JPH0419924B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for painting resin molded articles.

BACKGROUND OF THE INVENTION It is widely practiced to provide letters and designs on molded products made of molding resin materials such as acrylic resins and styrene resins by thermal transfer or silk printing, or to provide patterns with metal foil. However, since it is expensive to create multicolor patterns by silk printing, thermal transfer methods, which require fewer steps, have recently been preferred. The thermal transfer is often performed simultaneously during the molding of a molded article. Since the patterns obtained by these transfer methods generally do not have sufficient surface abrasion resistance, it is necessary to form a hard resin coating on the surface to protect the surface. However, resin coatings with high hardness generally have poor adhesion to the coloring agent layer forming the pattern, and cracks in the protective coating due to delamination between the protective coating and the coloring agent layer occur frequently.
It was not possible to obtain a product with satisfactory surface hardness.

The purpose of the present invention is to eliminate the above-mentioned drawbacks of the prior art, to construct a transfer sheet from a specific material, to use it to apply a pattern at the same time as injection molding, and to then perform post-processing. The object of the present invention is to provide a method for obtaining a decorated molded article that has extremely high surface hardness, excellent surface properties such as abrasion resistance, and does not cause delamination or cracks.

In the method for painting resin molded products of the present invention, a transfer sheet consisting of a base sheet, a release agent layer, a pattern layer, and an adhesive layer is placed in an injection mold, and the resin is injected and molded while coating the surface of the molded product. In the simultaneous injection painting method for molded products that transfers the above-mentioned designs,
Using a transfer sheet that is a layer of electron beam curable resin in which at least the release agent layer is not completely cured,
It is characterized by being completely cured by irradiating it with an electron beam after injection molding.

To explain, as shown in FIG. 1, the transfer sheet 1A used in the present invention is composed of a base sheet 11, a release agent layer 12, a pattern 13, and an adhesive layer 14, and of the three layers other than the base sheet, at least the release agent is Layer 12 consists of an electron beam curable composition that is not completely cured. The most preferred transfer sheet includes not only release agent layer 12 but also layer 13 and adhesive layer 1.
All of No. 4 are made of electron beam curable compositions that are not completely cured. As follows,
can be manufactured. That is, as a first step, a coating agent containing an electron beam curable composition is applied to one surface of the base sheet and dried to form a release agent layer. As a second step, a coating agent containing an electron beam curable composition containing a colorant is applied to the surface of the release agent layer formed in the first step and dried to form a pattern layer.

As the third step, the surface of the release agent layer including the pattern layer formed in the second step is coated entirely.
A coating agent containing an electron beam curable composition is applied and dried to form an adhesive layer to obtain a transfer sheet.

Note that the pattern layer may be a plain colorant layer formed uniformly over the entire surface, or may be a colorant layer with some ink omissions. In some cases, it may be a metal layer deposited by a metal vapor deposition method.

The drying process in the above steps must be carried out to such a degree that when the applied coating agent is touched with a fingertip, the coating agent does not adhere to the fingertip, that is, it is dry to the touch. To achieve such a dry state, it is necessary to use a coating agent that contains a solvent in each process and evaporate the solvent by heating after applying the coating agent, or to evaporate the solvent in the coating agent. It is preferable to use a method in which a photopolymerization initiator is added to the coating material, and the surface is hardened by UV irradiation treatment after coating.

The base sheet 11 used in the present invention may be a film of various plastics such as polyester, cellophane, or polypropylene, paper, metal foil, or a laminated sheet of two or more of these, if necessary. Furthermore, by using a base sheet with irregularities of 5μ or less on the sheet surface and forming a release agent layer thereon, irregularities are formed on the surface of the resulting transfer painting layer, and the base sheet and release agent layer are It is also possible to improve the releasability between the two. In addition, as the electron beam curable composition used for forming the release agent layer, pattern layer and adhesive layer, prepolymers or oligomers having ethylenically unsaturated bonds in the molecule, such as unsaturated polyesters, polyester acrylates, etc. , epoxy acrylate, urethane acrylate, polyether acrylate,
One or more types of various acrylates such as polyol acrylate and melamine acrylate, various methacrylates such as polyester methacrylate, polyether methacrylate, polyol methacrylate, and melamine methacrylate, and a monomer having an ethylenically unsaturated bond in the molecule, for example, Styrenic monomers such as styrene and α-methylstyrene; acrylic esters such as methyl acrylate, 2-ethylhexyl acrylate, methoxyethyl acrylate, butoxytyl acrylate, butyl acrylate, methoxybutyl acrylate, and phenyl acrylate Class; methyl methacrylate, ethyl methacrylate, propyl methacrylate, methoxyethyl methacrylate,
Methacrylic acid esters such as ethoxymethyl methacrylate, phenyl methacrylate, and lauryl methacrylate; Unsaturated carboxylic acid amides such as acrylamide and methacrylamide; Acrylic acid-2-
(N,N-dimethylamino)ethyl, 2-(N,N-dimethylamino)ethyl methacrylate, (N,N-dibenzylamino)ethyl methacrylate, (N,N-dimethylamino)methyl methacrylate, Substituted amino alcohol esters of unsaturated acids such as 2-(N,N-diethylamino)propyl acrylate; ethylene glycol diacrylate, propylene glycol diacrylate,
Neopentyl glycol diacrylate, 1,
Polyfunctional compounds such as 6-hexanediol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, dipropylene glycol diacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, diethylene glycol dimethacrylate, and (or ) A mixture of polyothyl compounds having two or more thiol groups in the molecule, such as trimethylolpropane trithioglycolate, trimethylolpropane trithiopropionate, pentaerythritol tetrathioglycolate, etc., can be used.

There is no limit to the mixing ratio of each component in the above electron beam curable composition, and they can be mixed as desired. However, in order to have normal coating suitability, the prepolymer or oligomer should be contained in an amount of 5% by weight or more. Similarly, it is preferable that the monomer and/or polythiol be 95% by weight or less.

Since this coating agent dries to a touch-dry state after being applied, it is preferable to use a solid or highly viscous coating agent, and if necessary, various resins such as acrylic resin, cellulose It is also possible to mix a resin, a rubber resin, a polyester resin, a polyurethane resin, etc. into the coating agent to facilitate dryness to the touch.

A polymerization inhibitor such as hydroquinone, hydroquinone monomethyl ether, or benzoquinone may be added to the coating agent as a stabilizer in order to prevent the electron beam curable composition therein from curing before electron beam irradiation. .

In the coating agent for forming the release agent layer, since this layer forms the outermost layer of the transferred painting, a slip agent, etc. is added as appropriate, taking into consideration the surface properties of the resulting product. You can also let
Of course it is possible.

As the coating agent for forming the pattern layer, a mixture of an electron beam curable composition and a coloring agent such as a pigment having a desired color can be used. The coating agent for forming the adhesive layer 3 preferably contains an opaque pigment, especially for the purpose of providing hiding properties.

Application methods for each coating agent include various coating methods such as natural roll coating, reverse roll coating, gravure roll coating, air knife coating, curtain flow coating, and mirror coating, gravure printing, offset printing, screen printing, and offset printing. Various printing methods such as gravure printing can be used.

The transfer sheet having the above structure is placed in a normal injection mold so that the adhesive layer 14 comes into contact with the surface of the molded product 12, and the mold is tightened. Styrene resin, AS
When the resin or other desired molding resin is injected in a conventional manner and the molded product is taken out after molding, the base sheet 11 is peeled off and the adhesive layer 14, pattern layer 13 and The release agent layer 12 is obtained by being integrally adhered to the surface of the molded product that is the transfer target 2. Then, the adhered transfer painting layer 1B is completely cured by electron beam irradiation E and B. Electron beam irradiation as a means of completely curing the electron beam curable composition is carried out in a nitrogen atmosphere using a low-energy electron accelerator, such as "Electro Curtain CB200/50/30" manufactured by Energy Science Industry Co., Ltd. or "NP -ESH150" etc. The amount of irradiation is usually sufficient to be absorbed by an amount sufficient to harden the electron beam curable composition in the applied coating agent, so 0.5 to 10 Mrad is usually sufficient.

In a preferred embodiment of the present invention, a coating agent containing an electron beam curable composition is used as a coating agent to form a release agent layer and an adhesive layer in a transfer sheet, and adheres to the transfer surface of the transfer object. The multi-layer structure consisting of agent layer/picture layer/release agent layer is transferred and then each layer is completely cured by electron beam irradiation, so each layer is three-dimensionally formed on the surface of the transferred object. It is possible to form a transferred painted layer which is composed of a cured layer that is cross-linked and has extremely excellent properties in terms of solvent resistance, chemical resistance, heat resistance, etc. Furthermore, since the transfer pattern layer is formed by cross-linking between the transfer object and the adhesive layer and between each layer, a transfer pattern layer having high adhesive strength between the transfer object and each layer is formed. be able to.

In addition, by transferring the metal vapor deposited layer sandwiched between the release agent layer and the adhesive layer onto the surface of the molded product and then performing electron beam irradiation, both layers sandwiching the metal vapor deposition layer can be removed. Because it is completely cured, a cured layer in which each layer is three-dimensionally cross-linked is formed on the surface of the transferred object, forming a metal vapor-deposited transfer pattern layer with excellent solvent resistance, chemical resistance, and heat resistance. I can do it.

Example 1 A polyester film (Toray "Lumirror") with a thickness of 38 μm was used as a base sheet. On one side of this sheet, coating agent A having the following composition was applied uniformly over the entire surface using a gravure plate with a plate depth of 40 μm, and heated at 80°C. The solvent was evaporated through a drying hood, and the applied coating agent layer was dry to the touch to form a release agent layer.

(Coating agent A) Oligoester acrylate 45 parts by weight (Toagosei "Aronix M8030") Epoxy acrylate 49.5 parts by weight (Showa Kobunshi "Epoxy VR90") Acrylic resin 5 parts by weight Hydroquinone 0.5 parts by weight Methyl ethyl ketone 20 parts by weight Obtained peeling Coating agent B with the following composition is printed on the surface of the agent layer with a pattern using a halftone gravure plate.
The coating was applied, passed through a drying hood at 80°C to evaporate the solvent, and the applied coating layer was dry to the touch to form a pattern.

(Coating agent B) Epoxy acrylate 50 parts by weight (Showa Kobunshi "Epoxy VR60") Sepia pigment 20 parts by weight Methyl ethyl ketone 20 parts by weight Next, on the surface of the release agent layer containing the pattern layer,
Coating agent C with the following composition was applied uniformly over the entire surface using a gravure plate with a plate depth of 60μ, the solvent was evaporated by passing it through a drying hood at 80°C, and the applied coating agent layer was dried to the touch, and then used for transfer. Got a sheet.

(Coating agent C) Acrylic resin 20 parts by weight Trimethylolpropane triacrylate
20 parts by weight Sepia pigment 30 parts by weight Methyl ethyl ketone 30 parts by weight The above steps were performed in-line at a printing speed of 30 m/min, and the resulting transfer sheet was wound up.

The above transfer sheet was placed in a mold of an injection molding machine, and after preliminary molding, the acrylic resin was molded using a molding acrylic resin. The picture pattern of the above-mentioned transfer sheet was transferred to this acrylic resin plate.

Finally, the obtained acrylic resin plate was heated at 150KeV-
A dose of 5 Mrad was irradiated with a curtain-shaped electron beam of 15 mA to obtain a completely cured transfer pattern layer consisting of an adhesive layer/picture layer/release agent layer.

The painted transfer layer was made by soaking cotton cloth (Kanakin No. 3) in ethyl acetate, toluene, methyl ethyl ketone, and ethyl alcohol, and there was no change in it even if it was rubbed 50 times with a load of 200 g using a Gakushin friction tester. I couldn't even see it.

Example 2 A polyester film (diamond foil) with a thickness of 38 μm was used as a base sheet, and coating agent D having the following composition was applied uniformly to the entire surface on one side using a gravure plate with a plate depth of 40 μm. Ultraviolet irradiation treatment was performed using two "Your Lamp" (Nippon Battery) lamps, and the applied coating agent layer was dry to the touch to form a release agent layer.

(Coating agent D) Oligoester acrylate 45 parts by weight (Toagosei "Aronix M8030") Ethyl cellulose 10 parts by weight 1,6-hexanediol acrylate 40 parts by weight Benzophenone 5 parts by weight Hydroquinone 0.5 parts by weight On the surface of the obtained release agent layer , in vacuum (10mmHg
evaporate aluminum to a thickness of about 500 mm,
A uniform metal vapor deposition layer was formed over the entire surface.

Coating agent E with the following composition is uniformly applied to the surface of this metal vapor-deposited layer using a gravure plate with a depth of 60μ, and then two 80w/cm "Hi-Kure Lamps" are used on the coated surface. The coated coating layer was then irradiated with ultraviolet rays, and the coated coating layer was dried to the touch to form an adhesive layer, thereby obtaining a transfer sheet.
The obtained transfer sheet was wound up.

(Coating agent E) Acrylic resin 10 parts by weight Oligoester acrylate 50 parts by weight (Toagosei "Aronix M5700") Sepia pigment 30 parts by weight Benzophenone 10 parts by weight Using the transfer sheet obtained in the above process,
The same operation as in Example 1 was carried out to obtain an acrylic resin plate having a transfer painting layer including a metal vapor deposited layer.

The transfer pattern layer on the surface of the obtained acrylic resin plate had excellent solvent resistance, similar to the transfer pattern layer obtained in Example 1.

[Brief explanation of drawings]

1 and 2 are schematic cross-sectional views for explaining the transfer painting method of the present invention, in which FIG. 1 shows the structure of the transfer sheet, and FIG. 2 shows the step of electron beam curing after transfer. , respectively. 1A...Transfer sheet, 1B...Transfer painting layer, 1
1... Base sheet, 12... Release agent layer, 13...
Pattern layer, 14...adhesive layer, 2...molded product.

Claims (1)

[Scope of Claims] 1. A transfer sheet consisting of a base sheet, a release agent layer, a pattern layer, and an adhesive layer is placed in an injection mold, a resin is injected and molded, and the above pattern is applied to the surface of the molded product. In the simultaneous injection painting method for molded products, at least the release agent layer is a layer of electron beam curable resin that has not been completely cured, and the transfer sheet is irradiated with an electron beam after injection molding. A method characterized by complete curing. 2. The painting method according to claim 1, wherein the transfer sheet comprises an electron beam curable composition in which none of the release agent layer, pattern layer, and adhesive layer are completely cured. 3. The painting method according to claim 1, wherein a vapor-deposited metal layer is present as the pattern layer. 4. The painting method according to claim 1, wherein the pattern layer has a colorless area.