Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-01-26
2003-07-01
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S495000, C524S322000, C524S394000
Reexamination Certificate
active
06586518
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a resin composition where, for example, a character, a symbol, a picture or a photograph can be marked with a laser on a surface of a molded article, to a method for the marking of a molded article obtained from the resin composition, and to a marked molded article.
BACKGROUND ART
Conventionally, as methods for laser printing on a surface of a molded article composed of a polyolefin resin, a method in which a silicon substance is incorporated into the resin as indicted in, for example, Japanese Unexamined Patent Application Publication No. 7-286074, and a method in which a metal such as aluminium or copper is incorporated into the resin as disclosed in Japanese Unexamined Patent Application Publication No. 1-224186 are known. However, such a silicon substance has a poor compatibility with a polyolefin and frequently becomes poorly dispersed. As a result, a sharp printing with a laser cannot be significantly expected. When
DISCLOSURE OF INVENTION
Accordingly, an object of the present Invention is to provide a resin composition and marking method which can form a mark having a sharp and uniform contrast on a surface of a molded article with a laser, as well as a molded article on a surface of which a mark having a sharp and uniform contrast is formed.
Another object of the present invention is to provide a resin composition and marking method which can laser mark without deterioration in workability and mechanical characteristics, as well as a molded article which is marked without deterioration in workability and mechanical characteristics.
After intensive investigations to achieve the above objects, the present inventors found that when a molded article obtained from a resin composition including a polyolefin resin in combination with specific components is irradiated with a laser, printing with a sharp and uniform contrast can be formed on a surface of the molded article. The present invention has been accomplished based on these findings.
Specifically, the present invention provides (i) a resin composition for white marking, which is capable of laser marking and includes a polyolefin resin in combination with a carbon black having a mean particle size of 10 to 100 nm and a dispersing aid selected from higher fatty acids and higher fatty acid amides, and is capable of white printing with a laser, and (ii) a resin composition so black marking, which is capable of laser marking, includes a polyolefin resin in combination with a carbon black having a mean particle size of 10 to 100 nm, a metallic compound white pigment, and a dispersing aid selected from higher fatty acid compounds, and is capable of black printing with a laser.
In another aspect, the present invention provides a method for white marking of a molded article, which includes the step of irradiating a surface of a molded article with a laser to thereby mark the surface in white, which molded article is obtained from the resin composition (i) for white marking, and a method for black marking of a molded article, which includes the step of irradiating a surface of a molded article with a laser to thereby mark the surface in black, which molded article Us obtained from the resin composition (ii) for black marking.
In addition and advantageously, the present invention provides a molded article which is composed of the resin composition (i) for white marking and has a surface marked in white with a laser, and a molded article which is composed of the resin composition (ii) for black marking and has a surface marked in black with a laser.
BEST MODE FOR CARRYING OUT THE INVENTION
A polyolefin resin for use in the present invention may be any of olefinic homopolymers and copolymers (random copolymers, and block copolymers) characteristics.
After intensive investigations to achieve the above objects, the present inventors found that when a molded article obtained from a resin composition including a polyolefin resin in combination with specific components is irradiated with a laser, printing with a sharp and uniform contrast can be formed on a surface of the molded article. The present invention has been accomplished based on these findings.
Specifically, the present invention provides a resin composition capable of laser marking, which includes a polyolefin resin in combination with a laser-sensitive component and a dispersing aid.
In another aspect, the present invention provides a method for marking a molded article, which includes the step of irradiating and marking a surface of a molded article with a laser, which molded article is obtained from the resin composition.
Additionally, the present invention provides a molded article which is composed of the resin composition and has a surface marked with a laser.
BEST MODE FOR CARRYING OUT THE INVENTION
Polyolefin resins for use in the present invention may be any of olefinic homopolymers and copolymers (random copolymers, and block copolymers), such as polypropylenes, polyethylenes, and other olefinic homopolymers; ethylene-propylene copolymers, and other copolymers each containing propylene as a monomeric component; and ethylene-vinyl acetate copolymers and other copolymers each containing ethylene as a monomeric component. Among them, a polypropylene (PP) can be most advantageously used, from the viewpoint of, for example, balance in physical properties, heat resistance, and price. The polypropylene preferably has a melt flow rate (MFR) of about 0.5 to 50 (g/10 min.) and a flexural modulus of about 10000 to 18000 kgf/cm
2
. If MFR is excessively low, a usual molding tends to be difficult, in contrast, if it is excessively high, sufficient mechanical strengths cannot be significantly obtained. If the flexural modulus is excessively low, the resulting resin becomes too soft and tends to invite creep in use, in contrast, if it is excessively high, the resulting resin becomes too hard and tends to invite cracking in use.
The invented resin composition may further comprise other resins in addition to the polyolefin resin. For example, the resin composition can comprise olefinic, styrenic, polyester-based, polyamide-based, and other elastomers (including natural rubbers, synthetic rubbers, and thermoplastic elastomers) to thereby control elastic modulus, when a resin having a high crystallinity and a high elastic modulus such as a polypropylene or polyethylene is used as the polyolefin resin. The amount of the elastomer is, for example, about 0.5 to 30 parts by weight, and preferably about 5 to 25 parts by weight relative to 100 parts by weight of the polyolefin resin when a polypropylene or the like is used as the polyolefin resin. If the amount of the elastomer is excessively small, advantages of the addition of the elastomer cannot be obtained. In contrast, if it is excessively large, the elastic modulus becomes excessively low to thereby deteriorate dimensional stability of the resulting molded article in some cases.
Laser-sensitive components (laser-susceptible components) for use in the present invention include, for example, components that physically or chemically change with laser irradiation. Known or conventional laser-susceptible components which are used in marking with the use of a laser can be used. Such components include, but are not limited to, a carbon black and other black pigments, metallic compound white pigments, and other inorganic pigments. Each of these components can be used alone or in combination. A mark in a desired color can be formed by appropriately selecting the type of the laser-sensitive component. Generally, the use of a black pigment such as a carbon black can yield white printing, and the use of a white pigment such as a metallic compound white pigment can yield black printing. In this connection, the combination use of a white pigment such as a metallic compound pigment and a black pigment such as a carbon black can yield a very sharp black marking.
A variety of carbon black can be used as the carbon black regardless of materials and production methods. Such carbon black includes, but is
Kita Masami
Matsumoto Takashi
Saeki Kazuhiko
Sagane Hiroshi
Cain Edward J.
Daicel Chemical Industries Ltd.
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