JP2000247077A - Certificate or the like - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reversibly change a color in response to a type of a light source and to easily discriminate a true one from a forgery by providing a reversibly discoloring ink layer obtained by blending specific rare earth element oxide ultrafine particles having a mean particle size within a specific range with a resin binder on parts of front and rear surfaces of bills. SOLUTION: In order to easily discriminate a true one of a bill or the like such as a gift certificate, a stock bill, a traffic ticket, an admission ticket, a card or the like from a forged one from a forgery, it is printed with an ink obtained by blending reversibly discoloring ultrafine particles reversibly changing in color in response to a type of an external light source and largely changing in its color tone. That is, a reversibly discoloring ink layer obtained by blending rare earth element oxide ultrafine particles represented by a formula of M2O3 having a mean particle size of 5 to 100 nm of a range with a resin binder is provided on each of front and rear surfaces of the bill, wherein M is Ho, Nd or Pr, a blending amount of the particles represented by the M2O3 is 5 to 65 wt.% or preferably 10 to 55 wt.% of the solid content of the ink.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to securities (commodity certificates,
(For stock certificates, traffic tickets, admission tickets, cards, etc.), the forgery prevention technology used to distinguish between genuine products and counterfeit products, the color of which changes reversibly according to the type of external light source, and the color change changes greatly. The present invention relates to securities printed with an ink containing ultra discolorable ultrafine particles.

[0002]

2. Description of the Related Art Conventionally, as a technology for preventing forgery, a photochromic molecule, which is an organic compound, has been known as a substance that causes the color of a compound to be reversibly changed by light irradiation.
Photochromic molecules change their chemical structure by absorbing energy from light irradiation, and as a result, the color of the compound changes. On the other hand, even with inorganic compounds such as oxides of Ho, Nd, and Pr, a photochromic phenomenon is observed. These oxides have a special reflection spectral distribution, and the color of the oxide changes according to the type of light source such as sunlight or a fluorescent lamp.

[0003]

However, when such an organic photochromic molecule is used as a dye material, the reversibility of the color change is often incomplete and the time required for the color change is long. In addition, repetition of color change due to light absorption causes light deterioration such as loss of reversibility of color change, and reversibility of light change often disappears due to heat or long-term UV irradiation. Not suitable for storage. On the other hand, the rare earth oxides of the inorganic compounds Ho, Nd and Pr have good qualities such as weather resistance and heat resistance, but their color change is so small that they cannot be applied to the technology for preventing forgery.

[0004] In view of the above problems, the present inventors have formulated reversible discolorable ultrafine particles whose color reversibly changes according to the type of light source and whose color tone changes largely. With some ink on the front and back of securities,
By providing an ink layer, it is used for discriminating a counterfeit product from a real product.

[0005]

According to the present invention, there is provided, on a part of the front and back sides of securities, a general formula M ₂ O ₃ (where M is Ho, Nd or Pr) having an average particle diameter in a range of 5 to 100 nm. The present invention also provides securities which are provided with a reversible discolorable ink layer in which a rare earth oxide ultrafine particle represented by the following formula (1) is mixed with a resin binder.

The rare-earth oxide ultrafine particles having an average particle diameter in the range of 5 to 100 nm according to the present invention have a different reflection spectral distribution from the conventional rare-earth oxide fine particles having a particle diameter of several μm. As an example, a conventional average particle diameter is about 2
When the average particle size and the reflection spectral distribution of Ho ₂ O ₃ fine particles of μm to compare reflection spectral distribution of Ho ₂ O ₃ ultrafine particles is 30 nm, 460 nm regardless of the particle size, 540 nm, 6
It has a major absorption peak in the wavelength region around 50 nm,
In particular, the reflectance in the wavelength range around 540 nm and 650 nm is:
Ultrafine particles have a reflectance of 20 to 30% (absorption is 70 to 8), while fine particles have 50% or more (absorption is 50% or less).
0%), showing extremely large absorption, and the reflectances of these two absorption peaks in the wavelength region are significantly different.

As a result, 490 nm, 550 nm, 62
When Ho ₂ O ₃ particles are illuminated to a three-wavelength emission fluorescent lamp having a large emission line near 0 nm, the Ho ₂ O ₃ ultrafine particles absorb more wavelengths around 540 nm and 650 nm, and the three-wavelength emission fluorescent light Since the bright line near 620 nm contained in the lamp is reflected, the color tone of the Ho ₂ O ₃ ultrafine particles becomes stronger in red, and as a result, pink color can be expressed.

[0008]

Embodiments of the present invention will be described with reference to the following examples. In the present invention, the average particle size is 5
General formula M ₂ O ₃ in the range of １００100 nm (provided that
(M represents Ho, Nd, or Pr). The compounding amount of the rare earth oxide ultrafine particles can be 5 to 65% by weight, preferably 10 to 55% by weight based on the solid content of the ink. If the compounding amount of the rare earth oxide ultrafine particles is less than 5% by weight, the color change becomes small, which is not preferable.
When the ratio exceeds the above, the transparency and flexibility of the ink layer become inferior, which is not preferable.

The reversible color changing ink containing the rare earth oxide ultrafine particles can contain a colorant in an amount of 5% by weight or less. In this case, a color variation can be achieved by a combination of the discoloration due to the absorption peak of the ultrafine rare earth oxide particles and the coloring of the colorant.
For example, when Ho ₂ O ₃ ultrafine particles and a yellow pigment are blended as a colorant in the transparent resin component, the color is yellow as it is when exposed to sunlight, but becomes light orange when exposed to a fluorescent lamp of the standard light source D65. In a three-wavelength band fluorescent lamp, the lamp emits orange.

The resin binder used in the reversible color-changing ink of the present invention includes vinyl chloride resins, vinyl acetate resins, polyester resins, epoxy resins, acrylic resins, urethane resins, and fluorine resins. A transparent curable resin or a thermoplastic resin is used, but a curable resin is preferable. The compounding amount of the rare earth oxide ultrafine particles mixed with these resin components is 5 to 6 in the solid content.
It is in the range of 5% by weight, preferably 10-55% by weight.

The securities of the present invention are provided with the above-mentioned reversible color-changing ink layer on part or all of the front and back surfaces thereof.
For example, the reversible color-change ink layer may be provided with a reflective layer such as a metal deposition layer on the back side of the reversible color-change ink layer.

[0012] The securities used in the present invention include gift certificates such as book coupons, department store gift certificates, and rice tickets; stock certificates; banknotes; buses, railways, airline company tickets, limited express tickets, commuter passes, Transportation tickets such as expressway tickets; entrance tickets for theme parks, movies, museums, etc .; cards such as highway cards, bank cards, telephone cards, bus cards, ID cards; etc., as well as stamps, stamps, bills, etc. Is also available.

[0013]

EXAMPLES Example 1 and Comparative Example 1 Ho having an average particle diameter of 30 nm with respect to 50 parts by weight (solid content) of a transparent resin ink containing an acrylic resin as a main component.
Using a transparent ink containing 50 parts by weight of ultrafine particles of ₂ O _{3, the} entire surface of the gift certificate is coated to a thickness of about 5 μm.
A reversible discolorable ink layer having a film thickness of The white portion of the gift certificate exhibits a very pale yellow color when exposed to sunlight, a pale pink color when exposed to the fluorescent light of the standard light source D65, and a pink color when exposed to the three-wavelength band fluorescent light. Present. On the other hand, Ho having an average particle diameter of about 8 μm
_In the case of a gift certificate manufactured by the same method using ₂ O ₃ fine particles, when exposed to a three-wavelength band fluorescent lamp, the skin color was pale.

Example 2 and Comparative Example 2 As a surface protective film of a card, a transparent polyethylene terephthalate resin film having a thickness of 12 μm was provided on the surface side.
H having an average particle diameter of 30 nm is used for 60 parts by weight of a transparent resin ink containing an ultraviolet-curable acrylic resin as a main component.
Using a transparent ink in which 40 parts by weight of o ₂ O ₃ ultrafine particles were mixed and dispersed, a 5 μm-thick ultraviolet-curable acrylic resin ink was applied and irradiated with ultraviolet rays to form a cured ink layer. The back side of this protective film and the printed white card base body were integrated by dry lamination. The white portion of the card remains almost white even when exposed to sunlight, and exhibits a pale pink color when exposed to the fluorescent light of the standard light source D65, and becomes pink when exposed to the three-wavelength band fluorescent light. Present. On the other hand, in the case of a card manufactured by the same method using Ho ₂ O ₃ fine particles having an average particle diameter of about 8 μm, the card had an extremely pale flesh color when exposed to a three-wavelength band fluorescent lamp.

Example 3 and Comparative Example 3 Pr having an average particle diameter of 30 nm was used for 50 parts by weight (solid content) of a transparent resin ink containing an acrylic resin as a main component.
_Using a transparent yellow ink containing 49 parts by weight of ₂ O ₃ ultrafine particles and 1 part by weight of a yellow pigment, a part of the decoration edge of the gift certificate was printed to provide a reversible color changing ink layer. A part of the decorative edge formed by the reversible color changing ink layer of this gift certificate is light yellow when exposed to sunlight, and has a standard light source D6.
When exposed to the fluorescent light of No. 5, it exhibits a light orange color, and further when exposed to a three-wavelength-range fluorescent light, it exhibits an orange color. On the other hand, in the case of a gift certificate manufactured by a similar method using Pr ₂ O ₃ fine particles having an average particle size of about 8 μm,
When exposed to a three-wavelength-range fluorescent lamp, the color becomes dull yellow. Thus, by using the Pr ₂ O ₃ ultrafine particles of the present invention, a larger change in color tone can be obtained.

[0016]

As described above in detail, according to the present invention, it is possible to exhibit a large discoloration in different environments of the light source, and the ultrafine particles of the present invention change the color tone more than the same oxide fine particles. Therefore, identification becomes possible with a small amount. In addition, the color change is due to the absorption and reflection characteristic of rare earth oxides, so the reversibility of the color change is perfect, the speed of the color change is fast, and there is no light deterioration, so the quality such as weather resistance and heat resistance is good. There are advantages. Further, the color of a printed or patterned portion can be changed by a combination with a coloring agent.

Claims (4)

[Claims] [Claim 1] A general formula M ₂ O ₃ having an average particle diameter in the range of 5 to 100 nm is partially or entirely provided on the front and back of securities.
(Where M represents Ho, Nd, or Pr) Securities characterized by having a reversible discolorable ink layer in which a rare-earth oxide ultrafine particle represented by the formula: 2. The securities according to claim 1, wherein the compounding amount of the rare earth oxide ultrafine particles in the solid content of the reversible color changing ink is in the range of 5 to 65% by weight. 3. The securities according to claim 1, wherein the reversible color-changing ink contains a colorant in an amount of 0 to 5% by weight. 4. The securities according to claim 1, wherein the resin binder is at least one of an acrylic resin, a urethane resin, an epoxy resin, and a fluororesin.