WO2024181192A1 - Flake, printed matter, article provided with printed matter, and identification medium - Google Patents

Abstract

This invention is a flake of a layered body (C), the layered body having cholesteric regularity and comprising a liquid crystal cured layer (A) and a phase difference layer (B) that imparts phase difference to incident light.

Description

Flakes, printed matter and articles including same, and identification medium

The present invention relates to flakes, printed matter and articles comprising the same, and identification media.

In order to make it easier to determine whether an item is genuine or not, it is common for items to be provided with an identification medium. 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 performance of the identification medium being such that it cannot be easily replicated using common printing or other techniques. The identification function of the identification medium refers to the ability, by some means, to distinguish with a high degree of reliability a genuine identification medium from a counterfeit identification medium that has been forged using common techniques.

Identification media often have a special structure that produces optical effects not seen in ordinary materials. In particular, they may have optical properties that, depending on the observation method, produce special changes in the display state that cannot be obtained with display media manufactured by general manufacturing techniques. Apart from their function as identification media, such optical properties can also be used as properties that are aesthetically pleasing and produce design effects. For this reason, optical display media having the same structure as identification media may be used both as identification media and as decorative media, or optical display media having the same structure as identification media may be used simply as decorative media without being used as identification media.

As such an identification medium, a configuration including a light reflective layer that reflects circularly polarized light and a patterned retardation layer is known (see, for example, Patent Document 1).
Furthermore, as a pigment for decorating an article, a platelet-shaped pigment containing molecules fixed while maintaining cholesteric regularity is known (see, for example, Patent Document 2).
A method is known in which a thin film of a cholesteric resin is formed on a base film, and then the thin resin film is peeled off from the base film to form a peeled piece of the thin resin film (see Patent Documents 3 and 4, etc.).

International Publication No. 2021/153761 (Corresponding Foreign Publication: U.S. Patent Application Publication No. 2023/0076172) Japanese Patent Application Publication No. 07-304983 International Publication No. 2019/189256 International Publication No. 2019/189246 (Corresponding Foreign Publication: U.S. Patent Application Publication No. 2021/0115336)

It is desirable for the identification medium to have a portion having the identification function concealed, that is, the presence of the portion having the identification function cannot be detected by normal observation. In other words, if the presence of the portion having the identification function cannot be 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 is less likely to be counterfeited by imitating the identification function.
In order to provide such a discrimination function, two types of liquid crystal layers having opposite twist structures and cholesteric regularity may be used in the discrimination medium. These two types of liquid crystal layers can selectively reflect circularly polarized light having opposite rotation directions.
Such two kinds of liquid crystal cured layers can be manufactured by using a composition containing a common liquid crystal compound and suitable chiral agents different from each other as a liquid crystal composition for forming the liquid crystal cured layers. By using a common liquid crystal compound, the reflected light of the two kinds of liquid crystal cured layers can be made to approach the same color tone when observed with the naked eye, and these reflected lights can be distinguished from each other when observed with a suitable viewer.

However, in practice, it may be difficult to find a suitable chiral agent, or even if it can be found, it may be difficult to produce it industrially. Also, in order to align the color tone when the reflected light of liquid crystal cured layer flakes containing different chiral agents is observed with the naked eye, it may be necessary to adjust the composition of the liquid crystal composition. In general, adjusting the composition in this way is complicated.

On the other hand, if the identification medium could be produced by printing, it would be advantageous from the standpoint of productivity.

Therefore, there is a demand for novel flakes that can impart identification functionality to printed matter; printed matter using such flakes; articles that include printed matter; and identification media that use the novel flakes.

As a result of intensive research to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by flakes of a laminate (C) including a liquid crystal cured layer (A) having cholesteric regularity and a retardation layer (B) that imparts a retardation to incident light, and have completed the present invention.
That is, the present invention provides the following.

<1> A flake of a laminate (C) including a liquid crystal cured layer (A) having cholesteric regularity and a retardation layer (B) that imparts a retardation to incident light.
<2> The flake according to <1>, wherein the laminate (C) is a laminate in which the retardation layer (B) is laminated in a thickness direction on the entire surface of the cured liquid crystal layer (A).
<3> The flakes according to <1> or <2>, wherein the ratio (D50/d) of the volume-based average particle diameter D50 of the flakes to the thickness d of the flakes is 4 or more.
<4> The flake according to any one of <1> to <3>, wherein the thickness d(B) of the retardation layer (B) is 3 μm or less.
<5> The flake according to any one of <1> to <4>, wherein the retardation layer (B) is a cured layer of a liquid crystal composition containing a liquid crystalline compound having a birefringence Δn of 0.2 or more.
<6> The flake according to any one of <1> to <5>, wherein a retardation ReB(0) in a front direction of the retardation layer (B) at a wavelength of 550 nm is 250 nm or more and 350 nm or less.
<7> The flake according to any one of <1> to <5>, wherein the retardation layer (B) has a retardation in a front direction, ReB(0), at a wavelength of 550 nm is 10 nm or less.
<8> The flake according to any one of <1> to <7>, wherein the retardation layer (B) in a polar angle direction of 45° at a wavelength of 550 nm, ReB(45), is 50 nm or more and 100 nm or less, or 250 nm or more and 350 nm or less.
<9> The flake according to any one of <1> to <8>, wherein the selective reflection band in the front direction of the liquid crystal cured layer (A) includes a wavelength range of 420 nm to 650 nm, and the width of the selective reflection band in the front direction is 200 nm or more.
<10> The flake according to any one of <1> to <8>, wherein the selective reflection band in the front direction of the liquid crystal cured layer (A) is in the range of 380 nm to 780 nm, and the width of the selective reflection band is 50 nm to 150 nm.
<11> The flake according to any one of <1> to <10>, wherein the thickness of the cured liquid crystal layer (A) is 6 μm or less.
<12> The flakes according to any one of <1> to <11>, having a volume-based average particle diameter D50 of 50 μm or less.
<13> The flakes according to any one of <1> to <12>, wherein each flake has an irregular shape when viewed in the thickness direction.
<14> The flakes according to any one of <1> to <13>, wherein each flake has a rectangular shape when viewed in the thickness direction.
<15> The flake according to any one of <1> to <14>, further comprising an adhesive layer between the liquid crystal cured layer (A) and the retardation layer (B).
<16> The flake according to any one of <1> to <15>, wherein a thickness ratio (d(B)/d(A)) of a thickness d(B) of the retardation layer (B) to a thickness d(A) of the liquid crystal cured layer (A) is 0.8 or less.
<17> A printed matter comprising a layer of ink containing the flakes according to any one of <1> to <16>.
<18> An article comprising the printed matter according to <17>.
<19> An identification medium having a display surface,
A first ink layer provided in a region _R1 occupying a part of the display surface;
a second ink layer provided in a region _R2 occupying a part of the display surface and occupying a part or all of the region other than the region _R1 ;
The first ink layer contains a first flake according to any one of <1> to <16>, wherein the retardation layer (B) is a retardation layer (B1) that gives a retardation ReB1(φ) to incident light having a wavelength of 550 nm from a predetermined polar angle φ;
The second ink layer contains second flakes, which are flakes of the cured liquid crystal layer (A) or flakes of a laminate (C2) including the cured liquid crystal layer (A) and a retardation layer (B2) that imparts a retardation ReB2(φ) to incident light having a wavelength of 550 nm from a predetermined polar angle φ;
An identification medium, wherein |ReB2(φ)-ReB1(φ)|>0 nm.

The present invention can provide novel flakes that can impart identification functionality to printed matter; printed matter using the flakes; articles equipped with printed matter; and identification media using the novel flakes.

FIG. 1 is a cross-sectional view showing a schematic diagram of one flake according to embodiment F1 of the present invention. FIG. 2 is a cross-sectional view showing a schematic diagram of one flake according to embodiment F2 of the present invention. FIG. 3 is a cross-sectional view that illustrates a printed matter according to an embodiment of the present invention. FIG. 4 is a top view that illustrates a printed matter according to an embodiment of the present invention.

The present invention will be described in detail below with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and may be modified and implemented as desired without departing from the scope of the claims of the present invention and their equivalents. The components of the embodiments shown below may be combined as appropriate. In addition, in the figures, the same components are given the same reference numerals, and their description may be omitted.

In the following description, unless otherwise specified, the front direction of a certain layer means the normal direction of the principal surface of the layer, specifically the direction of the polar angle of 0° and the azimuth angle of 0° of the principal surface.

In the following description, unless otherwise specified, the oblique direction of a certain layer means a direction that is neither parallel nor perpendicular to the principal surface of the layer, and more specifically, refers to a direction in which the polar angle of the principal surface is in the range greater than 0° and less than 90°.

In the following description, the term "(meth)acrylic" includes "acrylic", "methacrylic", and combinations thereof. Similarly, the term "(thio)epoxy group" includes "epoxy group", "thioepoxy group", and combinations thereof, and the term "iso(thio)cyanate group" includes "isocyanate group", "isothiocyanate group", and combinations thereof.

In the following description, the in-plane retardation Re of a layer is a value expressed by Re = (nx - ny) x d, unless otherwise specified. Furthermore, the retardation Rth in the thickness direction of a layer is a value expressed by Rth = [{(nx + ny)/2} - nz] x d, unless otherwise specified. 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 direction of nx. nz represents the refractive index in the thickness direction of the layer. d represents the thickness of the layer. The measurement wavelength is 550 nm, unless otherwise specified. These values can be measured using a phase difference meter (Axometrics' "AxoScan").

In this application, the phase difference in the oblique direction is also described. The in-plane retardation Re is usually measured by optically observing the layer from a direction of a polar angle of 0°, while the retardation in the oblique direction corresponds to the apparent in-plane retardation value when the observation direction is changed to an oblique direction of a polar angle of more than 0° and the surface perpendicular to the observation direction is considered to be the surface of the layer. In this application, the retardation in the oblique direction observed from a certain polar angle may be indicated by adding the numerical value of the polar angle. For example, the oblique retardation of the retardation layer (B) observed from a polar angle of 45° may be indicated as ReB(45). In contrast to this, the in-plane retardation of the retardation layer (B) observed from a polar angle of 0°, i.e., from the front direction, may be indicated as ReB(0) to clearly indicate that. When simply referring to "in-plane retardation," it means the retardation observed from the front direction (retardation in the front direction).

Specifically, the retardation Reφ in an oblique direction at a polar angle φ can be calculated by the formula Reφ=|ny−nx′|·dφ.
Here, dφ is the optical path length in the layer in the oblique direction, and is calculated by the formula dφ=d/cosφ.
nx' is calculated by the following formula (e1).

In the following description, the direction of the slow axis of a layer refers to the direction of the slow axis in the in-plane direction unless otherwise specified. However, when retardation in an oblique direction is mentioned, the definition is as described above.

In the following description, unless otherwise specified, the directions of elements as "parallel," "vertical," and "orthogonal" may include an error within a range that does not impair the effect of the present invention, for example, within the range of ±3°, ±2°, or ±1°.

In the following description, unless otherwise specified, the adhesive refers not only to adhesives in the narrow sense (adhesives having a shear storage modulus of 1 MPa to 500 MPa at 23°C after irradiation with energy rays or after heat treatment) but also to pressure-sensitive adhesives having a shear storage modulus of less than 1 MPa at 23°C.
Therefore, the term "adhesive layer" encompasses not only a layer of an adhesive in the narrow sense, but also a layer of a pressure-sensitive adhesive.

In the following description, unless otherwise specified, the terms "polarizer" and "plate" are not limited to rigid members, but also include flexible members such as resin films.

For the sake of convenience, in the following 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 the light from the source of the light. In other words, when observing the destination of the light from the source of the light, polarized light whose polarization direction rotates clockwise as the light travels is called right-handed circularly polarized light, and polarized light whose direction rotates in the opposite direction is called left-handed circularly polarized light.

<1. Flakes>
<1.1. Overview of flakes>
(Flake Composition)
The flakes of this embodiment are flakes of a laminate (C) including a liquid crystal cured layer (A) having cholesteric regularity and a retardation layer (B) that imparts a retardation to incident light.

Here, the laminate (C) is usually a laminate in which the retardation layer (B) is superimposed in the thickness direction on the entire surface of the cured liquid crystal layer (A). Therefore, in the flakes of the laminate (C), the retardation layer (B) is usually superimposed in the thickness direction on the entire surface of the cured liquid crystal layer (A).

The flakes of this embodiment are flakes of a laminate (C) including a cured liquid crystal layer (A) and a retardation layer (B), and therefore include the cured liquid crystal layer (A) and the retardation layer (B).
Hereinafter, the flakes of the laminate (C) including the cured liquid crystal layer (A) and the retardation layer (B) are also referred to as flakes (AB).
The flakes of the cured liquid crystal layer (A) are also referred to as flakes (A).

Here, the flakes (AB) may be flakes of a laminate (C) including a liquid crystal cured layer (A) and a plurality of retardation layers (B). In this case, the total thickness d _tot (B) of the retardation layer (B) in the thickness ratio (d _tot (B)/d(A)) described later is the sum of the thicknesses d(B) of the plurality of retardation layers (B).
For example, the flake (AB) may be a flake of a laminate (C) including a first retardation layer (Ba) as the retardation layer (B), a liquid crystal cured layer (A), and a second retardation layer (Bb) as the retardation layer (B) in this order. In this case, the total thickness d _{tot (B) of the retardation layer (B) in the thickness ratio (d tot} (B)/ _d (A)) described later is the sum (d(Ba)+d(Bb)) of the thickness d(Ba) of the first retardation layer (Ba) and the thickness d(Bb) of the second retardation layer (Bb).

(Flake Action)
The operation when unpolarized light is irradiated onto the flakes (AB) and (A) and the reflected light is observed will be described.
In the flake (AB), the reflected light from the liquid crystal cured layer (A) enters the retardation layer (B). The incident light to the retardation layer (B) is given a phase difference by traveling through the retardation layer (B), and the light exiting the retardation layer (B) has a polarization state different from that of the reflected light from the liquid crystal cured layer (A).
On the other hand, the reflected light by the flake (A) not including the retardation layer (B) is not affected by such an action of the retardation layer (B). Even in the case of the flake (AB) of the laminate (C) including the retardation layer (B), in the case of a flake having only one retardation layer (B) and having the liquid crystal cured layer (A) facing the observation side, the reflected light by the liquid crystal cured layer (A) included in the flake is not affected by the retardation layer (B), but there are usually flakes having the retardation layer (B) facing the observation side, and the reflected light by the liquid crystal cured layer (A) included in this flake is affected by the retardation layer (B), so that the reflected light by the entire flake (AB) includes light having a different polarization state from the reflected light by the flake (A).
Therefore, in the following description, the flake (AB) may be a flake (AB) having only one retardation layer (B), or may be a flake (AB) having two retardation layers (B), that is, a retardation layer (B), a liquid crystal cured layer (A), and a retardation layer (B) in this order.
Similarly, the flake (AB1) described later may be a flake (AB1) having only one retardation layer (B1), or may be a flake (AB1) having two retardation layers (B1), that is, a retardation layer (B1), a liquid crystal cured layer (A), and a retardation layer (B1) in this order.
Furthermore, the flake (AB2) described later may be a flake (AB2) having only one retardation layer (B2), or may be a flake (AB2) having two retardation layers (B2), i.e., a retardation layer (B2), a liquid crystal cured layer (A), and a retardation layer (B2) in this order.

Normally, differences in polarization states cannot be distinguished with the naked eye. Therefore, when flakes (AB) of the laminate (C) including the retardation layer (B) and flakes (A) of the liquid crystal cured layer (A) not including the retardation layer (B) are placed on a certain surface and the reflected light is observed with the naked eye, all the flakes have approximately the same or the same color tone.
However, when observed using an appropriate viewer that can distinguish polarization states, such as through a linear polarizing plate (such as commercially available polarized sunglasses) or a circular polarizing plate, the color tones of flakes (AB) and flakes (A) arranged on a certain surface can be distinguished.

In order to obtain a polarization state different from that of the reflected light by the flakes (A), a method of changing the chiral agent contained in the liquid crystal composition, which is the material of the liquid crystal cured layer (A), may be adopted. However, there are cases where a suitable chiral agent cannot be found, and even if a suitable chiral agent is found, it is not easy to industrially manufacture the found chiral agent. Furthermore, when the flakes of the liquid crystal cured layer obtained by changing the material of the liquid crystal cured layer (A) are observed with the naked eye, the color tone may be different between the flakes of the liquid crystal cured layer and the flakes of the liquid crystal cured layer (A).
Since the flakes (AB) and (A) have a common liquid crystal cured layer (A), the color tones of the two are almost the same or the same when observed with the naked eye, and therefore, adjustment of the material of the liquid crystal cured layer to make the color tones the same is not usually required.

In addition, the effect of incident non-polarized light on a flake of a laminate (C1) of the cured liquid crystal layer (A) and the retardation layer (B1) and a flake of a laminate (C2) of the cured liquid crystal layer (A) and the retardation layer (B2) and observing the reflected light will be described.
Here, the laminate (C1) and the laminate (C2) have the same liquid crystal cured layer (A). The retardation layer (B1) and the retardation layer (B2) give different phase differences to the incident light. Specifically, the retardation layer (B1) gives a phase difference ReB1(φ) to the incident light having a wavelength of 550 nm from a predetermined polar angle φ, and the retardation layer (B2) gives a phase difference ReB2(φ) to the incident light having a wavelength of 550 nm from a predetermined polar angle φ, where |ReB2(φ)-ReB1(φ)|>0 nm. The polar angle φ is 0° or is greater than 0° and less than 90°.
The flakes of the laminate (C1) are also called flakes (AB1), and the flakes of the laminate (C2) are also called flakes (AB2).

In the flake (AB1), the reflected light from the liquid crystal cured layer (A) is incident on the retardation layer (B1) at a predetermined polar angle φ, and in the flake (AB2), the reflected light from the liquid crystal cured layer (A) is incident on the retardation layer (B2) at a predetermined polar angle φ. The light emitted from the retardation layer (B1) is given a phase difference ReB1(φ) and has a different polarization state from the reflected light from the liquid crystal cured layer (A). In addition, the light emitted from the retardation layer (B2) is also given a phase difference ReB2(φ) and has a different polarization state from the reflected light from the liquid crystal cured layer (A), and further, since |ReB2(φ)-ReB1(φ)|>0 nm, the polarization state is also different from that of the light emitted from the retardation layer (B2).
As described above, differences in polarization states cannot be distinguished with the naked eye, so when flake (AB1) and flake (AB2) are placed on a surface and the reflected light is observed with the naked eye, both flakes have approximately the same or the same color tone.
However, when observed using an appropriate viewer capable of distinguishing polarization states, the color tones of a flake (AB1) and a flake (AB2) arranged on a certain surface can be distinguished.

When observed with the naked eye, the color tones of flake (AB1) and flake (AB2) are almost the same or the same. Therefore, adjustment of the material of the liquid crystal cured layer to make the color tones the same is not usually required.

By forming the laminate (C) in the form of flakes, the following effects are achieved.
When the laminate (C) is used as it is, such as by attaching it to the underlayer without making it into flakes, the in-plane slow axis of the retardation layer (B) of the laminate (C) is in a fixed direction with respect to the underlayer. Therefore, when the laminate (C) is observed from the front direction (polar angle 0 ° direction) using a viewer such as a linear polarizing plate, the amount of light transmitted through the viewer changes depending on the angle between the direction parallel to the in-plane slow axis of the retardation layer (B) and the transmission axis of the viewer. Therefore, for example, there may be no difference between the amount of light transmitted when the front reflected light of the liquid crystal cured layer (A) is observed using a viewer and the amount of light transmitted when the front reflected light of the laminate (C) is observed using a viewer. As a result, it may be impossible to distinguish the area where the laminate (C) is arranged from the area where the liquid crystal cured layer (A) is arranged, whether by naked eye observation or by observation using a viewer.
On the other hand, when the laminate (C) is crushed or the like and arranged on the underlayer as flakes (AB), even if the retardation layer (B) of each flake (AB) has an in-plane slow axis, the entirety of the multiple flakes (AB) does not have an in-plane slow axis in a specific direction relative to the underlayer. Therefore, when observed from the front direction (polar angle 0°), the amount of light transmitted by the viewer is usually constant regardless of the orientation of the transmission axis of the viewer.

When the retardation ReB(0) in the front direction of the retardation layer (B) is λ/2 or close to λ/2, the flakes (AB) further have the following effect.
When the retardation ReB(0) in the front direction of the retardation layer (B) is λ/2 or close to λ/2, the left-handed circularly polarized light or the right-handed circularly polarized light reflected in the front direction from the liquid crystal cured layer (A) is changed in polarization state to the circularly polarized light with the opposite rotation direction by the action of the retardation layer (B). Since the circularly polarized light cannot have a principal axis direction, when the circularly polarized light is observed using a circular polarizer, the amount of transmitted light of the circular polarizer does not change depending on the rotation angle even if the circular polarizer is rotated around the axis of the front direction. In other words, even if the entire flake (AB) does not have an in-plane slow axis in a specific direction, there is usually no effect on the observation using the circular polarizer.

When the retardation ReB(0) in the front direction of the retardation layer (B) is 0 nm or close to 0 nm and is 10 nm or less, the flakes (AB) further have the following effect.
The retardation layer (B) (usually a C plate) having a retardation ReB(0) of 0 nm or close to 0 nm in the front direction usually gives a retardation greater than 0 nm to the transmitted light in the oblique direction. Since the retardation ReB(0) in the front direction is 0 nm or close to 0 nm, when the light emitted from the retardation layer (B) is observed from a direction of a certain polar angle and an arbitrary azimuth angle with respect to the retardation layer (B), the direction in which the refractive index of the retardation layer (B) is maximum or minimum in the plane perpendicular to the traveling direction of the observed light is perpendicular to the traveling direction of the light and parallel to the plane of the retardation layer (B).
That is, in a certain polar angle direction, regardless of the azimuth angle direction from which the emitted light of the retardation layer (B) is observed, the slow axis or fast axis of the retardation layer (B) in a plane perpendicular to the traveling direction of the observed light is in the same direction with respect to the traveling direction of the observed light and is parallel to the plane of the retardation layer (B).
Therefore, when the reflected light of the flake (AB) is observed from a certain polar angle direction using a linear polarizing plate, if the angular relationship between the transmission axis of the linear polarizing plate and a plane that includes the traveling direction of the observed light and is perpendicular to the surface of the retardation layer (B) is the same, the amount of transmitted light of the linear polarizing plate is usually constant regardless of the azimuth angle from which the observation is made.
In addition, when the reflected light of the flakes (AB) is observed from a certain polar angle direction using a linear polarizer, if the transmission axis of the linear polarizer and a plane that includes the traveling direction of the observed light and is perpendicular to the surface of the retardation layer (B) form an angle of 45° or 135°, the amount of transmitted light of the linear polarizer becomes the largest or smallest regardless of the azimuth angle from which the observation is made. Therefore, the difference in the amount of transmitted light between the flakes (AB) and the flakes (A) can be increased.

(Thickness ratio (d _tot (B)/d (A))
The flakes (AB) have a thickness ratio (d _tot (B)/d(A)) of the total thickness d _tot (B) of the retardation layer (B) to the thickness d(A) of the liquid crystal cured layer (A) of preferably 0.8 or less, more preferably 0.4 or less, and usually greater than 0.
When the thickness ratio (d _tot (B)/d(A)) is 0.8 or less, it becomes easier to produce the flakes (AB) by crushing the laminate (C). In addition, when the aspect ratio of the flakes described later becomes high and the flakes (AB) are arranged on a certain surface, the proportion of the flakes (AB) in which the main surface of either the liquid crystal cured layer (A) or the retardation layer (B) faces the observation side becomes higher than the proportion of the flakes (AB) in which the side faces the observation side. Therefore, the retardation layer (B) provided in the flakes (AB) can effectively exert the above-mentioned effect.
Here, when the flake (AB) has only one retardation layer (B), the total thickness d _tot (B) is equal to the thickness d(B) of one retardation layer (B) that the flake (AB) has.

(Flake thickness)
The thickness of the flakes (AB) is preferably 25 μm or less, more preferably 12 μm or less, and is usually greater than 0 μm, preferably 7 μm or more.
By having the thickness of the flake (AB) be equal to or greater than the lower limit, the desired optical effects such as high reflectance can be satisfactorily exhibited. On the other hand, by having the thickness be equal to or less than the upper limit, when the flake (AB) is placed on a surface, the proportion of the flake (AB) in which either the main surface of the liquid crystal cured layer (A) or the retardation layer (B) faces the observation side is greater than the proportion of the flake (AB) in which the side faces the observation side. Therefore, the retardation layer (B) provided in the flake (AB) can effectively exert the above-mentioned action.

(Flake particle size)
The flakes (AB) have a volume-based average particle diameter D50 of preferably 100 μm or less, more preferably 50 μm or less, and usually more than 0 μm. When the average particle diameter D50 of the flakes (AB) is within the above range, the ink containing the flakes (AB) can be more suitable for various printing methods such as screen printing.
As the average particle diameter D50 of the flakes (AB), the value of the median diameter D50 at which the cumulative volume is 50% in the particle diameter distribution measured using a laser diffraction/scattering type particle size distribution measuring device (for example, Horiba, Ltd., product name "LA-960") can be used.

(Flake aspect ratio)
Since the thickness d of the flake (AB) usually depends on the thickness d(C) of the laminate (C) before pulverization, the thickness d of the flake (AB) may be the thickness d(C). The aspect ratio of the flake (AB) may be the ratio (D50/d) of the volume-based average particle diameter D50 of the flake to the thickness d of the flake. Furthermore, the ratio value (D50/d(C)) obtained by dividing the volume-based average particle diameter D50 of the flake (AB) by the thickness d(C) of the laminate (C) may be used as the ratio (D50/d) of the volume-based average particle diameter D50 of the flake to the thickness d of the flake. The value of the ratio is preferably 4 or more, more preferably 5 or more, particularly preferably 7 or more, and preferably 20 or less, more preferably 15 or less, particularly preferably 10 or less.
When the ratio (D50/d) is equal to or greater than the lower limit, when the flakes (AB) are arranged on a surface, the ratio of the flakes (AB) whose main surface of either the liquid crystal cured layer (A) or the retardation layer (B) faces the observation side is greater than the ratio of the flakes (AB) whose side faces the observation side. Therefore, the retardation layer (B) of the flakes (AB) can effectively exert the above-mentioned function.

(shape of each flake)
In one embodiment, the flakes (AB) have an irregular shape when viewed from the thickness direction of each of the flakes (AB). Usually, when the laminate (C) is pulverized by a mill such as a cutter mill, flakes (AB) having various and irregular shapes can be obtained.

In another embodiment, the flakes (AB) have a regular shape when viewed from the thickness direction. Examples of the shape of each of the flakes (AB) include a triangle, a rectangle, a hexagon, and a cross, and a rectangle is preferable. The flakes (AB) may have a single, or two or more, regular shapes when viewed from the thickness direction. By cutting the laminate (C) into a regular shape, flakes (AB) having a regular shape when viewed from the thickness direction can be obtained. When the flakes (AB) of this embodiment are observed under magnification according to the particle size of the flakes, it can be confirmed that each flake (AB) has a regular shape, and therefore the authenticity of the ink layer containing the flakes (AB) can be easily confirmed.

<1.2. Liquid crystal hardened layer (A)>
The liquid crystal cured layer (A) has cholesteric regularity.
Here, cholesteric regularity refers to a state in which the molecular axes are aligned in a certain direction on a certain plane inside the material, but on the next plane that overlaps it, the direction of the molecular axes is shifted at a slight angle, and on the next plane The angle of the molecular axis in the plane is shifted (twisted) as the light passes through the overlapping planes. When the internal molecules have cholesteric regularity, the molecules are aligned on a first plane inside the layer such that the molecular axes are in a certain direction. In the second plane, the direction of the molecular axis is slightly offset from the direction of the molecular axis in the first plane. In the third plane, which overlaps the second plane, the direction of the molecular axis is slightly offset from the direction of the molecular axis in the first plane. The direction of the molecular axis in the first plane is further displaced from the direction of the molecular axis in the second plane at an angle. In this way, the angles of the molecular axes in the planes are sequentially displaced (twisted) in the overlapping planes. go. A structure in which the molecular axis direction is twisted in this way is usually a helical structure, which is an optically chiral structure.

The liquid crystal cured layer (A), which has an optically chiral structure, has a circularly polarized light selective reflection function that selectively reflects normal circularly polarized light. When the liquid crystal cured layer (A) "selectively reflects" light in a specific wavelength range, it means that it reflects one circularly polarized component of unpolarized light (i.e., natural light) in a specific wavelength range and transmits the other circularly polarized component.

In this specification, the term "selective reflection band" refers to a wavelength range of circularly polarized light that is selectively reflected. Specifically, the selective reflection band is a wavelength range in which the reflectance of unpolarized light incident on the liquid crystal cured layer (A) by the liquid crystal cured layer (A) is 30% or more and 50% or less.
In the selective reflection band, the reflectance of the cured liquid crystal layer (A) for unpolarized light incident on the cured liquid crystal layer (A) is at most 50%.

In this specification, the "width of the selective reflection band" means the half-width of the selective reflection band.
The half-width Δλ of the selective reflection band is the difference between the maximum wavelength and the minimum wavelength in the wavelength region showing a reflectance of 50% or more of the peak reflectance in the selective reflection band. For example, when the peak reflectance is 40%, the half-width Δλ is the difference between the maximum wavelength and the minimum wavelength in the wavelength region showing a reflectance of 20% or more. The selective reflection central wavelength λc is the average value of the maximum wavelength and the minimum wavelength (i.e., the sum of these divided by 2). The units of Δλ and λc can usually be expressed in nm.

(Selective reflection band of the cured liquid crystal layer (A))
In one embodiment, the liquid crystal cured layer (A) provided in the flake (AB) preferably has a selective reflection band in the front direction that includes a wavelength range of 420 nm or more and 650 nm or less, and the width of the selective reflection band in the front direction is 200 nm or more, more preferably 250 nm or more, and even more preferably 300 nm or more. The upper limit is not particularly limited, but is, for example, 400 nm or less.
When the width of the selective reflection band is so wide, the flake (AB) having the cured liquid crystal layer (A) can exhibit a color tone close to silver.

In another embodiment, the liquid crystal cured layer (A) of the flake (AB) preferably has a selective reflection band in the front direction within the range of 380 nm or more and 780 nm or less, and the width of the selective reflection band is preferably 10 nm or more, more preferably 15 nm or more, even more preferably 20 nm or more, particularly preferably 50 nm or more, and preferably 150 nm or less, more preferably 130 nm or less, even more preferably 120 nm or less, and even more preferably 90 nm or less. In this case, the flake (AB) having the liquid crystal cured layer (A) can exhibit a color tone according to the central wavelength λc of the selective reflection band. For example, when λc is in the blue wavelength region, the flake (AB) having the liquid crystal cured layer (A) can exhibit a blue color.

The selective reflection band in the front direction refers to the selective reflection band when the liquid crystal cured layer (A) is observed from the front direction.

The central wavelength λc of the selective reflection band can be adjusted by the type of material constituting the liquid crystal cured layer (A) and the ratio of those components, as well as the manufacturing conditions of the liquid crystal cured layer (A). In particular, the pitch of the cholesteric regular helix can be adjusted by the type of liquid crystal compound and the chiral agent, as well as the content ratio of the chiral agent, and in particular, slight adjustments to the pitch can be easily achieved by changing the content ratio of the chiral agent. By such adjustments, the central wavelength λc of the selective reflection band can be easily adjusted to the desired value.

The selective reflection band of the liquid crystal cured layer (A) in the flakes (AB) usually coincides with the selective reflection band of the liquid crystal cured layer (A) before crushing, so the value of the selective reflection band of the liquid crystal cured layer (A) before crushing can be used as it is as the value of the selective reflection band of the liquid crystal cured layer (A) in the flakes (AB).

The reflectance of the liquid crystal cured layer (A) can be the integrated reflectance measured using unpolarized light as the incident light. The integrated reflectance can be measured using an ultraviolet-visible spectrophotometer equipped with an integrating sphere (e.g., the UV-Vis 550 manufactured by JASCO Corporation).

(Material and manufacturing method of the liquid crystal cured layer (A))
The liquid crystal cured layer (A) having cholesteric regularity is a layer obtained by curing a curable liquid crystal compound exhibiting a cholesteric liquid crystal phase. Hereinafter, the liquid crystal cured layer (A) having cholesteric regularity is also referred to as a cholesteric liquid crystal cured layer (A).

The cholesteric liquid crystal cured layer (A) can be obtained, for example, by polymerizing a polymerizable liquid crystal compound in a state in which the compound exhibits a cholesteric liquid crystal phase. More specifically, the cholesteric liquid crystal cured layer (A) can be obtained by forming a layer of a liquid crystal composition containing a polymerizable liquid crystal compound, for example by applying the liquid crystal composition to a suitable substrate, orienting the layer in a cholesteric liquid crystal phase, and curing the layer.

As the polymerizable liquid crystal compound, a photopolymerizable liquid crystal compound is preferred. As the photopolymerizable liquid crystal compound, a photopolymerizable liquid crystal compound that can be polymerized by irradiation with active energy rays can be used. As the active energy ray, an energy ray that can promote the polymerization reaction of the photopolymerizable liquid crystal compound can be adopted from a wide range of energy rays such as visible light, ultraviolet light, and infrared light, and ionizing radiation such as ultraviolet light is particularly preferred. Among them, as the photopolymerizable liquid crystal compound that is suitably used in the cholesteric liquid crystal composition, a rod-shaped liquid crystal compound having two or more reactive groups in one molecule is preferred, 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)

In formula (1), ^R3 and ^R4 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, a liquid crystal composition cured layer having high mechanical strength can be obtained when the liquid crystal composition is cured.

In formula (1), ^D3 and ^D4 each independently represent 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.

In formula (1), C ³ to C ⁶ each independently represent a group selected from the group consisting of a single bond, -O-, -S-, -S-S-, -CO-, -CS-, -OCO-, -CH _{2 -, -OCH 2 -} , -CH=N-N=CH-, -NHCO-, -O-(C=O)-O-, -CH ₂ -(C=O)-O-, and -CH ₂ O-(C=O)-.

In formula (1), M represents a mesogenic group. Specifically, M represents a group in which 2 to 4 skeletons, which may be unsubstituted or substituted, and which are the same or different from one another and are 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, are bonded by a bonding group such as -O-, -S-, -S-S-, -CO-, -CS-, -OCO-, -CH ₂ -, -OCH ₂ -, -CH═N-N═CH-, -NHCO-, -O-(C═O)-O-, -CH ₂ -(C═O)-O-, and -CH ₂ O-(C═O)-.

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, -O-R ⁵ , -O-C(=O)-R ⁵ , -C(=O)-O-R ⁵ , -O-C(=O)-O-R ⁵ , -NR ⁵ -C(=O)-R ⁵ , -C(=O)-NR ⁵ R ⁷ , and -O-C(=O)-NR ⁵ R ^7. Here, R ⁵ and R ⁷ represent a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. When R ⁵ and R ⁷ are alkyl groups, the alkyl groups may be interrupted by -O-, -S-, -O-C(=O)-, -C(=O)-O-, -O-C(=O)-O-, -NR ⁶ -C(=O)-, -C(=O)-NR ^6- , -NR ^6- , or -C(=O)- (excluding the cases where two or more -O- and -S- are adjacent to each other).) Here, R ⁶ represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

　Examples of the substituent in the "alkyl group having 1 to 10 carbon atoms which may have a substituent" include halogen atoms, hydroxyl groups, carboxyl groups, cyano groups, amino groups, alkoxy groups having 1 to 6 carbon atoms, alkoxyalkoxy groups having 2 to 8 carbon atoms, alkoxyalkoxy groups having 3 to 15 carbon atoms, alkoxycarbonyl groups having 2 to 7 carbon atoms, alkylcarbonyloxy groups having 2 to 7 carbon atoms, and alkoxycarbonyloxy groups having 2 to 7 carbon atoms.

The rod-shaped liquid crystal compound preferably has an asymmetric structure. Here, the asymmetric structure refers to a structure in which R ³ -C ³ -D ³ -C ⁵ -M- and -M-C ⁶ -D ⁴ -C ⁴ -R ⁴ are different from each other with the mesogenic group M at the center in formula (1). By using a rod-shaped liquid crystal compound having an asymmetric structure, the alignment uniformity can be further improved.

Specific examples of preferred rod-shaped liquid crystal compounds include the following compounds (B1) to (B12). However, rod-shaped liquid crystal compounds are not limited to the following compounds.

When the liquid crystal composition contains the above-mentioned rod-like liquid crystal compound, the liquid crystal composition preferably contains a compound represented by formula (2) as an alignment assistant in combination with the rod-like liquid crystal compound.
R ¹ -A ¹ -B-A ² -R ² (2)

In formula (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 arbitrary bonding group interposed therebetween, an epoxy group, a mercapto group, an isocyanate group, an amino group, and a cyano group.

The alkyl group and alkylene oxide group may be unsubstituted or may be 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 an alkyl group having 1 to 2 carbon atoms and an alkylene oxide group.

Preferred examples of R ¹ and R ² 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.

At least one of ^R1 and ^R2 is preferably a reactive group. By having a reactive group as at least one of ^R1 and ^R2 , the compound represented by the formula (2) is fixed in the liquid crystal composition cured layer during 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.

In formula (2), A ¹ and A ² each independently represent a group selected from the group consisting of 1,4-phenylene, 1,4-cyclohexylene, cyclohexen-1,4-ylene, 4,4'-biphenylene, 4,4'-bicyclohexylene, and 2,6-naphthylene. The 1,4-phenylene, 1,4-cyclohexylene, cyclohexen-1,4-ylene, 4,4'-biphenylene, 4,4'-bicyclohexylene, and 2,6-naphthylene groups may be unsubstituted or 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, and a halogenated alkyl group. When two or more substituents are present in each of A ¹ and A ² , they may be the same or different.

Particularly preferred examples of A ¹ and A ² include groups 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 high affinity with the mesogens of rod-like liquid crystal compounds, resulting in higher alignment uniformity.

In formula (2), B is selected from the group consisting of a single bond, -O-, -S-, -S-S-, -CO-, -CS-, -OCO-, -CH ₂ -, -OCH ₂ -, -CH═N-N═CH-, -NHCO-, -O-(C═O)-O-, -CH ₂ -(C═O)-O-, and -CH ₂ O-(C═O)-.
Particularly preferred values for B include a single bond, --O--(C.dbd.O)-- and --CH.dbd.N--N.dbd.CH--.

Specific examples of particularly preferred compounds 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.

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

The weight ratio represented by (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 making the weight ratio equal to or greater than the lower limit, the alignment uniformity in the layer of the liquid crystal composition can be improved. Also, by making the weight ratio equal to or less than the upper limit, the alignment uniformity can be increased. Also, the stability of the liquid crystal phase of the liquid crystal composition can be increased. Furthermore, since the refractive index anisotropy (birefringence Δn) of the liquid crystal composition can be increased, for example, a liquid crystal cured layer having desired optical performance such as selective reflection performance of circularly polarized light can be stably obtained. Here, the total weight of the 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 the 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.

In addition, when the compound represented by formula (2) is used in combination with a rod-shaped liquid crystal compound, it is preferable that the molecular weight of the compound represented by formula (2) is 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 the gaps of the rod-shaped liquid crystal compound with a larger molecular weight, thereby improving the alignment uniformity.

The liquid crystal composition for forming the cholesteric liquid crystal cured layer (A) may further contain optional components constituting the cholesteric liquid crystal cured layer (A) and a solvent for facilitating handling of the liquid crystal composition. Examples of 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, and in particular, examples of surfactants include F-563 from DIC, KZ-GDP02 from AGC Seimi Chemical, and KZ-GDP05 from AGC Seimi Chemical. As surfactants with a fluoroalkyl group chain length of less than 6, F-563 from DIC, and KZ-GDP02 and KZ-GDP05 from AGC Seimi Chemical are preferred.

A liquid crystal composition is applied to the surface of a support having an orientation restricting force to form a layer of the liquid crystal composition, and the layer is oriented in a cholesteric liquid crystal phase and cured to obtain a film that can be used as the liquid crystal cured layer (A). As the support having an orientation restricting force, a film having a rubbing treatment on the surface, a film having an orientation restricting force on the surface by stretching, etc. can be used. The liquid crystal composition may be oriented in a cholesteric liquid crystal phase immediately after application, but alignment can be achieved by applying a treatment such as heating as necessary to conditions that exhibit a cholesteric liquid crystal phase. As a curing method for curing the liquid crystal composition, a method according to the components contained in the cholesteric liquid crystal composition can be selected. A layer of the cholesteric liquid crystal composition is usually cured by polymerizing a polymerization component such as a polymerizable liquid crystal compound contained in the cholesteric liquid crystal composition. Examples of the polymerization method include a method of irradiating active energy rays and a thermal polymerization method. Among them, the method of irradiating active energy rays is preferable because the polymerization reaction can proceed at room temperature. Here, the active energy rays to be irradiated may include any energy rays such as visible light, ultraviolet light, and infrared light, as well as electron beams. When the layer of the cholesteric liquid crystal composition is cured by irradiation with active energy rays, the preferred intensity of the active energy rays to be irradiated varies depending on the liquid crystal composition used, but can be, for example, 50 mJ/cm ² to 10,000 mJ/cm ² .

In addition, after the liquid crystal compound is aligned, the layer of the cholesteric liquid crystal composition may be subjected to a band-widening treatment before the layer of the cholesteric liquid crystal composition is cured. Such a band-widening treatment can be performed, for example, by a combination of one or more irradiation treatments with active energy rays and a heating treatment. In this case, the energy of the light irradiated varies depending on the liquid crystal composition used, but may be, for example, 0.01 mJ/cm ² to 50 mJ/cm ^2. In addition, the heat treatment can be performed, for example, by heating to a temperature of preferably 40° C. or higher, more preferably 50° C. or higher, preferably 200° C. or lower, more preferably 140° C. or lower. By performing such a band-widening treatment, the size of the pitch of the helical structure can be continuously and greatly changed to obtain a wide reflection wavelength band.

(Thickness of Cured Liquid Crystal Layer (A))
The thickness of the liquid crystal cured layer (A) of the flake (AB) is preferably 2 μm or more, more preferably 3 μm or more, and is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 6 μm or less. By having a thickness of the above lower limit or more, the desired optical effects such as high reflectance can be satisfactorily exhibited. On the other hand, by having a thickness of the above upper limit or less, the occurrence of poor alignment can be effectively suppressed. In addition, the flake (AB) having a desired high aspect ratio can be easily obtained.

<1.3. Retardation layer (B)>
The retardation layer (B) is a layer that gives a phase difference to incident light. The light emitted from the retardation layer (B) has a polarization state changed from that of the incident light.

(When the retardation layer (B) is a λ/2 plate)
For example, in the case where the retardation layer (B) functions as a λ/2 plate that imparts a phase difference of λ/2 to light incident in a frontal direction, when circularly polarized light having a certain rotation direction enters the retardation layer (B), a phase difference of λ/2 is imparted to the circularly polarized light having a rotation direction opposite to that of the incident light, and the circularly polarized light is emitted from the retardation layer (B).

On the other hand, when flakes (A) are disposed on a certain surface, the flakes (A) do not have a retardation layer (B), so that the reflected light of the flakes (A) is circularly polarized light having a certain rotation direction.
Therefore, when the retardation layer (B) is a layer that functions as a λ/2 plate, the reflected light of the flake (AB) and the reflected light of the flake (A) can be distinguished by observation using a viewer that can distinguish between left and right circularly polarized light. A circular polarizing plate can be used as a viewer that can distinguish between left and right circularly polarized light. By transmitting the reflected light of the flake through a circular polarizing plate, the amount of reflected light of either the flake (AB) or the flake (A) is significantly reduced, so that the reflected light of the flake (AB) of this embodiment can be distinguished from the reflected light of the flake (A).

(When the retardation layer (B) is a λ/4 plate)
Also, for example, when the retardation layer (B) is a layer that functions as a λ/4 plate that gives a phase difference of λ/4 to the incident light in the front direction, the circularly polarized light having a certain rotation direction is given a phase difference of λ/4, and the polarization state is changed to linearly polarized light and is emitted from the retardation layer (B). In this case, when the flakes (AB) are arranged on a certain surface, the slow axis of the retardation layer (B) that each of the flakes (AB) has is arranged randomly, so that the orientation of the slow axis of the retardation layer (B) that functions as a λ/4 plate is usually not biased. Therefore, the reflected light of the flakes (AB) is observed as linearly polarized light that vibrates in all directions from the front direction.
Therefore, when the retardation layer (B) functions as a λ/4 plate, the reflected light of the flake (AB) and the reflected light of the flake (A) can be distinguished by observing with a viewer that can distinguish between linearly polarized light that vibrates in any direction and circularly polarized light with a certain rotation direction. A linear polarizing plate can be used as a viewer that can distinguish between linearly polarized light and circularly polarized light with a certain rotation direction.
When the reflected light of flake (A) is transmitted through a linear polarizer, the reflected light is circularly polarized, so the transmitted light of the linear polarizer is usually 1/2 of the original light amount. On the other hand, the reflected light of flake (AB) is linearly polarized light that vibrates in all directions, so when transmitted through a linear polarizer, the light amount becomes much smaller than 1/2 of the original reflected light amount. In this way, the reflected light of flake (AB) and the reflected light of flake (A) can be distinguished due to the significant difference in light amount.

(When the retardation layer (B) is a C plate)
For example, when the retardation layer (B) is a so-called C plate, the retardation in the oblique direction in the retardation layer (B) is usually larger than the in-plane retardation. On the other hand, although the details are not clear, the liquid crystal cured layer (A) reflects light in a certain oblique direction when non-polarized light is incident, and the reflected light is elliptically polarized light having a certain rotation direction or linearly polarized light having a certain vibration direction. This is because the liquid crystal cured layer (A) having cholesteric regularity generally functions as a C plate in which the principal refractive indexes nx, ny and nz are nx=ny or are close to it as a whole layer, and the retardation in the oblique direction of the liquid crystal cured layer (A) is usually larger than the in-plane retardation.

The elliptically polarized light or linearly polarized light emitted obliquely by the liquid crystal cured layer (A) has its polarization state changed by the retardation layer (B) and is emitted obliquely from the retardation layer (B). The retardation value in the oblique direction of the flake (AB) comprising the liquid crystal cured layer (A) and the retardation layer (B) is considered to be a composite value of the retardation in the oblique direction of the liquid crystal cured layer (A) and the retardation in the oblique direction of the retardation layer (B). Elliptically polarized light having a certain rotation direction or linearly polarized light having a certain vibration direction emitted obliquely from the liquid crystal cured layer (A) can be distinguished from the polarized light emitted obliquely from the retardation layer (B), which has a different polarization state, by using a viewer that can distinguish polarization states.

For example, a case where a linear polarizing plate is used as a viewer will be described.
When polarized light emitted in an oblique direction with different polarization states is observed using a linear polarizer from an oblique direction, the amount of light transmitted through the linear polarizer differs from one another due to the difference in polarization state.

For example, if the light emitted obliquely by flake (A) is linearly polarized, and the retardation layer (B) imparts a phase difference of λ/2 to the light incident from the oblique direction, then the light emitted obliquely from flake (AB) will be linearly polarized light whose vibration direction is perpendicular to that of the linearly polarized light emitted obliquely from flake (A). When such linearly polarized light whose vibration direction is perpendicular is observed using a linear polarizing plate, the amount of transmitted light differs significantly. Therefore, the reflected light from flake (A) can be distinguished from the reflected light from flake (AB).

For example, if the light emitted in an oblique direction by flake (A) is elliptically polarized light, and the retardation layer (B) imparts a phase difference of λ/2 to the light incident from the oblique direction, then the light emitted in a more oblique direction from flake (AB) will be elliptically polarized light that has the opposite rotation direction to the light reflected in the oblique direction from flake (A) and has a principal axis orientation that is orthogonal. When such elliptically polarized light with orthogonal principal axis orientations is observed using a linear polarizing plate, the amount of transmitted light is significantly different. Therefore, the reflected light from flake (AB) and the reflected light from flake (A) can be distinguished.

Here, the C plate is a positive C plate or a negative C plate. The positive C plate is an optical member having a plate shape in which the principal refractive indices nx, ny, and nz are nx=ny or a relationship close thereto, and nx<nz. The negative C plate is an optical member having a plate shape in which the principal refractive indices nx, ny, and nz are nx=ny or a relationship close thereto, and ny>nz.
The in-plane retardation Re of a layer is a value expressed by Re=(nx-ny)×d, so that it is possible to determine whether nx=ny or a relationship close to this by using the in-plane retardation value as an index.
For example, when the retardation layer (B) has retardation in an oblique direction, and the retardation ReB(0) in the front direction of the retardation layer (B) is close to 0 nm, the retardation layer (B) may be a C plate. Specifically, the ReB(0) of the retardation layer (B) that is a C plate is preferably 10 nm or less, more preferably 5 nm or less, and usually 0 nm or more, but may be 0 nm.

In one embodiment, the retardation layer (B) is preferably a layer that functions as a negative C plate, since it can impart a larger phase difference to light in an oblique direction.

(Material and manufacturing method of retardation layer (B))
The retardation layer (B) can be formed of any material depending on the desired retardation.

For example, the retardation layer (B) may be formed from a cured liquid crystal composition containing a liquid crystal compound. By appropriately adjusting factors such as the type of liquid crystal compound, the alignment state of the liquid crystal compound, and the thickness, the desired retardation can be obtained.

In the case where the retardation layer (B) is formed of a cured product of a liquid crystal composition containing a liquid crystal compound, the birefringence Δn of the liquid crystal compound is preferably 0.1 or more, more preferably 0.2 or more, and the larger the better. However, it may be, for example, 0.7 or less.
Here, the birefringence Δn of a liquid crystal compound can be determined by measuring the in-plane retardation Re and the thickness d of a sample of a liquid crystal cured layer obtained by curing a liquid crystal composition containing a liquid crystal compound, and dividing the in-plane retardation Re by the thickness d (Re/d).
A sample of the liquid crystal cured layer can be prepared by homogeneously aligning a liquid crystal compound and curing a layer of a liquid crystal composition containing the liquid crystal compound while maintaining the alignment. "Homogeneously aligning a liquid crystal compound" means forming a layer containing the liquid crystal compound and aligning the direction of the maximum refractive index in the refractive index ellipsoid of the molecules of the liquid crystal compound in the layer in a certain direction parallel to the surface of the layer.

When the retardation layer (B) functions as a λ/2 plate or λ/4 plate that imparts a predetermined phase difference to light incident from the front direction, it is preferable to align the liquid crystal compound homogeneously.

For example, when the retardation layer (B) is made to function as a negative C plate, the retardation layer (B) may be obtained by forming a layer of a material having cholesteric regularity using a liquid crystal compound that can also be used as the material of the liquid crystal cured layer (A), and having a selective reflection band that is partly or entirely outside the visible range.

The retardation layer (B) may be obtained by a film forming method such as a solution casting method using a solution containing a polymer. For example, a retardation layer (B) that can function as a positive C plate may be obtained by using a solution containing a cellulose-based polymer.

(Retardation of Retardation Layer (B))
The retardation layer (B) has a value such that either or both of the front retardation and the oblique retardation can function as a λ/2 plate, specifically, it is preferably 250 nm or more, more preferably 260 nm or more, and preferably 350 nm or less, more preferably 300 nm or less. When the front retardation and/or the oblique retardation of the retardation layer (B) are values capable of functioning as a λ/2 plate, when the reflected light of the flake (AB) and the reflected light of the flake (A) are observed from the front or oblique direction using a linear polarizing plate or a circular polarizing plate, the difference in the light amount between the two reflected lights becomes larger, so that the two reflected lights can be more easily distinguished.

In one embodiment, the retardation ReB(0) in the front direction of the retardation layer (B) is λ/2 or close to λ/2, preferably 250 nm or more, more preferably 260 nm or more, even more preferably 270 nm or more, and preferably 350 nm or less, more preferably 330 nm or less, even more preferably 310 nm or less.

In one embodiment, the retardation ReB(45) of the retardation layer (B) in the polar angle 45° direction is λ/2 or close to λ/2, and is preferably 250 nm or more, more preferably 260 nm or more, even more preferably 270 nm or more, and is preferably 350 nm or less, more preferably 330 nm or less, even more preferably 310 nm or less.

In one embodiment, the retardation ReB(0) in the front direction of the retardation layer (B) is preferably 10 nm or less, more preferably 5 nm or less, and is usually 0 nm or more, but may be 0 nm.

In one embodiment, the retardation ReB(45) of the retardation layer (B) in the polar angle 45° direction is preferably 50 nm or more, more preferably 60 nm or more, and is preferably 100 nm or less, more preferably 90 nm or less.

In one embodiment, the retardation layer (B) preferably has a retardation ReB(0) in the front direction of the retardation layer (B) and a retardation ReB(45) in the polar angle 45° direction of the retardation layer (B) within the following ranges. The retardation layer (B) having a retardation within such a range can be said to be a C plate.
ReB(0) is preferably 10 nm or less, more preferably 5 nm or less, and is usually 0 nm or more, but may be 0 nm; and
ReB(45) is preferably 50 nm or more, more preferably 60 nm or more, and is preferably 100 nm or less, more preferably 90 nm or less.
Alternatively, ReB(0) is preferably 10 nm or less, more preferably 5 nm or less, and is usually 0 nm or more, but may be 0 nm; and
ReB(45) is preferably 250 nm or more, more preferably 270 nm or more, and is preferably 350 nm or less, more preferably 330 nm or less.

(Thickness of Retardation Layer (B))
The thickness d(B) of the retardation layer (B) is preferably 3 μm or less, more preferably 2 μm or less, and may be 0.5 μm or more.
Here, when the flake (AB) has a plurality of retardation layers (B), each of the plurality of retardation layers (B) is preferably within the thickness range. When the thickness d(B) is equal to or less than the upper limit, it is easier to crush the laminate (C) to produce flakes. When the thickness d(B) is equal to or more than the lower limit, the retardation of the retardation layer (B) can be easily set to a desired range.

1.4. Optional Layer
The flake (AB) may include an optional layer in addition to the liquid crystal cured layer (A) and the retardation layer (B). The optional layer may have optical anisotropy or optical isotropy. Preferably, the optional layer has optical isotropy.
Specifically, the retardation Re(0) in the in-plane direction of any layer is preferably 10 nm or less, more preferably 5 nm or less, and is usually 0 nm or more, but may be 0 nm.
The absolute value of retardation Rth in the thickness direction of any layer is preferably 20 nm or less, more preferably 10 nm or less, and is usually 0 nm or more, but may be 0 nm.

An example of an optional layer is an adhesive layer, which is a layer of adhesive. For example, by providing an adhesive layer between the liquid crystal cured layer (A) and the retardation layer (B), it is possible to prevent the retardation layer (B) from peeling off from the liquid crystal cured layer (A). An example of an adhesive layer is, but is not limited to, a layer of an ultraviolet-curable adhesive.

1.5. Flake embodiments
The flake (AB) is a flake of the laminate (C) including the liquid crystal cured layer (A) and the retardation layer (B), and each flake (AB) is a small piece of the laminate (C). Therefore, each flake (AB) has the same layer structure as the laminate (C) and includes the liquid crystal cured layer (A) and the retardation layer (B). Hereinafter, an embodiment of the flake (AB) will be described with reference to the drawings.

Flake embodiment F1
FIG. 1 is a cross-sectional view showing a schematic diagram of one flake according to embodiment F1 of the present invention.
The flake 100 includes a first retardation layer 111 as the retardation layer (B), a cured liquid crystal layer 120 as the cured liquid crystal layer (A), and a second retardation layer 112 as the retardation layer (B) in this order in the thickness direction.
The first phase difference layer 111 is provided directly on one surface of the liquid crystal cured layer 120, and the second phase difference layer 112 is provided directly on the other surface of the liquid crystal cured layer 120. That is, no layer is interposed between the liquid crystal cured layer 120 and the first phase difference layer 111, and between the liquid crystal cured layer 120 and the second phase difference layer 112. In another embodiment, an arbitrary layer such as an adhesive layer may be interposed between the liquid crystal cured layer 120 and the first phase difference layer 111 and/or between the liquid crystal cured layer 120 and the second phase difference layer 112.

When the flakes 100 are placed on a surface, the first retardation layer 111 or the second retardation layer 112 faces the observation side. That is, the reflected light of the liquid crystal cured layer 120 is given a phase difference by the first retardation layer 111 or the second retardation layer 112 as the retardation layer (B), and the polarization state is changed. Therefore, by observing the light with such a changed polarization state using an appropriate viewer, the reflected light by the collection of flakes 100 can be distinguished from the reflected light from the flakes of the liquid crystal cured layer (A).

Flake embodiment F2
FIG. 2 is a cross-sectional view showing a schematic diagram of one flake according to embodiment F2 of the present invention.
The flake 200 includes a first retardation layer 111 as the retardation layer (B) and a liquid crystal cured layer 120 as the liquid crystal cured layer (A).
The first retardation layer 111 is provided directly on one surface of the liquid crystal cured layer 120. That is, no layer is interposed between the liquid crystal cured layer 120 and the first retardation layer 111. In another embodiment, an arbitrary layer such as an adhesive layer may be interposed between the liquid crystal cured layer 120 and the first retardation layer 111.

When the flakes 200 are arranged on a surface, the liquid crystal cured layer 120 or the first retardation layer 111 faces the observation side. That is, the reflected light of the liquid crystal cured layer 120 is observed as it is without being affected by the first retardation layer 111 as the retardation layer (B), or is observed after being given a phase difference by the first retardation layer 111 as the retardation layer (B).
The reflected light by the collection of flakes 200 contains light whose polarization state has been changed from that of the reflected light of the liquid crystal cured layer 120 by being given a phase difference by the first retardation layer 111. Therefore, the reflected light by the collection of flakes 200, which contains such light whose polarization state has been changed, can be distinguished from the reflected light from the flakes of the liquid crystal cured layer (A) by observing it using an appropriate viewer.

<1.6. Flake manufacturing method>
The flakes of this embodiment can be produced by any method, for example, a method in which a laminate (C) is produced and then crushed; a method in which a laminate (C) is produced on a supporting substrate, incisions are formed in the laminate (C) using a cutting tool such as a roll cutter, and then a high-pressure fluid is sprayed onto the laminate (C) that has become a fixed-sized piece to peel it off from the supporting substrate, thereby obtaining a fixed-sized flake; and the like.

The laminate (C) may be produced by forming a liquid crystal cured layer (A) and then forming a retardation layer (B) on the liquid crystal cured layer (A), or by producing the liquid crystal cured layer (A) and the retardation layer (B) separately and laminating the liquid crystal cured layer (A) and the retardation layer (B). A suitable adhesive such as an ultraviolet-curable adhesive may be used for lamination. In addition, the adhesive strength of the retardation layer (B) to the liquid crystal cured layer (A) may be improved by performing a surface treatment such as a corona treatment on the liquid crystal cured layer (A).

Examples of the manufacturing method for the liquid crystal cured layer (A) and the retardation layer (B) are the same as those mentioned above.

<1.7. Uses of flakes>
The flakes of this embodiment can be suitably used as an identification medium for distinguishing genuine products from counterfeit products, or as a highly designed display medium that displays a different pattern when viewed with the naked eye and when viewed using a viewer. By applying an ink containing the flakes of this embodiment to a surface to form an ink layer, a printed matter useful as an identification medium or display medium can be obtained. The components in the ink other than the flakes are not particularly limited, and commercially available ink media, diluents, and other substances can be used.

2. Printed materials
The ink containing the flakes can be applied to a desired surface by any printing method and cured to obtain a printed matter containing a layer of the ink containing the flakes. As the printing method, screen printing and inkjet printing are preferred because they allow efficient printing.
By utilizing the action of the flakes, it is possible to obtain a printed matter having a special optical effect, in which a pattern such as letters is not observed with the naked eye, but a pattern such as letters is observed when observed using an appropriate viewer that can distinguish between polarization states. A printed matter having such an optical effect is useful as an identification medium that can distinguish genuine items from counterfeits, or as a display medium with a special design.

The printed matter according to the embodiment of the present invention will be described below. The printed matter can be an identification medium. In the following description, the ink layer containing the flakes (AB) is also called the ink layer (AB), and the ink layer containing the flakes (A) of the liquid crystal cured layer (A) is also called the ink layer (A). The ink layer containing the flakes (AB1) is also called the ink layer (AB1), and the ink layer containing the flakes (AB2) is also called the ink layer (AB2). As described above, the retardation layer (B1) of the flakes (AB1) and the retardation layer (B2) of the flakes (AB2) give different phase differences to the incident light.

(Printed matter embodiment P1)
The printed matter according to embodiment P1 is
A printed matter having a display surface,
A first ink layer provided in a region _R1 occupying a part of the display surface;
a second ink layer provided in a region _R2 occupying a part of the display surface and occupying a part or all of the region other than the region _R1 ;
The first ink layer contains a first flake of a laminate (C) including a liquid crystal cured layer (A) and a retardation layer (B), the retardation layer (B) being a retardation layer (B1) that gives a retardation ReB1(φ) to incident light having a wavelength of 550 nm from a predetermined polar angle φ;
The second ink layer contains second flakes which are flakes of the cured liquid crystal layer (A). The printed matter can be an identification medium.

Fig. 3 is a cross-sectional view that shows a schematic diagram of a printed matter according to an embodiment of the present invention. Fig. 4 is a top view that shows a schematic diagram of a printed matter according to an embodiment of the present invention.
The printed matter 1 includes a print base layer 30, a first ink layer 10 (in this embodiment, ink layer (AB)), and a second ink layer 20 (in this embodiment, ink layer (A)). The first ink layer 10 and the second ink layer 20 are provided in contact with the upper surface 30U of the print base layer 30. The first ink layer 10 (ink layer (AB)) and the second ink layer 20 (ink layer (A)) are arranged so that their side surfaces are in contact with each other at the boundary 12. In this way, it is preferable that the first ink layer 10 is arranged so that the side surface of the edge of all or a part of the first ink layer 10 is in contact with the side surface of the edge of the second ink layer 20 from the viewpoint of enhancing the concealment of the identification function of the printed matter 1. The first ink layer 10 and the second ink layer 20 may be separated from each other, but from the viewpoint of enhancing the concealment of the identification function, it is preferable that the distance when they are separated is small. The distance is usually 200 μm or less, preferably 100 μm or less, more preferably 50 μm or less, even more preferably 20 μm or less, and particularly preferably 10 μm or less. The first ink layer 10 and the second ink layer 20 can be obtained by a method called tweezers printing or seamless printing. The print base layer 30 is preferably an absorbing layer that absorbs light. The region R ₁ occupied by the first ink layer 10 (ink layer (AB) in this embodiment) and the region R ₂ occupied by the second ink layer 20 (ink layer (A) in this embodiment) are provided on the printed matter 1, and these form a latent image. A latent image is an image that cannot be observed by the naked eye with normal unpolarized light, and is observed only in a specific observation of the printed matter. In the printed matter of the example of FIG. 3 to FIG. 4, the letter "T" can function as a latent image.

The ink layers (AB) and (A) appear to the naked eye to be approximately the same or have the same color tone, and the edges of the ink layers (AB) and (A) are in contact or are at a short distance from each other, so the boundary between the ink layers (AB) and (A) cannot be distinguished by the naked eye. Also, as mentioned above, the reflected light of the flakes (AB) contained in the ink layer (AB) and the reflected light of the flakes (A) contained in the ink layer (A) have different polarization states, so when the ink layers (AB) and (A) are observed using an appropriate viewer that can distinguish between polarization states, the boundary between the ink layers (AB) and (A) can be distinguished.

The retardation layer (B1) of the first flake (AB) may be a layer that functions as a λ/2 plate that imparts a retardation of λ/2 to incident light in the front direction, and specifically, the retardation ReB1(0) when φ is 0° may be λ/2 or close to λ/2, specifically 250 nm or more and 350 nm or less. In this case, the boundary between the ink layer (AB) and the ink layer (A) can be distinguished by observing from the front direction of the display surface using a circular polarizing plate as a viewer.
In another embodiment, the retardation layer (B1) may be a layer that functions as a so-called C plate, and for example, the retardation ReB1 (45) when φ is 45° may be 50 nm or more and 100 nm or less, or 300 nm or more and 350 nm or less. In this case, the boundary between the ink layer (AB) and the ink layer (A) can be distinguished by using a linear polarizing plate as a viewer and observing from an oblique direction of the display surface.

(Embodiment P2 of printed matter)
The printed matter according to embodiment P2 is
A printed matter having a display surface,
A first ink layer provided in a region _R1 occupying a part of the display surface;
a second ink layer provided in a region _R2 occupying a part of the display surface and occupying a part or all of the region other than the region _R1 ;
The first ink layer contains a first flake of a laminate (C) including a liquid crystal cured layer (A) and a retardation layer (B), the retardation layer (B) being a retardation layer (B1) that gives a retardation ReB1(φ) to incident light having a wavelength of 550 nm from a predetermined polar angle φ;
The second ink layer contains a second flake, which is a flake of a laminate (C2) including the liquid crystal cured layer (A) and a retardation layer (B2) that gives a retardation ReB2(φ) to incident light having a wavelength of 550 nm from a predetermined polar angle φ;
|ReB2(φ)-ReB1(φ)|>0 nm. The printed matter can be an identification medium.

The printed matter of this embodiment has the same configuration as the printed matter of embodiment P1, except that the first ink layer 10 in Figures 3 and 4 is the ink layer (AB1) and the second ink layer 20 is the ink layer (AB2).

In this embodiment, too, a region _R1 occupied by a first ink layer 10 (in this embodiment, ink layer (AB1)) and a region R2 occupied by a second ink layer 20 (in this embodiment, ink layer (AB2)) are provided on the printed matter ₁ , and these form a latent image.

The ink layers (AB1) and (AB2) appear to the naked eye to be approximately the same or have the same color tone, and the edges of the ink layers (AB1) and (AB2) are in contact or are at a short distance from each other, so the boundary between the ink layers (AB1) and (AB2) cannot be distinguished by the naked eye. Also, as mentioned above, the reflected light from the flakes (AB1) contained in the ink layer (AB1) and the reflected light from the flakes (AB2) contained in the ink layer (AB2) have different polarization states, so when the ink layers (AB1) and (AB2) are observed using an appropriate viewer that can distinguish between polarization states, the boundary between the ink layers (AB1) and (AB2) can be distinguished.

The following are examples of combinations of the retardation layer (B1) of the flake (AB1) as the first flake and the retardation layer (B2) of the flake (AB2) as the second flake, provided that |ReB2(φ)-ReB1(φ)|>0 nm is satisfied.

The retardation layer (B1) is a layer that functions as a λ/2 plate that imparts a retardation of λ/2 to incident light in the front direction, specifically, the retardation ReB1(0) when φ is 0° is λ/2 or close to λ/2, specifically, 250 nm to 350 nm, and the retardation layer (B2) is a layer that functions as a so-called C plate, specifically, ReB2(0) when φ is 0° is 10 nm or less. In this case, the boundary between the ink layer (AB1) and the ink layer (AB2) can be distinguished by using a circular polarizing plate as a viewer and observing from the front direction of the display surface.
The retardation layer (B1) is a layer that functions as a so-called C plate, and the retardation layer (B2) is a layer that functions as a so-called C plate, and for example, when φ is 45°, the absolute value of the difference between ReB1(45) and ReB2(45), |ReB2(45)-ReB1(45)|, is greater than 0 nm, and preferably is 50 nm or more and 100 nm or less, or 300 nm or more and 350 nm or less. In this case, the boundary between the ink layer (AB1) and the ink layer (AB2) can be distinguished by using a linear polarizing plate as a viewer and observing from an oblique direction of the display surface.

<3. Articles>
The printed matter can be attached to another component to form an article having an identification function, or the printed matter itself can be used as an article having an identification function.
Examples of articles include various articles such as clothing, shoes, hats, accessories, jewelry, and daily necessities. The article can have an identification function by being provided with the printed matter of the present invention. By having such an identification function, the article can be identified as being genuine and not a counterfeit. In addition, the printed matter can impart a design effect to the article. The printed matter can be provided on the article as an ornament, part, or accessory of the article, such as a tag, charm, patch, or sticker.

The article of the present invention may further include a viewer in addition to the printed matter of the present invention. Examples of viewers include a linear polarizing plate and a circular polarizing plate.

The viewer can be, for example, in the shape of a tag, and can be attached to the main body of the item via a string or the like. In this way, by providing a viewer in addition to the printed matter, general item users can easily identify the printed matter.

The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the examples shown below, and can be modified as desired without departing from the scope of the claims of the present invention and the scope of equivalents thereto.

In the following explanation, the amounts in "%" and "parts" are by weight unless otherwise specified. Furthermore, the operations described below were carried out at room temperature (20°C ± 15°C) and normal pressure (1 atm) unless otherwise specified. As the commercially available adhesive, Nitto Denko Corporation's transparent adhesive tape "LUCIACS CS9621T" (thickness 25 μm, visible light transmittance 90% or more, in-plane retardation 3 nm or less) was used unless otherwise specified.

<Method of measuring in-plane retardation>
The in-plane retardation was measured at a measurement wavelength of 550 nm using a phase difference meter (Axoscan manufactured by Axometrics).

<Method of measuring reflectance of cholesteric liquid crystal layer>
The support substrate film was peeled off from the multilayer film to obtain a cholesteric liquid crystal cured layer (hereinafter also referred to as a cholesteric liquid crystal layer). The integrated reflectance of this cholesteric liquid crystal layer when non-polarized light (wavelength 400 nm to 800 nm) was incident thereon was measured using an ultraviolet-visible spectrophotometer equipped with an integrating sphere ("UV-Vis 550" manufactured by JASCO Corporation).

<Average particle size D50 of flakes>
The volumetric particle size distribution of the flakes was measured using a laser diffraction/scattering particle size distribution measuring device (manufactured by Horiba, Ltd., product name "LA-960"). The average particle size was determined by using the median diameter D50, which is the cumulative volume of 50% in the particle size distribution measured using the particle size distribution measuring device.

<Production Example A1: Production of a broadband reflective cholesteric liquid crystal layer (CLC_W) capable of reflecting right-handed circularly polarized light>
A liquid crystal composition was prepared by mixing 100 parts of a photopolymerizable liquid crystal compound represented by the following formula (X1) (the above formula (B5)), 25 parts of a photopolymerizable non-liquid crystal compound represented by the following formula (X2) (the above formula (A10)), 7.5 parts of a chiral agent ("LC756" manufactured by BASF), 5 parts of a photopolymerization initiator ("Irgacure 907" manufactured by Ciba Japan), 0.2 parts of a surfactant ("S-420" manufactured by AGC Seimi Chemical Co., Ltd.), and 120 parts of cyclopentanone and 200 parts of 1,3-dioxolane as solvents.

A long polyethylene terephthalate film (Toyobo Co., Ltd. "A4300"; thickness 100 μm) was prepared as the supporting substrate film. This substrate film was attached to the unwinding section of the film transport device, and the following operations were carried out while transporting the substrate film in the longitudinal direction.

The surface of the support substrate film was subjected to rubbing treatment in the longitudinal direction parallel to the transport direction. Next, a liquid crystal composition was applied to the surface of the support substrate film that had been subjected to rubbing treatment using a die coater to form a layer of the liquid crystal composition. The layer of the liquid crystal composition was subjected to an alignment treatment of heating at 120°C for 5 minutes. Thereafter, the layer of the liquid crystal composition was subjected to a band-widening treatment. In this band-widening treatment, weak ultraviolet irradiation at 5 to 30 mJ/ ^cm2 and heating treatment at 100 to 120°C were alternately repeated multiple times to control the bandwidth to the desired bandwidth. Then, 900 mJ/ ^cm2 ultraviolet light was irradiated onto the layer of the liquid crystal composition to harden the layer of the liquid crystal composition. This resulted in a multilayer film comprising a support substrate film and a cholesteric liquid crystal layer. The reflectance of the cholesteric liquid crystal layer of this multilayer film was measured by the above-mentioned measurement method. As a result of the measurement, the cholesteric liquid crystal layer had a wavelength range in which the reflectance for unpolarized light was 40% or more over almost the entire wavelength range from 450 nm to 700 nm, and the half-width of the selective reflection band was 250 nm or more. The film thickness of the cholesteric liquid crystal layer was adjusted to 5.3 μm.

<Production Example A2: Production of a red-reflecting cholesteric liquid crystal layer (CLC_R) capable of reflecting right-handed circularly polarized light>
In Manufacturing Example A1, the chiral agent (BASF's "LC756") was changed to 6.8 parts, and the layer of the liquid crystal composition was irradiated with 900 mJ/ ^cm2 ultraviolet light without performing the broadband treatment to harden the layer of the liquid crystal composition. A multilayer film was produced in the same manner as Manufacturing Example A1 except for this. The reflectance of the cholesteric liquid crystal layer of this multilayer film was measured by the same measurement method as Manufacturing Example A1. As a result of the measurement, the cholesteric liquid crystal layer had a central wavelength near 650 nm, a half-width of about 100 nm, and a wavelength range that was visually recognized as red with a reflectance of 40% or more for unpolarized light. The film thickness of the cholesteric liquid crystal layer was adjusted to 3.6 μm.

<Production Example A3: Production of a green-reflecting cholesteric liquid crystal layer (CLC_G) capable of reflecting right-handed circularly polarized light>
In the manufacturing example A1, the layer of the liquid crystal composition was irradiated with 900 mJ/ ^cm2 ultraviolet light without performing the broadband treatment, and the layer of the liquid crystal composition was cured. Except for this, a multilayer film was produced in the same manner as in manufacturing example A1. The reflectance of the cholesteric liquid crystal layer of this multilayer film was measured using the same measurement method as in manufacturing example A1. As a result of the measurement, the cholesteric liquid crystal layer had a central wavelength near 550 nm, a half-width of about 85 nm, and a wavelength range that was visually recognized as green with a reflectance of 40% or more for unpolarized light. The film thickness of the cholesteric liquid crystal layer was adjusted to 3.6 μm.

<Production Example A4: Production of a blue-reflecting cholesteric liquid crystal layer (CLC_B) capable of reflecting right-handed circularly polarized light>
In Manufacturing Example A1, the chiral agent (BASF's "LC756") was changed to 9.5 parts, and the layer of the liquid crystal composition was irradiated with 900 mJ/ ^cm2 ultraviolet light without performing the broadband treatment to harden the layer of the liquid crystal composition. Other than this, a multilayer film was produced in the same manner as Manufacturing Example A1. The reflectance of the cholesteric liquid crystal layer of this multilayer film was measured by the same measurement method as Manufacturing Example A1. As a result of the measurement, the cholesteric liquid crystal layer had a central wavelength near 450 nm, a half-width of about 75 nm, and a wavelength range that was visually recognized as blue with a reflectance of 40% or more for unpolarized light. The film thickness of the cholesteric liquid crystal layer was adjusted to 3.6 μm.

<Production Example A5: Production of λ/2 Retardation Film Layer (H1)>
A liquid crystal composition was prepared by mixing 100 parts of the photopolymerizable liquid crystal compound represented by (X1) used in Production Example A1, 4 parts of a photopolymerization initiator ("Irgacure 907" manufactured by Ciba Japan), 0.15 parts of a surfactant ("Megafac F-562" manufactured by DIC Corporation), 120 parts of cyclopentanone as a solvent, and 200 parts of 1,3-dioxolane.

A long polyethylene terephthalate film (Toyobo Co., Ltd. "A4300"; thickness 100 μm) was prepared as the supporting substrate film. This substrate film was attached to the unwinding section of the film transport device, and the following operations were carried out while the substrate film was transported in the longitudinal direction.

The surface of the support substrate film was subjected to rubbing treatment in the longitudinal direction parallel to the transport direction. Next, a liquid crystal composition was applied to the surface of the support substrate film that had been subjected to rubbing treatment using a die coater to form a layer of the liquid crystal composition. The layer of the liquid crystal composition was subjected to an orientation treatment of heating at 120 ° C. for 4 minutes. Then, the layer of the liquid crystal composition was irradiated with ultraviolet light of 900 mJ / cm ² to harden the layer of the liquid crystal composition. This resulted in a multilayer film comprising a support substrate film and a liquid crystal cured layer (retardation film layer). The in-plane retardation of this multilayer film was measured by the above-mentioned measurement method to obtain the in-plane retardation value of the liquid crystal cured layer. As a result of the measurement, the in-plane retardation of the liquid crystal cured layer was 280 nm at a wavelength of 550 nm, and the direction of the slow axis relative to the support substrate film was parallel to the longitudinal direction of the film and was approximately 0 °. The film thickness of the liquid crystal cured layer was adjusted to 1.1 μm.
Moreover, the birefringence Δn of the liquid crystal compound represented by the formula (X1) was calculated by dividing the in-plane retardation of the obtained cured liquid crystal layer by the film thickness of the cured liquid crystal layer, and was found to be 0.25.

The surfactant and photopolymerization initiator used in the preparation of the liquid crystal composition do not have birefringence, and the amount thereof is small. Furthermore, the solvent used in the preparation of the liquid crystal composition evaporates before the formation of the liquid crystal cured layer. Therefore, the effect of the surfactant, photopolymerization initiator, and solvent contained in the liquid crystal composition on the birefringence Δn of the liquid crystal cured layer is negligibly small. Therefore, the birefringence Δn of the liquid crystal compound can be obtained using the in-plane retardation and thickness values of the above-mentioned liquid crystal cured layer. The same applies to the birefringence Δn of the following liquid crystal compounds.

<Production Example A6: Production of λ/2 Retardation Film Layer (H2)>
The liquid crystal compound of Production Example A5 was replaced by LC242 manufactured by BASF in an equal weight ratio, and the film thickness was adjusted so that the in-plane retardation was approximately λ/2, similar to Production Example A5. A multilayer film having a retardation film layer was produced in the same manner as Production Example A5 except for this.
When the in-plane retardation was measured by the above-mentioned method, the retardation of the liquid crystal cured layer (retardation film layer) was 275 nm at a wavelength of 550 nm. The direction of the slow axis of the retardation film layer relative to the support substrate film was parallel to the longitudinal direction of the support substrate film and was approximately 0°. The film thickness of the liquid crystal cured layer was adjusted to 2.4 μm.
Further, the birefringence Δn of the liquid crystal compound LC242 was calculated by dividing the in-plane retardation of the cured liquid crystal layer by the film thickness of the cured liquid crystal layer, and was found to be 0.11.

<Production Example A7: Production of λ/2+α Retardation Film Layer (H3)>
A retardation film layer was produced in the same manner as in Production Example A5 except that the thickness of the cured liquid crystal layer was adjusted to 1.5 μm.
When the in-plane retardation was measured by the above-mentioned method, the in-plane retardation of the retardation film layer was 350 nm at a wavelength of 550 nm. When the retardation was measured when tilted at an angle of 30° from both sides with the slow axis as the rotation axis, it was 260 nm. The direction of the slow axis of the retardation film layer relative to the support substrate film was parallel to the longitudinal direction of the support substrate film and was approximately 0°.

<Production Example A8: Production of Cholesteric Liquid Crystal C Plate (C1)>
In Manufacturing Example A1, the chiral agent ("LC756" manufactured by BASF) was changed to 27.3 parts, and the layer of the liquid crystal composition was irradiated with ultraviolet light of 900 mJ/ ^cm2 without performing the broadband treatment to harden the layer of the liquid crystal composition. A multilayer film was produced in the same manner as Manufacturing Example A1 except for this. The reflectance of the cholesteric liquid crystal layer of this multilayer film was measured by the same measurement method as Manufacturing Example A1. As a result of the measurement, the cholesteric liquid crystal layer had a central wavelength near 160 nm, and formed a transparent layer in which reflected light could not be recognized by the naked eye. When the in-plane retardation was measured by the above-mentioned method, the in-plane retardation of the cholesteric liquid crystal layer was approximately 0 nm at a wavelength of 550 nm. In addition, when the retardation was measured when tilted at 45° from both sides with the longitudinal direction of the cholesteric liquid crystal layer as the rotation axis, it was 75 nm. The film thickness of the cholesteric liquid crystal layer was adjusted to 1.9 μm.

<Production Example A9: Production of Cholesteric Liquid Crystal C Plate (C2)>
In Manufacturing Example A1, the chiral agent ("LC756" manufactured by BASF) was changed to 27.5 parts, and the layer of the liquid crystal composition was irradiated with ultraviolet light of 900 mJ/ ^cm2 without performing the broadband treatment, and the layer of the liquid crystal composition was cured. A multilayer film was produced in the same manner as Manufacturing Example A1 except for this. The reflectance of the cholesteric liquid crystal layer of this multilayer film was measured by the same measurement method as Manufacturing Example A1. As a result of the measurement, the cholesteric liquid crystal layer had a central wavelength near 160 nm, and formed a transparent layer in which reflected light could not be recognized visually. When the in-plane retardation was measured by the above-mentioned method, the in-plane retardation of the cholesteric liquid crystal layer was approximately 0 nm at a wavelength of 550 nm. In addition, when the retardation was measured when tilted at 45° from both sides with the longitudinal direction of the cholesteric liquid crystal layer as the rotation axis, it was 335 nm. The film thickness of the cholesteric liquid crystal layer was adjusted to 8.8 μm.

<Production Example A10: Production of multilayer film (WH1)>
A UV adhesive (Aronix) manufactured by Toa Gosei Co., Ltd. was applied to the cholesteric liquid crystal layer side of the CLC_W film of Production Example A1 with a bar coater while conveying the film to a thickness of 0.5 μm, and then the liquid crystal cured layer side of the H1 film of Production Example A5 was laminated by roll-to-roll. After that, 800 mJ/cm ² of ultraviolet light was irradiated from the H1 film side to cure the layer of the ultraviolet (UV) curable adhesive, and the support base film on the CLC_W film side was peeled off and wound up to produce a multilayer film WH1.

<Production Example A11: Production of multilayer film (WH2)>
The H1 film used in Production Example A10 was replaced with the H2 film used in Production Example A6. Otherwise, a multilayer film WH2 was produced in the same manner as in Production Example A10.

<Production Example A12: Production of multilayer film (WH3)>
The H1 film used in Production Example A10 was replaced with the H3 film used in Production Example A7. Otherwise, a multilayer film WH3 was produced in the same manner as in Production Example A10.

<Production Example A13: Production of multilayer film (WC1)>
The H1 film used in Production Example A10 was replaced with the C1 film used in Production Example A8. Otherwise, a multilayer film WC1 was produced in the same manner as in Production Example A10.

<Production Example A14: Production of multilayer film (WC2)>
A multilayer film WC2 was produced in the same manner as in Production Example 9, except that the H1 film used in Production Example A10 was replaced with the C2 film used in Production Example A9.

<Production Example A15: Production of multilayer film (RH1)>
The CLC_W film used in Production Example A10 was replaced with the CLC_R film used in Production Example A2. Otherwise, a multilayer film RH1 was produced in the same manner as in Production Example A10.

<Production Example A16: Production of multilayer film (GH1)>
The CLC_W film used in Production Example A10 was replaced with the CLC_G film used in Production Example A3. Otherwise, a multilayer film GH1 was produced in the same manner as in Production Example A10.

<Production Example A17: Production of multilayer film (BH1)>
The CLC_W film used in Production Example A10 was replaced with the CLC_B film used in Production Example A4. Otherwise, a multilayer film BH1 was produced in the same manner as in Production Example A10.

<Production Example A18: Production of multilayer film (WH1D)>
The liquid crystal composition solution used in Production Example A5 was applied to the cholesteric liquid crystal layer side of the CLC_W film of Production Example A1 with a die coater while conveying the film to a thickness of 1.1 μm. After that, the liquid crystal composition layer was irradiated with ultraviolet light of 900 mJ/ ^cm2 to harden the liquid crystal composition layer. Thus, a multilayer film WH1D was produced.

<Production Example A19: Production of multilayer film (H1WH1)>
The H1 film of Production Example A5 was bonded to the exposed CLC_W film side of the WH1 film produced in Production Example A10 in the same manner as in Production Example A10, and the supporting substrate on one of the H1 film sides was peeled off while rolling up to produce a multilayer film H1WH1.

<Production Example A20: Production of multilayer film (H2WH2)>
The H1 film produced in Production Example A5 used in Production Example A19 was replaced with the H2 film produced in Production Example A6. Otherwise, a multilayer film H2WH2 was produced in the same manner as in Production Example A19.

<Production Example A21: Production of multilayer film (H3WH3)>
The H1 film produced in Production Example A5 used in Production Example A19 was replaced with the H3 film produced in Production Example A7. Otherwise, a multilayer film H3WH3 was produced in the same manner as in Production Example A19.

<Production Example A22: Production of multilayer film (C1WC1)>
The WH1 film used in Production Example A19 was replaced with the WC1 film produced in Production Example A13, and the H1 film was replaced with the C1 film produced in Production Example A8. Otherwise, a multilayer film C1WC1 was produced in the same manner as in Production Example A19.

<Production Example A23: Production of multilayer film (C2WC2)>
The WH1 film used in Production Example A19 was replaced with the WC2 film produced in Production Example A14, and the H1 film was replaced with the C2 film produced in Production Example A9. Otherwise, a multilayer film C2WC2 was produced in the same manner as in Production Example A19.

<Production Example A24: Production of multilayer film (H1RH1)>
The WH1 film used in Production Example A19 was replaced with the RH1 film produced in Production Example A15. Otherwise, a multilayer film H1RH1 was produced in the same manner as in Production Example A19.

<Production Example A25: Production of multilayer film (H1GH1)
The WH1 film used in Production Example A19 was replaced with the GH1 film produced in Production Example A16. Otherwise, a multilayer film H1GH1 was produced in the same manner as in Production Example A19.

<Production Example A26: Production of multilayer film (H1BH1)
The WH1 film used in Production Example A19 was replaced with the BH1 film produced in Production Example A17. Otherwise, a multilayer film H1BH1 was produced in the same manner as in Production Example A19.

<Production Example A27: Production of multilayer film (H1WH1D)>
The WH1 film used in Production Example A19 was replaced with the WH1D film produced in Production Example A18. Otherwise, a multilayer film H1WH1D was produced in the same manner as in Production Example A19.

<Production Example B1: Production of cholesteric liquid crystal flakes (F_CLC_W)>
The CLC_W film produced in Production Example A1 was peeled off from the supporting substrate by jetting high-pressure air, and then pulverized in a jet mill to produce cholesteric liquid crystal flakes F_CLC_W having an average particle size (D50) of about 50 μm.

<Production Example B2: Production of cholesteric liquid crystal flakes (F_CLC_R)>
Cholesteric liquid crystal flakes F_CLC_R having an average particle size (D50) of about 50 μm were produced in the same manner as in Production Example B1, except that the CLC_R film produced in Production Example A2 was used.

<Production Example B3: Production of cholesteric liquid crystal flakes (F_CLC_G)>
Cholesteric liquid crystal flakes F_CLC_G having an average particle size (D50) of about 50 μm were produced in the same manner as in Production Example B1, except that the CLC_G film produced in Production Example A3 was used.

<Production Example B4: Production of cholesteric liquid crystal flakes (F_CLC_B)>
Cholesteric liquid crystal flakes F_CLC_B having an average particle size (D50) of about 50 μm were produced in the same manner as in Production Example B1, except that the CLC_B film produced in Production Example A4 was used.

<Production Example B5: Production of cholesteric liquid crystal flakes (F_WH1)>
Cholesteric liquid crystal flakes F_WH1 having an average particle size (D50) of about 50 μm were produced in the same manner as in Production Example B1, except that the WH1 film produced in Production Example A10 was used.

<Production Example B6: Production of cholesteric liquid crystal flakes (F_WH3)>
Cholesteric liquid crystal flakes F_WH3 having an average particle size (D50) of about 50 μm were produced in the same manner as in Production Example B1, except that the WH3 film produced in Production Example A12 was used.

<Production Example B7: Production of cholesteric liquid crystal flakes (F_H1WH1)>
Cholesteric liquid crystal flakes F_H1WH1 having an average particle size (D50) of about 50 μm were produced in the same manner as in Production Example B1, except that the H1WH1 film produced in Production Example A19 was used.

<Production Example B8: Production of cholesteric liquid crystal flakes (F_H2WH2)>
Cholesteric liquid crystal flakes F_H2WH2 having an average particle size (D50) of about 50 μm were produced in the same manner as in Production Example B1, except that the H2WH2 film produced in Production Example A20 was used.

<Production Example B9: Production of cholesteric liquid crystal flakes (F_H3WH3)>
Cholesteric liquid crystal flakes F_H3WH3 having an average particle size (D50) of about 50 μm were produced in the same manner as in Production Example B1, except that the H3WH3 film produced in Production Example A21 was used.

<Production Example B10: Production of cholesteric liquid crystal flakes (F_C1WC1)>
Cholesteric liquid crystal flakes F_C1WC1 having an average particle size (D50) of about 100 μm were produced in the same manner as in Production Example B1, except that the C1WC1 film produced in Production Example A22 was used.

<Production Example B11: Production of cholesteric liquid crystal flakes (F_C2WC2)>
Cholesteric liquid crystal flakes F_C2WC2 having an average particle size (D50) of about 100 μm were produced in the same manner as in Production Example B1, except that the C2WC2 film produced in Production Example A23 was used.

<Production Example B12: Production of cholesteric liquid crystal flakes (F_H1RH1)>
Cholesteric liquid crystal flakes F_H1RH1 having an average particle size (D50) of about 50 μm were produced in the same manner as in Production Example B1, except that the H1RH1 film produced in Production Example A24 was used.

<Production Example B13: Production of cholesteric liquid crystal flakes (F_H1GH1)>
Cholesteric liquid crystal flakes F_H1GH1 having an average particle size (D50) of about 50 μm were produced in the same manner as in Production Example B1, except that the H1GH1 film produced in Production Example A25 was used.

<Production Example B14: Production of cholesteric liquid crystal flakes (F_H1BH1)>
Cholesteric liquid crystal flakes F_H1BH1 having an average particle size (D50) of about 50 μm were produced in the same manner as in Production Example B1, except that the H1BH1 film produced in Production Example A26 was used.

<Production Example B15: Production of Fixed-Type Cholesteric Liquid Crystal Flakes (FT_H1WH1)>
While conveying the H1WH1 film produced in Production Example A19, it was sandwiched between a cutter roll 1 equipped with line cutters spaced 50 μm apart and a rubber roll, and a cut was made on the surface of the multilayer film. The cutter roll 1 was processed so that the line cutter was oriented at 45° to the rotation axis of the roll. After that, the film was wound up once, and while conveying the film again, a cut was made on the surface of the multilayer film using a cutter roll 2 instead of the cutter roll 1. The cutter roll 2 was processed so that the line cutter was oriented at 45°, which is the opposite direction to the cutter roll described above. Then, the laminated film flakes were peeled off with high-pressure air to produce cholesteric liquid crystal flakes FT_H1WH1 having a rectangular flake shape and a constant average particle diameter (D50) of 50 μm.

<Production Example B16: Production of multilayer film (H1WH1D)>
The WH1 film used in Production Example A19 was replaced with the WH1D film produced in Production Example A18. Otherwise, a multilayer film H1WH1D was produced in the same manner as in Production Example A19.

<Production Example B17: Production of cholesteric liquid crystal flakes (F_H1WH1D)>
Cholesteric liquid crystal flakes F_H1WH1D having an average particle size (D50) of about 50 μm were produced in the same manner as in Production Example B1, except that the H1WH1D film produced in Production Example B16 was used.

Tables 1 and 2 list the properties of each layer that makes up the flakes.

Table 3 lists the obtained cholesteric liquid crystal flakes.
The abbreviations in the flake layer configuration section of Table 3 have the following meanings.
"W": broadband reflective cholesteric liquid crystal layer (CLC_W) obtained in Production Example A1
"R": Red-reflecting cholesteric liquid crystal layer (CLC_R) obtained in Production Example A2
"G": Green-reflecting cholesteric liquid crystal layer (CLC_G) obtained in Production Example A3
"B": Blue-reflecting cholesteric liquid crystal layer (CLC_B) obtained in Production Example A4
"A": Adhesive layer (cured layer of UV adhesive (Aronix) manufactured by Toa Gosei Co., Ltd.)
"H1": λ/2 retardation film layer (H1) obtained in Production Example A5
"H2": λ/2 retardation film layer (H2) obtained in Production Example A6
"H3": λ/2 + α retardation film layer (H3) obtained in Production Example A7
"C1": Cholesteric liquid crystal C plate (C1) obtained in Production Example A8
"C2]: Cholesteric liquid crystal C plate (C2) obtained in Production Example A9
"Thickness": Thickness d (C) of the laminate
"D50/thickness": D50 of flake/thickness of laminate d(C)
"Thickness ratio": the thickness ratio of the total thickness d _tot (B) of the retardation layer (B) to the thickness d(A) of the liquid crystal cured layer (A) (d _tot (B)/d(A))

<Comparative Ink Preparation Examples 201 to 204, Ink Preparation Examples 205 to 216>
Ink Nos. C201 to C204 and 205 to 216 were prepared by mixing 5 parts of any of the cholesteric liquid crystal cured layer flakes (flake Nos. 101 to 116 in Table 3) prepared in the above-mentioned manufacturing examples, 85 parts of screen ink ("No. 2500 Medium" manufactured by Jujo Chemical Co., Ltd.), and 5 parts of a dedicated diluent for the screen ink (Tetoron standard solvent). The list of the prepared inks is summarized in Table 4.

<Examples 1 to 11 and Comparative Examples 1 to 4>
(Preparation of Screen Printing Samples)
Screen printing samples were prepared by varying the combinations of the various inks listed in Table 4. As the screen printing sample, a so-called tweezers printing (seamless printing) pattern was adopted, which represents the letter "T" as shown in Fig. 4 and is composed of a first ink layer 10 (letter portion) and a second ink layer 20 (background portion). The ink combinations used for the letter portion and the background portion are shown in Table 5.

(Evaluation of Screen Printed Samples)
The resulting screen print samples were each evaluated as follows.

(1) Visual evaluation: When the print sample was observed from the front with the naked eye under normal fluorescent lighting conditions, it was evaluated whether the letter "T" was clearly identifiable.
A: It is recognized as a uniform surface and the letters are not clearly distinguishable.
B: It cannot be recognized as a uniform surface, and the letters are somewhat discernible.

(2) Observation with a circularly polarized viewer: When the print sample was observed from the front through a circularly polarized viewer, it was evaluated whether the letter "T" was clearly identifiable. The circularly polarized viewer used was a cholesteric liquid crystal cured layer portion of the CLC_W film of Production Example A1 transferred onto a glass plate with an adhesive.
A: Characters are clearly recognizable.
B: The characters are slightly unclear but can be recognized.
C: It is recognized as a uniform surface and the letters are not clearly distinguishable.

(3) Observation with polarized sunglasses: An observer wore polarized sunglasses equipped with a linear polarizing plate and observed the printed sample at continuously changing angles from the front to an oblique angle (polar angle of approximately 60°). An evaluation was made as to whether there was an angle at which the letter "T" could be clearly identified.
A: When observed obliquely, the characters can be clearly recognized at a specific angle.
B: There is an angle at which the characters can be recognized when observed obliquely.
B2: At an observation position with a polar angle of 45°, the characters can be recognized by rotating the polarized sunglasses counterclockwise or clockwise around the observation direction of the print sample as the rotation axis.
C: The characters cannot be recognized at any angle when observed obliquely.

(4) Magnified observation with a loupe: When the printed portion was magnified and observed with a loupe, how the flake shape was recognized was evaluated.
A: Flakes of uniform shape can be recognized.
B: Only randomly shaped flakes are recognizable.

(Observation results)
The evaluation results for the screen print samples are shown in Table 5.

As is clear from the evaluation results of Examples 1 to 11 in Table 5, the character portion printed with the ink containing the flakes including the cured liquid crystal layer (A) and the retardation layer (B) and the background portion printed with the ink containing the flakes of the cured liquid crystal layer (A) cannot be distinguished with the naked eye. However, when observed from the front direction through a circularly polarized viewer or from a specific oblique direction through polarized sunglasses, the character portion and the background portion can be distinguished, and the characters can be recognized.
Furthermore, as is clear from the evaluation results of Examples 12 to 13 in Table 5, even when the flakes contained in the ink used in the character portion and the flakes contained in the ink used in the background portion each contain a liquid crystal cured layer (A) and a retardation layer (B), and the retardation layers (B) contained therein have different retardations from each other, the character portion and the background portion cannot be distinguished with the naked eye. However, when observed from a specific oblique direction through polarized sunglasses, the character portion and the background portion can be distinguished, and the characters can be recognized.
Furthermore, as is clear from the evaluation results of Example 13, when an ink containing flakes including a C plate as a retardation layer (B) is used for the character part and the background part, the character part and the background part cannot be distinguished even when observed from the front using a circularly polarized viewer. However, when observed from a specific oblique direction through polarized sunglasses, the character part and the background part can be distinguished, and the characters can be recognized.
These special effects can provide a sense of surprise to the viewer.

It also shows that such special optical effects can be achieved by screen printing using flakes that contain a liquid crystal cured layer (A) and a retardation layer (B).

As is clear from the evaluation results of Example 7, a printed matter can be realized in which flakes having a regular shape can be recognized when observed under magnification with a magnifying glass, by including a liquid crystal cured layer (A) and a retardation layer (B) and using flakes having a regular shape.
The flakes have a fixed shape and cannot be visually recognized, so they can be included in printed matter without being noticed by observers, and therefore can be used as an excellent security material.

REFERENCE SIGNS LIST 1 Printed matter 10 First ink layer 12 Boundary 20 Second ink layer 30 Printing base layer 30U surface 100 Flake 200 Flake 111 First retardation layer (retardation layer (B))
120 Liquid crystal hardened layer (liquid crystal hardened layer (A))
112 Second retardation layer (retardation layer (B))

Claims (19)

A flake of a laminate (C) containing a liquid crystal cured layer (A) having cholesteric regularity and a retardation layer (B) that imparts a phase difference to incident light. The flake according to claim 1, wherein the laminate (C) is a laminate in which the retardation layer (B) is laminated in the thickness direction on the entire surface of the liquid crystal cured layer (A). The flakes according to claim 1, wherein the ratio (D50/d) of the volume-based average particle diameter D50 of the flakes to the thickness d of the flakes is 4 or more. The flake according to claim 1, wherein the thickness d(B) of the retardation layer (B) is 3 μm or less. The flake according to claim 1, wherein the retardation layer (B) is a hardened layer of a liquid crystal composition containing a liquid crystal compound having a birefringence Δn of 0.2 or more. The flake according to claim 1, wherein the retardation ReB(0) in the front direction of the retardation layer (B) at a wavelength of 550 nm is 250 nm or more and 350 nm or less. The flake according to claim 1, wherein the retardation ReB(0) in the front direction of the retardation layer (B) at a wavelength of 550 nm is 10 nm or less. The flake according to claim 1, wherein the retardation ReB(45) of the retardation layer (B) in the polar angle direction of 45° at a wavelength of 550 nm is 50 nm or more and 100 nm or less, or 250 nm or more and 350 nm or less. The flakes according to claim 1, wherein the selective reflection band in the front direction of the liquid crystal cured layer (A) includes a wavelength range of 420 nm or more and 650 nm or less, and the width of the selective reflection band in the front direction is 200 nm or more. The flakes according to claim 1, wherein the selective reflection band in the front direction of the liquid crystal cured layer (A) is in the range of 380 nm to 780 nm, and the width of the selective reflection band is 50 nm to 150 nm. The flakes according to claim 1, wherein the thickness of the liquid crystal cured layer (A) is 6 μm or less. The flakes according to claim 1, having a volume-based average particle diameter D50 of 50 μm or less. The flakes according to claim 1, each of which has an irregular shape when viewed in the thickness direction. The flakes according to claim 1, each of which has a rectangular shape when viewed in the thickness direction. The flake according to claim 1, comprising an adhesive layer between the liquid crystal cured layer (A) and the retardation layer (B). The flake according to claim 1, wherein a thickness ratio (d _tot (B)/d(A)) of a total thickness d _tot (B) of the retardation layer (B) to a thickness d(A) of the liquid crystal cured layer (A) is 0.8 or less. A printed matter comprising a layer of ink containing the flakes according to any one of claims 1 to 16. An article comprising the printed matter described in claim 17. An identification medium having a display surface,
A first ink layer provided in a region _R1 occupying a part of the display surface;
a second ink layer provided in a region _R2 occupying a part of the display surface and occupying a part or all of the region other than the region _R1 ;
The first ink layer contains a first flake according to any one of claims 1 to 16, wherein the retardation layer (B) is a retardation layer (B1) that gives a retardation ReB1(φ) to incident light having a wavelength of 550 nm from a predetermined polar angle φ;
The second ink layer contains second flakes, which are flakes of the cured liquid crystal layer (A) or flakes of a laminate (C2) including the cured liquid crystal layer (A) and a retardation layer (B2) that imparts a retardation ReB2(φ) to incident light having a wavelength of 550 nm from a predetermined polar angle φ;
An identification medium, wherein |ReB2(φ)-ReB1(φ)|>0 nm.

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