JP5528757B2 - Decorative sheet for molding having flow-resistant pattern layer and method for decorating injection molded body - Google Patents

Description

  The present invention relates to a decorative sheet for molding suitable for decorating the surface of an in-mold injection-molded product, and particularly relates to a decorative sheet for molding whose pattern layer is excellent in fluid resistance.

  A method of decorating or protecting the surface of an injection molded body such as a plastic part or an exterior product using a decorative sheet has been conventionally known. For example, in Patent Document 1, a decorative sheet for molding in which a decorative layer is provided on one side of a base sheet as a support, and the decorative sheet for molding are inserted into an injection mold, and in-mold injection is performed. It is described that a molded injection molded body is obtained by molding (simultaneous injection molding decoration).

  The decorative layer is generally a laminate in which a pattern, a colorant, an adhesive, and the like are laminated in layers. After being attached to the surface of the article, the decorative layer forms a coating having a decorative function and a protective function. Layers such as a pattern and a colorant are formed by sequentially printing or coating a printing ink such as gravure ink or a coating on a base sheet.

  In general, gravure inks, flexo inks, screen inks, paints, and the like include one-part thermoplastics and two-part thermosets. For example, a one-part thermoplastic ink contains a thermoplastic resin such as an acrylic resin as a binder resin. On the other hand, a two-component thermosetting ink contains a thermosetting resin such as polyol and polyisocyanate as a binder resin.

  When the pattern layer or colored layer of the decorative sheet for molding is formed using the one-component thermoplastic ink, the thermoplastic resin as the binder resin is softened by the heat of the injection resin and flows by the pressure of the injection resin. The appearance defect of the pattern tends to occur. In particular, the appearance of a glittering pigment made of a thin metal thin film remarkably changes when the orientation of the pigment changes even slightly. Therefore, in the colored layer and the pattern layer to which the metallic appearance is given by the glitter pigment, the appearance defect of the pattern due to the heat and pressure of the injection resin is particularly noticeable. The appearance defect of the pattern generated by the flow of ink by the heat and pressure of the injection resin is particularly called “ink flow”.

  On the other hand, when a two-component thermosetting ink is used, a three-dimensional network structure is formed in the binder resin, so that the stretchability of the pattern layer is lowered, and cracks are likely to occur in the curved surface portion of the injection molded body. In addition, when the three-dimensional shape of the injection molded body is complicated or deep, the pattern layer becomes difficult to follow the three-dimensional shape.

JP 2006-264321 A

  This invention solves the said conventional problem, The place made into the objective is to improve fluid resistance, maintaining a drawability about the pattern layer of the decorative sheet for shaping | molding.

The present invention is a decorative sheet for molding in which a decorative layer is formed on the main surface of the base sheet,
The decorative layer has a pattern layer containing a pigment and a binder resin,
The binder resin is a compatible mixture of polyethyl methacrylate and cellulose acetate propionate ;
Provided is a decorative sheet for molding, in which the pigment comprises a thin metal film strip.

In one certain form, mass ratio of the said poly (meth) acrylic acid ester and a cellulose derivative is 2/1 on the basis of solid content.

The present invention also includes a step of feeding one of the above-described decorative sheets for molding into the molding die in such a direction that the base sheet is in contact with the inner surface of the mold;
Closing the mold and filling the mold with molten resin so that the molten resin contacts the surface of the decorative sheet on the adhesive layer side (opposite side of the base sheet); and cooling the resin and opening the mold Taking out the injection molded body;
A method of decorating the surface of an injection molded body including

  In the present specification, the “main surface” refers to a surface having the largest area. In the sheet and film, both the front surface and the back surface correspond to the main surface. In the present specification, the term “picture layer” includes a colored layer having no pattern.

  The decorative sheet of the present invention does not generate ink flow in the pattern layer when injection molding is performed simultaneously, and the pattern layer is sufficiently solid even when applied to a complicated or deep three-dimensional shape. Following this, no cracks occur on the curved surface.

It is sectional drawing which shows the structure of the decorating sheet which is one Embodiment of this invention. It is a photograph which shows the state which expanded the binder resin obtained in Example 1 40000 times with the electron microscope. It is a photograph which shows the state which expanded the binder resin obtained by the comparative example 1 40000 times with the electron microscope.

Decorating Sheet FIG. 1 is a cross-sectional view showing the structure of a decorating sheet that is one embodiment of the present invention. A decorative layer 2 is provided in contact with one surface of the base sheet 1. The decorative layer 2 includes a pattern layer 3 and an adhesive layer 4 that are sequentially stacked from the base sheet side.

  Of the layers constituting the decorative layer, each resin layer can be formed by the same method as before unless otherwise specified. Examples of conventional layer forming methods include coating methods such as gravure coating, roll coating, and comma coating, printing methods such as gravure printing, and screen printing.

Base sheet The base sheet 1 is composed of a sheet material or a film material conventionally used for supporting a picture layer or a colored layer on a sheet. Film material refers to a sheet material made of synthetic resin. As the synthetic resin, polypropylene resin, polyethylene resin, polyamide resin, polyester resin, acrylic resin, polyvinyl chloride resin and the like can be used.

  When the base sheet is bonded to the decorative layer to form the outermost layer of the injection molded body even after the simultaneous injection molding, and when the base sheet is peeled off from the decorative layer after the simultaneous injection molding There is. When the base sheet forms the outermost layer of the injection-molded body, the base sheet protects the pattern layer and the injection-molded body from scratches and the like. In this case, the base sheet is preferably excellent in heat stretchability. This is because the followability to the three-dimensional shape of the decorative sheet for molding is improved. As the base sheet, for example, an acrylic resin film, a polycarbonate resin film, a polycarbonate resin / polyester resin alloy film, and the like are preferable.

  In the case of such a material, the thickness of the base sheet is about 70 to 200 μm, preferably about 80 to 160 μm, and more preferably about 90 to 140 μm. If the thickness of the base sheet is less than 70 μm, the strength is insufficient, and there is a risk of damage when performing simultaneous injection molding, and if it exceeds 200 μm, the heat of the injection resin will not easily escape to the mold and ink flow will occur. It becomes easy.

  In the case where the base sheet is peeled off from the injection-molded body leaving the decorative layer after the simultaneous injection molding, the base sheet is preferably thin and excellent in toughness. As the base sheet, for example, a stretched polyester resin film is preferable.

  In the case of such a material, the thickness of the base sheet is 10 to 100 μm, preferably 20 to 80 μm, more preferably about 30 to 70 μm. If the thickness of the base sheet is less than 10 μm, the strength may be insufficient and damage may occur when performing simultaneous injection molding, and if it exceeds 100 μm, the followability to the three-dimensional shape of the decorative sheet for molding may be reduced. There is.

The decorative layer decorative layer 2 is provided on the main surface of the base sheet. The decorative layer may be provided on one side or both sides of the base sheet. The decorative layer has at least the pattern layer 3. A plurality of pattern layers may be formed by being stacked, or may be formed on a part of the sheet surface. The decorative layer 2 is colored between the base sheet 1 and the pattern layer 3 if necessary, adjacent to the hard coat layer (non-display), the anchor layer (non-display), and the exposed surface of the pattern layer 3. There may be a layer (not shown), an additional anchor layer (not shown) or an adhesive layer 4.

  When the base sheet 1 is peeled off from the injection-molded body leaving the decorative layer 2 after the simultaneous injection molding, the decorative layer 2 needs to have releasability from the base sheet 1. In such a case, a release layer (not shown) is formed between the base sheet 1 and the pattern layer 3 so as to be in contact with the base sheet 1.

  The release layer may be separated from the transfer layer together with the base sheet during transfer, or may be separated from the base sheet to form the outermost surface of the transfer layer. As the material of the release layer, melamine resin, silicone resin, fluorine resin, cellulose derivative, urea resin, polyolefin resin, paraffin resin, and composites thereof can be used.

  The adhesive layer 4 is provided on the surface closest to the object to be decorated of the decorative sheet for molding, that is, the injection-molded body, as necessary. An adhesive layer adheres a decoration layer and an injection molded object at the time of injection molding simultaneous decoration. As the adhesive layer, a heat-sensitive or pressure-sensitive resin suitable for an injection-molded product is appropriately used. For example, when the material of the injection molded body is an acrylic resin, an acrylic resin may be used.

  In addition, when the material of the injection-molded product is polyphenylene oxide / polystyrene resin, polycarbonate resin, styrene copolymer resin, or polystyrene blend resin, acrylic resin, polystyrene resin, polyamide having affinity with these resins A series resin or the like may be used. Furthermore, when the material of the injection-molded product is polypropylene resin, chlorinated polyolefin resin, chlorinated ethylene-vinyl acetate copolymer resin, cyclized rubber, and coumarone indene resin can be used.

The pattern layer 3 is formed by spreading ink or paint on the surface of the base sheet 1, for example. When a hard coat layer or an anchor layer is formed between the base sheet 1 and the pattern layer 3, the ink or paint is spread on the surface of these layers. Examples of methods for spreading ink or paint include, for example, printing methods such as gravure printing, flexographic printing, and screen printing; and gravure coater, gravure reverse coater, flexo coater, blanket coater, roll coater, knife coater, air knife coater, kiss Coating methods such as a touch coater, a kiss touch reverse coater, a comma coater, a comma reverse coater, and a micro gravure coater can be used.

  The thickness of the pattern layer is not particularly limited, but is preferably 0.1 to 5 μm, particularly preferably 0.5 to 3 μm, because it has excellent concealability and design properties and is less likely to cause color unevenness during thermoforming. . For the purpose of controlling the adhesion between the base sheet and the picture layer, the surface of the base sheet may be subjected to a surface treatment such as corona treatment or primer coating.

  In order to form a picture layer, a high-brightness ink layer made of an ink having a mirror-like metallic luster (hereinafter referred to as a high-brightness ink) in which metal thin film strips are dispersed in a binder resin can be used. It is preferable that content with respect to the non volatile matter in the ink of a metal thin film piece is the range of 3-60 mass%. High brightness inks using metal thin film strips as a pigment, metallic thin film using conventional metal powder as a result of the metal thin film strips being oriented parallel to the surface of the object when the ink is printed or applied. A high-brightness mirror-like metallic luster that cannot be obtained with ink is obtained.

  The metal of the metal thin film strip used in the high gloss ink used in the high gloss ink layer includes aluminum, gold, silver, copper, titanium, chromium, nickel, indium, molybdenum, tungsten, palladium, iridium, silicon, and tantalum. Nickel chrome, chrome copper, aluminum silicon, brass, stainless steel, etc. can be used. As a method for forming a metal into a thin film, in the case of a metal having a low melting point such as aluminum, vapor deposition is used for a metal having a malleability such as aluminum, gold, silver, copper, etc. Sputtering etc. can be mentioned.

  Among these, the metal thin film strip obtained from the vapor deposition metal thin film is preferably used. The thickness of the metal thin film is preferably 0.01 to 0.10 μm, more preferably 0.02 to 0.08 μm. The size in the plane direction of the metal thin film pieces dispersed in the ink is preferably 5 to 25 μm, more preferably 10 to 15 μm. Within the above range, the metal thin film strips are easily oriented, so that sufficient brightness is obtained, and when the ink is printed or applied by the gravure method or the screen printing method, it does not cause clogging of the plate.

  The metal thin film strip is preferably surface-treated in order to enhance dispersibility in the ink. Examples of the surface treatment agent include organic fatty acids such as stearic acid, oleic acid, and palmitic acid; and cellulose derivatives such as methylsilyl isocyanate, nitrocellulose, cellulose acetate propionate, cellulose acetate butyrate, and ethyl cellulose. It is made to adsorb | suck to the metal thin film strip surface by the method.

  As a binder resin for the ink or paint that forms the pattern layer, a compatible mixture of poly (meth) acrylic acid ester and cellulose derivative is used. This is because the flow resistance of the pattern layer is improved and ink flow is prevented. When both resins are compatible, the molecular chains are entangled, and it is considered that the matrix of the binder resin is difficult to flow even when pressure is applied at a high temperature. This effect is particularly prominent when high-brightness ink containing metal thin film strips is used as a pigment.

  Examples of poly (meth) acrylate esters include methyl poly (meth) acrylate, poly (meth) ethyl acrylate, poly (meth) acrylate propyl, poly (meth) acrylate isopropyl, poly (meth) acrylate butyl, At least one selected from the group consisting of isobutyl poly (meth) acrylate and sec-butyl poly (meth) acrylate is preferred. Among these, particularly preferred is ethyl poly (meth) acrylate, and most preferred is polyethyl methacrylate.

  The molecular weight of the poly (meth) acrylic acid ester is about 100,000 to 300,000, preferably 180 to 280,000, more preferably about 200 to 250,000. When the mass average molecular weight of the poly (meth) acrylic acid ester is less than 100,000, the molecular chain is shortened and the entanglement between the molecules is reduced, so that the resistance to ink flow is lowered. On the other hand, when the molecular weight exceeds 300,000, the solution viscosity becomes high and printing becomes difficult.

  The cellulose derivative is preferably at least one selected from the group consisting of nitrocellulose, cellulose acetate propionate, cellulose acetate butyrate and ethyl cellulose. Among these, cellulose acetate propionate is particularly preferable.

  Cellulose acetate propionate is a cellulose ester resin mainly having an acetyl group and a propionyl group as substituents. Cellulose acetate propionate is used as a binder for printing inks and is commercially available in the form of powder or a solution dissolved in a suitable organic solvent. This type of cellulose acetate propionate has, for example, an acetyl group content of 0.5 to 3.0 mass%, preferably 1.5 to 2.0 mass%, a propionyl group content of 40 to 50 mass%, Preferably it is 47-49 mass%, hydroxyl group content is 1.0-5.0 mass%, Preferably it is 1.5-2.0 mass%, and melting | fusing point is 188-210 degreeC (glass transition temperature is 140-160). ° C).

  The poly (meth) acrylic acid ester and the cellulose derivative are mixed at a ratio suitable for compatibility. The compatibility of both is confirmed by the transparent appearance of the mixture. If the appearance of the resin after mixing is magnified and observed with a microscope or the like, they are compatible if they are homogeneous.

  The specific mixing ratio of the poly (meth) acrylic acid ester and the cellulose derivative is 1/1 to 3/1, preferably 3/2 to 5/2, more preferably 2/1 based on the solid content mass. It is. If the mixing ratio of the two is less than 1/1, the ink flow is effective, but the printability is deteriorated. That is, an ink having an excessive cellulose derivative content has low conformability to commonly used printing inks, and the color pattern tends to be disturbed when the layers are printed in layers. If the mixing ratio of both exceeds 3/1, the effect of suppressing ink flow is hardly seen.

  For high gloss inks, defoaming, settling prevention, pigment dispersion, fluidity modification, anti-blocking, antistatic, antioxidation, light stability in the ink are required as long as the design and spreadability are not impaired. Various additives used in conventional gravure inks, flexographic inks, screen inks, paints and the like can be used for the purpose of ultraviolet absorption, internal crosslinking and the like. Examples of such additives include coloring pigments, dyes, waxes, plasticizers, leveling agents, surfactants, dispersants, antifoaming agents, chelating agents, polyisocyanates, and the like.

  As the solvent used for the high-gloss ink used in the high-gloss ink layer, known conventional solvents used in conventional gravure ink, flexo ink, screen ink, paint, and the like can be used. Specifically, for example, aromatic hydrocarbons such as toluene and xylene; aliphatic or alicyclic hydrocarbons such as n-hexane and cyclohexane; esters such as ethyl acetate and propyl acetate; methanol, ethanol and isopropyl alcohol Alcohols; ketones such as acetone and methyl ethyl ketone; alkylene glycol monoalkyl ethers such as ethylene glycol monoethyl ether and propylene glycol monomethyl ether.

  Generally, in order to stably disperse the ink blending raw material, the pigment and other additives are finely divided to submicron by kneading using a roll mill, ball mill, bead mill, or sand mill. However, the metal thin film strip to be blended in order to develop metallic luster in the high gloss ink used in the high gloss ink layer of the thermoforming laminated sheet having excellent sharpness of the present invention has a size of 5 to 25 μm. preferable. When the above-mentioned kneaded meat is performed, the metal thin film pieces become fine particles, and the metallic luster is extremely lowered. Therefore, in the present invention, it is desirable not to perform kneading, but to simply mix the above-mentioned blending raw materials into an ink. For this purpose, for the purpose of improving dispersibility, it is preferable to surface-treat the metal thin film strip as described above.

Article decoration method The article can be decorated by hot roll transfer, in-mold molding or the like using the decoration sheet of the present invention. For example, in thermal roll transfer, the surface of the decorative sheet on the adhesive layer side (opposite side of the base sheet) is superimposed on the surface of the object to be decorated, and is added using a transfer machine such as a roll transfer machine or an up-down transfer machine. Heat and pressure are applied from the base sheet side of the decorative sheet. By doing so, the decorative sheet adheres to the surface of the object to be decorated, and the surface of the article is decorated.

  In the in-mold injection molding, first, the decorative sheet is fed into the molding die in such a direction that the base sheet is in contact with the inner surface of the die. Next, the mold is closed so that the molten resin is in contact with the surface of the decorative sheet on the adhesive layer side (opposite side of the base sheet), that is, the decorative sheet is sandwiched between the molten resin and the inner surface of the mold. Fill the mold with molten resin. As a result, the molten resin is molded, and at the same time, the decorative sheet is bonded to the surface of the injection molded body. When the resin is cooled, the mold is opened, and the injection molded body is taken out, the decorative layer is adhered to the surface of the injection molded body, and the surface of the injection molded body is decorated.

  When a release layer is formed between the base sheet and the decorative layer, the base sheet is finally peeled off.

  The present invention will be specifically described by the following examples, but the present invention is not limited thereto. In addition, unless otherwise indicated, the quantity represented by "part" or "%" in an Example is represented on the basis of mass.

Example 1
10 parts of polyethyl methacrylate having a molecular weight of 230,000 and a glass transition temperature (Tg) of 65 ° C., an acetyl group content of 1.3% by mass, a propionyl group content of 48% by mass, a hydroxyl group content of 1.7% by mass, and a melting point of 188 to 210 A binder resin was obtained by mixing 5 parts (solid content) of cellulose acetate propionate (“CAP-482-20” manufactured by Eastman Chemical Co., Ltd.) at ℃ (Tg is 147 ° C.). FIG. 2 is a photograph showing a state in which the obtained binder resin is magnified 40000 times with an electron microscope. The morphology of the resin shown in the photograph was confirmed to be homogeneous and compatible.

  14 parts (solid content) of this binder resin, 5 parts of aluminum thin film strips as metal thin film strips, 23 parts of ethyl acetate, 26 parts of methyl ethyl ketone, and 10 parts of isopropanol were mixed, and the concentration of aluminum thin film strips in the nonvolatile content was A glittering ink having a content of 42% by mass was prepared.

  An acrylic film having a thickness of 125 μm was prepared as a base sheet. On this film, glitter ink was applied as a pattern layer using a gravure coater so as to have a dry film thickness of 2 μm. Furthermore, a paint containing an acrylic resin was applied and dried to form an adhesive layer, and a decorative film was obtained. In the above process, all the resin layers were formed by a gravure coating method.

  The obtained decorative film was put into a mold, and in-mold injection molding of a polycarbonate / ABS alloy resin was performed to create a switch base for automobile interior.

  The appearance of the obtained switch base molded product had a uniform high-brightness mirror-like gloss, and no ink flow was observed at the site corresponding to the resin injection nozzle. In addition, no cracks occurred in the three-dimensional curved surface portion.

Comparative Example 1
A binder resin was obtained in the same manner as in Example 1 except that 10 parts (solid content) of polyisobutyl methacrylate having a molecular weight of 250,000 and a glass transition temperature (Tg) of 65 ° C. was used instead of polyethyl methacrylate. FIG. 3 is a photograph showing a state in which the obtained binder resin is magnified 40000 times with an electron microscope. It was confirmed that the resin morphology shown in the photograph was inhomogeneous and incompatible.

  14 parts (solid content) of this binder resin, 5 parts of aluminum thin film strips as metal thin film strips, 23 parts of ethyl acetate, 26 parts of methyl ethyl ketone, and 10 parts of isopropanol were mixed, and the concentration of aluminum thin film strips in the nonvolatile content was A glittering ink having a content of 42% by mass was prepared.

  An acrylic film having a thickness of 125 μm was prepared as a base sheet. On this film, glitter ink was applied as a pattern layer using a gravure coater so as to have a dry film thickness of 2 μm. Furthermore, a paint containing an acrylic resin was applied and dried to form an adhesive layer, and a decorative film was obtained. In the above process, all the resin layers were formed by a gravure coating method.

  The obtained decorative film was put into a mold, and in-mold injection molding of a polycarbonate / ABS alloy resin was performed to create a switch base for automobile interior.

  Although the appearance of the obtained switch base molded product had a uniform high-brightness mirror-like gloss, ink flow was observed at a site corresponding to the resin injection nozzle.

1 ... Base sheet,
2 ... decorative layer,
3 ... pattern layer,
4 ... Adhesive layer.

Claims (3)

A decorative sheet for molding in which a decorative layer is formed on the main surface of the base sheet,
The decorative layer has a pattern layer containing a pigment and a binder resin,
The binder resin is a compatible mixture of polyethyl methacrylate and cellulose acetate propionate ;
A decorative sheet for molding, wherein the pigment comprises a thin metal film strip. The decorative sheet for molding according to claim 1 , wherein a mass ratio of the polyethyl methacrylate and the cellulose acetate propionate is 2/1 based on solid content. The step of feeding the decorative sheet for molding according to claim 1 or 2 into the molding die so that the base sheet is in contact with the inner surface of the mold;
Closing the mold and filling the mold with molten resin so that the molten resin contacts the surface of the decorative sheet on the adhesive layer side (opposite side of the base sheet); and cooling the resin and opening the mold Taking out the injection molded body;
A method for decorating the surface of an injection-molded body including

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