JPH08127670A - Resin composition for laser-marking - Google Patents

Abstract

PURPOSE: To obtain a resin composition, suitable for marking by laser beam irradiation, with high sensitivity, characters, signs, patterns, etc., excellent in visuality and white-clarity on the surface of resin molded products, by incorporating a thermoplastic resin with a titanium oxide oxidized to a lower degree in specific proportions. CONSTITUTION: This composition is obtained by incorporating (A) 100 pts. wt. of a thermoplastic resin such as an aromatic polycarbonate resin, an aromatic polyester resin, a polyamide resin or styrene-based resin. with (B) 0.001 to 20 pts.wt., esp. 0.1 to 1 pt.wt. of a titanium oxide oxidized to a lower degree of e.g. composition of formula TiOk ((k) is 1.00 to 1.86) (e.g. titanium monoxide, dititanium trioxide, trititanium pentoxide). The component B is obtained e.g. by either mixing metallic titanium with titanium dioxide in desired stoichiometric proportions and calcining in an inert gas, or by reducing titanium dioxide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser marking for irradiating a surface of a molded material with a laser beam so that a mark such as a character or a symbol can be developed into a clear white color with high sensitivity and high visibility. It relates to a composition.

[0002]

2. Description of the Related Art As a method of marking desired characters, symbols, patterns, etc. on the surface of a resin molded product, a method such as printing using a thermosetting ink or a UV curable ink has been generally performed conventionally. However, this method has problems that it takes a long time for marking, a part of the marking is removed due to insufficient curing, or the durability is poor due to insufficient ink adhesion. On the other hand, a laser marking method for marking characters, symbols, patterns and the like using laser light has been proposed and attracted attention as a method for performing marking with good reproducibility, simply and at high speed. However, when marking is performed by irradiating the surface of a molded product with laser light, the irradiated portion is locally heated, and the additive or resin in the resin surface layer portion undergoes thermal changes such as melting, vaporization, and carbonization. Since marking is performed by this thermal change, the obtained marking character becomes a concave etched character or a character charred in a blackish color. The marking characters thus obtained have poor contrast, are difficult to identify, and are considerably inferior to the printed characters, and thus are not practical.

To effectively apply laser marking,
It is necessary to modify the plastic so that it is easily exposed to light. This is because when a filler that absorbs light and heat is mixed in the material beforehand, foaming occurs during laser irradiation,
This is a technology that enables marking by disassembly, etc. For example, Japanese Unexamined Patent Publication No. 1-254743 discloses that white titanium dioxide or white titanium dioxide or carbon black is blended with a means for improving the marking property of plastics by a YAG laser. In addition, JP-A-4-24645
No. 6 proposes that marking with good contrast is possible by adding carbon black and / or graphite having high thermal conductivity. However, the markings applied to these compositions have insufficient visibility and no clear markings have been obtained, and further improvement has been required.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide an industrially useful resin composition for laser marking. Particularly, a molded product having a black ground color is irradiated with a laser beam. Thus, it is to provide a composition capable of obtaining a clear white mark with high sensitivity and high visibility.

[0005]

That is, the present invention provides a resin composition for laser marking which comprises (A) 100 parts by weight of a thermoplastic resin and (B) 0.001 to 20 parts by weight of a lower titanium oxide. The object can be achieved by the thing.

The present invention will be described in detail below. The resin of the present invention is preferably a thermoplastic resin, and a thermosetting resin is unfavorable because the resin has a low fluidity at the time of laser irradiation, so that foaming due to decomposition is small and visibility is low. The thermoplastic resin used as the component (A) in the present invention is not particularly limited, and examples thereof include polyethylene terephthalate resin,
Any known thermoplastic resin such as polyester resin such as polybutylene terephthalate resin, aromatic polycarbonate resin, polyamide resin, polyolefin resin, styrene resin, polysulfone resin, polyether sulfone resin can be used. These resins may be used alone or 2
It is also possible to use a mixture of two or more species. Among these thermoplastic resins, in the present invention, aromatic polyester resins such as aromatic polycarbonate resins, polyethylene terephthalate resins or polybutylene terephthalate resins, polyamide resins, styrene resins are used alone or in combination of two or more. The aromatic polycarbonate resin is preferable.

The aromatic polycarbonate resin used in the present invention is produced by the reaction of a dihydric phenol and a carbonate precursor. Representative examples of dihydric phenols include 2,2-bis (4-hydroxyphenyl)
Propane [commonly known as bisphenol A], 1,1-bis (4-hydroxyphenyl) ethane, 1,1-bis (4
-Hydroxyphenyl) cyclohexane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 2,2-bis (4-hydroxy-3,5-dibromophenyl) propane, 2,2-bis (4-hydroxy-
Examples thereof include 3-methylphenyl) propane, bis (4-hydroxyphenyl) sulfide, bis (4-hydroxyphenyl) sulfone and the like. Preferred polyhydric phenols are 2,2-bis (4-hydroxyphenyl) alkane-based ones, particularly those containing bisphenol A as a main raw material.
Examples of the carbonate precursor include carbonyl halide, carbonate ester or haloformate,
Specific examples thereof include phosgene, diphenyl carbonate and dihaloformate of dihydric phenol. In producing the aromatic polycarbonate resin, the above dihydric phenols can be used alone or in combination of two or more. The obtained aromatic polycarbonate resins may be used as a mixture of two or more kinds. Further, an appropriate molecular weight regulator, branching agent, catalyst for accelerating the reaction and the like can also be used.

The polyethylene terephthalate resin used in the present invention is a polymer obtained by condensation reaction of terephthalic acid or its ester-forming derivative with ethylene glycol or its ester-forming derivative as a main raw material. It may be a copolymer in which part or part of the ethylene glycol component, usually 30 mol% or less, is replaced with another dicarboxylic acid, oxycarboxylic acid or diol. As the third component used in such a copolymer, for example, isophthalic acid, alkyl-substituted terephthalic acid, adipic acid, oxybenzoic acid, polymethylene-α,
ω-diols, neopentyl glycol, diethylene glycol and the like. The molecular weight of the polyethylene terephthalate resin is 0.4 to 1.2 as represented by the intrinsic viscosity measured at 25 ° C. using o-chlorophenol as a solvent. The polybutylene terephthalate resin used in the present invention is a polymer obtained by subjecting terephthalic acid or an ester-forming derivative thereof to tetramethylene glycol or an ester-forming derivative thereof as a main raw material to undergo a condensation reaction. It may be a copolymer in which part or part of the tetramethylene glycol component, usually 30 mol% or less, is replaced with another dicarboxylic acid, oxycarboxylic acid or diol. Examples of the third component used in such a copolymer include isophthalic acid, alkyl-substituted terephthalic acid, adipic acid, oxybenzoic acid, polymethylene-α, ω-diols, neopentyl glycol, diethylene glycol and the like. The molecular weight of the polybutylene terephthalate resin used in the present invention is ο.
-Intrinsic viscosity measured at 25 ° C using chlorophenol as a solvent of 0.6 to 1.3.

Examples of the polyamide resin used in the present invention include ring-opening polymerization products of cyclic lactams, polycondensation products of aminocarboxylic acids, and polycondensation products of dibasic acids and diamines. Specifically, nylon is used. 6, nylon 6
6, nylon 46, nylon 610, nylon 612,
Aliphatic polyamides such as nylon 11 and nylon 12,
Poly (meta-xylene adipamide), poly (hexamethylene terephthalamide), poly (hexamethylene isophthalamide), poly (tetramethylene isophthalamide)
And aliphatic-aromatic polyamides, and copolymers and mixtures thereof. Of these, nylon 46 is particularly preferable. As the nylon 46 resin, adipic acid or a derivative thereof is used as an acid component, and a polyamide obtained by a condensation reaction using tetramethylenediamine or a derivative thereof as an amine component is mainly targeted. A part of the diamine component may be replaced with another copolymer component.

The nylon 46 resin used in the present invention is
The intrinsic viscosity measured with m-cresol at 35 ° C. is preferably in the range of 0.80 to 1.90, more preferably 0.90 to 1.50. When nylon 46 having an intrinsic viscosity of more than 1.90 is used, the fluidity at the time of molding is poor, the gloss of the appearance of the resulting molded article is lost, and the mechanical and thermal characteristics vary greatly. Is not preferable. On the other hand, if the intrinsic viscosity is less than 0.80,
This causes a defect that the mechanical strength of the molded product is reduced.

Examples of the polyacetal resin used in the present invention include homopolymers, copolymers and block copolymers.

Examples of the polyolefin resin used in the present invention include polyethylene, polypropylene and poly-
4-methylpentene-1, and the like.

Examples of the styrene polymer used in the present invention include ABS resin, AES resin, polystyrene / AS resin, MBS resin and the like.

The polysulfones and polyether sulfones used in the present invention can be prepared by methods well known in the art, such as, for example, in a substantially anhydrous state with certain liquid organic sulfoxides or sulfone solvents. It is a substantially single-molar one-step reaction of an alkali metal double salt of a dihydric phenol with a dihalobenzenoid compound in the presence. The polymer can also be produced in a two-step process.
In this method, first, a dihydric phenol is reacted with an alkali metal double salt, an alkali metal hydride, an alkali metal hydroxide, an alkali metal alkoxide or an alkali metal alkyl compound in an initial reaction solvent to give an alkali in situ. Convert to metal salt. Alkali metal hydroxides are preferably used. The dialkali metal salt of the dihydric phenol is mixed and reacted with an approximately stoichiometric amount of the dihalobenzenoid compound after removal of the water present or formed to ensure a substantially anhydrous state.

The polymerization reaction is allowed to proceed at elevated temperature in the liquid phase of the organic sulfoxide solvent or sulfone solvent.

To ensure the high molecular weight polymer, the system must be substantially anhydrous, preferably less than 0.5 weight percent water in the reaction mixture.

The polymer has an intrinsic viscosity of about 0.4 to 1.5, measured at a suitable temperature in a suitable solvent depending on the particular sulfone, for example at 25 ° C. in methylene chloride. .

Low order titanium oxide used as component (B)
Then, the carbon black used conventionally has a yellowish color
While the marking is tinged, the white part of the marking
The chromaticity is remarkably high and high visibility marking is obtained.
You. Classified according to the manufacturing method or the difference in raw materials
You. For example, targeting titanium metal and titanium dioxide
Of the oxides of Ti and O in a stoichiometric manner.
There is a method of firing in an inert gas. in this way
Typical low order titanium oxide obtained by
Tan, Titanium ditrioxide, Titanium tripentoxide, etc.
Generally, Ti _nO_2n-1Expressed as (n = 1, 2, 3)
Be done. There is also a method of reducing titanium dioxide.
Low-order titanium oxide obtained by reducing titanium dioxide is
The oxidation number depends on the degree of reduction, and in general Ti
O_mIt is represented by (m = 1 to 1.99). Low order like this
Titanium oxide varies depending on its manufacturing method or raw material.
In the present invention, any low-order oxidized titanium is classified.
Can also be used. Both lower titanium oxides are collectively referred to as Ti
O_kIs preferable, k is preferably 1.00 to 1.86.
The blending ratio of this low-order titanium oxide depends on the heat of the component (A).
Low order titanium oxide is added to 100 parts by weight of the plastic resin.
001 to 20 parts by weight, particularly preferably 0.1 to 1
Parts by weight. The amount of low-order titanium oxide is 0.001
If the amount is less than 20 parts, sufficient marking cannot be performed.
If the weight is exceeded, the amount of heat generated by the laser increases and the resin
Thermal discoloration progresses, the marking color turns yellow, and the visibility is improved.
Deteriorate.

The resin composition used in the present invention may further contain a small amount of carbon black. The carbon black used is classified into furnace black, channel black, thermal black and the like depending on the production method, and acetylene black, ketjen black, oil black, gas black and the like depending on the raw material, but in the present invention, any of these is used. Can also be used. Particularly preferred are acetylene black, Ketjen black and the like, which have high conductivity. The blending ratio of this carbon black is the thermoplastic resin composition 10 which is the component (A).
It is 0.01 to 1 part by weight of carbon black with respect to 0 part by weight. When the blending ratio of carbon black to the blending amount of low-order titanium oxide becomes large, the amount of heat generated by the laser increases, the heat discoloration of the resin proceeds, the marking color changes to yellow, and the visibility deteriorates, so the amount used is limited.

The thermoplastic resin composition used in the present invention may be blended with a white or black colorant, but from the point of importance of the whiteness of the marking, a colorant other than white or black is used. It is better not to mix. Further, the thermoplastic resin composition may further contain an inorganic filler. There is no particular limitation on the shape of the inorganic filler to be blended,
It may be powdery, fibrous, or plate-shaped. Particularly preferred are glass fiber, glass powder, glass beads, talc, calcium carbonate, titanium white (titanium dioxide), silicon beads and the like. When these inorganic fillers are further compounded, the addition amount thereof is preferably 1 to 50 parts by weight, and more preferably 5 to 30 parts by weight, relative to 100 parts by weight of the component (A). Further, an effective expression amount of a heat stabilizer, a release agent, an ultraviolet absorber, a flame retardant and the like may be added within a range that does not impair the present invention.

Any method may be used to produce the resin composition for laser marking of the present invention. For example, a method in which a thermoplastic resin, low-order titanium oxide, and other additives as appropriate are sufficiently mixed using a mixing means such as a V-type blender, and then pelletized by a vent-type uniaxial ruder,
Prepare a mixture of thermoplastic resin, low-order titanium oxide, and other additives in advance with a powerful means such as a super mixer, and supply this from the first chute of a vent-type twin-screw ruder. The filler is appropriately supplied by a generally industrial method such as a method in which it is supplied from a second chute in the ruder, kneaded, and pelletized.

In the present invention, a clear white marking can be easily performed on a molded article made of such a resin composition by irradiating a desired position with a laser beam. In order to perform marking of a desired shape, for example, a method of scanning the surface of an object with a suitable spot of a laser beam, a method of forming a laser beam of a desired shape by masking the laser beam, and irradiating the surface of the object with the laser beam are desired. Can be mentioned. The type of laser used is not particularly limited, and carbon dioxide gas laser, ruby laser, semiconductor laser, argon laser, excimer laser, Y
Both AG lasers and the like are possible. A YAG laser is particularly preferable. The YAG laser has a wavelength of 1.06
Since it is μm, and its energy is hardly absorbed by the resin itself, the combustion and vaporization of the resin hardly occur. The oscillation mode may be continuous oscillation or pulsed oscillation, but a scan type Nd: YAG laser which is continuous oscillation using a Q switch is particularly preferable.

[0023]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited thereto. The marking conditions and evaluation method are as follows. <Marking condition> Device: Laser marker SL475E manufactured by NEC Corporation Current value: 19A Scan speed: 100mm / sec Bite size: 30μm <Evaluation method> A 7mm x 25mm rectangle is printed according to the above conditions and the marking mark Was observed with the naked eye.

The contrast of the marking property was evaluated by the difference in lightness (ΔL) between the surface of the molded product and the surface of the colored surface formed by laser light. The brightness difference is evaluated by Tokyo Denshoku Co., Ltd.
This was performed using a color analyzer TC-1800MK-II manufactured by KK.

The following abbreviations are used for the thermoplastic resin, low order titanium oxide, carbon black and inorganic filler used in the examples.

PC: Aromatic polycarbonate resin having a viscosity average molecular weight of 25,000 produced from bisphenol A and phosgene (Panlite L-12, Teijin Chemicals Ltd.)
50) PET; polyethylene terephthalate resin (Teijin Ltd.)
TR8580, Intrinsic viscosity 0.8) PBT; Polybutylene terephthalate resin (Teijin Ltd.)
TRB-H, intrinsic viscosity 1.07) ABS; styrene resin (Mitsui Toatsu Chemical Co., Ltd. UT
-61) Low-order titanium oxide; 13M Furnace Black manufactured by Mitsubishi Materials Corporation; MA-1 manufactured by Mitsubishi Kasei Kogyo Co., Ltd.
00 Ketjen Black; EC Ketjen Black International Co., Ltd. Titanium dioxide; Ishihara Sangyo Co., Ltd. Taipaque CR-9
3 Talc; manufactured by Nippon Talc Co., Ltd. Microace P-2

[Examples 1 to 8 and Comparative Examples 1 to 5] Table 1,
The compounding agents such as the thermoplastic resin described in 2 and the low order titanium oxide were compounded in a tumbler in the amounts described in Tables 1 and 2 (parts by weight), and pelletized at 280 ° C. in a 40 mmφ vented extruder. The obtained pellets were dried at 120 ° C. for 5 hours with a hot air circulation dryer, and the cylinder temperature was 290 ° C. with an injection molding machine [FANUC T-150D].
As a test piece for evaluation at a mold temperature of 90 ° C, 150 mm ×
A 150 mm × 3 mmt square plate was obtained. Next, the test piece was marked with a scanning Nd: YAG laser. The evaluation results are shown in Tables 3 and 4.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

[Table 4]

[0032]

As is clear from Tables 3 and 4, the composition of the present invention is very useful because it can produce a clear white marking with high visibility by irradiation with a laser beam.

Claims (2)

[Claims] 1. A resin composition for laser marking, which comprises 100 parts by weight of a thermoplastic resin (A) and 0.001 to 20 parts by weight of (B) a low-order titanium oxide. 2. The resin composition for laser marking according to claim 1, wherein the thermoplastic resin (A) is at least one thermoplastic resin selected from aromatic polycarbonate resins, aromatic polyester resins, polyamide resins and styrene resins. Stuff.