CA1054373A - Process for treating a glass sheet adapted to be bent to a relatively sharp angle - Google Patents
Process for treating a glass sheet adapted to be bent to a relatively sharp angleInfo
- Publication number
- CA1054373A CA1054373A CA218,324A CA218324A CA1054373A CA 1054373 A CA1054373 A CA 1054373A CA 218324 A CA218324 A CA 218324A CA 1054373 A CA1054373 A CA 1054373A
- Authority
- CA
- Canada
- Prior art keywords
- sheet
- glass
- treating
- glass sheet
- coloring agent
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B18/00—Shaping glass in contact with the surface of a liquid
- C03B18/02—Forming sheets
- C03B18/04—Changing or regulating the dimensions of the molten glass ribbon
- C03B18/10—Changing or regulating the dimensions of the molten glass ribbon using electric means
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B23/00—Re-forming shaped glass
- C03B23/02—Re-forming glass sheets
- C03B23/023—Re-forming glass sheets by bending
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- C03B27/00—Tempering or quenching glass products
Abstract
ABSTRACT OF THE DISCLOSURE
A process for altering the residual stain remain-ing along the relatively sharp bend of a glass sheet resulting from the fusion of an electrically conducting glass frit suspension applied to the sheet along a path coincident with the line about which it is desired to sharply bend the sheet by passing electrical current therethrough to heat the glass adjacent thereto and effect the bend. The process includes interposing a strip of coloring agent between the glass sheet surface and the electrically conducting path lenthwise of the latter prior to electrically charging the same to form a resultant stain along the sharp bend of desired appearance.
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A process for altering the residual stain remain-ing along the relatively sharp bend of a glass sheet resulting from the fusion of an electrically conducting glass frit suspension applied to the sheet along a path coincident with the line about which it is desired to sharply bend the sheet by passing electrical current therethrough to heat the glass adjacent thereto and effect the bend. The process includes interposing a strip of coloring agent between the glass sheet surface and the electrically conducting path lenthwise of the latter prior to electrically charging the same to form a resultant stain along the sharp bend of desired appearance.
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Description
~L~59~373 Various glass bending techniques have been developed in recent years to accommodate the numeroua~ gla~is con~lgurations incorporated in ~he design of automobiles, such as the commcnly referred to "cap" and~"wrap-around" windshields and backlights.
Sometimes it i~ desirable ~o shape or form the glass compatible wl~h Ftyling features~found ln the ad~acent sheet metal panel ' in or'der to create the appearance of unity between the gla58 and the sheet metal. By wsy of example, it may be desirable to ~ I
provide a generally vertically extending sharp bend in a wlnd-. . . . , ~ 10 shield or backlight in continuation of a bead or molding strip on, the surface ~f the hood, roof panel or deck lid. At time~
' it~may al~o be des,irable to form a aharp bend in either a hori-zontal or vertical direction to effect wrap-ar,ound of the wind-ahield or backlight into the roof line of the vehicle or the ' sidé surfaces thereof. The formation of,~uch bend~, i.e., "~ Y-sha~ped bends'or bends having very ~mall radii of curvQtures, pose pro'blems in fabrication.
The glass bending methoda disclosed and clalmed in Uni~ed States patent~ No~. 3,762,903 and 3,762,904, provided a ', 20 solution to thes~ problem~ by utillYing an improved method for ~ angularly bandin~ one or more glas~ ~heet~ a~ a relatively ~harp ,; . , , 'I , ~ .
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' ~L~5~23'73 angle wiehOut adversely affectlng or dlstorting portions of the glass ad~acent the bend. To this end, an electrically conduct-ing path is formed on at leasL one surface of the glass sheet along a line about which lt i8 desired to bPnd the sheet. Subse-quently, an electrical potential is applied acro~s such path of a sufficient magnitude and for a time adequate to heat the sheet in the area immediately ad;acent said path to a temperature above the bending point of the glass, causing the glass sheet to ~ ~ ;
bend along the line of the electrically conducting path to form --the desired relatively sharp angle therein, The electrically conducting path i8 formed by apply~
ing to a~ least one surface of the glass, a conductive metallic paste, such as a silver paste material, along the line about which the bend is desired. While such a silver paste provides an efficlent electrically conductive path to provide the neces-sary localized heat~ng at the V-shaped bend, it adheres to the finished bent glass as an integral part thereof in the form of an elongated narrow stain or line having a yello~-brown appear-ance. This yellowish-brown stain is ob~ectionable from the standpoint of design and aesthetics) often presenting a harsh ; : :
contrast to the color or combination of colors employed on the automobile body, roof, etc., to detract from the general appear-ance thereof.
It i8 accordingly, an ob~ect of the pre~ent invention ;~
to provide a method for altering the appearance of the residual stain normally remaining along the relatively sharp angular bend in~a glas~ sheet as a result of the fusing of the electrically conductive metallic paste to the glass sheet initially applied thereto for localized heating.
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It i8 another obJect of this invention to interpose an undercoating of a coloring agent between the glass sheet sur-face and the foregoing electrlcally conductive paste material to alter the color of the resldual stain resulting from the fusion of the electrically conductive paste material to the glass sheet.
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It Ls a further obJect of the present invention to provide an undercoating for the foregoing electrically conductive paste material to preclude adherence of the latter to the glas~
interface. ~ ~
According to the present invention, there is provided ~ -a process for treating a glass sheet adapted to be bent to a relatively sharp angle, characterized by applying a band of coloring agent to at least one surface of the sheet along the line about which it i8 desired to bend the sheet, superimposing an electrically conducting path on said band lengthwise thereof heating the sheet to a temperature above the strain point of the glass but below the bending temperature thereof to fuse the coloring agent and electrically conducting path to the glass, `
and applying an electrical potential across said path of a suffi~
cient magnitude and for a time adequate to heat the sheet in the area immediately adJacent said path to a temperature above ~he -bendlng point of the glass causing said sheet to bend along said line and forming a stain ~herealong of desired appearance. -, ~ , , In the accompanying drawings: -~'~ Fig. 1 is a perspective view of an automobile includ-ing a bent glass back window or backlight produced in accordance i with the present invention;
i Fig. 2 is a perspective view of the backlight illus-trated in Fig. l; i~
j Fig. 3 is a sectional view taken along the line 3--3 - o~ Fi8. 2, showing the application oE an undercoa~ing beneath ¦ the electrically conducting path formed on the inner gurfsce of the backlight; ' Fig. 4 is a perspectlve view ~howing a glass sheet in position on a mold prior to initiation of the bending process;
- Fig. 5 iB a sectional view taken along the line 5--5 of Fig. 4; and Fig. 6 is a sectional view showing the glass ~heet supported on the mold upon the conclusion oE the bending proces~.
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,: . ,;, " , 11~5~373 ~eferring now in detail to the illustrative embodiment depicted in the accompanying drawing, there is shown in Fig. 1, a backligh~ 10 constructed in accordance with this invention as it appears from the outside of an automobile 11 in ~hich the backlight is mounted. The backlight 10 i9 comprised of a single glass sheet 12 of V-3haped configuration, belng bent along a straight line path indicated generally at 13 extending from one longitudinal edge sf the glass shee~ to the other, intermediate of and parallel to ~he transverse edges. The path or axis of the bend is defined by a fired electrically conducting frit line 14, hereinafter described in detail. While it will be conven-ient to de~cribe the method of this invention in connection with the formation of the backlight 10, lt should b~ understood that the principles o~ this invention are equslly applicable in the production of multiple layered sheets of glass, such a8 in the - ~ ;
conventional laminated construction of a windshield ~or example, ,, .
which generally comprises two sheets of glass and a non-brittle thermoplaatic interlayer, all bonded together to form an inte-gral 8 tructure.
The glaaa sheet 12 can be bent upon a ring or skeleton type mold indicated generally at 15 in Figs.~ 4 and 6. Molds of ., ~
this type are conventionally used for the bending of glass and have a peripheral rail 16, the top edge of which forms the shap- -ing surface for forming the gla~s. In ~ccordance with pre~ent-day practice, the rail 16 may be either a substantially single piece s~ationary member, as shown, or formed of articulated ~ec-tions which are moved during the bending of the glasa from an open glass recei~ing position to a closed~ flnal position.
Prior to po~itioning the glsss sheet on the bending 30 ~ mold 15, the electrically conducting frit line or re2istance el~ment 14 can be formed thereon in accordance with the method set forth in United States patent No. 3,762,903. If desired, a . ' .
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~L~5~37~
groove may be formed in one or both surfaces of the glass sheet 12 along the line of the sub~equent bend to facilita~e the bend-ing operation as set forth in detail in United States patent No.
39762,904, and the electrically conducting frit line 14 may then be formed in such~groove. While various materi21s m3y be u~ed to form these electrically conducting paths or resistance heat-ing element~ 14, preferred compositiona are compri~ed of con-ductive metal pa~tes. The~e materials, sometimes 8190 referred ?
i to a9 inks, are applied to the gla5~ sheet by conventional silk screen processes, painting, or other conveDtional uniform c03t-ing method~ and then are heated or fired to fuse the moterial to the sheet.
Typically, the paste3 compri~e conductive metal par-ticles, e.g., silver, glas~ f~it particles and organic binder~
and solvent. The glass frit, in addition to fusing the heating elements or strips to the sheet, al30 serves as an extender by ~ which the desired conductivity or resistivity ~ 8 achieved in the - paths or element~ 14. Thus, for a given cro~s sectional area of the elements, the silver, which imparts electrical conductivity thereto, can be diluted or extended with the glass frit to attain ~f, ' the deslred resistance which in turn determines the heat devel~
oped in the paths and glass immediately ad~arent thereto.
Although the conductive silver pa3tes are ideally suited for forming the electrically conducting paths, other conductlve metal pastes may be used, e.g., tho~e containing - gold, palladium, platinum and alloy~ thereof. In addition, air drying dispersions of conductive metals may be employed. One par-ticular material of this type which has been u~ed 3ucces~fully ~;~
is "Dag 422", a di~persion of silver plus graphite in a water carrier obtained from the Acheson Colloids Company, Port Huron, Michigan, U.S.A. Al~o, materials auch as electrically conduc~-ing t3pe~ which may or may not be removed after the bending step can be employed.
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lOS43'73 After the electrically conducting llne or resi3tance element 14 has been satisfactorily laid down, the glas~ sheet 12 ~s positioned on the bending mold by supporting the ~ransverse edges of the sheet on a shaping surface of the mold (Fig. 4).
Leads 17 and 18 from a suitable electrical power source (not shown~ are then placed in electrical contact with the line 14 through alligator cllps or the like 19 and 20, respectively, (Figs. 4 and 5).
Prior to supplying power to the leads 17 and 18, the bending mold and glass sheet carried thereby are preferably ~ ~
heated to a relatively high temperature, for example, above the ~ -strain point of the glass but below the bending point or the temperature at which the glass bends to any significant degree.
In this respect, temperatures in the range from approximately 900F. to 1150~. have been found satisfactory. The purpose of this preliminary heating, whlch may be accomplished by con-veying the mold through a furnace, is to fuse the metal-glass frit suspension to the glass, prevent the formation of permanent stresses in the glass, obviate the tendency of the glass to - ;
crack when subsequently heated locally along the electrically conducting line 14 to its bending ~emperature, and also to -~ ~
enable the accomplishment of this latter step within a time ~ ~ -acceptable frsm a commercial standpoint and wlth the use of a reasonable amount ~f electrical energy.
Upon the glass sheet reaching the desired over-all temperature, power is supplied to the leads 17 and 18 and con-sequently ~o the resis~ance element 14. This ln turn heats the glass sheet immediately adjacent resistance element 14 to a tem-perature above the bending temperature of the glass, for example, above approximately 1200F., at which time the sheet bends sharply along the path 13 and settles by gravity into the gen-erally V-shaped configuration illustrated in Fig. 6. The sheet is then allowed to cool at room temperature.
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1~5~373 ~ -A8 a result of the preheating of the glass sheet prior ~o the application of power ~hrough the elec~r~cally conducting path, thP silver paste material forming the latter adheres to the glass sheet and forms an objectionable yellow-brown stain thereon extending longitudinally of the bend.
It is desirable that such stain be at least altered to obtain a color pattern less ob~ectlonable from the standpoint of aesthet~
ics and more compatible with the color combinations of the auto-mobile body so as to enhance the general appearance of the auto-~, ...
mobile.
It has been found that the application of a suitablecoloring agent as an undercoating or substrate for the electrical-ly cDnducting silver paste material serves to alter the residual silver stain sufficiently to yield a more compatible color wlth automobile body design requirements. To this end, and in ac-cordance with this invention, prior to forming the electrically -conducting path or resistance element 14 on the glass surface9 a ;;
coloring agent is applied to at least one surface of the glass sheet 12 along a strip or band 21 ~Fig. 3) upon which the elec- ;~
trically conducting path will be formed and about which it is desired to bend the shee~. Whlle various materlals, such as blue, red and green pigments and various shades the~eof, may be used to form this undercoating, preEerred compositlons comprise ~
pure black pigments and mixtures of pure black pigments and black - ; ;
enamels, i. e., black pigments containing a minor percentage of frit. These materials can be applied ~o the glass sheet surface ;~
by conventional silk screen processes, painting or other known . : , .
roating processes and then allowed to dry at room temperature.
A preferred specific coloring agent, which has yield-.: . .
ed good results, is a fritless, pure black pigment composition sold by Drakenfeld Company, a division of Hercules Incorporated, ~-Washington, Pennsylvania, U.S.A., under the designation of - .
~ 7 '~ ,~ ' -, ' .. .. ~ . . . .
59~3~73 Drakenfeld 1795 Black which i~ a composition comprised of ap-pro~imately 30% by weight of chrome oxide, 32% by weight of cobalt oxide, and 382 by weight of iron oxide. Thls composition is employed in an oily mixture of pine oil and resln sold under the tradename of Drakenfeld 900 to form a mixture designated "Drakenfeld 1795 Black Oxlde in 900 Oil".
AB a specific example of altering the residual stain remaining along the Y-shaped bend in a ~inlshed glass sheet as a result of the firing of the conductive metallic paste initial-ly applied thereto for localized heating in accordance with the method of this invention, a glass sheet of nominal 0.235 inch thickness was procured. A uniform coating of a fr~tless pure black pigment, such as that referred to above as Drakenfeld ;~
1795 Black Oxide in 900 Oil, was applied by a silk screen print-ing process in a band or strip having a width of one-half inch to one surface of the glass sheet along the line abou~ which the ; ~;~
glass sheet was to be bent, the band ex~ending in~ermediate the opposite edges of the sheet and parallel thereto. After the `
band of pigment dried at room temperature, a silver composition comprised of abou~ 85% by weight of conductive silver particles, and the remainder composed of solvent, binder and frit, marketed by E. I. duPont de Nemours and Company, Wilmington, Delaware, U.S.A., under the designation "8966", was then superimpo3ed in ~ ;
a width of .120 inch on the band of black pigment lengthwise thereof by a conventional silk screen printing process.
This sheet was supported at the two opposite or transverse edgee only on a mold and heated in a furnace set to a temperature of 1150F. During this heating, the finely divided metal ceramic frit fused onto tha glass surface. The glass and "
integral frit line were then allowed to cool to room temperature and electrical connections such as those shown in Figs. 4, 5 and 6 were made to the frit line and the mold supported sheet again , .::
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:~, ~L~54373 placecl in the furnace and heated to a temperature of 1150F.
When this temperature was obtained, electrical energy was sup-plied to the frit line, and more particularly, a current of 16 ampere~ was passed therethrough. This current was supplied for approximately one minute at which time the sheet had assumed a generally V-shaped appearancP, the bend occurring at and along the frit line or electrically conducting element 14. The sheet was then removed from the. furnace and cooled quickly to produce a tempered structure. ~;
It should be noted that it is not nece~sary that the sheet be allowed to cool down aEter firing of the frlt and then ;
reheated for the bending operation. The electrical connections may be made prlor to the firlng step, which firing step can be accomplished during preheating of the sheet to fuse the metal-ceramic frit onto the glass surace.
After the finished glass sheet had cooled sufficient~ ~ ~
ly, only that por~ion of the black oxide pigment directly beneath -~ -the silver paste material, indicated at 21a in Flg. 3, adhered to the glass surface and the remainder, shown in dotted outline, was readily removed as by wiping, for example. This yielded a ~ -glass sheet product having a long, relatively narrow line along the sharp bend which appeared white on the surface to which the electrically conductive paste material was applied and black on the opposite surface, i.e., the glass side of the sheet O Also , . -' it was found that vigorous rubbing would remove all traces of the silver paste material, even though it initially contained ;
glass frit~ resulting in a line which appear~d black when view0d ~: .
from both sides of the finished glass product and is especially desirable in some applications.
Since the coloring agent di~posed outwardly of the marginal edges of the frit line is easily removed, the strip 21 - of coloring agent can be quickly applied in a relatively wide band without special regard to lndexing, i.e., accurate alignment !~
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~II;IS~373 of its marginal edges with those of the subsequently applied re~istance elen-ent 14. Thls saves time and becomes especially advantageous in a ma3s production operation.
Another conductlve paste material which was success-fully employed in combination with the pure black pigment des-cribed above was a fritless, conductive silver paste preparation comprlsed of approximately 85% by weight of silver pal;ticles, the remainder consisting of a suitable solvent and binder, marketed by E. I. DuPont de Nemours and Company under the desig-10 nation "9105". It wa~ found that the utilization of a fritless silver paste material a~ the electrlcally conductive path 0n-ables the residual ~ilver stain ~o be completely removed, thu~
leaving only a black line visible on the opposite surfaces of : the finished gla~s product, which ha3 beeD found desirable in many design applications.
While the pure black oxide pigment de73cribed above i9 preferable, it should be understood that the black pigments :, containing frit can be successfully employed as colorln~ agents in carry~ng out the method of the pre~ent invention. One such .
`~ 20 coioring agent is available under the tradename "Drakenfeld 24-339" in 175 oil. This is a black pigment -- glass frit com-positlon or enamel containing approximately 10% by weight of gla~s frit. The Drakenfeld 24-339 composi~tlon and Drakenfeld 1795 pure black pigment composition were blended in the follo~7-ing ratios: 10/90; 25t75; and 50/50. These blended compo~ttions ~, , .
were applied, such a7 by suitable F7ilk screen prlnting proces3e3 for example, in a one-half inch wide band acros77 the gla373 sheet.
After beine dried at room temperature, a silver paste prepara-- tion, identified a3 duPont "8966'7~ W~8 superimposed on the band .: . .
30 as a line llaving a width of .120 inch extending lengthwis2 of the band .,"
- 10 _ ' ~C~5~373 After firing the electrically conductive material to effect the relatively sharp bend as de~cribed above, it was found that the 10/90 a~d 25/75 mixtures fused to the gla~ only in the area beneath ~he electrically conductive path as defined by the silver paste material. The excess of the 10/90 mixture, i.e., those portions disposed outwardly beyond the marginal edges of the silver paste line could be readily removed, as by wiping for e~ample, while removal of the ex~ess 25J75 mixture required slightly more effort. In both instances, the sllver electrically conductive material adhered to the glaa8 surface which appeared as a black line when viewed from the glass alde, l.e., the surface opposite of that to which the electrically conductive mate~ial was applied and white when viewed from the opposite side oi the gla~s. -~
All of the 50/50 mixture fused to the glass, creating a relatively wide band across the surface of the finished gl~s~
prcduct. Thus, the lesser the percentage of frit contained in j -~ the coloring agent undercoating, the lesser the pos~lbillty of adherence to the glass with consequent easier removal of the exce~s portions of the coloring agent.
From the foregoing, it is apparent that the ob~ects of the invention have been fully accomplished. By interposing an undercoating of coloring agent between ~he electrically conduc- ;
tive paste ma~erial and the ~urface o the glasa sheet, the un-desirable color of the residual stain resulting from the firing thereo can be altered in accordance with optically acceptable ~
specification~ without adversely affecting the appear~nce o the windshield or backlight or obstructing visibility therethrough.
It should be u=derstood that when lt ia deslred to apply elec-trically conducting paths to the opposlte surfaces of a gla~s sheet, or lnto a groove formed thP~rein, the coloring sgent al90 .
would be appl~ed to such oppoaite aurface~ or into such groo~e, , .
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1~5~373 re~pecti~ely~ as a substrate or undercoating for the elertrically conduccive materlsl forming ssid p~ths, ~f .~ . , ~ :.
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Sometimes it i~ desirable ~o shape or form the glass compatible wl~h Ftyling features~found ln the ad~acent sheet metal panel ' in or'der to create the appearance of unity between the gla58 and the sheet metal. By wsy of example, it may be desirable to ~ I
provide a generally vertically extending sharp bend in a wlnd-. . . . , ~ 10 shield or backlight in continuation of a bead or molding strip on, the surface ~f the hood, roof panel or deck lid. At time~
' it~may al~o be des,irable to form a aharp bend in either a hori-zontal or vertical direction to effect wrap-ar,ound of the wind-ahield or backlight into the roof line of the vehicle or the ' sidé surfaces thereof. The formation of,~uch bend~, i.e., "~ Y-sha~ped bends'or bends having very ~mall radii of curvQtures, pose pro'blems in fabrication.
The glass bending methoda disclosed and clalmed in Uni~ed States patent~ No~. 3,762,903 and 3,762,904, provided a ', 20 solution to thes~ problem~ by utillYing an improved method for ~ angularly bandin~ one or more glas~ ~heet~ a~ a relatively ~harp ,; . , , 'I , ~ .
:~: . . .:, , : ~:
' ~L~5~23'73 angle wiehOut adversely affectlng or dlstorting portions of the glass ad~acent the bend. To this end, an electrically conduct-ing path is formed on at leasL one surface of the glass sheet along a line about which lt i8 desired to bPnd the sheet. Subse-quently, an electrical potential is applied acro~s such path of a sufficient magnitude and for a time adequate to heat the sheet in the area immediately ad;acent said path to a temperature above the bending point of the glass, causing the glass sheet to ~ ~ ;
bend along the line of the electrically conducting path to form --the desired relatively sharp angle therein, The electrically conducting path i8 formed by apply~
ing to a~ least one surface of the glass, a conductive metallic paste, such as a silver paste material, along the line about which the bend is desired. While such a silver paste provides an efficlent electrically conductive path to provide the neces-sary localized heat~ng at the V-shaped bend, it adheres to the finished bent glass as an integral part thereof in the form of an elongated narrow stain or line having a yello~-brown appear-ance. This yellowish-brown stain is ob~ectionable from the standpoint of design and aesthetics) often presenting a harsh ; : :
contrast to the color or combination of colors employed on the automobile body, roof, etc., to detract from the general appear-ance thereof.
It i8 accordingly, an ob~ect of the pre~ent invention ;~
to provide a method for altering the appearance of the residual stain normally remaining along the relatively sharp angular bend in~a glas~ sheet as a result of the fusing of the electrically conductive metallic paste to the glass sheet initially applied thereto for localized heating.
:
It i8 another obJect of this invention to interpose an undercoating of a coloring agent between the glass sheet sur-face and the foregoing electrlcally conductive paste material to alter the color of the resldual stain resulting from the fusion of the electrically conductive paste material to the glass sheet.
_ .,; : .
.:. , .
,,-~ :' ..
... . .
It Ls a further obJect of the present invention to provide an undercoating for the foregoing electrically conductive paste material to preclude adherence of the latter to the glas~
interface. ~ ~
According to the present invention, there is provided ~ -a process for treating a glass sheet adapted to be bent to a relatively sharp angle, characterized by applying a band of coloring agent to at least one surface of the sheet along the line about which it i8 desired to bend the sheet, superimposing an electrically conducting path on said band lengthwise thereof heating the sheet to a temperature above the strain point of the glass but below the bending temperature thereof to fuse the coloring agent and electrically conducting path to the glass, `
and applying an electrical potential across said path of a suffi~
cient magnitude and for a time adequate to heat the sheet in the area immediately adJacent said path to a temperature above ~he -bendlng point of the glass causing said sheet to bend along said line and forming a stain ~herealong of desired appearance. -, ~ , , In the accompanying drawings: -~'~ Fig. 1 is a perspective view of an automobile includ-ing a bent glass back window or backlight produced in accordance i with the present invention;
i Fig. 2 is a perspective view of the backlight illus-trated in Fig. l; i~
j Fig. 3 is a sectional view taken along the line 3--3 - o~ Fi8. 2, showing the application oE an undercoa~ing beneath ¦ the electrically conducting path formed on the inner gurfsce of the backlight; ' Fig. 4 is a perspectlve view ~howing a glass sheet in position on a mold prior to initiation of the bending process;
- Fig. 5 iB a sectional view taken along the line 5--5 of Fig. 4; and Fig. 6 is a sectional view showing the glass ~heet supported on the mold upon the conclusion oE the bending proces~.
J'' _3_ ,,,-: . :, ,: , -, . . - . :
,: . ,;, " , 11~5~373 ~eferring now in detail to the illustrative embodiment depicted in the accompanying drawing, there is shown in Fig. 1, a backligh~ 10 constructed in accordance with this invention as it appears from the outside of an automobile 11 in ~hich the backlight is mounted. The backlight 10 i9 comprised of a single glass sheet 12 of V-3haped configuration, belng bent along a straight line path indicated generally at 13 extending from one longitudinal edge sf the glass shee~ to the other, intermediate of and parallel to ~he transverse edges. The path or axis of the bend is defined by a fired electrically conducting frit line 14, hereinafter described in detail. While it will be conven-ient to de~cribe the method of this invention in connection with the formation of the backlight 10, lt should b~ understood that the principles o~ this invention are equslly applicable in the production of multiple layered sheets of glass, such a8 in the - ~ ;
conventional laminated construction of a windshield ~or example, ,, .
which generally comprises two sheets of glass and a non-brittle thermoplaatic interlayer, all bonded together to form an inte-gral 8 tructure.
The glaaa sheet 12 can be bent upon a ring or skeleton type mold indicated generally at 15 in Figs.~ 4 and 6. Molds of ., ~
this type are conventionally used for the bending of glass and have a peripheral rail 16, the top edge of which forms the shap- -ing surface for forming the gla~s. In ~ccordance with pre~ent-day practice, the rail 16 may be either a substantially single piece s~ationary member, as shown, or formed of articulated ~ec-tions which are moved during the bending of the glasa from an open glass recei~ing position to a closed~ flnal position.
Prior to po~itioning the glsss sheet on the bending 30 ~ mold 15, the electrically conducting frit line or re2istance el~ment 14 can be formed thereon in accordance with the method set forth in United States patent No. 3,762,903. If desired, a . ' .
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~L~5~37~
groove may be formed in one or both surfaces of the glass sheet 12 along the line of the sub~equent bend to facilita~e the bend-ing operation as set forth in detail in United States patent No.
39762,904, and the electrically conducting frit line 14 may then be formed in such~groove. While various materi21s m3y be u~ed to form these electrically conducting paths or resistance heat-ing element~ 14, preferred compositiona are compri~ed of con-ductive metal pa~tes. The~e materials, sometimes 8190 referred ?
i to a9 inks, are applied to the gla5~ sheet by conventional silk screen processes, painting, or other conveDtional uniform c03t-ing method~ and then are heated or fired to fuse the moterial to the sheet.
Typically, the paste3 compri~e conductive metal par-ticles, e.g., silver, glas~ f~it particles and organic binder~
and solvent. The glass frit, in addition to fusing the heating elements or strips to the sheet, al30 serves as an extender by ~ which the desired conductivity or resistivity ~ 8 achieved in the - paths or element~ 14. Thus, for a given cro~s sectional area of the elements, the silver, which imparts electrical conductivity thereto, can be diluted or extended with the glass frit to attain ~f, ' the deslred resistance which in turn determines the heat devel~
oped in the paths and glass immediately ad~arent thereto.
Although the conductive silver pa3tes are ideally suited for forming the electrically conducting paths, other conductlve metal pastes may be used, e.g., tho~e containing - gold, palladium, platinum and alloy~ thereof. In addition, air drying dispersions of conductive metals may be employed. One par-ticular material of this type which has been u~ed 3ucces~fully ~;~
is "Dag 422", a di~persion of silver plus graphite in a water carrier obtained from the Acheson Colloids Company, Port Huron, Michigan, U.S.A. Al~o, materials auch as electrically conduc~-ing t3pe~ which may or may not be removed after the bending step can be employed.
.
: .~: . .. .. .
.... . .. ..
:~: . . .
.
lOS43'73 After the electrically conducting llne or resi3tance element 14 has been satisfactorily laid down, the glas~ sheet 12 ~s positioned on the bending mold by supporting the ~ransverse edges of the sheet on a shaping surface of the mold (Fig. 4).
Leads 17 and 18 from a suitable electrical power source (not shown~ are then placed in electrical contact with the line 14 through alligator cllps or the like 19 and 20, respectively, (Figs. 4 and 5).
Prior to supplying power to the leads 17 and 18, the bending mold and glass sheet carried thereby are preferably ~ ~
heated to a relatively high temperature, for example, above the ~ -strain point of the glass but below the bending point or the temperature at which the glass bends to any significant degree.
In this respect, temperatures in the range from approximately 900F. to 1150~. have been found satisfactory. The purpose of this preliminary heating, whlch may be accomplished by con-veying the mold through a furnace, is to fuse the metal-glass frit suspension to the glass, prevent the formation of permanent stresses in the glass, obviate the tendency of the glass to - ;
crack when subsequently heated locally along the electrically conducting line 14 to its bending ~emperature, and also to -~ ~
enable the accomplishment of this latter step within a time ~ ~ -acceptable frsm a commercial standpoint and wlth the use of a reasonable amount ~f electrical energy.
Upon the glass sheet reaching the desired over-all temperature, power is supplied to the leads 17 and 18 and con-sequently ~o the resis~ance element 14. This ln turn heats the glass sheet immediately adjacent resistance element 14 to a tem-perature above the bending temperature of the glass, for example, above approximately 1200F., at which time the sheet bends sharply along the path 13 and settles by gravity into the gen-erally V-shaped configuration illustrated in Fig. 6. The sheet is then allowed to cool at room temperature.
. . . . .
:: ' . ' ' :"
1~5~373 ~ -A8 a result of the preheating of the glass sheet prior ~o the application of power ~hrough the elec~r~cally conducting path, thP silver paste material forming the latter adheres to the glass sheet and forms an objectionable yellow-brown stain thereon extending longitudinally of the bend.
It is desirable that such stain be at least altered to obtain a color pattern less ob~ectlonable from the standpoint of aesthet~
ics and more compatible with the color combinations of the auto-mobile body so as to enhance the general appearance of the auto-~, ...
mobile.
It has been found that the application of a suitablecoloring agent as an undercoating or substrate for the electrical-ly cDnducting silver paste material serves to alter the residual silver stain sufficiently to yield a more compatible color wlth automobile body design requirements. To this end, and in ac-cordance with this invention, prior to forming the electrically -conducting path or resistance element 14 on the glass surface9 a ;;
coloring agent is applied to at least one surface of the glass sheet 12 along a strip or band 21 ~Fig. 3) upon which the elec- ;~
trically conducting path will be formed and about which it is desired to bend the shee~. Whlle various materlals, such as blue, red and green pigments and various shades the~eof, may be used to form this undercoating, preEerred compositlons comprise ~
pure black pigments and mixtures of pure black pigments and black - ; ;
enamels, i. e., black pigments containing a minor percentage of frit. These materials can be applied ~o the glass sheet surface ;~
by conventional silk screen processes, painting or other known . : , .
roating processes and then allowed to dry at room temperature.
A preferred specific coloring agent, which has yield-.: . .
ed good results, is a fritless, pure black pigment composition sold by Drakenfeld Company, a division of Hercules Incorporated, ~-Washington, Pennsylvania, U.S.A., under the designation of - .
~ 7 '~ ,~ ' -, ' .. .. ~ . . . .
59~3~73 Drakenfeld 1795 Black which i~ a composition comprised of ap-pro~imately 30% by weight of chrome oxide, 32% by weight of cobalt oxide, and 382 by weight of iron oxide. Thls composition is employed in an oily mixture of pine oil and resln sold under the tradename of Drakenfeld 900 to form a mixture designated "Drakenfeld 1795 Black Oxlde in 900 Oil".
AB a specific example of altering the residual stain remaining along the Y-shaped bend in a ~inlshed glass sheet as a result of the firing of the conductive metallic paste initial-ly applied thereto for localized heating in accordance with the method of this invention, a glass sheet of nominal 0.235 inch thickness was procured. A uniform coating of a fr~tless pure black pigment, such as that referred to above as Drakenfeld ;~
1795 Black Oxide in 900 Oil, was applied by a silk screen print-ing process in a band or strip having a width of one-half inch to one surface of the glass sheet along the line abou~ which the ; ~;~
glass sheet was to be bent, the band ex~ending in~ermediate the opposite edges of the sheet and parallel thereto. After the `
band of pigment dried at room temperature, a silver composition comprised of abou~ 85% by weight of conductive silver particles, and the remainder composed of solvent, binder and frit, marketed by E. I. duPont de Nemours and Company, Wilmington, Delaware, U.S.A., under the designation "8966", was then superimpo3ed in ~ ;
a width of .120 inch on the band of black pigment lengthwise thereof by a conventional silk screen printing process.
This sheet was supported at the two opposite or transverse edgee only on a mold and heated in a furnace set to a temperature of 1150F. During this heating, the finely divided metal ceramic frit fused onto tha glass surface. The glass and "
integral frit line were then allowed to cool to room temperature and electrical connections such as those shown in Figs. 4, 5 and 6 were made to the frit line and the mold supported sheet again , .::
: . . . .
:~, ~L~54373 placecl in the furnace and heated to a temperature of 1150F.
When this temperature was obtained, electrical energy was sup-plied to the frit line, and more particularly, a current of 16 ampere~ was passed therethrough. This current was supplied for approximately one minute at which time the sheet had assumed a generally V-shaped appearancP, the bend occurring at and along the frit line or electrically conducting element 14. The sheet was then removed from the. furnace and cooled quickly to produce a tempered structure. ~;
It should be noted that it is not nece~sary that the sheet be allowed to cool down aEter firing of the frlt and then ;
reheated for the bending operation. The electrical connections may be made prlor to the firlng step, which firing step can be accomplished during preheating of the sheet to fuse the metal-ceramic frit onto the glass surace.
After the finished glass sheet had cooled sufficient~ ~ ~
ly, only that por~ion of the black oxide pigment directly beneath -~ -the silver paste material, indicated at 21a in Flg. 3, adhered to the glass surface and the remainder, shown in dotted outline, was readily removed as by wiping, for example. This yielded a ~ -glass sheet product having a long, relatively narrow line along the sharp bend which appeared white on the surface to which the electrically conductive paste material was applied and black on the opposite surface, i.e., the glass side of the sheet O Also , . -' it was found that vigorous rubbing would remove all traces of the silver paste material, even though it initially contained ;
glass frit~ resulting in a line which appear~d black when view0d ~: .
from both sides of the finished glass product and is especially desirable in some applications.
Since the coloring agent di~posed outwardly of the marginal edges of the frit line is easily removed, the strip 21 - of coloring agent can be quickly applied in a relatively wide band without special regard to lndexing, i.e., accurate alignment !~
_ g _ . . .
' ':' ~ ,' ' ' ~-:''. :
. ~ , . . .
~II;IS~373 of its marginal edges with those of the subsequently applied re~istance elen-ent 14. Thls saves time and becomes especially advantageous in a ma3s production operation.
Another conductlve paste material which was success-fully employed in combination with the pure black pigment des-cribed above was a fritless, conductive silver paste preparation comprlsed of approximately 85% by weight of silver pal;ticles, the remainder consisting of a suitable solvent and binder, marketed by E. I. DuPont de Nemours and Company under the desig-10 nation "9105". It wa~ found that the utilization of a fritless silver paste material a~ the electrlcally conductive path 0n-ables the residual ~ilver stain ~o be completely removed, thu~
leaving only a black line visible on the opposite surfaces of : the finished gla~s product, which ha3 beeD found desirable in many design applications.
While the pure black oxide pigment de73cribed above i9 preferable, it should be understood that the black pigments :, containing frit can be successfully employed as colorln~ agents in carry~ng out the method of the pre~ent invention. One such .
`~ 20 coioring agent is available under the tradename "Drakenfeld 24-339" in 175 oil. This is a black pigment -- glass frit com-positlon or enamel containing approximately 10% by weight of gla~s frit. The Drakenfeld 24-339 composi~tlon and Drakenfeld 1795 pure black pigment composition were blended in the follo~7-ing ratios: 10/90; 25t75; and 50/50. These blended compo~ttions ~, , .
were applied, such a7 by suitable F7ilk screen prlnting proces3e3 for example, in a one-half inch wide band acros77 the gla373 sheet.
After beine dried at room temperature, a silver paste prepara-- tion, identified a3 duPont "8966'7~ W~8 superimposed on the band .: . .
30 as a line llaving a width of .120 inch extending lengthwis2 of the band .,"
- 10 _ ' ~C~5~373 After firing the electrically conductive material to effect the relatively sharp bend as de~cribed above, it was found that the 10/90 a~d 25/75 mixtures fused to the gla~ only in the area beneath ~he electrically conductive path as defined by the silver paste material. The excess of the 10/90 mixture, i.e., those portions disposed outwardly beyond the marginal edges of the silver paste line could be readily removed, as by wiping for e~ample, while removal of the ex~ess 25J75 mixture required slightly more effort. In both instances, the sllver electrically conductive material adhered to the glaa8 surface which appeared as a black line when viewed from the glass alde, l.e., the surface opposite of that to which the electrically conductive mate~ial was applied and white when viewed from the opposite side oi the gla~s. -~
All of the 50/50 mixture fused to the glass, creating a relatively wide band across the surface of the finished gl~s~
prcduct. Thus, the lesser the percentage of frit contained in j -~ the coloring agent undercoating, the lesser the pos~lbillty of adherence to the glass with consequent easier removal of the exce~s portions of the coloring agent.
From the foregoing, it is apparent that the ob~ects of the invention have been fully accomplished. By interposing an undercoating of coloring agent between ~he electrically conduc- ;
tive paste ma~erial and the ~urface o the glasa sheet, the un-desirable color of the residual stain resulting from the firing thereo can be altered in accordance with optically acceptable ~
specification~ without adversely affecting the appear~nce o the windshield or backlight or obstructing visibility therethrough.
It should be u=derstood that when lt ia deslred to apply elec-trically conducting paths to the opposlte surfaces of a gla~s sheet, or lnto a groove formed thP~rein, the coloring sgent al90 .
would be appl~ed to such oppoaite aurface~ or into such groo~e, , .
. ~ . , -:
. ,~, .
.
.~ .
1~5~373 re~pecti~ely~ as a substrate or undercoating for the elertrically conduccive materlsl forming ssid p~ths, ~f .~ . , ~ :.
;- ~
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~- . .-j . . : :
1 - -.
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.' . : ~ . ' . .' I . .
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.. . . .
,,, - ~ :- : ,'" ' :
.
Claims (10)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for treating a glass sheet adapted to be bent to a relatively sharp angle, characterized by applying a band of coloring agent to at least one surface of the sheet along the line about which it is desired to bend the sheet, superimposing an electrically conducting path on said band lengthwise thereof, heating the sheet to a temperature above the strain point of the glass but below the bending temperature thereof to fuse the coloring agent and electrically conducting path to the glass, and applying an electrical potential across said path of a sufficient magnitude and for a time adequate to heat the sheet in the area immediately adjacent said path to a temperature above the bending point of the glass causing said sheet to bend along said line and forming a stain therealong of desired appearance.
2. A process for treating a glass sheet as claimed in claim 19 characterized in that said coloring agent comprises a black pigment applied to said sheet by a silk screen process.
3. A process for treating a glass sheet as claimed in claim 1, characterized in that said coloring agent comprises a black pigment containing frit.
4. A process for treating a glass sheet as claimed in claim 1, characterized in that said coloring agent comprises a mixture of pure black pigment in a black enamel containing about 10% by weight of frit in a ratio of about 9:1, respectively.
5. A process for treating a glass sheet as claimed in claim 1, characterized in that said coloring agent comprises a mixture of pure black pigment in n black enamel containing about 10% by weight of frit in a ratio of about 3:1, respectively.
6. A process for treating a glass sheet as claimed in any of claims 1 to 3, characterized in that said coloring agent is applied along an elongated groove previously formed along the line about which it is desired to bend the sheet.
7. A process for treating a glass sheet as claimed in any of claims 1, 3 and 5, characterized in that said sheet is heated to a temperature in the range of from about 900°F. to 1150°F. prior to applying said electrical potential across said path.
8. A process for treating a glass sheet as claimed in any of claims 1, 3 and 5, characterized in that said sheet is heated in the area immediately adjacent said path to a temp-erature above about 1200°F.
9. A process for treating a glass sheet as claimed in claim 1, characterized in that said band of coloring agent is applied in a strip having a relatively wide dimension relative to said electrically conducting path.
10. A process for treating a glass sheet as claimed in claim 9, characterized in that the excess coloring agent is removed to leave a relatively narrow residual stain line of desired color along said bend.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US438234A US3879184A (en) | 1972-08-23 | 1974-01-31 | Process for treating a glass sheet bent to a relatively sharp angle |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1054373A true CA1054373A (en) | 1979-05-15 |
Family
ID=23739805
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA218,324A Expired CA1054373A (en) | 1974-01-31 | 1975-01-21 | Process for treating a glass sheet adapted to be bent to a relatively sharp angle |
Country Status (9)
| Country | Link |
|---|---|
| JP (1) | JPS5529938B2 (en) |
| AR (1) | AR201536A1 (en) |
| BR (1) | BR7500584A (en) |
| CA (1) | CA1054373A (en) |
| ES (1) | ES434273A1 (en) |
| FI (1) | FI58113C (en) |
| IT (1) | IT1026480B (en) |
| SE (1) | SE412580B (en) |
| ZA (1) | ZA75464B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3257824A1 (en) * | 2016-06-15 | 2017-12-20 | Corning Incorporated | Apparatus and method for bending thin glass sheets |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5910091Y2 (en) * | 1977-08-02 | 1984-03-30 | 旭硝子株式会社 | sharply curved glass plate |
-
1975
- 1975-01-21 CA CA218,324A patent/CA1054373A/en not_active Expired
- 1975-01-22 ZA ZA00750464A patent/ZA75464B/en unknown
- 1975-01-27 IT IT4786175A patent/IT1026480B/en active
- 1975-01-29 FI FI750237A patent/FI58113C/en not_active IP Right Cessation
- 1975-01-29 BR BR584/75A patent/BR7500584A/en unknown
- 1975-01-30 ES ES434273A patent/ES434273A1/en not_active Expired
- 1975-01-30 SE SE7501004A patent/SE412580B/en not_active IP Right Cessation
- 1975-01-30 AR AR257466A patent/AR201536A1/en active
- 1975-01-31 JP JP1325475A patent/JPS5529938B2/ja not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP3257824A1 (en) * | 2016-06-15 | 2017-12-20 | Corning Incorporated | Apparatus and method for bending thin glass sheets |
| WO2017218652A1 (en) * | 2016-06-15 | 2017-12-21 | Corning Incorporated | Apparatus and method for bending thin glass sheets |
Also Published As
| Publication number | Publication date |
|---|---|
| ZA75464B (en) | 1976-01-28 |
| AR201536A1 (en) | 1975-03-21 |
| FI58113B (en) | 1980-08-29 |
| FI58113C (en) | 1980-12-10 |
| SE412580B (en) | 1980-03-10 |
| FI750237A (en) | 1975-08-01 |
| JPS5529938B2 (en) | 1980-08-07 |
| BR7500584A (en) | 1975-11-11 |
| ES434273A1 (en) | 1976-09-16 |
| SE7501004L (en) | 1975-08-01 |
| IT1026480B (en) | 1978-09-20 |
| JPS50109209A (en) | 1975-08-28 |
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