JP6434785B2 - Transparent resin laminate molded into a curved surface, display cover including the same, and mobile terminal including the same - Google Patents

Description

  The present invention relates to a transparent resin laminate molded into a curved surface, a display cover including the same, and a mobile terminal including the same.

  Conventionally, a synthetic resin film or sheet used for a cover such as a liquid crystal display is not only surface hardness, heat resistance, impact resistance and rigidity, but also highly transparent for the purpose of displaying information and viewing images and videos. , Surface smoothness and flatness have been emphasized.

  The present inventors have so far developed a flat synthetic resin film that satisfies all the above-mentioned characteristics at the same time (Patent Document 1).

  In recent years, in fields where liquid crystal displays have been used, organic EL displays have started to be used, and curved displays that have been difficult with conventional liquid crystal displays have started to be put into practical use. On the other hand, in the field of liquid crystal display covers, not only hard-coated plastic display covers but also tempered glass display covers have begun to be used.

  However, a curved display cover made of tempered glass has a problem that the processing cost is very high, and has not been put into practical use. On the other hand, a display cover made of plastic such as polycarbonate has a drawback that since the rigidity is low, the display cover is easily bent and the appearance, heat resistance and moisture resistance are poor.

JP 2012-183822

  An object of this invention is to provide the transparent resin laminated body shape | molded in the curved surface shape excellent in an external appearance, heat resistance, and moisture resistance.

  Conventionally, it has been difficult to obtain a curved molded product having excellent appearance, heat resistance and moisture resistance by thermoforming a thermoplastic such as polycarbonate.

Therefore, the present inventors made a glass transition temperature of the transparent resin layer (on the both sides of the transparent resin layer) with respect to the transparent resin laminate having an ultraviolet curable resin composition layer, a polyester resin layer and a hard coat layer in this order ( T1) and the glass transition temperature (T2) higher than the glass transition temperature (T2) of the polyester resin layer and lower than the crystalline melting point (T3) of the polyester resin layer (MT), and then the glass transition of T1 or T2 whichever is lower It has been found that a transparent resin laminate molded into a curved surface obtained by performing a heat treatment (annealing) at a temperature (AT) higher than the temperature and lower than the thermoforming temperature (MT) can achieve the above object. It was. Based on this knowledge, further studies have been made to complete the present invention. That is, the present invention provides the following transparent resin laminate, a display cover including the same, and a mobile terminal including the same.
Item 1.
A transparent resin layer; and a transparent resin laminate formed into a curved shape having an ultraviolet curable resin composition layer, a polyester resin layer, and a hard coat layer sequentially formed on both surfaces of the transparent resin layer.
Item 2.
Item 2. The transparent resin laminate according to Item 1, wherein the transparent resin layer is a polycarbonate film.
Item 3.
Item 3. The transparent resin laminate according to Item 1 or 2, wherein the polyester resin layer is a biaxially stretched polyethylene terephthalate film.
Item 4.
The transparent resin laminate according to any one of Items 1 to 3, obtained by the following steps (1) and (2):
Step (1): Heating at a temperature (MT) higher than the glass transition temperature (T1) of the transparent resin layer and the glass transition temperature (T2) of the polyester resin layer and lower than the crystalline melting point (T3) of the polyester resin layer. Step of forming (heat forming step) and step (2): at a temperature (AT) higher than the glass transition temperature of T1 or T2 which is lower and lower than the heat forming temperature (MT) of step (1) Step for heat treatment (heat treatment step).
Item 5.
The transparent resin laminate according to Item 4, wherein
The ratio of the radius of curvature (R2) of the laminate obtained in the step (1) and the radius of curvature (R3) of the laminate obtained in the step (2) is 1: 1.1 to 1: 6.0 Resin laminate.
Item 6.
Item 6. The transparent resin laminate according to any one of Items 1 to 5, wherein printing is performed on a surface of the transparent resin layer and / or a surface of the polyester resin layer.
Item 7.
Item 7. The transparent resin laminate according to any one of Items 1 to 6, wherein the change in the radius of curvature before and after the 72-hour test is 15% or less in a high-temperature and high-humidity environment at 85 ° C. and 85% relative humidity.
Item 8.
An ultraviolet curable resin composition layer; and a transparent resin laminate formed into a curved surface having a polyester resin layer and a hard coat layer in order on both surfaces of the ultraviolet curable resin composition layer.
Item 9.
Item 9. A display cover comprising the transparent resin laminate according to any one of items 1 to 8.
Item 10.
Item 9. A mobile terminal comprising the transparent resin laminate according to any one of items 1 to 8.

  The transparent resin laminate of the present invention has a curved surface shape and is excellent in appearance, heat resistance and moisture resistance.

It is sectional drawing of the transparent resin laminated body shape | molded by the curved surface form of this invention. It is sectional drawing of the transparent resin laminated body shape | molded by the curved surface form of this invention. It is the schematic of an example of the equipment used for manufacture of a planar transparent resin laminated body. It is the schematic of an example of the equipment used for manufacture of a planar transparent resin laminated body. It is the schematic of an example of the mold material used at a process (1) thermoforming process. It is the schematic of an example of the state which does not apply stress.

  The transparent resin laminate of the present invention, the display cover including the transparent resin laminate, and the mobile terminal including the same will be described in detail below.

  In the present specification, (meth) acrylate means methacrylate or acrylate, and (meth) acrylic acid means methacrylic acid or acrylic acid.

Transparent resin laminate The transparent resin laminate of the present invention has a transparent resin layer; and an ultraviolet curable resin composition layer, a polyester resin layer, and a hard coat layer that are sequentially formed on both surfaces of the transparent resin layer, and It is formed into a curved surface.

  The transparent resin laminate of the present invention having the above configuration has excellent characteristics in appearance, heat resistance and moisture resistance.

  Specifically, the layer constitution of the transparent resin laminate of the present invention is as follows: hard coat layer / polyester resin layer / ultraviolet curable resin composition layer / transparent resin layer / ultraviolet curable resin composition layer / polyester resin layer / hard It becomes a coat layer. Other layers can be added to these layer structures as long as the effects of the present invention are achieved. An example of the transparent resin laminate of the present invention is shown in FIG.

  Another embodiment of the transparent resin laminate of the present invention has an ultraviolet curable resin composition layer; and a polyester resin layer and a hard coat layer formed in order on both surfaces of the ultraviolet curable resin composition layer, And it is shape | molded by the curved surface shape, It is characterized by the above-mentioned.

  Specifically, the layer configuration of the embodiment of the transparent resin laminate is hard coat layer / polyester resin layer / ultraviolet curable resin composition layer / polyester resin layer / hard coat layer.

  Other layers can be added to these layer structures as long as the effects of the present invention are achieved. An example of this aspect of the transparent resin laminate of the present invention is shown in FIG.

  Hereinafter, each structure of the transparent resin laminated body of this invention is demonstrated.

<Transparent resin layer>
The transparent resin layer is not particularly limited as long as the effects of the present invention can be obtained, and those having a certain degree of rigidity are desirable. As such a transparent resin layer, a biaxially stretched polyethylene terephthalate film and a polycarbonate film are preferable in terms of heat resistance, transparency, processing characteristics, market availability, and the like. And in order to obtain a thick laminated body, a polycarbonate is suitable.

  The method for producing the polyethylene terephthalate film is not particularly limited, and any one produced by either a direct esterification method or a melt polycondensation method can be used. There is no particular limitation on the molecular weight. The polyethylene terephthalate film may contain other resins as long as the effects of the present invention are obtained.

  As the polycarbonate film, a polymer derived from a divalent phenolic compound typified by bisphenol A can be used. The method for producing the polycarbonate film is not particularly limited, and any one produced by any of the phosgene method, the transesterification method, and the solid phase polymerization method can be used. There is no particular limitation on the molecular weight. The polycarbonate film may contain other resins as long as the effects of the present invention are obtained.

  The thickness of the transparent resin layer is preferably 100 μm or more, more preferably 250 to 1500 μm. Further, the total light transmittance (JIS K7105) measured in the form of a sheet having a thickness of 2 mm of the transparent resin layer is preferably 87% or more, more preferably 89 to 95%.

  The transparent resin layer may contain various additives such as a general heat stabilizer, ultraviolet absorber, light resistance stabilizer, colorant, mold release agent, lubricant, and antistatic agent.

<Ultraviolet curable resin composition layer>
The ultraviolet curable resin composition layer of the present invention is formed on both surfaces of the transparent resin layer. Moreover, as another aspect, a polyester resin layer is formed on both surfaces of the ultraviolet curable resin composition layer of the present invention.

  The ultraviolet curable resin composition layer used in the present invention is not particularly limited. Examples thereof include those containing a photopolymerizable prepolymer and / or a photopolymerizable monomer and, if desired, a photopolymerization initiator.

  The photopolymerizable prepolymer includes a radical polymerization type and a cationic polymerization type. Examples of the radical polymerization type photopolymerizable prepolymer include polyester acrylate, epoxy acrylate, urethane acrylate, and polyol acrylate. Can be mentioned. Here, the polyester acrylate-based prepolymer is obtained by, for example, esterifying hydroxyl groups of a polyester oligomer having hydroxyl groups at both ends obtained by condensation of a polyvalent carboxylic acid and a polyhydric alcohol with (meth) acrylic acid, or It can be obtained by esterifying the terminal hydroxyl group of an oligomer obtained by adding an alkylene oxide to a polyvalent carboxylic acid with (meth) acrylic acid. The epoxy acrylate-based prepolymer can be obtained, for example, by reacting (meth) acrylic acid with an oxirane ring of a relatively low molecular weight bisphenol type epoxy resin or novolak type epoxy resin and esterifying it. The urethane acrylate-based prepolymer can be obtained, for example, by esterifying a polyurethane oligomer obtained by reaction of polyether polyol or polyester polyol and polyisocyanate with (meth) acrylic acid. Furthermore, the polyol acrylate-based prepolymer can be obtained by esterifying the hydroxyl group of the polyether polyol with (meth) acrylic acid. These photopolymerizable prepolymers may be used alone or in combination of two or more. On the other hand, as a cationic polymerization type photopolymerizable prepolymer, an epoxy resin or an oxetane resin is usually used. Examples of the epoxy resin include compounds obtained by oxidizing a compound obtained by epoxidizing polyhydric phenols such as bisphenol and novolac resin with epichlorohydrin, a linear olefin compound, and a cyclic olefin compound with a peroxide or the like. Etc.

  Examples of the photopolymerizable monomer include 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and polyethylene glycol di (meth). Acrylate, neopentyl glycol adipate di (meth) acrylate, hydroxypivalic acid neopentyl glycol di (meth) acrylate, dicyclopentanyl di (meth) acrylate, caprolactone modified dicyclopentenyl di (meth) acrylate, ethylene oxide modified diphosphate (Meth) acrylate, allylated cyclohexyl di (meth) acrylate, isocyanurate di (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid modified dipenta Thritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide modified trimethylolpropane tri (meth) acrylate, tris (acryloxyethyl) isocyanurate, propionic acid modified dipentaerythritol penta (meth) acrylate, dipentaerythritol Examples thereof include polyfunctional acrylates such as hexa (meth) acrylate and caprolactone-modified dipentaerythritol hexa (meth) acrylate. These photopolymerizable monomers may be used singly or in combination of two or more, or may be used in combination with the photopolymerizable prepolymer.

  As the photopolymerization initiator of these ultraviolet curable resin compositions, for the radical polymerization type photopolymerizable prepolymer or photopolymerizable monomer, for example, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, Benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropane -1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one, 4- (2-hydroxyethoxy) phenyl- 2 (Hydroxy-2-propyl) keto Benzophenone, p-phenylbenzophenone, 4,4'-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tertiarybutylanthraquinone, 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 the photopolymerization initiator for the cationic polymerization type photopolymerizable prepolymer include oniums such as aromatic sulfonium ions, aromatic oxosulfonium ions, aromatic iodonium ions, tetrafluoroborate, hexafluorophosphate, hexa Examples thereof include compounds comprising anions such as fluoroantimonate and hexafluoroarsenate. These may be used alone or in combination of two or more, and the blending amount is usually 0.2 with respect to 100 parts by weight of the photopolymerizable prepolymer and / or photopolymerizable monomer. It is selected in the range of ˜10 parts by weight.

  In addition, the ultraviolet curable resin composition layer includes various fillers such as silica, alumina, hydrated alumina, antioxidants, ultraviolet absorbers, light stabilizers, antistatic agents, leveling agents, antifoaming agents, coloring pigments, etc. May be added.

  The thickness of the ultraviolet curable resin composition layer is preferably 5 to 300 μm, more preferably 10 to 70 μm. Here, the thickness of the ultraviolet curable resin composition layer means the thickness of one layer.

<Polyester resin layer>
The polyester resin layer of the present invention is laminated on both sides of the transparent resin layer via an ultraviolet curable resin composition layer. In another embodiment, the polyester resin layer of the present invention is formed between the ultraviolet curable resin composition layer and the hard coat layer.

  The polyester resin layer is not particularly limited as long as the effects of the present invention can be obtained. Examples thereof include a polyethylene terephthalate film and polyethylene naphthalate. For uses such as a front plate of an optical display, a touch panel, etc., it is preferable to use a polyethylene terephthalate film in terms of transparency, processing characteristics, market availability, and the like. Moreover, as a polyester resin film, what was biaxially stretched is preferable and a biaxially stretched polyethylene terephthalate film is especially preferable.

  The method for producing the polyethylene terephthalate film is not particularly limited, and any one produced by either a direct esterification method or a melt polycondensation method can be used. There is no particular limitation on the molecular weight. The polyethylene terephthalate film may contain other resins as long as the effects of the present invention are obtained.

  The thickness of the polyester resin layer is preferably 50 μm or more, more preferably 100 to 250 μm. Here, the thickness of the polyester resin layer means the thickness of one film.

  The polyester resin layer may contain various additives such as a general heat stabilizer, ultraviolet absorber, light resistance stabilizer, colorant, mold release agent, lubricant, and antistatic agent.

<Hard coat layer>
The hard coat layer of the present invention is formed on the surface of the polyester resin layer opposite to the surface in contact with the ultraviolet curable resin composition layer.

  The purpose of the hard coat in the present invention is not only to improve the scratch resistance of the surface, which is the purpose of general hard coat, but also to prevent dust adhesion due to static electricity, reduce fingerprint adhesion or improve fingerprint wiping, and surface reflection. In general, the surface is modified by a hard coat, such as an antiglare improvement to relieve heat.

  In general, an inorganic hard coat layer, an organic hard coat layer, an organic inorganic hard coat layer, a silicone hard coat layer, or the like can be used as the hard coat layer in the present invention.

The inorganic hard coat layer is composed of, for example, SiO ₂ , Al ₂ O ₃ , TiO ₂ , ZrO ₂ or the like, and the layer is formed by vacuum deposition, sputtering or the like on a polyethylene terephthalate film.

  Examples of the organic hard coat layer include a type in which a melamine type, alkyd type, urethane type and acrylic resin paint is heat-cured, a type in which a polyfunctional acrylic resin paint is UV-cured, and the like.

  Examples of the organic / inorganic hard coat layer include those in which a photopolymerization reactive functional group is introduced on the surface of silica ultrafine particles and uniformly dispersed in the organic component of the ultraviolet curable hard coat material. Ultraviolet curable hard coat components and photosensitive groups of inorganic ultrafine particles undergo a polymerization reaction, resulting in the formation of a network-like crosslinked coating film in which ultrafine silica particles mediated by chemical bonds are uniformly dispersed in an organic matrix, etc. Is mentioned.

  Examples of the silicone hard coat layer include polycondensation of partial hydrolysates such as carbon functional alkoxysilane, alkyltrialkoxysilane, and tetraalkoxysilane, and those containing colloidal silica.

  In addition, various fillers such as silica, alumina and hydrated alumina, antioxidants, ultraviolet absorbers, light stabilizers, antistatic agents, leveling agents, antifoaming agents, coloring pigments, etc. are added to the hard coat layer. Also good.

  Furthermore, it is possible to have an antireflection film on these hard coat films. As a method for obtaining a low refractive index layer by wet coating, there are a method using a material containing fluorine having a refractive index lower than that of a hard coat film, a method using a material containing metal fine particles having a low refractive index, and the like. This anti-reflection film is possible even if it is not on the hard coat film, but when a low refractive index layer is obtained on the polyester resin layer, it tends to be accompanied by a decrease in scratch resistance, so that the low refractive index on the hard coat film is low. It is desirable to have a rate layer.

  As a hard coat layer for imparting anti-glare properties, a method that suppresses reflection by scattering light mainly by fine irregularities on the surface, a single layer of a transparent inorganic coating layer or an organic coating layer Examples of the method of forming the surface as described above include a method of suppressing reflection using light interference.

  As a method of forming fine irregularities on the surface, a method of making fine irregularities on the surface by using an organic hard coat agent and inorganic fine particles in combination, and utilizing the difference in solubility between two or more types of organic hard coat agents. Examples thereof include a method of finely forming irregularities by phase separation, and a method of transferring, etc., by copying an irregular surface of a mold having fine irregularities on the surface with a hard coat agent.

  Antiglare treatment with irregularities on the surface is roughly divided into non-glare or matte, and the former is mainly used for the entire surface of transparent liquid crystal display, etc., with Haze value (haze value) of 1% to 30% say. The latter is often used for building materials and the like and has a Haze value of around 20% to 80%.

  Anti-glare treatment with a thin film includes a method of forming a thin film by vacuum deposition, sputtering, etc. using an inorganic coating, a method of forming a thin film having a lower refractive index than a hard coat film on a hard coat layer by wet coating, etc. There is.

  In the present invention, by using a scratch-resistant organic hard coat film of a type that is cured by irradiating with ultraviolet rays, stable production is possible under high productivity.

  A type of scratch-resistant organic hard coat film that cures when irradiated with ultraviolet rays. Organic films containing monomers, oligomers, photopolymerization initiators, photosensitizers, leveling agents, antistatic agents, antifogging agents, ultraviolet absorbers, etc. It is obtained by coating a substrate with a solvent solution, drying, and curing by irradiation with ultraviolet rays. Depending on the type of resin constituting the monomer or oligomer, there are a cationic polymerization system using an epoxy resin or an oxetane resin, and a radical polymerization system using an unsaturated polyester or (meth) acrylate. Among radical polymerization systems, a (meth) acrylate system having many varieties for controlling hardness, curing rate, adhesion, flexibility, and the like is preferable.

  Monomers used in (meth) acrylate-based hard coating agents include monofunctional (meth) acrylates such as alkyl (meth) acrylate and cyclohexyl (meth) acrylate, neopentyl (meth) acrylate, polytetramethylene glycol di (meth) ) Bifunctional (meth) acrylates such as acrylate and trifunctional or higher functional (meth) acrylates such as pentaerythritol tetra (meth) acrylate can be used in appropriate combination. Moreover, urethane acrylate, epoxy acrylate polyester acrylate, etc. can be mix | blended as an oligomer used for a (meth) acrylate type hard coat agent.

  Examples of the photopolymerization initiator include benzoin ethyl ether, diethoxyacetophenone, benzyl dimethyl ketal, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, and the like. it can.

  The thickness of the hard coat layer is preferably about 2 to 50 μm, particularly about 3 to 30 μm, whereby both hardness and durability can be satisfied. Here, the thickness of the hard coat layer means a thickness of one layer.

  The transparent resin laminate of the present invention is used as a front plate of electronic equipment (liquid crystal display, organic EL display, touch panel, etc.) for optical applications.

  The thickness of the transparent resin laminate of the present invention is appropriately determined according to its use, but the total thickness is usually 0.4 to 1.5 mm, preferably 0.5 to 1.0 mm.

<Printed layer>
The transparent resin laminate of the present invention may be preliminarily printed on the surface of the transparent resin layer and / or the surface of the polyester resin layer. This eliminates the need to print the laminated body formed into a curved surface later, and also allows the design of the display cover to be smooth because both surfaces of the formed display cover become smooth. Thus, since the surface is smooth, it becomes easy to further form a transparent conductive film on the surface of the transparent resin laminate, which is suitable as a surface material for a touch panel.

  The front surface may be either the front or back surface of the transparent resin layer, or may be the front or back polyester resin layer as long as the surface is laminated with the transparent resin layer.

  There is no restriction | limiting in particular as a method of printing on the surface of a transparent resin layer and / or the surface of a polyester resin layer, For example, well-known printing methods, such as gravure printing, flexographic printing, offset printing, screen printing, inkjet printing, are mentioned. Can be mentioned. Among these, gravure printing or screen printing is preferable in terms of printability on the surface of the transparent resin layer and / or the surface of the polyester resin layer, and printing accuracy.

Display cover The transparent resin laminate of the present invention is formed into a curved shape as a film, sheet, or plate, and the transparent resin laminate is excellent in high transparency, high surface hardness and rigidity, and has an appearance and heat resistance. And excellent in moisture resistance. Therefore, although the use of the transparent resin laminate of the present invention is not particularly limited, it can be used particularly for liquid crystal display covers (liquid crystal protective sheets and liquid crystal protective films) such as mobile phones and tablet terminals.

  In addition to display covers, for example, transparent sheets for building materials, interior parts, etc., sheets for molding (vacuum / pressure air molding, hot press molding, etc.), colored plates, transparent plates, automotive interior materials, home appliance products, OA equipment members, etc. Can be used for

Mobile terminal As a mobile terminal in the present invention, a mobile terminal such as a mobile phone, a smart phone, a portable game machine, a tablet-type mobile display, a notebook computer; a part worn on a body part such as an arm, glasses, clothing, etc. A wearable portable terminal that is worn and used.

Method for Producing Transparent Resin Laminate Molded in Curved Surface The method for producing a transparent resin laminate of the present invention comprises a step (A): a step of obtaining a planar transparent resin laminate, and a step (B): the step ( A step of forming the planar transparent resin laminate obtained in A) into a curved shape is included.

Step (A): Step of obtaining a planar transparent resin laminate A planar transparent resin laminate can be produced according to the method described in JP 2012-183822 A. Specifically, the following Embodiments 1 and 2 can be exemplified.

Embodiment 1 of the method for producing a planar transparent resin laminate includes the following steps (A1-1) to (A1-3):
Step (A1-1): a step of applying an ultraviolet curable resin composition on both sides of the transparent resin film,
Step (A1-2): The surface of the polyester resin film having a hard coat layer on one side without the hard coat layer is the surface of the ultraviolet curable resin composition of the transparent resin film obtained in step (A1-1). And the step (A1-3): a step of drying and curing the ultraviolet curable resin composition in the laminate obtained in the step (A1-2) by irradiating with ultraviolet rays.

<Process (A1-1)>
Examples of the method for applying the ultraviolet curable resin composition on the transparent resin film include the following. For example, there is a roll coating method in which coating is performed by supplying paint to two metal or rubber rolls and passing a plate through the gap between the rolls. This is suitable for coating a plate or film. There is a spin coating method in which a coating material is dropped on the center of the product to be painted and rotated to spread the coating material on the surface of the product. This is suitable for the case where a shape close to a circle is coated with a uniform film thickness. There is a spray coating method in which the paint is sprayed on the surface of the coated product. This is suitable for painting a molded article having a three-dimensional shape. There is a dip coating method in which an article to be coated is dipped in a paint liquid and gently pulled up. Thereby, the front and back, such as plate shape, a curved surface, and a three-dimensional shape, can be painted at a time. There is a flow coat method in which a paint is cast on a product to be painted. This can be applied to both sides such as a plate shape and a curved surface, or one side.

<Process (A1-2)>
As a method of laminating the surface of the polyester resin film having a hard coat layer on one side without the hard coat layer on the surface of the ultraviolet curable resin composition of the transparent resin film obtained in the step (A1-1), For example, a roll-type laminating process in which a film is pressed and processed by passing a plate through a gap between two metal or rubber rolls can be mentioned.

  Examples of the method for laminating the hard coat layer on the polyester resin film include the methods described in the item of the above step (A1-1).

<Process (A1-3)>
The ultraviolet curable resin composition in the laminate obtained in the step (A1-2) can be dried, for example, by placing it in an atmosphere at 50 to 80 ° C. for 1 to 10 minutes.

Examples of the ultraviolet rays irradiated to the ultraviolet curable resin composition after drying include those using a high pressure mercury lamp, a low pressure mercury lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a black light, a metal halide lamp, etc. as a light source. The cumulative amount of ultraviolet light to be irradiated may be an amount that can cure the ultraviolet curable resin composition, and is usually 300 to 1500 mJ / cm ² .

Embodiment 2 of the method for producing a planar transparent resin laminate includes the following steps (A2-1) to (A2-3):
(A2-1): a step of applying an ultraviolet curable resin composition to a surface of a polyester resin film having a hard coat layer on one side and not having a hard coat layer;
(A2-2): The surface of the polyester resin film having a hard coat layer on one side without the hard coat layer is placed on the surface of the UV curable resin composition of the polyester resin film obtained in the step (A2-1). Step of laminating and (A2-3): A step of drying and curing the ultraviolet curable resin composition in the laminate obtained in step (A2-2) by irradiating with ultraviolet rays.

  The operation of each process is basically the same as described above.

  Next, Embodiment 1 of the manufacturing method of the transparent resin laminated body of this invention is demonstrated based on FIG.

  First, the ultraviolet curable resin composition is applied to both surfaces of the transparent resin film 100 using the roll coater 200. Next, after the PET film 300 is laminated on both surfaces of the applied ultraviolet curable resin composition, the ultraviolet curable resin composition is cured by irradiating ultraviolet rays from both surfaces with an ultraviolet lamp 400. Finally, the protective film 500 is laminated on the manufactured transparent resin laminate, and the cutting unit 600 cuts and removes the end of the laminate.

  Based on FIG. 4, Embodiment 2 of the manufacturing method of the transparent resin laminated body of this invention is demonstrated. First, the ultraviolet curable resin composition is applied to one side of the PET film 700 using a roll coater 800. Next, after laminating the PET film 900 on the applied ultraviolet curable resin composition, the ultraviolet curable resin composition is cured by irradiating ultraviolet rays from both sides with an ultraviolet lamp 1000. Finally, the protective film 1100 is laminated on the manufactured transparent resin laminate, and the cutting device 1200 cuts and removes the end of the laminate.

Step (B): The step (B) for obtaining a transparent resin laminate molded into a curved surface includes the following steps (1) and (2).

Step (1): Thermoforming step In the thermoforming step (1) of the present invention, the glass transition temperature of the transparent resin layer is T1, the glass transition temperature of the polyester resin layer is T2, and the crystal melting point of the polyester resin layer is T3. In some cases, the heat forming is performed at a temperature (MT) higher than T1 and T2 and lower than T3. Thereby, the molded laminated body of a favorable external appearance can be obtained.

  The specific material of each layer will be exemplified to explain the heating temperature in the thermoforming process in more detail.

  When a polycarbonate film is used as the transparent resin layer and a biaxially stretched polyethylene terephthalate film is used as the polyester resin layer, T1 is about 150 ° C, T2 is about 80 ° C, and T3 is about 240 ° C. Examples of the thermoforming temperature (MT) in (1) include temperatures higher than 150 ° C and lower than 240 ° C. By performing heat molding at such a heating temperature, a good molded laminate can be obtained.

  In particular, in order to maintain the appearance during molding and improve moldability, the heat molding temperature (MT) is preferably in the range of 160 ° C to 200 ° C, more preferably in the range of 170 ° C to 190 ° C. It is.

As described above, as the thermoforming temperature (MT) in the step (1), the following formula:
T1 or T2 <MT <T3
It can be expressed by the relationship.

  There is no restriction | limiting in particular in the heating time in a thermoforming process (1), For example, they are 2 minutes-60 minutes, Preferably they are 3 minutes-30 minutes, More preferably, they are 5 minutes-20 minutes.

  The method of forming the curved transparent surface is not particularly limited as long as the flat transparent resin laminate can be formed into a curved shape, for example, a pair of mold materials as shown in FIG. There is a step of heating the laminate in a state where the laminate is pressed with the mold material and the laminate is curved with a predetermined radius of curvature.

  The mold material is not particularly limited, and examples thereof include a wooden mold using wood, a resin mold using synthetic resin, and a mold using a metal such as aluminum and iron. FIG. 5 illustrates a mold in which an iron plate is bent to a curvature of 92 mm, and a nell cloth having a thickness of about 0.5 mm is attached to the surface in contact with the laminate with an adhesive film.

  The pressing force only needs to be a force that can achieve a predetermined radius of curvature. For example, the pressing force applied to the upper mold illustrated in FIG. 5 is 12 kg.

  A step of cooling the laminate obtained by the heat treatment forming step (1) may be included after the heat forming step (1) and before the heat treatment step (2) described later.

Step (2): Heat treatment step In the heat treatment step (2) in the present invention, the heat-molded laminate obtained by the above step (1) is higher than the glass transition temperature of T1 or T2, whichever is lower, and This is a step (also referred to as an annealing step) in which heat treatment is performed at a temperature (AT) lower than the heat molding temperature (MT) in step (1).

  In the heat treatment step, it is preferable to heat-treat the molded laminated body heat-molded in the step (1) while maintaining the state without applying stress.

  In this specification, “holding without applying stress” means, for example, that the laminate is erected so that the curved end piece of the curved laminate becomes the lower end as shown in FIG. (To stand up).

  The heat treatment temperature in the present invention will be described in more detail by exemplifying specific materials of each layer.

  When a polycarbonate film is used as the transparent resin layer and a biaxially stretched polyethylene terephthalate resin is used as the polyester resin layer, T1 is about 150 ° C., T2 is about 80 ° C., and the thermoforming temperature (MT) is 190. Assuming that it is ° C., the heat treatment temperature (AT) includes a temperature higher than 80 ° C. and lower than 190 ° C. By performing the heat treatment at such a heating temperature, a molded laminate excellent in appearance, heat resistance and moisture resistance can be obtained.

  Furthermore, in order to increase the shape stability of the molded product, the heat treatment temperature (AT) is preferably in the range of 100 ° C to 170 ° C, more preferably in the range of 120 ° C to 150 ° C.

As described above, as the heat treatment temperature (AT) in the step (2), the following formula:
T1 or T2 <AT <MT
It can be expressed by the relationship.

  The heating time in the heat treatment step is not particularly limited, and is, for example, 10 minutes to 2 hours, preferably 15 minutes to 1.5 hours, and more preferably 20 minutes to 1 hour.

  After the heat treatment step (2), a step of cooling the laminate obtained by the heat treatment step may be included.

  In the method for producing a curved transparent resin laminate of the present invention, the dimensional stability of a curved molded product is put into practical use by including the two steps of the heat molding step (1) and the heat treatment step (2). Can be raised to a possible level.

  In general, in thermoforming a thermoplastic sheet or film, it is important to select an appropriate heating temperature. Usually, a thermoplastic sheet or film is molded after being heated to a temperature equal to or higher than its glass transition temperature. Therefore, when obtaining a curved molded body, the radius of curvature is generally substantially the same as the radius of curvature of the molded product after molding. Further, at the time of molding, as described above, it is common to heat above the glass transition temperature, but there is a method of molding at a heating temperature below the glass transition temperature, for example, an ultra-high pressure molding method, Even in this case, the curvature of the molded product is almost the same as the curvature during molding, and the process of heating the molded product after molding (annealing process) has no significant change in the curvature before and after the process. Is common.

In contrast, the manufacturing method of the present invention has the following characteristics. Specifically, the radius of curvature of the laminate set by the pair of molds in the thermoforming step (1) is R1, and after the thermoforming step (1), the laminate is removed from the mold, and then the cooling step is performed. When the radius of curvature of the laminate is R2, and the radius of curvature of the laminate after the heat treatment step (2) is R3, the relationship between R1, R2 and R3 is as follows:
R1 <R2 <R3
The relationship represented by is satisfied.

  Accordingly, a transparent resin laminate having a predetermined radius of curvature can be produced by variously changing the heating temperature and the heating time in the thermoforming step (1) and the heat treatment step (2). For example, the ratio of the radius of curvature (R2) of the laminate obtained in the step (1) and the radius of curvature (R3) of the laminate obtained in the step (2) is not particularly limited. The range can be: 1.1 to 1: 6.0. Among them, the range of 1: 1.1 to 1: 4.0 is preferable, and the range of 1: 1.1 to 1: 2.0 is more preferable.

  Examples are given below to illustrate the present invention in more detail. However, the present invention is not limited to these examples.

[Process (A)]
Production Example 1
As a paint used for the outermost hard coat layers 1, 7, 8, and 12, urethane acrylate oligomer, UV-7640B (100% solid content by Nippon Synthetic Industry Co., Ltd.) 100 parts by mass, hydroxyalkylphenone as a polymerization initiator 3 parts by weight of a photopolymerization initiator (trade name Irgacure-184, manufactured by Ciba-Geigy Co., Ltd.) and adding methyl ethyl ketone and propylene glycol monomethyl ether as a diluent solvent, and stirring and mixing uniformly, a resin composition A having a solid content of 30% Obtained.

Production Example 2
As an acrylate oligomer used for the UV curable resin composition layers 3, 5, and 10 as the intermediate layer, 75 parts by mass of UN-901T (manufactured by Negami Kogyo Co., Ltd., 80% solids), UN-333 (manufactured by Negami Kogyo Co., Ltd.) 10 parts by mass of solid content (100% solids) and 15 parts by mass of A-200 (100% solids by Shin-Nakamura Chemical Co., Ltd.), hydroxyalkylphenone photopolymerization initiator (product name: Ciba Geigy) -184) was added in an amount of 3 parts by mass, and the mixture was uniformly stirred and mixed to obtain a resin composition B having a solid content of 84.2%.

Production Example 3
The above resin composition A is applied to one side of a polyethylene terephthalate film (product name: A4300, manufactured by Toyobo Co., Ltd.) having a thickness of 188 μm which is a polyester resin layer 2, 6, 9, 11 with a roll coater so as to have a film thickness of 4 μm. Then, after heating and ultraviolet irradiation, a PET film having a hard coating on one side was obtained (hereinafter, the obtained film may be referred to as “single-side coated PET film”).

Production Example 4
The resin composition B was coated on both surfaces of a 650 μm-thick polycarbonate film (Panlite film 2151 manufactured by Teijin Chemicals Limited), which is the transparent resin layer 4, so that the thickness after drying with a roll coater was 15 μm. Next, the uncoated surface of the two single-side coated PET films obtained in Production Example 3 and the resin composition B were bonded to each other, heated in a drying furnace at 80 ° C. for 2 minutes, and then using a high-pressure mercury lamp. The resin composition B was cured by irradiating ultraviolet rays so that the integrated light amount was 1000 mJ / cm ^2, and a laminate having a total thickness of about 1 mm was obtained.

[Process (B)]
Example 1
(1) The laminate obtained in Production Example 4 was heat-molded at 150 ° C. for 15 minutes with a pair of molds shown in FIG. Then, it cooled at room temperature for 0.5 hour, and removed this laminated body from the said instrument. Thereafter, the laminate was held for 1 hour in a state of standing as shown in FIG. 6 (a state where no stress was applied).

  (2) The obtained molded laminate was held in a state where no stress was applied as shown in FIG. 6, and was heat-treated (annealed) at 120 ° C. for 30 minutes. Then, the transparent resin laminate 1 of the present invention was obtained by holding the laminate at room temperature for 1 hour without applying stress.

Example 2
A transparent resin laminate 2 of the present invention was obtained in the same manner as in Example 1 except that the temperature in the thermoforming step (1) was changed to 160 ° C.

Example 3
A transparent resin laminate 3 of the present invention was obtained in the same manner as in Example 1 except that the temperature in the thermoforming step (1) was changed to 180 ° C.

Example 4
A transparent resin laminate 4 of the present invention was obtained in the same manner as in Example 1 except that the temperature in the thermoforming step (1) was changed to 190 ° C.

Example 5
A transparent resin laminate 5 of the present invention was obtained in the same manner as in Example 1 except that the temperature in the thermoforming step (1) was changed to 200 ° C.

Comparative Example 1
A comparative laminate 1 was obtained in the same manner as in Example 1 except that the temperature in the thermoforming step (1) was changed to 90 ° C.

Comparative Example 2
A comparative laminate 2 was obtained in the same manner as in Example 1 except that the temperature in the thermoforming step (1) was changed to 120 ° C.

Comparative Example 3
A comparative laminate 3 was obtained in the same manner as in Example 1 except that the temperature in the thermoforming step (1) was changed to 140 ° C.

Comparative Example 4
A comparative laminate 4 was obtained in the same manner as in the thermoforming step (1) of Example 1 except that the temperature in the thermoforming step (1) was changed to 220 ° C. The next step (2) was not performed.

Comparative Example 5
A comparative laminate 5 was obtained in the same manner as in the heat forming step (1) of Example 1 except that the temperature in the heat forming step (1) was changed to 250 ° C. The next step (2) was not performed.

Comparative Example 6
A comparative laminate 6 was obtained in the same manner as in Comparative Example 2 except that the temperature of the heat treatment step (2) was changed to 60 ° C.

Example 6
A transparent resin laminate 6 of the present invention was obtained in the same manner as in Example 4 except that the temperature of the heat treatment step (2) was changed to 100 ° C.

Example 7
A transparent resin laminate 7 of the present invention was obtained in the same manner as in Example 4 except that the temperature in the heat treatment step (2) was changed to 170 ° C.

Comparative Example 7
A comparative laminate 7 was obtained in the same manner as in Example 4 except that the heat treatment step (2) was not performed.

Comparative Example 8
A comparative laminate 8 was obtained in the same manner as in Example 4 except that the temperature of the heat treatment step (2) was changed to 200 ° C.

  The following tests were conducted on the laminates obtained in Examples 1 to 7 and Comparative Examples 1 to 8. The results are shown in Tables 1 and 2.

[Test method]
<Appearance>
The appearance was visually inspected for the presence of defects such as surface irregularities such as irregularities, distortion of the fluoroscopic image, and coloring.
○ = No change in appearance × = Defect on appearance

<Change in radius of curvature before and after exposure test (heat resistance and humidity resistance test)>
The resin laminate molded into a curved surface is exposed for 24 hours in a high-temperature and high-humidity environment at 85 ° C and 85% relative humidity, and then the radius of curvature of the molded laminate is measured and compared with the radius of curvature before the exposure test. Then, the heat resistance and moisture resistance tests were evaluated based on the following calculation formula.

Formula: Change in curvature radius before and after exposure test (%) = [(curvature radius after exposure test−curvature radius before exposure test) × 100] −100
○ = Pass (curvature change is 15% or less)
× = Fail (curvature change exceeds 15%)

[Evaluation results]
The transparent resin laminate molded into a curved shape according to the present invention has a good appearance, has very little shape change in actual use, and is excellent in heat resistance and moisture resistance. Therefore, the transparent resin laminate molded into a curved shape according to the present invention is a material suitable for a curved display cover and a mobile terminal including the curved display cover. On the other hand, the laminate of the comparative example is difficult to use for a curved display cover because it does not have a desired shape, has a defect in appearance, and has a large shape change in actual use.

DESCRIPTION OF SYMBOLS 1 Hard coat layer 2 Polyester resin layer 3 UV curable resin composition layer 4 Transparent resin layer 5 UV curable resin composition layer 6 Polyester resin layer 7 Hard coat layer 8 Hard coat layer 9 Polyester resin layer 10 UV curable resin composition Physical layer 11 Polyester resin layer 12 Hard coat layer 13 Upper mold 14 Laminate 15 Lower mold 100 Transparent resin film 200 Roll coater 300 Polyester resin film 400 UV lamp 500 Protective film 600 Cutting device 700 Polyester resin film 800 Roll coater 900 Polyester Resin film 1000 UV lamp 1100 Protective film 1200 Cutting device

Claims (8)

A transparent resin layer; and a transparent resin laminate formed into a curved shape having an ultraviolet curable resin composition layer, a polyester resin layer and a hard coat layer formed in order on both surfaces of the transparent resin layer ,
Obtained by the following steps (1) and (2),
Step (1): Heating at a temperature (MT) higher than the glass transition temperature (T1) of the transparent resin layer and the glass transition temperature (T2) of the polyester resin layer and lower than the crystalline melting point (T3) of the polyester resin layer. Forming step (heat forming step), and
Step (2): a heat treatment step (heat treatment step) at a temperature (AT) that is higher than the lower glass transition temperature of T1 or T2 and lower than the thermoforming temperature (MT) of step (1) (AT),
Transparent resin laminate . The transparent resin laminate according to claim 1, wherein the transparent resin layer is a polycarbonate film. The transparent resin laminate according to claim 1 or 2, wherein the polyester resin layer is a biaxially stretched polyethylene terephthalate film. The transparent resin laminate according to any one of claims 1 to 3 ,
The ratio of the radius of curvature (R2) of the laminate obtained in the step (1) and the radius of curvature (R3) of the laminate obtained in the step (2) is 1: 1.1 to 1: 6.0 Resin laminate. The transparent resin laminate according to any one of claims 1 to 4 , wherein printing is performed on a surface of the transparent resin layer and / or a surface of the polyester resin layer. The transparent resin laminate according to any one of claims 1 to 5 , wherein a change in the radius of curvature before and after the 24 hour exposure test is 15% or less in a high-temperature and high-humidity environment at 85 ° C and a relative humidity of 85%. The display cover provided with the transparent resin laminated body as described in any one of Claims 1-6 . The mobile terminal provided with the transparent resin laminated body as described in any one of Claims 1-6 .

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