JP2010095396A - Bismuth oxide-based additive for laser marking and production method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an additive for laser marking that enables marking excellent in blackness and contrast without causing undesirable coloring in a resin molded article. <P>SOLUTION: The additive for laser marking contains (a) an oxide of bismuth and (b) an oxide of at least one metal selected from gadolinium and neodymium. A preferable metal oxide is expressed by general formula of Bi<SB>(1-x)</SB>M<SB>x</SB>O<SB>y</SB>, wherein M represents at least one metal selected from gadolinium and neodymium and x and y are values satisfying respective relationships of 0.001<x<0.5 and 1<y<2.5. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an additive that can be used for laser marking to mark management information etc. on a resin molded article using laser light, that is, a manufacturing method thereof, and more specifically, the type and shape of the resin molded article Regardless of the present invention, the present invention relates to an additive for laser marking and a method for producing the same, which can make a suitable marking regardless of the above and can minimize undesirable effects such as coloring of the molded product by addition to the resin molded product.

  Laser marking is a marking method in which letters, numbers, trademarks, barcodes, etc. are printed or images are directly applied to a substrate using laser light.

For marking system with laser light,
(1) Because it is a non-contact marking method, marking can be performed at high speed on a substrate of any shape,
(2) Since no ink is used, the marking is excellent in abrasion resistance, difficult to tamper with, and since there is no volatilization of organic solvents, etc., it has a low environmental impact.
There is a big feature.

  As a result, in many industries, conventional ink systems are now moving to laser marking systems.

For laser marking, a CO ₂ laser, an Nd: YAG laser, or the like is used. In order to enable fine printing, an Nd: YAG laser is mainly preferably used.

  However, when laser marking is applied to a resin molding material with an Nd: YAG laser, in most of the main resin molding materials, marking with sufficient quality in terms of visibility and definition is often not obtained, and printing cannot be performed at all. Not a few resins.

  Therefore, an additive capable of improving the visibility of the laser marking is required for the resin molding material, and several additives for laser marking have been proposed.

  For example, Patent Document 1 discloses that particles of a mixed oxide of tin and antimony having a particle size of 10 to 70 nm are added to a molding material (base material) as an additive for laser marking.

Patent Document 2 discloses that a pigment coated with tin oxide doped with antimony, arsenic, bismuth, copper, gallium, germanium or their oxide is added to a flaky substrate such as mica flakes or SiO ₂ flakes for laser marking. Thermoplastics included as agents are described as being laser-markable.

  Patent Document 3 describes that a resin composition containing bismuth oxide can be marked black by irradiation with laser light.

  Patent Document 4 includes bismuth, Zn, Ti, Fe, Cu, Al, Zr, P, Sn, Sr, Si, Y, Nb. Laser markable compounds containing oxides with at least one additional metal selected from La, Ta, Pr, Ca, Mg, Mo, W, Sb, Cr, Ba and Ce are disclosed.

  However, when laser marking is applied to resin moldings containing the additives described in these patent documents, the effect of improving visibility is recognized to some extent, but marking properties such as marking blackness and contrast are still not satisfactory. Absent.

On the other hand, the inventors have found in Patent Document 5 that a complex oxide composed of copper and molybdenum changes color tone with high blackness upon irradiation with laser light. The composite oxide gives excellent laser marking properties to almost all resin moldings. However, since the complex oxide is colored yellow, the composite oxide has an undesirable problem that the resin molded product is slightly colored.
Special table 2007-512215 gazette Japanese National Patent Publication No. 10-500149 Japanese Patent No. 2873249 JP 2002-206062 A JP 2005-75674 A

  In view of the above problems, an object of the present invention is to provide an additive for laser marking that does not cause undesirable coloring of a resin molded product and enables marking with excellent blackness and contrast.

  Another object of the present invention is to provide a method for producing an additive for laser marking that does not cause undesirable coloring of a resin molded product and enables marking with excellent blackness and contrast.

  Still another object of the present invention is to provide a resin molding containing an additive for laser marking that does not cause undesirable coloring of the resin molding and enables marking with excellent blackness and contrast.

The additive for laser marking according to the present invention is:
a) an oxide of bismuth;
b) It contains at least one metal oxide selected from gadolinium and neodymium.

  The metal oxide is preferably represented by the following general formula.

Bi _(1-x) M _x O _y
(In the formula, M is at least one metal selected from gadolinium and neodymium, and x and y are values having a relationship of 0.001 <x <0.5 and 1 <y <2.5, respectively.)
The additive for laser marking according to the present invention is a dry processing of a raw material blend in which a compound that becomes an oxide by applying heat or an oxide that forms an oxide by adding heat in a predetermined ratio is processed by a pulverizer. Thus, it can be suitably produced by a method including a step of giving energy sufficient to cause a mechanochemical reaction to the raw material blend and a step of firing it at a temperature of 300 ° C. or higher.

  The present invention also provides a laser markable molded article containing the laser marking additive.

Examples of the laser used for laser marking on the molded product include a solid pulse laser, an excimer laser, a YAG: Nd laser, and a CO ₂ laser, and a YAG: Nd laser can be preferably used.

  Hereinafter, the present invention will be described in more detail.

  The laser marking additive according to the present invention comprising a) an oxide of bismuth and b) an oxide of at least one metal selected from gadolinium and neodymium, as demonstrated by the examples below. Bismuth oxide alone or bismuth and Zn, Ti, Fe, Cu, Al, Zr, P, Sn, Sn, Si, Y, Nb, La, Ta, Pr, Ca, Mg, Mo, W, Sb, Marking with a clearly superior blackness is possible compared to those containing at least one additional metal oxide selected from Cr, Ba and Ce. Furthermore, the color of this compound is either white or very pale yellow, so that it can be added with little coloring of the molding.

General formula, Bi _(1-x) M _x O _y (wherein M is at least one metal selected from gadolinium and neodymium, x and y are 0.001 <x <0.5, 1 <y <, respectively) In the preferable metal oxide represented by the formula (2), the marking property is deteriorated even when x and y in the formula are below or above the above range.

  The additive for laser marking according to the present invention enables higher-definition marking as the particle diameter is smaller. As for the particle diameter of the additive, the average particle diameter D50 is preferably 10 μm or less, and more preferably D50 is 1 μm or less.

  Next, the manufacturing method of the additive for laser marking by this invention is demonstrated.

A preferable production method for producing this additive is a dry pulverization of a raw material blend in which a compound which becomes an oxide by adding heat, or a compound which becomes an oxide by applying heat in a predetermined ratio, is pulverized by a pulverizer. By doing so, it includes a step of giving the raw material formulation sufficient energy to cause a mechanochemical reaction, and a step of firing it at a temperature of 300 ° C. or higher. Here, the “predetermined ratio” is, for example, a general formula, Bi _(1-x) M _x O _y (wherein M is at least one metal selected from gadolinium and neodymium, and x and y are each 0. 001 <x <0.5 and 1 <y <2.5.) The ratio of the raw material compounds necessary to obtain the metal oxide represented by:

  The raw material compound is not particularly limited as long as it is an oxide of an element constituting the additive, or a compound that becomes an oxide when heated. Examples of the bismuth source include bismuth oxide, bismuth oxychloride, bismuth nitrate, and bismuth hydroxide. Bismuth oxide, bismuth hydroxide and the like that do not generate harmful gas in the subsequent firing step are preferable. As the gadolinium source and the neodymium source, either of these oxides or a compound that becomes an oxide when heated can be used. For example, oxides, hydroxides, nitrates, chlorides, sulfates and the like of these metals can be used, and oxides and hydroxides are preferably used from the viewpoint of exhaust gas generation in the firing process.

  These raw material compounds are mixed at a predetermined ratio, and this mixture is subjected to dry pulverization with a pulverizer. By continuing the dry pulverization process, energy more than that required for pulverization is added to the raw material powder. As a result, it is known as mechanochemical reaction that amorphization (amorphization) from the surface of the raw material particles, strong bonding between the raw material particles, and addition of the composite are added to the raw material powder. It is a big feature. Progress of the mechanochemical reaction in the pulverization process is progress of amorphization by X-ray diffraction patterns before and after the pulverization process, exotherm in thermal analysis such as TG-DTA, DSC, disappearance and shift of endothermic peak, scanning electron microscope It is possible to observe and manage by means of element mapping using an energy dispersive X-ray analyzer associated therewith. Therefore, the pulverization time required to give the raw material mixture sufficient energy to cause a mechanochemical reaction in the pulverization step varies greatly depending on the pulverizer to be used. It can be determined using a combination of a plurality of methods. By going through the pulverization step and the firing step described later, an additive with remarkably excellent laser marking performance can be obtained.

  The grinder to be used may be a general-purpose one, and for example, a rolling ball mill, a vibration mill, a stone mill type mill, a disc mill, a pin mill, a medium stirring mill, a planetary ball mill, or the like can be used. In dry pulverization using these pulverizers, a small amount of liquid such as alcohol such as ethanol and propanol, polyhydric alcohols such as ethylene glycol, and alcoholic amines such as diethanolamine may be added as a pulverization aid.

  The performance as a laser marking additive can be remarkably improved by baking the pulverized material thus prepared at a temperature of 300 ° C. or higher, preferably 600 ° C. to 820 ° C. The firing atmosphere may be in the air. The performance of the additive obtained is not sufficient at 300 ° C. or lower, and the bismuth raw material is dissolved at 820 ° C. or higher. That is, the temperature range of 300 ° C. to 820 ° C. is a firing temperature range in which sufficient performance can be obtained as an additive for laser marking and can be pulverized by pulverization after firing described below.

  After firing, the fired product is pulverized by a general-purpose pulverizer. The pulverization method is not particularly limited, but wet pulverization is suitably applied to reduce the particle size of the additive. After the pulverization, the laser marking additive of the present invention is obtained by passing through drying and crushing steps.

  Next, a laser markable molded article containing the laser marking additive according to the present invention will be described.

  A typical example of the base material of the molded product is made of a synthetic resin, but the base material may be made of glass or ceramic that does not require a high processing temperature to cause deterioration.

  The kind of the synthetic resin is not particularly limited, and may be a thermoplastic resin or a thermosetting resin.

  Examples of thermoplastic resins include polyolefin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, polytetrafluoroethylene, acrylonitrile butadiene styrene, polyacryl methacrylate, polyamide, nylon, polyacetal, polycarbonate, polybutylene terephthalate, polyethylene Examples thereof include terephthalate, polyphenylene sulfide, polysulfone, polyimide, polyamide, a mixture thereof, and a copolymer based on these.

  Examples of thermosetting resins include phenolic resins, epoxy resins, melamine resins, urea resins, unsaturated polyester resins, alkyd resins, polyurethanes, thermosetting polyimides, and mixtures thereof.

  The additive for laser marking according to the present invention can be applied to a silicon skeleton polymer such as silicone.

  The shape and size of the substrate may be arbitrary. Examples thereof include members, containers, packages, electronic parts, cards, and coating compositions.

  The optimum amount of the laser marking additive in the molded product varies depending on the type of resin and the shape of the substrate. Therefore, the optimum addition amount is determined each time depending on the use conditions, but in the case of the additive for laser marking of the present invention, sufficient laser marking performance can be obtained from the addition amount of about 0.01% by weight at the minimum. When it is desired to further improve the blackness of the marking, or when the shape of the base material is a thin film such as a film or paint, the additive for laser marking of the present invention is used to impart sufficient laser marking performance. The necessary laser marking performance can be ensured by increasing the amount of addition. As a guide, the addition amount may be up to about 30% by weight at the maximum, and the addition amount may be increased within a range that does not affect other physical properties such as moldability.

  The additive for laser marking according to the present invention can be added to a substrate in the form of a combination with an inorganic or organic pigment and a dye for the purpose of coloring the substrate.

  Examples of inorganic pigments include white pigments such as titanium oxide, zinc oxide, antimony oxide, and zinc sulfide; extender pigments such as magnesium oxide and calcium oxide; iron oxide, ultramarine blue, bitumen, carbon black; titanium yellow, cobalt blue, etc. Color pigments such as complex oxide pigments; high luster pigments such as mica pigments coated with bismuth oxychloride, titanium oxide and the like.

  Examples of organic pigments include azo, azomethine, methine, anthraquinone, phthalocyanine, perylene, thioindigo, quinacridone, and quinophthalone pigments.

  Examples of the dye include anthraquinone series, metal complexes of azo dyes, and fluorescent dyes such as coumarin, naphthalimide, xanthene, and thiazine.

  Moreover, you may use together the additive generally used for processing of resin, such as a light stabilizer, antioxidant, a flame retardant, glass fiber, according to a use. Furthermore, it can be used in combination with known additives such as an ultraviolet absorber, an antistatic agent, and an electromagnetic wave shielding additive.

  By using the additive for laser marking of the invention, it is possible to provide a resin molded product that does not cause undesirable coloring of the resin molded product and enables marking with excellent blackness and contrast.

  Next, in order to specifically explain the present invention, some examples of the present invention and comparative examples for showing comparison with the examples will be given.

Example 1
Bismuth trioxide (198.6 g) and gadolinium trioxide (1.4 g) were placed in a rolling ball mill having an internal volume of 2 liters containing 2 kg of alumina balls having a diameter of 15 mm, and pulverized and mixed for 12 hours. The mixture was packed in a crucible and placed in an electric furnace and baked at 800 ° C. for 3 hours. The obtained fired product was wet pulverized with a rolling ball mill until the average particle size became 2 to 3 μm and dried to obtain a light yellow laser marking additive.

Example 2
A light yellow laser marking additive was obtained in the same manner as in Example 1 except that the raw materials were changed to 199.3 g of bismuth trioxide and 0.7 g of neodymium trioxide.

Comparative Example 1
Commercially available bismuth trioxide (average particle size 2.9 μm) was prepared.

Comparative Example 2
According to the method described in Patent Document 4, bismuth zirconate compound 267-024a was produced. That is, 95.7 g of bismuth trioxide and 4.3 g of zirconium oxide were mixed and melted in a crucible at 1000 ° C. for 10 minutes, and the obtained melt was then poured into a water bath. Then, the yellow laser marking additive was obtained through drying and pulverization.

Comparative Example 3
According to the method described in Patent Document 4, bismuth niobate compound 267-059a was produced. That is, 98.8 g of bismuth trioxide and 1.2 g of niobium pentoxide were mixed and heated in a crucible at 1000 ° C. for 10 minutes and 1093 ° C. for 10 minutes, and then the mixture was poured into a water bath. Then, after drying and grinding, a light yellow laser marking additive was obtained.

Comparative Example 4
According to the method described in Patent Document 4, bismuth zinc oxide compound 174-115e was produced. That is, 97.7 g of bismuth trioxide and 2.3 g of zinc oxide were mixed and heated in cordierite sagar at 749 ° C. for 65 hours. Thereafter, this mixture was pulverized to obtain a light yellow laser marking additive.

Comparative Example 5
According to the method described in Patent Document 4, bismuth titanate compound 174-013a was produced. That is, 97.2 g of bismuth trioxide and 2.8 g of titanium oxide were mixed and melted in a crucible at 1000 ° C. for 10 minutes, and the obtained melt was then poured into a water bath. Then, after drying and grinding, a light yellow laser marking additive was obtained.

Comparative Example 6
Strontium bismuth oxide compound 267-047a was produced according to the method described in Patent Document 4. That is, 87.1 g of bismuth trioxide and 12.9 g of strontium carbonate were mixed and melted in a crucible at 1000 ° C. for 10 minutes, 1093 ° C. for 10 minutes, and 1149 ° C. for 1 minute, and the resulting melt was then added. It was poured into a water bath. Then, the yellow laser marking additive was obtained through drying and pulverization.

Comparative Example 7
According to the method described in Patent Document 4, bismuth aluminate compound 267-022a was produced. That is, 99.1 g of bismuth trioxide and 0.9 g of aluminum oxide were mixed and melted in a crucible at 1000 ° C. for 10 minutes, and the obtained melt was then poured into a water bath. Then, the yellow laser marking additive was obtained through drying and pulverization.

Comparative Example 8
A light yellow laser marking additive was obtained in the same manner as in Example 1 except that the raw material was changed to 198.5 g of bismuth trioxide and 1.6 g of samarium oxide.

Comparative Example 9
A light yellow laser marking additive was obtained in the same manner as in Example 1 except that the raw materials were changed to 199.2 g of bismuth trioxide and 0.8 g of europium oxide.

Comparative Example 10
A light yellow laser marking additive was obtained in the same manner as in Example 1 except that the raw materials were changed to 199.2 g of bismuth trioxide and 0.8 g of dysprosium oxide.

Comparative Example 11
A light yellow laser marking additive was obtained in the same manner as in Example 1 except that the raw material was changed to 199.2 g of bismuth trioxide and 0.8 g of holmium oxide.

Comparative Example 12
A light yellow laser marking additive was obtained in the same manner as in Example 1, except that the raw materials were changed to 199.2 g of bismuth trioxide and 0.8 g of ytterbium oxide.

Comparative Example 13
A copper-molybdenum-based composite oxide described in Patent Document 5 (42-903A manufactured by Toago Material Technology Co., Ltd., average particle size of 1.5 μm) was prepared.

Evaluation Test With respect to the additives for laser marking obtained in Examples and Comparative Examples, the initial coloring property to the resin and the laser marking characteristics were evaluated by the following methods. The obtained results are summarized in Table 1.

(1) Initial colorability The above additives were dispersed in a high-density polyethylene resin at 0.025 PHR (parts by weight of the additive with respect to 100 parts by weight of the resin). This composition was dried at 70 ° C. for 3 hours, and then molded into a plate at 200 ° C. using an injection molding machine (manufactured by Nippon Steel Works, JSW, J505A11). The initial colorability of the resulting molded plate was visually evaluated according to the following criteria.

Initial colorability: Coloring degree when forming plate x dark coloring
○ Almost no coloring

(2) Laser marking characteristics
The molded plate prepared in (1) was irradiated with a YAG laser (manufactured by NEC Corporation, SL475K) to discolor the molded plate. The laser irradiation conditions were an input current of 20 A, a feed rate of 500 mm / second, and a Q-sw frequency of 5 kHz.

  The discolored portion was measured with a spectrophotometer (Daiichi Seika Kogyo Co., Ltd., Karakom C), and the blackness calculated from the L * value at that time was evaluated according to the following criteria.

Blackness of printing: Blackness of printing when irradiated with laser (expressed as an index where the blackness of Example 1 is 100)
× Almost imprintable (less than 20 for blackness 100 of Example 1),
△ blackness defect (20 or more and less than 80 with respect to blackness 100 of Example 1),
○ Good blackness (80 to less than 90 with respect to 100 blackness in Example 1),
◎ Excellent blackness (90 or more with respect to 100 blackness in Example 1)

Print fineness: Print fineness when irradiated with laser × Almost impossible to print,
△ The print is faint,
○ Good printing,
◎ Delicate printing

  As is apparent from Table 1, the molded product containing the additive for laser marking according to the examples is excellent in both initial colorability and laser marking characteristics.

Claims (4)

a) an oxide of bismuth;
b) An additive for laser marking, comprising an oxide of at least one metal selected from gadolinium and neodymium. The additive for laser marking according to claim 1, wherein the metal oxide is represented by the following general formula.
Bi _(1-x) M _x O _y
(In the formula, M is at least one metal selected from gadolinium and neodymium, and x and y are values having a relationship of 0.001 <x <0.5 and 1 <y <2.5, respectively.)   It is sufficient to cause a mechanochemical reaction by dry-processing with a pulverizer a raw material mixture in which the oxides of the elements constituting the above additives or the compounds that become oxides when heated are blended at a predetermined ratio. The method for producing an additive for laser marking according to claim 1 or 2, comprising a step of imparting sufficient energy to the raw material blend and a step of firing it at a temperature of 300 ° C or higher.   A molded article capable of laser marking, comprising the additive for laser marking according to claim 1.