JP2008100421A - Security device, its verifying method, and printed matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a security device, its verifying method, and a printed matter advantageous in enhancing designability and forging-preventing effect. <P>SOLUTION: An oriented layer 2 is formed on a base material 1, an image forming layer 3 comprising a liquid crystal molecule is formed on the same, and a scattering reflecting layer 4 is formed on the same. A grid-like pattern a plurality of grids parallel each other formed with recessed portions (grooves) and projecting portions is arranged in the oriented layer 2. The image forming layer 3 is constituted of at least two areas with different film thicknesses. The liquid crystal molecule in the image forming layer 3 is oriented along the grooves of the grid-like pattern of the oriented layer 2 and fixed by polymerization. The liquid crystal molecule is oriented along the grooves of the grid-like pattern, thereby the liquid crystal molecule can be visually recognized when observing via a polarizing film. Phase difference given to the transmitting light changes when the film thickness changes due to the double diffraction of the liquid crystal, so that different colors are observed according to the film thicknesses when observing via the polarizing film. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a security device that forms a visible image when a polarizing film or a polarizing layer is interposed, and can be verified by a color change, a verification method thereof, and a printed matter.

Conventionally, various methods using a latent image for preventing forgery have been proposed.
For example, there are a method of putting hidden characters etc. using gaps between the pitches of the lines and hiding the lines, and a method of showing hidden characters when the angle is tilted using intaglio printing. is there.
In these methods, a latent image can be seen when viewed closely even in a normal state.

There is also a method of forming a latent image with special luminescent ink.
One of them is fluorescent ink. The fluorescent ink is an ink that emits light when irradiated with ultraviolet rays. If a latent image is formed with fluorescent ink, the image can be confirmed only when irradiated with an ultraviolet lamp.
Another method is to use infrared absorbing ink. An image formed with infrared absorbing ink can be confirmed only with an infrared camera or the like. In these methods, a specific detection device is required for confirming the latent image, and in particular, a detection method using an infrared camera or the like becomes large.

In recent years, a latent image forming method using the birefringence of a liquid crystal material has been proposed.
This is a method in which a latent image is formed by partially aligning a liquid crystal material, and the latent image can be visually recognized by looking through a polarizing film.

  For the latent image by the liquid crystal material, apply the liquid crystal material only to the necessary part of the base material that has been rubbed, or apply the liquid crystal material to the base material that has been subjected to various alignment processing such as photo-alignment film, and only the latent image part It is formed by a technique such as aligning the liquid crystal.

In recent years, it has been proposed to enhance the forgery prevention effect by combining a latent image technology using liquid crystal with a hologram (see Patent Document 1).
Holograms are used as one of anti-counterfeiting means because they have a special visual effect that shines in rainbow colors and changes color depending on the viewing angle.
However, in order to further enhance the forgery prevention effect and to prevent forgery of the hologram itself, it is increasingly used in combination with different forgery prevention means such as a latent image technique.
When the hologram is combined with the latent image technology using liquid crystal, only the hologram image can be visually recognized, and only when viewed through the polarizing film, the latent image can be visually recognized by the orientation of the liquid crystal. Judgment and double authenticity determination are possible, and anti-counterfeiting effect is expected to increase.

However, a method of simply combining a latent image technique using liquid crystal is a known technique, and further improvement in designability and improvement in forgery prevention effect are desired.
JP 2001-63300 A

  The present invention has been made in view of such circumstances, and an object thereof is to enable an unprecedented color, color change function, and verification method when an image is observed through a polarizing film or a polarizing layer. Thus, an object of the present invention is to provide a security device, a verification method thereof, and a printed matter that are advantageous in further improving the designability and the forgery prevention effect.

  In order to achieve the above object, a security device according to claim 1 of the present invention includes an alignment layer provided with a substantially lattice-like pattern formed by unevenness, and a liquid crystal formed on the alignment layer. An image forming layer that has molecules and forms an image that is visible only through a polarizing film by aligning the liquid crystal molecules along the lattice-like pattern; and opposite to the alignment layer with the image forming layer interposed therebetween A scattering reflective layer formed on the side for imparting a scattering property for scattering light to incident light and maintaining the polarization property of the incident light, and the image forming layer is a film It has at least 2 or more area | regions from which thickness differs.

  According to a second aspect of the present invention, there is provided a security device having a polarizing layer having a function of transmitting predetermined linearly polarized light, and a lattice-like pattern formed on the polarizing layer and substantially parallel to each other formed by unevenness. And the alignment layer is formed at a position opposite to the side facing the polarizing layer, and the liquid crystal molecules are aligned along the lattice-like pattern by aligning the liquid crystal molecules. An image forming layer that forms an image that can be viewed only when the image forming layer is interposed between the image forming layer and the alignment layer, and has a scattering property that scatters light with respect to incident light. And a scattering reflecting layer that reflects and maintains the polarization of the incident light, wherein the image forming layer has at least two or more regions having different film thicknesses.

  In the security device according to claim 3 of the present invention, the alignment layer has at least two regions having different depths, so that at least two regions having different film thicknesses are formed in the image forming layer. It is characterized by being.

  In the security device according to claim 4 of the present invention, the lattice-like pattern includes a plurality of regions having different lattice angles constituting the lattice-like pattern, and extends on a plane on which the alignment layer extends. When the angle formed by the longitudinal direction of the lattice forming the lattice-like pattern with respect to the reference line is defined as the lattice angle, the lattice angle of each region is different.

  In the security device according to claim 5 of the present invention, the image forming layer is made of a photopolymerizable nematic liquid crystal, and the alignment is fixed by polymerization after the liquid crystal molecules are aligned along the grooves of the lattice-like pattern. It is characterized by being.

  The security device according to claim 6 of the present invention is characterized in that the grating-like pattern is a diffraction grating or a unidirectional diffusion pattern.

  In the security device according to claim 7 of the present invention, the grooves of the lattice-like pattern have a pitch of 0.1 to 10 μm and a depth of 0.05 to 1 μm.

  The security device according to claim 8 of the present invention is characterized in that the depth of the region with different depth provided in the orientation layer is 0.1 to 3 μm.

  The security device according to claim 9 of the present invention is characterized in that the scattering reflective layer is a metal reflective film having minute unevenness.

  The security device according to claim 10 of the present invention is characterized in that the scattering reflective layer is a single-layer or multilayer dielectric film having minute irregularities.

  A security device verification method according to claim 11 of the present invention is the security device according to claim 1 observed through a polarizing film from a direction inclined with respect to a virtual plane in which the security device extends. The authenticity is determined by confirming the color change of the image appearing on the screen.

  In the security device verification method according to claim 12 of the present invention, the security device according to claim 2 is observed through the polarizing layer from a direction inclined with respect to a virtual plane in which the security device extends. The authenticity determination is performed by confirming the color change of the image that appears at the time.

  A security device verification method according to a thirteenth aspect of the present invention is the security device according to the first aspect when the security device is observed through a polarizing film from a direction inclined with respect to a virtual plane in which the security device extends. And confirming the color change of the latent image that occurs when the security device is rotated around a virtual axis orthogonal to the virtual plane while maintaining the state. Judgment is performed.

  In the security device verification method according to claim 14 of the present invention, the security device according to claim 2 is observed through the polarizing layer from a direction inclined with respect to a virtual plane in which the security device extends. Confirming the color change of the latent image that occurs when the security device is rotated around the virtual axis orthogonal to the virtual plane while maintaining the state It is characterized by authenticity determination.

  According to a fifteenth aspect of the present invention, a printed matter includes the security device according to any one of the first to tenth aspects.

The security device according to the present invention is formed by forming an image forming layer made of a liquid crystal material having a region having a different film thickness, a scattering reflective layer, and optionally a polarizing layer on an alignment layer made of a lattice-like pattern. The image appearing when the security device of the invention is tilted and observed through a polarizing film or a polarizing layer enables color expression that is not possible in the past, and enhances the design and anti-counterfeit effect.
The security device verification method according to the present invention enables verification of unprecedented color expression possessed by the security device of the present invention, and enables color change verification by tilting and rotating, and Designability and anti-counterfeiting effect can be enhanced.
In addition, the printed matter according to the present invention has a visual effect different from that of normal printing, can prevent forgery due to copying, etc., and can determine the authenticity by the security device verification function of the present invention.

  The security device of the present invention will be described below based on examples.

FIG. 1 shows a typical configuration of the present invention.
An alignment layer 2 made of a lattice-like pattern is formed on a base material 1 that can transmit light, an image forming layer 3 made of a liquid crystal material is formed thereon, and a scattering reflective layer 4 is formed thereon. Yes.

FIG. 2 shows another typical configuration of the present invention.
An alignment layer 2 made of a lattice-like pattern is formed on the substrate 1, an image forming layer 3 made of a liquid crystal material is formed thereon, a scattering reflective layer 4 is formed thereon, and the substrate 1 is scattered A polarizing layer 5 is formed at a position opposite to the side facing the reflective reflective layer 4. In other words, the alignment layer 2 is formed on the polarizing layer 5 with the substrate 1 interposed therebetween. In this case, it is not necessary to use a polarizing film at the time of verification.

The liquid crystal molecules of the image forming layer 3 are aligned along the grooves of the lattice-like pattern and fixed by polymerization.
The alignment direction at this time is such that the groove direction and the major axis direction of the liquid crystal molecules coincide. In this way, the liquid crystal molecules are aligned in the grooves of the lattice-like pattern, thereby forming an image that is visible only when the polarizing film or the polarizing layer 5 is observed.

  The polarizing film to be used is a linear polarizing film.

The image forming layer 3 includes at least two regions having different thicknesses. For example, as illustrated in FIG. 3A which is a schematic diagram of the alignment layer 2, the image forming layer 3 includes two regions 6a and 6b. .
At this time, because of the birefringence of the liquid crystal, when the film thickness changes, the phase difference given to the transmitted light changes, so when observed through the polarizing film or the polarizing layer 5, depending on the film thickness as described in detail later Different colors are observed.

Such regions having different film thicknesses of the image forming layer 3 can be obtained by providing regions having different depths in the alignment layer 2 as shown in FIG. 3B which is a cross-sectional view of FIG. It is done.
At this time, the depth of the region having a different depth provided in the alignment layer 2 is 0.1 to 3 μm.

The alignment layer 2 is provided with a lattice-like pattern composed of a plurality of lattices substantially parallel to each other formed by concave portions (hereinafter also referred to as grooves) and convex portions.
Further, the lattice-like pattern formed in the alignment layer 2 is composed of regions having at least two lattice angles. For example, as shown in FIG. 4, the lattice-like pattern is composed of two regions 7a and 7b.
In other words, the lattice-like pattern includes a plurality of regions having different lattice configurations constituting the lattice-like pattern, and the lattice-like pattern with respect to the reference line extending on the plane on which the alignment layer 2 extends. The grid angles of the regions 7a and 7b are different when the angle formed by the longitudinal direction of the grid forming the grid is the grid angle.
At this time, if the image forming layer 3 is formed in regions having different lattice angles, the liquid crystal is aligned in the lattice direction, so that regions having different alignment directions are formed.
When this is observed through the polarizing film or the polarizing layer 5, different colors are observed depending on the orientation direction, as will be described in detail later.

  Note that the regions of the image forming layer 3 having different film thicknesses and the regions of the alignment layer 2 having different lattice angles may or may not coincide with each other.

The grating-like pattern formed on the alignment layer 2 at this time may be a structure having a grating-like groove, such as a diffraction grating or a unidirectional diffusion pattern, and may be a periodic structure like a diffraction grating. It may be random to some extent like a unidirectional diffusion pattern.
However, the unidirectional diffusion pattern is a structure in which the longitudinal direction of the lattice-like groove structure is arranged in one direction on average even though the longitudinal direction is somewhat random.
Further, regarding the grooves of the lattice-like pattern, the pitch is 0.1 to 10 μm and the depth is 0.05 to 1 μm.

The scattering reflective layer 4 is formed on the opposite side of the alignment layer 2 with the image forming layer 3 interposed therebetween, and imparts a scattering property to the incident light to scatter the light and polarizes the incident light. In other words, the reflected light is reflected without disturbing the polarized light.
In this example, the scattering reflective layer 4 is a metal reflective film having minute irregularities.
That is, the scattering reflection layer 4 is provided by imparting scattering properties to the metal reflection film that does not disturb the polarization by minute unevenness.
Such a scattering metal reflective layer is obtained, for example, by depositing a metal such as aluminum on a minute surface uneven structure.

Further, the scattering reflective layer 4 may be a single-layer or multilayer dielectric film having minute irregularities.
That is, in this case, the scattering reflective layer 4 is provided by imparting scattering properties to a single or multi-layer dielectric film that does not disturb polarization by minute unevenness.
Such a scattering dielectric layer can be obtained, for example, by depositing a high refractive index material such as zinc sulfide and a low refractive index material such as magnesium fluoride on a minute surface uneven structure.

As a verification method, there is a method of confirming an image through a polarizing film or a polarizing layer 5 and confirming a color change when the security device of the present invention is tilted and observed.
That is, it is a method of performing authenticity determination by confirming a latent image that appears when observed through a polarizing film or a polarizing layer 5 from a direction inclined with respect to a virtual plane in which the security device extends.
The latent image observed at this time has a unique color. This is because the effect of the image forming layer 3 due to the anisotropy of liquid crystal molecules, which is usually difficult to observe, appears prominently when observed with an inclination by the scattering reflective layer 4.

Further, as another verification method, the color is confirmed when the image is confirmed through the polarizing film or the polarizing layer 5, the color change is observed when the security device of the present invention is tilted, and the image is rotated horizontally. There are ways to observe changes.
That is, while confirming and maintaining the state of the latent image that appears when the security device is observed through the polarizing film or the polarizing layer 5 from a direction inclined with respect to the virtual plane in which the security device extends. This is a method of performing authenticity determination by confirming a color change of a latent image that occurs when a security device is rotated about a virtual axis orthogonal to the virtual plane.
The image observed at this time exhibits a unique color, and changes in color when rotated. This is because rotating the security device of the present invention produces the same effect as rotating the alignment direction of the liquid crystal molecules. Since the observed color is derived from the alignment direction of the liquid crystal molecules, the observed color changes when the alignment direction is different.

For example, as shown in FIG. 5A, which is a schematic diagram of the alignment layer 2, the alignment layer 2 has regions 8a and 8b each having a lattice-like pattern in the 0 ° direction and regions each having a lattice-like pattern in the 90 ° direction. The case where 8c and 8d are arranged and observed with the polarizing film 9 as shown in FIG.
At this time, as shown in FIG. 5B, which is a cross-sectional view of FIG. 5A, the depths of the regions 8a and 8c and 8b and 8d in the alignment layer 2 are the same. Note that the depths of the regions 8a and 8b are different, and therefore the depths of the regions 8c and 8d are also different.
The transmission axis of the polarizing film 9 is 45 °.
When observed from the front direction through the polarizing film 9, the regions 8a, 8b, 8c and 8d can be observed as latent images.
At this time, the colors of the regions 8a and 8c having the same depth are the same, and the colors of the regions 8b and 8d having the same depth are the same. Note that the colors of the regions 8a and 8b are different, and therefore the colors of the regions 8c and 8d are also different.
Next, when the security device is tilted and observed, the regions 8a, 8c, 8b, and 8d look different colors.
For example, the region 8a is red, the region 8c is green, the region 8b is yellow, and the region 8d is blue.
These color differences are derived from the difference in the alignment direction and the difference in the film thickness of the liquid crystal layer in the image forming layer 3 as shown in FIG.

First, the difference in color derived from the alignment direction of the liquid crystal will be described.
In particular, when considering the case of 0 ° orientation and 90 ° orientation, the anisotropy of liquid crystal molecules has the largest influence, that is, the refractive index in the minor axis direction is dominant in the 0 ° orientation region, and 90 ° This is because the refractive index in the major axis direction is dominant in the alignment direction region.

Such coloration is most noticeable when the transmission axis of the polarizing film 9 and the alignment direction of the liquid crystal molecules are different by 45 °.
Assuming that the image forming layer 3 made of liquid crystal molecules gives a phase difference of exactly π / 2, when polarized light in the 45 ° direction passes, it is converted into clockwise circularly polarized light in the region 5a oriented in the 0 ° direction. It can be considered that the region 5c oriented in the ° direction is converted into counterclockwise circularly polarized light.
Each circularly polarized light is reflected by the scattering reflective layer 4, passes through the image forming layer 3 made of liquid crystal molecules once again, and is converted into linearly polarized light. At this time, if the scattering reflection layer 4 disturbs the polarization, the final efficiency is deteriorated. Therefore, it is important that the scattering reflection layer 4 does not cancel the polarization.
Since the linearly polarized light finally returning to the observation side is polarized in the direction of 135 °, the color is observed without passing through the polarizing film 9 on the observation side.
Note that the direction of circularly polarized light may be reversed clockwise and counterclockwise, and may be elliptically polarized light instead of completely circularly polarized light.

Next, the difference in color resulting from the difference in film thickness of the liquid crystal will be described.
This is because the phase difference caused by the birefringence of the liquid crystal depends on the film thickness and the wavelength, and is clear from the following equation.
Re = Δnd
(Δn = ne−no)
I = I ₀ sin ² (2θ) sin ² (Reπ / λ)
Re: phase difference Δn: birefringence d: liquid crystal film thickness ne: ordinary light refractive index no: extraordinary light refractive index I: incident light intensity I ₀ : transmitted light intensity θ: liquid crystal alignment direction and polarizing plate transmission Axis angle λ: wavelength

  In this way, by combining the color difference derived from the liquid crystal alignment direction with the color difference derived from the liquid crystal film thickness, various color representations are possible.

Further, when the security device of the present invention as shown in FIG. 7 is tilted and observed through the polarizing film 9 (polarizing plate) to confirm the latent image, the color change can be observed by rotating it horizontally.
That is, the latent image that appears when the security device is observed through the polarizing film 9 from the direction inclined with respect to the virtual plane in which the security device extends is confirmed, and the security device is maintained while maintaining the state. A color change can be observed by rotating around a virtual axis orthogonal to the virtual plane.
Specifically, the region 8a is red and the region 8c is green. If the region 8a is rotated 90 ° horizontally while being tilted as shown in FIG. 7, the region 8a looks green and the region 8c looks red. Become. This is because rotating the whole produces the same effect as rotating the orientation direction. That is, the region 8a is oriented in the 0 ° direction, but when rotated 90 °, it becomes the same as the orientation in the 90 ° direction from the observation side.

  This effect is not limited to the combination of 0 ° and 45 °, and the same effect can be obtained by combining other angles.

  As a method of forming a grating-like pattern, there are a method of recording a hologram pattern by a two-beam interference method, a method of drawing a diffraction grating pattern by an electron beam, a method of forming a diffraction grating pattern by cutting tools, and the like.

  The lattice-like pattern formed in this way is made into a metal plate by electroforming, etc., and an original plate is produced. By transferring the pattern from the original plate to a thermoplastic resin by an embossing method, a large amount of the lattice-like pattern is replicated. it can. Further, instead of transferring to the thermoplastic resin by an embossing molding method, the pattern may be transferred by a molding method using an ultraviolet curable resin.

  As the liquid crystal material, a photopolymerization type nematic liquid crystal is desirable. After applying and aligning on the lattice-like pattern, the alignment can be fixed by exposing with a UV lamp or the like.

  In addition, printed matter that requires security, such as securities, banknotes, identification cards, credit cards, etc. equipped with the security device of the present invention has a visual effect different from normal printing and prevents counterfeiting due to copying, etc. The authentication can be performed by the security device verification function of the present invention.

It is a schematic sectional drawing of the layer structure of this invention. It is a schematic sectional drawing of the layer structure of this invention. (A) is a schematic diagram of the orientation layer which consists of a lattice-like pattern of this invention, (B) is a schematic sectional drawing of (A). It is a schematic diagram of the orientation layer which consists of a lattice-like pattern of the present invention. (A) is a schematic diagram of an alignment layer comprising a lattice-like pattern of the present invention, (B) is a schematic sectional view of (A), and (C) is an explanatory view of the lattice-like pattern. It is a schematic diagram at the time of polarizing film observation of this invention. It is a schematic diagram which shows the verification method of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Base material, 2 ... Orientation layer, 3 ... Image formation layer, 4 ... Scattering light reflection layer, 5 ... Polarizing layer, 6a ... One of the area | regions from which film thickness differs, 6b ... One of the area | regions from which film thickness differs 7a: one of the regions composed of the lattice-like pattern, 7b: one of the regions composed of the lattice-like pattern, 8a: one of the regions having different film thicknesses and one of the regions having different lattice angles, 8b ... One of regions having different lattice angles, 8c... One of regions having different film thicknesses and one of regions having different lattice angles, 8d... One of regions having different film thicknesses and one of regions having different lattice angles, 9.

Claims (15)

An alignment layer provided with lattice-like patterns substantially parallel to each other formed by irregularities;
An image forming layer that is formed on the alignment layer and has liquid crystal molecules to form an image that is visible only when the liquid crystal molecules are aligned along the lattice-like pattern through the polarizing film;
A scattering property that is formed on the opposite side of the alignment layer with the image forming layer in between, imparts a scattering property to the incident light and scatters while maintaining the polarization property of the incident light. A reflective layer,
The image forming layer has at least two regions having different thicknesses;
A security device characterized by that. A polarizing layer having a function of transmitting predetermined linearly polarized light;
An alignment layer formed on the polarizing layer and provided with lattice-like patterns substantially parallel to each other formed by irregularities;
The alignment layer is formed at a position opposite to the side facing the polarizing layer, and has liquid crystal molecules, and the liquid crystal molecules are aligned along the lattice-like pattern so that the alignment layer is visible only through the polarizing layer. An image forming layer for forming an image;
A scattering property that is formed on the opposite side of the alignment layer with the image forming layer in between, imparts a scattering property to the incident light and scatters while maintaining the polarization property of the incident light. A reflective layer,
The image forming layer has at least two regions having different thicknesses;
A security device characterized by that. When the alignment layer has at least two regions having different depths, at least two regions having different film thicknesses are formed on the image forming layer.
The security device according to claim 1 or 2, wherein The lattice-like pattern includes a plurality of regions having different lattice angles constituting the lattice-like pattern,
When the angle formed by the longitudinal direction of the lattice forming the lattice-like pattern is a lattice angle with respect to a reference line extending on a plane on which the alignment layer extends, the lattice angle of each region is different. ,
The security device according to claim 1, 2, or 3.   5. The image forming layer according to claim 1, wherein the image forming layer is made of a photopolymerizable nematic liquid crystal, and the alignment is fixed by polymerization after the liquid crystal molecules are aligned along the grooves of the lattice-like pattern. The security device according to any one of claims.   The security device according to claim 1, wherein the grating-like pattern is a diffraction grating or a unidirectional diffusion pattern.   The security device according to claim 1, wherein the grooves of the lattice-like pattern have a pitch of 0.1 to 10 μm and a depth of 0.05 to 1 μm.   8. The security device according to claim 1, wherein a depth of a region having a different depth provided in the alignment layer is 0.1 to 3 [mu] m.   The security device according to claim 1, wherein the scattering reflective layer is a metal reflective film having minute unevenness.   10. The security device according to claim 1, wherein the scattering reflective layer is a single-layer or multi-layer dielectric film having minute irregularities. The security device according to claim 1 is subjected to authenticity determination by confirming a color change of an image appearing through a polarizing film from a direction inclined with respect to a virtual plane in which the security device extends.
And a security device verification method. The security device according to claim 2, wherein authentication is performed by confirming a color change of an image that appears when the security device is observed through the polarizing layer from a direction inclined with respect to a virtual plane in which the security device extends.
And a security device verification method. The color change of the image that appears when the security device according to claim 1 is observed through a polarizing film from a direction inclined with respect to a virtual plane in which the security device extends is confirmed, and the state is maintained. While authenticating by checking the color change of the latent image that occurs when the security device is rotated around a virtual axis orthogonal to the virtual plane,
And a security device verification method. The color change of an image that appears when the security device according to claim 2 is observed through the polarizing layer from a direction inclined with respect to a virtual plane in which the security device extends is confirmed and maintained. However, authenticity is determined by confirming the color change of the latent image that occurs when the security device is rotated around a virtual axis orthogonal to the virtual plane.
And a security device verification method.   A printed matter comprising the security device according to claim 1.

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