U.S. patent application number 09/780729 was filed with the patent office on 2002-10-24 for thermoplastic resin compositions for laser welding and articles formed therefrom.
Invention is credited to Hatase, Yoshiteru, Koshida, Reiko.
Application Number | 20020156161 09/780729 |
Document ID | / |
Family ID | 26877491 |
Filed Date | 2002-10-24 |
United States Patent
Application |
20020156161 |
Kind Code |
A1 |
Koshida, Reiko ; et
al. |
October 24, 2002 |
Thermoplastic resin compositions for laser welding and articles
formed therefrom
Abstract
Thermoplastic resin compositions are disclosed that incorporate
1:2 metallic azo complex dyes and are particularly suitable for
laser welding. These compositions include a variety of
thermoplastic resins such as polyamides and copolymers and blends
thereof. The compositions offer superior welding properties and
provide for the welding of articles identically colored with these
dyes.
Inventors: |
Koshida, Reiko; (Utsunomiya,
JP) ; Hatase, Yoshiteru; (Nara, JP) |
Correspondence
Address: |
E I DU PONT DE NEMOURS AND COMPANY
LEGAL PATENT RECORDS CENTER
BARLEY MILL PLAZA 25/1128
4417 LANCASTER PIKE
WILMINGTON
DE
19805
US
|
Family ID: |
26877491 |
Appl. No.: |
09/780729 |
Filed: |
February 9, 2001 |
Current U.S.
Class: |
524/190 |
Current CPC
Class: |
B29C 65/1635 20130101;
B29K 2995/002 20130101; B29C 66/7332 20130101; C08K 5/0041
20130101; B29C 65/1616 20130101; B29K 2101/12 20130101; B29C 65/00
20130101; C08L 77/00 20130101; B29K 2077/00 20130101; B29C 66/71
20130101; B29C 66/71 20130101; C08L 77/00 20130101; C08K 5/0041
20130101; B29C 66/43 20130101; B29C 66/7332 20130101; C08K 5/0091
20130101; C08K 5/0091 20130101; B29C 65/16 20130101; B29C 66/1122
20130101; B29K 2995/0027 20130101; B29K 2077/00 20130101 |
Class at
Publication: |
524/190 |
International
Class: |
C08K 005/23 |
Claims
1. A composition suitable for laser welding comprising a
thermoplastic resin and a 1:2 type metallic azo complex dye.
2. A themoplastic resin composition for laser welding comprising:
1) at least one thermoplastic resin; and, 2) a black colorant
having at least one of the metal azo complex dyes of the following
formulas: The formula [I] 11Wherein R.sup.39,R.sup.41,which may be
the same or different, are Cl, 12,or SO.sub.2R.sup.43, R.sup.44,
R.sup.45, which may be the same or different, are independently
hydrogen atom, liner or branched C1-C4alkyl, R.sup.43is linear or
branched C1-C4alkyl, R.sup.40, R.sup.42, which may be the same or
different, are hydrogen, liner or branched C1-C18alkyl group, liner
or branched C2-C18alkenyl group,sulfonamide group,carboxyl
group,mesyl group, hydroxyl group, C1-C18 alkoxy group,acethylamino
group,benzoylamino group,a halogen atom or
--CONH--R.sup.46,R.sup.46is functional group selected from
unsubstituted or substituted liner or branched C1-C18alkyl or
unsubstituted substituted C6-C18 aryl group, L.sub.1 and L.sub.2are
independently O or COO, (E).sup.+ are H.sup.+;cation of alkali
metal,ammonium ion, cations of organic amine including aliphatic
primary, secondary and ternary amines,quaternary ammonium ion.
,K.sup.3 is an integer,m.sup.3 is 0,1 or 2, M.sup.1 is a kind of
metals, preferably metals having coordination numbers of from 2 to
4, more preferably trivalent metal such as Cr, Fe, Cu; The formula
[II] 13wherein R.sup.30and R.sup.3 , which may be the same of
different,are Cl, 14SO.sub.2R.sup.32, or H, R.sup.33 and R.sup.34,
which may be the same or different, are independently hydrogen
atom, linear or branchedC1-C4alkyl, R.sup.32is linear or branched
C1-C4alkyl, L.sub.3 and L.sub.4are independently O or COO,
(D).sup.+is hydrogen ion, cation of alkali metals,ammonium
ion,cations of organic amine including aliphatic primary, secondary
and ternary amines,quaternary ammonium ion, K.sup.2 is an
integer,m.sup.2 is 0,1 or 2, M.sup.2 is metals of atomic numbers of
from 2 to 4 such as Zn,Sr,Cr,Al,Ti,Fe,Zr,Ni,Co,Mn,B,Si and Sn,
preferably metal of atomic numbers of 3 such asCr,Co,Cu,Ni,Al. B is
represented by formula 15wherein R.sup.35 and R.sup.37, which may
be the same of different,are Cl, 16,SO.sub.2R.sup.32,or H, R.sup.33
and R.sup.34 , which may be the same or different, are
independently hydrogen atom, linear or branchedC1-C4alkyl, and
R.sup.36 and R.sup.38, which may be the same or different, are
independently hydrogen atom, linear or branched C1-C18 alkyl,
carboxyl, hydroxyl,C1-C18 alkoxy, amino or halogen atoms.
3. The composition of claim 1 wherein said 1:2 type metallic azo
complex dye is selected from the group consisting of: 17Wherein R
is a residual group of a coupling agent, M is divalent or trivalent
metal, and A is hydrogen, aliphatic amine with 4 to 18 carbon
atoms, or alkylene oxide added amine; or formula (2) 18or
formula(3) 19
4. The composition of claim 2 wherein said 1:2 type metallic azo
complex dye is selected from formula (2) or formula (3) .
5. The composition of claim 2 wherein said 1:2 type metallic azo
complex dye is present in an amount of from 0.01 to 1% by weight
based upon the total weight of the composition.
6. The composition of claim 1 further comprising glass fiber or
glass flake.
7. The composition of claim 1 wherein said thermoplastic resin is a
polyamide resin.
8. The composition of claim 1 wherein said thermoplastic resin is a
polyamide copolymer.
9. The composition of claim 1 wherein said thermoplastic resin is a
blend of polyamide resins.
10. A shaped article of the composition of claim 1.
Description
FIELD OF THE INVENTION
[0001] The instant invention relates to thermoplastic resin
compositions incorporating organic dyes. More particularly, the
instant invention relates to such compositions used in the laser
welding of articles and wherein the dye is a metallic azo complex
dye.
BACKGROUND OF THE INVENTION
[0002] It is known in the art to join together articles of two
resins (one colored and opaque and the other colored and
transparent) by applying energy with laser beams. This is
accomplished by positioning the articles in contact with each
other, and transmitting a predetermined amount of laser beam energy
focused on the area of contact, thereby causing the junction
portion to be melted and joined together (known generally as "laser
welding"). Several advantages flow from laser welding. For example,
laser welding is widely perceived as a simple, labor saving
operation, with attendant improvements in productivity and
reductions in production cost. This technique is useful in various
applications including the preparation of molded articles suitable
for automotive applications.
[0003] Recent attention has been directed to laser welding using
blends of thermoplastic resins and colorants. The colorants
typically contain an organic dye or pigment to control the
conversion of laser energy to heat. In a conventional arrangement,
the laser beam penetrates through a transparent colored article,
positioned closest to laser beam source, and is then largely
absorbed in the opaque colored article. The latter article has a
relatively higher absorption coefficient in comparison with the
transparent article, and this is attributed to the use of an
appropriate amount of colorants. The net effect is that the area of
contact of the transparent and opaque articles is melted and the
surfaces are thereby joined together. See for example Japanese
Published (Koukoku) Patent No.62-49850, Japanese Published
(Koukoku) Patent No.5 (93)-42336.
[0004] Other resin composition associated with laser welding are
described in U.S. Pat. No.5,893,959, which discloses transparent
and opaque workpiece parts welded together by a laser beam along a
joining zone. Both parts contain black dye pigments such as carbon
black to cause them to offer a substantially homogenous visual
impression even after welding.
[0005] However, a difficulty associated with conventional
compositions used in laser welding is that when a laser beam is
transmitted through a first article (having laser beam transmitting
colorants) to a second article (containing laser beam absorbing
colorants), the two articles must have different transmission and
absorption coefficients. This unfortunately makes it difficult to
weld together articles having the same color. Moreover,
thermoplastic components may be blackened by the addition of carbon
black or nigrosine, as is commonly done in for example automotive
applications. However, carbon black and nigrosine cannot transmit a
laser beam with a main wavelength (1200 nm to 800 nm), such as
Nd:YAG laser and a diode laser.
[0006] Surprisingly, it has now been found that including a
specific weight percentage of 1:2 type metallic azo complex dye in
thermoplastic resin compositions such as polyamide resin
compositions used for laser-weldable molded articles results into
both the transparent and opaque articles for the laser beam having
the same color of black. This allows for a significantly improved
transmission coefficient for the near-infrared spectrum of the
laser beam, with excellent and balanced heat- resistance and
mechanical properties required in automobile application.
SUMMARY OF THE INVENTION
[0007] Improved compositions suitable for laser welding are
disclosed herein, comprising a thermoplastic resin and a 1:2 type
metallic azo complex dye.
[0008] Moreover, there are disclosed and claimed herein
themoplastic resin compositions for laser welding comprising:
[0009] 1) at least one thermoplastic resin; and,
[0010] 2) a black colorant having at least one of the metal azo
complex dyes of the following formulas:
[0011] The formula [I] 1
[0012] Wherein R.sup.39,R.sup.41,which may be the same or
different, are Cl, 2
[0013] ,or SO.sub.2R.sup.43, R.sup.44, R.sup.45, which may be the
same or different, are independently hydrogen atom, linear or
branched C1-C4alkyl, R.sup.43is linear or branched C1-C4alkyl,
R.sup.40, R.sup.42, which may be the same or different, are
hydrogen, linear or branched C1-C18alkyl group, linear or branched
C2-C18alkenyl group,sulfonamide group,carboxyl group,mesyl group,
hydroxyl group, C1-C18 alkoxy group,acethylamino group,benzoylamino
group,a halogen atom or --CONH--R.sup.46,R.sup.46is functional
group selected from unsubstituted or substituted linear or branched
C1-C18alkyl or unsubstituted substituted C6-C18 aryl group, L.sub.1
and L.sub.2 are independently O or COO,
[0014] (E).sup.+ are H.sup.+;cation of alkali metal,ammonium ion,
cations of organic amine including aliphatic primary, secondary and
ternary amines,quaternary ammonium ion.
[0015] ,K.sup.3 is an integer,m.sup.3 is 0,1 or 2,
[0016] M.sup.1 is a kind of metals, preferably metals having
coordination numbers of from 2 to 4, more preferably trivalent
metal such as Cr, Fe, Cu;
[0017] The formula [II] 3
[0018] wherein R.sup.30 and R.sup.31, which may be the same of
different, are Cl, 4
[0019] SO.sub.2R.sup.32, or H,
[0020] R.sup.33 and R.sup.34, which may be the same or different,
are independently hydrogen atom, linear or branched C1-C4alkyl,
[0021] R.sup.32is linear or branched C1-C4alkyl, L.sub.3 and
L.sub.4are independently O or COO, (D).sup.+ is hydrogen ion,
cation of alkali metals,ammonium ion,cations of organic amine
including aliphatic primary, secondary and ternary
amines,quaternary ammonium ion,
[0022] K.sup.2 is an integer,m.sup.2 is 0,1 or 2,
[0023] M.sup.2 is metals of atomic numbers of from 2 to 4 such as
Zn,Sr,Cr,Al,Ti,Fe,Zr,Ni,Co,Mn,B,Si and Sn, preferably metal of
atomic numbers of 3 such as Cr,Co,Cu,Ni,Al.
[0024] B is represented by formula 5
[0025] wherein R.sup.35 and R.sup.37, which may be the same of
different,are Cl, SO.sub.2R.sup.32, or H, 6
[0026] R.sup.33 and R.sup.34 , which may be the same or different,
are independently hydrogen atom, linear or branched C1 -C4alkyl,
and R.sup.36 and R.sup.38, which may be the same or different, are
independently hydrogen atom, linear or branched C1-C18 alkyl,
carboxyl, hydroxyl,C1-C18 alkoxy, amino or halogen atoms.
[0027] This dye may preferably be selected from any of formula (1)
7
[0028] Wherein R is a residual group of a coupling agent, M is
divalent or trivalent metal, and A is hydrogen, aliphatic amine
with 4 to 18 carbon atoms, or alkylene oxide added amine;
[0029] or formula (2) 8
[0030] or formula(3) 9
[0031] Other aspects of the invention are directed not only to the
improvement in laser weldability seen with the resin compositions
described and claimed herein, but also the articles formed
therefrom. This includes shaped articles formed from discrete
sections and subsequently welded together with the laser beam. The
invention is further directed to the method for actually welding
these articles together.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] The invention will become better understood upon having
reference to the drawings herein.
[0033] FIG. 1 is a view of articles of differing colors to be laser
welded in contact with each other and with a laser beam applied
thereto; and
[0034] FIG. 2 is a view of articles of identical colors to be laser
welded in contact with each other and with a laser beam applied
thereto.
DETAILED DESCRIPTION OF THE INVENTION
[0035] The resins utilized as the molded resins for laser welding
may be any resin as long as they are thermoplastic resins, but
polyamide resins and polyester resins are preferred from the point
of view of heat-resistance and transmitting property.
[0036] Polyamides useful in this invention include not only
conventional nylons, but also copolymers of amides and/or other
monomers and blends of different polyamides. The blends may include
other thermoplastic polymers and/or blends of the aforementioned
copolymers with a polyamide and/or blends of different copolymers
with or without thermoplastic polymers. Examples of polyamides
suitable for the practice of this invention are polyamide 6 or 6/6,
in which the addition of azo-metal complex dyes illustrate the
substantial and surprising increase in laser weldability without
sacrificing other important properties of the molded article.
Polyamide 6 is especially advantageous because its low rate of
crystallization results in an increased transmission coefficient
for laser beams with particular wavelengths but without any adverse
effect on required toughness and warpage. Further it is
advantageous in applications such as automobile parts with its
balanced range of heat-resistance and mechanical properties.
[0037] A wide range of the most common polyester molding
compositions useful for blending with colorants in the practice of
the present invention are known in the art and includes
polyethylene terephthalate homopolymers, polybutylene terephthalate
homopolymers, polyethylene terephthalate/polybutylene terephthalate
copolymers, polyethylene terephthalate/polybutylene terephthalate
mixtures, and mixtures thereof, although other polyesters can be
used as well, alone, in combination with each other, or in
combination with those polyesters listed above.
[0038] Azo-metal complex dyes suitable for use in this invention
vary widely and include any azo-metal complex. As used herein the
term "azo-metal complex dyes" refers to 1:2 type metallic azo
complex dyes. Illustrative of such useful dyes are azo-metal
complex dyes as identified above. Other useful azo-metal complex
dyes are those described in detail in U.S. Pat. No. 4,527,994 which
is incorporated by reference herein.
[0039] In the preferred embodiment of the invention, the azo-metal
complex dyes for use in the invention are those respectively having
the formula(2) as above or the formula (3) as above. Moreover, the
azo-metal complex dye is preferably present in amount of from 0.01
to 1% by weight, when the composition comprises polyamide 6 or
polyamide 66 as at least the major component of the polyamide resin
composition.
[0040] Azo-metal dyes of colors other than black and/or other dyes
of colors other than black, such as anthraquinone, perinone, or
quinophthalone dyes, can be also added to the composition of the
present invention for the purposes of appearance adjustment
providing such additional dyes are used in such amounts that they
do not harm the characteristic properties of the composition of the
present invention.
[0041] The composition of the present invention may also contain an
inorganic filler or reinforcing agent. These include, for example,
fibrous reinforcement such as glass fiber, glass flake, carbon
fiber, glass beads, talc, kaolin, wollastonite and mica. Glass
fiber or glass flake is particularly preferred. Glass fibers
suitable for use in the present invention are those generally used
as a reinforcing agent for thermoplastic resins and thermosetting
resins.
[0042] One or more optional compounds tailored for different
applications of the resin compositions of this invention can be
included in the composition according to the present invention.
Typically, additive compounds can include flame retardants, impact
modifiers, viscosity modifiers, heat resistance improvers,
lubricants, antioxidants and UV-and other stabilizers. The
polyamide resin composition of the present invention may have such
additive compounds in such amounts that they do not harm its
characteristic properties.
[0043] FIG. 1 best illustrates the problems associated with
conventional compositions used in laser welding. The laser beam 1
is applied and the energy is transmitted through the first article
2 to the second article 3 (containing laser beam absorbing
colorants). The surface 4 of the second article 3 having absorbed
the laser energy is thereby melted and pressed with the surface of
the first article 2. However, for this weld to form, the two
thermoplastic articles 2 and 3 must have different transmission and
absorption coefficients.
[0044] In contrast, the inventive technique illustrated in FIG. 2
allows for both articles 5 and 6 to be identical in color. The
effective use of the azo complex dyes in both articles 5 (colored
but transparent) and 6 (colored but opaque) provides that some
energy is absorbed at surface 7 (but not enough to
disadvantageously impact the integrity of the surface) and other
energy is absorbed at surface 8. The welding of the articles occurs
along surface 8, despite both articles being of identical
color.
[0045] In effect, the creative use of the metallic azo complex dyes
herein prepare the transparent colored articles for laser beam
treatment and achieve welding together with the opaque colored
article. Suitable opaque articles and their compositions are
described for example in DE-A-443208 1.
EXAMPLES
[0046] The present invention is illustrated by the following
examples and comparative examples.
[0047] Polyamide 6 was mixed with the colorants below in amounts as
shown in the table.
[0048] Dye-A: 1:2 type metallic azo complex salt dye having the
formula [2]
[0049] Dye-B: Sumiplast Black H3B
[0050] Dye-C:Nigrosine
[0051] Dye-D: carbon black
[0052] Dye-E: 1:2 type metallic azo complex salt dye having the
following formula [4] 10
[0053] Such colorants can be blended with the polyamide as neat
dyes or a master batch containing the dyes.
[0054] All samples contain 30% glass fibers, and the remainder of
each composition was polyamide.
[0055] The mixtures were melted and kneaded with an extruder to
provide pellets. The pelletized mixtures were injection-molded into
test bars and plates with an injection molding machine.
[0056] The properties were measured as follows:
[0057] Transmission Property
[0058] Transmittance of the samples with near-infrared laser beam
having wavelength of 1064 nm was measured with the molded plates
(3.2 mm thick) using a spectrometer (NIRS-6500 produced by Foss
NIRS Systems).
[0059] Heat Stability
[0060] Heat stability of the samples (ASTM type I: 3.2 mm thick)
were examined by aging such samples in an air-oven set at
150.degree. C. for 1000 hours and surface appearances of them were
visually inspected.
[0061] Tensile Strength and Elongation
[0062] Tensile strength and elongation were measured according to
ISO 527.
[0063] Laser Welding Test
[0064] The 60 mm.times.18 mm.times.1.5 mm test pieces were placed
so that 20 mm of each be overlapped. The overlapped area was
irradiated with Nd:YAG laser (Olion 510, 1064 nm continuous) set at
4W with 3 mm diameter for 2 seconds. Welding performance is
measured in laser welding the test pieces of the compositions set
forth in Table 1 with an opaque workpiece part for a laser beam
(lower test piece), being made of the reference composition with
black appearance:
1 Polyamide 6 69.4 wt % Glass fibers 30 wt % Dye C 0.5 wt % Dye D
0.1 wt %
[0065] As to laser weldability, in each of Example 1 through
Comparative Example 4, two resin parts that are respectively
transparent and opaque for such laser beams and formed of the
compositions indicated in the following Table 1 being welded were
judged by visual inspection.
2 TABLE 1 Examples Comparative Examples No. 1 2 3 1 2 3 4 Polyamide
6 (wt %) 69.9 69.8 69.8 70 69.9 69.5 69.8 Fiberglass (wt %) 30 30
30 30 30 30 30 Dye A (wt %) 0.1 0.2 0.17 Dye B (wt %) 0.1 Dye C (wt
%) 0.5 Dye D (wt %) 0.2 Dye E (wt %) 0.03 Transmittance (1064 nm)
(%) 45 45 46 47 23 <1 <1 Appearance Black Black Black Creamy
white Black Black Black Appearance after air-oven aging No No
change No Changed to -- Changed to No change change dark brown dark
brown change Laser weld results welded welded welded welded No No
No adhesion adhesion adhesion Tensile strength (MPa) 174 184 171
190 Elongation (%) 3.1 3.7 3.4 3.8
[0066] Black resins with 1:2 type metallic azo complex salt
exhibited equally black appearance as traditional black resins with
nigrosine or carbon black as used in the above mentioned Reference
composition but showed as high transmittance and welding capability
as a natural color resin. Moreover, black resins with 1:2 type
metallic azo complex salt retained good appearance after air-oven
aging which is required especially for automotive under-the-hood
parts. Other black resins as in Comparative Examples 2,3 and 4 can
not afford welding capability.
EXAMPLE 4
[0067] 400 grams of (unreinforced) Nylon 6 ZYTEL pellets (available
from E.I. DuPont de Nemours and Co.) were dried under vacuum at
120.degree. C., for more than 8 hours, then mixed with a mixture of
black metal azo complex dye A (represented by formula [2] )(0.67 g)
with yellow metal azo complex dye E represented by the formula [4]
(0.13 g) in a stainless tumble mixer with stirring for one hour.
The mixture was then injection molded to form the injection molded
test specimens (whose sizes are 48 mm.times.86 mm.times.3 mm) using
K50-C produced by Kawaguchi Steel K. K. and the cylinder
temperature was set to 250.degree. C. Mold temperature was
60.degree. C. Good and uniformly black appearance and surface gloss
without color shading of the specimens were observed.
EXAMPLES 5-11
[0068] Unreinforced Nylon 6 ZYTEL pellets (available from E.I.
DuPont de Nemours and Co.) were dried under vacuum at 120.degree.
C., for more than 8 hours, then mixed with a mixture of black metal
azo complex dye A (represented by formula [2]) with yellow metal
azo complex dye E represented by the formula [4] in amounts set
forth in Table 2 in a stainless tumble mixer with stirring for one
hour. The mixture was then injection molded to form the injection
molded test specimens (whose sizes are 48 mm.times.86 mm.times.3
mm) using K50-C produced by Kawaguchi Steel K. K. and the cylinder
temperature was set to 250.degree. C. Mold temperature was
60.degree. C. Good and uniformly black appearance and surface gloss
without color shading of the specimens were observed. Transmission
properties, appearance and surface gloss were measured by the
following test procedures:
[0069] (1) Transmission Properties
[0070] Transmittance (T) in the range of 400 nm to 1200 nm of the
test plates with laser beams having respective wavelengths of 950
nm(Semiconductor laser) and 1050 nm (YAG laser) was measured using
a U-3410 spectrometer producted by Hitachi with 60 .phi. sphere
photometer for wavelength from ultraviolet to nexr-infrared. The
ratio (TA) of transmission with 950 nm: transmission with 1050 nm
and the ratio (TB) of transmission with 1050 nm : transmission of
natural resin are determined and compared between the examples.
[0071] (2) Appearance and Surface Gloss
[0072] Appearance of the test plates were evaluated by measuring
Reflection Density (OD) of the test plates by Reflection Density
meter TR-927 produced by Macbeth. Test plates having higher OD
values are judged to have better surface smoothness and rich in
gloss.
[0073] (3) Hue Difference AE
[0074] Hue difference AE between the test plate and the reference
plate molded with a dye-mixed pellets prepared by 5 kg of Nylon 6
Zytel.RTM. pellets ( available from E.I. du Pont de nemours and
Company) being dried in a dehumifified dryer set at 80.degree. C.
for more than 4 hour and mixed with 5 grams of carbon black and 28
grams of nigrosine dye by the following the procedures of Examples
5 through 11 was determined and measured using a colorimeter
(produced by Juki, tarde name: JP 7000).
[0075] The results are set forth in Table 2.
3 TABLE 2 Example Example Example Example Example Example Example
Example 4 5 6 7 8 9 10 11 Polyamide 6 (g) 400 500 500 500 500 500
500 500 Dye A (g) 0.67 1 0.95 0.91 0.87 0.83 0.80 0.67 Dye E (g)
0.13 0 0.05 0.09 0.13 0.17 0.20 0.33 Transmission TA 0.43 0.43 0.43
0.43 0.43 0.43 0.43 0.49 TB 1.00 0.96 0.96 0.98 1.00 1.00 1.01 1.03
OD .DELTA.E 2.57 2.55 2.57 2.57 2.57 2.57 2.56 2.56 Hue difference
.DELTA.E -- 0.37 0.29 0.27 0.24 0.25 0.37 0.40
[0076] The resin compositions as in Examples 4 and 6 through 11,
with a mixture of black 1:2 type metallic azo complex dye with
yellow 1:2 type metallic azo complex dye, exhibit high transmitting
property in the near infrared region.
[0077] The compositions set forth in Table 2 provide little if any
difference in hue during laser welding with opaque articles made of
compositions comprising mixtures of carbon black and nigrosine
dyes. Hence, the compositions of these Examples enable two articles
to be welded without hue difference and achieve laser welding of
the two articles with a substantially homogenous visual
impression.
* * * * *