JP2019214172A - Hologram transfer foil - Google Patents

Abstract

To improve a hologram transfer foil making adjustment of size of a hologram image by control of elongation quantity of a transfer layer (the hologram image) easy even under a processing condition in which pressure must be applied at a strength over yield point of a PET film which is a substrate of the hologram transfer foil during forming the hologram image to a body to be transferred by hot stamp (heat sensitive transfer).SOLUTION: There is provided a hologram transfer foil by laminating at least a peeling layer, a hologram formation layer, a reflective layer, and an adhesive layer on one surface of a substrate in this order, and having a structure that an acrylic resin layer having average molecular weight (Mw) of 1,000,000 to 2,000,000 formed on a surface of the substrate consisting of a PET film.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an improvement in a hologram transfer foil.

2. Description of the Related Art Conventionally, a hologram image (hereinafter collectively referred to as a “hologram” including a relief type diffraction grating pattern and an OVD (Optical Variable Device) pattern) is transferred and formed on a transfer target body by a hot stamp, and a decoration effect and forgery are provided. Hologram transfer foils for the purpose of adding a prevention effect are often used. (For example, see Patent Documents 1, 2, and 3)
The hologram transfer foil 10 generally has a layer configuration (see FIG. 2) including a base material 11, a release layer 12, a hologram forming layer 13, a reflective layer 14 (protective layer 15), and an adhesive layer 16. At the interface between the release layer 11 and the release layer 12, the layers (12, 13, 14, 15, and 16) after the release layer 12 are transferred to a transfer target (not shown) as the transfer layer 20 to perform transfer formation. In many cases, the release layer 12 functions as a protective layer for the transfer layer 20. As the substrate 11, a plastic film represented by PET is used.

  When a force equal to or higher than the yield point is applied to the substrate during the heating embossing by the thermal head during transfer formation, the amount of elongation of the substrate is unstable (not proportional to the external force) as shown in the graph of FIG. Become. It exhibits a phenomenon similar to the case where the metal material behaves plastically beyond the elastic deformation region.

  It has been confirmed that with a thermoplastic resin, the yield stress and the tensile strength decrease extremely with an increase in the test temperature, and conversely, the elongation increases extremely. In the graph of FIG. 5, the yield point decreases as the curve a → b → c and the test temperature increase, and the amount of elongation (horizontal axis) increases remarkably with an increase in stress (test force: vertical axis).

  When the transfer layer is formed on the transfer object, the transfer layer is pressurized by an apparatus called a bonding machine for the main purpose of improving adhesion and eliminating a step between the transfer object and the transfer layer. There are cases. In the pressure treatment, there is also a meaning of extending the hologram image of the transfer layer and finely adjusting the size.

When a PET film is used as the base material of the hologram transfer foil, when the pressure is applied with a strength exceeding the yield point of the PET film, the control of the elongation amount of the transfer layer becomes unstable, and the size of the hologram image is not stabilized. In addition, a phenomenon caused by unevenness in the arrangement position and the pitch on the transfer object has been confirmed. (See Fig. 4)
FIG. 4 shows that the transfer layer 21 on the left side is transferred and formed on the base material by pressing at a strength of about the yield point, and the transfer layer 22 on the right side is transferred and formed on the base material by pressing at a strength exceeding the yield point. FIG. The elongation of the right transfer layer 22 in the vertical direction is large, and the elongation of the hologram image indicated by the heart pattern is also large, which indicates that the transfer state is not uniform.

  There is an error in the strength at the time of the pressurizing treatment by the attaching machine, and it is difficult to strictly control each time with changes in working conditions (environmental temperature) and heating temperature.

JP 2003-255115 A JP-A-2015-68883 JP-A-61-208073

  The present invention provides a method for forming a hologram image on an object to be transferred by hot stamping (thermal transfer) even under processing conditions in which a pressure must be applied with a strength exceeding a yield point of a PET film as a base material of a hologram transfer foil. It is easy to adjust the size of the hologram image by controlling the amount of elongation of the transfer layer (hologram image), and to improve the hologram transfer foil effective in eliminating unevenness in the arrangement position and pitch on the object to be transferred. The purpose is to propose.

The hologram transfer foil according to the present invention,
On one surface of the substrate, at least a release layer, a hologram forming layer, a reflective layer, and an adhesive layer, a hologram transfer foil obtained by laminating in this order,
An acrylic resin layer having an average molecular weight (Mw) of 1,000,000 to 2,000,000 is formed on the surface of a substrate made of a PET film.

  When forming a hologram image on an object to be transferred by a hot stamp using the hologram transfer foil of the present invention, even if the hologram transfer foil is pressed with a strength exceeding the yield point of a PET film as a base material of the hologram transfer foil, the transfer is performed. The size of the hologram image can be easily adjusted by controlling the amount of expansion of the layer (hologram image), and unevenness in the arrangement position and pitch of the hologram image on the transfer object can be eliminated.

FIG. 3 is an explanatory cross-sectional view showing an example of a hologram transfer foil according to the present invention. Sectional drawing which shows the conventional hologram transfer foil. 5 is a graph showing the relationship between the amount of elongation (horizontal axis) and the yield point with an increase in stress (test force: vertical axis) applied to the base material (thermoplastic resin) of the hologram transfer foil. (Prior art) FIG. 5 is an explanatory diagram showing a state where the size of a hologram image transferred and formed by a conventional hologram transfer foil is unstable. Sectional explanatory drawing which shows the other example of the hologram transfer foil by this invention. 5 is a graph showing the relationship between the amount of elongation (horizontal axis) and the yield point with increasing stress (test force: vertical axis) applied to the base material (thermoplastic resin) of the hologram transfer foil. (The present invention)

  Embodiments of the present invention will be described below with reference to the drawings. In each of the drawings, components having the same or similar functions are denoted by the same reference numerals, and redundant description will be omitted. Further, for convenience of explanation, the size may be exaggeratedly illustrated in a size different from the actual scale. Each drawing shows an example of an embodiment of the present invention, and the present invention is not limited by the following description and illustration.

FIG. 1 is an explanatory sectional view showing an example of a hologram transfer foil according to the present invention.
FIG. 1 is a diagram illustrating a configuration in which an acrylic resin layer 18 applied and formed on a substrate 11 made of a PET film also serves as a release layer 12 (shown in the conventional configuration in FIG. 2). As described above, the acrylic resin layer 18 and the release layer 12 may have different layer configurations.

<Substrate 11>
The substrate 11 preferably has a thickness of about 10 to 50 [mu] m, and the PET film is suitably used in terms of heat resistance, physical strength, smoothness, and low fish eyes.

The tensile yield stress of the PET film, which varies depending on the manufacturer and the grade, is in the range of 48 to 73 (MPa).
<Acrylic resin layer 18>
The acrylic resin layer 18 has a tensile yield stress different from 65 to 77 (MPa) depending on the manufacturer and grade.

In the case of acrylic acrylate resin, the high molecular weight reduces the tackiness after evaporating the solvent, decreases the volumetric shrinkage during curing, and reduces the surface area in various fields such as photosensitive resists, coating materials, and adhesives. Hardness with excellent hardness, abrasion resistance, abrasion resistance, flexibility, heat resistance, mechanical strength, adhesion to substrate, adhesion strength, initial adhesion, chemical resistance, water resistance, weather resistance It is said to have an advantage in providing resins.
In a cured coating film as a protective film, it has been confirmed that as the content of the low molecular weight compound increases, the curing rate by ultraviolet rays tends to decrease, and the toughness of the cured coating film as a whole decreases. In the present invention, an index having an average molecular weight (Mw) of 1,000,000 to 2,000,000 is selected as an index for forming an acrylic resin layer of a cured coating film which is tough and hard to expand.

<Release layer 12>
The release layer 12 is provided for efficiently transferring the hologram-forming layer to the transfer target. The release layer 12 is activated in response to heating during hot stamping, and is activated at the interface with the base material 11 (including the acrylic resin layer 18). It peels off and also serves to protect the transfer layer 20 including the hologram image after the transfer.

As the material of the release layer 12, use is made of thermoplastic acrylic resin, chlorinated rubber-based resin, and nitrocellulose, acetylcellulose, cellulose acetate butyrate, polystyrene, vinyl chloride, vinyl chloride-based resin as resins that can be used in combination with these resins. it can. It is also possible to use thermosetting resins such as melamine resin, alkyd resin, epoxy resin, urea resin and acrylic resin alone or in a mixed system. Use of silicone resin, paraffin wax, reactive fluorine resin, etc. Is also possible.
The release layer 12 is formed by applying a selected material to the base material 11 (acrylic resin layer 18) with a thickness of about 0.1 to 10 μm by a known coating method such as a gravure method or a microgravure method.

<Hologram forming layer 13>
The hologram forming layer 13 is formed by using a photo-curable resin, a thermosetting resin, or a thermoplastic resin, shaping a desired fine uneven pattern, and performing photo-curing. That is, the hologram forming layer 13 is made of a cured product of a thermosetting resin or a photocurable resin, or a plastic molded product of a thermoplastic resin, and forms a fine uneven pattern constituting a hologram (including a diffraction grating and OVD). Become.

  Hologram (records and reproduces a three-dimensional image using coherent light such as laser using light interference), Diffraction grating (high-definition and versatile using mechanical or electron beam drawing using diffraction of light Image representation) and OVD (optical image representation other than the principle of interference and diffraction) are formed on the surface of the hologram forming layer 13 in the form of a relief (unevenness) by a duplicating stamper, and the relief surface has improved visibility. The reflective layer 14 is formed following the film.

  When a photocurable resin is used for the hologram forming layer 13, the cured resin has a refractive index of about 1.5. When such a photocurable resin is used for the hologram forming layer 13, the shape of the fine uneven pattern formed on the hologram forming layer 13 due to the heat and pressure applied when the hologram transfer foil 10 is thermally transferred to the object to be transferred. Deformation is less likely to occur, and the visibility of the hologram image is improved.

  It is preferable that the film thickness of the hologram forming layer 13 is in the range of 0.8 μm or more and 1.5 μm or less.

  This is because if the film thickness of the hologram forming layer 13 is less than 0.8 μm, problems such as poor heat resistance of the hologram forming layer 13 and collapse of a fine uneven pattern occur. On the other hand, if the thickness of the hologram forming layer 13 is larger than 1.5 μm, problems such as deterioration of foil cutting property and transfer property at the time of transfer and inaccurate transfer may occur.

  In addition, the hologram transfer foil 10 is required to have the same sharpness as the release layer 12 in the hologram forming layer 13 in order to perform the thermal transfer partially and accurately. Therefore, it is more preferable to add inorganic fine particles such as silica to the above materials.

  The photocurable resin includes a reactive diluent such as monofunctional or polyfunctional acrylate, an oligomer such as epoxy acrylate, urethane acrylate, or polyester acrylate, and a photopolymerization initiator such as benzophenone, acetophenone, or thiothithanthone. And a photopolymerization accelerator such as a tertiary amine as a main component.

  When light is applied to the uncured coating surface of the photocurable resin, the terminal methacryloyl group undergoes a radical polymerization reaction, crosslinks and cures. In addition, a strong intermolecular force due to a hydrogen bond of a hydroxyl group in the molecule acts, and after irradiation with light, a hardened product having excellent heat resistance is obtained. This is more effective as the number of hydroxyl groups in the molecule increases.

Examples of the thermosetting resin include an epoxy resin having an epoxy group, an epoxy resin or an acrylic resin obtained by adding a polyamide to a (meth) acrylate having a glycidyl group, and an acrylic polyol or a polyester polyol having a reactive hydroxyl group. It is possible to use a urethane resin, a melamine resin, a phenol resin or the like which is cross-linked by adding a polyisocyanate or a polyamide.
As the thermoplastic resin, an acrylic resin, an epoxy resin, a cellulose resin, a vinyl resin, and the like are preferable. For example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), cellulose acetate, acetic acid Examples include cellulose butyrate, cellulose acetate propionate, nitrocellulose, polyethylene (PE), polypropylene (PP), acrylic styrene copolymer (AS), vinyl chloride, and polymethyl methacrylate (PMMA).

<Reflective layer 14>
The reflective layer 14 can use a transparent coating material, a metal coating material, or the like as a material.

  When a semi-transparent transparent film material is used as the material of the reflection layer 14, a difference in refractive index between the hologram forming layer 13 and the reflection layer 14 is required.

  If the difference in the refractive index between the hologram forming layer 13 and the reflective layer 14 is smaller than 0.5, the visual effect of the diffracted light by the fine uneven pattern formed on the hologram forming layer 13 will be weakened. Therefore, the difference in the refractive index between the hologram forming layer 13 and the reflective layer 14 is preferably 0.5 or more, and ZnS, TiO2, PbTiO2, ZrO, ZnTe having a transparent material having a refractive index of 2.0 or more. , PbCrO4 or the like is more preferably used.

  Further, the thickness of the reflective layer 14 is preferably in the range of 50 nm or more and 100 nm or less.

  This is because if the thickness of the reflective layer 14 is less than 50 nm, unevenness in light reflection occurs, and a sufficient visual effect cannot be exhibited. On the other hand, if the thickness of the reflective layer 14 is larger than 100 nm, the sharpness of the foil at the time of transfer deteriorates, and accurate transfer cannot be performed.

  When a metal film material is used as the material of the reflective layer 14, a simple substance selected from chromium, nickel, aluminum, iron, titanium, silver, gold, and copper, or a mixture or alloy thereof is used. It is possible.

  Also in this case, it is preferable that the thickness of the reflective layer 14 be in the range of 50 nm or more and 100 nm or less.

  This is because if the thickness of the reflective layer 14 is less than 50 nm, unevenness in light reflection occurs, and a sufficient visual effect cannot be exhibited. On the other hand, if the thickness of the reflective layer 14 is larger than 100 nm, the problem is that the foil sharpness at the time of transfer deteriorates, and accurate transfer cannot be performed.

  In forming the reflective layer 14, a vacuum film forming means such as a vacuum evaporation method and a sputtering method is suitably adopted.

  In addition to forming the reflective layer 14 over the entire relief forming surface of the hologram forming layer 13, a configuration in which the reflective layer 14 is intentionally patterned may be employed.

  By forming a pattern that partially excludes the reflective layer on the hologram image (generally, it looks shiny in silver), authenticity can be determined even by checking the presence or absence of the silver part. It will contribute to improvement.

In patterning the reflective layer 14, other than the technique of vapor deposition through a mask having an opening corresponding to the pattern, known techniques exemplified below can be employed.
(1) Rinsing ink is printed on a substrate in a negative pattern (a place other than forming a reflective layer in a pattern), and a reflective layer is formed on the entire surface by vapor deposition and sputtering, and printed. Rinse sealight processing in which the reflective layer formed on the rinse ink is synchronously removed when the rinse ink is rinsed off with water.
(2) A masking agent is printed in a positive pattern (a portion where the reflective layer is formed in a pattern) on the reflective layer formed by vapor deposition and sputtering on the entire surface, and a portion not printed with the masking agent is corroded by a corrosive agent. Patterning by removal. (Etching)
(3) Patterning by irradiating a strong laser to a portion to be removed of the reflective layer formed by vapor deposition and sputtering on the entire surface to selectively destroy the reflective layer. (Laser processing)

<Protective layer 15>
As the protective layer 15, a thermosetting resin or a thermosetting resin such as a polyester resin, an epoxy resin, a urethane resin, and a chloride resin which is excellent in heat resistance, scratch resistance, chemical resistance, and transparency can be used. An appropriate thickness is 1 to 5 μm.

<Adhesive layer 16>
The adhesive layer 16 can be made of a thermoplastic resin such as a propylene resin, a polyethylene terephthalate resin, a polyacetal resin, or a polyester resin.
The material of the adhesive layer 16 is not particularly limited as long as it has a transparent coating material, an adhesive force with another resin, and a printing property. In addition, since the material of the adhesive layer 16 must also have foil sharpness at the time of thermal transfer, it is more preferable to include an inorganic material such as silica in the above resin.

The thickness of the adhesive layer 16 is not particularly limited, but is preferably in the range of 0.5 μm or more and 1.5 μm or less.
This is because if the thickness of the adhesive layer 16 is smaller than 0.5 μm, there is a possibility that a problem such as a failure to maintain a sufficient adhesive strength with the transferred object may occur when the surface of the transferred object is rough. That's why. On the other hand, if the thickness of the adhesive layer 16 is larger than 1.5 μm, the heat conduction at the time of transfer is not uniform, resulting in poor transfer, poor foil sharpness at the time of transfer, and inaccurate transfer. This is because such a problem may occur.

<Hologram transfer foil 10>
Hereinafter, a method for manufacturing the hologram transfer foil 10 will be described.
First, the acrylic resin layer 18, the release layer 12, and the hologram forming layer 13 are sequentially coated on the substrate 11 by a known wet coating method, and then the solvent component is dried and removed. However, the hologram forming layer 13 can be formed simultaneously with the formation of the concavo-convex pattern in the next step.

  Here, as the wet coating method, roll coating, gravure coating, reverse coating, die coating, screen printing, spray coating, or the like can be used. Using these wet coating methods, the material of the acrylic resin layer 18, the material of the release layer 12, and the material of the relief layer 13 are applied to one surface of the substrate 11. As a method for drying the solvent component, a known drying method such as hot air drying, hot roll drying, or infrared irradiation can be used.

  Next, a relief pattern forming a hologram image is formed using a metal plate having a desired concavo-convex pattern wound around an embossing roll.

  Here, when a thermosetting resin is used for the hologram-forming layer 13, an uneven pattern is formed on the hologram-forming layer 13 by pressing a heated metal plate against the hologram-forming layer 13.

  On the other hand, when a photocurable resin is used for the hologram forming layer 13, light irradiation is performed simultaneously with pressing of the metal plate, and the resin is cured to form a pattern on the hologram forming layer 13.

  Next, the reflection layer 14 is laminated on the hologram forming layer 13 on which the uneven pattern is formed.

  Here, as a method of providing the reflective layer 14, for example, a vapor deposition method such as vacuum evaporation or sputtering can be used. At this time, it is more preferable to perform a corona treatment on the hologram forming layer 13 in order to increase the adhesion between the hologram forming layer 13 and the reflective layer 14.

  Next, the material of the protective layer 15 and the adhesive layer 16 is applied onto the reflective layer 14 by using a known wet coating method in the same manner as described above, and then the solvent component is dried and removed. At this time, the hologram transfer foil 10 is manufactured by slitting the adhesive layer 16 to a desired width.

  A PET film (38 μm) was used as a substrate.

  On one side of the PET film, a release layer was formed by gravure coating to a thickness of 0.5 μm.

  An acrylic resin (BR-88: average molecular weight (Mw) = 150,000, manufactured by Mitsubishi Rayon (currently Mitsubishi Chemical)) was used as a main material of the release layer.

  On the release layer, a urethane-based two-component curable resin is applied as a hologram-forming layer by gravure coating, and a mold (stamper) having a concave-convex pattern of a diffraction grating is pressed (heating condition: 200 ° C.) on the surface thereof. After transferring and forming the inverse of the pattern, the urethane-based two-component cured resin layer was cured to form a diffraction grating pattern.

  Aluminum serving as a reflection layer was formed by vapor deposition to a thickness of 50 nm on the entire surface of the uneven surface of the diffraction grating pattern.

  An etching process for forming a specific pattern on the reflective layer was performed by printing a mask agent in a specific positive pattern on the reflective layer and removing the reflective layer in a portion where the mask agent was not formed by corrosive removal.

  A protective layer and an adhesive layer were sequentially formed on the reflective layer.

  The adhesive used was an acrylic resin as a main component, in which a silica filler was dispersed, and was applied by gravure coating to a thickness of 2 to 6 μm.

  With respect to the hologram transfer foil obtained as described above, the amount of stress-elongation was measured using a tensile tester provided with a thermostat.

  As a result of the measurement under the condition where the inside of the bath was kept at 90 ° C. in order to approximate the condition at the time of forming the hologram transfer, as shown in the graph of FIG. (The slope rising to the right increases.)

  Compared with the graph curve (dotted line) of the conventional configuration in which the release layer containing the acrylic resin is not applied to the PET film, the control of the elongation amount by the tensile stress becomes easier.

  When the hologram transfer foil was slit to a width of 12 mm and hologram transfer (pressing by a sticking machine) was performed, there was no variation in the elongation of the hologram image, and transfer formation with a stable transfer layer size and arrangement pitch was possible. there were.

REFERENCE SIGNS LIST 10 hologram transfer foil 11 base material 12 release layer 13 hologram formation layer 14 reflection layer 15 protective layer 16 adhesive layer 18 acrylic resin layer 20, 21, 22 transfer layer

Claims (2)

On one surface of the substrate, at least a release layer, a hologram forming layer, a reflective layer, and an adhesive layer, a hologram transfer foil obtained by laminating in this order,
A hologram transfer foil comprising an acrylic resin layer having an average molecular weight (Mw) of 1,000,000 to 2,000,000 formed on the surface of a substrate made of a PET film.   2. The hologram transfer foil according to claim 1, wherein the acrylic resin layer also functions as a release layer.

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