BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded perspective view illustrating the basic components of a hermetically-sealed OLED display embodying the present invention;
FIG. 2 is a top plan view of the OLED display;
FIG. 3 is a flow chart illustrating the steps of an embodiment for manufacturing the hermetically-sealed OLED display;
FIG. 4 is a cross-sectional side view of a first embodiment of the OLED display taken along the line IV-IV, FIG. 2;
FIG. 5 is a cross-sectional side view of a second embodiment of the OLED display;
FIG. 6 is a perspective and schematic view of a system employed to manufacture the OLED display;
FIG. 7 is a cross-sectional side view of a third embodiment of the OLED display; and
FIG. 8 is a flow chart illustrating the steps of a method for manufacturing the third embodiment of the hermetically-sealed OLED.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
For purposes of description herein, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the invention as oriented in FIGS. 1 and 3. However, it is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise.
Reference numeral 10 (FIG. 1) generally designates a top emission, organic light-emitting diode display embodying the present invention. The display 10 comprises an organic light-emitting diode 12 (OLED) configured in a manner as is well known in the art and including an organic layer or stack 14 sandwiched between a pair of electrodes including an anode layer 16 and a cathode layer 18. Although the OLED 12 of the illustrated example includes a single organic layer 14, a single anode layer 16, and a single cathode layer 18, other multiple layered OLEDs as are known in the art may be utilized within the display 10. A first substrate 20 includes an inner surface 24 and an outer surface 26, while a second substrate 22 includes an inner surface 28 and an outer surface 30. As illustrated, the display 10 is a top-emitting display, wherein the light output from the OLED 12 is emitted in a direction as represented by directional arrow 34, but may also include top-bottom emitting displays, wherein the light output from the OLED 12 is emitted in the direction 34, as well as in an opposite direction as represented by directional arrow 36. The light is emitted at blue (approximately 460 nm), green (approximately 530 nm), and red (approximately 600 nm) parts of the visible spectrum with line width of 20 to 30 nm.
A preferred method for manufacturing the hermetically-sealed OLED display 10 is illustrated in FIG. 3 and includes a first step 38 of providing the first substrate plates 20 and a second step 40 of providing the second substrate plate 22. In a preferred embodiment, the first and second substrate plates 20, 22 are transparent glass plates such as those sold by Corning Incorporated under the brand name of Eagle 2000™ glass. Alternatively, the first and second substrates 20, 22 may be manufactured out of other suitable materials. A third step 42 includes forming a pocket 44 (FIG. 4) within the cover or second substrate 22. In the illustrated example, the pocket 44 is roll formed into the second substrate 22 by heating the substrate 22 and applying a physical roller, a vacuum and/or a pressure to the inner surface 28 and/or the outer surface 30 of the second substrate 22 in a manner as generally known in the art. The roll-forming process is described in detail in U.S. Pat. No. 5,885,315 entitled METHOD FOR FORMING GLASS SHEETS and assigned to Corning Incorporated, which is incorporated by reference herein in its entirety. It is noted that the outer surface 30 of the second substrate 22 is non-planar subsequent to the deformation thereof. In the illustrated example, the pocket 44 within the second substrate 22 is formed such that a distance between the inner surface 28 of the second substrate 22 and the inner surface 24 of the first substrate 20 is sufficient so as to reduce or eliminate the formation of Newton rings within the display 10. Preferably, the distance d is greater than or equal to 60 μm, and more preferably is greater than or equal to 80 μm.
Alternatively, the pocket 44a (FIG. 5) is etched into the inner surface 28a of the second substrate 22a, thereby providing a planer outer surface 30a to the second substrate 22a. Since the display 10a is similar to the display 10, similar parts appearing in FIG. 4 ad FIG. 5, respectively, are represented by the same, corresponding reference numeral, except for the suffix “a” in the numerals of the latter. It is contemplated that the etching process would include applying a photo-resistant material and using lithography or a similar method, placing the glass sheet into a HF/water or HF/HCl/water solution for a sufficient amount of time to remove the required amount of exposed glass. Subsequent to the acid etching, the photo-resistant material is removed. It is noted that other suitable glass etching processes may also be utilized.
At step 45, the OLED 12 and other required circuitry are deposited onto the inner surface 24 of the first substrate 20. Step 46 includes depositing the frit 32 along the edges of the second substrate 22, as best illustrated in FIG. 2. As an example, the frit 32 is placed approximately 1 mm away from the free edges of the second substrate 22. In the present embodiment, the frit 32 comprises a low temperature glass frit that contains one or more absorbing ions chosen from a group including iron, copper, vanadium and neodymium. The frit 32 can also be doped with a filler (e.g., inversion filler, additive filler) which lowers the co-efficient of thermal expansion of the frit 32 so that the coefficient of thermal expansion of the frit matches or substantially matches the coefficient of thermal expansions of the first and second substrates 20, 22. In an optional step 48, the frit 32 may be pre-sintered to the second substrate 22 by heating the frit 32 so that it becomes attached to the second substrate 22.
The step 50 includes heating the frit 32 (FIG. 6) by an irradiation source (e.g., laser 54 and a focusing lens 56, or an infrared lamp (not shown), and the like) in a manner so that the frit 32 forms an hermetic seal that connects and bonds the first substrate 20 and the second substrate 22. The hermetic seal between the first substrate and the second substrate 22 protects the OLED 12 by preventing oxygen and moisture in the ambient environment from entering into the OLED display 10.
The reference numeral 10b (FIG. 7) generally designates yet another embodiment of the hermetically-sealed OLED display manufactured from a method illustrated by the flow chart of FIG. 8. As the OLED display 10b is similar to the OLED display 10, similar parts appearing in FIG. 4 and FIG. 7, respectively, are represented by the same, corresponding reference numeral, except for the suffix “b” in the numerals of the latter. Steps 58, 60 include providing the first substrate 20b and the second substrate 22b, while step 62 includes depositing the OLED 12a onto the first substrate 20b, each similar to that previously described. Step 64 includes depositing a frit 32a along the edges of the second substrate 22a, in a manner similar to that described above. In the instant example, the frit 32a comprises a strong laser absorbing material, and a relatively weak laser radiation absorbing material. The distance d between the inner surface 24b of the first substrate 30b and the inner surface 28b of the second substrate 22b is adjusted by controlling the amount and composition of the material of frit 32b, and can be optimized so as to reduce or eliminate the formation of Newton rings in the display 10b. Preferably, the distance d is greater than or equal to 60 μm and is more preferably greater than or equal to 80 μm. The layer of frit material that highly absorbs the radiation is described in U.S. Pat. Nos. 6,998,776, as previously incorporated herein. It is noted that the strong laser radiation absorbing material and the relatively weak laser radiation absorbing material that comprise the frit 32a may be deposited as separate layers. Compositions utilized for the frit 32a that exhibit relatively high radiation absorption characteristics include:
|
CTE(10−7° C. to
|
Composition
SiO2
B2O3
Al2O3
Fe2O3
CuO
V2O5
Li2O
TiO2
400° C. Heating
|
|
Mole %
64
20.5
4
1.5
8
0.5
1
0.5
37
|
|
Examples of the transparent frit material include:
|
Wt %
Example 1
Example 2
|
|
|
SiO2 %
76.97
78.77
|
Na2O %
5.27
0.00
|
K2O %
0.00
2.39
|
B2O3 %
15.32
18.30
|
Al2O3 %
1.89
0.00
|
Cl-%
0.50
0.50
|
TiO2 %
0.02
0.02
|
SO3 %
0.01
0.00
|
Fe2O3 %
0.02
0.02
|
MgO %
0.00
0.00
|
CTE
33
28
|
Softening
818° C.
820° C.
|
Point
|
|
The present inventive top emission, organic light-emitting diode display and related method provides the necessary hermetic seal to protect the associated OLED components, while simultaneously providing the necessary spacing between the included substrates to reduce or eliminate optical distortions, such as Newton rings in the display. The display and related method result in reduced manufacturing costs, provide a durable display capable of a long operating life, and are particularly well adapted for the proposed use.
It will become apparent to those skilled in the art that various modifications to the preferred embodiment of the invention as described herein can be made without departing from the spirit or scope of the invention as defined in the appended claims. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and the equivalents thereto.
Patent Application
20080048556
