An improved adhesive is disclosed for the automated assembly and alignment of kinescopes and yokes. The adhesive consists of a polymer matrix and a filler. The polymer matrix comprises an isocyanate component, a polyol component comprising one or more polyols having an average functionality greater than 2.0 and an average hydroxyl equivalent of from about 2000 to about 2500, a chain extender, a suitable catalyst and, optionally, other ingredients such as an antioxidant. The inorganic or organic filler comprises from about 32 to about 60 percent by volume of the adhesive. The subject adhesive is blended into a slow-curing and a fast-curing formulation, which are applied to a portion of the gap between the kinescope and the yoke. The fast-curing adhesive allows the completed assembly to be rapidly withdrawn from the assembly apparatus, or robot, and maintains the alignment during curing of the slower-curing adhesive. When both compositions are fully cured, there is produced an excellent, durable bond.

This invention pertains to a kinescope-yoke assembly for a television 
receiver or video monitor bonded together with an improved adhesive. 
BACKGROUND OF THE INVENTION 
Automation and robotization of an assembly process in any industry is 
desirable for the improvement of productivity and for cost reduction. This 
is particularly true in a complex manufacturing process such as the 
manufacture of television receivers or video monitors. The present 
invention is concerned with the automation, in particular the 
robotization, of one step in this process, i.e. the assembly of the 
kinescope to the external magnetic deflection yoke (hereinafter "yoke"). 
In a television receiver or video monitor, the yoke, which is an assembly 
of coils, surrounds the neck portion of the kinescope, i.e. the cathode 
ray tube or picture tube. In the conventional method of assembling a yoke 
and kinescope, the yoke is positioned on the neck of the kinescope for 
maximum color purity and convergence and manually secured thereto with a 
clamp. The yoke is then tilted slightly with respect to the kinescope 
until maximum focusing is achieved and self-adhering rubber wedges are 
manually inserted between the yoke and the kinescope to maintain the 
correct tilt. These operations require about 0.75 man-hours to perform. 
It is readily apparent that an adhesive which would permit the assembly and 
proper relative alignment of the kinescope and the yoke by an automated 
process, particularly utilizing robotics, would represent a significant 
advantage in cost and time savings as well as improving the uniformity and 
performance of the assembled display. There is, however, a substantial 
list of critical criteria which an adhesive must meet in order to 
facilitate robotizing of the kinescope/yoke assembly process. 
First, the adhesive must have particular setting characteristics. A 
suitable adhesive cannot set instantly since that would not permit any 
final fine alignment of the kinescope relative to the yoke and would not 
permit transfer of the adhesive dispensing apparatus to the next assembly 
without clogging of the dispenser tubes. On the other hand, in order that 
the process can be cost effective, the adhesive must firmly set within 
about one minute so that the assembly apparatus, or robot, can release the 
assembly and rapidly engage the next. 
A suitable adhesive must be compatible with and adhere well to the various 
materials to be contacted in the assembly, i.e. magnetic wires, a glass 
funnel, plastic casings and the like. A suitable adhesive must also 
maintain excellent dimensional stability so that the alignment of the 
parts will not change to the detriment of convergence and color purity in 
the final product. It is necessary that the adhesive not undergo more than 
a two percent change in dimension on curing or over the service life of 
the assembled receiver or monitor. 
A suitable adhesive must be sufficiently thixotropic to maintain a uniform 
dispersion of the filler particles and, more importantly, to maintain the 
shape of the dispensed adhesive during curing in the space between the 
yoke and the kinescope which can vary between about 10 and 2000 mils. 
In addition to the foregoing, a suitable adhesive must be fire-resistant, 
shock resistant to 35 g of impact which might be encountered in shipping; 
able to withstand thermal cycling of from -25.degree. C. to 85.degree. C., 
which is the possible operating temperature range of a television set, and 
be reasonable in cost. The adhesives provided in accordance with this 
invention meet all of these required criteria. 
SUMMARY OF THE INVENTION 
A kinescope and yoke are affixed with a polyurethane adhesive consisting of 
a polymer matrix and a suitable filler. The polymer matrix comprises: from 
about 40 to about 50 percent by weight of an isocyanate component, from 
about 40 to about 50 percent by weight of a polyol component comprising 
one or more polyols having an average functionality greater than 2.0 and 
an average hydroxyl equivalent of from about 2000 to about 2500; from 
about 2.8 to about 5 percent by weight of a suitable chain extender; from 
about 0 to 2.5 percent by weight of one or more suitable catalysts; and 
minor amounts of additives such as coloring agents, antioxidants and the 
like. The filler component comprises one or more inorganic or organic 
fillers which comprise from about 32 to about 60 percent by volume of the 
total adhesive formulation.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to the FIGURE, there is shown a kinescope 10 comprising a glass 
envelope 12 having a faceplate or cap 14 and a tubular neck 16 connected 
by a funnel 18. The yoke 20 surrounds the neck 16 of the kinescope 10. The 
magnetic coils 22 in the yoke 20 subject the three electron beams 24 to 
magnetic fields thereby properly aligning them. The electron beams 24 are 
generated by an inline electron gun, not illustrated, in the neck 16 of 
the kinescope 10. Once the yoke 20 has been properly positioned so that 
the electron beams 24 are properly focused on a three-color phosphor 
screen on the faceplate 14, not illustrated, the subject adhesive is 
applied between the yoke 20 and the kinescope 10 at a predetermined number 
of spots around the circumference of the neck 16 at areas 26 and 28 to 
maintain the relative positions of the yoke 20 and the kinescope 10. 
In accordance with this invention, a kinescope and a yoke are bonded by an 
adhesive comprising: a polymer matrix consisting of an isocyanate 
component, a polyol component, a suitable chain extender, one or more 
catalysts and optionally, minor amounts of additives such as antioxidants, 
coloring agents and the like; and an inorganic or organic filler. 
The isocyanate component of the subject adhesives comprises one or more 
aliphatic or cycloaliphatic isocyanates containing at least two isocyanate 
groups. Suitable examples of this art-recognized group of compounds 
include: 2,4- or 2,6-toluene diisocyanate; diphenylmethane diisocyanate; 
1,5-naphthalene diisocyanate; 1,6-hexamethylene diisocyanate; 
4,6'-dicylohexylmethane diisocyanate; 4,6'-xylylene diisocyanate; 
isopherone diisocyanate; para-phenylene diisocyanate; 2,2,4- or 
2,4,4-trimethylhexamethylene diisocyanate, cyclohexyl diisocyanate; 
3,3'-tolidene-4,4'-diisocyanate; and 
3,3'-dimethyl-diphenylmethane-4,4'-diisocyanate. The polymer matrix of the 
subject adhesives contains from about 40 to 50, preferably from about 45 
to 48, percent by weight of the isocyanate component. 
The polyol component of the polymer matrix is suitably comprised of one or 
more polyols having an average hydroxyl functionality, i.e. the number of 
hydroxyl groups per molecule, greater than 2.0 and preferably, at least 
about 2.5. The polyols particularly suitable in the subject adhesives have 
a high molecular weight, and, therefore, an average hydroxyl equivalent of 
from about 2000 to about 2500. The hydroxyl equivalent is calculated by 
dividing the molecular weight of a compound by the number of hydroxyl 
groups it contains. The polyol component is one or, preferably, a mixture 
of di-, tri- and tetra-polyols having the requisite functionality and 
molecular weight. Suitable representatives of this art-recognized class of 
compounds include diols such as tetramethylene glycol, ethylene diol or 
hexamethylene glycol; triols such as 1,1,1-trimethylol propane or 
1,2,3-hexanetriol; tetrols such as erythritol or pentaerythritol; 
ether-type polyols which are adduct products of the above polyols with 
alkylene oxides having 2 to 5 carbon atoms, such as ethylene oxide, 
propylene oxide, isobutylene oxide and mixtures of such adducts; 
ester-type polyols which are condensation products of the above polyols 
with polycarboxylic acids such as glutaric, adipic or phthalic acids, 
caprolactone polyesters of the above polyols, and mixtures thereof. A 
particularly suitable polyol for the subject adhesives is a high molecular 
weight, ethylene oxide capped polymeric polyol available under the 
Trademark NIAX Polyol D-440 from the Union Carbide Company. The polymer 
matrix of the subject adhesives contains from about 40 to 50, preferably 
from about 40 to 45, percent by weight of the polyol component. 
The chain extender of the subject adhesives is generally a low molecular 
weight diamine or aliphatic diol or triol. Typical diamine chain extenders 
include 3,3'-dichloro-4,4'-diaminophenylmethane, methylene diamine, 
m-phenylene diamine and the like. Typical diol chain extenders include 
ethylene diol, 1,4-butane diol, 1,1,1-trimethylol propane, and the like, 
with ethylene diol being preferred. The chain extender may comprise 
combinations of compounds from either group. The chain extender functions 
in the subject adhesives to aid the dimensional stability of the cured 
resin. The polymer matrix of the subject adhesives contains from about 2.8 
to 5, preferably about 3.2 to about 4.5, percent by weight of the chain 
extender. 
Although the chain extender component of an isocyanate/polyol composition 
such as described herein is frequently not counted in determining the 
average functionality ratio of the polyol, it is important in terms of the 
subject adhesives that the average functionality be greater than 2.0, 
preferably at least about 2.5. Therefore, when the chain extender is a 
diol, the polyol component must contain sufficient tri- and 
tetra-functional compounds so that the chain extender content does not 
bring the average functionality below the desired level. 
The catalyst component of the subject adhesives comprises one or a mixture 
of compounds recognized as catalysts for isocyanate/hydroxyl reactions. 
Examples of suitable compounds include N,N,N',N'-tetramethylbutane 
diamine, triethylene diamine, dibutyl tin dilaurate, tin(II) octoate and 
the like. The polymer matrix of the subject adhesives contains from 0 to 
about 2.5, preferably from 0 to 0.25, or from 0.25 to 1.5, percent by 
weight of the catalyst component. The reason that the subject adhesives 
have two preferred ranges for the catalyst component will be detailed 
hereinafter. 
The filler component of the subject adhesives comprises one or more finely 
divided particulate inorganic and/or organic substances such as alumina 
trihydrate, silica, antimony oxide, chlorinated or brominated polymers and 
the like. In general, it is preferred to use a combination of fillers 
which strengthens the bond, maintains dimensional stability of the 
adhesive when it is applied between the kinescope and the yoke and imparts 
thixotropy to the adhesive. This latter characteristic is important in 
maintaining the distribution of the filler particles and overall 
uniformity of the adhesive, as well as assuring a uniform cure time when 
isocyanate and polyol component compositions are mixed. The filler should 
also impart fire-retardance to the assembly. In general, the subject 
adhesives contain from about 50 to 75 percent by weight of one or more 
fillers. However, these percentages could vary considerably depending on 
the density of the fillers used. Therefore, it is more important that the 
filler particles comprise from about 32 to about 60, preferably from about 
45 to about 50, percent by volume of the subject adhesives, regardless of 
the weight percent thereof. A preferred filler component comprises alumina 
trihydrate and fumed or colloidal silica in a volume ratio of about 15 to 
1. 
The subject adhesives may also contain conventional additives such as 
antioxidants, coloring agents and the like. Suitable antioxidants include, 
for example, phenols, phosphites, thioesters and amines. Suitable 
commercial antioxidants are hindered phenolic compounds such as 
tetrakis[methylene 
3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane, available 
under the tradename Irganox 1010 frm Ciba-Geigy, Inc. The total of such 
additives in the polymer matrix of the subject adhesives is typically not 
more than about 1 percent by weight, preferably from about 0.25 to 1 
percent by weight. 
The subject adhesives are prepared as two separate compositions, as is 
conventional. An isocyanate composition comprises the isocyanate component 
and a portion of the filler including a portion of the thixotrope. A 
polyol composition comprises the polyol component, the chain extender, the 
catalyst component, the remainder of the filler and other additives such 
as one or more antioxidants. The amount of filler in each composition may 
vary over a wide range depending on the thixotropy requirement and the 
requirement that there cannot be more filler in a given composition than 
can be readily wetted by the liquid ingredients therein. It is also 
preferred that the volume of the two compositions be approximately equal, 
regardless of whether there is a disparity in their weights. It is 
preferred to have a differentiating color additive in at least one of the 
compositions. 
The subject adhesives are preferably formulated into three compositions, 
i.e. an isocyanate composition and two polyol compositions which differ 
principally in the amount of the catalyst they contain. The catalyst 
content in fast-curing and comparatively slow-curing polyol compositions 
is preferably from about 0.25 to 1.5 and from 0 to about 0.25 percent by 
weight, respectively, based on the weight of the polymer matrix. These 
compositions are dispensed in equipment having the capability to blend the 
isocyanate composition alternately with each polyol composition. 
The fast-curing polyol composition, when mixed with the isocyanate 
composition, will cure in under one minute, preferably in about thirty 
seconds. The slower-curing polyol composition will produce a cured resin 
in under one hour, preferably in from about thirty to about sixty minutes. 
It is necessary that a sufficient bond strength be established by the 
curing of the first adhesive so that the assembly may be released within 
one minute in order that the automated process may be economically 
attractive. Subsequently, the blend of the isocyanate composition and the 
second polyol composition cures, thus completing the bond. 
A second important function of the mixture of the isocyanate composition 
and the slower-curing polyol composition is that it purges the dispensing 
apparatus to prevent clogging by the fast-curing mixture. The dispensing 
apparatus is programmed so that a yoke/kinescope assembly receives several 
injections of the fast-curing mixture followed by one or more injections 
of the slower-curing mixture, all of which are spaced around the 
circumference of the gap 26 and 28 between the neck 16 of the kinescope 10 
and the yoke 20. The slower-curing composition purges the dispenser of the 
fast-curing composition thereby preventing clogging. The adhesive may be 
applied either before or after the assembly has been aligned. It will be 
appreciated that the succeeding assembly will initially receive a small 
quantity of the slow-curing adhesive mixture during purging by the 
fast-curing adhesive mixture. This is in no way considered detrimental. 
When assembly is complete as described herein, the adhesive has formed 
what is conventionally referred to as a "green strength" cure. The 
yoke/kinescope assembly is then allowed to fully cure to maximum strength 
over about two days, thus forming an excellent, permanent bond which meets 
all of the criteria discussed above and which possesses exceptional shear 
strength and dimentional stability. 
Although the assembly and curing operations described herein are suitably 
carried out under ambient conditions, the final curing of the adhesive may 
be carried out in a shorter period of time by raising the temperature 
somewhat, e.g. to about 60.degree. to 100.degree. C. At these 
temperatures, final curing may require only one to two hours. 
The following Example further illustrates this invention, it being 
understood that the invention is in no way intended to be limited to the 
details described therein. In the Example, all parts and percentages are 
on a weight basis and all temperatures are in degrees Celsius, unless 
otherwise stated. cl EXAMPLE 1 
Component compositions for a polyurethane adhesive were prepared by 
blending the following formulations: 
______________________________________ 
Ingredient Parts 
______________________________________ 
Isocyanate Composition 
4,4'-Diphenylmethane 
92.2 
diisocyanate 
Alumina trihydrate 79.0 
Fumed Silica 3.0 
Total 174.2 
Polyol Composition 
NIAX D-440 82.0 
Ethylene Glycol 18.0 
Dibutyltin dilaurate 
1.5 
Triethylene diamine 
1.1 
Alumina Trihydrate 144.0 
Fumed Silica 1.0 
Color Pigment 4.0 
Total 251.6 
______________________________________ 
The two compositions, mixed in the weight amounts given, were equal in 
volume. The adhesive formed by combining equal volumes of these 
compositions cured in thirty seconds. The functionality of the polyol 
composition was 2.8. 
A similar composition containing only 0.1 part of dibutyltin dilaurate and 
triethylene diamine in the weight ratio of 4:3 cured in thirty minutes. 
A sample of the mixture of the isocyanate composition and the first polyol 
composition was uniformly applied to a production kinescope and a 
production yoke brought in alignment therewith. The assembly was marked to 
reference alignment and focus and held in place for thirty seconds. The 
bond produced surpassed minimum requirements for commercial television 
receivers in thermal stability, shock resistance, fire retardance and 
adherance. The dimensional stability of the bond, i.e. the deviation from 
alignment and focus, caused by curing of the adhesive, was 1.2 percent. 
CONTROL 
The fast-curing mixture of Example 1 was compared with two commercial 
adhesive preparations recommended for similar applications, i.e. Tyrite of 
Lord Chemical Co. and Pliogrip by Goodyear Chemicals, Inc. The chemical 
makeup of these preparations is not known with certainty. These 
compositions were applied and cured in accordance with the manufacturer's 
instructions. 
The shrinkage of all three compositions on a glass substrate was 
determined. The force required to separate a coating of each composition 
from a glass substrate and a wire substrate were also determined. A device 
made by Instron Textile Equipment was utilized to determine the strength 
of the bonds. The results are reported in the following Table. In each 
instance, it was attempted to pull the coating from the substrate. Because 
the area of the wire was known with certainty, the results for the wire 
are expressed in pounds per square inch. In contrast, the results for the 
glass rod are expressed only in pounds of pull force exerted. 
TABLE 
______________________________________ 
Glass Wire 
Adhesive Shrinkage (Pounds) (psi) 
______________________________________ 
Tyrite 2.5 percent 7.7 2210 
Pliogrip 2.9 percent 3.4 1900 
Example 1 1.2 percent 14.6 &gt;3000 
______________________________________ 
In the wire test with the composition of Example 1, the wire broke at a 
pull force of 3000 pounds per square inch leaving the coating intact. 
The superior bond provided by the subject adhesives is clearly demonstrated 
by these results.