JP2005271357A - Metallic tone transfer foil - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a feel of metallic luster from becoming hazed by a white spot in a metallic tone transfer foil, even when a surface strength such as wear resistance or scratch resistance is imparted in addition to a metallic luster. <P>SOLUTION: In the metallic tone transfer foil 10, a surface protecting layer 4 having a crosslinked cured product of a transparent curable resin and a reinforced particle 3 which is dispersed in the crosslinked cured product and has higher rigidity than the former, a sealing layer 5 composed of a transparent resin which makes an unevenness of the back surface formed by the projecting reinforced particle 3 on the back surface of the surface protecting layer 4 as flat as possible, a metallic thin film layer 6 and an adhesive layer 7, may be formed, in that order, as a transfer layer 2 on a support sheet 1. The relationship among the maximum particle diameter Dmax of the reinforced particle, the thickness Top of the surface protecting layer and the thickness Ts of the sealing layer 5, is preferably represented by Dmax/2≤Ts. and further, Dmax≤(Top+Ts). More preferably, the transparent resin of the sealing layer 5 is a curable resin composed of an ionizing radiation-curable resin, so that the sealing layer itself is the crosslinked cured product of the resin. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a metallic tone transfer foil having metallic gloss. In particular, the present invention relates to a metallic tone transfer foil that can impart surface strength such as abrasion resistance and scratch resistance, and can prevent white spots where the metallic gloss after transfer is partially cloudy.

In order to impart metallic gloss to the transfer foil, a metal foil such as aluminum urine was used as a constituent layer of the transfer layer (see Patent Document 1), or a metal thin film layer formed by vacuum deposition of a metal such as aluminum was provided. The thing etc. are known (refer patent document 2, patent document 3, etc.).
In addition, as a transfer foil capable of imparting surface strength such as abrasion resistance and scratch resistance, an ionizing radiation curable resin or a thermosetting resin is used as a surface protective layer that becomes the outermost surface layer after transfer among the constituent layers of the transfer layer. There is known a transfer foil provided with a cross-linked cured product of a transparent curable resin such as alumina and a layer having reinforcing particles such as alumina having a hardness higher than that of the cross-linked cured product dispersed in the cross-linked cured product. (See Patent Document 3, etc.).

Japanese Patent No. 135218 Japanese Utility Model Publication No. 36-7905 Japanese Patent No. 2883555

  When imparting both metallic luster and surface strength to the transfer foil, a surface protective layer containing reinforcing particles described in Patent Document 3 or the like as a transfer layer in a curable resin is provided on a releasable support sheet. If the metal thin film layer described in Patent Document 2, Patent Document 3 or the like is further provided thereon, the purpose can be achieved.

  However, as disclosed in Patent Document 3, when the reinforcing particles are included in the surface protective layer for imparting surface strength, in particular, the use of closely viewing the transferred transcript (for example, display on a mobile phone) In a window member or the like, minute defects are easily recognized visually. Therefore, even a transfer foil that does not become a defect in the past becomes a defective product. One specific example of the minute defect is a white spot. The white point is a defect which is felt to be lower gloss than the surroundings in the metallic glossy surface and has a size of, for example, a circle having a diameter of 0.1 mm or less, and is usually scattered. Due to the presence of such white spots, the light reflectance as a whole decreases, and as a result, the metallic glossiness of the transferred material becomes cloudy. In addition, this white spot is not conspicuous because it is buried in the metallic luster if it is matte, but it is easily noticeable in the case of luster (mirror surface), that is, in the case of glossy metallic tone.

  That is, the problem of the present invention is that even when surface strength such as abrasion resistance and scratch resistance is further imparted to a metallic tone transfer foil capable of imparting metallic gloss, cloudiness of metallic gloss due to white spots is generated. Is to prevent.

  In order to solve the above-described problems, the metal-tone transfer foil of the present invention is a metal-tone transfer foil including a metal thin film layer having a metallic luster as a transfer layer on a support sheet, wherein the transfer layer is from the support sheet side. In order, a cross-linked cured product of a transparent curable resin, a surface protective layer having reinforcing particles having a hardness higher than that of the cross-linked cured product dispersed in the cross-linked cured product, and a reinforcing particle protruding from the back surface of the surface protective layer It has the structure which has the eye stop layer, metal thin film layer, and adhesive bond layer which consist of transparent resin which makes a back surface unevenness | corrugation approach a flat surface.

  By adopting such a configuration, the metal thin film layer is formed on the surface protective layer (the back surface thereof) via the sealing layer, so that the back surface of the surface protective layer is uneven due to the protrusion of the reinforcing particles. However, the back surface irregularities are filled with a filler layer so as to be close to a flat surface. As a result, the unevenness of the back surface of the surface protective layer, which was the cause of whitening, is alleviated. As a result, even if reinforcing particles are included in the surface protective layer to provide surface strength such as abrasion resistance and scratch resistance, Prevents cloudiness of metallic luster caused by dots.

Further, in the metallic tone transfer foil of the present invention, the relationship between the maximum particle diameter Dmax of the reinforcing particles, the thickness Top of the surface protective layer, and the thickness Ts of the sealing layer in the above configuration is Dmax / 2 ≦ It was set as the structure which is Ts and Dmax <= (Top + Ts).
By setting it as such a structure, the back surface unevenness | corrugation by the reinforcement | strengthening particle | grains of a surface protective layer can be brought closer to a flat surface more by the eye stop layer, As a result, a white spot can be prevented more reliably.

In the metal-tone transfer foil of the present invention, the curable resin for the surface protective layer is an ionizing radiation curable resin, and the transparent resin for the sealing layer is also an ionizing radiation curable resin. And the sealing layer is made of a crosslinked cured product of the curable resin.
With such a configuration, the heat resistance and toughness of the filler layer that becomes the lower layer of the surface protective layer after transfer can be improved, the thermal deterioration during the formation of the metal thin film layer can be prevented, and the surface strength of the surface protective layer can be increased. Can be raised. Further, by adopting such a configuration, it is possible to prevent cracks in the transfer layer even when the transfer layer is deformed during transfer.

(1) According to the metallic tone transfer foil of the present invention, surface strength such as abrasion resistance and scratch resistance can be imparted, and the occurrence of cloudiness of metallic luster due to white spots can be prevented.
(2) Furthermore, white spots can be prevented more reliably by making the relationship between the maximum particle size of the reinforcing particles, the thickness of the surface protective layer, and the thickness of the sealing layer a specific relationship.
(3) Further, if both the surface protective layer and the sealing layer are cross-linked cured products of ionizing radiation curable resin, it is possible to prevent thermal deterioration during the formation of the metal thin film layer and to increase the surface strength of the surface protective layer. .

  The best mode for carrying out the present invention will be described below with reference to the drawings.

First, FIG. 1 is a cross-sectional view illustrating a certain form of a metallic tone transfer foil 10 according to the present invention. The metallic tone transfer foil 10 illustrated in FIG. 1 was dispersed in the crosslinked cured product of a transparent curable resin and the crosslinked cured product in order from the support sheet 1 side as the transfer layer 2 on the support sheet 1. Surface protective layer 4 having reinforcing particles 3 having a hardness higher than that of the crosslinked cured product, eye stop layer 5 made of a transparent resin that brings back surface unevenness due to the reinforcing particles protruding on the back surface of the surface protective layer closer to a flat surface, metal thin film layer 6 is a transfer foil having a structure in which an adhesive layer 7 is sequentially formed.
In addition, the metal-tone transfer foil illustrated in FIG. 1 is more preferably a flat surface in which the back surface irregularities due to the reinforcing particles 3 of the surface protective layer 4 are completely filled with the sealing layer 5 (of course, this flat surface). Is the surface on the back side of the eye stop layer). That is, the relationship between the maximum particle diameter Dmax of the reinforcing particles, the thickness Top of the surface protective layer, and the thickness Ts of the sealing layer satisfies the relational condition that Dmax / 2 ≦ Ts and Dmax ≦ (Top + Ts). It is a configuration.

  Hereinafter, the metallic tone transfer foil and the manufacturing method thereof according to the present invention will be described in order from the support sheet 1 for each layer.

[Support sheet]
The support sheet 1 is releasable from the transfer layer, and in the case of use that needs to be transferred to the uneven surface by following the metal-tone transfer foil to the uneven surface shape of the transfer surface during transfer, Furthermore, as long as it has the shape followability to the uneven | corrugated surface requested | required, a conventionally well-known thing may be sufficient and there is no limitation in particular. Therefore, if the transfer sheet is flat or two-dimensional uneven surface and the transfer sheet is not stretched, or if it is stretched slightly, other than a general biaxially stretched polyethylene terephthalate film (sheet), etc. Alternatively, a sheet using paper or the like having no stretchability may be used. When the transfer surface is a three-dimensional uneven surface and the transfer sheet needs to be further stretched, a stretchable sheet is used at least during transfer. An example of the stretchable sheet is a thermoplastic resin sheet. For example, polypropylene, polyethylene, polymethylpentene, ethylene-propylene-butene terpolymer, olefin resin such as olefinic thermoplastic elastomer, ethylene glycol-terephthalic acid-isophthalic acid copolymer, thermoplastic such as polybutylene terephthalate A low-stretched or non-stretched resin sheet (film) made of a resin such as a polyester resin, a vinyl chloride resin, a polyamide resin, or an elastomer such as a urethane-based thermoplastic elastomer is preferably used. The support sheet may be a single layer or a laminate composed of different materials. The thickness of the support sheet is usually about 20 to 200 μm.

  Further, the support sheet may be provided with a release layer on the transfer layer side, if necessary, in order to improve the release property with the transfer layer. This release layer is peeled off from the transfer layer together with the support sheet when the support sheet is peeled off. As the release layer, for example, a simple substance such as a silicone resin, a melamine resin, a polyamide resin, a urethane resin, a polyolefin resin, a wax, or a mixture containing these is used. For example, when the transfer surface is flat, a support sheet obtained by melt extrusion coating polypropylene as a release layer on high-quality paper can be used. In order to adjust the releasability, the surface of the support sheet on the transfer layer side may be subjected to corona discharge treatment, ozone treatment or the like.

[Surface protective layer]
The surface protective layer 4 is transferred as a part of the transfer layer to the transferred material after transfer, and protects the surface of the transferred material from abrasion, scratches, chemicals, ultraviolet rays, etc., and is resistant to abrasion and abrasion. It is a layer that imparts chemical resistance, weather resistance, and the like. It also has a function of adjusting the adhesiveness of the transfer layer to the support sheet and making the release layer of the transfer layer moderate with the support sheet.
In particular, in the present invention, in order to enhance the scratch resistance, wear resistance, etc., this surface protective layer is composed of a crosslinked cured product of a transparent curable resin and the crosslinked cured product dispersed in the crosslinked cured product. Was a layer having reinforcing particles with high hardness.

Further, the thickness of the surface protective layer is required to be at least 3 μm, more preferably 4 μm, from the viewpoint of the present metallic tone transfer foil aiming at improving the surface strength such as wear resistance and scratch resistance. Note that the upper limit is preferably 10 μm, more preferably 6 μm, in view of formability (shape follow-up to an uneven surface) as a use of the metallic tone transfer foil. When the thickness exceeds these upper limits, shape followability is lowered, and cracks and the like are likely to occur. If formability is not required, the thickness may be appropriately determined in consideration of the coating feeling, cost, and the like. However, considering a general-purpose product that can also be used for molding applications, it is better to impart a certain degree of moldability. In consideration of the above points, the thickness of the surface protective layer is 3 to 10 μm, more preferably 4 to 4 μm. It should be 6 μm.
The surface protective layer may be formed by a known forming method as appropriate, for example, a coating method such as roll coating or a printing method such as gravure printing.

  As the transparent curable resin, known resins such as an ionizing radiation curable resin and a thermosetting resin can be used. A typical example of the thermosetting resin is a two-component curable urethane resin. As the transparent curable resin, a thermosetting resin may be used, but an ionizing radiation curable resin is more preferable in terms of more excellent scratch resistance and wear resistance.

  Specifically, the ionizing radiation curable resin is prepared by ionizing radiation in which prepolymers (including so-called oligomers) having a polymerizable unsaturated bond or a cationic polymerizable functional group in the molecule and / or monomers are appropriately mixed. A crosslinkable composition is preferably used. These prepolymers or monomers are used alone or in combination. In addition, ionizing radiation means what has an energy quantum which can superpose | polymerize or bridge | crosslink among electromagnetic waves or a charged particle beam, and an ultraviolet-ray (UV) or an electron beam (EB) is normally used here.

  Specifically, the prepolymer or monomer is a compound having a radically polymerizable unsaturated group such as a (meth) acryloyl group or (meth) acryloyloxy group, a cationically polymerizable functional group such as an epoxy group in the molecule. Become. Further, a polyene / thiol prepolymer based on a combination of polyene and polythiol is also used. For example, the (meth) acryloyl group means an acryloyl group or a methacryloyl group. Moreover, the following (meth) acrylates are the meanings of an acrylate or a methacrylate similarly. In addition, the acrylate compound and the methacrylate compound are collectively referred to simply as an acrylate (compound).

  Examples of prepolymers having radically polymerizable unsaturated groups include polyester (meth) acrylate, urethane (meth) acrylate, epoxy (meth) acrylate, melamine (meth) acrylate, triazine (meth) acrylate, and silicone (meth) acrylate. Etc. can be used. The molecular weight is usually about 250 to 100,000.

  Examples of the monomer having a radically polymerizable unsaturated group include, as monofunctional monomers, methyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, phenoxyethyl (meth) acrylate, and the like. In addition, as a polyfunctional monomer of a monomer having a radical polymerizable unsaturated group, diethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane ethylene oxide tri (meth) ) Acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and the like.

  Examples of the prepolymer having a cationic polymerizable functional group include prepolymers of epoxy resins such as bisphenol type epoxy resins and novolac type epoxy resins, and vinyl ether type resins such as fatty acid type vinyl ethers and aromatic vinyl ethers.

  Examples of thiols include polythiols such as trimethylolpropane trithioglycolate and pentaerythritol tetrathioglycolate. Examples of the polyene include those obtained by adding allyl alcohol to both ends of polyurethane by diol and diisocyanate.

  In the case of an ionizing radiation curable resin, a photopolymerization initiator is further added to the ionizing radiation curable resin when it is crosslinked and cured with ultraviolet rays or visible light. In the case of a resin system having a radically polymerizable unsaturated group, acetophenones, benzophenones, thioxanthones, benzoin, and benzoin methyl ethers can be used alone or in combination as a photopolymerization initiator. In the case of a resin system having a cationic polymerizable functional group, an aromatic diazonium salt, an aromatic sulfonium salt, an aromatic iodonium salt, a metallocene compound, a benzoin sulfonic acid ester or the like is used alone or as a mixture as a photopolymerization initiator. be able to. In addition, as addition amount of these photoinitiators, it is about 0.1-10 mass parts with respect to 100 mass parts of ionizing radiation curable resin.

  Further, as the ionizing radiation, electromagnetic waves or charged particles having energy capable of causing a crosslinking curing reaction of molecules in the ionizing radiation curable resin (composition) are used. Usually used are ultraviolet rays or electron beams, but in addition, visible light, X-rays, ion rays and the like can also be used. As the ultraviolet light source, a light source such as an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc lamp, a black light, a metal halide lamp or the like is used. As a wavelength of ultraviolet rays, a wavelength range of 190 to 380 nm is mainly used. As the electron beam source, various electron beam accelerators such as Cockcroft-Walton type, Bandegraft type, resonant transformer type, insulated core transformer type, linear type, dynamitron type, high frequency type, etc. are used, preferably 70 to 1000 keV, preferably That irradiates electrons having energy of 100 to 300 keV is used.

  In addition, the ionizing radiation curable resin may further include an ionizing radiation non-curable resin such as a vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, an acrylic resin, or a cellulose resin, as necessary for adjusting the physical properties. A thermoplastic resin such as a thermosetting resin or the like may be added within the range of the subcomponent resin.

Next, the reinforcing particles 3 are particles dispersed in a crosslinked cured product obtained by crosslinking and curing the curable resin as described above, and are particles having higher hardness than the crosslinked cured product. Examples of such reinforcing particles include inorganic particles such as silica, alumina, cerium oxide, kaolinite, aluminosilicate, diamond, and glass, or organic substances such as polyamide, polyurethane, acrylic resin, urea resin, and phenol resin. Examples thereof include particles (resin beads). The organic particles have less physical properties required for surface strength such as abrasion resistance and scratch resistance, and when the hardness of the cross-linked cured product of the curable resin can be reduced, the organic particles become higher hardness than the cross-linked cured product. Can be adopted. Therefore, in general, inorganic particles are preferable to organic particles in that the surface strength can be increased.
In addition, the hardness which sees the hardness difference between the reinforcing particles and the crosslinked cured product is a Mohs hardness, a Vickers hardness, etc., and the hardness difference can be grasped by looking at the same hardness (reference).

  The particle shape of the reinforcing particles is not particularly limited, such as an indefinite shape or a spherical shape, but a spherical shape is preferable. The reason for this is that spherical particles have a greater effect of improving surface strength such as wear resistance and scratch resistance compared to irregularly shaped particles of the same material, and the surface after transfer does not wear the coating device. Other things in contact with the protective layer are not worn, and since the strength improvement effect is great, it can be realized with a smaller content to obtain the same effect, so the advantage that the transparency of the coating film becomes high is obtained. Because. In addition to the spherical shape, the spherical shape includes particles whose surface is surrounded by a smooth curved surface, such as a spheroid that is a flat sphere, or a shape that is close to a sphere or a spheroid. .

  With respect to the particle diameter of the reinforcing particles, the maximum particle diameter Dmax is preferably Dmax / 2 ≦ Ts, and more preferably Dmax ≦ ( (Top + Ts) is more preferable. In the formula, Top is the thickness of the surface protective layer 4, and Ts is the thickness of the sealing layer. When the particle shape deviates from the true sphere, the particle size can be grasped by the diameter of the particle circumscribed sphere.

Dmax / 2 means the radius of the particle diameter of the reinforcing particles. On the other hand, when the reinforcing particles protrude from the back surface of the surface protective layer, the extent of the protrusion is practically at most Dmax / 2 of the reinforcing particles. It is. Therefore, if the thickness of the eye stop layer is Dmax / 2 ≦ Ts, the reinforcing particles protruding from the rear surface of the surface protective layer can be completely buried in the eye stop layer.
Further, the portion of the reinforcing particles protruding from the back surface of the surface protective layer is at most Dmax / 2, that is, the portion of the reinforcing particles already embedded in the surface protective layer exceeds Dmax / 2. After the surface protective layer is formed on the support sheet at the time of producing the transfer foil, the surface protective layer surface (the eyepiece layer farther from the support sheet) is formed in a stage before further formation of the seal layer on the surface protective layer. Even if a part of the reinforcing particles is exposed from the surface forming the surface), the reinforcing particles are embedded in the surface protective layer with more than half of their volume, so it is difficult to drop off the surface protective layer. The substantial reduction of the content by prevents an unexpected decrease in the effect of surface strength such as wear resistance and scratch resistance.
Of course, if Dmax itself is set to be equal to or less than the thickness Top of the surface protective layer, the exposure of the reinforcing particles from the surface protective layer surface can be improved as described above.

  Then, Dmax ≦ Top may be set from the beginning, but in that case, the surface protective layer directly imparts surface strength, so that the crosslinked cured product of the surface protective layer is generally as hard as possible. Therefore, defects such as cracks in the surface protective layer tend to occur at portions that are bent (formed) during transfer. Accordingly, considering a certain degree of moldability, there is a limit to increasing the thickness Top of the surface protective layer, and it is necessary to apply reinforcing particles under such conditions. Further, the reinforcing particles in the surface protective layer are not always buried in the layer by making full use of the entire thickness of the surface protective layer, and the layers are floated from the surface of the surface protective layer on the support sheet side. This is because the reinforcing particles protruding on the back surface of the surface protective layer cannot be eliminated at all.

  And even if the reinforcing particles are exposed from the surface protective layer surface, if the back surface unevenness due to the exposed reinforcing particles is filled with the eye stop layer so that the unevenness is close to the flat surface or even slightly, White spots are eliminated or improved. The condition for this is Dmax ≦ (Top + Ts), and if Dmax is less than the total thickness Top + Ts of the thickness of the surface protective layer and the thickness of the sealing layer, the reinforcing particles are separated from the surface protective layer. It is possible to secure a layer thickness that can be completely buried in both layers. Therefore, the white spot is eliminated or improved.

  By the way, specific examples of the maximum particle size of the reinforcing particles vary depending on the thicknesses of the surface protective layer and the sealing layer, and required physical properties, but 10 μm or less makes it easy to obtain a white spot improvement effect. Is preferable. The reinforcing particles usually have a particle size distribution, but if the average particle diameter is taken, the range of 0.5 to 2 μm makes it easy to keep the maximum particle diameter Dmax within a value at which the white spot improvement effect can be easily obtained. Is preferable.

  The content of the reinforcing particles is preferably in the range of 3 to 9% by mass with respect to the total resin content of the surface protective layer. If it is less than 3% by mass, the effect of improving the scratch resistance cannot be obtained sufficiently in the surface strength. On the other hand, if it exceeds 9% by mass, the transparency of the surface protective layer decreases and clouding occurs (specifically, the haze value increases). Although the transparency depends on the application, high transparency is required for applications such as a display window member of a mobile phone that allows the object to be seen through, and maintaining the transparency is an important performance requirement.

  The surface protective layer is composed of at least the above-described curable resin and reinforcing particles, but in addition to these, known various additives may be added as necessary. Examples of additives include colorants such as dyes and pigments, light stabilizers such as ultraviolet absorbers and radical scavengers, heat stabilizers, lubricants, and fungicides.

[Medication layer]
The sealing layer 5 has a surface (back surface) of the surface protective layer formed on the support sheet at the time of production of the metallic tone transfer foil. The reinforcing particles exposed from the surface are uneven on the back surface. It is a layer that improves the appearance of surface defects on the observation surface side of the metal thin film layer, resulting in appearance defects such as white spots. By this eye stop layer, the back surface unevenness due to the reinforcing particles protruding from the back surface of the surface protective layer approaches the flat surface, and the white spots that are manifested by using the reinforcing particles can be improved. That is, the filler layer 5 is an ideal layer that is ideally filled with the back surface irregularities formed by the reinforcing particles protruding from the back surface of the surface protective layer so as to be a flat surface. Of course, the back surface irregularities are not completely filled. Even if it stops on an incomplete flat surface, the original back surface unevenness becomes closer to the flat surface, and the corresponding white spot improvement effect can be obtained.

The eye stop layer is preferably about 2 to 3 μm when a thermoplastic resin is used and about 4 to 6 μm when an ionizing radiation curable resin is used. If the thickness of each resin is less than the above range, coating unevenness cannot be formed, and a coating film having a uniform thickness cannot be formed, resulting in a problem before the purpose of flattening the back surface unevenness of the surface protective layer. Moreover, when both resin thickness exceeds the said range, shape followability will fall and a moldability will fall. Considering general-purpose products that can also be used for molding applications, it is better to impart a certain degree of moldability, and considering the above points, the upper limit of thickness is as described above. Further, excessive thickness in terms of performance with respect to the required surface strength results in useless cost.
In addition, the formation of the eye stop layer may be appropriately performed by a known forming method, for example, a coating method such as roll coating or a printing method such as gravure printing.

Such a sealing layer 5 may be formed of a transparent resin. Further, since the sealing layer is under the surface protective layer after the transfer, it is not directly related to the surface strength such as abrasion resistance and scratch resistance. Therefore, as the transparent resin used for the sealing layer, a thermoplastic resin such as an acrylic resin or a thermoplastic urethane resin may be basically used in addition to the curable resin. However, in order to further improve the surface strength such as abrasion resistance and scratch resistance, it is more preferable to use a curable resin and to form the sealing layer as a crosslinked cured product thereof.
As such a curable resin, a known resin such as an ionizing radiation curable resin or a thermosetting resin as described in the surface protective layer can be used. The specific contents of the ionizing radiation curable resin and the thermosetting resin have been described in the case of the surface protective layer, and are omitted here. However, since the filler layer is not the outermost surface layer, additives specific to the outermost surface layer such as lubricants and fungicides are not usually used.

In addition, since the filler layer serves as an underlayer for forming the metal thin film layer, it preferably has adhesion to the metal thin film layer, heat resistance against heat at the time of forming the metal thin film layer by vacuum deposition or the like. Also in this respect, the resin for the sealing layer is preferably a curable resin rather than a thermoplastic resin. In addition, in relation to the adhesion between the filler layer and the metal thin film layer, if the adhesion is poor, the metal thin film layer is visually observed if there is a portion where the metallic tone transfer foil is stretched (formed) during transfer. Possible cracks may occur. The generation of cracks is also related to the moldability of the sealing layer, and it is preferable to appropriately select a resin that does not cause cracks in the sealing layer from among curable resins.
For example, the mechanism is unknown, but experimentally obtained knowledge shows that ionizing radiation curable resins such as ultraviolet curable resins and electron beam curable resins are more transferable than two-part curable urethane resins. This is good because there are few cracks at the time, especially when the transfer layer is deformed during transfer. In particular, when the surface protective layer and the sealing layer are both made of an ionizing radiation curable resin, first the surface protective layer is formed and cured by ionizing radiation irradiation, and then the sealing layer is formed and cured by ionizing radiation irradiation. It is favorable in terms of both the crack prevention effect and the scratch resistance. In this case, ionizing radiation is inevitably irradiated twice for the surface protective layer and once for the sealing layer. Therefore, the surface protective layer becomes harder at a higher crosslink density and expresses scratch resistance here, and the filler layer becomes softer at a lower crosslink density and expresses crack prevention during transfer here. Guessed.

  The thickness of the sealing layer has preferable value conditions as described in the above surface protective layer, but by providing a corner and a sealing layer on the heel, a layer with a finite thickness exceeding zero is formed on the back surface of the surface protective layer. Therefore, some white point improvement effect can be obtained according to the finite thickness. However, a more preferable thickness condition is a thickness at which the back surface irregularities of the reinforcing particles protruding from the back surface of the surface protective layer are completely filled and filled to form a completely flat surface. Conditions satisfying this are the above-mentioned conditions that the maximum particle diameter Dmax of the reinforcing particles, the thickness Top of the surface protective layer, and the thickness Ts of the sealing layer are Dmax / 2 ≦ Ts and Dmax ≦ (Top + Ts). Met.

  In the case where the total thickness of the surface protective layer and the sealing layer is realized by only one layer of the surface protective layer, the same maximum grain size as that used in the case of the two layers that are relatively small relative to the total thickness is used. Even if reinforcing particles having a diameter are used, protrusion of reinforcing particles to the back surface of one surface protective layer cannot be completely avoided. Therefore, the back surface unevenness due to the protrusion of the reinforcing particles can be avoided and the white point can be improved by the multilayer laminated structure including the surface protective layer including the reinforcing particles and the sealing layer not including the reinforcing particles.

[Metal thin film layer]
The metal thin film layer 6 is formed on the back side of the eye stop layer by a known thin film forming method. As the metal thin film layer 6, for example, a metal such as aluminum, chromium, tin, indium, gold, silver, or copper is used, and a known thin film formation such as vacuum vapor deposition, sputter vapor deposition, ion beam vapor deposition, plasma vapor deposition, or plating is performed. Can be formed by the method. The metal thin film layer may be designed on the entire surface, or may be designed partially in a pattern by a known method. In addition, the thickness of a metal thin film layer should just be a thickness of the grade which can obtain a metallic luster feeling, for example, is about 100-2000 mm.

[Adhesive layer]
There is no restriction | limiting in particular as the adhesive bond layer 7, According to the material etc. of a to-be-transferred body, a suitable thing can be employ | adopted suitably from conventionally well-known adhesive agents. For example, in addition to general heat fusion adhesives, pressure sensitive adhesives, solvent activated adhesives, thermosetting adhesives, moisture curable adhesives, ionizing radiation curable adhesives, etc., depending on the application What is necessary is just to use suitably. Specifically, in the case of a heat fusion adhesive, for example, an adhesive made of vinyl acetate resin, vinyl chloride-vinyl acetate copolymer, acrylic resin, thermoplastic polyester resin, thermoplastic urethane resin, polyamide resin, or the like. Is mentioned. In the case of using a pressure-sensitive adhesive, a transfer sheet having a structure in which a release paper (or a release film) that protects the adhesive layer is laminated on the back surface of the adhesive layer until just before transfer is usually obtained.
In addition, the thickness of an adhesive bond layer is about 1-50 micrometers normally. The adhesive layer may be formed by a known forming method as appropriate, for example, a coating method such as roll coating or a printing method such as gravure printing.

  The adhesive layer 7 is directly laminated on the back surface of the metal thin film layer 6 in contact with the layer as in the metallic tone transfer foil 10 illustrated in FIG. 1, and other layers such as an easy adhesion primer layer are interposed therebetween. May be laminated.

[Other layers: Pattern layer]
Although illustration is omitted, a picture layer may be provided on the observer side (surface protective layer side) with respect to the metal thin film layer as a constituent layer of the transfer layer in order to achieve a higher design. In terms of position, it is preferably between the metal thin film layer and the sealing layer. The reason is that the surface protection effect by the surface protective layer can be obtained, and the occurrence of defective printing omission in which the ink is not partially transferred due to the unevenness of the back surface by the reinforcing particles protruding on the back surface of the surface protective layer can be prevented.

  The pattern of the pattern layer will be according to the application, for example, letters, symbols, figures, geometric patterns, etc., skin pattern, wood pattern, stone pattern, cloth pattern, tile tone pattern, brick tone pattern, The entire surface is a solid pattern. The pattern layer can be formed by a known printing method such as gravure printing, screen printing, offset printing, and ink jet printing. In addition, as the ink at that time, a vehicle made of a binder or the like, a colorant such as a pigment or a dye, and various known additives appropriately added thereto can be appropriately used. Binder resins include thermoplastic resins and curable resins (such as thermosetting resins and ionizing radiation curable resins) such as acrylic resins, vinyl chloride-vinyl acetate copolymers, polyester resins, cellulose resins, and polyurethane resins. One or two or more mixed resins are used. In addition, as a colorant, in addition to inorganic pigments such as titanium white, carbon black, petal, yellow lead, ultramarine, organic pigments such as aniline black, quinacridone, isoindolinone, phthalocyanine blue, or dyes, metallic pigments, Pearl pigments are used.

[Uses of metallic tone transfer foil]
The use of the metallic tone transfer foil according to the present invention is not particularly limited, but is particularly intended to improve a microscopic appearance defect called a white spot. In addition, applications that are observed closely are suitable. In addition, since transparency is also taken into consideration, it is preferable to see through other objects through the metal thin film layer-unformed portion, such as the display window member of the cellular phone.

[Metallic transfer foil transfer method]
The transfer method of the metallic tone transfer foil of the present invention is not particularly limited, and various transfer methods may be employed depending on the application. For example, there is a roller transfer method in which a transfer foil is pressed and transferred to an object to be transferred with an elastic roller made of rubber or the like. In addition, when the material to be transferred is a resin molded product, there is a transfer method in which the product is transferred to the surface simultaneously with the molding of the molded product. For example, it is a simultaneous molding transfer method called in-mold transfer, injection molding simultaneous painting method (see JP-A-6-315950, JP-B-2-42080, etc.) and the like. There are various forms of injection molding simultaneous painting methods, especially the characteristics with the preforming, and the transfer foil can be preformed and transferred to a deeply drawn product, but in the form without the preforming There is also a form in which the transfer foil is transferred to a substantially flat surface without any deformation (molding) of the transfer foil or slightly deformed (molded) by using hot pressure of the injection resin. The latter form without preforming is a so-called in-mold transfer method called a simultaneous molding transfer method.

  Here, the molding simultaneous transfer method by the injection molding simultaneous painting method will be outlined with reference to the conceptual diagram of FIG. In addition, the form demonstrated here is a form suitable for a molded article with a deep drawing, and is a form which preliminarily molds the transfer foil on an injection mold.

  First, as shown in FIG. 2 (A), as an injection mold, a mold Ma having a runner communicating with an injection nozzle and a gate (gate), a suction hole 41 on the cavity surface, and a preliminary transfer foil. A pair of molds Mb that also serves as a mold is used. These molds are made of metal such as iron or ceramics. In the mold open state, the (metal-like) transfer foil 10 is supplied between both molds Ma and Mb, and the transfer foil 10 is fixed to the mold Mb by pressing it with a sheet clamp 42 having a frame shape in plan view. In this case, it is needless to say that the transfer layer side of the transfer foil is the injection resin side on the right side of the drawing. Next, the transfer foil is heated and softened by a heater (not shown) inserted between both molds. The heating is, for example, non-contact radiation heating, but may be conduction heating by contact. Then, vacuum suction is performed through the suction holes, and the transfer foil is preformed along the cavity surface of the mold Mb. Note that the vacuum forming may be vacuum / pressure forming using pressure air together, and includes this. Next, the heater is retracted from both molds, both molds are clamped as shown in FIG. 2 (B), and a resin in a fluid state such as a heat-melted state is injected and filled into a cavity formed by both molds. And after resin solidifies by cooling etc., a mold is opened and a molding is taken out. At this time, the molded product is taken out with the support sheet of the transfer foil left on the mold Mb side, or the molded product is taken out with the entire transfer foil laminated, and then the support sheet is peeled off and transferred. This is a method of obtaining a transfer molded product in which only layers are laminated.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

[Example 1]
First, as a transfer layer 2, a surface protective layer 4 having a thickness of 3 μm is formed on the release surface of the releasable support sheet 1 obtained by releasing one side of a biaxially stretched polyethylene terephthalate film having a thickness of 38 μm with a release layer. A sealing layer 5 having a thickness of 2 μm was sequentially formed. The surface protective layer 3 has a maximum particle size Dmax = 8 μm and an average particle size as reinforcing particles 3 in 100 parts by mass of an ionizing radiation curable resin that can be crosslinked and cured with ultraviolet rays containing a urethane acrylate prepolymer and a benzophenone photopolymerization initiator. A coating liquid containing 5 parts by mass of Dav = 2 μm silica powder was applied, and after forming a stop layer, it was formed by crosslinking and curing by irradiation with ultraviolet rays using a mercury lamp with an output of 80 W / cm. The eye stop layer 5 is made of a two-component curable urethane resin in which a bifunctional aliphatic isocyanate cross-linking agent is blended with an acrylic polyol having a weight average molecular weight Mw of 60,000, and a coating that does not contain the reinforcing particles 3 is applied. It was cured by heat curing.

  Subsequently, aluminum was vacuum-deposited on the filler layer 5 to form a metal thin film layer 6 having a thickness of 450 mm. Finally, a coating liquid made of a mixed resin having a 1: 1 mass ratio of vinyl chloride-vinyl acetate copolymer and acrylic resin was applied to form an adhesive layer 7 having a thickness of 2.5 μm. The desired metallic tone transfer foil 10 as shown in FIG.

  Further, the above-mentioned metallic tone transfer foil 10 is formed by molding an acrylic resin mobile phone display window member by in-mold transfer without preforming the transfer foil (vertical 45 mm, horizontal 35 mm, four corners are rounded rectangles of 2 mmR). In addition, at the same time as the molding of the surface side plane and the four side surfaces at the angle of 1 mmR and the thickness of 2 mm), the injection is applied to the front side plane of the molded product and the front side part of the four peripheral side surfaces through the rounded portion from the surface plane. Transferring simultaneously with resin molding using the hot pressure of the resin, a transfer molded product having a desired mirror-like metallic gloss was obtained. Transfer is placed in an injection mold so that the transfer layer side of the metallic tone transfer foil is on the injection resin side, then the mold is clamped and acrylic resin is injected to integrate the molded product and transfer layer. Then, the mold was opened and the support sheet was peeled off. The injection molding conditions are: injection resin temperature is 250 ° C., injection mold temperature is 60 ° C., and the gate is a side gate. In addition, in the case of a mobile phone display window member, since the central portion is originally a transparent window portion and its periphery is a specular metallic luster design, the metal thin film layer is patterned in a portion excluding the central portion. The formed metal tone transfer foil was used, but this time, the metal thin film layer was transferred to the entire surface including the central portion so that the improvement performance with respect to the white spot could be more easily discriminated.

[Example 2]
In Example 1, except that the particle size of the silica powder used for the reinforcing particles was changed to the maximum particle size Dmax = 2 μm and the average particle size Dav = 0.5 μm, the same as in Example 1, A metallic tone transfer foil was prepared. Further, a transfer molded product was produced in the same manner as in Example 1.

Example 3
In Example 1, the particle size of the silica powder used for the reinforcing particles was changed to the maximum particle size Dmax = 2 μm and the average particle size Dav = 0.5 μm, and the resin of the filler layer was changed, A coating solution made of an ionizing radiation curable resin that contains a urethane acrylate prepolymer and a benzophenone-based photopolymerization initiator and does not contain the reinforcing particles and that can be crosslinked and cured with ultraviolet rays was used as an eye stop layer. Then, after the surface protective layer was crosslinked and cured, the above-mentioned coating solution for the sealing layer was applied, irradiated with ultraviolet rays under the same conditions as the surface protective layer, and crosslinked and cured to form the sealing layer. The ultraviolet irradiation amount of the surface protective layer was twice the ultraviolet irradiation amount of the eye stop layer. Other than this, in the same manner as in Example 1, a desired metallic tone transfer foil was produced. Further, a transfer molded product was produced in the same manner as in Example 1.

[Comparative Example 1]
A desired metallic tone transfer foil was prepared in the same manner as in Example 1 except that the formation of the filler layer was omitted in Example 1. Further, a transfer molded product was produced in the same manner as in Example 1.

[Performance evaluation]
The performance evaluation was carried out by visually observing the metallic glossiness of the mirror surface from a close distance of 10 cm on the transfer molded product produced by using the metallic tone transfer foils of Examples and Comparative Examples for in-mold transfer. Cracks and transfer layer adhesion were evaluated.
(1) If there was no white spot, it was good, and if there was, it was judged as bad.
(2) Cracks are likely to occur particularly at the rounded portion, but overall, good if not present, and defective if present.
(3) Transfer layer adhesion is formed by crossing four vertical stripes and four horizontal stripes on the surface of the transferred layer after transfer (crossed by a total of 16 scratches). The cellophane pressure-sensitive adhesive tape (manufactured by Nichiban Co., Ltd., registered trademark “cello tape” 25 mm width) was affixed thereon and peeled by hand. The case where no squares were removed was judged as good, and the case where even one square was removed was regarded as defective.

  As a result, as shown in Table 1, a large number of white spots were observed in Comparative Example 1 in which the eye stop layer was not provided, but all the examples in which the eye stop layer was provided were improved in all cases. Among these examples, in Example 2 and Example 3 in which the maximum particle diameter Dmax, Top and Ts satisfy the relationship defined by the present invention, the slight white spot existing in Example 1 was not recognized. On the other hand, cracks were also observed in Example 2 in which the resin of the sealing layer was a two-component curable urethane resin, but an ionizing radiation curable resin (ultraviolet curable resin) was used as the sealing layer resin. Not observed in Example 3.

Sectional drawing which illustrates a certain form of the metallic tone transfer foil by this invention. The conceptual diagram explaining one form of the injection molding simultaneous painting method as an example of utilization of metallic tone transfer foil.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Support sheet 2 Transfer layer 3 Reinforcement particle 4 Surface protective layer 5 Sealing layer 6 Metal thin film layer 7 Adhesive layer 10 Metal tone transfer foil 41 Suction hole 42 Sheet clamp Ma Injection mold (male)
Mb injection mold (female)
Dmax Maximum particle size of reinforcing particles Top Surface protective layer thickness Ts Sealing layer thickness

Claims (3)

In a metallic tone transfer foil including a metal thin film layer having a metallic luster as a transfer layer on a support sheet,
A surface protective layer in which the transfer layer has, in order from the support sheet side, a crosslinked cured product of a transparent curable resin and reinforcing particles having a hardness higher than that of the crosslinked cured product dispersed in the crosslinked cured product, the surface A metallic tone transfer foil comprising a sealing layer, a metal thin film layer, and an adhesive layer made of a transparent resin that brings back surface irregularities due to reinforcing particles protruding on the back surface of a protective layer closer to a flat surface. The relationship between the maximum particle diameter Dmax of the reinforcing particles, the thickness Top of the surface protective layer, and the thickness Ts of the sealing layer is as follows:
Dmax / 2 ≦ Ts and Dmax ≦ (Top + Ts)
The metal-tone transfer foil according to claim 1, wherein The curable resin of the surface protective layer is an ionizing radiation curable resin, and the transparent resin of the eye stop layer is also a curable resin made of an ionizing radiation curable resin, and the eye stop layer is made of a crosslinked cured product of the curable resin. The metal-tone transfer foil according to claim 1 or 2.

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