JPH04320466A - Security ink - Google Patents

Abstract

PURPOSE:To obtain a security ink improved in colorant solubility, heat resistance, light resistance, molar absorptivity and economic profitability by mixing a specified near-infrared absorber with a cyclohexanone solvent. CONSTITUTION:This ink comprises a near-infrared absorber comprising a phthalocyanine pigment of formula I [wherein R1, R6 and R7 are each H, linear or branched alkyl, cyclohexylalkyl, alkoxyalkyl, acyloxyalkyl, acylaminoalkyl, haloalkyl, cyanoalkyl or the like; R2, to R5 are each H, linear or branched alkyl, cycloalkyl, linear or branched alkoxy, cycloalkyloxy or the like; X is H, halogen, alkoxy or OH; (a) is 1-4; (b) is 0-5; (c) is 0-14; 2a+b+c=16; M is a metal (oxide)], a cyclohexanone solvent of formula II (wherein R is H, alkyl, alkoxy or halogen), a binder resin component and a polymerization initiator.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to security inks. More specifically, the present invention relates to a security ink comprising a near-infrared absorber and a solvent.

In recent years, reflecting the cashless era, prepaid cards have been used in a wide variety of fields, including telephone cards, orange cards, gift certificates, parking lot tickets, and food and drink tickets.

[0003] A recent problem in this system is counterfeit prevention measures. That is, when gift certificates and the like become expensive, counterfeit prevention becomes essential. There are several methods to prevent counterfeiting, but the most common method is to use security ink that cannot be read by ordinary visible light sensors. In this case, a near-infrared absorber is usually used.

[0004] As a specific method, a security ink containing a near-infrared absorber and a binder resin is printed on the back side of a prepaid card.

[0005] As a near-infrared absorber, 700 to 110
A dye having an absorption wavelength of 0 nm is used.

[0006] As the binder resin, those commonly used for film coating may be used, such as urethane resins, acrylic resins, and the like. Since a thickness of 3μ or more can be detected by the touch, the thickness of the print is 3μ.
It is necessary to do the following.

[0007] When a prepaid card printed using the security ink produced by the above method is irradiated with near-infrared rays (700 to 1100 nm), it absorbs light in the wavelength range, making it readable. Authenticity can be determined using this principle.

[0008]

BACKGROUND OF THE INVENTION These near-infrared absorbers are required to have various physical and chemical properties as shown below. (1) The dye must have an absorption band in the wavelength range of 700 to 1100 nm. (2) The pigment must be completely dissolved in the ink. If the dye particles are large, poor dissolution may be felt by the touch. (3) Good heat resistance and light resistance as a near-infrared absorber. If it is defective, absorption of near-infrared wavelengths may be incomplete, resulting in reading errors. (4) It has a large molar extinction coefficient. If it is small, it is necessary to add a large amount to the ink, and the printing thickness may exceed 3μ. (5) The dye should be inexpensive.

Among the known near-infrared absorbers, no dye has been reported that satisfies all of these points. for example,
Many of the dyes developed for use in optical discs satisfy conditions (1) to (4), but they are currently not put to practical use because they are extremely expensive.

0010

[Means for Solving the Problems] As a result of extensive studies to solve the problems of the above-mentioned near-infrared absorbers, the present invention has developed a general formula that has absorption over a wide range (700 to 1100 nm) in the near-infrared region. (1) (Chem.3)

[0011]

[Chemical formula 3]

[In the formula, R1, R6 and R7 are the same or each independently a hydrogen atom, a linear or branched alkyl group, a cyclohexylalkyl group, a hydroxyalkyl group, an alkoxyalkyl group, an acyloxyalkyl group, an acylaminoalkyl group , represents a halogenated alkyl group, cyanoalkyl group, alkoxycarbonylalkyl group, alkenyl group or aralkyl group, R2, R3, R4 and R
5 are the same or each independently a hydrogen atom, a linear or branched alkyl group, a cycloalkyl group, a linear or branched alkoxy group, a cycloalkyloxy group, an alkoxyalkyl group, an alkoxyalkoxy group, an aralkyl group or a halogen atom, Furthermore, R2 and R3 or R4 and R5 may be connected to each other to form a ring, X represents a hydrogen atom, a halogen atom, an alkoxy group, or a hydroxyl group, a represents an integer of 1 to 4, and b represents 0 to 5. c represents an integer of 0 to 14, 2a+b+c is 16, and M represents a metal atom or a metal oxide. The phthalocyanine dye represented by

[0013]

[C4]

[In the formula, R represents a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom. It was discovered that the use of a cyclohexanone solvent represented by the following formula has very excellent properties as a dissolving type security ink, and the present invention was completed. That is, the present invention is based on the general formula (1
) (C5)

[0015]

[C5]

[In the formula, R1, R6 and R7 are the same or each independently a hydrogen atom, a linear or branched alkyl group, a cyclohexylalkyl group, a hydroxyalkyl group, an alkoxyalkyl group, an acyloxyalkyl group, an acylaminoalkyl group , represents a halogenated alkyl group, cyanoalkyl group, alkoxycarbonylalkyl group, alkenyl group or aralkyl group, R2, R3, R4 and R
5 are the same or each independently a hydrogen atom, a linear or branched alkyl group, a cycloalkyl group, a linear or branched alkoxy group, a cycloalkyloxy group, an alkoxyalkyl group, an alkoxyalkoxy group, an aralkyl group or a halogen atom, Furthermore, R2 and R3 or R4 and R5 may be connected to each other to form a ring, X represents a hydrogen atom, a halogen atom, an alkoxy group, or a hydroxyl group, a represents an integer of 1 to 4, and b represents 0 to 5. c represents an integer of 0 to 14, 2a+b+c is 16, and M represents a metal atom or a metal oxide. ] and at least one kind of near-infrared absorber represented by the general formula (2) (Chemical formula 6)

[0017]

[C6]

[In the formula, R represents a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom. ] This is a security ink containing a cyclohexanone solvent.

Dye (1) (Chemical formula 5) of the near-infrared absorber of the present invention is a phthalocyanine compound described in JP-A-63-270765, which we previously filed, and can be easily produced, for example, by the following method. can do.

For example, perchlorocopper phthalocyanine (common name: phthalocyanine green) is dispersed in an aprotic solvent such as dimethylformamide or quinoline, and o-
A compound obtained by reacting with aminothiophenols at a reaction temperature of 70 to 160°C, preferably 110 to 140°C, is reacted with a reagent such as an alkyl halide in a polar solvent such as dimethylformamide in the presence of a base such as potassium carbonate. It can be obtained by reacting with

General formula (1) obtained by such a method
) (Chemical formula 5) exhibits a pale neutral gray color, and can be used alone or in combination with one or more of the general formulas (1) (Chemical formula 5) as an important component of security ink.
Furthermore, it is also possible to use it in combination with other known near-infrared absorbers.

[0022] Security ink can be obtained by incorporating a dye into a binder resin, and specifically, it is produced by dissolving the dye in a solvent and adding a binder resin component and a polymerization initiator thereto.

[0023] The amount of these near-infrared absorbers added is determined depending on the desired amount of absorption of the near-infrared absorbing portion or the thickness of the coating, and is not uniformly limited; It is desirable to use it in a range of about 0.1 to 10 (wt%) based on the resin.

All known binder resins can be used, including styrene copolymers, urethane resins, polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, Polypropylene, polyester, polyurethane, polyamide, polyvinyl butyral, polyamide, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenolic resin, aliphatic or alicyclic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin Wax etc. can be used alone or in combination.

[0025] As the solvent, ketones such as methyl ethyl ketone, which are commonly used in gravure printing, etc., aromatics such as toluene, etc. can be used, but the following general formula (2) (Chemical formula 7)

[0026]

[C7]

[In the formula, R represents a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom. ] By using the cyclohexanone solvent represented by the following, the solubility of the dye increases and the properties of the security ink are further improved. At this time, it is preferable to use commonly used ketones, aromatic solvents, and alcohol solvents in combination.

As the compound of general formula (2) (chemical formula 7),
Specifically, cyclohexanone, 4-methylcyclohexanone, 3-methylcyclohexanone, 2-i-propylcyclohexanone, 4-methoxycyclohexanone, 4
-Ethoxycyclohexanone, 2-n-butoxycyclohexanone, 4-chlorocyclohexanone, 3-chlorocyclohexanone, 2-chlorocyclohexanone, 4-
Examples include bromocyclohexanone, among which cyclohexanone, 4-methylcyclohexanone, and 2-chlorocyclohexanone are preferred.

[0029]

[Operations and Effects] The security ink obtained by the near-infrared absorbent of the present invention
Since it absorbs the wavelength of m) and can solve all of the required characteristics of (1) to (5) above, it is possible to provide an inexpensive prepaid card that is free from reading errors and is not detected by the sense of touch. This is extremely valuable in practical terms.

[0030]

[Examples] The present invention will be explained in more detail with reference to Examples below. Note that the numbers in the examples represent parts by weight. Example 1 The following formula (Chemical formula 8)

[0031]

[Chemical formula 8]

Dissolve 2.5 parts of the dye represented by the formula in 23 parts of cyclohexanone and 23 parts of toluene, and then dissolve 15 parts of the prepolymer (polyacrylate carbamate in 17.5 parts of methyl ethyl ketone and 17.5 parts of toluene) in this solution. Add 50 parts of Furthermore, a polymerization initiator (
A security ink is prepared by adding 1.4 parts of trimethylolpropane triacrylate containing 0.1 part of benzophenone. Apply this security ink to a PET film (thickness: 10μ) using a coil bar (No. 10).
coating. 840nm on the obtained film
The absorption rate at this wavelength was 97%. Furthermore, the light resistance of the printed matter was good, with a decrease in light absorption of 5% or less after irradiation with a carbon arc lamp for 40 hours at 63°C.

Examples 2 to 21 Table 1 (Table 1) (Table 2) was used instead of the formula (Chemical formula 8) in Example 1.
As a result of testing under similar conditions using the compound shown in
As in Example 1, the light absorption rate at the maximum absorption wavelength is 95%.
Under the above conditions and under the conditions of 63° C., the decrease in light absorption rate after irradiation with a carbon arc lamp for 40 hours was 5% or less, which was good.

Comparative Example 1 A test was conducted under the same conditions as in Example 1 except that 4-methylcyclohexanone was used in place of the cyclohexanone in Example 1. As a result, the compound of formula (8) in the security ink was The ink did not dissolve sufficiently and even after application, the applied area could be felt to the touch due to the influence of undissolved matter, and the purpose of the security ink could not be achieved.

[0035]

[Table 1]
(Table 1)

[0036]

Claims (1)

[Claims] Claim 1: General formula (1) (Formula 1) [In the formula, R1, R6 and R7 are the same or each independently a hydrogen atom, a linear or branched alkyl group, a cyclohexylalkyl group, a hydroxy It represents an alkyl group, an alkoxyalkyl group, an acyloxyalkyl group, an acylaminoalkyl group, a halogenated alkyl group, a cyanoalkyl group, an alkoxycarbonylalkyl group, an alkenyl group, or an aralkyl group, and R2, R3, R4 and R5 are the same or each independently. represents a hydrogen atom, a straight-chain or branched alkyl group, a cycloalkyl group, a straight-chain or branched alkoxy group, a cycloalkyloxy group, an alkoxyalkyl group, an alkoxyalkoxy group, an aralkyl group, or a halogen atom, and R2 and R3 or R4 and R5 may be connected to each other to form a ring, X represents a hydrogen atom, a halogen atom, an alkoxy group, or a hydroxyl group, a represents an integer of 1 to 4, and b represents 0 to 4.
represents an integer of 5, and c represents an integer of 0 to 14, but 2a+
b+c is 16, and M represents a metal atom or a metal oxide. ] and at least one near-infrared absorber represented by the general formula (2) (Chemical formula 2) [Chemical formula 2] [In the formula, R represents a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom. ] Security ink containing a cyclohexanone solvent.