Stock material or miscellaneous articles – Composite – Of addition polymer from unsaturated monomers
Reexamination Certificate
2000-09-05
2003-10-07
Tarazano, D. Lawrence (Department: 1773)
Stock material or miscellaneous articles
Composite
Of addition polymer from unsaturated monomers
C428S522000, C264S494000
Reexamination Certificate
active
06630246
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a non-adhesive photocuring sheet capable of giving molded articles with excellent outer appearance, design properties, mar-proof properties, chemical resistance and weather resistance, and to molded articles and a process for their manufacture. The photocuring sheet is particularly useful as an automobile interior material for instrument panels, console boxes, meter covers, door lock bezels, steering wheels and the like, as an automobile exterior material for weather-strips, bumpers, strut mounts, side molds, door molds, window molds and the like, as a material for front panels and buttons for AV devices and household appliances, and as an exterior furniture material or a building and house interior and exterior material.
BACKGROUND ART
As methods for shaping plastic articles while providing decorated surfaces there have been proposed (1) a method in which a pattern is preformed in the die surface, (2) a method in which a transfer film is fitted on the inside of the die and the pattern of the film is transferred to the outside of the molded article during molding, and (3) a method in which a functionalized or printed sheet is attached to the inside of the die and the sheet is attached to the molded article surface during molding. Methods (2) and (3) include the methods described in Japanese Unexamined Patent Publication No. 60-250925, Japanese Examined Patent Publication No. 59-36841 and Japanese Examined Patent Publication No. 8-2550, whereby a weather-resistant sheet or printed sheet is formed on the inside of the die, and a molding resin is used for injection molding to produce a molded article whose surface is covered with the sheet.
However, because this technique is carried out with transfer of thermoplastic sheets or printing to provide decoration and functionality, the surface hardness of the resulting molded articles is insufficient. For example, a highly weather resistant sheet made of polyvinylidene fluoride (PVDF) or the like may be used to give the molded article weather resistance, but its problem is a lack of sufficient surface hardness. To counter this, pre-crosslinked high-surface-hardness sheets must be used in order to obtain molded articles with high surface hardness. Such sheets, however, cannot be easily employed for molded articles with three-dimensional shapes.
There have also been proposed, in Japanese Examined Patent Publication No. 7-323, for example, photocuring sheets comprising a laminate of a sheet base and a photocuring resin layer formed using a resin composition containing an acrylic resin, a compound with a reactive vinyl group and a photopolymerization initiator.
According to this process, however, since the sheet prior to photocuring contains a low molecular weight compound with a reactive vinyl group, the surface is tacky and the tackiness of the surface alters with time, such that its storage stability in the form of a roll is poor. Specifically, this causes problems in that, unless it is stored at low temperature, adhesion occurs and prevents unwinding, and the resin oozes out from both edges. The tackiness has also resulted in inconvenience during the printing step when the sheet is used as a printing sheet.
Japanese Unexamined Patent Publication No. 2-289611 discloses a resin composition comprising an acrylic resin containing an alicyclic epoxy group, and a cationic photopolymerization initiator; however, when this resin composition is used alone to form a sheet, an acrylic resin with a low glass transition temperature tends to cause clinging of the sheet to the die when it is used as an insert molding sheet. On the other hand, when an acrylic resin with a high glass transition temperature is used, the resulting fragility of the sheet presents the problem of poorer handleability.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a photocuring laminated sheet with excellent workability and storage stability and a lack of tackiness, that may be used in the manufacture of molded articles with satisfactory decorative designs and that gives molded articles with excellent mar-proof properties, weather resistance and chemical resistance.
In order to achieve this object, the invention provides a photocuring sheet wherein a photocuring resin composition (A) comprising an acrylic resin with a photopolymerizable functional group on the side chains (a-1) and a photopolymerization initiator (a-2), is laminated on a transparent base sheet (B), as well as photocuring decorative sheets and photocuring insert molding sheets employing it, molded articles employing these and a process for their manufacture.
BEST MODE FOR CARRYING OUT THE INVENTION
Preferred embodiments of the invention will now be explained.
The photocuring sheet of the invention has a photocuring resin composition (A) comprising an acrylic resin with a photopolymerizable functional group on the side chains (a-1) and a photopolymerization initiator (a-2), laminated on a transparent base sheet (B). The structure with a photopolymerizable functional group on the polymer side chains promotes crosslinking reaction between the polymer side chains, so that it is not necessary to include a low molecular weight compound with a reactive vinyl group. This offers the advantage of giving a sheet with no tackiness and excellent storage stability.
The photopolymerizable functional group may be any one whose polymerization is promoted by light irradiation, and as a preferred group there may be mentioned the alicyclic epoxy group represented by the following structural formula (1).
The compound having an alicyclic epoxy group on the side chain is not particularly restricted so long as it can undergo copolymerization with other (meth)acrylates, and compounds represented by the following structural formula (2) may be specifically mentioned.
wherein R represents methyl or hydrogen, and n is an integer of 0-5.
The copolymerization of the compound with a photopolymerizable functional group on the side chain is preferably to 1-100 parts by weight per 100 parts by weight of the acrylic resin (a-1). At less than 1 part by weight, sufficient crosslinking may not occur within the polymer and the desired curing properties may not be achieved. In order to obtain a photocuring sheet with excellent mar-proof properties, the copolymerization of the compound with a photopolymerizable functional group on the side chain is even more preferably to 50-100 parts by weight.
By introducing into the acrylic resin a functional group that participates in crosslinking, it is possible to improve the curing property efficiently with a lower degree of crosslinking.
Known vinyl polymerizable monomers suitable for radical polymerization may also be copolymerized with the acrylic resin (a-1), if necessary. As examples of such vinyl polymerizable monomers there may be mentioned (meth)acrylates such as methyl (meth)acrylate, tricyclodecanyl (meth)acrylate and isobornyl (meth)acrylate; imide derivatives such as N-phenylmaleimide, cyclohexyl maleimide and N-butylmaleimide; hydroxyalkyl group-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and 2-hydroxypropyl (meth)acrylate; amide group-containing vinyl monomers such as acrylamide, methacrylamide and acrylonitrile; epoxy group-containing vinyl monomers such as allyl glycidyl ether and glycidyl (meth)acrylate; and olefinic monomers such as butadiene.
The acrylic resin (a-1) preferably has a glass transition temperature adjusted to 40-150° C. When the glass transition temperature is lower than 40° C., the die release properties of the sheet during insert molding may be inferior. When the glass transition temperature is higher than 150° C., the sheet properties may be rendered fragile, thus impairing the handleability.
Considering the glass transition temperature of the resulting acrylic resin copolymer, it is preferred to use a vinyl polymerizable monomer with a high glass transition temperature of the homopolymer.
The molecular weight of the acrylic resin (a-1) is preferably in the range of 10,
Fujiwara Tadayuki
Kakuno Yoko
Wakisaka Yukiya
Yanagase Akira
Mitsubishi Rayon Co. Ltd.
Tarazano D. Lawrence
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