JPS6351193A - Card for preventing forgery - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides a card that can easily detect forgeries of various cards such as magnetic cards, optical cards, and IC cards, and is effective in preventing counterfeiting. .

<Conventional technology> In recent years, the number of cards issued, mainly magnetic cards, has increased dramatically, and there is an extremely wide variety of cards, including cash cards issued by banks and other financial institutions, and credit cards used in the distribution field. used in the field. These have become widely popular due to their simplicity and the ease of not having to carry cash, and are expected to continue to increase in the future.

However, with the spread of cards, card crimes such as card theft, misuse, and counterfeiting are also rapidly increasing.
Card manufacturers, banks, and other card users are struggling to take countermeasures. In the near future, cards with personal information such as ID cards will become widespread, and if we enter a cashless era, card crimes such as card forgery will become more common in order to maintain personal confidentiality and property. It seems that the need to prevent this will increase even more than now.

Currently, magnetic carts, which make up the majority of cards, have magnetic records that can be easily erased and written to.
It is extremely easy to forge, which has become a serious problem, and various efforts are being made to prevent counterfeiting.

For example, a method of embedding, engraving, or transferring a face photo on a regular magnetic card for visual identification, a method of special printing such as fine/precision printing or fluorescent printing to make counterfeiting difficult, or a method of printing an optical interference image (hologram). The method used has been devised. However, facial photos, special printing, etc. are costly and have the disadvantage that they are not sufficiently effective in preventing counterfeiting, and the use of holograms naturally increases the card cost. Methods have also been devised in which the magnetic layer itself is modified, although the layer itself is not modified. For example, methods that make erasing difficult by using a high coercivity material in the magnetic layer, methods that use multiple magnetic material layers, methods that hide magnetic recording by providing a magnetic shielding layer, and non-erasable magnetic recording such as the water mark method. There are methods such as using the law. However, these methods are still costly and
A significant drawback is that it requires significant changes to the systems currently in widespread use. Other systems are being considered that use optical, electrical, and magnetic sensors to give cards a property that can be detected by these sensors to determine authenticity, but this would complicate card manufacturing and would be difficult. However, it still has the disadvantage of requiring changes to the system.

As described above, there is currently no means for preventing card counterfeiting that is simple, effective, and does not require major changes to the system without increasing the cost of magnetic cards.

Furthermore, optical cards are being developed as next-generation high-performance cards due to their large storage capacity, and IC cards are being developed as next-generation high-performance cards due to their calculation and information processing functions. Counterfeiting is possible by reading the pits with a microscope, and an effective counterfeit prevention method is desired.

<Problems to be solved by the invention> The present invention solves the above-mentioned problems, can be applied to various carts such as magnetic cards, optical cards, and IC cards, is economically superior, and significantly improves system performance. To provide a card with a large anti-counterfeiting effect, whose authenticity can be easily determined without requiring any modification.

Means for Solving the Problems> The present invention provides at least a part of the surface of various cards such as magnetic cards, optical cards, and IC cards, which is made of cholesteric liquid crystal polymer and has a fixed cholesteric liquid crystal structure. Concerning a card with a film.

The present inventors have discovered that counterfeit cards can be easily identified by utilizing the properties of wavelength selective reflection, circularly polarized light selective reflection, and color change due to changes in viewing angle that cholesteric liquid crystals have, and that the cholesteric liquid crystal structure is fixed. The present invention was achieved by discovering that it can be stably used as a card by forming a polymer film that is kept at room temperature.

The helical pitch length of cholesteric liquid crystal is P.

The average refractive index is D, and the angle of incidence of light on the cholesteric surface is O.
Then, light with a wavelength λ expressed as λ=npsin O is selectively reflected. Moreover, at this time, the structure is determined by the absolute configuration of the asymmetric carbon.

It selectively reflects only either the right-handed circularly polarized component or the left-handed circularly polarized component of light with wavelength λ. Also, λ=npsin
As is clear from the equation of O, λ varies depending on the angle of light incident on the cholesteric surface (film surface), and therefore the visible wavelength λ, or color in the case of visible light, changes depending on the angle at which the cholesteric surface is viewed. These colors, called cholesteric colors, are unique and beautiful colors that cannot be produced by any other means and are visible to the human eye. These wavelength-selective reflectivity, circularly polarized light-selective reflectivity, visual angle dependence of colors, and beautiful colors of cholesteric colors are all difficult to express with other substances or methods, so cards that utilize these properties are It is difficult to forge, and a counterfeit card can be easily identified, making it extremely effective in preventing card forgery.

In the present invention, the method for producing a polymer film having a cholesteric liquid crystal structure includes, for example: (1) A lyotropic liquid crystal polymer is dissolved and held in a polymerizable polymer to grow a cholesteric liquid crystal, and then a lyotropic liquid crystal is grown using light or radiation. A method of polymerizing Zuma to immobilize the cholesteric structure.

■ A method in which a thermotropic cholesteric liquid crystal polymer is heated above its liquid crystal transition point to grow a liquid crystal structure, and then rapidly cooled to fix the liquid crystal structure.

Examples include. Among these methods, the method using lyotropic liquid crystalline polymers requires a long time for liquid crystal growth and requires precise control of solution concentration, temperature, etc. in order to obtain the desired selective reflection wavelength λ. It is not necessarily suitable for industrial production. As an industrially suitable manufacturing method, method (2) is preferred. (According to method D, a liquid crystal structure can be formed in a short time by simply heating and melting without using a solvent, and a film with a fixed cholesteric liquid crystal structure can be easily obtained by air cooling or water cooling. Can be done.

It is desirable that the liquid crystalline polymer used be one that can easily and completely obtain a cholesteric liquid crystal structure, that can be easily fixed and maintained at room temperature, and that can be easily formed into a film. Preferred cholesterin liquid crystal polymers include, for example, j) a main chain type liquid crystal having a mesogen and a chiral component in the main chain; n) a homopolymer or copolymer of an acrylic ester or a methacrylic ester in which some of the ester groups are A new type of liquid crystal is a side-chain type liquid crystal in which a chiral component such as a cholesterol derivative is bonded to a thermotropic cholesteric liquid crystal. .

Type i) is generally expressed by the following formula.

The bonding mode that connects these chiral components, achiral components, and mesogens is ``○ ○ Among them, polymers bonded by -〇-〇-, that is, thermotropic cholesteric liquid crystalline polyesters, have a wide variety of types and are easy to synthesize. Things.

Due to the stability of the material, it can be cited as the most suitable example of a main chain type liquid crystal.

For example, as a chiral component, -C-CH, -CH-CH, -CH2-0-.

CI (□ N) is often used. Also, as the achiral component, ○ O CH3 (p is an integer from 2 to 20) etc. are preferably used. As the mesogen, CH, OCR, 0 (X, Y are each independently (X represents hydrogen, halogen, or an alkyl group having 4 or less carbon atoms) X ○ (X represents hydrogen, halogen, or an alkyl group having 4 or less carbon atoms) ○ is preferably used. By various combinations of these three components, thermotropic cholesteric liquid crystalline polymers having various properties can be obtained, and the molecules can be designed freely depending on the desired reflection wavelength range or circular polarization property. Can be done.

Representative examples of type ii) include acrylic ester copolymers and methacrylic ester copolymers. For example, a copolymer having a structural unit represented by the following formula % is preferably used. In the formula, X is H or CH, Y represents a chiral component, and 2 represents a mesogen. Preferred examples of Y include -CH2-C-CH, -CH3, cholesteryl, etc.

and a preferable example of 2 is ◎-CO○-◎-OC
H.

-◎-◎-2-◎-◎-CN, -◎-◎-○CI(,.

-@-CI-(=N-◎-CN.

One ◎-coo-@-◎-〇CH, etc. can be given. By selecting the ratio of Q and m and various combinations of X, Y, and Z, it is possible to design a thermodropink cholesteric liquid crystalline polymer suitable for the purpose of the present invention. Another example of type (2) is a type of polymer in which chiral components and mesogens are bonded to the side chains of polysiloxane, which can also be used in the present invention, but considering the strength when made into a film, Acrylic ester copolymers and maryacrylic ester copolymers are more preferred.

Examples of this type of liquid crystal include poly(γ-methylglutamate), poly(γ-benzylglutamate), and hydroxypropyl cellulose, which are known as otropink cholesteric liquid crystals, and are thermoplastic by introducing flexible long-chain alkyl groups into them. Examples include tropic polymers. Among them, thermotropic cholesteric liquid crystalline polypeptides such as poly(γ-methyl D-glutamate C○-γ-hexyl D-glutamate) and poly(γ-benzyl L-glutamate co-γ-alkyl L-glutamate) are It is easy to fix the structure, has excellent film formability, has a sharp selective reflection spectrum and a wide wavelength range, and has the desired selective reflection wavelength λ.
Since it is difficult to counterfeit and can easily identify counterfeit cards, it can be exemplified as the most effective polymer for preventing counterfeiting in the present invention.

These cholesteric liquid crystal polymers differ in single selective reflection wavelength region and circular polarization selectivity depending on their molecular structure. Therefore, there is a wide range of choices regarding which property or wavelength range to use for counterfeit prevention, and an appropriate polymer can be selected depending on the purpose. Next, the counterfeit prevention means in the present invention will be specifically described.

1) Select a polymer with a reflection wavelength in the visible region, and use a film with a fixed cholesteric structure so that it exhibits a yellow to red cholesteric color.
It takes advantage of the property that colors on the lower wavelength side can be seen in response to changes in θ (in response to changes in viewing angle).

2) A film having a specific reflection wavelength λ is produced, irradiated with white light, reflected light of the wavelength λ is detected, and authenticity is determined based on the presence or absence of the reflected light. Or instead of white light, light of wavelength λ (
For example, the 0.63 μm light of He-Ne laser,
The authenticity is determined by the presence or absence or strength of the reflected light by irradiating it with 0.84 μm light from a semiconductor laser. At this time, if a transparent film with a reflection spectrum in the infrared region is used, it looks the same as a normal transparent film, but when irradiated with light such as a semiconductor laser, it shows a clear reflection, so it is easy to tell whether it is genuine or not. can be determined.

3) In addition to detecting a specific reflected wavelength, the authenticity can be determined more easily by detecting right-handed or left-handed circularly polarized light using a circularly polarizing filter or the like.

4) Different reflection wavelengths λ4. Two or more cholesteric films having λ2... are bonded together and white light is irradiated thereto to detect a reflection spectrum having a plurality of reflection peaks.

5) When cholesteric liquid crystal is formed, a transparent film without a liquid crystal structure is made by casting using a polymer that exhibits a reflection spectrum in the ultraviolet or infrared region, and then a desired pattern such as letters or images is formed. By heating cholesteric liquid crystals to grow cholesteric liquid crystals and then rapidly cooling and fixing them, we can create films that are transparent in appearance but can only be read by detecting reflected light (ultraviolet or infrared light). to make. Authenticity is determined by detecting hidden patterns.

In addition to those exemplified in 1) to 5), various methods utilizing the properties of cholesteric liquid crystals can be used.
These methods allow the authenticity of cards to be determined very easily, and the use of specific cholesteric liquid crystalline polymers has an excellent effect in preventing counterfeiting.

These properties naturally appear in low-molecular cholesteric liquid crystals, so low-molecular liquid crystals can be used as means for preventing card counterfeiting. However, it is desirable to use polymers in terms of stability and ease of forming into a film. The molecular weight of these polymers is such that the intrinsic viscosity ([η]) measured in a solvent in which the polymer is dissolved is 0. Those with an O of 1 to 3.0 are preferred, and those with an O of 0.5 to 2.0 are particularly preferred. If [η] is 0.01 or less, the strength when formed into a film is low, and in some cases, cholesteric liquid crystallinity may not be exhibited, which is not preferable. If [η] is larger than 3.0, the viscosity is too high and sufficient cholesteric orientation cannot be obtained, and synthesis and film forming are also difficult and undesirable.

When using films obtained from these polymers in cards, there is no need to perform complicated processing on the card, just by pasting or laminating the film on the surface of the card, so there is no need to increase the cost of the card. By using the viewing angle dependence of cholesteric colors, it is possible to determine authenticity by visual discrimination alone.

Even when detecting reflected light, there is no need to significantly improve the system by simply incorporating a simple optical system.

The film in which the cholesteric liquid crystal structure of the present invention is immobilized only needs to be pasted or laminated on a portion of the surface of the card in an area necessary for authenticity determination, but cholesteric liquid crystal has a unique and beautiful color tone. Therefore, it is possible to increase the fashionability of the card by using it on the entire surface of the card other than the recording layer. The film may be used as it is, or may be used in a laminated structure of other transparent films such as polymethyl methacrylate, polycarbonate 1-, polyethylene terephthalate, and the like.

As explained above, the card of the present invention is difficult to counterfeit, and since counterfeit cards can be easily identified, it is extremely effective in preventing counterfeiting.

<Examples> The present invention will be specifically described below with reference to Examples, but the present invention is not limited thereto.

Reference Example I Poly(γ-benzyl monoglutamate) (molecular weight: 85,000) synthesized by the NCA method was transesterified with dodecyl alcohol to transesterify 40 mo1% of the benzyl ester using para-toluenesulfonic acid as a catalyst in dichlorothane. , poly(γ-benzyl monoglutamate〇〇-
γ-dodecyl monoglutamate) was synthesized. Next, the polymer was sandwiched between two 50 μm thick polyethylene terephthalate films (one is a transparent film and the other is a fading film), and a 12
It was pressed at 0'C. The obtained press film was
After heat treatment for 1 hour in an air constant temperature bath kept at ℃, the mixture was poured into water and rapidly cooled. The obtained film was a bright orange film having a three-layer laminated structure. This film was cut into 2×2 an square pieces to prepare Sample A.

Step 2 ■ Recitation Ethylene glycol, dimethyl terephthalate, P-acetoxybenzoic acid, hydroquinone diacetate and (
R)-3-methyladipic acid as a raw material [η] (3
A thermodropink cholesteric liquid crystalline polyester represented by the following formula was synthesized at 0°C, using a mixed solvent of phenol/tetrachloroethane = 60/40, and having a content of 0.9 (0.5 wt%).

O This polymer was pressed at 280° C. for 15 minutes and then put into ice water to be rapidly cooled to obtain a transparent film with a thickness of 100 μm. This film was cut into 2 an x 2 an square pieces to prepare sample B.

The cholesteric liquid crystal film A for determining authenticity produced in Reference Example 1 was laminated on the surface of a U-standard size polyvinyl chloride magnetic card as shown in FIG. 1 to obtain a card ■. In the figure, 1 is a magnetic strip, 2 is a vinyl chloride card, and 3 is a film for determining authenticity. Next, as a comparative example, a commercially available polyvinyl chloride film 2 having the same orange color was similarly sandwiched between two PET films.
fJ!x2■ film as shown in Figure 1. A card (■) was prepared by layering. Regarding the authenticity determination portion 3 of cards ■ and H, the viewing angle dependence of color, the reflection spectrum and CD spectrum determined at t1g using a spectrophotometer (Hitachi 330 type self-recording spectrophotometer) using an integrating sphere (Hitachi Spectroscopic Industry ■) Table 1 shows the manufactured optical rotation spectroscopy recorder (Model J-20).

Card I and Card ■ are completely identical in appearance, but as shown in Table 1, there are significant differences in viewing angle dependence of color, reflection spectrum, and circular polarization. Therefore, the card (2) is difficult to forge and has the excellent property that it can be easily determined whether it is genuine or not.

A card (2) having a structure as shown in FIG. 1 was prepared by using sample B of Reference Example 2 of the spindle disc as the film 3 for determining authenticity. As a comparative example, a card (2) having the structure shown in FIG. 1 was also prepared using a 2 cm x 2 square polyethylene film.

The reflection spectra and circular polarization properties of the card ■ and the authenticity determination portion 3 of the card ■ were examined in the same manner as in Example 1. The results are shown in Table 2.

It can be seen that although carts ■ and ■ have the same appearance, there is a large difference in their optical properties.

Cards ■ and ■ each have nine semiconductor lasers (wavelength 0.84).
When irradiated with light of .mu.m), the card ■ showed clear reflection, while the card ■ hardly reflected, showing a clear difference.

Reference Example 3 Poly(γ-benzyl L-glutamate - γ-dodecyl L-glutamate) synthesized in Reference Example 1 was
0 μm thick polyethylene terephthalate film (2
Both sheets were sandwiched between transparent films (transparent films) and pressed at 120°C with a 50 μm spacer interposed therebetween. The obtained press film was heat-treated for 1 hour in an air constant temperature bath kept at 125°C, and then poured into water to be rapidly cooled. The obtained film was a bright purple film, which was cut into 20 x 2 square pieces and pasted on top of the 2 x 2+an square orange film prepared in Reference Example 1 to give a maroon (reddish-purple) color. It was designated as sample C.

End cover group 1 Using sample C obtained in Reference Example 3, a card V having the structure shown in FIG. 1 was produced. Separately, a card (2) having the structure shown in FIG. 1 was prepared using a 2 x 2 an square film which was laminated with four 50 μm polyvinylene terephthalate films centered around a polyvinyl chloride film of the same color. The characteristics of the cards ■ and ■ were determined in the same manner as in Example 1.

The results are shown in Table 3.

(Margins below):,'y)',,',1,1 Both cards cannot be distinguished from each other from the outer ml, but card ■ shows two sharp reflection spectra (right-handed circularly polarized light) and is clearly distinguishable. was completed. Card ■ is made of two cholesteric films pasted together, making it even more difficult to counterfeit.

<Effects of the Invention> The card of the present invention is difficult to counterfeit because it utilizes the viewing angle dependence of the cholesteric color of cholesteric liquid crystal, the wavelength selective reflection property, and the circular polarization selectivity.

In addition, it is extremely easy to determine authenticity and has excellent anti-counterfeiting effects. Furthermore, since the authenticity can be determined only by visual discrimination or by using a simple optical system, there is no need for major system improvements.

[Brief explanation of drawings]

The figure shows an example of a magnetic card produced using the cholesteric liquid crystalline polymer film for preventing counterfeiting of the present invention. 1...magnetic stripe, 2...vinyl chloride card;
3. Film for determining authenticity. 1...Magnetic stripe 0 2.°Sil and other similar car F゛3...Su4Kyugyu1yJ1yenFij,B,Procedural correction belt (master) 1. Display of the case 19861 Patent Application No. 193886 2, Invention name forgery prevention card 3, Person making the amendment Relationship to the case Patent applicant (444) Nippon Stone? Yui Shushiki Company 4, Agent Address: 1-20 Toranomon, Minato-ku, Tokyo 105 Item 6 of the "Detailed Description of the Invention" of the Specification Contents of the Amendment The Statement of Specification a of the present application has been amended as follows. To do. Page Line Before correction After correction 124-minute one minute, -■-〇. (y(y 1715~16 Polymethyl meth Polymethyl methacrylate Acrylate

Claims (1)

[Claims] A card comprising a film made of a cholesteric liquid crystal polymer and having a fixed cholesteric liquid crystal structure on at least a portion of its surface.