Identification and authentication using liquid crystal material markings

Identification and authentication using liquid crystal material labels

Identification and Authentication Using Liquid Crystal Material Markings

Full description

Background of the invention

The present invention relates to machine-readable tags for the purpose of distinguishing, identifying and authenticating specific items. The mark consists of a liquid crystal material that is placed on a substrate using various known methods to print information. The mark can be detected and/or identified by passive detection methods such as optical filters under non-polarized (ambient) lighting conditions, such as by illumination with polarized light. Marks are added in the form of connotations, such as a one- or two-dimensional bar code, a matrix code, or the like.

Track and trace systems are currently used in various areas of industry. Many industries suffer from counterfeit or diverted products, especially in the field of products that are produced in large quantities such as beverages, perfumes, prescription drugs, cigarettes, CDs and DVDs, in addition to other types of consumer goods.

It is easier to carry out counterfeiting and redirection operations if quantitative products are dealt with in quantitative units rather than at the single-piece level. In this case, it is easy to introduce counterfeit or rerouted products into the supply chain. Producers and distributors want to be in a position to differentiate between genuine products and counterfeit or diverted products (imported in parallel) at the level of the single item that can be sold. The inherent technical problem was addressed by assigning a distinctive tag to each salable item as it entered the supply chain. Previous methods were based on choosing the mark in a way that did not make it vulnerable to photography. That is, it was preferable to use hidden signs that cannot be seen by the naked eye or photocopiers.

A “covert” mark is defined, in the context of the present invention, as any mark or security element that cannot be authenticated using the naked eye, but relies for authentication on a detection or reading device of any kind, such as optical filters or electronic authentication equipment. equipment.

In the context of the present invention, an “overt” mark is defined as any mark or security element that does not rely on a reading or detection device in the authentication process. That is, it can be authenticated with the naked eye.

The word “color” is used, in the context of the present invention, to denote any spectrally selected bounce of light (or electromagnetic radiation) from an illuminated object, whether it is in the visible space, in the infrared space, or in the UV space. range of the electromagnetic spectrum (that is, in the entire wavelength range from 200 nm to 2500 nm).

The term "visible" is used to indicate that a property can be detected with the naked eye. While the term “detectable” is used to denote a property that can be detected by an optical machine, and not necessarily by the naked eye, the term “invisible” is used to denote a property that cannot be detected by the naked eye. The term "visible color" specifically refers to a spectrally selected bounce in the wavelength range from 400 nm to 700 nm, which can be detected with the naked eye.

A first type of marking assigned to each product, which is useful in preventing counterfeiting and diversion, is described in Patent Nos. 5569317, 5502304, 5542971, and 5525798. According to these documents, a bar code mark is placed on the item using ink that cannot be detected in light. The visible range is visible (wavelength from 400 to 700 nm), but it becomes visible when illuminated with light in the ultraviolet range (200-380 nm).

There is a second type of mark assigned to each product, which is stated in patent numbers 5611958 and 5766324. According to these documents, the mark is placed on a commercial product using ink that cannot be detected in the visible spectrum, but can be detected using illumination in the infrared spectrum (wavelength 800-1600 nanometers).

There is also another type of marking designated for each product that is placed by ink, and it has been described in patent numbers 5360628 and 6612494. This marking needs to be illuminated using two lights combined of UV- and IR-light so that it can Show it. Another type of marking assigned to each product also relies on ink that contains a phosphorus that raises the frequency, as shown in Patent No. 5,698,397.

All the signs mentioned in the previous methods that were mentioned are hidden signs that cannot be seen at all with the naked human eye. Reading such hidden marks depends on a corresponding reading or detection device, which can detect or read the mark. This can become a disadvantage in the mall or outlet as the appropriate reading device may not always be available. Visible signs that have “optically variable” properties, such as those that change color according to the viewing angle, have previously been proposed as a “man in the street” authentication method. These tags include holograms (see Rudolf L. van Renesse, “Optical Document Security,” 2nd ed., 1998, Chapter 10), optical thin-chip security devices (ibid., Chapter 13), and liquid crystal security devices (ibid., Chapter 14). .

Cholesteric liquid crystals are particularly useful as security devices. When illuminated with white light, the composition of the cholesterol liquid crystal reflects light of a particular color, which depends on the substance in question and generally varies with the viewing angle and body temperature. The cholesteric substance itself has no color, and the visible color is only the result of a physical reflection effect when the cholesteric helical formation takes place at a certain temperature by the liquid crystal substance. (See J.L. Ferguson, Molecular Crystallography, vol. 1, pp. 293-307 (1966). Particularly within liquid crystal materials, in cholesteric liquid crystal polymers (CLCPs), the cholesteric helical structure can be made "frozen" in a certain state by a polymerization process, thus becoming temperature-independent. If the cholesterol liquid crystal material is placed on a dark or black background, the color reflected from it becomes very visible to the naked eye, because the light sent by the cholesterol material is largely absorbed by the background, and thus the background scattering remaining from the background does not affect the perception of the outgoing reflection. Of the cholesterol itself. Therefore, carefully choosing the background color can contribute to the visibility of such a visible sign. On a white or light background, the color reflection from cholesteric liquid crystal polymers (CLCPs) is hardly visible as a result of the combination of the reflection of the cholesteric material itself with the strong backscatter resulting from the background. But cholesteric liquid crystal material can always be distinguished with the help of a circular polarization filter because the selectivity of the filter reflects only one of the two possible components of circularly polarized light, according to its chiral configuration. European Patents Nos. 1,381,520-1b and 1,681,586-1a refer to a birefringent marker and a method for representing a liquid crystalline layer having an irregular configuration of regions of varying thickness. The liquid crystal layer or coating that has been applied can provide the opportunity to place a hidden image on a reflective substrate, which is invisible when viewed in unpolarized light but becomes visible in the presence of polarized light or with the help of a polarization filter.

US Patent 5,678,863 refers to a method for identifying important documents that include a paper or polymer portion that is transparent or translucent. A liquid crystalline material is added to this part to produce a light effect that differs when seen in transmitted light and reflected light. The liquid crystalline material is in a liquid state at room temperature and must be placed inside a container such as a microcapsule so that it can be used in a printing process such as stamp, roller, spray, or inkjet printing. The area that was imprinted with the liquid crystal material can be in the form of an inscription, such as a bar code, for example. This pattern can be verified visually or by examining the states of polarization using a machine for areas that have liquid crystalline shapes in the direction of the right hand or the left hand.

U.S. Patent 5,798,147 refers to compositions for a cladding material consisting of polymerizable liquid crystal monomers that can be added by conventional printing methods such as letterpress printing, rotary stamping, flexographic printing, or offset printing. Or silk screen or inkjet. Printing inks can be used to produce security marks and engravings that are not visible to the human eye. Markers can be detected by their circular polarization or the color of their angle-dependent reflection. US Patent 6,899,824 refers to the process of printing or coating a substrate by means of several layers of a liquid crystal compound and at least one coating that does not use liquid crystals. This process and the substrate it is printed on are useful in producing anti-counterfeiting labels for items. The preferred methods for such printing or coating are: screen printing, printing from a flat surface, flexographic printing, or letterpress printing.

However, none of the marks discussed in the previous methods provide a solution to the technical problem that lies in “track and trace” applications, where, in addition to placing machine-readable marks on the products, it is required to have a mark that can be easily authenticated by eye. Abstract.

There are many well-known “Track & Trace” applications such as postal services, where each piece of mail is individually marked and tracked throughout the delivery chain. 1D-barcodes, such as stacked 1D-barcodes, 2D barcodes, or matrix-codes, are usually used as a means of labeling and identification.

There are no research efforts concerned with the authentication process in the case of the aforementioned postmarks. Since the postal piece is handled internally through the postal company’s services through all stages of the delivery chain, there is no need for authentication. Postal “track and trace” operations focus solely on identifying the piece of mail. But authentication processes become vitally important in commercial applications, where there is a potential risk of the original item being replaced by a counterfeit or misbranded item. For this reason, “track and trace” applications in this field must be combined with at least one insurance element that can certify that the commodity on which the mark is placed is authentic.

The phrase “secure tracking and tracing” will hereinafter mean the combination of “track and trace” applications, which allow the identification of a specific product, with at least one security element, which additionally allows this commodity to be authenticated as authentic.

Technical problem: There is a need in “safe tracking and tracing” applications, where there is a commodity that is traded in an open manner and must have a mark on it itself indicating its authentication and identity and it is followed up throughout its life cycle or for a specific period of time to determine responsibility for the error, for example, to use verification marks. following:

A) It has a specific code so that it can be identified specifically.

B) It can be read by a machine.

c) Resists copying (counterfeiting).

d) It can be authenticated by the human user.

e) It can be authenticated by a machine. In addition, for some applications, it is also preferable for a part of the mark to be invisible to the naked eye.

General description of the invention

The mark of the present invention includes, for the purposes of secure tracking and tracing of a specific item or thing, a mark consisting of a polymerized liquid crystalline material that has certain optical properties that allow it to be authenticated and read by a machine and also to be authenticated by the human eye. The mark is produced on a substrate by printing variable information in the form of connotations representing a specific symbol, allowing it to be identified. It is preferable that the shape of the mark include a part that is not visible to the naked human eye.

The mark of the present invention is applied to items and objects such as value documents, banknotes, passports, identity documents, driving licenses, official permissions, access documents, stamps, hallmarks and marks. Distinctive tax stamps and banderoles, transportation tickets, concert tickets, stickers, foils, parcels, parts, and merchandise Consumer goods, which thus bear that mark, whether placed directly on its surface or indirectly on a sticker placed on its surface.

It is preferable that the polymeric liquid crystal material be of the cholesterol type (i.e. twisted nematic), and filamentous liquid crystal materials (birefringent) can also be used for some applications.

The polymeric liquid crystal material may exist either as a polymeric liquid crystal material on the substrate surface or alternatively consist of pigment flakes of polymeric liquid crystal material of the marking, contained within the coating composition placed on the substrate.

This substrate can be of any type of substrate, woven or non-woven, and in particular it can be of paper, cardboard, wood, glass, ceramic, metal, or plastic. Or textile, or leather...etc.; The substrate can be coated or uncoated, or contain a textured or untextured surface.

It is preferable that the liquid crystal polymeric material of the mark contain other securing materials, which are there to increase its resistance to counterfeiting. These insurance materials are chosen from the group that consists of inorganic luminescent compounds, organic luminescent materials, IR-absorbers, magnetic materials, forensic markers, and materials resulting from the combination of each other.

This insurance material may exist as a mere mixture or, depending on the nature of the insurance material, it may be one of the components involved in the polymerization within the liquid crystal dye, or within the initial formation of the liquid crystal, or within the ink binder. In particular, organic insurance materials can contain an acrylic or vinylic function or be polymerized within the corresponding main polymer. Alternatively, the insurance material can be implanted, that is, chemically attached to a pre-existing polymer chain.

The substrate that represents the background on which the liquid crystal material is placed can be of any color; It is preferable to have a white background to achieve a mark that is hidden to the naked eye, meaning that no visible color will be noticed. A reflective metallic background is a more preferred choice, especially in the case of a birefringent liquid crystal material. The substrate can generally be chosen from a range of reflective substrates, colored substrates, or transparent substrates.

To enable an easy authentication process with the human eye, it is preferable that there be a background of a contrasting color in at least part of the background parts on which the liquid crystal material will be placed. Such as red, green, blue, or black, which together with liquid crystal marking allow the sensation of a visible color and an angle-dependent color when viewed with the naked eye.

Therefore, it is preferable that the substrate be composed of at least two different surface areas in color, each of which is selected from the group consisting of areas with a white surface, areas with a black surface, areas with a visible color surface, areas with a reflective surface, areas with a transparent surface, and the areas resulting from the combination of these. Spaces together. Thus, it becomes clear to those skilled in the field that the surface of the substrate that carries the liquid crystal material can be composed of two or more colored areas under the liquid crystal material.

In addition, the substrate surface - on which the liquid crystal material will be placed - can carry meanings, which can be of any shape and color, such as an inscription, image, logo, text, one- or two-dimensional bar code, or a matrix code. ...etc. These connotations can be added by any method of printing or covering. The substrate may also contain at least one securing element selected from the group consisting of inorganic luminescent compounds, organic luminescent compounds, IR-absorbers, magnetic materials, forensic markers, or compounds resulting from the combination of these compounds with each other. The insurance element can exist in the form of meanings on the substrate surface or be included (integrated) into the substrate itself.

It is preferable that the liquid crystal material be present in the form of connotations. Such as text or code. The preferred connotations are chosen from the group that contains the one-dimensional bar code, the one-dimensional stacked bar code, and the two-dimensional bar code. Bob Williams explained the current types of bar code symbols in the book “Understanding the Bar Code,” PERA International Limited, 2004 (ISBN 1 85802 917 1).

The liquid crystal label of the present invention is preferably produced by adding a first liquid crystalline compound to the substrate and hardening the compound into the ordered liquid crystalline state. This first compound contains actual reactive monomers or oligomers within at least one nematic liquid crystalline compound. It is preferable that monomolecules or oligomers be curable against ultraviolet rays; In this case, the added compound is treated against the UV range and also contains a photoinitiator system, as is known to the skilled person. The ordered liquid crystalline state depends on the presence of a chiral dopant. In the absence of the identical activator, nematic liquid crystals are arranged in a molecular structure characterized by being birefringent. Nematodes protozoa are known from European Patents 0216712-A, 0847432-B and 589445-B.

To produce a cholesteric liquid crystal polymer (i.e., twisted nematic), this first compound must also contain a chiral activator. Such an activator can be chosen from derivatives of Isosorbides, Isomannides, and mixtures between them; As is known from European patent 0847432-B, Japanese patent 2330139-A, and American patent 6589445-B. It is known that isosorbides stimulate helical coiling in the right-handed direction while isomannides stimulate helical coiling in the left-handed direction.

The aforementioned activator produces a helical formation in the nematic liquid crystal compound, and is characterized by a helical step whose length is close to the wavelength of visible light, which leads to the reflection of light at specific wavelengths, and thus an interference color appears, and a change in color occurs that depends on the angle. .

The light reflected from the cholesteric liquid crystalline phases has circular polarization (either left-handed or right-handed), and according to the direction of rotation of the cholesteric helical. The mark is produced according to the present invention by placing the first liquid crystalline compound on a substrate and then hardening this compound on the substrate. It is preferable for hardening to take place by exposing the subject compound to radiation with ultraviolet light, which stimulates the polymerization of the reactive monomers or oligomers to form a liquid crystalline polymer. Thus, the molecular arrangement of the liquid crystals is preserved, that is, the stringy or cholesteric texture is constant in the state that existed before it was exposed to radiation. In the case of cholesterol liquid crystal material, the helical pitch and thus optical properties such as reflection color and angle-dependent color change remain constant.

Thus, the method of placing the mark on the item or thing consists of steps that begin with providing the appropriate item or thing to place the mark on, then placing at least one type of liquid crystalline polymeric material in the form of connotations that represent a unique code in a way of imprinting variable information on the chosen item or thing. In particular, the unique code expressed by the meanings may contain encrypting information, and the method may include a step to encrypt that information.

The first mentioned compound can be placed on a substrate by any printing or coating method. It is preferable to add the compound by a method of variable information printing, such as laser or inkjet printing, either continuously or by a drip-on-demand method. This method of printing variable information allows a unique tag code to be given to each printed item.

To apply the mark by laser printing, dye chips of the liquid crystal polymer can be placed within the printing powder composition. For this purpose, liquid crystalline polymer pigment particles are added at a weight ratio between 1% and 50% to the printing powder composition, which contains the binding resin and may optionally contain some additives such as waxes or charge-controlling auxiliaries.

The aforementioned binder resin is present with a weight percentage ranging between 45% and 95%, and it consists of thermoplastic polymers such as:

polyamides, polyolefines, polyurethanes, vinyl resins, epoxides, styrene butadiene, styrene acrylate copolymers or polyester resins

It has a glass transitions temperature (Tg) ranging from 40°C to 120°C. It is preferable that it be between 60 micrometers and 70 micrometers, and have an average polymer particle size ranging between 2-30 micrometers, according to the accuracy required in the printed image. Liquid crystal polymer pigment flakes can be placed inside the aforementioned connective resin.

Optionally, liquid crystalline polymer dye films placed within a printing powder composition as described above may be added to a carrier liquid at a weight ratio of between 5% and 60%; Thus, a display liquid is formed which can later be used as ink for printing, as is known to the skilled person. Preferred carrier fluids include aliphatic hydrocarbons, alicyclic hydrocarbons, or polysiloxanes.

The most preferred among these liquids are paraffin solvents (petroleum wax) and isoparaffin solvents.

For ink-jet printing applications, the compound also contains an organic solvent, so that the viscosity of the compound can be adjusted to be compatible with the chosen printing method, as is known to the skilled person.

In continuous inkjet printing, the compound also contains a conductive agent (salt), which must be soluble in the compound used. The need for this connection aid arises as a technical requirement for this printing process. As it is known to the skilled person.

As another alternative implementation, the liquid crystal label of the present invention may be produced by coating a substrate with a compound containing flakes of the liquid crystal polymer dye in a suitable binder.

It is preferable that the liquid crystalline polymer dye chips be made of a cholesterol liquid crystalline polymer, which has the property of reflecting light at specific wavelengths (interference color), and also has the ability to shift color in an angle-dependent manner. Such chromosomes are known to the skilled person from international patent 000755/2008-1a (and related documents) and from European patents 1213338-1b, 0685749-1b, German 19922158-1a, European 0601483-1a, German 4418490-1a and European 088739 8- 1B, International No. 063926-2006, and US Patents 5,211,877, 5,362,315, and 6,423,246.

The appropriate binding materials can be chosen from vinylic resins, acrylic acrylic resins, styrene-maleic anhydride copolymer resins, polyacetal resins, polyester resins, fatty acid modified polyester resins, and materials resulting from mixing these materials with each other. . The binder can also be chosen from monomers and oligomers treated with UV radiation, such as acrylates, vinyl ethers, epoxides, and mixtures of these materials together.

It is preferable that the mark be placed by ink-jet printing. To obtain reliable printing and acceptable print quality, the nozzle of the inkjet equipment used must be of a large enough diameter. The nozzle diameter must be at least ten times larger than the average diameter of the liquid crystal pigment polymer flakes. For example, if the average chip diameter is 25 micrometers, the nozzle diameter must be at least 250 micrometers. Systems that achieve these properties are called valve-jet printers, which are a special type of inkjet printer that operates on a drip system when needed.

In general, the method of authenticating an item or thing bearing a mark in accordance with this invention involves the following steps: a) Obtaining the item or thing bearing a mark in accordance with the present invention. b) Illuminating the mark on the aforementioned item or thing with at least one type of light from at least one light source. c) Detecting the optical properties of the mark by sensing the light reflected from the mark. d) Determining the authenticity of the item or thing based on the optical characteristics of the mark that have been detected. A mark made in accordance with this invention may be authenticated by a first method based on simple visual inspection in normal light. For this purpose, the background on which the liquid crystal material is placed must provide a sufficient amount of light contrast so that the viewer can feel the reflected light and the change in color of the liquid crystal material.

Depending on the background, part of the mark may remain invisible to the naked eye.

The mark can be authenticated in a second way in normal light and with the help of a passive detection method such as an optical filter. An example of a preferred passive detection method is a circular polarization filter in the direction of the right hand, the left hand, a combination of both, or both. This allows determining the direction of the helical step of cholesteric liquid crystal polymers (CLCPs), by determining the state of polarization of light reflected from the material in question.

Optionally, the polarizing filter can be combined with color filters to reduce the width of the spectral band to the value of the spectral reflectance band of the liquid crystal material, thus reducing background effects. More than one light filter can be used together.

In a third method, the mark can be authenticated with the help of circularly polarized light from at least one polarized light source. The liquid crystal material reflects light in a different way according to circular polarization. Thus, it is possible to differentiate between materials with a spiral step in the right-hand direction or the left-hand direction by the reaction of each of them to circularly polarized light. Optionally, the mark can be illuminated with a polarized light source and the light reflected from the mark can be observed using a color filter. More than one polarized light source can be used together. In a fourth method, the mark can be authenticated with the help of an electro-optical authentication device. This may be implemented in such a way that the device consists of at least one photocell plus a circular polarization filter and/or a circularly polarized light source. In another implementation such device may consist of an electro-optic camera, such as a linear array of charge-coupled sensors, a two-dimensional array of charge-coupled sensors, a linear array of complementary metal oxide semiconductor image sensors, or a two-dimensional array Dimensions of image sensors operating with complementary metal anodized semiconductor technology, plus a circular polarizing filter and/or a circularly polarized light source.

The circular polarizing filter or circularly polarized light mentioned in the implementation methods mentioned above can optionally be combined with color filters, to select a specific spectral range and to improve the contrast ratio between the light reflected from the liquid crystal material and the light reflected from the background.

In general, an electro-optical polarization switch can also replace circular polarization filters. Such a key is known before. Such as German Application No. 10211310-4B, which allows selecting a circular polarization state or the corresponding state by exposing it to a specific potential difference for each state.

In all cases of use of cholesterol liquid crystalline substances, the mark produced in accordance with the present invention is authenticated by verifying one or more of its characteristics; It is the state of circular polarization and/or color that depends on the viewing angle in the light reflected from the sign. Either a polarized light source or polarized light detection equipment, or both, can be chosen to operate in the visible, infrared or ultraviolet range of the electromagnetic spectrum, or in a combination of more than one according to the optical properties of the mark.

The mark produced according to the present invention can be identified by reading the meanings it represents and by subsequently linking the information read from the mark with the information stored in a database. In a certain implementation method, the information represented by the meanings of the sign can be encoded, and then the aforementioned recognition includes the step of decoding the information. Preferably, the meanings are read with an electro-optical camera such as a charge-coupled sensor array or a complementary metal oxide semiconductor array.

In general, the process of identifying a marked item or thing according to the present invention consists of the following steps. a) Obtaining an item or thing bearing a mark according to the present invention. b) Illuminating the mark on the aforementioned item or thing with at least one type of light from at least one light source. C) Reading the meanings represented on the mark and deducing the corresponding information. D) Conducting the correlation process between the information retrieved from the meanings of the mark and the information stored in a database. e) Obtaining confirmation or denial regarding the identity of the item or thing.

The process of identifying a specific item or thing bearing a mark according to the present invention can be performed using the same equipment and fixture positions used in the authentication process.

In a first implementation method, the indicated meanings can be represented by a one- or two-dimensional bar code, and the image recovered from the electro-optical camera is analyzed in its digital form according to a corresponding algorithm. The information contained in the bar code is retrieved, decoded if necessary, and compared to information stored in a database, thus identifying the item. Optionally, the database can be updated with supplementary information, such as information about the item's history. The camera can be part of a reading device with its own communications capabilities, or it can be part of a communication device such as a mobile phone, and the information can be retrieved using the mobile phone's internal resources. The database may be located on the communication device (such as internal memory or memory that can be changed), or located on an external server accessed via the communications network.

In another method of implementation, these meanings can be represented by an alphanumeric code, and the image retrieved by the electro-optical camera (reading device) can be analyzed in the digital image using an algorithm corresponding to optical character recognition. The information contained in the code is retrieved and compared to the information stored in a database. Thus, the item is identified and the database can optionally be updated. As in the first method of implementation, the database can be either in the reading device (built inside or on memory that can be exchanged), or on an external server accessed via a communications network. The alphanumeric code can be printed using standard font or using a special font that is recognized by the machine. The alphanumeric code can optionally be read by eye and then either sent via a communication system (eg the Internet or mobile SMS) to a data center for verification or compared to data placed on the item in the form of a label, bookmark or other alphanumeric code.

Tags made in accordance with the present invention and made of a polymerized liquid crystalline material with certain optical properties can be used for secure tracking and tracing of items, objects or goods that have a special anti-counterfeiting code for the purpose of secure tracking and tracing of such items, objects or goods. Setting a custom code for each commodity or thing requires a method of printing variable information. The preferred method for printing variable information in the context of this invention is chosen from the group represented by ink-jet printing or drip-on-demand ink-jet printing; These printing methods allow the custom code to be placed quickly and without contact on any type of surface. This custom code allows each element to be identified individually at a later stage in its life cycle.

To prevent any original item from being replaced by a counterfeit one carrying a copy of the indicated custom code, that custom code must be counterfeit-resistant. The anti-counterfeiting feature can be added through a specific insurance material that has certain physical and preferably optical properties. This material can be one of the component materials or be included within the mark. The specific insurance material may be a liquid crystalline polymeric material with specific optical properties, or it may be an additive selected from a group of inorganic luminous compounds, organic luminous compounds, IR-absorbers, magnetic materials, forensic markers, and a combination of those. Components each other.

The mark proposed in the present invention can be used on items or things such as valuable documents, banknotes, passports, identity documents, driver’s licenses, official permits, transit documents, stamps, imprints and distinctive marks (especially on tobacco products and alcoholic beverages), and tickets. Transportation, concert tickets, labels, foils, parcels (particularly in the case of pharmaceutical products), and generally in the labeling of spare parts and consumer goods (particularly to solve problems relating to the identification of responsibilities).

When the mark proposed in the present invention is placed on items, goods and things, it is suitable for use in safe tracking and tracking of those items, goods and things. Such secure tracking of the item or object consists essentially of the first two unstructured steps: a) placing a mark in accordance with the invention on the item or object to be traced and b) storing information relating to the marked item or object in a database; As well as the following two unordered steps: c) authenticating the item or thing according to the authentication method described here; Or identify the item or thing according to the identification method described here and using information previously stored in the database. Optionally, the database can be updated accordingly with some new information about the item or object.

The code that is placed on the item or commodity represents digital data, which can be stored in a database so that the item or commodity can be identified at a later stage. The referred code can be encrypted to protect the information it contains when transferred to and from the database. The referenced database may be part of a database management system. All types of encryption algorithms are suitable, such as the public secret key (RSA).

The referenced database may be a local database located within the authentication device. It can alternatively be a remote database, connected to the authentication device via a wired or wireless link. The local database can also be updated regularly from the remote server.

On the other hand, the present invention enables custom labeling by means of a variable information printing system. The preferred method is ink-jet printing, either using continuous inkjet or using drop-on-demand (DOD) or valve jet inkjet. Industrial inkjet printers, which are commonly used for numbering and coding applications on product configuration lines and printing machines, are particularly suitable.

The preferred inkjet printers are continuous single-nozzle inkjet printers (also known as raster or multi-level skew printers), drop-in inkjet printers, and especially valve-jet printers.

Nematic liquid crystalline materials are used to give a completely invisible and machine-readable mark. Choleretic or chiral (symmetric) liquid crystalline materials are used to give a visible or semi-invisible mark that can be read by machine.

Brief explanation of the drawings

To understand the current invention more comprehensively, refer to the detailed description of the invention and the attached drawings.

Figure No. 1 shows a plan of a cardboard package such as a pharmaceutical package bearing distinctive marks a), b) and c) in accordance with the invention and printed with a liquid crystalline substance on different places of said cardboard package:

Shows matrix data code on a very dark background such as a black background.

COG shows matrix data on a mixed-color background, such that some parts are light and others are dark.

Shows matrix data code on a white background.

Figure 2 shows images taken of an ECC200 matrix printed with a UV range-treated liquid crystal material on coated cardboard:

The liquid crystal matrix data code was retrieved from a black background in the presence of circularly polarized white lighting towards the right hand in front of a complementary metal oxide semiconductor (CMOS) camera.

The liquid crystal matrix data code was retrieved from a white/black background in the presence of right-hand circularly polarized white light using a right-hand circular polarization filter in front of a complementary metal oxidized semiconductor (CMOS) camera.

The liquid crystal matrix data code was retrieved from a white/black background in the presence of right-handed circularly polarized white light and no filter in front of a complementary metal oxidized semiconductor (CMOS) camera.

The liquid crystal matrix data code was retrieved from a white/black background in the presence of unpolarized white light without a filter in front of a complementary metal oxidized semiconductor camera.

Detailed description

In the first method of implementation, the mark is made according to the present invention from a liquid crystalline raw material, which is placed in a liquid state on the surface of a substrate, and is then polymerized (cured) in the ordered liquid crystalline state by irradiation with ultraviolet light or by a beam of electrons such as He is known to the skilled person in the field.

Thus, the liquid crystal material added in this method is a single-molecule (monomer) or small-molecule (oligomer) primary compound of the liquid crystalline polymer. This first polymer contains at least one linear liquid crystalline oligomer or monomer, and these monomers or oligomers have polymerizable groups. Suitable monomers and nematic liquid crystal monomer or oligomers belong to a group such as:

benzoic acid 4-[4-[(1-oxo-2-propenyl)oxy]butoxy]-1,4-phenylene ester,

benzoic acid 4-[4-[(1-oxo-2-propenyl)oxy]butoxy]-, 2-methyl-1,4-phenylene ester,

benzoic acid 4-[4-[(1-oxo-2-propenyl)oxy] hexoxy]-, 2-methyl-1, 4-phenylene ester, benzoic acid 4-[4-[(1-oxo-2-propenyl) )oxy]butoxycarboxy]-1, 4-phenylene ester,

benzoic acid 4-[4-[(1-oxo-2-propenyl)oxy]butoxycarboxy]-, 2-methyl-1,4-phenylene ester

A nematic liquid crystal monomer can be present in the starting material in the range of 10% to 100% by weight.

If the curing process is carried out by means of ultraviolet irradiation, the starting material includes at least one photoinitiator and may optionally contain a stabilizer. Suitable photoinitiators can be selected from the Airgacure group (such as Airgacure 369, 651, 907 or 1300), genomers (such as BP/EPD) or any free radical scavengers.

Suitable stabilizers are Florstab UV-1 supplied by Kromachem and Genorad 16 supplied by Rahn.

The photoinitiator can be present in the feedstock in the range of 0.5% to 5% by weight.

To obtain cholesteric phases

(i.e. twisted nematic) The aforementioned starting material also contains at least one chiral activator (chiral inducer), such as:

(3R, 3aR, 6R, 6aR)-hexahydrofuro[3, 2-b]furan-3, 6-diyl bis(4-(acryloyloxyethoxy) benzoate),

(3R, 3aR, 6R, 6aR)-hexahydrofuro[3, 2-b]furan-3, 6-diyl bis(4-(acryloyloxybutoxy) benzoate),

(3R, 3aR, 6R, 6aR)-hexahydrofuro[3, 2-b]furan-3, 6-diyl bis(4-(acryloyloxybutoxy)-2-methylbenzoate),

(3R, 3aR, 6R, 6aR)-hexahydrofuro[3, 2-b]furan-3, 6-diyl bis(4-(acryloyloxybutoxy)-3-methoxybenzoate),

(3R, 3aR, 6R, 6aR)-hexahydrofuro[3, 2-b]furan-3, 6-diyl bis(4-(4'-(acryloyloxybutoxy) benzoyloxy)-3-methoxybenzoate),

(3R, 3aR, 6R, 6aR)-hexahydrofuro[3, 2-b]furan-3, 6-diyl bis(4-(acryloyloxy)-2-methylbenzoate),

(3R, 3aR, 6R, 6aR)-hexahydrofuro[3, 2-b]furan-3, 6-diyl bis(4-(acryloyloxy)-3-methylbenzoate),

(3R, 3aR, 6R, 6aR)-hexahydrofuro[3, 2-b]furan-3, 6-diyl bis(4-(4-(acryloyloxy) butoxy)benzoate),

(3R, 3aR, 6R, 6aR)-hexahydrofuro[3, 2-b]furan-3, 6-diyl bis(4-25 (acryloyloxy)-3,5-dimethylbenzoate),

(3R, 3aR, 6R, 6aR)-hexahydrofuro[3, 2-b]furan-3, 6-diyl bis(4-(4-(acryloyloxy) benzoyloxy)benzoate),

(3R, 3aR, 6R, 6aR)-hexahydrofuro[3, 2-b]furan-3, 6-diyl bis(4-(4-(4-(acryloyloxy) butoxy)benzoyloxy)benzoate),

(3R, 3aR, 6R, 6aR)-hexahydrofuro[3, 2-b]furan-3, 6-diyl bis(4-(4-(4-(acryloyloxy) butoxy)benzoyloxy)-3-methoxybenzoate,

(3R, 3aR, 6S, 6aR)-hexahydrofuro[3, 2-b]furan-3, 6-diyl bis(4- (acryloyloxyethoxy)benzoate),

(3R, 3aR, 6S, 6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4-(acryloyloxybutoxy) benzoate),

(3R, 3aR, 6S, 6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4-(acryloyloxybutoxy)-2-methylbenzoate),

(3R, 3aR, 6S, 6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4-(acryloyloxybutoxy)-3-methoxybenzoate),

(3R, 3aR, 6S, 6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4-(4'-(acryloyloxybutoxy) benzoyloxy)-3-methoxybenzoate),

(3R, 3aR, 6S, 6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4-(acryloyloxy)-2-methylbenzoate),

(3R, 3aR, 6S, 6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4-(acryloyloxy)-3-methylbenzoate),

(3R, 3aR, 6S, 6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4-(4-(acryloyloxy)butoxy)benzoate),

(3R, 3aR, 6S, 6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4-(acryloyloxy)-3,5-dimethylbenzoate),

(3R, 3aR, 6S, 6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4-(4-(acryloyloxy) benzoyloxy)benzoate),

(3R, 3aR, 6S, 6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4-(4-(4-(acryloyloxy)butoxy)benzoyloxy)benzoate) and

(3R, 3aR, 6S, 6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4-(4-(4-(acryloyloxy)butoxy)benzoyloxy)-3-methoxybenzoate),

And composite materials from each other. The chiral inducer can be present in the starting material in the range of 0.1% to 25% by weight.

The mark should preferably be applied by inkjet printing, either continuous inkjet or drip type inkjet on demand, preferably by nozzle/line printing or by valve jet printing. To apply the mark by inkjet printing, the compound may also contain a solvent, to adjust its viscosity to the low values required for that printing method. Normal viscosity values for inkjet printing inks range from 4 to 30 mPascals per second at 25°C.

Choose the solvents that can be used from a group of non-protein, low-polar, low-density organic solvents, such as:

methyl-ethyl-ketone (MEK), acetone, ethylacetate, ethyl 3-ethoxypropionate or toluene. Solvents to which chlorine is added are:

Dichloromethane, trichloromethane or trichloroethylene are technically suitable but undesirable in printing inks due to their toxicity.

The solvent in the inkjet feedstock is present in the range of 10% to 95% and usually in the range of 55% to 85% by weight.

In the case of continuous ink-jet printing, the feedstock also contains a dissolved conductive catalyst, usually in the form of a salt, such as:

lithium nitrate, lithium perchlorate, tetrabutylammonium chloride or tetrabutylammonium tetrafluoroborate

Salt is found in concentrations ranging from 0.1 to 5% by weight.

It is preferable that the primary material also contain insurance substances, which are found in low to medium concentrations, in order to increase the mark’s resistance to counterfeiting. These insurance materials are chosen from the group that consists of inorganic luminous compounds, organic luminous compounds, IR-absorbers, magnetic materials, forensic markers, and a mixture of these materials with each other. Concentration percentages range from 0.01% to 5% for luminous compounds, from 0.1% to 10% for IR-absorbers or magnetic materials, and from 0.001% to 1% for forensic markers.

The preferred cholesteric liquid crystalline starting material for implementing the present invention by inkjet printing equipment comprises a mixture of at least one chiral compound, at least one chiral compound, an organic solvent and a photoinitiator.

It is preferable that the referred to filamentous compound be of the chiral or bis-acrylic type, as explained in Patent Nos. 0216712-A, 0847432-B, and US Patent No. 6589445, which are included here as references. The preferred amount of the filamentous compound present in the initial cholesterol liquid crystalline mixture ranges from about 10% to 60% by weight, and more preferably from 10% to 45% by weight.

The chiral catalysts are selected from derivatives of isosorbides and isomannides, which are described in Patent 0739403-B, Japanese Patent 2-330139-A, and American Patent 6589445-B, which are included here as references. The amount of chiral inducer present in the initial cholesterol liquid crystalline mixture ranges between 0.1% by weight and 25% by weight, and preferably between 0.5% and 15% by weight.

The liquid crystalline raw material used in the production of the mark according to the present invention may also include dyes, colors, coloring agents, thinners, conductive salts, surface active compounds, surface adhesion promoters, wetting agents, defoamers, and dispersion agents.

According to the present invention, the mark may preferably be placed in the form of a signifier representing a unique code, either a one-dimensional bar, one-dimensional stacked, two-dimensional, or a matrix code. It is preferable to choose symbols from those used in the field of sales to mark commercial goods. These codes are subject to internationally recognized standard systems, and the algorithms used in the processes of reading and understanding the signs are known and implemented in commercially available devices.

Proper one-dimensional and one-dimensional stacked code symbols are known to the skilled person and are available under symbol names such as:

Plessey, UPC, Codabar, Code 25-Non-interleaved 2 of 5, Code 25-Interleaved 2 of 5, Code 39, Code 93, Code 128, Code 128A, Code 128B, Code 128C, Code 11, CPC Binary, DUN 14 , EAN 2, EAN 5, EAN 8, EAN 13, GS1-128 (formerly known as UCC/EAN-128), EAN 128, UCC 128, GS1 DataBar formerly Reduced Space Symbology (RSS), ITF-14, Pharmacode, PLANET , POSTNET, OneCode, MSI, PostBar, RM4SCC/KIX, or Telepen

Suitable binary codes for 2D barcodes are known to the skilled person and are available under code names such as:

-DI, ArrayTag, Aztec Code, Small Aztec Code, bCODE, Bullseye, Codablock, Code 1, Code, 16K, Code 49, Color code, CP Code, DataGlyphs, Datamatrix, Datastrip Code, Dot Code A, EZcode, High Capacity Color Barcode, HueCode, INTACTA.CODE, InterCode, MaxiCode, mCode, MiniCode, PDF417, Micro PDF417, PDMark, PaperDisk, Optar, QR Code, Semacode, SmartCode, Snowflake Code, ShotCode, SuperCode, Trillcode, UltraCode, VeriCode, VSCode, WaterCode , and ECC200.

This last code contains an error correction code and is defined in the international standard system ISO/CEI 16022:2006.

The types of fonts suitable for optical character recognition are known to the skilled person.

Figure 1 shows a schematic diagram of a product package bearing a cholesterol liquid crystal label according to the present invention. The mark is represented in the form of the data matrix code ECC200 on the surface of the indicated package. The ECC200 data matrix is a symbol available in the public domain. The mark can be placed anywhere desired on the package. Therefore, it can be present entirely on one background color (A) or partially overlapping with the first background color and another color present within the packaging design. (b) Or located entirely on a white or colorless area of the package (c).

The reading device used to read a tag made according to the present invention may be based on commercially available bar code readers, in particular based on CCD/CMOS camera-based reading equipment and reading terminals used in sales. In the event that the mark does not match the available (narrow band) illumination, the indicated reading devices can be directly enabled to read the liquid crystal codes.

In other cases, the reading device can be adapted (enabled) to read the reaction of the specific security elements placed within the tag. Flatbed scanners can also be used after alignment. CCD camera based bar code readers are known to the skilled person and are produced by many industrial companies such as AccuSort, Cognex, DVT, Microscan, Omron, Sick, RVSI, Keyence, etc.

Said accommodation of the reading device may include one or more optical filters selected from a group of linear polarizing filters, right-facing circular polarizing filters, left-facing circular polarizing filters, electro-optical polarizing filters, wave plates, color filters with spectral selectivity of any type, and a combination thereof. Filters. In a certain method of implementation, at least two optical filters must be used. Said alignment may also include the implementation of one or more light sources selected from the group of light sources with spectral selectivity (i.e., color), linearly polarized light sources, left and right circularly polarized light sources, and a combination thereof.

However, light sources can be chosen from ambient light, incandescent lamp light, diode laser units, light-emitting units, and all types of light sources that have color filters.

The mentioned light sources may have spectral emission in the region of the visible light spectrum (wavelength 400-700 nanometers), in the infrared region close to light waves (wavelength 700-1100 nm), or infrared waves far from light waves (wavelength 1100-2500 nm) or ultraviolet radiation (wavelength 200-400 nm) of the electromagnetic spectrum.

Thus, the mentioned reading device is not only possible to read the mark, but also to authenticate it to ensure that it is made of the correct insurance material, that is, it contains the required insurance elements. It sends digital information that expresses the code that was read and points to one of the database entries corresponding to the item that carries that tag and that code. This digital information can be compared with the information stored in the reading device or can be exchanged between the reading device and an external database. This exchange can be done in an encrypted manner; That is, using RSA private/public key encryption. This exchange of information can occur by all types of transmission means, such as linear transmission, wireless links, infrared links, etc....

In the special case where the starting material does not contain a chiral inducer, a nematic liquid crystalline polymer is obtained. Such a polymer usually has the property of birefringence, meaning that the molecules in a printed layer are aligned in a dominant direction, and the component of the refractive index in the direction of the molecular axis is different from the component of the refractive index in the direction perpendicular to the molecular axis.

Such a nematic liquid crystal polymer can act as an insurance element by using its birefringent properties, in which case it acts as a wave plate that can convert linear polarization to circular polarization or vice versa at the appropriate layer thickness. In the case of a reflective substrate, the presence or absence of the applied liquid crystalline polymer can be detected using a linear optical filter placed above the mark in an appropriate direction. In the case of a transparent substrate, there is a need to place either a reflector or a second polarization filter on the back of the substrate to make the mark visible.

In another method of implementation, the mark made according to the present invention consists of dye flakes of a liquid crystalline polymer; These dye flakes are located inside the cladding component that is placed on the surface of the substrate.

One preferred type of liquid crystal polymer dye is that described in patent WO 2008/000755 A1 and is cited herein by reference. A tag according to the present invention containing such a dye has at least two reflection bands in the wavelength range from 200 nm to 2500 nm.

Cholesteric liquid crystal polymers (CLCPs) that are useful in implementing the present invention are detailed in European Patent Nos. 1213338-1B and 0685749-1B, German Patent No. 19922158-1A, European Patent No. 0601483-1A, German No. 4418490-1A, and European Patent No. 19922158-1A. No. 0887398-1B and International No. 063926/2006. There is also a reference to US patents Nos. 5,211,877 and 5,362,315. Such particles have a thickness in the range of 1 to 10 micrometers and a thickness in the range of 10 to 100 micrometers and are obtained by crushing a thin film of the corresponding liquid crystalline polymer. The preferred thickness of the foil for use with the present invention ranges from 1 to 10 micrometers and the average diameter of the foil ranges from 20 to 50 micrometers.

The aforementioned coating composition contains at least one binder as a mandatory component, and optionally there may be dyes, colors, extenders, additives, photoinitiators, etc., according to what is required by the process of applying the mark and the substrate on which the mark will be placed. The preferred bonding materials are chosen from the group of vinylic resins and acrylic resins and:

Acrylic resins, styrene-maleic anhydride copolymer and polyacetal resins, polyester resins, fatty acid monomers and oligomers treated with ultraviolet radiation, such as acrylates, vinyl ethers, peroxides (epoxides), and mixtures of these materials with each other.

It is preferable that the coating composition additionally contain insurance materials, which are present in low to medium concentrations in order to increase resistance to counterfeiting. These insurance materials are chosen from a group consisting of inorganic luminescent compounds, organic luminous compounds, IR-absorbers, magnetic materials, forensic markers, and a mixture of these materials with each other. Concentration values range from 0.01% to 5% for luminous materials, from 0.1% to 10% for IR-absorbers or magnetic materials, and from 0.001% to 0.1% for forensic markers.

To accommodate certain special conditions, the coating composition used to produce the mark according to the present invention may also contain colours, pigments, discolouration agents, thinners, conductive salts, surface active compounds, surface adhesion promoters, wetting agents, defoamers and dispersion agents as are known in the art. .

Authentication and identification of the liquid crystal marking of the present invention requires a light source and must be accomplished by one of the following methods:

a) By illuminating the mark with linearly or circularly polarized light and detecting the reflection of the mark,

b) By illuminating the mark with unpolarized light (i.e., ambient light) and detecting the reflection of the mark using a linear or circular polarization filter,

c) By a combination of circularly and linearly polarized illumination and detection by a linear or circular polarized filter.

Thus, the element on which the mark is placed is illuminated with a light source chosen from non-polarized light sources, polarized light sources, circularly polarized light sources towards the left, or circularly polarized light sources towards the right.

In all cases, detection can be performed by eye or with the help of electro-optical detection equipment, such as a photocell or a CCD or CMOS camera. Light sources and detectors can be made or selected to have spectral selectivity by the use of light emitters and/or color filters. It is preferable to detect in the visible region (wavelength of 400-700 nanometers) of the electromagnetic spectrum.

In a certain method of implementation, the sign is illuminated for the purpose of authenticating an element or thing using at least two different light sources chosen from non-polarized light sources (randomly polarized), linearly polarized light sources, left-polarized light sources, and right-polarized light sources.

Figure 2 shows images of ECC200 data matrix codes printed on liquid crystal material on laminated cardboard. These images clearly demonstrate the advantage of using the polarizing properties of the sign made of liquid crystal material in reading the code printed on a clear background or with some textures. Using a combination of a polarized light source for lighting and using a polarized filter in front of the camera is the best method. All images were taken using the same light source and camera settings, all in black-and-white mode with or without polarizing filters before the light source and/or camera. The images have been digitally processed to give maximum contrast and best light intensity.

In one preferred option, the liquid crystal marking made according to the present invention becomes visible in unpolarized lighting (preferably ambient lighting) by means of passive detection such as a circular or linear polarizing filter. However, the mark can also be recognized and authenticated outside the visible light spectrum (wavelength from 400-700 nm) in the infrared range, for example (wavelength from 700 to 2500 nm), and it is preferable for it to be in areas of the infrared range close to light ( (wavelength 700-1100 nm) or the far-infrared (wavelength 1100-2500 nm) or ultraviolet (wavelength 200-400 nm) portion of the electromagnetic spectrum, assuming that the mark has a reflective band in these areas.

The cholesteric liquid crystal polymer is inherently a spectral selectivity reflector with a reflection spectrum that can be tuned across part of the electromagnetic spectrum by appropriate choice of helical pitch. It should be noted that this step depends on the ratio between the filamentous starting material and the chiral induced compound in the liquid crystalline starting material, and on the polymerization temperature. After the polymerization process, the spiral step, and thus the reflection color of the material, remains constant. As is known to the skilled person; Small amounts of chiral inducer result in little helical twist and thus large helical pitch.

Therefore, small amounts of the chiral inducer generate a reflection space for the resulting polymer on the long-wavelength side of the spectrum, usually in the infrared or red wave range, while larger amounts of the inducer generate a reflection space for the resulting polymer that is located on the short-wavelength side of the spectrum. Usually in the color region, blue or ultraviolet rays.

It is also necessary to pay attention to the direction of the chiral inducer, that is, whether a particular inducer gives a helical pitch in the direction of the left hand or in the direction of the right hand, resulting in circular polarization in the opposite direction of this direction of the reflected light. Isomannides derivatives are known to induce reflection of circularly polarized light in the left direction, while Isosorbides derivatives are known to induce circular reflection of light in the right direction.

The following is a typical example of the composition of a cholesteric liquid crystalline polymeric precursor that can be developed via a continuous inkjet printing process:

MEK

benzoic acid 4-[4-[(1-oxo-2-propenyl)oxy]butoxycarboxy]-,

2-methyl-1,4-phenylene ester

(3R,3aR,6S,6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4- (acryloyloxybutoxy)benzoate)

Irgacure 907

LiCl04

55.7% by weight

40.1% by weight

1.70% by weight

1.3% by weight

1.20% by weight

The following example is a typical formulation of a cholesterol liquid crystalline polymer dye, which can be added via a valve-jet printing method (drip where appropriate).

Pioloform BL18 5.0% by weight

MEK 64.4% by weight

Diethylene glycol 10.0% by weight

Ethanol 8.0% by weight

Liquid crystalline polymer pigment 10.0% by weight

Byk-430 1.5% by weight

Byk-410 0.9% by weight

Pioloform BL18 is a polyvinyl butyral resin with CAS No. 63148-65-2 is produced by Wacker Company. Byk-410 is a modified urea solution produced by Byk. Byk-430 is a polar polyamide solution of macromolecular urea produced by Byk Company.

The following is an alternative example of a cholesterol liquid crystalline polymer precursor, which can be added by jet valve printing:

MEK

benzoic acid 4-[4-[(1-oxo-2-propenyl)oxy]butoxy]-,2-methyl-1,4-phenylene ester

(3R,3aR,6S,6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl bis(4- (acryloyloxybutoxy)benzoate)

Irgacure 907

55.7% by weight

14.7% by weight

1.50% by weight

0.8% by weight

A skilled person can, based on the details and examples of implementation methods given in the previous section, devise other methods of implementing the present invention.