identification medium. (2) The discrimination medium according to (1), wherein the in-plane retardation Re of the three or more regions is distributed in a range of 412.5 nm or less. (3) The discrimination medium according to (1) or (2), wherein each of the three or more regions has a uniform in-plane retardation Re within the respective region, and the three or more regions have different in-plane retardations Re. (4) Each of the three or more regions is a low retardation sub-region SR L and high phase contrast subregion SR H and the low retardation sub-regions SR in the three or more regions. L and the area of ​​the high phase difference sub-region SR H The discrimination medium according to (1) or (2), wherein the ratios of the areas of the respective regions to the respective regions are different from each other. (5) The retardation layer is a liquid crystal cured layer that is a layer of a cured product of a liquid crystal compound, The discrimination medium according to any one of (1) to (4), wherein a part of the cured product in the liquid crystal cured layer is a liquid crystal compound cured in a state of exhibiting a liquid crystal phase. (6) The discrimination medium according to any one of (1) to (5), wherein the retardation layer is provided at a position closer to the viewer than the light reflecting layer. (7) The identification medium according to any one of (1) to (6), wherein the light-reflecting layer is a reflective circular polarizer or a reflective linear polarizer. (8) The identification medium according to (7), wherein the light-reflecting layer is the reflective circular polarizer. (9) The identification medium according to (8), wherein the light-reflecting layer is a cured product of ink containing a pigment made of a material having cholesteric regularity. (10) An identification medium according to any one of (1) to (9), wherein the reflectance of unpolarized light incident on the material forming the light-reflecting layer by the material is 35 to 50% for all wavelengths in the wavelength range of 420 nm to 650 nm. (11) The identification medium according to any one of (1) to (10), further comprising a light absorbing layer on the side opposite to the viewing side of the light reflecting layer. (12) An article comprising the identification medium according to any one of (1) to (11). (13) The article according to (12), further comprising a polarizer viewer. (14) A method for using the discrimination medium according to any one of (1) to (11), Incident light is incident on the display surface of the identification medium, reflected by the light-reflecting layer to form reflected light, and the reflected light is observed; A method of use in which unpolarized light is incident as the incident light, and in observing the reflected light, a linearly polarized component or a circularly polarized component of the reflected light is selectively observed. (15) The method of use according to (14), wherein the selective observation is performed by visually observing the reflected light through a linear polarizer spaced apart from the identification medium. (16) The method of use according to (15), wherein the linear polarizer is polarized sunglasses. (17) A method for using the discrimination medium according to any one of (1) to (11), Incident light is incident on the display surface of the identification medium, reflected by the light-reflecting layer to form reflected light, and the reflected light is observed; The incident light may be linearly polarized, circularly polarized, or elliptically polarized light. [Effects of the Invention]

[0012] According to the present invention, there are provided an identification medium, an article equipped with an identification medium, and a method for determining authenticity using the same, which have high anti-counterfeiting performance, high identification function, the ability to produce high design effects, and high confidentiality. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view schematically showing an example of the discrimination medium of the present invention. [Figure 2] FIG. 2 is a longitudinal cross-sectional view showing a cross section of the discrimination medium shown in FIG. 1 taken along a plane along line A1. [Figure 3] FIG. 3 is an exploded vertical cross-sectional view showing a part of the discrimination medium shown in FIGS. 1 and 2 and an example of how to use the discrimination medium. [Figure 4] FIG. 4 is a perspective view schematically showing another example of the discrimination medium of the present invention. [Figure 5] FIG. 5 is a vertical cross-sectional view showing a cross section of the discrimination medium shown in FIG. [Figure 6] FIG. 6 is an exploded vertical cross-sectional view showing a part of the discrimination medium shown in FIGS. 4 and 5 and an example of how to use the discrimination medium. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below with reference to examples and embodiments. However, the present invention is not limited to the examples and embodiments shown below, and can be implemented with any modifications within the scope of the claims of the present invention and their equivalents.

[0015] In the following description, the term "(meth)acrylic" includes "acrylic", "methacrylic", and combinations thereof. For example, "(meth)acrylic group" includes "acrylic group", "methacrylic group", and mixtures thereof. Furthermore, the term "(thio)epoxy" includes "epoxy", "thioepoxy", and combinations thereof. Furthermore, the term "iso(thio)cyanate" includes "isocyanate", "isothiocyanate", and combinations thereof.

[0016] In the following description, unless otherwise specified, the in-plane retardation Re of a certain layer is a value expressed as Re = (nx - ny) x d. Here, nx represents the refractive index in the direction perpendicular to the thickness direction of the layer (in-plane direction) that gives the maximum refractive index. ny represents the refractive index in the in-plane direction of the layer that is perpendicular to the nx direction. d represents the thickness of the layer. The wavelength for measuring retardation is 550 nm unless otherwise specified. The in-plane retardation Re can be measured using a phase difference meter (Axometrics' "AxoScan").

[0017] In the following description, the direction of the slow axis of a certain layer refers to the direction of the slow axis in the in-plane direction, unless otherwise specified.

[0018] In the following description, for convenience of explanation, "right-handed circularly polarized light" and "left-handed circularly polarized light" are defined based on the direction of rotation of circularly polarized light when observing the destination of light from the source of light. That is, when observing the destination of light from the source of light, polarized light whose polarization direction rotates clockwise as the light travels is called right-handed circularly polarized light, and polarized light whose polarization direction rotates in the opposite direction is called left-handed circularly polarized light.

[0019] In the drawings and the following description, the following symbols are used for the convenience of easy understanding: The vibration direction of polarized light refers to the vibration direction of an electric field. (N): Unpolarized (X): Right-handed circularly polarized light and linearly polarized light are mixed (L): Left-handed circularly polarized light (R): Right-handed circularly polarized light, or right-handed reflective circular polarizer (i.e., a reflective circular polarizer that selectively reflects the right-handed circularly polarized component of incident light) (E): Elliptical polarization (I): Linearly polarized light

[0020] In the following description, unless otherwise specified, the identification medium will be described as being placed horizontally with the display surface, i.e., the surface to be observed, facing upward. Therefore, the side from which the identification medium is viewed may simply be referred to as the "upper" side, and the opposite side as the "lower" side. For example, of one surface and the other surface of a layer, the surface closer to the display surface of the identification medium may be referred to as the "upper" surface. Furthermore, the direction perpendicular to these "upper" and "lower" directions may be referred to as the "horizontal" direction.

[0021] The discrimination medium of the present invention is · Unpolarized light is incident on the identification medium, and the light reflected from the identification medium is observed in a normal manner (without any particular selection of polarization components). -Unpolarized light is incident on the identification medium, and the polarized component of the light reflected from the identification medium is selectively observed. - Polarized light is incident on the identification medium, and the light reflected from the identification medium is observed in the normal manner. For ease of explanation, in the following description, the first of the three modes may be referred to as "observation with non-polarized light," the second as "non-polarized-polarized observation," and the third as "polarized-non-polarized observation." The second and third modes may also be collectively referred to as "observation with polarized light."

[0022] (Outline of identification medium) The discrimination medium of the present invention comprises a light-reflecting layer and a retardation layer.

[0023] A light-reflecting layer is a layer that reflects a specific polarized component of incident light as reflected light. The specific polarized component is either a circularly polarized component or a linearly polarized component. Specifically, when non-polarized light containing various polarized components is incident on the light-reflecting layer, the light-reflecting layer reflects the polarized component as circularly polarized light or linearly polarized light. The light-reflecting layer is usually a reflective polarizer. That is, the light-reflecting layer transmits part or all of the polarized component of a certain wavelength of the incident light and reflects part or all of the other polarized components. A reflective circular polarizer or a reflective linear polarizer can be used as the light-reflecting layer.

[0024] A reflective circular polarizer is an optical element that transmits one of a right-handed circularly polarized component and a left-handed circularly polarized component of incident light of a certain wavelength and reflects the other. A reflective linear polarizer is an optical element that transmits one of a certain linearly polarized component and a linearly polarized component perpendicular to the certain linearly polarized component of incident light of a certain wavelength and reflects the other. Examples of light-reflecting layers and the materials that make them up will be described in more detail later.

[0025] The retardation layer is usually provided at a position closer to the viewer than the light reflecting layer, and therefore the display surface of the identification medium is usually the surface of the identification medium on the retardation layer side.

[0026] The retardation layer is divided into three or more regions. Each of the three or more regions is a layer that outputs a part or all of the specific polarized component incident from the light reflecting layer as a polarized component to be observed. The polarized component to be observed is a polarized component that is the object of observation among the light emitted from the identification medium when observed with polarized light. The three or more regions have different emission rates of the polarized component to be observed. The emission rate of the polarized component to be observed is the ratio of the amount of emitted polarized component to the amount of incident light on the identification medium per unit area.

[0027] Specific examples of such a retardation layer include the following two examples. Specific example (i): Each of the three or more types of regions has a uniform in-plane retardation Re within the respective region, and the three or more types of regions have different in-plane retardations Re. Specific example (ii): Each of the three or more regions is a low retardation sub-region SR L and high phase contrast subregion SR H and a low retardation sub-region SR in three or more regions. L Area of ​​high phase contrast subregion SR H The ratio of the area to the area of ​​each is different.

[0028] The retardation layer has a substantially constant thickness. Specifically, the retardation layer may have no or very small steps between regions with different retardation in the plane corresponding to the display surface of the identification medium. More specifically, the average thickness d of the retardation layer in the display surface av Maximum film thickness d max and minimum film thickness d min Percentage of difference between ((d max -d min ) / d av )×100(%) is preferably 6% or less, more preferably 5% or less, even more preferably 4% or less, and ideally 0%. When the retardation layer has such a substantially constant film thickness, the secrecy of the identification function of the identification medium can be improved.

[0029] The thickness of the retardation layer can be appropriately adjusted within a range in which a desired retardation is exhibited and sufficient light transmittance is obtained. Specifically, the thickness of the retardation layer is preferably 0.5 μm or more, more preferably 1 μm or more, and is preferably 12 μm or less, more preferably 10 μm or less.

[0030] Preferably, the retardation layer is a liquid crystal cured layer which is a layer of a cured product of a liquid crystal compound. In the liquid crystal cured layer, it is preferable that a part of the cured product is a liquid crystal compound cured in a state exhibiting a liquid crystal phase. More specific explanations of examples of retardation layers, their constituting materials and manufacturing methods will be described separately later.

[0031] (Optical properties of specific example (i)) FIG. 1 is a perspective view schematically showing an example of an identification medium of the present invention. FIG. 2 is a longitudinal cross-sectional view showing a cross section of the identification medium shown in FIG. 1 cut along line A1. This example is a more specific example of the specific example (i) described above. In FIGS. 1 and 2, the identification medium 100 comprises a light-reflecting layer 101(R) and a retardation layer 102. The identification medium 100 further comprises a light-absorbing layer 109 as an optional component.

[0032] 1 and 2, a right-handed reflective circular polarizer (i.e., a reflective circular polarizer that selectively reflects the right-handed circularly polarized component of incident light) is used as the light-reflecting layer 101(R). Therefore, in this example, the specific polarized component is the right-handed circularly polarized component.

[0033] 1 and 2, the upper surface 102U on the side of the retardation layer 102 functions as a display surface. That is, a part of light incident on the surface 102U of the identification medium 100 is reflected within the identification medium 100 and emitted from the surface 102U, and when an observer observes this, the function of the identification medium is realized.

[0034] In the example of FIGS. 1 and 2, the retardation layer 102 has four regions: a region 102RA having the shape of the letter A, a region 102RB having the shape of the letter B, a region 102RC having the shape of the letter C, and a background region 102RZ. In this example, these four regions have uniform in-plane retardation Re within each region, with the values ​​ReA, ReB, ReC, and ReZ being 143 nm, 71 nm, 40 nm, and 3 nm, respectively, and therefore are different from one another. The slow axes of the regions 102RA, 102RB, 102RC, and 102RZ are parallel to one another, and the transmittance of unpolarized light is the same. Here, having a uniform in-plane retardation Re means that there are no subregions with different retardations within the region, as in specific example (ii). Specifically, the variation in the in-plane retardation Re within each region is within ±3 nm.

[0035] (Example (i) Usage: Part 1) In the method of using the discrimination medium of the present invention, incident light is made incident on the display surface of the discrimination medium, is reflected by the light-reflecting layer to become reflected light, and the reflected light is observed.

[0036] Examples of light incident on the identification medium include unpolarized light and polarized light, and examples of polarized light include linearly polarized light, circularly polarized light, and elliptically polarized light. Using these, observation with unpolarized light and observation with polarized light (unpolarized-polarized observation, or polarized-unpolarized observation) can be performed.

[0037] As the incident unpolarized light, general ambient light such as sunlight and indoor lighting can be used.

[0038] Selective observation of the linearly polarized component of reflected light can be performed by visually observing the reflected light through a linear observation polarizer. Selective observation of the circularly polarized component of reflected light can be performed by visually observing the reflected light through a circular observation polarizer. To avoid interfering with the incidence of ambient light, the linear observation polarizer and circular observation polarizer are usually used at a distance from the identification medium. The lower limit of the distance can be adjusted as appropriate depending on the dimensions of the identification medium and the linear observation polarizer, but is usually 100 mm or more. On the other hand, the upper limit of the distance can be adjusted as appropriate within the range in which the reflected light of the identification medium can be observed, but is usually 30 m or less.

[0039] Thus, the observation linear polarizer used at a position away from the identification medium may be a dedicated product for the method of use of the present invention, or may be a general linear polarizer used for other purposes. For example, many commercially available polarized sunglasses can function as linear polarizers, so such commercially available polarized sunglasses may be used as the observation linear polarizer. Examples of observation circular polarizers include circular polarizers formed by combining a linear polarizer and a retardation film, and circular polarizers containing a layer of cholesteric material (for example, those described in International Publication No. 2020 / 121791).

[0040] Fig. 3 is an exploded vertical cross-sectional view showing a part of the identification medium shown in Fig. 1 and Fig. 2 and an example of its use. For the purpose of explaining the optical function, the components of the identification medium are shown separated in Fig. 3, but in an actual identification medium, they may be in contact with each other directly or via another layer.

[0041] 3, for the convenience of explaining basic matters, only areas 102RA, 102RB, and 102RZ are shown among the areas of the retardation layer 102. In this example, incident light A11A(N), A11B(N), and A11Z(N), which is natural light, enters the identification medium, passes through areas 102RA, 102RB, and 102RZ of the retardation layer, and exits as transmitted light A12A(N), A12B(N), and A12Z(N), which is partially reflected by the light reflecting layer 101(R) and exits as reflected light A13A(R), A13B(R), and A13Z(R), The diagram shows a state in which the light is divided into transmitted light A19A(L), A19B(L), and A19Z(L), of which reflected light is transmitted again through regions 102RA, 102RB, and 102RC of the retardation layer to emerge as transmitted light A14A(I), A14B(E), and A14Z(R), and a state in which these are further transmitted through a viewer 191 to become transmitted light A15A(I), A15B(I), and A15Z(I). In this example, a linear polarizer for observation is used as the viewer 191.

[0042] Incident light A11A(N), A11B(N), and A11Z(N) are transmitted through regions 102RA, 102RB, and 102RZ of the retardation layer 102. When unpolarized light passes through a layer having a retardation, even if the phases of the individual polarization components contained therein change, the light as a whole ultimately becomes unpolarized, and therefore, the transmitted light A12A(N), A12B(N), and A12Z(N) are all unpolarized. These are emitted downward and reach the light-reflecting layer 101(R). Because the light-reflecting layer 101(R) is a right-handed reflective circular polarizer, the right-handed circularly polarized components of light A12A(N), A12B(N), and A12Z(N) are reflected on the surface or inside of the light-reflecting layer 101(R) and become reflected light A13A(R), A13B(R), and A13Z(R). On the other hand, the left-handed circularly polarized light components of the light A12A(N), A12B(N), and A12Z(N) are transmitted through the light reflecting layer 101(R) to become transmitted light A19A(L), A19B(L), and A19Z(L). The transmitted light A19A(L), A19B(L), and A19Z(L) are absorbed by the light absorbing layer 109 and are not visible.

[0043] The light A13A(R), A13B(R), and A13Z(R) again passes through the regions 102RA, 102RB, and 102RZ of the retardation layer 102, and is emitted from the display surface of the identification medium as transmitted light A14A(I), A14B(E), and A14Z(R).

[0044] In this example, the in-plane retardation ReA of the region 102RA is 143 nm, which is approximately ¼ of the central wavelength of visible light, 550 nm, and therefore the region 102RA functions as a λ / 4 wave plate. As a result, the transmitted light A14A(I) becomes linearly polarized light.

[0045] The in-plane retardation ReZ of the region 102RZ is 3 nm, i.e., is approximately isotropic, and therefore the region 102RZ transmits light with almost no change in its phase. As a result, the transmitted light A14Z(R) becomes right-handed circularly polarized light.

[0046] The in-plane retardation ReB of region 102RB is 71 nm, which is smaller than ReA and larger than ReZ. Therefore, transmitted light A14B(E) is elliptically polarized. The amount of linearly polarized light component of transmitted light A14B(E) with the same polarization direction as that of linearly polarized transmitted light A14A(I) is smaller than that of transmitted light A14A(I) and larger than that of transmitted light A14Z(R).

[0047] The transmitted light A14A(I), A14B(E), and A14Z(R) are all light beams with the same polarization state, but no other differences. Human vision cannot discern these differences in polarization state, so if the transmitted light A14A(I), A14B(E), and A14Z(R) are viewed directly without a viewer and observed unpolarized, they cannot be distinguished.

[0048] On the other hand, when the transmitted light A14A(I), A14B(E), and A14Z(R) are observed through the viewer 191 using polarized light (non-polarized-polarized observation in this case), the observer will visually recognize the transmitted light A15A(I), A15B(I), and A15Z(I). Therefore, the polarization components contained in the transmitted light A14A(I), A14B(E), and A14Z(R) that correspond to the transmitted light A15A(I), A15B(I), and A15Z(I) correspond to the polarization components to be observed. Because the viewer 191 is a linear polarizer, all of this transmitted light is linearly polarized.

[0049] Here, taking the example of a case where the transmission axis of the viewer 191 and the polarization axis of the transmitted light A14A(I) are aligned, the amount of light per unit area of ​​the transmitted light A15A(I), A15B(I), and A15Z(I) is such that the light A15A(I) is the brightest and the light A15Z(I) is the darkest. The light A15B(I) is brighter than the light A15Z(I) and darker than the light A15A(I). On the other hand, the amount of incident light entering the identification medium 100, i.e., the incident light A11A(N), A11B(N), and A11Z(N), per unit area is the same. Therefore, the emission rates of the polarization components to be observed from the regions 102RA, 102RB, and 102RZ are greatest in the region 102RA, next greatest in the region 102RB, and smallest in the region 102RZ. Moreover, in a region 102RC not shown in FIG. 3, the output ratio is smaller than that of the region 102RB and larger than that of the region 102RZ.

[0050] The relative magnitude relationship of the observation target polarization component output efficiencies can change when the viewer 191 is rotated to change the relationship between its transmission axis and the polarization direction of the transmitted light, thereby changing the polarization component that is the observation target polarization component. However, when the transmission axis of the viewer 191 is oriented in at least one direction, the observation target polarization component output efficiencies of the regions 102RA, 102RB, 102RC, and 102RZ usually have different values ​​in almost all orientations (except for exceptional cases where the output efficiencies happen to be the same). In this way, the observation target polarization component output efficiencies are different due to the different phase differences of the retardation layers in three or more types of regions.

[0051] As a result, when the identification medium 100 with non-polarized light incident thereon is observed with non-polarized light without using the viewer 191, the viewer will not recognize the presence of areas 102RA, 102RB, and 102RC in the background area 102RZ, whereas when non-polarized-polarized light is observed through the viewer 191, areas 102RA, 102RB, and 102RC are visible as latent images, and moreover, these are visible as images with different brightnesses.

[0052] This visual appearance of the latent image is a feature that cannot be easily replicated by general printing or other techniques, and therefore the identification medium of the present invention can exhibit high anti-counterfeiting performance. Furthermore, the feature that the latent images are visually recognized as images with different brightnesses is a feature that clearly distinguishes it from counterfeit identification media forged using general techniques, and therefore the identification medium of the present invention can exhibit high identification functionality. In addition, the feature that the latent images can be configured with different brightnesses also makes it possible to achieve a high design effect by the appearance of complex latent images.

[0053] The above-mentioned non-polarized-polarized observation can be achieved by using ambient light as incident light, separating the identification medium from a linear polarizer for observation, and visually observing the reflected light through the linear polarizer for observation. Furthermore, a common polarizer, such as commercially available polarized sunglasses, can be used as the linear polarizer for observation. Therefore, this observation can be performed without any special operation, such as bringing the evaluation tool close to the identification medium, and a relatively easily available evaluation tool can be used. For example, identification can be achieved by a simple operation, such as visually observing an identification medium placed at a distance from the observer while wearing polarized sunglasses. Therefore, the identification medium of the present invention exhibits high identification functionality when used in this manner. 3 illustrates an example in which the discrimination medium and the linear polarizer for observation are observed at a distance from each other, but the positional relationship between the discrimination medium and the linear polarizer for observation during observation is not limited to this. For example, such a latent image can also be observed by placing the linear polarizer for observation on the discrimination medium and bringing them close to each other.

[0054] In the above example, a linear polarizer is used as the observation polarizer, but the present invention is not limited to this, and a polarizer other than a linear polarizer may also be used as the observation polarizer. For example, even when a right-handed circular polarizer, a left-handed circular polarizer, or a combination thereof is used instead of a linear polarizer as the observation polarizer and the polarization component to be observed is circularly polarized, the latent image is visually recognized as an image with different brightnesses based on the difference in the proportions of the circularly polarized components of the output light from three or more regions, and the effect of the present invention can be exerted.

[0055] (Example (i) Usage: Part 2) The above-described example is an example of a method of using unpolarized light as the light incident on the identification medium 100, and a linear polarizer for observation, to perform unpolarized observation and unpolarized-polarized observation. On the other hand, below, an example of a method of using unpolarized light and polarized light as the light incident on the identification medium 100 without using a linear polarizer for observation will be described.

[0056] When the incident polarized light is linearly polarized light, linearly polarized light obtained by transmitting unpolarized light through a linear polarizer can be used as the linearly polarized light. The device for supplying linearly polarized light may be a device dedicated to the method of use of the present invention, or may be a combination of a general light source and a general linear polarizer used for other purposes. Alternatively, a device in which a general light source and a linear polarizer used for other purposes are combined may be used.

[0057] When the incident polarized light is circularly polarized light, the circularly polarized light can be obtained by transmitting unpolarized light through a circular polarizer. The device for supplying circularly polarized light may be a device dedicated to the method of use of the present invention, or may be a combination of a general light source and a general circular polarizer used for other purposes. Alternatively, a device in which a general light source and a circular polarizer used for other purposes are combined may be used.

[0058] When the incident polarized light is elliptically polarized light, elliptically polarized light obtained by transmitting unpolarized light through an appropriate optical element can be used as the elliptically polarized light. The device for supplying elliptically polarized light may be a device dedicated to the method of use of the present invention, or may be a device in which a general light source and a general linear polarizer or circular polarizer used for other applications are combined. Alternatively, a device in which a general light source and a general linear polarizer or circular polarizer used for other applications are combined may be used.

[0059] For example, many electronic devices equipped with a display screen, such as general personal computers and smartphones with liquid crystal display screens, emit linearly polarized light as light emitted from the display screen, and therefore such electronic devices can be used as devices for supplying linearly polarized light. More specifically, by bringing such an electronic device close to an identification medium, the identification medium can be positioned in an environment where there is little incident unpolarized ambient light and relatively more incident light emitted from the electronic device, thereby achieving the supply of linearly polarized light.

[0060] As another example, some electronic devices equipped with a display screen, such as general personal computers and smartphones with liquid crystal display screens, emit circularly polarized light as light emitted from the display screen, and therefore such electronic devices can be used as devices for supplying circularly polarized light. More specifically, by bringing such an electronic device close to the identification medium, the identification medium can be positioned in an environment where there is little incident unpolarized ambient light and relatively more incident light emitted from the electronic device, thereby achieving the supply of circularly polarized light.

[0061] As yet another example, a retrofit film may be attached to the display screen of the electronic device that emits the linearly polarized or circularly polarized light described above for various purposes. Examples of such retrofit films include those attached for various purposes, such as protecting the display screen, adjusting the viewing angle of the display screen, and improving visibility when the display screen is viewed through polarized sunglasses. Many of these films have some kind of phase difference, and therefore can exhibit the function of converting linearly polarized light to circularly polarized light or elliptically polarized light, or converting circularly polarized light to linearly polarized light or elliptically polarized light. Using an electronic device with such a retrofit film, it is also possible to achieve the supply of linearly polarized light, circularly polarized light, or other elliptically polarized light.

[0062] In polarized and non-polarized light observation, polarized light enters the identification medium 100, passes through the regions 102RA, 102RB, 102RC, and 102RZ of the retardation layer, and is emitted downward as polarized light with a changed polarization state. The proportion of the right-handed circularly polarized component in the emitted polarized light differs depending on the difference in the phase difference between the regions 102RA, 102RB, 102RC, and 102RZ. Only the right-handed circularly polarized component of the downward emitted light from the retardation layer 102 is reflected by the light reflecting layer 101(R) and enters the retardation layer 102 again. When the light passes through the regions 102RA, 102RB, 102RC, and 102RZ, the polarization state of the emitted light changes from that of the incident light, but the amount of light does not change. Therefore, the amount of light per unit area emitted from the regions 102RA, 102RB, 102RC, and 102RZ to the outside of the identification medium 100 reflects the amount of the right-handed circularly polarized component reflected by the light reflecting layer 101(R), and these amounts are different from each other. In this polarized / non-polarized light observation, the light emitted from the identification medium 100 becomes the polarized component to be observed. In this way, the output rates of the polarized component to be observed differ due to the different phase differences of the retardation layer in the three or more regions.

[0063] As a result, when observed with polarized light and non-polarized light, the regions 102RA, 102RB, and 102RC are visible as latent images with different brightness levels, which provides high anti-counterfeiting performance, high identification capabilities, and high design effects, just as in the case of non-polarized light and polarized light observation.

[0064] (Optical properties of specific example (ii)) FIG. 4 is a perspective view schematically showing another example of the identification medium of the present invention. FIG. 5 is a longitudinal cross-sectional view showing a cross section of the identification medium shown in FIG. 4. This example is a more specific example of the specific example (ii) described above. For convenience of illustration, the dimensions of the regions 202RA, 202RB, and 202RC are shown larger in FIG. 5 than in FIG. 4. In FIGS. 4 and 5, the identification medium 200 comprises a light-reflecting layer 101(R) and a retardation layer 202. The identification medium 200 further comprises a light-absorbing layer 109 as an optional component.

[0065] 4 and 5, the light-reflecting layer 101(R) and the light-absorbing layer 109 are the same as those used in the examples shown in FIGS. 1 to 3, and therefore, in this example, the specific polarized light component is a right-handed circularly polarized light component. In the identification medium 200, the upper surface 202U on the retardation layer 202 side functions as a display surface. That is, a part of the light incident on the surface 202U of the identification medium 200 is reflected within the identification medium 200 and exits from the surface 202U, and when an observer observes this, the function of the identification medium is realized.

[0066] 4 and 5, the retardation layer 202 has four regions: a region 202RA having the shape of the letter A, a region 202RB having the shape of the letter B, a region 202RC having the shape of the letter C, and a background region 202RZ. In this example, the regions 202RA, 202RB, 202RC, and 202RZ are all low retardation sub-regions 202SR L and high phase difference sub-region 202SR H The low phase difference sub-region 202SR is composed of: L and high phase difference sub-region 202SR H are minute regions present inside the regions 202RA, 202RB, 202RC, and 202RZ, and specifically, the low phase difference sub-regions 202SR L are halftone dots, that is, tiny dot-shaped regions, and the high retardation sub-region 202SR H In this example, the low retardation sub-region 202SR may be a region surrounding a halftone dot where no halftone dot exists. L and high phase difference sub-region 202SR H In this example, the low retardation subregions 202SR in the regions 202RA, 202RB, 202RC, and 202RZ have uniform in-plane retardation Re in each region, with values ​​ReL and ReH of 3 nm and 143 nm, respectively. L and high phase difference sub-region 202SR H The low retardation sub-region 202SR with respect to the total area of ​​100% LThe area ratios of the low phase difference sub-regions 202RA, 202RB, 202RC, and 202RZ are 0%, 50%, 70%, and 100%, respectively. L and high phase difference sub-region 202SR H The area ratios of the four low retardation sub-regions 202SR are different from each other. L and high phase difference sub-region 202SR H The slow axes of the films are all parallel to one another, and the transmittance of unpolarized light is the same.

[0067] The sub-regions can function independently as retardation layers, but can be sized so that they are difficult to recognize as regions having independent shapes by normal human vision. L and high phase difference sub-region 202SR H The light emitted from the region where the light components are mixed is visually recognized as a mixed state by normal human vision. From the viewpoint of achieving such a mixed state, it is preferable that the pitch at which the sub-regions are arranged is sufficiently small. On the other hand, from the viewpoint of ease of manufacturing, it is preferable that the pitch is at least a certain size. For example, the low retardation sub-region 202SR L and high phase difference sub-region 202SR H In the case of a so-called AM screen (where the dots are spaced equally and the shade is expressed by the size of the dots), the pitch of the dots is preferably 150 lpi or more, more preferably 175 lpi or more, and is preferably 340 lpi or less, more preferably 280 lpi or less.

[0068] As shown in the examples of FIGS. 4 and 5, the low phase difference sub-region 202SR L has a relatively small in-plane retardation Re, and the high retardation sub-region 202SR H The low retardation subregion 202SR has a relatively large in-plane retardation Re. L The in-plane retardation value ReL of the high retardation subregion 202SR is preferably 10 nm or less, more preferably 5 nm or less, and ideally can be 0 nm. HThe in-plane retardation value ReH is preferably 135 nm or more, more preferably 140 nm or more, and is preferably 150 nm or less, more preferably 145 nm or less. When ReL and ReH are within these ranges, grayscale gradation with a wide range of brightness can be easily depicted.

[0069] (Example (ii) Usage: Part 1) Figure 6 is an exploded vertical cross-sectional view showing a part of the identification medium shown in Figures 4 and 5 and an example of how to use the same. In Figure 6, as in Figure 3, the components of the identification medium are shown separated from each other, but in an actual identification medium, they may be in contact with each other directly or via another layer.

[0070] 6, for the convenience of explaining basic matters, only areas 202RA, 202RB, and 202RZ are shown among the areas of the retardation layer 202. In this example, incident light A21A(N), A21B(N), and A21Z(N), which is natural light, enters the identification medium, passes through areas 202RA, 202RB, and 202RZ of the retardation layer, and exits as transmitted light A22A(N), A22B(N), and A22Z(N), which is partially reflected by the light reflecting layer 101(R) and exits as reflected light A23A(R), A23B(R), and A23Z(R), The diagram shows a state in which the light is divided into transmitted light A29A(L), A29B(L), and A29Z(L), of which reflected light is transmitted again through regions 202RA, 202RB, and 202RC of the retardation layer to emerge as transmitted light A24A(I), A24B(X), and A24Z(R), and a state in which these are further transmitted through the viewer 191 to become transmitted light A25A(I), A25B(I), and A25Z(I). In this example, a linear polarizer for observation is used as the viewer 191.

[0071] Incident light A21A(N), A21B(N), and A21Z(N) are transmitted through regions 202RA, 202RB, and 202RZ of the retardation layer 202. When unpolarized light passes through a layer having a retardation, even if the phases of the individual polarization components contained therein change, the light as a whole ultimately becomes unpolarized, and therefore, the transmitted light A22A(N), A22B(N), and A22Z(N) are all unpolarized. These are emitted downward and reach the light reflecting layer 101(R). Because the light reflecting layer 101(R) is a right-handed reflective circular polarizer, the right-handed circularly polarized components of light A22A(N), A22B(N), and A22Z(N) are reflected on the surface or inside of the light reflecting layer 101(R) and become reflected light A23A(R), A23B(R), and A23Z(R). On the other hand, the left-handed circularly polarized light components of the light A22A(N), A22B(N), and A22Z(N) are transmitted through the light reflecting layer 101(R) to become transmitted light A29A(L), A29B(L), and A29Z(L). The transmitted light A29A(L), A29B(L), and A29Z(L) are absorbed by the light absorbing layer 109 and are not visible.

[0072] The light A23A(R), A23B(R), and A23Z(R) are transmitted again through the regions 202RA, 202RB, and 202RZ of the retardation layer 202, and are emitted from the display surface of the identification medium as transmitted light A24A(I), A24B(X), and A24Z(R).

[0073] In this example, the region 202RA includes a high retardation subregion 202SR with an in-plane retardation Re of 143 nm. H The area 202RA is made up of 100% of the polarizer. Therefore, the area 202RA functions as a λ / 4 wave plate. As a result, the transmitted light A24A(I) becomes linearly polarized light.

[0074] The region 202RZ has a low retardation subregion 202SR with an in-plane retardation of 3 nm, i.e., a substantially isotropic retardation. L Therefore, the region 202RZ transmits the light with almost no change in its phase. As a result, the transmitted light A24Z(R) becomes right-handed circularly polarized light.

[0075] The region 202RB has a low retardation subregion 202SR with an in-plane retardation of 3 nm. L 50%, and a high retardation subregion 202SR having an in-plane retardation Re of 143 nm. H 50%. Low phase difference sub-region 202SR L The light emitted from the high retardation sub-region 202SR is right-handed circularly polarized. H The light emitted from the sub-region is linearly polarized, but because the sub-region is very small, the transmitted light A24B(X) is a mixture of right-handed circularly polarized light and linearly polarized light. The amount of the linearly polarized component of the transmitted light A24B(X) that is polarized in the same direction as the linearly polarized transmitted light A24A(I) is smaller than that of the transmitted light A24A(I) but larger than that of the transmitted light A24Z(R).

[0076] The transmitted light A24A(I), A24B(X), and A24Z(R) are all light beams with different polarization states, but no other differences. Human vision cannot discern these differences in polarization state, so if the transmitted light A24A(I), A24B(X), and A24Z(R) are viewed directly without a viewer and observed unpolarized, they cannot be distinguished.

[0077] On the other hand, when the transmitted light A24A(I), A24B(X), and A24Z(R) are observed through the viewer 191 using polarized light (non-polarized-polarized observation in this case), the observer will see the transmitted light A25A(I), A25B(I), and A25Z(I). Therefore, the polarization components contained in the transmitted light A24A(I), A24B(X), and A24Z(R) that correspond to the transmitted light A25A(I), A25B(I), and A25Z(I) correspond to the polarization components to be observed. Because the viewer 191 is a linear polarizer, all of this transmitted light is linearly polarized.

[0078] Here, taking the example of a case where the transmission axis of the viewer 191 and the polarization axis of the transmitted light A24A(I) are aligned, the amount of light per unit area of ​​the transmitted light A25A(I), A25B(I), and A25Z(I) is such that light A25A(I) is the brightest and light A25Z(I) is the darkest. Light A25B(I) is brighter than light A25Z(I) and darker than light A25A(I). On the other hand, the amount of incident light entering the identification medium 100, i.e., incident light A21A(N), A21B(N), and A21Z(N), per unit area is the same. Therefore, the emission rates of the polarization components to be observed from the regions 202RA, 202RB, and 202RZ are greatest in the region 202RA, next greatest in the region 202RB, and smallest in the region 202RZ. Moreover, in a region 202RC not shown in FIG. 6, the output ratio is smaller than that of the region 202RB and larger than that of the region 202RZ.

[0079] The relative magnitude relationship of the observation target polarization component output efficiencies can change when the viewer 191 is rotated to change the relationship between its transmission axis and the polarization direction of the transmitted light, thereby changing the polarization component that is the observation target polarization component. However, when the transmission axis of the viewer 191 is oriented in at least one direction, the observation target polarization component output efficiencies of the regions 202RA, 202RB, 202RC, and 202RZ usually have different values ​​in almost all orientations (except for exceptional cases where the output efficiencies happen to be the same). In this way, the observation target polarization component output efficiencies are different due to the different phase differences of the retardation layers in three or more regions.

[0080] As a result, when the identification medium 200 with non-polarized light incident thereon is observed with non-polarized light without using the viewer 191, the viewer will not recognize the presence of areas 202RA, 202RB, and 202RC in the background area 202RZ, whereas when non-polarized-polarized light observation is performed through the viewer 191, areas 202RA, 202RB, and 202RC are visible as latent images, and these are visible as images with different brightnesses.

[0081] This visual appearance of the latent image is a feature that cannot be easily replicated by general printing or other techniques, and therefore the identification medium of the present invention can exhibit high anti-counterfeiting performance. Furthermore, the feature that the latent images are visually recognized as images with different brightnesses is a feature that clearly distinguishes it from counterfeit identification media forged using general techniques, and therefore the identification medium of the present invention can exhibit high identification functionality. In addition, the feature that the latent images can be configured with different brightnesses also makes it possible to achieve a high design effect by the appearance of complex latent images.

[0082] 6 illustrates an example in which the discrimination medium and the linear polarizer for observation are observed at a distance from each other, but the positional relationship between the discrimination medium and the linear polarizer for observation during observation is not limited to this. For example, such a latent image can also be observed by placing the linear polarizer for observation on the discrimination medium and bringing them close to each other.

[0083] In the above example, a linear polarizer is used as the observation polarizer, but the present invention is not limited to this, and a polarizer other than a linear polarizer may also be used as the observation polarizer. For example, even when a right-handed circular polarizer, a left-handed circular polarizer, or a combination thereof is used instead of a linear polarizer as the observation polarizer and the polarization component to be observed is circularly polarized, the latent image is visually recognized as an image with different brightnesses based on the difference in the proportions of the circularly polarized components of the output light from three or more regions, and the effect of the present invention can be exerted.

[0084] (Example (ii) Usage: Part 2) The above-described example is an example of a method of using unpolarized light as the light incident on the identification medium 200 and a linear polarizer for observation, and performing unpolarized observation and unpolarized-polarized observation. On the other hand, below, an example of a method of using unpolarized light and polarized light as the light incident on the identification medium 200 without using a linear polarizer for observation will be described.

[0085] In polarized and non-polarized light observation, polarized light is incident on the identification medium 200, and when it passes through the regions 202RA, 202RB, 202RC, and 202RZ of the retardation layer, it is emitted downward as polarized light whose polarization state has been changed. The proportion of the right-handed circularly polarized component in the polarized light that is emitted is L and high phase difference sub-region 202SR H The difference is based on the ratio of the right-handed circularly polarized component of the downward output light from the retardation layer 202. Only the right-handed circularly polarized component is reflected by the light reflecting layer 101(R) and enters the retardation layer 202 again. When passing through the regions 202RA, 202RB, 202RC, and 202RZ, the polarization state of the output light changes from that of the input light, but the amount of light does not change. Therefore, the amount of light per unit area output from the regions 202RA, 202RB, 202RC, and 202RZ to the outside of the identification medium 200 reflects the amount of the right-handed circularly polarized component reflected by the light reflecting layer 101(R), and these amounts are different from each other. In this polarized / non-polarized light observation, the light output from the identification medium 200 is the polarized component to be observed. As described above, the output rates of the polarized components to be observed differ due to the different phase differences of the retardation layer in the three or more regions.

[0086] As a result, when observed with polarized light and non-polarized light, the regions 202RA, 202RB, and 202RC are visible as latent images with different brightness levels, which provides high anti-counterfeiting performance, high identification capabilities, and high design effects, just as in the case of non-polarized light and polarized light observation.

[0087] (Specific examples of light-reflecting layers) The light-reflecting layer is a layer that reflects incident light as circularly polarized light or linearly polarized light. Examples of the light-reflecting layer include a reflective circular polarizer and a reflective linear polarizer, as exemplified by the light-reflecting layer 101(R) described above. The light-reflecting layer may exhibit such a function by only one layer, or may exhibit such a function by a combination of multiple layers.

[0088] An example of a reflective circular polarizer is a layer of a material with cholesteric regularity. Cholesteric regularity is a structure in which the molecular axes are aligned in a fixed direction on a certain plane within the material, but the direction of the molecular axes is slightly shifted on the next overlapping plane, and then even more so on the next plane. As the light passes through successive overlapping planes, the angle of the molecular axes in the plane shifts (twists). That is, when molecules within a layer of a material have cholesteric regularity, the molecules are aligned so that their molecular axes are aligned in a fixed direction on a first plane within the layer. On a second plane overlapping the first plane, the direction of the molecular axes shifts at a slight angle from the direction of the molecular axes on the first plane. On a third plane overlapping the second plane, the direction of the molecular axes shifts at an even greater angle from the direction of the molecular axes on the second plane. In this way, the angles of the molecular axes in the overlapping planes shift (twist) successively. Such a structure in which the direction of the molecular axis is twisted is usually a helical structure, and is an optically chiral structure.

[0089] A more specific example of a material having cholesteric regularity is a cholesteric resin layer. A cholesteric resin layer is a layer obtained by curing a curable liquid crystal compound that exhibits a cholesteric liquid crystal phase. A cholesteric resin layer can be obtained, for example, by polymerizing a polymerizable liquid crystal compound in a state in which it exhibits a cholesteric liquid crystal phase. More specifically, a cholesteric resin layer can be obtained by applying a liquid crystal composition containing a polymerizable liquid crystal compound to a suitable substrate to form a layer, aligning the layer in a cholesteric liquid crystal phase, and curing the layer.

[0090] The polymerizable liquid crystal compound is preferably a photopolymerizable liquid crystal compound. The photopolymerizable liquid crystal compound may be a photopolymerizable liquid crystal compound that can be polymerized by irradiation with active energy rays. The active energy rays may be selected from a wide range of energy rays, such as visible light, ultraviolet light, and infrared light, as long as they can promote the polymerization reaction of the photopolymerizable liquid crystal compound. Ionizing radiation such as ultraviolet light is particularly preferred. Among these, the photopolymerizable liquid crystal compound that is preferably used in the cholesteric liquid crystal composition is preferably a rod-shaped liquid crystal compound having two or more reactive groups in one molecule, and a compound represented by formula (1) is particularly preferred. R 3 -C 3 -D 3 -C 5 -MC 6 -D 4 -C 4 -R 4 Formula (1)

[0091] In formula (1), R 3 and R 4 are reactive groups, each independently representing a group selected from the group consisting of a (meth)acrylic group, a (thio)epoxy group, an oxetane group, a thietanyl group, an aziridinyl group, a pyrrole group, a vinyl group, an allyl group, a fumarate group, a cinnamoyl group, an oxazoline group, a mercapto group, an iso(thio)cyanate group, an amino group, a hydroxyl group, a carboxyl group, and an alkoxysilyl group. By having these reactive groups, it is possible to obtain a cured liquid crystal composition layer having high mechanical strength when the liquid crystal composition is cured.

[0092] In equation (1), D 3 and D 4 each independently represents a group selected from the group consisting of a single bond, a linear or branched alkyl group having 1 to 20 carbon atoms, and a linear or branched alkylene oxide group having 1 to 20 carbon atoms.

[0093] In formula (1), C 3 ~C 6each independently represents a group selected from the group consisting of a single bond, -O-, -S-, -SS-, -CO-, -CS-, -OCO-, -CH-, -OCH-, -CH=NN=CH-, -NHCO-, -O-(C=O)-O-, -CH-(C=O)-O-, and -CHO-(C=O)-.

[0094] In formula (1), M represents a mesogenic group. Specifically, M represents a group in which two to four identical or different skeletons selected from the group consisting of azomethines, azoxys, phenyls, biphenyls, terphenyls, naphthalenes, anthracenes, benzoates, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes, and alkenylcyclohexylbenzonitriles, which may be unsubstituted or substituted, are bonded together by a bonding group such as -O-, -S-, -SS-, -CO-, -CS-, -OCO-, -CH-, -OCH-, -CH=NN=CH-, -NHCO-, -O-(C=O)-O-, -CH-(C=O)-O-, or -CHO-(C=O)-.

[0095] Examples of the substituent that the mesogenic group M may have include a halogen atom, an alkyl group having 1 to 10 carbon atoms which may have a substituent, a cyano group, a nitro group, -OR 5 , -OC(=O)-R 5 , -C(=O)-OR 5 , -OC(=O)-OR 5 , -NR 5 -C(=O)-R 5 , -C(=O)-NR 5 R 7 , or -OC(=O)-NR 5 R 7 Here, R 5 and R 7 represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. 5 and R 7is an alkyl group, the alkyl group may include -O-, -S-, -OC(=O)-, -C(=O)-O-, -OC(=O)-O-, -NR 6 -C(=O)-, -C(=O)-NR 6 -, -NR 6 - or -C(=O)- may be present (except when two or more adjacent -O- and -S- are present). 6 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

[0096] Examples of the substituent in the "optionally substituted alkyl group having 1 to 10 carbon atoms" include a halogen atom, a hydroxyl group, a carboxyl group, a cyano group, an amino group, an alkoxy group having 1 to 6 carbon atoms, an alkoxyalkoxy group having 2 to 8 carbon atoms, an alkoxyalkoxyalkoxy group having 3 to 15 carbon atoms, an alkoxycarbonyl group having 2 to 7 carbon atoms, an alkylcarbonyloxy group having 2 to 7 carbon atoms, and an alkoxycarbonyloxy group having 2 to 7 carbon atoms.

[0097] The rod-shaped liquid crystal compound preferably has an asymmetric structure. Here, the asymmetric structure is defined as a structure in which, in formula (1), R 3 -C 3 -D 3 -C 5 -M- and -MC 6 -D 4 -C 4 -R 4 The term "asymmetric" refers to a structure that differs from the "asymmetric" structure. By using a rod-like liquid crystal compound with an asymmetric structure, the alignment uniformity can be further improved.

[0098] Preferred specific examples of the rod-shaped liquid crystal compound include the following compounds (B1) to (B10), however, the rod-shaped liquid crystal compound is not limited to the following compounds.

[0099] [ka]

[0100] [ka]

[0101] When the liquid crystal composition contains the rod-shaped liquid crystal compound described above, the liquid crystal composition preferably contains a compound represented by formula (2) as an alignment aid in combination with the rod-shaped liquid crystal compound. In particular, when a broadening treatment is performed to obtain a cured layer having a wide reflection band and exhibiting a silver color or a color tone similar to silver, the inclusion of the alignment aid is preferred because such a broadening treatment can be easily performed. R 1 -A 1 -BA 2 -R 2 (2)

[0102] In equation (2), R 1 and R 2 are each independently a group selected from the group consisting of a linear or branched alkyl group having 1 to 20 carbon atoms, a linear or branched alkylene oxide group having 1 to 20 carbon atoms, a hydrogen atom, a halogen atom, a hydroxyl group, a carboxyl group, a (meth)acrylic group which may have an optional bonding group interposed therebetween, an epoxy group, a mercapto group, an isocyanate group, an amino group, and a cyano group.

[0103] The alkyl group and alkylene oxide group may be unsubstituted or substituted with one or more halogen atoms. Furthermore, the halogen atom, hydroxyl group, carboxyl group, (meth)acrylic group, epoxy group, mercapto group, isocyanate group, amino group, and cyano group may be bonded to the alkyl group having 1 to 2 carbon atoms and the alkylene oxide group.

[0104] R 1 and R 2Preferred examples of the alkyl group include a halogen atom, a hydroxyl group, a carboxyl group, a (meth)acrylic group, an epoxy group, a mercapto group, an isocyanate group, an amino group, and a cyano group.

[0105] Also, R 1 and R 2 At least one of R is preferably a reactive group. 1 and R 2 By having a reactive group as at least one of the above, the compound represented by formula (2) is fixed in the cured layer of the liquid crystal composition upon curing, and a stronger layer can be formed. Examples of the reactive group include a carboxyl group, a (meth)acrylic group, an epoxy group, a mercapto group, an isocyanate group, and an amino group.

[0106] In equation (2), A 1 and A 2 each independently represents a group selected from the group consisting of a 1,4-phenylene group, a 1,4-cyclohexylene group, a cyclohexen-1,4-ylene group, a 4,4'-biphenylene group, a 4,4'-bicyclohexylene group, and a 2,6-naphthylene group. The 1,4-phenylene group, the 1,4-cyclohexylene group, the cyclohexen-1,4-ylene group, the 4,4'-biphenylene group, the 4,4'-bicyclohexylene group, and the 2,6-naphthylene group may be unsubstituted or may be substituted with one or more substituents such as a halogen atom, a hydroxyl group, a carboxyl group, a cyano group, an amino group, an alkyl group having 1 to 10 carbon atoms, or a halogenated alkyl group. A 1 and A 2 In each of the groups, when two or more substituents are present, they may be the same or different.

[0107] A 1 and A 2Particularly preferred examples of the aromatic ring skeleton include a group selected from the group consisting of a 1,4-phenylene group, a 4,4'-biphenylene group, and a 2,6-naphthylene group. These aromatic ring skeletons are relatively rigid compared to alicyclic skeletons, and have a high affinity with the mesogens of rod-shaped liquid crystal compounds, resulting in higher alignment uniformity.

[0108] In formula (2), B is selected from the group consisting of a single bond, -O-, -S-, -SS-, -CO-, -CS-, -OCO-, -CH2-, -OCH2-, -CH=NN=CH-, -NHCO-, -O-(C=O)-O-, -CH2-(C=O)-O-, and -CHO-(C=O)-. Particularly preferred values ​​for B include a single bond, -O-(C=O)-, and -CH=NN=CH-.

[0109] Particularly preferred specific examples of the compound represented by formula (2) include the following compounds (A1) to (A10). These may be used alone or in combination of two or more in any ratio.

[0110] [ka]

[0111] In the above compound (A3), "*" represents a chiral center.

[0112] The weight ratio (total weight of compounds represented by formula (2)) / (total weight of rod-shaped liquid crystal compounds) is preferably 0.001 or more, more preferably 0.01 or more, even more preferably 0.05 or more, and preferably 1 or less, more preferably 0.65 or less. By setting the weight ratio at or above the lower limit, the alignment uniformity in the liquid crystal composition layer can be improved. On the other hand, by setting the weight ratio at or below the upper limit, the alignment uniformity can be increased. In addition, the stability of the liquid crystal phase of the liquid crystal composition can be improved. Furthermore, since the refractive index anisotropy Δn of the liquid crystal composition can be increased, a cured liquid crystal composition layer having desired optical properties, such as selective reflection performance of circularly polarized light, can be stably obtained. Here, the total weight of compounds represented by formula (2) refers to the weight when only one type of compound represented by formula (2) is used, and refers to the total weight when two or more types are used. Similarly, the total weight of rod-shaped liquid crystal compounds refers to the weight when only one type of rod-shaped liquid crystal compound is used, and refers to the total weight when two or more types are used.

[0113] When the compound represented by formula (2) is used in combination with a rod-shaped liquid crystal compound, the molecular weight of the compound represented by formula (2) is preferably less than 600, and the molecular weight of the rod-shaped liquid crystal compound is preferably 600 or more. This allows the compound represented by formula (2) to enter into the gaps of the rod-shaped liquid crystal compound having a larger molecular weight, thereby improving the alignment uniformity.

[0114] The liquid crystal composition for forming the cholesteric resin layer may further contain optional components constituting the cholesteric resin layer and a solvent for facilitating handling of the liquid crystal composition. Examples of the optional components include a chiral agent, a polymerization initiator, and a surfactant. Specific examples of optional components and solvents include those described in JP 2019-188740 A. Other optional components include, preferably, surfactants having a fluoroalkyl group (Rf) chain length of less than 6, such as F-563 from DIC Corporation and KZ-GDP02 and KZ-GDP05 from AGC Seimi Chemical Co., Ltd.

[0115] The cholesteric resin layer obtained by the above method can be used as a light-reflecting layer as is. Alternatively, a light-reflecting layer can be obtained by pulverizing the obtained cholesteric resin layer to form a particulate pigment, preparing an ink containing the particulate pigment, applying the ink to an appropriate substrate, and curing the ink to form a pigment layer. In this way, by forming the light-reflecting layer as a cured product of the ink, a light-reflecting layer having a desired shape can be easily obtained. Particulate pigments usually become particles having a flat, plate-like shape, and when applied, the surface of the plate-like shape is piled up in an arrangement roughly parallel to the coating surface. Therefore, even in the cured ink, the same optical properties as the cholesteric resin layer before pulverization can be exhibited.

[0116] Examples of reflective linear polarizers include films formed by laminating multiple thin films (for example, product name "DBEF" manufactured by 3M) and wire grid polarizers.

[0117] Whether the light-reflecting layer is a reflective circular polarizer or a reflective linear polarizer, the reflectance of the light-reflecting layer to unpolarized light incident on the light-reflecting layer is a maximum of 50%. The light-reflecting layer visually exhibits various colors depending on the reflection band and reflectance. When the reflectance of unpolarized light incident on the light-reflecting layer by the light-reflecting layer is high at all wavelengths in the wavelength range of 420 nm to 650 nm, the light-reflecting layer is observed as a silver layer. When the band of high reflectance is narrower than this, the light-reflecting layer may exhibit various colors depending on the band. For example, when the reflection band is near 450 nm, near 550 nm, or near 650 nm, the light-reflecting layer may exhibit colors such as blue, green, or red, respectively. When forming a silver-colored light-reflecting layer, the material used is preferably one that exhibits a reflectance of unpolarized light incident on the material of 35 to 50% at all wavelengths in the wavelength range of 420 nm to 650 nm.

[0118] The identification medium of the present invention may have only one light-reflecting layer or multiple light-reflecting layers. The identification medium may also have only one type of light-reflecting layer or multiple types of light-reflecting layers with different polarization states of reflected light. For example, the identification medium may have multiple types of reflective polarizers that exhibit multiple colors, such as red, green, blue, and silver, stacked as the light-reflecting layer. From the viewpoint of making the latent image clearly visible, it is preferable that the light reflecting layer is silver or a combination of silver and another color.

[0119] (Specific example of retardation layer) The retardation layer is a layer including a region having retardation. The region having retardation occupies the whole or part of the region of the display surface of the identification medium. In the case of the above-mentioned specific example (ii), the retardation layer includes at least the low retardation sub-region SR L and a high retardation subregion SR H On the other hand, in the case of the specific example (i) described above, the retardation layer includes three or more regions having different in-plane retardations Re.

[0120] The in-plane retardation Re of the regions included in the retardation layer is preferably distributed in a range of 412.5 nm or less. That is, the in-plane retardation Re of each region of the retardation layer is preferably any value within the range of 0 nm to 412.5 nm. The inventors have found that when the in-plane retardation Re is in this range, the contrast between regions is improved when observed with polarized light, and a grayscale gradation with a wide range of brightness can be depicted.

[0121] Materials constituting the retardation layer include various solid materials having optical anisotropy. One example is a liquid crystal cured layer, i.e., a cured product of a liquid crystal compound. Specifically, it is a layer obtained by curing a curable liquid crystal compound that is oriented in a liquid crystal state exhibiting retardation. A cured product of a liquid crystal compound is particularly preferred because it is a single film having different retardation between certain regions and other certain regions, and the difference in film thickness between regions is very small and the film thickness is approximately constant, making it easy to form a film with high concealment of the latent image.

[0122] More specifically, the liquid crystal cured layer that can be used as the retardation layer can be produced by a production method including the following steps. Step (I): A step of forming a liquid crystal composition layer by applying a photopolymerizable liquid crystal composition containing a polymerizable liquid crystal compound onto the surface of a substrate, orienting the liquid crystal compound in the liquid crystal composition layer in an orientation state such as a nematic orientation state, and drying the liquid crystal composition layer to obtain a multilayered product having the substrate and a dried liquid crystal composition layer. Step (II): A step of semi-curing the liquid crystal composition layer by irradiating the multilayered product with light of 350 to 400 nm through an exposure mask having multiple regions with different transmittances under conditions maintained at a relatively low temperature of 20 to 40°C. Step (III): A step of heating the multilayered product to a temperature higher than that in step (II) to make the uncured components in the liquid crystal composition isotropic. Step (IV): A step of irradiating the liquid crystal composition layer with light while maintaining the heating temperature in step (III) to fully cure the liquid crystal composition layer and form a liquid crystal cured layer containing multiple types of regions with different in-plane retardation Re on the substrate.

[0123] More specific examples of the liquid crystal cured layer, materials for forming the same, and methods for producing the same are described in, for example, JP 2015-87472 A.

[0124] In step (I), the orientation direction of the liquid crystal compound can be controlled by the orientation restraining force on the surface of the substrate. By applying an orientation restraining force in a uniform direction to the entire surface of the substrate, it is possible to impart a uniform in-plane retardation Re in the slow axis direction to each region of the resulting retardation layer. In this way, when all regions have a uniform slow axis direction, it is preferable because it is easy to manufacture and can display good contrast.

[0125] The exposure mask used in step (II) may have a plurality of regions with different transmittances of irradiated light, which may correspond to regions in the cured liquid crystal layer to be produced. The regions of the cured liquid crystal layer irradiated with the regions with higher transmittance have higher optical anisotropy, while the regions of the cured liquid crystal layer irradiated with the regions with lower transmittance have lower optical anisotropy.

[0126] Therefore, for example, when a liquid crystal cured layer that can be used as the retardation layer of the specific example (i) described above is produced as a liquid crystal cured layer, an exposure mask can be used that has a plurality of regions corresponding to three or more regions of the retardation layer, with high transmittance in the regions corresponding to the liquid crystal cured layer regions where high in-plane retardation Re is required and low transmittance in the regions corresponding to the liquid crystal cured layer regions where low in-plane retardation Re is required. Furthermore, by producing an exposure mask having a uniform transmittance in each region according to a conventional method and performing step (II) using this, a retardation layer having a uniform in-plane retardation Re in each region, such as a variation in in-plane retardation Re in each region within ±3 nm, can be easily produced.

[0127] When a liquid crystal cured layer that can be used as the retardation layer of the above-mentioned specific example (ii) is produced, the exposure mask is L and high phase difference sub-region SR H A mask in which a plurality of regions corresponding to high phase difference sub-regions SR are set H The transmittance is high in the region corresponding to the low retardation sub-region SR LIn this case, even if the exposure dose is adjusted in two stages, the resulting retardation layer can depict three or more stages of gradation. Therefore, from the viewpoint of easily producing a retardation layer capable of depicting a variety of gray scale gradations, it is preferable to employ the embodiment of specific example (ii) in the above-described method.

[0128] In steps (III) to (IV), the liquid crystal compound in the liquid crystal composition that did not cure in step (II) cures. As a result, in a portion of the cured product in the liquid crystal cured layer, the liquid crystal compound cures in a liquid crystal phase state, while the remainder cures in an isotropic phase state. Regions containing a large amount of cured product cured in a liquid crystal phase state become regions of high optical anisotropy, while regions containing a small amount of cured product cured in a liquid crystal phase state become regions of low optical anisotropy. Because the polymer molecules formed in the high optical anisotropy region and the low optical anisotropy region are in the same state except for the degree of orientation, there is usually little difference in thickness, and there is little difference in the transparency and transmittance spectrum when non-polarized light is transmitted. Therefore, the liquid crystal cured layer produced in this manner can be suitably used as a highly confidential retardation layer.

[0129] (Optional component) The identification medium of the present invention may contain optional components in addition to the light-reflecting layer and the retardation layer, such as a light-absorbing layer and a protective layer.

[0130] The light-absorbing layer is a layer that absorbs incident light. The light-absorbing layer can be a black layer. The material of the light-absorbing layer may be any material, for example, a black-colored film. The light-absorbing layer can be provided on the back side of the light-reflecting layer, i.e., on the side opposite the visible side of the light-reflecting layer. When the light-reflecting layer is either a reflective circular polarizer or a reflective linear polarizer, much of the incident light that is not reflected is transmitted. When a light-absorbing layer is provided on the back side of the light-reflecting layer, the transmitted light is absorbed, and as a result, the effect of the reflected light can be more clearly seen. On the other hand, when a light-absorbing layer is not provided on the back side of the light-reflecting layer, the back side of the light-reflecting layer is visible, making the effect of the reflected light unclear, but a design effect of making the identification medium a see-through object can be obtained.

[0131] The protective layer can be a transparent layer provided on the viewing side of the retardation layer. The protective layer is preferably provided on the outermost surface of the viewing side of the identification medium. By providing the protective layer, the retardation layer and other layers can be protected when the identification medium is used. When the liquid crystal cured layer produced by the above-described steps (I) to (IV) is used as the retardation layer, the base material used in the production can be used as the protective layer as it is by arranging it on the viewing side of the retardation layer.

[0132] (Specific examples of identification media: modified examples) In the above-described identification media 100 and 200, a reflective circular polarizer that selectively reflects right-handed circularly polarized light is used as the light-reflecting layer 101(R), but the light-reflecting layer is not limited to this and may be a reflective circular polarizer that selectively reflects left-handed circularly polarized light, or a reflective linear polarizer. When a reflective linear polarizer is used as the light-reflecting layer, the specific polarized light component becomes a linearly polarized component.

[0133] Although four types of regions are defined in the retardation layers 102 and 202 of the identification media 100 and 200 shown above, the retardation layers are not limited to this, and the types of regions may be three, five, or more. By defining many types of regions, it is possible to provide variations in brightness in the latent image, and to express a highly aesthetic grayscale gradation.

[0134] In the above-described identification media 100 and 200, the light absorbing layer 191 is provided on the back side of the light reflecting layer, but it is also possible to configure a see-through identification medium in which the back side of the light reflecting layer is visible through the identification medium without providing the light absorbing layer. Furthermore, in this case, another retardation layer may be provided on the back side of the light reflecting layer. In this case, an identification medium can be configured in which different latent images are observed when observed from the front side and the back side.

[0135] In the above-described identification media 100 and 200, the entire upper surface is used as the display surface, but the identification media is not limited to this. For example, only the central portion of the upper surface may be used as the display surface, and the periphery may be surrounded by a frame.

[0136] In the discrimination medium 200, which is a more specific example of the specific example (ii) shown above, the retardation layer 202 has a low retardation sub-region SR L and high phase difference sub-region SR H However, the retardation layer of specific example (ii) is not limited to this and may have another sub-region whose retardation is different from any of these. However, from the viewpoint of ease of production and adjustment of gradation, it is preferable that the sub-region consists of only two types.

[0137] (Goods) The article of the present invention comprises the identification medium of the present invention. The article may be any article for which authenticity is required. Examples of articles include certificates such as banknotes, gift certificates, securities, ID cards, cash cards, and credit cards, as well as various devices and articles such as clothing, shoes, hats, accessories, jewelry, home appliances, and daily necessities. The article of the present invention may have an identification function by comprising the identification medium. Such an identification function allows the identification medium and the article to be identified as genuine and not counterfeit. In addition, the identification medium can impart a design effect to the article when a latent image is observed. The identification medium may be attached to the article as an ornament, part, or accessory to the article, such as a tag, charm, patch, or sticker.

[0138] The article of the present invention may further include a polarizer viewer in addition to the identification medium of the present invention. Examples of polarizer viewers include those equipped with an observation polarizer such as the above-described observation linear polarizer or observation circular polarizer, and provided on the article so that the identification medium can be observed through the observation polarizer. The polarizer viewer may be, for example, in the form of a tag, and may be attached to the article body via a string or the like. Thus, by providing a polarizer viewer in addition to the identification medium, general article users can easily identify the identification medium. [Example]

[0139] The present invention will be described in detail below with reference to examples. However, the present invention is not limited to the examples shown below, and can be practiced with any modifications within the scope of the claims of the present invention and their equivalents.

[0140] In the following description, the units "%" and "parts" that represent amounts are by weight unless otherwise specified. Furthermore, the operations described below were carried out in air at room temperature and normal pressure unless otherwise specified.

[0141] (Evaluation method) (Evaluation of identification media) The display surfaces of the discrimination media obtained in the examples and comparative examples were observed with the naked eye and through a viewer, and the observation results were classified according to the following evaluation criteria. The viewer used was one specified in each example and comparative example. "Excellent": No latent image is visible to the naked eye. Furthermore, when viewed through a viewer, the latent image has a gradation of shade, with a clear difference between the darkest and lightest parts, providing a very high level of discrimination functionality as a discrimination medium. "Good": No latent image is visible to the naked eye. Also, when viewed through a viewer, the latent image has a gradation of shade, but the difference between the darkest and lightest parts is small, so the discrimination function is inferior to "Excellent." "Poor": A latent image is visible when observed with the naked eye, or when observed through a viewer, the density of the latent image is only binary, consisting of dark and light areas, and the discrimination function is poor.

[0142] (Method for measuring in-plane retardation Re) The in-plane retardation Re was measured at a measurement wavelength of 550 nm using a phase difference meter (Axoscan manufactured by Axometrics).

[0143] (Exposure mask) Masks A to E were used in this example and comparative example. Masks A and B were masks with UV-cut printing, and C to E were emulsion masks. Each of masks A to E had an exposure area consisting of four areas: area A having the shape of the letter A, area B having the shape of the letter B, area C having the shape of the letter C, and background area Z. Details of each mask are shown below. Mask A: The 365 nm transmittance differs in four regions. The 365 nm transmittance is uniform within each region. Due to differences in the thickness of the UV-cutting layer in each region, the transmittance of each region was 92% in region A, 56% in region B, 33% in region C, and 0% in region Z, and the thicknesses of the UV-cutting layers were 0 μm, 8.6 μm, 12.8 μm, and 19 μm, respectively. Mask B: The 365 nm transmittance differs in four regions. The 365 nm transmittance is uniform within each region. Due to differences in the thickness of the UV-cutting layer in each region, the transmittance of each region was 92% in region A, 74% in region B, 40% in region C, and 19% in region Z, and the thicknesses of the UV-cutting layers were 0 μm, 2.9 μm, 11 μm, and 14.4 μm. Mask C: Halftone dots are present in the exposed area. The screen ruling of the halftone dots is 175 lpi. The 365 nm transmittance where halftone dots are present is 0%, and the 365 nm transmittance where halftone dots are not present is 92%. Due to differences in the diameter of the halftone dots in each area, the proportion of the area occupied by the halftone dots in each area is 0% in area A, 50% in area B, 70% in area C, and 100% in area Z. Mask D: Halftone dots are present in the exposed area. The screen ruling of the halftone dots is 175 lpi. The 365 nm transmittance in the areas where halftone dots are present is 0%, and the 365 nm transmittance in the areas where halftone dots are not present is 92%. The area ratio occupied by the halftone dots in each area is 0% for area A, 30% for area B, 60% for area C, and 80% for area Z. Mask E: The 365 nm transmittance is different between areas A to C and area Z. The 365 nm transmittance is uniform within each area. The transmittance of each area is 92% for areas A to C and 0% for area Z.

[0144] <Production Example 1: Cholesteric Material Layer (R) (G) (B)> A liquid crystal compound (trade name "Paliocolor LC242", manufactured by BASF), a chiral agent (trade name "Paliocolor LC756", manufactured by BASF), a photopolymerization initiator (trade name "Irgacure OXE02", manufactured by BASF), a leveling agent (trade name "Surflon S420", manufactured by AGC Seimi Chemical Co., Ltd.), and a solvent (methyl ethyl ketone) were mixed in the proportions shown in Table 1 below to obtain liquid crystal compositions (R), (G), and (B).

[0145] [Table 1]

[0146] The surface of a raw substrate (PET film, manufactured by Toyobo Co., Ltd., product name "A4100") was subjected to a rubbing treatment. Liquid crystal compositions (R), (G), and (B) were each applied to the surface using a bar coater to form a liquid crystal composition layer. The thickness of the liquid crystal composition layer was adjusted so that the final thickness of the cholesteric material layer would be 3.5 μm. This was heated in an oven at 100°C for 2 minutes to dry and align the liquid crystal composition layer. Subsequently, the dried liquid crystal composition layer was irradiated with ultraviolet light in a nitrogen gas atmosphere (oxygen concentration 400 ppm or less). For irradiation, a high-pressure mercury lamp was used, and the illuminance at 365 nm (i-line) was 280 mW / cm. 2 , exposure dose 2000mJ / cm 2 The irradiation conditions were adjusted so that the residual monomer ratio was about 2% by weight. As a result, polymerization was achieved, and the liquid crystal composition layer was cured to form a cholesteric material layer. In this way, a raw sheet including the raw substrate and the cholesteric material layer was obtained.

[0147] <Production Example 2: Cholesteric Material (S)> A liquid crystal composition (S) was obtained by mixing 14.63 parts by weight of a liquid crystal compound (a compound represented by (X1) below), 3.66 parts by weight of an alignment aid (a compound represented by (X2) below), 1.09 parts by weight of a chiral agent (trade name "Paliocolor LC756", manufactured by BASF), 0.02 parts by weight of a leveling agent (trade name "Surflon S420", manufactured by AGC Seimi Chemical Co., Ltd.), 0.60 parts by weight of a photopolymerization initiator (trade name "Irgacure OXE02", manufactured by BASF), and 80.00 parts by weight of a solvent (methyl ethyl ketone).

[0148] [ka]

[0149] [ka]

[0150] The surface of a raw substrate (PET film, manufactured by Toyobo Co., Ltd., product name "A4100") was subjected to a rubbing treatment. A liquid crystal composition (S) was applied to the surface using a bar coater to form a layer of the liquid crystal composition. The thickness of the liquid crystal composition layer was adjusted so that the thickness of the final cholesteric material layer would be approximately 5 μm. This was heated in an oven at 140°C for 2 minutes to dry and align the liquid crystal composition layer.

[0151] Subsequently, a broadening treatment was carried out by irradiating the dried liquid crystal composition layer with weak ultraviolet light in an air atmosphere and then heating it. The ultraviolet light was irradiated using a high-pressure mercury lamp with an illuminance of 25 mW / cm at 365 nm (i-line). 2 The sample was then heated at 90°C for 1 minute.

[0152] Subsequently, the dried liquid crystal composition layer was irradiated with ultraviolet light for curing under a nitrogen gas atmosphere (oxygen concentration 400 ppm or less). For irradiation, a high-pressure mercury lamp was used, and the illuminance at 365 nm (i-line) was 280 mW / cm. 2 , exposure dose 2000mJ / cm 2 The irradiation conditions were adjusted so that the liquid crystal composition layer was cured to form a cholesteric material layer (S). In this way, a raw sheet including the raw substrate and the cholesteric material layer (S) was obtained.

[0153] <Production Example 3: Cholesteric Pigments (R), (G), (B), and (S)> The raw sheets containing the cholesteric material layer obtained in Production Examples 1 and 2 were folded and blown with air to peel off the cholesteric material layer, yielding peeled pieces. The peeled pieces were pulverized using a cutter mill and passed through a 51 μm sieve. The particles that passed through the sieve were collected to obtain cholesteric pigments (R), (G), (B), and (S), respectively. The particle size distribution of the pigments was measured using a laser diffraction / scattering method with a particle size distribution analyzer (product name "LA-960" manufactured by Horiba, Ltd.). The average particle size of the pigments (R), (G), (B), and (S) was determined to be 30 μm.

[0154] <Production Example 4: Multilayer film P1> Liquid crystal composition Q was prepared by mixing 3.76 parts by weight of a liquid crystal compound (product name "Paliocolor LC242", manufactured by BASF), 3.66 parts by weight of an alignment aid (compound represented by (X2) above), 0.45 parts by weight of ATMPT (trimethylolpropane triacrylate; manufactured by Shin-Nakamura Chemical Co., Ltd.), 0.15 parts by weight of a photopolymerization initiator ("Omnirad379EG" manufactured by IGM Resins BV), 0.02 parts by weight of a surfactant ("Megafac F-562" manufactured by DIC Corporation), 7.43 parts by weight of methyl ethyl ketone as a solvent, and 1.98 parts by weight of 1,3-dioxolane.

[0155] The surface of an isotropic substrate (manufactured by Zeon Corporation, product name "ZEONORFILM ZF14-100") was subjected to a rubbing treatment. Liquid crystal composition Q was applied to the surface using a bar coater to form a layer of the liquid crystal composition. The thickness of the liquid crystal composition layer was adjusted so that the thickness of the final cured liquid crystal layer would be approximately 3 μm. This was heated in an oven at 60°C for 2 minutes to dry the layer of the liquid crystal composition and align it into a nematic liquid crystal phase.

[0156] The dried liquid crystal composition layer was irradiated with 7.2 mJ / cm 2 from the substrate side through Mask A in an environment of 25°C. 2 The liquid crystal composition layer was then irradiated with ultraviolet light of 500 mJ / cm 2 in a nitrogen gas atmosphere while heated at 90°C. 2 The ultraviolet irradiation was carried out without using a mask. As a result, the layer of the liquid crystal composition was cured to form a liquid crystal cured layer, and a multilayer film P1 comprising an isotropic substrate and a liquid crystal cured layer was obtained. The multilayer film P1 was a film in which regions with different transmittances were mixed due to the different transmittances of the regions of the mask A. Hereinafter, the regions of the multilayer film P1 corresponding to the regions of the mask will be referred to by the same names as the regions of the mask (regions A to C and region Z). In the multilayer film P1, the in-plane retardations Re of region A, region B, region C, and region Z were 143 nm, 71 nm, 40 nm, and 3 nm, respectively. The average film thickness d of the liquid crystal cured layer of the multilayer film P1 avis 3.18μm, and the variation (((d max -d min ) / d av )×100) was 2.8%.

[0157] <Production Example 5: Multilayer film P1'> The same procedure as in Production Example 4 was carried out except that Mask C was used instead of Mask A, to obtain a multilayer film P1' having an isotropic substrate and a cured liquid crystal layer. The in-plane retardation Re at the position of the multilayer film P1' corresponding to the position where the halftone dots of Mask C were present and the position of the multilayer film P1' corresponding to the position where the halftone dots were not present were 3 nm and 143 nm, respectively. The average film thickness d of the cured liquid crystal layer of the multilayer film P1' av is 3.17μm, and the variation (((d max -d min ) / d av )×100) was 2.9%.

[0158] <Production Example 6: Multilayer film P2> The same procedure as in Production Example 4 was carried out to obtain a multilayer film P2 having an isotropic substrate and a cured liquid crystal layer, except that the coating amount of liquid crystal composition Q was changed and the thickness of the final cured liquid crystal layer was adjusted to about 6 μm. The in-plane retardations Re of regions A, B, C, and Z were 273 nm, 141 nm, 85 nm, and 3 nm, respectively. The average thickness d of the cured liquid crystal layer of multilayer film P2 av is 6.1μm, and the variation (((d max -d min ) / d av )×100) was 3.0%.

[0159] <Production Example 7: Multilayer film P2'> Except for the following changes, the same operations as in Production Example 4 were carried out to obtain a multilayer film P2' having an isotropic substrate and a cured liquid crystal layer. The amount of liquid crystal composition Q applied was changed so that the thickness of the final cured liquid crystal layer was adjusted to about 6 μm. Mask C was used instead of Mask A. The in-plane retardation Re at the positions of the multilayer film P2' corresponding to the positions where the halftone dots of the mask C were present and the positions of the multilayer film P2' corresponding to the positions where the halftone dots were not present were 3 nm and 273 nm, respectively. av is 6.0μm, and the variation (((d max -d min ) / d av )×100) was 3.3%.

[0160] <Manufacturing Example 8: Multilayer film P3> Except for the following changes, the same operations as in Production Example 4 were carried out to obtain a multilayer film P3 having an isotropic substrate and a cured liquid crystal layer. The amount of liquid crystal composition Q applied was changed so that the thickness of the final cured liquid crystal layer was adjusted to about 9 μm. Mask B was used instead of Mask A. The in-plane retardations Re of the regions A, B, C, and Z were 411 nm, 299 nm, 178 nm, and 136 nm, respectively. av is 9.13μm, and the variation (((d max -d min ) / d av )×100) was 2.8%.

[0161] <Production Example 9: Multilayer film P3'> Except for the following changes, the same operations as in Production Example 4 were carried out to obtain a multilayer film P3' having an isotropic substrate and a cured liquid crystal layer. The amount of liquid crystal composition Q applied was changed so that the thickness of the final cured liquid crystal layer was adjusted to about 9 μm. Mask D was used instead of Mask A. The in-plane retardation Re at the positions of the multilayer film P3' corresponding to the positions where the halftone dots of the mask D were present and the positions of the multilayer film P3' corresponding to the positions where the halftone dots were not present were 136 nm and 411 nm, respectively. av is 9.2μm, and the variation (((d max -d min ) / dav )×100) was 3.3%.

[0162] <Production Example 10: Multilayer film P4> The same procedure as in Production Example 4 was carried out except that Mask E was used instead of Mask A, to obtain a multilayer film P4 having an isotropic substrate and a cured liquid crystal layer. The in-plane retardation Re of regions A to C was 144 nm. The in-plane retardation Re of region Z was 2 nm. The average film thickness d of the cured liquid crystal layer of multilayer film P4 av is 3.2μm, and the variation (((d max -d min ) / d av )×100) was 3%.

[0163] <Production Example 11: Multilayer film P5> The surface of an isotropic substrate (manufactured by Zeon Corporation, product name "ZEONORFILM ZF14-100") was subjected to a rubbing treatment. Regions A to C and region Z were defined on the surface. Regions A to C and region Z had the same inverted shapes as regions A to C and background region Z in masks A to E. Liquid crystal composition Q, the same as that obtained in Production Example 4, was applied to each of regions A to C by screen printing to form a liquid crystal composition layer. The thickness of the liquid crystal composition layer was adjusted so that the thickness of the final cured liquid crystal layer would be approximately 3 μm in region A, approximately 1.6 μm in region B, and 0.9 μm in region C. This was heated in an oven at 60°C for 2 minutes to dry the liquid crystal composition layer and align it into a nematic liquid crystal phase.

[0164] The resulting liquid crystal composition layer was irradiated with 900 mJ / cm at room temperature. 2 The in-plane retardation Re of the region A, region B, region C, and region Z was 142 nm, 69 nm, 45 nm, and 1 nm, respectively.

[0165] Example 1 An ink was prepared by mixing 90 parts by weight of transparent ink (manufactured by Seiko Advance Corporation, product name "SG240") with 10 parts by weight of the cholesteric pigment (S) obtained in Production Example 3. The ink was applied to the surface of the cured liquid crystal layer side of the multilayer film P3 obtained in Production Example 8 using an applicator to a dry thickness of 30 μm and dried to form a light-reflecting layer. A light-absorbing layer paint (manufactured by Seiko Advance Corporation, product name "SG700") was then applied to the surface using an applicator to a dry thickness of 30 μm and dried to form a black light-absorbing layer. This procedure yielded an identification medium with a layer structure of (isotropic substrate) / (cured liquid crystal layer) / (light-reflecting layer) / (light-absorbing layer). The surface of the obtained identification medium on the isotropic substrate side was used as the display surface, and the identification medium was observed with the naked eye and through a viewer for evaluation. Commercially available polarized sunglasses with a linear polarizer in the field of view were used as the viewer.

[0166] The latent image was not visible to the naked eye, but when viewed through a viewer, the latent image had a gradation of shade, with a clear difference between the darkest and lightest parts, demonstrating its extremely high discrimination function as an identification medium.

[0167] <Example 2> The same operations as in Example 1 were carried out except for the following changes, and a discrimination medium was obtained and evaluated. Instead of 10 parts by weight of pigment (S), 10 parts by weight of pigment (G) of the cholesteric material obtained in Production Example 3 was used. The multilayer film P2 obtained in Production Example 6 was used in place of the multilayer film P3. A circularly polarized viewer was used as the viewer. The circularly polarized viewer was equipped with a linear polarizer and a λ / 4 wave plate (Re at a wavelength of 550 nm is 140 nm) superimposed on one surface of the linear polarizer. The transmission axis of the linear polarizer and the in-plane slow axis of the λ / 4 wave plate intersected at a 45° angle. The linear polarizer of the circularly polarized viewer was used as the viewing side, and the λ / 4 wave plate side was used as the objective side. Using it in this way, it was possible to selectively observe right-handed circularly polarized light.

[0168] The latent image was not visible to the naked eye, but when viewed through a viewer, the latent image had a gradation of shade, with a clear difference between the darkest and lightest parts, demonstrating its extremely high discrimination function as an identification medium.

[0169] Example 3 The same operations as in Example 1 were carried out except for the following changes, and a discrimination medium was obtained and evaluated. Instead of 10 parts by weight of pigment (S), a mixture of 5 parts by weight of pigment (G) and 5 parts by weight of pigment (R) of the cholesteric material obtained in Production Example 3 was used. The multilayer film P1 obtained in Production Example 4 was used in place of the multilayer film P3.

[0170] The latent image was not visible to the naked eye. On the other hand, when observed through a viewer, the latent image had a gradation of shade, but the difference between the darkest and lightest parts was smaller than in Example 1.

[0171] Example 4 The same operations as in Example 1 were carried out except for the following changes, and a discrimination medium was obtained and evaluated. Instead of 10 parts by weight of pigment (S), a mixture of 3.3 parts by weight of pigment (R), 3.3 parts by weight of pigment (G) and 3.3 parts by weight of pigment (B) of the cholesteric material obtained in Production Example 3 was used. The multilayer film P1' obtained in Production Example 5 was used in place of the multilayer film P3. A circularly polarized viewer was used as the viewer. The circularly polarized viewer and its usage method were the same as those used in Example 2.

[0172] The latent image was not visible to the naked eye. On the other hand, when observed through a viewer, the latent image had a gradation of shade, but the difference between the darkest and lightest parts was smaller than in Example 1.

[0173] <Example 5> The raw sheet containing the cholesteric material layer (R) obtained in Production Example 1 was laminated on the surface of the cured liquid crystal layer side of the multilayer film P3' obtained in Production Example 9 using a laminator, with the cholesteric material layer side facing the multilayer film, via an adhesive layer (CS6192T, manufactured by Nitto Denko Corporation).The substrate of the raw sheet was then peeled off.This operation resulted in the transfer of the cholesteric material layer (R), yielding a multilayer product 1 having a layer structure of (isotropic substrate) / (cured liquid crystal layer) / (adhesive layer) / (cholesteric material layer (R)).

[0174] Using the original sheet containing the cholesteric material layer (G) and the original sheet containing the cholesteric material layer (B) obtained in Production Example 1, the cholesteric material layer (G) and the cholesteric material layer (B) were sequentially transferred onto the surface of the cholesteric material layer (R) side of the multi-layered product 1 in the same procedure as for transferring the cholesteric material layer (R). By this operation, a multi-layered product 2 having a layer structure of (isotropic substrate) / (cured liquid crystal layer) / (adhesive layer) / (cholesteric material layer (R)) / (adhesive layer) / (cholesteric material layer (G)) / (adhesive layer) / (cholesteric material layer (B)) was obtained.

[0175] A coating material for the light-absorbing layer (the same as that used in Example 1) was applied with an applicator to the surface of the cholesteric material layer (B) side of the multilayer structure 2 so that the thickness after drying was 30 μm, and then dried to form a light-absorbing layer. This operation resulted in an identification medium having a layer structure of (isotropic substrate) / (cured liquid crystal layer) / (adhesive layer) / (cholesteric material layer (R)) / (adhesive layer) / (cholesteric material layer (G)) / (adhesive layer) / (cholesteric material layer (B)) / (light-absorbing layer). The surface of the obtained identification medium on the isotropic substrate side was used as the display surface, and evaluation was performed by observing with the naked eye and through a viewer. As the viewer, commercially available polarized sunglasses with a linear polarizer in the field of view were used.

[0176] The latent image was not visible to the naked eye, but when viewed through a viewer, the latent image had a gradation of shade, with a clear difference between the darkest and lightest parts, demonstrating its extremely high discrimination function as an identification medium.

[0177] Example 6 A linear reflective polarizer (3M, DBEF) was laminated on the surface of the liquid crystal cured layer side of the patterned retardation layer P2' obtained in Production Example 7 via an adhesive layer (Nitto Denko CS6192T). A light absorbing layer coating (the same as that used in Example 1) was applied thereon with an applicator so that the thickness after drying was 30 μm, and then dried to form a light absorbing layer. This operation resulted in an identification medium having a layer structure of (isotropic substrate) / (liquid crystal cured layer) / (adhesive layer) / (linear reflective polarizer) / (light absorbing layer). The surface of the obtained identification medium on the isotropic substrate side was used as the display surface, and the identification medium was observed with the naked eye and through a viewer for evaluation. Commercially available polarized sunglasses with a linear polarizer in the field of view were used as the viewer.

[0178] The latent image was not visible to the naked eye, but when viewed through a viewer, the latent image had a gradation of shade, with a clear difference between the darkest and lightest parts, demonstrating its extremely high discrimination function as an identification medium.

[0179] <Comparative Example 1> The same operations as in Example 1 were carried out except for the following changes, and a discrimination medium was obtained and evaluated. The multilayer film P4 obtained in Production Example 6 was used in place of the multilayer film P3.

[0180] The latent image was not visible to the naked eye, but when viewed through a viewer, the density of the latent image was only binary, with dark and light areas, making it difficult to distinguish.

[0181] <Comparative Example 2> The same operations as in Example 1 were carried out except for the following changes, and a discrimination medium was obtained and evaluated. The multilayer film P5 obtained in Production Example 11 was used in place of the multilayer film P3.

[0182] When observed through a viewer, the latent image had a gradation of shade, but the latent image was visible when observed with the naked eye, and the function of concealing the parts with identifiable functions was poor.

[0183] Table 2 shows the outline and evaluation results of the examples and comparative examples.

[0184] [Table 2]

[0185] From the above results, it can be seen that the present invention has an identification medium with high anti-counterfeiting performance, which also has high identification function and is capable of depicting a latent image with high concealment. Furthermore, it can depict a good gradation, which means that it has the ability to exhibit a high design effect. [Explanation of symbols]

[0186] 100 Identification medium 101(R) Light reflective layer 102 Retardation layer 102RA area 102RB area 102RC area 102RZ area 102U upper surface 109 Light absorbing layer 191 Viewer 202RA area 202RB area 202RC area 202RZ area 202SR H High phase contrast sub-region 202SR L Low phase difference sub-region A1 Line A11A(N) Hikari A11B(N) light A11Z(N) light A12A(N) light A12B(N) light A12Z(N) light A13A(R) Light A13B(R) Light A13Z(R) Light A14A(I) light A14B(E) Light A14Z(R) Light A15A(I) light A15B(I) Light A15Z(I) light A19A(L) Light A19B(L) Light A19Z(L) Light A21A(N) Light A21B(N) Light A21Z(N) Light A22A(N) Light A22B(N) Light A22Z(N) Light A23A(R) Light A23B(R) Light A23Z(R) Light A24A(I) Light A24B(X) light A24Z(R) Light A25A(I) Light A25B(I) Light A25Z(I) Light A29A(L) Light A29B(L) Light A29Z(L) Light

Claims

1. An identification medium comprising a light reflecting layer and a retardation layer, the light reflecting layer is a layer that reflects a specific polarized component of incident light as reflected light, the specific polarized component being either a circularly polarized component or a linearly polarized component; The retardation layer is divided into three or more regions, each of the three or more types of regions is a layer that outputs a part or all of the specific polarized component incident from the light reflecting layer as an observation target polarized component; the three or more regions have different emission rates of the polarized component to be observed, and the emission rate of the polarized component to be observed is a ratio of the amount of emission of the polarized component to the amount of incident light on the identification medium per unit area; The retardation layer has a substantially constant film thickness. identification medium.

2. 2. The discrimination medium according to claim 1, wherein the in-plane retardation Re of the three or more regions is distributed in a range of 412.5 nm or less.

3. 2. The discrimination medium according to claim 1, wherein each of the three or more types of regions has a uniform in-plane retardation Re within the respective region, and the three or more types of regions have mutually different in-plane retardations Re.

4. Each of the three or more regions is a low retardation sub-region SR. Ｌ and high phase contrast sub-region SR Ｈ and the low retardation sub-regions SR in the three or more regions. Ｌ and the area of ​​the high retardation sub-region SR Ｈ The identification medium according to claim 1 , wherein the ratios of the areas of the first and second electrodes to the area of ​​the second electrode are different from each other.

5. the retardation layer is a liquid crystal cured layer that is a layer of a cured product of a liquid crystal compound, 2. The identification medium according to claim 1, wherein a part of the cured material in the liquid crystal cured layer is a liquid crystal compound cured in a state of exhibiting a liquid crystal phase.

6. The identification medium according to claim 1 , wherein the retardation layer is provided at a position closer to the viewer than the light reflecting layer.

7. The identification medium according to claim 1 , wherein the light-reflecting layer is a reflective circular polarizer or a reflective linear polarizer.

8. The identification medium according to claim 7 , wherein the light-reflecting layer is the reflective circular polarizer.

9. 9. The identification medium according to claim 8, wherein the light-reflecting layer is a cured product of ink containing a pigment made of a material having cholesteric regularity.

10. 2. The identification medium according to claim 1, wherein the reflectance of the material forming the light-reflecting layer for unpolarized light incident on the material is 35 to 50% for all wavelengths in the wavelength range of 420 nm to 650 nm.

11. The identification medium according to claim 1 , further comprising a light absorbing layer on a side of the light reflecting layer opposite to the viewing side.

12. An article comprising the identification medium according to any one of claims 1 to 11.

13. The article of claim 12 further comprising a polarizer viewer.

14. A method for using the discrimination medium according to any one of claims 1 to 11, comprising: Incident light is incident on the display surface of the identification medium, reflected by the light-reflecting layer to form reflected light, and the reflected light is observed; A method of use in which unpolarized light is incident as the incident light, and in observing the reflected light, a linearly polarized component or a circularly polarized component of the reflected light is selectively observed.

15. The method of claim 14, wherein the selective observation is performed by viewing the reflected light through a linear polarizer spaced apart from the identification medium.

16. The method of claim 15, wherein the linear polarizer is polarized sunglasses.

17. A method for using the discrimination medium according to any one of claims 1 to 11, comprising: Incident light is incident on the display surface of the identification medium, reflected by the light-reflecting layer to form reflected light, and the reflected light is observed; The incident light may be linearly polarized, circularly polarized, or elliptically polarized light.

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