JP2000057306A - Security card containing thin glass layer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a security card which is hardly forged, satisfactorily protected from causes to bring information loss due to the mechanical impacts and the permeation of solvents, oxygen, water, etc., and also has the sufficient flexibility so as not to be damaged by bending. SOLUTION: This security card is a laminated material of a flexible glass layer having thickness of 350 μm or less and a supporter. The thin glass layer has flexibility enough to permit the substantial bending of the card without breaking the glass. The glass layer also has a security feature since it's very hard to exfoliate the glass without breakage of the glass to forge the information stored in the card. The glass serves as an effective barrier layer which protects the information stored in the cord from being lost caused by the decomposition due to the mechanical impacts and also the permeation of gaseous bodies such as oxygen and steam.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to security cards that are difficult to counterfeit because they include a thin layer of glass laminated as a security feature.

[0002]

BACKGROUND OF THE INVENTION A security card is used for identification (ID card) or financial (financial tra).
nsfers) (credit cards). Such cards typically consist of a laminated structure including various plastic layers,
One or more layers of information, e.g., alphanumeric information,
It holds logos and images of cardholders. Also known are writable cards on which the user can store random information, such as cards containing magnetic strips, cards that can be optically recorded or cards that contain electronic chips, sometimes called "smart cards". .

The main purpose of such a security card is that it cannot be easily modified or reproduced in such a way that it is difficult to distinguish it from the original. Accordingly, security cards are provided with security features that are difficult to modify or reproduce, eg, a "security seal" between the information layer and a protective sheet adhered thereto. Attempts to separate the protective sheet from the information layer will destroy or remove the security seal, revealing that the information held by the card has been tampered or changed. Such security seals are, for example, US
For example, as described in US Pat. No. 4,322,461 and references therein, it can be provided by applying a heat-sealable polymer to obtain a sealed envelope-type pouch.

A problem associated with information recording materials is that they are susceptible to mechanical shock, which can cause defects such as scratches and can cause significant loss of the data being recorded. The recordable layer of most of these security cards includes a plastic foil as a protective layer on the recording medium. The life of such a recording material, which needs to be 10 years in some applications, is inadequate, because the plastic foil is not capable of removing solvents, oxygen, moisture and other sources of potential data loss. Because it is not an effective barrier.

Some disclosures refer to the use of glass as a substrate for making security cards. JP-A 60/214996 describes a laser recording card in which the substrate carrying the recording layer can be glass. EP-A 272875 also has an optical recording card (op) in which glass can be used as a constituent layer.
physical recording card). In these patent applications, the glass layer is used as a suitable substrate because the glass layer is very transparent and a light source can be used for writing and reading information. However, the glass layer disclosed therein is a non-flexible layer and can be easily broken by accident, for example, by slight bending during handling or holding the card in a wallet.

[0006] EP-A 669 205 describes a glass / plastic laminate for use as vehicle safety glass, which laminate comprises a glass plate, an intermediate adhesive layer and a plastic plate, the glass being 30 to 1000 μm.
Having a thickness of A functional layer can be applied to the glass, which is sandwiched between the glass layer and the plastic layer after lamination, thereby protecting it from external influences. US
3,471,356 and 4,600,640 also disclose thin glass laminates for use in automotive and architectural applications.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a system that is difficult to counterfeit, is well protected against mechanical shock and possible sources of information loss, such as the transmission of solvents, oxygen and moisture, The purpose of the present invention is to provide a security card having sufficient flexibility so that the security card cannot be damaged by the security card. This object is achieved by a security card as defined in claim 1. Preferred embodiments of the invention are described in the dependent claims (d
independent claims). Further advantages of the present invention will become clear from the description hereinafter.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The security card of the present invention includes a thin glass layer as a constituent layer. The glass layer offers several advantages. First, the glass layer itself is an effective security feature. Attempts to counterfeit the card by peeling off the constituent layers cause breakage of the thin glass layer, which is easily detectable and difficult to repair. The second advantage is associated with the excellent barrier properties of glass, which effectively reduces gas and liquid permeation,
It is also characterized by a high hardness, thereby preventing damage from scratches and other forms of mechanical damage. After all, the information-bearing or recording layer of the card is well protected from the environment, and the card has a long life. In addition, thin glass has sufficient flexibility to allow substantial bending of the card without damaging the glass layer. Finally, the high specific weight of the glass layer as well as its high clarity make it possible to distinguish the security card of the present invention from a conventional plastic-based security card or a copy made without such a glass layer. Can be easily detected.

[0009] The thin glass layer is a flexible glass layer. As used herein, the term "flexibility" should be understood as meaning "can be wound around a core without breakage." The preferred glass layer used in the card of the present invention can be wound without break around a cylindrical core having a radius of 1.5 m. The basic requirements for obtaining flexible glass are low thickness and high strength. The thinner the glass, the higher its flexibility and thus the smaller the minimum radius of the core around which the glass can be wound without breaking. The maximum thickness of the glass layer that allows bending of the card with low potential for breakage depends on the glass composition and manufacturing method and several parameters such as the composition, thickness, number and location of the other constituent layers of the card I do. To obtain sufficient flexibility, the glass layer used in the security card of the present invention has an upper thickness limit of 350 μm. Above this limit, the likelihood of glass breakage is too high to bend sufficiently. For greater flexibility, the thickness is preferably less than 200 μm and more preferably less than 100 μm. The minimum thickness is preferably at least 30 μm, more preferably at least 50 μm
m, because glass having a lower thickness is too brittle and bending of the card can cause glass breakage. As described above, the lower limit of the glass thickness depends on the composition of the glass layer and the manufacturing method.

[0010] Flexible glass is known in the art. EP-A 716 339 describes a method using a flexible glass web that can be wound around a core to obtain a roll of glass. Unwind the glass,
The functional layer can be coated by a continuous web coating method. The flexible glass has (i) a thickness of less than 1.2 mm, (ii) a breaking stress of 1 × 10 ⁷ Pa or more (under tensile stress) and (iii) an elastic modulus of 1 × 10 ¹¹ Pa or less (Young's modulus). ).

The glass can be, for example, sodium float glass, chemically strengthened glass or borosilicate glass. Such glasses can be made by squeezing semi-molten glass between metal rollers to produce a thin web. US 4,388,368 describes the following method for the production of flexible glass sheets. Soda-lime glass melted at 1550 ° C. (Na ₂
O. CaO. SiO ₂ = 15: 13: 72 by weight)
Is drawn and wound. The glass thus formed is supported by clips at both ends and heated at about 350 ° C. Thereafter, a temperature lower than the heating temperature, for example, 70
The glass sheet is stretched to 1.05 to 10 times the area of the first sheet while blowing hot air on the glass sheet at 0 ° C. In this way, the glass sheet is cooled faster in the thin sections, so that the thickness of the drawn glass sheet is kept uniform. A similar method is JP-
A58, 095, 622. JP-A
In another method described in US Pat.
The molten glass web is pulled upward, immediately afterwards pulled horizontally using a large roller onto the surface of the molten metal bath and subsequently cooled slowly. The glass thus obtained has an improved flatness.

It is known that chemically strengthened float glass has a higher strength than ordinary float glass. Chemically strengthened glass is glass in which the initial alkali ions in both surface layers are at least partially replaced by alkali ions having a larger radius. In the case of chemically hardened sodium lime silica glass, sodium ions near the surface of the glass are at least partially replaced by potassium, and in the case of chemically hardened lithium lime silica glass, lithium ions near the surface have at least It has been partially replaced by sodium and / or potassium. Known methods for the production of chemically strengthened glass are described, for example, in JP-A 56,041,859, GB
1,208,153 and US Pat. No. 3,639,198, a method of exposing a glass to ion exchange conditions. Further details on chemical strengthening of glass can be found, for example, in "Glass Technology".
y ", Vol. 6, No. 3, pages 90-9.
7, June 1965.

[0013] Thin borosilicate glass is much stronger than ordinary sodium float glass. Borosilicate glass is Si
It contains O ₂ and B ₂ O ₃ . The detailed composition of some types of borosilicate glass is described, for example, in US Pat. No. 4,870,03.
4, 4,554,259 and 5,547,904.

[0014] Glass having low flexibility is, for example, Pilk.
inton, Corning and Deutsche
Spezialglass AG (Desag, Ger
many, a Shott Group compa
ny). De in 1995
The technical brochure “Alkal” published by Sag
i Free and Low Alkali Thi
n Glasses ", subtitle" AF45 and D2
63: Thin Glasses for Elect
According to "Ronic Applications", thin borosilicate glass is 30 μm, 50 μm, 70 μm, 10 μm,
0 μm, 145 μm, 175 μm, 210 μm, 300
Available in thicknesses of μm, 400 μm, 550 μm and 700 μm.

[0015] The glass layer can also be a pre-broken glass layer or a glass layer containing crevices as described in European Patent Application No. 98202380 filed on July 15, 1998. Such pre-structured glass (pre-structured glass)
glass) is particularly preferred when very high flexibility is required. According to a preferred embodiment, the glass does not contain cracks throughout the layer, but rather contains pre-formed grooves of a certain depth smaller than the thickness of the glass. The grooves can be formed, for example, by a polishing method such as grinding or by laser engraving. For example, by scanning the groove pattern, encoding the scanned pattern into digital information, and storing the information on a card (eg, as a barcode, on a storage chip, on a magnetic strip, etc.) or in a computer file, The pre-configured glass groove pattern can also be used as a security feature. This information can then be consulted for verification, for example, when the card is used for identification purposes. A discrepancy between the previously stored groove pattern information and the actual pattern in the glass layer of the card is a significant indicator that the card is not authentic. For easy scanning, the grooves preferably have a sufficient width, for example within 1-100 μm. The groove pattern is preferably scanned in reflection mode for accurate groove detection.

According to the invention, the glass layer is laminated to a support. The term “support-supporting” is used to distinguish it from a layer that can be coated on the support but is not self-supporting (“self-supporting layer”).
layer "). The term" laminate "as used herein is to be understood as" material consisting of multiple layers bonded together ".

The support is preferentially (preferentiali).
all) 5 μm to 850 μm, more preferably 100 μm
It has a thickness between μm and 600 μm. The support can be paper or metal, but preferably is a plastic foil such as a cellulose acetate film, a poly (vinyl acetal) film, a polystyrene film, a polycarbonate film, a poly (ethylene terephthalate) film, a polyethylene film, a polypropylene film or These copolymers are, for example, copolymers of acrylonitrile, styrene and butadiene. The support is preferably a transparent material.

[0018] Methods for laminating glass to a support are well known. So-called vacuum lamination allows both layers to be laminated without using an adhesive layer. In order to obtain effective adhesion between the glass layer and the support by vacuum lamination, both of these materials are preferably characterized by low surface roughness, e.g., preferably the support is often a plastic foil to prevent sticking Or contains no so-called spacing agent introduced into the coating on the foil.

In addition to vacuum lamination, double-sided adhesive tape or, for example, hot melt, pressure or heat sensitive adhesives or UV
Alternatively, it is possible to use an adhesive layer obtained by applying an electron beam-curable adhesive. Alternatively, a slightly moistened gelatin layer can be used as the adhesive layer. Further information on suitable adhesive layers is described in WO 98/6455, filed October 7, 1998. The adhesive layer can be applied to the glass sheet, the support, or both, and can be protected by a release layer that is removed just prior to lamination. Polyethylene is a very preferred adhesive, which can be applied as a foil between the glass and the support. The adhesion between the glass and the support is preferably permanent and cannot be separated without breaking the glass layers.

The lamination of the glass layer and the support can be performed manually, but is preferably performed by laminating means called a laminator. A typical laminator includes a pair of heatable rollers, which have an adjustable pressure and move at a fixed or adjustable speed. Lamination is carried out, optionally after applying an adhesive layer between the materials, by bringing the materials into close contact with one another between the rollers of the laminator.

[0021] In addition to the glass layer, other barrier layers can be provided on the security card to reduce the permeability of gases such as oxygen or water vapor. Organic and inorganic barrier layers are known in the art. Organic barrier layers include, for example, Coating, no. 9/98, p. Three
14 and 10/97, p. Organically modified ceramics, Macromol as described in US Pat.
ecules, vol. 31, p. 8281 (198
Poly (hydroxyamide ethers), such as the compounds described in 8), poly (vinyl alcohol), polyacrylonitrile and poly (vinyl butyral), which can be mixed with the epoxy resin, or gelatin may be included. Inorganic barrier layer oxide is typically sputtered, for example, a thin film of SiO _x or Ta ₂ O _5. To obtain some flexibility, the thickness of such an inorganic barrier layer is preferably less than 2 μm, preferably about 1 μm.
m. Combining inorganic and organic barrier layers, for example S
may organically to iO _x layer is to overcoat the ceramic layer that has been modified is advantageous, it is typically deposited or to the uneven surface of the applied inorganic layer overcoating the organic layer by sputtering This is because they can be averaged. The additional barrier layer can be between the glass layer and the support of the laminate used in the security card of the present invention.

The information layer of the security card is preferably applied on a support prior to lamination to glass. Alternatively, the information layer can be provided on the glass before lamination to the support or on one of the faces of the glass / support laminate obtained after lamination of the glass layer and the support. Glass layers can be laminated on both sides of the information layer to effectively protect the information layer. The information layer itself can serve as an adhesive layer between the support and the glass layer. In yet another embodiment, the side of the support opposite the information layer can be laminated to glass. The information layer can be over the entire security card, or it can be a strip on a portion of the security card. The information medium can be applied on one or both sides of the support or glass.

To improve the adhesion of the layer applied on the glass, the following formula:

[0024]

Embedded image [Wherein R1, R2 and R3 are hydrogen, alkyl or a substituted alkyl group, and n is 1 to 10, preferably 1
範 囲 3]. Such compounds can be added, for example, to the coating solution of the layer to be provided on the glass.

In a preferred embodiment, the information layer of the security card is a laser recording medium, for example, EP-A-1.
58906 is a thin metal layer as described in US Pat.
Most preferably, the laser recording layer is a heat mode recordable medium, meaning that data can be recorded by local heating of the medium, for example, when exposed to a laser beam having sufficient power. The local heating is fusion,
Recorded data can be obtained that can be read by optical means, causing melting, particle coagulation, decomposition or other (physical-) chemical processes that cause a local change in the optical reflectivity or optical density of the medium.

Various materials suitable for heat mode recording media are known in the art. A particularly suitable material is a metal layer. The ablation of a metal layer having a relatively high reflectivity can produce a recording spot with a lower reflectivity. The thickness of the metal layer is preferably 700 nm or less, more preferably in the range of 50-600 nm. Tellurium and tellurium alloys have been widely used to form highly reflective thin metal films, where heating with an incident laser beam locally reduces the reflectivity through pitting. For example, the journal Physi
kin unser Zeit, 15. Jahr
g. 1984 / Nr. 5,129-130 Joche
n Fricke's dissertation "Optimische Da
However, tellurium is toxic and other relatively low melting metals such as Ag, Se, Sn and Bi are preferred as suitable heat mode recording media in the security card of the present invention. An overview of suitable metals is US-P-44
99 178 and 4 388 400.

In another case, an improvement in light transmittance can be obtained in the laser beam heated area of the low reflection heat mode recording medium at first. Materials suitable for use in the latter embodiment include, for example, Journal o
f Applied Photographic En
ginering, Vol. 9, No. 1, Feb.
1983, p. 12, for example, on a transparent support, a low-melting metal and a sulfide such as GeS.
Or co-deposition of SnS (co-deposition)
This is a mixture obtained by the For the production of optical media for reading information in reflection mode, the low-reflection heat mode recording medium is applied on a relatively high-melting reflective support or a layer carried by the support, for example an aluminum layer. can do.

Thin layers of metals, alloys or salts suitable for heat mode recording can be produced by vacuum evaporation. In a preferred embodiment of the invention, the recording medium is a thin vacuum deposited layer of Bi or Ag because of its low toxicity, low energy required for fusion or evaporation, and these elements form films easily by deposition. Used as For example, coating a bismuth layer by vapor deposition is E
As described in PA-0 384401, 10
It can be carried out at a reduced pressure in the range of ^-2 Pa to 8 × 10 ^-1 Pa.

The thin Ag layer is formed by a so-called diffusion transfer reversal (DT).
It can also be deposited using the R) method. The principle of the DTR method is described, for example, in US-P-2,352,014 and An.
Reference "Photographic Silver" by dre Rott and Edith Weyde
r Hide Diffusion Procedures
ses ", The Focal Press, London
on and New York, (1972). D of silver halide material exposed as information
Due to the TR treatment, the non-
The developed silver halide is converted to a soluble silver complex compound using a so-called silver halide solvent, which is allowed to diffuse into the image receiving element, where it is generally reduced using a developing agent in the presence of physical development nuclei. . Thus, two silver images are obtained: a chemically developed negative image in the emulsion layer and a physically developed positive "DTR image" in the nucleus layer. Although the two-sheet embodiment is also known in the art, in a preferred embodiment the nucleation layer is in the same material as the photosensitive layer, thereby forming a so-called mono-sheet DTR material. Thus, an unexposed DT comprising a support, a silver halide emulsion layer and a thin physical development nucleus layer.
When the R material is subjected to DTR-processing, a uniform layer of silver metal is deposited on the nucleus layer. The silver metal layer thus obtained can be used as a heat mode laser recording medium as will be shown in Examples.

In addition to the fusible metal, the heat mode recording medium can further include a substance that improves recording sensitivity, for example, by reducing the reflectivity or increasing the absorption of laser light. Examples of such materials are metal oxides, sulfides and halides, for example as described in GB 2 036 597. GeS and SnS are preferred for this purpose, and are applied as a non-reflective layer at a thickness dependent on the wavelength of the recording light, for example a thickness in the range of 5 to 100 nm, without disturbing the ablation of the metal layer. be able to.

Other compounds suitable as laser recording media are composite films whose reflectivity can be reduced by evaporation,
It can be a thin film of a dye whose reflectivity can be changed by ablation, a dielectric material whose refractive index can change and cause light scattering when scanned with a laser, and a photochromic layer of a dye such as bacteriorhodopsin.
A preferred medium containing a laser recordable dye is US-P
5,264,327.

Visible light laser such as Ar or He / N
Information can be stored on the recording medium by using an e-laser, a red laser diode or the like, and the specific wavelength is selected based on the laser recording medium used. Infrared lasers are highly preferred because infrared light is least affected by scratches and dirt on the glass layer.

Preferably, the recording medium has a favorable signal-to-noise ratio, ie high contrast between exposed and unexposed areas, where contrast is defined as the difference in density or reflectance between these areas. Preferably, the laser recording is performed at a speed of at least several thousand bits / second. This generally eliminates the use of materials that require long heating times that may only allow recording at a few bits per second or that rely on slow chemical reactions in the presence of heat.

In the case of a reflection type medium, the reflectance of the non-exposed area is preferably 50% or more, while the reflectance of the data spot obtained by exposure is preferably less than 10%.
This produces a contrast ratio greater than 5: 1. In other cases, data can be recorded by increasing the reflectivity of the strip. For example, a recording laser can melt certain areas of a matte microscopic spike on a strip to produce a flat glowing spot. This method is described in SPIE Vol. 329, Optic
al Disk Technology (1982)
p. 202. The reflectivity of the spot, which is higher than twice the reflectivity of the surrounding spike area, results in a contrast ratio of at least 2: 1, which is sufficient contrast for reading.

The recording medium is preferably characterized by a high resolution and has dimensions of less than 50 μm, more preferably 5 × 20 μm
Recording spot or 5 μm to 10 μm
Allows for a circular spot having a diameter of The storage capacity of the laser recording medium is preferably greater than 250,000 bits, more preferably greater than 1 million bits.

The writing laser beam must have sufficient laser pulse energy at the surface of the recording material to produce a data spot. Typically between 5 and 20 milliwatts are required, depending on the recording material. 5
A 20 milliwatt semiconductor laser focused on a micron beam size can be recorded at a temperature of about 200 ° C. and can produce a spot in less than 25 microseconds. In read mode, the output can be reduced to about 5% of the recorded output.

In addition to the recordable information layer described above, the information layer can be a non-recordable layer. The information layer can also be a discontinuous layer, for example, consisting of optical security information such as letters, numbers, patterns, logos, images, etc. applied on one of the constituent layers of the card. Optical information is
For example, lithographic offset printing, gravure printing, intaglio printing,
Screen printing, flexographic printing, letterpress printing, tampon printing, ink jet printing, laser printing, thermal transfer printing,
It can be applied by a printing method such as dye diffusion thermal transfer printing and toner transfer printing from an electrophotographic recording material.

An optical information layer is present between the opaque layers of the card, and the information concealed by the opaque layer cannot be read visually in a reflective mode, but in a transmissive mode, ie a light source with sufficient intensity It is possible that the image can be detected only by irradiating the card from one side and reading the transmitted image from the other side. Such "hidden"
Alongside other complementary information layers where information can be present on the outer surface of the card, the balanced optical patterns, images, etc., on both of these layers are summed together to form extra security features. Can be configured.

A lens-shaped foil can also be present on the security card of the present invention. EP-A 323108
The combination of such a lens-shaped foil and a plurality of parallel image bands present in the underlying photographic layer, as described in
This is a particularly advantageous security feature when combined with the glass layer of the present invention. A slight rotation of the card about an axis parallel to the lens-shaped foil gives a varying image as various image bands become visible through the lens. The intermediate glass layer between the lens-shaped foil and the image layer does not disturb the optical effect of the changing image during rotation,
On the one hand, it protects the image layer from counterfeiting and mechanical damage from scratches, decomposition by permeation of solvents or gases such as oxygen, water vapor and the like.

The security card may also include other types of security information that can be read by humans or machines,
For example, it may include holographs, watermarks, fingerprints, microlettering, signatures or other printed personal data, marks or layers, which may be liquid crystals, fluorescent pigments, pearlescent foils that provide special light reflecting effects Pigments and / or for example GB-P-15
It can be applied using printing inks which can be read visually or read with UV light, as described in US Pat. No. 18,946 and US-P-4 105 333. Information can also be stored on the card as a storage chip, a radio or radio frequency chip using an antenna, a 1D-2D barcode, a magnetic strip, and the like. Security information can be mixed in the same layer or in several layers. The mixing is performed on a frequency modulation screen.
d

Pseudo-random generator using a screen
s).

Another optional security feature is a digital or optical mask. Digital mask is
It can be an algorithm whereby the digital data (image or text) of the coherent signal is converted into a wideband unreadable pseudorandom signal. The optical mask serving as the optical encryption medium can be a spatial phase mask film or a phase-distorted medium that includes a patterned row of diffuse and non-diffuse pixels. At the time of verification, it is necessary for the user to enter, for example, a pin code and to select a complementary optical mask or a digital mask that allows the decoding of the pseudo-random number signal to recover the coherent signal.

[0043]

EXAMPLES First, a mono-sheet DTR imaging element was prepared comprising a polyester support, a base layer, a silver halide emulsion layer, and a physical development nucleus layer in the order shown. The polyester support had a thickness of 175 μm and was provided with a double subbing layer to promote adhesion of the other layers. The base layer and the silver emulsion layer were coated in a single pass using a cascade coating method, and after one week of storage, a physical development nucleus layer was coated thereon as an uppermost layer using an air knife coating method.

The coating solution for the base layer has a pH of 5.0
H and was coated at a wet thickness of 50 μm.
Base layer contained the following ingredients: -2.84g / m ² of gelatin; silica matting agent having a diameter of 3.5~5.0μm of -0.12g / m ^2; -0.21g / m ² , another silica matting agent having a diameter of 1.3 to 2.1 μm ² ; 0.11 g / m added as a dispersion in gelatin
² carbon powder; - 2.63 where also added as a dispersion in gelatin
Carbon dioxide powder g / m ^2; - dimethyl phenidone of 0.40 g / m ² as a developing agent; - surfactant.

The silver halide emulsion contained 78.6 mol% of A
It contains cubic crystals consisting of gCl, 21.0 mol% AgBr and 0.4 mol% AgI, and is doped with iridium and rhodium. These crystals were obtained using the well-known silver halide precipitation method by simultaneous or alternating addition of aqueous solutions of silver nitrate, sodium chloride, potassium bromide and potassium iodide. After precipitation, the emulsion was flocculated by adding polystyrene sulfonate and lowering the pH to 3.4. The soluble salts were then removed by decantation of the supernatant and washing with water (the procedure was repeated three times). Thiosulfate and Au ³⁺ salts are added and then 50
By ripening at 3.5 ° C. for 3.5 hours, the silver halide crystals were chemically ripened. 185 g of silver halide emulsion
/ Kg of silver halide (expressed as silver nitrate) and 88
g / kg of gelatin and the pH was about 5.2.
The silver halide grains had an average diameter of about 0.40 μm.

The above emulsion was prepared at a pH of about 4.3, about 22 μm.
Wet thickness of 1.55 g / m ² (expressed as silver nitrate)
And a gelatin coverage of 1.50 g / m ² of gelatin. The emulsion layer further contained the following additional non-gelatin components: 1.68 mg / m ² of the following compounds as supersensitizers:

[0047]

Embedded image 1.34 mg / m ² and 0.54 g / m ^{2 respectively} of the following spectral sensitizers:

[0048]

Embedded image -11 mg / m ² of the following stabilizers:

[0049]

Embedded image -33mg / m ² of ethyl acrylate latex; -240mg / m ² of dimethyl phenidone; silica matting agent having a diameter of 3.5~5.0μm of -196mg / m ^2; hydroquinone -226mg / m ² -158 mg / m ² formaldehyde; physical development nucleus layer 0.36 g / m ² hydroquinone;
67 g / m ² of formaldehyde, of 0.66 g / m ² P
It contained a dS nucleus and a surfactant and was coated at a pH of about 8.0 and a wet thickness of about 13 μm.

A strip of the above material is partially exposed through a step wedge and then Agfa-Geva
ert N.E. V. D800, a standard DTR developer and stabilizer G820 available from Belgium.
The treatment was performed using In this way, a material containing two silver layers was obtained: in the exposed areas the silver halide crystals were chemically developed to form silver grains in the emulsion layer (negative image of the step wedge) and were not exposed. In the region, finely pulverized silver particles were formed on the physical development nucleus layer (reversed image).

Next, both of these silver layers were coated on both sides of the above material with a 100 μm polyester sheet and a 75 μm
Was used as a laser recording medium in a security card by laminating a polyethylene adhesive layer (standard contact-warm lamination using a roller laminator). In short, the card thus obtained had the structure shown in Table 1 as Example 1.

[0052]

[Table 1] “X”: no layer; “=”: same layer as in Example 1. “Glass”: 70 μm borosilicate glass, type AF45 from Desag, as defined above.

In addition to the comparative example, Example 1, two materials, Examples 2 and 3, were made in accordance with the present invention. As indicated by the symbol "=" in Table 1, both of these materials contained the same constituent layers as in Example 1, except that Example 2 contained one layer between the physically developed silver layer and the polyethylene adhesive layer. Contains two additional glass layers. No additional adhesive layer was required because the gelatin binder of the recording medium adhered very well to the glass surface when wetted with water and subsequently hot laminated. Example 3 contained the same layers as Example 2, except that as shown in Table 1, a second glass layer was present on the opposite side of the support.

The material was exposed to a Nd: YAG laser (1064 nm) at increasing power steps of 50, 150, 250, 350 and 450 mW and a scan speed of 2 m / s.
The comparative material, Example 1, showed a gradual differentiation between exposed and unexposed areas, ie, the physically developed silver layer and the chemically developed silver layer were made more transparent. The titanium dioxide containing base layer reflected the incident light to the reader, thereby enhancing the visible contrast.

The reflection density D (+) of the non-exposed area and 450
The density difference (ΔD) between the reflection densities D (−) of the areas exposed to the Nd: YAG laser at an output of mW was used as an indicator of the sensitivity of these materials. Surprisingly, Example 2
And the material of Example 3 was characterized by a higher ΔD value than the material of Example 1 (values are shown in column 4 of Table 2). Thus, the glass layer somehow enhances the visible contrast when exposed. This effect is difficult to explain, but it was very reproducible.

Further, by comparing the ΔD value of the new material with the ΔD value of the artificially aged material, a significantly extended shelf life of the material of the present invention could be observed. The ΔD values in Table 2 indicate that the shelf life of the unexposed and exposed laser recording media is significantly extended by the barrier properties of the glass layer.

[0057]

[Table 2] (*) Stored at 67 ° C. and 50% relative humidity for one week.

The cards of Examples 2 and 3 are very difficult to counterfeit because any attempt to peel the glass layer to alter the data in the silver layer results in glass breakage. The card can be bent without breaking the glass layer and is tough.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Bartholomewise Verlinden, Belgium 2640 Maltcell Septes Trat 27 Agfa-Gevuert na Mrose Fennoutjap (72) Inventor Leo Vermiuren Belgium B2640 Maltsel Septes Trat 27 Agfa-Gevert Na Murose Fennoutjap (72) Inventor Herman Van Gaupe Belgium 2640 Maltcell Septes Trat 27 Agfa-Gevert Na Mlose Fennoutjap

Claims (4)

[Claims] 1. A security card comprising a laminate of a flexible glass layer and a support, wherein the glass layer has a thickness of 350 μm or less. 2. The security card according to claim 1, further comprising a lens-shaped foil. 3. Laminating the glass layer on a support, forming a pattern of fractures or grooves in the glass layer, scanning the pattern of fractures or grooves, encoding the scanned pattern with coded information. And v. Storing the coded information. 4. The method according to claim 3, wherein the coded information is stored in or on a security card.