JPWO2019176880A1 - Authenticity judgment viewer, imaging device, and authenticity judgment method - Google Patents

Abstract

A linear polarizing plate and a retardation plate provided on one side in the thickness direction of the linear polarizing plate are provided, and at least one of the linear polarizing plate and the retardation plate is rotatably provided, and an absorption axis of the linear polarizing plate is provided. A viewer for authenticity determination that can switch the angle of the retarding plate with respect to the slow axis between + 45 ° ± 5 ° and -45 ° ± 5 °.

Description

The present invention relates to an authenticity determination viewer, a photographing device, and an authenticity determination method.

An identification medium with markings that cannot be easily duplicated may be attached to the surface of the article in order to determine whether the article is genuine or not supplied by an authorized manufacturer. As one of the materials for such marking, a resin having cholesteric regularity (hereinafter, may be appropriately referred to as "cholesteric resin") is known.

The cholesteric resin usually has a circular polarization separation function. The "circularly polarized light separation function" means a function of transmitting one of the right-handed circularly polarized light and the left-handed circularly polarized light and reflecting a part or all of the other circularly polarized light. The reflection by the cholesteric resin reflects the circularly polarized light while maintaining its chirality. Further, the wavelength range in which the circular polarization separation function is exhibited in this way is sometimes referred to as a “selective reflection band”.

Therefore, in the marking formed by using the cholesteric resin, different images appear depending on whether the marking is observed by the right circular polarizing plate or the left circular polarizing plate. Therefore, the authenticity can be determined based on the difference between the images (see Patent Documents 1 and 2). The observation for determining the authenticity as described above is generally performed using two circular polarizing plates, a right circular polarizing plate and a left circular polarizing plate.

Japanese Patent No. 3821940 Special Table 2010-525343

In recent years, systems that allow consumers and users to access information held by manufacturers via the Internet are becoming widespread. In this system, for example, a user photographs a marking such as an identifier (bar code or the like) attached to a product with a photographing device such as a smartphone. The marking information obtained from this captured image is sent to the manufacturer via the Internet. Then, the manufacturer returns the product information (for example, detailed product information, related information, etc.) corresponding to the sent information to the user. This allows the user to obtain product information.

The present inventor has considered using the above system for determining authenticity. In order to determine such authenticity, it is required to draw the marking with a cholesteric resin and to photograph the marking with an imaging apparatus equipped with a circular polarizing plate. However, for general consumers and users, preparing a dedicated imaging device equipped with a circularly polarizing plate is considered to be costly and hinder the introduction of the system.

Further, as described above, in order to determine the authenticity of the marking formed by using the cholesteric resin, the above-mentioned photographing apparatus is subjected to observation with a right circular polarizing plate and observation with a left circular polarizing plate. It is required that both are possible. In order to satisfy this requirement, it is conceivable to provide both a right circular polarizing plate and a left circular polarizing plate in the photographing apparatus. However, when two circularly polarizing plates are used in this way, the area of those two pieces is required. Therefore, it is considered that the size of the device becomes large and the handleability becomes insufficient.

The present invention was devised in view of the above problems, and by attaching it to the main body of the apparatus as a general-purpose imaging apparatus, it is possible to photograph markings formed by using cholesteric resin, and the size is small. Provided is a sex determination viewer; an imaging device provided with the authenticity determination viewer and capable of photographing markings formed by using a cholesteric resin; and an authenticity determination method using the imaging device. The purpose is.

The present inventor has conducted diligent studies in order to solve the above-mentioned problems. As a result, the present inventor includes a linear polarizing plate and a retardation plate, at least one of the linear polarizing plate and the retardation plate is rotatable, and the absorption axis of the linear polarizing plate is the slow axis of the retardation plate. The present invention has been completed by finding that a viewer capable of switching the angle with respect to the polarized light can solve the above-mentioned problems.
Therefore, the present invention includes the following.

[1] A linear polarizing plate and a retardation plate provided on one side of the linear polarizing plate in the thickness direction are provided.
At least one of the linear polarizing plate and the retardation plate is rotatably provided.
An authenticity determination viewer capable of switching the angle formed by the absorption axis of the linear polarizing plate with respect to the slow axis of the retardation plate between + 45 ° ± 5 ° and −45 ° ± 5 °.
[2] The authenticity determination viewer according to [1], wherein the in-plane retardation of the retardation plate is 140 nm ± 40 nm.
[3] The authenticity determination viewer according to [1] or [2], wherein the retardation plate has anti-wavelength dispersibility.
[4] An imaging device for photographing an identification medium having markings containing a resin having cholesteric regularity.
An imaging device including a device main body provided with a photographing unit and an authenticity determination viewer according to any one of [1] to [3] attached to the photographing unit of the device main body.
[5] A method for determining the authenticity of an identification medium having markings containing a resin having cholesteric regularity.
The identification medium is photographed by the photographing apparatus according to [4] in a state where the absorption axis of the linear polarizing plate is at an angle of + 45 ° ± 5 ° with respect to the slow axis of the retardation plate, and the first image is taken. And the process of obtaining
A step of photographing the identification medium with the photographing apparatus in a state where the absorption axis of the linearly polarizing plate forms with respect to the slow axis of the retardation plate at −45 ° ± 5 ° to obtain a second image. When,
A method for determining the authenticity of an identification medium, which comprises a step of determining the authenticity of the identification medium based on the first image and the second image.

According to the present invention, a small-sized authenticity determination viewer capable of photographing markings formed by using a cholesteric resin by being attached to an apparatus main body as a general-purpose imaging apparatus; the above-mentioned authenticity determination. It is possible to provide an imaging device provided with a viewer and capable of photographing markings formed by using a cholesteric resin; and a method for determining authenticity using the above-mentioned photographing device.

FIG. 1 is a perspective view schematically showing a viewer for authenticity determination according to an embodiment of the present invention. FIG. 2 is a perspective view schematically showing a viewer for authenticity determination according to an embodiment of the present invention through a case. FIG. 3 is a schematic view schematically showing a linear polarizing plate and a retardation plate included in the authenticity determination viewer according to the embodiment of the present invention. FIG. 4 is a schematic view schematically showing a linear polarizing plate and a retardation plate included in the authenticity determination viewer according to the embodiment of the present invention. FIG. 5 is a perspective view schematically showing an example of a state in which the authenticity of the identification medium attached to the article is determined. FIG. 6 is a cross-sectional view schematically showing a cross section of the identification medium according to an example.

Hereinafter, the present invention will be described in detail with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples described below, and can be arbitrarily modified and carried out within the scope of the claims of the present invention and the equivalent scope thereof.

In the following description, the slow axis of the retardation plate represents the slow axis of the retardation plate in the in-plane direction unless otherwise specified.

In the following description, the angle formed by the optical axes (absorption axis, transmission axis, slow phase axis, etc.) of the linear polarizing plate and the retardation plate is the angle when viewed from the thickness direction of the linear polarizing plate, unless otherwise specified. Represent.

In the following description, the "linear polarizing plate", "phase difference plate" and "wave plate" are not only rigid members but also flexible members such as resin films unless otherwise specified. Also includes.

In the following description, the in-plane retardation Re of the retardation plate is a value represented by Re = (nx−ny) × d unless otherwise specified. Here, nx represents the refractive index in the direction perpendicular to the thickness direction of the retardation plate (in-plane direction) and in the direction giving the maximum refractive index. ny represents the refractive index in the in-plane direction of the retardation plate and orthogonal to the nx direction. d represents the thickness of the retardation plate.

In the following description, unless otherwise specified, the directions of the elements are "parallel", "vertical" and "orthogonal" within a range that does not impair the effect of the present invention, for example ± 5 ° (that is, −5 ° to +5). It may include errors within the range of °).

[1. Embodiment]
FIG. 1 is a perspective view schematically showing an authenticity determination viewer 100 according to an embodiment of the present invention. Further, FIG. 2 is a perspective view schematically showing the authenticity determination viewer 100 according to the embodiment of the present invention through the case 110. In FIG. 2, the case 110 is shown by an alternate long and short dash line.

As shown in FIGS. 1 and 2, the authenticity determination viewer 100 according to the embodiment of the present invention includes a case 110; a linear polarizing plate 120 housed in the case 110; and a phase difference housed in the case 110. The plate 130; and the switching unit 140 provided on the linear polarizing plate 120; are provided. The linear polarizing plate 120 and the retardation plate 130 may be in contact with each other, but in the present embodiment, an example in which the linear polarizing plate 120 and the retardation plate 130 are separated from each other is shown.

The case 110 has a wall portion 111 formed in a tubular shape, and an optical path chamber 112 for accommodating the linear polarizing plate 120 and the retardation plate 130 is formed as an internal space surrounded by the wall portion 111. There is. In this embodiment, an example using a cylindrical case 110 having a cylindrical optical path chamber 112 inside is shown. Further, the wall portion 111 of the case 110 is formed with an elongated hole 113 penetrating the wall portion 111. The elongated hole 113 is formed so as to extend in the circumferential direction of the case 110.

The linear polarizing plate 120 is provided in the optical path chamber 112 of the case 110 so that the in-plane direction of the linear polarizing plate 120 and the radial direction of the cylinder of the case 110 are parallel to each other. Therefore, the thickness direction of the linear polarizing plate 120 is parallel to the axial direction of the cylinder of the case 110. In this embodiment, an example using a disk-shaped linear polarizing plate 120 is shown.

The linear polarizing plate 120 has an absorption axis. Therefore, the linear polarizing plate 120 can transmit linearly polarized light having a vibration direction perpendicular to the absorption axis and block the linearly polarized light having a vibration direction parallel to the absorption axis. Here, the vibration direction of linearly polarized light means the vibration direction of an electric field of linearly polarized light.

The retardation plate 130 is provided in the optical path chamber 112 of the case 110 so that the in-plane direction of the retardation plate 130 and the cylindrical radial direction of the case 110 are parallel to each other. Therefore, the thickness direction of the retardation plate 130 is parallel to the cylindrical axial direction of the case 110 and the thickness direction of the linear polarizing plate 120. Further, the retardation plate 130 is provided on one side of the linear polarizing plate 120 in the thickness direction so that the light entering the optical path chamber 112 of the case 110 can pass through the retardation plate 130 and the linear polarizing plate 120 in this order. There is. In this embodiment, an example using a disk-shaped retardation plate 130 is shown.

The retardation plate 130 has an in-plane retardation. The specific in-plane retardation of the retardation plate 130 is such that the circularly polarized light entering the viewer 100 can be converted into linearly polarized light or elliptically polarized light capable of determining authenticity at the wavelength of light used for authenticity determination. It is preferable to set it. The above-mentioned "wavelength of light used for determining authenticity" specifically represents the wavelength of the selective reflection band of the cholesteric resin included in the marking observed by using the viewer 100. Therefore, the specific in-plane retardation of the retardation plate 130 is preferably set so that the retardation plate 130 can function as a 1/4 wave plate in the selective reflection band of the cholesteric resin included in the marking.

In a particularly desirable embodiment, the in-plane retardation of the retardation plate 130 is preferably 140 nm ± 40 nm (ie, 100 nm to 180 nm) at a measurement wavelength of 560 nm. More specifically, the in-plane retardation of the retardation plate 130 at the measurement wavelength of 560 nm is preferably 100 nm or more, more preferably 120 nm or more, particularly preferably 130 nm or more, preferably 180 nm or less, more preferably 160 nm or less. Especially preferably, it is 150 nm or less. The retardation plate 130 having the in-plane retardation in the above range at the measurement wavelength of 560 nm can usually function as a quarter wave plate in the visible wavelength region. Therefore, by using such a retardation plate 130, a viewer 100 that can be used in the visible wavelength range can be realized.

The retardation plate 130 preferably has an inverse wavelength dispersibility. Here, the inverse wavelength dispersibility means that the in-plane retardations Re (450) and Re (560) at the measurement wavelengths of 450 nm and 560 nm satisfy the following formula (1).
Re (450) <Re (560) (1)
The retardation plate 130 having anti-wavelength dispersibility can exhibit its optical function in a wide wavelength range. Therefore, by using the retardation plate 130 having the opposite wavelength dispersibility, the viewer 100 that can be used in a wide wavelength range can be realized.

The retardation plate 130 has a slow axis in the in-plane direction of the retardation plate 130. When the angle formed by the slow axis of the retardation plate 130 and the absorption axis of the linear polarizing plate 120 is set to approximately 45 °, the combination of the linear polarizing plate 120 and the retardation plate 130 can be used as a circular polarizing plate. Can function.

In the above-described embodiment, at least one of the linear polarizing plate 120 and the retardation plate 130 is rotatably provided. Then, in the range of rotation in this way, the angle θ formed by the absorption axis of the linear polarizing plate 120 with respect to the slow axis of the retardation plate 130 is + 45 ° ± 5 ° (that is, + 40 ° to + 50 °) and −. It is set so that it can be switched between 45 ° ± 5 ° (that is, -50 ° to -40 °). The positive and negative signs of the angle θ represent the direction of rotation. Therefore, depending on whether the angle θ is a positive value or the angle θ is a negative value, the direction in which the absorption axis of the linear polarizing plate 120 forms an angle θ with respect to the slow axis of the retardation plate 130 is , In the opposite direction.

3 and 4 are schematic views schematically showing a linear polarizing plate 120 and a retardation plate 130 included in the authenticity determination viewer 100 according to the embodiment of the present invention, respectively. In FIGS. 3 and 4, a straight line L130 extending in the same direction as the slow axis A130 of the retardation plate 130 is indicated by a chain double-dashed line. FIG. 3 shows an example in which the absorption axis A120 of the linear polarizing plate 120 forms an angle θ counterclockwise with respect to the slow axis A130 of the retardation plate 130. Further, FIG. 4 shows an example in which the absorption axis A120 of the linear polarizing plate 120 forms an angle θ clockwise with respect to the slow axis A130 of the retardation plate 130. In this case, the sign of the angle θ shown in FIG. 3 is one of positive and negative, and the sign of the angle θ shown in FIG. 4 is the other of positive and negative.

When the angle θ is + 45 ° ± 5 °, the angle θ is preferably + 45 ° ± 4 ° (ie, + 41 ° to + 49 °), more preferably + 45 ° ± 3 ° (ie, + 42 ° to + 42 ° to). + 48 °), particularly preferably + 45 ° ± 2 ° (ie, + 43 ° to + 47 °). When the angle θ is −45 ° ± 5 °, the angle θ is preferably −45 ° ± 4 ° (that is, −49 ° to −41 °), more preferably −45 ° ± 3. ° (ie, −48 ° to −42 °), particularly preferably −45 ° ± 2 ° (ie, −47 ° to −43 °). When the angle θ is within the above range, it is easy to clarify the difference between the first image and the second image, which will be described later, so that the authenticity can be easily determined.

In the present embodiment, as shown in FIGS. 1 and 2, the linear polarizing plate 120 passes through the center of the disk shape of the linear polarizing plate 120 and is parallel to the thickness direction of the linear polarizing plate 120. An example of being rotatably provided is shown. However, the rotation axis R120 is described to indicate the rotation direction of the linear polarizing plate 120, and may not necessarily be formed by a specific member.

Further, the edge portion 120E of the linear polarizing plate 120 is provided with a rod-shaped switching portion 140 so as to project in the radial direction of the linear polarizing plate 120. The switching portion 140 is passed through an elongated hole 113 formed in the wall portion 111 of the case 110. Further, the switching unit 140 is provided so as to be movable along the elongated hole 113. Therefore, the switching unit 140 is provided so that the linear polarizing plate 120 can be rotated by the movement of the switching unit 140 by moving the switching unit 140 in the circumferential direction of the case 110 along the elongated hole 113. ing.

The switching portion 140 is provided so as to hit the wall portion 111 and stop at the end portion of the elongated hole 113 in the extending direction. In this case, the positions of both ends of the elongated hole 113 in the extending direction are preferably set so as to satisfy the following requirements (A1) and (A2).
(A1) When the switching portion 140 is located at one end of the elongated hole 113, the angle θ is + 45 ° ± 5 °.
(A2) When the switching portion 140 is located at the other end of the elongated hole 113, the angle θ is −45 ° ± 5 °.

When the positions of both ends of the elongated hole 113 are set in this way, the angle θ becomes + 45 ° ± 5 ° when the switching unit 140 stops at one end of the elongated hole 113. Further, when the switching portion 140 stops at the other end of the elongated hole 113, the angle θ becomes −45 ° ± 5 °. Therefore, the switching unit 140 is provided so that the angle θ can be easily switched by moving the switching unit 140.

The viewer 100 according to the present embodiment has the above-mentioned structure. Therefore, the light that has entered the optical path chamber 112 of the case 110 of the viewer 100 can pass through the retardation plate 130 and the linear polarizing plate 120 in this order. When the light is circularly polarized light, the circularly polarized light passes through the retardation plate 130 to become linearly polarized light and is incident on the linearly polarizing plate 120. When the vibration direction of the linearly polarized light is perpendicular to the absorption axis of the linearly polarizing plate 120, the linearly polarized light can pass through the linearly polarized light 120. On the other hand, when the vibration direction of the linearly polarized light is parallel to the absorption axis of the linearly polarized light plate 120, the linearly polarized light cannot pass through the linearly polarized light plate 120. As described above, the combination of the linear polarizing plate 120 and the retardation plate 130 provides a function as a circular polarizing plate.

Further, in the above-mentioned viewer 100, the angles θ formed by the absorption axis of the linear polarizing plate 120 with respect to the slow axis of the retardation plate 130 by the rotation of the linear polarizing plate 120 are set to + 45 ° ± 5 ° and −45 ° ±. It can be switched between 5 ° and 5 °. When the angle θ is one of + 45 ° ± 5 ° and −45 ° ± 5 °, the vibration direction of the linearly polarized light transmitted through the retardation plate 130 is perpendicular to the absorption axis of the linear polarizing plate 120. When the angle θ is the other of + 45 ° ± 5 ° and −45 ° ± 5 °, the vibration direction of the linearly polarized light transmitted through the retardation plate 130 is parallel to the absorption axis of the linear polarizing plate 120. Therefore, in the viewer 100, the circularly polarized light blocked by the viewer 100 can be easily switched between right-handed circularly polarized light and left-handed circularly polarized light by switching the angle θ. Therefore, if this viewer 100 is used, the authenticity can be smoothly determined by using the marking containing the cholesteric resin.

Further, the viewer 100 realizes a circular polarizing plate capable of exhibiting both a function of blocking right circularly polarized light and a function of blocking left circularly polarized light by combining at least one set of linear polarizing plate 120 and a retardation plate 130. it can. In this way, the viewer 100 according to the present embodiment, which can determine the authenticity by the area of one circular polarizing plate by the combination of the linear polarizing plate 120 and the retardation plate 130, has two circular polarizing plates (that is, right-handed circular polarization). Compared with the conventional viewer that uses a plate and a left circular polarizing plate), the area can be reduced by the amount that the number of circular polarizing plates can be reduced. Therefore, the viewer 100 according to the present embodiment can be miniaturized.

Next, a method of determining authenticity using the viewer 100 will be described with reference to an example. FIG. 5 is a perspective view schematically showing an example of a state in which the authenticity of the identification medium 200 attached to the article 10 is determined.
In this example, as shown in FIG. 5, by determining the authenticity of the identification medium 200, the authenticity of the article 10 to which the identification medium 200 is attached is determined.

FIG. 6 is a cross-sectional view schematically showing a cross section of the identification medium 200 according to the above example. FIG. 6 schematically shows the path of the light reflected by the marking 230. In the actual identification medium 200, various light absorptions and reflections may occur in addition to those described below. However, in the following description, for convenience of explanation of the action, the main light paths are schematically described. explain. Further, in the example shown in FIG. 6, a part of the right circularly polarized light (specifically, light in the selective reflection band) is reflected in the visible light region, and the remaining part of the right circularly polarized light and all of the left circularly polarized light are reflected. A marking 230 containing a cholesteric resin to be transmitted is provided.

As shown in FIG. 6, the identification medium 200 includes a base material 210, a base layer 220 provided on the base material 210, and a marking 230 containing a cholesteric resin provided on the base layer 220 in this order. When light L including right circularly polarized light is incident on the upper surface of the marking 230, a part of the right circularly polarized light is reflected by the marking 230 to become reflected light LR, and the rest becomes transmitted light LL. Here, the reflection can occur not only on the surface of the marking 230 but also inside, but as a schematic representation, in FIG. 6, the reflection is shown assuming that it occurs on the surface of the marking 230.

In the authenticity determination method shown in this example, as shown in FIG. 5, an apparatus main body 310 having a photographing unit (not shown) capable of photographing the identification medium 200 as a subject is prepared. As such a device main body 310, FIG. 5 shows a smartphone provided with a lens unit as a photographing unit. The viewer 100 is attached to the photographing unit of the apparatus main body 310. At this time, the viewer 100 is mounted so that the linear polarizing plate 120 and the retardation plate 130 are arranged in this order from the photographing unit side. As a result, as a device for photographing the identification medium 200, an imaging device 300 including an apparatus main body 310 and a viewer 100 is prepared.

After the photographing device 300 is prepared in this way, the identification medium 200 is photographed by the photographing device 300. In particular,
The identification medium 200 is photographed by the photographing apparatus 300 in a state where the angle θ formed by the absorption axis A120 of the linear polarizing plate 120 with respect to the slow axis A130 of the retardation plate 130 is + 45 ° ± 5 °. With the process of obtaining an image;
The identification medium 200 is photographed by the photographing apparatus 300 in a state where the angle θ formed by the absorption axis A120 of the linear polarizing plate 120 with respect to the slow axis A130 of the retardation plate 130 is −45 ° ± 5 °. (2) The process of obtaining an image;
I do. Either of these two steps may be performed first.

More specifically, the identification medium 200 is photographed by the photographing apparatus 300 in a state where the switching unit 140 of the viewer 100 is moved to one end of the elongated hole 113 formed in the case 110. As a result, imaging is performed in a state where the angle θ is one of + 45 ° ± 5 ° and −45 ° ± 5 °. Then, by moving the switching unit 140 to the other end of the elongated hole 113, the angle θ is switched between + 45 ° ± 5 ° and −45 ° ± 5 °. Then, in this state, the identification medium 200 is photographed by the photographing apparatus 300. As described above, according to the photographing apparatus 300 including the viewer 100, the first image and the second image can be easily obtained.

At the time of the above-mentioned photographing, the reflected light LR as right-handed circularly polarized light has an absorption axis of the linear polarizing plate 120 by the retardation plate 130 when the angle θ is one of + 45 ° ± 5 ° and −45 ° ± 5 °. It is converted into linearly polarized light having a vibration direction perpendicular to A120, and can pass through the linear polarizing plate 120. Therefore, the marking 230 appears in the image taken through the viewer 100.
However, the reflected light LR as right-handed circularly polarized light is parallel to the absorption axis A120 of the linear polarizing plate 120 by the retardation plate 130 when the angle θ is on the other side of + 45 ° ± 5 ° and −45 ° ± 5 °. It is converted into linearly polarized light having a vibration direction and blocked by the linear polarizing plate 120. Therefore, the marking 230 does not appear in the image taken through the viewer 100.
Therefore, different images appear in the first image and the second image. Specifically, the marking 230 appears on one of the first image and the second image, but the marking 230 does not appear on the other of the first image and the second image.

After obtaining the first image and the second image in this way, a step of determining the authenticity of the identification medium 200 is performed based on the first image and the second image. Specifically, when there is an image difference as described above between the first image and the second image, it can be determined that the identification medium 200 is genuine, and therefore the identification medium 200 is attached. Article 10 can be determined to be a genuine product. On the other hand, if there is no difference in the image as described above between the first image and the second image, it can be determined that the identification medium 200 is non-authentic, and therefore, the article 10 to which the identification medium 200 is attached is determined. Can be judged to be a counterfeit product.

Further, in the step of determining the authenticity of the identification medium 200, the authenticity may be determined by the contrast between the first image and the second image. When the genuine identification medium 200 is photographed, a contrast difference usually occurs between the first image and the second image depending on whether or not the marking 230 appears. Therefore, it is possible to determine the authenticity based on the difference in contrast rather than the difference in image depending on the presence or absence of the marking 230. Specifically, when there is a difference in contrast between the first image and the second image, it can be determined that the identification medium 200 is genuine. On the other hand, when there is no difference in contrast between the first image and the second image, it can be determined that the identification medium 200 is non-authentic.

When the photographing device 300 has a display unit for displaying the first image and the second image, the determination may be made by the user. In this case, the user can determine the authenticity by looking at the first image and the second image displayed on the display unit.
Further, when the photographing device 300 has a transmission unit for transmitting the information of the first image and the second image, the determination may be performed by the server in response to the transmission of the information. In this case, the user can know the authenticity determination result by performing the authenticity determination on the server based on the information of the first image and the second image and returning the result to the user.

Although one embodiment of the present invention has been described above, the above-described embodiment may be further modified and implemented.
For example, the shape of the case 110 is not limited to the cylindrical shape, and may be another shape. Further, for example, the viewer 100 does not have to be provided with the case 110. As a specific example, instead of the case 110 that houses the linear polarizing plate 120 and the retardation plate 130, a frame material that supports the linear polarizing plate 120 and the retardation plate 130 may be used.

For example, the shapes of the linear polarizing plate 120 and the retardation plate 130 are not limited to the disk shape, and may be different shapes.

For example, the retardation plate 130 may be provided rotatably, or both the linear polarizing plate 120 and the retardation plate 130 may be rotatably provided. When the linear polarizing plate 120 can be rotated relative to the retarding plate 130, the angle θ formed by the absorption axis of the linear polarizing plate 120 with respect to the slow axis of the retarding plate 130 is + 45 ° as described above. It is possible to switch between ± 5 ° and −45 ° ± 5 °.

For example, the viewer 100 does not have to be provided with the switching unit 140. To give a specific example, when the user grips and rotates the linear polarizing plate 120 or the retardation plate 130, the switching unit 140 is unnecessary.

For example, the viewer 100 may be provided with members other than the case 110, the linear polarizing plate 120, the retardation plate 130, and the switching unit 140. To give a specific example, covers may be provided at the entrance and exit of the optical path chamber 112 of the case 110. To give another specific example, the case 110 may be provided with a fixture for detachably attaching the viewer 100 to the apparatus main body 310. To give yet another specific example, a spacer material that suppresses contact between the linear polarizing plate 120 and the retardation plate 130 may be provided.

For example, the identification medium 200 may not include the base material 210 and may not include the base layer 220. The above-mentioned authenticity determination can be performed if there is a marking 230 containing a cholesteric resin. Therefore, for example, even when the marking 230 containing the cholesteric resin is directly formed on the surface of the article 10, the above-mentioned authenticity determination can be performed.

For example, as the device main body 310, a mobile phone, a tablet terminal, a digital camera, a webcam, a personal computer with a camera, or the like may be used.

In the above-described embodiment, an example is shown in which the circularly polarized light that has entered the viewer 100 is converted into linearly polarized light by the retardation plate 130, but as long as the authenticity can be determined, for example, the circularly polarized light that has entered the viewer 100 is , May be converted to elliptically polarized light by the retardation plate 130. Even when the circularly polarized light is converted into elliptically polarized light by the retardation plate 130, the degree to which the elliptically polarized light can pass through the linearly polarized light 120 is usually the case where the angle θ is + 45 ° ± 5 ° and the angle θ is It differs depending on whether it is at −45 ° ± 5 °. Therefore, as in the above-described embodiment, if the identification medium 200 is genuine, there will be a difference between the first image and the second image, so that the authenticity can be determined.

In the above-described embodiment, the viewer 100 capable of transmitting or blocking the entire reflected light LR at the marking 230 is shown as an example, but as long as the authenticity can be determined, for example, a part of the reflected light LR is transmitted or blocked. The determination may be made using a viewer 100 that can be blocked.

[2. Linear polarizing plate]
As the linear polarizing plate, for example, a film provided with a linear polarizer may be used. As the linear polarizer, for example, a film obtained by subjecting a film of an appropriate vinyl alcohol polymer to an appropriate treatment such as a dyeing treatment with a dichroic substance, a stretching treatment, and a cross-linking treatment in an appropriate order and method can be used. .. Examples of the vinyl alcohol-based polymer include polyvinyl alcohol, partially formalized polyvinyl alcohol, and the like. Examples of the dichroic substance include iodine and a dichroic pigment. Above all, from the viewpoint of improving heat resistance, a linear polarizer containing a dichroic dye is preferable. Further, the linear polarizing plate may be provided with a polarizer protective film in combination with a linear polarizer. The linear polarizing plate preferably has an excellent degree of polarization. The thickness of the linear polarizing plate is generally, but is not limited to, 5 μm to 80 μm.

[3. Phase difference plate]
As the retardation plate, for example, a stretched film can be used. The stretched film is a film obtained by stretching a resin film, and an arbitrary in-plane retardation can be obtained by appropriately adjusting factors such as the type of resin, stretching conditions, and thickness.

As the resin, a thermoplastic resin is usually used. The thermoplastic resin may contain a polymer and optionally any component. Examples of the polymer include polycarbonate, polyethersulfone, polyethylene terephthalate, polyimide, polymethylmethacrylate, polysulfone, polyarylate, polyethylene, polyphenylene ether, polystyrene, polyvinyl chloride, cellulose diacetate, cellulose triacetate, and alicyclic type. Examples include structure-containing polymers. Further, one type of polymer may be used alone, or two or more types may be used in combination at an arbitrary ratio. Among them, an alicyclic structure-containing polymer is preferable from the viewpoints of transparency, low hygroscopicity, dimensional stability and processability. The alicyclic structure-containing polymer is a polymer having an alicyclic structure in the main chain and / or the side chain, and for example, those described in JP-A-2007-057791 can be used.

A stretched film as a retardation plate can be manufactured by producing a resin film from the above resin and then subjecting the resin film to a stretching treatment.

Examples of the method for producing the resin film include a cast molding method, an inflation molding method, an extrusion molding method, and the like, and the extrusion molding method is particularly preferable.

The stretching treatment can be performed by, for example, a roll method, a float method, a tenter method, or the like. In the stretching treatment, the stretching direction is preferably set appropriately so that the slow axis of the stretched film is in a desired direction. Therefore, the stretching treatment may be stretching in the width direction (transverse stretching) of the resin film, or stretching in the longitudinal direction (longitudinal stretching), depending on the direction of the slow axis to be expressed in the stretched film. It may be stretched in an oblique direction that is neither a width direction nor a longitudinal direction, or may be a combination of these stretches.

The stretching temperature and stretching ratio can be arbitrarily set within a range in which the desired in-plane retardation can be obtained. Specifically, the stretching temperature is preferably Tg-30 ° C. or higher, more preferably Tg-10 ° C. or higher, preferably Tg + 60 ° C. or lower, and more preferably Tg + 50 ° C. or lower. The draw ratio is preferably 1.1 times or more, more preferably 1.2 times or more, particularly preferably 1.5 times or more, preferably 30 times or less, more preferably 10 times or less, and particularly preferably. It is 5 times or less. Here, Tg represents the glass transition temperature of the resin.

The thickness of the stretched film is not particularly limited, but is preferably 5 μm or more, more preferably 10 μm or more, particularly preferably 20 μm or more, preferably 1 mm or less, more preferably 500 μm or less, and particularly preferably 200 μm or less. ..

As the retardation plate, for example, a film containing a liquid crystal curing layer can be used. The liquid crystal cured layer is a layer formed of a cured product of a liquid crystal composition containing a liquid crystal compound. Here, the material referred to as a "liquid crystal composition" for convenience includes not only a mixture of two or more substances but also a material composed of a single substance. Usually, a liquid crystal cured layer is obtained by forming a layer of the liquid crystal composition, orienting the molecules of the liquid crystal compound contained in the layer of the liquid crystal composition, and then curing the layer of the liquid crystal composition. In this liquid crystal cured layer, an arbitrary in-plane retardation can be obtained by appropriately adjusting factors such as the type of the liquid crystal compound, the orientation state of the liquid crystal compound, and the thickness.

The type of the liquid crystal compound is arbitrary, but when it is desired to obtain a retardation plate having a reverse wavelength dispersibility, it is preferable to use a reverse wavelength dispersive liquid crystal compound. The reverse wavelength dispersible liquid crystal compound refers to a liquid crystal compound that exhibits reverse wavelength dispersibility when homogenically oriented. Further, homogenically aligning a liquid crystal compound means forming a layer containing the liquid crystal compound and orienting the mesogen of the molecule of the liquid crystal compound in the layer in a certain direction parallel to the plane of the layer. It means to let. Specific examples of the inverse wavelength-dispersible liquid crystal compound include the compounds described in International Publication No. 2014/069515, International Publication No. 2015/064851 and the like.

The thickness of the liquid crystal cured layer is not particularly limited, but is preferably 0.5 μm or more, more preferably 1.0 μm or more, preferably 10 μm or less, more preferably 7 μm or less, and particularly preferably 5 μm or less.

[4. marking]
The markings observed by the viewer include cholesteric resin. As described above, the cholesteric resin is a resin having cholesteric regularity. Cholesteric regularity means that the molecular axes are aligned in a certain direction on a certain plane inside the resin, but the direction of the molecular axes shifts at a slight angle on the next plane that overlaps with it, and further angles on the next plane. It is a structure in which the angle of the molecular axis in the plane shifts (twists) as it sequentially passes through the planes that are arranged in an overlapping manner. That is, when the molecules inside a layer of a material have cholesteric regularity, the molecules are aligned so that their molecular axes are oriented in a certain direction on a first plane inside the layer. In the next second plane that overlaps the first plane inside the layer, the direction of the molecular axis deviates slightly from the direction of the molecular axis in the first plane. In the next third plane that further overlaps the second plane, the direction of the molecular axis is further angled from the direction of the molecular axis in the second plane. In this way, in the planes that are arranged in an overlapping manner, the angles of the molecular axes in the planes are sequentially shifted (twisted). Such a structure in which the direction of the molecular axis is twisted is usually a spiral structure, and is an optically chiral structure. Since this cholesteric resin has a circular polarization separation function, the marking can reflect the circular polarization of the color corresponding to the selective reflection band of the cholesteric resin.

As the cholesteric resin, for example, a cured product of the cholesteric liquid crystal composition can be used. The cholesteric liquid crystal composition refers to a composition capable of exhibiting a liquid crystal phase (cholesteric liquid crystal phase) in which the liquid crystal compound has cholesteric regularity when the liquid crystal compound contained in the liquid crystal composition is oriented. When the cholesteric liquid crystal composition is cured, the liquid crystal compound is usually polymerized in a state of exhibiting a cholesteric liquid crystal phase, so that a layer of a non-liquid crystal cholesteric resin cured while exhibiting cholesteric regularity can be obtained.

As the cholesteric resin as a cured product of the cholesteric liquid crystal composition, for example, those described in JP-A-2014-174471, JP-A-2015-27743 and the like can be used.

The markings can usually be formed as a layer containing a cholesteric resin. Such markings can be provided, for example, on an identification medium such as a label as a layer having a desired planar shape. In this case, the article can be marked by attaching the identification medium to the article. Further, the marking may be formed by drawing a desired planar shape on the article, for example, with a paint containing a pigment containing a layer containing a cholesteric resin.

There are no restrictions on the articles to be marked, and a wide range of articles can be adopted. Examples of these articles include cloth products such as clothing; leather products such as bags and shoes; metal products such as screws; paper products such as price tags; rubber products such as tires; Not limited to.

10 Article 100 Viewer 110 Case 111 Wall 112 Optical path chamber 113 Long hole 120 Straight polarizing plate 130 Phase difference plate 140 Switching part 200 Identification medium 210 Base material 220 Base layer 230 Marking 300 Imaging device 310 Device body A120 Absorption axis A130 Slow phase axis R120 rotating shaft

Claims (5)

A linear polarizing plate and a retardation plate provided on one side of the linear polarizing plate in the thickness direction are provided.
At least one of the linear polarizing plate and the retardation plate is rotatably provided.
An authenticity determination viewer capable of switching the angle formed by the absorption axis of the linear polarizing plate with respect to the slow axis of the retardation plate between + 45 ° ± 5 ° and −45 ° ± 5 °. The authenticity determination viewer according to claim 1, wherein the in-plane retardation of the retardation plate is 140 nm ± 40 nm. The authenticity determination viewer according to claim 1 or 2, wherein the retardation plate has anti-wavelength dispersibility. An imaging device for photographing an identification medium having markings containing a resin having cholesteric regularity.
An imaging device including a device main body including a photographing unit and an authenticity determination viewer mounted on the photographing unit of the device main body according to any one of claims 1 to 3. A method for determining the authenticity of an identification medium having markings containing a resin having cholesteric regularity.
The identification medium is photographed by the photographing apparatus according to claim 4 in a state where the absorption axis of the linear polarizing plate is at an angle of + 45 ° ± 5 ° with respect to the slow axis of the retardation plate, and the first image is taken. And the process of obtaining
A step of photographing the identification medium with the photographing apparatus in a state where the absorption axis of the linearly polarizing plate forms with respect to the slow axis of the retardation plate at −45 ° ± 5 ° to obtain a second image. When,
A method for determining the authenticity of an identification medium, which comprises a step of determining the authenticity of the identification medium based on the first image and the second image.

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