Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/26—Thermography ; Marking by high energetic means, e.g. laser otherwise than by burning, and characterised by the material used
  • B41M5/267—Marking of plastic artifacts, e.g. with laser

Definitions

• thermoplastic resin composition having laser marking ability. More specifically, the invention relates to a thermoplastic resin composition which can form distinct marking with excellent contrast upon exposure to laser irradiation.
• This technology comprises incorporating a light- or heat-absorbing additive in raw materials in advance, thereby to cause foaming, decomposition or carbonization under the laser irradiation to induce changes in the surface of the material or bleach of pigment or dye, whereby the desired marking is achieved.
• Japanese Patent Publication No.61-11771 discloses a method in which distinct marking with laser beam is formed by incorporating a mount of a carbon black or graphite.
• Japanese Laid-open Patent Publication No.1-254743 discloses a method for improving marking ability of plastics with YAG laser, which comprises adding titanium oxide and optionally further carbon black with the plastics.
• Japanese Patent Publication No.61-41320 and Laid-open Patent Publication No.61-192737 describe methods of marking, utilizing decoloration or discolor-ation of pigments, dyestuffs etc.
• Japanese Patent Publication No.2-47314 discloses a marking method in which volatile component(s) in the resin to be marked, such as unpolymerized monomers or decomposition products, are foamed by laser beam to form projection on the resin surface, whereby marking is formed.
• Japanese Laid-open Patent Publication No.4-246456 teaches that marking with good contrast can be obtained by adding to plastics carbon black and/or graphite which are highly thermoconductive.
• Japanese Laid-open Patent Publication No.2-59,663 discloses a process for making plastic key members, using a coloring powder which responds to heat irradiation or a dye powder sensitive to heat radiation.
• the laser marking portion formed by foaming have a low degree of blackness.
• use of carbon black markedly enhances the foaming, which causes notable decrease in black color development.
• thermoplastic resin composition having laser marking ability.
• Another object of the present invention is to provide a thermoplastic resin composition which is capable of forming distinct marking of excellent contrast upon exposure to laser irradiation.
• Still another object of the present invention is to provide a thermoplastic resin composition which gives marking with clear black color development under laser irradiation.
• thermoplastic resin composition having laser marking ability which comprises a thermoplastic resin and at least two kinds of metal oxides, the content of total metal oxides being 0.001 to 10 parts by weight per 100 parts by weight of said thermoplastic resin.
• thermoplastic resins used for the present invention include such general-purpose resins as polyethylene, polypropylene, ABS and the like; and such engineering plastics as aromatic saturated polyesters, polycarbonates, polyamides, polyacetals and the like.
• the preferred aromatic saturated polyesters are those whose main acid component is derived from terephthalic acid, 2,6-naphthalenedicarboxylic acid, or their ester-forming derivatives and main diol component is composed of at least one aliphatic diol such as ethylene glycol, trimethylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol and the like.
• aromatic polyesters of high crystallization rate e.g., polybutylene terephthalate, polypropylene terephthalate, polyethylene terephthalate, polybutylene-2,6-naphthalenedicarboxylate are particularly preferred, the most preferred being polybutylene terephthalate.
• thermoplastic aromatic polyesters may be partially substituted with a copolymerizable component.
• copolymerizable components include aromatic dicarboxylic acids, e.g., alkyl-substituted phthalic acids such as isophthalic acid, phthalic acid, methylterephthalic acid and methylisophthalic acid, naphthalenedicarboxylic acids such as 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid and 1,5-naphthalenedicarboxylic acid, diphenyldicarboxylic acids such as 4,4'-diphenyldicarboxylic acid and 3,4'-diphenyldicarboxylic acid, and diphenoxyethanedlcarboxylic acids such as 4,4'-diphenoxyethanedicarboxylic acid, etc.; aliphatic or alicyclic dicarboxylic acids such as succinic acid, adipic acid, sebacic acid,
• the above aromatic polyesters may further be copolymerized with not more than 1.0 mol%, preferably not more than 0.5 mol%, more preferably not more than 0.3 mol%, of a polyfunctional ester-forming acid such as trimesic acid, trimellitic acid or the like or a polyfunctional ester-forming alcohol such as glycerine, trimethylol propane, pentaerythritol, etc., as a branching component.
• a polyfunctional ester-forming acid such as trimesic acid, trimellitic acid or the like
• a polyfunctional ester-forming alcohol such as glycerine, trimethylol propane, pentaerythritol, etc.
• Preferred polycarbonate resins to be used in this invention are those which are derived from dihydric phenols and have molecular weight ranging 10,000 to 100,000, more preferably 15,000 to 60,000, as expressed in terms of viscosity-average molecular weight.
• Such polycarbonate resins are usually obtained through reaction of dihydric phenols with carbonate precursors according to the solution phase or melt phase method.
• the dihydric phenols include 2,2-bis(4-hydroxyphenyl)propane (bisphenol-A), 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxy-3-methylphenyl)propane and bis(4-hydroxyphenyl) sulfone, etc.
• bis(4-hydroxyphenyl) alkanes are preferred, the most preferred being bisphenol-A.
• the ABS resin used for the invention is selected from known resins formed by adding acrylonitrile and butadiene, in various forms, to polystyrene.
• AS resin styrene-acrylonitrile copolymer resin
• BR polybutadiene
• AS resin styrene-acrylonitrile copolymer resin
• BR polybutadiene
• AS resin styrene-acrylonitrile copolymer resin
• BR polybutadiene
• BR polybutadiene
• AS resin styrene-acrylonitrile copolymer resin
• BR polybutadiene
• AS resin styrene-acrylonitrile copolymer resin
• AS resin styrene-acrylonitrile copolymer resin
• BR polybutadiene
• AS resin styrene-acrylonitrile copolymer resin
• AS resin styrene-acrylonitrile copolymer resin
• thermoplastic resins to be used in the present invention polyethylene terephthalate, polybutylene terephthalate, polybutylene naphthalenedicarboxylate, polycarbonate, polyamide, polyacetal, ABS, polyethylene and polypropylene are particularly preferred. These may be used either singly or as mixtures.
• the resin composition of the present invention contains at least two kinds of metal oxides.
• Said at least two kinds of metal oxides are selected from a group consisting of (a) oxides of monovalent or divalent metals, (b) oxides of trivalent metals and (c) oxides of tetra- to hexa-valent metals.
• oxides of monovalent or divalent metals are K 2 O, Na 2 O, Li 2 O, Cu 2 O, CaO, MgO, CoO, PbO, ZnO, BaO, FeO, MnO, CdO, CuO, NiO and SrO.
• the oxides of trivalent metals include, for example, Al 2 O 3 , B 2 O 3 , Fe 2 O 3 , Sb 2 O 3 , Cr 2 O 3 , Mn 2 O 3 and As 2 O 3 .
• the oxides of tetra- to hexa-valent metals include, for examples, SiO 2 , TiO 2 , SnO 2 , ZrO 2 , CeO 2 , Sb 2 O 5 , V 2 O 5 , P 2 O 5 , UO 3 and MoO 3 .
• Such at least two kinds of metal oxides are used in a combined amount of 0.001 to 10 parts by weight per 100 parts by weight of the thermoplastic resin.
• the total content of said at least two metal oxides preferably ranges 0.001 to 5 parts by weight, more preferably 0.01 to 2 parts by weight, per 100 parts by weight of the thermoplastic resin.
• the at least two kinds of metal oxides may each form a compound independently of each other, or may together form a complex.
• said at least two kinds of metal oxides form a composition represented by the formula below; R 1-2 O ⁇ xR' 2 O 3 ⁇ yR''O 2-3 wherein R 1-2 O stands for an oxide of a monovalent or divalent metal; R' 2 O 3 stands for an oxide of a trivalent metal; R''O 2-3 stands for an oxide of a tetra- to hexa-valent metal; x is a number ranging 0.1 to 1.2; and y is a number ranging 1 to 12.
• the at least two kinds of metal oxides form a state of "glaze", which has no fixed chemical structure, like glass. While such "glaze” can be classified in various manner, e.g., china glaze and porcelain glaze, etc. according to the kinds of the calcination product; feldspars glaze, lime glaze, etc. according to the starting material which is the source of main component; or frit glaze, salt glaze, etc. according to the type of production system. It is of little significance to which of these classes does the "glaze” state as referred to in this invention belongs.
• thermoplastic resin composition of the present invention may further contain a black pigment or black dye, in an amount of not more than 2 parts by weight per 100 parts by weight of the thermoplastic resin.
• black pigments or black dyes for example, carbon-based black pigments, black metal oxides and black dyes are conveniently used. Of these, black metal oxides are more preferred.
• pigments and dyes may be added, depending on the intended use of individual compositions.
• inorganic pigments e.g., basic lead carbonate, basic lead sulfate, basic lead silicate, metal sulfide such as lithopone or zinc sulfide
• organic pigments such as azo-, azomethine-, methine-, indanthrone-, anthraquinone-, pyranthrone-, flavanthrone-, benzanthrone-, phthalocyanine-, perinone-, perylene-, dioxadine-, thioindigo-, isoindoline-, isoindolinone-, quinacridone- and quinophthalone-type pigments may be used.
• inorganic pigments e.g., basic lead carbonate, basic lead sulfate, basic lead silicate, metal sulfide such as lithopone or zinc sulfide
• organic pigments such as azo-, azomethine-, methine-, indanthrone-,
• organic dyes examples include anthraquinone disperse dyes, metal complexes of azo dyes and fluorescent dyes.
• thermoplastic resin composition of the present invention may further contain, within the range not impairing the objects of the invention, ordinary additives such as a glass-reinforcing agent, a granular or platy filler, a flame-retardant, a releasing agent, a lubricant, a slip additive, a nucleating agent, a colorant, an antioxidant, a heat stabilizer, a weather-ability (light) stabilizer and a modifying agent such as impact resistance-improving agent, etc.
• ordinary additives such as a glass-reinforcing agent, a granular or platy filler, a flame-retardant, a releasing agent, a lubricant, a slip additive, a nucleating agent, a colorant, an antioxidant, a heat stabilizer, a weather-ability (light) stabilizer and a modifying agent such as impact resistance-improving agent, etc.
• thermoplastic resin composition of the present invention can be obtained by blending a thermoplastic resin with metal oxides of the prescribed amount by an arbitrary blending method. It is preferred to disperse the components to be blended more uniformly. More specifically, the whole or a part may be simultaneously or separately blended in a mixing machine such as, for example, a blender, a kneader, a Bumbury mixer, a roll, an extruder, etc. to be homogenized. Furthermore, it is also possible to granulate the composition by melt-kneading a composition formed by advance dry-blending, in a heated extruder to homogenize the composition, extruding the melt into a wire form, and thereafter cutting the product to any desired length.
• a mixing machine such as, for example, a blender, a kneader, a Bumbury mixer, a roll, an extruder, etc.
• thermoplastic resin composition of the present invention can be quite easily practiced by ordinary means using common molding machines of thermoplastic resin in general.
• marking was carried out with YAG laser (Laser Marker SL 475 E 2 , manufactured by NEC Corporation).
• Marking was evaluated according to the degree of color difference (contrast) between a molded article surface and a marking portion at which a color was developed upon exposure to the laser beam, and to the foaming condition.
• a Color Analyzer TC-1800 MK-11 manufactured by Tokyo Denshoku Co., Ltd was used, and the result was expressed by the difference in brightness, ⁇ L*.
• the foaming condition it was confirmed whether a uniform and fine foam was formed.
• Comparative Example 1 a good contrast was not obtained because the molded product surface was colored and the marked portion developed a color of high brightness.
• the various starting materials as identified in Table 2 were homogeneously dry-blended in advance at the prescribed quantitative ratios, and the mixtures were each melt-kneaded in a vented twin screw extruder with the screw diameter 44 mm, under conditions of a cylinder temperature of 180°C to 260°C, screw rotation speed of 160 rpm and a discharge rate of 40 kg/hr.
• the molten mixture was discharged as threads through the die, cooled and cut to provide pellets for molding.

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• Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Thermal Transfer Or Thermal Recording In General (AREA)

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Citations (14)

• 1995
  • 1995-07-13 DE DE1995616862 patent/DE69516862T2/de not_active Expired - Lifetime
  • 1995-07-13 EP EP19950304916 patent/EP0753536B1/fr not_active Expired - Lifetime

Patent Citations (15)

Non-Patent Citations (1)

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