ES2609812T3 - Authentication procedure based on the content of material of biological origin - Google Patents

Abstract

Authentication or identification procedure for a secure document, this document comprising at least one security or reinforcement element comprising at least one synthetic hydrocarbon polymer derived from at least partially plant resources, the content of which is analyzed in said procedure. material of biological origin of the element and / or the document and information regarding identity or authenticity being generated based on the comparison between the measured content and a reference value.

Description

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DESCRIPTION

Authentication procedure based on the content of material of biological origin.

The present invention relates to secure documents.

By "secure document", a security or value document is designated, such as a means of payment, for example a banknote, a check, a credit card or a restaurant voucher, an identity document, such as an identity card, a visa, a passport or a driver's license, a lottery ticket, a transport ticket or even a ticket for cultural or sporting events.

In order to protect against attempts to falsify or alter a secure document, it is known how to attach security elements that are presented, for example, in the form of fibers, plates, films, knitted structures or security threads .

Secure documents are particularly secure by the addition of synthetic security elements added. These elements can be introduced either during the production of the paper (fibers, films, threads, knitted structures) or after manufacturing (films).

Most security and reinforcement elements that can be added to or introduced into the substrate are made from synthetic polymers from fossil oil resources (polyamide, poly (ethylene terephthalate), ...). The addition of reinforcement elements, in particular in the form of fibers or films, of synthetic polymers from fossil petroleum resources allows to improve the mechanical properties of the final material, mainly tear resistance (according to ISO 1974) and / or when folding (according to ISO 5626).

The elements of type thread and film are made as! generally based on poly (ethylene terephthalate) for economic reasons and mechanical resistance, in particular in terms of elongation during application.

The reinforcing fibers are generally introduced at a rate of more than 3% dry weight with respect to the total dry weight mass of the paper fibers and most often they are based on synthetic polymers type polyamide 6.6 (PA 6.6) or made of poly (ethylene terephthalate) (PET) due to the mechanical resistance conferred by these polymers and for economic, manufacturing and good interaction with the natural fibers of the paper.

In addition to synthetic polymers, today certain qualities of safety fibers are prepared from artificial polymers of modified or regenerated cellulosic polysaccharide (cellulose acetate, viscose, rayon) from renewable plant resources, in order to favor uniformity with the natural cellulose fibers that form the substrate. Such fibers are generally introduced at a rate of less than 3%, preferably less than 2%, by dry weight with respect to the total mass of the other fibers of the paper.

"Synthetic polymers" should be understood to mean polymers obtained from chemical synthesis, in particular by a polymerization or crosslinking reaction of monomers.

"Artificial polymers" should mean polymers obtained by chemical modification of a natural polymer, for example from plant materials, such as cellulose acetate, viscose or rayon in the case of a cellulosic polysaccharide. By natural polymer, a polymer is understood to have a polymeric structure in the state in which it is extracted. Such polymers are not considered synthetic polymers within the meaning of the present invention.

French application FR 2 932 804 discloses a polymer derived from acrolelna that comprises organic carbon from biomass. This polymer is used as a preservative or biocidal agent in ink, paper and textile applications.

The GB 990 256 patent discloses a security document or a sheet comprising radioactive marks, which emit a predefined radiation level. The latter allows the activation of systems through electronic circuits connected to sensors.

There is a need to further increase document security, and the invention aims to respond to it.

The invention presents as! as an object, according to the first of its aspects, a procedure for the authentication or identification of a secure document, this document comprising at least one security or reinforcement element comprising at least one hydrocarbon synthetic polymer from at least partially plant resources, also qualified as a polymer of biological origin, being analyzed in the procedure the content of material of biological origin of the element and / or the document and information regarding identity or authenticity is generated based on the comparison between the measured content and a value of

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refer

It is for example the material of biological origin of the element that is analyzed.

As a variant, it is the content of the document, in particular of a substrate of the document, including the two, in particular that of the element and that of the document, that is analyzed.

By "hydrocarbon synthetic polymer from at least partially from plant resources", a polymer obtained by chemical synthesis from at least one monomer of plant origin should be understood, this monomer may be obtained from certain parts of vegetables, for example by fermentation, mechanical extraction, chemical extraction, enzymatic treatment and / or catalyzed chemical reaction.

By "content of material of biological origin" the content is designated as determined according to ASTM D6866-11.

Thanks to the invention, it is possible to authenticate or identify the document without modifying the manufacturing technique of the document, the security or reinforcement element made from a polymer of biological origin can be used and therefore loaded with the 14C isotope instead of the same element made from a synthetic polymer from fossil oil resources that therefore lacks the 14C isotope.

The invention allows the document to be authenticated thanks to the precise analysis of the rate of compounds from renewable plant resources, present in the security and / or reinforcement elements, which carry the 14C isotope.

The use of one or more synthetic polymers of biological origin instead of classic synthetic or artificial polymers allows to make both the substrate and the safety elements added to the substrate safe, since the determination of the content of material of biological origin:

- can verify the authenticity of the security element, loaded with the 14C isotope, and

- it may allow, during the use within the substrate of reinforcing elements loaded with the isotope 14C, to also verify the authenticity of the substrate.

During the synthesis of the synthetic polymers of biological origin, it is possible to use a more or less large proportion of compounds of plant origin instead of non-biological based compounds, to bring the rate of materials of plant origin to a lower value than 100%, and allow to distinguish more easily the synthetic polymer of biological origin used in the invention of a material that will come entirely from plant resources.

Thus, in the examples of implementation of the invention, polymers are synthesized by reacting monomers from which some come entirely from fossil resources and others from plant resources. In embodiments, the previous polymers are mixed with polymers from fossil resources and / or with other polymers from plant resources. Such mixtures are obtained in particular by extrusion and pellet formation before the production of the safety and reinforcement elements. These polymers then serve to make security or reinforcement elements, for example in the form of security threads, knitted structures, films and fibers, with a content of material of known biological origin and which can subsequently be used to identify or authenticate the document or security element or reinforcement.

The document may comprise information related to a material content of biological origin of the security or reinforcement element, or of the document.

This information can be useful during the identification or authentication stage by providing, for example, a reference value with which the analysis result is compared.

The reference value can be stored in the document or stored in a remote place, the reference value being accessed with the help of information carried or stored in the document.

The invention also presents as an object, according to other aspects, a security or reinforcement element suitable for the implementation of the method according to the previous invention, intended to be incorporated into a substrate of a secure document, in particular a fibrous substrate, comprising a hydrocarbon synthetic polymer from at least partially from plant resources, therefore loaded with isotope 14C.

The security element is preferably chosen from a security thread, a secure knitted structure, a safety film or a security fiber.

The reinforcing element is preferably chosen from reinforcing fibers and reinforcing films.

The document may comprise a fibrous substrate comprising cellulosic fibers and security fibers, being

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the mass proportion of security fibers for example less than 10%, preferably less than 3% and more preferably less than 2%, by dry weight with respect to the total dry weight mass of the other fibers of the substrate.

The document may comprise a fibrous substrate comprising cellulosic fibers and reinforcing fibers, the mass proportion of reinforcing fibers being comprised between 3 and 35% by dry weight with respect to the mass of the substrate fibers.

To obtain the desired content of material of biological origin in the safety or reinforcement element, polymers can either be synthesized by reacting in well-defined monomer proportions from which some come entirely from fossil resources and others from plant resources, or mixtures may be applied. of polymers from fossil resources and from polymers from plant resources as indicated above.

The security or reinforcement element may comprise as! a hydrocarbon synthetic polymer that does not come entirely from plant resources, which can be revealed by comparing the content of material of biological origin measured with what would be expected in case of use of synthetic polymers with a totally biological base.

According to a variant, the invention therefore presents as an object a security or reinforcement element suitable for the implementation of the method according to the previous invention, intended to be incorporated into a substrate of a secure document, in particular a fibrous substrate, comprising a hydrocarbon synthetic polymer from at least partially from plant resources, therefore loaded with isotope 14C, such that the content of material of biological origin of the safety or reinforcement element is between 1 and 99%, preferably between 3 and 97%.

The hydrocarbon polymer is preferably a polyamide, a poly (ethylene terephthalate), a poly (ethylene furanoate), a poly (butylene succinate) or a polyhydroxyalkanoate.

Substratum

The secure document comprises a substrate in which it is integrated or on which a security or reinforcement element is added according to the invention.

This substrate can be fibrous, and comprise the fibers and adjuvants used in a classical manner in the field of paper, in particular cellulose fibers. The substrate may comprise a mixture of long and short cellulosic fibers.

The substrate may comprise one or more fibrous layers (also called layers) assembled after formation, in particular in the wet phase.

The substrate may comprise one or more security structures obtained in the manufacture, and the substrate may in particular comprise a fibrous layer carrying a watermark.

The fibrous layer or layers of the substrate can be made in a paper machine with a flat table or round shape, and the watermark (s) can be made in the wet part according to the classical procedures known to the person skilled in the art.

At least one fibrous layer of the substrate, including the substrate itself, can have a weight (according to ISO 536) between 60 and 120 g / m2, preferably between 70 and 90 g / m2.

At least one fibrous layer of the substrate, including the substrate itself, may have a thickness (according to ISO 534) between 60 and 120 pm, preferably between 70 and 110 pm, for example approximately 100 pm.

In an exemplary implementation of the invention, at least one fibrous layer of the substrate comprises a recess, for example a reserve-shaped opening without fibers, made for example in a paper machine or out of a paper machine, for example by drainage reduction, in the die, by laser cutting or by water jet.

The hole (s) present in at least one fibrous layer of the substrate can each have a surface between 0.1 and 10 cm2. The hole (s) may have any geometric shape, in particular rectangular or circular.

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Security elements

The security elements according to the invention can be detected by eye, daylight or artificial light, without the use of a particular device. These security elements comprise, for example, colored fibers or plates, security threads ("security thread" in English) printed or metallized in whole or in part. These security elements are called first level.

According to the invention, other types of safety elements can only be detected with the help of a relatively simple device, such as a lamp emitting in ultraviolet (UV) or infrared (IR). These security elements comprise, for example, fibers, plates, bands, threads or particles. These safety elements may be visible to the naked eye or not, for example being luminescent with illumination of a Wood lamp that emits at a wavelength of 365 nm. These security elements are called second level.

According to the invention, other types of security elements require a more sophisticated detection apparatus for detection. These security elements can generate, for example, a specific signal when they are subjected, simultaneously or not, to one or more sources of external excitation. Automatic signal detection allows the document to be authenticated, if necessary. These safety elements comprise, for example, indicators that are presented in the form of particles or fibers, which can generate a specific signal when these indicators are subjected to an oponic, electrical, magnetic or electromagnetic excitation. These security elements are called third level.

According to the invention, the security element (s) comprising a hydrocarbon synthetic polymer from at least partially from plant resources, therefore loaded with isotope 14C, may have first, second or third level safety features.

Particularly preferred security elements according to the invention are a security thread, a security fiber, a plate or a film.

The security element may comprise a support, in particular transparent, made at least partially with a hydrocarbon synthetic polymer from at least partially from plant resources.

The element may comprise a metallization or demetalization, a luminescent, magnetic compound, an optically variable device, an RFID device, a microlens network, an iridescent or interference pigment, a thermochromic or photochromic compound or liquid crystals.

The element may comprise a heat activatable adhesive.

Security thread

A particularly preferred security element is a security thread.

Such a thread is classically introduced at least partially in bulk into the substrate in the fabrication thereof, and extends from one edge to the other of the secure document. For example, it is entered in bulk or in a window.

The width of the thread is, for example, between 2 and 10 mm and its thickness between 6 and 50 pm, preferably between 6 and 30 pm.

The thread most often comprises a transparent support, preferably made of at least partially biological base synthetic polymer, which carries information, for example a text or an image obtained by metallization / demetallization or printing, for example of positive or negative writing .

The at least partially biological base hydrocarbon synthetic polymer used to make the security thread is preferably chosen from polymers based on poly (ethylene terephthalate).

The security thread may comprise a metallization or demetalization, a luminescent, magnetic compound, an optically variable device, an RFID device, a network of microlenses, an iridescent or interference pigment, a thermochromic or photochromic compound or liquid crystals.

Plates

The plates are flat and relatively small format security elements, similar to confetti that have different shapes, for example circular or hexagonal. They have a size of the order of 1 to 6 mm.

Plates may in particular have one or more of the following optical surface effects: effects of

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interferences such as iridescence or dicrolsm, effects associated with reflection or polarization of light or even luminescent effects, and in particular fluorescent. These effects can be obtained in particular by printing, of areas and / or motifs, or inclusion of specific compounds. On the other hand, these plates may comprise authentication agents such as chemical reagents or liquid crystals, for example.

These plates can be obtained from sheets of plastic material in particular by die-casting, the dies being arranged in metal cylinders, by perforation thanks to punches, cradles or needles, by cutting made thanks to a laser. They can also be made according to patent application WO2005 / 077622, by rotary cutting of blades using a succession of synchronized cutting cylinders and comprising respective cutting blades that are completed so that a figure corresponding to the shape of said plates is formed. .

There are different methods to incorporate plates in a support.

In the case of a sheet of paper as a support, the plates can be introduced in sowing, for example as described in the application WO2005 / 003458. A sheet is obtained in which the plates are randomly distributed.

According to a second method used, in particular when the paper machine has at least one flat table, said plates are introduced into a web by a layer disposed above the fibrous suspension with drainage on the forming fabric of the paper machine. This last method is described, for example, in patent application EP1253241. The plates are therefore arranged in strip on the sheet.

According to a third method used when the paper machine has at least one round shape, said plates are introduced in a band through a feeding duct that flows into the tub close to the aspirating cylinder and before the start of the drainage of the fibrous suspension. .

Then security documents can be made from the supports as! formed; They are described in particular in applications and patent EP342929, EP546917, EP544611 and US 4,037,007.

These plates have the advantage of transmitting a large number of security elements, among which fluorescent printing can be mentioned in particular.

Safe knitted structure

A secure knitted structure is introduced at least partially in bulk into the substrate. Such a structure and its method of introduction into the substrate are described in application EP1766138.

The secure knitted structure preferably comprises at least two threads made of different materials.

The secure knitted structure preferably has an elongation between 1 and 5% according to a predetermined direction.

The secure knitted structure preferably comprises at least one thread of plastic material, of at least partially biological basis, in particular of polyamide, acrylic or polyester material, and preferably of polyamide or polyester.

The secure knitted structure has, for example, a thickness of less than 100 mm, in particular less than 50 mm, and a width of less than 50 mm, for example between 5 and 30 mm.

Movie

A film is introduced at least partially in bulk into the substrate during its manufacture or deposited on the substrate after its manufacture, either:

- at the level of the hole (s) present in at least one fibrous layer of the substrate, for example an opening in the form of a reserve without fibers, made for example in a paper machine or outside a paper machine, for example by reduction of drainage, in the die, by laser cutting or by water jet.

- for all of the security document surface (s).

The thickness of the film is preferably between 6 and 50 mm, preferably between 6 and 30 mm.

The film can be hot or cold rolled, or even extruded on a fibrous substrate. The movie too

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it can be obtained by applying a composition comprising the synthetic hydrocarbon base polymer at least partially biological on the substrate.

The film can carry security elements such as a hologram, luminescence, in particular fluorescence (from Stokes, anti-Stokes ...), markers, optically variable effect elements. These safety elements can be introduced during or after the fabrication of the film.

The synthetic hydrocarbon polymer of at least partially biological base that serves to perform the safety film is preferably chosen from polymers based on poly (ethylene terephthalate).

Safety fibers

The security fibers are introduced in a classical manner in the substrate in the manufacture thereof.

The security fibers are introduced for example at a rate of less than 10%, preferably less than 3% and more preferably less than 2% by dry weight with respect to the total dry weight of the other fibers of the substrate.

The length of the fibers is, for example, between 3 and 10 mm.

The linear density of the fibers is between 1.5 and 33 dtex, preferably being greater than 3 dtex, and more preferably greater than 10 dtex.

The synthetic hydrocarbon polymer of at least partially biological base used to make the security fibers is preferably chosen from polymers based on polyamide and / or poly (ethylene terephthalate).

The fibers can carry safety elements such as luminescence, in particular fluorescence (from Stokes, anti-Stokes ...), markers, optically variable effect elements. These safety elements can be introduced during or after the manufacture of the fibers.

Reinforcement elements

The secure document according to the invention may comprise one or more reinforcement elements based on synthetic hydrocarbon polymer (s) of biological origin.

This or these elements contribute to improve tear or folding resistance. These reinforcing elements may be in the form of a film or of fibers.

A reinforcing element can also be a safety element, for a characteristic other than the presence of 14C.

Reinforcement film

The reinforcing element may be a synthetic hydrocarbon polymer film, at least partially biological based.

This film is, for example, a transparent film, of protection of variable indications. The secure document can be a personal data page of a passport or a card, and comprise such films on one side or on their opposite faces.

The film can cover a fibrous substrate of the security document, for example hot or cold rolled on it, with or without the use of an additional additive.

The thickness of the film is, for example, between 6 and 50 pm, preferably between 6 and 30 pm.

The film may be in the form of a protective layer, for example of a transparent polymer, for example in the form of a film or of a laminating bag, of a thickness comprised for example between 50 and 250 pm, in order to obtain for example a structure more resistant to wear and use.

The film can be a synthetic hydrocarbon polymer of at least partially biological base, selected from among the polyolefins, for example polyethylene, poly (ethylene terephthalate), polyester, polycarbonate, polystyrene, cellulose ester, polysulfone or polyamide.

The film can be laminated on at least one fibrous layer of the structure, for example by means of an adhesive comprising, for example, polyethylene, polyester, polyester-urethane, this adhesive having

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arranged example, extruded or transferred to one of the faces of the film.

The film can also be directly laminated by fusion on at least one fibrous layer of the structure, for example according to the procedure described in EP 1 556 228.

The film can carry security elements such as a hologram, luminescence, in particular fluorescence (from Stokes, anti-Stokes ...), markers, optically variable effect elements. These safety elements can be introduced during or after the manufacture of the film.

Reinforcing fibers

The secure document, and in particular the fibrous substrate, may comprise reinforcing fibers made from a synthetic hydrocarbon polymer of biological origin.

Synthetic reinforcing fibers may be selected from polyester fibers of biological origin or polyamide of biological origin, and mixtures thereof.

According to a particular case of the invention, the reinforcing fibers are poly (ethylene terephthalate) (PET) fibers of biological origin, and are present in an amount in dry weight greater than 3%, preferably between 3 and 35 % with respect to the total fibers of the substrate.

According to a particular case of the invention, the reinforcing fiber also has an authentication function.

The reinforcing fiber may have luminescent properties, for example fluorescent.

For example, it may be a polyester fiber of biological origin, in particular poly (ethylene terephthalate) (PET) of biological origin, which has a reactive compound (fluorescent for example) by grafting or by addition during extrusion of the fiber.

The length of the reinforcing fibers is preferably between 4 and 6 mm, preferably approximately 4 mm.

The linear density of the fibers is preferably less than 3 dtex, preferably approximately 1.7 dtex.

The tenacity of the fibers is preferably greater than 4 cN / dtex.

The tear index, according to ISO 1974, of the substrate reinforced with the reinforcing fibers according to the invention may be greater than or equal to 10 mNm2 / g.

The paper insertion rate is, for example, between 3 and 35% dry weight with respect to the total substrate fibers. It is preferably about 10%.

Determination of the content of material of biological origin

The security or reinforcement element, including the secure document itself, is analyzed by a destructive method to precisely quantify the content of material of biological origin. This element or a part thereof suitable for analysis should be able to be individualized in order to make an effective measurement.

The measurement is carried out according to ASTM D6866-11: Determining the Biobased Content of Solid, Liquid, and Gaseous Samples Using Radiocarbon Analysis (Determination of the content of biological origin of solid, liquid and gaseous samples, using radiocarbon dating). This standard allows the content of material of biological origin to be obtained from the quantification of carbon 14 isotope (14C).

 Examples of synthetic polymers of biological origin

 % of biological origin

 Polyamide: PA 6.6

 fifty

 Polyamide: PA 11

 100

 Polyamide: PA 10.10

 100

 Polyamide: PA 6.10

 62

 Polyamide: PA 10.12

 Four. Five

 Poly (ethylene terephthalate): PET

 100

 Poly (ethylene furanoate): PEF

 100

 Poly (butylene succinate): PBS

 100

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Examples

Example 1: Reinforcement fibers (length of 4 mm and linear density of 1.7 dtex) are manufactured from polyamide 11 of biological origin by melt spinning. The melt spinning line allows filaments to be made from polymer granules (pellets) and treated (ready) in order to facilitate handling! As your cut. The fibers are introduced as! obtained at 8% by mass with respect to cotton fibers. The content of material of biological origin of the fibers is equal to 99%. This content can be analyzed and compared with an expected reference value, during the identification or authentication of a document incorporating these fibers.

Example 2: Reinforcement fibers (length of 5 mm and linear density of 1.7 dtex) are introduced in PA6.10 of biological origin (30%) and PA10.10 of biological origin (70%) at 10% by mass with Regarding cotton fibers.

Example 3: Reinforcement fibers (6 mm linear density, 1.7 dtex) are introduced in PA12.10 of biological origin (50%) and PA6.6 of non-biological basis (50%) at 6% by mass with respect to to cotton fibers.

Example 4: A 6 pm thick reinforcing film is made in PET of biological origin. The content of material "of biological origin" is 100%.

Example 5: A 6 pm thick reinforcing film is made in PET of biological origin (80%) and non-biological based PET (20%). The content of material of biological origin is 80%.

Example 6: UV fluorescent safety fibers (length of 6 mm and linear density of 17 dtex) are used in PET of biological origin. The content of material of biological origin is 98%.

Example 7: Safety fibers of the anti-Stokes type (length of 3 mm and linear density of 10 dtex) are used in PET of biological origin (80%) and PET of non-biological base (20%). The content of material of biological origin is 78%.

In Examples 2 to 7, we can proceed as in Example 1 for an analysis of the content of source material

Biological element and compare them with the expected value, to reach a conclusion about identity or

authenticity of the document or substrate comprising this element.

The expression "comprising a" should be understood as being synonymous with "comprising at least one,"

unless otherwise specified.

Claims (15)

5 10 fifteen twenty 25 30 35 40 Four. Five fifty 55 60 1. Procedure for the authentication or identification of a secure document, this document comprising at least one security or reinforcement element comprising at least one hydrocarbon synthetic polymer from at least partially of plant resources, the procedure being analyzed in said procedure. content of material of biological origin of the element and / or the document and information regarding identity or authenticity being generated based on the comparison between the measured content and a reference value. 2. Security or reinforcement element, suitable for the implementation of the process according to claim 1 and intended to be incorporated into a secure document, comprising a hydrocarbon synthetic polymer from at least partially of plant resources, preferably the element being of safety or reinforcement characterized in that the content of material of biological origin of the security element is comprised between 1 and 99%, preferably between 3 and 97%. 3. Method or element according to claim 1 or 2, the hydrocarbon synthetic polymer being a polyamide, a poly (ethylene terephthalate), a poly (ethylene furanoate) or a poly (butylene succinate). 4. Method or element according to any of the preceding claims, the security or reinforcement element being selected from a security thread, a secure knitted structure, a security film and a security fiber, preferably the security element or of reinforcement a fiber of security. 5. The method or element according to any one of claims 1 to 4, the security or reinforcement element being selected from reinforcement fibers and reinforcing films. 6. Method or element according to claim 4, the length of the security fiber being between 3 and 10 mm. 7. Method or element according to claim 4, the linear density of the security fiber being between 1.5 and 33 dtex, preferably greater than 3 dtex and more preferably greater than 10 dtex. 8. Method or element according to claim 4, the security fiber comprising a magnetic, chemical, biochemical or luminescent marker, in particular fluorescent. 9. A method or element according to any one of claims 1 to 4, the security or reinforcement element comprising a support, in particular transparent, made at least partially with said hydrocarbon synthetic polymer. 10. Method or element according to claim 11 or 12, the security or reinforcement element comprising a metallization or demetalization, a luminescent, magnetic compound, an optically variable device, an RFID device, a microlens network, an iridescent pigment or interference, a thermochromic or photochromic compound or liquid crystals. 11. Method or element according to any of the preceding claims, the security or reinforcement element comprising a heat activatable adhesive. 12. Method according to claim 1, the reference value being stored in the document or stored in a remote location, the reference value being accessed with the help of information carried or stored in the document, preferably the value of reference stored or information carried or stored in the document. 13. Secure document comprising at least one security or reinforcement element according to any of claims 2 to 11, preferably the secure document comprising cellulosic fibers and reinforcing fibers, the mass ratio of reinforcing fibers being between 3 and 35% dry weight with respect to the mass of the substrate fibers. 14. A secure document comprising security fibers according to claim 4 and any of claims 6 to 8. 15. Document according to claim 13, comprising information related to the content of material of biological origin of the security or reinforcement element, or of the document.