JP4967566B2 - Transfer sheet - Google Patents

Description

  The present invention provides measures for preventing fraud such as counterfeiting, falsification, or theft of information that should be kept secret, and measures for facilitating determination of the presence or absence of fraud even if such fraud is concerned. Are collectively referred to as anti-counterfeiting measures].

  More specifically, forgery prevention measures for securities such as gift certificates and credit cards, forgery prevention measures to prove that they are genuine products that are often applied to generally expensive items such as branded goods and luxury goods. It is a technology suitable for needs such as, and a technology that can obtain a visual effect with excellent decorativeness depending on the design, and it is a transfer for anti-counterfeiting that can obtain even higher effects in combination with holograms and diffraction gratings etc. Regarding the sheet.

  In recent years, as an example of a technique for producing an optical effect, a hologram, a diffraction grating, or an optical device that can express a stereoscopic image, a special decoration image, or a special color change by using interference between reflected lights or dispersion of reflected light. A so-called OVD using a technique such as a multilayer thin film that causes a color change (color shift) according to a viewing angle by superimposing thin films having different characteristics on an optically appropriate multilayer is used [OVD is “Optical (ly) Abbreviation for Variable Device ". DOVID is known as a synonym for OVD, which stands for “Diffractive Optical (ly) Variable Imaging Device”.

  As for the color change, there is a phenomenon in which the color changes or the color changes due to the material or structure of the OVD without depending on the absorption of the colored light of a specific wavelength by the material itself. It derives from the fact that the nature of the light itself differs. In the present specification, such a color is referred to as a structural color. Examples of optical phenomena related to the development of structural colors include multilayer film interference, thin film interference, refraction, dispersion, light scattering, Mie scattering, diffraction, and diffraction grating. In these OVDs, an optical thin film having a film thickness of 1 μm or less formed by a vacuum film forming technique such as vacuum deposition or sputtering is often used.

  This OVD requires advanced manufacturing technology, and has a unique visual effect and can determine authenticity at a glance. Therefore, as an effective counterfeiting measure, this OVD can be applied to some or all of credit cards, securities, certificates, etc. Formed and used. Recently, in addition to securities, it is also affixed to sports equipment, computer parts and other electrical products, software packages, etc., and is widely used as an authentication seal to prove the authenticity of the product and as a seal for the product. It has come to be.

  Thus, when attaching OVD to paper media, such as a gift certificate, a banknote, a passport, and a stock certificate, the OVD transfer sheet of the thermal transfer system which is not easy to replace is often employed. Such an OVD transfer sheet is provided on a sheet-like support with a transfer layer that can be peeled off from the support during transfer and transferred to the transfer target, and the transfer layer is on the side close to the support. From a transparent diffractive structure forming layer having a concavo-convex surface for generating diffracted light, an optical thin film provided in close contact with the concavo-convex surface of the concavo-convex surface, and reflecting the light transmitted through the diffractive structure forming layer It has a structure in which an effect layer and an adhesive layer provided so as to cover the diffraction effect layer are laminated. If an OVD that has been thermally transferred using such an OVD transfer sheet is to be replaced, the optical thin film used in the OVD is physically destroyed and the original visual effect is impaired. This is because it remains clear.

  However, since OVD has been used in various environments in recent years, the required quality required for OVD transcripts is increasing. For example, in an application applied to a package of chemicals or special inks, it is necessary that the OVD after transfer has resistance to various organic solvents contained in the contents. In this case, solvent resistance is required for each layer of the diffractive structure forming layer, the diffraction effect layer, and the adhesive layer and for each layer. Among these layers, the adhesive layer is particularly required to have the most solvent resistance because it is related to the adhesion between the transfer layer and the transfer target.

  In consideration of adhesion to a transfer medium and transfer suitability, a thermoplastic resin that is generally softened at 60 to 140 ° C. is often used for the adhesive layer of the transfer sheet. Examples of the thermoplastic resin used for the adhesive layer of the transfer sheet include vinyl chloride vinyl acetate copolymer resin and acrylic resin (see Patent Document 1).

  On the other hand, organic solvents contained in chemicals and special printing inks are not limited, but include ethyl ether, diethyl ether, diethylamine, cyclohexane, butyl acetate, xylene, toluene, ethyl acetate, tetrahydrofuran, benzene, methyl ethyl ketone, Examples include benzaldehyde, ethylene glycol monobutyl ether, 2-ethylhexanol, methyl acetate, acetone, cyclohexanone, ethanol, and the like.

However, when the adhesive layer of a conventional transfer sheet is immersed in an organic solvent contained in chemicals or special printing inks or is rubbed in the presence of an organic solvent, partial or total peeling occurs. It has been found that the resistance to solvents is poor.
JP 2005-7624 A

  In view of these problems, an object of the present invention is to provide a transfer sheet exhibiting durability against an organic solvent contained in chemicals or special printing inks.

The transfer sheet according to the present invention is provided with a transfer layer that can be separated from the support during transfer and transferred to the transfer target on the sheet-like support, and the transfer layer is on the side close to the support. From at least,
(A) a transparent diffractive structure forming layer having an uneven surface for generating diffracted light;
(B) a diffraction effect layer made of an optical thin film provided in close contact with the irregularities of the irregular surface, and reflecting light transmitted through the diffraction structure forming layer;
And (c) an adhesive layer provided so as to cover the diffraction effect layer,
Comprising
The adhesive layer is made of urethane resin or polyacrylonitrile resin, acrylic resin, and silica powder, and contains the urethane resin or polyacrylonitrile resin in a weight ratio of 5% or more.
It is characterized by.
The urethane resin or polyacrylonitrile resin has a solubility parameter (σ) of 10.0 to 12.5 or 13.0 to 20.0 (excluding the range of 12 to 14), and a melting temperature of 40 ° C. It is preferable that it is -150 degreeC.

  In the transfer sheet of the present invention, it is preferable that the adhesive layer has a thickness of 2 to 10 μm, and the thermoplastic resin is present in the adhesive layer in the form of particles having an average particle diameter of 10 μm or less.

  ADVANTAGE OF THE INVENTION According to this invention, the transfer sheet which shows durability with respect to the organic solvent contained in a chemical | medical agent, special printing ink, etc. can be provided.

  The reason why the present inventors have poor resistance to the organic solvent contained in the chemical or the special printing ink of the adhesive layer of the conventional transfer sheet is that the vinyl chloride vinyl acetate copolymer resin contained in the adhesive layer of the transfer sheet We thought that it might be due to the high affinity of organic resins with thermoplastic resins such as acryl resin and acrylic resin, and considered forming an adhesive layer containing a material with low affinity for organic solvents. At this time, it was considered to evaluate the affinity between the organic solvent and the adhesive layer on the basis of the solubility parameter (σ).

  The solubility parameter (σ) of the organic solvent described above is in the range of 12.7 for ethanol and 7-10 for other organic solvents. On the other hand, the solubility parameter (σ) of vinyl chloride vinyl acetate copolymer resin and acrylic resin used for the adhesive layer of the conventional transfer sheet is included in the range of the solubility parameter (σ) of the organic solvent. Yes. From this, it can be explained that the adhesive layer of the conventional transfer sheet has poor resistance to the organic solvent.

  In contrast, in the present invention, by using a thermoplastic resin having a solubility parameter (σ) that does not match the solubility parameter (σ) of the organic solvent in the adhesive layer, the adhesive layer has resistance to the organic solvent. Improve.

  Hereinafter, embodiments of a transfer sheet according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a transfer sheet according to the present invention. This transfer sheet (1) comprises a protective layer (3), a transparent diffractive structure forming layer (4) having a concavo-convex surface for generating diffracted light on one side of a sheet-like support (2), and the concavo-convex surface. A diffraction effect layer (5) made of an optical thin film that is provided in close contact with the unevenness of the material and reflecting light transmitted through the diffraction structure forming layer (4), and an adhesive covering the diffraction effect layer (5) It has a structure in which the layers (6) are sequentially laminated. Hereafter, each member which comprises the transfer sheet of this invention is demonstrated in detail.

  In the transfer sheet of the present invention, a polyethylene terephthalate resin film having a stable thickness and high heat resistance is generally used for the support 2, but the material is not particularly limited. As other film materials, a polyethylene naphthalate resin film, a polyimide resin film, or the like exhibiting high heat resistance can be used for the same purpose. Other film materials such as polyethylene, polypropylene, and heat-resistant vinyl chloride can also be used if coating conditions for the coating liquid and drying conditions permit.

  In the transfer sheet of the present invention, the protective layer 3 may be peelable from the support 2. In addition, although the layer called a peeling layer or a mold release layer may be provided instead of the protective layer 3, neither of these layers is essential. That is, these layers are options that may be appropriately provided depending on the design in order to protect the transferred transfer layer or to improve the transfer performance when transferring. Examples of the protective layer 3 include polymethyl methacrylate resin and other thermoplastic resins such as a mixture of vinyl chloride / vinyl acetate copolymer or nitrocellulose resin, or a mixture of polymethyl methacrylate resin and polyethylene wax. A preferable example is one obtained by applying a mixture of a cellulose acetate resin and a thermosetting resin such as an epoxy resin, a phenol resin, a thermosetting acrylic resin, or a melamine resin, and then curing it by heat.

  In the transfer sheet of the present invention, the diffractive structure forming layer 4 is processed so as to have a concavo-convex surface for generating diffracted light on its surface, and light transmitted through the diffractive structure forming layer 4 is provided along the concavo-convex surface. The reflecting diffraction effect layer 5 exhibits a diffraction effect. The diffracted lights reflected by the uneven surface of the diffraction effect layer 5 interfere with each other and exhibit a structural color. In general, the structural color obtained by this diffraction phenomenon shows different colors depending on the position of the observer.

  The diffractive structure forming layer 4 is required to have a capability of forming a concavo-convex surface with a press plate on the surface thereof. The main material of the diffractive structure forming layer 4 may be any of a thermoplastic resin, a thermosetting resin, an ultraviolet ray, or an electron beam curable resin. Examples of materials used for the diffraction structure forming layer 4 include polyisocyanates for thermoplastic resins such as acrylic resins, epoxy resins, cellulose resins, and vinyl resins, acrylic polyols having a reactive hydroxyl group, polyester polyols, and the like. Examples thereof include urethane resins added and crosslinked as a crosslinking agent, thermosetting resins such as melamine resins and phenol resins, and ultraviolet or electron beam curable resins such as epoxy (meth) acrylate and urethane (meth) acrylate. These may be used alone or in combination of two or more. Moreover, even if it is a thing other than these, if an uneven surface can be formed in the surface, it can be used suitably.

  A holography technique in which an interference fringe obtained by causing two coherent light beams to interfere with each other can be used for the diffraction grating constituting the fine uneven shape. With this holography technique, for example, a structural color can be controlled to form a stereoscopic image with a sense of depth.

  In addition, holography technology is applied to each minute pixel to form a diffraction grating, and a large number of pixels having these diffraction gratings are arranged to form the entire screen, thereby expressing an image having high brightness and contrast. You can also. In addition to the holographic technique, for example, a pixel having a diffraction grating can be provided by directly drawing a diffraction grating on a photosensitive material with an electron beam.

  A method of forming each pixel having a diffraction grating into an appropriate shape (for example, a star shape), a method of forming fine characters (so-called micro characters) that cannot be seen with the naked eye by these pixels, and a photo as if using a diffraction grating As described above, a method for faithfully reproducing the color of a subject or a method for expressing a plurality of images that are completely different depending on the viewing angle using a diffraction grating has been developed. These techniques can also be used.

  Examples of the material of the diffraction effect layer 5 include simple substances such as Al, Sn, Cr, Ni, Cu, Au, and Ag, or compounds thereof. These materials are formed by known vacuum deposition or sputtering.

  High-brightness light-reflecting ink obtained by dispersing fine metal powder or metal nanoparticles such as aluminum, silver, nickel, gold, copper, tin, indium, and cobalt in an organic polymer resin as the material of the diffraction effect layer 5 Can also be used. In this case, care must be taken not to attack the relief forming surface of the diffractive structure forming layer 4 with a solvent, but it can be formed by a known printing method such as a gravure printing method, a flexographic printing method, or a screen printing method. When the diffraction effect layer 5 is provided by such a printing method, the film thickness after drying may be adjusted to be about 0.1 to 10 μm.

  By using a high refractive index material having a higher refractive index than that of the diffractive structure forming layer 4 as the material of the diffraction effect layer 5, a diffraction effect can be obtained. In this case, the difference in refractive index between the two layers is preferably 0.2 or more. By setting the difference in refractive index to 0.2 or more, refraction and reflection occur at the interface between the diffraction effect layer 5 and the diffraction structure forming layer 4, and the OVD effect is obtained by good light reflection while maintaining translucency. be able to. That is, a visually effective hologram (or diffraction grating) can be obtained.

Examples of high refractive index materials that can be used are given below. The numerical value in parentheses following the chemical formula or compound name shown below indicates the refractive index n. As ceramics, Sb ₂ O ₃ (3.0), Fe ₂ O ₃ (2.7), TiO ₂ (2.6), CdS (2.6), CeO ₂ (2.3), ZnS (2 .3), PbCl ₂ (2.3), CdO (2.2), Sb ₂ O ₃ (2.0), WO ₃ (2.0), SiO (2.0), Si ₂ O ₃ (2 .5), In ₂ O ₃ (2.0), PbO (2.6), Ta ₂ O ₃ (2.4), ZnO (2.1), ZrO ₂ (2.0), MgO (1. 6), Si ₂ O ₂ (1.5), MgF ₂ (1.4), CeF ₃ (1.6), CaF ₂ (1.3 to 1.4), AlF ₃ (1.6), Al ₂ O ₃ (1.6), GaO (1.7) and the like. Examples of the organic polymer include polyethylene (1.51), polypropylene (1.49), polytetrafluoroethylene (1.35), polymethyl methacrylate (1.49), polystyrene (1.60) and the like. These materials are appropriately selected based on optical characteristics such as refractive index, reflectance, and transmittance, weather resistance, interlayer adhesion, and the like, and are formed in the form of a thin film. As a formation method, a known method such as a vacuum evaporation method, a sputtering method, or a CVD method capable of controlling the film thickness, the film formation speed, the number of stacked layers, the optical film thickness, and the like can be appropriately used. In this specification, the optical film thickness means an amount given by n · d (where n is a refractive index and d is a film thickness).

  In the transfer sheet of the present invention, the adhesive layer (6) has a function of adhering to the transfer object by being applied with heat and pressure in contact with various transfer objects (for example, paper / plastic). Contains thermoplastic resin. The thermoplastic resin contained in the adhesive layer (6) has a solubility parameter (σ) of 10.0 to 12.5 or 13.0 to 20.0, and a melting temperature of 40 ° C to 150 ° C. One or more types of thermoplastic resins are used, and it is preferable that the total amount of the thermoplastic resin is 5% or more of the adhesive layer.

  When the solubility parameter (σ) of the thermoplastic resin deviates from the range of 10.0 to 12.5 or 13.0 to 20.0, the solubility parameter (σ) of the organic solvent contained in the chemical or special printing ink It becomes in agreement, and good solvent resistance is not obtained. The thermoplastic resin having the solubility parameter (σ) in the above range includes polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polybutyl acrylate, polyacrylonitrile, polyurethane, polyester, polyamide, polyisoprene, polyacetal, ethylene-vinyl alcohol. A copolymer etc. are mentioned. If the weight ratio of the thermoplastic resin in the adhesive layer is less than 5%, good solvent resistance cannot be obtained. When the melting temperature of the thermoplastic resin is 40 ° C. to 150 ° C., transfer adhesion at a relatively low temperature is possible.

  2-10 micrometers is preferable and, as for the thickness of an adhesive bond layer (6), 2-6 micrometers is more preferable. When the thickness is less than 2 μm, it is difficult to follow the unevenness of the adherend, and thus sufficient adhesive force cannot be obtained. When the thickness exceeds 10 μm, the peel strength of the coating film becomes strong, transferability is poor, and productivity is lowered.

  The thermoplastic resin contained in the adhesive layer (6) may be present in the adhesive layer in the form of spherical or irregular particles, in which case the average particle diameter of the particles may be 10 μm or less. desirable. If the average particle diameter of the particles is 10 μm or less, the foil cutting property of the transfer sheet can be improved.

  In the adhesive layer (6), in order to further improve the foil cutting property of the transfer sheet, any material such as silica, precipitated barium sulfate, barium carbonate, zinc oxide, alumina, and kaolinite may be used as long as the adhesiveness is not impaired. Inorganic fine particles or any organic fine particles having a Tg equal to or higher than the transfer temperature may be added.

  In the transfer sheet according to the present invention, in order to improve the design, each layer may be colored or printed on the surface or between layers. Such coloring and printing can be appropriately used according to the purpose of use. Moreover, for the purpose of improving the interlayer adhesion of each layer, an anchor layer may be provided between each layer, or various easy adhesion processes such as a corona discharge process, a plasma process, and a frame process may be performed.

  Hereinafter, the present invention will be described in more detail based on specific examples.

<Example 1>
In this example, a transfer sheet having the configuration of FIG. 1 was manufactured as follows. A protective layer ink composition having the following composition is applied and dried on a support (2) made of a transparent polyethylene terephthalate (PET) film having a thickness of 25 μm so that the film thickness after drying is 2 μm, and the protective layer (3) is thus formed. Formed. Next, a diffraction structure forming layer ink composition having the following composition was applied so that the film thickness after drying was 1 μm, and baked under the conditions of 150 ° C. and 10 seconds to form a diffraction structure forming layer (4). Subsequently, the relief pattern of the minute unevenness which comprises a diffraction grating was formed in the surface of the diffraction structure formation layer (4) by the roll embossing method. Next, aluminum was vacuum-deposited to a thickness of 50 nm to form a diffraction effect layer (5). Thereafter, an adhesive layer ink composition having the following composition was applied and dried so that the film thickness after drying was 3 μm to form an adhesive layer (6). Thus, a transfer sheet (1) was produced.

"Protective layer ink composition"
Polyamideimide resin (Tg 250 ° C.) 19.2 parts by weight Polyethylene powder 0.8 parts by weight Dimethylacetamide 45.0 parts by weight Toluene 35.0 parts by weight “Diffraction structure forming layer ink composition”
Urethane resin 20.0 parts by weight Methyl ethyl ketone 50.0 parts by weight Ethyl acetate 30.0 parts by weight “Adhesive layer ink composition”
Urethane resin dispersion (melting temperature 55 ° C., average particle size 0.5 μm, solubility parameter (σ) 10.1) Solid weight ratio 60%
Silica powder Solid weight ratio 40%.

  In addition, the average particle diameter of the thermoplastic resin contained in the adhesive layer is a value obtained by microscopy (measured by an electron microscope).

<Example 2>
A transfer sheet (1) of Example 2 was produced in the same manner as in Example 1 except that the adhesive layer was formed using an adhesive layer ink composition having the following composition.

"Adhesive layer ink composition"
Urethane resin dispersion (melting temperature 55 ° C., average particle size 0.5 μm, solubility parameter (σ) 10.1) Solid weight ratio 10%
Acrylic resin (melting temperature 40 ° C., average particle size 0.5 μm, solubility parameter (σ) 8.5) Solid weight ratio 50%
Silica powder Solid weight ratio 40%.

<Example 3>
A transfer sheet (1) of Example 3 was produced in the same manner as in Example 1 except that the adhesive layer was formed using an adhesive layer ink composition having the following composition.

"Adhesive layer ink composition"
Polyacrylonitrile resin (melting temperature 60 ° C., average particle size 0.5 μm, solubility parameter (σ) 14.5) Solid weight ratio 20%
Acrylic resin (melting temperature 40 ° C., average particle size 0.5 μm, solubility parameter (σ) 8.5) Solid weight ratio 40%
Silica powder Solid weight ratio 40%.

<Comparative Example 1>
A transfer sheet (1) of Comparative Example 1 was produced in the same manner as in Example 1 except that an adhesive layer was formed using an adhesive layer ink composition having the following composition. As shown below, the adhesive layer contains only a thermoplastic resin having a solubility parameter (σ) of less than 10.

"Adhesive layer ink composition"
Vinyl chloride vinyl acetate copolymer resin (melting temperature 65 ° C., average particle size 0.5 μm, solubility parameter (σ) 9.2) Solid weight ratio 50%
Acrylic resin (melting temperature 40 ° C., average particle size 0.5 μm, solubility parameter (σ) 8.5) Solid weight ratio 30%
Silica powder Solid weight ratio 20%.

<Comparative example 2>
A transfer sheet (1) of Comparative Example 2 was produced in the same manner as in Example 1 except that the adhesive layer was formed using an adhesive layer ink composition having the following composition. As shown below, the adhesive layer contains only 5% by weight of a urethane resin dispersion having a solubility parameter (σ) of 10.1.

"Adhesive layer ink composition"
Urethane resin dispersion (melting temperature 55 ° C., average particle size 0.5 μm, solubility parameter (σ) 10.1) Solid weight ratio 3%
Acrylic resin (melting temperature 40 ° C., average particle size 0.5 μm, solubility parameter (σ) 8.5) Solid weight ratio 57%
Silica powder Solid weight ratio 40%.

<Comparative Example 3>
A transfer sheet (1) of Comparative Example 3 was produced in the same manner as in Example 1 except that the adhesive layer was formed using an adhesive layer ink composition having the following composition.

"Adhesive layer ink composition"
Polymethyl methacrylate resin (melting temperature 95 ° C., average particle size 0.5 μm, solubility parameter (σ) 12.8) Solid weight ratio 60%
Silica powder Solid weight ratio 40%.

[Evaluation of solvent resistance of transfer sheet]
The solvent resistance of the transfer sheet produced as described above was evaluated as follows.

Each transfer sheet was hot stamped on high-quality paper having a thickness of about 200 μm, which is a transfer target, under conditions of a plate surface temperature of 120 ° C., a pressure of 500 kg / cm ² , and a pressing time of 0.3 seconds. Thereafter, the substrate was immersed in an ethyl acetate solution, a methyl ethyl ketone solution or ethanol for 3 minutes, and the presence or absence of peeling of the transferred product during the immersion was confirmed to evaluate the solvent resistance. The results are shown in Table 1.

  As can be seen from Table 1, the transfer sheets of Examples 1 to 3 had good solvent resistance, but the transfer sheets of Comparative Examples 1 to 3 had poor solvent resistance.

Sectional drawing of the transfer sheet which concerns on embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Transfer sheet, 2 ... Support body, 3 ... Protective layer, 4 ... Diffraction structure formation layer, 5 ... Diffraction effect layer, 6 ... Adhesive layer.

Claims (2)

A sheet-like support is provided with a transfer layer that can be peeled off from the support during transfer and transferred to the transfer target, and the transfer layer is at least from the side close to the support,
(A) a transparent diffractive structure forming layer having an uneven surface for generating diffracted light;
(B) a diffraction effect layer made of an optical thin film provided in close contact with the irregularities of the irregular surface, and reflecting light transmitted through the diffraction structure forming layer;
And (c) an adhesive layer provided so as to cover the diffraction effect layer,
Comprising
The adhesive layer is made of urethane resin or polyacrylonitrile resin, acrylic resin, and silica powder, and contains the urethane resin or polyacrylonitrile resin in a weight ratio of 5% or more.
A transfer sheet characterized by The urethane resin or polyacrylonitrile resin has a solubility parameter (σ) of 10.0 to 12.5 or 13.0 to 20.0 (excluding the range of 12 to 14), and a melting temperature of 40 ° C. The transfer sheet according to claim 1, which has a temperature of ˜150 ° C.

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