JP2010194978A - Color variable medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color variable ink which enables a new color change since the color change of conventional color change inks is always "blue shift" and those making the similar color changes are easily available to the public, and thus are insufficient for authentication of security targets. <P>SOLUTION: The color variable medium is characterized in that it is a color variable ink composition which makes what is called "red shift" when observed, by laminating a color change ink layer containing a dye which shifts from a visible area where the wavelength of the reflected light is 500 nm or less to an ultraviolet area, and a color change ink layer containing a dye which shifts from an infrared area to a visible area of 500 nm or more. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

The present invention includes gift vouchers such as gift certificates, securities, stock certificates, various cards such as credit cards, prepaid cards, ID cards, tickets, banknotes, passports, identification cards, public competition voting tickets, video software, PC software, etc. The present invention relates to a color variable medium having an excellent anti-counterfeit effect and constituting various anti-counterfeit bodies such as authenticity determination seals used in (hereinafter referred to as security objects).
In general, electromagnetic waves can be classified as ultraviolet rays, visible rays, and infrared rays. In the present invention, the visible light region, that is, the visible region is 360 nm to 830 nm (JIS Z8120), and light having a shorter wavelength than the visible light is used. Ultraviolet light, and that region is the ultraviolet region. Further, light having a wavelength longer than that of visible light is infrared, and the region is an infrared region.
In general, the visible region is “purple”: 380 nm to 450 nm, “blue”: 450 nm to 495 nm, “green”: 495 nm to 570 nm, “yellow”: 570 nm to 590 nm, “orange”: 590 nm to 620 nm, “red”: 620 nm Although it is divided into ˜750 nm, the change is continuous, and this classification is an example.
Further, the ultraviolet region in the present invention refers to a region whose range is determined from the characteristics of the color variable ink layer of the present invention, and refers to one region in a general near ultraviolet region: 380 nm to 200 nm. Furthermore, the infrared region in the present invention refers to a region whose range is determined from the characteristics of the color variable ink layer of the present invention, but it refers to one region in a general near infrared region: 830 nm to 2500 nm. .
In the present invention, “the incident angle of light to be observed”, that is, “the light to be observed whose angle with respect to the reference direction is a direction perpendicular to the color variable ink layer surface” is “0 ° to 70 °”. When observing the color variable ink layer surface, according to the incident angle, “the wavelength of the selectively reflected light” (the light exiting in the regular reflection direction is selected from the wavelength components of the incident light) This means a color variable ink layer having a property of changing only a part of wavelength components), and the color variable ink layer is laminated, and each color variable ink layer includes a color variable pigment. That is, the present invention relates to a color variable medium containing a pearl pigment, an effect pigment, a liquid crystal pigment, and the like. The present invention also relates to a color variable medium in which two kinds of liquid crystal layers having predetermined characteristics are laminated.

Pearl pigments are natural mica flakes (also called mica flakes) coated with a transparent metal oxide. Effect pigments are natural alumina flakes, artificially synthesized alumina flakes, silicon oxide flakes (silica). Flakes), borosilicate glass flakes and the like are coated with a transparent metal oxide.
Usually, when the color variable ink layer is observed and visually determined, it is performed at an angle of 0 to 70 degrees with respect to the reference direction. Observation at 80 to 90 degrees is not performed unless otherwise specified.
As the liquid crystal or liquid crystal pigment, a three-dimensional cross-linking substance having a liquid crystal structure having a chiral phase can be used. In particular, cholesteric liquid crystals having wavelength-selective reflected light and cholesteric liquid crystal pigments are suitable.
Cholesteric liquid crystals are induced by adding a small amount of optically active substances (chiral agents) to nematic liquid crystals, and have a constant refractive index change in the liquid crystal layer by having a helical structure with a constant period with respect to the reference direction. Layers are stacked. The multilayer structure having this refractive index distribution has the property of reflecting incident light for observation at a predetermined angle after selecting the wavelength. The wavelength of the selectively reflected light is determined by the refractive index value (distribution) of the cholesteric liquid crystal and the thickness of the refractive index changing layer, that is, the interval between layers of the multilayer structure.
This cholesteric liquid crystal can be laminated as a color variable ink layer having two kinds of predetermined optical characteristics by an appropriate method (adding an alignment film, etc.).
Further, each of the cholesteric liquid crystals is flaked (this state is referred to as a cholesteric liquid crystal pigment) and mixed with an appropriate resin, additive, or other solvent to obtain a color variable ink composition. The pearl pigment also becomes a color variable ink composition by the same method.
Using these color variable ink compositions, a color variable ink layer is formed on the surface of a plastic film or the like to form a forgery prevention body, or various printing methods or the like are directly applied on the surface of a security object. A color variable medium is formed by forming a color variable ink layer by the method. Of course, a color variable medium can also be obtained by using a co-extrusion molding method or the like and having two color variable ink layers.

(Main applications)
The main use of the color variable medium of the present invention is as a counterfeit prevention field, specifically, a credit card or the like that can cause damage to a cardholder or a card company when used forgery, driving Identification card such as driver's license, employee ID card, membership card, admission ticket for entrance examination, passport, banknote, gift certificate, point card, stock certificate, securities, lottery ticket, horse ticket, bank passbook, boarding pass, pass ticket, There are air tickets, admission tickets for various events, play tickets, prepaid cards for transportation and various telephones.
All of these are information records that hold information of economic or social value, identity identification, etc., and can identify the authenticity of the record itself for the purpose of preventing damage caused by forgery. Although it is desired to have a function, the present invention is applied to a method in which the confirmation method is visual and it is particularly desired to have a function to prove the authenticity of the visual determination.
In addition to the uses described above, expensive products such as luxury watches, luxury leather products, precious metal products, jewelry, etc., often referred to as luxury brand products, or storage boxes for these expensive products And cases can also be forged. In addition, mass-produced products of famous brands, such as audio products, electrical appliances, etc., or tags that are hung on them are also subject to forgery.
Furthermore, a storage body in which music software, video software, computer software, game software, or the like, which is a copyrighted work, or cases thereof can also be forged. In addition, it is desirable that products such as printer toner, paper, and the like in which supplies to be replaced are limited to genuine materials have a function of identifying their authenticity for the purpose of preventing damage caused by forgery.
A forgery prevention body or the like that can be visually judged is added to these things in a form such as sticking, and the authenticity of the security object is proved by the visual judgment.
In the present specification, “ratio”, “part”, “%” and the like indicating the blending are based on mass unless otherwise specified, and the “/” mark indicates that they are integrally laminated.

(Background technology)
Conventionally, in order to prevent forgery of this kind of cash vouchers, forgery prevention technology has been performed in which a color variable printing layer whose color changes depending on the viewing angle is provided. Such a color variable printing layer is a color variable ink whose color changes depending on the viewing angle, such as pearl ink, and is formed by printing or the like. The ink whose color changes includes a pigment that multi-reflects light, and the color appears to change due to interference of light reflected by the pigment. Therefore, the color change effect increases as the amount of light reflected by the pigment increases. Therefore, the color variable printing layer is often printed by stencil printing such as screen printing or intaglio printing such as gravure printing so that the thickness of the color variable printing layer is increased so that the number of pigments that multiple reflect light is increased. .
Specifically, forgery prevention that provided a color variable printing layer such as pearl printing on printing media such as gift certificates, stock certificates, etc., and concealed a part of the color variable printing layer in a pattern so as not to be visible, forming specific information Print media has been proposed. (For example, refer to Patent Document 1).
This print medium has a feature that the color tone of the medium base material and the color tone of the specific information appear to be synchronized. However, general pearl ink itself can be obtained unless its optical performance is specified, and if it is a normal printing manufacturer, pearl ink is obtained and matte ink is printed thereon. Thus, it is possible to make a similar printed matter.

Therefore, in order to further improve anti-counterfeiting, a color variable printing layer whose color changes depending on the viewing angle, and a photoreactive printing layer that emits fluorescence by irradiation of ultraviolet rays or infrared rays on the color variable printing layer are arranged in a pattern At least a portion of the printed portion using an anti-counterfeit printing medium (for example, see Patent Document 2), or an anti-counterfeit ink composition containing at least a pearl pigment and a fluorescent pigment whose color tone is changed by ultraviolet irradiation or infrared irradiation. However, forgery prevention printed matter (for example, refer to Patent Document 3) having a configuration in which a single color or a plurality of colors are printed is known.
In addition, as another pigment having pleochroicity depending on the observation angle as described above, for example, a composition comprising a cholesteric liquid crystal, a three-dimensional crosslinkable resin, a photoinitiator, and the like is applied to a plastic film by a doctor. There is a method of using a liquid crystal pigment or the like obtained by aligning and forming by a shear gradient at the time of peeling, and then peeling and crushing from a plastic film. (For example, refer to Patent Document 4).
The above-mentioned pigment has a feature that the hue varies depending on the viewing angle and the reflected light is circularly polarized. Depending on the normal copying means, it is not possible to make the duplicates have such optical characteristics. Therefore, it is very effective to use liquid crystal pigments for preventing counterfeiting of securities and credit cards. In addition, since the hue changes depending on the observation angle, there is a feature that an excellent design can be obtained.

JP 2000-006564 A JP 2002-274000 A JP 2002-285061 A JP 1994-220350

However, in these pigments showing color variability, the basic principle of color variability is that for pearl pigments and effect pigments, natural mica flakes (mica flakes), alumina flakes, silica flakes, On the surface of the silicate glass flakes, a transparent metal oxide thin film having a thickness smaller than the visible light wavelength and a refractive index larger than those of the transparent substrate is formed, and the light incident on the pigment is multiplexed in the thin film. The wavelength of the reflected light is made selective by reflection and the interference phenomenon.
In other words, when the light is multiple-reflected, the multiple reflected light causes an interference phenomenon, and the reflected light wavelength is transparent due to the fundamental property of light that concentrates the reflected light wavelength and increases its intensity. It is automatically determined depending on the refractive index value and thickness of the metal oxide thin film, and the “color changes” and the “change pattern” (degree of change, range of change, etc.) are also uniquely determined.
Due to the effect of this multiple reflection, the “change pattern” is as follows. That is, it enters the thin film perpendicularly (“angle 0 °” with respect to the reference direction), and is incident perpendicularly, for example, at an angle of 45 degrees, and again 45 in the opposite direction. The wavelength of light that is selectively reflected differs greatly from the case of light that reflects at a degree, and “45-degree reflected light (after 45 degrees incidence)” differs from “vertically reflected light (after perpendicular incidence)” Theoretically, the wavelength value is 0.71 times (from cos 45 ° / cos 0 ° ≈0.71).
That is, in a certain pigment, if the vertically reflected light (after normal incidence) is 700 nm (red), the 45 degree reflected light (after 45 degrees incident) becomes 490 nm (blue). A so-called “blue shift” occurs.
This is a basic property of “transparent thin film” (transparent metal oxide thin film in pearl pigment), and the color change is monotonously changed from long wavelength to short wavelength according to this theory (“blue shift”). To do.
That is, the color of the vertical reflected light and the color of the 45 ° or 70 ° reflected light are uniquely determined by the thickness of the transparent metal oxide thin film layer, the refractive index value, and the like. It is the same. Therefore, even when the above-described various color variable inks are used, the color change situation is the same. As a result of the popularization of these pigments, the same color change is confirmed. Therefore, it can no longer be said that it has anti-counterfeiting properties.
In addition, the liquid crystal pigment has a refractive index distribution in the liquid crystal itself, and this refractive index distribution has the same function as the above-described thin film, and therefore exhibits the same selective reflectivity. Accordingly, the wavelength change of the reflected light becomes “blue shift” as in the thin film.
As described above, all of the items that are called “color variable” are “blue shifted” at the same rate of change, so even if various color variable items are applied to the security object, they are visually observed. As a result, the appearance is almost the same, and the security is somewhat inferior in terms of the anti-counterfeit effect by visual judgment.

Accordingly, the present invention has been made to solve such problems. Its purpose is
It is an object of the present invention to provide a color variable ink that exhibits a color change not found in conventional color variable inks.
That is, the “blue shift” that is the basic principle of the transparent thin film is not performed, for example, “blue shift” is exhibited as vertical reflected light, and “red” is exhibited as reflected light near 70 degrees. Provided is a color variable medium.

To solve the above problem,
The first aspect of the present invention is:
A color variable ink layer in which the wavelength of light selectively reflected shifts from a visible region of 500 nm or less to an ultraviolet region when the incident angle of light to be observed changes from 0 degree to 70 degrees;
A color-variable ink layer that shifts the wavelength of selectively reflected light from the infrared region to the visible region of 500 nm or more when the incident angle of light to be observed changes from 0 degree to 70 degrees is laminated. It is characterized by.
According to a first aspect of the invention,
A color variable ink layer in which the wavelength of light selectively reflected shifts from a visible region of 500 nm or less to an ultraviolet region when the incident angle of light to be observed changes from 0 degree to 70 degrees;
A color-variable ink layer that shifts the wavelength of selectively reflected light from the infrared region to the visible region of 500 nm or more when the incident angle of light to be observed changes from 0 degree to 70 degrees is laminated. A color variable medium characterized by the above is provided.
Pearl pigments, effect pigments, etc. are fine flakes and theoretically calculated when the flat surface of the flake is parallel to the surface formed by the color variable ink layer when it becomes a color variable ink layer. However, when the flakes are directed in various other directions, the incident angle and the reflection angle of the light on the transparent oxide thin film formed on the flakes are different. As a result, various colors of reflected light (hereinafter referred to as scattered light) are generated in directions other than a predetermined reflection angle.
Further, the incident light may pass through a plurality of flakes and finally appear as reflected light. The shape of the flake itself, the properties of the flake surface, the refractive index and its distribution also affect the reflection on the flake surface and the attenuation of transmitted light.
However, light that has passed through a plurality of flakes has a large attenuation, has little effect on visual observation, and an angle at which the light is regularly reflected with respect to the incidence of light at a predetermined incident angle. Since only the light that has passed through a predetermined path reaches the reflected light that comes out of the light, the wavelength selection process is limited, and as a result, only light having a predetermined wavelength is reflected.
In order to ensure the intensity of light of this predetermined wavelength and reduce unnecessary scattered light, the flake shape is flat, the flake surface is smooth, the transparent oxide thin film has a uniform thickness, and the color variable ink layer The flakes that are parallel to the ink layer forming surface have a large proportion, and the light incident on the ink layer is reflected only by one or two flakes, and the ink is reflected as reflected light. Design to come out of the layer.

In the visual observation, since this scattered light becomes an obstacle to determination, the formation method is devised so that the flakes are parallel to the surface formed by the color variable ink layer when the color variable ink layer is formed. For example, a flat pigment (a disk shape with a flatness ratio of 2 to 5. The flatness ratio is an ellipsoid, and is a value obtained by dividing the major axis length by the minor axis length. When the flatness ratio is 5 or more, the pigment is deformed in the inking process and the scattered light also increases.), And the pigment size (average particle diameter) is, for example, 10 μm, When the thickness of the color variable ink layer after drying is ½ or less, the ratio of the pigment in the inclined state decreases, and many of them are parallel to the color variable ink layer. Furthermore, as a method of forming the color variable ink layer, as in blade coating, a printing pressure is applied in the coating direction, and during coating, a color variable ink layer is formed with a low viscosity, and the time for flakes to overlap with its own weight is set. After securing, the scattered light can be reduced by making various solvent evaporations at the time of drying and suppressing the flakes being pushed up during the evaporation.
Accordingly, when composing the ink composition, depending on the printing method employed, the solvent ratio is 50% to 90%, and the solid content (color variable ink layer forming component, consisting of pigment, resin and additive). Of these, the pigment ratio is 10% to 50%. In order to obtain a predetermined reflected light intensity, mixing of 10% or more is necessary. However, if it exceeds 50%, the interaction between pigments such as aggregation between pigments works strongly, and the surface of the color variable ink layer is formed. It becomes difficult to become parallel to.
When the color variable ink layer forming method is an ultraviolet ray curing method or an electron beam curing method, the color variable ink can be made to have a low viscosity and the color variable ink layer is cured without using almost any solvent. Since it is possible to secure the time until the flakes are made, it becomes easy to perform the process of aligning the flakes, such as securing the time of overlapping with its own weight, or performing a calendar process.
Since the flakes used in the present invention are transparent, they are particularly suitable for these ionizing radiation forming methods.

Of course, the affinity between the pigment and the resin is important. The better the adhesiveness, the simpler the reflection / transmission (refraction) at the pigment / resin interface, and the less the scattered light. When the surface of the pigment is not a smooth surface, complicated reflection and transmission (refraction) occur at the interface, and light travels in various directions. Since the reflection at this interface is a portion that does not contribute to the wavelength selectivity due to multiple reflection in the transparent metal thin film layer of the present invention, it is desirable that this surface simply transmit. That is, it is desirable that the surface is smooth, has little reflected light, and that almost all incident light simply passes through this surface.
For this purpose, it is desirable that the difference in refractive index between the resin and the transparent metal thin film is small. For example, for a transparent metal thin film having a refractive index of 1.80 or more, the refractive index of the resin is 1.40 or more, preferably Is preferably 1.60 or more.
However, since there is no transparent resin having a refractive index near 1.80, conversely, a transparent metal thin film having a low refractive index, for example, a refractive index of 1.50 is used, and a resin having the same refractive index is adopted. Thus, unnecessary reflection at the interface between the resin and the transparent metal thin film can be almost eliminated.
Examples of the resin include polymethyl acrylate (n = 1.47), polyvinyl acetate (n = 1.47), polyvinyl chloride / vinyl acetate (n = 1.54), melamine resin (n = 1.56), An epoxy resin (n = 1.61), a phenol resin (n = 1.60), or a mixture thereof can be used as appropriate.
The optimum solvent is selected depending on the color variable ink layer forming method.
As the solvent, esters, ethers, alicyclic hydrocarbons, aliphatic hydrocarbons, aromatics, alcohols, and the like and mixtures thereof are used.
These are classified into low boiling point solvents (boiling point 100 ° C or lower), medium boiling point solvents (boiling point 100 ° C to 150 ° C), and high boiling point solvents (boiling point 150 ° C or higher) according to the boiling point. Adjust the flakes to be parallel to the surface of the color variable ink layer, such as mixing with boiling point solvents and devising to gradually dry out while suppressing rapid solvent volatilization.
Furthermore, in consideration of transparency, various additives, dispersants, leveling agents, lubricants, plasticizers, coupling agents, antifoaming agents, ultraviolet absorbers, various curing accelerators and the like are used.
The color variable ink forming method is used in various methods such as offset printing, letterpress printing, gravure printing, nozzle printing, curtain coat printing, silk screen printing, intaglio printing, inkjet printing, etc. in order to fully demonstrate the functions of the present invention. The solvent composition, ink viscosity adjustment and drying / curing methods can be devised.
Of course, in consideration of the environment, it is also suitable to use a water-based ink composition using a water-soluble resin such as polyvinyl alcohol.

As pearl pigments and effect pigments,
Natural mica flakes (mica flakes), etc., pigments coated with metal oxides such as titanium oxide and iron oxide, synthetic alumina flakes (particle size 1-30 μm, thickness 0.5 μm-5 μm), synthetic silica flakes (particle size 5-30 μm, thickness 0.5 μm-5 μm), borosilicate glass flakes coated with titanium oxide (particle size 10-30 μm, thickness 0.5 μm-5 μm), synthetic mica flakes (aluminum oxide, magnesium oxide, silicon dioxide, A pigment in which a metal oxide such as titanium oxide or iron oxide is coated (coated with 50 nm to 400 nm) on a fluorine compound or the like can be used.
Artificially synthesized materials are preferable because they have a sharp particle size distribution with little variation in particle size, a smooth surface, and a uniform shape.
Moreover, if the thickness of the bright metal thin film formed on the flake surface is not a predetermined thickness, the wavelength of light reflected to a predetermined reflection angle is shifted. For this reason, the variation in the thickness of the transparent metal thin film on the flakes needs to be within ± 20%, and further within ± 10%. At 20%, the wavelength variation is almost 17%. At 10%, it is about 10%.
Of course, this wavelength changes depending on the refractive index variation of the transparent metal thin film, but the accuracy of formation by the liquid phase method or the CVD method (compound vapor deposition method) is very high, which affects the color change of the present invention. There is not much variation.
When this transparent metal thin film is made of titanium dioxide (the refractive index changes depending on the degree of oxidation) and the thickness is 90 nm to 100 nm, the vertical reflected light becomes the infrared region, and the color changes even when observed from the vertical direction. Although it cannot be recognized, red reflected light (“red”: 620 nm to 750 nm) is exhibited by reflected light of 60 to 70 degrees, and thus red can be recognized in oblique observation.
By using this color variable pigment as a color variable ink composition and using a suitable forming method as a color variable ink layer, when the incident angle of light to be observed changes from 0 degrees to 70 degrees, it is selectively used. A color variable ink layer in which the wavelength of reflected light is shifted from the visible region to the ultraviolet region of 500 nm or less can be formed.
When the thickness of the titanium dioxide of this transparent metal thin film is 300 nm to 330 nm, the vertical reflected light becomes blue (“blue”: 450 nm to 495 nm), but when the observation angle is increased, the reflected light becomes in the ultraviolet region. Because it enters, the color can no longer be recognized.

By using this color variable pigment as a color variable ink composition and using a suitable forming method as a color variable ink layer, when the incident angle of light to be observed changes from 0 degrees to 70 degrees, it is selectively used. A color variable ink layer in which the wavelength of the reflected light is shifted from the infrared region to the visible region of 500 nm or more can be formed.
When these color variable ink layers are laminated, the laminate (color variable medium) exhibits “blue” as vertical reflected light, and “red” when reflected at 70 degrees when viewed at 70 degrees. In other words, it becomes a color variable medium showing “red shift”.
From the optical objectability of the color variable pigment (meaning that it shows the same optical properties when viewed from above or below the pigment), the laminate is from the observing side,
A color variable ink layer is formed in which the wavelength of the selectively reflected light shifts from the infrared region to the visible region of 500 nm or more when the incident angle of the light to be observed changes from 0 degree to 70 degrees. When the incident angle of the light to be observed changes from 0 degrees to 70 degrees, the color variable is formed with a color variable ink layer in which the wavelength of the selectively reflected light shifts from the infrared region to the visible region of 500 nm or more. The medium may be used, and conversely, when the incident angle of the light to be observed changes from 0 degree to 70 degrees from the observation side, the wavelength of the selectively reflected light is 500 nm or more from the infrared region. A color variable ink layer that shifts to the visible region is formed, and when the incident angle of light to be observed changes from 0 degrees to 70 degrees, the wavelength of the selectively reflected light is 500 nm from the infrared region. Colors shifting to the above visible range It may be color variable medium to form a variable ink layer.
The light to be observed is incident on the color variable ink layer positioned on the upper layer when viewed from the observation side, and the reflected light having the selected wavelength and the light transmitted through the layer (this light has no wavelength selectivity). The light transmitted through the flakes described above is transmitted through the optical object and is not subject to interference other than the reduction in intensity.) Only the light transmitted through the layer is under the layer. The light reaches one color variable ink layer, and is divided into reflected light having a wavelength selected in the layer and light transmitted through the layer.
The light having a selective wavelength reflected in the lower layer is not affected by the reflection angle or the wavelength (except for intensity reduction) for the reason described above when transmitted through the upper layer, and is reflected only in that layer. Observed as was.

Therefore, the pigment shape and dispersibility of the upper layer and the lower layer can be selected appropriately when each layer is independent. However, in order to adjust the strength, the solid content of the upper layer (color variable ink layer formation) The ratio of the pigment in the component (consisting of pigment, resin, and additive) is 10% to 30%. In order to obtain a predetermined reflected light intensity, mixing of 10% or more is necessary. However, if it exceeds 30%, the reflected light intensity of the lower layer becomes weak.
On the other hand, the ratio of the pigment in the lower layer is 30% to 50%. If it exceeds 50%, the interaction between the pigments, such as aggregation between the pigments, becomes strong, and it becomes difficult to be parallel to the color variable ink layer forming surface, and if it is less than 30%, the reflection is equivalent to the reflected light intensity of the upper layer. It becomes difficult to obtain the light intensity.
In addition, a method of increasing the uniformity of the upper layer transmitted light by making the size of the upper layer color variable pigment smaller than the size of the lower layer color variable pigment is also suitable. At this time, it is preferable that the size of the upper layer pigment is 1/2 to 1/5 of the size of the lower layer pigment. Here, the size is “the longest length of the pigment” in order to provide a simple index while corresponding to the area that reflects the observation light.
If it is 1/2 or more, the reflected light of the lower layer is weakened, and if it is 1/5 or less, the selective reflectivity of the reflected light is affected.
The thickness of the color variable ink layer can be adjusted similarly.
Normally, the thickness of the color variable ink layer is 3 μm to 30 μm depending on the color variable pigment used, but for the same reason as described above, the thickness of the upper color variable ink layer is changed to the color of the lower layer. It is also preferable to set it to 1/2 to 1/5 of the thickness of the variable ink layer.
Of course, the configuration of the color variable ink layer is preferably not only two layers, but also four layers or more alternately. When a layer having a small color thickness and a color variable pigment with increased parallelism is laminated, the optical characteristics are uniform and high quality.
Furthermore, each layer may be patterned into a predetermined shape (band shape, checkered pattern shape, halftone dot shape, or other shape).

As the liquid crystal and the liquid crystal for the liquid crystal pigment, a three-dimensional cross-linking substance having a liquid crystal structure having a chiral phase can be used. As the liquid crystal substance having a chiral phase, various cholesteric liquid crystals can be used, and the liquid crystal substance can be manufactured by adding a chiral substance to a nematic, smectic, or discotic structure.
The three-dimensional crosslinkable resin has a polymerizable group, a polycondensable group, or a group capable of polyaddition, and a part of these groups is preferably a polyfunctional group having two or more functions. For example, a methacryloxy group or an acryloxy group. More preferred three-dimensional crosslinkable resins include polyorganosiloxane.
Both of the above are mixed and then reacted by heating under reflux to isolate the product. The resulting product is further melt-mixed with a photopolymerization initiator to form a coating composition, and appropriately on a film such as a polyethylene terephthalate resin film, and further directly on a security object by an appropriate printing method. The security variable object can be formed by stacking the color variable medium of the present invention or the color variable medium of the present invention. At this time, the orientation of the liquid crystal may be improved by using a commonly used alignment film, or may be easily formed by using an appropriate dilution solvent.
In addition, this coating composition is hot-melt coated on a polyethylene terephthalate resin film, oriented by a doctor, then irradiated with ultraviolet rays to crosslink the coating film, and the crosslinked coating film is separated from the film, Finally, it is pulverized by a pulverizer to obtain a liquid crystal pigment.
For the purpose of improving the dispersibility in the ink composition, the liquid crystal pigment may have an organic polymer, oligomer, or low molecular dispersant of about 0.01 mg / m 2 or more on the surface of the liquid crystal pigment. Good.
Cholesteric liquid crystals are induced by adding a small amount of an optically active substance (chiral agent) to nematic liquid crystals, and have a spiral structure with a constant period with respect to the reference direction, thereby showing a refractive index change in the liquid crystal layer. Are layered. The multilayer structure having this refractive index distribution has a property of reflecting the incident light for observation after selecting the wavelength at a predetermined angle.
The wavelength of the selectively reflected light is determined by the refractive index (distribution) of the cholesteric liquid crystal and the interval between the refractive index changing layers. This interval is adjusted by the molecular length of the three-dimensional crosslinkable resin, the position of the functional group, the addition amount of the chiral substance, and the like.
Accordingly, the liquid crystal itself has a refractive index distribution, and this refractive index distribution is formed by laminating the above-described thin films in multiple layers (the portion where the twist of the cholesteric liquid crystal goes around is one layer, and this layer is repeatedly present). By producing the same effect as that of the thin film, selective reflectivity is exhibited, and the wavelength of the reflected light “blue shifts” like the thin film.

However, when the number of the layers increases, “Bragg reflection” occurs, so that only a single wavelength is obtained (meaning that the width of the reflected wavelength is narrowed), and only a predetermined angle is reflected. Therefore, the thickness of the liquid crystal pigment is set so that the refractive index distribution in the liquid crystal pigment is 3 or more and 20 or less (one layer is 200 nm to 1000 nm), and the incident angle is 0 degree to 70 degrees. It is assumed that it has necessary reflected light. If the number of layers is less than 3, the wavelength selectivity is insufficient, and if it exceeds 20, the width of the reflection wavelength is 50 nm or less, and the reflection angle is limited. Preferably, when the number is 5 layers or more and 10 layers or less, the wavelength selectivity and the width of the reflection angle are desired.
That is, when the incident angle of the light to be observed changes from 0 degree to 70 degrees, the wavelength of the selectively reflected light shifts from the visible region of 500 nm or less to the ultraviolet region. The reflection conditions need to be relaxed, and the situation can be shifted from the infrared region to the visible region of 500 nm or more by the same method. Of course, it is not necessary to emit strong reflected light over the entire range of the predetermined angle, and when the authenticity of the continuity of the color change is determined, it is set so that the continuity can be recognized.
When this cholesteric liquid crystal (resined by curing or the like) changes the incident angle of light to be observed from 0 degrees to 70 degrees, the wavelength of the light that is selectively reflected is a visible light having a wavelength of 500 nm or less. A color variable ink layer that shifts from the region to the ultraviolet region and a color variable ink layer that shifts from the infrared region to the visible region of 500 nm or more are laminated to obtain the color variable medium of the present invention.

Further, the cholesteric liquid crystal (resined by curing or the like) is made into flakes, and when the incident angle of light to be observed is changed from 0 degree to 70 degrees as in the case of the pearl pigment, Color-tunable ink layer using a pigment that shifts the wavelength of selectively reflected light from a visible region of 500 nm or less to the ultraviolet region, and a color variable using a pigment that shifts from the infrared region to a visible region of 500 nm or more The ink layer is laminated to obtain the color variable medium of the present invention.
Various resins for ink can be used as the resin for converting the liquid crystal pigment into an ink. In particular, an ionizing radiation curable resin is preferred because of its high curability and physical properties. As the ionizing radiation curable resin, aliphatic acrylates, cycloaliphatic acrylates, and acrylics such as these methacrylates can be used. Furthermore, a vinyl photopolymerizable monomer or oligomer can be used.
In addition, rosin and other natural resins, soybean oil-modified alkyd resins, and other oxidative polymerizable resins, acrylic resins, polyesters, polyvinyl acetate, melamine resins, epoxy resins, phenol resins, etc. Alternatively, a mixture or copolymer of these can be used as appropriate.
As other additives, those similar to the color variable ink composition using a pearl pigment or the like can be used.
Like the pearl pigment, this color variable medium is observed as if the wavelength of the reflected light is “red shifted” when the incident angle of the observed light changes from 0 degrees to 70 degrees. The

The second aspect of the present invention is:
In the color variable medium,
A color variable pigment contained in a color variable ink layer in which the wavelength of the selectively reflected light shifts from a visible region of 500 nm or less to an ultraviolet region;
The ratio with the color variable pigment contained in the color variable ink layer in which the wavelength of the selectively reflected light is shifted from the infrared region to the visible region of 500 nm or more is from 9/1 to 5/5. To do.
According to a second aspect of the invention,
In the color variable medium,
A color variable pigment contained in a color variable ink layer in which the wavelength of the selectively reflected light shifts from a visible region of 500 nm or less to an ultraviolet region;
The ratio with the color variable pigment contained in the color variable ink layer in which the wavelength of the selectively reflected light is shifted from the infrared region to the visible region of 500 nm or more is from 9/1 to 5/5. It is possible to provide a color variable medium.
Usually, when observing the color variable ink layer, first, it is often observed from the vertical direction. Therefore, the color variable ink layer first exhibits red, and changes to blue when the observation angle is changed. That is, “blue shift” is observed.
Therefore, when observing in the vertical direction, blue is displayed from the beginning, changing the angle a little, entering the invisible region (ultraviolet region), and when the color disappears, the observation is terminated at that point, and the observation angle is further increased, It is hard to notice that it becomes 60 degrees to 70 degrees, and again exhibits “red” which is another color.

That is, the unexpectedness can be enhanced by making the pigment exhibiting “red” less than the pigment exhibiting “blue” and reducing it to the same amount or less and further to 1/9. (Here, the same amount means a predetermined mixing ratio of each pigment according to the first aspect of the present invention as “the same amount” and means a ratio to the amount.)
However, if the ratio is less than 1/9, the determination of “red” coloration itself becomes unstable, making it unsuitable for authenticity determination.
As described above, when the observation angle is changed after exhibiting “blue”, the invisible region (the ultraviolet region portion and the infrared region portion overlap each other to a certain large angle, that is, about 50 to 70 degrees, and the color disappears. It is also preferable to design so that it suddenly appears “red” when it is further tilted. The anti-counterfeiting property, that is, the stronger the degree of disappearance of the color (the more no color is caused by scattered light and the colorless state continues), the higher the forgery prevention property is.
The stability of these “color changes” improves the reliability of authenticity proof in authenticity determination.

According to the present invention,
When the incident angle changes from 0 degrees to 70 degrees in a color variable medium including a color variable ink layer including a pigment whose wavelength of selectively reflected light changes according to the incident angle of light to be observed. The wavelength of light selectively reflected by the pigment is
It changes from “blue” and exhibits “red”. In other words, a novel color variable medium exhibiting “red shift” can be provided.
Due to its novelty, it can be applied to various security products to prove its authenticity.
In addition, by adjusting the thickness and pattern shape of the color variable ink layer and the mixing ratio of the color variable pigments to be included, the color change can be adjusted, creating unexpected color change, etc., and further improving anti-counterfeiting Can do.

1 is a cross-sectional view of a color variable medium A showing an embodiment of the present invention, in which light to be observed is incident perpendicularly to a color variable ink layer forming surface (reference direction) and reflected light is reflected vertically. It is. 1 is a cross-sectional view of a color variable medium A showing an embodiment of the present invention, in which light to be observed is incident at a large angle with respect to a reference direction of a color variable ink layer forming surface, and reflected light is as large as the incident angle. It is the figure currently reflected in the opposite direction.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(Color variable ink layer)
The color variable medium A of the present invention includes two types of color variable ink layers A1 and A2 having different optical characteristics. These two types of ink layers are ink layers in which the wavelength of light selectively reflected changes according to the incident angle of light to be observed, respectively, and appropriate color variable pigments are dispersed in appropriate resins and solvents. Thus, the color variable medium A is formed as a color variable ink composition on the surface of a plastic film or the like and forms various anti-counterfeit bodies such as authenticity determination seals and the like and has an excellent anti-counterfeit effect.
Or, by forming two kinds of color variable ink layers directly on the surface of the security object by various methods such as various printing methods, it is used for authenticity judgment by visual observation in various scenes and authenticity verification. It is done.
(Color variable pigment)
The color variable pigment used in the present invention is:
When the incident angle of the light to be observed on the color variable ink layer A changes from 0 degree (3 in the figure) to 70 degrees (4 in the figure), each of the pigments and finally the color is variable. As the light exiting from the ink layer, the wavelength of the selectively reflected light shifts from the visible region of 500 nm or less to the ultraviolet region (for example, 1 in the figure) and 500 nm or more from the infrared region. The pigments are shifted to the visible region (similarly, 2 in the figure).
As the pigment, a pearl pigment, an effect pigment, and a liquid crystal pigment are used.
As a pearl pigment,
Merck Iriodin 100 Silver Pearl, 103 Rutile Sterling Silver, 111 Rutile Fine Satin, 120 Raster Satin, 123 Bright Raster, 151 Rutile Pearl, 153 Flash Pearl, 163, Simmer Pearl, 183 Super Nova White, 201 Rutile Fine Gold, 211 Rutile Fine Red, 221 Rutile Fine Blue, 223 Rutile Fine Lilac, 231 Rutile Fine Green, 205 Rutile Platinum, 215 Rutile Red Pearl, 217 Rutile Red Pearl, 219 Rutile Lilac Pearl, 225 Rutile Blue Pearl, 235 Rutile Green Pearl, 249 Flash Gold, 259 Flash Red, 289 Flash Blue, 299 Flash Green, 300 Gold Ludo Pearl, 302 Gold Satin, 303 Royal Gold, 306 Olympic Gold, 309 Medallion Gold, 320 Bright Gold, 323 Royal Gold, 351 Sunny Gold, 355 Glitter Gold, 500 Bronze, 502 Red Brown, 504 Red, 505 Red Violet, 507 Sheila Bread, 520 bronze satin, 522 red brown, 524 red satin, 530 glitter bronze, 532 glitter red brown, 534 glitter red, etc. are used.

Further, Pearl Glaze MM-100R, MF-100, MF-100RN, ME-100, MS-100R, MY-100RF, MRB-100RF, MV-100RF, MB-100RF, MG-100RF, MC-, manufactured by Sano Paint Co., Ltd. 302, MC-323R, MC-326R, MC-520, MC-522, MC-524, etc.
BASF Corp. DESERT REFLECTIONS CANYON SUNSET, DESERT REFLECTIONSPAINTED DESERT PLUM, TIMICA SILK WHITE, TIMICA NU-ANTIQUE SILVER, FLAMENCO SATIN BLUE, FLAMENCO SATIN PEARL 3500, CLOISONNE RED, CLOISONNE VIOLET, CLOISONNE BLUE, CLOISONNE SATIN BRONZE, SATAIN BLUE, DUOCROME RO , DUOCROME RO, DUOCROME VB, GEMTONE GARNET, GEMTON MAUVE QUARTZ, CELLINI RED, CELLINI BLUE, REFLECKS AYS OF RED, REFLECKS BEAMS OF BLUE, CHROMA-LITE DARK BLUE, CHROMA-LITE MAGENTA, COSMICA BLUE, RED, ORANGE or the like is used.
As an effect pigment,
SILALIC F60-50SW FIREDIDE COPPER, F60-51SW RADIANT RED, T60-10SW CRYSTAL SILVER, T60-20 SW SUNBEAME GOLD, T60-21 SW SOLARIS RED, T60-23 SWGAL ELG T60-22 WNT AMETHYST DREAM, T60-25 SW COSMIC TURQUIOISE, etc.
Also, Merck Color Stream F20-00WNT AUTAMN MYSTERY, F20-01 WNT VIOLA FANTASY, F20-02 Arctic FIRE, F20-03 TROPIC SUNRISE, F20-03 LAPIS SUNLIGHT H
Merck biflare 49, 83, 84, L200, Minatec 230A-IR, Pyrisma T40-20SW YELLOW, T40-21SWRED, T40-22 SW VIOLET, T40-23 BLUE, T40-24 GREEN, T40-25 TURQUIOISE, T40 -27 INDIGO etc.
In addition, Merck's Miraval SCENIC WHITE, SCENIC GOLD, SCENIC COPPER, SCENIC TURQOISE, MAGIC WHITE, MAGIC GOLD, MAGIC COPPER, MAGIC RED, MAGIC LILAC, MAGIC BLUE, MAGIC BLUE, MAGIC BLUE, MAGIC BLUE

(Cholesteric liquid crystal / cholesteric liquid crystal pigment)
Cholesteric liquid crystals and cholesteric liquid crystals used as the basis for cholesteric liquid crystal pigments include cholesterol halides, monocarboxylic acid cholesterol esters, monocarboxylic acid sitosterol esters, benzoic acid derivative cholestanol esters, dibasic acid dicholesteryl esters, Examples include a chain type liquid crystal polymer compound, a side chain type liquid crystal polymer compound, and a rigid main chain type liquid crystal polymer compound.
More specifically, for example, cholesteryl chloride, cholesteryl acetate, cholesteryl nonanoate, methyl carbonate, ethyl cholesterol, cholesteryl p-methoxybenzoate, sitosteroyl benzoate, sitosteroyl p-methyl benzoate, cholestanyl benzoate, 10, 12- Docosadiin dicarboxylic acid dicholesteryl ester, 8,12-eicosadicarboxylic acid dicholesteryl ester, 10,12-pentacosadiin dicarboxylic acid dicholesteryl ester, dodecadicarboxylic acid dicholesteryl ester, 12,14-hexacosadiin dicarboxylic acid Dicholesteryl ester, 4- (7-cholesteryloxycarbonylheptyloxy) phenoxyoctanoic acid cholesteryl ester, L-glu Min acid -γ- benzyl / L-glutamate -γ- dodecyl copolymers and the like.
Further, cholesteryl formate, cholesteryl acetate, cholesteryl propionate, cholesteryl butyrate, cholesteryl pentanate, cholesteryl hexanate, cholesteryl heptanoate, cholesteryl octanate, cholesteryl nonanoate, cholesteryl decanate, cholesteryl decanate (cholesteryl laurate) Cholesteryl myristate, cholesteryl palmitate, cholesteryl stearate, cholesteryl oleate, cholesteryl oleyl carbonate, cholesteryl linoleate, cholesteryl 12-hydroxystearate, cholesteryl mercaptan, cholesterol chloride, cholesteryl fluoride, cholesteryl bromide, cholesteryl iodide, etc. Can be mentioned.
Preferably, a mixture of three kinds of alkylcholesterol (for example, cholesterol nanoate) and cholesteryl halide (for example, cholesterol chloride) cholesteryl oleyl carbonate is used, and these three types of liquid crystals are used so as to be used at room temperature. Is common.
In addition, it is not limited to the compound shown here, Moreover, these cholesteric liquid crystal compounds can be used 1 type or in mixture of 2 or more types.
As a liquid crystal compound in which a chiral compound is added to a nematic liquid crystal compound to form a cholesteric liquid crystal, 4-substituted benzoic acid 4′-substituted phenyl ester, 4-substituted cyclohexanecarboxylic acid 4′-substituted phenyl ester, 4-substituted cyclohexane Carboxylic acid 4′-substituted biphenyl ester, 4- (4-substituted cyclohexanecarbonyloxy) benzoic acid 4′-substituted phenyl ester, 4- (4-substituted cyclohexyl) benzoic acid 4′-substituted phenyl ester, 4- (4- Substituted cyclohexyl) benzoic acid 4'-substituted cyclohexyl ester, 4-substituted 4'-substituted biphenyl, 4-substituted phenyl 4'-substituted cyclohexane, 4'-substituted cyclohexane, 2- (4-substituted phenyl) -5-substituted pyridine Etc. are used.

Further, a liquid crystal compound having a cyano group or a fluorine atom at least at one end of the molecule and various suitable chiral agents added to these liquid crystal compounds are used. As the chiral compound, “CB-15”, “C-15” (manufactured by BDH), “CM-21”, “CM-22”, “CM-19”, “CM-20”, “CM” (Above, manufactured by Chisso Corporation), "S1082", "S-811", "R-811" (above, manufactured by Merck & Co., Inc.), and the like.
Furthermore, a three-dimensionally crosslinkable liquid crystalline polymerizable monomer molecule or polymerizable oligomer molecule can be used. A layer containing cholesteric liquid crystal molecules can be obtained by adding an arbitrary chiral agent to a predetermined polymerizable monomer molecule or polymerizable oligomer molecule.
Examples of the three-dimensionally crosslinkable monomer molecule include a mixture of a liquid crystal monomer and a chiral compound as disclosed in, for example, JP-A-7-258638 and JP-T-10-508882. As a more specific example, for example, liquid crystalline monomers represented by the following general chemical formulas (1) to (11) can be used. In the case of the liquid crystalline monomer represented by the general chemical formula (11), X is preferably an integer in the range of 2 to 5.

  Moreover, as a chiral agent, a chiral agent as shown, for example by the following general chemical formula (13)-(16) can be used. In the case of the chiral agent represented by the general chemical formulas (12) and (13), X is preferably an integer in the range of 2 to 12, and in the case of the chiral agent represented by the general chemical formula (14), X Is preferably an integer in the range of 2-5.

When oligomer molecules are used, a cyclic organopolysiloxane compound having a cholesteric phase as disclosed in, for example, JP-A-57-165480 can be used. For example, a cholesteric liquid crystal layer can be obtained by adding about several to 10% of a chiral agent to polymerizable monomer molecules or polymerizable oligomer molecules.
Further, a cholesteric liquid crystal having no cholesterol group in which a group having an asymmetric carbon is introduced into a terminal group of a nematic liquid crystal obtained by organic synthesis, or a mixed liquid crystal in which a Schiff nematic liquid crystal is added to a cholesterol derivative is also used. Furthermore, halogen substitution products and esterified products of natural cholesterol (cholesteryl benzoate, cholesteryl chloride, cholesteryl oleate, cholesteryl nonanoate, and the like are also suitable.
Particularly preferably, it has a liquid crystal structure having a chiral phase formed by adding a chiral substance to a nematic, smectic, or discotic structure, and has a polymerizable group, a polycondensable group, or a group capable of polyaddition. For example, an oriented three-dimensional cross-linking substance having a bifunctional or higher polyfunctional group such as a methacryloxy group or an acryloxy group can be used. As the three-dimensional crosslinkable resin, polyorganosiloxane is most suitable because of its performance stability and workability.
Both of the above are mixed and reacted by heating under reflux to isolate the product. The resulting product is further melt-mixed with a photopolymerization initiator to form a coating composition. This coating composition is hot-melt coated on a polyethylene terephthalate resin film, oriented by a doctor, and then irradiated with ultraviolet rays. Is used to crosslink the coating film, and the crosslinked coating film is formed on the film as the first layer, and the second layer is formed on the first layer using the same technique to obtain a laminate. . The number of stacked layers can be selected as appropriate, and it is also preferable to use a multilayer.
Further, a crosslinked coating film is formed on the film, the coating film is separated from the film, and pulverized into a liquid crystal pigment.
In any case, after forming into a film (resin) once, it is made into flakes through a fragmentation process such as crushing and cutting.
For the purpose of improving the dispersibility in the ink composition, those having an organic polymer, oligomer or low molecular dispersant of about 0.01 mg / m 2 or more on the surface of the liquid crystal pigment are also suitable.
(Pearl pigment inks)
Resins used for inks such as pearl pigments include polymethyl methacrylate (refractive index n = 1.49), polymethyl acrylate (n = 1.47), polybenzyl methacrylate (n = 1.57), polybutyl acrylate (N = 1.44), polyisobutyl acrylate (n = 1.48), cellulose nitrate (n = 1.54), methyl cellulose (n = 1.50), cellulose acetate propionate (n = 1.47) ), Polystyrene (n = 1.60), polyethylene terephthalate (n = 1.64), polyvinyl acetate (n = 1.47), polyvinyl chloride / vinyl acetate (n = 1.54), melamine resin (n = 1.56), epoxy resin (n = 1.61), phenol resin (n = 1.60), etc., or a mixture thereof can be used as appropriate. .
The optimum solvent is selected depending on the color variable ink layer forming method.
Solvents include esters: ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, etc., ethers: ethyl ether, etc., ketones: methyl ethyl ketone, isobutyl ketone, methyl isobutyl ketone, glycol ether (Celsolve) ): Ethylene glycol monoethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monoethyl ether acetate, etc., alicyclic hydrocarbons: cyclohexanone, methylcyclohexanone, methylcyclohexanol, etc., aliphatic hydrocarbons: Normal hexane, etc., aromatics: toluene, xylene, etc., alcohols: ethanol, isopropyl alcohol, normal butanol, normal amyl alcohol , Isoamyl alcohol, using isobutanol and mixtures thereof.
These are classified into low boiling point solvents (boiling point 100 ° C or lower), medium boiling point solvents (boiling point 100 ° C to 150 ° C), and high boiling point solvents (boiling point 150 ° C or higher) according to the boiling point. Adjust the flakes to be parallel to the surface of the color variable ink layer, such as mixing with boiling point solvents and devising to gradually dry out while suppressing rapid solvent volatilization.
Furthermore, in consideration of transparency, various additives, dispersants, leveling agents, lubricants, plasticizers, coupling agents, antifoaming agents, ultraviolet absorbers, various curing accelerators and the like are used.
The color variable ink forming method is used in various methods such as offset printing, letterpress printing, gravure printing, nozzle printing, curtain coat printing, silk screen printing, intaglio printing, inkjet printing, etc. in order to fully demonstrate the functions of the present invention. The solvent composition, ink viscosity adjustment and drying / curing methods can be devised.
Of course, in consideration of the environment, it is also preferable to use a water-soluble resin such as polyvinyl alcohol and form the color variable ink layer as a water-based ink composition.

(Cholesteric liquid crystal ink / cholesteric liquid crystal pigment ink)
The following acrylic resins can be used as the ionizing radiation curable resin as a resin for converting the liquid crystal pigment into an ink. That is, acrylic acid, aliphatic acrylate, allyl acrylate, allylated cyclohexyl acrylate, benzyl acrylate, bisphenol A diacrylate, epichlorohydrin modified bisphenol A diacrylate, ethylene oxide modified bisphenol A diacrylate, epichlorohydrin / ethylene oxide modified bisphenol A diacrylate , Ethylene oxide modified bisphenol S diacrylate, ethylene glycol acrylate, propylene glycol acrylate, butylene glycol acrylate, neopentyl glycol acrylate, butoxyethyl acrylate, epichlorohydrin modified aliphatic acrylate, cycloaliphatic acrylate, N, N- Dimethylaminoethyl acrylate, N-diethylaminoethyl acrylate, pentaerythritol tetraacrylate, pentaerythritol triacrylate, dipentaerythritol hexaacrylate, dipentaerythritol monohydroxypentaacrylate, alkyl-modified dipentaerythritol pentaacrylate, alkyl-modified dipentaerythritol tetraacrylate, alkyl-modified di Pentaerythritol triacrylate, caprolactone modified pentaerythritol hexaacrylate, ethylene oxide modified bisphenol A diacrylate, ditrimethylolpropane tetraacrylate, bisphenol epoxy acrylate, glycerol acrylate, glycidyl acrylate, oligoester acrylate, polyester Acrylate, phosphate type acrylate, ethylene oxide-modified phthalic acid acrylates, ethylene oxide-modified phthalic acid acrylate, epichlorohydrin-modified phthalic acid acrylate or urethane acrylate can be used.
Moreover, the following methacrylic type can also be used, and specifically, the corresponding methacrylic acid and the corresponding methacrylic acid ester listed above as the acrylic type can be used. In addition, as the ionizing radiation curable resin, a vinyl-based photopolymerizable monomer or oligomer such as N-vinylpyrrolidone can be used. As the ionizing radiation curable resin, one type or two or more types of monomers or oligomers of the substances described above can be used.

When an ionizing radiation curable resin is used as a resin and ultraviolet rays are used as ionizing radiation, a known photopolymerization initiator is blended. As the photopolymerization initiator, benzophenone-based, benzyl-based, benzoin-based, benzoic acid-based, thioxanthone-based, phenyl ketone-based, oxime-based organic low-molecular compounds, oligomers, or high-molecular compounds can be used. When the blending ratio is excessive, the degree of polymerization decreases. When the blending ratio is too small, the polymerization rate and the polymerization rate decrease. In any case, the drying characteristics and the film strength after printing. Etc. are preferably used at a mass ratio of 0.3 to 20 parts with respect to 100 parts of ionizing radiation curable resin which is a resin.
Dilute this resin with an appropriate dilution solvent, and use a suitable printing method, offset printing method, gravure printing method, screen printing method, intaglio printing method, etc. on a substrate such as a predetermined plastic film or security object. Can be formed and laminated.
When the incident angle of light to be observed changes from 0 degrees (3 in the figure) to 70 degrees (4 in the figure), the wavelength of the light that is selectively reflected is changed from the visible region to the ultraviolet region where the wavelength is 500 nm or less. By changing the liquid crystal to be shifted into a color variable ink composition and using a color variable ink layer (for example, A1 in the figure) by using an appropriate forming method, the incident angle of light to be observed is changed from 0 degrees to 70 degrees. In this case, it is possible to form a color variable ink layer (for example, A1 in the figure) in which the wavelength of selectively reflected light shifts from the visible region to the ultraviolet region of 500 nm or less.
Moreover, when the incident angle of the light to be observed changes from 0 degree to 70 degrees, the color variable ink composition is a liquid crystal in which the wavelength of selectively reflected light shifts from the infrared region to the visible region of 500 nm or more. When the incident angle of the light to be observed is changed from 0 degrees (3 in the figure) to 70 degrees and 70 degrees (4 in the figure) by using a color variable ink layer using an appropriate formation method, A color variable ink layer (for example, A2 in the figure) in which the wavelength of selectively reflected light is shifted from the infrared region to the visible region of 500 nm or more can be formed.
When these color variable ink layers are laminated, the laminate (color variable medium A) exhibits “blue” as the vertical reflected light, and “red” in the 70 ° reflected light that appears in the observation at 70 degrees. The color variable medium A exhibiting so-called “red shift” is obtained.

In the case of liquid crystal pigments, the particle size is larger than the particle size of pigment particles used in general lithographic inks and letterpress inks, so if blended excessively, the fluidity of the ink may be poor, Alternatively, the curability may be lowered, and if it is too small, the color rendering effect as a pigment is reduced. Therefore, the mass ratio is preferably 5 to 100 parts with respect to 100 parts of ionizing radiation curable resin as a resin. It is preferable to use it.
The following can be used for the oxidatively polymerizable resin as a resin for converting the liquid crystal pigment into an ink.
That is, natural resins such as rosin, cured rosin, rosin ester, rosin-derived maleic acid resin, or natural resin derivatives such as rosin-derived fumaric acid resin, phenol resin, rosin-modified phenol resin, rosin-modified xylene resin, fatty acid-modified xylene resin, A synthetic resin such as an oil-modified alkyd resin or soybean oil-modified alkyd resin can be used.
For the purpose of adjusting the viscosity and adjusting the drying speed, the above oxidatively polymerizable resin is usually blended with an oil component. Specific oils are obtained by processing vegetable oils such as linseed oil, linden oil, jute oil, hemp seed oil, safflower oil, soybean oil, palm oil, tall oil, castor oil, or cottonseed oil, or vegetable oil. Polymerized oils, processed oils such as maleic acid, or mineral oils such as machine oil or spindle oil can be used.
When using the oxidation polymerizable resin, various solvents or additives can be blended in addition to the oil. As the solvent, aliphatic hydrocarbon-based, aromatic hydrocarbon-based, alcohol-based, glycol-based, ester-based, or ketone-based solvents can be used. In addition, plasticizers (phthalate ester, adipic acid ester, or sebacic acid ester, etc.), wax (carnauba wax, wax, paraffin wax, polyethylene wax, polytetrafluoroethylene, etc.), dryer (cobalt, etc.) Or manganese metal soap), dispersant (polymer or low molecular surfactant, etc.), thickener (aluminum chelate, etc.), antifoaming agent (silicone, etc.), antioxidant (phenolic or An oxime type or the like), a leveling agent (silicone or the like), or an ultraviolet absorber (benzophenone type or triazole type or the like) can be used.

When using an oxidatively polymerizable resin as a resin, the vehicle component mainly composed of an oxidatively polymerizable resin, an oil component, and a solvent component generally has a higher acid value than an ionizing radiation curable resin. Since the compound itself exhibits a dispersant effect, the blending ratio of the liquid crystal pigment can be increased. However, since the liquid crystal pigment has a large particle size, if it is excessively mixed, the fluidity of the ink may be poor or the curability may be lowered. If it is too small, the color rendering effect as a pigment may be reduced. Preferably, it is preferably used in a mass ratio of 5 to 150 parts with respect to 100 parts of the total amount of the oxidatively polymerizable resin as a resin and the oil.
Further, acrylic resin, cellulose resin, polystyrene, polyester, polyvinyl acetate, melamine resin, epoxy resin, phenol resin, etc., or a mixture or copolymer thereof is appropriately used as a resin for forming a liquid crystal pigment into an ink. be able to.
As other additives, those similar to the color variable ink composition using a pearl pigment or the like can be used.
The same solvent as the color variable ink composition using a pearl pigment or the like can be used.
When the incident angle of light to be observed changes from 0 degrees (3 in the figure) to 70 degrees (4 in the figure), the wavelength of the light that is selectively reflected is changed from the visible region to the ultraviolet region where the wavelength is 500 nm or less. By making the color variable pigment to be shifted into a color variable ink composition and using the appropriate formation method as a color variable ink layer (for example, A1 in the figure), the incident angle of light to be observed is 0 to 70 degrees. A color variable ink layer (A1 in the figure as an example) in which the wavelength of light that selectively reflects is shifted from the visible region to the ultraviolet region with a wavelength of 500 nm or less can be formed.
In addition, when the incident angle of the light to be observed changes from 0 degree to 70 degrees, a color variable ink composition that changes the wavelength of the selectively reflected light from the infrared region to the visible region of 500 nm or more is used. When an incident angle of light to be observed is changed from 0 degree (3 in the figure) to 70 degrees and 70 degrees (4 in the figure) by forming a color variable ink layer using an appropriate formation method. In addition, a color variable ink layer (A2 in the figure as an example) in which the wavelength of selectively reflected light is shifted from the infrared region to the visible region of 500 nm or more can be formed.
When these color variable ink layers are laminated, the laminate (color variable medium A) exhibits “blue” as the vertical reflected light, and “red” in the 70 ° reflected light that appears in the observation at 70 degrees. The color variable medium A exhibiting so-called “red shift” is obtained.
As in the case of pearl pigments and the like, this color variable ink layer has a wavelength of selectively reflected light of 500 nm or more from the infrared region when the incident angle of light to be observed changes from 0 degrees to 70 degrees. When the color changeable ink layer A1 that shifts to the visible region is formed and the incident angle of the light to be observed changes from 0 degree to 70 degrees, the wavelength of the selectively reflected light is changed from the infrared region. The color variable medium A may be formed with the color variable ink layer A2 that shifts to a visible region of 500 nm or more, and conversely, the incident angle of light to be observed changes from 0 degree to 70 degrees from the observation side. In this case, a color variable ink layer A1 in which the wavelength of selectively reflected light is shifted from the infrared region to the visible region of 500 nm or more is formed, and the incident angle of the light to be observed is changed from 0 degree to 70 degrees below it. And selective when changing Wavelength of the reflected light may be color variable medium A to form a color changeable ink layer A2 to shift from the infrared region to 500nm or more in the visible region.

The light to be observed is incident on the color variable ink layer A1 positioned in the upper layer when viewed from the observation side, and the reflected light having the selected wavelength and the light transmitted through the layer (this light is specific to the liquid crystal pigment). Only the light that has passed through the layer reaches the other color variable ink layer A2 under the layer. The light is divided into reflected light having a wavelength selected in the layer and light transmitted through the layer.
The light having a selective wavelength reflected in the lower layer is not affected by the reflection angle or the wavelength (except for intensity reduction) for the reason described above when transmitted through the upper layer, and is reflected only in that layer. Observed as was.
Therefore, the pigment shape and dispersibility of the upper layer and the lower layer can be selected appropriately when each layer is independent. However, in order to adjust the strength, the solid content of the upper layer (color variable ink layer formation) The ratio of the pigment in the component (consisting of pigment, resin, and additive) is 10% to 30%. In order to obtain a predetermined reflected light intensity, mixing of 10% or more is necessary. However, if it exceeds 30%, the reflected light intensity of the lower layer becomes weak.
On the other hand, the ratio of the pigment in the lower layer is 30% to 50%. If it exceeds 50%, the interaction between the pigments, such as aggregation between the pigments, becomes strong, and it becomes difficult to be parallel to the color variable ink layer forming surface, and if it is less than 30%, the reflection is equivalent to the reflected light intensity of the upper layer. It becomes difficult to obtain the light intensity.
In addition, a method of increasing the uniformity of the upper layer transmitted light by making the size of the upper layer color variable pigment smaller than the size of the lower layer color variable pigment is also suitable. At this time, it is preferable that the size of the upper layer pigment is 1/2 to 1/5 of the size of the lower layer pigment. Here, the size is “the longest length of the pigment” in order to provide a simple index while corresponding to the area that reflects the observation light.
If it is 1/2 or more, the reflected light of the lower layer is weakened, and if it is 1/5 or less, the selective reflectivity of the reflected light is affected.
The thickness of the color variable ink layer can be adjusted similarly.
Usually, depending on the color variable pigment used, the thickness of the color variable ink layer is 3 μm to 30 μm, but for the same reason as described above, the thickness of the upper color variable ink layer A1 is It is also preferable to set it to 1/2 to 1/5 of the thickness of the color variable ink layer A2.
Of course, the configuration of the color variable ink layer is preferably not only two layers, but also four layers or more alternately. As a layer with a small thickness, a layer with enhanced parallelism of color variable pigments is laminated, and the optical properties are uniform and of high quality, that is, the scattered light is reduced when the color changes, and the wavelength selection of reflected light is highly accurate. Become.
When alternately laminating, each layer of 1 μm to 5 μm is changed from 4 layers to 8 layers, and the total thickness is set to 4 μm to 30 μm.
Furthermore, each layer may be patterned into a predetermined shape (band shape, checkered pattern shape, halftone dot shape, or other shape).
In the case of a strip shape, when one color variable ink layer is in the shape of a strip, a pattern, halftone dots, or other shapes, the unit size may be set to 100 μm to 5 mm width, and a predetermined character, symbol, figure, or the like may be designed. . As a result, only a part of this part formed can observe a so-called “red shift”.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, it is not limited to this. In addition, except a solvent, each composition of each layer is a mass part of solid content conversion.
Example 1
A color variable ink composition was prepared using a pearl pigment as the color variable pigment 1.
As the color variable pigment 1, Iriodin type pigment B (manufactured by Merck & Co., Inc., coated with 300 nm of titanium oxide on a natural mica flake, particle size of 5 to 25 μm, thickness of 2 to 5 μm: 0 degree reflection 450 nm, 70 degree reflection 200 nm) The following ink composition was prepared and treated for 30 minutes in a ball mill containing 2 mm diameter glass beads for prevention of pigment aggregation and uniform dispersion to obtain a color variable ink composition.
<Ink composition>
Pigment B 10 parts by mass Urethane acrylate (refractive index n = 1.49) 30 parts by mass Ethyl acetate 30 parts by mass Isobutyl acetate 20 parts by mass Methyl isobutyl ketone 10 parts by mass Benzophenone photoinitiator 0.1 part by mass This color variable ink The composition was subjected to blade coating (coating while applying a blade share) on a PET film having a thickness of 25 μm to a thickness of 5 μm after drying, and cured by irradiating with ultraviolet rays to obtain a color variable ink layer A1.
Next, the following ink composition was used by using Iriodin type pigment C (manufactured by Merck & Co., Inc., natural mica flakes coated with titanium oxide 100 nm, particle size 5 to 25 μm, thickness 2 to 5 μm: 0 degree reflection 1500 nm, 70 degree reflection 700 nm). It was a thing. In order to prevent the pigment from agglomerating and to uniformly disperse, it was treated with a ball mill containing 2 mm diameter glass beads for 30 minutes to obtain a color variable ink composition.
<Ink composition>
Pigment C 10 parts by mass Urethane acrylate (refractive index n = 1.49) 30 parts by mass Ethyl acetate 30 parts by mass Isobutyl acetate 20 parts by mass Methyl isobutyl ketone 10 parts by mass Benzophenone photoinitiator 0.1 part by mass This color variable ink The composition is coated on the color variable ink layer A1 by blade coating (coating while applying a blade share) to a thickness of 5 μm after drying, and cured by irradiating with ultraviolet rays to obtain a color variable ink layer A2. Thus, a color variable medium A as a laminate was obtained.
In this color variable medium layer A, when the light 3 to be observed was in a direction perpendicular to the ink layer surface and the reflected light 4 was observed in almost the same direction, a purple to blue color could be observed.
Further, when the light 3 to be observed is incident at an angle of 70 degrees from the direction perpendicular to the ink layer surface and the reflected light 4 that appears in the opposite direction at the same angle is observed, red can be observed. As a result, a so-called “red shift” was confirmed.
When this color variable ink layer formed product is applied as a small piece of 20 mm × 20 mm on the color variable ink layer A2 and affixed on a credit card which is a security object, the appearance according to the observation angle is normal. Since it seemed to be a so-called “red shift” instead of “blue shift”, its authenticity could be confirmed very easily by visual observation.

(Example 2)
Example 2 was obtained in the same manner as in Example 1 except that the stacking order of the color variable ink layers A1 and A2 of Example 1 was reversed. (The adhesive is applied on the color variable ink layer A1.)
The effect was the same as in Example 1.
(Example 3)
The ratio of the pigment B in the color variable ink layer A1 of Example 1 is 6 parts by mass with 10 parts by mass in the ink composition, and the ratio of the pigment C in the color variable ink layer A2 is the ink composition. Example 3 was obtained in the same manner as in Example 1 except that the content of 10 parts by mass was changed to 20 parts by mass.
As compared with Example 1, the effect of blue and red was well balanced and observed with almost the same intensity, and the authenticity could be confirmed very easily by visual observation.
Example 4
A color variable ink composition was prepared using a liquid crystal pigment as the color variable pigment 1.
As the color variable pigment 1,
Using Liquid Crystal Pigment 1 (Helicone HC Sapphire XS, manufactured by Wacker, Germany), the following ink composition was prepared, treated for 30 minutes with a ball mill containing 2 mm glass beads to prevent pigment aggregation and uniformly disperse the color. An ink composition was obtained.
<Ink composition>
Liquid crystal pigment 1 10 parts by weight Polyester acrylate 30 parts by weight Ethyl acetate 30 parts by weight Isobutyl acetate 20 parts by weight Methyl isobutyl ketone 10 parts by weight Benzophenone photoinitiator 0.1 part by weight This color variable ink composition is PET having a thickness of 25 μm The film was subjected to blade coating (coating while applying a blade share) to a thickness of 5 μm after drying, and cured by irradiating with ultraviolet rays to obtain a color variable ink layer A1.
Next, a liquid crystal pigment 2 (Helicone HC Maple XS manufactured by Wacker, Germany) was used to prepare the following ink composition. In order to prevent the pigment from agglomerating and to uniformly disperse, it was treated with a ball mill containing 2 mm diameter glass beads for 30 minutes to obtain a color variable ink composition.
<Ink composition>
Liquid crystal pigment 2 10 parts by weight Polyester acrylate 30 parts by weight Ethyl acetate 30 parts by weight Isobutyl acetate 20 parts by weight Methyl isobutyl ketone 10 parts by weight Benzophenone photoinitiator 0.1 part by weight This color variable ink composition is mixed with the above color variable ink layer. Blade coating (coating while applying a blade share) on A1 to a thickness of 5 μm after drying, curing by irradiating with ultraviolet rays to obtain a color variable ink layer A2, and a color variable medium as a laminate A was obtained.
The following was the same as Example 1, and Example 4 was obtained.
In the same observation as in Example 1, a so-called “red shift” could be confirmed, and authenticity could be easily confirmed.

(Example 5)
Prepare a film having an alignment film formed by rubbing a polyimide resin thin film on one side of a 50 μm thick polyethylene terephthalate film, and apply the following polymerizable cholesteric liquid crystal solution on the alignment film. The film was coated to 5 μm and dried at 90 ° C. for 10 minutes to align the liquid crystal layer. Thereafter, the aligned liquid crystal layer was irradiated with ultraviolet rays at 100 mJ / cm 2 (365 nm) using an ultraviolet irradiation device to polymerize the liquid crystal layer to form a three-dimensionally crosslinked liquid crystal layer.
<Cholesteric liquid crystal solution (1)> Polymerizable cholesteric liquid crystal solution Polymerizable monomer exhibiting a nematic liquid crystal phase (chemical formula (11)) 25 parts by mass Chiral agent (chemical formula (14)) 1 part by mass Irgacure manufactured by Ciba Specialty Chemicals 907 1 part by mass Cyclohexanone 73 parts by mass This cholesteric liquid crystal layer had no reflected light in the vertical direction, and turned red at 50 degrees when the angle was changed. This obtained the 1st layer of the color variable ink layer. (A2 in FIGS. 1 and 2 corresponds to the case without pigment 2)
In the same manner, a cholesteric liquid crystal solution (2) containing 4 parts by mass of a chiral agent (chemical formula (14)) was prepared, and 5 μm was formed on the first layer of the color variable ink layer described above. Example 5 was obtained by doing this (corresponding to A1 in FIG. 1 and FIG. 2 without pigment 1).
When the laminated body which is the color variable medium A is observed, it is said that “red” exhibits blue in the vertical direction (4 in FIG. 1) and red at 70 degrees (4 in FIG. 2) when the angle is changed. We were able to recognize "shift". The angle range of the color tone that can be observed with a different texture from Example 1 was narrow, and it seemed difficult to reproduce the same easily. Moreover, since it has a unique observation angle dependency, it seems to have a high anti-counterfeiting property.

(Comparative Example 1)
Comparative Example 1 was obtained in the same manner as Example 1, except that Mercury Pearl Pigment Color Stream Standard Model F10-01 Viola Fantasy was used as the pearl pigment.
When observed in the same manner as in Example 1, “blue shift” generally observed from red to green and blue was confirmed.
This change was common and seemed insufficient to verify authenticity.
(Evaluation test) The observation light is an ordinary white light source, and the observation object is visually observed from the vertical direction as shown in FIG. Observation. Further, as shown in FIG. 2, the light reflected from the direction inclined by 70 degrees from the vertical direction was visually observed.
(Evaluation results)
In Examples 1 to 5, a so-called “red shift” could be observed.
Compared to Example 1, in Example 2, each color was observed slightly clearly. In Example 3, the amount of red color was slight, but “red” could be confirmed with certainty, and unexpectedness was brought about. Although Example 4 had a different texture from Examples 1-3, the so-called “red shift” was sufficiently confirmed. Although Example 5 also had a different texture, the so-called “red shift” could be sufficiently confirmed. From this, it was judged that sufficient authenticity could be confirmed.
As described above, Comparative Example 1 confirmed the “blue shift” generally observed. This color change seemed insufficient to verify authenticity.

A: Color variable medium showing one embodiment of the present invention A1: Color variable ink layer (shown when pigment 1 is included)
A2: Color variable ink layer (shown when pigment 2 is included)
1: Pigment whose wavelength of selectively reflected light changes (pearl pigment, liquid crystal pigment, etc.)
2: A pigment whose wavelength of selectively reflected light changes (pearl pigment, liquid crystal pigment, etc. different from pigment 1)
3: Light to be observed 4: Light reflected

Claims (2)

A color variable ink layer in which the wavelength of light selectively reflected shifts from a visible region of 500 nm or less to an ultraviolet region when the incident angle of light to be observed changes from 0 degree to 70 degrees;
A color-variable ink layer that shifts the wavelength of selectively reflected light from the infrared region to the visible region of 500 nm or more when the incident angle of light to be observed changes from 0 degree to 70 degrees is laminated. A color variable medium characterized by In the color variable medium,
A color variable pigment contained in a color variable ink layer in which the wavelength of the selectively reflected light shifts from a visible region of 500 nm or less to an ultraviolet region;
The ratio with the color variable pigment contained in the color variable ink layer in which the wavelength of the selectively reflected light is shifted from the infrared region to the visible region of 500 nm or more is from 9/1 to 5/5. To change color.

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