Antimony-free glass, antimony-free frit and a glass package that is hermetically sealed with the frit

Abstract

An antimony-free glass suitable for use in a frit for producing a hermetically sealed glass package is described. The hermetically sealed glass package, such as an OLED display device, is manufactured by providing a first glass substrate plate and a second glass substrate plate and depositing the antimony-free frit onto the first substrate plate. OLEDs may be deposited on the second glass substrate plate. An irradiation source (e.g., laser, infrared light) is then used to heat the frit which melts and forms a hermetic seal that connects the first glass substrate plate to the second glass substrate plate and also protects the OLEDs. The antimony-free glass has excellent aqueous durability, good flow, low glass transition temperature and low coefficient of thermal expansion.

Claims

1. A glass article, comprising: a glass substrate; a frit sealing material attached to the glass substrate, the frit sealing material including an antimony-free glass comprising: V.sub.2O.sub.540 mole % and 52.5 mole %; P.sub.2O.sub.515 mole % and <25 mole %; ZnO0 mole % and 10 mole %; Fe.sub.2O.sub.3>0 mole % and <25 mole %; TiO.sub.2>0 mole % and <25 mole %; B.sub.2O.sub.3>0 mole % and 20 mole %; and wherein TiO.sub.2+Fe.sub.2O.sub.3 is in a range from 15 mole % to 30 mole %, and a T.sub.g of the antimony-free glass is 365 C.

2. The glass article according to claim 1, wherein the antimony-free glass comprises: V.sub.2O.sub.540 mole % and 50 mole %; P.sub.2O.sub.520 mole % and <23 mole %; ZnO2 mole % and 5 mole %; Fe.sub.2O.sub.310 mole % and 20 mole %; TiO.sub.25 mole % and 20 mole %; and B.sub.2O.sub.31 mole % and 20 mole %.

3. The glass article according to claim 1, wherein the T.sub.g of the antimony-free glass is 350 C.

4. The glass article according to claim 1, wherein a CTE of the sealing material substantially matches a CTE of the glass substrate.

5. The glass article according to claim 1, wherein the frit sealing material comprises a CTE-lowering filler.

6. The glass article according to claim 1, further comprising a second glass substrate, the second glass substrate sealed to the first glass substrate by the frit sealing material.

7. The glass article according to claim 6, wherein the glass article comprises an electronic device.

8. The glass article according to claim 7, wherein the glass article comprises one of a sensor, a photovoltaic device or a display device.

9. The glass article according to claim 8, wherein the glass article is an OLED display device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a cross sectional illustration of the sealing of an exemplary OLED device using a frit according to embodiments of the present invention;

(2) FIG. 2 is a plot of coefficient of thermal expansion (CTE) as a function of the substitution of Fe.sub.2O.sub.3 for TiO.sub.2 in an Sb-free frit according to embodiments of the present invention in mole % where Fe.sub.2O.sub.3+TiO.sub.2 is between 20 mole % and 35 mole %;

(3) FIG. 3 is a plot comparing CTE as a function of temperature for an Sb-free frit according to embodiments of the present invention and an Sb-containing frit under both heating and cooling conditions;

(4) FIG. 4 is a photograph of the supernatant after temperature and humidity exposure of boron-containing antimony-free glasses compared to an antimony-containing glass;

(5) FIG. 5 is a graph of glass transition temperature of both antimony-containing and antimony-free glasses as a function of B.sub.2O.sub.3 concentration;

(6) FIGS. 6 and 7 are photographs of the supernatant after temperature and humidity exposure of various compositions of boron-containing antimony-free glasses as disclosed herein;

(7) FIG. 8 is a top-down view of a portion of a glass package showing a seal made with a frit comprising a boron-containing antimony-free glass as disclosed herein.

DETAILED DESCRIPTION

(8) In the following detailed description, for purposes of explanation and not limitation, example embodiments disclosing specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to one having ordinary skill in the art, having had the benefit of the present disclosure, that the present invention may be practiced in other embodiments that depart from the specific details disclosed herein. Moreover, descriptions of well-known devices, methods and materials may be omitted so as not to obscure the description of the present invention. Finally, wherever applicable, like reference numerals refer to like elements.

(9) FIG. 1 depicts a cross-sectional side view illustrating the sealing of the basic components of a hermetically sealed OLED display 10. OLED display 10 includes a multilayer sandwich of a first glass substrate plate 12, one or more OLEDs 14, frit 16 and a second glass substrate plate 18. OLED display 10 comprises hermetic seal 18 formed from frit 16 that protects OLEDs 14 located between the first glass substrate plate 12 and the second glass substrate plate 18. Hermetic seal 20 is typically located around the perimeter of OLED display 10. OLEDs 14 are located within a perimeter of hermetic seal 20. The composition of frit 16, and more particularly the composition of the glass of frit 16, as well as how the hermetic seal 20 is formed from frit 16 is described in greater detail below.

(10) In one embodiment, first and second substrate plates 12 and 18 are transparent glass plates. Frit 16 is deposited along the edges of second glass substrate plate 18. For instance, frit 16 can be placed approximately 1 mm away from the free edges of the second glass substrate plate 18. In the preferred embodiment, frit 16 is a low temperature antimony-free glass frit containing vanadium to enhance the optical absorbance of the frit. Frit 16 may also include a filler material, such as beta eucryptite or beta quartz, that lowers the coefficient of thermal expansion (CTE) of the frit so that it matches or substantially matches the CTEs of the two glass substrate plates 12 and 18.

(11) OLEDs 14 and other circuitry are deposited onto second glass substrate plate 18. The typical OLED 14 includes an anode electrode, one or more organic layers and a cathode electrode. However, it should be readily appreciated that other environmentally sensitive components can be deposited onto second glass substrate plate 18.

(12) Optionally, frit 16 can be pre-sintered to first glass substrate plate 12 prior to sealing glass substrates 12 and 18 together. To accomplish this, first substrate plate 12 comprising frit 16 deposited thereon is heated in a furnace or oven so that it becomes attached to the first glass substrate plate 12.

(13) Next, first and second glass substrate plates 12 and 18 are brought together with frit 16 with one or more OLEDs positioned between them, and frit 16 is irradiated by irradiation source 22 (e.g. a laser or an infrared lamp) so that the frit 16 forms hermetic seal 20 that connects and bonds first substrate plate 12 to second substrate plate 18. Hermetic seal 18 also protects OLEDs 14 by preventing oxygen and moisture in the ambient environment from entering into the OLED display 10.

(14) It should be readily appreciated that the irradiating wavelength should be within the band of high absorption in the particular frit 16. For instance, Ytterbium (900 nm<<1200 nm), Nd:YAG (=1064 nm), Nd:YALO (=1.08 m), and erbium (1.5 m) CW lasers can be used depending on the optical properties of the particular frit 16 and glass substrate plates 12 and 18.

(15) It should also be noted that most traditional low temperature sealing frits are PbO-based, because PbO frits have good flow, and adhesion properties. However, the antimony-free frits disclosed herein not only have a lower CTE than PbO-based frits, but also possess better aqueous durability, as well as being comparable to the traditional Pb-based frits with respect to adhesion.

(16) In addition, although the role played by P.sub.2O.sub.5 in a successful sealing frit is important, since it permits stable glasses to be formed, from a laser-sealing and post-seal performance standpoint the effect of Sb.sub.2O.sub.3 and V.sub.2O.sub.5 should not be ignored. In previous testing, seals made with Sb-free, Zn-based vanadium-phosphate frits could only survive the relatively benign environment of 60 C./40% relative humidity (RH), while seals made from mixed SbZn vanadium phosphate frits survived 60 C./85% RH before failing. Conversely, only seals made with Sb-vanadium-phosphate frits survived 85 C./85% RH exposure. However, despite the role that Sb.sub.2O.sub.3 plays in improving aqueous durability, feedback from potential customers consistently raise concerns about its presence. Moreover, Sb.sub.2O.sub.3 is thought to impede achieving desirably low glass transition temperatures (Tg). Thus, recent emphasis has been placed on development of a glass suitable for a sealing frit that is more environmentally friendly, noting that antimony is a toxic element.

(17) Work on Sb.sub.2O.sub.3-free compositions began by first expressing a basic OLED device sealing frit composition as a three component system (20 mole % Sb.sub.2O.sub.3-50 mole % V.sub.2O.sub.5-30 mole % P.sub.2O.sub.5), simplifying the composition to a two component Sb.sub.2O.sub.3-free system (either 50 mole % V.sub.2O.sub.5-30 P.sub.2O.sub.5, 45 mole % V.sub.2O.sub.5-30 mole % P.sub.2O.sub.5, or 40 mole % V.sub.2O.sub.5-20 mole % P.sub.2O.sub.5), and then identifying the remaining components from the standpoint of their effect on aqueous durability, flow, glass transition temperature (T.sub.g), and laser-sealability. Both aqueous durability, laser-sealability, and flow of any candidate frit compositions needed to be comparable to the Sb.sub.2O.sub.3-containing control sample, while the Tg requirements were relaxed with the criterion that T.sub.g had to be equal to or less than 400 C. (Frits with T.sub.g>400 C. are unlikely to flow sufficiently during the presintering step for OLED frits to be handleable in subsequent processing.) The following oxides were investigated as potential substitutes for antimony (Sb.sub.2O.sub.3): WO.sub.3, MoO.sub.3, TeO.sub.2, Bi.sub.2O.sub.3, Fe.sub.2O.sub.3, and TiO.sub.2. ZnO was also investigated, although in view of the poor durability results obtained for a ZnOV.sub.2O.sub.5P.sub.2O.sub.5 frit, it was considered only as a minor component (5-10 mole %) to lower T.sub.g and maintain flow. The various oxides selected were chosen on the basis that they formed stable binary glasses with V.sub.2O.sub.5.

(18) All of the compositions investigated were melted, poured as glass patties, then ball-milled to form fine-particle frits (typically with a d.sub.50=3-5 m). A key bench test to screen the different compositions was to prepare and fire flow buttons of the various frits, and then to assess their aqueous durability. The flow buttons were fired in N.sub.2 to 400 C.-450 C. (depending upon T.sub.g and crystallization tendency). After firing, the flow buttons were immersed in 90 C. deionized water for 48 hours to assess their aqueous durability. Control samples of the OLED frit (either as the D1 base glass, or as a 70:30 by weight blend of the base glass with a -eucryptite filler material) were also included in each evaluation. Of the potential replacements for Sb.sub.2O.sub.3 that were investigated (see above), only TiO.sub.2 and Fe.sub.2O.sub.3 appeared promising.

(19) Listed in Tables 1 and 2 are results for a 50 mole % V.sub.2O.sub.5-30 mole % P.sub.2O.sub.5 composition series with WO.sub.3, MoO.sub.3, WO.sub.3+ZnO, Bi.sub.2O.sub.3, and TeO.sub.2 as the third component. Also shown are data on the standard OLED base glass, D1, as a comparison standard. All compositions (given in mole %) were evaluated for quality of glass formed from the pour, glass transition temperature (T.sub.g) by DSC, flow and sinterability as a 3 m powder hand-pressed into a pellet (flow button) and fired at 400 C. for 1 hour in N.sub.2, and aqueous durability (as gauged by the color of the supernatant for a fired flow button samplethe darker the color, the less durable the sample) in the bench aqueous durability test described above. Note that none of the potential Sb.sub.2O.sub.3 replacements listed in Tables 1 and 2 produced the acceptable level of glass quality, T.sub.g, flow, and aqueous durability exhibited by the Sb.sub.2O.sub.3-containing control (as judged by the appearance of the supernatant after 48 hrs, 90 C. deionized H.sub.2O).

(20) TABLE-US-00001 TABLE 1 D1 (control) D2 D3 Composition Sb.sub.2O.sub.3, 22.9 V.sub.2O.sub.5, 50 V.sub.2O.sub.5, 50 (molar basis) V.sub.2O.sub.5, 46.4 P.sub.2O.sub.5, 30 P.sub.2O.sub.5, 30 P.sub.2O.sub.5, 26.3 WO.sub.3, 20 MoO.sub.3, 20 Fe.sub.2O.sub.3, 2.4 Al.sub.2O.sub.3, 1.0 TiO.sub.2, 1.0 Glass quality at Excellent Fluid, good Very fluid, good pour quality quality T.sub.g 355 C. 349 C. 315 C. Flow (400-1 hr, Very good flow Semi-glossy, well- Glossy and black N.sub.2) and sinterability sintered, no flow with some slump Aqueous V. slightly Black Black durability, tinted appearance of supernatant (48 hrs, 90 C. D.I. H.sub.2O)

(21) TABLE-US-00002 TABLE 2 D4 D5 D6 Composition V.sub.2O.sub.5, 50 V.sub.2O.sub.5, 50 V.sub.2O.sub.5, 50 (molar basis) P.sub.2O.sub.5, 30 P.sub.2O.sub.5, 30 P.sub.2O.sub.5, 30 WO.sub.3, 10 Bi.sub.2O.sub.3, 20 TeO.sub.2, 20 ZnO, 10 Glass quality Good glass, fluid, Crystallized More viscous pour, at pour poured well after pouring glass looked good T.sub.g 323 C. Not eval. 329 C. Flow (400 C.- Poor flow Not eval. Semi-glossy black, 1 hr, N.sub.2) no slump Aqueous Black Not eval. Black durability

(22) More positive results for Sb.sub.2O.sub.3-free vanadium phosphate frits were obtained by Fe.sub.2O.sub.3 and/or TiO.sub.2 replacement of Sb.sub.2O.sub.3 (see Tables 3 and 4). All compositions are expressed in mole %. Several combinations of Fe.sub.2O.sub.3+TiO.sub.2 produced good glasses at pouring. High TiO.sub.2 glasses (i.e., 25 mole %) such as D8 had acceptable T.sub.g and flow properties, but also exhibited poor aqueous durabilities. Higher Fe.sub.2O.sub.3 glasses (i.e., 25 or 30 mole %) such as D7 and D11 tended to produce poor glasses at pour, as evidenced by substantial surface devitrification. The relatively poor stability of these glasses (as indicated by the high amount of surface devitrification formed in the patty at pouring) resulted in poor flow as frits. They also tended to be unstable with respect to oxidation state, with a fired flow button from the same lot of powder alternately appearing either black (reduced) or red (oxidized) after the same firing conditions. Also included in Table 4 is D14, a glass with relatively high Fe.sub.2O.sub.3 and TiO.sub.2 levels, but with 10 mole % ZnO to lower the expected increase in T.sub.g from the Fe.sub.2O.sub.3. Note that a second approach to accommodating high Fe.sub.2O.sub.3 levels is increasing the V.sub.2O.sub.5 content. But as may be seen for D9 and D10, aqueous durability was compromised at higher V.sub.2O.sub.5 content.

(23) TABLE-US-00003 TABLE 3 D7 D8 D9 D10 Composition V.sub.2O.sub.5, 45 V.sub.2O.sub.5, 45 V.sub.2O.sub.5, 50 V.sub.2O.sub.5, 50 (molar basis) P.sub.2O.sub.5, 30 P.sub.2O.sub.5, 30 P.sub.2O.sub.5, 30 P.sub.2O.sub.5, 30 Fe.sub.2O.sub.3, 25 TiO.sub.2, 25 TiO.sub.2, 15 TiO.sub.2, 10 Fe.sub.2O.sub.3, 5 Fe.sub.2O.sub.3, 10 Glass quality Substantial Poured Poured Poured at pour surface devit nicely nicely nicely T.sub.g 353 345 323 322 Flow (400 C., Poorly Semi-glossy Sintered, Sintered, 1 hr, N.sub.2) sintered black, some slight no slump flow flow Aqueous Not tested Black Med. green Med. durability, green appearance of supernatant (48 hrs, 90 C. D.I. H.sub.2O)

(24) TABLE-US-00004 TABLE 4 D11 D12 D13 D14 Composition V.sub.2O.sub.5, 42 V.sub.2O.sub.5, 40 V.sub.2O.sub.5, 45 V.sub.2O.sub.5, 40 (molar basis) P.sub.2O.sub.5, 28 P.sub.2O.sub.5, 25 P.sub.2O.sub.5, 25 P.sub.2O.sub.5, 20 TiO.sub.2, 0 TiO.sub.2, 17.5 TiO.sub.2, 0 TiO.sub.2, 15 Fe.sub.2O.sub.3, 30 Fe.sub.2O.sub.3, 17.5 Fe.sub.2O.sub.3, 30 Fe.sub.2O.sub.3, 15 ZnO, 10 Glass quality Viscous, Good Viscous, Good at pour surface glass, surface glass, no devit no devit devit devit T.sub.g 371 364 376 360 Flow Poor- Poor- Poor Semi-glossy (400 C., powdery and powdery black, 1 hr, N.sub.2) unconsolidated sintered, no slump Aqueous Not eval. Not eval. Not eval. Lt. brown durability

(25) It should also be noted that although the test samples of Tables 3 and 4 having P.sub.2O.sub.5 levels equal to or greater than 25 mole % performed poorly, it is anticipated that P.sub.2O.sub.5 levels less than 25 mole % can be successfully employed. Table 5 summarizes the results of a second set of Fe.sub.2O.sub.3 and TiO.sub.2 melts at 10 mole % ZnO. All compositions are expressed in mole %. As for the initial series, some combination of Fe.sub.2O.sub.3 and TiO.sub.2 is preferred, since Fe.sub.2O.sub.3 contributes excellent aqueous durability (but at the cost of high T.sub.g and reduced frit sintering at 400), and TiO.sub.2 results in lower T.sub.g and improved flow (but at the cost of aqueous durability).

(26) TABLE-US-00005 TABLE 5 D15 D16 D17 D18 D19 Composition V.sub.2O.sub.5, 50 V.sub.2O.sub.5, 50 V.sub.2O.sub.5, 50 V.sub.2O.sub.5, 50 V.sub.2O.sub.5, 50 (molar P.sub.2O.sub.5, 20 P.sub.2O.sub.5, 20 P.sub.2O.sub.5, 20 P.sub.2O.sub.5, 20 P.sub.2O.sub.5, 20 basis) ZnO, 10 ZnO, 10 ZnO, 10 ZnO, 10 ZnO, 10 Fe.sub.2O.sub.3, 0 Fe.sub.2O.sub.3, 5 Fe.sub.2O.sub.3, 10 Fe.sub.2O.sub.3, 15 Fe.sub.2O.sub.3, 20 TiO.sub.2, 20 TiO.sub.2, 15 TiO.sub.2, 10 TiO.sub.2, 5 TiO.sub.2, 0 Glass quality Poured Poured Poured Poured Poured at pour nicely nicely nicely nicely nicely T.sub.g 297 310 322 333 348 Flow (400- Well- Well- Sintered, Sintered, Sintered, 1 hr, N.sub.2) sintered, sintered, slight some little good flow good flow flow flow flow Aqueous Dark black Dark Dark Clear Clear durability black black

(27) An additional series of melts were made at higher levels of [Fe.sub.2O.sub.3+TiO.sub.2] with ZnO maintained at 5 mole % (see Tables 6 and 7 below). All compositions are expressed in mole %. Note that to accommodate the higher T.sub.g of the high Fe.sub.2O.sub.3 glasses, flow was evaluated at 425 C., rather than the 400 C. previously used.

(28) TABLE-US-00006 TABLE 6 D20 D21 D22 D23 Composition V.sub.2O.sub.5, 40 V.sub.2O.sub.5, 40 V.sub.2O.sub.5, 40 V.sub.2O.sub.5, 40 (molar basis) P.sub.2O.sub.5, 20 P.sub.2O.sub.5, 20 P.sub.2O.sub.5, 20 P.sub.2O.sub.5, 20 ZnO, 5 ZnO, 5 ZnO, 5 ZnO, 5 Fe.sub.2O.sub.3, 35 Fe.sub.2O.sub.3, 30 Fe.sub.2O.sub.3, 25 Fe.sub.2O.sub.3, 20 TiO.sub.2, 0 TiO.sub.2, 5 TiO.sub.2, 10 TiO.sub.2, 15 Glass quality Substantial surface + Surface devit Surface devit Good glass, no at pour bulk devit devit T.sub.g 416 407 400 389 Flow (425- Not sinterable at Not sinterable at Not sinterable at Sintered, no 1 hr, N.sub.2) 425 425 425 flow Aq. durability Not tested Not tested Not tested Clear

(29) TABLE-US-00007 TABLE 7 D24 D25 D26 D27 D28 Composition V.sub.2O.sub.5, 40 V.sub.2O.sub.5, 40 V.sub.2O.sub.5, 40 V.sub.2O.sub.5, 40 V.sub.2O.sub.5, 40 (molar basis) P.sub.2O.sub.5, 20 P.sub.2O.sub.5, 20 P.sub.2O.sub.5, 20 P.sub.2O.sub.5, 20 P.sub.2O.sub.5, 20 ZnO, 5 ZnO, 5 ZnO, 5 ZnO, 5 ZnO, 5 Fe.sub.2O.sub.3, 17.5 Fe.sub.2O.sub.3, 15 Fe.sub.2O.sub.3, 10 Fe.sub.2O.sub.3, 5 Fe.sub.2O.sub.3, 0 TiO.sub.2, 17.5 TiO.sub.2, 20 TiO.sub.2, 25 TiO.sub.2, 30 TiO.sub.2, 35 Glass quality Good glass, Good glass, Good glass, Good glass, no Good glass, no at pour no devit no devit no devit devit devit T.sub.g 3790 367 351 333 324 Flow (425- Sintered, Sintered Sintered, Sintered, mod. Sintered, good 1 hr, N.sub.2) slight flow slight flow mod, flow flow flow Aq. Clear with v. Clear Med. green Med. green Med. green durability slight tint (residue) (residue)

(30) As seen in previous results from Tables 1, 2 and 3, 4, Fe.sub.2O.sub.3 levels not much higher than 20 mole % (e.g. about 25 mole %) resulted in frits with high T.sub.g, poor stability, and unacceptable flow during 400 C.-425 C. sintering. Similarly, TiO.sub.2 not much higher than 20 mole % (e.g. about 25 mole %), resulted in frits with acceptable T.sub.g, flow, and stability, but with unacceptable aqueous durability. Frits with Fe.sub.2O.sub.3 levels ranging between from about 10 mole % to less than 25 mole %, and with TiO.sub.2 levels from about 15 mole % to less than 25 mole % (at 5-10 mole % ZnO) combine excellent aqueous durability with acceptable flow, T.sub.g, and glass stability.

(31) The aqueous durability of the (Fe.sub.2O.sub.3+TiO.sub.2+ZnO) Sb.sub.2O.sub.3-free V.sub.2O.sub.5P.sub.2O.sub.5 frits were found to be comparable to or slightly superior to the Sb.sub.2O.sub.3-containing standard composition. An unexpected result of the Sb.sub.2O.sub.3-free work is that the coefficient of thermal expansion (CTE) becomes dramatically lower for the (Fe.sub.2O.sub.3+TiO.sub.2+ZnO) frits at higher Fe.sub.2O.sub.3 levels. Shown below in FIG. 2 are CTE data for sintered frits whose composition is listed in Tables 3, 4 and 5. Data are presented for all sinterable frits in the 20 mole % (Fe.sub.2O.sub.3+TiO.sub.2) series of Tables 3, 4, (curve 120) and for the 35 mole % (Fe.sub.2O.sub.3+TiO.sub.2) series of Table 5 as indicated by curve 122. CTE data for sintered frit bars are plotted as a function of Fe.sub.2O.sub.3 level in each series up to 20 mole % Fe.sub.2O.sub.3, the apparent upper limit to achieving frits with good sinterability and oxidative stability. Note that CTE values are highest at 0 mole % Fe.sub.2O.sub.3/maximum TiO.sub.2 (20 mole % and 35 mole %, respectively), become essentially constant with increasing Fe.sub.2O.sub.3 level at 60-6510.sup.7/ C., and then decrease substantially at Fe.sub.2O.sub.3>15 mole % (5 mole % and 20 mole % TiO.sub.2, respectively), reaching a value of approximately 4010.sup.7/ C. at 17.5-20 mole % Fe.sub.2O.sub.3. By comparison, the CTE of the Sb.sub.2O.sub.3-containing base frit is approximately 70-8010/ C.

(32) A more direct comparison of CTE between the Sb.sub.2O.sub.3-containing and Sb.sub.2O.sub.3-free frits is shown in FIG. 3 where CTE curves are plotted for D1 under both heating and cooling conditions (curves 124 and 126, respectively) and D29 (remelt of D24, Table 7) also under both heating and cooling conditions (curves 128 and 130, respectively). With a CTE value of approximately 4010.sup.7/ C. for an unfilled frit, it is possible, with the addition of fillers such as -eucryptite or beta quartz, to lower the CTE value of this frit close to that of fused silica.

(33) The lab scale aqueous durability results for Sb-free frits were corroborated in a large scale sealing trial involving 85 C./85% RH exposure of laser-sealed samples. Shown in Table 8 are results of the trial and comparison between the standard OLED frit (D1, Table 1; used as a 70:30 blend by weight with low CTE filler (-eucryptite), and an Sb-free frit (D29, remelt of D24, Table 7; used as an 80:20 wt. blend with low CTE filler (-quartz). Each frit blend was made into a paste, dispensed on several sheets of EAGLE.sup.XG display glass, presintered (Sb-containing standard, heated at 325 C. for 2 hours in air+400 C. for 1 hr in N.sub.2; Sb-free, heated at 325 C. for 2 hours in air+425 C. for 1 hour in N.sub.2), sealed to sheets of EAGLE.sup.XG, placed in an 85 C./85% relative humidity (RH) environmental chamber, and then examined periodically for evidence of seal leakage and Ca metal breakdown. In total, there were 3 sheets of the Sb-containing control composition and 7 sheets of the antimony-free composition included in the study, with 9 sealed arrays of Ca metal tabs per sheet. As may be seen in Table 8, several arrays failed either immediately after sealing or within 100 hrs of placing them in a 85 C./85% RH chamber for both the Sb-control and the Sb-free frits; these failures were related, most likely, to gross defects such as contamination present at random for each frit. However, after 96 hrs, no additional failures were observed for either the Sb-control or the Sb-free frit seals.

(34) TABLE-US-00008 TABLE 8 No. of good cells Laser- At start of After 96 hrs After 1056 hrs of sealed 85/85 of 85/85 85/85 Standard Sb-frit blend (70:30, 27 (3 25 24 24 D1: -eucryptite) sheets) Sb-free frit blend (80:20, 63 (7 61 57 57 D29: -quartz) sheets)

(35) In summary, the excellent aqueous durability performance of Sb-vanadium phosphate frits was maintained without Sb.sub.2O.sub.3 by replacing the antimony oxide with a combination of Fe.sub.2O.sub.3+TiO.sub.2, along with a small addition of ZnO to maintain flow and glass transition temperature (T.sub.g). The presence of Fe.sub.2O.sub.3 was found to have the greatest effect in improving durability. However, in large amounts it raised T.sub.g, thus degrading frit flow during sealing. In addition, frits with high Fe.sub.2O.sub.3 levels (equal to or greater than about 25 mole %) tended to be oxidatively unstable, with repeat samples fired to the same schedule (425 C. in N.sub.2) exhibiting different colors (brown or black), with marked differences in the degree of flow. Although TiO.sub.2 actually degraded aqueous durability to some extent when added by itself, the combination of (Fe.sub.2O.sub.3+TiO.sub.2) appeared to be an ideal combination from the standpoint of obtaining laser-sealable frits with both high aqueous durability and low T.sub.g 400 C.).

(36) Both lab bench tests in 90 C. deionized water as well as 85 C./85% RH environmental chamber testing of laser-sealed samples indicate that frits based on the Fe.sub.2O.sub.3TiO.sub.2ZnOV.sub.2O.sub.5P.sub.2O.sub.5 system are capable of forming a hermetic seal after laser-sealing that will withstand high humidity conditions for extended times (1000 hrs). An unexpected result of the (Fe.sub.2O.sub.3+TiO.sub.2) replacement of Sb.sub.2O.sub.3 was that the CTE of the Sb-free frit without fillers decreased by approximately half (from 70-8010.sup.7/ C. to 35-4510.sup.7/ C.), with only a minor increase in T.sub.g (from 355 C. to 370 C.). Frits with CTE values near 4010.sup.7/ C. have the potential, with the addition of fillers such as -eucryptite or -quartz, of being able to seal fused silica and other low CTE substrates such as Kovar.

(37) However, in spite of the success in developing the foregoing antimony-free frits, the high T.sub.g (380 C.) resulted in a higher pre-sintering temperature (425 C.) than comparable antimony-containing frits like D1, and needed to be sustained for a longer period of time at the pre-sintering temperature. Thus, while environmentally friendly, such antimony-free frits tend to increase process times and therefore process costs. Moreover, the antimony-free frits described above were found to crystallize to at least some extent during the pre-sintering cycle, leading to somewhat reduced adhesion properties. Accordingly, additional work was conducted on a lower T.sub.g, but still Sb-free, variant. The T.sub.g of this newer frit, D30, was approximately 30 C. lower than D24, and was essentially identical to D1 in T.sub.g and flow. This decreased T.sub.g in D30 was achieved by incorporating about 7.5 mole % more V.sub.2O.sub.5 at the expense of ZnO and TiO.sub.2, indicating the role that small composition changes have on certain properties of the V.sub.2O.sub.5P.sub.2O.sub.5 glasses. Shown in Table 9 is a comparison between D24 and the revised composition D30. All compositional values are in mole %.

(38) TABLE-US-00009 TABLE 9 D24 D30 V.sub.2O.sub.5 40 47.5 P.sub.2O.sub.5 20 22.5 ZnO 5 2.5 TiO.sub.2 17.5 10 Fe.sub.2O.sub.3 17.5 17.5 Al.sub.2O.sub.3 0 0 T.sub.g 378 C. 351 C.

(39) A key component in both D24 and D30 is Fe.sub.2O.sub.3, which may serve as a redox moderator of V.sub.2O.sub.5 (as did Sb.sub.2O.sub.3 in D1). Fe.sub.2O.sub.3, however, also acts to increase T.sub.g. The other components of D24, namely ZnO and TiO.sub.2, serve to counteract to some extent the role of Fe.sub.2O.sub.3 in raising T.sub.g, although they can also tend to lessen resistance to aqueous attack.

(40) FIG. 4 shows photographs of sintered glass pellets of selected glass compositions suitable for the manufacture of glass frits in laboratory beakers for after being immersed in 90 C. deionized water for 48 hours. Prior to immersion the pellets were heat treated by exposing each flow button to 300 C. for one hour in air followed by 400 C. for one hour in nitrogen. FIG. 4 depicts, in order, from left to right, (a) D1, (b) D24, and (c) D30.

(41) Although the lowering of T.sub.g in Sb-free composition D30 to 350 C. was highly desirable, further composition efforts were undertaken to determine whether additional decreases in T.sub.g were possible. Accordingly, B.sub.2O.sub.3, a low T.sub.g glass former, was added. In making the B.sub.2O.sub.3 additions, the addition should be done in such as manner as to not degrade glass stability, aqueous durability, and flow. Indeed, the following guidelines were followed: (a) B.sub.2O.sub.3 should not be substituted for P.sub.2O.sub.5, since, as noted, P.sub.2O.sub.5 plays an important role in stabilizing the frit. When P.sub.2O.sub.5 is present at moderate levels (approximately 20 mole %), the vanadate glass frit tends to exhibit minimal crystallization, and as a result, the frit exhibits an extended region of viscous flow during the sealing process, leading to improved adhesion; (b) B.sub.2O.sub.3 should not be substituted for V.sub.2O.sub.5, since, as noted, this component is important for good flow and low CTE; (c) Fe.sub.2O.sub.3 should be maintained as close as possible to the level (17.5 mole %) present in the starting D24 and D30 compositions, or durability could be impaired. However, small decreases in Fe.sub.2O.sub.3 (down to about 12.5 mole %) can be tolerated with acceptable loss in aqueous durability; and (d) to maintain glass stability, the total amount of glass former (e.g., V.sub.2O.sub.5+P.sub.2O.sub.5+B.sub.2O.sub.3) should be at least 60 mole %, with 65-70 mole % more preferred for glass stability. With these prescriptions in mind, B.sub.2O.sub.3 was added as follows: B.sub.2O.sub.3 for (ZnO+TiO.sub.2+Fe.sub.2O.sub.3), with Fe.sub.2O.sub.3 maintained at 12.5 mole %). It should be noted that while the following discussion is centered around D1, D24 and D30, this samples are representative of families of compositions. For example, as shown below in Table 10, each of the samples D31-D35 is a glass composition essentially the same as the D24 composition, with the exception that B.sub.2O.sub.3 was substituted for Fe.sub.2O.sub.3 and TiO.sub.2 in varying amounts. The same is true for Table 11, except that the glass is the D30 glass and the variations are D36-D41 (and D40 had decreased P.sub.2O.sub.5).

(42) Listed below in Table 10 is the B.sub.2O.sub.3 substitution series, including for reference D24. B.sub.2O.sub.3 was added in an amount up to 20 mole % following the substitution schema presented above. T.sub.g decreased by approximately 70 C., from a temperature of 376 C. recorded for a remelt of D24 to a low of 305 C. for D34. The onset of crystallization is designated by T.sub.x. All compositional values are in mole %.

(43) TABLE-US-00010 TABLE 10 D24 D31 D32 D33 D34 D35 V.sub.2O.sub.5 40 40 40 40 40 40 P.sub.2O.sub.5 20 20 20 20 20 20 B.sub.2O.sub.3 0 5 7.5 10 15 20 Fe.sub.2O.sub.3 17.5 15 13.7 12.5 10 7.5 TiO.sub.2 17.5 15 13.8 12.5 10 7.5 ZnO 5 5 5 5 5 5 T.sub.g 376 C. 364 C. 356 C. 348 C. 325 C. 305 C. T.sub.x (onset) 497 C. 507 C. 506 C. 506 C. 511 C. 485 C.

(44) Additionally, B.sub.2O.sub.3 substitutions were also made to D30, using the substitution schema presented earlier. B.sub.2O.sub.3 was added in an amount up to 15 mole %. The glass transition temperature T.sub.g for this series decreased by approximately 50 C., from 351 C. to 299 C.

(45) TABLE-US-00011 TABLE 11 D30 D36 D37 D38 D39 D40 D41 V.sub.2O.sub.5 47.5 47.5 47.5 47.5 47.5 47.5 47.5 P.sub.2O.sub.5 22.5 22.5 22.5 22.5 22.5 22.5 20 B.sub.2O.sub.3 0 1 3 5 7.5 10 15 Fe.sub.2O.sub.3 17.5 17 16 15 13.5 12.5 12.5 TiO.sub.2 10 9.5 8.5 7.5 6.5 5 2.5 ZnO 2.5 2.5 2.5 2.5 2.5 2.5 2.5 T.sub.g 351 350 345 331 320 311 299 T.sub.x (onset) 493 476 442 510 512 515 511

(46) FIG. 5 is a graph illustrating the effect of including boron (B.sub.2O.sub.3) in certain frit glasses. For example, curve 200 depicts the effect on T.sub.g for varying amounts of B.sub.2O.sub.3 in the general composition for D24, while curve 202 depicts the effect on T.sub.g for varying amounts of B.sub.2O.sub.3 in the general composition for D30. Note that the addition of B.sub.2O.sub.3 into these glasses resulted in a monotonic, linear decrease in T.sub.g, indicating that no abrupt structural changes are occurring in the base vanadium phosphate glass with boron addition over the composition range studied. Equally interesting is the data represented by curve 204, wherein B.sub.2O.sub.3 was added to the glass of D1, an antimony-containing glass. Curve 204 illustrates virtually no change in T.sub.g, suggesting that the simple addition of boron per se may not result in a significant effect on T.sub.g.

(47) FIG. 6 shows photographs of sintered glass frit pellets in laboratory beakers for D24 glass, with varying amounts of B.sub.2O.sub.3 added, after being immersed in 90 C. deionized water for 48 hours. The pellets were produced by forming a glass melt, grinding the solidified glass to form a glass frit, compressing the frit into pellets and sintering the pellets by exposing each pellet to 300 C. for one hour in air followed by 400 C. for one hour in nitrogen. FIG. 4 depicts, in order, from left to right, (a) 0 mole % B.sub.2O.sub.3, (b) 5 mole % B.sub.2O.sub.3, (c) 7.5 mole % B.sub.2O.sub.3, (d) 10 mole % B.sub.2O.sub.3, (e) 15 mole % B.sub.2O.sub.3, and (f) 20 mole % B.sub.2O.sub.3. Aqueous durability can be judged based on the darkness (opacity) of the supernatant: The darker the supernatant, the less durable the glass. The results shown in FIG. 6 indicate acceptable aqueous durability for B.sub.2O.sub.3 in amounts up to about 10 mole %. It should be understood, however, that the acceptability of aqueous durability will depend on the end use of the glass.

(48) FIG. 7 shows photographs of sintered glass pellets in laboratory beakers for D30 glass, with varying amounts of B.sub.2O.sub.3 added, after being immersed in 90 C. deionized water for 48 hours. The pellets were produced as above, by forming a glass melt, grinding the solidified glass to form a glass frit, compressing the frit into pellets and sintering the pellets by exposing each pellet to 300 C. for one hour in air followed by 400 C. for one hour in nitrogen. FIG. 7 depicts, in order, from left to right, (a) 0 mole % B.sub.2O.sub.3, (b) 1 mole % B.sub.2O.sub.3, (c) 3 mole % B.sub.2O.sub.3, (d) 5 mole % B.sub.2O.sub.3, (e) 7.5 mole % B.sub.2O.sub.3, (f) 10 mole % B.sub.2O.sub.3, and 15 mole % B.sub.2O.sub.3. As illustrated, aqueous durability in the samples of FIG. 7 are improved over a range from about 5 mole % to about 7.5 mole %, compared with other concentrations shown.

(49) Shown in FIG. 8 is a bright field image of a section of a laser-sealed section of two LOTUS.sup.XT display glasses 12, 18 sealed with a frit 16 made with a blend of the 5 mole % B.sub.2O.sub.3-modified D30 frit and a CTE-lowering glass-ceramic filler using a method as previously described in the present disclosure. The view in looking downward through glass substrate 12 to glass substrate 18. The frit connecting the glass plates includes a sealed portion 206 and unsealed portions 208. Note that the width 210 of the sealed portion of the frit, i.e. that portion of the frit actually bonded to the glass substrates, is approximately 90% of the total frit width 212 (968 m/1083 m=89.38%), indicating excellent flow and sealing behavior for a boron-containing, antimony-free frit as disclosed herein.

(50) Sb-free frits containing boron (B.sub.2O.sub.3) are described for sealing electronic devices, such as OLED displays, that offer comparable-to-lower Tg and comparable-to-improved aqueous durability than current Sb-containing frits, such as represented by D1. These same boron-containing Sb-free frits also possess lower Tg and comparable aqueous durability than non-boron-containing but Sb-free frits.

(51) Although embodiments disclosed herein have been illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it should be understood that these embodiments are not limited to those disclosed, but are capable of numerous rearrangements, modifications and substitutions without departing from the spirit of the disclosure as set forth and defined by the following claims.