WO2019176880A1

WO2019176880A1 - Viewer for determining authenticity, photographing device, and method for determining authenticity

Info

Publication number: WO2019176880A1
Application number: PCT/JP2019/009792
Authority: WO
Inventors: 泰秀藤野
Original assignee: 日本ゼオン株式会社
Priority date: 2018-03-16
Filing date: 2019-03-11
Publication date: 2019-09-19
Also published as: JP7238883B2; TWI793281B; JPWO2019176880A1; TW201945714A

Abstract

Provided is a viewer for determining authenticity, comprising: a linear polarizer; and a retardation plate disposed on one side in the thickness direction of the linear polarizer, wherein at least one of the linear polarizer and the retardation plate is rotatably disposed and an angle between the absorption axis of the linear polarizer and the slow axis of the retardation plate is changeable within the range from +45°±5° to -45°±5°.

Description

Authenticity determination viewer, photographing apparatus, and authenticity determination method

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

In order to determine whether or not an article is a genuine product supplied from an authorized manufacturer, an identification medium with a marking that cannot be easily copied may be attached to the surface of the article. As one of such marking materials, a resin having cholesteric regularity (hereinafter sometimes referred to as “cholesteric resin” as appropriate) is known.

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

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

Japanese Patent No. 3821940 Special table 2010-525343 gazette

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 the photographed image is sent to the manufacturer via the Internet. Then, the manufacturer returns product information (for example, detailed product information and related information) corresponding to the sent information to the user. Thereby, the user can obtain product information.

The present inventor considered using the above-described system for authenticity determination. In order to determine the authenticity as described above, it is required to draw the marking with a cholesteric resin and photograph the marking with a photographing apparatus provided with a circularly polarizing plate. However, for general consumers and users, preparing a dedicated photographing device equipped with a circularly polarizing plate is considered to be costly and hinder system introduction.

Furthermore, as described above, in order to determine the authenticity of the marking formed using the cholesteric resin, the photographing apparatus includes the observation with the right circular polarizing plate and the observation with the left circular polarizing plate. Both are required to be possible. In order to satisfy this requirement, it is conceivable to provide both the right circularly polarizing plate and the left circularly polarizing plate in the photographing apparatus. However, when two circularly polarizing plates are used in this way, the area for these two sheets is required. Therefore, it is considered that the size of the apparatus becomes large and the handleability becomes insufficient.

The present invention was devised in view of the above-described problems, and can be used to shoot a marking formed using a cholesteric resin by being attached to a main body as a general-purpose photographing device. Provided are a sex determination viewer; an imaging device including the authenticity determination viewer and capable of shooting a marking formed using a cholesteric resin; and an authenticity determination method using the imaging device. For the purpose.

The present inventor has intensively studied to solve the above problems. As a result, the inventor includes a linearly polarizing plate and a retardation plate, at least one of the linearly polarizing plate and the retardation plate is rotatable, and the absorption axis of the linearly polarizing plate is a slow axis of the retardation plate. The present inventors have found that a viewer capable of switching the angle formed with respect to can solve the above-mentioned problems and completed the present invention.
Therefore, the present invention includes the following.

[1] A linearly polarizing plate, and a retardation plate provided on one side in the thickness direction of the linearly polarizing plate,
At least one of the linearly polarizing plate and the retardation plate is rotatably provided,
A viewer for authenticity determination, wherein the angle formed by the absorption axis of the linearly polarizing plate with respect to the slow axis of the retardation plate can be switched between + 45 ° ± 5 ° and −45 ° ± 5 °.
[2] The authenticity judging viewer according to [1], wherein an 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 reverse wavelength dispersion.
[4] An imaging device for imaging an identification medium provided with a marking including a resin having cholesteric regularity,
An imaging apparatus comprising: an apparatus main body including an imaging unit; and the authenticity determination viewer according to any one of [1] to [3] attached to the imaging unit of the apparatus main body.
[5] A method for determining the authenticity of an identification medium provided with a marking containing a resin having cholesteric regularity,
[4] Using the imaging apparatus described above, the identification medium is imaged in a state where the angle formed by the absorption axis of the linearly polarizing plate with respect to the slow axis of the retardation plate is + 45 ° ± 5 °, and the first image Obtaining
Step of obtaining the second image by photographing the identification medium with the photographing device in a state where the angle formed by the absorption axis of the linearly polarizing plate with respect to the slow axis of the retardation plate is −45 ° ± 5 °. When,
Determining the authenticity of the identification medium based on the first image and the second image.

According to the present invention, an authenticity determination viewer having a small size that can be photographed with a marking formed using a cholesteric resin by being attached to a main body as a general-purpose image capturing apparatus; And a viewer for photographing a marking formed using a cholesteric resin; and a method for determining authenticity using the photographing device.

FIG. 1 is a perspective view schematically showing an authenticity determination viewer according to an embodiment of the present invention. FIG. 2 is a perspective view schematically showing a genuineness determination viewer according to an embodiment of the present invention through a case. FIG. 3 is a schematic view schematically showing a linearly 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 linearly 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 when determining the authenticity of the identification medium attached to the article. FIG. 6 is a cross-sectional view schematically showing a cross section of an 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 implemented with any modifications without departing from the scope of the claims of the present invention and the equivalents thereof.

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

In the following description, the angle formed by the optical axis (absorption axis, transmission axis, slow 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. To express.

In the following description, “linear polarizing plate”, “retardation plate”, and “wave plate” are not only rigid members but also flexible members such as resin films, unless otherwise specified. Including.

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 a refractive index in a direction (in-plane direction) perpendicular to the thickness direction of the retardation plate and giving the maximum refractive index. ny represents the refractive index in the in-plane direction of the retardation plate and in the direction orthogonal to the nx direction. d represents the thickness of the retardation plate.

In the following description, unless the direction of the element is “parallel”, “vertical” or “orthogonal”, unless otherwise specified, for example, ± 5 ° (ie, −5 ° to + 5 °) The error may be included 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. FIG. 2 is a perspective view schematically showing the authenticity determination viewer 100 according to an embodiment of the present invention through a case 110. In FIG. 2, the case 110 is indicated by a one-dot chain line.

As shown in FIGS. 1 and 2, an authenticity determination viewer 100 according to an embodiment of the present invention includes a case 110; a linear polarizing plate 120 housed in the case 110; a phase difference housed in the case 110. Plate 130; and a switching unit 140 provided on the linearly polarizing plate 120. The linearly 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 linearly 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 cylindrical shape, and an optical path chamber 112 for accommodating the linearly polarizing plate 120 and the phase difference plate 130 is formed as an internal space surrounded by the wall portion 111. Yes. In the present embodiment, an example in which a cylindrical case 110 having a columnar optical path chamber 112 inside is used is shown. In addition, the wall portion 111 of the case 110 is formed with a long hole 113 that penetrates the wall portion 111. The elongated hole 113 is formed extending 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 cylindrical radial direction of the case 110 are parallel to each other. Therefore, the thickness direction of the linear polarizing plate 120 is parallel to the cylindrical axial direction of the case 110. In this embodiment, an example using a disc-shaped linearly polarizing plate 120 is shown.

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

The phase difference plate 130 is provided in the optical path chamber 112 of the case 110 so that the in-plane direction of the phase difference plate 130 and the cylindrical radial direction of the case 110 are parallel to each other. Therefore, the thickness direction of the retardation film 130 is parallel to the cylindrical axial direction of the case 110 and the thickness direction of the linear polarizing plate 120. The retardation plate 130 is provided on one side of the linear polarizing plate 120 in the thickness direction so that 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. Yes. In the present embodiment, an example using a disc-shaped retardation plate 130 is shown.

The retardation film 130 has in-plane retardation. The specific in-plane retardation of the retardation film 130 is such that circularly polarized light entering the viewer 100 can be converted into linearly polarized light or elliptically polarized light capable of authenticity determination at the wavelength of light used for authenticity determination. It is preferably set. The above-mentioned “wavelength of light used for authenticity determination” specifically represents the wavelength of the selective reflection band of the cholesteric resin included in the marking observed using the viewer 100. Accordingly, the specific in-plane retardation of the retardation film 130 is preferably set so that the retardation film 130 can function as a quarter-wave plate in the selective reflection band of the cholesteric resin included in the marking.

In a particularly desirable mode, the in-plane retardation of the retardation film 130 is preferably 140 nm ± 40 nm (that is, 100 nm to 180 nm) at a measurement wavelength of 560 nm. More specifically, the in-plane retardation of the retardation plate 130 at a 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 in-plane retardation in the above range at a measurement wavelength of 560 nm can usually function as a quarter wavelength plate in the visible wavelength region. Therefore, by using such a retardation plate 130, the viewer 100 usable in the visible wavelength range can be realized.

The retardation plate 130 preferably has reverse wavelength dispersion. Here, the reverse wavelength dispersion 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 reverse wavelength dispersion can exhibit its optical function in a wide wavelength range. Therefore, the viewer 100 that can be used in a wide wavelength range can be realized by using the retardation plate 130 having reverse wavelength dispersion.

The retardation film 130 has a slow axis in the in-plane direction of the retardation film 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 about 45 °, the combination of the linear polarizing plate 120 and the retardation plate 130 is a circular polarizing plate. Can function.

In the above-described embodiment, at least one of the linearly polarizing plate 120 and the phase difference plate 130 is rotatably provided. In this range of rotation, the angle θ formed by the absorption axis of the linear polarizer 120 with respect to the slow axis of the phase difference plate 130 is + 45 ° ± 5 ° (ie, + 40 ° to + 50 °) and − It is set so that it can be switched between 45 ° ± 5 ° (ie, −50 ° to −40 °). The sign of the angle θ represents the direction of rotation. Therefore, in the case where the angle θ is a positive value and the case where the angle θ is a negative value, the direction in which the absorption axis of the linearly polarizing plate 120 forms the angle θ with respect to the slow axis of the phase difference plate 130 is determined. , Reverse.

3 and 4 are schematic views schematically showing the linearly polarizing plate 120 and the phase difference plate 130 provided in the authenticity determination viewer 100 according to the embodiment of the present invention, respectively. 3 and 4, a straight line L130 extending in the same direction as the slow axis A130 of the retardation film 130 is indicated by a two-dot chain line. FIG. 3 shows an example in which the absorption axis A120 of the linearly polarizing plate 120 forms an angle θ counterclockwise with respect to the slow axis A130 of the retardation film 130. 4 shows an example in which the absorption axis A120 of the linearly 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 + 48 °), particularly preferably + 45 ° ± 2 ° (ie, + 43 ° to + 47 °). When the angle θ is −45 ° ± 5 °, the angle θ is preferably −45 ° ± 4 ° (ie, −49 ° to −41 °), more preferably −45 ° ± 3. ° (ie, -48 ° to -42 °), particularly preferably -45 ° ± 2 ° (ie, -47 ° to -43 °). When the angle θ is in the above range, it is easy to clarify the difference between a first image and a second image, which will be described later, so that authenticity can be easily determined.

In this embodiment, as shown in FIGS. 1 and 2, the linearly polarizing plate 120 passes through the center of the disk of the linearly polarizing plate 120 and is parallel to the thickness direction of the linearly polarizing plate 120. An example in which it is provided to be rotatable around the center is shown. However, the rotation axis R120 is described in order to indicate the rotation direction of the linearly polarizing plate 120, and is not necessarily formed by a specific member.

Furthermore, a rod-shaped switching unit 140 is provided at the edge 120E of the linear polarizing plate 120 so as to protrude in the radial direction of the linear polarizing plate 120. The switching part 140 is passed through a long hole 113 formed in the wall part 111 of the case 110. The switching unit 140 is provided so as to be movable along the long 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 along the elongated hole 113 in the circumferential direction of the case 110. ing.

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

In this way, when the positions of both ends of the long hole 113 are set, when the switching unit 140 stops at one end of the long hole 113, the angle θ becomes + 45 ° ± 5 °. When the switching unit 140 stops at the other end of the long 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 the movement of the switching unit 140.

The viewer 100 according to the present embodiment has the above-described 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 phase difference plate 130 to become linearly polarized light and enters 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 polarizing plate 120. On the other hand, when the vibration direction of the linearly polarized light is parallel to the absorption axis of the linearly polarizing plate 120, the linearly polarized light cannot pass through the linearly polarizing plate 120. Thus, the function as a circularly polarizing plate is obtained by the combination of the linearly polarizing plate 120 and the retardation plate 130.

Further, the viewer 100 described above makes the angle θ that the absorption axis of the linear polarizing plate 120 forms with respect to the slow axis of the retardation plate 130 by the rotation of the linear polarizing plate 120, + 45 ° ± 5 ° and −45 ° ±. It can be switched between 5 °. When the angle θ is one of + 45 ° ± 5 ° and −45 ° ± 5 °, the vibration direction of the linearly polarized light transmitted through the phase difference plate 130 is perpendicular to the absorption axis of the linearly 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 phase difference plate 130 is parallel to the absorption axis of the linearly polarizing plate 120. Therefore, in the viewer 100, the circularly polarized light blocked by the viewer 100 can be easily switched between the right circularly polarized light and the left circularly polarized light by switching the angle θ. Therefore, if this viewer 100 is used, the authenticity determination using the marking containing the cholesteric resin can be performed smoothly.

Furthermore, the viewer 100 realizes a circularly polarizing plate that can exhibit both the function of blocking the right circularly polarized light and the function of blocking the left circularly polarized light by combining at least one pair of the linearly polarizing plate 120 and the retardation plate 130. it can. Thus, the viewer 100 according to the present embodiment, which can determine the authenticity by the area of one circularly polarizing plate by the combination of the linearly polarizing plate 120 and the retardation plate 130, has two circularly polarizing plates (that is, right circularly polarized light). Compared to a conventional viewer using a plate and a left circularly polarizing plate), the area can be reduced by reducing the number of circularly polarizing plates. Therefore, the viewer 100 according to the present embodiment can be downsized.

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

FIG. 6 is a cross-sectional view schematically showing a cross section of the identification medium 200 according to the above example. In FIG. 6, the path of light reflected at the marking 230 is schematically shown. In the actual identification medium 200, various light absorption and reflection can occur in addition to those described below. However, in the following description, the main light paths are schematically illustrated for convenience of description of the operation. explain. In the example shown in FIG. 6, 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 210, a base layer 220 provided on the base 210, and a marking 230 including 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 and becomes 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 on the inside, but as a schematic expression, in FIG. 6, the reflection is illustrated as occurring 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 an apparatus main body 310, FIG. 5 shows a smartphone including 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 linearly polarizing plate 120 and the phase difference plate 130 are arranged in this order from the photographing unit side. Thereby, an imaging apparatus 300 including the apparatus main body 310 and the viewer 100 is prepared as an apparatus for imaging the identification medium 200.

After the imaging apparatus 300 is prepared in this way, the identification medium 200 is imaged by the imaging apparatus 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 film 130 is + 45 ° ± 5 °. Obtaining an image;
With the imaging device 300, the identification medium 200 is imaged 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 °, Obtaining two images;
I do. Any 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 long hole 113 formed in the case 110. Thus, photographing is performed in a state where the angle θ is at one of + 45 ° ± 5 ° and −45 ° ± 5 °. Next, the angle θ is switched between + 45 ° ± 5 ° and −45 ° ± 5 ° by moving the switching unit 140 to the other end of the elongated hole 113. Thereafter, the identification medium 200 is photographed by the photographing apparatus 300 in this state. Thus, according to the imaging device 300 including the viewer 100, the first image and the second image can be easily obtained.

In the above photographing, the reflected light LR as the right circularly polarized light is absorbed by the retardation plate 130 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 linearly polarizing plate 120. Therefore, the marking 230 appears in the image photographed through the viewer 100.
However, the reflected light LR as right circularly polarized light is parallel to the absorption axis A120 of the linearly polarizing plate 120 by the phase difference plate 130 when the angle θ is at the other of + 45 ° ± 5 ° and −45 ° ± 5 °. It is converted into linearly polarized light having a vibration direction and is blocked by the linearly polarizing plate 120. Therefore, the marking 230 does not appear in the image photographed through the viewer 100.
Therefore, different images appear in the first image and the second image. Specifically, the marking 230 appears in one of the first image and the second image, but the marking 230 does not appear in 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 based on the first image and the second image is performed. Specifically, if 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 authentic, and therefore the identification medium 200 is attached. The article 10 can be determined to be a regular product. On the other hand, if there is no image difference as described above between the first image and the second image, it can be determined that the identification medium 200 is improper, and therefore the article 10 to which the identification medium 200 is attached. Can be determined to be counterfeit.

Further, in the step of determining the authenticity of the identification medium 200, the authenticity may be determined based on the contrast between the first image and the second image. When the authentic identification medium 200 is photographed, a contrast difference is usually generated between the first image and the second image depending on whether or not the marking 230 appears. Therefore, authenticity can be determined based on a difference in contrast rather than an image difference 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 authentic. On the other hand, if there is no difference in contrast between the first image and the second image, it can be determined that the identification medium 200 is not authentic.

When the imaging apparatus 300 includes a display unit that displays the first image and the second image, the determination may be performed 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.
Moreover, when the imaging device 300 includes a transmission unit that transmits information on the first image and the second image, the determination may be performed by a server in response to the transmission of the information. In this case, the authenticity determination is performed by the server based on the information of the first image and the second image, and the result is returned to the user, so that the user can know the determination result of the authenticity.

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

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

For example, the retardation plate 130 may be rotatably provided, and both the linear polarizing plate 120 and the retardation plate 130 may be rotatably provided. When relative rotation of the linear polarizing plate 120 with respect to the retardation plate 130 is possible, 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 ° as described above. It is possible to switch between ± 5 ° and −45 ° ± 5 °.

For example, the switching unit 140 may not be provided in the viewer 100. As a specific example, when the user holds and rotates the linearly 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 phase difference plate 130, and the switching unit 140. As a specific example, covers may be provided at the entrance and exit of the optical path chamber 112 of the case 110. As another specific example, the case 110 may be provided with a fixture for detachably attaching the viewer 100 to the apparatus main body 310. As another specific example, a spacer material that suppresses contact between the linearly polarizing plate 120 and the retardation film 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 authenticity determination described above 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 determination of the authenticity can be performed.

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

In the above-described embodiment, an example in which the circularly polarized light that has entered the viewer 100 is converted into linearly polarized light by the phase difference plate 130, but as long as the authenticity can be determined, for example, the circularly polarized light that has entered the viewer 100 is The phase difference plate 130 may convert the light into elliptically polarized light. Even when the circularly polarized light is converted into elliptically polarized light by the phase difference plate 130, the angle θ is normally + 45 ° ± 5 ° and the angle θ is such that the elliptically polarized light can pass through the linearly polarized light 120. It differs depending on the case of −45 ° ± 5 °. Therefore, as in the above-described embodiment, if the identification medium 200 is authentic, there is a difference between the first image and the second image, so authenticity can be determined.

In the embodiment described above, the viewer 100 that can transmit or block all of the reflected light LR at the marking 230 is shown as an example. However, as long as the authenticity can be determined, for example, a part of the reflected light LR is transmitted or You may perform determination using the viewer 100 which can be interrupted | blocked.

[2. Linear polarizing plate]
As a linear polarizing plate, you may use the film provided with a linear polarizer, for example. As the linear polarizer, for example, a film in which an appropriate vinyl alcohol polymer film is subjected to an appropriate process such as a dyeing process, a stretching process, and a crosslinking process with a dichroic substance in an appropriate order and method can be used. . Examples of the vinyl alcohol polymer include polyvinyl alcohol and partially formalized polyvinyl alcohol. Examples of dichroic substances include iodine and dichroic dyes. Among these, from the viewpoint of improving heat resistance, a linear polarizer containing a dichroic dye is preferable. Moreover, the linearly polarizing plate may be provided with a polarizer protective film in combination with a linear polarizer. The linearly polarizing plate is preferably excellent in the degree of polarization. The thickness of the linear polarizing plate is generally 5 μm to 80 μm, but is not limited thereto.

[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. This thermoplastic resin may contain a polymer and optional components as necessary. Examples of the polymer include polycarbonate, polyethersulfone, polyethylene terephthalate, polyimide, polymethyl methacrylate, polysulfone, polyarylate, polyethylene, polyphenylene ether, polystyrene, polyvinyl chloride, cellulose diacetate, cellulose triacetate, and alicyclic. Examples include a structure-containing polymer. Moreover, a polymer may be used individually by 1 type and may be used combining two or more types by arbitrary ratios. Among these, from the viewpoints of transparency, low hygroscopicity, dimensional stability and processability, alicyclic structure-containing polymers are preferred. The alicyclic structure-containing polymer is a polymer having an alicyclic structure in the main chain and / or side chain, and for example, those described in JP-A-2007-057971 can be used.

A stretched film as a retardation film can be produced 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 a resin film include a cast molding method, an inflation molding method, an extrusion molding method, and the like. Among these, an extrusion molding method is preferable.

The stretching treatment can be performed by a method such as a roll method, a float method, or a tenter method. 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 of the resin film (lateral stretching) or stretching in the longitudinal direction (longitudinal stretching) depending on the direction of the slow axis desired to be developed in the stretched film. It may be stretching in an oblique direction which is neither the width direction nor the longitudinal direction, or may be stretching combining these.

The stretching temperature and the stretching ratio can be arbitrarily set as long as desired in-plane retardation is 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, 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, particularly preferably. 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, particularly preferably 200 μm or less. .

As the retardation plate, for example, a film including a liquid crystal cured 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, for convenience, the material called “liquid crystal composition” includes not only a mixture of two or more substances but also a material made of a single substance. Usually, a liquid crystal cured layer is obtained by forming a liquid crystal composition layer and orienting the molecules of the liquid crystal compound contained in the liquid crystal composition layer and then curing the liquid crystal composition layer. This liquid crystal cured layer can obtain arbitrary in-plane retardation by appropriately adjusting factors such as the type of liquid crystal compound, the alignment state of the liquid crystal compound, and the thickness.

The kind of the liquid crystal compound is arbitrary, but in order to obtain a retardation plate having reverse wavelength dispersion, it is preferable to use a reverse wavelength dispersion liquid crystal compound. The reverse wavelength dispersive liquid crystal compound refers to a liquid crystal compound that exhibits reverse wavelength dispersibility when homogeneously aligned. Also, the liquid crystal compound is homogeneously aligned means that a layer containing the liquid crystal compound is formed and the major axis direction of the mesogens of the molecules of the liquid crystal compound in the layer is aligned in one direction parallel to the plane of the layer. It means to make it. Specific examples of the reverse wavelength dispersive liquid crystal compound include compounds described in International Publication No. 2014/0669515, International Publication No. 2015/064581, 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 molecular axes are arranged in a certain direction on a plane inside the resin, but the direction of the molecular axis is shifted by a little angle on the next plane that overlaps it. In this structure, the angles of the molecular axes in the planes are shifted (twisted) as they sequentially pass through the overlapping planes. That is, when molecules in a layer of a certain material have cholesteric regularity, the molecules are aligned such that the molecular axis is in a certain direction on a first plane inside the layer. In the next second plane inside the layer that overlaps the first plane, 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 deviates further from the direction of the molecular axis in the second plane. In this way, in the planes 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 helical structure, and an optically chiral structure. Since this cholesteric resin has a circularly polarized light separating function, the marking can reflect circularly polarized light of a color corresponding to the selective reflection band of the cholesteric resin.

As the cholesteric resin, for example, a cured product of a cholesteric liquid crystal composition can be used. The cholesteric liquid crystal composition refers to a composition that can exhibit a liquid crystal phase (cholesteric liquid crystal phase) having cholesteric regularity when the liquid crystal compound contained in the liquid crystal composition is aligned. 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 crystalline 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 Nos. 2014-174471 and 2015-27743 can be used.

The marking can usually be formed as a layer containing a cholesteric resin. Such marking can be provided as a layer having a desired planar shape on an identification medium such as a label. In this case, by marking the identification medium on the article, the article can be marked. Moreover, you may form marking by drawing a desired plane shape on articles | goods with the coating material containing the pigment containing the layer containing a cholesteric resin, for example.

There are no restrictions on the items to be marked, and a wide range of items can be used. 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; and rubber products such as tires. It is not limited to.

DESCRIPTION OF SYMBOLS 10 article | item 100 viewer 110 case 111 wall part 112 optical path chamber 113 long hole 120 linearly polarizing plate 130 phase difference plate 140 switching part 200 identification medium 210 base material 220 underlayer 230 marking 300 imaging | photography apparatus 310 apparatus main body A120 absorption axis A130 slow axis R120 rotating shaft

Claims

A linear polarizing plate, and a retardation plate provided on one side of the thickness direction of the linear polarizing plate,
At least one of the linearly polarizing plate and the retardation plate is rotatably provided,
A viewer for authenticity determination, wherein the angle formed by the absorption axis of the linearly polarizing plate with respect to the slow axis of the retardation plate can be switched between + 45 ° ± 5 ° and −45 ° ± 5 °.
The authenticity determination viewer according to claim 1, wherein an in-plane retardation of the retardation plate is 140 nm ± 40 nm.
3. The authenticity judging viewer according to claim 1, wherein the retardation plate has reverse wavelength dispersion.
An imaging apparatus for imaging an identification medium having a marking including a resin having cholesteric regularity,
An imaging apparatus comprising: an apparatus main body including an imaging unit; and an authenticity determination viewer according to any one of claims 1 to 3 attached to the imaging unit of the apparatus main body.
A method for determining the authenticity of an identification medium provided with a marking containing a resin having cholesteric regularity,
5. The first image is obtained by photographing the identification medium in a state where the angle formed by the absorption axis of the linearly polarizing plate with respect to the slow axis of the retardation plate is + 45 ° ± 5 °. Obtaining
Step of obtaining the second image by photographing the identification medium with the photographing device in a state where the angle formed by the absorption axis of the linearly polarizing plate with respect to the slow axis of the retardation plate is −45 ° ± 5 °. When,
Determining the authenticity of the identification medium based on the first image and the second image.