JP5574377B2 - Hard coat film, decorative hard coat film - Google Patents

Description

The present invention relates to a hard coat film decorated directly on the surface of the hard coat by thermal transfer printing.

In recent years, there are many cases where a hard coat film is attached to the outermost surface of a mobile device such as a mobile phone or a smartphone via an adhesive layer for the purpose of preventing scratches. At the same time, in order to improve the design of mobile devices, there is an increasing number of cases where printing is performed on the surface opposite to the hard coat layer of the hard coat film and decorated on the display of the mobile device (Patent Document 1). .

  When the hard coat film is attached to a mobile device having a touch panel function, the surface quality of the hard coat film is deteriorated by a heat treatment step (hereinafter referred to as annealing treatment) applied during the manufacturing process of the touch panel. This is because the hard coat layer shrinks simultaneously with the shrinkage of the PET film as the substrate by heating. That is, when a hard coat film coated with a hard coat on only one side is used, the surface quality deterioration of the hard coat film generated in the heating process is likely to adversely affect the function of the touch panel. Therefore, the hard coat film that is adhered to the outermost surface of the display unit of a mobile device having a touch panel function is generally a film obtained by performing hard coat processing on both surfaces of a base material. Therefore, in the case of decorating, a method of directly printing on the back side hard coat surface by a screen printing method or the like is used.

Japanese Patent No. 4021925 Japanese Patent Application No. 2009-271701

Recently, due to diversification of customer requests and shorter delivery times, the number of units produced per mobile device has been decreasing, and it has been pointed out that decorating using the screen printing method mentioned above causes cost increases. Has been. For this reason, various studies have been made to decorate the hard coat layer by a method instead of the screen printing method.

A particularly promising method is a thermal transfer printing method using a thermal transfer printer. This method is a printing method that is excellent in on-demand printability and can be used for various designs at low cost. However, although thermal transfer printing on the hard coat layer has been studied for some time, the adhesion between the hard coat layer and the thermal transfer ribbon cannot be obtained, and satisfactory quality cannot be obtained. As described in Patent Document 2, the present inventor sets the surface tension of the hard coat layer of the hard coat film to 35 mN / m or more, and prints the decorative hard coat film on the hard coat layer surface with a thermal transfer ribbon. I was able to get it.
However, when black solid printing was performed with a thermal transfer ribbon, very fine interference fringes appeared.

  In order to solve the above-mentioned problem of interference fringes, the present invention does not generate interference fringes even when directly printed on a hard coat layer by a thermal transfer printing method using a thermal transfer printer, and is based on an annealing process applied during the touch panel manufacturing process. The present invention provides a decorated hard coat film that does not deteriorate the surface quality of the hard coat film.

According to a first aspect of the present invention, there is provided a hard coat film having a hard coat layer provided on at least one surface of a substrate by a thermal transfer printing method using a thermal transfer ribbon in which at least a colored ink layer and an adhesive layer are sequentially laminated on the substrate. The decorative hard coat film is characterized by being decorated on a coat layer, and the adhesive layer is mainly composed of a thermoplastic resin having a melt viscosity in the range of 5 to 1000 P / 140 ° C.
2nd invention contains 1-13% of inorganic fine particles in the said contact bonding layer, The decorating hard coat film of Claim 1 characterized by the above-mentioned.

By using the hard coat film and the thermal transfer ribbon of the present invention, it is possible to perform thermal transfer printing directly on the film, there is no interference fringes, and there is no surface quality deterioration of the hard coat film due to the annealing treatment applied during the touch panel manufacturing process. Hard coat film can be made.

  The base material of the hard coat film used in the present invention is not particularly limited as long as it is a film made of various plastics. Examples include films made of polyolefin, polyester, polyamide, polycarbonate, fluororesin, polyphenylene oxide, polyimide, polyamideimide, acrylic resin, polyvinyl chloride, polyvinylidene chloride, polyacrylonitrile, cellulose resin, etc. It is not limited to. A polyester film is preferably used from the viewpoints of handleability, improvement in adhesive strength with the adhesive layer, and cost. The thickness of the substrate may be appropriately selected according to the use, but usually a thickness in the range of 4 to 400 μm is used.

The compound used in the hard coat layer of the present invention is preferably formed mainly from a compound that polymerizes by ionizing radiation, and forms a compound having a (meth) acryloyl group that forms a radical polymerization reaction or a cationic polymerization reaction. A compound is preferred. The compound having a (meth) acryloyl group means a compound having one or more (meth) acryloyl groups in the molecule, and may be a monomer or an oligomer.

In the present invention, the acryloyl group and the methacryloyl group are collectively referred to as a (meth) acryloyl group. That is, the compound having a (meth) acryloyl group may be a compound having only an acryloyl group, or a compound having only a methacryloyl group, and having both an acryloyl group and a methacryloyl group. It may be. The same applies to (meth) acrylates and (meth) acrylic esters described below.

Examples of the compound having a (meth) acryloyl group according to the present invention include monomers or oligomers of polyfunctional (meth) acrylates and monofunctional (meth) acrylates described below.

Multifunctional (meth) acrylates include trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) Acrylate, dipentaerythritol hexa (meth) acrylate, glycerin tri (meth) acrylate, tris (2-hydroxyethyl) isocyanurate tri (meth) acrylate, ethylene glycol di (meth) acrylate, 1,3-butanediol di ( (Meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, die Renglycol di (meth) acrylate, triethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, bis (2-hydroxyethyl) isocyanurate di (meth) acrylate, and ethylene oxide to these starting alcohols Or propylene oxide adduct poly (meth) acrylates, oligoester (meth) acrylates having two or more (meth) acryloyl groups in the molecule, oligoether (meth) acrylates, oligourethane (meth) acrylates, And oligoepoxy (meth) acrylates.

Monofunctional (meth) acrylates include methyl (meth) acrylate, ethyl (meth) acrylate, acrylonitrile, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, Phenoxyethyl (meth) acrylate, 2-phenoxy-2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate, glycerol mono (meta) ) Acrylate, glycidyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, tricyclodecanyl (meth) acrylate, disic Pentenyl (meth) acrylate, n-butyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, Dodecyl (meth) acrylate, n-stearyl (meth) acrylate, benzyl (meth) acrylate, phenol ethylene oxide modified (n = 2) (meth) acrylate, nonylphenol propylene oxide modified (n = 2.5) (meth) acrylate, Half (meth) acrylate, furfuryl (meta) of phthalic acid derivatives such as 2- (meth) acryloyloxyethyl acid phosphate and 2- (meth) acryloyloxy-2-hydroxypropyl phthalate Acrylate, carbitol (meth) acrylate, benzyl (meth) acrylate, butoxyethyl (meth) acrylate, allyl (meth) acrylate 2-acryloyloxyethyl acid phosphate monoester, cyclohexanedimethanol monoacrylate, 4-hydroxybutyl acrylate, acryloyl Examples include morpholine, 4-glycidyloxybutyl acrylate, diacetone acrylamide and the like.

These compounds having a (meth) acryloyl group may be used alone or in combination of two or more.

On the other hand, an epoxy resin is usually used as a compound that forms cationic polymerization. Examples of the epoxy resins include compounds obtained by epoxidizing polyphenols such as bisphenol resins and novolac resins with epichlorohydrin, etc., and compounds obtained by oxidizing a linear olefin compound or a cyclic olefin compound with a peroxide or the like. Etc.

Examples of the photopolymerization initiator used in the ionizing radiation polymerization reaction include radical polymerization type compounds such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, and acetophenone. Dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one, 4- (2-hydroxyethoxy) phenyl-2 (hydroxy-2-propyl) ketone, benzophenone, p- Phenylbenzophenone, 4,4′-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylamine benzoate, and the like. Examples of photopolymerization initiators for cationic polymerization type compounds include oniums such as aromatic sulfonium ions, aromatic oxosulfonium ions, aromatic iodonium ions, tetrafluoroborate, hexafluorophosphate, hexafluoroantimonate, hexa The compound which consists of anions, such as fluoroarsenate, is mentioned. These may be used alone or in combination of two or more, and the blending amount is usually selected in the range of 0.2 to 10 parts by mass with respect to 100 parts by mass of the polymerizable compound. It is.

In addition to the ionizing radiation curable compound, a thermoplastic polymer can be added as long as the hard coat property is not significantly impaired. Examples of the thermoplastic polymer include acrylic resins, vinyl acetate resins, epoxy resins, polyester resins, polycarbonate resins, butyral resins, gelatin, cellulose resins, polyamide resins, vinyl chloride resins, urethane resins. Examples thereof include resins.

Furthermore, if necessary, an antifoaming agent, a coating property improver, a thickener, a surfactant, an organic lubricant, an organic fine particle, an inorganic fine particle, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, It may contain pigments, antistatic agents and the like.

The thickness of the hard coat coating film is 1 μm or more and 20 μm or less, preferably 3 μm or more and 15 μm or less. If it is less than this range, sufficient hard coat properties cannot be obtained, and the coating film tends to be damaged. On the other hand, exceeding this range leads to an increase in cost. Moreover, when a hard coat is applied on both sides, it is preferable to suppress the difference in film thickness between the two layers within 30%. If this range is exceeded, curling of the hard coat film will increase, which may adversely affect the handling of the next process transition, and may adversely affect the touch panel function when the touch panel is assembled.

In order to decorate the hard coat film, at least one surface is decorated using a screen printing method, gravure printing method, pad printing method, offset printing method, inkjet printing method, thermal transfer printing method, etc. Among them, the thermal transfer printing method is particularly preferable because it is excellent in small-lot productivity, on-demand property, printing diversity, and the like. When printing on the hard coat surface by the thermal transfer printing method, interference fringes do not occur if the colored layer is transferred onto the hard coat layer via an adhesive layer.

The thermal transfer ribbon used for decorating by the thermal transfer printing method of the present invention is provided with a colored layer and an adhesive layer on a substrate. The colored layer is composed of a binder and a color material. In particular, when an acrylic resin is contained as a binder, the releasability between the ink and the substrate is improved, and thermal transfer to the hard coat layer is improved. Examples of the acrylic resin include polymers and copolymers in which at least one selected from (meth) acrylic acid methyl ester resin, (meth) acrylic acid ethyl ester resin, (meth) acrylic acid butyl ester resin and the like is included in the structure. It is preferable to become. When the acrylic resin is contained at least 10% by weight or more in the binder, the thermal transfer property is excellent. If the content is less than the above range, the releasability between the ink and the substrate is lowered, peeling sound is generated during printing, or the primary color is peeled off during secondary color printing, which is called collect during overprinting. Transfer defects are likely to occur. A more preferable content is 20 to 80% by weight, and a particularly preferable content is 40 to 60% by weight.

Examples of other binders include wax and thermoplastic resin. Examples of waxes include natural waxes such as wax, beeswax, carnauba wax, candelilla wax, montan wax, and ceresin wax; petroleum waxes such as paraffin wax and microcrystalline wax; oxidized wax, ester wax, polyethylene wax, and fisher Synthetic waxes such as Tropsch wax and α-olefin-maleic anhydride copolymer wax; higher fatty acids such as myristic acid, palmitic acid, stearic acid and behenic acid; higher aliphatic alcohols such as stearyl alcohol and docosanol; higher fatty acid monoglycerides, Esters such as fatty acid esters of sugar and fatty acid esters of sorbitan; one or two amides such as stearamide, oleylamide, and bisamides Above it can be used.

Examples of the thermoplastic resin include olefin-based copolymer resins such as ethylene-vinyl acetate copolymer and ethylene-acrylate ester copolymer, polyamide-based resin, polyester-based resin, epoxy-based resin, polyurethane-based resin, and vinyl chloride-based resin. Resins, cellulose resins, vinyl alcohol resins, petroleum resins, phenol resins, styrene resins, vinyl acetate resins, natural rubber, styrene-butadiene rubber, isoprene rubber, chloroprene rubber and other elastomers, polyisobutylene, polybutene 1 type, or 2 or more types.

As a color material, organic and inorganic pigments and / or dyes can be used in addition to carbon black.

The thickness of the colored layer is preferably in the range of 0.1 to 5.0 μm, more preferably 0.3 to 2.0 μm. If it is less than the above range, the print density will be insufficient.

The adhesive layer provided on the colored layer is mainly composed of a thermoplastic resin. Examples of the thermoplastic resin include olefin copolymer resins such as ethylene-vinyl acetate copolymer and ethylene-acrylate ester copolymer, polyamide resin, polyester resin, epoxy resin, polyurethane resin, and vinyl chloride resin. Resins, cellulose resins, vinyl alcohol resins, petroleum resins, phenol resins, styrene resins, vinyl acetate resins, natural rubber, styrene-butadiene rubber, isoprene rubber, chloroprene rubber and other elastomers, polyisobutylene, polybutene 1 type or 2 types or more, such as, are mentioned.

  In addition to the thermoplastic resin, a thermosetting resin or a photocurable resin may be contained. Moreover, you may add waxes as needed. In particular, when a thermosetting resin or a photocurable resin is added, the strength of the adhesive layer is increased, and surface quality deterioration due to annealing (150 ° C. × 60 minutes treatment) can be suppressed. As a photocurable resin, the monomer and photoinitiator which were mentioned by the said hard-coat layer are mentioned.

  In order to prevent interference fringes due to thermal transfer printing, the thermoplastic resin should have a melt viscosity in the range of 5 to 1000 P / 140 ° C. If it is less than the above range, the adhesive layer is softened during the annealing treatment and surface quality deterioration is likely to occur. If the range is exceeded, the interference fringe reduction effect is reduced. If the colored layer is heat transfer printed directly on the hard coat layer without an adhesive layer, an extremely thin air layer appears to be formed at the interface between the colored layer and the hard coat layer. Therefore, it is considered that interference fringes are generated. By providing the adhesive layer, it is considered that the adhesive layer and the hard coat layer are in close contact with each other and no air layer is generated.

  The preferable melt viscosity of the thermoplastic resin of the adhesive layer is in the range of 10 to 900 P / 140 ° C. A more preferable range of melt viscosity is 100 to 800 P / 140 ° C. (Measured with MR300V II solid meter manufactured by UBM Co., Ltd. using dynamic viscoelasticity measurement mode and cone plate) The thickness of the adhesive layer is preferably in the range of 0.05 to 1 μm. If it is less than the above range, the interference fringe reduction effect is small. Beyond the above range, it is economically inefficient. A more preferable range of thickness is 0.1 to 0.8 μm.

  In order to prevent surface quality deterioration due to the annealing treatment and to improve the printing quality, it is preferable to contain 1 to 13 wt% of inorganic fine particles in the adhesive layer. If it is less than the above range, the surface quality deterioration preventing effect is small. When the above range is exceeded, the transfer characteristics of thermal transfer printing are deteriorated, and the print quality tends to deteriorate. More preferably, it is 1.5 to 10% by weight.

  Inorganic fine particles include single oxide particles such as silica, alumina, zirconia, ceria, yttria, boronia, magnesia, calcia, ferrite, amorphous titania, and hafnia; and composite oxides such as barium titanate and calcium silicate And more preferably silica fine particles. These inorganic fine particles are preferably in the form of an aqueous colloid using water as a dispersion medium; or an organosol dispersed colloidally in a hydrophilic solvent such as ethyl alcohol, isopropyl alcohol, or ethylene glycol, and particularly preferably colloidal silica. It is.

  According to a preferred embodiment of the present invention, the inorganic fine particles have an average particle size in the range of 5 to 40 nm, more preferably in the range of 5 to 30 nm, and still more preferably in the range of 10 to 30 nm. When the average particle size is less than 5 nm, it is difficult to prevent surface quality deterioration of the annealing process.

The average particle diameter is calculated as a number average value obtained by measuring the length of any 100 particles that enter a 200,000-fold field of view with a scanning electron microscope. As the shape of the particle, a perfect sphere is the best, but it may be approximately circular or elliptical, and the length of the particle in this case is approximately calculated as (major axis + minor axis) / 2).

As the base material of the thermal transfer ribbon, a polyethylene terephthalate film having a thickness of 2 to 9 μm is preferably used. A heat-resistant layer made of silicone resin is provided on the opposite surface of the colored layer.

The thermal transfer ribbon can be constituted by coating and drying a colored layer ink and an adhesive layer ink on a substrate.

The present invention will be described more specifically with reference to the following examples. In addition, this invention is not limited by these Examples.

[Formation of thermal transfer ribbon]
The colored ink coating agent described below was coated at a dry film thickness of 1 μm on the front side of a 4.5 μm thick PET film having a heat resistant slipping layer on the back surface to form a colored layer.

[Colored ink coating agent]
Dianal BR83 (acrylic resin, manufactured by Mitsubishi Rayon) 10 parts by weight LFF MA-7 (carbon black, Mitsubishi Chemical) 10 parts by weight Dispersant 1 part by weight MEK 79 parts by weight

The adhesive layer coating agents 1 to 6 shown below were coated on the colored layer prepared as described above to a thickness of 0.5 μm to form a thermal transfer ribbon.
[Coating agent for adhesive layer 1]
Versamide JP550 (polyamide resin, manufactured by Cognis Japan) 10 parts by weight Toluene 70 parts by weight IPA 20 parts by weight
[Coating agent for adhesive layer 2]
Diacron ER799 (polyester resin, manufactured by Mitsubishi Rayon) 10 parts by weight MEK 90 parts by weight
[Coating agent for adhesive layer 3]
Diacron ER799 (polyester resin, manufactured by Mitsubishi Rayon) 9.25 parts by weight MEK-ST (silica sol, average particle size 15 nm, manufactured by Nissan Chemical Industries) 0.75 parts by weight MEK 90 parts by weight
[Coating agent for adhesive layer 4]
Araldite AER6071 (epoxy resin, manufactured by Ciba Geigy) 10 parts by weight MEK 90 parts by weight
[Coating agent 5 for adhesive layer]
Diacron ER799 (polyester resin, manufactured by Mitsubishi Rayon) 8 parts by weight MEK-ST (silica sol, average particle size 15 nm, manufactured by Nissan Chemical) 2 parts by weight MEK 90 parts by weight
[Coating agent 6 for adhesive layer]
Bondin HX-8210 (EEA-maleic anhydride resin, manufactured by Sumitomo Chemical) 10 parts by weight MEK 90 parts by weight

[Formation of hard coat film]
The following hard coating agent was coated on both sides of optical PET having a thickness of 100 μm by 5 μm, each was irradiated with ultraviolet rays having an integrated light amount of 500 mj / cm ² , and the coating film was cured to form a hard coating layer having a thickness of 5 μm.

[Hard coat agent]
Light ester TMP (acrylate monomer, manufactured by Kyoeisha) 20 parts by weight NK oligo U-4HA (urethane acrylate, manufactured by Shin-Nakamura Chemical) 18.5 parts by weight Irgacure 184 (photoinitiator, manufactured by Ciba Specialty Chemicals) 1.5 parts by weight MEK 60 parts by weight

The following evaluation was performed on the thermal transfer ribbon with an adhesive layer and the hard coat film produced as described above. Evaluation items and evaluation criteria are as follows.
1. Using an interference fringe thermal transfer printer (manufactured in-house), black solid printing is performed on the hard coat layer of the hard coat film. The degree of interference fringes is visually observed from the opposite side (surface) to the printed surface.
○: No interference fringes are visible Δ: Interference fringes appear thin ×: Interference fringes are clearly visible Print evaluation Using a thermal transfer printer (manufactured in-house), the ink transferability when printing on the hard coat layer of the hard coat film at a speed of 25 mm / sec and a print energy of 40 mj / mm ² is evaluated according to the following criteria. .
5: Very good
4: Good 3: Part of the print is chipped 2: Print chipping is noticeable
1: Measurement results and evaluation results are summarized in Table 1 in accordance with the above method where printing cannot be performed at all.

Claims (2)

On a hard coat layer of a hard coat film in which a hard coat layer is provided on at least one surface of the substrate by a thermal transfer printing method using a thermal transfer ribbon in which at least a colored ink layer and an adhesive layer are sequentially laminated on the substrate. A decorative hard coat film comprising a thermoplastic resin having a melt viscosity of 5 to 1000 P / 140 ° C. as a main component . The decorative hard coat film according to claim 1, wherein the adhesive layer contains 1 to 13% of inorganic fine particles.